![]() Procedure Handbook of Arc Welding - Lincoln Electric Jefferson's Welding Encyclopedia, 18th Edition - American Welding Society ReferencesĪWS Welding Handbook - American Welding Society AC is used when performing multiple wire welding, typically with a DC leading wire and AC for all trailing wires to reduce arc blow problems. Submerged arc welding is similar to MIG/MAG, with DCEP being the most commonly used polarity, but DCEN is seen more often in this process, particularly for surfacing applications, where reduced penetration and dilution with the substrate is preferred. This heat is again transferred to the weld pool through the passage of molten droplets, helping balance the anode and cathode. The DCEP condition also aids melting of the wire due to the impingement of electrons. Equipment manufacturers are increasingly looking to develop power sources that can use these conditions however. ![]() The overruling factor however is still the electrode flux coating, which is inherent to the welding electrode, and results in polarity restrictions specified by the manufacturer.įor completeness, information is given here about the MIG/MAG and submerged arc process and the influence of polarity.įor MIG/MAG welding, DCEN and AC are not commonly used because it is difficult to achieve a stable spray condition, mostly operating in globular transfer, which does not necessarily result in an acceptable weld. AC is also used as a method of reducing the potential for arc blow. DCEN can also be used for surfacing applications in order to minimise penetration, and thin sheet welding. The DCEN mode is often used on open root runs to reduce the risk of burn-through, whereas DCEP is used to reduce the risk of lack of fusion defects. This is important for electrodes that are capable of being used on both DC polarities (and AC). In general, operating on DCEP results in greater penetration, and DCEN results in reduced penetration and a reduction in dilution of the weld metal with the substrate. What is more important than the heat distribution is the effect of polarity on penetration in MMA welding. In particular, the movement of material directly from the consumable electrode to the workpiece results in significant balancing of the heat between the two points. The heat distribution between the electrode and the workpiece is also different, and is not as strongly controlled by the polarity. The MMA process however, with its consumable electrode, does not have these concerns. The use of DCEP for TIG welding necessitates larger diameter tungsten electrodes and water-cooling, and is most commonly used as only part of the cycle in AC welding. For this reason, DCEN polarity is the most common choice for TIG welding when the cleaning action of the DCEP process is not needed. For example, the tungsten electrode is thermionic, so will experience this cooling effect. The negative cathode does not experience this effect, and can even undergo cooling by thermionic emission dependent on the material. Approximately 2/3rds of the heat is generated at the positive anode, due to the impingement of high speed, high energy electrons. In TIG welding, the split of heat between the anode and cathode is significant. ![]() DCEP was also historically known as Direct Current Reverse Polarity (DCRP) or simply "Reverse", whereas DCEN was also known as Direct Current Straight Polarity (DCSP) or simply "Straight". This results in either Direct Current Electrode Positive (DCEP) or Direct Current Electrode Negative (DCEN). When the welding process is performed in DC mode, the electrode (either MMA electrode, MIG/MAG/flux- or metal-cored wire or tungsten electrode), can be either positive or negative. A useful mnemonic for this is PANiC (Positive Anode, Negative Cathode). The part of the welding circuit that is negative (produces electrons in the arc) is the cathode. The part of the welding circuit that is positive (attracts electrons in the arc) is the anode. It is necessary to define terms to specify the polarity of the welding process. Click here to see our latest technical engineering podcasts on YouTube. A welding procedure should specify the polarity for each weld run. The choice of polarity also depends on the type of the material, welding position and joint design. Electrode manufacturer information and specifications such as BS EN ISO 2560:2009 and AWS A5.1-2012, define the polarity with which different coated electrodes may be used. The first important point is that not all MMA electrodes can be used with all polarities. National Structural Integrity Research Centre.Structural Integrity Research Foundation.
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