Jfe Steel Corporation

Yoshie Nakai

Naoki Kikuchi

Yusuke Vincent Fujii

Takashi Yamauchi

Yuji Miki

Yasuo Kishimoto

Masamichi Kikuchi

Masaki Koizumi

Takahiko Maeda

Tomoharu Ishida

Tomoyoshi Ogasahara

Shinichi Nagai

Kenji Nakase

Yusuke Fujii

Shuji Kuyama

Akifumi Harada

Naoya Shibuta

Keisuke Mizobata

Rei Yamada

Hideya Masaki

Mikihiro Mori

Noritaka Nishiguchi

Maki Iwasa

Takehito Matsuda

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.

Decarburization end point determination method, decarburization end point determination device, secondary refining operation method for steel making, and method for producing molten steel

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 (&#xb0; C.) which is lower than a melting temperature (T) 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.

Method for removing phosphorus from phosphorus-containing substance

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.

Method for dephosphorization of hot metal, and refining agent

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=&#x3c1;&#xd7; U/2 . . . (1) wherein P is the dynamic pressure (kPa) of the jet flow at an exit of the top blowing lance, &#x3c1;the density (kg/Nm) of the jet flow, and U the velocity (m/sec) of the jet flow at the exit of the top blowing lance.

Method for refining molten steel in vacuum degassing equipment

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Tokyo, Japan

Yoshie Nakai