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
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • 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
  • C22F1/047—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 magnesium as the next major constituent

Definitions

• the invention relates to the field of thin sheets of highly ductile aluminum alloy, in particular for producing decorative parts such as, for example, interior parts of motor vehicles.
• the invention relates more particularly to aluminum alloy sheets of the AA5xxx series, the composition and transformation process of which are particularly suited to this type of application and which have excellent ductility.
• Aluminum alloys are commonly used in the manufacture of decorative parts, in particular for the automotive industry, but also in the household appliances or medical equipment industries, in competition with wood, steel and plastics.
• interior finishing elements are produced, for example for the central console, such as the dashboard, the trim of the gear box, the door handles, the interior decorative strips, the body belts and exterior finishing elements such as, in particular, window surrounds, body or door side moldings, tailgate trim strips, radiator grille trim and bumper strips.
• These products can undergo a surface treatment such as in particular anodizing, varnishing and/or lacquering.
• AA5005 aluminum alloy rolled products with different heat treatment states are widely used in conductors, kitchen utensils, dashboards, architectural decorations, building materials, vehicle interior and exterior materials, etc. .
• International patent application WO2014203077 relates to a process for manufacturing an outer molding ring of a motor vehicle, in particular such as a window frame or a body molding, in aluminum alloy, by shaping and polishing a sheet or strip produced by continuous vertical casting of a AA5xxx series high-purity alloy sheet, sheet homogenization-reheating, hot rolling, cooling, cold rolling with intermediate annealing in a continuous flow furnace, or holding between solvus temperature and combustion temperature of the alloy typically for B s to 5 min., quenching in air or water, and optionally annealing at a temperature of 100°C to 200°C.
• This application also relates to a casting ring of a motor vehicle manufactured using such a process.
• Patent US4715901 describes aluminum alloys of the 1XXX and 5XXX type comprising 0.01 to 0.08% chromium or manganese, preferably both.
• Patent US3793089 describes an alloy comprising 0.05-0.20% silicon, 0.15-0.40% iron, 0.15-0.30% copper, 0.10-0.30% manganese, 0.6-1.0% magnesium, 0.04-0.12% chromium and the balance aluminum.
• the product when full color anodized, forms an anodic coating having a color ranging from gold to black within a commercially acceptable thickness range.
• Patent application CN107805746A describes a rolled product in aluminum alloy 5005H34, of composition in mass percentage: Si less than or equal to 0.2%, Fe less than or equal to 0.55%, Cu less than or equal to 0.15 %, Mn less than or equal to 0.2%, Mg 0.75 to 1.0%, Cr less than or equal to 0.1%, Zn less than or equal to 0.2% e Ti, 0.01 to 0, 05%.
• Patent application CN109266924A describes an aluminum substrate for an anodized aluminum curtain panel.
• the chemical components of the aluminum substrate include, by weight, 0.10-0.20% Si, 0.16-0.30% Fe, 0.65-0.10% Cu, 0.7-1 , 3% Mg, 0.01-0.02% Ti and the rest Al and impurities.
• Patent application CN109825746 A describes a high quality aluminum base material for some walls, having a surface roughness Ra 0.3-0.5 [mu] m, Ra 0.3- 0.5 [mu] m , Rz 1.4-2.4 [mu] m, a stable after being subjected to anodic oxidation.
• Patent application EP2862952 describes an aluminum alloy plate comprising peritectic elements and Mg.
• Patent US3164494 describes an aluminum alloy suitable for chemical and electrolytic polishing, consisting essentially of magnesium up to about 1.20%, copper, 0.01 to 0.08%, manganese at 0.03% max. , 0.01-0.12% iron and 0.01-08% silicon; in weight percent, the rest aluminum.
• the 5005 alloy is also used in the field of plated products, which is not the subject of the present invention.
• Patent application EP2924136 relates to an architectural facade product, with a central layer of AIMg-based aluminum alloy, in particular the AA5xxx series, and with at least one coating layer plated on one side of the central layer containing 0 0.03 to 0.06 wt% silicon (Si), 0.15 to 0.20 wt% iron (Fe), 008 to 0.12 wt% copper (Cu), 0.08 to 0 .12% by weight of manganese (Mn), 0.85 to 0.95% by weight of magnesium (Mg) and the rest of aluminum as well as unavoidable impurities due to production.
• Si silicon
• Fe iron
• Cu copper
• Mn manganese
• Mg magnesium
• international application WO2010144997A1 describes an aluminum architectural product in which a clad layer is applied to at least one side of a central layer, preferably, the central layer being made of an alloy chosen from alloys of the AA5XXX series with a magnesium content greater than 3% by weight, and the plated layer (or each plated layer) being of an alloy chosen from among the alloys AA5005, AA5205, AA5052, AA5252 and AA5005A.
• Alloys 5457, 5557 and 5657 are known for applications requiring a bright appearance e.g. from ASM Handbook, Volume 2B, Properties and Selection of Aluminum Alloys, ⁇ 2019
• Recycled aluminum is in fact a low emitter of greenhouse gases compared to aluminum obtained by electrolysis. To improve the carbon footprint of aluminum products, it is particularly useful to limit the use of aluminum obtained by electrolysis and to maximize the use of recycled aluminum.
• a first object of the invention is a thin aluminum alloy sheet of composition, in% by weight,
• a second object of the invention is a process for manufacturing a thin sheet according to the invention in which, successively,
• the plate thus scalped is preferably heated to a temperature between 480° C. and 500 "C, (d) the plate thus heated is hot rolled to obtain a sheet having a thickness of between 3 and 10 mm (e) the sheet thus obtained is cooled (f) the sheet thus cooled is cold rolled to obtain a thin sheet of final thickness
• the thin sheet thus obtained is degreased and/or pickled and/or polished
• the thin sheet is annealed at a temperature of 330°C to 420°C.
• Another object of the invention is the use of a thin sheet according to the invention to produce a part of complex shape shaped in the three dimensions of space in particular by stamping.
• FIGURES
• Figure 1 represents the elongation Aso as a function of the breaking strength R m .
• the static mechanical characteristics in tension in other words the breaking strength Rm, the yield strength at 0.2% elongation Rpo , 2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1.
• the elongation (A%) at break was measured using a 50 mm basic extensometer and is noted as A50.
• a thin sheet is a rolled product with a rectangular cross-section whose uniform thickness is between 0.20 mm and 6 mm. In the context of the invention, a thin sheet is not a clad sheet.
• the Applicant has found that, surprisingly, it is possible to obtain thin sheets of 5XXX aluminum alloy having improved formability while being recyclable and having surface quality and mechanical strength properties. sufficient, thanks to a narrow selection of the composition and a suitable manufacturing process.
• the thin sheets according to the invention have the composition, in% by weight, of Mg: 0.65 - 0.85, Fe: 0.10 - 0.20, Si: 0.05 - 0.09, Mn: ⁇ 0 .03, Cu: ⁇ 0.05, Cr: ⁇ 0.02, Zn: ⁇ 0.10, Ti: ⁇ 0.03, other elements or impurities ⁇ 0.05 each and ⁇ 0.15 total, remainder aluminium.
• the minimum iron content is therefore 0.10% by weight and preferably 0.12% by weight or even 0.14% by weight.
• the maximum iron content enabling the desired mechanical properties to be achieved is 0.20% by weight and preferably 0.18% by weight.
• the minimum silicon content of 0.05% by weight and preferably 0.06% by weight makes it possible not to limit the possibilities of recycling.
• the present inventors have found that, surprisingly, it is possible to improve the formability of products having an iron content of at least 0.10 by weight and a silicon content of at least 0.05% by weight by selecting the composition of the elements Si, Cr, Mn and Ti.
• the Fe/Si ratio is at least equal to 1.9, preferably at least equal to 1.95, preferably at least equal to 2.0 and preferentially at least equal to 2.2.
• the present inventors believe that the Fe/Si ratio influences in particular the size of the intermetallic phases formed during casting, a high ratio making it possible to obtain finer intermetallic phases that are more favorable to shaping.
• the maximum silicon content of the products according to the invention is 0.09% by weight and preferably 0.08% by weight
• the maximum chromium content is 0.02% by weight and preferably 0, 01% by weight
• the maximum manganese content is 0.03% by weight and preferably 0.02% by weight
• the maximum titanium content is 0.03% by weight and preferably 0.02% in weight.
• the sum of the Cr + Mn + Ti contents is at most 0.06% by weight and preferably at most 0.04% by weight. weight.
• the sum of the Fe+Si+Mn contents is at least 0.22% by weight or even at least 0.24% by weight.
• the sum of the Fe+Si contents is at least 0.20% by weight, preferably at least 0.21% by weight or even at least 0.23% by weight.
• the Mg content of the products according to the invention is from 0.65% by weight to 0.85% by weight, which makes it possible in particular to obtain sufficient mechanical characteristics, such as the breaking strength R m while avoiding defects. surfaces such as defects known as the Lüders band or Portevin-Le Chatelier instabilities.
• the Mg content of the products according to the invention is at least 0.69% by weight.
• the Mg content of the products according to the invention is at most 0.83% by weight.
• the Mg content of the products according to the invention is from 0.65% by weight to 0.78% by weight and preferably from 0.68% by weight to 0.75% by weight.
• the Mg content of the products according to the invention is from 0.72% by weight to 0.82% by weight and preferably from 0.76% by weight to 0.83% by weight.
• the Cu content of the products according to the invention must also be controlled in order to obtain the desired mechanical properties and also in order not to obtain an undesirable surface appearance after shaping and surface treatment.
• the maximum Cu content is 0.05% by weight and preferably 0.03% by weight.
• the Cu content is greater than 0.05% by weight, a yellowish appearance risks being obtained on the finished, shaped and ready-to-use parts, which is detrimental to the decorative appearance.
• the other elements or impurities have a content of less than 0.05% by weight each and less than 0.15% by weight in total. Preferably they have a content of less than 0.03% by weight each and ⁇ 0.10% by weight in total. These are elements present in the electrolysis or recycling metal used to prepare the alloy and are not added individually on a voluntary basis.
• the products according to the invention have an essentially recrystallized microstructure. By essentially recrystallized it is understood that more than 85%, preferably more than 90% and more preferably more than 95% of the microstructure is recrystallized.
• the essentially recrystallized structure is obtained by the combination of the composition, in particular the control of the Mn, Cr and Ti contents, and the manufacturing process.
• the process for manufacturing the products according to the invention comprises casting an alloy of composition according to the invention in the form of a rolling plate, reheating the plate, hot rolling, cold rolling and annealing. After casting an alloy of composition according to the invention in the form of a rolling plate, the latter is scalped and then reheated, preferably to a temperature of between 480°C and 500°C. The plate is then hot rolled to obtain a sheet having a thickness between B and 10 mm, cooled and then cold rolled to the final thickness of the thin sheet.
• the thin sheet thus obtained can then optionally be degreased and/or pickled and/or polished, then it is annealed, typically in a batch furnace, at a temperature of 330 to 420°C and preferentially of 350 to 400°C.
• the annealing temperature according to the invention makes it possible in particular to obtain the recrystallized microstructure according to the invention, while achieving satisfactory homogeneity in the coil and avoiding oxidation and loss of gloss.
• the polishing can be carried out in particular by rolling with rolls of low roughness and/or by any other appropriate surface treatment method such as chemical or electrochemical methods.
• the thin sheet according to the invention has a thickness of between 0.35 and 1.5 mm and more preferably between 0.4 and 1 mm.
• the mechanical properties of the sheets according to the invention are advantageous.
• the thin sheets according to the invention advantageously have in the transverse-long direction TL a breaking strength Rm of at least 100 MPa and preferably of at least 110 MPa and an elongation A50 of at least 28% and preferably of at least 30%.
• the thin sheets according to the invention have, in the transverse-long direction TL, an elastic limit R po, 2 of at least 45 MPa and preferably of at least 50 MPa and an elongation A50 of at least 28% and preferably at least 30%.
• the thin sheets according to the invention are used in particular to produce parts of complex shape shaped in the three dimensions of space, in particular by stamping.
• the thin sheets according to the invention are suitable for undergoing any decorative surface treatment before or after their shaping, such as in particular anodizing, varnishing or lacquering.
• the thin sheets according to the invention are advantageously used as interior or exterior decorative part of a motor vehicle or of a household appliance or of medical equipment.
• the thin sheets according to the invention are used to produce decorative motor vehicle parts such as interior finishing elements chosen from the center console, such as the dashboard, the trim of the gearbox, the door handles, interior decorative moldings, belt lines and/or exterior finishing elements chosen from window surrounds, body or door side moldings, tailgate trim strips, grille trims and trim strips bumper.
• rolling plates with a thickness of 428 mm were cast in aluminum alloy whose composition in % by weight is given in Table 1.
• Alloys B and C have a composition according to the invention.
• Table 1 The plates were scalped, reheated to a temperature of approximately 490°C and then hot rolled to a thickness of 6.5 mm and then cold rolled to a thickness of 0.76 mm.
• the thin sheets thus obtained were annealed at 380°C.
• the microstructure of thin sheets after annealing was completely recrystallized.
• the mechanical properties were determined in the LT direction.
• the mechanical properties and the surface appearance after shaping and surface treatment of the products obtained are presented in Table 2.
• FIG. 1 represents the elongation Aso as a function of the breaking strength R m .
• the thin sheets B and C according to the invention have a particularly advantageous compromise of properties.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Metal Rolling (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2020
  • 2020-11-27 FR FR2012300A patent/FR3116835B1/fr active Active
• 2021
  • 2021-11-19 WO PCT/EP2021/082244 patent/WO2022112110A1/fr unknown
  • 2021-11-19 EP EP21806772.6A patent/EP4251779A1/de active Pending

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