0001]
The present invention relates to a hot -dip zinc-based plated steel sheet.
Background Art
[0002]
These days, to protect the environment and prevent global warming, the
suppression of the consumption of fossil fuel is increasingly demanded, and the
demand influences various manufacturing industries. For example, automobiles,
15 which are indispensable to daily life and activity as a moving means, are no
exception, and improvements in fuel efficiency etc. by the weight reduction of car
bodies etc. are required. However, for automobiles, simply achieving a weight
reduction of the car body is not permitted in terms of the functionality of the product,
and it is necessary to ensure proper safety.
20 [0003]
Most of the structure of the automobile is formed of iron-based materials, in
particular steel sheets, and the reduction in the weight of the steel sheet is important
to the weight reduction of the car body. However, as described above, simply
reducing the weight of the steel sheet is not permitted, and ensuring the mechanical
25 strength of the steel sheet is required at the same time. Such a demand on the steel
sheet is placed not only in the automobile manufacturing industry but also in various
manufacturing industries similarly. Hence, research and development are being
made to enhance the mechanical strength of the steel sheet and thereby obtain a steel
sheet in which the mechanical strength can be maintained or improved even when the
30 wall thickness is made smaller than those of conventionally used steel sheets.
[0004]
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In general, a material having high mechanical strength tends to decrease in
shape fixability in molding such as bending, and is difficult to mold into a
complicated shape. As a means for solving such a problem with moldability, what
is called "the hot pressing method (also called the hot stamping method or the die
5 quenching method)" is given. In the hot pressing method, a material to be molded
is once heated to high temperature, the steel sheet softened by heating is pressed to
be molded, and then cooling is performed. By the hot pressing method, the material
of the object can be easily pressed because the material is once heated to high
temperature and softened. Furthermore, the mechanical strength of the material can
10 be enhanced by the quenching effect by the cooling after molding. Thus, a molded
product in which both good shape fixability and high mechanical strength are
achieved can be obtained by the hot pressing method.
[0005]
However, when the hot pressing method is used for a steel sheet, the surface
15 of the steel sheet is oxidized by the steel sheet being heated to a high temperature of
800°C or more, and scales (compounds) are produced. Hence, the process of
removing the scales (what is called a descaling process) is needed after hot pressing
is performed, and productivity is reduced. In addition, in a member etc. requiring
corrosion resistance, it is necessary to perform anti-rust treatment or metal covering
20 on the surface of the member after processing, and a surface cleaning process and a
surface treatment process are needed; consequently, productivity is further reduced.
[0006]
As a method to suppress such a reduction in productivity, for example, a
method in which a steel sheet to be hot pressed is provided with a covering in
25 advance is given. Various materials such as organic-based materials and inorganicbased
materials are generally used as the covering on the steel sheet. Among these,
plated steel sheets based on zinc (Zn), which has a sacrificial anti-corrosion action on
the steel sheet, are widely used as automotive steel sheets etc. from the viewpoints of
the anti-corrosion capacity and the steel sheet production technique.
30 [0007]
By providing a zinc-based metal covering, the production of scales on the
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surface of the steel sheet can be prevented, and processes such as de scaling become
unnecessary; thus, the productivity of molded products is improved. In addition,
the zinc-based metal covering has also an anti-rust effect, and therefore also
corrosion resistance is improved. Patent Literature 1 to Patent Literature 4 below
5 disclose a method of hot pressing a plated steel sheet that is obtained by providing a
zinc-based metal covering to a steel sheet having a prescribed component
composition.
[0008]
In Patent Literature 1 to Patent Literature 3 below, a hot -dip galvanized steel
10 sheet or an alloyed hot-dip galvannealed steel sheet is used as a steel sheet for hot
pressmg. By using a hot-dip galvanized steel sheet or an alloyed hot-dip
galvannealed steel sheet for hot pressing, a structure member can be molded without
iron oxides (that is, scales) being formed on the surface. Further, in view of the fact
that, when a zinc oxide layer is formed thick on the surface of a heat-treated steel
15 material obtained by hot pressing a zinc-based plated steel sheet, the coating film
adhesiveness and the post -coating corrosion resistance of the heat -treated steel
material are adversely affected, Patent Literature 4 below discloses an invention in
which a heat-treated steel material is subjected to shot blasting to remove a zinc
oxide layer or is subjected to coating after the thickness of a zinc oxide layer is
20 reduced.
[0009]
Patent Literature 5 and Patent Literature 6 below disclose inventions that
improve the coating film adhesiveness and the post-coating corrosion resistance of a
heat-treated steel material obtained by hot pressing a zinc-based plated steel sheet.
25 Patent Literature 5 below discloses an invention in which a hot-dip galvanized steel
sheet with its surface covered with a silicone resin coating film is used as a steel
sheet for hot pressing, and Patent Literature 6 below discloses an invention in which
a hot-dip galvanized steel sheet covered with a barrier layer containing phosphorus
(P) and silicon (Si) (a phosphate is given as an example of P, and colloidal silica is
30 given as an example ofSi) is used as a steel sheet for hot pressing.
[0010]
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Patent Literature 7 below discloses a technology in which elements that are
easier to oxidize than Zn (easily oxidizable elements) are added into a galvanized
layer and an oxide layer of these easily oxidizable elements is formed on the outer
layer of the galvanized layer during the temperature increase in hot pressing, and
5 thereby the volatilization of zinc is prevented.
[0011]
According to the inventions disclosed by Patent Literature 5 to Patent
Literature 7 below, since a galvanized layer is covered with the barrier layer
described above, the vaporization of zinc is suppressed, and thus the adhesiveness of
10 an intermediate coating film and an over-coating film and post -coating corrosion
resistance are good.
Citation List
Patent Literature
15 [0012]
Patent Literature 1: JP 2003-73774A
Patent Literature 2: JP 2003-129209A
Patent Literature 3: JP 2003-126921A
Patent Literature 4: JP 2004-323897A
20 Patent Literature 5: JP 2007-63578A
Patent Literature 6: JP 2007-291508A
Patent Literature 7: JP 2004-270029A
Summary of Invention
25 Technical Problem
[0013]
However, in the zinc-based plated steel sheet, particularly in the case where
a hot-dip galvanized steel sheet or an alloyed hot-dip galvanized steel sheet is hot
pressed, oxidation of zinc during heating of hot pressing cannot be avoided, and the
30 amount of metal zinc remaining in the plating layer after the hot pressing decreases.
With decrease of the mount of metal zinc, there is a case in which not only postPCT/
JP2016/060798
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coating corrosion resistance but also conosion resistance at an uncoated portion may
deteriorate.
[0014]
In addition, wben the present inventors conducted a check experiment on a
5 heat-treated steel material disclosed by Patent Literature 5 above that was obtained
by using, as a steel sheet for hot pressing, a hot-dip galvanized steel sheet with its
surface covered with a silicone resin coating film, it has been found that, although
post -coating corrosion resistance in a cycle corrosion test in which a dry and a wet
environment are repeated is good, zinc is excessively oxidized during heating of hot
10 pressing, and the corrosion resistance at an uncoated portion is not necessarily good.
Hence, a heat-treated steel material obtained by the invention disclosed in Patent
Literature 5 above is not suitable for use as it is for a part or a member at a joint of
steel materials (for example, a portion at which sheets are put together for
reinforcement, near a spot-welded portion inside a locker, etc.), for example.
15 [0015]
On the other hand, with the addition of easily oxidizable elements into a
galvanized layer disclosed in Patent Literature 7 above, although the oxidation of
zinc is suppressed, new operational actions are necessary, such as the temperature
control of the plating bath and dross measures.
20 [0016]
Thus, the present invention has been made in view of the issue mentioned
above, and an object of the present invention is to provide a hot-dip zinc-based plated
steel sheet which suppresses excessive production of zinc oxides on the outer layer
after hot pressing more conveniently and is excellent in corrosion resistance at an
25 uncoated pmiion.
Solution to Problem
[0017]
On the basis of the findings obtained by extensive studies on the plated steel
30 sheet for hot pressing of the object mentioned above, the present inventors have
thought up the following hot-dip zinc-based plated steel sheet.
5
[0018]
(1)
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The gist of the present invention is as follows.
A hot-dip zinc-based plated steel sheet including:
a base steel sheet that is a metal substrate;
a hot-dip zinc-based plating layer provided on the base steel sheet; and
a surface treatment layer formed on at least one surface of the hot -dip zincbased
plating layer, in which
the surface treatment layer contains more than or equal to 0.1 g/m2 and less
10 than or equal to 1.2 g/m2 of granular oxide per one surface on a metal basis in which,
in a temperature range of 900 to 1300 K, standard free energy of formation (!-.G0
) of
oxide is smaller than standard free energy of formation (L'.G0zn) of zinc oxide and
larger than standard free energy of formation (L'.G0
A1) of aluminum oxide at an
identical temperature, and
15 the granular oxide has a particle size of more than or equal to 3 nrn and less
than or equal to 100 nrn.
(2)
The hot-dip zinc-based plated steel sheet according to (1), in which
the surface treatment layer fiuiher contains at least one of one or more
20 phosphorus-containing compounds, one or more vanadium-containing compounds,
one or more copper-containing compounds, one or more aluminum-containing
compounds, or one or more chromium-containing compounds in the following range
as a content per one surface,
the one or more phosphorus-containing compounds: more than or equal to
25 0.0 g/m2 and less than or equal to 0.01 g/m2 on a P basis,
the one or more vanadium-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.01 g/m2 on a V basis,
the one or more copper-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.02 g/m2 on a Cu basis,
30 the one or more aluminum-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.005 g/m2 on an AI basis, and
5
10
15
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the one or more chromium-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.01 g/m2 on a Cr basis.
(3)
The hot-dip zinc-based plated steel sheet according to (1) or (2), in which
the base steel sheet has a chemical composition of, in mass%,
C: 0.05 to 0.4%,
Si: less than or equal to 0.5%,
Mn: 0.5 to 2.5%,
P: less than or equal to 0.03%,
S: less than or equal to 0.01 %,
sol. AI: less than or equal to 0.1 %,
N: less than or equal to 0.01 %,
B: 0 to 0.005%,
Ti: 0 to 0.1%,
Cr: 0 to 0.5%,
Nb: 0 to 0.1%,
Ni: 0 to 1.0%,
Mo: 0 to 0.5%, and
the balance: Fe and impurities.
20 (4)
25
30
The hot-dip zinc-based plated steel sheet according to (1) or (2), in which
the base steel sheet has a chemical composition of, in mass%,
C: 0.05 to 0.4%,
Si: less than or equal to 0.5%,
Mn: 0.5 to 2.5%,
P: less than or equal to 0.03%,
S: less than or equal to 0.01 %,
sol. AI: less than or equal to 0.1 %,
N: less than or equal to 0.01 %,
B: 0 to 0.005%,
Ti: 0 to 0.1%,
5
(5)
10 in which
(6)
in which
15
(7)
in which
8/51
Cr: more than 0% and less than or equal to 0.5%,
Nb: 0 to 0.1%,
Ni: 0 to 1.0%,
Mo: 0 to 0.5%, and
the balance: Fe and impurities, and
the base steel sheet satisfies a relationship of
Mn+Cr: 0.5 to 3.0%.
PCT/JP2016/060798
The hot-dip zinc-based plated steel sheet according to any one of (1) to (4),
the granular oxide is metal oxide.
The hot-dip zinc-based plated steel sheet according to any one of (1) to (5),
the granular oxide is an oxide of titanium or an oxide of silicon.
The hot-dip zinc-based plated steel sheet according to any one of (1) to (6),
the granular oxide has a particle size of more than or equal to 5 nm and less
20 than or equal to 30 nm.
(8)
The hot-dip zinc-based plated steel sheet according to any one of (1) to (7),
in which
a content of the granular oxide per one surface on a metal basis is more than
25 or equal to 0.2 g/m2 and less than or equal to 0.8 g/m2
.
(9)
The hot-dip zinc-based plated steel sheet according to any one of (1) to (8),
in which
the surface treatment layer contains more than or equal to 0.05 g/m2 and less
30 than or equal to 0.35 g/m2 of an oxide of an alkaline-earth metal per one surface on a
metal basis in which, in a temperature range of 900 to 1300 K, standard free energy
5
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of formation (L\.G0
) of oxide is smaller than standard free energy offormation (L\.G0
A1)
of aluminum oxide at an identical temperature.
(10)
The hot -dip zinc-based plated steel sheet according to (9), in which
the oxide of the alkaline-earth metal is an oxide of calcium or an oxide of
magnesium.
(11)
The hot-dip zinc-based plated steel sheet according to (9) or (1 0), in which
the content of the oxide of the alkaline-earth metal per one surface on a
10 metal basis is more than or equal to 0.05 g/m2 and less than or equal to 0.2 g/m2
.
(12)
The hot-dip zinc-based plated steel sheet according to any one of (1) to (11 ),
in which
the hot-dip zinc-based plated steel sheet is a hot-dip zinc-based plated steel
15 sheet for hot pressing.
Advantageous Effects of Invention
[0019]
As described above, according to the present invention, it becomes possible
20 to improve the corrosion resistance at the uncoated portion by suppressing
production of zinc oxides on the outer layer during hot pressing and ensuring the
amount of metal zinc remaining in the plating layer after the hot pressing.
Description of Embodiments
25 [0020]
30
Hereinafter, preferred embodiments of the present invention are described in
detail.
[0021]
<1. Hot-dip zinc-based plated steel sheet>
A hot-dip zinc-based plated steel sheet according to an embodiment of the
present invention includes a hot-dip zinc-based plating layer on a base steel sheet,
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and also includes a surface treatment layer to be described in detail below on at least
one surface of the hot-dip zinc-based plating layer. The surface treatment layer
contains more than or equal to 0.1 g/m2 and less than or equal to 1.2 g/m2 of granular
oxide per one surface on a metal basis in which, in a temperature range of 900 to
5 1300 K, standard free energy of formation (i1G0
) of oxide is smaller than standard
free energy of formation (i1G0zn) of zinc oxide and larger than standard free energy
of formation (i1G0
A1) of aluminum oxide at an identical temperature, and the granular
oxide has a particle size of more than or equal to 3 nm and less than or equal to 100
nm. The hot -dip zinc-based plated steel sheet having such a configuration can be
10 suitably used for the hot pressing method described above. Hereinafter,
15
configuration of such a hot-dip zinc-based plated steel sheet will be described in
detail.
[0022]
( 1) Base steel sheet
The base steel sheet used for the hot-dip zinc-based plated steel sheet
according to the present embodiment is not particularly limited, and various steel
sheets having known characteristics and chemical compositions may be used. The
chemical composition of the steel sheet is not particularly limited, but is preferably a
chemical composition with which high strength is obtained by quenching. For
20 example, when it is attempted to obtain a heat-treated steel material with a tensile
strength of 980 MPa or more, an example of the base steel sheet is made of steel for
quenching having a chemical composition of, in mass%, C: 0.05 to 0.4%, Si: less
than or equal to 0.5%, Mn: 0.5 to 2.5%, P: less than or equal to 0.03%, S: less than or
equal to 0.01%, sol. AI: less than or equal to 0.1%, N: less than or equal to 0.01%, B:
25 0 to 0.005%, Ti: 0 to 0.1 %, Cr: 0 to 0.5%, Nb: 0 to 0.1 %, Ni: 0 to 1.0%, Mo: 0 to
0.5%, and the balance: Fe and impurities.
[0023]
When it is attempted to obtain a heat-treated steel material with a relatively
low strength in which the strength becomes less than 980 MPa during quenching, the
30 chemical composition of the base steel sheet is not necessarily be in the range
described above.
PCT/JP2016/060798
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[0024]
The total amount ofMn and Cr contained is preferably 0.5 to 3.0% from the
viewpoint of quenchability during the quenching described above and the viewpoint
of forming Mn oxides and Cr oxides contained in a zinc oxide layer after heating.
5 The total amount ofMn and Cr contained is more preferably 0.7 to 2.5%.
[0025]
When Mn and Cr are contained as the chemical composition of the steel
sheet, part of the zinc oxide layer formed on the outer layer after hot pressing
becomes composite oxides containing Mn and Cr. Adhesiveness between a coating
10 film component and a plating component is improved and mold-adhesion resistance
becomes excellent by forming these composite oxides containing Mn and Cr.
Although details are unknown, it is presumed that, by these composite oxides being
formed, the formed coating film is dense as compared to zinc oxide, and satisfactory
mold-adhesion resistance is exhibited.
15 [0026]
In the case where Mn and Cr are contained as the chemical composition of
the steel sheet, the content of Mn+Cr is preferably in the range of, in mass%, more
than or equal to 0.5% and less than or equal to 3.0%, and more preferably in the
range of more than or equal to 0. 7% and less than or equal to 2.5%. In the case
20 where the content of Mn+Cr is less than 0.5%, zinc oxide that is formed on the outer
layer after hot pressing and composite oxides that contain Mn and Cr are insufficient,
and it may be difficult to bring out more satisfactory mold-adhesion resistance. On
the other hand, in the case where the content ofMn+Cr exceeds 3.0%, although there
is no problem with coating adhesiveness, the cost is increased, and furthermore the
25 toughness of the spot welded portion may be significantly reduced and the
wettability of plating may be significantly degraded.
[0027]
(2) Hot-dip zinc-based plating layer
The hot-dip zinc-based plating layer according to the present embodiment is
30 not particularly limited, and commonly known hot-dip zinc-based plating may be
used. Specifically, examples of the hot-dip zinc-based plating layer according to
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the present embodiment include hot-dip galvanizing, alloyed hot-dip galvanizing,
hot-dip Zn-55%AI plating, hot-dip Zn-11 %AI plating, hot-dip Zn-11 %AI-3%Mg
plating, hot-dip Zn-7%AI-3%Mg plating, and hot-dip Zn-11%AI-3%Mg-0.2%Si
plating.
5 [0028]
Note that the hot-dip zinc-based plating dealt with by the present invention
contains AI in a plating bath and a plating layer even in cases other than Zn-AI-based
alloy plating containing aluminum (Al) as a main component. The reason is as
follows. That is, the temperature of the plating bath is approximately 440 to 480°C;
10 in this temperature range, when Zn and Fe come into contact, Fe and Zn are
continuously alloyed, and consequently dross occurs. By putting Al in the plating
bath, the reaction between Fe and AI occurs before the reaction between Fe and Zn
occurs, and consequently the occurrence of dross is suppressed. For this reason,
usually Al is contained in a hot-dip galvanizing bath.
15 [0029]
In general, in hot-dip galvanizing, AI is contained at 0.2 to 0.3% in the
plating bath, and 0.2 to 1.0 mass% of Al is contained in the plating layer; in alloyed
hot-dip galvanizing, AI is contained at 0.1 to 0.2% in the plating bath, and 0.1 to 0.5
mass% of AI is contained in the plating layer.
20 [0030]
The AI in the plating layer diffuses and moves to the outer layer of the
plating layer not only during the formation of a plating coating film but also during
the heating of hot pressing. At this time, Al is oxidized preferentially as compared
to Zn, and forms anAl oxide film made of Ah03.
25 [0031]
In the present embodiment, as a specific plating operation, an operation in
which a steel sheet is dipped in a plating bath in which Zn or a Zn alloy in a molten
state is retained and the steel sheet is pulled up from the plating bath is performed.
The amount of plating attached to the steel sheet is controlled by adjusting the speed
30 of the pulling-up of the steel sheet, the flow rate and the flow velocity of wiping gas
jetted from a wiping nozzle provided above the plating bath, etc. Alloying
PCT/JP2016/060798
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treatment is performed by, after plating treatment like the above, additionally heating
the plated steel sheet using a gas furnace or an induction heating furnace, a heating
furnace in which these are combined, or the like. The plating operation may also be
performed by the method of continuously plating a coil or the method of plating a cut
5 sheet single body.
[0032]
The thickness of the hot-dip zinc-based plating layer (that is, the amount of
the hot-dip zinc-based plating layer attached) is preferably in the range of 20 g/m2 to
100 g/m2 per one surface. In the case where the thickness of the hot-dip zinc-based
10 plating layer is less than 20 g/m2 per one surface, the effective amount of Zn after hot
pressing cannot be ensured and corrosion resistance is insufficient; thus, this is not
preferable. In the case where the thickness of the hot-dip zinc-based plating layer is
more than 100 g/m2 per one surface, the processability and the adhesiveness of the
plating layer are reduced; thus, this is not preferable. A more preferred thickness of
15 the hot-dip zinc-based plating layer is in the range of 30 g/m2 to 90 g/m2 per one
surface.
[0033]
(3) Surface treatment layer
On the hot-dip zinc-based plating layer described above, a surface treatment
20 layer is further formed, the surface treatment layer containing granular oxide in
which, in a temperature range of 900 to 1300 K, standard free energy of fmmation
(L1G0
) of oxide is smaller than standard free energy of formation (L1G0z0) of zinc
oxide and larger than standard free energy of formation (L1G0
AI) of aluminum oxide at
an identical temperature. Such oxide is reduced by AI contained in the zinc-based
25 plating layer, and is oxidized preferentially as compared to Zn, thus, it is presumed
that production of zinc oxide is suppressed.
[0034]
Here, the "granular oxide" represents a substance that contains oxide as a
main component, which exists in a state of being dispersed in a treatment liquid as a
30 solid having a size of several nanometers or more as a primary particle size, and does
not exist in a state of being dissolved in the treatment liquid like a compound of
PCT/JP2016/060798
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nitrate, sulfate, lithium salt, or the like. Using the granular oxide which is dispersed
in the treatment liquid in the solid state and in which, in the temperature range of 900
to 1300 K, the standard free energy of formation (llG0
) of oxide is smaller than the
standard free energy of formation (llG0 zn) of zinc oxide and larger than the standard
5 free energy of formation (llG0
AI) of aluminum oxide at an identical temperature,
there can be provided a heat-treated steel material having excellent durability
particularly in an environment of a portion at which sheets are put together where
coating is not delivered. Note that such granular oxide exists in a state of particles
in the surface treatment layer.
10 [0035]
Here, specific values of the standard free energy of formation of zinc oxide
(ZnO) and the standard free energy of formation of aluminum oxide (AI20 3) in the
temperature range of 900 to 1300 K can be found by referring to known data such as
"Anticorrosion handbook edited by Japan Society of Corrosion Engineering". For
15 example, the standard free energy of formation (llG0zn) of zinc oxide (ZnO) at 900 K
and the standard free energy of formation (llG0zn) of zinc oxide (ZnO) at 1300 K are
approximately -535 kJ/mol and -460 kJ/mol, respectively, and the standard free
energy of formation (llG0
AI) of aluminum oxide (Ab03) at 900 K and the standard
free energy of formation (llG0
AI) of aluminum oxide (Ab03) at 1300 K are
20 approximately -945 kJ/mol and -880kJ/mol, respectively.
[0036]
Examples of the granular oxide in which, in the temperature range of 900 to
1300 K, the standard free energy of formation (llG0
) of oxide is smaller than the
standard free energy of formation (llG0zn) of ZnO and larger than the standard free
25 energy of formation (llG0
A1) of Ab03 at an identical temperature include oxides of
silicon (Si), oxides of titanium (Ti), oxides of chromium (Cr), oxides of vanadium
(V), oxides of manganese (Mn), and oxides of boron (B).
[0037]
Of those, oxides of metal elements (that is, metal oxides) are stable, and are
30 appropriate for reasons of availability. Examples of such metal oxides include Si
oxides, Ti oxides, Cr oxides, and V oxides. Note that an oxide of an element which
PCT/JP2016/060798
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belongs to a semiconductor or a metal depending on the crystal structure, such as Si,
is also included in the metal oxides.
[0038]
In view of the current tendency of attention to environmental protection
5 being strongly required, it is preferred that the Cr oxides do not contain chromium
content including trivalent chromium, let alone hexavalent chromium, that is, the Cr
oxides are preferably chromium-free. Therefore, Si oxides and Ti oxides are
preferably used as the granular oxide satisfying the condition of the standard free
energy of formation described above.
10 [0039]
Further, the particle size (primary particle size) of the granular oxide
satisfying the condition of the standard free energy of formation described above is
more than or equal to 3 nm and less than or equal to I 00 nm. For the particle size
of the oxide, a smaller size is advantageous in terms of post-coating corrosion
15 resistance, but those with a particle size of less than 3 nm are difficult to obtain and
are disadvantageous in terms of cost. Further, in the case where the particle size of
the granular oxide exceeds 500 nm, the surface area is reduced, and accordingly it is
feared that the reactivity with the underlying plating during heating will be reduced;
thus, this is not preferable. The particle size of magnesium oxide is preferably more
20 than or equal to 5 nm and less than or equal to 30 nm.
[0040]
The particle size (primary particle size) of the granular oxide described
above can be measured by a known method; for example, the measurement can be
performed by a method in which a cross section-embedded sample is prepared after
25 coating, several particle sizes of oxide particles in the coating film are measured, and
the average of the obtained measurement results is taken as the particle size.
[0041]
The surface treatment layer according to the present embodiment is formed
from a treatment liquid containing the granular oxide satisfying the condition of the
30 standard free energy of formation described above. The surface treatment layer
according to the present embodiment contains more than or equal to 0.1 g/m2 and
5
PCT/JP2016/060798
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less than or equal to 1.2 g/m2 of granular oxide per one surface on a metal basis, the
granular oxide satisfying the condition of the standard free energy of formation
described above.
[0042]
In the hot-dip zinc-based plated steel sheet including such a surface
treatment layer containing more than or equal to 0.1 g/m2 and less than or equal to
1.2 g/m2 of granular oxide per one surface on a metal basis, an Al oxide that is
present in the hot-dip galvanized layer before hot pressing and is formed during hot
pressing reduces the oxide contained in the surface treatment layer. Since the metal
10 particles obtained by reducing the oxide more easily form an oxide as compared to
Zn, the metal particle is oxidized preferentially as compared to Zn. Consequently, it
is assumed that the production of zinc oxide is suppressed.
[0043]
In the case where the amount of the granular oxide attached to the surface
15 treatment layer per one surface on a metal basis is less than 0.1 g/m2
, the metal
particles obtained by reducing the oxide which are necessary for suppressing
production of zinc oxide during hot pressing are not sufficiently present, and hence,
the production of zinc oxide cannot be suppressed and sufficient corrosion resistance
cannot be ensured. On the other hand, in the case where the amount of the granular
20 oxide attached to the surface treatment layer per one surface on a metal basis exceeds
1.2 g/m2
, the cost of the hot -dip zinc-based plated steel sheet according to the present
embodiment is increased, and it is presumed that the cohesive force of the smface
treatment layer is weakened and a coating film that is formed on the surface
treatment layer after hot pressing is likely to peel off.
25 [0044]
30
The amount of granular oxide attached to the surface treatment layer per one
surface on a metal basis is preferably more than or equal to 0.2 g/m2 and less than or
equal to 0.8 g/m2
•
[0045]
Here, the amount of the granular oxide attached to the surface treatment
layer on a metal basis can be measured by a known method; for example, the
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measurement can be performed by dissolving the surface treatment layer and using
inductively coupled plasma (ICP) emission spectrometric analysis.
[0046]
As the treatment liquid containing the granular oxide satisfying the
5 condition of the standard free energy of formation described above, there can be used
a treatment liquid in which powder of oxide of silicon, titanium, manganese, or the
like is dispersed. Further, as an already dispersed treatment liquid, it is more
preferred that titania sol and silica sol be used. Specific example of commercially
available products of titania sol includes TKS (registered trademark) series
10 manufactured by Tayca Corporation. Specific example of commercially available
products of silica sol includes Snowtex (registered trademark) series manufactured
by Nissan Chemical Industries, Ltd.
[0047]
In forming the surface treatment layer, the above-mentioned titania sol and
15 silica sol may be applied as they are to the hot-dip galvanized steel sheet, however, in
order to improve stability of the treatment liquid and adhesiveness of the surface
treatment layer, it is more preferred that the treatment liquid have a resin or a
crosslinking agent mixed therein, and the treatment liquid be applied to the hot -dip
zinc-based plated steel sheet.
20 [0048]
In the case where the above titania sol and silica sol are used, a watersoluble
or water-dispersible resin is preferably used as the resin, and examples of the
resin include a polyurethane resin, a polyester resin, an epoxy resin, a (meth)acrylic
resin, a polyolefin resin, a phenol resin, and modified products of those resins. In
25 the case where titania powder and silica powder are used, a solvent resin in which
any of various solvents is used as the solvent may be used in addition to the abovementioned
water-based resin.
[0049]
Examples of the crosslinking agent include a silane coupling agent, a
30 zirconium carbonate compound, an organic titanium compound, an oxazoline
polymer, a water-soluble epoxy compound, a water-soluble melamine resin, a waterPCT/
JP2016/060798
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dispersible blocked isocyanate, and a water-based aziridine compound.
[0050]
Note that also in the case where the above-mentioned resin or crosslinking
agent is mixed, the content of the granular oxide satisfYing the condition of the
5 standard free energy of formation described above is, as described above, more than
or equal to 0.1 g/m2 and less than or equal to 1.2 g/m2 per one surface on a metal
basis in the surface treatment layer.
[0051]
Further, as another component that is preferably contained in the surface
10 treatment layer according to the present embodiment, for example, there is given an
oxide of alkaline-earth metal in a broad sense (that is, beryllium, magnesium,
calcium, strontium, barium, and radium, which are elements in the second group of
the periodic table) in which, in the temperature range of 900 to 1300 K, the standard
free energy of formation (AG0
) of oxide is smaller than the standard free energy of
15 formation (AG0 At) of aluminum oxide at an identical temperature.
[0052]
When the oxide of alkaline-earth metal is contained in the surface treatment
layer, it is surmised that the oxide of alkaline-earth metal exists stably in a state of
ordinary metal oxide during hot pressing, but reacts with zinc oxide formed during
20 heating in hot pressing and forms a composite oxide with zinc oxide, and thus, it is
assumed that thereby suppresses excessive oxidation and vaporization of zinc. As
the oxide of alkaline-earth metal that can obtain this effect more efficiently,
magnesium oxide or calcium oxide is preferably used.
[0053]
25 In the case where the surface treatment layer contains magnesium oxide or
calcium oxide, the content thereof is preferably more than or equal to 0.05 g/m2 and
less than or equal to 0.35 g/m2 per one surface on a metal basis, and is more
preferably more than or equal to 0.05 g/m2 and less than or equal to 0.2 g/m2 per one
surface on a metal basis. In the case where the content of magnesium oxide or
30 calcium oxide is less than 0.05 g/m2 per one surface on a metal basis, a sufficient
amount of a composite oxide with zinc oxide cannot be formed, and it may be
PCT/JP2016/060798
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difficult to efficiently suppress the oxidation and vaporization of Zn. On the other
hand, in the case where the content of magnesium oxide or calcium oxide exceeds
0.35 g/m2 per one surface on a metal basis, decrease in the cohesive force of the
surface treatment layer may cause defects in adhesiveness.
5 [0054]
The surface treatment layer according to the present embodiment may
contain, in addition to oxides like the above, at least one of one or more P-containing
compormds, one or more V-containing compounds, one or more Cu-containing
compounds, one or more At-containing compounds, and one or more Cr-containing
10 compounds described in detail below in the range of a predetermined content.
[0055]
The P-containing compound is a compound containing phosphorus as a
constituent element. Examples of the P-containing compound include compounds
such as phosphoric acid, phosphorous acid, phosphonic acid, phosphonous acid,
15 phosphinic acid, phosphinous acid, a phosphine oxide, and phosphine, an ionic
compormd containing any of these compounds as an anion, and the like. All these
P-containing compounds are commercially available as reagents or products, and can
be easily obtained. These P-containing compounds exist in a state of being
dissolved in a treatment liquid or in a state of being dispersed as powder in a
20 treatment liquid, and exist, in the surface treatment layer, in a state of being dispersed
as solid.
[0056]
The V-containing compound is a compound containing vanadium as a
constituent element. Examples of the V-containing compound include vanadium
25 oxides such as vanadium pentoxide, metavanadic acid-based compounds such as
anrmonium metavanadate, vanadium compounds such as sodium vanadate, and other
V-containing compounds. Those V-containing compounds are commercially
available as reagents or products, and can be easily obtained. Those V-containing
compounds exist in a state of being dissolved in a treatment liquid or in a state of
30 being dispersed as powder in a treatment liquid, and exist, in the surface treatment
layer, in a state of being dispersed as solid.
PCT/JP2016/060798
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[0057]
The surface treatment layer according to the present embodiment preferably
contains one or more compounds selected from one or more P-containing compounds
and one or more V-containing compounds mentioned above individually in the range
5 of more than or equal to 0.0 g/m2 and less than or equal to 0.01 g/m2 per one surface
on a P and V basis.
[0058]
One or more compounds selected from one or more P-containing
compounds and one or more V-containing compounds mentioned above are oxidized
10 into an oxide during hot pressing, and the oxide exists locally at the interface
between the hot-dip Zn-based plating layer and the surface treatment layer and forms
an oxide layer that contains at least one of P and V and has weak cohesive force.
Since the content of the one or more compounds selected from one or more Pcontaining
compounds and one or more V-containing compounds contained is
15 individually in the range of more than or equal to 0.0 g/m2 and less than or equal to
0.01 g/m2 per one surface on a P and V basis, the thickness of an oxide layer like the
above that is formed during hot pressing and has weak cohesive force is reduced, and
the adhesiveness between the hot-dip Zn-based plating layer and the surface
treatment layer after hot pressing is further improved.
20 [0059]
In the case where the content of the one or more selected from one or more
P-containing compounds and one or more V-containing compounds in the surface
treatment layer exceeds 0.01 g/m2 per one surface, the thickness of the oxide layer
that is formed during hot pressing and has weak cohesive force is increased;
25 consequently, the adhesiveness between the hot-dip Zn-based plating layer and the
surface treatment layer is reduced. As a result, the surface treatment layer easily
peels off after hot pressing, and the surface treatment layer that has been peeled off
may adhere to the mold for hot pressing. From the viewpoint of the adhesiveness
between the hot-dip Zn-based plating layer and the surface treatment layer after hot
30 pressing, the content of the one or more compounds selected fiom one or more Pcontaining
compounds and one or more V-containing compounds in the surface
PCT/JP2016/060798
21151
treatment layer is more preferably individually more than or equal to 0.0 g/m2 and
less than or equal to 0.003 g/m2 per one surface on a P and V basis.
[0060]
The Cu-containing compound is a compound containing copper as a
5 constituent element. Examples of the Cu-containing compound include metal Cu,
copper oxide, various organic copper compounds, various inorganic copper
compounds, and various copper complexes. Those Cu-containing compounds are
commercially available as reagents or products, and can be easily obtained. Those
Cu-containing compounds exist in a state of being dissolved in a treatment liquid or
10 in a state of being dispersed as powder in a treatment liquid, and exist, in the surface
treatment layer, in a state of being dispersed as solid.
[0061]
The surface treatment layer according to the present embodiment preferably
contains one or more compounds selected from one or more Cu-containing
15 compounds mentioned above in the range of more than or equal to 0.0 g/m2 and less
than or equal to 0.02 g/m2 per one surface on a Cu basis.
[0062]
One or more compounds selected from one or more Cu-containing
compounds mentioned above are oxidized into an oxide during hot pressing, and the
20 oxide exists locally at the interface between the Zn-based plating layer and the
surface treatment layer and forms an oxide layer that contains Cu and has weak
cohesive force. Since the content of the one or more compounds selected from one
or more Cu-containing compounds is in the range of more than or equal to 0.0 g/m2
and less than or equal to 0.02 g/m2 per one surface on a Cu basis, the thickness of an
25 oxide layer like the above that is formed during hot pressing and has weak cohesive
force is reduced, and the adhesiveness between the hot-dip Zn-based plating layer
and the surface treatment layer after hot pressing is finiher improved.
[0063]
In the case where the content of the one or more selected from one or more
30 Cu-containing compounds in the surface treatment layer exceeds 0.02 g/m2 per one
surface, the thickness of the oxide layer that is formed during hot pressing and has
PCT/JP2016/060798
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weak cohesive force is increased; consequently, the adhesiveness between the hot-dip
Zn-based plating layer and the surface treatment layer is reduced. As a result, the
surface treatment layer easily peels off after hot pressing, and the surface treatment
layer that has been peeled off may adhere to the mold for hot pressing. In addition,
5 since Cu is an element nobler than Fe, which is a main component of the base steel
sheet, also the con·osion resistance tends to decrease. From the viewpoint of the
adhesiveness between the hot-dip Zn-based plating layer and the surface treatment
layer after hot pressing, the content of the one or more compounds selected from one
or more Cu-containing compounds in the surface treatment layer is more preferably
10 more than or equal to 0.0 g/m2 and less than or equal to 0.005 g/m2 per one surface
on a Cu basis.
[0064]
The Al-containing compound is a compound containing aluminum as a
constituent element. Examples of the Al-containing compound include metal AI,
15 aluminum oxide, aluminum hydroxide, an ionic compound containing an aluminum
ion as a cation, and the like. Those Al-containing compounds are commercially
available as reagents or products, and can be easily obtained. Those Al-containing
compounds exist in a state of being dissolved in a treatment liquid or in a state of
being dispersed as powder in a treatment liquid, and exist, in the surface treatment
20 layer, in a state of being dispersed as solid.
[0065]
The surface treatment layer according to the present embodiment preferably
contains one or more compounds selected from one or more Al-containing
compounds mentioned above in the range of more than or equal to 0.0 g/m2 and less
25 than or equal to 0.005 g/m2 per one surface on an AI basis.
[0066]
One or more compounds selected from one or more Al-containing
compounds mentioned above are oxidized into an oxide during hot pressing, and the
oxide concentrates on the surface of the surface treatment layer. Since the content
30 of the one or more compounds selected from one or more Al-containing compounds
is in the range of more than or equal to 0.0 g/m2 and less than or equal to0.005 g/m2
PCT/JP2016/060798
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per one surface on an AI basis, the existence ratio of the oxides containing AI that are
formed on the surface of the surface treatment layer during hot pressing is reduced,
and those oxides containing AI can be prevented from being adhered to the mold for
hot pressing.
5 [0067]
In the case where the content of the one or more selected from one or more
Al-containing compounds in the surface treatment layer exceeds 0.005 g/m2 per one
surface, the existence ratio of the oxides containing AI that are formed during hot
pressing is increased. Those oxides containing AI adhere to the mold for hot
10 pressing and inhibit the formation of a chemical conversion treatment coating film;
therefore, when the existence ratio of the oxides containing Al that are formed during
hot pressing is increased, adhesion of the oxides containing AI to the mold for hot
pressing increases, and the operability is deteriorated. From the viewpoint of the
operability, the content of the one or more compounds selected from one or more Al-
15 containing compounds in the surface treatment layer is more preferably more than or
equal to 0.0 g/m2 and less than or equal to 0.002 g/m2 per one surface on an AI basis.
[0068]
The Cr-containing compound is a compound containing chromium as a
constituent element. Examples of the Cr-containing compound include metal Cr,
20 chromium compounds having various valences, and an ionic compound containing a
chromium ion having any of various valences as a cation. Those Cr-containing
compounds exist in a state of being dissolved in a treatment liquid or in a state of
being dispersed as powder in a treatment liquid, and exist, in the surface treatment
layer, in a state of being dispersed as solid.
25 [0069]
The Cr-containing compound vanes m performance and propetiies m
accordance with the valence, and many hexavalent chromium compounds are
harmful. As mentioned above, in view of the current tendency of attention to
environmental protection being strongly required, the surface treatment layer
30 according to the present embodiment preferably contains as little amount of Crcontaining
compounds mentioned above as possible, and is more preferably
PCT/JP2016/060798
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chromium-free.
[0070]
From the above point of view, the surface treatment layer according to the
present embodiment preferably contains one or more compounds selected from one
5 or more Cr-containing compounds mentioned above in the range of more than or
equal to 0.0 gin?- and less than or equal to 0.01 g/m2 per one surface on a Cr basis,
and more preferably contains no Cr-containing compound.
[0071]
As the method for forming the surface treatment layer, a treatment liquid
10 containing the granular oxide satisfYing the condition of the standard free energy of
formation described above may be applied to the surface of a zinc-plated steel sheet,
and drying and baking may be performed.
[0072]
The coating method is not limited to a specific method, and examples
15 include a method in which a base steel sheet is dipped in a treatment liquid or a
treatment liquid is sprayed to the surface of a base steel sheet, and then the attached
amount is controlled by a roll or gas spraying so as to obtain a prescribed attached
amount, and a method of coating using a roll coater or a bar coater.
20
[0073]
The method of drying and baking is not limited to a specific method, either,
as long as it is a method that can volatilize a dispersion medium (mainly water).
Here, if heating is performed at an excessively high temperature, it is feared that the
uniformity of the surface treatment layer will be reduced; conversely, if heating is
performed at an excessively low temperature, it is feared that productivity will be
25 reduced. Thus, to produce a surface treatment layer having excellent characteristics
30
stably and efficiently, the surface treatment layer after coating is preferably heated at
a temperature of approximately 80°C to l50°C for approximately 5 seconds to 20
seconds.
[0074]
The formation of the surface treatment layer is preferably perfmmed in-line
in the production line of the plated steel sheet because this is economical; but the
PCT/JP2016/060798
25/51
surface treatment layer may be formed also in another line, or may be formed after
blanking for molding is performed.
[0075]
Here, the content of above-mentioned one or more P-containing compounds,
5 one or more V-containing compounds, one or more Cu-containing compounds, one
or more Al-containing compounds, one or more Si-containing compounds, and one
or more Cr-containing compounds in the surface treatment layer can be measured by
a known method; for example, the fact that the various compounds included in the
surface treatment layer are the above-mentioned compounds of attention is checked
10 beforehand by cross-sectional energy dispersive X-ray (EDX) analysis or the like,
and then the coating film is dissolved; thus, the measurement can be made using
inductively coupled plasma (ICP) emission spectrometric analysis or the like.
15
[0076]
<2. Regarding hot pressing process>
In the case where the hot pressing method is used for a hot-dip zinc-based
plated steel sheet like that described above, the hot -dip zinc-based plated steel sheet
is heated to a prescribed temperature, and is then press-molded. In the case of the
hot-dip zinc-based plated steel sheet according to the present embodiment, heating is
usually performed to 700 to 1 000°C because hot press molding is performed; but in
20 the case where a martensite single phase is formed after rapid cooling or martensite
is formed at a volume ratio of 90% or more, it is impmiant that the lower limit of the
heating temperature be the Ac3 point or more. In the case of the present invention,
also the case where a two-phase region of martensite/ferrite is formed after rapid
cooling is included, and therefore the heating temperature is preferably 700 to
25 1 000°C as described above.
[0077]
Examples of the hot pressing method include two methods of hot pressing
by slow heating and hot pressing by rapid heating. Examples of the heating method
used include heating with an electric furnace or a gas furnace, flame heating,
30 energization heating, high-frequency heating, and induction heating, and the
atmosphere during heating is not particularly limited; as a heating method to obtain
PCT/JP2016/060798
26/51
the effect of the present invention significantly, energization heating, induction
heating, and the like, which are rapid heating, are preferably used.
[0078]
In the hot pressing method by slow heating, the radiation heating of a
5 heating furnace is used. First, the hot-dip zinc-based plated steel sheet according to
the present embodiment that is used as a steel sheet for hot pressing is placed in a
heating furnace (a gas furnace, an electric furnace, or the like). The steel sheet for
hot pressing is heated at 700 to 1 000°C in the heating furnace, and is, depending on
the condition, kept at this heating temperature (soaking). Thereby, molten Zn in the
10 hot-dip zinc-based plating layer is combined with Fe and forms a solid phase (Fe-Zn
solid solution phase). After the molten Zn in the hot-dip zinc-based plating layer is
combined with Fe and forms a solid phase, the steel sheet is taken out of the heating
furnace. Alternatively, by combining molten Zn in the hot-dip zinc-based plating
layer with Fe by soaking, the solid phase may be formed as an Fe-Zn solid solution
15 phase and a ZnFe alloy phase; and then the steel sheet may be taken out of the
heating furnace.
[0079]
Alternatively, the hot-dip zinc-based plated steel sheet may be heated to 700
to 1 000°C while no keeping time is provided or the keeping time is set to a short
20 time, and the steel sheet may be taken out of the heating furnace. In this case, after
the steel sheet is heated to 700 to 1 000°C, cooling is performed without applying
stress to the steel sheet by press molding or the like until molten Zn in the hot -dip
zinc-based plating layer is combined with Fe and forms a solid phase (Fe-Zn solid
solution phase or ZnFe alloy phase). Specifically, cooling is performed until at least
25 the temperature of the steel sheet becomes the temperature at which the hot-dip zincbased
plating layer forms a solid phase. For example, in the hot-dip galvanized
layer and the alloyed hot-dip galvanized layer, cooling is performed until the
temperature of the steel sheet becomes lower than or equal to 782°C. After the
cooling, as described below, cooling is performed while the steel sheet is pressed
30 using a mold. On the other hand, in the case where the heating temperature is lower
than or equal to 782°C, since the hot-dip zinc-based plating layer stays as the solid
PCT/JP2016/060798
27/51
phase, press molding may be quickly performed after the steel sheet is taken out of
the heating furnace.
[0080]
Also in hot pressing by rapid heating, similarly, the hot-dip zinc-based
5 plated steel sheet according to the present embodiment that is used as a steel sheet for
hot pressing is rapidly heated to 700 to 1 000°C. The rapid heating is performed by,
for example, energization heating or induction heating. The average heating rate in
this case is 20°C/second or more. In the case of rapid heating, after the hot-dip
zinc-based plated steel sheet is heated to 700 to 1 000°C, cooling is performed
10 without applying stress to the steel sheet by press molding or the like until molten Zn
in the hot-dip zinc-based plating layer is combined with Fe and forms a solid phase
(Fe-Zn solid solution phase or ZnFe alloy phase). Specifically, cooling is
performed until at least the temperature of the steel sheet becomes the temperature at
which the hot-dip zinc-based plating layer forms a solid phase. For example, in the
15 hot-dip galvanized layer and the alloyed hot-dip galvanized layer, cooling is
performed until the temperature of the steel sheet becomes lower than or equal to
782°C. After the cooling, as described below, cooling is performed while the steel
sheet is pressed using a mold. In the case where the heating temperature is lower
than or equal to 782°C, since the hot-dip zinc-based plating layer stays as the solid
20 phase, press molding may be quickly performed after the steel sheet is taken out of
the heating furnace.
[0081]
The taken-out steel sheet is pressed using a mold. When pressing the steel
sheet, the steel sheet is cooled by the mold. A cooling medium (for example, water
25 or the like) is circulated through the mold, and the mold removes heat from the steel
sheet and cools it. By the above process, a hot pressed steel material is produced by
normal heating.
[0082]
The hot pressed steel material produced using the hot-dip zinc-based plated
30 steel sheet including the surface treatment layer according to the present embodiment
has excellent durability.
PCT/JP2016/060798
28/51
[0083]
In the case where hot pressing by normal heating is performed using a
conventional plated steel sheet, the steel sheet is soaked in a heating furnace. In this
case, although a zinc oxide film is formed on the outer layer of the plating layer of
5 the steel sheet for hot pressing, a larger amount of the zinc oxide film is formed due
to long time soaking heating, and the amount of metal zinc remained in the coating
film after hot pressing decreases. Accordingly, compared to the galvanized steel
material before heating, the corrosion resistance at an uncoated portion of the hot
pressed steel material may decrease significantly.
10 [0084]
However, the hot-dip zinc-based plated steel sheet according to the present
embodiment contains, in the surface treatment layer, the granular oxide satisfYing the
condition of the standard free energy of formation described above, and thereby
suppresses the production of zinc oxide during hot pressing and ensures amount of
15 metal zinc after hot pressing; and can thus exhibit satisfactory corrosion resistance at
an uncoated portion.
[Examples]
[0085]
The action and effect of the hot-dip zinc-based plated steel sheet according
20 to an embodiment of the present invention will now be described still more
specifically with reference to Examples. Examples shown below are only examples
of the hot-dip zinc-based plated steel sheet according to the present invention, and
the hot -dip zinc-based plated steel sheet according to the present invention is not
limited to Examples below.
25 [0086]

In the following, first, p1eces of molten steel having the chemical
compositions shown in Table l below were produced. After that, the produced
pieces of molten steel were used to produce slabs by the continuous casting method.
30 The obtained slab was hot rolled to produce a hot rolled steel sheet. Subsequently,
the hot rolled steel sheet was pickled, and then cold rolling was perfmmed to produce
PCT/JP2016/060798
29/51
a cold rolled steel sheet; thus, steel sheets of steel #I to #8 having the chemical
compositions described in Table 1 were prepared. As shown in Table 1, the sheet
thicknesses of the steel sheets of all the steel types were 1.6 mm.
Table 1
Type of Sheet
steel thickness (mm) c
#1 1.6 0. 2
#2 1.6 0. 2
#3 1 . 6 0. 2
#4 1 . 6 0.2
#5 1 . 6 0.2
#6 1 . 6 0.2
#7 1 . 6 0.2
#8 1.6 0.2
Chemical composition (mass%, the balance: Fe and impurities)
Si Mn p s so I. AI N B Ti Cr Mo Nb
0.2 1 . 3 0. 01 0.005 0.02 0.002 0.002 0.02 0.2 - -
0. 5 1.3 0. 01 0.005 0.02 0.002 0.002 0.02 0.2 - -
0.5 1.3 0. 01 0.005 0.02 0.002 0.002 0.02 0.2 - 0.05
0.5 1 . 3 0. 01 0.005 0. 02 0.002 0.002 0. 02 0. 2 - -
0.5 1 . 3 0. 01 0.005 0.02 0. 002 0.002 0.02 0. 2 0.5 -
0.5 1.3 0. 01 0.005 0. 02 0.002 - - - - -
0.2 0. 2 0. 01 0.005 0. 02 0.002 0.002 0.02 0. 2 - -
0.2 0.4 0. 01 0.005 0.02 0. 002 0.002 0.02 0.2 - -
Ni
-
-
-
1.0
-
-
-
-
~ g -cr .o.o., -" ~ ~
w
-~
'1:1
~
".0.. "..
;3
a:>
0_ ,
co
00
PCT/JP2016/060798
31/51
[0088]

The steel sheets of steel #1 to #8 were subjected to hot-dip galvanizing
treatment, and were then subjected to alloying treatment. With the maximum
5 temperature in each alloying treatment set to 530°C, heating was performed for
approximately 30 seconds; and then cooling was performed to room temperature;
thus, an alloyed hot-dip galvanized steel sheet (GA) was produced. Using steel #1,
hot-dip galvanizing treatment was performed, and a hot-dip galvanized steel sheet
(GI) was produced without performing alloying treatment.
10 [0089]
15
Further, steel #1 was subjected to various types of hot-dip galvanizing using
three types of plating baths of hot-dip Zn-55%Al plating, hot-dip Zn-6%Al-3%Mg
plating, and hot-dip Zn-11 %Al-3%Mg-0.2%Si plating, and hot-dip zinc-based plated
steel sheets AI to A3 were produced.
A 1: hot-dip Zn-55%Al plating
A2: hot-dip Zn-6%Al-3%Mg plating
A3: hot-dip Zn-11 %Al-3%Mg-0.2%Si plating
[0090]
Further, steel #1 was subjected to zinc electroplating treatment, and a zinc
20 electroplated steel sheet (EG) was produced.
[0091]
25
Here, the amount of the hot-dip zinc-based plating layer attached to the hotdip
zinc-based plated steel sheet was set to 50 g/m2
.
[0092]
Note that the AI concentration in the plating coating film of the hot-dip
galvanized steel sheet described above was found by the following method. That is,
a sample was collected fi·om each hot-dip zinc-based plated steel sheet. The hot-dip
zinc-based plating layer of the collected sample was dissolved in a 10% HCI aqueous
solution, and the composition of the hot-dip zinc-based plating layer was analyzed by
30 ICP emission spectrometric analysis. The AI concentration (mass%) per one
surface was determined on the basis of the obtained analysis result. The obtained
PCT/JP2016/060798
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results are collectively shown in Table 3 below.
[0093]

Subsequently, in order to form coating films having the compositions and
5 the attached amounts shown in Table 2, oxides and chemical agents were blended
using water. The oxides in powder state were used after the powder is dispersed in
resin-added water and the powder is pulverized using a ball mill to a degree so as to
be dispersed in the resin dispersed solution. The obtained treatment liquid was
applied with a bar coater, and drying was performed using an oven under conditions
10 for keeping a maximum peak temperature of 1 00°C for 8 seconds; thus, a plated steel
sheet for hot pressing was produced. The amount of the treatment liquid attached
was adjusted by the dilution of the liquid and the count of the bar coater so that the
amount of oxides attached to the surface treatment layer per one surface on a metal
basis might be the numerical values shown in Table 2.
15 The components (symbols) in Table 2 are as follows.
20
[0094]
(i) Oxide, etc.: oxide of Ti, oxide of Si
TPA: titania powder (manufactured by IoLiTec GmbH), particle size 10 to
30 nm (catalog value)
TPB: titania powder (TITANIX JA-1, manufactured by Tayca Corporation),
patiicle size: 180 nm (catalog value)
TZ: titania sol (titania sol TKS-203, manufactured by Tayca Corporation),
particle size: 6 nm (catalog value)
SZ: silica sol (Snowtex ST-C, manufactured by Nissan Chemical Industries,
25 Ltd.), particle size: 10 to 20 nm (catalog value)
MP: manganese oxide (Mn304) powder (manufactured by lOX Co.,Ltd.),
average particle size: 25 nm (catalog value)
Note that the above-mentioned five oxides are each a substance in which the
standm·d free energy of formation (L\.G0
) is smaller than the standard free energy of
30 formation (L\.G0 zn) of ZnO and larger than the standard fi·ee energy of formation
(L\.G0
AI) of Ah03 at an identical temperature.
5
PCT/JP2016/060798
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[0095]
(ii) Alkaline earths: oxide of alkaline-earth metal
Mg: Mg oxide (magnesium oxide, manufactured by Japan Pure Chemical
Co., Ltd.)
Ltd.)
Ltd.)
[0096]
Ca: Ca oxide (calcium oxide, manufactured by Japan Pure Chemical Co.,
Sr: Sr oxide (strontium oxide, manufactured by Japan Pure Chemical Co.,
10 (iii) Resin
15
A: a urethane-based resin emulsion (Superflex (registered trademark) E-
2000, manufactured by DKS Co. Ltd.)
B: a urethane-based resin emulsion (Superflex (registered trademark) 150,
manufactured by DKS Co. Ltd.)
C: a polyester resin emulsion (Vylonal (registered trademark) MD 1480,
manufactured by Toyobo Co., Ltd.)
[0097]
(iv) Crosslinking agent
M: a melamine resin (Cyme! (registered trademark) 325, manufactured by
20 Mitsui Cytec Ltd.)
Z: ammonium zirconium carbonate (an ammonium zirconium carbonate
solution, manufactured by Kishida Chemical Co.,Ltd.)
S: a silane coupling agent (Sila-Ace S51 0, manufactured by Nichibi Trading
Co.,LTD.)
25 [0098]
(v) Pigment
PZ: zinc phosphite (NP-530, manufactured by Toho Gamyo Co., Ltd.) (Pcontaining
compound)
AI: an alumina sol (AS-200, manufactured by Nissan Chemical Industries,
30 Ltd.) (AI-containing compound)
V: potassium vanadate (general reagent) (V-containing compound)
PCT/JP2016/060798
34/51
Cr: Cr(VI) oxide (general reagent) (Cr-containing compound)
Cu: copper(II) oxide (general reagent) (Cu-containing compound)
[0099]
[Table 2]
Table 2-1
1\ Type
S1 sz
S2 sz
S3 sz
S4 sz
S5 sz
S6 sz
S7 sz
S8 sz
S9 sz
S10 sz
S11 sz
S12 sz
S13 sz
S14 sz
S15 sz
S16 sz
S17 sz
S18 sz
T1 TPA
T2 TPA
T3 TPA
T4 TPA
T5 TPA
T6 TPA
T7 TPA
T8 TPA
T9 TPA
T10 TPA
T11 TPA
T12 TPA
T13 TPA
T14 TPA
T15 TPA
T16 TPA
T17 TPA
T18 TPB
T19 TZ
T20 TZ
T21 TZ
T22 TZ
T23 TZ
T24 TZ
T25 TZ
M1 MP
Cl
C2 -
Ox ide, etc.
Concentration
(mass%)
100
80
40
20
50
50
50
50
50
50
50
50
50
50
50
50
80
80
100
80
40
20
50
50
50
50
50
50
50
50
50
50
50
50
50
80
100
80
50
50
50
50
50
50
0
0
35/51
A I ka I i ne-earth
metal
Type Concentration
(mass%)
- 0
- 0
0
0
- 0
- 0
- 0
Mg 10
Mg 10
Mg 5
Mg 10
Mg 20
Mg 30
Ca 10
Ca 10
Sr 10
- 0
- 0
- 0
- 0
- 0
0
0
0
- 0
Mg 10
Mg 10
Mg 5
Mg 10
Mg 20
Mg 30
Ca 10
Ca 10
Sr 10
- 0
- 0
- 0
- 0
- 0
Mg 10
Mg 10
Ca 10
Ca 10
0
0
0
PCT/JP2016/060798
Resin Cross I inking agent
/Pigment
Type Concentration Type Concentration
(mass%) (mass%)
- 0 - 0
A 20 - 0
A 60 0
A 80 - 0
A 50 - 0
A 45 z 5
A 45 s 5
A 35 z 5
A 35 s 5
A 45 - 0
A 40 - 0
A 30 0
A 20 - 0
A 35 s 5
A 35 z 5
A 35 s 5
B 20 - 0
c 20 - 0
- 0 - 0
B 20 - 0
B 60 - 0
B 80 0
B 50 - 0
B 45 z 5
B 45 s 5
B 35 z 5
B 35 s 5
B 45 - 0
B 40 - 0
B 30 - 0
B 20 - 0
B 35 s 5
B 35 z 5
B 35 s 5
c 45 M 5
B 20 - 0
- 0 - 0
A 20 - 0
A 50 - 0
A 40 - 0
B 35 s 5
B 40 0
B 35 z 5
A 50 0
B 100 - 0
- 0 - 0
[0100]
[Table 3]
Table 2-2
~ S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
S32
T26
T27
T28
T29
T30
T31
T32
T33
T34
T35
T36
T37
T38
T39
5 [0101]
Oxide, etc.
Type Concentration
(mass%)
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
sz 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50
TPA 50

36/51
Alkaline-earth
metal
Type Concentration
(mass%)
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
- 0
PCT/JP2016/060798
Resin Crosslinking agent/
Pigment
Type Concentration Type Concentration
(mass%) (mass%)
A 49 AI 1
A 49.5 AI 0.5
A 49.8 AI 0. 2
A 46 PZ 4
A 48 PZ 2
A 49.5 PZ 0.5
A 48 v 2
A 49 v 1
A 49.6 v 0.4
A 48 Cu 2
A 49 Cu 1
A 49. 7 Cu 0. 3
A 48 Cr 2
A 49 Cr 1
B 49 AI 1
B 49.5 AI 0.5
B 49.8 AI 0.2
B 46 PZ 4
B 48 PZ 2
B 49.5 PZ 0.5
B 48 v 2
B 49 v 1
B 49.6 v 0.4
B 48 Cu 2
B 49 Cu 1
B 49.7 Cu 0.3
B 48 Cr 2
B 49 Cr 1
After the formation process of the surface treatment layer, the steel sheet of
each test number was subjected to hot press heating by a heating system of furnace
heating, and thus hot pressing was performed. In the furnace heating, the
10 atmosphere in the furnace was set to 910°C and the air-fuel ratio was set to 1.1, and
the steel sheet was taken out of the furnace immediately after the temperature of the
PCT/JP2016/060798
37/51
steel sheet reached 900°C.
[0102]
After the hot press heating, cooling was performed until the temperature of
the steel sheet became 700°C. After the cooling, the steel sheet was sandwiched by
5 a flat sheet mold equipped with a water cooling jacket, and thus a hot pressed steel
material (steel sheet) was produced. Cooling was performed up to approximately
360°C, which is the martensite transformation starting point, so as to ensure a
cooling rate of 50°C/second or more even in a portion where the cooling rate had
been low during the hot pressing, and thus quenching was performed.
10 [0103]

[Measurement of amount of zinc oxide]
As a method of measuring a zinc oxide layer by chemical analysis, there
may be used: a method involving dissolving a plating layer in a 5% iodine-methanol
15 solution, dissolving the produced residue in hydrochloric acid, and performing the
measurement; and a method involving dissolving an oxide film on the surface using
an ammonium bichromate aqueous solution and performing the measurement. Here,
the dissolved solutions can be measured using blanks of the respective solutions
through emission analysis such as inductively coupled plasma atomic emission
20 spectroscopy.
[0104]
As a method of measuring a zinc oxide layer by physical analysis, the peak
intensity derived from ZnO may be determined using X -ray diffraction. In this case,
by preparing in advance a calibration curve showing a relationship between the
25 amount of zinc oxide and the peak intensity derived from ZnO using a standard
sample in which the amount of zinc oxide is known, the amount of produced zinc
oxide can be measured from the peak intensity of a specific diffraction plane.
[01 05]
In the present embodiment, an X-ray diffractometer with a Co anode was
30 used, and the amount of produced zinc oxide was calculated from a diffraction peak
intensity on the [100] plane ofZnO on the basis of Formula (1) below.
PCT/JP2016/060798
38/51
[0106]
Amount of produced zinc oxide = XZ-XZO Formula (1)
[0107]
Here, in Formula (1) above, XZ represents a diffraction peak intensity on
5 the ZnO [100] plane after hot press heating, and XZO represents a diffraction peak
intensity on the ZnO [100] plane before hot press heating. As compared to GA with
no surface treatment layer and the zinc-based plated steel sheet which were carried
out as comparative examples, the case where the determined amount of produced
zinc oxide was almost none was evaluated as A, the case where the determined
10 amount of produced zinc oxide was small was evaluated as B, and the case where the
determined amount of produced zinc oxide was large was evaluated as C.
[01 08]
[Corrosion resistance test]
An end face and a back surface of an evaluation test piece were masked
15 with a polyester tape, and a cycle corrosion test of the following cycle conditions was
performed 90 cycles.
[0109]
- Cycle conditions
A cycle corrosion test was performed in which a procedure of two hours of
20 salt water spraying (SST; 5% NaCl; atmosphere: 35°C), then two hours of drying
(60°C), and then four hours of wetting (50°C; RH: 98%) was taken as one cycle.
[0110]
After that, the polyester tape was removed, and then a corrosion product
was dissolved in an ammonium citrate solution and was removed. An evaluation
25 plane was divided into eight equal sections, the thickness of a corrosion part in each
section was measured with a pin point micrometer, and thickness reduction due to
corrosion in each section was detennined fi·om a difference with an unaffected part
which had been masked. An average of the top three values among the determined
thickness reduction values of the respective sections was calculated, and the
30 calculated average was used as a corrosion depth of each test piece.
[0111]
PCT/JP2016/060798
39/51
"G" of the "Corrosion resistance" section in Table 3 means that a corrosion
depth exceeding 0.5 mm occurred. "F" means that a corrosion depth of more than
or equal to 0.4 mm and less than 0.5 mm occurred. "E" means that a corrosion
depth of more than or equal to 0.3 mm and less than 0.4 mm occurred. "D" means
5 that a corrosion depth of more than or equal to 0.2 mm and less than 0.3 mm
occurred. "C" means that a corrosion depth of more than or equal to 0.15 mm and
less than 0.2 mm occurred. "B" means that a corrosion depth of more than or equal
to 0.10 mm and less than 0.15 mm occurred. "A" means that a corrosion depth of
less than or equal to 0.10 mm occurred. The case of "F", "E", "D", "C", "B" or "A"
10 in the corrosion resistance test was assessed as excellent in corrosion resistance.
[0112]
[Adhesion resistance test]
Quantification was performed by measuring, as an index for quantifYing
adhesion to a mold, adhesion of the coating film to the surface of the steel sheet
15 obtained by hot pressing using the above-mentioned flat sheet mold.
To be specific, on the surface of the obtained steel sheet, a peeling test of the
outer layer coating film after hot press molding was performed using a polyester tape
manufactured by Nichiban Co., Ltd. In this case, a peeled amount of the peeling
tape was used as a transmittance of a substrate, and was evaluated as a lightness
20 index using Chroma Meter CR-300 manufactured by Minolta Co., Ltd. The
evaluation was performed as follows. The case where N=3 average (L *ave) of a
lightness index L * was less than or equal to 55 was evaluated as "C", which indicates
that a large amount of the outer layer coating film was peeled off and the adhesion
resistance to the mold was poor. Further, the case where L *ave was larger than 55
25 and less than or equal to 60 was evaluated as "B", and the case where L *ave was
larger than 60 was evaluated as "A". For "A" and "B", the peeling off of the outer
layer coating film was suppressed, and "A" and "B" were each assessed as excellent
in adhesion resistance to the mold.
Table 3-1 I\ Zinc-based plating
I ayer
Steel type AI Type concentration Type
(mass%)
1 #1 GA 0. 2 S5
2 #2 GA 0. 2 S5
3 #3 GA 0.2 S5
4 #4 GA 0.2 S5
5 #5 GA 0. 2 S5
6 #6 GA 0. 2 S5
7 #7 GA 0.2 S5
8 #8 GA 0.2 S5
9 #1 GA 0.2 T5
10 #2 GA 0. 2 T5
11 #3 GA 0. 2 T5
12 #4 GA 0. 2 T5
13 #5 GA 0.2 T5
14 #6 GA 0.2 T5
15 #7 GA 0.2 T5
16 #8 GA 0.2 T5
17 #1 GI 0. 4 T1
18 #1 Gl 0. 4 T2
19 #1 GI 0. 4 T3
20 #1 GI 0. 4 T4
21 #1 GI 0. 4 S5
Surface treatment layer
Attached amount of Attached amount of ZnO Corrosion
oxide, etc. , on alkaline-earths on suppression resistance
meta I basis (g/m2) meta I basis (g/m2)
0. 8 B D
0. 8 B D
0. 8 B D
0. 8 B D
O.B B D
0. B B D
0. 8 B D
0.8 B D
0.8 B D
O.B B 0
0. B B D
0. 8 B D
0. 8 B D
0. 8 B D
0. 8 B D
0.8 B D
0.8 B A
0.8 B A
0.8 B A
0. 8 B D
0. 8 B A
Moldadhesion
Notes
resistance
A
A
A
A
A
A
c
B
A
A
A
A
A
A
A
A
A
A
A
A
A
~ ~ rl 0 '" - c- r' -w (D ~
~
_,.
-~
'"d
~
."0. "..
"0'
".0.. .',
"00'
Table 3-2 \ Zinc-based plating Surface treatment layer
Steel
layer
type AI Attached amount of Attached amount of
Type concentration Type oxide. etc., on a I ka I i ne-earths on
(mass%) meta I basis (g/m1
) meta I basis (g/m1)
22 #1 GI 0. 4 T5 0. 8
23 #1 GJ 0. 4 15 0.05
24 #1 Gl 0.4 15 0.2
25 #1 GJ 0.4 T5 1.2
26 #1 GJ 0. 4 T5 2
27 #1 GA 0. 2 15 0.05
28 #1 GA 0.2 15 0. 2
29 #1 GA 0.2 15 1. 2
30 #1 GA 0.2 15 2
31 #1 GA 0.2 S1 0.8
32 #1 GA 0.2 S2 0. 8
33 #1 GA 0. 2 S3 0. 8
34 #1 GA 0. 2 S4 0. 8
35 #1 GA 0.2 S6 0. 8
36 #1 GA 0.2 S7 0. 8
37 #1 GA 0.2 S8 0. 8 0.2
38 #1 GA 0.2 S9 0.8 0.2
39 #1 GA 0.2 S10 0.8 0. 025
40 #1 GA 0.2 S11 0.8 0.2
41 #1 GA 0. 2 S12 0. 8 0.3
42 #1 GA 0. 2 S13 0. 8 0. 4
ZnO Corrosion Mold- suppression resistance adhesion resistance
8 A A
c G B
B A A
B A A
B G B
c G B
B A A
B A A
B G B
B D A
B D A
B D A
B D A
B D A
B D A
A D A
A D A
B D A
A D A
A D A
B D A
~ ;'
-o" (I)
Notes V>
~
Comparative Example
Comparative Example
Comparative Example
Comparative Example
~
--0 ..,.
~
..,. -V-;
"' ~ 0" '
~'"""
~
0__ ,
(!)
00
Table 3-3 \ Zinc based plating
layer
Steel
type AI
Type concentration Type
(mass%)
43 #1 GA 0.2 S14
44 #1 GA 0.2 S15
45 #1 GA 0.2 S16
46 #1 GA 0. 2 S17
47 #1 GA 0. 2 S18
48 #1 GA 0.2 T1
49 #1 GA 0.2 T2
50 #1 GA 0.2 T3
51 #1 GA 0. 2 T4
52 #1 GA 0. 2 T6
53 #1 GA 0. 2 T7
54 #1 GA 0. 2 T8
55 #1 GA 0. 2 T9
56 #1 GA 0. 2 T10
57 #1 GA 0. 2 T11
58 #1 GA 0.2 T12
59 #1 GA 0.2 T13
60 #1 GA 0.2 T14
61 #1 GA 0.2 T15
62 #1 GA 0.2 T16
63 #1 GA 0.2 T17
Surface treatment layer
Attached amount of Attached amount of ZnO oxide, etc., on alkaline-earths on suppression
meta I basis (g/m2
) meta I basis (g/m2
)
0.8 0. 2 A
0.8 0.2 A
0. 8 0.2 A
0. 8 B
0. 8 B
0.8 B
0.8 B
0. 8 B
0. 8 B
0. 8 B
0.8 B
0.8 0.2 A
0. 8 0.2 A
0.8 0. 025 B
0.8 0. 2 A
0.8 0. 3 A
0.8 0. 4 B
0.8 0. 2 A
0.8 0. 2 A
0.8 0.2 A
0. 8 B
Corrosion Mold- resistance adhesion resistance
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
D A
Notes
~ 0
"' - -<:r "- ' "'~ 0~
_.,.
-~
"d
~ "d 0" "
~
23
"0_ ",
(!)
00
T. a--b·le- 3- -4 \ Zinc based plating
layer
Steel
type AI
Type concentration Type
(mass%)
64 #1 GA 0. 2 118
65 #1 GA 0. 2 119
66 #1 GA 0. 2 120
67 #1 GA 0. 2 121
68 #1 GA 0. 2 122
69 #1 GA 0. 2 123
70 #1 GA 0.2 124
71 #1 GA 0. 2 125
72 #1 GA 0. 2 M1
73 #1 EG 0 S5
74 #1 EG 0 15
75 #1 EG 0 C2
76 #1 A1 55 15
77 #1 A2 6 15
78 #1 A3 11 15
79 #1 GA 0. 2 C1
80 #1 GA 0. 2 C2
81 #1 Gl 0. 4 C2
82 #1 A1 55 C2
83 #1 A2 6 C1
84 #1 A3 11 C2
Surface treatment layer
Attached amount of Attached amount of ZnO oxide, etc .. on alkaline-earths on suppression
meta I basis (g/m2) meta I basis (g/m2)
0.8 c
0.8 B
0.8 B
0. 8 B
0. 8 0.2 A
0. 8 0. 2 A
0. 8 0. 2 A
0. 8 0, 2 A
0.8 B
0.8 c
0.8 c
0 c
0.8 8
0. 8 B
0. 8 B
0 c
0 standard
0 standard
0 standard
0 standard
- standard
Corrosion Moldresistance
adhesion
resistance
G B
D A
D A
D A
D A
D A
D A
0 A
0 A
G B
G B
G c
D A
D A
D A
G c
G c
D c
G c
G c
G c
~ ;;;'
cr'
~ " Notes _,
~
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
~
0 --..:::::
.,.
"V";
~
"d
~
"0 " ......
m
0
m
0
-.J
(!)
00
Table 3-5 I\ Zinc-based plating Ia yer Surface treatment layer
Steel
type AI Attached amount of Attached amount of
Type concentration Type oxide, etc., on alkaline-earths on
(mass%) meta I basis (g/m2) meta I basis (g/m2)
85 #1 GA 0.2 S19 0. 8
86 #1 GA 0.2 S20 0.8
87 #1 GA 0.2 S21 0.8
88 #1 GA 0. 2 S22 0.8
89 #1 GA 0. 2 S23 0.8
90 #1 GA 0. 2 S24 0. 8
91 #1 GA 0. 2 S25 0. 8
92 #1 GA 0. 2 S26 0. 8
93 #1 GA 0.2 S27 0. 8
94 #1 GA 0.2 S28 0. 8
95 #1 GA 0.2 S29 0. 8
96 #1 GA 0.2 S30 0. 8
97 #1 GA 0.2 S31 0.8
98 #1 GA 0.2 S32 0.8
ZnO Corrosion Mold- suppression resistance adhesion resistance
B D c
B D B
B D A
B D c
B D B
B D A
B D c
B D B
B D A
B F c
B E B
B D A
B D A
B D A
~ <;'
-a" (!)
Notes 00
~
AI; 0.0085 g/m2
AI: 0.0042 g/m2
AI: 0.0017 g/m2
P: 0.0137 g/m2
P: 0.0068_gfm2
P: 0.0017_£'m2
V: 0.0118 g/m2
V: 0.0059 g/m2
V; 0.0024gfm2
Cu: 0.025tL_g(m2
Cu: 0.01213J!m2
Cu: 0.0038___&(m2
Cr: 0.0166_.&L'm2
Cr: 0.0083 g/m2
~
0 --
__,
~
-!>-
~-
'"0
C1
~
0" "
>-'
~
Cl
.0.. ,
~
00
T. a-b-·le- 3- -6-
\\ Zinc based plating Surface treatment laYer I avec
Stee I AI Attached amount of Attached amount of
type Type concentration Type oxide, etc., on alkaline-earths on
(mass%) meta I basis (g/m2) meta I basis (g/m2)
99 #1 GA 0,2 T26 0.8
100 #1 GA 0. 2 T27 0.8
101 #1 GA 0. 2 T28 0.8
102 #1 GA 0.2 T29 0. 8
103 #1 GA 0.2 T30 0. 8
104 #1 GA 0.2 T31 0.8
105 #1 GA 0. 2 T32 0.8
106 #1 GA 0. 2 T33 0.8
107 #1 GA 0.2 T34 0. 8
108 #1 GA 0.2 T35 0. 8
109 #1 GA 0.2 T36 0. 8
110 #1 GA 0.2 T37 0. 8
111 #1 GA 0.2 T38 0. 8
112 #1 GA 0.2 T39 0. 8 -- -
ZnO Corrosion Mold- suppression resistance adhesion resistance
8 A c
B A B
B A A
8 A c
B A 8
B A A
8 A c
B A B
B A A
8 c c
B 8 B
B A A
B A A
B A A
• Notes
AI: 0.0085~m2
Al: 0.0042 g/m2
AI: 0.0017 g/m2
P: 0.0137 g/m2
P: 0.0068 g/m2
P: 0.0017 g/m2
V: 0.0118 g/m2
V: 0.0059 g/m2
V: 0.0024 g/m2
Cu: 0.0256 g/m2
Cu: 0.0128_g/m2
Cu: 0.0038JL"m2
Cr: 0.0166....£m2
Cr _ Q,_Q083 g/m2
~ ~
~ -0 g: -00 " ~
\0
~
-~>V-"';
'"d
~
"0"
;'"3""
_"0_ .',
'0"0'
PCT/JP2016/060798
46/51
[0119]
As is clear from Table 3 above, it is found that the hot-dip zinc-based plated
steel sheet according to the present invention not only suppresses excessive
production of zinc oxides on the outer layer after hot pressing and exhibits excellent
5 corrosion resistance, but also has excellent mold-adhesion resistance.
[0120]
The preferred embodiment( s) of the present invention has/have been
described above with reference to the accompanying drawings, whilst the present
invention is not limited to the above examples. A person skilled in the art may find
10 various alterations and modifications within the scope of the appended claims, and it
should be understood that they will naturally come under the technical scope of the
present invention.
5
Claim 1

CLAIMS
A hot-dip zinc-based plated steel sheet comprising:
a base steel sheet that is a metal substrate;
PCT/JP2016/060798
a hot -dip zinc-based plating layer provided on the base steel sheet; and
a surface treatment layer formed on at least one surface of the hot -dip zincbased
plating layer, wherein
the surface treatment layer contains more than or equal to 0.1 g/m2 and less
than or equal to 1.2 g/m2 of granular oxide per one surface on a metal basis in which,
10 in a temperature range of 900 to 1300 K, standard free energy of formation (~G0) of
oxide is smaller than standard free energy of formation (~G0zn) of zinc oxide and
larger than standard free energy of formation (~G0
AI) of aluminum oxide at an
identical temperature, and
the granular oxide has a particle size of more than or equal to 3 nm and less
15 than or equal to 100 nm.
Claim2
The hot-dip zinc-based plated steel sheet according to claim 1, wherein
the surface treatment layer further contains at least one of one or more
20 phosphorus-containing compounds, one or more vanadium-containing compounds,
one or more copper-containing compounds, one or more aluminum-containing
compounds, or one or more chromium-containing compounds in the following range
as a content per one surface,
the one or more phosphorus-containing compounds: more than or equal to
25 0.0 g/m2 and less than or equal to 0.01 g/m2 on a P basis,
the one or more vanadium-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.01 g/m2 on a V basis,
the one or more copper-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.02 g/m2 on a Cu basis,
30 the one or more aluminum-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.005 g/m2 on an AI basis, and
5
10
15
20
25
30
PCT/JP2016/060798
48/51
the one or more chromium-containing compounds: more than or equal to 0.0
g/m2 and less than or equal to 0.01 g/m2 on a Cr basis.
Claim 3
Claim4
The hot-dip zinc-based plated steel sheet according to claim 1 or 2, wherein
the base steel sheet has a chemical composition of, in mass%,
C: 0.05 to 0.4%,
Si: less than or equal to 0.5%,
Mn: 0.5 to 2.5%,
P: less than or equal to 0.03%,
S: less than or equal to 0.01 %,
sol. AI: less than or equal to 0.1 %,
N: less than or equal to 0.01 %,
B: 0 to 0.005%,
Ti: 0 to 0.1%,
Cr: 0 to 0.5%,
Nb: 0 to 0.1%,
Ni: 0 to 1.0%,
Mo: 0 to 0.5%, and
the balance: Fe and impurities.
The hot -dip zinc-based plated steel sheet according to claim 1 or 2, wherein
the base steel sheet has a chemical composition of, in mass%,
C: 0.05 to 0.4%,
Si: less than or equal to 0.5%,
Mn: 0.5 to 2.5%,
P: less than or equal to 0.03%,
S: less than or equal to 0.01 %,
sol. AI: less than or equal to 0.1 %,
N: less than or equal to 0.01 %,
5
10
15
20
Claim 5
B: 0 to 0.005%,
Ti: 0 to 0.1 %,
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Cr: more than 0% and less than or equal to 0.5%,
Nb: 0 to 0.1 %,
Ni: 0 to 1.0%,
Mo: 0 to 0.5%, and
the balance: Fe and impurities, and
the base steel sheet satisfies a relationship of
Mn+Cr: 0.5 to 3.0%.
PCT/JP2016/060798
The hot-dip zinc-based plated steel sheet according to any one of claims 1 to
4, wherein
the granular oxide is metal oxide.
Claim 6
The hot-dip zinc-based plated steel sheet according to any one of claims 1 to
5, wherein
the granular oxide is an oxide oftitanium or an oxide of silicon.
Claim 7
The hot-dip zinc-based plated steel sheet according to any one of claims 1 to
6, wherein
the granular oxide has a particle size of more than or equal to 5 nm and less
25 than or equal to 30 nm.
Claim 8
The hot-dip zinc-based plated steel sheet according to any one of claims I to
7, wherein
30 a content of the granular oxide per one surface on a metal basis is more than
or equal to 0.2 g/m2 and less than or equal to 0.8 g/m2
.
5
10
15
PCT/JP2016/060798
50/51
Claim9
The hot -dip zinc-based plated steel sheet according to any one of claims 1 to
8, wherein
the surface treatment layer contains more than or equal to 0.05 g/m2 and less
than or equal to 0.35 g/m2 of an oxide of an alkaline-earth metal per one surface on a
metal basis in which, in a temperature range of 900 to 1300 K, standard free energy
offormation (LlG0
) of oxide is smaller than standard free energy of formation (LlG0
AI)
of aluminum oxide at an identical temperature.
Claim 10
The hot-dip zinc-based plated steel sheet according to claim 9, wherein
the oxide of the alkaline-earth metal is an oxide of calcium or an oxide of
magnesmm.
Claim 11
The hot-dip zinc-based plated steel sheet according to claim 9 or 10,
wherein
the content of the oxide of the alkaline-earth metal per one surface on a
20 metal basis is more than or equal to 0.05 g/m2 and less than or equal to 0.2 g/m2
.
25
Claim 12
The hot-dip zinc-based plated steel sheet according to any one of claims 1 to
11, wherein
the hot-dip zinc-based plated steel sheet is a hot-dip zinc-based plated steel
sheet for hot pressing.