# US 11,078,558 B2 · Steel material, oil-well steel pipe, and method for producing steel material

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- Number: US 11,078,558 B2
- Document ID: US11078558B2
- Status: Granted
- Kind: B2
- Application number: 16/339,577
- Filed: 2017-10-06
- Published: 2020-02-06
- Granted: 2021-08-03
- Earliest claimed: 2016-10-06
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel Corporation
- Inventors: Yuji Arai; Shinji Yoshida; Atsushi Soma; Hiroki Kamitani
- Web page: https://patentgrep.com/patent/US11078558B2

## CPC

- C22C 38/42: with copper
- C21D 7/13: by hot working
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/08: for tubular bodies or pipes
- C21D 9/085: {Cooling or quenching}
- C21D 9/46: for sheet metals
- 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 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/30: with cobalt
- C22C 38/32: with boron
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/52: with cobalt
- C22C 38/54: with boron
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- 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

The steel material according to the present invention contains a chemical composition consisting of, in mass %, C: 0.25 to 0.50%, Si: 0.05 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.25 to 1.50%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.002 to 0.010% and O: 0.0100% or less, with the balance being Fe and impurities. The steel material also contains an amount of dissolved C within a range of 0.010 to 0.050 mass%. The steel material also contains an yield strength is in a range of 862 to less than 965 MPa, and an yield ratio is 90% or more.

## Claims

### Claim 1

A steel material having:
a chemical composition consisting of, in mass %,
C: 0.26 to 0.50%,
Si: 0.05 to 0.50%,
Mn: 0.05 to 1.00%,
P: 0.025% or less,
S: 0.0100% or less,
Al: 0.005 to 0.100%,
Cr: 0.30 to 1.50%,
Mo: 0.25 to 1.50%,
Ti: 0.002 to 0.050%,
B: 0.0001 to 0.0050%,
N: 0.002 to 0.010%,
O: 0.0100% or less,
V: 0 to 0.30%,
Nb: 0 to 0.100%,
Ca: 0 to 0.0100%,
Mg: 0 to 0.0100%,
Zr: 0 to 0.0100%,
Co: 0 to 0.50%,
W: 0 to 0.50%,
Ni: 0 to 0.50%, and
Cu: 0 to 0.50%,
with the balance being Fe and impurities,
an amount of dissolved C within a range of 0.010 to 0.050 mass %,
a yield strength within a range of 862 to less than 965 MPa, and
a yield ratio of 90% or more.

### Claim 2 (depends on 1)

The steel material according to claim 1, wherein the chemical composition contains one or more types of element selected from the group consisting of:
V: 0.01 to 0.30%, and
Nb: 0.002 to 0.100%.

### Claim 3 (depends on 2)

The steel material according to claim 2, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ca: 0.0001 to 0.0100%,
Mg: 0.0001 to 0.0100%, and
Zr: 0.0001 to 0.0100%.

### Claim 4 (depends on 3)

The steel material according to claim 3, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Co: 0.02 to 0.50%, and
W: 0.02 to 0.50%.

### Claim 5 (depends on 4)

The steel material according claim 4, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 6 (depends on 3)

The steel material according claim 3, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 7 (depends on 2)

The steel material according to claim 2, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Co: 0.02 to 0.50%, and
W: 0.02 to 0.50%.

### Claim 8 (depends on 7)

The steel material according claim 7, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 9 (depends on 2)

The steel material according claim 2, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 10 (depends on 1)

The steel material according to claim 1, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ca: 0.0001 to 0.0100%,
Mg: 0.0001 to 0.0100%, and
Zr: 0.0001 to 0.0100%.

### Claim 11 (depends on 10)

The steel material according to claim 10, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Co: 0.02 to 0.50%, and
W: 0.02 to 0.50%.

### Claim 12 (depends on 11)

The steel material according claim 11, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 13 (depends on 10)

The steel material according claim 10, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 14 (depends on 1)

The steel material according to claim 1, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Co: 0.02 to 0.50%, and
W: 0.02 to 0.50%.

### Claim 15 (depends on 14)

The steel material according claim 14, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 16 (depends on 1)

The steel material according claim 1, wherein the chemical composition contains one or more types of element selected from the group consisting of:
Ni: 0.02 to 0.50%, and
Cu: 0.01 to 0.50%.

### Claim 17 (depends on 1)

The steel material according to claim 1, wherein the steel material is in an oil-well steel pipe.

### Claim 18 (depends on 1)

A method for producing the steel material according to claim 1, comprising:
a preparation process of preparing an intermediate steel material containing a chemical composition consisting of, in mass % C: 0.26 to 0.50%, Si: 0.05 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.25 to 1.50%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.002 to 0.010%, O: 0.0100% or less, V: 0 to 0.30%, Nb: 0 to 0.100%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, Zr: 0 to 0.0100%, Co: 0 to 0.50%, W: 0 to 0.50%, Ni: 0 to 0.50%, and Cu: 0 to 0.50%, with the balance being Fe and impurities,
a quenching process of, after the preparation process, cooling the intermediate steel material that is at a temperature in a range of 800 to 1000° C. at a cooling rate of 300° C./min or more; and
a tempering process of holding the intermediate steel material after quenching at a temperature in a range of 670° C. to an Ac1 point for 10 to 180 minutes, and thereafter cooling the intermediate steel material at an average cooling rate in a temperature region from 600° C. to 200° C. of 5 to 100° C./sec.

### Claim 19 (depends on 18)

The method for producing the steel material according to claim 18, wherein the preparation process includes:
a starting material preparation process of preparing a starting material containing a chemical composition consisting of, in mass %, C: 0.25 to 0.50%, Si: 0.05 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.25 to 1.50%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.002 to 0.010%, O: 0.0100% or less, V: 0 to 0.30%, Nb: 0 to 0.100%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, Zr: 0 to 0.0100%, Co: 0 to 0.50%, W: 0 to 0.50%, Ni: 0 to 0.50%, and Cu: 0 to 0.50%, with the balance being Fe and impurities, and
a hot working process of subjecting the starting material to hot working to produce an intermediate steel material.