Evolution rules of inclusions in high quality bearing steel produced by LF-VD process

High quality GCr15 steel produced by EAF-LF-VD-CC process was systematically studied by sampling in various sta-ges for a domestic factory. For the random characteristics of DS inclusions, the evolution rules of inclusions in bearing steel smelting process were investigated by ASPEX inclusion quick analysis equipment, which can scan the specimen surface in large enough area. The results indicate that the main inclusions are MgO-Al₂O₃-CaO and MnS, and there are also a small quantity of SiO₂-Al₂O₃ and MgO-Al₂O₃. The size of the majority of inclusions is 3-8μm, few DS inclusions have a large size range, the biggest one can be more than 70μm, and the morphologies of the inclusions are round or nearly circular. Inclusions will be significantly removed by VD process and the content of CaO in inclusions increases after VD process. The content of Al₂O₃ in inclusions increases during the tundish to continuous casting process. Finally, the content of Al₂O₃ in inclusions is more than 80%, the content of MgO is less than 20%, and the content of CaO is less than 5% in the ternary system of MgO-Al₂O₃-CaO. The formation and removal behaviors of DS inclusions in bearing steel are of higher degree randomness.