The critical point measurement and continuous cooling transformation test with cooling rate 0.02 ~40 °C/s of high temperature bearing steel M50 (/% ：0. 82C

4. 25Cr

4. 17Mo

1. 03V) are carried out by expansion method in DIL805A quenching dilatometer

and the static CCT curve is drawn. Combined with the microstructure and Vickers hardness analysis at room temperature

the effects of cooling rate and austenitizing temperature ( 1 000 °C and 1 120 °C)on the microstructure transformation as well as the static CCT curve of high temperature bearing steel M50 are systematically studied. The results show that the critical point of high temperature bearing steel M50 is not influenced by austenitizing temperature. The temperatures of A

c1

and Accm are 808 °C and 852 °C respectively ； the critical cooling rate of pe

arlite transformation is 0. 05 °C/s. The increase of austenitizing temperature promotes the decrease of the initial temperature of martensite transformation and the right shift of bainite transformation interval on the static CCT curve

and significantly improves the room temperature hardness of high temperature bearing steel M50 at lower cooling rate.