Study On Arc Coupling And Flow Behavior Of Multi-wire GMA Welding

High-speed gas metal arc welding(GMAW)is an effective method of solving heavy welding problems in heavy industries such as shipbuilding.In the past,researches on single and double wire gas metal arc welding have been relatively mature,while few researches have focused on the triple-wire GMAW process.This is mainly due to the fact that the arc interference between the three wires in the three-wire GMAW is far more complicated than the double-wire arc interference model.The addition of the third wire changes arc behavior,heat source distribution,droplet transfer,etc.throughout the welding process.The complex multi-field coupling increases the difficulty of the research process,especially the modeling of such process.Therefore,this study focuses on building a comprehensive triple-wire GMAW experimental system and detection system.Firstly,the combination of traditional electric signal detection system and high-speed photography system is used to analyze the three-wire electrical signal and arc behavior of different current parameters and wire spacing,and qualitatively analyze the influence of different parameters on arc interference.Then the quantitative analysis of the intermediate arc is carried out by spectral analysis.The temperature distribution and electron density distribution of the arc under multi-wire working conditions are studied based on the Boltzmann mapping method and the Stark broadening method.Combined with the qualitative results obtained by high-speed photography,the quantitative analysis of the interference among the arcs is given.In this study,Flow-3D software was used to simulate the flow of the three-wire stationary GMAW welding pool.The simulation model was modified in order to make the simulation results close to the actual results.It is found that for the case where the three-wire spacing is constant,when the current ratio is L400T300T300 A,the arc working state is relatively stable.Under other parameters,the arc interference is obvious.At the same time,it is found that the intermediate arc is more sensitive to the arc interference than the leading arc and the trailing arc.Therefore,the subsequent spectral research will mainly focus on the intermediate arc.For the condition that the current of the leading arc and the trailing arc are different,when the distance between the leading arc and the intermediate arc are large,it will cause an overall drop of the arc interference.While the distance between the small current arc and the intermediate arc becomes larger,the degree of arc interference rises.This shows that the leading arc current plays a more important role in arc interference under this parameter.For the spectrum analysis results,it is found that in the case of double wire,when the leading arc current is greater than that of the intermediate arc,the center temperature of the original intermediate arc is stably shifted toward the leading arc,and the electron density on the side of the leading arc is significantly increased.When the arc current is equal to the intermediate arc,the arc temperature and the electron density distribution both show instability in the working state for the intermediate arc.In the case of the triple wire,the temperature distribution of the intermediate arc becomes complicated due to the addition of the third arc.The temperature is low at the center position of the intermediate arc and the electron density distribution is closer to the one-wire working state under the three-wire GMAW,which indicates the intermediate arc working state in this case is more stable.In this study,combined with the arc photograph obtained by the highspeed camera system,the arc illuminance information is processed by using the Abel inverse transform method.It is found that the illuminance distribution data obtained meets the Gaussian distribution,and the effective radius of the three arcs can be accurately obtained by the graphic method.In addition,there is a horizontal velocity component in the actual drop captured by the high-speed photography.Through the theoretical calculation,the vertical drop velocity when the droplet is generated can be obtained.The horizontal velocity component can be obtained by using the geometric relationship in combination with the drop angle observed by the high-speed photography.Using the Flow-3D software,the horizontal velocity component is added to the droplet model.The simulation shows that the molten pool on both sides moves to the intermediate molten pool.The flow pattern of the triple-wire molten pool and the final shape of the weld joint correspond to the actual results.