Heat exchanger based on an alumnimium alloy obtained by brazing

Abstract

The present invention relates to a strip or sheet intended for the manufacture of brazed heat exchangers, which strip or sheet comprises a core layer 18, optionally a cover layer 16, 17 on one or both sides of the core layer 18 and optionally an interlayer on one or both sides of the core layer 18 positioned between the core layer 18 and the cover layer 16, 17, the core layer 18 being made of the 6xxx series of aluminium alloy having the following composition: Si: from 0.45 to 0.75 wt%; Fe: from 0.18 to 0.40 wt%; Cu: ≤ 0.40 wt%; Mn: ≤ 0.30 wt%; Mg: from 0.25 to 0.56 wt%; Ti: < 0.050 wt%; optionally V: from 0.05 to 0.16 wt%; unavoidable impurities: < 0.05 wt% each and < 0.15 wt% in total; the remainder being aluminium.

Description

[0001] DESCRIPTION

[0002] Title: Heat exchanger based on an aluminum alloy obtained by brazing

[0003] TECHNICAL FIELD

[0004] The invention relates to thin strips or sheets (generally with a thickness of 0.1 to 2.5 mm) made of an aluminium-magnesium-silicon core alloy (6xxx series according to the nomenclature of the Aluminium Association), optionally clad on one or both sides with a covering alloy, most often an aluminium-silicon brazing alloy (4xxx series according to the nomenclature of the Aluminium Association) or a sacrificial aluminium, aluminium-manganese or aluminium-zinc alloy (lxxx, 3xxx or 7xxx series according to the nomenclature of the Aluminium Association), and / or an interlayer alloy, placed between the core layer and the possible brazing alloy, made of an aluminium or aluminium-manganese alloy (lxxx or 3xxx series according to the nomenclature of the Aluminium Association). These strips or sheets are particularly intended for the manufacture of elements, such as heat exchanger plates assembled by brazing, particularly for the automotive industry, such as battery coolers for electric vehicles.The brazing techniques for aluminium alloys are described, for example, in the article by JC Kucza, A. Uhry and JC Goussain "Strong brazing of aluminium and its alloys", published in Soudage et Techniques Connexes, Nov.-Dec. 1991, pp. 18-29. The strips or sheets according to the invention can in particular be used in brazing techniques with non-corrosive flux of the NOCOLOK® or CAB ("controlled atmosphere brazing") type.

[0005] PREVIOUS ART

[0006] With the development of electric vehicles, the battery cooler market is booming. The current purpose of this part is to control the operating temperature of batteries, generally in a range of 20 to 100°C, preferably 30 to 80°C. The parts can be large (1 to 2 meters).

[0007] An example of a current design of an electric vehicle battery cooler is shown in Figure 1. It is composed of two parts with a core layer of 3xxx series alloy 15: a flat part 11 and a stamped part 12, assembled so as to create a channel 13. In the present description, the term "flat part" refers to a part that is not stamped before assembly. On the other hand, the term "stamped part" refers to a part that is stamped before assembly, so as to create a channel after assembly with a flat part. In use, the channel serves for the circulation of the coolant in the electric vehicle battery cooler. In addition to the core layer of 3xxx series alloy 15, a sacrificial layer 16, for example of 7xxx or lxxx series 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 4xxx series alloy brazing layer 17, on the other side of the 3xxx series 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.

[0008] The properties required for aluminum alloy strips or sheets used for the manufacture of brazed exchangers include sufficient formability for easy shaping of the plates before brazing, good brazing ability, high mechanical strength after brazing, so as to use thicknesses as small as possible and to ensure part of the strength of the complete structure of the battery box, good resistance to fatigue stress in service, and good resistance to corrosion after brazing. Of course, it is important that the alloy chosen is easy to cast and roll, and that the manufacturing cost of the strips or sheets is compatible with the requirements of the automotive industry.

[0009] In order to promote the reduction of plate thickness for heat exchangers (such as battery coolers for electric vehicles, which can also potentially serve as structural parts), it is particularly interesting to increase the mechanical properties of the material after brazing, in particular the yield strength (Rpo,?) of the tensile curve obtained according to ISO 6892-1 (“Yield Strength” or “YS” in English), without reducing corrosion resistance or brazing.

[0010] Solutions have been proposed in this regard. Examples include the following patents and patent applications, which disclose the following compositions and configurations:

[0011] - JP2005 / 261026 discloses a core made of alloy of the 3xxx series comprising in particular, in mass percentages: > 0.8% Mn; 0.3-0.6% Mg; < 0.5% Si, notably used for tubes.

[0012] - EP1254965 discloses a structurally hardened aluminum alloy having the following composition, in mass percentages: 0.6-0.9% Si; 0.1-0.36% Mg; 0.4-0.7% Mn; 0.1-0.25% Ti; 0.25-0.35% Cu; <0.7% Fe; optionally 0.05-0.25% Zr.

[0013] - EP1687456 relates to the field of fluxless brazing and discloses a core comprising, in mass percentages: 0.3-1.0% Si; <1.0% Fe; 0.3-1.0% Cu; 0.3-2.0% Mn; 0.3-3.0% Mg; <6% Zn; <0.1% Ti; <0.3% Zr; <0.3% Cr; <2.0% Ni; <2.0% Co; <0.5% Bi; <0.5% Y; other elements < 0.05% each and < 0.15% in total, remainder aluminum, coated on at least one side with an aluminum brazing alloy comprising, in mass percentages: 4-15% Si and 0.01-0.5% of at least one of the elements Ag, Be, Bi, Ce, La, Pb, Pd, Sb, Y or mischmetal.

[0014] - EP3423607 discloses a 6xxx series alloy solution comprising, in mass percentages: 0.2-1.3% Si; 0.40-1.3% Mg; <0.80% Cu; 0.05-1.0% Fe;

[0015] 0.05-0.70% Mn; optionally one or two elements chosen from 0.05-0.35% Zr and 0.04-0.35% Cr; < 25% Zn; < 0.25% Ti; remaining unavoidable impurities and aluminum, or the Fe / Mn ratio is less than 1.90.

[0016] - WO2021204929 discloses an alloy core of the AA6xxx series, having the following composition, in mass percentages: 0.5-0.9% Si; <0.5% Fe; <0.5% Cu;

[0017] < 0.5% Mn; 0.4-0.8% Mg; < 0.3% Cr; < 0.3% Zn; < 0.3% Ti; < 0.1% Zr; remaining aluminium and unavoidable impurities 0.05% maximum each and 0.15% maximum in total.

[0018] But the proposed solutions do not necessarily allow for the right compromise to be found between good mechanical strength after brazing, particularly in terms of Rpo.2, good corrosion resistance and good brazing, particularly with a solidus temperature of the core layer alloy high enough to allow the brazing layer to melt while avoiding the core layer to melt.

[0019] Faced with growing market demand, there remains a need for a new core alloy with improved mechanical strength compared to existing alloys, particularly in terms of Rpo.2, without degradation of corrosion resistance or brazeability. Such a core alloy could help meet the ever-present demand for product thickness reduction and the demand to develop solutions with high mechanical properties for battery coolers to improve their contribution to the overall strength of the structure protecting the batteries (which includes the heat cooler, but also the parts encapsulating the batteries, whether integrated into the vehicle body or not).

[0020] STATEMENT OF THE INVENTION

[0021] The applicant has determined a composition range which, surprisingly, makes it possible to improve mechanical strength without degradation of corrosion resistance or brazing. For example, the target according to the present invention may be to achieve a yield strength Rpo,2 greater than or equal to approximately 130 MPa, preferably 150 MPa, preferably 180 MPa, or even greater than or equal to approximately 190 MPa, or even greater than or equal to approximately 200 MPa, for industrial strips or sheets after brazing. The solution according to the present invention is notably based on at least one of the following elements, which may relate to the composition of the alloy of the core layer, the configuration of the flat and stamped parts or the manufacturing process:

[0022] - Using a core layer of 6xxx series alloy, having a composition as described according to the present invention, preferably maintaining a solidus temperature for example greater than 615°C, in particular in the case where the core is plated with a brazing layer comprising a 4xxx series aluminum alloy whose solidus temperature is approximately 577°C, for example an AA4343 or AA4045 alloy. Generally, the solidus temperature of the 6xxx series alloy core layer is preferably at least 20°C higher, preferably at least 30°C higher, preferably at least 40°C higher, than the solidus temperature of the brazing layer;

[0023] - Use a sacrificial layer on both sides of this 6xxx series alloy core layer for the flat part 11 of the heat exchanger, to ensure good corrosion resistance on the external side of the heat exchanger, i.e. on the side of the flat part 11 opposite that where the stamped part 12 is located.

[0024] - Assembling a flat part 11, having a core layer of 6xxx series alloy 18 plated on both sides with a sacrificial layer 16, and another part 12, having a core layer of 6xxx series alloy 18 plated on one side with a brazing layer 17 and on the other side with a sacrificial layer 16, which is stamped to form a channel 13, between the flat part 11 and the stamped part 12, as shown in Figure 2. After assembly, according to the non-limiting configuration of Figure 2, the brazing layer 17 of the stamped part 12 is located between the core layer of 6xxx series alloy 18 of the stamped part 12 and one of the sacrificial layers 16 of the flat part 11. It should be noted that the two core layers of 6xxx series alloy 18 or the two layers sacrificial 16 may have the same composition or different compositions.It is also noted that, alternatively, there could be a sacrificial layer between the 6xxx series alloy core layer 18 and the brazing layer 17.

[0025] - Brazing, for example in a CAB furnace (controlled atmosphere brazing, for example with control of the quantity of nitrogen or argon and / or oxygen) at a temperature preferably below 615°C, preferably below 610°C, preferably below 605°C. Above 570°C, limiting the quantity of oxygen to less than 100 ppm, preferably less than 50 ppm, can improve the quality of the brazing.

[0026] - Preferably ensure cooling at the end of the brazing cycle, preferably at a rate greater than 25°C / min, preferably greater than 40°C / min, preferably greater than 50°C / min below 380°C and up to 100°C. Rapid cooling can prevent or reduce the formation of coarse-sized (Mg,Si) precipitates, for example greater than 150 nm, which can reduce the hardening potential of the alloy, in particular Rpo,2.

[0027] - Optionally add a post-brazing tempering step, preferably at a temperature of 180 to 220°C, preferably for a duration of less than 6 hours, preferably less than 3 hours, preferably less than or equal to 2 hours (for example 2 hours at 195°C or 30 minutes at 205°C)

[0028] The invention thus relates to a strip or sheet, intended for the manufacture of brazed heat exchangers, preferably battery coolers for electric vehicles, comprising, preferably consisting of, a core layer, optionally a cover layer on one or two faces of the core layer and optionally an interlayer on one or two faces of the core layer placed between the core layer and the cover layer, the core layer being made of an aluminium alloy of the 6xxx series having the following composition (% by mass):

[0029] - If: from 0.45 to 0.75; preferably from 0.50 to 0.70%, - preferably from 0.55 to 0.65%, -

[0030] - Fe: from 0.10 to 0.40%; preferably from 0.12 to 0.35%; preferably from 0.14 to 0.30%; preferably more than 0.18 to 0.26%;

[0031] - Cu: < 0.50%, - preferably < 0.45%, - preferably < 0.25%, - preferably < 0.15%; and preferably > 0.05% according to a first variant; or preferably from 0.25 to 0.45%; preferably from 0.29 to 0.40% according to a second variant;

[0032] - Mn: < 0.30%, - preferably < 0.20%, - preferably < 0.15%, - preferably < 0.10%;

[0033] - Mg: from 0.25 to 0.56%; preferably from 0.25 to 0.45%; preferably from 0.30 to 0.39%;

[0034] - Ti: < 0.050%, - preferably < 0.045%, - preferably < 0.040%, -

[0035] - optionally V: from 0.05 to 0.16%;

[0036] - unavoidable impurities: < 0.05% each and < 0.15% in total;

[0037] - aluminum remains.

[0038] The invention also relates to a set of two sheets or strips comprising, preferably consisting of:

[0039] - a flat part formed from a strip or sheet according to the present invention;

[0040] - a stamped part formed from a strip or sheet according to the present invention; the two parts being intended to be assembled by brazing and forming a channel thanks to the deformation of the stamped part, the outermost layer of the stamped part and / or of the flat part in contact with the other part being a brazing layer.

[0041] The invention also relates to a method of manufacturing a strip or sheet according to the present invention, comprising the successive steps of: - casting a core alloy plate;

[0042] - optionally homogenization of the plate at a temperature of 450 to 580°C, preferably 520 to 560°C for 1 to 24 hours;

[0043] - possible cladding with a covering aluminum alloy on one or two faces of the core layer and possibly an interlayer aluminum alloy on one or two faces of the core layer;

[0044] - preheating to a temperature of 400 to 550°C, preferably 450 to 530°C, preferably 480 to 510°C, preferably with maintenance at the maximum temperature for less than 30 hours, preferably for less than 20 hours, preferably for less than 12 hours, more preferably for less than 3 hours;

[0045] - hot rolling of the plate, optionally homogenized and optionally plated, at a temperature of 390 to 530°C, preferably 470 to 530°C, to a thickness of 2 to 6 mm,

[0046] - cold rolling to the desired thickness, the thickness of the strip or sheet after cold rolling preferably being 0.15 to 3 mm and

[0047] - heat treatment in a pass-through furnace at a temperature of 250 to 560°C, preferably 320 to 430°C, preferably 320 to 360°C with maintenance at the maximum temperature for less than 5 minutes, preferably less than 1 minute, preferably for less than 30 seconds and preferably more than 15 seconds, or in a batch furnace, i.e. a furnace operating discontinuously, at a temperature of 250 to 390°C, preferably 310 to 360°C, with maintenance at the maximum temperature preferably for less than 3 hours, preferably for less than 2 hours and preferably less than 1 hour, so as to obtain a small-grain recrystallization.

[0048] The invention also relates to a heat exchanger made at least in part from a strip or sheet according to the present invention or from a set of two sheets or strips according to the present invention.

[0049] The invention also relates to the use of a strip or sheet according to the present invention or of a set of two sheets or strips according to the present invention, for the manufacture of a heat exchanger, preferably a battery cooler for an electric vehicle.

[0050] FIGURES

[0051] [Figure 1] Figure 1 is a cross-sectional diagram depicting a current design of an electric vehicle battery cooler.

[0052] [Figure 2] Figure 2 is a cross-sectional diagram depicting a design of a battery cooler for an electric vehicle according to the present invention. [Figure 3] Figure 3 is a diagram depicting the assembly of the sheets for the solderability test of Example 1.

[0053] [Figure 4] Figure 4 is a schematic diagram describing the setup and perforation analysis during the SWAAT corrosion resistance test of Example 3.

[0054] DETAILED DESCRIPTION OF THE INVENTION

[0055] In the description and claims, unless otherwise indicated:

[0056] - the designation of aluminum alloys is in accordance with the nomenclature of The Aluminum Association;

[0057] - the contents of chemical elements are designated in mass percentages.

[0058] Aluminum alloy of the core layer

[0059] The composition limits of the 6xxx series aluminum alloy of the core layer used according to the present invention are expressed in mass percentages and can be justified as follows.

[0060] Silicon: A minimum Si content of 0.45% improves mechanical properties, particularly through the formation of hardening precipitates containing magnesium and silicon during post-brazing tempering. The silicon content is therefore preferably greater than or equal to 0.45%, or greater than or equal to 0.46%, or greater than or equal to 0.47%, or greater than or equal to 0.48%, or greater than or equal to 0.49%, or greater than or equal to 0.50%, or greater than or equal to 0.51%, or greater than or equal to 0.52%, or greater than or equal to 0.53%, or greater than or equal to 0.54%, or greater than or equal to 0.55%.

[0061] Too high a Si content can reduce the solidus temperature of the core and compromise brazing. It is then preferable to limit the Si content to a content less than or equal to 0.75%, or less than or equal to 0.74%, or less than or equal to 0.73%, or less than or equal to 0.72%, or less than or equal to 0.71%, or less than or equal to 0.70%, or less than or equal to 0.69%, or less than or equal to 0.68%, or less than or equal to 0.67%, or less than or equal to 0.66%, or less than or equal to 0.65%.

[0062] Preferably, the Mg / Si mass ratio is from 0.4 to 1.0, preferably from 0.5 to 0.9. Iron: A maximum Fe content of 0.40%, or 0.39%, or 0.38%, or 0.37% or 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%, may also be beneficial for corrosion resistance and formability, in particular by reducing the fraction of coarse precipitates containing Fe. However, it is not necessary to go down to very low contents, for example below 0.08%, which would lead to high cost prices. Therefore, the preferred minimum Fe content is 0.10%, or 0.11%, or 0.12%, or 0.13%, or 0.14%, or 0.15%, or 0.16%, or 0.17%, or 0.18%.

[0063] Copper: Cu is a hardening element that contributes to mechanical strength. When an additional layer is present, a copper gradient is created during brazing and has the effect of reducing corrosion on the internal side of the exchanger, i.e., on the side of the channels where the fluid circulates. However, beyond a certain content, the risk of cracking during casting is higher, and the sensitivity to corrosion in the core can be increased. Coarse intermetallic compounds can also form during casting, which affect the homogeneity of the metal and can constitute sites for corrosion initiation. Cu is also an element that reduces the solidus temperature.The Cu content is therefore 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 0.40%, or less than or equal to 0.35%, or less than or equal to 0.30%, or less than or equal to 0.25%, or less than or equal to 0.20%, or less than or equal to 0.15%. Preferably, the Cu content is greater than 0.05%, or greater than or equal to 0.20%, or greater than or equal to 0.21%, or greater than or equal to 0.22%, or greater than or equal to 0.23%, or greater than or equal to 0.24%, or greater than or equal to 0.25%, or greater than or equal to 0.26%, or greater than or equal to 0.27%, or greater than or equal to 0.28%, or greater than or equal to 0.29%.

[0064] Manganese: The addition of Mn can increase the solidus. To do this, the Mn content is preferably greater than or equal to 0.01%, or greater than or equal to 0.02%, or greater than or equal to 0.025%, 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%. To avoid forming a significant number of coarse phases at casting which can reduce formability, and dispersoids which can deteriorate hardenability during brazing cooling by serving as nucleation sites for Mg-containing precipitates, it is recommended to limit the Mn content to a content 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%, or less than or equal to 0.14%, or less than or equal to 0.13%, or less than or equal to 0.12%, or less than or equal to 0.11%, or less than or equal to 0.10%. To maximize the mechanical properties, in particular the Rpo,2, it is preferred to limit the Mn content to a content less than or equal to 0.10%.,

[0065] Magnesium: The Mg content according to the present invention is controlled to allow two parts (the flat part and the stamped part) to be brazed together, each having a core made of 6xxx series aluminum alloy. This would be different if one of the two cores were made of 3xxx series aluminum alloy. Mg is an element which, in association with silicon, allows for structural hardening during post-brazing tempering. Also, the minimum Mg content according to the present invention is preferably greater than or equal to 0.25%, or greater than or equal to 0.26%, or greater than or equal to 0.27%, or greater than or equal to 0.28%, or greater than or equal to 0.29%, or greater than or equal to 0.30%, or greater than or equal to 0.31%, or greater than or equal to 0.32%, or greater than or equal to 0.33%.Furthermore, the maximum Mg content according to the present invention is preferably less than or equal to 0.56%, or less than or equal to 0.55%, or less than or equal to 0.54%, or less than or equal to 0.53%, or less than or equal to 0.52%, or less than or equal to 0.51%, or 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%.

[0066] Titanium: Ti can be used to control grain size in casting. Its content according to the present invention is preferably less than 0.050%, or less than 0.049%, or less than 0.048%, or less than 0.047%, or less than 0.046%, or less than 0.045%, or less than 0.044%, or less than 0.043%, or less than 0.042%, or less than 0.041%, or less than 0.040%.

[0067] Vanadium: Vanadium may be optionally added to provide additional hardening and increase the solidus temperature of the alloy. If its content exceeds 0.16%, primers may form during casting. Its content according to the present invention is preferably less than 0.16%, or less than 0.15%, or less than 0.14%, or less than 0.13%, or less than 0.12%, or less than 0.11%, or less than 0.10%. Preferably, the minimum content of V is 0.05% when it is added.

[0068] Preferably, the solidus temperature of the 6xxx series aluminum of the core layer is greater than 595°C, preferably greater than 600°C, preferably greater than 605°C, preferably greater than 610°C, preferably greater than 615°C. Preferably, the solidus temperature of the 6xxx series alloy core layer is at least 20°C higher, preferably at least 30°C higher, preferably at least 40°C higher, than the solidus temperature of the brazing layer. The solidus temperature of the 6xxx series aluminum of the core layer is to be adapted according to the brazing conditions in a manner known to those skilled in the art.

[0069] It should be noted that the 6xxx series aluminum alloy of the core layer of flat and stamped parts can be the same or two different alloys. Preferably, it is the same alloy.

[0070] Aluminum alloy of the cover layer

[0071] According to the present invention, the covering layer may be a sacrificial layer or a solder layer.

[0072] Sacrificial layer:

[0073] According to a variant of the present invention, the strip or sheet comprises a cover layer which is a sacrificial layer 16 on at least one face of the core layer 18. Preferably, the aluminum alloy of the sacrificial layer 16 comprises less than 2.50%, and preferably at least 0.50% by mass of Zn.

[0074] According to a variant of the present invention, the aluminum alloy of the sacrificial layer is chosen from an aluminum alloy of the lxxx, 7xxx or 3xxx series, preferably of the 7xxx or 3xxx series.

[0075] Alternatively, the aluminum alloy of the sacrificial layer may be a 7xxx series aluminum alloy, preferably having the following composition, in mass percentages: less than 0.50% Si; less than 0.50% Fe; less than 0.25% Cu; less than 0.30% Mn; less than 0.20%, preferably less than 0.15% Mg; from 0.70 to 5.00%, preferably from 0.70 to less than 4.50%, alternatively from 0.50 to less than 2.50%, preferably from 0.70 to less than 2.50%, preferably from more than 0.80 to less than 1.30% Zn; less than 0.15% Ti; other elements less than 0.05% each and less than 0.15% in total; remainder aluminum.

[0076] For example, the composition AA7072 is an aluminum alloy that may be suitable as a sacrificial layer according to the present invention. Its composition is, in mass percentages: less than 0.05% Si; less than 0.05% Fe; less than 0.10% Cu; less than 0.10% Mn; less than 0.10% Mg; from 0.80 to 1.30% Zn; other elements less than 0.05% each and less than 0.15% in total; remainder aluminum.

[0077] According to another variant, the aluminum alloy of the sacrificial layer may be an aluminum alloy of the 3xxx series, preferably having the following composition, in mass percentages: from 0.10 to 0.35% of Si; less than 0.70% of Fe; less than 0.20% of Cu; from 0.70 to 2.00%, preferably from 0.90 to 1.30% of Mn; from 0.70 to 5.00%, preferably from 0.70 to less than 4.50%, preferably from 0.70 to less than 2.50%, preferably from more than 0.80 to less than 1.30% of Zn; less than 0.15% of Ti; other elements less than 0.05% each and less than 0.15% total; remainder aluminum. Preferred values ​​of each of the elements of the 3xxx series or 7xxx series alloys, which could be suitable as a sacrificial anode according to the present invention, are given as examples in Table 1 below (columns 3xxx-l, 7xxx-l and 7xxx-2), in mass percentages.

[0078] [Table 1]

[0079] Solder layer:

[0080] The aluminum alloy of the brazing layer is preferably an aluminum alloy of the 4xxx series with a sufficiently low liquidus temperature compared to the solidus of the core alloy to provide a sufficient temperature range for brazing, acceptable mechanical strength and good wettability. These alloys may contain additional elements, for example strontium, preferably in a mass content of less than 0.05%.

[0081] According to one variant, the brazing alloy of the present invention comprises Y, Sn and / or Bi. This variant has in particular an advantage for fluxless brazing. Preferably, the brazing alloy comprises:

[0082] - from 0.01 to 0.10%, preferably from 0.015 to 0.08%, preferably from 0.02 to 0.065% of Y;

[0083] - from 0.01 to 0.10%, preferably from 0.015 to 0.08%, preferably from 0.02 to 0.065% of Sn; and / or

[0084] - at most 0.04%, preferably at most 0.03%, preferably at most 0.02% of Bi according to a first variant; or at most 0.15%, preferably at most 0.12%, preferably less than 0.10%, and preferably at least 0.05%, preferably more than 0.06% of Bi according to a second variant.

[0085] Preferably, the aluminum alloy of the brazing layer does not comprise Bi.

[0086] Preferably, the aluminum alloy of the brazing layer is a 4xxx series alloy comprising from 4.00 to 13.00 mass % of Si and less than 1.00 mass % of Fe. Preferably, the aluminum alloy of the 4xxx series brazing layer comprises (mass %):

[0087] - If: from 5.00 to 13.00%, preferably from 6.00 to 11.00%;

[0088] Fe: less than 0.60%, preferably less than 0.50%, preferably less than 0.30%;

[0089] - Cu: less than 0.40%, preferably less than 0.10%, preferably less than 0.05%;

[0090] - Mn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%;

[0091] - Mg: according to a first variant less than 0.20%, preferably less than 0.10%, preferably less than 0.05%; or according to a second variant from 0.50 to 2.50%, preferably from 1.00 to 2.00%;

[0092] - Zn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%, preferably less than 0.02%;

[0093] - Ti: less than 0.30%, preferably less than 0.10%, preferably less than 0.05%;

[0094] - possibly Bi, Y, Sr and / or Sn;

[0095] - other elements: less than 0.05% each and less than 0.15% in total;

[0096] - aluminum remains.

[0097] For example, the composition AA4045 is an aluminum alloy that may be suitable as an alloy for the brazing layer according to the present invention. Its composition is, in mass percentages: from 9.0 to 11.0% Si, less than 0.80% Fe, less than 0.30% Cu, less than 0.05% Mn, less than 0.05% Mg, less than 0.10% Zn, less than 0.20% Ti, other elements less than 0.05% each and less than 0.15% in total, the remainder being aluminum.

[0098] For example, the preceding composition preferably comprises less than 0.60% Fe. For example, the preceding composition preferably comprises less than 0.10% Cu. For example, the composition AA4343 is an aluminum alloy which may be suitable as a brazing alloy according to the present invention. Its composition is, in mass percentages: from 6.80 to 8.20% Si, less than 0.80% Fe, less than 0.25% Cu, less than 0.10% Mn, less than 0.05% Mg, other elements less than 0.05% each and less than 0.15% in total, the remainder being aluminum.

[0099] For example, the preceding composition preferably comprises less than 0.30% Fe. For example, the preceding composition preferably comprises less than 0.10% Cu. For example, the composition AA4004 is an aluminum alloy that may be suitable as a brazing alloy according to the present invention. Its composition is, in mass percentage: from 9.00 to 10.50% Si, less than 0.80% Fe, less than 0.25% Cu, less than 0.10% Mn, from 1.00 to 2.00% Mg, less than 0.20% Zn, other elements less than 0.05% each and less than 0.15% in total, the remainder being aluminum. For example, the composition AA4104 is an aluminum alloy that may be suitable as a brazing alloy according to the present invention.Its composition is, in mass percentage: from 9.00 to 10.50% Si, less than 0.80% Fe, less than 0.25% Cu, less than 0.10% Mn, from 1.00 to 2.00% Mg, less than 0.20% Zn, from 0.02 to 0.20% Bi, other elements less than 0.05% each and less than 0.15% in total, the remainder being aluminum.

[0100] Aluminum alloy of the interlayer

[0101] According to one embodiment, the strip or sheet according to the present invention is plated, on one or two faces of the core layer, with an aluminum alloy called an interlayer, preferably of the lxxx or 3xxx series, placed between the core layer and a covering layer, preferably a brazing layer, preferably comprising (in mass %):

[0102] - If: less than 0.50%, more preferably less than 0.20%;

[0103] - Fe: less than 0.70%, more preferably less than 0.30%, even more preferably less than 0.20%;

[0104] - Mn: from 0.30 to 1.40%, more preferably from 0.50 to 0.90%, more preferably from 0.60 to 0.80%, or according to a variant from 1.00 to 1.30%, -

[0105] - Cu: less than 0.30%, preferably less than 0.10%, even more preferably less than 0.05%;

[0106] - possibly Mg, Zn and / or In;

[0107] - other elements < 0.05% each and < 0.15% in total;

[0108] - aluminum remains.

[0109] Preferably, the interlayer aluminum alloy of the strip or sheet according to the present invention comprises (% by mass): Si < 0.15%; Fe < 0.20%; Cu < 0.10%; Mn from 0.60 to 0.80%; Mg < 0.02% according to a first variant or Mg < 0.50%, preferably < 0.25% according to a second variant; other elements < 0.05% each and < 0.15% in total, remainder aluminum.

[0110] Preferably, the interlayer aluminum alloy is an AA3xxx series alloy.

[0111] According to one variant, the intercalated aluminum alloy may further comprise:

[0112] - Zn at a content of 1.5 to 2.3%; and / or

[0113] - In according to a content of 0.005 to 0.04%.

[0114] According to a variant, the strip or sheet according to the present invention comprises an interlayer between the core and the covering layer only in the case where the covering layer is a brazing layer.

[0115] According to a variant, the strip or sheet according to the present invention does not comprise an interlayer. Strip or sheet and set of two strips or sheets

[0116] Strip or sheet:

[0117] The strip or sheet according to the present invention is a so-called brazing strip or sheet, which can be used for the manufacture of different parts of a heat exchanger, for example tubes, plates, collectors, battery cooling systems for electric vehicles, etc.

[0118] The strip or sheet according to the present invention may have a configuration with several layers, and in particular with 2, 3, 4 or 5 layers.

[0119] The two-layer configuration includes a core layer clad on one side with a cover layer, in particular either with a solder layer or with a sacrificial layer.

[0120] The three-layer configuration can include:

[0121] - either a core layer plated on both sides with a brazing layer;

[0122] - either a core layer plated on both sides with a sacrificial layer;

[0123] - either a core layer plated on one side only with an interlayer, itself plated with a brazing layer or a sacrificial layer, preferably a brazing layer;

[0124] - either a core layer plated on one side with a brazing layer and on the other side with a sacrificial layer.

[0125] The four-layer configuration can include:

[0126] - either a core layer plated on a first face with an interlayer, itself plated with a brazing layer or a sacrificial layer, preferably a brazing layer, and on the other face with a brazing layer;

[0127] - either a core layer plated on a first face with an interlayer, itself plated with a brazing layer or a sacrificial layer, preferably a brazing layer, and on the other face with a sacrificial layer.

[0128] The five-layer configuration includes a core layer plated on both sides with an interlayer itself plated with a solder layer or a sacrificial layer, preferably a solder layer.

[0129] In each of the above-mentioned configurations, when two solder layers, two interlayers or two sacrificial layers are provided, then they may be the same or different in composition. Preferably, the layers are identical in composition.

[0130] Preferred configurations are three-layer configurations, including:

[0131] - either a core layer plated on two sides with a sacrificial layer; - or a core layer plated on one side with a sacrificial layer and on the other side with a brazing layer.

[0132] According to a variant, at least one interlayer may be present between the core layer and the sacrificial layer or the brazing layer. However, preferably, there is no interlayer in the strip or sheet according to the invention.

[0133] Preferably, the strip or sheet according to the present invention consists of a core layer of aluminum alloy of the 6xxx series, a cover layer on one or both faces of the core layer and optionally an interlayer on one or two faces of the core layer placed between the core layer and the cover layer.

[0134] According to a first variant, the strip or sheet according to the present invention comprises a covering layer on a single face of the core layer, and:

[0135] - the cover layer is a brazing layer; or

[0136] - the cover layer is a sacrificial layer.

[0137] According to a second variant, the strip or sheet according to the present invention comprises a covering layer on both sides of the core layer, and:

[0138] - one of the cover layers is a sacrificial layer and the other cover layer is a solder layer; or

[0139] - both cover layers are sacrificial layers; or

[0140] - both cover layers are brazing layers.

[0141] As regards the total thickness of the strip or sheet according to the present invention, it is preferably 0.40 to 2.50 mm.

[0142] The thicknesses discussed here correspond to the thicknesses before brazing. Regarding the thicknesses of each layer, it should be noted that these are target values, for which a margin of error of approximately 2% is commonly accepted in the field of plated sheets or strips for heat exchangers.

[0143] According to a first variant where the strip or sheet according to the present invention is intended for the manufacture of a flat part, the minimum total thickness of the strip or sheet is 1.05 mm, or 1.15 mm, or 1.25 mm, or 1.35 mm, or 1.45 mm, or 1.55 mm, or 1.65 mm or 1.75 mm, or 1.85 mm or 1.95 mm. According to this first variant, the maximum total thickness of the strip or sheet is preferably 2.50 mm, or 2.40 mm, or 2.30 mm, or 2.20 mm, or 2.10 mm.

[0144] According to a second variant where the strip or sheet according to the present invention is intended for the manufacture of a stamped part, the minimum total thickness of the strip or sheet is 0.50 mm, or 0.60 mm, or 0.70 mm, or 0.80 mm, or 0.90 mm. According to this second variant, the maximum total thickness of the strip or sheet is preferably 2.50 mm, or 2.30 mm, or 2.10 mm, or 1.90 mm, or 1.70 mm, or 1.50 mm or 1.30 mm or 1.10 mm.

[0145] As regards the thickness of the intermediate layer or the sacrificial layer, it preferably represents from 4 to 15% of the total thickness of the strip or sheet according to the present invention. The minimum thickness of the intermediate layer or the sacrificial layer preferably represents 5%, or 6% or 7% or 8% or 9% of the total thickness of the strip or sheet according to the present invention. The maximum thickness of the intermediate layer or the sacrificial layer preferably represents 14%, or 13% or 12% or 11% of the total thickness of the strip or sheet according to the present invention.

[0146] As regards the thickness of the brazing layer, it preferably represents from 3 to 15% of the total thickness of the strip or sheet according to the present invention. The minimum thickness of the brazing layer preferably represents 4% of the total thickness of the strip or sheet according to the present invention. The maximum thickness of the brazing layer preferably represents 14%, or 13% or 12% or 11% or 10% or 9% or 8% or 7% or 6% of the total thickness of the strip or sheet according to the present invention.

[0147] Set of two sheets or strips:

[0148] The sheets or strips according to the present invention can be combined with each other, after possible shaping, to form a heat exchanger with channels. The assembly of two sheets or strips according to the present invention can be that after assembly but before brazing or that after brazing. Brazing does not modify the configuration, that is to say the order of the different layers and the respective position of the flat part in relation to the stamped part.

[0149] According to the present invention, the set of two sheets or strips comprises, preferably consists of:

[0150] - a flat part formed from a strip or sheet according to the present invention;

[0151] - a stamped part formed from a strip or sheet according to the present invention; the two parts being intended to be assembled by brazing and forming a channel thanks to the deformation of the stamped part, the outermost layer of the stamped part and / or of the flat part in contact with the other part being a brazing layer.

[0152] The set of two sheets or strips according to the present invention can be presented in different variants.

[0153] According to a first preferred variant:

[0154] - one of the parts, flat or stamped, consists of a core according to the present invention, plated on both sides with a sacrificial layer, and - the other part, stamped or flat, consists of a core according to the present invention, plated on one side with an optional interlayer and a brazing layer, and on the other side with a sacrificial layer.

[0155] According to a second preferred variant, the two parts, flat and stamped, consist of a core according to the present invention, plated on one face with an optional interlayer and a brazing layer, and on the other face with a sacrificial layer.

[0156] In each of the variants presented above, the brazing layer of at least one of the parts is located between the flat part and the stamped part.

[0157] Process

[0158] The invention also relates to a method of manufacturing a strip or sheet according to the present invention, comprising the successive steps of:

[0159] - casting of a core alloy plate;

[0160] - optionally homogenization of the plate at a temperature of 450 to 580°C, preferably 520 to 560°C for 1 to 24 hours;

[0161] - possible cladding with a covering aluminum alloy on one or two faces of the core layer and possibly an interlayer aluminum alloy on one or two faces of the core layer;

[0162] - preheating to a temperature of 400 to 550°C, preferably 450 to 530°C, preferably 480 to 510°C, preferably with maintenance at the maximum temperature for less than 30 hours, preferably for less than 20 hours, preferably for less than 12 hours, more preferably for less than 3 hours;

[0163] - hot rolling of the plate, optionally homogenized and optionally plated, at a temperature of 390 to 530°C, preferably 470 to 530°C, to a thickness of 2 to 6 mm,

[0164] - cold rolling to the desired thickness, the thickness of the strip or sheet after cold rolling preferably being 0.15 to 3 mm and

[0165] - heat treatment in a pass-through furnace at a temperature of 250 to 560°C, preferably 320 to 430°C, preferably 320 to 360°C with maintenance at the maximum temperature for less than 5 minutes, preferably less than 1 minute, preferably for less than 30 seconds and preferably more than 15 seconds, or in a batch furnace at a temperature of 250 to 390°C, preferably 310 to 360°C, with maintenance at the maximum temperature preferably for less than 3 hours, preferably for less than 2 hours and preferably less than 1 hour, so as to obtain a small-grain recrystallization. Said cover alloy of the method according to the present invention may in particular be a brazing alloy, or a sacrificial layer, or two brazing alloys, or two sacrificial layers, or a brazing alloy and a sacrificial layer.

[0166] Preferably, there is no intermediate annealing during the rolling steps in the methods according to the present invention.

[0167] Before installing any cladding materials, it is possible to homogenize the alloy plate of the core layer at a temperature of 450 to 580°C, preferably 520 to 560°C, preferably for 1 to 24 hours.

[0168] Use

[0169] The invention also relates to a heat exchanger made at least in part from a strip or sheet according to the present invention or from a set of two sheets or strips according to the present invention.

[0170] The invention also relates to the use of a strip or sheet according to the present invention or of a set of two sheets or strips according to the present invention, for the manufacture of a heat exchanger, preferably a battery cooler for an electric vehicle.

[0171] The strips or sheets according to the present invention can be used in the manufacture of brazed heat exchangers, especially for automobiles, such as engine cooling radiators, evaporators, heater cores and charge air coolers, manifolds, battery coolers of electric vehicles, as well as in air conditioning systems.

[0172] The manufacture of a heat exchanger according to the present invention may in particular comprise at least one of the following steps:

[0173] - Braze in a CAB (controlled atmosphere) furnace, preferably at a temperature of 590 to 615°C, preferably 590 to 610°C, preferably 590 to 605°C, preferably 590 to 600°C;

[0174] - Ensure cooling preferably at a rate greater than 25°C / min, preferably greater than 35°C / min, preferably greater than 50°C / min below 380°C and up to 100°C at the end of the brazing cycle;

[0175] - Carry out a post-brazing tempering step at a temperature of 150 to 240°C, preferably 180 to 220°C, for a duration preferably less than 6 hours, preferably less than 3 hours, preferably less than or equal to 2 hours (for example for 2 hours at approximately 195°C or for 30 minutes at 205°C). Preferably, the minimum temperature of the post-brazing tempering is greater than 180°C, or greater than or equal to 181°C, or greater than or equal to 182°C, or greater than or equal to 183°C, or greater than or equal to 184°C, or greater than or equal to 185°C, or greater than or equal to 186°C, or greater than or equal to 187°C, or greater than or equal to 188°C, or greater than or equal to 189°C, or greater than or equal to 190°C. An increase in the temperature of the post-brazing tempering may make it possible to reduce the duration of this tempering. For example, for a post-brazing tempering temperature greater than or equal to 185°C, the duration may be less than 4 hours.

[0176] EXAMPLES

[0177] Example 1: Solderability

[0178] Different aluminum alloy ingots of core layers, brazing layers and sacrificial layers were cast by vertical semi-continuous casting (DC casting) with aluminum alloys having the compositions given in Table 2 below, in mass percentages:

[0179] [Table 2]

[0180] Before assembling the different layers together:

[0181] - the core layer aluminium alloy ingots were homogenised (temperature above 530°C for more than 2 hours and less than 24 hours) and hot rolled, at a temperature of 380 to 500°C, to a thickness of approximately 30 mm;

[0182] - the brazing layer alloy ingots were scalped and then hot rolled at a temperature of approximately 480-500°C to a thickness of 1.8 mm;

[0183] - the sacrificial layer alloy ingot was hot rolled, at a temperature of about 480-500°C, to a thickness of about 3.5 mm.

[0184] After brushing the contact faces, 35.3 mm thick sandwiches were made, having the following configuration: brazing layer / core layer / sacrificial layer. The brazing layer represented approximately 5% of the total sandwich thickness and the sacrificial layer represented approximately 10% of the total sandwich thickness.

[0185] The following two sandwiches were made:

[0186] - Config-1: solder layer-1 / core layer-1 / sacrificial layer;

[0187] - Config-2: Brazing layer-1 / Core layer-2 / Sacrificial layer. The sandwiches were then preheated to a temperature of about 490°C for less than 5 hours and then hot rolled to a thickness of about 1.5 mm or about 0.8 mm. Annealing for 2 hours at about 360°C was carried out.

[0188] Sandwiches with a thickness of about 0.8 mm were stamped to create two lines and obtain stamped sheets, as shown in Figure 3. Sandwiches with a thickness of about 1.5 mm were not stamped to obtain unstamped or flat sheets.

[0189] The solderability of the different sandwiches was then evaluated. The soldering test was carried out according to the following protocol, which simulates the assembly soldering between a stamped sheet and a non-stamped sheet. To do this, 50 mm x 60 mm sheets were stamped in the absence of lubricant to add two longitudinal stamped lines 3 as illustrated in Figure 3. Then, the stamped and non-stamped sheets were degreased with an acetone solution and then air-dried. A stamped sheet and a non-stamped sheet with the same configuration and composition were then assembled as illustrated in Figure 3.In Figure 3, part number 1 corresponds to a stamped sheet, part number 2 corresponds to an unstamped sheet, part number 3 corresponds to two stamped lines, part number 16 corresponds to a sacrificial layer, part number 17 corresponds to a 4xxx series aluminum alloy brazing layer, and part number 18 corresponds to a 6xxx series aluminum alloy core. The assembled sheets were then flat brazed with 0 or 2 or 5 g / m. 2 Nocolok® type flux on the brazing layer 17. The brazing cycle was carried out with a hold of approximately 2 minutes at approximately 600°C in a controlled atmosphere (O2 < 50 ppm).

[0190] The length of each brazing joint was then measured. For each configuration, three samples were made. For each sample, two measurements were made at the two longitudinal stamped lines. The results can be expressed in terms of brazed length in mm, or in terms of percentage of brazed length relative to the maximum possible length. “A” corresponds to more than 90%; “B” corresponds to a range of 50 to 90%; “C” corresponds to a range of 10 to less than 50%; “D” corresponds to less than 10%.

[0191] The results of the soldering test are shown in Table 3 below.

[0192] [Table 3]

[0193] Good solderability was achieved with 5 g / m 2 of flow for all configurations. Example 2: Mechanical properties of a three-layer sandwich

[0194] On the samples of Example 1 above (according to configurations Config-1 and Config-2), after cold rolling to a thickness of 1.5 mm, different annealing operations were carried out: a strip line type annealing (30 seconds at approximately 400°C or 45 seconds at approximately 550°C) or a batch type annealing (2 hours at approximately 360°C).

[0195] A CAB (controlled atmosphere) type brazing of approximately 2 minutes at approximately 600°C with cooling at a rate greater than 40°C / min below 380°C and up to 100°C was carried out.

[0196] A 2-hour tempering at approximately 195°C was then carried out.

[0197] The tensile mechanical properties were measured in the rolling direction after annealing, and after annealing + brazing + tempering according to ISO 6892-1.

[0198] [Table 4]

[0199] It would appear that the duration and temperature of annealing have no influence on the value of Rpo,2 after annealing + brazing + tempering. In all cases, the value of Rpo,2 of the assembly is greater than 165 MPa. It is higher for the assembly with a 6xxx-l alloy core (Config-1) which contains more magnesium than the assembly with a 6xxx-2 alloy core (Config-2).

[0200] Example 3: Corrosion

[0201] Corrosion resistance measurements according to the SWAAT test were carried out on the configurations Config-1 and Config-2 described in examples 1 and 2 above, on samples having a thickness of approximately 1 mm, on the face plated with the sacrificial layer and after annealing for 2 hours at approximately 360°C then brazing for 2 minutes at approximately 600°C then tempering for 2 hours at approximately 195°C.

[0202] The corrosion resistance was determined using the following protocol: - prepare for each configuration a sample with dimensions 126 mm (L direction) x 90 mm (TL direction), previously degreased with white absorbent paper soaked in acetone;

[0203] - protect the untested side (side plated with the solder layer) as well as the four edges over a width of approximately 0.5 cm with a transparent vinyl adhesive (for example type 3M vinyl 764);

[0204] - clean the face to be tested (face plated with the sacrificial layer) with absorbent paper soaked in acetone;

[0205] - place the samples thus prepared on a rack with an inclination of approximately 60° to the horizontal;

[0206] - carry out for each sample a cyclic SWAAT (Sea Water Acidified Acetic Test) test according to the ASTM G85 A3 standard, including in particular an alternation of 30 min salt spray phases and 1h30 wet phases at a temperature of approximately 49°C.

[0207] The number of punctures was monitored daily for each specimen throughout the 20-day test period. The punctures can be seen on the back of each specimen as they form blisters in the adhesive applied to the untested side, as shown in Figure 4. In Figure 4, reference 6 corresponds to the specimen; reference 7 corresponds to the adhesive; reference 8 corresponds to a puncture; reference 9 corresponds to a blister formed by a puncture.

[0208] The results obtained are that there were no perforations after 20 days of testing, for any of the configurations Config-1 and Config-2.

[0209] The samples were then observed in polished section under a microscope: the depth of the pits (non-through) was less than 60 pm for both configurations Config-1 and Config-2.

[0210] Example 4: Mechanical properties

[0211] Simulation tests of a brazing cycle (heating to approximately 600°C, holding for 2 minutes, then cooling at a rate greater than 50°C / min from 380°C to 100°C) and post-brazing tempering (several temperatures and holding times were tested - see Table 6 below) were carried out on different compositions of 6xxx series aluminum alloy cores (see Table 5 below) without plating. The 6xxx series aluminum alloy sheets were obtained by homogenization at a temperature above 500°C for a time above 3 hours, then hot rolling at a temperature of 350 to 450°C to a thickness of about 2.8 mm, then cold rolling to a thickness of about 0.8 mm, then annealing at a temperature of 440 to 500°C for a time of 30 to 45 seconds. [Table 5]

[0212] The tensile mechanical properties were measured in the rolling direction after annealing + brazing + tempering according to ISO 6892-1. The results obtained are presented in Table 6 below.

[0213] [Table 6]

[0214] Alloy 6xxx-4 exhibited improved post-brazing mechanical characteristics compared to alloy 6xxx-3, at the expense of a decrease in solidus temperature to 618°C (see Table 6 above).

[0215] Example 5: Mechanical properties

[0216] Castings of different compositions of 6xxx series aluminum alloys were made.

[0217] Table 7 below shows the element contents of the different alloys, in mass percentages. [Table 7]

[0218] The 6xxx series aluminum alloy sheets were obtained by homogenization at a temperature of approximately 540°C for a period of approximately 6 hours (except for alloy B' which did not undergo homogenization), then hot rolling at a temperature of approximately 490°C to a thickness of approximately 4.5 mm, then cold rolling to a thickness of approximately 2.0 mm, then annealing at a temperature of approximately 360°C for a period of approximately 2 hours. Simulation tests of a brazing cycle (heating to approximately 600°C, holding for 2 minutes, then cooling at a rate greater than 50°C / min from 380°C to 100°C) and post-brazing tempering (1 hour at 195°C, 4 hours at 195°C, 2 hours at 205°C or

[0219] 2 hours at 210°C - see Table 8 below) were carried out on alloys A to G from Table 7 above. The oxygen content during the brazing simulation was less than 50 ppm.

[0220] The tensile mechanical properties were measured in the rolling direction after annealing + brazing + tempering according to ISO 6892-1. The results obtained are presented in Table 8 below, in which the values ​​of Rpo,2 and Rm are expressed in MPa. [Table 8]

[0221] On the other hand, a corrosion resistance test (not shown here) was carried out on core alloys A, B, F and G sandwiched between a brazing layer-1 from Table 2 above (7.5% of the total sandwich thickness) and the sacrificial layer from Table 2 above (10% of the total sandwich thickness). A SWAAT test according to ASTM G85 A3 (as described above in Example 3) was carried out. The results were obtained by microscopic analysis in polished section after 40 days of testing. The total thickness of the sandwiches was approximately 0.8 mm. It was found that the corrosion resistance of the sandwich comprising core alloy F was worse than that of the sandwiches comprising core alloys A, B and G, since a greater pitting depth was observed for core alloy F.

[0222] It should also be noted that core alloy G contains an Fe content which is not very suitable for recycling.

[0223] Example 6: Mechanical properties

[0224] Simulation tests of a brazing cycle (heating to approximately 600°C, holding for 2 minutes, then cooling at a rate greater than 50°C / min from 380°C to 100°C) and post-brazing tempering (several temperatures and holding times were tested - see Table 10 below) were carried out on a sheet comprising a core of 6xxx series aluminum alloy (alloy 6xxx-5) clad on two sides with a sacrificial layer of 7xxx series aluminum alloy (alloy 7xxx-l), the two sacrificial layers each representing 10% of the total thickness of the sheet. The compositions of the aluminum alloys are given in Table 9 below, in mass percentages.

[0225] [Table 9] The core layer of 6xxx series aluminum alloy was homogenized at a temperature of 540 to 600°C for a period of more than 3 hours, then assembled with the two sacrificial layers of 7xxx series aluminum alloy, which were previously hot rolled. The resulting sandwich was preheated, then hot rolled to a thickness of approximately 4 mm, then cold rolled to a thickness of approximately 2 mm, and then annealed at a temperature of approximately 350°C for a period of approximately 30 minutes.

[0226] The tensile mechanical properties were measured in the rolling direction after annealing + brazing + tempering according to ISO 6892-1. The results obtained are presented in Table 10 below.

[0227] [Table 10]

Claims

Tl CLAIMS Strip or sheet, intended for the manufacture of brazed heat exchangers, preferably battery coolers for electric vehicles, comprising, preferably being made of, a core layer (18), optionally a cover layer (16, 17) on one or two faces of the core layer (18) and optionally an interlayer on one or two faces of the core layer (18) placed between the core layer (18) and the cover layer (16, 17), the core layer (18) being made of aluminum alloy of the 6xxx series having the following composition, in mass percentages: - If: from 0.45 to 0.75%; preferably from 0.50 to 0.70%; preferably from 0.55 to 0.65%; - Fe: from 0.18 to 0.40%; preferably from 0.18 to 0.35%; preferably from 0.18 to 0.30%; preferably from more than 0.18 to 0.26%; - Cu: < 0.40%; preferably < 0.25%; preferably < 0.15%; and preferably > 0.05% according to a first variant; or preferably from 0.25 to 0.40%; preferably from 0.29 to 0.40% according to a second variant; - Mn: < 0.30%; preferably < 0.20%; preferably < 0.15%; preferably < 0.10%; - Mg: from 0.25 to 0.56%; preferably from 0.25 to 0.45%; preferably from 0.30 to 0.39%; - Ti: < 0.050%; preferably < 0.045%; preferably < 0.040%; - optionally V: from 0.05 to 0.16% - unavoidable impurities: < 0.05% each and < 0.15% in total; - remaining aluminum. Strip or sheet according to claim 1, characterized in that it consists of said core layer (18) made of 6xxx series aluminum alloy, a cover layer (16, 17) on one or both faces of the core layer (18), and optionally an interlayer on one or two faces of the core layer (18) placed between the core layer (18) and the cover layer (16, 17). Strip or sheet according to claim 2, characterized in that it comprises a cover layer (16, 17) on one face of the core layer, and in that: the covering layer (16, 17) is a brazing layer (17); or the covering layer (16, 17) is a sacrificial layer (16).

4. Strip or sheet according to claim 2, characterized in that it comprises a covering layer (16, 17) on both faces of the core layer, and in that: - one of the covering layers (16, 17) is a sacrificial layer (16) and the other covering layer (16, 17) is a brazing layer (17); or - the two covering layers (16, 17) are sacrificial layers (16); or - the two covering layers (16, 17) are brazing layers (17).

5. Strip or sheet according to any one of claims 2 to 4, characterized in that it comprises a cover layer which is a sacrificial layer (16) on at least one face of the core layer (18), the aluminium alloy of the sacrificial layer (16) preferably comprising less than 2.50%, and preferably at least 0.50% by mass of Zn.

6. Strip or sheet according to any one of claims 3 to 5, characterized in that the aluminium alloy of the sacrificial layer (16) is selected from an alloy of the lxxx, 7xxx or 3xxx series.

7. Strip or sheet according to claim 6, characterized in that the aluminium alloy of the sacrificial layer (16) is an alloy of the 7xxx series, preferably having the following composition, in mass percentages: - less than 0.50% of Si; - less than 0.50% of Fe; - less than 0.25% Cu; - less than 0.30% of Mn; - less than 0.20%, preferably less than 0.15% of Mg; - from 0.50 to less than 2.50%, preferably from 0.70 to less than 2.50%, preferably from more than 0.80 to less than 1.30% of Zn; - less than 0.15% Ti; - other elements less than 0.05% each and less than 0.15% in total; - remains aluminum.

8. Strip or sheet according to claim 6, characterized in that the aluminum alloy of the sacrificial layer (16) is a 3xxx series alloy, preferably having the composition The following, in mass percentages: - from 0.10 to 0.35% of Si; - less than 0.70% of Fe; - less than 0.20% Cu; - from 0.70 to 2.00%, preferably from 0.90 to 1.30% of Mn; - from 0.80 to less than 1.30% of Zn; - less than 0.15% Ti; - other elements less than 0.05% each and less than 0.15% total; - remains aluminum.

9. Strip or sheet according to any one of claims 3 or 4, characterized in that the aluminum alloy of the brazing layer (17) is an alloy of the 4xxx series, preferably comprising from 4.00 to 13.00% by mass of Si and less than 1.00% by mass of Fe, and more preferably having the following composition, in mass percentages: - If: from 5.00 to 13.00%, preferably from 6.00 to 11.00%, - - Fe: less than 0.60%, preferably less than 0.50%, preferably less than 0.30%; - Cu: less than 0.40%, preferably less than 0.10%, preferably less than 0.05%; - Mn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%; - Mg: according to a first variant, less than 0.20%, preferably less than 0.10%, preferably less than 0.05%; or according to a second variant, from 0.50 to 2.50%, preferably from 1.00 to 2.00%, - - Zn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%, preferably less than 0.02%; - Ti: less than 0.30%, preferably less than 0.10%, preferably less than 0.05%; - possibly Bi, Y, Sr and / or Sn; - other elements: less than 0.05% each and less than 0.15% in total; - remains aluminum.

10. A set of two sheets or strips comprising, preferably made of: - a flat piece (11) formed from a strip or sheet according to any one of the preceding claims, preferably according to any one of claims 2 to 9; - a stamped part (12) formed from a strip or sheet according to any one of the preceding claims, preferably according to any one of the claims 2 to 9; the two parts being intended to be joined by brazing and forming a channel through the deformation of the stamped part (12), the outermost layer of the stamped part (12) and / or the flat part (11) in contact with the other part being a brazing layer (17). Method for manufacturing a strip or sheet according to any one of claims 1 to 9, comprising the successive steps of: - casting of a core alloy plate (18); - optionally homogenizing the plate at a temperature of 450 to 580°C, preferably 520 to 560°C for 1 to 24 hours; - possible plating with a covering aluminium alloy (16, 17) on one or two faces of the core layer (18) and possibly an interlayer aluminium alloy on one or two faces of the core layer (18); - preheating to a temperature of 400 to 550°C, preferably 450 to 530°C, preferably 480 to 510°C, preferably with maintenance at maximum temperature for less than 30 hours, preferably for less than 20 hours, preferably for less than 12 hours, more preferably for less than 3 hours; - hot rolling of the plate, possibly homogenized and possibly plated, at a temperature of 390 to 530°C, preferably 470 to 530°C, up to a thickness of 2 to 6 mm, - cold rolling to the desired thickness, the thickness of the strip or sheet after cold rolling preferably being 0.15 to 3 mm and - Heat treatment in a pass-through furnace at a temperature of 250 to 560°C, preferably 320 to 430°C, preferably 320 to 360°C, with holding at maximum temperature for less than 5 minutes, preferably less than 1 minute, preferably less than 30 seconds, and preferably more than 15 seconds, or in a batch furnace at a temperature of 250 to 390°C, preferably 310 to 360°C, with holding at maximum temperature preferably for less than 3 hours, preferably less than 2 hours, and preferably less than 1 hour, so as to obtain small-grain recrystallization. Heat exchanger made at least in part from a strip or sheet according to any one of claims 1 to 9, preferably according to any one of the claims 2 to 9, or from an assembly of two sheets or strips according to claim 10. Use of a strip or sheet according to any one of claims 1 to 9, preferably according to any one of claims 2 to 9, or of an assembly of two sheets or strips according to claim 10, for the manufacture of a heat exchanger, preferably a battery cooler for an electric vehicle. Use according to claim 13, comprising at least one of the following steps: - Brazing in a CAB (controlled atmosphere) furnace, preferably at a temperature of 590 to 615°C, preferably 590 to 610°C, preferably 590 to 605°C, preferably 590 to 600°C; - Cooling preferably having a speed greater than 25°C / min, preferably greater than 35°C / min, preferably greater than 50°C / min below 380°C and down to 100°C at the end of the brazing cycle; - Post-brewing tempering at a temperature preferably of 150 to 240°C, preferably of 180 to 220°C, for a period preferably less than 6 hours, preferably less than 3 hours.

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