U.S. patent application number 10/279108 was filed with the patent office on 2003-05-15 for nickel-free white copper alloy, and method of producing nickel-free white copper alloy.
This patent application is currently assigned to YKK CORPORATION. Invention is credited to kita, Kazuhiko, Koizumi, Takuya, Yoshimura, Yasuharu.
Application Number | 20030091461 10/279108 |
Document ID | / |
Family ID | 19145046 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030091461 |
Kind Code |
A1 |
Yoshimura, Yasuharu ; et
al. |
May 15, 2003 |
Nickel-free white copper alloy, and method of producing nickel-free
white copper alloy
Abstract
An Ni-free white copper alloy of formula
Cu.sub.aZn.sub.bTi.sub.c or Cu.sub.aZn.sub.bTi.sub.cX.sub.d wherein
X is at least one element selected from the group consisting of Al,
Sn, Ag and Mn, b, c and d are, in mass %, 0.5.ltoreq.b.ltoreq.30,
1.ltoreq.c.ltoreq.7 and 0.1.ltoreq.d.ltoreq.4, and a is the
balance, with unavoidable elements, and also a producing method
therefor, comprising: preparing a material alloy for the above
white copper alloy; heating the alloy to 700 to 885.degree. C.; and
cooling the alloy. The Ni-free white copper alloy has a strength
and excellent hardness comparable to those of nickel silver, as
well as excellent workability, corrosion resistance and whiteness
in addition to ductility, and is free from an Ni allergy problem
because of containing no nickel, and moreover tends not to cause
needle detectors to malfunction.
Inventors: |
Yoshimura, Yasuharu;
(Kurokawa-gun, JP) ; kita, Kazuhiko; (Sendai-shi,
JP) ; Koizumi, Takuya; (Sendai-shi, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
YKK CORPORATION
|
Family ID: |
19145046 |
Appl. No.: |
10/279108 |
Filed: |
October 24, 2002 |
Current U.S.
Class: |
420/484 ;
148/686; 420/476; 420/478 |
Current CPC
Class: |
C22C 9/04 20130101; C22F
1/08 20130101 |
Class at
Publication: |
420/484 ;
420/476; 420/478; 148/686 |
International
Class: |
C22C 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2001 |
JP |
2001-329089 |
Claims
What is claimed is:
1. A nickel-free white copper alloy represented by the general
formula Cu.sub.aZn.sub.bTi.sub.c wherein b and c are, in mass %,
0.5.ltoreq.b.ltoreq.30 and 1.ltoreq.c<7, and a is the balance,
with other unavoidable elements also possibly being contained.
2. A nickel-free white copper alloy represented by the general
formula Cu.sub.aZn.sub.bTi.sub.cX.sub.d wherein X is at least one
element selected from the group consisting of Al, Sn, Ag and Mn, b,
c and d are, in mass %, 0.5.ltoreq.b.ltoreq.30, 1.ltoreq.c<7 and
0.1<d<4, and a is the balance, with other unavoidable
elements also possibly being contained.
3. The nickel-free white copper alloy according to claim 1, being
composed of a single .alpha.-phase at room temperature.
4. The nickel-free white copper alloy according to claim 2, being
composed of a single .alpha.-phase at room temperature.
5. The nickel-free white copper alloy according to claim 1, having
a magnetization of 80 memu/g or less in a magnetic field of 18
kOe.
6. The nickel-free white copper alloy according to claim 2, having
a magnetization of 80 memu/g or less in a magnetic field of 18
kOe.
7. The nickel-free white copper alloy according to claim 1, having
a conductivity of 20% IACS or less.
8. The nickel-free white copper alloy according to claim 2, having
a conductivity of 20% IACS or less.
9. The nickel-free white copper alloy according to claim 1, wherein
the b and c are, in mass %, 2.ltoreq.b.ltoreq.13 and
3.ltoreq.c.ltoreq.6.
10. The nickel-free white copper alloy according to claim 2,
wherein the b and c are, in mass %, 2.ltoreq.b.ltoreq.13 and
3.ltoreq.c.ltoreq.6.
11. A method of producing a nickel-free white copper alloy,
comprising: preparing an alloy represented by the general formula
Cu.sub.aZn.sub.bTi.sub.c wherein b and c are, in mass %,
0.5.ltoreq.b.ltoreq.30 and 1.ltoreq.c<7, and a is the balance,
with other unavoidable elements also possibly being contained;
heating the alloy to 700 to 885.degree. C.; and cooling the
alloy.
12. A method of producing a nickel-free white copper alloy,
comprising: preparing an alloy represented by the general formula
Cu.sub.aZn.sub.bTi.sub.cX.sub.d wherein X is at least one element
selected from the group consisting of Al, Sn, Ag and Mn, b, c and d
are, in mass %, 0.5.ltoreq.b.ltoreq.30, 1.ltoreq.c<7 and
0.1<d<4, and a is the balance, with other unavoidable
elements also possibly being contained; heating the alloy to 700 to
885.degree. C.; and cooling the alloy.
13. The method of producing a nickel-free white copper alloy
according to claim 11, wherein the nickel-free white copper alloy
is composed of a single .alpha.-phase at room temperature.
14. The method of producing a nickel-free white copper alloy
according to claim 12, wherein the nickel-free white copper alloy
is composed of a single .alpha.-phase at room temperature.
15. The method of producing a nickel-free white copper alloy
according to claim 11, wherein the nickel-free white copper alloy
has a magnetization of 80 memu/g or less in a magnetic field of 18
kOe.
16. The method of producing a nickel-free white copper alloy
according to claim 12, wherein the nickel-free white copper alloy
has a magnetization of 80 memu/g or less in a magnetic field of 18
kOe.
17. The method of producing a nickel-free white copper alloy
according to claim 11, wherein the nickel-free white copper alloy
has a conductivity of 20% IACS or less.
18. The method of producing a nickel-free white copper alloy
according to claim 12, wherein the nickel-free white copper alloy
has a conductivity of 20% IACS or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a nickel-free white copper
alloy that is suitable, for example, for use in elements, sliders,
stops and so on of slide fasteners, or for accessories such as
metal buttons, clothing fasteners and so on, has excellent
strength, hardness, workability and corrosion resistance, does not
cause nickel allergy, and does not cause needle detectors to
malfunction, and to a method of producing such a nickel-free white
copper alloy.
[0003] 2. Description of the Prior Art
[0004] Hitherto, copper-nickel-zinc alloys such as nickel silver,
which has a white alloy color tone, copper-zinc alloys represented
by red brass and brass, and so on have been used, for example, as
copper alloys for slide fasteners as mentioned above. However,
nickel silver contains nickel as an alloying element, and thus has
excellent corrosion resistance, but if used for a slide fastener or
the like, then because the fastener will often come into contact
with the skin, the problem of nickel allergy may arise. Moreover,
copper-zinc alloys represented by red brass and brass do not
contain nickel and hence the problem of nickel allergy does not
arise, but the color tone thereof is yellowish, and hence a white
alloy cannot be obtained.
[0005] The present inventors thus developed and filed patent
applications for nickel-free white copper alloys as disclosed in
Japanese Patent Application Publication No. 11-124644, Japanese
Patent Application Publication No. 2000-303129, Japanese Patent
Application Publication No. 2000-303130 and Japanese Patent
Application Publication No. 2001-3125. The nickel-free white copper
alloys disclosed in Japanese Patent Application Publication No.
11-124644, Japanese Patent Application Publication No. 2000-303129,
Japanese Patent Application Publication No. 2000-303130 and
Japanese Patent Application Publication No. 2001-3125 have
excellent strength, hardness, workability and corrosion resistance,
and do not contain nickel, and hence the problem of nickel allergy
does not arise, and moreover these alloys have high decorative
value, with an attractive degree of whiteness being maintained.
[0006] However, since manganese contained in the above alloys is a
magnetic substance, the above alloys have a magnetic nature, and
thus they have a problem that, when carrying out an investigation
using a needle detector to find pins in a sewn article such as
clothing, the needle detector is caused to malfunction, and hence
pins cannot be identified. In the case of Cu--Mn copper alloys to
which Mn added is added in small amounts, the magnetization is low
and hence the alloy does not tend to cause needle detectors to
malfunction, but there is a problem in that the color tone of the
alloy tends not to be white, and hence a high-quality impression
tends not to be given.
[0007] As a needle detector countermeasure for the above alloys,
one can envisage carrying out surface treatment by plating or the
like such that needle detectors are not caused to malfunction;
however, the plating film or the like formed on the alloy surface
may peel off due to changes over time, contact with other members
or the like, and in this case problems will arise in that, if the
substrate alloy that has been plated contains a magnetic element as
described above, then needle detectors will be caused to
malfunction and hence it will not be possible to identify pins as
described above, and moreover there will deteriorate its
decorativeness. Moreover, although copper alloys that do not cause
needle detectors to malfunction also exist, for example the color
tone of the alloy is not white, or the alloy contains nickel which
causes the problem of nickel allergy; there has been no alloy that
satisfies all of the above requirements.
SUMMARY OF THE INVENTION
[0008] It is thus an object of the present invention to provide a
nickel-free white copper alloy that has a strength and excellent
hardness comparable to those of nickel silver, as well as excellent
workability, corrosion resistance and whiteness in addition to
ductility, and is free from the fear of nickel allergy problem
because of containing no nickel, and moreover when carrying out an
investigation using a needle detector to identify pins in a sewn
article, tends not to cause the needle detector to malfunction.
Another object of the present invention is to provide a method of
producing such a nickel-free white copper alloy.
[0009] The present invention is constituted as follows.
[0010] (1) A nickel-free white copper alloy represented by the
general formula Cu.sub.aZn.sub.bTi.sub.c wherein b and c are, in
mass %, 0.5.ltoreq.b.ltoreq.30 and 1.ltoreq.c<7, and a is the
balance, with other unavoidable elements also possibly being
contained.
[0011] (2) A nickel-free white copper alloy represented by the
general formula Cu.sub.aZn.sub.bTi.sub.cX.sub.d wherein X is at
least one element selected from the group consisting of Al, Sn, Ag
and Mn, b, c and d are, in mass %, 0.5.ltoreq.b.ltoreq.30,
1.ltoreq.c<7 and 0.1<d<4, and a is the balance, with other
unavoidable elements also possibly being contained.
[0012] (3) The nickel-free white copper alloy according to (1) or
(2) above, being composed of a single .alpha.-phase at room
temperature.
[0013] (4) The nickel-free white copper alloy according to any of
(1) through (3) above, having a magnetization of 80 memu/g or less
in a magnetic field of 18 kOe.
[0014] (5) The nickel-free white copper alloy according to any of
(1) through (4) above, having a conductivity of 20% IACS
(International Annealed Copper Standard) or less.
[0015] (6) The nickel-free white copper alloy according to any of
(1) through (5) above, wherein the b and c are, in mass %,
2.ltoreq.b.ltoreq.13 and 3.ltoreq.c.ltoreq.6.
[0016] (7) A method of producing a nickel-free white copper alloy,
comprising: preparing an alloy represented by the general formula
Cu.sub.aZn.sub.bTi.sub.c wherein b and c are, in mass %,
0.5.ltoreq.b.ltoreq.30 and 1.ltoreq.c<7, and a is the balance,
with other unavoidable elements also possibly being contained;
heating the alloy to 700 to 885.degree. C.; and cooling the
alloy.
[0017] (8) A method of producing a nickel-free white copper alloy,
comprising: preparing an alloy represented by the general formula
Cu.sub.aZn.sub.bTi.sub.cX.sub.d wherein X is at least one element
selected from the group consisting of Al, Sn, Ag and Mn, b, c and d
are, in mass %, 0.5.ltoreq.b.ltoreq.30, 1.ltoreq.c<7 and
0.1<d<4, and a is the balance, with other unavoidable
elements also possibly being contained; heating the alloy to 700 to
885.degree. C.; and cooling the alloy.
[0018] (9) The method of producing a nickel-free white copper alloy
according to (7) or (8) above, wherein the nickel-free white copper
alloy is composed of a single .alpha.-phase at room
temperature.
[0019] (10) The method of producing a nickel-free white copper
alloy according to any of (7) through (9) above, wherein the
nickel-free white copper alloy has a magnetization of 80 memu/g or
less in a magnetic field of 18 kOe.
[0020] (11) The method of producing a nickel-free white copper
alloy according to any of (7) through (10) above, wherein the
nickel-free white copper alloy has a conductivity of 20% IACS or
less.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Following is a description of the composition of the
nickel-free white copper alloy of the present invention.
[0022] The object of the present invention can be attained by the
composition specified above.
[0023] Zn has an effect of improving the mechanical properties of
the alloy through its solid solution strengthening effect, a
deoxidizing action in the melt during melting, and an effect of
reducing the cost of the alloy. If the Zn content is less than the
above-mentioned 0.5 mass %, then the reduction in the cost of the
alloy will be insufficient, and the degree of strengthening and the
deoxidizing action in the melt will be insufficient. Moreover, if
the Zn content is greater than 30 mass %, then the season cracking
resistance will deteriorate.
[0024] Ti has an effect of improving the mechanical properties of
the alloy through its solid solution strengthening effect, and an
effect of whitening the color tone of the copper alloy. Moreover,
by adding Ti instead of Zn, there is an effect of improving the
season cracking resistance. Moreover, Ti has an effect of reducing
the conductivity of the alloy, and hence an effect of preventing
malfunctioning due to the generation of eddy currents with a needle
detector. If the Ti content is less than 1 mass %, then it will not
be possible to expect the effect of whitening the color tone of the
copper alloy, whereas if the Ti content is 7 mass % or more, then a
large amount of oxides will be generated upon melting, and hence
melt casting will become difficult, and also it will no longer be
possible to secure sufficient cold workability, and moreover the
cost of the material will rise.
[0025] X is at least one element selected from the group consisting
of Al, Sn, Ag and Mn; by further adding these elements to the
Cu--Zn--Ti alloy described above within a range of 0.1 to 4 mass %
(wherein the upper limit and the lower limit are not included), the
following effects can be expected.
[0026] Al and Sn have an effect of improving the season cracking
resistance through formation of a stable oxide film on the surface
of the alloy. Moreover, they have an effect of improving the
mechanical properties of the alloy through their solid solution
strengthening effect, and an effect of reducing the cost of the
alloy. If the content is 0.1 mass % or less, then the season
cracking resistance of the alloy will be insufficient, and the
strengthening effect will also be insufficient. Moreover, if the
content is 4 mass % or more, then the structure will be formed of
an .alpha.+.beta. phase, and hence it will no longer be possible to
secure sufficient cold workability.
[0027] Ag has an effect of improving the mechanical properties of
the alloy through its solid solution strengthening effect, and an
effect of whitening the color tone of the copper alloy. Moreover,
by adding Ag instead of Zn, there is an effect of improving the
season cracking resistance. If the Ag content is 0.1 mass % or
less, then the effect of whitening the color tone of the copper
alloy will diminish. Moreover, if the Ag content is 4 mass % or
more, then it will no longer be possible to secure sufficient cold
workability, and moreover the cost of the material will rise.
[0028] Mn has an effect of whitening the color tone of the copper
alloy. Moreover, by adding Mn instead of Zn, there is an effect of
improving the season cracking resistance. Furthermore, Mn has an
effect of reducing the conductivity of the alloy, and hence an
effect of preventing malfunctioning caused due to the generation of
eddy currents with a needle detector can be expected. If the Mn
content is 0.1 mass % or less, then the effect of whitening the
color tone of the copper alloy will diminish. Moreover, if the Mn
content is 4 mass % or more, then a large amount of oxides will be
generated upon melting, and hence problems will arise with the
properties of the product, and moreover it will no longer be
possible to secure sufficient cold workability, and also the
magnetization will increase, and hence needle detectors will be
caused to malfunction.
[0029] Through the structure of the alloy composed of a single
.alpha.-phase, it is possible to make the cold workability
excellent, and make malfunctioning of needle detectors less prone
to occur.
[0030] Moreover, through the magnetization in a magnetic field of
18 kOe being 80 memu/g or less, when carrying out an investigation
using a needle detector to identify pins in a sewn article, the
needle detector will not be caused to malfunction, i.e. the alloy
can be made to have excellent ability to cope with needle
detectors. Ordinarily, an alloy can be made to have needle detector
coping ability by making the magnetization in a magnetic field of
18 kOe be 200 memu/g or less, but with the present invention this
magnetization is 80 memu/g or less as mentioned above, and hence
the alloy has yet better needle detector coping ability.
[0031] Furthermore, the conductivity being 20% IACS or less is a
very effective condition for making eddy currents not prone to
occur during measurements with a needle detector.
[0032] Regarding the composition described above, in the case that
the Zn content is 2 to 13 mass % and the Ti content is 3 to 6 mass
% (wherein the upper and lower limits are included), the alloy has
a degree of whiteness comparable to that of a conventional nickel
silver or high manganese Cu--Mn copper alloy, and is yet better in
terms of workability.
[0033] In the production of the alloy having these characteristic
features required in the present invention, it can be obtained by
preparing a material alloy (starting alloy) having the
above-specified composition, heating the alloy to 700 to
885.degree. C., and then cooling it. Specifically, at the stage of
preparing the material alloy, the magnetization of the material
alloy in a magnetic field of 18 kOe will be more than 80 memu/g,
but by heating the material alloy to 700 to 885.degree. C. and then
cooling it, the magnetization in a magnetic field of 18 kOe becomes
80 memu/g or less, i.e. the magnetization is reduced, and hence the
resultant alloy can be made to have better needle detector coping
ability, i.e. the resultant alloy will not cause needle detectors
to malfunction. If the heating temperature is below the
above-mentioned temperature range, then a precipitate will be
present, and hence the magnetization may rise, and moreover the
structure will no longer be a single .alpha.-phase, and hence the
cold workability will be poor. Moreover, if the heating temperature
is conversely higher than the above-mentioned temperature range,
then the alloy will be heated above the eutectic temperature of
Cu--Ti and brought to a molten state (a state of solid-liquid
coexistence), thereby leading to a drop in product quality.
[0034] Moreover, in this method, the cooling after the heating is
important, and it is important to carry out this cooling rapidly by
quenching or the like. As the cooling method, rapid cooling by
quenching or the like using water, air, a gas or another cooling
medium is preferable. In particular, it is preferable to make the
cooling rate during the cooling be at least 10 K/s. By carrying out
cooling in this way, the structure becomes a single .alpha.-phase,
which is useful for cold working, and hence an alloy that is also
useful from a working perspective can be provided.
[0035] The alloy produced through the present invention is in
ranges of -2<a*<7 and -3<b*<20 based on the
chromaticity diagram of the (L*, a*, b*) colorimetric system
stipulated in JIS Z 8729.
[0036] Note that the `color tone` mentioned in the present
specification is expressed using the method for indicating the
color of objects stipulated in JIS Z 8729 and is represented by the
values of the lightness index L* (lightness: L star) and the
chromaticity indexes a* (greenness to redness: a star) and b*
(blueness to yellowness: b star). In particular, it is a
characteristic feature of the of the present invention that the
color tone is white, and hence the closer to being achromatic the
better, and thus the color tone is specified by the chromaticity
indexes a* and b* as mentioned above.
[0037] Moreover, in the present invention, since the alloy itself
is an alloy that does not cause needle detectors to malfunction, a
coating layer may be formed on the surface of the alloy. Even if
the coating layer peels off, the problem of a needle detector being
caused to malfunction and hence it not being possible to identify
pins will not arise. In the case of forming a coating layer, the
ranges of a* and b* must be set to be similar to those for the
above-mentioned alloy, and by forming the coating layer, a yet
whiter material can be provided. In this case as well, even if the
coating layer happens to peel off, because the alloy forming the
substrate has a color close to that of the coating layer, there
will be no problem, particularly with regard to color.
[0038] Examples of such a coating layer are an Sn plating layer, a
Cr plating layer, an Ag plating layer, and a Cu--Sn plating layer,
although so long as the coating layer exhibits a color tone as
described above, a coating layer other than these plating layers
can be used. In the case of forming a coating layer, the technique
may be a wet type or dry type plating; for example, as a wet type
plating, electrolytic plating, electroless plating, melt plating or
the like can be used, and as a dry type plating, physical vapor
deposition (PVD), chemical vapor deposition (CVD) or the like can
be used.
[0039] Regarding the thickness of the coating layer, 0.001 to 10
.mu.m is an effective range in which the coating will be expected
to have an effect, and problems such as peeling off will not occur,
and also in consideration of cost. Moreover, depending on the
usage, such a material may be subjected to post-processing such as
cutting or bending. In such a case, in consideration of peeling
off, wear and so on due to such processing, it is preferable to
make the thickness of the coating layer be in a range of 0.005 to 5
.mu.m.
EXAMPLES
[0040] Following is a specific description of the present invention
through examples, but the present invention is of course not
limited by the following examples. In the following examples, all
percentages are indicated by mass % unless otherwise specified.
[0041] Test Samples Made from Alloys of the Present Invention:
[0042] Test samples made from alloys of the present invention as
shown in Tables 1 and 2 were prepared as follows, and were
subjected to evaluation. Test samples of comparative examples were
also prepared in the same way.
[0043] Pure Cu (99.9%), pure Zn (99.9 to 99.99%), pure Ti (99.9%),
pure Al, pure Sn, pure Ag, pure Mn and pure Ni were measured for
making up an ingot of 200 cm.sup.3 for each of the prescribed
compositions shown in Tables 1 and 2. Each composition was
subjected to high-frequency melting in an Ar atmosphere (10 cmHg),
and after leaving for 4 minutes, the melt was poured into a copper
casting mold (40 mm in diameter.times.28 mm in length). The ingot
(200 cm.sup.3) obtained was cut into lengths of about 7 mm, thus
producing billets for extrusion.
[0044] Extrusion was carried out at a billet temperature of
800.degree. C. and a container temperature of 600.degree. C. The
extruded material (8 mm in diameter x approx. 1300 mm in length)
was subjected to heat treatment comprising heating at 800.degree.
C. for 1 hour followed by furnace cooling (hereinafter referred to
as the `heat treatment`). After this heat treatment, the extruded
material (wire) was further heated to a temperature of 700 to
885.degree. C., and then quenching was carried out using water as
the cooling medium; the material obtained was taken as the test
sample.
1 TABLE 1 Alloy composition (mass %) Color Conductivity Ni
Magnetization Cu Zn Ti Mn Ni tone IACS% allergy Structure memu/g
Examples of the present invention 1 Balance 10 1 -- -- White 11
.largecircle. .alpha. -4 2 Balance 10 3 -- -- White 10
.largecircle. .alpha. -9 3 Balance 13 5 -- -- White 9 .largecircle.
.alpha. -8 4 Balance 27 2 -- -- White 10 .largecircle. .alpha. -7 5
Balance 26 3 -- -- White 9 .largecircle. .alpha. -3 6 Balance 21 2
-- -- White 9 .largecircle. .alpha. -5 7 Balance 28 2 -- -- White 9
.largecircle. .alpha. -7 8 Balance 6 2 -- -- White 12 .largecircle.
.alpha. -1 9 Balance 5 3 -- -- White 12 .largecircle. .alpha. -2
Comparative examples 1 Balance 35 0.5 -- -- Yellow 20 .largecircle.
.alpha. -2 2 Balance 20 10 -- -- White 8 .largecircle. .alpha. +
.beta. -5 3 Balance 15 -- -- -- Yellow 37 .largecircle. .alpha. --
4 Balance 24 -- -- 14 White 7 X .alpha. -- 5 Balance 15 -- 10 --
White 3 .largecircle. .alpha. 157
[0045]
2 TABLE 2 Alloy composition (mass%) Color Conductivity Ni
Magnetization Cu Zn Ti Al Sn Ag Mn Ni tone IACS% allergy Structure
memu/g Examples of the present invention 1 Balance 10 1 0.4 -- --
-- -- White 11 .largecircle. .alpha. -4 2 Balance 10 3 -- -- -- 2
-- White 6 .largecircle. .alpha. 47 3 Balance 13 5 0.5 -- -- -- --
White 9 .largecircle. .alpha. -8 4 Balance 27 2 0.3 -- -- -- --
White 10 .largecircle. .alpha. -7 5 Balance 26 3 1 1 -- -- -- White
9 .largecircle. .alpha. -3 6 Balance 21 2 1 -- -- -- -- White 9
.largecircle. .alpha. -5 7 Balance 28 2 2 -- -- -- -- White 9
.largecircle. .alpha. -7 8 Balance 6 2 -- -- -- 2 -- White 7
.largecircle. .alpha. 49 9 Balance 5 3 -- -- 1 -- -- White 12
.largecircle. .alpha. -2 Comparative examples 1 Balance 35 0.5 0.2
-- -- -- -- Yellow 3 .largecircle. .alpha. -2 2 Balance 20 10 -- 5
-- -- -- Yellow 3 .largecircle. .alpha. + .beta. -5 3 Balance 15 2
-- -- -- 10 -- White 3 .largecircle. .alpha. 157 4 Balance 24 -- --
-- -- -- 14 White 7 X .alpha. --
[0046] Evaluation of Test Samples:
[0047] Regarding the color tone, the test samples obtained were
mirror-polished using an SiC abrasive paper and a diamond paste,
measurements were taken using a colorimeter (CR-300, made by
Minolta Co., Ltd.), and the measurement results were expressed by
means of L*, a* and b* as stipulated in JIS Z 8729; if a* and b*
were expressed within the ranges stated earlier then the color tone
was recorded as being `white`, whereas otherwise the principal
color was recorded. For all of the test samples of the present
invention, the color tone was white, specifically a white close to
achromatic.
[0048] Regarding the conductivity, a sample surface taken from each
test sample was mirror-polished, the measuring probe of a digital
conductivity meter (AutoSigma 3000 made by Hocking Kabushiki
Kaisha) was placed in contact with the sample surface, and the
conductivity value was measured. For the test samples of the
present invention, it was found that the values were extremely good
at 12% IACS or less. It can thus be seen that eddy currents will
occur only with extreme difficulty during measurements with a
needle detector. For coping with needle detectors, this is an
extremely important property, along with the magnetization,
described below.
[0049] Regarding nickel allergy, evaluation was carried out
according to whether or not the test samples contained Ni, with the
symbol `O` being given to ones that did not contain Ni, and the
symbol `x` to ones that did contain Ni. All of the test samples of
the present invention did not contain Ni, and hence were materials
having no allergic problem due to nickel.
[0050] Regarding the structure, the test samples obtained were
subjected to structure observation. The test samples of the present
invention were composed of an .alpha.-phase only.
[0051] The magnetization of each test sample obtained was measured
using an alternating gradient force magnetometer (model AFGM
2900-04C made by Princeton Measurements Corp.); approximately 0.1 g
of the test sample was placed in the magnetic field of an
electromagnet, a magnetic field of 18 kOe was generated using the
electromagnet, and the magnetization of the test sample was
measured by changing the magnetic field. The measurement speed was
50 msec/point. It was found that the test samples of the present
invention have an extremely low magnetization of 50 memu/g or less
even in a strong magnetic field of 18 kOe. Note that in the tables,
a negative value of the magnetization indicates diamagnetism, and
implies that the magnetization is a value close to 0. Moreover,
`--` indicates that no measurement was taken.
[0052] It can be seen from the above results that to obtain a
material that is excellent in terms of magnetization and
conductivity, it is extremely important to use an alloy composition
according to the present invention and the producing method
according to the present invention.
[0053] Moreover, for the test samples of the present invention, the
hardness was 100 Hv or more, there was no cracking or the like
after 80% deformation, and excellent results were also obtained
with regard to discoloration resistance and season cracking
resistance.
[0054] According to the nickel-free white copper alloy and the
method of producing the nickel-free white copper alloy of the
present invention, the alloy has excellent strength and hardness,
is ductile, has excellent workability, corrosion resistance,
discoloration resistance and season cracking resistance, and has
excellent whiteness, and hence an alloy having high decorative
value can be provided; moreover, since the alloy does not contain
nickel, there is no nickel allergy problem. Furthermore, the
magnetization is extremely small even in a strong magnetic field of
18 kOe, and hence when carrying out an investigation using a needle
detector to identify pins in a sewn article, the alloy tends not to
cause the needle detector to malfunction. Due to these points, the
alloy is extremely useful as an alloy used for accessories, in
particular as an alloy used in articles that are attached by
sewing. Furthermore, according to the method of producing a
nickel-free white copper alloy of the present invention, the alloy
having excellent properties as described above can be produced
easily, and hence an alloy having excellent properties as described
above can be provided for various uses.
* * * * *