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is a cutting process that uses an arc and a high-velocity, ionized gas coming through a nozzle to cut all metals that can not be cut with flame
Such as:
Stainless steel
Aluminum
Copper

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Plasma is a super heated gas that is ionized.
IonizedElectrons in the gas have broken away form their atoms and will conduct electricity.
Gases used for plasma cutting includes:
Hydrogen
Argon
Nitrogen and mixture ,plus air and oxygen

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How it cuts
◦ The plasma gas (compressed air) is forced through a nozzle and heated by the arc which reaches to 5,0000 °F

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Can cut all metals
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Fast cutting speeds
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Little distortion from heat
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No hazardous gases
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Oxygen based system do not leave nitride deposits
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Nitrogen based systems are for aluminum, stainless steel and nickel

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Plasma Torch is expensive
Not portable (needs electricity)
Metal fumes created can be a health hazard
Puts tremendous heat into the metal around the cut
Creates HAZ
Hardens materials next to the cut

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A minimum of a #9 filter shield should be used
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Need proper ventilation to remove harmful gases
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Dip electrode into anti-spatter compound
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Do not allow Pilot Arc to continue for long periods of time

If torch amps is set too high travel speed needs to be increased
Thickness
1/16”
1/8”
1/4”
1/4”
3/8”
3/8”
1/2”
1/2”
Current
35 amps
40 amps
40 amps
80 amps
40 amps
80 amps
40 amps
80 amps
Travel Speed
175 in/min
90 in/min
40 in/min
100 in/min
18 in/min
55 in/min
20 in/min
35 in/min

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Clean metal
Hook up ground cable
Draw cutting pattern on metal
Hold torch 1/16-1/8” from metal
(torch stand will help maintain this)
Hold torch at a 70 to 90 ° angle
Pull button when arc begins pull torch across metal

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Too Slow- Molten metal will collect on bottom of work piece and need to be ground off ( this is called Dross )
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Too Fast- Metal will not be cut all the way through

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Definition:
Burning is the rapid oxidation of a material
Does Metal Burn?
◦ Virtually all materials will burn if they are first heated to their ignition temperature.
◦ Steel ignition temp is when it is cherry red, 1300-1400 ° C
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Oxygen burns preheated metal and blows it away from the work piece.

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Oxyacetylene welding (OAW)
Oxygen and acetylene gas are mixed in the torch tip. The mixture burns at the torch tip.
The heat from this flame is used to melt the base metal and welding rod. This melted material forms a weld joint.

Combination Cutting Torch with Cutting Attachment
Straight Cutting Torch

Cutting Tips
3690 Cutting Tip
3690-P Cutting Tip

CUTTING TIP SELECTION CHART
Thickness of Metal in Inches
Light gauge to 3/16
3/16 - 3/8
3/8 - 5/8
5/8-1
1-2
2-3
3-6
Tip Cutting Oxygen Acetylene Oxygen Acetylene
Size Orifice Pressure Pressure Consumption Consumption
Number Drill Size (P.S.I.G.) (P.S.I.G.) (SCFH) (SCFH)
000
00
1
0
3
2
4
#68
#64
#60
#56
#52
#48
#42
15-20
20-25
35-40
35-40
40-45
45-50
50-75
5-15
5-15
5-15
5-15
5-15
5-15
10-15
35-40
45-50
75-85
97-107
180-195
270-290
450-600
10-15
10-15
15-20
15-20
20-30
20-35
25-40

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All set up the same as oxy-fuel welding except:
◦ To set working pressure for oxygen must open cutting valve

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Clean metal
Draw line
Make jig to keep cut straight
Hold tip 1/16-1/8” above metal
Preheat metal to cherry red color
Open oxygen valve and push torch through metal
◦ (Angle tip slightly toward direction of cut)

Carburizing Flame
Neutral Flame
Neutral Flame with Oxygen Cutting Stream
Oxidizing Flame

Advantages
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Can cut complex shape
Can cut carbon and low carbon steel
Inexpensive process
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Can have multiple cutting torch
Disadvantages
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It is slower than other cutting systems
Cut accuracy is not as good as plasma, water jet
,laser
Creates heat affected zone