A welding sequence developed in the shipyards for welding ship hull plates which is adaptable to many welding situations which involve the closing of butt joints. This sequence was developed to establish the order of deposition of weld metal in butt joints to minimize cracking in the root pass caused by thermal stresses, slag inclusions and oxidized craters at points of withdrawal of the electrode from the molten puddle. In the application illustrated, a variation of the block sequence was developed for welding vertical butt joints for which E-6010 electrodes were specified.
As shown in Figure B-8, the first increment of the root pass was started about 25 cm (10 in.) from the top and welded up to the top. The second root increment was started 50 cm (20 in.) Erom the top, welded up to the first increment, and up over it to the top without breaking the arc. The third increment was started 75 cm (30 in.) from the top, welded up to and over the second increment, and up over the first increment.
This technique of lapping passes avoids defects caused by stopping a weld pass and leaving a crater at the point of poor fusion where another pass is started.
Residual stresses in vertical butt welds were minimized by block welding with skips between, by preheating in cold weather and by chipping out tack increments as the welding progressed. Peening each pass immediately after deposition was found to be sufficient to minimize residual stresses.