U.S. patent application number 12/095615 was filed with the patent office on 2009-08-27 for low-migration copper alloy.
This patent application is currently assigned to GEBR. KEMPER GMBH & CO. KG METALLWERKE. Invention is credited to Frank Leistritz, Katrin Muller, Patrik Zeiter.
Application Number | 20090214380 12/095615 |
Document ID | / |
Family ID | 36499302 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090214380 |
Kind Code |
A1 |
Muller; Katrin ; et
al. |
August 27, 2009 |
LOW-MIGRATION COPPER ALLOY
Abstract
The present invention relates to a copper alloy, in particular
for components which carry media or drinking water, in particular
fittings, valves or compression joints and also an advantageous use
of the copper alloy and components for lines carrying media or
drinking water. It is an object of the present invention to provide
a copper alloy which has good corrosion resistance, good
castability and mechanical workability and also good mechanical
properties and displays good migration values, particularly in
respect of the migration of lead and nickel ions into drinking
water. The copper alloy provided for this purpose by the present
invention comprises from 2% by weight to 4.5% by weight of silicon,
from 1 to 15% by weight of zinc and from 0.05% by weight to 2% by
weight of manganese. Furthermore, from 0.05 to 0.4% by weight of
aluminium and from 0.05 to 2% by weight of tin can optionally be
present. As balance, the copper alloy contains copper and
unavoidable impurities.
Inventors: |
Muller; Katrin; (Berlin,
DE) ; Zeiter; Patrik; (Riken, CH) ; Leistritz;
Frank; (Drolshagen, DE) |
Correspondence
Address: |
Fay Sharpe LLP
1228 Euclid Avenue, 5th Floor, The Halle Building
Cleveland
OH
44115
US
|
Assignee: |
GEBR. KEMPER GMBH & CO. KG
METALLWERKE
Olpe
DE
JRG GUNZENHAUSER AG
Sissach
CN
R. NUSSBAUM AG METALLGIESSEREI UND ARMATURENFABRIK
Olten
CN
VIEGA GMBH & CO. KG
Attendorn
DE
|
Family ID: |
36499302 |
Appl. No.: |
12/095615 |
Filed: |
December 13, 2006 |
PCT Filed: |
December 13, 2006 |
PCT NO: |
PCT/EP06/12008 |
371 Date: |
March 24, 2009 |
Current U.S.
Class: |
420/471 ;
420/472; 420/473; 420/476; 420/480; 420/482 |
Current CPC
Class: |
C22C 9/10 20130101; C22C
9/04 20130101 |
Class at
Publication: |
420/471 ;
420/472; 420/473; 420/476; 420/480; 420/482 |
International
Class: |
C22C 9/04 20060101
C22C009/04; C22C 9/02 20060101 C22C009/02; C22C 9/05 20060101
C22C009/05; C22C 9/10 20060101 C22C009/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2005 |
EP |
05027341.6 |
Claims
1. Use of a copper alloy for the manufacture of components for gas
or water lines which carry media, in particular drinking water
lines as well as fittings and valves of the same, wherein the
copper alloy comprises, in % by weight: 2.8.ltoreq.Si.ltoreq.4.5;
1.ltoreq.Zn.ltoreq.15; 0.05.ltoreq.Mn.ltoreq.2;
80.ltoreq.Cu.ltoreq.96.95 optionally further comprising;
0.05.ltoreq.Al.ltoreq.0.5 0.05.ltoreq.Sn.ltoreq.2;
0.0005.ltoreq.Zr.ltoreq.0.05 0.01.ltoreq.P.ltoreq.0.2 and
unavoidable impurities.
2. Use according to claim 1, characterized in that the copper alloy
is used for the manufacture of compression joints.
3. Use according to claim 1, characterized in that the copper alloy
is used for the manufacture of valves with a fixed compression
connection.
4. Use according to claim 1, characterized in that 5% by
weight.ltoreq.Zn.ltoreq.15% by weight.
5. Use according to one of claims 1 to 4, characterized in that
0.2% by weight.ltoreq.Mn.ltoreq.0.6% by weight.
6. Use according to claim 5, characterized in that the unavoidable
impurities are contained with not more than altogether 0.5% by
weight.
7. Use according to claim 6, characterized in that the unavoidable
impurities are contained with not more than altogether 0.25% by
weight.
8. Use according to claim 6 or 7, characterized in that Ni and/or
Pb are contained as unavoidable impurities with not more than
altogether 0.25% by weight.
9. Components for gas or water lines which carry media, in
particular drinking water lines as well as fittings and valves of
the same, at least partially consisting of a copper alloy,
comprising in % by weight: 2.8.ltoreq.Si.ltoreq.4.5;
1.ltoreq.Zn.ltoreq.15; 0.05.ltoreq.Mn.ltoreq.2;
80.ltoreq.Cu.ltoreq.96.95 optionally further comprising;
0.05.ltoreq.Al.ltoreq.0.5 0.05.ltoreq.Sn.ltoreq.2;
0.0005.ltoreq.Zr.ltoreq.0.05 0.01.ltoreq.P.ltoreq.0.2 and
unavoidable impurities.
10. Component according to claim 9, characterized in that the
elements Cu, Zn and Si are present in an amount of more than 98% by
weight in the form of an .alpha.-solid solution.
11. Components according to claim 9, characterized in that the
components are compression joints.
12. Components according to claim 11, characterized in that the
components are valves with fixed compression connection.
13. Component according to claims 9 or 11, characterized in that 5%
by weight.ltoreq.Zn.ltoreq.15% by weight.
14. Component according to claims 9 or 11, characterized in that
0.2% by weight.ltoreq.Mn.ltoreq.0.6% by weight.
15. Component according to claim 9, characterized in that the
unavoidable impurities are contained with altogether not more than
0.5% by weight.
16. Component according to claim 15, characterized in that the
unavoidable impurities are contained with altogether not more than
0.25% by weight.
17. Component according to claim 15, characterized in that Ni
and/or Pb are contained as unavoidable impurities with altogether
not more than 0.25% by weight.
18. Components for gas or water lines which carry media, in
particular drinking water lines as well as fittings and valves of
the same, at least partially consisting of a copper alloy,
comprising in % by weight: 2.8.ltoreq.Si.ltoreq.4.5;
1.ltoreq.Zn.ltoreq.15; 0.05.ltoreq.Mn.ltoreq.2;
80.ltoreq.Cu.ltoreq.96.95 optionally further comprising;
0.05.ltoreq.Al.ltoreq.0.5 0.05.ltoreq.Sn.ltoreq.2;
0.0005.ltoreq.Zr.ltoreq.0.05 0.01.ltoreq.P.ltoreq.0.2 and
unavoidable impurities and wherein the elements Cu, Zn and Si are
present in an amount of more than 98% by weight in the form of an
.alpha.-solid solution.
19. Components according to claim 18, characterized in that the
components are compression joints.
20. Components according to claim to 18, characterized in that the
components are valves with fixed compression connection.
21. Component according to claim 18, characterized in that 5% by
weight.ltoreq.Zn.ltoreq.15% by weight.
22. Component according to claim 18, characterized in that 0.2% by
weight.ltoreq.Mn.ltoreq.0.6% by weight.
23. Component according to claim 18, characterized in that the
unavoidable impurities are contained with altogether not more than
0.5% by weight.
24. Component according to claim 23, characterized in that the
unavoidable impurities are contained with altogether not more than
0.25% by weight.
25. Component according to claim 18 or 24, characterized in that Ni
and/or Pb are contained as unavoidable impurities with altogether
not more than 0.25% by weight.
Description
[0001] The present invention relates to a copper alloy. In
particular. the present invention relates to a low-migration copper
alloy for the manufacture of components for gas and sanitary
installations, especially for components which are employed in
drinking water installations and are in direct contact with the
drinking water carried in the components, as a rule pipes, fittings
and valves.
[0002] Materials for the manufacture of components for gas and
water installations are subject to particular demands which are in
particular placed on lines carrying drinking water as well as their
elements. Here, primarily the corrosion resistance of the
components has to be mentioned, for the installed components must
not corrode even if they are employed for several years. Moreover,
particular demands are placed on the manufacturability and
processability, where it must not only be possible to cast the
alloys easily and economically but where it moreover is necessary
for the cast components to be easily mechanically worked. Here, in
particular good machinability has to be paid attention to. Finally,
the components made of the copper alloy also have to withstand the
mechanical strains required for the field of employment. Thus, in
copper-tin-zinc alloys, a tensile strength of more than 180
N/mm.sup.2 at a 0.2% proof stress of 85 N/mm.sup.2 is always
considered to be necessary. With bronzes (copper-tin alloys) the
tensile strength should be 240 N/mm.sup.2 and the 0.2% proof stress
130 N/mm.sup.2 and more.
[0003] Furthermore, the behavior of the materials with respect to
the emission of ions of the alloy components of the materials or of
reaction products with water ingredients is of particular interest.
Here, very narrow limits with respect to the allowed emission of
metal ions from the components into the drinking water have to be
observed for protecting the consumer.
[0004] Apart from other alloys, today also highly coppery
nonferrous heavy metal alloys, such as bronze or red bronze, are
employed for the manufacture of the components of gas and water
lines carrying media. With respect to good mechanical workability,
certain amounts of lead are added to these nonferrous heavy metal
alloys. For increasing corrosion resistance and strength, the
addition of nickel is to be preferred.
[0005] Common representatives of bronze-cast alloys are summarized
in DIN EN 1982. By way of example, here the red bronze alloy
CuSn5Zn5Pb5 with between 4 to 6% by weight of tin, zinc and lead
each, with a content of up to 2.0% by weight of nickel and up to
0.1% by weight of phosphorous as well as additions of up to 0.3% by
weight of iron and up to 0.25% by weight of antimony are mentioned.
It is true that this material is characterized by good castability
as well as good corrosion resistance even with respect to sea
water. With respect to the emission of metal ions into the water,
however, this material has to be considered as not being
satisfactory in view of the limiting values to be expected in
future. Here, in particular the high lead emission of CuSn5Zn5Pb5
is criticized.
[0006] With the EP-1 045 041, a lead-free copper alloy has already
been suggested which is said to have satisfactory machinability and
which comprises up to 79% by weight of copper, between 2 and 4% by
weight of silicon, and as balance zinc. This alloy is especially
taken into consideration for the manufacture of valves, fittings
and similar parts for water carrying pipe systems. However, in
particular with respect to corrosion resistance, the alloy does not
behave as red bronze and can consequently not substitute the
same.
[0007] GB-1 443 090 discloses a copper alloy improved with respect
to dezincification with between 80 and 90% by weight of copper,
between 6.3 and 17.5% by weight of zinc, and between 2.8 and 4.75%
by weight of silicon as essential alloy components with between
0.03 and 0.05% by weight of arsenic. For improving the corrosion
properties, according to the solution of the GB-1 443 090, a heat
treatment of the cast parts is suggested. In this heat treatment,
the cast parts are annealed at temperatures of between 600.degree.
C. and 750.degree. C. over a period of 5 to 10 days and
subsequently quenched. This heat treatment is performed with the
aim of obtaining the .alpha. and .zeta.-phases to be preferred with
respect to corrosion. By quenching, in particular the formation of
phases of which the corrosion resistance is low, e.g. the .mu.- and
.chi.-phases, is to be avoided.
[0008] From GB-1 385 411, a copper alloy is known which has up to
10% by weight of aluminum and up to 5% by weight of iron and is
employed for the manufacture of components of water installations
carrying water. This alloy, however. has an insufficient corrosion
behavior and in particular migration of metal ions into the water
is too high.
[0009] The problem underlying the present invention is to provide a
copper alloy improved with respect to the migration behavior which
is in particular suited for the manufacture of gas and water lines
carrying media and their parts and which has good corrosion
resistance with respect to media, good strength and good
workability and castability. For the workability, in particular the
machining properties of the copper alloy are very important.
Moreover, the invention wants to provide corresponding
medium-carrying components, in particular fittings or valves, as
well as an advantageous use of the copper alloy according to the
invention.
[0010] With respect to the substance-related aspect of the present
invention, the same suggests a copper alloy with the features of
claim 1. This copper alloy comprises between 2 and 4.5% by weight
of silicon, between 1 and 15% by weight of zinc and between 0.05
and 2% by weight of manganese. Apart from these necessary elements,
the copper alloy can contain between 0.05 and 0.5% by weight of
aluminum and/or between 0.05 and 2% by weight of tin. As balance,
copper and unavoidable impurities are contained in the alloy. These
impurities are preferably restricted to a proportion of 0.5% by
weight. Particularly preferred, the upper limit for the impurities
is 0.25%. This upper limit in particular applies to the cumulative
proportion of nickel and lead in the alloy, which proved to be a
particularly effective measure for suppressing the migration of
lead or nickel, respectively. With respect to this, the alloy is
preferably free from lead and/or nickel. An alloy in which the
proportion of lead is less than 0.25% is considered as lead-free
alloy. An alloy in which the proportion of nickel is less than
0.15% is considered as nickel-free alloy.
[0011] The alloy should contain between 0.01 and 0.05% by weight of
zirconium. Preferably, the zirconium proportion should be between
0.01% by weight and 0.03% by weight; particularly preferred, the
upper limit is determined to be 0.02% by weight. This interval
applies for essentially all cast components, except for sand
castings. Grain refining usually results only as of 0.01% by
weight, above 0.02% by weight, the risk of zirconium formation in
the grain boundary zone is increased. Zirconium improves the
solidification morphology and reduces the formation of heat cracks,
mainly in permanent mold casting. In particular in castings which
are made by means of sand casting, a deliberate addition of
zirconium, however, can be dispensed with. In these components, the
zirconium proportion can be below 0.01% by weight, preferably even
below 5 ppm (0.0005%).
[0012] The stated preferred upper limit for zirconium of 0.02%
should be observed to avoid zirconium formation in the grain
boundary zone of the texture which leads to increased tool wear in
the machining of the components cast from the alloy for
water-carrying lines.
[0013] Optionally, phosphorous should also be provided in certain
proportions. Phosphorous is preferably present with a proportion of
0.01% by weight to 0.2% by weight. Phosphorous is controlled in
stated limits in particular with respect to an improvement of
castability (flowability and feeding behavior of the alloy).
Further, phosphorous reduces the dezincification of the alloy and
improves corrosion resistance. However, it showed that with a
phosphorous content of more than 0.2% by weight, the alloy becomes
increasingly harder, which results in problems in the machining of
cast components.
[0014] It showed that with a copper alloy according to the
invention, as it is stated in claim 1, the demands to be placed on
components for medium-carrying gas or water lines can be met best.
The alloy shows good casting behavior. The components made by
casting can be easily machined. Tests with test pieces showed that
the strength corresponds to the demands to be placed. Moreover, the
corrosion resistance of the alloy is high. It showed that by
controlling the phosphorous content in the alloy, the reject rate
of the castings can be limited. Correspondingly, the degree of
impurities for phosphorous is preferably controlled to a range of
0.01 to 0.05% by weight.
[0015] The aluminum content of the copper alloy according to the
invention is determined with regard to the corrosion resistance of
the same. At present, it is assumed that with an aluminum content
of between 0.05 and 0.5% by weight, good corrosion resistance can
be achieved. Without considerable quality losses, the upper
limiting value for the aluminum content can be determined to 0.4%
by weight.
[0016] It could be confirmed in practical tests that the relevant
components for medium-carrying lines can be easily made with the
usual casting methods, for example sand casting. permanent mold
casting, centrifugal casting or continuous casting. With respect to
the quenching conditions from the melt, there are no particular
demands. The casting obtained in this manner can be easily
machined. For reducing the migration tendency of the casting. the
same can preferably be subjected to a heat treatment before
machining. In the process, the casting is preferably annealed at
between 400.degree. C. and 800.degree. C. for at least half an
hour. Preferably, the heat treatment is performed at a temperature
interval of between 600.degree. C. and 700.degree. C. The annealing
time can be arbitrarily long. With respect to economic margin
conditions, it is, however, determined to between 2 and 16 hours.
The heat up phase is not included in this annealing time.
[0017] Annealing is performed in particular with the aim of
adjusting the .alpha.-phase in the cast component which permits the
combination of various properties to be achieved according to the
present idea of the inventors. It should be pointed out, however,
that already the major part of the necessary alloy elements copper,
zinc and silicon solidifies in the form of an .alpha.-solid
solution with natural quenching from the melt without separate heat
treatment.
[0018] An addition of silicon within the given intervals further
favors chip breakage during working. With an increased silicon
content, however, the tool wear in the machining of the components
made from the alloy is also increased. Correspondingly, the upper
limit for the silicon content is determined to 4.5% by weight, not
least also in view of the mechanical workability of the alloy.
[0019] In view of the required corrosion resistance, in the copper
alloy according to the invention, the zinc content is limited to
15% by weight. A minimum content of 1% by weight of zinc in
contrast guarantees a minimum of machinability.
[0020] Manganese is added to the alloy within the limits of 0.05 to
2% by weight to improve the texture. Manganese improves the texture
and has a positive influence on the solidification behavior of the
copper alloy. However, the manganese content is limited to 2% by
weight with regard to the migration tendency of manganese.
[0021] With a restriction of the sum of impurities to maximally
0.5% by weight, the content of ingredients which could possibly
migrate into the drinking water is also restricted to a minimum
selected under economic points of view. With a further restricted
upper limiting value for the unavoidable impurities of 0.25% by
weight, better security against migration can be achieved, however
at the cost of the manufacturing costs.
[0022] Preferably, the alloy according to the invention contains
between 5 and 15% by weight of zinc. In this restricted interval, a
best possible combination of corrosion resistance and machinability
can be achieved.
[0023] For optimizing the strength with adequate strain properties
of the material in combination with good migration values, the
silicon content is determined to between 2.8% by weight and 4% by
weight.
[0024] For further reducing the migration tendency of manganese,
its content is preferably determined to 0.2 to 0.6% by weight. For
the same reasons, the alloy preferably does not contain any nickel
or lead, respectively. The copper content in the alloy should be at
least 80 and maximally 96.95% by weight.
[0025] According to a second aspect of the present invention, the
use of the copper alloy according to the invention is suggested for
the manufacture of components for medium-carrying gas and water
lines, respectively. These are in particular such components which
form drinking water lines, such as in particular fittings and
valves as well as parts thereof. Not least due to the good
stress-strain properties of the copper alloy according to the
invention. preferably a compression joint is to be made from the
copper alloy according to the invention. The compression joints can
be either formed as separate components or be provided at the
fitting or the valve with a substance- or form-fit. The compression
joints can be also realized as integral parts in the casting of the
valve or the fitting from the copper alloy according to the
invention. The casting alloy according to the invention is in
particular suited for the manufacture of an element of a
compression joint arrangement, as they are known, for example, from
EP 0 343 395 or DE 10 2004 031 247.
[0026] The invention will be illustrated below with reference to an
embodiment in connection with the drawing, wherein:
[0027] FIG. 1 shows a diagram with a comparison of the lead
migration of an embodiment of the copper alloy according to the
invention with respect to a conventional red-bronze alloy;
[0028] FIG. 2 shows a diagram with a comparison of the nickel
migration of an embodiment of the copper alloy according to the
invention with respect to a conventional red-bronze alloy;
[0029] FIG. 3 shows a diagram with a comparison of the copper
migration of an embodiment of the copper alloy according to the
invention with respect to a conventional red-bronze alloy; and
[0030] FIG. 4 shows a diagram with a comparison of the zinc
migration of an embodiment of the copper alloy according to the
invention with respect to a conventional red-bronze alloy.
[0031] FIGS. 1 to 4 show the time history of the emission of
certain metal ions in a set-up of measuring instruments according
to DIN 50931-1 over a time of altogether 26 weeks. Here, the DIN
determines the test set-up and the test conditions by means of
which the corrosion probability of materials for metallic
components of a drinking water installation in case of a corrosion
contamination of drinking water can be determined.
[0032] In each case, the time history for the use of an embodiment
of a copper alloy according to the invention with the following
composition is shown:
[0033] Si: 3.5% by weight;
[0034] Zn: 1.6% by weight;
[0035] Mn: 0.5% by weight;
[0036] sum of unavoidable impurities: max. 0.5% by weight;
[0037] and as balance copper.
[0038] The results in the respective representations of FIGS. 1 to
4 are compared with those measured values that can be achieved in a
conventional red-bronze alloy with the same test conditions. The
red-bronze alloy has the following composition:
[0039] Zn: 5.5% by weight;
[0040] Sn: 4.5% by weight;
[0041] Pb: 3.0% by weight;
[0042] Ni: 0.5% by weight;
[0043] Balance: copper and unavoidable impurities.
[0044] The measuring results with the embodiment of the copper
alloy according to the invention are marked with A. The comparison
measurement with the red-bronze alloy is marked with B.
[0045] Apart from the aforementioned comparison, FIGS. 1 to 3 also
contain a limiting value according to the German Drinking Water
Regulation (DrinkwR) for the emission of certain ions into water
and the parameter value W(15) to be observed in migration tests.
This parameter value W(15) has to be observed if an excess of the
value of the DrinkwR is to be avoided when the tested component is
used. The parameter value W(15) results from the product of the
limiting value according to the DrinkwR and the relation of the
form factors A and B. The form factor A results according to DIN
50931 -1 from the relation of the surface of the material contacted
by water to the surface of the complete test arrangement contacted
by water. The form factor B is a scaling factor according to DIN
50930-6 which takes into consideration the type of the
components.
[0046] FIG. 1 illustrates that the amount of lead emission of the
red-bronze alloy falls within the first four test weeks nearly
exponentially from a very high value, higher tan 50 .mu.g/l, to a
value which settles just above the limiting value of the German
DrinkwR of 10 .mu.g/l after 12 to 26 test weeks. It is assumed that
this clear excess at the beginning of the tests is due to the fact
that lead that has reached the surface of the component to be
tested due to the working and manufacture migrates into the
drinking water After the first weeks, the surface-near lead has
migrated from the sample body and the amount of the emitted lead
remains approximately constant.
[0047] The embodiment according to invention A, however, emits
nearly no lead to the drinking water. An increased value at the
beginning of the tests can neither be identified. As the measured
values are at the boarder of discrimination of the measuring
analysis, the fluctuations of the measured values are attributed to
the measuring accuracy of the measuring instruments. Essentially,
the measured value for the lead emission remains clearly below the
limiting value of the DrinkwR of 10 .mu.g/l in the sample according
to the invention.
[0048] The same goes for the nickel emission of the compared
samples represented in FIG. 2. The comparison sample from the
red-bronze alloy shows a typical course where the conventional
alloy exceeds the limiting value according to the German DrinkwR
after nine weeks and slowly falls back again towards the limiting
value of the DrinkwR after a maximum approximately in the 18.sup.th
week. It is true that the increase of the nickel concentration in
the drinking water by the red-bronze alloy B could yet not be
exactly explained. However, the increase is reproducible. The
limiting value given by the DrinkwR is not observed.
[0049] In comparison thereto, the copper alloy A according to the
invention does not emit any mentionable nickel ions into the
drinking water. Here, too, the measured values of approximately 2
.mu.g/l are within the range of discrimination of the analysis used
in the measuring devices.
[0050] In the copper emission (FIG. 3), the two compared alloys
show essentially the same course. The alloy A according to the
invention, however, takes lower values for the copper emission in
.mu.g/l within the timely significant test results. The maximum for
both alloys is the measured value after 18 test weeks. Then, the
copper emission is reduced for both alloys. The better migration
values for the element copper with respect to conventional red
bronze evidence the improved corrosion resistance of the alloy
according to the invention and were first not to be expected as the
alloy according to the invention has a higher copper proportion
than conventional red bronze. It showed, however, that just this
high copper proportion of 80% and more represents the essential
cause for the improved migration behavior. By the way, both alloys
have a sufficient distance to the W(15-value) even when they have
reached their maximum. Taking into consideration the test set-up,
thus an observation of the limiting values according to the DrinkwR
results. In a comparison, however, it strikes that the alloy A
according to the invention has a more favorable behavior with
respect to the conventional alloy B with a difference amount of
approx. 500 .mu.g/l, corresponding to 20 to 25%.
[0051] Finally, FIG. 4 shows the amount of zinc emitted into the
drinking water by the alloy. For zinc, no limiting value have been
determined according to the DrinkwR. The course for the zinc
emission in the copper alloy A according to the invention differs
considerably from the corresponding course for the comparison alloy
B. The migration of the embodiment A of the alloy of zinc according
to the invention is at any time below 100 .mu.g/l. The conventional
alloy B exceeds this value many times over.
[0052] The diagrams shown in FIGS. 1 to 4 illustrate the advantages
of the copper alloy according to the invention, in particular the
influence of the silicon for the suppression of undesired metal ion
migration into the drinking water.
* * * * *