A182 F9 and F91 metallurgical differences 1

[Johnwoo1991]

Is A182 F9 steel (P9) very much different from F91 (P91) steel of the 9-1-cr-mo-v family?

 

[weldstan]

Yes. Especially regarding tensile and creep strength.

 

[weldstan]

I would also say that P91 heat treatment, welding and PWHT parameters are much more critical than for P9.

 

[ShabsRBI]

Looking into the difference between P9 and P91 material, addition of around 0.18-0.25% Vanadium is done to P91 material to provide higher Tensile and Yield Strength.

P9 P91

Tensile strength (ksi) 60 ksi 85 kis
Yield strength (ksi) 30 ksi 60 ksi

Thus looking above values, P91 has better high temperature Tensile and Yield strengths

 

[jessieleo99]

P91 has high creep strength and thermal stability and can be used for a long time in high-temperature and high-pressure environments above 600°C.

 

[Krausen]

F91/P91 is a bitch to weld properly. Be very cautious if going with this material & get ready to go down a rabbit hole with your weld procedure

 

[EdStainless]

EPRI has a large amount of information on 91, both welding and service.