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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 is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Insufficient current to melt the wire off cleanly
12 to 22 arc volts
Wire feeds smoothly (yet will slip should a problem occur in the gun)

2. List several industries that would use GMAW
15 feet (4.5 meters)
Pressure vessels and the piping industry
Voltage is the force that overcomes resistance to allow amperage flow
Constant voltage (CV)

3. List 3 wire drive systems and give a short description of each
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
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
National Electrical Manufactures Association
Short- circuiting transfer - Globular transfer - Spray transfer

4. Why is a fiber washer required and what cylinder gas requires it?
Constant voltage (CV)
To prevent leakage - Carbon Dioxide (CO2)
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

5. What 2 organizations designate specifications for GMAW wires?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
AWS and CSA
The resistace to electrical current flow increases with it. Causing the electrode to heat

6. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Voltage is the force that overcomes resistance to allow amperage flow
Insufficient current to melt the wire off cleanly
AWS and CSA

7. What is the preferred drive roll design for solid wires?
Penetration and burn - off rate of the electrode
National Electrical Manufactures Association
V groove or U groove
(DCEP) Direct Current Electrode Positive or Reverse polarity

8. What type of power source is used with a constant speed wire feeder?
National Electrical Manufactures Association
Constant voltage (CV)
Gives arc voltage values to the control system of the feeder
Dry ice can form within the flow control openings and cause blockage of shielding gas

9. What is a typical flow rate of CO2 for short circuit transfer?
Gives arc voltage values to the control system of the feeder
Wire feeds smoothly (yet will slip should a problem occur in the gun)
The time rate of response for the current rise and fall
5.8 to 12.5 L/min

10. Give a brief description of the GMAW process
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
To limit the short circuiting current so that spatter is reduced
Reducing the gas source pressure to a constant working pressure
Welding process that joins metals by heating them with an electric arc

11. What is the key advantage of short circuiting transfer?
Minimum distortion due to low heat input
Flux cored wires
Shielding the molten weld metal from atmospheric contamination
Insufficient current to melt the wire off cleanly

12. How many times per second does short circuiting take place?
1/4 inch to 1/2 inch
20 to 200 times per second
To limit the short circuiting current so that spatter is reduced
Wire feed speed - Voltage control

13. List the factors that determine the mode of metal transfer
Duty cycle
Voltage is the force that overcomes resistance to allow amperage flow
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
If you dont know this check your phone

14. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
20 to 200 times per second
Gas metal arc welding
The negative side of a welding unit

15. What is an advantage of pulsed arc transfer with GMAW?
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
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Constant current (CC)

16. What does the term GMAW identify?
Gas metal arc welding
1/4 inch to 1/2 inch
AWS and CSA
Wire feed speed

17. What effect does increasing and decreasing the inductance have on the weld?
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
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

18. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
Dry ice can form within the flow control openings and cause blockage of shielding gas
The negative side of a welding unit
Welding process that joins metals by heating them with an electric arc
Gives arc voltage values to the control system of the feeder

19. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
If you dont know this check your phone
SMAW - GTAW
1/4 inch to 1/2 inch
Spatter problems and poor weld appearance

20. Why is globular transfer generally avoided with GMAW?
Spatter problems and poor weld appearance
5.8 to 12.5 L/min
Generally not as accurate
SMAW - GTAW

21. Why must CO2 cylinders be used in the vertical position?
Wire feed speed - Voltage control
The Arc voltage
To prevent drawing of liquid CO2 (Carbon Dioxide)
To prevent leakage - Carbon Dioxide (CO2)

22. 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
Voltage is the force that overcomes resistance to allow amperage flow
These terms are quite restrictive and often technically incorrect
Constant voltage (CV)

23. List the basic equipment requirements for the GMAW process
These terms are quite restrictive and often technically incorrect
Gives arc voltage values to the control system of the feeder
DCEP (Direct Current Electrode Positive) Reverse Polarity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

24. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Pressure - The rate of flow of a shielding gas
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
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

25. What wire are knurled drive rolls most commonly used on?
Flux cored wires
Pressure vessels and the piping industry
To limit the short circuiting current so that spatter is reduced
3

26. 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
Pressure - The rate of flow of a shielding gas
Guns
Penetration and burn - off rate of the electrode

27. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Aluminum wire
Duty cycle
These terms are quite restrictive and often technically incorrect
Guns

28. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Speed of the feed motor and - starting / stopping electrode feed
DCEP (Direct Current Electrode Positive) Reverse Polarity
Cause flaking - which can clog the liner and contact tube
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

29. In the GMAW process what does amperage control?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
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
When the filler wire is in direct contract with the base metal

30. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Controls the rate of flow of a shielding gas to the gun nozzle
3
Motor driven generators - Transformer rectifiers - and Inverter designs
Wire feeds smoothly (yet will slip should a problem occur in the gun)

31. What power sources are used with the GMAW Process?
...
Flux cored wires
Motor driven generators - Transformer rectifiers - and Inverter designs
Minimum distortion due to low heat input

32. How are GMAW guns rated?
By there current carrying capacity
Duty cycle
Wire feed speed
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

33. What would be an indication that the drive roll pressure is adjusted correctly?
When the filler wire is in direct contract with the base metal
Constant current (CC)
SMAW - GTAW
Wire feeds smoothly (yet will slip should a problem occur in the gun)

34. What does the abbreviation NEMA stand for?
Duty cycle
85%
AWS and CSA
National Electrical Manufactures Association

35. What is the maximum distance that hard wire can be successfully pushed?
15 feet (4.5 meters)
Wire feeds smoothly (yet will slip should a problem occur in the gun)
The time rate of response for the current rise and fall
Aluminum wire

36. With straight polarity where is 2/3 of the arc energy?
The negative side of a welding unit
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
1/4 inch to 1/2 inch
Duty cycle

37. What is the main purpose of 'slope'?
Speed of the feed motor and - starting / stopping electrode feed
Higher 26 to 35 arc volts
Flux cored wires
To limit the short circuiting current so that spatter is reduced

38. What controls amperage when using GMAW?
Generally not as accurate
Guns
Wire feed speed
Wire feeds smoothly (yet will slip should a problem occur in the gun)

39. Draw a typical volt amp curve for a machine that is designed for GMAW
DCEP (Direct Current Electrode Positive) Reverse Polarity
12 to 22 arc volts
85%
If you dont know this check your phone

40. What does voltage do in an electrical circuit?
Voltage is the force that overcomes resistance to allow amperage flow
Welding process that joins metals by heating them with an electric arc
When the filler wire is in direct contract with the base metal
If you dont know this check your phone

41. Regulators control_____________ flowmeters SHOW____________.
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Pressure - The rate of flow of a shielding gas
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Penetration and burn - off rate of the electrode

42. Why is the term GMAW preferred over MIG or MAG?
These terms are quite restrictive and often technically incorrect
If you dont know this check your phone
Penetration and burn - off rate of the electrode
The negative side of a welding unit

43. What is another term for electrode holders for GMAW?
Spatter problems and poor weld appearance
Guns
Voltage is the force that overcomes resistance to allow amperage flow
3

44. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
If you dont know this check your phone
Welding process that joins metals by heating them with an electric arc
Higher 26 to 35 arc volts
Gas metal arc welding

45. List the three methods of metal transfer with GMAW
Cause flaking - which can clog the liner and contact tube
Short- circuiting transfer - Globular transfer - Spray transfer
Duty cycle
Wire feed speed - Voltage control

46. When is the metal transferred with short circuit 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
When the filler wire is in direct contract with the base metal
Higher 26 to 35 arc volts
Welding process that joins metals by heating them with an electric arc

47. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
To prevent leakage - Carbon Dioxide (CO2)
...
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Reducing the gas source pressure to a constant working pressure

48. What current and polarity is generally used with GMAW?
Wire feed speed
DCEP (Direct Current Electrode Positive) Reverse Polarity
AWS and CSA
Aluminum wire

49. What is the purpose of a regulator and what does it indicate on its gauges?
SMAW - GTAW
15 feet (4.5 meters)
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

50. What is a solenoid valve and what actuates it?
If you dont know this check your phone
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
The Arc voltage
Pressure - The rate of flow of a shielding gas