Inclusion Formation in Si-Mn Killed Steel Exposed to Al-containing MgO-C Refractory Under Vacuum Conditions

摘要

Si-Mn killed steel for saw wire and valve spring applications, is very sensitive to hard and non-deformable Al_2O_3-rich inclusions. These inclusions are very likely to cause crack initiation and strongly impair the drawability of saw wire and fatigue restraint properties of valve springs. To avoid the generation of Al_2O_3-rich inclusions, a technology of Si-Mn deoxidation combined with low basicity top slag refining is widely applied in the production of both saw wire and valve spring steels. This technology has also been employed to limit the [Al] content in saw wire steel to a very low level (0.0005 wt-%). However Al_2O_3-rich inclusions were still detected in the wire rod and large-sized Al_2O_3-rich inclusions were frequently observed on the fracture surface of saw wire (Fig. 1). In order to avoid the generation of these Al_2O_3-rich inclusions, this study was designed to investigate their potential source.