The test steel 305B (/%: 0. 048C

3. 32Si

1. 34Mn

19. 46Cr

13. 32Ni

0. 46Nb)

steel 304 (/%: 0.050C

0. 30Si

0.90Mn

18. 05Cr

9. 23Ni) and steel 310S (/%: 0. 051C

0.44Si

1. 17Mn

25. 36Cr

21.32Ni) are melted by a 200 kg vacuum induction furnace. The high-temperature mechanical properties at 500 ~ 1 000 °C of test steels

and quenched structure of steel 305B are studied by using Gleeble-3800 thermo-simulation machine

optical microscope and transmission electron microscope

and the equilibrium phase diagram with 15% -25% Cr for steel 305B is obtained by using Thermo-calc software. Results show that at 500 ~ 1 000 °C the yield strength of steel 305 B (261 MPa at 500℃，45 MPa at 1 000 ℃) is high than that of steel 304 and steel 310S

and the tensile strength of steel 305 B ( 536 MPa at 500 °C

75 MPa at 1 000 ℃ ) is close to that of steel 310S and far more higher than that of steel 304

the NbC precipitate phase in steel 305 B leads to it has higher strength at elevated temperature ； the reduction of area of steel 305 B at elevated temperature is higher than that of steel 310S and lower than that of steel 304.