SUBMERGED ARC WELDING AND ITS PROCESS

Sub merged-arc welding, sometimes called hidden arc or sub-arc welding, is an automatic process developed primarily for the production of high quality butt-welds in thicker steel plate than is normally suited to other manual arc welding processes. The arc is formed between the end of a continuous, i.e., depositing surface, under a layer of protective mineral powder, known as the flux of melt, which can also be used to add alloying cements to the joint ahead of the welding wire and while the weld is being made the arc is submerged under the powder and is invisible. The operator judges the proper location by observing the general direction of the wire and the welded material. Various kinds of equipment are available for clamping the parts in position, and for feeding the wire electrode.

The flux may be made of silica, metal oxides, and other compounds fused together and then crushed to proper size. Another group of fluxes is made of similar material "bonded" and formed into granules.

The bare electrode is fed from a reel down through the gun or nozzle. The operator can move it slowly, a little at a time for the start of the arc and then set the proper feed rate on the control box. Wire of several alloys for steel, stainless steel, copper etc. is available in diameters from 3 to 6 mm. Voltage used is from 25 to 40 V. Current used depends considerably on a workpiece thickness. Normally dc is employed using 600 to 1000A current for welding alloy and stainless steel, although ac is preferable particularly for low-carbon steel. The current for ac is usually 2000A.

The advantages of submerged-arc welding are listed below :

1. Partly because it is often automated , it is much faster than regular than welding. Speeds up to 3800 m/min are possible on 3 mm thick steel at 100 percent efficiently.

2. Deep penetration with high quality weld is possible.

3. Less Distortion occurs from the high speed and uniform heat input, especially when automated.

4. The operator can work more easily without safety equipment

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