A close-up of GMAW.
Gas metal arc welding (GMAW) is an automatic or semi-automatic welding process. Shielding gas and a continuous consumable wire electrode are fed through a welding gun. GMAW uses a constant power source, such as voltage or direct current, to weld materials such as steel and aluminum. GMAW is popular in industries such as automobile manufacturing because of its speed and versatility.
GMAW is commonly used for sheet metal fabrication.
GMAW was first developed at the turn of the 19th century when carbon was used. In the late 19th century, metal electrodes were invented, and in 1920, General Electric invented the first predecessor of the GMAW. In 1953, the use of carbon dioxide for soldering was developed. It quickly gained popularity as it made welding more economical.
GMAW is widely used by the sheet metal industry. Spot arc welding has replaced resistance or rivet welding. It is also used in robot welding, where robots operate the welding gun and sheet metal to save time and cost. GMAW is generally not suitable for outdoor use as changes in the atmosphere can cause the shielding gas to dissipate and the quality of the weld to be degraded. It is also not suitable for underwater welding for the same reasons.
A shielding gas protects the seam from contamination as it forms and cools during GMA welding.
The equipment used in the GMAW is a welding gun, a wire feed unit, an electrode wire and a supply of shielding gas. When the control switch is turned on on the wire feeder, electrical power and gas flow are started. This causes an electrical arc to open. The gas nozzle is used to direct the welding gas evenly into the welding zone.
The basic technique used in GMAW is quite simple. The operator guides the welding gun with care and guidance along the area to be welded. It is important to maintain a consistent tip-to-work distance as the electrode can overheat or waste shielding gas. The correct angle of the weapon is also important; should be kept at 45° when welding at an angle and at 90° when welding a flat surface.
GMAW requires safety equipment, including special goggles and leather gloves.
GMAW can be extremely dangerous if proper precautions are not taken. Welders must wear protective clothing, including long-sleeved jackets capable of withstanding heat and flame. Leather gloves should also be worn when handling the welding gun. Arc flash can also cause burns to the retina of the eye, so helmets with protective faceplates should be worn to prevent exposure. GMAW should never be attempted without all proper security procedures in place.