# US 12,006,557 B2 · Steel material and component

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- Number: US 12,006,557 B2
- Document ID: US12006557B2
- Status: Granted
- Kind: B2
- Application number: 17/423,964
- Filed: 2020-01-21
- Published: 2022-05-12
- Granted: 2024-06-11
- Earliest claimed: 2019-01-21
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel Corporation
- Inventors: Kei Miyanishi; Makoto Egashira
- Web page: https://patentgrep.com/patent/US12006557B2

## CPC

- C21D 9/32: for gear wheels, worm wheels, or the like
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/00: 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)
- C21D 8/06: during manufacturing of rods or wires
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/16: containing copper
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/40: with nickel
- C22C 38/60: containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
- C21D 2211/008: Martensite
- Y02P 10/25: Process efficiency
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## 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.

## Claims

### Claim 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)
9.7Mnθ+32.4Crθ≤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”; Mnθ in Formula (5) is to be substituted by a concentration of Mn (mass %) in cementite, and Crθ in Formula (5) is to be substituted by a concentration of Cr (mass %) in cementite.

### Claim 2 (depends on 1)

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%.

### Claim 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)
9.7Mnθ+32.4Crθ≤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 %), Mnθ in Formula (5) is to be substituted by a concentration of Mn (mass %) in cementite, and Crθ in Formula (5) is to be substituted by a concentration of Cr (mass %) in cementite.

### Claim 4 (depends on 3)

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%.