# US 10,246,765 B2 · Martensitic Cr-containing steel and 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 10,246,765 B2
- Document ID: US10246765B2
- Status: Granted
- Kind: B2
- Application number: 15/109,139
- Filed: 2014-12-24
- Published: 2016-11-10
- Granted: 2019-04-02
- Earliest claimed: 2014-01-17
- Assignees: Nippon Steel & Sumitomo Metal Corporation
- Applicants: Nippon Steel & Sumitomo Metal Corporation
- Inventors: Tomohiko Omura; Yusaku Tomio; Hideki Takabe; Toshio Mochizuki
- Web page: https://patentgrep.com/patent/US10246765B2

## CPC

- C22C 38/54: with boron
- C21D 1/22: Martempering
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- 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 38/18: containing chromium
- 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 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- E21B 17/00: Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; {Cables;} Casings; Tubings
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/085: {Cooling or quenching}
- C21D 2201/05: Grain orientation
- C21D 2211/001: Austenite
- C21D 2211/005: Ferrite
- 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

A martensitic Cr-containing steel having excellent corrosion resistance, SSC resistance, and IGHIC resistance is provided. A martensitic Cr-containing steel according to the present invention includes: a chemical composition consisting of, by mass %, Si: 0.05 to 1.0%, Mn: 0.1 to 1.0%, Cr: 8 to 12%, V: 0.01 to 1.0%, sol. Al: 0.005 to 0.10%, with the balance being Fe and impurities, wherein an effective Cr amount defined by “Cr−16.6×C” is not less than 8%, and an Mo equivalent defined by “Mo+0.5×W” is 0.03 to 2%; a micro-structure wherein a grain size number of prior-austenite crystal grain is not less than 8.0; and a yield strength of less than 379 to 551 MPa, wherein a grain-boundary segregation ratio of Mo and W is not less than 1.5.

## Claims

### Claim 1

A martensitic Cr-containing steel, comprising:
a chemical composition consisting of, by mass %,
Si: 0.05 to 1.00%,
Mn: 0.1 to 1.0%,
Cr: 8 to 12%,
V: 0.01 to 1.0%,
sol. Al: 0.005 to 0.10%,
N: not more than 0.100%,
Nb: 0 to 1%,
Ti: 0 to 1%,
Zr: 0 to 1%,
B: 0 to 0.01%,
Ca: 0 to 0.01%,
Mg: 0 to 0.01%, and
rare earth metal (REM): 0 to 0.50%, and further consisting of one or two selected from the group consisting of
Mo: 0 to 2% and
W: 0 to 4%, with the balance being Fe and impurities, wherein the impurities include
C: not more than 0.10%,
P: not more than 0.03%,
S: not more than 0.01%,
Ni: not more than 0.5%, and
O: not more than 0.01%, and wherein
an effective Cr amount defined by Formula (1) is not less than 8%, and
an Mo equivalent defined by Formula (2) is 0.03 to 2%;
a micro-structure wherein a grain size number (ASTM E112) of prior-austenite crystal grain is not less than 8.0, and which consists of, in volume fraction, 0 to 5% of ferrite and 0 to 5% of austenite, with the balance being tempered martensite; and
a yield strength of 379 to less than 551 MPa, wherein
a grain-boundary segregation ratio, which is defined, when either one of Mo and W is contained, as a ratio of a maximum content at grain boundaries to an average content within grains of the contained element, and when Mo and W are contained, as an average of ratios of a maximum content at grain boundaries to an average content within grains of each element, is not less than 1.5:
Effective Cr amount=Cr−16.6×C (1)
Mo equivalent=Mo+0.5×W (2)
where, symbols of elements in Formulae (1) and (2) are substituted by corresponding contents (by mass %) of the elements.

### Claim 2 (depends on 1)

The martensitic Cr-containing steel according to claim 1, wherein:
the chemical composition contains one or more selected from the group consisting of
Nb: 0.01 to 1%,
Ti: 0.01 to 1%, and
Zr: 0.01 to 1%.

### Claim 3 (depends on 1)

The martensitic Cr-containing steel according to claim 1, wherein:
the chemical composition contains B: 0.0003 to 0.01%.

### Claim 4 (depends on 2)

The martensitic Cr-containing steel according to claim 2, wherein:
the chemical composition contains B: 0.0003 to 0.01%.

### Claim 5 (depends on 1)

The martensitic Cr-containing steel according to claims 1, wherein:
the chemical composition contains one or more selected from the group consisting of
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%.

### Claim 6 (depends on 2)

The martensitic Cr-containing steel according to claim 2, wherein:
the chemical composition contains one or more selected from the group consisting of
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%.

### Claim 7 (depends on 3)

The martensitic Cr-containing steel according to claim 3, wherein:
the chemical composition contains one or more selected from the group consisting of
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%.

### Claim 8 (depends on 4)

The martensitic Cr-containing steel according to claim 4, wherein:
the chemical composition contains one or more selected from the group consisting of
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%.

### Claim 9 (depends on 1)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 1.

### Claim 10 (depends on 2)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 2.

### Claim 11 (depends on 3)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 3.

### Claim 12 (depends on 4)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 4.

### Claim 13 (depends on 5)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 5.

### Claim 14 (depends on 6)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 6.

### Claim 15 (depends on 7)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 7.

### Claim 16 (depends on 8)

Oil country tubular goods, wherein:
the oil country tubular goods are produced using the martensitic Cr-containing steel according to claim 8.