EP0985466B1 - Method of making a punching tool in concrete at least partially covered with a metal plate - Google Patents

Abstract

The tool is made from a metal outer shell (9) made to the required shape and acting as a mold for a fiber-reinforced concrete filling, poured in after applying an adhesive compound which has a liquid adhesive phase (13) and a solid phase (14) to anchor the concrete in place. The liquid and solid phases are applied in sequence, so that the solid phase projects partially from the liquid phase to provide an anchoring surface for the concrete. The metal shell is produced by electrodeposition in a polymer mold.

Description

The invention relates to stamping tools for concrete steel sheets. hydraulics and the manufacturing processes of these tools.

Stamping consists of making, from a precut sheet of thin metal called "blank", a piece of complex shape not developable called "stamped".

A stamping installation includes several stamping tools : a "punch" with a "head", a "matrix" with a "bottom" and a "Hold-down"; the punch head and the die bottom are shaped according to the complex shape of the stamp to be obtained, and in a complementary shape adapted to be able to obtain a complete nesting of the punch head in the bottom of the matrix.

To obtain a stamped according to the imprint of the bottom of the matrix (or the punch head) from a pre-cut blank, while maintaining the blank in the blank holder, using the punch head, we drive the blank towards the bottom of matrix until engagement and complete nesting of the head in the background.

For the production of stampings in large series, one generally uses stamping tools in cast iron or steel.

For the production of stampings in small and medium series, we can use less expensive stamping tools, for example resin, directly molded or machined according to the shape of the tool, or in hydraulic concrete or resin poured onto a surface gel coat.

However, given the poor mechanical characteristics of these materials at the "working surface" of these tools, these tools wear out quickly on contact with the stamping plates, which leads to series too short of stamping.

• dans le document FR 2 669 842 pour du béton de résine,
• dans le document US 1 935 916 pour du béton hydraulique,
• ou dans l'article intitulé « A functional approach to die and process development : the « composite » die and hydroforming »- Auteurs : G.GALLINARO - Revue : ATA - Ingegneria Automotoristica, Novembre-Décembre 1997, vol.50, n°11/12, pp.635-646.

To improve the surface condition and the wear resistance of these tools, it is therefore necessary to reinforce these materials, at the working surfaces, by providing them with a metallic "skin" or "shell", as described for example :

• in document FR 2 669 842 for resin concrete,
• in document US 1,935,916 for hydraulic concrete,
• or in the article entitled "A functional approach to die and process development: the" composite "die and hydroforming" - Authors: G. GALLINARO - Review: ATA - Ingegneria Automotoristica, November-December 1997, vol.50, n ° 11 / 12, pp. 635-646.

The metallic “skin” or “shell” then serves as a support for the concrete. hydraulic or resin and forms, at least partially, the "surface working ”of the tool which comes into contact with the sheet during stamping.

The metal shell can be prepared by stamping, by projection of metallic particles as described in document FR 2 669 842, for example electrodeposition, or by vapor deposition, or even by other methods.

This metal shell is generally more than 1 mm thick.

The invention relates to a hydraulic concrete stamping tool with of a metallic skin.

• préparer une coque métallique présentant une face dite « externe » correspondant à la forme prédéterminée de l'embouti et une face opposée dite « interne »,
• préparer un moule pour l'outil d'emboutissage en utilisant ladite coque comme fond ou élément de moule, face interne tournée vers l'intérieur du moule, et en utilisant, le cas échéant, d'autres éléments de moulage,
• couler dans ledit moule une composition de préparation dudit béton, et solidifier ladite composition,
• démouler ladite composition solidifiée en enlevant les éventuels autres éléments de moulage, tout en maintenant la coque en place liée par collage au béton solidifié.

To make a stamping tool in hydraulic concrete whose surface intended to come into contact with the sheet metal blank to be stamped is covered at least partially with a metal shell, a process is known comprising the steps consisting in:

• preparing a metal shell having a so-called "external" face corresponding to the predetermined shape of the stamping and an opposite face called "internal",
• preparing a mold for the stamping tool using said shell as the bottom or element of the mold, internal face facing the interior of the mold, and using, if necessary, other molding elements,
• pouring into said mold a composition for preparing said concrete, and solidifying said composition,
• demold said solidified composition by removing any other molding elements, while keeping the shell in place bonded by bonding to the solidified concrete.

The metal shell and concrete have very mechanical characteristics different; during a stamping cycle, especially at the end of the cycle, the shell-concrete interface is stressed by very high shear stresses important, especially in areas with a small radius of curvature; these heavy loads can cause local breaks in the connection between concrete and hull, which limits the performance of the tool.

To reinforce the shell-concrete connection in the case where concrete of resin, according to document FR 2 669 842, before pouring the resin concrete, an intermediate layer of bonding resin compatible with the resin flows concrete (see page 4, lines 27 to 32).

To strengthen the shell-concrete connection in the case where concrete is used hydraulic, according to document US 1,935,916, the internal face of the hull metal is equipped with mechanical means for anchoring concrete (see page 2, lines 61 to 67); prior to pouring concrete, do not apply collage composition.

If bonding is a bonding technique well suited to concrete resin, it is poorly suited to hydraulic concrete because, when pouring concrete hydraulic on a layer of glue, the water of the concrete composition would prevent obtaining a sufficiently resistant bond at the adhesive-concrete interface.

It has indeed been observed that the bond between an adhesive and a “fresh” concrete or "Wet" generally had much poorer performance, in terms of shear strength, that the bond between the same glue and a concrete "Old", ie "set" and dry concrete: Example 1 below illustrates this performance degradation.

We are therefore discouraged from using the bonding technique when using hydraulic concrete.

In addition, document US 1,935,916 describes mechanical means anchor directly secured to the metal shell (reference 16 on the figures); such a shell-concrete connection method is therefore very expensive.

The invention aims to economically improve the shell-concrete connection a hydraulic concrete stamping tool and improve performance of this tool.

• préparer ladite coque métallique de manière à ce qu'elle présente une face dite « externe » correspondant à la forme prédéterminée de l'embouti et une face opposée dite « interne »,
• préparer un moule pour l'outil d'emboutissage en prenant ladite coque comme fond ou élément de moule, face interne tournée vers l'intérieur du moule,
• couler dans ledit moule une composition de préparation dudit béton comprenant des granulats,
• solidifier ladite composition,

   caractérisé en ce que, préalablement à l'étape de coulage, on applique, sur ladite face interne, une composition de collage comprenant une phase liquide de colle et une phase solide adaptée pour former des moyens mécaniques d'ancrage au béton.To this end, the subject of the invention is a method of manufacturing a stamping tool in hydraulic concrete, suitable for the preparation of stampings of predetermined shape from sheet metal blanks, tool whose surface intended to come to the contact of the sheet metal blank to be stamped is covered at least partially with a metal shell, comprising the steps consisting in:

• preparing said metal shell so that it has a so-called "external" face corresponding to the predetermined shape of the stamping and an opposite face called "internal",
• preparing a mold for the stamping tool by taking said shell as the bottom or element of the mold, internal face facing the inside of the mold,
• pouring into said mold a composition for preparing said concrete comprising aggregates,
• solidify said composition,

characterized in that, prior to the pouring step, a bonding composition is applied to said internal face comprising a liquid adhesive phase and a solid phase suitable for forming mechanical means for anchoring to concrete.

The term “liquid glue phase” designates an applicable conventional glue in liquid form.

The term "solid phase" refers to anchors which are homogeneously dispersed in the bonding composition.

Thanks to this manufacturing process, an economical bond is obtained and very resistant between the metal shell and the concrete.

As mechanical anchoring means, aggregates can be used classic minerals, which is very economical; to further strengthen the shell-concrete connection, preferably aggregates of the same type than those of the concrete composition; the granulometry of the aggregates of the bonding composition is suitable for the aggregates to emerge partially of the liquid phase of the bonding composition, after application.

Other advantageous characteristics of the process according to the invention are indicated in the dependent claims.

• l'étape de préparation de la coque comprend les étapes consistant à :
  • réaliser une réplique présentant une surface correspondant à la forme prédéterminée de l'embouti,
  • le cas échéant, rendre conductrice ladite surface de la réplique,
  • revêtir ladite surface de réplique ou, le cas échéant, ladite surface conductrice, d'une couche métallique par électrodéposition jusqu'à former une coque métallique, la face interne de la coque correspondant alors au dépôt métallique de fin d'électrodéposition.
• ladite couche métallique est à base de nickel et l'électrodéposition est réalisée dans un bain d'électrodéposition à base de sulfamate de nickel.
• ladite couche métallique est à base de cuivre.
• ladite réplique est en matériau polymère et/ou la surface conductrice de la réplique comprend du graphite.

In the case where the shell is prepared by electrodeposition, the invention may also have one or more of the following characteristics:

• the stage of preparation of the hull comprises the stages consisting in:
  • make a replica with a surface corresponding to the predetermined shape of the stamping,
  • if necessary, make said surface of the replica conductive,
  • coating said replica surface or, where appropriate, said conductive surface, with a metallic layer by electrodeposition until forming a metallic shell, the internal face of the shell then corresponding to the metallic deposit at the end of electrodeposition.
• said metal layer is based on nickel and the electroplating is carried out in an electroplating bath based on nickel sulfamate.
• said metal layer is based on copper.
• said replica is made of polymeric material and / or the conductive surface of the replica comprises graphite.

The invention also relates to a hydraulic concrete stamping tool whose surface intended to come into contact with the sheet blank to be stamped is covered, at least partially, of a metal shell linked to the concrete, capable of being obtained by the method according to the invention, characterized in that said shell is linked to the concrete to using a layer of adhesive, mechanical anchoring means being inserted in part in concrete, and partly in said layer of glue.

Other advantageous characteristics of the stamping tool according to the invention are indicated in the dependent claims.

The invention will be better understood on reading the description which follows where the shell is prepared by electrodeposition, this description being given by way of nonlimiting example.

• à la figure 1 qui est un schéma de principe des essais de cisaillement de l'exemple 1.
• aux figures 2 à 4 qui correspondent à différentes étapes de fabrication d'un outil d'emboutissage par le procédé selon l'invention tel que décrit à l'exemple 2 : figure 2 : réalisation de la réplique - figure 3 : fabrication de la coque - figure 4 : outil d'emboutissage selon l'invention.

The examples which follow this description serve to illustrate it more precisely, always without limitation and with reference:

• in Figure 1 which is a block diagram of the shear tests of Example 1.
• in Figures 2 to 4 which correspond to different stages of manufacturing a stamping tool by the method according to the invention as described in Example 2: Figure 2: making the replica - Figure 3: manufacturing the shell - Figure 4: stamping tool according to the invention.

The process for manufacturing a stamping tool according to the invention therefore mainly comprises the following stages: preparation of the shell metallic, preparation of a concrete casting mold integrating this shell, preparation of a concrete composition, preparation and application of a bonding composition for the concrete-shell connection, concrete pouring, solidification of the concrete and crosslinking of the adhesive, demoulding of the concrete.

• réaliser une réplique présentant une surface correspondant à la forme prédéterminée de l'embouti,
• le cas échéant, rendre conductrice ladite surface de la réplique,
• revêtir ladite surface conductrice d'une couche métallique par électrodéposition jusqu'à former une coque métallique,

   la face interne de la coque correspondant alors à l'épaisseur de couche métallique déposée en fin d'électrodéposition.To prepare a metal shell by electrodeposition or electroforming, the document DE 40 21 384 describes a process comprising the steps consisting in:

• make a replica with a surface corresponding to the predetermined shape of the stamping,
• if necessary, make said surface of the replica conductive,
• coating said conductive surface with a metallic layer by electrodeposition until forming a metallic shell,

the internal face of the shell then corresponding to the thickness of metallic layer deposited at the end of electrodeposition.

We can make a replica for example by pre-cutting a block of soft material then by machining it to bring it exactly and precisely to desired dimensions.

As a soft material, a matrix composite material can be used organic, prepared for example from a thermosetting resin added charges; if these charges are conductive, one can obtain a composite material conducting the electric current.

We can also make a replica by molding on a “master model »Of a resin, a resin concrete or a hydraulic concrete on a "Gel-coat" or in any other material compatible with constraints of electroforming; these constraints relate in particular to the temperature and chemistry of the plating bath and the surface condition of the replica.

One of the sides of the replica must therefore correspond to the shape predetermined stamped; the state of this surface will condition that of the surface of the stamping tool and also the ease of replica-shell separation, usually after pouring concrete; so it is particularly important to control this surface condition, and surface treatments, such as polishing, can be useful for this purpose.

In order to guarantee the geometry of the electroformed part, and in particular when the electrolytic deposition is carried out in a bath at a different temperature of ambient temperature, for the replica, it is necessary to use a material whose coefficient of expansion is close to that of the metal of the shell, or take this coefficient into account in the initial dimensions of the replica.

Thus, it is common to make copper shells in baths plating at room temperature, while the nickel shells are prepared by electrodeposition at generally higher temperatures high of the order of 55 ° C.

If the material used to make the replica is not conductive, it the face of the replica which corresponds to the form of the stamped, so that, by immersing this surface in a electroplating bath, you can pass an electroplating current between this surface and a counter-electrode immersed in the bath.

The surface can be made conductive for example by applying a layer of conductive paint or by chemical or physical deposition of a conductive material (silver or palladium, for example); preferably, the conductive material includes graphite.

If the thickness of the deposited layer is too great with regard to dimensional tolerances of the tool, it will be advisable to carry out a strips the surface of the replica to a depth corresponding to that paint layer; the surface quality of the deposited layer is also important than that of the replica as previously described.

In order to limit the thickness of this layer and obtain a surface conductor reproducing more faithfully that of the replica, we prefer proceed by chemical or physical deposition, rather than by painting.

The next step includes a suitable plating operation for coating the conductive surface with a thick metallic layer suitable for forming the metal shell of the stamping tool.

As plating material capable of forming a tool shell stamping, nickel, or copper, or alloys of these, can be used metals such as nickel-cobalt alloys.

The thickness of the metal shell depends on the shape of the stamping, the mechanical characteristics of the tool concrete and the metal of its shell, and planned conditions for using the tool; so for example, shapes stamping complexes, with small radii of curvature, range cause significant stress on the hull and require thickness more important; the thickness which should be given to the shell can be evaluated by methods known per se which will not be described here in detail; this thickness is generally greater than 1 mm.

For electrodeposition, we therefore immerse the conductive surface in a electroplating bath and a plating current is passed between this surface and a counter-electrode immersed in the bath.

Electroplating conditions, such as composition and bath temperature, such as current density and charge electrodeposition are adapted in a manner known per se depending on the composition and thickness of the metal layer to be deposited; this deposited layer forms the metal shell of the stamping tool.

Thus, in the case of nickel shells, baths are preferably used containing mainly sulfamate and nickel chloride, and acid boric; can be added to these baths organic additives suitable for improve the mechanical properties of the metal shell.

The deposit for the start of electrodeposition being intended to constitute the surface working of the stamping tool, the deposit conditions are particularly important during this phase; in particular, in the event of low conductivity of the conductive layer of the replica and / or so as to obtain a good quality homogeneous plating with low roughness, a very low current density should be applied during this phase, much less than 1 A / dm2; the current density is then increased according to the performances authorized by the bath and within the limits of internal constraints permitted in the thickness deposited.

Baths containing nickel sulfamate allow to reach high deposition rates, which reduces manufacturing costs.

For average current densities generally less than 10 A / dm2, it is thus possible to obtain thick metallic layers of nickel having a Vickers hardness between 150 and 250 HV, a constraint elastic limit between 250 and 660 MPa, a limiting stress of rupture between 370 and 1050 MPa.

Adding cobalt to the bath increases the hardness of the metal got ; the increase in the current density generally causes a decrease in hardness.

After electrodeposition, we obtain a metal shell applied against the replica by its so-called "external" face, the free surface of the shell constituting the so-called "internal" face of the shell which corresponds to the layer thickness metal deposited at the end of electroplating.

At this point, you can separate the shell from the replica; we prefer however, perform this separation later.

From the molding elements, a mold is then prepared for the tool stamping, the metal shell being used as the bottom or element of mold, "internal" side facing the inside of the mold; other elements of molding are arranged on the periphery of the shell so as to form a mold adapted to the dimensions of the stamping tool to be manufactured; these others elements can be fixed on the replica of the hull.

One then prepares in a manner known per se a composition of hydraulic concrete suitable for the manufacture of a stamping tool; it's about in general of composition called "BHP" or High Performance Concrete which contain, in addition to the conventional components of concrete, namely a binder hydraulic and aggregates, fumed silica and a superplasticizer.

The aggregates are for example made up of sand and / or gravel.

For these “BHP” compositions, the proportion of mixing water and the shrinkage upon solidification are very small.

The complete solidification of these concretes can be obtained by storage at room temperature for at least 28 days; she can also be obtained in an accelerated manner by heat treatment.

For these compositions, after complete solidification, concretes whose ultimate tensile stress exceeds 50 MPa in compression and 7 MPa in traction.

Preferably, the concrete preparation composition that is used contains reinforcing fibers; these metallic fibers allow limit the propagation of cracks in concrete, which increases its resistance to compression, especially tensile and fatigue and further improve the performance of the stamping tool.

A bonding composition is then prepared and applied to the face internal metal shell, bottom or mold element.

One proceeds for example as described in tests n ° 4 to 6, or n ° 13 to 15 of Example 1; according to these tests according to the invention, to prepare the bonding composition, dispersed in the liquid phase consisting of a classic adhesive suitable for bonding to concrete, a solid phase suitable for forming mechanical means of anchoring to concrete.

Preferably, this adhesive is based on thermosetting polymers, for example of epoxy type; these types of glues are generally two-component, the mixing of the organic components being carried out just before the application; preferably, this adhesive is suitable for crosslinking completely under the conditions of concrete solidification.

The use of polymer-based adhesives should be avoided thermoplastics, because the shell-concrete cohesion of the tool could be degraded by overheating of the stamping tool in use at high rate, which would seriously affect the performance of this tool.

The mechanical anchoring means have at least one dimension which extends perpendicular to the surface of the metal shell so as to protrude from the surface of the liquid phase of the bonding composition after application on this hull, so that, after pouring the concrete, these anchoring means are partially embedded in the adhesive layer and for the other part in concrete.

• des éléments isolés, comme les granulats minéraux ou les clous métalliques cités en exemple 1 ;
• un fil « bi-dimensionnel » du type « fil de fer barbelé » ou un treillis « tri-dimensionnel », présentant des éléments régulièrement espacés s'étendant transversalement à la direction générale respectivement du fil ou du treillis, dont au moins une extrémité est destinée à être noyée dans le béton.

As mechanical anchoring means, one can use:

• isolated elements, such as mineral aggregates or metal nails mentioned in example 1;
• a “two-dimensional” wire of the “barbed wire” type or a “three-dimensional” lattice, having regularly spaced elements extending transversely to the general direction of the wire or lattice respectively, at least one end of which is intended to be embedded in concrete.

The use of aggregates has an economic advantage and a advantage in terms of anchoring in concrete, especially when these aggregates are of the same nature as those of concrete.

To apply the bonding composition, one generally starts with coat the inside of the metal shell with a uniform layer of glue classic in the fluid state and the anchoring means are then applied by causing the adhesive layer to penetrate in the fluid state; it is very important that these anchoring means are partially embedded in the adhesive layer and the other part emerges from the free surface of the glue layer so that be able to be embedded later in concrete; after pouring the concrete, the anchoring means must be inserted both into the thickness of the layer of glue and into concrete.

Preferably, the dimension of the anchoring means which extends perpendicular to the surface of the shell or to the surface of the layer of glue is greater than the thickness of the layer of glue applied.

When using isolated anchors, apply preferably these elements by distributing them uniformly over and in the glue layer.

The advantage of using a wire or trellis as an anchor is that the anchoring elements carried by this wire or this mesh are regularly pre-divided.

We can then proceed to the casting operation of the composition of concrete in the mold.

• selon la nature de la colle classique utilisée, on peut, d'une manière connue en elle-même, laisser réticuler partiellement la colle ;
• si besoin, on peut prévoir des armatures de renforcement du béton et des inserts métalliques que l'on dispose alors dans le moule.

Before pouring:

• depending on the nature of the conventional adhesive used, it is possible, in a manner known per se, to partially allow the adhesive to crosslink;
• if necessary, concrete reinforcements and metal inserts can be provided, which are then placed in the mold.

We then pour the concrete composition into the mold, we vibrate the concrete in a fluid state so as to degas and densify it, then we leave solidify this concrete in a manner known in itself and adapted to the concrete composition used; under solidification conditions, the glue the bonding composition is completely crosslinked.

After solidification or at least after beginning of solidification, while the glue of the bonding composition is completely crosslinked, one can unmold, removing if necessary the other molding elements, except the metal shell which is secured by gluing and anchoring with concrete.

When the adhesive is suitable for crosslinking completely in the concrete solidification conditions, it is not necessary to provide a separate crosslinking step after pouring the concrete.

The glue then provides a chemical bond between the shell and the concrete, then that the mechanical anchoring means essentially provide a connection mechanical since they are embedded both in the crosslinked adhesive layer and in solidified concrete.

The advantage of using aggregates as anchors is that the distances between anchor points are very small, especially when the average diameter of these aggregates is relatively small, ie by example between 1.5 and 3 times the thickness of the liquid phase of the collage composition, after application.

It is also possible to use aggregates not only of the same kind but also of the same particle size as those of the concrete composition, which is more economical.

It is also appropriate, if this has not yet been done, to separate the replica of the metal shell, which uncovers the external surface of the shell which corresponds to the working surface of the stamping tool.

Advantageously, when the replica is made of polymer material and / or when the conductive layer applied to this replica is based on graphite, this separation is facilitated.

A hydraulic concrete stamping tool is thus obtained, adapted to the preparation of stamps of predetermined shape from sheet metal blanks, tool whose surface intended to come into contact with the sheet blank to be stamped is covered, at least partially, with a metal shell.

Tool manufacturing can be completed by light machining to correct the dimensions of the tool if necessary and / or by treating the surface working to harden it and / or to adapt its roughness and / or to improve the effect of lubrication in stamping.

We can practice on the metal shell of the tool the same treatments than those used on conventional stamping tools in melting ; for heat treatments, care must be taken not to reach temperatures that could damage the crosslinked glue of the bonding composition which ensures the connection between the shell and the concrete.

Thanks to the invention, the stamping tool that is obtained offers significantly improved performance compared to those of the same type of art because the bond between the hull and the concrete is very strong, in particular to shear stresses; improving the resistance of this connection with respect to the prior art is illustrated in Example 1 below.

Thanks to the invention, tools can be manufactured at reduced cost. stamping machines usable for larger production series stampings and / or stampings of more complex shapes, i.e. shapes with small radii of curvature.

The following examples complete the description.

Example 1 :

The purpose of this example is to illustrate the effect of solid anchoring means added to the glue on the resistance of the connection between the shell of a tool stamping and the concrete that is poured into this shell.

To assess this effect, we measure the shear strength of glue applied between a concrete block and a metal plate according to the protocol defined in §1 below, for several types of glued joints defined in §2 below; the results are reported in §3.

1 - Protocol for measuring the shear strength of adhesive joints applied between a concrete block and a metal plate:

The principle of measurement is illustrated in Figure 1.

1.1- Preparation of the assembly of a concrete block 1 and a metal plate 2 joined together using an adhesive joint 3, to be characterized.

The metal plate 2 is made of a bare sheet steel of thickness 1.5 mm; the plate is degreased using trichlorethylene.

After having mixed the various components of the glue, one of the faces of the plate 2 is coated with glue, the coating method being adapted to the type of glue used (see below).

Then, if necessary, the mechanical anchoring means are applied. according to the invention (see below); the collage composition then includes the glue itself and the mechanical anchoring means.

The preparation of the assembly then differs depending on whether it is assembly on "old" concrete or assembly on "wet" concrete.

1.1.1 - Assembly on " old " concrete :

From concrete composition n ° 1 (without fibers) described in example 2 (Table III), a concrete block 1 with parallel faces is prepared; after maintenance at least 28 days in the conservation room, the block obtained has a compressive strength of the order of 55 MPa.

To obtain the assembly, we then apply the plate 2 glued on one of the faces of block 1.

After drying under conditions suitable for the adhesive used, the bond 3 between block 1 and plate 2 is then provided by the bonding composition.

1.1.2 - Assembly on " wet" concrete :

On the glued side of the plate 2, and after the start of polymerization glue (1 to 2 hours depending on the type of glue used), we mold a block 1 of concrete from a concrete composition identical to that described in paragraph 1.1.1 above.

After vibrating the composition in the fluid state, let the concrete set en masse and dry under the same conditions as those described in paragraph 1.1.1 above, that is to say that the assembly is kept at least 28 days in the conservation room.

As in paragraph 1.1.1, the connection 3 between block 1 and plate 2 is then provided by the bonding composition.

1.2 - Measurement of shear strength :

The measurement of the shear strength of the connecting joint 3 is then carried out as follows: by holding the block 1 between a support 4 under its lower face and another support 5 on its upper face, a vertical force F is applied to the plate 2 (see arrow in FIG. 1) and the breaking force F _r of the joint of the joint 3 is measured.

The stress on the joint 3 is then essentially in shear.

To obtain a more precise evaluation of the shear strength of a joint 3 of connection, one carries out at least three assemblies using the same joint of connection and one measures the breaking strength F _r1 , F _r2 , F _r3 of each assembly; the average of the three measurements obtained gives a more precise evaluation of the shear strength of the joint 3.

The choice of a steel sheet is explained as follows: tests rupture were previously carried out by taking, as plate metallic, electroformed plates under the same conditions as those the metal shell of the stamping tool according to the invention; we have then observed that the break in the bonding of the adhesive joint was always done at the concrete-adhesive interface; we therefore deduced that measurements made using of metallic steel plates would give the same results as those performed on electroformed plates; to simplify the tests, we have so then carried out most of the measurements on steel plates.

2 - Type of concrete-metal connections tested : 2.1 - Nature of the adhesives used and suitable application method:

• « Sikadur 31 »® de la Société SIKA : il s'agit d'une colle époxy bi-composants, adaptée au collage de métaux et de béton frais sur béton ancien ; cette colle peut être considérée comme un mortier de résine ; cette colle est appliquée à l'aide d'une raclette à dents triangulaires de 2 mm de hauteur.
• « Sikadur Imprégnation »® de la Société SIKA : colle époxy bi-composants, fluide, adaptée au collage de béton frais sur béton ancien et à la reprise de bétonnage ; il s'agit d'une résine pure s'imprégnant bien dans le béton ; cette colle est appliquée au pinceau.
• « Mybond Epiphen »® 1800 » de la Société LAMBIOTTE : résine époxy bi-composants, fluide ; il s'agit d'une résine pure généralement employée pour la fabrication de composites stratifiés et de bétons de résine ; cette colle est appliquée sur 1 à 2 mm d'épaisseur par coulage dans un moule dont le fond est la plaque métallique ; avant application sur la plaque, on laisse réticuler partiellement pendant 2 heures environ, de manière à obtenir une colle de viscosité plus élevée mais encore suffisamment fluide pour être coulée dans le moule.

Three glues were tested:

• “Sikadur 31” ® from the SIKA Company: it is a two-component epoxy adhesive, suitable for bonding metals and fresh concrete to old concrete; this glue can be considered as a resin mortar; this glue is applied using a squeegee with triangular teeth 2 mm high.
• “Sikadur Impregnation” ® from the SIKA Company: two-component epoxy adhesive, fluid, suitable for bonding fresh concrete to old concrete and resuming concreting; it is a pure resin which impregnates well in concrete; this glue is applied with a brush.
• "Mybond Epiphen" ® 1800 "from LAMBIOTTE: two-component epoxy resin, fluid; it is a pure resin generally used for the manufacture of laminate composites and resin concretes; this glue is applied on 1 to 2 mm thick by pouring into a mold whose bottom is the metal plate; before application to the plate, it is left to partially crosslink for approximately 2 hours, so as to obtain an adhesive of higher viscosity but still sufficiently fluid to be poured into the mold.

2.2 - Preparation joints "composite" link on concrete "wet":

• Double couche de colle : colle « Sikadur 31 » + « Sikadur Imprégnation » : on applique d'abord sur la plaque métallique une couche de « Sikadur 31 », on laisse cette colle réticuler partiellement pendant environ 2 h, puis on applique sur cette couche partiellement réticulée une couche de « Sikadur Imprégnation », bien adaptée au collage sur matériaux poreux.
• colle « Sikadur 31 » + liaison « minérale » : la polymérisation de la colle étant plus difficile en milieu humide, l'objectif poursuivi est de compléter la liaison par des liaisons mécaniques de même nature que le béton ; après application de la couche de colle sur la plaque métallique, on disperse des granulats sur cette couche, avant le début de polymérisation ; le diamètre moyen des granulats est largement supérieur à l'épaisseur de la couche de colle appliquée ; le taux de couverture des granulats dispersés est adapté pour que l'espace moyen entre les granulats soit du même ordre de grandeur que la taille moyenne des granulats ; on fait pénétrer les granulats dans la couche de colle.
• colle « Sikadur 31 » + liaison « métallique » : la polymérisation de la colle étant plus difficile en milieu humide, l'objectif poursuivi est de compléter la liaison par des liaisons métalliques comparables à des armatures de béton ; après application de la couche de colle sur la plaque métallique et avant le début de polymérisation, on disperse des clous de 40 mm de long environ sur cette couche, en noyant la tête de ces clous dans la couche de colle , la direction générale des clous étant transversale à la surface de la plaque ; le taux de couverture des clous dispersés est adapté pour que l'espacement minimum entre chaque clou soit supérieur au diamètre minimum des graviers du béton.

Three types of composite bonds were tested on "wet" concrete, the last two corresponding to bonding compositions according to the invention:

• Double layer of glue: "Sikadur 31" glue + "Sikadur Impregnation": first apply a layer of "Sikadur 31" on the metal plate, allow this glue to partially crosslink for approximately 2 h, then apply to this layer partially crosslinked a layer of "Sikadur Impregnation", well suited for bonding on porous materials.
• “Sikadur 31” glue + “mineral” bond: since the polymerization of the glue is more difficult in a humid environment, the objective is to complete the bond with mechanical bonds of the same nature as concrete; after application of the layer of adhesive on the metal plate, aggregates are dispersed on this layer, before the start of polymerization; the average diameter of the aggregates is much greater than the thickness of the layer of adhesive applied; the coverage rate of the dispersed aggregates is adapted so that the average space between the aggregates is of the same order of magnitude as the average size of the aggregates; the aggregates are made to penetrate the adhesive layer.
• "Sikadur 31" glue + "metallic" bond: the polymerization of the glue being more difficult in a humid environment, the objective is to complete the bond with metallic bonds comparable to concrete reinforcements; after application of the layer of glue on the metal plate and before the start of polymerization, nails are dispersed about 40 mm long on this layer, by embedding the head of these nails in the layer of glue, the general direction of the nails being transverse to the surface of the plate; the coverage rate of the dispersed nails is adapted so that the minimum spacing between each nail is greater than the minimum diameter of the gravels of the concrete.

3 - Results of the shear strength measurements of the various concrete-metal connections :

The results obtained as well as the type and location of the rupture after test are reported in Table I below. Shear strength of different concrete-metal bonds. TYPE OF LINK test no. Breaking force (kN) Type and location of failure Sikadur 31 25 11.5 at the glue / old concrete interface on concrete 26 14.4 Same "Old" 27 17.2 Same Sikadur 31 1 7.9 progressive - at the adhesive / concrete interface on concrete 2 9.2 Same "Wet" 3 6.5 Same Sikadur® 22 8.6 at the glue / steel interface Impregnation on 23 6.3 Same "wet" concrete 24 10.1 Same Lambiotte resin 16 9.4 at the glue / steel interface on concrete 17 13.5 Same "Wet" 18 10.2 Same Sikadur 31 + 19 10.6 progressive - at the glue / glue interface Impregnation ... on 20 15.5 Same "wet" concrete 21 14.3 Same Sikadur 31 + link 4 19.2 at the glue / steel and glue / concrete interface "Mineral" on 5 18.2 at the adhesive / concrete interface "wet" concrete 6 19.4 at the glue / steel interface Sikadur 31 + link 13 20.3 at the glue / steel interface "Metallic" on 14 22.6 Same "wet" concrete 15 22.6 Same

Comparison of the results of tests 1, 2 and 3 with those of the tests n ° 25, 26 and 27 clearly shows that an adhesive applied to “fresh” concrete or "Wet" generally has much poorer performance, in terms shear strength, as the same glue applied to concrete "Old", that is to say "set" and dry concrete.

It is precisely an essential aim of the invention to avoid or compensate for this deterioration in performance.

The performances obtained with other adhesives on wet concrete (tests # 16 to 18 and # 22 to 24) may be slightly higher but still insufficient to withstand the heavy loads between the concrete and the hull metal of a stamping tool.

It is also an object of the invention to propose a concrete-metal connection much better shear resistance.

Thus tests no. 4 to 6 and no. 13 to 15, in accordance with the invention, show that the composite bonds according to the invention resist much better shear that "glue" connections according to the prior art, on wet concrete (tests n ° 1 to 3 and n ° 16 to 24); the invention therefore relates to the use of a bonding composition comprising mechanical anchoring means such as aggregates (tests n ° 4 to 6) or metal nails (tests n ° 13 to 15).

Using this type of composite bond for the manufacture of a tool concrete stamping with a metal shell, it improves substantially the cohesion between the shell and the concrete and, consequently, the tool performance.

An advantage of the composite bond according to the invention lies in the reliability of the resistance of this link: the dispersion of the test results effect on composite bond is indeed much lower than that of results of tests carried out on conventional bonded bond (see Table I); this advantage therefore improves the reliability of stamping tools manufactured according to the invention.

Example 2 :

The purpose of this example is to illustrate the manufacture of a concrete mold hydraulics according to the invention, with reference to Figures 2 to 4.

1.- Creation of replica 6 with reference to Figure 2.

We pre-cut a block of soft material then we machine it to bring it exactly and precisely to the desired dimensions and in such a way that one of the faces 7 corresponds to the predetermined shape of the stamped.

As the soft material, one of the polymeric materials described in Table II below can be used. Examples of polymeric materials for the replica. Basic polymer: poly-
Commercial reference: -carbonate
Lexan® epoxy
LAB 900 -uréthanne
Ren Shape® 540 Company Features: Axson CIBA Density (g / cm ³ ) 1.2 1.62 1.65 Water absorption at 24 h: 0.3% 0.2% 0 Compressive strength (MPa) 77 120 73 Elongation at break (%) 60-100 50 90 Flexural modulus (GPa) 2.24 4.5 5 Hardness M70 - R118 88 Shore D 90 Shore D Heat resistance temperature (° C) (Tg: glass transition) 120 123 (Tg) 110 (Tg) Coefficient of thermal expansion (/ ° C) 70.10 ^-6 55.10 ^-6 45.10 ^-6 Action of weak acids nothing - resistant Action of strong acids slow attack - attack

• coefficient de dilatation supérieur mais relativement proche de celui du nickel (17.10^-6 environ) dans la gamme de température 20 - 100°C,
• densité supérieure à 1 kg/dm3 pour faciliter l'immersion dans le bain d'électrodéposition, température de transition vitreuse largement supérieure à la température d'utilisation du bain, bonne résistance à l'action chimique acide du bain et au gonflement à l'eau,
• bonne usinabilité à cause des propriétés mécaniques (résistance à la compression, allongement à la rupture, dureté).
• excellent état de surface après usinage, notamment au niveau de la rugosité et de la porosité, ce qui facilite la séparation coque-réplique.

The materials described in this table II have the following characteristics:

• coefficient of expansion higher but relatively close to that of nickel (17.10 ^-6 approximately) in the temperature range 20 - 100 ° C,
• density greater than 1 kg / dm3 to facilitate immersion in the electroplating bath, glass transition temperature much higher than the temperature of use of the bath, good resistance to the acid chemical action of the bath and to swelling on water,
• good machinability due to mechanical properties (compressive strength, elongation at break, hardness).
• excellent surface condition after machining, particularly in terms of roughness and porosity, which facilitates the separation between shell and replica.

After degreasing, the face 7 is then made conductive by application a very thin layer of conductive paint containing particles silver: the replica 6 is then provided with a conductive film 8 on its surface 7; the thickness of the conductive film 8 is of the order of a micrometer.

You can also use a paint containing particles of graphite, which facilitates the shell-replica separation.

2. Manufacture by electrodeposition of a shell 9 made of nickel approximately 0.8 mm thick, with reference to FIG. 3.

By electrodeposition in a bath, the conductive film 8 is therefore coated a layer of nickel, which will form the metal shell 9 of the tool stamping.

• acide borique H₃BO₃ :   80 g/l
• chlorure de nickel, NiCl₂, 6 H₂O   5 à 10 g/l
• sulfamate de nickel Ni(NH₂ SO₃)₂   200 g/l
  ... de manière à obtenir |Ni2⁺| =   40 g/l
• agent mouillant   <1% en poids

Composition of the electroplating bath:

• boric acid H ₃ BO ₃ : 80 g / l
• nickel chloride, NiCl ₂ , 6 H ₂ O 5 at 10 g / l
• nickel sulfamate Ni (NH ₂ SO _{3) 2} 200 g / l
  ... so as to obtain | Ni2 ⁺ | = 40 g / l
• wetting agent <1% by weight

• Bain : 4,2 < pH < 4,8 et température comprise entre 50 et 55°C,
• densité de courant : 0,1 A/dm2 au début, portée progressivement à 5 A/dm2.

Electroplating conditions:

• Bath: 4.2 <pH <4.8 and temperature between 50 and 55 ° C,
• current density: 0.1 A / dm2 at the start, gradually increased to 5 A / dm2.

• contrainte limite d'élasticité (à 0,2%) :   485 MPa,
• Module d'élasticité :   182,5 GPa,
• contrainte limite à la rupture :   840 MPa,
• Allongement à la rupture :   8,3 %
• dureté sur la face externe (vers film 8) :   210 HV
• dureté sur la face interne (fond de moule)   238 HV

Mechanical characteristics of the nickel obtained:

• yield stress (at 0.2%): 485 MPa,
• Modulus of elasticity: 182.5 GPa,
• ultimate breaking stress: 840 MPa,
• Elongation at break: 8.3%
• hardness on the external face (to film 8): 210 HV
• hardness on the internal face (bottom of mold) 238 HV

We also evaluated the value of the residual stresses in the thickness of the nickel layer by making measurements on layers deposited under the same conditions, but on a steel sheet.

On this substrate and unlike the conductive film 8 or on the surface of the reply 7, nickel is reputed to be strongly adherent; after depositing nickel, we glue a strain gauge on the uncoated side of the sheet and measure using this gauge the relaxation that appears when you remove by EDM of the successive layers of the nickel deposit.

These measurements made it possible to estimate that the residual stresses are between 90 and 150 MPa in tension.

Low residual stress limits risk of “detachments” from certain areas of the hull in relation to the replica during electroplating or before pouring concrete, which allows better further guarantee compliance with the geometric tolerances of the surface working the tool.

After electrodeposition, we thus obtain on replica 6, a shell metallic 9 having a so-called "external" face in contact with the conductive film 8 and an opposite face called "internal".

Given the shape of the shell 9 described in Figure 3, no molding element is here to be added to form the mold for casting the concrete.

3 - Preparation of the concrete composition :

• liant hydraulique de type ciment et sable : mortier dénommé Clavex ® Lanko 701 de la Société LAFARGE ; ce mortier est déjà formulé avec des additifs limitant le retrait comme de la silice pyrogénée.
• graviers de granulométrie comprise entre 3 et 8 mm,
• fibres de renforcement : fibres de fonte amorphe se présentant sous forme de rubans souples très minces de dimensions 15 x 1 x 0,03 mm environ, dénommées Fibralex de la Société SEVA.
• fluidifiant ou agent superplastifiant : dénommé Sikament FF86 de la Société SIKA.
• eau de gâchage.

Compositions are prepared with the following constituents:

• hydraulic binder of cement and sand type: mortar called Clavex ® Lanko 701 from LAFARGE; this mortar is already formulated with additives limiting shrinkage such as fumed silica.
• gravel with a grain size between 3 and 8 mm,
• reinforcing fibers: amorphous cast iron fibers in the form of very thin flexible ribbons of dimensions approximately 15 x 1 x 0.03 mm, called Fibralex from the company SEVA.
• fluidizer or superplasticizer: called Sikament FF86 from the company SIKA.
• mixing water.

The aggregates are therefore here formed by the sand of the mortar and the gravel.

Three types of composition are prepared, differing in the proportions of these constituents, as indicated in Table III. Concrete compositions for stamping tool. Concrete fibers Mortar gravels Water W / C fluidizersGypsum # 1 0 1270 1250 200 0.41 1.35 (0.3%) # 2 36 (0.5%) 1250 1133 200 0.42 4.75 (1%) # 3 72 (1%) 1500 480 240 0.42 5.7 (1%)

• dans la colonne « fibres », le volume de fibres par rapport au volume de béton,
• dans la colonne « fluidifiant », le volume de fluidifiant par rapport au volume de ciment.

In this Table III, the proportions are indicated by density (kg / m3), the figures in parentheses indicate:

• in the "fibers" column, the volume of fibers in relation to the volume of concrete,
• in the “fluidizer” column, the volume of fluidizer relative to the volume of cement.

The W / C ratio designates the weight of water divided by the weight of cement.

4 - Preparation and application of the bonding composition on the internal face of the metal shell 9.

In Example 1, two types of bonding composition are used: first corresponding to tests n ° 4 to 6, and the second corresponding to tests 13 to 15; the bonding composition is prepared and applied to the metal plate 2.

We use here in the same way either the first or the second bonding composition, on the metal shell 9 still supported by the reply 6.

5 - Pouring and solidification of the concrete with reference to FIG. 4 in the case of the use of the first bonding composition (mineral bonds).

Before casting, metal inserts 10 and 11 are positioned.

The concrete composition is then poured into the mold formed by the shell 9 supported by the replica 6, then the concrete is vibrated in the fluid state at using a vibrating needle suitable for this purpose.

As the shell 9 forms the mold corresponding to the shape of the tool to manufacture, there are no other molding elements here, and therefore there is no subsequent release step.

The concrete is then allowed to set under the following conditions: storage for 28 days in a constant temperature atmosphere (≈ 21 ° C) and constant humidity (around 95%), protecting from desiccation of fresh concrete surfaces exposed to the atmosphere.

Test pieces of the same concrete are prepared under conditions identical, to assess the mechanical properties.

It is noted that the withdrawal at 30 days is of the order of 0.05 mm / m for the three concrete compositions.

• résistance à la compression σ _max.c : sur des éprouvettes de diamètre 110 mm et de longueur 220 mm ;
• résistance en traction σ _max.t1 : par des essais de flexion (de type « trois points ») à déplacement imposé sur des éprouvettes de dimensions : 70 x 70 x 280 mm ;
• résistance en traction σ _max.t2 : par des essais de flexion (de type « trois points ») à force imposée sur des éprouvettes pré-entaillées de dimensions : 47 x 70 x 280 mm ; ces essais sont effectués à un an.
• module d'élasticité en compression E_c et en flexion E_f.

The mechanical properties are evaluated as follows:

• compressive _strength σ _max.c : on 110 mm diameter and 220 mm long test _pieces ;
• tensile strength σ _max.t1 : by bending tests (of the "three point" type) with imposed displacement on test pieces of dimensions: 70 x 70 x 280 mm;
• tensile strength σ _max.t2 : by bending tests (of the “three point” type) with force imposed on pre-notched test pieces of dimensions: 47 x 70 x 280 mm; these tests are carried out at one year.
• modulus of elasticity in compression E _c and in bending E _f .

The results obtained are reported in Table IV for each concrete composition (cf. §3 above) Mechanical properties of concrete from Tab.lll. Concrete s _maxc (MPa) s _{max t 1} (MPa) s _{max t 2} (MPa) E _c (GPa) E _t (GPa) # 1 55.5 8.5 9.4 33.6 43.4 # 2 67.5 10.6 11.1 34.5 46.7 # 3 62.7 17.1 16.4 37.3 45.6

This table illustrates the reinforcing effect of the fibers introduced into the concrete composition.

After casting and solidification, the replica 6 is separated from the hull metal 9 secured to the solidified concrete part 12, and the tool is obtained stamping as shown in Figure 4.

Figure 4 illustrates the connection between the concrete part 12 and the shell 9 provided by the bonding composition comprising crosslinked glue 13 and aggregates 14.

The combination of the chemical bonding effect provided by the glue 13 and the mechanical bonding effect provided by the aggregates 14 makes it possible to achieve a very strong cohesion of the shell 9 and the concrete part.

The inserts and the part of the surface of the tool which is concrete are machined in order to obtain the desired dimensions and centering; shell 9 electroformed does requires no special treatment before using the tool in press stamping.

A particularly efficient stamping tool is thus obtained, very resistant to wear and allowing high-speed stamped quality.

A complete study on friction in stamping and in particular on the effect of nickel as a tool surface material has shown that practically equivalent friction conditions with a material of tool surface made of steel and with a tool surface material of nickel electroformed; on a steel sheet simply coated with a lubricating film temporary corrosion protection, the friction coefficient has been estimated at around 0.22.

The stamping tools obtained were tested on an industrial press and have given satisfaction under conventional stamping conditions; the tests have shown that a single tool can perform several hundred thousands of stamps.

Claims (16)

1. Method of manufacturing a pressing tool made of hydraulic concrete (12), suitable for the production of pressings of predetermined shape from sheet blanks, that surface of the tool which is intended to come into contact with the sheet blank to be pressed being at least partly covered with a metal shell (9), comprising the steps consisting in:

   producing the said metal shell (9) so that it has a face called the "external" face corresponding to the predetermined shape of the pressing and an opposite face called the "internal" face;

   producing a mould for the pressing tool by taking the said shell (9) as mould element or bottom, with the internal face turned towards the inside of the mould;

   pouring a composition for producing the said concrete, which includes aggregates, into the said mould;

   solidifying the said composition;

   characterized in that, prior to the pouring step, a bonding composition is applied to the said internal face, the said bonding composition comprising a liquid adhesive phase and a solid phase that is suitable for forming means (14) for mechanical anchoring to the concrete.
2. Method according to Claim 1, characterized in that the said solid phase of the bonding composition is formed by aggregates.
3. Method according to Claim 2, characterized in that the aggregates of the bonding composition are of the same kind as those of the concrete composition.
4. Method according to any one of the preceding claims, characterized in that the dimension of the said anchoring means (14) which extends perpendicular to the surface of the shell (9) is greater than the thickness of the liquid phase (13) of the applied bonding composition.
5. Method according to any one of the preceding claims, characterized in that, to apply the said bonding composition, the liquid phase (13) of the bonding composition is firstly applied and then the said anchoring means (14) are applied by making them partially penetrate into the said liquid phase (13).
6. Method according to Claim 5, characterized in that the anchoring means (14) are applied so that they partially emerge from the free surface of the said liquid phase (13).
7. Method according to any one of the preceding claims, characterized in that the liquid phase (13) of the bonding composition is thermosetting under the conditions for solidification of the said concrete composition.
8. Method according to any one of the preceding claims, characterized in that the said composition for producing concrete contains reinforcing fibres.
9. Method of manufacture according to any one of the preceding claims, characterized in that the said shell (9) is produced by electrodeposition.
10. Method according to Claim 9, characterized in that the said shell production comprises the steps consisting in:

    making a replica (6) having a surface (7) corresponding to the predetermined shape of the pressing;

    if required, making the said surface (7) of the replica (6) conducting; and

    coating the said surface (7) or, if required, the said conducting surface (8) with a metal layer by electrodeposition until a metal shell (9) is obtained,

    the internal face of the shell (9) then corresponding to the metal coating deposited at the end of electrodeposition.
11. Method according to either of Claims 9 and 10, characterized in that the said metal layer is based on nickel and in that the said electrodeposition is carried out in an electrodeposition bath containing essentially nickel sulphamate.
12. Method according to either of Claims 9 and 10, characterized in that the said metal layer is based on copper.
13. Method according to any one of Claims 9 to 12, characterized in that the said replica (6) is made of a polymer material.
14. Pressing tool made of hydraulic concrete, whose surface intended to come into contact with the sheet blank to be pressed is covered, at least partly, with a metal shell (9) bonded to the concrete (12), capable of being obtained by the method according to any one of the preceding claims, characterized in that the said shell (9) is bonded to the concrete (12) by means of a layer of adhesive, mechanical anchoring means (14) being partly inserted into the concrete (12) and partly into the said adhesive layer.
15. Tool according to Claim 14, characterized in that the mechanical anchoring means (14) are aggregates.
16. Tool according to Claim 15, characterized in that the said aggregates are of the same kind as those of the concrete.

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