THE INFLUENCE OF ALUMINUM DEOXIDATION AND SULFUR-CONTENT ON OXIDE MODIFICATION AND MACHINABILITY OF STEEL

The influence of Al-deoxidation and various amounts of sulphur on Ca-treated steel has been investigated. The effect of sulphur and aluminium on the modification of oxide inclusions has been reasoned by theoretical thermodynamic equilibrium analysis. The type of inclusion formed depends on the aluminium and sulphur contents. For complete oxide shape control in which CaO-rich inclusions form, the sulphur content must be relatively low for Al-killed steel. The oxide inclusion type of the experiments was in surprisingly good agreement with the prediction of thermodynamics. The influence of calcium and sulphur on the machinability and mechanical properties has also been demonstrated as well as the improvement of isotropy in steel obtained by Ca-addition.