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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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1. What does the term GMAW identify?
Welding process that joins metals by heating them with an electric arc
Short- circuiting transfer - Globular transfer - Spray transfer
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Gas metal arc welding

2. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
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Constant- speed wire feeders and Voltage- sennsing wire feeders
85%

3. List several industries that would use GMAW
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Pressure vessels and the piping industry
When the filler wire is in direct contract with the base metal
The Arc voltage

4. What does a flowmeter do and what does it measure?
85%
Controls the rate of flow of a shielding gas to the gun nozzle
Guns
Wire feeds smoothly (yet will slip should a problem occur in the gun)

5. In the GMAW process what does amperage control?
Penetration and burn - off rate of the electrode
(DCEP) Direct Current Electrode Positive or Reverse polarity
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

6. What is the maximum distance that hard wire can be successfully pushed?
Shielding the molten weld metal from atmospheric contamination
Minutes of elapsed time continually run (out of 10 minutes)
Reducing the gas source pressure to a constant working pressure
15 feet (4.5 meters)

7. What is a solenoid valve and what actuates it?
SMAW - GTAW
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Speed of the feed motor and - starting / stopping electrode feed
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

8. What wire are knurled drive rolls most commonly used on?
Minutes of elapsed time continually run (out of 10 minutes)
Welding process that joins metals by heating them with an electric arc
Flux cored wires
Constant current (CC)

9. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
Constant voltage (CV)
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Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
(DCEP) Direct Current Electrode Positive or Reverse polarity

10. Why must CO2 cylinders be used in the vertical position?
To prevent drawing of liquid CO2 (Carbon Dioxide)
SMAW - GTAW
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20 to 200 times per second

11. List 3 wire drive systems and give a short description of each
Guns
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
Wire feed speed - Voltage control
Speed of the feed motor and - starting / stopping electrode feed

12. What does the wire feeder control?
Higher 26 to 35 arc volts
Speed of the feed motor and - starting / stopping electrode feed
Short- circuiting transfer - Globular transfer - Spray transfer
Voltage is the force that overcomes resistance to allow amperage flow

13. List the three methods of metal transfer with GMAW
(DCEP) Direct Current Electrode Positive or Reverse polarity
Short- circuiting transfer - Globular transfer - Spray transfer
Insufficient current to melt the wire off cleanly
Pressure vessels and the piping industry

14. List the factors that determine the mode of metal transfer
To prevent drawing of liquid CO2 (Carbon Dioxide)
5.8 to 12.5 L/min
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Speed of the feed motor and - starting / stopping electrode feed

15. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
3
Wire feeds smoothly (yet will slip should a problem occur in the gun)
The resistace to electrical current flow increases with it. Causing the electrode to heat
To prevent leakage - Carbon Dioxide (CO2)

16. What is the purpose of a regulator and what does it indicate on its gauges?
Aluminum wire
Generally not as accurate
Reducing the gas source pressure to a constant working pressure
Constant voltage (CV)

17. What is another term for electrode holders for GMAW?
Guns
Welding process that joins metals by heating them with an electric arc
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Gives arc voltage values to the control system of the feeder

18. What is the effect of too much slope?
Constant voltage (CV)
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Insufficient current to melt the wire off cleanly
SMAW - GTAW

19. What 2 controls are found on a GMAW set- up?
Wire feed speed - Voltage control
The time rate of response for the current rise and fall
Insufficient current to melt the wire off cleanly
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20. List the basic equipment requirements for the GMAW process
The resistace to electrical current flow increases with it. Causing the electrode to heat
Minutes of elapsed time continually run (out of 10 minutes)
Voltage is the force that overcomes resistance to allow amperage flow
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

21. What effect does increasing and decreasing the inductance have on the weld?
15 feet (4.5 meters)
National Electrical Manufactures Association
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
12 to 22 arc volts

22. What is the required arc voltage used for short circuit transfer?
Reducing the gas source pressure to a constant working pressure
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
85%
12 to 22 arc volts

23. In the GMAW process what does voltage control?
(DCEP) Direct Current Electrode Positive or Reverse polarity
Puddle fluidity
Guns
Aluminum wire

24. What is the key advantage of short circuiting transfer?
Minimum distortion due to low heat input
Shielding the molten weld metal from atmospheric contamination
To prevent drawing of liquid CO2 (Carbon Dioxide)
AWS and CSA

25. How many times per second does short circuiting take place?
Constant voltage (CV)
20 to 200 times per second
The negative side of a welding unit
Gives arc voltage values to the control system of the feeder

26. Give a brief description of the GMAW process
When the filler wire is in direct contract with the base metal
Reducing the gas source pressure to a constant working pressure
Voltage is the force that overcomes resistance to allow amperage flow
Welding process that joins metals by heating them with an electric arc

27. Why is the term GMAW preferred over MIG or MAG?
Wire feed speed
Guns
...
These terms are quite restrictive and often technically incorrect

28. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Duty cycle
Gas metal arc welding
Shielding the molten weld metal from atmospheric contamination
Minutes of elapsed time continually run (out of 10 minutes)

29. What are the 2 types of wire feeders available?
Puddle fluidity
Constant- speed wire feeders and Voltage- sennsing wire feeders
Welding process that joins metals by heating them with an electric arc
15 feet (4.5 meters)

30. Why is a fiber washer required and what cylinder gas requires it?
Voltage is the force that overcomes resistance to allow amperage flow
Flux cored wires
5.8 to 12.5 L/min
To prevent leakage - Carbon Dioxide (CO2)

31. 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
...
85%
Shielding the molten weld metal from atmospheric contamination

32. Draw a typical volt amp curve for a machine that is designed for GMAW
Spatter problems and poor weld appearance
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
These terms are quite restrictive and often technically incorrect
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33. What current and polarity is generally used with GMAW?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Dry ice can form within the flow control openings and cause blockage of shielding gas
Gives arc voltage values to the control system of the feeder
The resistace to electrical current flow increases with it. Causing the electrode to heat

34. How are GMAW guns rated?
When the filler wire is in direct contract with the base metal
By there current carrying capacity
The Arc voltage
Short- circuiting transfer - Globular transfer - Spray transfer

35. Give a description of 'pinch effect'
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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
Pressure - The rate of flow of a shielding gas

36. What power sources are used with the GMAW Process?
Penetration and burn - off rate of the electrode
Motor driven generators - Transformer rectifiers - and Inverter designs
V groove or U groove
National Electrical Manufactures Association

37. What happens when the electrode extension is increased?
SMAW - GTAW
Puddle fluidity
The resistace to electrical current flow increases with it. Causing the electrode to heat
Welding process that joins metals by heating them with an electric arc

38. What is a typical flow rate of CO2 for short circuit transfer?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
5.8 to 12.5 L/min
Duty cycle

39. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Controls the rate of flow of a shielding gas to the gun nozzle
Gives arc voltage values to the control system of the feeder
15 feet (4.5 meters)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

40. Regulators control_____________ flowmeters SHOW____________.
5.8 to 12.5 L/min
Aluminum wire
Pressure - The rate of flow of a shielding gas
12 to 22 arc volts

41. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Higher 26 to 35 arc volts
When the filler wire is in direct contract with the base metal
Pressure - The rate of flow of a shielding gas
Pressure vessels and the piping industry

42. Why is a line heater required when using GMAW?
Dry ice can form within the flow control openings and cause blockage of shielding gas
When the filler wire is in direct contract with the base metal
Penetration and burn - off rate of the electrode
15 feet (4.5 meters)

43. Why is globular transfer generally avoided with GMAW?
20 to 200 times per second
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
The time rate of response for the current rise and fall
Spatter problems and poor weld appearance

44. What does the abbreviation NEMA stand for?
Dry ice can form within the flow control openings and cause blockage of shielding gas
National Electrical Manufactures Association
Penetration and burn - off rate of the electrode
Welding process that joins metals by heating them with an electric arc

45. What would be an indication that the drive roll pressure is adjusted correctly?
Duty cycle
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
AWS and CSA
Wire feeds smoothly (yet will slip should a problem occur in the gun)

46. What is an advantage of pulsed arc transfer with GMAW?
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Motor driven generators - Transformer rectifiers - and Inverter designs
Reducing the gas source pressure to a constant working pressure
5.8 to 12.5 L/min

47. A pull type drive system is usually used on what type of material?
When the filler wire is in direct contract with the base metal
Motor driven generators - Transformer rectifiers - and Inverter designs
Aluminum wire
Constant current (CC)

48. What is the recommended electrode stick- out for .035 solid wire?
Constant- speed wire feeders and Voltage- sennsing wire feeders
85%
To prevent leakage - Carbon Dioxide (CO2)
1/4 inch to 1/2 inch

49. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
...
Dry ice can form within the flow control openings and cause blockage of shielding gas
1/4 inch to 1/2 inch
3

50. List 3 forms compressed gases may be supplied for welding
Controls the rate of flow of a shielding gas to the gun nozzle
Insufficient current to melt the wire off cleanly
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