Effect of CaO–Al₂O₃–SiO₂–MgO(–CaF₂) refining slag system on inclusions in silicon–manganese deoxidized spring steel

Abstract

In order to make the refined slag match various grades of spring steel, high-temperature equilibrium experiments were conducted in the laboratory to study the effect of CaO–Al2O3–SiO2–MgO refining slag with varying basicity, Al2O3 content, and CaF2 additives on inclusions containing Al (Al2O3) in silicon–manganese-deoxidised steel. The results show that the control effect of low basicity refining slag on inclusions is better than that of high basicity slag. The soluble aluminium increases with the increase of the basicity of steel slag and the Al2O3 content in inclusions is positively correlated with the Al2O3 content in slag. When the relative adsorption capacity of the refined slag is 6 × 10−3, the area density of Al-containing inclusions in steel is at a low level. Low basicity slag with low Al2O3 is good, and it is more suitable for producing high-end spring steel. To produce middle- and low-end spring steel, the refining slag system with a basicity of about 2–2.5, Al2O3, MgO, and CaF2 content is about 10% can be used. Among them, a small amount of CaF2 improves the liquidity of steel liquid, improves its relative adsorption capacity to Al-containing inclusions, and can control the production of Al-containing inclusions in the steel.