水素割れ環境下における炭素鋼の破壊過程解析(腐食防食小特集)

概要

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The fracture behavior of carbon steel was examined by slow strain rate test (SSRT) and the fracture process was analyzed to determine the effect of hydrogen in soil environment. The results obtained are as follows : (1) In an overprotective environment, a crack initiated and grew on the external surface of specimen. After growing to a certain size, the crack coalesced with another newly formed crack to from a large crack and final failure occurred. The crack initiation sites were identified on the SEM photograph to be at the quasi-cleavage fracture surface. (2) In soil, a crack initiated when the load reached a maximum and the final failure occurred after it elongated to approximately 400 μm. The elongation in air from a maximum load point is two or three times greater than that in soil. (3) The fracture toughness of the specimen, K_<IC>was calculated to be 62.2 MPa√<m> in this experimental condition. (4) Hydrogen influenced the mechanical properties such as fracture toughness and elongation, but its effect is considered to be small for non-precracked steel unless load is larger than a maximum value.
1994-11-15