Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘L’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘L’
Label – It is an informative small document attached to an object. It is a piece of paper, plastic film, cloth, metal, or other material affixed to a product, on which is written or printed information or symbols about the product or item.
Laboratory information management system (LIMS) – It performs in-process analysis as well as quality assurance inspections.
Laboratory sample – It is a sample, intended for testing or analysis, prepared from a gross sample or otherwise got, the laboratory sample is required to retain the composition of the gross sample. Reduction in particle size is frequently necessary in the course of reducing the quantity.
Lack of fusion (LOF) – It is a condition in a welded joint in which fusion is less than complete. Lack of fusion is the failure of the filler metal to fuse with the adjacent base metal (or weld metal from previous pass) because the surface of base metal has not reached to the melting temperature during welding. This typically occurs when welding large components which can dissipate heat quickly especially when it is at a relatively low temperature before welding. Lack of fusion is frequently seen at the beginning of the first pass and in such case, it is normally called a cold start. Also, lack of fusion can occur when the surface of the previous pass is not properly cleaned from slag where slag reduces the heating of the under-laying surface.
Lack of penetration (LOP) – It is a condition in a welded joint in which joint penetration is less than that specified. Lack of penetration is insufficient (less than specified) penetration of the weld metal into the root of the joint. This is mostly caused by improper welding parameters such as low amperage, oversized electrode, improper angle, high travel speed, or inadequate surface pre-cleaning. Also, lack of penetration can happen when the root face is too large, the root opening is too narrow, or the bevel angle is too small.
Lacquer – It is a coating formulation based on thermoplastic film-forming material dissolved in organic solvent. The coating dries primarily by evaporation of the solvent. Typical lacquers include those based on lac, nitro-cellulose, other cellulose derivatives, vinyl resins, acrylic resins, and so forth. In lubrication, it is a deposit resulting from the oxidation and / or polymerization of fuels and lubricants when exposed to high temperatures. Softer deposits are described as varnishes or gums.
Ladder network – It is a string of many, frequently equally dimensioned, impedances connected between two reference voltages.
Ladle – It is the metal receptacle frequently lined with refractories used for transporting and pouring molten metal. It is a ‘bucket’ lined with refractory (heat resistant) bricks, used to transport molten steel from process to process in a steel plant.
Ladle brick – It is the refractory brick suitable for lining ladles used to hold molten metal.
Ladle coating – It is the material which is used to coat metal ladles to prevent iron pickup in aluminum alloys. The material can only consist of sodium silicate, iron oxide, and water, applied to the ladle when it is heated.
Ladle free open performance – Upon arrival of the ladle at the tundish of the continuous casting machine, it has to be opened to allow the steel to flow into the tundish. When the ladle slide gate is stroked open and steel starts to flow without operator assistance, the procedure is classified as ‘free open’. If poking or oxygen lancing is required to open the ladle, the process is classified as ‘assisted open’. When all attempts to open the ladle are unsuccessful, it is classified as ‘non-free open’. Several factors determine the opening performance of a ladle. The most dominant factor is the residence time of the steel in the ladle, followed by the ladle pre-heat practice, the elapsed time between the end of stirring and the opening of the ladle at the CCM, the cycle time for an empty ladle, and the argon stirring practice.
Ladle furnace – A ladle furnace is used to relieve the primary process of steelmaking of several of the secondary refining operations. It is one of the key components of ladle metallurgy processes. The main functions of a ladle furnace are (i) reheating of liquid steel by electric power which is conducted by graphite electrodes, (ii) homogenization of steel temperature and chemistry through argon gas rinsing, (iii) formation of slag layer which protects refractory from arc damage, concentrates and transfer heat to the liquid steel, trap inclusions and metal oxides, and provides means for desulphurization, (iv) additions of ferro-alloys to provide for bulk or trim chemical control, (v) cored wire addition for trimming and morphology control, (vi) provide a means for deep desulphurization, (vii) provide a mean for dephosphorization, and (viii) act as a buffer for downstream equipment and process.
Ladle injection – Liquid steel can be reheated by oxidizing aluminum and / or silicon by means of oxygen injection through a lance. Reheating of steel in the ladle with submerged oxygen injection is being practiced in some steel plants. Injection techniques have the advantages of dispersing the reactants in the steel bath and at the same time provide a large reaction surface area. The type of powders used is governed by the purpose of injection.
Ladle metallurgy – Ladle metallurgy plays a crucial role in ensuring the quality of steel products. Ladle metallurgy is sometimes also called ladle refining or secondary steelmaking. Ladle metallurgy processes are normally performed in ladles. The precise role of the ladle metallurgy varies depending on the configuration and the product range of the steel plant but there are three parameters which are required to be controlled in the processes of ladle metallurgy for ensuring high quality of steel products. These three parameters are (i) homogeneity and final value of temperature, (ii) homogenization of chemistry controlling the final levels of carbon, sulphur, phosphorus, oxygen, nitrogen, calcium, silicon, manganese, aluminum, and other alloying elements, and (iii) control of inclusions characteristics consisting of number, size, morphology, and chemistry. During the ladle metallurgy, control of these key parameters is achieved through the manipulation of three main variables namely (i) addition of chemical reagents and fluxes, (ii) heating through electrodes mounted in the roof of the ladle metallurgy station or through chemical methods, and (iii) stirring of the liquid steel in the ladle by the injection of an inert gas mainly argon gas. For achieving these controls, the operator at the ladle metallurgy station is normally provided with (i) the incoming steel chemistry, (ii) the incoming steel temperature, and (iii) the quantity of carry-over slag and its chemistry. The objectives of ladle metallurgy are (i) homogenization of chemical composition and temperature of liquid steel in the ladle, (ii) deoxidization or killing of steel for the removal of dissolved oxygen, (iii) adjustment of superheat, i.e., heating of the liquid steel to a temperature suitable for its continuous casting, (iv) additions of ferro-alloys and carburizer for making adjustments in the chemistry of liquid steel, (v) vacuum degassing for the removal of dissolved hydrogen and nitrogen gases, (vi) decarburization for the removal of carbon for meeting the requirement of certain grades of steel, (vii) desulphurization for the reduction of sulphur concentrations to levels as low as 0.002 %, (viii) micro-cleanliness i.e., removal of undesirable non-metallic inclusions, (ix) inclusion morphology i.e., changing the composition of remaining non-metallic inclusions for improving the micro-structure of the steel, and (x) improvement in the mechanical properties such as toughness, ductility, and transverse properties etc.
Ladle metallurgy furnace (LMF) – It is an intermediate steel processing unit which further refines the chemistry and temperature of molten steel while it is still in the ladle. The ladle metallurgy step comes after the steel is melted and refined in the electric arc or basic oxygen furnace, but before the steel is sent to the continuous casting machine.
Ladle preheating – It is the process of heating a ladle prior to the pouring of molten metal in it. This procedure reduces metal heat loss and eliminates moisture-steam safety hazards.
Ladle refining – The refining of steel in the ladle is broadly defined here as comprising of the operations such as deoxidation, desulphurization, dephosphorization, controlled additions of alloying elements and inclusion modification. There are a number of benefits which are available with the use of ladle refining furnace (LRF) are (i) homogenizing the composition and temperature of the liquid steel, (ii) making the steel cleaner, by the removal of oxygen inclusions, (iii) improving grain refinement in the micro-structure, (iv) degassing of the steel, through inert gas purging, (v) saving on ferro-alloys consumption, and (vi) increasing productivity, as the melting furnace gets emptied earlier. A ladle refining furnace looks similar to a ladle furnace but without the electric heating facility. The refining steel in the ladle is normally done by deoxidation of steel with ferro-manganese, ferro-silicon, silico-manganese, and aluminum.
Ladle refractories – These are the refractories which are used for the lining of ladles. These can be shaped refractories or monolithic refractories.
Ladle shroud – It is a refractory tube located between the ladle and the tundish whose main function is to protect the steel flow from secondary oxidation. Ladle shrouds do not need preheating before initial use but do if they are to be re-used after cooling down.
Ladle to ingot mould degassing – Preheated ingot mould with hot top is placed in vacuum chamber. Above the chamber a tundish is placed. Liquid steel tapped in the ladle is at superheat equivalent of 30 deg C. The ladle is placed above the tundish. Bottom pouring of liquid steel is into the tundish is desirable.
Ladle to ladle degassing – In ladle-to-ladle degassing, a ladle with the stopper rod is placed in a vacuum chamber. Ladle containing liquid steel from primary steelmaking furnace is placed on top of the vacuum chamber and the gap is vacuum sealed. Alloy additions are made under vacuum. Stream is allowed to fall in the ladle where liquid steel is degassed. Alloy additions are made under vacuum.
Lag – It is retardation or delay in the response which the instrument has to the changes in the measurement.
Lagging – In mining, it consists of planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks. In boiler, it is a light gauge steel covering used over a boiler, normally combined with insulation, to provide a low temperature outer surface.
Lag, lag time – It is a necessary break or delay between activities.
Lamb waves – Lamb waves refer to a type of wave recognized for its potential in structural health monitoring systems, despite challenges such as sensitivity to environmental and operational conditions. They propagate in solid plates or spheres. They are elastic waves whose particle motion lies in the plane that contains the direction of wave.
Lamellar corrosion – It is the corrosion which proceeds laterally from the sites of initiation along planes parallel to the surface, normally at grain boundaries, forming corrosion products which force metal away from the body of the material, giving rise to a layered appearance.
Lamellar tear – It is a terrace-like fracture in the base metal with a basic orientation parallel to the wrought surface. It is caused by the high stress in the thickness direction that results from welding.
Lamellar tearing – It occurs in the base metal adjacent to weldments because of the high through-thickness strains introduced by weld metal shrinkage in highly restrained joints. Tearing occurs by decohesion and linking along the working direction of the base metal. Cracks normally run roughly parallel to the fusion line and are steplike in appearance. Lamellar tearing can be minimized by designing joints to minimize weld shrinkage stresses and joint restraint.
Lamina – It is a single ply or layer in a laminate, which is made up of a series of layers.
Laminar cooling process (LCP) – It is an important process in hot steel strip rolling. It is carried out for cooling of hot strip on the run-out cooling table after the last finishing stand. It is used to cool the steel strip from an initial temperature of around 800 deg C to 950 deg C down to a coiling temperature of around 550 deg C to 700 deg C.
Laminar flow – It is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another smoothly. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface. Laminar flow is a flow regime characterized by high momentum diffusion and low momentum convection.
Laminate – It consists of a composite metal, normally in the form of flat sheets, composed of two or more metal layers so bonded that the composite metal forms a structural member. It also means forming a metallic product of two or more bonded layers. It also means to unite laminae with a bonding material, normally with pressure and heat (normally used with reference to flat sheets, but also rods and tubes). Laminate is a product made by such bonding.
Laminate coordinates – It consists of a reference coordinate system (used to describe the properties of a laminate), normally in the direction of principal axes, when they exist.
Laminated metal composites (LMCs) – These are a unique form of composite material in which alternating metal or metal containing layers are bonded together with discrete interfaces. The mechanical properties of these materials are reviewed.
Laminated object manufacturing – It is a rapid prototyping system. In it, layers of adhesive-coated paper, plastic, or metal laminates are successively glued together and cut to shape with a knife or laser cutter.
Laminate orientation – It is the configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.
Laminate ply – It consists of one fabric-resin or fiber-resin layer of a product which is bonded to adjacent layers in the curing process.
Lamination – It is a type of discontinuity with separation or weakness normally aligned parallel to the worked surface of a metal. It can be the result of pipe, blisters, seams, inclusions, or segregation elongated and made directional by working. In forged products, laminations are large porosity, pipe and non-metallic inclusions in slabs, blooms, or billets which are flattened and spread out during forging process. Laminations can also occur in powder metallurgy compacts. In electrical products such as motors, it is a blanked piece of electrical sheet which is stacked up with several other identical pieces to make a stator or rotor.
Lampblack – It is the fine soot which is used in the reduction and carburization of tungsten tri-oxide and titanium di-oxide to produce tungsten carbide, and titanium carbide powders respectively.
Lamprophyre – It is an igneous rock, composed of dark minerals, which occurs in dykes. It sometimes contains diamonds.
LAN – It is local area network, which is an interconnection of computers over a building or small campus.
Lance – In a blast furnace, it is a small diameter pipe fitted at an angle in the blow pipe through which auxiliary fuel / oxygen is injected in the blast furnace. In the basic oxygen furnace steelmaking, it is a long metallic tube through which oxygen is blown into the converter under high pressure. The water-cooled lance is used for injecting a high velocity (super-sonic) stream of oxygen onto the liquid bath for its refining. The velocity or momentum of the oxygen jet results in the penetration of the liquid slag and metal to promote oxidation reactions over a relatively small area. The velocity of the oxygen jet and the penetration characteristics are functions of the nozzle (lance tip) design. The top-blowing lance oxygen jet works as the source of feeding oxygen and energy for stirring of the liquid metal in the bath. Major in-furnace phenomena of a basic oxygen converter that involve the top-blowing lance oxygen jet are formation of a cavity as a result of physical interaction between the oxygen jet and liquid metal, stirring of liquid metal, generation of spitting and dust, and post combustion of carbon mono-oxide gas generated by decarburization and reaction with oxygen.
Lance bubbling equilibrium (LBE) process – It is a combined blowing process which is much more closely related to the basic oxygen furnace process in that all the oxygen is supplied from the top lance. The combined blowing aspect is achieved by a set of porous elements installed in the bottom of the converter through which argon or nitrogen is blown. In this process, nitrogen gas is typically used almost exclusively for the majority of the blow in the range of 3 normal cubic meter per minute to 11 normal cubic meter per minute. However, in the later part of the blow, when nitrogen absorption can create a problem, argon gas is used for stirring. The inert gases are introduced at the bottom of the furnace by means of permeable elements.
Lancing – It is a press operation in which a single-line cut is made in strip stock without producing a detached slug. It is mainly used to free metal for forming, or to cut partial contours for blanked parts, particularly in progressive dies. It is also a piercing (cutting) process carried out by metal powder cutting or oxy-fuel gas cutting. Lancing with oxygen is a cutting process. In this process, oxygen is supplied through a consumable steel pipe to pierce holes in metallic and mineral work-pieces. The lance is lighted and steadily consumed. It involves a number of steel wires packed into the steel tube.
Land – For profile-sharpened milling cutters, it is the relieved portion immediately behind the cutting edge. For reamers, drills, and taps, it is the solid section between the flutes. On punches, it is the portion adjacent to the nose which is parallel to the axis and of maximum diameter. In welding, it is a non-standard term for root face.
Landscape drawing – The landscape drawing is the aerial view of the whole area in which the building is built. It includes the areas designated for trees, street lights, parks, pools, and everything else. Landscape plan is more frequently used to depict the external aesthetics of the building. One can also include in them the paths, roads, pavements, parking areas, and several other things.
Langelier saturation index – It is an index calculated from total dissolved solids, calcium concentration, total alkalinity, pH, and solution temperature which shows the tendency of a water solution to precipitate or dissolve calcium carbonate.
Lang lay – In lang lay, the wires form an angle with the axis of the rope. The wire lay and strand lay around the core in the same direction. The wires and strands appear to run at a diagonal to the centre line of the rope. Lang lay wire ropes are distinguished between left hand lang lay (LHLL) and right hand lang lay (RHLL). Because of the longer length of the exposed outer wires, lang lay ropes have higher flexibility. These ropes are more likely to twist, kink, and crush. Lang lay ropes have a higher fatigue-resistance and are more resistant to abrasion. The advantages of lang lay ropes are (i) better contact in the groove of the sheaves, (ii) superior resistance to wear, (iii) longer lifetime in case of high dead loads, and (iv) considerably better spooling behaviour on a multi-layer drum.
Lanthanum – It is a chemical element having symbol ‘La’ and atomic number 57. It is a soft, ductile, silvery-white metal which tarnishes slowly when exposed to air. It is traditionally counted among the rare earth elements. Like most other rare earth elements, its normal oxidation state is +3, although some compounds are known with an oxidation state of +2.
Lap – It is a surface imperfection, with the appearance of a seam, caused by hot metal, fins, or sharp corners being folded over and then being rolled or forged into the surface but without being welded. In case of forging, lap is a surface imperfection in worked metal caused by folding over a fin overfill or similar surface condition, then impressing this into the surface by subsequent working without welding it. In filament winding, it is the quantity of overlay between successive windings, normally intended to minimize gapping. In bonding, it is the distance one adherend covers another adherend.
Lapping process – It is a precision machining technique which is used for achieving high levels of flatness, surface finish, and dimensional accuracy. It is an abrasive machining method which involves use of a highly abrasive slurry or paste, along with a rotating lap or work-piece, to remove material from the surface of a work-piece. This process produces flat and smooth surfaces.
Lap joint – A lap joint is formed when the surfaces of the two pieces overlap one another. The weld is deposited in the joint where the two intersect. A lap joint shows good mechanical properties, especially when a person weld both sides of the overlapped pieces, which provides extra reinforcement. The quantity of overlap needed in the joint id determined by the thickness of the two work-pieces. The thicker is the material, the more overlap is needed. Lap joints are very common for joining plates or sheet metal. With lap joints, it is important to make sure there are no gaps between the two workpieces. One wants them to be as flush as possible. In composites, lap joint is a joint made by placing one adherend partly over another and bonding the overlapped portions.
Lap joint flange – Lap joint flange is used with a lap joint stub end fitting and comprised of a hub or ‘stub end’ welded to the pipe and a backing flange or capped flange which is used to bolt the joint together. This means the stub end always makes the face. It is similar to a slip-on flange, but with two differences. The radius and the flat face, both allow the flange to secure against the stub end fitting. This is useful where alignment of bolt holes is difficult, such as with spools to be attached to flanged nozzles of the vessels. This type of flanged joint is typically found on high alloy pipework.
Lapping – It is a surface finishing process involving motion against an abrasive embedded in a soft metal. It is a finishing operation which uses fine abrasive grits loaded into a lapping material such as cast iron. It is also rubbing of two surfaces together, with or without abrasives. Lapping provides major refinements in the work-piece including extreme accuracy of dimension, correction of minor imperfections of shape, refinement of surface finish, and close fit between mating surfaces.
Large-end bearing – It is a bearing at the larger (crankshaft) end of a connecting rod in an engine.
Large-scale integration – It is the process of creating an integrated circuit by combining millions or billions of metal-oxide-semiconductor (MOS) transistors onto a single chip.
Larmor frequency – It is the classical frequency at which a charged body precesses in a uniform magnetic field. wL = -eB/2mc, where ‘e’ is the electron charge, ‘B’ is the magnetic field intensity, ‘m’ is mass, and ‘c’ is the velocity of light. Larmor precession is the precession of the magnetic moment of an object about an external magnetic field. The phenomenon is conceptually similar to precession of a tilted classical gyroscope in an external torque-exerting gravitational field.
Larmor period – It is the inverse of the Larmor frequency. the
Larson–Miller parameter (LMP) – It is also known as the Larson–Miller relation. It is a parametric relation used to extrapolate experimental data on creep and rupture life of engineering materials.
Laser – It is an acronym for light amplification by stimulated emission of radiation. Laser is a device which produces a concentrated coherent light beam by stimulating electronic or molecular transitions to lower energy levels.
Laser alloying – It is the use of lasers for surface (laser) alloying. In it the alloying elements are added to the melt pool to change the composition of the surface. The new structures produced by laser surface melting and alloying can show improved electro-chemical and tribological behaviour.
Laser beam cutting – It is a thermal cutting process which severs materials by melting or vapourizing them with the heat got from a laser beam, with or without the application of gas jets to augment the removal of material.
Laser beam machining – It consists of the use of a highly focused mono-frequency collimated beam of light to melt or sublime material at the point of impingement on a work-piece.
Laser beam welding (LBW) – It is a welding process which produces coalescence of materials with the heat got from the application of a concentrated coherent light beam impinging upon the joint. In this process a high energy laser beam is targeted on the work-piece. The laser beam heats and melts the edges of the work-piece, forming a joint. Laser beam welding uses a moving high-density coherent optical energy source called a laser as the source of heat. The coherent nature of the laser beam allows it to be focused to a small spot, leading to high energy densities. The energy of a narrow laser beam is highly concentrated, so a weak weld pool is formed very rapidly. The solidification of the weld pool surrounded by cold metal occurs as rapidly as the melt. Since the time the molten metal is in contact with the atmosphere is low, there is no contamination and hence no gradient (neutral gas, flow) is needed. In laser beam welding the joint is made either as a sequence of overlapped spot welds or as a continuous weld.
Laser chemical vapour deposition (LCVD) – It is also known as laser induced chemical vapour deposition. It is a chemical process which is used to produce high purity, high performance films, fibres, and mechanical hardware. It is a form of chemical vapour deposition in which a laser beam is used to locally heat the semi-conductor substrate, causing the vapour deposition chemical reaction to proceed faster at that site. The process is used in the semi-conductor industry for spot coating, the MEMS (micro-electro-mechanical systems) industry for 3-D printing of hardware such as springs and heating elements, and the composites industry for boron and ceramic fibres.
Laser confocal scanning microscopy, laser scanning confocal microscopy – It is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation.
Laser cutting – It is a technology which uses a laser to vapourize materials, resulting in a cut edge. Laser cutting works by directing the output of a high-power laser most commonly through optics. The laser optics and CNC (computer numerical control) are used to direct the laser beam to the material. A commercial laser for cutting materials uses a motion control system to follow a CNC or G-code of the pattern to be cut onto the material. The focused laser beam is directed at the material, which then either melts, burns, vapourizes away, or is blown away by a jet of gas, leaving an edge with a high-quality surface finish.
Laser diode (LD) – It is a semi-conductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode’s junction.
Laser engineered net shaping (LENS) – It is an additive manufacturing technique for producing finished parts / products of any shape. This technique uses a high-power laser to melt metallic powder, which is fed through a deposition head coaxially to the focus of the laser beam.
Laser etching – It is an engraving process where lasers are used to engrave a design, pattern or text into a material.
Laser hardening – It is a surface-hardening process which uses a laser to quickly heat a surface. Heat conduction into the interior of the part quickly cool the surface, leaving a shallow martensitic layer.
Laser ionization mass spectroscopy (LIMS) – It is based on a process similar to vapourization-dominated drilling. A laser beam is used to vapourize the surface of the sample and then the vapour or plasma cloud produced can be spectroscopically analyzed.
Laser inspection – Lasers are used in inspection and measuring systems because laser light provides a bright, undirectional, and collimated beam of light with a high degree of temporal (frequency) and spatial coherence. These properties can be useful either singly or together. For example, when lasers are used in interferometry, the brightness, coherence, and collimation of laser light are all important. However, in the scanning, sorting, and triangulation applications, lasers are used because of the brightness, unidirectionality, and collimated qualities of their light, temporal coherence is not a factor. Lasers can be used in several different ways to measure the dimensions and the position of parts. Some of the techniques include (i) profile gauging of stationary and moving parts with laser scanning equipment, (ii) profile gauging of stationary parts by shadow projection on photo-diode arrays, (iii) profile gauging of small gaps, and small-diameter parts from diffraction patterns, (iv) gauging of surfaces that cannot be seen in profile (such as concave surfaces, gear teeth, or the inside diameters of bores) with laser triangulation sensors, (v) measuring length, alignments, and displacements with interferometers, (vi) sorting of parts, (vii) three-dimensional gauging of surfaces with holograms, and (viii) measuring length from the velocity of moving, continuous parts.
Laser safety goggles – These are specialty goggles to protect against intense concentrations of light produced by lasers. The type of laser safety goggles to be used depends upon the equipment and operating conditions in the work-place.
Laser-shot peening -It is a surface treatment, which uses laser-induced shocks to create deep compressive stresses beyond a 1-millimeter depth with magnitudes comparable to that produced by shot peening. Laser-shot peening has proven to considerably improve the damage tolerance of components and has generated sufficiently impressive results to move it from a laboratory-demonstration phase into a significant industrial process technology.
Laser soldering – It is a technique where a precisely focused laser beam provides controlled heating of the solder alloy leading to a fast and non-destructive of an electrical joint. The process uses a controlled laser beam to transfer energy to a soldering location where the absorbed energy heats the solder until it reaches its melting temperature leading to the soldering of the contact and this completely eliminates any mechanical contact. Laser soldering uses solder, which in liquid state wet the materials to be joined and provide mechanically and electrically stable connections when solidified.
Laser surface processing – It consists of the use of lasers with continuous outputs of 0.5 kilowatts to 10 kilowatts to modify the metallurgical structure of a surface and to tailor the surface properties without adversely affecting the bulk properties. The surface modification can take in three forms. The first is transformation hardening in which a surface is heated so that thermal diffusion and solid-state transformations can take place. The second is surface melting, which results in a refinement of the structure because of the rapid quenching from the melt. The third is surface (laser) alloying, in which alloying elements are added to the melt pool to change the composition of the surface. The new structures produced by laser surface melting and alloying can show improved electro-chemical and tribological behaviour.
Latent heat – It is the thermal energy absorbed or released when a substance undergoes a phase change.
Latent heat of fusion – It is also known as enthalpy of fusion. It is the quantity of energy which is to be supplied to a solid substance (typically in the form of heat) in order to trigger a change in its physical state and convert it into a liquid (when the pressure of the environment is kept constant).
Latent heat of melting – It is the heat which causes a phase / state change of a solid without raising its temperature. In case of ice, a total of 334 kilojoule of energy is needed to melt 1 kilogram of ice at 0 deg C into 1 kilogram of water at 0 deg C.
Latent heat of vapourization – It is the heat which causes a phase / state change of a liquid without raising its temperature. In case of water, 2,257 kilojoule of energy is needed to evaporate 1 kilogram of water at 100 deg C into 1 kilogram of steam at 100 deg C.
Latent solvent – It is a liquid which cannot itself dissolve a binder but increases the tolerance of the paint for a diluent.
Lateral bow – It is the deviation from straight of a longitudinal edge.
Lateral extrusion – It is an operation in which the product is extruded sideways through an orifice in the container wall.
Lateral thinking – Lateral thinking involves using a roundabout method to inspire new ideas or solutions. It can be done in a variety of ways, from using a random word to choosing an object in a room as a basis for thought.
Laterite – It is residual soil which is normally found in tropical countries, out of which the silica has been leached. It can form ore-bodies of iron, nickel, bauxite, and manganese.
Latest start time of an activity – It is the latest time in a programme evolution review technique (PERT) network at which the activity can start without delaying the subsequent events. It is the latest moment at which an activity can start without delaying completion of the overall project.
Latest finish time of an activity – It is the latest time in a programme evolution review technique (PERT) network at which the activity can be completed without delaying the subsequent events. It is the latest time at which an activity can be completed without delaying the completion of the overall project. Latest finish time of an activity is equal to the smallest of the latest start times of its immediate successors.
Lathe – It is a machine tool which rotates a work-piece around an axis of rotation to perform different operations such as cutting, sanding, knurlinng, drilling, deformation, facing, threading and turning, with tools which are applied to the work-piece to create an object with symmetry around that axis. Lathes are used in metalworking, metal spinning, roll turning, thermal spraying, reclamation, and glass-working.
Lath martensite – It is the martensite formed partly in steels containing less than around 1 % carbon and solely in steels containing less than around 0.5 % carbon as parallel arrays of packets of lath-shape units 0.1 micrometer to 0.3 micrometer thick.
Lattice – A space lattice is a set of equal and adjoining parallelopipeds formed by dividing space by three sets of parallel planes, the planes in any one set being equally spaced. There are seven ways of so dividing space, corresponding to the seven crystal systems. The unit parallelopiped is normally chosen as the unit cell of the system. It is also a point lattice is a set of points in space located so that each point has identical surroundings. There are 14 ways of so arranging points in space, corresponding to the 14 Bravais lattices.
Lattice constants, lattice parameter – It is one of the physical dimensions and angles which determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. It is the length of any side of a unit cell of a given crystal structure. The term is also used for the fractional coordinates (‘x’, ‘y’, and ‘z) of lattice points when these are variable.
Lattice diffusion – It is one of the primary diffusion mechanisms during sintering. It is predominant for large particles and higher temperatures, and its diffusion coefficient for the same conditions is smaller than that of grain boundary diffusion, and much smaller than that for surface diffusion.
Lattice pattern – It is a pattern of filament winding with a fixed arrangement of open voids.
Laue equations – These three simultaneous equations which state the conditions to be met for diffraction from a three-dimensional network of diffraction centres.
Laue method (for crystal analysis) – It is a method of X-ray diffraction using a beam of white radiation, a fixed single crystal sample, and a flat photographic film normally normal to the incident beam. If the film is located on the same side of the sample as the X-ray source, the method is known as the back reflection Laue method, if on the other side, as the transmission Laue method.
Launder – It is a channel for transporting molten metal. It is also a box conduit conveying particles suspended in water. It is also a chute or trough for conveying pulp, water or powdered ore in a mill.
Lava – It is a general name for the molten rock ejected by volcanoes.
Laval nozzle – It consists of a convergent inlet and a divergent outlet duct. Frequently, the term convergent-divergent (CD) nozzle is used.
Law of conservation of energy – It states that the total energy of an isolated system remains constant and it is said to be conserved over time. In the case of a closed system, the principle says that the total quantity of energy within the system can only be changed through energy entering or leaving the system.
Law of conservation of mass – It is the principle of mass conservation which states that for any system closed to all transfers of matter, the mass of the system remains constant over time. During a chemical reaction, the total mass of the products is to be equal to the total mass of the reactants. In other words, mass cannot be created or destroyed during a chemical reaction, but is always conserved.
Lay – It is the direction of predominant surface pattern remaining after cutting, grinding, lapping, or other processing. In the wire rope, lay is the helix or spiral of the wires and strands. The word ‘lay’ has got three meanings in the rope design. The first two meanings are descriptive of the wire and strand position in the rope. The first meaning describes the direction in which strands rotate around in the wire rope i.e. right lay or left lay. If the strands rotate around the wire rope in a clock wise direction, the rope is said to be right lay. When the strands rotate in the counter-clockwise direction, the wire rope is left lay. The second meaning shows the relationship between the direction strands lay in the wire rope and the direction wire lay in the strands. The third meaning is a length measurement used in manufacturing and inspection. In the third meaning it is the linear length along the rope that a strand makes one complete spiral around the rope core. Lay length is measured in straight line parallel to the centre line of the rope, not by following the path of the strand.
Layer bearing – It is a bearing constructed in layers such as bi-metal bearing and tri-metal bearing.
Layer-lattice material – It is a material having a layer like crystal structure, but particularly solid lubricants of this type.
Layout -It refers to the arrangement of physical facilities such as machines, equipment, tools, utilities, furnaces, and control rooms etc. in such a manner so as to have quickest flow of material at the lowest cost and with the least quantity of handling in the production of the product from the receipt of the input materials to the dispatch of the finished products.
Layout design – It normally involves getting a suitable arrangement of equipments or units and their connections within a pre-defined area based on pre-specified criteria. These items can be process-equipment, furnaces, electric control rooms, instruments and control rooms, product inspection area, and quality control laboratory, stores, workshops, offices, canteen and change rooms, and fire station etc. with connections by pipes, conveyors, vehicular transport or any other suitable material handling equipment. Plant layout includes plant roads and rail tracks.
Layout drawing – A layout drawing depicts design development requirements. It is similar to a detail, assembly, or installation drawing, except that it presents pictorial, notational, or dimensional data to the extent necessary to convey the design solution used in preparing other engineering drawings. The layout drawing normally does not establish item identification. The layout drawing is prepared either as (i) a conceptual design layout to present one or more solutions for meeting the basic design parameters and to provide a basis for evaluation and selection of an optimum design approach, (ii) a design approval layout to present sufficient details of the design approach for cost estimating and design approval, (iii) a detailed design layout drawing depicting the final development of the design in sufficient detail to facilitate preparation of detail and assembly drawings, (iv) a geometric study to develop movement of mechanical linkages, clearances, or arrangements. The layout drawing includes (i) location of primary components, (ii) interface and envelope dimensions including a cross-reference to applicable interface control documentation, (iii) paths of motion, (iv) operating positions, (v) critical fits and alignments, (vi) selected materials, finishes, and processes, (vii) cellars, pipeline routing and sizes, (viii) adjustments, (ix) critical assembly details and sequence, and (x) identification of change parts and critical spare parts.
Layout sample – It is a prototype forging or a cast used to determine conformance to designed dimensions.
Lay-up – It consists of the reinforcing material placed in position in the mould. It is the process of placing the reinforcing material in position in the mould. It is also the resin-impregnated reinforcement. Lay-up is also a description of the component materials, geometry, and so on, of a laminate. It is also a fabrication process involving the assembly of successive layers of resin-impregnated material.
LC circuit – It is also called a resonant circuit, tank circuit, or tuned circuit; It is an electric circuit consisting of an inductor, represented by the letter ‘L’, and a capacitor, represented by the letter ‘C’, connected together.
LD converter – The LD converter, named after the Austrian towns Linz and Donawitz, is a refined version of the Bessemer converter, where blowing of air is replaced with blowing oxygen.
L-direction – It is the ribbon direction, that is, the direction of the continuous sheets of honeycomb.
L/D ratio – In bearing technology, it is the ratio of the axial length of a plain bearing to its diameter.
Leachable – It means extractable by chemical solvents.
Leaching – It is a chemical process for the extraction of valuable minerals from ore. It is also, a natural process by which ground waters dissolve minerals, hence leaving the rock with a smaller proportion of some of the minerals than it contained originally.
Lead – It is the axial advance of a helix in one complete turn. It is also the slight bevel at the outer end of a face cutting edge of a face mill.
Lead (Pb) – It is a chemical element which has atomic number 82. It is a heavy metal and is denser than majority of the common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray colour when exposed to air. Lead is an undesirable element in steel. It increases the machinability of steel. It is virtually insoluble in liquid or solid steel. However, it is sometimes added to carbon and alloy steels by means of mechanical dispersion during pouring to improve the machinability. The addition of around 0.25 % lead improves machinability. It also causes a reduction in fatigue strength, ductility and toughness but this only becomes serious in the transverse direction and at high tensile levels. In creep resisting alloys, very small quantities of lead can be harmful. It has no effect upon the other properties of the steel.
Lead angle – In cutting tools, it is the helix angle of the flutes.
Lead burning -It is a misnomer for welding of lead.
Leaded bronzes – These are copper-base alloys containing up to 10 % tin and up to 30 % lead.
Leaded steels– These are steels to which lead, in quantities ranging from 0.15 % to 0.35 %, is normally added along with sulphur to improve the machinability of the steel product.
Lead, fastener – It is the linear distance which a point on a fastener thread advances axially in one revolution (equal to the pitch of the fastener).
Lead, lead time – it is the quantity of time an activity can be brought forward with respect to the activity it is dependent upon.
Leads – In pile foundations, it is a wooden or steel frame with one or two parallel members for guiding the hammer and piles in the correct alignment. There are three basic types of leads namely (i) fixed, which is fixed to the pile rig at the top and bottom, (ii) swinging, which is supported at the top by a cable attached to the crane, and (iii) semi-fixed or telescopic, which is allowed to translate vertically with relation to the boom tip.
Lead time – It is the time from the initial contract / order to the time it takes the customer to receive their products. It is the delivery time for an item of inventory to be moved from a source location to a destination through a specific route. Detail is specific to the level of the location. It is also the time to produce a customer’s order from order placement to shipment.
Lead-tin alloy coated sheet and strip (terne plate) – This coated product is produced by coating with lead-tin alloy either by dipping in a bath of molten alloy or electrolytically. In general, the highest nominal mass specified for the coating corresponds to a minimum of 120 grams per square metre including both sides.
Leaf chain – It is an assembly of alternating sets of pin links and articulating links on pins which are free to articulate in the holes of the articulating links. The pin link plates normally are press fitted onto the ends of the pins in the chain. The centre link plates are normally slip fitted on the pins. Leaf chains are intended to run over sheaves, so there is no provision for them to engage a sprocket. Leaf chains are used almost exclusively for lifting and counterbalancing. Tensions are very high, but speeds are slow. Normally the chains work intermittently. The main considerations in the design of the leaf chains are tensile loads, joint wear, and link plate and sheave wear.
Leaf spring – It is a simple form of spring normally used for suspension in wheeled vehicles. A leaf spring is one or more narrow, arc-shaped, thin plates which are attached to the axle and chassis in a way that allows the leaf spring to flex vertically in response to irregularities in the road surface. Lateral leaf springs are the most commonly used arrangement, running the length of the vehicle and mounted perpendicular to the wheel axle, but numerous examples of transverse leaf springs exist as well.
Leak – It is an undesirable flow of gas or liquid through the wall of a vessel through an imperfection such as a hole, crack or bad seal. Leaks need a pressure difference to generate the flow; They always flow from higher pressure to lower pressure. Typically, leaks are thought of as travelling from positive pressure (inside an object) to atmospheric pressure (outside an object). This is not always the case as a leak can be from atmosphere to inside an evacuated object.
Leakage – It is the uncontrolled quantity of fluid which enters or leaves through the enclosure of air or gas passages.
Leakage inductance – It is the inductance of a transformer which results from magnetic flux not linked by both primary and secondary windings.
Leak-before-break (LBB) – It is a term which is used in reference to a methodology which means that a leak is going to be discovered prior to a fracture occurring in service. Leak-before-break has been applied to gas and oil pipelines, pressure vessels, and nuclear piping etc.
Leak proof doors – Leaking doors of a coke oven battery are always a major source of pollution. The design of oven doors has gone through a process of evolution, starting from luted doors to the present generation self-regulating zero leak doors. The imported features of the leak proof doors are (i) a thin stainless-steel diaphragm with a knife edge as a sealing frame built in between the door body and the brick retainer, (ii) spring loaded regulation on the knife edge for self-sealing, (iii) provision for air cooling of the door body, and (iv) large size gas canals for easier circulation of gas inside the oven. The advantage of leak proof doors is minimization of door leakages, regulation free operation, longer life because of less warping of the air-cooled door body and reduced maintenance.
Leak testing – It is a non-destructive test for determining the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leak testing concerns the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leaking fluids (liquid or gas) can penetrate from inside a component or assembly to the outside, or vice versa, as a result of a pressure differential between the two regions or as a result of permeation through a somewhat extended barrier. Leak testing encompasses procedures for one or a combination of the these (i) locating (detecting and pinpointing) leaks, (ii) determining the rate of leakage from one leak or from a system, and (iii) monitoring for leakage. Leak testing systems use a variety of gas detectors, are used for locating (detecting and pinpointing) leaks, determining the rate of leakage from one leak or from a system, or monitoring for leakage.
Lean manufacturing – It is a method of manufacturing goods aimed mainly at reducing times within the production system as well as response times from suppliers and customers. It is closely related to another concept called just-in-time manufacturing. It is a production methodology based on the idea of streamlining and doing more with less, such as by providing customers with the same product value while eliminating waste and thus reducing production costs.
Lean six sigma – Lean six sigma combines the no-waste ideals of lean manufacturing with the no-defects target of six sigma. The goal of lean six sigma is to eliminate waste and defects so that products cost less and deliver more consistent quality.
Learning curve – It is a curve which shows the way that production time or manufacturing cost decreases with cumulative production because of greater worker experience.
Least commitment policy of design – It is the concept that it is best to allow as much freedom as possible for downstream decisions in the design process so that engineers are free to develop the best possible solutions unconstrained by previous unnecessary commitments (decisions).
Least count of a measuring instrument – It is the smallest value in the measured quantity which can be resolved on the instrument’s scale.
Leather gloves – These are sturdy and provide protection against cuts and burns. Leather gloves also protect against sustained heat. They protect against sparks, moderate heat, blows, chips and rough objects. These gloves can be used for tasks such as welding.
Ledeburite – It is the eutectic of the iron-carbon system, the constituents of which are austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below Ar1 temperature, the temperature at which transformation of austenite to ferrite or ferrite plus cementite is completed during cooling.
Left-hand cutting tool – It is a cutter, whose all-flutes twist away in a counter-clockwise direction when viewed from either end.
Legal Metrology – It is the application of measurement standards to the control of the daily transactions of trade and commerce. It is more commonly known as ‘Weights and Measures’. Internationally, coordination among nations on Legal Metrology matters is, by international agreement, handled by a quasi-official body ‘the International Organization for Legal Metrology (OIML)’.
Legal requirement – It can be anything which is demanded of a person or an organization by statute, regulation, common law, or by-law.
Leidenfrost phenomenon – It is slow cooling rates associated with a hot vapour blanket which surrounds a part being quenched in a liquid medium such as water. The gaseous vapour envelope acts as an insulator, hence slowing the cooling rate.
Lemon bearing (elliptical bearing) – It is a two-lobed bearing.
Length, fastener – It is the axial distance between the bearing surface of the head and the extreme point.
Length, grip – It is the length of the unthreaded portion of the fastener (i.e. shank) measured axially from the underside of the bearing surface to the starting thread
Length, thread – It is the length of the threaded portion of the fastener. In all the commercial fasteners, threaded length is a function of fastener diameter.
Lens – It is a transparent optical element, so constructed that it serves to change the degree of convergence or divergence of the transmitted rays.
Lens, mining – It is normally used to describe a body of ore that is thick in the middle and tapers towards the ends.
Lenticular – It is a deposit having roughly the form of a double convex lens.
Lethal dose (LD) – A lethal dose of radiation is the dose needed to cause death to 50 % of an exposed population within 30 days (LD 50/30). Typically, the LD 50/30 is in the range from 400 rem to 450 rem (4 Sievert to 5 Sieverts) received over a very short period. Duration of the exposure is important here as the dose received by patients in radiotherapy treatments can reach 20 Sieverts over time.
Letter of credit (LC) – It is also known as a documentary credit or bankers’ commercial credit, or letter of undertaking. It is a payment mechanism used in international trade to provide an economic guarantee from a creditworthy bank to an exporter of goods.
Level – In mining, it is the horizontal openings on a working horizon in a mine. It is customary to work mines from a shaft, establishing levels at regular intervals, normally around 50 metres or more apart.
Level control valve – It is an altitude control valve which automatically responds to changes in the height of a liquid in some storage system.
leveler chatter (roll or leveler) – It consists of several intermittent lines or grooves which are normally of full width and perpendicular to the rolling or extrusion direction.
Leveler lines – Thses are lines on sheet or strip running transverse to the direction of roller leveling. These lines can be seen upon stoning or light sanding after leveling (but before drawing) and can normally be removed by moderate stretching.
Leveler mark – It is the repeating depression caused by a particle adhering to a rotating roll over which the metal has passed.
Leveler streak – It is a streak on the sheet surface in the rolling direction caused by transfer from the leveler rolls.
Leveling – It is the mechanical flattening of rolled sheet, strip, plate or foil by reducing or eliminating distortions.
Leveling action -It is the ability of a plating solution to produce a plated surface smoother than that of the substrate.
Leveling process – It is the process by which a leveling machine flattens metal strip, coil, or sheets by bending it up and down over the interrupting arcs of upper and lower sets of long, slender work rolls. Leveling machines normally use 17, 19, or 21 relatively small diameter rolls whose deflection under load is controlled by additional back-up rollers and a rigid frame.
Leveling, roller – It is leveling carried out by bending.
Leveling, stretcher – It is leveling carried out by uniaxial tension.
Leveling, tension – It is leveling continuously carried out by uniaxial stretching, normally with the assistance of bending.
Leveling, thermal – It is leveling carried out at a high temperature underan applied load normal to the surface to be flattened.
Level of effort – It consists of work which is not directly associated with components of a work breakdown structure but which can instead be thought of as support work. Examples of level of effort include maintenance and accounting. It is one of three types of activities used to measure work performance as part of earned value management.
Levels of automation – There are five levels of automations which are normally used in the industry. These levels are level 0, level 1, level 2, level 3, and level 4. Under level 0, there is practically no automation and every control of the equipment and process consists of manual control. The level I automation is restricted to the production processes. It includes control of equipments and production processes. It includes dedicated digital controller (DDC). It does not include networking. The level 1 automation utilizes more and more modern field instruments, remote I/Os (input / output), field busses and graphical interfaces. Normally the level 1 control systems today are capable to handle more and more complex MIMO (multi-input and multi-output) systems and cascade systems with improved accuracy. Level 2 automation level includes supervisory control. Supervisory control combines the production scheduling and management information functions with the process control functions to form a hierarchical control system. It also includes process models, automatic material handling, tool setting, packing and other auxiliary systems. It utilizes physical process models to supplement the level 1 control giving calculated set-values to level 1 process control. The process monitoring and diagnostics play also important role in level 2 systems. The level 2 automation systems offer two main capabilities namely (i) tight optimized control of each operating unit of the plant based upon the production levels and constraints set by level 3 production planning and control (PPC) system by providing optimal operating set points to the manufacturing processes with this control reacting directly to any emergencies that occur in its own unit, and (ii) improved overall reliability and availability of the total control system through fault detection, fault tolerance, redundancy, and other applicable techniques built into the system’s specification and operation. Level 3 automation system contains scheduling and delivery status monitoring features. It includes production planning and control functions. Both production planning and production control functions are included in this level. It also includes maintenance planning and analysis of data. This system is a total integrated automation system. With this level of automation, the remote operation in-charge can view all the data. Enterprise resource planning (ERP) is a popular software-based technology related to level 3 automation. Level 4 control connects customer orders and material and makes capacity allocation to production. This complex enterprise resource planning system is used to manage the complete order-supply-chain follow-up and documentation.
Level winding – In filament- wound reinforced plastics, It is a winding with the filaments essentially perpendicular to the axis (90 -degree or level winding).
Lever – It is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is divided into three types. A lever amplifies an input force to provide a higher output force, which is said to provide leverage, which is mechanical advantage gained in the system, equal to the ratio of the output force to the input force. As such, the lever is a mechanical advantage device, trading off force against movement.
Lever rule – It says that the fraction of one phase is computed by taking the length of tie-line from the overall alloy composition to the phase boundary for the other phase, and dividing by the total tie line length. In an alloy or a mixture with two phases, liquid and solid, which themselves contain two elements, A and B, the lever rule states that the mass fraction of the solid phase is given by equation phase percent = (opposite arm of the lever / total length of tie-line) x 100. Lever rule is used to determine the mole fraction or the mass fraction of each phase of a binary equilibrium phase diagram. It can be used to determine the fraction of liquid and solid phases for a given binary composition and temperature which is between the liquidus and solidus line. The lever rule is a mechanical analogy to the mass balance calculation.
Levigation – It is separation of fine powder from coarser material by forming a suspension of the fine material in a liquid. It is a means of classifying a material as to particle size by the rate of settling from a suspension.
Levitation melting – It is an induction melting process in which the metal being melted is suspended by the electro-magnetic field and is not in contact with a container.
Lid – It is a removable or attached top for a ladle.
LIDAR survey – Laser Induced Differential Absorption Radar (LIDAR) is a high-resolution digital elevation maps generated by airborne Lidar have led to significant advances in the ability to detect subtle topographic features. Very precise topographical map data is created through Lidar surveys.
Life cycle assessment (LCA) – It is also known as life cycle analysis. It is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product, process, or service. For example, in the case of a manufactured product, environmental impacts are assessed from raw material extraction and processing (cradle), through the product’s manufacture, distribution and use, to the recycling or final disposal of the materials composing it (grave).
Life cycle costing – It is an accounting method of costing where expenses are allocated over the life of the product. Life cycle costs for a product are frequently lower than its alternatives despite a higher initial outlay since the product normally last longer and need little maintenance.
LIFO – LIFO stands for ‘Last-In, First-Out’. It is an inventory valuation method where the most recently acquired items are sold or used first. This approach can impact financial statements and tax liabilities by reflecting current costs more accurately during periods of inflation.
Lift (force) – When a fluid flows around an object, the fluid exerts a force on the object. Lift is the component of this force which is perpendicular to the oncoming flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and hence can act in any direction. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force.
Lift beam furnace – It is a continuously operating sintering furnace. It is also known as walking beam furnace.
Lift height – The rated lift height means the distance between the upper and lower elevations of travel of the load block and arithmetically it is normally the distance between the beam and the floor, minus the height of the hoist. This dimension is critical in most applications as it determines the height of the runway from the floor and is dependent on the clear inside height of the building. It is to be remembered that any slings or below the hook devices which influence this value are to be included.
Lifting beams – They are made from solid or fabricated metal, or from wood and are suspended from a hoist/crane to provide multiple load lifting points for better security and control of the load’s movement. A spreader beam uses two or more hooks to spread the load over more than one lifting point.
Lifting forks – These consist of two or more arms fixed to an upright with an upper arm, essentially to lift palletized or similar loads.
Lifting magnets – These are the lifting devices which are used for lifting and transporting of steel and ferrous metal stock or manufactured components. They are normally installed and used as single magnets or as arrangements of multiple magnets. In all of these cases, they are suspended from chains or wires or otherwise attached to the lifting equipment such as cranes. Electrically operated lifting magnets are widely used in the iron and steel plants. Lifting magnets can be provided with no power supply i.e. permanent magnets, or where power is supplied by cable from an external source or through an in-built battery. The magnet and any associated electrical equipment are to be designed for its intended purpose and constructed to withstand the environment in which it is required to operate. When used correctly lifting magnets handle magnetic materials and components safely, and without the need for slingers.
Lifting points – These are connectors (sometimes temporary) directly on the steel work-pieces article which help the galvanizer in handling the work-piece throughout the galvanizing process.
Lifting tackles – These are also known as lifting accessories. These are pieces of equipment which are used to attach the load to lifting equipment, providing a link between the two. Examples of lifting tackles are slings, hooks, shackles, eyebolts, lifting eyes, spreader beams, magnetic and vacuum devices, and lifting and plate clamps.
Liftout – It is the mechanism which is also known as knockout.
Ligand – It is the molecule, ion, or group bound to the central atom in a chelate or a coordination compound.
Light – It is the radiant energy in a spectral range visible to the normal human eye (around 380 nano-meters to 780 nano-meters).
Light coated electrodes – Light coated welding electrodes have a definite composition. A light coating has been applied on the surface by washing, dipping, brushing, spraying, tumbling, or wiping. The coatings improve the characteristics of the arc stream. The coating normally serves several functions namely (i) it dissolves or reduces impurities such as oxides, sulphur, and phosphorus, (ii) it changes the surface tension of the molten metal so that the globules of metal leaving the end of the electrode are smaller and more frequent and this helps make flow of molten metal more uniform, (iii) it increases the arc stability by introducing materials readily ionized (i.e., changed into small particles with an electric charge) into the arc stream, and (iv) some of the light coatings can produce a slag. However, the slag is quite thin and does not act in the same manner as the shielded arc electrode type slag.
Light crude oil – It is liquid petroleum that has a low density and flows freely at room temperature. It has a low viscosity, low specific gravity and high API gravity because of the presence of a high proportion of light hydrocarbon fractions. It normally has a low wax content.
Light diesel oil (LDO) – It is having flash point above 66 deg C. It is a blend of distillate components and a small quantity of residual components. It is used as a fuel in certain boilers and furnaces.
Light drawn – It is an imprecise term, applied to drawn products such as wire and tubing, which indicates a lesser quantity of cold reduction than for hard drawn products.
Light-emitting diode (LED) – It emits light when current flows through it. Electrons in the semi-conductor recombine with electron holes, releasing energy in the form of photons. The colour of the light is determined by the energy needed for electrons to cross the band gap of the semi-conductor. It is a semi-conductor device which produces light or infrared or ultraviolet radiation when properly energized.
Lightening holes – These are holes in structural components of machines and buildings to make structures lighter. The edges of the hole can be flanged to increase the rigidity and strength of the component. The holes can be circular, triangular, elliptical, or rectangular and need to have rounded edges, but they are not to have sharp corners, to avoid the risk of stress risers, and they are not to be very close to the edge of a structural component.
Light-field illumination – For reflected light, it is the form of illumination which causes specularly reflected surfaces normal to the axis of the microscope to appear bright. For transmission electron microscopy, it is the illumination of an object so that it appears on a bright background.
Light filter – It is a device which transmits principally a predetermined range of wave-lengths.
Light fraction – It is the first liquid produced during the distillation of a crude oil.
Light gauge steel – This steel is in the form of very thin steel sheet which has been temper rolled or passed through a cold rolling mill. Light gauge steel normally is plated with tin or chromium for making cans to be used as food containers.
Lightly coated electrode – It is a filler-metal electrode used in arc welding, consisting of a metal wire with a light coating, normally of metal oxides and silicates, applied subsequent to the drawing operation mainly for stabilizing the arc.
Light metal – It is one of the low-density metals, such as aluminum, magnesium, titanium, beryllium, or their alloys.
Lightning arrester – It is a device, essentially an air gap between an electric wire and ground, used on electric power transmission and telecommunication systems to protect the insulation and conductors of the system from the damaging effects of lightning.
Light water reactor – Light water reactors use ordinary water as both a moderating material and a reactor coolant. It includes boiling water reactors (BWR) and pressurized water reactors (PWR), which are the most common types reactors used.
Light-weight structures -These are normally made up of fibre-reinforced polymer matrix composites, light alloys, or a combination of both which can be assembled with high-performance structural epoxy adhesives.
Lignite coal – It is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered to be the lowest rank of coal due to its relatively low heat content. It has lowest carbon content amongst all types of coals. It is mined all around the world and is mainly used as a fuel for steam and electric power generation. Since it is not economical to transport lignite coal, it is not traded extensively on the world market when compared with higher grades of coal.
LILO – It means ‘Last-In Last-Out’. It is the inventory management method by which the origin of the number of units of the materials or consumables last received into the inventory is considered as the origin in equal number of units of the materials or consumables removed last from the inventory. In computer technology, it means a method of storing data where the data stored last is accessed last.
Lime – It is calcium oxide (CaO) produced on heating (calcination) of limestone to a temperature of 900 deg C and above (normally 1,100 deg C). It is a versatile compound. It is a white crystalline solid with a melting point of 2,572 deg C. It is a basic oxide and is used to react with the acidic oxides (e.g. silica) in different smelting operations. With water, it makes milk of lime used for neutralizing acidic waste water. It is also being known as quick lime, lime flux, unslaked lime, and fluxing lime. Lime having some percentage of magnesium oxide (normally 2 % to 4 %) is also known as dolomitic lime. Lime is a hygroscopic material and absorbs moisture from the air. With the absorption of moisture, it loses its reactivity and gets hydrated. Different forms of lime are used in environmental, metallurgical, construction, and chemical / industrial applications etc. The largest single use of lime is in iron and steel production, where it serves as a flux for removing impurities (silica, phosphorus, and sulphur) during refining of steel. The fastest growing use of lime is in environmental applications, where lime is used for treatment of flue gases, waste-water, solid waste, and drinking water.
Lime concrete – It is a composite mixture of hydraulic lime (or slaked lime) as binding material, sand as fine aggregate, and gravel as coarse aggregate in appropriate proportions.
Lime, hydrated – Hydrated lime is also known as slaked lime. It is in the form of a dry white powder. Hydrated lime is an alkali and used for neutralizing acidic solutions.
Lime mortar – It is composed of lime (hydraulic, or non-hydraulic), water and an aggregate such as sand. The soft and porous properties of lime mortar provide certain advantages when working with softer building materials such as natural stone and terracotta.
Lime reactivity – Reactivity of lime is its activity for hydration and is the relative capacity of lime to reciprocate chemical change with water. Reactivity is a function of purity, particle size and other factors such as particle porosity. The slaking rate is a measurement of the time for the slaking process to reach completion. The reaction is considered complete when the temperature of a given sample reaches a maximum. As reactivity increases, the slaking rate, ultimate temperature rise, and surface area of hydrated lime increases also. The reactivity of lime is dependent on the homogeneity of lime, the degree of thermal decomposition of limestone, the specific surface area lime.
Lime saturation factor – It is a ratio of calcium oxide to the other three main oxides (alumina, silica, and ferric oxide). Frequently, it is referred to as a percentage and hence multiplied by 100.
Limestone –It is an odourless white, grayish-white or tan material which ranges from sized stone to a granular powder. It consists mostly of calcium carbonate and used as a fluxing material. Limestone is a naturally occurring mineral. The term limestone is applied to any calcareous sedimentary rock consisting essentially of calcium carbonate (CaCO3) in the form of the mineral calcite. It forms predominantly on the sea floor where material rich in calcium carbonate (‘calcareous’ material) accumulates. This calcareous material can be organic, chemical or detrital in origin. Types of limestone include (i) bituminous limestone, (ii) carboniferous limestone, (iii) coquina which is a sedimentary rock composed mostly of fragments of shells, (iv) coral rag, (v) chalk which is a soft, white, porous sedimentary rock made of calcium carbonate, (vi) fossiliferous limestone, (vii) lithographic limestone, (viii) oolite which is a sedimentary rock formed from ooids, (viii) rag-stone which represents work done with stones that are quarried in thin pieces, (ix) shelly limestone, (x) travertine which is a form of limestone deposited by mineral springs, (xi) marl, and (xii) tufa which is a porous limestone rock formed when carbonate minerals precipitate out of ambient temperature water. Limestones altered by dynamic or contact metamorphism become coarsely crystalline and are referred to as ‘marbles’ and ‘crystalline limestones’. The limestone which is used by iron and steel industry in bulk quantity is a bedded type sedimentary limestone.
Limit – It is the value of a quantity used in certain specified activities or circumstances which is not to be exceeded.
Limiting static friction – It is the resistance to the force tangential to the interface which is just sufficient to initiate relative motion between two bodies under load. The term static friction, which properly describes a tangential resistance called into operation by a force less than this, is not to be substituted for limiting static friction.
Limits and fits – Thes are a set of rules regarding the measurements and tolerances of mating machine parts to achieve the best working conditions.
Limit control – It is a switching device which completes or breaks an electrical circuit at pre-determined pressures or temperatures. It is also known as an interlock.
Limited approach boundary – It is an approach limit at a distance from an exposed live part within which a shock hazard exists.
Limited ductility or workability – The limited ductility is inherent to the material or caused by some micro-structural feature. Examples are large prior transformation grain size, presence of embrittling phases or elements and inclusions etc.
Limited solid solution – It is a crystalline miscibility series whose composition range does not extend all the way between the components of the system, i.e., the system is not isomorphous.
Limiting condition for operation – It is the lowest functional capability or performance level of safety-related structures, systems, and components and their support systems needed for normal, safe operation of a facility.
Limiting control setting – It is the settings on safety systems which control process variables to prevent exceeding a safety limit.
Limiting current density – It is the maximum current density which can be used to get a desired electrode reaction without undue interference such as from polarization.
Limiting dome height (LDH) test – It is a mechanical test which is normally performed unlubricated on sheet metal, which simulates the fracture conditions in a practical press-forming operation. The results are dependent on the sheet thickness.
Limiting drawing ratio (LDR) test – It evaluates the deep drawability of sheet metals. It indicates the maximum ratio of circular blanks to the diameter of the die, by deep drawing the blank into a cup, without crack formation.
Limonite – It is a brown, hydrous iron oxide.
Limonite ore – Limonite is one of the principal iron ore which has been mined from the production of iron since at least 2500 BCE. It is a ferric oxide containing crystal water, and the chemical formula can be expressed by mFe2O3.nH2O. It is actually composed of a mixture of goethite (Fe2O3.H2O), water needle iron ore (2Fe2O3.H2O), iron hydroxide and mud. Most of the limonite in nature exists in the form of 2Fe2O3.3H2O. According to different crystal water content, limonite can be divided into water hematite, needle hematite, limonite, and the like. Limonite is weathered from other iron ore, so its structure is relatively soft, small specific gravity and large water content. The streak is yellowish brown. The crystal water of limonite is easily removed when it is dried. The limonite (the limonite after dehydration) has many pores and is easy to be reduced. However, because of the small hardness of the limonite structure and a large quantity of powder, it is normally necessary to pass the agglomeration before it is suitable for ironmaking. Limonite is relatively dense with a specific gravity varying from 2.7 to 4.3. It varies in colour from a bright lemony yellow to a drab greyish brown. The streak of limonite on an unglazed porcelain plate is always brownish, a character which distinguishes it from hematite with a red streak, or from magnetite with a black streak. The hardness is variable, but generally in the 4 – 5.5 range on the Mohs scale.
Limit state design (LSD) – It is also known as load and resistance factor design (LRFD). It refers to a design method used in structural engineering. A limit state is a condition of a structure beyond which it no longer fulfills the relevant design criteria. The condition can refer to a degree of loading or other actions on the structure, while the criteria refer to structural integrity, fitness for use, durability or other design requirements. A structure designed by limit state design is proportioned to sustain all actions likely to occur during its design life, and to remain fit for use, with an appropriate level of reliability for each limit state. Building codes based on limit state design implicitly define the appropriate levels of reliability by their prescriptions.
Line blinds – These are also known as line blanks. These are used to isolate a portion of pipe, normally for maintenance purposes. There are different types of line blinds used to isolate piping by normally inserting a solid disc with seals to eliminate the ability of upstream process liquids and gases to migrate downstream. Even if the seals failed, it is not possible for process fluids to migrate downstream.
Lineage structure – It consists of deviations from perfect alignment of parallel arms of a columnar dendrite as a result of interdendritic shrinkage during solidification from a liquid. This type of deviation can vary in orientation from a few minutes to as much as two degrees of arc. It is also a type of sub-structure consisting of elongated sub-grains.
Linear particle accelerator – It is a type of particle accelerator which accelerates charged sub-atomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beamline.
Linear actuator – It is an actuator which creates linear motion (i.e., in a straight line), in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in several other places where linear motion is needed. Hydraulic or pneumatic cylinders inherently produce linear motion. Several other mechanisms are used to generate linear motion from a rotating motor.
Linear alternator – It is an electrical machine which generates electric power from the relative straight-line motion of its parts.
Linear dispersion – In spectroscopy, it is the derivative dx/dL, where ‘x’ is the distance along the spectrum and ‘L’ is the wave-length. Linear dispersion is normally expressed as millimeters per angstrom.
Linear elastic fracture mechanics – It is a method of fracture analysis that can determine the stress (or load) needed to induce fracture instability in a structure containing a crack-like flaw of known size and shape when the relationship between local stress and strain is assumed to be linear.
Linear elasticity – It is a mathematical model as to how solid objects deform and become internally stressed by prescribed loading conditions. It is a simplification of the more general nonlinear theory of elasticity and a branch of continuum mechanics.
Linear expansion – It is the increase of a given dimension, which is measured by the expansion or contraction of a sample or component subject to a thermal gradient or changing temperature.
Linear motor – It is an electrical machine which generates electric force in a straight line by the interaction of its moving parts and magnetic fields.
Linear programming – It is a type of optimization algorithm which is very effective for problems where the objective and constraint functions are linear.
Linear scheduling method – It is a graphical scheduling technique which used to assign resources when project work consists of repetitive tasks. It focuses on maximizing resource use and reducing time wastage due to interruptions.
Linear sequential model – It is a linear sequential model which moves through the phases of project life cycle systematically and sequentially. It is typically used for small projects with straightforward requirements, since sequential development makes it difficult to revise design based on testing or preliminary feedback.
Linear shrinkage – It is the shrinkage in one dimension of a compact during sintering.
Linear (tensile or compressive) strain – It is the change per unit length because of the force in an original linear dimension. An increase in length is considered positive.
Linear variable differential transformer (LVDT) – It is a transducer which produces an electrical signal proportional to the movement between its parts. It converts the linear motion into an electrical signal using an inductive transducer. Because of to its superior sensitivity and accuracy over other inductive transducers, the linear variable differential transformer is extensively used in several different fields. For measuring linear distance, the linear variable differential transformer is a precise and trustworthy tool.
Line cutting – It consists of straight clearings through the bush to permit sightings for geophysical and other surveys.
Line, in x-ray diffraction patterns – It consists of an array of small diffraction spots arranged so that they appear to form a continuous line on the film.
Line indices – These are the Miller indices of the set of planes producing a diffraction line.
Line, looper – It consists of closely spaced symmetrical lines on the surface of metal which has undergone non-uniform deformation, normally in a drawing operation.
Line, Lueders – It consists of elongated surface markings or depressions appearing in patterns caused by localized plastic deformation which results from nonuniform yielding.
Lineman – It is a specialist technician who installs outside plant wiring (overhead circuits, power transmission lines).
Line of balance – It is a graphical technique which is used to show relationships between repetitive tasks in process. Each set of repetitive tasks is shown as a single line on a chart. People are to look for places where dependent tasks intersect, indicating that the successor task is to be delayed.
Line pair – In spectroscopy, it is an analytical line and the internal standard line with which it is compared.
Line pipe – It is the pipe used in the surface transmission of oil, natural gas and other fluids.
Liner – It is the slab of coating metal which is placed on the core alloy and is subsequently rolled down to clad sheet as a composite. In extrusion, it is a removable alloy steel cylindrical chamber which is having an outside longitudinal taper firmly positioned in the container or main body of the press, into which the billet is placed for extrusion. In a filament-wound pressure vessel, the continuous, normally flexible coating on the inside surface of the vessel, used to protect the laminate from chemical attack or to prevent leakage under stress.
Line reaming – It consists of simultaneous reaming of coaxial holes in different sections of a work-piece with a reamer having cutting faces or piloted surfaces with the desired alignment.
Liners – These are thin strips of metal inserted between the dies and the units into which the dies are fastened.
Line, weld – It is the junction line of metal which has passed through a hollow die, separated and rejoined at the exit point. Seams are present in all extruded hollows produced from the direct extrusion process and in several cases are not visible.
Lining –It is the internal refractory layer of firebrick, clay, sand, or other material in a furnace or ladle. It is the material used on the furnace side of a furnace wall. It is normally of high-grade refractory tile, or brick, or plastic refractory material.
Linishing – It is a method of finishing by grinding on a continuous abrasive belt.
Linkage, mechanical – It is an assembly of systems connected so as to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for example, and are called joints. A linkage modeled as a network of rigid links and ideal joints is called a kinematic chain.
Lintel beam layout – Lintel beam is another form of support structure which is made above the doors and windows. It is reinforced structures which is made to provide strength to the part of the building that is made above the windows and doors. In this kind of drawings, one finds the correct positions, dimensions, and the number of lintel beams on every floor.
Lintels – These are the horizontal members placed over window, door and other openings to carry loads to the adjoining studs.
Lipophilic – It means having an affinity for oil. See also hydrophilic and hydrophobic .
Lip-pour ladle – It is the ladle in which the molten metal is poured over a lip, much as water is poured out of a bucket.
Liquation – It is the separation of a low-melting constituent of an alloy from the remaining constituents, normally apparent in alloys having a wide melting range. It is also the partial melting of an alloy, normally as a result of coring or other compositional heterogeneities. It is also the bleeding of the low-melting constituents through the solidified ingot surface.
Liquation temperature – It is the lowest temperature at which partial melting can occur in an alloy which shows the highest possible degree of segregation.
Liquefied gas – It is sometimes referred to as liquid gas. It is a gas which has been turned into a liquid by cooling or compressing it. Examples of liquefied gases include liquid air, liquefied natural gas, and liquefied petroleum gas.
Liquefied natural gas (LNG) – It is natural gas which has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up around 1/600th the volume of natural gas in the gaseous state at standard conditions for temperature and pressure.
Liquefied petroleum gas (LPG) – It is a gas which is used is as a fuel gas for heating in various furnaces and in flame cutting machines. It is popularly known by its abbreviation or short form which is LPG. Liquefied petroleum gas is also used for oxy-LPG gas cutting and welding. Sometimes it is used for carburization of steel, flame heating, flame gouging, flame hardening, flame cleaning, and flame straightening. Like all fossil fuels, liquefied petroleum gas is a non-renewable source of energy. It is extracted from crude oil and natural gas. It is a safe, clean burning, reliable, high calorific value fuel. The main composition of Liquefied petroleum gas are hydrocarbons containing three or four carbon atoms. The normal components of Liquefied petroleum gas hence, are propane (C3H8) and butane (C4H10). Small concentrations of other hydrocarbons can also be present. Depending on the source of the Liquefied petroleum gas and how it has been produced, components other than hydrocarbons can also be present.
Liquid air – It is the air which that has been cooled to very low temperatures, so that it has condensed into a pale blue mobile liquid. It is stored in specialized containers, such as vacuum flasks, to insulate it from room temperature. Liquid air can absorb heat rapidly and revert to its gaseous state. It is normally richer in oxygen. It is frequently used for condensing other substances into liquid and / or solidifying them, and as an industrial source of nitrogen, oxygen, argon, and other inert gases through a process called air separation.
Liquid argon – It is a cryogenic colourless liquid. It has a boiling point of -186 deg C. Each volume of liquid argon gives 822 volumes of argon gas when it is converted to gas at room temperature and atmospheric pressure. Liquid argon is frequently used as a source of very pure argon gas for use in liquid steel rinsing, hot isostatic pressing and heat treatment atmospheres.
Liquidated damages – These are damages, whose amount the parties designate during the formation of a contract for the injured party to collect as compensation upon a specific breach. This is most applicable where the damages are intangible.
Liquidation cracks -These are also known as hot tearing which occur in the heat affected zone. When the temperature in that region reaches to the melting temperature of low melting point constituents causing them to liquidate and segregate at grain boundaries. As the weld cools down, shrinkage stresses cause the formation of small micro-scale cracks which later can link up due to the applied stresses to form a continuous surface or sub-surface crack.
Liquid carbon dioxide (LCO2) – It is the liquid state of carbon di-oxide (CO2), which cannot occur under atmospheric pressure. It can only exist at a pressure above 0.51 MPa, under 31.1 deg C (temperature of critical point) and above −56.6 deg C (temperature of triple point). Low-temperature carbon di-oxide is commercially used in its solid form, normally known as ‘dry ice’. The uses and applications of liquid carbon di-oxide is in fire extinguishers, and as a coolant.
Liquid carburizing – It is the surface hardening of steel by immersion into a molten bath consisting of cyanides and other salts.
Liquid chromatography (LC) – It is an analytical technique in which the mobile phase is a liquid. It is carried out either in a column or a plane. The sample with the mobile phase is passed through a column or plane, accompanied by the stationary phase. Liquid chromatography is a separation method based on the distribution of sample compounds between a stationary phase and a liquid mobile phase.
Liquid crystal – It is a state of matter whose properties are between those of conventional liquids and those of solid crystals. As an example, a liquid crystal can flow like a liquid, but its molecules can be oriented in a common direction as in a solid.
Liquid-crystal display (LCD) – It is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information.
Liquid crystal elastomers – These are slightly crosslinked liquid crystalline polymer networks. These materials combine the entropy elasticity of an elastomer with the self-organization of the liquid crystalline phase.
Liquid crystal polymers – These are polymers with the property of liquid crystal, normally containing aromatic rings as mesogens. Despite uncrosslinked liquid crystal polymers, polymeric materials like liquid crystal elastomers and liquid crystal networks can show liquid crystallinity as well.
Liquid disintegration – It is the process of producing powders by pouring molten metal on a rotating surface.
Liquid fuels – These are combustible or energy generating molecules which take the shape of their container. Majority of the liquid fuels are derived from fossil fuels mainly from crude oil. Main liquid fuels used in industry are (i) furnace oil, (ii) low sulphur heavy stock, (iii) light diesel oil, and (iv) high speed diesel oil. Coal tar fuel is a byproduct liquid fuel produced during the cleaning of the raw coke oven gas in the coke oven and byproduct plant. Liquid fuels are normally used in industry for the production of steam for power generation, for heating purpose in different furnaces, for injection in blast furnace, and for the operation of locomotives and the mobile equipment. Liquid fuels are chemically stable and incompatible with strong oxidizers. They do not react vigorously with common materials but can react with oxidizing agents. Liquid fuels are stored in a dry cool, well – ventilated area away from heat and flame. They are also kept away oxidizing agents.
Liquid honing – It consists of producing a finely polished finish by directing an air-ejected chemical emulsion containing fine abrasives against the surface to be finished.
Liquid hydrogen – It is abbreviated as LH2. It is the liquid state of the element hydrogen. It has a boiling point of -252.8 deg C. Hydrogen is normally transported and delivered as a liquid when high-volume transport is needed in the absence of pipelines. To liquefy hydrogen, it is to be cooled to cryogenic temperatures through a liquefaction process. The strong point about the liquid hydrogen is high hydrogen mass density as compared to pressurized hydrogen.
Liquid impact erosion – It is the loss of material from a solid surface because of the relative motion in contact with a fluid which contains solid particles. In it the erosion is because of the relative motion of particles is nearly parallel to the solid surface.
Liquid impingement erosion – It is the loss of material from a solid surface because of the relative motion in contact with a fluid which contains solid particles. In it the erosion is because of the relative motion of particles is nearly normal to the solid surface is called impingement erosion.
Liquid-in-glass thermometers – The major types have used mercury or alcohol as the liquid. The element mercury is liquid in the temperature range of around -38.9 deg C to 356.7 deg C. As a liquid, mercury expands as it gets warmer. Its expansion rate is linear and can be accurately calibrated. Because of toxicity of mercury and the strict governing laws, the use of the mercury-in-glass thermometer has declined. However, for high accuracy applications, laboratory grade and reference standard models are available with calibration certification to standards.
Liquid iron – It is the hot metal which is the output of the blast furnace.
Liquid-liquid chromatography (LLC) – Liquid chromatography with a stationary phase composed of a liquid dispersed onto an inert supporting material. It is also termed liquid-partition chromatography.
Liquid-liquid contraction – It occurs as a result of the liquid cooling from its pouring temperature, normally 110 deg C to 165 deg C above its melting point, down to the melting point or solidification temperature. This particular factor is of little consequence to designers and is fairly easily dealt with by the foundry engineer.
Liquid lubricants – Liquids are normally preferred as lubricants because they can be drawn between moving parts by hydraulic action. Apart from keeping the parts separated they also act as heat carriers. Liquid lubricants are classified based on the origin from which liquid has been extracted and can be (i) mineral oils, (ii) fixed oils, (iii) synthetic fluids, and (iv) soluble oils and compounds.
Liquid metal – It is a metal or a metal alloy which is liquid at or near room temperature. The only stable liquid elemental metal at room temperature is mercury, which is molten above −38.8 deg C.
Liquid metal cleanliness analyzer (LiMCA) – It measures total concentration and size distribution of inclusions suspended in the metal alloys. The heart of the measuring system consists of a closed glass tube (electrically insulating material) bearing a small orifice at its bottom. The tube is positioned in liquid metal.
Liquid metal embrittlement (LME) – It is the catastrophic brittle failure of a normally ductile metal when in contact with a liquid metal and subsequently stressed in tension. Liquid metal embrittlement is a phenomenon of practical importance, where certain ductile metals experience drastic loss in tensile ductility or undergo brittle fracture when exposed to specific liquid metals.
Liquid metal induced embrittlement – It is the decrease in ductility and toughness of a metal caused by contact with another metal in liquid form. It results in intergranular fracture.
Liquid metal infiltration – It is the process for immersion of metal fibres in a molten metal bath to achieve a metal-matrix composite, for example, graphite fibres in molten aluminum.
Liquid nitriding – It is a method of surface hardening in which ferrous metal parts are exposed to molten nitrogen-bearing fused-salt baths containing cyanates, cyanides, or both at sub-critical temperatures. A typical commercial bath is a mixture of sodium and potassium salts. The anions are 30 % to 40 % cyanate, 1 % to 5 % cyanide, and the balance carbonate. The operating temperature for these salt baths is 510 deg C to 595 deg C.
Liquid nitro-carburizing – It is a nitro-carburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature. Liquid nitro-carburizing processes are used to improve wear resistance and fatigue properties of steels and cast irons.
Liquid nitrogen – It is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of -196 deg C. It is produced industrially by fractional distillation of liquid air. It is a colourless, mobile liquid whose viscosity is about one-tenth that of acetone. Liquid nitrogen is widely used as a coolant.
Liquid oxygen – Liquid oxygen is abbreviated as LOX. It is a clear cryogenic liquid form of di-oxygen (O2). It has a boiling point -183 deg C. It is produced industrially by fractional distillation of liquid air.
Liquid-partition chromatography (LPC) – It is the liquid chromatography with a stationary phase composed of a liquid dispersed onto an inert supporting material.
Liquid penetrant inspection – It is a type of non-destructive inspection which locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent which causes the penetrant to seep back out of the discontinuity and register as an indication. Liquid penetrant inspection is suitable for both ferrous and non-ferrous materials, but is limited to the detection of open surface discontinuities in non-porous solids.
Liquid penetrant testing – The basic principle of liquid penetrant testing is that when a very low viscosity (highly fluid) liquid (the penetrant) is applied to the surface of a part, it penetrates into fissures and voids open to the surface. Once the excess penetrant is removed, the penetrant trapped in those voids flow back out, creating an indication. Penetrant testing can be performed on magnetic and non-magnetic materials, but does not work well on porous materials. In order of decreasing sensitivity and decreasing cost, the liquid penetrant testing processes can be listed as (i) post emulsifiable fluorescent dye penetrant, (ii) solvent removable fluorescent dye penetrant, (iii) water washable fluorescent dye penetrant, (iv) post emulsifiable visible dye penetrant, (v) solvent removable visible dye penetrant, and (vi) water washable visible dye penetrant. The advantages of liquid penetrant testing are (i) relatively low cost, (ii) highly portable NDT technique, (iii) highly sensitive to fine, tight discontinuities, (iv) applicable to a variety of materials, and (v) large area inspection. The limitations of liquid penetrant technique are (i) test surface is to be free of all dirt, oil, grease, paint, and rust, etc., (ii) detects surface discontinuities only, (iii) cannot be used on porous and very rough surfaces, (iv) removal of all penetrant materials, following the test, is frequently needed, and (v) there is no easy method to produce permanent record.
Liquid phase epitaxy – It is a solution growth process whereby the driving force for crystallization is provided by the slow cooling of a saturated solution consisting of the material to be grown in a suitable solvent, while in contact with a single crystal substrate.
Liquid phase sintering – It is the sintering of a compact or loose powder aggregate under conditions where a liquid phase is present during part of the sintering cycle.
Liquid shim – It is the material used to position components in an assembly where dimensional alignment is critical. For example, epoxy adhesive is introduced into gaps after the assembly is placed in the desired configuration.
Liquid shrinkage – It is the reduction in volume of liquid metal as it cools to the liquidus.
Liquid-solid chromatography (LSC) – It is liquid chromatography with silica or alumina as the stationary phase.
Liquid-solid contraction – Majority of metals contract as they pass from the liquid to the solid state. Certain compositions of gray and ductile iron are the exceptions to this rule in the major alloys produced by foundries. The entire founding process is possible only since the volumetric contraction locates itself in solidifying castings in a systematic way.
Liquid spray quench – It is a quenching process using spray nozzles to spray water or other liquids on a part. The quench rate is controlled by the velocity and volume of liquid per unit area per unit of time of impingement.
Liquidus – It is the lowest temperature at which a metal or an alloy is completely liquid. In a phase diagram, it is the locus of points representing the temperatures at which the different compositions in the system begin to freeze on cooling or finish melting on heating.
Lithium (Li) – It is a chemical element having atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element.
Lithography – It is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It has been used mostly for maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography.
Little-end bearing – It is a bearing at the smaller (piston) end of a connecting rod in an engine.
Litz wire – It is a kind of stranded wire used to minimize losses in coils.
Live loads—Live loads are produced by personnel, tools, and maintenance equipment and materials. The live loads used in design are to be the maximum loads expected during the service life of the equipment. For the majority of the designs, live loads are uniformly distributed over the floor areas of platforms of elevated support structures or to the access areas around at grade foundations. Typical live loads vary from 2.9 kilopascals (kPa) for personnel to as much as 7.2 kilopascals for maintenance equipment and materials.
Load – Load is a term frequently used in engineering. It means the force exerted on a surface or body. It is also the rate of output needed. It is also the weight carried. For testing machines, load is the force applied to a test piece which is measured in units such as pound-force, newton, or kilogram-force. In tribology, it is the force applied normal to the surface of one body by another contacting body or bodies. The term normal force is more precise and hence preferred. However, the term normal load is also in use. If applied vertically, the load can be expressed in mass units, but it is preferable to use force units such as newtons (N).
Load bearing – It describes a structural element which has been designed to support its own dead load in addition to the weight of other structural and non-structural elements. The weight of this load is carried down to the foundations of the building.
Load capacity, forklift – The load capacity of the forklift truck is a measure to indicate the maximum weight load which can be handled as a ‘load’ on the forks at a given ‘load centre’ with the mast held in a vertical position. The load capacity rating is expressed in kilograms and the load centre in millimeters.
Load-carrying capacity (of a lubricant) – It is the maximum load which a sliding or rolling system can support without failure. It is also the maximum load or pressure which can be sustained by a lubricant (when used in a given system under specific conditions) without failure of moving bearings or sliding contact surfaces as evidenced by seizure or welding.
Load cell – It converts a force such as tension, compression, pressure, or torque into a signal which can be measured and standardized. It is a force transducer. As the force applied to the load cell increases, the signal changes proportionally.
Load-deflection curve – It is a curve in which the increasing tension, compression, or flexural loads are plotted on the ordinate axis and the deflections caused by those loads are plotted on the abscissa axis.
Load factor – It is the ratio of the average load in a given period to the maximum load carried during that period.
Load flow study – It is a mathematical prediction of the flow of electric power in a network, based on a model of the actual or proposed system. It is necessary for planning of electrical grids.
Load following power plant – It is a power plant which can economically be operated over a significant range of output, so as to meet varying electric power demand.
Loading – In cutting, it is the building up of a cutting tool back of the cutting edge by undesired adherence of material removed from the work. In grinding, it is the filling the pores of a grinding wheel with material from the work, normally resulting in a decrease in production and quality of finish. In powder metallurgy, it is the filling of the die cavity with powder. In lubrication, it is the filling of an abrasive paper or other bound abrasive material by abraded material from a second body. It is also the concentration of abrasive bound in a matrix material or added to a lap wheel as a loose abrasive.
Loading pressure – It is the fluid, normally compressed air, applied to the diaphragm or piston in a pneumatic actuator.
Loading sheet – It is the part of a die assembly which is used as a container for a specific quantity of powder to be fed into the die cavity. Sometimes it is part of the feed shoe.
Loading weight – It is the weight of a unit volume of powder, normally expressed as grams per cubic centimeter which is determined by a specified method.
Load lifting accessories – These are attachments to facilitate lifting of the load. These are end effectors or below the hook equipments. These consist of a variety of different, application-specific, attachments which can be added to the hoist to handle the lifting or positioning of different loads. Load lifting accessories are the components or equipment which are not part of the load lifting equipments but are either attached to the lifting equipment or load to be lifted and are placed either between the lifting device and the load or on the load in order to attach it. Examples are slings, spreader beams, lifting beam, magnet, lifting eyelet, clamps, shackle, C-hook, gripping lifters, lifting forks, and crane scales etc. Some of the load lifting accessories are described below.
Load lifting equipment – It refers to any equipment or machinery which is used to lift or move heavy loads or materials from one place to another. This can include cranes, hoists, lifts, forklifts, and other types of machinery which are specifically designed to lift and move heavy objects safely and efficiently.
Load lifting slings – These are accessories used for lifting and transferring of loads with the help of cranes, telphers, or hoists. Load lifting slings enable in the activities related to create anchors, attach to loads, lift loads, pull loads, and lower loads. The dominant characteristics of load lifting slings are determined by the components from which they are made. As an example, the strengths and weaknesses of a load lifting sling made of steel wire rope are essentially the same as the strengths and weaknesses of the wire rope from which it is made. Load lifting slings are normally one of six types namely (i) chain, (ii) wire rope, (iii) metal mesh, (iv) natural fibre rope, (v) synthetic fibre rope, or (vi) synthetic web. In general, use and inspection procedures tend to place these slings into three groups (i) chain, (ii) wire rope and mesh, and (iii) fibre rope web. Each type has its own particular advantages and disadvantages.
Load-loss factor – It is a factor for estimating energy lost in a distribution network due to load current.
Load management – It is a strategy for altering the operation of customer loads so as to reduce peak demand on an electrical grid.
Load pre-heating – It refers to any efforts to use waste heat leaving a system to preheat the load entering the system. The most common example is boiler feed water preheating, where an economizer transfers heat from hot combustion exhaust gases to the water entering the boiler. Other applications utilize direct heat transfer between combustion exhaust gases and solid materials entering the furnace.
load profile – It is the daily, weekly, or annual graph of electrical load against time.
Loam – It is a moulding material consisting of sand, silt, and clay which is used over brickwork or other structural back-up material for making massive castings, normally of iron or steel.
Lobed bearing – It is a journal bearing with two or more lobes around its periphery produced by machining or by elastic distortion to increase stability or to provide adjustable clearance.
Lobed impeller gas totalizers – These consist of two rotating impellers, designed with a figure eight cross-section. The impellers rotate in opposite directions due to the forces exerted by the gas being measured. The shape of the impellers prevents contact while the gap between them remains constant. A gear drive external to the measuring chamber synchronizes the impellers. During each rotation four crescent shaped volumes are moved through the measuring chamber. The number of rotations is proportional to the gas flow. The rotation is coupled using an adjustable fine tooth gear train to the totalizer.
Local action – It is the corrosion because of the action of local cells, i.e., galvanic cells resulting from inhomogeneities between adjacent areas on a metal surface exposed to an electrolyte.
Local brittle zones (LBZs) – These are small regions of hard, brittle phase that form in the heat affected zones (HAZs) of multi-pass welds. They normally contain untempered martensite which can lead to scatter in toughness data when the test sample shows a brittle zone.
Local cell – It is a galvanic cell resulting from inhomogeneities between areas on a metal surface in an electrolyte. The inhomogeneities can be of physical or chemical nature in either the metal or its environment.
Local current density – It is the current density at a point or on a small area.
Localized corrosion – It is the corrosion at discrete sites, e.g., crevice corrosion, pitting, and stress-corrosion cracking.
Localized precipitation – It is the precipitation from a super-saturated solid which is similar to continuous precipitation, except that the precipitate particles form at preferred locations, such as along slip planes, grain boundaries, or incoherent twin boundaries.
Local necking – It is the development of a non-uniform strain gradient in tensile sheet samples with a large width-to-thickness ratio. The strain gradient results in the formation of a narrow trough across the face (width) of the sample. For uniaxial loading, the strain gradient is normally inclined at an angle to the load (typically around 55 degrees for isotropic materials). The local neck develops under plane-strain loading conditions, while diffuse necking develops under conditions of axisymmetric deformation, which is initially plane stress.
Local positioning system – It is a navigation system which does not cover the whole earth, such as over a continent, or even within a building.
Local thermodynamic equilibrium – It refers to a state where intensive thermodynamic variables become functions of position and time, allowing for the determination of specific entropy and internal energy at every point, similar to substances in equilibrium.
Locating boss – It is a boss -shaped feature on a casting to help locate the casting in an assembly or to locate the casting during secondary tooling operations.
Location drawing – It is also referred to as general arrangement drawings. It is made to showcase the composition of the entire project. If the project has several parts and buildings to be constructed, then the location drawing is required to include details for all of them. Under it, one can consider adding elevations, projections, different plans, and sections.
Location plan – A location plan is a supporting document which is needed to be included as part of the detailed project report. The location plan provides an illustration of the proposed development in the surrounding area of the project. The location plan covers a wide area. This kind of drawing needs the engineer to check out the whole area where the project is to be constructed. The location plan represents the objects and more importantly, it shows the relationship between the different stages of project development.
Lock – In forging, it is a condition in which the flash line is not entirely in one plane. Where two or more
plane changes occur, it is called compound lock. Where a lock is placed in the die to compensate for die shift caused by a steep lock, it is called a counter-lock.
Locked dies – These are dies with mating faces which lie in more than one plane.
Locked up stress -It is a non-standard term for residual stress.
Lockin – It is a procedure in maintenance which maintains an event or prohibits an individual, an object, force, or other factor from leaving a safe zone.
Lockout -It is a procedure in maintenance which prevents an individual, an object, force, or other factor from entering a dangerous zone.
Locomotive – It is a rail transport vehicle which provides the motive power for a train.
Lode – It consists of a mineral deposit in solid rock.
Log – It is the starting stock for extrusion billet. Extrusion log is normally produced in lengths from which shorter extrusion billets are cut.
Logging – It is the process of recording geological observations of drill core either on paper or on computer disk.
Logic circuit diagram. It depicts the logic functions of a system at any level of assembly. It is prepared to (i) illustrate logic functions, and (ii) facilitate circuit analysis and diagnosis of equipment problems. It includes (i) logic functions depicted by logic symbols connected by lines which represent signal paths, and (ii) pin numbers, test points, assembly boundaries, and non-logic functions necessary to describe the physical and electrical aspects of the circuit.
Logic network – It is a chronologically arranged diagram which shows relationships between project activities.
Logical relationship – It is a dependency between project activities or between project activities and milestones.
Logistic regression – The logistic regression method contains multiple regressions with dichotomous outcome variables and categorical or metric predictor variables. Logistic regression derives its name from the sigmoid function, which is also known as the logistic function. The logistic function is an S-shaped curve which stretches from zero to one, while never being exactly zero and never being exactly one, either. There are three main types of logistic regression namely (i) binary, (ii) multinomial, and (iii) ordinal. They differ in execution and theory. Binary regression deals with two possible values, essentially ‘yes or no’. Multinomial logistic regression deals with three or more values. And ordinal logistic regression deals with three or more classes in a pre-determined order.
Long-fibre-reinforced thermoplastic – It is a type of easily mouldable thermoplastic used to create a variety of components. Long-fibre-reinforced thermoplastics are one of the fastest growing categories in thermoplastic technologies.
Long flame burners – These are the burners which produce a long flame. A large variety of long flame burners of various characteristics and different capacities are available. These burners are available in various capacities and to suit use of different fuels such as oil, gas or multiple fuels. Long flame burners produce high velocity gases which entrain and recirculate the combustion gases to achieve temperature uniformity in the furnace with minimum of excess air.
Longitudinal axis – It is the axis of sample which is parallel to the major direction of grain flow.
Longitudinal bow – It is the curvature in the plane of sheet or plate in the rolling direction.
Longitudinal cracks – These cracks normally found in continuous cast products, are formed in the direction of extraction of the steel. The presence of these defects results into the rejection of the steel. Longitudinal cracks occur mainly because of the (i) uneven primary cooling in the mould, (ii) turbulent flow of liquid steel and a meniscus level variation in the mould, (iii) non uniform or very intensive secondary cooling, (iv) variance in thermal conductivity coefficient along the mould length causing unequal, advanced wear of the mould, (v) casting of liquid steel with high superheat, (vi) high speed of casting, and (vii) use of the casting powder with improper characteristics.
Longitudinal corrugations – These corrugations make the cylindrical shell to have a non-zero curvature in the direction of the central axis, and the trough can take part of the buckling deformation. In short, the corrugations improve the material utilization rate of cylindrical shells, so the mechanical performance is improved.
Longitudinal direction – It is the direction of major metal flow in a working operation. It is that direction which is parallel to the direction of maximum elongation in a worked material. Two labeling conventions are common for designating the orientations of rolled sheet and plate material. The first is ‘L’, ‘T’, and ‘S’ designations in which ‘L’ means longitudinal, ‘T’ means long transverse, and ‘S’ means short transverse. The second is ‘RD’, ‘ND’, and ‘TD’ designations, in which ‘RD’ means rolling direction, ‘ND’ means normal direction, and ‘TD’ means transverse direction.
Longitudinal field – It is a magnetic field which extends within a magnetized part from one or more poles to one or more other poles and which is completed through a path external to the part.
Longitudinal (parallel) fillet weld – It is the weld in which the applied force is parallel to the length of the weld.
Longitudinal resistance seam welding – It is the making of a resistance seam weld in a direction essentially parallel to the throat depth of a resistance welding machine.
Longitudinal rolling – In longitudinal rolling, rolls are driven and they draw the material in-between and press it through the height. Because of it, the rolled material is considerably extended (elongated) and spread to a lesser extent. The longitudinal rolling is most popular method of rolling. Longitudinal rolling with plain rolls is used to roll flat rolled products (sheets, plates, strips), while longitudinal rolling in grooved rolls is used for shaped rolled products (rails, sheet piles, bars, sections, and wire rod).
Longitudinal sections – These are those which are cut lengthwise along the line of the long axis of a object or one of its constituent parts. They can be cut in any plane and are independent of the position of the object, unlike vertical sections.
Longitudinal stress – It is the applied stress which is parallel to the major direction of grain flow, in the plane of the component.
Longitudinal stringers – These are because of non-metallic inclusions or pearlite banding. They are related to melting and solidification practices. In severe cases, these defects can lead to lamination which drastically reduces the strength in the thickness direction.
Long-line current – It is the current which flows through the earth from an anodic to a cathodic area of a continuous metallic structure. It is normally used only where the areas are separated by considerable distance and where the current results from concentration-cell action.
Longos – It is low-angle helical or longitudinal windings.
Long product rolling mills – These are the rolling mills which roll long products. Based on the product being rolled, these mills are called, merchant bar mill, bar and rod mill, light section mill, rebar mill, light merchant mill, special bar quality (SBQ) mill, and wire rod mill etc.
Long product steel – This steel is used for rolling long products. As per the classification of steel products bar, rod and structural products are the long products.
Long steel products – These are the steel products which include wire, rod, rail, and bars as well as types of steel structural sections and girders. The term long steel products can include hot rolled bar, cold rolled or drawn bar, reinforcement bar, railway rails, wire, rope (stranded wire), woven cloth of steel wire, shapes (sections) such as ‘U’, ‘I’, or ‘H’ sections, and can also include continuous cast blooms and billets. Fabricated structural units, such bridge sections are also classed as long products. The definition excludes flat products such as slab, plate, strip and coil, tinplate, and electrical steel; and also excludes certain tubular products including seamless and welded tube.
Long-term etching – It is the etching in which the etching times range from a few minutes to hours.
Long terne steel sheet – It is carbon steel sheet continuously coated by the hot dip process with terne metal (lead with 3 % to 15 % tin). This coated sheet is duller in appearance than tin coated sheet, hence the name (terne) from the French, which means dull or tarnished. The smooth, dull coating gives the sheet corrosion resistance, formability, excellent solderability, and paintability. The term long terne is used to describe terne-coated sheet, while short terne is used for terne-coated plate.
Long transverse – It is a direction or plane which is perpendicular to the direction of working. In rolled plate or sheet, it the direction across the width which is the direction through the thickness, short transverse. Long transverse for thin components is the axis of sample perpendicular to the axis of major grain flow, in the plane of the component.
Long transverse direction. For plate, sheet, and forgings, It is the direction which is perpendicular to the longitudinal direction which is also at right angles to the thickness of the product.
Long transverse stress – It is the applied stress perpendicular to the axis of major grain flow, in the plane of the component
Loop classifier – It is a cyclone-type classifier, sometimes connected with a conical ball mill in an airtight system.
Looper control by torque (LCT) – The looper control by torque achieves the regulation of the inter-stand tension by acting on the torque reference used by the hydraulic torque controller. Normally, the looper control by torque is fed by the tension error generated by a load cell mounted on the looper or, alternatively, by the estimation of the inter-stand tension derived by the looper hydraulic force.
Looper control by speed (LCS) – It aims at regulating the looper angular position by acting on the speed reference of the upstream stand (i.e., by acting on the reference for the speed controller acting on the upstream stand). This regulator is also referred to as the mass flow regulator.
Looper line – It consists of closely spaced symmetrical lines on the surface of metal which has undergone non-uniform deformation, normally in a drawing operation.
Loopers – Loopers are placed between the mill stands. They manage the material in steel rolling mills by regulating the movement and processing of hot steel bars. These loopers comprise a set sequence of rollers which assist in moving hot steel bars across the rolling mill. They not only control the mass flow of the two stands but also to generate a constant specific strip tension during rolling.
Looping – It is a type of error in a network diagram. Looping error is also known as cycling error
Looping mill – It is an arrangement of hot rolling stands such that a hot bar, while being discharged from one stand, is fed into a second stand in the opposite direction.
Loop tenacity – It is the tenacity or strength value got by pulling two loops, as two links in a chain, against each other in order to demonstrate the susceptibility which a fibrous material has for cutting or crushing itself. It is the loop strength.
Loose metal – It refers to an area in a formed panel which is not stiff enough to hold its shape. It can be confused with oil canning.
Loose powder – It is uncompacted powder.
Loose powder sintering – It is the sintering of uncompacted powder using no external pressure.
Loose wrap – It is a condition in a coil because of insufficient tension which creates a small void between adjacent wraps.
Lorentz force law -It is the mathematical relation between currents in conductors and the resulting magnetic forces between them.
Loss factor – It is the product of the dissipation factor and the dielectric constant of a dielectric material.
Lossless data compression – It is a data compression method where the source can be reconstructed exactly, where approximations are tolerable, lossy data compression can be used.
Loss modulus – It is a damping term describing the dissipation of energy into heat when a material is deformed.
Loss-of-coolant accident (LOCA) – It is the is a mode of failure for a nuclear reactor. If not managed effectively, the results of a loss-of-coolant accident can result in reactor core damage. Nuclear plants have emergency core cooling system (ECCS) specifically to deal with a loss-of-coolant accident.
Loss on ignition – It is a test used in inorganic analytical chemistry and soil science, particularly in the analysis of minerals and the chemical makeup of soil. It consists of strongly heating a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change. In composites, it is the weight loss, normally expressed as percent of total, after burning off an organic sizing from glass fibres, or an organic resin from a glass fiber laminate.
Loss tangent – It is the ratio of the power loss in a dielectric material to the total power transmitted through it, hence, the imperfection of the dielectric. It is equal to the tangent of the loss angle.
Loss time injury – It is an industrial injury causing loss of time from the job on which the injured person in normally employed beyond the day or shift on which the injury occurred. In addition, cases where loss of time does not immediately follow the injury, but where there is a direct relation between absence and injury, are regarded as lost time injuries.
Lossy data compression – It is a data compression method which allows only a close approximation of the source to be reconstructed. It is useful for images, where the human perceptual system compensates for the errors.
Lost foam casting – It is a type of evaporative-pattern casting process which is similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of foam to simplify the investment casting process by removing the need to melt the wax out of the mould. It is an expendable pattern process in which an expandable polystyrene pattern surrounded by the unbonded sand, is vapourized during pouring of the molten metal. Lost foam casting is also known as full-mould, poly-cast, cavity’s molding, evaporative-pattern, or expendable-pattern casting.
Lost time injuries (LTI) – It is any work-related injury, resulting in the organization, contractor or third-party contractor employee not being able to return to work for their next scheduled work period. Returning to work with work restrictions does not constitute a lost time injury status, no matter how minimal or severe the restrictions, provided it is the employee’s next scheduled shift
Lost time injury frequency rate (LTIFR) – It is calculated as number of lost time injuries per million man-hours.
Lost wax process – It is an investment casting process in which a wax pattern is used.
Lot – It is a specific quantity of material which is produced at one time using one process and constant conditions of production, and offered for sale as a unit quantity. It is also a quantity of material which is thought to be uniform in one or more stated properties such as isotopic, chemical, or physical characteristics. It is also a quantity of bulk material of similar composition whose properties are under study. In powder metallurgy, it is the total output of on mixing. It is also a tray or basket of compacts placed in a sintering furnace.
Lot, heat treat – It is the material of the same mill form, alloy, temper, section, and size traceable to one heat treat furnace load (or extrusion charge or billet in the case of press heat treated extrusions) or, if heat treated in a continuous furnace, charged consecutively during an 8 hours period.
Lot, inspection – For non-heat-treated products, it an identifiable quantity of material of the same mill form, alloy, temper, section, and size submitted for inspection at one time. For heat treated products, it is an identifiable quantity of material of the same mill form, alloy, temper, section, and size traceable to a heat treat lot or lots and submitted for inspection at one time. (For sheet and plate, all material of the same thickness is considered to be of the same size).
Lot sample – It consists of one or more increments of material taken from a larger quantity (lot) of material for assay or record purposes. It is also termed bulk sample or lot sample.
Loudspeaker – It is a transducer which converts electrical current into sound, perceptible to more than one listener.
Low-alloy steels – It is a category of ferrous materials which show mechanical properties superior to plain carbon steels as the result of additions of such alloying elements as nickel, chromium, and molybdenum. Several attempts have been made to differentiate low alloy steels from high alloy steels but the definition of low alloy steel vary from country to country and between the standard setting organizations. As a general indication, low alloy steels can be regarded as alloy steels (by the International Organization for Standardization, ISO definition) containing more than 1 % and less than 5 % of alloying elements deliberately added for the purpose of modifying properties.
Low-angle boundaries (LAB) – These are boundaries with small angles of crystallographic misorientation between neighboring grains. They can be represented by arrays of dislocations in the boundary and have energies approximately proportional to the misorientation.
Low-angle grain boundaries (LAGB) – These are boundaries with a misorientation less than about 15 degrees. Normally they are composed of an array of dislocations and their properties and structure are a function of the misorientation.
Low-carbon steel – It is the steel with less than 0.005 % carbon. It is more ductile (malleable) and is capable of being drawn out or rolled thin for use in automotive body applications. Carbon is removed from the steel bath through vacuum degassing.
Low-cycle fatigue – It is the fatigue which occurs at relatively small numbers of cycles (less than 10,000 cycles). Low-cycle fatigue can be accompanied by some plastic, or permanent, deformation.
Low-density polyethylene (LDPE) – It is a type of thermoplastic in the polyethylene family. It’s formed of long chains of ethylene molecules called monomers. Its chemical formula is (C2H4)n, the same as high-density polyethylene. Their differences lie in density, as their names suggest. Once LDPE is created, it is typically flexible and transparent in colour. It is a common choice for manufacturing plastic goods. It is corrosion-resistant, flexible, durable, and low-cost.
Low-energy ion scattering spectroscopy (LEISS) – It is sometimes referred to simply as ion scattering spectroscopy. It is a surface-sensitive analytical technique which is used to characterize the chemical and structural makeup of materials.
Low-energy electron diffraction (LEED) – It is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons and observation of diffracted electrons as spots on a fluorescent screen.
Low enriched uranium (LEU) – it is the enriched uranium which contains less than 20 % of Uranium-235 U-235).
Lower bainite – Lower bainite has a micro-structure and crystallographic features which are very similar to those of upper bainite. The major distinction is that cementite particles also precipitate inside the plates of ferrite. There are, hence, two kinds of cementite precipitates namely (i) those which grow from the carbon-enriched austenite which separates the platelets of bainitic ferrite, and others which appear to precipitate from supersaturated ferrite. These latter particles show the ‘tempering’ orientation relationship which is found when carbides precipitate during the heat treatment of martensite, frequently described as the Bagaryatski orientation relationship.
Lower control limit – It is the minimum acceptable variation from the mean for a process which is in a state of control. It is the control limit on the lower side of the central line of a control chart. A value below this line indicates presence of an assignable cause and need for corrective action.
Lower critical temperature – It is the temperature below which ferrite is the stable phase. It is also called the A1 temperature.
Lower explosive limit (LEL) – It is defined as the lowest concentration (by percentage) of a gas or vapour in air which is capable of producing a flash of fire in presence of an ignition source (arc, flame, heat, etc.). Concentrations lower than the lower explosive limit are ‘too lean’ to burn. The explosive range is delineated by the upper and lower explosive limits.
Lower flammability limit – It is normally expressed in volume per cent. It is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is delineated by the upper and lower flammability limits.
Lower punch – It is the lower member of a die assembly which form the bottom of the die cavity. It may or may not move with respect to the die body.
Lower ram – It is the part of a pneumatic or hydraulic press which is moving in a lower cylinder and transmits pressure to the lower punch.
Lower specification limit (LSL) – It is the minimum value as per the specification.
Lowest permissible water level – The lowest permissible water level is the lowest water level at which the boiler can be safely operated without damaging or overheating any part of the boiler.
Low-expansion alloys – These are materials with dimensions which do not change appreciably with temperature. These alloys include different binary iron-nickel alloys and several ternary alloys of iron combined with nickel-chromium, nickel-cobalt, or cobalt-chromium alloying.
Low gas pressure control – It is a control to stop the burner if gas pressure is too low.
Low heat cement – Hydration of the cement is exothermic process which liberates high quantity of the heat. This causes the formation of the cracks. A low heat evolution is brought by reducing the C3A (tri-calcium aluminate) and C3S (tri-calcium silicate) which are the compounds evolving the greater heat of hydration and increasing C2S (di-calcium silicate). Rate of evolution of heat of hydration is therefore less and evolution of heat extends over a large period. The limits for the heat of hydration of this cement are 259 joules per gram at 7 days age and 300 joules per gram at 28 days age. It has lower early strength (half the strength at 7 days age and two third the strength at 28 days age) compared with ordinary portland cement (OPC). Its fineness is not less than 3200 square centimeter per gram. Hence in case of low heat cements, the rate of the development of the strength is very low. It is used for the mass construction works. The rise of temperature in mass concrete due to progression in heat of hydration can cause serious cracks. Hence, it is important to limit the rate of heat evolution in this type of construction, by using the low heat cement.
Low hydrogen carbon steel electrodes – These high-quality welding electrodes are coated with low hydrogen iron powders and are used primarily for welding carbon and low alloy steels. The normal tensile strength which welding can have using these electrodes is under 480 mega pascals (MPa). These electrodes are for versatile applications and can be used for welding through all directions. It results in advanced, long-lasting, and non-cracking weld deposits on steel materials. Relatively high-stress welding can also be done using these electrodes.
Low intensity magnetic separators (LIMS) – These separators are designed to recover magnetic material from non-magnetic matter. The separators have modular design with several frames and process tank designs using a common magnetic drum for ease of selection of the best machine for each individual application. Strong magnetic minerals (ferromagnetic) can be processed by these separators. Only very few naturally occurring materials are sufficiently magnetic (i.e., high magnetic susceptibility) to be captured by the relatively low magnetic field of these separators. Examples are, maghemite, magnetite, and pyrrhotite etc. The only mineral with economic importance in the mining industry for separation by the low intensity magnetic separators, is the magnetite ore.
Low-hydrogen electrode – It is a covered arc welding electrode which provides an atmosphere around the arc and molten weld metal that is low in hydrogen.
Low-level waste (LLW) – It consists of nuclear waste which includes metals, soil, building rubble and organic materials, arising principally as lightly contaminated miscellaneous scrap. These are wastes other than those suitable for disposal to landfill, but not normally not exceeding 4 giga-becquerels per ton (GBq/t) of alpha or 12 giga-becquerels per ton of beta / gamma activity. Metals are mostly in the form of redundant equipment or from decommissioning of radioactive / nuclear facilities. Organic materials are mainly in the form of paper towels, clothing and laboratory equipment which have been used in areas where radioactive materials are used, such as research laboratories, and general industry etc. as well as the nuclear industry.
Low level waste repository (LLWR) – It is a central place for long-term storage of the low-level radioactive waste arising from nuclear power stations, research laboratories, and general industry etc.
Low-noise block downconverter – It is a device which amplifies and converts signals to a lower frequency band which has lower losses in interconnecting cables.
Low oil temperature control (cold oil switch) – It is a control to prevent burner operation if the temperature of the oil is too low.
Low-pass filter – It is an electric filter network which passes lower frequencies and blocks higher ones.
Low pressure casting – It is a process where molten metal is introduced to the mould by the application of pressure to a hermetically-sealed metal bath forcing the molten metal up through a narrow diameter fill stalk tube from a furnace normally residing below the casting machine, although, there is a version using electromagnetic forces to lift metal into the mould. The process is considered for low to high volumes of castings from 5 grams to 100 grams and normally incorporates the use of iron or steel permanent moulds. Recent developments in sand-moulding technology have made precision sand moulds a viable choice for high-volume, low-pressure casting as well. A wide range of casting core options such as expendable sand and shell cores and mechanical single or multipiece permanent cores are successfully used in the low-pressure process.
Low pressure chemical vapour deposition (LPCVD) – It is a chemical vapour deposition technology which uses heat to initiate a reaction of a precursor gas on the solid substrate. This reaction at the surface is what forms the solid phase material. The process takes place at pressures between 13.33 pascals and 1,333 pascals and temperatures between 200 deg C and 800 deg C. A dedicated shower head which is part of a precursor delivery system is used to introduce the reactants into the chamber. To encourage heterogeneous surface reactions, the shower head and the chamber walls are made colder, while the substrate is made warmer. After the reaction is finished, the by-products are extracted using vacuum pumps as soon as possible. The manufacture of resistors, capacitor dielectrics, MEMS (micro-electro-mechanical system), and anti-reflective coatings are the primary applications for low-pressure chemical vapour deposition.
Low-pressure laminates – In general, these are laminates moulded and cured in the range of pressures from 2,760 kilo-pascal down to and including pressure got by the mere contact of the plies.
Low-pressure permanent mould casting – It uses a gas at low pressure, usually between 20 kilo-pascal to 100 kilo-pascal to push the liquid metal into the mould cavity. The pressure is applied to the top of the pool of liquid, which forces the liquid metal up a refractory pouring tube and finally into the bottom of the mould. The pouring tube extends to the bottom of the ladle so that the liquid metal being pushed into the mould is very clean. No risers are required because the applied pressure forces liquid metal in to compensate for shrinkage. Yields are normally more than 85 % because there is no riser and any metal in the pouring tube just falls back into the ladle for reuse. The vast majority of low-pressure permanent mould castings are from aluminum and magnesium, but some are copper alloys. Advantages include very little turbulence when filling the mould because of the constant pressure, which minimizes gas porosity and dross formation. Mechanical properties are around 5 % better than gravity permanent mould castings. The disadvantage is that cycles times are longer than gravity permanent mould castings.
Low pressure plasma spraying (LPPS) – It is a thermal spray process variation in which the process is carried out under controlled atmosphere conditions. The process is carried out in a vacuum chamber and the thermal spray gun is normally operating in a low-pressure environment of an inert gas, normally argon.
Low-pressure steam boiler – Low-pressure steam boiler is a boiler which operates at a pressure not above 103 kilo pascals.
Low-recovery valve – It is a valve design which dissipates a considerable quantity of flow stream-energy because of turbulence created by the contours of the flow path. Hence, pressure downstream of the valve vena contracta recovers to a lesser percentage of its inlet value than is the case with a valve having a more streamlined flow path. Although individual designs vary, conventional globe-style valves normally have low pressure recovery capability.
Low residual, black foundry busheling – It constitutes 1000 series black carbon steel scrap, with 3 millimeters and above in thickness, size not more than 300 millimeters x 600 millimeters, manganese content is 0.5 % maximum. Other parameters are subject to agreement between the user and the supplier.
Low residual, ductile quality shredded clips – It constitutes shredded black 1000 series carbon steel scrap, with 3 millimeters and above in thickness, minimum average density of 1.2 tons per cubic meter, and manganese content 0.5 % maximum. Other parameters are subject to agreement between the user and the supplier.
Low-residual-phosphorus copper – It is the deoxidized copper with residual phosphorus present in quantities (normally 0.004 % to 0.012 %) normally too small to decrease appreciably the electrical conductivity of the copper.
Low-stress abrasion – It is a form of abrasion in which relatively low contact pressures on the abrading particles or protuberances cause only fine scratches and microscopic cutting chips to be produced.
Low stress grinding (LSG) – It is a process in which materials are ground in a non-abusive manner. Special refined grinding equipment is utilized. The process takes place with equipment using highly accurate temperature controlled hydrostatic bearings. Low stress grinding would be an effective method for producing aerospace bearing surfaces as well as precision gauging and fixtures. Low stress grinding uses wheel speeds of about 20 metres per second and can normally be done on conventional grinding machines in any of the grinding modes. Majority of the surface grinding operations use wheel speeds of 30 metres per second to 35 metres per second.
Low styrene emission (LSE) resins – These resins are produced by adding vapour suppressant additives to the resin formulation. These additives form a film over the resin surface once the moulding is left to stand.
Low sulphur heavy stock (LSHS) – It is a residual fuel processed from indigenous crude oil. This fuel is normally used in lieu of furnace oil in the same applications where the furnace oil is suitable. The main difference with low sulphur heavy stock and furnace oil is the higher pour point, higher calorific value and lower sulphur content in low sulphur heavy stock as compared to furnace oil. Since low sulphur heavy stock is having pour point higher than the ambient temperature, it needs specially designed oil handling systems such as steam traced or electrically traced storage tanks, pipelines, pumps and filters. Low sulphur heavy stock is handled hot at all stages and is maintained at 75 deg C. Special care is also taken so that no ‘boil over’ of low sulphur heavy stock takes place in the storage tank. The main advantage in the use of low sulphur heavy stock lies is its low sulphur content.
Low temperature – The term ‘low temperature’ is typically defined in terms of boundaries, where metallurgical processes change. One general definition of ‘low-temperature’” is ‘T’ is less than 0.5 ‘Tm’ where ‘T’ is the exposure temperature, and ‘Tm’ is the melting point of a material (both given on the absolute temperature scale, K). For several structural metals, another definition of low temperature Is ‘T’ is less than 0.3 ‘Tm’, where recovery processes are not possible in metals and where the number of slip systems is restricted. For these definitions, room temperature (293 K) is almost always considered a low temperature for a metal with a few exceptions, such as metals which have melting temperatures below 200 deg C (indium and mercury). In a structural engineering sense, low temperature can be one caused by extreme cold weather. For several applications, low temperature refers to the cryogenic temperatures associated with liquid gases. Gas liquefaction, aerospace applications, and super-conducting machinery are examples of areas in engineering which need the use of materials at very low temperatures. The term cryogenic typically refers to temperatures below 150 K. Service conditions in superconducting magnets that use liquid helium for cooling are in the 1.8 K to 10 K range.
Low temperature sensitization – It normally refers to a heat treatment below 500 deg C. However, a low temperature sensitization heat treatment of 500 deg C/24 hours has become common, and frequently, low temperature sensitization (if not otherwise defined) means 500 deg C/24 hours.
Low temperature steels – These are steels which are especially suited for extremely cold climates and for the handling of liquefied gases such as oxygen, nitrogen, propane, anhydrous ammonia, carbon di-oxide, and ethane.
Low velocity impact damage – Low velocity impact occurs at velocities below 10 metres per seconds and is likely to cause some dents and visible damage on the surface due to matrix cracking and fibre breaking, as well as delamination of the material.
Low water cut-off – It is a safety device which shuts off the boiler / burner in the event of low water, preventing pressure vessel failure.
L-radiation – It is the characteristic X-rays produced by an atom or ion when a vacancy in the ‘L’ shell is filled by an electron from another shell.
L-series – It is the set of characteristic X-ray wave-lengths making up L-radiation for the various elements.
L shell – It is the second shell of electrons surrounding the nucleus of an atom, having electrons with principal quantum number 2.
Lube – It is short for lubricant.
lube, high – It means that the lubricant limit exceeds the maximum agreed-upon limit measured in weight per unit area.
lube, low – It is the failure of the lubricant to meet the agreed-upon minimum limit measured in weight per unit area.
Lubricant – It is a substance interposed between two surfaces in relative motion for the purpose of reducing the friction or wear between them. This definition implies intentional addition of a substance to an interface. However, species such as oxides and tarnishes on certain metals can also act as lubricants even though they are not added to the system intentionally. Lubricant is also a material applied to dies, moulds, plungers, or work-pieces which promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part. It is also a substance mixed with a powder to facilitate compacting and subsequent mould ejection of the compact, frequently a stearate or a proprietary wax. It can also be applied as a film to the surfaces of the punches or the die cavity wall such as spray coating. In composites, it is a material added to most sizings to improve the handling and processing properties of textile strands, especially during weaving.
Lubricant compatibility – In tribology, it is a measure of the degree to which lubricants or lubricant components can be mixed without harmful effects such as formation of deposits.
Lubricant residue – It is the carbonaceous residue resulting from lubricant which is burned onto the surface of a hot forged part.
Lubricate – It is the application of lubricant for lubrication.
Lubricated friction – It is characterized by the presence of a thin film of the pressurized lubricant (squeeze film) between the two moving surfaces. The ratio of the squeeze film (oil film) thickness to the surface roughness determines the type of the lubrication regime.
Lubricating – It is the mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity. It is also applying a lubricant to die walls and / or punch surfaces.
Lubricating oils – They are made from the more viscous portion of the crude oil which remains after removal by distillation of the gas oil and lighter fraction. The chemical structure of lubricating oils contains (i) hydrocarbons of the crude oils which consist of namely paraffinic components, (ii) naphthenic components, (iii) aromatic components, and (iv) non hydrocarbon components. The classifying of hydrocarbon as paraffinic, naphthenic and aromatic groups which are normally used for characterizing the base oil is not to be taken as absolute but as an expression of the predominating chemical tendencies of the base stocks.
Lubrication – The principle of supporting a sliding load on a friction reducing film is known as lubrication. The main purpose of lubrication is to reduce wear and heat between the contacting surfaces in relative motion. While wear and heat cannot be completely eliminated, they can be reduced to negligible or acceptable levels. Other purposes of the lubrication include (i) reduce friction, (ii) reduce oxidation and prevent corrosion, (iii) disperse contaminants, (iv) act as a sealant against dust, dirt, and water, (v) transmit mechanical power in hydraulic fluid power applications, and (vi) provide insulation in the transformer applications. In powder metallurgy, it is mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity. It is also, applying a lubricant to die walls and / or punch surfaces.
Lubrication regimes – These are the ranges of operating conditions for lubricated tribo-systems which can be distinguished by their frictional characteristics and / or by the manner and quantity of separation of the bearing surfaces.
Lubricious (lubricous) – It is relating to a substance or surface condition which tends to produce relatively low friction.
Lubricity – It is the ability of a lubricant to reduce wear and friction, other than by its purely viscous properties.
Luder bands – They are also known as Luder lines or stretcher strain marks. They become visible after press forming of a sheet and have a typical ‘flame-like’ pattern. This surface pattern in most applications is unacceptable for visible parts. The phenomenon is well known in most steels and in certain aluminum alloys. Luder bands can easily be detected with a simple tensile test. Materials which are prone to form Luder bands during press forming always show a ‘yield point elongation’ or ‘Luder strain’ in the stress–strain curves obtained in a tensile test. The reason for these Luder strains is the pinning of dislocations by carbon atoms in steel or by substitutional atoms in aluminum. In steel, the effect can be eliminated by giving the skin pass rolling or by roll leveling (bending/unbending). This liberates the dislocations from their pinning points. In aluminum, the effect can be avoided by grain size control (a grain size of above 10 micrometers to 15 micrometers is needed).
Luders lines – These are elongated surface markings or depressions in sheet metal, frequently visible with the unaided eye. Luders lines are formed along the length of sheet metal or a tension sample at an angle of around 45-degree to the loading axis. These are caused by localized plastic deformation. These result from discontinuous (inhomogeneous) yielding. These are also known as Luders bands, Hartmann lines, Piobert lines, or stretcher strains.
Lug – It consists of any projection, like an ear, used for supporting or grasping.
Luggin probe – It is a small tube or capillary filled with electrolyte, terminating close to the metal surface under study, and used to provide an ionically conducting path without diffusion between an electrode under study and a reference electrode.
Lumen – It is the SI (International System of Units) unit of luminous flux, the energy of visible light.
Luminous intensity – It is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI (International System of Units) unit of luminous intensity is the candela, which is a SI base unit.
lumped-parameter model – It is a mathematical model in which the distributed properties of physical quantities are replaced with their lumped equivalents. When a problem can be analyzed in terms of a finite number of discrete elements, it can be expressed by ordinary differential equations. To describe the more realistic case of distributed parameters having several values spread over a field in space needs the use of partial differential equations.
Lumped parameters – It describes an electrical network where the circuit elements are small compared to the wave-lengths of the signals passing through it.
Lumps – These are the defects in porcelain enamel caused by coarse enamel particles, spitting of guns, or falloff of accumulation on guns.
Lumpy zone – It is a zone in the blast furnace. It is also known as stack zone. In this zone, coke and ore particles make a stratified descent down the furnace and indirect reduction takes place.
Lustre – Lustre is gentle shining light which is reflected from a surface, e.g., from polished metal. It is also a physical property which is used to help identify minerals. Lustre describes how a mineral’s surface reflects light and how the interior of the mineral can refract or bend light. Some minerals have a metallic lustre while some other have a non-metallic lustre.
Lustre finish – It is a bright, as-rolled finish, produced on ground metal rolls. It is suitable for decorative painting or plating, but normally is to undergo additional surface preparation after forming.
Lyapunov stability -It is a criterion for stability of a dynamical system. If disturbances from a stable point reduce and the system returns to that stable point, it can be said to be Lyapunov stable.
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