Weld Distortion and defects are an annoying, but unavoidable part of welding. But they can be mitigated!
Porosity is where Holes/Bubbles appear in the weld. This is created when gas becomes trapped in the weld pool as it solidifies. Causes include:
Weld Distortion is caused by two factors:
The first is impossible to avoid, but can be mitigated:
Weld Metal Shrinking is, again, impossible to avoid.
When a weld is created you’re producing a molten pool of metal. Like most materials, this hot metal will be in an expanded state. Thus, as it cools and solidifies, it contracts (or shrinks).
As the weld metal cools and shrinks it pulls on the metal around it, creating stresses and distortion.
Welding Distortion can be corrected by stretching the weld metal to relieve the stress caused by shrinking.
For butt and outside corner welds, this can be done by peening.
Do this by holding a metal block behind the weld and peening evenly along the weld with a hammer.
Be careful to avoid over peening as this will overstretch the weld and re-distort the workpiece, this cannot be corrected easily!!!
So peen the whole weld a little, assess the effect, then if necessary, peen a little more.
Most Weld Distortion and Defects that You’ll encounter can be avoided, simply by preparing properly.
Distortion can be minimised by ensuring metal parts fit tightly together as gaps will mean bigger weld deposits and therefore more weld shrinking!
So a bit of time spent on preparation can minimise the time spent fixing Weld Distortion and Defects after welding!
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