Select a welding symptom and process to find likely causes, diagnostic checks and practical corrective actions.
A visible weld defect is often the result of several interacting variables rather than one isolated setting. A useful troubleshooting process checks the simplest causes first and changes one variable at a time.
Start with shielding, cleanliness, consumable condition and equipment setup. Then examine current, voltage, travel speed, electrode or torch angle, stickout, gas flow and joint preparation as appropriate for the welding process.
| Symptom | Common Causes | First Checks |
|---|---|---|
| Porosity | Shielding problem, contamination, moisture, drafts | Gas supply, flow, leaks, nozzle, material cleanliness |
| Undercut | High heat, excessive travel speed, angle or manipulation | Current, voltage, travel speed, torch/electrode angle |
| Excessive spatter | Incorrect parameters, poor shielding, long arc, unstable transfer | Voltage, current, polarity, gas, stickout |
| Lack of fusion | Low heat, high travel speed, poor angle, contamination | Amperage, travel speed, joint cleaning, angle |
| Incomplete penetration | Poor joint preparation, low heat, excessive root gap variation | Root gap, bevel, current, travel speed |
| Burn-through | Excessive heat, excessive root gap, slow travel | Current, travel speed, root gap, technique |
| Cracking | Hydrogen, restraint, cooling, material or procedure issues | Consumable condition, preheat, joint restraint, procedure |
| Distortion | Uneven heating and shrinkage | Weld sequence, heat input, fixturing, joint design |
Porosity is commonly associated with gas being trapped in the solidifying weld metal. The source may be inadequate shielding, contamination, moisture or process instability.
Undercut is a groove melted into the base metal near the weld toe or root. It can be associated with excessive heat, excessive travel speed or unsuitable electrode/torch manipulation.
Corrective changes should be made according to the qualified welding procedure rather than simply reducing every parameter.
Lack of fusion occurs when the deposited weld metal does not adequately fuse with the base metal or a previous weld layer.
Incomplete penetration occurs when the weld does not penetrate to the required depth at the joint root.
Check root opening, joint preparation, root face, electrode diameter, welding current, travel speed and access to the root.
For a groove weld, incorrect bevel geometry can prevent the arc from reaching the intended fusion zone even when the current appears adequate.
Excessive spatter can indicate unstable arc conditions, incorrect voltage/current relationships, poor shielding or unsuitable stickout.
Burn-through occurs when excessive heat melts through the root or creates a hole.
For thin material, a smaller consumable and appropriate pulsed or controlled process may be preferable where supported by the qualified procedure.
Cracking requires a more cautious investigation because several metallurgical and mechanical mechanisms can produce cracks.
Weld distortion is caused by uneven heating and contraction as the weld and surrounding material cool.
Common controls include suitable weld sequencing, balanced welding, appropriate fixturing, controlled heat input and joint design.
Reducing weld volume where engineering requirements allow can also reduce unnecessary shrinkage.
Tungsten inclusions or contamination can occur when the tungsten electrode contacts the molten weld pool or filler material.
| Variable | Too Low / Too Fast | Too High / Too Slow |
|---|---|---|
| Current | Possible poor fusion or penetration | Possible burn-through, undercut or excessive heat |
| Voltage | Potentially narrow/high bead and unstable arc depending on process | Potentially wide/flat bead, excessive spatter or poor control |
| Travel speed | Higher heat per unit length, possible burn-through or excessive reinforcement | Lower heat per unit length, possible lack of fusion or inadequate penetration |
| Shielding gas flow | Insufficient protection and possible porosity | Excessive flow can create turbulence and draw surrounding air into the shield |
| Stickout | Process-dependent effect | Excessive stickout can alter heating and arc characteristics |
The exact effect of each variable depends on the welding process, transfer mode, consumable, polarity and procedure.
This tool provides troubleshooting guidance for common welding symptoms. It does not determine the single definitive cause of a defect from a symptom alone.
Actual causes can depend on welding process, material, consumable, joint geometry, machine settings, environment, operator technique and welding procedure.
What is the fastest way to troubleshoot a weld defect? Start with the simplest controllable causes: cleanliness, moisture, shielding, consumable condition, polarity and equipment setup. Then check the welding parameters and technique.
Can one welding defect have multiple causes? Yes. Porosity, lack of fusion, cracking and spatter can each result from several interacting variables.
Why is shielding gas one of the first checks for MIG welding? Because inadequate or turbulent shielding can allow atmospheric contamination into the arc and weld pool, producing porosity and other problems.
What commonly causes lack of fusion? Insufficient heat at the fusion boundary, excessive travel speed, poor electrode or torch angle, contamination and unsuitable joint preparation are common contributors.
What commonly causes undercut? High heat, excessive travel speed, incorrect electrode or torch angle and unsuitable manipulation can contribute.
What should I check when a weld suddenly becomes porous? Check shielding-gas supply and flow, leaks, drafts, torch/nozzle condition, material cleanliness and moisture first.
Why can too much shielding gas cause problems? Very high flow can create turbulence that draws surrounding air into the shielding envelope instead of improving protection.
What should I do if I find a crack? Stop and identify the crack and applicable repair requirements. Do not simply weld over it without following the applicable repair procedure.
Can this tool automatically tell me which parameter to change? It provides likely causes and checks. The correct parameter change depends on the qualified welding procedure and actual conditions.
Does this tool replace a welding procedure? No. The WPS and applicable welding requirements remain controlling for production work.