US2024263291A1PendingUtilityA1
Highly corrosion-resistant plated steel sheet having excellent corrosion resistance and surface quality, and manufacturing method therefor
Est. expiryJun 18, 2041(~14.9 yrs left)· nominal 20-yr term from priority
C22C 18/04C23C 2/40C23C 2/29B21B 1/22C23C 2/28B21B 2001/221B21B 1/36C23C 28/025C23C 28/02C23C 2/06C23C 2/26C23C 2/02
59
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
One aspect of the present invention provides a plated steel sheet and a manufacturing method therefor, the plated steel sheet comprising: a base steel sheet; a Zn—Mg—Al-based plated layer provided on at least one surface of the base steel sheet; and an Fe—Al-based inhibition layer provided between the base steel sheet and the Zn—Mg—Al-based plated layer, wherein, on the surface of the Zn—Mg—Al-based plated layer, the total area fraction of an Al single phase and MgZn2 phase is 45-60%, and the area ratio of the MgZn2 phase to the Al single phase is 1.2-3.3.
Claims
exact text as granted — not AI-modified1 . A plated steel sheet, comprising:
a base steel sheet; a Zn—Mg—Al-based plating layer provided on at least one surface of the base steel sheet; and an Fe—Al-based inhibition layer provided between the base steel sheet and the Zn—Mg—Al-based plating layer, wherein on a surface of the Zn—Mg—Al-based plating layer, a total area fraction of an Al single phase and MgZn 2 phase is 45 to 60%, and an area ratio of the MgZn 2 phase to the Al single phase is 1.2 to 3.3.
2 . The plated steel sheet of claim 1 , wherein the Zn—Mg—Al-based plating layer comprises, by weight:
Mg: 4 to 6%, Al: 8.2 to 14.2%, with a balance of Zn and other inevitable impurities.
3 . The plated steel sheet of claim 1 , wherein with respect to a cross-section of the Zn—Mg—Al-based plating layer, an area fraction of the MgZn 2 phase is 20 to 40%, and an area fraction of the Al single phase is 8 to 26%.
4 . The plated steel sheet of claim 1 , wherein on the surface of the Zn—Mg—Al-based plating layer, the area fraction of the MgZn 2 phase is 30 to 40%.
5 . The plated steel sheet of claim 1 , wherein on the surface of the Zn—Mg—Al-based plating layer, the area fraction of the Al single phase is 15 to 20%,
wherein the Al single phase is a phase in which Zn is dissolved at less than 27%, in atomic percentage, the Al single phase including a balance of Al and other impurities.
6 . The plated steel sheet of claim 1 , wherein a ratio (S1/C1) of a total area fraction S1 of the MgZn 2 phase and the Al single phase on the surface of the Zn—Mg—Al-based plating layer to a total area fraction C1 of the MgZn 2 phase and the Al single phase on a surface of a point corresponding to any one of regions from ¼t to ¾t in a thickness direction of the Zn—Mg—Al plating layer is in a range of 0.8 to 1.2.
7 . The plated steel sheet of claim 1 , wherein a total area fraction of a Zn phase and a Zn—MgZn 2 —Al-based ternary eutectic phase on the surface of the Zn—Mg—Al-based plating layer is 20 to 30%.
8 . The plated steel sheet of claim 1 , wherein a ratio (S2/C2) of a total area fraction S2 of the Zn phase and the Zn—MgZn 2 —Al-based ternary eutectic phase on the surface of the Zn—Mg—Al-based plating layer to a total area fraction C2 of the Zn phase and the Zn—MgZn 2 —Al-based ternary eutectic phase on a surface of any point of regions from ¼t to ¾t in a thickness direction of the Zn—Mg—Al plating layer is in a range of 0.6 to 1.2.
9 . The plated steel sheet of claim 1 , wherein on the surface of the Zn—Mg—Al-based plating layer, an area fraction of a second Al single phase in which 27 to 60% of Zn is dissolved, in atomic percentage, is 2 to 9%.
10 . The plated steel sheet of claim 1 , wherein under atmospheric environments and chloride environments of ISO14993, LDH((Zn,Mg) 6 Al 2 (OH) 16 (CO 3 )·4H 2 O) is formed on the surface of the Zn—Mg—Al-based plating layer prior to Simonkolleite (Zn 5 (OH) 8 Cl 2 ) and hydrozinsite (Zn 5 (OH) 6 (CO 3 ) 2 ) formation.
11 . The plated steel sheet of claim 1 , wherein under atmospheric environments and chloride environments of ISO14993, LDH((Zn,Mg) 6 Al 2 (OH) 16 (CO 3 )·4H 2 O) is formed on the surface of the Zn—Mg—Al-based plating layer is within 6 hours in the atmospheric environment and within 5 minutes in the chloride environment.
12 . The plated steel sheet of claim 1 , wherein under chloride environments of ISO14993 including salt spray and immersion environments, a time it takes for red rust to occur is 40 to 50 times longer in a flat plate portion; and 20 to 30 times in a 90 degree bending portion, compared to Zn plating of the same thickness.
13 . A manufacturing method of a plated steel sheet, comprising operations of:
hot dip galvanizing a base steel sheet, including by weight: Mg: 4 to 6%, Al: 8.2 to 14.2%, with a balance Zn and other inevitable impurities, by immersing the base steel sheet in a plating bath maintained at a temperature of 20 to 80° C. higher than a solidification initiation temperature in an equilibrium state; and cooling the hot-dip galvanized steel sheet using an inert gas at an average cooling rate of 2 to 12° C./s from the solidification initiation temperature to a solidification end temperature, wherein in the cooling operation, cooling is performed so that the following relations 1-1 and 1-2 are satisfied, and a ratio (De/Dc) of a damper opening rate De of an edge portion to a damper opening rate Dc of a center portion satisfies 60 to 99%.
A
<
{
(
5
-
2
lnt
)
/
(
7
-
3
lnt
)
}
×
B
[
Relation
1
-
1
]
15
t
(
-
0.8
)
≤
B
≤
20
t
(
-
0.8
)
[
Relation
1
-
2
]
In the above relations 1-1 and 1-2, t is a thickness of the steel sheet (mm), A is an average cooling rate (° C./s) from a solidification initiation temperature to 375° C., and B is an average cooling rate (° C./s) from 375° C. to 340° C.
14 . The manufacturing method of claim 13 , wherein in the cooling operation, cooling is performed by changing the ratio (De/Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion, depending on a temperature section, and
the ratio (De/Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion is 60 to 70% from the solidification initiation temperature to 375° C., and is 90 to 99% from 375° C. to 340° C.
15 . The manufacturing method of claim 14 , further comprising an operation of, after the cooling operation:
improving a surface and shape of the base steel sheet by performing a skin pass rolling treatment, wherein the skin pass rolling treatment is performed by applying a roll reduction of 50 to 300 tons to the surface of the steel sheet using a bright roll with surface roughness (Ra) of 0.2 to 1.0 μm.
16 . The manufacturing method of claim 13 , further comprising an operation of, before the hot-dip galvanizing:
performing a pre-skin pass rolling treatment of applying a roll reduction of 200 to 300 tons to the surface of the steel sheet using a bright roll with surface roughness (Ra) of 0.2 to 0.4 μm.
17 . The manufacturing method of claim 16 , wherein during the pre-skin pass rolling treatment, the roll reduction is 250 to 300 tons.Cited by (0)
No later patents cite this yet.
References (0)
No backward citations on record.