The thermodynamic equilibrium phases in T122 heat-resistant steel (0.11 ~ 0.12C

11.37 ~ 11.97Cr

1.90〜1.93W

0.38Mo

0.86 〜0.90Cu

0.05Nb

0.19- 0.20V

0.58- 0.67N

0.002 3 〜0.002 8B) and the effect of alloying element Cr

Al

Ti on S ferrite and major precipitated phases at temperature between 820 °C and 1 200 °C have been studied by Thermo-Calc software. The results show that there is a large amount of S ferrite in T122 heat-resistant steel and the main precipitated phases in steel are ， Laves phase and MX

At temperature between 950 °C and 1 050 °C the amount of S phase is lowest

of which the content is 15.7% ~ 18.9% .The initial precipitated temperature for M

23

C

6

is 940 °C

for Laves phase is 750 °C

but for MX is more t

han 1 250 °C which is a very stable phase. It is found that chromium has a great influence on formation of 8 ferrite and has minor influence on that of precipitated phases; to lower Al and Ti content is available to decrease 3 ferrite amount and increase MX phase amount.