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

Patent metadata

Field	Value
Publication number	US-10287644-B2
Application number	US-201214123688-A
Country	US
Kind code	B2
Filing date	Aug 8, 2012
Priority date	Aug 12, 2011
Publication date	May 14, 2019
Grant date	May 14, 2019

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 SO2 and an analyzing step wherein SO2-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 desulfurizing molten steel, the method comprising:
taking out a sample from molten steel after tapping from a converter;
analyzing S concentration of the sample using an ultraviolet fluorescence method;
determining at least one of (i) acceptance or rejection of S and (ii) a subsequent desulfurizing condition,
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,
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 %, and
combusting the sample includes adding a combustion enhancer selected from the group consisting of Sn and W.

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

3. The method for desulfurizing 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 treating time.

4. The method for desulfurizing molten steel according to claim 1 , wherein when molten steel after the tapping from the converter is continuously subjected to a secondary refining, S concentration of a sample taken out from molten steel during the secondary refining is analyzed to determine the subsequent desulfurizing condition based on the S concentration.

5. The method for desulfurizing molten steel according to claim 1 , further comprising suppressing excessive charge of a desulfurizer during desulfurizing by charging the desulfurizer so that the S concentration of the molten steel after desulfurization is lower than a predetermined value.

6. The method for desulfurizing molten steel according to claim 1 , wherein removing the dust includes filtering the dust with a dust filter and controlling a flow amount of the gas having an oxygen concentration of 99.5 vol % to reduce clogging of the dust filter.

7. The method for desulfurizing molten steel according to claim 1 , wherein quantifying S concentration of the sample includes measuring a fluorescence intensity of SO 2 in the SO 2 -containing gas and comparing the measured intensity to a calibration curve to determine the S concentration of the sample before combustion.

8. A method of manufacturing molten steel by using a desulfurization method as claimed in claim 1 .

Assignees

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

Inventors

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

Classifications

• Y02A50/248

  Cross-Sectional Technologies · mapped topic

• G01N21/645

  Specially adapted constructive features of fluorimeters · CPC title

• C21C2007/0093

  Duplex process; Two stage processes · CPC title

• C21C7/10

  Handling in a vacuum · CPC title

• C21C7/0645 Primary

  Agents used for dephosphorising or desulfurising · CPC title