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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 2 controls are found on a GMAW set- up?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Cause flaking - which can clog the liner and contact tube
Wire feed speed - Voltage control
These terms are quite restrictive and often technically incorrect

2. List the three methods of metal transfer with GMAW
Short- circuiting transfer - Globular transfer - Spray transfer
Shielding the molten weld metal from atmospheric contamination
The negative side of a welding unit
By there current carrying capacity

3. Why must CO2 cylinders be used in the vertical position?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Cause flaking - which can clog the liner and contact tube
Pressure vessels and the piping industry
To prevent drawing of liquid CO2 (Carbon Dioxide)

4. What does the abbreviation NEMA stand for?
Aluminum wire
Wire feed speed
National Electrical Manufactures Association
Constant- speed wire feeders and Voltage- sennsing wire feeders

5. List the factors that determine the mode of metal transfer
Welding process that joins metals by heating them with an electric arc
Constant- speed wire feeders and Voltage- sennsing wire feeders
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Insufficient current to melt the wire off cleanly

6. What is a typical flow rate of CO2 for short circuit transfer?
5.8 to 12.5 L/min
To limit the short circuiting current so that spatter is reduced
If you dont know this check your phone
Generally not as accurate

7. What is the purpose of a regulator and what does it indicate on its gauges?
Wire feed speed - Voltage control
By there current carrying capacity
Reducing the gas source pressure to a constant working pressure
(DCEP) Direct Current Electrode Positive or Reverse polarity

8. Regulators control_____________ flowmeters SHOW____________.
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Pressure - The rate of flow of a shielding gas
Voltage is the force that overcomes resistance to allow amperage flow
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

9. What happens when the electrode extension is increased?
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
Gas metal arc welding
The resistace to electrical current flow increases with it. Causing the electrode to heat

10. What controls the wire speed on a voltage sensing wire feeder?
Minimum distortion due to low heat input
Duty cycle
The Arc voltage
DCEP (Direct Current Electrode Positive) Reverse Polarity

11. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
Dry ice can form within the flow control openings and cause blockage of shielding gas
Higher 26 to 35 arc volts
85%
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system

12. Why is globular transfer generally avoided with GMAW?
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
To prevent leakage - Carbon Dioxide (CO2)
Spatter problems and poor weld appearance

13. What is the effect of too much slope?
To prevent leakage - Carbon Dioxide (CO2)
Insufficient current to melt the wire off cleanly
These terms are quite restrictive and often technically incorrect
Wire feed speed - Voltage control

14. What is the purpose of the shielding gas used in GMAW?
Shielding the molten weld metal from atmospheric contamination
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
15 feet (4.5 meters)
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

15. A 10 minute cycle of welding time vs cooling time a given machine can handle.
Guns
Duty cycle
Constant current (CC)
National Electrical Manufactures Association

16. A pull type drive system is usually used on what type of material?
Generally not as accurate
To prevent leakage - Carbon Dioxide (CO2)
The negative side of a welding unit
Aluminum wire

17. What processes are constant current (CC) power sources designed to be used with?
Higher 26 to 35 arc volts
SMAW - GTAW
15 feet (4.5 meters)
Pressure - The rate of flow of a shielding gas

18. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
DCEP (Direct Current Electrode Positive) Reverse Polarity
(DCEP) Direct Current Electrode Positive or Reverse polarity
Pressure vessels and the piping industry
Speed of the feed motor and - starting / stopping electrode feed

19. What type of power source is commonly used with a voltage sensing wire feeder?
Constant current (CC)
The negative side of a welding unit
To prevent drawing of liquid CO2 (Carbon Dioxide)
Spatter problems and poor weld appearance

20. List several industries that would use GMAW
Puddle fluidity
12 to 22 arc volts
Pressure vessels and the piping industry
Shielding the molten weld metal from atmospheric contamination

21. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
Constant voltage (CV)
Higher 26 to 35 arc volts
The negative side of a welding unit
Welding process that joins metals by heating them with an electric arc

22. What is the required arc voltage used for short circuit transfer?
By there current carrying capacity
12 to 22 arc volts
Penetration and burn - off rate of the electrode
To prevent drawing of liquid CO2 (Carbon Dioxide)

23. Give a description of 'pinch effect'
The time rate of response for the current rise and fall
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

24. List the basic equipment requirements for the GMAW process
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
These terms are quite restrictive and often technically incorrect
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Guns

25. What is the disadvantage of the gauge preset type of regulator/flowmeter?
Pressure - The rate of flow of a shielding gas
Puddle fluidity
Generally not as accurate
Pressure vessels and the piping industry

26. Why is a line heater required when using GMAW?
Shielding the molten weld metal from atmospheric contamination
To prevent drawing of liquid CO2 (Carbon Dioxide)
When the filler wire is in direct contract with the base metal
Dry ice can form within the flow control openings and cause blockage of shielding gas

27. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
...
Generally not as accurate
V groove or U groove
Insufficient current to melt the wire off cleanly

28. What type of power source is used with a constant speed wire feeder?
Minimum distortion due to low heat input
15 feet (4.5 meters)
Constant voltage (CV)
12 to 22 arc volts

29. What current and polarity is generally used with GMAW?
Short- circuiting transfer - Globular transfer - Spray transfer
DCEP (Direct Current Electrode Positive) Reverse Polarity
Wire feeds smoothly (yet will slip should a problem occur in the gun)
To prevent leakage - Carbon Dioxide (CO2)

30. What is the recommended electrode stick- out for .035 solid wire?
If you dont know this check your phone
Reducing the gas source pressure to a constant working pressure
85%
1/4 inch to 1/2 inch

31. What does inductance control?
The time rate of response for the current rise and fall
V groove or U groove
Generally not as accurate
Motor driven generators - Transformer rectifiers - and Inverter designs

32. List 3 wire drive systems and give a short description of each
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
Guns
Pressure - The rate of flow of a shielding gas

33. 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
Wire feed speed - Voltage control
To limit the short circuiting current so that spatter is reduced
V groove or U groove

34. Why is the term GMAW preferred over MIG or MAG?
These terms are quite restrictive and often technically incorrect
...
Wire feed speed - Voltage control
Flux cored wires

35. Why is a fiber washer required and what cylinder gas requires it?
Minimum distortion due to low heat input
Constant voltage (CV)
National Electrical Manufactures Association
To prevent leakage - Carbon Dioxide (CO2)

36. How are GMAW guns rated?
Duty cycle
If you dont know this check your phone
By there current carrying capacity
Wire feed speed

37. Draw a typical volt amp curve for a machine that is designed for GMAW
By there current carrying capacity
To prevent drawing of liquid CO2 (Carbon Dioxide)
Guns
If you dont know this check your phone

38. What is the main purpose of 'slope'?
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
Wire feed speed - Voltage control
1/4 inch to 1/2 inch

39. When using flat drive rolls with too much pressure on copper coated solid wires what problem could take place?
Generally not as accurate
Cause flaking - which can clog the liner and contact tube
Guns
Pressure - The rate of flow of a shielding gas

40. What wire are knurled drive rolls most commonly used on?
If you dont know this check your phone
Wire feed speed - Voltage control
Wire feed speed
Flux cored wires

41. Give a brief description of the GMAW process
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Welding process that joins metals by heating them with an electric arc
These terms are quite restrictive and often technically incorrect
Wire feed speed - Voltage control

42. What is the maximum distance that hard wire can be successfully pushed?
National Electrical Manufactures Association
15 feet (4.5 meters)
V groove or U groove
Wire feed speed - Voltage control

43. What are the 2 types of wire feeders available?
By there current carrying capacity
Constant- speed wire feeders and Voltage- sennsing wire feeders
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
20 to 200 times per second

44. What would be an indication that the drive roll pressure is adjusted correctly?
National Electrical Manufactures Association
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Flux cored wires
Wire feeds smoothly (yet will slip should a problem occur in the gun)

45. What effect does increasing and decreasing the inductance have on the weld?
SMAW - GTAW
Constant current (CC)
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

46. What output on the welding machine is used to rate the duty cycle?
Flux cored wires
Minutes of elapsed time continually run (out of 10 minutes)
85%
The time rate of response for the current rise and fall

47. What is the key advantage of short circuiting transfer?
Cause flaking - which can clog the liner and contact tube
Minutes of elapsed time continually run (out of 10 minutes)
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

48. When is the metal transferred with short circuit transfer?
15 feet (4.5 meters)
Spatter problems and poor weld appearance
When the filler wire is in direct contract with the base metal
Motor driven generators - Transformer rectifiers - and Inverter designs

49. What does the wire feeder control?
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
DCEP (Direct Current Electrode Positive) Reverse Polarity
Speed of the feed motor and - starting / stopping electrode feed
National Electrical Manufactures Association

50. In the GMAW process what does voltage control?
Puddle fluidity
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Gives arc voltage values to the control system of the feeder
Speed of the feed motor and - starting / stopping electrode feed