Submerged Arc Welding
Submerged arc welding (SAW) is an arc welding process wherein welding is performed by heating with an electric arc installed between a bare metal electrode/electrodes and the job.
In the submerged arc welding process, the arc and molten pool are completely covered by granular fusible flux material and we don’t see the arc, this is why it is called submerged arc welding. No pressure is used in this process.
Features of Submerged Arc welding
The submerged arc welding process is very unique especially in terms of its features such as
- Thermal efficiency as high as 80 to 90%
- Heat loss is minimum as compared to other processes., because the arc is fully covered
- by a shield of flux.
- The high deposition rate of welding
- Spatter free
- Down hand welding process
- Constant current/voltage type of power source is used .
Some of the common equipment used in submerged arc welding process are as follows:
The function of the head is important. It supplies the filler material along with the flux to the joint and is where the welding electrode is energized.
The flux is stored in the hopper and from here the flux is applied to the joint and from here the rate of its deposition is controlled.
The constant current/voltage type of power sources are used in this process, such as
- For larger diameter electrodes or for thicker sections, such as sizes greater than 24 mm, a constant-current type power source is used.
- For small diameter electrodes or for sizes less than 24 mm, constant voltage type power sources are commonly used.
When works with DC constant-current type of the power source with the reverse polarity or ” DCEP” (Direct current electrode positive )polarity is invariably used to take the advantage of the high heat generation in the electrode side so that we can have a very high melting rate of the electrode. This is done to achieve a high melting rate. The high melting rate facilitates in two ways,
It helps in increasing the deposition rate or the productivity, it also helps in increasing the high melting rate it helps in realizing the self-regulating arc Because when the melting rate of the electrode with the small diameter electrodes is high it responds very rapidly for the change in current and that helps to maintain the self-regulating arc to maintain the arc length through the self-regulating arc principle.
The composition of the electrodes used in “Submerged arc welding process”depends on the material of the metal to be welded, according to the metal, mixed elements are also added to it. Welding electrodes are available for joining various metals, such as, mild steel, high carbon steel, low carbon steel, special alloy steels, stainless steel and some non-ferrous alloys of copper and nickel, etc.
Generally, the welding electrodes used in submerged arc welding are coated with copper, so that the electrodes do not rust and their electrical conductivity increases. These electrodes are available in straight lengths and coils also.
The flux acts as a shield and protects the molten weld pool from atmospheric pollution. It is a unique way of protecting weld pools from atmospheric pollution.
To be continued