Method of producing steel material

Patent metadata

Field	Value
Publication number	US-2016145718-A1
Application number	US-201414903103-A
Country	US
Kind code	A1
Filing date	Jun 4, 2014
Priority date	Jul 10, 2013
Publication date	May 26, 2016
Grant date	—

Abstract

A method of producing a steel material includes a step of adding Ca to molten steel with an amount of Ca adjusted within a range satisfying the formula (1) below:

0.5
≤

{

Ca
·
y



/


100

-

(

[

S
·
W



/


100

)

·
40.08



/


32.07

}



56.08
40.08

(

[

Al
2



O
3

]

·
W



/


100

)

≤
1.5

(
1
)

where Ca is the amount [kg] of Ca added, y is an yield [%] of Ca, [S] is a concentration [% by mass] of S in the steel before addition of Ca, [Al 2 O 3 ] is an amount [% by mass] of Al 2 O 3 in the steel before addition of Ca, and W is a weight [kg] of the molten steel.

First claim

1 . A method of producing a steel material, the method comprising a step of adding Ca to molten steel with an amount of Ca adjusted within a range satisfying the formula (1) below:

0.5
≤

{

Ca
·
y



/


100

-

(

[
S
]

·
W



/


100

)

·
40.08



/


32.07

}



56.08
40.08

(

[

Al
2



O
3

]

·
W



/


100

)

≤
1.5

(
1
)

where Ca is the amount [kg] of Ca added,
y is an yield [k] of Ca,
[S] is a concentration [% by mass] of S in the steel before addition of Ca,
[Al 2 O 3 ] is an amount [% by mass] of Al 2 O 3 in the steel before addition of Ca, and
W is a weight [kg] of the molten steel.

2 . The method of producing a steel material according to claim 1 , further comprising a step of analyzing, after secondary refining, the amount of Al 2 O 3 in the molten steel, and thereafter adding CaSi to the molten steel in a ladle.

3 . The method of producing a steel material according to claim 1 , the method producing the steel material with the amount of Al 2 O 3 in the molten steel analyzed by spark discharge atomic emission spectroscopy, the method further comprising
an intensity ratio computing step of determining aluminum/iron light emission intensity ratios of a plurality of discharge pulses, an alumina fraction computing step of computing an alumina fraction determined using the formula (2) below, a step of arranging the light emission intensity ratios of the respective discharge pulses obtained in the intensity ratio computing step in ascending order, using a light emission intensity ratio at a certain position equal to or lower than 30% of the total number of discharge pulses as a representative aluminum intensity ratio, and then computing an alumina intensity ratio (=the alumina fraction×a representative aluminum intensity ratio) using a product of the alumina fraction computed in the alumina fraction computing step and the representative aluminum intensity ratio, and a quantitative step of computing the amount of alumina (in the steel) using a relational formula between the alumina intensity ratio and the amount of alumina (in the steel) determined by chemical analysis:
Alumina fraction=Number of discharge pulses with Al/Fe intensity ratio larger than threshold value α/total number of pulses  (2)

where the threshold value α is determined using a frequency distribution diagram having a horizontal axis representing the light emission intensity ratios for the discharge pulses and a vertical axis representing frequency, the threshold value α being a value obtained by multiplying a mode of the light emission intensity ratios by a factor of f 1 (1.5≦f 1 ≦2.5).

4 . The method of producing a steel material according to claim 2 , the method producing the steel material with the amount of Al 2 O 3 in the molten steel analyzed by spark discharge atomic emission spectroscopy, the method further comprising
an intensity ratio computing step of determining aluminum/iron light emission intensity ratios of a plurality of discharge pulses, an alumina fraction computing step of computing an alumina fraction determined using the formula (2) below, a step of arranging the light emission intensity ratios of the respective discharge pulses obtained in the intensity ratio computing step in ascending order, using a light emission intensity ratio at a certain position equal to or lower than 30% of the total number of discharge pulses as a representative aluminum intensity ratio, and then computing an alumina intensity ratio (=the alumina fraction×a representative aluminum intensity ratio) using a product of the alumina fraction computed in the alumina fraction computing step and the representative aluminum intensity ratio, and a quantitative step of computing the amount of alumina (in the steel) using a relational formula between the alumina intensity ratio and the amount of alumina (in the steel) determined by chemical analysis:
Alumina fraction=Number of discharge pulses with Al/Fe intensity ratio larger than threshold value α/total number of pulses  (2)

where the threshold value α is determined using a frequency distribution diagram having a horizontal axis representing the light emission intensity ratios for the discharge pulses and a vertical axis representing frequency, the threshold value α being a value obtained by multiplying a mode of the light emission intensity ratios by a factor of f 1 (1.5≦f 1 ≦2.5).

Assignees

• Jfe Steel Corp

Inventors

• Furumai Kohei
• Aramaki Norichika
• Miki Yuji
• Murai Takeshi
• Inoue Toru
• Usui Yukio
• Ishida Tomoharu

Classifications

• G01N21/69

  specially adapted for fluids {, e.g. molten metal} · CPC title

• C22C1/02

  by melting {(C22C1/1036 takes precedence)} · CPC title

• G01N2021/695

  Molten metals · CPC title

• G01N21/67

  using electric arcs or discharges · CPC title

• C22C1/06 Primary

  with the use of special agents for refining or deoxidising · CPC title