U.S. patent application number 10/798082 was filed with the patent office on 2004-09-16 for aluminium wrought alloy.
This patent application is currently assigned to Miba Gleitlager GmbH. Invention is credited to Manner, Markus, Mergen, Robert.
Application Number | 20040177902 10/798082 |
Document ID | / |
Family ID | 32234879 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040177902 |
Kind Code |
A1 |
Mergen, Robert ; et
al. |
September 16, 2004 |
Aluminium wrought alloy
Abstract
The invention relates to an aluminium wrought alloy with an
aluminium matrix, in which at least a soft phase and hard particles
are incorporated, the soft phase being at least one element from a
first group of elements consisting of tin, antimony, indium and
bismuth and the hard particles being scandium and/or zirconium and
at least one element from a second group of elements consisting of
copper, manganese, cobalt, chromium, zinc, magnesium, silicon and
iron, or inter-metallic phases of scandium, zirconium with
aluminium or aluminium with the elements from the second group of
elements. The first element(s) from the first group of elements is
(are) present in a quantity of a total of 4.5% by weight maximum,
the element(s) from the second group of elements is (are) present
in a quantity of a total of 8.5% by weight maximum and the scandium
and/or zirconium is (are) present in a quantity of a total of 0.8%
by weight maximum.
Inventors: |
Mergen, Robert; (Altmunster,
AT) ; Manner, Markus; (Mauer, AT) |
Correspondence
Address: |
COLLARD & ROE, P.C.
1077 Northern Boulevard
Roslyn
NY
11576
US
|
Assignee: |
Miba Gleitlager GmbH
|
Family ID: |
32234879 |
Appl. No.: |
10/798082 |
Filed: |
March 11, 2004 |
Current U.S.
Class: |
148/437 ;
428/614 |
Current CPC
Class: |
F16C 33/121 20130101;
F16C 2204/20 20130101; Y10T 428/12486 20150115; C22C 21/00
20130101 |
Class at
Publication: |
148/437 ;
428/614 |
International
Class: |
C22C 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2003 |
AT |
A404/2003 |
Claims
What is claimed is:
1. Aluminium wrought alloy with an aluminium matrix, incorporating
at least a soft phase and hard particles, in which the soft phase
is at least one element from a first group of elements consisting
of tin, antimony, indium and bismuth and the hard particles are
scandium and/or zirconium, and at least one element from a second
group of elements consisting of copper, manganese, cobalt,
chromium, zinc, magnesium, silicon and iron, and inter-metallic
phases of scandium, zirconium with aluminium or aluminium with the
elements from the second group of elements, characterised in that
the element (s) of the first group of elements is (are) present in
a quantity of a total of 4.5% by weight maximum, the element(s) of
the second group of elements is (are) present in a quantity of a
total of 8.5% by weight maximum, preferably 3.5% by weight,
scandium and/or zirconium is (are) present in a quantity of a total
of 0.8% by weight maximum, and the rest is aluminium with the usual
impurities contained in the melt.
2. Aluminium alloy as claimed in claim 1, characterised in that the
proportion of the soft phase is at least 0.1% by weight.
3. Aluminium alloy as claimed in claim 1, characterised in that the
proportion of the element(s) of the second group of elements
represent(s) at least a total of 0.1% by weight.
4. Aluminium alloy as claimed in claim 1, characterised in that the
proportion of scandium and/or zirconium is at least a total of
0.05% by weight, in particular 0.1% by weight.
5. Aluminium alloy as claimed in claim 1, characterised in that the
proportion of zirconium is in the range of between 0.01% by weight
and 0.5% by weight, in particular in the range of between 0.05% by
weight and 0.23% by weight.
6. Aluminium alloy as claimed in claim 1, characterised in that the
proportion of scandium is between 0.05% by weight and 0.5% by
weight, in particular in the range of between 0.05 and 0.25% by
weight.
7. Base layer made from an aluminium alloy for a bearing element,
which may be disposed between a protective shell and a running
layer of the bearing element, characterised in that the aluminium
alloy is as claimed in one of claims 1 to 6.
8. Bearing element, in particular a plain bearing or thrust ring,
with a protective shell, a running layer and a base layer disposed
in between, characterised in that the base layer is made from an
aluminium alloy as claimed in one of claims 1 to 6.
9. Bearing element as claimed in claim 8, characterised in that the
base layer is disposed directly on the protective shell.
10. Bearing element as claimed in claim 8, characterised in that
the running layer is made from an alloy with a base of lead, tin,
bismuth, indium or copper.
11. Bearing element as claimed in claim 8, characterised in that
the running layer is a layer of plastic.
12. Bearing element as claimed in claim 11, characterised in that
the plastic layer is selected from a group consisting of polyamide
6, polyarnide 66, POM, silicones, PEK, PI, TPI, P SEK, PPS, PVDF,
as well as mixtures thereof.
13. Bearing element as claimed in claim 11, characterised in that
the plastic layer contains a solid lubricant, such as MoS.sub.2,
graphite, for example.
14. Bearing element as claimed in claim 8, characterised in that
the running layer is a lubricating varnish.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to an aluminium wrought alloy with an
aluminium matrix in which a soft phase and hard particles are
incorporated, the soft phase being an element from a first group of
elements consisting of tin, antimony, indium and bismuth and the
hard particles being scandium and/or zirconium and at least one
element from a second group of elements consisting of copper,
manganese, cobalt, chromium, zinc, magnesium, silicon and iron, as
well as scandium and/or zirconium or inter-metallic phases of
scandium, zirconium with aluminium or aluminium with the elements
from the second group, a base layer for a bearing element made
therefrom, which can be disposed between a protective shell and a
running layer of the bearing element, as well as a bearing element
with a protective shell, a running layer and a base layer disposed
in between.
[0003] 2. The Prior Art
[0004] Alongside many other development trends in the
engine-building industry today, there are two main aspects which
can be singled out. First of all, engines are becoming increasingly
more powerful and, secondly, these engines are becoming
increasingly lightweight. The so-called "three-litre car", which is
promoted in the various media at regular intervals, is an example
of this trend. These specifications pursued by the automotive
industry have had a knock-on effect on the various industries
supplying accessories, such as the manufacturers of bearing
elements, for example. As a result, bearings, such as plain
bearings for example, have developed accordingly in recent years.
The starting point was originally the single-layer bearing, from
which the current multi-layer bearing was developed in order to
meet the various requirements placed on such bearings, such as
capacity to withstand load, lubricating capacity, etc.. This type
of bearing generally consists of a protective shell (usually made
of steel) designed to absorb mechanical stress, on top of which a
layer of the respective bearing alloy is applied. Another thin
coating, also known as an "overlay", is usually disposed on top of
the bearing alloy, which may be galvanically produced, for example.
This other, very thin layer normally contains a very high
proportion of so-called soft phases, such as lead or tin for
example, which impart to this layer an ability to adapt to and
embed abraded material from the parts to be mounted, such as
shafts. Due to the fine thickness of this "overlay", this layer is
also mechanically capable of withstanding a sufficient degree of
stress and serves as the so-called running layer. The bearing metal
layer underneath ensures that the bearing also remains serviceable
even if the running layer is extensively worn, for which purpose
this bearing metal layer also contains an appropriate proportion of
so-called soft phases. In order to prevent soft phases from
migrating from the running layer into the bearing metal layer,
thereby preventing a degree of brittleness that would otherwise
occur, a barrier may be provided between the running and bearing
metal to prevent migration, for example of tin. This diffusion
barrier may be made from nickel.
[0005] It is also standard practice to apply a so-called binding
film between the protective shell and the bearing metal, in order
to compensate for the properties specific to the materials of the
two layers with a view to obtaining sufficient cohesion of the
bearing, even when subjected to extensive stress. This binding film
may be made from aluminium, for example.
[0006] A bearing of this type is known from patent specification WO
98/17833 A. This WO-A patent describes in particular an aluminium
alloy for a layer, specifically for a plain bearing, which is free
of silicon except for the impurities resulting from the melting
process, and, in addition to tin, contains as the main alloying
element, at least one element each from the group of elements
consisting of lead and bismuth on the one hand and from the group
consisting of magnesium and zinc on the other. The minimum
proportion of tin is 16% by weight. All the other elements in the
alloy are limited to a total of at most 11% by weight. The
proportion of the respective element from the group which also
contains antimony and indium in addition to lead and bismuth is
between 10% and 75% of the maximum solubility of the respective
element by reference to the total tin content.
[0007] From the background art, it has been suggested--e.g. in
patent specification WO 97/22725 A--that in order to improve the
tribological properties, aluminium alloys for plain bearings which
contain tin as the main alloying element should contain an added
hard substance selected from at least one element from the group of
elements consisting of iron, manganese, nickel, chromium, cobalt,
copper, platinum, magnesium and antimony in order to create
inter-metallic phases, e.g. aluminides, in the boundary regions of
the matrix, in which case another element from a second group of
elements consisting of manganese, antimony, chromium, tungsten,
niobium, vanadium, cobalt, silver, molybdenum and zirconium should
be added as a substitute for a part of at least one hard substance
from the first group of elements in order to increase almost
spherical or cuboid aluminides. This reduces the nicking effect of
these hard particles, so that the aluminium alloy can contain a
higher proportion of soft phases, which also specifically improves
resistance to galling.
[0008] The properties which can be achieved from bearing metals
always represent compromise solutions. On the one hand it is
desirable to improve the resistance of such bearing metals or
bearing metal alloys to galling by increasing soft materials such
as tin or lead, as described above, but this can only be achieved
at the cost of resistance to mechanical stress. In order to improve
resistance to mechanical stress, it has been suggested in the prior
art that silicon, amongst other materials, be added to the alloy.
An alloy of this type is known from patent specification DE 197 30
549 A1. This DE-A1 patent describes an aluminium alloy containing
10% by weight to 25% by weight of tin as well as added copper,
nickel and manganese, which can be added to the alloy respectively
in a quantity of from 0.2% by weight to 2.0% by weight. This
aluminium alloy also contains silicon in a quantity of from 0.2% by
weight to 2.0% by weight and it is specified that the ratio of the
proportion of copper as a percentage by weight to the proportion of
nickel as a percentage by weight and the proportion of manganese as
a percentage by weight to the proportion of silicon as a percentage
by weight should be between 0.6 and 1.5. The silicon increases
hardness and reduces susceptibility to corrosive wear, preventing
the formation of coarse aluminium-copper-manganese phases, instead
of which preferred nickel-copper-aluminides and manganese-silicon
aluminides are formed. After a heat treatment at 250.degree. C.,
these aluminides are also finely distributed.
[0009] An aluminium-tin alloy containing 7% to 20% of tin is known
from patent specification DE 43 32 433 A1. The bearing alloy
additionally contains up to 4% silicon along with other alloying
elements, such as manganese, magnesium, vanadium, nickel, chromium,
zirconium, copper, antimony or titanium, for example. The mechanism
whereby silicon causes the matrix to harden is said to be due to
the fact that it crystallises out of the aluminium matrix in the
form of silicon particles, which thereby increases the strength of
the bearing alloy overall. Since the silicon particles are
distributed throughout the structure, only the soft aluminium
matrix at the surface becomes worn, so that the surface becomes
microscopically uneven. As a result, the silicon particles left
behind as convex particles are capable of withstanding a high load,
whilst simultaneously preserving the property of not bonding. The
concave parts hold the oil so that the bearing alloys are able to
withstand high load provided they have a thin film of oil and are
in metal-to-metal contact. The finely distributed silicon particles
fulfil another finction in that they wear down minute
irregularities and burrs on the co-operating shaft, thereby
improving resistance to corrosive wear.
[0010] Tests have been already been conducted with transition
metals, such as scandium for example, to determine whether they
will produce a harder matrix when added to aluminium alloys. This
was proposed in the case of cast alloys in patent specification WO
96/10099 A, where the scandium content may be between 0.01% by
weight and 10% by weight.
[0011] Scandium has also been suggested as a means of producing a
harder matrix in the case of wrought alloys (see e.g. WO 96/10099
A), which are different, and patent specification WO 00/06787 A
makes this suggestion for a bearing metal alloy, whilst patent
specification WO 00/06788 A takes this same approach in the case of
a binding layer. An alloy described in both of the above-mentioned
documents may contain, for example, 0.15% by weight to 1.0% by
weight of scandium, a total of 3% by weight of one of the elements
selected from manganese, copper or zirconium, a total of 4% by
weight of one of the elements selected from chromium, iron and
cobalt as well as tin in a quantity of up to 6.5% by weight. The
hardening effect is based on the fact that scandium forms so-called
A.sub.3M phases with aluminium and the finely dispersed
distribution of these A.sub.3M phases imparts a high ductility to
these alloys, which nevertheless exhibit no marked hardening
behaviour. In spite of the fact that solidification is reduced due
to the production process by heat treatments, these alloys have
high values of mechanical strength. Patent specification DE 36 40
698 A1 discloses a bearing alloy with an aluminium base, which
contains at least one element for the purpose of forming soft
phases, selected from the group consisting of lead, tin, indium,
antimony or bismuth, as well as silicon as a hard element and other
reinforcing elements selected from the group consisting of copper,
chromium, magnesium, manganese, nickel, zinc and iron, as well as
refining elements from the group consisting of titanium, boron,
zirconium, vanadium, gallium, scandium, yttrium and elements
selected from the rare earths with atomic numbers 57 to 71.
[0012] Patent specification DE 43 19 867 A discloses a multi-layer
plain bearing, which, in addition to a protective shell of steel
and an overlay containing polytetrafluoroethylene, contains 5% by
volume to 30% by volume of a metal filler and 5% by volume to 40%
by volume of polyvinylidene fluoride, and has a bearing layer of
bronze, such as a tin bronze or tin-lead bronze, disposed in
between.
[0013] A comparable multi-layer bearing is known from patent
specification EP 0 005 560 A, onto the metal support layer of which
a porous base layer is sintered, containing 5% by weight to 25% by
weight of lead, 5% by weight to 15% by weight of tin, the rest
being copper, with polytetrafluoroethylene in turn deposited in the
pores of the base layer.
SUMMARY OF THE INVENTION
[0014] The objective of the invention is to propose a multi-layer
plain bearing of simplified structure and at least the same
durable, tribological properties as conventional multi-layer plain
bearings.
[0015] This objective is achieved by the invention, in each case
independently, by means of an aluminium alloy of the type outlined
above, in which the element(s) of the first group of elements is
(are) used in a total quantity of 4.5% by weight maximum, the
element (s) of the second group of elements is (are) used in a
total quantity of 8.5% by weight maximum, preferably 3.5% by
weight, scandium and zirconium are present in a total quantity of
0.8% by weight maximum and the rest is aluminium and the usual
impurities formed during melting, and by a base layer made
therefrom and a bearing element incorporating a base layer made
from an aluminium alloy proposed by the invention. The resultant
advantage is that the composition of the aluminium alloy proposed
by the invention is such that the overlay can be applied directly
onto the base layer, which is disposed on the protective shell,
which is made from steel for example, which means that the
conventionally used binding layer and the nickel barrier can be
dispensed with. The composition also obviates the need for the lead
bronzes used as standard in high-performance bearings, enabling the
use of materials and metals which are as far as possible harmless
in terms of their toxicity and suitability for recycling. In
particular, the use of lead alloys can be dispensed with. The
strength and in particular the dynamic strength of the resultant
bond can be produced to higher values than is currently possible
with standard three-layer bearings and using conventional
steel/AlZn4,5 bonding. The tribological properties are also
comparable with those of AlSn6CuNi. A further advantage is the high
resistance to corrosion in contact with heavy oil and during use in
gas-powered engines as well as resistance to cavitation as compared
with AlZn4,5. The bond with steel can be produced without the need
for an adhesion-imparting intermediate layer. The base layer may
also be used for sputter bearings. Yet another advantage is the
fact that the cost of manufacturing these types of bearing elements
is comparable with that of existing standard multi-layer bearings
of the same quality. The aluminium alloy proposed by the invention
has the requisite resistance to galling due to its capacity for
plastic deformation, enabling it to adapt to geometric faults and
variations, i.e. even if faults occur in the overlay due to stress,
the bearing element will still continue to be serviceable. An
appropriate matrix toughness is obtained by means of the A.sub.3M
phases of scandium and zirconium with aluminium known from the
prior art.
[0016] These properties are further improved due to the fact that
the proportion of soft phase in the aluminium alloy is at least
0.1% by weight and the proportion of the element(s) from the second
group of elements represent(s) at least a total of 0.1% by weight,
and the proportion of scandium and zirconium totals at least 0.05%
by weight, in particular 0.1% by weight, whilst the proportion of
zirconium is in the range of between 0.01% by weight and 0.5% by
weight, in particular in the range of between 0.05% by weight and
0.23% by weight, and the proportion of scandium is between 0.05% by
weight and 0.5% by weight, in particular in the range of from 0.05%
by weight to 0.25% by weight.
[0017] In one advantageous embodiment of the bearing element, the
base layer is disposed directly on the protective shell, which
simplifies the structure accordingly.
[0018] It is also possible to use an alloy with a base of lead,
tin, bismuth, indium or copper for the overlay or the overlay may
be a layer of plastic, in particular selected from a group
consisting of polyamide 6, polyamide 66, POM, silicone, PEK, PI,
TPI, PEEK, PPS, PVDF, PTFE, as well as mixtures thereof, enabling
the aluminium alloy proposed by the invention and the bearing
element containing it to be adapted to a whole range of different
applications.
[0019] It is of particular advantage if the layer of plastic
contains a solid lubricant, such as MoS.sub.2, graphite or similar
for example, in which case the bearing properties of this plastic
layer will be further enhanced, enabling the bearing element to be
used without any or with only the smallest quantities of lubricant,
such as a lubricating oil or lubricating grease, for example.
[0020] Finally, the overlay may also be provided in the form of a
lubricating varnish.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to provide a clearer understanding, the invention
will be described in more detail below with reference to examples
illustrated in the appended drawings. Of the simplified schematic
diagrams:
[0022] FIG. 1 illustrates a bearing element in the form of a plain
bearing half-shell;
[0023] FIG. 2 is a table setting out various aluminium alloys
proposed by the invention;
[0024] FIG. 3 plots a comparison of tension-elongation values for
various aluminium alloys.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] Firstly, it should be pointed out that the same parts
described in the different embodiments are denoted by the same
reference numbers and the same component names and the disclosures
made throughout the description can be transposed in terms of
meaning to same parts bearing the same reference numbers or same
component names. Furthermore, the positions chosen for the purposes
of the description, such as top, bottom, side, etc,. relate to the
drawing specifically being described and can be transposed in terms
of meaning to a new position when another position is being
described. Individual features or combinations of features from the
different embodiments illustrated and described may be construed as
independent inventive solutions or solutions proposed by the
invention in their own right.
[0026] FIG. 1 illustrates a bearing element 1 proposed by the
invention in the form of a plain bearing half-shell.
[0027] It should be pointed out at this stage, that the invention
is not restricted to bearing elements 1 in the form of plain
bearing half-shells and may also be used for other bearing elements
1 of the type made from aluminium alloy, such as thrust rings, for
example. Moreover, bearing elements can be produced not only as
half-shells but also as full shells.
[0028] The bearing element 1 illustrated in FIG. 1 is made up of a
protective shell 2, a base layer 3 proposed by the invention and a
running layer 4. The protective shell 2 is usually made from steel,
but may naturally also be made from other similar materials which
fulfil the same or a similar function, that is to say will provide
the mechanical strength required of the bearing element 1. The
mechanical strength of the bearing element 1 as a whole will depend
on the respective application for which it will be used, and, this
being the case, a whole variety of copper alloys may be used, such
as brass, bronzes, for example. The protective shell 2 also imparts
a certain degree of dimensional stability.
[0029] The base layer 3 is made from the aluminium alloy proposed
by the invention. It consists of an aluminium matrix incorporating
at least one soft phase as well as hard particles. The at least one
soft phase is at least one element selected from a group of
elements consisting of tin, antimony, indium and bismuth. The hard
particles are at least one element selected from a second group of
elements consisting of copper, manganese, cobalt, chromium and iron
or the elements scandium and/or zirconium. These hard particles
might also be provided in the form of inter-metallic phases
comprising the latter elements or the elements from the second
group of elements with aluminium or inter-metallic phases
comprising said elements.
[0030] The soft phases on the one hand impart to the base layer 3
the capacity to form a strong enough bond with the running layer 4
disposed on top and on the other hand impart the requisite galling
resistance to the bearing element 1 if faults occur in the running
layer 4 whilst the bearing element 1 is in operation, thereby
enabling the base layer 3 to come into almost direct contact with a
component to be supported, such as a shaft, for example. The
bearing element 1 is also rendered capable of embedding any hard
particles which emerge due to wear when the bearing element 1 is in
service. The hard particles impart the requisite mechanical
strength to the aluminium alloy.
[0031] Suitable alloys for the running layer 4 are those with a
base of tin, bismuth, indium or aluminium and optionally with a
lead base or an alloy with a base of CuPb and a high lead content.
Tin alloys with a high content of tin offer particular
advantages.
[0032] Bearing metals with a lead base which might be used include,
for example, PbSb10Sn6, PbSb15Sn10, PbSb15SnAs, PbSb14Sn9CuAs,
PbSn10Cu2, PbSn18Cu2, PbSn10TiO2, PbSn9Cd, PbSn10.
[0033] Bearing metals with a tin base include SnSb8Cu4 and
SnSb12Cu6Pb, for example.
[0034] The running layer 4, on the other hand, may also be made
from a coating of plastic. Particularly advantageous examples are
polyamide 6, polyamide 66, polyoxymethylene (POM), various
silicones, polyaryl ether ketone (PEK), polyimide (PI), TPI,
polyaryl ether ether ketone (PEEK), polyphenylene sulphide (PPS),
polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE)
and various mixtures thereof.
[0035] If the sliding capacity of the plastic alone is not good
enough, it is of advantage to add solid lubricants, such as
molybdenum disulphide (MoS.sub.2), graphite or similar, to the
various plastics. Quantities of various silicones may also be
added.
[0036] Other additives may also be used in order to increase the
mechanical strength of the plastic layer, such as fibre matrices,
such as aramide fibres, for example, or hard substances such as
carbides, oxides, nitrides, for example.
[0037] The plastic layer may also be provided in the form of a
so-called lubricating varnish.
[0038] Said plastics enable running layers 4 with good sliding and
anti-galling properties to be obtained, which may also be used dry.
They are distinctive due to their low maintenance requirements. It
is possible to operate with only a small quantity of lubricant or
no lubricant at all. Water may optionally be used for lubricating
purposes, which is of particular advantage if the bearing element 1
proposed by the invention is used for pumps, for example. Apart
from offering a corresponding weight reduction, susceptibility to
nicking has also been found to be low.
[0039] In addition to the application described here, the bearing
element 1 proposed by the invention may also be used for a whole
range of other applications and in particular can be used as a
plain bearing or as a thrust ring in the automotive industry.
[0040] For the purposes of the invention, the aluminium alloy
proposed by the invention contains the element(s) from the first
element group in a quantity totalling a maximum of 4.5% by weight,
the element(s) from the second group of elements in a maximum
quantity of 3.5% by weight, scandium and zirconium in a total
quantity of. 0.8% by weight maximum, the rest being aluminium and
the usual impurities resulting from the melt. It is of advantage if
the proportion of soft phase, in other words the elements from the
first group of elements, represent at least 0.1% by weight.
Similarly, it has been found to be of advantage if the proportion
of the element(s) from the second group of elements represent(s) a
total of at least 0.1% by weight. It is also of advantage if the
proportion of scandium and zirconium also represents a total of at
least 0.1% by weight. The proportion of zirconium may be in the
range of between 0.05% by weight and 0.5% by weight, in particular
in the range of between 0.05% by weight and 0.23% by weight, and
the proportion of scandium may be between 0.05% by weight and 0.5%
by weight, in particular in the range of between 0.05% by weight
and 0.25% by weight.
[0041] Said figures given for the specified ranges should be
understood as meaning lower and upper limits of the respective
ranges, which also includes the respective peripheral ranges of
0.23% by weight to 0.5% by weight for zirconium and 0.25% by weight
to 0.5% by weight for scandium.
[0042] Copper is absorbed in the aluminium as a solid solution,
resulting in aluminium-rich mixed crystals, producing hardenable
composite alloys, which are deformable and readily lend themselves
to rolling. Copper also has the effect of strengthening the matrix
due to the hardening of the mixed crystals, whereby Al.sub.2Cu and
Al.sub.3Zr are formed independently of one another, preferably from
aluminium and zirconium, so that the resultant nucleus formation is
not heterogeneous. These crystallites start to separate more or
less at the same time. Using copper increases the resistance of the
aluminium alloy to fatigue and also improves the resistance of the
aluminium alloy to corrosion due to the corrosive effect of
oil-containing substances.
[0043] In order to improve the hardness properties, it is of
advantage to add iron to the aluminium alloy. As explained above,
like scandium, zirconium also forms so-called Al.sub.3M phases with
aluminium, enabling solidification by means of inter-metallic hard
phases. The addition of silicon can be dispensed with as a result,
the advantage of which is that the nicking effect caused by higher
contents of silicon can be at least alleviated or reduced. These
two elements also help to produce a finer grain due to the
formation of tri-aluminides.
[0044] The addition of manganese helps hardening and improves
resistance to corrosion. This also enables the recrystallisation
temperature to be raised. It also prevents the formation of
long-spiked, brittle Al.sub.3Fe needles, especially if the iron
content is low, because iron is absorbed by the AlMn crystals which
are formed by preference.
[0045] Adding cobalt and chromium can also help to harden the
aluminium alloy.
[0046] The effects of the individual elements are known in
principle from the prior art, for example from the documents
mentioned above. Using these elements for an aluminium alloy, in
particular for an aluminium wrought alloy in said range of
quantities, especially for a base layer 3 disposed between the
protective shell 2 and the running layer 4 and combining said
properties, e.g. anti-galling properties, adhesion, anti-corrosion
properties, advantageously offers the possibility of dispensing
with various other layers which are provided as standard on
existing multi-layer bearings, such as barriers to prevent
migration, and these effects have not been described until now.
[0047] In other embodiments of the aluminium alloy, compositions
were made up as set out in table of FIG. 2 and their properties
measured.
[0048] It should be pointed out that the alloy compositions listed
in the table should not be construed as limiting the scope of the
invention as they are merely given as selected examples and the
person skilled in the art will be in a position, from the teaching
disclosed here, to make up other compounds within the specified
limits and these compounds are not excluded from the protective
scope of the patent.
[0049] In the examples listed, it was found that the mechanical
properties of the aluminium alloy remain essentially constant
within a specific bandwidth. By bandwidth is meant that it is
possible the adapt the properties to suit a specific purpose, for
example by adding one or more elements in a greater or smaller
proportion. By adding a larger proportion of copper as specified in
example 9, for example, higher toughness can be obtained due to
mixed crystal hardening.
[0050] The toughness behaviour and the properties of the aluminium
alloy generally speaking can be optimised to suit the situation in
terms of cost by varying the scandium or zirconium contents.
[0051] It is also possible to optimise the properties of the
aluminium alloy with regard to the addition of the elements forming
the soft phase, because mixtures adapted to the specific field of
application can be produced, depending on the ductility of the
element, which also have a higher mechanical strength to a certain
degree, in addition to the desired anti-galling properties, albeit
not to the same extent as achieved by the hard particles.
[0052] An aluminium alloy was also produced on the basis of a
composition comprisingAlSn1,3Sc0,2Zr0,26Fe0,1 and its
tension-elongation behaviour measured and plotted in comparison
with AlSn25CuMn and AlZn4SiPb. The result is set out in FIG. 3, in
which the elongation .epsilon. is plotted on the X axis and the
nominal tensile stress .sigma..sub.z[N/mm.sup.2] on the Y axis. The
measurements were conducted on strips prepared in accordance with
UN EN1002-1 using tension samples E 3.times.8.times.30 mm as
specified in DIN 50 120.
[0053] As is clearly evident from FIG. 3, the aluminium alloy
proposed by the invention (uppermost curve) had an elongation of
0.1% compared with AlZn4SiPb (lowermost curve) and exhibited
significantly higher values than AlSn25CuMn (middle curve) with
effect from an elongation of 0.05%. In other words, in order to
obtain the same elongation, the alloy proposed by the invention
must be exposed to significantly higher forces or tensions, i.e.
the aluminium alloy has a correspondingly higher strength than the
aluminium alloys with which it was compared.
[0054] At a value of 241 N/mm.sup.2 compared with a value of 181
N/mm.sup.2 for AlZn4SiPb, the ultimate breaking strength of the
alloy proposed by the invention was also found to be significantly
higher, as was the limit of elasticity at 191 N/mm.sup.2 compared
with 85 N/mm.sup.2 for AlZn4SiPb.
[0055] The corresponding values for AlSn25CuMn are 174 N/mm.sup.2
for ultimate breaking strength and 59 N/mm.sup.2 for the limit of
elasticity.
[0056] In short, it can therefore be said that mechanical
properties can be improved by using the aluminium alloy proposed by
the invention whilst preserving at least comparable anti-galling
properties, such as required of bearing elements 1, particularly
for plain bearings.
[0057] The aluminium alloy and the bearing elements 1 made from it
can be produced using methods known from the prior art. Pure
elements or highly pure elements are used as the starting
materials. The aluminium alloy can be applied to the protective
shell by rolling, plating, e.g. electro-plating, for example. The
running layer 4 can be disposed on this binding by said methods or
alternatively by galvanic processes by spraying, etc..
[0058] Apart from rolling, the plastic layer may also be applied by
spraying, dipping or by offset printing. Galvanic processes could
also be used.
[0059] Although not absolutely necessary for the bearing elements 1
proposed by the invention, various auxiliary intermediate layers
may naturally also be provided between the individual functional
layers, depending on requirements, such as diffusion barriers, pure
aluminium layers, a nickel insulation. etc..
[0060] For the sake of good order, it should finally be pointed out
that, in order to provide a clearer understanding of the structure
of the bearing element 1, it and its constituent parts are
illustrated to a certain extent out of proportion and/or on an
enlarged scale and/or on a reduced scale.
[0061] The individual objectives achieved by the invention may be
found in the descriptions.
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