# US 9,039,962 B2 · Steel for induction hardening, roughly shaped material for induction hardening, producing method thereof, and induction hardening steel part

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- Number: US 9,039,962 B2
- Document ID: US9039962B2
- Status: Granted
- Kind: B2
- Application number: 13/637,414
- Filed: 2011-02-15
- Published: 2013-01-31
- Granted: 2015-05-26
- Earliest claimed: 2010-03-30
- Assignees: Nippon Steel & Sumitomo Metal Corporation
- Applicants: Manabu Kubota; Toshiharu Aiso; Kei Miyanishi
- Inventors: Manabu Kubota; Toshiharu Aiso; Kei Miyanishi
- Web page: https://patentgrep.com/patent/US9039962B2

## CPC

- C22C 38/60: containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/42: Induction heating
- C21D 9/30: for crankshafts; for camshafts
- C21D 9/32: for gear wheels, worm wheels, or the like
- C21D 9/40: for rings; for bearing races
- 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 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/16: containing copper
- C22C 38/18: containing chromium
- C22C 38/20: with copper
- C22C 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/34: with more than 1.5% by weight of silicon
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C 38/42: with copper
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/54: with boron
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/009: Pearlite
- Y02P 10/25: Process efficiency
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A steel for an induction hardening including, by mass %, C: more than 0.75% to 1.20%, Si: 0.002 to 3.00%, Mn: 0.20 to 2.00%, S: 0.002 to 0.100%, Al: more than 0.050% to 3.00%, P: limited to 0.050% or less, N: limited to 0.0200% or less, O: limited to: 0.0030% or less, and the balance composing of iron and unavoidable impurities, wherein an Al content and a N content satisfy, by mass %, Al−(27/14)×N>0.050%.

## Claims

### Claim 1

A roughly shaped material for an induction hardening comprising, by mass %,
C: more than 0.75% to 1.20%,
Si: 0.002 to 3.00%,
Mn: 0.20 to 2.00%,
S: 0.002 to 0.100%,
Al: more than 0.050% to 3.00%,
P: limited to 0.050% or less,
N: limited to 0.0200% or less,
O: limited to 0.0030% or less,
at least one of
V: 0.005 to less than 0.20%,
Nb: 0.005 to 0.10%, and
Ti: 0.005 to 0.10%, and
the balance of iron and unavoidable impurities,
wherein an Al content and a N content, by mass %, satisfy Al−(27/14)×N>0.050%, and wherein the roughly shaped material has a number of graphite grains with an average grain size of 0.5 μm or more, which is included in the roughly shaped material for induction hardening is 40 pieces/mm2 or less.

### Claim 2 (depends on 1)

The roughly shaped material for induction hardening according to claim 1, further comprising, by mass %,
B: 0.0005 to 0.0050%.

### Claim 3 (depends on 1)

The roughly shaped material for induction hardening according to claim 1, further comprising at least one of, by mass %,
Cr: 0.05% to less than 0.30%,
Mo: 0.01 to 1.00%,
Cu: 0.05 to 1.00%, and
Ni: 0.05 to 2.00%.

### Claim 4 (depends on 1)

The roughly shaped material for induction hardening according to claim 1, further comprising at least one of, by mass %,
Ca: 0.0005 to 0.0030%,
Zr: 0.0005 to 0.0030, and
Mg: 0.0005 to 0.0030%.

### Claim 5 (depends on 2)

The roughly shaped material for induction hardening according to claim 2, further comprising at least one of, by mass %,
Cr: 0.05% to less than 0.30%,
Mo: 0.01 to 1.00%,
Cu: 0.05 to 1.00%, and
Ni: 0.05 to 2.00%.

### Claim 6 (depends on 2)

The roughly shaped material for induction hardening according to claim 2, further comprising at least one of, by mass %,
Ca: 0.0005 to 0.0030%,
Zr: 0.0005 to 0.0030%, and
Mg: 0.0005 to 0.0030%.

### Claim 7 (depends on 3)

The roughly shaped material for induction hardening according to claim 3, further comprising at least one of, by mass %,
Ca: 0.0005 to 0.0030%,
Zr: 0.0005 to 0.0030%, and
Mg: 0.0005 to 0.0030%.

### Claim 8 (depends on 5)

The roughly shaped material for induction hardening according to claim 5, further comprising at least one of, by mass %,
Ca: 0.0005 to 0.0030%,
Zr: 0.0005 to 0.0030%, and
Mg: 0.0005 to 0.0030%.

### Claim 9 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A producing method of a roughly shaped material for induction hardening, the method comprising the following successive steps:
warm working or hot working, cooling, and annealing a steel for induction hardening having a chemical composition of the roughly shaped material for induction hardening according to any one of claims 1-3, 4, 5 and 6-8,
wherein the annealing is performed at an annealing temperature of 680 to 800° C. and an annealing time of 10 to 360 minutes, and wherein an average cooling rate in a temperature range of 750 to 650° C. during the cooling is 300° C./hour or less.

### Claim 10 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A producing method of a roughly shaped material for induction hardening, the method comprising the following successive steps:
hot working and cooling a steel for induction hardening having a chemical composition of the roughly shaped material for the induction hardening according to any one of claims 1-3, 4, 5 and 6-8,
wherein an average cooling rate in a temperature range of 750 to 650° C. during the cooling is 300° C./hour or less.

### Claim 11 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

An induction hardening steel part which is produced using the roughly shape material according to any one of claims 1-3, 4, 5 and 6-8,
wherein a hardness of a hardened surface layer at a depth of 50 nm from a topmost surface of the induction hardening steel part is HV650 or more,
wherein a hardness of a non-induction hardening area is HV180 or more, and
wherein a number of graphite grains with an average grain size of 0.5 μm or more which exist in the non-induction hardening area is 40 pieces/mm2 or less.