U.S. patent application number 12/014274 was filed with the patent office on 2008-07-24 for method for the alloying of aluminum to form components.
Invention is credited to Zi Li, Enrico Mahlig.
Application Number | 20080175750 12/014274 |
Document ID | / |
Family ID | 36888968 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080175750 |
Kind Code |
A1 |
Li; Zi ; et al. |
July 24, 2008 |
Method For The Alloying Of Aluminum To Form Components
Abstract
To achieve the object of providing a method by which the
disadvantages entailed in the production of components made from
materials that contain aluminum are avoided, a method for alloying
aluminum to form components is described, the alloying of aluminum
taking place by adding an aluminum-containing material, the
component being surrounded by at least one means for receiving
aluminum-containing material and the element that is formed in such
a way being sintered. Preferably, the component is surrounded in at
least one metal nonwoven material, aluminum foil being disposed
between the nonwoven material and the component.
Inventors: |
Li; Zi; (Wuppertal, DE)
; Mahlig; Enrico; (Remscheid, DE) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
CIRA CENTRE, 12TH FLOOR, 2929 ARCH STREET
PHILADELPHIA
PA
19104-2891
US
|
Family ID: |
36888968 |
Appl. No.: |
12/014274 |
Filed: |
January 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP2006/005938 |
Jun 21, 2006 |
|
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12014274 |
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Current U.S.
Class: |
420/590 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 3/26 20130101; B22F 3/26 20130101; B22F 3/10 20130101; B22F
2998/10 20130101 |
Class at
Publication: |
420/590 |
International
Class: |
C22C 1/00 20060101
C22C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2005 |
DE |
10 2005 033 073.8 |
Claims
1. A method for making an alloyed-aluminum component, comprising
providing at least one aluminum-containing material; providing a
component to be alloyed with aluminum; surrounding the component
with at least one means for receiving the at least one
aluminum-containing material; and sintering the resulting
element.
2. The method in accordance with claim 1, wherein the means for
receiving the aluminum-containing material is a non-woven
material.
3. The method in accordance with claim 1, wherein the means for
receiving the aluminum-containing material is a non-woven material
made from metal, ceramic, or a combination thereof.
4. The method in accordance with claim 1, wherein the sintering
step is carried out above the vaporization temperature of the
aluminum-containing material.
5. The method in accordance with claim 1, wherein the sintering
temperature is at least 1000.degree. C.
6. The method in accordance with claim 1, wherein said provided
component is sintered or unsintered.
7. The method of claim 6, wherein the provided component is a
powder compact, a non-woven material, fiber mat, or powder
muck.
8. The method in accordance with claim 1, wherein the provided
component is aluminum-free or has a low content of aluminum.
9. The method in accordance with claim 1, wherein the
aluminum-containing material is in the form of a metal foil, a
powder, wire, woven material, or a fiber.
10. The method in accordance with claim 1, wherein the
aluminum-containing material is made from essentially pure
aluminum.
11. The method in accordance with claim 1, wherein the
aluminum-containing material is first brought into contact with the
component and, subsequently, the component is surrounded with the
means for receiving the at least one aluminum-containing
material.
12. The method in accordance with claim 1, wherein the
aluminum-containing material is first placed on the means for
receiving the aluminum-containing material and, subsequently, the
material is brought into contact with the component by wrapping the
component with the means for receiving the aluminum-containing
material.
13. The method in accordance with claim 1, wherein the
aluminum-containing material is arranged between the component and
the means for receiving the aluminum-containing material.
14. The method in accordance with claim 1, wherein the
aluminum-containing material is aluminum foil and the means for
receiving the aluminum-containing material comprises at least one
metallic non-woven material and wherein the component is surrounded
with the at least one metallic non-woven material and the aluminum
foil is between the non-woven material and the component.
15. An aluminum-alloyed component produced in accordance with the
method of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/EP2006/05938, filed Jun. 21, 2006, which claims
the benefit of German Application No. 10 2005 033 073.8, filed Jul.
15, 2005
FIELD OF THE INVENTION
[0002] The present invention concerns methods for alloying aluminum
to form components, as well as components produced using these
methods.
BACKGROUND OF THE INVENTION
[0003] Because of its special properties, aluminum is a preferred
material, in particular in the field of space and automotive
engineering. Components made from aluminum and/or
aluminum-containing materials are lighter compared with common
components, e.g. components made from cast iron. Reducing weight in
automobiles, for example, makes it possible to increase the
efficiency rate as well as decrease fuel consumption and improve
exhaust gas values. For example, in engines and transmissions, at
this point in time, pieces that were formerly made from steel and
cast iron are gradually being replaced by those made from aluminum
and/or components produced by using aluminum. Since combining steel
and/or cast iron parts with parts made from aluminum creates
problems in terms of the different physical behaviors of the
materials involved, it is desirable to replace as many conventional
components made from steel or cast iron as possible by those
manufactured by using aluminum. This avoids problems in terms of
the differences of the materials used insofar as the thermal
expansion coefficients, thermal conductivity, elastic properties,
etc. are concerned. By using closely matching components
manufactured by using aluminum, in particular, higher efficiency
rates can also be attained.
[0004] Since many engine, clutch, and transmission components are
manufactured by using powder metallurgical technology, there is a
large interest in providing methods which permit the production of
aluminum components by using powder metallurgical technology.
However, the powder metallurgical manufacture of components by
using aluminum is disadvantageous, in particular insofar as
aluminum and its alloys tend to become coated with a very stabile
metal oxide whenever they come into contact with air. In
particular, the specific surface is increased as a result thereof.
The oxide layers that are located on the aluminum-containing
material that is used hinders the diffusion of the particles of the
powder material that is used, which is necessary for sintering. In
addition, components that are made from aluminum-containing
materials exhibit reduced strength values compared with components
made from steel or cast iron, in particular lower hardness.
Additionally, the oxide layers that are located on the
aluminum-containing initial material inhibit cold bonding among the
particles during the usual compression molding.
[0005] For example, steel with the German material number 1.4767 is
a typical aluminum-containing steel. When using such
aluminum-containing steels, however, it is particularly
disadvantageous that they perform poorly during the sintering step
due to the high oxygen affinity of the aluminum already described
above. In addition, water atomization of such aluminum-containing
steels is not acceptable from an economical point of view. In case
such aluminum-containing steels are intended to be used as fibers
and, consequently, actual sintering is planned to be preceded by a
wire-drawing step, the metal oxide layer also causes significant
tear of the drawing die used.
[0006] As a result, there is a need for a method by means of which
aluminum-containing components are manufactured while
simultaneously, during the manufacture, the known disadvantages of
state-of-the-art methods are avoided. The object of the present
invention is therefore to provide a method for alloying aluminum to
form such components which avoids the aforementioned
disadvantages.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to methods for making
alloyed-aluminum components, the methods comprising providing at
least one aluminum-containing material; providing a component to be
alloyed with aluminum; surrounding the component with at least one
means for receiving the at least one aluminum-containing material;
and sintering the resulting element. The present invention is
further directed to components produced in accordance with the
described methods.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0008] In accordance with the present invention, the object is
achieved by a method for alloying aluminum to form components
wherein the alloying of aluminum is carried out by adding an
aluminum-containing material, wherein a component is surrounded by
a means for receiving at least one aluminum-containing material,
and the resulting element is sintered. For the purposes of the
present invention, insofar as the method in accordance with the
present invention is concerned, the term "sintering" particularly
refers to achieving a sufficient temperature at which aluminum is
transferred to the gaseous phase and, as a result, at least
partially, precipitates on the surface of the component in question
and, subsequently, in case sufficient temperatures are present,
diffuses into the material of the component. As a result, by using
the method in accordance with the present invention, in particular,
components are obtained which, in a surface-near layer, have a
higher content of aluminum. Needless to say, carrying out the
method in accordance with the present invention requires that the
component to be provided with aluminum does not itself liquefy at
the temperatures that are required for the diffusion of the
aluminum into the component. The component to be provided with
aluminum itself may contain aluminum (a low content of aluminum, in
particular with an aluminum content of less than 2 of percent by
weight), although preferably, such component is essentially
aluminum-free. One advantage over the incorporation of
powder/fibers, provided such powder/fibers are/would be available,
is that there are no changes in material consistency in terms of
pores, which are caused by melting of the aluminum.
[0009] The method in accordance with the present invention is
particularly advantageous insofar as, for example, based on common
iron-chromium steels, which optionally contain other metals, in
particular rare earths, first, components including green compacts
with high resistance values can be produced which, during another
step and in respect of their properties, can be manipulated in
particular in the surface-near areas by alloying aluminum and whose
aluminum content can be specifically set.
[0010] The aluminum-containing material, which, for example, is an
aluminum alloy, preferably pure aluminum, liquefies during the
sintering step once it reaches the melting temperature, which, for
example in the case of pure aluminum, has a value of approx.
660.degree. C., wherein the aluminum-containing material, which is
liquid at that temperature, is diffused throughout the means
receiving the aluminum-containing material. As a result, dropping
of the aluminum-containing molten material is reduced, and the
concentration of aluminum in immediate proximity of the component
to be provided with aluminum is maintained at a high level as a
result thereof. When dropping below the vapor pressure, preferably
above approx. 1000.degree. C., of the aluminum-containing molten
material, aluminum becomes gaseous and is enriched in the vapor.
Since the aluminum-containing vapor develops in immediate proximity
of the component to be provided with aluminum, the gaseous aluminum
may at least partly precipitate on the surface of the respective
component and, once the sintering temperature of the component is
reached, will diffuse into the surface-near layers of the same. The
dissolved aluminum exhibits a thermodynamically lower vapor
pressure and remains stable in the component. As a result, the
method in accordance with the present invention is characterized by
a total of at least three temperature levels during the sintering
step, wherein at the first temperature level, the
aluminum-containing material liquefies, the second temperature
level characterizes the vaporization of the aluminum, and at the
third temperature level, actual sintering and diffusion of the
aluminum into at least the surface-near areas of the component
takes place.
[0011] The means for receiving the aluminum-containing material
preferably has a sufficiently large, in particular high pore volume
and has preferably a non-woven structure, wherein in a particularly
preferable manner, a non-woven material made from metal and/or
ceramic is used. Preferably and as a basic rule, the means for
receiving the aluminum-containing material should have a large
surface, as a result of which the aluminum and/or
aluminum-containing material which has melted after reaching the
first temperature level is absorbed in a uniform manner and over a
large surface and, as a result thereof, it is also uniformly
distributed throughout the component surrounded by the means
receiving the aluminum-containing material. As a result, if
desired, a very uniform diffusion of the aluminum in the entire
surface-near layer of the component can be achieved.
[0012] The sintering step of the method in accordance with the
present invention is preferably carried out above the vaporization
temperature of the aluminum-containing material, as already
addressed above. The temperature at which the aluminum is alloyed
through diffusion into the surface-near layers of the component is
preferably at least 1000.degree. C. The vaporization temperature of
the aluminum and/or of the aluminum-containing material may be
lower.
[0013] In a preferred embodiment in accordance with the present
invention, the component is selected from a group comprising
sintered and/or unsintered parts, in particular compacts, non-woven
materials, powder muck or fiber mats. The method in accordance with
the present invention can therefore be applied for yet unsintered
components as well as already sintered components. For example,
compacted green compacts may be surrounded, prior to sintering in
accordance with the method in accordance with the present
invention, with the means for receiving the aluminum-containing
material and be sintered while adding the aluminum-containing
material, wherein at the same time as sintering, the aluminum is
also alloyed. Sintering of the component and alloying of aluminum,
however, can also be performed in separate steps.
[0014] The aluminum-containing material is preferably used in the
form of a metal foil, as a powder, as a wire, as a woven material,
and/or as a fiber. The use in the form of an aluminum foil which,
additionally, is embossed on at least one side to increase the
surface and simplify the transfer of the aluminum into the vapor
phase is particularly preferred. Preferably, the
aluminum-containing material is made from pure aluminum.
[0015] The aluminum-containing material, however, may also be made
from aluminum-containing alloys. These alloys may, for example, be
manufactured from powder mixtures comprising between 60 and 98.5
percent by weight, based on the total quantity of the powder
mixture, preferably between 75 and 92 percent by weight, of an
aluminum base powder from metals and/or their alloys, comprising
aluminum, between 0.2 and 30 percent by weight of magnesium,
between 0.2 and 40 percent by weight of silicon, between 0.2 and 15
percent by weight of copper, between 0.2 and 15 percent by weight
of zinc, between 0.2 and 15 percent by weight of titanium, between
0.2 and 10 percent by weight of tin, between 0.2 and 5 percent by
weight of manganese, between 0.2 and 10 percent by weight of nickel
and/or less than 1 percent by weight of arsenic, antimony, cobalt,
beryllium, lead and/or boron, wherein all percentages by weight are
based on the total quantity of an aluminum base powder. In
addition, into the powder mixture for the manufacture of an
aluminum-containing alloy, additionally or alternatively, between
0.8 and 40 percent by weight, preferably between 7 and 15 percent
by weight, based on the total quantity of the powder mixture, of a
metal powder selected from a group of metals and/or their alloys
comprising iron, molybdenum, wolframium (tungsten), chromium,
vanadium, zirconium and/or yttrium, can be incorporated.
[0016] In an alternative embodiment in accordance with the present
invention, first, the aluminum-containing material is brought into
contact with the component and, subsequently, the component is
surrounded with the means for receiving at least one
aluminum-containing material. For the purposes of the present
invention, "bringing into contact" not only refers to any direct
contact between the aluminum-containing material and the component,
but also to partial contact and/or contact with a part of the
surface as well as the arrangement of the aluminum-containing
material close to and/or immediately adjacent to the component.
[0017] In another alternative embodiment in accordance with the
present invention, first, the aluminum-containing material is
placed on the means for receiving the aluminum-containing material
and, subsequently, the material is brought into contact with the
component by surrounding the same with the means. In another
alternative embodiment, it is also possible that, after surrounding
the component with the means for receiving the aluminum-containing
material, the aluminum-containing material is used in the area
between the component and the means. Such an alternative embodiment
is particularly suited in case aluminum-containing material is used
as a powder and/or fiber and/or their mixtures.
[0018] In another preferred embodiment in accordance with the
present invention, the component is surrounded by at least one
metallic non-woven material, wherein between the non-woven material
and the component, an aluminum foil is arranged, in particular also
an embossed aluminum foil. This preferred embodiment is
particularly advantageous insofar as it makes it possible to
dispose a relatively high quantity of aluminum in a simple and safe
manner in immediate proximity of the component, and insofar as the
resulting wrapping is easy to handle during the subsequent
sintering step and/or alloying step. In addition, by using a foil,
the concentration of aluminum during the vapor phase can be
uniformly set throughout the entire area surrounding the component.
It is also possible that either a single-layer or multilayer
aluminum foil is used, or several foil layers are used individually
on top of each other. Conventional embossed and non-embossed
aluminum foils, also known from the packaging industry, are
used.
[0019] In case a green compact is used in accordance with the
present invention, such green compact may also be subject to
subsequent compression (which may also be called intermediate
compression). For example, a compacted green compact may once again
be placed in a common matrix mold where it can at least partly be
subsequently compressed by using the respective plungers.
Preferably, the tools used for subsequent compression may entirely
or partly have a conical design, as a result of which, in certain
predefined parts of the green compact, particularly high
compressions can be achieved. Prior to the alloying of aluminum
and/or prior to sintering of the green compact, the green compact
is preferably dewaxed. Dewaxing is preferably carried out under
nitrogen, oxygen, air and/or mixtures of the aforementioned gases,
in particular also with the specific supply of air. In addition,
dewaxing may involve endogas and/or exogas, in this case preferably
in vacuum. Preferably, dewaxing may use microwaves and/or
ultrasound or only microwaves for temperature control. Finally,
dewaxing may also be achieved by using solvents such as alcohol or
the like or critical carbon dioxide with or without the use of
temperature, microwaves or ultrasound or via a combination of the
aforementioned methods.
[0020] After the step of alloying the aluminum, the actual
sintering step can be carried out. In case the component is already
a sintered component or a massive component, afterwards, a
necessary heat treatment, in particular homogenization annealing,
may be optionally performed. Heat treatment can be conducted
depending on the chemical composition of the resulting component.
Alternatively or in addition to heat treatment, the sintered
component may also be quenched--based on the sintering and/or
homogenization annealing temperature--preferably in water or via
gas quenching.
[0021] Prior to or after sintering or alloying of the aluminum,
additional surface densification, or more generally: the
application of internal compression stresses in superficial areas,
in particular by means of sandblasting or shot peening, rolling or
the like, may be carried out. Also, prior to or after
homogenization annealing, calibration may be carried out.
Calibration is performed at room temperature or at an elevated
temperature up to the forging temperature, also with the use of
pressure of up to 900 N/mm.sup.2. Optionally, calibration can even
be carried out above the solidus line, in which case the component
can also be removed directly at the sintering heat and/or at the
temperature used for alloying the aluminum.
[0022] The present invention furthermore concerns a component
manufactured in accordance with the method in accordance with the
present invention. A component manufactured in accordance with the
present invention is particularly characterized in that, in the
surface-near areas, an increased aluminum content can be detected.
The resulting component may at least partly have a higher aluminum
content in such areas.
[0023] The components that are produced by using the method in
accordance with the present invention may be used in particular for
hot gas filtering, but also in particular for waste gas filtering
for combustion engines, and in this case in particular as carriers
for catalytic converters or as a soot filter. In addition, the
components produced by using the method in accordance with the
present invention may be used in membrane reactors in which gas
reactions take place.
[0024] Nonetheless, they can also be used as other substrates for
non-metallic layers. As a basic rule, the components manufactured
by using the method in accordance with the present invention
display an increased oxidation resistance compared with components
without any increased aluminum content in the surface-near
layer.
[0025] These and further embodiment shall be illustrated in more
detail in the following examples:
Example 1
[0026] From an Inconel 600 (nickel-chromium alloy) powder with the
German material number 2.4816 (aluminum-free), a green compact was
produced in the form of a tube. The powder mixture was
isostatically compressed into a tube-shaped green compact at room
temperature. The density of the green compact was approx. between
2.35 and approx. 2.38 g/cm.sup.3. Afterwards, the green compact
produced in such a manner was dewaxed for approx. 30 minutes at
approx. 430.degree. C.
[0027] Afterwards, the green compact produced in such a manner was
wrapped in a single layer of common commercial aluminum foil,
embossed on at least one side, and care was taken to ensure that
the aluminum foil was in uniform and close contact with the tubular
green compact. Such aluminum foil-wrapped component was
subsequently placed between two metallic non-woven materials with a
composition of 75% of iron, 20% of chromium, and 5% of aluminum,
with these metallic non-woven materials having a porosity of
85%.
[0028] The resulting wrap was placed in a vacuum furnace. Once the
temperature reaches the melting temperature of aluminum at approx.
660.degree. C., the aluminum foil begins to melt, and the liquid
aluminum is received by the two metallic non-woven materials in a
uniform manner and over a large surface. This prevents dropping of
the molten aluminum and, consequently, a reduction in the quantity
of aluminum in the immediate proximity of the component. In case
the vaporization temperature for aluminum is exceeded, the aluminum
evaporates and precipitates over a large surface of the green
compact made from aluminum-free steel that was used. As a result of
subsequent or simultaneous sintering of the green compact at a
temperature of approx. 1100.degree. C. itself, the aluminum
diffuses in the surface-near areas of the green pump impeller
compact. The temperature in the furnace can be gradually increased,
although it is also possible to immediately set a temperature above
the vaporization temperature and, as long as this is desired, also
above the sintering temperature at the same time.
Example 2
[0029] In another example, a fiber mat was sintered from the
material with the German material number 1.4113 (aluminum-free)
under the usual conditions. Afterwards, the sintered fiber mat was
uniformly wrapped on both sides with aluminum foil, and the
aluminum foil-wrapped fiber mat was subsequently placed between two
metallic non-woven materials with a lower porosity and a larger
surface than the fiber mat produced. Afterwards, aluminum was
alloyed as already described above for the green pump impeller
compact. As a result, a fiber mat was obtained with an alloyed
aluminum content of more than 5 percent by weight, based on the
total quantity of the fiber mat. For example, in the case of fiber
mats made from the material with the German material number 1.4404
(aluminum-free), after alloying of aluminum under comparable
conditions, the aluminum content of the finished fiber mat exceeded
1 percent by weight, based on the total quantity of the fiber mat.
For example, after manufacturing a green compact from Inconel 600
powder, the aluminum content of the finished sintered component,
after alloying in accordance with the above-described method by
using an aluminum foil, exceeded 1 percent by weight, based on the
total quantity of the component, which matches that of Inconel
601.
[0030] The present invention therefore provides a simple method
which makes it possible, in particular, to provide aluminum-free
materials with aluminum at least in the surface-near areas even
after the manufacture of sintered components and therefore ensure
the advantageous properties of the same.
* * * * *