It is often said that "composition determines organization, and organization determines performance." This statement is generally true, but it is not comprehensive. Because, in the past, chemical composition was usually only five elements and alloy elements; In addition to component factors, crystallization control is also important for tissue formation, such as the cooling rate associated with cast iron wall thickness, casting conditions, presetting of crystallization core, and orientation of graphite morphology. Putting aside the external cause of cooling speed, the smelting of cast iron should focus on four aspects: accurate chemical composition, clean molten iron, less interfering elements and controlled graphite core.