後熱による湿式水中溶接部の割れ防止について : 水中溶接部の性能向上に関する研究(第2報)

概要

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The effect of postheating on occurrence of underbead cracks and root cracks in underwater wet welds by gravity welding process is investigated. Lime titania type coated electrode (D5003) of 4 mm in diameter and SM50A steel base metal of 12 mm in thickness are used. Main results obtained are summerized as follows : 1) Underbead cracks occur in HAS of underwater welds about 5 min after the welding. 2) Occurrence of underbead cracks and root cracks can be prevented by postheating above 100℃. The critical concentration of hydrogen in weld metal to prevent the occurrence of cracks C_<wc> is 0.3 ml/100g W.M. 3) As the condition of postheating, the critical time factor c, by which the critical concentration of hydrogen C_<wc> is obtained, should be selected. 4) An argolism to obtain the condition of postheating (τ_c, t_c) from dimensions of weld (l_o, l), initial concentration of diffusible hydrogen (C_o≃Hw), temperature of postheating (T_h) and critical concentration of hydrogen (C_<wc>) is proposed.
1985-11-05