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[Document Type] SPECIFICATION
[Title of the Invention] SURFACE-TREATED HOT-DIP PLATED STEEL
[Technical Field]
[0001]
The present invention relates to a surface-treated hot-dip plated steel.
Priority is claimed on Japanese Patent Application No. 2011-182916, filed on August 24, 2011, and the content of which is incorporated herein by reference. [Background Art]
[0002]
In the related art, a hot-dip Zn-Al plated steel has been widely used for building materials, automobile materials, and materials for home electric appliances. Among products using such a hot-dip Zn-Al plated steel, a high aluminum (25 mass% to 75 mass%)-zinc alloy plated steel sheet represented by a 55% aluminum-zinc alloy plated steel sheet (Galvalume Steel Sheet (registered trademark)) is superior in corrosion resistance as compared to an ordinary hot-dip galvanized steel sheet. Therefore, the demand for the hot-dip Zn-Al plated steel has been increased. In addition, recently, since flirther improvement in corrosion and workability has been required particularly for building materials, techniques of adding Mg or the like to a plating layer to improve the corrosion resistance and the like of a hot-dip Zn-Al plated steel have been studied (refer to Patent Documents 1 to 4).
[0003]
However, in a high aluminum-zinc alloy steel sheet containing Mg, wrinkling is likely to occur on a surface of a plating layer, which causes deterioration in surface appearance. Further, steep protrusions are formed on the surface of the plating layer by this wrinkling. Therefore, when the plating layer is subjected to a chemical
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conversion treatment to form a chemical treatment layer or is subjected to coating or the like to form a coating layer, the thickness of the chemical treatment layer or the coating layer is likely to be non-uniform. As a result, there is a problem in that an effect of improving the corrosion resistance of a plated steel sheet obtained by coating or the like cannot be sufficiently exhibited.
[0004]
For example. Patent Document 1 discloses an Al-based hot-dip Al-Si-Mg-Zn plated steel sheet. A surface of this steel sheet includes a hot-dip plating layer that contains 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, and a balance consisting of Al and unavoidable impurities. Patent Document 1 discloses that the hot-dip plating layer may further contain 0.002 mass% to 0.08 mass% of Be and 0 mass% to Q. 1 mass% of Sr. Alternatively, the hot-dip plating layer may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0.003 mass% to 0.05 mass% of Be, and 0 mass% to 0.1 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0 mass% to 0.003 mass% of Be, and 0.07 mass% to 1.7 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0 mass% to 0.003 mass% of Be, and 0.1 mass% to 1.0 mass% of Sr; may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass% to 10 mass% of Zn, 0.003 mass% to 0.08 mass% of Be, and 0.1 mass% to 1.7 mass% of Sr; or may contain 3 mass% to 13 mass% of Si, 2 mass% to 8 mass% of Mg, 2 mass%to 10mass%ofZn, 0.003 mass%to0.05 mass%ofBe, and 0.1 mass%to 1.0 mass% of Sr.
[0005]
In the technique disclosed in Patent Document 1, Mg is added to a plating
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layer to improve the corrosion resistance of a hot-dip plated steel. However, wrinkling is likely to occur on the plating layer due to the addition of Mg. Patent Document 1 also discloses a technique of adding Sr or Be to a plating layer to suppress oxidation of Mg, thereby suppressing wrinkling. However, wrinkling is not sufficiently suppressed.
[0006]
It is difficult to sufficiently remove such wrinkles formed on the plating layer even with temper rolling and the like, and the wrinkles cause deterioration in the appearance of a hot-dip plated steel.
[0007]
hi addition, in a high aluminum (25 iTiass% to 75 mass%)-zinc alloy plated steel sheet of the related art, the durability (corrosion rate of a plating layer) and red rust resistance (resistance to red rust formed on a steel sheet) of a plating layer, or the red rust resistance and coating film swelling resistance of a cut end surface of a coated steel sheet are improved; however, the white rust resistance of a plating layer (performance to suppress deterioration in appearance 'caused by white rust which is formed by corrosion of the plating layer) is not considered, particularly, the improvement in white rust resistance, scratch resistance, and contamination resistance of a treated part are not considered. [Prior Art Document] [Patent Document]
[0008]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. HI 1-279735
[Patent Document 2] Japanese Patent No. 3718479

[Patent Document 3] PCT International Publication No. WO2008/025066
[Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2007-284718 [Disclosure of the Invention] [Problem to be Solved by the Invention]
[0009]
The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a surface-treated hot-dip plated steel that is superior in the white rust resistance, scratch resistance, and contamination resistance of a treated part, has no appearance defects caused by a plating layer, and has a favorable appearance. [Means for Solving the Problem]
[0010]
The present inventors have found the following facts regarding the above-described problem of deterioration in the appearance of a plating layer. During a hot-dip plating treatment in which a hot-dip plating bath containing Mg is used, since Mg is an element which is more easily oxidized than the other elements constituting a plating layer, Mg reacts with oxygen in the atmosphere to form an Mg-based oxide on a surface of a hot-dip plating metal attached onto steel. As a result, Mg is concentrated on the surface of the hot-dip plating metal, and the formation of an Mg-based oxide film (coating film formed of a metal oxide containing Mg) on the surface of the hot-dip plating metal is promoted, hi a process of cooling a hot-dip plating metal to be solidified, an Mg-based oxide film is formed before the inside of the hot-dip plating metal is completely solidified. Therefore, there is a difference in fluidity between the surface and the inside of the hot-dip plating metal. Therefore, even if the

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inside of the hot-dip plating metal flows, the Mg-based oxide film on the surface does not follov/ the flow. As a result, it is considered that wrinkling and sagging occurs.
[0011]
In order to suppress the above-described difference in the fluidity of the inside of a hot-dip plating metal during a hot-dip plating treatment, the present inventors have intensively studied and found a method of suppressing deterioration in appearance such as wrinkling and sagging.
[0012]
The present inventors has intensively studied a surface treatment of a hot-dip plated material such that deterioration in the corrosion resistance of a treated part caused by the deterioration in workability can be suppressed; white rust, which is formed by a sacrificial corrosion preventing action of Zn or Mg in a hot-dip plating metal and, particularly, is likely to be formed in a treated part, can be suppressed to maintain a beautiful appearance over a long period of time; and scratch resistance and contamination resistance are superior. As a result, the present invention has been completed.
[0013]
That is, preferable embodiments of the present invention are as follows.
(1) According to an aspect of the present invention, there is provided a surface-treated hot-dip plated steel including: a steel; and a coating material that is provided on a surface of the steel, wherein the coating material includes, in order from the steel, a plating layer and a coating film containing an organic resin that is fonned on a surface of the plating layer, the plating layer contains Al, Zn, Si, and Mg as constituent elements in which an Al content is 25 mass% to 75 mass% and an Mg content is 0.1 mass% to 10 mass%, the plating layer contains 0.2 vol% to 15 vol% of

Si-Mg phase, a mass ratio of Mg in the Si-Mg phase to a total amount of Mg in the plating layer is 3% to 100%, and the organic resin is cross-linked by at least one selected from the group consisting of a silane coupling agent, a cross-linking zirconium compound, a cross-linking titanium compound, an epoxy compound, and an amino resin.
[0014]
(2) In the surface-treated hot-dip plated steel according to (1), an Mg
content in any region having a diameter of 4 mm and a depth of 50 nm inside an
outermost layer, which is located at a depth of 50 nm from the surface of the plating
layer, may be 0 mass% to less than 60 mass%.
[0015]
(3) In the surface-treated hot-dip plated steel according to (1) or (2), the
plating layer may further contain 0.02 mass% to 1.0 mass% of Cr as a constituent
element.

CLAIMS
1. (Amended) A surface-treated hot-dip plated steel comprising:
a steel; and
a coating material that is provided on a surface of the steel,
wherein the coating material includes, in order from the steel, a plating layer
and a coating film which contains an organic resin that is formed on a surface of the
plating layer,
the plating layer contains Al, Zn, Si, Mg, and Cr as constituent elements in
which an A1 content is 25 mass% to 75 mass%, an Mg content is 0.1 mass% to 10
mass% and a Cr content is 0.02 mass% to 1.0 mass%,
the plating layer contains 0.2 vol% to 15 vol% of an Si-Mg phase,
a mass ratio of Mg in the Si-Mg phase to a total amount of Mg in the plating
layer is 3% to loo%, and
the organic resin is cross-liked by at least one selected from the group
consisting of a silane coupling agent, a cross-linking zirconium compound, a crosslinking
titanium compound, an epoxy compound, and an amino resin.
2. The surface-treated hot-dip plated steel according to Claim 1,
wherein an Mg content in any region having a diameter of 4 mm and a depth
of 50 nm inside an outermost layer, which is located at a depth of 50 nm from the
surface of the plating layer, is 0 mass% to less than 60 mass%.
A(.3 ( Amended) The surface-treated hot-dip plated steel according to Claim 1 or 2,
wherein a thickness of the coating film is 0.1 pm to 10 pm.
The surface-treated hot-dip plated steel according to any one of Claims 1 6. to 4,
wherein the coating film further contains silica particles.
fl
. The surface-treated hot-dip plated steel according to Claim 5,
wherein when the organic resin is denoted by A and the silica are
denoted by B, a solid content mass ratio A/B is 2 to 20.
2 The surface-treated hot-dip plated steel according to Claim 5 or 6,
wherein the silica particles contain spherical silica particles having an average
particle size of 5 nm to 20 nm and spherical silica particles having an average particle
size of 0.08 pm to 2 pm.
'7'
& The surface-treated hot-dip plated steel according to any one of Claims 1 to 7,
wherein the coating film further contains a lubricant.
B 4T The surface-treated hot-dip plated steel according to any one of Claims 1 to 8,
wherein the coating film further contains a phosphate compound.
7 443. The surface-treated hot-dip plated steel according to any one of Claims 1 to 9,
wherein the coating film further contains a color pigment.
\"
H. The surface-treated hot-dip plated steel according to any one of Claims 1 to
wherein an undercoating layer which contains components derived from an
organic resin and a silane coupling agent is provided below the coating film.
t The surface-treated hot-dip plated steel according to any one of Claims 1 to 11,
wherein the organic resin and the plating layer are cross-linked with each
other by at least one selected from the group consisting of a silane coupling agent, a
cross-linking zirconium compound, a cross-linking titanium compound, an epoxy
compound, and an amino resin