AWS Weld Discontinuities & Defects 4 — Questions and Answers
Question 1: Which discontinuity is most likely to occur when welding austenitic stainless steel with excessive heat input?
- Porosity
- Hot cracking (Correct answer)
- Cold cracking
- Undercut
Correct answer: Hot cracking
Austenitic stainless steels are susceptible to hot cracking (solidification cracking) when high heat input causes low-melting impurity films to form along grain boundaries.
Question 2: A weld exhibiting 'wagon tracks' on a radiograph most likely contains which discontinuity?
- Slag inclusions (Correct answer)
- Incomplete fusion
- Linear porosity
- Overlap
Correct answer: Slag inclusions
Wagon tracks on a radiograph are parallel lines of slag inclusions typically found between weld passes in multi-pass welds.
Question 3: Which condition is the PRIMARY cause of lamellar tearing in structural weldments?
- Excessive preheat temperature
- Low through-thickness ductility of the base metal (Correct answer)
- High welding current
- Insufficient filler metal deposition
Correct answer: Low through-thickness ductility of the base metal
Lamellar tearing occurs when through-thickness shrinkage stresses exceed the low through-thickness ductility of base metal containing planar inclusions.
Question 4: A welder notices a groove melted into the base metal adjacent to the weld toe that is not filled by weld metal. This is called:
- Overlap
- Undercut (Correct answer)
- Incomplete penetration
- Burn-through
Correct answer: Undercut
Undercut is a groove melted into the base metal at the weld toe or weld root that is left unfilled by weld metal.
Question 5: Which nondestructive testing method is MOST effective for detecting subsurface porosity in a thick weld section?
- Liquid penetrant testing (PT)
- Magnetic particle testing (MT)
- Radiographic testing (RT) (Correct answer)
- Visual testing (VT)
Correct answer: Radiographic testing (RT)
Radiographic testing (RT) is most effective for detecting internal volumetric discontinuities like subsurface porosity in thick sections.
Question 6: What type of crack typically initiates at the weld toe and propagates into the heat-affected zone?
- Transverse crack
- Crater crack
- Toe crack (Correct answer)
- Longitudinal root crack
Correct answer: Toe crack
Toe cracks initiate at the geometric stress concentration at the weld toe and propagate into the heat-affected zone, often caused by hydrogen-induced cracking.
Question 7: Which welding parameter change would MOST effectively reduce the risk of burn-through on thin sheet metal?
- Increase travel speed (Correct answer)
- Decrease travel speed
- Increase wire feed speed
- Use a larger electrode diameter
Correct answer: Increase travel speed
Increasing travel speed reduces heat input per unit length, preventing excessive melt-through (burn-through) on thin base materials.
AWS Weld Discontinuities & Defects 4
Which discontinuity is most likely to occur when welding austenitic stainless steel with excessive heat input?