Deck 16: Gas Tungsten Arc Welding Equipment, Setup, and Operation

Question 1

Why is an inert shielding gas required for GTA welding?

A) To keep the air away from the hot tungsten and molten weld metal
B) To help remove the welding fumes to make it easier to see the weld pool
C) To help reduce the UV light that can cause skin burns
D) All of the above

Answer 1

A

Question 2

Which of the following is true of DCEP?

A) With DCEP, the preferred electrode tip is pointed.
B) Because DCEP does not put much heat on the tip, it is relatively cool.
C) DCEP has the highest heat concentration on the electrode tip.
D) With DCEP, the point of the electrode tip is stable.

Answer 2

C

Question 3

Which of the following is true of grinding tungsten electrodes?

A) A grinder should never be used to clean contaminated tungsten.
B) The grinder used to sharpen tungsten should have a coarse stone.
C) A fine, hard grinding stone will result in more tungsten breakage and a poor finish.
D) If the grinder is used for metals other than tungsten, particles of these metals may become trapped on the tungsten as it is ground, resulting in contamination when the arc is started.

Answer 3

D

Question 4

DCEN concentrates about ____ of its welding heat on the work, and about ____ on the tungsten.

A) 1/3, 2/3
B) 1/4, 3/4
C) 1/2, 1/2
D) 2/3, 1/3

Question 5

With ____, penetration and bead profile are sensitive to arc length, and the long arcs needed for feeding filler wires are more difficult to control.

A) helium
B) nitrogen
C) hydrogen
D) argon

Question 6

Which of the following is a way to minimize erosion of the tungsten electrode?

A) Use as high a current as possible.
B) Use an air-cooled torch.
C) Use as small a size of tungsten electrode as possible.
D) Use DCEN current.

Question 7

The ____ protects the molten weld pool, the filler rod, and the tungsten electrode as they cool to a temperature at which they will not oxidize rapidly.

A) preflow period
B) postflow period
C) shielding gas
D) nozzle

Question 8

Which of the following is true of DCEN?

A) DCEN concentrates the heat in the tip of the electrode.
B) With DCEN, a pointed tip concentrates the arc.
C) With DCEN, arc starting with a high-voltage electrical discharge is more difficult.
D) With DCEN, the electrode becomes damaged in a short period of time.

Question 9

Adding ____ has the same effect on the electrode characteristic as thorium, but it is not radioactive.

A) pure tungsten
B) cerium
C) zirconium
D) lanthanum

Question 10

Which of the following is true of erosion of the tungsten electrode?

A) Slow erosion results in limited tungsten inclusions in the weld.
B) Erosion can be limited using DCEP current.
C) Erosion can be completely eliminated.
D) The eroded metal does not transfer across the arc.

Question 11

DCEP concentrates ____ of the arc heat on the plate, and ____ of the heat on the electrode.

A) 1/3, 2/3
B) 1/4, 3/4
C) 1/2, 1/2
D) 2/3, 1/3

Question 12

The improved electron emission of the ____ allows it to carry approximately 20% more current than pure tungsten.

A) thoriated tungsten
B) cerium tungsten
C) zirconium tungsten
D) lanthanum tungsten

Question 13

____ electrodes have a current-carrying capacity similar to that of pure tungsten, and may be used for both AC and DC welding currents.

A) Thoriated tungsten
B) Cerium tungsten
C) Zirconium tungsten
D) Lanthanum tungsten

Question 14

AC concentrates about ____ of its welding heat on the work and ____ on the tungsten.

A) 1/3, 2/3
B) 1/4, 3/4
C) 1/2, 1/2
D) 2/3, 1/3

Question 15

Which of the following is true of breaking and remelting tungsten?

A) It should be melted with a DCEN current.
B) It should be broken squarely.
C) It should be melted by striking an arc on a piece of carbon.
D) It should not be melted by striking an arc on copper, as it will contaminate the tungsten.

Question 16

Tungsten with the highest level of lanthanum oxide is classified as ____.

A) EWTh-2
B) EWLa-1.5
C) EWLa-2
D) EWZr-1

Question 17

Tungsten electrodes that contain elements such as lanthanum or yttrium are referred to as _____.

A) alternating current only electrodes
B) low-alloy tungsten electrodes
C) low-hydrogen tungstens
D) rare earth tungstens

Question 18

Which of the following is an inert gas?

A) Hydrogen
B) Oxygen
C) Nitrogen
D) Helium

Question 19

____ results in welds with deep penetration, and a smaller-size tungsten can be used.

A) DCEN
B) DCEP
C) DCRP
D) ACHF

Question 20

In GTAW, the arc temperature is around ____ Fahrenheit.

A) 3,000 °
B) 6,000 °
C) 11,000 °
D) 17,000 °

Question 21

The squarewave provides the welder with a current that allows the molten weld pool to _______________.

A) have both deeper penetration and faster solidification
B) have more gas coverage of the weld at a slower flow rate
C) be cleaner and reduces the need to clean all of the oxides off of the underside of the weld joint
D) flow freely onto the base metal with minimum fusion for thinner metals

Question 22

Flowmeters measure the flow rate of a shielding gas in __________units.

A) CFH or L/min
B) BTU or mm/sec
C) GPH or K/min
D) PSI or kPa

Question 23

When the shielding gas flow rate is high, air is drawn into the gas envelope by a(n) ____________________ effect around the edge of the nozzle.

Question 24

Due to its hardness, when hand grinding tungsten, it will become hot, and its high ____________________ means that the heat will be transmitted quickly to your fingers.

Question 25

If high frequency is not used, it will be necessary to use the ____________________ technique to start the arc .

Question 26

What is the purpose of a gas lens?

A) It helps to see the molten weld pool by magnifying it.
B) It filters out most of the harmful UV and some of the IR light.
C) It reduces the turbulence in the shielding gas.
D) It filters out dust and dirt that might be in the shielding gas due to a dirty shielding gas hose.

Question 27

The ____________________ at which the current cycles is the rate at which it makes a full change in direction.

Question 28

The useful life of a ceramic nozzle is affected by the _____________.

A) current level and proximity to the work
B) tungsten type and shielding gas flow rate
C) whether the torch is air or water cooled
D) type of current and type of base metal

Question 29

The tungsten point angle can be set between a range of _____ degrees.

A) 5-15
B) 10-60
C) 50-80
D) 150-200

Question 30

In order to get a good GTA weld on thick sections of metal, especially ____________________, you will need to preheat it.

Question 31

____________________, when added in percentages of up to 0.6 percent to tungsten, improves its current-carrying capacity.

Question 32

____________________ is the time during which the gas continues flowing after the welding current has stopped.

Question 33

____________________ is the time during which gas flows to clear out any air in the nozzle or surrounding the weld zone.

Question 34

How must tube- and ball-type flowmeters be mounted?

A) Horizontally
B) On a solid surface
C) Vertically
D) Between 5 ft and 5.5 feet above the floor

Question 35

Which of the following is not true of the water-cooled GTA welding torch?

A) It is more efficient than an air-cooled torch
B) It is more portable than an air-cooled torch.
C) It can use a smaller power cable.
D) Water pressures higher than 35 psi may cause the water hoses to burst.

Question 36

Explain how and why to remelt tungsten.

Question 37

Explain how tungsten electrodes are produced.

Question 38

The ____________________ directs the shielding gas directly on the welding zone.

Question 39

Explain why the heat of the arc, which is much higher than the melting point of tungsten, does not actually melt the tungsten electrode.

Question 40

____________________ is a by-product of the natural gas industry that is removed from natural gas as the gas undergoes separation for purification or refinement.

Question 41

What is the most likely explanation for why DCEP has a cleaning action?