# US 11,111,566 B2 · Low alloy high strength seamless steel pipe for oil country tubular goods

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,111,566 B2
- Document ID: US11111566B2
- Status: Granted
- Kind: B2
- Application number: 16/078,919
- Filed: 2018-08-22
- Published: 2019-02-14
- Granted: 2021-09-07
- Earliest claimed: 2016-02-29
- Assignees: Jfe Steel Corporation
- Applicants: JFE Steel Corporation
- Inventors: Mitsuhiro Okatsu; Masao Yuga; Hiroki Ota; Kazuki Fujimura
- Web page: https://patentgrep.com/patent/US11111566B2

## CPC

- C22C 38/32: with boron
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 6/02: Hardening by precipitation
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/08: for tubular bodies or pipes
- 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 38/20: 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
- E21B 17/00: Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; {Cables;} Casings; Tubings
- C21D 2211/002: Bainite
- C21D 2211/008: Martensite
- 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)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

The steel pipe of the present invention is a low alloy high strength seamless steel pipe for oil country tubular goods including a composition containing, in terms of mass %, C: 0.23 to 0.27%, Si: 0.01 to 0.35%, Mn: 0.45 to 0.70%, P: 0.010% or less, S: 0.001% or less, O: 0.0015% or less, Al: 0.015 to 0.080%, Cu: 0.02 to 0.09%, Cr: 0.8 to 1.5%, Mo: 0.5 to 1.0%, Nb: 0.02 to 0.05%, B: 0.0015 to 0.0030%, Ti: 0.005 to 0.020%, and N: 0.005% or less, and having a ratio of the Ti content to the N content (Ti/N) of 3.0 to 4.0, with the balance being Fe and inevitable impurities, the steel pipe having a ratio of a stress at a strain of 0.7% to a stress at a strain of 0.4% in a stress-strain curve of 1.02 or less and a yield strength of 655 MPa or more.

## Claims

### Claim 1

A low alloy high strength seamless steel pipe for oil country tubular goods comprising a composition containing, in terms of mass %,
C: 0.23 to 0.27%,
Si: 0.01 to 0.35%,
Mn: 0.45 to 0.70%,
P: 0.010% or less,
S: 0.001% or less,
O: 0.0015% or less,
Al: 0.015 to 0.080%,
Cu: 0.02 to 0.09%,
Cr: 0.8 to 1.5%,
Mo: 0.5 to 1.0%,
Nb: 0.02 to 0.05%,
B: 0.0015 to 0.0030%,
Ti: 0.005 to 0.020%, and
N: 0.005% or less,
and having a value of a ratio of the Ti content to the N content (Ti/N) of 3.0 to 4.0,
with the balance being Fe and inevitable impurities,
the steel pipe having a value (σ0.7/σ0.4), as a ratio of a stress at a strain of 0.7% to a stress at a strain of 0.4% in a stress-strain curve, of 1.02 or less and a yield strength of 655 MPa or more.

### Claim 2 (depends on 1)

The low alloy high strength seamless steel pipe for oil country tubular goods according to claim 1, which further contains, in addition to the composition, one or more selected from, in terms of mass %,
V: 0.01 to 0.06%,
W: 0.1 to 0.2%, and
Zr: 0.005 to 0.03%.

### Claim 3 (depends on 1)

The low alloy high strength seamless steel pipe for oil country tubular goods according to claim 1, which further contains, in addition to the composition, in terms of mass %,
Ca: 0.0005 to 0.0030%,
and has the number of oxide-based non-metallic inclusions in steel comprised of Ca and Al and having a major diameter of 5 μm or more, whose composition ratio satisfies, in terms of mass %, the following equation (1), of 20 or less per 100 mm2:
(CaO)/(Al2O3)≥4.0 (1).

### Claim 4 (depends on 2)

The low alloy high strength seamless steel pipe for oil country tubular goods according to claim 2, which further contains, in addition to the composition, in terms of mass %,
Ca: 0.0005 to 0.0030%,
and has the number of oxide-based non-metallic inclusions in steel comprised of Ca and Al and having a major diameter of 5 μm or more, whose composition ratio satisfies, in terms of mass %, the following equation (1), of 20 or less per 100 mm2:
(CaO)/(Al2O3)≥4.0 (1).