Solution-quenching heat treatment method for aluminum alloy profiles

Abstract

A solution-quenching heat treatment method for an aluminum alloy profile, located in an orthogonal coordinate system ( , ), where is the spinning direction, and whose cross-section comprises a web that is decomposed according to EN2066-2022 into at least one elementary rectangle of dimensions A1, B1 with an aspect ratio A1 / B1 from 4 to 50, where A1 is the largest dimension and is parallel to , with A1 from 100 mm to 500 mm and B1 is parallel to and from 10 to 50 mm, said method comprises a solution-quenching step and an immersion quenching step in a quenching tank filled with liquid such that during the immersion step the plane ( , ) of the profile is substantially parallel to the normal to the surface of the liquid. Abbreviated figure: 7

Description

Title of the invention: Solution-quenching heat treatment method for aluminum alloy profiles. Technical field

[0001] The invention relates to a solution-quenching heat treatment method for improving the machinability of profiles. The invention also relates to a method for manufacturing a profile using the solution-quenching heat treatment method and the resulting product exhibiting greater homogeneity of properties within the section considered, as well as improved machinability. Prior art

[0002] Extruded products, also called profiles, made of aluminum alloy are developed to produce high-strength parts intended in particular for the aeronautical and aerospace industries.

[0003] Extruded aluminium alloy products are used in the aeronautical industry for many applications, such as fuselage stiffeners or stringers, fuselage frames, wing stiffeners, floor crossbeams and beams, as well as seat rails.

[0004] Generally speaking, a profile is defined by the geometry of its cross-section. The cross-section of the profile corresponds to the section of the profile taken perpendicular to the direction of extrusion.

[0005] According to standard NF-EN 2066-2022 paragraph 3, the cross-section of a profile can be divided into elementary rectangles of dimensions A and B; A always being the largest dimension of the elementary part and B being considered as the thickness of this elementary rectangle of the profile (see [Fig. 1], taken from standard EN2066). A shape ratio can be defined with the ratio A / B.

[0006] Generally, the central parts of the profile, which in most cases have a high aspect ratio, are called the "web," and the parts that intercept or are adjacent to the web, which in most cases have lower aspect ratios, are called the "flange." In general, a web designates the central part of a profile, and a flange corresponds to a lateral part of the profile, intercepting or adjacent to the web, and one of whose directions is substantially perpendicular to the direction of the longest dimension of the web. A flange is a particular type of flange located at one end of the web.

[0007] According to standard NF-EN 2066-2022, the web and the side(s) of a profile can be divided into elementary rectangles. The web is in contact with the side(s) of the cross-section. An elementary rectangle of a side intercepts (case of a side extending symmetrically on either side of the web) or is adjacent (case of an asymmetric side, example of an L-shaped cross-section) to the elementary rectangle(s) of the web. In the case of [Fig. 1], the web corresponds to the elementary rectangle 20 and the cross-section has three flanks 30, 30', 30". In the case of a J-profile shown in [Fig. 2], the cross-section can be described by three elementary rectangles 20, 30, 35. The elementary rectangles 20 and 30 correspond respectively to the web and the flank of the J-profile. The elementary rectangle 35, which is located at the end of the flank 30, is not a flank in the sense of the invention because the elementary rectangle 35 does not intersect or is not adjacent to the elementary rectangle of the web.

[0008] EP3080319 (Constellium Issoire) discloses a raw spun product for the manufacture of a machined spun product for the aeronautical industry, in alloy composition in % by weight, Cu: 2.0 - 6.0; Li: 0.5 - 2.0; Mg: 0- 1.0; Ag: 0 - 0.7; Zn 0 - 1.0; and at least one element chosen from Zr, Mn, Cr, Sc, Hf and Ti, the quantity of said element, if chosen, being 0.05 to 0.20 % by weight for Zr, 0.05 to 0.8 % by weight for Mn, 0.05 to 0.3 % by weight for Cr and for Sc, 0.05 to 0.5 % by weight for Hf and 0.01 to 0.15 % by weight for Ti, Si < 0.1; Fe < 0.1; other < 0.05 each and < 0.15 in total, having a rough web and a rough flank such that the dimension of the rough flank whose direction is perpendicular to the dimension of the length of the rough web is at least 20% greater than the length of the machined flank.

[0009] Extruded aluminum alloy products, particularly those used in aerospace, are in most cases machined to obtain the final geometry of parts. It is important to be able to machine such profiles without deformation. Deformation of profiles during machining is related to internal stress levels. High levels of internal stress cause significant distortion during machining, making it impossible to machine these profiles.

[0010] It is known that quenching after solution heating of 2xxx or 7xxx series aluminum alloys can induce internal stresses. The presence of strong thermal gradients in the cross-section of the profile during quenching leads to inhomogeneous plastic deformation. When the product is completely cooled, it contains internal stresses, also called residual stresses.

[0011] The most common methods for relieving residual stresses in 2xxx and 7xxx series alloy profiles involve plastic deformation by tensile stress in the direction of the extrusion. CN108754363 (Central South University) discloses a thermomechanical treatment comprising a 1 to 10% drawing step to reduce residual stresses. Water quenching is also possible. hot, or even boiling, to reduce residual stresses as presented in Techniques de l'ingénieur M 1 290v2 Heat treatments of aluminium alloys - Materials and recommendations - M. Stucky page 19. However, this solution has the disadvantage of obtaining lower final properties than when the profile is quenched in water at room temperature.

[0012] There is a need to improve the machinability of aluminium alloy profiles, in particular profiles whose cross section has a web and at least one flank for which the drawing solution is not sufficient. Description of the invention

[0013] A first object of the invention relates to a solution-quenching heat treatment method for an aluminum alloy profile belonging to the 2XXX or 7XXX series. The profile is located in an orthogonal coordinate system (x, Y, Z) – Y being the extrusion direction. The cross-section of said profile comprises a web and at least one flange. The core is decomposed according to standard EN2066-2022 into at least one elementary rectangle with dimensions Al, B1 with an aspect ratio Al / Bl between 4 and 50. Al is the largest dimension and is parallel to x. Al is between 100 mm and 500 mm. B1 is parallel to z and is between 10 and 50 mm. The side panel is decomposed according to standard EN2066-2022 into at least one second elementary rectangle with dimensions A2, B2, where A2 is the larger dimension. The dimension in mm of the second elementary rectangle perpendicular to the x direction is greater than or equal to 1.2 * B1 (in mm). The solution-quenching heat treatment method comprises the following steps: - (dl) the aluminium profile is placed in solution at a temperature of approximately 400°C to 550°C for a period of approximately 5 minutes to 15 hours, - (d2) the aluminium profile in solution is quenched in a quenching tank filled with liquid (10). During step (d2) the plane (y, z) of the profile is substantially parallel to the normal N to the surface of the liquid.

[0014] Preferably, the first elementary rectangle of the web and the second rectangle of the flank are intersecting or adjacent. Preferably, at least one first rectangle of the web satisfies that the dimension Al is between 100 mm and 500 mm, the dimension B1 is between 10 and 50 mm, and that Al / Bl is between 4 and 50. Preferably, the first elementary rectangle of the web is considered to be the one that is intersecting or adjacent to the second elementary rectangle of the flank and having the largest dimension Bl.

[0015] Preferably, the spinning direction forms an angle alpha with the normal N to the surface of the liquid when the profile is immersed in the quenching tank filled with liquid such that the value of the angle alpha in degrees satisfies 70° < angle alpha < 90°, preferably 80° < angle alpha < 87°.

[0016] Preferably, the largest dimension A2 of the second elementary rectangle is perpendicular to the x direction.

[0017] Preferably, the shape ratio A2 / B2 of the second elementary rectangle is between 2 and 6.

[0018] Another object of the invention relates to a method for manufacturing an aluminum alloy profile comprising the following successive steps: (a) a rough form is cast in 2XXX or 7XXX aluminum alloy, (b) Optionally, the said raw form is homogenized, (c) The said rough form is hot-formed by extrusion to obtain an aluminium profile (1) located in an orthogonal coordinate system (x, y, z), where y is the extrusion direction, and whose cross-section has a web and at least one flange. The said web is decomposed according to standard EN2066-2022 into at least a first elementary rectangle of dimensions Al, B1 with an aspect ratio Al / Bl from 4 to 50, where Al is the largest dimension and is parallel to x, with Al from 100 mm to 500 mm, and B1 is parallel to z and from 10 to 50 mm, and said at least one side is decomposed according to standard EN2066-2022 into at least a second elementary rectangle of dimension A2, B2 where A2 is the largest dimension, and such that the dimension in mm of the second elementary rectangle perpendicular to the x direction of the first elementary rectangle is greater than or equal to 1.2 *B1, (d) said aluminium profile (1) is put into solution and then quenched by immersion according to the first object of the invention relating to a heat treatment method of solution quenching, (e) the said solution-quenched aluminium profile is subjected to controlled traction, (f) optionally the said drawn product is straightened or shaped, (g) income is realized from said spun-pulled product.

[0019] Preferably, the aluminum alloy 7XXX is an alloy designated according to standard AA7075 or AA7175 or AA7010 or AA7050 or AA7349 or AA7449.

[0020] Preferably, the 2XXX aluminum alloy is an Al-Cu-Li alloy designated according to standard AA2065 or AA2195 or AA2295 or AA2196 or AA2296 or AA2076 or AA2099 or AA2199.

[0021] Preferably, the aluminum alloy is an Al-Cu-Li alloy with the following weight percentage composition: Cu: 1-5; Li: 0.5-2; Mg: 0-4; Ag: 0-0.7; Zn: 0-1; and at least one element chosen from Zr, Mn, Cr, Sc, Hf and Ti, the quantity of said element, if chosen, being 0.04 to 0.20% by weight for Zr, 0.05 to 0.8% by weight for Mn, 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, Si <0.1; Fe < 0.1; other elements < 0.05 each and < 0.15 in total, remainder aluminium.

[0022] Preferably, the aluminium alloy is an Al-Cu-Li alloy with the following composition by weight % Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remainder aluminium.

[0023] Another object of the invention is an Al-Cu-Li aluminum alloy profile, obtainable by the manufacturing method, wherein the aluminum alloy is an Al-Cu-Li alloy with the following composition in %: Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements <0.05 each and <0.15 in total, the remainder being aluminum. The profile is located in an orthogonal coordinate system (y, y, z), where y is the extrusion direction, and whose cross-section has a web and at least one flange.The said core is decomposed according to standard EN2066-2022 into at least one first elementary rectangle of dimensions Al, B1 with an aspect ratio Al / Bl of 4 to 50, where Al is the largest dimension and is parallel to x, with Al from 100 mm to 500 mm, and B1 is parallel to z and from 10 to 50 mm, and said at least one side is decomposed according to standard EN2066-2022 into at least one second elementary rectangle of dimension A2, B2 where A2 is the largest dimension, and such that the dimension of the second elementary rectangle perpendicular to the x direction of the first elementary rectangle is greater than or equal to 1.2 *B1. The aluminum alloy profile is characterized by the fact that the deviation (in %) of the yield strength measured in the L direction, corresponding to the y-spinning direction, is less than 18% in absolute value regardless of the position in the cross-section of the profile.

[0024] Preferably, the aluminum alloy profile is such that the maximum strain measured in the extrusion direction is less than 150 µm / m in any area of ​​the web, such that said web area is not in contact with a flange. The strain is measured using a strain gauge positioned at one end of the web in the extrusion direction y during successive machining operations that reduce the web dimension parallel to the x direction, starting from the side opposite the gauge, after all protruding flanges of the web have been machined. Figures

[0025] Fig. 1 represents the principle of decomposition of a section of profiles into elementary rectangle(s) according to standard EN2066-2022.

[0026] Fig. 2 represents a J-shaped profile.

[0027] Fig. 3 represents the case of a hardened profile according to the principle of the invention. Figure 3 a) shows the perspective view of a profile (1) with a web (2) and two sides (3) and (3'). Figure 3 b) shows the cross-section decomposed into elementary rectangles. Figure 3 c) shows the perspective view of the profile above the surface of the liquid in the quenching tank according to one embodiment.

[0028] Figure 4 represents the projection of Figure 3 c) into the plane defined by the spinning direction y and the normal N to the surface of the liquid (100) of the quenching tank.

[0029] Figure 5 shows the cross-section of the profile in examples 1 and 2, as well as its decomposition into elementary rectangles.

[0030] Fig. 6 represents the positioning of a profile on a stretcher (40) corresponding to the positioning during the quenching step of the reference case (case C of the example).

[0031] Fig. 7 represents the positioning of a profile on a stretcher corresponding to an embodiment according to the invention (case D of the example).

[0032] Fig. 8 represents a principle of implementation of the quenching solution process according to the invention.

[0033] Fig. 9 represents an embodiment allowing the immersion of the profile on a stretcher at an angle alpha with a sling system.

[0034] Fig. 10 represents the cross-sectional view of a profile immersed in the quenching tank according to the positioning of Fig. 6 (reference).

[0035] Fig. 11 represents the cross-sectional view of a profile immersed in the quenching tank according to the positioning of Fig. 7 (invention).

[0036] Fig. 12, Fig. 13, Fig. 14, Fig. 15 and Fig. 16 represent the steps of the deformation measurement method used to assess the machinability of the profile.

[0037] Fig. 17 represents the evolution of the measured deformation as a function of positioning in the machined web, using the method described in Fig. 12 to Fig. 16 for the profile described in Fig. 5, after quenching according to the reference method or according to the method of the invention. Detailed description of the invention

[0038] Unless otherwise stated, all indications concerning the chemical composition of the alloys are 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 as a percentage by weight is multiplied by 1.4. The designation of the alloys is in accordance with The regulations of The Aluminium Association are known to those skilled in the art. The definitions of metallurgical states are given in the European standard EN 515.

[0039] The static mechanical characteristics in tension, in other words the breaking strength Rm, the conventional yield strength at 0.2% elongation Rp0.2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1, the sampling and direction of the test being defined by standard EN 485-1.

[0040] According to the invention, a profile 1 is considered to comprise a web and at least one flange. Figure 3 represents the case of a profile with a web 2 and two flanges 3 and 3'. This illustration is provided to understand the invention and is not limiting; the profile may contain one or more than two flanges.

[0041] The core can be decomposed ([Fig.3] b) according to standard EN2066-2022 into at least a first elementary rectangle 20 of dimensions Al, B1 where Al is the largest dimension.

[0042] The dimensions Al and B1 are such that Al is from 100 mm to 500 mm and B1 from 10 to 50 mm, and the aspect ratio Al / Bl is from 4 to 50. Preferably, the dimension Al is at least 150 mm or 200 mm and at most 400 mm or 350 mm. Preferably, B1 is at least 15 mm or 20 mm and at most 40 mm or 30 mm. If the dimension B1 is less than 10 mm, the invention offers no advantage. Preferably, the Al / Bl ratio is at least 6 or 8 and at most 40 or 30.

[0043] A frame of reference (y, y, Z) is defined such that the dimension Al is parallel to the x- direction, the y direction is parallel to the spinning direction and the dimension B1 is parallel to the z direction

[0044] Each side can be decomposed according to standard EN2066-2022 into a second elementary rectangle (30 and 30' [Fig. 3] b)) of dimensions A2, B2 and A2', B2' where A2 and A2' are the larger dimensions. According to the invention, the first elementary rectangle (of the core) and the second elementary rectangle (of the side) are considered to be adjacent or intersecting.

[0045] According to the invention, the term "first elementary rectangle" is used for an elementary rectangle defining the core and "second elementary rectangle" for an elementary rectangle defining a flank.

[0046] According to the invention, the dimension of the at least second elementary rectangle, which is perpendicular to the x-direction of the first elementary rectangle, is greater than or equal to 1.2 * B1, preferably 1.5*B1 or 2*B1, or even 2.2*B1. In the case shown in Figure 3, the dimensions A2 and A2' are perpendicular to the y-direction of the first elementary rectangle 20.

[0047] It is possible that the web can be described by several first elementary rectangles. In the case where the web can be described by more than one elementary rectangle (Al, B1), (Al', B1')... the value B1 to be considered corresponds to the maximum value (Bl, Bl', ...) of the first elementary rectangles (of the web) adjacent or intersecting the side considered.

[0048] In the case where the core can be described by more than one first elementary rectangle, it is considered that at least one first elementary rectangle satisfies the dimensions mentioned.

[0049] Preferably the dimension of at least a second elementary rectangle perpendicular to the x direction of the first elementary rectangle of the core corresponds to dimension A2. Preferably the aspect ratio (A2 / B2 or A2' / B2' or ...) of at least a second elementary rectangle (side 20, 20', 20''...) is between 2 and 6.

[0050] The solution-quenching heat treatment method for an aluminum alloy profile according to the invention comprises solution quenching and immersion quenching. The inventors have observed that it is possible to improve the machinability of aluminum alloy profiles, particularly 2xxx or 7xxx series aluminum alloys, and especially Al-Cu-Li alloys, by adjusting the positioning of the profile's web during immersion quenching. The impact of quenching on the properties is amplified if the largest dimension of the web is significant.

[0051] The surface of the quenching liquid at rest is considered as a plane with normal N.

[0052] The inventors observed that it was detrimental to orient the web of the profile vertically relative to the liquid surface during quenching. "Orienting the web of the profile vertically" means that the x-direction, parallel to the longest dimension of the web, is oriented substantially parallel to the normal to the quenching liquid surface. This practice, however, has the advantage of allowing a larger number of profiles to be processed simultaneously. Indeed, for space reasons, a greater number of profiles can be immersed for a given liquid surface area when they are positioned with their web vertical.

[0053] According to the invention, a direction is understood to be "substantially parallel" to another direction if these two directions are identical or form an angle of less than 10°, preferably less than 5°.

[0054] The inventors found that, on the contrary, it was advantageous for the web to be positioned substantially horizontally with respect to the surface of the quenching liquid. "Orienting the web of the profile horizontally" means that the x-direction parallel to the longest dimension of the web is oriented substantially perpendicular to the normal M of the liquid surface. According to the invention, a direction is understood to be substantially perpendicular to another if the angle between these two directions is 90° + / - 10°, preferably + / - 5°.

[0055] The inventors have indeed found that it is possible to reduce the residual stresses measured in the profile if the (y, z) plane of the profile is substantially parallel to the normal N of the surface of the quenching liquid. This arrangement corresponds to "orienting the web of the profile horizontally." According to the invention, a plane is understood to be "substantially parallel" to a direction if the normal to this plane forms an angle of 80° to 90°, preferably 85° to 90°, with said direction.

[0056] The inventors believe that this arrangement according to the invention allows the entire profile to be dipped almost simultaneously, which is beneficial with regard to the homogeneity of the properties.

[0057] Advantageously, the profile is inclined at the moment of immersion and during immersion (Figure 4). This allows for better immersion and, above all, better evacuation of any heat-forming bubbles that may form on the surface of the profile during the initial stages of quenching. Advantageously, the drawing direction y of the profile forms an angle alpha with the direction N, corresponding to the normal direction of the surface of the quenching liquid, such that the angle alpha (in degrees) is strictly less than 90°, preferably at least 70°, 75°, or 80°, and preferably at most 89°, 88°, or 87°.

[0058] Aluminum alloy profiles are manufactured according to a well-known process comprising a casting step, preferably a homogenization step, a heating step, a drawing step, an optional cutting-to-length step, a solution heating step, a quenching step, a tensile stress-relieving step, an optional straightening step, and a tempering step. The quenching step considered here by the invention is an immersion quenching step. It consists of plunging the profiles into a liquid as quickly as possible after the end of the solution heating heat treatment. The profiles are usually held using slings or positioned on a stretcher itself supported by slings that can be immersed in a quenching tank.

[0059] In the manufacturing process of a profile according to the invention, a rough form is cast from a 2XXX or 7XXX aluminum alloy, preferably an Al-Cu-Li alloy. Preferably, the rough form is a billet. It is possible that the rough form is a plate from which a cylindrical shape can be extracted.

[0060] Preferably, the 2XXX aluminum alloy has a composition corresponding to an AlCuLi alloy. Advantageous 2XXX aluminum alloys for implementing the invention include, in particular, AA2065, AA2195, AA2295, AA2196, AA2296, AA2076, AA2099, AA2199. AA2196, AA2296, AA2076 alloys are particularly preferred.

[0061] Preferably, the aluminum alloy 2XXX has a composition corresponding to an Al-Cu-Li alloy with the composition in % by weight Cu: 1 - 5; Li: 0.5 - 2; Mg: 0 - 4; Ag: 0 - 0.7; Zn 0 - 1; and at least one element chosen from Zr, Mn, Cr, Sc, Hf and Ti, the quantity of said element, if chosen, being from 0.04 to 0.20 % by weight for Zr, 0.05 to 0.8 % by weight for Mn, 0.05 to 0.3 % by weight for Cr and for Sc, 0.05 to 0.5 % by weight for Hf and from 0.01 to 0.15 % by weight for Ti, Fe <0.1; Si < 0.1; other elements < 0.05 each and < 0.15 in total, remainder aluminum.

[0062] Preferably, the aluminum alloy 2XXX is an Al-Cu-Li alloy with the following composition by weight % Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remainder aluminum.

[0063] Preferably, the aluminum alloy 2XXX is an Al-Cu-Li alloy with the following composition by weight % Cu 2.8-3.2; Li 1.6-1.8; Mg 0.2-0.5; Ag 0.2-0.4; Zn<0.15; Mn 0.2-0.4; Zr 0.04-0.18; Ti 0.02-0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remainder aluminum.

[0064] Advantageous 7XXX aluminium alloys for carrying out the invention include, in particular, AA7075 or AA7175 or AA7010 or AA7050 or AA7349 or AA7449 alloys.

[0065] The resulting rough form is preferably homogenized. The homogenization temperature is preferably between 470 °C and 540 °C for 5 to 60 hours. Preferably, the homogenization temperature is between 500 °C and 530 °C. After homogenization, the rough form is generally cooled to ambient temperature before being preheated for hot forming. The preheating aims to reach an initial forming temperature preferably between 400 °C and 500 °C, and preferably in the range of 450 °C to 480 °C, enabling the deformation of the rough form. The reheating step can also serve as a homogenization step if the latter is not carried out beforehand.

[0066] Hot deformation is carried out by extrusion to obtain a profile with a core and at least one flange. In the context of the invention, the cross-section of the extruded product can be described using elementary rectangles according to the recommendations of standard EN2066-2022 as defined earlier in the description.

[0067] The spinning conditions (speed and temperature) are determined empirically to ensure good productivity while guaranteeing surface quality and the absence of defects. The exact extrusion speeds and temperatures depend on the size of the starting billet, the size and shape of the spun section, and the number of dyed openings, the capacity of the spinning press, the spinning method (direct or indirect), parameters well known to the man of the trade.

[0068] The spun product thus obtained is then dissolved and quenched according to the solution-quenching heat treatment method of the invention. Advantageously, the dissolution is carried out at a temperature of approximately 400 to 550 °C, for 5 minutes to 15 hours, preferably from 440 to 540 °C. The duration may advantageously be from 15 minutes to 10 hours.

[0069] Quenching is carried out by immersion in a tank filled with liquid. The liquid may be water, an aqueous solution, or any other suitable liquid. The temperature of the liquid is preferably temperature-controlled between 15 °C and 30 °C, preferably between 20 °C and 25 °C.

[0070] The inventors found it advantageous for the (y, z) plane of the profile to be substantially parallel to the normal / v of the liquid surface at the time of immersion of the profile in the liquid contained in the quenching tank ([Fig. 3]). Preferably, the profile is kept immersed in the liquid in this position, preferably for a period of at least approximately 30 seconds. The total immersion time is typically from 30 seconds to 1 hour, preferably from 1 minute to 30 minutes.

[0071] This arrangement allows for faster complete immersion of the profile section and reduces the thermal gradients between the top and bottom of the web (i.e., the thermal gradient in the x direction). The inventors believe this is advantageous because it reduces the residual stress gradient along the web height (Al). In the presence of at least one flange, the inventors believe this arrangement allows for the fastest possible immersion of at least part of the flange in order to cool the web-flange junction as quickly as possible by thermal conductivity. This limits the thermal gradients. The inventors believe this results in lower residual stresses in the y direction. This effect remains valid if the profile has at least two or more flanges.It is preferable to immerse all the sides and the web almost simultaneously in order to limit the thermal gradients between the web and the sides, as well as between each of the sides themselves. In addition to reducing residual stress gradients after quenching, reducing thermal gradients ensures good homogeneity of mechanical properties within the cross-section, which is advantageous in itself and also improves stress-relieving efficiency and reduces residual stresses after stress-relieving. All of this helps to reduce the residual stress levels in the y-direction, which are responsible for the deflection observed after machining in the y-spinning direction, also known as saber.

[0072] We speak of saber deformation, for example, when, if the flange of a profile is placed on a surface plate with the x-direction of the profile's cross-section oriented perpendicular to the surface of the plate, the flange of the profile does not touch the plate at certain points in the y-direction of the extrusion. The saber is defined by the height of the deflection corresponding to the maximum distance between the surface of the plate and the flange of the profile. This deflection height is measured in the y-direction.

[0073] Preferably, the profile is inclined at the time of immersion such that the y-direction, corresponding to the extrusion direction of the profile, forms an angle alpha with the N-direction of the liquid surface, and such that the angle alpha (in degrees) is strictly less than 90° and preferably greater than or equal to 70°. Preferably, the angle alpha is such that 70° < angle alpha < 90°, or 70° < angle alpha < 87°, or 75° < angle alpha < 87°, or 80° < angle alpha < 87°, so that heat-retaining bubbles do not remain trapped at the flank(s). The removal of bubbles promotes heat exchange and consequently improves the quenching rate, which is beneficial for the mechanical properties and the homogeneity of the properties in the cross-section of the profile.

[0074] The spun product, thus dissolved and quenched, then undergoes controlled tensile stress relieving, preferably of 1 to 5% and preferably of at least 2% in plastic strain value. Known steps such as straightening or shaping can optionally be carried out before or after the controlled tensile stress relieving.

[0075] Income is preferably generated at a temperature of 100 to 190 °C for 5 to 100 h, preferably from 120 to 185 °C for 12 to 40 h.

[0076] The inventors have found that a process such as described above makes it possible to reduce the heterogeneities of the yield strength measured in the L direction in the cross section of the profile.

[0077] In particular, on an Al-Cu-Li aluminum alloy profile with a weight composition of % Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remains aluminium, with a core 2 and at least one flange (3, 3'), said core 2 is decomposed according to standard EN2066-2022 into at least one first elementary rectangle 20 of dimensions Al, B1 with an aspect ratio Al / B1 from 4 to 50, where Al is the largest dimension and is parallel to x, with Al from 100 mm to 500 mm, and B1 is parallel to z and from 10 to 50 mm, and the at least one flange (3, 3') is decomposed according to standard EN2066-2022 into at least one second elementary rectangle 30 of dimension A2, B2 where A2 is the largest dimension, and such that the dimension in mm of the second elementary rectangle perpendicular to the x direction of the first elementary rectangle is greater than or equal to 1.2 * B1 presents a deviation (in %) of the elastic limit measured in the L direction of less than 18% in absolute value regardless of the position in the cross section of the profile.

[0078] Preferably, the aluminum alloy 2XXX is an Al-Cu-Li alloy with the following composition by weight % Cu 2.8-3.2; Li 1.6-1.8; Mg 0.2-0.5; Ag 0.2-0.4; Zn<0.15; Mn 0.2-0.4; Zr 0.04-0.18; Ti 0.02-0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remainder aluminum.

[0079] The inventors have observed that the maximum deformation measured during a machining operation is reduced when the profile is obtained according to the invention. The inventors have shown that machinability can be correlated with a measurement of the deformation in the y-spinning direction. The inventors have found that the maximum absolute deformation measured in the y-spinning direction is less than 150 µm in any area of ​​the web not in contact with a flange. The inventors believe that such deformation levels make it possible to reduce the deformation of the profile during machining.

[0080] The deformation is measured using a strain gauge positioned at one end of the web in the spinning direction y. It is bonded to the (z, θ) face. The deformation is measured during successive machining operations that reduce the web dimension parallel to the x direction, starting from the side opposite the gauge, after the protruding flanges have been machined. This amounts to reducing the web dimension Al by successive machining. The deformation is measured after one machining pass. The measurement is preferably carried out until the web dimension parallel to the x direction is less than 25 mm. According to the invention, it is preferably considered that the deformation measured in the spinning direction y is less than 150 µm / m in any area of ​​the web not in contact with a flange and located more than 25 mm from the end of the web where the gauge is bonded. The measurement method is described in more detail in example 2.

[0081] The spun product can in particular be machined to obtain a wing stiffener, a fuselage stiffener, a fuselage frame, a floor beam or a floor cross member. Examples

[0082] Example 1

[0083] Two billets with a diameter of 380 mm were cast, with a similar composition (Table 1) corresponding to an Al-Cu-Li alloy according to the invention. The billets underwent a homogenization treatment of approximately 8 hours at 524 °C. These billets were then reheated to a temperature of approximately 420 °C and then drawn using a reverse drawing process at a speed of approximately 1.2 m / min. After drawing, the profile was cut to a length of approximately 15 m.

[0084] The profile has a cross-section with a web and three flanks extending symmetrically with respect to the web (see [Fig. 5]). The cross-section of the profile is such that it is possible to decompose its section into five elementary rectangles according to the recommendations of standard EN 2066-2022 ([Fig. 5]). The web is described by two first elementary rectangles 20 and 20', a first elementary rectangle 20 with dimension Al of 242 mm and dimension B1 of 19 mm (aspect ratio 12.7), another first elementary rectangle 20' with dimension Al' of 195 mm and dimension Bl' of 21 mm. The sides are described by three second elementary rectangles 30, 30' and 30”. A second elementary rectangle 30 corresponds to the base of the profile with dimension A2 of 57 mm and dimension B2 of 13 mm (aspect ratio 4.4), another second elementary rectangle 30' corresponds to a side with dimension A2' of 53 mm and dimension B2' of 20 mm (aspect ratio 2.65) and another second elementary rectangle 30'' corresponding to another side of dimension A2'' of 55 mm and of dimension B2'' of 20 mm (aspect ratio 2.75) (see [Fig.5]). .

[0085] Let y be the spinning direction. The direction parallel to the length Al and Al' of the elementary rectangles of the web 20 and 20' is denoted x and the direction parallel to the dimension Bl and Bl' of the elementary rectangles of the web 20 and 20' is denoted

[0086] For each of the sides, the dimensions A2, A2', and A2” of the corresponding elementary rectangle are perpendicular to the x-direction and such that the length of the corresponding elementary rectangles is greater than 1.2 * Bl'. More precisely, for elementary rectangle 30, we have a ratio A2 / B1' = 57 / 21 = 2.7; for elementary rectangle 30', a ratio A27B1' = 53 / 21 = 2.5; for elementary rectangle 30”, a ratio A2” / B1' = 55 / 21 = 2.6. The ratio A2 / B1' is calculated because Bl' is the maximum dimension of the first two elementary rectangles of the core that intercept the sides 30, 30', and 30” under consideration.

[0087] The profiles are dissolved at a temperature of 524 °C for 45 minutes and quenched in a quenching tank filled with water maintained at an ambient temperature of approximately 20-30 °C according to the principle shown in Figure 8. The profiles are positioned on a stretcher 40. In one case corresponding to the reference case, used for profiles from billet C, the profiles are positioned such that the plane (y, z) is perpendicular to the normal N of the liquid surface at the time of quenching, according to the principle shown in Figures 6 and 10. In another case corresponding to the invention, used for profiles from billet D, the profiles are positioned such that the plane (y, z) is parallel to the normal 2V of the liquid surface at the time of quenching, according to the principle shown in Figures 7 and 11. It is possible to use wedges to hold the profile in position.In each case, the direction y makes an angle alpha of approximately 84° with respect to the normal N of the liquid surface at the time of . The immersion and during immersion are such that the heat retention bubbles can escape along the spinning direction y of the core. This is particularly relevant for the positioning according to the invention (case D).

[0088] In both cases, the profiles are arranged on a stretcher 40 that can be placed in the solution furnace 50 and in the quenching tank 10 (Figure 8). A rail system 60 can facilitate the removal 51 of the profiles from the furnace. The profiles are arranged on the stretcher such that, at the time of immersion in the quenching tank, the plane (y, Z) is perpendicular (reference) or parallel (invention) to the normal N of the liquid surface at the time of quenching. The 84° inclination of the profile according to the invention is obtained using a lifting means 70 and lifting components, also called slings: the stretcher is held by means of slings 70, and the lifting means is configured to orient the stretcher at an angle of approximately 84° ([Fig. 9]). The inclination is maintained throughout the immersion time.

[0089] The tensile mechanical properties were measured at different positions in the cross-section (see [Fig. 5]) for both cases. The tensile test specimens were loaded in the direction of the spinning. Positions 1, 2, and 3 are located in the web corresponding to the elementary rectangle 20 and 20', and positions 3 and 4 are located in the flank corresponding to the elementary rectangle 30'.

[0090] [Table 1] - Chemical composition by weight % Ref. Si Fe Cu Mn Mg Ti Zr Li Ag C 0.03 0.05 3.1 0.31 0.35 0.03 0.11 1.8 0.28 D 0.03 0.05 3.1 0.33 0.36 0.04 0.11 1.7 0.28

[0091] [Table 2] - Mechanical properties in tension in different positions of the section. Direction L (spinning direction) Composition Type of hardening Rm (MPa) Rp0.2 (MPa) A% C Reference position 1 580 528 6 position 2 572 513 7 position 3 644 630 4 position 4 671 653 7 D Invention position 1 594 566 10 position 2 595 560 10 position 3 675 643 7 position 4 668 661 6

[0092] The inventors observed improved homogeneity of tensile properties within the cross-section of the hardened profile according to the invention. Proportionally, the difference in yield strength measured between two positions is minimized (in absolute value) when the hardening treatment is carried out according to the invention (see Table 3).

[0093] [Table 3] - Variation in yield strength in % between different positions in the section of the profile. Delta Rp0.2 (%) direction L Position within the same elementary rectangle Position within different elementary rectangles Compound Type of temper Position 1 —> 2 Position 3 —> 4 Position 1 —> 3 Position 2 —> 3 Position 1 —> 4 Position 2 —> 4 C Reference -3% 4% 16% 19% 19% 21% D Invention -1% 3% 12% 13% 14% 15%

[0094] According to the invention, a deviation (in %) of the elastic limit measured in the direction L is less than 18% in absolute value regardless of the position in the section of the profile.

[0095] Example 2

[0096] A measurement method has been developed to account for the propensity of the profile to deform during machining on profiles of the same type as Example 1.

[0097] A length of 1 m of profile was considered for each of the tested cases. A unidirectional strain gauge 200 with a nominal resistance of 120 Ohms is glued in the y-direction of the profile at mid-length of the cut length on the underside of the sole, mid-distance from the edges in the direction ([Fig. 12]).

[0098] Initially, the sides corresponding to the elementary rectangles 30, 30' and 30" are machined in several stages alternately from one side and the other so that the profile deforms very little in a saber shape.

[0099] The machining passes (No. 1, No. 2, ...) are indicated by the numbered dashed lines in order on [Fig. 12]. The number of passes is preferably adjusted to have a minimum depth of cut of 1 mm and a maximum depth of cut of 4 mm in order to limit the deformation of the profile. Once the portions of the flanks protruding from the web have been machined, only the portion of the web corresponding to the two elementary rectangles 20 and 20' already described in Example 1 ([Fig. 13]) remains. A first measurement of the deformation The measurement is then performed after positioning the profile on supports placed near its ends, and the gauge is reset to zero ([Fig. 14]). The web is then machined to reduce the dimension Al, then Al', starting from the side opposite the gauge ([Fig. 15]). Machining passes are a minimum of 1 mm and a maximum of 4 mm. The pass before measurement is a minimum of 1 mm and a maximum of 2 mm. Periodically, at the end of machining after the metal has cooled, the deformation is measured ([Fig. 16]). [Fig. 16] illustrates the saber deformation. The measurement is stopped when the remaining dimension Al is less than 25 mm. The machining parameters are chosen to avoid heating during machining and thus limit the creation of local residual stresses during machining.

[0100] Figure 17 shows the evolution of the deformation in the extrusion direction measured by the gauge in the case of quenching according to the invention or according to the reference, as a function of the pass position, i.e., as a function of the new dimension Al of the remaining profile piece after machining in the X-direction. The reduction of dimension Al begins on the side opposite the gauge. A lower level of deformation in absolute value is observed for the profile quenched according to the invention. The difference is particularly visible in the part corresponding to the area initially without flanks of the profile: at the center of this part (ordinate = 68 mm), approximately -120 µm / m are measured by the gauge instead of approximately -200 / -240 µm / m for quenching according to the reference. The inventors consider that this type of measurement makes it possible to account for the lower propensity of the profile to deform after machining when it is quenched according to the invention.Indeed, the most problematic deformations during the machining of this type of profile are saber deformations (a deflection in the x direction resulting from a deformation of the flange in the y direction that differs from the deformations of the rest of the profile in the y direction, thus creating bending). Therefore, the proposed test allows us to classify the different cases in the order in which they occur during the machining of a profile with a web and one or more flanges in the extrusion direction.

[0101] List of drawing references 1: profile 2: web 3: side 10: quenching tank 20: basic rectangular web 30: basic rectangular side 40: stretcher 50: Solution furnace 51: Oven door 60: rail 70: Slings 100: surface area of ​​the quenching liquid 200: gauge

Claims

Demands

1. Solution-quenching heat treatment method for an aluminum alloy profile (1) 2XXX or 7XXX, located in an orthogonal coordinate system (y, y, ZY), where y is the spinning direction, and whose cross-section comprises a web (2) and at least one flange (3), said web being decomposed according to EN2066-2022 into at least one first elementary rectangle (20) of dimensions A1, B1 with an aspect ratio A1 / B1 of 4 to 50, where A1 is the largest dimension and is parallel to x, with A1 from 100 mm to 500 mm and B1 is parallel to z and from 10 to 50 mm, said at least one flange (3) being decomposed according to EN2066-2022 into at least one second elementary rectangle (30) of dimensions A2, B2, where A2 is the largest dimension, and such that the dimension of the second elementary rectangle is perpendicular to the x direction is greater than or equal to 1.2 * B1 (in mm), said method comprises the following steps: (d1) the aluminium profile (1) is put into solution at a temperature of approximately 400°C to 550°C for a period of approximately 5 min to 15h, (d2) the aluminium profile (1) put into solution is quenched in a quenching tank filled with liquid (10), characterized in that during step (d2) the plane (y, z) of the profile is substantially parallel to the normal x to the surface of the liquid (100).

2. Solution-quenching heat treatment method according to claim 1 wherein the spinning direction y forms an angle alpha with the normal x to the surface of the liquid when the profile is immersed in the quenching tank filled with liquid such that the value of angle alpha in degrees satisfies 70° < angle alpha < 90°, preferably 80° < angle alpha < 87°.

3. Solution-quenching heat treatment method according to claim 1 or 2 where the largest dimension A2 of the second elementary rectangle (30) is perpendicular to the x direction.

4. Solution-quenching heat treatment method according to any one of claims 1 to 3 wherein the shape ratio A2 / B2 of the second elementary rectangle (30) is from 2 to 6.

5. Method of manufacturing an aluminum alloy profile comprising the following successive steps: (a) a rough form of 2XXX or 7XXX aluminum alloy is cast, (b) optionally said rough form is homogenized, (c) said rough form is hot-extruded by drawing to obtain an aluminum profile (1) located in an orthogonal coordinate system (O, F, Z), where Y is the drawing direction, the cross-section of which has a web (2) and at least one flank (3), said web (2) being decomposed according to standard EN2066-2022 into at least one first elementary rectangle (20) of dimensions Al, B1 with an aspect ratio Al / B1 of 4 to 50, where Al is the largest dimension and is parallel to x, with Al from 100 mm to 500 mm, and B1 is parallel to z and from 10 to 50 mm, and said at least one flank (3) is decompose according to standard EN2066-2022 into at least one second elementary rectangle (30) of dimension A2, B2 where A2 is the largest dimension,and such that the dimension in mm of the second elementary rectangle perpendicular to the x direction of the first elementary rectangle is greater than or equal to 1.2 *B1, (d) said aluminium profile (1) is solution-quenched and then quenched by immersion, (e) said solution-quenched aluminium profile is subjected to controlled tensile stress, (f) optionally said drawn product is straightened or shaped, (g) said drawn product is tempered, characterized in that step (d) is carried out according to any one of claims 1 to 4.

6. Method of manufacturing an aluminum alloy profile according to claim 5 wherein the aluminum alloy 7XXX is an alloy designated according to standard AA7075 or AA7175 or AA7010 or AA7050 or AA7349 or AA7449.

7. Method of manufacturing an aluminum alloy profile according to claim 5 wherein the aluminum alloy 2XXX is an Al-Cu-Li alloy designated according to standard AA2065 or AA2195 or AA2295 or AA2196 or AA2296 or AA2076 or AA2099 or AA2199.

8. Method of manufacturing an aluminum alloy profile according to claim 5 wherein the composition of the aluminum alloy profile is an Al-Cu-Li alloy of composition by weight % Cu: 1 - 5; Li: 0.5 - 2; Mg: 0 - 4; Ag: 0 - 0.7; Zn: 0 - 1; and at least one element selected from Zr, Mn, Cr, Sc, Hf and Ti, the quantity of said element, if selected, being from 0.04 to 0.20 wt% for Zr, 0.05 to 0.8 wt% for Mn, 0.05 to 0.3 wt% for Cr and for Sc, 0.05 to 0.5 wt% for Hf and from 0.01 to 0.15 wt% for Ti, Si <0.1; Fe < 0.1; other elements < 0.05 each and < 0.15 in total, remainder aluminium.

9. Method of manufacturing an aluminium alloy profile according to claim 8 wherein the composition of the aluminium alloy profile is an Al-Cu-Li alloy of composition by weight % Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remainder aluminium.

10. Al-Cu-Li aluminum alloy profile, obtainable by the method according to claim 9, of composition in % in Cu 2.3-3.3; Li 1.4-2.1; Mg 0.2-0.8; Ag 0.2-0.6; Zn <0.35; Mn <0.45; Zr 0.04-0.18; Ti <0.10; Fe <0.15; Si <0.12; other elements < 0.05 each and < 0.15 in total, remains aluminium, located in an orthogonal coordinate system (x, Y, z), where y is the direction of extrusion of the profile, whose cross-section has a web (2) and at least one flank (3) said web (2) is decomposed according to standard EN2066-2022 into at least a first elementary rectangle (20) of dimensions Al, B1 with an aspect ratio Al / Bl between 4 and 50, where Al is the largest dimension and is parallel to x, with Al between 100 mm and 500 mm, and B1 is parallel to z and between 10 and 50 mm, and said at least one flank (3) is decomposed according to standard EN2066-2022 into at least a second elementary rectangle (30) of dimension A2,B2 where A2 is the largest dimension, and such that the dimension in mm of the second elementary rectangle perpendicular to the x direction of the first elementary rectangle is greater than or equal to 1.2 * B1, characterized in that the deviation (in %) of the yield strength measured in the L direction, corresponding to the y-spinning direction, is less than 18% in absolute value regardless of the position in the cross-section of the profile.

11. Al-Cu-Li aluminum alloy profile according to claim 10 wherein the maximum strain measured in the spinning direction is less than 150 µm / m in any area of ​​the web, wherein said area of ​​the web is not in contact with a flank and wherein the strain is measured using a strain gauge (200) positioned at one end of the web in the spinning direction y during successive machining reducing the dimension of the web parallel to the direction x ( Al, A' 1) from the side opposite the gauge after all the flanks protruding from the web have been machined.

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