Nb-V系高張力鋼再現溶接熱影響部の応力除去焼なまし脆化におよぼす溶接入熱の影響

概要

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Studies are made on stress relief embrittlement of duplicated weld HAZ for 50 kgf/mm^2 HTS. Degree of stress relief embrittlement expressed by △_V T_S is a function of weld thermal cycle cooling rate, and results showed that the highest notch toughness of stress-relieved weld HAZ was achieved in microstructure containing slight polygonal ferrite. That sort of microstructure can be obtained with thermal cycles cooling time of around 30 seconds from 800℃ to 500℃ for steels investigated, which shows the effectiveness for obtaining the safety of welded joints and the efficiency of welding fabrication by using comparatively high heat input of around C_f' cooling time in SH-CCT diagram. Furthermore, grain boundary fracture was little found for both as duplicated and duplicated and stress-relieved HAZ, showing the significance of niobium and vanadium nitride and carbide coherent precipitation for stress relief embrittlement in weld HAZ, as it occurs transgranular cleavage fracture easily.
社団法人溶接学会の論文
1984-11-05