The manganese in the original molten iron can play a certain role in desulphurization. The manganese and sulfur combine to form MnS and enter the slag to be removed. After spheroidization, the molten iron contains sulfur and has little oxygen. Sulfur oxygen and magnesium or rare earth can form stable compounds, and manganese no longer plays a desulphurization role. Therefore, a small amount of manganese in ductile iron can also play the role of alloy, giving full play to the role of stabilizing carbide and pearlite. Appropriate increase of manganese, due to promote pearlite increase and refinement, can improve the strength and hardness, but reduce the plasticity and toughness. High manganese content will lead to carbides and deterioration of mechanical properties.