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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 forms compressed gases may be supplied for welding
Motor driven generators - Transformer rectifiers - and Inverter designs
Welding process that joins metals by heating them with an electric arc
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
To limit the short circuiting current so that spatter is reduced

2. List 3 wire drive systems and give a short description of each
Controls the rate of flow of a shielding gas to the gun nozzle
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
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
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

3. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Cause flaking - which can clog the liner and contact tube
Duty cycle
...
Dry ice can form within the flow control openings and cause blockage of shielding gas

4. What is the purpose of the pick- up lead on a voltage sensing wire feeder?
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
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Gives arc voltage values to the control system of the feeder

5. 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
If you dont know this check your phone
V groove or U groove
Wire feeds smoothly (yet will slip should a problem occur in the gun)

6. What power sources are used with the GMAW Process?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Duty cycle
These terms are quite restrictive and often technically incorrect
Motor driven generators - Transformer rectifiers - and Inverter designs

7. A pull type drive system is usually used on what type of material?
Aluminum wire
The negative side of a welding unit
Speed of the feed motor and - starting / stopping electrode feed
Pressure vessels and the piping industry

8. What controls amperage when using GMAW?
Wire feed speed
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
The Arc voltage

9. What is the effect of too much slope?
V groove or U groove
Controls the rate of flow of a shielding gas to the gun nozzle
Insufficient current to melt the wire off cleanly
Dry ice can form within the flow control openings and cause blockage of shielding gas

10. How many times per second does short circuiting take place?
12 to 22 arc volts
Generally not as accurate
85%
20 to 200 times per second

11. What does the term GMAW identify?
85%
Gas metal arc welding
Spatter problems and poor weld appearance
The Arc voltage

12. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
1/4 inch to 1/2 inch
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
If you dont know this check your phone

13. What does a flowmeter do and what does it measure?
Pressure - The rate of flow of a shielding gas
To prevent drawing of liquid CO2 (Carbon Dioxide)
Controls the rate of flow of a shielding gas to the gun nozzle
85%

14. In the GMAW process what does voltage control?
3
Puddle fluidity
Minutes of elapsed time continually run (out of 10 minutes)
Pressure vessels and the piping industry

15. What is the purpose of the shielding gas used in GMAW?
Pressure - The rate of flow of a shielding gas
Welding process that joins metals by heating them with an electric arc
85%
Shielding the molten weld metal from atmospheric contamination

16. What is the recommended electrode stick- out for .035 solid wire?
1/4 inch to 1/2 inch
Pressure - The rate of flow of a shielding gas
By there current carrying capacity
If you dont know this check your phone

17. Draw a typical volt amp curve for a machine that is designed for GMAW
If you dont know this check your phone
Gives arc voltage values to the control system of the feeder
Motor driven generators - Transformer rectifiers - and Inverter designs
To limit the short circuiting current so that spatter is reduced

18. What is the preferred drive roll design for solid wires?
Reducing the gas source pressure to a constant working pressure
If you dont know this check your phone
Spatter problems and poor weld appearance
V groove or U groove

19. What current and polarity is generally used with GMAW?
Cause flaking - which can clog the liner and contact tube
Spatter problems and poor weld appearance
DCEP (Direct Current Electrode Positive) Reverse Polarity
85%

20. How are GMAW guns rated?
5.8 to 12.5 L/min
By there current carrying capacity
Aluminum wire
Constant voltage (CV)

21. Give a brief description of the GMAW process
Welding process that joins metals by heating them with an electric arc
If you dont know this check your phone
Insufficient current to melt the wire off cleanly
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

22. Why must CO2 cylinders be used in the vertical position?
Penetration and burn - off rate of the electrode
To prevent drawing of liquid CO2 (Carbon Dioxide)
Guns
Controls the rate of flow of a shielding gas to the gun nozzle

23. What is the key advantage of short circuiting transfer?
When the filler wire is in direct contract with the base metal
Gas metal arc welding
Minimum distortion due to low heat input
...

24. What happens when the electrode extension is increased?
Minimum distortion due to low heat input
Generally not as accurate
Reducing the gas source pressure to a constant working pressure
The resistace to electrical current flow increases with it. Causing the electrode to heat

25. What are the 2 types of wire feeders available?
Constant- speed wire feeders and Voltage- sennsing wire feeders
Welding process that joins metals by heating them with an electric arc
The Arc voltage
AWS and CSA

26. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
...
Constant voltage (CV)
To prevent leakage - Carbon Dioxide (CO2)
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

27. In the GMAW process what does amperage control?
Wire feed speed
Penetration and burn - off rate of the electrode
If you dont know this check your phone
Speed of the feed motor and - starting / stopping electrode feed

28. List the three methods of metal transfer with GMAW
Short- circuiting transfer - Globular transfer - Spray transfer
Spatter problems and poor weld appearance
The Arc voltage
Wire feed speed - Voltage control

29. 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
Pressure - The rate of flow of a shielding gas
Higher 26 to 35 arc volts
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

30. What is the maximum distance that hard wire can be successfully pushed?
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
Insufficient current to melt the wire off cleanly
To prevent drawing of liquid CO2 (Carbon Dioxide)

31. 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
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Higher 26 to 35 arc volts
Gives arc voltage values to the control system of the feeder

32. Why is a fiber washer required and what cylinder gas requires it?
Constant- speed wire feeders and Voltage- sennsing wire feeders
To prevent leakage - Carbon Dioxide (CO2)
15 feet (4.5 meters)
Speed of the feed motor and - starting / stopping electrode feed

33. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
5.8 to 12.5 L/min
Duty cycle
1/4 inch to 1/2 inch
85%

34. Why is a line heater required when using GMAW?
Dry ice can form within the flow control openings and cause blockage of shielding gas
SMAW - GTAW
Controls the rate of flow of a shielding gas to the gun nozzle
Gas metal arc welding

35. Why is globular transfer generally avoided with GMAW?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Wire feed speed
These terms are quite restrictive and often technically incorrect
Spatter problems and poor weld appearance

36. List the factors that determine the mode of metal transfer
Dry ice can form within the flow control openings and cause blockage of shielding gas
Pressure - The rate of flow of a shielding gas
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
The resistace to electrical current flow increases with it. Causing the electrode to heat

37. What wire are knurled drive rolls most commonly used on?
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
Penetration and burn - off rate of the electrode
Flux cored wires

38. What does voltage do in an electrical circuit?
AWS and CSA
Motor driven generators - Transformer rectifiers - and Inverter designs
Wire feed speed
Voltage is the force that overcomes resistance to allow amperage flow

39. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Guns
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
3

40. What is an advantage of pulsed arc transfer with GMAW?
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
To prevent drawing of liquid CO2 (Carbon Dioxide)
Spatter problems and poor weld appearance

41. What is the required arc voltage used for short circuit transfer?
Dry ice can form within the flow control openings and cause blockage of shielding gas
12 to 22 arc volts
Gives arc voltage values to the control system of the feeder
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

42. What type of power source is used with a constant speed wire feeder?
Constant voltage (CV)
Generally not as accurate
85%
National Electrical Manufactures Association

43. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Gas metal arc welding
...
(DCEP) Direct Current Electrode Positive or Reverse polarity

44. What does the wire feeder control?
Speed of the feed motor and - starting / stopping electrode feed
Minimum distortion due to low heat input
Spatter problems and poor weld appearance
3

45. List several industries that would use GMAW
Minimum distortion due to low heat input
Pressure vessels and the piping industry
Puddle fluidity
Gives arc voltage values to the control system of the feeder

46. What is a typical flow rate of CO2 for short circuit transfer?
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
5.8 to 12.5 L/min
V groove or U groove
AWS and CSA

47. What does the abbreviation NEMA stand for?
Constant- speed wire feeders and Voltage- sennsing wire feeders
When the filler wire is in direct contract with the base metal
National Electrical Manufactures Association
Flux cored wires

48. What output on the welding machine is used to rate the duty cycle?
Insufficient current to melt the wire off cleanly
Minutes of elapsed time continually run (out of 10 minutes)
Shielding the molten weld metal from atmospheric contamination
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground

49. What 2 organizations designate specifications for GMAW wires?
AWS and CSA
If you dont know this check your phone
To prevent drawing of liquid CO2 (Carbon Dioxide)
Puddle fluidity

50. A 10 minute cycle of welding time vs cooling time a given machine can handle.
The negative side of a welding unit
Duty cycle
12 to 22 arc volts
Constant current (CC)