U.S. patent application number 10/786470 was filed with the patent office on 2004-12-02 for lead-free copper alloy and a method of manufacture.
Invention is credited to Boegel, Andreas, Breu, Monika, Hofmann, Uwe, Humpenoeder-Boegel, Doris, Seeger, Joerg, Siegele, Harald.
Application Number | 20040241038 10/786470 |
Document ID | / |
Family ID | 32748116 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040241038 |
Kind Code |
A1 |
Hofmann, Uwe ; et
al. |
December 2, 2004 |
Lead-free copper alloy and a method of manufacture
Abstract
A lead-free copper alloy on the base of Cu--Zn--Sn and a method
of manufacture. The copper alloy is built on the base of copper,
zinc and tin without toxic additives and consists of: 60 to 70% Cu,
0.5 to 3.5% Sn and the further matrix-active elements: 0.01 to 0.5%
Fe and/or Co, 0.01 to 0.5% Ni, 0.01 to 0.5% Mn and/or Si, the
remainder Zn and unavoidable impurities. Selectively up to 3% Mg,
up to 0.2% P and up to 0.5% Ag, Al, As, Sb, Ti, Zr can be added.
The demands for a health-conscious and ecological compatibility are
thus naturally met.
Inventors: |
Hofmann, Uwe; (Neu-Ulm,
DE) ; Breu, Monika; (Ulm, DE) ; Siegele,
Harald; (Weissenhorn, DE) ; Boegel, Andreas;
(Weissenhorn, DE) ; Humpenoeder-Boegel, Doris;
(Weissenhorn, DE) ; Seeger, Joerg; (Ulm,
DE) |
Correspondence
Address: |
FLYNN THIEL BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008-1699
US
|
Family ID: |
32748116 |
Appl. No.: |
10/786470 |
Filed: |
February 25, 2004 |
Current U.S.
Class: |
420/472 ;
420/476 |
Current CPC
Class: |
F16C 33/121 20130101;
C22C 9/04 20130101; F16C 2326/01 20130101; F16C 2204/14
20130101 |
Class at
Publication: |
420/472 ;
420/476 |
International
Class: |
C22C 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2003 |
DE |
103 08 779.6 |
Claims
What is claimed is:
1. A copper alloy (base Cu--Zn--Sn), consisting of (in weight %) 60
to 70% Cu, 0.5 to 3.5% Sn and the further matrix-active elements:
0.01 to 0.5% Fe and/or Co, 0.01 to 0.5% Ni, 0.01 to 0.5% Mn and/or
Si, and selectively up to 3% Mg, selectively up to 0.2% P,
selectively each up to 0.5% Ag, Al, As, Sb, Ti, Zr, the remainder
Zn and unavoidable impurities.
2. The copper alloy according to claim 1, wherein the alloy
includes: 60 to 70% Cu, 0.5 to 3.5% Sn, 0.07 to 3% Mg, 0.003 to
0.01% P, the remainder Zn and unavoidable impurities.
3. The copper alloy according to claim 1, wherein the alloy
includes: 60 to 70% Cu, 0.5 to 3.5% Sn, 0.07 to 3% Mg, 0.03 to 0.1%
P, the remainder Zn and unavoidable impurities.
4. The copper alloy according to claim 1, wherein the alloy
includes: 60 to 70% Cu, 1.5 to 2.5% Sn, 0.07 to 3% Mg, 0.03 to 0.1%
P, the remainder Zn and unavoidable impurities.
5. The copper alloy according to claim 1, wherein the alloy
includes: 60 to 70% Cu, 2.0 to 2.5% Sn, 0.07 to 3% Mg, 0.03 to 0.1%
P, the remainder Zn and unavoidable impurities.
6. The copper alloy according to claim 1, wherein the total content
of the further matrix-active elements, including the selectively
added elements, is 0.5 to 5%, preferably 0.7 to 1%.
7. A method of manufacturing a contact, pin or fastening element
utilized in electrical engineering and telecommunication in which
the improvement comprises a step of manufacturing said contact, pin
or fastening element from the copper alloy of claim 1.
8. A method of manufacturing containers utilized for the transport
or storage of gases or liquids or for pipes, water fixtures, faucet
extensions, pipe joints and valves utilized in sanitation processes
in which the improvement comprises a step of manufacturing said
container or pipes, water fixtures, faucet extensions, pipe joints
and valves from the alloy of claim 1.
9. A method of manufacturing a tensile- or torsion-stressed
component in which the improvement comprises a step of
manufacturing said tensile- or torsion-stressed component from the
alloy of claim 1.
10. A method of manufacturing a recyclable component having a low
contaminant emission in which the improvement comprises a step of
manufacturing said recyclable component from the alloy of claim
1.
11. A method of manufacturing die-formed parts in which the
improvement comprises a step of manufacturing said die-formed parts
from the alloy of claim 1.
12. A method of manufacturing sliding bearings in which the
improvement comprises a step of manufacturing said sliding bearings
from the alloy of claim 1.
13. A method of manufacturing easily millable or punchable bands,
sheet metal and plates in which the improvement comprises a step of
manufacturing said easily millable or punchable bands, sheet metal
and plates from the alloy of claim 1.
14. A method of manufacturing a malleable, rolling or testing alloy
in which the improvement comprises a step of manufacturing said
malleable, rolling or casting alloy from the alloy of claim 1.
15. The method of claim 8, wherein said alloy is used in the
manufacture of containers utilized in refrigeration
engineering.
16. The method of claim 9, wherein said alloy is used in the
manufacture of screws and nuts.
17. The method of claim 13, wherein said easily millable or
punchable bands, sheet metal and plates are utilized for decorative
purposes or pressed-screen applications.
18. The method of claim 13, wherein said alloy is used in the
manufacture of keys or engravings.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a copper alloy on the base of
Cu--Zn--Sn and a method of manufacture.
BACKGROUND OF THE INVENTION
[0002] Brass is being utilized in different areas of mechanical
engineering, electrical engineering and sanitation technology.
[0003] The components in mechanical engineering and in electrical
engineering are becoming increasingly smaller and more filigree due
to the trend toward miniaturization. Also components of brass are
often connected with other metallic and non-metallic materials to
form complicated groups of components. However, both make a
recycling of the materials based on a separation or division more
difficult.
[0004] Further difficulties occur in particular when the components
to be recycled contain toxic or health-threatening elements or
substances. These can directly endanger the workers in a factory
which produces and processes these materials. An environmental
impact is created when such materials must be stored for a
prolonged period of time and are thereby subjected to atmospheric
influences. In addition, the toxic substances may contaminate the
accessory agents, for example the separating means, which are
utilized during the preparation of shredder fractions via the
sinking or floating method. An expensive waste disposal of the
accessory agents would then be needed. Of course health-threatening
substances and elements are also undesired during the use of the
components if an emission into the environment or the living
organism cannot be completely avoided.
[0005] Thus, a composition which is non-threatening with respect to
ecological and toxic reasons is important for such products. The
increased concerns about the environment, which can be found in
many standards and technical controls, for example the re-enacted
drinking-water regulation DIN 50930-6 or the scrap-material
regulation, demands suitable materials.
[0006] The field of electrical engineering utilizes mainly
Pb-containing brass as a contact material, namely as stationary
contacts or solid contacts, part of which are, for example,
clamping joints and plug connectors or connector contacts. When
choosing the material, its easy processing stands in the
foreground. The respective componentry can be manufactured with a
high degree of productivity out of a machinable Pb-containing
brass.
[0007] The Pb particles in the structure create disadvantages. The
particles act indeed as chip breakers, however, reduce the strength
or ductility of the material due to a notching tendency and
reduction of the load bearing cross section. These disadvantages
must be compensated for by suitably dimensioning the component.
[0008] All fastening elements have, caused by their manufacture,
more or less inherently high mechanical stress. These are often
superposed by tensile-load tensions which are caused by screw
connections. When the clamping joints are manufactured out of
common Pb-containing brass, there exists due to such tensions a
great danger for tension stress corrosion cracking.
[0009] In addition, there also exists a need for ecologically
compatible materials in the field of electrical engineering.
Looking at the directives given by the European Parliament
regarding used electrical and electronic apparatus, it can be seen
that, within a reasonably short period of time into the future, Pb
will become an undesired alloy part. The goal of this initiative is
in this connection to increase the portion of environmentally
friendly materials in the material cycle.
[0010] Furthermore, components or containers for the transport or
the storage of liquids are made out of Pb-containing brass. An
important area is the sanitation technology. Negligence regarding
the metal is especially here particularly problematic. The
materials being used should thus be hardly susceptible to any type
of corrosion. The components for the transport or the storing of
liquids are as a rule manufactured by machining. A hot forming via
die-forging often precedes.
[0011] Such lead-containing brass alloys are known, for example,
from the Reference DE 43 08 371 C2, which are used as material for
slide elements in cars, ships and airplanes. This alloy receives
also its good machining ability from an admixture of a considerable
amount of lead.
[0012] The further development of easily machinable lead-free
malleable alloys on a copper base is known from the Reference DE
691 24 835 T2. The alloy is supposed to replace present
lead-containing materials without changing the processing
conditions. Instead of lead, bismuth and the further elements
phosphor, indium and tin are added in small amounts for this
purpose to the alloy.
[0013] The basic purpose of the invention is to provide an improved
lead-free copper alloy with respect to its characteristics and to
set forth its use.
SUMMARY OF THE INVENTION
[0014] The purpose is attained by providing a copper alloy on a
base of copper, zinc and tin, consisting of: 60 to 70% Cu, 0.5 to
3.5% Sn and the further matrix-active elements: 0.01 to 0.5% Fe
and/or Co, 0.01 to 0.5% Ni, 0.01 to 0.5% Mn and/or Si, the
remainder Zn and unavoidable impurities.
[0015] The copper alloy selectively contains in addition up to 3%
Mg, up to 0.2% P and selectively each in addition up to 0.5% Ag,
Al, As, Sb, Ti, Zr.
[0016] All parts of the alloy are disclosed in weight %.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention will be discussed in greater detail in
connection with the drawing, in which:
[0018] FIG. 1 illustrates the relationship between the standard
deviations of the product characteristics and the content of
matrix-active elements without majority components.
DETAILED DESCRIPTION
[0019] The invention is based on the premise that the suitable
combination of the alloy elements and the characteristics resulting
from a cooperation of the individual parts all together meet the
expectations demanded from the alloy and thus the requirement for
the material should be covered. The material should for this
purpose at the same time be distinguished by
[0020] the absence of toxic elements,
[0021] good machining property,
[0022] good workability,
[0023] high corrosion resistance,
[0024] an increased strength level with an equally high ductility
compared to lead-containing machinable brass,
[0025] capability for mass production in a mill for partially
finished products, and
[0026] a robust manufacture, namely, a manufacture not sensitive
with respect to fluctuating operating parameters, in a mill for
partially finished products.
[0027] The copper alloy is for this purpose designed as a
Sn-containing CuZn alloy (naval brass) without toxic additives.
Naturally the demands for a health-conscious and ecological
compatibility are thus met.
[0028] The Cu-content of the inventive alloy lies between 60% and
70%.
[0029] Cu-contents below 60% would lead to a brittleness, which
would result in a significantly low ductile yield or impact bending
resistance. For example, disadvantages in the non-cutting forming
would be created through this. When the Cu-content exceeds 70%,
long, bulky chips would be created during an uninterrupted cut of
machining process.
[0030] Analogous situations exist regarding the Sn-content: In the
case of Sn-concentrations below 0.5%, the advantage of the short
chips would be lost; above 3.5% the toughness would drop off too
far.
[0031] Fe or Co is necessary in order to control the grain size of
the alpha phase and of the beta phase. In addition, Fe lowers the
specific chip-forming operation in the alloy. The effect would not
exist sufficiently below 0.01%. The risk of coarse precipitations
would exist above 0.5% even together with Si. These would be
disadvantageous for cold forming.
[0032] Ni, Mn and Si are used to purposefully influence the
structural constitution at a given copper content. Mn and Si
increase the part of the cubic-space-centered beta phase, Ni
stabilizes the part of the cubic-surface-centered copper-zinc mixed
crystal.
[0033] Ni below 0.01% would not be sufficient to sufficiently
stabilize the copper mixed crystal, in addition the favorable
effect on the resistance to a surface-like corrosion attack would
be eliminated. Ni above 0.5% would lead to an increased
solidification during cold forming and would therefore not be
advantageous.
[0034] Mn below 0.01% would not be advantageous since the beta
phase would then exist in amounts which would be too small. Mn
above 0.5% would influence the malleability and the resistance to
stress corrosion cracking.
[0035] Si below 0.01% would not be advantageous since the amount of
beta phase would be too low, Si above 0.5% would influence the
cold-forming ability.
[0036] Mg reduces the specific chip-forming operation in alloys and
contributes significantly to the improvement of the machinability
property. The cause lies in the formation of low-melting eutectic
phase parts in the binary bounding system Cu--Mg and Zn--Mg. The
eutectic composition behaves brittle and thus represents
predetermined breaking point in the structure whereat a chip
breaking can be started. The toughness would drop off too far above
3% and a manufacture via continuous casting would no longer be
possible.
[0037] P is selectively provided in order to favorably influence
the formation of the initial cast structure and the corrosion
characteristics. Phosphor increases the flowing ability of the melt
and acts favorably against the susceptibility of a stress corrosion
cracking. In addition P acts against an elutriation of zinc from
brass. In particular, starting with an amount of 0.003% are these
effects significant. Above 0.2%, however, the disadvantages would
be predominant due to an increased tendency for an intercrystalline
corrosion at grain boundaries.
[0038] It is optional to add up to 0.5% aluminum by alloying in
order to enable the creation of starting layers. This is
particularly advantageous for decorative purposes. This effect is
particularly significant starting with an amount of 0.003%. Amounts
above 0.5% would be no longer advantageous for this use because the
formation of a beta phase would be favored.
[0039] Partially finished products made out of the inventive
material are preferably manufactured by conventional continuous
casting, extrusion at temperatures of between 600.degree. C. to
750.degree. C. and a cold forming, for example by drawing.
[0040] The composition has proven to be able to be manufactured
without any problems and has proven to be surprisingly constant in
its characteristics in this manufacturing sequence. This is not the
case with ternary alloys Cu--Zn--Sn, as they are commonly discussed
in literature. They lack the favorable characteristics in the
continues casting and a stable structure formation, which depends
little on the variations of the operating parameters, for example
during extrusion. This is true for both the steady course of the
technological characteristic values in the finished product itself,
and also for the unchanged characteristics between various
processed cast charges. It appears that the extent of variations of
the finished round bars depends in its characteristics in the first
approximation of the content of the matrix-active elements. On the
base of the majority components Cu, Zn and Sn there is the content
in the sum of the matrix-active elements Fe, Co, Ni, Mn and Si,
which are at least partially soluble in the matrix, alone or in
connection with the selective elements Mg, P, Ag, Al, As, Sb, Ti
and Zr obviously of a significant importance for the robust
manufacture in the mill for partially finished products, which
manufacture is insensitive with respect to fluctuating operating
parameters.
[0041] The copper alloy consists in a preferred embodiment of 60 to
70% Cu, 0.5 to 3.5% Sn, 0.07 to 3% Mg and 0.003 to 0.01% P, the
remainder Zn and unavoidable impurities.
[0042] The copper alloy consists alternatively and in
[0043] further preferred embodiment of 60 to 70% Cu, 0.5 to 3.5%
Sn, 0.07 to 3% Mg and 0.03 to 0.1% P, the remainder Zn and
unavoidable impurities.
[0044] The copper alloy consist alternatively and in a further
preferred embodiment of 60 to 70% Cu, 1.5 to 2.5% Sn, 0.07 to 3% Mg
and 0.03 to 0.1% P, the remainder Zn and unavoidable
impurities.
[0045] The copper alloy consists alternatively and in
[0046] further preferred embodiment of 60 to 70% Cu, 2.0 to 2.5%
Sn, 0.07 to 3% Mg and 0.03 to 0.1% P, the remainder Zn and
unavoidable impurities.
[0047] All of the above-mentioned preferred embodiments contain
phosphor in order to, in particular, favorably influence the
creation of the initial cast structure and the corrosion
characteristics. These alloy compositions with an amount of 0.03 to
0.1% P meet in a particularly favorable manner the expectations
placed on the material.
[0048] It appears that with contents of the matrix-active elements
but for Cu, Zn and Sn below a certain amount such large dispersions
of technological characteristics occur that this has a lasting
effect on the manufacture and in the extreme case a safe control of
the production process is not possible. In order to counteract
this, 0.5 to 5% of the total content of the further matrix-active
and the selectively added elements is advantageously in the copper
alloy.
[0049] The dispersion is already clearly reduced at these amounts
and finds its optimum in many standard processes in a particularly
preferred embodiment with a total content of between 0.7 to 1%.
[0050] Depending on the process it can, however, also be sensible
to instead supply a high amount of matrix-active elements. The
practicability exists, however, only up to a total content of 5% at
a maximum. However, no practically meaningful improvements of the
dispersions can be observed beyond contents of 5% since
considerable unpredictable superposed additive effects are noticed,
which ruin the intended purpose.
[0051] The copper alloy is advantageously utilized for contacts,
pins or fastening elements in electrical engineering, for example
as stationary contacts or solid-state contacts, part of which are
also clamping joints and plug connectors or connector contacts, and
also in the telecommunication technology.
[0052] The alloy has compared with liquidy and gaseous media a high
corrosion resistance. In addition, it is extremely resistant to
dezincing and stress corrosion cracking. Consequently, the alloy is
advantageously suited for use in containers for the transport or
storage of liquids or gases, in particular containers in the field
of refrigeration technology or for tubes, water fittings, faucet
extensions, pipe joints and valves in the field of sanitation
technology.
[0053] The insensitivity with respect to stress corrosion cracking
suggests the use of the alloy in screw connections or clamping
joints, where, technically caused, high elastic energies are
stored. Thus, particularly advantageous is the use of the alloy for
all tensile-stressed and/or torsion-stressed components, in
particular for screws and nuts. The inventive material reaches
after cold forming higher values for the yield strength than
Pb-containing CuZn alloys. Thus, it is possible to realize in screw
connections, which may not plastically deform, greater tightening
torques. The apparent yielding point ratio Rp.sub.0.2/R.sub.m is
smaller for the CuZnSn alloy than in free-cutting brass. Screw
connections, which are only tightened once and are thereby
intentionally overstressed, achieve with this particularly high
retention forces. Because of the higher strength level, savings in
weight of at least 10% are possible through a miniaturization.
[0054] The low corrosion rates guarantee also that the negligence
regarding the metal, that is the characteristic of removing through
the action of liquidy or gaseous media alloy parts, is actually
low. In this respect, the material is suited for areas of use which
demand low emission of contaminants in order to protect the
environment. Thus, the use of the inventive alloy lies
advantageously in the field of recyclable components.
[0055] The inventive alloy shows a distinctive temperature
dependency of the impact tenacity. The impact tenacity drops at
temperatures of above 600.degree. C. to values which correspond to
those of some Pb-containing alloys and promise an advantageous use
for die-formed parts.
[0056] The inventive alloy has even without lead as an alloy part a
good cutting property. It thus is also suited for the manufacture
of slide elements for the car industry and the air-travel and
space-travel technologies.
[0057] Possibilities for use of the copper alloy result both for
tube-shaped and also strip-shaped starting materials.
Advantageously, easily millable or punchable strips, sheet metal
and plates are suited in particular for keys, engravings,
decorative purposes or for pressed-screen applications. For
manufacture a conventional continuous casting is preferred, hot
rolling between 500 to 850.degree. C. with a subsequent forming, as
for example cold rolling and if needed supplemented by further
annealing and forming steps, to form suitable partially finished
strip products. The alloy can be utilized as a malleable, rolling
or casting alloy.
[0058] The advantages achieved with the invention consists in
particular in these having a good cutting property and good forming
ability in connection with a high corrosion resistance. The
resistance to dezincing and stress corrosion creaking is hereby
especially distinctive.
[0059] In addition, toxic elements are absent which, due to
increasingly stricter standards for protecting the environment,
enable a free use, in particular in connection with drinking-water
systems.
[0060] A further important advantage is an increased strength level
with an equally high ductility compared to lead-containing
machinable brass.
[0061] Narrow manufacturing tolerances play an important role in
the manufacture of the alloy. Particularly advantageous is the
inventive alloy in its suitability for the mass production in the
mill for partially finished products with respect to a robust
manufacture, namely a manufacture insensitive to fluctuating
operating parameters.
[0062] FIG. 1 illustrates the relationship between the standard
deviation of the product characteristics and the content of
matrix-active elements without majority components. The curve shows
the to be expected trend for the standard deviation without
consideration of further effects. Thus, it appears that in the case
of contents of the matrix-active elements but for Cu, Zn and Sn the
dispersions of the technological characteristics decrease
asymptotically over a certain part, from which the conclusion
results that an as high as possible part of matrix-active elements
is to be supplied. However, practice shows that the desired
material characteristics occur only up to a total content of 5% at
a maximum. Above contents of 5% no further improvements of the
dispersions can be observed since considerable unpredictable
superposed additive effects are observed, which do not lead to any
further improvement.
[0063] The variability of the material characteristics which,
through use of the inventive composition, move particularly into
the foreground, are the apparent yielding point, the tensile
strength, the ductile yield, the hardness, the grain size and the
hardening ability of the material. During the further course of the
processing through cold forming and annealing, if desired,
corresponding observations are made.
[0064] Tests on Mg-containing alloys have shown that after a
forming operation by extrusion at 690.degree. C. the eutectic phase
parts are formed into the structure as brittle precipitations. This
change in the structure can be further reinforced through a heat
after-treatment at 500.degree. C. The partially finished products
receive their final form and strength by a cold forming through
drawing.
* * * * *