CH629421A5

CH629421A5 - METALLIC COATED PRODUCT.

Info

Publication number: CH629421A5
Application number: CH1125778A
Authority: CH
Inventors: John Ulam
Original assignee: Clad Metals Inc
Priority date: 1978-01-06
Filing date: 1978-11-01
Publication date: 1982-04-30
Also published as: FR2413972A1; SE7811688L; DE2900333A1; FR2413972B1; NO155999C; BE873322A; GB2011809B; AU4133178A; NO155999B; GB2011809A; NO790047L; IT1195069B; CA1125629A; SE438818B; IT7852262A0; JPS5494456A

Description

Cette invention peut être mieux comprise si l'on se réfère aux exemples suivants de produits et de procédés qui en découlent ainsi qu'à la figure unique qui montre une coupe du matériau composite. This invention can be better understood if reference is made to the following examples of products and processes which result therefrom as well as to the single figure which shows a section of the composite material.

Exemple I: Example I:

Une tôle de cuivre de 0,254 mm d'épaisseur est décapée au moyen d'une brosse métallique, puis placée entre deux tôles d'aluminium de type 3003 de 1,9 mm d'épaisseur qui sont elles-mêmes recouvertes d'une fine couche d'aluminium pur de type 1145 sur les deux côtés qui seront nettoyés de même. Le cuivre et l'alliage d'aluminium recouvert d'aluminium pur sont réduits de 50 à 65% de façon à les allier. Ce noyau préformé de cuivre plaqué aluminium de 1,3 mm d'épaisseur a été nettoyé par abrasion sur sa face exposée d'aluminium pur, puis mis en contact avec deux tôles d'acier inox de type 304 de 0,25 mm d'épaisseur, l'acier inox reposant sur les faces d'aluminium pur. Cet assemblage de métaux a été porté à 370°C et passé au laminoir pour réduire l'épaisseur à 1,65 mm, puis passé une seconde fois pour réduire l'épaisseur à 1,27 mm. Le produit final a été chauffé à nouveau à 370°C de manière à provoquer une diffusion entre les différentes couches de métaux. Le produit recuit final, dans lequel la couche de cuivre forme la majeure partie de l'épaisseur, est alors formé par emboutissage pour produire des ustensiles de cuisine tels que des poêles. A 0.254 mm thick copper sheet is etched using a wire brush, then placed between two 1.9 mm thick 3003 type aluminum sheets which are themselves covered with a thin layer. of pure aluminum type 1145 on both sides which will be cleaned in the same way. Copper and aluminum alloy coated with pure aluminum are reduced by 50 to 65% in order to combine them. This 1.3 mm thick aluminum-plated copper preformed core was cleaned by abrasion on its exposed face of pure aluminum, then brought into contact with two 0.25 mm thick 304 stainless steel sheets. thickness, stainless steel resting on the faces of pure aluminum. This metal assembly was brought to 370 ° C and passed to the rolling mill to reduce the thickness to 1.65 mm, then passed a second time to reduce the thickness to 1.27 mm. The final product was again heated to 370 ° C so as to cause diffusion between the different layers of metals. The final annealed product, in which the copper layer forms most of the thickness, is then formed by stamping to produce kitchen utensils such as frying pans.

Là où on désire une surface d'acier inox et l'autre de cuivre, le noyau préformé de cuivre plaqué d'aluminium est fabriqué selon le procédé décrit ci-dessus à l'exception du fait que seul un côté du cuivre est plaqué. Where a surface of stainless steel and the other of copper is desired, the preformed core of copper plated with aluminum is produced according to the process described above except for the fact that only one side of the copper is plated.

Exemple II: Example II:

Une feuille de cuivre de 1,27 mm d'épaisseur a été nettoyée par abrasion, puis placée entre deux feuilles d'alliage d'aluminium de type Alclad 3004 recouvert d'aluminium pur de type 1145 de 3,18 mm d'épaisseur qui ont été nettoyées de manière similaire. A 1.27 mm thick copper foil was cleaned by abrasion, then placed between two sheets of Alclad 3004 type aluminum alloy coated with 3.18 mm thick pure 1145 type aluminum which have been cleaned similarly.

Les métaux sont alors chauffés à 230°C puis laminés et réduits une première fois de 2% puis laminés à une épaisseur d'environ 2,8 mm. Le produit laminé est alors chauffé à 370°C pour provoquer la diffusion entre les différentes couches de métaux. Le produit final est coupé en flans et transformé par emboutissage en ustensiles de cuisine. The metals are then heated to 230 ° C then rolled and reduced a first time by 2% then rolled to a thickness of about 2.8 mm. The rolled product is then heated to 370 ° C to cause diffusion between the different layers of metals. The final product is cut into blanks and transformed by stamping into kitchen utensils.

Là où on désire une surface d'acier inox et l'autre de cuivre ou d'aluminium, on procède comme ci-dessus, mais on omet la couche non utilisée. Where we want a surface of stainless steel and the other of copper or aluminum, we proceed as above, but we omit the unused layer.

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Exemple III: Example III:

Une feuille de cuivre de 1,27 mm d'épaisseur a été nettoyée par abrasion au moyen d'une brosse métallique et placée entre deux tôles d'alliage d'aluminium de type 3003 recouvert d'aluminium de type 1145, ayant chacune 1,9 mm d'épaisseur et qui ont été nettoyées de manière similaire. Deux feuilles d'acier inox de type 304 de 0,254 mm d'épaisseur sont placées, une de chaque côté, sur les faces d'aluminium pur de l'alliage d'aluminium. Ces tôles d'acier inox ont également été nettoyées par abrasion avant l'assemblage. L'assemblage est alors chauffé à 370°C, puis passé au laminoir pour amener l'épaisseur à 3,0 mm. Le produit final est recuit à 370°C pendant un temps suffisant pour provoquer la diffusion entre les différentes couches métalliques. Le produit final recuit, dans lequel la couche de cuivre forme la majeure partie de l'épaisseur, est transformé en ustensiles de cuisine par emboutissage. A 1.27 mm thick copper sheet was cleaned by abrasion using a wire brush and placed between two sheets of aluminum alloy type 3003 covered with aluminum type 1145, each having 1, 9 mm thick and similarly cleaned. Two sheets of stainless steel type 304, 0.254 mm thick are placed, one on each side, on the faces of pure aluminum of the aluminum alloy. These stainless steel sheets were also cleaned by abrasion before assembly. The assembly is then heated to 370 ° C, then passed to the rolling mill to bring the thickness to 3.0 mm. The final product is annealed at 370 ° C for a time sufficient to cause diffusion between the different metal layers. The annealed final product, in which the copper layer forms most of the thickness, is transformed into kitchen utensils by stamping.

Nous avons constaté que le produit de cette invention peut être utilisé dans le domaine des ustensiles de cuisine sous diverses formes. Par exemple, un matériau à neuf couches, décrit dans la figure, consistant en un noyau de cuivre 10 plaqué sur chaque côté par une feuille d'alliage d'aluminium 11, elle-même plaquée par de l'aluminium pur 12, le tout étant recouvert des deux côtés par une feuille d'acier inox 13, peut être utilisé dans la fabrication d'ustensiles de cuisine possédant les propriétés de l'acier inox en surface, mais qui conduisent uniformément la chaleur d'une manière inatteignable avec les anciens matériaux. We have found that the product of this invention can be used in the field of kitchen utensils in various forms. For example, a nine-layer material, described in the figure, consisting of a copper core 10 plated on each side by a sheet of aluminum alloy 11, itself plated by pure aluminum 12, the whole being covered on both sides with a sheet of stainless steel 13, can be used in the manufacture of kitchen utensils having the properties of stainless steel on the surface, but which uniformly conduct heat in a way unattainable with the old materials.

Un matériau de sept ou huit couches, formé d'un noyau de cuivre formant la majeure partie de l'épaisseur du matériau et recouvert d'alliage d'aluminium plaqué d'aluminium pur et ayant une couche extérieure d'acier inox, est utilisé avec satisfaction dans la fabrication d'ustensiles de cuisine qui seront recouverts de porcelaine ou autre après traitement de la surface d'aluminium. Ce matériau peut aussi être utilisé sous forme de disques attachés au fond d'ustensiles classiques. Là aussi, on obtient un bon transfert de chaleur. Dans les cas où on utilise des disques, le recouvrement d'aluminium pur de la surface exposée est omis. Finalement, un matériau à cinq couches peut être fabriqué selon le procédé décrit ci-dessus, qui comporte une couche de cuivre recouverte d'un côté par une couche d'alliage d'aluminium plaqué d'aluminium pur, elle-même recouverte d'une couche cuivrée d'acier inox. Ce produit peut être utilisé dans la fabrication d'ustensiles de cuisine ayant une surface décorative en cuivre qui améliore le transfert de chaleur et une surface interne en acier inox, cela sur un noyau en aluminium. A material of seven or eight layers, formed of a copper core forming the major part of the thickness of the material and covered with aluminum alloy plated with pure aluminum and having an outer layer of stainless steel, is used with satisfaction in the manufacture of kitchen utensils which will be covered with porcelain or other after treatment of the aluminum surface. This material can also be used in the form of discs attached to the bottom of conventional utensils. Here too, good heat transfer is obtained. In cases where discs are used, the pure aluminum covering of the exposed surface is omitted. Finally, a five-layer material can be produced according to the method described above, which comprises a layer of copper covered on one side by a layer of aluminum alloy plated with pure aluminum, itself covered with a copper-plated layer of stainless steel. This product can be used in the manufacture of kitchen utensils with a decorative copper surface which improves heat transfer and an internal surface in stainless steel, this on an aluminum core.

Nous avons présenté les utilisations de ce produit surtout dans le domaine des ustensiles de cuisine, étant donné que ce secteur est le principal utilisateur de ce genre de matériau; cependant, on peut étendre ces applications à un grand nombre d'usages industriels dans lesquels le transfert de chaleur est un paramètre important, tout comme la résistance à la décoloration, à l'oxydation, etc. We have presented the uses of this product mainly in the field of kitchen utensils, since this sector is the main user of this kind of material; however, these applications can be extended to a large number of industrial uses in which heat transfer is an important parameter, as is resistance to discoloration, to oxidation, etc.

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Claims

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1. Coated metal product, characterized in that it consists of a layer of copper or copper alloy, in at least one layer of aluminum alloy containing less than 99% aluminum, covered with aluminum substantially pure containing at least 99% aluminum, the copper layer forming a major part of the thickness of the product, and at least one outer coating layer of stainless steel, bonded to aluminum on the side opposite to copper, so that the aluminum layers are between the stainless steel and the copper, the substantially pure aluminum being in contact with the copper and with the stainless steel.

2. Product according to claim 1, characterized in that it comprises a layer of aluminum alloy covered with substantially pure aluminum on each side of the copper and a layer of external coating of stainless steel on at least one of the aluminum layers.

3. Product according to claim 2, characterized in that it comprises a layer of stainless steel on each side, the aluminum layers being between stainless steel and copper on each side.

4. Product according to claim 1, characterized in that it consists of a layer of aluminum alloy covered with pure aluminum on both sides and an external coating of copper on one side and an external coating of stainless steel on on the other side, so that the aluminum alloy layer covered with substantially pure aluminum is between the stainless steel and the copper.

5. Method for manufacturing a coated metal product according to claim 1, characterized in that a copper sheet is joined, at least one sheet of an aluminum alloy coated with substantially pure aluminum on the surfaces to join and at least one sheet of stainless steel and that these sheets are bonded together by compressing them under sufficient pressure to cause at least a reduction of at most 80% in thickness.

6. Method according to claim 5, characterized in that a copper sheet and at least one aluminum alloy sheet coated with substantially pure aluminum are first joined on the surfaces to be joined under sufficient pressure to cause a reduction of at most 80%, in that they are subjected to a subsequent heat treatment, in that the aluminum surface is mechanically cleaned, in that the prelaminated aluminum / copper composite is placed , mechanically cleaned, on at least one sheet of stainless steel, the aluminum being adjacent to the stainless steel, in that the superimposed metals are heated to a temperature between 150 and 425 ° C and in that subjects the superimposed metals to sufficient pressure for an initial reduction of approximately 2%, followed by a reduction of 5 to 25%.

7. Method according to claim 5, characterized in that a copper sheet is assembled, at least one aluminum sheet coated with substantially pure aluminum on the surfaces to be joined and at least one sheet of stainless steel, the sheet aluminum between the copper sheets and stainless steel, in that the metal sheets are heated to a temperature between 150 and 425 C and in that the assembled heated sheets are joined under sufficient pressure to produce a reduction of 20 to 70%.

8. Method according to one of claims 6 or 7, characterized in that the sheets to be joined consist of a central copper sheet, an aluminum alloy sheet covered on each side with substantially pure aluminum, on opposite sides of the copper foil, and a stainless steel sheet on at least one side of the aluminum opposite copper.

9. Method according to claim 6, characterized in that the preheated aluminum / copper composite and the stainless steel sheet are heated in separate ovens, after which they are superimposed.

10. Method according to one of claims 6 or 7, characterized in that the sheets are joined by passing them through a rolling mill.

11. Method according to one of claims 6 or 7, characterized in that the leaves are subjected to a subsequent heat treatment at about 375 ° C.

12. Method according to claim 5, characterized in that firstly joins a copper sheet and at least one sheet of aluminum alloy covered with substantially pure aluminum on the faces to be joined, under sufficient pressure. to cause a reduction of at most 80%, in that they are subjected to a subsequent heat treatment, in that the aluminum surface is mechanically cleaned, in that the prelaminated composite, mechanically cleaned is placed, on at least one sheet of stainless steel, in that the superimposed metals are subjected to a first reduction of approximately 2%, followed by a reduction of 5 to 25%.

13. Method according to claim 5, characterized in that a copper sheet is cleaned, at least one aluminum sheet coated with substantially pure aluminum on the faces to be joined and at least one stainless steel sheet to be joined, this cleaning comprising the mechanical cleaning of the aluminum surfaces to be joined, in that the sheets are assembled by placing the aluminum sheet between the copper and stainless steel sheets and in that the assembled sheets are joined under enough pressure to produce a reduction of 20 to 70%.

14. Method according to one of claims 12 or 13, characterized in that the sheets to be joined consist of a central copper sheet, an aluminum alloy sheet covered with substantially pure aluminum on each side placed on the faces opposite of the copper foil and a sheet of stainless steel on at least one side of the aluminum opposite the copper.

15. The method of claim 12 or 13, characterized in that the sheets are joined by passing them through a rolling mill.

16. Method according to claim 12 or 13, characterized in that the leaves are subjected to a subsequent heat treatment at approximately 375 ° C, after having joined them.

17. The method of claim 5, characterized in that first heating a copper foil and at least one aluminum alloy sheet coated with substantially pure aluminum on the surfaces to be joined, to a temperature of 150 to 425 ° C, by joining the heated sheets under sufficient pressure to produce a reduction of 20 to 70%, by subjecting them to a subsequent heat treatment, by mechanically cleaning the surface of aluminum, in that the pre-cleaned composite, mechanically cleaned, is placed on at least one sheet of stainless steel, placing the stainless steel in contact with the cleaned aluminum surface, in that the superimposed metals are heated at a temperature between 150 and 425 ° C and in that the superimposed metals are subjected to a pressure sufficient for a first reduction of approximately 2%, followed by a reduction of 5 to 25%.

18. The method of claim 17, characterized in that the sheets to be joined consist of a central copper sheet and an aluminum alloy sheet coated with substantially pure aluminum on each surface, on the opposite faces of the copper sheet , and a sheet of stainless steel on at least one face of the aluminum opposite copper.

19. The method of claim 17, characterized in that the prelaminated aluminum / copper composite and the stainless steel sheet are heated in separate ovens, then superimposed.

20. The method of claim 17, characterized in that the sheets are joined by passing them through a rolling mill.

21. The method of claim 5, characterized in that firstly heating a copper foil and at least one sheet of aluminum alloy covered with substantially pure aluminum on the surfaces to be joined, to a temperature of 150 at 425 ° C, then in that the heated sheets are joined under a pressure sufficient to produce a reduction of 20 to 70%, in that they are subjected to a subsequent heat treatment, in that the machine is mechanically cleaned aluminum surface, in that the pre-cleaned composite, mechanically cleaned, is placed on at least one sheet of stainless steel, placing the stainless steel in contact with the aluminum surface

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cleaned, in that the superimposed metals are subjected to a first reduction of approximately 2%, followed by a reduction of 5 to 25%.

22. The method of claim 21, characterized in that the sheets to be joined consist of a central copper sheet and an aluminum alloy sheet coated with substantially pure aluminum on each side of the copper sheet and a sheet of stainless steel on at least one side of the aluminum opposite copper.

23. The method of claim 21, characterized in that the superimposed metals are heated in separate ovens.

24. The method of claim 21, characterized in that the sheets are joined by passing them through a rolling mill.

25. The method of claim 21, characterized in that the leaves are subjected to a subsequent heat treatment at about 370 ° C.

26. The method as claimed in claim 5, for the manufacture of a coated metallic product which is distinguished by a high coefficient of thermal transmission and by the resistance to corrosion, characterized in that:

a) the surfaces of a copper or copper alloy sheet and at least one aluminum alloy sheet covered with substantially pure aluminum are mechanically cleaned;

b) the mechanically cleaned sheets are placed one on top of the other and at least one sheet of stainless steel is applied to the aluminum;

c) the sheets are heated to a temperature of 150 to 425 ° C;

d) the sheets are joined under sufficient pressure to reduce the total thickness of the sheets by approximately 2% in the first reduction step and from 5 to 25% in the second reduction step;

e) the internal tensions of the joined sheets are eliminated at a temperature of approximately 370 ° C.

27. The method as claimed in claim 5, for the manufacture of a coated metallic product which is distinguished by a high coefficient of thermal transmission and by the resistance to corrosion, characterized in that:

b) the mechanically cleaned sheets are placed one on top of the other and sufficient pressure is applied to join the sheets together and form a pre-formed composite;

c) at least one sheet of stainless steel is applied to the aluminum;

d) the sheets are heated to a temperature of 150 to 425 ° C;

e) the sheets are joined under sufficient pressure to reduce the total thickness of the sheets by about 2% in a first reduction step and from 5 to 25% in a second reduction step, and f) internal tensions are eliminated sheets attached at a temperature of about 370 ° C.

28. Method according to one of claims 26 or 27, characterized in that the superimposed metals are subjected to a reduction of 20 to 70%.

29. Method according to claim 26 or 27, characterized in that the sheets are joined by passing them through a rolling mill.

30. The method of claim 27, characterized in that the prelaminated aluminum / copper composite and the stainless steel sheet are heated in separate ovens, after which they are superimposed.

31. Method according to claim 5, characterized in that a copper sheet and at least one aluminum alloy sheet covered with substantially pure aluminum are first joined on the surfaces to be joined, under sufficient pressure to produce a reduction of not more than 80%, in that they are subjected to a subsequent heat treatment, in that the aluminum surface is mechanically cleaned, in that the prelaminated aluminum / copper composite is placed, mechanically cleaned , on at least one sheet of stainless steel, placing the aluminum against the stainless steel, in that the superimposed metals are heated to a temperature of 150 to 425 ° C and in that the superimposed heated metals are subjected at sufficient pressure to produce a reduction of 20 to 70%.

32. A method according to claim 5, characterized in that a copper sheet and at least one aluminum alloy sheet covered with substantially pure aluminum are first joined to the surfaces to be joined, under sufficient pressure to produce a

5 reduction of at most 80%, by subjecting them to a subsequent heat treatment, by cooling them, by mechanically cleaning the aluminum surface, by placing the pre-bonded composite, mechanically cleaned, on at least one sheet of stainless steel, in that the superimposed metals are subjected to a pressure sufficient to produce a reduction of 20 to 70%.

33. Method according to claim 5, characterized in that firstly heating a copper foil and at least one sheet of aluminum alloy covered with substantially pure aluminum on the surfaces to be joined, to a temperature of 150 at 425 ° C, in that

15 joins the heated sheets under sufficient pressure to produce a reduction of 20 to 70%, in that they are subjected to a subsequent heat treatment, in that the aluminum surface is mechanically cleaned, in that places the preloaded composite, mechanically cleaned, on at least one sheet of stainless steel, in that the superimposed metals are heated to a temperature of 150 to 425 ° C., and in that the superimposed metals are subjected to a sufficient pressure to produce a reduction of 20 to 70%.

34. Method according to claim 5, characterized in that firstly heating a copper foil and at least one sheet

25 of aluminum alloy coated with substantially pure aluminum on the surfaces to be joined, at a temperature of 150 to 425 ° C, in that the heated sheets are joined under sufficient pressure to produce a reduction of 20 to 70% , in that they are subjected to a subsequent heat treatment, in that the aluminum surface is mechanically cleaned, in that the pre-cleaned, mechanically cleaned composite is placed on at least one sheet of stainless steel , in that the superimposed metals are subjected to a pressure sufficient to produce a reduction of 20 to 70%.

35. Method according to one of claims 27 and 31 to 33,

35 characterized in that the sheets to be joined consist of a central copper sheet and an aluminum alloy sheet coated with substantially pure aluminum on each side of the copper sheet and a stainless steel sheet on at least one side of the preformed copper / aluminum core.

40 36. Method according to one of claims 31 to 34, characterized in that the sheets are joined by passing them through a rolling mill.

37. Method according to one of claims 31 to 34, characterized in that the leaves are subjected to a subsequent heat treatment at a temperature of about 375 ° C.

45 38. Method according to one of claims 26 and 31 to 34, characterized in that the sheets are heated in separate ovens, after which they are superimposed.

39. Method according to claim 5, characterized in that firstly joins a copper sheet and at least one sheet of aluminum alloy 50 covered with substantially pure aluminum on the surfaces to be joined, under sufficient pressure. to produce a reduction of about 80%, in that the aluminum / copper composite bonded is subjected to a subsequent heat treatment, in that the prelaminated aluminum / copper composite is heated to a temperature of 55 1 50 to 425 ° C, in that the heated aluminum / copper composite is placed on at least one sheet of stainless steel by placing the aluminum against the stainless steel and in that the superimposed metals are subjected to a pressure sufficient to produce a first reduction of approximately 2%, followed by a reduction of 5 to 25%. 60 40. Method according to claim 5, characterized in that a copper sheet and at least one sheet of aluminum alloy covered with substantially pure aluminum are first joined on the surfaces to be joined, under sufficient pressure. to produce a reduction of about 80%, by subjecting the alumi-65 nium / copper composite bonded to a subsequent heat treatment, by heating the prelaminated aluminum / copper composite to a temperature of 150 to 425 ° C, in that the heated composite is placed on at least one sheet of stainless steel with aluminum against stainless steel

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and in that the superimposed metals are subjected to a pressure sufficient to produce a reduction of 20 to 70%.

41. Method according to one of claims 39 or 40, characterized in that the sheets to be joined consist of a central sheet of copper and a sheet of aluminum alloy covered with substantially pure aluminum, on each side of the sheet of copper, and a sheet of stainless steel on at least one face of the preformed copper / aluminum core.

42. Method according to one of claims 39 or 40, characterized in that the sheets are joined by passing them through a rolling mill.

43. Method according to one of claims 39 or 40, characterized in that the leaves are subjected to a subsequent heat treatment at a temperature of about 370 ° C.

44. Method according to one of claims 39 or 40, characterized in that the sheets are heated in separate ovens, after which they are superimposed.

An object of this invention is a coated metal product, more particularly that formed from a copper core plated with aluminum and stainless steel, called stainless steel for short.

The use of rolled metal products formed from three or less rolled layers is well-known in the industry. For example, stainless steel utensils with copper bottoms are well known as well as stainless steel products with an aluminum core. These materials have all been available for some time and have been used on a large scale in the manufacture of kitchen utensils. The common problem with these old materials is their difficulty in rapidly transmitting heat over the entire surface of the pan in a homogeneous manner. These early composite products, however, are far superior to items made from a single metal layer.

A coated metal product has recently been developed formed from an aluminum core covered with copper or a copper core surrounded by layers of aluminum, the whole being coated with one or more layers of stainless steel. This product eliminates the above-mentioned problems of old materials. It distributes heat quickly and evenly. If copper is used as the core, it eliminates the problem of unsightly oxidation of copper from old stainless steel clad utensils. It provides better heat distribution than that obtained with aluminum utensils plated with stainless steel. It combines all the thermal properties specific to copper and aluminum with the abrasion and corrosion resistance properties of stainless steel.

However, when only pure aluminum is used as a coating for copper, there are cases where an orange peel effect appears. This effect cannot be controlled by any known mechanical or thermal process. It has been discovered that this orange peel effect can be eliminated by the use of an aluminum alloy support covered on its faces by a film of pure aluminum which will then be welded to copper and / or 'stainless steel. Therefore, the subject of the invention is the coated metal product defined in claim 1, as well as the process for manufacturing this product which is defined in claim 5. This eliminates the problem of orange peel by preserving the excellent alloy properties of pure aluminum. The support can be an aluminum alloy of the type 3003,3004, 5005 or any other alloy containing less than 99% of aluminum. As a coating film of pure aluminum, the qualities of aluminum EC, 1100,1130, 1230,1145,1175 or 7072 can be used. This pure aluminum must be plated on the faces of the aluminum alloy which will then be welded with copper and stainless steel.

This aluminum clad copper can then be clad with stainless steel on one or both sides. The aluminum must be sufficiently pure (such as types 1100,1130,1230,1145,1175 or 7072) to be applied to an aluminum alloy of type 3003,3004, 5005. An alloy of type 1145 is preferably used. on one or both sides of an aluminum alloy type 3003,3004,5005. Preferably, all the layers of this composite material are cleaned and their surfaces are treated by abrasion so as to remove the oxide layer. However, this treatment can be avoided in the case of stainless steel, but it must be carried out in the case of pure aluminum which will cover the aluminum alloy. Preferably, a first composite material of copper 10 and aluminum can be made first, either of copper plated on one side of pure aluminum bonded to the aluminum alloy or of copper surrounded by aluminum of the two. sides, and then you can apply a layer of stainless steel on or on the sides covered with pure aluminum bonded to the aluminum alloy. This preformed coating or core is preferably cleaned and the surface or surfaces of pure aluminum are treated by abrasion, brushing or other mechanical means, so as to remove the oxide layer. This can be avoided for stainless steel. In this way, the aluminum alloy clad copper pure aluminum clad was cleaned as described above, cold soldered by vigorous reduction of the order of 20 40 to 80% in one or more rolling passes , then annealed if desired to strengthen cohesion. This preformed coating or core made of aluminum alloy plated with pure aluminum and copper is heated in the company of stainless steel to a temperature of about 150 to 425 ° C, reduced by 20 to 70% in one pass or otherwise reduced by 5% in one pass, then by 10 to 25% in a second step, then reheated to about 350 to 425 ° C, but preferably to 370 ° C.

This diffusion operation increases the cohesion between the three metals and partially decreases the internal tensions. The final product is ready to be stamped to make kitchen utensils. 3o In a second way, the product can be obtained starting from a preformed composite material made of aluminum alloy plated with pure aluminum and copper which will be covered with stainless steel on one or both sides. In this way, the aluminum alloy clad with pure aluminum and the copper are cleaned by abrasion, brought into contact, heated between 150 and 370 ° C and subjected to a reduction of 30 to 70%. The composite material made of aluminum alloy clad with pure aluminum and copper can then be heated to enhance cohesion. The resulting product is then cleaned by abrasion on its face or faces of pure aluminum, then is used as coating 40 or core of a plating with stainless steel. In this way of operating, the assembly of the coating and the stainless steel is again heated to about 150 to 425 ° C., subjected to a first reduction of between 2 and 5%, then to a second d 'between 5 and 25%, or else, in another way, the assembly can be reduced in a single pass 45 by about 20 to 70%. The product obtained is then annealed at around 370 ° C to cause the diffusion mentioned above.

In a third way, one or two sheets of aluminum alloy clad with pure aluminum are cleaned mechanically, heated between 150 and 425 ° C and brought into contact with one or both of the two faces of a copper sheet. which is at room temperature, the whole then being reduced in one or two operations, as mentioned above. This preformed composite material made of aluminum alloy plated with pure aluminum and copper can be annealed if desired to reinforce cohesion. This core can then be placed 55 between two sheets of stainless steel, reduced and annealed according to the method described above.

A fourth possibility would be to manufacture the primitive composite material made of aluminum alloy clad with pure aluminum clad on one or both sides of a copper sheet by cold or hot alloy as described in the first case. , then cold welding of stainless steel on one or both sides of this composite material by means of a large reduction of the order of 30 to 70% in one or two passes. The resulting composite material made of stainless steel, aluminum and copper is annealed as described in the first way of operating.

In a fifth method, all the parts, that is to say the copper, the aluminum alloy coated with pure aluminum and the stainless steel are cleaned by surface abrasion so as to remove the

oxides of the exposed faces, with the possible exception of stainless steel. The pieces are either heated separately or put together before heating, heated to a temperature of about 150 to 425 ° C, reduced from 20 to 70% in one pass or, otherwise, reduced to about 5% in a pass , then reduced by 10 to 25% in a second pass and heated again to approximately 350 to 425 ° C (preferably to 370 ° C) to allow diffusion between the different adjacent layers of metals. This diffusion causes a strengthening of the bond between the three different metals.