INFLUENCE OF TEXTURE ON SURFACE-ROUGHENING DURING PRESS FORMING IN Ti ADDED HIGH PURITY FERRITIC STAINLESS STEEL SHEETS

Ferritic stainless steels have been widely used recently: However, "surface-roughening", which is one of the most harmful defects that arises during forming, often occurs. Generally, surface-roughening becomes apparent in steels having large grain sizes. Since in the case of high purity ferritic stainless steels surface-roughening occurs in spite of small grain sizes, it is considered to be related to the textures of the sheets. So the influence of initial textures on surface-roughening was investigated using Ti added high purity stainless steel sheets having two types of different textures. The magnitude of surface-roughening was affected by initial textures. Shear bands were observed uni-directionally in the sample with severe surface-roughening, while shear bands were extended in two directions in the sample with small surface-roughening. According to the analysis of textures, the shear band morphology strongly depended on the directions of crystal rotation in the surface area during forming. These results indicate that initial texture influenced the direction of crystal rotation during forming, resulting in the different shear band morphologies depending on the texture, which should be the main factor for the surface-roughening.