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

Question 1

____ is very well suited for making welds on steel, steel alloys (including stainless), nickel alloys, and most other metals other than aluminum or magnesium.

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

Answer 1

C

Question 2

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

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

Answer 2

C

Question 3

In GTAW, the arc temperature is around ____ degrees Fahrenheit.

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

Answer 3

C

Question 4

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) nitrogen
B) argon
C) hydrogen
D) helium

Question 5

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

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

Question 6

Water hose fittings have ____ threads, and gas hose fittings have ____ threads.

A) right-hand, left-hand
B) left-hand, left-hand
C) right-hand, right-hand
D) left-hand, right-hand

Question 7

____ has the poorest heat resistance and electron emission characteristic of all the tungsten electrodes.

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

Question 8

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

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

Question 9

Which of the following is an inert gas?

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

Question 10

____ additions are restricted to stainless steels because it is the primary cause of porosity in aluminum welds.

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

Question 11

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

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

Question 12

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

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

Question 13

Which of the following is true of DCEP?

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

Question 14

____ is denser than air, so it effectively shields welds in deep grooves in the flat position.

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

Question 15

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

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

Question 16

Which of the following is true of DCEN?

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

Question 17

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

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

Question 18

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

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

Question 19

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

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

Question 20

Which of the following is true of grinding tungsten electrodes?

A) 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.
B) A fine, hard grinding stone will result in more tungsten breakage and a poor finish.
C) The grinder used to sharpen tungsten should have a coarse stone.
D) A grinder should never be used to clean contaminated tungsten.

Question 21

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

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

Question 22

​What is the purpose of a gas lens?

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

Question 23

​Which nozzle material is clear?

A) ​ceramic
B) ​alumina
C) ​fused quartz
D) ​silicon nitride

Question 24

​The high frequency may be set so that it ______________for DC and ________________ for AC.

A) ​automatically cuts off after the arc is established; is kept on continuously
B) ​is kept on continuously; goes off
C) ​is kept on continuously; automatically cuts off after the arc is established
D) ​automatically cuts off; goes off after one minute

Question 25

The ____________________ is the cone-shaped sleeve that holds the electrode in the torch.

Question 26

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

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

Question 27

The gas tungsten arc welding process is sometimes referred to as ____________________.

Question 28

​Which type of tungsten electrode does not break evenly when trying to break off contamination?

A) ​EWZr-1
B) ​EWLa-1
C) ​EWP
D) ​EWCe-2

Question 29

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

A) ​vertically
B) ​horizontally
C) ​on a solid surface
D) ​Between 5 ft and 5.5 feet above the floor

Question 30

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

Question 31

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

Question 32

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

Question 33

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

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

Question 34

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

Question 35

​Why does the return water on a water-cooled GTAW torch flow out around the power cable?

A) ​The electricity in the cable has to be protected from emitting RF from the high frequency starting voltage.
B) ​To reduce the number of hoses to the torch.
C) ​So a smaller power cable can be used.
D) ​It helps to heat the water a little more to prevent algae and mold from growing.

Question 36

​What material should shielding gas hoses be made of?

A) ​Any material is fine; the gas is inert
B) ​plastic
C) ​rubber
D) ​copper

Question 37

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

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

Question 38

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

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

Question 39

​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) ​It helps to reduce the UV light that can cause skin burns.
D) ​All of the above

Question 40

​____ is relatively easy to ionize and thus is suitable for alternating-current applications and easier starts.

A) ​Hydrogen
B) ​Helium
C) ​Argon
D) ​Nitrogen

Question 41

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

Question 42

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 43

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

Question 44

Argon and helium are _________________________ gases, which means they will not combine chemically with any other material, and will not affect the molten weld pool in any way.

Question 45

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

Question 46

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 47

Explain how hydrogen is used in shielding gases, and why it is restricted to stainless steels.

Question 48

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

Question 49

Explain how tungsten electrodes are produced.

Question 50

Explain how to clean and point a tungsten electrode.