極低温用構造材料溶接部の微視破壊過程と破壊じん性評価

概要

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In order to evaluate the fracture toughness of structural steels for superconducting magnets of fusion reactor, elastic-plastic fracture toughness testing was performed at 4.2K on AISI 310S base metal, weld metal and 20Mn steel. Fracture toughnesses were evaluated by a single specimen technique using the Key Curve reported previously. Elastic-plastic fracture toughness J_<IC> and tearing modulus T_<mat> of weld metal were significantly lower than those of base metal. As the result of AE measurement, microfracturing was detected at the early stage of loading, and pop-in cracking was observed at the later stage. Fractographic and metallographic examination of fracture surfaces and fracture paths revealed a difference in dimple sizes between the weld metal and the base metal, and also micro void formation ahead of a growing crack tip, which resulted in smaller crack opening angle of the weld metal than the base metal. Finally, the significance of crack growth analysis of weld metal was emphasized to ensure the structural integrity of superconducting magnet.
一般社団法人日本機械学会の論文
1986-01-25