p10-2 task 4

Question 1

tungsten is used for GTAW electrodes because it

1. has a very high melting point
2. transfers electrons across at a very slow rate
3. is highly magnetic
4. has low thermal conductivity

Answer 1

a. has a very high melting point

Question 2

match the correct classification codes with the GTAW electrode compositions listed below.

1. ___ 2% thorium added
2. ___ pure tungsten
3. ___ 1% thorium added
4. ___ 0.15-0.40% zirconium added
5. ___ 1 or 2% thorium strip added
6. EWP
7. EWTh-1
8. EWTh-2
9. EWTh-3
10. EWZr

Answer 2

1. _c__ 2% thorium added
2. _a__ pure tungsten
3. _b__ 1% thorium added
4. _e__ 0.15-0.40% zirconium added
5. _d__ 1 or 2% thorium strip added
6. EWP
7. EWTh-1
8. EWTh-2
9. EWTh-3
10. EWZr

Question 3

match the correct colour code with each type of GTAW electrode listed below.

1. ___ EWP
2. ___ EWTh-1
3. ___ EWTh-2
4. ___ EWTh-3
5. ___ EWZr
6. red
7. blue
8. green
9. yellow
10. brown

Answer 3

1. _c__ EWP
2. _d__ EWTh-1
3. _a__ EWTh-2
4. _b__ EWTh-3
5. _e__ EWZr
6. red
7. blue
8. green
9. yellow
10. brown

Question 4

which of the following tungsten electrodes is widely used for precision work on aluminum and alloys?

1. 1% thoriated tungsten
2. 2% thoriated tungsten
3. pure tungsten
4. zirconium tungsten

Answer 4

d. zirconium tungsten

Question 5

which electrode finish is recommended for precision work?

1. standard
2. ground

Answer 5

b. ground

Question 6

which electrode and is used with DCEN?

1. pointed end
2. rounded end
3. balled end
4. squared end

Answer 6

a. pointed end

Question 7

which electrode end is used with DCEP?

1. pointed end
2. rounded end
3. tapered - balled end
4. squared end

Answer 7

c. tapered - balled end

Question 8

which electrode end is used with ACHF?

1. pointed end
2. rounded end
3. balled end
4. squared end

Answer 8

b. rounded end

Question 9

the pointed end can be shaped by grinding or by

1. chiseling
2. filing
3. sanding
4. dipping in a chemical compound

Answer 9

d. dipping in a chemical compound

Question 10

the length of the tapered portion should be approximately

1. 1 to 1 ½ electrode diameter
2. 2 to 2 ½ electrode diameter
3. 3 to 3 ½ electrode diameter
4. 4 to 4 ½ electrode diameter

Answer 10

b. 2 to 2 ½ electrode diameter

Question 11

if you are welding with 150 A, you should maintain the shielding gas post flow for

1. 8 seconds
2. 10 seconds
3. 12 seconds
4. 15 seconds

Answer 11

d. 15 seconds

Question 12

which of the following is the most common source of electrode contamination?

1. contact between the electrode and the weld puddle or filler rod
2. laminar shielding gas flow
3. poor contact between collet and electrode
4. higher than recommended currents for the electrode

Answer 12

a. contact between the electrode and the weld puddle or filler rod

Question 13

if the distance the electrode protrudes from the collet is too great there will be

1. excessive spitting from the electrode
2. heat buildup in the body of the electrode
3. rapid deterioration of the electrode tip
4. an increased risk of voltage drop

Answer 13

b. heat buildup in the body of the electrode

Question 14

which type of electrode is least likely to become contaminated if it touches the weld puddle?

1. pure tungsten
2. thoriated tungsten
3. zirconium tungsten
4. striped tungsten

Answer 14

b. thoriated tungsten

Question 15

which type of electrode is best suited for welding with DC?

1. thoriated tungsten
2. pure tungsten
3. zirconium tungsten
4. Striped tungsten

Answer 15

a. thoriated tungsten

Question 16

which electrode combines good balling and stability characteristics with higher current-carrying capacity?

1. EWTh-1
2. EWTh-2
3. EWTh-3
4. EWZr

Answer 16

c. EWTh-3