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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. In the GMAW process what does voltage control?
Puddle fluidity
AWS and CSA
Short- circuiting transfer - Globular transfer - Spray transfer
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

2. What does voltage do in an electrical circuit?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Voltage is the force that overcomes resistance to allow amperage flow
(DCEP) Direct Current Electrode Positive or Reverse polarity

3. 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
Spatter problems and poor weld appearance
Higher 26 to 35 arc volts
The Arc voltage

4. How many times per second does short circuiting take place?
20 to 200 times per second
To limit the short circuiting current so that spatter is reduced
Insufficient current to melt the wire off cleanly
By there current carrying capacity

5. What is the disadvantage of the gauge preset type of regulator/flowmeter?
The Arc voltage
Wire feed speed
85%
Generally not as accurate

6. Give a brief description of the GMAW process
These terms are quite restrictive and often technically incorrect
Duty cycle
Welding process that joins metals by heating them with an electric arc
The resistace to electrical current flow increases with it. Causing the electrode to heat

7. What is the key advantage of short circuiting transfer?
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Wire feed speed - Voltage control
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Minimum distortion due to low heat input

8. What does a flowmeter do and what does it measure?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Insufficient current to melt the wire off cleanly
Controls the rate of flow of a shielding gas to the gun nozzle
Constant- speed wire feeders and Voltage- sennsing wire feeders

9. What controls amperage when using GMAW?
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Duty cycle
Higher 26 to 35 arc volts
Wire feed speed

10. Why is a fiber washer required and what cylinder gas requires it?
Pressure vessels and the piping industry
To prevent leakage - Carbon Dioxide (CO2)
Higher 26 to 35 arc volts
20 to 200 times per second

11. List the basic equipment requirements for the GMAW process
To prevent drawing of liquid CO2 (Carbon Dioxide)
The Arc voltage
Constant current (CC)
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

12. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Puddle fluidity
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When the filler wire is in direct contract with the base metal
Gives arc voltage values to the control system of the feeder

13. Draw a typical volt amp curve for a machine that is designed for GMAW
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AWS and CSA
Minutes of elapsed time continually run (out of 10 minutes)
3

14. What is the maximum distance that hard wire can be successfully pushed?
Minutes of elapsed time continually run (out of 10 minutes)
15 feet (4.5 meters)
Spatter problems and poor weld appearance
3

15. Why is globular transfer generally avoided with GMAW?
Pressure vessels and the piping industry
Insufficient current to melt the wire off cleanly
1/4 inch to 1/2 inch
Spatter problems and poor weld appearance

16. Why must CO2 cylinders be used in the vertical position?
5.8 to 12.5 L/min
To prevent drawing of liquid CO2 (Carbon Dioxide)
Constant voltage (CV)
Generally not as accurate

17. Regulators control_____________ flowmeters SHOW____________.
Pressure - The rate of flow of a shielding gas
(DCEP) Direct Current Electrode Positive or Reverse polarity
Wire feed speed
Speed of the feed motor and - starting / stopping electrode feed

18. What does the term GMAW identify?
Flux cored wires
Short- circuiting transfer - Globular transfer - Spray transfer
Gas metal arc welding
Pressure vessels and the piping industry

19. What is a typical flow rate of CO2 for short circuit transfer?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
5.8 to 12.5 L/min
The Arc voltage
Insufficient current to melt the wire off cleanly

20. List 3 forms compressed gases may be supplied for welding
V groove or U groove
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
The resistace to electrical current flow increases with it. Causing the electrode to heat
To prevent drawing of liquid CO2 (Carbon Dioxide)

21. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Dry ice can form within the flow control openings and cause blockage of shielding gas
Duty cycle
Motor driven generators - Transformer rectifiers - and Inverter designs
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22. What is the purpose of a regulator and what does it indicate on its gauges?
Flux cored wires
Reducing the gas source pressure to a constant working pressure
V groove or U groove
Welding process that joins metals by heating them with an electric arc

23. What is the purpose of the shielding gas used in GMAW?
By there current carrying capacity
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Shielding the molten weld metal from atmospheric contamination
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

24. What is a solenoid valve and what actuates it?
Aluminum wire
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
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

25. When is the metal transferred with short circuit transfer?
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V groove or U groove
When the filler wire is in direct contract with the base metal
3

26. What is an advantage of pulsed arc transfer with GMAW?
Duty cycle
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Constant- speed wire feeders and Voltage- sennsing wire feeders
Pressure - The rate of flow of a shielding gas

27. How are GMAW guns rated?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
By there current carrying capacity
Guns

28. With straight polarity where is 2/3 of the arc energy?
The negative side of a welding unit
V groove or U groove
DCEP (Direct Current Electrode Positive) Reverse Polarity
Motor driven generators - Transformer rectifiers - and Inverter designs

29. What processes are constant current (CC) power sources designed to be used with?
SMAW - GTAW
Insufficient current to melt the wire off cleanly
Constant current (CC)
Penetration and burn - off rate of the electrode

30. What would be an indication that the drive roll pressure is adjusted correctly?
20 to 200 times per second
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Constant- speed wire feeders and Voltage- sennsing wire feeders
To prevent leakage - Carbon Dioxide (CO2)

31. What does the wire feeder control?
Reducing the gas source pressure to a constant working pressure
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
AWS and CSA
Speed of the feed motor and - starting / stopping electrode feed

32. What does inductance control?
SMAW - GTAW
Pressure - The rate of flow of a shielding gas
The time rate of response for the current rise and fall
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

33. What current and polarity is generally used with GMAW?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
DCEP (Direct Current Electrode Positive) Reverse Polarity
Short- circuiting transfer - Globular transfer - Spray transfer
Reducing the gas source pressure to a constant working pressure

34. What power sources are used with the GMAW Process?
By there current carrying capacity
Reducing the gas source pressure to a constant working pressure
Insufficient current to melt the wire off cleanly
Motor driven generators - Transformer rectifiers - and Inverter designs

35. A pull type drive system is usually used on what type of material?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Aluminum wire
Generally not as accurate
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

36. List the three methods of metal transfer with GMAW
The Arc voltage
Minimum distortion due to low heat input
Speed of the feed motor and - starting / stopping electrode feed
Short- circuiting transfer - Globular transfer - Spray transfer

37. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
5.8 to 12.5 L/min
V groove or U groove
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

38. What is another term for electrode holders for GMAW?
1/4 inch to 1/2 inch
Duty cycle
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
Guns

39. What effect does increasing and decreasing the inductance have on the weld?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
By there current carrying capacity
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Cause flaking - which can clog the liner and contact tube

40. What type of power source is used with a constant speed wire feeder?
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Generally not as accurate
Wire feed speed
Constant voltage (CV)

41. What wire are knurled drive rolls most commonly used on?
Constant current (CC)
Flux cored wires
Dry ice can form within the flow control openings and cause blockage of shielding gas
V groove or U groove

42. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
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By there current carrying capacity
20 to 200 times per second
Puddle fluidity

43. List the factors that determine the mode of metal transfer
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Flux cored wires
The resistace to electrical current flow increases with it. Causing the electrode to heat
To prevent leakage - Carbon Dioxide (CO2)

44. What is the main purpose of 'slope'?
Speed of the feed motor and - starting / stopping electrode feed
Voltage is the force that overcomes resistance to allow amperage flow
Pressure vessels and the piping industry
To limit the short circuiting current so that spatter is reduced

45. List several industries that would use GMAW
Pressure vessels and the piping industry
12 to 22 arc volts
Flux cored wires
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

46. Why is a line heater required when using GMAW?
V groove or U groove
Dry ice can form within the flow control openings and cause blockage of shielding gas
Pressure - The rate of flow of a shielding gas
Motor driven generators - Transformer rectifiers - and Inverter designs

47. What are the 2 types of wire feeders available?
Welding process that joins metals by heating them with an electric arc
Constant- speed wire feeders and Voltage- sennsing wire feeders
The negative side of a welding unit
Penetration and burn - off rate of the electrode

48. What controls the wire speed on a voltage sensing wire feeder?
The Arc voltage
Generally not as accurate
V groove or U groove
Gas metal arc welding

49. Give a description of 'pinch effect'
The Arc voltage
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Short- circuiting transfer - Globular transfer - Spray transfer
To prevent drawing of liquid CO2 (Carbon Dioxide)

50. List 3 wire drive systems and give a short description of each
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
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
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5.8 to 12.5 L/min