Study On High Speed GMAW Process Assisted By Compound Magnetic Fields

Gas metal arc welding(GMAW)occupies the leading position because of its advantages of low cost,easy operation and convenience to realize automatic control.Increasing welding speed of GMAW is an important way to improve welding productivity and to reduce production cost.When welding speed of GMAW increases to a certain extent,the appearance of weld defect(undercut)becomes the bottleneck of improvement of welding speed and welding productivity.Therefore achieving the goal of high quality,high efficiency and low cost welding based on traditional GMAW has important research significance and engineering practical value.In this study,new ideas of using compound magnetic fields to control the weld pool’s flow behavior in directions parallel and vertical to the welding direction simultaneously was put forward.The new method is to achieve the goal of suppression of undercut and improvement of welding speed of GMAW.Self-designed special-shaped compound magnetic generator can produce pulse compound magnetic fields in the regions of magnetic poles and welding arc.Compound magnetic fields consist of parallel component and transverse one working in the arc zone together.High speed GMAW experimental system was built up with compound magnetic generator coupling with welding torch.The effect of excitation current frequency and excitation peak current on weld form was analyzed.Dual camera visual inspection system and flow fields visual inspection system were built up.Angles of deflection of arc and droplet as well as surface flow field on weld pool were measured.The effect of compound magnetic fields on arc,droplet and flow behavior of weld pool was analyzed.The suppression mechanism of undercut in high speed GMAW with compound magnetic fields was preliminarily revealed.Compound magnetic fields can control the forward inclination angle as well as the amplitude,frequency and duration of stay on the side of the weld seam.Under the proper welding condition and magnetic field parameters compound magnetic fields can improve the transverse movement of molten metal as well as backward flow.Consequently welding speed of good quality weld seam(without undercut)was increased to 1.7 m/min.