By analyzing on ingredient of nozzle clogging and mechanism of clogging-forming it is obtained

that the nozzle clogging in casting process of Ti-bearing Al-killed ultra-low carbon steel has a hierarchical structure

consisting of a reaction layer and a bonding layer; inside

the reaction layer is caused by the reaction of the acid material in refractory with Al in the steel and the precipitation of inclusions caused by the temperature of molten steel decreasing due to contact with the wall surface of the clogging

while the bonding layer is caused by the accumulation of inclusions accompanied by cold steel； the mass percentage of Al in the bonding layer increases from the inner to the outer layer

and the mass percentage of Ti decreases. By taking such measures as (FeO + MnO) is controlled below 8% by modifying top slags

the mass percent [0] after RH decarburization is controlled within 0. 030%

the tundish argon replacement process before casting is implemented and so on

the number of continuous casting heats of Ti-bearing Al-killed ultra-low carbon steel increases from original 3 to 5

and the nozzle clogging rate has been reduced from original 80% to 30%.