Study On The Procedure Of Double-Bypass Coupled Arc MIG Welding

For achieving high-speed welding, the melting current through the wire must be increased while the heat input of base metal and arc pressure should be controlled at a lower level, this is a contradiction. The Double-Bypass coupled arc MIG welding is constituted by adding two TIG torches to a conventional MIG torch that are symmetrical on each side, the bypass torches create two bypass coupled arcs and bypass currents, this makes it possible to decouple the current through the base metal in order to reduce the arc pressure, the reduction of arc pressure could enhance the welding speed so as to achieve high-speed welding under the certain welding procedure parameters, so the Double-Bypass coupled arc MIG welding solved the contradiction preferable. The following several aspects of study work were mainly done in this paper.A set of experimental platform was fabricated which was used in the Double-Bypass coupled arc MIG welding process research, the experimental platform consists of welding system and multi-channel synchronous data acquisition system of the welding current and voltage,arc image and the temperature, plus the man-machine interface, and the Lab VIEW software was used to write the multi-channel synchronous data acquisition program.A large number of experiments have been done to find out the appropriate geometrical parameters of torch combination which can assure the stability of two bypass arcs.This paper applied established theories to analyze the arc force acting on the surface of the welding pool,theoretical analysis shows that the bypass arcs actually reduce the arc force that acts on the surface of the welding pool, so the novel welding process could restrain the occurrence of weld defects in particular range of bypass currents so as to enhance the welding speed.It has been proved that the arc force acting on the surface of the welding pool decreases with the increasing of bypass currents through comparing the penetration of these beads under different bypass currents. The theoretical analysis shows the bypass arcs could reduce base metal heat input,and Experimental results also have proved that base metal heat input is decreasing with the increasing of bypass currents when the total welding current was fixed.The forces acting on the droplet of DB-MIG are discussed, The influences of bypass arcs to values and distribution of arc forces acting on the droplet are apparent. The mainly effects of arc forces is to promote metal transfer and reduce the critical current of spray transfer. Analysis shows that the bypass arcs and currents lower the critical current needed to achieve the desired spray transfer. Experimental results proved that the metal transfer could be changed by changing the bypass currents.High-speed welding tests for thin plate were carried out, the relationship between the bypass current and the correspondingly maximum welding speed was discovered when the wire feed speed was fixed.The experiment results have also proved that Double-Bypass coupled arc MIG welding could enhance the welding speed so as to achieve high-speed welding compared the conventional MIG welding under the same welding procedure parameters.