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
  • C22F1/002—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 rod or rod type spun products, made of aluminum alloy of the AA6xxx series, and in particular parts which have undergone post-machining surface treatment.
• Bar turning refers to a field of manufacture by machining, in large series, mechanical parts typically of revolution (screw, bolt, shaft, piston, etc.) by removal of material from bars or rods of metal.
• the parts are produced at high speeds on manual or digital cutting machines.
• the productivity and the surface condition as well as the dimensional accuracy of the final part are the main objectives attached to this type of manufacturing.
• the parts may undergo a protective surface treatment, typically by anodizing.
• the so-called hard anodization 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.
• the pieces thus produced find their application in various fields, from watchmaking to medical equipment, through the fields of transport (aeronautics, railway, automobile) and industrial (electrical, electronic, hydraulic ).
• the international application WO2005 / 100623 discloses alloys, preferably in spun form, suitable for free cutting and composition in 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.
• the problem that the present invention seeks to solve is to obtain spun products which are simultaneously capable of free cutting and resistant to intergranular corrosion and which after machining and anodizing a low roughness.
• a first object of the invention is a spun product suitable for cutting aluminum alloy 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 ⁇ 0.10; Bi ⁇ 0.8; Pb ⁇ 0.4; other elements ⁇ 0.05 each and ⁇ 0.15 remains aluminum, characterized in that its granular structure is essentially recrystallized.
• a second object of the invention is the use of a spun product according to the invention for the manufacture of a brake piston or a gearbox element.
• Another subject of the invention is a process for producing a spun product according to the invention in which, successively,
• an aluminum alloy of composition according to the invention is produced, and is typically cast in the form of a billet
• said billet is homogenized at a temperature of at least 550 ° C
• said billet is homogenized to obtain a spun product, the initial spinning temperature being less than 550 ° C,
• said spun product is brought into solution and is preferably quenched with water, said dissolution being able to be carried out either by virtue of the heat generated during the spinning or by a separate heat treatment,
• an income is produced at a temperature between 150 and 200 ° C for a period of between 5 and 25 hours
• said spun product is typically cold deformed by drawing.
• Yet another object of the invention is a method of manufacturing a mechanized and anodized mechanical part in which successively
• the spun product is machined to obtain a low-cut mechanical part
• the mechanical part thus obtained is shaped
• Yet another object of the invention is a mechanized and anodized mechanical part obtained by the method of manufacturing a mechanical part according to the invention.
• Figure 1 Observation of the samples after the standardized corrosion test according to EN ISO 1846: 2008 (method B).
• the static mechanical characteristics in other words the ultimate tensile strength Rm, the conventional yield stress at 0.2% elongation Rp0.2 and the elongation at break A%, are determined by a tensile test according to ISO 6892-1, the sampling and the direction of the test being defined by EN 485-1.
• the bar turning ability is evaluated by a machining test as described in international application WO2013 / 170953 in paragraph [0039].
• the test consists in determining the fragmentation ability of the chips by measuring the number of chips in a determined mass of chips collected, here 100g. Machining is carried out using a SP 12 CNC lathe and a rhombic insert with a basic 80 ° shape sold under the registered trademark S AND VIK Coromant Coroturn® 107 with the reference CCGX 09 T3 04-AL, designed for alloys with 'aluminum.
• the machining parameters used are a rotation speed of 3000 rpm, a feed of 0.3 mm / revolution and a cutting depth of 3.5 mm.
• the products spun according to the invention are suitable for bar turning, that is to say that they present the test described in international application WO2013 / 170953 in paragraph [0039] a number of chips per 100g of chips of at least 3000 and preferably at least 4000.
• the corrosion resistance was evaluated according to the standardized test EN ISO 1846: 2008 (method B).
• the surface 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., rinsing and immersion for 2 minutes in 2% nitric acid.
• Rmax maximum height of the roughness profile, which is the largest of the R Z i values over the evaluation length
• R z Average profile height R 2 , which is the arithmetic mean of the individual values R Z i over the evaluation length
• ⁇ Ra Average roughness difference is the arithmetic mean of all the ordinates of the profile over the evaluation length.
• a substantially recrystallized granular structure is called a granular structure such that the degree of recrystallization at a thickness is greater than 70% and preferably greater than 90%.
• the recrystallization rate is defined as the surface fraction 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 to obtain a layer of oxide of thickness of at least 20 ⁇ and much greater than the roughness before anodization.
• the roughness after anodization is at least 1.80 ⁇ 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 free cutting according to the invention are aluminum alloy 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 ⁇ 0.10; Bi ⁇ 0.8; Pb ⁇ 0.4; other elements ⁇ 0.05 each and ⁇ 0, 15 remains 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 preferably 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 by controlling the manganese content and the 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.
• the control of the zirconium content can also be important for obtaining the essentially recrystallized granular 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 spinnability is excellent, in particular the pressure necessary to initiate the 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 yield strength is preferably in the T6 state of at least 300 MPa and their elongation being at least 10% and their elastic limit being preferably in the T9 state of at least 330 MPa and their elongation being at least 8%.
• the present inventors have found that a substantially recrystallized spun product of the invention has improved intergranular corrosion resistance.
• the spun products according to the invention have a 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 ⁇ and that the relative 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 anodizing.
• a solution comprising 180 g / l of sulfuric acid and 14 g / l of oxalic acid and 15 g / l of glycerol to obtain an oxide layer.
• Thickness 30 ⁇ the product spun according to the invention has a roughness Rz on a generatrix parallel to the spinning axis less than or equal to 1.7 ⁇ and preferably less than 1, 2 ⁇ .
• the spun products according to the invention are also advantageous in that for a so-called "hard” anodization, the anodizing time is reduced, which is favorable for productivity.
• a spun product according to the invention is characterized in that the anodizing time to obtain an anode layer of thickness 30 ⁇ in a 200 g / l H 2 SO 4 solution at 5 ° C. is less than 30 minutes for a current density. of 3 A / dm 2 or in other words the oxide growth rate is greater than 1 ⁇ / min.
• the subject of the invention is also the process for producing the spun products according to the invention.
• an aluminum alloy of composition according to the invention is produced and is typically cast in the form of a billet.
• the billet is then homogenized at a temperature of at least 550 ° C and preferably at least 580 ° C.
• the chosen homogenization temperature contributes in particular to obtaining a substantially recrystallized granular structure.
• the billet thus homogenized is then spun, the initial spinning temperature being less than 550 ° C and preferably less than 540 ° C.
• An initial spinning temperature of at least 450 ° C is preferred.
• the resultant spun product is dissolved and the water product obtained is preferably quenched with water, the solution being able to be carried out by means of the heat generated during the spinning or in a separate heat treatment.
• the quenching carried out at the die outlet on spinning heat, typically with water is advantageous.
• colder and / or cold deformation is typically carried out by pulling and / or drawing, and / or ripening the spun product.
• the cold deformation is sufficient, typically at least 7%, to influence the mechanical properties after income.
• the eventual maturation is typically from a few hours to a few days.
• the spun product is then returned to a temperature between 150 and 200 ° C for a period of between 5 and 25 hours to obtain a T6 or T8 state.
• the subject of the invention is also a process for manufacturing a mechanized and anodized mechanical part in which, successively,
• the spun product is machined to obtain a low-cut mechanical part, c. optionally, the mechanical part thus obtained is shaped
• the mechanical part thus obtained is anodized, the oxide thickness being at least 20 ⁇
• 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 / dm 2 with a oxide growth greater than 1 ⁇ / min.
• the spun products according to the invention make it possible in these conditions to reduce the anodizing time compared to products according to the prior art.
• the anodization is carried out at a temperature of 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 of 2 and 4 A / dm 2 .
• the anodic layer thickness obtained is between 15 and 40 ⁇ .
• the invention also relates to mechanical parts cut and anodized obtained by the method according to the invention. These mechanical parts are advantageous because simultaneously they have a roughness Rz on a generatrix parallel to the spinning axis less than or equal to 2.3 ⁇ and preferably less than or equal to 1, 7 ⁇ 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 ⁇ and that the relative area of the attack is less than 50%.
• the alloys were cast in the form of 254 mm diameter billets, homogenized at 585 ° C. and then spun in the form of 15 ⁇ 100 mm cross-section bars, by direct spinning, the initial spinning temperature being 530 ° C.
• the pressure necessary to initiate the spinning was 140 bar for the alloy A according to the invention, significantly lower than the pressure necessary to initiate the spinning of the alloy B which was 160 bar.
• the spinning speed was 8.3 m / min for alloy billet A whereas it was 7.2 m / min for alloy B. Pull-out during spinning was observed for alloy B then that these cracks were not observed for the alloy A.
• the alloy A thus had a better flowability than the alloy B.
• the spun products were dipped at the outlet of the press.
• the bars thus obtained were split by 1% and then had an income to obtain a T6 state.
• the alloy bar A thus obtained had a granular structure recrystallized 1 ⁇ 4 thickness while the alloy bar B had a granular structure not recrystallized 1 ⁇ 4 thickness.
• the mechanical properties of the bars thus obtained, measured in the direction of the spinning are presented in Table 2.
• the bars obtained were suitable for bar turning.
• the alloys were cast in the form of billets 254 mm in diameter, homogenized at 585 ° C. and then spun in the form of cylindrical bars and quenched at the outlet of the press. The bars thus obtained were fractionated by 1% and then were tempered and stretched to obtain 14 mm diameter bars.
• the alloy bar A thus obtained had a granular structure recrystallized 1 ⁇ 4 thickness while the alloy bar B had a granular structure not recrystallized 1 ⁇ 4 thickness.
• the bars obtained were suitable for bar turning.
• the alloys were cast in the form of billets, homogenized and then spun in the form of 30 mm diameter bars.
• the spun products were dipped at the outlet of the press.
• the bars thus obtained were fractionated by 1% and then had an income to obtain bars in T6 state.
• the spun products were dipped at the outlet of the press.
• the bars thus obtained were fractionated by 1%, then underwent an income followed by a cold deformation to obtain a product in the T9 state.
• the alloy F was stretched so as to obtain a bar of diameter 24.5 mm and the alloy G a bar of diameter 26 mm.
• the alloy bars F and G thus obtained have a granular structure recrystallized 1 ⁇ 4 thickness.
• the alloy was cast in the form of billets 261 mm in diameter, homogenized and then spun in the form of bars.
• a bar was dipped at the outlet of the press, pulled by 1% and then deformed cold to obtain a final diameter of 24.6 mm and then suffered an income to obtain a product in the T8 state.
• Another bar was quenched at the press outlet, cold-chilled by about 1%, then was tempered followed by cold deformation to obtain a final diameter of 24.5 mm to obtain a product in the T9 state.
• the alloy bars H thus obtained have a granular structure recrystallized to 1 ⁇ 4 thickness.
• the bar turning ability was evaluated by a machining test as described in the international application WO2013 / 170953 in paragraph [0039].
• the test consists in determining the fragmentation ability of the chips by measuring the number of chips in a determined mass of chips collected, here 100g. The weight of 50 chips also determined. The results are shown in Table 11.
• Machining is carried out using a SP 12 CNC lathe and a rhombic insert with a basic 80 ° shape sold under the registered trademark SANDVI 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 / revolution and a cutting depth of 3.5 mm.

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• 2014
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