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 the superplastic production of workpieces from a kneadable aluminum alloy.
• Superplastic formable aluminum alloys have been known for a long time. The most important prerequisite for superplastic forming is the fine-grained nature of the alloy to be formed. In the case of superplastically formed aluminum sheets, for example, the grain size in practice is at most 25 ⁇ m, preferably less than 10 f..lm. The grains should also be almost globulitic. Finally, there must be no significant coarsening of the regularly distributed grains during superplastic forming, which is generally carried out at a metal temperature of around 500 ° C.
• the plastic elongation of a superplastic aluminum alloy is usually in the range of 400 to 800% at its optimal forming temperature, i.e. far above the plastic elongation values of conventional alloys.
• This allows a wide range of design options in terms of function and design with economical one-piece production.
• the various shapes are reproducible with high dimensional accuracy, there is no "springback".
• 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 and at a reasonable cost.
• the aluminum alloys suitable for superplastic forming essentially require complex thermomechanical pretreatment.
• Superplastic primary material is manufactured according to the known state of the art in industrial production as a rolled product with a high degree of cold rolling. Certain applications, such as fuel tanks and gas cylinders designed as hollow bodies, require a long forming time and a high degree of forming. In this case, two half shells must also be connected.
• the inventors have set themselves the task of creating a method of the type mentioned at the outset, with which the manufacture of workpieces of complicated design is simplified, the forming time is reduced and the degree of forming is reduced.
• the workpieces should be able to be made in one piece.
• the object is achieved according to the invention in that the aluminum alloy is homogenized after the continuous casting, is produced by cold kneading (without rollers), superplastic preforms designed in a manner similar to the workpieces, and is shaped superplastically to form the workpiece.
• the object is achieved according to the invention by homogenizing the aluminum alloy after continuous casting, shaping it by warm kneading into a primary material of large cross section, cold kneading (without rollers), producing superplastic preforms similar to the workpieces and shaping them superplastically into the workpiece .
• a primary material of large cross section for example, a 1 to 30 mm, in particular 4 to 10 mm thick rolled strip, an extruded 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 primary materials can be divided into pieces immediately after production or after storage, that is to say at any time.
• AIMg or AIZnMg alloys are of great interest, for example, which, thanks to the formation of hardening precipitates, lead to cold and warm hardenability and thus to high strength values.
• the strength values of AIZnMg alloys can be increased even further by adding copper, which are manufactured and offered by ALUSUISSE-LONZA AG as PERUNAL alloys.
• a hardenable 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, residual aluminum of commercially available purity, after the continuous casting, are homogenized by heating and holding and are shaped to form a superplastic starting material with a large cross section.
• percentages are always understood to mean percentages by weight.
• the AIZnMg alloy mentioned is expediently used as an alloy with 6.5 to 7% zinc, 2.5 to 3% magnesium and 1.5 to 3% copper, the rest of the above-mentioned optional elements and aluminum of commercially available purity.
• Such an AIZnMgCu alloy not only has an extraordinarily high strength, it is also particularly simple by cold forming into a preform and then by superplastic forming forming a workpiece.
• the alloy of a cast format is subsequently cooled.
• heterogenization that is not necessary follows a slow cooling.
• the cast, heat-treated formats are preferably shaped with a degree of hot rolling or a compression ratio of at least 10: 1 to form the starting material.
• the primary material is not divided.
• the cold slugs or round blanks are deformed by cold kneading (without rollers) with a degree of deformation of at least 4: 1.
• the slugs or round blanks are shaped by cold pressing, cold extrusion, ironing or ironing into cup-shaped preforms which have superplastic properties. Cut pieces can also be shaped by extrusion or cold extrusion into a preform with superplastic properties, which is similar to the workpiece.
• the preform Before the superplastic forming into a workpiece, the preform can be recrystallized in fine-grained form by rapid heating. This is advantageous for the alloys examined, but not necessary.
• the rapid warm-up for recrystallization takes place, for example, in a salt bath.
• the method according to the invention for the superplastic production of workpieces is characterized in that, thanks to similar preforms with superplastic properties, the forming time and the degree of forming can be reduced considerably, which results in a more rational production than with the conventional SPF.
• Hollow bodies can be manufactured particularly easily by inflating a molded part in a superplastic manner.
• the product is also improved in that there are no inner folds, which results in better mechanical properties.
• the wall thickness of the workpiece can be adapted more precisely to the technical requirements than with superplastic sheet as the starting material.
• An aluminum alloy with 6.9% zinc, 2.7% magnesium, 1.7% copper, 0.18% manganese, 0.14% zircon, 0.08% silicon and 0.08% iron are cast in a conventional continuous casting process to form press bolts with a diameter of 220 mm.
• the bolts are brought to a first homogenization temperature of 450 ° C. for about 5 hours and kept at this temperature for about 6 hours.
• the metal temperature is raised to 470 ° C. over 3 hours and kept at this temperature for 18 hours. Then the bolts are cooled in still air.
• 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.
• the round bars are cut into 5 mm thick rondelles, which is referred to as dividing in the sense of the present invention.
• the cold extrusion of the round blanks takes place in a preform designed as a cylinder closed on one side. This is recrystallized or solution-annealed in a salt bath at 470 ° C. for about 10 minutes and then cooled in water.
• a metallographic examination showed a grain size of about 10 f..lm, which leads to superplastic properties.
• the superplastic forming to reach the workpiece takes place immediately after cooling or after storing the preforms.
• 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. for 11 hours and kept at this temperature for 3 hours.
• the metal temperature is raised to 480 ° C. in the course of 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. Slugs are punched out of the rolled strip and further treated as in Example 1.

Landscapes

• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Forging (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Extrusion Of Metal (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=4259102

Family Applications (1)

Country Status (4)

Families Citing this family (1)

Citations (4)

Family Cites Families (1)

• 1990
  • 1990-11-12 CH CH3582/90A patent/CH682081A5/de not_active IP Right Cessation
• 1991
  • 1991-10-30 DE DE59106143T patent/DE59106143D1/de not_active Expired - Fee Related
  • 1991-10-30 EP EP91810842A patent/EP0486426B1/fr not_active Expired - Lifetime
  • 1991-10-30 AT AT91810842T patent/ATE125880T1/de active

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events