構造用鋼の溶接熱影響部における J_<IC> 破壊靭性に関する研究(<特集>中小企業を対象とした : 溶接構造物の技術・施工管理の要点)

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The fracture toughness in a simulated weld heat-affected zone (HAZ) of the high tensile strength steel (HT80) were evaluated through J_<IC> values using a Charpy-size three point bending specimen at a temperature range between 18℃ and -150℃. The effect of the microstructure on crack initiation was investigated by a fractographic method using the scanning electron microscope (SEM). In the tempreature range from about -50℃ to 18℃, for the base metal and HAZ whose cooling time from 800 to 500℃ (TC) was 17 sec, the J_<IC> values increased with decreasing test temperature. The SEM examination showed that the area fraction of martensite-austenite constituent (M-A) in the microstructures mentioned above was less than 4%. The fracture occurred by stable crack extension after the formation of the stretched zone at the precrack tip. On the other hand, the J_<IC> values decreased with decreasing test temperature on HAZ microstructures whose T_C were 89 and 223 sec. In these microstructures, which had more than 8% of area fraction of M-A, cleavage fracture occurred immediately after the formation of the stretched zone. J_<IC> values in the microstructures which included more than 8% of area fraction of M-A were nearly a quarter of the one in the microstructures whose M-A were less than 4%, at about -50℃. The critical stretched zone width (SZW_C) and J_<IC> were found to be related as follows : J_<IC>=α・σ_y・SZW_C where-σ_y is the yield stress of steel and α is an experimental constant which was found to be 8.5.
社団法人溶接学会の論文
1982-11-05

構造用鋼の溶接熱影響部における J_<IC> 破壊靭性に関する研究(<特集>中小企業を対象とした : 溶接構造物の技術・施工管理の要点)

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