The metallurgical flowsheet of tested steel 1Cr12Ni3Mo2VN (/%: 0.13C

0.16Si

0.70Mn

11.42Cr

2.78Ni

1.67Mo

0.30V

0.0360N) is 30t EAF-LF-VD-3t ESR-forged to Φ350mm products. The effect of quenching at 950~1100°C and tempering at 200 ~700℃ on structure and properties of steel 1Cr12Ni3Mo2VN and the tensile properties of steel aging at 500°C for 500~10000h have been studied. Results show that the effect of quenching temperature at 950~1100°C on mechanical properties of steel 1Cr12Ni3Mo2VN is not obvious；the temper brittleness zone of steel is at about 600°C

nevertheless tempered at this temperature the decrease of plasticity of steel is smaller；as compared with the mechanical properties of steel 1Cr12Ni3Mo2VN quenched at 1040°C. and tempered at 540°C

with ageing at 500°C for 500h the tensile strength and yield strength of steel decrease respectively by 7.7% and 5.8%

and with ageing at 500°C for 10000h the tensile strength and yield strength of steel decrease respectively by 13.4% and 14.6%

and the reduction of area of steel decreases by 40%

its main cause is aggregation of impurity elements and deposition of carbide at grain boundary.