456A GTAW TIG 2 — Questions and Answers
Question 1: What is a gas lens in a GTAW torch and what advantage does it provide?
- A magnifying lens for the welder to see the arc
- A fine mesh screen that produces a smooth, laminar gas flow for better shielding coverage, especially at extended stick-out distances and on joints with restricted access (Correct answer)
- A filter that cleans the shielding gas
- A glass cover over the gas cup
Correct answer: A fine mesh screen that produces a smooth, laminar gas flow for better shielding coverage, especially at extended stick-out distances and on joints with restricted access
A gas lens replaces the standard collet body and uses multiple layers of fine stainless steel mesh to convert turbulent gas flow into smooth, laminar flow. This provides more effective shielding coverage, allows longer tungsten stick-out for better visibility and access to tight joints, and reduces gas consumption while improving weld quality.
Question 2: What causes tungsten contamination in a GTAW weld?
- Using the wrong shielding gas
- Dipping the tungsten electrode into the weld pool, which deposits tungsten particles in the weld (Correct answer)
- Welding at too low an amperage
- Using a gas lens
Correct answer: Dipping the tungsten electrode into the weld pool, which deposits tungsten particles in the weld
Tungsten contamination occurs when the electrode tip contacts the molten weld pool, depositing tungsten particles in the weld. Tungsten inclusions appear as bright white spots on radiographs and are considered weld defects in critical applications. If contamination occurs, the affected area must be ground out, and the tungsten must be re-prepared.
Question 3: What is the function of a foot pedal (foot amptrol) in GTAW welding?
- To turn the shielding gas on and off
- To provide real-time variable amperage control during welding, allowing the welder to increase or decrease heat input while welding (Correct answer)
- To control the wire feed speed
- To rotate the workpiece
Correct answer: To provide real-time variable amperage control during welding, allowing the welder to increase or decrease heat input while welding
The foot pedal (amptrol) gives the GTAW welder precise, real-time control over welding current from zero to maximum while welding. This allows the welder to increase heat for thicker sections, reduce heat approaching edges to prevent burn-through, and taper the current down at the end to properly fill the crater.
Question 4: What is the purpose of adding filler metal in GTAW welding?
- To provide electrical conductivity to the joint
- To add material to the weld joint for building up the weld cross-section, filling gaps, and matching the base metal composition and strength (Correct answer)
- To stabilize the arc
- To replace the shielding gas
Correct answer: To add material to the weld joint for building up the weld cross-section, filling gaps, and matching the base metal composition and strength
Filler metal is added separately (by hand-feeding a rod) to provide additional weld metal for filling joints, building up weld reinforcement, bridging gaps, and matching the base metal's composition and mechanical properties. Some GTAW welds on thin material can be made autogenously (without filler) by fusing the base metal edges together.
Question 5: What is a GTAW walking the cup technique used for?
- A technique for welding flat plate only
- Rocking the ceramic gas cup alternately on each side of the joint to maintain consistent travel speed, torch angle, and arc length while welding pipe or tubing (Correct answer)
- A method of cleaning the tungsten electrode
- A technique for cutting metal with the TIG torch
Correct answer: Rocking the ceramic gas cup alternately on each side of the joint to maintain consistent travel speed, torch angle, and arc length while welding pipe or tubing
Walking the cup is a GTAW pipe welding technique where the welder rocks the ceramic gas cup from side to side on the pipe bevel, alternating contact points like walking. This provides consistent torch angle, travel speed, and arc length, producing uniform weave beads — particularly valuable in pipe root and fill passes where consistency is critical.
Question 6: What is the recommended cup (nozzle) size selection for GTAW welding?
- Always use the smallest cup available
- Select a cup diameter that provides adequate shielding coverage — generally the cup size number equals the inside diameter in sixteenths of an inch (e.g., #8 cup = 1/2 inch / 12.7 mm) (Correct answer)
- Cup size doesn't matter for weld quality
- Always use the largest cup available
Correct answer: Select a cup diameter that provides adequate shielding coverage — generally the cup size number equals the inside diameter in sixteenths of an inch (e.g., #8 cup = 1/2 inch / 12.7 mm)
Cup size selection depends on the joint configuration, tungsten size, and gas flow rate. The cup must be large enough to provide adequate shielding coverage without excessive gas consumption. Cup size numbers indicate the inside diameter in sixteenths of an inch (e.g., #8 = 8/16 = 1/2 inch). Larger cups are used for wider welds and higher amperages.
456A GTAW TIG 2
What is a gas lens in a GTAW torch and what advantage does it provide?