AWS Welding Defects & Quality Control 4 — Questions and Answers
Question 1: Which welding defect is characterized by a groove melted into the base metal adjacent to the weld toe that is left unfilled by weld metal?
- Overlap
- Undercut (Correct answer)
- Underfill
- Cold lap
Correct answer: Undercut
Undercut is a groove melted into the base metal at the weld toe that remains unfilled, reducing the effective cross-section and creating a stress concentration.
Question 2: A welder notices that the weld metal has rolled over onto the base metal without fusing. This defect is called:
- Undercut
- Overlap (Correct answer)
- Burn-through
- Underfill
Correct answer: Overlap
Overlap occurs when weld metal flows over the base metal surface without fusing to it, creating a notch-like condition at the toe of the weld.
Question 3: What is the primary cause of lamellar tearing in weldments?
- Excessive heat input
- Low sulfur content in base metal
- Poor through-thickness ductility due to sulfide inclusions (Correct answer)
- Hydrogen embrittlement
Correct answer: Poor through-thickness ductility due to sulfide inclusions
Lamellar tearing occurs due to poor through-thickness ductility caused by elongated sulfide and silicate inclusions in the base metal, triggered by transverse stresses during welding.
Question 4: Which NDE method is MOST effective for detecting surface-breaking cracks in non-magnetic austenitic stainless steel welds?
- Magnetic particle testing (MT)
- Liquid penetrant testing (PT) (Correct answer)
- Radiographic testing (RT)
- Ultrasonic testing (UT)
Correct answer: Liquid penetrant testing (PT)
Liquid penetrant testing is the preferred surface examination method for non-magnetic materials like austenitic stainless steel, where magnetic particle testing cannot be used.
Question 5: In radiographic testing of welds, a lighter (less dense) area on the film compared to the surrounding base metal typically indicates:
- A slag inclusion
- A tungsten inclusion
- A crack
- A void or porosity (Correct answer)
Correct answer: A void or porosity
Voids and porosity appear as lighter areas on radiographic film because they allow more radiation to pass through, creating darker images — but compared to denser base metal, they appear as lighter round indications relative to surrounding structure in standard terminology.
Question 6: What type of weld crack forms in the base metal heat-affected zone (HAZ) days or weeks after welding?
- Hot crack
- Solidification crack
- Delayed hydrogen-induced crack (Correct answer)
- Liquation crack
Correct answer: Delayed hydrogen-induced crack
Delayed hydrogen-induced cracking (also called cold cracking or underbead cracking) occurs in the HAZ hours to weeks after welding due to diffusible hydrogen, residual stress, and a susceptible microstructure.
Question 7: When performing a bend test on a weld coupon, the specimen cracks on the tension side. Which of the following is the MOST likely cause?
- Excessive reinforcement height
- Lack of fusion in the weld (Correct answer)
- Incorrect bend radius
- Excessive interpass temperature
Correct answer: Lack of fusion in the weld
Lack of fusion creates planes of weakness in the weld that open under the tensile stress applied during a bend test, causing cracking on the tension side.
AWS Welding Defects & Quality Control 4
Which welding defect is characterized by a groove melted into the base metal adjacent to the weld toe that is left unfilled by weld metal?