Evaluation of strain distribution in cold bent high-Mn steel plate with heterogenous microstructure

不均一組織を有する冷間曲げ高Mn鋼板のひずみ分布評価

徐 平光   ; 蒋 立*; Zhang, S. C.*; 那須 翔太*; Su, Y. H.  ; 岩本 ちひろ*; 王 紅鴻*; 浜 孝之*; 菖蒲 敬久  

Xu, P. G.; Jiang, L.*; Zhang, S. C.*; Nasu, Shota*; Su, Y. H.; Iwamoto, Chihiro*; Wang, H. H.*; Hama, Takayuki*; Shobu, Takahisa

For achieving the carbon neutralization through reducing the greenhouse gas emission, the liquefied natural gas (LNG) has been widely employed as the fuel for electric power plants. As an economical cryogenic steel for LNG transport and storage, high-Mn steels with excellent cryogenic strength-ductility-toughness performance have been paid much attention for a high possibility to replace expensive high-Ni martensite steels and high Ni-Cr austenite steels. However, in the mass production of such steel plates, high manganese steels usually exhibit obvious chemical segregation, and omitting such heterogeneous microstructure distribution may bring significant uncertainty in the quantitative residual strain distribution evaluation of the related semi-finished parts. In this research, the numerical correction of a strain-free comb steel sample cut from same high-Mn steel plate was performed throughout the plate thickness using gradient-distributed neutron diffraction patterns. Our experimental results from RESA triaxial strain measurement together with microstructure observation confirmed that the through-thickness strain distribution in high-Mn cold bent steel plate is similar to that in other cold bent steel plates. This is justified by the fact that no transformation induced plasticity phenomenon occurs at 10% cold bending.