The effect of grain size and initial texture on microstructure, texture, and formability of Nb stabilized ferritic stainless steel manufactured by two-step cold rolling

Abstract

The present study investigated the influence of grain size and initial texture on the microstructure, texture, and formability of a niobium-stabilized ferritic stainless steel processed by two-step cold rolling. The characterization of the samples was performed by X-ray diffraction, electron backscatter diffraction, and tensile tests in order to evaluate the formability by the average normal anisotropy coefficient. The results showed that the reduction in grain size from 110 ± 21 to 50 ± 7 μm, in the hot rolled band, was favorable to obtain a more homogenous microstructure and smaller grain size after annealing. Coarse grain size and α-fiber (||RD) favored a strong α-fiber after cold rolling. In addition, γ-fiber (||ND) was more intense in the deformation texture of fine grain size samples. The recrystallization texture was constituted by intense γ-fiber (||ND) and weak θ-fiber (||ND) for both conditions. However, the reduction in grain size increased the γ-fiber fraction. Therefore, the r¯=1.92 and γ/θ = 8.12 were obtained to the sample originated from the initial fine grain size. The fine grain size and weak texture in the starting materials were effective in developing a high r¯ value in the samples manufactured by two-step cold rolling. Keywords: Ferritic stainless steel, Grain size, Texture, Formability, Two-step cold rolling