GTAW Flashcards
The word ‘TUNGSTEN’ refers to what?
The pure element
Tungsten’s melting point is…
6170 degrees Fahrenheit
All GTAW electrodes start with the letters…
EW
The ‘E’ stands for…
Electrode
The ‘W’ stands for…
include the German name as well
Tungsten
From Wolfram, which is German for tungsten
Electrodes are further identified by the element with which they are alloyed. Identify the following by what they stand for…
Th... La... Ce... Zr... P...
Th…Thoriated
La…Lanthanated
Ce…Ceriated
Zr…Zirconiated
P…pure
EWla-1.5%
In the electrode classification above what does the 1.5% stand for?
Indicated the percentage of element that is in the electrode…
1.5% lanthanated
The key material GTAW electrodes are comprised of…
Tungsten
GTAW electrodes with a red color code indicate:
A. Pure tungsten
B. 1.7% - 2.2% Thoriated
C. 1.3% Lanthanated
D. 1.8% -2.2% ceriated
B. 1.7% - 2.2% Thoriated
GTAW electrodes come in diameters of:
1/8”
0.040”
5/32”
All of the above
All of the above
What type of electrode is EWP?
Color code?
Current?
Perfect for welding on what kind of material?
Pure
Green
AC
Aluminum
What electrode type is EWCe-2?
Color code?
Current?
2% Ceriated
Orange
DCEN, AC
What electrode type is EWLa-1?
Color code?
Current?
1% Lanthanated
Black
DCEN, AC
What electrode type is EWLa-1.5%?
Color code?
Current?
1.5% Lanthanated
Gold
DCEN, AC
What electrode type is EWLa-2%?
Color code?
Current?
2% Lanthanated
Blue
DCEN, AC
What electrode type is EWZr-1?
Color code?
Current?
1% Zirconiated
Brown
AC
What electrode type is EWTh-1?
Color code?
Current?
1% Thoriated
Yellow
DCEN, Inverter AC
What electrode type is EWTh-2?
Color code?
Current?
2% Thoriated
Red
DCEN, Inverter AC
What electrode type is EWG?
Color code?
Current?
General
Gray
Manufacturer Specified
GTAW electrodes with a green color code indicate:
Pure tungsten
EWP electrodes contain a minimum of _____ tungsten, with no additional __________ ___________.
99.5%
Alloying elements
EWP (pure tungsten) provides good _____ __________ when used with _________ current.
Arc stability
AC current either balanced-wave or continuous high frequency
The tip of the EWP electrode maintains…
A clean, balled end that promotes good arc stability
EWP electrodes are usually used with AC but may also be used with ______ but doesn’t provide the arc initiation and arc stability characteristics
DC
EWP electrodes are generally used for welding what?
Aluminum and Magnesium alloys
EWTh electrode characteristics include
Easy are starting
Excellent arc performance
Long service life
Withstands high amps
Note: contains Thoria which is radioactive.
EWLa electrode characteristics include:
Easy arc start
Arc stability
Good service life
What is the best non-radioactive alternative to EWTh-2 electrodes?
EWLa-1.5
ELa-2 is better suited for ________ ________ __________ and numerous _____________.
Short weld cycles
Re-ignitions
GTAW electrode that offers the best performance and longevity for welding higher current mild steel in DC - polarity
1.7% - 2.2% Thoriated
If the amount of current used exceeds the capability of the electrode (diameter), tungsten inclusions in the weld may result. This can be identified with radiographic inspection and is known as:
Tungsten spitting
As a general rule, the inside diameter of the gas nozzle should be a minimum of:`
3x the diameter of the electrode
Tungsten boasts the highest melting point of any metal:
6191 degrees Fahrenheit
The AWS standard that guides GTAW electrodes is:
A5.12
AWS GTAW electrode classification EWG:
A. Zirconiated
B. Rare earth tungsten(varies per manufacturer)
C. Ceriated
D. Pure tungsten
Rare earth tungsten
AWS GTAW electrode color classification EWP:
Green
EWTh electrodes are superior to EWP electrodes in several ways:
Higher current capacity Longer life Greater resistance to contamination of the weld Arc starting is easier More stable arc
EWTh electrodes maintain what kind of tip?
Sharpened
Sharpened tips are desired for __________ welding operations
DCEN
Electrode tip preferred for AC welding:
Balled end
Compared to EWP electrodes, the EWCe electrode advantages are:
Facilitate arc starting
Improve arc stability
Reduce rate of vaporization or burn-off
Work well with either AC/DC polarity
AWS GTAW electrode classification with excellent low amperage arc staring:
EWP
Electrodes that can be used as a non-radioactive substitute for EWTh-2
EWLa-1
EWLa-1.5
EWLa-2
EWZr electrode advantages v.s pure tungsten
Arc stability and starting
Recommended over EWP for radiographic-quality weld on aluminum and magnesium
Balls up easier
Higher resistance to contamination
With AC welding, EWP or EWZr electrodes form a _______ ______.
Balled end
With DC welding, EWTh, EWCe and EWLa electrodes are usually used, and the electrode end is usually ground to a specific included angle and is often __________.
Truncated
Small-diameter electrodes can be used with a _________ ____________ preparation for _______ welding
Square end
DCEN
Tungsten tips are generally prepared by:
Grinding
Balling
Chemical sharpening
What are the 3 main advantages of GTAW electrodes
One of the highest melting points of all metals @ 6170’ F
Low electrical resistance
Good heat conductivity
If tungsten spitting occurs:
Change the type of electrode
Use a larger diameter electrode
Decrease the welding current
GTAW-P is usually applied with electrode negative(DCEN)
TRUE OR FALSE
TRUE
Generally, the GTAW-P adjustments are pre-set in the power source with the minimal adjustability from the operator.
True of false
False
PPS stands for:
Pulses per second
In pulsed DC welding, the pulse current level is usually set at:
2-10x the background current
Advantages of pulsed current include:
Greater penetration
Minimizes distortion
Equal penetration to joints with dissimilar metal thicknesses
Ceriated tungsten requires special precautions due to radioactive dust concerns
True or false
False
When it come to shielding gas flow, more is better
True or false
False
Use the heat of the arc to melt the arc
True or false
False
A grinding wheel dedicated to sharpening tungsten electrodes is essential to prevent______________
Contamination
A __________ point is recommended for AC welding of aluminum. This provides better __________ __________
Blunted
Directional control
A _______ _______ uses a mesh screen to distribute the shielding gas more evenly
Gas lens
As a general rule, tungsten extension should NOT exceed the _______ _______ of the cup or nozzle
Inside diameter
On material prone to ________, such as thin gauge stainless steel, use additional tacks
Warping
The preferred GTAW technique to melt filler metal is to touch the end of the _____ _____ to the leading edge of the ______ ______
Filler rod
Molten(weld) pool
Torches are rated in accordance with the max. _________ that can be used without overheating.
Current
GTAW torched for manual applications are designed:
With a head angle of 120 degrees
Adjustable angle heads
With 90 degree or straight heads
The heat generated in a GTAW torch during welding is removed by:
A. Gas cooling B. Water cooling C. Both D. None Look it up
Gas cooled(air cooled) torches are limited to welding currents of
200A
Water cooled GTAW torches can run continuously at currents reaching ________.
?
________ or patterned jets incorporated into the torch body to feed shielding gas into the nozzle
Diffusers
Gas nozzles are made of various ____ _____ materials ranging in different shapes, diameters and lengths
Heat resistant
The least expensive but most brittle GTAW nozzles:
Ceramic
_______ _______ contain a porous barrier diffuser and are designed to fit around the electrode or collet.
Gas lenses
Gas lenses produce a longer, undisturbed flow of shielding gas and enable operators to weld with the nozzle ________ inch or more from the workpiece
1 inch
Pulsed current is useful for welding stainless steel because it
Produces less heat input that a steady current
Shielding gas flow rates should be decreased when welding in the overhead position
True or false
False
When the GTAW power source is set to DCEP…
Most of the heat is directed toward the electrode
Which of the following methods is used to start GTAW arc without touching the base metal?
—high frequency start
—lift start
—scratch start
—pulse start
High frequency start
High frequency currents is added to alternating current to…
Maintain the arc
It’s not necessary to keep the hot end of the filler wire in the gas-shielding zone
True or false
False
AC is used for welding aluminum because…
Of the cleaning action and medium penetration of the arc
When using GTAW to weld aluminum with AC, the tip of the tungsten electrode should be…
Rounded at the tip
The shielding gas most commonly used for welding low carbon steel with GTAW is…
Argon
Which is not an advantage of GTAW?
—all pos. Welding
—very little spatter and post-weld cleaning
—high quality welds in a great variety of metals
—high deposition rate
High deposition rate
What approximate percentage of the heat of the arc is directed toward the electrode when welding with DCEP
70%
Pulsed current is useful for welding out of position because
The weld pool is easier to control
How long should the post purge (shielding gas) be allowed to flow after the welding arc is broken?
Long enough to allow the base metal and the electrodes to cool
Chemical symbol for tungsten is
W (wolfram)
The voltage present when the welding machine power switch is in the ON position, but no welding is taking place is called
Open-circuit voltage
Filler metal with an AWS classification of ER4043 is used to weld…
Aluminum
Copper coated mild steel filler metals used for oxyacetylene welding are also recommended for GTAW
True or false
False
Color brown is associated with what type of tungsten electrode?
Zirconiated
Color black is associated with what type of tungsten electrode?
Lanthanated
Color red is associated with what type of tungsten electrode?
2% thoriated
Color green is associated with what type of tungsten electrode?
Pure
Color yellow is associated with what type of tungsten electrode?
Thoriated
Color orange is associated with what type of tungsten electrode?
Ceriated
Filler metal with an AWS classification of ER308 is used to weld…
Stainless steel
Filler metal with an AWS classification of er4043 is used to weld:
Aluminum
Filler metal with an AWS classification of er308 is used to weld
Stainless steel
GTAW is…
An arc welding process in which shielding gas protects the arc between a non consumable tungsten electrode and a base metal.
High frequency
Is high voltage, low current pulses over 16,000 cycles per second. Is used to start an arc without touching an electrode to the work.
DC
Is an electrical current that flows in one direction only
GTAW machines are _______ current power sources.
Constant
What current has the quality of both DCEN & DCEP and is used for aluminum and magnesium?
AC
Filler metal rods usually come in _____” lengths
36
A GTAW electrode is held in the torch by a…
Collet
A short ____ and electrode permit use of torches in difficult-to-reach places
Cap
What 2 types of electrodes are preferred when AC is used for a GTAW project?
Pure
Zirconiated
Which method of starting a GTAW arc involves touching an electrode to the base metal, then withdrawing about 1/8”?
Touch starting
What kind of arc can cool a weld in the overhead position?
Pulsed
What is the most common power source used for GTAW
Transformer-rectifier
What is the MAX. Size of the electrode balled tip compared to the diameter of the electrode?
1 1/2 size the diameter
Which of the following methods is used for starting a GTAW arc?
High-voltage
In which of the following 2 GTAW positions should you weld using the lowest possible surrender settings?
Vertical and overhead
InDCEN
Elektron flow from the electro to the work piece
DCEP
Electron’s flow from the work piece to the electros along with about 70% of the heat
Alternating current
Is an electrical current that has alternating positive and negative values
Conventional sine wave transformer rectifier
Is a well power source that produces a sinusoidal waveform
Sinusoidal waverform
Is a 60 cycle per 2nd sine wave. It is considered balance because it has equal amounts of electro positive current and electro negative current
Conventional square wave transformer rectifier
Is a welding power source that produces a relatively square 60HZ Wave form . It provides 3 advantages the 1st is the change from positive to negative is immediate resulting in a smoother Ark.. Sag in, a conventional square wave form is more efficient than a sine wave because the Ark. Spends more time at peak EP for cleaning and peak EN and for penetration.
3rd, a conventional square wave has an adjustable balance
Conventional square wave transformer rectifier ratio of cycle time
Approximately 30% cleaning action and 70% penetration to 5 5% cleaning action and 45% penetration
Inverter
Is a welding power source that produces a true square AC Wave form
Argon helium mixtures
Helium produces an increase teeth and put in a deeper penetration required to wild thicker material while Oregon aids in arc starting helps to stabilize the Ark. And provide cleaning action
Post flow
Is the shielding gas after the arc is extinguished
Argon
Smooth at Ark. At Lord Ambridge and voltage settings, easy art starting, heavier-than-air which means lower gas flow rates, better cleaning action, less expensive
Helium
Is lighter-than-air which means that it requires higher flow rates to provide adequate coverage And higher ionization potential which means arik starting is harder it is also more expensive
GTAW-P
Pulsed GTAW Is a gas tungsten Ark. Welding variation in which direct current is pulsed Between A peak current and a background current
PPS
Pulses per 2nd is the number of times per 2nd that current Achieves peak current
Stainless Steals are of the what series
Three hundred
Stainless steels are commonly welded with what using what
GTAW
DCEN, EQUIPPED WITH HIGH FREQUENCY
GTAW Is particularly adaptable for welding what
Thin-gauge Stainless steel and high pressure stainless steel piping
The procedure for welding all types of stainless steel
Is the same. Filler metals for welding stainless steels are alloyed To prevent cracking. Welding parameters such as proper current, electro diameter, shielding gas flow rate, and filler metal diameter should we set based on thickness of stainless steel
Aluminum
Nonferrous metla
Heta treatable aluminum alloys above _____ are not weldable
7039
Contaminants such as oil and grease should be removed by wiping the surface with a suitable cleaner.________ Is commonly used on aluminum
Acetone
With aluminum, best results are obtained by using____ current with _______ as a shielding gas
AC
Argon
When welding aluminum
What link premitur such as current, electro diameter, argon flow rate, and filler metal diameter are based on the thickness of the aluminum and the welding position
Aluminum and magnesium both have what
High thermal conductivity, low melting points, high thermal expansion, and rapid oxidation
DCENs heat balance in the arc
70% at the work end, 30% at the electrode end
DCEPs heat balance in the arc
70% workpiece, 30% electrode
ACs heat balance in the arc
70% workpiece, 30% electrode
