Chapter 20 GTAW Flashcards
How should cylinders containing compressed gas be secured?
They should be secured to a wall, column, welding cart or welding hand truck with chains or steel bands.
If a ball float-type flowmeter is used, the flowmeter must be _____________
In a vertical position
What part of the torch must be loosened before adjusting the electrode extension?
Endcap or tailend
What is the recommended extension beyond the gas nozzle for welding a butt joint?
1/8”-3/16” max
3mm - 5mm
What is considered when selecting the weld current?
- What type of metal to be welded
- How thick is the metal
- What type of joint will be used
- In what position will welding be done
High frequency voltage is always used with which type of electrical current?
For AC welding you must use continuous high frequency voltage
What position is the contactor switch set for GTAW to use a foot pedal to turn on the welding current?
In the remote position, the current can be changed while welding by pressing a foot pedal or thumb switch.
If you want to set the current to a certian amount and not vary it during welding, what position should it be in?
To set a specific amount, the current remote switch is placed in the panel position.
Flowmeters use a ______ or adjusting ________ to control gas flow.
knob/ screw
How do you read a flowmeter
some flowmeters have a gauge to indicate the gas flow. The most common type has a ball float in a clear tube, which is read from the top of the ball.
How do you calculate how much postflow to use?
You divide the amps by 10
If you are using 100 amps, how much postflow should you have?
100 amps divided by 10 = 10 seconds
What is a characteristic of a pure tungsten electrode?
Forms a ball on the end when heated
What are the three characteristics of Zirconia tungsten electrodes?
- Similar to pure tungsten but with easier arc setting abilities
- Carries the same current are the thoria tungsten
- Used only for AC welding
zirconia tungsten electrodes are recommended only for ____________ welding
AC welding
Thoria and ceria tungsten electrodes are most common for _________ welding.
DC welding
__________ and __________ tungsten electrodes are normally used for welding steel and stainless steel.
thoria and ceria
Each tungsten electrode type is given classification by the AWS. In this system, the E stands for ____________.
electrode
Each tungsten electrode type is given classification by the AWS. In this system, the W stands for ____________.
tungsten
Each tungsten electrode type is given classification by the AWS. In this system, the P stands for ____________.
pure
Each tungsten electrode type is given classification by the AWS. In this system, the Th stands for ____________.
contains thoria
Each tungsten electrode type is given classification by the AWS. In this system, the Zr stands for ____________.
contains zirconia
Each tungsten electrode type is given classification by the AWS. In this system, the Ce stands for ____________.
contains ceria
Each tungsten electrode type is given classification by the AWS. In this system, the La stands for ____________.
contains lanthana
What colour is pure tungsten and what is its AWS classification?
green and EWP
What colour is 2% ceria and what is its AWS classification?
grey and EWCe-2
What colour is 1% lanthana and what is its AWS classification?
Black and EWLa-1
What colour is 1% thoria and what is its AWS classification?
Yellow and EWTh-1
What colour is 2% thoria and what is its AWS classification?
Red and EWTh-2
What colour is zirconia and what is its AWS classification?
Brown and EWZr-1
What are the most common diameters of tungsten electrodes?
0.040” (1.0 mm) to 3/16” (4.8mm)
What shape should the electrode tip used for DCEN welding have?
Tapered with a blunted tip.
in DC welding, grind electrode to a point then griding marks on the electrode should run lengthwise.
What type of current is used to form a ball on the end of tungsten electrode?
For AC welding, the electrode tip is formed into a ball. This is done by striking an arc on a piece of steel or copper with AC or DCEP current.
Which of the following is a filler metal used to weld nickel?
a. ER4043
b. ERZr-2
c. ER308L
d. ERNiCr-3
d. ERNiCr-3
What type of electrical current is recommended for welding high carbon steels?
DCEN
