Does polarity matter power supply? Firstly, Let us know about what is the polarity of the DC power supply, which mainly refers to the selection of DC reverse polarity. The welding process is stable and spatter is small. In positive polarity welding, the melting speed is fast, the penetration depth is small, the excess height is large, and the spatter is also more. Usually MIG welding should use DC power supply. Because AC power will destabilize the arc, it is difficult to reignite the arc when the current crosses zero.
Usually MIG welding should use DC power supply. Because AC power will destabilize the arc, it is difficult to reignite the arc when the current crosses zero. During DC welding, there are two connection methods of current polarity, DC positive connection (reverse polarity) method and DC reverse connection (positive polarity) method. The DC positive connection method means that the electrode is the cathode and the workpiece is the anode; the DC reverse connection method is just the opposite. MIG welding mostly adopts DC reverse connection. The main reasons are as follows:
1. The arc is stable. Because the anode spot is firmly present at the wire tip, the arc does not drift. On the contrary, when the DC positive polarity connection method is used, the welding wire is the cathode. Because the cathode spot always looks for the oxide film, the cathode spot constantly drifts up and down along the welding wire, and the maximum movement can reach 20-30mm, thus destroying the stability of the arc. .
2. Cathode breakage occurs near the weld. Because the workpiece is a cathode, the metal oxide film near the weld can be removed by the cathode crushing action. This is just right for welding aluminum, magnesium and their alloys.
3. When the DC is reversed, the melting speed of the welding wire is accelerated, and the production efficiency is high.
Note: The domestic direct current connection in China corresponds to the international direct current reverse polarity connection.