Effect of Strain Partitioning on the Microstructure, Texture, and Ridging Resistance of Ferritic Stainless Steel in Two-Stage Cold Rolling

The microstructure and texture evolution of ferritic stainless steel (FSS) during two-stage cold rolling and surface ridging along the rolling direction (RD) were investigated. The thickness reductions of the final annealed sheet prepared by low cold rolling in the first stage and high cold-rolling in the second stage exhibited larger grain sizes (approximately 54.99 μm) and inhomogeneous γ-fiber textures (presence of distinct strongest peaks {111}<112>). In contrast, increasing the first-stage cold-rolling thickness reduction significantly decreased the recrystallized grain size (approximately 11.94 μm) and enhanced the uniformity of the γ-fiber texture in the final sheet. The final sheet recrystallization grain size decreased and then increased, level of homogeneity of the γ-fibers gradually increased, and strength gradually decreased as functions of the first-stage cold-rolling thickness reduction. Ultimately, a strain value (approximately 0.69) was selected in the first stage that ensured appropriate strain partitioning (1:2.2) to obtain an excellent microstructure and texture of the final FSS sheet and to enhance the ridging resistance in the two-stage cold-rolling process. Furthermore, the ridging behavior of large-sized (grains larger than 1.5 times the average size) and oriented grain colonies are discussed in detail. In addition to the conventional orientation of grain colonies, large-sized grain colonies can deteriorate the surface ridging.