T91/P91 (X10CrMoVNb9-1)

Definition
Grade T/P91 is a ferritic-martensitic (9 % chromium, 1 % molybdenum) steel micro-alloyed with vanadium and niobium, and has a controlled nitrogen content according to ASTM A 335, A 213 or to EN 10216-2 standard under the designation X10CrMoVNb9-1.
 

Application
On fossil-fuelled power plants, this grade is mainly used for high-temperature applications in superheater and reheater tubes, headers and steam piping (main steam and hot reheat).
 
 
 
 

Challenges
Grade T/P91 exhibits excellent elevated-temperature strength and creep behavior up to 580 °C - 600 °C. Its 9 % chromium content offers better corrosion and oxidation resistance than grade 22. In addition, the reduced weight of boiler and piping components resulting from the steel's superior performance compared with other standard steels allows higher resistance to thermal fatigue. Compared with austenitic steels, grade T/P91 has higher heat transfer and lower thermal expansion coefficients.