04-02-2013, 10:18 AM
Arc Welding:
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Submerged Arc Welding:
Submerged arc welding is an arc welding process in which heat is generated by an arc which is produced between bare
consumable electrode wire and the workpiece. The arc and the weld zone are completely covered under a blanket of granular,
fusible flux which melts and provides protection to the weld pool from the atmospheric gases.
The molten flux surrounds the arc thus protecting arc from the atmospheric gases. The molten flux flows down continuously and
fresh flux melts around the arc. The molten flux reacts with the molten metal forming slag and improves its properties and later floats
on the molten/solidifying metal to protect it from atmospheric gas contamination and retards cooling rate. Process of submerged arc
welding is illustrated in Figure 7.1.
Extremely high welding currents can be used without the danger of spatter and atmospheric contamination giving deep penetration
with high welding speeds. A proper selection of flux-wire combination can produce welds of very high quality. This makes the
process very suitable for the welding of high strength steel at welding speeds much higher than conventional manual metal arc
welding. It is found that the desired composition of the weld metal can be more economically obtained through adding alloying
elements in the flux and using a relatively unalloyed wire as compared with welding with alloyed wire and ordinary flux.
A continuous consumable wire electrode is fed from a coil through contact tube which is connected to one terminal of power source.
Wires in the range 1 – 5 mm diameters are usually employed and with wires at the lower end of this range (upto 2.4 mm) constantpotential
DC power source can be used allowing arc length control by the self-adjusting effect. For higher diameter electrodes
constant current DC source is used.
Submerged arc welding head may be mounted on self-propelled tractors carrying a flux hopper and the coiled electrode. A suction
device may also be carried to recover the unused flux for reuse.
Since the end of the electrode and the welding zone are completely covered at all times during the actual welding operation, the
weld is made without the sparks, spatter, smoke or flash commonly observed in other arc welding processes.
Power source requirement may be DC or AC. Normally electrode is connected to positive terminal of DC power source. Sometime
depending on the nature of flux AC can be used with single electrode wire or with multiple electrodes where one electrode may be
connected to DC and other to AC if independent power sources are to be used.