Effect of Ce–Mg–Fe Alloy Adding Timing on Formation and Evolution of Inclusions in SCr420H Gear Steel

Abstract

In the present study, the effect of different adding time of Ce–Mg–Fe alloy during the refining process was investigated by laboratory experiments and equilibrium thermodynamic calculation. In experiments, samples from different stages were analyzed by SEM-EDS and EPMA for revealing the evolution mechanism of inclusions. Combined with thermodynamic calculation, results indicated that different adding time can affect the yield of Ce and Mg in steel directly, and the difference of types of inclusions in as-cast samples was caused. CaO-containing inclusions as a main type of inclusions in the refining process can be modified by Ce after adding Ce–Mg–Fe alloy. A high Ce content can promote the formation of Ce–S and Ce–O–S in steel and suppress the precipitation of MnS. In consideration of microalloying effect, Ce–Mg–Fe alloy should be added at a later stage of steelmaking process for ensuring a certain content of Ce and Mg.