Abstract
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°C. The critical concentration of hydrogen in weld metal to prevent the occurrence of cracks Cwc 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 Cwc is obtained, should be selected.4) An argolism to obtain the condition of postheating (τc, tc) from dimensions of weld (l0, l), initial concentration of diffusible hydrogen (C0≈Hw), temperature of postheating (Th) and critical concentration of hydrogen (Cwc) is proposed.
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