U.S. patent application number 13/054666 was filed with the patent office on 2011-05-19 for method for producing steel sheet for gasket, and gasket.
This patent application is currently assigned to NOK Corporation. Invention is credited to Takashi Nakao, Nobuaki Tanaka.
Application Number | 20110114232 13/054666 |
Document ID | / |
Family ID | 42268512 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110114232 |
Kind Code |
A1 |
Nakao; Takashi ; et
al. |
May 19, 2011 |
Method for Producing Steel Sheet for Gasket, and Gasket
Abstract
The present invention aims at providing: a method for
manufacturing such a kind of gasket-oriented steel plate excellent
in elasticity and formability, in a manner to allow for reduction
of a breaking elongation of the steel plate to thereby improve a
formability (punchability) thereof while improving a proof stress
of the steel plate against a repeated stress from a discharge valve
to thereby maintain a higher elasticity of the steel plate; and a
gasket able to withstand the repeated stress from the discharge
valve. The manufacturing method of a gasket-oriented steel plate of
the present invention comprises the steps of: annealing a starting
steel material having a composition of: Mn less than 0.5%, Ni less
than 2.0%, and Cr less than 12.0%; and subsequently temper rolling
the annealed starting steel material at a rolling reduction ratio
of 10% or more; and the gasket of the present invention is formed
by adopting a gasket-oriented steel plate obtained by the above
manufacturing method.
Inventors: |
Nakao; Takashi; (Fukushima,
JP) ; Tanaka; Nobuaki; (Fukushima, JP) |
Assignee: |
NOK Corporation
Minato-ku, Tokyo
JP
|
Family ID: |
42268512 |
Appl. No.: |
13/054666 |
Filed: |
December 2, 2009 |
PCT Filed: |
December 2, 2009 |
PCT NO: |
PCT/JP2009/006541 |
371 Date: |
January 18, 2011 |
Current U.S.
Class: |
148/609 ;
148/325; 148/333; 148/645 |
Current CPC
Class: |
C21D 8/0236 20130101;
C22C 38/04 20130101; C21D 8/0273 20130101; F16J 15/0806 20130101;
C22C 38/40 20130101; C21D 8/0226 20130101; C21D 9/0068
20130101 |
Class at
Publication: |
148/609 ;
148/645; 148/325; 148/333 |
International
Class: |
C22C 38/40 20060101
C22C038/40; C21D 8/02 20060101 C21D008/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2008 |
JP |
2008-324346 |
Claims
1. A manufacturing method of a gasket-oriented steel plate,
comprising the steps of: annealing a starting steel material having
a composition of: Mn less than 0.5%, Ni less than 2.0%, and Cr less
than 12.0%; and subsequently temper rolling the annealed starting
steel material at a rolling reduction ratio of 10% or more.
2. The manufacturing method of a gasket-oriented steel plate
according to claim 1, further comprising the steps in the order of:
passing the starting steel material through a hot rolling step, an
acid pickling step, and a cold rolling step, before the annealing
step.
3. The manufacturing method of a gasket-oriented steel plate
according to claim 1, wherein the starting steel material contains
Mn in an amount of 0.3% or less.
4. A gasket formed by adopting a gasket-oriented steel plate
obtained by the manufacturing method of a gasket-oriented steel
plate according to any one of claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a manufacturing method of a
gasket-oriented steel plate and a gasket formed by adopting the
gasket-oriented steel plate obtained by the manufacturing method of
a gasket-oriented steel plate, which may be used in a compressor of
an automobile air conditioner or the like, and particularly to a
manufacturing method capable of manufacturing a gasket-oriented
steel plate excellent in elasticity and formability, and a gasket
able to withstand a repeated stress from a discharge valve.
BACKGROUND ART
[0002] Conventionally, as a sealing part for oil, gas, and the like
to be used at high temperatures in a field of automobile, a rubber
coated metal having a structure shown in FIG. 1 is known. In FIG.
1, reference numeral 1 designates a steel plate, 2 an adhesive
layer, 3 a rubber layer, and 4 a surface coating material
layer.
[0003] The rubber coated metal shown in FIG. 1 is formed into a
gasket as shown in FIG. 2, which is to be widely used in a
compressor of an automobile air conditioner. In FIG. 2, reference
numeral 5 designates a bead, and 6 a retainer.
[0004] Examples of functions of a gasket include a shape keeping
function as a basic one, and a fluid sealing function by an
embossed bead of the gasket.
[0005] Further, the functions of the gasket include a particularly
important one to be achieved by a "retainer" drawn at a central
part of the gasket. Automobile air conditioners are each configured
to use flon as a cooling medium, and to conduct an exchange of
thermal energy by a cycle of compression, liquefaction, and
evaporation of flon. The compressed flon is transferred to a next
stage by opening and closing of a discharge valve. The discharge
valve is controlled in an opening/closing amount thereof by the
retainer fabricated on the gasket. Since the discharge valve is
contacted with the gasket at a frequency on the order of 4,000 to
9,000 times/minute, the retainer is required to possess a higher
strength and a higher elasticity.
[0006] Conventionally, SPCC materials excellent in formability have
been used, because more inexpensive dies (such as SKD11 (JIS
G4404)) are to be used in a punching step for a lower cost, for
example. However, materials equivalent to those prescribed in JIS
G3141, which are versatilely available from steel plate
manufacturers, for example, are excellent in formability and
insufficient in elasticity, so that such a phenomenon is recognized
that the formed gasket fails to fully withstand a stress from a
discharge valve, thereby causing damages of a retainer of the
gasket.
[0007] Further, although it is possible to provide a countermeasure
to cracks of a retainer when a metal having a higher elasticity
such as a high tensile strength steel plate is adopted therefor, it
is then required to use a punching die having a higher hardness
(such as high speed steel, cemented carbide, or the like), which is
disadvantageous in cost.
[0008] Disclosed in Patent Document 1 is a manufacturing method of
a stainless steel plate for a flapper valve, and particularly a
method for manufacturing a stainless steel plate for a flapper
valve, which steel plate has an improved fatigue property, is high
in hardness and is thus less in occurrence of burrs after punching,
and is subjected to a cold rolling at a rolling reduction ratio of
5% or more. Apparently, it is classified into a stainless steel
plate, because it contains 2.0 to 6.0 mass % of Ni, and 12.0 to
20.0 mass % of Cr.
[0009] However, no disclosures are found in the technique of Patent
Document 1 about a cold rolled steel plate (SPCC), because the
technique relates to a stainless steel plate.
[0010] Meanwhile, described in Patent Document 2 is a manufacturing
method of a cold rolled steel plate for a gasket material,
comprising the steps of: hot rolling a continuously cast article
produced by a continuous casting method comprising Mn: 0.5 to 3.0%,
Ni:.ltoreq.1.2%, and balance Fe and inevitable impurities; hot
rolling it; acid pickling it; and, cold rolling it at a rolling
reduction ratio of 30 to 90%. In the Patent Document 2, it is
clarified in its paragraph [0032] that Mn is a component required
to be included at 0.5% or more so as to prevent red shortness of a
primitive plate due to S as an impurity, and to provide the plate
with a higher refining degree.
[0011] However, when Mn possessing a reinforcing property is added
into steel in an amount of 0.5% or more, the steel is considerably
increased in strength, thereby bringing about such a problem of
formability (punchability) that a specific die made of high speed
steel, cemented carbide, or the like as a press material is
required upon punching of a product. [0012] Patent Document 1:
JP2003-41350A [0013] Patent Document 2: JP2005-36266A
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0014] It is therefore an object of the present invention to
provide: a method capable of manufacturing such a kind of
gasket-oriented steel plate excellent in elasticity and
formability, in a manner to allow for reduction of a breaking
elongation of the steel plate to thereby improve a formability
(punchability) thereof while improving a proof stress of the steel
plate against a repeated stress from a discharge valve to thereby
maintain a higher elasticity of the steel plate; and a gasket
withstandable to the repeated stress from the discharge valve.
[0015] The other objects of the present invention will become
apparent from the following description.
Means for Solving Problem
[0016] The above object is carried out by the following
inventions.
[0017] The invention recited in claim 1 resides in a manufacturing
method of a gasket-oriented steel plate, comprising the steps
of:
[0018] annealing a starting steel material having a composition of:
Mn less than 0.5%, Ni less than 2.0%, and Cr less than 12.0%;
and
[0019] subsequently temper rolling the annealed starting steel
material at a rolling reduction ratio of 10% or more.
[0020] The invention recited in claim 2 resides in the
manufacturing method of a gasket-oriented steel plate according to
claim 1, further comprising the steps in the order of:
[0021] passing the starting steel material through a hot rolling
step, an acid pickling step, and a cold rolling step, before the
annealing step.
[0022] The invention recited in claim 3 resides in the
manufacturing method of a gasket-oriented steel plate according to
claim 1 or 2, wherein the starting steel material contains Mn in an
amount of 0.3% or less.
[0023] The invention recited in claim 4 resides in a gasket formed
by adopting a gasket-oriented steel plate obtained by the
manufacturing method of a gasket-oriented steel plate according to
any one of claims 1 to 3.
Effect of the Invention
[0024] According to the present invention, it becomes possible: to
manufacture such a kind of gasket-oriented steel plate excellent in
elasticity and formability, in a manner to allow for reduction of a
breaking elongation of the steel plate to thereby improve a
formability (punchability) thereof while improving a proof stress
of the steel plate against a repeated stress from a discharge valve
to thereby maintain a higher elasticity of the steel plate; and to
provide a gasket withstandable to the repeated stress from the
discharge valve.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a cross-sectional view of an example of a rubber
coated metal; and
[0026] FIG. 2 is a plan view of an example of a gasket in a
compressor of an automobile air conditioner.
EXPLANATIONS OF LETTERS OR NUMERALS
[0027] 1: steel plate [0028] 2: adhesive layer [0029] 3: rubber
layer [0030] 4: surface coating material layer [0031] 5: bead
[0032] 6: retainer
BEST MODE(S) FOR CARRYING OUT THE INVENTION
[0033] Embodiments of the present invention will be described
hereinafter.
[0034] In the present invention, the starting steel material upon
manufacturing a gasket-oriented steel plate is provided by
preparing a general-purpose product such as SPCC, SPCD, SPCE, SPCF,
and SPCG prescribed by JIS G3141 (cold rolled steel plate and steel
band) in a manner to contain Mn as a chemical component in an
amount less than 0.5%. Further, the starting steel material is
configured to contain carbon as an additional component in an
amount of 0.15% or less. Other additional components contained in
the starting steel material are P, S, and the like, and Fe as a
remaining component.
[0035] The starting steel material in the present invention
contains, in its chemical composition, Ni in an amount less than
2.0%, preferably less than 1.5%, and Cr in an amount less than
12.0%, and preferably less than 10%. Thus, Ni and Cr, if any, are
contained in such smaller amounts as noted just above,
respectively, so that the starting steel material of the present
invention is never matured into such a stainless steel plate as
described in JP2005-36266A (Patent Document 2).
[0036] In the present invention, Mn is contained in the starting
steel material in an amount less than 0.5%, thereby exhibiting the
following effects. Namely, addition of manganese exhibiting a
reinforcing property in an amount of 0.5% or more has considerably
increased a strength of a steel, thereby bringing about such a
problem of punchability that a specific die made of high speed
steel, cemented carbide, or the like as a press material is
required upon punching a product. However, addition of manganese in
an amount less than 0.5% brings about such an advantage that a die
made of SKD11, which is a general-purpose material, can form the
steel plate.
[0037] The method of the present invention for manufacturing a
gasket-oriented steel plate is characterized in that the method
comprises the steps of: annealing the above described starting
steel material; and subsequently conducting a temper rolling
treatment at a rolling reduction ratio of 10% or more.
[0038] Further, although the present invention is not limited in
terms of a step(s) before the annealing, it is possible for the
starting steel material to be successively passed through the steps
in the order of a hot rolling step, an acid pickling step, and a
cold rolling step, for example.
[0039] The molten steel having been prepared to have the above
chemical components is smelted by a typically known smelting method
using a converter or the like, and then prepared by a typically
used casting method such as a continuous casting method into a
material to be rolled then.
[0040] Next, the material to be rolled is heated to about
1,200.degree. C., and then successively stretched by rolls while
the material is still in a hot state, in a manner to hot roll the
material into a thickness on the order of 2 to 4 mm at about
600.degree. C. The hot rolling may be adjusted in terms of a
temperature for processing, a rate for cooling, and the like,
thereby allowing for obtainment of various steel materials.
[0041] The thermally stretched plate having been hot rolled into a
thickness of 2 to 4 mm is to be preferably acid pickled. The method
for acid pickling is not particularly limited, and examples of
usable acids include various organic acids or inorganic acids.
[0042] After acid pickling, the plate is cold rolled at an ordinary
temperature into a thickness on the order of 0.1 mm to several mm.
"Cold" means that a heat is not particularly applied. It is
possible here to conduct annealing after cold rolling.
[0043] In the present invention, temper rolling is conducted after
annealing. It is important in the present invention to set the
rolling reduction ratio at 10% or more.
[0044] The rolling reduction ratio is also called a "temper rolling
reduction ratio" hereinafter.
[0045] Even if all requirements are the same as the present
invention, when the temper rolling reduction ratio is less than
10%, it will lead to insufficient strain hardening, thereby failing
to obtain an appropriate proof stress (of 290 MPa or more,
preferably 315 MPa or more) and failing to withstand a stress from
a discharge valve, and thereby causing a damage of a steel
plate.
[0046] Contrary, as in the present invention, when the temper
rolling reduction ratio is made to be 10% or more, the temper
rolled steel plate is subjected to occurrence of a strain hardening
phenomenon where the steel plate is enabled to withstand a repeated
stress from a discharge valve, thereby enabling to manufacture such
a kind of gasket-oriented steel plate excellent in elasticity and
formability, in a manner that the strain hardening phenomenon
allows to decrease a breaking elongation of the plate down to less
than 33% (preferably down to 30% or less) to thereby improve the
formability (punchability) thereof while improving a proof stress
thereof to maintain a higher elasticity. Namely, it is then
possible to obtain an SPCC plate having a breaking elongation
decreased down to less than 33% (preferably down to 30% or less) to
thereby exemplarily decrease burrs, which plate can be in turn
formed by an inexpensive die.
[0047] The gasket of the present invention is obtainable by
exemplarily forming and fabricating the above manufactured
gasket-oriented steel plate into a rubber coated metal. Examples of
its shape include one shown in FIG. 2.
[0048] The obtained gasket exhibits an effect to withstand a
repeated stress from a discharge valve, by virtue of the properties
of the steel plate as a starting material of the gasket.
EXAMPLES
[0049] The effects of the present invention will be exemplified
hereinafter based on Examples.
Example 1 to Example 3, and Comparative Example 1 to Comparative
Example 4
[0050] Steel plates listed in Table 1 were formed into rubber
coated metals, respectively, and the following evaluations were
conducted.
[0051] Component analysis values of reinforcing components were
obtained as analysis values of molten steels, respectively.
[0052] <Evaluation>
[0053] (Mechanical Properties)
[0054] No. 5 test pieces specified in JIS Z 2201 were used, and
were each subjected to measurement of a proof stress (MPa), a
tensile strength (MPa), and a breaking elongation (%) all in
conformity to JIS Z 2241 by the following measurement, while
adopting a rolling direction of each steel plate as a test
direction.
[0055] (Punchability)
[0056] Die: SKD11 was used. In case of failure of punching by means
of SKD11, a high speed steel was used.
[0057] Amount of burr: An amount of burr was measured by a shape
measuring instrument after punching, setting the clearance of 0.06
mm between the punch and the die.
[0058] Cross-section state: A sheared section or broken section
after punching was visually observed, to evaluate whether it was
homogeneous or inhomogeneous.
[0059] (Durability to Repeated Stress)
[0060] Each rubber coated metal was formed into a gasket, and
evaluated for presence/absence of retainer-crack due to a repeated
load from a discharge valve.
[0061] <Evaluation Result>
[0062] The evaluation result is shown in Table 1.
TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Com. Ex. 1 Com. Ex. 2 Com.
Ex. 3 Com. Ex. 4 Thickness (mm) 0.6 0.6 0.6 0.6 0.6 0.6 0.6
Reinforcing Carbon 0.06 0.06 0.06 0.04 0.14 0.11 0.06 component
amount (%) Manganese 0.3 0.3 0.3 0.3 0.7 1.2 0.3 amount (%) Rolling
reduction ratio (%) 10 12 14 2 2 2 5 Mechanical Proof 310 340 400
286 326 530 290 property stress (MPa) Tensile 400 400 412 394 462
800 400 strength (MPa) Breaking 30 23 17 35 35 17 34 elongation (%)
Punchability Die SKD11 SKD11 SKD11 SKD11 SKD11 High speed SKD11
steel.sup.+ Burr amount 60 60 60 100 100 -- 60 (.mu.m)
Cross-section Homo- Homo- Homo- Inhomo- Inhomo- -- Inhomo- state
geneous geneous geneous geneous geneous goneous Durability against
Cracks not Cracks not Cracks not Occurrence Occurrence Cracks not
Occurrence repeated stress caused caused caused of cracks of cracks
caused of cracks Note Condition of mass- production .sup.+Not
punchable by means of SKD11
[0063] The steel plates of Examples 1 to 3 were each punchable by
means of SKD11, less in amount of burr, and homogeneous in
cross-section state. Further, retainer-cracks were not caused in
gaskets manufactured from Examples 1 to 3. Example 2 is more
suitable for mass-production.
[0064] Comparative Example 1 (rolling reduction ratio of 2%)
exhibited a proof stress and a breaking elongation, out of
appropriate ranges, respectively. Comparative Example 2 (rolling
reduction ratio of 2%, and manganese amount of 0.7%) exhibited a
proof stress by virtue of the increased manganese amount, but
exhibited a breaking elongation exceeding an appropriate range.
Comparative Examples 1 and 2 exhibited more amounts of burr than
Examples 1 to 3, and cross-section states of Comparative Examples 1
and 2 were inhomogeneous, respectively. Retainer-cracks were found
in gaskets formed from Comparative Examples 1 and 2.
[0065] Comparative Example 3 (rolling reduction ratio of 2%, and
manganese amount of 1.2%) exhibited an excessively increased
strength, and was not punchable by means of SKD11.
[0066] Comparative Example 4 (rolling reduction ratio of 5%)
exhibited a breaking elongation exceeding an appropriate range, and
its cross-section state was inhomogeneous. Further, retainer-cracks
were found in a gasket formed from Comparative Example 4.
* * * * *