LU84162A1 - PROCESS FOR OBTAINING A WELDABLE COMPOSITE SHEET - Google Patents

Description

t 2 Ÿ58i Claim of priority - of (s) ia demar.de (0 correspondent (s) deposited in Cidjp'Jj + u. - le_- · —-- i- under the number mx. iââ -fl- | -ίο 2133/8105.

METALLURGICAL RESEARCH CENTER -CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Non-profit association -Vereniging zonder winstoogmerk in BRUXELLES, (Belgium).

Process for obtaining a weldable composite sheet.

The present invention relates to weldable composite sheets which have very advantageous properties of use.

The fight against noise is one of the indisputable driving forces in the development of composite sheets. This struggle is an important concern of the industrial world, and in particular of the metal fabrications sector, with the preferred fields of application that are automobile construction and household appliances, large consumers of steel sheets and building.

In this perspective, it is known to manufacture these composite sheets (or sandwich sheets) composed of at least two: sheets assembled by an intermediate layer of material which is both adhesive and acoustically insulating. / /

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The composite sheets thus manufactured allow efficient sound insulation and production using industrial stampings.

However, such composite sheets present serious assembly difficulties, in particular in the case of welding.

In particular, electric spot welding, which is of common application in mass productions, is made impossible because of the presence of the intermediate layer, the constituent material of which is insulating not only acoustically, but also electrically in most cases. .

The Applicant has proposed a solution to this problem and described it in its Luxembourg patent application No. 81.301.

This recommended creating, on at least one of the two faces of the sheets in contact with the intermediate layer of adhesive and acoustically insulating material, surface roughness having a height of the same order of magnitude as that of the thickness of said layer intermediate, roughness preferably distributed evenly.

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Continuing her research with a view to developing this type of sheet, the Applicant has highlighted the following points: - if the intermediate layer is weak (for example 0.05 mm) the sheet has this good soundproofing properties, is weldable , but if one wishes to maintain a rigidity equivalent to a homogeneous sheet, for example of steel, the weight gain is low, - if the intermediate layer is thick enough (for example 0.5 mm), the sheet has very good sound insulation properties, a significant gain in weight, while keeping a rigidity close to that of an equivalent homogeneous sheet, while its weldability, for example by / '. . . , / Domts, is Dratiouement impossible. /, · /// - 3 -

Based on these observations, the applicant has developed a process for manufacturing a composite sheet which very well absorbs noise, while allowing a significant gain in weight; this sheet has a very satisfactory rigidity and moreover, is spot weldable.

The method, object of the present invention, to obtain a weldable composite sheet, made up of at least three metal sheets, some called "outside sheets" and forming the outside faces of said composite sheet, the other called one or more "inside sheets ”And comprised between the above-mentioned outer sheets, the whole forming a structure commonly called a“ sandwich ”, is essentially characterized in that at least two sheets are made of different metals and that between said sheets forming the sandwich structure, one forms at least two intermediate layers which may be of different nature and thickness depending on the relative position of the sheets in the sandwich structure.

In the context of the invention, the words intermediate layer can also designate a layer which would not completely, but partially fill the space between two adjacent sheets.

According to a first mode of application of the method of the invention, the aforementioned intermediate layer or layers are composed of natural or synthetic resins.

According to another mode of application of the process of the invention, the above-mentioned intermediate layers are not of identical composition and some or even all of them may contain cavities filled with a gas, the latter preferably being air.

According to another method of implementing the method of the invention, the sum of the thicknesses of the sheets called "interior" is between 0.1 and 5 times the sum of the thicknesses / / / of the "exterior" sheets.

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According to a fourth method of implementing the method of the invention, the thickness of each intermediate layer is between 0.01 mm and 0.20 mm.

According to a fifth mode of application of the method of the invention, at least one of the two faces of all or only of some of the sheets forming the composite sheet has "regular asperities or not, arranged homogeneously or not on the surface of the aforementioned sheet or sheets.

According to a sixth method of implementing the method of the invention, the average height of the asperities present on a surface is between 0.4 to 2 times the thickness of the intermediate layer with which said surface is in contact, allowing , if necessary, a mechanical attachment by penetration of said roughness into the adjacent sheet through the intermediate layer.

According to another embodiment of the process of the invention, the resin is deposited continuously in the form of a film on the surface of one or more sheets constituting the composite, preheated to the appropriate temperature so that the film adheres , the sheets forming the composite sheet can then be joined when passing between rollers.

According to yet another embodiment of the process of the invention, the resin is continuously deposited by the coating extrusion system and the sheets forming the composite sheet can then be assembled during the passage between the rollers.

According to a ninth method of implementing the process of the present invention, the two outer cited sheets are made of steel, at least one of which may be made of high-strength steel.

According to another preferential embodiment of the r / r-process of the invention, the quoted or internal sheet (s) _! - 5 - are made of aluminum or alloys containing them.

According to yet another embodiment of the method of the invention, one or both so-called "external" steel sheets have received a protective coating against corrosion, for example by galvanization and this on at least one face.

According to yet another preferred mode of implementation of the process of the invention, the composite sheet obtained has a cross section in which we can distinguish in order: steel sheet - resin - aluminum sheet - resin - galvanised steel.

In order to show the advantage of applying the method of the present invention, we will develop by way of nonlimiting example, the case of the following composite sheet: 0.5 mm of steel + 0.05 mm of resin +0 0.5 mm Al + 0.05 mm resin + 0.5 mm steel, i.e. a total thickness of 1.60 mm maximum.

The surface of each steel sheet in contact with the resin has asperities of a height of 0.05 mm in the form of parallel ridges spaced 0.5 mm apart.

In this specific case, we observe: - a weight gain of 20% compared to a homogeneous steel sheet of 1.5 mm, - a bending stiffness equivalent to a homogeneous steel sheet of 1.5 mm, - during repeated impact tests, a damping of the noise compared to a homogeneous sheet steel this 1.5 mm equal to the following values: - 16 dE when the noise is expressed in units d B A.

- 15 dB when the noise is expressed in units d B B

| - 13 dB when the noise is expressed in units of BC / - 10 to 20 cB in the cairme this frequency ranging from 1000 to r // 8000 Hz. / - 6 - (the expressions d BA, d BB, d BC, represent the units standardized by the International Electrotechnical Committee for the measurement of sound levels), - the ability to spot resistance welding under machine setting conditions similar to those applicable to a homogeneous sheet of steel 1.5 mm thick .j * ^ * \ *

Claims (14)

1. Method for obtaining a weldable composite sheet, made up of at least three metal sheets, some called "outside sheets" and forming the outside faces of said sheet, the other (s) called "inside sheets" and comprised between the sheets above mentioned exterior, the whole forming a structure commonly known as a "sandwich", characterized in that at least two sheets consist of different metals and that between said sheets forming the * sandwich structure, at least two intermediate layers are formed which can be of different types and thicknesses depending on the relative position of the sheets in the sandwich structure. 2. Method according to claim 1, characterized in that the above-mentioned intermediate layer or layers are composed of * natural or synthetic resins. 3. Method according to claim 2, characterized in that the above-mentioned intermediate layers are not necessarily of identical composition and some or even all may contain cavities filled with a gas, the latter preferably being air. 4. Method according to either of these claims 1 to 3, characterized in that the sum of these thicknesses of the so-called "inside" sheets is between 0.1 and 5 times the sum of the thicknesses of the so-called "outside" sheets. 5. Method according to one or more of claims 1 to 4, characterized in that the thickness of each intermediate layer is between 0.01 mm and 0.20 mm. ^ / // * - 8 - 6. Method according to one or more of claims 1 to 5 / characterized in that an au. less than the two faces of all or only some of the sheets forming the composite sheet has regular roughness or not, arranged in a homogeneous manner or not on the surface of the aforementioned sheet or sheets. 7. Method according to claim 6, characterized in that the average height of the asperities present on a surface. is between 0.4 to 2 times the thickness of the intermediate layer with which said surface is in contact. M 8. Method according to one or more of claims 1 to 7, characterized in that the resin is continuously deposited in the form of a film on the surface of one or more sheets constituting the composite preheated to the appropriate temperature so that the film adheres, the sheets forming the composite sheet can then be joined during the passage between. rollers. 9. Method according to one or more of claims 1 to 7, characterized in that the resin is continuously deposited by the coating extrusion system and the sheets forming the composite sheet are then assembled during the passage between rcu- . leaux. 10. Method according to one or more of these claims 1 to S, characterized in that the two so-called external sheets are made of steel, at least one of which may be made of high-strength steel. 11. Method according to one or more of these claims 10 there, characterized in that the sheet or sheets called "interior" are made of aluminum or alloys containing them. 12. Method according to one or more of these claims 1 to 11, characterized in that one or the two so-called "external" steel sheets have received an orotection coating against corrp- / * / f / y - 9 - sion, for example by galvanizing and this on at least one side. 13. Method according to one or more of claims 1 to 12, characterized in that the composite sheet obtained has a cross section in which one can distinguish in order steel sheet - resin - aluminum sheet - resin - sheet of steel. * 14. Products obtained by application of the processes according to one or more of claims 1 to 13. Drawings: —planks _2— pages of which —d— cover page —S ....... description pages * ----- --- â ..._ claim pages; ——Stl descriptive abridged Luxembourg, MAY 18, 19B2 The representative: / ~ y * Charles München