ASYMMETRIC CRYOROLLING OF THE AUSTENITIC STAINLESS STEEL AISI 304

The ultra-fine grained austenitic AISI 304 stainless steel sheets were prepared using various rolling techniques. The room temperature symmetric rolling (SR) as well as the sub-zero temperature cryorolling (CR) were performed. In addition to conventional rolling techniques the asymmetric rolling (ASR) and the asymmetric cryorolling (ACR) experiments were set up. Different rolling techniques were compared with regard to the resulting mechanical properties and feasibility. In comparison with the symmetric rolling, the asymmetric rolling process imposes additional shear strain to the normal plane strain. A large plastic strain has a direct influence on the process of the grain refinement. Cooling the steel to the sub-zero temperatures supresses the dynamic recovery and recrystallization, thus improving the grain refinement process. A high velocity ratio ACR (1:2.3) and the CR (liquid N2) techniques give rise to the austenitic stainless steel with high values of the yield strength, the tensile strength and the ductility at the same time.