高張力鋼溶接熱サイクル再現試験片の水素による遅れ破壊試験について

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A delayed failure test was done with notched specimens of synthetic heat-affected zone of high-strength steel. The test method was a so-called "charge and stress" method, in which the specimen was subjected, at first, to a weld thermal cycle, charged with hydrogen electrolytically and then loaded in sustained manner. The main conclusions obtained in the study are as follows : (1) Root crack susceptibility of the heat-affected zone in the first layer weld of a low-alloy high-strength steel can be examined in the delayed failure test of the synthetic heat-affected zone of steel. (2) A new criterion was proposed for comparison of susceptibilities to hydrogen embrittlement of the synthetic heat-affected zones of steels. The ratio of a critical stress in the delayed failure test (σ_c) to a normal notch strength (σ_t) of synthetic specimens of a steel was plotted against a diffusible hydrogen content of the specimen in a graph with logarithmic graduation. The value of the ratio at a specific hydrogen content (e.g. 1.0cc/100gr) was adopted as the criterion. (3) A critical stress increased with an increase of cooling time in a weld thermal cycle except for a 9% Ni steel. The stress also increased with decreases in diffusible hydrogen content and notch sharpness. (4) Susceptibility to hydrogen embrittlement of a low-carbon martensite was affected by other alloying elements even if the carbon content and the hardness were not changed. (5) Susceptibility to hydrogen embrittlement of a low-carbon martensite was increased by rapid quenching and also by repeated quenching. (6) A bainitic structure which was isothermally transformed just above the M_s temperature had a high susceptibility to hydrogen embrittlement. The susceptibility was nearly equal to that of an autotempered martensite. (7) There was a relation between the new criterion in the delayed failure test and the critical restraining stress for root cracking in the heat-affected zone in the weld of the same steel in the TRC (Tensile Restraint Cracking) test.
社団法人溶接学会の論文
1969-09-25

高張力鋼溶接熱サイクル再現試験片の水素による遅れ破壊試験について

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