Here are some break down weld defects into the following main categories:
- Inclusions.
- Lack of fusion.
- Porosity.
- Undercut.
- Under-fill.
- Cracks.
- Excess reinforcement and excess penetration.
- Over-roll/Overlap.
Here are 7 common welding defects that often occur in sheet metal fabrication:
1. Porosity
Description: Small gas pockets or voids trapped in the weld metal.
Causes: Contaminated base metal, moisture, rust, oil, or incorrect shielding gas flow.
Prevention: Clean the workpiece, use proper shielding gas, and control arc length.
2. Undercut
Description: A groove melted into the base metal along the weld toe that is not filled with weld metal.
Causes: Excessive welding current, fast travel speed, or poor electrode angle.
Prevention: Reduce current, slow travel speed, and adjust torch/electrode angle properly.
3. Incomplete Fusion
Description: The weld metal fails to fuse completely with the base metal or previous weld bead.
Causes: Low heat input, improper torch angle, or presence of oxide layers.
Prevention: Increase current or voltage, clean metal surface, and maintain correct torch angle.
4. Incomplete Penetration
Description: The weld metal does not extend through the full thickness of the joint.
Causes: Low current, improper joint preparation, or incorrect root gap.
Prevention: Use proper joint design, increase heat input, and maintain correct root opening.
5. Cracks
Description: Fractures in the weld or heat-affected zone (HAZ).
Types: Hot cracks, cold cracks, and crater cracks.
Causes: High restraint, rapid cooling, or improper filler material.
Prevention: Preheat thick sections, control cooling rate, and use suitable filler metal.
6. Slag Inclusions
Description: Nonmetallic solid material (slag) trapped in the weld metal.
Causes: Improper cleaning between passes, wrong electrode angle, or low heat input.
Prevention: Clean slag between passes and maintain proper arc characteristics.
7. Spatter
Description: Small droplets of molten metal that stick to the surface near the weld.
Causes: Too high current, incorrect polarity, or excessive arc length.
Prevention: Optimize current and voltage settings, use anti-spatter spray, and maintain proper arc length.
Would you like me to include a diagram showing these defects on a weld cross-section? It can make them easier to visualize.
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