著者

藤井 秀樹 大宮 慎一

出版者

一般社団法人 日本高圧力技術協会

雑誌

圧力技術 (ISSN:03870154)

巻号頁・発行日

vol.47, no.2, pp.85-94, 2009-03-25 (Released:2009-04-27)

参考文献数

11

被引用文献数

2

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To accelerate the construction of hydrogen energy society featuring fuel cell vehicles by enlarging the kinds of materials safely used in hydrogen circumstances in addition to JIS SUS316L, several steels having Ni contents lower than SUS316L and Cr contents equivalent to SUS316L are prepared and their tensile properties in high pressure gaseous hydrogen are investigated at room temperature and -40°C. [Ni]+0. 35[Cr] ([Ni] and [Cr] are their concentrations in mass%) is proposed as an indicator to properly indicate whether hydrogen environmental embrittlement (HEE) occurs or not in45MPa hydrogen gas at both temperatures. HEE is basically related to strain-induced martensite having bcc crystallographic structure. However, there are some steels which do not exhibit any significant HEE although noticeable amount of martensite phase forms. In this case, HEE mainly occurs at the later stage of deformation just before fracture. Steels containing more than 12mass% Ni including SUS316L do not show HEE if there is not serious segregation of alloying elements such as Ni, Cr, Mo. It is also indicated that SUS316 probably do not show HEE if more than 12mass% Ni is contained. Furthermore, steels having Ni content close to 10mass%, which corresponds to the lower limit of the standard of JIS SUS316 and AISI 316L, have considerably higher resistance against HEE compared to SUS304 based steels although HEE occurs at the late stage of deformation. It may be possible for them to be used in high pressure hydrogen circumstances if temperature range at which they are used is fully taken into account and small level of HEE is acceptable.

著者

松本 和久 秦野 正治 大宮 慎一 藤井 秀樹

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.103, no.1, pp.54-63, 2017 (Released:2016-12-31)

参考文献数

40

被引用文献数

4 5

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To investigate an effect of internal hydrogen on mechanical properties of a new austenitic stainless steel “STH2” having a nominal composition of Fe-15%Cr-9%Mn-6%Ni-2.5%Cu-0.15~0.2%N, tensile tests and fatigue crack growth tests were conducted for the specimens containing around 80 ppm hydrogen charged by the exposure in 45 MPa hydrogen gas at 300˚C for 200 h and the ones heat treated in air with the same heat pattern.At room temperature and –40˚C, no significant ductility drop by hydrogen charging was observed and about 80% of relative reduction of area was obtained, which is the same as that of JIS SUS316L with the same amount of internal hydrogen. In the specimens tensile tested at –40˚C, a small quantity of quasicleavage fracture surfaces were observed. In the banded areas in which Mn, Ni and Cu were negatively segregated, some relatively coarse voids coalesced with cracks extended along the maximum shear stress plane, which is similar to what is called void-sheet type of fracture. It is quite different from the case for tensile tests in 90 MPa hydrogen gas, in which coarse longitudinal cracks form, suggesting that the concentration of hydrogen at crack tips in 90 MPa hydrogen gas is higher than 80 ppm. It was also confirmed that fatigue crack growth rates were not accelerated by 80 ppm internal hydrogen although some faceted fracture surfaces composed of (111) γ formed.It is confirmed that STH2 has excellent properties not only in high pressure hydrogen gas but also in the circumstance of internal hydrogen of around 80 ppm.