Thermomechanical Processing of Steel –Past, Present and Future–

After ausforming appeared as the first thermomechanical processing of steels in the first half of the 1960 s, various thermomechanical processings have been developed for the improvement of mechanical properties over the last fifty years. Their application was mainly to martensitic steels in the 1960 s such as ausforming and TRIP, and moved to ferrite (+ pearlite) structures by the development of controlled rolling and accelerated cooling of HSLA steels in the 1970 similar to 4980 s. However, recently, interest has returned to martensite (and also bainite) because of the demand for higher strength, and the ausforming and TRIP have been revived and successfully applied to commercial practice. Very recently, severe plastic deformation (SPD) is the focus of attention as a new method of producing a very fine-grained structure with grain size of less than 1 mu m. By the application of SPD, dynamic phenomena such as dynamic recrystallization and dynamic ferrite transformation occur in the process. We need more systematic studies on such phenomena for the development of new type of thermomechanical processing in steels.