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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. Draw a typical volt amp curve for a machine that is designed for GMAW
Speed of the feed motor and - starting / stopping electrode feed
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
If you dont know this check your phone
12 to 22 arc volts

2. A pull type drive system is usually used on what type of material?
The negative side of a welding unit
Aluminum wire
Wire feed speed
Generally not as accurate

3. What is the effect of too much slope?
Minutes of elapsed time continually run (out of 10 minutes)
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
Insufficient current to melt the wire off cleanly

4. What is the key advantage of short circuiting transfer?
Constant voltage (CV)
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
(DCEP) Direct Current Electrode Positive or Reverse polarity
Minimum distortion due to low heat input

5. In the GMAW process what does voltage control?
Puddle fluidity
Speed of the feed motor and - starting / stopping electrode feed
Pressure vessels and the piping industry
Constant- speed wire feeders and Voltage- sennsing wire feeders

6. What is the recommended electrode stick- out for .035 solid wire?
Higher 26 to 35 arc volts
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
1/4 inch to 1/2 inch

7. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Gives arc voltage values to the control system of the feeder
Duty cycle
These terms are quite restrictive and often technically incorrect
85%

8. What are the 2 types of wire feeders available?
20 to 200 times per second
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Constant- speed wire feeders and Voltage- sennsing wire feeders
The Arc voltage

9. What does a flowmeter do and what does it measure?
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
Controls the rate of flow of a shielding gas to the gun nozzle
National Electrical Manufactures Association
If you dont know this check your phone

10. Why is a line heater required when using GMAW?
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
Voltage is the force that overcomes resistance to allow amperage flow
...
Dry ice can form within the flow control openings and cause blockage of shielding gas

11. List the basic equipment requirements for the GMAW process
Voltage is the force that overcomes resistance to allow amperage flow
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
5.8 to 12.5 L/min
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

12. What power sources are used with the GMAW Process?
Controls the rate of flow of a shielding gas to the gun nozzle
These terms are quite restrictive and often technically incorrect
Motor driven generators - Transformer rectifiers - and Inverter designs
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

13. What does the abbreviation NEMA stand for?
Minimum distortion due to low heat input
3
Wire feed speed - Voltage control
National Electrical Manufactures Association

14. Why is globular transfer generally avoided with GMAW?
Spatter problems and poor weld appearance
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The Arc voltage
Constant current (CC)

15. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Higher 26 to 35 arc volts
Puddle fluidity
85%
Penetration and burn - off rate of the electrode

16. List the factors that determine the mode of metal transfer
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
AWS and CSA
When the filler wire is in direct contract with the base metal

17. Give a brief description of the GMAW process
To prevent leakage - Carbon Dioxide (CO2)
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
Constant voltage (CV)
Welding process that joins metals by heating them with an electric arc

18. What is the preferred drive roll design for solid wires?
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To limit the short circuiting current so that spatter is reduced
V groove or U groove
The Arc voltage

19. How are GMAW guns rated?
The negative side of a welding unit
Reducing the gas source pressure to a constant working pressure
By there current carrying capacity
(DCEP) Direct Current Electrode Positive or Reverse polarity

20. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Cause flaking - which can clog the liner and contact tube
Constant voltage (CV)
National Electrical Manufactures Association

21. What current and polarity is generally used with GMAW?
Minutes of elapsed time continually run (out of 10 minutes)
Guns
DCEP (Direct Current Electrode Positive) Reverse Polarity
Constant voltage (CV)

22. Give a description of 'pinch effect'
20 to 200 times per second
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Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
1/4 inch to 1/2 inch

23. What does the wire feeder control?
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Speed of the feed motor and - starting / stopping electrode feed
Flux cored wires
SMAW - GTAW

24. With straight polarity where is 2/3 of the arc energy?
The negative side of a welding unit
Duty cycle
85%
Spatter problems and poor weld appearance

25. What happens when the electrode extension is increased?
Aluminum wire
Wire feed speed
The resistace to electrical current flow increases with it. Causing the electrode to heat
5.8 to 12.5 L/min

26. Why must CO2 cylinders be used in the vertical position?
To prevent drawing of liquid CO2 (Carbon Dioxide)
The time rate of response for the current rise and fall
Short- circuiting transfer - Globular transfer - Spray transfer
Guns

27. In the GMAW process what does amperage control?
Minimum distortion due to low heat input
5.8 to 12.5 L/min
Penetration and burn - off rate of the electrode
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

28. What is a typical flow rate of CO2 for short circuit transfer?
Puddle fluidity
5.8 to 12.5 L/min
Wire feed speed - Voltage control
Reducing the gas source pressure to a constant working pressure

29. What does inductance control?
Minutes of elapsed time continually run (out of 10 minutes)
The time rate of response for the current rise and fall
National Electrical Manufactures Association
(DCEP) Direct Current Electrode Positive or Reverse polarity

30. Regulators control_____________ flowmeters SHOW____________.
Pressure - The rate of flow of a shielding gas
3
Higher 26 to 35 arc volts
Aluminum wire

31. What is the maximum distance that hard wire can be successfully pushed?
15 feet (4.5 meters)
Generally not as accurate
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Gives arc voltage values to the control system of the feeder

32. What is another term for electrode holders for GMAW?
Pressure - The rate of flow of a shielding gas
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
Guns

33. What is a solenoid valve and what actuates it?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Minimum distortion due to low heat input
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Short- circuiting transfer - Globular transfer - Spray transfer

34. What type of power source is used with a constant speed wire feeder?
To limit the short circuiting current so that spatter is reduced
Cause flaking - which can clog the liner and contact tube
Pressure - The rate of flow of a shielding gas
Constant voltage (CV)

35. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
Duty cycle
(DCEP) Direct Current Electrode Positive or Reverse polarity
Aluminum wire
SMAW - GTAW

36. What is an advantage of pulsed arc transfer with GMAW?
To prevent drawing of liquid CO2 (Carbon Dioxide)
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Minutes of elapsed time continually run (out of 10 minutes)

37. How many times per second does short circuiting take place?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Wire feeds smoothly (yet will slip should a problem occur in the gun)
20 to 200 times per second
Constant- speed wire feeders and Voltage- sennsing wire feeders

38. 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
Constant voltage (CV)
Insufficient current to melt the wire off cleanly
3

39. What is the disadvantage of the gauge preset type of regulator/flowmeter?
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
1/4 inch to 1/2 inch
Higher 26 to 35 arc volts

40. What output on the welding machine is used to rate the duty cycle?
Minutes of elapsed time continually run (out of 10 minutes)
Generally not as accurate
These terms are quite restrictive and often technically incorrect
Controls the rate of flow of a shielding gas to the gun nozzle

41. What does the term GMAW identify?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Minimum distortion due to low heat input
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Gas metal arc welding

42. Why is the term GMAW preferred over MIG or MAG?
Spatter problems and poor weld appearance
These terms are quite restrictive and often technically incorrect
20 to 200 times per second
National Electrical Manufactures Association

43. What controls amperage when using GMAW?
Wire feed speed
Flux cored wires
20 to 200 times per second
The resistace to electrical current flow increases with it. Causing the electrode to heat

44. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
SMAW - GTAW
Cause flaking - which can clog the liner and contact tube
Gives arc voltage values to the control system of the feeder

45. What 2 organizations designate specifications for GMAW wires?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Constant current (CC)
Cause flaking - which can clog the liner and contact tube
AWS and CSA

46. When is the metal transferred with short circuit transfer?
When the filler wire is in direct contract with the base metal
12 to 22 arc volts
The Arc voltage
20 to 200 times per second

47. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
To prevent leakage - Carbon Dioxide (CO2)
Gas metal arc welding
Flux cored wires

48. What effect does increasing and decreasing the inductance have on the weld?
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Pressure - The rate of flow of a shielding gas
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

49. What type of power source is commonly used with a voltage sensing wire feeder?
Cause flaking - which can clog the liner and contact tube
Welding process that joins metals by heating them with an electric arc
Constant current (CC)
Pressure - The rate of flow of a shielding gas

50. What 2 controls are found on a GMAW set- up?
15 feet (4.5 meters)
AWS and CSA
Wire feed speed - Voltage control
12 to 22 arc volts