Thermal simulation study on the effect of ladle glaze on inclusions and refractories during the smelting process of Si-Mn killed spring steel 55SiCr

Ladle glaze is considered to be one of the major sources of non-metallic inclusions in steel. The effect on inclusions of molten steel and the corrosion behavior of MgO-C refractory by ladle glaze in the production process were simulated by laboratory 1 kg Si 2 Mo resistance furnace. The results show that the content of T.O in steel increases with the increase of basicity of glaze layer and ladle use times. The mixed use of ladles (Ladles for Si killed and Al killed steel) and the use of ladles for Al killed steel can significantly increase the Al content in steel, and using special ladle for Si killed steel is beneficial to the control of T.O and Al. The inclusions in the experimental steel are predominantly SiO 2 –Al 2 O 3 –MnO–(MgO), in which the proportion of Al 2 O 3 increases with the increase of basicity of glaze, whereas the proportion of MgO is the highest when mixed use of ladles, and increases with the increase of ladle use times. Thermodynamic calculation results show that the MnO component in inclusions is gradually replaced by Al 2 O 3 , resulting in Al 2 SiO 5 inclusions. The glaze of special ladle has low interfacial tension with MgO in refractory material, and it is easy to react with MgO, which causes strong penetration and chemical corrosion on MgO-C refractory materials, so it will reduce the service life of refractory materials. However, special ladle is beneficial to the control of vital elements and inclusions in spring steel. The mixed use of ladles will cause structural spalling of refractory materials and significantly increase the number density of inclusions in steel. The use of ladle for Al killed steel is advantageous to the protection of MgO-C refractory materials, but it will increase the proportion of Al 2 O 3 in inclusions. Special ladle is recommended when smelting outstanding performance Si-Mn killed valve spring steel to reduce the influence of hard and brittle inclusions on the fatigue life of valve springs.