Carbon is the principal of hardening in steel with iron carbon combines to form carbide which is hard & brittle. The increment in steel, increase the hardness of steel. The hardness becomes correspondingly less in steel containing more then 85% carbon then low carbon ranges. Ductility & weld ability decreases as the carbon increases.

Chromium is used to increase depth harden ability and promote carburization it refines the grain structure. Chromium forms the most stable carbide resulting to increase the wear resistance. The carburization thereby becomes relatively easy and makes the steel for oil or air hardening. The corrosion resistance requires a 13% AL of chromium with increase carbon content up to 3% will be boost reminisce as coercive force. In steel chromium above 3% the corrosion resistance is greatly promoted.

Copper used in small amount carbon steel has no significant effect. Scarily used because of it’s permanently effect impact in the steel, causing of surface harmful for hot working. Most grades of steel already contain (0.15 - 0.20%) copper, which doesn’t represent a noxious factor. In the same case copper is added in the order to increase the resistance of steel to atmospheric corrosion. High alloy stainless becomes highly resistance to hydrochloric and sulphuric acids by a copper addition of more then 1%.

The steel used in light tensile alloy for aircraft. Aids formatting of S.G. (spheroid graphite) in cast iron.

Manganese is deoxidizer. It is important to free cutting steel as the risk of hot shortness is reduced , it’s added to the strength and hardness of carbon steel. Steel contains more then 18%Mn. will remains non magnetic even after important cold working operations. They are used for special purpose.

Molly is used with other elements and beneficial effect on steel. With chrome and manganese. it improves and adds the harden ability of steel being non oxizable elements impacting a large measures of harden ability. It is useful where close harden ability control is requires, effecting increasing resistance to corrosion it is used in high chromium and chromium nickel steel. Molly has powerful effect in increasing the high temp. tensile and creep strength of ferrous steel. Steel containing molly les susceptible to temper brittleness then alloy steel in which molly is not present.

Ni. Provides improved toughness particularly at low temp. Ni. Steel are suitable for case hardening and tempering as well as low temp. steel, Ni. Doesn’t form any carbides or other compound which might be difficult to dissolve during heating for Austen sing. By consider ability enlarging the gamma area nickel contents of more then 7% impact high chromium stainless steel as austenitic structure what is retained below room temp. with chromium the nickel – chromium austenitic steel provides high resistance to reducing chemicals and conductivity are considerably reduced. High Ni. Percentage if used within strictly control chemical ranges lead to steel with special physical properties required by aircrafts engines gear roller bearings and such other applications, outstanding characteristic of nickel is that nickel steels are successfully heat treated without any risk.

Si is a deoxidizing agent. It improves tensile strength and abrasion resistance. (Si-Mn quenched temp. of steel). As it markedly raises the yield point it use in spring steel. Si. Enhances resistance to scaling and therefore is used in high temp. steel, although used in both hot n cold working percentage of Si should be strictly controlled. Si content in killed steel varies according to it’s Mn. Content between 0.20% to 0.40% up to 0.60%.