20 GTAW (TIG) Practice Questions & Answers
Every GTAW (TIG) practice question from the Welding Practice Test, with the correct answer and a short explanation.
Start practice test →1. In gas tungsten arc welding, how is filler metal delivered to the joint, and what does that arrangement allow?
- A.It melts off the tungsten electrode itself, so arc length sets the deposition rate
- B.It comes from a melting flux coating, so coating thickness sets the deposition rate
- C.It is fed continuously through the torch, so travel speed sets the deposition rate
- D.It is fed by hand as a separate rod, so heat and filler are controlled apart✓ Answer
GTAW uses a non-consumable tungsten electrode that only carries the arc; filler is a bare rod fed by the welder's other hand. Because the arc energy and the filler are two separate controls, the welder can hold a small puddle and add metal only when needed, or run autogenously with no filler at all.
Source: AWS A3.0, Standard Welding Terms and DefinitionsReport a problem with this question
2. A welder sets the machine to direct current electrode negative (DCEN) for GTAW on carbon steel. How is the arc energy divided, and what does that produce?
- A.About 90% into the work and 10% into the electrode, giving no arc cleaning at all
- B.About 50% into each, giving medium penetration plus an oxide cleaning action
- C.About 70% into the work and 30% into the electrode, giving deep, narrow penetration✓ Answer
- D.About 70% into the electrode and 30% into the work, giving wide, shallow penetration
With the electrode negative, electrons leave the tungsten and strike the work, so roughly seventy percent of the arc energy lands in the base metal. The tungsten therefore stays relatively cool and can be small and pointed, and the concentrated energy at the work gives the deep, narrow bead wanted on steel and stainless.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
3. At the same amperage, why does GTAW on direct current electrode positive (DCEP) require a much larger diameter tungsten than DCEN?
- A.Most of the arc heat goes into the electrode on DCEP, so a bigger tungsten is needed to survive it✓ Answer
- B.Most of the arc heat goes into the work on DCEP, so a bigger tungsten is needed to spread the current
- C.DCEP runs a longer arc than DCEN, so a bigger tungsten is needed to carry the extra voltage
- D.DCEP produces no cathodic cleaning, so a bigger tungsten is needed to widen the arc cone
Electrode positive reverses the electron flow so the tungsten becomes the target of the electron stream and takes roughly seventy percent of the arc energy. A tungsten of the size that works on DCEN would melt and shed into the puddle, which is why DCEP is current limited and seldom used except on thin aluminum.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
4. Alternating current is the usual choice for GTAW on aluminum. What does the electrode-positive half of each cycle contribute?
- A.Cathodic cleaning that breaks up the refractory oxide film on aluminum✓ Answer
- B.Extra penetration that pushes the arc deeper into the base metal
- C.A cooling interval that lets the tungsten shed heat into the gas stream
- D.A rise in arc voltage that adds heat without raising the amperage
On the electrode-positive half cycle the work becomes the cathode and the emission of electrons from the surface tears the tough oxide skin apart. AC is chosen for aluminum precisely because it alternates that cleaning half with an electrode-negative half that supplies penetration, giving both in one arc.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
5. Aluminum oxide is called a refractory film. Why does that make it a problem for GTAW?
- A.It absorbs shielding gas as it heats, so it starves the puddle of argon coverage
- B.It melts far above the aluminum, so it stays solid and traps inclusions in the puddle✓ Answer
- C.It melts far below the aluminum under it, so it boils off and blows the puddle apart
- D.It conducts heat far better than the aluminum, so it draws the arc away from the joint
The oxide skin melts at roughly three times the temperature of the aluminum beneath it, so the base metal is already molten while the film is still solid. The unmelted film is dragged into the puddle as grey inclusions and traps gas, which is why it must be removed mechanically or broken up by the cleaning half of the AC cycle.
Source: AWS Welding Handbook, Materials and ApplicationsReport a problem with this question
6. An aluminum joint is coated with cutting oil and carries an oxide film. What is the correct cleaning order before GTAW?
- A.Degrease only, because the arc's own cleaning action removes the oxide film for you
- B.Brush with the shop's general steel brush, then degrease and weld before oxide reforms
- C.Brush the oxide off first, then degrease with solvent to wash away the loosened powder
- D.Degrease with solvent first, then remove the oxide with a brush kept only for aluminum✓ Answer
Degreasing has to come first because a wire brush run over an oily surface drives the hydrocarbons into the metal and into the joint, where they break down and cause porosity. Only after the oil is gone does mechanical removal of the oxide work, and the brush must be reserved for aluminum so it carries no iron.
Source: AWS Welding Handbook, Materials and ApplicationsReport a problem with this question
7. Why must a stainless steel workpiece be brushed only with a wire brush reserved for stainless?
- A.A brush used on carbon steel leaves iron particles that rust and ruin corrosion resistance✓ Answer
- B.A brush used on carbon steel carries mill scale that raises the carbon content of the weld
- C.A brush used on carbon steel holds oil that turns to phosgene under the ultraviolet arc
- D.A brush used on carbon steel is softer and burnishes the oxide deeper into the stainless
A brush that has touched carbon steel embeds free iron in the stainless surface, and that iron rusts and destroys the passive chromium oxide layer the alloy relies on. The contamination shows up as rust staining along an otherwise sound weld, so brushes, files and grinding media are kept dedicated to stainless.
Source: AWS Welding Handbook, Materials and ApplicationsReport a problem with this question
8. Per AWS A5.12, a tungsten electrode carries a red color band at the end. What does that identify?
- A.EWP, a pure tungsten electrode used mainly for AC welding on aluminum
- B.EWTh-2, a 2% thoriated electrode used for DC welding on steel and stainless✓ Answer
- C.EWLa-1.5, a lanthanated electrode used as a versatile AC and DC substitute
- D.EWZr-1, a zirconiated electrode used for AC work where a ball tip is wanted
The classification system marks each oxide addition with its own color band, and red is assigned to the two percent thoriated electrode. The thoria raises electron emission so the electrode starts easily, holds a ground point without balling and carries high current, which is why it became the standard choice for DC work on steel and stainless.
Source: AWS A5.12, Specification for Tungsten and Oxide Dispersed Tungsten Electrodes for Arc Welding and CuttingReport a problem with this question
9. A welder will run DCEN on stainless and then AC on aluminum. How should the tungsten tip be prepared for each?
- A.Ground to a taper point for both, since a pointed tip always focuses the arc better
- B.Cut square with no preparation for both, since the arc shapes the tip within seconds
- C.Ground to a taper point for the DCEN work, and balled to a hemisphere for the AC work✓ Answer
- D.Balled to a hemisphere for the DCEN work, and ground to a sharp taper for the AC work
On DCEN the tungsten runs relatively cool, so a ground taper survives and concentrates the arc for a narrow bead. On AC the electrode-positive half heats the tip far more and it will melt back anyway, so a hemispherical ball is formed deliberately because it is stable, holds its shape and gives an even arc on aluminum.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
10. How should a tungsten electrode be ground on the wheel, and why?
- A.Lengthwise on a wheel also used for steel, so the wheel stays dressed and cuts freely
- B.At a flat angle on the side, so the enlarged surface sheds heat and slows tip erosion
- C.Across its axis around the circumference, so the ridges anchor the arc at the tip
- D.Lengthwise along its axis, so the grinding marks run with the arc and it stays steady✓ Answer
Grinding marks act as paths for the arc to follow. Marks that run lengthwise along the electrode lead the arc straight off the tip, while circumferential marks ring the point and let the arc jump from ridge to ridge so it wanders. A wheel dedicated to tungsten is used so no steel or aluminum is transferred to the electrode.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
11. What does fitting a gas lens in place of a plain collet body change?
- A.It chills the gas before it leaves the cup, so the tungsten runs cooler at high current
- B.It smooths the gas into laminar flow, so longer tungsten extension still stays shielded✓ Answer
- C.It meters the gas at the torch, so the flowmeter can be left at any setting
- D.It swirls the gas into a turbulent cone, so a shorter tungsten extension is required
A gas lens contains layered fine mesh screens that straighten the gas into smooth, parallel streamlines instead of a turbulent swirl. The steadier column covers a wider area and reaches farther, so the electrode can stick out more to see into a corner or a joint root without losing shielding.
Source: AWS EG2.0, Guide for the Training of Welding Personnel: SENSE Level I-Entry WeldersReport a problem with this question
12. A common guideline relates the inside diameter of a GTAW nozzle to the electrode. What is that guideline?
- A.About three times the electrode diameter✓ Answer
- B.About half the electrode diameter
- C.About the same as the electrode's diameter
- D.About ten times the electrode diameter
The cup has to deliver a gas column wide enough to blanket the arc and the puddle around the electrode, and roughly three times the electrode diameter does that without wasting gas. Too small a cup leaves the puddle edges exposed, while an oversized one wastes gas and gets in the way of seeing the joint.
Source: AWS EG2.0, Guide for the Training of Welding Personnel: SENSE Level I-Entry WeldersReport a problem with this question
13. What is the purpose of a foot pedal or thumb amptrol on a GTAW machine?
- A.It varies current while welding, so the puddle can be started and the crater filled✓ Answer
- B.It varies travel speed while welding, so bead width is held on a tapered part
- C.It varies gas flow while welding, so shielding rises as the joint gets hotter
- D.It varies arc voltage while welding, so arc length is held without moving the torch
Remote current control lets the welder change amperage without stopping, which matters because the part heats up as the weld progresses and because the arc must be tapered off rather than cut. Easing the pedal down at the end fills the crater and prevents the crater crack that an abrupt stop leaves.
Source: AWS EG2.0, Guide for the Training of Welding Personnel: SENSE Level I-Entry WeldersReport a problem with this question
14. Scratch starting a GTAW arc by dragging the tungsten on the plate is discouraged. What does it cause, and what is used instead?
- A.It contaminates the tungsten and the weld; a high-frequency or lift-arc start is used✓ Answer
- B.It burns the cup and warps the collet; a longer tungsten extension is used instead
- C.It weakens the shielding gas envelope; a larger nozzle and gas lens are used instead
- D.It draws too much gas through the torch; a longer preflow time is used instead
Touching the hot tungsten to the base metal transfers metal onto the electrode and tungsten into the plate, so the arc spits and the weld carries an inclusion. High frequency ionizes the gap so the arc jumps without contact, and lift arc touches at a low current and establishes the arc as the torch is raised.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
15. A shop switches from argon to helium shielding on a thick aluminum joint. What changes?
- A.Arc voltage and heat go down, and the flow rate can be cut because helium is heavy
- B.Arc voltage goes up, and the gas becomes reactive, so the tungsten must be larger
- C.Arc voltage stays the same, and the flow rate must be cut to stop the arc wandering
- D.Arc voltage and heat go up, and the flow rate must be raised because helium is light✓ Answer
Helium needs a higher arc voltage to sustain the same arc, so at a given current the arc puts more energy into the joint and penetrates deeper and faster, which suits thick, heat-conductive aluminum. Because helium is lighter than air it rises away from the puddle, so the flow must be increased to keep coverage.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
16. Why are carbon dioxide and oxygen never used as the shielding gas for GTAW?
- A.They are too heavy to leave the cup, so the arc is starved of shielding at the tip
- B.They react with the argon in the mix, so the flowmeter cannot be calibrated for them
- C.They are not inert; they oxidize and rapidly destroy the tungsten electrode✓ Answer
- D.They are not inert; they cool the arc so much that the puddle cannot be started
GTAW depends on a truly inert atmosphere because the electrode is not consumed and must survive the whole weld. Oxidizing gases attack the incandescent tungsten, eroding and pitting the tip within seconds so the arc wanders and tungsten drops into the puddle, which is why only argon, helium and their mixes are used.
Source: AWS Welding Handbook, Welding ProcessesReport a problem with this question
17. Why must shielding gas keep flowing for a few seconds after the arc is broken?
- A.The hot weld and the hot tungsten both keep oxidizing until they cool under gas✓ Answer
- B.The gas pushes the remaining heat out of the joint and shortens the cooling time
- C.The cup must be purged of smoke before the next start or porosity will follow
- D.The regulator must bleed down slowly or the diaphragm inside it will be damaged
Metal keeps reacting with air as long as it is hot, and when the arc stops both the crater and the electrode are still incandescent. Postflow holds the inert blanket over them until they drop below the oxidizing range, which keeps the crater bright and stops the tungsten from being burned back and contaminated for the next start.
Source: AWS EG2.0, Guide for the Training of Welding Personnel: SENSE Level I-Entry WeldersReport a problem with this question
18. A stainless butt joint is welded open root with no gas on the underside. What appears on the root, and why?
- A.A hard martensitic layer, because the unshielded root cooled faster than the face
- B.A rough granular oxide called sugaring, because air reached the hot root surface✓ Answer
- C.A bright silver root face, because the arc's own gas column reaches through the gap
- D.A row of round pores called worm tracks, because moisture was trapped in the gap
The chromium in austenitic stainless oxidizes readily at welding temperature, and the underside of an open root is red hot and fully exposed to air. The result is a crusty granular scale, and the chromium consumed in forming it is no longer available to protect the metal, so the root loses corrosion resistance and must be purged with backing gas.
Source: AWS D10.11, Guide for Root Pass Welding of Pipe Without BackingReport a problem with this question
19. GTAW filler metal is often not the same alloy as the base metal. Which pairing follows accepted practice?
- A.ER70S-2 to weld 304 stainless, chosen because it tolerates mill scale and rust
- B.ER4043 to weld 6061-T6 aluminum, chosen because it resists solidification cracking✓ Answer
- C.ER5356 to weld low carbon steel, chosen because it gives a better color match
- D.ER308L to weld 6061-T6 aluminum, chosen because it resists carbide precipitation
A 6xxx alloy used as its own filler solidifies in a composition range that is highly crack sensitive, so a silicon-bearing rod is added instead to shift the weld metal out of that range and make the puddle more fluid. Filler is chosen for how the deposit behaves and performs, not for a literal match with the plate.
Source: AWS A5.10, Specification for Bare Aluminum and Aluminum-Alloy Welding Electrodes and RodsReport a problem with this question
20. During a root pass the tungsten touches the puddle and the arc turns erratic and starts spitting. What is the correct response?
- A.Stop, increase the gas flow, and reset the postflow to clear the contaminated electrode
- B.Stop, grind the contaminated end off the tungsten and the deposit out of the weld✓ Answer
- C.Keep welding with a longer arc; the tungsten will clean itself once the puddle settles
- D.Stop, raise the amperage, and burn the contamination off the tungsten on the next pass
Base metal picked up on the tip alloys with the tungsten and lowers its melting point, so the contaminated end keeps shedding particles and the arc never steadies again. The contaminated length has to be broken or ground away and the tip reshaped, and any tungsten already left in the weld is a hard inclusion that must be ground out.
Source: AWS EG2.0, Guide for the Training of Welding Personnel: SENSE Level I-Entry WeldersReport a problem with this question
Practice questions based on the AWS SENSE Level I (Entry Welder) written modules, ANSI Z49.1 safety practice, and AWS A2.4 welding symbols. This bank covers the KNOWLEDGE half of entry-level welding only — the workmanship and welder performance qualification tests are hands-on and cannot be practised here, and this is not preparation for the separate, performance-based AWS Certified Welder credential. AWS, SENSE, and NCCER are marks of their respective organizations; this site is not affiliated with or endorsed by them. Work from your program's current materials, and follow the welding procedure and drawings on your own job rather than any number you remember. About AWS SENSE →