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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. Why is the term GMAW preferred over MIG or MAG?
Higher 26 to 35 arc volts
Wire feeds smoothly (yet will slip should a problem occur in the gun)
These terms are quite restrictive and often technically incorrect
Voltage is the force that overcomes resistance to allow amperage flow

2. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Duty cycle
12 to 22 arc volts
To limit the short circuiting current so that spatter is reduced
The time rate of response for the current rise and fall

3. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Wire feed speed
SMAW - GTAW
Cause flaking - which can clog the liner and contact tube
Welding process that joins metals by heating them with an electric arc

4. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
85%
If you dont know this check your phone
Penetration and burn - off rate of the electrode
Higher 26 to 35 arc volts

5. What are the 2 types of wire feeders available?
Gas metal arc welding
Constant- speed wire feeders and Voltage- sennsing wire feeders
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
5.8 to 12.5 L/min

6. What is the main purpose of 'slope'?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Gas metal arc welding
The resistace to electrical current flow increases with it. Causing the electrode to heat
To limit the short circuiting current so that spatter is reduced

7. Give a brief description of the GMAW process
12 to 22 arc volts
Welding process that joins metals by heating them with an electric arc
To prevent leakage - Carbon Dioxide (CO2)
Dry ice can form within the flow control openings and cause blockage of shielding gas

8. What is the effect of too much slope?
Aluminum wire
Pressure - The rate of flow of a shielding gas
Insufficient current to melt the wire off cleanly
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

9. How are GMAW guns rated?
By there current carrying capacity
Flux cored wires
Speed of the feed motor and - starting / stopping electrode feed
5.8 to 12.5 L/min

10. What controls the wire speed on a voltage sensing wire feeder?
Guns
Pressure - The rate of flow of a shielding gas
Higher 26 to 35 arc volts
The Arc voltage

11. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
...
Dry ice can form within the flow control openings and cause blockage of shielding gas
To prevent drawing of liquid CO2 (Carbon Dioxide)

12. Why is a fiber washer required and what cylinder gas requires it?
Guns
Flux cored wires
Motor driven generators - Transformer rectifiers - and Inverter designs
To prevent leakage - Carbon Dioxide (CO2)

13. What is the purpose of a regulator and what does it indicate on its gauges?
Reducing the gas source pressure to a constant working pressure
(DCEP) Direct Current Electrode Positive or Reverse polarity
Puddle fluidity
Minimum distortion due to low heat input

14. What 2 controls are found on a GMAW set- up?
12 to 22 arc volts
Pressure - The rate of flow of a shielding gas
Wire feed speed - Voltage control
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

15. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
V groove or U groove
Gives arc voltage values to the control system of the feeder
Minimum distortion due to low heat input
To limit the short circuiting current so that spatter is reduced

16. What does inductance control?
Gives arc voltage values to the control system of the feeder
The time rate of response for the current rise and fall
Generally not as accurate
Welding process that joins metals by heating them with an electric arc

17. What current and polarity is generally used with GMAW?
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
DCEP (Direct Current Electrode Positive) 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
Wire feeds smoothly (yet will slip should a problem occur in the gun)

18. What does voltage do in an electrical circuit?
Controls the rate of flow of a shielding gas to the gun nozzle
If you dont know this check your phone
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Voltage is the force that overcomes resistance to allow amperage flow

19. How many times per second does short circuiting take place?
To prevent leakage - Carbon Dioxide (CO2)
Puddle fluidity
Higher 26 to 35 arc volts
20 to 200 times per second

20. Draw a typical volt amp curve for a machine that is designed for GMAW
Flux cored wires
Constant voltage (CV)
Minimum distortion due to low heat input
If you dont know this check your phone

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

22. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Pressure vessels and the piping industry
Speed of the feed motor and - starting / stopping electrode feed
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

23. Why is a line heater required when using GMAW?
3
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Dry ice can form within the flow control openings and cause blockage of shielding gas
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

24. In the GMAW process what does amperage control?
SMAW - GTAW
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
Penetration and burn - off rate of the electrode

25. What processes are constant current (CC) power sources designed to be used with?
...
Wire feed speed - Voltage control
Pressure - The rate of flow of a shielding gas
SMAW - GTAW

26. Why is globular transfer generally avoided with GMAW?
12 to 22 arc volts
Voltage is the force that overcomes resistance to allow amperage flow
Spatter problems and poor weld appearance
V groove or U groove

27. What power sources are used with the GMAW Process?
Motor driven generators - Transformer rectifiers - and Inverter designs
The negative side of a welding unit
Pressure vessels and the piping industry
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

28. Give a description of 'pinch effect'
Voltage is the force that overcomes resistance to allow amperage flow
The negative side of a welding unit
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

29. What does the wire feeder control?
The time rate of response for the current rise and fall
Spatter problems and poor weld appearance
Speed of the feed motor and - starting / stopping electrode feed
Penetration and burn - off rate of the electrode

30. Why must CO2 cylinders be used in the vertical position?
Reducing the gas source pressure to a constant working pressure
Dry ice can form within the flow control openings and cause blockage of shielding gas
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

31. What does the abbreviation NEMA stand for?
Shielding the molten weld metal from atmospheric contamination
National Electrical Manufactures Association
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
5.8 to 12.5 L/min

32. With straight polarity where is 2/3 of the arc energy?
Generally not as accurate
The negative side of a welding unit
5.8 to 12.5 L/min
Penetration and burn - off rate of the electrode

33. What is a solenoid valve and what actuates it?
To prevent drawing of liquid CO2 (Carbon Dioxide)
20 to 200 times per second
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
These terms are quite restrictive and often technically incorrect

34. What is the recommended electrode stick- out for .035 solid wire?
1/4 inch to 1/2 inch
Generally not as accurate
When the filler wire is in direct contract with the base metal
SMAW - GTAW

35. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Generally not as accurate
V groove or U groove
Guns
When the filler wire is in direct contract with the base metal

36. What wire are knurled drive rolls most commonly used on?
Flux cored wires
Duty cycle
AWS and CSA
Speed of the feed motor and - starting / stopping electrode feed

37. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Voltage is the force that overcomes resistance to allow amperage flow
These terms are quite restrictive and often technically incorrect
Minimum distortion due to low heat input

38. What would be an indication that the drive roll pressure is adjusted correctly?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Wire feed speed
Speed of the feed motor and - starting / stopping electrode feed
Wire feeds smoothly (yet will slip should a problem occur in the gun)

39. What is a typical flow rate of CO2 for short circuit transfer?
National Electrical Manufactures Association
V groove or U groove
5.8 to 12.5 L/min
Generally not as accurate

40. List 3 wire drive systems and give a short description of each
Generally not as accurate
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
Aluminum wire

41. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Aluminum wire
Insufficient current to melt the wire off cleanly
Higher 26 to 35 arc volts
Short- circuiting transfer - Globular transfer - Spray transfer

42. List the three methods of metal transfer with GMAW
Short- circuiting transfer - Globular transfer - Spray transfer
Reducing the gas source pressure to a constant working pressure
AWS and CSA
Minimum distortion due to low heat input

43. In the GMAW process what does voltage control?
National Electrical Manufactures Association
Spatter problems and poor weld appearance
Puddle fluidity
To limit the short circuiting current so that spatter is reduced

44. What type of power source is used with a constant speed wire feeder?
Constant voltage (CV)
To prevent drawing of liquid CO2 (Carbon Dioxide)
Puddle fluidity
12 to 22 arc volts

45. What does a flowmeter do and what does it measure?
Controls the rate of flow of a shielding gas to the gun nozzle
Puddle fluidity
Constant voltage (CV)
Spatter problems and poor weld appearance

46. What effect does increasing and decreasing the inductance have on the weld?
20 to 200 times per second
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
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

47. What is an advantage of pulsed arc transfer with GMAW?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Higher 26 to 35 arc volts

48. Regulators control_____________ flowmeters SHOW____________.
Pressure - The rate of flow of a shielding gas
Pressure vessels and the piping industry
Constant current (CC)
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

49. What does the term GMAW identify?
The resistace to electrical current flow increases with it. Causing the electrode to heat
1/4 inch to 1/2 inch
5.8 to 12.5 L/min
Gas metal arc welding

50. What 2 organizations designate specifications for GMAW wires?
To limit the short circuiting current so that spatter is reduced
These terms are quite restrictive and often technically incorrect
AWS and CSA
Guns