| Specialty Metals That Make Our WorldTM |
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| GENERAL
WORKING CHARACTERISTICS |
| Two
unusual features affect the working characteristics of
niobium. First, no appreciable softening occurs below
400° C, the temperature at which niobium reacts vigorously
with the atmosphere, because of its high melting pointÑapproximately
2400° C. Secondly, sheathing for protection is not
practical, because the sheathing material is likely to
be softer that the metal to be worked. Fortunately, niobium's
cold working properties are excellent, and the metal can
be easily forged, rolled, or swaged directly from the
ingot at room temperature. After the cross-sectional area
has been reduced by about 90 percent, annealing is necessary.
Heat treatment at 1200° C for one hour causes complete
recrystallization of material cold worked over 50 percent.
The annealing process must be performed in an inert gas
or in a high vacuum at pressures below 1 x 10 -4 Torr.
The use of a vacuum is preferred, because it is difficult
to ensure the purity of inert gas. It is also less expensive
to use vacuum furnaces for these operations. Niobium is
well suited to deep drawing, and the metal may be cupped
and drawn to tube, although special care must be taken
with lubrication. The sheet metal can be formed easily
by general sheet metal working techniques. The low rate
of work hardening facilitates these operations by reducing
springback. |
| MACHINING |
|
Niobium
may be machined by the usual techniques although, due
to the tendency of the material to gall, special attention
should be paid to tool angles and lubrication.
TURNING
Lathe turning is best carried out with High Speed Steel
tools, using air, soluble oil, Rapid-Tap, or other suitable
products for cooling and lubricating. This material
turns very much like lead or soft copper. It must be
sheared and the chip allowed to slide off the tool surface.
If any buildup of the material is allowed, the pressure
will break the cutting edge and ruin the tool. Carbide
tooling should be used only for fast, light cuts, with
a depth of .010 to .015 inches, to work efficiently.
Tooling recommendations are given in Table 3, which
contains data applying to High Speed Steel and Carbide
tools. Contact Wah Chang for special tooling information
and technical assistance.
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TABLE
3 - TOOLING RECOMMENDATIONS for MACHINING Nb
|
| Approach
AngIe |
15° to 20° |
| Side
Rake |
30° to 35° |
| Side
and End Clearance |
5° |
| Plan
Relief AngIe |
15° to 20° |
| Nose
Radius |
0.020" to 0.030" |
| Cutting
Speed |
60 to 80 feet/minute
with HSS |
| |
250 to 300 feet/minute
with carbide |
| Feed,
Roughing |
0.008" to 0.01 2"/revolution |
| Feed,
Finishing |
0.005" maximum/revolution |
| Depth
of Cut |
0.030" to 0.125" |
Page
15 of 34 Next
INDEX •
CORROSION RESISTANCE
PROPERTIES • FABRICATION
NIOBIUM
PRODUCTS • SPECIFICATIONS
of NIOBIUM
NIOBIUM ELECTRONICS APPLICATIONS
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