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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
  • H01B1/023—Alloys based on aluminium

Definitions

• the present invention relates to an improved process for the manufacture of aluminum base alloys. More specifically, the present invention resides in a greatly improved process for the preparation of aluminum base alloys in wrought form, especially conductors, wherein the alloy contains magnesium and silicon.
• the present invention relates specifically to heat treatable aluminum alloys in which the major portion of alloying elements are magnesium and silicon which will be principally in the form of the intermetallic compound magnesium silicide, Mg Si.
• aluminum alloy 6201 is a high strength aluminum-magnesium-silicon alloy which in the heat treated condition shows a tensile strength of about 46,000 p.s.i. minimum, and elongation of 3% minimum and an electrical conductivity of 53.5% IACS minimum.
• this alloy is manufactured commercially by DC casting, reheating to about 700 to 850 F., hot rolling to redraw rod, cold drawing, solutionizing at around 1000 F. for 1 hour or more followed by water quenching, additional cold drawing and artificial aging between 250 and 450 F. to specification properties.
• the present invention comprises:
• step (C) the alloy is hot rolled in step (C) to redraw rod, preferably having a diameter of about inch.
• step (D) the following steps are preferably employed subsequent to step (D):
• the present invention is utilizable with aluminum base alloys in wrought form, e.g., sheet and plate. Particularly advantageous is the preparation of plate of inch thickness and up.
• the preferred embodiment is aluminum base alloy conductors; hence, the ensuing discussion will be particularly related to this preferred emhodiment.
• the aluminum alloy may be conventionally cast in the customary manner.
• the cast bar is then completely solutionized by holding in the temperature range of 850 to 1150 F. for a period of time of at least 5 minutes and preferably at a temperature of 900 to 1050 F. for a period of time of between minutes and 16 hours.
• the solutionized cast bar is hot rolled into redraw rod, conventionally having a diameter of about /8 of an inch.
• the solutionized bar is hot rolled to redraw rod so that during hot rolling the cooling rate is greater than 400 F. per minute.
• the cooling rate should be greater than 100 F. per minute.
• the redraw rod existing from the hot rolling mill will be substantially free of precipitated magnesium silicide.
• the redraw rod is then cooled to below 250 F. and preferably to room temperature at a rate greater than 100 F. per minute with a delay of no more than 20 seconds, preferably less than 15 seconds, between application of the cooling treatment and exiting of the last hot rolling pass.
• the rate at which the material is cooled from 250 F. to room temperature is not critical, although for convenience the material is cooled directly to room temperature at a rate greater than 100 F. per minute.
• the magnesium silicide is thereby retained in solution thus eliminating the need for a flash solutionizing operation.
• the solutionized redraw rod can then be cold drawn without an intermediate softening treatment in excess of 98% reduction in cross sectional area.
• This is in distinction to the present commercial process in which an upper limitation is applied to the amount of cold reduction after solutionizing.
• aluminum alloy 6201 it is necessary to apply at least 70% cold reduction, and preferably at least 75% cold reduction, before the final aging treatment.
• Combinations of mechanical and electrical properties comparable or superior to those of present commercial material can be obtained at final diameter by the ap plication of an appropriate and conventional softening treatment consisting of holding at between 250 and 450 F. for 15 minutes minimum. Preferably this treatment should be conducted between 300 to 350 F. for 1 to 8 hours. Specification and mechanical and electrical properties are obtained using the above process with cold reduction after solutionizing from 70 to 99% reduction in area without intermediate softening treatments.
• the present invention is amenable to use with any aluminum base alloy containing from 0.20 to 1.3% silicon and from 0.3 to 1.4% magnesium, with the 6201 alloy being preferred.
• the 6201 alloy may contain 1.0% iron max., 1.0% copper max., 0.8% manganese max., 0.35% chromium max., 0.5% zinc max., 0.001- 006% boron, 0.2% titanium max., and others each 0.05% max., total 0.15%.
• Boron is a particularly advantageous alloying addition.
• ExampleI An alloy containing 0.72% magnesium, 0.68% silicon, 0.22% iron and 0.018% boron was horizontally DC cast to a diameter of 2%". The casting was reheated to around 750 F., held at that temperature for minutes and rolled to redraw rod in a ten-stand, continuous hot mill to a diameter of /5". The rod exited the rolling mill at 550 F. and was air cooled to room temperature. The resulting redraw rod had a coarse dispersion of Mg Si out of solution. The redraw rod was cold drawn 80% and aged for 4 hours at 325 F. Four samples of aged wire showed a low average tensile strength of around 35,000 p.s.i.
• Example 11 The redraw rod of Example I was heated at 1025 F. for 10 minutes at temperature, total time in the furnace of 16 minutes, and then quenched in water without a de liberate intermediate delay. This served to solutionize the coarse Mg Si completely.
• the solutionized redraw rod was drawn and aged at 325 F. for 4 hours. Eight tensile samples of the wire showed a satisfactory average tensile strength of 48,000 p.s.i. This essentially duplicates present commercial processing.
• Example IH The cast alloy bar of Example I was heated to 1025 F. and held at that temperature for 15 minutes5 hours. It was then rolled in a ten-stand tandem mill to redraw rod. The cast bar entered the rolling mill at 1025 F. and exited at 650 F. The average cooling rate during hot rolling was 1600 F./minute. The rod was then cooled to room temperature in still air at an average rate of around 10 F./minute. Examination of the microstructure showed a fine dispersion of precipitated Mg Si. The redraw rod was cold drawn 80% to 0.160" diameter and aged at 325 F. for 4 hours. Four samples of aged wire showed a low average tensile strength of around 35,000 p.s.i.
• Example IV The cast bar of Example I was hot rolled according to the practice in Example III with an exit temperature of 650 -F. and an average cooling rate of 1600 F./ minute during hot rolling.
• the redraw rod exiting the hot mill was quenched in cold water to room temperature with no more than 2 seconds delay before entering the coolant.
• the cooling rate of the rod in the coolant was very high and was around 10,000 F/minute.
• the redraw rod so treated showed no significant precipitation of Mg Si in its microstructure. It was then drawn 80% to 0.160" diameter and aged at 325 F. for four hours. Eight samples of the wire showed a satisfactory average tensile strength of around 49,000 p.s.i., an average elongation of around 5% and an average electrical conductivity of around 54% IACS.
• Example V A cast bar of Example I was hot rolled as shown in Example III.
• the redraw rod exited the hot mill at around 650 F. and had an average cooling rate of 1600 F./hour during hot rolling.
• the redraw rod was permitted to stand in still air for a period of 15 seconds before being quenched in water as in Example IV.
• the microstructure of the redraw rod showed barely detectable and occasional traces of Mg Si precipitate.
• the redraw rod was then drawn 80% to 0.160" diameter and aged at 325 F. for four hours.
• Four samples of the aged wire showed an average tensile strength of 48,000 p.s.i., an average elongation of 6% and an average electrical conductivity of 54% IACS.
• step (-D) at a rate greater than 100 F. per minute is to room temperature.
• step (D) at a rate greater than 100 -F. per minute is to room temperature and wherein said delay between said cooling and said hot rolling is less than 15 seconds.
• heating step (F) is at 300 to 350 F. for from 1 to 8 hours.
• said alloy (A) contains 1.0% iron max., 1.0% copper max, 0.8% manganeses maX., 0.35% chromium max., 0.5% zinc max., 0.2% titanium max., and others each 0.05% max., total 0.15%.

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Citations (4)

• 1968
  • 1968-07-01 US US741280A patent/US3464866A/en not_active Expired - Lifetime
  • 1968-08-23 SE SE11430/68A patent/SE341476B/xx unknown
  • 1968-09-10 GB GB43018/68A patent/GB1183568A/en not_active Expired
  • 1968-09-25 FR FR167492A patent/FR95623E/fr not_active Expired

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