Cast iron is a general term for high-carbon ferrosilicon alloys, and its carbon content is between 1.8 and 4.5. Cast iron can be divided into gray cast iron, ductile iron, pearlitic iron, malleable iron and white iron according to the distribution of carbon in the alloy.

Since the mid-1960s, my country began to study the mechanism and processing technology of rare earth and iron, and successively solved the problems of rare earth nodularizing agent, smelting preparation of inoculant, and rare earth adding method.

At present, rare earth-treated cast iron is mainly divided into three categories: ductile iron, vermicular iron and high-strength gray iron, and rare-earth-treated alloy iron.

The main role of rare earth in cast iron:

Metamorphism: The outstanding performance is to change the flake graphite into spherical graphite. Graphite spheroidization can reduce stress concentration, refine the as-cast structure, improve the shape and distribution of non-metallic inclusions, and is conducive to the improvement of material properties. Therefore, rare earth ductile iron has higher mechanical properties than gray cast iron, and its shock resistance, resistance to Grinding and machinability are better than steel.

Purification: The molten iron often contains harmful impurities such as oxygen and sulfur. These impurities will cause pores, cracks and slag inclusions in the casting, which will reduce the strength, toughness and plasticity of the material. The rare earth elements have strong binding ability with sulfur and oxygen, forming refractory compounds, which can play the role of desulfurization and deoxidation in molten iron. At the same time, rare earth can also eliminate the adverse effects of harmful elements such as Pb, Zn, Bi, etc. in molten iron.

Improve casting performance: The addition of rare earth to molten iron can significantly improve the fluidity of molten iron and reduce casting defects such as segregation and hot cracking.