Porosity, undercut and spatter are useful symptoms to record when reviewing a fiber laser weld. They are not a complete defect list, and appearance alone cannot establish the cause or prove that a weld meets its requirements. Use this guide to prepare a discussion with your equipment supplier or qualified welding specialist.
Porosity: cavities are not cracks
Gas cavities may form from contamination, inadequate shielding or an unstable keyhole. Aluminium porosity can involve hydrogen associated with moisture or surface oxide. Solidification cracking is a different mechanism: filler selection depends on the alloy and procedure, not a blanket rule that all aluminium needs wire to prevent pores. Both excessive and insufficient shielding flow can be problematic. TWI explains porosity and cracking separately.
For the review: record the alloy, coating, joint preparation, gas specification and actual machine settings. Use the supplier-approved cleaning method and procedure; this guide does not prescribe a solvent, flow rate or focal offset.
Undercut: inspect the weld toe
Undercut is a groove at the edge of the weld. Record its location and measured extent using the inspection method required for the job. Ask the reviewer to assess joint geometry, alignment and process conditions together. Slowing travel or reducing power is not an automatic correction.
Spatter: record the pattern and timing
Spatter is expelled weld metal deposited around the seam. Capture where and when it occurs, including whether it follows a change of material, setup or consumable. Do not assume that cleaning or changing gas flow will resolve every case; a supplier-led review should establish the cause before selecting a trial.
Save the machine model, software/program version, material grade and thickness, joint drawing, settings, consumables, photographs and sample identification. Compare these with the approved procedure. Agree on trial changes and inspection requirements before returning affected parts to production.
Telling the Three Apart at a Glance
| Defect | How It Looks | When You Notice It |
|---|---|---|
| Porosity | Small round voids, often internal | Surface inspection or specified internal examination |
| Undercut | Groove or thinning along bead edge | During surface inspection |
| Spatter | Molten droplets around the weld | During surface inspection |
Check out the HW Series
Considering a new machine? Review the HW Series product information and bring your joint drawings and acceptance requirements to a sample-weld discussion. Confirm the exact configuration, accessories and service scope in your quotation.
Download the laser-welder quote checklist
Inspection and further reading
Use the inspection and acceptance requirements for your application; surface appearance is not a substitute for required testing. Other concerns, including cracking and incomplete fusion, need separate assessment. TWI discusses laser-weld defects in structural steels; its process-specific guidance is not a universal handheld-welder settings chart.