Heat exchanger made from an aluminum alloy

Abstract

The present invention relates to an assembly of two sheets comprising, preferably, of: a stamped part (12), formed from an aluminum alloy having the following composition, in mass percentages: Si: from 2.50 to 6.50%; Fe: up to 0.50% and at least 0.05%; Cu: up to 0.20%; Mn: up to 0.40%; Mg: from 0.05 to 0.50%; Cr: from 0.05 to 0.35%; Ti: from 0.02 to 0.30%; Sr: up to 500 ppm; unavoidable impurities < 0.05% each and < 0.15% in total, remainder aluminum; and a flat part (11), formed from an aluminum alloy; The two parts are intended to be joined, preferably by laser welding, to form a channel (13) through the deformation of the stamped part (12). Abbreviated figure: -

Description

Title of the invention: Heat exchanger based on an aluminum alloy technical field

[0001] The invention relates to thin strips or sheets (generally with a thickness of 0.5 to 3 mm) made of aluminum alloy. These strips or sheets are particularly intended for the manufacture of components, such as heat exchanger plates assembled in pairs or more, especially for the automotive industry, such as battery coolers for electric vehicles. Previous art

[0002] With the development of electric vehicles, the battery cooler market is booming. The current purpose of this component is to control the operating temperature of batteries within a range generally of 20 to 100°C, preferably from 30 to 80°C. These components can be quite large (1 to 2 meters).

[0003] An example of a current design for an electric vehicle battery cooler is shown in [Fig. 1]. It consists of two parts with a core layer of 3xxx series aluminum alloy 15: a flat part 11 and a stamped part 12, assembled to create a channel 13. In this description, the term "flat part" refers to a part that is not stamped prior to assembly. On the other hand, the term "stamped part" refers to a part that is stamped prior to assembly, so as to create a channel after assembly with a flat part. In operation, the channel 13 serves to circulate the cooling fluid in the electric vehicle battery cooler. Besides the 3xxx series aluminium alloy core layer 15, a sacrificial layer 16, for example of 7xxx or Ixxx series aluminium alloy, can be added to ensure SWAAT corrosion resistance on the external face of each of the two parts 11 and 12.The stamped part 12 also includes a brazing layer of 4xxx series aluminum alloy 17, on the opposite side of the 3xxx series aluminum alloy core layer 15 from the sacrificial layer 16, to ensure brazing of the two parts 11 and 12 together. The batteries 14 are in contact with the flat part 11, but not with the stamped part 12.

[0004] The properties required for aluminum alloy strips or sheets used in the manufacture of heat exchangers include sufficient formability for easy shaping of the plates before assembly, good assembly properties, and high mechanical strength after assembly, so as to be used The thicknesses must be as small as possible to ensure a portion of the overall strength of the battery box structure, good resistance to fatigue stress in service, and good corrosion resistance after assembly. Naturally, it is important that the chosen aluminum alloy be easy to cast and roll, and that the manufacturing cost of the strips or sheets be compatible with the requirements of the automotive industry.

[0005] In order to promote the reduction of the thickness of the plates for heat exchangers (such as battery coolers for electric vehicles, which may also serve as structural parts), it is particularly advantageous to increase the mechanical properties of the material after assembly, without reducing corrosion resistance.

[0006] Another current market demand is to improve the recycling possibilities of aluminum alloy strips or sheets used for the manufacture of heat exchangers, in particular battery coolers for electric vehicles.

[0007] Solutions have been proposed along these lines. The following patents and patent applications are examples: - EP3790100 (Novelis): discloses a 3xxx alloy comprising 0.5 to 1.15% of Mn and up to 0.15% of Mg; - EP3741876 (Novelis): discloses a 3xxx alloy comprising 0.5 to 1.15% Mn and up to 0.06% Mg, which is plated with a 4xxx alloy; - WO2013 / 06853 (Novelis): discloses an Al-Si-Cu alloy for welding, but not in the field of battery coolers; - WO2018 / 115638 (Constellium Neuf-Brisach): discloses an aluminium alloy comprising 2.5 to 14% Si, 0.05 to 0.8% Fe, 0.25 to 1.0% Cu, 0.05 to 0.8% Mg, up to 0.70% Mn, up to 0.35% Cr, 0.02 to 0.30% Ti, up to 500 ppm Sr, up to 200 ppm Na and up to 0.15% Sb, for welding in the field of automotive sheet metal; - WO2017 / 001790 (Constellium Neuf-Brisach): discloses an aluminum alloy comprising 2.5 to 14% Si, 0.05 to 0.8% Fe, up to 0.20% Cu, 0.05 to 0.80% Mg, up to 0.70% Mn, up to 0.35% Cr, 0.02 to 0.30% Ti, up to 500 ppm Sr, up to 200 ppm Na and up to 0.15% Sb, for welding in the field of automotive sheet metal.

[0008] But the proposed solutions do not necessarily allow for the right compromise between good mechanical strength after assembly, good corrosion resistance and better recyclability.

[0009] Faced with increasing market demand, there remains a need for a new core alloy with improved mechanical strength compared to existing alloys, without degradation of corrosion resistance and allowing for improved recycling. compatibility. Such a core alloy could help meet the ever-present demand for reduced product thickness and the demand to develop high mechanical properties solutions for battery coolers in order to improve their contribution to the overall strength of the structure protecting the batteries (which includes the battery cooler, but also the parts encapsulating the batteries, whether integrated into the vehicle body or not). Description of the invention

[0010] The applicant has determined a composition range which, surprisingly, improves mechanical strength and recyclability without degrading corrosion resistance.

[0011] The solution according to the present invention is based in particular on the use of: - A monolithic material, which can be recycled more easily than a multilayered material, because it is not necessary to manage the differences in composition of the alloys used for the different layers; and - Laser welding, which does not affect the mechanical properties of the material as brazing might.

[0012] The combination of these two elements allows for the use of stronger materials and a lighter final structure, while improving recyclability and maintaining corrosion resistance. Thus, the solution according to the present invention meets market demands: mechanical performance, corrosion resistance, recyclability / environmental performance, and cost-effectiveness.

[0013] Corrosion resistance is generally measured by a 40-day SWAAT test according to ASTM G85 (August 2003).

[0014] The environmental performance of an aluminum alloy product can be measured, in particular, by its carbon footprint at the time of delivery. This carbon footprint can be improved, i.e., reduced, by increasing the level of recycled content included in the aluminum alloy. It should be noted that the more tolerant an alloy is to impurities, the more suitable it is for recycling.

[0015] Profitability can be measured in particular by the cost of the raw material used for the manufacture of the strip or sheet and by the cost of the treatment of the strip or sheet to obtain a heat exchanger.

[0016] In the case of a laser-welded heat exchanger (without filler wire), the possibility of using a monolithic material improves the cost compared to a multilayer material (core combined with one or more plated covers), which is more expensive to prepare. However, to further reduce the cost, it is possible to reduce the size of both the flat and stamped parts. To reduce this size while maintaining mechanical performance, the mechanical strength of the plates in service appears to be the key parameter. and in particular the yield strength (YS or Rp0.2) and the maximum tensile strength (UTS or Rm). Currently developed multilayer solutions target a YS preferably greater than or equal to 160 MPa, and preferably greater than or equal to 200 MPa. This target is maintained for the present invention.

[0017] On the other hand, since significant lengths must be welded to prepare large cooling plates, the cost of laser processing is directly proportional to the welding speed: the faster the welding, the shorter the welding cycle (tak time) and the lower the processing cost. However, ensuring good weld quality is also important. This quality is generally determined by the weld depth in the second sheet, given that the first sheet is completely penetrated, as this is an overlap weld (see Fig. 2). A typical target is a weld penetration depth of 20 to 80% of the thickness of the second sheet.

[0018] In summary, the present invention proposes a material: - satisfactory in terms of corrosion (maximum 30% pitting depth after 40 days of SWAAT test, relative to the sheet thickness); - as resistant as possible (YS preferably greater than or equal to 160 MPa, preferably greater than or equal to 200 MPa); - fast to weld (preferably at a welding speed of around 10 to 30 m / min) by laser lap welding, with acceptable weld quality (according to ISO 13919-2: weld penetration depth of 20% to 80%, undercut height, overfill height, weld interface width (= bead), presence of cracks and / or porosity, etc. - see [Fig. 3]); The present invention can make it possible to obtain welds of class A or B quality according to ISO 13919-2; -Ideally monolithic for reasons of cost and environmental performance / recyclability.

[0019] The invention thus relates to a set of two sheets comprising, preferably, being made of: - a stamped part 12, formed from an aluminum alloy having the following composition, in mass percentages: If: from 2.50 to 6.50%; preferably from 3.0 to 6.0%, preferably from 3.50 to 5.50%, preferably from 4.0 to 5.0%, from 4.25 to 4.75%; Fe: up to 0.50%, preferably up to 0.40%, preferably up to 0.30%, preferably up to 0.25%; and at least 0.05%, preferably at least 0.10%, preferably at least 0.15%; Cu: up to 0.20%, preferably up to 0.17%, preferably up to 0.15%, of preferably up to 0.12%; and preferably at least 10 ppm, preferably at least 20 ppm, preferably at least 40 ppm, preferably at least 60 ppm; Mn: up to 0.40%, preferably up to 0.30%, preferably up to 0.20%; and preferably at least 0.05%, preferably at least 0.08%, preferably at least 0.10%; Mg: from 0.05 to 0.50%, preferably from 0.08 to 0.45%, preferably from 0.10 to 0.40%, preferably from 0.10 to 0.35%; Cr: from 0.05 to 0.35%, preferably from 0.06 to 0.30%, preferably from 0.08 to 0.25%, preferably from 0.10 to 0.20%, preferably from 0.10 to 0.15%; Ti: from 0.02 to 0.30%, preferably from 0.04 to 0.25%, preferably from 0.05 to 0.25%, preferably from 0.07 to 0.20%, preferably from 0.10 to 0.20%; Sr: up to 500 ppm, preferably up to 450 ppm, preferably up to 400 ppm, preferably up to 350 ppm, and preferably at least 50 ppm, preferably at least 100 ppm, preferably at least 150 ppm, preferably at least 200 ppm, preferably at least 250 ppm; unavoidable impurities < 0.05% each and < 0.15% in total, remainder aluminum; and - a flat piece 11, formed from an aluminum alloy, preferably the same aluminum alloy as the stamped piece 12 or a 6xxx alloy or a 5xxx alloy; the two pieces being intended to be assembled, preferably by laser welding, so as to form a channel 13 by deformation of the stamped piece 12.

[0020] The invention according to the first object uses an aluminum alloy that maintains good corrosion resistance while simultaneously improving: - the environmental performance and recyclability of the material, as it is more tolerant of waste, such as scraps, than usual 6xxx alloys or plated materials; - the mechanical resistance of the material, preferably using specific metallurgical states; - the speed of laser welding.

[0021] The invention also relates to a method for manufacturing a strip, intended to produce a sheet used according to the present invention, comprising the successive steps of: a. Casting of the aluminium alloy according to claim 1 into a plate, preferably by semi-continuous vertical casting; b. Homogenization of the plate, preferably at a homogenization temperature of 490 to 540°C, for a holding time preferably greater than or equal to 2 hours; c. Hot rolling to obtain a strip, the starting rolling temperature at hot rolling preferably being 450 to 540°C and the final hot rolling temperature preferably being 250 to 380°C; d. Cold rolling of the strip, with optional intermediate annealing, the reduction in strip thickness during cold rolling preferably being 50 to 75%; e. Dissolving and then quenching, preferably in air; f. Optionally pre-tempered, at a pre-tempering temperature preferably of 50 to 120°C, for a period preferably of 2 to 16 hours, preferably obtained by winding and then cooling to ambient temperature; g. Optionally further tempered in a batch oven, with temperature held for a period of 20 minutes to 24 hours and a metal temperature of 100 to 210°C.

[0022] The invention also relates to a method for manufacturing a sheet of metal, used as a flat part 11 according to the present invention, comprising the successive steps of: - manufacturing a strip according to the process of the present invention; - cutting to the desired dimensions.

[0023] The invention also relates to a method for manufacturing a sheet metal part, used as a stamped part 12 according to the present invention, comprising the successive steps of: - manufacturing a strip according to the process of the present invention; - cutting to the desired dimensions; - stamping to create a channel 13 after assembly between a flat part 11 and a stamped part 12; cutting and stamping can be carried out in any order.

[0024] The invention also relates to a method for manufacturing a set of two sheets according to the present invention, comprising the steps of: - supply of two sheets, one of the sheets forming a flat part 11 and the other sheet forming a stamped part 12, manufactured respectively according to the corresponding processes of the present invention; - assembly of the two flat parts 11 and stamped part 12, preferably by laser welding, preferably remotely without filler wire, preferably by overlap, so as to form a channel 13 thanks to the deformation of the stamped part 12.

[0025] The invention also relates to a heat exchanger, preferably a battery re-cooler for an electric vehicle, made at least partly from a set of two sheets according to the present invention.

[0026] The invention also relates to the use of a set of two sheets according to the present invention or obtained according to the process of the present invention, for the fa construction of a heat exchanger, preferably a battery cooler for an electric vehicle. Figures

[0027] Fig. 1 is a cross-sectional diagram describing a current design of a battery cooler for an electric vehicle.

[0028] Fig. 2 is a cross-sectional diagram of a laser-welded lap-welded assembly.

[0029] The [Fig.3] is a cross-sectional diagram of a lap weld with quality criteria according to EN ISO 13919-2 (January 2021). Detailed description of the invention

[0030] In this description and claims, unless otherwise stated: - All aluminum alloys are designated according to the rules and designations defined by the "Aluminum Association" in the "Registration Record Series" that it publishes regularly. - The compositions are expressed as mass percentages. The expression 1.4 Cu means that the copper content expressed as mass percentages is 1.4%. - Alloy groups, also called series, are defined according to the European standard EN 573-1 (February 2005). - Metallurgical states are defined according to the European standard EN-515 (April 2017). - 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 the standard NF EN ISO 6892-1, the sampling and the direction of the test being defined by the standard EN 485-1 (December 2009), the direction or direction L corresponds to the direction of length with respect to the principal direction of rolling and the direction or direction TL corresponds to the cross-length direction. - The definitions of standard EN 12258-1 (July 2012) apply. Aluminum alloy

[0031] The composition limits of the aluminium alloy of the stamped part used according to the present invention are expressed in mass percentages and can be justified in the following way.

[0032] Silicon: A minimum silicon content of 2.50% can improve weldability and mechanical properties, particularly through the formation of hardening precipitates containing magnesium and silicon during post-assembly heat treatments. Therefore, the silicon content is greater than or equal to 2.50%, preferably greater than or equal to 2.60%, or greater than or equal to 2.75%, or greater than or equal to 2.90%, or greater than or equal to 3.00%, or greater than or equal to 3.10%, or greater than or equal to 3.25%, or greater than or equal to 3.40%, or greater than or equal to 3.50%, or greater than or equal to 3.60%, or greater than or equal to 3.75%, or greater than or equal to 3.90%, or greater than or equal to 4.00%, or greater than or equal to 4.10%, or greater than or equal to 4.25%. Excessive Si content can reduce formability. It is therefore desirable to limit the Si content to less than or equal to 6.50%, preferably less than or equal to 6.40%, or less than or equal to 6.25%, or less than or equal to 6.10%, or less than or equal to 6.00%, or less than or equal to 5.90%, or less than or equal to 5.75%, or less than or equal to 5.60%, or less than or equal to 5.50%, or less than or equal to 5.40%, or less than or equal to 5.25%, or less than or equal to 5.10%, or less than or equal to 5.00%, or less than or equal to 4.90%, or less than or equal to 4.75%.

[0033] Iron: A minimum Fe content of 0.05% can unexpectedly improve weldability, while for a content above 0.50% formability can be significantly degraded. The maximum Fe content is therefore 0.50%, or preferably 0.49%, 0.48%, 0.47%, 0.46%, 0.45%, 0.44%, 0.43%, 0.42%, 0.41%, 0.40%, 0.39%, 0.38%, or 0.37%. 0.36%, or 0.35%, or 0.34%, or 0.33%, or 0.32%, or 0.31%, or 0.30%, or 0.29%, or 0.28%, or 0.27%, or 0.26% or 0.25%. However, it is not necessary to go down to very low levels, for example less than 0.05%, which would lead to high production costs. Therefore, the minimum Fe content is 0.05%, or preferably 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, or 0.15%.

[0034] Copper: Copper (Cu) is a hardening element that contributes to mechanical strength. However, beyond a certain concentration, the risk of cracking during casting increases. Coarse intermetallic compounds can also form during casting, impairing the metal's homogeneity and potentially creating corrosion initiation sites. Surprisingly, the inventors found that adding up to 0.20% Cu by mass can improve mechanical properties without significantly degrading weldability or corrosion resistance. Therefore, the Cu content should be less than or equal to 0.20%, or less than or equal to 0.19%, or less than or equal to 0.18%, or less than or equal to 0.17%, or less than or equal to 0.16%, or less than or equal to 0.15%, or less than or equal to 0.14%, or less than or equal to 0.13%, or less than or equal to 0.12%. Preferably, the Cu content is greater than or equal to 10 ppm, or greater than or equal to 15 ppm, or greater than or equal to 20 ppm, or greater than or equal to 25 ppm, or greater than or equal to 30 ppm, or greater than or equal to 35 ppm, or greater than or equal to 40 ppm, or greater than or equal to 45 ppm, or greater than or equal to 50 ppm, or greater than or equal to 55 ppm, or so greater than or equal to 60 ppm.

[0035] Manganese: An addition of manganese above 0.05% can increase mechanical properties by solid solution effect, but above 0.50% it can decrease formability. Also, according to the present invention, the Mn content is preferably greater than or equal to 0.05%, or greater than or equal to 0.06%, or greater than or equal to 0.07%, or greater than or equal to 0.08%, or greater than or equal to 0.09%, or greater than or equal to 0.10%.To avoid the formation of a significant number of coarse phases during casting, which can reduce formability, it is recommended according to the present invention to limit the Mn content to a level less than or equal to 0.40%, or less than or equal to 0.39%, or less than or equal to 0.38%, or less than or equal to 0.37%, or less than or equal to 0.36%, or less than or equal to 0.35%, or less than or equal to 0.34%, or less than or equal to 0.33%, or less than or equal to 0.32%, or less than or equal to 0.31%, or less than or equal to 0.30%, or less than or equal to 0.29%, or less than or equal to 0.28%, or less than or equal to 0.27%, or less than or equal to 0.26%, or less than or equal to 0.25%, or less than or equal to 0.24%, or less than or equal to 0.23%, or less than or equal to 0.22%, or less than or equal to 0.21%, or less than or equal to 0.20%.

[0036] Magnesium: A minimum Mg content of 0.05% is sufficient to allow the formation of Mg2Si precipitates to achieve adequate mechanical properties. Its negative impact on welding necessitates a maximum content of 0.50%. Also, the minimum Mg content according to the present invention is greater than or equal to 0.05%, or greater than or equal to 0.06%, or greater than or equal to 0.07%, or greater than or equal to 0.08%, or greater than or equal to 0.09%, or greater than or equal to 0.10%. Furthermore, the maximum Mg content according to the present invention is less than or equal to 0.50%, or less than or equal to 0.49%, or less than or equal to 0.48%, or less than or equal to 0.47%, or less than or equal to 0.46%, or less than or equal to 0.45%, or less than or equal to 0.44%, or less than or equal to 0.43%, or less than or equal to 0.42%, or less than or equal to 0.41%, or less than or equal to 0.40%, or less than or equal to 0.39%, or less than or equal to 0.38%, or less than or equal to 0.37%, or less than or equal to 0.36%, or less than or equal to 0.35%.

[0037] Chrome: The addition of chromium can improve weldability. Furthermore, an addition of 0.05% or more chromium can have a hardening effect, but above 0.35%, chromium can form harmful intermetallic phases. The Cr content according to the present invention is thus less than or equal to 0.35%, or less than or equal to 0.34%, or less than or equal to 0.33%, or less than or equal to 0.32%, or less than or equal to 0.31%, or less than or equal to 0.30%, or less than or equal to 0.29%, or less than or equal to 0.28%, or less than or equal to 0.27%, or less than or equal to 0.26%, or less than or equal to 0.25%, or less than or equal to 0.24%, or less than or equal to 0.23%, or less than or equal to 0.22%, or less than or equal to 0.21%, or less than or equal to 0.20%, or less than or equal to 0.19%, or less than or equal to 0.18%, or less than or equal to 0.17%, or less than or equal to 0.16%, or less than or equal to 0.15%.Furthermore, the minimum Cr content according to the present invention is greater than or equal to 0.05%, or greater than or equal to 0.06%, or greater than or equal to 0.07%, or greater than or equal to 0.08%, or greater than or equal to 0.09%, or greater than or equal to 0.10%.

[0038] Titanium: It has been noted that Ti refines the solidification structure and thus reduces susceptibility to cracking. A minimum Ti content of 0.02% is therefore recommended according to the present invention. Furthermore, a maximum Ti content of 0.30% appears to prevent the formation of primary phases during (vertical) casting, which have a detrimental effect on mechanical properties and formability. The Ti content according to the present invention is thus less than or equal to 0.30%, or less than or equal to 0.29%, or less than or equal to 0.28%, or less than or equal to 0.27%, or less than or equal to 0.26%, or less than or equal to 0.25%, or less than or equal to 0.24%, or less than or equal to 0.23%, or less than or equal to 0.22%, or less than or equal to 0.21%, or less than or equal to 0.20%. Furthermore, the minimum Ti content according to the present invention is greater than or equal to 0.02%, or greater than or equal to 0.03%, or greater than or equal to 0.04%, or greater than or equal to 0.05%, or greater than or equal to 0.06%, or greater than or equal to 0.07%, or greater than or equal to 0.08%, or greater than or equal to 0.09%, or greater than or equal to 0.10%.

[0039] Strontium: The addition of Sr is optional. At a concentration below 500 ppm, it can influence the shape of the Al-Si eutectic during solidification and promote the formation of circular and homogeneously distributed Si particles after reheating and before hot rolling. Above this concentration, its effect on the Gassing of the cast plate can become significant. The maximum strontium content is less than or equal to 500 ppm, or less than or equal to 490 ppm, or less than or equal to 480 ppm, or less than or equal to 470 ppm, or less than or equal to 460 ppm, or less than or equal to 450 ppm, or less than or equal to 440 ppm, or less than or equal to 430 ppm, less than or equal to 420 ppm, or less than or equal to 410 ppm, or less than or equal to 400 ppm, or less than or equal to 390 ppm, or less than or equal to 380 ppm, or less than or equal to 370 ppm, or less than or equal to 360 ppm, or less than or equal to 350 ppm.In addition, the minimum strontium content is preferably greater than or equal to 50 ppm, or greater than or equal to 60 ppm, or greater than or equal to 70 ppm, or greater than or equal to 80 ppm, or greater than or equal to 90 ppm, or greater than or equal to 100 ppm, or greater than or equal to 110 ppm, or greater than or equal to 120 ppm, or greater than or equal to 130 ppm, or greater than or equal to 140 ppm, or greater than or equal to 150 ppm, or greater than or equal to 160 ppm, or greater than or equal to 170 ppm, or greater than or equal to 180 ppm, or greater than or equal to 190 ppm, or greater than or equal to 200 ppm, or greater than or equal to 210 ppm, or greater than or equal to 220 ppm, or greater than or equal to 230 ppm, or greater than or equal to 240 ppm, or greater than or equal to 250 ppm.

[0040] The use of other so-called "modifying" elements, such as sodium (Na) at levels up to 200 ppm or antimony (Sb) at levels up to 0.15%, is also possible as an option. A preferred Na content is 20 to 200 ppm. A preferred Sb content is 0.04 to 0.15%. In an advantageous embodiment, the addition of Sr alone is chosen.

[0041] The other elements are not added intentionally. They are unavoidable impurities, each containing less than 0.05% and totaling less than 0.15%. The remainder is aluminum.

[0042] It should be noted that the aluminum alloy of the flat part 11 and the stamped part 12 can be the same alloy or two different alloys. According to one embodiment, it is the same alloy. According to another embodiment, it is two different alloys, the alloy of the flat part 11 preferably being a 5xxx or 6xxx type alloy, preferably of type AA5083, or AA 5754, or AA6005, or AA6016.

[0043] According to one variant, the 5xxx type alloy used for the stamped part is an AA5083 type alloy, which preferably has the following composition, in mass percentages: up to 0.40% Si; up to 0.40% Fe; up to 0.10% Cu; from 0.40 to 1.0% Mn; from 4.0 to 4.9% Mg; from 0.05 to 0.25% Cr; up to 0.25% Zn; up to 0.15% Ti; unavoidable impurities whose content is less than 0.05% each and less than 0.15% in total; the remainder being aluminium.

[0044] According to one variant, the 5xxx type alloy used for the stamped part is an AA5754 type alloy, which preferably has the following composition, in percentages mass fractions: up to 0.40% Si; up to 0.40% Fe; up to 0.10% Cu; up to 0.50% Mn; 2.6 to 3.6% Mg; up to 0.30% Cr; up to 0.20% Zn; up to 0.15% Ti; 0.10 to 0.6% Mn+Cr; unavoidable impurities of which the content is less than 0.05% each and less than 0.15% in total; the remainder being aluminium.

[0045] According to one variant, the 6xxx type alloy used for the stamped part is an AA6005 type alloy, which preferably has the following composition, in mass percentages: from 0.6 to 0.9% Si; up to 0.35% Fe; up to 0.10% Cu; up to 0.10% Mn; from 0.40 to 0.6% Mg; up to 0.10% Cr; up to 0.10% Zn; up to 0.10% Ti; unavoidable impurities whose content is less than 0.05% each and less than 0.15% in total; the remainder being aluminium.

[0046] According to one variant, the 6xxx type alloy used for the stamped part is an AA6016 type alloy, which preferably has the following composition, in mass percentages: from 1.0 to 1.5% Si; up to 0.50% Fe; up to 0.20% Cu; up to 0.20% Mn; from 0.25 to 0.6% Mg; up to 0.10% Cr; up to 0.20% Zn; up to 0.15% Ti; unavoidable impurities whose content is less than 0.05% each and less than 0.15% in total; the remainder being aluminium. Strip or sheet metal:

[0047] As is known to those skilled in the art, the term "plate" refers to the aluminum alloy from the casting stage until the beginning of rolling. The term "strip" refers to the aluminum alloy from the beginning of rolling until the end of winding. The term "sheet" refers to the aluminum alloy after the strip has been cut.

[0048] According to a first embodiment where the strip or sheet according to the present invention is intended for the manufacture of a flat part 11, the minimum total thickness of the strip or sheet is 0.60 mm, or 0.65 mm, or 0.70 mm, or 0.75 mm, or 0.80 mm. According to this first embodiment, the maximum total thickness of the strip or sheet is preferably 3.50 mm, or 3.40 mm, or 3.30 mm, or 3.20 mm, or 3.10 mm, or 3.00 mm, or 2.90 mm, or 2.80 mm, or 2.70 mm.

[0049] According to a second embodiment in which the strip or sheet according to the present invention is intended for the manufacture of a stamped part 12, the minimum total thickness of the strip or sheet is 0.50 mm, or 0.55 mm, or 0.60 mm, or 0.65 mm, or 0.70 mm. According to this second embodiment, the maximum total thickness of the strip or sheet is preferably 1.50 mm, or 1.45 mm, or 1.40 mm, or 1.35 mm, or 1.30 mm. Set of two sheet metal plates:

[0050] The sheets according to the present invention can be combined with each other, after being in a possible shape, to form a heat exchanger with channels. The assembly of two sheets according to the present invention can be that after assembly but before welding or that after welding.

[0051] According to the present invention, the set of two sheets preferably comprises: - a stamped part 12, formed from an aluminum alloy having the following composition, in mass percentages: If: from 2.50 to 6.50%; preferably from 3.0 to 6.0%, preferably from 3.50 to 5.50%, preferably from 4.0 to 5.0%, from 4.25 to 4.75%; Fe: up to 0.50%, preferably up to 0.40%, preferably up to 0.30%, preferably up to 0.25%; and at least 0.05%, preferably at least 0.10%, preferably at least 0.15%; Cu: up to 0.20%, preferably up to 0.17%, preferably up to 0.15%, preferably up to 0.12%; and preferably at least 10 ppm, preferably at least 20 ppm, preferably at least 40 ppm, preferably at least 60 ppm; Mn: up to 0.40%, preferably up to 0.30%, preferably up to 0.20%; and preferably at least 0.05%, preferably at least 0.08%, preferably at least 0.10%; Mg: from 0.05 to 0.50%, preferably from 0.08 to 0.45%, preferably from 0.10 to 0.40%, preferably from 0.10 to 0.35%; Cr: from 0.05 to 0.35%, preferably from 0.06 to 0.30%, preferably from 0.08 to 0.25%, preferably from 0.10 to 0.20%, preferably from 0.10 to 0.15%; Ti: from 0.02 to 0.30%, preferably from 0.04 to 0.25%, preferably from 0.05 to 0.25%, preferably from 0.07 to 0.20%, preferably from 0.10 to 0.20%; Sr: up to 500 ppm, preferably up to 450 ppm, preferably up to 400 ppm, preferably up to 350 ppm, and preferably at least 50 ppm, preferably at least 100 ppm, preferably at least 150 ppm, preferably at least 200 ppm, preferably at least 250 ppm; inevitable impurities < 0.05% each and < 0.15% in total, remainder aluminium; And - a flat part 11, formed from an aluminum alloy, preferably the same aluminum alloy as the stamped part 12 or a 6xxx alloy or a 5xxx alloy; the two parts being intended to be joined by welding, preferably remotely without filler wire, preferably by laser welding, preferably of the "Remote Laser Welding" type, so as to form a channel 13 by deformation of the stamped part 12.

[0052] Remote Laser Welding is a type of laser welding that is performed remotely, and it is not the laser effector (or welding head) itself that moves to The technique involves welding at various points, using a moving mirror to reflect the laser beam to those points. ISO 15609-4 (May 2009) and ISO 4063 (August 2009) describe the operating procedure for this technique. ISO 13919-2 (January 2021) provides quality recommendations for the resulting welds.

[0053] Preferably, the weld between the flat part 11 and the stamped part 12 is continuous. Method for manufacturing a strip

[0054] The invention also relates to a method for manufacturing a strip, intended to produce a sheet according to the present invention, comprising the successive steps of: a. Casting of the aluminum alloy according to the present invention into a plate, preferably by semi-continuous vertical casting; b. Homogenization of the plate, preferably at a homogenization temperature of 490 to 540°C, for a holding time preferably greater than or equal to 2 hours; c. Hot rolling, the starting temperature of hot rolling preferably being 450 to 540°C and the ending temperature of hot rolling preferably being 250 to 380°C; d. Cold rolling of the strip, optionally with an intermediate annealing, the reduction in strip thickness during cold rolling preferably being 50 to 75%; e. Dissolving and then quenching, preferably in air; f. Optionally pre-tempered, at a pre-tempering temperature preferably of 50 to 120°C, for a period preferably of 2 to 16 hours, preferably obtained by winding and then cooling to ambient temperature; g. Optionally further tempered in a batch oven, with temperature held for a period of 20 minutes to 24 hours and a metal temperature of 100 to 210°C.

[0055] The manufacturing process for monolithic strips or sheets according to the present invention typically comprises casting, heating / homogenization, hot rolling, cold rolling, solution heating and quenching.

[0056] The manufacturing process for strips or sheets according to the invention comprises casting a plate, preferably by semi-continuous vertical casting, followed by scalping. In one embodiment, the casting may be continuous.

[0057] The preferred dimensions of the plates according to the invention are 200 to 600 mm, preferably 450 to 510 mm, in thickness, 1000 to 3000 mm in width and 2000 to 8000 mm in length.

[0058] Advantageously, the manufactured sheet metal is monolithic. This is less expensive than plated sheet metal and more suitable for recycling.

[0059] The plate is homogenized, typically at a homogenization temperature of- above the alloy's solvus temperature, while avoiding local melting or burning, preferably for a minimum of 2 hours, preferably 3 hours, and preferably for a maximum of 7 hours, preferably 6 hours. The homogenization temperature is preferably a maximum of 540°C, preferably 530°C, and preferably a minimum of 490°C, preferably 500°C. A temperature that is too high or too low can degrade the mechanical properties of the sheet metal.

[0060] The plate is then transferred to the hot rolling mill. Optionally, it is transferred directly from the homogenization unit to the hot rolling unit, the temperature being able to decrease naturally by 5 to 40°C during this transfer. Optionally, the plate is cooled from the homogenization temperature to the hot rolling start temperature by forced cooling. This forced cooling is preferably carried out with a direct cooling rate of at least 150°C per hour. Advantageously, the direct cooling rate is a maximum of 500°C / h. The cooling can typically be carried out by a machine such as that described in application WO2016012691. Preferably, this cooling is done in two stages, one of spraying and the other of homogenization. Optionally, this cooling can be carried out in two passes through the machine such as that described in application WO2016012691.

[0061] The homogenized plate is then hot-rolled, preferably to a strip thickness of 2 to 7.3 mm. The hot rolling start temperature is preferably 450 to 540°C. Preferably, the hot rolling start temperature is at least 460°C, or at least 470°C, or at least 480°C, or at least 490°C. Preferably, the hot rolling start temperature is at most 530°C, or at most 525°C.

[0062] The temperature change between the beginning and end of hot rolling results from the cooling of the strip through the usual heat exchange with the ambient air of the plant, with the hot rolling mill equipment such as, for example, but not limited to, the conveyor cylinders or rollers, as well as with the usual lubricating or cooling fluids, and from the heating related to the deformation energy. Preferably, the end temperature of hot rolling is between 250°C and 380°C. Preferably, the end temperature of hot rolling is at least 260°C, or at least 270°C, or at least 280°C, or at least 290°C. Preferably, the final hot rolling temperature is at most 370°C, or at most 360°C, or at most 350°C, or at most 340°C, or at most 330°C, or at most 320°C.

[0063] The hot-rolled strip is then cold-rolled, preferably to a strip thickness of 0.5 to 3.5 mm. Preferably, the thickness reduction of the The strip thickness during cold rolling is 50 to 75%. Intermediate annealing can also take place between two cold rolling stages. Intermediate annealing can optionally take place in a static or continuous furnace, preferably at a temperature of 300 to 350°C.

[0064] The strip is then solution-treated, typically at a solution temperature above the solvus temperature of the alloy, while avoiding local melting or burning, and then quenched, preferably in a continuous furnace. Too cold a solution temperature and / or too short a solution temperature can degrade the mechanical properties of the strip or sheet due to insufficient solution treatment. Too hot a solution temperature can cause burning, degrading the mechanical properties. Too long a solution temperature can reduce productivity. Preferably, the solution treatment lasts from 15 to 300 seconds. The solution temperature is preferably a minimum of 530°C and a maximum of 560°C.

[0065] Next, the strip is quenched, typically at a rate of more than 30°C / s and preferably at least 100°C / s, with water or air or a successive combination of water and / or air. Preferably, the strip is quenched to a temperature of 60 to 100°C. Insufficient cooling can degrade the mechanical properties of the strip or sheet, as the solution treatment is then incomplete.

[0066] The strip can optionally be preheated to perform pre-tempering at a pre-tempering temperature of 50 to 120°C, preferably 50 to 110°C, or 100°C, or 90°C, or 80°C, for a period preferably of 2 to 16 hours. Reheating can be useful when the strip undergoes, between quenching and pre-tempering, a surface treatment at a temperature lower than that of the pre-tempering. The surface treatment can, for example, be pickling followed by the application of a conversion coating. Preferably, pre-tempering is carried out by winding, then cooling to ambient temperature, preferably for at least 40 hours.

[0067] The pre-tempered tape is in the T4 state and can then optionally mature at room temperature for 72 hours to 6 months. This step is a constraint related to storage before forming. The tape according to the invention can be formed despite the maturation. Maturation occurs naturally between the end of winding and the time the reel is actually used.

[0068] The metallurgical state T4 thus obtained has the advantage of good formability.

[0069] The strip can then optionally be subjected to further tempering in a batch furnace, with temperature holding for a period of 20 minutes to 24 hours and a metal temperature of 100 to 210°C. This further tempering can produce different metallurgical conditions, such as T61, T6, or T7. The T61 metallurgical condition, in particular, has the advantage of It is harder than the T4 metallurgical state, while offering slightly less formability. The T6 metallurgical state has the advantage of being the hardest of the T6x and T7x metallurgical states. The T7 metallurgical state offers the advantage of better resistance to SWAAT corrosion and intergranular corrosion. Manufacturing process for a flat part:

[0070] To obtain a flat part 11 according to the present invention, it is sufficient to cut the strip obtained previously according to the present invention, into the desired dimensions, which can preferably be from 100 mm x 200 mm to 2000 mm x 3500 mm. Manufacturing process for a stamped part:

[0071] To obtain a stamped part 12, the manufacturing process for a strip as described above according to the present invention must be followed, and said strip must be cut to the desired dimensions and stamped to form a channel 13 after assembly with a flat part 11, said channel 13 being adapted for the circulation of a cooling fluid. The aforementioned cutting and stamping steps can be in either order, that is to say, the strip can first be cut to obtain a sheet, and then the sheet is stamped, or the strip can first be stamped and then cut to obtain a stamped sheet.

[0072] The dimensions of the stamped part 12 are preferably between 100 mm x 200 mm and 2000 mm x 3500 mm. Manufacturing process for a set of two sheet metal parts:

[0073] The method for manufacturing a set of two sheets according to the present invention comprises the steps of: - Supply of two sheets, one of the sheets forming a flat part 11 and the other sheet forming a stamped part 12, manufactured respectively according to the corresponding processes of the present invention; - Assembly of the two flat parts 11 and stamped part 12, preferably by laser welding, preferably remotely without filler wire, preferably by overlap, so as to form a channel 13 thanks to the deformation of the stamped part 12.

[0074] The manufacturing process for an assembly of two sheets according to the invention may, in particular, involve overlap welding, as illustrated in [Fig. 2], also known as lap welding. It has also been noted that the tendency to crack during welding is significantly lower when the stamped part 12 of composition according to the invention is positioned below the flat part 11 during welding, i.e., on the side of the laser beam impact. This advantage is obtained in the case of overlap welding. Thus, in an advantageous embodiment, the part stamped 12 of composition according to the invention is positioned on the side of the laser beam impact during welding.

[0075] The essential advantage of the invention is the possibility of using a monolithic rolled sheet, exhibiting improved weldability, in particular when laser welding, preferably remote without filler wire, a welding process generally known to those skilled in the art as "Remote Laser Welding", as well as formability and corrosion resistance properties at least comparable to those of the AA6xxx family alloys classically used for their high mechanical characteristics.

[0076] Welding techniques, in particular laser welding, of aluminium alloys are described for example in ISO 15609-4 (May 2009), ISO 4063 (August 2009) and ISO 13919-2 (January 2021).

[0077] The applications targeted include the manufacture of heat exchangers such as electric vehicle battery coolers. Use

[0078] The invention also relates to a heat exchanger, preferably a battery re-cooler for an electric vehicle, made at least partly from a set of two sheets according to the present invention.

[0079] The invention also relates to the use of a set of two sheets according to the present invention or obtained according to the present invention, for the manufacture of a heat exchanger, preferably a battery cooler for an electric vehicle. Examples Example 1: Weldability

[0080] A weldability test using the remote laser welding method (see [Fig. 2]) was performed on sheets made of three different aluminum alloys: a 6016 alloy, a 5182 alloy, and an alloy according to the invention. The chemical compositions of these alloys are given in Table 1 below.

[0081] [Tables 1] % mass 6016 5182 Inv. Si 0.94 0.08 4.47 Fe 0.24 0.20 0.16 Cu 0.09 0.07 0.001 Mn 0.17 0.37 0.00 Mg 0.42 4.78 0.29 Cr 0.04 0.00 0.10 Ti 0.03 0.01 0.165

[0082] The tested sheets were obtained by following the steps described below.

[0083] Method for manufacturing 6016 type alloy sheets: - casting then scalping to obtain a sheet of approximately 582 mm thick; - heating to approximately 560°C for approximately 2 hours, then to approximately 530°C for approximately 1 hour; - cooling down to approximately 415°C; - hot rolling up to a thickness of about 7.3 mm, with a hot rolling start temperature of about 415°C and a hot rolling end temperature of about 300°C; - cold rolling to an intermediate thickness of approximately 4 mm (Reduction rate 45%); - intermediate annealing at approximately 350°C for approximately 4 hours of holding; - cold rolling to a final thickness of approximately 1.01 mm output (Reduction rate 75%); - Dissolution at approximately 555°C, with a holding time of approximately 5 seconds above 550°C, then quenching.

[0084] Method for manufacturing alloy sheets of type 5182: - casting then scalping to obtain a sheet of approximately 582 mm thick; - heating to approximately 490°C; - hot rolling up to a thickness of 2.5 mm, with a hot rolling start temperature of approximately 470°C and a hot rolling end temperature of approximately 330°C; - cold rolling up to a thickness of approximately 0.9 mm (Reduction rate 64%); - Dissolution at approximately 385°C, then quenching.

[0085] Method for manufacturing alloy sheets according to the invention: - casting then scalping to obtain a sheet of approximately 582 mm thick; - homogenization at approximately 500°C for a total duration of approximately 18 hours; - hot rolling up to a thickness of about 3.5 mm, with a hot rolling start temperature of about 500°C and a hot rolling end temperature of about 340°C; - cold rolling up to a thickness of approximately 1.04 mm; - Dissolution at approximately 550°C, with a holding time of approximately 30 seconds above 530°C, then quenching.

[0086] Two sheets of the same alloy were welded together by lap welding (see [Fig. 2]), for each of the three alloys described above. In [Fig. 2], reference numeral 1 represents a lap weld, reference numeral 2 represents the first sheet to be welded, and reference numeral 3 represents the second sheet to be welded. The term "lap weld" means that the weld passes completely through the first sheet to be welded 2 and at least partially through the second sheet to be welded 3.

[0087] The quality of the welds obtained was determined according to the criteria of standard EN ISO 13919-2 (January 2021). The quality criteria of standard EN ISO 13919-2 (January 2021) are illustrated in [Fig. 3]. In [Fig. 3], reference 1 corresponds to a lap weld, reference 2 corresponds to the first plate to be welded, and reference 3 corresponds to the second plate to be welded, reference 4 corresponds to a channel, reference 5 corresponds to the channel height, reference 6 corresponds to the weld bead allowance of weld 1, reference 7 corresponds to the height of the weld bead allowance of weld 6, reference 8 corresponds to the penetration depth of weld 1, and reference 9 corresponds to the weld width at the interface between plates 2 and 3 (weld bead).

[0088] The results obtained are given in Table 2 below.

[0089] [Tables2] Sheet Metal Welding Speed ​​(m / min) Laser Power (W) Channel Height x (mm) Overthickness Height (mm) Weld Bead Width (mm) Crack s Visual Appearance 6016 10 3250 0 0 1.06 Yes Fairly Regular 30 5500 0 0.19 0.8 Yes Regular 6000 0 0.2 0.87 Yes Regular 7500 0.10 and 0.07 0 0.85 Yes Fairly Regular 5182 10 3250 0.18 and 0.15 0 0.85 No Irregular 30 5500 0.07 and 0.08 0.18 0.85 No Irregular 6000 0.18 and 0.13 0.2 0.94 No Irregular 7500 0.38 and 0.42 0.12 1.01 Non-Irregular Inv. 10 3250 0 0 0.98 Non-Regular 30 5500 0 0.17 0.96 Non-Regular 6000 0 0.18 0.8 Non-Regular 7500 0.09 and 0.06 0 0.90 Non-Regular

[0090] According to Table 2 above, the best results were obtained with the sheets based on the alloy according to the invention, particularly in terms of visual appearance and cracking.

[0091] Several welding speeds were tested (not all illustrated in Table 2): 10 m / min (3250 W), 15 m / min (4500 W), 20 m / min (5500 W), 25 m / min (6500 W) and 30 m / min (7500 W), and for all these speeds, the best results were obtained with the sheets based on the alloy according to the invention, particularly in terms of visual appearance and cracking.

[0092] It should be noted that it has been possible to weld at speeds as high as 10 m / min, 15 m / min, 20 m / min, 25 m / min or 30 m / min, whereas the welding speed is usually around 4 to 5 m / min. Example 2: Mechanical Performance

[0093] The same alloy according to the invention as that used in Example 1 above was used to measure the mechanical performance according to standard NF EN ISO 6892-1. In addition to a sheet in the metallurgical state T4 obtained by following the process described in Example 1 above, sheets having the metallurgical states T6 and T7 were manufactured by following the processes described below.

[0094] Method for manufacturing an alloy sheet according to the invention in the metallurgical state T6: In addition to the steps described above in Example 1 of the process for manufacturing alloy sheets according to the invention, temper for approximately 90 minutes at approximately 205°C in an air furnace, hot at the time of introduction of the sheet, then allow to cool in open air to ambient temperature.

[0095] Method for manufacturing an alloy sheet according to the invention in the metallurgical state T7: In addition to the steps described above in Example 1 of the process for manufacturing alloy sheets according to the invention, temper for approximately 200 minutes at approximately 205°C in an air furnace, hot at the time of introduction of the sheet, then allow to cool in open air to ambient temperature.

[0096] The mechanical performances obtained are given in Table 3 below.

[0097] [Tables3] Metallurgical state Rm (MPa) Rp0.2 (MPa) A80 (%) T4 222 107 23.5 T6 271 216 14.4 T7 251 200 13.1

[0098] According to Table 3 above, the mechanical performance obtained is satisfactory for use in the field of heat exchangers, and in particular electric vehicle battery coolers, with in particular an Rp0.2 which can be greater than or equal to 200 MPa.

[0099] It should also be noted that the mechanical properties of a sheet according to the present invention having the metallurgical state T61 (values ​​not illustrated here) make it possible to propose a sheet presenting a good compromise between formability and mechanical resistances. Example 3: Corrosion resistance

[0100] The same alloy according to the invention as that used in Example 1 above was used to measure the corrosion resistance of different sheets. In addition to the sheets having the metallurgical states T4, T6, and T7 described in Examples 1 and 2 above, a sheet having the metallurgical state T61 was manufactured following the process described below. The sheets all had a thickness of approximately 1 mm + / - 0.05 mm.

[0101] Method for manufacturing an alloy sheet according to the final stage in the metallic state T61 lurgical system: In addition to the steps described above in Example 1 of the process for manufacturing alloy sheets according to the invention, temper for about 30 minutes at about 205°C in an air furnace, hot at the time of introduction of the sheet, then allow to cool in open air to ambient temperature.

[0102] To determine corrosion resistance, a cyclic SWAAT (Sea Water Acidified Acetic Test) according to ASTM G85 A3 was performed on the sheets having different metallurgical states. The SWAAT test includes, in particular, alternating 30-minute salt spray phases and 1.5-hour wet phases at a temperature of approximately 49°C.

[0103] The results obtained are as follows: - T4 and T61: intergranular corrosion, corrosion depth greater than 30% of the sheet thickness, and some perforations after 40 days of testing; - T6: intergranular corrosion and corrosion depth greater than 30% of the sheet thickness, but no perforation after 40 days of testing; - T7: no intergranular corrosion, corrosion depth less than 30% of the sheet thickness, and no perforation after 40 days of testing.

[0104] The results therefore show that the sheet metal having the metallurgical state T7 has better corrosion resistance than the sheets having the metallurgical states T4, T6 and T61. Example 4: Environmental Performance / Recyclability

[0105] No detailed analysis of the scrap that can be incorporated into the alloy according to the present invention has been carried out, but it seems at least theoretically possible to incorporate into the present alloy all the scrap that can be incorporated into the AAôxxx series alloys for monolithic automotive body panels. Furthermore, the present alloy appears to be able to absorb certain primary casting alloys, such as A365.1.

[0106] It should also be noted that the sheet metal according to the present invention, which is monolithic, i.e., composed of a single alloy, allows for the recycling of all waste generated throughout its life cycle, from its manufacture to its end-of-life recycling. This is a significant advantage compared to multi-layered sheets, which are common in the field of heat exchangers.

Claims

Demands

1. An assembly of two sheets joined together, preferably by laser welding, comprising, preferably consisting of: - a stamped part (12), formed from an aluminum alloy having the following composition, in mass percentages: If: from 2.50 to 6.50%; preferably from 3.0 to 6.0%, preferably from 3.50 to 5.50%, preferably from 4.0 to 5.0%, from 4.25 to 4.75%; Fe: up to 0.50%, preferably up to 0.40%, preferably up to 0.30%, preferably up to 0.25%; and at least 0.05%, preferably at least 0.10%, preferably at least 0.15%; Cu: up to 0.20%, preferably up to 0.17%, preferably up to 0.15%, preferably up to 0.12%; and preferably at least 10 ppm, preferably at least 20 ppm, preferably at least 40 ppm, preferably at least 60 ppm; Mn: up to 0.40%, preferably up to 0.30%, preferably up to 0.20%; and preferably at least 0.05%, preferably at least 0.08%, preferably at least 0.10%; Mg: from 0.05 to 0.50%, preferably from 0.08 to 0.45%, preferably from 0.10 to 0.40%, preferably from 0.10 to 0.35%; Cr: from 0.05 to 0.35%, preferably from 0.06 to 0.30%, preferably from 0.08 to 0.25%, preferably from 0.10 to 0.20%, preferably from 0.10 to 0.15%; Ti: from 0.02 to 0.30%, preferably from 0.04 to 0.25%, preferably from 0.05 to 0.25%, preferably from 0.07 to 0.20%, preferably from 0.10 to 0.20%; Sr: up to 500 ppm, preferably up to 450 ppm, preferably up to 400 ppm, preferably up to 350 ppm, and preferably at least 50 ppm, preferably at least 100 ppm, preferably at least 150 ppm, preferably at least 200 ppm, preferably at least 250 ppm; inevitable impurities < 0.05% each and < 0.15% in total, remainder aluminium; And - a flat part (11), formed from an aluminium alloy, preferably the same aluminium alloy as the stamped part (12) or a 6xxx alloy or a 5xxx alloy; the two pieces being assembled in such a way as to form a channel (13) thanks to the deformation of the stamped part (12).

2. Assembly of two sheets according to claim 1, characterized in that it is welded and the weld between the flat piece (11) and the stamped piece (12) is continuous.

3. A method for manufacturing a strip, intended to produce a sheet used according to any one of the preceding claims, comprising the successive steps of: a. Casting the aluminum alloy according to claim 1 into a plate, preferably by semi-continuous vertical casting; b. Homogenizing the plate, at a homogenization temperature preferably from 490 to 540°C, for a holding time preferably greater than or equal to 2 hours; c. Hot rolling to obtain a strip, the hot rolling start temperature preferably being from 450 to 540°C and the hot rolling finish temperature preferably being from 250 to 380°C; d. Cold rolling the strip, optionally with intermediate annealing, the reduction in strip thickness during cold rolling preferably being from 50 to 75%; e. Solution heating and then quenching, preferably in air; f.Optionally pre-tempered, at a pre-tempering temperature preferably of 50 to 120°C, for a period preferably of 2 to 16 hours, preferably obtained by winding and then cooling to room temperature; g. Further tempering in a batch furnace, with holding at temperature for a period of 20 minutes to 24 hours and a metal temperature of 100 to 210°C.

4. A method for manufacturing a sheet metal used as a flat part (11) according to claim 1 or 2, comprising the successive steps of: - manufacturing a strip according to the method of claim 3; - cutting into the desired dimensions.

5. A method for manufacturing a sheet metal used as a stamped part (12) according to claim 1 or 2, comprising the successive steps of: - manufacturing a strip according to the method of claim 3; - cutting into the desired dimensions; - stamping so as to create a channel (13) after assembly between a flat part (11) and a stamped part (12); the cutting and stamping being able to be carried out in any order.

6. A method for manufacturing an assembly of two sheets according to any one of claims 1 or 2, comprising the steps of: - supplying two sheets, one of the sheets forming a flat part (11) and the other sheet forming a stamped part (12), manufactured respectively according to the method of claim 4 and the other according to the method of claim 5; - Assembling the two flat (11) and stamped (12) parts, preferably by laser welding, preferably remotely without filler wire, preferably by overlap, so as to form a channel (13) by deformation of the stamped part (12).

7. Method according to the preceding claim, characterized in that the welding of the two parts is continuous.

8. Heat exchanger, preferably battery cooler for an electric vehicle, made at least in part from an assembly of two sheets according to any one of claims 1 or 2.

9. Use of at least one set of two sheets according to any one of claims 1 or 2, or obtained according to the process of claim 6 or 7, for the manufacture of a heat exchanger, preferably a battery cooler for an electric vehicle.

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