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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S420/00—Alloys or metallic compositions
  • Y10S420/902—Superplastic

Definitions

• the invention relates to a method for producing a fine-grained recrystallized sheet suitable for superplastic forming from a cold-hardenable, hardenable aluminum alloy.
• the plastic elongation of a superplastic aluminum alloy is usually in the range of 400-800%, i.e. far above the values of conventional alloys. This allows a wide range of design options in terms of function and design with economical one-piece production.
• the diverse shapes are reproducible with high dimensional accuracy, there is no "spring-back".
• the simple tools that can be used have a particularly advantageous effect, since they also allow small and medium-sized production series to be produced cost-effectively and can be produced in short delivery times. Shape changes can be made quickly at affordable costs.
• the present invention has for its object to provide a method of the type mentioned, which allows a cost-effective production of an air-cooled, hardenable, non-corrosion-prone aluminum sheet with superplastic properties.
• the object is achieved according to the invention in that an alloy with 3-5.5% magnesium, 2-8% zinc, 0-4% copper, 0-1% manganese, 0-0.5% iron, 0-0.4 % Chromium, 0-0.4% molybdenum, 0-0.4% zircon, 0-0.3% silicon and 0-0.05% titanium, rest of aluminum of commercial purity, homogenized after continuous casting, hot rolled, with high Cold rolling degree cold rolled to the final thickness and annealed and cooled in a final heat treatment with rapid heating for recrystallization.
• An alloy with 4-5% magnesium and 2-6%, preferably 3-4% zinc is particularly suitable as the cold-hardenable, hardenable AlMgZn alloy. Here and for the rest, percentages by weight are always used.
• the preferred proportions are 0-0.1% copper, 0.2-0.4% manganese, 0.15-0.25% chromium, 0-0.2% iron, 0-0.2 % Molybdenum, 0-0.1% zircon and 0-0.1% silicon, although the chromium content can also be 0-0.1% and the zirconium content can also be 0.15-0.25%.
• the cast aluminum alloy blocks are freed from the cast skin and cut to length. These formats can be heated to a metal temperature of 420-450 ° C in a first homogenization stage for 2-12 hours, kept at this temperature for 4-12 hours and in a second homogenization stage to 480-530 ° C for 0.5-4 hours heated and kept at this temperature for 2-12 hours.
• the formats can be heated to a metal temperature of 420-480 ° C. in a continuous homogenization for 4-12 hours and kept at this temperature for 10-30 hours.
• the hot rolling is expediently carried out immediately after the homogenization annealing or after cooling and reheating to 350-500 ° C.
• the homogenized formats are rolled onto a 4-30 mm thick band, especially around 6-10 mm.
• the metal temperature is preferably between 325 and 345 ° C.
• the hot-rolled strip is preferably intermediate annealed at 300-400 ° C. for 6-36 hours before cold rolling.
• the hot-rolled strip which can be hardened due to the alloy composition, is additionally strengthened by cold working, in which it is preferably rolled with a degree of cold deformation of 60-95%, in particular 70-90%.
• the final thickness is e.g. between 1.5 and 3 mm, especially around 2 mm.
• the homogenization annealing serves to reduce the structural non-uniformities, such as segregations and precipitations, which arise when casting rolled ingots.
• the cold deformation increases the mechanical strength, the 0.2% proof stress, tensile strength and hardness increase.
• the recrystallization of the cold-rolled strip serves for extensive softening and is accompanied by a complete recrystallization of the aluminum alloy.
• rapid heating is essential, which is preferably carried out in a salt bath at 490-510 ° C or in a continuous temperature furnace.
• the recrystallization annealing should take place with a heating time of at most 8 minutes, in particular at most 3 minutes.
• the softened belts are cooled in air or in water.
• the softened aluminum strips have superplastic properties. In addition to the great elasticity with relatively high mechanical strength, they are particularly characterized by their extraordinarily low susceptibility to corrosion, also in relation to stress corrosion.
• An aluminum alloy with 4.4% magnesium, 3.7% zinc, 0.5% copper, 0.7% manganese, 0.12% iron, 0.19% zircon and 0.07% silicon is produced in a vertical continuous casting process with electromagnetic molds cast into bars of 70x200x800 mm, using the usual Tib2 grain refining technique.
• the casting temperature is around 720 ° C.
• the cast skin is removed, the bar head and bar base are separated and the bar divided. These are heated to 440 ° C. for 3 hours in a first homogenization stage, kept at this temperature for 8 hours, heated to 500 ° C. for 1 hour in a second homogenization stage and kept at this temperature for 3 hours.
• the ingots are rolled in several passes at 9 mm, the final temperature of the metal being between 325 and 345 ° C.
• the recrystallization annealing is carried out with a heating time of 5 minutes in a liquid mixture of potassium and sodium nitrate at 500 ° C. After cooling in water, the tapes are cleaned and dried.
• Example 1 In a method corresponding to Example 1 for producing a fine-grain recrystallized sheet suitable for superplastic deformation, an aluminum alloy is used with 4.3% magnesium, 3.6% zinc, 0.3% manganese, 0.11% iron, 0.20% zircon and 0.07% silicon.
• the sheets of both examples show superplastic properties, they are checked for their expansion at 500 ° C, 520 ° C and 540 ° C.
• Metallographic examinations show finely divided, globulitic grains of less than 10 ⁇ m, which are regularly distributed.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Metal Rolling (AREA)
• Conductive Materials (AREA)

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Citations (5)

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• 1990
  • 1990-06-11 CH CH1959/90A patent/CH682326A5/de not_active IP Right Cessation
• 1991
  • 1991-05-30 EP EP91810411A patent/EP0462056A1/de not_active Withdrawn
  • 1991-06-04 US US07/710,056 patent/US5122196A/en not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (3)

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