Effect of Lining Refractory and High-Basicity Slag on Non-Metallic Inclusions in a High Carbon Al-killed Steel

Laboratory experiments on the effect of lining refractory and high-basicity slag on non-metallic inclusions in a high carbon Al-killed steel were carried out. Alumina inclusions in the steel could hardly be affected by the Al2O3 refractory, however, would be transformed into MgO · Al2O3 when the MgO refractory was used. After the steel-slag-MgO lining-inclusion reaction, the high-basicity slag was saturated with MgO due to the dissolution of MgO from the refractory into the slag, meanwhile, original Al2O3 inclusions were transformed into MgO via MgO · Al2O3, regardless of the slag basicity. After the steel-slag-Al2O3 lining-inclusion reaction, the CaO/Al2O3 ratio of slag decreased significantly due to the dissolution of Al2O3 refractory into the slag, resulting in the slight increase of the magnesium content in steel and the transformation of Al2O3 inclusions into MgO · Al2O3. The reduction of the MgO in the lining refractory and top slag by the dissolved aluminum ([Al]) in molten steel occurred independently, and a higher CaO/Al2O3 ratio of slag would result in a higher activity of MgO, which was beneficial for the reduction of MgO. The CaO in the slag was hardly reduced by the [Al] in the molten steel, thus, it was proposed that CaO-Al2O3 type inclusions could hardly be generated from the steel-slag reaction during the production of high carbon Al-killed steels.