激光深熔焊接厚板孔壁局部蒸发诱导的熔池行为及焊缝成形控制

Deep penetration laser welding of thick plate has noticeable advantages, such as low welding distortion and high production efficiency. However, there are several problems during deep penetration laser welding of thick plates via high power fiber laser, such as poor welding stability, difficult to control the welding quality, and prone to generate weld appearance defects, for example, undercut and root sagging, and narrow welding process parameters window. In order to make great breakthrough in some key scientific problems on the formation mechanism and control processes of the above weld appearance defects, the following researches are deserved to be carried out: (1) to study the influence rules of local morphologies of the keyhole wall on the energy coupling of fiber laser on the front keyhole wall on the basis of the observed keyhole wall morphologies; (2) to investigate the recoil pressure induced by the local evaporation on the front keyhole wall, and its associated molten pool behavior; and (3) to reveal the formation mechanism of the weld appearance defects of, such as undercut and root sagging, and to put forward and research the control processes of weld appearance on the basis of prefabricating flow channels. Finally, the key scientific problems implied in the research contents will be solved, and high-quality and high-stability laser welding technology of thick plate with independent intellectual property rights will be developed. The research achievements of the project will enrich and develop the laser welding theory, and strongly promote the development of high-quality, high-efficiency, low-welding stress and low-energy consumption laser welding of large critical components of nuclear power equipment.

激光深熔焊接厚板具有焊接变形小、生产效率高的突出优点。然而，高功率光纤激光深熔焊接厚板存在焊接稳定性差，焊接质量控制难度大，易出现塌陷、根漏等焊缝成形缺陷，且焊接工艺参数窗口窄的问题。本项目为了在塌陷、根漏等焊缝成形缺陷产生机理和控制方法的若干关键科学问题方面取得研究的突破，主要开展以下研究：（1）基于直接观测的小孔内壁形态，研究孔壁局部形态对小孔前壁光纤激光能量耦合的影响规律；（2）研究小孔前壁局部蒸发反冲压力及其驱动的熔池行为；（3）探究塌陷、根漏等焊缝成形缺陷的产生机理，提出并研究基于预制流道的厚板焊接焊缝成形控制方法。攻克研究内容中蕴含的关键科学问题，形成具有自主知识产权的高质量、高稳定性厚板激光焊接技术。项目研究成果将丰富和发展激光焊接理论，大力推动核电设备关键部件的高质量、高效率、低应力和低能耗激光焊接技术的发展。

激光深熔焊接厚板具有焊接变形小、生产效率高的突出优点。然而，高功率光纤激光深熔焊接厚板存在焊接稳定性差，焊接质量控制难度大，易出现塌陷、根漏等焊缝成形缺陷，且焊接工艺参数窗口窄的问题。项目组针对“高功率光纤激光深熔焊接小孔形状及孔内能量耦合，孔壁蒸发反冲压力及熔池流动特征和厚板焊缝成形（底部驼峰和表面塌陷）控制方法”这三个方面开展了理论和试验研究。采用理论计算、数值仿真和试验（直观观测和工艺试验）的方法，对小孔内壁形貌及小孔动态行为进行了直观观测，分析了孔壁能量耦合吸收特征，明确了孔壁蒸发反冲压力对熔池流动的影响机制，探究了厚板焊接塌陷、根漏焊缝成形缺陷的产生机理，提出了基于预制流道的厚板焊接焊缝成形控制方法，并申报了国家发明专利。发表SCI收录论文6篇；申请发明专利6项，授权3项；参加激光加工和焊接技术国内国际会议11次；培养硕士生5名。项目研究成果丰富和发展了激光焊接理论，为厚板高质量、高效率、低应力和低能耗激光焊接技术的推广应用提供了技术支撑。