Steel material and component

Patent metadata

Field	Value
Publication number	US-12006557-B2
Application number	US-202017423964-A
Country	US
Kind code	B2
Filing date	Jan 21, 2020
Priority date	Jan 21, 2019
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

There is provided a steel material that is excellent in machinability, and that provides a high roller-pitting fatigue strength, a high high-cycle bending fatigue strength, and a high low-cycle bending fatigue strength when being subjected to induction hardening to be produced into an induction-hardened component. The steel material according to the present disclosure includes a chemical composition consisting of, in mass %, C: 0.40 to 0.70%, Si: 0.15 to 2.10%, Mn: 0.30 to 1.15%, Cr: 0.01 to less than 0.50%, S: 0.005 to 0.070%, N: 0.0020 to 0.0200%, Ti: 0.0080 to 0.2000%, B: 0.0005 to 0.0050%, Al: 0.005 to 0.100%, and P: less than 0.050%, with the balance being Fe and impurities, and satisfying Formula (1) to Formula (5) described herein, and has a ferrite area fraction of 40% or less and a martensite area fraction of 10% or less.

First claim

The invention claimed is:

1. A steel material comprising
a chemical composition consisting of, in mass %:
C: 0.40 to 0.70%,
Si: 0.15 to 2.10%,
Mn: 0.30 to 1.15%,
Cr: 0.01 to less than 0.50%,
S: 0.005 to 0.070%,
N: 0.0020 to 0.0200%,
Ti: 0.0080 to 0.2000%,
B: 0.0005 to 0.0050%,
Al: 0.005 to 0.100%,
P: less than 0.050%,
Mo: 0 to 1.00%,
Ni: 0 to 1.00%,
Cu: 0 to 1.00%,
Ca: 0 to 0.0050%,
Mg: 0 to 0.0050%,
Te: 0 to 0.20%,
rare earth metal: 0 to 0.0050%,
Zr: 0 to 0.0050%,
Nb: 0 to 0.20%,
V: 0 to 0.35%,
Sb: 0 to 0.015%,
Pb: 0 to 0.09%, and
with the balance being Fe and impurities, and
satisfying Formula (1) to Formula (5), wherein
a ferrite area fraction is 40% or less, and a martensite area fraction is 10% or less:
290C+50Si+430≥631.0  (1)

C+( 1/7)Si+(⅕)Mn+( 1/9)Cr+V+( 1/25)Mo≤0.900  (2)

(1+0.7Si)×(1+3.3333Mn)×(1+2.16Cr)×(1+3.00Mo)×(1+1.73V)×(1+0.365Cu)×(1+0.363Ni)×(2.616−1.6C)≥5.80  (3)

Ti−4×N≥0  (4)

9.7Mn θ +32.4Cr θ ≤25.9  (5)

where each symbol of an element in Formula (1) to Formula (4) is to be substituted by a content of a corresponding element (mass %), and if the corresponding element is not contained, the symbol of an element is to be substituted by “0”; Mn θ in Formula (5) is to be substituted by a concentration of Mn (mass %) in cementite, and Cr θ in Formula (5) is to be substituted by a concentration of Cr (mass %) in cementite.

2. The steel material according to claim 1 , wherein
the chemical composition further contains, in lieu of a part of Fe, one or more types of element selected from the group consisting of:
Mo: 0.01 to 1.00%,
Ni: 0.01 to 1.00%,
Cu: 0.01 to 1.00%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001 to 0.0050%,
Te: 0.01 to 0.20%,
rare earth metal: 0.0001 to 0.0050%,
Zr: 0.0001 to 0.0050%,
Nb: 0.01 to 0.20%,
V: 0.01 to 0.35%,
Sb: 0.001 to 0.015%, and
Pb: 0.01 to 0.09%.

3. A component comprising
a hardened layer, and
a core portion inner than the hardened layer, wherein
the hardened layer has a martensite area fraction of 90% or more, and
the core portion has
a chemical composition consisting of, in mass %:

C: 0.40 to 0.70%,
Si: 0.15 to 2.10%,
Mn: 0.30 to 1.15%,
Cr: 0.01 to less than 0.50%,
S: 0.005 to 0.070%,
N: 0.0020 to 0.0200%,
Ti: 0.0080 to 0.2000%,
B: 0.0005 to 0.0050%,
Al: 0.005 to 0.100%,
P: less than 0.050%,
Mo: 0 to 1.00%,
Ni: 0 to 1.00%,
Cu: 0 to 1.00%,
Ca: 0 to 0.0050%,
Mg: 0 to 0.0050%,
Te: 0 to 0.20%,
rare earth metal: 0 to 0.0050%,
Zr: 0 to 0.0050%,
Nb: 0 to 0.20%,
V: 0 to 0.35%,
Sb: 0 to 0.015%,
Pb: 0 to 0.09%, and
with the balance being Fe and impurities, and
satisfying Formula (1) to Formula (5), wherein
a ferrite area fraction is 40% or less, and a martensite area fraction is 10% or less:
290C+50Si+430≥631.0  (1)

C+( 1/7)Si+(⅕)Mn+( 1/9)Cr+V+( 1/25)Mo≤0.900  (2)

(1+0.7Si)×(1+3.3333Mn)×(1+2.16Cr)×(1+3.00Mo)×(1+1.73V)×(1+0.365Cu)×(1+0.363Ni)×(2.616−1.6C)≥5.80  (3)

Ti−4×N≥0  (4)

9.7Mn θ +32.4Cr θ ≤25.9  (5)

where each symbol of an element in Formula (1) to Formula (4) is to be substituted by a content of a corresponding element (mass %), Mn θ in Formula (5) is to be substituted by a concentration of Mn (mass %) in cementite, and Cr θ in Formula (5) is to be substituted by a concentration of Cr (mass %) in cementite.

4. The component according to claim 3 , wherein
the chemical composition further contains, in lieu of a part of Fe, one or more types of element selected from the group consisting of:
Mo: 0.01 to 1.00%,
Ni: 0.01 to 1.00%,
Cu: 0.01 to 1.00%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001 to 0.0050%,
Te: 0.01 to 0.20%,
rare earth metal: 0.0001 to 0.0050%,
Zr: 0.0001 to 0.0050%,
Nb: 0.01 to 0.20%,
V: 0.01 to 0.35%,
Sb: 0.001 to 0.015%, and
Pb: 0.01 to 0.09%.

Assignees

• Nippon Steel Corp

Inventors

• Miyanishi Kei
• Egashira Makoto

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/40

  with nickel · CPC title

• C22C38/32

  with boron · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/16

  containing copper · CPC title