外加磁场对高速GMAW电弧和熔池行为的主动调控效应

在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当焊接速度超过临界值后,焊缝成形变差,出现咬边和驼峰焊道,无法满足生产要求。研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因。自主研发外加磁场发生装置,向熔池施加横向电磁力,对后向液体流进行主动干预,并调控熔池流态,从而抑制驼峰焊道的形成。在Q235低碳钢板上开展焊接工艺试验,获得了不同磁感应强度下的焊缝表面成形;采用高速摄像技术,拍摄焊接过程中的电弧和熔池图像,分析外加磁场对电弧形态、熔池流场和焊缝成形的影响规律,初步揭示外加磁场抑制驼峰焊道的机理。试验结果表明,外加横向磁场能明显调控熔池流态,减小后向液体流的动量,并能有效抑制驼峰焊道和咬边等缺陷,显著改善焊缝成形,提高临界焊接速度。

Proactive Control Effect of Arc and Weld Pool Behaviors by an External Magnetic Field in High Speed GMAW

In high speed gas metal arc welding (GMAW) process, the weld formation quality will get worsen and weld defects like humping bead and undercutting will appear when welding speed exceeds the critical value. The previous investigations have proved that the backward flowing molten jet with high momentum in the weld pool is responsible for the formation of humping bead in high speed GMAW process. An external electromagnetic field generator is developed to conduct proactive control of the backward flowing molten jet in the weld pool, and adjust the weld pool fluid flow field, in order to suppress the occurrence tendency of the humping bead. Bead-on plate welding experiments are performed on mild steel Q235 test-pieces, and the weld bead appearance under different magnetic flux density are obtained. The high speed camera is used to capture the images of the arc and the weld pool during the welding process. The influences of the exerted magnetic flux density to the arc behavior, the fluid flow inside the weld pool, and the weld bead shape are investigated. The reason why the external electromagnetic field can suppress the humping bead is explained. The results show that external magnetic field can remarkably adjust the weld pool fluid flow field and decrease the momentum of backward flowing molten jet. Therefore, weld defects like humping bead and undercutting can be effectively suppressed, the quality of weld bead is remarkably improved, and the critical welding speed is notably increased.