CWI Weld Discontinuities and Defects Questions and Answers — Questions and Answers
Question 1: A weld discontinuity is distinguished from a weld defect in that:
- A discontinuity is any interruption in the normal structure of the weld, whereas a defect is a discontinuity that renders the part unable to meet acceptance standards. (Correct answer)
- A defect is a flaw visible on the surface, while a discontinuity is always subsurface and requires NDE to be found.
- A discontinuity is only a cosmetic issue with no impact on weld strength, but a defect is always a crack.
- A defect is an acceptable flaw according to the code, whereas a discontinuity must always be repaired.
Correct answer: A discontinuity is any interruption in the normal structure of the weld, whereas a defect is a discontinuity that renders the part unable to meet acceptance standards.
According to AWS A3.0, a discontinuity is an interruption in the typical structure of a material. A defect is a discontinuity that, by its nature or accumulated effect, renders a part or product unable to meet minimum applicable acceptance standards or specifications. Therefore, all defects are discontinuities, but not all discontinuities are defects. A discontinuity only becomes a defect when it exceeds the limits of the applicable code or standard.
Question 2: A visual inspection of a multi-pass fillet weld in a non-tubular, statically loaded structure reveals slag trapped along the toe of the weld between passes. This type of discontinuity is best described as:
- Incomplete fusion
- Undercut
- Slag inclusion (Correct answer)
- Porosity
Correct answer: Slag inclusion
Slag inclusion is a non-metallic solid material entrapped in the weld metal or between the weld metal and base metal. It commonly occurs in multi-pass welds when the slag from a previous pass is not completely removed before the next pass is deposited. Undercut is a groove melted into the base metal adjacent to the weld toe that is left unfilled. Incomplete fusion is the failure of the weld metal to fuse completely with the base metal or an adjacent bead. Porosity is gas pores found in the weld.
Question 3: Which of the following welding parameters or techniques is most likely to cause undercut?
- Travel speed that is too slow
- Excessively high welding current or voltage (Correct answer)
- An arc length that is too short
- Using a small electrode for a large weld
Correct answer: Excessively high welding current or voltage
Excessive welding current or voltage generates too much heat, causing the edges of the joint to melt away faster than the filler metal can fill the area, resulting in a groove or undercut at the toe of the weld. While incorrect travel speed and arc length can also contribute, excessively high heat input is a primary cause.
Question 4: A welder is producing a groove weld but fails to melt the groove face or the root of a previously deposited bead. This results in a discontinuity where the weld metal does not bond with the base metal. This condition is known as:
- Overlap
- Incomplete Joint Penetration
- Underfill
- Incomplete Fusion (Correct answer)
Correct answer: Incomplete Fusion
Incomplete fusion is a weld discontinuity where fusion did not occur between the weld metal and the fusion faces or adjoining weld beads. This is often caused by insufficient heat input, incorrect torch angle, or contamination on the surfaces to be welded. Incomplete Joint Penetration is when the weld metal doesn't extend through the entire joint thickness.
Question 5: According to AWS D1.1 for statically loaded non-tubular connections, which of the following discontinuities is always unacceptable, regardless of its size or location?
- Undercut
- Porosity
- Slag Inclusion
- Cracks (Correct answer)
Correct answer: Cracks
AWS D1.1/D1.1M Table 8.1 (formerly Table 6.1) for Visual Inspection Acceptance Criteria states that any crack shall be unacceptable, regardless of its size or location, for both statically and cyclically loaded structures. The code provides specific allowable limits for other discontinuities like undercut, porosity, and slag inclusions based on the loading condition and material thickness.
Question 6: During a visual inspection of a completed weld, you observe weld metal protruding beyond the weld toe without fusing to the base metal. This condition is referred to as:
- Excessive convexity
- Overlap (Correct answer)
- Reinforcement
- Undercut
Correct answer: Overlap
Overlap is the protrusion of weld metal beyond the weld toe or weld root that is not fused to the base metal. It's often caused by incorrect welding technique, such as too slow of a travel speed or an improper electrode angle, which allows the molten metal to roll over onto the plate surface without fusing.
CWI Weld Discontinuities and Defects Questions and Answers
A weld discontinuity is distinguished from a weld defect in that: