Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
  • B32B15/011—Layered products comprising a layer of metal all layers being exclusively metallic all layers being formed of iron alloys or steels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions
  • B32B3/06—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions for securing layers together; for attaching the product to another member, e.g. to a support, or to another product, e.g. groove/tongue, interlocking
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12444—Embodying fibers interengaged or between layers [e.g., paper, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12479—Porous [e.g., foamed, spongy, cracked, etc.]

Definitions

• the present invention relates to a sandwich sheet, suitable for a forming and welding operation, and having excellent resistance to high temperatures, comprising two sheet metal facings and a metal core, its manufacturing process and its use for making parts for motor vehicles.
• the main advantage of sandwich sheets compared to conventional metal sheets lies in the weight gain that is achieved in the production of parts having predetermined mechanical strength specifications; this advantage is very important in automotive applications, in particular for reducing the fuel consumption of the vehicle.
• the sandwich sheets used for the manufacture of parts for motor vehicles must satisfy not only welding and forming requirements, for example by stamping, bending, crimping, but also requirements of temperature resistance. Indeed, during the painting operation of the sheet which may include a prior anti-corrosion treatment, the sheet is subjected to high temperatures and for sufficient periods, generally between 140 and 220 ° C for 20 to 30 min, to allow the curing and / or crosslinking of the different layers of coating applied.
• sandwich sheets comprising two sheet metal facings connected by a core formed by a layer based on polymers comprising a continuous textile web of thermoplastic polymer fibers impregnated with a thermoset polymer material for impregnating the web and adhesion with siding. These sheets have good formability as well as good temperature resistance.
• the object of the present invention is therefore to remedy these drawbacks and to provide formable and weldable sandwich sheets, having good resistance to high temperatures and a good surface appearance, and the manufacturing process of which is easy to implement.
• the subject of the invention is a sandwich sheet, suitable for a forming and welding operation, and having excellent resistance to high temperatures, comprising two sheet metal facings having a melting point Tp, and a metal core. having a melting point Ta, Ta which may be equal to or different from Tp, according to which the core has a density less than the density of each of the facings, and in that the core and each of the facings are linked together by means of a metallic bonding agent having a melting point Tm lower than Ta and Tp.
• the metallic core occupies between 10 and 80% of the volume separating the two metal sheet facings
• the metal core occupies between 20 and 60% of the volume separating the two sheet metal facings
• the core consists of a metallic wool, a metallic knitted fabric, a metallic woven fabric, a metallic foam or a metallic sponge, - the core is made of steel,
• the sheet metal facings are made of steel
• the sheet metal facings and the metallic core are made of steel, and the metallic bonding agent is chosen from tin and its alloys, zinc and its alloys, and aluminum and its alloys.
• the invention also relates to a method of manufacturing a sandwich sheet, suitable for a forming and welding operation, and having excellent resistance to high temperatures, comprising two sheet metal facings having an internal face and an external face. and having a melting point Tp, linked by a metallic core having a melting point Ta, Ta possibly being equal to or different from Tp, the internal face of each of the two facings being located opposite the core, according to which it comprises the stages consisting in:
• the method of manufacturing a sandwich sheet according to the invention can also have the following characteristics: - between the heating and cooling stages, pressure is applied to the assembly formed by the sheet metal facings and the metal core , said pressure being adjusted so as not to damage the structure of the metallic core, - the assembly formed of metal sheet facings and the metallic core is heated by induction,
• the thickness of the metallic coating of each of the sheet metal facings is between 5 and 350 ⁇ m, the thickness of the metallic coating of each of the sheet metal facings is between 20 and 80 ⁇ m,
• the heating rate of the assembly formed of the sheet metal facings and of the metallic core is greater than or equal to 30 ° C / s
• the duration of heating of the assembly formed of the sheet metal facings and of the metallic core is less than 15 s
• the melting point of the coating Tr is less than 0.9 times the melting point of the sheet metal facing Tp and less than 0.9 times the melting point of the metallic core Ta,
• each of the sheet metal facings is coated by hot dipping in a bath of liquid metal chosen from tin and its alloys, zinc and its alloys, and aluminum and its alloys,
• the sheet metal facings are made of steel
• the density of the metallic core is less than the density of each of the sheet metal facings
• the core consists of metallic wool, a metallic knitted fabric, a metallic woven fabric, a metallic foam or a metal sponge,
• the external face of at least one of the two sheet metal facings (1, 1 ′) is coated with a coating whose melting point Te is greater than the melting point of the metallic coating coating the internal face of each of the two facings (1, 1 ') Tr plus 200 ° C.
• the invention also relates to the use of the preceding sandwich sheet for the production of shaped automobile body parts, painted, then heat treated.
• the invention also relates to the heat treatment of these parts at more than 160 ° C.
• the invention consists in using the metal layer covering the internal face of the sheet metal facing, the internal face of the facing being located opposite the core, as a brazing element to ensure adhesion between the sheet metal facing and the metallic core.
• each facing 1, the of the sandwich sheet 2 according to the invention consists of a metal sheet having a melting point Tp, and of thickness comprised, for example, between 0.1 mm and 2 mm, preferably between 0.2 mm and 0.5 mm.
• steel sheets are chosen which have better mechanical properties than aluminum sheets, and are more easily stampable.
• the type of steel will be chosen according to the application for which the sandwich sheet 2 is intended, so for example to manufacture a hood or a door we will choose a carbon steel, and to manufacture an exhaust line tube we will choose a stainless steel.
• the metallic core 4 of the sandwich sheet 2 according to the invention has a melting point Ta equal to or different from the melting point Tp of each of the facings 1, l ', and a density lower than that of the facings 1, 1' of so as to lighten the sheet 2.
• the core 4 consists of a metallic wool, a metallic knitted fabric, a metallic woven fabric, a metallic foam or a metallic sponge.
• it occupies between 10 and 80% of the volume separating the two metal sheet facings 1, 1 ', preferably between 20 and 60%, and has a thickness of between 0.5 and 2 mm.
• the core 4 becomes fragile and risks being crushed during the shaping of the sandwich sheet 2.
• the core 4 offers a good compromise between weight gain and resistance.
• the material of the metallic core 4 is preferably steel, either carbon steel or stainless steel, since this material has better formability than aluminum, for example.
• Steel wool is obtained by shaving, preferably in the hardened state, to increase the mechanical characteristics of the structure.
• the strands of steel wool have an average length of 70 cm and their diameter can vary from 50 to 500 ⁇ m.
• the diameter of the steel wool strands is approximately 200 ⁇ m. This diameter must be uniform to avoid embrittlement which leads to breakage.
• Steel knitting consists of several steel wires with a diameter between 10 and 50 ⁇ m, knitted together.
• the steel woven fabric also consists of one or more steel wires of diameter between 10 and 50 ⁇ m, woven together.
• the adhesion between the core 4 and each of the facings 1, 1 ' is ensured by a metallic bonding agent 3, 3' having a melting point Tm lower than the melting point of each of the facings Tp and lower than the melting point of the Ta soul.
• the metallic bonding agent 3, 3 ′ is chosen from tin and its alloys, zinc and its alloys, and aluminum and its alloys.
• the metallic bonding agent can be in the form of either a discontinuous layer or preferably a continuous layer so as to ensure the best possible adhesion between the core and the two facings.
• the internal face of each of the two metal sheet facings is coated with a metallic coating having a melting point Tr lower than the melting point of the metal sheet facing Tp, and lower than the melting point of the metallic core Ta, so that the coating, when melting, brazes the metallic core.
• the melting point of the metallic coating Tr which here plays the role of filler metal, be lower than the melting point of the facing Tp and at the melting point of the core Ta, so that the coating material melts well before the core material and the sheet metal facing material.
• the internal face of each of the two sheet metal facing 1, l ' is coated with a metallic coating, the melting point Tr of which is preferably less than 0.9 times the melting point of the metal sheet Tp, and 0.9 times the melting point of the metallic core Ta.
• a sandwich sheet comprising two facings made of sheet steel with a steel core
• the facings are coated on at least one of their faces with a metallic coating chosen from the following materials:
• - zinc melting point 420 ° C
• - zinc alloys such as for example the zinc-aluminum alloy containing about 5% by weight of aluminum, the melting point of which is 381 ° C,
• a metal coating with a thickness of between 5 and 350 ⁇ m is deposited on the internal face of each of the two metal sheet facings 1, 1 ′ intended to be placed opposite the core, either by electrodeposition or by deposition under vacuum, preferably by hot dipping in a liquid bath of the coating material in the molten state.
• the thickness of the metal coating is less than 5 ⁇ m, the impregnation of the core 4 by the coating during brazing is not sufficient; consequently the adhesion between the metal sheet facing 1, 1 ′ and the core 4 is insufficient, and the sandwich sheet 2 risks delaminating.
• coating the internal face of the facing with a coating with a thickness greater than 350 ⁇ m represents an additional cost, and moreover it does not improve the adhesion between the core 4 and the facing 1, 1 '.
• the thickness of the metal coating is between 20 and 80 ⁇ m. Indeed, at this level of thickness, the adhesion between the facings 1, l 'and the core 4 is sufficient so that the sandwich sheet 2 does not delaminate, even after a severe forming operation, such as for example the folding.
• the metallic core 4 is interposed between two metal sheet facings 1, l ′ whose internal face has been previously coated, so that the internal face coated with the facings 1, l ′ is facing the core 4,
• the material of the metallic coating brazes the facing 1, l 'on the metallic core 4 by impregnation of the surface of the metallic core 4, which ensures mechanical adhesion to the whole facing 1, Core 4.
• the softened or melted metallic material permeates the metal strands making up the wool, woven fabric or knitted fabric of core 4 located on the surface. If the assembly formed by the two facings 1, the and the core 4 is heated to a temperature T below the melting point of the metallic coating Tr minus 50 ° C., the coating material does not soften sufficiently and does not permeate not the material of the core 4. At this temperature level, brazing between the facing 1, the and the core 4 is impossible and the sandwich sheet 2 cannot be formed.
• the heating rate is less than 30 ° C / s, it is necessary to obtain a softening or a complete melting of the coating material to maintain the heating temperature Tr for a period greater than 15 s, which is detrimental for productivity.
• the metallic core composed of wool, woven fabric, knitted fabric, foam or sponge begins to absorb part of the coating material, which degrades the adhesion between the core 4 and facing 1, 1 '.
• the duration of the heating is less than 3 s.
• the two sides of the assembly are placed, and over its entire width, at least one heating element, such as for example an inductor.
• the core 4 is heated by calendering between two heated cylinders.
• pressure is applied to the sandwich sheet 2 by adjusting the pressure so as not to deteriorate the structure of the core 4, and not to deform facing 1, 1 '.
• the pressure applied to the sandwich sheet 2 must be low enough so that, for example, the metallic wool or the metallic knit does not crush and thus retains the integrity of its mechanical characteristics.
• This pressure can be applied by the calendering cylinders, by spraying a fluid on either side of the set of facings 1, 17th core 4, or by scrolling the set of facings 1, 17th core 4 on a magnetized cylinder. .
• the embodiments of the sandwich sheet 2 according to the invention which have just been described are not limiting.
• the external face with at least one of the two metal sheet facings 1, 1 ′ with a coating whose melting point Te is greater than the point of melting of the metallic coating coating the internal face of each of the two facings 1, 1 'Tr plus 200 ° C. If it is desired to use facings 1, 1 'coated on their external face, it is indeed necessary to ensure that the coating used does not melt when the assembly formed by the two facings between which is interposed is heated the metallic core 4.
• the internal face of the facings 1, 1 ' will be coated with a layer of zinc and the external face of the facings 1, 1' will be coated with a layer of aluminum-iron alloy, or aluminum-silicon.
• the sheet metal facing 1, 1 ′ will only be coated on its internal face, and the coating of the external face of the facing 1, 1 ′ will only be carried out, for example in an electroplating bath, only when the sandwich sheet 2 has been manufactured.
• the shaping of the sandwich sheet 2 according to the invention is preferably carried out by stamping, folding or profiling.
• the core 4 consists of a metal having good ductility, such as steel
• the sandwich sheet 2 according to the invention resists severe conditions of stamping and / or bending and / or profiling. This makes it possible to use the sandwich sheet 2 according to the invention to produce shaped automobile body parts, such as for example hoods, doors or exhaust line tubes.
• the sandwich sheet 2 Prior to the painting operation, the sandwich sheet 2 can undergo an anti-corrosion pretreatment of the cataphoresis type.
• the application of the paint can then be applied by depositing powder (electrostatic, fluidized bed, etc.), or by spraying or coating a liquid paint in solution or of a molten polymer sheet.
• the sandwich sheet 2 is treated at temperatures above 160 ° C., preferably above 180 ° C., temperatures which are generally reached during the stages of cooking the anti-corrosion pretreatments or the cooking of the paint itself. even.
• the sandwich sheets 2 obtained according to this process have the following advantages over sandwich sheets made of metallic wool welded between two metal facings:
• the brazing of the steel facing on the metallic core 4 is never carried out at a temperature above 700 ° C.
• the microstructure of the steel does not change, and retains all its properties, for example a dual-phase steel will retain its structure.
• welding with a temperature of 1300 ° C. melts the sheet steel facing (as well as the metal core if it is made of steel for example) and during cooling the steel risks losing its structure and therefore its mechanical characteristics.
• a dual-phase type steel heated to 1300 ° C. is transformed, upon cooling, into martensite which is hard and brittle, and therefore not suitable for drawing.
• sandwich sheets according to the invention have the following advantages over sandwich sheets made of a core comprising a polymer:
• the sandwich sheets according to the invention have the following main advantages:

Landscapes

• Laminated Bodies (AREA)
• Metal Rolling (AREA)
• Coating With Molten Metal (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-11-28 FR FR0214932A patent/FR2847846B1/fr not_active Expired - Fee Related
• 2003
  • 2003-11-14 JP JP2004556403A patent/JP2006507947A/ja not_active Abandoned
  • 2003-11-14 PL PL03375594A patent/PL375594A1/xx not_active Application Discontinuation
  • 2003-11-14 MX MXPA05005656A patent/MXPA05005656A/es unknown
  • 2003-11-14 BR BR0316547-7A patent/BR0316547A/pt not_active IP Right Cessation
  • 2003-11-14 WO PCT/FR2003/003376 patent/WO2004050349A1/fr active Application Filing
  • 2003-11-14 EP EP03782561A patent/EP1567330A1/fr not_active Withdrawn
  • 2003-11-14 CA CA002506994A patent/CA2506994A1/fr not_active Abandoned
  • 2003-11-14 US US10/535,177 patent/US20060147743A1/en not_active Abandoned
  • 2003-11-14 KR KR1020057009722A patent/KR20050085209A/ko not_active Application Discontinuation
  • 2003-11-14 CN CNA2003801046093A patent/CN1720135A/zh active Pending
  • 2003-11-14 AU AU2003290198A patent/AU2003290198A1/en not_active Abandoned

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