Control Of Welding Residual Stress And Strain By Welding With Trailing Cooling Of Drikold

Aluminum alloy structure,with its low density and high strength,has been widely used in the field of marine technology.But large residual stress and distortion is usually accompanied after the process of welding.Welding stress and strain can be decreased by the method named welding with trailing cooling,but the efficiency of cooling media need to be further studied.Based on the welding method,the new method named welding with trailing drikold is proposed,and the granulous drikold is used as the cooling media.Combining with numerical simulation and experiment,research on the control of residual stress and deformation is conducted.First of all,the temperature fields formed by spraying dry ice was measured.Based on the finite element analysis software named MSC.Marc,the welding process of welding with trailing cooling was simulated.Then the analysis of the effects of different rectangular cooling source on the control of residual stress and deformation was discussed,so as to optimize the cooling source shape and provide the theoretical guidance for the design of drikold nozzle.The results showed that the length of the optimal cooling source was the smallest when the width is 40mm;the effect increased with the increasing of the length of the cooling source within a certain range.Then,the design of the nozzle was discussed.The temperature field model was then proposed after the temperature field formed by spraying drikold being measured.Based on the model,the process of welding with cooling was simulated.And the effect of different cooling distance on the welding method was discussed.The results showed that the effect was better residual stress and strain reduced with the decrease of the distance within a certain range.Finally,focused on the method of welding with trailing cooling of drikold,the mechanism was explained.Relevant welding trials were applied.The experiment to measurethe temperature field distribution was carried out,compared with the temperature field of the finite element analysis,the error is within 50 ?.So the analysis was reasonable.The measurement of the stress and deformation showed that,compared with conventional welding,the residual distortion decreased by 67.2%,the maximum longitudinal residual stress and the maximum compress stress decreased by 47.7% and 41.3%,when the cooling distance was40 mm.So the method was feasible.The microstructure trails showed that,under certain conditions,welding with cooling source can refine the size of the microstructure on the welding zone,but produce little impact as a whole.So the method was reliable.Moreover,the welding tress and strain were decreased,the welding surface was cleaned meanwhile.