脉冲双丝GMAW熔滴过渡过程中熔池波动行为数值分析

Numerical analysis of weld pool fluctuation behavior induced by droplet transfer in twin-wire GMAW

研究了脉冲双丝GMAW过程中熔池自由表面受周期性熔滴冲击引起的动态波动行为.根据二维波动理论建立了熔池液面受迫振动以及由此产生的二维波动行为的瞬态数学模型,推导出控制微分方程,给出了相应的初始条件和边界条件并编制程序进行了数值分析.得到了熔池自由表面的位移和振动速度分布规律、不同熔滴过渡条件下熔池自由表面的瞬时波动规律及焊接过程中表面波动所引起的干涉现象.结果表明,表面波主要起源于前丝、后丝中心附近,导致熔池表面有较强的凹陷.选用直径1.0 mm的焊丝可以减小熔池表面波动,防止出现较粗的焊缝波纹;当熔滴过渡频率为1000 Hz时,容易出现焊接波纹粗大、咬边等缺陷,波动干涉随熔滴过渡频率减小而减小.文中的工作能够为脉冲双丝GMAW的工业化生产和焊接工艺参数的优化提供基础数据和理论指导.

The dynamic fluctuation behavior of the free surface of molten pool during pulsed twin wire GMAW was studied.Based on the two-dimensional wave theory,the transient mathematical model of the shock vibration of molten pool surface and the two-dimensional wave behavior resulting from it are established.The governing differential equation is derived.The corresponding initial and boundary conditions are given,and the numerical analysis is carried out by programming.The displacement and vibration velocity distribution of the free surface of the molten pool,the instantaneous fluctuation of the free surface of the molten pool under different droplet transition conditions and the interference caused by the surface fluctuation during welding are obtained.The results show that the surface wave mainly originates near the center of the front wire and the back wire,resulting in a strong depression on the surface of the molten pool.The welding wire with diameter of 1.0 mm can reduce the surface fluctuation of molten pool and prevent the occurrence of coarse weld ripple;When the droplet transfer frequency is 1000 Hz,defects such as rough welding ripple and undercut are easy to appear.The fluctuation interference decreases with the decrease of droplet transfer frequency.The work in this paper can provide basic data and theoretical guidance for the industrial production of pulsed twin wire GMAW and the optimization of welding parameters.