AH36薄板激光-电弧复合焊熔滴过渡与熔池分析

Analysis on Droplet Transition and Molten Pool during Laser-arc Hybrid Welding of AH36 Sheets

采用激光-电弧复合焊,激光前置焊接海工钢AH36薄板。利用高速摄像分析熔滴过渡特征与影响因素。运用计算流体力学体积分数法建立固液气三相流体动力学模型。采用高斯面热源、高斯旋转体热源和双椭球热源表征复合焊热源。数值模型考虑了表面张力、电磁力、浮力、反冲压力、蒸发冷凝、蒸发换热等多种物理场的耦合作用。对熔滴过渡冲击及其对熔池形貌、流动与温度的影响进行研究。结果表明,熔滴冲击熔池可促进熔池流动与传热。熔滴过渡受电磁力与蒸气反冲压力抑制,致使大熔滴出现。适当增加激光功率可降低熔滴表面张力,增加熔滴过渡频率,减小熔滴尺寸。激光功率过大或光丝间距过小时,出现熔滴破裂与飞溅。

Laser-arc hybrid welding was used to weld AH36 sheets of marine steel with a laser preposition state.The characteristics and influencing factors of droplet transition were analyzed by high speed camera.The solid-liquid-gas three-phase fluid dynamics model was established by using computational fluid dynamics,the volume of fluid(VOF)method.Then the combination of Gaussian surface heat source,Gaussian rotating body heat source and double ellipsoid heat source was used to characterize the composite welding heat source.Furthermore,the coupling effects of such multiple physical fields as surface tension,electromagnetic force,buoyancy force,recoils pressure,evaporative condensation,evaporative heat transfer were considered in the numerical model.Finally,the droplet transition impact and its effect on the morphology,flow and temperature of the molten pool were studied.The results showed that the droplet impact on molten pool could promote the flow and heat transfer.The droplet transition was inhibited by electromagnetic force and steam recoil pressure,resulting in appearing of large droplet.Appropriate increasing of laser power could reduce the droplet surface tension,increase the droplet transition frequency and decrease the size of droplet.If the laser power was too large or the distance between optical fibers was too small,the melt droplets would break and splash.