日本金属学会誌

J. Japan Inst. Met. Mater, Vol. 82, No. 02 (2018),
pp. 52-57

Effect of Initial Grain Size Prior to ECAP-Cold Rolling Processing on the Riding and Formability of Ferritic Stainless Sheets

Mitsuaki Adachi 1, Motohiro Yuasa 1, Hiroyuki Miyamoto 1, Hiroshi Fujiwara 2 and Masaharu Hatano 3

1 Department of Mechanical Engineering, Doshisha University
2 Department of Mechanical Engineering, Shizuoka Institute of Science and Technology
3 Nippon Steel & Sumikin Stainless Steel Corporation

Abstract:

Equal-channel angular pressing (ECAP) was applied to hot-bands by one pass prior to cold-rolling and annealing in order to modify the texture, and improve the ridging and formability of ferritic stainless steel sheets. The present study focuses on the effect of initial grain size before ECAP, using the samples having extremely large grain size of 210 μm and smaller ones of 30 μm. The final grain sizes of cold-rolled and annealed sheets were about 30 μm for both processes. It was found that Rankford value (r-value) of large grain size was higher compared with that of smaller one while ridging was alleviated in the latter. The recrystallization temperature of cold-rolled sheets was about 50°C lower in the larger grain size. It is considered that higher density of grain-scale shear bands in the sample of larger grain size promotes recrystallization and reduction of <001>//ND grains and increase <111>//ND grains, resulting in higher r-value. However, coarser arrangement of <001>//ND colony parallel to the rolling direction in large grain size may causes higher ridging in spite of the lower fraction <001>//ND grains.

[doi:10.2320/jinstmet.J2017044]


(Received 2017/09/27)

Keywords:

severe plastic deformation, equal-channel angular pressing, ferritic stainless steel, texture, shear band, Rankford value, ridging


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