EP1573080B1 - Method for making structural elements by machining thick plates - Google Patents

Method for making structural elements by machining thick plates Download PDF

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Publication number
EP1573080B1
EP1573080B1 EP03813619A EP03813619A EP1573080B1 EP 1573080 B1 EP1573080 B1 EP 1573080B1 EP 03813619 A EP03813619 A EP 03813619A EP 03813619 A EP03813619 A EP 03813619A EP 1573080 B1 EP1573080 B1 EP 1573080B1
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EP
European Patent Office
Prior art keywords
process according
plate
machined
machining
sheet
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EP03813619A
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German (de)
French (fr)
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EP1573080A2 (en
Inventor
Fabrice Heymes
David Godard
Timothy Warner
Julien Boselli
Raphael Muzzolini
Sjoerd Van Der Veen
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Constellium Issoire SAS
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Alcan Rhenalu SAS
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Priority claimed from FR0215997A external-priority patent/FR2848480B1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/047—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with magnesium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent

Definitions

  • the present invention relates to the manufacture of structural elements of heat-treated alloy, in particular aluminum alloy, by machining thick plates. These structural elements can be used in aeronautical construction.
  • Achieving a structural element by assembling medium sheets and profiles requires a very large number of riveting operations which, performed under the necessary reliability conditions for an aeronautical structural element, represent a significant cost.
  • the realization of an integrated structural element by machining a thick sheet consumes much more metal, because a large fraction of the sheet metal thick is reduced in chips, but in return it reduces to a minimum the riveting operations that are expensive.
  • the second approach suffers from other disadvantages.
  • the thick plate is before machining in the metallurgical state corresponding to its end use, because according to the state of the art, no thermomechanical treatment is carried out after machining. More particularly, this final metallurgical state was obtained by dissolving and quenching.
  • two physical mechanisms limit the quenching speed in a thick plate: the thermal conductivity of the material which constitutes said thick plate, and the heat exchange between the surface and the sheet and the quenching medium.
  • the mechanical properties of the quenched thick sheet vary depending on the thickness. As a result, certain mechanical characteristics become less good as one moves away from the surface of the sheet.
  • the machining thus removes the areas in which the hardened sheet exhibits the best mechanical characteristics, and the loading of the structural element in the service conditions involves metal zones whose mechanical properties can be quite variable depending on the depth relative to the area near the initial surface of the sheet.
  • the calculation of the structures is, as a precaution, carried out on the basis of rather conservative models of the real performances of the part, said models being typically based on the mechanical characteristics of the areas of the sheet which are distant from the surface and thus have the mechanical characteristics the weakest. This prevents, when sizing parts, to make the most of the real properties of the material.
  • German patent DE 955 042 (Friedrichsbou Aktiengesellschaft) describes a horizontal quenching process in which the edges of the sheet are cooled more strongly than the center, and the lower face more strongly than the upper face.
  • the patent EP 578 607 seeks to optimize the quenching process of extruded profiles by individual or group control of the water spray nozzles; such a device, controlled by computer, in principle allows to adjust the positions of the nozzles to each profile, but the focus remains empirical.
  • the patent EP 695 590 develops a similar idea for sheet quenching.
  • French patent 1.503835 (Atomic Energy Commission) proposes to increase the quenching speed during the immersion of the piece in a cold liquid by the application of a thin layer with low thermal conductivity which limits the vaporization of the quenching medium.
  • French patent 2,524,001 Patent Rhenalu proposes to apply on some sides of the product a coating that conducts heat less well than the underlying metal. By this improved control of the cooling rate, it would be possible to avoid altering the use properties of the product.
  • This rather heavy process has several disadvantages. It is limited to sheets or profiles of substantially constant thickness; in the case of aluminum alloys, this thickness should not exceed about 15 mm.
  • the coatings proposed in this patent may pollute the quench liquid reservoir.
  • the aim of the invention is to present a new process for manufacturing machined metal parts that can serve as structural elements, or blanks for such parts, which makes it possible to improve the compromise between the static mechanical characteristics (limit of elasticity, tensile strength, elongation at break) and the tolerance to damage (especially toughness) in the volume of the workpiece and to minimize the distortions induced during quenching, and which can be implemented with a cost of particularly advantageous exploitation.
  • the Applicant invented a new integrated process which makes it possible to manufacture from large plates machined structural elements of large size, with excellent dimensional tolerances, and having improved mechanical characteristics.
  • the present invention proposes a new manufacturing process which makes it possible to obtain machined parts having a better compromise between the minimum values of the static mechanical characteristics (conventional yield strength, elongation at break, tensile strength) and the damage tolerance. , compared to similar shaped parts produced by a method according to the state of the art.
  • the variation of the mechanical characteristics within the part is smaller, compared to a machined part of similar form produced by a method according to the state of the art.
  • a second object is the use of a metal part obtained by said method as structural element in the aeronautical construction.
  • a third object is an aluminum alloy structural element for aeronautical construction obtained by said method.
  • the static mechanical characteristics i.e., the ultimate strength R m , the yield point R p0 , 2 , and the elongation at break A, are determined by a tensile test according to EN 10002-1 standard, the location and direction of specimen collection being defined in EN 485-1.
  • the K IC toughness was measured according to ASTM E 399.
  • the curve R is determined according to ASTM 561-98.
  • the critical stress intensity factor K C is calculated, ie the intensity factor which causes the instability of the crack.
  • the intensity factor of stress K CO by assigning to the critical load the initial length of the crack at the beginning of the monotonic loading. These two values are calculated for a specimen of the desired shape.
  • K app designates the K CO corresponding to the test specimen used for the R curve test.
  • the resistance to exfoliating corrosion was determined according to the EXCO test described in the ASTM G34-72 standard.
  • the definitions of the European standard EN 12258-1 apply. Contrary to the terminology of this standard EN 12258-1, here is called “thin sheet” a sheet with a thickness of not more than 6 mm, “medium sheet” a sheet with a thickness between 6 mm and about 20 to 30 mm, and “thick plate” a sheet of a thickness typically greater than 30 mm.
  • machining includes any material removal process such as turning, milling, drilling, reaming, tapping, EDM, grinding, polishing.
  • structural element refers to an element used in mechanical engineering for which the static and / or dynamic mechanical characteristics are of particular importance for the performance and integrity of the structure, and for which a calculation of the structure is usually prescribed or performed. It is typically a mechanical part whose failure is likely to endanger the safety of said construction, its users, its users or others.
  • these structural elements include the elements that make up the fuselage (such as fuselage skin (fuselage skin in English), stiffeners or stringers, bulkheads, fuselage (circumferential frames), wings (such as wing skin), stiffeners (stiffeners), ribs (ribs) and spars) and empennage including horizontal stabilizers and vertical stabilizers horizontal or vertical stabilizers, as well as floor beams, seat tracks and doors.
  • fuselage such as fuselage skin (fuselage skin in English
  • stiffeners or stringers such as fuselage skin
  • bulkheads fuselage (circumferential frames)
  • wings such as wing skin
  • stiffeners stiffeners (stiffeners), ribs (ribs) and spars
  • empennage including horizontal stabilizers and vertical stabilizers horizontal or vertical stabilizers, as well as floor beams, seat tracks and doors.
  • the problem is solved by not soaking the thick plate in which the metal part referred to is then machined, but an already pre-machined blank. Pre-machining can lead to a form more or less close to the final form.
  • this pre-machined blank has a profile consisting of one or more channels. These channels may be parallel to the rolling direction, but other orientations are possible, for example a diagonal orientation. If it is envisaged to carry out a pull after quenching, this profile is advantageously parallel to the rolling direction and substantially constant over its length, but other types of profiles are possible.
  • the blank may be in a horizontal position, in a vertical position, or in any other position.
  • the quenching may be carried out by immersion in a quenching medium, by spraying, or by any other appropriate means.
  • Said quenching medium may be water or another medium such as glycol; its temperature can be chosen between its solidification point and its boiling point, knowing that the ambient temperature (about 20 ° C) may be suitable.
  • the pre-machined blank may be subjected to other machining operations to obtain a machined metal part, it being understood that the shape of the blank must be compatible with that of the intended machined part. Furthermore, the shape of said channels of the blank must be chosen so as to minimize the quenching deformation of the blank, and to optimize the mechanical characteristics of the final machined part. It is preferred that one of the two faces of the blank is flat. In this case, it is preferred that during horizontal quenching, the machined channels of the sheet be oriented downwards.
  • a length of between 50 mm and 1000 mm, and preferably between 50 mm and 500 mm at the beginning and at the end of the sheet does not include machined channels and has a substantially constant thickness (this part devoid of machined channels being called "heel"), to allow a proper grip of the traction jaws.
  • Said traction is advantageously carried out so as to lead to a permanent elongation of between 0.5% and 5%. A minimum value of greater than 1.0 or even greater than 1.5% is preferred for this permanent elongation.
  • said blank advantageously comprises between the heels and the central zone having machined channels a transition zone whose thickness decreases from the heel to the central zone having machined channels. It is advantageous for this heel and the transition zone to be trimmed after the controlled pull, either mechanically, for example by sawing or shearing, or by other known means such as the laser beam or the liquid jet. But it can also at least partially retain this heel, for example to facilitate the assembly of the structural elements.
  • the process according to the invention can advantageously be applied to sheet metal alloys with structural hardening, in particular aluminum alloys with structural hardening, and more particularly alloys of the series 2xxx, 6xxx and 7xxx.
  • the sheets comprise the following alloying elements (in mass%): Zn 5.5 - 11 Mg 1.5 - 3 Cu 1.0 - 3.0.
  • the zinc content is between 8 and 11%.
  • the alloy further comprises dispersoid-forming elements, i.e., one or more members selected from the group consisting of Zr, Sc, Hf, La, Ti, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Y, Yb, the content of each of said elements, if selected, being between 0.02 and 0.7%, and the total content of these elements not exceeding not, preferably, 2%.
  • the alloys of the 72xxx series the alloys 7449, 7349, 7049, 7050, 7055, 7040 and 7150 are particularly preferred.
  • the sheets are advantageously large, that is to say with a length greater than 2000 mm and preferably greater than 5000 mm, with a width greater than 600 mm and preferably greater than 1200 mm.
  • the manufacture of a structural element with integrated stiffeners for the wing of a large civil aircraft is used to make a thick sheet of aluminum alloy 7449 with a thickness of about 100 to 110 mm, leading to a pre-machined blank with a maximum thickness of the order of 90 to 100 mm.
  • a thick sheet of a thickness of the order of 30 to 60 mm is used for the manufacture of a stiffener skin component with integrated stiffener, leading to a pre-machined blank of a maximum thickness of the order of 25 to 55 mm.
  • the problem related to the gradients of the mechanical properties hardly arises below a thickness of about fifteen to twenty millimeters.
  • the advantages provided by the present invention are therefore important for thicknesses greater than about 30 to 40 mm, that is to say in particular for the manufacture of structural wing elements.
  • Machining operations to form the blank from the thick plate and to fabricate the finished part from the blank can be performed at high speed, i.e. with a speed of at least 5000 revolutions per minute, and preferably greater than 10,000 revolutions per minute.
  • the method according to the invention makes it possible to optimize the chips and falls generated during the machining. For this purpose, their mixing with other metallic or non-metallic materials, including other alloys of the same type, should be avoided.
  • the method according to the invention in order to be operated with a cost as low as possible, encourages that the machining is carried out in the factory of the manufacturer of the sheet or under its industrial control, and the availability of falls and chips , in particular in alloys 2xxx and 7xxx, perfectly identified and resulting from a known process, leads to the possibility of being able to recycle larger chip fractions in the manufacture of heavy plates in alloys 2xxx and 7xxx for aeronautical application.
  • the Applicant has thus been able to incorporate up to 40% of machining chips in the process according to the invention, by using methods of treatment of collected chips and liquid metal which are known to man of career. Incorporation of at least 5% of selectively collected chips has been found to be possible in almost all cases, and a level of at least 15% is preferred.
  • the metal parts obtained by the process according to the invention can be used as a structural element in the aeronautical construction.
  • the invention makes it possible to produce wing panels, fuselage elements, longitudinal members, ribs or central wing boxes.
  • the method according to the invention has many advantages over known methods. In particular, it allows the manufacture of parts with an improved compromise between damage tolerance and static mechanical characteristics. Those skilled in the art can adapt the metallurgical state of the pre-machined blank to the target properties of the finished part, to favor a gain in static mechanical characteristics or in damage tolerance, or to improve both types of characteristics at a time. By way of example, the Applicant has been possible to obtain with the 7449 alloy finished parts having a improvement of 20 to 25% of toughness K 1C, without any degradation of the static mechanical properties.
  • Block 3 has not been pre-machined.
  • the three blocks were dissolved for 4 hours at 472 ° C with a rise in temperature of 4 hours, and quenched by vertical immersion in stirred cold water, the ribs being oriented perpendicular to the surface of the water.
  • the blocks were then cut according to the cutting plane shown on the figure 2 .
  • Some of the specimens thus obtained were subjected to a 48 hour treatment at 120 ° C to put them in the T6 state.
  • Other specimens were subjected to controlled traction with a permanent elongation of 2%, and then to the same treatment of income as the other specimens, to put them in state T651.
  • the toughness in the pre-machined blank according to the invention increases by about 10 MPa ⁇ m with respect to a workpiece according to the prior art, which corresponds to a gain of about 20 to 25%, without any degradation. on static mechanical characteristics.
  • the sheet was put in solution and then quenched by vertical immersion in cold water stirred, the ribs being oriented parallel to the surface of the water.
  • the sheet was then subjected to controlled traction with a permanent elongation of 2% observed in the pre-machined zone and a zero elongation in the solid zones.
  • a block was then taken from the pre-machined area and a block in the non-machined area for characterization. Blanks were taken from the non-machined block and subjected to controlled pulling with a permanent elongation of 2 to 2.5%. Vickers hardness kinetics were used to determine the peak incomes that were made on the pre-machined part and the solid part (respectively 36h at 130 ° C and 24h at 130 ° C).
  • planar stress toughness K app (LT) in the pre-machined blank according to the invention increases by approximately 14 MPa ⁇ m with respect to a piece according to the prior art, which corresponds to a gain of approximately 20 to 25%, without any degradation on the static mechanical characteristics.
  • the plane stress toughness according to the LT orientation (K app (LT) ) in the pre-machined blank according to the invention increases between 8 and 18 MPa ⁇ m according to the income practiced with respect to a workpiece according to the art. previous, which corresponds to a gain of about 10 to 25%, without any degradation on static mechanical characteristics and exfoliation corrosion.

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Description

Domaine technique de l'inventionTechnical field of the invention

La présente invention concerne la fabrication d'éléments de structure en alliage à traitement thermique, notamment en alliage d'aluminium, par usinage de tôles épaisses. Ces éléments de structure peuvent être utilisés en construction aéronautique.The present invention relates to the manufacture of structural elements of heat-treated alloy, in particular aluminum alloy, by machining thick plates. These structural elements can be used in aeronautical construction.

Etat de la techniqueState of the art

Afin d'obtenir des éléments de structure d'avions caractérisés par une excellente tenue mécanique, on utilise actuellement principalement deux approches différentes :

  • Selon une première approche, on utilise des tôles d'épaisseur typiquement comprise entre 10 mm et 40 mm (appelée ici « tôle moyenne »), qui se trouvent dans l'état métallurgique correspondant à l'utilisation finale de l'élément structural, et les raidit en fixant, par exemple par rivetage, des raidisseurs constitués par des profilés filés, par exemple des profilés de section " T ".
  • Selon une seconde approche, on usine les raidisseurs directement dans une tôle d'une épaisseur plus importante, typiquement entre 30 mm et 200 mm, qui se trouve également dans un état métallurgique correspondant à l'utilisation finale de l'élément structural.
In order to obtain aircraft structural elements characterized by excellent mechanical strength, two different approaches are currently used:
  • According to a first approach, sheets of thickness typically between 10 mm and 40 mm (here called "medium sheet"), which are in the metallurgical state corresponding to the end use of the structural element, are used, and the stiffens by fixing, for example by riveting, stiffeners consisting of extruded profiles, for example section profiles "T".
  • According to a second approach, the stiffeners are machined directly into a sheet of greater thickness, typically between 30 mm and 200 mm, which is also in a metallurgical state corresponding to the end use of the structural element.

La réalisation d'un élément de structure par assemblage de tôles moyennes et de profilés nécessite un très grand nombre d'opérations de rivetage qui, effectuées dans les conditions de fiabilité nécessaires pour un élément structural aéronautique, représentent un coût important. La réalisation d'un élément structural intégré par usinage d'une tôle épaisse consomme certes beaucoup plus de métal, car une fraction importante de la tôle épaisse est réduite en copeaux, mais en contrepartie elle permet de réduire au minimum les opérations de rivetage qui coûtent cher.Achieving a structural element by assembling medium sheets and profiles requires a very large number of riveting operations which, performed under the necessary reliability conditions for an aeronautical structural element, represent a significant cost. The realization of an integrated structural element by machining a thick sheet consumes much more metal, because a large fraction of the sheet metal thick is reduced in chips, but in return it reduces to a minimum the riveting operations that are expensive.

La disponibilité de techniques d'usinage à grande vitesse (high speed machining), de l'ordre de 5 000 à 15 000 tours par minute, modifie sensiblement les données économiques du choix du mode de conception, car la durée de l'opération d'usinage se trouve fortement réduite, permettant en même temps d'envisager l'usinage de formes de plus en plus complexes dans des conditions économiquement accessibles. Ceci est vrai à la fois pour des pièces de taille de l'ordre du mètre, et pour des pièces de très grande taille, pouvant atteindre plus de 20 m de longueur et plus de 3 m de largeur.The availability of high speed machining techniques, of the order of 5,000 to 15,000 revolutions per minute, substantially modifies the economic data of the choice of design mode, because the duration of the operation of Machining is greatly reduced, allowing at the same time to consider the machining of more complex shapes in economically accessible conditions. This is true both for pieces of the order of one meter, and for very large pieces, up to more than 20 m in length and more than 3 m in width.

La seconde approche souffre toutefois d'autres inconvénients. La tôle épaisse se trouve avant usinage dans l'état métallurgique correspondant à son utilisation finale, car selon l'état de la technique, on n'effectue pas de traitement thermomécanique après usinage. Plus particulièrement, cet état métallurgique final a été obtenu par mise en solution et trempe. Or, deux mécanismes physiques limitent la vitesse de trempe dans une tôle épaisse : la conductivité thermique du matériau qui constitue ladite tôle épaisse, et l'échange thermique entre la surface et de la tôle et le milieu trempant. Il en résulte que les propriétés mécaniques de la tôle épaisse trempée varient en fonction de l'épaisseur. De ce fait, certaines caractéristiques mécaniques deviennent moins bonnes lorsque l'on s'éloigne de la surface de la tôle. Selon l'état de la technique, l'usinage enlève donc les zones dans lesquelles la tôle trempée montre les meilleures caractéristiques mécaniques, et la sollicitation de l'élément structural dans les conditions de service fait intervenir des zones de métal dont les propriétés mécaniques peuvent être assez variables en fonction de la profondeur par rapport à la zone proche de la surface initiale de la tôle. Le calcul des structures est, par précaution, effectué sur la base de modèles assez conservateurs des performances réelles de la pièce, lesdits modèles étant typiquement basés sur les caractéristiques mécaniques des zones de la tôle qui sont éloignées de la surface et présentent donc les caractéristiques mécaniques les plus faibles. Cela empêche, lors du dimensionnement des pièces, de tirer le meilleur parti des propriétés réelles du matériau. Un autre inconvénient de ce procédé selon l'état de la technique réside dans le fait que les tôles fortes trempées peuvent, même après traction contrôlée, enfermer des contraintes résiduelles qui entraînent une déformation des pièces lors de l'usinage. Selon une troisième approche, on fabrique des éléments structuraux avec raidisseurs intégrés directement par filage. Cette approche souffre de plusieurs inconvénients, et n'est guère utilisée. Afin d'obtenir des profilés de largeur suffisamment importante, il faut utiliser des presses à filer très puissantes dont le coût d'exploitation est très élevé. La largeur maximale que l'on peut ainsi atteindre reste bien inférieure à la largeur d'une tôle laminée habituelle. Par ailleurs, certains alliages se prêtent mal au filage. Et finalement, la microstructure d'une pièce filée, et plus particulièrement d'un profilé filé, n'est pas homogène, ni sur la section du profilé ni sur la longueur du profilé.The second approach, however, suffers from other disadvantages. The thick plate is before machining in the metallurgical state corresponding to its end use, because according to the state of the art, no thermomechanical treatment is carried out after machining. More particularly, this final metallurgical state was obtained by dissolving and quenching. However, two physical mechanisms limit the quenching speed in a thick plate: the thermal conductivity of the material which constitutes said thick plate, and the heat exchange between the surface and the sheet and the quenching medium. As a result, the mechanical properties of the quenched thick sheet vary depending on the thickness. As a result, certain mechanical characteristics become less good as one moves away from the surface of the sheet. According to the state of the art, the machining thus removes the areas in which the hardened sheet exhibits the best mechanical characteristics, and the loading of the structural element in the service conditions involves metal zones whose mechanical properties can be quite variable depending on the depth relative to the area near the initial surface of the sheet. The calculation of the structures is, as a precaution, carried out on the basis of rather conservative models of the real performances of the part, said models being typically based on the mechanical characteristics of the areas of the sheet which are distant from the surface and thus have the mechanical characteristics the weakest. This prevents, when sizing parts, to make the most of the real properties of the material. Another disadvantage of this method according to the state of the art lies in the fact that the hardened plates can, even after controlled pulling, enclose residual stresses which cause deformation of the parts during machining. According to a third approach, structural elements with integrated stiffeners are manufactured directly by spinning. This approach suffers from several disadvantages, and is hardly used. In order to obtain profiles of sufficiently large width, it is necessary to use very powerful spinning presses whose operating cost is very high. The maximum width that can thus be achieved remains well below the width of a conventional rolled sheet. In addition, some alloys do not lend themselves well to spinning. And finally, the microstructure of a spun part, and more particularly of a spun section, is not homogeneous, neither on the section of the profile nor on the length of the profile.

Divers moyens ont été proposés pour contrôler les distorsions du produit ou ses propriétés mécaniques.Various means have been proposed for controlling the distortions of the product or its mechanical properties.

Plusieurs brevets cherchent à optimiser le procédé de trempe afin de minimiser les déformations des produits métallurgiques lors de leur trempe. Ces procédés cherchent en général à compenser la déformation par un refroidissant inhomogène lors de la trempe.Several patents seek to optimize the quenching process in order to minimize the deformations of the metallurgical products during their quenching. These processes generally seek to compensate for the deformation by an inhomogeneous coolant during quenching.

Le brevet allemand DE 955 042 (Friedrichshütte Aktiengesellschaft) décrit un procédé de trempe horizontale dans lequel les bords de la tôle sont refroidis plus fortement que le centre, et la face inférieure plus fortement que la face supérieure.The German patent DE 955 042 (Friedrichshütte Aktiengesellschaft) describes a horizontal quenching process in which the edges of the sheet are cooled more strongly than the center, and the lower face more strongly than the upper face.

Le brevet EP 578 607 cherche à optimiser le procédé de trempe de profilés filés par un pilotage individuel ou groupé des buses de pulvérisation d'eau ; un tel dispositif, piloté par ordinateur, permet en principe d'adapter les positions des buses à chaque profilé, mais la mise au point reste empirique. Le brevet EP 695 590 développe une idée analogue pour la trempe de tôles.The patent EP 578 607 seeks to optimize the quenching process of extruded profiles by individual or group control of the water spray nozzles; such a device, controlled by computer, in principle allows to adjust the positions of the nozzles to each profile, but the focus remains empirical. The patent EP 695 590 develops a similar idea for sheet quenching.

La demande de brevet WO 98/42885 (Aluminum Company of America) décrit un procédé combiné de trempe à l'eau et de trempe à l'air pour diminuer la déformation des tôles minces à la trempe, et pour améliorer leurs caractéristiques mécaniques statiques.The patent application WO 98/42885 (Aluminum Company of America) describes a combined process of water quenching and air quenching to reduce the deformation of thin sheets during quenching, and to improve their static mechanical characteristics.

Le brevet français 1,503835 (Commissariat à l'Energie Atomique) propose d'augmenter la vitesse de trempe lors de l'immersion de la pièce dans un liquide froid par l'application d'une couche mince à faible conductivité thermique qui limite la vaporisation du milieu de trempe.French patent 1.503835 (Atomic Energy Commission) proposes to increase the quenching speed during the immersion of the piece in a cold liquid by the application of a thin layer with low thermal conductivity which limits the vaporization of the quenching medium.

Le brevet français 2 524 001 (Pechiney Rhenalu) propose d'appliquer sur certaines faces du produit un revêtement qui conduit la chaleur moins bien que le métal sous-jacent. Par ce contrôle amélioré de la vitesse de refroidissement, on serait capable d'éviter d'altérer les propriétés d'emploi du produit. Ce procédé assez lourd a plusieurs inconvénients. Il est limité aux tôles ou profilés d'épaisseur sensiblement constante ; dans le cas des alliages d'aluminium, cette épaisseur ne devrait pas dépasser environ 15 mm. Les revêtements proposés dans ce brevet risquent de polluer le réservoir de liquide de trempe.French patent 2,524,001 (Pechiney Rhenalu) proposes to apply on some sides of the product a coating that conducts heat less well than the underlying metal. By this improved control of the cooling rate, it would be possible to avoid altering the use properties of the product. This rather heavy process has several disadvantages. It is limited to sheets or profiles of substantially constant thickness; in the case of aluminum alloys, this thickness should not exceed about 15 mm. The coatings proposed in this patent may pollute the quench liquid reservoir.

D'autres approches cherchent à diminuer la sensibilité des alliages d'aluminium à la trempe.Other approaches seek to decrease the sensitivity of aluminum alloys to quenching.

Aucun de ces procédés ne résout le problème de la variation des propriétés mécaniques en fonction de l'épaisseur qui est liée aux gradients thermiques présentes lors de la trempe.None of these methods solves the problem of the variation of the mechanical properties as a function of the thickness which is related to the thermal gradients present during quenching.

Objet de l'inventionObject of the invention

L'invention a pour but de présenter un nouveau procédé de fabrication de pièces métalliques usinées aptes à servir comme éléments de structure, ou d'ébauches pour de telles pièces, qui permet d'améliorer le compromis entre les caractéristiques mécaniques statiques (limite d'élasticité, résistance à la traction, allongement à la rupture) et la tolérance aux dommages (notamment la ténacité) dans le volume de la pièce et de minimiser les distorsions induites lors de la trempe, et qui peut être mis en oeuvre avec un coût d'exploitation particulièrement avantageux.The aim of the invention is to present a new process for manufacturing machined metal parts that can serve as structural elements, or blanks for such parts, which makes it possible to improve the compromise between the static mechanical characteristics (limit of elasticity, tensile strength, elongation at break) and the tolerance to damage (especially toughness) in the volume of the workpiece and to minimize the distortions induced during quenching, and which can be implemented with a cost of particularly advantageous exploitation.

Au lieu de chercher à améliorer des étapes isolées des procédés de fabrication, la demanderesse a inventé un nouveau procédé intégré qui permet de fabriquer à partir de tôles épaisses des éléments de structure usinés de grande dimension, avec d'excellentes tolérances dimensionnelles, et présentant des caractéristiques mécaniques améliorées. La présente invention propose un procédé de fabrication nouveau qui permet d'obtenir des pièces usinées présentant un meilleur compromis entre les valeurs minimales des caractéristiques mécaniques statiques (limite conventionnelle d'élasticité, allongement à rupture, résistance à la traction) et la tolérance aux dommages, comparé à des pièces de forme analogues produites par un procédé selon l'état de la technique. Dans une variante du procédé selon l'invention, la variation des caractéristiques mécaniques au sein de la pièce est plus faible, par rapport à une pièce usinée de forme analogue élaborée par un procédé selon l'état de la technique.Instead of seeking to improve isolated steps of the manufacturing processes, the Applicant invented a new integrated process which makes it possible to manufacture from large plates machined structural elements of large size, with excellent dimensional tolerances, and having improved mechanical characteristics. The present invention proposes a new manufacturing process which makes it possible to obtain machined parts having a better compromise between the minimum values of the static mechanical characteristics (conventional yield strength, elongation at break, tensile strength) and the damage tolerance. , compared to similar shaped parts produced by a method according to the state of the art. In a variant of the method according to the invention, the variation of the mechanical characteristics within the part is smaller, compared to a machined part of similar form produced by a method according to the state of the art.

Un premier objet de l'invention est un procédé de fabrication d'une pièce métallique usinée, comportant

  1. a) la fabrication d'une tôle métallique par un procédé comportant
    • a1) la coulée d'une plaque de laminage, suivie éventuellement d'une homogénéisation,
    • a2) une ou plusieurs opérations de laminage à chaud ou à froid, éventuellement séparées d'une ou plusieurs opérations de réchauffage, pour obtenir une tôle,
    • a3) éventuellement une ou plusieurs opérations de découpe ou finition de la tôle,
  2. b) le préusinage de ladite tôle sur l'une ou les deux faces pour obtenir une ébauche préusinée,
  3. c) un traitement de mise en solution de ladite ébauche préusinée,
  4. d) un traitement de trempe.
A first subject of the invention is a method of manufacturing a machined metal part, comprising
  1. a) the manufacture of a metal sheet by a process comprising
    • a1) casting a rolling plate, optionally followed by homogenization,
    • a2) one or more hot or cold rolling operations, optionally separated from one or more reheating operations, to obtain a sheet,
    • a3) optionally one or more cutting or finishing operations of the sheet,
  2. b) pre-machining said sheet on one or both sides to obtain a pre-machined blank,
  3. c) a solution treatment of said pre-machined blank,
  4. d) quenching treatment.

Ce procédé peut être éventuellement suivi d'une ou plusieurs des étapes suivantes

  • e) traction contrôlée,
  • f) revenu,
  • g) découpe.
This process may possibly be followed by one or more of the following steps
  • e) controlled traction,
  • f) income,
  • g) cutting.

Un deuxième objet est l'utilisation d'une pièce métallique obtenue par ledit procédé comme élément de structure dans la construction aéronautique.A second object is the use of a metal part obtained by said method as structural element in the aeronautical construction.

Un troisième objet est un élément de structure en alliage d'aluminium pour construction aéronautique obtenu par ledit procédé.A third object is an aluminum alloy structural element for aeronautical construction obtained by said method.

Description des figuresDescription of figures

  • La figure 1 montre les dimensions et le plan d'échantillonnage de tôles épaisses préusinées selon l'invention, comme expliqué dans l'exemple 1.The figure 1 shows the dimensions and the sampling plan of pre-machined thick plates according to the invention, as explained in Example 1.
  • La figure 2 montre l'éprouvette utilisée pour la caractérisation des propriétés mécaniques du produit.The figure 2 shows the specimen used for the characterization of the mechanical properties of the product.
  • Les figures 3 et 4 montrent schématiquement une ébauche préusinée selon l'invention.The figures 3 and 4 schematically show a pre-machined blank according to the invention.
  • La figure 5 montre schématiquement la forme d'une tôle épaisse préusinée et le plan d'échantillonnage de tôles épaisses préusinées (fig. 5a) ou non (fig. 5b), comme expliqué dans l'exemple 2.The figure 5 schematically shows the shape of a pre-machined thick sheet and the sampling plan of pre-machined thick sheets ( Fig. 5a ) or not ( Fig. 5b ), as explained in Example 2.
  • La figure 6 montre schématiquement la forme d'une tôle épaisse préusinée et le plan d'échantillonnage de tôles épaisses préusinées (figure 6a) ou non (fig. 6b), comme expliqué dans l'exemple 3.The figure 6 schematically shows the shape of a pre-machined thick sheet and the sampling plan of pre-machined thick sheets ( figure 6a ) or not ( Fig. 6b ), as explained in Example 3.
Description détaillée de l'inventionDetailed description of the invention a) Terminologie a) Terminology

Sauf mention contraire, toutes les indications relatives à la composition chimique des alliages sont exprimées en pourcent massique. Par conséquent, dans une expression mathématique, « 0,4 Zn » signifie : 0,4 fois la teneur en zinc, exprimée en pourcent massique ; cela s'applique mutatis mutandis aux autres éléments chimiques. La désignation des alliages suit les règles de The Aluminum Association, connues de l'homme du métier. Les états métallurgiques sont définis dans la norme européenne EN 515. La composition chimique d'alliages d'aluminium normalisés est définie par exemple dans la norme EN 573-3. Sauf mention contraire, les caractéristiques mécaniques statiques, c'est-à-dire la résistance à la rupture Rm, la limite élastique Rp0,2, et l'allongement à la rupture A, sont déterminées par un essai de traction selon la norme EN 10002-1, l'endroit et le sens du prélèvement des éprouvettes étant définis dans la norme EN 485-1. La ténacité KIC a été mesurée selon la norme ASTM E 399. La courbe R est déterminée selon la norme ASTM 561-98. A partir de la courbe R, on calcule le facteur d'intensité de contrainte critique KC, c'est à dire le facteur d'intensité qui provoque l'instabilité de la fissure. On calcule également le facteur d'intensité de contrainte KCO, en affectant à la charge critique la longueur initiale de la fissure, au début du chargement monotone. Ces deux valeurs sont calculées pour une éprouvette de forme voulue. Kapp désigne le KCO correspondant à l'éprouvette ayant servi à faire le test de courbe R. La résistance à la corrosion exfoliante a été déterminée selon l'essai EXCO décrit dans la norme ASTM G34-72.Unless stated otherwise, all the information relating to the chemical composition of the alloys is expressed in percent by weight. Therefore, in a mathematical expression, "0.4 Zn" means: 0.4 times the zinc content, expressed in mass percent; this applies mutatis mutandis to other chemical elements. The designation of the alloys follows the rules of The Aluminum Association, known to those skilled in the art. The metallurgical states are defined in the European standard EN 515. The chemical composition of standardized aluminum alloys is defined for example in the standard EN 573-3. Unless otherwise stated, the static mechanical characteristics, i.e., the ultimate strength R m , the yield point R p0 , 2 , and the elongation at break A, are determined by a tensile test according to EN 10002-1 standard, the location and direction of specimen collection being defined in EN 485-1. The K IC toughness was measured according to ASTM E 399. The curve R is determined according to ASTM 561-98. From the curve R, the critical stress intensity factor K C is calculated, ie the intensity factor which causes the instability of the crack. The intensity factor of stress K CO , by assigning to the critical load the initial length of the crack at the beginning of the monotonic loading. These two values are calculated for a specimen of the desired shape. K app designates the K CO corresponding to the test specimen used for the R curve test. The resistance to exfoliating corrosion was determined according to the EXCO test described in the ASTM G34-72 standard.

Sauf mention contraire, les définitions de la norme européenne EN 12258-1 s'appliquent. Contrairement à la terminologie de cette norme EN 12258-1, on appelle ici « tôle mince » une tôle d'une épaisseur de dépassant pas 6 mm, « tôle moyenne » une tôle d'une épaisseur comprise entre 6 mm et environ 20 à 30 mm, et « tôle épaisse » une tôle d'une épaisseur typiquement supérieure à 30 mm.Unless otherwise stated, the definitions of the European standard EN 12258-1 apply. Contrary to the terminology of this standard EN 12258-1, here is called "thin sheet" a sheet with a thickness of not more than 6 mm, "medium sheet" a sheet with a thickness between 6 mm and about 20 to 30 mm, and "thick plate" a sheet of a thickness typically greater than 30 mm.

Le terme « usinage » comprend tout procédé d'enlèvement de matière tel que le tournage, le fraisage, le perçage, l'alésage, le taraudage, l'électroérosion, la rectification, le polissage.The term "machining" includes any material removal process such as turning, milling, drilling, reaming, tapping, EDM, grinding, polishing.

Le terme « élément de structure » se réfère à un élément utilisé en construction mécanique pour lequel les caractéristiques mécaniques statiques et / ou dynamiques ont une importance particulière pour la performance et l'intégrité de la structure, et pour lequel un calcul de la structure est généralement prescrit ou effectué. Il s'agit typiquement d'une pièce mécanique dont la défaillance est susceptible de mettre en danger la sécurité de ladite construction, de ses utilisateurs, des ses usagers ou d'autrui. Pour un avion, ces éléments de structure comprennent notamment les éléments qui composent le fuselage (tels que la peau de fuselage (fuselage skin en anglais), les raidisseurs ou lisses de fuselage (stringers), les cloisons étanches (bulkheads), les cadres de fuselage (circumferential frames), les ailes (tels que la peau de voilure (wing skin), les raidisseurs (stringers ou stiffeners), les nervures (ribs) et longerons (spars)) et l'empennage composé notamment de stabilisateurs horizontaux et verticaux (horizontal or vertical stabilisers), ainsi que les profilés de plancher (floor beams), les rails de sièges (seat tracks) et les portes.The term "structural element" refers to an element used in mechanical engineering for which the static and / or dynamic mechanical characteristics are of particular importance for the performance and integrity of the structure, and for which a calculation of the structure is usually prescribed or performed. It is typically a mechanical part whose failure is likely to endanger the safety of said construction, its users, its users or others. For an aircraft, these structural elements include the elements that make up the fuselage (such as fuselage skin (fuselage skin in English), stiffeners or stringers, bulkheads, fuselage (circumferential frames), wings (such as wing skin), stiffeners (stiffeners), ribs (ribs) and spars) and empennage including horizontal stabilizers and vertical stabilizers horizontal or vertical stabilizers, as well as floor beams, seat tracks and doors.

b) Description de l'invention et de quelques modes de réalisations particuliers (b) Description of the invention and some particular embodiments

Selon l'invention, le problème est résolu en trempant non pas la tôle épaisse dans laquelle sera ensuite usiné la pièce métallique visée, mais une ébauche déjà préusinée. Le préusinage peut conduire à une forme plus ou moins proche de la forme finale visée.According to the invention, the problem is solved by not soaking the thick plate in which the metal part referred to is then machined, but an already pre-machined blank. Pre-machining can lead to a form more or less close to the final form.

Dans une réalisation préférée de l'invention, cette ébauche préusinée présente un profil constitué par un ou plusieurs canaux. Ces canaux peuvent être parallèles au sens de laminage, mais d'autres orientations sont possibles, par exemple une orientation en diagonale. Si on envisage d'effectuer une traction après la trempe, ce profil est avantageusement parallèle au sens de laminage et sensiblement constant sur sa longueur, mais d'autres types de profils sont possibles.In a preferred embodiment of the invention, this pre-machined blank has a profile consisting of one or more channels. These channels may be parallel to the rolling direction, but other orientations are possible, for example a diagonal orientation. If it is envisaged to carry out a pull after quenching, this profile is advantageously parallel to the rolling direction and substantially constant over its length, but other types of profiles are possible.

Lors de la trempe, l'ébauche peut se trouver en position horizontale, en position verticale, ou en toute autre position. La trempe peut être réalisé par immersion dans un milieu trempant, par aspersion, ou par tout autre moyen approprié. Ledit milieu trempant peut être de l'eau ou un autre milieu tel que le glycol ; sa température peut être choisie entre son point de solidification et son point d'ébullition, sachant que la température ambiante (environ 20 °C) peut convenir.During quenching, the blank may be in a horizontal position, in a vertical position, or in any other position. The quenching may be carried out by immersion in a quenching medium, by spraying, or by any other appropriate means. Said quenching medium may be water or another medium such as glycol; its temperature can be chosen between its solidification point and its boiling point, knowing that the ambient temperature (about 20 ° C) may be suitable.

Le procédé selon l'invention comporte

  1. a) la fabrication d'une tôle métallique par un procédé comportant
    • a1) la coulée d'une plaque de laminage, suivie éventuellement d'une homogénéisation,
    • a2) une ou plusieurs opérations de laminage à chaud ou à froid, éventuellement séparées d'une ou plusieurs opérations de réchauffage, pour obtenir une tôle,
    • a3) éventuellement une ou plusieurs opérations de découpe ou finition de la tôle,
  2. b) le préusinage de ladite tôle sur l'une ou les deux faces pour obtenir une ébauche préusinée,
  3. c) un traitement de mise en solution de ladite ébauche préusinée,
  4. d) un traitement de trempe.
The process according to the invention comprises
  1. a) the manufacture of a metal sheet by a process comprising
    • a1) casting a rolling plate, optionally followed by homogenization,
    • a2) one or more hot or cold rolling operations, optionally separated from one or more reheating operations, to obtain a sheet,
    • a3) optionally one or more cutting or finishing operations of the sheet,
  2. b) pre-machining said sheet on one or both sides to obtain a pre-machined blank,
  3. c) a solution treatment of said pre-machined blank,
  4. d) quenching treatment.

L'ébauche ainsi obtenue peut être soumise à une ou plusieurs des étapes suivantes:

  • e) traction contrôlée,
  • f) revenu,
  • g) découpe.
The blank thus obtained may be subjected to one or more of the following steps:
  • e) controlled traction,
  • f) income,
  • g) cutting.

A l'issue de ce procédé représenté par les étapes a) à d), c'est-à-dire après la trempe, et avantageusement après la traction contrôlée (s'il y en a une) et apès le revenu (s'il y en a un), l'ébauche préusinée peut être soumise à d'autres opérations d'usinage pour obtenir une pièce métallique usinée, étant entendu que la forme de l'ébauche doit être compatible avec celle de la pièce usinée visée. Par ailleurs, la forme desdits canaux de l'ébauche doit être choisie de façon à minimiser la déformation à la trempe de l'ébauche, et à optimiser les caractéristiques mécaniques de la pièce usinée finale. Il est préféré qu'une des deux faces de l'ébauche soit plate. Dans ce cas, il est préféré que lors de la trempe horizontale, les canaux usinées de la tôle soient orientés vers le bas.At the end of this process represented by the steps a) to d), that is to say after quenching, and advantageously after the controlled pull (if there is one) and after the income (s) there is one), the pre-machined blank may be subjected to other machining operations to obtain a machined metal part, it being understood that the shape of the blank must be compatible with that of the intended machined part. Furthermore, the shape of said channels of the blank must be chosen so as to minimize the quenching deformation of the blank, and to optimize the mechanical characteristics of the final machined part. It is preferred that one of the two faces of the blank is flat. In this case, it is preferred that during horizontal quenching, the machined channels of the sheet be oriented downwards.

Dans la plupart des cas, il sera nécessaire de soumettre l'ébauche préusinée à une traction contrôlée. Pour ce faire, il est avantageux de prévoir lors du préusinage de l'ébauche qu'une longueur comprise entre 50 mm et 1000 mm, et préférentiellement comprise entre 50 mm et 500 mm en début et à la fin de la tôle ne comporte pas de canaux usinés et a une épaisseur sensiblement constante (cette partie dépourvue de canaux usinés étant appelée « talon »), afin de permettre une prise correcte des mors de traction. Ladite traction est avantageusement effectuée de façon à conduire à un allongement permanent compris entre 0,5 % et 5 %. On préfère une valeur minimale supérieure à 1,0 ou même supérieure à 1,5% pour cet allongement permanent. On peut maintenir, pendant au moins une partie de la durée de la traction, un appui transversal sur l'une au moins des faces de la tôle, par exemple par application d'un ou plusieurs rouleaux sur la tôle, lesdits rouleaux pouvant éventuellement être mobiles longitudinalement sur la face de la tôle. Cela est décrit, pour une tôle non usinée, dans le brevet US 6,216,521 de la demanderesse.In most cases, it will be necessary to subject the pre-prepared blank to a controlled pull. To do this, it is advantageous to provide during pre-machining of the blank that a length of between 50 mm and 1000 mm, and preferably between 50 mm and 500 mm at the beginning and at the end of the sheet does not include machined channels and has a substantially constant thickness (this part devoid of machined channels being called "heel"), to allow a proper grip of the traction jaws. Said traction is advantageously carried out so as to lead to a permanent elongation of between 0.5% and 5%. A minimum value of greater than 1.0 or even greater than 1.5% is preferred for this permanent elongation. It is possible to maintain, for at least a portion of the duration of the traction, a transversal support on at least one of the faces of the sheet, for example by applying one or more rollers to the sheet, said rollers possibly being movable longitudinally on the face of the sheet. This is described, for an unmachined sheet, in the patent US 6,216,521 of the plaintiff.

Dans un mode de réalisation préféré impliquant une traction contrôlée de l'ébauche, ladite ébauche comporte avantageusement entre les talons et la zone centrale possédant des canaux usinés une zone de transition dont l'épaisseur décroît du talon vers la zone centrale possédant des canaux usinés. Il est avantageux que ce talon ainsi que la zone de transition soient éboutés après la traction contrôlée, soit mécaniquement, par exemple par sciage ou cisaillage, soit par d'autres moyens connus tels que le faisceau laser ou le jet liquide. Mais on peut aussi conserver au moins partiellement ce talon, par exemple pour faciliter l'assemblage des éléments de structure.In a preferred embodiment involving controlled pulling of the blank, said blank advantageously comprises between the heels and the central zone having machined channels a transition zone whose thickness decreases from the heel to the central zone having machined channels. It is advantageous for this heel and the transition zone to be trimmed after the controlled pull, either mechanically, for example by sawing or shearing, or by other known means such as the laser beam or the liquid jet. But it can also at least partially retain this heel, for example to facilitate the assembly of the structural elements.

Le procédé selon l'invention peut être appliqué avantageusement aux tôles en alliages métalliques à durcissement structural, notamment aux alliages d'aluminium à durcissement structural, et plus particulièrement aux alliages des séries 2xxx, 6xxx et 7xxx. Dans un mode de réalisation particulier, les tôles comprennent les éléments d'alliage suivants (en % massiques) : Zn 5,5 - 11 Mg 1,5 - 3 Cu 1,0 - 3,0.The process according to the invention can advantageously be applied to sheet metal alloys with structural hardening, in particular aluminum alloys with structural hardening, and more particularly alloys of the series 2xxx, 6xxx and 7xxx. In a particular embodiment, the sheets comprise the following alloying elements (in mass%): Zn 5.5 - 11 Mg 1.5 - 3 Cu 1.0 - 3.0.

Dans une variante de ce mode de réalisation particulier, la teneur en zinc est comprise entre 8 et 11%. Dans d'autres variantes, l'alliage comprend en plus des éléments pouvant former des dispersoïdes, c'est-à-dire un ou plusieurs éléments sélectionnés dans le groupe composé de Zr, Sc, Hf, La, Ti, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Y, Yb, la teneur de chacun desdits éléments, s'il est sélectionné, étant comprise entre 0,02 et 0,7 %, et la teneur totale de ces éléments ne dépassant pas, de manière préférée, 2%. Parmi les alliages de la série 72xxx, les alliages 7449, 7349, 7049, 7050, 7055, 7040 et 7150 sont particulièrement préférés.In a variant of this particular embodiment, the zinc content is between 8 and 11%. In other embodiments, the alloy further comprises dispersoid-forming elements, i.e., one or more members selected from the group consisting of Zr, Sc, Hf, La, Ti, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Y, Yb, the content of each of said elements, if selected, being between 0.02 and 0.7%, and the total content of these elements not exceeding not, preferably, 2%. Among the alloys of the 72xxx series, the alloys 7449, 7349, 7049, 7050, 7055, 7040 and 7150 are particularly preferred.

Les tôles sont avantageusement de grande taille, c'est-à-dire d'une longueur supérieure à 2000 mm et préférentiellement supérieure à 5000 mm, d'une largeur supérieure à 600 mm et préférentiellement supérieure à 1200 mm. Elles ont avantageusement, avant usinage, une épaisseur supérieure à 15 mm, préférentiellement supérieure à 30 mm et encore plus préférentiellement supérieure à 50 mm.The sheets are advantageously large, that is to say with a length greater than 2000 mm and preferably greater than 5000 mm, with a width greater than 600 mm and preferably greater than 1200 mm. Advantageously, before machining, a thickness greater than 15 mm, preferably greater than 30 mm and even more preferably greater than 50 mm.

Dans un mode de réalisation avantageux, on utilise pour la fabrication d'un élément de structure à raidisseurs intégrés pour la voilure d'un avion civil de grande capacité une tôle épaisse en alliage d'aluminium 7449 d'une épaisseur de l'ordre de 100 à 110 mm, conduisant à une ébauche préusinée d'une épaisseur maximale de l'ordre de 90 à 100 mm.In an advantageous embodiment, the manufacture of a structural element with integrated stiffeners for the wing of a large civil aircraft is used to make a thick sheet of aluminum alloy 7449 with a thickness of about 100 to 110 mm, leading to a pre-machined blank with a maximum thickness of the order of 90 to 100 mm.

Dans un autre mode de réalisation avantageux, on utilise pour la fabrication d'un élément de structure pour peau de voilure à raidisseur intégrés une tôle épaisse d'une épaisseur de l'ordre de 30 à 60 mm, conduisant à une ébauche préusinée d'une épaisseur maximale de l'ordre de 25 à 55 mm.In another advantageous embodiment, a thick sheet of a thickness of the order of 30 to 60 mm is used for the manufacture of a stiffener skin component with integrated stiffener, leading to a pre-machined blank of a maximum thickness of the order of 25 to 55 mm.

Dans les alliages d'aluminium à traitement thermique, pour des épaisseurs faibles, le problème lié aux gradients des propriétés mécaniques ne se pose guère en dessous d'une épaisseur de quinze à vingt millimètres environ. Les avantages que procure la présente invention sont donc importants pour des épaisseurs supérieures à environ 30 à 40 mm, c'est-à-dire notamment pour la fabrication d'éléments structuraux de voilure.In heat-treated aluminum alloys, for small thicknesses, the problem related to the gradients of the mechanical properties hardly arises below a thickness of about fifteen to twenty millimeters. The advantages provided by the present invention are therefore important for thicknesses greater than about 30 to 40 mm, that is to say in particular for the manufacture of structural wing elements.

Les opérations d'usinage pour former l'ébauche à partir de la tôle épaisse et pour fabriquer la pièce finie à partir de l'ébauche peuvent être effectuées à grande vitesse, c'est-à-dire avec une vitesse d'au moins 5000 tours par minute, et préférentiellement supérieur à 10 000 tours par minute. Le procédé selon l'invention permet de valoriser au mieux les copeaux et chutes générés lors de l'usinage. A cette fin, il convient d'éviter leur mélange avec d'autres matériaux métalliques ou non-métalliques, y compris avec d'autres alliages du même type. A titre d'exemple, dans le cas des alliages d'aluminium, il n'est pas souhaitable de mélanger les alliages du groupe 2xxx avec ceux du groupe 7xxx (désignation selon EN 573-1), et à l'intérieur du groupe 7xxx par exemple, il est préférable de séparer les alliages tels que le 7449 et le 7010 ; ceci nécessite une gestion rigoureuse des copeaux que le fabricant de la tôle forte est mieux à même d'assurer qu'un atelier d'usinage multi-matériaux. Le procédé selon l'invention, pour pouvoir être exploité avec un coût aussi bas que possible, encourage à ce que l'usinage soit effectué dans l'usine du fabricant de la tôle ou sous son contrôle industriel, et la disponibilité de chutes et copeaux, notamment en alliages 2xxx et 7xxx, parfaitement identifiés et issus d'un procédé connu, conduit à la possibilité de pouvoir recycler des fractions plus importantes des copeaux dans la fabrication de tôles fortes en alliages 2xxx et 7xxx pour application aéronautique. Pour certains alliages et produits, la demanderesse a pu ainsi incorporer jusqu'à 40 % de copeaux d'usinage dans le procédé selon l'invention, en utilisant des méthodes de traitement des copeaux collectés et du métal liquide qui sont connus de l'homme du métier. L'incorporation d'au moins 5 % de copeaux sélectivement collectés s'est avérée possible dans pratiquement tous les cas, et un taux d'au moins 15 % est préféré.Machining operations to form the blank from the thick plate and to fabricate the finished part from the blank can be performed at high speed, i.e. with a speed of at least 5000 revolutions per minute, and preferably greater than 10,000 revolutions per minute. The method according to the invention makes it possible to optimize the chips and falls generated during the machining. For this purpose, their mixing with other metallic or non-metallic materials, including other alloys of the same type, should be avoided. By way of example, in the case of aluminum alloys, it is undesirable to mix the alloys of the 2xxx group with those of the 7xxx group (designation according to EN 573-1), and within the group 7xxx for example, it is preferable to separate alloys such as 7449 and 7010; this requires rigorous chip management that the sheet metal manufacturer is better able to ensure than a multi-material machine shop. The method according to the invention, in order to be operated with a cost as low as possible, encourages that the machining is carried out in the factory of the manufacturer of the sheet or under its industrial control, and the availability of falls and chips , in particular in alloys 2xxx and 7xxx, perfectly identified and resulting from a known process, leads to the possibility of being able to recycle larger chip fractions in the manufacture of heavy plates in alloys 2xxx and 7xxx for aeronautical application. For certain alloys and products, the Applicant has thus been able to incorporate up to 40% of machining chips in the process according to the invention, by using methods of treatment of collected chips and liquid metal which are known to man of career. Incorporation of at least 5% of selectively collected chips has been found to be possible in almost all cases, and a level of at least 15% is preferred.

Les pièces métalliques obtenues par le procédé selon l'invention peuvent être utilisées comme élément de structure dans la construction aéronautique. A titre d'exemple, l'invention permet de réaliser des panneaux de voilure, éléments de fuselage, longerons, nervures ou caissons centraux d'ailes.The metal parts obtained by the process according to the invention can be used as a structural element in the aeronautical construction. By way of example, the invention makes it possible to produce wing panels, fuselage elements, longitudinal members, ribs or central wing boxes.

Le procédé selon l'invention a de nombreux avantages par rapport aux procédés connus. Notamment, il permet la fabrication de pièces présentant un compromis amélioré entre la tolérance aux dommages et les caractéristiques mécaniques statiques. L'homme du métier peut adapter l'état métallurgique de l'ébauche préusinée aux propriétés visées de la pièce finie, pour privilégier un gain en caractéristiques mécaniques statiques ou en tolérance aux dommages, ou pour améliorer les deux types de caractéristiques à la fois. A titre d'exemple, la demanderesse a pu obtenir avec l'alliage 7449 des pièces finies présentant une amélioration de 20 à 25 % de la ténacité K1C, sans aucune dégradation des caractéristiques mécaniques statiques. De même, par rapport au Kapp(L-T) mesuré sur une tôle pleine à 1/8 d'épaisseur, on trouve sur une ébauche selon l'invention, mesuré entre au fond d'un canal à une profondeur d'environ 1/8 d'épaisseur, une amélioration d'environ 20 à 25%. Sur une tôle en alliage 7449, on a ainsi pu atteindre une valeur de Kapp(L-T) d'au moins 90 MPa√m, et même d'au moins 95 MPa√m (éprouvette de type CT avec W = 75 mm selon ASTM E561-98), avec des valeurs de Rm(L) mesurées en traction dépassant 550 MPa.The method according to the invention has many advantages over known methods. In particular, it allows the manufacture of parts with an improved compromise between damage tolerance and static mechanical characteristics. Those skilled in the art can adapt the metallurgical state of the pre-machined blank to the target properties of the finished part, to favor a gain in static mechanical characteristics or in damage tolerance, or to improve both types of characteristics at a time. By way of example, the Applicant has been possible to obtain with the 7449 alloy finished parts having a improvement of 20 to 25% of toughness K 1C, without any degradation of the static mechanical properties. Similarly, compared to the K app (LT) measured on a solid sheet 1/8 thick, found on a blank according to the invention, measured between the bottom of a channel to a depth of about 1 / 8 thick, an improvement of about 20 to 25%. On an alloy sheet 7449, it was thus possible to reach a value of K app (LT) of at least 90 MPa√m, and even of at least 95 MPa√m (CT type test specimen with W = 75 mm according to ASTM E561-98), with values of R m (L) measured in tension exceeding 550 MPa.

L'invention sera mieux comprise à l'aide des exemples, qui n'ont toutefois pas de caractère limitatif. Dans chacun de ces trois exemples, le repérage des échantillons est indépendant des autres, c'est-à-dire il n'y a pas de relation entre l'échantillon A de l'exemple 1, l'échantillon A de l'exemple 2, et l'échantillon A de l'exemple 3.The invention will be better understood with the aid of the examples, which are however not limiting in nature. In each of these three examples, the location of the samples is independent of the others, that is to say there is no relationship between the sample A of Example 1, the sample A of the example 2, and sample A of Example 3.

Exemple 1Example 1

Dans une tôle en alliage 7449 (composition : Zn 8,52 %, Cu 1,97 % , Mg 2,17 %, Zr 0,11 %, Si 0,05 %, Fe 0,09 %, Mn 0,03 %, Ti 0,03 %) d'une épaisseur de 101,6 mm brute de laminage à chaud, mais rivée et éboutée, on a découpé dans la pleine épaisseur trois blocs de dimension 600 mm (sens L) x 700 mm (sens TL). On a effectué un surfaçage symétrique de 10,5 mm pour obtenir des blocs d'une épaisseur de 80,5 mm.In a 7449 alloy sheet (composition: Zn 8.52%, Cu 1.97%, Mg 2.17%, Zr 0.11%, Si 0.05%, Fe 0.09%, Mn 0.03% , 0.03% Ti) with a thickness of 101.6 mm hot rolled, but riveted and trimmed, was cut in the full thickness three blocks of dimension 600 mm (L direction) x 700 mm (TL direction ). A 10.5 mm symmetrical surfacing was performed to obtain 80.5 mm thick blocks.

Après détourage des faces latérales, on a préusiné dans les blocs 1 et 2 des nervures selon la figure 1, avec les dimensions suivantes (voir Tableau 1) : Tableau 1 Repère (voir figure 1) Dimension Bloc 1 [mm] Dimension Bloc 2 [mm] (1) 692 672 (2) 80,5 80,5 (3) 164 184 (4) 50 30 (5) 20 30 After trimming the lateral faces, pre-machining in the blocks 1 and 2 of the ribs according to the figure 1 , with the following dimensions (see Table 1): Table 1 Landmark (see figure 1 ) Dimension Block 1 [mm] Dimension Block 2 [mm] (1) 692 672 (2) 80.5 80.5 (3) 164 184 (4) 50 30 (5) 20 30

Le bloc 3 n'a pas été préusiné.Block 3 has not been pre-machined.

Les trois blocs ont été mis en solution pendant 4 heures à 472 °C avec une montée en température de 4 heures, et trempés par immersion verticale dans de l'eau froide agitée, les nervures étant orientées perpendiculairement à la surface de l'eau.The three blocks were dissolved for 4 hours at 472 ° C with a rise in temperature of 4 hours, and quenched by vertical immersion in stirred cold water, the ribs being oriented perpendicular to the surface of the water.

On a ensuite découpé les blocs selon le plan de découpe montré sur la figure 2. Certaines des spécimens ainsi obtenus ont été soumis à un traitement de revenu de 48 h à 120 °C pour les mettre à l'état T6. D'autres spécimens ont été soumis à une traction contrôlée avec un allongement permanent de 2 %, et ensuite au même traitement de revenu que les autres spécimens, pour les mettre à l'état T651.The blocks were then cut according to the cutting plane shown on the figure 2 . Some of the specimens thus obtained were subjected to a 48 hour treatment at 120 ° C to put them in the T6 state. Other specimens were subjected to controlled traction with a permanent elongation of 2%, and then to the same treatment of income as the other specimens, to put them in state T651.

Ensuite, on a déterminé les caractéristiques mécaniques. Les résultats sont rassemblés dans le tableau 2. Tableau 2 Echantillon Etat Rm [MPa] Rp0.2 [MPa] A [%] KIC (T-L) [MPa√m] KIC (L-T) [MPa√m] A1 T6 622 570 10,7 32,1 (*) 31,8 (*) A2 T6 641 595 11,7 31,8 37,6 (*) A3 T6 599 548 12,0 B1 T651 614 593 12,4 25,6 29,8 B2 T651 647 617 12,4 29,1 37,3 C1 T6 585 535 15,0 36,7 (*) 34,9 (*) C2 T651 618 594 12,9 28,9 35,4 (*) H1 T6 593 538 7,7 H2 T6 633 584 7,3 H3 T6 597 542 8,3 H4 T6 580 527 11,0 D1 T6 621 570 11,3 28,9 (*) 36,2 (*) D2 T6 644 598 13,0 32,1 (*) 43,8 (*) D3 T6 600 548 13,0 26,4 32,8 E1 T651 614 594 11,9 27,3 35,2 (*) E2 T651 650 621 13,1 29,8 41,4 (*) F1 T6 592 539 14,3 29,0 (*) 36,8 (*) F2 T651 604 584 13,6 26,5 33,1 J1 T6 593 538 7,7 J2 T6 633 584 7,3 J3 T6 597 542 8,3 J4 T6 580 527 11,0 G1 T6 580 527 11,0 19,7 (*) 26,6 (*) G2 T6 597 542 8,3 19,2 (*) 25,1 (*) G3 T6 633 584 7,3 21,0 29,7 (*) G4 T6 593 538 7,7 19,8 (*) 22,8 (*) (*) valeurs de Kq au lieu de KIC. Then, the mechanical characteristics were determined. The results are collated in Table 2. Table 2 Sample State Rm [MPa] R p0.2 [MPa] AT [%] K IC (TL) [MPa√m] K IC (LT) [MPa√m] A1 T6 622 570 10.7 32,1 (*) 31,8 (*) A2 T6 641 595 11.7 31.8 37.6 (*) A3 T6 599 548 12.0 B1 T651 614 593 12.4 25.6 29.8 B2 T651 647 617 12.4 29.1 37.3 C1 T6 585 535 15.0 36.7 (*) 34.9 (*) C2 T651 618 594 12.9 28.9 35.4 (*) H1 T6 593 538 7.7 H2 T6 633 584 7.3 H3 T6 597 542 8.3 H4 T6 580 527 11.0 D1 T6 621 570 11.3 28.9 (*) 36.2 (*) D2 T6 644 598 13.0 32,1 (*) 43.8 (*) D3 T6 600 548 13.0 26.4 32.8 E1 T651 614 594 11.9 27.3 35,2 (*) E2 T651 650 621 13.1 29.8 41.4 (*) F1 T6 592 539 14.3 29.0 (*) 36.8 (*) F2 T651 604 584 13.6 26.5 33.1 J1 T6 593 538 7.7 J2 T6 633 584 7.3 J3 T6 597 542 8.3 J4 T6 580 527 11.0 G1 T6 580 527 11.0 19,7 (*) 26.6 (*) G2 T6 597 542 8.3 19,2 (*) 25,1 (*) G3 T6 633 584 7.3 21.0 29,7 (*) G4 T6 593 538 7.7 19,8 (*) 22,8 (*) (*) values of K q instead of K IC .

On constate que la ténacité dans l'ébauche préusinée selon l'invention augmente d'environ 10 MPa√m par rapport à une pièce selon l'art antérieur, ce qui correspond à un gain d'environ 20 à 25 %, sans aucune dégradation sur les caractéristiques mécaniques statiques.It is found that the toughness in the pre-machined blank according to the invention increases by about 10 MPa√m with respect to a workpiece according to the prior art, which corresponds to a gain of about 20 to 25%, without any degradation. on static mechanical characteristics.

Exemple 2Example 2

Dans une tôle en alliage 7050 (composition : Zn 6,2 %, Cu 2,1 % , Mg 2,2 %, Zr 0,09 %, Si 0,04 %, Fe 0,09 %, Mn 0,01 %, Ti 0,03 %) d'une épaisseur de 95 mm brute de laminage à chaud, mais rivée et éboutée, on a découpé dans la pleine épaisseur une tôle de dimensions 8945 mm (sens L) x 1870 mm (sens TL). On a effectué un surfaçage symétrique de 2,5 mm pour obtenir une tôle d'une épaisseur de 90 mm. On a alors usiné des nervures dans le sens L sur une longueur de 7705 mm (repère 15) centrée dans la tôle laissant une zone pleine (repères 16 et 17) à chaque extrémité (voir Figure 3). La géométrie de la section pré-usinée est décrite dans la figure 4, avec les dimensions indiquées dans le Tableau 3. Tableau 3 Repère (voir figure 4) Dimension [mm] (1) 1870 (2) 90 (3) 140 (4) 50 (5) 25 In a 7050 alloy sheet (composition: Zn 6.2%, Cu 2.1%, Mg 2.2%, Zr 0.09%, Si 0.04%, Fe 0.09%, Mn 0.01% , 0.03% Ti) with a thickness of 95 mm gross Hot rolling, but riveted and trimmed, was cut in the full thickness a sheet of dimensions 8945 mm (L direction) x 1870 mm (TL direction). A 2.5 mm symmetrical surfacing was performed to obtain a 90 mm thick sheet. We then machined ribs in the direction L over a length of 7705 mm (mark 15) centered in the sheet leaving a solid zone (marks 16 and 17) at each end (see Figure 3 ). The geometry of the pre-machined section is described in figure 4 , with the dimensions shown in Table 3. Table 3 Landmark (see figure 4 ) Dimension [mm] (1) 1870 (2) 90 (3) 140 (4) 50 (5) 25

La tôle a été mise en solution et puis trempée par immersion verticale dans de l'eau froide agitée, les nervures étant orientées parallèlement à la surface de l'eau. La tôle a alors été soumise à une traction contrôlée avec un allongement permanent de 2 % observé dans la zone pré-usiné et un allongement nul dans les zones pleines. On a ensuite prélevé un bloc dans la zone pré-usinée ainsi qu'un bloc dans la zone non-usinée pour caractérisation. Des ébauches ont été prélevées dans le bloc non-usiné et soumises à une traction contrôlée avec un allongement permanent de 2 à 2.5%. Une cinétique de revenu par mesure de dureté Vickers a permis de déterminer les revenus au pic qui ont été pratiqués sur la partie pré-usinée et la partie pleine (respectivement 36h à 130°C et 24h à 130°C). Des prélèvements ont été pris selon le plan de découpe de la Figure 5. Les caractéristiques mécaniques obtenues dans le voile du pré-usiné et dans la tôle pleine sont répertoriées dans le tableau 4. Le Kapp a été mesuré sur des éprouvettes de type CT avec un W égal à 75 mm (selon ASTM E561-98). Tableau 4 Echantillon Rp0.2(L) [MPa] (*) Rp0.2(L) [MPa] (**) Rm(L) [MPa] (**) A[%] (L) (**) Kapp (L-T) [MPa√m] Kapp(T-L) [MPa√m] A 514 551 17.4 B 82.9 64.2 C 82.5 65 D 506 514 553 17.6 E 524 547 591 13.8 F 493 545 592 12.5 G 67.9 58.7 (*) valeur déterminée en compression (**) valeur déterminée en traction The sheet was put in solution and then quenched by vertical immersion in cold water stirred, the ribs being oriented parallel to the surface of the water. The sheet was then subjected to controlled traction with a permanent elongation of 2% observed in the pre-machined zone and a zero elongation in the solid zones. A block was then taken from the pre-machined area and a block in the non-machined area for characterization. Blanks were taken from the non-machined block and subjected to controlled pulling with a permanent elongation of 2 to 2.5%. Vickers hardness kinetics were used to determine the peak incomes that were made on the pre-machined part and the solid part (respectively 36h at 130 ° C and 24h at 130 ° C). Samples were taken according to the cutting plan of the Figure 5 . The mechanical characteristics obtained in the pre-machined web and in the solid sheet are listed in Table 4. The K app was measured on CT type specimens with a W equal to 75 mm (according to ASTM E561-98). Table 4 Sample Rp 0.2 (L) [MPa] (*) R p0 . 2 (L) [MPa] (**) R m (L) [MPa] (**) A [%] (L) (**) K app (LT) [MPa√m] K app (TL) [MPa√m] AT 514 551 17.4 B 82.9 64.2 VS 82.5 65 D 506 514 553 17.6 E 524 547 591 13.8 F 493 545 592 12.5 BOY WUT 67.9 58.7 (*) value determined in compression (**) value determined in traction

On constate que la ténacité en contrainte plane Kapp (L-T) dans l'ébauche préusinée selon l'invention augmente d'environ 14 MPa√m par rapport à une pièce selon l'art antérieur, ce qui correspond à un gain d'environ 20 à 25 %, sans aucune dégradation sur les caractéristiques mécaniques statiques.It can be seen that the planar stress toughness K app (LT) in the pre-machined blank according to the invention increases by approximately 14 MPa√m with respect to a piece according to the prior art, which corresponds to a gain of approximately 20 to 25%, without any degradation on the static mechanical characteristics.

Exemple 3Example 3

Dans une tôle en alliage 7449 (composition : Zn 8,8 %, Cu 1,8 % , Mg 1,8 %, Zr 0,12 %, Si 0,04 %, Fe 0,06 %, Mn 0,01 %, Ti 0,03 %) d'une épaisseur de 90 mm brute de laminage à chaud, mais rivée et éboutée, on a découpé dans la pleine épaisseur une tôle de dimensions 9950 mm (sens L) x 2000 mm (sens TL). Cette tôle a été découpée dans la longueur (sens L) de façon à obtenir une première tôle de dimensions 9950 mm (sens L) x 775 mm (sens TL) et une seconde tôle de dimensions 9950 mm (sens L) x 1225 mm (sens TL). Pour cette seconde tôle, on a alors usiné des nervures dans le sens L sur une longueur de 8400 mm centré dans la tôle laissant une zone pleine à chaque extrémité (voir Figure 3). La géométrie de la section pré-usinée est décrite dans la Figure 4, avec les dimensions indiquées dans le Tableau 3. Tableau 5 Repère (voir figure 4) Dimension [mm] (1) 1275 (2) 90 (3) 122 (4) 32 (5) 16 In a sheet of alloy 7449 (composition: Zn 8.8%, Cu 1.8%, Mg 1.8%, Zr 0.12%, Si 0.04%, Fe 0.06%, Mn 0.01% , 0.03% Ti) of a thickness of 90 mm hot rolling mill, but riveted and trimmed, was cut in the full thickness a sheet of dimensions 9950 mm (L direction) x 2000 mm (TL direction). This sheet was cut in length (direction L) so as to obtain a first sheet of dimensions 9950 mm (L direction) x 775 mm (TL direction) and a second sheet of dimensions 9950 mm (L direction) x 1225 mm ( TL sense). For this second sheet, we then machined ribs in the direction L over a length of 8400 mm centered in the sheet leaving a solid zone at each end (see Figure 3 ). The geometry of the pre-machined section is described in Figure 4 , with the dimensions shown in Table 3. Table 5 Landmark (see figure 4 ) Dimension [mm] (1) 1275 (2) 90 (3) 122 (4) 32 (5) 16

La tôle de pleine épaisseur et la tôle pré-usinée ont été mises en solution puis trempées par immersion verticale dans de l'eau froide agitée, les nervures étant orientées parallèlement à la surface de l'eau. Les deux tôles ont alors été soumises à une traction contrôlée avec un allongement permanent de 2 à 2.5 % (observé dans la zone pré-usiné pour la tôle pré-usinée). On a ensuite prélevé un bloc dans la tôle pré-usinée ainsi qu'un bloc dans la tôle de pleine épaisseur pour caractérisation. Des prélèvements ont été pris selon le plan de découpe de la Figure 6. Plusieurs revenus ont été appliqués afin d'évaluer les gains liés au pré-usinage. Les caractérisations effectuées dans le voile du pré-usiné et à 1/8 d'épaisseur sous la surface de la tôle pleine sont répertoriées dans le tableau 6. Tableau 6 Echantillon Etat Rp0.2(L) [MPa] (*) Rp0.2(L) [MPa] (**), Pm(L) [MPa] (**) A (L) [%] (**) Kapp(L-T) [MPa√m] EXCO A1 T651 551 564 598 18.0 93.7 EA A2 T7951 566 564 580 14.8 91.5 EA A3 T7651 528 534 558 16.5 95.0 EA B1 T651 545 552 581 16.7 77.7 EB B2 T7951 553 561 571 13.7 83.9 EA B3 T7651 524 535 556 15.0 77.6 EA (*) valeur déterminée en compression (**) valeur déterminée en traction The full thickness sheet and the pre-machined sheet were dissolved and then quenched by vertical immersion in cold chilled water, the ribs being oriented parallel to the surface of the water. The two sheets were then subjected to controlled traction with a permanent elongation of 2 to 2.5% (observed in the pre-machined zone for the pre-machined sheet). A block was then taken from the pre-machined sheet and a block from the full thickness plate for characterization. Samples were taken according to the cutting plan of the Figure 6 . Several revenues were applied to evaluate the gains related to pre-machining. The characterizations made in the pre-machined web and 1/8 of thickness under the surface of the solid sheet are listed in Table 6. Table 6 Sample State R p0 . 2 (L) [MPa] (*) R p0.2 (L) [MPa] (**), P m (L) [MPa] (**) A (L) [%] (**) K app (LT) [MPa√m] EXCO A1 T651 551 564 598 18.0 93.7 EA A2 T7951 566 564 580 14.8 91.5 EA A3 T7651 528 534 558 16.5 95.0 EA B1 T651 545 552 581 16.7 77.7 EB B2 T7951 553 561 571 13.7 83.9 EA B3 T7651 524 535 556 15.0 77.6 EA (*) value determined in compression (**) value determined in traction

La même éprouvette que celle décrite dans l'exemple 2 a été utilisée pour les mesures de ténacité.The same specimen as described in Example 2 was used for the toughness measurements.

On constate que la ténacité en contrainte plane selon l'orientation L-T (Kapp (L-T)) dans l'ébauche préusinée selon l'invention augmente entre 8 et 18 MPa√m selon le revenu pratiqué par rapport à une pièce selon l'art antérieur, ce qui correspond à un gain d'environ 10 à 25 %, sans aucune dégradation sur les caractéristiques mécaniques statiques et la corrosion exfoliante.It can be seen that the plane stress toughness according to the LT orientation (K app (LT) ) in the pre-machined blank according to the invention increases between 8 and 18 MPa√m according to the income practiced with respect to a workpiece according to the art. previous, which corresponds to a gain of about 10 to 25%, without any degradation on static mechanical characteristics and exfoliation corrosion.

Claims (27)

  1. Process for manufacturing a machined metal part comprising:
    a) manufacturing of a metal plate made of an alloy subjected to a heat treatment, using a method consisting of:
    a1) casting of a rolling plate, possibly followed by homogenisation,
    a2) one or several hot or cold rolling operations,
    possibly separated by one or several heating operations, to make a plate,
    a3) possibly one or several plate cutting or finishing operations,
    b) pre-machining of the said plate on one or two faces to obtain a premachined blank
    c) solution heat treatment of the said premachined blank
    d) a hardening treatment.
  2. Process according to claim 1, also comprising one or more of the following steps after the hardening treatment:
    e) controlled stretch;
    f) ageing treatment;
    g) cutting.
  3. Process according to claim 1, characterised in that the plate is made of an aluminium alloy.
  4. Process according to claim 3, characterised in that the aluminium alloy is an alloy in the 2xxx, 6xxx or 7xxx series.
  5. Process according to any one of claims 1 to 3, characterised in that the zinc content in the alloy is between 5.5 and 11% (and preferably at least 8%) (by unit mass), the magnesium content is between 1.5 and 3% and the copper content is between 1.0 and 3.0.
  6. Process according to any one of claims 1 to 5, characterised in that the profile is composed of one or several channels parallel to the rolling direction.
  7. Process according to claim 6, characterised in that the profile is approximately constant over its length.
  8. Process according to any one of claims 1 to 7, characterised in that machining is done at a speed of at least 5000 revolutions per minute, and preferably more than 10 000 revolutions per minute.
  9. Process according to any one of claims 1 to 8, characterised in that the part obtained is subjected to one or several new machining or drilling operations after hardening or after controlled stretch.
  10. Process according to any one of claims 1 to 9, characterised in that controlled stretch is applied to create a permanent elongation between 0.5% and 5%.
  11. Process according to any one of claims 1 to 10, characterised in that cutting is done mechanically by shearing or sawing, or by laser beam or a liquid jet.
  12. Process according to any one of claims 1 to 11, characterised in that the melt is composed of at least 5% and preferably of at least 15% of machining chips.
  13. Process according to any one of claims 1 to 12, characterised in that a length of between 50 mm and 1000 mm, and preferably between 50 mm and 500 mm at the beginning and at the end of the plate, has no profile and has an approximately constant thickness.
  14. Process according to claim 13, characterised in that the plate comprises a transition area between the heels without any machined channels and the central area with machined channels, the thickness of the transition area decreases from the heel without any machined channels towards the central area with machined channels.
  15. Process according to any one of claims 1 to 14, characterised in that the plate width is greater than 60 cm and preferably greater than 120 cm.
  16. Process according to any one of claims 1 to 15, characterised in that the plate length is greater than 200 cm and preferably greater than 500 cm.
  17. Process according to any one of claims 1 to 16, characterised in that the plate thickness is greater than 15 mm and preferably greater than 30 mm before machining.
  18. Process according to any one of claims 1 to 17, characterised in that the ends of the unmachined heel and the transition area are cropped after the controlled stretch has been applied.
  19. Process according to any one of claims 1 to 18, characterised in that the controlled stretch is applied using two jaws to create a permanent controlled elongation of more than 0.5% and preferably more than 1%, and a transverse pressure is applied on at least one of the faces of the plate during at least part of the stretch duration.
  20. Process according to claim 19, characterised in that the permanent elongation is greater than 1.5%.
  21. Process according to either claim 19 or 20, characterised in that the bearing force on the face(s) of the plate is applied by one or several rolls pressed onto the plate.
  22. Process according to claim 21, characterised in that the rolls are free to move longitudinally on the face of the plate.
  23. Machined metal part that can be obtained using the process according to any one of claims 1 to 22.
  24. Machined metal part according to claim 23, characterised in that the said plate is made from a 7449 alloy and has the following values in the bottom of a machined channel:
    - a Kapp(L-T) value equal to 90 MPa√m, and preferably even 95 MPa√m (CT type sample with W = 75 mm according to ASTM E561-98), and
    - and an Rm(L) value measured in tension exceeding 550 MPa.
  25. Metal part that can be obtained using the process according to any one of claims 1 to 22 and used as a structural member in aeronautics.
  26. Metal part made from an aluminium alloy that can be obtained using the process according to any one of claims 1 to 22, and used as a wing panel, a fuselage element, a spar, a rib or a central wing box.
  27. Aluminium alloy structural member for aeronautics, that can be obtained using the process according to any one of claims 1 to 22.
EP03813619A 2002-12-17 2003-12-17 Method for making structural elements by machining thick plates Expired - Lifetime EP1573080B1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FR0215997 2002-12-17
FR0215997A FR2848480B1 (en) 2002-12-17 2002-12-17 METHOD OF MANUFACTURING STRUCTURAL ELEMENTS BY MACHINING THICK TOLES
US44699303P 2003-02-13 2003-02-13
US446993P 2003-02-13
PCT/FR2003/003753 WO2004056501A2 (en) 2002-12-17 2003-12-17 Method for making structural elements by machining thick plates

Publications (2)

Publication Number Publication Date
EP1573080A2 EP1573080A2 (en) 2005-09-14
EP1573080B1 true EP1573080B1 (en) 2010-10-27

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EP03813619A Expired - Lifetime EP1573080B1 (en) 2002-12-17 2003-12-17 Method for making structural elements by machining thick plates

Country Status (7)

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EP (1) EP1573080B1 (en)
JP (1) JP2006510808A (en)
AU (1) AU2003300632A1 (en)
BR (1) BR0317336B1 (en)
CA (1) CA2508534C (en)
RU (1) RU2341585C2 (en)
WO (1) WO2004056501A2 (en)

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FR2900160B1 (en) * 2006-04-21 2008-05-30 Alcan Rhenalu Sa METHOD FOR MANUFACTURING A STRUCTURAL ELEMENT FOR AERONAUTICAL CONSTRUCTION COMPRISING A DIFFERENTIAL NUT
MX2008016076A (en) * 2006-06-30 2009-01-15 Alcan Rolled Products Ravenswood Llc High strength, heat treatable al-zn-mg aluminium alloy.
US9314826B2 (en) 2009-01-16 2016-04-19 Aleris Rolled Products Germany Gmbh Method for the manufacture of an aluminium alloy plate product having low levels of residual stress
CN102282284A (en) * 2009-01-16 2011-12-14 阿勒里斯铝业科布伦茨有限公司 Method for the manufacture of an aluminium alloy plate product having low levels of residual stress
CN102179422B (en) * 2010-12-29 2013-03-27 山东华盛荣镁业科技有限公司 Method for preparing metal plane plate
CN102303064A (en) * 2011-09-13 2012-01-04 王辉 Trapezoidal teeth dual-roller extrusion steel plate forming machine device
FR2997706B1 (en) * 2012-11-08 2014-11-07 Constellium France METHOD FOR MANUFACTURING A VARIABLE THICKNESS STRUCTURE ELEMENT FOR AERONAUTICAL CONSTRUCTION
JP6093192B2 (en) * 2013-01-25 2017-03-08 三菱航空機株式会社 Aircraft fuselage panel, aircraft wing
KR102055051B1 (en) 2015-05-08 2019-12-11 노벨리스 인크. Impact Heat Treatment of Aluminum Alloy Articles
RU2621499C2 (en) * 2015-11-17 2017-06-06 Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский технологический университет "МИСиС" Method for producing castings of high-strength aluminium-based alloys
WO2018075353A1 (en) 2016-10-17 2018-04-26 Novelis Inc. Metal sheet with tailored properties
FR3059578B1 (en) 2016-12-07 2019-06-28 Constellium Issoire METHOD FOR MANUFACTURING A STRUCTURE ELEMENT
MX2021010324A (en) * 2019-06-03 2021-09-28 Novelis Inc Ultra-high strength aluminum alloy products and methods of making the same.
RU2771167C1 (en) * 2021-06-10 2022-04-27 Акционерное общество "Государственный Рязанский приборный завод" (АО "ГРПЗ") Method for manufacturing an aluminum wrought alloy casing

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JPH086160B2 (en) * 1987-10-28 1996-01-24 日産自動車株式会社 Method for manufacturing conical tubular member
JP2510729B2 (en) * 1989-07-12 1996-06-26 日産自動車株式会社 Method for manufacturing heat-treatable aluminum alloy member
JPH083139B2 (en) * 1990-11-22 1996-01-17 日本鋼管株式会社 Method for manufacturing thick and complex heat-treating aluminum alloy member
FR2744136B1 (en) * 1996-01-25 1998-03-06 Pechiney Rhenalu THICK ALZNMGCU ALLOY PRODUCTS WITH IMPROVED PROPERTIES
JPH10298692A (en) * 1997-04-22 1998-11-10 Sky Alum Co Ltd Frame-shaped member with high strength and high precision, and its production
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FR2802946B1 (en) * 1999-12-28 2002-02-15 Pechiney Rhenalu AL-CU-MG ALLOY AIRCRAFT STRUCTURAL ELEMENT

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RU2341585C2 (en) 2008-12-20
WO2004056501A3 (en) 2004-08-19
AU2003300632A8 (en) 2004-07-14
JP2006510808A (en) 2006-03-30
AU2003300632A1 (en) 2004-07-14
EP1573080A2 (en) 2005-09-14
WO2004056501A2 (en) 2004-07-08
BR0317336A (en) 2005-11-08
RU2005122471A (en) 2006-02-10
CA2508534C (en) 2011-06-21
BR0317336B1 (en) 2013-07-09
CA2508534A1 (en) 2004-07-08

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