US2025333825A1PendingUtilityA1
New duplex stainless steel
Est. expiryApr 12, 2042(~15.7 yrs left)· nominal 20-yr term from priority
C21D 8/10C22C 38/04C22C 38/02C22C 38/002C22C 38/001C21D 2211/005C21D 7/13C21D 7/02C21D 1/26C21D 8/0273C21D 8/0247C21D 9/08C21D 9/46C21D 1/18C21D 6/02C21D 6/004C22C 38/44C22C 38/06C22C 38/005C22C 38/58C22C 38/48C22C 38/50C22C 38/46C22C 38/54C22C 38/52C22C 38/42
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Claims
Abstract
The present invention relates to a duplex stainless steel comprising the following elements in weight %: C max 0.030; Si max 0.30; Mn 0.20 to 2.50; P max 0.030; S max 0.030; Cr 28.5 to 30.5; Ni 6.0 to 8.0; Mo 0.70 to 3.00; W 2.00 to 4.40; Cu≤0.50; N 0.30 to 0.55; Balance is Fe and unavoidable impurities; and wherein the ferrite content is of 40-60 vol %; and wherein the duplex stainless steel fulfills the requirements of: a. [Cr]+4.0*[Mo]+2.0*[W]<42.5 wherein the values of [Cr], [Mo] and [W] are in weight %; and b. having less than 10% coverage of quenched-in nitrides in the ferrite grain boundaries when in solution annealed condition. The present invention also relates to objects made of the present duplex stainless steel having a Rp0.2 higher than 650 MPa, ISO 6892-1 2019.
Claims
exact text as granted — not AI-modified1 . A duplex stainless steel, comprising the following elements in weight %:
C
max 0.030;
Si
max 0.30;
Mn
0.20 to 2.50;
P
max 0.030;
S
max 0.030;
Cr
28.5 to 30.5;
Ni
6.0 to 8.0;
Mo
0.70 to 3.00;
W
2.00 to 4.40;
Cu
≤0.50;
N
0.30 to 0.55;
balance is Fe and unavoidable impurities,
wherein the ferrite content is of 40-60 vol %, and
wherein the duplex stainless steel fulfills the requirements of:
a. [Cr]+4.0*[Mo]+2.0*[W]<42.5, wherein the values of [Cr], [Mo] and [W] are in weight %, and
b. having less than 10% coverage of quenched-in nitrides in the ferrite grain boundaries when in solution annealed condition.
2 . The duplex stainless steel according to claim 1 , wherein the content of Cr is from 29.0 to 30.5 wt %.
3 . The duplex stainless steel according to claim 1 , wherein the content of Ni is from 6.0 to 7.6 wt %.
4 . The duplex stainless steel according to claim 1 , wherein the content of Mo is from at least 0.70 to 2.00 wt %.
5 . The duplex stainless steel according to claim 1 , wherein the content of W is from 2.50 to 4.40 wt % or 3.00 to 4.00 wt %.
6 . The duplex stainless steel according to claim 1 , wherein the content of Mn is from 0.30 to 2.00 weight %.
7 . The duplex stainless steel according to claim 1 , wherein the content of Si is 0.10 to 0.30 weight %.
8 . The duplex stainless steel according to claim 1 , wherein the content of Cu is 0.15 to 0.50 weight %.
9 . The duplex stainless steel according to claim 1 , wherein the content of N is from 0.35 to 0.55 weight % or 0.38 to 0.55 weight % or 0.38 to 0.50 weight %.
10 . An object comprising a duplex stainless steel, wherein said duplex stainless steel comprises the following elements in weight %:
C
max 0.030;
Si
max 0.30;
Mn
0.20 to 2.50;
P
max 0.030;
S
max 0.030;
Cr
28.5 to 30.5;
Ni
6.0 to 8.0;
Mo
0.70 to 3.00;
W
2.00 to 4.40;
Cu
≤0.50;
N
0.30 to 0.55;
balance is Fe and unavoidable impurities,
wherein the ferrite content is of 40-60 vol %, and
wherein the duplex stainless steel fulfills the requirements of:
a) [Cr]+4.0*[Mo]+2.0*[W]<42.5, wherein the values of [Cr], [Mo] and [W] are in weight %, and
b) having less than 10% coverage of quenched in-nitrides in the ferrite grain boundaries when in solution annealed condition.
11 . The object according to claim 10 , wherein said object has a Rp0.2 higher than 650 MPa ISO 6892-1, 2019.
12 . The object according to claim 10 , wherein said object will contain less than 0.2 vol % sigma phase after cooling 40° C./min from 1 100° C. to room temperature when in solution annealed condition.
13 . The object according to claim 10 , wherein the content of Cr is from 29.0 to 30.5 wt %,
wherein the content of Ni is from 6.0 to 7.6 wt %, wherein the content of Mo is from at least 0.70 to 2.00 wt %, wherein the content of W is from 2.50 to 4.40 wt %, wherein the content of Mn is from 0.30 to 2.00 weight %, wherein the content of Si is 0.10 to 0.30 weight %, wherein the content of Cu is 0.15 to 0.50 weight %, and wherein the content of N is from 0.35 to 0.55 weight %.
14 . The object according to claim 10 , wherein said object is a tube, a sheet, a hollow, a billet, a strip, or a wire.
15 . The object according to claim 10 , wherein the object is a solution annealed condition object.
16 . Use of the object according to claim 10 , in applications wherein resistance against high pressure is required such as applications wherein the inner pressure is above about 20 kpsi.
17 . A process for manufacturing an object according to claim 10 , comprising the steps of
melting; casting; hot working; cold working; solution annealing which is performed at a temperature range of to about 1000 to about 1200° C., such as about 1050 to about 1150° C.; cooling from the solution annealing temperature to a temperature of about 900 to about 1000° C.; and quenching.
18 . The duplex stainless steel according to claim 1 , wherein the content of Ni is from 6.0 to 7.6 wt %,
wherein the content of Mo is from at least 0.70 to 2.00 wt %, wherein the content of W is from 2.50 to 4.40 wt %, wherein the content of Mn is from 0.30 to 2.00 weight %, wherein the content of Si is 0.10 to 0.30 weight %, wherein the content of Cu is 0.15 to 0.50 weight %, and wherein the content of N is from 0.35 to 0.55 weight %.
19 . The duplex stainless steel according to claim 2 , wherein the content of Ni is from 6.0 to 7.6 wt %,
wherein the content of Mo is from at least 0.70 to 2.00 wt %, wherein the content of W is from 2.50 to 4.40 wt %, wherein the content of Mn is from 0.30 to 2.00 weight %, wherein the content of Si is 0.10 to 0.30 weight %, wherein the content of Cu is 0.15 to 0.50 weight %, and wherein the content of N is from 0.35 to 0.55 weight %.Join the waitlist — get patent alerts
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