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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 controls amperage when using GMAW?
The Arc voltage
Wire feed speed
Cause flaking - which can clog the liner and contact tube
Speed of the feed motor and - starting / stopping electrode feed

2. Draw a typical volt amp curve for a machine that is designed for GMAW
V groove or U groove
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
If you dont know this check your phone
Voltage is the force that overcomes resistance to allow amperage flow

3. In the GMAW process what does voltage control?
Puddle fluidity
15 feet (4.5 meters)
Penetration and burn - off rate of the electrode
Pressure vessels and the piping industry

4. A pull type drive system is usually used on what type of material?
Shielding the molten weld metal from atmospheric contamination
The resistace to electrical current flow increases with it. Causing the electrode to heat
Aluminum wire
AWS and CSA

5. Why is globular transfer generally avoided with GMAW?
Spatter problems and poor weld appearance
To prevent leakage - Carbon Dioxide (CO2)
Constant voltage (CV)
To limit the short circuiting current so that spatter is reduced

6. List several industries that would use GMAW
Pressure vessels and the piping industry
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
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Dry ice can form within the flow control openings and cause blockage of shielding gas

7. What happens when the electrode extension is increased?
The resistace to electrical current flow increases with it. Causing the electrode to heat
SMAW - GTAW
Puddle fluidity
Aluminum wire

8. What controls the wire speed on a voltage sensing wire feeder?
The negative side of a welding unit
Insufficient current to melt the wire off cleanly
The Arc voltage
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun

9. List 3 wire drive systems and give a short description of each
Minimum distortion due to low heat input
Insufficient current to melt the wire off cleanly
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
Wire feed speed - Voltage control

10. What are the 2 types of wire feeders available?
Constant- speed wire feeders and Voltage- sennsing wire feeders
National Electrical Manufactures Association
AWS and CSA
DCEP (Direct Current Electrode Positive) Reverse Polarity

11. What does the abbreviation NEMA stand for?
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Flux cored wires
Cause flaking - which can clog the liner and contact tube
National Electrical Manufactures Association

12. What does a flowmeter do and what does it measure?
Controls the rate of flow of a shielding gas to the gun nozzle
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
Spatter problems and poor weld appearance
Insufficient current to melt the wire off cleanly

13. What is the recommended electrode stick- out for .035 solid wire?
1/4 inch to 1/2 inch
Constant voltage (CV)
By there current carrying capacity
Pressure - The rate of flow of a shielding gas

14. Why is the term GMAW preferred over MIG or MAG?
Motor driven generators - Transformer rectifiers - and Inverter designs
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
These terms are quite restrictive and often technically incorrect
AWS and CSA

15. 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
3
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

16. List 3 forms compressed gases may be supplied for welding
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld
Shielding the molten weld metal from atmospheric contamination
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze

17. Is the arc voltage for spray transfer higher or lower than that used for short circuit transfer?
By there current carrying capacity
Higher 26 to 35 arc volts
These terms are quite restrictive and often technically incorrect
DCEP (Direct Current Electrode Positive) Reverse Polarity

18. In the GMAW process what does amperage control?
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Guns
3
Penetration and burn - off rate of the electrode

19. How are GMAW guns rated?
By there current carrying capacity
Higher 26 to 35 arc volts
If you dont know this check your phone
Wire feeds smoothly (yet will slip should a problem occur in the gun)

20. What is the minimum % value of argon that must be present to use the spray transfer method of GMAW?
Guns
3
Cause flaking - which can clog the liner and contact tube
85%

21. What is a typical flow rate of CO2 for short circuit transfer?
Insufficient current to melt the wire off cleanly
5.8 to 12.5 L/min
Gas metal arc welding
Gives arc voltage values to the control system of the feeder

22. What term is used to describe when the workpiece is hooked to the negative pole on the power source?
Pressure - The rate of flow of a shielding gas
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
(DCEP) Direct Current Electrode Positive or Reverse polarity
Gas metal arc welding

23. Why is a line heater required when using GMAW?
Voltage is the force that overcomes resistance to allow amperage flow
DCEP (Direct Current Electrode Positive) Reverse Polarity
Dry ice can form within the flow control openings and cause blockage of shielding gas
12 to 22 arc volts

24. What is another term for electrode holders for GMAW?
Speed of the feed motor and - starting / stopping electrode feed
Guns
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field
SMAW - GTAW

25. What effect does increasing and decreasing the inductance have on the weld?
(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
Insufficient current to melt the wire off cleanly
Voltage is the force that overcomes resistance to allow amperage flow

26. What wire are knurled drive rolls most commonly used on?
These terms are quite restrictive and often technically incorrect
Flux cored wires
Spatter problems and poor weld appearance
...

27. What is the reason glass 'tube' type flowmeters must have the tube mounted truly vertical?
Wire feed speed
...
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Flux cored wires

28. Give a description of 'pinch effect'
The Arc voltage
The resistace to electrical current flow increases with it. Causing the electrode to heat
The negative side of a welding unit
Molten metal is separated from the end of the filler wire by a squeezing force created by a magnetic field

29. 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
National Electrical Manufactures Association
The negative side of a welding unit
SMAW - GTAW

30. What does the wire feeder control?
Speed of the feed motor and - starting / stopping electrode feed
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Spatter problems and poor weld appearance
1/4 inch to 1/2 inch

31. 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
Aluminum wire
Gives arc voltage values to the control system of the feeder
To prevent drawing of liquid CO2 (Carbon Dioxide)

32. 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
Constant current (CC)
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
Minimum distortion due to low heat input

33. What is the effect of too much slope?
Generally not as accurate
Insufficient current to melt the wire off cleanly
Minimum distortion due to low heat input
...

34. Give a brief description of the GMAW process
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
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Welding process that joins metals by heating them with an electric arc

35. Draw a typical volt/amp curve that would be found with a power source designed for SMAW or GTAW
To limit the short circuiting current so that spatter is reduced
Guns
Penetration and burn - off rate of the electrode
If you dont know this check your phone

36. When is the metal transferred with short circuit transfer?
When the filler wire is in direct contract with the base metal
Penetration and burn - off rate of the electrode
Insufficient current to melt the wire off cleanly
Constant voltage (CV)

37. What power sources are used with the GMAW Process?
Pressure - The rate of flow of a shielding gas
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
Motor driven generators - Transformer rectifiers - and Inverter designs
The resistace to electrical current flow increases with it. Causing the electrode to heat

38. What does inductance control?
85%
Dry ice can form within the flow control openings and cause blockage of shielding gas
The resistace to electrical current flow increases with it. Causing the electrode to heat
The time rate of response for the current rise and fall

39. What 2 organizations designate specifications for GMAW wires?
AWS and CSA
If you dont know this check your phone
...
When the filler wire is in direct contract with the base metal

40. What is the preferred drive roll design for solid wires?
V groove or U groove
Generally not as accurate
20 to 200 times per second
Constant voltage (CV)

41. What is a solenoid valve and what actuates it?
1/4 inch to 1/2 inch
20 to 200 times per second
Electricaly operated valves that control the flow of shielding gas to the weld zone. The control switch located on the gun
Gives arc voltage values to the control system of the feeder

42. What is the main purpose of 'slope'?
To limit the short circuiting current so that spatter is reduced
85%
Shielding the molten weld metal from atmospheric contamination
Insufficient current to melt the wire off cleanly

43. What 2 controls are found on a GMAW set- up?
To limit the short circuiting current so that spatter is reduced
Minutes of elapsed time continually run (out of 10 minutes)
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Wire feed speed - Voltage control

44. What does voltage do in an electrical circuit?
Voltage is the force that overcomes resistance to allow amperage flow
Heat input is less than spray transfer - resulting in less distortion - Used in all positions due to controlling the weld metal freeze
Compressed gas cylinder - Liquid filled cylinder - or a Liquid bulk system
Guns

45. List the three methods of metal transfer with GMAW
Spatter problems and poor weld appearance
V groove or U groove
20 to 200 times per second
Short- circuiting transfer - Globular transfer - Spray transfer

46. List the factors that determine the mode of metal transfer
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
Power source - wire feeder - welding gun - Spooled filler wire - Shielding gas - and a ground
(DCEP) Direct Current Electrode Positive or Reverse polarity

47. What is the maximum distance that hard wire can be successfully pushed?
15 feet (4.5 meters)
Wire feed speed
Guns
Welding Current - Filler wire diameter - arc length - type of shielding - position of the weld

48. Regulators control_____________ flowmeters SHOW____________.
85%
Increasing inductance increases puddle fluidity - improves penatration - makes the bead flatter and smoother - and reduces spatter. To much inductance though will create erratic starts
Pressure - The rate of flow of a shielding gas
If you dont know this check your phone

49. What is the key advantage of short circuiting transfer?
Pressure - The rate of flow of a shielding gas
To prevent leakage - Carbon Dioxide (CO2)
Minimum distortion due to low heat input
Constant- speed wire feeders and Voltage- sennsing wire feeders

50. Why is a fiber washer required and what cylinder gas requires it?
(DCEP) Direct Current Electrode Positive or Reverse polarity
To prevent leakage - Carbon Dioxide (CO2)
If you dont know this check your phone
To prevent drawing of liquid CO2 (Carbon Dioxide)