激光焊中侧吹保护气质量分布的数值分析

Numerical analysis of mass distribution in side shielding gas in laser welding

保护气对激光焊接过程中等离子体、小孔和熔池行为有重要影响.考虑小孔内喷出等离子体作用,建立了侧吹保护气、空气和小孔内喷出等离子体的三维组份输运数学模型,计算了保护气在工件表面和高度方向的质量分布,分析了侧吹保护气管的倾角、与小孔的相对位置及保护气流量变化对焊接的影响.结果表明,小孔内喷出等离子体改变了工件表面保护气质量分布,保护气管位置离热源距离过大和倾角过小不能形成有效的气体保护,过大的保护气流量会吹散蒸汽离子体.采用TC4钛合金、6061铝合金和Q235钢等板材做焊接试验,气体保护效果良好.

The plasma,keyhole and molten pool were affected by shielding gas in laser welding.Considering the effect of plasma ejecting from keyhole,a three dimensional composition transport model of side shielding gas,air and plasma was established.The mass fraction of each species was calculated on the surface of workpiece and thickness direction.The effects of the angle,position of side shielding gas tube and flow of shielding gas on weld quality were analyzed.The results demonstrated that the distribution of mass fraction of shielding gas is changed by plasma ejecting from keyhole,the weld seam and heat affected zone cannot be protected if the distance between shielding gas tube and keyhole center is too large,or the angle is too small.In addition,the plasma will be blown off by too large shielding gas.The workpiece can be protected effectively through welding experimental of TC4 titanium alloy,6061 aluminium alloy and Q235 steel plate.