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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 3 wire drive systems and give a short description of each
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
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
Shielding the molten weld metal from atmospheric contamination

2. Why is globular transfer generally avoided with GMAW?
Penetration and burn - off rate of the electrode
Spatter problems and poor weld appearance
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DCEP (Direct Current Electrode Positive) Reverse Polarity

3. What is the effect of too much slope?
National Electrical Manufactures Association
Insufficient current to melt the wire off cleanly
Generally not as accurate
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4. What effect does increasing and decreasing the inductance have on the weld?
Aluminum wire
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Wire feed speed

5. What processes are constant current (CC) power sources designed to be used with?
SMAW - GTAW
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The resistace to electrical current flow increases with it. Causing the electrode to heat
Voltage is the force that overcomes resistance to allow amperage flow

6. What is an advantage of pulsed arc transfer with GMAW?
When the filler wire is in direct contract with the base metal
To limit the short circuiting current so that spatter is reduced
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Pressure - The rate of flow of a shielding gas

7. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
85%
...
Minutes of elapsed time continually run (out of 10 minutes)
When the filler wire is in direct contract with the base metal

8. Give a brief description of the GMAW process
Minutes of elapsed time continually run (out of 10 minutes)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Controls the rate of flow of a shielding gas to the gun nozzle
Welding process that joins metals by heating them with an electric arc

9. What happens when the electrode extension is increased?
Pressure - The rate of flow of a shielding gas
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
Minimum distortion due to low heat input

10. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
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
Spatter problems and poor weld appearance
20 to 200 times per second
...

11. What is a solenoid valve and what actuates it?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Controls the rate of flow of a shielding gas to the gun nozzle
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Guns

12. Why is the term GMAW preferred over MIG or MAG?
Higher 26 to 35 arc volts
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
These terms are quite restrictive and often technically incorrect

13. With straight polarity where is 2/3 of the arc energy?
By there current carrying capacity
Puddle fluidity
Generally not as accurate
The negative side of a welding unit

14. A pull type drive system is usually used on what type of material?
SMAW - GTAW
Aluminum wire
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Dry ice can form within the flow control openings and cause blockage of shielding gas

15. List the factors that determine the mode of metal transfer
Pressure - The rate of flow of a shielding gas
Higher 26 to 35 arc volts
85%
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

16. What does the term GMAW identify?
Welding process that joins metals by heating them with an electric arc
1/4 inch to 1/2 inch
Gas metal arc welding
Spatter problems and poor weld appearance

17. What wire are knurled drive rolls most commonly used on?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
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
Flux cored wires

18. Regulators control_____________ flowmeters SHOW____________.
15 feet (4.5 meters)
Constant current (CC)
Pressure - The rate of flow of a shielding gas
Duty cycle

19. What power sources are used with the GMAW Process?
Reducing the gas source pressure to a constant working pressure
Motor driven generators - Transformer rectifiers - and Inverter designs
The Arc voltage
Aluminum wire

20. What is the required arc voltage used for short circuit transfer?
12 to 22 arc volts
(DCEP) Direct Current Electrode Positive or Reverse polarity
To prevent leakage - Carbon Dioxide (CO2)
The resistace to electrical current flow increases with it. Causing the electrode to heat

21. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
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Cause flaking - which can clog the liner and contact tube
3
Motor driven generators - Transformer rectifiers - and Inverter designs

22. What does the wire feeder control?
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Insufficient current to melt the wire off cleanly
Speed of the feed motor and - starting / stopping electrode feed
Higher 26 to 35 arc volts

23. Give a description of 'pinch effect'
Puddle fluidity
SMAW - GTAW
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
When the filler wire is in direct contract with the base metal

24. How are GMAW guns rated?
By there current carrying capacity
Wire feed speed - Voltage control
Gas metal arc welding
Pressure vessels and the piping industry

25. What does inductance control?
Higher 26 to 35 arc volts
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
The time rate of response for the current rise and fall
Controls the rate of flow of a shielding gas to the gun nozzle

26. What does a flowmeter do and what does it measure?
Controls the rate of flow of a shielding gas to the gun nozzle
Constant voltage (CV)
Duty cycle
Welding process that joins metals by heating them with an electric arc

27. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
When the filler wire is in direct contract with the base metal
20 to 200 times per second
Minutes of elapsed time continually run (out of 10 minutes)
Higher 26 to 35 arc volts

28. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Shielding the molten weld metal from atmospheric contamination
To prevent leakage - Carbon Dioxide (CO2)
Generally not as accurate

29. What controls amperage when using GMAW?
Voltage is the force that overcomes resistance to allow amperage flow
Controls the rate of flow of a shielding gas to the gun nozzle
Gas metal arc welding
Wire feed speed

30. In the GMAW process what does amperage control?
Flux cored wires
Penetration and burn - off rate of the electrode
Cause flaking - which can clog the liner and contact tube
85%

31. What 2 organizations designate specifications for GMAW wires?
Short- circuiting transfer - Globular transfer - Spray transfer
AWS and CSA
Higher 26 to 35 arc volts
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32. What is a typical flow rate of CO2 for short circuit transfer?
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Gives arc voltage values to the control system of the feeder
Penetration and burn - off rate of the electrode
5.8 to 12.5 L/min

33. What 2 controls are found on a GMAW set- up?
...
Motor driven generators - Transformer rectifiers - and Inverter designs
Shielding the molten weld metal from atmospheric contamination
Wire feed speed - Voltage control

34. What current and polarity is generally used with GMAW?
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Pressure vessels and the piping industry
DCEP (Direct Current Electrode Positive) Reverse Polarity
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

35. List 3 forms compressed gases may be supplied for welding
Cause flaking - which can clog the liner and contact tube
The Arc voltage
Shielding the molten weld metal from atmospheric contamination
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

36. What is the main purpose of 'slope'?
Minimum distortion due to low heat input
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
To limit the short circuiting current so that spatter is reduced

37. When is the metal transferred with short circuit transfer?
Flux cored wires
Gives arc voltage values to the control system of the feeder
Spatter problems and poor weld appearance
When the filler wire is in direct contract with the base metal

38. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
(DCEP) Direct Current Electrode Positive or Reverse polarity
These terms are quite restrictive and often technically incorrect
3
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

39. Why must CO2 cylinders be used in the vertical position?
Short- circuiting transfer - Globular transfer - Spray transfer
To prevent drawing of liquid CO2 (Carbon Dioxide)
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Cause flaking - which can clog the liner and contact tube

40. What would be an indication that the drive roll pressure is adjusted correctly?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Wire feeds smoothly (yet will slip should a problem occur in the gun)
20 to 200 times per second
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

41. What type of power source is commonly used with a voltage sensing wire feeder?
20 to 200 times per second
15 feet (4.5 meters)
Constant current (CC)
Insufficient current to melt the wire off cleanly

42. Why is a line heater required when using GMAW?
Speed of the feed motor and - starting / stopping electrode feed
Dry ice can form within the flow control openings and cause blockage of shielding gas
Pressure - The rate of flow of a shielding gas
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43. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Duty cycle
Wire feed speed - Voltage control
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
V groove or U groove

44. Draw a typical volt amp curve for a machine that is designed for GMAW
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Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
SMAW - GTAW
...

45. What controls the wire speed on a voltage sensing wire feeder?
...
The Arc voltage
Higher 26 to 35 arc volts
Gives arc voltage values to the control system of the feeder

46. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Flux cored wires
V groove or U groove
DCEP (Direct Current Electrode Positive) Reverse Polarity
Gives arc voltage values to the control system of the feeder

47. List the basic equipment requirements for the GMAW process
Shielding the molten weld metal from atmospheric contamination
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Constant- speed wire feeders and Voltage- sennsing wire feeders
Constant voltage (CV)

48. What is the purpose of a regulator and what does it indicate on its gauges?
Voltage is the force that overcomes resistance to allow amperage flow
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Reducing the gas source pressure to a constant working pressure
The negative side of a welding unit

49. 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
To prevent leakage - Carbon Dioxide (CO2)
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Cause flaking - which can clog the liner and contact tube

50. What is the maximum distance that hard wire can be successfully pushed?
Shielding the molten weld metal from atmospheric contamination
15 feet (4.5 meters)
Generally not as accurate
To prevent drawing of liquid CO2 (Carbon Dioxide)