Research On Elaborate Electromagnetic Control Of "Arc-Short Circuit" Process In High Current CO₂ Welding

CO₂gas shielded welding is a traditional arc welding technology,which has many advantages such as low cost,energy-efficient.It is widely used in automobile manufacturing,marine and shipbuilding,aerospace and other industries.However,CO₂gas shielded welding also has disadvantages,such as high spatter and poor forming in the welding process.In order to solve the problems in the short-circuit transfer CO₂welding process,the article proposes to apply a synchronous magnetic field to control the welding process finely.First,by detecting the arcing and short circuit signals of the welding process,complete the introduction of the magnetic pulse at the beginning of the arcing or short circuit phases,then cut off the magnetic pulse at the end of the arcing and short circuit phases.Study the changes in the process of droplet transfer under the action of a synchronous magnetic field,explore the influence of the synchronous magnetic field on arcing time,droplet shape,short circuit time,transfer frequency,spatter loss coefficient,weld formation,etc..Under the action of the synchronous magnetic field,during the arcing phase,it found that the arcing time was reduced to a certain extent,the dimension of the droplet was reduced and the size of the droplet was more uniform,the transfer frequency of the droplet was increased,the maximum average transfer frequency was 161.3Hz,and the range of the droplet transfer frequency was reduced.The transfer process was more stable.At the synchronous longitudinal magnetic field excitation current I_m（LMF）=100A,under the premise of ensuring a high droplet transfer frequency,the fluctuation range of the droplet transfer frequency was also significantly reduced,and the effect was better.At the same time,the synchronous magnetic field had a significant effect on reducing the spatter in the welding process.The effect of the synchronous longitudinal magnetic field was better than that of the transverse magnetic field.At the welding current I=180A and the excitation current I_m（LMF）=100A,the spatter during the welding process was the least and the spatter loss coefficient from the original 8.32%to 2.75%,a decrease of 5.57%.Under the action of the synchronous magnetic field in the arcing phase,the weld surface was improved,the weld penetration depth became shallower,the change of the weld penetration width was not obvious,the hardness of the weld zone was improved,and the maximum value was increased about 65.6 HV0.5,the microstructure of the weld zone had also been refined to a certain extent.Under the action of the synchronous magnetic field in the short circuit phase,the short circuit time was shortened and the minimum value of the droplet transfer frequency was increased.In terms of increasing the droplet transfer frequency,the effect of the synchronous magnetic field in the short-circuit phase was not as significant as the effect of the synchronous magnetic field in the arcing phase,but the short-circuit phase synchronous magnetic field had a certain promotion effect on improving the stability of the droplet transfer process and reducing the spatter during the welding process.The surface of the weld under the action of the synchronous magnetic field in the short-circuit phase was flat and smooth,which was better than the surface of the weld without magnetic field.At the welding current I=140A-180A,the weld penetration depth decreased,but the weld penetration depth increased at I=200A.After adding the synchronous longitudinal magnetic field,with the increase of the excitation current,the increase extent of the weld penetration width gradually reduced.At the welding current I=180A and the excitation current I_m（LMF）=100A,the weld penetration width increased most significantly,and the weld reinforcement reduced obviously.The application of the synchronous magnetic field in the short circuit phase had a significant effect on the grain refinement in the weld zone.When the welding current I=180A,and the grades of grain size by calculating under each magnetic field parameter were all greater than 13,the maximum was 13.61.In this welding current,the hardness increased with the increase of the excitation current,and the maximum was 257.6 HV0.5.