|
MACHINING OPERATIONS,
Normal machining techniques may be
used for niobium, however it does have a tendency to gall,
tear and weld to the face of the cutting tool, which makes
tool design and lubricant selection very important. Both carbide
and high-speed steel tools may be used, although the tendency
to gall is greater with the carbide tools. Water-soluble cutting
oils that contain sulfur or chlorine are preferred for most
machining operations on niobium, except in turning, where
a soluble-oil emulsion is satisfactory. A dilute soluble-oil
emulsion as a grinding fluid is also recommended, which is
better for producing fine finishes. Information for specific
operations are given below:
Turning
Niobium and niobium alloys can be turned
using standard shop equipment, however there are a few special
guidelines to follow. It is important to use high positive
rake angles to reduce cratering and abrasive wear. Also, chip
breakers have not proven to be practical because of niobiumÕs
tough, stringy nature. This makes tool design and selection
critical to turning operations. Recommended operating parameters
are given in Tables 3 and 4.
TABLE 3: SINGLE POINT TURNING OF NIOBIUM
| |
|
Carbide Tool |
|
|
High
Speed
Steel Tool
|
|
| DEPTH
OF CUT
in
(mm)
|
TOOL
MATERIAL
AISI
(ISO)
|
SPEED
fpm
(m/min)
|
FEED
ipr
(mm/r)
|
TOOL
MATERIAL
AISI
(ISO)
|
SPEED
fpm
(m/min)
|
FEED
ipr
(mm/r)
|
| 0.040
|
C-2
|
300
|
0.005
|
T15,
M42 |
80
|
0.005
|
| 0.150
|
C-2
|
265
|
0.005
|
T15,
M42 |
70
|
0.005
|
| (1.0)
|
(K20,
M20) |
(90)
|
(0.13)
|
(S9,
S11 |
(24)
|
(0.13)
|
| (4.0)
|
(K20,
M20) |
(81)
|
(0.13)
|
(S9,
S11) |
(21)
|
(0.13)
|
TABLE 4: CUTOFF AND FORM TOOL TURNING OF NIOBIUM
| |
|
FEED
|
| |
|
ipr
|
| |
|
(mm/r)
|
| TOOL
|
SPEED
|
Cutoff Tool Width
|
Form Tool Width
|
| AISI
|
fpm
|
.062
in |
.125in
|
.250in
|
.500
in |
.750
in |
1.00
in |
1.50
in |
2.00
in |
| (ISO)
|
(m/m)
|
(1.5mm)
|
(3mm)
|
(6mm)
|
(12mm)
|
(18mm)
|
(25mm)
|
(35mm)
|
(50mm)
|
| T15,
M42 |
55
|
.001
|
.001
|
.0015
|
.0015
|
.0015
|
.001
|
.0007
|
.0007
|
| C-2
|
185
|
.001
|
.001
|
.0015 |
.0015 |
.0015 |
.001 |
.0007 |
.0007 |
| (S9,
S11) |
(20)
|
(.025)
|
(.025)
|
(.038) |
(.038)
|
(.038)
|
(.025)
|
(0.018) |
(0.018)
|
| (K40,
M40) |
(58)
|
(.025)
|
(.025) |
(.038) |
(.038) |
(.038) |
(.025)
|
(0.018) |
(0.018)
|
Three of Eleven 1
2 3 4
5 6
7 8
9 10
11
|
