日本機械学会論文集
Online ISSN : 2187-9761
ISSN-L : 2187-9761
材料力学,機械材料,材料加工
転位の水素トラップ占有率に基づく高圧水素ガス中における水素拡散特性と各種破壊特性の統一的解釈―オーステナイト系ステンレス鋼と低合金鋼
松岡 三郎髙桑 脩岡崎 三郎吉田 聡子山辺 純一郎松永 久生
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2020 年 86 巻 888 号 p. 20-00172

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A binding energy, EB, and the number of trap sites, NX, of hydrogen trapped in cold-rolled austenitic stainless and quenched-tempered low alloy steels exposed in high-pressure hydrogen gas were determined from a linear relationship between the concentration of the trapped hydrogen, NHX, and the trap-site occupancy, θX, which is a function of EB and NX, being calculated from the Oriani’s local equilibrium theory. The determinations identified that EB = 28 kJ/mol and NX = 2.12×1025 /m3 for 30% cold-rolled SUS316L (heat of B); EB = 28 kJ/mol and NX = 3.83×1025 /m3 for 60% cold-rolled SUS316L (heat of B); EB = 24 kJ/mol and NX = 2.29×1025 /m3 for 30% cold-rolled SUS304 (heat of B); EB = 43 kJ/mol and NX = 2.68×1024 /m3 for SCM435 (heat JL); EB = 42 kJ/mol and NX = 2.80×1024 /m3 for SCM435 (heat KL); EB = 42 kJ/mol and NX = 2.20×1024 /m3 for SNCM439 (heat BL); EB = 42 kJ/mol and NX = 2.42×1024 /m3 for SNCM439 (heat GL). From binding energies reported in existing literatures and the size of dislocation cores, the trapped hydrogen in cold-rolled austenitic stainless and quenched-tempered low alloy steels was mainly trapped by dislocation cores. For the low alloy steels, furthermore, hydrogen-induced degradations (HIDs) of various fracture characteristics were linearly proportional to θX and the following values of EB were obtained: EB = 44 kJ/mol for fatigue crack growth characteristics in hydrogen gas at pressures, p, of 0.1 ~ 95 MPa and temperatures, T, of 25 ~ 95℃ for SCM435 (heat TS); EB = 44 kJ/mol for fracture toughness characteristics in hydrogen gas at p = 0.7 ~ 115 MPa and T = 25℃ for SCM435 (heat of KL); EB = 43 ~ 46 kJ/mol for slow strain rate tensile characteristics in hydrogen gas at p = 115 MPa and T = −45 ~ 120℃ for SCM435 (heats JL and KL) and SNCM439 (heats BL and GL). The values of EB obtained from the strength characteristics were nearly equal to those from the hydrogen-diffusion. A series of analyses implied that the hydrogen-diffusion characteristics and the HIDs of various facture characteristics were dominated by the interaction of hydrogen and dislocation cores; then, the characteristics under various combinations of p and T could be predicted by the unified parameter, θX.

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