压力对水下焊条局部干法焊接电弧稳定性的影响

Influence of ambient pressure on the electrode arc stability of local dry underwater welding

在压力舱中进行不同压力下的水下焊条局部干法焊接试验，采用统计分析和快速傅立叶变换研究了压力对水下电弧稳定性的影响．结果表明，铁粉低氢钾型焊条焊接主要进行粗熔滴短路过渡，随着压力的增加，短路时间由常压焊接的5-7ms增加到8～10ms，表明熔滴的平均尺寸增大．压力环境下，焊条熔化速度增大，弧压反馈调节系统的工作点上移，电弧电压增大．傅里叶变换结果表明，常压电弧电压信号的主要特征频率低于10Hz，压力下电压信号的频谱图中出现大量高于10Hz的谱线，说明信号突变性更强，电弧稳定性降低．

In order to investigate the arc characteristic of local dry underwater welding,various pressure of compressed air was inflated into a chamber to simulate the various water depths.The arc signals were acquired and analyzed in time and frequency domain,respectively. Results show that the metal transfer mode of iron powder low-hydrogen potassium electrode is large droplet short circuiting transfer. The increase of the pressure results in the increase of droplet size. The average short circuiting time was changed from 5-7 ms under atmospheric pressure to 8-10 ms under pressure condition. Under pressured condition,the electrode melting rate increases and meanwhile the stable working point of the arc voltage feedback control system moves upward leading to the increase of arc voltage. The frequency domain analysis shows that the main characteristic frequency is less than10 Hz under atmospheric pressure,whereas large amounts of the characteristic spectrums with frequency of more than 10 Hz appeared under high pressure condition,indicating an instability of the welding process.