铝合金TIG+CMT复合热源焊接成形与控制基础研究

A novel hybrid arc welding method isproposed in “ Research on the shaping and control fundament for the TIG-CMT hybrid welding of aluminum alloy”, in which the arc of tungsten inert gas (TIG) arc welding preheats the workpiece to the desired temperature and then the cold metal transfer (CMT) technique is employed to reduce the spatters in the short-circuiting metal transfer process of welding. Compared with the common hybrid heat sources in which the heat input is increased by the interaction of hybrid arc, the TIG-CMT hybrid welding takes advantage of two separated arcs to control the heat input, in which way the shaping, microstructure and mechanical properties will be improved for the increase depth of weld penetration and improved wetting property in the hybrid TIG-CMT welding of aluminum alloys. Namely, the shaping and mechanical properties can be both controlled in the hybrid TIG-CMT welding. And the study of the TIG-CMT hybrid welding will promote the CMT technique and improve the hybrid welding fundaments..Shaping, microstructure and mechanical properties for butt joint/surfacing specimen in the hybrid TIG-CMT welding of aluminum alloy will be investigated for different welding parameters and different modes of heat sources. A numerical model for the hybrid TIG-CMT welding, in which heat transfer, mass transfer and computational fluid mechanics are all considered, will be established to study the welding temperature filed and weld pool flow fluid, to study the shaping fundament, in further to propose optimal control strategies for the hybrid TIG-MIG welding of aluminum alloys.

“铝合金TIG+CMT复合热源焊接成形与控制基础研究”提出了一种新的电弧复合热源焊接方法，即采用TIG电弧预热，调节工件的热输入量，应用CMT焊接实现无飞溅的熔滴短路过渡；一般电弧复合是通过电弧相互作用、增加电弧能量，而TIG+CMT复合是通过分离电弧对工件热输入量的复合来解决铝合金CMT焊接熔深浅、堆焊润湿性差等问题，改善焊缝成形、接头微观组织与性能，实现焊接的控形与控性；该研究对于丰富电弧复合热源焊接理论、促进CMT焊接发展、扩大其应用范围具有重要的理论意义和实际应用价值。.重点研究不同热源模式、焊接参数铝合金平板堆焊、对焊的TIG+CMT复合热源焊接成形规律、接头微观组织与性能变化规律；建立TIG+CMT复合热源焊接数值分析模型，应用传热传质理论、计算流体力学等分析焊接温度场、流场及其影响规律，弄清TIG+CMT复合热源焊接成形机理，提出铝合金TIG+CMT复合热源焊接的控制策略。

冷技术过渡（CMT）焊接是一种新的焊接方法，焊接过程稳定、熔滴短路过渡可控是其最大的特点；但低热输入、熔深浅的特点又极大地限制了其工程应用范围。如何充分发挥CMT焊接的特点，解决铝合金CMT焊接熔深浅、堆焊铺展性差等问题，是焊接研究工作者及工程应用单位所关心的问题。.本项目提出了 “TIG+CMT复合热源焊接”新方法，设计并搭建了TIG+CMT复合热源焊接及焊接参数与图像测试分析系统，重点开展了铝合金TIG+CMT复合热源焊接电弧形态和熔滴过渡行为、铝合金TIG+CMT复合热源焊接宏观成形和微观组织及性能等规律的研究，通过铝合金、镍基合金TIG+CMT复合热源焊接过程的数值模拟，进行复合热源焊接机理的研究；并进行了镍基合金、异种材料CMT焊接以及CMT增材制造等一系列的扩展研究。.研究结果表明，只有在一定的送丝速度范围内，才能实现熔滴短路过渡可控的、稳定的CMT焊接；当TIG+CMT复合热源焊接的两电弧交互作用较强时，CMT焊接熔滴过渡出现不稳定的大滴过渡；铝合金材料复合热源焊接的熔深大于单独CMT与单独TIG焊接的熔深之和；与单独CMT堆焊相比，TIG+CMT堆焊显著降低了熔敷金属的接触角，多道堆焊成形良好；复合热源焊接过程中，焊接工件的温度场具有两个热源高温区，焊接接头区域的热循环曲线具有双峰特征，双峰温度最高值与母材和焊丝材料的特性以及焊接参数密切相关；复合热源对接所获得的接头可以达到全熔透条件下单独CMT焊接接头的力学水平；复合热源多道堆焊焊缝表现出比CMT多道堆焊焊缝具有更好的耐磨性。.研究结果证明了TIG+CMT复合热源焊接方法能够在充分保留和发挥CMT焊接特点和优势的同时，解决CMT焊接热输入低而带来的各种问题，具有重要的工程应用推广价值。项目的研究结果对于丰富电弧复合热源焊接理论、促进CMT焊接发展具有重要的理论意义和实际应用价值。