Analysis and Control of Subsurface Inclusions of the Mould-Casting Bearing Steel

Continuous transverse wave alarm occurred to the mould-casting bearing steel during the automatic immersion-ultrasonic detection. Chemical composition analysis, macrostructure and non-metallic inclusion examination, scanning electron microscope and energy spectrum analysis were used to analyze the mechanism and causes of the defects. The results show that:the defects of the mould-casting bearing steel detected by ultrasonic were subsurface inclusions; the subsurface inclusions included the oxide of aluminum, silicon, calcium, and a small amount of the oxide of sodium, potassium and other elements; the cause of subsurface inclusions was that the protective slag was brought into the liquid steel in the casting process. The generation of such defects could be effectively avoided by measures such as slinging slag and baking slag.