EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Effects of the slags on the total oxygen contents and Ds formation in bearing steel were investigated by vacuum induction furnace experiments. The optimal middle basicity slags for VD treatment was selected in the range the CaO to SiO2 content ratio of 3~4, and the CaO to Al2O3 ratio of 1.6~1.8, resulting in lower total oxygen contents and less Ds inclusions. Evolution of inclusions in bearing steel during the practical LF-VD treatment was observed. It is found that more calcium aluminates Ds inclusions appears after VD treatment due to steel and slag intensive mixing and reacting resulting in calcium content of molten steel increasing and CaO content in inclusions enhanced. The Ds inclusions observed in the finished products derived from the endogenous inclusions, the entrapped inclusions aggregated under the covering agent and entrapment of ladle slag. Combining the experiments results and the inclusions observation,the Ds inclusions can be controlled less by controlling slag, depressing the entrapment of inclusions aggregated under the covering agent and ladle slag.