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Gas Tungsten Arc Welding > Line F > Flashcards

Line F Flashcards

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1
Q

What positions can be welded when using the GTAW process?

A

All positions.

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2
Q

What is an advantage of TIG when referring to post weld cleaning?

A

Post weld cleaning is reduced.

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3
Q

Can current be adjusted during the TIG welding process?

A

Yes.

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4
Q

What weldments does the TIG process produce?

A

Low-hydrogen weldments.

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5
Q

What is the after affect of distortion, corrosion, and ductility, after the TIG welding process?

A

Less distortion, more ductile, more corrosion resistant.

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6
Q

What are some disadvantages to GTAW?

A

Cost
Pre cleaning
Skill learning

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7
Q

What type of shielding gas is required for TIG?

A

Inert shielding gases.

Argon, helium etc.

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8
Q

At what material point thickness does GTAW have issues welding?

A

More than 10mm (3/8”)

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9
Q

What is the effect of excessive torch angle?

A

Air entrainment, porosity.

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10
Q

Explain air entrainment.

A

Air entrainment is caused by excessive torch angle. The air is sucked into the weld zone causing problems such as porosity.

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11
Q

At what degree does air entrainment become an issue.

A

> 35°.

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12
Q

How does one maintain adequate gas shielding during the GTAW process?

A

Smaller stick out.

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13
Q

How is it possible for a welder to use a larger nozzle-to-work distance?

A

With the use of a gas lens. The shielding gas is projected a greater distance making is possible for longer electrode stick out.

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14
Q

For thin materials, what is the appropriate stick out?

A

3-5mm.

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15
Q

For thick materials, what is the appropriate stick out?

A

8-10mm.

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16
Q

What is the preferred option when purging?

A

Solar flux.

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17
Q

What benefit comes with using Solar Flux?

A

It protects the backside of the piece from oxides as well as supports the molten weldment.

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18
Q

What does Solar Flux help prevent besides oxidation?

A

Burn-through.

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19
Q

Does Solar flux help control penetration?

A

Yes.

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20
Q

What must be done for multi-pass welds when using Solar Flux?

A

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.

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21
Q

What type of Solar Flux is specifically designed for stainless steels?

A

Solar Flux B.

The exception is stainless steels containing nickel.

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22
Q

What is the purpose of a gas lens?

A

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.

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23
Q

What are gas lenses made of?

A

Multiple layers of fine mesh screening designed to fit the tungsten electrode or collet.

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24
Q

Is a tungsten electrode considered a consumable?

A

No.

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25
Q

What is the melting point of tungsten?

A

3410° C (6170° F).

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26
Q

What is the difference between alloyed tungsten electrodes apposed to other non-alloyed tungsten electrodes?

A

Alloyed electrodes have a higher melting point.

Meaning they have a higher current capacity.

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27
Q

When welding aluminum, what is a particular concern?

A

The creation of ozone.

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28
Q

How is ozone produced?

A

The UV radiation emitted from GTAW can produce ozone (O3) from the oxygen in the surrounding air.

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29
Q

Why should one be wary of ozone?

A

It is highly toxic and chemically reactive.

It can cause severe lung and tissue damage, headaches, dryness of eyes, irritation of nose and throat.

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30
Q

What are shielding gas flow rates dependent on?

A

Gas nozzle outlet size
Weld joint design
Material
Current
Drafts, ie. wind
Travel speed and position
Shielding gas.

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31
Q

What is the outcome of excessive gas flow rates?

A

Waste of gas and turbulence resulting in weld contamination.

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32
Q

What is the outcome of little gas flow rates?

A

Oxidization and porosity due to lack of coverage.

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33
Q

How do gas flow rates and cups correspond?

A

The larger the nozzle (cup) the higher the flow rate can be without the effect of turbulence.

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34
Q

What is the gas flow rate of shielding gas for argon?

A

5-15 Ipm (10.5-31.5 cfh).

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35
Q

At what distance does high frequency arc starting occur?

A

within about 5mm of the workpiece. This high frequency closes the gap between the two.

36
Q

What is a drawback of high frequency GTAW?

A

It can be quite noisy depending on the frequency range.

It can also interfere with electronic devices such as pace makers.

37
Q

What type of brush or wire wheel should be used when cleaning stainless steel?

A

Stainless steel bristle or wire.

38
Q

How does one avoid cross contamination of tools when handling stainless steel?

A

Only use tools dedication to stainless and stainless only.

39
Q

What should be done prior to welding stainless steel?

A

Clean off dirt and grease.

40
Q

What type of shielding gas should not be used to weld on stainless steel?

A

100% CO2.

41
Q

What is the most common current and polarity used for GTAW?

A

DCEN aka straight polarity.

42
Q

What percentage of the heat from the arc is released into the workpiece?

A

70%.

43
Q

What is a characteristic of DCEN?

A

Deep penetration, narrow beads.

44
Q

Does DCEN have any cleaning action?

A

No. Unlike AC or DCEP, DCEN does not have any cleaning action.

45
Q

With DCEP 70% of the heat from the arc is released where?

A

Into the electrode.

46
Q

What is a characteristic of DCEP?

A

Reduced penetration, wide beads. Reduced tungsten life.

47
Q

Which current requires a larger tungsten?

A

DCEP.

48
Q

Does DCEP have any cleaning action?

A

Yes. Both DCEP and AC current have cleaning action due to the flow of electrons. This is useful for welding aluminum.

49
Q

When is AC current needed?

A

When the advantages of DCEN polarity and the cleaning action of DCEP are needed.

50
Q

What are the most common power sources of GTAW?

A

Transformer/rectifier. This is because they can produce both AC and DC current.

51
Q

What are two characteristics of an inverter?

A

Higher cost, greater electrical efficiency.

52
Q

How is the shielding gas supply controlled?

A

With the use of a flowmeter regulator.

53
Q

What does a flowmeter regulator do?

A

Reduces cylinder pressure and controls gas flow.

54
Q

Why are two-stage regulators recommended apposed to single?

A

For precision and high volume applications.

55
Q

What is the typical outlet pressure to a flowmeter?

A

40-60 psi (276-414 kPa)

56
Q

How do some tungsten electrodes have a round/balled end?

A

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.

57
Q

When are rounded/balled tipped electrodes used?

A

This shape is often used for welding on materials that require cleaning action.

58
Q

What position should the tungsten be held to produce a round/balled end?

A

Vertically.

59
Q

What shape of tungsten should be used when using DCEN?

A

Tapered or pointed end.

60
Q

What position should tungsten be ground?

A

Lengthwise. AKA grinding marks should go along with the length of the electrode.

61
Q

What is something to consider when using thoriated tungsten?

A

It is radioactive (on a low level).

62
Q

What are pure tungsten electrodes mainly used for?

A

AC welding of aluminum.

63
Q

What colour and classification is pure tungsten?

A

Green. EWP.

64
Q

What is a recommended alternate to thoriated tungsten?

A

Lanthanated tungsten or E3 tungsten.

65
Q

What safety steps should be used when using thoriated tungsten?

A

Avoid breathing in dust generated by grinding.

66
Q

Why is porosity such an issue in the GTAW process?

A

Due to the puddle forming to quickly, gases do not have a chance to escape.

67
Q

How can the issue of porosity be solved using filler rods?

A

Using a deoxidized filler rod.

Ie. A thin copper coating.

68
Q

For mild steel, what filler rod should be used?

A

ER70S-X.

69
Q

In the filler rod ER70S-X what does the ER represent?

A

Electrode Rod

70
Q

In the filler rod ER70S-X what does the 70 represent?

A

Minimum tensile strength in ksi.

71
Q

In the filler rod ER70S-X what does the S represent?

A

Filler metal is solid

72
Q

In the filler rod ERS70S-X what does the X represent?

A

Indicates chemical composition of solid electrode

73
Q

What is the affect of a longer arc?

A

Wide shallower beads.

74
Q

What is the affect of a short arc?

A

Deep narrow bead.

75
Q

What times the electrode diameter can the arc length be adjusted?

A

1.5 times.

76
Q

What does the Collet Body do?

A

Creates an electrical contact between the collet and torch body.

77
Q

How are tungsten electrodes held in the collet?

A

Through the use of friction and pressure.

78
Q

How can collets be damaged?

A

When paired with the incorrect size of electrode and/or collet body.

79
Q

What electrodes are used for welding aluminum with AC current?

A

Cerium, Zirconia, Pure tungsten, EWG

80
Q

What are some characteristics of using Argon?

A

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.

81
Q

Why is welding thin materials easier using argon?

A

Argon provides a stable arc and better control over heat input, reducing the risk of burning through the material.

82
Q

What type of joint protection is needed with stainless steels?

A

Full joint protection.

83
Q

How are the backsides of workpieces protected against atmospheric corrosion.

A

Purging or with the use of flux.

84
Q

What gases are used for purging?

A

Argon and nitrogen, due to their non-flammability.

85
Q

If no filler metal is added, the weld formed is called ___________ weld.

A

an autogenous

Gas Tungsten Arc Welding (1 decks)

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