CWI Weld Discontinuities and Defects 3 — Questions and Answers
Question 1: A weld inspector observes that a weld bead has a very rough, irregular surface profile. Which process parameter is the MOST likely cause?
- Excessive preheat
- Incorrect polarity (Correct answer)
- Insufficient amperage
- High arc voltage
Correct answer: Incorrect polarity
Incorrect polarity in SMAW or GMAW can cause irregular, rough bead profiles as the arc characteristics become unstable and transfer changes.
Question 2: What is 'burn-through' in welding and when does it most commonly occur?
- Excessive reinforcement on thin materials
- A hole melted completely through the base metal, common in thin sections (Correct answer)
- Hydrogen cracking in high-carbon steels
- Incomplete fusion in vertical-up welding
Correct answer: A hole melted completely through the base metal, common in thin sections
Burn-through is a hole melted completely through the base metal or weld, most commonly occurring when welding thin materials with excessive heat input.
Question 3: Which test method can directly measure the depth of undercut in a production weld?
- Magnetic particle testing
- Liquid penetrant testing
- Undercut gauge (fillet weld gauge) (Correct answer)
- Radiographic testing
Correct answer: Undercut gauge (fillet weld gauge)
An undercut gauge is a mechanical depth gauge used by welding inspectors to measure the actual depth of undercut at the weld toe.
Question 4: Stress corrosion cracking (SCC) in welds is promoted by which combination of conditions?
- Low temperature, compressive stress, and inert environment
- Tensile stress, susceptible material, and corrosive environment (Correct answer)
- High preheat, hydrogen, and thick sections
- Rapid cooling, austenite transformation, and oxidizing atmosphere
Correct answer: Tensile stress, susceptible material, and corrosive environment
SCC requires three simultaneous conditions: tensile residual or applied stress, a susceptible alloy microstructure, and a specific corrosive environment.
Question 5: In radiographic testing, a weld discontinuity that appears as an irregular dark area with no defined boundaries most likely indicates:
- Tungsten inclusion
- Porosity cluster
- Incomplete penetration
- Slag inclusion (Correct answer)
Correct answer: Slag inclusion
Slag inclusions typically appear as irregular dark areas with jagged or diffuse boundaries on radiographs, while porosity appears as rounded dark spots.
Question 6: Which welding defect is described as 'cold lap' and how does it differ from overlap?
- Cold lap = lack of fusion at root; overlap = at weld toe
- Cold lap and overlap are identical terms for the same defect
- Cold lap = fusion discontinuity at the weld interface; overlap = weld metal flowing onto base metal without fusion (Correct answer)
- Cold lap = porosity cluster; overlap = incomplete penetration
Correct answer: Cold lap = fusion discontinuity at the weld interface; overlap = weld metal flowing onto base metal without fusion
Cold lap refers to a fusion discontinuity between weld passes or between weld and base metal, while overlap specifically refers to weld metal protruding beyond the weld toe without fusion.
Question 7: A CWI finds cracks at the HAZ of a high-strength low-alloy (HSLA) steel weld, appearing 24–72 hours after welding. This is MOST likely:
- Hot cracking
- Reheat cracking
- Hydrogen-induced cold cracking (HICC) (Correct answer)
- Lamellar tearing
Correct answer: Hydrogen-induced cold cracking (HICC)
Hydrogen-induced cold cracking (HICC) typically appears hours to days after welding in the HAZ of hardenable steels when hydrogen, stress, and susceptible microstructure coincide.
CWI Weld Discontinuities and Defects 3
A weld inspector observes that a weld bead has a very rough, irregular surface profile.
Which process parameter is the MOST likely cause?