U.S. patent application number 10/069955 was filed with the patent office on 2002-11-21 for brazing filler metal.
Invention is credited to Shibuya, Yoshitsugu, Uchida, Hitoshi.
Application Number | 20020170633 10/069955 |
Document ID | / |
Family ID | 18706053 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020170633 |
Kind Code |
A1 |
Uchida, Hitoshi ; et
al. |
November 21, 2002 |
Brazing filler metal
Abstract
A brazing filler metal is composed of palladium, metal having
homogeneous solubility with the palladium, and phosphorus as main
constituents thereof, with addition of platinum and nickel as the
metal having homogeneous solubility with the Pd, wherein a
composition ratio of phosphorus falls within a range of about 3 to
about 17 wt. %, a composition ratio of platinum falls within a
range of about 5 to about 85 wt. %, and a composition ratio of
nickel falls within a range of about 5 to about 32 wt. %.
Inventors: |
Uchida, Hitoshi; (Tokyo,
JP) ; Shibuya, Yoshitsugu; (Saitama, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW.
SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
18706053 |
Appl. No.: |
10/069955 |
Filed: |
March 7, 2002 |
PCT Filed: |
July 11, 2001 |
PCT NO: |
PCT/JP01/06001 |
Current U.S.
Class: |
148/430 |
Current CPC
Class: |
C22C 5/08 20130101; C22C
9/00 20130101; B23K 35/322 20130101; C22C 14/00 20130101; B32B
15/01 20130101; C22C 5/02 20130101; C22C 5/04 20130101 |
Class at
Publication: |
148/430 |
International
Class: |
C22C 005/00; C22C
005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2000 |
JP |
2000-209685 |
Claims
What is claimed is:
1. A brazing filler metal having a composition comprising
palladium, metal having homogeneous solubility with the palladium,
and phosphorus as main constituents thereof, wherein a composition
ratio of the phosphorus falls within a range of 2 wt. % to less
than 20 wt. %.
2. A brazing filler metal having a composition comprising
palladium, platinum, nickel, and phosphorus as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of 2 wt. % to less than 20 wt. %.
3. A brazing filler metal according to claim 2, wherein a
composition ratio of the platinum falls within a range of 4 to less
than 86 wt. %.
4. A brazing filler metal according to claim 2, wherein a
composition ratio of the nickel falls within a range of 4 to less
than 36 wt. %.
5. A brazing filler metal according to claim 3, wherein a
composition ratio of the nickel falls within a range of 4 to less
than 36 wt. %.
6. A brazing filler metal according to claim 5, wherein a
composition ratio of the phosphorus falls within a range of about 3
to about 17 wt. %.
7. A brazing filler metal according to claim 5, wherein a
composition ratio of the platinum falls within a range of about 5
to about 85 wt. %.
8. A brazing filler metal according to claim 5, wherein a
composition ratio of the nickel falls within a range of about 5 to
about 32 wt. %.
9. A brazing filler metal having a composition comprising
palladium, copper, nickel, and phosphorus, as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of about 4 to about 18wt. %.
10. A brazing filler metal according to claim 9, wherein a
composition ratio of the copper falls within a range of about 2 to
about 64 wt. %.
11. A brazing filler metal according to claim 9, wherein a
composition ratio of the nickel falls within a range of about 7 to
about 36 wt. %.
12. A brazing filler metal according to claim 10, wherein a
composition ratio of the nickel falls within a range of about 7 to
about 36 wt. %.
13. A brazing filler metal having a composition comprising
palladium, gold, nickel, and phosphorus, as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of 2 to less than 20 wt. %.
14. A brazing filler metal according to claim 13, wherein a
composition ratio of the gold falls within a range of 2 to less
than 60 wt. %.
15. A brazing filler metal according to claim 13, wherein a
composition ratio of the nickel falls within a range of 4 to less
than 32 wt. %.
16. A brazing filler metal according to claim 14, wherein a
composition ratio of the nickel falls within a range of 4 to less
than 32 wt. %.
17. A brazing filler metal according to claim 16, wherein a
composition ratio of the phosphorus falls within a range of about 3
to about 19 wt. %.
18. A brazing filler metal according to claim 16, wherein a
composition ratio of the gold falls within a range of about 3 to
about 59 wt. %.
19. A brazing filler metal according to claim 16, wherein a
composition ratio of the nickel falls within a range of about 5 to
about 31 wt. %
20. A brazing filler metal having a composition comprising
platinum, metal having homogeneous solubility with the platinum,
and phosphorus, as main constituents thereof, wherein a composition
ratio of the phosphorus falls within a range of about 4 to about 21
wt. %.
21. A brazing filler metal having a composition comprising
platinum, copper, nickel, and phosphorus, as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of about 4 to about 19 wt. %.
22. A brazing filler metal according to claim 21, wherein a
composition ratio of the copper falls within a range of about 2 to
about 66 wt. %.
23. A brazing filler metal according to claim 21, wherein a
composition ratio of the nickel falls within a range of about 7 to
about 36 wt. %.
24. A brazing filler metal according to claim 22, wherein a
composition ratio of the nickel falls within a range of about 7 to
about 36 wt. %.
25. A brazing filler metal having a composition comprising
platinum, gold, nickel, and phosphorus, as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of about 4 to about 21 wt. %.
26. A brazing filler metal according to claim 25, wherein a
composition ratio of the gold falls within a range of about 5 to
about 62 wt. %.
27. A brazing filler metal according to claim 25, wherein a
composition ratio of the nickel falls within a range of about 5 to
about 22 wt. %.
28. A brazing filler metal according to claim 26, wherein a
composition ratio of the nickel falls within a range of about 5 to
about 22 wt. %.
Description
TECHNICAL FIELD
[0001] The invention relates to a brazing filler metal with which
brazing having excellent corrosion resistance and sufficient
joining strength can be implemented, and in particular, to a
brazing filler metal which is suitable for use in brazing of metals
of which decorativeness in external appearance is required, such as
titanium metal, and stainless steel, and with which brazing can be
implemented at a temperature not higher than the transformation
temperature of pure titanium.
BACKGROUND TECHNOLOGY
[0002] Brazing has been known for ages as one of metalworking
techniques whereby mating metals can be joined with each other with
relative ease. Since brazing is among important metalworking
techniques of even today, it is applied to a wide variety of
industrial sectors, and kinds of brazing filler metal for use in
the brazing cover a broad spectrum.
[0003] For some kinds of metals and their alloy, however, there has
not been found an effective brazing filler metal as yet. Titanium
metal (pure titanium metal and titanium alloy included) is one of
such metals. As titanium (Ti) metal has excellent properties such
as light weight, high strength, and high corrosion resistance, it
is in widespread use in various industrial sectors, and, as with
stainless steel, is used even for metallic articles (for example, a
wrist watch, the frame of eyeglasses) of which decorativeness in
external appearance is required.
[0004] Crystals of pure titanium have a hexagonal close-packed
structure at room temperature, however, they will have a
body-centered cubic structure at a temperature not lower than
882.degree. C. which is the transformation temperature (the
temperature at which a phase change occurs) of pure titanium.
Further, 5 Ti metal has a property of causing poor wettability of a
brazing filler metal because the Ti metal has a thin oxide film,
called a passivity film, formed on the surface thereof due to the
effect of air, moisture, and so forth, and the passivity film is
solid and difficult to remove, so that sufficient joining strength
has not been obtained upon brazing. Accordingly, it is a normal
practice adopted when brazing the Ti metals to use a flux (an
organic solvent) for removal of the passivity film. The trouble,
however, is that there has arisen a possibility that the interior
of a furnace is polluted by organic substance when brazing is
carried out in the furnace because the flux contains the organic
substance such as resin, and so froth.
[0005] By the way, as described in an article titled "Fabrication
Technique of Titanium" compiled by Japan Titanium Society (issued
by the Nikkan Kogyo Shimbun, Ltd.), silver solder and titanium
solder have been well known as conventional brazing filler metals
for use in brazing of members made of Ti (referred to hereinafter
merely as "Ti members").
[0006] Silver solder as a brazing filler metal has its own melting
point in a range of from about 800 to 1000.degree. C. Examples of a
brazing filler metal include a brazing filler metal with which
brazing can be executed at a temperature not higher than the
transformation temperature of pure titanium, for example, BVAg-8
(melting point: 780.degree. C.) according to the JIS specification,
which is at times put to use in brazing of the Ti members. However,
such a brazing filler metal as described is not in much use for
brazing in fabrication of metallic articles such as a wrist watch,
and the frame of eyeglasses, of which decorativeness in external
appearance is required, because the brazing filler metal has poor
corrosion resistance and is prone to initiation of corrosion after
brazing.
[0007] Examples of titanium solder include a Ti--Cu--Ni based
brazing filler metal. In this case, however, since the Ti--Cu--Ni
based brazing filler metal has a melting point not lower than
900.degree. C., brazing has to be executed inevitably at a
temperature higher than the transformation temperature of pure
titanium, and consequently, it has a drawback in that the Ti
members as brazed undergo a phase change after brazing, thereby
causing the crystal structure thereof to be coarsened. Accordingly,
in the case of brazing the Ti members with the titanium solder,
there is the need for taking steps of removing coarsened portions
of the crystal structure thereof by grinding, and so forth, and
subsequently applying thereto mirror finish, and the like.
[0008] Now, a brazing filler metal capable of implementing joining
of pure titanium metal or titanium alloy with pure gold or gold
alloy without causing erosion of parts of the pure gold and the
gold alloy is disclosed in JP 9-85485, A. This brazing filler
metal, however, is composed of silver (Ag), as the base
constituent, mixed with indium (In) and copper (Cu), so that the
same has a drawback in that joining has to be executed at
1023.degree. C. not lower than the transformation temperature of
pure titanium.
[0009] On the other hand, as a method of joining Ti members
together, welding is in widespread use besides brazing. Welding has
no problem in respect of joining strength and corrosion resistance,
however, it has a problem in that there is the need for heating the
Ti members locally to a high temperature for implementing joining.
As a result, there have emerged spots where a temperature is in
excess of the transformation temperature of pure titanium, causing
the crystal structure thereof to be coarsened, so that welding has
a drawback in that portions of the Ti members, worked on by
welding, require post-working. Also, there are times when
projection welding is applied for joining of Ti members whereby
welding is executed by causing electric current to flow through
projections of the Ti members, formed for the purpose of welding.
The projection welding, however, has had a drawback in that, if the
Ti members to be joined with each other are complex in
construction, it becomes difficult to cause uniform concentration
of electric current on the projections of the Ti members, thus
resulting in difficulty with welding.
[0010] As described in the foregoing, conventional techniques for
joining metallic articles made up of Ti metal, stainless steel, and
so forth have not offered any joining method capable of securing
excellent corrosion resistance and sufficient joining strength, and
further, capable of implementing joining at a temperature not
higher than the transformation temperature of pure titanium.
[0011] A The invention has been developed to solve the problems as
described above, and it is an object of the invention to provide a
brazing filler metal for use in brazing of metals such as Ti metal
and stainless steel, used in members of which decorativeness in
external appearance is required, wherein brazing can be implemented
at a temperature not higher than the transformation temperature of
pure titanium while securing excellent corrosion resistance and
sufficient joining strength.
DISCLOSURE OF THE INVENTION
[0012] A brazing filler metal according to the invention has a
composition comprising palladium, metal having homogeneous
solubility with the palladium, and phosphorus as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of 2 wt. % to less than 20 wt. %.
[0013] The brazing filler metal described above is preferably added
with platinum and nickel, as the metal having homogeneous
solubility with the palladium.
[0014] With the brazing filler metal described above, it is
preferable that a composition ratio of the platinum falls within a
range of 4 to less than 86 wt. %, and a composition ratio of the
nickel falls within a range of 4 to less than 36 wt. %.
[0015] Further, the composition ratio of the phosphorus preferably
falls within a range of about 3 to about 17 wt. %, and the
composition ratio of the platinum more preferably falls within a
range of about 5 to about 85 wt. %. The composition ratio of the
nickel preferably falls within a range of about 5 to about 32 wt.
%.
[0016] The invention further provides a brazing filler metal having
a a composition comprising palladium, metal having homogeneous
solubility with the palladium, and phosphorus as main constituents
thereof, and added with copper and nickel, as the metal having
homogeneous solubility with the palladium, wherein a composition
ratio of the phosphorus falls within a range of about 4 to about 18
wt. %.
[0017] With the brazing filler metal described above, a composition
ratio of the copper preferably falls within a range of about 2 to
about 64 wt. %, and a composition ratio of the nickel more
preferably falls within a range of about 7 to about 36 wt. %.
[0018] The invention still further provides a brazing filler metal
having a composition comprising palladium, metal having homogeneous
solubility with the palladium, and phosphorus as main constituents
thereof, and added with gold and nickel, as the metal having
homogeneous solubility with the palladium. With the brazing filler
metal described above, a composition ratio of the gold preferably
falls within a range of 2 to less than 60 wt. %, and a composition
ratio of the nickel more preferably falls within a range of 4 to 5
less than 32 wt. %.
[0019] Further, a composition ratio of the phosphorus preferably
falls within a range of about 3 to about 19 wt. %, and the
composition ratio of the gold may fall within a range of about 3 to
about 59 wt. %. The composition ratio of the nickel preferably
falls within a range of about 5 to about 31 wt. %.
[0020] The invention yet further provides a brazing filler metal
having a composition comprising platinum, metal having homogeneous
solubility with the platinum, and phosphorus, as main constituents
thereof, wherein a composition ratio of the phosphorus falls within
a range of about 4 to about 21 wt. %.
[0021] The brazing filler metal described above is preferably a
brazing filler metal having a composition comprising platinum,
metal having homogeneous solubility with the platinum, and
phosphorus as main constituents thereof, and added with copper and
nickel, as the metal having homogeneous solubility with the
platinum. In such a case, it is preferable that a composition ratio
of the phosphorus falls within a range of about 4 to about 19 wt.
%, and a composition ratio of the copper falls within a range of
about 2 to about 66 wt. %. It is more preferable that a composition
ratio of the nickel falls within a range of about 7 to about 36 wt.
%.
[0022] Further, the brazing filler metal described above may be a
brazing filler metal having a composition comprising platinum,
metal having homogeneous solubility with the platinum, and
phosphorus as main constituents thereof, and added with gold and
nickel, as the metal having homogeneous solubility with the
platinum. In such a case, it is preferable that a composition ratio
of the gold falls within a range of about 5 to about 62 wt. %, and
a composition ratio of the nickel falls within a range of about 5
to about 22 wt. %.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a phase diagram of a binary system of Pd--P, the
horizontal axis thereof showing a composition ratio of P to Pd
while the vertical axis thereof showing a melting point;
[0024] FIG. 2 a phase diagram of a binary system of Pt--P, the
horizontal axis thereof showing a composition ratio of P to Pt
while the vertical axis thereof showing a melting point;
[0025] FIG. 3 is a phase diagram of a binary system of Cu--P, the
horizontal axis thereof showing a composition ratio of P to Cu
while the vertical axis thereof showing a melting point;
[0026] FIG. 4 is a plan view showing a metallic member consisting
of two pure titanium metal sheets, overlapped so as to cross each
other;
[0027] FIG. 5 is a sectional view taken on line 5-5 in FIG. 4;
[0028] FIG. 6 is a sectional view of one of watch appearance
portions shown in FIG. 7, cut along a plane containing a end-piece
hole;
[0029] FIG. 7 is a perspective view showing a case fabricated by
joining four pieces of the watch appearance portions to a case
body; and
[0030] FIG. 8 is an assembly view showing the case body and the
four pieces of the watch appearance portions before joining the
four pieces of the watch appearance portions to the case body.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] Embodiments of a brazing filler metal according to the
invention are described in detail hereinafter with reference to the
accompanying drawings.
[0032] First Brazing Filler Metal
[0033] Firstly, a Pd--P based brazing filler metal which is a first
brazing filler metal according to the invention is described
hereinafter. The Pd--P based brazing filler metal is composed of
palladium (Pd) and phosphorus (P) with addition of metals having
homogeneous solubility with the Pd, and examples thereof include a
Pd--Pt--Ni--P based brazing filler metal obtained by addition of
platinum (Pt) and nickel (Ni) to the Pd--P based brazing filler
metal.
[0034] The Pd--Pt--Ni--P based brazing filler metal is produced by
a process comprising the steps of weighing respective quantities of
palladium (Pd), platinum (Pt), nickel (Ni), and phosphorus (P) such
that composition ratios as desired are obtained, respectively,
producing an alloy by melting the respective metals by means of the
high frequency melting process, and subsequently working the alloy
into a slender foil-like shape (ribbon-like shape) about 60 gm
thick in an argon (Ar) atmosphere.
[0035] Now, 16 samples of different Pd--Pt--Ni--P based brazing
filler metals, numbered from 1) to 16), were prepared by varying a
composition ratio (wt. %) of each of four metal elements, that is,
Pd, Pt, Ni, and P, as appropriate, and the melting point and
wettability against titanium metal of the respective samples were
examined. Table 1 shows the results of tests conducted.
1TABLE 1 Sample Pd Pt Ni P ** wettability against ti 1) 79 4 10 7
915.degree. C. .DELTA. 2) 72 11 10 7 833.degree. C. .largecircle.
3) 65 7 8 20 932.degree. C. .largecircle. 4) 68 5 10 17 870.degree.
C. .largecircle. 5) 36 27 20 17 721.degree. C. .largecircle. 6) 45
15 32 8 863.degree. C. .largecircle. 7) 47 11 36 6 889.degree. C.
.largecircle. 8) 60 25 5 10 847.degree. C. .largecircle. 9) 75 16 4
5 865.degree. C. .DELTA. 10) 50 38 9 3 642.degree. C.
.circleincircle. 11) 34 53 8 5 578.degree. C. .circleincircle. 12)
24 62 10 4 586.degree. C. .circleincircle. 13) 56 31 11 2
910.degree. C. .largecircle. 14) 12 76 7 5 702.degree. C.
.largecircle. 15) 4 85 6 5 860.degree. C. .largecircle. 16) 2 86 7
5 910.degree. C. .DELTA. (unit: wt %) **: melting point
.circleincircle.: very good .largecircle.: good .DELTA.: slightly
good
[0036] It can be said on the basis of Table 1 that a composition
ratio of the respective metal elements, that is, P, Pt, and Ni,
necessary for the respective Pd--Pt--Ni--P based brazing filler
metals to conform to the brazing filler metal as an object of the
invention is as follows.
[0037] In view of findings that in the case of the composition
ratio of P being at 2 wt. % as with Sample 13), the melting point
is at 910.degree. C. while in the case of the composition ratio of
P being at 3 wt. % as with Sample 10), the melting point is lowered
to 642.degree. C., thereby enabling joining by brazing to be
effected at a low temperature not higher than the transformation
temperature of pure titanium, (referred to hereinafter as low
temperature joining), which is an object of the invention, the
composition ratio of P needs to be in excess of 2 wt. %, and is
preferably not less than about 3 wt. %. Further, in view of
findings that in the case of the composition ratio of P being at 20
wt. % as with Sample 3), the melting point is at 932.degree. C.
while in the case of the composition ratio of P being at 17 wt. %
as with Samples 4), and 5), respectively, the melting point is
lowered to 870.degree. C., and 721.degree. C., respectively,
thereby enabling low temperature joining to be effected, the
composition ratio of P needs to be less than 20 wt. %, and is
preferably not more than about 17 wt. %. Accordingly, the
composition ratio of P has a range necessary for the Pd--Pt--Ni--P
based brazing filler metal to conform to the brazing filler metal
as the object of the invention, and the range is from 2 wt. % to
less than 20 wt. %, and is preferably from about 3 wt. % to about
17 wt. %.
[0038] Then, the composition ratio of Pt is as follows. In view of
findings that in the case of the composition ratio of Pt being at 4
wt. % as with Sample 1), the melting point is at 915.degree. C.
while in the case of the composition ratio of Pt being at 5 wt. %
as with Samples 4), the melting point is lowered to 870.degree. C.,
thereby enabling low temperature joining to be effected, the
composition ratio of Pt needs to be in excess of 4 wt. %, and is
preferably not less than about 5 wt. %. Further, in view of
findings that in the case of the composition ratio of Pt being at
86 wt. % as with Sample 16), the melting point is at 910.degree. C.
while in the case of the composition ratio of Pt being at 85 wt. %
as with Sample 15), the melting point is lowered to 860.degree. C.,
thereby enabling low temperature joining to be effected, the
composition ratio of Pt needs to be less than 86 wt. %, and is
preferably not more than about 85 wt. %. Accordingly, the
composition ratio of Pt has a range necessary for the Pd--Pt--Ni--P
based brazing filler metal to conform to the brazing filler metal
as the object of the invention, and the range is from 4 wt. % to
less than 86 wt. %, and is preferably from about 5 wt. % to about
85 wt. %.
[0039] Further, the composition ratio of Ni is as follows. In the
case of the composition ratio of Ni being at 4 wt. % as with Sample
9), the melting point becomes lower than the transformation
temperature of pure titanium, however, there is observed a tendency
that wettability against titanium metal becomes insufficient. In
the case of the composition ratio of Ni being at 5 wt. % as with
Sample 8), however, the melting point becomes lower than the
transformation temperature of pure titanium, and the wettability
against titanium metal becomes sufficient. Then, in the case of the
composition ratio of Ni being at 36 wt. % as with Sample 7), the
melting point comes to exceed the transformation temperature of
pure titanium although the wettability against titanium metal is
excellent. However, if the composition ratio of Ni becomes 32 wt. %
as with Sample 6), the melting point drops below the transformation
temperature of pure titanium. Accordingly, the composition ratio of
Ni has a range necessary for the Pd--Pt--Ni--P based brazing filler
metal to conform to the brazing filler metal as the object of the
invention, and the range is from 4 wt. % to less than 36 wt. %, and
is preferably from about 5 wt. % to about 32 wt. %.
[0040] It is samples 10), 11), and 12), having the melting point at
a temperature in the order of 500 to 600.degree. C., that have
particularly excellent wettability against titanium metal, and any
of these samples was found spreading extensively even on pure
titanium metal. Further, as described in detail later on, these
samples were found having satisfactory corrosion resistance and
joining strength.
[0041] As described in the foregoing, the Pd--Pt--Ni--P based
brazing filler metal is suited for low temperature joining provided
that the composition ratio of P falls within the abovementioned
range, and further, provided that the composition ratio of Pt as
well falls within the abovementioned range, the Pd--Pt--Ni--P based
brazing filler metal becomes a brazing filler metal satisfying all
of three requirements, that is, securing of excellent corrosion
resistance, and securing of sufficient joining strength in addition
to the low temperature joining, and having improved wettability
against titanium metal as well. Furthermore, provided that the
composition ratio of Ni as well falls within the abovementioned
range, the Pd--Pt--Ni--P based brazing filler metal no longer has
brittleness, and becomes a more preferable brazing filler metal
having further improved wettability against titanium metal.
[0042] Next, the reason why the Pd--Pt--Ni--P based brazing filler
metal composed of those metal elements at respective specified
ratios as described above can conform to the brazing filler metal
as the object of the invention is described in detail hereinafter
with reference to a phase diagram of an alloy, shown in FIGS. 1 and
2, respectively. FIG. 1 is a phase diagram of a binary system of
Pd--P, the horizontal axis thereof showing a composition ratio of P
to Pd while the vertical axis thereof showing a melting point, and
FIG. 2 a phase diagram of a binary system of Pt--P, the horizontal
axis thereof showing a composition ratio of P to Pt while the
vertical axis thereof showing a melting point. Detailed description
on either of both is stated in detail, respectively, in Literature
1 given below.
[0043] Literature 1: "Binary Alloy Phase Diagrams", Vol. 1, Vol. 2,
American Society for Metals, Metals Park, Ohio 44073
[0044] As shown in FIG. 1, in the case of a Pd--P alloy, its
melting point is lowered from 1555.degree. C. according as the
composition ratio of P is increased, and upon the composition ratio
of P reaching 6 wt. % with the composition ratio of Pd at 94 wt. %,
there occurs a eutectic composition with a melting point being
drastically lowered to about 800.degree. C. A state of such a
eutectic composition is designated as a first eutectic of Pd--P.
Also, according as the composition ratio of P is further increased,
the melting point rises up to the neighborhood of about
1000.degree. C. once, and thereafter, upon the composition ratio of
P reaching 12 wt. % with the composition ratio of Pd at 88 wt. %,
there occurs a eutectic composition again with a melting point
drastically dropping down to the neighborhood of about 800.degree.
C. A state of such a eutectic composition is designated as a second
eutectic of Pd--P.
[0045] As shown in FIG. 2, in the case of a Pt--P alloy, its
melting point is lowered from 1769.degree. C. according as the
composition ratio of P is increased, and upon the composition ratio
of P reaching 4 wt. % with the composition ratio of Pt at 96 wt. %,
there occurs a eutectic composition with a melting point being
drastically lowered to about 600.degree. C. A state of such a
eutectic art composition is designated as a eutectic of Pt--P.
[0046] Thus, in view of the fact that the Pd--P alloy has the
property of the melting point thereof being lowered due to the
formation of the eutectic composition, it is reasoned that a case
where the Pd--Pt--Ni--P based brazing filler metal is able to
conform to the brazing filler metal as the object of the invention
represents a case of the same having a specific composition wherein
the first eutectic of Pd--P or second eutectic of Pd--P can be
utilized. Further, in view of the fact that the Pt--P alloy as well
has the property of the melting point thereof being lowered due to
the formation of the eutectic composition, it is also reasoned that
the case where the Pd--Pt--Ni--P based brazing filler metal is able
to conform to the brazing filler metal as the object of the
invention represents also a case of the same having a specific
composition wherein the eutectic composition of Pt--P can be
utilized. It is further reasoned that if the Pd--Pt--Ni--P based
brazing filler metal has a composition wherein both the first or
second eutectic of Pd--P and the eutectic composition of Pt--P can
be utilized, the melting point can be sharply lowered. In either
case, in view of the fact that the Pd--P alloy will no longer has
the first eutectic of Pd--P upon the composition ratio of P
exceeding 6 wt. %, and will have the second eutectic of Pd--P upon
the composition ratio of P reaching 12 wt. %, it is reasoned that
the first eutectic of Pd--P is utilized with a composition of the
Pd--Pt--Ni--P based brazing filler metal, containing P at a
composition ratio in a range of 3 to 10 wt. %, while the second
eutectic of Pd--P is utilized with a composition thereof,
containing P at a composition ratio in a range of 10 to 17 wt.
%.
[0047] The Pd--Pt--Ni--P based brazing filler metal may be
considered to be an alloy composed of Pd, P and Pt at the specific
composition ratios described above, respectively, with addition of
Ni which is a metal having homogeneous solubility with the Pd. With
addition of Ni, there is obtaining an advantageous effect in that
wettability of the Pd--Pt--Ni--P based brazing filler metal,
against metallic members to be joined together therewith, is
improved, and quality thereof in respect of brittleness is
improved. Since Ni added is in effect substituted for Pd together
with Pt, however, addition of Ni in an improper amount results in
deviation of the composition ratios of Pd and P, respectively, from
those required for the eutectic composition, thereby raising a
possibility that a preferable brazing filler metal as the object of
the invention is no longer obtainable due to a rise in a melting
point and lack of occurrence of uniform solid solution.
Accordingly, it is reasoned that the composition ratio of Ni has a
range necessary for the Pd--Pt--Ni--P based brazing filler metal to
conform to the brazing filler metal as the object of the
invention.
[0048] From the viewpoints described above, it is reasoned that the
respective composition ratios of P, Pt, and Ni, composing the
Pd--Pt--Ni--P based brazing filler metal, have respective ranges
required for obtaining the brazing filler metal as the object of
the invention, and the respective ranges found from the results of
the tests, shown with reference to Samples 1) to 16) described
above, are preferable ranges of the respective composition
ratios.
[0049] To sum up, it is reasoned that the Pd--Pt--Ni--P based
brazing filler metal according to the invention is turned into a
brazing filler metal with which low temperature joining can be
executed by utilizing the first or second eutectic of Pd--P
provided that the same has a composition wherein the composition
ratio of P falls within a range of 2 to less than 20 wt. %,
preferably within a range of about 3 to about 10 wt. %, and a range
of about 10 to about 17wt. %. It is further reasoned that provided
that the Pd--Pt--Ni--P based brazing filler metal according to the
invention has a composition wherein the composition ratio of Pt
falls within a range of 4 to less than 86 wt. %, preferably within
a range of about 5 to about 85 wt. %, in addition to the previously
described composition, the same is turned into a brazing filler
metal with which brazing can be implemented at a still lower
melting point by utilizing the eutectic of Pt--P as well, such a
brazing filler metal being a brazing filler metal satisfying all of
the three requirements, that is, securing of excellent corrosion
resistance and securing of sufficient joining strength in addition
to the low temperature joining, and having improved wettability
against titanium metal as well. In either of the abovementioned
cases, if the composition ratio of Ni exceeds 4 wt. %, and is less
than 36 wt. %, preferably falling within a range of 5 to 32 wt. %,
there results an alloy having homogeneity at a low melting point,
so that a brazing filler metal having no brittleness and having
more excellent wettability can be obtained.
[0050] Pd--Cu--Ni--P Based Brazing Filler Metal
[0051] Next, a Pd--P based brazing filler metal which is another of
the first embodiment of the brazing filler metal according to the
invention is described hereinafter. This brazing filler metal is a
Pd--Cu--Ni--P based brazing filler metal composed of palladium (Pd)
and phosphorus (P) with addition of copper (Cu) and nickel (Ni) as
metals having homogeneous solubility with the Pd. The Pd--Cu--Ni--P
based brazing filler metal is produced by the same method as that
for the Pd--Pt--Ni--P based brazing filler metal described
hereinbefore, omitting therefore detailed description of a method
of producing the same.
[0052] As with the case of the Pd--Pt--Ni--P based brazing filler
metal described hereinbefore, the Pd--Cu--Ni--P based brazing
filler metal conforms to the brazing filler metal as the object of
the invention provided that the same is composed of metal elements
at respective specified composition ratios, which is presumed to
represent the case where the first or second eutectic of Pd--P as
described above is utilized, or a case where a eutectic of Cu--P as
described later is utilized.
[0053] FIG. 3 is a phase diagram of a binary system of Cu--P, the
horizontal axis thereof showing a composition ratio of P to Cu
while the vertical axis thereof showing a melting point, which is
referred to in Literature 1 described hereinbefore. As shown in
FIG. 3, in the case of a Cu--P alloy, its melting point is lowered
from about 1084.degree. C. according as a composition ratio of P is
increased, and upon the composition ratio of P reaching about 8 wt.
% with a composition ratio of Cu at about 92 wt. %, there occurs a
eutectic composition, thereby a melting point thereof being lowered
to about 714.degree. C. A state of such a eutectic composition is
designated as a eutectic of Cu--P.
[0054] The composition ratio of P, necessary for the Pd--Cu--Ni--P
based brazing filler metal to conform to the brazing filler metal
as the object of the invention, is in a range of about 4 to about
18 wt. %. Further, it is reasoned that if the Pd--Cu--Ni--P based
brazing filler metal comes to have a composition wherein the
eutectic of Cu--P can be utilized, the same is turned into a
brazing filler metal with which brazing can be implemented at a
still lower melting point, and a composition ratio of Cu, required
in such a case, is in a range of about 2 to about 64 wt. %. In such
a case, a brazing filler metal having excellent corrosion
resistance, sufficient joining strength, and improved wettability
against titanium metal can be obtained. Further, there exists an
optimum range for a composition ratio of Ni as well, and if the
composition ratio of Ni falls within a range of about 7 to about 36
wt. %, there results an alloy not only capable of implementing low
temperature joining but also having homogeneity at a low melting
point, so that it is possible to obtain a brazing filler metal
which has quality improved in respect of brittleness, and has more
improved wettability.
[0055] Pd--Au--Ni--P Based Brazing Filler Metal
[0056] With reference to the Pd--P based brazing filler metals
described in the foregoing, there have so far been described the
Pd--Pt--Ni--P based brazing filler metal obtained by adding Pt and
Ni thereto as metals having homogeneous solubility with Pd, and the
Pd--Cu--Ni--P based brazing filler metal obtained by adding Cu and
Ni thereto as metals having homogeneous solubility with Pd,
however, the Pd--P based brazing filler metals are not limited
thereto, and include a Pd--Au--Ni--P based brazing filler metal as
well.
[0057] The Pd--Au--Ni--P based brazing filler metal is composed of
palladium (Pd) and phosphorus (P) with addition of gold (Au) and
nickel (Ni) as metals having homogeneous solubility with the Pd.
The Pd--Au--Ni--P based brazing filler metal is produced by the
same method as that for the Pd--Pt--Ni--P based brazing filler
metal, omitting therefore detailed description of a method of
producing the same.
[0058] Now, 11 samples of different Pd--Au--Ni--P based brazing
filler metals, numbered from 17) to 27), were prepared by varying a
composition ratio (wt. %) of each of four metal elements, that is,
Pd, Au, Ni, and P, as appropriate, and the melting point and
wettability against titanium metal of the respective samples were
examined. Table 2 shows the results of tests conducted.
2TABLE 2 Sample Pd Au Ni P ** wettability against ti 17) 61 30 4 5
871 .DELTA. 18) 49 20 20 11 830 .largecircle..largecircle. 19) 52
21 7 20 927 .largecircle. 20) 41 20 32 7 891 .largecircle. 21) 47
38 9 6 774 .largecircle. 22) 60 24 10 6 702 .largecircle. 23) 72 11
10 7 644 .circleincircle. 24) 77 6 11 6 619 .circleincircle. 25) 55
30 13 2 902 .largecircle. 26) 76 2 15 7 889 .DELTA. 27) 27 60 8 5
933 .DELTA. (unit: wt %) **: melting point .circleincircle.: very
good .largecircle.: good .DELTA.: slightly good
[0059] In the case of a composition ratio of P being at 2 wt. % as
with Sample 25), the melting point is at 902.degree. C., and
accordingly, the composition ratio of P needs to be in excess of 2
wt. % in order to enable low temperature joining to be executed,
however, in the case of the composition ratio of P being at 20 wt.
% as with Sample 19), the melting point is at 927.degree. C., and
accordingly, the composition ratio of P needs to be less than 20
wt. %. However, from the viewpoint of forming a composition wherein
the first or second eutectic of Pd--P can be utilized, the
composition ratio of P is preferably in a range of about 3 to less
than 19 wt. %.
[0060] In view of findings that in the case of a composition ratio
of Au being at 2 wt. % as with Sample 26), the melting point is at
889.degree. C. while in the case of the composition ratio of Au
reaching 6 wt. % as with Sample 24), the melting point is lowered
to 619.degree. C., the composition ratio of Au needs to be in
excess of 2 wt. %, and is preferably not less than about 3 wt. %.
Further, in view of findings that in the case of the composition
ratio of Au being at 60 wt. %--as with Sample 27), the melting
point is at 933.degree. C. while in the case of the composition
ratio of Au becoming 38 wt. % as with Sample 21), the melting X
point is lowered to 774.degree. C., the composition ratio of Au
needs to be less than 60 wt. %, and is preferably less than 59 wt.
%.
[0061] Further, in the case of a composition ratio of Ni being at 4
wt. % as with Sample 17), the melting point becomes lower than the
transformation m temperature of pure titanium, however, there is
observed a tendency that wettability against titanium metal becomes
insufficient. The composition ratio of Ni at not less than about 5
wt. % is preferable for obtaining sufficient wettability against
titanium metal. Further, in the case of the composition ratio of Ni
becoming 32 wt. % as with Sample 20), the melting point exceeds the
transformation temperature of pure titanium although the
wettability against titanium metal is excellent. The composition
ratio of Ni at not more than about 31 wt. % is preferable to render
the melting point lower than the transformation temperature of pure
titanium. Accordingly, the composition ratio of Ni, necessary for
the Pd--Au--Ni--P based brazing filler metal to conform to the
brazing filler metal as the object of the invention is in a range
of 4 to less than 32 wt. %, and is preferably in a range of about 5
to about 31 wt. %.
[0062] In view of the foregoing, it can be said that the
Pd--Au--Ni--P based brazing filler metal is turned into a brazing
filler metal capable of effecting low temperature joining provided
that the composition ratio of P falls within the abovementioned
range, and is further turned into a brazing filler metal having
satisfactory corrosion resistance, and joining strength provided
that the composition ratio of Au as well falls within the
abovementioned range. Furthermore, in the case of the composition
ratio of Ni falling within the abovementioned range, there results
an alloy having homogeneity at a low melting point, thereby forming
a more preferable brazing filler metal which has quality improved
in respect of brittleness, and, in addition, has improved
wettability against titanium metal. It is to be pointed out,
however, that Au has homogeneous solubility with Pd in common with
Pt and Cu, but does not form a eutectic composition with P, so
that, unlike the other Pd--P based brazing filler metals (the
Pd--Pt--Ni--P based, and Pd--Cu--Ni--P based), the Pd--Au--Ni--P
based brazing filler metal is not turned into a brazing filler
metal utilizing a eutectic of Au--P.
[0063] Second Brazing Filler Metal
[0064] Now, a Pt--P based brazing filler metal which is a second
brazing filler metal according to the invention is described
hereinafter. The Pt--P based brazing filler metal is composed of
platinum (Pt) and phosphorus (P) with addition of metals having
homogeneous solubility with the Pt, and examples thereof include a
Pt--Cu--Ni--P based brazing filler metal obtained by addition of
copper (Cu) and nickel (Ni) to the Pt--P based brazing filler
metal.
[0065] The Pt--Cu--Ni--P based brazing filler metal as well is
produced by the same method as that for the Pd--Pt--Ni--P based
brazing filler metal described hereinbefore, omitting therefore
detailed description of a method of producing the same.
[0066] As with the case of the Pd--Pt--Ni--P based brazing filler
metal described hereinbefore, the Pt--Cu--Ni--P based brazing
filler metal as well is able to conform to the brazing filler metal
as the object of the invention provided that the same is composed
of metal elements at respective specified composition ratios, which
is presumed to represent the case where the eutectic of Pt--P shown
in FIG. 2 is utilized, or a case where the eutectic of Cu--P shown
in FIG. 3 is utilized.
[0067] It is reasoned that the Pt--Cu--Ni--P based brazing filler
metal is able to conform to a brazing filler metal capable of low
temperature joining, which is the object of the invention, provided
that the same has a composition wherein the eutectic of Pt--P can
be utilized, and to that end, a composition ratio of P is to be in
a range of about 4 to about 19 wt. %. With the composition ratio of
P falling in that range, there results an alloy having homogeneity
at a low melting point, thereby forming a brazing filler metal
capable of effecting low temperature joining. It is further
reasoned that there will be formed a brazing filler metal with
which brazing can be implemented at a still lower melting point if
the alloy comes to have a composition wherein the eutectic of Cu--P
can be utilized, and a composition ratio of Cu, required for that
purpose, is in a range of about 2 to about 66 wt. %. With the
composition ratio of Cu falling in that range, there can be
obtained a brazing filler metal not only capable of implementing
brazing at a still lower melting point below the transformation
temperature of pure titanium, but also having excellent corrosion
resistance, and sufficient joining strength, thereby satisfying all
of the three requirements, and improved wettability against
titanium metal as well. Further, there exists an optimum range for
a composition ratio of Ni, and if the composition ratio of Ni falls
within a range of about 7 to about 36 wt. %, there results an alloy
not only capable of implementing low temperature joining but also
having homogeneity at a low melting point, so that it is possible
to obtain a preferable brazing filler metal which has improved
quality in respect of brittleness, and has more improved
wettability against titanium metal.
[0068] Pt--Au--Ni--P Based Brazing Filler Metal
[0069] The Pt--P based brazing filler metal may be added with a
metal other than Cu as a metal having homogeneous solubility with
Pt, and even if, for example, Au is added thereto, there results a
preferable brazing filler metal as the brazing filler metal
according to the invention, and such a brazing filler metal is a
Pt--Au--Ni--P based brazing filler metal.
[0070] It is reasoned that the Pt--Au--Ni--P based brazing filler
metal as well is able to conform to a brazing filler metal capable
of low temperature joining, which is the object of the invention,
provided that the same has a composition wherein the eutectic of
Pt--P can be utilized, and to that end, a composition ratio of P is
to be in a range of about 4 to about 21 wt. %. With the composition
ratio of P falling in that range, there results an alloy having
homogeneity at a low melting point, thereby forming a brazing
filler metal capable of effecting low temperature joining. There
exists an optimum range for a composition ratio of Au, and if the
composition ratio of Au falls within a range of about 5 to about 62
wt. %, it is possible to obtain a brazing filler metal not only
satisfying all of the three requirements, that is, ability to
enable low temperature joining to be implemented, excellent
corrosion resistance, and sufficient joining strength, but also
having improved wettability against titanium metal. Further, there
exists an optimum range for a composition ratio of Ni as well, and
if the composition ratio of Ni falls within a range of about 5 to
about 22 wt. %, there results an alloy not only capable of
implementing low temperature joining, but also having homogeneity
at a low melting point, so that it becomes possible to obtain a
preferable brazing filler metal which has quality improved in
respect of brittleness and has more improved wettability against
titanium metal.
[0071] Corrosion Resistance and Joining Strength of a Brazing
Filler Metal
[0072] Now, corrosion resistance and joining strength of the first
and second brazing filler metal according to the invention,
respectively, are described hereinafter.
[0073] In order to check the corrosion resistance and joining
strength of the first and second brazing filler metal described
hereinbefore, respectively, a metallic member 17 as shown in FIG. 4
were prepared to conduct the following tests thereon. The metallic
member 17 consist of two pure titanium metal sheets, 15, 16, each
about 25 mm in length.times.about 5 mm in width.times.about 1 mm in
thickness, overlapped so as to cross each other, and the first
brazing filler metal described above (the Pd--Pt--Ni--P based, the
Pd--Cu--Ni--P based, and Pd--Au--Ni--P based) or the second brazing
filler metal described above (the Pt--Cu--Ni--P based, and
Pt--Au--Ni--P based)19 is sandwiched between the two pure titanium
metal sheets 15, 16 at an intersection 18 where the two pure
titanium metal sheets 15, 16 are in contact with each other,
thereby preparing 14 samples including Examples 1 to 8 shown in
Table 3, and Examples 9 to 14 shown in Table 4. Each of Samples was
prepared by securing the intersection 18 with a tool(not shown),
and subsequently heating the Samples at respective brazing
temperatures shown in Tables 3 and 4, respectively, at a pressure
of 6.times.10.sup.-6 Torr for ten minutes, followed by rapid
cooling of the same in an argon atmosphere.
3TABLE 3 Example a b c d e 1) Pd.sub.34Pt.sub.53Ni.sub.8P.sub.5
.largecircle. 980 MPa 750.degree. C. no 2)
Pd.sub.47Pt.sub.38Ni.sub.9P.sub.6 .largecircle. 880 MPa 750.degree.
C. no 3) Pd.sub.72Pt.sub.11Ni.sub.10P.sub.7 .largecircle. 800 MPa
850.degree. C. no 4) Pd.sub.80Pt.sub.10Ni.su- b.8P.sub.2
.largecircle. 800 MPa 920.degree. C. exist 5)
Pd.sub.78Cu.sub.4Ni.sub.11P.sub.7 .largecircle. 850 MPa 750.degree.
C. no 6) Pd.sub.24Cu.sub.66Ni.sub.4P.sub.6 x 740 MPa 950.degree. C.
exist 7) Pt.sub.87Cu.sub.2Ni.sub.7P.sub.4 .largecircle. 790 MPa
800.degree. C. no 8) Pt.sub.11Cu.sub.69Ni.sub.10P.sub.10 x 710 MPa
950.degree. C. exist
[0074]
4TABLE 4 Example a b c d e 9) Pd.sub.77Au.sub.6Ni.sub.11P.sub.6
.largecircle. 840 750 no 10) Pd.sub.72Au.sub.11Ni.sub.10P.sub.7
.largecircle. 880 750 no 11) Pd.sub.47Au.sub.38Ni.sub.9P.sub.6
.largecircle. 800 850 no 12) Pd.sub.61Au.sub.30Ni.sub.4P.sub.5
.largecircle. 550 950 exist 13) Pt.sub.72Au.sub.10Ni.sub.11P.sub.7
.largecircle. 850 750 no 14) Pt.sub.54Au.sub.36Ni.sub.4P.sub.6
.largecircle. 640 950 exist a brazing filler metal (wt %) b
corrosion resistance c joining strength (MPa) d brazing temperature
(.degree. C.) e TI transformation
[0075] A corrosion resistance test was conducted on the respective
Samples of the metallic member 17 in accordance with the CASS test
specified by ISO3370, and joining strength was measured by
conducting a tensile test on the respective Samples whereby the
pure titanium metal sheets 15, 16 were pulled in the direction of
thickness, a and b, respectively, by use of a tool(not shown).
[0076] Further, for the sake of comparison, similar samples using
silver solder (58 wt. % of Ag, 32 wt. % of Cu, and 10 wt. % of Pd)
and titanium solder (60 wt. % of Ti, 25 wt. % of Cu, and 15 wt. %
of Ni), well known as the conventional brazing filler metal, were
prepared by the previously described procedure, and corrosion
resistance tests and joining strength tests were conducted thereon.
The results of such tests are shown in Table 5. In Tables 3 to 5,
the composition ratio of the respective metal elements composing
the respective brazing filler metals is indicated by a number
affixed to a symbol for the respective metal elements. For example,
in the case of Example 1, the composition ratio of Pd is 34 wt. %,
that of Pt 53 wt. %, that of Ni 8 wt. %, and that of P 5 wt. %.
5TABLE 5 Comp Exp a b c d e 1) Ti.sub.60Cu.sub.25Ni.sub.15
.largecircle. 820 MPa 1000.degree. C. exist 2)
Ag.sub.58Cu.sub.32Pd.sub.10 x 530 MPa 780.degree. C. no a brazing
filler metal (wt %) b corrosion resistance c joining strength (MPa)
d brazing temperature (.degree. C.) e TI transformation
[0077] Examples 1 to 4, shown in Table 3, indicate the results of
tests conducted on the Pd--Pt--Ni--P based brazing filler metals,
and Examples 1 to 3, among these Examples, indicate the results of
the tests conducted on the Pd--Pt--Ni--P based brazing filler
metals wherein the composition ratio of the respective metal
elements is within the respective ranges as described hereinbefore.
Examples 5 and 6, shown in Table 3, indicate the results of tests
conducted on the Pd--Cu--Ni--P based brazing filler metals, and
Example 5, among these Examples, indicates the results of the tests
conducted on the Pd--Cu--Ni--P based brazing filler metal wherein
the composition ratio of the respective metal elements is within
the respective ranges as described hereinbefore. Examples 7 and 8,
shown in Table 3, indicate the results of tests conducted on the
Pt--Cu--Ni--P based brazing filler metals, and Example 7, among
these Examples, indicates the results of the tests conducted on the
Pt--Cu--Ni--P based brazing filler metal wherein the composition
ratio of the respective metal elements is within the respective
ranges as described hereinbefore.
[0078] Examples 9 to 12, shown in Table 4, indicate the results of
tests conducted on the Pd--Au--Ni--P based brazing filler metals
obtained by adding Ni and Au to the Pd--P based brazing filler
metal, and Examples 9 to 11, among these Examples, indicate the
results of the tests conducted on the Pd--Au--Ni--P based brazing
filler metals wherein the composition ratio of the respective metal
elements is within the respective ranges as described hereinbefore.
Examples 13 and 14, shown in Table 4, indicate the results of tests
conducted on the Pt--Au--Ni--P based brazing filler metals obtained
by adding Au and Ni to the Pt--P based brazing filler metal, and
Examples 13, among these Examples, indicates the results of the
tests conducted on the Pt--Au--Ni--P based brazing filler metal
wherein the composition ratio of the respective metal elements is
within the respective ranges as described hereinbefore.
[0079] As is evident from the abovementioned Tables 3, 4, and 5,
any of the brazing filler metals according to the invention
exhibits excellent corrosion resistance. Further, the joining
strength of Example 7 at 790 MPa and that of Example 11 at 800 MPa
are slightly lower than that of Comparative Example 1, however, the
joining strength of any of other Examples indicates better values
than those for Comparative Examples 1 and 2. Upon checking brazing
temperatures, however, it is found that brazing with any of the
brazing filler metals according to the invention is feasible at a
temperature not higher than the transformation temperature of pure
titanium, and in contrast, the brazing temperature for Comparative
Example 1 is at 1000.degree. C. which is in excess of the
transformation temperature of pure titanium. Thus, the brazing
filler metals according to the invention are found to satisfy all
of the three requirements, that is, securing of excellent corrosion
resistance and sufficient joining strength, along with capability
of implementing brazing at a temperature not higher than the
transformation temperature of pure titanium. Accordingly, it can be
said that the brazing filler metals according to the invention are
superior to a conventional Ti--Cu--Ni based brazing filler metal
(Comparative Example 1) because even if the former are used in
joining together metallic articles made of Ti, the surface
condition of the respective metallic articles, prior to joining,
can be maintained without causing the crystal structure of the
metallic articles to be coarsened. It can also be said that the
brazing filler metals according to the invention are significantly
superior to silver solder (Comparative Example 2) in respect of
corrosion resistance and joining strength in comparison with the
latter.
[0080] Joining of Components to a Case with the Brazing Filler
Metal
[0081] Now, with a case which is an exterior component of a
timepiece, description is given hereinafter on a case of joining
watch appearance portions thereof to a case body with the brazing
filler metals according to the invention.
[0082] FIG. 7 is a perspective view showing a case 2 fabricated by
joining 4 pieces of the watch appearance portions 3, 5, 7, and 9 to
a case body 1 with the Pd--Pt--Ni--P based brazing filler metal
which is the first brazing filler metal according to the invention.
The case body 1 comprises a sidewall made of Ti, formed in the
shape of a cylinder thin in wall thickness, and a bottom made of
Ti, and is polished so as to have a mirror-finished surface
including contacting surfaces thereof, opposite to the watch
appearance portions. Each of the watch appearance portions 3, 5, 7,
and 9, made of titanium alloy, is formed by applying grinding and
polishing thereto, and the outside surface thereof except a
contacting surface with the case body 1, is polished so as to have
a hairline finished surface. Further, each of the watch appearance
portions 3, 5, 7, and 9 is worked on beforehand for drilling a
end-piece hole 11 therein. The case body 1 and the watch appearance
portions 3, 5, 7, and 9 are formed by forging, respectively.
[0083] As shown in FIG. 8, a Pd--Pt--Ni--P based brazing filler
metal 19 (Pd at 34 wt. %, Pt at 53 wt. %, Ni at 8 wt. %, and P at 5
wt. %) according to the invention was sandwiched between the faying
surface of the case body 1 and that of the respective watch
appearance portions 3, 5, 7, and 9, and was pressed into contact
with the respective contacting surfaces before secured by tools
(not shown). Thereafter, the case body 1 and respective watch
appearance portions 3, 5, 7, and 9 were heated to a temperature at
700.degree. C. under a pressure at 6.times.10.sup.-6 Torr for 20
minutes, and subsequently, was rapidly cooled in an argon
atmosphere. In place of the Pd--Pt--Ni--P based brazing filler
metal 19, however, use may be made of a Pd--Au--Ni--P based brazing
filler metal (Pd at 72 wt. %, Au at 11 wt. %, Ni at 10 wt. %, and P
at 7 wt. %).
[0084] As a result, there occurred full penetration of the brazing
filler metal according to the invention into joined portions
between the case body 1 and the respective watch appearance
portions 3, 5, 7 and 9, whereupon the case 2 wherein the case body
1 was found fully integral with the respective watch appearance
portions 3, 5, 7, and 9 in the external appearance was
obtained.
[0085] With the case 2, a temperature at which the same was heated
was not higher than the transformation temperature of pure
titanium, and consequently, the surface condition of the components
thereof, prior to joining, was found maintained without causing the
crystal structure of Ti metal to be coarsened, thereby forming
clean interfaces between the case body 1 and the respective watch
appearance portions 3, 5, 7 and 9. Furthermore, the joined potions
therebetween were able to have a sufficient tensile strength
(joining strength).
[0086] As described in the foregoing, if the metallic articles,
that is, the case body 1 and the respective watch appearance
portions 3, 5, 7 and 9, are joined with each other by use of the
brazing filler metal according to the invention, both the metallic
articles can be joined together in a preferable condition.
[0087] Meanwhile, in view of recent demand for expanding
flexibility in designing, there has been increasing requirement
that a case body and respective watch appearance portions are to be
fabricated separately, and finished in a different surface
condition, respectively. For example, the case body is to be
finished so as to have a mirror-finished surface while the
respective watch appearance portions are to be finished so as to
have a hairline finished surface. However, since a conventional
case has been fabricated as an integrally formed component
comprising the respective watch appearance portions to be linked
with a bracelet, and the interface between case and watch
appearance portion is continuous surface, it has been difficult to
definitely identify the interfaces between the case body to be
finished to have the mirror-finished surface, and the respective
watch appearance portions to be finished to have the hairline
finished surface.
[0088] Further, in the case of forming a single-piece case, it has
an advantage in terms of cost to fabricate the same by forging,
however, there is then a drawback in that the shape of the
respective watch appearance portions is subject to considerable
constraints in terms of designing. The respective watch appearance
portions is provided with a end-piece hole for inserting a spring
bar with which the bracelet is secured thereto, formed in a
post-working process using a drill, and there has been no choice
but to drill the end-piece hole from the inside of the respective
watch appearance portions on the ground that the end-piece hole
opened in the respective watch appearance portions, if it can be
seen from the outside, is undesirable from the external appearance
point of view. This has rendered a working for drilling the
end-piece hole difficult to execute, and furthermore, the
respective watch appearance portions, disposed opposite to each
other, interfere with the working for drilling the end-piece hole,
so that it has become impossible to form the end-piece hole 11
vertically to a work face 7a of the watch appearance portion 7, as
shown in FIG. 6 by way of example, and consequently, there has been
no choice but to form the same on the skew. For this reason, there
has arisen the need for forming the end-piece hole 11 somewhat
larger in size than the spring bar, resulting in an excess
clearance formed between the spring bar and the end-piece hole 11,
and thereby creating a cause for the slack (rattle).
[0089] As described hereinbefore, however, if the case body 1 is
joined to the respective watch appearance portions 3, 5, 7, and 9
by use of the brazing filler metal according to the invention, it
is possible to obtain the case 2 wherein both components thereof
are found fully integral with each other in external appearance as
well, thereby completely preventing occurrence of the problems as
encountered with the conventional case.
[0090] A kind of metal suitable for satisfactory joining to the
other of the same by use of the brazing filler metal according to
the invention is titanium metal. Since a typical titanium alloy,
for example, Ti-6Al-4V, has its transformation temperature at
995.degree. C., the brazing filler metal according to the invention
is adequate for application to a titanium alloy. Furthermore, the
scope of application of the brazing filler metal according to the
invention is not limited to titanium metal, but include other
metals, for example, stainless steel, so that the brazing filler
metal according to the invention is applicable to various metals of
which decorativeness in external appearance is required.
[0091] In addition, the brazing filler metal according to the
invention has no limitation in its shape. Considering convenience
in executing a joining work, the same is preferably produced in the
shape of a sheet, foil, wire, and so forth, however, there can be
cases where its shape is accompanied by brittleness to some extent,
depending on the chemical composition thereof, in which case the
brazing filler metal according to the invention may be used after
reducing the same to powders, and pressing the powders for
molding.
[0092] A heating temperature at the time of brazing is in a range
of 620 to 850.degree. C., preferably in a range of 650 to
750.degree. C., brazing time is preferably in the order of from
about 5 minutes to about 1 hour, and an atmosphere in a furnace at
the time of brazing is preferably at a pressure not higher than 10
Torr.
[0093] INDUSTRIAL APPLICABILITY
[0094] With the brazing filler metal according to the invention,
joining of metallic articles by brazing can be implemented at a
temperature not higher than the transformation temperature of pure
titanium, and sufficient joining strength as well as excellent
corrosion resistance of the metallic articles joined together can
be secured. Accordingly, the brazing filler metal according to the
invention is suitable for use in brazing of metals such as titanium
metal, and stainless steel, of which decorativeness in external
appearance is required. In addition, since the brazing filler metal
according to the invention has improved wettability against
titanium metal, flux is unnecessary in executing brazing, and there
is no need for post-working after the brazing, so that the brazing
filler metal according to the invention is suited for brazing of
metallic articles complex in construction.
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