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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. What controls amperage when using GMAW?
Wire feed speed
Cause flaking - which can clog the liner and contact tube
The resistace to electrical current flow increases with it. Causing the electrode to heat
Flux cored wires

2. Why must CO2 cylinders be used in the vertical position?
Reducing the gas source pressure to a constant working pressure
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
To prevent drawing of liquid CO2 (Carbon Dioxide)
Spatter problems and poor weld appearance

3. List 3 forms compressed gases may be supplied for welding
Pressure - The rate of flow of a shielding gas
85%
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
3

4. What are the 2 types of wire feeders available?
These terms are quite restrictive and often technically incorrect
Constant- speed wire feeders and Voltage- sennsing wire feeders
Guns
Motor driven generators - Transformer rectifiers - and Inverter designs

5. List 3 wire drive systems and give a short description of each
Shielding the molten weld metal from atmospheric contamination
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
Gives arc voltage values to the control system of the feeder
...

6. What is an advantage of pulsed arc transfer with GMAW?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
20 to 200 times per second
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)

7. Why is globular transfer generally avoided with GMAW?
Motor driven generators - Transformer rectifiers - and Inverter designs
Spatter problems and poor weld appearance
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

8. What current and polarity is generally used with GMAW?
Speed of the feed motor and - starting / stopping electrode feed
To prevent leakage - Carbon Dioxide (CO2)
If you dont know this check your phone
DCEP (Direct Current Electrode Positive) Reverse Polarity

9. What 2 organizations designate specifications for GMAW wires?
Short- circuiting transfer - Globular transfer - Spray transfer
AWS and CSA
Welding process that joins metals by heating them with an electric arc
20 to 200 times per second

10. What is a solenoid valve and what actuates it?
Wire feed speed - Voltage control
Voltage is the force that overcomes resistance to allow amperage flow
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
3

11. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Higher 26 to 35 arc volts
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
The Arc voltage

12. What is another term for electrode holders for GMAW?
3
Guns
...
Pressure vessels and the piping industry

13. What does voltage do in an electrical circuit?
AWS and CSA
Voltage is the force that overcomes resistance to allow amperage flow
5.8 to 12.5 L/min
Spatter problems and poor weld appearance

14. What type of power source is commonly used with a voltage sensing wire feeder?
Constant current (CC)
When the filler wire is in direct contract with the base metal
Spatter problems and poor weld appearance
Pressure - The rate of flow of a shielding gas

15. Regulators control_____________ flowmeters SHOW____________.
12 to 22 arc volts
Pressure - The rate of flow of a shielding gas
(DCEP) Direct Current Electrode Positive or Reverse polarity
Gives arc voltage values to the control system of the feeder

16. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
To prevent leakage - Carbon Dioxide (CO2)
3
The negative side of a welding unit
Wire feed speed

17. A pull type drive system is usually used on what type of material?
If you dont know this check your phone
20 to 200 times per second
Wire feed speed - Voltage control
Aluminum wire

18. What would be an indication that the drive roll pressure is adjusted correctly?
Cause flaking - which can clog the liner and contact tube
Welding process that joins metals by heating them with an electric arc
Reducing the gas source pressure to a constant working pressure
Wire feeds smoothly (yet will slip should a problem occur in the gun)

19. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
...
(DCEP) Direct Current Electrode Positive or Reverse polarity
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

20. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
Puddle fluidity
85%
Guns
National Electrical Manufactures Association

21. Why is the term GMAW preferred over MIG or MAG?
Constant current (CC)
Voltage is the force that overcomes resistance to allow amperage flow
DCEP (Direct Current Electrode Positive) Reverse Polarity
These terms are quite restrictive and often technically incorrect

22. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Higher 26 to 35 arc volts
Constant current (CC)
By there current carrying capacity

23. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
These terms are quite restrictive and often technically incorrect
Aluminum wire
Gives arc voltage values to the control system of the feeder

24. What is the effect of too much slope?
Insufficient current to melt the wire off cleanly
Constant voltage (CV)
Shielding the molten weld metal from atmospheric contamination
Gives arc voltage values to the control system of the feeder

25. What does inductance control?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Insufficient current to melt the wire off cleanly
The time rate of response for the current rise and fall
SMAW - GTAW

26. What happens when the electrode extension is increased?
Pressure vessels and the piping industry
If you dont know this check your phone
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

27. What is the purpose of a regulator and what does it indicate on its gauges?
Gives arc voltage values to the control system of the feeder
Reducing the gas source pressure to a constant working pressure
Pressure vessels and the piping industry
3

28. What does a flowmeter do and what does it measure?
Guns
The Arc voltage
Controls the rate of flow of a shielding gas to the gun nozzle
1/4 inch to 1/2 inch

29. List the factors that determine the mode of metal 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
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

30. What type of power source is used with a constant speed wire feeder?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
When the filler wire is in direct contract with the base metal
15 feet (4.5 meters)
Constant voltage (CV)

31. In the GMAW process what does voltage control?
Puddle fluidity
DCEP (Direct Current Electrode Positive) Reverse Polarity
Welding process that joins metals by heating them with an electric arc
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

32. What is the required arc voltage used for short circuit transfer?
12 to 22 arc volts
Gas metal arc welding
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Generally not as accurate

33. What output on the welding machine is used to rate the duty cycle?
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
National Electrical Manufactures Association
Minutes of elapsed time continually run (out of 10 minutes)
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

34. What wire are knurled drive rolls most commonly used on?
Flux cored wires
To limit the short circuiting current so that spatter is reduced
Wire feed speed - Voltage control
Generally not as accurate

35. What power sources are used with the GMAW Process?
Welding process that joins metals by heating them with an electric arc
Motor driven generators - Transformer rectifiers - and Inverter designs
To prevent leakage - Carbon Dioxide (CO2)
To limit the short circuiting current so that spatter is reduced

36. What is the preferred drive roll design for solid wires?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Speed of the feed motor and - starting / stopping electrode feed
To prevent leakage - Carbon Dioxide (CO2)
V groove or U groove

37. 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
Welding process that joins metals by heating them with an electric arc
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

38. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Higher 26 to 35 arc volts
To prevent drawing of liquid CO2 (Carbon Dioxide)
When the filler wire is in direct contract with the base metal

39. What is the recommended electrode stick- out for .035 solid wire?
Duty cycle
Motor driven generators - Transformer rectifiers - and Inverter designs
When the filler wire is in direct contract with the base metal
1/4 inch to 1/2 inch

40. What 2 controls are found on a GMAW set- up?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Aluminum wire
Wire feed speed - Voltage control
15 feet (4.5 meters)

41. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
Flux cored wires
If you dont know this check your phone
Penetration and burn - off rate of the electrode
(DCEP) Direct Current Electrode Positive or Reverse polarity

42. How many times per second does short circuiting take place?
...
Speed of the feed motor and - starting / stopping electrode feed
20 to 200 times per second
3

43. Why is a fiber washer required and what cylinder gas requires it?
To prevent leakage - Carbon Dioxide (CO2)
Aluminum wire
The resistace to electrical current flow increases with it. Causing the electrode to heat
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

44. Why is a line heater required when using GMAW?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Flux cored wires
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Constant current (CC)

45. Draw a typical volt amp curve for a machine that is designed for GMAW
Guns
If you dont know this check your phone
Aluminum wire
Pressure - The rate of flow of a shielding gas

46. How are GMAW guns rated?
Aluminum wire
Motor driven generators - Transformer rectifiers - and Inverter designs
By there current carrying capacity
Higher 26 to 35 arc volts

47. With straight polarity where is 2/3 of the arc energy?
Cause flaking - which can clog the liner and contact tube
The negative side of a welding unit
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
15 feet (4.5 meters)

48. List several industries that would use GMAW
Penetration and burn - off rate of the electrode
V groove or U groove
Pressure vessels and the piping industry
Voltage is the force that overcomes resistance to allow amperage flow

49. What controls the wire speed on a voltage sensing wire feeder?
National Electrical Manufactures Association
The Arc voltage
12 to 22 arc volts
SMAW - GTAW

50. What is the key advantage of short circuiting transfer?
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
Cause flaking - which can clog the liner and contact tube
Minimum distortion due to low heat input