from ATI:
Heat Treatment
The heat treatment consists of solution treating followed by a double aging treatment. Depending on the mechanical properties
desired, one of the following two heat treatments is utilized:
• For optimum impact properties:
Solution treat at 1,950° F (1,066° C) for 1 to 2 hours. Air cool.
Age at 1400° F (760° C) for 10 hours. Furnace cool to 1,200° F (649° C). Hold for total elapsed time of 20 hours. Air cool.
• For optimum tensile and creep-rupture properties:
Solution treat at 1,700-1,850° F (927 - 1,010° C) for 1 hour. Air cool.
Age at 1,325-1,400° F (718 - 760° C) for 8 hours. Furnace cool at 100° F (38° C) per hour to 1,150-1,200° F (621 - 649° C).
Hold 8 hours. Air cool.
Since the standard aging treatments require controlled cooling to 1150F(620C) I have always relied on subsequent heating below that level not changing the properties.
There is a different aging used for oil field applications and a different one yet for direct aging of cold worked material.
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P.E. Metallurgy, consulting work welcomed