{"id":413,"date":"2022-04-21T05:42:00","date_gmt":"2022-04-21T05:42:00","guid":{"rendered":"https:\/\/mewelding.com\/?p=413"},"modified":"2024-03-18T10:45:20","modified_gmt":"2024-03-18T10:45:20","slug":"arc-welding","status":"publish","type":"post","link":"https:\/\/mewelding.com\/arc-welding\/","title":{"rendered":"Arc Welding"},"content":{"rendered":"\n
The term arc welding is a very broad term that includes a wide variety of welding processes, that can all be grouped under this one term. As the name indicates, in arc welding \u2013 the heat of an electric arc is utilized to melt the base metal and obtain coalescence.<\/p>\n\n\n\n
The electric arc has a very high temperature of the order of 18000\u00b0F (10000\u00b0C). When an arc is struck between the electrode and the work-piece, the intense heat of the arc melts the metal.<\/p>\n\n\n\n
Arc welding may or may not involve use of pressure between the two mating parts to obtain joining. Likewise, the arc welding may or may not involve use of a filler metal for making the joint. When filler rod is not used, such welding is called autogenous welding.<\/p>\n\n\n\n
Also, the electrode for arc welding (which carries the current, and strikes the arc with work-piece) may be a consumable or a non-consumable. If the electrode is a consumable, it means that the electrode gets consumed during the welding process. In other words, the electrode itself acts as the filler metal. Examples of welding with a consumable electrode are shielded metal arc welding, submerged arc welding, gas metal arc welding, and so on.<\/p>\n\n\n\n
A consumable electrode is produced with a few requirements in mind: it must conduct electricity well and sustain the electric arc, it must match the chemical composition of base metal to be welded, and it must melt and get deposited as weld metal in the weld joint.<\/p>\n\n\n\n
Sometimes these electrodes come with a flux covering for providing shielding to the arc from atmospheric gases. In such processes, the weld metal has a covering of slag after the deposition of a pass.<\/p>\n\n\n\n
If the electrode is a non-consumable, it means that it does not get consumed in the course of welding. The filler rod is fed separately into the molten pool of weld metal. An example of welding with a non-consumable is gas tungsten arc welding.<\/p>\n\n\n\n
The movement of the welding torch along the work-piece in arc welding can be done with the hand, or it can be done mechanically with a machine. Sometimes, the torch remains stationary, while the job is moved mechanically at a uniform rate beneath the arc.<\/p>\n\n\n\n
The equipment for arc welding can be of direct current type or alternating current type. The direct current machines can operate on DCEN (direct current electrode negative), or on DCEP (direct current reverse polarity). Both have their own features <\/a>that determine their suitability on applications.<\/p>\n\n\n\n The power source of the welding equipment is generally of two types \u2013 expressed by their voltage-ampere output characteristics: constant current<\/a> power source, and constant voltage<\/a> power source. Some welding processes operate on CC characteristics \u2013 such as SMAW, GTAW, etc.; while some of them operate on CV characteristics \u2013 such as SAW process. Both types have their own features, advantages and disadvantages.<\/p>\n\n\n\n Besides the power source, there are other welding equipment such as clamps, goggles, cables, electrode, holders, back-up bars, accessories that constitute the arc welding equipment.<\/p>\n\n\n\n Arc welding is broadly classified in two types of processes: Metal electrode welding and carbon arc welding.<\/p>\n\n\n\n In metal electrode welding, as the name suggests \u2013 the electrode is a metal<\/em>. The arc <\/a>is struck between the electrode and the work-piece. The electrode can be bare or it can be coated with flux. The metal electrode welding includes the following welding processes:<\/p>\n\n\n\n In carbon arc welding, the arc is struck between carbon electrodes, instead of metal electrodes. We shall see in very brief detail about each of the above mentioned welding processes.<\/p>\n\n\n\n In this process, the arc is struck between a covered electrode and the work-piece. The covering on the electrode comprises of flux materials designed to provide shielding to the arc from atmospheric gases, and to stabilize the arc. The flux decomposes and turns gaseous on melting. These gaseous covering envelopes the arc and shields it.<\/p>\n\n\n\n Sometimes the flux covering also acts as the vehicle for delivery of alloying elements to the weld metal. This process does not involve use of pressure for obtaining coalescence, and relies only on fusion of the molten metal with the base metal for joining.<\/p>\n\n\n\n This process is sometimes also called manual metal arc welding (MMAW). However, SMAW \u2013 short for shielded metal arc welding is the more accepted term.<\/p>\n\n\n\n The SMAW process can be used for welding almost any metal. There is a wide variety of SMAW electrodes in market today to cater to welding of any metal or alloy. Be it carbon and low alloy steels, or stainless steels, or cast iron, or aluminum, copper, nickel, or any their alloys, shielded metal arc welding<\/a> electrodes come in a variety of compositions to cater to any commercially used metal. <\/p>\n\n\n\n The figure below illustrates the shielded metal arc welding process.<\/p>\n\n\n\n\n
Shielded Metal Arc Welding (SMAW)<\/strong><\/h2>\n\n\n\n