变极性焊接电弧动态行为之机理及控制策略研究

In view of the difficulty of arc reignition with small current, the limitation of variable polarity frequency with large current during variable polarity arc welding, the impact of welding loop inductance on the dynamic process of variable polarity arc welding, a new type of variable polarity circuit topology is put forward to allown the production of a stable and controllable arc reignition voltage. Based on the deeply investigating on the relationship between the reliability of arc reignition for variable polarity with the welding current value before the polarity reversal, the current change speed during polarity exchange, the change direction of welding current polarity, the types of electrode, arc voltage, the relational model of arc reignition voltage is constructed. Through collecting and processing to the output voltage of welding power supply, arc voltage and welding current, the detection and identification of the welding loop circuit inductance is implemented on-line. By means of the in-depth analysis on the high-speed photography images of welding arc and its corresponding relationship with welding current, the mechanism of dynamic behavior of welding arc and arc ignition during polarity reversal process is revealed. Based on the relational model of arc reignition voltage and the estimated value of welding loop circuit inductance, an effective control strategy is builded for the control of welding arc dynamic behavior, which broaden the scope of the application of the variable polarity welding current, improve the variable polarity welding frequency with large current, increase the arc stiffness and welding process stability, improve the microstructure and mechanical properties of welded joint, to further promote the development and application of variable polarity welding technology.

针对小电流变极性电弧焊接的再燃弧困难、大电流变极性焊接的变极性频率受限、焊接回路电感对变极性电弧焊接动态过程的影响等问题，提出能够产生稳定且可控的再燃弧电压的新型变极性电路拓扑。在深入探究变极性电弧再引燃可靠性与极性变换前焊接电流值、变极性电流变化速度、极性变换方向、电极类型、电弧电压等关系的基础上，构建再燃弧电压关系模型。通过对电源输出电压、电弧电压和焊接电流的采集与处理，实现对焊接回路电感的在线检测和辨识。通过对高速拍摄的焊接电弧图像及其与焊接电流对应关系的深入分析，揭示极性变换过程的焊接电弧动态行为机理及再引燃机理。基于再燃弧电压关系模型和焊接回路电感估计值，构建对焊接电弧动态行为进行有效控制的策略，拓宽变极性焊接的适用电流范围，提升大电流变极性焊接频率，提高电弧挺度和焊接过程稳定性，改善焊接接头的微观组织和力学性能，进一步促进变极性焊接技术的发展和应用。

变极性电弧焊接适用于多种焊接工艺，可广泛应用于铝合金等轻金属材料的优质焊接、薄壁或厚壁钢结构的高效焊接和堆焊，具有传统直流和普通正弦交流电弧焊接无法比拟的优势，具有广阔的应用价值和发展前景。.针对小电流变极性电弧焊接的再燃弧困难和电弧稳定性差、大电流变极性焊接的变极性频率受限、焊接回路电感对变极性焊接电弧动态过程有较大影响等问题，围绕申请书提出的关键科学问题，本项目主要开展了如下研究工作：.首先，构建了变极性焊接试验研究平台及电弧图像错时拍摄与电流采集同步系统；基于电流变极性过程的电弧图像与电流关联性，试验研究了变极性电弧焊接的电流换向过程稳定性及其影响因素，对电弧动态行为机理及小电流变极性电弧焊接的电流换向过程熄弧机理进行了深入探究，提出了小电流变极性电弧焊接的电弧再引燃可靠性和燃烧稳定性改善方向；.其次，提出了旨在提高变极性TIG焊电弧燃烧稳定性的多种控制方法和策略，包括：电源输出电流变极性期间的一次逆变恒脉冲占空比控制方法；针对小电流变极性TIG焊，提出了“一次逆变不关闭+二次逆变开环时间节点控制”的电流变极性换向协同控制策略，实现了变极性TIG焊在10 A小电流输出时焊接电弧的稳定燃烧，且小电流波形规则，无畸变；针对大电流变极性焊接，从有效保障电源二次逆变功率开关器件工作安全性的角度，提出了在二次逆功率开关器件共同导通一段时间的基础上，“一次逆变关闭+二次逆变电流反馈”的电流变极性换向控制策略。.第三，给出了新型变极性焊接电源全范围电流输出控制策略选择原则，构建了基于极点配置的逆变焊接电源最小拍控制系统，研究了其适用性、稳定性和鲁棒性；在对变极性焊接电源输出电流进行低频调制的基础上，初步研究了脉冲调制变极性焊接的焊缝成形及裂纹敏感性。.项目研究工作按年度计划顺利开展，完成了主要研究内容，发表学术论文22篇，培养博士研究生3人，硕士研究生5人，达到了预期研究和人才培养目标。