U.S. patent number 3,772,093 [Application Number 05/196,004] was granted by the patent office on 1973-11-13 for copper base alloys.
This patent grant is currently assigned to Olin Corporation. Invention is credited to Alan J. Goldman, Richard D. Lanam, Stanley Shapiro, Derek E. Tyler.
United States Patent |
3,772,093 |
Shapiro , et al. |
November 13, 1973 |
COPPER BASE ALLOYS
Abstract
The disclosure teaches novel copper base alloys having improved
toughness and stress corrosion resistance. The copper alloys
contain from 12.5 to 30 percent nickel, from 12.5 to 30 percent
manganese, a material selected from the group consisting of
aluminum from 0.01 to 5 percent, boron from 0.001 to 0.1 percent,
magnesium from 0.01 to 5 percent and mixtures thereof and tin in an
amount from 0.01 to 2 percent.
Inventors: |
Shapiro; Stanley (New Haven,
CT), Goldman; Alan J. (Silver Spring, MD), Tyler; Derek
E. (Cheshire, CT), Lanam; Richard D. (Hamden, CT) |
Assignee: |
Olin Corporation (New Haven,
CT)
|
Family
ID: |
22723728 |
Appl.
No.: |
05/196,004 |
Filed: |
November 5, 1971 |
Current U.S.
Class: |
148/412; 420/473;
420/471 |
Current CPC
Class: |
C22C
9/06 (20130101); C22C 9/05 (20130101) |
Current International
Class: |
C22C
9/05 (20060101); C22C 9/06 (20060101); C22c
009/02 (); C22c 009/06 (); C22f 001/08 () |
Field of
Search: |
;75/154,153,157.5,159,161,162,164 ;148/12.7,32,32.5,160 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
578,223 |
|
Jun 1946 |
|
GB |
|
557,170 |
|
May 1946 |
|
GB |
|
577,597 |
|
May 1946 |
|
GB |
|
719,979 |
|
Apr 1942 |
|
DD |
|
224,220 |
|
Oct 1964 |
|
JA |
|
Other References
Electrolytic Manganese and Its Alloys, 1952, Ronald Press Co.,
pages 146, 147 & 188-191..
|
Primary Examiner: Lovell; Charles N.
Claims
What is claimed is:
1. A wrought copper base alloy having improved toughness and stress
corrosion resistance consisting essentially of from 12.5 to 30
percent nickel, from 12.5 to 30 percent manganese, from 0.01 to 2
percent tin, and a material selected from the group consisting of
aluminum from 0.01 to 5 percent, magnesium from 0.01 to 5 percent,
boron from 0.001 to 0.1 percent and mixtures thereof, balance
essentially copper, wherein the nickel to manganese ratio is from
0.75 to 1.5, said alloy having an average grain size less than
0.015 mm. and an intragranular precipitation of discrete
manganese-nickel rich particles.
2. An alloy according to claim 1 wherein the nickel content is from
15 to 25 percent and the manganese content is from 15 to 25
percent.
3. An alloy according to claim 1 wherein said material is aluminum
in an amount from 0.6 to 5 percent.
4. An alloy according to claim 1 wherein said material is magnesium
in an amount from 0.6 to 5 percent.
5. An alloy according to claim 1 wherein said material is aluminum
in an amount from 0.01 to 0.75 percent.
6. An alloy according to claim 1 wherein said material is magnesium
in an amount from 0.01 to 0.75 percent.
7. An alloy according to claim 1 wherein the tin content is from
0.5 to 1.0 percent.
8. An alloy according to claim 1 containing a material selected
from the group consisting of iron from 0.05 to 1 percent, cobalt
from 0.05 to 1 percent and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
Copper base alloys are known which contain relatively large amounts
of nickel and manganese. Alloys of this type are highly desirable
since they are capable of obtaining yield strengths in excess of
200 ksi upon aging. In addition, these alloys appear to have
reasonable processing and in particular are not quench
sensitive.
The presence of a marked aging response to obtain high strengths in
copper-nickel-manganese alloys is known. It has been found that
different types of precipitation reactions may occur in this alloy
system, depending on the aging temperature. For example, aging at a
low temperature, such as 350.degree.C., yields a cellular
precipitate which nucleates at the grain boundaries and with time
grows throughout the entire grain. The cellular precipitate
consists of adjacent lamellae of a manganese-nickel rich phase and
the copper-rich solid solution. Aging at higher temperatures, such
as 450.degree.C., yields mainly finely dispersed, spherical
precipitates of the manganese-nickel rich phase within the grains
and only a small amount of the cellular precipitate at the grain
boundaries.
However, in any event, the presence of a cellular precipitate at
grain boundaries is generally found to have deleterious effects on
alloy properties, such as fracture toughness and stress corrosion
resistance. This is indeed found to be the case in these alloys and
is a significant factor in the limited commerical success which
these alloys have enjoyed.
It would be highly desirable to develop an alloy within the
copper-manganese-nickel alloy system which has increased fracture
toughness. It would also be highly desirable to improve the stress
corrosion resistance of such alloys.
Accordingly, it is a principal object of the present invention to
develop a copper base alloy containing relatively large amounts of
nickel and manganese.
It is an additional object of the present invention to develop an
alloy as aforesaid which is capable of obtaining yield strengths in
excess of 200 ksi upon aging.
It is a still further object of the present invention to develop an
alloy as aforesaid which is readily processed commercially and
which is characterized by improved fracture toughness.
It is a still further object of the present invention to provide a
copper base alloy with good stress corrosion resistance, good
ductility, toughness and excellent yield strength
characteristics.
Further objects and advantages of the present invention will appear
from the ensuing discussion.
SUMMARY OF THE INVENTION
In accordance with the present invention, it has now been found
that the foregoing objects and advantages may be readily
obtained.
The alloy of the present invention consists essentially of from
12.5 to 30 percent nickel, from 12.5 to 30 percent manganese, from
0.01 to 2 percent tin and a material selected from the group
consisting of aluminum from 0.01 to 5 percent, magnesium from 0.01
to 5 percent, boron from 0.001 to 0.1 percent and mixtures thereof,
balance essentially copper, wherein the nickel to manganese ratio
is at least 0.75 and preferably 1.0 or higher.
BRIEF DESCRIPTION OF DRAWINGS
The drawing which forms a part of the present specification is a
graph plotting the fracture toughness as a function of yield
strength for the alloy of the present invention (Alloy B) and a
comparative alloy (Alloy A) .
DETAILED DESCRIPTION
In accordance with the present invention, the foregoing alloy has
been found to obtain surprisingly improved fracture toughness while
retaining the excellent strength characteristics of this alloy
system.
This enables the attainment of several significant advantages. The
alloy of the present invention is an excellent lower priced
replacement for beryllium-copper, with increased fracture
toughness. The alloy of the present invention achieves levels of
fracture toughness approaching high alloy steels which are limited
in applicability by poor corrosion resistance. The alloys of the
present invention are superior to maraging steels in marine
environments since the alloys of the present invention are not
susceptible to hydrogen embrittlement. In addition, the alloys of
the present invention are characterized by excellent stress
corrosion resistance.
In accordance with the present invention, the instant alloys
contain from 12.5 to 30 percent nickel, and from 12.5 to 30 percent
manganese. Preferably, both the nickel and manganese contents
should range from 15 to 25 percent. The nickel to manganese ratio
must be at least 0.75 and preferably 1.0 or higher.
The nickel and manganese contents have an affect on aging response,
yield strength and workability of the alloys. The lower the
manganese and nickel content, the slower the aging response and
lower the maximum yield strength obtainable upon aging, especially
below 12.5 percent nickel and manganese. On the other hand,
increasing the amount of nickel and manganese has deleterious
effects on the workability of the alloys during processing,
especially over 30 percent each of nickel and manganese.
As indicated hereinabove, the preferred nickel to manganese ratio
is 1.0 or higher. The maximum aging response is obtained for a
given amount of nickel and manganese when the nickel to manganese
ratio is about 1.0. If the ratio is less than 1.0, an excess of
manganese exists which can have adverse effects on the stress
corrosion resistance of the alloy. A ratio greater than about 1.5
does not give improved results over a ratio of about 1.0 and is
more expensive due to the high cost of the nickel.
In addition to the foregoing, the alloy of the present invention
contains a material selected from the group consisting of aluminum
in an amount from 0.01 to 5.0 percent, magnesium from 0.01 to 5.0
percent, boron from 0.001 to 0.1 percent and mixtures thereof. Each
of these elements act as deoxidizers and assist in the melting of
the alloys. Aluminum is the preferred addition since it tends to
form a protective oxide coating during melting. When aluminum is
used as a deoxidant only, the aluminum should be added in an amount
from 0.01 to 0.75 percent. Similarly, magnesium should be used in
an amount from 0.01 to 0.75 percent as a deoxidant. In addition,
the aluminum and magnesium may be used as advantageous alloying
additions in amounts of greater than 0.6 percent for increased
corrosion resistance and fracture toughness. The aluminum when used
at the higher levels, also tends to modify the cellular precipitate
at the grain boundaries.
The tin component is particularly important and is used in an
amount from 0.01 to 2 percent and preferably from 0.5 to 1.0
percent. Tin tends to alter the morphology of the cellular
precipitate at the grain boundary.
In addition to the foregoing, several additives are particularly
advantageous. A zinc component may be present in an amount from 0.1
to 3.5 percent and preferably 1 to 3 percent. Increased amounts of
zinc give rise to a decrease in the stress corrosion resistance and
fracture toughness.
The zinc addition controls the grain size, reduces the cellular
precipitate at the grain boundaries, changes the morphology of the
inclusions, promotes sound castings and increases the aging
response of the alloy.
In addition, zirconium and/or titanium are preferred alloying
additions in amounts 0.01 to 2.0 percent each, and preferably from
0.15 to 0.30 each. These materials tend to desirably change
morphology and chemistry of inclusions and desirably change
morphology of cellular precipitate at grain boundaries.
In addition, chromium is a desirable addition in an amount from
0.01 to 1.0 percent, and preferably from 0.15 to 0.30 percent.
Chromium tends to control the grain size and change the morphology
and chemistry of inclusions.
Additional desirable alloying additions are cobalt and/or iron in
amounts from 0.05 to 1.0 percent each, and preferably from 0.2 to
0.5 percent each. These materials also tend to control the grain
size.
Naturally, other additives may be desirable in order to achieve or
accentuate a particular property and conventional impurities may be
tolerated.
The casting of the alloy of the present invention is not
particularly significant. Any convenient method of casting may be
employed. Pouring temperatures in the range of about 1,000 to
1,200.degree.C. are preferably employed, with an optimum pouring
temperature in the range of 1,050.degree. to 1,100.degree.C.
Generally, the alloy of the present invention is processed by
breakdown of ingot into strip using a hot rolling operation
followed by cold rolling and annealing cycles to reach final gage.
Preferred properties are obtained using an aging treatment.
It is preferred that the starting hot rolling temperature be in the
range of 700.degree. to 900.degree.C. and preferably 780 to
900.degree.C. The cooling rate from hot rolling should preferably
be in excess of 25.degree.C. per hour down to 300.degree.C. in
order to avoid precipitation of manganese-nickel rich phases. The
alloy is capable of cold rolling reductions in excess of 90
percent, but the cold rolling reduction should preferably be
between 30 and 80 percent in order to control the grain size.
It has been found that an average grain size less than 0.015 mm
gives the optimum fracture toughness. An average grain size of this
order can be obtained by control of the cold rolling reduction,
annealing times and annealing temperatures. In general, annealing
temperatures in the range of 550.degree. to 900.degree.C. for times
from one minute to 10 hours can give the required grain size.
After annealing, the material is cooled in excess of 25.degree.C.
per hour down to 300.degree.C., as indicated above, and the cold
rolling and annealing cycles repeated as desired depending on gage
requirements.
The alloy of the present invention, as previously stated, may be
aged in the range of 250.degree. to 475.degree.C., with
temperatures of 380.degree. to 460.degree.C. being preferred. Aging
times of 30 minutes to 10 hours, with preferred times of 1 to 6
hours, are used to obtain the desired properties. In addition, it
has been found that controlling the amount of cold work prior to
aging has an effect on fracture toughness and aging response. In
particular, it has been observed that the cold work gives rise to
increased nucleation sites for the intragranular precipitation of
the discrete manganese-nickel rich particles. Hence, cold working
of the alloys prior to aging at the higher temperatures of the
aging range increases the aging response and decreases the amount
of cellular precipitate. The amount of cold rolling can vary from
10 to 50 percent, with from 15 to 45 percent yielding the optimum
fracture toughness.
The present invention will be more readily understandable from a
consideration of the following illustrative examples.
EXAMPLE I
The Durville method was used to cast the two alloys listed in Table
I. The copper and nickel were melted under a charcoal cover.
Aluminum was added to deoxidize the melt. Following the removal of
the charcoal cover, the manganese and tin additions were made. The
slag was removed and the melt was poured from approximately
1,080.degree.C.
TABLE I
Composition -- Weight %
Manga- Alumin- Alloy Nickel nese um Tin Copper A 19.72 19.92 0.36
-- Substantially balance B 20.00 20.00 0.50 0.50 Substantially
balance
EXAMPLE II
The alloys prepared in Example I were processed in the following
manner. Both alloys were homogenized at 840.degree.C. for about 2
hours. The alloys were hot rolled from 1.500 inches to 0.418 inches
and water quenched. The alloys were cold rolled 60 percent to 0.167
inches. Both alloys were annealed at 600.degree.C. for about 30
minutes. After a water quench, the alloys were cold rolled 60
percent to 0.067 inches and annealed. Subsequent to the water
quench, the alloys were cold rolled 25 percent to 0.090 inches.
Tensile and tear test specimens were prepared. These were aged at
450.degree.C. for various times and the properties determined. The
yield strength and unit propagation energy transverse to the
rolling direction are given in Table II. The term "UPE" is a
relative value of the fracture toughness determined by the Kahn
Tear Test. The average grain diameter of the alloys tested was
0.005 to 0.010 mm.
TABLE II
Transverse Properties
Alloy Aging Time at Yield Strength UPE 450.degree.C., hours 0.2%
Offset 2 ksi A 2.5 150 172 A 3.0 161 80 A 3.5 163 25 B 2.0 148.5 75
B 3.0 172.0 10
the tin addition tends to decrease the slope of the UPE versus
yield strength relation. Therefore, it gives rise to higher values
of fracture toughness at the higher, more useable yield strengths.
Heretofore, the combination of high toughness at the higher yield
strengths was unobtainable in this alloy system. This can be seen
from an examination of FIG. 1.
This invention may be embodied in other forms or carried out in
other ways without departing from the spirit or essential
characteristics thereof. The present embodiment is therefore to be
considered as in all respects illustrative and not restrictive, the
scope of the invention being indicated by the appended claims, and
all changes which come within the meaning and range of equivalency
are intended to be embraced therein.
* * * * *