AWS Welding Defects & Quality Control 5 — Questions and Answers
Question 1: During visual inspection of a completed weld, the inspector finds the weld crown is 1/8 inch below the base metal surface. This defect is called:
- Undercut
- Concavity
- Underfill (Correct answer)
- Incomplete penetration
Correct answer: Underfill
Underfill is a condition where the weld face is below the adjacent base metal surface, reducing the weld's cross-sectional area and load-carrying capacity.
Question 2: Which destructive test is used to evaluate the through-thickness ductility of base metal to detect susceptibility to lamellar tearing?
- Charpy impact test
- Z-direction tensile test (Correct answer)
- Bend test
- Macro-etch test
Correct answer: Z-direction tensile test
The Z-direction (through-thickness) tensile test measures ductility perpendicular to the plate surface, directly assessing a material's susceptibility to lamellar tearing.
Question 3: A weld made using GTAW on stainless steel exhibits a dark, sooty appearance on the back side of the weld. This is most likely caused by:
- Excessive heat input
- Inadequate back-purging with inert gas (Correct answer)
- Wrong filler metal alloy
- Too low a travel speed
Correct answer: Inadequate back-purging with inert gas
Inadequate back-purging allows atmospheric oxygen to contact the hot weld root, causing oxidation (sugaring) that degrades corrosion resistance and indicates poor quality.
Question 4: In phased array ultrasonic testing (PAUT), what is the primary advantage over conventional single-element UT for weld inspection?
- Lower equipment cost
- Ability to electronically steer and focus the beam without moving the probe (Correct answer)
- Detection of surface-only defects
- Elimination of calibration requirements
Correct answer: Ability to electronically steer and focus the beam without moving the probe
PAUT uses multiple elements fired in programmed sequences to electronically steer and focus the ultrasonic beam, allowing more complete volumetric coverage of the weld without physically repositioning the transducer.
Question 5: What is the purpose of a weld procedure qualification test (PQR) in AWS quality control?
- To qualify a welder's personal skill
- To demonstrate that a welding procedure produces welds meeting specified mechanical property requirements (Correct answer)
- To establish the visual acceptance criteria for production welds
- To certify the welding inspector
Correct answer: To demonstrate that a welding procedure produces welds meeting specified mechanical property requirements
A Procedure Qualification Record (PQR) documents the results of testing a Welding Procedure Specification (WPS) to verify that the procedure produces welds with the required mechanical properties.
Question 6: Hot cracking in austenitic stainless steel welds is best prevented by:
- Increasing travel speed to reduce heat input
- Maintaining a ferrite content of approximately 3-8 FN in the weld metal (Correct answer)
- Using a higher preheat temperature
- Reducing shielding gas flow rate
Correct answer: Maintaining a ferrite content of approximately 3-8 FN in the weld metal
A ferrite number (FN) of 3-8 in austenitic stainless steel weld metal interrupts the continuous austenite grain boundary network, preventing liquid films from forming and causing solidification (hot) cracking.
Question 7: During RT film interpretation, a linear indication with parallel edges running along the weld axis most likely represents:
- Porosity
- Tungsten inclusion
- Incomplete fusion or incomplete joint penetration (Correct answer)
- Burn-through
Correct answer: Incomplete fusion or incomplete joint penetration
Linear indications with parallel edges oriented along the weld axis are characteristic of incomplete fusion or incomplete joint penetration, which create planar discontinuities visible as elongated dark lines on radiographic film.
AWS Welding Defects & Quality Control 5
During visual inspection of a completed weld, the inspector finds the weld crown is 1/8 inch below the base metal surface.
This defect is called: