# US 10,246,757 B2 · Bearing part

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- Number: US 10,246,757 B2
- Document ID: US10246757B2
- Status: Granted
- Kind: B2
- Application number: 15/110,390
- Filed: 2015-01-09
- Published: 2016-11-17
- Granted: 2019-04-02
- Earliest claimed: 2014-01-10
- Assignees: Nippon Steel & Sumitomo Metal Corporation
- Applicants: Nippon Steel & Sumitomo Metal Corporation
- Inventors: Masashi Sakamoto; Junichi Kodama; Yutaka Neishi
- Web page: https://patentgrep.com/patent/US10246757B2

## CPC

- C21D 9/40: for rings; for bearing races
- B22D 23/00: Casting processes not provided for in groups B22D1/00 - B22D21/00 (making metallic powder by casting B22F9/08; alumino-thermic welding B23K23/00; remelting metals C22B9/16)
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/32: Soft annealing, e.g. spheroidising
- C21D 8/06: during manufacturing of rods or wires
- C21D 9/36: for balls; for rollers
- C21D 9/38: for roll bodies
- 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 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/18: containing chromium
- C22C 38/20: with copper
- C22C 38/22: with molybdenum or tungsten
- C22C 38/32: with boron
- C22C 38/40: with nickel
- C22C 38/44: with molybdenum or tungsten
- C22C 38/54: with boron
- F16C 33/30: Parts of ball or roller bearings
- F16C 33/62: Selection of substances
- F16C 33/64: Special methods of manufacture
- C21D 2211/001: Austenite
- C21D 2211/003: Cementite
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/005: Ferrite
- C21D 2211/008: Martensite
- F16C 2204/66: High carbon steel, i.e. carbon content above 0.8 wt%, e.g. through-hardenable steel
- F16C 2204/70: with chromium as the next major constituent
- F16C 2204/72: with nickel as further constituent, e.g. stainless steel
- F16C 2220/44: by rolling
- F16C 2223/02: Mechanical treatment, e.g. finishing
- F16C 2223/10: Hardening, e.g. carburizing, carbo-nitriding
- 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)
- B22D: CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES (shaping of plastics or substances in a plastic state B29C; metallurgical processing, selection of substances to be added to metal C21, C22)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS

## Abstract

A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 μm or less; and a number density of a void having a circle equivalent diameter of 0.02 μm to 3.0 μm is 2000 mm−2 or less in the metallographic structure.

## Claims

### Claim 1

A bearing part comprising, as a chemical composition, by mass %,
C: 0.95% to 1.10%,
Si: 0.10% to 0.70%,
Mn: 0.20% to 1.20%,
Cr: 0.90% to 1.60%,
Al: 0.010% to 0.100%,
N: 0.003% to 0.030%,
P: 0.025% or less,
S: 0.025% or less,
O: 0.0010% or less, and
optionally
Mo: 0.25% or less,
B: 0.0050% or less,
Cu: 1.0% or less,
Ni: 3.0% or less, and
Ca: 0.0015% or less, and
a remainder including Fe and impurities,
wherein a metallographic structure includes a retained austenite, a spherical cementite and a martensite,
wherein an amount of the retained austenite is 15% to 25%, by volume %,
wherein an average grain size of a prior-austenite is 8.0 μm or less, and
wherein a number density of a void having a circle equivalent diameter of 0.02 μm to 3.0 μm is 2000 mm−2 or less in the metallographic structure.

### Claim 2 (depends on 1)

The bearing part according to claim 1 comprising, as the chemical composition, by mass %, one or more of
Mo: 0.01% to 0.25%,
B: 0.0001% to 0.0050%,
Cu: 0.1% to 1.0%,
Ni: 0.05% to 3.0%, and
Ca: 0.0003% to 0.0015%.

### Claim 3 (depends on 1)

The bearing part according to claim 1,
wherein a Vickers hardness is 750 Hv or more, and
wherein a rolling contact fatigue life in a contaminated environment is 5.0×106 or more, the contaminated environment being an environment where 1 g of an iron powder having a hardness of 750 Hv to 800 Hv and a particle size of 100 μm to 180 μm is mixed into 1 L of a lubricating oil.

### Claim 4 (depends on 2)

The bearing part according to claim 2,
wherein a Vickers hardness is 750 Hv or more, and
wherein a rolling contact fatigue life in a contaminated environment is 5.0×106 or more, the contaminated environment being an environment where 1 g of an iron powder having a hardness of 750 Hv to 800 Hv and a particle size of 100 μm to 180 μm is mixed into 1 L of a lubricating oil.