When cast iron is slowly cooled, the cementite decomposes into iron and carbon in the form of graphite which is called graphitization. Cast irons where a large percentage of cementite is decomposed by graphitization are called grey cast irons. Here in the following are the comparison table of the gray rion grade in different countries. They have different names, but generally they have the similar chemical composision and mechanical properties, so the can be called equivalent materials from different standards.