Texture Development and Formability of Strip Cast 17% Cr Ferritic Stainless Steel

Abstract

In order to optimize the formability of ferritic stainless steel (FSS), control of the crystallographic texture is essential. In the present work, texture development of cast strips with different initial solidification structure during rolling and subsequent annealing and the formability of final sheets were investigated. Fully equiaxed and columnar grained cast strips of Fe17%Cr FSS were fabricated by a pilot twin-roll strip caster. The equi-axed and columnar grained bars cut from a conventional continuous cast slab were used as comparable specimens. It was shown that in the cold rolled and annealed sheet of fully equi-axed cast strip, uniform and strong g-fiber recrystallization texture was formed and {001}͗110͘ component was almost eliminated. By contrast, the recrystallization texture in the conventional sheets with equi-axed and columnar initial solidification structures exhibited typical shift towards high-index {334}͗483͘, which led to a reduced r-value as compared to that of the equi-axed cast strip. The final annealed sheet of fully columnar cast strip, however, showed weaker g-fiber recrystallization texture and lower r-value than those of conventional sheets. It is, therefore, believed that twin-roll strip casting can improve the formability of 17 % Cr FSS only under the precondition that appropriate solidification structure is obtained.KEY WORDS: ferritic stainless steel; twin-roll strip casting; solidification structure; texture; formability. ent strips in cold rolling and annealing were studied. Equiaxed and columnar bars were cut from a continuous cast slab, and hot rolling, hot band annealing, cold rolling and final recrystallization annealing were performed for both bars to simulate the industrial processes. The texture developments of the two bars were also studied and compared with those of cast strips to understand the evolutions of microstructure, texture and properties in the cast strips. Experimental ProceduresFe17%Cr FSS with a composition of Cr, 16.9; Ni, 0.114; C, 0.03; Mn, 0.154; Si, 0.243; P, 0.016; S, 0.004 (in mass%) was used. Cast strips were produced by using a pilot twinroll strip caster, in which the molten steel was poured into a preheated tundish under Ar shield to flow through a nozzle into the rotated water-cooled rolls.15) The casting speed was set up to be 0.25 m/s and the initial roll gap was set to be 1.5 mm to produce strips with thickness of about 1.8 mm. The pool melt temperature was measured by a thermo-detector installed above the melting pool. In the present work, pool melt superheats were controlled to be about 140 K and 20 K, respectively, to produce fully columnar and fully equi-axed cast strips, Fig. 1. The average diameters of columnar and equi-axed grains were about 400 mm and 200 mm, respectively. Both strips were cold rolled by using a laboratory rolling mill with a thickness reduction of 80 %, and were annealed at 860°C for 2 min.Columnar and equi-axed bars in the size of 250 Lϫ 110 Wϫ45 T (mm) were cut from a cast slab of Cr17 FSS, Fig. 2. The average...

Effects of rolling temperature on microstructure, texture, formability and magnetic properties in strip casting Fe-6.5 wt% Si non-oriented electrical steel

“…In the case of higher temperature (650-850°C) rolling, the stored energy at rolling and the boundary mobility (micro-growth of grains) decided the evolution of final annealing texture instead. It is known that, in bcc steels, the deformed γ-grains with high stored energy tend to preferentially form new recrystallized γ-grains in grain interiors and boundary regions in the early stage [31][32][33][34], which subsequently grow up and merge the adjacent non-recrystallized α-grains and λ-grains during annealing [18]. Thus, in the sheets rolled at 650°C, relatively strong rolled γ-fiber texture (Fig.…”

“…On the one hand, it can create extremely fine solidification microstructure owing to its relatively high cooling rate. On the other hand, it can generate desired microstructure and texture in the initial as-cast sheet [9][10][11][12][13][14], which has an influence on the evolution of microstructure and texture during rolling and annealing and the final properties [15][16][17][18][19][20][21][22]. Thus, it may be a new promising low-cost and compact way to produce 6.5 wt% silicon steel sheet by means of strip casting and rolling method.…”

Texture evolution and formability under different hot rolling conditions in ultra purified 17%Cr ferritic stainless steels

“…Ferritic stainless steels (FSSs) stabilized with micro-alloy elements such as Nb and/or Ti are finding wide applications in a number of areas due to their unique corrosion resistance and less expensive cost than austenitic stainless steels [1][2][3][4][5][6]. However, FSSs possess low formability in comparison with austenitic stainless steels, which may restrict the application of FSS, and hence extensive work should be carried out for improvement in formability.…”

Microstructure, Texture, and Deep Drawability Under Two Different Cold-Rolling Processes in Ferritic Stainless Steel

“…Furthermore, the formation of ridges is closely related to anisotropic plastic strain of grain colonies with similar orientations, although the ridging formation mechanism has not yet been adequately clarified ( . Improvement of the c-fiber recrystallization texture and grain colony distribution for FSSs has been attempted using several approaches, such as controlling the chemical composition, solidification structure, thermo-mechanical processing, annealing condition after hot-rolling and cold-rolling reduction ratio, introducing intermediate annealing during cold rolling, cross rolling, and spread rolling, employing the strip casting and changing the strain path by a unique deformation such as equal channel angular pressing ( Ref 5,[8][9][10][11][12][13][14]. Some studies have paid attention to modifying the characteristics of c-fiber recrystallization texture and spatial distribution of grain colonies through optimization of the cold-rolling process and introducing intermediate annealing during cold rolling.…”