Steel material

Patent metadata

Field	Value
Publication number	US-2025382687-A1
Application number	US-202318876350-A
Country	US
Kind code	A1
Filing date	Jul 14, 2023
Priority date	Jul 20, 2022
Publication date	Dec 18, 2025
Grant date	—

Abstract

A steel material of the present disclosure has the chemical composition described in the specification, Fn defined by formula (1) is 0.45 to 1.05, at a depth of 0.08R from a surface of the steel material (R is a radius), a number density of fine Bi particles, which are Bi particles having an equivalent circular diameter of 0.1 to 1.0 μm, is 15.00 pieces/mm 2 or more and a number density of coarse Bi particles, which are Bi particles having an equivalent circular diameter of 10.0 μm or more, is 0.25 pieces/mm 2 or less, and at a depth of 0.65R from the surface of the steel material, the number density of the fine Bi particles is less than 15.00 pieces/mm 2 and the number density of the coarse Bi particles is more than 0.25 pieces/mm 2 .

First claim

1 . A steel material whose cross section perpendicular to an axial direction thereof is circular, consisting of, by mass %,
C: more than 0.30 to 0.60%, Si: 0.01 to 0.90%, Mn: 0.50 to 1.70%, P: 0.030% or less, S: 0.200% or less, Bi: 0.0051 to 0.2500%, Al: 0.001 to 0.100%, N: 0.0250% or less, O: 0.0050% or less, Cr: 0 to 1.30%, V: 0 to 0.200%, Sn: 0 to 0.1000%, Sb: 0 to 0.0500%, As: 0 to 0.0500%, Pb: 0 to 0.09%, Mg: 0 to 0.0100%, Ti: 0 to 0.0400%, Nb: 0 to 0.0500%, W: 0 to 0.4000%, Zr: 0 to 0.2000%, Ca: 0 to 0.0100%, Te: 0 to 0.0100%, B: 0 to 0.0050%, rare earth metal: 0 to 0.0100%, Co: 0 to 0.0100%, Se: 0 to 0.0100%, In: 0 to 0.0100%, Mo: 0 to 0.30%, Cu: 0 to 0.50%, Ni:0 to 0.50%, and with the balance being Fe and impurities, and Fn defined by formula (1) is 0.45 to 1.05, wherein: at a depth of 0.08R from a surface of the steel material, where R defines a radius of the steel material,
a number density of fine Bi particles having an equivalent circular diameter of 0.1 to 1.0 μm, is 15.00 pieces/mm 2 or more, and
a number density of coarse Bi particles having an equivalent circular diameter of 10.0 μm or more, is 0.25 pieces/mm 2 or less,
at a depth of 0.65R from the surface of the steel material,
the number density of the fine Bi particles is less than 15.00 pieces/mm 2 , and
the number density of the coarse Bi particles is more than 0.25 pieces/mm 2 , and

Fn
=

C
+

(

Si
/
10

)

+

(

Mn
/
5

)

-

(

5
⁢
S
/
7

)

+

(

5
⁢
Cr
/
22

)

+

1.65
V

,

(
1
)

where, a content in percent by mass of a corresponding element is substituted for each symbol of an element in the formula (1), and if an element is not contained, “0” is substituted for the corresponding symbol of an element.

2 . The steel material according to claim 1 , comprising one or more elements selected from a group consisting of:
Cr: 0.01 to 1.30%, V: 0.001 to 0.200%, Sn: 0.0001 to 0.1000%, Sb: 0.0001 to 0.0500%, As: 0.0001 to 0.0500%, Pb: 0.01 to 0.09%, Mg: 0.0001 to 0.0100%, Ti: 0.0001 to 0.0400%, Nb: 0.0001 to 0.0500%, W: 0.0001 to 0.4000%, Zr: 0.0001 to 0.2000%, Ca: 0.0001 to 0.0100%, Te: 0.0001 to 0.010000, B: 0.0001 to 0.0050%, rare earth metal: 0.0001 to 0.0100%, Co: 0.0001 to 0.0100%, Se: 0.0001 to 0.0100%, In: 0.0001 to 0.0100%, Mo: 0.01 to 0.30%, Cu: 0.01 to 0.50%, and Ni: 0.01 to 0.50%.

Assignees

• Nippon Steel Corp

Inventors

• Aiso Toshiharu
• Miyanishi Kei

Classifications

• C22C38/54

  with boron · CPC title

• C22C38/46

  with vanadium · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title

• C22C38/42

  with copper · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title