超声耦合厚壁铝合金窄间隙摇动电弧GMA焊缝组织均匀性及气孔抑制

Nonuniform weld microstructure and serious pores have a direct impact on the narrow gap GMA welding quality of aluminum alloy. There is not a complete solution at home and abroad. This project proposes that exciting the ultrasonic field from the arc by coupling the ultrasonic frequency electric pulse with the swing arc. The ultrasonic acts on the thick-walled aluminum alloy narrow gap GMA weld pool. The uniformity of the weld microstructure is realized by ultrasonic refining the solidification microstructure. The weld pore is suppressed by ultrasonic promoting the escape of bubbles. The excitation of the ultrasonic field in the swing arc and the coupling mechanism between the ultrasonic field and the arc field are investigated, and the plasma physics relationship of the coupled field in the narrow gap is scientifically explained and the physical quantity is characterized. The weld microstructure and pore behavior under the action of the coupled field are mainly investigated, and the propagation and distribution of the coupled field in the narrow gap weld pool of the aluminum alloy are clarified. The interaction mechanism between the coupled field and the thermal field and flow field in the weld pool on weld microstructure evolution, bubble generation and motion during solidification are investigated, revealing the relationship between thermodynamic and dynamic for the weld microstructure inhomogeneity and bubble behavior. The control strategy of weld microstructure uniformity and the parameter control method of weld pore are established based on the principle of ultrasonic field correction. The ultrasonic-arc composite research is applied to the narrow gap welding of aluminum alloy by this project.

焊缝组织不均匀、严重的气孔对铝合金窄间隙GMA焊接质量有直接的影响，国际国内未见完备的解决方案。本项目提出在摇动电弧中耦合超声频电脉冲，从电弧中激发出超声场，作用于厚壁铝合金窄间隙GMA焊接熔池，通过超声细化凝固组织的作用实现焊缝组织均匀化，通过超声促进气泡逸出的作用实现对焊缝气孔的抑制的基本思想。研究摇动电弧中超声场的激发、超声能场与电弧能场的耦合机制，对耦合场在窄间隙中的等离子体物理学关系做出科学阐述和物理量表征。深入研究耦合场作用下焊缝组织及气孔行为，阐明耦合场在铝合金窄间隙焊接熔池中的传播与分布，以及耦合场与熔池内在的热场、流场等的共同作用机制，即对焊缝凝固与组织演变、凝固中气泡产生及其运动的影响和科学机制，揭示焊缝组织不均匀性和气泡行为的热力学和动力学关系规律。基于声场修正原则，建立焊缝组织均匀性调控策略、焊缝气孔的参数控制方法，将超声-电弧复合研究推进到铝合金窄间隙焊接中。

焊缝组织不均匀、严重的气孔对铝合金窄间隙GMA焊接质量具有直接的影响，国际国内未见完备的解决方案。本项目提出在摇动电弧中叠加超声频电流，从电弧中激发出超声场，作用于厚壁铝合金窄间隙GMA焊接熔池，通过超声细化凝固组织的作用实现焊缝组织均匀化，通过超声促进气泡逸出的作用实现对焊缝气孔的抑制的基本思想。本项目针对窄间隙约束下超声能场与摇动电弧能场的耦合机制、耦合场作用下厚壁铝合金窄间隙GMA 焊缝组织及气孔行为、焊缝性能调控开展了具体研究。研究表明：超声频电流叠加时，窄间隙坡口内电弧摇动与非摇动的电弧行为是不同的，坡口侧壁位置，非摇动电弧的扩张程度明显大于摇动电弧的扩张程度。坡口底部位置，摇动电弧的扩张程度大于非摇动电弧的扩张程度。结合电弧的膨胀及收缩速度，依据超声频电流波形，获得了超声频电流叠加下的电弧面积变化规律，阐明了电弧扩张机制。电弧力及电磁热的超声频变化是激发超声的主要声源，超声频率可以改变电弧空间的声场分布，超声频电流幅值改变电弧空间的声压大小。熔池内，超声频电流幅值及频率均会改变声场分布。不同超声频电流波形具有不同的额外热输入，焊接实验表明，叠加额外热输入最小的超声频电流波形时，焊缝成形更加均匀、气孔率最低、焊缝区组织显著细化、接头硬度明显提高。超声频电流叠加对焊缝区及熔合区的组织细化作用较大，对热影响区组织细化作用较小，组织细化程度与超声频电流参数之间是非线性的。通过向熔池内引入周期性的超声能量，可以调控粗晶与细晶的占比，最后达到调控接头性能的目的，利用随焊超声冲击的方式进行了实验验证，结果表明，在低频机械冲击基础上耦合周期超声后，与无超声相比，塑性指标最高提升62.84%，强度指标最高提升35.38%。本项目成果进一步丰富了超声辅助摇动电弧窄间隙焊接理论，对促进船用厚壁铝合金窄间隙GMA焊接技术的发展具有重要意义。