AWS Gas Tungsten Arc Welding (GTAW/TIG) 4

Question 1

When welding aluminum with GTAW, which current type is typically used to achieve the cleaning action needed to break up the oxide layer?

Accepted Answer

AC (alternating current)

Answer

AC current is used for aluminum GTAW because the electrode-positive half-cycle provides the cathodic cleaning action that breaks up the tenacious aluminum oxide layer.

Question 2

In GTAW, what is the primary purpose of the high-frequency (HF) arc starting feature?

Accepted Answer

To initiate the arc without touching the tungsten to the workpiece

Answer

High-frequency arc starting allows the welder to establish an arc without contact, preventing tungsten contamination and workpiece damage.

Question 3

What condition is indicated when a GTAW weld bead shows excessive porosity on stainless steel?

Accepted Answer

Inadequate shielding gas coverage or contamination

Answer

Porosity in stainless steel GTAW welds is most commonly caused by insufficient or contaminated shielding gas allowing atmospheric gases to enter the weld pool.

Question 4

Which tungsten electrode geometry is recommended for use with DC welding of steel and stainless steel?

Accepted Answer

Pointed or truncated tip

Answer

A pointed or slightly truncated tungsten tip concentrates the arc for precise control and deep penetration when welding steel and stainless steel with DCEN.

Question 5

During GTAW, a welder notices the tungsten electrode turning black. What is the most likely cause?

Accepted Answer

Inadequate post-flow shielding gas

Answer

A blackened tungsten indicates oxidation caused by insufficient post-flow time, where the hot electrode is exposed to atmosphere before it cools sufficiently.

AWS Practice Test

AWS Practice Test

AWS Gas Tungsten Arc Welding (GTAW/TIG) 4