Classifications

• • 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
  • C22F1/05—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 of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
• • 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

Definitions

• the invention relates to the field of low-cut parts obtained from single spun or extruded products, essentially of the bar or rod type, made of aluminum alloy of the AA ⁇ xxx series whose chemical composition is optimized according to the spinnability and free cutting and which is in particular devoid of low melting point elements such as in particular lead, bismuth, indium or tin.
• Bar turning refers to a field of manufacture by machining, in large series, of parts generally of revolution (screw, bolt, shaft, etc.) by removal of material from bars or rods of metal. These, especially in the case of aluminum alloys, are generally obtained by spinning or extrusion from billets.
• 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 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 positive result thus obtained lies in the fragmentation of chips of small sizes during said machining or machining operation.
• This fragmentation allows a rapid evacuation of the material, thus a gain in productivity, but also an evacuation of the heat produced, thus avoiding a possible degradation of the final surface state of the part.
• composition is based on the presence of substitution elements also low melting point such as tin, bismuth or indium.
• patents EP 07937324 and EP 1214456 of "Reynolds Metal Company” claim respectively alloys families AA6xxx and AA2xxx with addition of tin and indium, and family AA6xxx with addition of only bismuth or bismuth and tin.
• EP 761834 of "Kaiser Aluminum” relates to alloys of the AA6xxx series with addition of tin and bismuth
• EP 0964070 and EP 0982410 of "Alusuisse” apply to alloys of the AA2xxx series with addition of tin or bismuth and tin, respectively.
• alloys containing low-melting substitution elements such as tin, bismuth or indium, do not exhibit exactly the same performance in bar turning as alloys containing lead, while the total prohibition The latter could intervene in the relatively short term. Moreover, these alloys sometimes pose brittleness problems due to the total wetting of the grain boundaries during bar turning by the phases resulting from the low-melting substitution elements.
• a solution to this problem is the use of an alloy whose aluminum-based matrix has harder particles, the origin of the creation and propagation of cracks during the bar turning operation, these cracks favoring chip fragmentation.
• the silicon alloy thus formed comprises hard phases based on silicon, at the origin of the creation and propagation of the aforementioned cracks. Indeed, these phases prevent slippage of the grains during the deformation induced by the machining operation, or bar turning, which gives rise to cavities and cracks and thus promotes chip fragmentation.
• the subject of the invention is therefore a spun product, of the bar or rod or tube type, having a very good bar turning ability, without the addition of silicon at levels greater than or equal to 1.5%, of wrought aluminum alloy wrought of chemical composition, expressed in percentages by weight: 0.8 ⁇ Si ⁇ 1.5%, preferably: 1.0 ⁇ Si ⁇ 1.5% 1.0 ⁇ Fe ⁇ 1.8%, preferably: 1.0 ⁇ Fe ⁇ 1.5% Cu: ⁇ 0.1% Mn: ⁇ 1%, preferably ⁇ 0.6%
• Mg 0.6 - 1.2%, preferably 0.6 - 0.9% Ni: ⁇ 3.0%, preferably 1.0 - 2.0% Cr: ⁇ 0.25% Ti: ⁇ 0.1% other elements ⁇ 0.05% each and 0.15% in total, remains aluminum.
• the invention also relates to a turned part from the spun product as defined above.
• FIG. 1 represents the spinning pressures, in MPa, obtained for the same length of billet according to the various alloys tested: 6xxx according to the invention, AA6262 and H Si by reference, including compositions in the chapter "Examples”.
• FIG. 2 shows the axial cutting pressures, in MPa, during the drilling tests, as a function of the cutting speed in m / min, for a constant drilling advance of 0.15 mm / rev and according to the various alloys tested, such as above.
• FIG. 3 represents the axial pressures in MPa as a function of the drilling advance in mm / rev, for a constant cutting speed of 55 m / min, according to these same alloys tested.
• the invention is based on the finding by the applicant that it is possible to obtain a very good bar turning ability, without addition of silicon to levels greater than or equal to 1.5%, unlike the prior art, ensuring the presence in sufficient amounts of intermetallic iron phases dispersed homogeneously. This characteristic allows the chip fragmentation required for this purpose during the machining operation.
• intermetallic phases are of the Al x Fe y (Mn 5 Ni) 2 S i v type , the presence of the Mn and Ni elements being optional because they provide a complement by creating particles that are also favorable to bar turning.
• the single spun products that is to say of the type bars, rods or tubes, according to the invention, exhibit a behavior during bar turning similar to the products of the prior art made from AA6262 or AA2011 series alloys containing both lead and bismuth. Furthermore, the mechanical properties, corrosion resistance and anodizing ability of the products according to the invention are similar to those obtained from said alloys.
• a minimum content of 0.8% is necessary to obtain sufficient structural hardening via the Mg 2 Si phase, taking into account the "trapping" of this element in the intermetallic phases of the AlFeSi type characteristic of the alloys according to the invention. Preferably, this minimum is increased to 1%.
• the content is strictly less than 1.5% in order to limit the risk of burning by raising the temperature during the spinning operation, resulting in particular in surface defects of the extruded product.
• Iron it is, with silicon, one of the major elements of the alloys according to the invention. Indeed, its concentration governs the amount of secondary phases mentioned above, especially at the base of the bar turning behavior. For this purpose, a minimum content strictly greater than 1.0% is prescribed.
• the upper limit of 1.8% avoids the precipitation of primary iron phases during casting of the billets, which reduces the spinnability.
• a still more preferential maximum is 1.5%.
• Manganese optional, it can participate in the formation of secondary phases favorable to bar turning behavior. Its content is limited to 1.0% because of its adverse effect on the spinning ability. An even more preferable maximum is 0.6%.
• Magnesium with silicon, it participates in the structural hardening via the Mg 2 Si phase. For this purpose, a minimum of 0.6% is required.
• Nickel just like manganese, it can participate in the formation of secondary phases favorable to bar turning behavior. Its content is limited to 3.0% to prevent the formation of primary phases with the weakening effect. A preferred range is 1.0 to 2.0%.
• Copper Its content must be less than 0.1% because of its strong curing effect which is unfavorable with regard to the spinnability.
• Chromium This is an anti-recrystallizing element which, just like manganese can form secondary phases influencing the granular structure of the alloy. Its content is kept below 0.25% because of its unfavorable impact on the spinning ability.
• Titanium acts in two joint modes: on the one hand, it promotes the refining of the primary aluminum grain, on the other hand, it influences the distribution of the aforementioned secondary phases.
• the alloy 6xxx is according to the invention while the alloys AA6262 and H Si are alloys of the prior art, the former containing lead and bismuth, the second, devoid of these elements, coupling a high silicon content to the presence of manganese and magnesium.
• the pions were then homogenized at a temperature of 545 ° C. for 5 h 30 min.
• Billet diameters of 29.6 mm and length 38 mm were machined and spun into bars of 6.7 mm diameter.
• the spinning was carried out under the same conditions of billet temperature of 480 ° C and speed of 0.6 m / min. This relatively low speed results from a similarity operation because of the size of the test samples compared with industrial conditions.
• Figure 1 shows the spinning pressures of each variant for the same length of billet.
• the variant according to the invention has a better spinnability resulting in a lower pressure of about 20% relative to the reference AA6262 and about 10% relative to the reference H Si.
• the spun bars were heat-treated, type T6, dissolved at a temperature of 56 ° C. for 15 minutes, quenched with water and tempered. to obtain the maximum mechanical strength, also known to those skilled in the art under the name of "peak income", ie 10 h at 175 ° C for the alloys 6xxx according to the invention and H Si and 10 h to 160 0 C for alloy AA6262.
• the mechanical resistance characteristics Rpo, 2 and Rm of the alloy according to the invention are very close to those of alloy AA6262 and slightly inferior to those of alloy H Si, with elongations at break of the same order.
• microstructure of the variant according to the invention was studied by scanning electron microscopy in order to determine the nature, the dispersion and the size of the intermetallic phases at the micrometric scale.
• the three variants have a stable operating range throughout the relatively large range of cutting speeds (from 10 to 140 m / min).
• the AA6262 variant of the prior art requires a force of about 20% lower than the alloy according to the invention as well as with respect to the alloy H Si of the prior art also, this for a drilling advance constant of 0.15 mm / rev (figure
• Chip fragmentation was scored according to the same European standard NFE66-520-8, from A.l, the most favorable case, to D.6, the most unfavorable case.

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• Chemical & Material Sciences (AREA)
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• Mechanical Engineering (AREA)
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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Extrusion Of Metal (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Forging (AREA)

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• 2009
  • 2009-04-03 FR FR0901631A patent/FR2944029B1/fr active Active
• 2010
  • 2010-03-26 US US13/376,871 patent/US20120121456A1/en not_active Abandoned
  • 2010-03-26 EP EP10716375.0A patent/EP2421996B1/de active Active
  • 2010-03-26 WO PCT/FR2010/000262 patent/WO2010112698A1/fr active Application Filing
  • 2010-03-26 RU RU2011144509/02A patent/RU2522413C2/ru active
  • 2010-03-26 ES ES10716375T patent/ES2695906T3/es active Active

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