Rick Girard wrote:
 >
 > I spent three years documenting and inspecting the heat treat operations
 > at a Boeing facility. While the process depends on the alloy, it is
 > generally the same for all aircraft alloys. First the material is placed
 > in an anaerobic oven where the temperature is around 850 to 900 degrees
 > F for up to eight hours. It is shock cooled in a water tank. At that
 > point the material is in "O" condition. If it is placed in a freezer, it
 > will remain soft. If it stays at room temperature it will naturally
 > harden up to a "T4" condition in 24 to 96 hours. at that point it has
 > about 75% of the properties of fully processed material. To reach a "T3"
 > or "T6" condition (we're talking 2024, 6061, and 7075 alloys) the part
 > is placed in the oven at a lower temperature for two to three hours.
 > This is referred to as artificial aging.
 >
 > Rick Girard

 I suspected this. No telling how old the bends are when you get them
 from Burns.

 Paul Lamar

Thanks,
Well that means that the elbows have gone back to ~T4 by now, which should be
good enough.

Bill Schertz
KIS Cruiser #4045

Yes. A product of my ignorance on the self hardening of aluminum :)

Paul Lamar

Not necessarily so. If the material was left as wrought and never heat treated it will not harden
up. Years ago I found some 6061-O tubing at a salvage yard that had sat outside in the Kansas
weather for years. It was still soft as a babies behind.

Rick Girard

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