Transcript Plasma and oxifuel

Metal Cutting
Plasma
Oxy
Fuel
Plasma Arc Cutting (PAC)
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
PAC
Plasma is a super heated gas that is ionized.
 Ionized- Electrons 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

PAC

How it cuts
◦ The plasma gas (compressed air) is forced through a
nozzle and heated by the arc which reaches to 5,0000°F
Advantages of PAC

Can cut all metals

Fast cutting speeds

Little distortion from heat

No hazardous gases

Oxygen based system do not leave nitride deposits

Nitrogen based systems are for aluminum, stainless
steel and nickel
Disadvantages
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

Safety/ Maintenance

A minimum of a #9 filter shield should be used

Need proper ventilation to remove harmful gases

Dip electrode into anti-spatter compound

Do not allow Pilot Arc to continue for long
periods of time
Setting the PAC Torch
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
How to Use
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

Cutting Speed

Too Slow- Molten metal will collect on
bottom of work piece and need to be
ground off (this is called Dross)

Too Fast- Metal will not be cut all the way
through
Oxy-Fuel Cutting
Oxy-Fuel Cutting, Welding
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
◦ Oxygen burns preheated metal and blows it away from the
work piece.

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.
OFC Equipment
Combination Cutting Torch with Cutting Attachment
Straight Cutting Torch
Cutting Tips
3690 Cutting Tip
3690-P Cutting Tip
OFC Cutting Tip Information
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
CUTTING TIP SELECTION CHART
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
0
1
2
3
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
Oxy-Fuel Cutting Set-up

All set up the same as oxy-fuel welding except:
◦ To set working pressure for oxygen must open cutting
valve
Oxy-Fuel Cutting Process
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)
Cutting Flame Types
Carburizing Flame
Neutral Flame
Neutral Flame with Oxygen Cutting Stream
Oxidizing Flame
Advantages
Can cut complex shape
 Can cut carbon and low carbon steel
 Inexpensive process
 Can have multiple cutting torch
Disadvantages
 It is slower than other cutting systems
 Cut accuracy is not as good as plasma, water jet
,laser
 Creates heat affected zone
