U.S. patent application number 10/693014 was filed with the patent office on 2004-08-12 for homogeneous shaped charge liner and fabrication method.
Invention is credited to Ocher, Vlad, Polese, Frank J., Rubin, Jack A..
Application Number | 20040156736 10/693014 |
Document ID | / |
Family ID | 32829560 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040156736 |
Kind Code |
A1 |
Ocher, Vlad ; et
al. |
August 12, 2004 |
Homogeneous shaped charge liner and fabrication method
Abstract
A shaped charged liner for oil well perforating is made from
composite metal powder of clusters of pre-agglomerated particles of
a denser metal with an agglutinating metal which is press-molded or
tap-molded into a near net-shape liner preform which is then
sintered to form a sintered body which is hot-coined or forged to
form the final shape liner. The powder is formed by different
density metal particles which are preclustered.
Inventors: |
Ocher, Vlad; (San Diego,
CA) ; Polese, Frank J.; (San Diego, CA) ;
Rubin, Jack A.; (San Diego, CA) |
Correspondence
Address: |
CHARMASSON & BUCHACA & LEACH LLP
1545 HOTEL CIRCLE SOUTH
SUITE 150
SAN DIEGO
CA
92108-3412
US
|
Family ID: |
32829560 |
Appl. No.: |
10/693014 |
Filed: |
October 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60421499 |
Oct 26, 2002 |
|
|
|
Current U.S.
Class: |
419/28 |
Current CPC
Class: |
F42B 1/036 20130101;
F42B 1/032 20130101; B22F 2998/10 20130101; B22F 1/148 20220101;
B22F 2998/10 20130101; B22F 1/0003 20130101; B22F 1/148 20220101;
B22F 3/02 20130101; B22F 2998/10 20130101; B22F 3/10 20130101; B22F
3/16 20130101; B22F 2998/10 20130101; B22F 1/0003 20130101; B22F
1/148 20220101; B22F 3/02 20130101 |
Class at
Publication: |
419/028 |
International
Class: |
B22F 003/24 |
Claims
What is claimed is:
1. A process for manufacturing to a desired shape and dimensions, a
homogeneous shaped charge liner which comprises: selecting a
free-flowing powder of agglomerated nodules of a first metal and of
a second metal having a higher specific gravity and a higher
melting point than said first metal, wherein each of said nodules
comprises an agglutination of sub-nodules wherein each of said
sub-nodules include at least one particle of said first metal and
at least one particle of said second metal bonded together;
pressing a volume of said powder into a compact; sintering said
compact at a temperature sufficient to melt said first metal to
form a sintered body; and coining said sintered body into a
composite body having said desired shape and dimensions.
2. The process of claim 1, wherein said step of pressing comprises
shaping said compact to a near net-shape of said desired shape.
3. The process of claim 1, wherein said pressing comprises
tap-molding said volume.
4. The process of claim 1, wherein said pressing comprises
compacting said volume into a mold at room temperature.
5. The process of claim 1, wherein said selecting comprises
selecting said second metal from a group consisting of metals and
alloys having a specific gravity of at least 10 grams/cm.sup.3.
6. The process of claim 5, wherein said second metal is selected
from the group consisting of tungsten, molybdenum, and alloys
thereof.
7. The process of claim 5, wherein said first metal is selected
from the group consisting of copper and alloys thereof.
8. The process of claim 1, wherein: said selecting comprises
selecting copper as said first metal and tungsten as said second
metal; and said sintering comprises sintering at a temperature
between about 1090.degree. C. and 1230.degree. C.
9. The process of claim 1, wherein said step of selecting comprises
selecting a aggregate powder consisting of particles of the first
and second metals, breakably bonded together into nodules and
sub-nodules.
10. In the process of manufacturing a shaped charge liner for use
in perforating wells by pressing a volume of powdered metal
particles of different densities, an improvement which comprises:
using a free-flowing powder of preclustered nodules of said metal
particles of different densities.
11. A process for fabricating a shaped charge liner for perforating
a well comprises: selecting a free-flowing powder of
pre-agglomerated particles of different density metals; and forming
a volume of said powder into a shaped charge liner.
12. The process of claim 11, wherein said forming comprises
press-molding said volume into a compact.
13. The process of claim 11, wherein said forming comprises
tap-molding said volume into a compact.
Description
FIELD OF THE INVENTION
[0001] This invention relates to explosive shaped charges and more
particularly forming shaped charge metal liners used, for example,
in oil well perforating.
BACKGROUND OF THE INVENTION
[0002] It is well known to use shaped charges for the purpose of
creating perforations in well bores to extract a marketable flow of
oil, gas or other material from a given well, as disclosed in Reese
et al., U.S. Patent Application Publication No. US 2002,0007754 and
Jacoby et al., U.S. Pat. No. 6,349,649 incorporated herein by this
reference. In general, a metal liner is formed into a shape which,
during an explosion, guides and focuses explosive gasses to form a
high velocity jet which perforates the oil-producing strata. Liner
shapes are selected according to the strata being perforated and
can be conical, bi-conical, hemispherical, tulip or trumpet shaped,
among others.
[0003] Liners can be made from solid metal such as the deep-drawn
liners disclosed in Jacoby supra. Solid metal liners generally
suffer from the disadvantage of allowing a "slug" or "carrot" to
form. Carrots are sections of the shaped charge liner that form
into solid bodies after detonation and do not become part of the
shaped charge jet but rather can interfere with it and/or later
become lodged in the perforation created by the jet. To diminish
"carrots", porous metal liners have been formed by compressing
powdered metal into the desired liner shape. As disclosed in Pratt
et al., U.S. Pat. No. 6,354,219, liners have been formed by
mixtures of two or more different powdered metals along with
potentially binder and lubricant materials. Typically, one of the
metals is a higher density metal and the other metal acts as a
binder or forms a matrix to bind together particles of the heavier
metal. The use of powdered metals allows for inexpensively forming
the liners into the many different liner shapes. Many metals and
alloys have been used for the heavy metal including tungsten,
hafnium, depleted uranium, bismuth, molybdenum and various alloys
thereof among others, while metals used as the binding metal
include copper, lead, zinc, tin, cadmium and various alloys thereof
among others.
[0004] However, due to the differences in the specific gravities
and melting points of the two powdered metals, and the lack of
mutual solubility of metals such as copper and tungsten, for
example, it is difficult to form composites of those two metals
that exhibit a reliable degree of homogeneity using conventional
techniques of compression or compression and sintering.
[0005] It is also known that to maximize penetration depth for the
perforation, it is preferable to form a coherent jet generally
consisting of a continuous stream of small particles traveling at
as high a velocity possible without encountering the degrading
effects of surpassing sound speed for the given liner material. It
has been found that a more homogeneous distribution of higher
density particles within the liner material will enhance the
coherence of the jet.
[0006] One solution has been proposed by Brooks et al., U.S. Pat.
No. 6,296,044 and generally involves mixing particles of two
different melting point metals and an organic binder together into
a homogeneous feedstock for injection molding. Alternately, the
lower melting temperature metal of the two metals can act as the
binder. In general, the disadvantages of this method are that it
requires extended debinding time leading to low productivity rates,
and suffers from generating compact preforms having a high
percentage of cracking.
[0007] The instant invention results from an attempt to devise a
simpler and more practical process to manufacture shaped charge
liners using powdered metallurgy techniques but which also results
in improved homogeneity.
SUMMARY OF THE INVENTION
[0008] The principal and secondary objects of this invention are to
provide a practical and simple process to precisely form shaped
charge liners combining high density metal particles with lower
density binding or agglutinating metals in a homogeneous
structure.
[0009] These and other objects are achieved by pre-agglomerating
particles of a high specific gravity metal with an agglutinating,
different density metal to form a free-flowing powder of
pre-agglomerated particles which are then press-molded or
tap-molded to form near net-shape liner preforms. The preforms are
then partially sintered and then hot-coined or forged to form the
final shape liner.
[0010] Pre-agglomeration can occur in several ways. In a first
embodiment, particles of different density metals are pre-bonded
together by an adhesive in a way which allows the bond between the
two metals to be breakable during the press-molding step. In
another embodiment, free-flowing powder is selected of
pre-clustered nodules of the two metals, where each nodule
comprises a grouping of subnodules wherein each subnodule includes
a core made of the denser metal surrounded by a blanket of smaller
particles of the agglutinating metal bonded by coreduced metal
oxides. In another embodiment, free-flowing powder is selected of
pre-clustered nodules of the two metals, where each nodule
comprises a grouping of subnodules wherein each subnodule includes
at least one particle of each of the different density metals. The
nodules are breakably agglutinated by coreduced metal oxides.
Within each subnodule, the particles are paired by surface
diffusion occurring during the fabrication process.
BRIEF DESCRIPTION OF THE DRAWING
[0011] FIG. 1 is a block diagram illustration of the manufacturing
process according to the invention.
[0012] FIG. 2 is a diagrammatical illustration of a
pre-agglomerated metal powder.
[0013] FIG. 3 is a diagrammatical illustration of an alternate
pre-agglomerated metal powder.
[0014] FIG. 4 is a diagrammatical illustration of an alternate
pre-agglomerated metal powder.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
[0015] Referring now to the drawing, as shown in FIG. 3, there is
shown a simplified process of the invention where a volume of
free-flowing sinterable powder made of pre-agglomerated particles
of at least two metals is selected 1 and then press-molded 2 into a
compact preform 3 having the desired net shape of the shaped charge
liner for use in oil well perforation. The pressing is done under a
pressure of a range of approximately 1350 to 3400 atmospheres
(20,000 to 50,000 lbs/in.sup.2).
[0016] Alternately, the free-flowing powder can be suspended in a
volatile carrier such as an organic binder such as wax, polyester
resin, polyethylene or polypropylene to form a feedstock for an
injection molding step. Free-flowing powder refers those powders so
having a flowability defined by the Metal Powder Industry
Federation (MPIF).
[0017] The preform 3 is then partially sintered 4 at ambient
pressure and at a temperature just above the melting point of the
metal having a lower melting point to form a partially sintered
body 5. If the lower melting point metal is copper, then that
temperature will range between 1090.degree. C. and 1230.degree.
C.
[0018] The partially sintered body is strong enough to withstand
the rigors of further individual automated manipulation and
processing. Partial sintering also prevents unwanted overflow of
the melted lower temperature metal to the surface of the body. The
melted metal is partially constrained by adjacent unmelted
particles.
[0019] The partially sintered body is then maintained at a
temperature of between 200.degree. C. and 800.degree. C. and then
hot-coined or forged 6 in a hydraulic press under a pressure within
a range of approximately 1350 to 6800 atmospheres (20,000 to
100,000 lbs/in.sup.2) to form the final shape liner 7. The coining
or forging step allows for the inexpensive automated creation of
liners within acceptable tolerance without significant additional
machining. However, the liner may be machined 8 if necessary to
further desired tolerances. Final machining can also include
various other finalization steps such as annealing, grinding,
lapping, stripping, cleaning or other known processing.
[0020] In general, the term "coining" means pressing an existing
body or plug so as to reshape it without removing a large portion
of material. The term "forging" in this specification generally
means coining while the material has been heated.
[0021] Now will be described the preferred free-flowing powder for
use in the above described process. The preferred powder is made of
clusters of agglomerated particles of at least two metals having
different densities and melting points. A first type of particle is
made of a metal or alloy having a melting point of less than
1500.degree. C. such as copper and alloys thereof. A second type of
particle is made from a metal or alloy having a melting point of
more than 1500.degree. C. and a density of at least 10 g/cm.sup.3.
Tungsten and molybdenum are preferred choices that can be used
singly or together. These metals exhibit a higher density than
those of the first type, and a higher melting point. They also have
lesser coefficients of thermal expansion.
[0022] By adjusting the weight ratio of the first type to the
second type of metals within a range of between approximately 5 and
30 percent, one can create a sintered liner of adequate strength,
homogeneity and desired density.
[0023] Various different types of clusters of pre-agglomerated may
be used to form the preferred powder.
[0024] In a first embodiment, as shown in FIG. 4, each cluster of
pre-agglomerated particles is formed by particles of the first type
of metal 10 and particles of the second type of metal 11 bonded
together by a volatile adhesive 12. The bond between the two metals
is weak enough to be breakable during the press-molding step. This
allows the preform to attain a density which both maintains shape
under its own weight before the partial sintering step and brings
the particles into close enough proximity to prevent undue flow of
melted metal during partial sintering.
[0025] As disclosed in Polese et al. U.S. Pat. No. 5,413,751,
incorporated herein by this reference, the pre-agglomerated
clusters may be formed by mixing together separate powders of the
different density metals and adding a volatile liquid adhesive to
the mixture to form a slurry. The slurry is then atomized into
droplets through a process whereby the slurry is subjected to
blasts of a gas, typically air, heated to a temperature above the
melting point of the volatile liquid adhesive. After drying, the
droplets combining all types of particles are continuously
collected to form the pre-agglomerated powder.
[0026] In another embodiment, as shown in FIG. 5, free-flowing
powder is made of pre-clustered nodules, where each nodule
comprises a grouping of subnodules wherein each subnodule 20
includes a core 21 made of the denser metal surrounded by a blanket
of smaller particles 22 of the agglutinating metal.
[0027] In another embodiment, referring now to FIG. 6, free-flowing
powder is made of pre-clustered nodules, where each nodule 30
comprises a grouping of subnodules 31 wherein each subnodule
includes at least one particle 32 of the first type of metal and at
least one particle 33 of the second type of metal. The nodules are
breakably agglutinated by a binder. Within each subnodule, the
particles are paired by surface alloying occurring during the
fabrication process.
[0028] The desired proportion of the first metal to the second is
determined by the relative size or weight of the particles of each
subnodule. When this type of powder is compacted into a body, and
the body sintered at a temperature slightly above the melting point
of the agglutinating metal, the lower melting point agglutinating
metal is partially constrained by surrounding particles of
non-melted metal, and thereby, prevented from flowing further.
[0029] The powder of clustered pre-agglomerated particles shown in
FIG. 6 is formed according to a proprietary process developed by
OSRAM-SYLVANIA of Towanda, Pa. as disclosed in part in U.S. Pat.
No. 5,439,638 Houck et al., which is incorporated herein by this
reference. The powders of FIGS. 5 and 6 are commercially available
from that company. More specifically, the powders are respectively
designated as Type I and Type III powder electronic grade. The
diameters of the nodule range between about 40 and 350 microns. The
diameter of the particles range between about 0.5 and 7
microns.
EXAMPLE
[0030] A copper and tungsten powder available from Sylvania of
Towanda, Pa. sold under the designation TUNGSTAR-Type III was
selected that contained approximately 15% copper and 85% tungsten
by weight (27.7% and 72.3% per volume). The powder mixture
consisted of particles of metal averaging 0.6 to 2.5 microns in
diameter.
[0031] The powder was then press-molded at room temperature under
2050 atmospheres (30,000 lbs/in.sup.2) into the net shape of the
desired liner component. The resulting preform compact was placed
in a sintering furnace and subjected to temperatures of
approximately 1100.degree. C. for about 100 minutes under ambient
atmospheric pressure to form a partially sintered body. The body
was allowed to cool to a temperature of approximately 300.degree.
C. whereupon it was placed in a hot stamping press and forged under
a pressure of about 3400 atmospheres (50,000 lbs/in.sup.2) to form
a forged liner.
[0032] After cooling, the liner was then machined to tolerances of
about .+-.0.07 millimeter for the final shaped charge liner.
[0033] The final article exhibited a specific gravity of about 96%
of theoretical gravity of a perfectly solid composite, and a high
homogeneity. No surface bleeding of the copper could be observed on
the surface of the liner. The liner exhibited a coefficient of
thermal expansion of about 8.0.times.10.sup.-6/.degree. C.
[0034] Other liners were made with powder having a ratio of copper
to tungsten varying between 5 and 30 weight percent copper
according to the same process.
[0035] While the preferred embodiments of the invention have been
described, modifications can be made and other embodiments may be
devised without departing from the spirit of the invention and the
scope of the appended claims.
* * * * *