磁控熔化极立焊过程多参数实时控制关键技术研究

The dynamic stability of weld pool, weld quality and weld properties of gas metal arc welding in spatial position can be improved by employing magnetic fields on influencing and controlling the welding arc, droplet and molten metal flow. The main problems in such magnetically controlled arc welding is the instability of weld formation, including inconsistent bead shape, out-of-tolerance weld size and forming defects. The weld formation is closely related to various factors, including the weld pool behavior, changes in alignment and relative position and angle, control of magnetically controlled arc welding process parameters, etc. This project proposes to carry out researches on the electromagnetic fields generating and arc motion controlling, the on-line visual feature extraction of weld pool and signal acquisition, the modeling of complex dynamical process system, and the control of welding parameters in the magnetically controlled arc welding. Through these researches, the inner mechanisms among ‘arc motion-process parameters-fluid flow characteristics-welding quality’ are to be clarified, and the metal molten flow mechanisms of weld pool and the influencing factors on it are to be revealed. In addition, key technologies are to be developed in developing flexible motion control theme for arc in electromagnetic field, self-correcting of welding pose and position, and real-time optimizing and controlling of welding process during the magnetically controlled arc welding, so as to provide technical supports for expanding further its application in high-end manufacturing and the developments of intelligent all-position magnetically controlled arc welding technology and system.

借助外加磁场对焊接电弧、熔滴、熔池进行影响和控制，可实现对空间位置熔化极焊接过程熔池动态稳定性以及焊缝质量和性能的优化。目前存在的主要问题在于成形质量的稳定性，包括焊缝成形不均匀、尺寸超差和成形缺欠。焊缝成形与熔池行为、焊接过程焊枪对中及相对位姿变化、磁控焊接工艺参数控制等密切相关。本项目提出针对磁控熔化极立向焊接的电弧多模扫描运动控制、熔池视觉特征与多电量信息在线获取、复杂动态过程建模、焊接过程多参数实时反馈控制等问题开展研究。旨在阐明“磁致电弧运动-焊接工艺参数-熔池流动特征-焊缝成形”之间的内在机制，揭示磁控熔化极立向焊接过程动态熔池行为机制及影响因素，突破磁致电弧运动柔性控制、焊接位姿在线调节和焊接工艺参数实时优化控制等磁控熔化极焊接过程在线控制的关键环节，为进一步拓展磁控电弧焊接技术在高端制造重要领域的应用和发展智能化磁控全位置焊接技术和系统提供基础。

在熔化极气体保护立焊过程中，借助外部磁场对焊接电弧进行影响和控制，结合液体金属熔池区域视觉信息和电量信号特征进行焊缝成形质量在线预测，以实现焊接位姿与工艺参数实时闭环控制，对维持熔池动态稳定性、保证焊缝成形质量、提高焊接构件服役性能具有重要意义。针对磁致电弧运动柔性控制问题，本项目分析了磁控熔化极立向焊接过程熔池稳定的热、力学边界条件，研究了抑制熔池失稳或液态金属下坠的磁致电弧多模柔性扫描控制实现方法与电弧运动行为，提出了新型GMAW磁控焊枪装置，实现电弧低惯性、广速度域的多模式偏摆扫描焊接与电弧传感，解决了焊接过程中电弧扫描参数实时连续调整的问题。针对熔池视觉特征与多电量信息在线获取和实时处理问题，本项目深入分析了构建不同弧光环境下熔池自身辐射光谱、电弧光谱波长-能量特性以及成像元件感光特性，建立了多尺度熔池区域清晰成像所需光学传感条件，克服了强弧光干扰并改善光学倍率与景深之间的矛盾，实现熔池图像-焊接过程多电量参数同步采集，以及每种时空域特征信息的实时图像处理算法，并探讨工艺条件变化下不同视觉特征信息对瞬态熔池形态的表征特性。针对复杂动态过程建模问题，本项目深入分析了熔池瞬态图像和焊接过程参数信息融合在焊缝成形预测场合的适用性，根据不同接头坡口特征信息及工艺方法建立焊接参数自适应控制所适用的“焊接条件-熔池行为-适度熔透和焊缝成形”数据驱动模型，揭示了“磁致电弧运动-工艺参数-熔池特征-焊缝成形”之间的内在机制。基于上述研究成果，本项目在焊接位姿在线调节及工艺参数实时反馈控制等场合开展深入的实验研究，结果表明，所提出的焊接过程闭环控制新方法能克服重力因素、位姿偏差和散热条件变化等导致的成形质量不稳定和成形缺陷问题，为提升立焊结构质量可靠性与一次焊接合格率提供了新的技术途径。本项目研究结果可应用于海洋工程装备、船舶、重型机械和物流运输装备等领域关键焊接构件智能化焊接场合。