Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K1/00—Soldering, e.g. brazing, or unsoldering
  • B23K1/0008—Soldering, e.g. brazing, or unsoldering specially adapted for particular articles or work
  • B23K1/0012—Brazing heat exchangers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
  • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
  • B23K35/0233—Sheets, foils
  • B23K35/0238—Sheets, foils layered
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
  • B23K35/286—Al as the principal constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
  • B32B15/016—Layered products comprising a layer of metal all layers being exclusively metallic all layers being formed of aluminium or aluminium alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/04—Tubular or hollow articles
  • B23K2101/14—Heat exchangers

Definitions

• the present disclosure falls within the field of thin strips or sheets (of thickness generally comprised from 0.05 to 3.5 mm, preferably from 0.15 to 2.5 mm) used for alloy heat exchangers aluminum, and preferably with a core alloy of aluminum-manganese alloy (3xxx series according to the nomenclature of the Aluminum Association), plated on one or both sides with a layer of brazing alloy, preferably with 'aluminum-silicon alloy (4xxx series according to the nomenclature of the Aluminum Association), obtained by sawing and possibly an intermediate alloy, generally placed between the core and the brazing alloy.
• These strips or sheets are intended in particular for the manufacture of elements, such as tubes, plates and collectors, used in heat exchangers assembled by brazing.
• brazing aluminum alloys are described for example in the article by JC Kucza, A. Uhry and JC Goussain "Strong brazing of aluminum and its alloys", published in Soudage et Techniques Connexes, Nov.- Dec. 1991, pp. 18-29.
• the strips or sheets according to the invention may especially be used in brazing techniques in ovens in a controlled atmosphere CAB (controlled atmosphere brazing) with a flow of for example NOCOLOK ® kind or without flow, or else in brazing furnaces empty.
• CAB controlled atmosphere brazing
• the properties required for the strips or sheets of aluminum alloy used for the manufacture of brazed exchangers are in particular sufficient formability for easy shaping of the tubes, plates and collectors, before brazing, good suitability for brazing , high mechanical strength after brazing, and good resistance to corrosion after brazing.
• the alloys chosen are easy to cast and roll and / or co-roll and that the cost of manufacturing the strips or sheets is compatible with the requirements of the automotive industry.
• the co-rolling step of multi-layer strips or sheets it is important to have good cohesion between the different layers of core alloy, brazing alloy and possibly intermediate alloy without there being any blistering formations visible to the naked eye on the surface of strips or sheets.
• the present disclosure improves the situation.
• a method of manufacturing a strip or multilayer sheet comprising a layer of core aluminum alloy plated, on one or both main faces, with an alloy layer of brazing aluminum, characterized in that it comprises the successive steps of: a. casting of a brazing aluminum alloy in the form of a casting plate, preferably having a thickness of 400 to 700 mm, more preferably of 500 to 650 mm; preferably a width of 1500 to 2000 mm, preferably 1600 to 1850 mm; preferably a length of 2500 to 6000 mm, preferably 3000 to 4500 mm; b. optionally, stress relieving of the casting plate by heat treatment; vs.
• the first hot rolling pass inducing a reduction in thickness of the multilayer assembly greater than or equal to 0.5% of the thickness of the multilayer assembly before said hot rolling pass; the thickness of the multilayer strip or sheet obtained after all the hot rolling passes preferably being from 2 to 5.5 mm; g. optionally, cold rolling of the strip or multilayer sheet. to the desired thickness, the thickness of the strip or sheet after cold rolling preferably being 0.15 to 3 mm and h. optionally annealing, preferably at a temperature of 230 to 450 ° C., preferably with a maintenance at the maximum temperature for 1 minute to 15 hours, preferably for 1 minute to 5 hours.
• the strip or sheet with final thickness before brazing having at least one of the brazing layers which is obtained by sawing and which has a size of the silicon particles with a surface area greater than or equal to 0.011 ⁇ m 2 (measured in the L-TC plane ) such that the average equivalent diameter of these particles is less than 1.6 ⁇ m, preferably less than 1.5 ⁇ m, preferably less than 1.4 ⁇ m.
• a heat exchanger produced at least in part from a strip or sheet obtained according to the method of the invention.
• a strip or sheet according to the present invention for the manufacture of a heat exchanger, said strip or sheet having improved corrosion resistance without degradation of the heat exchanger.
• the brazing alloy layer or layers represent from 4 to 15%, preferably from 4 to 12% in thickness of the total thickness of the multilayer assembly before any rolling step.
• the brazing aluminum alloy casting plate is subjected, prior to the sawing step, to stress relieving, preferably thermal, at a temperature below 400 ° C, preferably below 380 ° C, more preferably less than 355 ° C and even more preferably less than or equal to 350 ° C, advantageously for a period of less than 24 hours, preferably less than 10 hours and more preferably still less than 3 hours.
• the casting plate made of brazing aluminum alloy is not subjected, prior to the sawing step, to stress relieving, for example thermal.
• the multilayer strip or sheet further comprises at least one interlayer aluminum alloy layer placed between the core aluminum alloy layer and a brazing layer of an aluminum alloy.
• the core alloy layer is subjected to a homogenization step prior to the plating step, preferably at a temperature of 560 to 630 ° C, preferably for 10 minutes to 18 hours.
• the core alloy layer is not subjected to a homogenization step prior to the plating step.
• the brazing alloy layer is made of 4xxx alloy, preferably of an alloy chosen from the alloys AA4045, AA4343, AA4004 and AA4104, more preferably in an alloy (for example 4xxx, AA4045, AA4343, AA4004 and / or AA4104) comprising an amount of Zn less than 0.05% by mass.
• the brazing alloy layer has, after sawing and before rolling, a surface roughness as defined in standard NF EN ISO 4287 of December 1998:
• - Rt less than 400 ⁇ m, preferably less than 350 ⁇ m, more preferably less than 280 ⁇ m, and preferably greater than 15 ⁇ m, preferably greater than 35 ⁇ m, measured with a Gaussian filter of 8 mm wavelength in the direction perpendicular to the saw cuts.
• the core alloy layer comprises, in percentages by weight:
• - Si at most 0.8%, preferably at most 0.6%, more preferably at most 0.5%; and even more preferably at most 0.25%;
• - Cu from 0.20 to 1.2%, preferably from 0.25 to 1.1%, more preferably from 0.3 to 1.0%, even more preferably from 0.5 to 0.8%, even more preferably from 0.55 to 0.75%;
• - Mn from 0.8 to 2.2%, preferably from 0.9 to 2.1%, more preferably from 1.0 to 2.0%, even more preferably from 1.0 to 1.5%, even more preferably from 1.25 to 1.45%;
• - Mg at most 0.6%, preferably at most 0.35%, more preferably at most 0.20%, even more preferably less than 0.05%;
• - Zn at most 0.30%, preferably at most 0.25%, more preferably at most 0.20%, and even more preferably less than 0.05%;
• - Ti at most 0.30%, preferably at most 0.25%, more preferably at most 0.20%, even more preferably at most 0.14%, and even more preferably at most 0.12%; preferably at least 0.05%;
• FIG. 1 is a photo showing the sample used for the example soldering tests.
• FIG. 2 is a diagram describing the perforation analysis during the corrosion resistance test of the examples.
• controlled atmosphere mean an atmosphere having a majority gas, for example nitrogen or argon, and having a limited amount of O 2, preferably comprising less than 150 ppm, more preferably less than 100 ppm, even more preferably less than 50 ppm, and even more preferably less than 20 ppm of oxygen.
• the present invention relates to a method of manufacturing a strip or multilayer sheet.
• the strip or multilayer sheet comprises a layer of core aluminum alloy plated, on one or both main faces, with a layer of brazing aluminum alloy, preferably of type 4xxx and comprises optionally one or two aluminum alloy layers interposed between the core aluminum alloy layer and the brazing aluminum alloy layer.
• the strip or multilayer sheet is obtained by rolling, hot and optionally cold, of the multilayer assembly.
• the total thickness of the strip or sheet is advantageously from 0.05 to 3.5 mm, preferably from 0.15 to 2.5 mm, more preferably from 0.18 to 1 mm.
• 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.
• the configuration with two layers comprises a plated core with a brazing layer on one side only.
• the configuration with three layers includes:
• a core layer plated on a first face with a brazing layer and on the other face with a protective layer to improve corrosion resistance for example made of lxxx, 3xxx or 7xxx type alloy.
• the configuration with four layers includes:
• the protective layer can be obtained by sawing.
• the configuration with five layers comprises a core layer plated on both sides with an interlayer and a brazing layer.
• the core aluminum alloy layer is made of a 3xxx type alloy.
• the core layer has been obtained by sawing.
• the core aluminum alloy layer comprises, in percentage by weight,:
• - Si at most 0.8%, preferably at most 0.6%, more preferably at most 0.5%; and even more preferably at most 0.25%;
• - Cu from 0.20 to 1.2%, preferably from 0.25 to 1.1%, more preferably from 0.3 to 1.0%, even more preferably from 0.5 to 0.8%, even more preferably from 0.55 to 0.75%;
• - Mn from 0.8 to 2.2%, preferably from 0.9 to 2.1%, more preferably from 1.0 to 2.0%, even more preferably from 1.0 to 1.5%, even more preferably from 1.25 to 1.45%;
• - Mg at most 0.6%, preferably at most 0.35%, more preferably at most 0.20%, even more preferably less than 0.05%;
• - Zn at most 0.30%, preferably at most 0.25%, more preferably at most 0.20%, and even more preferably less than 0.05%;
• - Ti at most 0.30%, preferably at most 0.25%, more preferably at most 0.20%, even more preferably at most 0.14%, and even more preferably at most 0.12%; preferably at least 0.05%;
• composition limits of the base alloy used as the core can be justified as follows.
• a limited iron content is favorable to corrosion resistance and to formability, but it is not necessary to go down to very low contents (for example ⁇ 0.10%) which would lead to high cost prices.
• Copper is a hardening element which contributes to the mechanical resistance, but above 1.2%, coarse intermetallic compounds can be formed on casting which adversely affect the homogeneity of the metal and constitute sites of initiation of corrosion, or cracks in the tray during casting.
• Manganese contributes to mechanical strength.
• a limited addition of zinc can have a beneficial effect on corrosion resistance, by modifying the electrochemical potentials, especially for alloys with the highest copper content. However, it must remain below 0.3% to avoid too high a susceptibility to generalized corrosion.
• the brazing alloy layer or layers represent from 4 to 15%, preferably from 4 to 12% in thickness of the total thickness of the multilayer assembly before rolling.
• the brazing aluminum layer is made from an alloy of the 4xxx family, preferably from an alloy chosen from the alloys AA4045, AA4343, AA4004 and AA4104, more preferably from an alloy (for example 4xxx, AA4045, AA4343, AA4004 and / or AA4104) comprising an amount of Zn less than 0.05% by mass.
• the strip or multilayer sheet further comprises at least one intermediate aluminum alloy layer placed between the core aluminum alloy layer and a brazing aluminum alloy layer. .
• the interlayer has been obtained by sawing.
• the intermediate aluminum alloy of the strip or sheet according to the present invention is of the 3xxx or lxxx type, for example AA3003, AA3207 or AA1050, more preferably of the 3xxx type, for example AA3003 or AA3207.
• the intermediate aluminum alloy of the strip or sheet according to the present invention can comprise (% by mass):
• - AA3003 less than 0.6% Si; less than 0.7% Fe; from 0.05 to 0.20% Cu; from 1.0 to 1.5% Mn; less than 0.10% Zn, impurities less than 0.05% each and less than 0.15% in total; remains Al; or
• - AA3207 less than 0.30% Si; less than 0.45% Fe; less than 0.10% Cu; from 0.40 to 0.8% Mn; less than 0.10% Mg; less than 0.10% Zn, impurities less than 0.05% each and less than 0.15% in total; remains Al; or
• - AA1050 less than 0.25% Si; less than 0.40% Fe; less than 0.05% Cu; less than 0.05% Mn; less than 0.05% Mg; less than 0.05% Zn, less than 0.03% Ti; less than 0.05% V; impurities less than 0.03% each; at least 99.50% Al.
• the intermediate aluminum alloy of the strip or sheet according to the present invention comprises (% by mass): Si ⁇ 0.25%, preferably ⁇ 0.18%; Fe ⁇ 0.2%; Cu ⁇ 0.1%; Mn from 0.6 to 0.8%; Mg ⁇ 0.02%; other elements ⁇ 0.05% each and ⁇ 0.15% in total, remainder aluminum.
• the method according to the present invention comprises the successive steps of: a. casting of a brazing alloy in the form of a casting plate, preferably having a thickness of 400 to 700 mm, more preferably of 500 to 650 mm; preferably a width of 1500 to 2000 mm, preferably 1600 to 1850 mm; preferably a length of 2500 to 6000 mm, preferably 3000 to 4500 mm; b. optionally, stress relieving of the casting plate by heat treatment; vs. sawing of the casting plate to obtain layers of brazing alloy sawn in a plane parallel to the plane of at least one of the main faces of said casting plate; d.
• the first hot rolling pass inducing a reduction in thickness of the multilayer assembly greater than or equal to 0.5% of the thickness of the assembly multilayer before said hot rolling pass; the thickness of the multilayer strip or sheet after all the hot rolling passes preferably being 2 to 5.5 mm; g. optionally, cold rolling of the strip or multilayer sheet. to the desired thickness, the thickness of the strip or sheet after cold rolling preferably being 0.15 to 3 mm and h. optionally annealing, preferably at a temperature of 230 to 450 ° C., preferably with a maintenance at the maximum temperature for 1 minutes to 15 hours, preferably for 1 minutes to 5 hours.
• the core alloy is generally cast in the form of a casting plate. This plateau is generally scalped on at least the two main faces.
• the brazing aluminum alloy layer is cast and then sawn in a plane parallel to the plane of at least one of the main faces of said brazing alloy layer.
• the sawing step is carried out on one, preferably the two main faces of the brazing aluminum alloy layer. Reducing the thickness of the brazing layer by sawing rather than rolling has many advantages. In particular, the manufacturing process is simplified and has a lower manufacturing cost. However, if such a sawing step is known from the prior art, it is in no way specified in the prior art how to avoid the formation of visible blisters on the surface of the final strip or sheet.
• this sawing step is necessarily followed by a surface preparation step, in particular a polishing step in order to reduce the surface roughness of the layer. and allow good cohesion of the layers of the strip or multilayer sheet during the co-rolling step. Cleaning after sawing does not constitute a surface preparation step and is therefore not excluded from the present invention.
• the method of the present invention makes it possible to dispense with such a step of preparing the surface of the sawn brazing layer and in particular a polishing step.
• the brazing alloy layer may have, according to a roughness measurement after sawing and before rolling, a maximum difference between peaks and valleys over a length of 150 mm in the direction perpendicular to the saw cuts of less than 0.55 mm and preferably less than 0.3 mm.
• the brazing alloy layer may have, after sawing and before rolling, a surface roughness as defined in standard NF EN ISO 4287 of December 1998:
• the roughness profile after sawing and before rolling of the brazing alloy layers was measured with a perthometer, over a distance of 150 mm, in the direction perpendicular to the saw cuts. The start and end of the profile have been removed (12.5 mm on each side). The profile was straightened with a second degree polynomial. The maximum-minimum difference between peaks and valleys was deduced from this.
• the values of Ra and Rt as defined in standard NF EN ISO 4287 of December 1998 were then calculated with two Gaussian filters of respective wavelength 0.8 mm and 8 mm over a distance of 125 mm.
• the roughness Ra (in pm) is the arithmetic mean of the profile.
• the roughness Rt (in pm) is the total height of the roughness profile.
• brazing alloy layer is then plated on the core aluminum alloy layer to obtain a multilayer assembly.
• at least one interlayer aluminum alloy layer is placed between the brazing alloy layer and the core alloy layer.
• the brazing aluminum alloy casting plate is subjected, prior to the sawing step, to stress relieving, preferably thermal, at a temperature below 400 ° C, preferably less than 380 ° C, more preferably less than 355 ° C and even more preferably less than or equal to 350 ° C, advantageously for a period of less than 24 hours, preferably less than 10 hours and more preferably still less than 3 hours.
• the casting plate, prior to the sawing step is on the contrary not subjected to stress relieving.
• the core alloy layer is subjected to a homogenization step prior to the plating step, preferably at a temperature of 560 to 630 ° C, preferably for 10 minutes at 18 hours.
• the casting plate made of brazing aluminum alloy is preferably not subjected to a homogenization step prior to the sawing step.
• the brazing alloy layer is preferably not subjected to a homogenization step prior to the plating step.
• the multilayer assembly comprising a sawn brazing alloy layer is subjected to a specific hot rolling step making it possible to dispense with the step of surface preparation of the sawn brazing alloy layer.
• the first hot rolling pass of the multilayer assembly induces a reduction in thickness of the multilayer assembly greater than or equal to 0.5% of the thickness of the multilayer assembly before said hot rolling pass.
• such a hot rolling step allows good cohesion between the different layers of core alloy, brazing alloy and possibly intermediate alloy without there being any visible blistering. on the surface of the strip or sheet, even when the brazing alloy layer (s) have not undergone surface preparation such as polishing prior to plating.
• the total thickness of the strip or sheet after all the hot rolling passes is preferably 2 to 5.5 mm.
• the strip or multilayer sheet is subjected to a cold rolling step following that of hot rolling, in order to obtain a strip or sheet of the desired final thickness.
• the thickness of the strip or sheet after cold rolling is preferably 0.15 to 3 mm.
• the strip or multilayer sheet can then be subjected to an annealing step, preferably at a temperature of 230 to 450 ° C.
• the maximum annealing temperature is maintained for 1 minute to 15 hours, preferably for 1 minute to 5 hours.
• the strip or sheet according to the invention can be used for the manufacture of different parts of a heat exchanger, for example tubes, plates, collectors, etc. More particularly, the strip or sheet obtained according to the present invention is intended for the manufacture of brazed heat exchangers.
• the strip or sheet obtained according to the method of the present invention advantageously comprises at least one brazing layer obtained by sawing and of which the average equivalent diameter of the silicon particles with a surface area greater than or equal to 0.011 ⁇ m 2 (measured in the plane L-TC) is less than 1.6 ⁇ m, preferably less than 1.5 ⁇ m, preferably less than 1.4 ⁇ m.
• the average equivalent diameter of the silicon particles is obtained by image analysis from photographs taken with an optical microscope at magnification x50 in the plane [(rolling direction) x (short transverse direction)]. It should be noted that the short transverse direction corresponds to the thickness of the strip or sheet.
• the minimum particle surface area analyzed is 0.011 ⁇ m 2 , measured in the L-TC plane. From the total area of each particle, an equivalent diameter is defined, which corresponds to that of a circular particle with the same area. Then an average is carried out with all the determined equivalent diameters.
• the present inventors have in particular demonstrated a non-degradation, or even an improvement in the corrosion resistance of the strips or sheets comprising such brazing layers.
• Another subject of the invention is a heat exchanger produced at least in part from a strip or sheet according to the present invention.
• a subject of the invention is also 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 corrosion resistance without degradation of the resistance. mechanical or solderability with respect to a strip or sheet having an identical configuration but comprising at least one brazing layer obtained by rolling.
• the strips or sheets according to the present invention can be used in the manufacture of radiators, in particular of automobiles, such as engine cooling radiators, oil radiators, heating radiators and air coolers. supercharging, as well as in air conditioning systems (especially evaporators and condensers), and battery cooling in the case of electric vehicles.
• Multilayer assemblies were formed by assembling a layer of core alloy (see the compositions Alloy A and Alloy C in Table 1 above, in percentages by mass) of thickness 480-540 mm and a layer AA4045 brazing alloy (see compositions 4045-1 and 4045-2 in Table 1 above, in percentages by weight).
• the brazing alloy was AA4045-1 for tests 1 to 5 and AA4045-2 for test 6.
• the core alloy was Alloy A for tests 1 to 5 and Alloy C for test 6
• the thickness of the multilayer assemblies before rolling is detailed in Table 2 below.
• the core alloy layer was scalped prior to the assembly step. None of the layers of the assembly have been homogenized.
• the assembly was preheated to a temperature of 480 to 520 ° C with a total time of 13 to 27 hours (see Table 2 below) and a temperature rise time of less than 15 hours, then hot rolled to 'to 2-3 mm of total thickness.
• the reduction in thickness of the first hot rolling pass is detailed in Table 2 below.
• Hot-rolled assemblies made it possible to obtain multilayer strips which were then subjected to cold rolling to a total thickness of 0.24 mm.
• the rolled strips were finally subjected to an annealing step at a temperature of 250-320 ° C for a holding time of less than 12 hours, the final strip was in a H24 metallurgical state.
• the roughness profile after sawing and before rolling of the AA4045 brazing alloy layers was measured with a perthometer, over a distance of 150 mm, in the direction perpendicular to the saw cuts. The start and end of the profile have been removed (12.5 mm on each side). The profile was straightened with a second degree polynomial. The maximum-minimum difference between peaks and valleys was deduced from this.
• the values of Ra and Rt as defined in standard NF EN ISO 4287 of December 1998 were then calculated with two Gaussian filters of respective wavelengths 0.8 mm and 8 mm over a distance of 125 mm.
• the roughness Ra (in pm) is the arithmetic mean of the profile.
• the roughness Rt (in pm) is the total height of the roughness profile.
• the maximum-minimum difference, Ra and Rt are reported in Table 2 below.
• a blister corresponds to a blistering of the metal due to an internal detachment at the interface between the brazing layer and the layer below said brazing layer, and is of a dimension greater than 1 mm in the direction of rolling.
• Table 2 The result of this evaluation is presented in Table 2 below. [0066] [Table 2]
• the average equivalent diameter of silicon particles with a surface area greater than or equal to 0.011 ⁇ m 2 was 1.37 ⁇ m.
• the average equivalent diameter of silicon particles with a surface area greater than or equal to 0.011 ⁇ m 2 was 1.74 ⁇ m.
• Example 2 The brazing quality was analyzed using mini prototypes with different amounts of brazing flux.
• Strips comprising a layer of AA4045-1 brazing alloy representing 10% in thickness of the total thickness of the strip and a core layer of Alloy A (see Table 1 of Example 1) in the metallurgical state H24 and 0.24 mm thick; and
• Brazing is just as good for sawn brazing layers as it is for rolled brazing layers.
• the number of piercings was recorded each day for each sample throughout the duration of the test, ie 3 or 9 days.
• the piercings were visible on the back of each sample as they blistered in the adhesive applied to the untested face, as shown in Figure 1.
• the reference 6 corresponds to the sample;
• reference 7 corresponds to the adhesive;
• the reference 8 corresponds to a perforation;
• reference 9 corresponds to a blister formed by a perforation.
• Table 6 The results of the monitoring of the number of piercings are presented in Table 6 below.

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