US2025051874A1PendingUtilityA1
Ferritic free-cutting stainless steel
Est. expiryAug 7, 2043(~17 yrs left)· nominal 20-yr term from priority
C21D 8/06C21D 2211/005C21D 9/525C22C 38/004C21D 6/002C22C 38/54C22C 38/001C22C 38/002C22C 38/06C22C 38/04C22C 38/02C22C 38/44C22C 38/42C22C 38/60C21D 6/008C21D 6/005C21D 6/004C21D 1/26C21D 1/18C21D 7/13C21D 9/0075C21D 9/08C21D 8/065
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Claims
Abstract
The present invention relates to a ferritic free-cutting stainless steel consisting of: C≤0.02 mass %, Si≤0.50 mass %, 0.20≤Mn≤1.00 mass %, P≤0.05 mass %, 0.20≤S≤0.70 mass %, Cu≤1.5 mass %, Ni≤1.5 mass %, 10.0≤Cr≤20.0 mass %, Mo≤2.0 mass %, 0.30≤Al≤1.00 mass % O≤0.010 mass %, N≤0.030 mass %, and optionally at least one selected from the group consisting of: B≤0.0100 mass %, Mg≤0.0100 mass %, and Ca≤0.0100 mass %, with a balance being Fe and unavoidable impurities, in which the following three expressions are satisfied: ([Cr]+[Mo]+1.5[Si]+4[Al])/([Ni]+0.5[Mn]+30[C]+30[N])≥7, 900([C]+[N])+170[Si]+450[P]+12[Cr]+30[Mo]+10[Al]≤300, and 0.285≤[Mn]/[S]≤1.5, where [X] represents a content (mass %) of an element X.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A ferritic free-cutting stainless steel consisting of:
C≤0.02 mass %, Si≤0.50 mass %, 0.20≤Mn≤1.00 mass %, P≤0.05 mass %, 0.20≤S≤0.70 mass %, Cu≤1.5 mass %, Ni≤1.5 mass %, 10.0≤Cr≤20.0 mass %, Mo≤2.0 mass %, 0.30≤Al≤1.00 mass % O≤0.010 mass %, N≤0.030 mass %, and optionally at least one selected from the group consisting of:
B≤0.0100 mass %,
Mg≤0.0100 mass %, and
Ca≤0.0100 mass %,
with a balance being Fe and unavoidable impurities, wherein the following expression (1) to expression (3) are satisfied:
(
[
Cr
]
+
[
Mo
]
+
1.5
[
Si
]
+
4
[
Al
]
)
/
(
[
Ni
]
+
0.5
[
Mn
]
+
30
[
C
]
+
30
[
N
]
)
≥
7
(
1
)
900
(
[
C
]
+
[
N
]
)
+
170
[
Si
]
+
450
[
P
]
+
12
[
Cr
]
+
30
[
Mo
]
+
10
[
Al
]
≤
300
(
2
)
0.285
≤
[
Mn
]
/
[
S
]
≤
1.5
(
3
)
where [X] represents a content (mass %) of an element X.
2 . The ferritic free-cutting stainless steel according to claim 1 , further satisfying at least one selected from the group consisting of:
0.0001 mass %≤B≤0.0100 mass %, 0.0005 mass %≤Mg≤0.0100 mass %, and 0.0005 mass %≤Ca≤0.0100 mass %.
3 . The ferritic free-cutting stainless steel according to claim 1 , having:
a number proportion of a MnS-based sulfide being 100 or more and 10,000 or less, and a number proportion of an inclusion being 20 or less, where the “MnS-based sulfide” refers to a compound containing Mn and S, the “inclusion” refers to a compound other than the MnS-based sulfide, the “number proportion” of the MnS-based sulfide refer to the number of the MnS-based sulfide contained within an observation view field of 10,000 μm 2 (=100 μm×100 μm), and the “number proportion” of the inclusion refer to the number of the inclusion contained within an observation view field of 10,000 μm 2 (=100 μm×100 μm).
4 . The ferritic free-cutting stainless steel according to claim 2 , having:
a number proportion of a MnS-based sulfide being 100 or more and 10,000 or less, and a number proportion of an inclusion being 20 or less, where the “MnS-based sulfide” refers to a compound containing Mn and S, the “inclusion” refers to a compound other than the MnS-based sulfide, the “number proportion” of the MnS-based sulfide refer to the number of the MnS-based sulfide contained within an observation view field of 10,000 μm 2 (=100 μm×100 μm), and the “number proportion” of the inclusion refer to the number of the inclusion contained within an observation view field of 10,000 μm 2 (=100 μm×100 μm).
5 . A method for producing the ferritic free-cutting stainless steel described in claim 1 , the method comprising:
a first step of producing a steel ingot or a billet having a predetermined component composition; a second step of subjecting the steel ingot or the billet to a homogenization heat treatment at 1250° C. to 1300° C. for 1 hour or longer; and a third step of subjecting the steel ingot or the billet after the homogenization heat treatment to hot-working at 700° C. to 1000° C.
6 . The method for producing the ferritic free-cutting stainless steel according to claim 5 , further comprising a fourth step of annealing the hot-worked body at 730° C. to 870° C.Join the waitlist — get patent alerts
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