U.S. patent application number 12/065771 was filed with the patent office on 2008-09-04 for forming tool.
This patent application is currently assigned to ALCAN TECHNOLOGY & MANAGEMENT LTD.. Invention is credited to Patrick Deneuville.
Application Number | 20080209976 12/065771 |
Document ID | / |
Family ID | 36202482 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080209976 |
Kind Code |
A1 |
Deneuville; Patrick |
September 4, 2008 |
Forming Tool
Abstract
A forming tool (20) it comprises a substrate (21) and a metallic
glass layer (23) on at least the working surface (22) of the
forming tool (20) wherein the forming tool is one of: a) a forming
tool of an extrusion press; b) a die of a wire-drawing machine; c)
a roll of a polymer processing unit.
Inventors: |
Deneuville; Patrick;
(Moirans, FR) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C.
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510
US
|
Assignee: |
ALCAN TECHNOLOGY & MANAGEMENT
LTD.
Neuhausen am Rheinfall
CH
|
Family ID: |
36202482 |
Appl. No.: |
12/065771 |
Filed: |
September 8, 2005 |
PCT Filed: |
September 8, 2005 |
PCT NO: |
PCT/EP2006/009629 |
371 Date: |
March 18, 2008 |
Current U.S.
Class: |
72/372 ;
72/462 |
Current CPC
Class: |
B21C 25/025 20130101;
B21C 3/02 20130101; B21J 1/006 20130101; B21K 5/20 20130101; B21C
25/04 20130101; F16D 3/74 20130101; B21C 3/16 20130101; B23P 15/24
20130101; B29C 33/56 20130101; B21C 3/00 20130101; C22C 45/00
20130101; B21C 3/18 20130101; B29C 33/424 20130101 |
Class at
Publication: |
72/372 ;
72/462 |
International
Class: |
B21D 37/00 20060101
B21D037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2005 |
DE |
10 2005 047 801.8 |
Claims
1-25. (canceled)
26. A forming tool comprises a tool body and at least a metallic
glass layer on at least a working surface of the forming tool
wherein the forming tool is one of: a) a forming tool of an
extrusion press; b) a die of a wire-drawing machine; c) a roll of a
polymer processing unit.
27. A forming tool as claimed in claim 26, wherein the metallic
glass layer possesses a smooth surface.
28. A forming tool as claimed in claim 26, wherein the metallic
glass layer comprises a structured surface for reproducing the
structured surface of the metallic glass layer in the surface of a
work-piece.
29. A forming tool as claimed in claim 26, including at least one
functional layer between the working surface of the forming tool
and the metallic glass layer.
30. A forming tool as claimed in claims 26, wherein the metallic
glass layer has a lower limit of thickness of 1 .mu.m, and an upper
limit of its thickness of 30 mm.
31. A forming tool as claimed in claims 26, wherein the metallic
glass layer has a lower limit of thickness of 10 .mu.m, and an
upper limit of its thickness of 10 mm.
32. A forming tool as claimed in claims 26, wherein the metallic
glass layer has a lower limit of thickness of 500 .mu.m, and an
upper limit of its thickness 5 mm.
33. A forming tool as claimed in claim 26, wherein the working
surface is substantially planar.
34. A forming tool as claimed in claim 28, wherein the structured
surface of the metallic glass is deterministic.
35. A forming tool as claimed in claim 34, wherein the
deterministic structure comprises features having dimensions below
1 .mu.m in size.
36. A forming tool as claimed in claim 26, wherein the composition
of the metallic glass layer is an alloy selected from the 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.
37. A forming tool as claimed in claim 26, wherein the forming tool
of an extrusion press is one of an extrusion die, a die assembly
(tool stack) or a mandrel.
38. A forming tool as claimed in claim 26, wherein the forming tool
of a polymer processing unit is one or more rolls, in particular an
embossing roll.
39. A forming tool as claimed in claim 26, wherein the polymer
processing is one of a calender process, a coating process, where a
sheet material is coated with a plastic layer, plastic surface
treatment process, such as an embossing calender process.
40. A forming tool as claimed in claim 26, wherein the die of the
extrusion press or the wire drawing machine is completely made of a
metallic bulk glass.
41. 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, wherein the
forming tool is comprised of a substrate and a metallic glass layer
on at least a working surface of the forming tool and the metallic
glass layer possesses a structured surface whereby the structured
surface of the metallic glass layer reproduces in a surface of the
work-piece.
42. A method as claimed in claim 41, including a plurality of
contacts between the work-piece and the forming tool.
43. A method as claimed in claim 41, wherein the forming tool is
one of a forming tool of an extrusion press, a die of a
wire-drawing machine and a roll of a polymer processing unit.
44. A method as claimed in claims 41, including applying a pressure
during forming which provides essentially no reduction in the
thickness of the work-piece.
45. A method of structuring the outer surface of a forming tool
wherein the forming tool comprises a substrate and at least a
metallic glass layer comprising the steps of: heating at least the
outer surface of the metallic glass layer to a temperature above
its glass transition temperature, 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
shaped surface is reproduced in the 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 sufficient to retain
an amorphous structure throughout the metallic glass layer, 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.
46. A method as claimed in claim 45, including repeating the steps
(a) to (d) at least once.
47. A method as claimed in claim 45, including carrying out the
heating step using an induction heater.
48. A method as claimed in claim 45, including carrying out the
heating step using an infrared heater.
49. A method as claimed in claim 45, including cooling of the
metallic glass layer with a cooling system within the
substrate.
50. A method as claimed in claim 45, wherein the template is a
nickel shim.
51. A method as claimed in claim 45, wherein the forming tool is
one of a forming tool of an extrusion press, a die of a
wire-drawing machine and a roll of a polymer processing unit.
52. A method as claimed in claim 45, wherein a release agent is
deposited onto a shaped surface of the template.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a forming tool, a method of
modifying the surface of a work-piece or a ductile compound wherein
at least one surface of the work-piece or the ductile compound
comes into contact with the surface of a forming tool at least once
and a method of structuring the outer surface of a forming
tool.
[0002] In the materials processing industries there are many types
of forming operation. In the metals industry forming operations can
include, for example:
[0003] an extrusion process which is defined as the process of
shaping material, such as aluminium, by forcing it to flow through
a shaped opening in a die. Extruded material emerges as an
elongated piece with the same profile as the die opening.
[0004] a wire drawing process, which is a metal-reducing process in
which a wire rod is pulled or drawn through a single die or a
series of continuous dies, thereby reducing its diameter. Because
the volume of the wire remains the same, the length of the wire
changes according to its new diameter.
[0005] In the plastics industry forming operation can include, for
example:
[0006] a polymer processing such as calendering.
[0007] A work-piece is a unformed or pre-formed body of determinate
or indeterminate size and shape. For example a solid block of metal
or plastic is a work-piece. In an extrusion process 08-182 the
work-piece is e.g. a billet. In a wire drawing processes the
work-piece is e.g. a rod. In polymer processing the work-piece is
e.g. a monofilm made of a plastic or a multi-layer film having at
least one layer made of plastic.
[0008] A ductile compound is an unformed material in a solid to
semi-solid state. In polymer processing the ductile compound is
e.g. an at least partially softened, melted or even flowable mass,
sheet, plate or film material made of plastic or having at least a
plastic surface layer.
[0009] 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.
[0010] A forming operations like this can be applied to polymer
processing. 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 can 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 can be exaggerated in order to
ensure the final surface on the work-piece is produced.
[0011] 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 can be modified for purely
decorative reasons. The surface of a work-piece can 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.
[0012] The forming tools can have on their surface a textured
surface prepared by one of a variety of methods. Such known methods
include EDT (Electro Discharge Machining) 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 the forming
process 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, a drawing, a grating or an imprint
of a trade mark. In the case of multiple pass embossing,
deterministic structures can lead to interference effects whilst
stochastic structures generally will not.
[0013] In work rolls used in the above mentioned polymer
processing, 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 can 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.
[0014] In most of the forming operations mentioned above there is
eventually a need to replace the tools used for forming, or to
refurbish the same.
[0015] 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.
[0016] It is possible to provide them with very fine detailed
designs of a deterministic nature. Smaller surface features are
interesting because they can lead to interesting effects. One known
effect is the creation of images from complex diffraction patterns.
In order to create complex diffraction patterns, 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
SUMMARY OF THE INVENTION
[0021] The problem is solved by providing a forming tool made of
metallic glass or containing at least a metallic glass layer
wherein the forming tool forms one of:
[0022] a) a forming tool of an extrusion press
[0023] b) a die of a wire-drawing machine
[0024] c) a roll of a polymer processing unit.
[0025] In first embodiment the mentioned tool of the extrusion
press contains at least a body, which is the substrate, and at
least a metallic glass layer according to the invention, which is
directly or indirectly applied on the tool body. The metallic glass
layer is applied at least at the working surface. The extrusion
tool having a metallic glass layer can be a tool, which is directly
involved in the forming process of the work-piece, such as an
extrusion die, a die assembly (tool stack) or a mandrel. A die
assembly can comprise a die, a bolster, a backer, a feeder, a die
mandrel or a die cap. Moreover, the mentioned extrusion tool having
a metallic glass layer can also be a tool, which is indirectly
involved in the forming process of the work-piece, such as a
container (wall), a press plunger, a press ram or a dummy block.
The substrate of these tools can be of one of a hard cast-iron or
hard steel.
[0026] In second embodiment the above mentioned extrusion tools can
also be completely made of a metallic glass. Hence the metallic
glass is used as bulk material.
[0027] The working surface of the tool, which is made of metallic
glass, is wear resistant and therefore durable. Moreover the
metallic glass surface makes it easier to rework the tool by
heating the worn surfaces and rebuilding the metallic glass
surface.
[0028] The extrusion press according to the invention can be used
to produces profile sections made of metal, in particular made of
aluminium or an aluminium alloy. It is also possible to use the
extrusion press having extrusion tools according to the invention
to produce profiles made of plastics.
[0029] The tools of a wire drawing machine containing a metallic
glass layer according to the invention can be as already mentioned
dies or drawing plates. The metallic glass layer is applied on the
tool at least at its working surface. The substrate of these tools
can be of one of a hard cast-iron, hard steel, diamond or ruby. It
is also possible that the complete forming tool (die) is made of a
metallic glass. Hence the metallic glass is used as bulk
material.
[0030] The machine can be a continuous wire-drawing machine or a
single-block machine. The continuous wire-drawing machine comprises
a series of dies, whereby the work-piece, i.e. metallic rod, is
reduced to the desired diameter and properties by repeated drawing
through progressively smaller dies.
[0031] The working surface of the dies, which is made of metallic
glass, is wear resistant and therefore durable. Moreover the
metallic glass surface makes it easier to rework the tool by
heating the worn surfaces and rebuilding the metallic glass
surface.
[0032] The wire drawing unit according to the invention can be used
to produce wires made of metal, e.g. aluminium, aluminium alloy,
copper, copper alloy, iron, or steel.
[0033] The polymer processing can be a calender process where the
tool coated with a metallic glass according to the invention is one
or more work rolls of a calender unit with a smooth or a
deterministic, structured surface.
[0034] The polymer processing can be a casting of thin films, sheet
or plates on, preferably chilled, rolls. The rolls can be embossed
and the structure of the bulk material glass would be transferred
onto the molten or soft polymer to give patterns or topographies.
The polymer is solidified after being embossed. The plastic
material can be extruded. One of the main application can be
packaging materials made of single- or multilayer-films.
[0035] The polymer processing can also be a coating process, where
a sheet material is coated with a plastic layer. In such a process
a sheet material, e.g. a packaging film, is coated with a plastic
material. The sheet material can be a single- or multi-layer film
composed of different materials. The coating can be an extrusion
coating process, a coating by means of a coating knife, a dip
coating, coating by means of rolls (roll-coater), or a calender
coating process. In all these processes the tool containing a
metallic glass layer according to the invention is one or more
rolls with a smooth or a deterministic, structured surface.
[0036] The polymer processing can also be a surface treatment
process of a coated sheet material, a laminated sheet material or a
monofilm or even a sheet or plate containing at least a surface
layer made of plastic. Such a surface treatment process can be
based on an embossing calender. In this case the tool containing a
metallic glass layer according to the invention can be an embossing
roller, preferably a chilled embossing roller with a deterministic,
structured surface.
[0037] The working surface of the roll(s), which is made of
metallic glass, is wear resistant and therefore durable. Moreover
the metallic glass surface makes it easier to rework the tool by
heating the worn surfaces and rebuilding the metallic glass
surface. Further the possibly structured surface of the roll(s) can
easily be modified according to another template. The body of the
rolls can be made of metal.
[0038] The work-pieces or ductile compounds formed in a polymer
processing unit can be in the form of a film, sheet, plate or
flowable bulk material. The film, sheet or plate material can be
made of a single plastic layer or can be a multi-layer system
containing at least one layer, preferably at least one surface
layer, made of plastic. Other materials of a multi-layer system can
be other plastic materials, metal foils, reinforcing fibres or
fibre fabrics. The plastic material is preferably a
thermoplastic.
[0039] In a forming process more than one forming tools can be
coated with or be made of metallic glass. The tools of such a
processing unit can be coated with or made of the same or different
metallic glass materials.
[0040] Accordingly a first aspect of the invention is a forming
tool characterised in that it comprises a substrate and a metallic
glass layer on at least the working surface of the forming tool and
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.
[0041] It will be readily appreciated that the metallic glass layer
need not be directly adjacent to the working surface of the forming
tool and that other intermediate and functional layers can be
incorporated, for example a compliant layer to accommodate
differences in thermal expansion coefficients.
[0042] 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.
[0043] 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.
[0044] 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 thick. Where the surface structure desired contains more
prominent features then the metallic glass layer will preferably be
thicker, between 0.5mm and 30 mm thick. For many applications 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 and
preferably 0.5 mm. The upper thickness limit of the metallic glass
depends on the intended application but is e.g. not more than 30
mm, preferably 20 mm, more preferably 8 mm, and even more
preferably 5 mm.
[0045] 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 surface.
In other words, the working surface is that face of the forming
tool through which load is applied to the work-piece. The working
surface 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 surface can be at least a
segment of the surface of a cylinder, as would be the case with a
work roll for a polymer processing unit. In the latter case the
substrate itself can be at least partly cylindrical or it could be
a complete cylinder.
[0046] 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.
[0047] 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, characterised in that the forming tool
is comprised of a substrate and a metallic glass layer on at least
the working surface of the forming tool and 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.
[0048] 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.
[0049] 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 contracts
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 can be needed to generate the final desired surface
on the work-piece.
[0050] In addition the transfer of the structure from the forming
tool to the work-piece can 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.
[0051] A preferred embodiment involves the use of this method in
the processing of plastic material where the forming tool is a work
roll of a polymer processing unit.
[0052] A further aspect of the invention is a method of structuring
the outer surface of a forming tool characterised in that the
forming tool comprises a substrate and a metallic glass layer
comprising the steps of:
[0053] heating at least the outer surface of the metallic glass
layer to a temperature above its glass transition temperature,
[0054] 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,
[0055] at least the structured outer surface of the metallic glass
layer is cooled down at a rate sufficient to retain an amorphous
structure or mostly amorphous structure throughout the metallic
glass layer,
[0056] 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,
[0057] 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 can 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 can 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.
[0058] 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 can be applied to the surface of the template prior
to coming into contact with the softened metallic glass.
[0059] 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.degree. .C/sec, preferably >100.degree. C./sec, more
preferably >200.degree. 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 can 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] The invention will now be illustrated by reference to the
following examples.
[0061] FIG. 1 shows a schematic drawing of an embossing
calender.
[0062] FIG. 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 of a polymer processing unit.
[0063] FIG. 3 shows a die assembly of an extrusion press.
[0064] FIG. 4 shows a wire draw machine.
[0065] FIG. 5 is an enlarged view of a wire reduction.
DETAILED DESCRIPTION
[0066] In FIG. 1 the embossing calender 1 contains an infrared
heater 2 to soften the continuous sheet material 7 or at least its
surface. The sheet material 7 can be a plastic sheet, or a sheet
made of one or more materials other than plastic, coated with a
plastic material, in particularly a thermoplastic material. Sheet
material can comprise e.g. a metal, reinforcing fibres or fibre
fabrics. The softened or melted plastic surface of the sheet
material is then embossed by means of a chilled embossing roll 4
coated with metallic glass, which interacts with a second roll 3
producing a counter-pressure to the sheet material 7 passing the
roll gap. The calender unit 1 further comprises a cooling roll 5 to
cool the counter-pressure roll 3 and cooling rolls 6 to cool the
sheet material.
[0067] In FIG. 2 the forming tool 20 is in the form of a
cylindrical work roll of a polymer processing unit as e.g.
described under FIG. 1. The forming tool 20 comprises a cylindrical
substrate 21 and a metallic glass layer 23 on the working surface
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 surface side and the outer surface. This method can be
a continuous system and it is within the bounds of the invention
that the surface modification method herein described can be
repeated a number of times. If this is the case in this embodiment,
the structured outer surface 27b of the metallic glass layer can,
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.
[0068] In another embodiment the template can 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 can 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.
[0069] A typical heater would be an induction heater, heating by
conduction or convection heater as an infrared heater but can also
include for example contact heaters, flame heaters, Joule effect
heaters or any other adequate heating device.
[0070] The structured surface of the metallic glass layer and the
metallic glass layer itself can 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.
[0071] The forming tool with its surface structured according to
the method illustrated by FIG. 2 can then be used in polymer
processing or plastic coating process to modify the structure of
work-pieces or ductile compounds such as laminates or films or
packaging as described in FIG. 1.
[0072] FIG. 3 shows a die assembly 31 of an extrusion press to
produce metal profiles 32a, 32b. The working surface of the die is
coated with a metallic glass layer which is wear resistant and
which make it easier to refurbish the worn die simply by rebuild
the metallic glass layer.
[0073] FIG. 4 shows a wire draw machine containing a wire rod 42,
first and second dies 45a,b, a draw block 43, a sheave and speed
control device 44 and a finish draw block 46. The working surface
of the dies 45a,b is coated with a metallic glass layer which is
wear resistant and which make it easier to refurbish the worn die
simply by rebuild the metallic glass layer.
[0074] FIG. 5 shows an enlarged view of a wire reduction containing
a wire 47 with a thicker part 48 and a thinner part 49 after
passing through a die.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
* * * * *