The production flow sheet for test steel 12Cr2Mo (/%: 0.09C

0. 30Si

0. 34Mn

0.007P

0. 006S

2

10Cr

0. 93Mo

0. 014A1) 406 mm x 40.5 mm tube is 120 t BOF-LF-RH-410 mm x 530 mm bloom casting-forging to 0390 mm tube stock-460 mm ASSEL mill rolling to tube. With using JMatPro software to calculate phase equilibrium diagram of test steel

it is obtained that the steel 12Cr2Mo phase transition point Ac

3

is 862 ℃; and the Ac

1

is 781 °C

and the examination on structure and mechanical properties of test steel normalizing-heat-treated at 910 °C and tempered at 700 ℃ has been carrie

d out. Results show that the matrix structure of normalized-tempered test steel 12Cr2Mo is bainite + minor ferrite

and a large amount of irregular M

23

C

6

precipitate at grain boundary and in intragranular

a small amount granular M6C carbides precipitate along grain boundary and a large amount fine pin-like Mo

2

C carbides precipitate in intragranular

and the mechanical properties of steel is excellent- strength /R

el

515 ~520 MPa and R

m

640 ~650 MPa

plasticity A 22% ~ 25% and Z 76% 80%

and impact energy at -60 TJ A

KV

268 ~293 J.