感应加热熔丝复合激光焊接厚板中热源及熔丝耦合机制研究

High power laser welding of thick plate is the new trend of larger equipment structure welding manufacturing. However, the technology of laser welding of thick plate has bottleneck problems, such as poor welding stability, easily generated welding defects, changeful welding appearance, and narrow welding process window. In the present project, the inductive heated molten filler / laser hybrid welding of thick plate has been proposed, and the related mechanisms and process are studied. The multiple-physical coupling model consisting of heat transfer and integrated flow field is contributed, which includes the process of inductive heating, molten filler transition, and laser keyhole welding. Based on the model, the coupling relationship between multiple heat sources and the influences of energy utilization factors of heat sources on welding result are investigated. The coupling mechanisms of heat sources are revealed, the optimization scheme of energy distribution is obtained, and the correlation theory of low-energy welding is summarized. The coupling behavior between molten filler and molten pool and the interactive relationships between molten filler, molten pool and welding keyhole are researched. The influence rules of hybrid welding molten filler on molten pool, welding keyhole and welding stability are revealed. The regulating mechanisms of molten filler to molten pool stability during thick plate welding are illuminated. And, the suppression mechanisms of molten filler to welding defects are revealed. The project results provide the theoretical and experimental foundations to realize high efficiency, low energy consumption, high quality, and high stability of thick plate welding. The project will enrich and develop the inductive heating, laser welding and hybrid welding technologies.

高功率激光焊接厚板技术是大型装备结构件焊接制造的发展新方向。然而，激光焊接厚板时存在焊接稳定性差、极易产生焊接缺陷、焊缝成型不稳定、优化焊接参数窗口窄的瓶颈问题。本项目提出感应加热熔丝复合高功率光纤激光焊接厚板的新工艺，并对其相关机理及工艺开展研究。项目通过建立包含感应加热、熔丝过渡、激光小孔焊接过程中的传热和复合流场的多物理场耦合数值计算理论模型，研究多热源相互耦合关系和多热源能量利用比例对焊接结果的影响，揭示热源耦合机制、获得能量分配优化方案、形成低能耗焊接的相关理论；研究熔丝与熔池间的耦合行为、熔丝-熔池-焊接小孔间的相互作用关系，揭示复合焊接熔丝对熔池、焊接小孔及焊接稳定性的影响规律，阐明熔丝对厚板焊接熔池稳定性的调控机制，揭示熔丝对抑制焊接缺陷的作用机制。项目成果为实现厚板的高效、低能耗、高质量、高稳定性焊接提供理论和试验基础。项目丰富和发展了感应加热、激光焊接和复合焊接技术。

高功率激光焊接厚板技术是大型装备结构件焊接制造的发展新方向。然而，激光焊接厚板时存在焊接稳定性差、极易产生焊接缺陷、焊缝成型不稳定、优化焊接参数窗口窄的瓶颈问题。本项目提出采用感应加热方法或电阻加热方法提前将焊丝加热到熔化温度，再送入的激光焊接熔池部位，实现高温焊丝复合激光的多热源复合焊接。项目围绕高温焊丝复合高功率光纤激光焊接的新工艺开展了机理理论及焊接应用研究。项目首先对感应加热基础理论进行了总结，借助现有软件建立了感应加热焊丝数值仿真模型，研究了不同的感应器参数对焊丝加热效果的影响规律，并进行了感应加热焊丝试验。结果显示，由于材料居里温度的限制以及现有设备的限制，感应加热铝合金焊丝不易在极短时间内达到接近熔化状态。为此项目选择电阻加热焊丝方法实现对焊丝的加热。进一步地，项目建立了高温焊丝与激光复合的焊接三维模型，仿真研究了不同焊丝温度对焊缝截面成型的影响规律。为验证高温焊丝复合激光焊接仿真，项目采用电阻加热焊丝方法对焊丝进行加热，并检测了焊丝温度与电流大小关系，试验研究了不同焊丝温度下激光热丝焊接焊缝成型规律。采用正交试验方法研究优化了高温焊丝复合激光焊接工艺参数，对比研究了纯激光焊和热丝激光焊时焊缝成型和焊缝性能的变化。在焊接机理方面，试验研究了高功率激光焊接时金属蒸汽的行为特征、焊接熔池流动特征、以及蒸汽与小孔的相互作用行为；探索性的研究了添加活性元素和活性保护气对高功率激光焊接熔池流动行为的控制作用，研究了不同工艺参数条件下活性元素对焊缝成型、焊接气孔、焊缝性能的影响规律。本项目的研究成果将进一步完善激光焊接的机理理论、推广激光焊接技术的应用，为材料焊接提供可靠、实用的焊接工艺方法和理论支持，推动复合焊接技术发展，相关成果可推广到异种金属焊接、金属与非金属连接等多种材料焊接领域。