Tweco 15XC Merlin - Manual (Page 44)

OPERATION 4-10 Manual 0-2251
4.4 GAS SELECTION FOR PLASMA CUTTING (continued)
Cut Quality Cut quality requirements differ depending on application.
For instance, nitride build-up and bevel angle may be
major factors when the surface that is cut will be welded
after the cutting operation. Dross-free cutting is important
when finish cut quality is desired to avoid a secondary
cleaning operation.
• The desired or specified condition (smooth or rough) of
the face of the cut.
• Nitride deposits can be left on the surface of the cut
when nitrogen is present in the plasma gas stream. The
presence of nitrogen may create porosity if the material
is to be welded after the cutting process.
• The angle between the surface of the cut edge and a
plane perpendicular to the surface of the plate. A per-
fectly perpendicular cut would result in a 0° bevel angle.
• The amount of rounding on the top edge of the cut.
• Molten material which is not blown away from the cut
area and re-solidify on the base of the plate. Excessive
dross build-up may require a secondary clean-up opera-
tion after the cutting process.
• The width of the cut (or the width of material removed
during the cut).
Table 4-C contains cut quality information for each plasma
and secondary combination on a variety of materials and
thicknesses.
Cut Surface
Nitride Deposits
Bevel Angle
Top-Edge Rounding
Dross Build-up
Kerf Width
Figure 4-F Cut Characteristics
Kerf Width
Cut Surface
Bevel Angle
Top Edge
Rounding
Cut Surface
Drag Lines
Dross
Build-Up
Top
Spatter
A-00007