Test steel CrNi3Si2MoV (/% ： 0.21C

1.75Si 0.29Mn

0.006 0P

0.0007S

1.03Cr

2.86Ni

0.31 Mo

0.08V) is melted by a 50 kg vacuum induction furnace and forged to φ15 mm bar product. The effect of hot deformation on structure and hardness of test steel CrNi3Si2MoV austenitized at 1 200 ℃

then hot deforming with 10% 〜 70% at 750 °C + quenching and partitioning (Q&P) treated by quenching to 330 °C and 550 ℃ for 1 min is studied by Gleeble-3800 thermal simulation machine

scanning and transmission electron microscope (SEM and TEM)

and X-ray diffractometer (XRD). Test results show that the structure of hot deformation + Q&P treated steel CrNi3Si2MoV is lath martensite + 5. 7% ~ 17.2% lamella residual austenite

with 30% hot deformation the residual austenite amount (17. 2%) in steel is maximum

with 50% hot deformation the hardness HV value of steel is maximum up to 448

and as hot deformation up to 70%

the obvious recrystallization of steel occurs with fine structure and the hardness of steel decreases.