High strength multi-phase steel having excellent burring properties at low temperature, and method for producing same
Abstract
Provided is a method for producing high strength multi-phase steel. the method includes: reheating a slab; hot-rolling the reheated slab to obtain a hot-rolled steel sheet; firstly cooling the hot-rolled steel sheet to a first cooling end temperature of 500° C. to 700° C. at a rate of 10° C./sec to 70° C./sec; air-cooling the firstly cooled hot-rolled steel sheet at the first cooling end temperature for 3 to 10 seconds; secondly cooling the air-cooled hot-rolled steel sheet to a second cooling end temperature of 400° C. to 550° C. at a rate of 10° C./sec to 70° C./sec; coiling the secondly cooled hot-rolled steel sheet at the second cooling end temperature; and thirdly cooling the coiled hot-rolled steel sheet to 200° C. or less at a rate of 25° C./hour or less, excluding 0° C./hour.
Claims
exact text as granted — not AI-modified1 . A method for producing high strength multi-phase steel, comprising:
reheating a slab comprising, by weight, carbon (C): 0.05% to 0.14%, silicon (Si): 0.01% to 1.0%, manganese (Mn): 1.0% to 3.0%, aluminum (Al): 0.01% to 0.1%, chromium (Cr): 0.005% to 1.0%, molybdenum (Mo): 0.003% to 0.3%, phosphorus (P): 0.001% to 0.05%, sulfur(S): 0.01% or less, nitrogen (N): 0.001% to 0.01%, niobium (Nb): 0.005% to 0.06%, titanium (Ti): 0.005% to 0.13%, vanadium (V): 0.003% to 0.2%, boron (B): 0.0003% to 0.003%, a remainder of iron (Fe), and other inevitable impurities, and satisfying the following Relationship 1, wherein [C]* defined by the following Equations 1 and 2 is 0.022 or more and 0.10 or less; hot-rolling the reheated slab to obtain a hot-rolled steel sheet; firstly cooling the hot-rolled steel sheet to a first cooling end temperature of 500° C. to 700° C. at a rate of 10° C./sec to 70° C./sec; air-cooling the firstly cooled hot-rolled steel sheet at the first cooling end temperature for 3 to 10 seconds; secondly cooling the air-cooled hot-rolled steel sheet to a second cooling end temperature of 400° C. to 550° C. at a rate of 10° C./sec to 70° C./sec; coiling the secondly cooled hot-rolled steel sheet at the second cooling end temperature; and thirdly cooling the coiled hot-rolled steel sheet to 200° C. or less at a rate of 25° C./hour or less, excluding 0° C./hour:
[
C
]
*
=
(
[
C
]
+
[
N
]
)
-
(
[
C
]
+
[
N
]
)
×
S
[
Equation
1
]
S
=
(
[
Nb
]
/
93
+
[
Ti
]
/
48
+
[
V
]
/
51
+
[
Mo
]
/
96
)
/
(
[
C
]
/
12
+
[
N
]
/
14
)
[
Equation
2
]
[
Mn
]
+
2.8
[
Mo
]
+
1.5
[
Cr
]
+
500
[
B
]
≤
4.
[
Relationship
1
]
where each of [C], [N], [Nb], [′Ti], [V], [Mo], [Mn], [Cr], and [Mo] refers to a weight percentage (wt %) of the element.
2 . The method according to claim 1 , wherein the reheating temperature of the slab is a temperature range of 1200° C. to 1350° C.
3 . The method according to claim 1 , wherein the hot-rolling is performed in a temperature range of 850° C. to 1150° C.Join the waitlist — get patent alerts
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