Certified Welder Weld Inspection and Defects 3 — Questions and Answers
Question 1: Which type of weld crack forms at elevated temperatures during or immediately after solidification of the weld pool?
- Hydrogen-induced cold crack
- Hot crack (solidification crack) (Correct answer)
- Stress corrosion crack
- Reheat crack
Correct answer: Hot crack (solidification crack)
Hot cracks, also called solidification cracks, form in the weld metal while it is still at high temperature and the grain boundaries contain liquid films.
Question 2: In ultrasonic testing of welds, the decibel (dB) gain control is used to:
- Adjust the pulse repetition frequency
- Amplify the received signal to compare indications against a reference level (Correct answer)
- Control the transducer frequency
- Set the scanning speed of the probe
Correct answer: Amplify the received signal to compare indications against a reference level
The dB gain control amplifies echo signals so inspectors can compare discontinuity echoes against calibration reflectors at a standard reference level.
Question 3: Porosity that is distributed uniformly throughout the entire weld is called:
- Cluster porosity
- Linear porosity
- Scattered (uniformly distributed) porosity (Correct answer)
- Piping porosity
Correct answer: Scattered (uniformly distributed) porosity
Uniformly distributed (scattered) porosity is spread evenly throughout the weld and typically results from consistently contaminated base metal, filler, or shielding.
Question 4: Which factor most increases susceptibility to hydrogen-induced cracking (HIC) in carbon steel welds?
- Low carbon equivalent and preheat above 200°F
- High carbon equivalent, high hydrogen, and high restraint (Correct answer)
- Low heat input with argon shielding gas
- Multi-pass welding with interpass cleaning
Correct answer: High carbon equivalent, high hydrogen, and high restraint
HIC risk increases with higher carbon equivalent (harder HAZ), higher diffusible hydrogen levels, and higher joint restraint that increases residual stress.
Question 5: A weld profile showing excessive convexity is problematic primarily because it:
- Reduces weld cross-sectional area below minimum
- Creates stress concentration at the weld toes that can initiate fatigue cracks (Correct answer)
- Causes the weld to cool too slowly
- Indicates insufficient filler metal deposition
Correct answer: Creates stress concentration at the weld toes that can initiate fatigue cracks
An excessively convex weld bead creates sharp toes with high stress concentration, increasing the risk of fatigue crack initiation under cyclic loading.
Question 6: During visual inspection, overlap (cold lap) on a fillet weld appears as:
- A groove melted into the base metal adjacent to the weld toe
- Weld metal rolled beyond the weld toe onto the base metal without fusion (Correct answer)
- A crack running along the weld centerline
- Excessive weld reinforcement above the base metal surface
Correct answer: Weld metal rolled beyond the weld toe onto the base metal without fusion
Overlap (cold lap) occurs when molten weld metal flows over the base metal surface but does not fuse to it, leaving an unfused flap at the weld toe.
Question 7: When performing a visual inspection, what tool is used to measure the actual throat of a fillet weld?
- Dial caliper
- Fillet weld gauge (bridge cam gauge) (Correct answer)
- Ultrasonic thickness gauge
- Radiographic film densitometer
Correct answer: Fillet weld gauge (bridge cam gauge)
A fillet weld gauge (bridge cam gauge) is specifically designed to measure fillet weld leg size and actual throat dimensions quickly during visual inspection.
Certified Welder Weld Inspection and Defects 3
Which type of weld crack forms at elevated temperatures during or immediately after solidification of the weld pool?