Bending annealed HSS?

Bending hot usually works best. However annealing HSS requires cooling it VERY slowly - minimum 1 hour from cherry red to comfortablle to the touch. Usually done by a blacksmith by burying it in hot ashes and letting it cool.

Try putting red hot part in 600 degree oven then turn down to 400, then 300, then shut off over a period of an hour and see what happens. If you can't easily cut it with a file it's not annealed.

The various high-speed steels are hardened in a process that generates hard (vanadium carbide etc.) crystals in the steel matrix. So, annealing requires heat and time to dissolve those crystals; it's NOT the steel, but the additives, that have to be considered. Re-hardening to recreate those crystals can be a complex process, too.

It's easier to use hardenable steels that haven't ever been hard.

Read:

Or simply google "anneal+tool+steel"

Thanks for the responses. Which is more important, the long bake at red heat or the super-slow cooling?

I could put the HSS in a crucible and dial back the power a little each hour using a variac.

Chris

Basically both. The long bake ensures that the "structure" of the steel is even throughout the steel and the slow cooling ensured that no "air hardening" for want of a better word, takes place.

I did once anneal a HSS tool bit by heating it for about 8 hours in a heat treating furnace and than cooling it over about 16 hours in the oven which had an automatic heat control that was set to reduce the heat every hour.

But why anneal HSS?

It's both - get the piece up to temp through and through, then cool VERY slowly so the crystals don't form

are many choices, this one has a short URL.

Carbon fiber insulation is much more durable and may be easier to find locally. It conducts electricity so I couldn't use it near the oven's exposed heater wiring.

I've used wood stove cement to insulate high temperature thermocouples.