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
• • 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
  • C22F1/04—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

Definitions

• ABSTRACT OF THE DISCLOSURE The hot deformability of aluminum alloy bodies of the type AlMgSi is improved by annealing such aluminum alloy body at a temperature between 500 and 590 C., and slowly cooling the thus-annealed aluminum alloy body at a rate of up to about 20 C. per hour at least down to a temperature of between about 450 C. and 300 C.
• the present invention relates to the heat treatment of aluminum alloys and, 'more particularly, the present invention is concerned with the heat treatment of continuous or semi-continuous aluminum alloy castings which are to be used as extrusion and rolling ingots.
• the aluminum alloys with which the present invention is concerned are alloys consisting essentially of aluminum, magnesium and silicon, primarily alloys which consist of between about 0.4 and 1.4% magnesium, 0.30 and 1.6% silicon, the balance being aluminum but may also include between 0.1% and 1% manganese and/ or between 0.001 and 0.3% chromium.
• special alloys which include diiierent quantitative ranges may also be treated according to the present invention, such as for instance, aluminum alloys having a magnesium content of between 2.3 and 3.5%.
• the alloys may also contain relatively small proportions of copper, for instance up to about 0.5% and, in addition, the aluminum of the alloy may contain the conventional impurities of for instance iron.
• the alloys which are treated according to the present invention may also contain relatively small proportions of zinc, such as 0.2%.
• the above described alloys will be referred to in the description and the claims as aluminum alloys of the type AlMgSi.
• Extruded profiles of aluminum alloys of the type AlMgSi are of progressively increasing importance for building purposes.
• profiles of the above composition have high strength characteristics and, after anodic oxidation, such profiles have a smooth surface of light color.
• extrusion thereof should be carried out at the highest speed possible. The extrusion speed, however, is limited by the heat deformation characteristics of the cast ingots.
• alloys of the type described above are conventionally annealed for between 6 and 48 hours at temperatures of between 530 and 590 C. and thereafter cooled by exposure to air.
• the present invention contemplates a method of heat treating aluminum alloy bodies of the type AlMgSi which comprises the steps of annealing the aluminum alloy bodies at a temperature between 500 C. and 590 C., and slowly cooling the thus-annealed aluminum alloy bodies at a rate of about 20 C. per hour, and not exceeding 50 C. per hour.
• the present invention also contemplates a method of heat treating and extruding an aluminum alloy body of the type AlMgSi, which method comprises the steps of annealing the aluminum alloy body at a temperature between 500 C. and 590 C., slowly cooling the thusannealed aluminum alloy body at a rate of about 20 C. per hour, and not exceeding 50 C. per hour to a temperature of between 450 C. and 300 C., further cooling the aluminum alloy body at a faster rate to a temperature below 300 C., thereafter heating the thus-cooled aluminum alloy body to an elevated temperature of between about 350 C. and 530 C., and subjecting the thusreheated aluminum alloy body to extrusion at the elevated temperature.
• the present invention is based on the surprising finding that with respect to aluminum alloys of the type- AlMgSi, the manner in which the cooling from the homogenizing temperature is carried out has a considerably greater influence with respect to the subsequent extrudability or possible extrusion speed of the ingots than the temperature and the length of time for which the homogenization heat treatment or annealing has been carried out.
• the Mg Si particles which were previously precipitated and which due to the quick air cooling are of relatively small size will be quickly dissolved again so that at the start of the extrusion process a more or less homogenous mixed crystal is present.
• the same condition is obtained by quickly cooling the ingot after the same has been subjected to homogenizing heating or annealing, for instance by spraying with water, or by extruding the annealed cast ingot without intermediate cooling.
• the desired structure of the cast aluminum alloy ingot is obtained according to the present invention by a method of heat treating continuously or semi-continuously cast extrusion or rolling ingots of aluminum alloys of the type AlMgSi, by annealing the ingots within a temperature range of between 500 and 590 C., preferably between 530 and 580 C., and thereafter cooling the thus-annealed ingots in a slow manner, namely so that the temperature drop will amount to not more than about 50 C. per hour, and preferably not more than 20 C. per hour. This slow cooling is particularly important while the annealed ingot is still at a relatively high temperature.
• the slow cooling is easily accomplished, for instance by allowing the annealed ingots to remain in the annealing furnace or under a suitable hood.
• the speed of cooling is to be so controlled according to the present invention that the temperature drop at the beginning, i.e., until the temperature has dropped to between 450 C. and 250 C., will be not more than 50 C. per hour and preferably about 20 C. per hour.
• the slow cooling according to the present invention may be continued until the temperature of the annealed ingot has dropped to 250 C. or below or, a stepwise cooling may be carried out so that the slow cooling by no more than 50 C. per hour and preferably about 20 C. per hour will be carried out until the temperature has dropped from the annealing temperature to between about 450 C. and 300 C. and preferably to between 400 C. and 300 C. and thereafter, in the second cooling step, the further cooling may be carried out at a faster rate of more than 150 C. per hour to a temperature of 200 C. and below.
• the heat treatment including the slow cooling after annealing is carried out according to the present invention with aluminum alloys containing silicon and magnesium as alloying elements and which may also contain copper, zinc, manganese and chromium, in addition to the conventional impurities of the aluminum.
• the present invention encompasses the treating of aluminum alloys within the range indicated in the table below.
• the aluminum should be of a purity of at least about 99.7%.
• the first method namely the slow cooling to 250 C. or below will result in a very considerable increase in the speed at which the thustreated ingots can be extruded while still maintaining sufficiently high strength characteristics for many practical applications, particularly with respect to yield strength and tensile strength
• the second method namely the twostep cooling, beginning at a slow rate and terminating at a faster rate will permit maintenance of about the same or only slightly reduced extrusion speeds as compared with the first method while at the same time resulting in an extruded product of improved strength characteristics.
• the faster cooling after a temperature of between 450 and 300 C. has been reached can be carried out in conventional manner by exposure of the ingot to air, or by blowing air or another suitable gas against the ingot, as well as by spraying the ingot with water or immersion of the ingot in a Water bath.
• ingots which were homogenized for one hour at 580 C. and then cooled to 300 C. at a maximum cooling speed of 20 C. per hour, and thereafter quickly further cooled by being sprayed with water could be equally well extruded as ingots which were homogenized at 5 C. for 48 hours, and then similarly subjected to the two-step cooling process.
• Example I Several cast ingots of varying composition were homogenized in an air furnace at 5 80 C. for varying periods of time and subsequently cooled in diiferent manners. Thereafter, the ingots having a diameter of 80 mm. were heated by induction heating to an extrusion temperature of 480 C., maintained for five minutes at such extrusion temperature and then extruded at a constant or unchanging extrusion force of 170 metric tons.
• Percent Mg A, 0.45; B, 0.69; C, 0.90.
• Percent Si A, 0.40; B, 0.57; C, 0.69.
• the balance of the alloys consisted of aluminum with conventional impurities.
• Ingot (1) Homogenization for 48 hours, followed by air cooling down to C. and below, at a rate of 80 to 100 C.;
• Ingot (2) Homogenization for 48 hours, followed by air cooling to 370 C., maintenance of 370 C. for 3 hours and subsequent further air cooling down to 100 C. and below, at a rate of 80 to 100 C.;
• Ingot (3) Homogenization for 48 hours, cooling in the annealing furnace at a rate of 20 C. per hour down to 200 C.;
• Ingot (4) Homogenization for 1 hour followed by cooling in the furnace at a rate of 20 C. per hour down to a temperature of 200 C.
• Example (percent Balance Example II The table hereinbelow will serve for comparison of the extrusion speed which is obtained with a given aluminum alloy of the type AlMgSi by exposing the annealed ingot either to quick air cooling or to several variations of the slow cooling in accordance with the present inven tion.
• test described in the present examples were carried out with cast ingots of an aluminum alloy containing 0.45% magnesium, 0.40% silicon, the balance being aluminum having a purity of 99.7% and containing the conventional impurities.
• the ingots were subjected to a homogenizing heat treatment of 570 C.il0 C. metal temperature for a period of one hour.
• the ingots were then cooled as indicated in the table below and thereafter subjected to induction heating up to an extrusion temperature of 480 C.
• the ingots were then maintained at such extrusion temperature for two minutes and thereafter extruded by means of a 315 T extrusion press.
• the extruded profile was then The results summarized in the table above show that the cast ingot treated according to experiment 1 could be extruded only at the low speed of 4.7 meters per minute, while according to experiment 2 the extrusion speed rose to 11.8 m./rnin.
• the extrusion speed according to experiments 3 and 4 is only slightly different from that achieved according to experiment 2, however, according to experiments 3 and 4 a significant increase in yield strength and tensile strength is achieved.
• the dilference in theextrusion speed which has been determined in the experiments described hereinabove, is useful as a general measure for the resistance to heat deformation.
• a method of deforming a heated aluminum alloy body of the type AlMgSi comprising the steps of annealing said aluminum alloy body at a temperature between 500 C., and 590 C.; slowly cooling the thus annealed aluminum alloy body at a slow rate not exceeding 50 C. per hour to a temperature not exceeding 450 C.; thereafter cooling the thus slowly cooled annealed aluminum alloy body at a rate faster than said slow rate; heating the thus first slower and than faster cooled annealed aluminum alloy body to an elevated temperature between 350 C. and 530 C.; and subjecting the thus reheated aluminum alloy body to hot deformation at said elevated temperature.
• said aluminum alloy body is an extrusion or rolling ingot formed by continuous or semicontinous casting of said aluminum alloy.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Forging (AREA)
• Continuous Casting (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Extrusion Of Metal (AREA)

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Cited By (12)

Citations (5)

• 1965
  • 1965-02-05 DE DEV27691A patent/DE1237332B/de active Pending
  • 1965-03-26 SE SE3975/65A patent/SE314831B/xx unknown
  • 1965-03-26 US US443067A patent/US3379583A/en not_active Expired - Lifetime
  • 1965-03-29 CH CH432865A patent/CH455300A/de unknown
  • 1965-04-07 BE BE662158D patent/BE662158A/xx unknown
  • 1965-04-09 GB GB15291/65A patent/GB1095034A/en not_active Expired
  • 1965-04-09 NL NL6504572A patent/NL6504572A/xx unknown

Patent Citations (5)

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