Effect of cooling rate on solute microsegregation and MnS inclusion precipitation and growth behaviour

Manganese sulphide (MnS) inclusions significantly influence the mechanical properties, processability and service durability of steel. Consequently, controlling the formation and evolution of these inclusions is crucial for enhancing the overall performance of steel products. Current studies primarily concentrate on modifying molten steel composition, alloy additions and process parameters, while limited attention is paid to the growth kinetics of MnS inclusions. Therefore, it is necessary to study the microsegregation of solutes and the precipitation and growth behaviour of MnS inclusions during the cooling and solidification process of molten steel. This article develops a coupled model integrating solute microsegregation with MnS precipitation and growth, evaluates common microsegregation models, and identifies the most appropriate one. The results show that, as the Voller–Beckermann (VB) model takes into account the influence of multiple components, dendrite coarsening on the concentration distribution of solute components and phase transformation and other factors, this model is more suitable for predicting the microsegregation of solutes and the precipitation and growth of MnS inclusions. Predictions show that higher cooling rates result in a smaller size of MnS inclusions and a greater accumulated amount of MnS. The precipitation temperature is also raised, which leads to the premature precipitation of MnS inclusions.