(19) |
|
|
(11) |
EP 1 796 860 B1 |
(12) |
EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
|
06.08.2008 Bulletin 2008/32 |
(22) |
Date of filing: 08.09.2005 |
|
(51) |
International Patent Classification (IPC):
|
(86) |
International application number: |
|
PCT/EP2005/009630 |
(87) |
International publication number: |
|
WO 2006/032369 (30.03.2006 Gazette 2006/13) |
|
(54) |
MODIFYING SURFACES OF WORK-PIECES AND FORMING TOOLS
MODIFIKATIONSFLÄCHEN VON WERKSTÜCKEN UND FORMWERKZEUG
MODIFICATION DE SURFACES DE PIECES A USINER ET OUTILS DE FORMAGE
|
(84) |
Designated Contracting States: |
|
AT BE CH DE FR HU IT LI |
(30) |
Priority: |
20.09.2004 EP 04405604
|
(43) |
Date of publication of application: |
|
20.06.2007 Bulletin 2007/25 |
(73) |
Proprietor: Alcan Technology & Management Ltd. |
|
8212 Neuhausen am Rheinfall (CH) |
|
(72) |
Inventor: |
|
- HOTZ, Walter
CH-8222 Beringen (CH)
|
(56) |
References cited: :
|
|
|
|
- PATENT ABSTRACTS OF JAPAN vol. 1999, no. 01, 29 January 1999 (1999-01-29) -& JP 10
265917 A (INOUE AKIHISA), 6 October 1998 (1998-10-06)
- PATENT ABSTRACTS OF JAPAN vol. 007, no. 031 (M-192), 8 February 1983 (1983-02-08)
-& JP 57 187127 A (NISSAN MOTOR LTD), 17 November 1982 (1982-11-17)
|
|
|
|
Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
|
[0001] The present invention relates to a forming tool, a method of modifying the surface
of a work-piece wherein at least one surface of the work-piece comes into contact
with the structured surface of a forming tool at least once and a method of structuring
the outer surface of a forming tool, according to the preambles of claims 1, 15 and
21 respectively (see for example
JP-A-10265917).
[0002] In the materials processing industries there are many types of forming operation.
In the metals industry forming operations can include, for example: press forming,
where the work-piece to be formed takes the shape imposed by a punch and a die; drawing,
where a work-piece in the form of a flat blank of sheet is formed into a cup shape
by forcing a punch against the central portion of the blank as it rests on a die ring;
coining, where a work-piece is squeezed between dies and is deformed such that the
details of its final form and surface appearance are defined by the shape and surface
of the dies; stretch forming, where a sheet blank work-piece is formed over a form
block of the required shape with the work-piece under tension; drop hammer processing;
stamping, which is similar to coining; embossing, which is generally the making of
shallow impressions in the surface of a work-piece by compression between two die
pieces under a relatively low load; texturing, which is similar to embossing but where
more load is applied leading to more deformation into the bulk work-piece; rolling,
where work-pieces in the form of sheets are pressed between two rotating cylindrical
rolls; and cold roll forming, where the rotating rolls are shaped such that the sheet
work-piece is formed into desired shapes of uniform cross-section.
[0003] A work-piece is a body of indeterminate size and shape. For example a block of metal
or plastic is a work-piece and so are pre-formed articles for use as vehicle panels.
Sheet, plate and foil, both in continuous form and in the form of cut pieces, are
further examples of work-pieces. In one form of the invention the work-piece is preferably
rolled sheet or strip and is more preferably rolled sheet or strip of aluminium and
aluminium-based alloys.
[0004] In this invention a structured surface is meant to be where the surface is not intended
to be smooth. Of course most surfaces are not perfectly smooth, but it will be readily
understand what is covered by the meaning of a structured surface if it is defined
as one possessing deliberate roughness, patterns, protuberances, depressions, ridges
and troughs or engraving-like features, such features to be transmitted to the surface
of the work-piece such that the work-piece surface is also not smooth.
[0005] Typically forming operations like this are applied to metals, in particular metals
based on iron, aluminium or copper as the main constituent, but they may also be applied
to plastic materials. In some cases a forming method like embossing can be applied
to paper-based materials.
[0006] During such forming operations, the appearance of the surface of the work-piece which
was in contact with the forming surface of the forming tool after forming is typically
the same as or similar to the surface appearance of forming surface of the forming
tool. The surface on the work-piece may not be an exact replica of the surface of
the forming tool because various factors like the amount of load applied through the
forming tool or the physical properties of the material of the work-piece have an
influence on the extent of deformation. It is routine practice to adjust forming conditions
to take account of such factors. Often the surface of the forming tool may be exaggerated
in order to ensure the final surface on the work-piece is produced.
[0007] There are also many situations where the surface of a work-piece is desirably modified
in order to bring about specific benefits. The surfaces of work-pieces may be modified
for purely decorative reasons. Examples are where a coining operation is used to produce
coins, buttons or medals to specific designs. Other examples are where a metallic
sheet work-piece is treated such that it has a certain range of roughness across the
surface in order to mask any defects that might be present after a rolling operation.
This is often done in order to give a uniform appearance to the final product. The
surface of a work-piece may also be modified in order to attain desirable physical
characteristics with the aim of improving the performance of an article in a specific
application, where that performance depends strongly on the surface characteristics
of the work-piece.
[0008] When modifying the surface of flat sheet the forming tools may have on their surface
a textured surface prepared by one of a variety of methods. Such known methods include
EDT texturing, sand blasting or shot peening, mechanical brushing, structured Cr deposition
(also known as Topocrom), and so on. These methods result in a working surface which
is stochastic in nature and after rolling this surface structure is substantially
transferred to the surface of the work-piece. Other known methods include laser beam
or electron beam texturing and these can produce a deterministic structure. A deterministic
structure would show a pattern, or would be one where a specific design is present
and could include, for example, an imprint of wording or an imprint of a trade mark.
Deterministic structures can also be a drawing or a parabolic topography or a grating.
In the case of multiple pass embossing, deterministic structures can lead to interference
effects whilst stochastic structures generally will not.
[0009] In work rolls used for forming metal sheet by rolling, a deterministic structure
could be imparted into the surface of the work roll by a machining operation, but
this would be expensive and such work rolls have a limited life whereafter they need
to be refurbished or re-machined, operations which can be expensive and time consuming.
Furthermore, the quality of indentation of the deterministic structure into the surface
of the work-piece may deteriorate over time due to wear of the forming surface of
the forming tool leading to variable quality in the final product over long production
runs.
[0010] Deterministic structures are more readily and more commonly produced in the surfaces
of work-pieces using methods such as coining, stamping or press forming where it is
common to machine the desired design into the surface of the die or punch.
[0011] In most of the forming operations mentioned above there is eventually a need to replace
dies, punches, rolls and other tools used for forming, or to refurbish the same. This,
of course, depends on the material from which the work-piece is made with harder work-pieces
leading to faster wear of forming tools than softer work-pieces.
[0012] The life of a forming tool is often extended by adding a protective layer to that
surface of the forming tool that comes into contact with the work-piece. In forming
operations using dies and punches, such protective coatings are usually deposited
onto the working surface of the tool without any subsequent profiling step, i.e. they
are applied in such a way that the shape required is still derived from the shape
defined by the main body and profile of the forming tool itself.
[0013] In metal rolling, particularly aluminium rolling, a steel work roll is often protected
with a chromium layer to extend the life of the working roll. Typically such work
rolls have their surfaces ground flat because the intended use of such rolls is merely
to reduce the thickness of plate, sheet or foil through a mill. When the main purpose
is thickness reduction a major consideration is to obtain as smooth a surface as possible
on the rolled sheet at the end of a series of rolling passes.
[0014] However, where a structured surface is desired, it is possible to modify the structure
of the chromium layer. It is also possible to structure the underlying steel of the
work roll and deposit a layer of chromium over the roll. For modifying the structure
of the chromium layer itself, one known technique involves applying a photosensitive
film to the chromium layer. A pulsed laser can be scanned across the surface and,
where it scans, the heat of the laser polymerises the film. The unpolymerised film
can be washed away exposing chromium underneath. The exposed chromium can be etched
away to a required depth whilst the chromium under the polymerised masking remains
as it was. This leads to the creation of an irregular roll surface with the final
form of the roll surface dictated by the path of the laser.
[0015] These protective coatings, whilst beneficial in many respects, have the disadvantage
that it is not possible to provide them with very fine detailed designs of a deterministic
nature. For example, the chromium method described above can give structural dimensions
down to 1 or 2 microns but not to dimensions below this.
[0016] Smaller surface features than this lead to interesting effects. One known effect
is the creation of images from complex diffraction patterns. Although sometimes referred
to as holograms, these images are not strictly holographic. Rather, variations in
the number, density, length, direction, depth and shape, of lines cut into the surface
of a work-piece can lead to very complex interference patterns that appear to be images.
Such images may also display variations in colour.
[0017] In order to create complex diffraction patterns like this, the cut lines are sub-micron
in width and it is not possible with conventional tooling methods to obtain this level
of resolution within a deterministic structure directly on the surface of a forming
tool.
[0018] The prior art surface structuring approaches possess a number of disadvantages. Eventually
forming tools wear out and are either expensive or difficult to refurbish. Also, it
is difficult and sometimes impossible to produce deterministic structures. It is especially
difficult to produce very fine, sub-micron, deterministic structures within the coating
on a forming tool. Furthermore, forming tools are generally used for single purposes,
that is, with one kind of shape or surface structure in mind. They do not provide
flexibility in the sense of it being easy and straightforward to change the surface
of the forming tool.
[0019] It is an object of this invention to provide a new forming tool, one that can have
its surface easily modified and one that can be produced with deterministic structures
and very fine deterministic structures, the said surface features being transferable
to a work-piece by any suitable forming method thereby giving the surface of the work-piece
itself a fine, deterministic structure.
[0020] It is a further object of this invention to provide a new method of modifying the
surface of a work-piece using a forming tool that itself has a structured surface.
[0021] It is a further object of the invention that the surface of the forming tool can
be easily and inexpensively produced and eventually refurbished and to provide a method
of preparing and refurbishing such forming tools.
[0022] Accordingly a first aspect of the invention is a forming tool comprising substrate
and a metallic glass layer on at least the working face of the forming tool, characterised
in that the metallic glass layer possesses a structured surface for the purpose of
reproducing the structured surface of the metallic glass layer in the surface of a
work-piece.
[0023] It will be readily appreciated that the metallic glass layer need not be directly
adjacent to the working face of the forming tool and that other intermediate and functional
layers may be incorporated, for example a compliant layer to accommodate differences
in thermal expansion coefficients.
[0024] Metallic glasses are multi-component metallic alloys that, when cooled from a molten
state at a fast enough rate, preferably retain an amorphous state when solid. Metallic
glasses can also be slightly or partially crystallised when solid after cooling. These
materials can be up to twice as strong as steel, have greater wear and corrosion resistance
and have higher elasticity values than steel.
[0025] Metallic glasses suitable for the purpose herein described can be, for example, any
one of the following group of general alloy systems: Au-Pb-Sb, Pd-Ni-P, La-Al-Ni,
La-Al-Cu, La-Al-Ni-Cu, Mg-Cu-Y, Zr-Al-Ni-Cu, Zr-Ti-Cu-Ni-Al, Zr-Ti-Cu-Ni-Be, Zr-Ti-Nb-Cu-Ni-Be,
Pd-Cu-Ni-P, Ni-Nb-Ta, Al-Co-Zr, Al-Ni-Ce-B, Al-Ni-Y-Co-B. These alloy systems are
particularly useful because they can be cooled at slower rates than other metallic
glasses yet still retain their amorphous state. One specific alloy that could be used
is one containing, by weight percent, Zr 56.2, Ti 13.8, Nb 5, Cu7, Ni 5.5, Be 12.5.
They can be cooled such that thickness of the metallic glass is of the order of 0.01
to 10 mm. This is important in this invention because the glass coating is on a substrate
and the combined thermal mass means that extremely fast cooling rates are not always
possible. In many situations the substrate itself can be used as an effective heat
sink, either alone or in combination with other cooling means.
[0026] Where the intention is to make very fine deterministic structures the thickness of
the metallic glass layer need not be very high. For example it could be a thin layer
between 0.001 mm and 2 mm, in particular between 0.01 mm and 2 mm thick. Where the
surface structure desired contains more prominent features then the metallic glass
layer will preferably be thicker, between 0.5 mm and 30 mm, in particular between
0.5 mm and 10 mm thick. There is no need to have a large excess of glass because that
would simply be a waste of material but there needs to be enough to enable the required
structure to be formed within its surface. The lower thickness limit of the metallic
glass is e.g. 0.001 mm, preferably 0.01 mm and more preferably 0.5 mm. The upper thickness
limit of the metallic glass depends on the intended application but is for example
not more than 30 mm, preferably 20 mm, more preferably 10 mm and even more preferably
5 mm.
[0027] The substrate could comprise any suitable shape typical of conventional forming tools
that might be used in any of the forming methods previously mentioned. Also there
is no particular requirement that the shape of the surface onto which the metallic
glass is deposited to be of a certain kind. The metallic glass layer need not be deposited
on the whole of the forming tool, merely on that face which comes into contact with
the work-piece to be formed or modified, herein referred to as the working face. In
other words, the working face is that face of the forming tool through which load
is applied to the work-piece. The working face could be substantially planar or profiled,
(in the sense that its shape face varies in at least two dimensions). Alternatively
the shape of the working face may be at least a segment of the surface of a cylinder,
as would be the case with a work roll for a metal rolling mill. In the latter case
the substrate itself may be at least partly cylindrical or it could be a complete
cylinder.
[0028] A particular advantage of the invention is that the structured surface of the metallic
glass layer can be provided with a very fine deterministic structure. It is a preferred
embodiment of the invention that the structured surface be deterministic and a more
preferred embodiment that the deterministic structured surface contain features which
are sub-micron in size.
[0029] A second aspect of the invention is a method of modifying the surface of a work-piece
wherein at least one surface of the work-piece comes into contact with the structured
surface of a forming tool at least once, the forming tool comprising a substrate and
a metallic glass layer on at least the working face of the forming tool, characterised
in that the metallic glass layer possesses a structured surface whereby the structured
surface of the metallic glass layer reproduces in the surface of the work-piece.
[0030] The nature of the metallic glass layer in terms of its composition and thickness
are typically the same as those described above in connection with the forming tool.
Likewise, the structured surface can be stochastic in nature but it is preferred that
it is deterministic and even more preferred that it contains features which are sub-micron
in size.
[0031] Often forming operations of this nature take place in a number of repeat actions
and therefore another embodiment of the invention is that this method involves a plurality
of contacts between the work-piece and forming tool. This is often desirable because
the transfer of the structural features from the surface of the forming tool to the
work-piece is rarely perfect and more than one impression may be needed to generate
the final desired surface on the work-piece.
[0032] In addition the transfer of the structure from the forming tool to the work-piece
may take place under very low loading such that there is little or no reduction in
the thickness of the work-piece. This is particularly useful in embossing operations.
[0033] A preferred embodiment involves the use of this method in the rolling of metal sheet
where the forming tool is a work roll of a metal rolling mill. This embodiment is
particularly suited to the rolling of aluminium and aluminium alloys.
[0034] A further aspect of the invention is a method of structuring the outer surface of
a forming tool, the forming tool comprising a substrate and a metallic glass layer
characterised by the steps of:
- (a) heating at least the outer surface of the metallic glass layer to a temperature
above its glass transition temperature,
- (b) bringing the outer surface of the metallic glass layer into contact with the structured
surface of a template for a period of time and under pressure such that the structured
surface of the template is reproduced in the outer surface of the metallic glass layer
to create a structured outer surface on the metallic glass layer,
- (c) at least the structured outer surface of the metallic glass layer is cooled down
at a rate sufficient to retain a mostly amorphous structure throughout the metallic
glass layer,
- (d) and the forming tool and the template are separated, the features of the structured
surface of the template being retained within the structured outer surface of the
metallic glass layer,
[0035] It has been surprisingly found that the surface of metallic glasses can be heated
up until they are soft and can then be pressed against a template, the template possessing
on its surface the structure or pattern desired in the surface of the metallic glass.
After coming into contact with the template, at least the outer surface of the metallic
glass layer is cooled and separated from the template. Of course the bulk of the metallic
glass layer itself will also cool to some extent, it may even cool at a rate similar
to the cooling rate of the outer surface. The cooling rate is sufficient such that
the amorphous state is retained throughout the metallic glass. The surface structure
of the template, which has been reproduced in the surface of the metallic glass, is
retained after cooling in the outer surface of the metallic glass layer. Where the
surface structure of the template contains large impressions or indentations then
some of the bulk of the metallic glass layer may also be deformed so that the metallic
glass layer as a whole displays the same external profile. A forming tool with a metallic
glass layer thus formed is then used to modify the surface of the chosen work-piece.
[0036] The template could be made from conventional materials such as copper, aluminium
or steel but is preferably made from a material that is able to withstand the high
temperatures and pressures involved. Therefore steel or nickel templates are preferred.
In order to facilitate the release of the template from the metallic glass at the
relatively high temperatures in question a release agent may be applied to the surface
of the template prior to coming into contact with the softened metallic glass.
[0037] The metallic glass, after coming into contact with the template, has to be cooled
down at a rate fast enough to ensure that the metallic glass retains its amorphous
structure below the glass transition temperature. The cooling rate necessary for this
will depend on the metallic glass used but will normally be >10°C/sec, preferably
>100°C/sec, more preferably >200°C/sec. In some situations, for example where the
metallic glass has a large critical casting thickness, or the thickness of the metallic
glass is small, effective cooling can be achieved by using forced gas, as for example
air but in other situations it may be necessary to use means such as a fluid, as for
example water or a water spray to bring about faster cooling rates. Other cooling
means are solid materials having a high thermal conductivity such as metals, preferably
copper and the like.
[0038] The invention will now be illustrated by reference to the following examples.
[0039] Figure 1 is a schematic of a simple forming tool incorporating the metallic glass
layer on its working face and a method of using the forming tool.
[0040] Figure 2 is a schematic of one method of structuring the outer surface of a metallic glass
layer, in this case in connection with a work roll suitable for metal sheet rolling.
[0041] Figure 3 is an image of the structured surface of a template made of tungsten carbide
used to create a structured surface in the surface of a piece of metallic glass.
[0042] Figure 4 is an image of the structured surface of the metallic glass produced after
coming into contact with the structured template having the surface of Figure 3.
[0043] Figure 5 is an image of the surface of aluminium sheet formed after a flat aluminium
sheet was pressed against the structured surface of the metallic glass.
[0044] In Figure 1, the forming tool (10) is made up of a substrate (11) and a metallic
glass layer (13) on the working face (12) of the forming tool. The metallic glass
layer has a structured surface (14). Under load, as shown by the arrow, the structured
surface (14) is brought into contact with the surface (16) of the work-piece (15).
In this example the work-piece (15) is supported on a base plate (17). With a sufficient
load applied, the surface of the work-piece will be modified and the features of the
structured surface of the forming tool will be reproduced in the surface of the work-piece.
It will be readily appreciated that the profile of the working face, as shown by line
A-A', need not be flat but could be profiled. Likewise the base plate (17) could be
a shaped die to match the profile of the forming tool. As mentioned above, the surface
of the work-piece may not be an exact replica of the structured surface of the forming
tool and the forming action may be repeated a number of times, preferably 2, 3, 4
times or more, to ensure the final surface of the work-piece has the desired features.
[0045] In Figure 2 the forming tool (20) is in the form of a cylindrical work roll intended
for further use in rolling metal sheet. The forming tool (20) comprises a cylindrical
substrate (21) and a metallic glass layer (23) on the working face (22). In this embodiment
the cylindrical forming tool is made to rotate and the outer surface (27a) at least
of the metallic glass layer (23) is heated up by a suitable heater (24) to a temperature
above the glass transition temperature of the metallic glass. Above the glass transition
temperature the metallic glass layer, or at least its outer surface, is soft enough
to be modified. The outer surface of the metallic glass layer is then brought into
contact with a template (25). In this example the template is a nickel shim which
possesses, at least on one face a structured surface (26), either stochastic or deterministic
in nature. The structured surface (26) of the template is brought into contact with
the soft outer surface of the metallic glass and pressure is applied with the aid
of two drive rolls (28a and 28b). After contact the outer surface of the metallic
glass layer is modified and is converted into a structured outer surface (27b) of
the metallic glass layer. In order to preserve the newly structured outer surface
of the metallic glass layer at least the structured outer surface of the metallic
glass layer is cooled down at a rate sufficiently fast to retain an amorphous structure
throughout the metallic glass layer. It is possible, as well, to cool down the metallic
glass layer from the working face side and the outer surface. This method may be a
continuous system and it is within the bounds of the invention that the surface modification
method herein described may be repeated a number of times. If this is the case in
this embodiment, the structured outer surface (27b) of the metallic glass layer may,
on further rotation, be heated up as before and structured a second or third time
by contact with the template. In this way, if the initial structured surface of the
metallic glass layer is not deemed to be adequate for its intended purpose it can
be further improved and refined.
[0046] In another embodiment the template may be fed round another series of rolls (not
illustrated) back to the start in a continuous loop. In such a case the length of
template may be carefully controlled to correspond to the diameter of the substrate
cylindrical work roll, especially if the structure to be created is deterministic.
The diameter of the cylindrical work roll is not critical. The forming tool and the
template are separated in the region of point B. In some circumstances, for example
when the glass transition temperature is high and there is a danger of the metallic
glass and the template sticking together, a suitable release agent is applied to the
structured surface of the template to make separation easier.
[0047] A typical heater would be an induction heater, heating by conduction or a convection
heater such as an infrared heater but may also include for example contact heaters,
flame heaters, Joule effect heaters, hot gas heaters, or any other adequate heating
device.
[0048] The structured surface of the metallic glass layer and the metallic glass layer itself
may start to cool down even as the template and forming tool are in contact, i.e.
before they are separated in this case. The cooling can be effected by the bulk of
the substrate itself acting as a heat sink, which can be improved with the use of
a cooling system built into the substrate. It is common for cylindrical work rolls
to contain a chilled fluid such as a water system and this can be used to help provide
the fast cooling required. Cooling can be further enhanced by forced gas, for example
air cooling, applied on the exit side in the vicinity of the area marked B.
[0049] The forming tool with its surface structured according to the method illustrated
by Figure 2 can then be used in a conventional rolling mill to modify the structure
of work-pieces such as steel, aluminium and copper sheet.
[0050] To demonstrate that it is possible to replicate a structured surface from a template
onto a surface of metallic glass and then onto a metallic work-piece a piece of metallic
glass with a composition, (in weight %), Pd 40%, Ni 20%, Cu 30% and P 10%, possessing
a glass transition temperature of 307°C and a recrystallization temperature of 407°C
was selected. A tungsten carbide template with a structured surface was used to structure
the surface of the metallic glass layer by heating both the template and the piece
of metallic glass to a temperature of 380°C and bringing them into contact under a
ramped pressure of 4 to 20MPa increasing over a duration of one second. The template
and metallic glass were then separated and the metallic glass piece was allowed to
cool down. The surface of the template consisted of a series of peaks and troughs
with a depth to height value of around 9µm.
[0051] The topography of the template is shown in Figure 3 and the topography formed in
the metallic glass surface is shown in Figure 4. The peak to trough distance in the
metallic glass layer was also around 9µm.
[0052] The metallic glass piece with the structured layer on one surface was then used to
stamp aluminium sheet. The aluminium sheet had a composition Fe 0.2%, Si 0.1%, balance
aluminium and impurities. At room temperature the metallic glass piece was pressed
against the aluminium sheet using a pressure of 70MPa for one second with the structured
surface of the metallic glass piece facing the aluminium strip. Figure 5 shows the
topography of the surface of the aluminium sheet thus formed. Comparison with Figure
3 shows that the structure from the template was very effectively transferred by the
metallic glass piece into the surface of the aluminium sheet, albeit with a slightly
smaller difference in height between peaks and troughs, the height being around 7µm.
[0053] The tool and processes according to the invention offer a range of advantages. They
allow a greater degree of reproducibility from one manufacturing plant to another.
For example, two similar forming tools can be created in different locations because
the same template can be used to produce almost identical tools. The template can
be moved from one manufacturing plant to another and the working surface of the forming
tool can be structured in exactly the same way at different locations. This will ensure
consistency in the final form of the work-pieces being manufactured. Further, the
very first structured forming tool can be used as a master tool and it can be used
to generate a number of templates for use in other locations, again making production
consistent from one manufacturing facility to another.
[0054] The processes described enable the creation of very small and deterministic surface
features in a simple and effective way. This will have a wide range of benefits in
many forming industries and has the potential to eliminate some subsequent processing
steps. For example, if the forming operation also enables marking of the work-piece,
a subsequent marking or printing step using another process can be dispensed with.
This provides the user with the means to individualise their manufactured products
more easily and distinctively.
[0055] The tool and processes according to the invention facilitate longer forming tool
life. The properties of the metallic glass layer are well suited to prolonging tool
life. Their high elastic strain limits, combined with high strength and high toughness
means that the metallic glass layer remains in the fully elastic range during forming
operations, far away from the metallic glass yield strength. As a result the structured
surface of the metallic glass layer retains its integrity for much longer than other
forming tool protective layers.
[0056] Furthermore, by re-heating the metallic glass surface layer and refurbishing the
structure in exactly the same way as it had previously been formed, the life of the
forming tool and its working surface can be further extended and any deterioration
in the quality of the surface structure can be easily corrected.
[0057] In addition, the same conditioning and refurbishing process allows the manufacturer
to change the structure of the working surface with a minimum of effort. This provides
enhanced flexibility in design and production scheduling.
[0058] A forming tool according to the invention and the method of modifying the surfaces
of work-pieces according to the invention may be used, by way of example, in the production
of sheet and shaped parts for automotive use, the production of lithographic sheet,
the production of coins and badges and the production of reflector sheet.
1. A forming tool (10, 20) comprising a substrate (11, 21) and a metallic glass layer
(13, 23) on at least the working face (12, 22) of the forming tool (10, 20), characterised in that the metallic glass layer (13, 23) possesses a structured surface (14, 27b) for the
purpose of reproducing the structured surface (14, 27b) of the metallic glass layer
in the surface (16) of a work-piece (15).
2. A forming tool as claimed in claims 1 characterised in that there is at least one other functional layer between the working face of the forming
tool and the metallic glass layer.
3. A forming tool as claimed in claims 1 and 2 characterised in that the metallic glass layer has an upper limit of its thickness of 30 mm, preferably
10 mm and a lower limit of 1 µm, preferably 10 µm.
4. A forming tool as claimed in claim 3 characterised in that the metallic glass layer has a lower limit of its thickness of 0.5 mm.
5. A forming tool as claimed in claim 3 characterised in that the metallic glass layer has an upper limit of its thickness of 8 mm.
6. A forming tool as claimed in claim 3 characterised in that the metallic glass layer has an upper limit of its thickness of 5 mm.
7. A forming tool as claimed in claim 1 and 2 characterised in that the metallic glass layer has a thickness between 10 µm and 10 mm.
8. A forming tool as claimed in claims 1 to 7 characterised in that the working face of the substrate is substantially planar.
9. A forming tool as claimed in claim 1 to 7 characterised in that the working face of the substrate is profiled.
10. A forming tool as claimed in claim 1 to 7 characterised in that the shape of the forming tool is at least partly cylindrical.
11. A forming tool as claimed in claim 10 characterised in that the forming tool is a cylindrical work roll.
12. A forming tool as claimed in claims 1 to 11 characterised in that the structured surface of the metallic glass is deterministic.
13. A forming tool as claimed in claim 12 characterised in that the deterministic structure comprises features having dimensions below 1 µm in size.
14. A forming tool as claimed in claims 1 to 13 characterised in that the composition of the metallic glass layer is an alloy from a group consisting of
the following alloy systems: Au-Pb-Sb, Pd-Ni-P, La-Al-Ni, La-Al-Cu, La-Al-Ni-Cu, Mg-Cu-Y,
Zr-Al-Ni-Cu, Zr-Ti-Cu-Ni-Al, Zr-Ti-Cu-Ni-Be, Zr-Ti-Nb-Cu-Ni-Be, Pd-Cu-Ni-P, Ni-Nb-Ta,
Al-Co-Zr, Al-Ni-Ce-B, Al-Ni-Y-Co-B.
15. A method of modifying the surface (16) of a work-piece (15) wherein at least one surface
(16) of the work-piece (15) comes into contact with the structured surface (14) of
a forming tool (10) at least once, the forming tool (10) comprising a substrate (11)
and a metallic glass layer (13) on at least the working face (12) of the forming tool
(10), characterised in that the metallic glass layer (13) possesses a structured surface (14) whereby the structured
surface (14) of the metallic glass layer (13) reproduces in the surface (16) of the
work-piece (15).
16. A method as claimed in claim 15 characterised in that there is a plurality of contacts, preferably 2, 3 or 4, between the work-piece and
the forming tool.
17. A method as claimed in claim 15 and 16 characterised in that the forming tool is a work roll of a metal rolling mill.
18. A method as claimed in claims 15 to 17 characterised in that the work-piece is at least a part of a metal sheet.
19. A method as claimed in claims 15 to 18 characterised in that the work-piece is aluminium or an aluminium alloy.
20. A method as claimed in claims 15 to 19 characterised in that the pressure applied during forming provides essentially no reduction in the thickness
of the work-piece.
21. A method of structuring the outer surface (27a) of a forming tool (20), the forming
tool (20) comprising a substrate (21) and a metallic glass layer (23)
characterised by the steps of:
(a) heating at least the outer surface (27a) of the metallic glass layer (23) to a
temperature above its glass transition temperature,
(b) bringing the outer surface (27a) of the metallic glass layer (23) into contact
with the structured surface (26) of a template (25) for a period of time and under
pressure such that the shaped surface (26) is reproduced in the structured outer surface
(27b) of the metallic glass layer (23),
(c) at least the structured outer surface (27b) of the metallic glass layer (23) is
cooled down at a rate sufficient to retain a mostly amorphous structure throughout
the metallic glass layer (23),
(d) and the forming tool (20) and the template (25) are separated, the features of
the structured surface (26) of the template (25) being retained within the structured
outer surface (27b) of the metallic glass layer (23).
22. A method as claimed in claim 21 characterised in that the steps (a) to (d) are repeated at least once.
23. A method as claimed in claims 21 and 22 characterised in that the heating step is carried out using an induction heater.
24. A method as claimed in claim 21 and 22 characterised in that the heating step is carried out using a convection heater.
25. A method as claimed in claims 21 to 24 characterised in that cooling of the metallic glass layer is assisted by a cooling system within the substrate.
26. A method as claimed in claims 21 to 25 characterised in that the template is a nickel shim.
27. A method as claimed in claims 21 to 26 characterised in that the forming tool is a cylindrical work roll for use in a metal rolling mill.
28. A method as claimed in claims 21 to 27 characterised in that a release agent is deposited onto the shaped surface of the template.
1. Formwerkzeug (10, 20), dadurch gekennzeichnet, dass es ein Substrat (11, 21) und eine Schicht aus metallischem Glas (13, 23) zumindest
auf der Arbeitsfläche (12, 22) des Formwerkzeugs (10, 20) umfasst und die Schicht
aus metallischem Glas (13, 23) eine strukturierte Oberfläche (14, 27b) zum Zweck des
Reproduzierens der strukturierten Oberfläche (14, 27b) der Schicht aus metallischem
Glas in der Oberfläche (16) eines Werkstücks (15) besitzt.
2. Formwerkzeug nach Anspruch 1, dadurch gekennzeichnet, dass es zwischen der Arbeitsfläche des Formwerkzeugs und der Schicht aus metallischem
Glas wenigstens eine weitere funktionelle Schicht gibt.
3. Verfahren nach Anspruch 1 und 2, dadurch gekennzeichnet, dass die Schicht aus metallischem Glas eine Dicke mit einer Obergrenze von 30 mm, vorzugsweise
10 mm, und einer Untergrenze von 1 µm, vorzugsweise 10 µm, hat.
4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass die Schicht aus metallischem Glas eine Dicke mit einer Untergrenze von 0,5 mm hat.
5. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass die Schicht aus metallischem Glas eine Dicke mit einer Obergrenze von 8 mm hat.
6. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass die Schicht aus metallischem Glas eine Dicke mit einer Obergrenze von 5 mm hat.
7. Verfahren nach Anspruch 1 und 2, dadurch gekennzeichnet, dass die Schicht aus metallischem Glas eine Dicke zwischen 10 µm und 10 mm hat.
8. Formwerkzeug nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Arbeitsfläche des Substrats im Wesentlichen eben ist.
9. Formwerkzeug nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Arbeitsfläche des Substrat mit einem Profil versehen ist.
10. Formwerkzeug nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Gestalt des Formwerkzeugs wenigstens teilweise zylindrisch ist.
11. Formwerkzeug nach Anspruch 10, dadurch gekennzeichnet, dass das Formwerkzeug eine zylindrische Arbeitswalze ist.
12. Formwerkzeug nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, dass die strukturierte Oberfläche des metallischen Glases deterministisch ist.
13. Formwerkzeug nach Anspruch 12, dadurch gekennzeichnet, dass die deterministische Struktur Merkmale umfasst, die Dimensionen in einer Größe unter
1 µm haben.
14. Formwerkzeug nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, dass die Zusammensetzung der Schicht aus metallischem Glas eine Legierung aus einer Gruppe
bestehend aus den folgenden Legierungssystemen ist: Au-Pb-Sb, Pd-Ni-P, La-Al-Ni, La-Al-Cu,
La-Al-Ni-Cu, Mg-Cu-Y, Zr-Al-Ni-Cu, Zr-Ti-Cu-Ni-Al, Zr-Ti-Cu-Ni-Be, Zr-Ti-Nb-Cu-Ni-Be,
Pd-Cu-Ni-P, Ni-Nb-Ta, Al-Co-Zr, Al-Ni-Ce-B, Al-Ni-Y-Co-B.
15. Verfahren zum Modifizieren der Oberfläche (16) eines Werkstücks (15), bei dem wenigstens
eine Oberfläche (16) des Werkstücks (15) wenigstens einmal mit der strukturierten
Oberfläche (14) eines Formwerkzeugs (10) in Kontakt kommt, dadurch gekennzeichnet, dass das Formwerkzeug (10) aus einem Substrat (11) und einer Schicht aus metallischem
Glas (13) wenigstens auf der Arbeitsfläche (12) des Formwerkzeugs (10) besteht und
die Schicht aus metallischem Glas (13) eine strukturierte Oberfläche (14) besitzt,
wodurch die strukturierte Oberfläche (14) der Schicht aus metallischem Glas (13) in
der Oberfläche (16) des Werkstücks (15) reproduziert wird.
16. Verfahren nach Anspruch 15, dadurch gekennzeichnet, dass sich zwischen dem Werkstück und dem Formwerkzeug mehrere Kontakte, vorzugsweise 2,
3 oder 4, befinden.
17. Verfahren nach Anspruch 15 und 16, dadurch gekennzeichnet, dass das Formwerkzeug eine Arbeitswalze eines Metallwalzwerks ist.
18. Verfahren nach einem der Ansprüche 15 bis 17, dadurch gekennzeichnet, dass das Werkstück wenigstens ein Teil eines Blechs ist.
19. Verfahren nach einem der Ansprüche 15 bis 18, dadurch gekennzeichnet, dass das Werkstück Aluminum oder eine Aluminiumlegierung ist.
20. Verfahren nach einem der Ansprüche 15 bis 19, dadurch gekennzeichnet, dass der während des Formens angewendete Druck im Wesentlichen keine Verringerung der
Dicke des Werkstücks bewirkt.
21. Verfahren zum Strukturieren der Außenfläche (27a) eines Formwerkzeugs (20),
dadurch gekennzeichnet, dass das Formwerkzeug (20) ein Substrat (21) und eine Schicht aus metallischem Glas (23)
umfasst, umfassend die folgenden Schritte:
a) Erwärmen wenigstens der Außenfläche (27a) der Schicht aus metallischem Glas (23)
auf eine Temperatur über ihrer Glasübergangstemperatur,
b) Inkontaktbringen der Außenfläche (27a) der Schicht aus metallischem Glas (23) mit
der strukturierten Oberfläche (26) einer Schablone (25) für eine Zeitspanne und unter
Druck, so dass die formgestaltete Oberfläche (26) in der strukturierten Außenfläche
(27b) der Schicht aus metallischem Glas (23) reproduziert wird,
c) Abkühlen von wenigstens der strukturierten Außenfläche (27b) der Schicht aus metallischem
Glas (23) mit einem Tempo, das ausreicht, um in der Schicht aus metallischem Glas
(23) weitgehend durchgehend ein amorphes Gefüge beizubehalten,
d) und Trennen des Formwerkzeugs (20) und der Schablone (25), wobei die Merkmale der
strukturierten Oberfläche (26) der Schablone (25) in der strukturierten Außenfläche
(27b) der Schicht aus metallischem Glas (23) beibehalten werden.
22. Verfahren nach Anspruch 21, dadurch gekennzeichnet, dass die Schritte a) bis d) wenigstens einmal wiederholt werden.
23. Verfahren nach Anspruch 21 und 22, dadurch gekennzeichnet, dass der Erwärmungsschritt mit einer Induktionsheizvorrichtung durchgeführt wird.
24. Verfahren nach Anspruch 21 und 22, dadurch gekennzeichnet, dass der Erwärmungsschritt mit einer Konvektionsheizvorrichtung durchgeführt wird.
25. Verfahren nach einem der Ansprüche 21 bis 24, dadurch gekennzeichnet, dass das Kühlen der metallischen Glasschicht durch ein Kühlsystem in dem Substrat unterstützt
wird.
26. Verfahren nach einem der Ansprüche 21 bis 25, dadurch gekennzeichnet, dass die Schablone eine Nickelbeilage ist.
27. Verfahren nach einem der Ansprüche 21 bis 26, dadurch gekennzeichnet, dass das Formwerkzeug eine zylindrische Arbeitswalze zur Verwendung in einem Metallwalzwerk
ist.
28. Verfahren nach einem der Ansprüche 21 bis 27, dadurch gekennzeichnet, dass ein Trennmittel auf die formgestaltete Oberfläche der Schablone aufgebracht wird.
1. Outil de formage (10, 20) caractérisé en ce qu'il comprend un substrat (11, 21) et une couche de verre métallique (13, 23) sur au
moins la face de travail (12, 22) de l'outil de formage (10, 20) et la couche de verre
métallique (13, 23) possède une surface structurée (14, 27b) afin de reproduire 1a
surface structurée (14, 27b) de 1a couche de verre métallique dans la surface (16)
d'une pièce (15).
2. Outil de formage selon la revendication 1, caractérisé en ce que l'on trouve au moins une autre couche fonctionnelle entre la face de travail de l'outil
de formage et la couche de verre métallique.
3. Procédé selon les revendications 1 et 2, caractérisé en ce que la couche de verre métallique a une limite supérieure de son épaisseur de 30 mm,
de préférence 10 mm et une limite inférieure de 1 µm, de préférence 10 µm.
4. Procédé selon la revendication 3, caractérisé en ce que la couche de verre métallique a une limite inférieure de son épaisseur de 0,5 mm.
5. Procédé selon la revendication 3, caractérisé en ce que la couche de verre métallique a une limite supérieure de son épaisseur de 8 mm.
6. Procédé selon la revendication 3, caractérisé en ce que la couche de verre métallique a une limite supérieure de son épaisseur de 5 mm.
7. Procédé selon les revendications 1 et 2, caractérisé en ce que la couche de verre métallique a une épaisseur comprise entre 10 µm et 10 mm.
8. Outil de formage selon les revendications 1 à 7, caractérisé en ce que la face de travail du substrat est sensiblement plane.
9. Outil de formage selon les revendications 1 à 7, caractérisé en ce que la face de travail du substrat est profilée.
10. Outil de formage selon les revendications 1 à 7, caractérisé en ce que la forme de l'outil de formage est au moins partiellement cylindrique.
11. Outil de formage selon la revendication 10, caractérisé en ce que l'outil de formage est un cylindre de travail cylindrique.
12. Outil de formage selon la revendication 1 à 11, caractérisé en ce que la surface structurée du verre métallique est déterministique.
13. Outil de formage selon la revendication 12, caractérisé en ce que la structure déterministique comprend des caractéristiques ayant des dimensions inférieures
à 1 µm du point de vue de la taille.
14. Outil de formage selon les revendications 1 à 13, caractérisé en ce que la composition de la couche de verre métallique est un alliage d'un groupe se composant
des systèmes d'alliage suivants : Au-Pb-Sb, Pd-Ni-P, La-Al-Ni, La-Al-Cu, La-Al-Ni-Cu,
Mg-Cu-Y, Zr-Al-Ni-Cu, Zr-Ti-Cu-Ni-Al, Zr-Ti-Cu-Ni-Be, Zr-Ti-Nb-Cu-Ni-Be, Pd-Cu-Ni-P,
Ni-Nb-Ta, Al-Co-Zr, Al-Ni-Ce-B, Al-Ni-Y-Co-B.
15. Procédé pour modifier la surface (16) d'une pièce (15) dans lequel au moins une surface
(16) de la pièce (15) vient en contact avec la surface structurée (14) d'un outil
de formage (10) au moins une fois, caractérisé en ce que l'outil de formage (10) est composé d'un substrat (11) et d'une couche de verre métallique
(13) sur au moins la face de travail (12) de l'outil de formage (10) et la couche
de verre métallique (13) possède une surface structurée (14) moyennant quoi la surface
structurée (14) de la couche de verre métallique (13) reproduit la surface (16) de
la pièce (15).
16. Procédé selon la revendication 15, caractérisé en ce que l'on trouve une pluralité de contacts, de préférence 2, 3 ou 4, entre la pièce et
l'outil de formage.
17. Procédé selon les revendications 15 et 16, caractérisé en ce que l'outil de formage est un cylindre de travail d'un laminoir à métal.
18. Procédé selon les revendications 15 à 17, caractérisé en ce que la pièce fait au moins partie d'une tôle.
19. Procédé selon les revendications 15 à 18, caractérisé en ce que la pièce est en aluminium ou un alliage d'aluminium.
20. Procédé selon les revendications 15 à 19, caractérisé en ce que la pression appliquée pendant le formage ne fournit sensiblement pas de réduction
de l'épaisseur de la pièce.
21. Procédé pour structurer la surface externe (27a) d'un outil de formage (20)
caractérisé en ce que l'outil de formage (20) comprend un substrat (21) et une couche de verre métallique
(23) comprenant les étapes consistant à :
(a) chauffer au moins la surface externe (27a) de la couche de verre métallique (23)
à une température supérieure à sa température de transition vitreuse,
(b) amener la surface externe (27a) de la couche de verre métallique (23) en contact
avec la surface structurée (26) d'un gabarit (25) pendant une période de temps et
sous pression de sorte que la surface formée (26) est reproduite dans la surface externe
structurée (27b) de la couche de verre métallique (23),
(c) au moins la surface externe structurée (27b) de la couche de verre métallique
(23) est refroidie à une vitesse suffisante pour conserver une structure principalement
amorphe dans toute la couche de verre métallique (23),
(d) et l'outil de formage (20) et le gabarit (25) sont séparés, les caractéristiques
de la surface structurée (26) du gabarit (25) étant retenues à l'intérieur de la surface
externe structurée (27b) de la couche de verre métallique (23).
22. Procédé selon la revendication 21, caractérisé en ce que les étapes (a) à (d) sont répétées au moins une fois.
23. Procédé selon les revendications 21 et 22, caractérisé en ce que l'étape de chauffage est réalisée en utilisant un dispositif de chauffage à induction.
24. Procédé selon les revendications 21 et 22, caractérisé en ce que l'étape de chauffage est réalisée en utilisant un dispositif de chauffage à convection.
25. Procédé selon les revendications 21 à 24, caractérisé en ce que le refroidissement de la couche de verre métallique est assisté par un système de
refroidissement à l'intérieur du substrat.
26. Procédé selon les revendications 21 à 25, caractérisé en ce que le gabarit est une cale de réglage en nickel.
27. Procédé selon les revendications 21 à 26, caractérisé en ce que l'outil de formage est un cylindre de travail cylindrique destiné à être utilisé
dans un laminoir à métal.
28. Procédé selon les revendications 21 à 27, caractérisé en ce qu'un agent de démoulage est déposé sur la surface formée du gabarit.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Patent documents cited in the description