The pouring time of single nozzle for low carbon and ultra-low carbon steel is more than 5 hours, the stopper and expansion rod is not more than 15 mm, and the nozzle plugging area is not more than 15%;
The total amount of inclusions in molten steel is less than 3mg/10kg, and the percentage of Al2O3 system inclusions in the total amount of inclusions is less than 25%；
The proportion of surface warping and linear defects caused by inclusions is less than 1%.
