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Gas Metal Arc Welding

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Higher 26 to 35 arc volts
Constant current (CC)
Gives arc voltage values to the control system of the feeder
12 to 22 arc volts

2. Why must CO2 cylinders be used in the vertical position?
Constant voltage (CV)
To prevent drawing of liquid CO2 (Carbon Dioxide)
Cause flaking - which can clog the liner and contact tube
15 feet (4.5 meters)

3. What is a solenoid valve and what actuates it?
...
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Constant- speed wire feeders and Voltage- sennsing wire feeders
Puddle fluidity

4. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Cause flaking - which can clog the liner and contact tube
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
The resistace to electrical current flow increases with it. Causing the electrode to heat
Constant- speed wire feeders and Voltage- sennsing wire feeders

5. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Speed of the feed motor and - starting / stopping electrode feed
Pressure vessels and the piping industry
Aluminum wire
Higher 26 to 35 arc volts

6. What type of power source is used with a constant speed wire feeder?
Constant voltage (CV)
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Wire feeds smoothly (yet will slip should a problem occur in the gun)
The negative side of a welding unit

7. Why is the term GMAW preferred over MIG or MAG?
Welding process that joins metals by heating them with an electric arc
National Electrical Manufactures Association
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These terms are quite restrictive and often technically incorrect

8. List the basic equipment requirements for the GMAW process
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
By there current carrying capacity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Guns

9. What output on the welding machine is used to rate the duty cycle?
Minutes of elapsed time continually run (out of 10 minutes)
Constant- speed wire feeders and Voltage- sennsing wire feeders
Duty cycle
1/4 inch to 1/2 inch

10. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
12 to 22 arc volts
Aluminum wire
The time rate of response for the current rise and fall

11. What controls amperage when using GMAW?
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Wire feed speed
When the filler wire is in direct contract with the base metal
Penetration and burn - off rate of the electrode

12. What does the term GMAW identify?
3
Gas metal arc welding
Shielding the molten weld metal from atmospheric contamination
Speed of the feed motor and - starting / stopping electrode feed

13. What is the key advantage of short circuiting transfer?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Higher 26 to 35 arc volts
Constant current (CC)
Minimum distortion due to low heat input

14. List several industries that would use GMAW
Pressure vessels and the piping industry
Shielding the molten weld metal from atmospheric contamination
15 feet (4.5 meters)
Generally not as accurate

15. What is another term for electrode holders for GMAW?
To prevent leakage - Carbon Dioxide (CO2)
Guns
The Arc voltage
These terms are quite restrictive and often technically incorrect

16. What is the main purpose of 'slope'?
The Arc voltage
Pressure vessels and the piping industry
To limit the short circuiting current so that spatter is reduced
3

17. What is the required arc voltage used for short circuit transfer?
The negative side of a welding unit
SMAW - GTAW
Duty cycle
12 to 22 arc volts

18. What is the purpose of the shielding gas used in GMAW?
Minutes of elapsed time continually run (out of 10 minutes)
Shielding the molten weld metal from atmospheric contamination
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V groove or U groove

19. What is the maximum distance that hard wire can be successfully pushed?
15 feet (4.5 meters)
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...

20. With straight polarity where is 2/3 of the arc energy?
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
The negative side of a welding unit
Constant voltage (CV)
DCEP (Direct Current Electrode Positive) Reverse Polarity

21. List the factors that determine the mode of metal transfer
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Cause flaking - which can clog the liner and contact tube
Gas metal arc welding
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

22. What 2 controls are found on a GMAW set- up?
Wire feed speed
Gas metal arc welding
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Wire feed speed - Voltage control

23. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
15 feet (4.5 meters)
(DCEP) Direct Current Electrode Positive or Reverse polarity
3
Push type: Wire is fed by a set of drive rolls located in the wire feed unit - Pull type: Drive rolls mounted in the gun itself - Push- pull type: Combination of the two

24. What does inductance control?
The time rate of response for the current rise and fall
Gives arc voltage values to the control system of the feeder
1/4 inch to 1/2 inch
5.8 to 12.5 L/min

25. A pull type drive system is usually used on what type of material?
3
The time rate of response for the current rise and fall
Constant voltage (CV)
Aluminum wire

26. What type of power source is commonly used with a voltage sensing wire feeder?
V groove or U groove
Constant current (CC)
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
12 to 22 arc volts

27. List 3 wire drive systems and give a short description of each
Wire feed speed - Voltage control
Push type: Wire is fed by a set of drive rolls located in the wire feed unit - Pull type: Drive rolls mounted in the gun itself - Push- pull type: Combination of the two
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Penetration and burn - off rate of the electrode

28. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Generally not as accurate
Dry ice can form within the flow control openings and cause blockage of shielding gas
Aluminum wire
Constant voltage (CV)

29. What is the effect of too much slope?
Pressure vessels and the piping industry
Insufficient current to melt the wire off cleanly
12 to 22 arc volts
When the filler wire is in direct contract with the base metal

30. How many times per second does short circuiting take place?
Wire feed speed
Reducing the gas source pressure to a constant working pressure
20 to 200 times per second
Motor driven generators - Transformer rectifiers - and Inverter designs

31. What does the wire feeder control?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
V groove or U groove
Speed of the feed motor and - starting / stopping electrode feed
Penetration and burn - off rate of the electrode

32. What controls the wire speed on a voltage sensing wire feeder?
To prevent leakage - Carbon Dioxide (CO2)
...
The Arc voltage
Pressure - The rate of flow of a shielding gas

33. Draw a typical volt amp curve for a machine that is designed for GMAW
1/4 inch to 1/2 inch
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85%
Flux cored wires

34. What does a flowmeter do and what does it measure?
Controls the rate of flow of a shielding gas to the gun nozzle
Gives arc voltage values to the control system of the feeder
The Arc voltage
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35. What processes are constant current (CC) power sources designed to be used with?
SMAW - GTAW
Push type: Wire is fed by a set of drive rolls located in the wire feed unit - Pull type: Drive rolls mounted in the gun itself - Push- pull type: Combination of the two
Welding process that joins metals by heating them with an electric arc
AWS and CSA

36. Regulators control_____________ flowmeters SHOW____________.
Dry ice can form within the flow control openings and cause blockage of shielding gas
Minimum distortion due to low heat input
Pressure - The rate of flow of a shielding gas
The Arc voltage

37. What effect does increasing and decreasing the inductance have on the weld?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Motor driven generators - Transformer rectifiers - and Inverter designs
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
The negative side of a welding unit

38. What happens when the electrode extension is increased?
Wire feed speed - Voltage control
20 to 200 times per second
The negative side of a welding unit
The resistace to electrical current flow increases with it. Causing the electrode to heat

39. Why is a line heater required when using GMAW?
When the filler wire is in direct contract with the base metal
Controls the rate of flow of a shielding gas to the gun nozzle
By there current carrying capacity
Dry ice can form within the flow control openings and cause blockage of shielding gas

40. What is the recommended electrode stick- out for .035 solid wire?
1/4 inch to 1/2 inch
Speed of the feed motor and - starting / stopping electrode feed
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

41. List the three methods of metal transfer with GMAW
Constant- speed wire feeders and Voltage- sennsing wire feeders
By there current carrying capacity
Short- circuiting transfer - Globular transfer - Spray transfer
The negative side of a welding unit

42. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
...
Shielding the molten weld metal from atmospheric contamination
When the filler wire is in direct contract with the base metal

43. Why is a fiber washer required and what cylinder gas requires it?
Dry ice can form within the flow control openings and cause blockage of shielding gas
(DCEP) Direct Current Electrode Positive or Reverse polarity
To prevent leakage - Carbon Dioxide (CO2)
Gas metal arc welding

44. What is the preferred drive roll design for solid wires?
When the filler wire is in direct contract with the base metal
V groove or U groove
Cause flaking - which can clog the liner and contact tube
Push type: Wire is fed by a set of drive rolls located in the wire feed unit - Pull type: Drive rolls mounted in the gun itself - Push- pull type: Combination of the two

45. What wire are knurled drive rolls most commonly used on?
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Flux cored wires
Guns
DCEP (Direct Current Electrode Positive) Reverse Polarity

46. What is an advantage of pulsed arc transfer with GMAW?
Higher 26 to 35 arc volts
DCEP (Direct Current Electrode Positive) Reverse Polarity
The resistace to electrical current flow increases with it. Causing the electrode to heat
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

47. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
Penetration and burn - off rate of the electrode
These terms are quite restrictive and often technically incorrect
The Arc voltage
85%

48. What current and polarity is generally used with GMAW?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Voltage is the force that overcomes resistance to allow amperage flow
Constant current (CC)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

49. When is the metal transferred with short circuit transfer?
Generally not as accurate
Pressure vessels and the piping industry
When the filler wire is in direct contract with the base metal
Short- circuiting transfer - Globular transfer - Spray transfer

50. Why is globular transfer generally avoided with GMAW?
AWS and CSA
Dry ice can form within the flow control openings and cause blockage of shielding gas
Spatter problems and poor weld appearance
Wire feed speed - Voltage control