Seam Welding-Selection of parameters

The selection of parameters for seam welding depends mainly on:

• weld nugget size which is related to weld strength.
• probability of porosity.
• designed surface condition of the finished weld.

The selection is usually done by first assuming a welding speed and electrode force. Then, suitable current is arrived at by trial and error, till satisfactory weld is obtained. Guidelines for the selection can be obtained from the hand books. To achieve a leak tight seam, the overlap should be 15 % to 20 % of the nugget length, the penetration must be in the range of 30 % to 80 %. The effects of various parameters viz., current, electrode force, time and preweld cleaning are the same as in spot welding. The edges of the electrodes are trimmed after their usage for a particular period. This can be done in a lathe. In some welding machines, forming rollers are fitted for this purpose.