US 2024/0368744 A1Published application

Steel material, and crankshaft made of the steel material

AssigneesNippon Steel Corporation, Honda Motor Co., Ltd.

InventorsMotoki TAKASUGA, Shigefumi NISHITANI, Masato YUYA, Hitoshi MATSUMOTO, Shota HAMA, Hiroki MASUDA, Hideki MATSUDA, Hiromasa TAKAHASHI

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Abstract

The steel material consists of, in mass %, C: 0.25% to 0.35%, Si: 0.05 to 0.35%, Mn: 0.85 to 1.20%, P: 0.080% or less, S: 0.030 to 0.100%, Cr: 0.10% or less, Ti: 0.050% or less, Al: 0.050% or less, N: 0.005 to 0.024%, and O: 0.0100% or less, with the balance being Fe and impurities, and Fn1 defined in the specification is 1.00 to 2.05, and Fn2 defined in the specification is 0.42 to 0.60. A surface number density of MnS single inclusions and MnS composite inclusions having an equivalent circular diameter of 5.0 μm or more is 20/mm2 or more. A ratio of the total number of MnS single inclusions and MnS composite inclusions with respect to the total number of inclusions is 70% or more. A ratio of the number of MnS composite oxides with respect to the total number of oxides is 30% or more.

Claims4

Dependent claims

A steel material consisting of, in mass %,

C:
0.25% to 0.35%,
Si:
0.05 to 0.35%,
Mn:
0.85 to 1.20%,
P:
0.080% or less,
S:
0.030 to 0.100%,
Cr:
0.10% or less,
Ti:
0.050% or less,
Al:
0.050% or less,
N:
0.005 to 0.024%, and
O:
0.0100% or less, with
the balance being Fe and impurities,
wherein:
Fn1 defined by Formula (1) is 1.00 to 2.05,
Fn2 defined by Formula (2) is 0.42 to 0.60, and
when, among inclusions in the steel material,
an inclusion in which a total of a content of Mn and a content of S in percent by mass is 80.0% or more is defined as an MnS single inclusion,
an inclusion in which a total of a content of Mn and a content of S in percent by mass is 15.0 to less than 80.0% is defined as an MnS composite inclusion,
an inclusion in which a total of a content of Al, a content of Ca, and a content of O in percent by mass is 80.0% or more, and a total of a content of Mn and a content of S in percent by mass is less than 15.0% is defined as a single oxide, and
an inclusion in which a total of a content of Al, a content of Ca, and a content of O in percent by mass is 15.0 to less than 80.0%, and a total of a content of Mn and a content of S in percent by mass is 15.0 to less than 80.0% is defined as an MnS composite oxide,
in the steel material:
a surface number density of a total of the MnS single inclusions having an equivalent circular diameter of 5.0 μm or more and the MnS composite inclusions having an equivalent circular diameter of 5.0 μm or more is 20/mm2 or more,
a ratio of a total number of the MnS single inclusions having an equivalent circular diameter of 1.0 μm or more and the MnS composite inclusions having an equivalent circular diameter of 1.0 μm or more with respect to a total number of inclusions having an equivalent circular diameter of 1.0 μm or more is 70% or more, and
a ratio of a number of the MnS composite oxides having an equivalent circular diameter of 1.0 μm or more with respect to a total number of the single oxides having an equivalent circular diameter of 1.0 μm or more and the MnS composite oxides having an equivalent circular diameter of 1.0 μm or more is 30% or more;
Fn
⁢
1
=
Mn
+
7.24
Cr
+
6.53
Al
(
1
)
Fn
⁢
2
=
C
+
0.1
Si
+
0.19
Mn
+
0.23
Cr
-
0.34
S
(
2
)
where, a content in percent by mass of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).

65 more elements

A crankshaft, comprising:

a pin section,
a journal section, and
an arm section arranged between the pin section and the journal section,
at least the pin section and the journal section comprising:
a nitrided layer that is formed at an outer layer, and
a core portion that is further inward than the nitrided layer;
wherein:
the core portion consists of, in mass %,
C:
0.25% to 0.35%,
Si:
0.05 to 0.35%,
Mn:
0.85 to 1.20%,
P:
0.080% or less,
S:
0.030 to 0.100%,
Cr:
0.10% or less,
Ti:
0.050% or less,
Al:
0.050% or less,
N:
0.005 to 0.024%, and
O:
0.0100% or less, with
the balance being Fe and impurities;
and wherein:
Fn1 defined by Formula (1) is 1.00 to 2.05,
Fn2 defined by Formula (2) is 0.42 to 0.60, and
when, among inclusions in the core portion,
an inclusion in which a total of a content of Mn and a content of S in percent by mass is 80.0% or more is defined as an MnS single inclusion,
an inclusion in which a total of a content of Mn and a content of S in percent by mass is 15.0 to less than 80.0% is defined as an MnS composite inclusion,
an inclusion in which a total of a content of Al, a content of Ca, and a content of O in percent by mass is 80.0% or more, and a total of a content of Mn and a content of S in percent by mass is less than 15.0% is defined as a single oxide, and
an inclusion in which a total of a content of Al, a content of Ca, and a content of O in percent by mass is 15.0 to less than 80.0%, and a total of a content of Mn and a content of S in percent by mass is 15.0 to less than 80.0% is defined as an MnS composite oxide,
in the core portion:
a surface number density of a total of the MnS single inclusions having an equivalent circular diameter of 5.0 μm or more and the MnS composite inclusions having an equivalent circular diameter of 5.0 μm or more is 20/mm2 or more,
a ratio of a total number of the MnS single inclusions having an equivalent circular diameter of 1.0 μm or more and the MnS composite inclusions having an equivalent circular diameter of 1.0 μm or more with respect to a total number of inclusions having an equivalent circular diameter of 1.0 μm or more is 70% or more, and
a ratio of a number of the MnS composite oxides having an equivalent circular diameter of 1.0 μm or more with respect to a total number of the single oxides having an equivalent circular diameter of 1.0 μm or more and the MnS composite oxides having an equivalent circular diameter of 1.0 μm or more is 30% or more;
Fn
⁢
1
=
Mn
+
7.24
Cr
+
6.53
Al
(
1
)
Fn
⁢
2
=
C
+
0.1
Si
+
0.19
Mn
+
0.23
Cr
-
0.34
S
(
2
)
where, a content in percent by mass of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).

73 more elements

Dependencies are inferred from the claim text.