Weld defect glossary and troubleshooting worksheet

Quick defect glossary

Defect	What it looks like	Common non-critical practice causes	Notes
Porosity	Small holes or pinholes in the bead	Contamination, poor shielding, damp consumables, wrong gas flow
Undercut	Groove melted along the toe of the weld	Travel speed too fast, heat too high, poor angle
Lack of fusion	Weld metal does not bond to base metal or previous pass	Heat too low, travel too fast, poor cleaning, wrong technique
Excess spatter	Scattered metal droplets around weld	Settings mismatch, arc length, polarity, wire or electrode issue
Overlap	Weld metal rolls over without fusing at the toe	Travel speed too slow, heat too low, poor angle
Burn-through	Hole through base metal	Heat too high, travel too slow, material too thin
Cracking	Visible crack in or near the weld	Restraint, contamination, wrong filler, cooling stress	Stop and seek qualified review

Practice bead record

Date	Process	Material	Thickness	Filler/wire/electrode	Settings	Shielding gas	Result
	MIG / TIG / stick / flux-core
	MIG / TIG / stick / flux-core
	MIG / TIG / stick / flux-core

Defect observation notes

Bead or sample	Defect observed	Where it appears	Likely cause to test	Next practice change
		Start / middle / crater / toe / root
		Start / middle / crater / toe / root
		Start / middle / crater / toe / root

Safer practice checklist

• Clean base metal before welding.
• Confirm PPE, ventilation, fire watch needs, and nearby combustibles.
• Verify polarity, gas, wire or electrode size, and ground connection.
• Practice on scrap material similar to the workpiece before welding the project.
• Change only one setting or technique variable at a time.
• Label practice samples so results match recorded settings.

Stop and get qualified help when

• The weld is structural, pressure-related, vehicle-related, lifting-related, or otherwise safety-critical.
• Cracking appears in the weld or heat-affected zone.
• You cannot identify the base metal, filler, or procedure requirement.
• The work is governed by a code, standard, employer procedure, or customer specification.