Chapter 16, 17, 18, 19 GTAW
____ is somewhat affected by cleanliness, requiring little pre-weld cleaning.
Stainless steel
_______ can result in premature cracking or failure of the weld at a load well under its expected strength.
Stress points
Why is it important to keep your hands and gloves clean and oil free?
They can recontaminate the base metal or filler rods.
__________ 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
Why are the ends of tack welds ground to a feather edge?
To make it easier to have 100% penetration at the ending and beginning of the root weld.
Which of the following is a way to minimize erosion of the tungsten electrode?
Using DCEN current.
Which of the following is a reason to use GTA welding?
When a close-tolerance, high-quality weld is required.
Incomplete fusion can be detected by ________.
a root bend test
An oxide layer on aluminum is _______, while on iron it is ________.
black, reddish
When a weld is contaminated by the tungsten touching the molten weld pool, _______ before resuming welding.
both the weld and the tungsten must be cleaned
Exceeding the maximum gas flow rates ________.
causes weld contamination
Which nozzle material is clear?
fused quartz.
Water hose fittings have ________ threads, and gas hose fittings have ________ threads.
left-hand, right-hand
Which of the following is not a way of cleaning the band around the end of a pipe for welding?
soap and water.
Concavity of the root surface is detected by _________.
visual inspection
The improved electron emission of the ______ allows it to carry approximately 20% more current than pure tungsten.
thoriated tungsten
When setting up to make a GTA weld on low carbon steel, the tungsten should be _________ and the welding machine set for____________.
pointed, DCEN
Both the _______ and the ________ can be easily flame cut or ground, which makes them the most frequently used groove joints for training.
single V-groove, single bevel-groove
Adding ________ has the same effect on the electrode characteristic as thorium, but is not radioactive.
zirconium
What is the maximum diameter of tungsten that can be used on the AWS SENSE workmanship samples?
1/8 in (3.2 mm)
What is the purpose of a gas lens?
It reduces the turbulence in the shielding gas.
Why might it be necessary to re-clean the surface of an aluminum AWS SENSE workmanship sample?
The surface oxides have reformed, the surface has become contaminated, it has been too long since the surface was cleaned.
Why would a welder need to make a list of machine settings?
To make it easier to reset the machine for different setups that might be needed.
________ has the poorest heat resistance and electron emission characteristic of all the tungsten electrodes.
Pure tungsten
Why does the return water on a water-cooled GTAW torch flow out around the power cable?
So a smaller power cable can be used.
Before welding on the AWS SENSE workmanship sample, what temperature must a plain carbon steel part be above?
50°F (9.4°C)
Carbon is the primary alloy in the classification of low carbon and mild steel, and ranges from ________ for mild steel.
0.15% to .30%
How much of the surface beside a weld groove must be cleaned for the AWS SENSE workmanship samples?
1 in. (25 mm)
Most codes and standards for GTA pipe welding require no more than _____ inch of root reinforcement.
1/16
The end of the pipe is prepared with a bevel, leaving a root face of ________ inch.
1/16 to 1/8
After the surface of an aluminum AWS SENSE workmanship sample has been cleaned, it should be welded within ____ minutes.
10
What is the minimum acceptance criteria for the depth of porosity for visual inspection of tubing welds?
25% of the base metal thickness.
The end of the pipe is prepared with a _______ bevel.
37 1/2 degree
_________ can be used to back any type of pipe if a welder is unsure about a less expensive substitution.
Argon
What can be done to make it easier to set the root opening for tack welding?
Bend a piece of filler rod in a U-shape and place it between the ends of the pipes.
Flow meters measure the flow rate of a shielding gas in __________units.
CHF or L/min
Which type of tungsten electrode does not break evenly when trying to break off contamination?
EWLa-1
Which of the following is an inert gas?
Helium.
Which of the following is a common cause of a concave root surface?
Insufficient filler metal.
Which of the following is true of breaking and remelting tungsten?
It should be broken squarely.