EP3122912B1 - Extruded product of alloy 6xxx suitable for free-cutting and with a low roughness after anodizing - Google Patents

Extruded product of alloy 6xxx suitable for free-cutting and with a low roughness after anodizing Download PDF

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Publication number
EP3122912B1
EP3122912B1 EP15711658.3A EP15711658A EP3122912B1 EP 3122912 B1 EP3122912 B1 EP 3122912B1 EP 15711658 A EP15711658 A EP 15711658A EP 3122912 B1 EP3122912 B1 EP 3122912B1
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Prior art keywords
extruded product
anodizing
temperature
alloy
less
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German (de)
French (fr)
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EP3122912A2 (en
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Lukasz Dolega
Jean-Sylvestre Safrany
Ivo Kolarik
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Constellium Extrusions Decin sro
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Constellium Extrusions Decin sro
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    • 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
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/10—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing organic acids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/02—Making uncoated products
    • B21C23/04—Making uncoated products by direct extrusion
    • B21C23/14—Making other products
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/16—Pretreatment, e.g. desmutting

Definitions

  • the invention relates to turned parts obtained from bar or rod type extruded products, made of aluminum alloy of the AA6xxx series, and in particular to parts having undergone a surface treatment after machining.
  • Bar turning designates a field of manufacturing by machining, in large series, of mechanical parts typically of revolution (screw, bolt, axis, piston, etc.) by removing material from metal bars or rods.
  • the parts are thus produced at high rates on manually or numerically controlled cutting machines.
  • the parts thus produced find their application in various fields, from watchmaking to medical equipment, including the fields of transport (aeronautics, railway, automobile) and industrial (electrical, electronic, hydraulic, etc.).
  • Requirement EP 0 176 187 reveals a process for obtaining a recrystallized structure after deformation.
  • Requirement JP 2004 292847 A discloses an extruded product having a recrystallized structure and having good dimensional tolerances after machining.
  • the problem that the present invention seeks to solve is to obtain spun products which are simultaneously suitable for bar turning and resistant to intergranular corrosion and which have low roughness after machining and anodizing.
  • the spun product suitable for bar turning in aluminum alloy according to the invention is defined by independent claim 1.
  • the use of a spun product according to the invention is defined by independent claim 7.
  • the method of manufacturing a spun product according to the invention is defined by independent claim 8.
  • the method of manufacturing a turned and anodized mechanical part according to the invention is defined by independent claim 9.
  • the preferred modes are defined by the dependent claims.
  • Figure 1 Observation of the samples after the standardized corrosion test carried out according to standard EN ISO 11846:2008 (method B).
  • the static mechanical characteristics in other words the breaking strength Rm, the conventional yield strength at 0.2% elongation Rp0.2 and the elongation at break A%, are determined by a tensile test according to standard ISO 6892-1, the sampling and direction of the test being defined by standard EN 485-1.
  • the suitability for bar turning is evaluated by a machining test as described in the international application WO2013/170953 in paragraph [0039].
  • the test consists of determining the chip fragmentation ability by measuring the number of chips in a determined mass of chips collected, here 100g. Machining is carried out using an SP 12 CNC lathe and a rhombic insert with a basic shape of 80° sold under the registered brand SANDVIK Coromant Coroturn ® 107 with the reference CCGX 09 T3 04-AL, designed for aluminum alloys .
  • the machining parameters used are a rotation speed of 3000 rpm, a feed of 0.3 mm/rev and a cutting depth of 3.5 mm.
  • the spun products according to the invention are suitable for bar turning, that is to say they pass the test described in the international application WO2013/170953 in paragraph [0039] a number of chips per 100g of chips of at least 3000 and preferably at least 4000.
  • Corrosion resistance was assessed according to the standardized test EN ISO 11846:2008 (method B).
  • the surface area of the samples was 20 cm 2 .
  • the samples were prepared by degreasing with an organic solvent, immersion for 2 minutes in 5% sodium hydroxide at a temperature of 55°C, rinsed and immersion for 2 minutes in 2% nitric acid.
  • an essentially recrystallized granular structure is a granular structure such that the recrystallization rate at 1 ⁇ 4 thickness is greater than 70% and preferably greater than 90%.
  • the recrystallization rate is defined as the fraction of surface area on a metallographic section occupied by recrystallized grains.
  • the present inventors have found that for known free-cutting alloys, such as the alloys AA6262, AA6064A or AA6042 or the alloy described in the international application WO2013/170953 , the roughness after anodization making it possible to obtain an oxide layer with a thickness of at least 20 ⁇ m and much greater than the roughness before anodization.
  • the roughness after anodizing is at least 1.80 ⁇ m or more.
  • the present inventors have found that this problem is solved by controlling the composition of the alloy according to the invention and its granular structure.
  • the spun products suitable for bar turning according to the invention are made of aluminum alloy of composition, in % by weight, Si 0.4 - 0.8; Mg 0.8 - 1.2; Cu 0.20 - 0.4; Fe 0.05 - 0.4; Mn ⁇ 0.10; Ti ⁇ 0.15; Cr ⁇ 0.08 Bi 0.4-0.8; Pb 0.2-0.4; other elements ⁇ 0.05 each and ⁇ 0.15 in total, remaining aluminum.
  • the copper content in this first embodiment is at least 0.23% by weight.
  • the copper content is at least 0.30% by weight.
  • the iron content is preferably at least 0.20% by weight and advantageously 0.25% by weight.
  • the composition is such that, in % by weight, Bi: 0.4 - 0.8 and Pb 0.2 - 0.4 and preferably Pb 0.2 - 0.34.
  • the silicon content is between 0.5 and 0.7% by weight and/or the magnesium content is between 0.9 and 1.1% by weight.
  • the essentially recrystallized granular structure is obtained in particular thanks to the control of the content of manganese and chromium content.
  • the manganese content is at most 0.05% by weight.
  • the chromium content is at most 0.08% by weight.
  • the sum of the chromium and manganese content is such that, in % by weight, Cr + Mn ⁇ 0.15 and preferably Cr + Mn ⁇ 0.10. Controlling the zirconium content may also be important in obtaining the essentially recrystallized grain structure.
  • the zirconium content is less than 0.04% by weight and preferably less than 0.03% by weight.
  • the alloy and the metallurgical structure of the spun products according to the invention are also advantageous because their spinning ability is excellent, in particular the pressure necessary to initiate spinning is lower, the spinning speed is higher than for known alloys and no spinning defects such as hot tearing are observed.
  • the spun products according to the invention have satisfactory static mechanical strength properties: their elastic limit being preferably in the T6 state of at least 300 MPa and their elongation being at least 10% and their elastic limit preferably being in the T9 state of at least 330 MPa and their elongation being at least 8%.
  • the present inventors have found that a spun product essentially recrystallized from an alloy according to the invention has improved resistance to intergranular corrosion.
  • the spun products according to the invention have resistance to intergranular corrosion according to the ISO 11846 method B test such that the maximum depth of corrosion on a cross section of the spun product is less than 200 ⁇ m and the relative surface area of the attack is less than 50%.
  • a spun product essentially recrystallized from an alloy according to the invention has improved roughness after machining and anodization.
  • a spun product according to the invention has a roughness Rz on a generatrix parallel to the spinning axis less than or equal to 1.7 ⁇ m and preferably less than 1.2 ⁇ m.
  • the spun products according to the invention are also advantageous in that for so-called “hard” anodizing the anodizing time is reduced, which is favorable for productivity.
  • a spun product according to the invention is characterized in that the anodization time to obtain an anodic layer with a thickness of 30 ⁇ m in a 200g/l H2SO4 solution at 5°C is less than 30 minutes for a current density of 3A/dm 2 or in other words the oxide growth speed is greater than 1 ⁇ m/min.
  • the invention also relates to the process for manufacturing the spun products according to the invention.
  • an aluminum alloy of composition according to the invention is produced, and it is typically cast in the form of a billet.
  • the billet is then homogenized at a temperature of at least at least 580°C.
  • the chosen homogenization temperature contributes in particular to obtaining an essentially recrystallized granular structure.
  • the billet thus homogenized is then spun, the initial spinning temperature being lower than 550°C and preferably lower than 540°C.
  • An initial spinning temperature of at least 450°C is preferred.
  • the spun product obtained is preferably dissolved and quenched with water, the solution being able to either be carried out using the heat generated during spinning or carried out in a separate heat treatment. Quenching carried out at the die outlet on spinning heat, typically with water, is advantageous.
  • the spun product is straightened and/or cold deformed typically by traction and/or stretching, and/or the spun product is matured.
  • the cold deformation is sufficient, typically at least 7%, to influence the mechanical properties after tempering.
  • the eventual maturation is typically a few hours to a few days.
  • the spun product is then returned to a temperature of between 150 and 200°C for a period of between 5 and 25 hours to obtain a T6 or T8 tempered state.
  • the anodization is carried out at a temperature between 0 and 10°C with a solution containing 100 to 250 g/l of sulfuric acid with a current density of 1 to 3 A/dm2 with a speed of oxide growth greater than 1 ⁇ m/min.
  • the spun products according to the invention make it possible in particular, under these conditions, to reduce the anodizing time compared to the products according to the prior art.
  • the anodization is carried out at a temperature between 15 and 40 ° C with a solution comprising 100 to 250 g/l of sulfuric acid and 10 to 30 g/l of oxalic acid and 5 to 30 g/l of at least one polyol.
  • at least one polyol is chosen from ethylene glycol, propylene glycol or glycerol.
  • the anodization is carried out with a current density of between 1 and 5 A/dm 2 and preferably 2 and 4 A/dm 2 .
  • the thickness of the anodic layer obtained is between 15 and 40 ⁇ m.
  • the invention also relates to the turned and anodized mechanical parts obtained by the process according to the invention.
  • These mechanical parts are advantageous because simultaneously they have a roughness Rz on a generator parallel to the spinning axis less than or equal to 2.3 ⁇ m and preferably less than or equal to 1.7 ⁇ m and their resistance to intergranular corrosion according to the ISO 11846 method B test is such that the maximum depth of corrosion on a cross section of the spun product is less than 200 ⁇ m and the relative surface area of the attack is less than 50%.
  • Table 1 Composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi HAS 0.6 0.26 0.24 0.03 1.1 0.05 0.02 ⁇ 0.01 ⁇ 0.01 0.25 0.5 B 0.7 0.40 0.30 0.11 1.0 0.11 0.02 ⁇ 0.01 0.01 0.38 0.7
  • the alloys were cast in the form of billets with a diameter of 254 mm, homogenized at 585 °C then spun in the form of bars with a cross section of 15 x 100 mm, by direct spinning, the initial spinning temperature being 530 °C.
  • the pressure necessary to initiate spinning was 140 bar for alloy A according to the invention, significantly lower than the pressure necessary to initiate spinning of alloy B which was 160 bar.
  • the spinning speed was 8.3 m/min for alloy A billet while it was 7.2 m/min for alloy B. Pull-offs during spinning were observed for alloy B while that these cracks were not observed for alloy A. Alloy A thus had better friability than alloy B.
  • the spun products were soaked after leaving the press.
  • the bars thus obtained were tensile by 1% then subjected to tempering to obtain a T6 state.
  • the alloy A bar thus obtained had a recrystallized granular structure at 1 ⁇ 4 thickness while the alloy B bar had a non-recrystallized granular structure at 1 ⁇ 4 thickness.
  • the mechanical properties of the bars thus obtained, measured in the spinning direction, are presented in Table 2.
  • Table 2 Mechanical properties obtained Alloy Rm (MPa) R p0.2 (MPa) HAS% HAS 327 306 12 B 370 348 13
  • the bars obtained were suitable for bar turning.
  • the alloys were cast in the form of billets with a diameter of 254 mm, homogenized at 585 °C then spun into the form of cylindrical bars and quenched at the end of the press.
  • the bars thus obtained were tensile by 1% then subjected to tempering and were stretched to obtain bars with a diameter of 14 mm.
  • the alloy A bar thus obtained had a recrystallized granular structure at 1 ⁇ 4 thickness while the alloy B bar had a non-recrystallized granular structure at 1 ⁇ 4 thickness.
  • the bars obtained were suitable for bar turning.
  • Corrosion resistance was evaluated in the middle of the bar according to the standardized test EN ISO 11846:2008 (method B). The results are presented in Table 6 and on the Figure 1 .
  • Table 6 - Corrosion test results Alloy Bar surface Cross section area Maximum attack depth ( ⁇ m) Relative area of attack (%) Maximum attack depth ( ⁇ m) Relative area of attack (%) HAS 330 20 50 10 HAS 300 10 80 10 VS 305 100 690 100 VS 300 100 720 100 VS 370 100 600 100
  • Table 7 composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi D 0.6 0.24 0.21 0.01 1.04 0.05 0.02 ⁇ 0.01 ⁇ 0.01 0.23 0.4 E 0.7 0.40 0.30 0.11 1.01 0.12 0.02 ⁇ 0.01 ⁇ 0.01 0.34 0.7
  • the alloys were cast in the form of billets, homogenized then spun into the form of bars with a diameter of 30 mm.
  • the spun products were soaked after leaving the press.
  • the bars thus obtained were tensile by 1% then subjected to tempering to obtain bars in T6 condition.
  • the two alloys D and E are tested in the T6 state and are different in their granular structure.
  • the alloy D bar thus obtained had a recrystallized granular structure at 1 ⁇ 4 thickness while the alloy E bar had a non-recrystallized granular structure at 1 ⁇ 4 thickness.
  • the mechanical properties of the bars thus obtained, measured in the direction of spinning, are presented in Table 8.
  • Table 8 Mechanical properties obtained Alloy State Bar Diameter (mm) Rm (MPa) R p0.2 (MPa) HAS% D T6 30 330 298 17.9 E T6 30 359 341 12.6
  • the alloys were cast in the form of 261 mm diameter billets, homogenized at 585 °C and then spun into bar form.
  • the spun products were soaked after leaving the press.
  • the bars thus obtained were tensile by 1%, then underwent tempering followed by cold deformation to obtain a product in the T9 state.
  • Alloy F was stretched in such a way as to obtain a bar with a diameter of 24.5 mm and alloy G a bar with a diameter of 26 mm.
  • the F and G alloy bars thus obtained have a recrystallized granular structure at 1 ⁇ 4 thickness.
  • the alloy was cast in the form of 261 mm diameter billets, homogenized and then spun into bar form.
  • a bar was quenched at the end of the press, tensile by 1% then cold deformed to obtain a final diameter of 24.6 mm and then tempered to obtain a product in the T8 state.
  • Another bar was quenched at the end of the press, cold pulled by approximately 1%, then tempered followed by cold deformation to obtain a final diameter of 24.5 mm to obtain a product in the T9 state.
  • the H alloy bars thus obtained have a recrystallized granular structure at 1 ⁇ 4 thickness.
  • the suitability for bar turning was evaluated by a machining test as described in the international application WO2013/170953 in paragraph [0039].
  • the test consists of determining the chip fragmentation ability by measuring the number of chips in a determined mass of chips collected, here 100g. The weight of 50 chips has also been determined. The results are presented in Table 11.
  • Machining is carried out using an SP 12 CNC lathe and a rhombic insert with a basic shape of 80° sold under the registered brand SANDVIK Coromant Coroturn ® 107 with the reference CCGX 09 T3 04-AL, designed for aluminum alloys .
  • the machining parameters used are a rotation speed of 3000 rpm, a feed of 0.3 mm/rev and a cutting depth of 3.5 mm.
  • Table 11 Results obtained after the bar turning ability test described in international application WO2013/170953 in paragraph [0039] Alloy State Bar diameter (mm) Rm (MPa) Rp0.2 (MPa) HAS% Number of chips in 100g Mass of 50 chips (g) H T9 24.5 380 357 8 4272 1.1705 T8 24.6 348 321 15.6 4744 1.0539

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Description

Domaine de l'inventionField of the invention

L'invention concerne les pièces décolletées obtenues à partir de produits filés de type barre ou tige, en alliage d'aluminium de la série AA6xxx, et en particulier des pièces ayant subi postérieurement à l'usinage un traitement de surface.The invention relates to turned parts obtained from bar or rod type extruded products, made of aluminum alloy of the AA6xxx series, and in particular to parts having undergone a surface treatment after machining.

Etat de la techniqueState of the art

Le décolletage désigne un domaine de fabrication par usinage, en grandes séries, de pièces mécaniques typiquement de révolution (vis, boulon, axe, piston, etc.) par enlèvement de matière à partir de barres ou tiges de métal.Bar turning designates a field of manufacturing by machining, in large series, of mechanical parts typically of revolution (screw, bolt, axis, piston, etc.) by removing material from metal bars or rods.

Celles-ci, notamment dans le cas des alliages d'aluminium, sont généralement obtenues par filage à partir de billettes.These, particularly in the case of aluminum alloys, are generally obtained by spinning from billets.

Les pièces sont ainsi produites à des cadences élevées sur des machines de coupe à commande manuelle ou numérique.The parts are thus produced at high rates on manually or numerically controlled cutting machines.

La productivité et l'état de surface ainsi que la précision dimensionnelle de la pièce finale sont les objectifs principaux attachés à ce type de fabrication. Après usinage, les pièces peuvent subir un traitement de surface de protection, typiquement par anodisation. L'anodisation dite dure, typiquement réalisée à basse température (0 - 5°C), forte densité de courant en présence d'acide sulfurique permet d'obtenir des revêtements particulièrement résistants.Productivity and surface finish as well as dimensional precision of the final part are the main objectives attached to this type of manufacturing. After machining, the parts can undergo a protective surface treatment, typically by anodizing. So-called hard anodizing, typically carried out at low temperature (0 - 5°C), high current density in the presence of sulfuric acid makes it possible to obtain particularly resistant coatings.

Les pièces ainsi produites trouvent leur application dans des domaines variés, de l'horlogerie au matériel médical, en passant par les domaines du transport (aéronautique, ferroviaire, automobile) et industriel (électrique, électronique, hydraulique...).The parts thus produced find their application in various fields, from watchmaking to medical equipment, including the fields of transport (aeronautics, railway, automobile) and industrial (electrical, electronic, hydraulic, etc.).

Il existe une demande croissante pour des pièces mécaniques obtenues par décolletage présentant simultanément une faible rugosité et un revêtement résistant. De plus la résistance à la corrosion intergranulaire des pièces mécaniques obtenues doit être suffisante pour que les pièces ne soient pas remplacées de façon trop fréquente. En particulier pour certaines applications telles que les pistons de freins ou les éléments de boite de vitesse, diminuer la rugosité tout en réalisant un revêtement résistant permettrait d'améliorer le contact entre la pièce mécanique et son joint et ainsi diminuer l'usure et prolonger la durée de vie des pièces. Cependant les alliages ayant une bonne aptitude au décolletage présentent généralement de nombreuses phases intermétalliques qui lors de l'anodisation dure génèrent une importante rugosité. Ainsi il est très difficile d'obtenir un produit filé présentant simultanément une bonne aptitude au décolletage et une rugosité de surface faible après anodisation.There is a growing demand for mechanical parts obtained by turning which simultaneously have low roughness and a resistant coating. In addition, the resistance to intergranular corrosion of the mechanical parts obtained must be sufficient so that parts are not replaced too frequently. In particular for certain applications such as brake pistons or gearbox elements, reducing the roughness while producing a resistant coating would improve the contact between the mechanical part and its seal and thus reduce wear and prolong the lifespan. lifespan of parts. However, alloys with good machinability generally have numerous intermetallic phases which during hard anodization generate significant roughness. Thus it is very difficult to obtain a spun product simultaneously exhibiting good bar-cutting ability and low surface roughness after anodization.

La demande internationale WO2005/100623 décrit des alliages, préférentiellement sous forme filée, aptes au décolletage et de composition en % en poids Si 0,6 - 2,0 ; Fe 0,2 - 1,0 ; Mg 0,5 - 2,0, Cu max 1,0, Mn max 1,5, Zn max 1,0, Cr max 0,35, Ti max 0,35 et Zr 0,04 - 0,3.International demand WO2005/100623 describes alloys, preferably in spun form, suitable for bar turning and of composition in % by weight Si 0.6 - 2.0; Fe 0.2 - 1.0; Mg 0.5 - 2.0, Cu max 1.0, Mn max 1.5, Zn max 1.0, Cr max 0.35, Ti max 0.35 and Zr 0.04 - 0.3.

La demande internationale WO 2007/027629 décrit un procédé de tempe sur presse de l'alliage 6020. Le produit obtenu ayant une bonne aptitude au décolletage.International demand WO 2007/027629 describes a press tempering process for alloy 6020. The product obtained has good bar turning ability.

La demande internationale WO 2008/112698 décrit un produit filé ayant une excellente aptitude au décolletage de composition en % en poids Si 0,8 - 1,5 ; Fe 1,0 - 1,8 ; Cu < 0,1 - Mn < 1 ; Mg 0,6 - 1,2; Ni < 3,0 ; Cr < 0,25 - Ti < 0,1.International demand WO 2008/112698 describes a spun product having excellent bar-cutting ability of composition in % by weight Si 0.8 - 1.5; Fe 1.0 - 1.8; Cu < 0.1 - Mn <1; Mg 0.6 - 1.2; Ni <3.0; Cr < 0.25 - Ti < 0.1.

La demande internationale WO 2013/170953 décrit un produit de composition, en % en poids, Si : 1,3 - 12 ; Fe 1,35 - 1,8, dans lequel Fe + Si est supérieur à 3,4 ; Cu 0,15 - 6 ; Mg 0,6 - 3 ; Mn < 1 ; Cr < 0,25 ; Ni < 3 - Zn < 1 - Ti < 0,1 - Bi < 0,7 - In < 0,7 - Sn < 0,7. Après usinage et anodisation pour obtenir une couche d'oxyde d'épaisseur 30 µm, la valeur la plus basse de rugosité atteinte est 1,80 µm.International demand WO 2013/170953 describes a product of composition, in % by weight, Si: 1.3 - 12; Fe 1.35 - 1.8, in which Fe + Si is greater than 3.4; Cu 0.15 - 6; Mg 0.6 - 3; Mn <1; Cr <0.25; Ni < 3 - Zn < 1 - Ti < 0.1 - Bi < 0.7 - In < 0.7 - Sn < 0.7. After machining and anodizing to obtain a 30 µm thick oxide layer, the lowest roughness value achieved is 1.80 µm.

Des procédés d'anodisation permettant de réaliser des couches d'oxydes notamment sur des alliages 6xxx sont connus, par exemple du brevet US 3,524,799 ou de la demande EP 1 980 651 . Les alliages testés dans ces documents, tels que l'alliage 6063 ou 6463 ne sont pas connus pour être aptes au décolletage.Anodizing processes making it possible to produce oxide layers in particular on 6xxx alloys are known, for example from the patent US 3,524,799 or request EP 1 980 651 . The alloys tested in these documents, such as alloy 6063 or 6463, are not known to be suitable for bar turning.

Le document « Rod & Bar Alloy 6064 Technical Datasheet », 6 janvier 2007(2007-01-06, pages 1-2 XP0055135334, Extrait de l'internet : URL : http://www.kaiseraluminium.com/wp-content/uploads/2007/05/rod-bar-alloy-6064.pdf [extrait le 2014-08-19 ] de Kayser Aluminum est une fiche technique qui décrit un produit filé d'alliage d'aluminium 6064. Ce document présente les propriétés de cet alliage, en particulier son aptitude à l'usinage et à l'anodisation.The document " Rod & Bar Alloy 6064 Technical Datasheet”, January 6, 2007 (2007-01-06, pages 1-2 XP0055135334, Retrieved from the internet: URL: http://www.kaiseraluminium.com/wp-content/uploads/2007 /05/rod-bar-alloy-6064.pdf [extracted on 2014-08-19 ] from Kayser Aluminum is a technical sheet that describes a spun product of 6064 aluminum alloy. This document presents the properties of this alloy, in particular its suitability for machining and anodizing.

Le brevet US 6,248,189 divulgue un produit permettant la fabrication de tubes extrudés pour des arbres de transmission.The patent US 6,248,189 discloses a product enabling the manufacture of extruded tubes for transmission shafts.

La demande EP 0 176 187 dévoile un procédé permettant d'obtenir une structure recristallisée après déformation.Requirement EP 0 176 187 reveals a process for obtaining a recrystallized structure after deformation.

La demande JP 2004 292847 A divulgue un produit extrudé ayant une structure recristallisée et ayant de bonnes tolérances dimensionnelles après l'usinage.Requirement JP 2004 292847 A discloses an extruded product having a recrystallized structure and having good dimensional tolerances after machining.

Le problème que la présente invention cherche à résoudre est d'obtenir des produits filés qui soient simultanément aptes au décolletage et résistants à la corrosion intergranulaire et qui présentent après usinage et anodisation une faible rugosité.The problem that the present invention seeks to solve is to obtain spun products which are simultaneously suitable for bar turning and resistant to intergranular corrosion and which have low roughness after machining and anodizing.

Objet de l'inventionObject of the invention

Le produit filé apte au décolletage en alliage d'aluminium selon l'invention est défini par la revendication indépendante 1. L'utilisation d'un produit filé selon l'invention est définie par la revendication indépendante 7. Le procédé de fabrication d'un produit filé selon l'invention est défini par la revendication indépendante 8. Le procédé de fabrication d'une pièce mécanique décolletée et anodisée selon l'invention est défini par la revendication indépendante 9. Les modes préférés sont définis par les revendications dépendantes.The spun product suitable for bar turning in aluminum alloy according to the invention is defined by independent claim 1. The use of a spun product according to the invention is defined by independent claim 7. The method of manufacturing a spun product according to the invention is defined by independent claim 8. The method of manufacturing a turned and anodized mechanical part according to the invention is defined by independent claim 9. The preferred modes are defined by the dependent claims.

Description des figuresDescription of figures

Figure 1 : Observation des échantillons après le test de corrosion standardisé réalisé selon la norme EN ISO 11846 :2008 (méthode B). Figure 1 : Observation of the samples after the standardized corrosion test carried out according to standard EN ISO 11846:2008 (method B).

Description de l'inventionDescription of the invention

Sauf mention contraire, toutes les indications concernant la composition chimique des alliages sont exprimées comme un pourcentage en poids basé sur le poids total de l'alliage. L'expression 1,4 Cu signifie que la teneur en cuivre exprimée en % en poids est multipliée par 1,4. La désignation des alliages se fait en conformité avec les règlements de The Aluminium Association, connus de l'homme du métier. Sauf mention contraire, les définitions de la norme EN12258-1 s'appliquent. Sauf mention contraire, les définitions des états métallurgiques de la norme EN 515 s'appliquent.Unless otherwise stated, all indications regarding the chemical composition of alloys are expressed as a weight percentage based on the total weight of the alloy. The expression 1.4 Cu means that the copper content expressed in % by weight is multiplied by 1.4. The designation of alloys is done in accordance with the regulations of The Aluminum Association, known to those skilled in the art. Unless otherwise stated, the definitions of standard EN12258-1 apply. Unless otherwise stated, the definitions of metallurgical conditions in EN 515 apply.

Sauf mention contraire, les caractéristiques mécaniques statiques, en d'autres termes la résistance à la rupture Rm, la limite d'élasticité conventionnelle à 0,2% d'allongement Rp0,2 et l'allongement à la rupture A%, sont déterminées par un essai de traction selon la norme ISO 6892-1, le prélèvement et le sens de l'essai étant définis par la norme EN 485-1.Unless otherwise stated, the static mechanical characteristics, in other words the breaking strength Rm, the conventional yield strength at 0.2% elongation Rp0.2 and the elongation at break A%, are determined by a tensile test according to standard ISO 6892-1, the sampling and direction of the test being defined by standard EN 485-1.

L'aptitude au décolletage est évaluée par un test d'usinage tel que décrit dans la demande internationale WO2013/170953 au paragraphe [0039]. Le test consiste à déterminer l'aptitude à la fragmentation des copeaux en mesurant le nombre de copeaux dans une masse déterminée de copeaux collectés, ici 100g. L'usinage est effectué en utilisant un tour SP 12 CNC et un insert rhombique avec une forme basique de 80° vendu sous la marque enregistrée SANDVIK Coromant Coroturn® 107 avec la référence CCGX 09 T3 04-AL, conçu pour les alliages d'aluminium. Les paramètres d'usinage utilisés sont une vitesse de rotation de 3000 tour/min, une alimentation de 0,3 mm/tour and une profondeur de découpe de 3,5 mm. Les produits filés selon l'invention sont aptes au décolletage c'est-à-dire qu'ils présentent au test décrit dans la demande internationale WO2013/170953 au paragraphe [0039] un nombre de copeaux pour 100g de copeaux d'au moins 3000 et de préférence d'au moins 4000.The suitability for bar turning is evaluated by a machining test as described in the international application WO2013/170953 in paragraph [0039]. The test consists of determining the chip fragmentation ability by measuring the number of chips in a determined mass of chips collected, here 100g. Machining is carried out using an SP 12 CNC lathe and a rhombic insert with a basic shape of 80° sold under the registered brand SANDVIK Coromant Coroturn ® 107 with the reference CCGX 09 T3 04-AL, designed for aluminum alloys . The machining parameters used are a rotation speed of 3000 rpm, a feed of 0.3 mm/rev and a cutting depth of 3.5 mm. The spun products according to the invention are suitable for bar turning, that is to say they pass the test described in the international application WO2013/170953 in paragraph [0039] a number of chips per 100g of chips of at least 3000 and preferably at least 4000.

La résistance à la corrosion a été évaluée selon le test normalisé EN ISO 11846 :2008 (méthode B). La surface des échantillons était de 20 cm2. Les échantillons ont été préparés par dégraissage avec un solvant organique, immersion 2 mn dans la soude 5% à la température de 55 °C, rincé et immersion 2 mn dans l'acide nitrique 2%.Corrosion resistance was assessed according to the standardized test EN ISO 11846:2008 (method B). The surface area of the samples was 20 cm 2 . The samples were prepared by degreasing with an organic solvent, immersion for 2 minutes in 5% sodium hydroxide at a temperature of 55°C, rinsed and immersion for 2 minutes in 2% nitric acid.

Le test de corrosion consiste à immerger pendant 24 heures à température ambiante l'échantillon ainsi préparé dans une solution contenant 30g/l NaCl et 10ml/l d'acide chlorhydrique concentré (p = 1,19 g/ml).The corrosion test consists of immersing the sample thus prepared for 24 hours at room temperature in a solution containing 30g/l NaCl and 10ml/l of concentrated hydrochloric acid (p = 1.19 g/ml).

Trois paramètres de rugosité mesurés selon la norme ISO 4287 sont utilisés :

  • Rmax : hauteur maximale du profil de rugosité, soit la plus grande des valeurs Rzi sur la longueur d'évaluation
  • Rz : Hauteur moyenne du profil Rz, soit la moyenne arithmétique des valeurs individuelles Rzi sur la longueur d'évaluation
  • Ra : Ecart moyen de rugosité soit la moyenne arithmétique de toutes les ordonnées du profil sur la longueur d'évaluation.
Three roughness parameters measured according to the ISO 4287 standard are used:
  • R max : maximum height of the roughness profile, i.e. the largest of the R zi values over the evaluation length
  • R z : Average height of the profile R z , i.e. the arithmetic mean of the individual values R zi over the evaluation length
  • Ra: Average roughness difference, i.e. the arithmetic average of all the ordinates of the profile over the evaluation length.

Dans le cadre de la présente invention, on appelle structure granulaire essentiellement recristallisée une structure granulaire telle que le taux de recristallisation à ¼ épaisseur est supérieur à 70% et de préférence supérieur à 90%. Le taux de recristallisation est défini comme la fraction de surface sur une coupe métallographique occupée par des grains recristallisés.In the context of the present invention, an essentially recrystallized granular structure is a granular structure such that the recrystallization rate at ¼ thickness is greater than 70% and preferably greater than 90%. The recrystallization rate is defined as the fraction of surface area on a metallographic section occupied by recrystallized grains.

Les présents inventeurs ont constaté que pour des alliages de décolletage connus, tels que les alliages AA6262, AA6064A ou AA6042 ou l'alliage décrit dans la demande internationale WO2013/170953 , la rugosité après une anodisation permettant d'obtenir une couche d'oxyde d'épaisseur d'au moins 20 µm et très supérieure à la rugosité avant anodisation. Typiquement même si après usinage on obtient une rugosité telle que Rz < 0,01 µm la rugosité après anodisation est au moins 1,80 µm ou plus. Ainsi lors de l'anodisation la présence de nombreux composés intermétalliques dans ce type d'alliage génère une rugosité importante.The present inventors have found that for known free-cutting alloys, such as the alloys AA6262, AA6064A or AA6042 or the alloy described in the international application WO2013/170953 , the roughness after anodization making it possible to obtain an oxide layer with a thickness of at least 20 µm and much greater than the roughness before anodization. Typically, even if after machining we obtain a roughness such that R z < 0.01 µm, the roughness after anodizing is at least 1.80 µm or more. Thus during anodizing the presence of numerous intermetallic compounds in this type of alloy generates significant roughness.

Les présents inventeurs ont constaté que ce problème est résolu en contrôlant la composition de l'alliage selon l'invention et sa structure granulaire.The present inventors have found that this problem is solved by controlling the composition of the alloy according to the invention and its granular structure.

Les produits filés aptes au décolletage selon l'invention sont en alliage d'aluminium de composition, en % en poids, Si 0,4 - 0,8 ; Mg 0,8 - 1,2 ; Cu 0,20 - 0,4 ; Fe 0,05 - 0,4 ; Mn ≤ 0,10 ; Ti < 0,15 ; Cr ≤ 0,08 Bi 0,4-0,8 ; Pb 0,2- 0,4 ; autres éléments < 0,05 chacun et < 0,15 en total, reste aluminium.The spun products suitable for bar turning according to the invention are made of aluminum alloy of composition, in % by weight, Si 0.4 - 0.8; Mg 0.8 - 1.2; Cu 0.20 - 0.4; Fe 0.05 - 0.4; Mn ≤ 0.10; Ti < 0.15; Cr ≤ 0.08 Bi 0.4-0.8; Pb 0.2-0.4; other elements < 0.05 each and < 0.15 in total, remaining aluminum.

Les valeurs minimales simultanées de silicium, magnésium, cuivre et fer, permettent notamment d'obtenir des produits filés aptes au décolletage. Des alliages ne présentant pas ces teneurs minimales tels que par exemple les alliages 6063 ou 6463 ne sont pas aptes au décolletage.The simultaneous minimum values of silicon, magnesium, copper and iron make it possible to obtain spun products suitable for bar turning. Alloys not having these minimum contents such as for example alloys 6063 or 6463 are not suitable for bar turning.

De préférence la teneur en cuivre dans ce premier mode de réalisation est au moins 0,23 % en poids. Dans un mode de réalisation de l'invention la teneur en cuivre est au moins 0,30 % en poids. La teneur en fer est de préférence au moins 0,20 % en poids et avantageusement 0,25 % en poids. Selon l'invention, la composition est telle que, en % en poids, Bi : 0,4 - 0,8 et Pb 0,2 - 0,4 et de préférence Pb 0,2 - 0,34.Preferably the copper content in this first embodiment is at least 0.23% by weight. In one embodiment of the invention the copper content is at least 0.30% by weight. The iron content is preferably at least 0.20% by weight and advantageously 0.25% by weight. According to the invention, the composition is such that, in % by weight, Bi: 0.4 - 0.8 and Pb 0.2 - 0.4 and preferably Pb 0.2 - 0.34.

De préférence la teneur en silicium est comprise entre 0,5 et 0,7 % en poids et/ou la teneur en magnésium est comprise entre 0,9 et 1,1 % en poids. La structure granulaire essentiellement recristallisée est obtenue notamment grâce au contrôle de la teneur en manganèse et de la teneur en chrome. Préférentiellement la teneur en manganèse est au plus de 0,05 % en poids. La teneur en chrome est au plus de 0,08 % en poids. Selon l'invention, la somme de la teneur en chrome et de manganèse est telle que, en % en poids, Cr + Mn ≤ 0,15 et de préférence Cr + Mn ≤ 0,10. Le contrôle de la teneur en zirconium peut également être important pour l'obtention de la structure granulaire essentiellement recristallisée. La teneur en zirconium est inférieure à 0.04 % en poids et de préférence inférieure à 0,03 % en poids.Preferably the silicon content is between 0.5 and 0.7% by weight and/or the magnesium content is between 0.9 and 1.1% by weight. The essentially recrystallized granular structure is obtained in particular thanks to the control of the content of manganese and chromium content. Preferably the manganese content is at most 0.05% by weight. The chromium content is at most 0.08% by weight. According to the invention, the sum of the chromium and manganese content is such that, in % by weight, Cr + Mn ≤ 0.15 and preferably Cr + Mn ≤ 0.10. Controlling the zirconium content may also be important in obtaining the essentially recrystallized grain structure. The zirconium content is less than 0.04% by weight and preferably less than 0.03% by weight.

L'alliage et la structure métallurgique des produits filés selon l'invention sont également avantageux car leur aptitude au filage est excellente, notamment la pression nécessaire pour initier le filage est plus faible, la vitesse de filage est plus élevée que pour des alliages connus et on n'observe pas de défauts de filage tels que des arrachements à chaud.The alloy and the metallurgical structure of the spun products according to the invention are also advantageous because their spinning ability is excellent, in particular the pressure necessary to initiate spinning is lower, the spinning speed is higher than for known alloys and no spinning defects such as hot tearing are observed.

Contrairement à ce qui aurait pu être prévu, les produits filés selon l'invention présentent des propriétés de résistance mécanique statiques satisfaisantes : leur limite d'élasticité étant de préférence à l'état T6 d'au moins 300 MPa et leur allongement étant d'au moins 10 % et leur limite d'élasticité étant de préférence à l'état T9 d'au moins 330 MPa et leur allongement étant d'au moins 8 %.Contrary to what could have been expected, the spun products according to the invention have satisfactory static mechanical strength properties: their elastic limit being preferably in the T6 state of at least 300 MPa and their elongation being at least 10% and their elastic limit preferably being in the T9 state of at least 330 MPa and their elongation being at least 8%.

Les présents inventeurs ont constaté qu'un produit filé essentiellement recristallisé en alliage selon l'invention présente une résistance à la corrosion intergranulaire améliorée. Ainsi les produits filés selon l'invention ont une résistance à la corrosion intergranulaire selon le test ISO 11846 méthode B telle que la profondeur maximale de corrosion sur une coupe transversale du produit filé est inférieure à 200 µm et que la superficie relative de l'attaque est inférieure à 50 %.The present inventors have found that a spun product essentially recrystallized from an alloy according to the invention has improved resistance to intergranular corrosion. Thus the spun products according to the invention have resistance to intergranular corrosion according to the ISO 11846 method B test such that the maximum depth of corrosion on a cross section of the spun product is less than 200 µm and the relative surface area of the attack is less than 50%.

De plus les présents inventeurs ont constaté que de manière surprenante un produit filé essentiellement recristallisé en alliage selon l'invention présente après usinage et anodisation une rugosité améliorée. Notamment, après polissage miroir et anodisation à une température de 30°C avec une solution comprenant 180 g/l d'acide sulfurique et 14g/l d'acide oxalique et 15 g/l de glycerol pour obtenir une couche d'oxyde d'épaisseur 30 µm le produit filé selon l'invention présente une rugosité Rz sur une génératrice parallèle à l'axe de filage inférieure ou égale à 1,7 µm et de préférence inférieure à 1,2 µm.Furthermore, the present inventors have noted that, surprisingly, a spun product essentially recrystallized from an alloy according to the invention has improved roughness after machining and anodization. In particular, after mirror polishing and anodizing at a temperature of 30°C with a solution comprising 180 g/l of sulfuric acid and 14g/l of oxalic acid and 15 g/l of glycerol to obtain a layer of oxide. thickness 30 µm the spun product according to the invention has a roughness Rz on a generatrix parallel to the spinning axis less than or equal to 1.7 µm and preferably less than 1.2 µm.

Les produits filés selon l'invention sont également avantageux en ce que pour une anodisation dite « dure » la durée d'anodisation est diminuée ce qui est favorable pour la productivité. Ainsi, un produit filé selon l'invention est caractérisé en ce que la durée d'anodisation pour obtenir une couche anodique d'épaisseur 30 µm dans une solution 200g/l H2SO4 à 5°C est inférieure à 30 minutes pour une densité de courant de 3A/dm2 ou autrement dit la vitesse de croissance d'oxyde est supérieure à 1 µm/min.The spun products according to the invention are also advantageous in that for so-called “hard” anodizing the anodizing time is reduced, which is favorable for productivity. Thus, a spun product according to the invention is characterized in that the anodization time to obtain an anodic layer with a thickness of 30 µm in a 200g/l H2SO4 solution at 5°C is less than 30 minutes for a current density of 3A/dm 2 or in other words the oxide growth speed is greater than 1 µm/min.

L'invention a également pour objet le procédé de fabrication des produits filés selon l'invention.The invention also relates to the process for manufacturing the spun products according to the invention.

Dans le procédé de fabrication selon l'invention, on élabore un alliage d'aluminium de composition selon l'invention, et on le coule typiquement sous forme de billette. La billette est ensuite homogénéisée à une température d'au moins d'au moins 580 °C. La température d'homogénéisation choisie contribue notamment à obtenir une structure granulaire essentiellement recristallisée. La billette ainsi homogénéisée est ensuite filée, la température initiale de filage étant inférieure à 550 °C et de préférence inférieure à 540 °C. Une température initiale de filage d'au moins 450 °C est préférée. Après filage on met en solution et on trempe de préférence avec de l'eau le produit filé obtenu, la mise en solution pouvant soit être effectuée grâce à la chaleur générée pendant le filage soit réalisée dans un traitement thermique séparé. La trempe effectuée en sortie de filière sur chaleur de filage, typiquement avec de l'eau est avantageuse.In the manufacturing process according to the invention, an aluminum alloy of composition according to the invention is produced, and it is typically cast in the form of a billet. The billet is then homogenized at a temperature of at least at least 580°C. The chosen homogenization temperature contributes in particular to obtaining an essentially recrystallized granular structure. The billet thus homogenized is then spun, the initial spinning temperature being lower than 550°C and preferably lower than 540°C. An initial spinning temperature of at least 450°C is preferred. After spinning, the spun product obtained is preferably dissolved and quenched with water, the solution being able to either be carried out using the heat generated during spinning or carried out in a separate heat treatment. Quenching carried out at the die outlet on spinning heat, typically with water, is advantageous.

Optionnellement on redresse et/ou on déforme à froid typiquement par traction et/ou étirage, et/ou on fait mûrir le produit filé. Avantageusement la déformation à froid est suffisante, typiquement d'au moins 7%, pour influencer les propriétés mécaniques après revenu. La maturation éventuelle est typiquement de quelques heures à quelques jours. Le produit filé est ensuite revenu à une température comprise entre 150 et 200 °C pendant une durée comprise entre 5 et 25 heures pour obtenir un état revenu T6 ou T8.Optionally the spun product is straightened and/or cold deformed typically by traction and/or stretching, and/or the spun product is matured. Advantageously, the cold deformation is sufficient, typically at least 7%, to influence the mechanical properties after tempering. The eventual maturation is typically a few hours to a few days. The spun product is then returned to a temperature of between 150 and 200°C for a period of between 5 and 25 hours to obtain a T6 or T8 tempered state.

Il est possible après revenu d'effectuer une déformation à froid typiquement par étirage de façon à obtenir un état T9.It is possible after tempering to carry out cold deformation typically by stretching so as to obtain a T9 state.

L'invention a également pour objet un procédé de fabrication d'une pièce mécanique décolletée et anodisée dans lequel, successivement,

  1. a. on prépare un produit filé selon l'invention,
  2. b. on usine le produit filé pour obtenir une pièce mécanique décolletée,
  3. c. optionnellement on met en forme la pièce mécanique ainsi obtenue
  4. d. on réalise une anodisation de la pièce mécanique ainsi obtenue, l'épaisseur d'oxyde étant au moins égale à 20 µm
The invention also relates to a method of manufacturing a turned and anodized mechanical part in which, successively,
  1. has. a spun product is prepared according to the invention,
  2. b. the spun product is machined to obtain a turned mechanical part,
  3. vs. optionally we shape the mechanical part thus obtained
  4. d. the mechanical part thus obtained is anodized, the oxide thickness being at least equal to 20 µm

Dans un mode de réalisation l'anodisation est réalisée à une température comprise entre 0 et 10 °C avec une solution contenant 100 à 250 g/l d'acide sulfurique avec une densité de courant de 1 à 3 A/dm2 avec une vitesse de croissance d'oxyde supérieure à 1 µm/min. Les produits filés selon l'invention permettent notamment dans ces conditions de diminuer la durée d'anodisation par rapport aux produits selon l'art antérieur.In one embodiment the anodization is carried out at a temperature between 0 and 10°C with a solution containing 100 to 250 g/l of sulfuric acid with a current density of 1 to 3 A/dm2 with a speed of oxide growth greater than 1 µm/min. The spun products according to the invention make it possible in particular, under these conditions, to reduce the anodizing time compared to the products according to the prior art.

Dans un autre mode de réalisation, l'anodisation est réalisée à une température comprise entre 15 et 40 °C avec une solution comprenant 100 à 250 g/l d'acide sulfurique et 10 à 30 g/l d'acide oxalique et 5 à 30 g/l d'au moins un polyol. Avantageusement au moins un polyol est choisi parmi l'ethylene glycol, le propylène glycol ou le glycérol. Préférentiellement l'anodisation est réalisée avec une densité de courant comprise entre 1 et 5 A/dm2 et de préférence de 2 et 4 A/dm2.In another embodiment, the anodization is carried out at a temperature between 15 and 40 ° C with a solution comprising 100 to 250 g/l of sulfuric acid and 10 to 30 g/l of oxalic acid and 5 to 30 g/l of at least one polyol. Advantageously at least one polyol is chosen from ethylene glycol, propylene glycol or glycerol. Preferably the anodization is carried out with a current density of between 1 and 5 A/dm 2 and preferably 2 and 4 A/dm 2 .

Préférentiellement l'épaisseur de couche anodique obtenue est comprise entre 15 et 40 µm.Preferably the thickness of the anodic layer obtained is between 15 and 40 µm.

L'invention concerne également les pièces mécaniques décolletées et anodisées obtenues par le procédé selon l'invention. Ces pièces mécaniques sont avantageuses car simultanément elles présentent une rugosité Rz sur une génératrice parallèle à l'axe de filage inférieure ou égale à 2,3 µm et de préférence inférieure ou égale à 1,7 µm et leur résistance à la corrosion intergranulaire selon le test ISO 11846 méthode B est telle que la profondeur maximale de corrosion sur une coupe transversale du produit filé est inférieure à 200 µm et que la superficie relative de l'attaque est inférieure à 50 %.The invention also relates to the turned and anodized mechanical parts obtained by the process according to the invention. These mechanical parts are advantageous because simultaneously they have a roughness Rz on a generator parallel to the spinning axis less than or equal to 2.3 µm and preferably less than or equal to 1.7 µm and their resistance to intergranular corrosion according to the ISO 11846 method B test is such that the maximum depth of corrosion on a cross section of the spun product is less than 200 µm and the relative surface area of the attack is less than 50%.

L'utilisation d'un produit filé selon l'invention pour réaliser une pièce mécanique décolletée telle qu'un piston de frein ou un élément de boite de vitesse est avantageuse.The use of a spun product according to the invention to produce a turned mechanical part such as a brake piston or a gearbox element is advantageous.

ExemplesExamples Exemple 1Example 1

Dans cet exemple, on a préparé deux alliages dont la composition est donnée dans le tableau 1. Tableau 1 : Composition des alliages (% en poids) Si Fe Cu Mn Mg Cr Ti Zr Ni Pb Bi A 0,6 0,26 0,24 0,03 1,1 0,05 0,02 < 0,01 < 0,01 0,25 0,5 B 0,7 0,40 0,30 0,11 1,0 0,11 0,02 < 0,01 0,01 0,38 0,7 In this example, two alloys were prepared, the composition of which is given in Table 1. Table 1: Composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi HAS 0.6 0.26 0.24 0.03 1.1 0.05 0.02 <0.01 <0.01 0.25 0.5 B 0.7 0.40 0.30 0.11 1.0 0.11 0.02 <0.01 0.01 0.38 0.7

Les alliages ont été coulés sous forme de billettes de diamètre 254 mm, homogénéisées à 585 °C puis filées sous forme de barres de section transversale 15 x 100 mm, par filage direct, la température initiale de filage étant 530 °C. La pression nécessaire pour initier le filage était de 140 bar pour l'alliage A selon l'invention, significativement inférieure à la pression nécessaire pour initier le filage de l'alliage B qui était de 160 bar. La vitesse de filage était de 8,3 m/min pour la billette en alliage A alors qu'elle était de 7,2 m/min pour l'alliage B. Des arrachements lors du filage ont été observées pour l'alliage B alors que ces fissurations n'ont pas été observée pour l'alliage A. L'alliage A présentait ainsi une meilleure friabilité que l'alliage B.The alloys were cast in the form of billets with a diameter of 254 mm, homogenized at 585 °C then spun in the form of bars with a cross section of 15 x 100 mm, by direct spinning, the initial spinning temperature being 530 °C. The pressure necessary to initiate spinning was 140 bar for alloy A according to the invention, significantly lower than the pressure necessary to initiate spinning of alloy B which was 160 bar. The spinning speed was 8.3 m/min for alloy A billet while it was 7.2 m/min for alloy B. Pull-offs during spinning were observed for alloy B while that these cracks were not observed for alloy A. Alloy A thus had better friability than alloy B.

Les produits filés ont été trempés en sortie de presse. Les barres ainsi obtenues ont été tractionnées de 1% puis ont subi un revenu pour obtenir un état T6.The spun products were soaked after leaving the press. The bars thus obtained were tensile by 1% then subjected to tempering to obtain a T6 state.

La barre en alliage A ainsi obtenue présentait une structure granulaire recristallisée à ¼ épaisseur tandis que la barre en alliage B présentait une structure granulaire non recristallisée à ¼ épaisseur. Les propriétés mécaniques des barres ainsi obtenues, mesurées dans la direction du filage sont présentées dans le Tableau 2. Tableau 2 : Propriétés mécaniques obtenues Alliage Rm (MPa) Rp0,2 (MPa) A% A 327 306 12 B 370 348 13 The alloy A bar thus obtained had a recrystallized granular structure at ¼ thickness while the alloy B bar had a non-recrystallized granular structure at ¼ thickness. The mechanical properties of the bars thus obtained, measured in the spinning direction, are presented in Table 2. Table 2: Mechanical properties obtained Alloy Rm (MPa) R p0.2 (MPa) HAS% HAS 327 306 12 B 370 348 13

Les barres obtenues étaient aptes au décolletage.The bars obtained were suitable for bar turning.

Les barres ont ensuite subi les traitements de préparation suivants : usinage de 2 mm, polissage miroir puis anodisation selon le procédé (1) ou le procédé (2) décrit dans le tableau 3 Tableau 3 - Description des procédés d'anodisation 1 et 2 Procédé Prétraitement avant anodisation Electrolyte pour anodisation Densité de courant (A/dm2) Température (°C) Epaisseur d'oxyde (µm) 1 Dégraissage Novaclean D708 200g/l H2SO4 3 5 30 2 Dégraissage Novaclean D708 180g/l H2SO4 + 14g/l acide oxalique + 15g/l glycerol 2 30 30 The bars then underwent the following preparation treatments: 2 mm machining, mirror polishing then anodizing according to process (1) or process (2) described in table 3 Table 3 - Description of anodizing processes 1 and 2 Process Pretreatment before anodizing Electrolyte for anodizing Current density (A/dm 2 ) Temperature (°C) Oxide thickness (µm) 1 Novaclean D708 degreasing 200g/l H 2 SO 4 3 5 30 2 Novaclean D708 degreasing 180g/l H 2 SO 4 + 14g/l oxalic acid + 15g/l glycerol 2 30 30

Les résultats obtenus pour la rugosité sont donnés dans le Tableau 4. Tableau 4. Résultats des mesures de rugosité après traitement d'anodisation. Ail iag e Procédé d'anodis ation Densité de courant (A/dm2) Temper ature (°C) Durée d'anodisati on (min) Moyenne Ra (µm) Moyenne Rz (µm) Moyenn e Rmax (µm) A 1 3 5 23 0,35 2,33 3,28 A 2 2 30 53 0,09 0,95 1,78 B 1 3 5 34 0,39 2,46 3,46 The results obtained for roughness are given in Table 4. Table 4. Results of roughness measurements after anodizing treatment. Garlic Anodizing process Current density (A/dm 2 ) Temperature (°C) Anodizing time (min) Average Ra (µm) Average Rz (µm) Average Rmax (µm) HAS 1 3 5 23 0.35 2.33 3.28 HAS 2 2 30 53 0.09 0.95 1.78 B 1 3 5 34 0.39 2.46 3.46

Exemple 2Example 2

Dans cet exemple, on a préparé deux alliages dont la composition est donnée dans le tableau 5. Tableau 5 : Composition des alliages (% en poids) Si Fe Cu Mn Mg Cr Ti Zr Ni Pb Bi A 0,6 0,26 0,24 0,03 1,1 0,05 0,02 < 0,01 < 0,01 0,25 0,5 C 0,7 0,37 0,32 0,12 1,0 0,12 0,03 < 0,01 < 0,01 0,35 0,7 In this example, two alloys were prepared, the composition of which is given in Table 5. Table 5: Composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi HAS 0.6 0.26 0.24 0.03 1.1 0.05 0.02 <0.01 <0.01 0.25 0.5 VS 0.7 0.37 0.32 0.12 1.0 0.12 0.03 <0.01 <0.01 0.35 0.7

Les alliages ont été coulés sous forme de billettes de diamètre 254 mm, homogénéisées à 585 °C puis filées sous forme de barres cylindriques et trempées en sortie de presse. Les barres ainsi obtenues ont été tractionnées de 1% puis ont subi un revenu et ont été étirées pour obtenir des barres de diamètre 14 mm.The alloys were cast in the form of billets with a diameter of 254 mm, homogenized at 585 °C then spun into the form of cylindrical bars and quenched at the end of the press. The bars thus obtained were tensile by 1% then subjected to tempering and were stretched to obtain bars with a diameter of 14 mm.

La barre en alliage A ainsi obtenue présentait une structure granulaire recristallisée à ¼ épaisseur tandis que la barre en alliage B présentait une structure granulaire non recristallisée à ¼ épaisseur.The alloy A bar thus obtained had a recrystallized granular structure at ¼ thickness while the alloy B bar had a non-recrystallized granular structure at ¼ thickness.

Les barres obtenues étaient aptes au décolletage.The bars obtained were suitable for bar turning.

La résistance à la corrosion a été évaluée en milieu de barre selon le test normalisé EN ISO 11846 :2008 (méthode B). Les résultats sont présentés dans le Tableau 6 et sur la Figure 1. Tableau 6 - Résultats des essais de corrosion Alliage Surface de la barre Surface de la coupe transversale Profondeur maximale de l'attaque (µm) Superficie relative de l'attaque (%) Profondeur maximale de l'attaque (µm) Superficie relative de l'attaque (%) A 330 20 50 10 A 300 10 80 10 C 305 100 690 100 C 300 100 720 100 C 370 100 600 100 Corrosion resistance was evaluated in the middle of the bar according to the standardized test EN ISO 11846:2008 (method B). The results are presented in Table 6 and on the Figure 1 . Table 6 - Corrosion test results Alloy Bar surface Cross section area Maximum attack depth (µm) Relative area of attack (%) Maximum attack depth (µm) Relative area of attack (%) HAS 330 20 50 10 HAS 300 10 80 10 VS 305 100 690 100 VS 300 100 720 100 VS 370 100 600 100

Exemple 3Example 3

Dans cet exemple, on a préparé deux alliages dont la composition est donnée dans le tableau 7. Tableau 7 : composition des alliages (% en poids) Si Fe Cu Mn Mg Cr Ti Zr Ni Pb Bi D 0,6 0,24 0,21 0,01 1,04 0,05 0,02 < 0,01 < 0,01 0,23 0,4 E 0,7 0,40 0,30 0,11 1,01 0,12 0,02 < 0,01 < 0,01 0,34 0,7 In this example, two alloys were prepared, the composition of which is given in Table 7. Table 7: composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi D 0.6 0.24 0.21 0.01 1.04 0.05 0.02 <0.01 <0.01 0.23 0.4 E 0.7 0.40 0.30 0.11 1.01 0.12 0.02 <0.01 <0.01 0.34 0.7

Les alliages ont été coulés sous forme de billettes, homogénéisées puis filées sous forme de barres de diamètre 30 mm.The alloys were cast in the form of billets, homogenized then spun into the form of bars with a diameter of 30 mm.

Les produits filés ont été trempés en sortie de presse. Les barres ainsi obtenues ont été tractionnées de 1% puis ont subi un revenu pour obtenir des barres en état T6.The spun products were soaked after leaving the press. The bars thus obtained were tensile by 1% then subjected to tempering to obtain bars in T6 condition.

Les deux alliages D et E sont testés à l'état T6 et sont différents par leur structure granulaire. La barre en alliage D ainsi obtenue présentait une structure granulaire recristallisée à ¼ épaisseur tandis que la barre en alliage E présentait une structure granulaire non recristallisée à ¼ épaisseur. Les propriétés mécaniques des barres ainsi obtenues, mesurées dans la direction du filage sont présentées dans le Tableau 8. Tableau 8 : Propriétés mécaniques obtenues Alliage Etat Barre Diamètre (mm) Rm (MPa) Rp0,2 (MPa) A% D T6 30 330 298 17,9 E T6 30 359 341 12,6 The two alloys D and E are tested in the T6 state and are different in their granular structure. The alloy D bar thus obtained had a recrystallized granular structure at ¼ thickness while the alloy E bar had a non-recrystallized granular structure at ¼ thickness. The mechanical properties of the bars thus obtained, measured in the direction of spinning, are presented in Table 8. Table 8: Mechanical properties obtained Alloy State Bar Diameter (mm) Rm (MPa) R p0.2 (MPa) HAS% D T6 30 330 298 17.9 E T6 30 359 341 12.6

Exemple 4Example 4

Dans cet exemple, on a préparé deux alliages dont la composition est donnée dans le tableau 9. Tableau 9 : composition des alliages (% en poids) Si Fe Cu Mn Mg Cr Ti Zr Ni Pb Bi F 0,6 0,23 0,27 0,04 1,06 0,05 0,02 <0.01 0.01 0.28 0.5 G 0,6 0,26 0,24 0,01 1,03 0,07 0,02 <0.01 0,01 0,24 0,4 In this example, two alloys were prepared whose composition is given in table 9. Table 9: composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi F 0.6 0.23 0.27 0.04 1.06 0.05 0.02 <0.01 0.01 0.28 0.5 G 0.6 0.26 0.24 0.01 1.03 0.07 0.02 <0.01 0.01 0.24 0.4

Les alliages ont été coulés sous forme de billettes de diamètre 261 mm, homogénéisées à 585 °C puis filées sous forme de barres.The alloys were cast in the form of 261 mm diameter billets, homogenized at 585 °C and then spun into bar form.

Les produits filés ont été trempés en sortie de presse. Les barres ainsi obtenues ont été tractionnées de 1%, puis ont subi un revenu suivi d'une déformation à froid pour obtenir un produit à l'état T9. L'alliage F a été étiré de telle sorte à obtenir une barre de diamètre 24.5 mm et l'alliage G une barre de diamètre 26 mm.The spun products were soaked after leaving the press. The bars thus obtained were tensile by 1%, then underwent tempering followed by cold deformation to obtain a product in the T9 state. Alloy F was stretched in such a way as to obtain a bar with a diameter of 24.5 mm and alloy G a bar with a diameter of 26 mm.

Les barres en alliage F et G ainsi obtenues présentent une structure granulaire recristallisée à ¼ épaisseur.The F and G alloy bars thus obtained have a recrystallized granular structure at ¼ thickness.

Les propriétés mécaniques des barres ainsi obtenues à l'état T9, mesurées dans la direction du filage sont présentées dans le Tableau 9. Tableau 9 : Propriétés mécaniques obtenues Alliage Etat Barre diamètre (mm) Rm (MPa) Rp0,2 (MPa) A% F T9 24.5 352 344 9 G T9 26 357 346 9 The mechanical properties of the bars thus obtained in the T9 state, measured in the spinning direction, are presented in Table 9. Table 9: Mechanical properties obtained Alloy State Bar diameter (mm) Rm (MPa) R p0.2 (MPa) HAS% F T9 24.5 352 344 9 G T9 26 357 346 9

Exemple 5Example 5

Dans cet exemple, on a préparé un alliage dont la composition est donnée dans le tableau 10. Tableau 10 : composition des alliages (% en poids) Si Fe Cu Mn Mg Cr Ti Zr Ni Pb Bi H 0,6 0,24 0,21 0,01 1,04 0,05 0,02 <0.01 0.01 0.23 0.4 In this example, an alloy was prepared whose composition is given in table 10. Table 10: composition of alloys (% by weight) If Fe Cu Mn Mg Cr Ti Zr Neither Pb Bi H 0.6 0.24 0.21 0.01 1.04 0.05 0.02 <0.01 0.01 0.23 0.4

L'alliage a été coulé sous forme de billettes de diamètre 261 mm, homogénéisées puis filées sous forme de barres.The alloy was cast in the form of 261 mm diameter billets, homogenized and then spun into bar form.

Une barre a été trempée en sortie de presse, tractionnée de 1% puis déformée à froid pour obtenir un diamètre final de 24.6 mm puis a subi un revenu pour obtenir un produit à l'état T8.A bar was quenched at the end of the press, tensile by 1% then cold deformed to obtain a final diameter of 24.6 mm and then tempered to obtain a product in the T8 state.

Une autre barre a été trempée en sortie de presse, tractionnée à froid d'environ 1%, puis a subi un revenu suivi d'une déformation à froid pour obtenir un diamètre final de 24.5 mm pour obtenir un produit à l'état T9.Another bar was quenched at the end of the press, cold pulled by approximately 1%, then tempered followed by cold deformation to obtain a final diameter of 24.5 mm to obtain a product in the T9 state.

Les barres en alliage H ainsi obtenues présentent une structure granulaire recristallisée à ¼ épaisseur.The H alloy bars thus obtained have a recrystallized granular structure at ¼ thickness.

Les propriétés mécaniques des barres ainsi obtenues à l'état T8 et T9, mesurées dans la direction du filage sont présentées dans le Tableau 11.The mechanical properties of the bars thus obtained in the T8 and T9 state, measured in the spinning direction, are presented in Table 11.

L'aptitude au décolletage a été évaluée par un test d'usinage tel que décrit dans la demande internationale WO2013/170953 au paragraphe [0039]. Le test consiste à déterminer l'aptitude à la fragmentation des copeaux en mesurant le nombre de copeaux dans une masse déterminée de copeaux collectés, ici 100g. Le poids de 50 copeaux a aussi déterminé. Les résultats sont présentés dans le tableau 11.The suitability for bar turning was evaluated by a machining test as described in the international application WO2013/170953 in paragraph [0039]. The test consists of determining the chip fragmentation ability by measuring the number of chips in a determined mass of chips collected, here 100g. The weight of 50 chips has also been determined. The results are presented in Table 11.

L'usinage est effectué en utilisant un tour SP 12 CNC et un insert rhombique avec une forme basique de 80° vendu sous la marque enregistrée SANDVIK Coromant Coroturn® 107 avec la référence CCGX 09 T3 04-AL, conçu pour les alliages d'aluminium. Les paramètres d'usinage utilisés sont une vitesse de rotation de 3000 tour/min, une alimentation de 0,3 mm/tour et une profondeur de découpe de 3,5 mm. Tableau 11 : Résultats obtenus après le test d'aptitude au décolletage décrit demande internationale WO2013/170953 au paragraphe [0039] Alliage Etat Diamètre de barre (mm) Rm (MPa) Rp0.2 (MPa) A% Nombre de copeaux dans 100g Masse de 50 copeaux (g) H T9 24.5 380 357 8 4272 1,1705 T8 24.6 348 321 15,6 4744 1,0539 Machining is carried out using an SP 12 CNC lathe and a rhombic insert with a basic shape of 80° sold under the registered brand SANDVIK Coromant Coroturn ® 107 with the reference CCGX 09 T3 04-AL, designed for aluminum alloys . The machining parameters used are a rotation speed of 3000 rpm, a feed of 0.3 mm/rev and a cutting depth of 3.5 mm. Table 11: Results obtained after the bar turning ability test described in international application WO2013/170953 in paragraph [0039] Alloy State Bar diameter (mm) Rm (MPa) Rp0.2 (MPa) HAS% Number of chips in 100g Mass of 50 chips (g) H T9 24.5 380 357 8 4272 1.1705 T8 24.6 348 321 15.6 4744 1.0539

Claims (13)

  1. Extruded product suitable for turning, made of an aluminum alloy having a composition in wt% of Si 0.4 - 0.8; Mg 0.8 - 1.2; Cu 0.20 - 0.4; Fe 0.05 - 0.4; Mn ≤ 0.10; Ti < 0.15; Cr ≤ 0.08; Zr<0.04, Bi 0.4 - 0.8; Pb 0.2 - 0.4; other elements < 0.05 each and < 0.15 in total remains aluminum, characterized in that its composition is such that Cr + Mn ≤ 0.15, and in that its granular structure has a recrystallization rate at ¼ thickness greater than 70%.
  2. Extruded product according to claim 1, characterized in that the copper content is at least 0.23 wt% and/or the iron content is at least 0.20 wt%.
  3. Extruded product according to any one of claims 1 through 2, characterized in that the composition thereof in wt% is Pb 0.2 - 0.34.
  4. Extruded product according to any one of claims 1 through 3, characterized in that, after mirror polishing and anodizing at a temperature of 30°C with a solution comprising 180 g/l sulfuric acid and 14 g/l oxalic acid and 15 g/l glycerol in order to make an oxide layer 30 µm thick, the product has a roughness Rz on a generatrix parallel to the extrusion axis, measured according to standard ISO 4287, that is equal to or less than 1.7 µm and preferably less than 1.2 µm.
  5. Extruded product according to any one of claims 1 through 4, characterized in that the anodizing time in order to obtain an anodic layer 30 µm thick in a solution of 200 g/l H2SO4 at 5°C is less than 30 minutes for a current density of 3 A/dm2.
  6. Extruded product according to any one of claims 1 through 5, characterized in that the intergranular corrosion resistance thereof per test ISO 11846, method B, is such that the maximum corrosion depth on a cross-sectional cut of the extruded product is less than 200 µm and the corresponding attacked surface area is less than 50%.
  7. Use of an extruded product according to any one of claims 1 through 6 to produce a brake piston or a gearbox part.
  8. Method for producing an extruded product according to any one of claims 1 through 3 through the following steps
    a. an aluminum alloy having a composition according to any one of claims 1 through 3 is prepared and is typically cast in the form of a billet
    b. said billet is homogenized at a temperature of at least 580°C,
    c. said homogenized billet is extruded to produce an extruded product, the initial extrusion temperature being less than 550°C,
    d. said extruded product is placed in a solution and quenched, preferably with water, with said immersion in solution being done either at the temperature generated during the extrusion process, or in a separate heat treatment,
    e. optionally, it is straightened and/or cold deformed, typically by traction and/or drawing, and/or said extruded product is naturally aged,
    f. artificial aging is performed at a temperature of between 150 and 200°C for 5 to 25 hours,
    g. optionally, cold deforming is typically done by drawing said extruded product.
  9. Method for producing a turned and anodized mechanical part through the following steps
    a. an extruded product is prepared according to the method of claim 8,
    b. the extruded product is machined to make a turned mechanical part,
    c. optionally, the resulting mechanical part is formed
    d. the resulting mechanical part is anodized, with the oxide thickness being at least 15 µm
  10. Production method according to claim 9 in which said anodizing is done at a temperature of between 0 and 10°C with a solution containing 100 to 250 g/l sulfuric acid with a current density of 1 to 3 A/dm2 with an oxide growth rate greater than 1 µm/min.
  11. Production method according to claim 9 in which said anodizing is done at a temperature of between 15 and 40°C with a solution comprising 100 to 250 g/l sulfuric acid and 10 to 30 g/l oxalic acid, and 5 to 30 g/l of at least one polyhydric alcohol.
  12. Method according to claim 11 in which at least one polyhydric alcohol is chosen from ethylene glycol, propylene glycol, or glycerol.
  13. Method according to any one of claims 9 through 12 in which said machining is performed by turning in order to obtain a turned mechanical part.
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WO2015144303A3 (en) 2016-06-02
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FR3018823B1 (en) 2018-01-05
CN106133163B (en) 2019-07-23
CA2942426A1 (en) 2015-10-01
CN106133163A (en) 2016-11-16
EP3122912A2 (en) 2017-02-01
US10724123B2 (en) 2020-07-28
US20180202026A1 (en) 2018-07-19

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