AWS Gas Tungsten Arc Welding (GTAW/TIG) Fundamentals 2

Question 1

For GTAW on titanium, which shielding gas is required, and why?

Accepted Answer

100% Argon or Argon/Helium — titanium reacts with nitrogen and oxygen at any elevated temperature

Answer

Titanium requires 100% argon or argon/helium shielding because it reacts with oxygen, nitrogen, and hydrogen above ~500°F, forming brittle interstitial compounds that embrittle the weld and HAZ.

Question 2

A gas lens in a GTAW torch replaces the standard collet body and provides:

Accepted Answer

A layered mesh screen that produces laminar shielding gas flow for better coverage at longer arc lengths

Answer

A gas lens contains fine mesh screens that straighten and laminarize shielding gas flow, providing more uniform coverage, allowing the tungsten to extend further from the nozzle for better access.

Question 3

When welding dissimilar metals by GTAW (e.g., 304 stainless steel to carbon steel), what filler metal is typically selected?

Accepted Answer

ER309L (austenitic stainless with higher chromium/nickel for dilution tolerance)

Answer

ER309L is preferred for joining stainless to carbon steel because its higher Cr and Ni content provides a buffer against dilution with the carbon steel, maintaining a tough, crack-resistant austenitic weld deposit.

Question 4

In GTAW, 'tungsten inclusion' is caused by and results in:

Accepted Answer

Physical contact of the tungsten with the weld pool — hard, brittle white particles embedded in the weld

Answer

Tungsten inclusion occurs when the electrode tip contacts the molten pool, depositing tungsten particles in the weld metal. They appear as bright white, high-density inclusions on radiographs.

Question 5

Pulse GTAW (GTAW-P) provides which primary benefit on thin material?

Accepted Answer

Reduced average heat input controlling distortion and burn-through on thin sections

Answer

Pulsed GTAW alternates between high (peak) and low (background) current, reducing average heat input and allowing precise control of the weld pool — critical for preventing burn-through and distortion on thin materials.

AWS Practice Test

AWS Practice Test

AWS Gas Tungsten Arc Welding (GTAW/TIG) Fundamentals 2