U.S. patent application number 13/864568 was filed with the patent office on 2014-01-16 for copper alloy containing cobalt, nickel and silicon.
This patent application is currently assigned to Wieland-Werke AG. The applicant listed for this patent is GBC Metals, LLC, Wieland-Werke AG. Invention is credited to Andreas Boegel, Frank M. Keppeler, Hans-Achim Kuhn, Frank N. Mandigo, Peter W. Robinson, Joerg Seeger, Derek E. Tyler.
Application Number | 20140014239 13/864568 |
Document ID | / |
Family ID | 30115641 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140014239 |
Kind Code |
A1 |
Mandigo; Frank N. ; et
al. |
January 16, 2014 |
COPPER ALLOY CONTAINING COBALT, NICKEL AND SILICON
Abstract
A process for manufacturing copper-nickel-silicon alloys
includes the sequential steps of casting the copper alloy; hot
working the cast copper-base alloy to effect a first reduction in
cross-sectional area; solutionizing the cast copper-base alloy at a
temperature and for a time effective to substantially form a single
phase alloy; first age annealing the alloy at a temperature and for
a time effective to precipitate an amount of a second phase
effective to form a multi-phase alloy having silicides; cold
working the multi-phase alloy to effect a second reduction in
cross-sectional area; and second age annealing the multiphase alloy
at a temperature and for a time effective to precipitate additional
silicides thereby raising conductivity, wherein the second age
annealing temperature is less than the first age annealing
temperature.
Inventors: |
Mandigo; Frank N.; (North
Branford, CT) ; Robinson; Peter W.; (Glen Carbon,
IL) ; Tyler; Derek E.; (Cheshire, CT) ;
Boegel; Andreas; (Weissenhorn, DE) ; Kuhn;
Hans-Achim; (Illertissen, DE) ; Keppeler; Frank
M.; (Stuttgart, DE) ; Seeger; Joerg; (Ulm,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wieland-Werke AG
GBC Metals, LLC |
Ulm
East Alton |
IL |
DE
US |
|
|
Assignee: |
Wieland-Werke AG
Ulm
IL
GBC Metals, LLC
East Alton
|
Family ID: |
30115641 |
Appl. No.: |
13/864568 |
Filed: |
April 17, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11588111 |
Oct 26, 2006 |
8430979 |
|
|
13864568 |
|
|
|
|
10610433 |
Jun 30, 2003 |
7182823 |
|
|
11588111 |
|
|
|
|
11246966 |
Oct 7, 2005 |
8257515 |
|
|
10610433 |
|
|
|
|
60393765 |
Jul 5, 2002 |
|
|
|
Current U.S.
Class: |
148/554 |
Current CPC
Class: |
C22C 9/06 20130101; H01L
2924/0002 20130101; H01R 13/03 20130101; H01L 2924/0002 20130101;
H01L 23/49579 20130101; C22F 1/08 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
148/554 |
International
Class: |
C22F 1/08 20060101
C22F001/08 |
Claims
1.-23. (canceled)
24. A process for the manufacture of a copper-base alloy,
comprising the sequential steps of: a). casting said copper-base
alloy containing, by weight, from 0.5% to 5.0% nickel and 0.1% to
1.5% silicon; b). hot working said cast copper-base alloy to effect
a first reduction in cross-sectional area; c). solutionizing said
cast copper-base alloy at a solutionizing temperature and for a
first time effective to substantially form a single phase alloy;
d). without any intervening cold work following said solutionizing,
first age annealing said substantially single phase alloy at a
first age anneal temperature and for a second time effective to
precipitate a second phase; e). cold working said multi-phase alloy
to effect a second reduction in cross-sectional area; and f).
second age annealing said multiphase alloy at a second age anneal
temperature and for a third time effective to precipitate an
additional amount of said second phase, wherein said second age
anneal temperature is less than said first age anneal
temperature.
25. The process of claim 24 wherein following said solutionizing
step, an average grain size of said wrought copper alloy is 20
microns or less.
26. The process of claim 24 including a step of cold working said
wrought copper alloy between said hot working step (b) and said
solutionizing step (c).
27. The process of claim 26 wherein both said hot working step and
said cold working steps constitute rolling and said wrought copper
alloy is formed into a strip.
28. A process for the manufacture of a copper-base alloy,
comprising the sequential steps of: a). casting said copper-base
alloy containing, by weight, from 0.5% to 5.0% nickel and 0.1% to
1.5% silicon; b). hot working said cast copper-base alloy in one or
more passes to form a hot worked product; c). solutionizing said
hot worked product at a temperature in excess of from 800.degree.
C. to a solidus temperature of said copper-base alloy; d). without
any intervening cold work following said solutionizing, first age
annealing said hot worked plate at a temperature of from
350.degree. C. to 600.degree. C. for from 30 minutes to 30 hours;
e). cold working said hot worked plate to a reduction in
cross-sectional area of from 10% to 50% to form a product; and f).
second age annealing said product at a temperature less than said
first precipitation annealing temperature.
29. The process of claim 28 wherein said hot working is at a
temperature of between 850.degree. C. and 1000.degree. C. and said
solutionizing temperature of between 800.degree. C. and
1000.degree. C.
30. The process of claim 29 further including a step of quenching
said copper base alloy following said hot working step (b).
31. The process of claim 30 wherein said first age anneal is at a
temperature of between 475.degree. C. and 550.degree. C. and said
second age anneal temperature is between 350.degree. C. and
500.degree. C.
32. The process of claim 31 further including a step of cold
working said copper alloy to a gauge effective for solutionizing
between said quench and said solutionizing step (c).
33. The process of claim 32 wherein said hot working step and said
cold working steps both constitute rolling thereby forming said
copper alloy into a strip.
34. The process of claim 32 wherein said copper alloy is selected
to have a composition of from 1% to 2.5% of nickel, from 0.5% to
2.0% of cobalt, with a total nickel plus cobalt content of from
1.7% to 4.3%, from 0.5% to 1.5% of silicon with a ratio of
(Ni+Co)/Si being between 2:1 and 7:1 and the balance copper and
inevitable impurities.
35. The process of claim 32 wherein said copper alloy is selected
to have a composition of from 1% to 2.5% of nickel, from 0.5% to
2.0% of cobalt, with a total nickel plus cobalt content of from
1.7% to 4.3%, from 0.5% to 1.5% of silicon with a ratio of
(Ni+Co)/Si being between 2:1 and 7:1, from an amount effective to
improve a combination of yield strength and electrical conductivity
up to 1.0% of silver, titanium, zirconium and combinations thereof,
up to 0.15% of magnesium and the balance copper and inevitable
impurities
36. The process of claim 32 wherein said copper alloy is selected
to have a composition of 2.2%-4.2% nickel, 0.25%-1.2% silicon,
0.05%-0.30% magnesium and the balance copper.
37. A process for the manufacture of a copper-base alloy,
comprising the sequential steps of: a). casting said copper-base
alloy containing, by weight, from 0.5% to 5.0% nickel and 0.1% to
1.5% silicon; b). hot working said cast copper-base alloy in one or
more passes to form a hot worked product; c). first age annealing
said hot worked product at a temperature of from 350.degree. C. to
600.degree. C. for from 30 minutes to 30 hours; d). cold working
said hot worked product to a reduction in cross-sectional area of
from 10% to 50% to form a product; and e). second age annealing
said product at a temperature less than said first precipitation
annealing temperature.
38. The process of claim 37 wherein said hot working is at a
temperature of between 850.degree. C. and 1000.degree. C.
39. The process of claim 38 further including a step of quenching
said copper base alloy following said hot working step (b).
40. The process of claim 39 wherein said first age anneal is at a
temperature of between 475.degree. C. and 550.degree. C. and said
second age anneal temperature is between 350.degree. C. and
500.degree. C.
41. The process of claim 40 wherein said copper alloy is selected
to have a composition of from 1% to 2.5% of nickel, from 0.5% to
2.0% of cobalt, with a total nickel plus cobalt content of from
1.7% to 4.3%, from 0.5% to 1% of silicon with a ratio of (Ni+Co)/Si
being between 3.5 and 5.5 and the balance copper and inevitable
impurities.
42. The process of claim 40 wherein said copper alloy is selected
to have a composition of from 1% to 2.5% of nickel, from 0.5% to
2.0% of cobalt, with a total nickel plus cobalt content of from
1.7% to 4.3%, from 0.5% to 1.5% of silicon with a ratio of
(Ni+Co)/Si being between 2:1 and 7:1, from an amount effective to
improve a combination of yield strength and electrical conductivity
up to 1.0% of silver, titanium, zirconium and combinations thereof,
up to 0.15% of magnesium and the balance copper and inevitable
impurities
43.-59. (canceled)
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This patent application claims priority to U.S. Provisional
Patent Application Ser. No. 60/393,765 that was filed on Jul. 5,
2002. The subject matter of that provisional patent application is
incorporated by reference in its entirety herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to copper alloys and to a
method for the manufacture of such alloys. In particular, in a
first embodiment, this invention relates to a copper alloy with
controlled additions of cobalt, nickel and silicon. In a second
embodiment, the invention relates to a copper alloy with controlled
additions of cobalt, nickel, silicon and silver. The alloys of the
invention are particularly suited to be formed into electrical
connectors, lead frames and other electric current carrying
components.
[0004] A third embodiment of the invention is drawn to a method to
process both.cndot.the alloys of the invention and other copper
alloys that contain nickel and silicon. More particularly, this
process includes hot working a copper-nickel-silicon alloy followed
by multiple annealing steps.
[0005] 2. Brief Description of Art
[0006] There is a need in the marketplace for metal alloys having a
combination of (1) good formability; (2) high strength; (3)
moderately high electrical conductivity; and (4) good stress
relaxation resistance. This combination of properties is
particularly important for parts that are loaned into various
electrical interconnections for use in under-the-hood automotive
connectors, multimedia (e.g. computers and consumer electronics)
electrical connectors, terminal applications, foils, wire and
powders, as well as other products. A number of commercial copper
alloys are available for use in these applications, but lack the
required combination of properties.
[0007] The first recited property, formability, is typically
evaluated by a bend test. A strip of the copper alloy at a
specified gauge and temper, is bent 90.degree. around a mandrel of
known radius. The minimum bend radius (mbr) as a function of strip
thickness (t) is then reported as mbr/t. The minimum bend radius is
the smallest radius mandrel about which a strip can be bent without
cracks visible at a magnification of 15.times.. Generally mbr/t is
reported for both good way bends, defined as the bend axis is
normal to the rolling direction, and for bad way bends, defined as
the bend axis is parallel to the rolling direction. An mbr/t of up
to 4t for both good way bends and bad way bends is deemed to
constitute good formability. More preferred is an mbr/t of up to
2.
[0008] The second recited property, moderate electrical
conductivity, is typically viewed as an electrical conductivity in
excess of 40% IACS. More preferably, the electrical conductivity is
in excess of 50% IACS. IACS refers to International Annealed Copper
Standard that assigns "pure" copper a conductivity value of 100%
IACS at 20.degree. C. Throughout this patent application, all
electrical and mechanical testing is performed at room temperature,
nominally 20.degree. C., unless otherwise specified. The qualifying
expression "about" indicates that exactitude is not required and
should be interpreted as .+-.10% of a recited value.
[0009] The third recited property, high strength, is viewed as a
yield strength in excess of 95 ksi (655.1 MPa) and preferably in
excess of 110 ksi (758.5 MPa). As the gauge of copper formed into
components decreases and as miniaturization of these components
continues, a combination of strength and conductivity for a given
temper will be more important than either strength or conductivity
viewed alone.
[0010] The fourth recited property, good resistance to stress
relaxation, is viewed as at least 70% of an imparted stress
remaining after a test sample is exposed to a temperature of
150.degree. C. for 3000 hours and at least 90% of an imparted
stress remaining after a test sample is exposed to a temperature of
105.degree. C. for 1000 hours.
[0011] Stress relaxation may be measured by a lift-off method as
described in ASTM (American Society for Testing and Materials)
Standard E328-86. This test measures the reduction in stress in a
copper alloy sample held at fixed strain for times up to 3000
hours. The technique consists of constraining the free end of a
cantilever beam to a fixed deflection and measuring the load
exerted by the beam on the constraint as a function of time at
temperature. This is accomplished by securing the cantilever beam
test sample in a specially designed test rack. The standard test
condition is to load the cantilever beam to 80% of the room
temperature 0.2% offset yield strength. If the calculated
deflection exceeds about 0.2 inch, the initial stress is reduced
until the deflection is less than 0.2 inch and the load is
recalculated. The test procedure is to load the cantilever beam to
the calculated load value, adjust a threaded screw in the test rack
to maintain the deflection, and locking the threaded screw in place
with a nut. The load required to lift the cantilever beam from the
threaded screw is the initial load. The test rack is placed in a
furnace set to a desired test temperature. The test rack is
periodically removed, allowed to cool to room temperature, and the
load required to lift the cantilever beam from the threaded screw
is measured. The percent stress remaining at the selected log times
is calculated and the data are plotted on semi-log graph paper with
stress remaining on the ordinate (vertical) and log time on the
abscissa (horizontal). A straight line is fitted through the data
using a linear regression technique. Interpolation and
extrapolation are used to produce stress remaining values at 1,
1000, 3000, and 100,000 hours.
[0012] The resistance to stress relaxation is orientation sensitive
and may be reported in the longitudinal (L) direction where
0.degree. testing is conducted with the long dimension of the test
sample in the direction of strip rolling and the deflection of the
test sample is parallel to the strip rolling direction. The
resistance to stress relaxation may be reported in the transverse
(T) direction where 90.degree. testing is conducted with the long
dimension of the test sample perpendicular to the strip rolling
direction and the deflection of the test sample is perpendicular to
the strip rolling direction.
[0013] One group of commercially available copper alloys commonly
used for electrical connectors are copper-nickel-silicon alloys.
The alloys are precipitation hardenable and achieve high strength
through the presence of nickel silicides as a second phase. One
copper-nickel-silicon alloy, designated copper alloy C7025 has a
composition of 2.2%-4.2% nickel, 0.25%-1.2% silicon, 0.05%-0.30%
magnesium and the balance copper. Alloy designations are in
accordance with the Copper Development Association (CDA) or New
York, N.Y. Copper alloy C7025 is disclosed in more detail in U.S.
Pat. Nos. 4,594,221 and 4,728,372 that are incorporated by
reference in their entireties herein.
[0014] U.S. Pat. No. 6,506,269 discloses copper alloys having
controlled additions of nickel, cobalt, silicon and either
magnesium or phosphorous. The patent discloses processing the
copper alloy by either a high temperature approach or a low
temperature approach. The high temperature approach yields
properties that fall short of the target combination of strength
and conductivity recited above. When processed by the high
temperature approach, Exemplary Alloy 1 is reported to have an
electrical conductivity of 51.9% IACS and a tensile strength of 709
MPa (102.9 ksi). When processed by the low temperature approach,
Exemplary Alloy 1 is reported to have an electrical conductivity of
51.5% IACS and a tensile strength of 905 MPa (131.3 ksi). However
the low temperature approach imparts excessive cold working into
the copper alloy which is expected to result in poor formability
and poor resistance to stress relaxation. U.S. Pat. No. 6,506,269
is incorporated by reference in its entirety herein.
[0015] Copper alloy C7027 has a composition of 0.28%-1.0% iron,
1.0%-3.0% nickel, 0.10%-1.0% tin, 0.20%-1.0% silicon and the
balance copper. Copper alloy C7027 is disclosed in more detail in
U.S. Pat. No. 6,251,199 that is incorporated by reference in its
entirety herein.
[0016] Japanese Kokai Hei 11 (1999)-222,641 discloses copper alloys
having controlled additions of nickel, silicon, magnesium and tin.
Optional additions include cobalt and silver.
[0017] The electrical and mechanical properties of precipitation
hardenable copper alloys are strongly influenced by the method of
manufacture of the copper alloy. One process for a
copper-nickel-silicon-indium-tin alloy is disclosed in U.S. Pat.
No. 5,124,124 and includes the processing sequence of continuous
cast, solutionize, quench, cold roll, precipitation anneal.
[0018] A different process for a copper-cobalt-phosphorous alloy
that may optionally contain up to 0.5% in combination of nickel and
silicon is disclosed in U.S. Pat. No. 5,147,469. This process
includes the process steps of cast, hot roll, quench, cold roll,
solutionize, quench, precipitation anneal, quench, cold roll,
anneal and quench.
[0019] The U.S. Pat. Nos. 5,124,124 and 5,147,469 are both
incorporated by reference in their entireties herein.
[0020] There remains a need for copper alloys and processes to
manufacture those copper alloys to have an improved combination of
properties for meeting the needs the automotive and multimedia
industries, as well as others where miniaturization is causing more
stringent strength and conductivity requirements to be imposed.
BRIEF SUMMARY OF THE INVENTION
[0021] A first aspect of the present invention is directed to a
wrought copper alloy that consists essentially of, by weight, from
1% to 2.5% of nickel, from 0.5% to 2.0% of cobalt, with a total
nickel plus cobalt content of from 1.7% to 4.3%, from 0.5% to 1.5%
of silicon with a ratio of (Ni+Co):Si of between 2:1 and 7:1, and
the balance copper and inevitable impurities. This wrought copper
alloy has an electrical conductivity in excess of 40% IACS.
[0022] A second aspect of the invention is drawn to the above
wrought copper alloy with a further inclusion of up to 1% of
silver, titanium, zirconium and mixtures thereof.
[0023] A third aspect of the invention is directed to a process for
the manufacture of a copper base alloy having a combination of high
electrical conductivity, high strength and good formability. The
process includes the sequential steps of (a). casting the
copper-base alloy; (b). hot working the cast copper-base alloy to
effect a first reduction in cross-sectional area; (c).
solutionizing the cast copper-base alloy at a temperature and for a
time effective to substantially form a single phase alloy; (d).
without any intervening cold work following solutionizing, first
age annealing the single phase alloy at a temperature and for a
time effective to precipitate an amount of a second phase effective
to form a multi-phase alloy having silicides; (e). cold working the
multi-phase alloy to effect a second reduction in cross-sectional
area; and (f). second age annealing the multiphase alloy at a
temperature and for a time effective to increase the volume
fraction of particles precipitated thereby raising conductivity,
wherein the second age annealing temperature is less than the first
age annealing temperature. This process is amenable to the copper
alloys of the first and second aspects of the invention as well as
selected other copper alloys.
[0024] Yet another aspect of the present invention is directed to a
second copper alloy that is amenable to processing by the
above-stated process. This copper alloy is suitable for forming
into an electrical connector and consists essentially of, by
weight, from 1% to 2.5% of nickel, from 0.5% to 2.0% of cobalt,
with a total nickel plus cobalt content of from 1.7% to 4.3%, from
0.5% to 1.5% of silicon with a ratio of (Ni+Co):Si being between
2:1 and 7:1, from an effective amount to improve a combination of
yield strength and electrical conductivity to 1.0% of silver,
titanium, zirconium and mixtures thereof, up to 0.15% of magnesium
and the balance is copper and inevitable impurities wherein the
wrought copper alloy has an electrical conductivity in excess of
40% IACS.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 graphically illustrates solvus temperature as a
function of nickel to cobalt weight ratio.
[0026] FIG. 2 shows in flow chart representation a first process
for the manufacture of the alloys of the invention and other
copper-nickel-silicon containing alloys.
[0027] FIG. 3 shows in flow chart representation an alternative
process for the manufacture of the alloys of the invention.
[0028] FIG. 4 shows in cross-sectional representation an electrical
connector assembly manufactured from the copper alloys of the
invention.
[0029] FIG. 5 graphically illustrates that the highest electrical
conductivity is achieved when (Ni+Co)/Si is between 3.5 and
6.0.
[0030] FIG. 6 illustrates the effect of age temperature on the
combination of electrical conductivity and yield strength of the
copper alloys of the invention processed according to a first prior
art process.
[0031] FIG. 7 illustrates the effect of age temperature on the
combination of electrical conductivity and yield strength of the
copper alloys of the invention processed according to a second
prior art process.
[0032] FIG. 8 illustrates the effect of age temperature on the
combination of electrical conductivity and yield strength of the
copper alloys of the invention processed according to a third prior
art process.
[0033] FIG. 9 illustrates the effect of second age temperature on
the combination of electrical conductivity and yield strength of
the copper alloys of the invention processed according to a process
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] In accordance with a first embodiment of the invention, the
copper alloy of the invention is a wrought alloy that contains
controlled amounts of nickel, cobalt and silicon and a controlled
ratio of nickel to cobalt. Further, the impurity levels,
particularly of zinc, chromium, magnesium, tin and phosphorous are
controlled. The copper alloy has an electrical conductivity in
excess of 40% IACS and is suitable for forming into an electrical
connector for applications such as automotive and multimedia.
[0035] Nickel and Cobalt
[0036] Nickel and cobalt combine with silicon to form silicides
that are effective for age hardening, to restrict grain growth and
to increase softening resistance. The nickel is present in an
amount of from 1% to 2.5%. When the nickel content is less than 1%,
the alloy has insufficient strength. When the nickel content
exceeds 2.5%, conductivity and hot working capability are reduced.
In a preferred embodiment, the nickel content is from 1.3% to 1.9%
and in a most preferred embodiment, the nickel content is from 1.3%
to 1.5%.
[0037] The cobalt is present in an amount of from 0.5% to 2.5%.
When the cobalt content is less than 0.5%, there is insufficient
precipitation of a cobalt-containing silicide second phase. In
addition, when there is a minimum cobalt content of 0.5% combined
with a minimum silicon content of 0.5%, the grain size of the alloy
after solutionizing is maintained at 20 microns or less. When the
cobalt content exceeds 2.5%, excessive second phase particles
precipitate leading to a reduction in formability and the copper
alloy may be imparted with undesirable ferromagnetic properties.
Preferably, the cobalt content is between about 0.5% and about 1.5%
and in a most preferred embodiment, the cobalt content is from
about 0.7% to about 1.2%.
[0038] During precipitation aging, a cobalt content of 1.0% or
higher is believed to suppress cellular precipitation in favor of
continuous precipitation. Cellular precipitation forms an irregular
array of parallel Cu-rich and Ni.sub.2Si lamellae forming behind a
moving grain boundary during an aging treatment. The silicide
lamellae are usually too large to provide effective age hardening
and the copper component is recrystallized or softened. More
preferred is continuous precipitation that provides sub-micron
coherent/semi-coherent particles that contribute to a strong age
hardening response.
[0039] The sum of the combination of nickel and cobalt is
maintained between 1.7 and 4.3 weight percent. Preferably, the sum
is from 2 to 4 weight percent and most preferably, the sum is
between 2.3 and 2.7 weight percent. Outside these ranges, it is
difficult to process the alloy to achieve the desired combination
of properties.
[0040] The nickel to cobalt weight ratio is maintained between
(Ni:Co)=0.5:1 and 5:1 to achieve the desired combination of
properties. Preferably, there is a small excess of nickel and the
nickel to cobalt with the weight ratio being between 1.01:1 and
2.6:1 and most preferably, the nickel to cobalt weight ratio is
between 1.05:1 and 1.5:1.
[0041] The interaction of nickel and cobalt in a copper alloy that
contains silicon is demonstrated with reference to FIG. 1, during
solutionizing, it is difficult to dissolve large amounts of cobalt
silicide into copper because the solvus temperatures of a
copper-cobalt-silicon alloy is relatively high, greater than
1050.degree. C. when cobalt+silicon equals 2.5% (reference point
2). Similarly, the solvus temperature of a copper-nickel-silicon
alloy is also relatively high, greater than 850.degree. C. when
nickel+silicon equals 4.0% (reference point 4). When a mixture of
nickel and cobalt is present, the nickel to cobalt ratio impacts
the solvus. When the amount of cobalt+nickel+silicon equals 3.0%,
the solvus is about 1000.degree. C. when the nickel to cobalt
weight ratio is 1:1 (reference point 6). The solvus is about
915.degree. C. when the nickel to cobalt weight ratio is 2:1
(reference point 7) and the solvus about 905.degree. C. when the
nickel to cobalt weight ratio is 4:1 (reference point 8).
Compositions with a lower solvus facilitate solid state dissolution
of cobalt, nickel and silicon into copper.
[0042] After the alloy has been processed as described below
whereby second phase silicides are caused to precipitate, electron
microscopy analysis of approximately 200 .ANG. diameter second
phase particles indicates that nickel substitutes directly for
cobalt; with nickel to cobalt ratios in the second phase particles
at a ratio that approximates that in the bulk alloy.
[0043] Silicon
[0044] Silicon is effective to increase strength by the formation
of second phase silicides when in the presence of silicide formers
such as nickel and cobalt. When the silicon content is less than
0.5%, an insufficient volume fraction of precipitate forms to
increase strength and it is difficult to control the solutionized
grain size. When the silicon content exceeds 1.5%, an excessive
number of coarse particles form. Preferably, the silicon content is
from 0.5% to 0.8% and most preferably, from 0.55% to 0.65%.
[0045] The electrical conductivities of the copper alloy of the
invention are highest when the weight ratio of (Ni+Co):Si ratio is
between 2:1 and 7:1. More preferably, the (Ni+Co):Si weight ratio
is between 3:1 and 6:1 and most preferably between 3.5:1 and 6:1.
Electrical conductivity is degraded if the alloying elements of
nickel, cobalt and silicon are present in the copper alloy in
amounts outside those defined by the ratios above.
[0046] Silver, Titanium and Zirconium
[0047] Small additions, less than 1% in total, of silver, titanium,
zirconium and combinations of these alloys improve the yield
strength/conductivity combination. Additions of silver also improve
the stress relaxation resistance.
[0048] In a second embodiment of the invention, the copper alloy
further includes up to 1% of silver, titanium, zirconium and
combinations thereof. Preferably, from 0.2% to 0.7% of these
elements. In preferred embodiments, the addition of one of silver
from 0.2% to 0.7%, titanium from 0.15% to 0.3% or zirconium from
0.2% to 0.5%.
[0049] Other Elements
[0050] The copper alloys of the invention may contain other,
unspecified, elements in amounts not effective to materially change
a basic property of the alloy and still be within the scope of the
claims that follow. In addition, the copper alloys will likely
contain certain inevitable impurities. However, impurities levels
and unspecified additions are limited as follows.
[0051] Zinc--the zinc content is maintained to a maximum of 0.5%
and preferably below 0.25%. When the zinc content exceeds this
maximum amount, the electrical conductivity decreases. Most
preferably the maximum zinc content is less than 0.1%.
[0052] Chromium--the chromium content is maintained to a maximum of
0.08%. When the chromium content exceeds this maximum amount, the
likelihood of forming coarse chromium-containing silicides
increases. Preferably, the chromium content is less than 0.02%.
[0053] Tin--the tin content is maintained to a maximum of 0.3% and
preferably less than 0.04%. When the tin content exceeds this
maximum amount, the electrical conductivity decreases. Most
preferably, the tin content is less than 0.02%.
[0054] Phosphorous--the phosphorous content is preferably less than
0.04%. When the phosphorous exceeds this level, cobalt phosphides
and nickel phosphides may precipitate reducing the amount of cobalt
and nickel available for silicide formation. Preferably, the
phosphorous content is less than 0.02%.
[0055] A small, but effective, amount of an element for
deoxidation, desulfurization and decarburization may also be
present. Typically these elements will be present in an amount of
less than 0.15% and preferably in an amount of from 0.005% up to
0.04%. Such elements include magnesium, calcium and misch metal.
Magnesium also increases stress relaxation resistance and softening
resistance during in-process aging anneal heat treatments and is
most preferred.
[0056] Other elements, that could be present in an amount of less
than 0.1% of any one element and 0.5%, in total, include iron,
manganese, aluminum, lead, bismuth, sulfur, tellurium, selenium,
beryllium, arsenic, antimony, and boron.
[0057] While this disclosure is particularly drawn to a process for
the manufacture of copper alloy strip, the alloys of the invention
and the processes of the invention are equally amenable to the
manufacture of other copper alloy products, such as foil, wire, bar
and tube. In addition, processes other than conventional casting,
such as strip casting, powder metallurgy and spray casting are also
within the scope of the invention.
[0058] With reference to FIG. 2, in accordance with a third
embodiment of the invention, the copper alloy is formed into strip
or other useful form. A mixture of the alloying components in the
proper proportions are added to molten copper. The molten metal is
poured into a mold suitable for direct chill (DC) casting and cast
10 to form an ingot. Other processes, such as spray casting, thin
strip casting and continuous or semi-continuous casting may be used
to present the alloy in a form suitable for hot rolling 12 or cold
rolling.
[0059] The alloy is hot worked 12 at a temperature of between
750.degree. C. and 1,050.degree. C. A preferred hot working
temperature is between 850.degree. C. and 1000.degree. C. For
strip, hot working typically is hot rolling, while for rod and
wire, extrusion may be employed. Following hot working the alloy is
typically cold worked 13 to a convenient gauge for solutionizing.
When in strip form, an exemplary thickness for solutionizing is
between about 0.002 inch and about 0.10 inch. The surface may be
conditioned, such as by milling or brushing, to obtain desired
surface characteristics.
[0060] The copper alloy is then solution annealed 14 at a first
temperature and a first time, the combination of temperature and
time being effective to substantially form a single phase alloy. A
suitable solutionizing temperature is between about 750.degree. C.
and about 1,050.degree. C. and a suitable time is from about 10
seconds to about one hour in a neutral or reducing atmosphere.
Generally, the more nickel present, the lower the solutionizing
temperature to reduce the formation of coarse grains, see Reference
Line 4 of FIG. 1. The more cobalt present, the higher the
solutionizing temperature to promote solid state dissolution, see
Reference Line 2 of FIG. 1. Referring back to FIG. 2, for strip, a
preferred solution anneal 14 is at a temperature of between about
800.degree. C. and about 1000.degree. C. for a time of between
about 10 seconds and about 5 minutes. A most preferred
solutionizing temperature is between 900.degree. C. and 975.degree.
C.
[0061] The solution anneal 14 is followed by a quench or rapid cool
16 to ambient temperature (ambient is nominally 20.degree. C.).
Preferably the cooling rate is in excess of 100.degree. C. per
minute. Following the quench or rapid cool, the copper alloy has an
electrical conductivity of less than about 25% IACS (14.5 MS/in)
and an equiaxed grain size that is preferably between about 5 and
20 .mu.m.
[0062] The sequence of solution anneal followed by quench may be
repeated multiple times, typically, an optional cold roll step is
inserted between such anneals. The multiple sequence may lead to a
more uniform particle distribution and texture. Generally, the
temperature of each solution anneal except the last one may be
anywhere within the broadly defined range above. The final solution
anneal temperature controls the grain size and is therefore more
precisely selected to achieve a preferred grain size and/or to
achieve a controlled volume, fraction of second phase particulate
with a preferred diameter.
[0063] Following the quench 16, the copper alloy is subjected to
first anneal 18 at a temperature and for a time effective to
precipitate an amount of second phase effective to form a
multiphase alloy having silicides. For strip, an exemplary first
anneal is at a temperature of between about 350.degree. C. and
about 600.degree. C. for a time of from 30 minutes to 30 hours in a
neutral or reducing atmosphere. More preferably, the first anneal
18 is at a temperature of between about 475.degree. C. and about
550.degree. C. for a time of from about 30 minutes to about 24
hours. A most preferred temperature range for the first age anneal
is from 490.degree. C. to 530.degree. C. An optimum combination of
electrical properties, mechanical properties, formability and
resistance to stress relaxation is achieved in the final product
when the first anneal 18 immediately follows the
solutionize.fwdarw.quench sequence, without any intervening cold
working.
[0064] An alternative process of the invention includes a cold roll
step between the quench and first age anneal, subject to the caveat
that the second age temperature is less than the first age
temperature.
[0065] Any of the anneals disclosed herein may be a step anneal
process. Typically, in a step anneal, the first step will be at a
higher temperature than the second step. Step anneals may result in
better combinations of strength and conductivity than a constant
temperature anneal.
[0066] The alloy is then cold worked 20 to a 5% to 50% reduction in
thickness and subjected to a second anneal 22 at a temperature and
time effective to increase conductivity. Preferably, the second
anneal 22 temperature is less than the first anneal 18 temperature.
For strip, an exemplary second anneal temperature is from about
350.degree. C. to about 600.degree. C. for a time of from about 10
seconds to 30 hours in a neutral or reducing atmosphere. More
preferably, the second anneal 26 is at a temperature of between
about 350.degree. C. and about 500.degree. C. for a time of from
about one hour to about 24 hours. The sequence of cold work 20
followed by second anneal 22 may be repeated multiple times until
the desired gauge and properties are achieved.
[0067] While the above process is particularly suited for the
copper alloys of the invention, the process is also amenable to
other precipitation hardening copper alloys. In particular
copper-M-silicon alloys where M is a silicide former that is
preferably nickel, cobalt or a mixture thereof, such as those
containing from 0.5% to 5% of M and 0.2% to 1.5% of silicon may
benefit from the process.
[0068] Another copper-base alloy system believed to also benefit
from the process of the invention is Cu--X--Ti where X is a
titanate former. Preferred compositions contain 0.35% to 5% of
titanium and 0.001% to 5% X, where X is selected from Ni, Fe, Sn,
P, Al, Zn, Si, Pb, Be, Mn, Mg, Bi, S, Te, Se, Ag, As, Sb, Zr, B, Cr
and Co and combinations thereof and the balance copper and
inevitable impurities. In a preferred embodiment, this alloy
contains 0.5% to 5% nickel and 0.35% to 2.5% of titanium as
disclosed in copending U.S. provisional patent application Ser. No.
60/410,592 that was filed Sep. 13, 2002.
[0069] In accordance with an alternative process, as illustrated in
FIG. 3, the copper alloy can be processed to finish gauge without
using an in-process solutionizing heat treatment. The steps of
casting 10, hot rolling 12 and first cold working 13 are as above.
After first cold work 13, the alloy is subjected to a first aging
anneal 18 at a temperature of between about 350.degree. C. and
about 600.degree. C. for a time of from about 30 minutes to about
30 hours in a neutral or reducing atmosphere. More preferably, the
first aging anneal 18 is at a temperature of from about 450.degree.
C. to about 575.degree. C. for a time of between about 30 minutes
and about 24 hours. As with the above process, the age anneals may
be in a step-wise fashion.
[0070] The first aging anneal 18 is followed by a second cold work
step 20 that preferably reduces the thickness of the copper alloy
by from about 10% to about 50% in thickness and is more preferably
from 15% to 30%. The second cold work step is followed by a second
aging anneal 22 that is at a lower temperature than the first aging
anneal, such as between about 350.degree. C. and about 500.degree.
C. for a time of between about 10 seconds and about 30 hours in a
neutral or reducing atmosphere. More preferably, the second aging
anneal 22 is at a temperature of between about 375.degree. C. and
about 475.degree. C. for a time of between about one hour and about
24 hours. A most preferred temperature range for the second age
anneal is from 400.degree. C. to 450.degree. C.
[0071] The steps of second cold work 20 followed by second aging
anneal 22 may be repeated multiple times until the copper alloy
strip is at final gauge. This alternative process is especially
good for making a product at higher electrical conductivity.
[0072] The alloys of the invention as well as other copper-nickel
(and/or cobalt)-silicon alloys made in accordance with the process
of the invention are particularly suited for the manufacture of
electrical and electronic connector assemblies of the type
illustrated in FIG. 4. This connector assembly 40 utilizes the
copper alloys of the invention and other copper alloys processed
according to the process of the invention. The connector assembly
40 includes a socket 42 and a plug or jack 44. The socket 42 is
formed from a strip of copper alloy and bent into a desired shape,
typically with a flat 46 for contacting the plug 44. Consistent
contact with the plug 44 is maintained by the stress generated in
the alloy strip by displacement of flats 46 caused by insertion of
the plug 44. When the connector assembly 40 is exposed to elevated
temperatures, and more notably when the temperature is in excess of
100.degree. C., this internal stress gradually dissipates (stress
relaxation) and contact between the flats 46 and the plug 44
deteriorates. The alloys of the invention and other copper alloys
processed according to the invention better resist elevated
temperature stress relaxation and produce an improved electrical
connector.
[0073] The invention is further described in detail by means of the
following Examples
EXAMPLES
[0074] Copper alloys having the compositions, in weight percent,
listed in Table 1 were prepared as either production bars
(identified with the prefix "RN") by direct chill (DC) casting into
6 inch.times.30 inch.times.25 foot bars or cast as 10 pound
laboratory ingots (identified with the prefix "3"). Unless
otherwise indicated in the Examples, production bars were processed
to mill plate by soaking at about 900.degree. C. and hot rolling to
0.6 inch. The hot rolled coil was soaked at about 600.degree. C.
for from about 5 to 15 hours and then milled to remove surface
oxides developed during hot rolling.
[0075] Unless otherwise indicated in the Examples, laboratory
ingots were processed to mill plate by melting in a silica crucible
and casting the molten metal into steel molds. After gating, the
ingots were 4 inch.times.4 inch.times.1.75 inch. The ingots were
soaked for about 3 hours at about 900.degree. C. and hot rolled to
1.1 inch. The hot rolled plate was reheated to about 900.degree. C.
and further hot rolled to about 0.5 inch. The 0.5 inch plate was
reheated to about 900.degree. C. and held at temperature for 5
minutes and then water quenched. The quenched plates were then
soaked at about 600.degree. C. for from about 5 to 15 hours,
trimmed and then milled to remove surface oxides developed during
hot rolling.
TABLE-US-00001 TABLE 1 Ingot ID Cobalt Silicon Magnesium Nickel
Ni:Co (Ni + Co)/Si J394 0.89 0.41 0.05 1.46 1.64 5.73 J395 -0- 0.62
0.08 2.72 -X- 4.39 J401 1.06 0.62 0.08 1.67 1.67 4.40 J620 2.26
1.02 0.11 2.39 1.06 4.56 J623 1.06 0.49 0.11 1.53 1.44 5.29 J624
1.59 0.78 0.11 2.32 1.45 5.01 J658 0.58 0.60 0.09 2.00 3.45 4.30
J659 1.04 0.60 0.09 1.45 1.39 4.15 J660 1.55 0.59 0.08 1.45 0.94
5.08 J661 2.02 0.60 0.09 1.50 0.74 5.87 J662 1.01 0.59 0.09 2.00
1.98 5.10 J663 1.42 0.59 0.08 1.97 1.39 5.75 J665 1.44 0.37 0.09
1.97 1.37 9.22 J666 1.86 0.80 0.09 1.46 0.78 4.15 J667 2.38 0.82
0.10 1.51 0.63 4.74 J668 1.95 0.77 0.09 1.95 1.04 4.97 J669 0.98
0.82 0.09 3.01 3.07 4.87 J671 2.92 1.00 0.10 1.52 0.52 4.44 J672
2.32 1.00 0.09 2.38 1.03 4.70 J673 1.55 1.07 0.08 2.88 1.86 4.14
J676 1.86 0.71 0.10 1.45 0.78 4.66 J684 2.02 0.72 0.10 1.53 + 0.76
4.93 0.23 Ti J686 1.92 0.71 0.11 1.50 + 0.78 4.82 0.28 Ag J687 1.82
0.69 0.11 1.46 + 0.80 4.75 0.14 Zr J716 1.73 0.74 0.10 1.72 0.99
4.60 J717 1.13 0.72 0.08 2.41 2.13 4.92 J718 0.51 0.73 0.09 3.08
6.04 4.92 J719 2.67 0.73 0.09 -0- -0- 3.65 J720 1.83 0.73 0.09 0.96
0.52 3.82 J721 1.37 0.73 0.09 1.45 1.06 3.86 J722 0.89 0.73 0.09
1.93 2.17 3.86 J723 0.55 0.70 0.10 2.27 4.13 4.03 J724 -0- 0.69
0.07 2.82 -X- 4.09 J727 0.43 0.71 0.09 1.73 4.02 3.03 J728 0.70
0.72 0.10 1.52 2.17 3.08 J729 0.95 0.75 0.10 1.14 1.20 2.79 J730
0.66 0.73 0.10 0.68 1.03 1.84 J731 -0- 0.49 0.10 2.44 -X- 4.98 J737
1.14 0.38 0.10 0.55 0.48 4.45 J738 1.32 0.44 0.10 0.68 0.52 4.55
J739 1.60 0.56 0.10 0.82 0.51 4.32 J740 2.06 0.71 0.10 0.98 0.48
4.28 J741 2.23 0.81 0.11 1.10 0.49 4.11 J742 2.57 0.94 0.08 1.24
0.48 4.05 J743 2.92 1.13 0.09 1.40 0.48 3.82 J772 4.35 1.40 0.09
1.92 0.44 4.48 J824 1.80 0.60 0.12 0.77 0.43 4.28 J834 1.77 0.60
-0- 0.76 + 0.43 4.22 0.20 Ag J835 1.88 0.64 -0- 0.75 0.40 4.11 J836
1.86 0.63 0.10 0.75 + 0.40 4.14 0.21 Ag J910 0.64 0.56 0.09 1.79
2.80 3.86 J954 1.17 0.60 -0- 1.22 + 1.04 3.98 0.052 Ag J955 1.18
0.59 -0- 1.21 + 1.03 4.05 0.099 Ag J956 1.17 0.59 -0- 1.22 + 0.19
1.04 4.05 Ag J969 1.04 0.61 0.001 1.37 1.32 3.95 J970 1.05 0.62
0.01 1.37 1.30 3.90 J971 1.04 0.62 0.021 1.38 1.33 3.90 J972 1.05
0.63 0.033 1.38 1.31 3.86 J973 1.05 0.62 0.044 1.39 1.32 3.94 J981
1.05 0.63 0.016 1.40 + 1.33 3.78 0.053 Ag J982 1.06 0.62 0.025 1.39
+ 1.31 3.95 0.099 Ag J983 1.07 0.63 0.023 1.40 + 1.31 4.05 0.195 Ag
J984 1.06 0.63 0.017 1.39 + 0.39 1.31 3.89 Ag J989 0.66 0.61 0.08
1.83 2.77 4.08 RN503014 1.97 0.74 0.09 1.48 0.75 4.60
Example 1
[0076] This example illustrates why the alloys of the invention
have silicon and cobalt contents both in excess of 0.5 percent by
weight.
[0077] Milled plate of the alloys listed in Table 2 was cold rolled
to 0.016 inch and solutionized at temperatures from 800.degree. C.
to 1,000.degree. C. for 60 seconds followed by a water quench 18.
The grain size was measured by optical microscopy and is reported
in Table 2. For alloy J724, at solutionizing temperatures of
900.degree. C. and 950.degree. C., the grain size is estimated
rather than measured.
TABLE-US-00002 TABLE 2 Average Grain Size Ingot ID Solution Heat
Treatment (microns) Alloys of the Invention J401 850.degree. C./60
seconds 6 950.degree. C./60 seconds 16 J667 925.degree. C./60
seconds 5 950.degree. C./60 seconds 5 975.degree. C./60 seconds 5
J671 925.degree. C./60 seconds 5 950.degree. C./60 seconds 5
975.degree. C./60 seconds 5 J719 900.degree. C./60 seconds 7
950.degree. C./60 seconds 8 1000.degree. C./60 seconds 14 J720
900.degree. C./60 seconds 6 950.degree. C./60 seconds 8
1000.degree. C./60 seconds 20 J721 900.degree. C./60 seconds 8
950.degree. C./60 seconds 8 1000.degree. C./60 seconds 30 J722
900.degree. C./60 seconds 9 950.degree. C./60 seconds 13
1000.degree. C./60 seconds 43 J723 900.degree. C./60 seconds 9
950.degree. C./60 seconds 12 1000.degree. C./60 seconds 39 RN503014
925.degree. C./60 seconds 5 950.degree. C./60 seconds 6 975.degree.
C./60 seconds 8 Comparative Examples J724 800.degree. C./60 seconds
7 Co = 0 840.degree. C./60 seconds 9 900.degree. C./60 seconds 60
950.degree. C./60 seconds 140 1000.degree. C./60 seconds 250 J394
850.degree. C./60 seconds 9 Si = 0.41% 880.degree. C./60 seconds 11
950.degree. C./60 seconds 34
[0078] The data of Table 2 illustrates that a controlled, fine
grain size of less than about 20 .mu.m in diameter is achieved at
solutionizing temperatures up to 950.degree. C. when the alloys
have greater than 0.5% of both cobalt and silicon. This grain size
control is not achieved when either the cobalt or the silicon
content is less than 0.5%.
Example 2
[0079] This example illustrates the effect of maintaining the
silicon content in excess of 0.5% and the total amount of nickel
and cobalt between 1.7% and 4.3% for a combination of high yield
strength and high electrical conductivity.
[0080] The milled plates were cold rolled to 0.016 inch and
solutionized at 950.degree. C. for 60 seconds followed by a water
quench. These alloys were first aged at 525.degree. C. for 3 hours,
cold rolled to a thickness reduction of 25% to 0.0120 inch gauge
and second aged at 425.degree. C. for 6 hours. The yield strength
and electrical conductivity combinations achieved are listed in
Table 3 as are 90.degree. good way and bad way bend
formability.
TABLE-US-00003 TABLE 3 Electrical Silicon Nickel + Cobalt Yield
Strength Conductivity 90.degree. MBR/t Alloy (weight %) (weight %)
(ksi) (% IACS) GW BW Alloys of the Invention J739 0.56 2.42 110
52.7 2.2 2.2 J740 0.71 3.04 113 52.8 2.7 2.3 J741 0.81 3.33 116
52.5 2.2 2.5 J742 0.94 3.81 118 51.7 2.3 3.9 J743 1.13 4.32 118
51.0 3.0 3.9 Comparative Examples J737 0.38 1.69 104 56.5 N.D. N.D.
J738 0.44 2.00 108 54.1 2.0 2.3 J772 1.40 6.27 121 47.0 3.9 3.9
[0081] The Table 3 data illustrates that 50% IACS electrical
conductivity is achieved at silicon levels from 0.4% to 1.13% and
(Ni+Co) levels from 1.7% to 4.3% when the Ni/Co and (Ni+Co)/Si
ratios are fixed at 0.5 and 3.8 to 4.6, respectively. The data
indicate alloys with greater than about 0.5% Si can reach the
combination of 110 ksi and 50% IACS. These data also illustrate
that increasing both the silicon and the (Ni+Co) levels within the
recited ranges raise the yield strength without a significant
change in electrical conductivity.
Example 3
[0082] This example illustrates that Ni/Co ratios above 2 provide
maximum yield strength while Ni/Co ratios less than 1 provide
better electrical conductivity at finish gauge. Milled plates of
the alloys listed in Table 4 were cold rolled to 0.016 inch and
solutionized at a temperature of between 900.degree. C. and
1000.degree. C. for 60 seconds followed by a water quench. These
alloys were first age annealed at 525.degree. C. for 3 hours, cold
rolled to a thickness reduction of 25% to 0.0120 inch gauge and
then second age annealed at 425.degree. C. for 6 hours.
[0083] The mechanical and electrical properties of the alloys at
finish gauge are recited in Table 4. The data show a reduced Ni/Co
ratio increases electrical conductivity and decreases yield
strength. The dependency of both yield strength and electrical
conductivity on Ni/Co ratio is unexpected.
TABLE-US-00004 TABLE 4 Finish Gauge Properties Yield Electrical
Strength Conductivity Alloy Ni:Co Ratio (ksi) (% IACS) J719 -0-
104.8 54.0 J720 0.52 113.0 47.7 J721 1.06 115.3 46.8 J722 2.17
116.6 45.3 J723 4.13 114.9 45.6
Example 4
[0084] This example illustrates that the highest combination of
yield strength and electrical conductivity is obtained when the
(Ni+Co)/Si ratio is between 3.5-6.0. Milled plate of the alloys
listed in Table 5 were cold rolled to 0.016 inch and solutionized
at 950.degree. C. for 60 seconds followed by a water quench. The
alloys were then first aged at 525.degree. C. for 3 hours, cold
rolled to a thickness reduction of 25% to 0.0120 inch gauge and
then second aged at 425.degree. C. for 6 hours. As shown in Table 5
and FIG. 5, a combination of a yield strength in excess of 110 ksi
and an electrical conductivity in excess of 40% IACS is achieved
when the (Ni+Co)/Si ratio is between 3.5 (reference line 50 in FIG.
5) and 6.0 (reference line 52 in FIG. 5).
TABLE-US-00005 TABLE 5 Finish Gauge Properties Yield Electrical
Strength Conductivity Alloy (Ni + Co)/Si (ksi) (% IACS) J730 1.84
94.0 29.6 J729 2.79 106.3 38.4 J727 3.03 102.7 36.7 J728 3.08 107.0
36.8 J722 3.86 116.6 45.3 J721 3.86 115.3 46.8 J723 4.03 114.9 45.6
J673 4.14 123.4 45.9 J659 4.15 114.7 49.2 J666 4.15 116.8 49.9 J716
4.60 116.8 47.7 J672 4.70 117.4 44.3 J669 4.87 123.6 43.0 J717 4.92
120.3 45.5 J718 4.92 123.9 45.8 J668 4.97 117.8 46.3 J660 5.08
112.1 47.7 J662 5.10 117.2 47.8 J663 5.75 114.7 41.7 J661 5.87
108.3 40.9 J665 9.22 97.7 33.3
Example 5
[0085] This example illustrates that small additions of silver,
titanium and zirconium increase the combination of yield strength
and electrical conductivity. Milled plates of the alloys listed in
Table 6 were cold rolled to 0.016 inch and solutionized at a
temperature of from 900.degree. to 975.degree. C. for 60 seconds
followed by a water quench. These alloys were first aged at
525.degree. C. for 3 hours, cold rolled 24 to a thickness reduction
of 25% to 0.0120 inch gauge and then second aged at 425.degree. C.
for 6 hours. The yield strength and electrical conductivity at
finish gauge are reported in Table 6 and illustrate that dilute
alloy additions of silver, titanium and zirconium improve the yield
strength/electrical conductivity combinations of the alloys.
TABLE-US-00006 TABLE 6 Finish Gauge Properties Yield Electrical
Solution Anneal Strength Conductivity Alloy Composition Temperature
(.degree. C.) (ksi) (% IACS) J676 1.86 - Co 900.degree. C. 110 49.6
1.45 - Ni 950.degree. C. 113 47.5 0.71 - Si 975.degree. C. 115 45.9
0.10 Mg J686 1.92 - Co 900.degree. C. 103 53.0 1.50 - Ni
950.degree. C. 114 48.7 0.71 - Si 975.degree. C. 117 47.8 0.11 - Mg
0.28 - Ag J684 2.02 - Co 900.degree. C. 104 54.0 1.53 - Ni
950.degree. C. 115 50.3 0.72 - Si 975.degree. C. 116 47.7 0.10 - Mg
0.23 - Ti J687 1.82 - Co 900.degree. C. 104 54.0 1.46 - Ni
950.degree. C. 115 49.6 0.69 - Si 975.degree. C. 119 48.8 0.11 - Mg
0.14 - Zr
[0086] Milled plates of the alloys listed in Table 7 were cold
rolled to 0.016 inch and solutionized at a temperature of
975.degree. C. for 60 seconds followed by a water quench. These
alloys were first aged at 525.degree. C. for 3 hours, cold rolled
24 to a thickness reduction of 25% to 0.0120 inch gauge and then
second aged at 400.degree. C. for 16 hours. The yield strength and
electrical conductivity at finish gauge are reported in Table 7 and
confirm that dilute alloy additions of silver improve the yield
strength/electrical conductivity combinations of the alloys even
when the processing is changed slightly compared to the Table 6
alloys.
TABLE-US-00007 TABLE 7 Finish Gauge Properties Yield Electrical
Solution Anneal Strength Conductivity Alloy Composition Temperature
(.degree. C.) (ksi) (% IACS) J835 1.88 - Co 975.degree. C. 111 54.5
0.75 - Ni 0.64 - Si J834 1.77 - Co 975.degree. C. 116 53.5 0.76 -
Ni 0.60 - Si 0.20 - Ag J836 1.86 - Co 975.degree. C. 114.5 52.8
0.75 - Ni 0.63 - Si 0.21 - Ag 0.10 - Mg
Example 6
[0087] This example illustrates how controlled additions of
magnesium and/or silver improve the stress relaxation resistance of
the alloys of the invention. The example further illustrates that
alloys having lower Ni:Co weight ratio (more Co-rich) have better
stress resistance relaxation than alloys having a higher Ni:Co
weight ration (more Ni-rich). This effect is observed whether or
not the alloy further includes silver.
[0088] Milled plates of the alloys listed in Table 8 were cold
rolled to a thickness of 0.0.16 inch. Alloys J824, J834, J835 and
J836 were then solutionized at 975.degree. C. for 60 seconds, first
aged at 525.degree. C. for 3 hours, cold rolled to a 25% reduction
and then second age annealed at 400.degree. C. for 16 hours.
[0089] The other alloys listed in Table 8 were solutionized at
925.degree. C. for 60 seconds, first aged at 500.degree. C. for 8
hours, cold rolled to a 25% reduction and second age annealed at
400.degree. C. for 16 hours.
TABLE-US-00008 TABLE 8 Percent Stress Remaining After 3000 hours
Alloy 105.degree. C.-L 150.degree. C.-L 150.degree. C.-T
175.degree. C.-L 200.degree. C.-L J835 89.5 80.2 -- 72.4 66.2 J824
96.3 90.0 -- 82.1 78.1 J834 -- 89.1 -- -- -- J836 97.1 91.2 -- 83.5
79.4 J969 91.3 79.5 77.1 66.9 63.2 J970 93.1 82.9 80.4 73.9 66.4
J971 93.8 85.0 83.7 78.7 68.4 3972 94.3 84.8 83.8 75.9 70.7 J973
94.1 85.8 83.3 77.0 68.1 J981 93.9 85.8 83.4 76.7 68.4 J954 86.3
75.7 -- 66.8 56.2 J982 95.6 87.2 85.0 77.1 70.6 J955 88.3 76.8 --
64.3 57.0 J983 95.8 88.6 87.8 78.3 72.6 J956 92.9 82.7 -- 71.0 65.1
J984 97.3 90.0 88.7 76.3 72.0
[0090] Comparing the stress remaining for alloys J824 (0.12% Mg)
and J834 (0.20% Ag) to the stress remaining for alloy J835 (no Mg
or Ag) shows that controlled additions of either Mg or Ag improve
resistance to stress relaxation. J836 shows that combinations of Mg
and Ag also enhance resistance to stress relaxation resistance.
[0091] Comparing alloy J956 (0.19% Ag) to alloys J954 and J955
shows that about 0.2% Ag is the minimum effective to significantly
improve stress relaxation resistance. Further comparing alloy J981
to alloy J954 or alloy J982 to alloy J955 shows that an addition of
magnesium to a silver-containing alloy of the invention further
enhances the resistance to stress relaxation.
[0092] Comparing alloy J835 (Ni:Co=0.40) to alloy J969 (Ni:Co=1.32)
and comparing alloy J834 (Ni:Co=0.43) to alloy J956 (Ni:Co=1.04)
shows that the cobalt-rich compositions have better resistance to
stress relaxation than the nickel-rich composition, both in the
presence of silver and in the absence of silver.
Example 7
[0093] This example demonstrates how the process of the invention
results in a copper-nickel-silicon alloy with higher electrical
conductivity when compared to similar alloys processed by
conventional process routes. When the alloy further contains
cobalt, this increase in electrical conductivity is accompanied by
an increase in yield strength.
[0094] Milled plate of the alloys listed in Table 9 was cold rolled
to either 0.016 inch or 0.0123 inch and solutionized between
800.degree. C. and 950.degree. C. for 60 seconds followed by a
water quench. After solutionizing, in accordance with prior art
processing, the quenched alloys were cold rolled either 25% in
thickness from 0.016 inch to 0.0120 inch or 35% in thickness from
0.123 inch to 0.008 inch gauge and aged at 450.degree. C. for 2
hours for the 25% cold roll reduction or 435.degree. C. for 3 hours
for the 35% cold roll reduction. The mechanical properties at
finish gauge are listed in Table 9.
TABLE-US-00009 TABLE 9 Ultimate Yield Tensile Solution Strength
Strength % Elon- % Alloy Anneal (ksi) (ksi) gation IACS J395 (0.008
inch 800.degree. C./60 sec 107 113 9 39.7 thick and 35% 840.degree.
C./60 sec 110 117 6 36.8 cold roll and age) 880.degree. C./60 sec
110 117 4 36.9 J394 (0.008 inch 800.degree. C./60 sec 84 88 6 47.6
thick and 35% 840.degree. C./60 sec 85 90 6 45.0 cold roll and age)
880.degree. C./60 sec 88 94 6 41.7 J401 (0.008 inch 800.degree.
C./60 sec 93 98 8 43.0 thick and 35% 840.degree. C./60 sec 94 99 8
41.6 cold roll and age) 880.degree. C./60 sec 98 104 7 39.9
RN503014 (0.012 950.degree. C./60 sec 101 107 3 35.6 inch thick and
25% cold roll and age) J719 (0.012 inch 950.degree. C./60 sec 92 97
6 43.7 thick and 25% cold roll and age)
[0095] Milled plate of the same alloys was cold rolled to 0.0160
inch and solutionized at temperatures between 850.degree. and
975.degree. C. for 60 seconds followed by a water quench. In
accordance with the process of the invention, without any
intervening cold work, the alloys were first aged at 525.degree. C.
for 3 hours, cold rolled to a thickness reduction of 25% to 0.0120
inch gauge and second aged at 400.degree. C. for 3 hours. The
mechanical properties at finish gauge are reported in Table 10.
TABLE-US-00010 TABLE 10 Ultimate Yield Tensile Solution Strength
Strength % Elon- % Alloy Anneal (ksi) (ksi) gation IACS J395
850.degree. C./60 sec 101 110 7 46.1 (No Co) 950.degree. C./60 sec
102 110 7 46.5 J394 850.degree. C./60 sec 93 98 6 50.3 950.degree.
C./60 sec 108 113 5 46.9 J401 850.degree. C./60 sec 99 104 4 49.2
950.degree. C./60 sec 117 122 5 45.7 RN503014 925.degree. C./60 sec
103 108 6 49.8 (0.012 950.degree. C./60 sec 111 116 5 48.8 inch
thick) 975.degree. C./60 sec 120 126 6 46.1 J719 900.degree. C./60
sec 96 100 6 55.4 (No Ni) 950.degree. C./60 sec 106 110 5 52.7
[0096] A comparison of data in Table 9 to that in Table 10 proves
that the process of the invention, using two aging anneals with the
first aging anneal following solutionizing without intervening cold
work, significantly increases electrical conductivity. For alloys
containing cobalt, this increase in electrical conductivity is
combined with an increase in strength.
Example 8
[0097] This example also illustrates that cobalt-containing alloys
with both higher strengths and higher electrical conductivities are
obtained using the process of the invention. Milled plates of the
alloys listed in Table 11 were cold rolled to 0.016 inch and
solutionized at either 850.degree. or 950.degree. C. for 60 seconds
followed by a water quench. These alloys were first aged at
525.degree. C. for 3 hours and then cold rolled to a thickness
reduction of either 15% or 25% to 0.0136 inch or 0.0120 inch gauge.
Following cold rolling, the alloys were second aged at either
400.degree. C. for 3 hours or 450.degree. C. for 3 hours. The
mechanical properties at finish gauge are reported in Table 10 and
demonstrate that the yield strength of the alloys is increased by
about 20-30 ksi if the solutionized and first aged (525.degree.
C./3 Hrs) strip is cold rolled 25%, and then second aged at
400-450.degree. C. for 3-6 hours. The alloys with the cobalt
additions show significantly higher yield strengths than the alloy
without cobalt, J395, an unexpected finding.
TABLE-US-00011 TABLE 11 Properties Second Yield Electrical Age
Strength Conductivity Tem- (ksi) (% IACS) Solutionize % Cold pera-
After After After After Temperature Roll ture 1.sup.st 2.sup.nd
1.sup.st 2.sup.nd Alloy (.degree. C.) Reduction (.degree. C.) Age
Age Age Age J395 850.degree. C. 15% 450.degree. C. 83.4 91.8 40.8
48.3 0 cobalt 25% 400.degree. C. 83.4 95.5 40.8 46.2 950.degree. C.
15% 450.degree. C. 87.6 95.6 40.9 50.0 25% 400.degree. C. 87.6 98.4
40.9 45.8 J398 850.degree. C. 15% 450.degree. C. 78.4 98.0 43.8
48.7 0.52 25% 400.degree. C. 78.4 102.7 43.8 47.0 cobalt
950.degree. C. 15% 450.degree. C. 90.6 108.6 40.0 43.9 25%
400.degree. C. 90.6 112.4 40.0 43.4 J394 850.degree. C. 15%
450.degree. C. 64.8 90.7 47.2 52.8 0.89 25% 400.degree. C. 64.8
95.1 47.2 51.1 cobalt 950.degree. C. 15% 450.degree. C. 78.9 101.4
43.2 48.4 25% 450.degree. C. 78.9 102.7 43.2 47.4 J623 850.degree.
C. 15% 450.degree. C. 65.9 88.4 46.1 50.1 1.06 25% 400.degree. C.
65.9 94.0 46.1 48.8 cobalt 950.degree. C. 15% 450.degree. C. 79.1
103.2 42.5 45.1 25% 400.degree. C. 79.1 109.8 42.5 45.4 J401
850.degree. C. 15% 450.degree. C. 71.1 93.4 44.1 51.0 1.06 25%
400.degree. C. 71.1 96.5 44.1 47.9 cobalt 950.degree. C. 15%
450.degree. C. 87.5 108.7 40.4 46.5 25% 400.degree. C. 87.5 112.8
40.4 44.6 J624 850.degree. C. 15% 450.degree. C. 71.8 92.4 44.2
47.4 1.59 25% 400.degree. C. 71.8 98.5 44.2 46.8 cobalt 950.degree.
C. 15% 450.degree. C. 85.1 110.0 39.7 42.0 25% 400.degree. C. 85.1
113.7 39.7 42.0 J620 850.degree. C. 15% 450.degree. C. 75.9 95.2
45.5 48.8 2.26 25% 400.degree. C. 75.9 101.1 45.5 48.3 cobalt
950.degree. C. 15% 450.degree. C. 93.9 114.2 40.4 44.3 25%
400.degree. C. 93.9 119.6 40.4 43.5
Example 9
[0098] This example illustrates that the process of the invention
results in copper alloys with a higher combination of yield
strength and electrical conductivity when compared to a number of
prior art processes. The example further illustrates that the
highest combination of properties is achieved when the temperature
of the second age anneal is less than the temperature of the first
age anneal.
[0099] Milled plate of alloy RN503014 was cold rolled to 0.016 inch
and solutionized at 950.degree. C. for 60 seconds followed by a
water quench. This solutionized strip was then processed according
to the process sequences delineated in Table 12. Process 4 is the
process of the invention. The effect of age temperature on yield
strength and electrical conductivity for Process 1 is illustrated
in FIG. 6. The effect of age temperature on yield strength and
electrical conductivity for Process 2 is illustrated in FIG. 7. The
effect of age temperature on yield strength and electrical
conductivity for Process 3 is illustrated in FIG. 8. The first age
temperature for Process 4 was 525.degree. C. for 3 hours. The
effect of second age temperature on yield strength and electrical
conductivity for Process 1 is illustrated in FIG. 9.
TABLE-US-00012 TABLE 12 Process 1 Process 2 Process 3 Process 4 Age
Cold Roll 25% Cold Roll 50% First Age Age Age Cold Roll 25% Second
Age
[0100] Table 13 reports the conductivity at maximum yield strength
and the yield strength at maximum conductivity for the alloy as
processed by each of the four process paths. Only Process 4
achieves the highest combination of high yield strength and
electrical conductivity.
TABLE-US-00013 TABLE 13 At Maximum Yield Strength At Maximum
Conductivity Yield Strength Conductivity Yield Strength
Conductivity Process (ksi) (% IACS) (ksi) (% IACS) 1 85 45 72 49 2
107 42 84 49 3 110 41 79 50 4 120 45 110 50
[0101] FIG. 9 further illustrates that under the process of the
invention with a first age temperature of about 525.degree. C., the
optimum combination of yield strength and electrical conductivity
is achieved when the second age temperature is at a lower
temperature and, preferably, the second age temperature is in the
range of 400.degree. C. and 450.degree. C.
Example 10
[0102] This example illustrates that improved combinations of
properties are obtained using the process of the invention as
compared to either the high temperature or the low temperature
process disclosed in U.S. Pat. No. 6,506,269. Milled plate of alloy
J910 was cold rolled to 0.016 inch and solutionized at 925.degree.
C. for 60 seconds. The alloy was first age annealed at 500.degree.
C. for 8 hours, cold rolled 25% to 0.012 inch and second age
annealed at 400.degree. C. for 16 hours.
[0103] Milled plate of alloy J989 was divided into half (alloys
J989-A and J989-B). Alloy J989-A was processed according to the
high temperature process of U.S. Pat. No. 6,506,269, cold roll to
0.030 inch, solutionize 925.degree. C. for 60 seconds, cold roll
60% to 0.012 inch and age anneal at 525.degree. C. for 6 hours.
[0104] Alloy J989-B was processed according to the low temperature
process of U.S. Pat. No. 6,506,269, cold roll to 0.12 inch, first
age anneal at 400.degree. C. for 6 hours, cold roll 60% to 0.048
inch, second age anneal at 400.degree. C. for 6 hours, cold roll
75% to 0.012 inch and third age anneal at 430.degree. C. for 6
hours.
[0105] Table 14 recites the measured properties of the alloys.
TABLE-US-00014 TABLE 14 Electrical Yield Strength Conductivity
MBR/t Process (ksi) (% IACS) GW BW J910 114.5 51.8 J989-A 94.4 45.5
2.2 3.9 J989-B 117.6 51.4 2.2 8.8
[0106] While the bend properties of J910 were not measured, based
on data from similar alloys processed according to the invention an
MBR/t for the good way is expected to be 2.2 and an MBR/t for the
bad way is expected to be 2.5. This shows that the process of the
invention results in a copper alloy having improved bends at a
similar combination of yield strength and electrical conductivity
when compared to a U.S. Pat. No. 6,506,269 process.
Example 11
[0107] This example illustrates that the electrical conductivity
response at finish gauge is dependent on both first and second age
treatments and that the electrical conductivity shows a larger
increase and higher values after the second age anneal when the
first age anneal is at 525.degree. C.
[0108] Milled plate of alloy J648 was cold rolled to 0.016 inch and
solution heat treated at temperatures from 950.degree. C. for 60
seconds followed by a water quench. The alloy was then first aged
for 3 hours at either 475.degree. C. or at 525.degree. C. for 3
hours. The mill plate was then cold rolled for a thickness
reduction of 25% to 0.0120 inch and second aged at temperatures of
from 400.degree. C.-450.degree. C. for either 3 or 6 hours.
[0109] As shown in Table 15, the electrical conductivity response
at finish gauge is dependent on both first and second age
treatments. These data also indicate the electrical conductivity
shows a larger increase and higher values after the second age
anneal when the first age anneal is at 525.degree. C. This
unexpected aging response enables the alloys to approach the
desired combination of high strength and high conductivity.
TABLE-US-00015 TABLE 15 Finish Gauge Properties First Age Second
Age Second Age Yield Temperature Temperature Time Strength
Conductivity .DELTA. % (.degree. C.) (.degree. C.) (hours) (ksi) (%
IACS) IACS 475 None None 111.4 36.8 -- 475 400 3 112.9 40.7 3.9 475
400 6 114.9 40.9 4.1 475 425 6 112.8 40.7 3.9 475 450 3 113.1 39.8
3.0 525 None None 111.2 41.2 -- 525 400 3 111.9 46.9 5.7 525 400 6
109.5 49.4 8.2 525 425 6 110.7 50.1 8.9 525 450 3 109.8 48.2
7.0
Example 12
[0110] This example illustrates that the electrical conductivity of
copper alloy C7025 is increased by processing according to the
current invention.
[0111] Milled plates of alloys J724 and J731 were cold rolled to
0.016 inch and solution heat treated at temperature of between
780.degree. C. and 840.degree. C. and then water quenched to
provide a recrystallized strip. Without intervening cold work, the
alloys were then age annealed at 525.degree. C. for 3 hours, cold
rolled to a finish gauge of 0.012 inch and aged at either
400.degree. C. for 3 hours or 425.degree. C. for 6 hours.
[0112] The mechanical properties at finish gauge are recited in.
Table 16. The combination of strength and bend properties is
comparable to conventionally processed copper alloy C7025 which in
a similar temper has a yield strength of between 95 and 100 ksi and
an electrical conductivity between 40% and 45% IACS. The process of
the invention achieved a conductivity exceeding that of
conventionally processed C7025 without a loss of yield
strength.
TABLE-US-00016 TABLE 16 Yield Tensile Elon- Electrical Second Age
Strength Strength gation Conductivity 90.degree. MBR/t Ingot Anneal
(ksi) (ksi) (%) (% IACS) GW BW J724 400.degree. C./3 hours 95.2
103.4 8 47.6 -- -- J724 425.degree. C./6 hours 95.1 103.9 8 52.5
1.5 0.9 J731 400.degree. C./3 hours 96.7 103.6 8 52.1 -- -- J731
425.degree. C./6 hours 95.0 102.9 8 55.8 1.4 1.3
[0113] While the invention has been described above with reference
to specific embodiments thereof, it is apparent that many changes,
modifications, and variations can be made without departing from
the inventive concept disclosed herein. Accordingly, it is intended
to embrace all such changes, modifications and variations that fall
within the spirit and broad scope of the appended claims. All
patent applications, patents and other publications cited herein
are incorporated by reference in their entirety.
* * * * *