Metallurgical and Stress State Factors Which Affect the Creep and Fracture Behavior of 9% Cr Steels

Table 3

Analysis of the effect of Sn on performance as a function of service temperature for a given stress of 80 MPa (11.6 ksi).

Grade 91 material	Expected life (hours) at 80 MPa (11.6 ksi) and indicated temperature
	550°C 1022°F	575°C 1067°F	600°C 1112°F	625°C 1157°F
Mean Grade 91	>1,000,000	>1,000,000	588,518	55,732
Min. Grade 91	>1,000,000	>1,000,000	204,913	19,983
Cast A (high Sn)	>1,000,000	360,250	32,340	3,320
Cast B (low Sn)	>1,000,000	>1,000,000	157,406	15,464

Data were taken from Figure 4 [27]. Note the dramatic drop off in anticipated life >550°C (1022°F).