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Welding Level 2 > Chapter 19 GTAW > Flashcards

Chapter 19 GTAW Flashcards

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1
Q

What is GTAW?

A

Gas Tungsten arc welding is a process that joins metals together by heating them with an arc between a non-consumable tungsten electrode and the work.

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2
Q

What are the two common terms for TIG?

A

GTAW is commonly referred to as TIG (tungsten inert gas). Some people also refer to it as heliarc welding.

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3
Q

What are the 4 basic parts of setup for GTAW?

A
  1. A welding machine
  2. A torch
  3. An electrode
  4. An inert gas supply and controls
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4
Q

When is a constant current welding machine used?

A

In GTAW and SMAW

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5
Q

What are the two types of direct currents used in GTAW?

A

DCEN (Straight) and DCEP (reverse)

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6
Q

What is another term for DCEN?

A

DCEN is also referred to as DCSP (direct current straight polarity)

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7
Q

What is another term for DCEP?

A

DCEP is also referred to as direct current reverse polarity (DCRP)

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8
Q

Which GTAW provides the deepest penetration?

A

DCEN

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9
Q

In ________, the electrons leave the negative electrode and flows to the base metal.

A

DCEN

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10
Q

In DCEN, approximately ______% of the heat is developed at the base metal.

A

70%

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11
Q

Which metals are used when DCEN welding ?

A
  1. steels
  2. stainless steels
  3. nickel alloys
  4. other materials that do not have surface oxides
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12
Q

In DCEP, 70% of the heat is developed __________________, and only 30% is developed ______________.

A

70% is developed in the electrode
30% is developed at the base metal. The bead is wide and shallow

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13
Q

Which uses a larger electrode at a given current? DCEP or DCEN?

A

DCEP

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14
Q

A larger electrode allows it to handle the higher heat of ______________. An electrode will melt using ___________ if there is too much current.

A

DCEP and DCEP

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15
Q

What is one major advantage of DCEP?

A

The cleaning action it has on certain metals such as aluminum and magnesium. Oxides on the base metal surface are removed. This results in better quality welds.

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16
Q

Alternating current welding combines the characteristics of ____________ and ___________

A

DCEN and DCEP

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17
Q

AC welding current switches polarities _________ times per second.

A

120 times per second

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18
Q

In AC, approximately ______% of the heat is developed at the base metal.

A

50%

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19
Q

Penetration in _________ welding is less than it is in _________, but greater than DCEP.

A

Penetration in AC welding is less than it is in DCEN, but greater than DCEP.

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20
Q

Which GTAW welding does not breakup surface oxides?

A

DCEN

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21
Q

Alternating current should flow __________ in both directions.

A

equally

22
Q

What does rectified mean?

A

When current does not flow in the electrode positive half of the cycle, it is said to be rectified.

22
Q

In AC welding, current in the electrode _____________ half cycle is less than in the electrode ____________ half cycle.

A

In AC welding, current in the electrode positive half cycle is less than in the electrode negative half cycle.

23
Q

What is a partially rectified current?

A

AC current in which the electrode positive half cycle is less than desired.

24
Q

What is pulsed current?

A

It is similar to direct current except that it has two current levels. High current period followed by a low current period.

25
Q

What is the peak current?

A

The higher current that is used for pulsed GTAW welding. The metal becomes molten during the peak current.

26
Q

What is background current?

A

The lower background current maintains the arc and allows the weld to cool. The welder moves the torch a short distance during the background current.

27
Q

What are the four main functions for GTAW torches?

A
  1. Hold the electrode
  2. Make a good electrical contact with the electrode
  3. Direct shielding gas to the weld area
  4. Provide a means to cool the electrode
28
Q

What is a collet?

A

A sleeve used in a GTAW torch to hold the electrode tightly enough tp ensure electrical contact with the welding power supply.

29
Q

What is a collet body?

A

The part of the torch or gun that accepts the collet

30
Q

What is the torch body?

A

The main portion of the welding torch to which fuel gas hoses are connected and the torch tip is attached.

31
Q

What is the gas nozzle?

A

A ceramic or metal device on a torch or gun used to direct the shielding gas to the weld area.

32
Q

Whenever the electrode size changes, the __________ and ________ must also be changed.

A

collet and collet body

33
Q

What is an end cap?

A

When the end cap is tightened, the collet tightens around the electrode. A tight fit holds the electrode in its proper place for welding.

34
Q

The heat that develops in the electrode, cables, and the nozzle must be removed or _______________________

A

The torch will overheat

35
Q

GTAW torches are either _________ or ______________ cooled

A

gas or water

36
Q

When are gas cooled torches used?

A

For light duty work and are not recommended for use with more than 200A.

37
Q

When are water cooled torches used?

A

To carry currents over 200A. They have a continuous flow of water passing through the torch body to remove heat. The water is carried by a hose to and from the torch body.

38
Q

____________ conveys the electric current to the torch.

A

cables

39
Q

What carries the shielding gas to the torch?

A

The hose

40
Q

What is an inert gas?

A

A gas that does not react with the weld

41
Q

What are two types of shielding gases used in GTAW?

A

argon and helium

42
Q

____________ provides a hotter arc and provides for faster travel speeds. It is commonly used in automatic GTAW.

A

Helium

43
Q

Why is argon used?

A

It is cheaper than Helium and it covers the weld area better when welding in the flat position.

44
Q

What is a regulator used for?

A

To reduce the cylinder pressure to a usable pressure.

45
Q

What is a flowmeter used for?

A

To control the amount of shielding gas that goes to the welding torch.

46
Q

What does a flowmeter measure gas flow in?

A

cubic feet per hour (cfh) or liters per minute (lpm)

47
Q

What does a sheilding gas do?

A

It covers and protects the metal during GTAW

48
Q

What would happen if you stopped welding and the shielding gas also stopped?

A

Oxygen and other gases would contaminate the weld before it cools

49
Q

How is contamination from oxygen and other gases as the weld cools prevented?

A

Postflow (shielding gas continues to flow for a short time after the weld current stops)

50
Q

Why is a postflow of shielding gas used with GTAW?

A

To prevent contamination of the weld from oxygen and to stop the tungsten electrode from being oxidized.

Welding Level 2 (21 decks)

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