Inclusions in steel: micro-macro modelling approach to analyse the effects of inclusions on the properties of steel

The performance requirements of steel sheets are becoming increasingly stringent. Inclusions present as nonmetallic phases affect the mechanical properties and workability in the down-stream processes of the sheet production adversely. By knowing how the inclusions affect the properties, suitable process parameters can be identified to avoid the defects formation during the forming operations. A very small size of the inclusions necessitates their behavioural study at the micro-scale. This requires a micro-macro modelling approach to identify the effects of the inclusions on forming operations such as hot rolling. In this work, a comprehensive micro-macro model is presented to quantify the effects of the inclusions and their characteristics on the properties of steel during solidification and forming. A micro-model developed using 2-D Finite Element Method is used to study void formation and its evolution at the inclusion/matrix interface (interfacial damage) and stress evolution in and around the inclusions. The model is then employed to study the effects of inclusion properties (hard/soft), its size and shape on the properties of the steel matrix. The constitutive equation for the macro-scale simulation of hot rolling is updated based on the findings of the micro-model. The modified constitutive equation at the macro-scale will allow the choice of a suitable process-parameters regime that will avoid failure during hot rolling and also lead to improved final properties in steel containing inclusions.