The pig iron is hard and brittle, but it is pressure and wear resistant. Gray iron and ductile iron. The carbon in white iron is silvery white with Fe3C fracture. It is hard and brittle and cannot be machined. It is the raw material for steel making, so it is also called steel pig iron.
The carbon is distributed in the form of flake graphite, which is called gray iron. The fracture is silver-gray, easy to cut, easy to cast and wear-resistant. If carbon is distributed in spheroidal graphite, it is called ductile iron, and its performance and processing performance are close to that of steel. Special iron alloy can be obtained by adding special alloying elements to cast iron. If Cr is added, the wear resistance can be greatly improved, and it is very important under special conditions.