The white color is due to the fact that the carbon is this iron is in combined form as iron carbide which is commonly specified as cementite. It is the hardest constituent of iron. It is produced in cupola furnace by refining or pig iron. The white cast iron may be produced by casting against metal chills or by regulating analysis. The chills are used when a hard and wear resistance surface is desired for products such as for wheels, rolls crushing jaw, crusher plates. The chemical composition of white cast iron is given as under.
C = 3.2 to 3.6%
Si = 0.4 to 1.1 %
Mg = 0.1 to 0.4%
P = less than 0.3%
S = less than 0.2%
Fe = Remaining
Properties
(i) Its name is due to the fact that its freshly broken surface shows a bright white fracture.
(ii) It is very hard due to carbon chemically bonded with iron as iron carbide ,which is brittle also.
(iii) It possesses excellent abrasive wear resistance.
(iv) Since it is extremely hard, therefore it is very difficult to machine.
(v) Its solidification range is 2650-2065°F.
(vi) Shrinkage is 1/8 inch per foot.(vii) The white cast iron has a high tensile strength and a low compressive strength.
Applications
(i) For producing malleable iron castings.
(ii) For manufacturing those component or parts which require a hard, and abrasion resistant surface such as rim of car.
(iii) Railway brake blocks.