Impacts of Modification of Alloying Method on Inclusion Evolution in RH Refining of Silicon Steel

This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH) process of low-carbon silicon steel production. A more economical method, described as “pre-alloying”, has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7–4) inclusions nucleate on the surface of pre-existing 3FeO·MnO. Spherical FeO·zMnO (z = 3–5) is further evolved from shelled 3FeO·MnO by diffusion. Because these MnO-FeO inclusions float up into the slag before degassing, the pre-alloying process does not affect the quality of the melt in the end. Both carbon content and inclusion size conform to industry standards.