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
  • C22F1/053—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 zinc as the next major constituent

Definitions

• the invention relates to a method for producing a starting material from a superplastic AlZnMg alloy and the use of the superplastic starting material.
• Superplastic materials especially aluminum alloys
• the most important prerequisite for superplastic forming is the fine-grained nature of the alloy to be formed.
• the grain size in practice is at most 25 ⁇ m, preferably less than 10 ⁇ m.
• the grains should also be almost globulitic.
• there must be no significant coarsening of the regularly distributed grains or subgrains during superplastic forming which is usually carried out at a metal temperature of around 500 ° C.
• the plastic elongation of a superplastic aluminum alloy at its optimum forming temperature is usually in the range of 400 to 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 aluminum alloys suitable for superplastic forming generally require complex thermomechanical pretreatment.
• no AlZnMg alloy is known, which is manufactured conventionally and has superplastic properties in the hot-rolled or pressed state.
• the present invention is therefore based on the object of providing a method of the type mentioned at the outset which allows the production of complicatedly shaped parts by means of superplastic forming in a simple and economical manner.
• the invention further relates to an application of the method.
• the object is achieved according to the invention in that an alloy with 6 to 10% zinc, 2 to 4% magnesium, 0 to 3% copper, 0 to 0.3% iron, 0 to 0.3% zirconium, 0 to 0.3% chromium, 0 to 0.3% manganese, 0 to 0.2% silicon and 0 to 0.2% titanium, the remainder aluminum of commercial purity, homogenized after the continuous casting by heating and holding and to a superplastic primary material large cross-section is deformed.
• Special embodiments and further developments of the invention are the subject of dependent claims.
• a primary material with a large cross section for example, a 1 to 30 mm, in particular 4 to 10 mm thick rolled strip, an extruded hollow profile with a wall thickness of 4 to 10 mm and / or an extruded, round solid or tubular profile with a diameter of 10 to 100 mm, in particular 30 to 50 mm, understood.
• These superplastic materials can then be used immediately to manufacture or after storage, that is, at any time, to further process an end product, be it by rolling, pressing, deep drawing, forging or another processing method known per se.
• AlZnMg alloy an alloy with 6.5 to 7% zinc, 2.5 to 3% magnesium and 1.5 to 3% copper, the rest of the optional elements specified above and aluminum of commercially available purity are preferably used. Here and the rest, the percentages always refer to percentages by weight.
• the alloy can be homogenized by gradual heating and holding. After homogenization, the alloy is appropriately cooled.
• the superplastic deformation after hot rolling or pressing can also take place without solution annealing.
• An AlZnMg alloy cast into hot-rolled bars is preferably heated in a first homogenization stage for 4 to 12 hours to a metal temperature of 440 to 480 ° C. and kept at this temperature for at least about 3 hours.
• the alloy is heated to 475 to 495 ° C. for 1 to 6 hours and kept at this second temperature for about 6 hours.
• the alloy After cooling, after a short or long period of time, the alloy can be heated to 350 to 450 ° C. for up to about 6 hours and then hot-rolled. That as Hot rolled strip preform is coiled or cut to a temperature of up to about 400 ° C.
• the alloy is heated to approximately 465 to 475 ° C. at the end of the first homogenization stage and to approximately 485 to 495 ° C. at the end of the second homogenization stage.
• the alloy is heated to a temperature of approximately 400 to 420 ° C. immediately afterwards or after the ingot has been stored. The hot rolling takes place on a strip thickness of a few millimeters.
• the tape which can be used as a raw material, has superplastic properties.
• an AlZnMg alloy cast into press bolts is homogenized in two stages as described above. After cooling, immediately afterwards or after storing the bolt, the alloy is heated to a metal temperature of 200 to 420 ° C and extruded. End temperatures of the homogenization stages of 465 to 475 ° C and 485 to 495 ° C have proven to be particularly suitable for the AlZnMg alloys.
• the homogenized aluminum alloy is preferably heated to 250 to 390 ° C for pressing.
• the profile which can be used as a raw material, has superplastic properties.
• the finished products are characterized by high corrosion resistance, good weldability, high mechanical strength values with good ductility and / or high stress corrosion resistance.
• other properties such as low density, anodizability, paintability, hygiene, dimensional stability, electrical and thermal conductivity and / or antistatic have an advantageous effect.
• An aluminum alloy with 6.7% zinc, 2.8% magnesium, 1.7% copper, 0.13% iron, 0.12% zircon, 0.06% silicon, 0.02% manganese, 0.02% chromium and 0.02% titanium is cast by means of electromagnetic continuous casting molds into standard ingots.
• the cut-to-length formats freed from the cast skin are heated to a first homogenization temperature of 465 ° C. over 11 hours and kept at this temperature for 3 hours.
• the metal temperature is raised to 480 ° C. over 5 hours and the final temperature is maintained for 6 hours.
• a homogenized billet is heated to a metal temperature of 410 ° C for 4 hours and hot rolled to 4.5 mm at this inlet temperature.
• the rolled strip is coiled at a temperature of 395 ° C.
• This superplastic primary material has a plastic elongation of about 700%.
• the bolts After removing the cast skin and cutting it to length, the bolts are brought to a first homogenization temperature of 460 ° C. over 6 hours. In a second homogenization step, the metal temperature is raised to 470 ° C. over 3 hours. In a third homogenization step lasting 18 hours, a final temperature of 480 ° C is reached.
• the homogenized bolts are inductively heated to a pressing temperature of 380 ° C within a few minutes and pressed at a speed of 1.5 m / min to round bars with a diameter of 40 mm.

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Cited By (12)

Citations (3)

• 1991
  • 1991-05-30 EP EP91810410A patent/EP0462055A1/fr not_active Ceased

Patent Citations (3)

Non-Patent Citations (3)

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