MX2013013665A

MX2013013665A - Method for manufacturing a metal foam provided with channels and resulting metal foam.

Info

Publication number: MX2013013665A
Application number: MX2013013665A
Authority: MX
Inventors: Frédéric POGGI
Original assignee: Filtrauto
Priority date: 2011-05-25
Filing date: 2012-05-23
Publication date: 2014-09-01
Also published as: FR2975613A1; JP2014515989A; US20140186652A1; CN103930223B; FR2975613B1; CN103930223A; BR112013030172A2; KR20140033163A; EP2714303A1; CA2837151A1; EP2714303B1; WO2012160275A1

Abstract

The invention relates to a method for manufacturing a metal foam provided with at least one channel and intended, in particular, for the manufacture of a heat exchanger from a preform (1) of beads. A central portion (2), consisting of a core (3) and a coating made of a low-temperature meltable material is arranged in a casting mold, then the preform is arranged around the central portion while establishing close contact with said central portion, the low-temperature meltable material is then removed via heating, the molten metal mass is then poured into the mold in order to fill in the free spaces between the beads and between the beads and the core (3), and then the beads are finally removed.

Description

METHOD FOR MANUFACTURING A METAL SPONGE PROVIDED WITH CHANNELS AND METAL SPONGE RESULTING The technical scope of the invention is that of the manufacture of metal sponges that incorporate channels that open on both sides.

These metal sponges can be used particularly in heat exchangers to dissipate or circulate heat. However, it is important to have one or more channels that pass from one side of the metal sponge to the other in order to produce more complex exchangers that allow the circulation of a second fluid within the permutator or otherwise to form preferred passages (known as deviations).

The proportion of one or more channels within a metal sponge has already been proposed. Therefore, the US document 2009/0085520 proposes the perforation of the sponge in order to introduce a tube, either forcing or latting after the introduction of the tube in order to make it complete with the sponge. It is understood that this technique requires first of all the elaboration of the metal sponge, then its perforation and finally the installation of an integral tube with the sponge. According to this document, the tube is held in place in the sponge in various ways, for example, by brassing, by compressing the sponge around the tube, by tight fitting the tube, etc. Finally, it is understood that this system only allows the insertion of straight tubes.

Patent EP-1808241 discloses a process for making channels through a metal sponge according to which metal tubes are pre-inserted into the preform before the molten aluminum or aluminum alloy is melted or even after that is founded. This system allows the insertion of a preformed tube.

The metal sponge technology is well known and reference can be made to the patents EP-1808241, US-3236706 and EP-2118328 which recommend the preparation of a preform in the form of salt-based granules or spheres, such as sodium chloride. sodium. In followed, the free space between the granules is filled by a molten metal, dissolving the salt to recover the metal sponge.

Whatever the process used to obtain a channel inside the metal sponge, the problem of impaired conductivity lies in the junction between the tube and the porous medium of the sponge. In addition, over time, the mechanical resistance between the tube and the sponge that forms two parts is altered. Finally, that is, to date, it is impossible to form both the channel and the metal sponge in a single operation using the same material.

The purpose of the invention is to provide a metal sponge incorporating a tube that passes through it and that is obtained during the making of the sponge in s i.

The sponge is produced in a conventional manner, using a preform with granules, as described, for example, in the document cited below.

However, the patent EP-2118328 describes a method that is particularly advantageous in providing the making of a preform using grain meal granules. This preform is cooked like this before melting the metal in order to destroy the carbon chains of the granules. This patent therefore provides, first of all, the preparation of a paste formed from flour, sodium chloride and water. The granules to be subsequently used to produce the preform are prepared using this paste.

The invention thus relates to a process for manufacturing a metal sponge provided with at least one channel and proposed mainly for the production of heat exchangers using a spherical preform, characterized in that a casting core, a central core and a coating of A meltable material at low temperature is placed in a casting mold, the preform is then fitted snugly around the core, the meltable material is then removed by heating at low temperature, then the molten metal mass is emptied in the molding with object of filling the spaces between the spheres and between spheres and the central core, and finally the spheres are eliminated.

According to a particular embodiment, the channel is constituted, after the metal mass has been melted, by the metal mass that replaces the wax coating.

According to another specific embodiment, the central nucleus of the core is formed by ceramic, steel, sand, a soluble material or a material identical to that which forms the preform.

According to another embodiment, the core is formed of three elements, a first element constituted by the core of ceramic, steel or sand, a second element constituted by a peripheral layer or refractory material and a third element constituted by a covering of meltable material at low temperature.

According to yet another embodiment, the core is formed of four elements, a first element constituted by a core of ceramic, steel or sand, a second element constituted by a peripheral layer of a refractory material, a third element constituted by a layer of ceramic material and a four element constituted by the covering of meltable material at low temperature.

According to another modality, the nucleus is rectilinear.

According to another modality, the nucleus has curves.

According to another embodiment, the core is tubular.

According to another embodiment, the meltable material at low temperature is a wax.

According to another embodiment, the coating has continuous or discontinuous projections on its internal surface.

The invention also relates to the metal sponge obtained by following the process according to the invention and is provided with at least one channel.

Advantageously, the channel is of a tubular, straight or curved shape.

Again advantageously, the channel and the sponge are aluminum based or a aluminium alloy.

A first advantage of the invention lies in the production of a sponge that incorporates a channel of the same nature as the sponge itself.

Another advantage of the invention lies in the production for the first time and simultaneously of the metal sponge and the channel or channels.

Another advantage of the invention lies in the fact of producing a channel of any shape, for example, straight, curved or other.

Still another advantage of the invention lies in the absence of any negative interaction between the channel and the metal sponge.

Yet another advantage of the invention lies in the elimination of any problem of mechanical strength or thermal conductivity between the channel or channels and the metal sponge.

Other features, advantages and features of the invention will become more apparent from the description of the further embodiments, given below by way of example and with reference to the appended figures, in which: Figure 1 is a view showing a preform in which a core has been inserted, Figures 2-6 show section views of different kernel modalities, Figure 7 is a sectional view showing another embodiment of the core, and Figures 8 and 9 are sectional views of the metal sponge with a channel made in situ.

In the next part of the description, the preform should be considered to have been made in a known manner, that is, using agglomerate spheres made of a salt, such as sodium chloride, and which have been used in a known manner to produce a metal sponge The material constituting the metal sponge is also known and, by way of example, aluminum, aluminum alloys and any other known material used in casting can be used. Reference may be made to the aforementioned patent for additional details.

As previously mentioned, from According to the invention, a core is inserted into the preform, said core being capable of being prepared in various ways. Generally speaking, the invention is based on the replacement of a stratum of meltable coating material by the same constituent material as the metal sponge in order to produce a channel in situ.

Figure 1 shows a view of a preform constituted of spheres 1, compressed or not, in which a core 2 is installed. This core is constituted by a central core 3 and a cover 4. For reasons of clarity, the preform 6 It has been shown removed from its mold. This preform is parallelepiped; the core 2, according to Figure 1, has been inserted therein. All spheres 1 can be observed in close contact with each other. The end of the cover 4 is flooded with the side wall of the preform while the core 3 is protruding. This illustration is by no means limiting and the invention can also be made only by allowing the wax to protrude in order to create a skin or to obtain a tube that protrudes with respect to the sponge.

Naturally, the core 2 is first installed in the molten metal injection mold in a vertical or inclined position according to the needs of the user and then the spheres are emptied into the mold. The sponge is then produced using known technology that does not require additional description here. Not to mention that it is possible to insert several cores in order to obtain several channels.

Figure 2 shows a sectional view of a first embodiment of the core 2 formed of the central core 3 and the covering 4. The central core 3 is constituted, for example, by a ceramic material, steel or sand normally used in casting technologies. The coating is here constituted by a layer of wax or any other meltable material at low temperatures. A meltable material at low temperature is considered to be one whose melting point is between 40 ° C and 150 ° C. Naturally, the diameter of the central core and the thickness of the Coating layer are determined according to the proposed applications for the metal sponge. Therefore, the diameters of the central core 3 of more than 2 mm can be imagined and a coating thickness of 0.5 mm to 10 mm (preferably 0.5 to 3 mm) can be adopted.

The Figure shows a rectilinear core, but without mentioning that a core can be used in any way. In this case, a central sand core is preferable.

This preform 1 integrating the core 2 is used to elaborate the metal sponge in a conventional manner. Therefore, since the temperature inside the mold rises, the spheres agglomerate to create a rigid preform, then the coating 4 melts and is simply removed by pouring. The molten metal is injected in a known manner to capture the spaces between the spheres and the free space left by the coating between the preform and the remaining core to constitute the channel. After cooling the central core 3 is extracted or eliminated if it is made of sand in order to clean the channel formed.

Figure 3 shows a sectional view of a variant embodiment of the core 2 made of three parts: the central part 3 on which a layer of refractory material 5 is applied and subsequently a coating 4 of wax or meltable material at low temperature. The advantage of this refractory material lies in that it facilitates removal of the core from the mold after the metal has cooled while the central core 3 ensures this rigidity. This refractory material also allows the diameter of the final channel to be modified without having to modify the central core.

Figure 4 shows the core 2 according to Figure 3 in which the central core 3 has been deepened longitudinally to form a channel 6. The advantage of this modality lies in the reduction of the material constituting the central core 3. An advantage Additional to such an embodiment lies in the possibility of being able to circulate an air flow through this channel in order to improve cooling after casting. He The central core is, in this case, in the shape of a tube that is more or less thick.

Figure 5 shows a sectional view of another embodiment of the core 2 made of four parts. The central core 3 is covered by a layer 5 of a refractory material, covered in itself with a layer of ceramic material 7 and finally the covering layer 4. The use of a ceramic material allows the rigidity of the refractory material to be improved and any potential infiltration of molten aluminum into the refractory material is avoided, thus avoiding micro-fracture.

Figure 6 shows a variant embodiment of that shown in Figure 5 in which a hollow central core 3 is provided in a tube shape. This modality allows a saving in the constituent material of the central core.

All the cores previously described in relation to the Figures are inserted into a preform in order to be able to produce one or several channels inside the metal sponge. For this purpose, the core is installed in the mold of sponge production and then the spheres are put in place and made compact in order to ensure their mutual contact. If necessary, the preform is compressed.

All these cores can incorporate a central core made of a ceramic material, steel or sand, and more generally any suitable material for emptying work. Not to mention that the central core is made of a ceramic or steel material if it is in the form of a straight rod in order to ensure its extraction, being rectilinear the channel obtained. The core can be placed in any position within the preform and the tube can be opened at any point, inlet or outlet, on any surface of the metal sponge.

Figure 7 shows another embodiment of the core 2 whose central core 9 incorporates several curves and which is covered by a coating 4 of wax or other meltable material at low temperature. In this case, the central core 9 is made of sand or other friable material. The channel obtained inside the sponge provides a greater surface area between the fluid that circulates through the metal sponge and the fluid that circulates in the channel.

Figure 8 shows a sectional view of a metal sponge block 10 formed by a wire mesh 11 inside which the tubular channel 12 is formed in the free space between the spheres and the central core after it has been fused the coating. It is understood that the thickness of the channel 12 is substantially equal to the thickness of the wax layer.

The benefit of the present invention is easy to observe since the sponge 10 and the channel 12 are processed simultaneously when the molten metal is emptied. Therefore, they are of the same nature, thus ensuring the identical conductivity of these two elements and eliminating any problem of mechanical resistance.

Figure 9 shows a view in longitudinal section along the channel 12, where it can be seen that the channel 12 is completely embedded in the mesh 11 of the metal sponge with a melting of the material.

Figures 10 and 11 show a variant mode consisting in the realization of grooves or notches on the external surface of the central core 3 (or on the refractory material). By filling such slots or notches with the coating 4, they cause continuous or discontinuous protrusions 13 along the inner surface of the coating 4, which, when the metal is melted, creates adapted exchange surfaces within the channel in order to improve the exchange thermal. These projections 13 are shown here by way of non-limiting illustration in the form of triangular and rectangular sections. Not to mention to one skilled in the art that they can be found in other forms in order to improve thermal exchange while preserving the flow of fluid into the channel. An advantage of this modality lies in the increase in the exchange surface within the channels and therefore the performance of the device.

The Figures illustrating the invention show, by way of non-limiting example, the core, the coating and the pipe with a substantially circular section, without mention that a person skilled in the art will be able to carry out the invention using different sections, that is, oval or rectangular.

The sponges according to the invention are particularly suitable in the production of heat exchangers, of any type, liquid / liquid, or liquid / gas, or gas / gas, or phase change fluids.

Claims

1. A process for the manufacture of a metal sponge provided with at least one channel and proposed mainly for the manufacture of heat exchangers using a spherical preform, characterized in that a core consisting of a central core and a coating of a meltable material at low temperature they are placed in a casting mold, the preform is then fitted snugly around the core, the meltable material is then removed by heating at a low temperature, then the mass of molten metal is emptied into the mold in order to fill the spaces free between the spheres and between the spheres and the central core, and finally the spheres are eliminated.

2. A process according to claim 1, characterized in that the channel 12 is constituted, after the metal mass has been melted, by the metal mass that replaces the wax coating.

3. A process according to claims 1 or 2, characterized in that the central core or the core are formed by a ceramic material, steel, soluble sand, or a material identical to the one that forms the preform.

4. A process according to one of claims 3, characterized in that the core is formed of three elements, a first element, consisting of the central core of ceramic, steel or sand, a second element consisting of a peripheral layer of refractory material and a third element constituted by a coating of meltable material at low temperature.

5. A process according to one of claims 1 to 3, characterized in that the core is formed of four elements, a first element constituted by a central core of ceramic, steel or sand, a second element constituted by a peripheral layer of a refractory material, a third element constituted by a layer of ceramic material and a fourth element constituted by the covering of meltable material at low temperature.

6. A process according to one of the preceding claims, characterized in that the central core is rectilinear. - 2 -

7. A process according to any of the preceding claims, characterized in that the central core has curves.

8. A process according to any of the preceding claims, characterized in that the central core is tubular.

9. A process according to any of the preceding claims, characterized in that the material meltable at low temperature is a wax.

10. A process according to one of the preceding claims, characterized in that the coating has continuous or discontinuous projections on its internal surface.

11. A metal sponge obtained by following the process according to the preceding claims and provided with at least one channel.

12. A metal sponge according to claim 11, characterized in that the channel is in the form of a rectilinear or curved tube.

13. A metal sponge according to claim 11 or 12, characterized in that the channel and the sponge are made of aluminum or aluminum alloy.