著者

古谷 仁志 田川 哲哉 石川 孝司

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.100, no.5, pp.678-687, 2014 (Released:2014-04-30)

参考文献数

23

被引用文献数

2

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Tensile behaviors of cryogenic steels, which contain 0 to 12wt% nickel, were examined to obtain the fundamental knowledge related to the role of retained austenite in the improvement of fracture toughness. Although retained austenite of 8% and 12% nickel steel, which were manufactured by the special heat treatment composed of quenching, intermediate heat treatment, and tempering, was stable under the deep cooling at –196 ºC, it transformed to martensite by straining around 10% at –196 ºC. The strain hardening behavior was divided into two categories. One is that the maximum strain hardening appears just after yielding, then the strain hardening gradually decreases with increasing strain. It was related to 0% to 2% nickel steels, which include less retained austenite. Another is that the strain hardening increases just after yielding with the increase of strain, then it gradually decreases. In this case, higher strain hardening was derived. It was related to 5% to 12% nickel steels which included a certain amount of retained austenite. The increase of strain hardening under low temperature was attributed to the solute nickel and the formation of martensite, which act as a hard second phase, by the work induced martensitic transformation.

著者

田川 哲哉

出版者

一般社団法人 溶接学会

雑誌

溶接学会誌 (ISSN:00214787)

巻号頁・発行日

vol.77, no.4, pp.304-311, 2008 (Released:2012-10-05)

参考文献数

19

被引用文献数

2

著者

北野 智靖 田川 哲哉 粟飯原 周二 Mirco Daniel CHAPETTI 宮田 隆司

出版者

The Iron and Steel Institute of Japan

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.83, no.6, pp.401-406, 1997-06-01 (Released:2009-06-19)

参考文献数

19

被引用文献数

2 1

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The influence of microstructure on non-propagating behavior of fatigue crack below the fatigue limit was investigated using low carbon steels with three different microstructures simulated heat affected zone of welds. Notched round bar specimens with different stress concentration factors were fatigued under axial loading at the stress ratios R=-1 (tension-compression). Fractographic and metallographic observations of non-propagating cracks at the stress level below fatigue limit were examined, and correlation between non-propagating crack and microstructures was investigated. Non-propagating cracks could be classified as Stage I or Stage II, depending on the microstructure and notch root radius. In the case of dull-notched specimens, where the notch factor in fatigue is proportional to stress concentration factor, the non-propagating crack is Stage I type regardless the microstructure, although Stage II type cracks were observed in sharp notched specimens for particular materials. The criteria for both Stage I and Stage II type non-propagating crack were discussed on the basis of the point stress model and fracture mechanics.