溶接殘留応力が脆性破壊に及ぼす影響の研究 : 第3報低温応力除去の影響

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The third series of slow notch bend test was performed to investigate the effect of residual welding stress on brittle fracture of steel. Chemical composition and mechanical properties of steels tested are shown in Table 1. Steel YA is more notch-sensitive and YB is more notch-tough than weld metal.For each steel, 2 kinds of unwelded specimens (as rolled and annealed) and 9 kinds of welded specimens (as welded, annealed, 3 pretensioned and 4 low temperature stress relieved) were prepared (Fig. 1). Detailes of welding procedure and low temperature stress relieving conditions are shown in Tables 2 and 3.On each one specimen among welded specimens, residual stress measurement was performed by resistance wire strain gauges. Fracture test procedure is the same as Van der Veen test. Trs. depo and longitudinal residual stress are shown in Table 5.We can conclude that stress relieving of welded joint increases notch toughness, but plastic strain of weld metal decreases notch toughness, so moderate heat input in low temperature stress relieving is preferable.
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