METAL FILM AND METHOD FOR HEATING THE SAME

Abstract

A metal film or plate, a method for obtaining thereof and some practical applications are described. The film is subject to heating by Joule effect created by parasitic currents induced by a time-varying magnetic field. The film is constituted by a metal alloy containing a first metal in a percentage comprised between 90% and 99% by mass of the total mass and a second metal in a percentage comprised between 1% and 10%. The thickness of the film is equal to, or lower than, 10 cm. The first metal is an amagnetic metal and the second metal is a ferromagnetic metal. In this way the film has ferromagnetic behavior still being mainly made by amagnetic metal. This allows exploiting in an optimal way both the mechanical features of amagnetic metals, and the magnetic features of ferromagnetic metals.

Claims

1. A method for making a metal film or film with metallic behavior (10), or a metal plate or plate with metallic behavior, subject to heating by Joule effect, comprising the steps of: a) preparing a metal alloy containing a first metal (1) or a first mixture of metals (1a, 1b, 1c, . . . In) in a percentage comprised in the range 90%-99% by mass of the total mass of the alloy, and containing a second metal or a second mixture of metals (2a, 2b, 2c, . . . 2n) in a percentage comprised in the range 1%-10% by mass of the total mass of the alloy; b) making a film or plate (10) constituted by said alloy and having thickness equal to or lower than 10 cm, characterized in that the first metal is an amagnetic metal and the first mixture of metals is amagnetic and/or exclusively comprises non-magnetic metals, and in that the second metal is a ferromagnetic or ferrimagnetic metal and the second mixture of metals exclusively comprises ferromagnetic metals, so that the film has ferromagnetic behavior.

2. Method according to claim 1, wherein the metals (1, 2) are respectively classified as non-magnetic, for example diamagnetic or paramagnetic or antiferromagnetic metals, or else magnetic metals, for example ferromagnetic and ferrimagnetic ones, depending on the magnetic permeability at room temperature, and the film has ferromagnetic behavior at room temperature.

3. Method according to claim, wherein the thickness of the film (10) is comprised between 5.Math. and 10 cm, preferably lower than 500 microns

4. Method according to claim 1, wherein the alloy is obtained by melting or sintering.

5. Method according to claim 1, wherein the alloy contains less than 1% by mass of: one or more rare-earth elements, wherein the rare-earth elements are identified according to IUPAC definition, or an oxide thereof, or else: MishMetal, in its turn composed of cerium 50%, lanthanum 25% and a little percentage of neodymium and praseodymium; non-metals, such as carbon, and/or semimetals, such as silicon.

6. Method according to claim 1, wherein the mass content of the first metal (1) or the first mixture of metals (1a, 1b, 1c, . . . In), with respect to the total mass of the alloy, is comprised in the range 95%-99%, and the mass content of the second metal (2) or the second mixture of metals (2a, 2b, 2c, 2n), with respect to the total mass of the alloy, is comprised in the range 1%-5%.

7. Method according to claim 1, wherein the first metal (1) is selected from silver, copper, aluminum, platinum, boron and the first mixture is a mixture of two or more first metals (1a, 1b, 1c, . . . In) and the second metal (2) is selected from nickel, iron, cobalt, and the second mixture is from two or more second metals (2a, 2b, 2c, . . . 2n).

8. Method according to claim 7, wherein: the titanium content in the alloy, if present, is lower than 0.5% by mass of the total mass, and is preferably comprised in the range 0.1%-0.2%; the boron content in the alloy, if present, is lower than 0.5% by mass of the total mass, and is preferably comprised in the range 0.1%-0.2%; the iron content in the alloy, if present, is lower than 3% by mass of the total mass, and is preferably comprised in the range 1%-3%.

9. Method according to claim 1, wherein the film (10) obtained by rolling, for example, is coupled with other metal or plastic materials, in order to define a multilayer structure, wherein the other materials are selected to lend the desired mechanical, thermal or electrical features to the film, for example to stiffen the film, maximize the heat exchange or electrically insulate the film itself.

10. Method according to claim 1, wherein the film is coupled with, or integrated in, manufactured products (P) per se unsuitable for being induction heated, so that they can be heating too.

11. A metal film (10) or plate subjected to an electromagnetic field, having the following features: a) is constituted by a metal alloy containing a first metal (1) or a first mixture of metals (1a, 1b, 1c, . . . In) in a percentage comprised between 90% and 99% by mass of the total mass and containing a second metal (2) or a second mixture of metals (2a, 2b, 2c, . . . 2n) in a percentage comprised between 1% and 10% by mass of the total mass; b) its thickness is equal to, or lower than, 10 cm; characterized in that the first metal (1) is an amagnetic metal, for example diamagnetic or paramagnetic or antiferromagnetic metal, and the first mixture of metals (1a, 1b, 1c, . . . In) or the first mixture of metals is amagnetic and/or exclusively comprises non-magnetic metals and in that the second metal (2) is a ferromagnetic or ferrimagnetic metal and the second mixture of metals (2a, 2b, 2c, . . . 2n) exclusively comprises ferromagnetic or ferrimagnetic metals, so that the film has ferromagnetic behavior.

12. Film (10) according to claim 11, having thickness lower than 500 microns.

13. Film (10) according to claim 11, wherein the alloy contains less than 1% by mass of: one or more rare-earth elements, wherein the rare-earth elements are identified according to IUPAC definition, or an oxide thereof, or else MishMetal, in its turn composed of cerium 50%, lanthanum 25% and a little percentage of neodymium and praseodymium; non-metals, such as carbon, and/or semimetals, such as silicon.

14. Film (10) according to claim 11, wherein the mass content of the first metal (1) or the first mixture of metals (1a, 1b, 1c, . . . In), with respect to the total mass of the alloy, is comprised between 95% and 99%, and the mass content of the second metal (2) or the second mixture of metals (2a, 2b, 2c, 2n), with respect to the total mass of the alloy, is comprised between 1% and 5%, and preferably between 1% and ..

15. Film (10) according to claim 11, wherein the first metal (1) is selected from silver, copper, aluminum, platinum, boron and the first mixture is a mixture of two or more first metals and the second metal (2) is one from nickel, iron, cobalt, and the second mixture is from two or more second metals.

16. Film (10) according to claim 11, wherein: the titanium content in the alloy, if present, is lower than 0.5% by mass of the total mass, and is preferably comprised in the range 0.1%-0.2%; the boron content in the alloy, if present, is lower than 0.5% by mass of the total mass, and is preferably comprised in the range 0.1%-0.2%; the iron content in the alloy, if present, is lower than 3% by mass of the total mass, and is preferably comprised in the range 1%-3%.

17. Film (10) according to claim 11, characterized by being coupled with other plastic materials or glasses, or borosilicate glasses or ceramics, in order to define a multilayer structure, wherein the other materials are selected to lend the desired mechanical, thermal or electrical features to the film, for example to stiffen the film, maximize the heat exchange or electrically insulate the film itself.

18. Film (10) according to claim 17, characterized by being confined in a cavity defined by layers of different materials, under vacuum conditions, so that it can switch to the liquid state when induction heated up to reach the melting point, and can return to solid state by getting cold with no induction, in order to allow exploiting the latent heat of fusion and latent heat of solidification of the alloy the film is constituted by.

19. Film (10) according to claim 11, characterized by being embossed to maximize the surface exposed to magnetic fields.

20. A film (10) directly obtained by the method according to claim 11.

21. (canceled)

22. (canceled)

Description

BRIEF LIST OF THE FIGURES

[0065] Further characteristics and advantages of the invention will be more evident by the review of the following specification of a preferred, but not exclusive, embodiment, which is depicted for illustration purposes only and without limitation, with the aid of the attached drawings, in which:

[0066] FIG. 1 is a schematic diagram relating to the method according to the present invention;

[0067] FIG. 2 is a schematic view of a first film subjected to a test, according to the present invention;

[0068] FIG. 3 is a schematic view of a second film subjected to a test according to the present invention;

[0069] FIG. 4 is a perspective view of the first film according to the present invention;

[0070] FIG. 5 is a perspective view of a pot coated with the first film according to the present invention;

[0071] FIG. 6 is a sectional view of the pot showed in FIG. 5;

[0072] FIG. 7 shows a car dashboard partially coated with a film according to the present invention;

[0073] FIG. 8 is a schematic view of a film according to the present invention, integrated in a multilayer structure.

DETAILED DESCRIPTION OF THE INVENTION

[0074] FIG. 1 is a simplified diagram of the method according to the present invention. A first metal 1, having non-magnetic behaviormeaning that at room temperature it doesn't noticeably interact with magnetic fieldsand a second ferromagnetic metal 2i.e. interacting at room temperature with magnetic fieldsare used to implement a metal alloy 3. The proportions of the two metals are those described above and in the claims.

[0075] The alloy can be obtained with different techniques, for example melting, sintering, dispersing a powdered metal in a liquid metallic phase.

[0076] Referring for the sake of simplicity to the melting, the alloy is solidified in billets, which are then used in a rolling mill for obtaining the film of the desired thickness, anyway lower than 10 cm.

[0077] The rolling technique is well known and the detailed description is not needed. For example, the following movie available on the YouTube internet platform explains how films made of food aluminum are produced in a rolling mill: https://www.youtube.com/watch?v=f4OTj9yNOak.

[0078] For example, the production 4 can occur precisely by the rolling, which is the preferred technique.

[0079] The so-produced film is thus ready for step 5 of induction heating 5.

[0080] The alloy can also be obtained starting from several first metals 1a, 1b, 1c, . . . 1n, and several second metals 2a, 2b, 2c, . . . 2n, as described above.

[0081] FIG. 2 is an example of effectiveness test. A film sheet 10 is located on an induction hob 11, whose power is adjustable between 10 W and 3000 W. When the induction hob 11 is operating, in few seconds the film 10 rapidly heats, because of the dissipation of energy by Joule effect cooperating with the dissipative re-orienting effect of the magnetic domains known in literature as hysteresis loop, which is typical and characteristic of ferromagnetic materials.

[0082] The following examples describe the phenomenon.

EXAMPLES

Example 1

[0083] Alloy constituted by silver, copper, nickel and rare-earth elements in the mass percentages depicted in the table below.

TABLE-US-00002 Diamagnetic metals Silver Copper 47% 49.5% Ferromagnetic Metal Nickel 3% Other Metals Rare Earth Silicide 0.5% or else MishMetal 0.5% Thickness of the film 200 m

[0084] In its turn, the rare-earth silicide is composed by Si=40%-45%, rare-earth elements 8%-10% and iron for the remainder; MishMetal is typically composed by cerium 50%, lanthanum 25% and a little percentage of neodymium and praseodymium.

[0085] The film has been heated with the induction hob 11 set to the power of 1000 W and reached the temperature of about 800 C. (red color).

Example 2

[0086] Alloy constituted by copper, nickel and rare-earth elements in the mass percentages depicted in the table below.

TABLE-US-00003 Diamagnetic metals Copper 89.5% Ferromagnetic Metal Nickel 10% Other Metals Rare Earth Silicide 0.5% or else MishMetal 0.5% Thickness of the film 100 m

[0087] In its turn, the rare-earth silicide is composed by Si=40%-45%, rare-earth elements 8%-10% and iron for the remainder; MishMetal is typically composed by.

[0088] The film has been heated with the induction hob 11 set to the power of 1000 W and reached the temperature of about 1100 C. (bright red color).

Example 3

[0089] Alloy constituted by aluminum and iron in the mass percentages depicted in the table below.

TABLE-US-00004 Diamagnetic metals aluminium 97.3% Ferromagnetic Metal Iron 2.7% Thickness of the film 100 m

[0090] The film has been heated with the induction hob 11 set to the power of 250 W and reached the temperature of about 250 C.

Example 4

[0091] Alloy constituted by aluminum and iron in the mass percentages depicted in the table below.

TABLE-US-00005 Diamagnetic metals aluminium 97% Ferromagnetic Metal Iron 3% Thickness of the film 1.2 cm

[0092] The film has been heated with the induction hob 11 set to the power of 400 W and reached the temperature of about 50 C.

Example 5

[0093] Alloy constituted by aluminum and iron in the mass percentages depicted in the table below.

TABLE-US-00006 Diamagnetic metals aluminium 97.3% Ferromagnetic Metal Iron 2.7% Thickness of the film 1.1 mm

[0094] The film has been heated with the induction hob 11 set to the power of 250 W and reached the temperature of about 200 C.

[0095] FIG. 3 shows a film 10 identical to the film 10 of the example 3, but embossed to increase the exchange surface with the magnetic field generated by the hob 11.

[0096] In FIG. 4 a portion of a first film 10 made of aluminum and iron alloy according to the invention, is schematically depicted. For graphical reasons, in the figures the thickness of the film 10 was deliberately denoted, by way of illustration, much bigger than the actual size and not proportioned to the other dimensions of the pot: as mentioned, in fact, the thickness of the film 10 is in the order of microns and a real representation thereof wouldn't have been noticeable in the drawings.

[0097] The film 10 is made of aluminum and iron alloy, with aluminum being present in quantity comprised between 97% and 99% by mass (wt. %) and iron being present in quantity comprised between 1% and 3% (wt. %), advantageously between 1% and 1.5% (wt. %). The alloy can further comprise titanium and/or boron, each in quantity not higher than 0.5%, advantageously comprised between 0.1% and 0.2%. These metals have the purpose to carry out a satisfactory refining of the alloy, thus allowing the formation of smaller and substantially spherical-shaped granules and improving its overall mechanical characteristics. Furthermore, other elements (metallic and non-metallic) can be present in traces, generally in an overall quantity lower than 0.1%.

[0098] The film 10 has thickness comprised between 5 m and 200 m and is preferably obtained by rolling.

[0099] In FIG. 5 a pot P is depicted and equipped with a bottom 12 and a lateral wall 13 which define an inner compartment 14 adapted to contain liquid or solid substances intended to be heated. Advantageously, at the lateral wall 13 there can be handles 15 for the user's grip. The handles 15 can be made of thermally non-conductive material or with appropriate thermal insulation from the body of the pot, for example made of Bakelite.

[0100] The bottom of the pot P is flat to provide optimum support on the induction hob and can be made by any material suitable for heating and/or cooking foodstuffs, foods or beverages, for example ceramic, glass, borosilicate glass, fiberglass, porcelain, plastic material, etc., as well as plastics able to withstand temperatures in the order of 180-200 C. without damages and without releasing toxic substances that would otherwise contaminate the dishes.

[0101] At least the bottom 12 of the pot P is coated by the film 10 of aluminum and iron alloy having the features described above. When the magnetic field of an induction hob is activated, induced currents within the film 10 heat it and, in turn, it transfers the heat to the material constituting the bottom 12 and the walls 13 of the pot.

[0102] In FIG. 6 how the film 10 can be provided also as a coating of the lateral wall 13 of the pot P is schematically depicted (partially represented), for aesthetic reasons or if it is desired to locate the inductor at the pot sides.

[0103] The film 10 can advantageously be applied to the bottom 12 and the walls 13 of the pot P by means of glues or resins able to withstand operating temperatures between 180 and 200 C.

[0104] As showed in FIG. 6 (with dashed line representation), the film 10 of aluminum and iron alloy according to the invention can only be provided at the external surface of the bottom 12 (and, in case, of the lateral wall 13) or also (or only) at the internal surfaces.

[0105] Anyway, the solution with external coating is the optimal solution both because it avoids a possible damage of the film itself that could occur (if present inside) in case the content of the pot needs to be blended or handled with spoons, forks, etc., and because it allows to keep the inside of the pot, directly in contact with the food to be heated or cooked, made of the material (glass, borosilicate glass, fiberglass, porcelain, ceramic, polymeric materials etc.) most suitable for that specific use.

[0106] A film of non-magnetic metals and ferromagnetic metals alloy according to the invention, applied to a pot P made of ceramic, glass, borosilicate glass, etc., guarantees ferromagnetic and electrical conductivity features to the pot P itself, that make it suitable for the operation with the induction hob, still maintaining all of the peculiar features of the materials constituting the body of the pot P.

[0107] FIG. 7 shows another example of application of the present invention. A film 10 is used to coat parts 20 of a car dashboard 20, for aesthetic purposes. One of the advantages offered by the present invention is the chance to obtain elements 20 that are thermoformed instead of die cast, molded or deep drawn. In the example showed in FIG. 7, coating elements are obtained starting from the film 10 having the composition of the example 3. The film 10 is located on a shape and subjected to induction heating up until the softening point is reached. At this point, the film 10 is laid down on the shape to copy its surfaces, i.e. to copy its tridimensional development. Thus, a step of cooling, separation from the shape and edging follows. The so obtained element 20 is polished and glued to the dashboard 20.

[0108] With the same method it is possible to make components in which the shape remains embedded in the coating obtained by softening or melting the film 10. In fact, the film can be heated up to the melting point to liquefy it, if necessary.

[0109] FIG. 8 shows two possible multilayer structures 30, 30 that can be obtained with a film 10 or 10 according to the present invention. In order to obtain a mechanically resistant structure 30, 30 or to lend particular thermal or electrical features thereto, it is possible to couple at least one additional layer 31 with the film 10. On the left in FIG. 8, the film 10 is sandwiched between two layers (of different thickness) 31, for example an electrically insulating material, such as glass, borosilicate glass, fiberglass, porcelain, ceramic, polymeric materials, etc. Thereby, it is possible to maximize the heat exchange of the film 10 by protecting it, i.e. avoiding its approach to the melting point. On the right in FIG. 8, two films 10 are sandwiching one layer of material 31.

[0110] If it is desired to lend flexural strength, for example, the film 10 can also be coupled with other layers, for example a steel or titanium foil, taking care that the same is not shielding the film 10 with respect to the induced magnetic field.