U.S. patent application number 10/767052 was filed with the patent office on 2004-10-21 for large diameter tungsten-lanthana rod.
Invention is credited to Dixon, Thomas J., Martin, Harry D. III, Morgan, Ricky D..
Application Number | 20040206429 10/767052 |
Document ID | / |
Family ID | 29583252 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040206429 |
Kind Code |
A1 |
Morgan, Ricky D. ; et
al. |
October 21, 2004 |
Large diameter tungsten-lanthana rod
Abstract
A large-diameter tungsten-lanthana rod having an elongated grain
structure substantially parallel to the longitudinal axis of the
rod is described. The large diameter rod is produced by rolling at
a temperature greater than 1400.degree. C. and less than
1700.degree. C. to achieve at least about a 40% reduction in
cross-sectional area. The high strength of the longitudinally
elongated grain structure is desirable for applications such as
rocket nozzles.
Inventors: |
Morgan, Ricky D.; (Milan,
PA) ; Dixon, Thomas J.; (Towanda, PA) ;
Martin, Harry D. III; (Troy, PA) |
Correspondence
Address: |
OSRAM SYLVANIA INC
100 ENDICOTT STREET
DANVERS
MA
01923
US
|
Family ID: |
29583252 |
Appl. No.: |
10/767052 |
Filed: |
January 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10767052 |
Jan 29, 2004 |
|
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10160751 |
May 31, 2002 |
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Current U.S.
Class: |
148/673 |
Current CPC
Class: |
B22F 3/16 20130101; C22C
32/0031 20130101; B22F 2003/248 20130101; B22F 2003/185 20130101;
C22C 27/04 20130101; B22F 2998/10 20130101; B22F 2998/10 20130101;
B22F 3/10 20130101; B22F 3/24 20130101; B22F 3/18 20130101; B22F
3/02 20130101 |
Class at
Publication: |
148/673 |
International
Class: |
C22F 001/18 |
Claims
1-7. (canceled).
8. A method of making a large-diameter tungsten-lanthana rod
comprising rolling a tungsten-lanthana rod at a temperature greater
than 1400.degree. C. and less than 1700.degree. C. until at least
about a 40% reduction in the cross-sectional area of the rod is
achieved.
9. The method of claim 8 wherein the rolling is performed by
multiple passes.
10. The method of claim 8 wherein at least about a 70% reduction in
cross-sectional area is achieved.
11. The method of claim 8 wherein the rod after rolling has a UTS
of from about 70 to about 85 ksi, a YS of from about 60 to about 80
ksi and a hardness of from about 40 to about 43 Rockwell C.
12. The method of claim 11 wherein the tungsten-lanthana rod
contains from 0.3 to 2.5 weight percent lanthana.
13. The method of claim 8 wherein the rod is stress relieved at a
point between 25 and 45% reduction in cross-sectional area.
14. The method of claim 8 wherein the rod is stress relieved after
rolling.
Description
TECHNICAL FIELD
[0001] This invention is related to tungsten rod and methods of
forming tungsten rod. More particularly, it is related to
large-diameter tungsten-lanthana rod with an elongated grain
structure.
BACKGROUND OF THE INVENTION
[0002] Tungsten-lanthana alloys are well-known. A description of
these alloys, their methods of making, and uses can be found in
U.S. Pat. Nos. 5,590,386, 5,742,891, 4,923,673, 3,159,908 and
3,086,103.
[0003] In addition to the uses referenced above, tungsten-lanthana
alloys are used to manufacture rocket nozzles. Rocket nozzles
require high strength along the nozzle's longitudinal axis because
of the high temperatures and internal combustive forces generated
during its operation. In order to provide this high strength, the
tungsten-lanthana rod from which the nozzle is machined should have
a microstructure in which the tungsten grains are elongated in a
direction substantially parallel to the longitudinal axis of the
rod. Current methods of forging and extrusion for forming
large-diameter tungsten rods (>0.625 in. dia.) achieve
acceptable mechanical properties but have been ineffective at
producing a longitudinal grain elongation.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to obviate the
disadvantages of the prior art.
[0005] It is another object of the invention to provide a large
diameter tungsten-lanthana rod having a grain structure which is
elongated in a direction substantially parallel to the longitudinal
axis of the rod.
[0006] It is still another object of the invention to provide a
large-diameter tungsten-lanthana rod having mechanical properties
desirable for rocket nozzle applications.
[0007] These and other objects and advantages of the invention have
been achieved by rolling large-diameter tungsten-lanthana rod at a
temperature greater than 1400.degree. C. and less than 1700.degree.
C. to achieve a reduction in the cross-sectional area of at least
about 40%. These rolling parameters yield a large-diameter
rod-having an elongated grain structure which is substantially
parallel to the longitudinal axis of the rod. The as-worked rod has
mechanical properties desirable for rocket nozzle applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a micrograph of the longitudinally elongated grain
structure of a rolled tungsten-lanthana rod subjected to a
reduction in cross-sectional area of about 40%.
[0009] FIG. 2 is a micrograph of the longitudinally elongated grain
structure of a rolled tungsten-lanthana rod subjected to a
reduction in cross-sectional area of about 70%.
DETAILED DESCRIPTION OF THE INVENTION
[0010] For a better understanding of the present invention,
together with other and further objects, advantages and
capabilities thereof, reference is made to the following disclosure
and appended claims taken in conjunction with the above-described
drawings.
[0011] A rolling process has been developed to produce
large-diameter tungsten-lanthana rod with grain elongation
substantially parallel to the longitudinal axis of the rod. As used
herein, large diameter means that the rod has a diameter greater
than 0.625 inches as worked. Acceptable mechanical properties were
achieved with at least about a 40% reduction in cross-sectional
area (RIA). Preferably, the diameter of the worked rod ranges from
greater than 0.625 inches to 2.250 inches and the lanthana contents
range from 0.3 wt. % to 2.5 wt. %.
[0012] The parallel-elongated structure was achieved by rolling
bars of tungsten-lanthana at temperatures greater than 1400.degree.
C. In particular, rolling temperatures must be greater than
1400.degree. C. and less than 1700.degree. C. Rod reheating can
occur at any point up to a maximum of four rolling passes. Starting
bar diameters of greater than 1.5 inches require an in-process
stress relief at a point between 25 and 45% reduction in area.
[0013] The following non-limiting examples are presented.
EXAMPLE 1
[0014] A pressed and sintered bar of tungsten containing 1.3 wt. %
lanthana (LT8103-008) and measuring 2.374 inches in diameter by
23.5 inches in length was rolled at 1500.degree. C. on a two-high
rod rolling mill to 1.850 inches in diameter by 38 inches in length
(a reduction-in-area of 39.27%) and stress relieved at 1400.degree.
C. for 1/2 hour. The rolling schedule is given in Table 1. The
material was then tested for tensile properties, density, and
hardness. The test results are provided in Table 0.4.
Microstructures showed grain elongation parallel to the
longitudinal axis of the rod.
1TABLE 1 1500.degree. C. Nominal. Nominal Groove Soak Diameter
Diameter Pass Dia. Time Before After RIA cumulative No. (in.)
(min.) (in.) (in.) (%) RIA (%) 1 2.393 15 -- -- -- -- 2 2.393 5 --
-- -- -- 3 2.146 5 -- 2.325 -- 4.1 4 2.146 5 2.325 -- -- -- 5 2.020
5 -- -- -- -- 6 2.020 5 -- 2.085 -- 22.9 7 1.875 15 2.085 1.985 9.4
30.1 8 1.875 5 1.985 1.850 13.1 39.3
EXAMPLE 2
[0015] A pressed and sintered bar of tungsten containing 1.3 wt. %
lanthana (LT8103-004) and measuring-1.400 inches in diameter by 33
inches in length was reduced by a two-high rod rolling method to
0.733 inches in diameter by 50 inches in length at 1500.degree. C.
The rod wasthen finish swaged to 0.682 in diameter by 56 inches in
length at 1300.degree. C.; a total reduction-in-area of 76%. The
rolling schedule is provided in Table 2. The measured mechanical
properties are given in Table 4. FIGS. 1 and 2 show the
microstructures of the rolled rods after about 40% RIA and about
70% RIA, respectively. Greater elongation is observed at the higher
RIA. Grain elongation was parallel to the longitudinal axis of the
rod. Grains are elongated from left to right in the micrographs.
The black specks in the micrographs are the lanthana particles.
2TABLE 2 1500.degree. C. Nominal. Nominal Groove Soak Diameter
Diameter Pass Dia. Time Before After RIA cumulative No. (in.)
(min.) (in.) (in.) (%) RIA (%) 1 1.320 15 1.400 -- -- -- 2 1.320 5
-- -- -- -- 3 1.219 5 -- -- -- 4.1 4 1.219 5 -- 1.290 -- 15.1 5
1.125 5 1.290 1.195 14.2 27.1 6 1.125 5 1.195 1.178 2.8 29.2 7
1.040 5 1.178 1.091 14.2 39.3 8 1.040 5 1.091 1.084 1.3 40.0 9
0.969 5 1.084 1.015 12.3 47.4 10 0.969 5 1.015 1.002 2.5 48.8 11
0.906 5 1.002 0.940 12.0 54.9 12 0.906 5 0.940 0.930 2.1 55.9 13
0.850 5 0.930 0.855 15.5 62.7 14 0.850 5 0.855 0.855 0.0 62.7 15
0.797 5 0.855 0.795 13.5 67.8 16 0.797 15 0.795 0.805 0.0 67.8 17
0.750 5 0.805 -- -- -- 18 0.750 5 -- 0.733 -- 72.6
EXAMPLE 3
[0016] Another bar of tungsten-1.3 wt. % lanthana (LT8103-009)
measuring 2.41 inches in diameter was reduced by a two-high rod
rolling method to a 2.050 inch diameter at 1400.degree. C., a 27.6%
reduction in area. At this point, the bar was rolled on a different
set of rolls at 1400.degree. C. to 2.025 inches in diameter for a
total reduction in area of 29.4%. At this point, the rod split
prematurely due to the 1400.degree. C. rolling temperature. After
stress relieving the rod at 1500.degree. C. for 30 minutes, the rod
was rolled successfully to a 1.265 inch diameter at 1500.degree. C.
for a total reduction in area of 72.4%. The rod was then stress
relieved at 1400.degree. C. for 30 minutes. The actual rolling
schedule is provided in Table 3. Density, hardness and tensile
properties are given in Table 4. As expected, grain elongation was
parallel to the longitudinal axis of the rod.
3TABLE 3 Nominal. Nominal Groove Diameter Diameter Dia.
1500.degree. C. Soak Before After cumulative Pass No. (in.) Time
(min.) (in.) (in.) RIA (%) RIA (%) 1 2.393 15 (1400.degree. C.) --
-- -- -- 2 2.393 5 (1400.degree. C.) -- -- -- -- 3 2.146 5
(1400.degree. C.) -- 2.325 -- 6.9 4 2.146 5 (1400.degree. C.) 2.325
-- -- -- 5 2.020 5 (1400.degree. C.) -- -- -- -- 6 2.020 5
(1400.degree. C.) -- 2.050 -- 27.6 7 1.875 15 (1400.degree. C.)
2.050 -- -- -- 8 1.875 5 (1400.degree. C.) -- 2.025 2.4 29.4 9
1.718 5 (1400.degree. C.) 2.025 1.850 16.5 41.1 10 1.718 15 1.850
1.733 2.5 48.3 11 1.718 5 -- -- -- -- 12 1.578 5 -- -- -- -- 13
1.578 5 -- 1.580 -- 57.0 14 1.445 5 1.580 -- -- -- 15 1.445 5 --
1.422-1.425 -- 65.1 16 1.320 5 1.423 -- -- -- 17 1.320 5 --
1.310-1.325 -- 70.1 18 2.002 5 1.317 1.281 5.4 71.7 19 2.020 5
1.281 1.265-1.266 2.4 72.4
[0017]
4TABLE 4 Sample Direction Density Hardness UTS YS Sample
(longitudinal) (g/cc) Rockwell C (ksi) (ksi) Elongation %
LT8103-004 As rolled Edge 18.76 42.7 -- -- -- Center 18.72 43 85.4
79.4 26 Stress Edge -- 42.8 -- -- -- relieved Center -- 42.9 80,
74.sup..dagger. 71, 66.sup..dagger. 27, 27.sup..dagger.
(1500.degree. C., 1/2 hour) Stress Edge -- 42.6 -- -- -- relieved
Center -- 42.5 77, 79.sup..dagger. 69, 72.sup..dagger. 25,
28.sup..dagger. (1600.degree. C., 1/2 hour) LT8103-008 Stress Edge
18.76 40 71, 73.sup..dagger. 67, 61.sup..dagger. 32,
35.sup..dagger. relieved Center 18.6 39.7 73, 74.sup..dagger. 61,
62.sup..dagger. 28, 30.sup..dagger. (1400.degree. C., 1/2 hour)
LT8103-009 Stress Edge 18.72 41 77, 78.sup..dagger. 62,
64.sup..dagger. 32, 34.sup..dagger. relieved Center 18.64 41.3 81
59 56 (1400.degree. C., 1/2 hour) .sup..dagger.values for two
samples
[0018] The mechanical properties compare favorably with the values
measured for forged materials. In particular, the ultimate tensile
strength (UTS) for forged materials ranges from 65 to 89 ksi; the
yield strength (YS) from 53 to 82 ksi; elongation from 12 to 32%;
and hardness from 41 to 42 Rockwell C. The results in Table 4
demonstrate that the large-diameter tungsten-lanthana rod of this
invention has a UTS of from about 70 to about 85 ksi, a YS of from
about 60 to about 80 ksi and a hardness of from about 40 to about
43 Rockwell C. Thus, the large-diameter rod of this invention
possesses both the grain structure and mechanical properties
desired for rocket nozzle applications.
[0019] While there has been shown and described what are at the
present considered the preferred embodiments of the invention, it
will be obvious to those skilled in the art that various changes
and modifications may be made therein without departing from the
scope of the invention as defined by the appended claims.
* * * * *