TWI Frequently asked questions
The sequence, or direction, of welding is important and should be towards the free end of the joint. For long welds, the whole of the weld is not completed in one direction. Short runs, for example usingthe back-step or skip welding technique, are very effective in distortion control (Fig.1).
Back-step welding involves depositing short adjacent weld lengths in the opposite direction to the general progression (Fig.1a).
Fig.1. Use of welding direction to control distortion a) Back-stop welding
b) Skip welding Skip welding is laying short weld lengths in a predetermined, evenly spaced, sequence along the seam (Fig 1b). Weld lengths and the spaces between them are generally equal to the natural run-out length of one electrode. Thedirection of deposit for each electrode is the same, but it is not necessary for the welding direction to be opposite to the direction of general progression. For more information on the control of distortion, see Job Knowledge for Welders 36.
| 