Mold flux for continuous-casting Ti-containing hypo-peritectic steel and method therefor

Patent metadata

Field	Value
Publication number	US-10328488-B2
Application number	US-201515311910-A
Country	US
Kind code	B2
Filing date	Jun 2, 2015
Priority date	Jun 10, 2014
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

A mold flux is used in continuous casting of Ti-containing hypo-peritectic steel so as to prevent longitudinal cracks from forming on a surface of a slab. The mold flux contains CaO, SiO 2 , an alkali metal oxide and a fluorine compound as major components. f(1), f(2) and f(3), which are calculated from the initial chemical composition, are (1.1−0.5×T) to (1.9−0.5×T), 0.05 to 0.40 and 0 to 0.40, respectively, if the Ti content of the molten steel (mass %) is T. The TiO 2 content in the melting state during the casting is no more than 20 mass % and the ratio of the first peak height of perovskite to the first peak height of cuspidine in the mold flux film is no more than 1.0.

First claim

The invention claimed is:

1. A method for continuous-casting Ti-containing hypo-peritectic steel, the method comprising: continuous-casting hypo-peritectic steel containing 0.1 to 1 mass % of Ti, using a mold flux,
wherein
the mold flux contains CaO, SiO 2 , an alkali metal oxide and a fluorine compound as major components,
a chemical composition of the mold flux before the mold flux is put into a mold satisfies the formulas (1), (2) and (3),
a TiO 2 content of the mold flux in a melting state during the casting is no more than 20 mass %, and
a strength ratio of a film of the mold flux in a solidifying state after the casting is no more than 1.0:
1.1−0.5× T≤f (1)≤1.9−0.5× T   (1)

0.05≤ f (2)≤0.40  (2)

0≤ f (3)≤0.40  (3),

wherein in the formulas (1) to (3),
f (1)=( CaO ) h /( SiO 2 ) h   (A)

f (2)=( CaF 2 ) h /{( CaO ) h +( SiO 2 ) h +( CaF 2 ) h }  (B)

f (3)={(alkali metal fluoride) h }/{( CaO ) h +( SiO 2 ) h +(alkali metal fluoride) h )}   (C),

wherein in the formulas (A) to (C),
( CaO ) h =W CaO −( CaF 2 ) h ×0.718  (D)

( SiO 2 ) h =W SiO2   (E)

( CaF 2 ) h =( W F −W Li2O ×1.27− W Na2O ×0.613− W K2O ×0.403)×2.05  (F)

(alkali metal fluoride) h =W Li2O ×1.74+ W Na2O ×1.35+ W K2O ×1.23  (G)

wherein T is a Ti content of molten steel (mass %), W CaO is a CaO content of the mold flux (mass %), W SiO2 is a SiO 2 content of the mold flux (mass %), W F is a F content of the mold flux (mass %), and W Li2O , W Na2O and W K2O are contents of Li 2 O, Na 2 O and K 2 O respectively, which are alkali metal oxides, of the mold flux (mass %), and
wherein the strength ratio of the film means a ratio of a first peak height of perovskite to a first peak height of cuspidine, the ratio being obtained from X-ray diffraction analysis of powder obtained by pulverizing the film of the mold flux.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Hanao Masahito
• Nagashima Masaki
• Ishibashi Masatsugu

Classifications

• B22D11/001 Primary

  of specific alloys · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title