US2024417836A1PendingUtilityA1
Steel plate having high strength and excellent low-temperature impact toughness, and method for manufacturing same
Est. expiryDec 21, 2041(~15.4 yrs left)· nominal 20-yr term from priority
C21D 8/00C21D 7/13C21D 1/60C22C 38/50C22C 38/48C22C 38/44C22C 38/06C22C 38/02C22C 38/001C21D 2211/005C21D 2211/002C21D 9/46C21D 8/0273C21D 8/0226C21D 1/63C22C 38/04C21D 6/004C21D 1/02C22C 38/58
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Claims
Abstract
The present invention pertains to a steel plate and a method for manufacturing same. More specifically, the present invention pertains to a steel plate having high strength and excellent low-temperature impact toughness, and a method for manufacturing same. A steel plate that has excellent strength and low-temperature impact toughness and may be applied as an extremely thick steel material for offshore wind power, and may also be used as a structural steel material for infrastructure industries such as construction and bridges, and a method for manufacturing the same may be provided.
Claims
exact text as granted — not AI-modified1 . A steel plate, comprising by weight %:
0.04 to 0.08% of carbon (C), 0.1 to 0.35% of silicon (Si), 1.4 to 1.8% of manganese (Mn), 0.01 to 0.035% of sol.Al (Al), 0.2 to 0.5% of nickel (Ni), 0.1 to 0.3% of chromium (Cr), 0.05 to 0.15% of molybdenum (Mo), 0.015 to 0.035% of niobium (Nb), 0.005 to 0.02% of titanium (Ti), 0.002 to 0.006% of nitrogen (N), 0.01% or less of phosphorous (P), 0.003% or less of sulfur (S), with a balance of iron (Fe) and other inevitable impurities, wherein an R value defined in Relational expression 1 below is 0.85 to 1.35, a microstructure at a point equal to ¼ of a thickness thereof has a mixed structure of acicular ferrite and bainite as a main structure, and comprises by area fraction, 2% or less of a sum of residual cementite and MA, and an average grain size of acicular ferrite at the point equal to ¼ of the thickness is 25 μm or less,
R
=
[
Ni
]
+
3
[
Mo
]
+
2
[
Cr
]
[
Relational
expression
1
]
where [Ni], [Mo], and [Cr] are a weight percent of each element.
2 . The steel plate of claim 1 , wherein the steel plate comprises by area fraction, 40 to 60% of acicular ferrite and 40 to 60% of bainite as the microstructure at the point equal to ¼ of the thickness of the steel plate.
3 . The steel plate of claim 1 , wherein the steel plate comprises by area fraction, 1% or less of a sum of cementite and MA.
4 . The steel plate of claim 1 , wherein the steel plate has an average grain size of acicular ferrite at the point equal to ¼ of the thickness of the steel plate of 15 to 25 μm.
5 . The steel plate of claim 1 , wherein the steel plate has a thickness of 50 to 100 mm.
6 . The steel plate of claim 1 , wherein the steel plate has a yield strength of 460 MPa or more, a tensile strength of 580 MPa or more, and an impact toughness of 100 J or more at −50° C.
7 . A method for manufacturing a steel plate, comprising:
reheating a steel slab comprising by weight %: 0.04 to 0.08% of carbon (C), 0.1 to 0.35% of silicon (Si), 1.4 to 1.8% of manganese (Mn), 0.01 to 0.035% of sol.Al (Al), 0.2 to 0.5% of nickel (Ni), 0.1 to 0.3% of chromium (Cr), 0.05 to 0.15% of molybdenum (Mo), 0.015 to 0.035% of niobium (Nb), 0.005 to 0.02% of titanium (Ti), 0.002 to 0.006% of nitrogen (N), 0.01% or less of phosphorous (P), 0.003% or less of sulfur (S), with a balance of iron (Fe) and other inevitable impurities, wherein an R value defined in the following Relational expression 1 is 0.85 to 1.35; rolling the reheated steel slab in a recrystallization zone at a temperature range of 900° C. or higher with an amount of reduction of final pass of 15 to 25 mm; rolling the steel plate rolled in the recrystallization zone in a non-recrystallization zone at a rolling finish temperature of Ar3+20 to Ar3+60; and water cooling the steel plate rolled in the non-recrystallization zone to a temperature range of 400° C. or lower based on the point equal to ¼ of the thickness of the steel plate,
R
=
[
Ni
]
+
3
[
Mo
]
+
2
[
Cr
]
[
Relational
Expression
1
]
where [Ni], [Mo], and [Cr] are a weight percent of each element.
8 . The method for manufacturing a steel plate of claim 7 , wherein the reheating is performed at a temperature range of 1020 to 1100° C., and
when rolling is performed in the non-recrystallized zone, a cumulative reduction ratio is 30 to 50%.
9 . The method for manufacturing a steel plate of claim 7 , wherein, during the cooling, cooling is performed at a cooling rate of 5 to 10° C./s, based on the point of ¼ of the thickness of the steel plate.
10 . The method for manufacturing a steel plate of claim 7 , wherein the steel plate has a thickness of 50 to 100 mm.Join the waitlist — get patent alerts
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