Grain Refinement in Austenitic Stainless Steel during Warm Screw Rolling

Abstract

The development of dynamic recrystallization in a 304-type austenitic stainless steel during warm multi-pass screw rolling was studied. The fraction recrystallized depended significantly on the distance from the centre of rolled rods. The highly elongated original grains were mainly observed in the centre of processed samples, while the portions close to the sample edge were characterized by relatively fast development of dynamic recrystallization leading to formation of almost equiaxed fine grains with a size of about 1 μm. The volume fraction of fine grains in the edge areas increased with straining and exceeded 0.7 after rolling to 63% cross area reduction. The structural mechanism responsible for the grain refinement was considered as continuous dynamic recrystallization. The difference in the recrystallization kinetics across the sample is associated with the variation in strain intensity.