Concasting process factors to form the cold rolled coil defect related slag entrapment have been analyzed. Results show that with production of low carbon aluminium-killed steel by 150 t converter-argon blowing station-LF-CAS or RH-(900 ~ 1 020)mm x210 mm casting process

the defect index of hot rolled plate with nozzle merging depth 130 ~ 155 mm is far less that with nozzle merging depth 125 mm and 160 mm； the average total oxygen content T[O

]

in steel with ladle nozzle self-open and oxygen lance open is respectively 15 x 10

-6

and 25 x 10

-6

slag entrapment defect index of hot rolled plate decreases obviously by using slagging detector to control slagging amount from ladle to tundish. The index of slag inclusion-skin defect of hot rolled plate decreases from original 3. 45 to 0. 73 by controlling amount of liquid in tundish

improving nozzle

structure of tundish

optimizing merging depth of submerging nozzle

increasing ratio of ladle self-open and operating ratio of control tundish slagging amount detector

and using low sodium mold powder.