冷間曲げした非均一組織を有するハイマンガン鋼のひずみと集合組織分布

Strain and texture distributions of high-Mn steel plate with heterogenous microstructure after cold bending

徐 平光   ; Jiang, L.*; Wang, H. H.*; Su, Y. H.  ; 浜 孝之*; 菖蒲 敬久  

Xu, P. G.; Jiang, L.*; Wang, H. H.*; Su, Y. H.; Hama, Takayuki*; Shobu, Takahisa

High-Mn steels are an economical option for the transport and storage of liquefied natural gas (LNG), offering excellent cryogenic properties. They are a promising alternative to the expensive high-Ni martensite and high-Ni-Cr austenite steels. However, obvious chemical segregation usually occurs during the mass production of such steel plates, and the strain distribution of the semi-finished products must be evaluated to enable wider industrial application. In this study, an experimental correction was performed on a cold-bent high-Mn steel plate using a stress-free comb steel sample cut from the same plate throughout its thickness. Neutron diffraction results revealed irregular diffraction angle distributions in both the cold-bent high-Mn steel plate and the stress-free reference sample, in all three directions (hoop, axial and radial). EPMA measurements confirmed that these irregular distributions were related to the heterogeneous microstructure induced by the chemical segregation. The irregular residual strain and Bragg-edge width distributions of the high-Mn steel plate also revealed the presence of macroscopic segregation bands. After correcting the heterogeneous microstructure using the stress-free reference sample, the triaxial strain distribution through the thickness of the cold-bent high-Mn steel plate was found to be similar with that of other cold-bent, homogenous steel plates.