SAWSubmerged arc welding uses the heat generated by an electric arc struck between a continuously fed wire electrode and the workpiece to produce fusion of metal in the joint area. The electrode is consumed during the process to form weld metal. The whole weld area is shielded from the atmosphere by a granular, fusible flux covering; some of this flux may also enter the weld metal. The process may be operated on DCEP, DCEN or AC power, and with a single wire electrode or multiple wires. It is normally operated as a mechanised process but may be used in a semi-automatic mode too. The main features of the process are high welding currents, high deposition rates, good weld fusion, and deeply penetrating welds. It is mainly applied to welding of carbon and carbon-manganese steels, alloy steels and stainless steels. As well as welding, the process may also be used for surfacing and hardfacing. Filler wires may be solid or tubular. Solid wires are usually copper-coated and if tubular they are bare wires but can be either basic flux cored wire or metal cored wire. Metal powder may also be added to the flux to give alloying or increase deposition rate. Submerged arc fluxes may be fused or agglomerated. Their formulation may also mean that the fluxes are acid, basic or neutral in character, and some may be enriched with alloying elements such as chromium for welding stainless steels. The main drawbacks to the process are the initial high cost of the equipment and that it is limited to operation in the flat or horizontal positions or the flux will fall off.
|
