AWS Gas Tungsten Arc Welding (GTAW/TIG) 5 — Questions and Answers
Question 1: In pulsed GTAW, what is the primary advantage of using a high pulse frequency?
- Reduces shielding gas consumption
- Improves arc stability and refines the weld microstructure (Correct answer)
- Increases deposition rate significantly
- Allows welding without filler metal
Correct answer: Improves arc stability and refines the weld microstructure
High pulse frequency in GTAW improves arc stability, refines grain structure, and reduces distortion, making it beneficial for thin materials and precision welds.
Question 2: What does a 'walking the cup' technique in GTAW involve?
- Moving the torch in a circular motion while freehand welding
- Bracing the gas cup against the pipe to guide the torch in a controlled weave (Correct answer)
- Using the cup as a heat sink to cool the weld
- Dragging the cup along the workpiece to maintain arc length
Correct answer: Bracing the gas cup against the pipe to guide the torch in a controlled weave
Walking the cup involves bracing the ceramic cup against the pipe joint and pivoting/rolling it to maintain a consistent arc length and travel angle, commonly used in pipe root passes.
Question 3: When GTAW welding a pipe root pass open to atmosphere on the inside, what process is used to protect the back side of the root from oxidation?
- Back-step welding sequence
- Purging with inert gas (back purging) (Correct answer)
- Applying flux paste to the inside
- Preheating the pipe to drive off moisture
Correct answer: Purging with inert gas (back purging)
Back purging displaces oxygen inside the pipe with inert gas (typically argon) to prevent oxidation of the root pass on the ID of the pipe.
Question 4: What is the effect of using too long an arc length in GTAW?
- Increased penetration and fusion
- Narrower bead with higher travel speeds
- Wider, flatter bead with more oxidation and reduced penetration (Correct answer)
- Faster deposition of filler metal
Correct answer: Wider, flatter bead with more oxidation and reduced penetration
An excessively long arc length diffuses the heat, producing a wide, shallow bead with reduced shielding effectiveness and increased risk of atmospheric contamination.
Question 5: According to AWS standards, what is the maximum acceptable tungsten inclusion size in a radiographically tested weld?
- Tungsten inclusions are always acceptable regardless of size
- They are evaluated per the applicable acceptance criteria in the governing code (e.g., AWS D1.1) (Correct answer)
- A maximum of 3mm in any direction is universally permitted
- Only surface-breaking tungsten inclusions need to be reported
Correct answer: They are evaluated per the applicable acceptance criteria in the governing code (e.g., AWS D1.1)
Tungsten inclusion acceptance criteria depend on the governing welding code or standard being applied, such as AWS D1.1, which specifies size and frequency limits.
Question 6: Which condition will most likely cause tungsten spitting (small tungsten particles depositing in the weld) during GTAW?
- Using too low amperage on carbon steel
- Exceeding the current-carrying capacity of the tungsten electrode (Correct answer)
- Using a trailing shield on titanium
- Welding with a negative electrode on aluminum
Correct answer: Exceeding the current-carrying capacity of the tungsten electrode
Exceeding the rated amperage for a given tungsten diameter causes the tip to overheat and partially melt, spitting tungsten particles into the weld pool.
Question 7: When qualifying a GTAW welder procedure on 3/8-inch (9.5mm) carbon steel plate, which additional thickness range is the welder typically qualified to weld per AWS D1.1?
- Only 3/8 inch exactly
- 3/16 inch to 3/4 inch
- 3/16 inch to unlimited thickness (Correct answer)
- 1/8 inch to 3/8 inch only
Correct answer: 3/16 inch to unlimited thickness
Per AWS D1.1, qualifying on material 3/8 inch or thicker typically qualifies the welder for base metal from 1/8 inch to unlimited thickness in the same position.
AWS Gas Tungsten Arc Welding (GTAW/TIG) 5
In pulsed GTAW, what is the primary advantage of using a high pulse frequency?