脉冲MIG焊熔滴过渡阶段的波形控制

Waveform Control in Droplet Transfer Phase During Pulsed MIG Welding

在自行研制的软开关逆变电源上改变脉冲MIG焊的控制波形,在电流波形的下降沿增加熔滴过渡阶段,以实现焊接过程的稳定可控.通过小波分析仪采集并统计瞬时电流、暂态电压、动态电阻、瞬时能量、电流电压概率密度分布等数据,考察了熔滴过渡电流和过渡时间对焊接质量的影响.实验结果表明:增加熔滴过渡阶段有助于实现焊接过程的稳定可控;过渡电流较小时,能量不足,易出现短路过渡、焊接不稳定等现象;过渡电流接近峰值电流时,焊接情况与普通脉冲MIG焊类似,达不到波形控制的目的;过渡电流不变时,焊接质量随着过渡时间的增加而提高,当过渡时间为7ms时焊接效果理想,随着时间的进一步增加,过多的能量使熔滴过渡不规则,焊接质量开始降低;本实验条件下的最佳工艺参数为熔滴过渡电流160A、过渡时间7ms.

In order to ensure the stability and controllability of the pulsed MIG welding, a self-developed soft-switching inverter was used to change the control waveform, and a droplet transfer phase was added in the falling edge of pulse waveform. The instantaneous current, the transient voltage, the dynamic resistance, the instantaneous energy, and the probability density distribution of current ＆ voltage were then acquired and analyzed using a wavelet analyzer. Moreover, the effects of the droplet transfer current and its duration on the welding quality were investigated. Experimental results show that （ 1 ） adding a droplet transfer phase may result in a stable and controllable welding process; （2） the energy shortage due to a small droplet transfer current may cause a short circuit transfer and an unstable welding process; （3） when the transfer current is close to the peak value, the welding process is similar to the ordinary pulsed MIG welding process, which deviates from the goal of controlling the waveform; （4） at a constant transfer current, the welding quality improves with the increase of droplet transfer duration, attaining an ideal state when the duration reaches 7ms; （5） with further increase in transfer duration, the welding quality lowers due to the irregular droplet transfer caused by excessive energy; and （6） the optimal droplet transfer current and the transfer duration in experiments are found to be 160A and 7ms, respectively.