Work on underwater arc welding is still under development stages. U. S.A., U. S.S. R., U. K. and Japan are still working upon the ways to improve the quality of “wet” welds in water. Under­water arc wet welding is the cheapest and most convenient of all the welding processes avail­able to-date. Future work may be carried out in the following areas:

1. There is no electrode as yet which can be said to be the final answer for underwater “wet” welding. Basic work is still needed to develop a special “underwater arc welding elec­trode”.

2. Underwater welds are produced at fast cooling rates. Distortion of the plates is low. The process could be used to weld at places where it is desired to have low distortion.

3. It is expected that hardfacing of metals if carried out underwater will deposit very hard beads. The process could be tried.

4. Hydrogen is a serious problem in underwater welds. Work is necessary to develop electrodes and welding precesses that could give low hydrogen weld deposits.

5. Salinity of sea water affects the weld characteristics. A systematic research work could be conducted to explore the effect of different levels of salinity on weld characteristics.

6. Work can also be done to study the effect of depth of water on underwater welds.

7. Special tools and techniques can be developed to shield the underwater arc from the effect of surrounding water.

8. Some technique can be developed for preheating the plates before welding or post heating-treating the welds for improving the metallurgical characteristics of welds produced in water.

[1] Consider an arc operating at 300 A, 35 V (point A in Fig. 3.6). If the arc length increases, voltage rises to point B (say). This causes significant decrease in current, giving lower burn-off rate. Arc length is immediately adjusted as the electrode tip in this situation will approach weld pool, and the arc length shortens. When this happens the current

[2]Bracketed code numbers for welding positions apply only to a smaller sizes and/or low levels of deposition efficiency.

[3]Bracketed code numbers for current conditions mean conditional qualification.

+Favoured for vertical down.

[4] + vw 5 4a

[5] The electrode material

[6]Drop-Transfer throughout.

[7]Lifetime of drop has largest apparent effect.