*Arc welding equipment *is comprised of a number of components, depending on the specif welding process used.
In electric arc welding processes, an arc is produced between an electrode and the work piece (base metal). The arc is formed by passing a current between the electrode and the workpiece across the gap. The current melts the base metal and the electrode (if the electrode is a consumable type), creating a molten pool. On solidifying, the weld is formed. An alternate method employs a non-consumable electrode, such as a tungsten rod. In this case, the weld is formed by melting and solidifying the base metal at the joint. In some instances, additional metal is required, and is added to the molten pool from a filler rod.
In** Gas metal arc welding (MIG welding or GMAW)** coalescence is produced by heating metals with an arc between a continuous filler metal (consumable) electrode and the workpiece. The arc, electrode tip and molten weld metal are shielded from the atmosphere by a gas. Shielding is obtained entirely from an externally supplied inert gas, gas mixture, or a mixture o f a gas and a flux. The electrode wire for MIG welding is continuously fed into the arc and deposited as weld metal.
In Shielded metal arc welding (SMAW Stick welding) the arc is drawn between a covered consumable metal electrode and work piece. The electrode covering is a source of arc stabilizers, gases to exclude air, metals to alloy the weld, and slags to support and protect the weld. Shielding is obtained from the decomposition of the electrode covering.
In Gas tungsten arc welding (TIG welding or GTAW) the arc is drawn between a non-consumable tungsten electrode and the work piece. Shielding is obtained from an inert gas or gas mixture. Pressure and/or filler metal may or may not be used. The arc fuses the metal being welded as well as filler metal, if used. The shield gas protects the electrode and weld pool and provides the required arc characteristics.
The* equipment required for arc welding* depends on the process being used as well as the source from which the electric power is obtained. If the power is obtained from public utility lines, one or more of the following devices are required: transformers (of which there are several types), rectifiers, motor generators, and control equipment. If public utility power is not available, portable generators driven by gasoline or diesel engines are used.
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