高氮钢激光-电弧复合焊接气孔控制方法研究

Study on Control Methods of Welding Porosity in Laser-arc Hybrid Welding for High Nitrogen Steels

为了掌握高氮钢复合焊接气孔控制的有效方法,研究电弧能量、激光能量和振动频率对焊缝气孔的影响。从气孔率方面分析焊缝气孔的产生原因,并从电流和电压波形及熔滴过渡方面分析其对焊接过程稳定性的影响。熔池流动与焊缝气孔具有一定的关联性,并从熔池流动状态方面分析其对气孔的影响。激光匙孔的形成需要一定的阈值能量,匙孔穿透状态对气孔率有直接影响,依据激光匙孔底部受力情况,分析匙孔状态对焊缝气孔率的影响。结果表明:气孔率随电弧能量或激光能量的增加而呈先升后降的变化趋势,电弧能量4 800 J(I=200 A,U=24 V)时,气孔率最低,仅为0.49%;而激光功率为2.8 k W时,气孔率降为最低,仅为0.14%;施加振动后焊缝气孔率均明显减小,气孔率随着振动频率的增加而先降后升。适当的电弧能量或激光能量可有效抑制焊缝内气孔数量,振动频率为35 Hz时抑制气孔效果最好。

In order to master the control methods of welding porosity on laser-arc hybrid welding for high nitrogen steel, the effect of weld porosity on arc energy and laser energy and the vibration frequency are studied. Causes of welding porosity are analyzed in terms of porosity rate, and its effect is investigated on stability of welding processes through waveforms of current and voltage and droplet transfer. There is certain relevance between fluid flow in the melt pool and formation of welding porosity, and the influence on welding porosity is analyzed in terms of fluid flow in the melt pool. The keyhole is generated when laser power reaches up to a certain extent and condition of keyhole will affect porosity rate. Influence of porosity rate on condition of keyhole is analyzed according to keyhole’s stress situation. The results shows that porosity rate of welding seam increased first and then decreased with the increasing of arc energy or laser energy, and porosity rate of welding seam is reduced to the lowest for just 0.49% while arc energy is 4 800 J（I=200 A, U=24 V） and the porosity rate of welding seam is only 0.14% when laser power is 2.8 k W, but porosity rate of welding seam is reduced greatly after work pieces are vibrated during hybrid welding. Porosity rate of welding seam decreased first and then increased with the increasing of vibration frequency. The number of welding porosity is inhibited efficiently by suitable arc energy or laser power, and inhibitory effect of welding porosity is best while vibration frequency amount to 35 Hz.