Welding is a method to join pieces of materials together, usually metals. There are several different methods to weld; the most common are MIG/MAG and TIG. The joint melts on both parts and they are pushed together at the same time.

During welding, a lot of energy is transferred to the workpiece. To do this a flame, an electric arc or a laser beam heats the material. In some cases other techniques are used. The energy melts the workpiece on the joining surfaces and they are pushed together at the same time. The end result is a strong joint.

Gas metal arc welding is a common welding technique, usually referred to as MIG or MAG welding. A nozzle (the welding gun) feeds an electrode continously and a shielding gas flows around the electrode. The shielding gas prevents atmospheric gases from reacting with the workpiece. During MIG (metal inert gas) welding the shielding gas is argon, sometimes mixed with helium. MIG welding is suitable for aluminium and alloys. The other kind of gas metal arc welding is MAG (metal active gas) welding, which uses argon mixed with carbon dioxide as a shielding gas. MAG welding is best suited for low-alloy and no-alloy steel.

Another common kind of welding is gas tungsten arc welding (TIG, tungsten inert gas). TIG welding is easily recognized because the electrode is not consumed. The electrode is made of tungsten and the shielding gas is consists of argon or helium. Generally, TIG welding is a method with a fine end result with less defects than other welding procedures. Also, tungsten arc welding is well suited for work in aluminium, steel, stainless steel and cupper. However, it tends to have very thin pipes in the joint, barely visible to the eye. This makes it inappropriate for applications that require an air or water tight joint.

Welding is commonly a part of machining or fabrication projects, as it is sometimes more efficient to manufacture two parts of one component and then weld them together.

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