Chapter 16 GTAW

Water hose fittings have____threads, and gas hose fittings have______threads.

Left-hand, Right-hand

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

Using DCEN current

What is true of DCEN?

With DCEN, a pointed tip concentrates the arc

What is true of breaking and remelting tungsten?

It should be melted by striking an arc on a piece of carbon

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

thoriated Tungsten

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

What is true of the grinding tungsten electrodes?

If a 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.

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

DCEN

Which of the following is an inert gas?

Helium

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

Helium

_____ electrodes have a current-carrying capacity similar to that of pure tungsten, and may be used for both AC and AD Welding current

lanthanum tungsten

What is true about DCEP?

DCEP has the highest heat concentration on the electrode tip.

(T/F) DCEP has the lowest heat concentration on the electrode tip.

False

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

1/2, 1/2

DECP concentrates_____of the arc heat on the plate, and_____ of the heat on the electrode.

1/3, 2/3

In GTAW, the arc temp is around_______degrees Fahrenheit

11,000

(T/F) As much 20% of the heat generated by a GTA welding torch does not enter the weld

False

(T/F) The Shielding gas flows rate should be high as possible

False

(T/F) When the GTAW process was first developed, argon was the primary shielding gas used.

False

______ has the poorest heat resistance and electron emission characteristics of all the tungsten electrode

Pure tungsten

What is true of erosion of the tungsten electrode?

Slow erosion results in limited tungsten inclusions in the weld

_____ 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

(T/F) A steep angle between the torch and the work may draw air

True

(T/F) A strong alkaline can be used to chemically clean and point tungsten

True

(T/F) All three types of welding current can be used for GTA welding

True

(T/F) Tungsten erosion can be limited by using a water-cooled torch

True

(T/F) Tungsten is hard but brittle, and has a low impact strength

True