The Whipping Technique
When the pipe nipples are tack welded in the 2G position, the weld is horizontal and it is necessary to use a slight whipping motion to control the molten metal in the puddle. The whipping motion, shown in Fig. 4-9, is a quick movement of the arc away from the puddle, in the direction of welding, after which it is returned to the puddle. The arc must be kept within the groove made by the weld joint and it should not be carried outside of this area. The length of this movement should be short, about iy2 electrode diameters, in order to maintain a gaseous shield over the molten metal at all times. After each whip the electrode should pause over the top edge of the keyhole, where the molten metal joins the solidified bead, to deposit filler metal and to keep the puddle fluid. The whipping motion should be made by moving the wrist, not the entire forearm. The purpose of whipping is to decrease the fluidity of the molten metal puddle, allowing it to become somewhat mushy but not to solidify completely.
Stopping the Weld
The procedure that is used for laying down the root bead is continued until the bead is about % inch long. At this point the weld
Fig. 4-9. Welder’s view when welding the tack weld in the horizontal position. A slight whip should be used, as shown, to prevent the molten metal in the puddle
Courtesy of the Hobart Brothers Co, Fig. 4-10. Quenching the arc by a stab through the keyhole when welding a root
is stopped. The procedure for stopping the weld is to push the electrode through the keyhole by a quick movement, as shown in Fig, 4-10. After the arc is extinguished, it is quickly withdrawn. This method of stopping a root bead helps to obtain full root penetration when restarting the weld at this point and when making a tie-in.
The tack welds should be cleaned and inspected before welding the remainder of the root bead. Ail of the slag coating must be removed with a chipping hammer, and the surface of the bead should be brushed vigorously with a wire brush. Any defects should be removed by grinding or with a hammer and a chisel. The defective areas should be rewelded, although this may be done after the remainder of the root bead has been welded. A perfect tack weld is shown in Fig. 4-11.
Fig. 4-11. View of a perfect tack weld.