EP2984195A1 - Method for transforming al-cu-li alloy sheets improving formability and corrosion resistance - Google Patents

Method for transforming al-cu-li alloy sheets improving formability and corrosion resistance

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Publication number
EP2984195A1
EP2984195A1 EP14721432.4A EP14721432A EP2984195A1 EP 2984195 A1 EP2984195 A1 EP 2984195A1 EP 14721432 A EP14721432 A EP 14721432A EP 2984195 A1 EP2984195 A1 EP 2984195A1
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EP
European Patent Office
Prior art keywords
weight
sheet
mpa
heat treatment
astm
Prior art date
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Granted
Application number
EP14721432.4A
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German (de)
French (fr)
Other versions
EP2984195B1 (en
Inventor
Christophe Sigli
Bernard Bes
Frank Eberl
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Constellium Issoire SAS
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Constellium Issoire SAS
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Publication of EP2984195A1 publication Critical patent/EP2984195A1/en
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Publication of EP2984195B1 publication Critical patent/EP2984195B1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/18—Alloys based on aluminium with copper as the next major constituent with zinc
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/005—Casting ingots, e.g. from ferrous metals from non-ferrous metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/14—Alloys based on aluminium with copper as the next major constituent with silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
    • 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

Definitions

  • the invention relates to aluminum-copper-lithium alloy products, more particularly, such products, their manufacturing and use processes, intended in particular for aeronautical and aerospace construction.
  • Aluminum alloy rolled products are developed to produce high strength parts for the aerospace industry and the aerospace industry in particular.
  • Aluminum alloys containing lithium are very interesting in this respect, since lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added.
  • No. 5,032,359 discloses a broad family of aluminum-copper-lithium alloys in which the addition of magnesium and silver, in particular between 0.3 and 0.5 percent by weight, makes it possible to increase the mechanical strength.
  • US Pat. No. 7,438,772 describes alloys comprising, in percentage by weight, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9.
  • US Pat. No. 7,229,509 describes an alloy comprising (% by weight): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0, 2-0.8) Ag, (0.2-0.8) Mn, 0.4 max Zr or other grain refining agents such as Cr, Ti, Hf, Se, V.
  • US patent application 2009/142222 A1 discloses alloys comprising (in% by weight), 3.4 to 4.2% Cu, 0.9 to 1.4% Li, 0.3 to 0.7% of Ag, 0.1 to 0.6% Mg, 0.2 to 0.8% Zn, 0.1 to 0.6% Mn and 0.01 to 0.6% of at least one element. for the control of the granular structure. This application also describes a process for manufacturing spun products.
  • Patent EP 1,966,402 describes a non-zirconium-containing alloy intended for fuselage sheets of essentially recrystallized structure comprising (in% by weight) (2.1%).
  • EP 1, 891, 247 discloses an alloy for fuselage plates comprising (in% by weight) (3.0-3.4) Cu, (0.8-1.2) Li, (0.2-0.2). , 6) Mg, (0.2-0.5) Ag and at least one of Zr, Mn, Cr, Se, Hf and Ti, wherein the Cu and Li contents are Cu + 5 / Li ⁇ 5.2.
  • This variant is used in particular when the targeted shaping is too important to be performed in a single operation from a state W, but can however be performed in two passes from a state O.
  • the plates in the state O being stable in time are easier to transform.
  • the manufacture of the sheet in the O state involves a final annealing of the raw rolling sheet, and therefore generally an additional manufacturing step, and also a dissolution and quenching of the product formed which is contrary the aim of simplification aimed at by the present invention.
  • the shaping of complex structural elements in the T8 state is limited to cases of small shaping because the elongation and the ratio R m / R p0 , 2 are too low in this state.
  • the sheets that are delivered to the aircraft manufacturer can be stored for a sometimes significant period before being shaped and to incur an income. he It should therefore be avoided that these sheets are susceptible to corrosion, in particular to simplify the storage conditions.
  • a first object of the invention is a process for manufacturing a laminated product based on aluminum alloy, in particular for the aeronautical industry in which, successively
  • an aluminum-based liquid metal bath comprising 2.1 to 3.9% by weight of Cu, 0.6 to 2.0% by weight of Li, 0.1 to 1.0% by weight of Mg, 0 to 0.6% by weight of Ag, 0 to 1% by weight of Zn, at most 0.20% by weight of the sum of Fe and Si, at least one element selected from Zr, Mn , Cr, Se, Hf and Ti, the amount of said element, if selected, being 0.05 to 0.18% by weight for Zr, 0.1 to 0.6% by weight for Mn, 0.05 0.3% by weight for Cr, 0.02 to 0.2% by weight for Se, 0.05 to 0.5% by weight for Hf and from 0.01 to 0.15% by weight for Ti, the other elements not more than 0.05% by weight each and 0.15% by weight in total, the balance aluminum;
  • said laminating plate is hot-rolled and optionally cold-rolled to a sheet thickness of between 0.5 and 10 mm,
  • f) optionally planing is carried out and / or controlled traction said sheet with a cumulative deformation of at least 0.5% and less than 3%
  • a short heat treatment is carried out in which said sheet reaches a temperature of between 145 ° C. and 175 ° C. and preferably between 150 ° C. and 170 ° C. for 0.1 to 45 minutes and preferably for 0.5 to 5 minutes, the heating rate being between 3 and 600 ° C / min.
  • Another subject of the invention is a laminated product obtainable by the process according to the invention having a yield strength R p0 , 2 (L) and / or R p oj2 (LT) of between 75% and 90%, preferably between 80 and 85% and preferably between 81% and 84% of the yield strength in the same direction of a sheet of the same composition in the T4 or T3 state having undergone the same controlled traction after quenching, at least one property selected from a ratio R m / R p0j2 (L) of at least 1.40 and preferably at least 1.45 and a ratio Rm / Rpo, 2 (LT) of at least 1.45 and preferably at least 1.50 and exhibits at least one corrosion resistance property chosen from a rating according to ASTM G34 for sheets subjected to the conditions of the ASTM G85 A2 test of P and / or EA and a poorly developed intergranular corrosion for plates subject to the conditions of ASTM Gl 10.
  • Yet another object of the invention is the use of a product obtained by a method according to the invention for the manufacture of a structural element for an airplane, in particular an aircraft fuselage skin.
  • Figure 1 Micrographic section of the sample S after exposure under ASTM Gl 10 conditions.
  • Figure 2 Micrographic section of the H2 sample after exposure under ASTM Gl 10 conditions.
  • Figure 3 Micrographic section of the A30 sample after exposure under ASTM Gl 10 conditions.
  • FIG. 4 Micrographic section of the sample Al 20 after exposure under ASTM Gl 10 conditions. Description of the invention
  • the static mechanical characteristics in tension in other words the tensile strength R m , the conventional yield stress at 0.2% elongation R p0; 2 , and the elongation at break A% are determined by a tensile test according to standard NF EN ISO 6892-1, the sampling and the direction of the test being defined by the EN 485-1 standard. Corrosion resistance tests are performed according to ASTM G34, ASTM G85 A2 and ASTM G110 standards.
  • solution, quenching and optionally planing and / or pulling are carried out at least one short heat treatment with a duration and a temperature such that the sheet reaches a temperature of between 145 ° C. and 175 ° C and preferably between 150 ° C and 170 ° C for 0.1 to 45 minutes, preferably 0.2 to 20 minutes, preferably for 0.5 to 5 minutes and preferably for 1 to 3 minutes , the heating rate being between 3 and 600 ° C / min.
  • the short heat treatment is advantageously carried out after natural aging for at least 24 hours after quenching and preferably at least 48 hours after quenching.
  • the yield strength R p o, 2 is significantly lower, that is to say at least 20 MPa or even at least 40 MPa in the L and LT directions. , compared to that of the same sheet in a state T3 or T4.
  • the short heat treatment is not an income with which one would obtain a T8 state but a particular heat treatment which makes it possible to obtain a non-standardized state particularly suitable for shaping.
  • a sheet in the T8 state has a yield strength greater than that of the same sheet in a T3 or T4 state while after the short heat treatment according to the invention the elastic limit is on the contrary weaker than that of a state T3 or T4.
  • the short heat treatment is carried out so as to obtain a time equivalent to 150 ° C. of 0.5 to 35 minutes, preferably of 1 to 20 minutes and preferably of 2 to 10 minutes, the equivalent time t, 150 ° C is defined by the formula:
  • T in Kelvin
  • T ref a reference temperature set at 423 K
  • tj is expressed in minutes
  • the present inventors have found that the mechanical properties obtained at the end of the short heat treatment are stable over time, which makes it possible to use the sheets in the state obtained at the end of the short heat treatment.
  • the sheet metal place in a state O or in a state W for the shaping.
  • the present inventors have found that, surprisingly, the high heating rate during the short heat treatment and / or a short duration of the short heat treatment make it possible to obtain an improved ability to shape while maintaining a resistance to corrosion of the sheet resulting from the short heat treatment, in particular with intergranular and exfoliating corrosion, equivalent to that of a sheet in the T3 or T4 state.
  • the heating rate is between 10 and 400 ° C / min and preferably between 40 and 300 ° C / min.
  • the heating rate is typically the average slope of the sheet temperature as a function of time during heating between room temperature and 145 ° C.
  • the heating rate is preferably at least 80 ° C./min.
  • the cooling rate is between 1 and 1000 ° C./min, preferably between 10 and 800 ° C./min.
  • the cooling rate is typically the average slope of the sheet temperature as a function of time during cooling between 145 ° C and 70 ° C or even between 145 ° C and 30 ° C.
  • the cooling is carried out by spraying a liquid such as for example water or by immersion in such a liquid.
  • the cooling is carried out in air with optional forced convection, the cooling rate then preferably being between 1 and 400 ° C./min, preferably between 40 and 200 ° C. / min.
  • the short heat treatment is carried out in a continuous treatment furnace.
  • a continuous treatment furnace is an oven such that the sheet is supplied in the form of a coil which is continuously unwound for heat treatment in the furnace and then cooled and wound.
  • the present inventors have found that, surprisingly, not only the short heat treatment makes it possible to simplify the manufacturing process of the products by eliminating the shaping on state O or W, but moreover that the compromise between static mechanical resistance and tolerance to damage to the tempering state is at least the same or even improved by the method of the invention, compared to a method not comprising short heat treatment.
  • the compromise obtained between static mechanical strength and toughness is improved compared with the state of the art.
  • the advantage of the process according to the invention is obtained for products having a copper content of between 2.1 and 3.9% by weight.
  • the copper content is at least 2.8% or 3% by weight.
  • a maximum copper content of 3.7 or 3.4% by weight is preferred.
  • the lithium content is between 0.6% or 0.7% and 2.0% by weight.
  • the lithium content is at least 0.70% by weight.
  • a maximum lithium content of 1.4 or even 1.1% by weight is preferred.
  • the magnesium content is between 0.1% and 1.0% by weight. Preferably, the magnesium content is at least 0.2% or even 0.25% by weight. In one embodiment of the invention, the maximum magnesium content is 0.6% by weight.
  • the silver content is between 0% and 0.6% by weight. In an advantageous embodiment of the invention, the silver content is between 0.1 and 0.5% by weight and preferably between 0.15 and 0.4% by weight. The addition of silver contributes to improving the compromise of mechanical properties of the products obtained by the process according to the invention.
  • the zinc content is between 0% and 1% by weight.
  • the zinc content is less than 0.6% by weight, preferably less than 0.40% by weight.
  • Zinc is generally an undesirable impurity, especially because of its contribution to the density of the alloy, in one embodiment of the invention the zinc content is less than 0.2% by weight and preferably less than 0. , 04% by weight.
  • zinc may be used alone or in combination with silver, a minimum zinc content of 0.2% by weight is then advantageous.
  • the alloy also contains at least one element that can contribute to controlling the grain size selected from Zr, Mn, Cr, Se, Hf and Ti, the amount of the element, if selected, being 0.05 to 0.18% by weight for Zr, 0.1 to 0.6% by weight for Mn, 0.05 to 0.3% by weight for Cr, 0.02 to 0.2% by weight for Se, 0 0.5 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti.
  • the zirconium content is at least 0.11% by weight.
  • the manganese content is between 0.2 and 0.4% by weight and the zirconium content is less than 0.04% by weight.
  • the sum of the iron content and the silicon content is at most 0.20% by weight.
  • the iron and silicon contents are each at most 0.08% by weight.
  • the iron and silicon contents are at most 0.06% and 0.04% by weight, respectively. Controlled iron and silicon content and Limited contributes to improving the compromise between mechanical resistance and tolerance - to damage.
  • the other elements have a content of at most 0.05% by weight each and 0.15% by weight in total, it is inevitable impurities, the rest is aluminum.
  • the manufacturing method according to the invention comprises the steps of production, casting, rolling, dissolution, quenching, optionally planing and / or pulling and short heat treatment.
  • a bath of liquid metal is produced so as to obtain an aluminum alloy of composition according to the invention.
  • the liquid metal bath is then cast as a rolling plate.
  • the rolling plate can then optionally be homogenized so as to reach a temperature between 450 ° C and 550 ° and preferably between 480 ° C and 530 ° C for a period of between 5 and 60 hours.
  • the homogenization treatment can be carried out in one or more stages.
  • the rolling plate is then hot-rolled and optionally cold-rolled into a sheet.
  • the thickness of said sheet is between 0.5 and 10 mm, advantageously between 0.8 and 8 mm and preferably between 1 and 6 mm.
  • the product thus obtained is then put in solution typically by a heat treatment making it possible to reach a temperature of between 490 and 530 ° C. for 5 min to 8 h, and then typically quenched with water at ambient temperature or, preferably, with water. Cold water.
  • the short heat treatment is carried out directly after quenching. without intermediate hardening, but advantageously after a natural aging of at least 24 hours. This embodiment without intermediate work-hardening is advantageous in particular when the steps of dissolution, quenching and short heat treatment are carried out continuously in a continuous treatment furnace. Moreover, the present inventors have found that in the absence of intermediate hardening between quenching and short heat treatment defects such as lines Luders appearing after shaping could be removed in some cases.
  • the product then undergoes a short heat treatment already described.
  • the sheet obtained by the process according to the invention advantageously has, typically for at least 50 days and even for at least 200 days, after short heat treatment, a yield strength R p0; 2 (L) and / or R p0 , 2 (LT) of between 75% and 90%, preferably between 80 and 85% and preferably between 81% and 84% of the yield strength in the same direction of a sheet of the same composition in the T4 or T3 state having undergone the same controlled pull after quenching, at least one property chosen from a ratio R m / R p0; 2 (L) of at least 1.40 and preferably at least 1.45 and a ratio R m R p o, 2 (LT) of at least 1.45 and preferably at least 1.50 and has at least one corrosion resistance property selected from a rating according to ASTM G34 for plates subject to the conditions of the ASTM G85 A2 test of P and / or EA and a poorly developed intergranular corrosion for sheets subject to the conditions of the ASTM Gl
  • the sheet obtained by the process according to the invention typically exhibits for at least 50 days and even for at least 200 days after a short heat treatment, a combination of at least one property selected from R p o , 2 (L) of at least 220 MPa and preferably at least 250 MPa, R p o , 2 (LT) of at least 200 MPa and preferably at least 230 MPa, R m (L) of at least 340 MPa and preferably at least 380 MPa, R m (LT) of at least 320 MPa and preferably at least 360 MPa with a property selected from A % (L) at least 14% and preferably at least 15%, A% (LT) at least 24% and preferably at least 26%, R m / R p0 , 2 (L) at least 1.40 and preferably at least 1.45, R m / R p0j 2 (LT) at minus 1.45 and preferably at least 1.50 and exhibits at least one corrosion resistance
  • the sheet obtained by the process according to the invention has a ratio R m / R p o, 2 in the direction LT of at least 1, 52 or 1.53.
  • the sheet obtained by the process according to the invention has a yield strength R p o j2 (L) of less than 290 MPa and of preferably less than 280 MPa and R p0; 2 (LT) less than 270 MPa and / or a rupture strength R m (L) less than 410 MPa and preferably less than 400 MPa and R p oj2 (LT) less than 390 MPa.
  • the rating according to ASTM G34 for sheets subject to the conditions of the ASTM G85 A2 test is P or P-EA.
  • the intergranular corrosion for the sheets subjected to the conditions of the ASTM G110 standard is not very developed if it corresponds to the images of FIG. 1 or 2.
  • the sheet obtained by the process according to the invention has a resistance to intercrystalline corrosion at least equal to that of a sheet of the same composition in the T3 or T4 state.
  • the sheet can be stored without particular difficulties thanks to its resistance to intercrystalline corrosion.
  • the sheet resulting from the short heat treatment is ready for additional cold deformation, in particular a 3-dimensional forming operation.
  • An advantage of the invention is that this additional deformation can locally or generally reach values of 6 to 8% or even up to 10%.
  • a minimum cumulative deformation of 2% between said additional deformation and the accumulated deformation by planing and / or controlled tension optionally performed before the short heat treatment is advantageous.
  • the additional cold deformation is locally or generally at least 1%, preferably at least 4% and preferably at least 6%.
  • an income is produced in which said sheet thus shaped reaches a temperature of between 130 and 170 ° C., advantageously between 145 and 165 ° C. and preferably between 150 and 160 ° C. for 5 to 100 hours, and preferably at 70h.
  • the income can be achieved in one or more levels.
  • the cold deformation is carried out by one or more shaping processes such as stretching, stretching-forming, stamping, spinning or folding.
  • it is a shaping in the three dimensions of the space to obtain a piece of complex shape, preferably by stretch-forming.
  • the product obtained after the short heat treatment can be shaped as a product in a state O or a product in a state W.
  • a simple income treatment is sufficient.
  • the product also has the advantage in general of not generating lines of Luders crippling during formatting.
  • one can for example perform the short heat treatment in the sheet metal manufacturer store it without special precautions due to its high resistance to intergranular corrosion and perform the shaping at the manufacturer of aeronautical structure, directly on the product delivered.
  • the method according to the invention makes it possible to carry out the 3-dimensional shaping of a sheet at the end of the short heat treatment without the sheet being in a state T8, a state O or a state W before this setting shaped in 3 dimensions.
  • the compromise between the static mechanical properties and the damage tolerance properties obtained at the end of the income is advantageous by compared to that obtained for a similar treatment not including short heat treatment.
  • the sheets were then subjected to a short heat treatment, the conditions of which are given in Table 2.
  • the highest heating rates, representative of the heating rates obtained in a continuous treatment furnace, were obtained by immersion in an immersion bath. oil while the lowest heating rates were obtained by controlled air treatment, representative of the industrial conditions in a furnace static.
  • the cooling rate was of the order of 60 ° C./min for all the tests.
  • the corrosion resistance properties of the sheets were evaluated under the conditions of standardized intergranular corrosion tests (ASTM G1 10) and exfoliation corrosion tests (MASTMAASIS dry bottom ASTM G85-A2).
  • ASTM G1 standardized intergranular corrosion tests
  • MASTMAASIS dry bottom ASTM G85-A2 exfoliation corrosion tests
  • the test immersion time of the ASTM Gl 10 test is 6h and the test duration of the MASTMAASIS test is 750h.
  • the characterizations were performed on the surface ("skin") and after machining one-tenth of the thickness ("T / 10").
  • Micrographic sections representative of poorly developed intergranular corrosion and pitting are given in Figures 1 (sample S) and 2 (sample H2). The observations were made under an optical microscope at magnifications of X200.
  • a representative micrograph section of intergranular corrosion developed and pitting is given in Figure 3 (sample A30).
  • a micrographic section representative of a developed intergranular corrosion is given in Figure 4 (sample Al 20).
  • Sample S is a sample in the T3 state. It does not have mechanical properties to consider its shaping for the highest deformations. Samples A30, A60, A 120, A240 have mechanical properties which make it possible to envisage shaping for the highest deformations but exhibit a resistance to corrosion requiring particular precautions during storage.
  • Samples H1, H2, H4, H8, H16 and H30 simultaneously have mechanical properties to consider its shaping for the highest deformations and corrosion resistance to consider storage without special precautions.
  • Sample H1 however, has somewhat less favorable mechanical properties, especially in terms of elongation in the LT direction.
  • Sample H30 has slightly less favorable properties, particularly in terms of corrosion resistance.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metal Rolling (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Steel (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

The invention concerns the method for producing a rolled product 0.5 to 10 mm thick made from an aluminium alloy comprising, in particular, copper and lithium, in which, after solution annealing and quenching, a short heat treatment is carried out in which the sheet reaches a temperature of between 145°C and 175°C for 0.1 to 45 minutes, the speed of heating being between 3 and 600 °C/min. The sheet obtained at the end of the method according to the invention has high corrosion resistance and is capable of being shaped for producing a structural element for an aircraft, in particular an aircraft fuselage skin.

Description

Procédé de transformation de tôles en alliage Al-Cu-Li améliorant la formabilité et la résistance à la corrosion  Process for converting Al-Cu-Li alloy sheets improving formability and corrosion resistance
Domaine de l'invention Field of the invention
L'invention concerne les produits en alliages aluminium-cuivre-lithium, plus particulièrement, de tels produits, leurs procédés de fabrication et d'utilisation, destinés en particulier à la construction aéronautique et aérospatiale. The invention relates to aluminum-copper-lithium alloy products, more particularly, such products, their manufacturing and use processes, intended in particular for aeronautical and aerospace construction.
Etat de la technique State of the art
Des produits laminés en alliage d'aluminium sont développés pour produire des pièces de haute résistance destinées notamment à l'industrie aéronautique et à l'industrie aérospatiale. Aluminum alloy rolled products are developed to produce high strength parts for the aerospace industry and the aerospace industry in particular.
Les alliages d'aluminium contenant du lithium sont très intéressants à cet égard, car le lithium peut réduire la densité de l'aluminium de 3 % et augmenter le module d'élasticité de 6 % pour chaque pourcent en poids de lithium ajouté. Aluminum alloys containing lithium are very interesting in this respect, since lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added.
Le brevet US 5,032,359 décrit une vaste famille d'alliages aluminium-cuivre-lithium dans lesquels l'addition de magnésium et d'argent, en particulier entre 0,3 et 0,5 pourcent en poids, permet d'augmenter la résistance mécanique. Le brevet US 5,455,003 décrit un procédé de fabrication d'alliages Al-Cu-Li qui présentent une résistance mécanique et une ténacité améliorés à température cryogénique, en particulier grâce à un écrouissage et un revenu appropriés. Ce brevet recommande en particulier la composition, en pourcentage en poids, Cu = 3,0 - 4,5, Li = 0,7 - 1,1, Ag = 0 - 0,6, Mg = 0,3-0,6 et Zn = 0 - 0,75. Le brevet US 7,438,772 décrit des alliages comprenant, en pourcentage en poids, Cu : 3-5, Mg : 0,5-2, Li : 0,01-0,9. No. 5,032,359 discloses a broad family of aluminum-copper-lithium alloys in which the addition of magnesium and silver, in particular between 0.3 and 0.5 percent by weight, makes it possible to increase the mechanical strength. No. 5,455,003 discloses a process for manufacturing Al-Cu-Li alloys which have improved mechanical strength and toughness at cryogenic temperature, in particular through proper work-hardening and tempering. This patent recommends in particular the composition, in percentage by weight, Cu = 3.0-4.5, Li = 0.7-1.1, Ag = 0-0.6, Mg = 0.3-0.6. and Zn = 0 - 0.75. US Pat. No. 7,438,772 describes alloys comprising, in percentage by weight, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9.
Le brevet US 7,229,509 décrit un alliage comprenant (% en poids) : (2,5-5,5) Cu, (0,1-2,5) Li, (0,2-1 ,0) Mg, (0,2-0,8) Ag, (0,2-0,8) Mn, 0,4 max Zr ou d'autres agents affinant le grain tels que Cr, Ti, Hf, Se, V. US Pat. No. 7,229,509 describes an alloy comprising (% by weight): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0, 2-0.8) Ag, (0.2-0.8) Mn, 0.4 max Zr or other grain refining agents such as Cr, Ti, Hf, Se, V.
La demande de brevet US 2009/142222 Al décrit des alliages comprenant (en % en poids), 3,4 à 4,2% de Cu, 0,9 à 1,4 % de Li, 0,3 à 0,7 % de Ag, 0,1 à 0,6% de Mg, 0,2 à 0,8 % de Zn, 0,1 à 0,6 % de Mn et 0,01 à 0,6 % d'au moins un élément pour le contrôle de la structure granulaire. Cette demande décrit également un procédé de fabrication de produits filés. US patent application 2009/142222 A1 discloses alloys comprising (in% by weight), 3.4 to 4.2% Cu, 0.9 to 1.4% Li, 0.3 to 0.7% of Ag, 0.1 to 0.6% Mg, 0.2 to 0.8% Zn, 0.1 to 0.6% Mn and 0.01 to 0.6% of at least one element. for the control of the granular structure. This application also describes a process for manufacturing spun products.
Le brevet EP 1,966,402 décrit un alliage ne contenant pas de zirconium destiné à des tôles de fuselage de structure essentiellement recristallisée comprenant (en % en poids) (2,1-Patent EP 1,966,402 describes a non-zirconium-containing alloy intended for fuselage sheets of essentially recrystallized structure comprising (in% by weight) (2.1%).
2,8)Cu, (1,1-1,7) Li, (0,2-0,6) Mg, (0,1-0,8) Ag, (0,2-0,6) Mn. Les produits obtenus à l'état T8 ne sont pas aptes à une mise en forme importante, avec notamment un rapport Rm // Rpo .2 inférieur à 1 ,2 dans les directions L et LT. Le brevet EP 1 ,891,247 décrit un alliage destiné à des tôles de fuselage comprenant (en % en poids) (3,0-3,4)Cu, (0,8-1,2) Li, (0,2-0,6) Mg, (0,2-0,5) Ag et au moins un élément parmi Zr, Mn, Cr, Se, Hf et Ti, dans lequel les teneurs en Cu et en Li répondent à la condition Cu + 5/3 Li < 5,2. Les produits obtenus à l'état T8 ne sont pas apte à une mise en forme importante, avec notamment un rapport Rm / Rp0 2 inférieur à 1 ,2 dans les directions L et LT. Il a de plus été constaté que l'énergie globale à rupture mesurée par test ahn qui est reliée à la ténacité diminue avec la déformation et de façon plus brutale pour une déformation de 6%, ce qui pose le problème de l'obtention d'une ténacité élevée quelque soit le taux de déformation local lors de la mise en forme. Le brevet EP 1045043 décrit le procédé de fabrication de pièces formées en alliage de type AA2024, et notamment de pièces fortement déformées, par l'association d'une composition chimique optimisée et de procédés de fabrication particuliers, permettant d'éviter autant que possible la mise en solution sur tôle formée. 2.8) Cu, (1.1-1.7) Li, (0.2-0.6) Mg, (0.1-0.8) Ag, (0.2-0.6) Mn. The products obtained in the T8 state are not suitable for significant shaping, with in particular a ratio R m / / R p o .2 of less than 1.2 in the directions L and LT. EP 1, 891, 247 discloses an alloy for fuselage plates comprising (in% by weight) (3.0-3.4) Cu, (0.8-1.2) Li, (0.2-0.2). , 6) Mg, (0.2-0.5) Ag and at least one of Zr, Mn, Cr, Se, Hf and Ti, wherein the Cu and Li contents are Cu + 5 / Li <5.2. The products obtained in the T8 state are not suitable for significant shaping, with in particular a ratio R m / R p0 2 of less than 1, 2 in the directions L and LT. It has also been found that the overall energy at break measured by ahn test which is related to the toughness decreases with the deformation and more brutally for a deformation of 6%, which poses the problem of obtaining a high tenacity whatever the rate of local deformation during the shaping. EP 1045043 describes the process for manufacturing parts made of AA2024 type alloy, and in particular of highly deformed parts, by the combination of a composition optimized chemistry and special manufacturing processes, to avoid as much as possible the dissolution in solution on formed sheet metal.
Dans l'article « Al-(4.5-6.3)Cu-1.3Li-0.4Ag--0.4Mg-0.14Zr Alloy Weldalite 049 » from Pickens, J R ; Heubaum, F H; Langan, T J ; Kramer, L S publié dans Aluminum— Lithium Alloys. Vol. III; Williamsburg, Virginia; . USA; 27-31 Mar. 1989. (March 27, 1989), différents traitements thermique sont décrits pour ces alliages à forte teneur en cuivre. In the article "Al- (4.5-6.3) Cu-1.3Li-0.4Ag-0.4Mg-0.14Zr Alloy Weldalite 049" from Pickens, J R; Heubaum, F H; Langan, T J; Kramer, L S published in Aluminum-Lithium Alloys. Flight. III; Williamsburg, Virginia; . USA; 27-31 Mar. 1989. (March 27, 1989), various heat treatments are described for these alloys with a high copper content.
Pour que ces alliages soient sélectionnés dans les avions, leur performance par rapport aux autres propriétés d'usage doit atteindre celle des alliages couramment utilisés, en particulier en terme de compromis entre les propriétés de résistance mécanique statique (limite d'élasticité, résistance à la rupture) et les propriétés de tolérance aux dommages (ténacité, résistance à la propagation des fissures en fatigue), ces propriétés étant en général antinomiques. L'amélioration du compromis entre la résistance mécanique la tolérance aux dommages est constamment recherchée. Par ailleurs leur résistance à la corrosion doit être suffisante que ce soit dans l'état final utilisé ou dans les états intermédiaires au cours de la gamme de fabrication. For these alloys to be selected in the aircraft, their performance compared to other properties of use must reach that of commonly used alloys, in particular in terms of a compromise between the static mechanical strength properties (yield strength, resistance to rupture) and the properties of damage tolerance (toughness, resistance to the propagation of fatigue cracks), these properties being in general antinomic. The improvement of the compromise between mechanical resistance and damage tolerance is constantly sought. Furthermore their corrosion resistance must be sufficient whether in the final state used or in the intermediate states during the manufacturing range.
Une autre propriété importante des tôles minces en alliage Al-Cu-Li, notamment celles dont l'épaisseur est comprise entre 0,5 et 10 mm, est l'aptitude à la mise en forme. Ces tôles sont notamment utilisées pour fabriquer des éléments de fuselage d'avion ou des éléments de fusée qui ont une forme générale complexe en 3 dimensions. Pour diminuer le coût de fabrication, les constructeurs aéronautiques cherchent à minimiser le nombre des étapes de formage des tôles, et à utiliser des tôles pouvant être fabriquées de manière peu onéreuse à l'aide de gammes de transformation courtes, c'est-à-dire comprenant aussi peu d'étapes individuelles que possible.  Another important property of thin sheets of Al-Cu-Li alloy, particularly those whose thickness is between 0.5 and 10 mm, is the fitness to form. These sheets are used in particular to manufacture aircraft fuselage elements or rocket elements that have a complex overall shape in 3 dimensions. To reduce the cost of manufacture, aircraft manufacturers seek to minimize the number of sheet forming steps, and to use sheets that can be manufactured inexpensively using short transformation ranges, that is to say, say including as few individual steps as possible.
Pour la fabrication des panneaux de fuselage, plusieurs procédés sont connus. Pour des faibles déformations lors de la mise en forme, typiquement inférieures à 4 %, il est possible d'approvisionner des tôles dans un état trempé mûri (état " T3 " peu écroui ou " T4 "), et de mettre en forme les tôles dans cet état. Cependant, dans la plupart des cas, la déformation recherchée est importante, localement d'au moins 5% ou 6%. Une pratique actuelle des constructeurs aéronautiques consiste en général alors à approvisionner des tôles laminées à chaud ou à froid selon l'épaisseur requise, à l'état brut de fabrication (état " F " selon la norme EN 515) à l'état trempé mûri (état " T3 " ou " T4 "), voire à l'état recuit (état « O »), à les soumettre à un traitement thermique de mise en solution suivi d'une trempe, puis à les mettre en forme sur trempe fraîche (état « W »), avant enfin de les soumettre à un vieillissement naturel ou artificiel, de manière à obtenir les caractéristiques mécaniques requises. For the manufacture of the fuselage panels, several methods are known. For small deformations during shaping, typically less than 4%, it is possible to supply the sheets in a hardened state matured (state "T3" little hardened or "T4"), and to shape the sheets in this state. However, in most cases, the deformation sought is important, locally at least 5% or 6%. A current practice of aeronautical manufacturers is generally to supply hot-rolled or cold-rolled sheets according to the required thickness, in the raw state of manufacture (state "F" according to EN 515) in the matured tempered state. (state "T3" or "T4"), even in the annealed state ("O" state), subject them to a solution heat treatment followed by quenching, and then to form them on fresh quenching (state "W"), before finally subjecting them to natural or artificial aging, so as to obtain the required mechanical characteristics.
Dans une autre pratique, on part d'une tôle dans un état O, voire un état T3, T4 ou à l'état F, on effectue une première opération de mise en forme à partir de cet état, et une deuxième mise en forme après mise en solution et trempe. Cette variante est notamment utilisée lorsque la mise en forme visée est trop importante pour pouvoir être effectuée en une seule opération à partir d'un état W, mais peut cependant être effectuée en deux passes à partir d'un état O. De plus les tôles à l'état O étant stables dans le temps sont plus aisées à transformer. Toutefois, la fabrication de la tôle à l'état O fait intervenir un recuit final de la tôle brute de laminage, et donc généralement une étape de fabrication supplémentaire, et également une mise en solution et une trempe sur le produit formé ce qui est contraire au but de simplification visé par la présente invention.  In another practice, one starts from a sheet in a state O, even a state T3, T4 or in the state F, one carries out a first operation of formatting starting from this state, and a second formatting after dissolution and quenching. This variant is used in particular when the targeted shaping is too important to be performed in a single operation from a state W, but can however be performed in two passes from a state O. In addition, the plates in the state O being stable in time are easier to transform. However, the manufacture of the sheet in the O state involves a final annealing of the raw rolling sheet, and therefore generally an additional manufacturing step, and also a dissolution and quenching of the product formed which is contrary the aim of simplification aimed at by the present invention.
La mise en forme d'éléments de structure complexes à l'état T8 se limite à des cas de mise en forme peu importante car l'allongement et le rapport Rm/Rp0,2 sont trop faibles dans cet état. The shaping of complex structural elements in the T8 state is limited to cases of small shaping because the elongation and the ratio R m / R p0 , 2 are too low in this state.
On notera que les propriétés optimales en termes de compromis de propriétés doivent être obtenues une fois la pièce mise en forme, notamment en tant qu'élément de fuselage, puisque que c'est la pièce mise en forme qui doit en particulier avoir de bonnes performances en tolérance aux dommages pour éviter une réparation trop fréquente d'éléments de fuselage. Il est généralement admis que les fortes déformations après mise en solution et trempe conduisent à une augmentation de la résistance mécanique mais à une forte dégradation de la ténacité.  It should be noted that the properties that are optimal in terms of compromise of properties must be obtained once the part has been shaped, in particular as a fuselage element, since it is the shaped part which must in particular have good performances. in damage tolerance to avoid too frequent repair of fuselage elements. It is generally accepted that the large deformations after dissolution and quenching lead to an increase in the mechanical strength but a strong degradation of the tenacity.
Par ailleurs, les tôles qui sont délivrées au fabricant d'avion peuvent être stockées pendant une durée parfois significative avant d'être mises en forme et de subir un revenu. Il convient donc d'éviter que ces tôles soient sensibles à la corrosion de façon notamment à simplifier les conditions de stockage. In addition, the sheets that are delivered to the aircraft manufacturer can be stored for a sometimes significant period before being shaped and to incur an income. he It should therefore be avoided that these sheets are susceptible to corrosion, in particular to simplify the storage conditions.
Il existe un besoin pour un procédé de fabrication simplifié permettant la mise en forme des produits laminés en alliage aluminium-cuivre-lithium pour obtenir notamment des éléments de fuselage de façon économique, tout en obtenant des caractéristiques mécaniques satisfaisantes, les produits présentant avant la mise en forme une résistance à la corrosion élevée. Objet de l'invention There is a need for a simplified manufacturing process allowing the shaping of aluminum-copper-lithium alloy rolled products to obtain in particular fuselage elements economically, while obtaining satisfactory mechanical characteristics, the products having before the implementation in form a high corrosion resistance. Object of the invention
Un premier objet de l'invention est un procédé de fabrication d'un produit laminé à base d'alliage d'aluminium notamment pour l'industrie aéronautique dans lequel, successivement A first object of the invention is a process for manufacturing a laminated product based on aluminum alloy, in particular for the aeronautical industry in which, successively
a) on élabore un bain de métal liquide à base d'aluminium comprenant 2,1 à 3,9 % en poids de Cu, 0,6 à 2.0 % en poids de Li, 0,1 à 1,0 % en poids de Mg, 0 à 0,6 % en poids d'Ag, 0 à 1% % en poids de Zn, au plus 0,20 % en poids de la somme de Fe et de Si, au moins un élément choisi parmi Zr, Mn, Cr, Se, Hf et Ti, la quantité dudit élément, s'il est choisi, étant 0,05 à 0,18 % en poids pour Zr, 0,1 à 0,6% en poids pour Mn, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,2 % en poids pour Se, 0,05 à 0,5 % en poids pour Hf et de 0,01 à 0,15 % en poids pour Ti, les autres éléments au plus 0,05% en poids chacun et 0,15% en poids au total, le reste aluminium ;  a) an aluminum-based liquid metal bath comprising 2.1 to 3.9% by weight of Cu, 0.6 to 2.0% by weight of Li, 0.1 to 1.0% by weight of Mg, 0 to 0.6% by weight of Ag, 0 to 1% by weight of Zn, at most 0.20% by weight of the sum of Fe and Si, at least one element selected from Zr, Mn , Cr, Se, Hf and Ti, the amount of said element, if selected, being 0.05 to 0.18% by weight for Zr, 0.1 to 0.6% by weight for Mn, 0.05 0.3% by weight for Cr, 0.02 to 0.2% by weight for Se, 0.05 to 0.5% by weight for Hf and from 0.01 to 0.15% by weight for Ti, the other elements not more than 0.05% by weight each and 0.15% by weight in total, the balance aluminum;
b) on coule une plaque de laminage à partir dudit bain de métal liquide ;  b) casting a rolling plate from said bath of liquid metal;
c) optionnellement, on homogénéise ladite plaque de laminage ;  c) optionally, homogenizing said rolling plate;
d) on lamine à chaud et optionnellement à froid ladite plaque de laminage en une tôle d'épaisseur comprise entre 0,5 et 10 mm,  d) said laminating plate is hot-rolled and optionally cold-rolled to a sheet thickness of between 0.5 and 10 mm,
e) on met en solution ladite tôle et on la trempe;  e) said sheet is dissolved and quenched;
f) optionnellement on réalise un planage et/ou on tractionne de façon contrôlée ladite tôle avec une déformation cumulée d'au moins 0,5% et inférieure à 3%, g) on réalise un traitement thermique court dans lequel ladite tôle atteint une température comprise entre 145°C et 175°C et de préférence entre 150°C et 170°C pendant 0,1 à 45 minutes et de préférence pendant 0,5 à 5 minutes, la vitesse de chauffage étant comprise entre 3 et 600 °C/min. f) optionally planing is carried out and / or controlled traction said sheet with a cumulative deformation of at least 0.5% and less than 3%, g) a short heat treatment is carried out in which said sheet reaches a temperature of between 145 ° C. and 175 ° C. and preferably between 150 ° C. and 170 ° C. for 0.1 to 45 minutes and preferably for 0.5 to 5 minutes, the heating rate being between 3 and 600 ° C / min.
Un autre objet de l'invention est un produit laminé susceptible d'être obtenu par le procédé selon l'invention présentant une limite d'élasticité Rp0,2(L) et/ou Rpoj2(LT) comprise entre 75% et 90 %, préférentiellement entre 80 et 85% et de préférence entre 81% et 84% de la limite d'élasticité dans la même direction d'une tôle de même composition à l'état T4 ou T3 ayant subi la même traction contrôlée après trempe, au moins une propriété choisie parmi un rapport Rm /Rp0j2 (L) d'au moins 1,40 et de préférence au moins 1,45 et un rapport Rm /Rpo,2 (LT) au moins 1,45 et de préférence au moins 1,50 et présente au moins une propriété de résistance à la corrosion choisie parmi une cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 de P et/ou EA et une corrosion intergranulaire peu développée pour des tôles soumises aux conditions de la norme ASTM Gl 10. Another subject of the invention is a laminated product obtainable by the process according to the invention having a yield strength R p0 , 2 (L) and / or R p oj2 (LT) of between 75% and 90%, preferably between 80 and 85% and preferably between 81% and 84% of the yield strength in the same direction of a sheet of the same composition in the T4 or T3 state having undergone the same controlled traction after quenching, at least one property selected from a ratio R m / R p0j2 (L) of at least 1.40 and preferably at least 1.45 and a ratio Rm / Rpo, 2 (LT) of at least 1.45 and preferably at least 1.50 and exhibits at least one corrosion resistance property chosen from a rating according to ASTM G34 for sheets subjected to the conditions of the ASTM G85 A2 test of P and / or EA and a poorly developed intergranular corrosion for plates subject to the conditions of ASTM Gl 10.
Encore un autre objet de l'invention est l'utilisation d'un produit obtenu par un procédé selon l'invention pour la fabrication d'un élément de structure pour avion, notamment d'une peau de fuselage d'avion. Yet another object of the invention is the use of a product obtained by a method according to the invention for the manufacture of a structural element for an airplane, in particular an aircraft fuselage skin.
Description des figures Description of figures
Figure 1 : Coupe micrographique de l'échantillon S après exposition dans les conditions ASTM Gl 10.  Figure 1: Micrographic section of the sample S after exposure under ASTM Gl 10 conditions.
Figure 2 : Coupe micrographique de l'échantillon H2 après exposition dans les conditions ASTM Gl 10.  Figure 2: Micrographic section of the H2 sample after exposure under ASTM Gl 10 conditions.
Figure 3 : Coupe micrographique de l'échantillon A30 après exposition dans les conditions ASTM Gl 10.  Figure 3: Micrographic section of the A30 sample after exposure under ASTM Gl 10 conditions.
Figure 4 : Coupe micrographique de l'échantillon Al 20 après exposition dans les conditions ASTM Gl 10. Description de l'invention Figure 4: Micrographic section of the sample Al 20 after exposure under ASTM Gl 10 conditions. Description of the invention
Sauf mention contraire, toutes les indications concernant la composition chimique des alliages sont exprimées comme un pourcentage en poids basé sur le poids total de l'alliage. L'expression 1,4 Cu signifie que la teneur en cuivre exprimée en % en poids est multipliée par 1,4. La désignation des alliages se fait en conformité avec les règlements de The Aluminium Association, connus de l'homme du métier. Les définitions des états métallurgiques sont indiquées dans la norme européenne EN 515. Unless stated otherwise, all the information concerning the chemical composition of the alloys is expressed as a percentage by weight based on the total weight of the alloy. The expression 1.4 Cu means that the copper content expressed in% by weight is multiplied by 1.4. The designation of alloys is in accordance with the regulations of The Aluminum Association, known to those skilled in the art. The definitions of the metallurgical states are given in the European standard EN 515.
Les caractéristiques mécaniques statiques en traction, en d'autres termes la résistance à la rupture Rm, la limite d'élasticité conventionnelle à 0,2% d'allongement Rp0;2, et l'allongement à la rupture A%, sont déterminés par un essai de traction selon la norme NF EN ISO 6892-1, le prélèvement et le sens de l'essai étant définis par la norme EN 485-1. Les tests de résistance à la corrosion sont effectués selon les normes ASTM G34, ASTM G85 A2 et ASTM G110. The static mechanical characteristics in tension, in other words the tensile strength R m , the conventional yield stress at 0.2% elongation R p0; 2 , and the elongation at break A% are determined by a tensile test according to standard NF EN ISO 6892-1, the sampling and the direction of the test being defined by the EN 485-1 standard. Corrosion resistance tests are performed according to ASTM G34, ASTM G85 A2 and ASTM G110 standards.
Selon l'invention, on réalise après laminage sous forme de tôle, mise en solution, trempe et optionnellement planage et/ou traction au moins un traitement thermique court avec une durée et une température telles que la tôle atteint une température comprise entre 145°C et 175°C et de préférence entre 150°C et 170°C pendant 0,1 à 45 minutes, avantageusement de 0,2 à 20 minutes, de préférence pendant 0,5 à 5 minutes et de manière préférée pendant 1 à 3 minutes, la vitesse de chauffage étant comprise entre 3 et 600 °C/min. Le traitement thermique court est avantageusement réalisé après un vieillissement naturel d'au moins 24 heures après la trempe et de préférence au moins 48 heures après la trempe. En effet, il est avantageux qu'un vieillissement ait lieu avec apparition de précipités durcissants pour que le traitement thermique court ait l'effet désiré. Typiquement, suite au traitement thermique court, la limite d'élasticité Rpo,2 est significativement plus faible, c'est-à-dire d'au moins 20 MPa ou même d'au moins 40 MPa dans les directions L et LT, par rapport à celle de la même tôle dans un état T3 ou T4. Le traitement thermique court n'est pas un revenu avec lequel on obtiendrait un état T8 mais un traitement thermique particulier qui permet d'obtenir un état non standardisé particulièrement apte à la mise en forme. En effet, une tôle à l'état T8 présente une limite d'élasticité supérieure à celle de la même tôle dans un état T3 ou T4 alors qu'après le traitement thermique court selon l'invention la limite d'élasticité est au contraire plus faible que celle d'un état T3 ou T4. Avantageusement, le traitement thermique court est réalisé de façon à obtenir un temps équivalent à 150 °C de 0,5 à 35 minutes, de préférence de 1 à 20 minutes et de manière préférée de 2 à 10 minutes, le temps équivalent t, à 150 °C est défini par la formule : According to the invention, after rolling in the form of sheet metal, solution, quenching and optionally planing and / or pulling are carried out at least one short heat treatment with a duration and a temperature such that the sheet reaches a temperature of between 145 ° C. and 175 ° C and preferably between 150 ° C and 170 ° C for 0.1 to 45 minutes, preferably 0.2 to 20 minutes, preferably for 0.5 to 5 minutes and preferably for 1 to 3 minutes , the heating rate being between 3 and 600 ° C / min. The short heat treatment is advantageously carried out after natural aging for at least 24 hours after quenching and preferably at least 48 hours after quenching. Indeed, it is advantageous that aging occurs with the appearance of hardening precipitates for the short heat treatment to have the desired effect. Typically, following the short heat treatment, the yield strength R p o, 2 is significantly lower, that is to say at least 20 MPa or even at least 40 MPa in the L and LT directions. , compared to that of the same sheet in a state T3 or T4. The short heat treatment is not an income with which one would obtain a T8 state but a particular heat treatment which makes it possible to obtain a non-standardized state particularly suitable for shaping. Indeed, a sheet in the T8 state has a yield strength greater than that of the same sheet in a T3 or T4 state while after the short heat treatment according to the invention the elastic limit is on the contrary weaker than that of a state T3 or T4. Advantageously, the short heat treatment is carried out so as to obtain a time equivalent to 150 ° C. of 0.5 to 35 minutes, preferably of 1 to 20 minutes and preferably of 2 to 10 minutes, the equivalent time t, 150 ° C is defined by the formula:
où T (en Kelvin) est la température instantanée de traitement du métal, qui évolue avec le temps t (en minutes), et Tref est une température de référence fixée à 423 K, tj est exprimé en minutes, la constante Q/R = 16400 K est dérivée de l'énergie d'activation pour la diffusion du Cu, pour laquelle la valeur Q = 136100 J/mol a été utilisée. where T (in Kelvin) is the instantaneous processing temperature of the metal, which changes with time t (in minutes), and T ref is a reference temperature set at 423 K, tj is expressed in minutes, the Q / R constant = 16400 K is derived from the activation energy for Cu diffusion, for which Q = 136100 J / mol was used.
De manière surprenante, les présents inventeurs ont constaté que les propriétés mécaniques obtenues à l'issue du traitement thermique court sont stables dans le temps, ce qui permet d'utiliser les tôles dans l'état obtenu à l'issue du traitement thermique court à la place de tôle dans un état O ou dans un état W pour la mise en forme. De plus les présents inventeurs ont constaté que de manière surprenante, la vitesse de chauffage élevée lors du traitement thermique court et/ou une faible durée du traitement thermique court permettent d'obtenir une aptitude améliorée à la mise en forme tout en maintenant une résistance à la corrosion de la tôle issue du traitement thermique court, notamment à la corrosion intergranulaire et exfoliante, équivalente à celle d'une tôle à l'état T3 ou T4.  Surprisingly, the present inventors have found that the mechanical properties obtained at the end of the short heat treatment are stable over time, which makes it possible to use the sheets in the state obtained at the end of the short heat treatment. the sheet metal place in a state O or in a state W for the shaping. Moreover, the present inventors have found that, surprisingly, the high heating rate during the short heat treatment and / or a short duration of the short heat treatment make it possible to obtain an improved ability to shape while maintaining a resistance to corrosion of the sheet resulting from the short heat treatment, in particular with intergranular and exfoliating corrosion, equivalent to that of a sheet in the T3 or T4 state.
De manière préférée, pour le traitement thermique court, la vitesse de chauffage est comprise entre 10 et 400 °C/min et préférentiellement entre 40 et 300 °C/min. La vitesse de chauffage est typiquement la pente moyenne de la température de la tôle en fonction du temps pendant le chauffage entre la température ambiante et 145°C. Preferably, for the short heat treatment, the heating rate is between 10 and 400 ° C / min and preferably between 40 and 300 ° C / min. The heating rate is typically the average slope of the sheet temperature as a function of time during heating between room temperature and 145 ° C.
Pour des tôles d'épaisseur inférieure à 6 mm la vitesse de chauffage est préférentiellement au moins 80 °C/min.  For sheets with a thickness of less than 6 mm, the heating rate is preferably at least 80 ° C./min.
De façon à limiter le temps équivalent à 150 °C, il est préférable également de refroidir suffisamment vite les tôles après le traitement court. Avantageusement, lors du traitement thermique court la vitesse de refroidissement est comprise entre 1 et 1000 °C/min, préférentiellement entre 10 et 800 °C/min. La vitesse de refroidissement est typiquement la pente moyenne de la température de la tôle en fonction du temps pendant le refroidissement entre 145°C et 70 °C ou même entre 145°C et 30 °C. Dans un mode de réalisation de l'invention le refroidissement est réalisé par aspersion d'un liquide tel que par exemple de l'eau ou par immersion dans un tel liquide. Dans un autre mode de réalisation de l'invention, le refroidissement est réalisé à l'air avec optionnellement une convection forcée, la vitesse de refroidissement étant alors de préférence comprise entre 1 et 400 °C/min, préférentiellement entre 40 et 200 °C/min. In order to limit the equivalent time to 150 ° C., it is also preferable to cool the sheets sufficiently quickly after the short treatment. Advantageously, during the short heat treatment, the cooling rate is between 1 and 1000 ° C./min, preferably between 10 and 800 ° C./min. The cooling rate is typically the average slope of the sheet temperature as a function of time during cooling between 145 ° C and 70 ° C or even between 145 ° C and 30 ° C. In one embodiment of the invention the cooling is carried out by spraying a liquid such as for example water or by immersion in such a liquid. In another embodiment of the invention, the cooling is carried out in air with optional forced convection, the cooling rate then preferably being between 1 and 400 ° C./min, preferably between 40 and 200 ° C. / min.
Avantageusement le traitement thermique court est réalisé dans un four de traitement en continu. Typiquement, un four de traitement en continu est un four tel que la tôle est approvisionnée sous la forme d'une bobine qui est déroulée de façon continue pour être traitée thermiquement dans le four puis refroidie et bobinée.  Advantageously, the short heat treatment is carried out in a continuous treatment furnace. Typically, a continuous treatment furnace is an oven such that the sheet is supplied in the form of a coil which is continuously unwound for heat treatment in the furnace and then cooled and wound.
Les présents inventeurs ont constaté que de manière surprenante, non seulement le traitement thermique court permet de simplifier le procédé de fabrication des produits en supprimant la mise en forme sur état O ou W, mais de plus que le compromis entre résistance mécanique statique et tolérance aux dommages à l'état revenu est au moins identique ou même amélioré grâce au procédé de l'invention, par rapport à un procédé ne comprenant pas de traitement thermique court. En particulier pour une déformation supplémentaire à froid d'au moins 5% après traitement thermique court, le compromis obtenu entre résistance mécanique statique et ténacité est amélioré par rapport à l'état de la technique. The present inventors have found that, surprisingly, not only the short heat treatment makes it possible to simplify the manufacturing process of the products by eliminating the shaping on state O or W, but moreover that the compromise between static mechanical resistance and tolerance to damage to the tempering state is at least the same or even improved by the method of the invention, compared to a method not comprising short heat treatment. In particular for a further cold deformation of at least 5% after short heat treatment, the compromise obtained between static mechanical strength and toughness is improved compared with the state of the art.
L'avantage du procédé selon l'invention est obtenu pour des produits ayant une teneur en cuivre comprise entre 2,1 et 3,9 % en poids. Dans une réalisation avantageuse de l'invention, la teneur en cuivre est au moins de 2,8 % ou 3% en poids. Une teneur en cuivre maximale de 3,7 ou 3,4 % en poids est préférée. The advantage of the process according to the invention is obtained for products having a copper content of between 2.1 and 3.9% by weight. In an advantageous embodiment of the invention, the copper content is at least 2.8% or 3% by weight. A maximum copper content of 3.7 or 3.4% by weight is preferred.
La teneur en lithium est comprise entre 0,6% ou 0,7% et 2,0 % en poids. Avantageusement, la teneur en lithium est au moins 0,70 % en poids. Une teneur en lithium maximale de 1,4 ou même 1,1 % en poids est préférée.  The lithium content is between 0.6% or 0.7% and 2.0% by weight. Advantageously, the lithium content is at least 0.70% by weight. A maximum lithium content of 1.4 or even 1.1% by weight is preferred.
La teneur en magnésium est comprise entre 0,1% et 1 ,0% en poids. Préférentiellement, la teneur en magnésium est au moins de 0,2 % ou même 0,25 % en poids. Dans un mode de réalisation de l'invention la teneur maximale en magnésium est de 0,6 % en poids. La teneur en argent est comprise entre 0 % et 0,6 % en poids. Dans une réalisation avantageuse de l'invention, la teneur en argent est comprise entre 0,1 et 0,5 % en poids et de manière préférée entre 0,15 et 0,4 % en poids. L'addition d'argent contribue à améliorer le compromis de propriétés mécaniques des produits obtenus par le procédé selon l'invention. The magnesium content is between 0.1% and 1.0% by weight. Preferably, the magnesium content is at least 0.2% or even 0.25% by weight. In one embodiment of the invention, the maximum magnesium content is 0.6% by weight. The silver content is between 0% and 0.6% by weight. In an advantageous embodiment of the invention, the silver content is between 0.1 and 0.5% by weight and preferably between 0.15 and 0.4% by weight. The addition of silver contributes to improving the compromise of mechanical properties of the products obtained by the process according to the invention.
La teneur en zinc est comprise entre 0 % et 1 % en poids. De manière préférée, la teneur en zinc est inférieure à 0,6 % en poids, de préférence inférieure à 0,40% en poids. Le zinc est généralement une impureté indésirable, notamment en raison de sa contribution à la densité de l'alliage, dans un mode de réalisation de l'invention la teneur en zinc est inférieure à 0,2% en poids et de préférence inférieure à 0,04 % en poids. Cependant dans un autre mode de réalisation le zinc peut être utilisé seul ou en combinaison avec l'argent, une teneur minimale en zinc de 0,2 % en poids est alors avantageuse.  The zinc content is between 0% and 1% by weight. Preferably, the zinc content is less than 0.6% by weight, preferably less than 0.40% by weight. Zinc is generally an undesirable impurity, especially because of its contribution to the density of the alloy, in one embodiment of the invention the zinc content is less than 0.2% by weight and preferably less than 0. , 04% by weight. However, in another embodiment zinc may be used alone or in combination with silver, a minimum zinc content of 0.2% by weight is then advantageous.
L'alliage contient également au moins un élément pouvant contribuer au contrôle de la taille de grain choisi parmi Zr, Mn, Cr, Se, Hf et Ti, la quantité de l'élément, s'il est choisi, étant de 0,05 à 0,18 % en poids pour Zr, 0,1 à 0,6% en poids pour Mn, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,2 % en poids pour Se, 0,05 à 0,5 % en poids pour Hf et de 0,01 à 0,15 % en poids pour Ti. De manière préférée on choisit d'ajouter entre 0,08 et 0,15 % en poids de zirconium et entre 0,01 et 0,10 % en poids de titane et on limite la teneur en Mn, Cr, Se et Hf à au maximum 0,05 % en poids, ces éléments pouvant avoir un effet défavorable, notamment sur la densité et n'étant ajoutés que pour favoriser encore l'obtention d'une structure essentiellement non-recristallisée si nécessaire. The alloy also contains at least one element that can contribute to controlling the grain size selected from Zr, Mn, Cr, Se, Hf and Ti, the amount of the element, if selected, being 0.05 to 0.18% by weight for Zr, 0.1 to 0.6% by weight for Mn, 0.05 to 0.3% by weight for Cr, 0.02 to 0.2% by weight for Se, 0 0.5 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti. In a preferred manner, it is preferred to add between 0.08 and 0.15% by weight of zirconium and between 0.01 and 0.10% by weight of titanium and the content of Mn, Cr, Se and Hf to be limited to maximum 0.05% by weight, these elements may have an adverse effect, especially on the density and being added only to further promote the obtaining of a substantially non-recrystallized structure if necessary.
Dans un mode de réalisation avantageux de l'invention, la teneur en zirconium est au moins égale à 0,11 % en poids. In an advantageous embodiment of the invention, the zirconium content is at least 0.11% by weight.
Dans un autre mode de réalisation de l'invention, la teneur en manganèse est comprise entre 0,2 et 0,4 % en poids et la teneur en zirconium est inférieure à 0,04 % en poids. In another embodiment of the invention, the manganese content is between 0.2 and 0.4% by weight and the zirconium content is less than 0.04% by weight.
La somme de la teneur en fer et de la teneur en silicium est au plus de 0,20 % en poids. De préférence, les teneurs en fer et en silicium sont chacune au plus de 0,08 % en poids. Dans une réalisation avantageuse de l'invention les teneurs en fer et en silicium sont au plus de 0,06 % et 0,04 % en poids, respectivement. Une teneur en fer et en silicium contrôlée et limitée contribue à l'amélioration du compromis entre résistance mécanique et tolérance - aux dommages. The sum of the iron content and the silicon content is at most 0.20% by weight. Preferably, the iron and silicon contents are each at most 0.08% by weight. In an advantageous embodiment of the invention, the iron and silicon contents are at most 0.06% and 0.04% by weight, respectively. Controlled iron and silicon content and Limited contributes to improving the compromise between mechanical resistance and tolerance - to damage.
Les autres éléments on une teneur au plus 0,05% en poids chacun et 0,15% en poids au total, il s'agit d'impuretés inévitables, le reste est de l'aluminium.  The other elements have a content of at most 0.05% by weight each and 0.15% by weight in total, it is inevitable impurities, the rest is aluminum.
Le procédé de fabrication selon l'invention comprend les étapes d'élaboration, coulée, laminage, mise en solution, trempe, optionnellement planage et/ou traction et traitement thermique court. The manufacturing method according to the invention comprises the steps of production, casting, rolling, dissolution, quenching, optionally planing and / or pulling and short heat treatment.
Dans une première étape, on élabore un bain de métal liquide de façon à obtenir un alliage d'aluminium de composition selon l'invention.  In a first step, a bath of liquid metal is produced so as to obtain an aluminum alloy of composition according to the invention.
Le bain de métal liquide est ensuite coulé sous forme de plaque de laminage.  The liquid metal bath is then cast as a rolling plate.
La plaque de laminage peut ensuite optionnellement être homogénéisée de façon à atteindre une température comprise entre 450°C et 550° et de préférence entre 480 °C et 530°C pendant une durée comprise entre 5 et 60 heures. Le traitement d'homogénéisation peut être réalisé en un ou plusieurs paliers. The rolling plate can then optionally be homogenized so as to reach a temperature between 450 ° C and 550 ° and preferably between 480 ° C and 530 ° C for a period of between 5 and 60 hours. The homogenization treatment can be carried out in one or more stages.
La plaque de laminage est ensuite laminée à chaud et optionnellement à froid en une tôle. L'épaisseur de ladite tôle est comprise entre 0,5 et 10 mm, avantageusement entre 0,8 et 8 mm et de préférence entre 1 et 6 mm. The rolling plate is then hot-rolled and optionally cold-rolled into a sheet. The thickness of said sheet is between 0.5 and 10 mm, advantageously between 0.8 and 8 mm and preferably between 1 and 6 mm.
Le produit ainsi obtenu est ensuite mis en solution typiquement par un traitement thermique permettant d'atteindre une température comprise entre 490 et 530 °C pendant 5 min à 8 h, puis trempé typiquement avec de l'eau à température ambiante ou préférentiellement de l'eau froide. The product thus obtained is then put in solution typically by a heat treatment making it possible to reach a temperature of between 490 and 530 ° C. for 5 min to 8 h, and then typically quenched with water at ambient temperature or, preferably, with water. Cold water.
On peut optionnellement réaliser ensuite un planage et/ou on tractionne de façon contrôlée la tôle ainsi mise en solution et trempée, avec une déformation cumulée d'au moins 0,5% et inférieure à 3%. Lorsque qu'un planage est réalisé, la déformation effectuée lors du planage n'est pas toujours connue précisément mais elle est estimée à environ 0,5 %. Quand elle est réalisée, la traction contrôlée est mise en œuvre avec une déformation permanente comprise entre 0,5 à 2,5 % et de préférence comprise entre 0,5 à 1,5 %. Cependant dans un mode de réalisation de l'invention on réalise le traitement thermique court directement après trempe sans écrouissage intermédiaire, mais avantageusement après un vieillissement naturel d'au moins 24 heures. Ce mode de réalisation sans écrouissage intermédiaire est avantageux en particulier lorsque les étapes de mise en solution, trempe et traitement thermique court sont réalisées en continu dans un four de traitement en continu. Par ailleurs les présents inventeurs ont constaté qu'en l'absence d'écrouissage intermédiaire entre trempe et traitement thermique court des défauts tels que les lignes de Luders apparaissant après mise en forme pouvaient être supprimés dans certains cas. It is optionally possible to carry out a planing and / or controlled traction of the sheet thus dissolved and quenched, with a cumulative deformation of at least 0.5% and less than 3%. When planing is performed, the deformation performed during planing is not always known precisely but it is estimated at about 0.5%. When it is performed, the controlled traction is implemented with a permanent deformation of between 0.5 to 2.5% and preferably between 0.5 to 1.5%. However, in one embodiment of the invention, the short heat treatment is carried out directly after quenching. without intermediate hardening, but advantageously after a natural aging of at least 24 hours. This embodiment without intermediate work-hardening is advantageous in particular when the steps of dissolution, quenching and short heat treatment are carried out continuously in a continuous treatment furnace. Moreover, the present inventors have found that in the absence of intermediate hardening between quenching and short heat treatment defects such as lines Luders appearing after shaping could be removed in some cases.
Le produit subit ensuite un traitement thermique court déjà décrit. The product then undergoes a short heat treatment already described.
A l'issue du traitement thermique court, la tôle obtenue par le procédé selon l'invention présente avantageusement, typiquement pendant au moins 50 jours et même pendant au moins 200 jours, après traitement thermique court, une limite d'élasticité Rp0;2(L) et/ou Rp0,2(LT) comprise entre 75% et 90%, préférentiellement entre 80 et 85% et de préférence entre 81% et 84% de la limite d'élasticité dans la même direction d'une tôle de même composition à l'état T4 ou T3 ayant subi la même traction contrôlée après trempe, au moins une propriété choisie parmi un rapport Rm /Rp0;2 (L) d'au moins 1,40 et de préférence au moins 1,45 et un rapport Rm Rpo,2 (LT) au moins 1,45 et de préférence au moins 1,50 et présente au moins une propriété de résistance à la corrosion choisie parmi une cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 de P et/ou EA et une corrosion intergranulaire peu développée pour des tôles soumises aux conditions de la norme ASTM Gl 10. At the end of the short heat treatment, the sheet obtained by the process according to the invention advantageously has, typically for at least 50 days and even for at least 200 days, after short heat treatment, a yield strength R p0; 2 (L) and / or R p0 , 2 (LT) of between 75% and 90%, preferably between 80 and 85% and preferably between 81% and 84% of the yield strength in the same direction of a sheet of the same composition in the T4 or T3 state having undergone the same controlled pull after quenching, at least one property chosen from a ratio R m / R p0; 2 (L) of at least 1.40 and preferably at least 1.45 and a ratio R m R p o, 2 (LT) of at least 1.45 and preferably at least 1.50 and has at least one corrosion resistance property selected from a rating according to ASTM G34 for plates subject to the conditions of the ASTM G85 A2 test of P and / or EA and a poorly developed intergranular corrosion for sheets subject to the conditions of the ASTM Gl 10 standard.
Dans un mode de réalisation avantageux, à l'issue du traitement thermique court, la tôle obtenue par le procédé selon l'invention présente typiquement pendant au moins 50 jours et même pendant au moins 200 jours après traitement thermique court, une combinaison d'au moins une propriété choisie parmi Rpo,2(L) d'au moins 220 MPa et de préférence d'au moins 250 MPa, Rpo,2(LT) d'au moins 200 MPa et de préférence d'au moins 230 MPa, Rm(L) d'au moins 340 MPa et de préférence d'au moins 380 MPa, Rm(LT) d'au moins 320 MPa et de préférence d'au moins 360 MPa avec une propriété choisie parmi A%(L) au moins 14% et de préférence au moins 15%, A%(LT) au moins 24% et de préférence au moins 26%, Rm /Rp0,2 (L) au moins 1,40 et de préférence au moins 1,45, Rm /Rp0j2 (LT) au moins 1,45 et de préférence au moins 1,50 et présente au moins une propriété de résistance à la corrosion choisie parmi une cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 de P et/ou EA et une corrosion intergranulaire peu développée pour des tôles soumises aux conditions de la norme ASTM G1 10. In an advantageous embodiment, at the end of the short heat treatment, the sheet obtained by the process according to the invention typically exhibits for at least 50 days and even for at least 200 days after a short heat treatment, a combination of at least one property selected from R p o , 2 (L) of at least 220 MPa and preferably at least 250 MPa, R p o , 2 (LT) of at least 200 MPa and preferably at least 230 MPa, R m (L) of at least 340 MPa and preferably at least 380 MPa, R m (LT) of at least 320 MPa and preferably at least 360 MPa with a property selected from A % (L) at least 14% and preferably at least 15%, A% (LT) at least 24% and preferably at least 26%, R m / R p0 , 2 (L) at least 1.40 and preferably at least 1.45, R m / R p0j 2 (LT) at minus 1.45 and preferably at least 1.50 and exhibits at least one corrosion resistance property chosen from a rating according to ASTM G34 for sheets subjected to the conditions of the ASTM G85 A2 test of P and / or EA and poorly developed intergranular corrosion for plates subject to the conditions of ASTM G1 10.
Dans un mode de réalisation avantageux de l'invention à l'issue du traitement thermique court, la tôle obtenue par le procédé selon l'invention présente un rapport Rm /Rpo,2 dans la direction LT d'au moins 1,52 ou 1,53. In an advantageous embodiment of the invention at the end of the short heat treatment, the sheet obtained by the process according to the invention has a ratio R m / R p o, 2 in the direction LT of at least 1, 52 or 1.53.
Avantageusement, pendant au moins 50 jours et manière préférée pendant au moins 200 jours après le traitement thermique court, la tôle obtenue par le procédé selon l'invention présente une limite d'élasticité Rpoj2(L) inférieure à 290 MPa et de préférence inférieure à 280 MPa et Rp0;2(LT) inférieure à 270 MPa et/ou une résistance à rupture Rm(L) inférieure à 410 MPa et de préférence inférieure à 400 MPa et Rpoj2(LT) inférieure à 390 MPa. Advantageously, for at least 50 days and preferably for at least 200 days after the short heat treatment, the sheet obtained by the process according to the invention has a yield strength R p o j2 (L) of less than 290 MPa and of preferably less than 280 MPa and R p0; 2 (LT) less than 270 MPa and / or a rupture strength R m (L) less than 410 MPa and preferably less than 400 MPa and R p oj2 (LT) less than 390 MPa.
Avantageusement la cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 est P ou P-EA. Dans le cadre de l'invention on considère que la corrosion intergranulaire pour les tôles soumises aux conditions de la norme ASTM G110 est peu développée si elle correspond aux images des figures 1 ou 2. Avantageusement, la tôle obtenue par le procédé selon l'invention présente une résistance à la corrosion intercristalline au moins égale à celle d'une tôle de même composition à l'état T3 ou T4. Advantageously, the rating according to ASTM G34 for sheets subject to the conditions of the ASTM G85 A2 test is P or P-EA. In the context of the invention, it is considered that the intergranular corrosion for the sheets subjected to the conditions of the ASTM G110 standard is not very developed if it corresponds to the images of FIG. 1 or 2. Advantageously, the sheet obtained by the process according to the invention has a resistance to intercrystalline corrosion at least equal to that of a sheet of the same composition in the T3 or T4 state.
A l'issue du traitement thermique court, la tôle peut être stockée sans difficultés particulières grâce à sa résistance à la corrosion intercristalline. La tôle issue du traitement thermique court est prête pour une déformation supplémentaire à froid, notamment une opération de mise en forme en 3 dimensions. Un avantage de l'invention est que cette déformation supplémentaire peut atteindre localement ou de façon généralisée des valeurs de 6 à 8% ou même jusque 10%. Pour atteindre des propriétés mécaniques suffisantes à l'issue du revenu à l'état T8, une déformation minimale cumulée de 2% entre ladite déformation supplémentaire et la déformation cumulée par planage et/ou on traction contrôlée optionnellement réalisée avant le traitement thermique court est avantageuse. De manière préférée, la déformation supplémentaire à froid est localement ou de façon généralisée d'au moins 1% de préférence au moins 4% et de manière préférée d'au moins 6%. At the end of the short heat treatment, the sheet can be stored without particular difficulties thanks to its resistance to intercrystalline corrosion. The sheet resulting from the short heat treatment is ready for additional cold deformation, in particular a 3-dimensional forming operation. An advantage of the invention is that this additional deformation can locally or generally reach values of 6 to 8% or even up to 10%. To achieve sufficient mechanical properties to the result of the income at the T8 state, a minimum cumulative deformation of 2% between said additional deformation and the accumulated deformation by planing and / or controlled tension optionally performed before the short heat treatment is advantageous. Preferably, the additional cold deformation is locally or generally at least 1%, preferably at least 4% and preferably at least 6%.
On réalise enfin un revenu dans lequel ladite tôle ainsi mise en forme atteint une température comprise entre 130 et 170°C, avantageusement entre 145 et 165 °C et de préférence entre 150 et 160°C pendant 5 à 100 heures et de préférence de 10 à 70h. Le revenu peut-être réalisé en un ou plusieurs paliers. Finally, an income is produced in which said sheet thus shaped reaches a temperature of between 130 and 170 ° C., advantageously between 145 and 165 ° C. and preferably between 150 and 160 ° C. for 5 to 100 hours, and preferably at 70h. The income can be achieved in one or more levels.
Avantageusement la déformation à froid est effectuée par un ou plusieurs procédés de mise en forme tels que l'étirage, Γ étirage-formage, l'emboutissage, le fluotournage ou le pliage. Dans une réalisation avantageuse, il s'agit d'une mise en forme dans les trois dimensions de l'espace pour obtenir une pièce de forme complexe, de préférence par étirage-formage. Advantageously, the cold deformation is carried out by one or more shaping processes such as stretching, stretching-forming, stamping, spinning or folding. In an advantageous embodiment, it is a shaping in the three dimensions of the space to obtain a piece of complex shape, preferably by stretch-forming.
Ainsi le produit obtenu à l'issue du traitement thermique court peut être mis en forme comme un produit dans un état O ou un produit dans un état W. Cependant, par rapport à un produit dans un état O il a l'avantage de ne plus nécessiter de mise en solution et trempe pour atteindre les propriétés mécaniques finales, un simple traitement de revenu étant suffisant. Par rapport à un produit à dans un état W, il a l'avantage d'être stable et de ne pas nécessiter de chambre froide et de ne pas poser de problèmes liés à la déformation de cet état. Le produit présente également l'avantage en général de ne pas générer de lignes de Luders rédhibitoires lors de la mise en forme. Ainsi on peut par exemple effectuer le traitement thermique court chez le fabriquant de tôle, le stocker sans précautions particulière grâce à sa résistance élevée à la corrosion intergranulaire et effectuer la mise en forme chez le fabricant de structure aéronautique, directement sur le produit livré. Le procédé selon l'invention permet d'effectuer la mise en forme en 3 dimensions d'une tôle à l'issue du traitement thermique court sans que la tôle ne soit dans un état T8, un état O ou un état W avant cette mise en forme en 3 dimensions. Thus the product obtained after the short heat treatment can be shaped as a product in a state O or a product in a state W. However, compared to a product in a state O it has the advantage of not more requiring solution and quenching to achieve the final mechanical properties, a simple income treatment is sufficient. Compared to a product in a state W, it has the advantage of being stable and not requiring a cold room and not to cause problems related to the deformation of this state. The product also has the advantage in general of not generating lines of Luders crippling during formatting. Thus one can for example perform the short heat treatment in the sheet metal manufacturer, store it without special precautions due to its high resistance to intergranular corrosion and perform the shaping at the manufacturer of aeronautical structure, directly on the product delivered. The method according to the invention makes it possible to carry out the 3-dimensional shaping of a sheet at the end of the short heat treatment without the sheet being in a state T8, a state O or a state W before this setting shaped in 3 dimensions.
De manière surprenante, le compromis entre les propriétés mécaniques statiques et les propriétés de tolérance aux dommages obtenues à l'issue du revenu est avantageux par rapport à celui obtenue pour un traitement semblable ne comprenant pas de traitement thermique court. Surprisingly, the compromise between the static mechanical properties and the damage tolerance properties obtained at the end of the income is advantageous by compared to that obtained for a similar treatment not including short heat treatment.
L'utilisation d'un produit susceptible d'être obtenu par le procédé selon l'invention comprenant les étapes de traitement thermique court, déformation à froid et revenu pour la fabrication d'un élément de structure pour avion, notamment d'une peau de fuselage est particulièrement avantageux. Exemple The use of a product that can be obtained by the process according to the invention, comprising the steps of short heat treatment, cold deformation and tempering for the manufacture of a structural element for an aircraft, in particular a skin of fuselage is particularly advantageous. Example
Dans cet exemple, on a comparé des conditions de traitement thermique court pour une tôle en alliage AA2198 d'épaisseur 4,3 mm. Une plaque de laminage en alliage AA2198 dont la composition est donnée dans le Tableau 1 a été homogénéisée puis laminée à chaud jusqu'à l'épaisseur 4,3 mm. Les tôles ainsi obtenues ont été mises en solution 30 mn à 505 °C puis trempées à l'eau. In this example, we compared short heat treatment conditions for an alloy sheet AA2198 with a thickness of 4.3 mm. An AA2198 alloy rolling plate, the composition of which is given in Table 1, was homogenized and then hot rolled to a thickness of 4.3 mm. The sheets thus obtained were dissolved for 30 minutes at 505 ° C. and then quenched with water.
Tableau 1. Composition de la tôle en alliage AA2198 utilisée, en % en poids. Table 1. Composition of the AA2198 alloy sheet used, in% by weight.
Les tôles ont ensuite été tractionnées de façon contrôlée. La traction contrôlée a été réalisée avec un allongement permanent de 2 %. Le vieillissement naturel a été d'au moins 24 heures après la trempe. The sheets were then trimmed in a controlled manner. Controlled traction was achieved with a permanent elongation of 2%. Natural aging was at least 24 hours after quenching.
Les tôles ont ensuite subi un traitement thermique court dont les conditions sont données dans le Tableau 2. Les vitesses de chauffage les plus élevées, représentatives des vitesses de chauffages obtenues dans un four de traitement en continu, ont été obtenues par immersion dans un bain d'huile tandis que les vitesses de chauffage les plus faibles ont été obtenues par traitement à l'air contrôlé, représentatif des conditions industrielles dans un four statique. La vitesse de refroidissement était de l'ordre de 60 °C / min pour l'ensemble des essais. The sheets were then subjected to a short heat treatment, the conditions of which are given in Table 2. The highest heating rates, representative of the heating rates obtained in a continuous treatment furnace, were obtained by immersion in an immersion bath. oil while the lowest heating rates were obtained by controlled air treatment, representative of the industrial conditions in a furnace static. The cooling rate was of the order of 60 ° C./min for all the tests.
Tableau 2 - Conditions de traitement thermique court Table 2 - Short Heat Treatment Conditions
Les propriétés mécaniques statiques après traitement thermique court ont été caractérisées dans les directions longitudinale (L) et transverse (LT) et sont présentées dans le Tableau 3. The static mechanical properties after short heat treatment were characterized in the longitudinal (L) and transverse (LT) directions and are presented in Table 3.
Tableau 3 - Propriétés mécaniques statiques en MPa (R 0,2 et Rm) ou en % (A%) Table 3 - Static mechanical properties in MPa (R 0.2 and R m ) or in% (A%)
Les propriétés de résistance à la corrosion des tôles ont été évaluées dans les conditions des essais normalisés de corrosion intergranulaire (ASTM G1 10) et de corrosion exfoliante (MASTMAASIS dry bottom ASTM G85-A2). La durée d'essai d'immersion du test ASTM Gl 10 est de 6h et la durée d'essai du test MASTMAASIS est de 750h. Les caractérisations ont été effectuées en surface (« peau ») et après usinage d'un dixième de l'épaisseur (« T/10 »). The corrosion resistance properties of the sheets were evaluated under the conditions of standardized intergranular corrosion tests (ASTM G1 10) and exfoliation corrosion tests (MASTMAASIS dry bottom ASTM G85-A2). The test immersion time of the ASTM Gl 10 test is 6h and the test duration of the MASTMAASIS test is 750h. The characterizations were performed on the surface ("skin") and after machining one-tenth of the thickness ("T / 10").
Les résultats des essais de corrosion intergranulaire selon ASTM G110 sont présentés dans le Tableau 4.  The results of intergranular corrosion tests according to ASTM G110 are shown in Table 4.
Les coupes micrographiques représentatives d'une corrosion intergranulaire peu développée et piqûres sont données sur les Figures 1 (échantillon S) et 2 (échantillon H2). Les observations ont été faites au microscope optique à des grandissements de X200. Une coupe micrographique représentative d'une corrosion intergranulaire développée et piqûres est donné sur la Figure 3 (échantillon A30). Une coupe micrographique représentative d'une corrosion intergranulaire développée est donnée sur la Figure 4 (échantillon Al 20).  Micrographic sections representative of poorly developed intergranular corrosion and pitting are given in Figures 1 (sample S) and 2 (sample H2). The observations were made under an optical microscope at magnifications of X200. A representative micrograph section of intergranular corrosion developed and pitting is given in Figure 3 (sample A30). A micrographic section representative of a developed intergranular corrosion is given in Figure 4 (sample Al 20).
Tableau 4 : résultats des essais de corrosion intergranulaire selon ASTM G1 10 Table 4: Results of intergranular corrosion tests according to ASTM G1 10
corrosion intergranulaire  intergranular corrosion
Les résultats des essais de corrosion exfoliante côtés selon la norme ASTM G34 pour les tôles soumises aux conditions du test MASTMAASIS (dry bottom ASTM G85-A2) sont présentés dans le Tableau 5. Tableau 5 - Résultats des essais de corrosion exfoliante dans les conditions du test MASTMAASIS (dry bottom ASTM G85-A2). The results of the exfoliating corrosion tests according to ASTM G34 for sheet subjected to MASTMAASIS test conditions (dry bottom ASTM G85-A2) are shown in Table 5. Table 5 - Results of exfoliation corrosion tests under MASTMAASIS test conditions (dry bottom ASTM G85-A2).
L'échantillon S est un échantillon à l'état T3. Il ne présente pas des propriétés mécaniques permettant d'envisager sa mise en forme pour les déformations les plus élevées. Les échantillons A30, A60 , A 120 , A240 présentent des propriétés mécaniques permettant d'envisager la mise en forme pour les déformations les plus élevées mais présentent une résistance à la corrosion nécessitant des précautions particulières lors du stockage. Sample S is a sample in the T3 state. It does not have mechanical properties to consider its shaping for the highest deformations. Samples A30, A60, A 120, A240 have mechanical properties which make it possible to envisage shaping for the highest deformations but exhibit a resistance to corrosion requiring particular precautions during storage.
Les échantillons Hl, H2, H4, H8, H16 et H30 présentent simultanément des propriétés mécaniques permettant d'envisager sa mise en forme pour les déformations les plus élevées et une résistance à la corrosion permettant d'envisager un stockage sans précautions particulières. L'échantillon Hl présente cependant des propriétés mécaniques un peu moins favorables, notamment en termes d'allongement dans la direction LT. L'échantillon H30 présente des propriétés un peu moins favorables, en particulier en termes de résistance à la corrosion.  Samples H1, H2, H4, H8, H16 and H30 simultaneously have mechanical properties to consider its shaping for the highest deformations and corrosion resistance to consider storage without special precautions. Sample H1, however, has somewhat less favorable mechanical properties, especially in terms of elongation in the LT direction. Sample H30 has slightly less favorable properties, particularly in terms of corrosion resistance.

Claims

Revendications claims
1. Procédé de fabrication d'un produit laminé à base d'alliage d'aluminium notamment pour l'industrie aéronautique dans lequel, successivement, 1. A process for manufacturing a laminated product based on aluminum alloy, in particular for the aeronautical industry in which, successively,
a) on élabore un bain de métal liquide à base d'aluminium comprenant 2,1 à 3,9 % en poids de Cu, 0,6 à 2.0 % en poids de Li, 0,1 à 1,0 % en poids de Mg, 0 à 0,6 % en poids d'Ag, 0 à 1% % en poids de Zn, au plus 0,20 % en poids de la somme de Fe et de Si, au moins un élément choisi parmi Zr, Mn, Cr, Se, Hf et Ti, la quantité dudit élément, s'il est choisi, étant 0,05 à 0,18 % en poids pour Zr, 0,1 à 0,6% en poids pour Mn, 0,05 à 0,3 % en poids pour Cr, 0,02 à 0,2 % en poids pour Se, 0,05 à 0,5 % en poids pour Hf et de 0,01 à 0,15 % en poids pour Ti, les autres éléments au plus 0,05% en poids chacun et 0,15% en poids au total, le reste aluminium ;  a) an aluminum-based liquid metal bath comprising 2.1 to 3.9% by weight of Cu, 0.6 to 2.0% by weight of Li, 0.1 to 1.0% by weight of Mg, 0 to 0.6% by weight of Ag, 0 to 1% by weight of Zn, at most 0.20% by weight of the sum of Fe and Si, at least one element selected from Zr, Mn , Cr, Se, Hf and Ti, the amount of said element, if selected, being 0.05 to 0.18% by weight for Zr, 0.1 to 0.6% by weight for Mn, 0.05 0.3% by weight for Cr, 0.02 to 0.2% by weight for Se, 0.05 to 0.5% by weight for Hf and from 0.01 to 0.15% by weight for Ti, the other elements not more than 0.05% by weight each and 0.15% by weight in total, the balance aluminum;
b) on coule une plaque de laminage à partir dudit bain de métal liquide ;  b) casting a rolling plate from said bath of liquid metal;
c) optionnellement, on homogénéise ladite plaque de laminage ;  c) optionally, homogenizing said rolling plate;
d) on lamine à chaud et optionnellement à froid ladite plaque de laminage en une tôle d'épaisseur comprise entre 0,5 et 10 mm,  d) said laminating plate is hot-rolled and optionally cold-rolled to a sheet thickness of between 0.5 and 10 mm,
e) on met en solution ladite tôle et on la trempe;  e) said sheet is dissolved and quenched;
f) optionnellement on réalise un planage et/ou on tractionne de façon contrôlée ladite tôle avec une déformation cumulée d'au moins 0,5% et inférieure à 3%, g) on réalise un traitement thermique court dans lequel ladite tôle atteint une température comprise entre 145°C et 175°C et de préférence entre 150°C et 170°C pendant 0,1 à 45 minutes et de préférence pendant 0,5 à 5 minutes, la vitesse de chauffage étant comprise entre 3 et 600 °C/min.  f) optionally, planing is carried out and / or said sheet is pulled in a controlled manner with a cumulative deformation of at least 0.5% and less than 3%, g) a short heat treatment is performed in which said sheet reaches a temperature between 145 ° C and 175 ° C and preferably between 150 ° C and 170 ° C for 0.1 to 45 minutes and preferably for 0.5 to 5 minutes, the heating rate being between 3 and 600 ° C / min.
2. Procédé selon la revendication 1 dans lequel le dit traitement thermique court est réalisé de façon à obtenir un temps équivalent à 150 °C de 0,5 à 35 minutes et de préférence de 1 à 20 minutes, le temps équivalent t, à 150 °C est défini par la formule : où T (en Kelvin) est la température instantanée de traitement du métal, qui évolue avec le temps t (en minutes), et Tref est une température de référence fixée à 423 K, tj est exprimé en minutes, la constante Q/R = 16400 K est dérivée de l'énergie d'activation pour la diffusion du Cu, pour laquelle la valeur Q = 136100 J/mol a été utilisée. 2. The method of claim 1 wherein said short heat treatment is carried out so as to obtain a time equivalent to 150 ° C from 0.5 to 35 minutes and preferably from 1 to 20 minutes, the equivalent time t, 150 ° C is defined by the formula: where T (in Kelvin) is the instantaneous processing temperature of the metal, which changes with time t (in minutes), and T ref is a reference temperature set at 423 K, tj is expressed in minutes, the Q / R constant = 16400 K is derived from the activation energy for Cu diffusion, for which Q = 136100 J / mol was used.
3. Procédé selon la revendication 1 ou la revendication 2 dans lequel, lors de l'étape g de traitement thermique court la vitesse de refroidissement est comprise entre 1 et 1000 °C/min, préférentiellement entre 10 et 800 °C/min. 3. Method according to claim 1 or claim 2 wherein, during step g of heat treatment runs the cooling rate is between 1 and 1000 ° C / min, preferably between 10 and 800 ° C / min.
4. Procédé selon une quelconque des revendications 1 à 3 dans lequel on réalise ledit traitement thermique court directement après trempe sans écrouissage intermédiaire. 4. Method according to any one of claims 1 to 3 wherein said short heat treatment is carried out directly after quenching without intermediate work-hardening.
5. Procédé selon une quelconque des revendications 1 à 4 dans lequel la teneur en cuivre est au moins de 2,8 % et au maximum de 3,4 % en poids. The process of any one of claims 1 to 4 wherein the copper content is at least 2.8% and at most 3.4% by weight.
6. Procédé selon une quelconque des revendications 1 à 5 dans lequel la teneur en lithium est au moins 0,70 % en poids et au maximum de 1 ,1 % en poids. 6. A process according to any one of claims 1 to 5 wherein the lithium content is at least 0.70% by weight and at most 1.1% by weight.
7. Procédé selon une quelconque des revendications 1 à 6 dans lequel la teneur en magnésium est au moins de 0,2 % et au maximum de 0,6 % en poids. 7. A process according to any one of claims 1 to 6 wherein the magnesium content is at least 0.2% and at most 0.6% by weight.
8. Procédé selon une quelconque des revendications 1 à 7 dans lequel l'alliage contient entre 0,08 et 0,15 % en poids de zirconium, entre 0,01 et 0,10 % en poids de titane et dans lequel la teneur en Mn, Cr, Se et Hf est au maximum 0,05 % en poids. 8. Process according to any one of claims 1 to 7 wherein the alloy contains between 0.08 and 0.15% by weight of zirconium, between 0.01 and 0.10% by weight of titanium and in which the content of Mn, Cr, Se and Hf is at most 0.05% by weight.
9. Procédé selon une quelconque des revendications 1 à 8 dans lequel après l'étape g, h) on réalise une déformation supplémentaire à froid de ladite tôle de telle sorte que la déformation supplémentaire soit inférieure à 10%, 9. Method according to any one of claims 1 to 8 wherein after step g, h) is carried out a further cold deformation of said sheet so that the additional deformation is less than 10%,
i) on réalise un revenu dans lequel ladite tôle atteint une température comprise entre 130 et 170°C avantageusement entre 145 et 165 °C et de préférence entre 150 et 160°C pendant 5 à 100 heures et de préférence de 10 à 70h. i) an income is produced in which said sheet reaches a temperature between 130 and 170 ° C, preferably between 145 and 165 ° C and preferably between 150 and 160 ° C for 5 to 100 hours and preferably from 10 to 70h.
10. Produit laminé susceptible d'être obtenu par le procédé selon une quelconque des revendications 1 à 8, présentant une limite d'élasticité Rp0,2(L) et/ou Rp0;2(LT) comprise entre 75% et 90 % , préférentiellement entre 80 et 85% et de préférence entre 81% et 84% de la limite d'élasticité dans la même direction d'une tôle de même composition à l'état T4 ou T3 ayant subi la même traction contrôlée après trempe, au moins une propriété choisie parmi un rapport Rm /Rp0,2 (L) d'au moins 1,40 et de préférence au moins 1 ,45 et un rapport Rm /Rp0,2 (LT) au moins 1,45 et de préférence au moins 1,50 et présente au moins une propriété de résistance à la corrosion choisie parmi une cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 de P et/ou EA et une corrosion intergranulaire peu développée pour des tôles soumises aux conditions de la norme ASTM Gl 10. 10. Laminated product obtainable by the method according to any one of claims 1 to 8, having a yield strength R p0 , 2 (L) and / or R p0; 2 (LT) of between 75% and 90%, preferably between 80 and 85% and preferably between 81% and 84% of the yield strength in the same direction of a sheet of the same composition in the T4 state or T3 having undergone the same controlled pull after quenching, at least one property selected from a ratio R m / R p0 , 2 (L) of at least 1.40 and preferably at least 1.45 and a ratio R m / R p0.2 (LT) at least 1.45 and preferably at least 1.50 and exhibits at least one corrosion resistance property chosen from a rating according to ASTM G34 for sheets subjected to ASTM G85 A2 test conditions. of P and / or EA and a poorly developed intergranular corrosion for plates subjected to the conditions of ASTM Gl 10.
1 1. Produit laminé selon la revendication 10 présentant une combinaison d'au moins une propriété choisie parmi Rp02(L) d'au moins 220 MPa et de préférence d'au moins 250A laminated product according to claim 10 having a combination of at least one property selected from R p02 (L) of at least 220 MPa and preferably at least 250
MPa, Rpoj2(LT) d'au moins 200 MPa et de préférence d'au moins 230 MPa, Rm(L) d'au moins 340 MPa et de préférence d'au moins 380 MPa, Rm(LT) d'au moins 320 MPa et de préférence d'au moins 360 MPa avec une propriété choisie parmi A%(L) au moins 14% et de préférence au moins 15%, A%(LT) au moins 24% et de préférence au moins 26%, Rm /Rpo,2 (L) au moins 1,40 et de préférence au moins 1,45, Rm /Rp0>2 (LT) au moins 1,45 et de préférence au moins 1,50. MPa, R p oj2 (LT) of at least 200 MPa and preferably at least 230 MPa, R m (L) of at least 340 MPa and preferably at least 380 MPa, R m (LT ) of at least 320 MPa and preferably at least 360 MPa with a property selected from A% (L) at least 14% and preferably at least 15%, A% (LT) at least 24% and preferably at least 26%, R m / R p o, 2 (L) at least 1.40 and preferably at least 1.45, R m / R p0> 2 (LT) at least 1.45 and preferably at least 1.50.
12. Produit laminé selon la revendication 10 ou la revendication 1 1 tel que la cotation selon la norme ASTM G34 pour des tôles soumises aux conditions du test ASTM G85 A2 est P ou P-EA. 12. A laminated product according to claim 10 or claim 1 1 such that the rating according to ASTM G34 for plates subject to the conditions of the ASTM G85 A2 test is P or P-EA.
13. Utilisation d'un produit obtenu par le procédé selon la revendication 9 pour la fabrication d'un élément de structure pour avion, notamment d'une peau de fuselage d'avion. 13. Use of a product obtained by the process according to claim 9 for the manufacture of a structural element for an aircraft, in particular an aircraft fuselage skin.
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CN105612266B (en) 2018-12-14
US20160304995A1 (en) 2016-10-20
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CA2908454C (en) 2021-05-18
BR112015025477B1 (en) 2020-04-28
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US10400313B2 (en) 2019-09-03

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