Wire and Rod Drawing Process for Steel Nov13

Wire and Rod Drawing Process for Steel...

Wire and Rod Drawing Process for Steel Drawing of wire from steel rod is a metal working process used for the reduction of the cross-section of the rod. Similarly rods are drawn from steel rounds of larger diameters. During drawing the volume remains the same and hence there is increased in the length of the drawn wire or rod. It is carried out by pulling the wire/rod through a single or a series of the drawing dies. In the case of series of drawing dies, the subsequent drawing die is to have smaller bore diameter than the previous drawing die. Drawing is usually performed in round sections at room temperature, thus it is classified as a cold working process. However, it can be performed at higher temperatures for large wires to reduce forces. Drawing process normally is most frequently used to produce round cross sections, but squares and other shapes can also be drawn. Wire/rod drawing is an important industrial process, providing commercial products. Rod and wire products cover a very wide range of applications which include shafts for power transmission, machine and structural components, blanks for bolts and rivets, electrical wiring, cables, wire stock for fences, rod stock to produce nails, screws, rivets, springs and many others. Drawing of rods from steel rounds is used to produce rods for machining, forging, and other processes etc. Advantages of drawing in the above applications include (i) close dimensional control, (ii) good surface finish, (iii) improved mechanical properties such as strength and hardness, and (iv) adaptability to economical batch or mass production. In the process of drawing, the cross section of a long rod or wire is reduced or changed by pulling (hence the term drawing) it through a die called a draw die. Pulling of rod...

High Strength Carbon and Low Alloy Steels...

High Strength Carbon and Low Alloy Steels High strength carbon (C) and low alloy steels have yield strength (YS) greater than 275 N/sq mm and can be classified generally in four types namely (i) as-rolled C – Mn (manganese) steels, (ii) as rolled high strength low alloy (HSLA) steels also known as micro-alloyed steels, (iii) heat treated (normalized or quenched and tempered) C steels, and (iv) heat treated low alloy steels (Fig 1). These four types of steels have higher YSs than mild C steel in the as hot rolled condition. The heat treated low alloy steels and the as rolled HSLA steels also provide lower ductile-to-brittle transition temperatures than do C steels. Fig 1 Classification of high strength carbon and low alloy steels The four types of high strength steels have some basic differences in mechanical properties and available product forms. In terms of mechanical properties, the heat treated low alloy steels offer the best combination of strength and toughness. However, these steels are available primarily as bar and plate products and only occasionally as sheet and structural shapes. In particular, structural shapes (I and H beams, channels, or special sections) can be difficult to produce in the quenched and tempered condition since shape warpage can occur during quenching. Heat treating steels is also a more involved process than the production of as rolled steels, which is one reason the as rolled HSLA steels are an attractive alternative. The as rolled HSLA steels are also commonly available in all the standard wrought product forms (sheet, strip, bar, plate, and structural shapes). HSLA steels are an attractive alternative in structural. High strength steels are used to reduce section sizes for a given design load, which allows weight savings. Reductions in section size are also...

Stainless Steel Reinforcement Bars...

Stainless Steel Reinforcement Bars  Premature deterioration of reinforced concrete structures is a serious problem worldwide due to corrosion of the embedded steel. The affected reinforced concrete structures are mainly those which are situated in an aggressive marine environment, and road bridges to which de-icing salts are applied during winter periods. Corrosion of the steel is initiated when the chloride ion from the salt (sodium chloride) permeates through the concrete to the level of the reinforcement steel which is attacked on contact. The solution, now favoured by highways authorities in Europe and North America, is to use stainless steel for rebars that has proven to be highly resistant to chloride ion. Stainless steel reinforcement bars or simply called stainless steel rebars are more expensive than carbon steel rebars. They do not corrode for the design life of the structure which is normally taken as 125 years in the case of highway bridges. The reductions on ongoing repair and maintenance costs that are usually incurred in case of carbon steel rebars are significant. Environmentally, the reduced downtime for maintenance and repair impacts upon traffic flow and disruption thus making the use of stainless steel rebars highly attractive. Only a small percentage of the steel rebars needs to be stainless steel to achieve a significant increase in durability. Stainless steel rebars can readily be used with conventional carbon steel rebars in reinforced concrete without causing galvanic effects. Stainless steel rebars are cost effective when used in the elements of the concrete structure at highest risk to corrosion (with carbon steel used for the balance of the reinforcement) or, where repair is difficult and expensive. Further by using stainless steel rebars, the concrete mix can also be simplified as it not necessary to provide passivity to the steel...

Microalloyed Steels

Microalloyed Steels Microalloyed steels are a type of alloy steels that contains small amounts of alloying elements (usually 0.05 % to 0.15 %). These steels are also sometimes called high strength low alloy (HSLA) steels. Though the work of strengthening steels through addition of small percentage of alloying elements started as early as 1916 in USA, the term ‘Microalloying’ (believed to be of Russian origin) was adopted by Prof. T. M. Noren-Brandel in 1962 and became pervasive as a result of the landmark conference ‘Microalloying 75’.  Strengthening by microalloying elements permits a dramatic reduction in carbon content which greatly improves weldability and notch toughness. Microalloyed steels have been developed originally for large diameter oil and gas pipelines. The technology of microalloying involves the addition of a fraction of a percent of the microalloying elements to simple low carbon mild steel. The use of ‘micro’ alloy concentrations, which produce remarkable changes in mechanical properties, distinguishes the technology from ‘alloying’ in the conventional sense (low alloy steels family) where concentration of the alloying elements may range from 0.25 % to one or two or possibly several percent. Microalloyed steels are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels. They are not considered to be alloy steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition. Microalloyed steels are a family of steels that contain 0.07 % to 0.12 % carbon, upto 2 % manganese and are strengthened by the elements niobium, vanadium and titanium added either singly or in combination. These elements are sometimes used in conjunction with other strengtheners such as boron, molybdenum and chromium, nickel, copper and rare earth metals. The microalloying elements are used to refine...