120101j Flashcards
1
Q
What is plasma?
A
Plasma is a gas that has been heated to an extremely high temperature by an electric arc. This causes the gas to ionized making it electrically conductive.
2
Q
In plasma arc cutting plasma is the
A) tungsten electrode
B) electrons travelling across the arc
C) ionized gas
D) outer shielding gas
A
C) ionized gas
3
Q
The plasma arc cutting process
A) can be used on materials 1/4” inch thick or less
B) can be used only on mild steel and stainless steel
C) is used on metals that are electrically conductive
D) is used mainly to clean up foundry spills
A
C) is used on metals that are electrically conductive
4
Q
List five safety hazards associated with plasma arc cutting
A
- Electric shock
- Fumes
- Noise
4.radiation - Compressed gasses
5
Q
Any available welding power source may be used for PAC (plasma arc cutting)
True or false
A
False
Power supplies designed for PC are DCSP rectifier or inverter type constant current machines with open circuit voltages ranging from 120 to 400 volts. They contain special circuits to produce a pilot arc that shuts off when the main arc initiates.
6
Q
How does a plasma torch work?
A
The torch functions are to transfer current to an electrode supply, a flow of orifice gas to the constricting nozzle and supply a flow of secondary shield and gas. The torch transfers current to fixed non-consumable electrode and directs the flow of plasma and shield and gases.
7
Q
Compressed air is generally used for PAC on which materials
A) carbon steels
B) copper alloys
C) magnesium
D) titanium
A
A) carbon steels
8
Q
What effect does improper PAC standoff distances have
A
Results in poor quality cuts, excessive nozzle wear and slow cutting speeds
9
Q
In the PAC process, what is dross?
A) a slag like non-metallic byproduct
B) resolidified oxidized molten metal
C) solidified non-metallic material
D) none of the above
A
B) resolidified oxidized molten metal
10
Q
What happens once the trigger lock is raised and the trigger is pressed
A) gas starts flowing through the torch
B) the high frequency unit starts ionic bombardment
C) the pilot arc starts immediately
A
C) the pilot arc starts immediately
11
Q
What is the minimum welding shade recommended when using the PAC process at 250 Amps
A)5
B) 8
C) 10
D) 14
A
B) 8
12
Q
PAC cutting produces no significant respiratory hazards
True or false
A
False PAC process produces particles much smaller than that created from OAC and create a greater health risk. Many of the fumes from these metals are carcinogenic and can lead to other health risks.
13
Q
The heat affected zone of a plasma arc cut is extremely wide
True or false
A
False as a result of high temperatures and fast cutting speeds PAC produces a very narrow heat affected zone ( HAZ ) along the kerf
14
Q
CAC – A maybe used to cut most ferrous and non-Ferris metals
True or false
A
True
15
Q
List three safety considerations when using CAC – A
A
- Proper protective clothing.
- Proper eye protection.
- Adequate hearing protection.
- Adequate ventilation.
16
Q
What type of power source is required for CAC – A
A) AC only
B) DC only
C) AC rectifiers only
D) either AC or DC
A
D) either AC or DC
17
Q
What is the purpose of compressed air with CAC – A?
A) to remove molten metal
B) to improve visibility
C) to cool the workpiece
D) to heat the workpiece
A
A) to remove molten metal
18
Q
List three metals that give off toxic fumes when cut with the CAC – a process
A
- Beryllium.
- Cadmium.
- Lead.
19
Q
Name the major components of the manual CAC – a electrode holder
A
Power cable, the means to grip the electrode and the air passages and orifices to direct the stream
20
Q
Electrodes for CAC – A are usually made of
A) cast-iron
B) aluminum
C) carbon steel
D) graphite and carbon
A
D) graphite and carbon
21
Q
What is the maximum length that a CAC – an electrode should extend from the holder to the workpiece when gouging carbon steals?
A) 180mm or 7”
B) 200mm or 8”
C) 250mm or 10”
D) 300mm or 12”
A
A) 180mm or 7”
22
Q
What is the range of air pressure normally used for CAC-A
A
550kPa to 700kPa or 80-100psi
23
Q
How are the air jets positioned when air carbon arc gouging in the flat position?
A) toward the operator
B) toward the work, above the electrode
C) toward the work, below the electrode
D) in any position because it has no effect on the metal removal
A
C) toward the work, below the electrode
24
Q
How can you reduce carbon deposits on the joint surface when using CAC – A?
A
Use the proper air, velocity, and electrode movement. Maintain a short arc without touching the electrode to the work without an air supply.
25
When is surface hardening a problem when using CAC – A
A) when working on high carbon steals and cast irons
B) air pressures are inadequate
C) when using AC current
D) when gouging nickel alloys
A) when working working on high carbon steals and cast irons
26
With CAC – A when excessive slag adheres to the edges of the cut what is likely the cause
A) incorrect polarity
B) electrode angle is too shallow
C) air pressure is too low
D) travel speed is too fast
C) air pressure is too low
27
Plasma arc cutting, cut all metals that :
a) are magnetic
b) contain iron
c) conduct electricity.
d) are not conductive
c) conduct electricity.
28
_________ uses several thousand volts and only a fraction of an ampere superimposed onto the secondary circuit and is used to initiate the pilot arc.
a) Low wavelength
b) High wavelength
c) Low frequency current
d) High frequency current
d) High frequency current
29
An arc was established between the electrode and the torch tip but does not transfer to the work piece is the description of what term:
a) plasma
b) transferred arc
c) pilot arc
d) non- transferred arc
d) non- transferred arc
30
The ____ _____ is used to establish a pathway to initiate the main cutting arc
a) plasma
b) transferred arc
c) pilot arc
d) ion
c) pilot arc
31
_________ is a gas that has been heated to an extremely high temp by an electric arc. This causes the gas to ionize, making it electrically conductive.
a) ion
b) high frequency current
c) transferred arc
d) plasma
d) plasma
32
_________ is the current flow in-between the electrode in the torch and the workpiece
a) ion
b) high frequency current
c) transferred arc
d) plasma
c) transferred arc
33
______ _______ relies on a high temp arc to melt the metal and a high velocity jet of plasma gas to blow the metal away.
a) plasma cutting
b) oxy-fuel cutting
c) laser cutting
d) water jet cutting
a) plasma cutting
34
Temps produced in a plasma arc stream range from:
a) 5000°F - 10,000°F
b) 8000°F - 12,000°F
c) 10,000°F - 14,000°F
d) 12,000°F - 15,000°F
c) 10,000°F - 14,000°F
35
What does PAC stand for?
Plasma Arc Cutting
36
The _____ ______ is established in high frequency current, the gas becomes ionized or converts to plasma because of the high voltage.
a) pilot stream
b) transferred arc
c) un transferred arc
d) pilot arc
d) pilot arc
37
If the PAC torch is set up with a separate passage way for plasma and shielding gases, the torch is referred to as a
a) dual flow torch
b) coupled flow torch
c) twinned flow torch
d) combined flow torch
a) dual flow torch
38
What voltage range does a PAC system use:
a) 80 to 100 volts
b) 100 to 300 volts
c) 120 to 400 volts
d) 200 to 420 volts
c) 120 to 400 volts
39
Chlorinated solvents break down in UV light emitted from a PAC system creating what?
a) ozone
b) chlorine dioxide gas
c) hydrogen Sulfide gas
d) phosphene gas
d) phosphene gas
40
Shades to be used for a PAC system
# ____ for <300 amps
# ____ for > 300 amps
#8 for < 300 amps
# 14 > 300 up to 800 amps
41
A PAC system suitable for auto body and light sheet metal work would have what output amperage?
a) 25 amps
b) 35 amps
c) 45 amps
d) 55 amps
b) 35 amps
42
A PAC system suitable for cutting metals up to 6" thick would use what current?
a) DCEN
b) DCEP
c) DCSP
d) both a & c
d) both a & c
DCEN - Direct current electrode negative
DCSP - Direct current straight polarity
both describe the same process
43
PAC systems using open circuit voltages range from ______
a) 80 to 100 volts
b) 120 to 400 volts
c) 200 to 420 volts
d) 350 to 500 volts
b) 120 to 400 volts
44
For a plasma cutting torch are there non consumable electrodes
Y / N?
Yes they are made of tungsten, zirconium, or hafnium
45
What is the technical name for a water jet table?
Water injection arc cutting
46
Why is a water jet table preferred over a plasma table?
Having the water capture many of the hazardous materials when cutting reduces the health hazards drastically
47
What is the general stand off distance when using a PAC system?
a) 1/8" - 1/4"
b) 1/4" - 1/2"
c) 1/4" - 3/8"
d) 3/8" - 1/2"
c) 1/4" - 3/8"
48
PAC torches come in two models; dual flow torches and_____
compressed air torches
49
What are the two shielding gasses generally used on a dual flow PAC system?
a) O2 & CO2
b) CO2 & N2
c) CO2 & AR
D) AR & He
b) CO2 & N2
50
What is dross?
oxidized molten metal that isn't blown away during the cutting process
51
What are 3 main causes of dross
- incorrect cutting speed
- incorrect amperage settings for the material being cut
- worn out nozzle
- incorrect stand off distance
52
T / F
Suggested metals for cutting with a PAC system are
Low carbon or SS, Al, cast iron, copper, and brass
True all of these metals can be cut with a PAC system
53
when using air carbon arc cutting, the molten metal is forced away from cut by the jet stream of ____ ______?
compressed air
54
What is the max stickout when using an air carbon arc cutting process?
a) max 1"
b) max 3"
c) max 5"
d) max 7"
d) max 7"
55
_________ is used for gouging, cutting and washing operations to cut or trim parts to size on both ferrous and non ferrous metals, flushing off (washing) rivets and bolts, and to gouge out defective weld metal for repair.
a) PAC
b) CAC-A
c) CAC-P
d) A-CAC
b) CAC-A
56
What does CAC- A stand for
Air Carbon Arc Cutting
57
Is air carbon arc cutting effective on both ferrous and non ferrous metals Y/N
-
58
What shade is recommended when using the CAC-A process upto 500 amps?
a) shade 5
b) shade 10
c) shade 11
d) shade 12
d) shade 12
for currents higher than 500 amps use a shade 14
59
What type of power source does a CAC-A use?
a) DCEP
b) DCEN
c) CC
d) CV
c) CC
60
When would you want to have 100% duty cycle when using a CAC-A process?
a) when gouging
b) when cutting plate 3" or thicker
c) when using for semi-auto or automatic processes
d) when cutting non ferrous metals
c) when using for semi-auto or automatic processes
61
Where 1 rectifier unit does not have sufficient current a second rectifier can be connected in
a)series
b) parallel
c) rectifiers can not be hooked up together
d) to do this you must use multiple inverters
b) parallel
both rectifiers are joined together at the + and that line is connected to the electrode while the - are connected to the work piece
62
a _________ power source runs DC current, while CC motor, generator, rectifier or multiple operator equipment
- this set up is recommend for all electrode sizes
a) PAC
b) CAC-A
c) oxyfuel cutting
d) laser cutting
b) CAC-A
63
What are electrode holders for carbon arc gouging also known as?
a) torch
b) cathode
c) anode
d) blowpipe
a) torch
64
When working in the flat position the electrode is placed so that the air is directed along the ________ of the electrode.
a) top side
b) underside
c) blowing across the surface
d) blowing across the underside
b) underside
65
Are manual heavy duty torches for gouging air or water cooled?
Usually water cooled due to the high current capabilities
66
Gouging uses a carbon electrode described as
a) non filler metal electrode
b) filler metal electrode
a) non filler metal electrode
67
Gouging electrodes may be coated with copper or there materials to prevent:
a)oxidization
b) increase conductivity at high currents
c) prevent rapid vaporization
d) both b & c
d) both b & c
68
What is the pressure range for compressed air supply needed for air carbon arc gouging?
a) 20-100 psi
b) 40-100 psi
c) 60 - 100 psi
d) 80-100 psi
d) 80-100 psi
69
An electrode with the following parameters would use what air pressure?
6.4 mm (1/4"), 550 kPa, _____ psi
a) 20 psi
b) 40 psi
c) 60 psi
d) 80 psi
d) 80 psi
if the electrode is smaller and only uses 280 kPa and 40 psi it would be considered a light duty electrode
70
What is the main problem when air arc gouging?
carbonization of the base metal
the second issue is surface hardening
71
How would you remove the carbonization caused by air arc gouging.
a) chemical cleaning
b) hand wire brush
c) grinding
d) this carbonization can not be removed
c) grinding
72
Surface hardening is a problem when arc air gouging cast irons and higher carbon steels. What could you do to reduce the hardness caused?
a) chemically treat the heat affected zone first
b) preheat the work area
c) remove all mill scale prior to adding heat
d) unfortunately there is no way to minimize the hardening affect of air arc gouging
b) preheat the work area
73
What is the amperage range of a 3/16" electrode using DCRP?
a) 100 - 200 amps
b) 100- 250 amps
c) 150 - 200 amps
d) 150 - 250 amps
c) 150 - 200 amps
74
What is the recommended ESO for all metals except Al?
a) 2"
b) 4"
c) 5"
d) 7"
d) 7"
when working with Al the ESO is 4"
75
Before starting an arc on an air arc gouging procedure what must you do before touching the electrode to the plate?
turn on the air stream (compressed air)
76
What should the electrode angle and inclination be when air arc gouging?
a) forehand & 90°
b) backhand & 90°
c) forehand & 1/2 the included angle
d) backhand & 1/2 the included angle
a) forehand & 90°
77
Match the following Troubles and causes when air arc gouging.
Troubles
1. Carbon deposits
2. Difficulty starting arc
3. Intermittent gouging action
4. slag adhering to the edges
5. sputtering arc with rapid heating electrode
Causes
a) incorrect polarity
b) Air not on prior to striking arc
c) touching electrode work without air supply
d) Inadequate air pressure
- incorrect electrode, inclination or work angle
- air jets in the wrong position
e) travel speed to slow
1 - c
2 - b
3 - e
4 - d
5 - a
78
With electrodes such as E4310, E4311, (E6010, E6011) if you ___________, you can pierce holes for severing purposes that use DCSP.
a) dampen with water
d) dry in oven to 10% hotter than normal
c) add compressed air
d) these electrodes can not be used for severing purposes
a) dampen with water
79
DCSP (DCEN) is used in a Carbon Arc Cutting (CAC) process as it has a tendency to vaporize the carbon electrode
T /F
True
the process also uses a pointed carbon electrode & no compressed air is needed
80
O2 arc cutting (AOC) use hollow or tubular electrodes with glass cloth sleeve saturated with a thermoplastic insulated electrode. This process is mainly used for underwater cutting material thickness of:
a) ≤ 1"
b) ≥ 1"
c) ≤ 5"
d) ≥ 5"
a) ≤ 1"
81
True or false.
With the AOC process the best choice is to use DCSP however you can use AC.
True
82
With AOC relatively high travel speeds are possible on steels up to ________ thick.
a) 1"
b) 3"
c) 5"
d) 7"
b) 3"
83
The CAC-A process is used for which type of application
a) flushing off bolts
b) cutting non-ferrous metals
c) gouging out weld defects for repair
d) all of the above
d) all of the above
84
What type of torch's are used for PAC?
a) single flow and dual flow
b) heavy duty and combination
c) compressed air and dual flow
d) water injection and air flow torch
c) compressed air and dual flow
85
What causes dross to form while cutting with the PAC process? (13)
a) worn nozzle
b) incorrect amperage
c) incorrect travel speed
d) all of the above
d) all of the above
86
The oxy-arc process: (30)
a) can cut steel up to 3 inches thick
b) is capable of cutting under water
c) requires a DCSP current connection
d) all of the above
d) all of the above
87
Plasma arc cutting can generate temperatures as high as: (3)
a) 10,000 degrees F
b) 18,000 degrees F
c) 25,000 degrees F
d) 35,000 degrees F
c) 25,000 degrees F
88
When two machines are connected in parallel, to provide extra current for gouging, which power source configuration is required.(18)
a) electrode is connected to both positive terminals
b) electrode is connected to both negative terminals
c) electrode is connected to pos. on one machine and neg. on the other machine
d) AC machines are required with electrode connected to either pos. or neg. terminal
a) electrode is connected to both positive terminals
89
One purpose of the copper coating on the air carbon arc electrode is: (21)
a) to keep them from rusting
b) for easy electrode identification
c) they can carry higher welding currents
d) to increase electrode melting temperatures
c) they can carry higher welding currents
90
Which current source would be used when gouging or cutting low carbon and stainless steel with CAC-A? (16)
a) AC
b) DCRP
c) AC or DCRP
d) AC or DCSP
c) AC or DCRP
91
What is the recommended air pressure when air carbon arc gouging? (22)
a) 070 - 210 kPa (10 - 30 psi)
b) 210 - 350 kPa (30 - 50 psi)
c) 350 - 550 kPa (50 - 80 psi)
d) 550 - 700 kPa (80 - 100 psi)
d) 550 - 700 kPa (80 - 100 psi)
92
Preheating is used with air carbon arc gouging, to control: (23)
a) metal removal
b) carbon saturation
c) surface hardening
d) surface imperfections
c) surface hardening
93
The purpose of the air jet for air carbon arc gouging is to: (15)
a) create a hotter arc
b) blow molten metal away
c) cool the heat affected zone
d) reduce the chance of carbonization
b) blow molten metal away
94
During plasma arc cutting the fumes produced are: (5)
a) non-irritating
b) a health risk
c) invisible and harmless
d) well below the threshold limits
b) a health risk
95
Which type of electrode is used for the PAC process? (7)
a) pure tungsten
b) carbon electrodes
c) titanium electrodes
d) tungsten hafnium or zirconium
d) tungsten hafnium or zirconium
96
Which type of shielding gas and plasma gas is normally used to cut carbon steel with dual flow torches? (11)
a) air and oxygen)
b) helium and argon
c) argon and hydrogen
d) carbon dioxide and nitrogen
d) carbon dioxide and nitrogen
97
What type of electrode is recommended for the air carbon arc gouging process: (21)
a) nickel
b) cellulose
c) graphite
d) Tungsten
c) graphite
98
Which of the following would be necessary to cut cast iron using the CAC cutting process (29)
a) DCSP
b) no air flow
c) carbon electrode
d) all of the above
d) all of the above
99
When performing the CAC-A process with a constant current machine what is the required open circuit voltage? (18)
a) 40 volts
b) 60 volts
c) 80 volts
d) 100 volts
b) 60 volts
100
Plasma arc cutting requires a current selection of: (7)
a) AC
b) DCSP
c) DCRP
d) AC high frequency
b) DCSP
101
The PAC process can be used to? (14)
a) cut cast iron
b) cut copper or brass
c) gouge aluminum or stainless steel
d) all of the above
d) all of the above
102
CAC-A can be used in the manual, semi-automatic or automated processes. (20)
True / False
True
103
What would cause slag to adhere to the edge of a groove, after gouging? (27)
a) incorrect polarity
b) low current settings
c) inadequate air pressure
d) excessive amperage settings
c) inadequate air pressure
104
In plasma arc welding or cutting the plasma is the: (2)
a) ionized gas
b) tungsten electrode
c) outer shielding gas
d) electrons travelling across the arc
a) ionized gas
105
Plasma arc is used to cut: (2)
a) aluminum
b) carbon steel
c) stainless steel
d) all metals that conduct electricity
d) all metals that conduct electricity
106
What current is required for severing mild steel with the SMAW process and a E6011 electrode? (29)
a) AC
b) DCRP
c) DCSP
d) AC or DCRP
c) DCSP
107
What would cause slag to adhere to the edge of a groove gouged with CAC-A? (27)
a) incorrect polarity
b) loose connections
c) travel speed to slow
d) incorrect electrode angle or inclination
d) incorrect electrode angle or inclination
108
The existence of carbonization in grooves made by air carbon arc gouging must be: (23)
a) removed by grinding
b) cleaned with a fluxing agent
c) wire brushed to remove slag
d) preheated to a minimum of 500 degrees F
a) removed by grinding
109
What shade of lens is required for CAC-A gouging in the 200-400 amperage range? (17)
a) 9
b) 10
c) 12
d) 14
c) 12
110
What is the definition of a transferred arc? (2)
a) when the electrode contacts the workpiece
b) an arc established between the electrode and the tip
c) current flow between the electrode and the workpiece
d) induced current from the primary to the secondary windings
c) current flow between the electrode and the workpiece
111
Standoff distance for PAC processes could be defined as: (10)
a) the distance from the end of the torch nozzle to work piece
b) 3/8 of an inch away from the work piece
c) dragging the nozzle on the work piece
d) all of the above
d) all of the above
112
What is the function of a pilot arc? (2)
a) it initiates the amperage to cut the metal
b) it heats the plasma gas to cut the metal
c) it establishes a pathway to initiate the cutting arc
d) it is the voltage that initiate's current flow in the machine
c) it establishes a pathway to initiate the cutting arc
113
A dual flow PAC torch has: (4)
a) water flow for cooling
b) two different gases for plasma
c) two plasma jets running in tandem
d) separate passageways for plasma and shielding gas
d) separate passageways for plasma and shielding gas
114
What is the recommended current for a 5 mm (3/16 inch) air carbon arc electrode using DCRP? (24)
a) 150 - 200 amps
b) 250 - 400 amps
c) 350 - 500 amps
d) 550 - 800 amps
a) 150 - 200 amps
115
What problem could occur when air carbon arc gouging high carbon steel and cast iron? (23)
a) erratic arcing
b) surface cracking
c) surface hardening
d) base metal dilution
c) surface hardening
116
How are the air jets positioned when air carbon arc gouging in the flat position? (19)
a) toward the operator
b) the top side of the electrode
c) the underside of the electrode
d) parallel with the electrode holder
c) the underside of the electrode
117
When air carbon arc gouging, the operator must be careful not to leave behind excess amounts of: (23)
a) copper oxide
b) copper gases
c) carbon gases
d) carbon deposits
d) carbon deposits
118
The PAC system uses a pilot arc, which also requires: (2)
a) argon gas
b) low voltage
c) high amperage
d) high frequency current
d) high frequency current
119
The plasma arc cutting process can cut metals up to what thickness? (7)
a) 10 inch
b) 6 inch
c) 2 inch
d) 1/2 inch
b) 6 inch
120
An electrode holder used for CAC-A must have: (19)
a) an orifice to allow air flow
b) a maximum amperage rating of 300 amps
c) an electrode holder with a twist head to accept electrodes
d) all of the above
a) an orifice to allow air flow
121
When using CAC-A, what would be the cause of intermittent gouging action? (27)
a) travel speed to fast
b) travel speed to slow
c) inadequate air pressure
d) air not on prior to striking the arc
b) travel speed to slow
122
What is one advantage of air carbon arc gouging over oxy-acetylene gouging? (16)
a) CAC-A is more portable
b) CAC-A has lower fume emissions
c) CAC-A can gouge non-ferrous metals
d) CAC-A has lower initial equipment cost
c) CAC-A can gouge non-ferrous metals
123
