Influence of B₂O₃ and Basicity of CaO–SiO₂–B₂O₃–Al₂O₃ Slag on the Saturation Concentration of Magnesium Oxide

The influence of boron oxide B₂O₃ and the basicity of CaO–SiO₂–B₂O₃–Al₂O₃ slag on the saturation concentration of magnesium oxide MgO is studied by means of simplex experiment-design lattices. That permits the formulation of mathematical models describing the dependence of the specific property on the composition in the form of a continuous function. Synthetic slags corresponding in composition to the vertices of the given simplex are produced in graphite crucibles from preroasted analytically pure oxides. The slag compositions corresponding to the other points of the local simplex design are obtained by cross-mixing of the slags at the vertices. The experimental data provide the basis for mathematical models describing the influence of the slag composition on the saturation concentration of magnesium oxide MgO. The results of mathematical modeling are presented as a graph of the slag composition against the saturation concentration of magnesium oxide MgO. By analysis of the results, new information is obtained regarding the influence of the boron oxide and the basicity of CaO–SiO₂–B₂O₃–Al₂O₃ slag on the saturation concentration of magnesium oxide MgO. It is found that, for slags formed in regions of basicity 2—3 with 1–3% B₂O₃, the saturation concentration of magnesium oxide MgO varies from 3 to 9%. Increase in the B₂O₃ content to 4% increases the saturation concentration of magnesium oxide MgO to 11–13%. Switching to slags of basicity 3–4 lowers the saturation concentration of magnesium oxide MgO to 2–5% with 1–3% B₂O₃ and to 7–9% with 3–4% B₂O₃ in the slag. Slag formation in the region of basicity 4–5 with 1–3% B₂O₃ does not significantly decrease the saturation concentration of magnesium oxide in the slag. In this basicity range, the saturation concentration of magnesium oxide MgO in the slag varies from 2 to 4% and hardly reaches 7% with increase in B₂O₃ content to 4%. In that case, the cost of the steel rises, on account of the increase in the consumption of lime and the material containing B₂O₃.