Ferrous Metal : Steel, Carbon Steel, Low-carbon Steel, High-carbon Steel, Stainless - Printable Version

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Ferrous Metal : Steel, Carbon Steel, Low-carbon Steel, High-carbon Steel, Stainless - sumit patni - 07-26-2014

Steel

Contains up to 1.5% of Carbon (Specific Gravity 7.7)
Of all the different metals and materials that we use in our trade, steel is by far the most important. When steel was developed, it revolutionized the American iron industry. With it came skyscrapers, stronger and longer bridges, and railroad tracks that did not collapse. Steel is manufactured from pig iron by decreasing the amount of carbon and other impurities and adding specific amounts of alloying elements.

Do not confuse steel with the two general classes of iron: cast iron (greater than 2% carbon) and pure iron (less than 0.15% carbon). In steel manufacturing, controlled amounts of alloying elements are added during the molten stage to produce the desired composition.
Carbon in excess of 1.5% does not combine with iron , but will be present as free graphite , Thus the dividing line of cast iron and steel is presence of free graphite . If there is free graphite then it is cast iron, otherwise it is steel.

Steel and wrought iron can be distinguished by putting a drop of nitric acid on metal , steel will produce a gray stain due to higher carbon content.

Carbon Steel

Carbon steel is a term applied to a broad range of steel that falls between the commercially pure ingot iron and the cast irons. This range of carbon steel may be classified into four groups:

Low-Carbon Steel 0.05% to 0.30% carbon
Medium-Carbon Steel 0.30% to 0.45% carbon
High-Carbon Steel 0.45% to 0.75% carbon
Very High-Carbon Steel 0.75% to 1.70% carbon

Low-carbon Steel

Steel in this classification is tough and ductile, easily machined, formed, and welded. It does not respond to any form of heat treating, except case hardening.



Medium-carbon Steel

These steels are strong and hard but cannot be welded or worked as easily as the low-carbon steels. They are used for crane hooks, axles, shafts, setscrews, and so on.



High-carbon Steel

Steel in these classes respond well to heat treatment and can be welded. When welding, spe­cial electrodes must be used along with preheating and stress-relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, mill tools, railroad car wheels, chisels, knives, and so on.



Stainless Steel

This type of steel is classified by the American Iron and Steel Institute (AISI) into two general series named the 200-300 series and 400 series. Each series includes several types of steel with different characteristics.

The 200-300 series of stainless steel is known as AUSTENITIC. This type of steel is very tough and ductile in the welded condition; therefore, it is ideal for welding and requires no annealing under normal atmospheric conditions. The most well-known types of steel in this series are the 302 and 304. They are commonly called 18-8 because they are composed of 18% chromium and 8% nickel. The chromium nickel steels are the most widely used and are normally nonmagnetic.

Characterized by their corrosion resistance, high strength and ductility, and high chromium content.

Stainless as a film of chromium oxide protects the metal from corrosion.

Five types of stainless steels:
Austenitic steels
Ferritic steels
Martensitic steels
Precipitation-hardening (PH) steels
Duplex-structure steels

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