PURPOSE: To efficiently smelt a stainless steel without using expensive reducing agent by using a top-bottom combined blowing converter, reducing chromium oxide content in decarburized slag produced in the previous heat with the charged molten iron and executing decarburization-refining in the same furnace after removing the slag.
CONSTITUTION: In the condition of leaving the slag 1 produced with the decarburizing in the previous heat, the molten iron I2 executing dephosphorizing and desulfurizing treatments and containing no chromium is charged into a converter, and oxygen-blowing and temp.-raising are executed while adding excess carbonaceous material having 10-60% of the slag wt. to reduce the chromium oxide in the slag. Successively, the furnace is tilted and a part or a large part of slag is removed and again, the molten iron II 3 executing dephosphorizing and desulfurizing treatments and containing no chromium is charged. Thereafter, the furnace is returned back to the original posture, and the oxygen-blowing is executed while adding ferro-chromium and flux to execute the decarburization-refining. At this time, the wt. ratio of molten iron I/(molten iron I + molten iron II) is made to be 45-75%. After lowering to the aimed carbon concn., again the furnace is tilted to tap only the molten steel and the slag 5 containing the chromium oxide is left in the furnace and the dephosphorized and desulfurized molten iron in the following heat is received.
OGAWA YUJI
YANO MASATAKA
