On Cooling of Underwater Welds

概要

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Thermal cycles of weld in underwater gravity arc welding were studied. The effects of welding factors on cooling process and cooling rate at the bond line were analysed. Moreover, experimental formulas and nomographs were proposed to estimate cooling rate of the underwater weld. Main results are summarized as follows : (1) Underwater weld is cooled rapidly owing mainly to the heat transfer from surface of weld to the surrounding water. Therefore, the cooling rate of underwater weld is much higher than that of open air weld. (2) Welding parameters which have a remarkable effect on cooling rate of underwater weld are heat input, water temperature, water pressure, thickness of base metal, welding position (slope of base metal) and location along weld bead. (3) Cooling rate (R) and cooling times (S_<500>, S_<300>) of underwater weld may be estimated by means of the following experimental formulas. R=6.25×10^5K(0.56sin^<2/3>θ+1)Q^<-0.95_t^<1/6>> S_<500>=455R^<-1.09> S_<300>=780R^<-1.09> where θ : slope angle of base metal, 0≦θ≦90° Q : weld heat input, 8≦Q≦35 KJ/cm t : thickness of base metal, 6≦t≦19 mm K=1 at middle part (in a quasi-stationary state) K=1.2 at starting point K=2 at crater. And nomographs based on the formulas for cooling rate and cooling times of underwater welds are made.
社団法人溶接学会の論文
1980-04-01