In order to study the control technology of nonmetallic inclusions in aluminum deoxidized 0. 20 C steel (/% ：0. 13 ~0.23C

0. 17 〜0.37Si

0.35 ~0.65Mn

≤ 0.035P

≤ 0.035S

0.020 - 0.050Al) produced by the process of “120 t BOF-LF-RH-160 mm x 160 mm billet CC”，the adding time of deoxidizer in LF refining process is adjusted

and the type and quantity of nonmetallic inclusions in the refining process are analyzed. The results show that the non-metallic inclusions in steel before LF refining are mainly Al

2

O

3

with deoxidizing by al

uminum block after BOF tapping

and some inclusions change from Al

2

O

3

to Al

2

O

3

CaO before LF refining

and the density of non-metallic inclusions is 3 ~4 /mm

2

after RH

and billet oxygen content is (7. 48 ~ 8. 18) x 10-6

But with liquid deoxidizing by silicon-manganese after BOF tapping

feeding aluminum wire before refining end

the inclusion in refining process is mainly MnO • SiO

2

and the CaO content is less than 5%

billet oxygen content is (4. 94 〜5. 53) x 10

-6

  and the non-metallic inclusion is controlled to Al

2

O

3

at the end of refining

and after RH vacuum treatment

the density of non-metallic inclusion is less than 1.5/mm

2

. Therefore

for the aluminum-containing steel produced by the " BOF-LF-RH-CC" process

it is proposed to control the nonmetallic inclusions to Al

2

O

3

before the end of refining

and at the same time

RH vacuum is used to remove the inclusions efficiently

so as to improve the cleanliness of molten steel.