J-R curves under continuous hydrogen charge were obtained to evaluate the effect of absorbed hydrogen on fracture toughness of SCM44O low alloy steel. The effect of absorbed hydrogen, loading rate and tempering temperature were investigated. Five materials which were tempered at different temperature to change Vickers hardness were used. Continuous hydrogen charge, which isolated the crack tip from the electrolyte and kept crack in dry condition, was conducted during the test. Material hardness and loading rate significantly affected J - R curves and 1c. Low loading rate and high hardness resulted in drastically decreased ic. The materials which were tempered at 803K showed 90% reduction of ic compared with that of uncharged specimen. The significant reduction was experienced in materials with Vickers hardness higher than 310. Quasi-cleavage fracture surface was predominantly observed in the tests which resulted in low ic. It is indicated that the hardness of low alloy steel used as a structural material should be limited below 300 on the viewpoint of fracture toughness. This study showed that low loading test that lasts for eighty hours at least is necessary to assess the ic of hydrogen charged material.
|ジャーナル||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|出版ステータス||出版済み - 12月 1 2011|
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