DIMEVISION

Weld Defect Identification Guide

A visual reference for common welding defects, what causes them, and how to fix them - based on AWS B4.0 standards

Why Defect Identification Matters

If you are going to pass a weld test or work as a welder, you need to know what makes a weld rejectable. This guide covers the most common defects, what they look like, and how to avoid them.

This is also what DimeVision checks when you upload a photo.

1. Porosity

Small holes or cavities in the weld metal.

Types: Distributed, cluster, linear, root porosity

caused by:

Contaminated base metal (oil, rust, paint)
Wet or contaminated filler metal
Travel speed too fast
Excessive wind or drafts

Fix: Always clean base metal with a grinder. Store filler metal properly. Slow down. Use wind shield outdoors.

2. Lack of Fusion

The weld metal did not fully fuse with the base metal or previous pass.

caused by:

Insufficient heat (amps too low)
Travel speed too fast
Incorrect torch angle

Fix: Increase amperage 10-15%. Reduce travel speed. Keep torch at 15-20 degrees.

3. Undercut

A groove melted into the base metal adjacent to the weld toe.

caused by:

Arc length too long
Travel speed too slow
Incorrect torch angle

Fix: Keep arc length short. Increase travel speed. AWS D1.1 limit: 1/32 inch maximum.

4. Overlap

The weld metal extends over the weld toe without fusion.

caused by:

Insufficient heat
Travel speed too slow
Wrong torch angle

Fix: Increase amperage. Adjust torch angle. Place filler correctly.

5. Excessive Reinforcement

The weld crown is taller than allowed.

Fix: Use stringer beads. Increase travel speed. Typical max: 1/8 inch per AWS D1.1.

6. Crater Cracks

Cracks in the crater at the end of a weld bead.

Fix: Do not stop abruptly. Use crater fill technique. Backstep 1/4 inch before lifting.

7. Spatter

Metal particles expelled during welding that adhere to surrounding areas.

Fix: Balance wire feed with voltage. Replace worn contact tips. Clean base metal.

8. Incomplete Penetration

The weld did not extend through the entire joint thickness.

Fix: Ensure adequate root opening (1/16 to 1/8 inch). Increase amperage for root passes. Slow down at root.

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Quick Reference

Defect	Main Cause	Quick Fix
Porosity	Contamination, speed	Clean metal, slow down
Lack of Fusion	Low heat, fast travel	Increase amps
Undercut	Long arc, slow travel	Short arc, go faster
Overlap	Low heat, wrong angle	More heat, adjust angle
Excessive Reinforcement	Too much filler	Faster travel
Crater Cracks	Abrupt stop	Crater fill technique
Spatter	High wire speed	Balance wire/voltage
Incomplete Penetration	Root too tight	Open root gap

Sources

AWS D1.1-2020, Structural Welding Code-Steel
AWS B4.0, Standard Methods for Visual Examination of Welds
Lincoln Electric Technical Guide
Miller Welder Resources