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Transverse weld crack: what it is and how to spot it

Fillet Gauge editorial teamSources checked 3 min read

A transverse crack runs across the weld, roughly at right angles to its length. It can stay inside the weld metal, or cross the full bead and continue into the heat-affected zone and base metal on either side. Transverse cracks usually come from shrinkage stress along the weld acting on metal that is hard, brittle or full of hydrogen.

A weld bead seen from above with two jagged lines at right angles to it: a long one crossing the bead and running into the plate on both sides, and a shorter one inside the weld metal
Read the direction against the weld axis: across it is transverse. Original drawing, not to scale.
Use this diagram

How to recognize a transverse crack

  1. Check the direction against the weld axis. Across the bead is transverse. Along it is longitudinal. That single check is the whole naming decision.
  2. Follow it to its ends. A transverse crack that runs past the toes into the plate is telling you the base metal or heat-affected zone was involved, not just the weld.
  3. Look for a family. Transverse cracks often come in a series spaced along the weld, especially in hard, high-strength weld metal.
  4. Don't stop at one pass. In multi-pass welds, transverse cracks can sit in an inner pass and never reach the cap.

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Welding Inspection and Discontinuities

A convex fillet weld replica is checked with a leaf-type fillet gauge. The drawing calls for a single fillet size. The vertical leg fits the 3/8 in blade and the horizontal leg the 5/16 in blade. What size is recorded?

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How it is found and recorded

Open surface cracks are visible with good side light and a magnifier. Penetrant testing confirms them on any non-porous metal. Magnetic particle testing finds them in ferromagnetic steel, as long as the magnetic field crosses the crack: a transverse crack needs the field running along the weld, which is the opposite of a longitudinal one. Buried transverse cracks are a challenge for both radiography and ultrasonic testing and often need the technique set up for that orientation. Record location, direction and length, then go to the governing document's crack criteria.

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Common mix-ups

  • Transverse crack or a ripple line. Ripples are curved, regular and shallow. A crack is a single sharp line with pointed ends that cuts through the ripples.
  • Transverse crack or a crater crack. Crater cracks are short, often star-shaped and sit in the crater at the end of a bead. A transverse crack can be anywhere along the weld.
  • Transverse crack or a grinding mark. Grind lines are straight, parallel and in a group. A crack is single and irregular.

Why it forms

The weld shrinks along its length as it cools, and the plate holds it back. If the weld metal or heat-affected zone is hard, brittle or loaded with hydrogen, it cracks across. Common causes are weld metal much stronger than needed, high restraint, damp consumables, too little preheat for the steel and thickness, and fast cooling.

Transverse cracks on the CWI exam

On Part B, cracks fall under Welding Inspection and Discontinuities, at least 34% of the practical. Field direction for magnetic particle testing belongs to NDE Application. On Part A, transverse cracks tie Visual Examination to Base Materials, Heat Treatments and Metallurgy, where hydrogen and hardness are covered. On Part C, look up the code's crack criteria in your own copy.

Practice it

Name crack directions against their look-alikes in the weld discontinuities quiz. Then read the other direction, longitudinal cracks, and the hydrogen crack that forms out of sight, underbead cracks. Every type is in the weld discontinuities guide.

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Facts checked 25 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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