I suggest you go the other way around and state the particular application, temperature range and size you are looking for.
Long before metal material limitates your upper temperature range, bearing and sealing materials (stem and seat) will limit what you can do.
Also the fluid, in combination with sealings and inner coating,(if any or other than the sealing material) will give you a temerature limitation.
The third is of course the actual valve detailed construction: what is the valve in detail actually built for.
A normal max limitation for a normal, soft sealed construction, centric industrial BFL valve would probably be araound 180-200 deg C, with PTFE based sealings.
There is normally a somewhat lower limit for type 'district heating', metal seated (or soft sealed) BFL valves, being normally built to demanded for temperatures below 140 deg C.
Standard valves with EPDM varies up to about 120 deg C.
Be also aware that outer epoxy coating on the valve will have a much lower limitation, about max 70 deg centigrade outside temperature, or lower for difference inside/outside temperature. Above this outer epoxy will be miscolored and damaged.
For higher temperature valves you will have to go in one of two directions:
1. Either specialised and very costly metal seated, often eccentric (double or triple offset) mounted BFL valves in various materials, for up to about 600 deg C (not GGG40). See for instance:
2. Or more simple applications and with lower sealing properties, valves and flaps built for instance for pipes and smokestacks for hot, gaseous media. Theese are often welded constructions, not cast, and often made diredctly adapted to the rest of the construction.
