Abstract: A molten steel refining method increases a circulating rate using an RH vacuum degassing apparatus. An immersion depth of an immersion tube into molten steel inside a vacuum tank or a circulating gas flow rate is determined such that a stirring power energy density ? for the molten steel meets the following formulae: ? = [371GT × ln{ 1 + (?LgH0/P)}]/Wv, Wv = (?·Dv2/4) × H0 × ?L/1000, H0 = hv + L - hG, hv = (P0 - P)/(?Lg) + 1 -L, 1.35 × 105 × DU/WV < ? < 2.1 × 104.

Abstract: Proposed is a method for removing phosphorus from a phosphorus-containing substance which is applicable in an industrial scale so as to effectively reduce phosphorus contained in the phosphorus-containing substance. In this method, the phosphorus-containing substance used as a raw material for metal smelting or metal refining is reacted with a nitrogen-containing gas at a treatment temperature T (° C.) which is lower than a melting temperature (Tm) of the substance, so that phosphorus is removed preferably in the form of phosphorus nitride (PN). In this regard, a nitrogen partial pressure and an oxygen partial pressure in the nitrogen-containing gas are preferably controlled, thereby reducing a load of dephosphorization process, for example.

Abstract: A decarburization refining method for molten steel under reduced pressure. The method includes an oxygen-blowing decarburization and a rimmed decarburization. Using operation data taken at a time when oxygen-blowing decarburization is started and a time when oxygen-blowing decarburization is ended, an amount of carbon removed while the oxygen-blowing decarburization is performed is estimated. Based on the estimated amount of carbon removed, a carbon concentration in molten steel at a time when the rimmed decarburization is started is estimated. Using the estimated value as the carbon concentration in molten steel at the time when the rimmed decarburization is started, a change over time in the carbon concentration in molten steel while the rimmed decarburization is performed is calculated. Based on the calculated change over time in the carbon concentration in molten steel while the rimmed decarburization is performed, a determination is made about a time when the rimmed decarburization is ended.

Abstract: A decarburization end point determination method includes: estimating the carbon concentration and oxygen concentration of the molten steel and carbon dioxide gas concentration of exhaust gas in the vacuum chamber by using measurement values of the carbon concentration and the oxygen concentration of the molten steel, a measurement value of internal pressure of the vacuum chamber, and a model formula; correcting a parameter included in the model formula to reduce at least one of a difference between an estimate value and a measurement value of the oxygen concentration and a difference between an estimate value and a measurement value of the carbon dioxide gas concentration of the exhaust gas; estimating the carbon concentration of the molten steel by using the model formula in which the parameter is corrected; and determining timing when an estimate value reaches a target value as the completion time point of the vacuum decarburization treatment.

Abstract: When performing dephosphorization treatment of hot metal by adding a refining agent as a lime source and an oxygen source (dephosphorizing agent(s) and a gaseous oxygen source into the hot metal accommodated in a hot metal holding container, the refining agent used is a refining agent having an Ig-loss value of from 4.0% by mass to 35.0% by mass and including 60% by mass or more of quicklime.

Abstract: A method removes phosphorus from a phosphorus-containing substance. In the method, the phosphorus-containing substance that is used as a raw material for metal smelting or refining is reacted with a nitrogen-containing gas so that phosphorus in the phosphorus-containing substance is removed through nitriding. Prior to a treatment of a nitriding removal of phosphorus from the phosphorus-containing substance, a treatment is performed in which the phosphorus-containing substance is heated to an unmolten state temperature range so as to react with a reducing agent, thereby reducing at least a part of metal oxide in the phosphorus-containing substance.

Abstract: Proposed is a method for removing phosphorus from a phosphorus-containing substance which is applicable in an industrial scale so as to effectively reduce phosphorus contained in the phosphorus-containing substance. In this method, the phosphorus-containing substance used as a raw material for metal smelting or metal refining is reacted with a nitrogen-containing gas at a treatment temperature T (° C.) which is lower than a melting temperature (Tm) of the substance, so that phosphorus is removed preferably in the form of phosphorus nitride (PN). In this regard, a nitrogen partial pressure and an oxygen partial pressure in the nitrogen-containing gas are preferably controlled, thereby reducing a load of dephosphorization process, for example.

Abstract: When performing dephosphorization treatment of hot metal by adding a refining agent as a lime source and an oxygen source (dephosphorizing agent(s) and a gaseous oxygen source into the hot metal accommodated in a hot metal holding container, the refining agent used is a refining agent having an Ig-loss value of from 4.0% by mass to 35.0% by mass and including 60% by mass or more of quicklime.

Abstract: A molten steel refining method includes throwing a powder to molten steel while heating the powder with a flame formed by combustion of a hydrocarbon gas at the leading end of a top blowing lance. The lance height of the top blowing lance (the distance between the static bath surface of the molten steel and the leading end of the lance) is controlled to 1.0 to 7.0 m, and the dynamic pressure P of a jet flow ejected from the top blowing lance calculated from equation (1) below is controlled to 20.0 kPa or more and 100.0 kPa or less. P=?g× U2/2 . . . (1) wherein P is the dynamic pressure (kPa) of the jet flow at an exit of the top blowing lance, ?g the density (kg/Nm3) of the jet flow, and U the velocity (m/sec) of the jet flow at the exit of the top blowing lance.

Abstract: A molten steel refining method includes throwing a powder to molten steel while heating the powder with a flame formed by combustion of a hydrocarbon gas at the leading end of a top blowing lance. The lance height of the top blowing lance (the distance between the static bath surface of the molten steel and the leading end of the lance) is controlled to 1.0 to 7.0 m, and the dynamic pressure P of a jet flow ejected from the top blowing lance calculated from equation (1) below is controlled to 20.0 kPa or more and 100.0 kPa or less. P=?g× U2/2 . . . (1) wherein P is the dynamic pressure (kPa) of the jet flow at an exit of the top blowing lance, ?g the density (kg/Nm3) of the jet flow, and U the velocity (m/sec) of the jet flow at the exit of the top blowing lance.

Abstract: A refining agent containing Al, MgO and CaO as main components, wherein dolomite is a MgO source and a CaO source. When the refining agent is supplied into molten iron, Mg vapor is produced due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

Abstract: A refining agent contains Al, MgO, and CaO as main components, and uses dolomite as a MgO source and CaO source. When the refining agent is supplied into molten iron, it produces Mg vapor due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

Abstract: The present invention provides a method of desulfurizing hot metal, which method utilizes desulfurization slag resulting from a KR hot metal desulfurizing treatment as a desulfurizing agent for hot metal again to reduce hot metal desulfurization costs and the amount of slag generated, thereby solving environmental problems.

Abstract: The present invention provides a method of desulfurizing hot metal, which method utilizes desulfurization slag resulting from a KR hot metal desulfurizing treatment as a desulfurizing agent for hot metal again to reduce hot metal desulfurization costs and the amount of slag generated, thereby solving environmental problems.