I would like to make part named "stem key" for valve.
It's a kind of joint/insert that is out side the valve on the stem of the valve.
The ambient temperature will be around -55C..-60C.
I doubt that any tool steel will hold such low temp.
Why does it have to be a tool steel (tool steels are for hard surfaces such as machining parts and manual cutting e.g. axe) , lots of low alloys are austenitic and strong?