Research on the Evolution of Inclusions in LX72A Steel Produced by LD-LF-CC Process

By using the thermodynamic calculation,systematic sampling from BOF,LF,tundish,casting billets and the wire rod combined with SEM analysis,the type and amount of inclusions as well astotal oxygen content and the nitrogen content in LX72 A steel which produced by LD-LF-CC process have been investigated and measured at various production steps. The results show that the type of inclusions at the end of BOF is mainly Al₂O₃-SiO₂-MnO. After LF treatment,the inclusions translates into spherical Al₂O₃-SiO₂-CaO-MgO particles which have a low melting point and easily floating up. At the stage of wire rod production the inclusions evolves into Al₂O₃-SiO₂-CaO-MgO system. The amount of inclusions in tundish and casting billets decrease dramatically,indicating that changing basicity benefits to inclusions modification. The total oxygen content was 25×10^-6 and the nitrogen content was 40×10^-6 in the wire rod,which meets the requirements for steel cord.