活性激光焊接厚板机理与技术基础研究

In allusion to the light-induced welding defects such as strong plasma, big recoil force of metal vapor, deep hole and poor stability, severe disturbance of weld pool fluid in the process of high power laser welding of thick plate, the technology of activating-flux laser welding thick plate is proposed and its complex physical and chemical process, quality control method are researched. The dynamic characteristics information such us slender hole behavior in the process of welding, plasma effect, weld pool temperature field and flow field are studied. And then the interaction relations between laser, active agent and stainless steel plate specimens is analyzed and the mathematical model of welding based on “laser–hole, plasma and weld pool–active agent” is established. Furthermore, the function mechanism that active agent increases welding penetration, reduces or inhibits welding defects is revealed. The mapping relationship of “multiple process parameters–features information in the process of welding–welding quality” is established. The preparation method of component matching of a new type of active agent is put forward, and the laser welding active agent composition system and the optimal control scope of elements are determined. Finally, the activating-flux laser welding thick plate process theory is formed through process parameters optimization. The project result can effectively solve defects such as blowhole, subsidence and crack produced in laser welding plate, enriches and develops activating-flux laser welding basic theory to provide important theoretical and experimental basis for promotion and application of activating-flux laser welding.

针对高功率激光焊接厚板过程中因其诱发光致等离子体能力强、金属蒸气反冲驱动力大、小孔深度大且稳定性差、熔池流体剧烈扰动等而易产生焊接缺陷的问题，本项目提出活性激光焊接厚板工艺技术，就其复杂物理化学过程及质量控制方法展开研究。开展焊接过程中细长小孔行为、等离子体效应、熔池温度场和流场等动态行为特征信息研究；分析激光、活性剂与试件的相互作用关系，建立基于“激光-小孔、等离子体、熔池-活性剂”系统的焊接数学模型；揭示活性剂增大焊接熔透性、减少或抑制焊接缺陷的作用机理；建立“多工艺参数-焊接过程特征信息-焊缝质量”的映射关系；提出新型活性剂组分配比与优化方法，确定激光焊活性剂组成体系及元素成分的最佳控制范围；通过多参数工艺优化，形成新型活性激光焊接厚板工艺理论。项目成果将有效解决激光焊接厚板产生的气孔、塌陷及裂纹等缺陷问题，丰富和发展活性激光焊接基础理论，为活性激光焊的推广应用提供重要理论和试验基础。

由于采用高功率激光焊接不锈钢厚板过程中因其诱发光致等离子体能力强、金属蒸气反冲驱动力大、细长小孔稳定性差、熔池流体剧烈扰动等易产生缺陷问题，使得焊接质量难以控制。本课题提出了活性激光焊接技术方法，针对活性剂增大焊接熔透性作用机理及提高小孔与熔池稳定性方法技术展开研究. 通过高速实时监测系统对活性剂作用下焊接过程中细长小孔行为、金属蒸气与等离子体效应、熔池流场等动态行为特征信息进行了监测分析，并与无活性剂时的焊接过程动态特征信息进行对比。结果表明，试样表面涂覆适宜厚度与类型的活性剂可提高其对入射激光能量的吸收，降低实际作用于焊接过程中的激光功率，进而抑制了孔内外等离子体的产生及削弱了随等离子体向上喷射的金属蒸气，金属蒸气反冲驱动力的降低提高了小孔和熔池的稳定性，实现了不锈钢厚板活性激光高焊接过程稳定性焊接。. 建立了基于“激光-活性剂-试样”相互作用关系的焊接过程数学模型，分析计算了有无活性剂作用下熔池温度场的变化，并采用红外热像仪实时监测了相应条件下试样焊接过程中熔池的温度变化情况，通过对数值计算与试验监测的熔池温度变化的拟合对比分析发现：两温度曲线变化趋势相近，数值计算值略高于实际监测值，且SiO2活性剂和TiO2活性剂可将熔池温度提升7-9%，而NaF活性剂则会微量降低熔池温度。. 进行了活性激光焊接不锈钢多工艺参数优化试验，并从焊缝表面和横截面形貌、接头微观组织、元素成分分布及力学性能等方面对表面涂覆不同活性剂试样的焊接质量进行了检测，并与未涂覆活性剂试样进行了对比分析。结果表明，试样表面涂覆适宜厚度SiO2和Cr2O3活性剂可在一定程度上改善焊缝表面成形、增大焊缝熔深、细化焊缝区晶粒组织、缩小热影响区范围、提高接头强度与硬度值，且未改变母材中主要元素成分的含量与分布。项目成果有效解决激光焊接厚板产生的气孔、塌陷及裂纹等缺陷问题，形成了新型活性激光焊接厚板工艺理论，为活性激光焊的推广应用提供重要理论和试验基础。