超声场耦合激光-MIG共熔池铝合金焊接技术及气孔消除机理

One of the problems with the laser-MIG hybrid welding of aluminium alloy is the formation of porosity in weld metal, especially during welding of thick aluminium alloy plates with a high speed. Although lots of methods are carried out to eliminate the porosity in weld bead, the problem can not be solved fundamentally. Some approaches can decrease the number of porosity effectively, but with sacrificing the advantages of laser-MIG hybrid welding such as high welding speed, small stress and deformation, deep depth of pool, etc. In our study, a novel joining technique of aluminium alloy laser-MIG hybrid welding coupled by ultrasonic field in pool is proposed. In the process, an ultrasonic generating device is designed to apply the ultrasonic field in laser-MIG hybrid welding pool. The bubbles in pool overflow from the surface of liquid metal quickly with the function of ultrasonic field, then the formation of porosity will be suppressed or even prevented without bringing adverse effects. The study focuses on the mechanism of porosity-eliminating and the effects brought by adding ultrasonic field in laser-MIG hybrid welding. How to apply the ultrasound into the pool will be optimized and the hardware system coupling ultrasonic field will be design to accomplish the new welding technique. The mechanism of action of ultrasound on the bubbles in pool will be studied by numerical simulation. The welding process of aluminium alloy will be optimized to obtain the joints with excellent properties without porosity, and the effects of ultrasound on the microstructure and mechanical properties will also be analyzed.

气孔问题一直是铝合金激光-MIG复合高效深熔焊接难以解决的技术难题，现有解决方法难以从根本上消除气孔，或者是以牺牲激光-MIG复合焊接优越性为代价缓解气孔问题。为此，本项研究提出了一种超声场耦合激光-MIG共熔池铝合金焊接新技术，通过设计超声耦合装置将超声作用于焊接熔池，加速熔池中的气泡溢出，从而达到消除焊接接头中气孔的目的，并对这种焊接方法中所涉及到的物理现象及超声作用规律进行研究。主要研究内容为：超声与激光-MIG复合焊接熔池的耦合方式选择及硬件系统的研制、超声与铝合金激光-MIG复合熔池中气泡的作用机理研究、超声场耦合激光-MIG共熔池铝合金焊接工艺研究、超声对铝合金激光-MIG复合焊接接头组织性能的影响规律研究等。

气孔问题一直是铝合金激光-MIG复合深熔焊接难以解决的技术难题。本项研究提出了一种超声场耦合激光-MIG共熔池铝合金焊接新技术，通过设计超声耦合装置将超声作用于焊接熔池，加速熔池流动，促进气泡聚集长大，使气泡快速溢出，从而达到消除或减少焊接接头中气孔的目的，并对这种焊接方法中所涉及到的物理现象及超声作用规律进行研究。主要研究了超声与激光-MIG复合焊接熔池的耦合方式，超声对熔池中气泡的作用规律、典型车体铝合金焊接工艺，以及超声对铝合金激光-MIG复合焊接接头组织性能的影响规律研究等。结果表明，超声机械振动耦合除气效果明显，但由于机械随动性和超声随着距离变化的衰减问题，不便工程化应用；超声电弧耦合对熔池上方的熔滴过渡和电弧影响明显，但由于气液界面的反射作用削弱了超声对熔池的作用；脉冲激光调制激励超声耦合可直接作用于熔池，焊缝气孔有明显加速上浮趋势，接头的组织性能也得到改善。获得了优化后的典型车体铝合金焊接工艺以及接头的组织性能，对该方法的工程应用具有指导意义。同时，超声辅助不仅是铝合金激光-MIG复合焊的除气手段，也可推广到其它气孔倾向明显的焊接工艺中，具有较好的应用前景。