The Research On Technology And Mechanism Of Double Electrode GMAW

According to the problems in high-efficiency MIG/MAG welding, such as complex devices and high cost, difficulty in process parameters matching, difficulty in welding thin plate and even requiring special shielding gas and welding materials in some high-efficiency welding methods, a new low-cost high-efficiency welding method--DE-GMAW was proposed. In DE-GMAW process, the force field distribution and heat input on droplet and welding pool can be adjusted appropriately by changing welding parameters of bypass arc. Therefore, the heat input on base metal and welding wire can be distributed reasonably and the arc force can be reduced effectively at large-current welding, decreasing weld defects in high-efficiency welding. This welding method can be applied to high-efficiency welding on sheet for automobile, high-efficiency surfacing on pressure and chemical containers, and so on. DE-GMAW is a novel, potential welding method, which has theoretical significance and practical engineering value.In order to study and understand the characteristics of coupled arc, mechanism of metal transfer and distribution law of heat input on base metal and welding wire further and lay a foundation for actual welding production, test research and theoretical analysis were done on influence law of bypass current/arc on coupled arc shape and metal transfer mode, distribution law of heat input, welding process control and high-speed welding technology. In order to study the influence law of bypass current/arc against metal transfer process and arc force on surface of welding pool, force analysis on droplet was done in non-consumable DB-GMAW process and simplified calculation was made on acceleration and resultant force when metal droplet fell through the coupled arc. Then the influence on falling speed, force of droplet and metal transfer mode under different bypass current but the same total current were analyzed. Both the theoretical analysis and calculation results showed that the addition of bypass current/arc not only promoted the metal transfer, reduced the critical current of metal transfer, but also decreased the arc force on surface of welding pool, thereby reducing the weld penetration.On the basis of stable welding process, the heat distribution mode between surface and body heat source was further studied and a composite heat source model suitable for DE-GMAW was developed. Numerical analysis and calculation were made for the welding temperature field of DE-GMAW. Then the distribution of temperature field of workpiece was simulated under different welding parameters and influence law of heat input under different welding parameters was analyzed. Corresponding surfacing verification tests were carried out and welding heat cycle curves of feature points on the back of the workpiece were acquired. The comparison and analysis results showed that the proposed composite heat source was reasonable and could reflect the heat distribution of DE-GMAW process suitably.The stability of consumable DE-GMAW process is poor due to the addition of a GMAW torch. A rapid prototyping control system was established to solve this problem. On this basis, control tests in consumable DE-GMAW process were carried out and obtained weld beads with good formation.The welding process of consumable DE-GMAW, non-consumable DE-GMAW and DB-GMAW were studied respectively. The influence of geometry parameters of welding torches on welding process stability and welding quality was studied and the optimal geometry parameters of welding torch were obtained. On this basis, the three different types of welding methods were applied to high-speed surfacing and overlap welding on mild steel and zinc-coated steel respectively. The parameters range of high-speed surfacing was determined and comparison and analysis on the test results were carried out.