溶接熱影響部の靱性と組織に及ぼす冷却時間の影響 : 圧力容器用低合金鋼SQV-2Aの再現溶接熱影響部の靱性とその改善(第1報)

概要

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The microstructure and Charpy impact energy of simulated weld HAZs of low alloy steel SQV-2A have been investigated with particular reference to the effect of the formation of M-A constituent and its morphology. Weld HAZ thermal cycles having cooling times △t_<8/5> from 6 to 1000 s, which reflect various welding heat inputs, were simulated with Gleeble 1500 thermal/mechanical simulator. The formation of M-A constituent and its morphology were examined with TEM and SEM. For this steel, the M-A constituent formed at cooling times △t_<8/5> more than 20 s. With increasing cooling time, the M-A constituent formed not only near the grain boundary but also in bulk region, and changed from elongated shape to massive shape. Both enlongated and massive M-A constituents seem to impair the HAZ toughness of SQV-2A steel. The M-A constituent acts as the initiation site of microcracking to induce the toughness loss, but the toughness may be affected by not only M-A constituent but also the matrix, because the matrix itself seems to become brittle with increasing cooling time.
社団法人溶接学会の論文
1996-02-05