U.S. patent application number 10/270112 was filed with the patent office on 2003-08-07 for corrosion-resisting and wear-resisting alloy and device using the same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Chiba, Yoshiteru, Kiyotoki, Yoshihisa, Kumagai, Shin, Ogawa, Yasuhiro, Sakamoto, Akira, Shinohara, Hiroyuki.
Application Number | 20030147769 10/270112 |
Document ID | / |
Family ID | 26598945 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030147769 |
Kind Code |
A1 |
Kiyotoki, Yoshihisa ; et
al. |
August 7, 2003 |
Corrosion-resisting and wear-resisting alloy and device using the
same
Abstract
To provide a corrosion-resisting and wear resisting alloy
including cobalt, nickel or iron as a base used for a sliding part
or a valve seat for a machine, and restraining erosion and
corrosion caused by eutectic carbide constituting the alloy in an
atmosphere with dissolved oxygen. A material is selected from a
cobalt base added with Cr and/or W, a nickel base added with Fe
and/or Cr, and an iron vase added with Cr and/or Ni. The material
is cast into an ingot or a slab to produce an intermediate
material. The intermediate material comprises mesh-like eutectic
carbide and a base material surrounded by the eutectic carbide. A
heat plastic forming is applied to the intermediate material at a
temperature 650.degree. C. or more and the solidus temperature or
less. The eutectic carbide is formed into multiple grains or
clusters as a discontinuous distribution. A resulting
corrosion-resisting and wear-resisting alloy has 0.1 to 0.5 of
coefficient of friction, and 300 to 600 Hv of Vickers hardness
without age-hardening process.
Inventors: |
Kiyotoki, Yoshihisa;
(Hitachinaka, JP) ; Chiba, Yoshiteru; (Hitachi,
JP) ; Kumagai, Shin; (Tokai-mura, JP) ; Ogawa,
Yasuhiro; (Choshi, JP) ; Sakamoto, Akira;
(Mito, JP) ; Shinohara, Hiroyuki; (Tokyo,
JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR, P.C.
1800 DIAGONAL ROAD
SUITE 370
ALEXANDRIA
VA
22314
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
26598945 |
Appl. No.: |
10/270112 |
Filed: |
October 15, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10270112 |
Oct 15, 2002 |
|
|
|
09939591 |
Aug 28, 2001 |
|
|
|
Current U.S.
Class: |
420/435 ;
123/188.3; 251/368; 376/352; 415/200 |
Current CPC
Class: |
F01L 2301/00 20200501;
C21D 7/13 20130101; C22C 19/07 20130101; F01L 1/047 20130101; C22C
38/04 20130101; C22C 38/58 20130101; C22C 38/34 20130101; Y10T
428/12931 20150115; F01L 1/16 20130101; F01L 3/02 20130101; C22C
38/02 20130101; C22C 19/057 20130101; C22C 38/44 20130101 |
Class at
Publication: |
420/435 ;
376/352; 415/200; 251/368; 123/188.3 |
International
Class: |
C22C 019/07 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2000 |
JP |
2000-263258 |
Aug 3, 2001 |
JP |
2001-235714 |
Claims
What is claimed is:
1. A corrosion-resisting and wear-resisting alloy, which is
obtained by selecting a material from cobalt base added with Cr
and/or W, nickel base added with Fe and/or Cr, and iron base added
with Cr and/or Ni, casting said material into an ingot or a slab as
an intermediate material, applying hot plastic forming at a
temperature which is 650.degree. C. or more and the solidus
temperature or less to said intermediate material, which includes a
structure comprising mesh-like eutectic carbide and a base material
surrounded by the eutectic carbide, forming the eutectic carbide as
a discontinuous distribution in a form of multiple grains or
clusters, wherein the coefficient of friction is 0.1 to 0.5, and
the Vickers hardness without age hardening process is 300 to 600
Hv.
2. A corrosion-resisting and wear-resisting alloy according to
claim 1, wherein the coefficient of friction is 0.3 or less.
3. A corrosion-resisting and wear-resisting alloy according to
claim 1, wherein the cobalt base added with Cr and/or W comprises
0.1 to 3.5% of C, 25% or less of Ni, 25 to 35% of Cr, 5% or less of
Fe, 20% or less of W, 1.5% or less of Mo, and 1.5% or less of Si in
weight ratio, the balance Co and inevitable impurities.
4. A corrosion-resisting and wear-resisting alloy according to
claim 1, wherein the nickel base added with Fe and/or Cr comprises
0.1 to 2.5% of C, 3 to 9% of Si, 7 to 25% of Cr, 0.5 to 5% of B, 2
to 6% of Fe, 1 to 5% of W, and 17% or less of Mo in weight ratio,
the balance Ni and inevitable impurities.
5. A corrosion-resisting and wear-resisting alloy according to
claim 1, wherein the iron base added with Cr and/or Ni comprises
0.1 to 1.5% of C, 0.3 to 4% of Si, 4 to 9% of Ni, 3% or less of Mo,
6 to 10% of Mn, and 15 to 25% of Cr in weight ratio, the balance Fe
and inevitable impurities.
6. A fluid device wherein the corrosion-resisting and
wear-resisting alloy according to claim 1 is used for a
wear-resisting part or an erosion shield part.
7. A fluid device wherein the corrosion-resisting and
wear-resisting alloy according to claim 1 with the coefficient of
friction of 0.1 to 0.3 is used for a wear-resisting part or an
erosion shield part.
8. A dynamic device wherein the corrosion-resisting and
wear-resisting alloy according to claim 1 is joined with a base
metal without changing the metal composition for application to a
sliding part or a contact part.
9. A dynamic device wherein the corrosion-resisting and
wear-resisting alloy according to claim 1 with the coefficient of
friction of 0.1 to 0.3 is joined with a base metal without changing
the metal composition for application to a sliding part or a
contact part.
10. A valve, which is provided with a valve element and a valve
casing, wherein valve seats are provided on contact faces of both
of the valve element and the valve casing, and a base body of said
valve seats is provided with a member which comprises one type of
alloy selected from a cobalt-base alloy, a nickel-base alloy, and
an iron-base alloy, in which grain-like or cluster-like eutectic
carbide is diffused as a discontinued distribution, and which has
the coefficient of friction of 0.1 to 0.3.
11. A nuclear power plant, which is provided with a piping system
including a valve on a piping through which a coolant flows,
wherein said valve is a valve according to claim 10.
12. A pump wherein a seat and a washer, which relatively rotate
about a rotating shaft of the pump, are in contact with each other
at a sealed end, and either of the contact faces of the said seat
or said washer is provided with a member which comprises one type
of alloy selected from a cobalt-base alloy, a nickel-base alloy,
and an iron-base alloy, in which grain-like or cluster-like
eutectic carbide is diffused as a discontinued distribution, and
which has the coefficient of friction of 0.1 to 0.3.
13. An internal combustion engine, wherein a valve seat part and a
valve are provided on a cylinder head of said internal combustion
engine, valve seats are respectively provided on contact faces of
both of said valve seat part and said valve, and surfaces of base
bodies of said valve seats is provided with a member which
comprises one type of alloy selected from a cobalt-base alloy, a
nickel-base alloy, and an iron-base alloy, in which grain-like or
cluster-like eutectic carbide is diffused as a discontinued
distribution, and which has the coefficient of friction of 0.1 to
0.3.
14. An internal combustion engine, wherein at least either of
contact faces of a valve lifter or a cam of the internal combustion
engine is provided with a member which comprises one type of alloy
selected from a cobalt-base alloy, a nickel-base alloy, and an
iron-base alloy, in which grain-like or cluster-like eutectic
carbide is diffused as a discontinued distribution, and which has
the coefficient of friction of 0.1 to 0.3.
15. A rotating device comprising: a casing in which liquid flows; a
rotating shaft which is inserted into said casing; and a mechanical
seal device which seals between said rotating shaft and said
casing; wherein said mechanical seal device is provided with a
first seal, which rotates with said rotating shaft, and a second
seal, which is provided on said casing and is in contact with said
first seal, at least either of said first seal or said second seal
includes a corrosion-resisting and wear-resisting alloy where
grain-like or cluster-like eutectic carbide is diffused in a matrix
part of a metal micro structure, and which is in contact with the
other seal, and a main body, and said corrosion-resisting and
wear-resisting alloy is diffusion-welded to said main body.
16. A liquid pressurizing device comprising: a casing; a rotating
shaft inserted into said casing; a fluid pressurizing mean which is
provided on said rotating shaft and pressurizes fluid; and a
mechanical seal device which seals between said rotating shaft and
said casing; wherein said mechanical seal device is provided with a
first seal, which rotates with said rotating shaft, and a second
seal, which is provided on said casing and is in contact with said
first seal, at least either of said first seal or said second seal
includes a corrosion-resisting and wear-resisting alloy where
grain-like or cluster-like eutectic carbide is diffused in a matrix
part of a metal micro structure, and which is in contact with the
other seal, and a main body, and said corrosion-resisting and
wear-resisting alloy is diffusion-welded to said main body.
17. A liquid pressurizing device according to claim 16 wherein said
corrosion-resisting and wear-resisting alloy has 0.1 to 0.3 of
coefficient of friction, and 300 to 600 Hv of Vickers hardness
without age hardening process.
18. A liquid pressurizing device according to claim 17 wherein said
corrosion-resisting and wear-resisting alloy is constituted with a
cobalt base material added with Cr and/or W comprises 0.1 to 3.5%
of C, 25% or less of Ni, 25 to 35% of Cr, 5% or less of Fe, 20% or
less of W, 1.5% or less of Mo, and 1.5% or less of Si in weight
ratio, the balance Co and inevitable impurities.
19. A liquid pressurizing device according to claim 17 wherein said
corrosion-resisting and wear-resisting alloy is constituted with a
nickel base material added with Fe and/or Cr comprises 0.1 to 2.5%
of C, 3 to 9% of Si, 7 to 25% of Cr, 0.5 to 5% of B, 2 to 6% of Fe,
1 to 5% of W, and 17% or less of Mo in weight ratio, the balance Ni
and inevitable impurities.
20. A liquid pressurizing device according to claim 17 wherein said
corrosion-resisting and wear-resisting alloy is constituted with an
iron base material added with Cr and/or Ni comprises 0.1 to 1.5% of
C, 0.3 to 4% of Si, 4 to 9% of Ni, 3% or less of Mo, 6 to 10% of
Mn, and 15 to 25% of Cr in weight ratio, the balance Fe and
inevitable impurities.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a corrosion-resisting and
wear-resisting alloy, and a fluid device and a dynamic device using
the alloy.
[0003] 2. Description of the Prior Art
[0004] A valve seat or a sliding part, where a corrosion-resisting
and wear-resisting alloy which includes cobalt as a base, which is
excellent in corrosion-resisting and wear-resisting capabilities,
and has a high degree of hardness, and is added with Cr and/or W,
is overlaid to prevent an erosion damage on a valve seat during
operation or a galling while a valve is in motion is used for
valves such as a safety valve in a plant facility such as a turbine
power generating facility.
[0005] In late years, hydrogen peroxide solution and the like is
introduced to adjust water quality in a plant facility such as a
turbine power generating facility. As the result, the amount of
dissolved oxygen increases on the down stream of the introduction
point, and an erosion damage is generated on eutectic carbide of
the corrosion-resisting and wear-resisting alloy, which includes
cobalt as a base, is added with Cr and/or W, comprises the eutectic
carbide and the base material of a cast structure, and is overlaid
on a seat surface of a valve and a sliding face to prevent erosion
and a galling.
[0006] It is also reported that the base material of the cast
structure is detached, thereby generating corrosion after the
erosion damage of the eutectic carbide when a flow (such as water
flow) is present.
[0007] The reports relevant to the earlier report include "Thermal
and Nuclear Power Vol. 30-5 Processing Method for Boiler Water with
Oxygen and Ammonia in a Steam System in a Thermal Power Plant",
"Damage on Machinery 1982 2 VEW Operation Experience in a Combined
Operation Method at Gerstein Power Generating Plant", and
"Materials and Environment Vol. 47, No.3, Effect of Heat Treatment
Condition on Grain Boundary Erosion at Welded Part of Cobalt-Base
Alloy".
[0008] Those reports conclude that there is no effective mean to
eliminate a generation of the erosion, and it has been a
problem.
[0009] On the other hand, an expansion valve preventing a
generation of erosion at a valve port provided with an orifice by
integrating an orifice member made of a metal material with higher
degree of hardness (150 to 500 in Vickers hardness) than that of a
valve body with the valve body is disclosed in Japanese application
patent laid-open publication No. Hei 08-334280 (corresponding to
U.S. Pat. No. 6,164,624 Specification).
[0010] An increased wear-resisting capability of a blade by
attaching a bar-like wear-resisting material including cobalt,
nickel, tungsten, manganese, and selenium to a rear edge of the
steam turbine blade with friction surfacing is disclosed in
Japanese application patent laid-open publication No. Hei 05-208325
(corresponding U.S. Pat. No. 5,183,390 Specification). It is
disclosed that a caution should be paid to avoid the bar-like
wear-resisting material from presenting melting in terms of
preventing a change in the degree of hardness and a crack due to
shrinkage when the wear-resisting material is attached to the blade
by friction surfacing,
[0011] A valve where a valve seat comprising 30 to 45 weight % of
Cr, 3.0 to 8.0 weight % of Ti, 0 to 10 weight % of Mo, and the
balance Ni is diffusion-bonded to a valve element and a valve
casing is disclosed in Japanese application patent laid-open
publication No. Sho 59-179283.
[0012] A valve where a valve seat comprising 10 to 45 weight % of
Cr, 1.5 to 6 weight % of at least either of Al or Ti, and 20 weight
% or less of Mo, and the balance Ni is diffusion-bonded to a valve
element and/or a valve casing is disclosed in Japanese application
patent laid-open publication No. Sho 60-86239.
[0013] A valve where a valve seat comprising a cemented carbide
material or a heat-resisting material is brazed through an
amorphous alloy layer to a valve seat part of a valve casing is
disclosed in Japanese application patent laid-open publication No.
Hei 4-19476.
[0014] A technique where material of high carbon martensitic
stainless steel is made into an intermediate material with an
intermediate dimension with hot plastic forming, the intermediate
material is applied with cold plastic forming, and the intermediate
material is applied with the hot plastic forming again at
850.degree. C. to obtain a steel material with an intended
dimension is disclosed in Japanese application patent laid-open
publication No. Hei 7-16610. The average dimension of the eutectic
carbide in the steel material with the intended dimension reaches
4.2 micrometer with the disclosed technique in the publication.
[0015] Valves including safety valves used for a turbine power
generating plant have a high flow speed at a valve seat during
operation. Cobalt has a high degree of hardness, and is excellent
in corrosion-resisting and wear-resisting capabilities. A valve
seat which is made of a corrosion-resisting and wear-resisting
alloy including cobalt as a base added with Cr and/or W is used for
these valves.
[0016] A valve casing where the corrosion-resisting and
wear-resisting alloy is used on a guide face for guiding a valve
element, and on an inner face of a cage to prevent a galling while
a vale is in operation, is used for a cage valve.
[0017] However, when the aforementioned valve seat made of the
corrosion-resisting and wear-resisting alloy is used in a high
temperature/high pressure water/steam atmosphere with high
dissolved oxygen, a base material layer of a cast structure and
eutectic carbide surrounding the base material layer of the cast
structure as a mesh shape in the alloy are selectively corroded by
the dissolved oxygen in the fluid. This makes the surface of the
valve seat rougher, the eutectic carbide is corroded and detached
with an additional effect of a tunnel effect (F. j. Heymann:
Machine Design. 42, 118 (1970)), which is caused by a penetration
of a high speed jet into a corroded and damaged part, the base
material of the cast structure which lost the support from the
mesh-like eutectic carbide is easily detached by the flow,
resulting in a generation of an erosion in the corrosion-resisting
and wear-resisting alloy.
SUMMARY OF THE INVENTION
[0018] The purpose of the present invention is to provide a
corrosion-resisting and wear-resisting alloy with increased
corrosion-resisting and erosion-resisting capabilities by
restraining continuing corrosion of eutectic carbide in the
corrosion-resisting and wear-resisting alloy in an atmosphere with
dissolved oxygen.
[0019] The purpose of the present invention is also to provide
devices where the corrosion-resisting and wear-resisting alloy with
increased wear-resisting and corrosion-resisting capabilities is
used at wear-resisting parts and erosion-shield parts.
[0020] The principal part of the present invention to attain the
purpose is described below.
[0021] A corrosion-resisting and wear-resisting alloy is obtained
by selecting a material from cobalt base added with Cr and/or W,
nickel base added with Fe and/or Cr, and iron base added with Cr
and/or Ni, casting the material into an ingot or a slab as an
intermediate material, applying hot plastic forming at a
temperature which is 650.degree. C. or more and the solidus
temperature or less to the intermediate material, which includes a
structure comprising mesh-like eutectic carbide and a base material
surrounded by it, forming the eutectic carbide as a discontinuous
distribution in a form of multiple grains or clusters. The
coefficient of friction of the corrosion-resisting and
wear-resisting alloy is 0.1 to 0.5, and the Vickers hardness
without age hardening process of it is 300 to 600 Hv.
[0022] The cobalt base added with Cr and/or W comprises 0.1 to 3.5%
of C, 25% or less of Ni, 25 to 35% of Cr. 5% or less of Fe, 20% or
less of W, 1.5% or less of Mn, and 1.5% or less of Si in weight
ratio, the balance Co and inevitable impurities. The nickel base
added with Fe and/or Cr comprises 0.1 to 2.5% of C, 3 to 9% of Si,
7 to 25% of Cr, 0.5 to 5% of B, 2 to 6% of Fe, 1 to 5% of W, and
17% or less of Mo in weight ratio, the balance Ni and inevitable
impurities. The iron base added with Cr and/or Ni comprises 0.1 to
1.5% of C, 0.3 to 4% of Si, 4 to 9% of Ni, 3% or less of Mo, 6 to
10% of Mn, and 15 to 25% of Cr in weight ratio, the balance Fe and
inevitable impurities.
[0023] For example, cobalt base added with Cr and/or W is cast into
an intermediate material typified by an ingot or a slab. This cast
material comprises a base material and eutectic carbide of a cast
structure. A hot plastic forming is applied to the eutectic
carbide, which has a high degree of hardness and low ductility, and
is fragile and distributed continuously as a mesh. The intermediate
material becomes fine grains or clusters. The structure of the base
material penetrates into gaps generated in the eutectic carbide.
The base material with a low degree of hardness, high ductility,
and strength is distributed around the grain-like or cluster-like
eutectic carbide, thereby making the eutectic carbide
discontinuous.
[0024] Simultaneously, the diffusion of large amount of chrome
existing in the eutectic carbide is accelerated by maintaining it
at 650.degree. C. or more, thereby reducing chrome-deficiency
layers around the eutectic carbide, resulting in a
corrosion-resisting and wear-resisting alloy simultaneously having
an increased corrosion-resisting capability of the eutectic
carbide.
[0025] With this, eutectic carbide, which is distributed as mesh,
and is in a cast structure which is made by dissolving cobalt as a
base along with Cr and/or W and comprises the base material and the
eutectic carbide, is made into multiple clusters and grains as
discontinued eutectic carbide, thereby making an erosion phenomenon
discontinued, very shallow and partial.
[0026] As the result, the progress of the erosion is restrained,
and a tunnel effect (F. j. Heymann: Machine Design. 42, 118
(1970)), which is caused by a penetration of a high speed jet into
a corroded and damaged part is restrained, thereby increasing the
erosion/corrosion-resisting capability.
[0027] The effect described above increases the erosion-resisting
and corrosion-resisting capabilities.
[0028] Also, the diffusion of large amount of chrome existing in
the eutectic carbide into the periphery of the eutectic carbide is
accelerated by maintaining it at 650.degree. C. or more, thereby
reducing chrome-deficiency layers around the eutectic carbide
containing Cr, resulting in a corrosion-resisting and
wear-resisting alloy simultaneously having an increased
corrosion-resisting capability of the eutectic carbide.
[0029] For a nickel base material added with Fe and/or Cr, or an
iron base material added with Cr and/or Ni, a corrosion-resisting
and wear-resisting material is obtained in the same way, thereby
increasing erosion/corrosion-resisting capability.
[0030] When the corrosion-resisting and wear-resisting alloy is
partially or entirely melted, the eutectic carbide at the melted
part forms mesh-like eutectic carbide with a low
corrosion-resisting capability. Thus, the corrosion-resisting and
wear-resisting alloy is machined into an arbitrary shape, and is
used after it is joined without melting to a base metal, which is a
base to which the corrosion-resisting and wear-resisting alloy is
attached.
[0031] Since the mesh-like eutectic carbide does not exist, and is
made into clusters or grains, a fluid machine using the alloy such
as a pump, a valve, a pressure device, and a turbine presents high
corrosion/erosion-resisting capabilities under a corrosive
atmosphere.
[0032] A dynamic machine such as a pump, a valve, a turbine, and an
engine where the corrosion-resisting and wear-resisting alloy
without chanting the metal composition is joined to a base metal
and used for a sliding part or a contact part, presents high
corrosion/erosion-resisting capability under a corrosive
atmosphere.
[0033] The obtained coefficient of friction can be 0.1 to 0.3,
which is as low as diamond (coefficient of friction of 0.1 when no
lubricant), sapphire (coefficient of friction of 0.2 when no
lubricant), and ruby, thereby reducing friction resistance compared
with 0.35 to 0.8 of other metals such as brass (coefficient of
friction of 0.35 when no lubricant) and steel (coefficient of
friction of 0.8 when no lubricant).
[0034] The corrosion-resisting and wear-resisting alloy is used for
a wear-resisting part or an erosion shield for a fluid machine, and
a sliding part or a contact part for a dynamic machine.
[0035] When the corrosion-resisting and wear-resisting alloy of the
present invention is attached to a fluid machine or a dynamic
machine, it is attached to the wear-resisting part and the erosion
shield part, and the sliding part and the contact part while
maintaining the composition of the corrosion-resisting and
wear-resisting alloy as much as possible. As the attaching method,
a joining method which does not melt the corrosion-resisting and
wear-resisting alloy is employed. As an example of the joining
method, liquid phase diffusion welding is available.
[0036] More specifically, the corrosion-resisting and
wear-resisting alloy of the present invention is applied to a valve
seat attached to contact faces of a valve element and a valve
casing provided on a piping system in an atomic power generating
plant and the like, a contact face material for at least either of
contact faces of a seat or a washer rotating relatively to each
other about a rotating shaft of a pump, valve seats attached to
contact faces of a valve seat part and a valve provided on a
cylinder head of an internal combustion engine, and a contact face
material for at least either of contact faces of a valve lifter and
a cam of an internal combustion engine.
[0037] The present invention reduces the degradation of entire
corrosion-resisting and wear-resisting capabilities caused by
corrosion and damage to eutectic carbide in a corrosion-resisting
and wear-resisting alloy.
[0038] Applying the corrosion-resisting and wear-resisting alloy of
the present invention to sliding parts and contact parts of
different devices reduces roughness on the sliding parts and the
contact parts of the devices caused by the corrosion and the damage
of the eutectic carbide under a corrosive environment, thereby
maintaining proper friction resistance on the sliding parts and the
contact parts. As the result, the present invention provides
devices including sliding faces and contact faces with low
friction.
[0039] A rotating device, which is an embodiment of the present
invention, includes a mechanical seal device sealing between a
rotating shaft and a casing. The mechanical seal device comprises a
first seal, which rotates with the rotating shaft, and a second
seal, which is installed on the casing, and is in contact with the
first seal. At least either the first seal or the second seal is a
corrosion-resisting and wear-resisting part where grain-like or
cluster-like eutectic carbide is diffused in the matrix part of the
metal micro structure, and includes the corrosion-resisting and
wear-resisting alloy part which comes in contact with the other
seal part, and a main body. The corrosion-resisting and
wear-resisting alloy part is diffusion-welded to the main body.
Since the seal part includes the corrosion-resisting and
wear-resisting alloy part, which is diffusion-welded to the main
body, the corrosion-resisting and wear-resisting alloy part, which
is diffusion-welded, includes grain-like or cluster-like eutectic
carbide as described before, not mesh-like eutectic carbide.
Seizure, wear, and acceleration of corrosion of the seal member
caused by an increase of the temperature at the seal due to heat
generated at the contact part of the first and the second seals is
restrained, thereby increasing the corrosion-resisting and
wear-resisting capabilities at the seal, decreasing the frequency
of maintenance for the mechanical seal device including the first
and second seals, and increasing the life of the mechanical seal
device. This leads to relieving the maintenance operation for the
rotating device. Since the corrosion-resisting and wear-resisting
alloy has a small coefficient of friction, the heat energy
generated at the contact part of the first seal and the second seal
decreases. This leads to a reduction of the power rotating the
rotating shaft of the rotating device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is an SEM photograph indicating a metal structure of
a surface of a corrosion-resisting and wear-resisting alloy
including cobalt as a base added with Cr and/or W (a), and its
schematic (b).
[0041] FIG. 2 is an enlarged part (a) of the metal structure of the
corrosion-resisting and wear-resisting alloy from FIG. 1, and its
schematic (b).
[0042] FIG. 3 is a metal structure indicated by a face analysis of
a surface of a corrosion-resisting and wear-resisting alloy
including cobalt as a base added with Cr and/or W (a), and its
schematic (b).
[0043] FIG. 4 is a metal structure of a surface of a
corrosion-resisting and wear-resisting alloy including cobalt as a
base added with Cr and/or W after heat plastic forming (a), and its
schematic (b).
[0044] FIG. 5 is a metal structure indicated by a face analysis of
a surface of a corrosion-resisting and wear-resisting alloy
including cobalt as a base added with Cr and/or W after heat
plastic forming (a), and its schematic (b).
[0045] FIG. 6 is a schematic of a repeated progress of a damage
caused by dissolved oxygen on a corrosion-resisting and
wear-resisting alloy including cobalt as a base added with Cr
and/or W.
[0046] FIG. 7 is a schematic of a restraining status of a damage
caused by dissolved oxygen on a corrosion-resisting and
wear-resisting alloy including cobalt as a base added with Cr
and/or W after heat plastic forming.
[0047] FIG. 8 is a SEM photograph indicating a metal structure
obtained by a Strauss test applied to a corrosion-resisting and
wear-resisting alloy including cobalt as a base added with Cr
and/or W after heat plastic forming.
[0048] FIG. 9 is a chart indicating a coefficient of friction
obtained by a sliding test applied to a corrosion-resisting and
wear-resisting alloy including cobalt as a base added with Cr
and/or W after heat plastic forming.
[0049] FIG. 10 is a piping system diagram of a nuclear power
generating plant.
[0050] FIG. 11 is a lengthwise section view of a gate valve adopted
for the piping system of the nuclear power generating plant
[0051] FIG. 12 is a section view indicating contact states between
a valve element and individual valve seats, and between a valve
casing and the individual valve seats for the gate valve in FIG.
11.
[0052] FIG. 13 is an entire view of an internal combustion engine
with a partial section view.
[0053] FIG. 14 is an enlarged section view around a valve indicated
in FIG. 13.
[0054] FIG. 15 is an enlarged section view of a contact part
between the valve and a seat in FIG. 14.
[0055] FIG. 16 is a section view of a pump.
[0056] FIG. 17 is a section view of a neighborhood of a mechanical
seal of a pump in FIG. 16.
DESCRIPTION OF THE PREFERRRED EMBODIMENT
[0057] A typical SEM photograph of a surface of a
corrosion-resisting and wear-resisting alloy including cobalt as a
base added with Cr and/or W is shown in FIG. 1 (Note that (a) is an
SEM photograph, (b) is the schematic of (a). Same arrangement is
repeated in FIGS. 2 to 5). An SEM photograph with a high magnitude
is shown in FIG. 2. An SEM photograph for Cr face analysis taken at
the same position on the face of the corrosion-resisting and
wear-resisting alloy as in FIG. 2 is shown in FIG. 3.
[0058] An SEM image of a metal structure of a face of the
corrosion-resisting and wear-resisting alloy after hot plastic
forming such as forging and rolling is shown in FIG. 4. An SEM
photograph for Cr face analysis taken at the same position on the
face of the corrosion-resisting and wear-resisting alloy as in FIG.
4 is shown in FIG. 5.
[0059] Eutectic carbide 1 with principal components of Cr and C in
FIGS. 1, 2, and 3 is continuously distributed as a mesh in a base
material 2 of a cast structure including cobalt as a principal
component on a surface of the surface-melted alloy.
[0060] An embodiment of the present invention is shown in FIGS. 4
and 5. The eutectic carbide 1 is distributed as grains or clusters
with respect to the base material 2 uniformly but discontinuously
on a surface of the corrosion-resisting and wear-resisting alloy.
The eutectic carbide 1 changes from mesh to grains or clusters,
thereby reducing the ratio of the eutectic carbide occupying the
surface.
[0061] FIG. 6 is a schematic showing a progress of repeated damage
to the corrosion-resisting and wear-resisting alloy including
cobalt as a base added with Cr and/or W due to dissolved
oxygen.
[0062] As the corrosion/erosion on the corrosion-resisting and
wear-resisting alloy progresses, the base layer 2 of the cast
structure tends to detach because the dissolved oxygen corrodes the
eutectic carbide 1.
[0063] As indicated in the SEA photograph in FIG. 3, the eutectic
carbide 1 continuous as a mesh exists in the conventional
corrosion-resisting and wear-resisting alloy including cobalt as a
base added with Cr and/or W. The corrosion of the eutectic carbide
1 and the detaching of the base layer 2 of the cast structure due
to the dissolved oxygen occur continuously, resulting in a progress
of the corrosion/erosion under an atmosphere of dissolved
oxygen.
[0064] On the other hand, in the corrosion-resisting and
wear-resisting alloy which includes cobalt as a base added with Cr
and/or W, and is applied with hot plastic forming, the eutectic
carbide 1 exists discontinuously as grains or clusters, the
corrosive damage to the eutectic carbide 1 due to the dissolved
oxygen is limited to the eutectic carbide 1 on a face facing to the
dissolved oxygen.
[0065] After the eutectic carbide 1 on the surface is corroded and
detached, the corrosive damage does not progress any further. This
is described using a schematic in FIG. 7 showing a restrained
damage due to the dissolved oxygen.
[0066] To verify the effect described before, JIS G 0575 "Sulfuric
acid/cupric sulphate corrosion test on stainless steel" (Strauss
test) is applied. According to a test conducted by Takahisa and
Honda where a similar test was applied to a corrosion-resisting and
wear-resisting alloy of cobalt base including a mesh-like
continuous distribution of eutectic carbide (Materials and
Environment Vol. 47, No.3, Effect of Heat Treatment condition on
Grain Boundary Erosion at Welded Part of Cobalt-Base Alloy), it is
reported that a progress of a corrosion is observed at
surface-melted alloy of the corrosion-resisting and wear-resisting
alloy of cobalt base.
[0067] The similar test is applied to the corrosion-resisting
resisting and wear-resisting alloy of cobalt base added with Cr
and/or W after a plastic forming such as forging and rolling,
little etching was observed on the surface, no progress of a
corrosion is present into the depth direction, and an excellent
corrosion-resisting capability is confirmed. The test result is
presented in FIG. 8 and Table 1. FIG. 9 shows a measuring result of
the coefficient of friction with respect to the increase/decrease
of the number of sliding.
1TABLE 1 Strauss test: Corrosion depth in Co-base alloy (mm)
Co-base alloy with Co-base alloy with eutectic eutectic carbide
with carbide with discontinuous continuous mesh-like grain- or
cluster-like Material distribution distribution Pre-heating
600.degree. C. 600.degree. C. 700.degree. C. temperature Testing
0.51 to 0.62 mm As slight as period etching No damage 16 hours
(impossible to measure) As slight as Testing 3 mm or more Up to 0.1
mm etching period (impossible to 150 hours measure)
[0068] The corrosion depth under a corrosive environment for the
corrosion-resisting and wear-resisting alloy of cobalt base added
with Cr and/or W, where the eutectic carbide 1 is distributed
discontinuously as grains or clusters, the corrosion depth is
restrained to about {fraction (1/30)} of that of conventional
alloys, and the corrosion depth is restrained further by increasing
a pre-heating temperature to diffuse Cr further.
[0069] As the result, the corrosion-resisting and wear-resisting
alloy with the eutectic carbide 1 distributed discontinuously as
grains or clusters restrains the corrosion due to the dissolved
oxygen, resulting in restraining the erosion.
[0070] When the cases where pre-heating temperature of the
corrosion-resisting and wear-resisting alloy of cobalt base added
with Cr and/or W is about 600.degree. C. and is 700.degree. C. are
compared, the corrosion-resisting capability of the grain-like or
cluster-like eutectic carbide 1 presents higher corrosion-resisting
capability in the case for 700.degree. C., where Cr diffuses more,
and joining the alloy with the base material at a higher
pre-heating temperature provides better corrosion-resisting and
wear-resisting capabilities.
[0071] For a corrosion-resisting and wear-resisting alloy of nickel
base added with Fe and/or Cr, and a corrosion-resisting and
wear-resisting alloy of iron base added with Cr and/or Ni,
conducting heat plastic forming in a state heated up to the solidus
temperature or less increases the corrosion-resisting and
wear-resisting capabilities as for the corrosion-resisting and
wear-resisting alloy of cobalt base added with Cr and/or W,
simultaneously providing a sliding surface with a low friction.
[0072] For a corrosion-resisting and wear-resisting alloy of iron
base added with Cr and/or Ni, conducting heat plastic forming in a
state heated up to the solidus temperature or less increases the
corrosion-resisting and wear-resisting capabilities as for the
corrosion-resisting and wear-resisting alloy of cobalt base added
with Cr and/or W, simultaneously providing a sliding surface with a
low friction.
[0073] The material components of the corrosion-resisting and
wear-resisting alloy of cobalt base added with Cr and/or W
comprises 0.1 to 3.5% of C, 25% or less of Ni, 25 to 35% of Cr, 5%
or less of Fe, 20% or less of W, 1.5% or less of Mo, and 1.5% or
less of Si in weight ratio, the balance Co and inevitable
impurities.
[0074] The material components of the corrosion-resisting and
wear-resisting alloy of nickel base added with Fe and/or Cr
comprises 0.1 to 2.5% of C, 3 to 9% of Si, 7 to 25% of Cr, 0.5 to
5% of B, 2 to 6% of Fe, 1 to 5% of W, and 17% or less of Mo in
weight ratio, the balance Ni and inevitable impurities.
[0075] The material components of the corrosion-resisting and
wear-resisting alloy of iron base added with Cr and/or Ni comprises
0.1 to 1.5% of C, 0.3 to 4% of Si, 4 to 9% of Ni, 3% or less of Mo,
6 to 10% of Mn, and 15 to 25% of Cr in weight ratio, the balance Fe
and inevitable impurities.
[0076] Applying a hot plastic forming to these corrosion-resisting
and wear-resisting alloys increases the corrosion-resisting and
wear-resisting capabilities, simultaneously providing a
corrosion-resisting and wear-resisting sliding surface with a low
friction.
[0077] The average coefficient of friction obtained by measuring
friction of a face of the corrosion-resisting and wear-resisting
alloy is 0.16 without lubrication in a room atmosphere, and is 0.19
in a saturated steam atmosphere at 288.degree. C. The metal
components of the corrosion-resisting and wear-resisting alloy used
for the friction measuring are described in Table 2, and the
eutectic carbide in the corrosion-resisting and wear-resisting
alloy takes a form of discontinuous distribution of multiple grains
or clusters.
2TABLE 2 Composition Ni Fe Mo C Si Cr Co W Weight % 2.59 2.67 0.07
1.03 0.59 29.73 Balance 3.86
[0078] The corrosion-resisting and wear-resisting alloy of the
present invention is used for different devices as described below.
FIG. 10 presents a piping system for a nuclear power generating
plant. A large number of gate valves and check valves are installed
on a water supplying pipe 11 of the piping system 10. Since the
gate valves and check valves installed on the water supplying pipe
11 are smaller than a water-supplying pump 12, individual supplied
water heaters 13, 14, and other devices installed in the course of
the water supplying pipe 11, and the number of the gate valves and
check valves is very large, the graphical representation of the
gate valves and the check valves are suppressed.
[0079] In the nuclear power generating plant, high temperature and
high pressure steam obtained inside a nuclear reactor pressure
vessel 16 is introduced into a high pressure turbine 18 through a
main steam piping 15. Then the steam exhausted from the high
pressure turbine 18 is introduced to a low pressure turbine 19. The
rotating forces of these turbines drive a generator 20. The steam
which has passed through the high pressure turbine 18 and the low
pressure turbine 19 is exhausted from the high pressure turbine 18
and the low pressure turbine 19, and is condensed into water in a
main condenser 22 and a gland steam condenser 21. The water is
returned to the nuclear reactor pressure vessel 16 through the
water supplying system 10 including the gate valves and the check
valves in addition to the water supplying pump 12, the individual
supplied water heaters 13, 14, and the water supplying pipe 11.
[0080] The following section describes an example where the present
invention is applied to a gate valve among the valves adopted for
the piping of a water supplying system 46.
[0081] The FIG. 11 shows a lengthwise section of the gate valve
installed on the water supplying pipe 11 of the water supplying
system 10. As in FIG. 12, a ring-like plate 31 made of a
cobalt-base alloy is mounted as a valve seat on a valve element 30
side of the gate valve. The ring-like plate 31 made of the
cobalt-base alloy is also installed on a slide face of a valve seat
33 of a valve casing 32 side.
[0082] The cobalt-base alloy includes 1.0 weight % of C, 30.0
weight % of Cr, and 3.9 weight % of W. Eutectic carbide in the
cobalt-base alloy is made into clusters or grains less than 30
micrometer by heat forging or heat rolling the cobalt-base alloy.
The cobalt-base alloy plate 31 is joined to the valve seat 33 of
the valve casing 32 and a valve seat part of the valve element 30
with liquid phase diffusion welding as indicated in FIG. 12.
[0083] The valve element 30 of the gate valve takes a disk-like
shape, which is thick at the top and thin at the bottom, and is
driven upward/downward in association with the upward/downward
motion of a valve stem, thereby opening/closing a flow of water or
steam flowing into the valve casing 32 in the left/right direction
in the Figure.
[0084] The following section describes a specific example for
installing a ring-like plate made of the cobalt-base alloy 31 to
the valve element 30. Protrusions 34 protruding toward left and
right is provided by providing steps on the left and the right
surfaces of the valve element 30 of the gate valve. An insert
material for joining is placed in recessed part which is generated
by providing the steps. The ring-like plate 31 with thick ness of
about 7 mm is placed on the surface of the insert material for
joining such that the plate 31 is engaged with the protrusions 34.
Only the insert material for joining is melted to attach the
ring-like plate 31 to the valve element 30 with liquid phase
diffusion welding.
[0085] The insert material used for the liquid phase diffusion
welding is an Ni-base alloy including 4.5 weight % of Si and 3
weight % of B, and is fully melted at about 1040.degree. C. or
more. The condition for the liquid phase diffusion welding is
1100.degree. C. for the joining temperature, 1 hour for the
maintained period, 1 to 2 mult 10.sup.-4 Torr for the degree of
vacuum, and 15 g/cm.sup.2 for the applied pressure. For the cooling
after the joining, about 150.degree. C./h is from 1000.degree. C.
to 650.degree. C., about 100.degree. C./h is from 650.degree. C. to
425.degree. C., and natural cooling with air cooling in room is
from 425.degree. C.
[0086] A ring-like protrusion 35 is also machined on the valve seat
33. An insert material for joining is placed in a recessed part
around the protrusion. The ring-like plate 31 with thick ness of
about 7 mm is placed on the surface of the insert material for
joining to engage with the protrusion 35. Only the insert material
for joining is melted to attach the ring-like plate 31 to a valve
seat 7 with liquid phase diffusion welding. The ring-like plate 31,
the material for joining, the conditions for the liquid phase
diffusion welding, and the cooling condition are the same as those
for the joining of the valve element 30 to the plate 31.
[0087] The valve element 30, the plate 31 and the valve seat 33 do
not melt at the joining temperature of 1100.degree. C. Material of
a part of the valve element 30 and the valve seat 33 where the
plates 31 are installed is S25C, carbon steel for machine
structure. The thermal expansion coefficient of the carbon steel
for machine structure S25C is smaller than that of the Co-base
alloy. The ring-like protrusions 34, 35 (steps) with the height of
2 mm are provided to internally come in contact with a ring-like
plates 6 to be joined on the surfaces of the valve element 30 and
the valve seat 33 opposing to each other as described in FIG. 12.
This facilitates positioning the plates 31 to the valve element 30
and the valve seat 33 during the joining, and simultaneously
increasing a resistance against a searing force added to a sliding
part and the joined part when the gate vale is in operation.
[0088] Both of the plates 31 which serve as a valve seat on the
valve element 30 side appear as a ring seen from the left and the
right of the page respectively in FIG. 12. The ring-like plates 31
are joined such that they are in contact with the outer periphery
of the circular protrusion 34 on the left and right sides of the
valve element 30.
[0089] The valve seat 33 on the side of the valve casing 32 is
cylindrical, and a valve set 33 is integrated into the valve casing
32. An end face on the side of the valve element 30 of the valve
seat 33 is a sliding face. The end face is structured such that the
ring like plate 31 is in contact with and is liquid-phase-diffusion
welded to the outer periphery of the ring-like protrusion 35. Both
of the protrusions 34, 35 are 2 mm in height, which is smaller than
7 mm of the thickness of the ring-like plates 31.
[0090] For the gate valve manufactured with this method, the mutual
contact faces of the valve element and the valve casing are
structured with the plates 31. Since the eutectic carbide in the
Co-base alloy, which is the material for the plate 31, is
distributed discontinuously as multiple grains or clusters after
the liquid phase diffusion welding, the phenomenon that an
atmosphere generating a corrosive environment such as dissolved
oxygen corrodes the eutectic carbide continuously is restrained.
This restrains the detach of matrix of the cast structure of the
Co-base alloy, thereby restraining the progress of the corrosion
and erosion of the valve seat, resulting in preventing the
deterioration of the leakage-resisting capability of the gate
valve.
[0091] For this embodiment, the Co-base alloy plates 31 are used as
the ring-like corrosion-resisting and wear-resisting alloy. As
described before, the corrosion-resisting and wear-resisting alloy
of nickel base added with Fe and/or Cr, the corrosion-resisting and
wear-resisting alloy of iron base added with Cr and/or Ni, and the
Ni-base alloy and the Fe-base alloy, where the alloy including
components described before in the Table 2 is applied with heat
forging or heat rolling to make the eutectic carbide in the alloy
distribute discontinuously are used as well.
[0092] Though in this embodiment, Ni-base alloy with a low melting
point is used as an insert material, an Fe-base or Co-base insert
with a low melting point is used as well. The same constitution as
in the embodiment-of the present invention can be applied to a
sliding part and a contact part of a valve seat and the like in a
check valve, a safety valve, and a globe valve in addition to a
gate valve to provide an effect on restraining the decrease of the
leakage-resisting capability, the controllability and the operation
capability of the individual valves.
[0093] This embodiment has an effect of maintaining the normal
function of a valve used for an atomic power generating plant for a
long period, thereby increasing the reliability of the atomic power
generating plant with the effect.
[0094] In a plant including a piping system integrated with the
valve described in this embodiment, corrosion and erosion of
sliding parts such as a valve seat due to dissolved oxygen are
restrained when hydrogen peroxide solution is infused in the piping
for the purpose of adjusting water quality, thereby providing an
effect on the increase of the safety of the plant.
[0095] Especially, when the valve of the present embodiment is
installed and used on a water supplying system of a nuclear power
generating plant, corrosion and detaching of the eutectic carbide
of the Co-base alloy applied to the valve seat, and effusion and
diffusion of cobalt into the water supplying system after the
corrosion and the detaching are restrained. As the result, the
effusion and diffusion of the cobalt and the activation of the
cobalt are restrained, thereby remarkably reducing exposure to
radiation of workers in the nuclear power generating plant.
[0096] The corrosion-resisting and wear-resisting alloy of the
present invention is applied to an internal combustion engine as
follows. An internal combustion engine using gasoline as fuel is
provided with a cylinder 40 for combusting gasoline as described in
FIGS. 13, 14, and 15. The cylinder 40 is closed by a cylinder head
41 at the top. The cylinder head 41 is provided with an intake port
and an exhaust port, and the individual intake port and exhaust
port are opened/closed by valves 42.
[0097] The valves 42 are operated to open/close by a valve system
provided on the cylinder head 41. The valve system comprises a
spring 43 provided around a driving shaft of the valve 42, a valve
lifter 44 connected at the top end of the driving shaft, an
adjusting shim 45 provided at the top of the valve lifter 44, a cam
46 which is in contact with the top face of the adjusting shim 45,
and a power transmitting mean which drives rotatingly the cam 46
using the output of the engine.
[0098] A part of the output of the engine is used to rotate the cam
46 in the valve system. The motion of the cam 46 pushes down the
valve lifter 44 through the adjusting shim 45 resisting against the
spring 43. The pushing down motion departs the valves 42 downward
from valve seats 47 of the individual intake ports and exhaust
ports, thereby opening the intake port and the exhaust port where
the valves 42 are installed.
[0099] As the cam 46 rotates further, the valves 42 come in contact
with the valve seats 47 to close the valves 42. The contact parts
between the valve seats 47 and valves 42 serve as a seal to prevent
the gas inside the cylinder 40 from leaking.
[0100] The valve system including this motion presents friction due
to a sliding motion between the adjusting shim 45 and the cam 46.
Friction also presents between the valve 42 and the valve seat 47.
Driving the valve system resisting against these frictions generate
a loss in the output of the engine, thereby reducing the engine
efficiency.
[0101] A Co-base alloy 48 as a corrosion-resisting and
wear-resisting alloy is joined to the contact parts between the
valve 42 and the valve seat 47 in the engine with a liquid phase
diffusing welding 49 as indicated in FIGS. 14 and 15. This joining
method is conducted as the liquid phase diffusion welding described
before, and the same cooling condition is applied. The Co-base
alloy 48 is at least heat forged before hand, and is made into a
metal structure where the eutectic carbide are composed into
multiple grains or clusters in the base material of the cobalt.
[0102] The Co-base alloy including the eutectic carbide composed as
multiple grains or clusters in the base material is joined with the
liquid phase diffusion welding to the top end of the valve lifter
45 to form the adjusting shim 4.
[0103] The compositions of the Co-base alloy 48 and the insert
material used for the liquid phase diffusion welding is indicated
in Table 3.
3TABLE 3 (Weight %) Co Cr W C Fe Ni Other Co-base Bal 29.4 3.9 1.0
2.7 2.4 Mo0.1/i0.6 alloy Ni-base -- 10.0 2.0 1.0 2.5 Bal Si5.4
alloy Fe-base -- 25.0 -- 1.0 Bal 4.0 Mo2.0 alloy Insert -- -- -- --
-- Bal Si0.6/B3.0 material
[0104] During the liquid phase diffusion welding, though the insert
material melts, Co-base alloy 48, the valve 42 and the valve seat
47 do not melt. The Co-base alloy 48 after the joining maintains
the metal structure where multiple grains or clusters of eutectic
carbide are distributed discontinuously in the base material.
[0105] After the welding, the eutectic carbide still exists as
grains or clusters on the surface or the inside of the Co-base
alloy 48. The existence of the grains or clusters of the eutectic
carbide in the Co-base alloy 48 limits the exposure of the eutectic
carbide, resulting in restraining the damage.
[0106] If the Co-base alloy 48 where the eutectic carbide is
diffused discontinuously as grains or clusters is exposed to a
corrosive environment of sulfur, the grains or clusters of the
eutectic carbide which are in contact with the corrosive
environment are detached from the surface as the result of the
corrosion or the sliding action, and only the base material without
the eutectic carbide exists on the surface which is in contact with
the corrosive environment. A phenomenon where corrosion and
detaching happen alternately and repeatedly is prevented, thereby
restraining the damage.
[0107] If the coefficient of friction of the Co-base alloy 48
including eutectic carbide composed as grains or clusters is
measured at room temperature under high surface pressure (about
2000 kg/cm.sup.2), and is indicated as a developed material in a
chart, the coefficient of friction is as low as 1/2 to 2/3 of that
of a conventional Co-base alloy having mesh-like eutectic carbide
as indicated in FIG. 9.
[0108] The engine valve 42 is assumed to be used at a high
temperature (up to about 500 to 600.degree. C.) and with a large
number of sliding motions. The test result shows the low friction
under the high surface pressure. Though the coefficient of friction
is governed by the ratio of shearing strength and degree of
hardness, the ratio of searing strength and degree of hardness of
the material has little dependency on temperature, and it is
assumed that no change is observed if materials have the same
composition. Thus the effect of the low friction is gained at a
high temperature and with a large number of sliding motions.
[0109] For comparing the corrosion-resisting capability, Strauss
test and an erosion test in diluted sulfuric acid were conducted.
As the result, the Co-base alloy 48 (developed material) shows a
corrosion-resisting capability 30 times as much as that of the
Co-base alloy including eutectic carbide composed as mesh as
indicated in Table 1 in the Strauss test. The Co-base alloy shows
durability 20 to 30 times as much as that of the Co-base alloy
including eutectic carbide composed as mesh in the erosion test in
diluted sulfuric acid.
[0110] With the present embodiment, high corrosion resistance, low
wearing and low friction achieves the durability and the reduction
of the power loss of the valve system, thereby increasing
efficiency, output and durability of the engine as a whole.
[0111] The Co-base alloy adopted for this embodiment can be the
Co-base alloy including components described in Table 2, or a
Ni-base alloy or a Fe-base alloy which includes grain-like or
cluster-like eutectic carbide and is made by hot forging from the
Ni-base alloy or the Fe-base alloy having components indicated in
Table 3 can replace the Co-base alloy 48, and increases efficiency,
output and durability of the engine as a whole.
[0112] In this case, a joining mean and a joining condition for
joining the Co-base alloy, the Ni-base alloy or the Fe-base alloy
to the valve 42 and the valve seat 47 are selected such that the
eutectic carbide exists as grains or clusters in the Co-base alloy,
the Ni-base alloy or the Fe-base alloy after the joining. The
preferable method as the joining mean is liquid phase diffusing
welding.
[0113] In the present embodiment, the Co-base alloy, the Ni-base
alloy or the Fe-base alloy including grain-like or cluster-like
eutectic carbide is joined with the liquid phase diffusion welding
to parts having a seal capability on the valve 42 and the valve
seat 47 of the engine, thereby providing seal faces having
strength, wear-resisting capability, corrosion-resisting capability
and low friction while maintaining a high degree of hardness.
[0114] Preventing corrosion caused by sulfuric component and the
like included in gasoline as the fuel of the engine, a progress of
crack starting from the corrosion, and the decrease of the seal
capability caused by erosion provide a seal face with a low
friction to prevent the decrease of the engine efficiency caused by
friction, thereby contributing the increase of the engine output in
addition to increasing the durability of an internal combustion
engine, and preventing the decrease of the engine efficiency.
[0115] Using the liquid phase diffusion welding to join the Co-base
alloy, the Ni-base alloy or the Fe-base alloy including grain-like
or cluster-like eutectic carbide from Table 2 and Table 3 to an
external peripheral surface of the valve lifter 44 constituting the
valve system of the engine increases the durability of the engine,
and prevents the decrease of the engine efficiency further.
[0116] If the Co-base alloy including the mesh-like eutectic
carbide is designated as a conventional example, and the Co-base
alloy including components shown in Table 2 diffused
discontinuously as grains or clusters is designated as the present
embodiment, the comparison between the both alloys shows the
differences in capability as in Table 4.
4TABLE 4 Evaluated item Conventional example Present embodiment
Tensile stremgth N/mm.sup.2 920 1064 Compressive stress N/mm.sup.2
1700 More than 1700 Impact value kgm/cm.sup.2 0.2 8 to 10
Coefficient of frictiom 0.4 0.16 to 0.19 Hardness (HRC) 43 43 to 45
SOx corrosion sensitivity Yes No
[0117] Since the alloys from the conventional example and the
present invention present differences in the capability as
described before, if the valve lifter is used after the alloy from
the present invention is attached with the liquid phase diffusion
welding, the engine output loss caused by the friction in the valve
system is reduced. If the valve and the seat are used after the
alloy from the present invention is attached with the liquid phase
diffusion welding, they do not present corrosion sensitivity under
SOx atmosphere and a high impact value, thereby maintaining the
health of the valve and the seat.
[0118] The corrosion-resisting and wear-resisting alloy of the
present invention is also applied to a pump facility as described
below. In a pump facility shown in FIG. 16, an electric motor or
the like rotates a shaft 50, and an impeller 51 fixed to the shaft
50 rotates in a pump casing 52. The rotation of the impeller 51
increase the pressure of liquid X which flows into the pump casing
52, and the liquid X is discharged outward from the pump casing
52.
[0119] A mechanical seal is adopted between the liquid X and gas Y
to prevent the liquid X from leaking into the gas Y side. The
mechanical seal is shown in FIG. 17. The mechanical seal in FIG. 17
is provided with the following constitution.
[0120] A fastener 55 is placed in a periphery of the shaft 50
inside a seal box 53 integrated with the pump casing 52. The
fastener 55 is fixed to the shaft 50 with a knock 54. In side the
fastener 55, a spring 56, a pressing member 57, a packing 58, and a
washer 59 are provided around the shaft 50.
[0121] A seal cover 60 provided in the periphery of the shaft 50 is
attached to an end of the seal box 53. A seat 61 provided in the
periphery of the shaft 50 is attached to the seal cover 60.
[0122] Since the spring 56 presses the pressing member 57, the
packing 58, and the washer 59 toward the right direction, a washer
59 is pressed against the seat 61 at a sealed end face S. Pressing
the washer 59 to the seat 61 with the spring 56 seals the liquid X
to prevent it from leaking to the gas Y side.
[0123] The fastener 55, the spring 56, the pressing member 57, the
packing 58, and the washer 59 rotate with the shaft 50, and the
seat 61 does not rotate. Heat is generated at the sealed end face
S, thereby accelerating seizure, wear, and corrosion at the sealed
end face S. Thus, a mechanical seal using a wear-resisting and
corrosion-resisting material is needed at the sealed end face.
[0124] To satisfy the requirement, in the present embodiment, a
plate 62 made of a corrosion-resisting and wear-resisting alloy is
attached to a part where the washer 59 comes in contact with the
seat 61 as indicated FIG. 17. Either of the alloys described before
is applied as the corrosion-resisting and wear-resisting alloy, and
the eutectic carbide is distributed discontinuously as grains or
clusters in the base of the alloy. The alloy is joined to the
washer 59 with liquid phase diffusing welding. The joining method
and the joining condition for the liquid phase diffusion welding
are the same as those described before. A similar
corrosion-resisting and wear-resisting alloy may be attached to a
part where the seat 61 comes in contact with the washer 59. The
corrosion-resisting and wear-resisting alloy may be attached both
to the washer 59 and the seat 61 where they come into contact with
each other to make the corrosion-resisting and wear-resisting alloy
on the both parts come in contact with at the sealed end face
S.
[0125] With this embodiment, since the corrosion-resisting and
wear-resisting alloy joined to at least either of the washer 59 or
the seat 61 includes the grain-like or cluster-like eutectic
carbide diffused as a discontinuous distribution, it is maintained
such that it hardly develops corrosion, and the coefficient of
friction is maintained as low as that of the corrosion-resisting
and wear-resisting alloy in FIG. 9.
[0126] Increased corrosion resisting capability and decreased
friction at the sealed end face S are achieved under a corrosive
environment including sulfuric component or dissolved oxygen. With
the present embodiment, the capability of the mechanical seal is
maintained for a long period, thereby providing a mechanical seal
with high reliability. Since the capability of the mechanical seal
is maintained for a long period, the reliability of a pump using
the mechanical seal and the reliability of a plant using the pump
increase.
[0127] Conventionally the washer 59 is used after a Co-base alloy
is overlaid on the sealed end face S of the washer 59, and the seat
61 is made of carbon impregnated with burnt phenol, carbon formed
with phenol, or carbon impregnated with white. The capability of
the corrosion-resisting and wear-resisting alloy (Co-base alloy)
used for either the washer 59 or the seat 61 or the both of the
washer 59 and the seat 61 in the present embodiment where the
grain-like or cluster-like eutectic carbide is distributed
discontinuously in the base material is compared with that of the
conventional example in Table 5. The Co-base alloy in the present
embodiment in Table 5 has the components described in Table 2, and
the grain-like or cluster-like eutectic carbide are diffused
discontinuously in the alloy.
5 TABLE 5 Conventional example Seat Carbon Embodiment of the
impregnated Carbon present invention with formed Carbon Washer Seat
Washer burnt with impregnated Co-base Co-base Item Overlay phenol
phenol with white alloy alloy Tensile 920 2.5 3 to 3.5 -- 1064 1064
strength N/mm.sup.2 Compressive 1700 8 17 to 17.5 14 More More
stress N/mm.sup.2 than than 1700 1700 Impact value 0.2 -- 2 to 3 --
8 to 10 8 to 10 kgm/cm.sup.2 Coefficient of 0.4 -- 0.25 -- 0.16 to
0.19 0.16 to 0.19 friction Hardness (HRC) 43 46 37 to 53 46 43 to
45 43 to 45 Withstanding More More -- 180 200 More temperature
(.degree. C.) than than than 300 300 300
[0128] With these differences in the capability, the mechanical
seal in the present embodiment restrains seizure, wear and
corrosion at the sealed end face S. The present embodiment provides
a mechanical seal which withstands a compressive stress and an
impact value higher than the conventional ones.
[0129] After the plate 62 made of the corrosion-resisting and
wear-resisting alloy is joined to a washer 59 or the like, the
grain-like or cluster-like eutectic carbide exists discontinuously
in the base material of the corrosion-resisting and wear-resisting
alloy, thereby providing a high corrosion-resisting capability and
restraining a leak at the sealed end face S, resulting in
preventing erosion at the sealed end face S caused by the leak. The
present embodiment provides a mechanical seal with a high
capability.
[0130] During the operation of the pump facility indicated in FIG.
16, the washer 59 rotates with the rotating shaft 50, and a plate
62 attached to the washer 59 rotates while the plate 62 is in
contact with the stationary seat 61 fixed to the pump casing 52.
The contact between the plate 62 and the seat 61 provides a seal
between the rotating shaft 50, which is a member of the rotating
side, and the pump casing 52, which is a member of the stationary
side, thereby preventing a leak of liquid. A mechanical seal device
in the pump facility comprises the washer 59, the plate 62 and the
seat 61. A first seal comprises the washer 59 (main body side) and
the plate 62 (the corrosion-resisting and wear-resisting alloy). A
second seal comprises the seat 61. The first seal may be provided
on the pump casing 52. The second seal may be provided on the
rotating shaft 50 side. The second seal provided on the pump casing
52 may be constituted in the same way as that of the first
seal.
[0131] The plate 62 rotates at a high speed while it is always in
contact with the seat 61 with an action of the spring 56 to
maintain the sealing capability. Though wear, seizure, and
corrosion of the plate 62 forming the seal face are suspected, the
plate is excellent in the wear-resisting capability and
corrosion-resisting capability since the eutectic carbide is formed
as grains or clusters as described before, thereby presenting
little wear. The plate 62 is also excellent in corrosion-resisting
capability, thereby preventing a corrosion caused by a contact with
liquid. This decreases the frequency of maintaining the mechanical
seal device, thereby extending the life of the mechanical seal
device. This leads to a reduction of maintenance operation of the
pump facility. Since the plate 62 constituted with the
corrosion-resisting and wear-resisting alloy including grain-like
or cluster-like eutectic carbide has coefficient of friction as
small as about 0.16, the ratio at which rotating power of the
rotating shaft 50 changes into heat energy at the contact part
between the plate 62 and the seat 61 is extremely small. The loss
of the rotating power of the rotating shaft 50 is small.
[0132] The mechanical seal device including a corrosion-resisting
and wear-resisting alloy having grain-like or cluster like eutectic
carbide such as the plate 62 of the present embodiment is applied
to a compressor pressurizing gas and a blower requiring a seal
between a rotating shaft and a casing in addition to the pump of
the present embodiment, which is a fluid pressurizing device. The
compressor and the blower are types of the fluid pressurizing
devices. The mechanical seal device is also applied to a turbine
where steam flows. The mechanical seal device including a
corrosion-resisting and wear-resisting alloy having grain-like or
cluster like eutectic carbide, which is applied to the pump
facility is applied as a mechanical seal device sealing between a
rotating shaft and a casing of the turbine. The pump facility, the
compressor, the blower, and the turbine are rotating devices inside
which fluid flows.
[0133] A preferable concept of the present invention including the
pump facility shown in FIG. 16, the compressor, the blower and the
turbine is also recognized as in claim 15.
[0134] A preferable concept of the present invention including the
pump facility shown in FIG. 16, the compressor, and the blower is
also recognized as in claim 16. It is also preferable to coincide
the concept with the concepts described in claim 17 or claim
20.
* * * * *