What is magnetic deflection in welding?

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In DC arc welding, the phenomenon in which the welding arc is deflected due to electromagnetic forces is known as magnetic deflection. It has a significant negative impact on the welding process and quality; only by overcoming this issue can welding quality be ensured. There are many factors that cause magnetic deflection. Specifically, when starting and ending the arc at the edge of the workpiece, the magnetic flux density is compressed and deformed, resulting in uneven magnetic flux densities in front of and behind the arc. The magnetic flux density is higher near the edge of the workpiece than farther from it. According to the physical law governing the force exerted on current in a magnetic field, this results in a magnetic deflection effect: the arc is deflected forward during arc initiation, and backward during arc extinction. Remedial measures: Add arc initiation plates and arc termination plates; change the travel angle of the electrode (or wire) (towards the side where the arc is deflected). The second ground wire is not in the correct position relative to the welding direction; since the magnetic flux density behind the arc is greater than that in front of it, the arc is deflected toward the front. Remedial measures: Connect the ground wire to the end where the arc is extinguished; change the travel angle of the electrode (or welding wire); use non-magnetic ground clamps. Third, when multiple arcs are used near each other during the welding of T-joints or corner joints, in order to reduce welding deformation and improve welding efficiency, it is common to weld on both sides of the vertical plate at the same time. However, if this welding technique is not implemented properly, it can lead to magnetic deflection of the arc. Remedial measures: Weld simultaneously using both AC and DC power sources; change the travel angle of the electrode (or wire). When welding workpieces of unequal thickness, the fourth factor is the variation in thickness; this leads to magnetic deflection of the arc (the arc being drawn toward the thicker side of the workpiece). The reason for this is that the thicker workpiece generates a stronger magnetic field, which exerts a greater attraction on the charged arc particles. Remedial measures: Use short-arc welding; use an angle of greater magnitude between the electrode and the flat plate; position the ground wire on the side of the thick plate (change the position of the ground wire). The arrangement of the fifth weld has a significant impact on magnetic deflection. Magnetic deflection is highly likely to occur in the following two situations: first, when the groove depth of the butt weld is large; second, in internal fillet welds. Remedial measures: Use short-arc welding; increase the number of tack welds; use an AC power supply for welding. Sixth, welding direction and sequence: when the weld is long, using straight-through welding not only leads to significant welding deformation but also causes magnetic deflection. In this case, the desoldering method is the best way to avoid magnetic deflection. The seventh fixture, as well as the fixture and shimming plate, also have a significant impact on magnetic deflection. Using non-magnetic materials for fixtures and shims, as well as adding additional plates, are effective measures to reduce magnetic deflection. This article is from the Design Institute website www.shejiyuan.com