U.S. patent application number 15/381785 was filed with the patent office on 2017-06-22 for manufacturing method of pressure sensor.
The applicant listed for this patent is NAGANO KEIKI CO., LTD.. Invention is credited to Nobutaka Yamagishi, Naoki Yamashita.
Application Number | 20170175220 15/381785 |
Document ID | / |
Family ID | 57737580 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170175220 |
Kind Code |
A1 |
Yamagishi; Nobutaka ; et
al. |
June 22, 2017 |
MANUFACTURING METHOD OF PRESSURE SENSOR
Abstract
A manufacturing method of a pressure sensor, in which the
pressure sensor includes: a metal joint having an introduction hole
configured to flow a measurement target fluid therethrough; and a
sensor module metal member including: a cylindrical portion
provided to the joint; a diaphragm; and a dent configured to
receive the measurement target fluid from the introduction hole,
includes: welding the joint to the sensor module metal member; and
subsequently, heating the joint and the sensor module metal
member.
Inventors: |
Yamagishi; Nobutaka; (Tokyo,
JP) ; Yamashita; Naoki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NAGANO KEIKI CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
57737580 |
Appl. No.: |
15/381785 |
Filed: |
December 16, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01L 19/143 20130101;
C21D 9/50 20130101; G01L 19/0038 20130101; C21D 6/004 20130101;
G01L 19/0618 20130101; G01L 19/147 20130101; C21D 1/18
20130101 |
International
Class: |
C21D 9/50 20060101
C21D009/50; C21D 6/00 20060101 C21D006/00; C21D 1/18 20060101
C21D001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2015 |
JP |
2015-250198 |
Claims
1. A manufacturing method of a pressure sensor, the pressure sensor
comprising: a metal joint attached to a target member and having an
introduction hole configured to flow a measurement target fluid
therethrough; and a sensor module metal member comprising: a
cylindrical portion provided to the joint; a diaphragm integrated
with an end of the cylindrical portion; and a dent configured to
receive the measurement target fluid from the introduction hole,
the manufacturing method comprising: welding the joint to the
sensor module metal member; and subsequently, heating the joint and
the sensor module metal member.
2. The manufacturing method of a pressure sensor according to claim
1, further comprising: attaching a detector comprising a strain
gauge to the diaphragm of the sensor module metal member, after the
heating of the joint and the sensor module metal member.
3. The manufacturing method of a pressure sensor according to claim
1, wherein the heating after the welding of the joint and the
sensor module metal member is a precipitation hardening treatment
comprising heating and leaving the joint and the sensor module
metal member to stand until cool for precipitation hardening.
4. The manufacturing method of a pressure sensor according to claim
1, wherein the heating comprises: a re-solid solution treatment;
and, after the re-solid solution treatment, a precipitation
hardening treatment comprising heating and leaving to stand until
cool for precipitation hardening.
Description
[0001] The entire disclosure of Japanese Patent Application No.
2015-250198 filed Dec. 22, 2015 is expressly incorporated by
reference herein.
TECHNICAL FIELD
[0002] The present invention relates to a manufacturing method of a
pressure sensor.
BACKGROUND ART
[0003] A pressure sensor including a joint attached to a target
member and a pressure detecting element provided to the joint has
been known.
[0004] The joint and the pressure detecting element of the pressure
sensor are welded to each other (Patent Literature 1: JP Patent
Publication No. 3556165).
[0005] The pressure detecting element is also referred to as a
sensor module. In Patent Literature 1, the pressure detecting
element is provided by integrating a metal diaphragm with an upper
surface of a cylindrical support made of a precipitation hardening
stainless steel. The cylindrical support and a metal joint are
beam-welded.
[0006] Conventionally, a sensor module is optionally heated for
manufacture.
[0007] For instance, a body of the metal diaphragm is formed by a
cold working using a predetermined alloy. An insulative film is
formed on the obtained body by a chemical vapor deposition while
the body is heated at 400 degrees C. or more, thereby providing a
pressure sensor (Patent Literature 2: JP Patent Publication No.
3084304).
[0008] Further, a precipitation hardening stainless steel in an
unhardened state is forged and the like to form an intermediate
molded body. The intermediate molded body is heated, thereby
providing a diaphragm for a pressure sensor (Patent Literature 3:
JP Patent Publication No. 3688063). The heating treatment of Patent
Literature 3 includes: a re-solid solution treatment for releasing
a processing strain generated during the forging and the like; and
a precipitation hardening treatment to be performed for eliminating
the processing strain after a cooling treatment after the re-solid
solution treatment.
[0009] When two heated metal members are welded to each other,
heating effects on a weld portion and surroundings thereof are
reset, so that a strength and a hardness of the weld portion and
the surroundings are inferior to those in other parts of a base
metal. For this reason, when a large pressure is applied on the
welded metal members, cracks are generated on the weld portion and
the surroundings in which the strength and the hardness are low,
resulting in breakage.
[0010] In a conventional example of Patent Literature 1, since the
cylindrical support made of a precipitation hardening stainless
steel is beam-welded to the metal joint, the weld portion between
the cylindrical support and the joint are weak. Even when a
pressure is applied to the weld portion, since materials for the
cylindrical support and the joint are determined depending on a
range of an applied pressure and a welding method is contrived, no
disadvantage is caused in a typical pressure range. However,
recently, the pressure range required in the market becomes
extremely high. When the pressure sensor of Patent Literature 1 is
used in a high pressure range, the weld portion and the
surroundings may be broken.
[0011] Patent Literature 2 only discloses that the body of the
metal diaphragm is formed and the body is heated at 400 degrees C.
or more, but fails to disclose the bonding of the body and the
joint. Although it can be conceived from Patent Literature 2 that
the heated body of the metal diaphragm is welded to the joint, the
weld portion and the surroundings may be broken when used in a high
pressure range as in Patent Literature 1.
[0012] Patent Literature 3 only discloses that the intermediate
molded body is subjected to the heat treatment including the
re-solid solution treatment and the precipitation hardening
treatment, but fails to disclose that the heated pressure sensor
diaphragm is bonded to the joint. Although it can be conceived that
the heated pressure sensor diaphragm is welded to the joint, the
weld portion and the surroundings may be broken when used in a high
pressure in the same manner as disclosed in Patent Literature
1.
SUMMARY OF THE INVENTION
[0013] An object of the invention is to provide a manufacturing
method of a pressure sensor capable of preventing a weld portion
and surroundings thereof from being broken even under a high
pressure.
[0014] According to an aspect of the invention, a manufacturing
method of a pressure sensor, the pressure sensor including: a metal
joint attached to a target member and having an introduction hole
configured to flow a measurement target fluid therethrough; and a
sensor module metal member including: a cylindrical portion
provided to the joint; a diaphragm integrated with an end of the
cylindrical portion; and a dent configured to receive the
measurement target fluid from the introduction hole, includes:
welding the joint to the sensor module metal member; and
subsequently, heating the joint and the sensor module metal
member.
[0015] In the above aspect of the invention, since the joint and
the sensor module metal member are heated after being welded,
strength of the weld portion and surroundings thereof is increased.
Hardness of the heated weld portion and surroundings thereof is
increased to be close to hardness of other parts. Accordingly, even
when the measurement target fluid to be introduced to the sensor
module metal member has a high pressure, the joint and the sensor
module metal member can be prevented from being broken at the weld
portion and the surroundings thereof.
[0016] In the above arrangement, it is preferable that the method
further includes attaching a detector having a strain gauge to the
diaphragm of the sensor module metal member, after the heating of
the joint and the sensor module metal member.
[0017] With this arrangement, since the detector having the strain
gauge is attached to the diaphragm after the sensor module metal
member is heated, a measurement error caused by heating the strain
gauge itself is avoidable.
[0018] In the above arrangement, it is preferable that the heating
after the welding of the joint and the sensor module metal member
is a precipitation hardening treatment including heating and
leaving the joint and the sensor module metal member to stand until
cool for precipitation hardening.
[0019] With this arrangement, since the heating treatment performed
after the welding treatment is only the precipitation hardening
treatment, a manufacturing procedure can be simplified.
[0020] In the above arrangement, it is preferable that the heating
includes: a re-solid solution treatment for uniformizing rough
texture of the joint and the sensor module metal member caused by
being welded; and, after the re-solid solution treatment, a
precipitation hardening treatment including heating and leaving the
joint and the sensor module metal member to stand until cool for
precipitation hardening to improve strength of the welded portion
and surroundings thereof.
[0021] With this arrangement, since the re-solid solution treatment
and the precipitation hardening treatment are consecutively
performed, the hardness of the weld portion and the surroundings
thereof becomes approximately equal to the hardness of the parts
other than the weld portion and the surroundings thereof.
BRIEF DESCRIPTION OF DRAWING(S)
[0022] FIG. 1 is a side elevational view of a pressure sensor
manufactured in an exemplary embodiment of the invention.
[0023] FIGS. 2A to 2D schematically illustrate a manufacturing
method in the above exemplary embodiment.
[0024] FIG. 3A is a front elevational view of a test piece used in
Examples.
[0025] FIG. 3B is a front elevational view of another test piece
used in Examples.
[0026] FIG. 4 is a graph showing a dimensional change of the heated
test pieces.
[0027] FIG. 5A is a copy of a microphotograph of an entirety of the
test piece in Example 1.
[0028] FIG. 5B is a copy of an enlarged microphotograph of a part
of the test piece at a position B in FIG. 5A in Example 1.
[0029] FIG. 5C is a copy of an enlarged microphotograph of a part
of the test piece at a position C in FIG. 5A in Example 1.
[0030] FIG. 5D is a copy of an enlarged microphotograph of a part
of the test piece at a position D in FIG. 5A in Example 1.
[0031] FIG. 6A is a copy of a microphotograph of an entirety of the
test piece in Example 2.
[0032] FIG. 6B is a copy of an enlarged microphotograph of a part
of the test piece at a position B in FIG. 6A in Example 2.
[0033] FIG. 6C is a copy of an enlarged microphotograph of a part
of the test piece at a position C in FIG. 6A in Example 2.
[0034] FIG. 6D is a copy of an enlarged microphotograph of a part
of the test piece at a position D in FIG. 6A in Example 2.
[0035] FIG. 7A is a copy of a microphotograph of an entirety of the
test piece in Reference Example 1.
[0036] FIG. 7B is a copy of an enlarged microphotograph of a part
of the test piece at a position B in FIG. 7A in Reference Example
1.
[0037] FIG. 7C is a copy of an enlarged microphotograph of a part
of the test piece at a position C in FIG. 7A in Reference Example
1.
[0038] FIG. 7D is a copy of an enlarged microphotograph of a part
of the test piece at a position D in FIG. 7A in Reference Example
1.
[0039] FIG. 8A is a copy of a microphotograph of an entirety of the
test piece in Comparative Example.
[0040] FIG. 8B is a copy of an enlarged microphotograph of a part
of the test piece at a position B in FIG. 8A in Comparative
Example.
[0041] FIG. 8C is a copy of an enlarged microphotograph of a part
of the test piece at a position C in FIG. 8A in Comparative
Example.
[0042] FIG. 8D is a copy of an enlarged microphotograph of a part
of the test piece at a position D in FIG. 8A in Comparative
Example.
[0043] FIG. 9 is a graph showing a hardness distribution at and
near a weld portion in Example 1.
[0044] FIG. 10 is a graph showing a hardness distribution at and
near a weld portion in Example 2.
[0045] FIG. 11 is a graph showing a hardness distribution at and
near a weld portion in Reference Example 1.
[0046] FIG. 12 is a graph showing a hardness distribution at and
near a weld portion in Comparative Example.
DESCRIPTION OF EMBODIMENT(S)
[0047] Exemplary embodiment(s) of the invention will be described
with reference to the attached drawings.
[0048] As shown in FIG. 1, a pressure sensor 1 includes: a joint 10
attached to a target member (not shown); a sensor module metal
member 20 provided to the joint 10; and a detector 30 provided to
the sensor module metal member 20.
[0049] The joint 10 is made of stainless steel SUS630 or other
metal materials and is structured to include a shaft 11 and a
flange 12 integrated with the shaft 11.
[0050] A male thread 13 is formed on an outer circumference of the
shaft 11. An introduction hole 11A configured to flow a measurement
target fluid therethrough is formed in the shaft 11 in an axial
direction thereof.
[0051] The sensor module metal member 20 is made of stainless steel
SUS630 or other metal materials and is structured to include a
cylindrical portion 21 provided to the joint 10 and a diaphragm 22
integrated with an end of the cylindrical portion 21.
[0052] The sensor module metal member 20 has a dent 20A configured
to receive the measurement target fluid through the introduction
hole 11A.
[0053] The joint 10 is bonded to the cylindrical portion 21 through
a weld portion 40.
[0054] A welding pipe 50 is provided at a position corresponding to
the weld portion 40 in the introduction hole 11A of the joint 10
and in the dent 20A of the sensor module metal member 20. The
welding pipe 50 is made of stainless steel SUS304 or other metal
materials.
[0055] The detector 30 includes a strain gauge 31 attached to a
flat surface of the diaphragm 22. The strain gauge 31 is attached
to the diaphragm 22, for instance, using a glass binder. It should
be noted that FIG. 1 shows the strain gauge 31 at a larger
thickness than an actual thickness in order that a structure of the
strain gauge 31 is easily understood.
[0056] FIGS. 2A to 2D show a manufacturing method of the pressure
sensor 1. A step for holding the welding pipe 50 is formed in the
introduction hole 11A of the joint 10 as shown in FIGS. 2A to 2D.
However, no step may be formed as shown in FIG. 1.
[0057] FIG. 2A shows that the joint 10 and the sensor module metal
member 20 are ready for assembly. As shown in FIG. 2A, the joint 10
and the sensor module metal member 20, which are not yet heated,
and the welding pipe 50 are prepared. In this state, the joint 10
and the sensor module metal member 20 which are not welded to each
other are subjected to a solid solution treatment defined in JIS
and the like.
[0058] The joint 10 and the sensor module metal member 20 are
brought into contact with each other while a first end of the
welding pipe 50 is inserted into the introduction hole 11A of the
joint 10 and a second end of the welding pipe 50 is inserted into
the dent 20A of the sensor module metal member 20. At this time, a
position of the welding pipe 50 corresponds to a position at which
the joint 10 is in contact with the sensor module metal member
20.
[0059] FIG. 2B shows the joint 10 and the sensor module metal
member 20 after being welded to each other.
[0060] Electron beam welding is applied to an outer circumference
of a contact portion between the joint 10 and the sensor module
metal member 20. The electron beam welding is applied along the
outer circumference on the contact portion between the joint 10 and
the sensor module metal member 20. By the electron beam welding,
the weld portion 40 is formed between the joint 10 and the sensor
module metal member 20.
[0061] FIG. 2C shows that the joint 10 and the sensor module metal
member 20 welded to each other are being heated.
[0062] FIG. 2C shows a furnace 2 provided with a heater H. Inside
the furnace 2, the joint 10 and the sensor module metal member 20
which are bonded to each other via the weld portion 40 are
housed.
[0063] Treatment in the furnace 2 includes: a first heating mode
(i.e., precipitation hardening treatment) in which the joint 10 and
the sensor module metal member 20 welded to each other are heated
and left to stand until cool, thereby performing precipitation
hardening; and a second heating mode including a re-solid solution
treatment for uniformizing rough texture of the joint 10 and the
sensor module metal member 20 caused by being welded and a
precipitation hardening treatment in which, after the re-solid
solution treatment, the joint 10 and the sensor module metal member
20 are heated and left to stand until cool, thereby performing
precipitation hardening.
[0064] The precipitation hardening treatment conducted in the first
heating mode is an H900 heating treatment defined in JIS. For
instance, when the joint 10 and the sensor module metal member 20
are made of stainless steel SUS630, the joint 10 and the sensor
module metal member 20 are kept at a temperature in a range from
470 degrees C. to 490 degrees C. in the furnace 2 for two
hours.
[0065] The precipitation hardening treatment conducted in the
second heating mode is the same as the precipitation hardening
treatment conducted in the first heating mode.
[0066] The re-solid solution treatment conducted in the second
heating mode is an S heating treatment defined in JIS and is also
referred to as a solution treatment. The re-solid solution
treatment refers to a treatment in which an alloy component of a
metal material is melted into a solid content while being heated
and kept at an appropriate temperature and is rapidly cooled so as
not to form precipitate. For instance, when the joint 10 and the
sensor module metal member 20 are made of stainless steel SUS630,
the joint 10 and the sensor module metal member 20 are heated and
kept in a range from 1020 degrees C. to 1060 degrees C. in the
furnace 2 and rapidly cooled.
[0067] FIG. 2D shows the detector 30 attached to the sensor module
metal member 20.
[0068] As shown in FIG. 2D, the detector 30 including the strain
gauge 31 is fixed by a glass binder on a flat surface of the
diaphragm 22 of the sensor module metal member 20 after the heating
treatment.
EXAMPLES
[0069] Next, Examples for verifying the advantages of the invention
will be described. Test Piece
[0070] FIGS. 3A and 3B show test pieces.
[0071] FIG. 3A shows a welded test piece 3A.
[0072] The welded test piece 3A is formed by integrating
large-diameter portions 5A with each of ends of a small-diameter
portion 4A. A member 6A corresponding to a welding pipe is buried
at an axial center of the small-diameter portion 4A and electron
beam welding is applied along an outer circumference of the
small-diameter portion 4A. A male thread is formed on each of the
large-diameter portions 5A of the welded test piece 3A.
[0073] A material of the welded test piece 3A is stainless steel
SUS630. Before the welding treatment, two pieces each formed by
integrating a half of the small-diameter portion with one of the
large-diameter portions are prepared. Electron beam welding is
applied on the two pieces while the small-diameter portions of the
two pieces abut on each other.
[0074] FIG. 3B shows an integrated test piece 3B.
[0075] The integrated test piece 3B is used for comparing with
experiment results of the welded test piece 3A. The outline and the
material of the integrated test piece 3B are the same as those of
the welded test piece 3A. The integrated test piece 3B is formed by
integrating large-diameter portions 5B with each of ends of a
small-diameter portion 4B.
Experiment 1
[0076] In Experiment 1, in the above test pieces each having a
72-mm axial basic dimension, a change in the axial dimension
between before and after being heated was measured using a digital
caliper.
[0077] The welded test piece 3A subjected to the first heating mode
is indicated as Example 1. The welded test piece 3A subjected to
the second heating mode is indicated as Example 2. The welded test
piece 3A subjected to a typical heating treatment is indicated as
Comparative Example. Although the second heating mode includes the
heating treatment twice, an experiment in which only the re-solid
solution treatment is conducted in the second heating mode is
indicated as Reference Example 1.
[0078] The integrated test piece 3B subjected to the "H900"
precipitation hardening treatment is indicated as Reference Example
2. The integrated test piece 3B subjected to the "H1025"
precipitation hardening treatment is indicated as Reference Example
3. The "H1025" heating treatment in Reference Example 3 refers to
heating of a test piece of stainless steel SUS630 in a range from
540 degrees C. to 560 degrees C.
[0079] Comparative Example refers to conducting the "H900"
precipitation hardening treatment before the welding treatment. In
order to obtain the dimensional change, two pieces forming the
welded test piece 3A abut on each other.
[0080] FIG. 4 shows a maximum value (Max), a minimum value (Min)
and an average value (Ave) in the dimensional change after the
heating treatment in a plurality of experiments conducted in each
of Examples 1 and 2, Comparative Example and Reference Examples 1
to 3.
[0081] As shown in FIG. 4, a dimensional change in Example 1 is
substantially the same as a dimensional change in each of Reference
Examples 2 and 3 using the integrated test piece 3B. In contrast,
since the re-solid solution treatment is conducted in Example 2 and
Reference Example 1, the change in dimension after the heating
treatment is larger than those in Reference Examples 2 and 3.
Accordingly, when the second heating mode is to be performed, it is
necessary to design a pressure sensor in consideration of the
change in dimension.
Experiment 2
[0082] In Experiment 2, one sample of each of Examples 1 and 2,
Reference Example 1 and Comparative Example was prepared. The
samples were the welded test pieces 3A shown in FIG. 3A. As shown
in FIG. 3A, each of the welded test pieces 3A was cut at a position
L1 axially away .+-.7 mm from the abutting portion (weld portion
L0) of the small-diameter portions 4A. The cut small-diameter
portion 4A including the abutting portion was cut along an axial
position L2 to provide the sample. The cut sample was buried in a
resin member (not shown) and polished. In Experiment 2, a surface
of the sample was treated with a Marble's reagent and observed
using a metallograph. A ratio of the Marble's reagent is 4 g of
copper sulfate, 20 cc of hydrochloric acid, and 20 cc of water. The
used metallograph was a "VC3500 (model number) Digital Fine Scope
(product name)" manufactured by OMRON Corporation.
[0083] Copies of the microphotographs in Example 1 are shown in
FIGS. 5A to 5D. Copies of the microphotographs in Example 2 are
shown in FIGS. 6A to 6D. Copies of the microphotographs in
Reference Example 1 are shown in FIGS. 7A to 7D. Copies of the
microphotographs in Comparative are shown in FIGS. 8A to 8D.
[0084] FIGS. 5A to 5D show the copies of the microphotographs in
Example 1. [0085] In FIG. 5A, the weld portion is shown in the
middle and the surroundings of the weld portion are shown on the
right and the left sides. [0086] A part indicated by an arrow B in
FIG. 5A indicates a position of the weld portion. An enlarged
microphotograph of the part is shown in FIG. 5B. [0087] A part
indicated by an arrow C indicates a thermally affected position
slightly away from the weld portion. An enlarged microphotograph of
the part is shown in FIG. 5C. [0088] A part indicated by an arrow D
indicates a thermally unaffected position away from the weld
portion. An enlarged microphotograph of the part is shown in FIG.
5D.
[0089] As shown in FIG. 5A, it is observed that a welding line
(which is light, though) is left on each of the weld portion
indicated by the arrow B and the thermally affected portion
indicated by the arrow C.
[0090] Precipitate is observed in a metal texture of the weld
portion shown in FIG. 5B and in a metal texture of the thermally
affected portion shown in FIG. 5C, which are slightly different
from a metal texture shown in FIG. 5D.
[0091] FIGS. 6A to 6D show the copies of the microphotographs in
Example 2. A part indicated by an arrow B in FIG. 6A indicates a
position of the weld portion. An enlarged microphotograph of the
part is shown in FIG. 6B. A part indicated by an arrow C indicates
a position of the thermally affected portion slightly away from the
weld portion. An enlarged microphotograph of the part is shown in
FIG. 6C. A part indicated by an arrow D indicates a position
unaffected from the welding treatment. An enlarged microphotograph
of the part is shown in FIG. 6D.
[0092] As shown in FIG. 6A, no welding line is observed on each of
the weld portion indicated by the arrow B and the thermally
affected portion indicated by the arrow C.
[0093] A metal texture of the weld portion shown in FIG. 6B and a
metal texture of the thermally affected portion shown in FIG. 6C
appear to be the same as a metal texture shown in FIG. 6D. It is
deduced that this is because the metal texture is uniformly
corroded by the re-solid solution treatment and recovered to a
texture similar to a typical texture of stainless steel SUS630
after being subjected to a solution treatment. As described in
Experiment 1, Example 2 shows a large dimensional change, which is
deduced to be caused by the recovery of the texture.
[0094] FIGS. 7A to 7D show the copies of the microphotographs in
Reference Example 1. In FIG. 7A, the weld portion is shown in the
middle and the surroundings of the weld portion are shown on the
right and the left sides. A part indicated by an arrow B in FIG. 7A
indicates a position of the weld portion. An enlarged
microphotograph of the part is shown in FIG. 7B. A part indicated
by an arrow C indicates a position of the thermally affected
portion slightly away from the weld portion. An enlarged
microphotograph of the part is shown in FIG. 7C. A part indicated
by an arrow D indicates a thermally unaffected position away from
the weld portion. An enlarged microphotograph of the part is shown
in FIG. 7D.
[0095] As shown in FIG. 7A, no welding line is observed on each of
the weld portion indicated by the arrow B and the thermally
affected portion indicated by the arrow C.
[0096] No black precipitate is observed in a metal texture of the
weld portion shown in FIG. 7B and in a metal texture of the
thermally affected portion shown in FIG. 7C. This is deduced to be
attributed to no precipitation hardening treatment applied in
Reference Example 1.
[0097] FIGS. 8A to 8D show the copies of the microphotographs in
Comparative. In FIG. 8A, the weld portion is shown in the middle
and the surroundings of the weld portion are shown on the right and
the left sides. A part indicated by an arrow B in FIG. 8A indicates
a position of the weld portion. An enlarged microphotograph of the
part is shown in FIG. 8B. A part indicated by an arrow C indicates
a position of the thermally affected portion. An enlarged
microphotograph of the part is shown in FIG. 8C. A part indicated
by an arrow D indicates a thermally unaffected position away from
the weld portion. An enlarged microphotograph of the part is shown
in FIG. 8D.
[0098] As shown in FIG. 8A, a clear welding line is observed on
each of the weld portion indicated by the arrow B and the thermally
affected portion indicated by the arrow C.
[0099] It is observed that a metal texture of the weld portion
shown in FIG. 8B and a metal texture of the thermally affected
portion shown in FIG. 8C are apparently different from a metal
texture shown in FIG. 8D.
[0100] As shown in FIGS. 5A to 8D, it is observed in Example 1
that, although the texture is not recovered, precipitate is formed
in the texture of the thermally affected portion near the weld
portion. It is observed in Example 2 that the metal texture of the
weld portion and the metal texture of the thermally affected
portion are similar to a typical texture of stainless steel SUS630
after being subjected to a solution treatment as compared with
Comparative Examples corresponding to conventional examples, so
that it is deduced that an influence by the welding treatment is
small in Example 2.
Experiment 3
[0101] Experiment 3 is an HRC (Rockwell) hardness test to be
performed using the samples used in Experiment 2.
[0102] The used hardness tester was a "MVK-H1 (model number)"
device manufactured by Akashi Corporation.
[0103] The sample of Example 1 shown in FIG. 5A, the sample of
Example 2 shown in FIG. 6A, the sample of Reference Example 1 shown
in FIG. 7A, and the sample of comparative shown in FIG. 8A were
measured in a right-left direction in the respective figures.
[0104] Since a width of a weld bead was 1.5 mm, a measurement pitch
in the right-left direction was defined as 0.1 mm. The hardness
test was performed in three columns from a top to a bottom of the
figures according to a welding depth. A central part of the welding
depth was located on a line passing a center of the part indicated
by the arrow B. An upper part of the welding depth was located on
an upper side from the central part (i.e., a shallow part of the
weld portion). A lower part of the welding depth was located on a
lower side from the central part (i.e., a deep part of the weld
portion). With respect to the upper part, the central part and the
lower part, the center of the weld portion was defined as 0, the
right side thereof was defined as a plus position, and the left
side thereof was defined as a minus position. A load was set so as
to avoid a distance between centers of adjacent indentations from
falling to 0.02 mm or less.
[0105] FIG. 9 is a graph in Example 1. In FIG. 9 and
later-described FIGS. 10 to 12, positions away about at -2 mm and
+2 mm from the center of the weld portion are indicated by the
arrow D.
[0106] In FIG. 9, values of the HRC hardness are approximately the
same values at -2 mm position, the center of the weld portion and
+2 mm position of each of the upper part, the central part and the
lower part. All the values exceed the lower limit (40.0).
[0107] FIG. 10 is a graph in Example 2.
[0108] In FIG. 10, values of he HRC hardness are approximately the
same values at -2 mm position, the center of the weld portion and
+2 mm position of each of the upper part, the central part and the
lower part. All the values exceed the lower limit (40.0). In
Example 2, a fluctuation in the HRC hardness at the upper part, the
central part and the lower part is smaller than that in Example
1.
[0109] FIG. 11 is a graph in Reference Example 1.
[0110] In FIG. 11, values of the HRC hardness are approximately the
same values at -2 mm position, the center of the weld portion and
+2 mm position of each of the upper part, the central part and the
lower part. All the values fall below the values of the HRC
hardness in Example 2.
[0111] FIG. 12 is a graph in Comparative Example.
[0112] In FIG. 12, in each of the upper part, the central part and
the lower part, values of the HRC hardness at and near -2 mm and +2
mm positions exceed the lower limit (40.0), but a value of the HRC
hardness at the center of the weld portion falls below the lower
limit.
[0113] Consequently, following advantages can be obtained according
to the exemplary embodiment. [0114] (1) Since the joint 10 and the
sensor module metal member 20 are heated after being welded,
strength of the weld portion and the surroundings thereof is
increased In other words, it can be understood from Experiment 2
that Example 1, in which the precipitation hardening treatment was
performed after the welding treatment, shows that the metal
textures of the weld portion and the surrounding thermally affected
portion are not so different from the metal texture of the parts
other than the weld portion and the surrounding thermally affected
portion as compared with Comparative Example (conventional
examples) in which the precipitation hardening treatment was
performed before the welding treatment, but precipitation hardening
appears on the weld portion and the surrounding thermally affected
portion by applying the precipitation hardening treatment after the
welding treatment, resulting in formation of precipitates.
Specifically, in Experiment 3, the values of the HRC hardness at
the weld portion and the sides thereof exceed the lower limit in
Example 1, but the values of the HRC hardness at and around the
weld portion fall below the lower limit in Comparative Example.
This is because the heating treatment after the welding treatment
causes precipitation hardening to lead the hardness to meet the
lower limit in Example 1, whereas the hardness is decreased by the
welding treatment in Comparative Example.
[0115] Accordingly, even when the measurement target fluid to be
introduced to the sensor module metal member 20 has a high
pressure, the sensor module metal member 20 and the joint 10 can be
prevented from being broken at the weld portion and the
surroundings thereof. [0116] (2) When the heating treatment is
performed in the first heating mode (i.e., precipitation hardening
treatment) in which the joint 10 and the sensor module metal member
20 welded to each other are heated and left to stand until cool for
precipitation hardening, the obtained strength of the joint 10 and
the sensor module metal member 20 is not so stable as that obtained
when the heating treatment is performed in the second heating mode.
However, since the heating treatment after the welding treatment is
only the precipitation hardening treatment, the manufacturing
procedure can be simplified. [0117] (3) When the heating treatment
is performed in the second heating mode including: the re-solid
solution treatment for uniforming rough texture of the joint 10 and
the sensor module metal member 20 caused by being welded; and the
precipitation hardening treatment in which, after the re-solid
solution treatment, the joint 10 and the sensor module metal member
20 are heated and left to stand until cool for precipitation
hardening, since the re-solid solution treatment and the
precipitation hardening treatment are consecutively performed, more
stable strength can be obtained. In other words, in comparison
between Example 1 and Example 2, the measurement values of the
hardness are almost flat in Example 2, whereas a fluctuation in the
measurement values of the hardness is larger in Example 1 than in
Example 2. Further, in Experiment 2, no recovery of the texture is
observed in Example 1, but the recovery of the texture is observed
in Example 2. It can be understood from the above that more stable
strength can be obtained in Example 2 than in Example 1. [0118] (4)
Since the detector 30 having the strain gauge is attached to the
diaphragm 22 of the sensor module metal member 20 after heating the
joint 10 and the sensor module metal member 20, a measurement error
caused by heating the strain gauge itself is avoidable.
[0119] It should be appreciated that the scope of the invention is
not limited to the above-described exemplary embodiment(s) but
includes modifications and improvements as long as such
modifications and improvements are compatible with the
invention.
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