日本金属学会誌

J. Japan Inst. Met. Mater, Vol. 77, No. 10 (2013),
pp. 440-447

Mechanisms on the Occurrence of Surface Roughening in the High Purity Ferritic Stainless Steel Having Strong {111}< 112 > Texture during Deep Drawing

Ken Kimura1,2, Satoshi Hirose1, Kohsaku Ushioda2,3, Masaharu Hatano4 and Akihiko Takahashi4

1Steel Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, Futtsu 293-8511
2Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192
3Nippon Steel and Sumitomo Metal Corporation, Futtsu 293-8511
4Research & Development Center, Nippon Steel and Sumikin Stainless Steel Corporation, Hikari 743-8550

Abstract:

In high purity ferritic stainless steel having strong {111}< 112 > texture, the occurrence of surface roughening after deep drawing cup test depends on the way of taking blanks. However, the cause has not been clarified. In this study, the mechanism was examined in two ways. In the first method heterogeneous deformation behavior was examined by crystal plasticity (CP) analysis in which an adjacent two grains model was assumed. In the case that showed higher surface roughening, the direction of crystal rotation across the grain boundaries (GB) was almost the same and the dislocation density in the vicinity of the GB was higher than that in the area apart from the GB. In the case that showed lower surface roughening, crystals rotated in inverse direction across the GB and the dislocation density in the vicinity of the GB was lower than that in the area apart from the GB. In the second method the distribution of strain taking into account surface roughening was examined by EBSD. In the specimen with higher surface roughening, the area with high dislocation densities predicted by Kernel Average Misorientation (KAM) value was recognized along the GB and the convex region tended to coincide with the area with high dislocation densities. These results obtained from CP and EBSD analyses imply that the surface roughening depending on the way of taking blanks is associated with the strong {111}< 112 > texture and is caused by the accumulated dislocation density along the grain boundaries. [doi:10.2320/jinstmet.J2013030]


(Received 2013/4/30)

Keywords:

ferritic stainless steel, surface roughening, orange peel, crystal plasticity, texture, electron backscattering diffraction (EBSD) analysis, kernel average misorientation (KAM) value, crystal rotation


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