Method for manufacturing a sheet made of 7XXX aluminum alloy and sheet made of 7XXX aluminum alloy

Abstract

The present invention relates to a sheet material with a thickness of 6 to 25 mm made of an aluminum alloy having a composition of, by weight%, Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and at least one element selected from Cr: 0.04 to 0.35, Zr: 0.04 to 0.15, and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and in total < 0.15, the balance being aluminum, and a method for manufacturing the same. The sheet material according to the present invention is extremely useful, in particular, as a precision plate for manufacturing machine frames, reference plates, conveyor tables, assembly jigs, and robot arms. The sheet material according to the present invention has sufficient static mechanical properties and good anodic oxidation suitability, and in particular has improved dimensional stability during machining steps.

Description

Technical Field

[0001] The present invention relates to a sheet material made of a 7XXX series aluminum alloy, particularly for use as a precision plate.

Background Art

[0002] For fields of use involving precision plates typically having a thickness of 6 to 150 mm, it is very important to have excellent dimensional stability. This type of product is typically used to fabricate mechanical elements, particularly as a reference plate for assembly or control tools. For these fields of use, it is extremely important to reduce any deformation of the sheet material during machining as much as possible, thereby avoiding supplementary operations such as pre-machining or final finishing.

[0003] Precision plates made of 6XXX alloys are known from International Publication No. WO 2021 / 064320, which discloses a sheet material made of an aluminum alloy having a composition of, in weight %, Si: 0.7 to 1.3; Mg: 0.6 to 1.2; Mn: 0.65 to 1.0; Fe: 0.05 to 0.35; and at least one element selected from Cr: 0.1 to 0.3 and Zr: 0.06 to 0.15; Ti < 0.15; Cu < 0.4; Zn < 0.1; other elements each < 0.05 and in total < 0.15, the balance being aluminum, with a thickness of 8 to 50 mm. These precision plates are extremely useful as precision plates for fabricating mechanical elements such as assembly or control tools.

[0004] Furthermore, precision plate ALPLAN® 7075 is known, which combines excellent dimensional stability with high mechanical strength and excellent flatness and low roughness of the surface (see https: / / www.constellium.com / sites / default / files / tid_product_documents / alplan_7075.pdf).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is a need for an improved sheet material made of a 7XXX series aluminum alloy that has sufficient static mechanical properties and excellent anodizing suitability, and in particular has improved dimensional stability during machining steps, especially for precision plates.

Means for Solving the Problems

[0007] A first object of the present invention is, in a method for manufacturing a sheet material made of an aluminum alloy with a final thickness of 6 to 25 mm, successively, a) Cast a rolling slab made of an aluminum alloy having a composition of, by weight, Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and at least one element selected from Cr: 0.04 to 0.35, Zr: 0.04 to 0.15, and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and in total < 0.15, the balance being aluminum, b) Homogenize the rolled plate, c) Hot-roll the rolled plate to obtain a sheet material with a thickness equal to at least 8 mm, where the reduction ratio during the last hot-rolling pass is at most 20%, d) Perform an intermediate heat treatment at a temperature of 100°C to 350°C for at least 1 hour, e) Cold-roll the heat-treated sheet material at a reduction ratio of 10% to 33%, f) Perform a solution treatment on the sheet material cold-rolled in this way and quench it, g) Stress-relieve the sheet material solution-treated and quenched in this way by tension controlled with a permanent elongation of 1 to 5%, h) Solution heat treat, quench, and optionally stress relieve the sheet material, then age the sheet material thus treated, i) Optionally, machine the thus-aged sheet material to obtain a sheet material having a final thickness equal to at least 6 mm, A method for manufacturing a sheet material made of an aluminum alloy.

[0008] A second object of the present invention is a sheet material made of an aluminum alloy having a composition of, by weight %, Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and Cr: 0.04 to 0.35, at least one element selected from Zr: 0.04 to 0.15 and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and in total < 0.15, the balance being aluminum, and having a thickness of 6 to 25 mm, obtained by the method according to the present invention.

[0009] Another object of the present invention is the use of the sheet material according to the present invention as a precision plate, particularly for producing mechanical elements such as tools for assembly or control.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Modes for Carrying Out the Invention

[0011] The alloy is designated in accordance with the Aluminum Association (AA) rules known to those skilled in the art. The metallurgical quality classification is indicated in European Standard EN515. Unless otherwise specified, the definition of Standard EN12258-1 applies.

[0012] Unless otherwise specified, the composition is expressed in weight %.

[0013] Unless otherwise specified, the static mechanical properties, that is, the tensile strength R m , the yield strength R p0.2 at 0.2% elongation and the elongation at break A% are determined by a tensile test in accordance with ISO6892-1 standard, and the sampling and test directions of the specimens are defined by EN485-1 standard.

[0014] According to the present invention, an improved sheet material made of 7XXX series aluminum alloy, particularly a precision plate, having sufficient static mechanical properties and excellent anodizing suitability, especially improved dimensional stability and excellent flatness during the machining step, is obtained by a manufacturing method in which the hot rolling step, the intermediate heat treatment step, and the cold rolling step are precisely controlled.

[0015] The manufacturing method according to the present invention includes a casting step, a homogenization step, a hot rolling step, a heat treatment step, a cold rolling step, a solution treatment step, a quenching step, a stress relieving step, an aging step, and optionally a machining step.

[0016] In the first step, a rolled slab of an aluminum alloy having a composition of, by weight%, Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and at least one element selected from Cr: 0.04 to 0.35, Zr: 0.04 to 0.15 and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and in total < 0.15, the balance being aluminum, is cast, preferably by direct-cooled vertical semi-continuous casting. The slab thus obtained can be scalped, i.e., machined, before the subsequent steps. The rolled slab is then homogenized. Preferably, the homogenization temperature is at most 500 °C. In an advantageous embodiment of the invention, the homogenization temperature is 450 °C to 500 °C, preferably 460 °C to 490 °C. The duration of homogenization is typically sufficient for the diffusion of the elements and is typically at least 3 hours, preferably at least 5 hours. The maximum homogenization duration is typically 40 hours or 50 hours. Thereafter, hot rolling is carried out to obtain a sheet having a thickness equal to at least 8 mm, preferably equal to at least 10 mm, immediately after homogenization or after reheating to a temperature of at least 340 °C, preferably at least 370 °C and suitably at least 380 °C. The hot rolling temperature is preferably maintained at at least 300 °C, preferably at least 310 °C, preferably at least 320 °C and further preferably at least 330 °C. The starting temperature of hot rolling is preferably at most 450 °C, suitably at most 420 °C. The exit temperature of hot rolling is preferably at most 355 °C, preferably at most 350 °C and suitably at most 345 °C. Preferably, the rolling speed during the last hot rolling pass is at most 1000 mm / s, suitably at most 900 mm / s and preferably at most 800 mm / s. The reduction ratio during the last hot rolling pass is at most 20%, suitably at most 19% and even more suitably at most 18%, or even more preferably at most 17%. In combination with the other parameters of the method, if the reduction ratio during the last hot rolling pass is excessively high, the desired dimensional stability characteristics cannot be achieved during machining.By combining the composition, homogenization, and hot rolling conditions, it becomes possible to obtain a structure that is essentially non-recrystallized throughout the entire thickness of the hot-rolled raw product. "Essentially non-recrystallized throughout the entire thickness" means that the recrystallization rate is less than 20%, preferably less than 10%, regardless of the position within the thickness.

[0017] Thereafter, an intermediate heat treatment is carried out at a temperature of 100°C to 350°C, preferably at a temperature of 130°C to 320°C, and more preferably at a temperature of 200°C to 300°C, for a duration of at least 1 hour, which can recover such hot-rolled sheet materials. It is the entire intermediate heat treatment that can include one or more steps with different durations and temperatures where the duration is at least 1 hour and the temperature is 100°C to 350°C. Cold rolling with a reduction rate of 10% to 33% is carried out following the intermediate heat treatment. Preferably, the reduction rate by cold rolling is 20% to 30%.

[0018] The sheet material thus hot-rolled, heat-treated, and cold-rolled is then subjected to a solution treatment followed by quenching. The solution treatment is preferably carried out at a temperature of 450°C to 500°C, more preferably at a temperature of 460°C to 490°C. Quenching is typically carried out by immersion in cold water or spraying with cold water. Thereafter, the sheet material thus solution-treated and quenched is stress-relieved by a controlled tension with a permanent elongation of 1% to 5%, preferably 1.5% to 3%.

[0019] Finally, aging is typically carried out at a temperature of 100°C to 170°C, preferably at a temperature of 110°C to 160°C, to preferably obtain a quality classification of T6, T651, or T7 or T7X51.

[0020] In one embodiment, the sheet material thus aged is finally machined to obtain a sheet material with a final thickness equal to at least 6 mm, preferably equal to at least 8 mm.

[0021] Advantageously, for obtaining a precision plate, it is machined at least 1 mm per side, preferably at least 1.5 mm per side, or preferably at least 2 mm per side. Typically, excessive machining exceeding 5 mm per side is disadvantageous, especially due to metal loss.

[0022] The method according to the present invention can, in particular, make the deformation during machining of the product negligible. The method and composition according to the present invention make it possible to obtain a more homogeneous metallurgical structure within the thickness of the product, namely in particular the recrystallization rate, the grain size and the texture, which advantageously affects the machinability.

[0023] The composition of the product according to the present invention is selected to obtain the desired metallurgical structure in combination with a thermomechanical treatment.

[0024] The presence of at least one recrystallization-preventing element selected from Cr: 0.04 to 0.35, Zr: 0.04 to 0.15 and Mn: 0.04 to 0.5 is necessary. Cr is the recrystallization-preventing element preferred within the framework of the present invention. Preferably, the minimum content of Cr is 0.12%, advantageously 0.15%, and preferably 0.18%. Preferably, the maximum content of Cr is 0.28%, advantageously 0.25%, and preferably 0.23%. In one embodiment of the present invention, the content of Cr is 0.18 to 0.28% by weight, and the contents of Zr and Mn are less than 0.04% by weight, preferably less than 0.03% by weight. In another embodiment of the present invention, the content of Cr is 0.18 to 0.28% by weight, the content of Zr is less than 0.04% by weight, preferably less than 0.03% by weight, and the content of Mn is 0.04 to 0.30% by weight. In another embodiment of the present invention, the content of Zr is 0.06 to 0.15% by weight, the content of Cr is less than 0.05% by weight, and the content of Mn is 0.04 to 0.30% by weight. In another embodiment of the present invention, the content of Zr is 0.06 to 0.15% by weight, and the contents of Cr and Mn are less than 0.04% by weight, preferably less than 0.03% by weight.

[0025] Zn, Mg, and Cu are added to achieve the desired mechanical properties.

[0026] The Zn content is 4.5 - 7.0 wt%. Preferably, the minimum Zn content is 4.6%, advantageously 4.8%, and suitably 5.1%. Preferably, the maximum Zn content is 6.8%, advantageously 6.6%, and suitably 6.4%, and further 6.1%. In one embodiment of the present invention, the Zn content is 5.2 - 6.0 wt%.

[0027] The Mg content is 1.2 - 3.5 wt%. Preferably, the minimum Mg content is 1.5%, advantageously 1.8%, and suitably 2.1%. Preferably, the maximum Mg content is 3.3%, advantageously 3.1%, and suitably 3.0%, and further 2.9%. In one embodiment of the present invention, the Mg content is 2.2 - 2.8 wt%.

[0028] The Cu content is 1.0 - 3.0 wt%. Preferably, the minimum Cu content is 1.1%, advantageously 1.2%, and suitably 1.3%. Preferably, the maximum Cu content is 2.8%, advantageously 2.6%, and suitably 2.3%, and further 2.0%. In one embodiment of the present invention, the Cu content is 1.3 - 1.9 wt%. Preferably, the Mg content is greater than the Cu content, suitably, Mg / Cu is greater than 1.1, more suitably greater than 1.2, and further greater than 1.3.

[0029] The Ti content is less than 0.25 wt%. It may be advantageous to add Ti, especially for controlling the grain size during casting. In one embodiment of the present invention, the Ti content is 0.01 - 0.20 wt%.

[0030] The iron content is less than 0.6 wt%. Preferably, the maximum Fe content is 0.50%, advantageously 0.35%, and suitably 0.15%. Preferably, the minimum Fe content is 0.05%, advantageously 0.10%, and suitably 0.15%.

[0031] The silicon content is less than 0.5% by weight. Preferably, the maximum content of Si is 0.45%, advantageously 0.40%, and preferably 0.35%. Preferably, the minimum content of Si is 0.05%, advantageously 0.10%, and preferably 0.15%.

[0032] The other elements can be present as inevitable impurities, each with a content of less than 0.05% by weight, preferably less than 0.04% by weight, and preferably less than 0.03% by weight, and in total less than 0.15% by weight, preferably in total less than 0.10% by weight, and the remainder is aluminum.

[0033] The sheet material obtainable by the method according to the invention has extremely advantageous properties.

[0034] The mechanical properties of the sheet material according to the invention are extremely advantageous. Preferably, the sheet material according to the invention has a yield strength R p0.2 LT of at least 450 MPa, preferably at least 460 MPa, and preferably at least 480 MPa, and / or a tensile strength R m LT of at least 500 MPa, preferably at least 520 MPa, and preferably at least 540 MPa, and / or an elongation at break A% of at least 6%, preferably at least 8%, and preferably at least 10%.

[0035] The sheet material according to the present invention typically has a low level of internal stress. Therefore, advantageously, the product of the maximum deflection deviation in the L and LT directions multiplied by the final thickness after machining is at most 3, preferably at most 2. The deflection deviation considered to obtain the value of the maximum deflection deviation is, in absolute value, on the one hand, the deflection deviation between the deflection measured for a bar of dimensions 400 mm × 30 mm × the thickness at the exit of cold rolling and the deflection measured for the same bar after machining to 1 / 4 of the thickness, and on the other hand, the deflection deviation between the deflection measured for the preceding bar, i.e., the bar after machining to 1 / 4 of the thickness in relation to the exit thickness of cold rolling, and the deflection measured for this preceding bar after additional machining to 1 / 4 of the thickness. All deflection measurements are carried out with the bar placed on two supports separated by 390 mm, the deflection being expressed in mm, and all measurements are carried out in two directions, L and LT, after aging and before any final machining step.

[0036] The texture of the product according to the present invention is similarly advantageous. The crystallographic texture can be represented by a three-dimensional mathematical function. This function is known in the art as the orientation distribution function (ODF). This function is defined as the volume fraction dV / V of the material having the orientation g within the dg margin:

Equation

[0037] The ODF of each sheet material is measured by the spherical harmonic function method from four pole figures measured by X-ray diffraction with a conventional texture goniometer. Within the framework of the present invention, the measurement of the pole figures was carried out on samples cut at the center of the sheet thickness of the sheet material.

[0038] As is known to those skilled in the art, the information contained in the ODF is simplified for the purpose of depicting the texture as the proportion of crystal grains contained in the discretized Euler space. The volume fractions of the different components of the texture are grouped into two categories: planar compression texture components, namely copper {112}<111>, brass {110}<112> and S{123}<634>, and shear texture components I{112}<110>, J{114}<110>, GT90DN{011}<0-11>, H{001}<1-10> and Z{111}<110>. Specifically, the sum of the volume fractions of each of these categories was considered according to the position within the thickness.

[0039] The sheet material according to the present invention typically has a texture balanced between planar compression and shear regardless of the position within the thickness. Advantageously, when there is machining, the ratio of the total volume fraction of the planar compression texture to the total volume fraction of the shear texture is 0.5 to 1.5, preferably 0.6 to 1.3, between the final surface after machining and the center of the plate thickness, or when there is no machining, between 1.5 mm below the surface. For the sheet material according to the prior art, this ratio reaches a value clearly exceeding 1.5 at a certain position within the thickness, particularly at the surface.

[0040] According to the present invention, the sheet material according to the present invention is used as a precision plate, particularly for machine frames, reference plates, conveyor tables, assembly jigs, robot arms or for manufacturing complex-shaped parts with a high material removal rate by machining, typically at least 30%, and further 50% of the material is removed. In fact, the sheet material according to the present invention has sufficient static mechanical properties while having improved dimensional stability particularly during the machining step and good anodic oxidation suitability.

[0041] [Example] In this example, a rolled slab made of alloy AA7075 with the composition shown in Table 1 was prepared.

[0042]

Table 1

[0043] The slab was homogenized at 480°C and hot-rolled to the thickness shown in Table 2. The inlet temperature of the hot rolling was 380 - 410°C. Examples 1, 2, 5, 8, and 9 were processed by methods outside the invention. For sheets 1, 2, and 5, a reference process with a reduction ratio of at least 21% during the last pass was applied, and for these sheets, the intermediate heat treatment was carried out in two consecutive steps at 410°C followed by 300°C. For Example 8, the conditions of hot rolling and intermediate heat treatment were in accordance with the present invention, but the reduction ratio by cold rolling was over 33%. For Example 9, the intermediate heat treatment was carried out at 250°C, but the finishing temperature of the hot rolling was maintained at a value above 355°C, and the reduction ratio during the last pass was 21%.

[0044]

Table 2

[0045] The sheet thus obtained was solution-treated at 475°C, quenched, stress-relieved by controlled tension, and aged to obtain a quality-separated T651. The aging conditions were 9 hours at 140°C. In the final step, machining of 3 mm (1.5 mm per side) was carried out so that the final thickness was 3 mm thinner than the rolling-finished thickness.

[0046] Tensile static mechanical properties, that is, the tensile strength R m , the conventional yield strength R p0.2 at 0.2% elongation, and the elongation at break A% were determined by a tensile test in accordance with the NF EN ISO 6892-1 standard (2016) in the longitudinal (LT) direction, where the sampling and test directions of the specimens were defined by the EN485 standard (2016). The specimen sampling was carried out before the last machining step. The characterization was carried out in the longitudinal direction.

[0047] The results are shown in Table 3.

[0048]

Table 3

[0049] The residual stress on the sheet before machining was evaluated by measuring the average deflection in bars machined in the L or LT direction with thicknesses of 1 / 4 and 1 / 2.

[0050] Two bars of full thickness were sampled in the L and LT directions by saw cutting before the final machining of the sheet. The dimensions of the sampling are as follows: - For the bar in the L direction: 430 mm (L direction) × 35 mm (LT direction) × thickness - For the bar in the LT direction: 450 mm (LT direction) × 35 mm (L direction) × thickness

[0051] Subsequently, the bars were machined to obtain bars with a length L = 400 mm, a width l = 30 mm, and a thickness e (after cold rolling and aging, but the thickness of the sheet before machining). The unprocessed rolling L-LT surface was not machined, so the thickness of the machined bar remained the same as the thickness of the sheet.

[0052] For the measurement of deflection, the bar is placed on two supports separated by 390 mm (the supports are represented by triangle 1 in Figure 3A). A displacement sensor (represented by arrow 2 in Figure 3A) is used to measure the deflection of the bar.

[0053] The steps are as follows: - Perform the first measurement of the deflection of the bar (see Figure 3A), and thus values in mm represented by Deflection L ini and Deflection LT ini are obtained. - Subsequently, machine the bar to remove 1 / 4 of its thickness (see the schematic in Figure 3B). - Perform the second measurement (see Figure 3C), and thus values in mm represented by Deflection L1 / 4 and Deflection LT1 / 4 are obtained. - Reprocess the bar stock to remove an additional 1 / 4 of its thickness. At this point, only half of the original thickness remains. - Take the third measurement, thus obtaining values in millimeters represented as Deflection L1 / 2 and Deflection LT1 / 2.

[0054] Limit the heating to 10 °C in each machining step to avoid any influence of the machining conditions on the deflection measurements being taken.

[0055] Report in Table 4 below in absolute value (Abs) the deflection deviations in the L and LT directions between 1 / 4 and the initial, and between 1 / 2 and 1 / 4. Similarly, report the product of the maximum deflection deviation multiplied by the rolled exit thickness.

[0056]

Table 4

[0057] In the reference method, the product of the maximum deflection deviation in the L and LT directions multiplied by the final thickness is greater than 3.2; while in the method according to the present invention, this product is at most 3.0.

[0058] Characterize the final grain structure after cold rolling and aging. The results are presented in Figures 1 and 2. Figure 1 shows the grain structure after anodizing of sheet 1 after the reference method. Figure 2 shows the grain structure after anodizing of sheet 3 after the method of the present invention. In Figure 1, a substantially recrystallized fine structure is observed near the surface, and a fine structure with a mixture of recrystallization and non-recrystallization is observed at the center of the sheet thickness. There is a significant non-uniformity in the grain size. In Figure 2, more recrystallization on more surfaces with a much more uniform grain size is also observed.

[0059] For a 50×50 mm sample in the plane L / LT, at the center of the plate thickness and on the surface (0.1 - 0.4 mm below the machined surface), the texture of the product was measured. The results are presented in Table 5. For the product according to the present invention, the texture of the milled surface is more balanced between shear and compression and closer to the texture at the center of the plate thickness compared to the case of the reference product.

[0060] [Table 5] [Explanation of Signs]

[0061] 1 Support 2 Displacement Sensor

Claims

1. In a method for manufacturing an aluminum alloy sheet having a final thickness of 6 to 25 mm, successively, a) Cast a rolling slab of an aluminum alloy having a composition of, by weight %, Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and at least one element selected from Cr: 0.04 to 0.35, Zr: 0.04 to 0.15, and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and total < 0.15, the balance being aluminum. b) Homogenize the rolling slab. c) Hot-roll the rolling slab to obtain a sheet having a thickness of at least 8 mm, where the reduction ratio in the last hot-rolling pass is at most 20%. d) Perform an intermediate heat treatment at a temperature of 100°C to 350°C for at least 1 hour. e) Cold-roll the heat-treated sheet at a reduction ratio of 10% to 33%. f) Perform a solution treatment on the cold-rolled sheet and quench it. g) Remove stress from the solution-treated and quenched sheet by tension controlled with a permanent elongation of 1 to 5%. h) Age the solution-treated, quenched, and optionally stress-relieved sheet. i) Optionally, machine the aged sheet to obtain a sheet having a final thickness of at least 6 mm. A method for manufacturing an aluminum alloy sheet.

2. The method according to claim 1, wherein the homogenization temperature is 450°C to 500°C.

3. The method according to claim 1 or 2, wherein the exit temperature of the hot rolling is at most 355°C.

4. The method according to any one of claims 1 to 3, wherein the heat treatment in step d performed after the hot rolling is carried out at a temperature of 130°C to 320°C, preferably at a temperature of 200°C to 300°C.

5. The method according to any one of claims 1 to 4, wherein the reduction ratio by cold rolling is 20% to 30%.

6. The method according to any one of claims 1 to 5, wherein the rolling speed in the last hot-rolling pass is at most 1000 mm / s, preferably at most 900 mm / s, more preferably at most 800 mm / s.

7. A sheet material with a thickness of 6 to 25 mm made of an aluminum alloy having the following composition by weight: Zn: 4.5 to 7.0; Mg: 1.2 to 3.5; Cu: 1.0 to 3.0; and Cr: 0.04 to 0.35, at least one element selected from Zr: 0.04 to 0.15 and Mn: 0.04 to 0.5; Ti < 0.25; Fe < 0.6; Si < 0.5; other elements each < 0.05 and in total < 0.15, the balance being aluminum, obtained by the method according to any one of claims 1 to 6.

8. A yield strength R of at least 450 MPa, preferably at least 460 MPa, more preferably at least 480 MPa ｐ０．２ LT, and / or a tensile strength R of at least 500 MPa, preferably at least 520 MPa, more preferably at least 540 MPa ｍ The sheet material according to claim 7, having an elongation at break A% of at least 6%, preferably at least 8%, more preferably at least 10%.

9. The product of the maximum deflection deviation in the L and LT directions multiplied by the final thickness is at most 3, preferably at most 2, and the deflection deviation expressed as an absolute value considered for obtaining the maximum value is, on the one hand, the deflection deviation between the deflection measured for a bar having dimensions of 400 mm × 30 mm × the thickness at the exit of cold rolling and the deflection measured for the same bar after machining of 1 / 4 of the thickness, and on the other hand, the deflection deviation between the deflection measured for a preceding bar and the deflection measured for this preceding bar after additional machining of 1 / 4 of the thickness and deflection measured for the preceding bar, all deflection measurements being carried out with the bar placed on two supports spaced 390 mm apart, the deflection being expressed in mm, and all measurements being carried out before any final machining step, the sheet material according to claim 7 or 8.

10. The ratio of the total volume fraction of the plane compression texture to the total volume fraction of the shear texture is 0.5 to 1.5, preferably 0.6 to 1.3, between the surface after machining and the center of the plate thickness when machining has been carried out, or between 1.5 mm below the surface when no machining has been carried out, for the sheet material according to any one of claims 7 to 9.

11. Use of the sheet material according to any one of claims 7 to 10, in particular as a mechanical frame, reference plate, transport table, assembly jig, robot arm or precision plate for producing complex-shaped parts with a high material removal rate by machining.

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