GTAW Equipment

Question 1

At what amperage should a water-cooling system be used? And why would you use one?

Answer 1

150A or higher and to cool down the lines and the collet

Question 2

What is it called when you don’t add filler metal to the weld? And what is this most commonly seen used on?

Answer 2

Autogrnous

Thin or light-gauge materials, flanges or corner joints

Question 3

Why was the GTAW process first made? What is GTAW usually used for in pipe fabricating shops and why isn’t it used for the whole weld?

Answer 3

To weld thin materials and difficult to weld metals such as corrosion resistant alloys, aluminum, titanium and magnesium.

Its used for critical root beads it virtually eliminates the problems of slag entrapment. The weld is then completed using an SMAW process, which has a higher deposition rate

Question 4

What can GTAW be used on and in what position?

What is the thickest metal usually welded on with GTAW?

Answer 4

GTAW can be used on virtually all metals and in all positions.

Because of the low deposition rate the thickest metal welded with GTAW is usually 3/8 in.

Question 5

What causes ozone to be created in the GTAW process and why?

Answer 5

Due to less smoke and fumes produced in GTAW the arc may emit intense UV radiations. The increased level of UV radiations can produce ozone

Question 6

How is phosgene created?

Answer 6

Welding on a piece of metal that has had decreasing or cleaning agents on it.

Question 7

What are important features about the CC power sources used in GTAW?

Answer 7

They have a steep volt-qmp output curve and good controls at low amperages.

Question 8

What do the 3 different types of polarity do?

Answer 8

DCEN- Deep and narrow with 70% heat on the work end and 30% directed at the electrode

DCEP- Shallow and wide with 30% on the work 3nd and 70% on electrode

AC- Balanced between the both 50% heat on the work end and 50% on the electrode

Question 9

What are the 3 different polarities used for?

Answer 9

DCEN- Used to weld steel, stainless steel, copper alloys, nickel alloys, titanium, beryllium and think sections of aluminum. A smaller electrode can be used since the heat is.

DCEP- Is used when you need less penetration but more cleaning action

When AC is used it combines both penetration and cleaning action but it has an uneven cycle becuase when it switched from DCEN to DCEP it doesn’t have the cleaning action and electrons don’t transfer as easy it doesn’t ignite as fast.

Question 10

What are the 3 different ignition types?

Answer 10

Scratch, lift and high frequency

Question 11

How does the high frequency start work?

What does the current operate at?

Answer 11

The electrode is brought to within 5mm and the high voltage, high-frequency current can cross the gap between electrode and workpiece bt ionizing the gas across the gap.

50 000 to 3 million and up to 3000V

Question 12

What is pre-flow and post-flow used for?

Answer 12

Pre-flow clears the air and moisture from the torch to prevent contamination during the initial stages of the weld

Post-flow provides shielding gas to the weld zone after the arc is extinguished. This ensures that the weld zone is cooled enough to prevent oxidation from exposure to the atmosphere.

Post-flow time is usually set to 1 second for every 10amps of welding current

Question 13

What is caused if your gas flow rate is to high?

Answer 13

Turbulence is caused a mixing of the the atmosphere with the shielding gas that contaminates the weld zone

Question 14

What is a typical water pressure valve and what is a usual flow rate? What happens if your water pressure is to high?

Answer 14

245 kPa (35 psi) and a flow rate of 1L per min.

If your water pressure is to high you can cause line leaks and gasket blowouts

Question 15

What are the 2 types of amperage controls?

Answer 15

Torch amperage control that you can put on your gun or a specialized torch or a foot petal

Question 16

What is Ar and He used for in GTAW?

Answer 16

Argon (Ar) is used to weld most metals because it can use lower arc voltages making it easier to weld thinner metals without burn-through.

Helium (He) is lighter than air so it is preferred for vertical and overhead. It requires greater voltages and amperage than argon leading to higher heat inputs and deeper penetration. It is relatively expensive and not usually used alone a mixture of argon and hellium is used to get a combination of both.

Question 17

What is the typical range of a primary flow rate?

Answer 17

5 to 15 lmp (10.6 to 31.9 cfh) for primary flow rate

2.4 to 9.4 lpm (5 to 20 cfh) for back purging

Question 18

What does a gan lens do and whats it made of?

Answer 18

Improves the shielding gas coverage by creating a laminar flow of gas before it leaves the cup and its made of several layers of mesh

Question 19

What are the shielding cups made of and how are they sized?

Answer 19

Ceramic cups are inexpensive and they can dissipate the heat. They cups go up in numbers and each number goes up in a 1/16 increments

Alumina or aluminum oxide (pink ceramic) are the most popular GTAW cups. They are made of high-temperature shock-resistant ceramic and have excellent insulating properties.

Fused-Quartz gas cups are transparent. Which provided the benefits of visibility to the weld area. They are also known as glass or Pyrex cups. They are the most expensive and rarely used.

Question 20

What is the melting point of tungsten?

Answer 20

3410C (6170F)

Question 21

What color is pure tungsten and what is it used for?

Answer 21

It has a green color band and uses AC welding current for aluminum and magnesium. It has a poor starting characteristic and is no longer used much

Question 22

Explain thoriated tungsten

Answer 22

2% thoriated is the most popular thoriated tungsten used and is identified by carbon steel, stainless steel, titanium, aluminum, and nickel. Its color band is red and AWS classification is EWTh-2

1% use lower amps they are comparably cooler and retain their shape during welding. This makes them ideal for DCEN. However with AC, the arc is difficult to control and tends to wander. These electrodes and sharpened to a point which makes for accurate welding and a smaller heat-affected zone. It is identified by a yellow color band and its classification is EWTh-1

Question 23

Explain Ceriated tungsten

Answer 23

Developed as an alternative to thoriated and can be used with DC and AC

Often used in low-amos applications and on thin shert, small parts, and tubing. Excellent arc starting at low amps and has a grey color band

Question 24

Explain Lanthanated tungsten

Answer 24

Another alternative to thoriated and can use both DC and AC. It has exceptional versatility and combines some of the best attributes found in other tungsten types. Excellent arc starting even at low amps, low consumption, and consistent re-ignition. Lanthanated electrodes is known in the industry as a do-all alternative to both thoriated and ceriated tungsten

1% lanthanated electrodes is EWLa-1 and the color is black

Question 25

Explain Zirconium alloyed tungsten

Answer 25

Have a high resistance to contamination they produce a stable arc and resist arc splitting. Like pure tungsten they form a balled tip and used for welding on aluminum and its alloys with AC. They are recommended for high quality welding. Their current carrying capacity is almost the same as thorium alloyed electrode of the same size. Its AWS classification is EWZr-1 and its color band is brown

Question 26

What is the color band of

0. 8% zirconia oxide color band
1. 5% lanthanum oxide

2% lanthanum oxide

Answer 26

0. 8% zirconia oxide color band -white
1. 5% lanthanum oxide - gold

2% lanthanum oxide - blue

Question 27

What is the typical stick-out for GTAW? What is the distance you should keep your filler rod from the weld pool?

Answer 27

1/8 to 1/4 in.

Your filler rod should be just at the edge of your gas shielding but still enough to be in your gas (around 1/4in away)

Question 28

What is another word for internal concavity?

Answer 28

Suck-back

Question 29

What is the optimal torch angle?

Answer 29

Less than 15° or 75°-80° from the work surface and your filler metal rod is 15° to 20° from the work surface

A work angle of 20° is recommended for flat lap joints

A work angle of 40° 7s recommended for tee joints

Question 30

What are highly conductive metals and should you speed up or slow down your travel speed when welding them?

Answer 30

Copper, aluminum and magnesium are some examples and you should speed up your travel speed

Question 31

What stainless steel rods do you need for these metals:
301,302,304,305,306
304L
316L
317
317L
321
347

Answer 31

301,302,304,305,306       - ER308
304L        -ER 347, 308L
316L         -ER 318, 316L
317           -ER 317
317L          -ER 317
321             -ER 347
347             -ER 347

Question 32

What must be used for multi-pass welding on thicker materials to provide complete protection? What is another solution?

Answer 32

Solar flux can be applied after every pass to provide complete protection

A backing bar with a relief groove can be used to protect the root against oxidation. Normally it is made out of copper for its conductivity so it can act as a heat sink.

Question 33

What is a purge dam?

Answer 33

When doing an open root butt joint on a pipe a purge dam can be used to protect the weld joint from contamination