U.S. patent application number 11/916413 was filed with the patent office on 2010-09-02 for aluminum plain bearing alloy.
Invention is credited to Juri Moiseev, Heinz Palkowski, Lorenz Ratke, Hubert Schwarze, Babette Tonn, Hennadiy Zak.
Application Number | 20100221141 11/916413 |
Document ID | / |
Family ID | 34971668 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100221141 |
Kind Code |
A1 |
Tonn; Babette ; et
al. |
September 2, 2010 |
ALUMINUM PLAIN BEARING ALLOY
Abstract
The invention relates to a monotectic aluminium plain bearing
alloy, comprising 5 to 20 wt. % bismuth, 3 to 20 wt. % zinc, 1 to 4
wt. % copper and additionally several of the components manganese,
vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten,
chromium, silver, calcium, scandium, cerium, beryllium, antimony,
boron, titanium, carbon and zirconium in amounts up to 5 wt. % and
aluminium to make 100 wt. %, produced by strip casting and during
the subsequent production process for plain bearings, after rolling
or roll-bonding, subjected to a heat treatment at ca. 270 to
400.degree. C. Long bismuth particles or sheets, produced by
rolling or roll-bonding can thus be recoagulated to give
finely-distributed spherical drops with a size in the 20 .mu.m
range and smaller.
Inventors: |
Tonn; Babette;
(Clausthal-Zellerfeld, DE) ; Moiseev; Juri;
(Clausthal-Zellerfeld, DE) ; Zak; Hennadiy;
(Clausthal-Zellerfeld, DE) ; Ratke; Lorenz; (St.
Augustin, DE) ; Palkowski; Heinz; (Werne, DE)
; Schwarze; Hubert; (Marburg, DE) |
Correspondence
Address: |
WHITHAM, CURTIS & CHRISTOFFERSON & COOK, P.C.
11491 SUNSET HILLS ROAD, SUITE 340
RESTON
VA
20190
US
|
Family ID: |
34971668 |
Appl. No.: |
11/916413 |
Filed: |
June 7, 2005 |
PCT Filed: |
June 7, 2005 |
PCT NO: |
PCT/EP05/06091 |
371 Date: |
April 19, 2010 |
Current U.S.
Class: |
420/531 ;
164/122; 164/459; 164/76.1 |
Current CPC
Class: |
C22C 21/00 20130101;
C21D 9/40 20130101; C22F 1/053 20130101; B22D 11/003 20130101; C22F
1/04 20130101; C22C 21/10 20130101 |
Class at
Publication: |
420/531 ;
164/122; 164/459; 164/76.1 |
International
Class: |
C22C 21/10 20060101
C22C021/10; B22D 27/04 20060101 B22D027/04; B22D 11/00 20060101
B22D011/00; B22D 23/00 20060101 B22D023/00 |
Claims
1. A monotectic aluminum plain bearing alloy comprising 5 to 20% by
weight bismuth, 3 to 20% by weight zinc, 1 to 4% by weight copper
and additionally one or more of the components manganese, vanadium,
niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium,
silver, calcium, scandium, cerium, beryllium, antimony, boron,
titanium, carbon and zirconium in a total of up to 5% by weight and
aluminum to make it up to 100% by weight.
2. The monotectic aluminum plain bearing alloy as claimed in claim
1, characterized in that the alloy contains between 7 and 12% by
weight bismuth.
3. The monotectic aluminum plain bearing alloy as claimed in claim
1, characterized in that the alloy contains between 3 and 6% by
weight zinc.
4. The monotectic aluminum plain bearing alloy as claimed in claim
1, characterized in that the alloy contains between 2 and 4% by
weight, in particular between 2 and 3% by weight, copper.
5. The monotectic aluminum plain bearing alloy as claimed in claim
1, characterized in that the alloy contains up to 2% by weight
Al--Ti--B or Al--Ti--C grain refiner.
6. A process for producing an aluminum plain bearing alloy using
the composition as claimed in claim 1, characterized in that the
alloying constituents are combined to form an alloy in a casting
process in which the cooling rate is 5 to 1000 K/s.
7. The process as claimed in claim 6, characterized in that the
drawing-off rate is 2 to 15 mm/s.
8. The process as claimed in claim 6, characterized in that a
continuous casting process is used as the casting process.
9. The process as claimed in claim 6, characterized in that, for
the preparation of a semifinished product, the alloy is provided
with at least one supporting layer.
10. The process as claimed in claim 6, characterized in that at
least one heat treatment at temperatures of from 270.degree. C. to
400.degree. C. is performed on the alloy in the course of
subsequent forming processes.
11. The process as claimed in claim 10, characterized in that the
heat treatment follows a rolling and/or roll-cladding
operation.
12. A plain bearing shell which contains an alloy comprising 5 to
20% by weight bismuth, 3 to 20% by weight zinc, 1 to 4% by weight
copper and additionally one or more of the components manganese,
vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten,
chromium, silver, calcium, scandium, cerium, beryllium, antimony,
boron, titanium, carbon and zirconium in a total of up to 5% by
weight and aluminum to make it up to 100% by weight as one of the
materials used in it or consists of this alloy.
13. A plain bearing with a shell which contains an alloy comprising
5 to 20% by weight bismuth, 3 to 20% by weight zinc, 1 to 4% by
weight copper and additionally one or more of the components
manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron,
tungsten, chromium, silver, calcium, scandium, cerium, beryllium,
antimony, boron, titanium, carbon and zirconium in a total of up to
5% by weight and aluminum to make it up to 100% by weight as one of
the materials used in it or consists of this alloy.
Description
[0001] The invention relates to a heavy-duty aluminum plain bearing
alloy, in particular for multilayer bearings, to a process for its
production and to associated plain bearing shells and plain
bearings.
[0002] Heavy-duty plain bearings are made up of a number of layers
to meet the variety of requirements that are demanded of the
bearings and to some extent conflict. Steel-aluminum composite
materials are predominantly used. While the steel supporting shell
ensures that mechanical loads are absorbed and that there is a firm
fit, the materials of the plain bearing have to withstand the
diverse tribological loads and be resistant to fatigue. In order to
meet this requirement, the materials of the plain bearing in the
aluminum matrix contain on the one hand hard phases, such as for
instance silicon and intermetallic precipitates, and on the other
hand soft phases, such as for example lead or tin. The heavy-duty
multilayer bearings often additionally have a sliding layer with a
high lead content that is galvanically applied on the functional
layer. This soft sliding layer provides the good emergency-running
properties of the bearing. It can embed abrasion particles and so
remove them from the sliding surface.
[0003] An environmentally friendly alternative to aluminum plain
bearing alloys that contain lead are plain bearings based on
aluminum-tin, which are used without an additional sliding layer.
However, there are limits to the mechanical properties of these
alloys, for example the fatigue resistance and heat resistance. The
relatively high tin content results during casting in the formation
of a tin network joined together at the grain boundaries, which
considerably impairs the load-bearing capacity of these alloys,
especially at relatively high temperatures.
[0004] By contrast with tin, bismuth has several advantages as the
soft phase in the aluminum matrix. For instance, bismuth has a
higher melting point and can be used at higher temperatures. In
addition, it is possible by special casting and heat treatment
measures to avoid a massive enrichment of the bismuth at the grain
boundaries of the plain bearing alloys and to obtain a sufficiently
uniform and fine distribution of the bismuth droplets in the
microstructure, which ultimately results in an improvement in its
load-bearing capacity and the tribological properties in comparison
with aluminum-tin alloys.
[0005] So it has been proposed in DE 4003018 A1 that an aluminum
alloy may contain one or more of the components 1 to 50% by weight,
preferably 5 to 30% by weight, lead, 3 to 50% by weight, preferably
5 to 30% by weight, bismuth and 15 to 50% by weight indium and
additionally one or more of the components 0.1 to 20% by weight
silicon, 0.1 to 20% by weight tin, 0.1 to 10% by weight zinc, 0.1
to 5% by weight magnesium, 0.1 to 5% by weight copper, 0.05 to 3%
by weight iron, 0.05 to 3% by weight manganese, 0.05 to 3% by
weight nickel and 0.001 to 0.30% by weight titanium. This alloy,
known from DE 4003018 A1, is cast by continuous casting vertically
into a strip or wire of 5 to 20 mm in thickness or diameter, the
melt being cast at a cooling rate of 300 to 1500 K/s. The rapid
cooling rate is intended to prevent large-volume precipitates of a
minority phase from forming in the time between the temperature
falling below the segregation temperature and the complete
solidification of the matrix metal. However, it is known from
practical experience with the continuous casting of aluminum alloys
that the very high cooling rates have the consequence that there is
a considerable risk of crack formation and that the process
stability required for mass production can only be ensured with
difficulty.
[0006] The process described in EP 0 940 474 A1 allows a monotectic
aluminum plain bearing alloy that is difficult to cast, comprising
up to 15% by weight bismuth and at least one element from the group
comprising silicon, tin and lead in total of 0.5 to 15% by weight
and possible additions from the group comprising copper, manganese,
magnesium, nickel, chromium, zinc and antimony to an extent of in
total up to 3%, to be cast with reproducible quality by strip
casting. A homogeneous distribution of the minority phase is in
this case achieved by intensive stirring of the melt in the
electromagnetic field. By adding grain refiners, the microstructure
of this alloy is additionally refined. Among the effects this has
is also an advantageous effect on the size of the bismuth
precipitates in the form of drops, which in the cast state have a
diameter of at most 40 .mu.m. The added amount of grain refiners is
calculated according to EP 0 940 474 A1 by a formula that allows
for the bismuth content in the melt. This invention does not
contain any indications of the kind of grain refining additions
that are used to obtain the results described in the patent.
[0007] EP 0 190 691 discloses an alloy comprising 4 to 7% by weight
bismuth, 1 to 4.5% by weight silicon, 0 to 1.7% by weight copper, 0
to 2.5% by weight lead and at least one element from the group
comprising nickel, manganese and chromium to an extent of in total
up to 1% and additionally at least one element from the group
comprising tin, zinc and antimony of in total up to 5% by weight.
Although high silicon contents strengthen the aluminum matrix, they
have an adverse influence on the size of the minority phase and
lead to a distinct worsening of the drop distribution in the
strand. During the rolling of such a cast structure, the originally
spherical lead or bismuth phase is deformed into very thick
filaments, which considerably reduce the mechanical load-bearing
capacity and the tribological properties of the material.
[0008] One possible solution for setting the desired material
properties is to transform the elongate precipitates of the
minority phase into compact structural forms by a subsequent heat
treatment. For example, according to DE 4014430 A1, a monotectic
aluminum-silicon-bismuth alloy is heat-treated at temperatures of
from 575.degree. C. to 585.degree. C. in order to achieve a fine
distribution of the bismuth phase, stretched in the form of
lamellae after rolling.
[0009] As a further advantage, the heat treatment offers the
possibility of improving the strength values of the aluminum plain
bearing alloy by hardening effects. The elements suitable for
achieving the possible hardening effects are, for example, silicon,
magnesium, zinc and zirconium. The addition of copper increases the
hardening rate and can be used in combination with these
elements.
[0010] U.S. Pat. No. 5,286,445 discloses an aluminum plain bearing
alloy with a bismuth content of from 2 to 15% by weight, 0.05 to 1%
by weight zirconium and a copper content and/or magnesium content
of up to 1.5%. In addition, this alloy contains at least one
element from the group comprising tin, lead and indium in a total
of 0.05 to 2% by weight or at least one element from the group
comprising silicon, manganese, vanadium, antimony, niobium,
molybdenum, cobalt, iron, titanium and chromium in a total of 0.05
to 5% by weight. The additions of tin, lead and indium assist the
re-coagulation of stretched bismuth drops to finer precipitates at
temperatures of from 200.degree. C. to 350.degree. C. The elements
zirconium, silicon and magnesium bring about the actual hardening
effect after annealing in the temperature range of 480.degree. C.
to 525.degree. C., which according to U.S. Pat. No. 5,286,445 is
carried out shortly before the roll-cladding operation. The
transition elements are intended to ensure an additional increase
in the mechanical load-bearing capacity of the material.
[0011] The unfavorable effect of silicon on the size and
distribution of the minority phase has already been reported. The
addition of magnesium is additionally accompanied by the
disadvantage that magnesium preferentially forms with bismuth the
intermetallic compound Mg.sub.3Bi.sub.2. This is intercalated in
the bismuth drops and distinctly reduces the ability of the bismuth
drops to embed abrasion particles. Adding tin considerably impairs
the mechanical load-bearing capacity of the plain bearing material
at higher temperatures. Furthermore, the temperatures for the heat
treatment of over 480.degree. C. that are proposed in DE 40144 30
A1 and in U.S. Pat. No. 5,286,445, are very unfavorably chosen with
regard to the formation of brittle intermetallic phases between the
steel supporting shell and the aluminum. According to the prior
art, the temperature range that is acceptable for cladding aluminum
with steel lies below 400.degree. C.
[0012] None of the bismuth-containing alloys described above have
so far gained any practical significance, since it has not yet been
possible to master adequately the complex processes that occur
during their production by continuous casting and subsequent
further processing to form the plain bearing shell. Apart from a
fine distribution of the minority phase in the cast state, a
pre-requisite for optimum characteristics of the aluminum plain
bearing alloys is in particular the possibility of being able to
establish a fine distribution of the minority phase even after the
necessary forming and roll-cladding operations. Other requirements
are high strength, mechanical load-bearing capacity--including at
high temperatures--wear resistance of the aluminum matrix and good
formability.
[0013] The invention is consequently based on the object of
providing a heavy-duty aluminum plain bearing alloy that avoids the
disadvantages of the prior art and makes it possible to achieve a
uniform and fine distribution of the bismuth phase and to preserve
and possibly improve this during the subsequent further processing
of the strips in the production phase to form the plain bearing
shell.
[0014] This object is achieved by an aluminum plain bearing alloy
containing the following constituents: about 5 to 20% by weight
bismuth, about 3 to 20% by weight zinc, about 1 to 4% by weight
copper and additionally one or more of the components manganese,
vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten,
chromium, silver, calcium, scandium, cerium, antimony, boron,
beryllium, titanium, carbon and zirconium in a total of up to about
5% by weight and the remainder aluminum, but without tin, lead and
silicon, apart from in an amount caused by smelting-related
impurities, or in an amount of up to at most 1% by weight of each.
This means that it is intended in principle that the alloy
according to the invention should not contain tin and silicon as
alloying constituents. However, not only tin (Sn) but also lead
(Pb) and silicon (Si) may be present in amounts caused by
impurities of up to about 0.3% by weight, or otherwise in small
amounts of up to about 1% by weight, but better up to about 0.5% by
weight, without impairing the advantages of the invention too much.
The plain bearing alloy according to the invention is preferably
continuously cast and is already distinguished in the cast state by
a fine distribution of the bismuth phase, which is largely
independent of the drawing-off and cooling rate. Long bismuth
lamellae created in the course of a further treatment when rolling
and roll-cladding can subsequently be re-coagulated completely by a
heat treatment at temperatures of from 270.degree. C. to
400.degree. C. to form finely distributed spherical drops, which
are smaller than 20 .mu.m if the process is conducted
appropriately.
[0015] The alloy preferably contains between about 7 and 12% by
weight bismuth. The zinc content may preferably lie between about 3
and 6% by weight, that of copper between about 2 and 4, in
particular between about 2 and 3% by weight. The contents of the
various elements are variable independently of one another within
the given limits.
[0016] The alloy according to the invention differs from the known
alloys by the use of bismuth as a single soft phase former, i.e.
there is no combination of bismuth with lead and/or tin, and by a
zinc content increased up to a maximum of 20% by weight and a
copper content increased up to a maximum of 4% by weight. Although
the stated amounts of added zinc and copper lead to a slight
worsening in the size of the bismuth drops in the cast state in
comparison with binary Al--Bi alloys, they permit a complete
re-coagulation of the highly stretched bismuth filaments after the
cladding pass to form fine spherical drops of up to 20 .mu.m in
size. For this purpose, annealing operations of up to 400.degree.
C. are provided. The annealing time depends on the chemical
composition. In addition, increased copper contents bring about an
increase in the strength of the aluminum matrix and in our
experience improve the corrosion resistance of the
bismuth-containing plain bearing material.
[0017] It has been found that use of the commercially available
grain refiner AlTi5B1 or AlTi3CO,15 in added amounts of about 0.3
to 2% by weight have a great grain-refining effect on the alloy
according to the invention and reliably prevent the formation of
heat cracks during continuous casting at different cooling rates.
The addition of the grain refiners mentioned has the additional
effect of distinctly reducing the size of the minority phase. It
has been possible by the use of grain refining additions to reduce
the maximum diameter of the bismuth drops in the cast state to less
than 30 .mu.m, even with relatively low cooling rates of about 5
K/s.
[0018] With the aid of the elements manganese, vanadium, niobium,
nickel, molybdenum, cobalt, iron, tungsten, chromium, silver,
calcium, scandium, cerium, beryllium, antimony, boron, titanium,
zirconium and carbon, it is possible to adapt the properties of the
alloy according to the invention specifically to the respective
intended use.
[0019] The invention further comprises a process for producing an
aluminum plain bearing alloy using the composition according to the
invention as described above. With preference, the alloying
constituents are combined to form an alloy in a casting process in
which the cooling rate is 5 to 1000 K/s. The alloy can otherwise
also be produced by other customary production processes, in
particular by other casting processes. Production by continuous
casting is currently preferred. The conditions are then to be
adapted in such a way that preferably bismuth intercalations in
drop form are created. During the continuous casting, the
drawing-off rate is preferably 2 to 15 mm/s.
[0020] According to a preferred embodiment of this invention, the
alloy obtained by casting is subjected to at least one heat
treatment at temperatures between about 270 and 400.degree. C. in
the course of subsequent forming processes. Such a heat treatment
preferably follows a rolling and/or roll-cladding operation, it
being possible for a number of rolling and/or cladding operations
to be carried out within the production process between the casting
of the alloy and the end product, and at least one heat treatment
to follow on after the final rolling and/or roll-cladding operation
or else after a number of or all of these operations.
[0021] For the preparation of a semifinished product or in the
course of the production of products such as for instance plain
bearings, the cast alloy may be provided with at least one
supporting layer. The supporting layer may be in particular a steel
layer. Further layers, for example adhesion promoting layers or
coatings, may be added.
[0022] The invention further comprises a plain bearing shell which
contains an alloy according to the invention as one of the
materials used in it or consists of this alloy.
[0023] Finally, the invention comprises a plain bearing with such a
plain bearing shell or the use of the plain bearing shell according
to the invention in a plain bearing.
[0024] The invention is explained in more detail below on the basis
of an exemplary embodiment.
[0025] In the drawing:
[0026] FIG. 1 shows a cast structure of an AlZn5Cu3Bi7 alloy,
[0027] FIG. 2 shows a rolled structure of an AlZn5Cu3Bi7 alloy,
total forming degree 94%, before the heat treatment,
[0028] FIG. 3 shows a rolled structure of an AlZn5Cu3Bi7 alloy,
total forming degree 94%, after the heat treatment at 360.degree.
C./3 h.
[0029] To produce the plain bearing material, in this example cast
strips with a cross section of 10 mm.times.100 mm are created on a
vertical continuous casting installation, as known in the prior
art, with the addition of 0.6% by weight AlTi5B1. In the production
of the strips, the drawing-off rate is 8 mm/s and the cooling rate
is 600 K/s. The strands are initially milled horizontally on the
wide sides to a thickness of approximately 8 mm.
[0030] Subsequently, a brushed and degreased adhesion promoter of
an aluminum alloy is clad onto the likewise brushed and degreased
AlZn5Cu3Bi7 alloy with the first rolling pass in the rolling stand.
The thickness of the clad raw material strip is 4 mm. This is
subsequently rolled to 1.3 mm in a number of rolling passes. Five
rolling passes are necessary for this. In order to improve the
cladding properties of the aluminum bearing material strip, it is
subjected to a recovery annealing operation at 370.degree. C. for
up to 3 hours. In the next processing step, the steel strip and the
aluminum bearing material strip are bonded to one another in a
cladding rolling mill.
[0031] Subsequently, the material combination created is subjected
to a heat treatment at a temperature of 360.degree. C. lasting
three hours, the bond between the steel and the aluminum bearing
material being increased by a diffusion process and the highly
stretched bismuth filaments after the cladding in the
aluminum-zinc-copper matrix being completely reformed into fine
spherical drops of up to 20 .mu.m in size. The high degree of
hardness likewise resulting from the heat treatment, of at least 43
HB 2.5/62.5/30, is also of advantage. After this heat treatment,
the clad strip can be subdivided and formed into bearing
shells.
[0032] FIGS. 1 to 3 show by way of example how an alloy according
to the invention, here an AlZn5Cu3Bi7 alloy, changes in its
microstructure during the working. FIG. 1 shows the microstructure
of the alloy after the production by continuous casting. The
bismuth phase, which is in the form of droplets, is shown as
dark.
[0033] FIG. 2 shows the microstructure of the alloy after the
rolling. The bismuth lamellae elongated by the rolling can be seen
in the rolled structure.
[0034] FIG. 3 shows the rolled structure after a heat treatment at
360.degree. C. for 3 hours. It has been possible for the elongated
Bi lamellae to be effectively re-coagulated by the heat treatment.
Larger drops, isolated instances of which can still be seen in FIG.
1, have been broken down by the stretching and re-coagulating, so
that the overall degree of fine distribution is increased by the
treatment.
[0035] It should be mentioned that the example merely serves the
purpose of illustration and does not restrict the invention. A
person skilled in the art also knows how plain bearings and bearing
shells are produced and how the production of the alloy according
to the invention can consequently be incorporated in the customary
bearing production processes.
* * * * *