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Types of Welding Defects
Understand the most common welding defects and their causes to ensure higher weld strength, better part reliability, and consistent manufacturing quality.
This quick-reference table helps engineers and manufacturers identify issues early and apply the right corrective actions for defect-free welds.
Welding Defect |
Description |
Common Causes |
Impact on Weld Quality |
Prevention / Solutions |
| Porosity | Formation of gas pockets or voids in the weld metal. | Moisture, oil, or contaminants, insufficient shielding gas. | Reduces weld strength and may cause leakage. | Clean surfaces, improve gas flow, keep materials dry. |
| Cracks | Fractures appearing in the weld or heat-affected zone. | Rapid cooling, high carbon content, residual stress. | Lead to serious structural failure. | Preheat materials, control cooling rate, reduce stress. |
| Undercut | A groove melted into the base metal next to the weld. | Excessive welding current, high travel speed. | Lowers fatigue strength and increases crack risk. | Reduce welding current, slow travel speed. |
| Lack of Fusion | Weld metal does not properly fuse with the base metal. | Low heat input, incorrect torch angle. | Weak joint strength. | Increase heat input, correct welding angle. |
| Incomplete Penetration | Weld does not fully penetrate the joint thickness. | Low current, insufficient root gap. | Poor load-bearing capacity. | Increase current, adjust root opening. |
| Slag Inclusion | Entrapped slag inside the weld. | Improper slag removal, wrong weaving technique. | Creates stress points and weakens the weld. | Remove slag after each pass, improve torch maneuvering. |
| Spatter | Small metal droplets ejected during welding. | High voltage, unstable shielding gas. | Poor surface appearance, requires extra cleaning. | Optimize parameters, stabilize gas flow. |
| Distortion | Warping or deformation of welded parts. | Excessive or uneven heat input. | Dimensional inaccuracies and assembly issues. | Control heat input, weld symmetrically, use fixtures. |
| Overlap | Weld metal flows over the base metal without fusion. | Low current, slow travel speed. | Weak, easily separable weld. | Increase current, adjust travel speed. |
| Burn-Through | Weld pool melts completely through the workpiece. | High heat input, excessive current. | Causes holes and scrapped parts. | Reduce current, use pulse welding. |
| Excessive Reinforcement | Weld bead too high or uneven. | Too much filler metal, slow travel. | Stress concentration and poor appearance. | Reduce filler deposition, increase travel speed. |
| Cold Lap | Weld bead fails to blend smoothly with base metal. | Insufficient heat input. | Weak weld, prone to peeling. | Increase heat or current; improve torch positioning. |
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