US2025066869A1PendingUtilityA1
Austenitic stainless steel and method for producing austenitic stainless steel
Assignee: NIPPON STEEL STAINLESS STEEL CORPPriority: Feb 10, 2022Filed: Jan 23, 2023Published: Feb 27, 2025
Est. expiryFeb 10, 2042(~15.5 yrs left)· nominal 20-yr term from priority
Inventors:Taichiro Mizoguchi
C21D 8/00C21D 2211/004C21D 6/02C21D 8/0273C21D 8/0263C21D 6/004C21D 9/46C22C 38/60C22C 38/58C22C 38/54C22C 38/52C22C 38/50C22C 38/48C22C 38/46C22C 38/44C22C 38/42C22C 38/34C22C 38/06C22C 38/04C22C 38/02C22C 38/008C22C 38/005C22C 38/004C22C 38/002C22C 38/001C21D 2211/001C21D 6/008C21D 6/007C21D 6/005C21D 2211/008C21D 8/0473C21D 8/005
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Claims
Abstract
Provided is an austenitic stainless steel which enables both a reduction in load of working during production and an increase in strength of an end product and which can be produced with high productivity. The austenitic stainless steel (i) contains 0.005-0.03% of C, 0.1-2.0% of Si, 0.3-2.5% of Mn, not more than 0.04% of P, not more than 0.015% of S, 3.0-6.0% of Ni, 16.0-18.5% of Cr, 1.5-4.0% of Cu, and 0.08-0.25% of N, in percent by mass, and the other part composed of Fe and an inevitable impurity, (ii) includes not less than 20% by volume of an austenite phase, a Cu-rich phase having a number density of not less than 1.0×103 μm−3 and a long diameter of not more than 30 nm, and a remaining part composed of a deformation-induced martensite phase and an inevitably formed phase, and (iii) has an Md30 value of 0.0 to 80.0.
Claims
exact text as granted — not AI-modified1 . An austenitic stainless steel, comprising not less than 0.005% and not more than 0.03% of C, not less than 0.1% and not more than 2.0% of Si, not less than 0.3% and not more than 2.5% of Mn, not more than 0.04% of P, not more than 0.015% of S, not less than 3.0% and less than 6.0% of Ni, not less than 16.0% and not more than 18.5% of Cr, not less than 1.5% and not more than 4.0% of Cu, and not less than 0.08% and not more than 0.25% of N, in percent by mass, and the other part composed of Fe and an inevitable impurity,
the austenitic stainless steel including (i) not less than 20% by volume of an austenite phase, (ii) a Cu-rich phase having a number density of not less than 1.0×10 3 μm −3 and a long diameter of not more than 30 nm, and (iii) a remaining part composed of a deformation-induced martensite phase and an inevitably formed phase, the austenitic stainless steel having an Md 30 value of not less than 0.0 and not more than 80.0 as represented by expression (1) below,
Md
3
0
=
551
-
462
(
C
+
N
)
-
9.2
Si
-
8.1
Mn
-
29
Ni
-
10.6
Cu
-
13.7
Cr
-
18.5
Mo
(
1
)
wherein in expression (1) above, a content, in percent by mass, of each element contained in the austenitic stainless steel is substituted into a corresponding element symbol, and 0 is substituted into an element symbol of an element not added to the austenitic stainless steel.
2 . The austenitic stainless steel as set forth in claim 1 , further comprising at least one selected from the group consisting of: not more than 1.0% of Mo; not more than 1.0% of W; not more than 0.5% of V; not less than 0.0001% and not more than 0.01% of B; not more than 0.8% of Co; not more than 0.1% of Sn; not more than 0.03% of Ca; not more than 0.03% of Mg; not more than 0.5% of Ti; not more than 0.5% of Nb; not more than 0.3% of Al; not more than 0.5% of Sb; not more than 0.5% of Zr; not more than 0.03% of Ta; not more than 0.03% of Hf; and not more than 0.2% of a rare earth metal, REM, in percent by mass.
3 . The austenitic stainless steel as set forth in claim 1 , having an average crystal grain size of not more than 10.0 μm.
4 . A method for producing an austenitic stainless steel, the austenitic stainless steel containing not less than 0.005% and not more than 0.03% of C, not less than 0.1% and not more than 2.0% of Si, not less than 0.3% and not more than 2.5% of Mn, not more than 0.04% of P, not more than 0.015% of S, not less than 3.0% and less than 6.0% of Ni, not less than 16.0% and not more than 18.5% of Cr, not less than 1.5% and not more than 4.0% of Cu, and not less than 0.08% and not more than 0.25% of N, in percent by mass, and the other part composed of Fe and an inevitable impurity, the austenitic stainless steel having an Md 30 value of not less than 0.0 and not more than 80.0 as represented by expression (1) below,
said method comprising a finishing annealing step of carrying out finishing annealing at a temperature of not lower than 750° C. and not higher than 980° C., wherein in a case where a peak temperature in the finishing annealing step is not lower than 850° C., time during which heating is carried out at not lower than 850° C. is not more than 30 seconds, and in the finishing annealing step, an average rate of cooling from 700° C. to 500° C. after the finishing annealing is not less than 1° C./s,
Md
3
0
=
551
-
462
(
C
+
N
)
-
9.2
Si
-
8.1
Mn
-
29
Ni
-
10.6
Cu
-
13.7
Cr
-
18.5
Mo
(
1
)
wherein in expression (1) above, a content, in percent by mass, of each element contained in the austenitic stainless steel is substituted into a corresponding element symbol, and 0 is substituted into an element symbol of an element not added to the austenitic stainless steel.
5 . The austenitic stainless steel as set forth in claim 2 , having an average crystal grain size of not more than 10.0 μm.Join the waitlist — get patent alerts
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