低炭素Ni-Cr-Mo鋼におけるマルテンサイトと残留フェライト二相混合組織の静的引張性質について
1977 年 63 巻 8 号 p. 1321-1330
詳細
1977 年 63 巻 8 号 p. 1321-1330
A study has been made of static tensile properties of mixed structure of martensite and residual ferrite in Ni-Cr-Mo steels containing low carbon. Results obtained are as follows:
(1) Both of the strength and ductility were approximately specified by volume fraction of residual ferrite.
(2) The 0.2% proof stress gradually deviated from the law of mixture with an increase in residual ferrite at 200°C temper, but approximately followed it at 600°C temper.
(3) Reduction in area gradually decreased at 200°C temper, but somewhat increased at 600°C temper with an increase in residual ferrite.
(4) From the analyses of true stress-true strain diagrams and microfractographs, it is considered that residual ferrite, when it appeared in lower tempered martensite, has a detrimental effect on ductility, because the residual ferrite in a low fraction fractures in a brittle manner due to plastic restraining of it by surrounding martensite matrix in the process of plastic deformation, and that with increasing in the residual ferrite both of the martensite matrix which become to be more brittle and the residual ferrite fracture in a brittle menner.
