The causes of the exceeding silicon content and poor pour ability of low carbon and low silicon-aluminum killed steel C4C-Q (/% ：0. 02 ~0. 06C

≤ 0. 06Si

0. 02 ~0. 05Al) produced by 120 t BOF-LF-RH-CC flow sheet are analyzed. Through process optimization

adopting BOF tapping twice slag blocking mode and decarburizing process after tap

molten steel to decrease tap oxygen content and reduce Al

2

O

3

inclusions forming in the later deoxidation process combining optimizing the deoxidation mode of LF furnace and adjusting the ladle bottom blowing stirring

the silicon increase in molten steel can be controlled within 0. 03% while the desulfurization is ensured

the [Si

]

≤ 0. 045% in the tundish

the LF refining slag has good fluidity and st

rong ability to absorb inclusions ； by casting improving the protective effect during the start casting

adopting high liquid steel level when start casting of first furnace

to promote the inclusion in the tundish to float upwards

improve the molten steel temperature in the tundish

increase the static pressure of the molten steel at the same time

and reduce the Al

2

O

3

inclusions nodulation on the inner wall of the nozzle

therefore good pour ability C4C-Q steel composition with /% ：0. 04 ~0. 06C

0. 034 ~ 0. 042Si and 0. 028 ~ 0. 034Al is produced.