flaus77;
Why do you need the allowable stresses for all these service temperatures for this material (C-Si plate)? Well, here is what I will do, I will give you three values and you can interpolate the others

SA 201 Grade B

600 deg F   15 ksi
750 deg F    13.85
900 deg F    5 ksi

For SA 53, you can use a recent edition of ASME B&PV Code, Section II, Part D
 

Thank you for the info. Please be aware that most interpolations are linear and that linearizing non-linear data
is not always accurate, that is why I asked for specific values at given temps.

Well, if accuracy is important to you I recommend ASME Section II, Part D.

Regards,

Mike