Submerged arc welding,working,advantages and disadvantages.
SUBMERGED ARC WELDING (SAW)
Flux Core
When the flux is required continuously or where the larger quantity of flux has to be supplied, on that time the flux is used in the form of wire wound on a rotating drum or reel called as flux care. It is ‘ separately supplied instead of using welding rod along with flux material. Flux is mainly used to avoid oxidation reaction with oxygen present in the atmosphere. If the flux is used along with filler material in the form of coated electrodes, the oxidation reaction may not be completely prevented. In order to avoid oxidation reaction completely, enough quantity of flux should be supplied with a separate control independently with filler material.
E. g. the complete welding setup is dipped in the flux powder named as submerged arc welding.
Submerged arc welding is also called as sub arc welding or hidden arc welding. In this welding, an electric arc is produced between consumable bare electrode and the work piece. But the arc is completely submerged i.e., hidden under the flux powder. The are is not visible outside. The metal electrode is continuously fed from the reel by a moving head. The flux powder is fed in front of the moving head. It is supplied from a hopper. When the arc is produced in the welding zone at the end of the electrode and the arc is completely covered by flux powder. So, there will not be any defect in the weld due to atmosphere effects.
The flux powder used here is made up of silica, metal oxides and other compounds fused together and then crushed to the proper size. Another group of fluxes is made of similar material bonded and formed into granules. The flux not only protects the weld surface from atmosphere and also acts as a deoxidiser and scavenger. It may also contain powder metal alloying elements. The flux covers the arc and molten metal. Some of the flux melts and forms the slag on the weld. The unused flux is sucked by a pipe. Voltage used here is 25 to 40V. Current used depends on work piece thickness. Normally, DC. is employed using 600A to 1000A and AC is usually 200A.
Since, the flux must cover the joint to be welded. This method is restricted to make straight welds in the flat position. Thus, it is suitable for cylinders, steel pipes etc.
Submerged arc welding is used specially fdr welding carbon steels and alloy steels. It can be used to weld chromium steels and austenitic chromium-nickel steels. Plates of 12 to 50mm can be welded with one pass.
Advantages:
1.Very high quality welds are produced.
2 It is a very fast method.
3 Deep penetration can be obtained.
4. Shielding accessory for the eyes is not needed.
5. Long joints can be easily welded.
Disadvantages:
1. It is not suitable for welding works which is inclined and vertical.
2. The welding zone is not seen. So, it is difficult to guide the electrode movement.
Videos of submerged arc welding:
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