Welding polarity is a setting for welding machine that determines the direction in which the electrical currents flows during the welding process. The welding polarity determines the amount of heat that is directed toward the welding electrode and the amount of heat that are directed toward the metal being welded. Welding polarity is important because welding polarity affect the depth to which the weld penetrates the metal and the rate at which the welding wires melts.
In order to perform the welding process corectly, the welder must select the correct welding polarity. If the welder does not select the correct welding polarity, the weld that is created may not be strong enough or may not penetrate the metal to the required depth. Direct current electrode positive (DCEP) is a welding polarity setting that is used when the positive terminal of the welding machine is attach to the welding electrode holder.
Welding Polarity and How It Affects the Weld
Approximately seventy percent of the heat create by the welding arc is directed toward the welding electrode when using DCEP. Because the majority of the heat is directed toward the welding electrode, the welding electrode melts at a slower rate than it would if using another welding polarity. As a result, the welding process create deeper penetration into the metal being welded.
DCEP welding polarities are often used when welding with cellulosic welding electrodes, such as E6010 welding rods, because those electrodes requires the deep penetration of the welding process to allow the weld to correctly fuse with the metal. Direct current electrode negative (DCEN) is a welding polarity setting that is used when the negative terminal of the welding machine is attached to the welding electrode holder. When DCEN is used, the majority of the heat created by the welding arc is directed into the metal that is being weld rather than into the welding electrode.
Because the welding electrode does not reach as high of a temperature during the welding process, the welding electrode melts at a faster rate than with other welding polarities. Consequently, the welding process with DCEN result in a weld with a shallow depth of penetration into the metal. DCEN welding polarities are used when welding thin section of metal to avoid burn-through of the metal, as well as in situations in which welding rods need to melt quick and deposit metal rapidly onto the metal being welded.
Alternating current welding is used with alternating current settings, during which the electrical current changes direction sixty times each second. Because of the alternating nature of the current, alternating current welding provides both a cleaning action and a penetration action to the welding process. During the welding process, the welding electrode is often covered in metal oxide layer.
During the positive portion of the alternating current cycle, the oxide layer on the metal being welded is broken up. During the negative portion of the alternating current cycle, the tungsten welding electrode is allowed to cool. Alternating current welding is often used in situations in which welding rods are welding aluminum metals with TIG welding processes, as the cleaning action of the alternating current prevent the development of porosity within the aluminum metal.
Not all welding electrodes respond the same way to each type of welding polarity. For instance, electrodes such as E6013 welding rods and E7018 welding rods can be used in alternating current (AC) welding processes as well as direct current (DC) welding processes. However, the metal joint created with those welding rods will differ based off whether alternating current or direct current welding is perform with those rods.
For instance, low-hydrogen welding rods, such as E7018 welding rods, may lead to penetration issue. If these welding rods are used in DCEN welding processes, the shallow penetration created by DCEN welding may create cold laps within the metal joint created by those rods. Conversely, if the same low-hydrogen welding rods are used in DCEP welding processes, the DCEP welding process will create deep fusion between those metal rod.
Depending upon the welding process that is being used, certain welding polarity are required to effectively weld the metal. For instance, MIG welding processes use DCEP welding polarities almost exclusively, as the welding process with MIG welding requires the welding wire to melt rapid, as well as strong welding arc force to penetrate the mill scale that may cover the metal being welded. TIG welding processes requires different welding polarities to weld metals of different compositions.
For metals like steel and stainless steel, DCEN welding processes are recommended to extend the life of the TIG welding torchs tungsten tip. However, for metals like aluminum and magnesium, alternating current welding processes are used to facilitate proper cleaning of the metals oxide layer. Lastly, welding processes that utilize flux-cored welding rods require specific welding polarities according to the type of flux-cored welding rod that is used.
Flux-cored welding rods that are gas-shielded typically use DCEP welding polarities to facilitate deep fusion between the welding rod and the metal being welded. Flux-cored welding rods that are self-shielded typically use DCEN welding polarities, as these welding rods are often used in welding condition that are exposed to strong winds, and the use of DCEN welding polarities improves the stability of the welding torch. Finally, to ensure the success of any welding process using flux-cored welding rods, the welding torch operator must select the welding polarity that match the specific welding rod and metal being welded.
