US2025043404A1PendingUtilityA1
Cold rolled steel sheet and method for manufacturing
Est. expiryDec 16, 2041(~15.4 yrs left)· nominal 20-yr term from priority
Inventors:Jaiik Kim
C21D 8/02C25D 5/50C25D 7/0614C22C 38/06C22C 38/04C22C 38/001C21D 9/46C21D 8/0236C21D 8/0226C25D 3/00C21D 8/0273C22C 38/002C21D 8/0263C22C 38/54C21D 8/0205
51
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Claims
Abstract
A cold rolled steel sheet according to an exemplary embodiment of the present invention comprises, by wt %: C: 0.01 to 0.10%; Mn: 0.1 to 0.4%; Al: 0.01 to 0.10%; P: 0.003 to 0.020%; N: 0.001 to 0.006%; S: 0.015% or less; Cr: 0.1 to 0.4%; B: 0.0005 to 0.0035%; Ni: 0.04 to 0.10%; and the balance Fe and other unavoidable impurities, and comprises a (Cr—B)(C—N)-based composite precipitate having a size of 0.01 to 0.1 μm, wherein a [I 222+I 554]/I 200 texture ratio is 5.0 to 10.0, an earing rate is less than 3.0%, and an alloying rate of an alloy layer may be 5 to 15%.
Claims
exact text as granted — not AI-modified1 . A cold rolled steel sheet comprising:
by wt %: C: 0.01 to 0.10%; Mn: 0.1 to 0.4%; Al: 0.01 to 0.10%; P: 0.003 to 0.020%; N: 0.001 to 0.006%; S: 0.015% or less; Cr: 0.1 to 0.4%; B: 0.0005 to 0.0035%; Ni: 0.04 to 0.10%; and the balance Fe and other unavoidable impurities, and a (Cr—B)(C—N)-based composite precipitate having a size of 0.01 to 0.1 μm, wherein a [I 222 +I 554 ]/I 200 texture ratio is 5.0 to 10.0, an earing rate is less than 3.0%, and an alloying rate of an alloy layer may be 5 to 15%.
2 . The cold rolled steel sheet of claim 1 , wherein:
the cold rolled steel sheet satisfies Equation 1 below:
0.0002
≤
(
[
Cr
]
/
52
)
×
1.6
(
[
B
]
/
11
)
)
/
(
(
[
C
]
/
12
)
+
(
[
N
]
/
14
)
)
≤
0.0006
<
Equation
1
>
(in Equation 1 above, [Cr], [B], [C], and [N] refer to the weights of Cr, B, C, and N, respectively)
3 . The cold rolled steel sheet of claim 1 , wherein:
during drawing processing, fracture does not occur during cupping under a condition that a blank diameter/drawing die diameter is 1.85.
4 . The cold rolled steel sheet of claim 1 , wherein:
through a salt spray test, red rust does not occur within 12 hours.
5 . The cold rolled steel sheet of claim 1 , wherein:
after the cold rolled steel sheet is heated at 600° C. for 100 hours, the degree of sagging of the steel sheet is less than 3 mm.
6 . The cold rolled steel sheet of claim 1 , wherein:
the yield strength at 600° C. is 95 MPa or more.
7 . A method for manufacturing a cold rolled steel sheet comprising:
heating a steel slab including, by wt %: C: 0.01 to 0.10%; Mn: 0.1 to 0.4%; Al: 0.01 to 0.10%; P: 0.003 to 0.020%; N: 0.001 to 0.006%; S: 0.015% or less; Cr: 0.1 to 0.4%; B: 0.0005 to 0.0035%; Ni: 0.04 to 0.10%; and the balance Fe and other unavoidable impurities; finish hot-rolling the heated steel slab at 860 to 930° C.; winding the finish hot-rolled hot rolled steel sheet at 580 to 700° C.; cold-rolling the wound hot rolled steel sheet at a reduction ratio of 78 to 92%; annealing the cold-rolled cold rolled steel sheet at 650 to 750° C.; cooling the annealed cold rolled steel sheet at a cooling rate of 30 to 70° C./sec; and electroplating the cold rolled steel sheet and then alloying and heating the cold rolled steel sheet at 650 to 750° C.
8 . The method for manufacturing the cold rolled steel sheet of claim 7 , wherein:
the cold rolled steel sheet satisfies Equation 1 below:
0.0002
≤
(
[
Cr
]
/
52
)
×
1.6
(
[
B
]
/
11
)
)
/
(
(
[
C
]
/
12
)
+
(
[
N
]
/
14
)
)
≤
0.0006
<
Equation
1
>
(in Equation 1 above, [Cr], [B], [C], and [N] refer to the weights of Cr, B, C, and N, respectively)Join the waitlist — get patent alerts
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