Microstructure formation in rapidly solidified AISI 304 stainless steel strip

It is recognised that the solidification sequence in austenitic stainless steels during strip casting plays an important role in the tendency to hot cracking. In order to investigate the competitive growth between the stable ferrite phase and the metastable austenite phase to optimise the microstructures obtained by strip casting, experiments using symmetrical water-cooled copper mould were designed to simulate strip casting of AISI 304 stainless steels. It was found that primary phase transition from stable ferrite (delta) to metastable austenite (gamma) takes place adjacent to the surface of the strip due to high heat extraction rate. Phase selection theory, based on the criterion of the highest interface temperature, was used to explore the primary phase prediction. The experimental results are compared with the theoretical predictions.