Weld discontinuities quiz: identify weld defects from drawings

Look at a cross-section or a surface view, name the discontinuity, and learn the one tell that separates it from its look-alike.

Original drawings · 15 questions

Weld discontinuities quiz

See all 13 types ↓

Name the discontinuity in each drawing. Every wrong option is a real look-alike, so each explanation shows you the tell that separates them.

Set 20261024 · 0 of 15 answered · 0 correct

Question 1 of 15

Show the answer

Crater crack. The short lines radiate from the dished crater where the arc was broken at the end of the bead, and the star pattern is typical. Porosity shows round holes, not sharp lines. A longitudinal crack runs along the weld length rather than out from a point. An arc strike is a melted spot on the base metal outside the weld.

Turn on JavaScript to check your answers, move through all 15 drawings and get a score.

Welding inspection and discontinuities is the biggest domain on CWI Part B, and most lost points start with the wrong name. Name it right and the Book of Specifications tells you the rest. Once you can name it, practice measuring it on the weld gauge trainer.

How the quiz works

Each set shows all 15 drawings in a shuffled order. Some are cross-sections, the view you get from a cut and etched macro or a replica sectioned across the weld. Others look straight down on the bead, the way you see a weld on the bench. Each question offers four names: the right one and three discontinuities that are easy to confuse with it. Check your answer and the explanation tells you what gave it away and why each look-alike doesn't fit.

Your score is one point per drawing, shown as correct answers out of 15. At the end you get a list of your mix-ups, such as undercut answered as underfill, so you know which pairs to drill. Hit New shuffle for a fresh order and fresh option order. Use the set number if you report an error.

Worked examples

Example 1: undercut or underfill?

Step 1: find the plate surface. Here it is the top of the horizontal plate. Step 2: find where metal is missing. The weld face runs full to its toe, and the low spot is a notch dipping into the plate just past the toe. Step 3: name it. Metal melted out of the base metal at the toe and not filled back is undercut. If instead the weld face had sagged below the plate surface across the joint, it would be underfill. On Part B the next step is depth: measure how far the notch goes into the plate, then compare it to the limit the question points you to.

Example 2: porosity or slag inclusion?

Step 1: check the shape. The dark pocket has straight edges and corners, not a round outline. Step 2: check the location. It sits on the dashed boundary between two passes. Step 3: name it. An angular pocket on a pass boundary is a slag inclusion, flux left behind when a pass wasn't fully cleaned. Gas porosity would be round and smooth, and it can sit anywhere in the weld metal. The fix differs too: slag points to interpass cleaning, porosity to shielding, moisture or contamination.

Types of weld discontinuities: the reference set

All 13 types in the quiz, one drawing each, with the look that identifies it. Read through them once, then go back to the quiz and try to beat your score.

Porosity

Round, smooth-walled gas holes in the weld metal, open at the face or buried inside.

Slag inclusion

Jagged, angular pocket of trapped flux inside the weld, often between passes or at a sidewall.

Incomplete fusion

A thin unfused line where weld metal lies against a groove face or an earlier pass without melting into it.

Incomplete joint penetration

The weld stops short of the root, leaving the root faces unmelted with a gap between them.

Undercut

A groove melted into the base metal at the weld toe and left unfilled.

Overlap

Weld metal that runs past the toe and rests on the plate without fusing to it.

Longitudinal crack

A sharp, jagged break running along the length of the weld.

Transverse crack

A sharp, jagged break running across the weld, often out into the base metal.

Crater crack

Short cracks, often star-shaped, in the dished crater at the end of a bead.

Underfill

The weld face sits below the surface of the adjacent plate: not enough weld metal.

Excess reinforcement

The weld face is built up well above the plate, though the toes are fused.

Arc strike

A small melted scar on the base metal outside the weld, where an arc was struck by accident.

Spatter

Small droplets of metal thrown from the arc and stuck to the plate beside the weld.

Want the causes and the NDE method that finds each one? Read weld discontinuities explained for the CWI exam.

For a full page on each type, including crack types, laminations and burn-through, see the weld discontinuities guide.

Weld discontinuity FAQ

What's the difference between a discontinuity and a defect?

A discontinuity is any break in the normal makeup of the weld or the metal next to it. It only becomes a defect, and a reason to reject, when its size, length or count goes past the limit in the code or specification that governs the job. So you name it first, measure it, then compare it to the limit.

How do I tell undercut from underfill on Part B?

Find the plate surface and ask where the metal is missing. If a groove is melted into the plate at the toe, it's undercut. If the weld face itself sits below the plate surface between the toes, it's underfill. Undercut is measured as depth into the plate at the toe; underfill as how far the face sits below the plate.

Do I need to memorize the acceptance limits for every discontinuity?

Not for Part B. It's open book, and the limits you need are in the Book of Specifications you're given. What you can't look up is the name, and a wrong name sends you to the wrong limit. That's what this quiz drills.