# Weld Defects Chart: Types, Causes, Detection and Remedies

> Source: https://netray.co/tools/weld-defects-causes-and-remedies-reference
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Troubleshooting table that maps each weld imperfection to likely causes, how it is found and what to change.

## Category

quality

## Industry

Welding & Fabrication

## Audience

- Welding inspector
- Quality engineer
- Welding engineer
- Welder

## Tool

**Kind:** worksheet

**Mode:** reference

**Columns:**

#### Imperfection

**Key:** defect

**Type:** text

#### What it is

**Key:** description

**Type:** text

#### Common causes

**Key:** causes

**Type:** text

#### Typically found by

**Key:** detect

**Type:** text

#### Remedy

**Key:** remedy

**Type:** text

**Rows:**

**Defect:** Porosity (scattered)

**Description:** Gas pockets trapped in weld metal

**Causes:** Shielding gas loss, wet electrode, contamination, oil or paint

**Detect:** Visual (surface), RT

**Remedy:** Check gas flow and leaks, dry consumables, clean joint

**Defect:** Wormholes (elongated pores)

**Description:** Elongated gas cavities

**Causes:** Excess moisture or primer, rust on joint

**Detect:** RT, sometimes UT

**Remedy:** Remove coating, dry consumables, adjust technique

**Defect:** Slag inclusion

**Description:** Non-metallic slag trapped between passes

**Causes:** Poor interpass cleaning, wrong travel angle, too low current

**Detect:** RT, UT

**Remedy:** Clean each pass, adjust angle, raise current

**Defect:** Lack of fusion

**Description:** Weld metal not fused to base metal or previous bead

**Causes:** Low heat input, fast travel, wrong angle, cold lapping

**Detect:** UT, RT, visual at toes

**Remedy:** Raise heat input, slow travel, correct angle and bead placement

**Defect:** Incomplete penetration

**Description:** Weld does not reach the root of the joint

**Causes:** Root opening too small, low current, wrong electrode size

**Detect:** RT, UT, visual from root side

**Remedy:** Widen gap or root face, raise current, use a smaller electrode for the root

**Defect:** Undercut

**Description:** Groove melted into base metal beside the toe

**Causes:** Excess current or voltage, long arc, wrong angle, fast travel

**Detect:** Visual, with gauge

**Remedy:** Lower current, shorten arc, pause at the edges

**Defect:** Overlap

**Description:** Weld metal flows over base metal without fusing

**Causes:** Low current, slow travel, wrong angle

**Detect:** Visual, MT or PT on toes

**Remedy:** Raise current, speed up travel, correct angle

**Defect:** Crater crack

**Description:** Star-shaped crack where the arc stops

**Causes:** Abrupt arc termination, shrinkage in the crater

**Detect:** Visual, PT, MT

**Remedy:** Fill crater, use crater fill control, back-step

**Defect:** Solidification (hot) crack

**Description:** Crack along weld centerline as metal solidifies

**Causes:** High sulfur or phosphorus, deep narrow bead, high restraint

**Detect:** PT, MT, UT

**Remedy:** Reduce restraint, widen bead profile, use low-impurity filler

**Defect:** Hydrogen (cold) crack

**Description:** Delayed crack in the heat affected zone or weld

**Causes:** Hydrogen, hard microstructure and stress together

**Detect:** MT, UT, often after hours or days

**Remedy:** Use low hydrogen consumables, preheat, control interpass, hold hydrogen bake out

**Defect:** Lamellar tearing

**Description:** Stepped cracking in rolled plate under through-thickness stress

**Causes:** Weak through-thickness plate, high restraint at tee or corner joints

**Detect:** UT, visual

**Remedy:** Use plate with through-thickness properties, change joint design, buttering

**Defect:** Spatter

**Description:** Droplets thrown out beside the weld

**Causes:** High CO2 shielding, wrong voltage, damp consumables

**Detect:** Visual

**Remedy:** Adjust voltage and wire speed, change gas mix, use anti-spatter

**Defect:** Excess reinforcement

**Description:** Weld face higher than the code allows

**Causes:** Slow travel, excess filler, low voltage

**Detect:** Visual, gauge

**Remedy:** Increase travel speed, lighten deposit, grind if permitted

**Defect:** Underfill

**Description:** Weld face below the surface of adjacent base metal

**Causes:** Insufficient filler, too fast travel, missing cap pass

**Detect:** Visual, gauge

**Remedy:** Add a cap pass, slow travel

**Defect:** Burn-through

**Description:** Hole melted through the base metal

**Causes:** Excess heat on thin material, large root gap

**Detect:** Visual

**Remedy:** Lower current, use pulsed process, add backing

**Defect:** Tungsten inclusion

**Description:** Tungsten fragments embedded in weld metal

**Causes:** Electrode touching the pool, overcurrent, wrong tip

**Detect:** RT

**Remedy:** Use proper electrode size, avoid contact, regrind

**Defect:** Arc strike

**Description:** Local burn on base metal outside the weld

**Causes:** Striking the arc off the joint

**Detect:** Visual, MT or PT

**Remedy:** Strike arc only in the joint or on run-on tabs

**Defect:** Misalignment (high-low)

**Description:** Offset between members at the joint

**Causes:** Poor fit-up, no clamps, tack weld movement

**Detect:** Visual, gauge

**Remedy:** Use fit-up fixtures, check before welding

**Defect:** Distortion

**Description:** Shrinkage-driven warping of the part

**Causes:** Heat input, weld sequence, unbalanced welds

**Detect:** Dimensional inspection

**Remedy:** Balance weld sequence, use fixtures, lower heat input

**Defect:** Root concavity

**Description:** Root surface below the base metal surface

**Causes:** Excess purge pressure, high heat, wrong root pass technique

**Detect:** Visual, RT

**Remedy:** Lower purge pressure, adjust root parameters

**Notes:** Acceptance limits come from the governing code and drawing, not from this table. NDT abbreviations: VT visual, PT penetrant, MT magnetic particle, RT radiography, UT ultrasonic.

## Content

**Intro:** Rejected welds cost rework hours, schedule and sometimes certificates. This table pairs each common weld imperfection with likely causes, the inspection method that finds it and the usual fix.

**Sections:**

#### How to use this table

**Body:** Search by what the inspector wrote, such as undercut or lack of fusion, and read across to the likely causes and the remedy. Welding engineers can use it as a starting point for a corrective action, and welders can use it as a quick coaching aid. Export it to Excel to attach to nonconformance procedures or training material.

#### How imperfections are classified

**Body:** ISO 6520-1 classifies imperfections into groups such as cracks, cavities, solid inclusions, lack of fusion and penetration, imperfect shape and miscellaneous. Surface imperfections can be found by visual and penetrant or magnetic particle testing, while internal ones need radiography or ultrasonic testing. Whether an imperfection is a defect depends on the acceptance level in the governing code, such as AWS D1.1, ASME B31.3 or ISO 5817.

#### Common mistakes in troubleshooting

**Body:** Fixing the symptom without finding the cause just repeats the nonconformance.

**Bullets:**

- Grinding out and rewelding without changing the parameters that caused the fault.
- Confusing lack of fusion with incomplete penetration: one is bonding, the other is root reach.
- Inspecting hydrogen cracking too early: delayed cracks may appear after hours or days.
- Blaming the welder when the WPS parameters are out of range.
- Skipping a record of the repair procedure and the number of repair attempts.

**Cta:** If you want weld repairs and nonconformances tracked against jobs, heats and welders in your ERP quality module, Netray can describe common patterns.

**Faq:**

#### What is the difference between lack of fusion and incomplete penetration?

**Answer:** Lack of fusion means weld metal did not bond to base metal or to a previous bead. Incomplete penetration means the weld did not extend to the root of the joint. Both reduce strength, but they have different causes and are often found in different locations.

#### What causes porosity in welds?

**Answer:** Gas trapped during solidification: shielding gas loss from drafts or leaks, damp electrodes, oil, paint, rust or moisture on the joint, and wrong parameters. Check gas flow, clean the joint, dry consumables and shield the arc from wind.

#### How do I prevent hydrogen cracking?

**Answer:** Control the three drivers: use low hydrogen consumables stored dry, apply preheat and interpass temperature suited to the steel and thickness, and limit restraint. Post-weld hydrogen bake out can help on sensitive steels. Follow your WPS and code.

#### Is every imperfection a rejectable defect?

**Answer:** No. Acceptance depends on the applicable code and quality level. Small amounts of porosity or minor undercut may be acceptable in one code and rejected in another. Cracks and lack of fusion are generally not accepted in most codes.

## Search terms

weld defects and causes, types of weld defects, porosity in welding causes, undercut welding cause, lack of fusion vs incomplete penetration, hydrogen cracking welding, weld defect remedies, welding inspection defects chart

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