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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 the basic equipment requirements for the GMAW process
3
Wire feed speed
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
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2. What is the recommended electrode stick- out for .035 solid wire?
Guns
The Arc voltage
1/4 inch to 1/2 inch
Reducing the gas source pressure to a constant working pressure

3. Regulators control_____________ flowmeters SHOW____________.
Pressure - The rate of flow of a shielding gas
85%
By there current carrying capacity
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4. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Pressure vessels and the piping industry
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
3
1/4 inch to 1/2 inch

5. What would be an indication that the drive roll pressure is adjusted correctly?
85%
...
Insufficient current to melt the wire off cleanly
Wire feeds smoothly (yet will slip should a problem occur in the gun)

6. In the GMAW process what does amperage control?
Penetration and burn - off rate of the electrode
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
Voltage is the force that overcomes resistance to allow amperage flow
3

7. Why is a fiber washer required and what cylinder gas requires it?
Minutes of elapsed time continually run (out of 10 minutes)
Gives arc voltage values to the control system of the feeder
Short- circuiting transfer - Globular transfer - Spray transfer
To prevent leakage - Carbon Dioxide (CO2)

8. Why is globular transfer generally avoided with GMAW?
Spatter problems and poor weld appearance
Controls the rate of flow of a shielding gas to the gun nozzle
Wire feed speed
15 feet (4.5 meters)

9. A 10 minute cycle of welding time vs cooling time a given machine can handle.
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
3
Speed of the feed motor and - starting / stopping electrode feed
Duty cycle

10. What is the purpose of the shielding gas used in GMAW?
20 to 200 times per second
Shielding the molten weld metal from atmospheric contamination
Constant- speed wire feeders and Voltage- sennsing wire feeders
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

11. What does the abbreviation NEMA stand for?
Constant current (CC)
Dry ice can form within the flow control openings and cause blockage of shielding gas
National Electrical Manufactures Association
15 feet (4.5 meters)

12. In the GMAW process what does voltage control?
Controls the rate of flow of a shielding gas to the gun nozzle
Puddle fluidity
12 to 22 arc volts
Wire feed speed

13. What is the maximum distance that hard wire can be successfully pushed?
Pressure vessels and the piping industry
15 feet (4.5 meters)
DCEP (Direct Current Electrode Positive) Reverse Polarity
Cause flaking - which can clog the liner and contact tube

14. Why must CO2 cylinders be used in the vertical position?
To prevent leakage - Carbon Dioxide (CO2)
To prevent drawing of liquid CO2 (Carbon Dioxide)
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

15. 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
Voltage is the force that overcomes resistance to allow amperage flow
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
85%

16. Draw a typical volt amp curve for a machine that is designed for GMAW
1/4 inch to 1/2 inch
Controls the rate of flow of a shielding gas to the gun nozzle
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5.8 to 12.5 L/min

17. List the factors that determine the mode of metal transfer
DCEP (Direct Current Electrode Positive) Reverse Polarity
15 feet (4.5 meters)
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
AWS and CSA

18. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
To prevent leakage - Carbon Dioxide (CO2)
Motor driven generators - Transformer rectifiers - and Inverter designs
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Higher 26 to 35 arc volts

19. What wire are knurled drive rolls most commonly used on?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
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Flux cored wires
Pressure - The rate of flow of a shielding gas

20. What power sources are used with the GMAW Process?
Motor driven generators - Transformer rectifiers - and Inverter designs
3
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

21. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Wire feed speed
Minimum distortion due to low heat input
SMAW - GTAW

22. How many times per second does short circuiting take place?
Generally not as accurate
Pressure - The rate of flow of a shielding gas
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
20 to 200 times per second

23. Why is the term GMAW preferred over MIG or MAG?
(DCEP) Direct Current Electrode Positive or Reverse polarity
15 feet (4.5 meters)
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These terms are quite restrictive and often technically incorrect

24. What controls amperage when using GMAW?
Wire feed speed
Dry ice can form within the flow control openings and cause blockage of shielding gas
Motor driven generators - Transformer rectifiers - and Inverter designs
If you dont know this check your phone

25. What 2 controls are found on a GMAW set- up?
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
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
Wire feed speed - Voltage control

26. What is the key advantage of short circuiting transfer?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Minimum distortion due to low heat input
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

27. Give a brief description of the GMAW process
Generally not as accurate
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
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

28. With straight polarity where is 2/3 of the arc energy?
Cause flaking - which can clog the liner and contact tube
Minimum distortion due to low heat input
The negative side of a welding unit
Shielding the molten weld metal from atmospheric contamination

29. When is the metal transferred with short circuit transfer?
Minutes of elapsed time continually run (out of 10 minutes)
When the filler wire is in direct contract with the base metal
1/4 inch to 1/2 inch
Insufficient current to melt the wire off cleanly

30. What effect does increasing and decreasing the inductance have on the weld?
Voltage is the force that overcomes resistance to allow amperage flow
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When the filler wire is in direct contract with the base metal
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

31. What is the preferred drive roll design for solid wires?
V groove or U groove
The resistace to electrical current flow increases with it. Causing the electrode to heat
...
Aluminum wire

32. List several industries that would use GMAW
Flux cored wires
Pressure vessels and the piping industry
The Arc voltage
National Electrical Manufactures Association

33. What does the wire feeder control?
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
Speed of the feed motor and - starting / stopping electrode feed
Higher 26 to 35 arc volts
Dry ice can form within the flow control openings and cause blockage of shielding gas

34. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
1/4 inch to 1/2 inch
Cause flaking - which can clog the liner and contact tube
Constant voltage (CV)
To prevent leakage - Carbon Dioxide (CO2)

35. What is a solenoid valve and what actuates it?
To prevent leakage - Carbon Dioxide (CO2)
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Speed of the feed motor and - starting / stopping electrode feed
Aluminum wire

36. 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
20 to 200 times per second
5.8 to 12.5 L/min

37. What happens when the electrode extension is increased?
Higher 26 to 35 arc volts
Wire feed speed - Voltage control
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

38. Give a description of 'pinch effect'
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
The Arc voltage
20 to 200 times per second
Penetration and burn - off rate of the electrode

39. What does a flowmeter do and what does it measure?
Constant current (CC)
Controls the rate of flow of a shielding gas to the gun nozzle
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Penetration and burn - off rate of the electrode

40. Why is a line heater required when using GMAW?
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 Arc voltage
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

41. What is the required arc voltage used for short circuit transfer?
When the filler wire is in direct contract with the base metal
Spatter problems and poor weld appearance
12 to 22 arc volts
To prevent leakage - Carbon Dioxide (CO2)

42. List 3 wire drive systems and give a short description of each
15 feet (4.5 meters)
Controls the rate of flow of a shielding gas to the gun nozzle
DCEP (Direct Current Electrode Positive) Reverse Polarity
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

43. What processes are constant current (CC) power sources designed to be used with?
SMAW - GTAW
Voltage is the force that overcomes resistance to allow amperage flow
Constant voltage (CV)
12 to 22 arc volts

44. What is the effect of too much slope?
Insufficient current to melt the wire off cleanly
The negative side of a welding unit
Constant current (CC)
12 to 22 arc volts

45. 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
V groove or U groove
1/4 inch to 1/2 inch
Gas metal arc welding

46. What does voltage do in an electrical circuit?
Minimum distortion due to low heat input
Voltage is the force that overcomes resistance to allow amperage flow
V groove or U groove
To limit the short circuiting current so that spatter is reduced

47. What are the 2 types of wire feeders available?
Constant- speed wire feeders and Voltage- sennsing wire feeders
(DCEP) Direct Current Electrode Positive or Reverse polarity
The negative side of a welding unit
Aluminum wire

48. What does the term GMAW identify?
Gas metal arc welding
Dry ice can form within the flow control openings and cause blockage of shielding gas
Constant current (CC)
Insufficient current to melt the wire off cleanly

49. What is a typical flow rate of CO2 for short circuit transfer?
5.8 to 12.5 L/min
Shielding the molten weld metal from atmospheric contamination
If you dont know this check your phone
To prevent drawing of liquid CO2 (Carbon Dioxide)

50. What type of power source is used with a constant speed wire feeder?
Dry ice can form within the flow control openings and cause blockage of shielding gas
(DCEP) Direct Current Electrode Positive or Reverse polarity
Pressure vessels and the piping industry
Constant voltage (CV)