Note: Descriptions are shown in the official language in which they were submitted.
Back~round
There is a need for a high strength structure with cor-
rosion resistant internal metal surfaces as, for example, a
gate valve installed in a line containing corrosive fluids
under high pressure~ Such a valve could be made of AISI 4130
steel and have an interior (valve chamber and passages~ lined
with a 300 Series stainless steel.
Many attempts have been made to provide such structures.
U.S. Patent Nos. 3,349,789 and 2,497,780 each provide valves
with liners which must be secured and sealed in the flow
passages but no provisions are made to line the valve chambers.
Products have been made by the hot isostatic pressure
process by creating a space which is filled wlth powdered
metal and surrounded with a flexible material which can main-
tain a seal under the forming temperature and pressure. The
powdered metal when subjected to the heat and pressure becomes
consolidated into the desired shape. The prior art methods
have been devoted to forming solid structures or coating the
exterior of a structure. Other e~amples of prior art may be
found in U.S. Patent Nos. 3,631,5~3, 3,992,202 and 4,142,888,
but such prior art does not disclose any method of using the
hot isostatic pressing process to form a lining within cavities
of a structure such as, for example, a valve body or a blowout
preventer body.
Summary
The present invention relates to an improved hot iso-
static pressing method of lining the cavities of a body. Hot
isostatic pressing (HIP) is well known in the art and is des-
cribed, for example, in Chapter 9 of the "Powder Metallurgy
Equipment Manual" of the Powder Metallurgy Equipment Association,
2nd Ed. 1977. The method includes the steps of establishing a
space within the body cavities bounded by the cavity walls and
a yieldable mold filling the space with a powdered metal, draw-
ing a vacuum on the space, and subjecting the body to forming
temperature and pressure whereby a lining of the consolidated
powdered metal is formed with the body cavity.
In accordance with one aspect, the invention is the
method of lining a body having a plurality of intersecting
cavities including the steps of positioning a thin metal struc-
ture within each of said cavities of said body in spaced relationto the walls of said cavities, securing said metal structures to
said body to provide an interconnected space within said
cavities, filling said space with metal powder, evacuating gas
from said space, and subjecting said body, said structures, and
said powder to elevated temperature and pressure sufficient to
consolidate the metal powder into a dense uniform interconnected
metal coating lining said cavities.
In accordance with another aspect, the invention is
the method of lining a body having a plurality of intersecting
cavities including the steps of securing and sealing a thin
metal sealed structure within the intersecting body cavities
in spaced relation to the walls of the cavities to provide an
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interconnected sealed space between said structure and the
walls of said cavities, filling said interconnected sealed
space with metal powder, evacuating gas from the said space,
subjecting the body with the sealed structure and metal powder
therein to a temperature of approximately 2100F and pressure
of approximately 15,000 psi for a period of approximately two
hours, to consolidate the metal powder into a dense uniform
interconnected lining in said cavities, cooling the lined body,
and machining the lined cavities to the desired dimensions.
In accordance with another aspect, the invention is
the method of lining a metal body having intersecting cavities
including the steps of positioning a pressure -transmitting
m~tal mold within and spaced from the walls of the intersecting
cavities in the body to provide an interconnected sealed space
within said cavities, filling the interconnected space between
the mold and the walls of said cavities with metal powder,
drawing a vacuum on said space filled with metal powder, and
subjecting the body and mold to sufficient temperature and
pressure for a sufficiently long period to consolidate the
metal powder into a dense uniform interconnected metal lining
of the cavities.
In accordance with another aspect, the invention is
the method of applying a corrosion resistant coating to inter-
secting internal surfaces of a high strength pressure vessel
comprising securing and sealing a yieldable mold in spaced
relationship to the surfaces to be coated to provide an inter-
connected sealed space lining said surfaces, filling the space
between the surfaces and the mold with metal powder, drawing a
vacuum in the space, and subjecting the mold, metal powder and
structure to elevated temperature and pressure sufficient to
consolidate the metal powder into a dense uniform interconnected
metal coating on the surfaces.
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In accordance with another aspect, the invention is
the method of producing a lined valve structure from a body
having a chamber and flow passages connected therewith including
the steps of machining the walls of the chamber and the flow
passages over-sized in a valve body, nickel plating the
machined walls of the chamber and the flow passages, inserting
a stainless steel can into the chamber, said can being sized to
be spaced from the machined, nickel-plated walls of the chamber,
a sleeve extending through and sealed to said can, inserting a
stainless steel tube into the body flow passages and through
the sleeve, said sleeve being spaced from the machined, nickel-
plated walls of the flow passages, securing end closure rings
around the open ends of said can and said tube, securing said
end closure rings to the exterior of said valve body to ensure
that said can and said sleeve are spaced uniformly from the
machined walls of the body, one of said closure rings having a
fill tube extending therethrough, flowing a stainless steel
metal powder through said fill tube into the space in said
cavity and passages surrounding said can and said tube, vibrating
said val~e body to assure complete filling of the space with the
metal powder, withdrawing gas from said space to reduce the
pressure therein, closing and sealing the fill tube, heating
the body, can, sleeve and metal powder under forming pressure
to forming tem~erature in an autoclave, maintaining the temperature and
pressure in the autoclave for the sufficient ti~e to cause the metal powder
to be consolidated into a lining, allowing the lined body to cool, and
machining the lined chamber and passages to their desired dimensions.
In accordance with another aspect, the invention is
the method of producing a lined valve structure from a body
having a chamber and flow passages connected therewith including
the steps of machining the walls of the chamber and the flow
passages over-sized in a valve body, nickel plating the machined
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walls of the chamber and the flow passages, inserting a stain-
less steel can into the chamber, said can being sized to be
spaced from the machined, nickel-plated walls of the chamber,
inserting a can into the body flow passages, said cans being
sized to be spaced from the machined, nickel-plated walls of
the flow passages and from the can in the chamber, securing end
closure rings around the open ends of said cans, securing said
end closure rings to the exterior of said valve body to ensure
that said cans are spaced uniformly from the machined walls of
the body, one of said closure rings having a fill tube extending
therethrough, flowing a stainless steel metal powder through
said fill tube into the space in said cavity and passages sur-
rounding said cans, vibrating said valve body to assure complete
filling of the space with the metal powder, withdrawing gas from
said space to reduce the pressure therein, closing and sealing
the fill tube, heating the body, cans, and metal powder under
forming pressure to forming temperature in an autoclave, main-
taining the temperature and pressure in the autoclave for the
sufficient time to cause the metal powder to be consolidated
into a lining, allowing the lined body to cool, and machining
the lined chamber and passages to their desired dimensions.
In accordance with another aspect, the invention is
a lined valve body comprising an alloy steel body having a
valve chamber and flow passages intersecting therewith, and a
hot isostatic pressure consolidated powdered metal lining the
walls of the valve chamber and the flow passages.
In accordance with another aspect, the invention is
a lined structure comprising a body having a plurality of inter-
secting cavities therein, and a hot isostatic pressure consoli-
dated powdered metal lining the walls of the cavities.
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Brief Description of the Drawings
These and other objects and advantages of the present
invention are hereinafter set forth and explained with
reference to the drawings wherein:
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'f,~
FIG. 1 is a cross-sectional view of a valve body illus-
trating the struc~ure used to provide the space within the
cavities of the structure.
FIG. 2 is a partial sectional view taken along line 2-2
in FIG. 1.
FIG. 3 is a cross-sectional view of the completed struc-
ture showing the finished structure with the consolidated
metal lining after machining.
Descri~tion of the Preferred Embodiments
Valve body 10, shown in FIG. 1, is an alloy steel struc-
ture having cavities including flow passages 12 and valve
chamber 14 which are to be provided with a corrosion resistant
lining.
To prepare for the addition of metal powder, can 16,
having thin tube 18, flat bottom 20 and thin sleeve 22 ex-
tending through the intermediate portion of tube 18 is in-
serted into valve chamber 14. Bottom 20 is sealed to the end
of tube 18 as by welding and sleeve 22 is also sealed to
tube 18 as by welding. Thin tube 24 is inserted through
passages 12 and sleeve 22 as shown. Ring 26 is welded to the
exterior of can 16 and to ~he exterior of body 10 as shown and
rings 28 and 30 are welded around the ends of tube 24 and to
the exterior of body 10. Fill tube 32 extends through ring 26
and fill tube 34 extends through ring 30. The structure of
can 16, tube 24 and their sealing rings 26, 28 and 30 provides
a space 36 within the walls of passages 12 and chamber 14.
This structure functions as a pressure transmitting yieldable
mold or thin metal sealed structure as hereinafter explained.
It is important that all of the welds in the structure of
can 16, sleeve 22 and tube 24 be air tight and remain so
during the consolidation step to exclude air from the heated
metal powder.
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Space 36 within body cavities 12 and 14 is then filled
through fill tubes 32 and 34 with a suitable metal po~der,
such as 316 stainless steel. It is recommended that body 10
be vibrated during filling of space 36 so that it is com-
pletely filled with the metal powder before proceeding to the
next step. It is preferred that the material of can 16,
tube 24 and rings 26, 28 and 30 be similar to the material
used for the lining. Also, it is suggested that space be
sufficiently large to provide a lining of consolida~ed metal
which is sufficiently thick to allow for machininy to the
final shape without any depressions or holidays in the fini-
shed lining. When the same material is used for can 16 and
tube 24, a portlon of the fininshed lining may be the material
of can 16 and tube 24.
When space 36 is completely filled, a vacuum is drawn
thereon by connection of suitable means such as a vacuum pump
(not shown) to either or both of fill tuhes 32 and 34. Suffi-
cient vacuum should be drawn so that the amount of gases
present in space 36 will not interfere with the formation of a
suitable consolidated metal lining. When the desired vacuum
is reached fill tubes 32 and 34 are closed and sealed. If
desired, suitable valves (not shown) may be secured thereon so
that they may be closed when the vacuum drawing step is fini-
shed. Such valve~ are recommended to be leak proof when
subjected to forming conditions.
Thereafter, body 10 is placed in an autoclave (not shown)
or other suitable device wharein it is subjected to forming
temperature (2100F approximately1 and pressure (15,000 psi
approximately). The body 10 is retained in such forming
condition for several hours and then it is allowed to cool.
During exposure to forming conditions in the autoclave,
can 16 and tube 24~ being yieldable, are expanded to compress
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the powdered metal against the walls of passages 12 and cham-
ber 14. The heat and pressure thus cause the metal to be
consolidated into a solid lining within the body which is
completely bonded to the walls of passages 12 and chamber 14.
If can 16 and tube 24 are made of the same material as the
lining, they will be integral with the lining and may form a
part of the final product.
The cooled body 10 is heat treated as required to obtain
the desired mechanical properties and then machined to the
shape shown in FIG. 3. It then has a uniform smooth corrosion
resistant lining 40 on the walls of passages 12 and cham-
ber 14. If can 16 and tube 24 are made of a different mater-
ial from the lining, they will preferably be en~irely removed
during the machining step.
It is suggested that the walls to be lined by the method
of the present invention be nickel plated as preparation for
the forming of a lining by the method of the present inven-
tion. It is believed that the nickel plating prevents oxida-
tion, helps obtain bond continuity and prevents the chrome in
the metal powder from migrating into the alloy and forming an
undesired martensitic structure.
It is contemplate~ that the method of the present inven-
tion may be used to provide linings of nickel, nick~l alloys,
tantalum, Hastelloy alloys, copper, copper alloysl cobalt base
alloys, stainless steels and titanium alloys and carbides
bonded to a body of various grades of alloy steel, carbon
- steel or stainless steels.
The method of the present invention provides a lining on
the walls of intersecting bores or cavities in a thick-walled
pressure vessel by using the pressuxe vessel as the base metal
to accept the hot isostatic pressed metal powder. The struc-
ture shown and described is an alloy steel valve body lined
X
with stainless steel. The method may be used to line the bore
and guideways of a blowout preventer body by using two stain-
less steel tubes as the mold around the space in which the
metal powder is placed in place of the tube and can described.
The formation conditions (temperature, pressure~ time and
degree of vacuu~) are well known and should be adjusted to the
particular materials being used.
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