Student Engineer  


M.I.G./M.A.G.S. Welding - Common Welding Defects

These are the most common defects with some of the most probable causes

Defect Probable Cause
Porosity -Gas flow too low or too high
-Blocked nozzle
-Leaking gas lines
-Draughty conditions
-Nozzles distance from work is too great
-Painted, wet or oily plate
-Wet or rusty electrode/wire
Lack of penetration -Current too low
-Preparation too narrow
-Root face too large
-Root gap too small
-Worn contact tip causing irregular arc
-Incorrect alignment of plates

-Inadequate inductance
-voltage too low
-Rusty or primed plate

Undercut -Speed too fast
-Current too high
-Poor technique
Lack of fusion -Voltage too low
-Current too low or too high
-Irregular surface
-Wrong torch angle
Cracking -Inadequate pre-heat on high tensile and low alloys
-Incorrect composition of electrode
-Root pass too small in restrained joint
-Spray transfer welding with current too high
-Deep narrow weld bead (with centre line cracking)
-Inadequate filling of crater

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