高速GMAW熔池流态的复合磁场调控及焊缝成形缺陷抑制机理的研究

The research has proved that the transverse spreading and backward flowing states of molten metal in the weld pool are the key factors to determine whether there exist weld bead defects (undercut and humping defects) or not during high speed GMAW process. This project is intended to install the generator of compound magnetic fields on the standard GMAW torch. Then the external compound magnetic fields are expected to suppress undercut and humping defects simultaneously by promoting the molten metal to flow transversely and reducing the speed of backward flow when it is applied upon the workpiece. The interaction mechanism between undercut and humping defects is illustrated based on feature extraction for arc shape, droplet transfer, weld pool behavior and temperature distribution of high speed welding. The multi-fields coupling models, which reflect the relationship of compound magnetic fields, thermal-force conditions of arc/droplet and molten metal behavior, are established to analyze 3D heat-exertion state, force-exertion state and fluid dynamics of weld pool. And the influence of compound magnetic fields on surface deformation, molten metal dynamics, and heat distribution of weld pool is also studied to illustrate their mechanism on regulate arc and molten metal behavior. Moreover, the suppression mechanism of weld bead defects by compound magnetic fields in high speed GMAW is revealed. Based on the numerical and experimental results, the parameters of compound magnetic fields and high speed GMAW process are optimized. It will provide a solid foundation for developing and applying high speed GMAW assisted with compound magnetic fields.

研究发现，高速GMAW焊接过程中熔池液态金属的横向铺展和后向流动状态是决定焊缝咬边和驼峰缺陷产生与否的关键因素。本项目拟在标准GMAW焊枪上安装复合磁场发生装置，将外加复合磁场从工件正面施加于熔池，既促进熔池液态金属的横向流动，又减小熔池内后向流的速度，期望达到同时抑制咬边和驼峰缺陷的目标。通过实时采集高速GMAW的电弧形态、熔滴过渡、流体流动、温度分布等信息，研究咬边和驼峰缺陷间的相互作用机制。建立“复合磁场-电弧/熔滴热力特性-熔池流体动力学行为”的多场耦合模型，定量分析熔池不同位置处三维受力受热状态对其表面变形、流体流动状态以及热量分布的影响规律，阐明外加复合磁场对电弧、熔池流体流动的调控机制，揭示复合磁场对高速GMAW焊缝成形缺陷的抑制机理。基于数值分析和实验测试结果，实现复合磁场参量与高速GMAW焊接工艺参数的优化。为促进复合磁场辅助高速GMAW焊接新工艺的实际应用奠定坚实基础。

熔化极气体保护焊(GMAW)在各类焊接方法中居于主导地位。如何在避免焊缝成形缺陷的基础上，低成本的大幅度提高GMAW焊接速度，是促进企业实现新旧动能转换、提高市场核心竞争力的关键助推器之一。本项目通过实时采集高速GMAW焊接过程中的电弧形态、熔滴过渡、流体流动、温度分布等信息，研究了咬边和驼峰缺陷间的相互作用机制。基于此，研发并改进具有自主知识产权的脉冲复合磁场辅助GMAW高速焊接新工艺，研制出第二代结构紧凑的励磁装置以及双路交变励磁电源，同时调控焊接熔池三维形貌和熔池内液态金属横、纵向流动行为。基于GMAW高速焊双目视觉流场检测系统及熔池红外测温系统，构建出适用于工业生产的低成本GMAW高速焊接-检测系统，开展了脉冲复合磁场辅助GMAW高速焊工艺试验，研究了不同焊接工艺参数及外加磁场参数对高速焊焊缝成形的影响。通过工艺优化，对于碳钢，最高焊接速度可达2.0 m/min;对于铝合金，最高焊速可达2.5 m/min，并已成功试焊轨道车辆典型构件。理论上，建立了磁控高速GMAW “复合磁场-电弧/熔滴热力特性-熔池流体动力学行为”的多场耦合模型，从电磁学、流体动力学以及传热学等多学科交叉的角度，阐明了“脉冲复合磁场-电弧-熔池”间相互作用规律，揭示了复合磁场与电弧-熔池间的相互作用机制，分析了复杂磁场参数对熔池形态及液态金属流动行为的影响规律。在此基础上，改进了SURF-BRISK-KAZE特征点提取匹配算法与RANSAC误匹配消除算法，并结合LOWESS三维拟合算法，实现熔池表面形貌精确三维重建，为未来改进闭环控制系统、促进复合磁场辅助高速GMAW焊接新工艺的实际应用奠定坚实基础。依托该项目，授权国家发明专利2项，在国内外重要期刊发表SCI学术论文16篇，培养博士生1名，协助培养博士生1名，培养硕士生9名。