Bolting grade for design temperature 350 [°C] with AD-2000 1

[JamyFilter]

Hello,
What could be a bolting grade which can be used at a design temperature of 350 [°C] complying with AD-2000.
I would need an "efficient" grade (high yield strength). Because we need to replace a bolt 12.9 by another grade on an existing vessel. So the room for bolt (studs) cannot be increased, ...

What is the yield strength of your proposal at 350 [°C].

Thanks for your replies.
Regards,

 

[CoryPad]

EN 10269 has X12CrNiMoV12-3 with 630 MPa minimum proof stress at 350 [°]C. This is considered a martensitic stainless steel. For a regular martensitic low alloy carbon steel, EN 10269 has 40CrMoV4-6 with 577 MPa minimum proof stress at 350 [°]C.