Method for operating converter and method for producing molten steel

A method for operating a converter that, when supplying a gaseous oxygen source to molten pig iron inside a converter-type refining furnace through a top-blowing lance and optionally further blowing in an oxidizing gas or an inert gas through a bottom-blowing tuyere to perform desiliconization refining of the molten pig iron and dephosphorization refining and decarburization refining of the molten pig iron, selects one of the following combinations of refining steps:

• a combination of one refining step of performing part of desiliconization refining of the molten pig iron, and another refining step of performing dephosphorization refining of the molten pig iron after the desiliconization refining alone or in combination with decarburization refining;
• and
• another combination of one refining step of performing one or both of desiliconization refining and dephosphorization refining of the molten pig iron, and another refining step of performing one or both of dephosphorization refining and decarburization refining of the molten pig iron,
• and performs, between the one refining step and the other refining step, an intermediate slag removal step of removing slag generated in the one refining step through a throat,
• characterized by,
• in the intermediate slag removal step, measuring one or two or more selected from a slag removal flow shape, a slag removal flow velocity, and a slag surface shape to estimate one or both of an amount and physical properties of removed slag;
• estimating an amount of slag remaining inside the converter-type refining furnace, or the amount and composition of slag remaining inside the converter-type refining furnace;
• and determining, based on the estimation result, an amount of auxiliary raw material to be fed in one of the types of refining in the other refining step.