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(11) | EP 1 726 421 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Die for shaping ceramic articles |
| (57) The die (1) for shaping ceramic articles comprises a plurality of walls (2a,2b,2c)
that can be associated with each other so as to define an inner article shaping housing
and the inner surfaces of which feature a multi-layer lining (7) comprising a first
layer (8a) of anchoring material in the state of shaped melted and/or semi-melted
powders associated with the inner surfaces and a second layer (8b) of anti-wear material
in the state of shaped melted and/or semi-melted powders associated with the first
layer (8a).
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[0002] It is well known that the traditional dies used to manufacture ceramic articles such as slabs, tiles and strip tiles consist of a plurality of walls able to define an internal housing into which to introduce the material to be shaped, generally in powder state.
[0003] By moving at least one of the walls of the die, it is possible to overcome the resistance opposed by the material loaded in the die and to compact this, so the shaped article has adequate density and mechanical resistance.
[0004] To resist the strong pressures and the friction produced by the ceramic material being shaped, the walls of the die usually consist of thin plates made of very hard and strong material and mounted on an external supporting structure.
[0005] Such materials usually consist of high-alloy steel and feature a high-alloy content and undergo heat treatment to harden and temper them so as to harden the wall surfaces.
[0006] These dies of known type made of high-alloy steel are not without drawbacks, among which the fact that they have very high production costs due to the high price of the raw materials, the difficulty in performing mechanical machining operations on them and the need to apply the above heat treatments.
[0007] The problem with the use of high-alloy steels also includes the difficulty in finding this material, increasingly less available on the market except at very high prices.
[0008] The production of high-alloy steel walls is furthermore very slow due to the numerous production phases required before the finished product is ready.
[0009] Furthermore, it should not be forgotten that the die wall working area consists only of the surface facing the inside of the die and in contact with the material to be shaped; such working area is very limited and the use of plates made entirely in high-alloy steel represents a considerable waste of prized material, above all in consideration of the fact that, whenever the working area is worn, the entire plate has to be replaced or the surface has to be mechanically worked to restore the initial shape.
[0010] Such restoration operation, which consists in the removal of the worn surface layer of the plate using a machine tool, besides being very costly, also presents the drawback of considerably reducing the resistant section of the plate and, consequently, can only be done a very few times before the plate becomes unusable.
[0011] As a result of use on the other hand, the performance of the walls made this way is not very high, and maximum hardness levels can only be achieved that are fairly limited and assessable at around 62 HRC.
[0012] As an alternative to the use of high-alloy steels, the manufacture is known of die walls in less-prized and costly materials, which are subsequently covered with protective linings of the thin rubber film or resin type.
[0013] Such solution, while on the one hand cutting production costs, on the other results in the production of ceramic dies with low shaping precision; the ceramic articles made using such dies can therefore feature irregular or badly calibrated profiles and/or corners and often require subsequent and fairly costly grinding operations.
[0014] Another type of dies for ceramics features the inserting of a layer of surface lining on the walls using the known facing method called CVD (Chemical Vapor Deposition).
[0015] By means of this method, the gas molecules in contact with the wall to be lined react chemically with the substrate surface until they form a solid material that sticks to it.
[0016] Such technology, however, does not permit obtaining dies for ceramics that are affordable and at the same time functional and precise and consequently, it is little used.
[0017] A primary aim of this invention is to eliminate the drawbacks complained of above and associated with known technology by excogitating a die for shaping ceramic articles which is particularly affordable thanks to the use of raw materials that are easy to obtain on the market and at considerably reduced overall production and installation costs, and which is strong and particularly hard-wearing and permits highly-precise shaping of ceramic articles.
[0018] As part of such technical aim, another purpose of the present invention is to achieve the preceding aims with a simple structure, of relatively practical implementation, safe use and effective operation.
[0019] This aim and these purposes are all achieved by the present die for shaping ceramic articles, comprising a plurality of walls that can be associated with each other so as to define an inner article shaping housing, characterized by the fact that at least one portion of the inner surface of at least one of said walls features a multi-layer lining comprising at least one first layer of anchoring material in the state of shaped melted and/or semi-melted powders associated with said inner surface and at least one second layer of anti-wear material in the state of shaped melted and/or semi-melted powders associated with said first layer.
[0020] Further characteristics and advantages of the present invention will appear even more evident from the detailed description of a preferred, but not exclusive, form of embodiment of a die for shaping articles, illustrated by way of non limiting example in the accompanying drawings, wherein:
figure 1 is an exploded view of the die according to the invention;
figure 2 is a perspective view of the die according to the invention;
figure 3 is a section view of a wall of the die according to the invention.
[0021] With special reference to such figures, a die for shaping articles, particularly ceramic articles, has been generally designated by reference numeral 1.
[0022] The die 1 comprises a plurality of walls that can be associated with each other to define an inner article shaping housing.
[0023] In the special form of embodiment of the invention shown in the illustrations, the walls of the die 1 are altogether six, four of which side walls 2a, that can be assembled inside a hollow supporting matrix 3, a lower wall 2b and an upper wall 2c, both of which horizontally flattened and fitted on a lower punch 4 and upper punch 5, respectively, associated with the rams 6 of a press or the like that can be reciprocally moved closer or away from one another.
[0024] Once fitted to the hollow matrix 3, the side walls 2a make up a frame inside which the lower wall 2b and the upper wall 2c can be inserted to measure.
[0025] The material to be shaped inside the die 1, for example ceramic powder to be pressed, can be loaded on the lower wall 2b and supported on the side by the side walls 2a, to be compacted during pressing by means of the closing in of the lower wall 2b and upper wall 2c.
[0026] According to the invention, the walls 2a, 2b and 2c are made of a poor metal, of a non-alloy or low-alloy steel type (for instance C40), and their inner surfaces feature a multi-layer lining 7 comprising at least one first layer 8a of anchoring material associated with the inner surfaces and at least one second layer 8b made of anti-wear material distributed on the first layer 8a.
[0027] Before proceeding with the application of the first and second layers 8a and 8b, the inner surfaces of the walls 2a, 2b and 2c must be flattened, for example by sandblasting, to reduce surface roughness to Ra values between 2.0 and 7.0.
[0028] Afterwards, the anchoring material and the anti-wear material, which appear in the form of more or less fine powders with a diameter between 2·10-6 m (2 µm) and 200 10-6 m (200 µm), can be applied to the walls 2a, 2b and 2c by means of a thermal spray process of plasma-spray type and/or of HVOF (High-Velocity Oxygen Fuel) type, which, in actual fact, enables the powders to melt together and stick to the walls 2a, 2b and 2c in the state of shaped melted and/or semi-melted powders.
[0029] Once the two layers 8a and 8b have deposited, an operation can be envisaged for rectifying the second layer 8b, so as to level the surface opposite the first layer 8a and reach the desired thickness and roughness values.
[0030] Furthermore, during heat-spraying, the possibility exists that inside the second layer 8b a number of cavities form which, following rectification, lead to the formation of tiny pores; the application process of the multi-layer lining 7 on the walls 2a, 2b and 2c may envisage a last phase involving the sealing of these pores, for example by filling them with a polymer-material paste.
[0031] In actual fact, the first layer 8a has the function of setting the powders of the second layer 8b and acting as a cushion to absorb the heat and mechanical stress caused by heat-spraying; the second layer 8b, on the other hand, represents a resistant and smooth film that enables the die 1 to achieve very high performances in terms of lasting use and precision in shaping the ceramic articles.
[0033] Once the second layer 8b has become worn in fact, by means of a simple mechanical procedure, it is possible to remove the remaining multi-layer lining 7 from the walls 2a, 2b and 2c on which it is applied and, therefore, apply a new first layer 8a and a new second layer 8b using the method described previously.
[0034] At each regeneration, the shape and thickness of the layers 8a and 8b can be restored without affecting the strength of the walls 2a, 2b and 2c.
[0035] Such regeneration can be done several times until the walls 2a, 2b and 2c give way structurally.
[0036] In the particular form of embodiment of the invention shown in the illustrations, the multi-layer lining 7 only consists of the first and second layers 8a and 8b; it cannot however be excluded one or more auxiliary layers made of different materials which, using methods similar to those described previously, can be applied over the second layer 8b or placed between the latter and the first layer 8a.
[0037] The compositions of the materials making up the first and second layers 8a and 8b can vary according to the specific strength and degree of hardness to be obtained from the multi-layer lining 7.
[0038] Preferably, the first layer 8a is a substance comprising nickel (Ni), aluminium (Al) and chrome (Cr), bound together in the following concentrations of weight evaluated compared to the overall weight of the first layer 8a:
| Ni | 74-100 % |
| Al | 0-6 % |
| Cr | 0-20 % |
[0039] In a possible form of embodiment of the invention, the second layer 8b consists of aluminium oxide (Al2O3) and titanium dioxide (TiO2), bound together in the following concentrations of weight evaluated compared to the overall weight of the second layer 8b:
| Al2O3 | 60-100 % |
| TiO2 | 0-40 % |
[0040] In an alternative form of embodiment, on the other hand, the second layer 8b comprises chrome oxide (Cr2O3), titanium dioxide (TiO2) and silicon dioxide (SiO2) bound together in the following weight percentages:
| Cr2O3 | 85-100% |
| TiO2 | 0-5 % |
| SiO2 | 0-10 % |
[0041] A further formulation of the second layer 8b requires this to contain cobalt (Co), tungsten carbide (WC), chrome (Cr), carbon (C) and nickel (Ni) in the following weight concentrations:
| Co | 3-40 % |
| WC | 1-100 % |
| Cr | 0-30 % |
| C | 0-6 % |
| Ni | 0-50 % |
[0042] The parameters of concentration and grain size of the powders for the first layer 8a and for the second layer 8b can be evaluated and changed from time to time according to resistance to wear and the effects on the ceramic material to be obtained.
[0043] In this respect, it should be pointed out that the surface hardness of the multi-layer lining 7 is able to reach values even higher than 80 HRC, making it particularly resistant to the abrasion caused by use by the ceramic material contained in die 1.
[0044] It has in fact been found how the described invention achieves the intended purposes and, in particular, it should be emphasised that the cost of the raw materials, mechanical machining operations and subsequent die wall lining operations according to the invention is quite inexpensive, above all in view of the possibility of strongly reducing the waste of materials and being able to regenerate the multi-layer lining many times over.
[0045] This invention also permits achieving performance levels superior to traditional dies in terms of long-life, hardness and resistance to wear.
1. Die for shaping ceramic articles, comprising a plurality of walls that can be associated
with each other so as to define an inner article shaping housing, characterized by the fact that at least one portion of the inner surface of at least one of said walls
features a multi-layer lining comprising at least one first layer of anchoring material
in the state of shaped melted and/or semi-melted powders associated with said inner
surface and at least one second layer of anti-wear material in the state of shaped
melted and/or semi-melted powders associated with said first layer.
2. Die according to claim 1, characterized by the fact that the powders of at least one between said anchoring material and said
anti-wear material have a diameter between 2· 10-6 m and 200 10-6 m.
3. Die according to one or more of the preceding claims, characterized by the fact that said powders are applied to said inner surface by means of a thermal
spray process.
4. Die according to one or more of the preceding claims, characterized by the fact that said thermal spray process is of the plasma spray and/or HVOF type.
5. Die according to one or more of the preceding claims, characterized by the fact that at least one of said walls is made of non-alloy or low-alloy steel.
6. Die according to one or more of the preceding claims, characterized by the fact that the inner surface of each of said walls features said multi-layer lining.
7. Die according to one or more of the preceding claims, characterized by the fact that said multi-layer lining can be regenerated after use.
8. Die according to one or more of the preceding claims, characterized by the fact that said first layer comprises nickel (Ni).
9. Die according to claim 8, characterized by the fact that said first layer also comprises aluminium (Al) and chrome (Cr).
10. Die according to claims 8 and 9, characterized by the fact that said first layer comprises Ni, Al and Cr in the following concentrations
of weight evaluated compared to the overall weight:
| Ni | 74-100 % |
| Al | 0-6 % |
| Cr | 0-20 % |
11. Die according to one or more of the preceding claims, characterized by the fact that said second layer comprises aluminium oxide Al2O3.
12. Die according to claim 11, characterized by the fact that said second layer also comprises titanium dioxide (TiO2).
13. Die according to claims 11 and 12, characterized by the fact that said second layer comprises Al2O3 and TiO2 in the following concentrations of weight evaluated compared to the overall weight:
| Al2O3 | 60-100 % |
| TiO2 | 0-40 % |
14. Die according to one or more of the preceding claims, characterized by the fact that said second layer comprises chrome oxide (Cr2O3).
15. Die according to claim 14, characterized by the fact that said second layer also comprises titanium dioxide (TiO2) and silicon dioxide (SiO2).
16. Die according to claims 14 and 15, characterized by the fact that said second layer comprises Cr2O3, TiO2 and SiO2 in the following concentrations of weight evaluated compared to the overall weight:
| Cr2O3 | 85-100 % |
| TiO2 | 0-5 % |
| SiO2 | 0-10 % |
17. Die according to one or more of the preceding claims, characterized by the fact that said second layer comprises cobalt (Co) and tungsten carbide (WC).
18. Die according to claim 17, characterized by the fact that said second layer also comprises chrome (Cr), carbon (C) and nickel
(Ni)
19. Die according to claims 17 and 18, characterized by the fact that said second layer comprises Co, WC, Cr, C and Ni in the following weight
percentages evaluated compared to the overall weight:
| Co | 3-40 % |
| WC | 1-100 % |
| Cr | 0-30 % |
| C | 0-6 % |
| Ni | 0-50 % |
20. Side for dies according to one or more of the claims from 1 to 19, characterized by the fact that it comprises at least one surface which features a multi-layer lining
comprising at least one first layer of anchoring material in the state of shaped melted
and/or semi-melted powders associated with said surface and at least one second layer
of anti-wear material in the state of shaped melted and/or semi-melted powders associated
with said first layer.