Steel

METALS Types Ferrous metals Non-Ferrous metals: Wherein iron is not the main constituent (Copper, Aluminum, Zinc and lead etc)

Ferrous metals: iron is the main constituent (Cast iron, wrought iron & different forms of steels) Ferrous metals ► not directly obtained from iron ores PIG IRON: From iron ore ► impure form of metal ► Pig iron It is the pig iron which further yields “Ferrous metals” Pig iron is not suitable for any mechanical use unless it is converted into cast iron, wrought iron or steel

CAST IRON: Pig iron ► re melted with limestone and coke and poured into moulds of desired shapes and sizes to get purer product known as cast iron Carbon content in cast iron varies from 2 to 5% During re melting of pig iron ► scrap iron may also be added for economy

Properties of Cast Iron It is brittle, non ductile, non malleable and cracks when subjected to shocks It cannot be magnetized It does not rust It is strong in compression but weak in tension & shear Its melting point is 12000C Its specific gravity is 7.5 USES Weak in tension therefore cannot be used in construction Can be used for parts of pumps, motors, engines etc Because of corrosion resistance ►can be used for pipes to some extent

Properties of Wrought Iron Wrought iron is very malleable and ductile Its tensile strength is 20-26 tons /in2 It is strong in compression but not so strong as steel It can be easily worked, welded and is tough Its melting point is 28000F Wrought iron became pasty and very plastic at red heat and could be easily forged at about 16500F USES: Since mild steel has replaced the wrought iron, therefore it is no longer produced in large extent. Still in use for roof sheets, wires and metal ornaments etc

STEEL Steel is an alloy of iron and carbon. Pure iron’s strength remarkably increases when alloyed with carbon. The tensile strength increases with increasing carbon content but the ductility reduces. Steel having its properties because of the presence of carbon alone is called “Plain carbon steel”

Low carbon steel or mild steel: The carbon content does not increases 0.25% Soft and ductile ► mostly used for construction purpose Uses ► Sheets, rods, wires, pipes, hammers, chains, shafts etc Medium-carbon steel : The carbon content is 0.25 to 0.5 % Stronger than the mild steel slightly less ductile Uses ► Shafts, connecting rods and rails etc High- carbon steel : Carbon content is above 0.5% Harder and stronger than mild steel and medium carbon steel Uses ► Keys, knifes, drills etc

Properties of Mild Steel Ductile and malleable It corrodes quickly It can be permanently magnetized It is tough and more elastic than cast iron and wrought iron and withstands shocks and impacts well It is equally strong in tension, compression and shear Its specific gravity is 7.8 It is not much affected by Saline water

Properties of High-carbon Steel Its structure is granular It is more tough and elastic than mild steel It is easier to harden and then to weld It is more difficult to forge and then to weld It can be permanently magnetized Comparatively it is stronger in compression than in tension or in shear It withstands vibration and shocks better

MANUFACTURE OF STEEL Three basic raw materials are needed in large quantities for the production of steel Iron Ore Coal Lime stone The first step in the steel manufacture begins at the blast furnace. To separate iron from iron ore ► coke (substance when gas is taken out of coal), limestone and dolomite are charged into the blast furnace

Temperature raised to 1600oF Temperature raised to 1600oF. This high temp causes the coke to burn and melt the iron. This red hot iron drained at an opening at the base of the furnace. Natural gas is often injected to reduce the amount of coke consumed. The dolomite and limestone combine with the non-ferrous elements of the ore to form a slag, which floats on the top of the molten iron and is removed separately. The product of the blast furnace is known as “Pig Iron” the basic ingredient of steel

It takes 2 tons of iron ore, 2/3 ton of coke, ½ ton of limestone, 4 tons of air to make 1 ton of Pig iron. Some of the pig iron goes to the foundries to make iron castings, but the vast majority is re melted and used in the production of steel in steel furnace. Several types of furnaces are used for the production of steel including Open Hearth Furnace Bessemer Furnace Electric Furnace New Oxygen Furnace

TMT STEEL RODS Bamboo has been used - for construction activities, later it has been replaced by CTD (Cold Twisted Deformed steel rods) or TOR steel rods. The manufacturers adopted the “Cold Twisting Process” in which the naturally cooled rods were twisted by means of motors. Thus the molecular structure of the core steel is weakened. Now, the TMT (THERMO MECHANICALLY TREATED) steel rods have emerged. This rod is not twisted; instead it is treated with the WATER JACKETING PROCESS and allowed to cool in the ambient condition.

COMPOSITION: The TMT chemistry BIS (bUREAU OF INDIAN STANDARDS)   BIS (bUREAU OF INDIAN STANDARDS) Rosun TMT Carbon (Max%) 0.30 0.25 to  0.30 Manganese (%) 0.5 to 1.2 0.5 to 0.8 Sulphur & Phosphorous as per IS:1786/85

Advantages of TMT:    Savings of 14 – 19% steel Reduction in Costs Better safety of structures Easy working at site Better ductility & bend-ability Better Corrosion Resistance Good Weld-ability Resistant to fire hazards

Higher strength with better elongation Excellent Weld-ability Special Features of TMT Bars: Higher strength with better elongation Excellent Weld-ability Resistance to fire hazards Excellent Ductility Higher Fatigue Strength Easy work – ability at site Better Bonding Strength Better Corrosion Resistance Achieves better results than BIS Standards