Purifying 7CrSiMnMoV Steel from Scrap Modified with Rare Earth Cerium Alloying

Abstract

It is crucial to control the sulfur and oxygen in the steel liquid to produce high-cleanliness rare earth steel. This study attempted to investigate the effect of rare earth Ce content on purifying the produced 7CrSiMnMoV steel from scrap steel by modified rare earth inclusions based on a proposed integrated process of high-alkalinity refining slag desulfurization, Si–Mn deoxidation, Al-enhanced deoxidation, and rare earth Ce alloying. The results show that the evolution mechanism of rare earth inclusions is 25% Al₂O₃⋅25% MgO⋅50% Ce₂O₃ → 25% Al₂O₃⋅75% Ce₂O₃, 12.5% Al₂O₃⋅MnS⋅Ce₂O₂S → Ce₂O₃, Ce₂O₂S → Ce₂S₃, Ce₂O₂S → (Mn Ce)₂S₃, Ce₂O₂S, with the rare earth Ce-added content of 0.009%, 0.012%, and 0.100%, respectively. And rare earth Ce can improve the cleanliness of steel liquid by controlling the rare earth Ce-added content to form the M1-Ce₂O₃ (M1 is Al, Mg, etc.) and M2-Ce₂SO₂ (M2 is Ca, Mn, etc.) rare earth inclusions; the oxygen and sulfur concentrations can reach 0.0031% and 0.0026%, respectively, with a rare earth Ce content of 0.012%. However, excessive amounts of rare earth Ce could deteriorate the cleanliness of steel liquid.

Graphical Abstract

To produce 7CrSiMnMoV rare earth steel by scrap steel based on an integrated process of high-alkalinity refining slag desulfurization, Si–Mn deoxidation, Al-enhanced deoxidation, and rare earth Ce alloying and purifying steel liquid.Purifying 7CrSiMnMoV rare earth steel liquid by modified rare earth inclusion.Rare earth Ce can improve the cleanliness of steel liquid by controlling the rare earth Ce-added content to form M-Ce2O3 (M is Al, Mg, etc.) and M-Ce2SO2 (M is Ca, Mn, etc.) rare earth inclusions; the oxygen and sulfur concentrations can reach 0.0031% and 0.0026%, respectively, with a rare earth Ce content of 0.012%.