Physico-chemical aspects of the behaviour of inclusions in steels

Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with a precise control of the composition, morphology and plasticity of oxide and sulphide inclusions that remain in the product. In liquid metal, the composition of complex inclusions can be monitored by appropriate deoxidation practice, calcium treatment and/or slag-metal reaction. Further transformation may occur during solidification or heat treatments prior to hot-rolling: reaction between oxides and sulphides, as well as crystallization of oxides. An analysis of these factors, and of tools (thermodynamic models and laboratory experiments) which have been developed to comprehend and control them is presented.