激光诱导等离子体引燃MAG电弧的引弧特性研究

发布时间：2018-09-12 11:21

【摘要】：本文以高氮钢为材料,研究了不同热源间距、电弧脉冲频率、激光能量对电弧引燃的影响结果表明:电弧能量对等离子体发射光谱产生了不利的影响,随着电弧能量的增加,等离子体发射光谱的光强和连续性变差。然而当脉冲激光的加入,这种现象得到改善并且随着激光能量的增加,等离子体发射光谱的强度和连续性也变强。通过对热源间距的分析知,等离子体发射谱线强度随着热源间距的增加先增加后降低。通过对熔滴过渡频率影响知,随着激光作用时间的增加熔滴过渡频率增加,熔滴过渡频率随着热源间距增大先增加后减小。通过对电弧形态变化、焊接电信号分析及等离子体电子温度和电子密度的变化规律研究,最终揭示了等离子体燃弧特性的机理即:1)首先工件与高能量密度的激光束作用形成金属蒸气。2)其次保护气体及金属蒸气的一部分起始自由电子通过吸收光子能量而被加速,当自由电子有足够的能量来碰撞带电粒子和保护气体而致使其发生电离状态。3)再次随着激光作用的加强,此时等离子体会迅速长大,最终接触到钨极。因为等离子体是一种高度电离的气体(等离子体的温度极高,温度能够达到几千度甚至上万度),因此为钨极电子发射提供了有利条件。4)随后电极之间的间隙被等离子体所填充,此时焊接电路被导通,MAG电弧被引燃。5)当激光电源被移走时,MAG电源所提供的后续电流比较稳定,并且维持电弧继续燃烧,但是电弧的形态发生了收缩。
[Abstract]:In this paper, the effects of different heat source spacing, arc pulse frequency and laser energy on arc ignition have been studied using high nitrogen steel as materials. The results show that arc energy has a negative effect on the plasma emission spectrum, and the arc energy increases with the increase of arc energy. The intensity and continuity of the plasma emission spectrum are poor. However, with the addition of pulsed laser, this phenomenon is improved and the intensity and continuity of the plasma emission spectrum become stronger with the increase of laser energy. Through the analysis of the distance between heat sources, it is found that the intensity of plasma emission lines increases first and then decreases with the increase of heat source spacing. With the increase of laser time, the droplet transfer frequency increases firstly and then decreases with the increase of heat source spacing. The variation of arc shape, the analysis of welding electric signal and the variation of plasma electron temperature and electron density were studied. Finally, the mechanism of plasma arc burning characteristics is revealed, that is, first of all, the workpiece acts with a high energy density laser beam to form metal vapor (.2) secondly, the initial free electrons of the protective gas and metal vapor are accelerated by absorbing photon energy. When the free electron has enough energy to collide the charged particle and the protective gas causing its ionization state 3) once again with the enhancement of the laser action the plasma will grow rapidly and finally come into contact with the tungsten electrode. Because the plasma is a highly ionized gas (the temperature of the plasma is extremely high, which can reach thousands or even tens of thousands of degrees), thus providing favorable conditions for tungsten electron emission, the gap between the electrodes is then filled with plasma. When the laser source is removed, the subsequent current provided by the MAG source is relatively stable, and the arc continues to burn, but the shape of the arc shrinks.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG457.11

【共引文献】