Non-magnetic austenitic stainless steel material and production method therefor

Patent metadata

Field	Value
Publication number	US-12577645-B2
Application number	US-202318142803-A
Country	US
Kind code	B2
Filing date	May 3, 2023
Priority date	May 10, 2022
Publication date	Mar 17, 2026
Grant date	Mar 17, 2026

Abstract

The present invention relates to a non-magnetic austenitic stainless steel material having a component composition containing, in terms of mass percent, C: <0.10%, Si: <0.3%, Mn: more than 4.5% to less than 10.0%, P: <0.05%, S: <0.0020%, Ni: 9.0% to 15.0%, Cr: 17.0% to 25.0%, Mo: 3.0% to 7.0%, and N: 0.3% to 0.6%, with the balance being Fe and unavoidable impurities; satisfying (40[N]+1.2[Cr]+0.07exp(0.3[Ni]+0.3[Cu]))×1.5[Mo]{circumflex over ( )}(−0.18)≤60, in which [M] represents a content of an element M in terms of mass %; having an austenite single phase structure; having a critical pitting temperature of 50° C. or higher; and having a 0.2% proof stress of 970 MPa or more.

First claim

What is claimed is:

1 . A non-magnetic austenitic stainless steel material:
having a component composition consisting of, in terms of mass percent:
C: <0.10%,
Si: <0.3%,
Mn: more than 4.5% to less than 10.0%,
P: <0.05%,
S: <0.0020%,
Ni: 9.0% to 15.0%,
Cr: 17.0% to 22.6%,
Mo: 3.0% to 7.0%,
N: 0.3% to 0.6%,
Nb: <0.2%,
W: <1.0%,
Al: <0.1%,
Ti: <0.2%,
V: <0.5%,
Ta: <0.2%,
B: ≤0.0050%,
Ca: <0.0200%,
Mg: <0.0200%,
Zr: <0.0200%
Cu: <1.0%, and
Co: <1.0%,
with the balance being Fe and unavoidable impurities;
satisfying:
(40[N]+1.2[Cr]+0.07 exp(0.3[Ni]+0.3[Cu]))×1.5[Mo]{circumflex over ( )}(−0.18)≤60,

756−555[C]−528[N]−10.3[Si]−12.5[Mn]−10.5[Cr]−24[Ni]−5.6[Mo]≤−110, and

48≤[Cr]+1.27[Ni]+3.2[Mo]+5.45[Cu],

in which [M] represents a content of an element M in terms of mass %;
having an austenite single phase structure; having a critical pitting temperature of 50° C. or higher in a test method according to Method C in ASTM G48; and having a 0.2% proof stress of 970 MPa or more at a position at a depth of 1 inch from a surface in the case where a thickness T or a diameter D is 4 inches or more, or at a position at a depth of T/4 or D/4 from the surface in the case where the thickness T or the diameter D is less than 4 inches.

2 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies the following Group A, in terms of mass percent:
Group A: at least one element selected from Nb: <0.1%, W: <0.1%, and Al: <0.01%.

3 . The non-magnetic austenitic stainless steel material according to claim 1 , having a round bar shape.

4 . The non-magnetic austenitic stainless steel material according to claim 3 , having a warm-forged structure in which a structure is inclined from a core portion to an outer peripheral portion.

5 . A steel material for a drill collar, which is obtained by boring the non-magnetic austenitic stainless steel material described in claim 4 to leave the outer peripheral portion.

6 . The non-magnetic austenitic stainless steel material according to claim 1 , having a hollow cylindrical shape.

7 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies, in terms of mass percent:
Ni: 9.0% to 13.9%.

8 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies, in terms of mass percent:
Mo: 4.5% to 7.0%.

9 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies, in terms of mass percent:
Cu: <0.35%.

10 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies, in terms of mass percent:
Ni: 9.0% to 13.9%, and Mo: 4.5% to 7.0%.

11 . The non-magnetic austenitic stainless steel material according to claim 1 , wherein the component composition further satisfies, in terms of mass percent:
Cu: 0.35% or less.

12 . A method for producing a non-magnetic austenitic stainless steel material, the material:
having a component composition consisting of, in terms of mass percent:
C: <0.10%,
Si: <0.3%,
Mn: more than 4.5% to less than 10.0%,
P: <0.05%,
S: <0.0020%,
Ni: 9.0% to 15.0%,
Cr: 17.0% to 22.6%,
Mo: 3.0% to 7.0%,
N: 0.3% to 0.6%,
Nb: <0.2%,
W: <1.0%,
Al: <0.1%,
Ti: <0.2%,
V: <0.5%,
Ta: <0.2%,
B: ≤0.0050%,
Ca: <0.0200%,
Mg: <0.0200%,
Zr: <0.0200%
Cu: <1.0%, and
Co: <1.0%,
with the balance being Fe and unavoidable impurities;
satisfying:
(40[N]+1.2[Cr]+0.07 exp(0.3[Ni]+0.3[Cu]))×1.5[Mo]{circumflex over ( )}(−0.18)≤60,

756−555[C]−528[N]−10.3[Si]−12.5[Mn]−10.5[Cr]−24[Ni]−5.6[Mo]≤−110, and

48≤[Cr]+1.27[Ni]+3.2[Mo]+5.45[Cu],

in which [M] represents a content of an element M in terms of mass %;
having an austenite single phase structure; having a critical pitting temperature of 50° C. or higher in a test method according to Method C in ASTM G48; and having a 0.2% proof stress of 970 MPa or more at a position at a depth of 1 inch from a surface in the case where a thickness T or a diameter D is 4 inches or more, or at a position at a depth of T/4 or D/4 from the surface in the case where the thickness T or the diameter D is less than 4 inches, and the method comprising:
subjecting a steel ingot having a predetermined component composition to hot working followed by a cooling treatment, and
performing warm working at an area reduction rate of 15% to 50% in a temperature range of 800° C. to 300° C. during the cooling treatment.

13 . The method for producing a non-magnetic austenitic stainless steel material according to claim 12 , wherein the component composition further satisfies the following Group A, in terms of mass percent:
Group A: at least one element selected from Nb: <0.1%, W: <0.1%, Al: <0.01%.

14 . The method for producing a non-magnetic austenitic stainless steel material according to claim 12 , further comprising providing a round bar-shaped material.

15 . The method for producing a non-magnetic austenitic stainless steel material according to claim 14 , further comprising: boring the round bar-shaped material, to provide a steel material for a drill collar having a hollow cylindrical shape.

16 . The method for producing a non-magnetic austenitic stainless steel material according to claim 12 , wherein the non-magnetic austenitic stainless steel material further satisfies:
756−555[C]−528[N]−10.3[Si]−12.5[Mn]−10.5[Cr]−24[Ni]−5.6[Mo]≤−110
in which [M] represents a content of an element M in terms of mass %.

17 . The method for producing a non-magnetic austenitic stainless steel material according to claim 12 , wherein the non-magnetic austenitic stainless steel material further satisfies:
48≤[Cr]+1.27[Ni]+3.2[Mo]+5.45[Cu]
in which [M] represents a content of an element M in terms of mass %.

Assignees

• Daido Steel Co Ltd

Inventors

• Furusho Chihiro
• Koyanagi Yoshihiko

Classifications

• C22C38/54

  with boron · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/46

  with vanadium · CPC title