Figure 1-16 Examples of plug and slot welds
Intermittent Welds
Note the positions of the welds shown below. See Figure 1-17.
Figure 1-17 Chain intermittent fillet weld (left) and staggered intermittent fillet weld (right)
Welding Terminology
These terms describe the position of the electrode in respect to the weld.
Axis of the weld—an imaginary line drawn parallel to the weld bead through the center of the weld.
Travel angle—is the smallest angle formed between the electrode and the axis of the weld.
Work angle—for a T-joint or corner joint, the smallest angle formed by a plane, defined by the electrode (wire) and the axis of the weld, and the work piece.
Push angle during forehand welding—this is the travel angle during push welding when the electrode (wire) is pointing toward the direction of weld progression.
Drag angle during backhand welding—this is the travel angle during drag welding when the when the electrode (wire) is pointing away from the direction of weld progression.
Travel speed—the velocity or speed of the electrode (wire) along the travel axis, usually in inches/minute or cm/minute.
See Figure 1-18.
Figure 1-18 Orientation of the electrode
TackWeld
Welders place small, initial welds along joints to hold the work pieces in place so the parts remain in alignment when they are welded. Tack welds hold work firmly in position, but can be broken with a cold chisel in the event further adjustment is needed. Beginning welders tend to make them too small. One inch is the standard length of a tack weld. A tack should be as strong as the weld itself as it becomes an integral part of the finished weld.
Figure 1-19 Make sure the work is aligned properly; keep it aligned by welding small sections at intervals to tack the metal in place
Figure 1-21 Joggle weld joint preparation
Joggle Joints
Joggle joints are used where a strong joint and flat surface is needed to join two pieces of sheet metal or light plate. There are hand tools available to put the joggle into sheet metal. They are useful whenever a finished surface concealing the weld is needed and where a butt joint would not work with thin sheet metal. See Figure 1-21.
Stringer and Weave Beads
In a stringer bead the path of the electrode is straight, with no appreciable side to side movement, and parallel to the axis of the weld, while a weave bead has a side-to-side motion which makes the weld bead wider (and the heat-affected zone larger) than that made with a stringer bead.
Padding
Padding is when weld filler metal is applied to a surface to build up a plate or shaft, to make a plate thicker, or to increase the diameter of a shaft. It is used either to restore a dimension to a worn part or to apply an extra hard wear surface. See Figure 1-20A shaft, bar, or pipe and 1-20B is resurfacing a plate.
Figure 1-20A Resurfacing on shaft, bar, or pipe axial and circumferential welds.
Figure 1-20B Resurfacing on a plate
Boxing
Boxing is when a fillet weld is continued around a corner. Normally a fillet weld is made from one abrupt end of the joint to the other abrupt end of the joint. See Figure 1-21.
Figure 1-21 Boxing weld
What are the special procedures for welding thick plates?
Root Pass Weld
A root pass uses weld filler metal to close the root space between the weld faces. It is especially helpful in welding pipe and thick plates where only one side of the weld is accessible and no backing material is used.
Back and Backing Weld
A back weld is applied after a groove weld is completed. The back weld is made to insure full penetration through the material being joined. Before we apply the back weld we must grind or gouge into the bottom of the groove weld until we reach sound weld metal then we may apply the back weld to the bottom of the groove weld. See Figure 1-22.
Figure 1-22 and 23 Back weld and backing weld
A backing weld is applied to the bottom or root of a groove weld before the groove weld is applied. Because the root or bottom of the weld is made first it becomes a backing for the groove. The difference between a back and backing weld is the sequence of welding. Before the groove weld is completed the backing weld must be ground or gouged to sound weld. See Figure above.
Backing Plates
A backing plate contains the large weld pool when joining two thick sections that are accessible from only one side. It takes the place of a root pass. The backing plate also shields the weld pool from atmospheric contamination coming in from the back of the weld. Backing plates are usually tack welded to the two sections of the weld, but there are proprietary ceramic tapes and metal-glass tapes that perform the same function and do not need to be tacked into place. Copper and other materials are also used as backing plates. See Figure 1-24.