IP Library › Granted Patent US 12,668,862

Granted Patent B2

US 12,668,862 · App. 18/564,389 · Granted Jun 30, 2026

Austenitic stainless steel and tube

Inventors: Masahiro Seto (Tokyo, JP); Takumi Nishimoto (Tokyo, JP); Katsuki Tanaka (Tokyo, JP)

C22C38/58 C21D1/18 C21D1/32 C21D6/004 C21D6/005 C21D6/007 C21D6/008 C21D8/10 C21D9/08 C22C38/001 C22C38/002 C22C38/004 C22C38/005 C22C38/008 C22C38/02 C22C38/04 C22C38/42 C22C38/44 C22C38/46 C22C38/48 C22C38/50 C22C38/52 C22C38/54 C21D2211/001

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Quick Facts

Patent No.: US 12,668,862
App. No.: 18/564,389
Granted: Jun 30, 2026
Kind: B2

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USPTO Patent Center↗ Full Patent PDF↗

Abstract

There is provided an austenitic stainless steel having a chemical composition that comprises, in mass %: C: 0.002 to 0.020%, Si: 0.10 to 0.60%, Mn: 0.2 to 2.0%, P: 0.035% or less, S: 0.010% or less, Cu: 2.50 to 4.50%, Ni: 9.00 to 16.00%, Cr: 15.00 to 20.00%, Mo: 0.20 to 1.50%, Nb: 0.15 to 0.60%, N: 0.05 to 0.15%, B: 0.0010 to 0.0060%, and optional elements, with the balance: Fe and impurities and that satisfies [0.010≤V ER +Ti ER +Nb ER ], [27.0≤1.13(Ni—Ni ER )+(Cr—Cr ER )+1.85(Mo—Mo ER )+1.79(Nb—Nb ER )<40.5], and [Nb ER <0.052].

Claims (119)

1 . An austenitic stainless steel having a chemical composition comprising, in mass %:

C: 0.002 to 0.020%,

Si: 0.10 to 0.60%,

Mn: 0.2 to 2.0%,

P: 0.035% or less,

S: 0.010% or less,

Cu: 2.50 to 4.50%,

Ni: 9.00 to 16.00%,

Cr: 15.00 to 20.00%,

Mo: 0.20 to 1.50%,

Nb: 0.15 to 0.60%,

N: 0.05 to 0.15%,

B: 0.0010 to 0.0060%,

V: 0 to 0.50%,

Ti: 0 to 0.500%,

Co: 0 to 1.00%,

W: 0 to 1.00%,

Ta: 0 to 0.40%,

Sn: 0 to 0.0300%,

Ca: 0 to 0.0100%,

Mg: 0 to 0.0100%, and

REM: 0 to 0.0800%,

with the balance: Fe and impurities, and

satisfies Formulas (i) to (iii) shown below:

0.01

≤

(

)

27.

≤

1.13

(

⁢

—

⁢

)

(

⁢

—

⁢

)

1.85

(

⁢

—

⁢

)

1.79

(

⁢

—

⁢

)

40.5

(

)

0.052

(

iii

)

where symbols in the formulas are defined as follows, symbols of elements indicate contents (mass %) of the elements contained in the steel, and zero is assigned to a symbol of an element when the element is not contained:

V ER : Content of V in precipitates obtained by extraction residue analysis (mass %)

Ti ER : Content of Ti in precipitates obtained by extraction residue analysis (mass %)

Nb ER : Content of Nb in precipitates obtained by extraction residue analysis (mass %)

Ni ER : Content of Ni in precipitates obtained by extraction residue analysis (mass %)

Cr ER : Content of Cr in precipitates obtained by extraction residue analysis (mass %)

Mo ER : Content of Mo in precipitates obtained by extraction residue analysis (mass %).

2 . The austenitic stainless steel according to claim 1 , wherein the chemical composition contains, in mass %, one or more of:

V: 0.01 to 0.50%, and

Ti: 0.001 to 0.500%.

3 . The austenitic stainless steel according to claim 1 , wherein the chemical composition contains, in mass %, one or more of:

Co: 0.02 to 1.00%,

W: 0.01 to 1.00%,

Ta: 0.01 to 0.40%,

Sn: 0.0010 to 0.0300%,

Ca: 0.0010 to 0.0100%,

Mg: 0.0002 to 0.0100%, and

REM: 0.0010 to 0.0800%.

4 . The austenitic stainless steel according to claim 2 , wherein the chemical composition contains, in mass %, one or more of:

Co: 0.02 to 1.00%,

W: 0.01 to 1.00%,

Ta: 0.01 to 0.40%,

Sn: 0.0010 to 0.0300%,

Ca: 0.0010 to 0.0100%,

Mg: 0.0002 to 0.0100%, and

REM: 0.0010 to 0.0800%.

5 . A tube comprising the austenitic stainless steel according to claim 1 .

6 . A tube comprising the austenitic stainless steel according to claim 2 .

7 . A tube comprising the austenitic stainless steel according to claim 3 .

8 . A tube comprising the austenitic stainless steel according to claim 4 .