Aluminum alloy strip or sheet for manufacturing brazed heat exchangers

Abstract

Strip or sheet, intended for the manufacture of brazed heat exchangers, having a core layer of aluminum alloy with the following composition (% by mass): Si: more than 0.25% and less than 0.60%; Fe: less than 0.25%; Cu: more than 0.60% and less than 1.10%; Mn: more than 1.40% and less than 2.00%; Ti: less than 0.10% and more than 0.05%; Mg: according to one variant less than 0.05%; or according to a second variant less than 0.30%; Zr: less than 0.01%; Cr: less than 0.01%; Zn: less than 0.20%; impurities: less than 0.05% each and less than 0.15% in total; remainder aluminum. Abbreviated figure: -

Description

Description Title of the invention: Aluminum alloy strip or sheet for the manufacturing of brazed heat exchangers technical field

[0001] The invention relates to thin strips or sheets (of thickness generally between (0.05 to 3 mm, preferably 0.15 to 2.5 mm) in aluminum core alloy manganese (3xxx series according to the Aluminum Association nomenclature), possibly typically plated on one or two sides with a covering alloy, most often a aluminum-silicon brazing alloy (4xxx series according to the nomenclature of the Aluminium Association) and / or an interlayer alloy, placed between the core and the possible brazing alloy, aluminum-manganese alloy (3xxx series according to the nomenclature) of the Aluminium Association). These strips or sheets are intended in particular for the fa- assembly of elements, such as tubes, manifolds and plates, of heat exchangers heat-resistant materials assembled by brazing, particularly for the automotive industry, such as radiators engine cooling, evaporators, heater cores and coolers charge air diffusers, manifolds, battery coolers electric vehicles, as well as in air conditioning systems. These exchangers found particularly in engine and air conditioning cooling systems Interior finishing of automobiles. Alloy brazing techniques aluminum is described, for example, in the article by JC Kucza, A. Uhry and JC Goussain “High-strength brazing of aluminum and its alloys”, published in Welding and Related Techniques, Nov.-Dec. 1991, pp. 18-29. Strips or sheets according to the invention They can be used, in particular, in brazing techniques with non-corrosive flux. NOCOLOK® or CAB (controlled atmosphere brazing) type. EARLIER ART

[0002] — The properties required for aluminum alloy strips or sheets used for The manufacture of brazed heat exchangers notably requires sufficient formability for a easy shaping of tubes, collector fins and plates, prior to brazing, a good aptitude for brazing, high mechanical strength after brazing, so as to Use the thinnest possible thicknesses, while ensuring good resistance to stress. in fatigue during service, and good corrosion resistance after brazing. Good Of course, it is important that the chosen alloy be easy to cast and roll, and that the cost of manufacturing of strips or sheets must be compatible with industry requirements. tomobile.

[0003] — In order to promote the reduction in tube thickness for heat exchangers (like radiators), it is particularly interesting to increase the mechanical properties of mechanical properties of the material after brazing (in particular the maximum load (Rm) of the tensile curve obtained according to ISO 6892-1 (“Ultimate Tensile Strength” or “UTS” in English), which is a key factor in fatigue resistance), without reducing corrosion resistance or brazingability. Solutions have already been proposed in this regard. For example, the following patent applications disclose the compositions listed below: - WO2020 / 178507: 0.1 - 0.3% Si; <0.2% Fe; 0.75 - 1.05% Cu; 1.2 - 1.7% Mn; < 0.03% Mg; <0.15% Ti; <0.1% Zn; - EP1183151: 0.4 - 0.8% Si; <0.4% Fe: 0.5 —- 2% Cu: 0.5 - 1.5% Mn; - EP2017032: 0.3 - 1.2% Si; 0.05 - 0.4% Fe; 0.3 - 1.2% Cu; 0.3 - 1.8% Mn; 0.05 - 0.6% Mg: < 0.3% Ti; <0.3% Zr; <0.3% Cr. However, the proposed solutions do not necessarily allow for the right compromise between good mechanical strength after brazing, good corrosion resistance and good brazingability. Faced with growing market demand, there remains a need for a new core alloy with improved mechanical strength compared to existing alloys, without compromising corrosion resistance or brazingability. Such a core alloy could meet the ongoing demand for reduced product thickness. Description of the invention Surprisingly, the applicant has identified a composition range that improves mechanical strength without degrading corrosion resistance or brazingability. As an example, the target according to the present invention may be to achieve a tensile strength Rm greater than 140 MPa, preferably greater than 145 MPa, preferably greater than 150 MPa, preferably greater than 160 MPa for industrial strips or sheets after brazing. As demonstrated in the examples, the present invention also has the unexpected advantage of improving corrosion resistance, for example corrosion in SWAAT testing. The invention thus relates to a strip or sheet, intended for the manufacture of brazed heat exchangers, having a core layer, optionally a covering 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 optional covering layer, the core layer being made of aluminium alloy of composition (% by mass): - If: more than 0.25%, preferably more than 0.30%, preferably more than 0.35%, of preferably more than 0.40%; and less than 1.00%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.55%: - Fe: less than 0.25%, preferably less than 0.20%; and preferably more than 0.10%: - Cu: more than 0.60%, preferably more than 0.70%, preferably more than 0.80%, preferably more than 0.85%; and less than 1.10%, preferably less than 1.00%, preferably less than 0.95%; - Mn: more than 1.40%, preferably more than 1.50%; and less than 2.00%, preferably less than 1.80%, preferably less than 1.65%; - Ti: less than 0.20%, preferably less than 0.15%, preferably less than 0.10%; and more than 0.05%; - Mg: according to a first variant less than 0.05%, preferably less than 0.01%, preferably less than 0.001%; ​​or according to a second variant less than 0.30%; - Zr: less than 0.01%, preferably less than 0.005%; - Cr: less than 0.01%, preferably less than 0.005%; - Zn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%, preferably less than 0.01%; - impurities: less than 0.05% each and less than 0.15% in total; - remains aluminum. The invention also relates to a method for manufacturing a strip or sheet according to the present invention, comprising the successive steps of: - casting of a core alloy plate; - possible plating 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; - preheating to a temperature of 450 to 550°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 non-homogenized and possibly plated plate at a temperature of 420 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 - annealed at a temperature of 240 to 450°C, preferably 240 to 400°C, preferably 280 to 370°C, with holding at maximum temperature for 10 minutes to 15 hours, preferably 20 minutes to 3 hours. According to one variant, the invention also relates to a manufacturing process of a strip or sheet according to the present invention, comprising the successive stages of: - casting of a core alloy plate, - homogenization of the plate from 550 to 630°C, preferably from 580 to 630°C for 1 to 24 hours; - possible plating 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; - preheating to a temperature of 450 to 550°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 homogenized and possibly plated plate at a temperature of 420 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 - annealed at a temperature of 240 to 450°C, preferably 240 to 400°C, preferably 280 to 370°C, with holding at maximum temperature for 10 minutes to 15 hours, preferably 20 minutes to 3 hours. The invention also relates to a heat exchanger made at least partly from a strip or sheet according to the present invention. The invention also relates to the use of a strip or sheet according to the present invention, for the manufacture of a heat exchanger, said strip or sheet having improved mechanical resistance without degradation of corrosion resistance or brazing. FIGURES [fig.1] The [fig.1] is a diagram describing the perforation analysis during the SWAAT corrosion resistance test of the examples. DETAILED DESCRIPTION OF THE INVENTION In the description and claims, unless otherwise stated: - the designation of aluminium alloys conforms to the nomenclature of The Aluminium Association; - The chemical element contents are indicated as mass percentages. Core aluminum alloy The strip or sheet according to the present invention is intended for the manufacture of brazed heat exchangers, and has 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 possible top layer, the core layer being made of aluminium alloy with the following composition (% by mass): - If: more than 0.25%, preferably more than 0.30%, preferably more than 0.35%, preferably more than 0.40%; and less than 1.00%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.55%: - Fe: less than 0.25%, preferably less than 0.20%; and preferably more than 0.10%: - Cu: more than 0.60%, preferably more than 0.70%, preferably more than 0.80%, preferably more than 0.85%; and less than 1.10%, preferably less than 1.00%, preferably less than 0.95%; - Mn: more than 1.40%, preferably more than 1.50%; and less than 2.00%, preferably less than 1.80%, preferably less than 1.65%; - Ti: less than 0.20%, preferably less than 0.15%, preferably less than 0.10%; and more than 0.05%; - Mg: according to a first variant less than 0.05%, preferably less than 0.01%, preferably less than 0.001%; ​​or according to a second variant less than 0.30%; - Zr: less than 0.01%, preferably less than 0.005%; - Cr: less than 0.01%, preferably less than 0.005%; - Zn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%, preferably less than 0.01%; - impurities: less than 0.05% each and less than 0.15% in total; - remains aluminum. The compositional limits of the core alloy can be justified in the following way. A minimum silicon content of 0.10% avoids the need for a costly pure base. It has been observed that silicon contents above 0.25% improve corrosion resistance, for example, in SWAAT tests. Therefore, the silicon content is preferably above 0.25%, preferably above 0.30%, preferably above 0.35%, and preferably above 0.40%. Excessive silicon content can lower the core solidus temperature and compromise the brazing. It is best to limit the silicon to less than 1.00%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.55%. An iron content limited to less than 0.25%, preferably less than 0.20%, is also favorable to corrosion resistance and formability, particularly by reducing the fraction of coarse precipitates containing iron. However, it is not necessary to go down to very low contents, for example below 0.08%. which would lead to high production costs. Therefore, the preferred iron content is greater than 0.10%. Copper is a hardening element that contributes to mechanical strength, but above 1.1%, the risk of cracking during casting is higher. Coarse intermetallic compounds can also form during casting, impairing the metal's homogeneity and potentially creating corrosion initiation sites. To achieve high mechanical strength, the copper content should be greater than 0.60%, preferably greater than 0.70%, preferably greater than 0.80%, and preferably greater than 0.85%. Preferably, the copper content should be less than 1.10%, preferably less than 1.00%, and preferably less than 0.95%. Manganese contributes to mechanical strength through solid solution and the formation of Al-Mn-Si dispersoids. For significant hardening, the manganese content is preferably greater than 1.40%, and preferably greater than 1.50%. To avoid the formation of a large number of coarse phases during casting, which can reduce formability, it is recommended to limit the Mn content to less than 2.00%, preferably less than 1.80%, and preferably less than 1.65%. A limited addition of zinc can have a beneficial effect on corrosion resistance by modifying electrochemical mechanisms, particularly for alloys with high copper content. However, it must remain below 0.20% to avoid excessive susceptibility to generalized core corrosion. Preferably, the zinc content is limited to less than 0.10%, preferably less than 0.05%, and preferably less than 0.01%. Magnesium provides a significant increase in mechanical strength. However, in the case of controlled atmosphere furnace (CAB) brazing with flux, it is preferable to limit its content to less than 0.2%. According to the present invention, the magnesium content is preferably less than 0.05%, preferably less than 0.01%, and preferably less than 0.001%. In the case of fluxless brazing, the preferred magnesium content is less than 0.30%. Titanium allows control of grain size during casting. Its content is less than 0.20%, preferably less than 0.15%, preferably less than 0.10%. Preferably, the Ti content is greater than 0.05%. Zirconium and chromium may be added optionally. However, they are preferably absent, or present at a level corresponding to impurities, i.e., less than 0.01%, preferably less than 0.005% each. Aluminum alloy cover The strips or sheets according to the present invention generally have a thickness of 0.05 to 3 mm, preferably 0.15 to 2.5 mm, depending on the type of part manufactured, and can be plated on one or two faces of the core layer and / or on a free face of any interlayer, with a covering alloy, which can be either a brazing alloy or an alloy acting as a sacrificial anode to protect the part from corrosion, such as a zinc-containing alloy, for example from the 7xxx series, like alloy AA7072, or from the 3xxx series. The free face of any interlayer corresponds to the face of the interlayer that is not in contact with the core layer. It should be noted that a brazing layer can be applied to one or two faces of a core layer and / or to the free face of an interlayer, whereas the sacrificial anode can be applied only to one or two faces of a core layer, without an interlayer between the core layer and the sacrificial anode. According to one variant, a sacrificial anode type cover alloy could be, according to the present invention, an alloy of the 7xxx series, 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 1.30%, preferably from 0.70 to less than 1.00% Zn; less than 0.15% Ti; other elements less than 0.05% each and less than 0.15% in total; remainder aluminum. As an example, composition AA 7072 is an aluminum alloy suitable for use as a sacrificial anode according to the present invention. Its composition, in mass percentages, is: 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; 0.80 to 1.30% Zn; other elements less than 0.05% each and less than 0.15% in total; the remainder being aluminum. According to one variant, the previous composition preferably includes less than 1.00% of Zn. According to another variant, a sacrificial anode type cover alloy could be, according to the present invention, an alloy of the 3xxx series, preferably having the following composition, in mass percentages: from 0.10 to 0.35% Si; less than 0.70% Fe; less than 0.20% Cu; from 0.70 to 2.00%, preferably from 0.90 to 1.30% Mn; from 0.50 to 1.60%, preferably from 0.90 to 1.20% Zn; less than 0.15% 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 by way of example in Table 1 below (columns 3xxx-1, 7xxx-1 and 7xxx-2), in mass percentages. [Table 1] 7xxx-2 0.15-0.40% <0.40% 7xxx-1 0.05 - 0.30% 0.25 - 0.45% <0.15% <0.15% <0.15% <0.10% <0.05% <0.10% <0.05% <0.05% < 0.05% 3.50 - 4.50% <0.05% 0.80 - 1.30% Preferred 0.80 to <1% jui <0.10 <0.10% <0.10% Pref. < 0.05% Pref. < 0.05% Pref. < 0.05% Zr |<0.05% <0.05% <0.05% <0.05% The brazing alloy is preferably a 4xxx series alloy with a liquidus temperature sufficiently low relative 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 alloying elements, for example, strontium. According to one embodiment, the brazing alloy of the present invention comprises Y, Sn, and / or Bi. This embodiment is particularly advantageous for fluxless brazing. Preferably, the brazing alloy comprises: - from 0.01 to 0.10%, preferably from 0.015 to 0.08%, preferably from 0.02 to 0.065% of Y; - from 0.01 to 0.10%, preferably from 0.015 to 0.08%, preferably from 0.02 to 0.065% of Sn: and / or - 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%, and preferably at least 0.05% of Bi according to a second variant. Preferably, the strip or sheet according to the present invention is plated on one or two faces of the core layer and / or on a free face of a possible interlayer with a brazing aluminum alloy, preferably an alloy of the 4xxx series comprising from 4.00 to 13.00% by mass of Si and less than 1.00% by mass of Fe. Preferably, the 4xxx series brazing aluminum alloy comprises (% in mass) : - 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 and / or Sn; - other elements: less than 0.05% each and less than 0.15% in total; - remainder aluminum. As an example, composition AA4045 is an aluminum alloy that can be suitable as a brazing alloy according to the present invention. Its composition is, in mass percentage: 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. As an example, the previous composition preferably includes less than 0.60% Fe. As an example, the previous composition preferably includes less than 0.10% Cu. As an example, composition AA4343 is an aluminum alloy that can be suitable as a brazing alloy according to the present invention. Its composition is, in mass percentage: 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. As an example, the previous composition preferably includes less than 0.30% Fe. As an example, the previous composition preferably includes less than 0.10% Cu. As an example, composition AA4004 is an aluminum alloy that can 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 aluminium. As an example, composition AA4104 is an aluminum alloy that can 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. Aluminum alloy interlayer g 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 intercalary aluminum alloy, preferably of the Ixxx or 3xxx series, placed between the core and the possible brazing alloy, preferably comprising (by mass %): - If: less than 0.50%, more preferably less than 0.20%; - Fe: less than 0.70%, more preferably less than 0.30%, even more preferably less than 0.20%: - 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%; - Cu: less than 0.30%, preferably less than 0.10%, even more preferably less than 0.05%; - possibly Mg, Zn and / or In; - other elements < 0.05% each and < 0.15% in total; - remains aluminum. Preferably, the aluminum alloy interlayer 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. Preferably, the interlayer aluminum alloy is an alloy from the AA3xxx series. According to one variant, the interlayer aluminum alloy may also include: - Zn at a concentration of 1.5 to 2.3%; and / or - In according to a content of 0.005 to 0.04%. Strip or sheet metal The strip or sheet according to the present invention is a so-called brazing strip or sheet, which can be used to manufacture different parts of a heat exchanger, for example tubes, plates, collectors, battery cooling systems for electric vehicles, etc. The strip or sheet according to the present invention can have a configuration with several layers, and in particular with 2, 3, 4 or 5 layers. The two-layer configuration includes a core plated on one side with a cover layer, specifically either with a brazing layer or with a sacrificial anode. The three-layer configuration includes: - either a core layer plated on both sides with a brazing layer; - either a layer of Soul plated on both sides with a sacrificial anode; - either a core layer plated on one side with an interlayer layer, itself plated with a brazing layer; - either a core layer plated on one side with a brazing layer and on the other side with a sacrificial anode. The four-layer configuration includes: - either a core layer plated on one face with an interlayer layer, itself plated with a brazing layer, and on the other face with a brazing layer; - either a core layer plated on one side with an intercalated layer, itself plated with a brazing layer, and on the other side with a sacrificial anode. The five-layer configuration includes a core layer plated on both sides with an interlayer layer itself plated with a brazing layer. In each of the configurations mentioned above, when two brazing layers, two interlayers, or two sacrificial anodes are provided, they may be identical or different in terms of composition and thickness. In particular, the thickness of each of the layers other than the core layer—that is, the brazing layer, the interlayer, and the sacrificial anode—is preferably 4 to 15%, and preferably 4 to 11%, of the total thickness of the strip or sheet according to the present invention. Process The invention also relates to a method for manufacturing a strip or sheet, comprising the successive steps of: - casting of a core alloy plate; - possible plating with a covering aluminum alloy on one or two faces of the core layer and possibly an interlayer aluminum alloy on one or two sides of the core layer: - preheating to a temperature of 450 to 550°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 non-homogenized and possibly plated plate at a temperature of 420 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 - annealed at a temperature of 240 to 450°C, preferably 240 to 400°C, preferably 280 to 370°C, with holding at maximum temperature for 10 minutes to 15 hours, preferably 20 minutes to 3 hours. According to one variant, the invention also relates to a method for manufacturing a strip or sheet according to the present invention, comprising the successive steps of: - casting of a core alloy plate; - homogenization of the plate at a temperature of 550 to 630°C, preferably 580 to 630°C for 1 to 24 hours; - possible plating 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: - preheating to a temperature of 450 to 550°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 homogenized and possibly plated plate, at a temperature of 420 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 - annealed at a temperature of 240 to 450°C, preferably 240 to 400°C, preferably 280 to 370°C, with holding at maximum temperature for 10 minutes to 15 hours, preferably 20 minutes to 3 hours. The said covering alloy of the processes according to the present invention may in particular be a brazing alloy, or a sacrificial anode, or two brazing alloys, or two sacrificial anodes, or a brazing alloy and a sacrificial anode. Preferably, there is no intermediate annealing in the processes according to the present invention. When intended for parts with significant shaping, the strip or Sheet metal can be used in the annealed condition (condition O) by undergoing final annealing at a temperature of 300 to 450°C, in a continuous or batch furnace. In a batch furnace, annealing is preferably at 320 to 400°C. This annealing improves formability. In other cases, it can be used in the work-hardened or restored condition, which leads to better mechanical strength, for example, condition H14 or H24 (according to standard NF EN 515), the latter condition being obtained by a restoration anneal at 250 to 300°C. Before installing any plating materials, the core alloy plate can be homogenized at a temperature between 550 and 630°C, preferably between 580 and 630°C. This homogenization is beneficial to the ductility of the rolled strip or sheet and is recommended when the strip or sheet is used in the 0 state. It promotes the coalescence of the Mn dispersoids. Use The invention also relates to a heat exchanger made at least partly from a strip or sheet according to the present invention. The invention also relates to the use of a strip or sheet according to the present invention, for the manufacture of a heat exchanger, said strip or sheet having improved mechanical resistance without degradation of corrosion resistance or brazing. The strips or sheets according to the present invention can be used in the manufacture of brazed heat exchangers, particularly for automobiles, such as engine cooling radiators, evaporators, heater cores and charge air coolers, manifolds, battery coolers for electric vehicles, as well as in air conditioning systems. EXAMPLES Example 1 Various core ingots were cast in semi-continuous vertical casting with aluminium alloys having the compositions given in Table 2 below, in mass percentages: [Tables 2] Alloys si Fe Cu Mn Ti |Reference 0.18 lo,16 |o64 |134 |0.08 |Core-Comparative-1 0.19 |o,18 [095 |138 |0.08 |Ame-Comparatit-2|0.19 [0.18 [097 |L67 [008 Ame-Innov-1 jo 49 l0.17 |o.66 |1.58 |o.09 Ame-Innov-2 0.49 0.17 [094 [157 [010 The core ingots were then bonded with a brazing plating of AA4045 alloy (9.71% Si; 0.2% Fe; <0.05% Cu; <0.05% Mg; <0.05% Mn; <0.05% Sr; 0.02% Ti), which represented 7.5% of the total assembly thickness. The assembly was preheated for 12 hours at 500°C, hot-rolled, and then cold-rolled from 60 mm at the hot-rolling inlet to 0.4 mm at the cold-roll outlet. A final annealing for 1 hour at 320°C achieved a H24 metallurgical state. Brazing simulations were then carried out on 21 µm x 30 cm samples to reproduce the conditions of controlled atmosphere brazing (CAB) with less than 50 ppm of O₂, with heating at 600°C for 2 minutes. Tensile strength measurements at different temperatures (20°C, 110°C and 130°C) and corrosion resistance according to the SWAAT test on the plated face were carried out on the brazed samples. Tensile strength measurements were carried out according to ISO 6892-1. Corrosion resistance was determined using the following protocol: - prepare for each configuration a sample of dimensions 126 mm (L direction) x 90 mm (TL direction), previously degreased with white absorbent paper soaked in acetone; - protect the untested face and the four edges over a width of approximately 0.5 mm with a transparent vinyl adhesive (for example, type 3M vinyl 764); - clean the area to be tested with absorbent paper soaked in acetone; - place the samples thus prepared on a rack with an inclination of approximately 60° relative to the horizontal; - perform for each sample a cyclic SWAAT (Sca Water Acidified Acetic Test) according to the ASTM G85 A3 standard, including in particular an alternation of 30 min fog phases and 1h30 wet phases at a temperature of 49°C. The number of perforations was recorded daily for each sample throughout the test period, either 13 or 18 days. The perforations were visible on the back of each sample as they formed blisters in the adhesive applied to the untested side, as illustrated in [Fig. 1]. In [Fig. 1], reference 6 corresponds to the sample; reference 7 to the adhesive; reference 8 to a perforation; and reference 9 to a blister formed by a perforation. The results are given in Table 3 below. [Tables 3] |Antiages Rm after brazing Number of 400 µm holes after (MPa) SWAAT test °C nec |ia0c |Reference 150 150 150 |14 4 |Ame-Comparat-1[160 174 166 100 [9 |Soul-Comparatit-2|169 |178 | 156 |74 [41 P 1 |Ame-Innov-1 [166 [179 [71 pe 6 Ame-Innov-2 | |161 167 168 7 6 In addition to the information given in Table 3 above, the corrosion morphology was determined for each alloy, based on microscopic observations after the SWAAT test: - Comparison-1: deep punctures; - Comparison-2: deep punctures; - Innovl: better than the reference, because the corrosion depth was less than that of the reference: - Innov2: better than the reference, because the corrosion depth was less than that of the reference. Based on Table 3 above, the following conclusions can be drawn: - the present invention makes it possible to obtain better mechanical resistances than the reference alloy; - the present invention makes it possible to obtain at least the same level of performance in terms of corrosion resistance and susceptibility to perforation after a SWAAT test as the reference alloy. Example 2 Various core ingots were cast in semi-continuous vertical casting with aluminium alloys having the compositions given in Table 4 below, in mass percentages: [Tables 4] |Altiages which [Fe game [Mn jar | Ame-Comparative-3 02 “Jo.13 \0.64 |L33 0.08 |Soul-Comparative-4 0.19 -jo.12 062 |L28 [0.08 |Soul-Comparative-5|0.18 fo.12 0.93 |1.52 |o.08 Ame-Innov-3 |045 lo.15 |o.93 |1.52 |o.08 The core ingots were homogenized at a temperature of 550 to 630°C for 1 to 24 hours. The core ingots were then bonded with a brazing alloy plating of type AA4045 on one side, representing 5% of the total assembly thickness, and with a sacrificial anode of type AA7072 alloy on the other side, representing 10% of the total assembly thickness. The compositions of the brazing alloys and sacrificial anodes are given in Table 5 below, as mass percentages. [Tables 5] Alloys si Fe cu Mn Ti Zn Brazing-1 9.83 (013 jpo1 Joo: [ooz |o.003 Brazing-2 9.73 [0.19 [por |o02 |oo3 |0.003 | Brazing-3 973 0.19 [oo1 [002 Joos [0003 | | Brazing-4 973 jo19 joo1 jooz |oo3 |o.00 | Anode-1 0.14 |0.32 |0.001 |0.003 [0.03 |0.97 |Anode-2 0.15 [0.33 [0.001 |o003 [003 0.98 Anode-3 0.15 |0.33 [0.001 |0.003 |o03 [0.08 Anode-4 0.15 |o33 |p.001 0.003 [003 |0.98 The brazing alloy and sacrificial anode #1 were plated onto the core (Comparative Core-3, Assembly-1). The brazing alloy and sacrificial anode #2 were The brazing alloy and sacrificial anode #3 were plated onto the core of Comparative Core #4 (Assembly-2). The brazing alloy and sacrificial anode #3 were plated onto the core of Comparative Core #5 (Assembly-3). The brazing alloy and sacrificial anode #4 were plated onto the core of Innovative Core #3 (Assembly-4). The assemblies were preheated to a temperature of 450 to 550°C, held at maximum temperature for less than 30 hours, hot rolled to a thickness of 3 mm, then cold rolled to a final total thickness of 1 mm for the sandwich. A final annealing for 1 hour at 350°C resulted in a metallurgical state O. Brazing simulations were then carried out on 21 µm x 30 cm samples to reproduce the conditions of controlled atmosphere brazing (CAB) with less than 50 ppm of O₂, with heating at 600°C for 2 minutes. Tensile strength (UTS), yield strength (TYS), and elongation (E%) measurements were performed on the samples before and after brazing. Corrosion resistance measurements using the SWAAT test were performed on the brazed samples on the face plated with AA4045 brazing alloy. The tensile strength (UTS), yield strength (TYS) and elongation (E%) measurements were carried out according to ISO 6892-1. Corrosion resistance was determined using the following protocol: - prepare for each configuration a sample of dimensions 126 mm (L direction) x 90 mm (TL direction), previously degreased with white absorbent paper soaked in acetone; - protect the untested side and the four edges over a width of approximately 0.5 cm with a transparent vinyl adhesive (for example, type 3M vinyl 764); - clean the area to be tested with absorbent paper soaked in acetone; - place the samples thus prepared on a rack with an inclination of approximately 60° relative to the horizontal; - perform a cyclic SWAAT (Sea Water Acidified Acetic Test) for each sample according to the ASTM G85 A3 standard, including alternating 30-minute fog phases and 1.5-hour wet phases at a temperature of 49°C, Each sample is then observed under a microscope on a polished section in the direction L-TC (rolling direction — thickness) with standard polishing. The results of the mechanical performance measurements before and after brazing are given in Table 6 below. [Tables 6] pe Before brazing After brazing a TYS UTS E% TYS UTS 1 5 is L…7 47 136 2 50 135 28.6 46 135 3 57 150 204 52 Je 4 53 145 25.5 51 qiso The results of the SWAAT test after 28 days are as follows: assemblies ! to 3 have perforated, while assembly 4 has not perforated. According to Table 6 above and the results of the SWAAT test, it is possible to conclude that the present invention makes it possible to obtain the best compromise between satisfactory mechanical resistances, in particular Rm (=UTS) greater than 140 MPa, and improved corrosion resistance, for example an absence of perforation due to corrosion for a longer period.

Claims

Demands

1. Strip or sheet metal, intended for the manufacture of brazed heat exchangers, having a core layer, possibly a cover layer on one or two faces of the core layer and possibly an inner layer tercalary on one or two faces of the core layer placed between the core layer and the possible cover layer, the core layer being made of aluminium alloy with the following composition (% by mass): - If: more than 0.25%, preferably more than 0.30%, preferably more 0.35%, preferably more than 0.40%; and less than 1.00%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.55%; - Fe: less than 0.25%, preferably less than 0.20%; and of preference more than 0.10%; - Cu: more than 0.60%, preferably more than 0.70%, preferably more 0.80%, preferably more than 0.85%; and less than 1.10%, preference less than 1.00%, preference less than 0.95%; - Mn: more than 1.40%, preferably more than 1.50%; and less than 2.00 %, preferably less than 1.80%, preferably less than 1.65%; - Ti: less than 0.20%, preferably less than 0.15%, preferably less than 0.10%; and more than 0.05%; - Mg: according to a first variant less than 0.05%, preferably less than 0.01%, preferably less than 0.001%; ​​or according to a second variant less than 0.30%; - Zr: less than 0.01%, preferably less than 0.005%; - Cr: less than 0.01%, preferably less than 0.005%; - Zn: less than 0.20%, preferably less than 0.10%, preferably less than 0.05%, preferably less than 0.01%; - impurities: less than 0.05% each and less than 0.15% in total; - remains aluminum.

2. Strip or sheet according to claim 1, characterized in that it is plated, on one or two faces of the core layer and / or on one face free of any interlayer, with a covering alloy which is a brazing aluminum alloy, preferably an alloy of the 4xxx series comprising from 4.00 to 13.00% by mass of Si and less than 1.00% by mass of Fe.

3. Strip or sheet according to claim 2, characterized in that the alloy 4xxx series brazing aluminum comprises (% by mass): - 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 of 0.50 to 2.50%, preferably of 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 and / or Sn; - other elements: less than 0.05% each and less than 0.15% at total ; - remains aluminum.

4. Strip or sheet according to claim 1, characterized in that it is plated, on one or two faces of the core layer, with an alloy of sacrificial anode type cover, which is preferably made of an alloy of series 7xxx, preferably having the following composition, in pour- 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 0.70 to 5.00%, preferably from 0.70 to less than 1.30%, of preferably 0.70 to less than 1.00% Zn; - less than 0.15% Ti; - other elements less than 0.05% each and less than 0.15% in total; - remains aluminum.

5. Strip or sheet according to claim 1, characterized in that it is plated, on one or two faces of the core layer, with an alloy of sacrificial anode type cover, which is preferably an alloy of the 3xxx series, preferably having the following composition, in pour- 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 0.50 to 1.60%, preferably from 0.90 to 1.20% of Zn; - less than 0.15% Ti: - other elements less than 0.05% each and less than 0.15% total; - remains aluminum.

6. Strip or sheet according to claim 2 or 3, characterized in that it plated, on one or two faces of the core layer, with an alloy of aluminium interlayer, preferably from the 1xxx or 3xxx series, placed between the core and the brazing alloy, preferably comprising (in mass percentages): - If: less than 0.50%, more preferably less than 0.20%; - Fe: less than 0.70%, more preferably less than 0.30%, still more preferably less than 0.20%; - Mn: from 0.30 to 1.40%, more preferably from 0.50 to 0.90%, plus preferably from 0.60 to 0.80%; or according to a variant from 1.00 to 1.30%; - Cu: less than 0.30%, preferably less than 0.10%, even more preferably- preferentially less than 0.05%; - possibly Mg, Zn and / or In; - other elements < 0.05% each and < 0.15% in total; - remains aluminum.

7. Strip or sheet according to claim 6, characterized in that the alloy The interlayer aluminum comprises (% by mass): - If < 0.15%; - Fe < 0.20%; - Cu < 0.10%; - Mnde 0.60 to 0.80%; - Mg < 0.02% according to a first variant or Mg < 0.50%, of preference < 0.25% according to a second variant; - other elements < 0.05% each and < 0.15% in total, - remains aluminum.

8. Method for manufacturing a strip or sheet according to any one of the Previous claims, including the successive steps of: - casting of a core alloy plate; - possible plating with a covering aluminum alloy on one or two faces of the core layer and possibly an alloy interlayer aluminum on one or two faces of the core layer; - preheating to a temperature of 450 to 550°C, preferably with a maintaining 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; - hot rolling of the non-homogenized plate and possibly plated at a temperature of 420 to 530°C up to a thickness of 2 to 6mm, - cold rolling to the desired thickness, the thickness of the strip or sheet after cold rolling, preferably from 0.15 to 3 mm - annealed at a temperature of 240 to 450°C, preferably from 240 to 400°C, preferably 280 to 370°C, with temperature maintenance maximum for 10 minutes to 15 hours, preferably for 20 minutes to 3 hours.

9. Method for manufacturing a strip or sheet according to any one of the claims | to 7, including the successive steps of: - casting of a core alloy plate, - homogenization of the plate from 550 to 630°C, preferably from 580 to 630°C for 1 to 24 hours; - possible plating with a covering aluminum alloy on one or two faces of the core layer and possibly an alloy interlayer aluminum on one or two faces of the core layer; - preheating to a temperature of 450 to 550°C, preferably with a maintaining 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; - hot rolling of the homogenized plate and possibly plated at a temperature of 420 to 530°C up to a thickness of 2 to 6mm: - cold rolling to the desired thickness, the thickness of the strip or sheet after cold rolling, preferably from 0.15 to 3 mm - annealed at a temperature of 240 to 450°C, preferably from 240 to 400°C, preferably 280 to 370°C, with temperature maintenance maximum for 10 minutes to 15 hours, preferably for 20 minutes to 3 hours.

10. Heat exchanger made at least in part from a strip or sheet metal according to any one of claims 1 to 7.

11. | Use of a strip or sheet according to any one of the claims instructions 1 to 7, for the manufacture of a heat exchanger, said strip or sheet metal exhibiting improved mechanical resistance without de- gradation of corrosion resistance or brazingability.