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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. List several industries that would use GMAW
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Duty cycle
Pressure vessels and the piping industry
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2. What does inductance control?
The time rate of response for the current rise and fall
Minimum distortion due to low heat input
85%
Dry ice can form within the flow control openings and cause blockage of shielding gas

3. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
When the filler wire is in direct contract with the base metal
Wire feed speed
85%
Aluminum wire

4. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Generally not as accurate
3
Shielding the molten weld metal from atmospheric contamination
Gives arc voltage values to the control system of the feeder

5. What is the required arc voltage used for short circuit transfer?
12 to 22 arc volts
Shielding the molten weld metal from atmospheric contamination
Dry ice can form within the flow control openings and cause blockage of shielding gas
85%

6. Why is the term GMAW preferred over MIG or MAG?
AWS and CSA
These terms are quite restrictive and often technically incorrect
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Puddle fluidity

7. What is a typical flow rate of CO2 for short circuit transfer?
5.8 to 12.5 L/min
Flux cored wires
Insufficient current to melt the wire off cleanly
SMAW - GTAW

8. Regulators control_____________ flowmeters SHOW____________.
Pressure - The rate of flow of a shielding gas
Shielding the molten weld metal from atmospheric contamination
5.8 to 12.5 L/min
Constant- speed wire feeders and Voltage- sennsing wire feeders

9. How many times per second does short circuiting take place?
V groove or U groove
20 to 200 times per second
Minutes of elapsed time continually run (out of 10 minutes)
Dry ice can form within the flow control openings and cause blockage of shielding gas

10. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Generally not as accurate
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Reducing the gas source pressure to a constant working pressure

11. What type of power source is used with a constant speed wire feeder?
Constant- speed wire feeders and Voltage- sennsing wire feeders
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
SMAW - GTAW
Constant voltage (CV)

12. What is the maximum distance that hard wire can be successfully pushed?
Motor driven generators - Transformer rectifiers - and Inverter designs
12 to 22 arc volts
15 feet (4.5 meters)
Higher 26 to 35 arc volts

13. What is the recommended electrode stick- out for .035 solid wire?
Shielding the molten weld metal from atmospheric contamination
1/4 inch to 1/2 inch
Gas metal arc welding
When the filler wire is in direct contract with the base metal

14. Why must CO2 cylinders be used in the vertical position?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Generally not as accurate
Guns
Motor driven generators - Transformer rectifiers - and Inverter designs

15. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
V groove or U groove
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Wire feeds smoothly (yet will slip should a problem occur in the gun)

16. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
By there current carrying capacity
Aluminum wire
Cause flaking - which can clog the liner and contact tube

17. List the three methods of metal transfer with GMAW
Duty cycle
Guns
...
Short- circuiting transfer - Globular transfer - Spray transfer

18. What is the main purpose of 'slope'?
...
Speed of the feed motor and - starting / stopping electrode feed
The Arc voltage
To limit the short circuiting current so that spatter is reduced

19. List the factors that determine the mode of metal transfer
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Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Controls the rate of flow of a shielding gas to the gun nozzle

20. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Cause flaking - which can clog the liner and contact tube
Voltage is the force that overcomes resistance to allow amperage flow
Insufficient current to melt the wire off cleanly

21. What type of power source is commonly used with a voltage sensing wire feeder?
Short- circuiting transfer - Globular transfer - Spray transfer
V groove or U groove
Constant current (CC)
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

22. What output on the welding machine is used to rate the duty cycle?
Minutes of elapsed time continually run (out of 10 minutes)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
3
Wire feed speed - Voltage control

23. What power sources are used with the GMAW Process?
85%
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Shielding the molten weld metal from atmospheric contamination
Motor driven generators - Transformer rectifiers - and Inverter designs

24. What 2 controls are found on a GMAW set- up?
Wire feed speed - Voltage control
15 feet (4.5 meters)
AWS and CSA
Motor driven generators - Transformer rectifiers - and Inverter designs

25. What is the purpose of a regulator and what does it indicate on its gauges?
Shielding the molten weld metal from atmospheric contamination
Reducing the gas source pressure to a constant working pressure
Wire feed speed - Voltage control
3

26. What 2 organizations designate specifications for GMAW wires?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Reducing the gas source pressure to a constant working pressure
AWS and CSA
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

27. List 3 wire drive systems and give a short description of each
Motor driven generators - Transformer rectifiers - and Inverter designs
When the filler wire is in direct contract with the base metal
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
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

28. In the GMAW process what does voltage control?
Higher 26 to 35 arc volts
Constant current (CC)
Controls the rate of flow of a shielding gas to the gun nozzle
Puddle fluidity

29. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Duty cycle
SMAW - GTAW
1/4 inch to 1/2 inch

30. What would be an indication that the drive roll pressure is adjusted correctly?
V groove or U groove
Guns
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Short- circuiting transfer - Globular transfer - Spray transfer

31. What is another term for electrode holders for GMAW?
Controls the rate of flow of a shielding gas to the gun nozzle
Guns
Motor driven generators - Transformer rectifiers - and Inverter designs
Penetration and burn - off rate of the electrode

32. What does the term GMAW identify?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
5.8 to 12.5 L/min
Gas metal arc welding
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

33. What wire are knurled drive rolls most commonly used on?
Flux cored wires
85%
Cause flaking - which can clog the liner and contact tube
The Arc voltage

34. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
3
Shielding the molten weld metal from atmospheric contamination
(DCEP) Direct Current Electrode Positive or Reverse polarity
Constant- speed wire feeders and Voltage- sennsing wire feeders

35. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
3
Wire feed speed
15 feet (4.5 meters)

36. In the GMAW process what does amperage control?
These terms are quite restrictive and often technically incorrect
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Penetration and burn - off rate of the electrode

37. Why is globular transfer generally avoided with GMAW?
Guns
To prevent leakage - Carbon Dioxide (CO2)
Cause flaking - which can clog the liner and contact tube
Spatter problems and poor weld appearance

38. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Guns
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Constant- speed wire feeders and Voltage- sennsing wire feeders

39. Give a description of 'pinch effect'
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Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
These terms are quite restrictive and often technically incorrect
To prevent drawing of liquid CO2 (Carbon Dioxide)

40. What is the key advantage of short circuiting transfer?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Gives arc voltage values to the control system of the feeder
Minimum distortion due to low heat input

41. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
15 feet (4.5 meters)
AWS and CSA
3

42. Why is a fiber washer required and what cylinder gas requires it?
Short- circuiting transfer - Globular transfer - Spray transfer
Welding process that joins metals by heating them with an electric arc
(DCEP) Direct Current Electrode Positive or Reverse polarity
To prevent leakage - Carbon Dioxide (CO2)

43. What is a solenoid valve and what actuates it?
The time rate of response for the current rise and fall
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
The resistace to electrical current flow increases with it. Causing the electrode to heat
When the filler wire is in direct contract with the base metal

44. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Higher 26 to 35 arc volts
Puddle fluidity
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

45. What does a flowmeter do and what does it measure?
Insufficient current to melt the wire off cleanly
Puddle fluidity
Constant current (CC)
Controls the rate of flow of a shielding gas to the gun nozzle

46. When is the metal transferred with short circuit transfer?
When the filler wire is in direct contract with the base metal
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Duty cycle
Voltage is the force that overcomes resistance to allow amperage flow

47. What does the wire feeder control?
Pressure vessels and the piping industry
Speed of the feed motor and - starting / stopping electrode feed
Pressure - The rate of flow of a shielding gas
Insufficient current to melt the wire off cleanly

48. A pull type drive system is usually used on what type of material?
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Aluminum wire
...
Constant voltage (CV)

49. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
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Spatter problems and poor weld appearance
Short- circuiting transfer - Globular transfer - Spray transfer
...

50. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
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Gives arc voltage values to the control system of the feeder
Pressure vessels and the piping industry
Guns