(Mechanical Engineer here with some metals training)
Suffice it to say it would be very hard for the shadetree mechanic to return it to its original state if it had any kind of a special heat treat done to it. If you just heat it up, bend it and let it cool in air, it will basically be annealed, meaning softened. The stiffness won't be different, but the ultimate breaking strength and fatigue strength will be lower. If you quench it quickly in oil, the strength will be higher, but it may become brittle, depending on the alloy, which we don't know. If you quench it in water it will probably become brittle because of cooling so fast.
Springs usually have a special and complex heat treat cycle done to them to give them maximum life, because of how much fatigue they're under. They may be heated very hot and held for a specific number of hours, quenched at a controlled rate, reheated to an intermediate temp and held for a specific number of hours then quenched again. Without knowing the times and temps it's impossible to duplicate.
If you don't care about all that crap and just want to give it a go, I'd try the oil quench.
Topic: Any metallurgists here? (Read 3699 times)