Line F Flashcards
What positions can be welded when using the GTAW process?
All positions.
What is an advantage of TIG when referring to post weld cleaning?
Post weld cleaning is reduced.
Can current be adjusted during the TIG welding process?
Yes.
What weldments does the TIG process produce?
Low-hydrogen weldments.
What is the after affect of distortion, corrosion, and ductility, after the TIG welding process?
Less distortion, more ductile, more corrosion resistant.
What are some disadvantages to GTAW?
Cost
Pre cleaning
Skill learning
What type of shielding gas is required for TIG?
Inert shielding gases.
Argon, helium etc.
At what material point thickness does GTAW have issues welding?
More than 10mm (3/8”)
What is the effect of excessive torch angle?
Air entrainment, porosity.
Explain air entrainment.
Air entrainment is caused by excessive torch angle. The air is sucked into the weld zone causing problems such as porosity.
At what degree does air entrainment become an issue.
> 35°.
How does one maintain adequate gas shielding during the GTAW process?
Smaller stick out.
How is it possible for a welder to use a larger nozzle-to-work distance?
With the use of a gas lens. The shielding gas is projected a greater distance making is possible for longer electrode stick out.
For thin materials, what is the appropriate stick out?
3-5mm.
For thick materials, what is the appropriate stick out?
8-10mm.
What is the preferred option when purging?
Solar flux.
What benefit comes with using Solar Flux?
It protects the backside of the piece from oxides as well as supports the molten weldment.
What does Solar Flux help prevent besides oxidation?
Burn-through.
Does Solar flux help control penetration?
Yes.
What must be done for multi-pass welds when using Solar Flux?
Solar flux is preferred for single pass welds. For multi-pass welds, the flux needs to be re-applied before each pass and the application time of such is increased.
What type of Solar Flux is specifically designed for stainless steels?
Solar Flux B.
The exception is stainless steels containing nickel.
What is the purpose of a gas lens?
For some torches, the flow of shielding gas from the gas cup can become finicky. When a torch is fitted with a gas lens, the shielding gas coverage of the weld is improved by creating laminar flow, preventing turbulence.
What are gas lenses made of?
Multiple layers of fine mesh screening designed to fit the tungsten electrode or collet.
Is a tungsten electrode considered a consumable?
No.
What is the melting point of tungsten?
3410° C (6170° F).
What is the difference between alloyed tungsten electrodes apposed to other non-alloyed tungsten electrodes?
Alloyed electrodes have a higher melting point.
Meaning they have a higher current capacity.
When welding aluminum, what is a particular concern?
The creation of ozone.
How is ozone produced?
The UV radiation emitted from GTAW can produce ozone (O3) from the oxygen in the surrounding air.
Why should one be wary of ozone?
It is highly toxic and chemically reactive.
It can cause severe lung and tissue damage, headaches, dryness of eyes, irritation of nose and throat.
What are shielding gas flow rates dependent on?
Gas nozzle outlet size
Weld joint design
Material
Current
Drafts, ie. wind
Travel speed and position
Shielding gas.
What is the outcome of excessive gas flow rates?
Waste of gas and turbulence resulting in weld contamination.
What is the outcome of little gas flow rates?
Oxidization and porosity due to lack of coverage.
How do gas flow rates and cups correspond?
The larger the nozzle (cup) the higher the flow rate can be without the effect of turbulence.
What is the gas flow rate of shielding gas for argon?
5-15 Ipm (10.5-31.5 cfh).
At what distance does high frequency arc starting occur?
within about 5mm of the workpiece. This high frequency closes the gap between the two.
What is a drawback of high frequency GTAW?
It can be quite noisy depending on the frequency range.
It can also interfere with electronic devices such as pace makers.
What type of brush or wire wheel should be used when cleaning stainless steel?
Stainless steel bristle or wire.
How does one avoid cross contamination of tools when handling stainless steel?
Only use tools dedication to stainless and stainless only.
What should be done prior to welding stainless steel?
Clean off dirt and grease.
What type of shielding gas should not be used to weld on stainless steel?
100% CO2.
What is the most common current and polarity used for GTAW?
DCEN aka straight polarity.
What percentage of the heat from the arc is released into the workpiece?
70%.
What is a characteristic of DCEN?
Deep penetration, narrow beads.
Does DCEN have any cleaning action?
No. Unlike AC or DCEP, DCEN does not have any cleaning action.
With DCEP 70% of the heat from the arc is released where?
Into the electrode.
What is a characteristic of DCEP?
Reduced penetration, wide beads. Reduced tungsten life.
Which current requires a larger tungsten?
DCEP.
Does DCEP have any cleaning action?
Yes. Both DCEP and AC current have cleaning action due to the flow of electrons. This is useful for welding aluminum.
When is AC current needed?
When the advantages of DCEN polarity and the cleaning action of DCEP are needed.
What are the most common power sources of GTAW?
Transformer/rectifier. This is because they can produce both AC and DC current.
What are two characteristics of an inverter?
Higher cost, greater electrical efficiency.
How is the shielding gas supply controlled?
With the use of a flowmeter regulator.
What does a flowmeter regulator do?
Reduces cylinder pressure and controls gas flow.
Why are two-stage regulators recommended apposed to single?
For precision and high volume applications.
What is the typical outlet pressure to a flowmeter?
40-60 psi (276-414 kPa)
How do some tungsten electrodes have a round/balled end?
Some electrodes have a round/balled end due to establishing an arc for a short interval of time while running AC or DCEP current. This is simply the electrode melting at the tip.
When are rounded/balled tipped electrodes used?
This shape is often used for welding on materials that require cleaning action.
What position should the tungsten be held to produce a round/balled end?
Vertically.
What shape of tungsten should be used when using DCEN?
Tapered or pointed end.
What position should tungsten be ground?
Lengthwise. AKA grinding marks should go along with the length of the electrode.
What is something to consider when using thoriated tungsten?
It is radioactive (on a low level).
What are pure tungsten electrodes mainly used for?
AC welding of aluminum.
What colour and classification is pure tungsten?
Green. EWP.
What is a recommended alternate to thoriated tungsten?
Lanthanated tungsten or E3 tungsten.
What safety steps should be used when using thoriated tungsten?
Avoid breathing in dust generated by grinding.
Why is porosity such an issue in the GTAW process?
Due to the puddle forming to quickly, gases do not have a chance to escape.
How can the issue of porosity be solved using filler rods?
Using a deoxidized filler rod.
Ie. A thin copper coating.
For mild steel, what filler rod should be used?
ER70S-X.
In the filler rod ER70S-X what does the ER represent?
Electrode Rod
In the filler rod ER70S-X what does the 70 represent?
Minimum tensile strength in ksi.
In the filler rod ER70S-X what does the S represent?
Filler metal is solid
In the filler rod ERS70S-X what does the X represent?
Indicates chemical composition of solid electrode
What is the affect of a longer arc?
Wide shallower beads.
What is the affect of a short arc?
Deep narrow bead.
What times the electrode diameter can the arc length be adjusted?
1.5 times.
What does the Collet Body do?
Creates an electrical contact between the collet and torch body.
How are tungsten electrodes held in the collet?
Through the use of friction and pressure.
How can collets be damaged?
When paired with the incorrect size of electrode and/or collet body.
What electrodes are used for welding aluminum with AC current?
Cerium, Zirconia, Pure tungsten, EWG
What are some characteristics of using Argon?
Smooth and quiet
Easier to weld thin materials
Greater cleaning on aluminum using AC
Easier arc starting
Lower flow rates
Better resistance to drafts
Heavier than air.
Why is welding thin materials easier using argon?
Argon provides a stable arc and better control over heat input, reducing the risk of burning through the material.
What type of joint protection is needed with stainless steels?
Full joint protection.
How are the backsides of workpieces protected against atmospheric corrosion.
Purging or with the use of flux.
What gases are used for purging?
Argon and nitrogen, due to their non-flammability.
If no filler metal is added, the weld formed is called ___________ weld.
an autogenous
