The Φ18 mm hot-rolled coil of steel 40CrMoV (/% ：0.36 ~0.44C

0. 15 ~0. 35 Si

0.45 ~0.70Mn

≤ 0.025P

≤ 0.025S

0.80 - 1. 15Cr

0.50 - 0.65Mo

0.25 ~0.35V) is produced by 80 t top and bottom combined blowing converter-LF-RH-325 mm x 280 mm bloom casting flowsheet at Xingtai Steel. Results show that with the process measures including controlling BOF end carbon 0. 08% ~0. 12%

tapping liquid temperature 1 640 ~ 1 660 Y

adding deoxidation agent and alloys during tapping

LF slag series CaO-SiO

2

-Al

2

O

3

finished refining white slag basicity 4 ~ 8 and T (FeO + MnO) ≤ 1.0%

RH vacuum ≤ 100 Pa

treated time for ≥20 min

feeding calcium wire

casting mold electromagnetic

stirring and controlling rolling and cooling

the average T [0

]

in coil of steel is 10 X 10

-6

average N content is 33 X 10

-6

tensile strength of steel 1 200 ~ 1 250 MPa

reduction of area 59% ~62%

rating of nonmetallic inclusions A 0.5 and D I.0

rating of each macrostructure 1.0

and each performance index all meets the requirement of user.