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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. Give a description of 'pinch effect'
Aluminum wire
Short- circuiting transfer - Globular transfer - Spray transfer
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
3

2. What controls amperage when using GMAW?
Puddle fluidity
(DCEP) Direct Current Electrode Positive or Reverse polarity
Penetration and burn - off rate of the electrode
Wire feed speed

3. What is a typical flow rate of CO2 for short circuit transfer?
5.8 to 12.5 L/min
To prevent leakage - Carbon Dioxide (CO2)
Minimum distortion due to low heat input
Voltage is the force that overcomes resistance to allow amperage flow

4. In the GMAW process what does voltage control?
Minimum distortion due to low heat input
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The resistace to electrical current flow increases with it. Causing the electrode to heat
Puddle fluidity

5. What 2 organizations designate specifications for GMAW wires?
AWS and CSA
20 to 200 times per second
Dry ice can form within the flow control openings and cause blockage of shielding gas
Constant current (CC)

6. What is the key advantage of short circuiting transfer?
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
V groove or U groove
Minimum distortion due to low heat input

7. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
(DCEP) Direct Current Electrode Positive or Reverse polarity
Puddle fluidity
Wire feed speed - Voltage control
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

8. What happens when the electrode extension is increased?
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
Higher 26 to 35 arc volts
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9. What does inductance control?
Puddle fluidity
Constant- speed wire feeders and Voltage- sennsing wire feeders
The time rate of response for the current rise and fall
National Electrical Manufactures Association

10. List the factors that determine the mode of metal transfer
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
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
AWS and CSA
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

11. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Pressure - The rate of flow of a shielding gas
The resistace to electrical current flow increases with it. Causing the electrode to heat
Generally not as accurate
Guns

12. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
The time rate of response for the current rise and fall
Cause flaking - which can clog the liner and contact tube
Dry ice can form within the flow control openings and cause blockage of shielding gas
Higher 26 to 35 arc volts

13. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
12 to 22 arc volts
DCEP (Direct Current Electrode Positive) Reverse Polarity
3
SMAW - GTAW

14. 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%
Constant current (CC)
Pressure - The rate of flow of a shielding gas

15. When is the metal transferred with short circuit transfer?
Higher 26 to 35 arc volts
Wire feed speed - Voltage control
When the filler wire is in direct contract with the base metal
To limit the short circuiting current so that spatter is reduced

16. With straight polarity where is 2/3 of the arc energy?
Pressure - The rate of flow of a shielding gas
20 to 200 times per second
V groove or U groove
The negative side of a welding unit

17. List several industries that would use GMAW
Insufficient current to melt the wire off cleanly
To prevent leakage - Carbon Dioxide (CO2)
DCEP (Direct Current Electrode Positive) Reverse Polarity
Pressure vessels and the piping industry

18. List the three methods of metal transfer with GMAW
Minimum distortion due to low heat input
Penetration and burn - off rate of the electrode
Short- circuiting transfer - Globular transfer - Spray transfer
Constant- speed wire feeders and Voltage- sennsing wire feeders

19. What is the effect of too much slope?
These terms are quite restrictive and often technically incorrect
Insufficient current to melt the wire off cleanly
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 negative side of a welding unit

20. 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
...
5.8 to 12.5 L/min
Spatter problems and poor weld appearance

21. What is the preferred drive roll design for solid wires?
V groove or U groove
When the filler wire is in direct contract with the base metal
Speed of the feed motor and - starting / stopping electrode feed
Gas metal arc welding

22. What does the term GMAW identify?
When the filler wire is in direct contract with the base metal
National Electrical Manufactures Association
Speed of the feed motor and - starting / stopping electrode feed
Gas metal arc welding

23. Draw a typical volt amp curve for a machine that is designed for GMAW
Aluminum wire
Cause flaking - which can clog the liner and contact tube
1/4 inch to 1/2 inch
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24. List 3 forms compressed gases may be supplied for welding
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12 to 22 arc volts
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Gas metal arc welding

25. What is the required arc voltage used for short circuit transfer?
Penetration and burn - off rate of the electrode
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
12 to 22 arc volts
Guns

26. What 2 controls are found on a GMAW set- up?
AWS and CSA
Wire feed speed - Voltage control
...
12 to 22 arc volts

27. In the GMAW process what does amperage control?
SMAW - GTAW
Penetration and burn - off rate of the electrode
(DCEP) Direct Current Electrode Positive or Reverse polarity
15 feet (4.5 meters)

28. What processes are constant current (CC) power sources designed to be used with?
Guns
Welding process that joins metals by heating them with an electric arc
To prevent leakage - Carbon Dioxide (CO2)
SMAW - GTAW

29. Why is globular transfer generally avoided with GMAW?
Spatter problems and poor weld appearance
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
Generally not as accurate
The negative side of a welding unit

30. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Duty cycle
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Gives arc voltage values to the control system of the feeder
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

31. A pull type drive system is usually used on what type of material?
...
Aluminum wire
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15 feet (4.5 meters)

32. What does the wire feeder control?
Speed of the feed motor and - starting / stopping electrode feed
These terms are quite restrictive and often technically incorrect
...
Wire feeds smoothly (yet will slip should a problem occur in the gun)

33. What is the main purpose of 'slope'?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Controls the rate of flow of a shielding gas to the gun nozzle
To limit the short circuiting current so that spatter is reduced
3

34. What controls the wire speed on a voltage sensing wire feeder?
Speed of the feed motor and - starting / stopping electrode feed
The Arc voltage
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Pressure - The rate of flow of a shielding gas

35. Why is a line heater required when using GMAW?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
3
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

36. What type of power source is used with a constant speed wire feeder?
Flux cored wires
Voltage is the force that overcomes resistance to allow amperage flow
Constant voltage (CV)
Duty cycle

37. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
Controls the rate of flow of a shielding gas to the gun nozzle
Gives arc voltage values to the control system of the feeder
Guns
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38. What would be an indication that the drive roll pressure is adjusted correctly?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
DCEP (Direct Current Electrode Positive) Reverse Polarity
Aluminum wire
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39. 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
Gas metal arc welding
20 to 200 times per second
Spatter problems and poor weld appearance

40. Why is the term GMAW preferred over MIG or MAG?
Generally not as accurate
These terms are quite restrictive and often technically incorrect
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Wire feed speed - Voltage control

41. What output on the welding machine is used to rate the duty cycle?
Speed of the feed motor and - starting / stopping electrode feed
Minutes of elapsed time continually run (out of 10 minutes)
Flux cored wires
Constant voltage (CV)

42. What type of power source is commonly used with a voltage sensing wire feeder?
Pressure - The rate of flow of a shielding gas
Constant current (CC)
Reducing the gas source pressure to a constant working pressure
Controls the rate of flow of a shielding gas to the gun nozzle

43. List 3 wire drive systems and give a short description of each
When the filler wire is in direct contract with the base metal
Gas metal arc welding
Motor driven generators - Transformer rectifiers - and Inverter designs
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

44. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
20 to 200 times per second
The negative side of a welding unit
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Higher 26 to 35 arc volts

45. Why is a fiber washer required and what cylinder gas requires it?
Controls the rate of flow of a shielding gas to the gun nozzle
Puddle fluidity
85%
To prevent leakage - Carbon Dioxide (CO2)

46. What are the 2 types of wire feeders available?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
20 to 200 times per second
12 to 22 arc volts
Constant- speed wire feeders and Voltage- sennsing wire feeders

47. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Constant voltage (CV)
Duty cycle
Constant- speed wire feeders and Voltage- sennsing wire feeders

48. What does the abbreviation NEMA stand for?
National Electrical Manufactures Association
Constant- speed wire feeders and Voltage- sennsing wire feeders
15 feet (4.5 meters)
Shielding the molten weld metal from atmospheric contamination

49. What is an advantage of pulsed arc transfer with GMAW?
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
12 to 22 arc volts
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

50. How are GMAW guns rated?
SMAW - GTAW
By there current carrying capacity
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system