U.S. patent application number 11/654864 was filed with the patent office on 2008-07-24 for cu-ni-si system copper alloy for electronic materials.
This patent application is currently assigned to Nippon Mining & Metals Co., Ltd.. Invention is credited to Naohiko Era, Kazuhiko Fukamachi, Hiroshi Kuwagaki.
Application Number | 20080175746 11/654864 |
Document ID | / |
Family ID | 39641406 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080175746 |
Kind Code |
A1 |
Era; Naohiko ; et
al. |
July 24, 2008 |
Cu-Ni-Si system copper alloy for electronic materials
Abstract
The present invention provides Corson alloy having remarkably
improved properties, in particular, by bringing out the effect of
added Cr more efficiently. A copper alloy for electronic materials
comprising 2.5-4.5% by mass of Ni; 0.50-1.2% by mass of Si;
0.0030-0.2% by mass of Cr; balance Cu and inevitable impurities,
wherein the weight ratio of Ni to Si is in the range of 3 to 7 and
the content of carbon is 50 ppm by mass or less is provided.
Inventors: |
Era; Naohiko; (Ibaraki-ken,
JP) ; Fukamachi; Kazuhiko; (Ibaraki-ken, JP) ;
Kuwagaki; Hiroshi; (Ibaraki-ken, JP) |
Correspondence
Address: |
DRINKER BIDDLE & REATH;ATTN: INTELLECTUAL PROPERTY GROUP
ONE LOGAN SQUARE, 18TH AND CHERRY STREETS
PHILADELPHIA
PA
19103-6996
US
|
Assignee: |
Nippon Mining & Metals Co.,
Ltd.
Tokyo
JP
|
Family ID: |
39641406 |
Appl. No.: |
11/654864 |
Filed: |
January 18, 2007 |
Current U.S.
Class: |
420/485 |
Current CPC
Class: |
C22C 1/02 20130101; C22C
9/06 20130101 |
Class at
Publication: |
420/485 |
International
Class: |
C22C 9/06 20060101
C22C009/06 |
Claims
1. A copper alloy for electronic materials comprising 2.5-4.5% by
mass of Ni; 0.50-1.2% by mass of Si; 0.0030-0.2% by mass of Cr;
balance Cu and inevitable impurities, wherein the weight ratio of
Ni to Si is in the range of 3 to 7 and the content of carbon is 50
ppm by mass or less.
2. The copper alloy according to claim 1, further comprising one or
more element selected from the group consisting of Mg, Mn, Sn and
Ag in a total amount of up to 0.5% by mass.
3. The copper alloy according to claims 1, further comprising one
or more element selected from the group consisting of Zn, P, As,
Sb, Be, B, Ti, Zr, Al, Co and Fe in a total amount of up to 2.0% by
mass.
4. A copper alloy product made of the copper alloy according to any
one of claims 1 to 3.
5. An electronic component using the copper alloy according to any
one of claims 1 to 3.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to age-hardening type copper
alloys, and, in particular, to age-hardening copper alloys suitable
for the use in various electronic components.
BACKGROUND OF THE INVENTION
[0002] Copper alloys for electronic materials used in electronic
components such as a leadframe, a connector, a pin, a terminal, a
relay and a switch are fundamentally required to have both high
strength and high electric conductivity (or thermal conductivity).
In accordance with the recent trend toward high integration,
miniaturization and thinning of electronic components, copper
alloys used in electronic components need to meet a higher
standard.
[0003] In terms of high strength and high electric conductivity, in
recent years, an increasing amount of age-hardening type copper
alloys has been used instead of conventional solid-solution
hardening type copper alloys such as phosphor bronze and brass.
Age-hardening type copper alloys are produced through an aging
treatment of supersaturated solid solution after a solution
treatment. The aging treatment develops a uniform dispersion of
fine precipitates in the alloys, resulting in improved strength. It
also decreases the amount of dissolved elements in the alloys,
resulting in improved electric conductivity. Accordingly,
age-hardening type copper alloys can possess high mechanical
properties such as strength and spring properties as well as high
electric and thermal conductivity.
[0004] Among the age-hardening type copper alloys, Cu--Ni--Si
system copper alloy, which is generally called Corson alloy, is a
typical copper alloy that possesses high electric conductivity and
strength as well as good stress-relaxation properties and
bendability. Cu--Ni--Si system copper alloy is thus one of the
alloys on which much research has been done in copper products
industry. In this copper alloy, strength and electric conductivity
can be improved by precipitating fine particles of Ni--Si
intermetallic compound in the copper matrix.
[0005] The precipitated particles of the Ni--Si intermetallic
compound generally have stoichiometric composition. Japanese
Unexamined Patent Application Publication No. 2001-207229 teaches
that electric conductivity can be improved by bringing the mass
ratio of Ni to Si in the alloy close to that of Ni.sub.2Si (atomic
weight of Ni.times.2: atomic weight of Si.times.1), that is, by
adjusting the weight ratio Ni/Si to 3-7.
[0006] To Cu--Ni--Si system copper alloy, Cr is sometimes added.
Japanese Patent No. 2862942 discloses a method for heat treatment
of Corson alloy comprising 1.5-4.0% by mass of Ni; 0.35-1.0% by
mass of Si; optionally 0.05-1.0% by mass of at least one metal
selected from the group consisting of Zr, Cr and Sn; balance Cu and
inevitable impurities, the method comprising heating or cooling the
alloy such that tensile and thermal strain is 1.times.10.sup.-4 or
less in a temperature range of 400-800 C degree. It is stated that
the method can prevent ingot cracking during the heat
treatment.
[0007] Japanese Patent No. 3049137 discloses a high-strength copper
alloy having improved bendability comprising 2-5% by mass of Ni;
0.5-1.5% by mass of Si; 0.1-2% by mass of Zn; 0.01-0.1% by mass of
Mn; 0.001-0.1% by mass of Cr; 0.001-0.15% by mass of Al; 0.05-2% by
mass of Co; balance Cu and inevitable impurities, wherein the
content of S, which is one of the inevitable impurities, is
controlled to 15 ppm or less. It is stated that Cr is an element
that reinforces the grain boundaries of ingot, improving hot
workability. It is also stated that Cr over 0.1% by mass may cause
oxidization of molten metal and worsen casting properties.
According to JP'137, the alloy is melted and cast under a charcoal
covering in a cryptol furnace in the atmosphere.
SUMMARY OF THE INVENTION
[0008] Though the properties of the alloy may be improved by
controlling the weight ratio of Ni/Si within a range of 3-7 as
disclosed in JP'229, it was difficult to achieve high strength
while maintaining relatively high electric conductivity. An
increase in Ni and Si concentrations by weight may lead to higher
strength but also to lower electric conductivity. In addition, it
may deteriorate hot workability, decreasing yield factor and
therefore cost efficiency. It is has been found difficult to
remarkably improve the properties of the alloy even if the amount
of Ni and Si is adjusted to strictly control the composition.
[0009] JP'942 fails to disclose or suggest any effect of Cr added
to the alloy. According to the method disclosed in JP'942,
temperature control will become difficult if ingot is upsized. It
is therefore more desirable to preventingot cracking by improving
the properties of Cu--Ni--Si system alloy based on an inherent
function that an alloying element renders rather than by
temperature control.
[0010] JP'137 teaches that Cr can enhance hot workability but does
not teach any other function of Cr. It also teaches the
concentration conditions that can bring out the effect of added Cr
on the properties of the alloy but does not teach any other
condition.
[0011] Therefore, it is an object of the present invention to
provide Corson alloy having remarkably improved properties, in
particular, by bringing out the effect of added Cr more
efficiently.
[0012] The present inventors have conducted extensive research in
order to solve the above problems and determined that Cr has a
noticeable influence on the improvement in strength and electric
conductivity of Corson alloy under a certain condition. In
particular, the present inventors have noticed the relationship
between Cr and carbon and determined that controlling the content
of carbon in Corson alloy can enhance the effect of Cr.
[0013] The present invention has been completed based on the above
findings. An aspect in accordance with the present invention
provides a copper alloy for electronic materials comprising
2.5-4.5% by mass of Ni; 0.50-1.2% by mass of Si; 0.0030-0.2% by
mass of Cr; balance Cu and inevitable impurities, wherein the
weight ratio of Ni to Si is in the range of 3 to 7 and the content
of carbon is 50 ppm by mass or less.
[0014] In accordance with one embodiment of the present invention,
the copper alloy may further comprise one or more element selected
from the group consisting of Mg, Mn, Sn and Ag in a total amount of
up to 0.5% by mass.
[0015] In accordance with another embodiment of the present
invention, the copper alloy may further comprise one or more
element selected from the group consisting of Zn, P, As, Sb, Be, B,
Ti, Zr, Al, Co and Fe in a total amount of up to 2.0% by mass.
[0016] Another aspect in accordance with the present invention
provides a copper alloy product made of the copper alloy of the
present invention.
[0017] A further aspect in accordance with the present invention
provides an electronic component using the copper alloy of the
present invention.
[0018] Corson copper alloy for electronic materials according to
the present invention may possess remarkably improved strength and
electric conductivity because the effect of added Cr, one of the
alloying elements, is brought out more efficiently.
BRIEF DESCRIPTION OF THE DRAWING
[0019] FIG. 1 shows the influence of the carbon content.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Added Amount of Ni and Si
[0021] By conducting a proper heat treatment, Ni and Si may form
nickel silicide intermetallic compounds such as Ni.sub.2Si,
contributing to an increase in strength without deteriorating
electric conductivity. As mentioned above, the weight ratio of Si
to Ni should be closer to the stoichiometric composition, and is
preferably 3 to 7, more preferably 3.5 to 5.0.
[0022] However, when the added amount of Si is less than 0.5% by
mass of the alloy, desired strength may not be obtained even if
Ni/Si ratio is within the above range. On the contrary, when the
added amount of Si is more than 1.2% by mass of the alloy, strength
may be improved but electric conductivity is significantly
decreased and hot workability is undesirably deteriorated due to
the formation of liquid phase in segregation portions. Hence, the
added amount of Si is 0.5 to 1.2% by mass, preferably 0.5 to 0.8%
by mass of the alloy.
[0023] The added amount of Ni may be defined so as to satisfy the
above preferable ratio of Ni to Si in accordance with the added
amount of Si. For example, the added amount of Ni may be 2.5 to
4.5% by mass, preferably 3.2 to 4.2% by mass, more preferably 3.5
to 4.0% by mass of the alloy to keep the balance with Si.
[0024] Added Amount of Cr
[0025] In conventional Cu--Ni--Si system alloy, an increase in Ni
and Si concentrations will increase the total number of
precipitated particles that contribute to age hardening, resulting
in an increase of strength. The increase in Ni and Si will also
lead to an increase in the amount of solid solution that does not
contribute to age hardening, resulting in a decrease of electric
conductivity. Eventually, the peak strength will be improved by age
hardening but electric conductivity at the peak strength will be
decreased. However, if Cr is added in an amount of 0.003 to 0.2% by
mass, preferably 0.01 to 0.1% by mass to the Cu--Ni--Si system
alloy, the alloy may have higher electric conductivity without
deteriorating the strength than before the addition of Cr. The
addition of Cr will also increase hot workability, improving yield
factor.
[0026] Cr precipitates preferentially at grain boundaries at the
cooling stage of casting process, reinforcing the grain boundaries,
preventing the generation of cracking during hot working and
therefore suppressing the decrease of yield factor. In addition, Cr
can readily precipitate as chromium silicides such as Cr.sub.3Si,
which are compounds with Si, through suitable heat treatment. In
particular, Cr can precipitate as Cr.sub.3Si, etc. with dissolved
Si that has not precipitated during the fabrication process of the
alloy in combination of solution treatment, cold rolling, and aging
treatment. Cr can therefore suppress the decrease in electric
conductivity caused by dissolved Si, resulting in improved electric
conductivity without deteriorating strength.
[0027] Though Cr precipitated at grain boundaries during casting
process is redissolved by solution treatment, etc., it precipitates
again as silicides during the subsequent aging treatment. In
conventional Cu--Ni--Si system alloy, among the added Si, Si that
has not precipitated during the aging treatment remains dissolved
in the matrix and suppresses an increase in electric conductivity.
However, by adding Cr, which is a silicide-forming element, and
further precipitating silicides, the amount of dissolved Si can be
reduced compared with conventional Cu--Ni--Si alloy, resulting in
an increase in electric conductivity without deteriorating
strength.
[0028] It should be noted that when the content of Cr is less than
0.003% by mass, the effect of Cr may not be sufficiently exhibited.
When the content of Cr is more than 0.2% by mass, Cr may be likely
to form coarse inclusions that do not contribute to an increase in
strength during hot rolling. In addition, as Cr--Si based
precipitates have lower ability of work hardening, an excess amount
of Cr may increase the number of Cr--Si compounds that do not
contribute to an increase in strength, undesirably deteriorating
workability and platability.
[0029] The Carbon Content
[0030] Ni--Si system alloy is usually melted and cast in the
reducing atmosphere to prohibit oxidization of Si, which is an
active metal. When the melting and casting process is conducted in
the air, carbon-containing materials such as charcoal and carbon
flux are often used to cover molten metal. As a result, the cast
alloy may include a relatively high amount of C as an impurity.
[0031] Cr has high carbide-forming ability in the molten metal. The
formation of carbide may decrease the amount of Cr precipitated at
grain boundaries during solidification, reducing the effect of
grain boundaries reinforcement and suppressing the improvement in
yield factor. Once Cr-based carbides are formed, they are not
likely to dissolve in solution treatment. Cr-based carbides not
only decrease the amount of Cr that precipitates during aging
treatment but also deteriorate bendability and platability, greatly
worsening the final properties.
[0032] The present inventors have found that strict control of
carbon content in the melting and casting process is necessary
since a very small amount of C greatly affects the improvement in
Cu--Ni--Si system alloy properties by the addition of Cr. It has
been also determined that hot workability may not be virtually
deteriorated and chromium silicides such as Cr.sub.3Si that
contributes to an increase in electric conductivity may not be
virtually suppressed, if the content of carbon is 50 ppm by mass or
less.
[0033] The method for controlling the content of carbon may
include, but not limited to, removing oil adherent to raw material,
stirring after melting raw material, adjusting the amount of
charcoal covering, covering the surface of molten metal with inert
gases such as Ar not with charcoal for the prevention of
oxidization of active metals, and vacuum melting. The content of
carbon may be controlled to 50 ppm by mass or less, 40 ppm by mass
or less, 30 ppm by mass or less, or 25 ppm by mass or less.
Cu--Ni--Si system alloy according to the present invention may
contain 10 to 30 ppm by mass of carbon, for example.
[0034] In this regard, JP patent No. 3049137 remains silent as to
what will happen when the amount of Cr that precipitates at grain
boundaries is drastically decreased due to the formation of
Cr-carbides and -oxides.
[0035] Mg, Mn, Sn and Ag
[0036] The addition of one or more element selected from the group
consisting of Mg, Mn, Sn and Ag in the total amount of up to 0.5%
by mass to the Cu--Ni--Si system alloy according to the present
invention may improve stress-relaxation properties, etc. without
significantly deteriorating strength and electric conductivity.
When the added amount is less than 0.01% by mass, a sufficient
effect cannot be obtained. When the added amount is more than 0.5%
by mass, manufacturability such as castability and hot workability,
and electric conductivity of the product will be deteriorated.
Therefore, they are preferably added in the total amount of 0.01 to
0.5% by mass.
[0037] Other Elements to be Added
[0038] The proper addition of Zn, P, As, Sb, Be, B, Ti, Zr, Al, Co
and Fe may exhibit various effects. For example, they,
complementary to one another, may improve strength and electric
conductivity, as well as bendability, platability and
manufacturability such as hot workability through refinement of
cast structure. Therefore, one or more of these elements may be
added up to 2.0% by mass in total to the Cu--Ni--Si system alloy of
the present invention in accordance with the required properties.
When the added amount is less than 0.001% by mass in total, a
desired effect cannot be obtained. When the added amount is more
than 2.0% by mass in total, electric conductivity and
manufacturability will be deteriorated significantly. Therefore,
they are preferably added in the total amount of 0.001 to 2.0% by
mass, more preferably 0.01 to 1.0% by mass.
[0039] Incidentally, other elements not specifically mentioned
herein may be added to the Cu--Ni--Si system alloy of the present
invention in an amount that does not have adverse effect on the
alloy properties.
[0040] The method of manufacturing the alloy according to the
present invention will be explained below. The Cu--Ni--Si system
alloy according to the present invention may be manufactured by any
conventional manufacturing methods for Cu--Ni--Si system alloy
except that the carbon content is controlled. So, those skilled in
the art could choose the optimal manufacturing method in accordance
with the composition and required properties. Though it may not be
necessary to provide detailed explanation, a general procedure for
manufacturing the alloy will be provided for the illustrative
purpose only.
[0041] Raw materials such as electrolytic copper, Ni, Si and Cr are
introduced into an atmospheric melting furnace to obtain a molten
metal having a desired composition. The molten metal is cast into
an ingot. The carbon content is controlled by adjusting oil content
of the introduced raw materials, adjusting the amount of charcoal
coating, introducing inert gases, and stirring the molten metal,
etc. Hot rolling is then conducted. Cold rolling and heat treatment
are repeated to produce into a strip or foil having desired
thickness and properties. Heat treatment includes solution
treatment and aging treatment. The solution treatment comprises
heating the alloy at 700-1000 degrees C. to dissolve Ni--Si based
compounds and Cr--Si based compounds into Cu matrix and also to
recrystallize Cu matix. The hot rolling sometimes serves as
solution treatment. The aging treatment comprises heating the alloy
at 350-550 degrees C. for one hour or more to precipitate fine
particles of the Ni--Si based compounds and Cr--Si based compounds
having been dissolved through the solution treatment. The aging
treatment increases strength and electric conductivity of the
alloy. Cold rolling may be conducted before and/or after the aging
treatment in order to obtain higher strength. In case where the
cold rolling is conducted after the aging treatment, stress relief
annealing (lower temperature annealing) may follow the cold
rolling.
[0042] The Cu--Ni--Si alloy in accordance with an embodiment of the
present invention may have a 0.2% yield strength of 780 MPa or
greater and an electric conductivity of 45% IACS or greater, a 0.2%
yield strength of 860 MPa or greater and an electric conductivity
of 43% IACS or greater, or a 0.2% yield strength of 890 MPa or
greater and an electric conductivity of 40% IACS or greater.
[0043] The Cu--Ni--Si alloy of the present invention may be
processed into various copper alloy products such as sheet, strip,
pipe, rod and wire. The Cu--Ni--Si alloy of the present invention
may also be used in electronic components such as a leadframe, a
connector, a pin, a terminal, a relay and a switch, as well as foil
used in secondary batteries, for which high strength and high
electric conductivity (or thermal conductivity) are required.
EXAMPLES
[0044] The invention and its advantages will be understood more
readily with reference to the following examples; however these
examples are intended to illustrate the invention and are not to be
construed to limit the scope of the invention.
[0045] The copper alloys used in Examples, as listed in Table 1,
have compositions of various contents of Ni, Si and Cr, and some of
them also contain elements selected from Mg, Mn, Sn, Ag, Ti, Fe, B
and Co. The copper alloys used in Comparative Examples are
Cu--Ni--Si system alloys having parameters outside the range of the
present invention.
[0046] After melting at 1,300 degrees C. in a high-frequency vacuum
melting furnace, casting was carried out to form copper alloy
ingots having a thickness of 30 mm of various compositions as
listed in table 1. During this process, the carbon content was
controlled by adjusting oil content of the introduced raw
materials, adjusting the amount of charcoal coating, introducing
inert gases, and stirring the molten metal, etc. Each ingot was
then heated at 1,000 degrees C. and was hot rolled into a sheet of
10 mm thickness, followed by rapid cooling. The sheet was then
scalped into 8 mm thickness for the removal of scale from the
surface before it was cold rolled into 0.2 mm thickness.
Subsequently, the obtained sheet was subjected to solution
treatment for 120 seconds at 850-1,000 degrees C. depending on the
added amounts of Ni and Cr, immediately followed by water-cooling.
After that, the sheet was cold rolled into 0.1 mm thickness and
finally subjected to aging treatment in the inert atmosphere at
400-550 degrees C. for 1-12 hours depending on the added amounts to
obtain a specimen.
[0047] Strength and Electric conductivity were evaluated on each
specimen obtained through the above-mentioned method. Strength was
evaluated with 0.2% yield strength (YS; MPa) measured by a tensile
test performed in a direction parallel to the rolling direction.
Electric conductivity (EC; % IACS) was evaluated with volume
resistivity using a double bridge. Bendability was evaluated as
follows. Each specimen was bent 90 degrees using a W-shaped die
under the condition such that the ratio of bend radius to specimen
thickness is equal to 1. The bent surface was observed using an
optical microscope. When the cracking was not observed, the
specimen was regarded as having practical use and evaluated as
good. When the cracking was observed, the specimen was evaluated as
bad.
[0048] The content of carbon was quantitatively analyzed by high
frequency melting-infrared absorption method after the specimen was
subjected to high frequency combustion using a LECO CS-400
instrument.
TABLE-US-00001 TABLE 1 composition (mass %) cracking during YS EC C
Ni Si Cr Mg, Mn, Sn, Ag others hot rolling (MPa) (% IACS)
bendability (ppm) claimed min 2.5 0.5 0.003 -- -- -- range max 4.5
1.2 0.2 0.5 2.0 50 Example 1 2.7 0.6 0.005 ND 750 48 good 16 2 2.7
0.6 0.05 ND 755 47 good 23 3 2.7 0.6 0.1 ND 770 46 good 38 4 2.7
0.6 0.05 0.2 Mg ND 780 46 good 23 5 2.7 0.6 0.05 0.1 Mn ND 780 45
good 23 6 2.7 0.6 0.05 0.3 Sn ND 780 45 good 23 7 2.7 0.6 0.05 0.3
Sn, 0.1 Ag ND 780 45 good 23 8 4.0 0.9 0.005 ND 860 43 good 18 9
4.0 0.9 0.05 ND 870 42 good 25 10 4.0 0.9 0.1 ND 870 42 good 40 11
4.0 0.9 0.17 ND 875 42 good 44 12 4.0 0.9 0.05 0.2 Mg ND 890 41
good 25 13 4.0 0.9 0.05 0.1 Mn ND 890 41 good 25 14 4.0 0.9 0.05
0.3 Sn ND 890 41 good 25 15 4.0 0.9 0.05 0.3 Sn, 0.1Ag ND 890 41
good 25 16 4.0 0.9 0.1 0.03 Ti, ND 890 40 good 40 0.03 Fe 17 4.5
1.00 0.005 ND 930 38 good 18 18 4.5 1.00 0.17 ND 940 42 good 43 19
4.5 1.00 0.05 0.005 B ND 940 37 good 28 20 4.5 1.00 0.1 0.1 Co ND
960 37 good 41 Compara- 1 2.7 0.6 -- slight cracking 750 40 good 2
tive 2 4.0 0.9 -- slight cracking 860 37 good 3 Example 3 2.7 0.6
0.0005 slight cracking 750 41 good 16 4 4.0 0.9 0.0005 slight
cracking 860 38 good 19 5 2.7 0.6 0.0005 unable to evaluate due to
cracking 53 6 4.0 0.9 0.0005 unable to evaluate due to cracking 56
7 4.0 0.9 0.05 slight cracking 860 36 bad 65 8 4.0 0.9 0.1 slight
cracking 860 36 bad 78 9 2.7 0.6 0.3 slight cracking 760 46 bad 40
10 4.0 0.9 0.3 slight cracking 860 42 bad 43 11 4.0 0.9 0.3 slight
cracking 860 35 bad 85 12 4.0 0.9 0.05 0.6 Mg cracking due to
casting surface degradation 15 13 4.0 0.9 0.05 0.8 Mn slight
cracking 900 21 bad 15
[0049] Cu--Ni--Si System Alloy Containing 2.7% by Mass of Ni and
0.6% by Mass of Si
[0050] Examples 1 to 7, and Comparative Examples 1, 3, 5 and 9 have
commonalities in that they contain 2.7% by mass of Ni and 0.6% by
mass of Si. As can be seen from Examples 1 to 3, an increase in the
Cr content has enhanced YS while suppressing the decrease in EC. As
can be seen from Examples 4 to 7, YS has been further improved by
addition of Mg, Mn, Sn and Ag.
[0051] On the contrary, in Comparative Example 1, the amount of
dissolved Si increased as it did not contain Cr, resulting in lower
EC. Slight cracking was occurred during the hot rolling.
[0052] Though Comparative Example 3 contained Cr, the content was
not enough and the desired effect was not obtained. As a result,
the amount of dissolved Si was still too much and EC was decreased.
Slight cracking was occurred during the hot rolling.
[0053] In Comparative Example 5, the content of Cr was insufficient
as in Comparative Example 3. Moreover, the content of C was
excessive. As a result, large cracking was occurred during the hot
rolling, making the subsequent evaluation impossible.
[0054] In Comparative Example 9, coarse Cr particles were generated
due to the excess content of Cr. As a result, slight cracking was
occurred during the hot rolling and bendability was also bad.
[0055] Cu--Ni--Si System Alloy Containing 4.0% by Mass of Ni and
0.9% by Mass of Si
[0056] Examples 8 to 16, and Comparative Examples 2, 4, 6 to 8 and
10 to 13 have commonalities in that they contain 4.0% by mass of Ni
and 0.9% by mass of Si. As can be seen from Examples 8 to 11, an
increase in the Cr content has enhanced YS while suppressing the
decrease in EC. They contained more Ni and Si than Examples 1 to 7,
resulting in higher YS and lower EC.
[0057] As can be seen from Examples 12 to 15, YS has been further
improved by addition of Mg, Mn, Sn and Ag. In Example 16, Ti and Fe
were added as other additives. Again, It can be seen YS was
improved.
[0058] On the contrary, in Comparative Example 2, the amount of
dissolved Si increased as it did not contain Cr, resulting in lower
EC. Slight cracking was occurred during the hot rolling.
[0059] Though Comparative Example 4 contained Cr, the content was
not enough and the desired effect was not obtained. As a result,
the amount of dissolved Si was still too much and EC was decreased.
Slight cracking was occurred during the hot rolling.
[0060] In Comparative Example 6, the content of Cr was insufficient
as in Comparative Example 4. Moreover, the content of C was
excessive. As a result, large cracking was occurred during the hot
rolling, making the subsequent evaluation impossible.
[0061] In Comparative Examples 7 and 8, chromium carbides were
generated due to the excess content of C while the generation of
chromium silicides was suppressed. As a result, the amount of
dissolved Si was increased and EC was decreased. Slight cracking
was occurred during the hot rolling. Bendability was also bad.
[0062] In Comparative Example 10, coarse Cr particles were
generated due to the excess content of Cr. As a result, slight
cracking was occurred during the hot rolling. Bendability was also
bad.
[0063] In Comparative Example 11, the Cr content was excessive as
in Comparative Example 10. The C content was also excessive. The
excess content of C caused chromium carbides to form while
suppressing the generation of chromium silicides. As a result, the
amount of dissolved Si was increased and EC was decreased.
Bendability was also bad.
[0064] In Comparative Examples 12 and 13, Mg and Mn were added
excessively. In Comparative Example 12, where Mg was added
excessively, cracking caused by fault of casting surface made the
subsequent evaluations impossible. In Comparative Example 13, where
Mn was added excessively, slight cracking was occurred during the
hot rolling. EC and Bendability were also bad Cu--Ni--Si system
alloy containing 4.5% by mass of Ni and 1.0% by mass of Si
[0065] Examples 17 to 20 contained 4.5% by mass of Ni and 1.0% by
mass of Si. They contained more Ni and Si than Examples 1 to 16,
resulting in higher YS and lower EC.
[0066] The Influence of the Carbon Content
[0067] FIG. 1 is a plot of YS (the vertical axis) versus EC
(horizontal axis) for Examples 9 and 10 in which the carbon content
was within the claimed range, and Comparative Examples 7 and 8 in
which the carbon content was outside the claimed range. The
contents of Ni, Si and Cr were within the claimed range for all
these Examples and Comparative Examples. Examples 9 contained the
same amount of Ni, Si and Cr, with Comparative Examples 7. Examples
10 contained the same amount of Ni, Si and Cr with Comparative
Examples 8. It can be seen that the difference of the carbon
content, which was only 40 ppm by mass, generated significant
differences in YS and EC.
* * * * *