Molten steel desulfurization method, molten steel secondary refining method, and molten steel manufacturing method

Patent metadata

Field	Value
Publication number	US-11035014-B2
Application number	US-201715592693-A
Country	US
Kind code	B2
Filing date	May 11, 2017
Priority date	Aug 12, 2011
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A method for desulfurizing molten steel comprising taking a sample out from molten steel after tapping from a converter or during secondary refining and analyzing the sample rapidly with high accuracy by a method comprising a high frequency induction heating step wherein the sample is combusted and oxidized under the high frequency induction heating in an oxygen atmosphere having an oxygen purity of 99.5 vol % or more to convert S in the sample into SO 2 and an analyzing step wherein SO 2 -containing gas produced in the high frequency induction heating step is analyzed through an ultraviolet fluorescence method to quantify S concentration of the sample.

First claim

The invention claimed is:

1. A method for secondarily refining molten steel tapped from a converter, the method comprising analyzing an S concentration of a sample taken out from molten steel during a secondarily refining by using an ultraviolet fluorescence method for determining subsequent desulfurizing condition based on an analytical value of the S concentration,
wherein the analyzing the S concentration of the sample using the ultraviolet fluorescence method comprises (1) a high frequency induction heating step wherein the sample is combusted and oxidized under the high frequency induction heating in an oxygen atmosphere supplied with a gas having an oxygen concentration of 99.5 vol % or more to convert S in molten steel into SO 2 , and (2) an analyzing step in which SO 2 -containing gas produced in the high frequency induction heating step is analyzed to quantify S concentration of the sample using the ultraviolet fluorescence method after removing dust from SO 2 -containing gas produced by combustion of the sample, and
a difference between the oxygen concentration in the gas supplied to the high frequency induction heating furnace and a free oxygen concentration in the SO 2 -containing gas produced by combustion of the sample is not more than 10 vol %.

2. The method for secondarily refining molten steel according to claim 1 , wherein a target S concentration in a desulfurization is not more than 0.003 mass %.

3. The method for secondarily refining molten steel according to claim 1 , wherein the desulfurizing condition is at least one of an amount of a desulfurizer added in the desulfurization and a molten steel stirring time.

4. A method of manufacturing molten steel by using a secondary refining method as claimed in claim 1 .

Assignees

• Jfe Steel Corp

Inventors

• Kinoshiro Satoshi
• Ito Toshiyuki
• Kawabata Ryo
• Ishige Toshiro
• Fujimoto Kyoko
• Inose Masao

Classifications

• G01N21/64 Primary

  Fluorescence; Phosphorescence · CPC title

• C21C7/0037

  by injecting powdered material · CPC title

• F27D21/00

  Arrangement of monitoring devices; Arrangement of safety devices · CPC title

• C21C1/02

  Dephosphorising or desulfurising · CPC title

• C21C7/0087

  Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal · CPC title