Chapter 31 Flashcards
Back-step welding method
provides for a more uniform heating and cooling of the metal which reduces distortion.
1) Begin several inches from one end and weld back to the end.
2) Start several inches in front of the previous weld and weld back to the beginning point of the first weld.
3) Continue this process until the weld is complete.
3. Space the base metal plates in such a way that they are
clamping
Clamp the base metal to a backing plate when performing short welds.
not recommended for longer welds because the clamps provide no outlet for the pressure created through the expansion and contraction of the metal due to heating and cooling. This may result in residual stresses which weaken both the base metal and the weld.
counterbalance
The expansion and contraction of the metal do not counterbalance each other. During long welds, one section of the metal is being heated and expanded while the previously welded sections are cooling and contracting. The result is a warping of the metal.
distortion
Rapid heating and slow cooling of metal leads to this. Welders learn to control this in arc welding. This can be prevented by using specific steps and methods such as back-step and skip welding
intermittent welds
Use this or tack welds when the strength of a full-length weld is not needed.
peening
expands the metal and relieves the pressure that causes distortion.
Use a light hammer to peen the base metal, both before and after the weld.
residual stresses
Stresses that remain after the weld has cooled off.
skip weld method
a series of short welds at intervals is followed by a second bead which fills in the gaps. Again, this evenly distributes the heat throughout the metal.
tack welds
Tack welds are small, spaced welds along the weld joint made before running the continuous bead along the same joint.
* Tack welds prevent expansion or contraction of the weld joint during continuous welding.
provides for a more uniform heating and cooling of the metal which reduces distortion.
1) Begin several inches from one end and weld back to the end.
2) Start several inches in front of the previous weld and weld back to the beginning point of the first weld.
3) Continue this process until the weld is complete.
3. Space the base metal plates in such a way that they are
Back-step welding method
Clamp the base metal to a backing plate when performing short welds.
not recommended for longer welds because the clamps provide no outlet for the pressure created through the expansion and contraction of the metal due to heating and cooling. This may result in residual stresses which weaken both the base metal and the weld.
clamping
Rapid heating and slow cooling of metal leads to this. Welders learn to control this in arc welding. This can be prevented by using specific steps and methods such as back-step and skip welding
distortion
Use this or tack welds when the strength of a full-length weld is not needed.
intermittent welds
expands the metal and relieves the pressure that causes distortion.
Use a light hammer to peen the base metal, both before and after the weld.
peening
Stresses that remain after the weld has cooled off.
residual stresses
