SLOPPING PREVENTION METHOD

PROBLEM TO BE SOLVED: To provide a slopping prevention method by which slopping can be prevented without reducing oxygen feeding speed even under high speed feeding of oxygen, and an amount of use of carboneceous material can be reduced and an inexpensive facility cost is actualized.SOLUTION: By using a top-bottom blowing type converter, the top-blowing oxygen is blown for 4-8 min toward molten iron at a top-blowing oxygen flow rate of 2.0-4.0 Nm/min/ton, and iron oxide of Mkg (10≤M≤30) per ton of the molten iron is charged in a lump or intermittently into the converter during elapse of 1-4 min from the blowing start of the top-blowing oxygen, and slag basicity (CaO%/SiO%) and T. Fe concentration at the blowing-finish time of the blowing oxygen are controlled to 2.0-2.5 and 5-15%, respectively and thus, a dephosphorizing treatment of the molten iron is performed. Then, the carbonaceous material of 0.4-1.0 Kg per ton of the molten iron is blown into a slag layer through a sub-lance layer at a speed of 0.4-1.0 Kg/min from the point of time when time T (T≥0) calculated by using {26/(M-1.4)-1.0}≤T≤{26/(M-1.4)} has passed after the charging completion time of the iron oxide. Thereby, the slopping during the dephosphorizing treatment is prevented.