US2024352563A1PendingUtilityA1
Steel material having high strength and excellent impact toughness, and manufacturing method therefor
Est. expiryDec 14, 2041(~15.4 yrs left)· nominal 20-yr term from priority
C21D 8/02C22C 38/06C22C 38/14C22C 38/12C22C 38/08C22C 38/04C22C 38/02C22C 38/002C22C 38/001C21D 2211/009C21D 2211/005C21D 9/46C21D 8/0226C22C 38/16C21D 8/0263C21D 8/0205
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Claims
Abstract
The present invention relates to: a steel material having high strength and excellent impact toughness, the steel material being usable for a land wind power generator and the like; and a method for manufacturing same.
Claims
exact text as granted — not AI-modified1 . A steel material having high strength and excellent impact toughness, comprising:
by weight, C: 0.12 to 0.18%, Si: 0.2 to 0.5%. Mn: 1.0 to 1.7%, P: 0.012% or less, S: 0.003% or less, Al: 0.015 to 0.045%, Nb: 0.02 to 0.05%, V: 0.01 to 0.08%, Ti: 0.005 to 0.017%, N: 0.002 to 0.01%, and a remainder of Fe and inevitable impurities; wherein a carbon equivalent (Ceq) of the following [Relationship 1] is 0.48 or less, a microstructure comprises 60 to 85% of ferrite by area fraction and remaining pearlite, and the microstructure includes at least one precipitate of NbC or VC, and a size of the precipitates is 50 nm or less:
Ceq
=
C
+
Mn
/
6
+
(
Cr
+
Mo
+
V
)
/
5
+
(
Cu
+
Ni
)
/
15
[
Relationship
1
]
Where C, Mn, Cr, Mo, V, Cu, and Ni are amounts (% by weight) of respective components.
2 . The steel material of claim 1 , further comprising at least one of Cu: 0.5% or less or Ni: 0.5% or less.
3 . The steel material of claim 1 , wherein a grain size of the ferrite is 30 μm or less.
4 . The steel material of claim 1 , wherein the at least one precipitate of NbC or VC is provided in a grain of the ferrite.
5 . The steel material of claim 1 , wherein, when the steel material is evaluated perpendicular to a rolling direction at a t/4 point in a thickness direction (where t means a thickness (mm) of the steel material), a yield strength is 370 MPa or more, a tensile strength is 520 MPa or more, and an average Charpy impact absorption energy (CVN, −20° C.) value at a temperature of −20° C. is 40 J or more.
6 . A method of manufacturing a steel material having high strength and excellent impact toughness, comprising:
heating a steel slab comprising, by weight, C: 0.12 to 0.18%, Si: 0.2 to 0.5%. Mn: 1.0 to 1.7%, P: 0.012% or less, S: 0.003% or less, Al: 0.015 to 0.045%, Nb: 0.02 to 0.05%, V: 0.01 to 0.08%, Ti: 0.005 to 0.017%, N: 0.002 to 0.01%, and a remainder of Fe and inevitable impurities, and in which a carbon equivalent (Ceq) of the following [Relationship 1] is 0.48 or less, under conditions of the following [Relationship 2]; and rough-rolling the heated steel slab at a temperature within a range of 900 to 1100° C., and then finishing hot-rolling to Ar3 or higher after the rough-rolling:
Ceq
=
C
+
Mn
/
6
+
(
Cr
+
Mo
+
V
)
/
5
+
(
Cu
+
Ni
)
/
15
[
Relationship
1
]
Where C, Mn, Cr, Mo, V, Cu, and Ni are amounts (% by weight) of respective components.
Slab
Extraction
Temperature
(
°
C
.
)
>
10300
/
{
4.09
-
log
(
[
Nb
]
[
C
]
0.24
[
N
]
0.65
)
}
-
273
[
Relationship
2
]
Where [Nb], [C], and [N] mean an amount (% by weight) in an alloy composition, respectively.
7 . The method of claim 6 , wherein the steel slab further comprises at least one of Cu: 0.5% or less or Ni:
0.5% or less.
8 . The method of claim 6 , wherein the slab extraction temperature is 1200° C. or lower.Join the waitlist — get patent alerts
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