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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. Draw a typical volt amp curve for a machine that is designed for GMAW
Higher 26 to 35 arc volts
Minimum distortion due to low heat input
Constant voltage (CV)
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2. What is the effect of too much slope?
The time rate of response for the current rise and fall
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Insufficient current to melt the wire off cleanly
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3. List the factors that determine the mode of metal transfer
To prevent drawing of liquid CO2 (Carbon Dioxide)
To prevent leakage - Carbon Dioxide (CO2)
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
3

4. What current and polarity is generally used with GMAW?
DCEP (Direct Current Electrode Positive) Reverse Polarity
5.8 to 12.5 L/min
Wire feeds smoothly (yet will slip should a problem occur in the gun)
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5. Why is a fiber washer required and what cylinder gas requires it?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
5.8 to 12.5 L/min
Controls the rate of flow of a shielding gas to the gun nozzle
To prevent leakage - Carbon Dioxide (CO2)

6. What is the preferred drive roll design for solid wires?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
V groove or U groove
5.8 to 12.5 L/min

7. What does the abbreviation NEMA stand for?
Minimum distortion due to low heat input
The time rate of response for the current rise and fall
Wire feeds smoothly (yet will slip should a problem occur in the gun)
National Electrical Manufactures Association

8. How many times per second does short circuiting take place?
20 to 200 times per second
Spatter problems and poor weld appearance
DCEP (Direct Current Electrode Positive) Reverse Polarity
Short- circuiting transfer - Globular transfer - Spray transfer

9. List 3 forms compressed gases may be supplied for welding
The Arc voltage
Spatter problems and poor weld appearance
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
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10. What is the maximum distance that hard wire can be successfully pushed?
3
Gives arc voltage values to the control system of the feeder
15 feet (4.5 meters)
To prevent drawing of liquid CO2 (Carbon Dioxide)

11. In the GMAW process what does amperage control?
Aluminum wire
Wire feed speed - Voltage control
Shielding the molten weld metal from atmospheric contamination
Penetration and burn - off rate of the electrode

12. What does voltage do in an electrical circuit?
15 feet (4.5 meters)
Gas metal arc welding
Voltage is the force that overcomes resistance to allow amperage flow
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

13. 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
15 feet (4.5 meters)
20 to 200 times per second
To limit the short circuiting current so that spatter is reduced

14. How are GMAW guns rated?
Speed of the feed motor and - starting / stopping electrode feed
To prevent drawing of liquid CO2 (Carbon Dioxide)
By there current carrying capacity
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15. What is the key advantage of short circuiting transfer?
Minimum distortion due to low heat input
Insufficient current to melt the wire off cleanly
DCEP (Direct Current Electrode Positive) Reverse Polarity
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

16. What power sources are used with the GMAW Process?
...
To limit the short circuiting current so that spatter is reduced
Motor driven generators - Transformer rectifiers - and Inverter designs
Wire feed speed - Voltage control

17. Why must CO2 cylinders be used in the vertical position?
Puddle fluidity
Minimum distortion due to low heat input
To prevent drawing of liquid CO2 (Carbon Dioxide)
Dry ice can form within the flow control openings and cause blockage of shielding gas

18. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
To prevent leakage - Carbon Dioxide (CO2)
Gives arc voltage values to the control system of the feeder
Spatter problems and poor weld appearance

19. What controls the wire speed on a voltage sensing wire feeder?
The Arc voltage
The negative side of a welding unit
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5.8 to 12.5 L/min

20. List the three methods of metal transfer with GMAW
Constant voltage (CV)
Puddle fluidity
Short- circuiting transfer - Globular transfer - Spray transfer
When the filler wire is in direct contract with the base metal

21. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Voltage is the force that overcomes resistance to allow amperage flow
Flux cored wires
Higher 26 to 35 arc volts
Spatter problems and poor weld appearance

22. In the GMAW process what does voltage control?
Cause flaking - which can clog the liner and contact tube
5.8 to 12.5 L/min
Puddle fluidity
20 to 200 times per second

23. What 2 controls are found on a GMAW set- up?
Constant voltage (CV)
Duty cycle
Wire feed speed - Voltage control
Guns

24. What would be an indication that the drive roll pressure is adjusted correctly?
Penetration and burn - off rate of the electrode
To prevent leakage - Carbon Dioxide (CO2)
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Aluminum wire

25. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Wire feed speed - Voltage control
Cause flaking - which can clog the liner and contact tube
Guns
Reducing the gas source pressure to a constant working pressure

26. Give a description of 'pinch effect'
Guns
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Speed of the feed motor and - starting / stopping electrode feed
Constant- speed wire feeders and Voltage- sennsing wire feeders

27. List 3 wire drive systems and give a short description of each
To prevent drawing of liquid CO2 (Carbon Dioxide)
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 Current - Filler wire diameter - arc length - type of shielding - position of the weld
1/4 inch to 1/2 inch

28. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Spatter problems and poor weld appearance
Duty cycle
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
To prevent leakage - Carbon Dioxide (CO2)

29. What is the main purpose of 'slope'?
AWS and CSA
Dry ice can form within the flow control openings and cause blockage of shielding gas
To limit the short circuiting current so that spatter is reduced
DCEP (Direct Current Electrode Positive) Reverse Polarity

30. What is a typical flow rate of CO2 for short circuit transfer?
Speed of the feed motor and - starting / stopping electrode feed
5.8 to 12.5 L/min
These terms are quite restrictive and often technically incorrect
When the filler wire is in direct contract with the base metal

31. Why is globular transfer generally avoided with GMAW?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Spatter problems and poor weld appearance
Penetration and burn - off rate of the electrode
85%

32. What does a flowmeter do and what does it measure?
12 to 22 arc volts
Dry ice can form within the flow control openings and cause blockage of shielding gas
Controls the rate of flow of a shielding gas to the gun nozzle
To limit the short circuiting current so that spatter is reduced

33. What wire are knurled drive rolls most commonly used on?
Flux cored wires
Constant current (CC)
V groove or U groove
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34. What is the purpose of the shielding gas used in GMAW?
Speed of the feed motor and - starting / stopping electrode feed
Constant voltage (CV)
Shielding the molten weld metal from atmospheric contamination
By there current carrying capacity

35. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Shielding the molten weld metal from atmospheric contamination
Welding process that joins metals by heating them with an electric arc
These terms are quite restrictive and often technically incorrect
Generally not as accurate

36. Why is a line heater required when using GMAW?
Generally not as accurate
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
Dry ice can form within the flow control openings and cause blockage of shielding gas

37. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
Pressure - The rate of flow of a shielding gas
Reducing the gas source pressure to a constant working pressure
Spatter problems and poor weld appearance
85%

38. A pull type drive system is usually used on what type of material?
Gas metal arc welding
Reducing the gas source pressure to a constant working pressure
Aluminum wire
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

39. What controls amperage when using GMAW?
Wire feed speed
Motor driven generators - Transformer rectifiers - and Inverter designs
Wire feeds smoothly (yet will slip should a problem occur in the gun)
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

40. What does the term GMAW identify?
Gas metal arc welding
(DCEP) Direct Current Electrode Positive or Reverse polarity
V groove or U groove
Higher 26 to 35 arc volts

41. What is the required arc voltage used for short circuit transfer?
12 to 22 arc volts
Speed of the feed motor and - starting / stopping electrode feed
These terms are quite restrictive and often technically incorrect
Aluminum wire

42. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
To prevent leakage - Carbon Dioxide (CO2)
Guns
Welding process that joins metals by heating them with an electric arc
3

43. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
Aluminum wire
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(DCEP) Direct Current Electrode Positive or Reverse polarity
Higher 26 to 35 arc volts

44. What is the purpose of a regulator and what does it indicate on its gauges?
Reducing the gas source pressure to a constant working pressure
To prevent drawing of liquid CO2 (Carbon Dioxide)
Gives arc voltage values to the control system of the feeder
Minutes of elapsed time continually run (out of 10 minutes)

45. List the basic equipment requirements for the GMAW process
The time rate of response for the current rise and fall
Higher 26 to 35 arc volts
DCEP (Direct Current Electrode Positive) Reverse Polarity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

46. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
AWS and CSA
Constant- speed wire feeders and Voltage- sennsing wire feeders
The time rate of response for the current rise and fall
(DCEP) Direct Current Electrode Positive or Reverse polarity

47. Why is the term GMAW preferred over MIG or MAG?
Puddle fluidity
3
These terms are quite restrictive and often technically incorrect
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

48. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
The time rate of response for the current rise and fall
V groove or U groove
...
Speed of the feed motor and - starting / stopping electrode feed

49. What are the 2 types of wire feeders available?
The time rate of response for the current rise and fall
Constant- speed wire feeders and Voltage- sennsing wire feeders
AWS and CSA
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

50. Give a brief description of the GMAW process
Spatter problems and poor weld appearance
Minutes of elapsed time continually run (out of 10 minutes)
Cause flaking - which can clog the liner and contact tube
Welding process that joins metals by heating them with an electric arc