Numerical Simulation And Process Research Of 5052 Aluminum Alloy Underwater Laser Wire-filling Welding

With the extensive development of marine resources and the rapid development of nuclear power industry,traditional underwater welding methods are gradually limited.Compared with traditional methods,underwater laser welding has the advantages of being less influenced by water pressure and high degree of automation.Aluminum alloy has been widely used in the field of ocean and nuclear power by virtue of its high specific strength and corrosion resistance.However,there is little research on the underwater laser welding technology of aluminum alloy in China,especially the local dry underwater laser wire filling welding technology of thin walled aluminum tube structure.In this paper,the finite element simulation software ANSYS was used to simulate the temperature field and stress field distribution of local dry underwater laser wire filling welding,and the influence rules of laser power and welding speed on temperature field and stress field were emphatically analyzed.It is found that with the increase of laser power and pool temperature,the maximum equivalent stress in the welding process increases,the residual stress after welding also increases gradually,and the overall displacement increases.When the laser power is 2.5 k W and the welding speed is 5 mm/s,the residual stress of the welding layer is small after laser welding,and only the welding end has obvious deformation.On the basis of the numerical simulation,the self-designed double local dry method underwater laser wire filling welding torch was used to construct platform for local dry method underwater laser wire filling welding,the single factor variable method was used respectively to study the effect of the laser power,welding speed and wire feed speed and protective gas flow rate on the local dry underwater laser welding wire filling welding quality,it is concluded that the optimal parameters of the welding process : the laser power is 2.75 k W,welding speed is 7 mm/s,wire feeding speed is 110 cm/min,the protective gas flow rate is 35 L/min.Finally,local dry underwater laser wire filling welding and onshore laser wire filling welding tests were carried out respectively under the above optimal technological parameters,so as to evaluate the local dry underwater laser wire filling welding process.Compared with onshore laser wire filling welding process,the degree of oxidation of underwater welding is slightly heavier,but both of them are well formed,continuous and uniform.The weld width of underwater welding is narrower,the excess height is larger,the weld depth is shallower,the dilution rate of the weld is lower,but the surfacing angle is larger.The composition of phase is same in welding zone;In terms of the microstructure of the welds,the fusion zone is composed of columnar dendritic crystals,while the welding zone is composed of equiaxed dendritic crystals.The content of adjacent magnesium elements in the underwater weld surfacing zone and in the onshore welding zone varies greatly and the burning degree of magnesium elements in the underwater welds is relatively light.For both underwater and onshore welds,the hardness distribution of the two is that the highest in the base material,followed by the fusion zone and welding zone,and the lowest in the heat-affected zone.Compared with onshore welds,the hardness of underwater welds is higher.