GTAW

Question 1

Gas Tungsten Arc Welding (GTAW)

Answer 1

Arc welding process in which shielding gas protects the arc between a non-consumable tungsten electrode and the base metal

Question 2

Non-consumable Electrode

Answer 2

An electrode that does not melt and become part of the weld

Question 3

What kind of power source does tig use?

Answer 3

A constant current (CC) machine that is capable of AC, DC and high frequency (HF)

Question 4

High Frequency (HF)

Answer 4

High-voltage, low-current pulses over 16,000 cycles per second (16 kHz)

Question 5

What is HF used for?

Answer 5

To start an arc without touching an electrode to the workpiece. In DC, for arc starting only. In AC, for maintaining the arc.

Question 6

Where is most of the heat concentrated on in DCEN polarity?

Answer 6

About 70% of the heat is directed towards the base metal. DCEN has the lowest heat concentration in the electrode tip.

Question 7

What metals use DCEN?

Answer 7

Carbon steel, stainless steel, other ferrous metals, copper, brass

Question 8

Which polarity has more narrower, deeper-penetrating action?

Answer 8

DCEN

Question 9

What kind of weld results from using DCEP?

Answer 9

A wide, shallow-penetrating weld, must use a large diameter electrode

Question 10

What kind of metals must use AC in order to weld them?

Answer 10

Nonferrous metals such as aluminum and magnesium that have tough oxide coatings that melt at much higher temperatures than the base metal. Coating must be removed before welding

Question 11

What is cathodic bombardment?

Answer 11

The removal of the oxide coating on the base metal by bombarding it with gas ions during the positive half-cycle of AC, also called Cleaning Action

Question 12

What are the three power sources that produce different AC waveforms?

Answer 12

Conventional sine wave transformer-rectifiers, conventional square wave transformer-rectifiers, inverters

Question 13

Conventional Sine Wave Transformer-Rectifier

Answer 13

A power source that produces a sinusoidal waveform

Question 14

Sinusoidal Waveform

Answer 14

60 cycle per second (60 Hz) sine wave with equal amounts of electrode positive current and electrode negative current

Question 15

How many times does a sinusoidal waveform pass through zero in a second?

Answer 15

120 times

Question 16

What happens to the arc when the current passes through zero in a sinusoidal waveform?

Answer 16

The arc extinguishes

Question 17

Conventional Square Wave Transformer-Rectifier

Answer 17

A power source that produces a relatively square 60 Hz waveform

Question 18

What are the advantages of a Square Wave Transformer-Rectifier relative to a Sine Wave Transformer-Rectifier?

Answer 18

1. The change from positive to negative is immediate, therefore resulting in a smoother arc
2. More efficient than a sine wave because the arc spends more time at peak
3. An adjustable balance between positive and negative

Question 19

Inverter

Answer 19

A power source that produces a true square AC waveform

Question 20

What is the advantage of using an inverter?

Answer 20

Allows for more precise control of the AC waveform (balance, frequency, amplitude)

Question 21

Electrode Extension

Answer 21

The distance from the end of the collet to the tip of the electrode

Question 22

Stickout

Answer 22

The distance from the end of the nozzle to the tip of the electrode

Question 23

Inert Gas

Answer 23

Gas that does not readily combine with other elements, ex: Argon and Helium

Question 24

Postflow

Answer 24

The flow of shielding gas after the arc is extinguished

Question 25

What is the general rule when applying postflow?

Answer 25

1 sec of postflow for every 10 amps

Question 26

What is the benefit of postflow?

Answer 26

Ensures that the weld zone has cooled enough to prevent oxidation from exposure to the atmosphere

Question 27

What is the benefit of preflow?

Answer 27

Ensures that the shielding gas is present during arc starting. Use sparingly, if timer is too high, results in wasted gas and arc will not start until timer runs out

Question 28

Where can remote current controls be located?

Answer 28

They can be foot operated with a pedal or located on the torch and operated by finger or hand

Question 29

What is the function of a remote current control?

Answer 29

Starts the flow of electricity and shielding gas and controls the amount of amperage sent to the torch

Question 30

Rheostat

Answer 30

A variable resistor used to control the flow of electric current by adjusting resistance

Question 31

What type of shielding gas is most commonly used?

Answer 31

Straight argon

Question 32

What happens when no shielding gas is used?

Answer 32

Porosity in the weld

Question 33

Autogenous Weld

Answer 33

A weld made without the addition of filler metal

Question 34

What advantages are there to using filler metal?

Answer 34

Reinforce the joint (especially butt and T-joints) and reduce weld cracking

Question 35

What is another name for tungsten in European countries?

Answer 35

Wolfram

Question 36

What is tungsten's symbol on the periodic table?

Answer 36

W which is derived from Wolfram

Question 37

What is the dip technique?

Answer 37

A method for adding filler metal to the weld with an in-and-out motion of the filler rod to the leading edge of the puddle

Question 38

ER70S-X, What does the E represent?

Answer 38

Electrode

Question 39

ER70S-X, What does the R represent?

Answer 39

Bare Rod

Question 40

ER70S-X, What does the 70 represent?

Answer 40

Tensile strength in 1000s of psi, i.e: 70,000psi

Question 41

ER70S-X, What does the S represent?

Answer 41

Solid Metal

Question 42

ER70S-X, What does the X represent?

Answer 42

The chemical composition revision with numbers 2-7

Question 43

How do you protect the filler metal from contamination?

Answer 43

By keeping the end of the rod in the argon shield during and after welding

Question 44

What do you do when the filler metal becomes contaminated/oxidized?

Answer 44

Cut the end off before restarting

Question 45

Which polarity should be used when welding aluminum?

Answer 45

AC - Alternating Current

Question 46

What is another name for GTAW?

Answer 46

TIG and heliarc

Question 47

What are the advantages of alloyed tungsten electrodes over pure tungsten electrodes?

Answer 47

Last longer and have a higher current carrying capacity

Question 48

What should the shielding gas flow rate be set to?

Answer 48

According to the manufacturer specification

Question 49

What are the advantages to TIG welding?

Answer 49

Capable to weld in all positions, can join nearly all metals, no slag

Question 50

What is a disadvantage to TIG welding?

Answer 50

Slower welding speed

Question 51

What shielding gas is most efficient when welding aluminum?

Answer 51

100% Argon

Question 52

What allows TIG to weld very thin metal possible?

Answer 52

The high degree of arc control

Question 53

What is a disadvantage to using 2% thoriated tungsten electrodes?

Answer 53

The electrodes give off radiation while grinding

Question 54

When does tungsten spitting most commonly occur?

Answer 54

When current is set too high for pure tungsten electrodes

Question 55

What happens when tungsten spitting occurs?

Answer 55

Tungsten inclusions in the weld

Question 56

What kind of tungsten electrode helps improve low-current arc starting?

Answer 56

Smaller diameter electrodes