Chapter 16

Which of the following is a way to minimize erosion of the tungsten electrode? A. Using as high a current as possible. B. Using an air-cooled torch. C. Using as small a size of tungsten electrode as possible. D. Using DCEN current.

D

Which of the following is an inert gas? A, Hydrogen B. Oxygen C. Nitrogen D. Helium

D

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.

D

____ is denser than air, so it effectively shields welds in deep grooves in the flat position. A. Helium B. Nitrogen C. Hydrogen D. Argon

D

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

Helium

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

Preflow

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

Postflow

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

B

Water hose fittings have ____ threads, and gas hose fittings have ____ threads. A. left-hand, left-hand B. left-hand, right-hand C. right-hand, left-hand D. right-hand, right-hand

B

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

Collet

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

D

Flowmeters measure the flow rate of a shielding gas in __________units. A. BTU or mm/sec B. CFM or L/min C. PSI or kPa D. GPH or K/min

B

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

A

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

A

____ has the poorest heat resistance and electron emission characteristic of all the tungsten electrodes. A. Pure tungsten B. Thoriated tungsten C. Zirconium tungsten D. Lanthanum tungsten

A

____ results in welds with deep penetration, and a smaller-size tungsten can be used. A. DCEN B. DCEP C. DCRP D. ACHF

A

​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

A

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.

B

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.

B

____ 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

B

____ 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. Pure tungsten B. Thoriated tungsten C. Zirconium tungsten D. Lanthanum tungsten

B

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

C

Adding ____ has the same effect on the electrode characteristic as thorium, but is not radioactive. A. pure tungsten B. cerium C. zirconium D. lanthanum

C

In GTAW, the arc temperature is around ____ degrees Fahrenheit. A. 3,000 B. 6,000 C. 11,000 D. 17,000

C

What material should shielding gas hoses be made of? A. Rubber B. Copper C. Plastic D. Any material is fine: the gas is inhert

C

____ additions are restricted to stainless steels because it is the primary cause of porosity in aluminum welds. A. Helium B. Nitrogen C. Hydrogen D. Argon

C

​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

C

​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.

C

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.

Inhert Gases

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

Nozzle