GTAW CH 15

Tungsten erosion can be limited by using a water-cooled torch.

True

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

inert gases

In general the current-carrying capacity at DCEN is about ____ than that at DCEP.

ten times greater

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.

Post-flow period

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

oxide

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

zirconium

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

2/3,1/3

When the GTAW process was first developed, argon was the primary shielding gas used.

False

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

postflow

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

preflow

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

DCEN

The shielding gas flow rate should be as high as possible

False

Which of the following is an inert gas?

Helium

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

Helium

____________________ 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

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

Hydrogen

Which of the following is true of grinding tungsten electrodes?

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.

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

left-hand, right-hand

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

nozzle

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

collet

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

frequency

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.

venturi

DCEP has the lowest heat concentration on the electrode tip.

False

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

Pure tungsten

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

thoriated tungsten

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

1/2,1/2

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

1/3, 2/3

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

11,000

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

Cerium tungsten

Which of the following is true of DCEP?

DCEP has the highest heat concentration on the electrode tip.

As much as 20% of the heat generated by a GTA welding torch does not enter the weld.

False

Fused quartz nozzles are no more expensive than ceramic nozzles, but are more easily broken.

False

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

Slow erosion results in limited tungsten inclusions in the weld.

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

TIG

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

Thoriated tungsten

____ produces wide welds with shallow penetration.

DCEP

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

Argon

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

Argon

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

It should be broken squarely.

A steep angle between the torch and the work may draw in air.

True

A strong alkaline can be used to chemically clean and point tungsten.

True

All three types of welding current can be used for GTA welding.

True

Tungsten is hard but brittle, and has a low impact strength.

True

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

Using DCEN current.

Which of the following is true of DCEN?

With DCEN, a pointed tip concentrates the arc.