T62

Source: Aluminum Association [5].

©The times and temperatures shown are typical for various forms, sizes and methods of manufacture and may not exactly describe the optimum treatment for a specific item.

© Material should be quenched from the solution heat-treating temperature as rapidly as possible and with minimum delay after removal from the furnace. Unless otherwise indicated, when material is quenched by total immersion in water, the water should be at room temperature and suitably cooled to remain below 100°F during the quenching cycle. The use of high-velocity high-volume jets of cold water is also effective for some materials. For additional details on aluminum alloy heat treatment and for recommendations on such specifics as furnace solution heat treat soak time see military Specification MIL-H-6088 or ASTM B597. © Th e nominal metal temperatures should be attained as rapidly as possible and maintained ±10°F of nominal during the time at temperature.

(©The time at temperature will depend on time required for load to reach temperature. The times shown are based on rapid heating, with soaking time measured from the time the load reached within 10°F of the applicable temperature.

© Cold work subsequent to solution heat treatment and, where applicable, prior to any precipitation heat treatment is required to attain the specified mechanical properties for these tempers.

352 ALUMINUM AND ALUMINUM ALLOYS TABLE 9.8 (Continued)

© Stress-relieved by stretching. Required to produce a specified amount of permanent set subsequent to solution heat treatment and, where applicable, prior to any precipitation heat treatment. © Th ese heat treatments also apply to alclad sheet and plate in these alloys. © An alternative treatment comprised of 8 hours at 350°F also may be used. © Quench after solution treatment in water at 140°F to 180°F.

© Stress-relieved by 1-5 percent cold reduction subsequent to solution heat treatment and prior to precipitation heat treatment. © Quench after solution heat treatment in water at 212°F. © Quench after solution heat treatment in air blast at room temperature. © An alternative treatment comprised of 8 hours at 340°F also may be used.

© Cold working subsequent to precipitation heat treatment is necessary to secure the specified properties for this temper. © By suitable control of extrusion temperature, product may be quenched directly from extrusion press to provide specified properties for this temper. Some products may be adequately quenched in air blast at room temperature. © An alternate treatment comprised of 1-2 hours at 400° F also may be used. © A n alternate treatment comprised of 6 hours at 360°F also may be used.

© An alternate two-stage treatment comprised of 4 hours at 205°F followed by 8 hours at 315°F also may be used. © An alternate three-stage treatment comprised of 5 hours at 210°F followed by 4 hours at 250°F followed by 4 hours at 300°F also may be used.

© Two -stage treatment comprised of 6 to 8 hours at 225°F followed by a second-stage of:

(a) 24-30 hours at 325°F for sheet and plate

(b) 8-10 hours at 350°F for rolled or cold-finished rod and bar.

(c) 6-8 hours at 350°F for extrusions and tube.

(d) 8-10 hours at 350°F for forgings in T73 temper and 6-8 hours at 350°F for forgings in T7352 temper. © Applies to tread plate only.

© Held at room temperature for 72 hours followed by two stage precipitation heat-treatment of 8 hours at 225°F plus 16 hours at 300°F.

© With optimum ingot homogenization, heat-treating temperatures as high as 928°F are sometimes acceptable. ©An alternate two-stage treatment for sheet, plate, tube and extrusions comprised of 6 to 8 hours at 225°F followed by a second stage of 14-18 hours at 335°F may be used providing a heating-up rate of 25°F per hour is used. For rolled or cold-finished rod and bar the alternate treatment is 10 hours at 350°F.

© A two-stage treatment comprised of 3-5 hours at 250°F followed by 15-18 hours at 325°F. ©A two-stage treatment comprised of 3-5 hours at 250°F followed by 18-21 hours at 320°F.

© The aging of aluminum alloys 7075 and 7178 from any temper to the T73 (applicable to alloy 7075 only) or T76 temper series requires closer than normal controls on aging practice variables such as time, temperature, heating-up rates, etc., for any given item. In addition to the above, when reaging material in the T6 temper series to the T73 to T76 temper series, the specific condition of the T6 temper material (such as its property level and other effect of processing variables) is extremely important and will affect the capability of the re-aged material to conform to the requirements specified for the applicable T73 and T76 temper series. © The aging practice will vary with the product, size, nature of equipment, loading procedures and furnace control capabilities. The optimum practice for a specific item can be ascertained only by actual trial treatment of the item under specific conditions. Typical procedures involve a two-stage treatment comprised of 3-30 hours at 250°F followed by 15-18 hours at 325° F for extrusions. An alternate two-stage treatment of 8 hours at 210°F followed by 24-28 hours at 325°F may be used. © Core alloy in No. 21, 22, 23 and 24 brazing sheet.

© Quenched directly from the extrusion press. Some extrusions may be adequately quenched using a room temperature air blast. © A two-stage treatment comprised of 3-6 hours at 250°F followed by 24-30 hours at 330°F. © A two-stage treatment comprised of 3-6 hours at 255°F followed by 12-15 hours at 330°F. © A two-stage treatment comprised of 4 hours at 250°F followed by 18-22 hours at 320°F.

© A multi-stage treatment comprised of 8 hours at 225°F followed by 8 hours at 250°F followed by 4-10 hours at 350°F. © Held at room temperature for a minimum of 48 hours followed by a two-stage treatment comprised of 24 hours at 250°F followed by 10-16 hours at 330°F.

© A two-stage treatment comprised of 24 hours at 250°F followed by 10-14 hours at 345°F. © A two-stage treatment comprised of 24 hours at 250°F followed by 8-10 hours at 345°F. © A two-stage treatment comprised of 4 hours at 250°F followed by 6-8 hours at 355°F.

© By definition, this temper designation is that which would apply after natural aging even though mechanical properties for this alloy-temper product have not been registered.

© For plate thickness over 4 inches and for rod diameters or bar thicknesses over four inches, a maximum temperature of 910° F is recommended to avoid eutectic melting.

© A two-stage treatment comprised of 4-8 hours at 210°F followed by 24-30 hours at 320°F. © A two-stage treatment comprised of 4-8 hours at 250°F followed by 26-32 hours at 310°F. © Without adequate thermal pretreatment, melting may occur at this temperature. © A two-stage treatment comprised of 250°F for 3 hours plus 320°F for 3 hours. © A two-stage treatment comprised of 250°F for 3 hours plus 325°F for 10 hours. © A two-stage treatment comprised of 250°F for 3 hours plus 325°F for 3 hours.

TABLE 9.9 Recommended Times and Temperatures for Heat-Treating Commonly Used Aluminum Sand and Permanent Mold Castings

The heat treat times and temperatures given in this standard are those in general use in the industry. The times and temperatures shown for solution heat treatment are critical. Quenching must be accomplished by complete immersion of the castings with a minimum delay after the castings are removed from the furnace.

Under certain conditions complex castings which might crack or distort in the water quench can be oil or air blast quenched. When this is done the purchaser and the foundry must agree to the procedure and also agree on the level of mechanical properties which will be acceptable. Aging treatments can be varied slightly to attain the optimum treatment for a specific casting or to give agreed upon slightly different levels of mechanical properties.

Temper designations for castings are as follows: F As cast—cooled naturally from the mold in room temperature air with no further heat treatment. 0 Annealed. Usually the weakest, softest, most ductile and most dimensionally stable condition.

T4 Solution heat treated and naturally aged to substantially stable condition. Mechanical properties and stability may change over a long period of time.

T5 Naturally cooled from the mold and then artificially aged to attain improved mechanical properties and dimensional stability.

T6 Solution heat treated and artificially aged to attain optimum mechanical properties and generally good dimensional stability.

T7 Solution heat treated and overaged for improved dimensional stability, but usually with some reduction from the optimum mechanical properties.

The T5, T6, and T7 designations are sometimes followed by one or more numbers which indicate changes from the originally developed treatment.

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