C, Si: C can promote graphitization and reduce the tendency of white mouth, but a high amount of ω (C) will make the CE too high and easily cause graphite to float, generally controlled at 3.7%~3.9%. Si can strengthen graphitization ability and eliminate cementite. When Si is added as an inoculant, it can greatly reduce the supercooling ability of molten iron.In order to improve the inoculation effect, the amount of ω (Si) in the original molten iron was reduced from 1.3% to 1.5% to 0.8% to 1.2%, and the amount of ω (final Si) was controlled at 2.60% to 3.00%.
Mn: During the crystallization process, Mn increases the tendency of cast iron to overcool and promotes the formation of carbides (FeMn) 3C. In the eutectoid transformation process, Mn reduces the eutectoid transformation temperature, stabilizes and refines pearlite. Mn does not have much influence on the spheroidization rate. Due to the influence of raw materials, generally control ω(Mn)<0.30%.
P: When ω(P)<0.05%, it is solid-soluble in Fe, and it is difficult to form a phosphorus eutectic, which has little effect on the spheroidization rate of ductile iron.
S: S is a despheroidizing element. S consumes Mg and RE in the spheroidizing agent during the spheroidizing reaction, hindering graphitization and reducing the spheroidizing rate. Sulfide slag will also return to sulfur before the molten iron solidifies, again consuming spheroidizing elements, accelerating the decline of spheroidization, and further affecting the spheroidizing rate. In order to achieve a high spheroidization rate, the amount of ω(S) in the raw iron should be reduced to less than 0.02%.