Research On Recombination And Welding Process Of Plasma-pulse MAG Under The Control Of Magnetic Field

The hybrid welding technology has been regarded as one of the effective ways to improve the quality and efficiency,which has become research focus in the field of welding at home and abroad.To make full use of the advantages of Plasma arc and Gas Metal Arc welding,Plasma-pulse MAG under the assistance of magnetic field is realized in this paper.And the droplet transition is controlled effectively.Plasma-pulse MAG under the control of magnetic field was realized by optimizing test parameters.The method reserves the deep penetration and perforation from plasma arc welding and pulse MAG welding high efficiency at the same time,achieving the space optimization and reconstruction of Plasma-pulse MAG,which improves welding quality and enhances the welding efficiency.In order to reveal the characteristics and advantages of the above welding methods,this paper makes a systematic study about the droplet transition and the physical characteristics of arc.Combined with the data of infrared thermographic testing,the influence of magnetic field on temperature field during welding process was studied.The results show that the magnetic field has hardly influence on the maximum temperature in the welding process,but the average temperature of the back surface of the specimen was inversely proportional to the magnetic field strength.The reason is that the contraction and coupling effect of the magnetic field on the composite arc concentrates the heat source increasing heat transfer efficiency,which causes further optimize the heat input in the welding process and improves the structure of welding joint.The droplet transfer process and behavior is analyzed using arc high-speed camera and data acquisition system for electrical signal.The results indicate that the continuous arc occurs during the Plasma-pulse MAG,which can reduce the heat input during the welding process.In addition,the magnetic field had a significant promoting effect on the droplet transition,the microscopic appearance is the refinement of the grain of the metallographic structure.The experimental research on the surfacing and butt welding under different process parameters has been carried out systematically.The following conclusion is drawn: the magnetic field has a significant influence on the weld formation and the cross-section morphology,which generally shows that the magnetic field can reduce the welding spatter and the weld depth effectively.Through the analysis of the macroscopic,microstructure and mechanical properties of the weld in the docking experiment,the results show that when the magnetic current is within the range of 0~4.5A,one-side welding with back formation is realized and the fracture of the tensile test samples occur on the base material.And the positive bending and back bending tests are more than 160 degrees in the bending test.When the magnetic field current is 5A,the tensile specimen fractures at the weld and cracks appear on the back-bend specimen.The tensile test of the weld fusion zone joint was carried out.The tensile strength of the upper part and the lower part of the 2A tensile specimen reached 521 MPa and 488 MPa respectively,which were higher than that in the non-magnetic field.Hardness test shows that the hardness of weld zone when magnetic field current is 2A is significantly higher than that of non-magnetic field.