Welding can be done with either an AC or DC welder. When using a DC welder, there are positive and negative connections, taking into account factors such as the welding rod used, the condition of the construction equipment and the quality of the weld.

Compared to AC power sources, DC power sources provide a stable arc and a smooth melt drop transition. -Once the arc is ignited, the DC arc can be kept burning continuously.

When welding with an AC power source, the arc does not burn continuously due to the change in current and voltage direction and the fact that the arc has to be extinguished and reignited 120 times per second.

At lower welding currents, the DC arc has a good wetting effect on the molten weld metal and regulates the weld channel size, so it is ideal for welding thin parts. DC power sources are more suitable for back and standing welds than AC power sources because the DC arc is shorter.

However, sometimes the arc blowing is a prominent problem with DC power sources and the solution is to convert to AC power sources. For AC and DC dual purpose welding electrodes designed for welding with AC or DC power sources, the vast majority of welding applications work better under DC power conditions.

(1) Ordinary structural steel welding

For ordinary structural steel welding rod, acid welding rod can be used in both AC and DC, when using a DC welding machine to weld thin plates with DC reverse connection is good.

Thick plate welding can generally use DC positive connection, to obtain a larger depth of melt, of course, DC reverse connection can also be, but for the beveled thick plate bottoming welding is still DC reverse connection is good.

Alkaline electrodes generally use DC reverse connection, which can reduce porosity and spatter.

(2) Melting electrode argon arc welding (MIG welding)

Fused electrode argon arc welding generally use DC reverse connection, not only arc stability, and welding aluminum can remove the oxide film on the surface of the welded parts.

(3) Tungsten arc welding (TIG welding)

Tungsten arc welding of steel, nickel and its alloys, copper and its alloys, Chin and its alloys can only use DC positive connection, the reason is that if the DC reverse connection, tungsten electrode connected to the positive electrode is high temperature, heat, tungsten melting fast, can not make the arc long-term stable combustion, and molten tungsten into the molten pool and will cause tungsten trapping, reducing the quality of the weld.

(4) CO2 gas shielded welding (MAG welding)

CO2 gas shielded welding in order to maintain arc stability, weld seam forming good, reduce spatter, the general use of DC reverse connection, but in the overlay and filler welding cast iron, the need to improve the metal deposition rate and reduce the heat of the workpiece, more DC positive connection.

(5) Stainless steel welding

Stainless steel welding rod to DC reverse connection is better. If you do not have a DC welding machine, quality requirements are not too high, you can use calcium Chin type welding rod with AC welding machine.

(6) Cast iron welding

Cast iron welding is generally used in the DC reverse method, welding arc stability, small spatter, shallow depth of melt, in line with the cast iron welding needs low dilution rate to reduce the formation of cracks.

(7) Submerged arc automatic welding

Submerged arc automatic welding can be used AC or DC power source welding, according to product welding requirements and flux type selected such as nickel-manganese low silicon flux, must choose DC power source welding to ensure the stability of the arc; DC reverse connection to reduce porosity, access to larger depth of melt.

(8) AC versus DC welding

Compared to AC power sources, DC power sources provide a stable arc and smooth melt drop transition. -Once the arc has been ignited, the DC arc is kept burning continuously.

When welding with AC power, the arc does not burn continuously due to the change in current and voltage direction and the fact that the arc has to be extinguished and reignited 120 times per second.

At lower welding currents, the DC arc has a good wetting effect on the molten weld metal and regulates the weld channel size, so it is ideal for welding thin parts. DC power sources are more suitable for back and standing welds than AC power sources because the DC arc is shorter.

However, sometimes the arc blowing is a prominent problem with DC power sources and the solution is to convert to AC power sources. For AC power source or DC power source welding and designed for AC, DC dual-use welding rod, the vast majority of welding applications in DC power source conditions better.

In manual arc welding, AC welding machine and some of its additional devices are inexpensive and can avoid the harmful effects of arc blowing force as far as possible. However, in addition to the lower cost of equipment, the results when welding with an AC power source are not as good as with a DC power source.

Arc welding power sources with steep drop characteristics (CC) are most suitable for manual arc welding. The change in voltage corresponding to the change in current shows that the current decreases as the arc length increases. This characteristic limits the maximum arc current even if the welder controls the size of the melt pool.

As the welder moves the electrode along the weld, constant changes in arc length are inevitable and an arc welding power source with steep drop characteristics ensures arc stability during these changes.