AWS Weld Discontinuities & Defects 2 — Questions and Answers
Question 1: Hot cracking in welds is most likely to occur when:
- The preheat temperature is too high before welding
- The base metal has low carbon content
- High-sulfur or high-phosphorus impurities are present in the weld metal (Correct answer)
- The travel speed is too slow
Correct answer: High-sulfur or high-phosphorus impurities are present in the weld metal
Hot cracking (solidification cracking) is promoted by impurities such as sulfur and phosphorus, which form low-melting eutectic films at grain boundaries that crack under solidification stresses.
Question 2: Which condition is the most common cause of porosity when using the Shielded Metal Arc Welding (SMAW) process?
- Using too large a diameter electrode for the joint
- Moisture in the electrode coating or base metal (Correct answer)
- Excessive arc voltage
- Using a direct current electrode positive (DCEP) polarity
Correct answer: Moisture in the electrode coating or base metal
Moisture in SMAW electrode coatings or on the base metal decomposes in the arc to produce hydrogen, which is absorbed into the weld pool and causes porosity upon solidification.
Question 3: Lamellar tearing in welded joints occurs primarily in which orientation?
- Parallel to the original rolling plane of the plate (Correct answer)
- Perpendicular to the plate surface at the weld toe
- Along the centerline of the weld bead
- Diagonally through the weld reinforcement
Correct answer: Parallel to the original rolling plane of the plate
Lamellar tearing occurs in base metals with low through-thickness ductility, cracking in a step-like pattern parallel to the rolling plane due to high through-thickness shrinkage stresses.
Question 4: Incomplete joint penetration (IJP) is most likely to occur when:
- The preheat temperature is too high
- The welding current is too high for the joint thickness
- The root opening or groove angle is insufficient for the welding process (Correct answer)
- The interpass temperature exceeds the recommended limit
Correct answer: The root opening or groove angle is insufficient for the welding process
IJP occurs when the weld metal fails to extend through the full thickness of the joint, which is commonly caused by an inadequate root opening or groove angle that limits access for fusion.
Question 5: To reduce undercut when welding, the welder should primarily:
- Increase the travel speed significantly
- Reduce welding current and slow travel speed at the weld toes (Correct answer)
- Switch to a larger diameter electrode
- Increase the arc length to reduce heat input
Correct answer: Reduce welding current and slow travel speed at the weld toes
Reducing the welding current and slowing travel speed at the weld toes allows the weld pool to fill the undercut groove, and a slight weave pause at the toe ensures proper tie-in.
Question 6: Hydrogen-induced cracking (HIC) in welds is also commonly referred to as:
- Hot cracking
- Cold cracking or delayed cracking (Correct answer)
- Solidification cracking
- Reheat cracking
Correct answer: Cold cracking or delayed cracking
HIC is called cold cracking or delayed cracking because it occurs at or below approximately 200°C (400°F), often hours or days after welding when hydrogen diffuses to high-stress regions.
Question 7: Slag inclusions in multi-pass welds are most often caused by:
- Using low-hydrogen electrodes
- Failure to completely remove slag between passes before depositing the next bead (Correct answer)
- Welding at too high an interpass temperature
- Insufficient shielding gas coverage in GMAW
Correct answer: Failure to completely remove slag between passes before depositing the next bead
Slag inclusions result when slag from a previous pass is not completely removed before the next weld bead is deposited, trapping non-metallic material within the weld metal.
AWS Weld Discontinuities & Defects 2
Hot cracking in welds is most likely to occur when: