As a nickel-saving stainless steel, ferritic stainless steel has excellent cost and recyclable advantages. However, it has some special properties, such as magnetism, low thermal expansion, excellent high-temperature oxidation resistance, high thermal conductivity, excellent creep resistance, not prone to stress corrosion cracking (SCC), easily cutting and forming, and so on. It is stated that ferritic stainless steel can also be used as an substitute for some carbon steels because of its special durable and low-maintenance advantages. [1] With high purification and alloying design, some ferritic stainless steel grades were developed recently to possess comparable corrosion resistance as AISI 304 or even AISI 316 austenitic stainless steels. [2,3] One problem that restricts the application of ferritic stainless steel is surface quality. After deep drawing or stretching, ferritic stainless steel sheet usually forms an undulation surface morphology, i.e., surface ridging. The deformed sheet displays a corrugated surface, with ridges on one side coinciding with troughs on the opposite side, deteriorating the surface quality, and increasing the polishing cost. [4] Some fluid or dirty chemicals would accumulate at the concave regions, resulting in a severe corrosion tendency. Especially, for recent years, due to the promotion of application fields and amounts of usage, attentions have been increasingly focused on the surface ridging behavior of this kind of steel. [5-7] Surface ridging is normally supposed to be generated by the different plastic deformation responses occurring for the grains with different crystal orientations. Ferritic stainless steel composes a single phase steel when the Cr content is higher than 17 wt%; i.e., no phase transformation occurs at high temperatures. Thus, the solidification structure with columnar and big grains can only be refined through deformation and recrystallization during hot/cold rolling and annealing processes to some extent. As a result, ferritic stainless steel often exhibits intense recrystallization texture after final annealing. [8,9] Meanwhile, the crystallographic orientations distribute inhomogeneously in mesoscale, because they are evolved from the grains with different initial orientations. Sinclair et al. (2003) reported that some columnar grains with <001>//normal direction (ND) orientations possess low Schmid factors and store less energy for subsequent recrystallization process, resulting in texture inhomogeneity. [10] These micro-textures would cause heterogeneous distributed strains in mesoscale during deformation, leading to the formation of surface ridging. Numerous researches have been devoted to improve the surface quality through optimizing the processing technology. For example, Lee et al. recently reported a method that reducing the grain size of as-cast state by increasing nitrogen can reduce the surface
