MXPA98006285A - A sheet of multilayer structure denominated chain sandwich or interlami - Google Patents

Abstract

A multilayer or multilayer structure sheet called a sandwich sheet, composed of two laminated metal skins, joined together by a core in which the core is made of stainless steel wool. Figur

Description

A SHEET OF MULTILAYER STRUCTURE DENOMINATED SANDWICH SHEET OR INTERLAMINATE The present invention relates to a sheet of multilayer structure called sandwich sheet composed of two laminated sheet metal, joined together by a core. The industrial sectors, particularly the automotive industry, are requesting materials that favor lightening, such as steel composite materials of the multilayer type, which have the properties of steel and a lower density. These multilayer materials can be particularly used in the manufacture of body parts of motor vehicles or pipes or exhaust lines. Numerous documents have already been deposited on multilayer structures consisting of two metallic skins associated with an organic resin core. It is known, for example, document FR 90.06.805 which relates to a method of making multi-layer sheet metal called sandwich sheet, the sheet obtained by the process comprising two metal skins and a core of polymer material whose purpose is to have a acoustic, vibratory damping function, or improve the rigidity / weight ratio. The conformation of this type of structure REF .: 28031 multilayer raises problems of drawing and welding. In effect, the weak mechanical characteristics of the material of which the core is composed generate the creep of said material during the drawing. From the point of view of welding, the material of which the soul is composed is an electrical insulator, which generates a problem of conductivity in the direction of thickness, during welding, even when the conductivity is improved, in practice, by the addition, in the material, of electrically conductive charges such as, for example, nickel balls. It is also known document FR 89.17.142 which describes a structure comprising two outer cover skins and joined together by a core of small density, core constituted by a less rigid material than said skins, such as, for example, a shaped textile core hot after impregnation of a synthetic resin. The technique described in this document allows the realization of a product composed of sandwich structure, surface and any shape, comprising areas of particular mechanical strength or specific feature, such as acoustic, vibratory, thermal. In the procedure, presented in the cited document, the soul is formed prior to the placement of the two skins, which are also formed before assembly. The object of the present invention is particularly to avoid the drawbacks of the structures described above by presenting a multilayer structure sheet called sandwich sheet, composed of two laminated metal skins, joined together by an electrically conductive core and whose conformation can be realized as in the case of a simple, single sheet. The invention relates to a multilayer structure sheet called a sandwich sheet, consisting of two laminated metal skins, joined together by a core made of stainless steel wool. The other features of the invention are: - stainless steel wool occupies 30% to 60% of the volume that separates the two skins. - the skins are made of steel chosen from stainless steel, carbon steel, aluminized stainless steel, aluminized carbon steel. Steel wool is a ferritic stainless steel wool. - The soul and the two skins are joined by welding.

- Welding is performed by arc welding, capacitor discharge. - the assembly of the two skins with the soul is carried out by means of an adhesive. the adhesive is chosen from a phenolic resin, an epoxy resin, a polyethylene or polypropylene comprising maleic anhydride. The invention also relates to a method of making a multilayer structure sheet called sandwich sheet, composed of two metal skins, joined together by a soul made of a steel wool, procedure in which: the two skins and the soul are assembled or joined by calendering, so that the thickness of the multilayer structure is defined, an arc is generated perpendicularly to the surface of the skins to cause in the area of the arc, on the one hand, the welding of steel wool fibers that are in contact with each other, in the core, which forms a rigid network , and on the other hand, the welding of steel wool fibers that are in contact with the internal surfaces of the two skins to ensure the union between the core and said skins. The invention also relates to a sheet in an application in the embodiment of an exhaust pipe for a motor vehicle in which the multilayer structure sheet is rolled, welded for example by induction to form a tube comprising a double wall and a stainless steel wool soul. The description that follows and the associated figures, given all by way of non-limiting example, will make the invention well understood. Fig. 1 presents, in section, a flat sheet of multilayer structure according to the invention. Fig. 2 presents, in section, an embossed shape made by deformation of the flat sheet of multilayer structure according to the invention. Fig. 3 is a section of a tube made from the flat sheet of multilayer structure according to the invention. As presented in fig. 1, the multilayer structure sheet 1, according to the invention, is composed, on the one hand, of two metallic 2 'skins, for example of austenitic or ferritic stainless steel whose thickness can vary from 0.05 mm to 0.3 mm and, on the other hand, part by a 3 soul of stainless steel wool. The core 3, of a thickness of approximately 1 mm, consists of wool 4 of ferritic stainless steel.

The steel wool 4 is obtained by scraping, preferably in a whipped state, to increase the mechanical characteristics of the structure. Steel wool yarns have an average length of 70 cm and their diameter can range from 30 microns to 100 microns. Preferably, the diameter of the yarns of the steel wool 4 is approximately 60 microns. This diameter must be homogeneous to avoid embrittlements that lead to breakage. In an application example, a calendering line is used in the production process in which: two coils are unwound in order to move parallel two steel bands that will form the skins 2 of the coiled multilayer structure. the structure. - simultaneously, a wool carpet 4 of stainless steel is unwound on the lower band, the carpet constituting the core 3, - the wool carpet 4 is pressed between the two steel bands on a calender to define the thickness. - the union or adhesion of the core 3 with the two skins 2 can be carried out by welding or gluing. In an example of embodiment by welding, an arc is generated, by discharge of the condenser, perpendicularly to the surface of the skins 2, in order to cause in the arc zone, on the one hand, the welding of the steel wool fibers 4 that they are in contact with each other, in the core, to form a rigid network, and on the other hand, the welding of steel wool fibers 4 that are in contact with the internal surfaces of the two skins to ensure the union between the core 3 and said skins 2. This application example ensures the realization of an all steel structure that can be used at relatively high temperatures, that is to say at temperatures exceeding 500 ° C, comparatively to structures comprising, for example, a soul stuck. In another more economical form of application, by gluing, the embodiment described above is used, a process in which the skins are dyed or laid continuously or discontinuously with an adhesive or glue or adhesive of epoxy type. As shown in fig. 1, the adhesive 5 is distributed in meshes on one of the faces of the two skins 2. After calendering, the structure is heated to bake the adhesive at an average temperature of 200 ° C. The adhesive 5 deposited on the two skins 2 can, by gravity and by capillarity, be inserted into the stainless steel wool carpet to form a rigid network during the firing of the adhesive. In addition, entangled steel wool fibers also ensure mechanical strength to the structure. Otherwise, it is possible to impregnate the metal wool carpet with an adhesive, which at the time of calendering, will wet the internal faces of the two skins and ensure its adherence at the time of cooking said adhesive. The impregnation can be done only for the purpose of forming a rigid network by gluing the steel wool threads that form the core, the adhesive being fluid and distributed in small amounts in the steel wool. Otherwise, the free space between the stainless steel wires that make up the wool carpet can be filled by impregnation of a filling material that can be adhesive, hardenable, foaming. The stainless steel wool then has the function of supporting the filling material when it is still fluid or in the pasty state, before calendering and cooking. In one embodiment of the structure by gluing, the materials for the constitution of the skins and the steel core can be different. According to the invention, the stainless steel core having, for example, a density of 400 g / m 2 is formed by a network, non-compact, disordered, of spaced fibers, in which the fibers can be welded or welded two by two, the fact of its contact at the time of discharge of the welding arc or, in another form of the invention, glued two by two by a resin. This structure forms a frame joined to the two skins either during the welding or during the gluing of the assembly. To ensure the mechanical strength of the stainless steel wool, said wool is laminated so as to constitute a tapestry of given thickness and density. The multilayer structure according to the invention, contrary to the known structures, has the advantage, during the shaping of parts, of generating in the deformed zones by embossing, as presented in FIG. 2, part parts of smaller thicknesses that preserve the mechanical properties of the structure. In effect, during the drawing, the stainless steel wool, in net, is compressed and supports a load during the deformation of the structure. In the case, for example, of an alveolar core of the prior art, the alveoli that have only a brace function, lose during a crushing, their mechanical properties by effect of lateral deformation by compression and folding. According to the invention, the core 3 constituted by stainless steel ensures an electrical conductivity between the two skins 2, which allows spot welding or any other technique. In an application, from the escape domain of motor vehicles, it is possible to carry out, for example, a pipe downstream of an exhaust pipe. In this type of application, as shown in fig. 3, the adhesive ensures the cohesion of the structure, during the shaping of the tube, on the induction welding line. After the manufacture of the tube, the adhesion of the steel wool 4 on the skins 2 may no longer be ensured. The inner skin of the tube can be previously perforated. The exhaust pipe 6 formed by a double wall and by a stainless steel core ensures damping of the vibrations along the entire length of the exhaust pipe and therefore a reduction of the sound noises and, also, a function of thermal screen. The lightening of the structure also contributes favorably to the protection of the environment by reducing the gasoline consumption of the vehicle.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the description of the present invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (10)

1. A multilayer structure sheet called sandwich plate composed of two laminated metal skins, joined together by a core, characterized in that the core is constituted by a stainless steel wool.

2. A sheet according to claim 1, characterized in that the steel wool occupies 30% to 60% of the volume that separates the two skins.

3. A sheet according to claims 1 and 2, characterized in that the two skins are made of steel chosen from stainless steel, carbon steel, aluminized stainless steel, aluminized carbon steel.

4. A sheet according to claims 1 and 2, characterized in that the wool of ferritic stainless steel.

5. A sheet according to claims 1 to 4, characterized in that the core and the two skins are joined by welding.

6. A sheet according to claim 5, characterized in that, the welding is performed by arc welding, capacitor discharge.

7. A sheet according to claims 1 to 4, characterized in that the assembly or assembly of the two skins with the core is performed by means of an adhesive.

8. A sheet according to claim 7, characterized in that the adhesive is selected from among a phenolic resin, an epoxy, a polyethylene or polypropylene comprising maleic anhydride.

9. A method for producing a multilayer structure sheet called sandwich sheet, consisting of two laminated metal skins, joined together by a core, consisting of a stainless steel wool according to claims 1 to 6, characterized in that: the two skins are joined and the core by calendering, so that the thickness of the multilayer structure is defined, an arc is generated perpendicularly to the surface of the skins to cause in the arc zone, on the one hand, the welding of steel wool fibers which are in contact with each other, in the soul, which forms a rigid network, and on the other hand, the welding of the steel wool fibers that are in contact with the internal surfaces of the two skins to ensure the union between the soul and said skins.

10. Use of the sheet according to claims 1 to 8, in an application in the embodiment of an exhaust pipe for a motor vehicle, characterized in that the multilayer structure sheet is rolled, welded for example by induction to form a tube comprising a double wall and a stainless steel wool soul.