超音频复合脉冲MIG焊接电弧及熔滴过渡行为研究

MIG welding technology is widely applied in the industries for its well weld appearance and high welding efficiency. However, there are still some problems in MIG welding such as porosities, significant growth of microstructure and poor mechanical properties because the arc stability is interfered easily as the low arc maintaining current. Study on droplet transfer process and arc stability of MIG welding is always a hot issue in welding research field. As a result, it is meaningful to explore the methods for improving MIG welding property. A new MIG welding process was proposed and developed by applicant who recombined an ultrasonic frequency pulse current with more than 100A value and 20kHz frequency with conventional continuous or pulsed MIG welding. With help of ultrasonic frequency pulse current, the weld quality may increase by influencing droplet transfer process and arc stability. An automatic welding platform, an arc force measuring equipment and a synchronous collecting system of high speed photography and electrical signals have been set up. The objective is to carry out the fundamental researches of droplet transfer behavior and the process applicability, to reveal the physical characters of droplet, heat and force under the function of ultrahigh frequency pulse current and to explore the effective route to improve welding quality of MIG welding. Further, this project will lay the foundation for the application of this new welding technology in the industrial fields.

传统脉冲MIG焊焊缝成形好，焊接效率高，应用十分广泛，然而其维弧期间电流小，易受干扰，电弧稳定性差，焊缝中易产生气孔缺陷，存在接头组织粗大、力学性能衰减等问题。MIG焊熔滴过渡、电弧稳定性等物理过程一直是学术界研究热点，进一步提高其焊接性能具有重要的工程意义。申请人提出并研发了一种全新的超音频复合脉冲MIG焊接技术，在传统脉冲MIG焊基础上，复合叠加幅值上百安培、频率20kHz以上的超音频脉冲电流，将对熔滴过渡产生影响，有效提高维弧期间电弧稳定性；建立了自动焊接、电弧力测量、高速摄像与电信号同步采集等试验及监测平台。拟针对超音频脉冲电流对熔滴过渡行为的影响开展基础研究，研究分析其工艺适用性，揭示超音频脉冲电流作用下熔滴过渡物理过程及其热、力特征，探索进一步提高MIG焊焊接质量的有效方法，为该技术的实际应用奠定基础。

超音频复合脉冲MIG焊接是一种新的MIG焊接工艺技术，本项目重点针对熔滴过渡动态行为、电弧动态行为、临界电流分析、焊接工艺适用性等方面进行了系统深入的研究，全面考查了熔滴形成、缩颈形态、熔滴脱落、电弧形态、熔滴冲击熔池、液态金属流动、温度分布及热质交换等典型物理过程。本报告详细介绍了项目研究计划的执行情况、研究工作主要进展和结果等方面的情况，分析总结了熔滴过渡与电弧行为对焊缝组织形貌、晶粒细化及接头力学性能的影响规律。