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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. Give a description of 'pinch effect'
Wire feed speed
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Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
To limit the short circuiting current so that spatter is reduced

2. What effect does increasing and decreasing the inductance have on the weld?
Gives arc voltage values to the control system of the feeder
85%
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
By there current carrying capacity

3. In the GMAW process what does voltage control?
20 to 200 times per second
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Puddle fluidity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

4. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
Constant- speed wire feeders and Voltage- sennsing wire feeders
Constant voltage (CV)
Constant current (CC)
...

5. What would be an indication that the drive roll pressure is adjusted correctly?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Puddle fluidity
Wire feeds smoothly (yet will slip should a problem occur in the gun)
AWS and CSA

6. Why is a fiber washer required and what cylinder gas requires it?
Welding process that joins metals by heating them with an electric arc
To prevent leakage - Carbon Dioxide (CO2)
5.8 to 12.5 L/min
SMAW - GTAW

7. List several industries that would use GMAW
Speed of the feed motor and - starting / stopping electrode feed
Penetration and burn - off rate of the electrode
AWS and CSA
Pressure vessels and the piping industry

8. How are GMAW guns rated?
By there current carrying capacity
AWS and CSA
Controls the rate of flow of a shielding gas to the gun nozzle
Minimum distortion due to low heat input

9. What is the required arc voltage used for short circuit transfer?
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12 to 22 arc volts
Motor driven generators - Transformer rectifiers - and Inverter designs
Voltage is the force that overcomes resistance to allow amperage flow

10. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Gives arc voltage values to the control system of the feeder
The time rate of response for the current rise and fall
AWS and CSA
Constant voltage (CV)

11. What does a flowmeter do and what does it measure?
Wire feed speed
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Controls the rate of flow of a shielding gas to the gun nozzle
Speed of the feed motor and - starting / stopping electrode feed

12. What does inductance control?
20 to 200 times per second
Dry ice can form within the flow control openings and cause blockage of shielding gas
Minutes of elapsed time continually run (out of 10 minutes)
The time rate of response for the current rise and fall

13. Why is a line heater required when using GMAW?
Motor driven generators - Transformer rectifiers - and Inverter designs
By there current carrying capacity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Dry ice can form within the flow control openings and cause blockage of shielding gas

14. Why is globular transfer generally avoided with GMAW?
Pressure - The rate of flow of a shielding gas
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Spatter problems and poor weld appearance
The negative side of a welding unit

15. What does voltage do in an electrical circuit?
Welding process that joins metals by heating them with an electric arc
To limit the short circuiting current so that spatter is reduced
Voltage is the force that overcomes resistance to allow amperage flow
The time rate of response for the current rise and fall

16. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
The time rate of response for the current rise and fall
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...
(DCEP) Direct Current Electrode Positive or Reverse polarity

17. List the three methods of metal transfer with GMAW
Motor driven generators - Transformer rectifiers - and Inverter designs
Cause flaking - which can clog the liner and contact tube
Short- circuiting transfer - Globular transfer - Spray transfer
Dry ice can form within the flow control openings and cause blockage of shielding gas

18. A 10 minute cycle of welding time vs cooling time a given machine can handle.
The Arc voltage
The time rate of response for the current rise and fall
Duty cycle
Aluminum wire

19. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Insufficient current to melt the wire off cleanly
Constant voltage (CV)
Generally not as accurate
Pressure vessels and the piping industry

20. Draw a typical volt amp curve for a machine that is designed for GMAW
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
To limit the short circuiting current so that spatter is reduced
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These terms are quite restrictive and often technically incorrect

21. A pull type drive system is usually used on what type of material?
Aluminum wire
Speed of the feed motor and - starting / stopping electrode feed
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
The Arc voltage

22. In the GMAW process what does amperage control?
1/4 inch to 1/2 inch
AWS and CSA
Minutes of elapsed time continually run (out of 10 minutes)
Penetration and burn - off rate of the electrode

23. List 3 wire drive systems and give a short description of each
1/4 inch to 1/2 inch
Pressure - The rate of flow of a shielding gas
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
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

24. What is the effect of too much slope?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Insufficient current to melt the wire off cleanly
Gas metal arc welding
By there current carrying capacity

25. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Minutes of elapsed time continually run (out of 10 minutes)
AWS and CSA
National Electrical Manufactures Association
Higher 26 to 35 arc volts

26. What is a typical flow rate of CO2 for short circuit transfer?
5.8 to 12.5 L/min
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Flux cored wires
The time rate of response for the current rise and fall

27. How many times per second does short circuiting take place?
Speed of the feed motor and - starting / stopping electrode feed
Higher 26 to 35 arc volts
Cause flaking - which can clog the liner and contact tube
20 to 200 times per second

28. What does the wire feeder control?
Speed of the feed motor and - starting / stopping electrode feed
Generally not as accurate
1/4 inch to 1/2 inch
Controls the rate of flow of a shielding gas to the gun nozzle

29. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
DCEP (Direct Current Electrode Positive) Reverse Polarity
20 to 200 times per second
12 to 22 arc volts

30. What wire are knurled drive rolls most commonly used on?
Flux cored wires
Speed of the feed motor and - starting / stopping electrode feed
Pressure - The rate of flow of a shielding gas
Constant current (CC)

31. What is a solenoid valve and what actuates it?
When the filler wire is in direct contract with the base metal
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Shielding the molten weld metal from atmospheric contamination
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32. What is the key advantage of short circuiting transfer?
Constant current (CC)
Gas metal arc welding
Minimum distortion due to low heat input
The negative side of a welding unit

33. What controls the wire speed on a voltage sensing wire feeder?
The negative side of a welding unit
12 to 22 arc volts
Penetration and burn - off rate of the electrode
The Arc voltage

34. When is the metal transferred with short circuit transfer?
Shielding the molten weld metal from atmospheric contamination
Speed of the feed motor and - starting / stopping electrode feed
...
When the filler wire is in direct contract with the base metal

35. What is an advantage of pulsed arc transfer with GMAW?
To prevent leakage - Carbon Dioxide (CO2)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
15 feet (4.5 meters)
Dry ice can form within the flow control openings and cause blockage of shielding gas

36. What does the abbreviation NEMA stand for?
These terms are quite restrictive and often technically incorrect
National Electrical Manufactures Association
Puddle fluidity
Flux cored wires

37. What is another term for electrode holders for GMAW?
Guns
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
The negative side of a welding unit
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38. What current and polarity is generally used with GMAW?
15 feet (4.5 meters)
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Wire feed speed - Voltage control
DCEP (Direct Current Electrode Positive) Reverse Polarity

39. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
If you dont know this check your phone
Welding process that joins metals by heating them with an electric arc

40. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
V groove or U groove
Guns
5.8 to 12.5 L/min

41. What does the term GMAW identify?
12 to 22 arc volts
(DCEP) Direct Current Electrode Positive or Reverse polarity
Gas metal arc welding
By there current carrying capacity

42. Regulators control_____________ flowmeters SHOW____________.
(DCEP) Direct Current Electrode Positive or Reverse polarity
Pressure - The rate of flow of a shielding gas
1/4 inch to 1/2 inch
Gas metal arc welding

43. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

44. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Minimum distortion due to low heat input
...
Cause flaking - which can clog the liner and contact tube
Wire feed speed

45. What processes are constant current (CC) power sources designed to be used with?
(DCEP) Direct Current Electrode Positive or Reverse polarity
Dry ice can form within the flow control openings and cause blockage of shielding gas
SMAW - GTAW
To prevent leakage - Carbon Dioxide (CO2)

46. What 2 organizations designate specifications for GMAW wires?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
AWS and CSA
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

47. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Short- circuiting transfer - Globular transfer - Spray transfer
3
The time rate of response for the current rise and fall
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

48. What is the recommended electrode stick- out for .035 solid wire?
1/4 inch to 1/2 inch
...
Aluminum wire
Constant current (CC)

49. What 2 controls are found on a GMAW set- up?
Wire feed speed - Voltage control
The Arc voltage
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Constant voltage (CV)

50. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
(DCEP) Direct Current Electrode Positive or Reverse polarity
Reducing the gas source pressure to a constant working pressure
Gas metal arc welding
Wire feeds smoothly (yet will slip should a problem occur in the gun)