Structural Steel – Preferred Material for Construction...

Structural Steel – Preferred Material for Construction Structural steel is not just a material which has only the technical competence. It has many other qualities that make it the preferred material for architects, designers and engineers. It is economical and provides great mechanical functionality; it permits the design of structures which are graceful, light and airy; it streamlines construction site processes; and it offers rapid execution. A major advantage, however, is the infinite freedom for creation which it provides to the architects, designers and engineers. The combination of structural steel with different materials lends themselves to rich and varied types of construction. When combined with glass, structural steel makes fabulous use of light and space. Structural steel is the material ‘par excellence’ when it comes to inventing new structures and forms. All solutions are possible, from the very simplest to the most challenging. Structural steel can be used for small buildings as well as large structures, for routine construction projects, and those subject to complex urban constraints. No other material is used to make structures which are so thin, light and airy. Forms can be created using different structural effects and envelopes with pure or finely sculpted curves. Architects, designers and engineers can give free reign to their imagination and creativity with structural steels. Structural steel is a standard construction material made from specific steel grades and is available in standard cross sectional shapes. This steel exhibits desirable physical properties such as strength, uniformity of properties, light weight and ease of use etc. This makes it one of the most versatile structural materials in use. Major applications for this steel is in high rise and tall multi-storey buildings, industrial buildings, towers, tunnels, bridges, road barriers, and industrial structures etc. Within the overall architectural concept,...

Properties of Steels

Properties of Steels When selecting a steel material for a particular application, user has to be confident that it will be suitable for the loading conditions and environmental challenges it will be subjected to while in service. Understanding and control of the properties of the steel material is therefore necessary. Further properties of steel can be controlled through different processes such as hot and cold working, heat treatment etc. There are many measurement systems used to define the properties of given steel. These measurement systems normally come under four categories. These are physical properties, chemical properties, microstructural properties and mechanical properties.  Physical properties of steels The physical properties of steel are related to the physics of the material, such as density, thermal conductivity, elastic modulus, Poison’s ratio etc. Typical physical properties of steels are given in Tab 1. Tab1 Physical properties of steels           Properties Carbon steels Alloy steels Stainless steels Tool steels Density (tons/Cum) 7.85 7.85 7.75-8.1 7.72-8.0 Elastic modulus (GPa) 190-210 190-210 190-210 190-210 Poisson’s ratio 0.27-0.3 0.27-0.3 0.27-0.3 0.27-0.3 Thermal expansion (10-6/K) 11-16.6 9.0-15 9.0-20.7 9.4-15.1 Melting point (deg C) 1371-1540 Thermal conductivity (W/m-K) 24.3-65.2 26-48.6 11.2-36.7 19.9-48.3 Specific heat (J/kg-K) 450-2081 452-1499 420-500   Electrical resistivity (10-9W-m) 130-1250 210-1251 75.7-1020   Chemical properties of steels Iron is the basic component of steel. When carbon (C), a nonmetal, is added to iron (Fe) in amounts up to 2.0 %, the result is an alloy known as steel. Composition of steel mainly consists of iron and other elements such as carbon, manganese, silicon, phosphorus, sulfur, and alloying elements. A large number of elements in wide ranging percentages are used for the purpose of alloying of steels. Variations in chemical composition of steels are responsible for a great variety...

Structural steels

Structural steels Structural steel is a standard construction material made from specific steel grades and is available in industry standard cross sectional shapes. This steel exhibits desirable physical properties such as strength, uniformity of properties, light weight and ease of use etc. This makes it one of the most versatile structural materials in use. Major applications for these steels are in high rise and tall multi-storey buildings, industrial buildings, towers, tunnels, bridges, road barriers and industrial structures etc. The common shapes in which structural steels are available consist of sections (beams, channels, Tees section and angles), squares and rounds, hexagons, plates, pipes, hollow square sections, steel cable, Z sections and cold formed sections etc. (Fig 1). Fig 1  Some shapes of structural steels Structural grade steels have specific chemical compositions and mechanical properties required as per their application. These steels are produced as per the specifications included in different standards which are issued for structural steels. Structural steels for use at ambient or moderately elevated temperatures are of the following types. Carbon and carbon-manganese steels – In these steels the maximum content for alloying elements does not exceed the following: (i) manganese – 1.65 %, silicon – 0.40 % and (iii) copper – 0.6 %. The specified minimum of copper does not exceed 0.4 % and also there is no minimum content is specified for other elements to obtain a desired alloying effect. High strength low alloy (HSLA) steels – These steels have specified minimum yield strengths greater than 280 Newtons /Sq cm and achieve that strength in hot rolled condition rather than by heat treatment. Heat treated high tensile steels – Both Carbon and HSLA steels can be heat treated to provide yield strengths in the range of 350 to 520 Newtons/Sq cm....

Pig iron

Pig iron  Pig iron is an intrmediate product of a steel plant produced during smelting of iron ore in a blast furnace. Iron ore is reduced by coke using limestone and dolomite as flux for removal of impurities. The resulting liquid iron (hot metal), when cast in the pig casting machine, produces pig iron. Fig 1 shows pig iron.                        Fig 1 Pig iron The term ‘pig iron’ has arisen from the old method of casting liquid iron from a blast furnace into moulds arranged in sand beds. The traditional shape of the molds used for these ingots was a branching structure formed in sand. It had many individual ingots at right angles to a central channel or runner. Such a configuration is similar in appearance to a litter of piglets suckling on a sow. Name of these ingots was given from the word “piglets”. When the metal had cooled and hardened, the smaller ingots (the pigs) were simply broken from the much thinner runner (the sow). Since pig iron was intended for remelting, the uneven size of the ingots and inclusion of small amounts of sand were insignificant when compared with its ease of casting and of handling. Presently most of the liquid iron is produced and consumed within integrated steel plants for steel making. In this context the term ‘pig iron’ is something of a misnomer within integrated steel plants since blast furnace iron (hot metal) is transferred directly to the steel melting shop in liquid form. The liquid iron from a blast furnace which is not sent for steel making is cast into pigs in pig casting machine for use in steel making later as cold charge or is sold to foundries or to mini steel plants having induction furnaces as merchant...