HOT-WORKING CHARACTERISTICS OF STEELS IN AUSTENITIC STATE

The behavior of C, HSLA, tool and stainless steels in the austenitic condition during industrial hot forming is reviewed. In the constitutive relations, it is primarily the activation energy which rises with alloy additions. Strain hardening is reduced mainly by dynamic recovery as indicated by its stress dependence and confirmed microscopically in the austenitic stainless steels. Dynamic recrystallization provides additional softening, possible grain refinement and enhanced ductility. After deformation, the metal undergoes static recovery and static recrystallization at longer times to provide grain refinement and stress reduction in any following stage. With rapid cooling, it is possible to retain either hot-work substructures in elongated grains or fine new grains which strengthen the product directly or through refined ferrite.