Effects of Initial Equiaxed Crystal Ratio in As-Cast Slab on Texture Evolution and Formability of Ferritic Stainless Steel

Abstract

In this study, as-cast ferritic stainless steel samples with columnar, equiaxed and mixed crystals were selected as initial specimens and subsequently subjected to various thermomechanical treatments, in order to investigate the effects of initial equiaxed crystal ratio on microstructure and texture evolution, final formability and ridging characteristics during subsequent processes. Results showed that the microstructures of samples with different initial equiaxed crystal ratios presented limited difference after appropriate cold-rolled annealing treatment at 880 °C and the grains were almost completely recrystallized and basically equiaxed. The texture of {111}//ND γ-fiber was mainly recorded in the final sheet, which was beneficial to improve formability. The sample with 50% initial equiaxed crystal ratio exhibited slightly rougher surface and larger ridging height after tensile straining of 20%, while Erichsen index values presented only 2.4% difference irrespective of initial equiaxed crystal ratio. It was found that initial equiaxed crystal ratio was not the main factor affecting final formability and ridging characteristics of ferritic stainless steel as limited difference was observed. Appropriate annealing treatment could improve textures and microstructures even if the initial structure contains typically mixed columnar-equiaxed grains.