AWS Gas Tungsten Arc Welding (GTAW/TIG) Fundamentals 5 — Questions and Answers
Question 1: In GTAW, what is the primary function of the foot pedal or fingertip amperage control?
- To adjust shielding gas flow during welding
- To vary the welding current in real time, allowing control of heat input (Correct answer)
- To switch between AC and DC polarity
- To activate the post-flow timer for gas shielding
Correct answer: To vary the welding current in real time, allowing control of heat input
Amperage controls let the welder reduce heat input at the end of a weld or on thin sections, preventing burn-through and crater cracking.
Question 2: What type of joint preparation is generally preferred for GTAW butt welds on base metal thicker than 3/16 inch (4.8 mm)?
- Square groove with no gap
- Single-V or double-V groove to allow full penetration (Correct answer)
- Lap joint with a fillet weld
- Flange joint to avoid filler metal use
Correct answer: Single-V or double-V groove to allow full penetration
Groove preparations like the V-groove open the joint so the narrow GTAW arc can achieve complete joint penetration in thicker materials.
Question 3: Which shielding gas mixture is often used in GTAW of carbon and low-alloy steels to improve arc stability and increase travel speed?
- 75% argon / 25% CO2
- 100% helium
- Argon with 2–5% hydrogen (Correct answer)
- Argon with small additions of nitrogen
Correct answer: Argon with 2–5% hydrogen
Small hydrogen additions increase arc voltage and heat input, improving travel speed and penetration on austenitic stainless and some steel applications.
Question 4: What welding defect is most likely caused by insufficient post-weld gas coverage (post-flow) in GTAW?
- Lack of fusion at the weld root
- Oxidation and discoloration of the weld and heat-affected zone (Correct answer)
- Porosity from nitrogen in the shielding gas
- Undercut along the weld toes
Correct answer: Oxidation and discoloration of the weld and heat-affected zone
Without adequate post-flow, the hot tungsten and weld metal are exposed to atmosphere, causing oxidation that appears as discoloration and can compromise corrosion resistance.
Question 5: In AWS GTAW qualification testing, what is the significance of a 'guided bend test'?
- It measures the tensile strength of the weld metal only
- It evaluates weld ductility and soundness by bending a coupon around a mandrel of specified diameter (Correct answer)
- It checks the hardness of the heat-affected zone
- It determines the correct preheat temperature for the material
Correct answer: It evaluates weld ductility and soundness by bending a coupon around a mandrel of specified diameter
Guided bend tests reveal internal discontinuities and assess ductility; coupons must not crack beyond the allowable limits to pass AWS qualification.
Question 6: What is 'arc length' in GTAW and how does it affect the weld?
- The distance the arc travels along the joint; longer arcs increase travel speed
- The distance from tungsten tip to the weld puddle; shorter arcs increase penetration and reduce arc voltage (Correct answer)
- The electrical path length inside the power supply; it controls output amperage
- The length of the tungsten electrode extending beyond the gas cup
Correct answer: The distance from tungsten tip to the weld puddle; shorter arcs increase penetration and reduce arc voltage
A shorter arc length concentrates heat, increases penetration, and reduces the tendency for atmospheric contamination of the puddle.
Question 7: Which AWS standard governs the qualification of welding procedures and welders for structural steel, including GTAW processes?
- AWS D1.1 Structural Welding Code — Steel (Correct answer)
- AWS B2.1 Specification for Welding Procedure and Performance Qualification
- AWS D1.6 Structural Welding Code — Stainless Steel
- AWS A5.12 Specification for Tungsten Electrodes
Correct answer: AWS D1.1 Structural Welding Code — Steel
AWS D1.1 is the primary structural welding code for steel and includes prequalified joint details and welder qualification requirements for GTAW.
AWS Gas Tungsten Arc Welding (GTAW/TIG) Fundamentals 5
In GTAW, what is the primary function of the foot pedal or fingertip amperage control?