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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 power sources are used with the GMAW Process?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Constant- speed wire feeders and Voltage- sennsing wire feeders
Motor driven generators - Transformer rectifiers - and Inverter designs
The Arc voltage

2. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
...
Minimum distortion due to low heat input
(DCEP) Direct Current Electrode Positive or Reverse polarity
V groove or U groove

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
Reducing the gas source pressure to a constant working pressure
To limit the short circuiting current so that spatter is reduced
When the filler wire is in direct contract with the base metal

4. Give a brief description of the GMAW process
20 to 200 times per second
Welding process that joins metals by heating them with an electric arc
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12 to 22 arc volts

5. What is the recommended electrode stick- out for .035 solid wire?
V groove or U groove
1/4 inch to 1/2 inch
By there current carrying capacity
Voltage is the force that overcomes resistance to allow amperage flow

6. What is an advantage of pulsed arc transfer with GMAW?
Higher 26 to 35 arc volts
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
5.8 to 12.5 L/min
Constant voltage (CV)

7. 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
National Electrical Manufactures Association
V groove or U groove
The negative side of a welding unit

8. What output on the welding machine is used to rate the duty cycle?
Minutes of elapsed time continually run (out of 10 minutes)
Gas metal arc welding
Minimum distortion due to low heat input
Wire feed speed - Voltage control

9. What does the abbreviation NEMA stand for?
National Electrical Manufactures Association
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
When the filler wire is in direct contract with the base metal

10. What is another term for electrode holders for GMAW?
Guns
To prevent drawing of liquid CO2 (Carbon Dioxide)
Aluminum wire
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

11. Why is the term GMAW preferred over MIG or MAG?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Voltage is the force that overcomes resistance to allow amperage flow
These terms are quite restrictive and often technically incorrect
Spatter problems and poor weld appearance

12. What current and polarity is generally used with GMAW?
National Electrical Manufactures Association
Aluminum wire
DCEP (Direct Current Electrode Positive) Reverse Polarity
Guns

13. What is the maximum distance that hard wire can be successfully pushed?
...
Pressure - The rate of flow of a shielding gas
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

14. List the three methods of metal transfer with GMAW
(DCEP) Direct Current Electrode Positive or Reverse polarity
Insufficient current to melt the wire off cleanly
Gives arc voltage values to the control system of the feeder
Short- circuiting transfer - Globular transfer - Spray transfer

15. Why is a line heater required when using GMAW?
When the filler wire is in direct contract with the base metal
The time rate of response for the current rise and fall
Spatter problems and poor weld appearance
Dry ice can form within the flow control openings and cause blockage of shielding gas

16. A machine with a 70% duty cycle can run at its max for 7 minutes with a cooling cycle of only _ minutes.
Minimum distortion due to low heat input
85%
To prevent leakage - Carbon Dioxide (CO2)
3

17. What are the 2 types of wire feeders available?
Constant- speed wire feeders and Voltage- sennsing wire feeders
12 to 22 arc volts
Shielding the molten weld metal from atmospheric contamination
National Electrical Manufactures Association

18. What type of power source is used with a constant speed wire feeder?
Constant voltage (CV)
Motor driven generators - Transformer rectifiers - and Inverter designs
Gives arc voltage values to the control system of the feeder
When the filler wire is in direct contract with the base metal

19. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Generally not as accurate
By there current carrying capacity
When the filler wire is in direct contract with the base metal

20. What does the wire feeder control?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
When the filler wire is in direct contract with the base metal
Speed of the feed motor and - starting / stopping electrode feed

21. 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
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
To limit the short circuiting current so that spatter is reduced
AWS and CSA

22. List 3 forms compressed gases may be supplied for welding
15 feet (4.5 meters)
The time rate of response for the current rise and fall
Wire feed speed - Voltage control
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

23. What effect does increasing and decreasing the inductance have on the weld?
85%
(DCEP) Direct Current Electrode Positive or Reverse polarity
...
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

24. What 2 controls are found on a GMAW set- up?
The resistace to electrical current flow increases with it. Causing the electrode to heat
Wire feed speed - Voltage control
The negative side of a welding unit
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts

25. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Duty cycle
Pressure vessels and the piping industry
3
Shielding the molten weld metal from atmospheric contamination

26. What is a typical flow rate of CO2 for short circuit transfer?
Constant- speed wire feeders and Voltage- sennsing wire feeders
5.8 to 12.5 L/min
Wire feed speed - Voltage control
By there current carrying capacity

27. What is the required arc voltage used for short circuit transfer?
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
Controls the rate of flow of a shielding gas to the gun nozzle
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

28. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
Flux cored wires
V groove or U groove
The time rate of response for the current rise and fall
(DCEP) Direct Current Electrode Positive or Reverse polarity

29. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
85%
If you dont know this check your phone
Cause flaking - which can clog the liner and contact tube
Gives arc voltage values to the control system of the feeder

30. 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
The Arc voltage
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

31. What is the preferred drive roll design for solid wires?
Welding process that joins metals by heating them with an electric arc
National Electrical Manufactures Association
Duty cycle
V groove or U groove

32. What type of power source is commonly used with a voltage sensing wire feeder?
V groove or U groove
1/4 inch to 1/2 inch
Constant current (CC)
By there current carrying capacity

33. In the GMAW process what does voltage control?
DCEP (Direct Current Electrode Positive) Reverse Polarity
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Puddle fluidity
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

34. How are GMAW guns rated?
Higher 26 to 35 arc volts
If you dont know this check your phone
3
By there current carrying capacity

35. What is the purpose of a regulator and what does it indicate on its gauges?
If you dont know this check your phone
Pressure vessels and the piping industry
Short- circuiting transfer - Globular transfer - Spray transfer
Reducing the gas source pressure to a constant working pressure

36. When is the metal transferred with short circuit transfer?
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
When the filler wire is in direct contract with the base metal
5.8 to 12.5 L/min
By there current carrying capacity

37. 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
12 to 22 arc volts
85%
The resistace to electrical current flow increases with it. Causing the electrode to heat

38. What happens when the electrode extension is increased?
Higher 26 to 35 arc volts
Welding process that joins metals by heating them with an electric arc
The resistace to electrical current flow increases with it. Causing the electrode to heat
When the filler wire is in direct contract with the base metal

39. What does the term GMAW identify?
Gas metal arc welding
SMAW - GTAW
Speed of the feed motor and - starting / stopping electrode feed
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

40. List the factors that determine the mode of metal transfer
Penetration and burn - off rate of the electrode
3
National Electrical Manufactures Association
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

41. What wire are knurled drive rolls most commonly used on?
Gas metal arc welding
Flux cored wires
If you dont know this check your phone
National Electrical Manufactures Association

42. What controls amperage when using GMAW?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
The Arc voltage
Wire feed speed
Constant- speed wire feeders and Voltage- sennsing wire feeders

43. Draw a typical volt amp curve for a machine that is designed for GMAW
3
Constant current (CC)
If you dont know this check your phone
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

44. What controls the wire speed on a voltage sensing wire feeder?
The Arc voltage
1/4 inch to 1/2 inch
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

45. What is the main purpose of 'slope'?
Constant current (CC)
To limit the short circuiting current so that spatter is reduced
Puddle fluidity
Voltage is the force that overcomes resistance to allow amperage flow

46. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Wire feeds smoothly (yet will slip should a problem occur in the gun)
Short- circuiting transfer - Globular transfer - Spray transfer
Guns

47. Why is globular transfer generally avoided with GMAW?
1/4 inch to 1/2 inch
If you dont know this check your phone
Spatter problems and poor weld appearance
Higher 26 to 35 arc volts

48. How many times per second does short circuiting take place?
20 to 200 times per second
Pressure - The rate of flow of a shielding gas
The Arc voltage
If you dont know this check your phone

49. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Higher 26 to 35 arc volts
Constant- speed wire feeders and Voltage- sennsing wire feeders
3
Penetration and burn - off rate of the electrode

50. What does a flowmeter do and what does it measure?
...
The time rate of response for the current rise and fall
Controls the rate of flow of a shielding gas to the gun nozzle
Short- circuiting transfer - Globular transfer - Spray transfer