Description
Title of Invention
ZINC-BASED PLATED STEEL SHEET
Teclmical Field
[OOOl]
The present invention relates to a zinc-based plated steel sheet.
Background Art
These days, to protect the envisoilment and prevent global warming, the
suppression of the consurnptioti of fossil file1 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 fitel efficiency etc. by the weight reduction of car
bodies etc. are required. Ilowever, 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 tlie weight of the steel sheet is importatit
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 tlie 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 mariufacturing industry but also in various
manufacturing industries similarly. Hence, research and developtnent are being
made to enhance the mechanical strength of the steel sheet aud thereby obtain a steel
sheet in which the ~nechanicasl trength can be maintained or iii~provede ven when the
30 wall thickness is made smaller than those of cot~veritionallyu sed steel sheets.
[0004]
In general, a material liaving high niechanical 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 nlolded, and tlien cooling is performed. By the hot pressing method, the ~naterial
of the object can be easily pressed because the material is once heated to high
temperature and softened. Furthermore, the tnechanical 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 n~eclianical strength are
achieved can be obtained by the hot pressing method.
[OOOS]
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-lust 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 filrther 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 tliese,
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 Zn-based ~netal covering, the production of scales on the
surface of the steel sheet car1 be prevented, and processes such as descaling become
unnecessary; thus, the productivity of molded products is improved. In addition,
the Zn-based metal covering has also an anti-rust effect, and therefore also corrosion
resistance is iniproved. Patent Literature 1 to Patent Literature 4 below disclose a
5 method of hot pressing a plated steel sheet that is obtained by providing a Zn-based
metal covering to a steel sheet having a prescribed component cotnposition.
[OOOS]
In Patent Literature 1 to Patent Literature 3 below, a hot-dip galvanized steel
sheet or an alloyed hot-dip galvanized steel sheet is used as a steel sheet for hot
10 pressing. By using a hot-dip galvanized steel sheet or an alloyed hot-dip galvanized
steel sheet for hot pressing, a struch~re member can be molded without iron oxides
(that is, scales) being formed on the surface. Further, in view of the fact that, when
a Zn oxide layer is formed thick on the surface of a heat-treated steel tilaterial
obtained by hot pressing a Zn-based plated steel sheet, the coating film adhesiveness
15 and the post-coating colrosion resistance of the heat-treated steel material are
adversely affected, Patent Literatnre 4 below discloses an invention in which a heattreated
steel material is subjected to shot blasting to remove a Zn oxide layer or is
subjected to coating after the thickness of a Zn oxide layer is reduced.
[0009]
20 Patent Literature 5 and Patent Literahwe 6 below disclose inventions that
improve the coating film adhesiveness and the post-coating cor~osionre sistance of a
heat-treated steel material obtained by hot pressing a Zn-based plated steel slieet.
Patent Literature 5 below discloses an invention in which a hot-dip galvanized steel
sheet with its surface covered with a silicone resin coating filtn is used as a steel
25 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
given as an example of Si) is used as a steel sheet for hot pressing.
[OO lo]
30 Patent Literature 7 below discloses a tecl~~ologiny w hich 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 elenients is formed on the outer
layer of tlie galvanized layer during the temperature increase in hot pressing, and
thereby tlie volatilization of Zn is prevented.
[OOI I]
5 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 Zn is suppressed, and thus tlie adhesiveness of
an intermediate coating film and an over-coating film and post-coating corrosion
resistance are good.
Citation List
Patent Literature
[OO 121
Patent Literature 1: JP 2003-73774A
Patent Literature 2: JP 2003-129209A
Patent Literature 3: JP 2003-126921A
Patent Literature 4: JP 2004-323897A
Patent Literature 5: JP 2007-63578A
Patent Literature 6: JP 2007-291508A
Patent Literature 7: JP 2004-270029A
Sumrna~yo f Invention
Technical Problem
[0013]
25 However, there rnay be a case where satisfactory post-coating adhesiveness
is tiat obtained in the follo\ving cases: the Zn-based plated steel sheet is liot pressed;
and the attached amount of a phosphate coating film formed through phosphate
treatmerit and a treatmerit coating film (FF treatmerit coating film) obtained by using
at1 aqueous solution containing Zr ions and/or Ti ions and fluorine, atid containing
30 100 to 1000 pptn of free fluoride ions (hereinafter, referred to as FF che~iiical
conversio~tlr eatment liquid).
[00 141
In general, in the case where chemical co~iversio~trle atability is not
sufficient (for example, in the case where attachment unevenness, lack of hiding, and
the like occur), the adhesiveness between the steel sheet and an electrodeposition
5 coating film is not sufficiently secured, and as a result, post-coating adhesiveness
becomes pooc Reasot~s why the chemical conversion treatability becomes
insufficient include that degreasing and surface cor~ditioning before the chemical
conversion treattnet~ta re insufficient, and that the concentration and the temperature
of the chemical conversion treatment liquid and the time of the che~nicalc onversio~l
10 treatment are insufficient.
[0015]
As another reason, there is given that the chemical con~~ertibiliitsy reduced
due to A1 contained in hot-dip galvanizing. Specifically, the A1 in the hot-dip
galvanizing layer diffuses and moves to the outer layer of the plating layer not only
15 during the formation of a plating coating film but also during the heating of hot
pressing, and forms an Al oxide film. Since the A1 oxide film does not dissolve in
phosphoric acid, the reaction between Zn and a phosphate (for example, zinc
phosphate) is inhibited, and a phosphate coating film is less likely to be formed in the
area where the Al oxide film is forrned. Consequently, phosphate treatability is low
20 in the area where the A1 oxide film is forn~ed. In particular, phosphate treatability is
significantly reduced in the case where, in the hot pressing process, the steel sheet is
rapidly heated to the Ac3 point or more by energization heating or induction heating
and then press molding is quickly performed, and as a result, coating adhesiveness is
also reduced.
25 [0016]
In addition, when the present inventors conducted a check experiment on a
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 ~34th a silicone resin coating film, it has been found that, as will be
30 described later, although post-coating corrosion resistance in a cycle corrosiotl test in
which a dry and a wet environnient are repeated is good, coating adhesiveness is not
always 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 in which water is likely to collect because of the structure (for example, a
bag-like structural part below the door, a member with a closed cross section in the
5 engine compartment, etc.), for example.
[0017]
On the other hand, the addition of easily oxidizable elements into a zinc
plating layer disclosed in Patent Literature 7 above requires new operational actions,
such as the temperature control of the plating bath and dross measures.
10 [0018]
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 zinc-based plated steel
sheet excellent in coating film adhesiveness alter hot pressing more conveniently.
15 Solution to Problem
[00 191
On the basis of the findings obtained by extensive studies on the plated steel
sheet for hot pressing of the object mentioned above, the present inventors have
thought up the following zinc-based plated steel sheet.
20 The gist of the present invention is as follows.
[0020]
(1)
A zinc-based plated steel sheet comprising:
a zinc-based plated steel sheet that is a base metal; and
25 a surface treatment layer formed on at least one surface of the zinc-based
plated steel sheet, in which
the surface treatment layer contains one or rnore oxides selected fiom
titanium oxide, nickel oxide, and tin(1V) oxide each having a particle size of more
than or equal to 2 mn and less than or equal to 100 nm, in a range of rnore than or
30 equal to 0.2 dm2 and less than or equal to 2 g/m2 per one surface.
(2)
The zinc-based plated steel sheet according to (I), in which
the surface treatment layer further contains at least one of one or more
phosphorus-containing compounds, one or more vanadium-containing compounds,
one or more copper-containing compounds, one or more aluminum-containing
5 conlpounds, one or more silicon-containing compounds, or one or more clnomiumcontaining
compounds in the following range as a content per one surface,
the one or more phosphorus-containing compounds: more than or equal to
0.0 g/m2 and less than or equal to 0.01 g/m2 on a P basis,
the one or more vanadium-containing conlpounds: more than or equal to 0.0
10 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 on a Cu basis,
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 Al basis,
15 the one or more silicon-containing compounds: tllore than or equal to 0.0
and less than or equal to 0.005 g/m2 on a Si basis, and
the one or more chomiutn-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 zinc-based plated steel sheet according to (1) or (2), in which
the particle size of each of the one or Inore oxides selected from titanium
oxide, nickel oxide, and tin(1V) oxide is more than or equal to 5 nm and less than or
equal to 50 nm.
(4)
The zinc-based plated steel sheet according to any one of (1) to (3), in which
the content of the one or more oxides selected from titanium oxide, nickel
oxide, and tin(lV) oxide is more than or equal to 0.4 g/t$ and less than or equal to
1.5 g/m2 per one surface.
(5)
The zinc-based plated steel sheet according to any one of (1) to (4), in which
the one or more oxides are titanium oxide.
The zinc-based plated steel sheet according to any one of (1) to (5), in which
the zinc-based plated steel sheet is a zinc-based plated steel sheet for liot
pressing.
5
Advantageous Effects of Invention
[0021]
As described above, according to the present invention, even though the
chemical conversion treatment is insufficient, it becomes possible to improve the
10 coating adllesiveriess to a coating film provided after hot pressing.
Description of Embodiments
[0022]
Hereinafter, preferred embodiments of the present invention are described in
15 detail.
[0023]
<1. Zinc-based plated steel sheet>
A Zn-based plated steel sheet according to an embodiment of the present
invention includes a Zn-based plating layer on a ground steel sheet, and further
20 includes a surface treatment layer described in detail below on at least one surface of
tlie hot-dip Zn-based plating layer. The surface treatment layer includes a coating
layer containing one or more oxides selected from titanium oxide, nickel oxide, and
tin(1V) oxide each having a particle size of more than or equal to 2 ntn and less than
or equal to LOO tun, in the range of more than or equal to 0.2 g/~~1an2d less than or
25 equal to 2 g/m2 per one surface as an attached amount. The Zn-based plated steel
sheet having such a configuration can be suitably used for the hot pressing method
described above. Hereinafter, the configuration of tlie Zn-based plated steel sheet
will be described in detail.
[0024]
30 (1) Ground steel sheet
The ground steel sheet used for the Zn-based plated steel sheet according to
the present embodiment is not particularly limited, and various steel sheets having
known characteristics and chemical co~npositions 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 example,
5 when it is attempted to obtain a heat-treated steel material with a tensile strength of
980 MPa or more, an exaniple of the ground 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. Al: less than or equal to 0.1%, N: less than or equal to 0.01%, B:
10 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.
[0025]
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
15 chemical composition of the ground steel sheet is not necessarily be in the range
described above.
[0026]
The total amount of Mn and Cr contained is preferably 0.5 to 3.0% f?om the
viewpoint of que~~chabilidtyu ring the quenching described above and the viewpoint
20 of forming Mn oxides and Cr oxides contained in a zinc oxide layer after heating.
The total amount of Mn and Cr contained is more preferably 0.7 to 2.5%.
(00271
When Mn and Cr are contained as the chemical conlposition of the steel
sheet, part of the zirlc oxide layer formed on the outer layer after hot pressing
25 becomes composite oxides containing Mn and Cr. Coatir~g adllesiveness after
phosphate-based chemical conversion treatment is further improved by these
composite oxides containing Mn and Cr being formed. Although details are
unkuown, it is presumed that, by these conlposite oxides being formed, the alkali
resistance of the pl~osphate-basedc hemical co~lversiontr eatment coating film formed
30 is improved as compared to zinc oxide, and good coating adhesiveness is exhibited.
COO281
In the case where Mn and Cr are contained as the chemical composition of
the steel slieet, the content of Mn and Cr is preferably in the range of, in mass%,
more than or equal to 0.5% and less than or equal to 3.0%, aud more preferably in
the range of, in mass%, more tlian or equal to 0.7% and less than or equal to 2.5%.
5 In the case where the content of Mn+Cr is less than 0.5%, zinc oxide that is formed
on tlie outer layer after hot pressing atid composite oxides that contain Mn and Cs are
insuflicietit, and it may be diflicult to bring out more satisfactory coating
adhesiveness. On the other hand, in tlie case where the content of Mn+Cr exceeds
3.0%, although there is tio problem with coating adhesiveness, tlie cost is increased,
10 and fi~rtherniore the toughness of tlie spot welded portion may be significantly
reduced and the wettability of plating may be significantly degraded.
[0029]
(2) Zn-based plating layer
The Zn-based plating layer according to the present emboditnent is not
15 particularly limited, and commonly known zinc-based plating may be used.
Specificallj: examples of the Zn-based plating layer according to the present
embodiment include hot-dip galvanizing, alloyed hot-dip galvanizing, hot-dip Zn-
55%Al-1.6%Si plating, hot-dip Zn-1 l%Al plating, hot-dip Zn-11 %AI-3%Mg plating,
hot-dip Zti-6%A1-3%Mg plating, hot-dip Zn-ll%Al-3%Mg-0.2%Si plating, Zn
20 electroplating, Zn-Ni electroplating, and Zn-Co electroplating. It is also effective to
form a covering of plating of the components mentioned above by a method such as
vapor deposition; thus, the method of plating is not particularly limited.
[0030]
In the present embodiment, as a specific hot-dip plating operation, an
25 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 f?om the plating bath is
performed. The arnoutit of plating attached to the steel slieet is controlled by
adjusting the speed 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,
30 etc. Alloying treatment is perforliied by, after plating treatment like the above,
additionally heating tlie plated steel sheet using a gas furnace or an induction lieating
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 sheet single body.
[0031]
5 In the present embodiment, as a specific plating operation in the case of
using electroplating, electrolysis treattnent is performed in an electrolyte solution
containing Zn ions, using the steel sheet, as a negative electrode, and a counter
electrode. The amount of plating attached to the steel sheet is controlled by the
composition of the electrolyte solution, the current density, and the electrolysis time.
10 [0032]
The thickness of the Zn-based plating layer (that is, the amount of the Znbased
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 Zn-based plating layer is less
than 20 g/m2 per one surface, the effective amount of Zn after hot pressing cannot be
15 ensured and corrosion resistance is insufficient; thus, this is not preferable. In the
case where the thickness of the Zn-based plating layer is more than 100 g/m2 per one
surface, the processability and the adhesiveness of the Zn-based plating layer are
reduced; thus, this is not preferable. A more preferred thickness of the Zn-based
plating layer is in the range of 30 g/m2 to 90 g/m2 per one surface.
20 [0033]
(3) Surface treatment layer
On the Zn-based plating layer, there is further fortned a surface treattnent
layer containing one or more oxides selected fiom titanium oxide, nickel oxide, and
tin(1V) oxide.
25 [0034]
Here, the "one or more oxides selected fiom titanium oxide, nickel oxide,
and tin(1V) oxide" represents, taking titanium oxide as an example, a substance that
contains oxide of titanium (Ti) as a main component, which exists in a state of being
dispersed in a treatment liquid as a solid having a size of several nanometers or Inore
30 as a primary particle size, and does not exist in a state of being dissolved in the
treatment liquid like titanium chelate. Also in the same manner, nickel oxide and
tin(1V) oxide represent a substance that contains oxide of nickel (Ni) as a main
conlponent and a substance that contains oxide of till (Sn) as a main component,
respectively, which each exist in a state of being dispersed in a treatment liquid as a
solid having a size of several nanometers or more as a primaiy particle size, and do
5 not exist in a state of being dissolved in the treatment liquid. Using the one or more
oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide being dispersed
in a treatment liquid as a solid, it becomes possible to provide a heat-treated steel
material excellent in durability even in an environment of dipping in salt water.
Note that the one or tnore oxides selected from titanium oxide, nickel oxide, and
10 tin(1V) oxide exist in a state of particles in the surface treatment layer.
[0035]
To be specific, the one or tnore oxides selected from titanium oxide, nickel
oxide, and tin(1V) oxide each have a particle size @rimary pa~ticles ize) of more than
or equal to 2 nm and less than or equal to 100 nm. For the particle size of the one
15 or more oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide, a
smaller size is advantageous in terms of post-coating corrosion resistance, but those
with a particle size of less than 2 nm are difficult to obtain and are disadvantageous
in terms of cost. Further, in the case where the particle size of the one or more
oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide exceeds 100 ~ I I ,
20 an influence given to the steel sheet by the titanium oxide particle decreases during
heating in hot pressing (because a contact area with the plated steel sheet is small);
thus, this is not preferable.
[0036]
I11 addition, among these oxides, titanium oxide not only has the feature
25 mentioned above but also can suppress excessive oxidation and vaporization of Zn
during hot pressing, and can enhance not only coating film adhesiveness after hot
pressing but also corrosion resistance after hot pressing. It is surmised that titanium
oxide usually exists in a state of a metal oxide stably, but reacts with zinc oxide
formed during heating in hot pressing and forms a composite oxide with zinc oxide,
30 and thereby suppresses excessive oxidation and vaporization of Zn. To obtain this
effect more efficiently, the particle size of titanium oxide mentioned above is
preferably more than or equal to 2 nm and less than or equal to 100 nm.
[0037]
The particle size of the one or more oxides selected from titanium oxide,
nickel oxide, and tin(1V) oxide is preferably more than or equal to 5 nm and less than
5 or equal to 50 nm.
[0038]
The particle size (primaly particle size) of the one or more oxides selected
from titanium oxide, nickel oxide, and tin(1V) oxide can be measured by a known
method; for example, the measurement can be made by a nlethod in which a cross
10 section-embedded sample is prepared after coating, several particle sizes of the one
or more oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide in the
coating film are measured, and the average of the obtained measurement results is
taken as the particle size.
[0039]
15 The surface treatment layer included in the Zn-based plated steel sheet
according to the present embodinlent contains the one or more oxides selected from
titanium oxide, nickel oxide, and tin(IV) oxide in the range of Inore than or equal to
0.2 g/n12 and less than or equal to 2 g/m2 per one surface. When the content of the
one or more oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide in
20 the surface tleatrnent layer is in the range of more than or equal to 0.2 g/m2 and less
than or equal to 2 g / pe~r o~ne s urface, satisfactory adhesiveness between the
surface of the steel sheet and an electrodeposition coating film is exhibited even in
the case where the attached amount of various types of chemical conversion
treatment (for example, phosphate treatment or FF chemical conversion treatment)
25 performed on the Zn-based plated steel sheet is not sufficie~it. Altllough a detailed
tnecllanistn is not clear, the one or more oxides selected from titanium oxide, nickel
oxide, and tin(1V) oxide are present on the surface of the steel sheet after heat
treatment; thereby, some influence is given to the cohesion deposition of the
electrodeposition coating film during electrodeposition coating, and the oxides and
30 the electrodeposition coating filrn adhere strongly; thus, it is presumed that strong
adhesiveness can be exhibited even when chemical conversion treatment (phosphate
treatment or FF chemical conversion treatment) is not sufficient.
[0040]
In the case where the content of the one or more oxides selected from
titanium oxide, nickel oxide, and tin(1V) oxide in the surface treatment layer is less
5 than 0.2 g/m2 per one surface, the one or more oxides selected from titanium oxide,
nickel oxide, and tin(1V) oxide after hot pressing are not sufficiently present, and
hence, coating adhesiveness after hot pressing cannot he ensured sufficiently. On
the otlier hand, in the case where the content of the one or more oxides selected fiom
titanium oxide, nickel oxide, and tin(1V) oxide in the surface treatment layer exceeds
10 2 g/m2 per one surface, the cost of the Zn-based plated steel sheet according to the
present embodiment is increased, and it is presun~ed that the cohesive force of the
surface treatment layer is weakened and a coating film that is formed on the surface
treatment layer after hot pressing is likely to peel off.
[0041]
15 In addition, in the case where the content of the titanium oxide is less than
0.2 g/1ii2 per one surface, a sufficient amount of a composite oxide with zinc oxide
cannot be formed, and the oxidation and vaporization of Zn cannot be efficiently
suppressed.
[0042]
20 The content of the one or more oxides selected fiom titanium oxide, nickel
oxide, and tin(1V) oxide in the surface treatment layer is preferably Inore than or
equal to 0.4 g/m2 and less than or equal to 1.5 g/m2 per one surface.
[0043]
Specific examples of the one or more oxides selected from titanium oxide,
25 nickel oxide, and tin(1V) oxide are shown below.
[0044]
Specific example of commercially available products of titania sol includes
TKS (registered trademark) series manufactured by Tayca Corporatiou.
[0045]
30 Example of nickel oxide includes nickel oxide pa~ticles of con~mercially
available (nano)powder.
[0046]
Typical example of tin(1V) oxide includes tin(1V) oxide sol that is a
treatment liquid containing tiu(IV) oxide, and specific example of commercially
available products includes Ceramace ~nanufacturedb y Taki Chemical Co., Ltd.
5 [0047]
In forming the surface treatment layer, the treatment liquid or the like in
which the one or more oxides selected fsom titanium oxide, nickel oxide, arid tin(1V)
oxide are dispersed may be applied as it is to the Zn-based plated steel sheet,
however, in order to improve stability of the treatment liquid and adhesiveness of the
10 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 Zn-based
plated steel sheet.
[0048]
In the case where the above sol in which the one or more oxides selected
15 from titanium oxide, nickel oxide, and tin(1V) oxide are dispersed is used, a watersoluble
or water-dispersible resin is preferably used as the resin. Examples of the
resin include a polyurethane resin, a polyester resin, an epoxy resin, a (meth)acrylic
resin, a polyolefin resin, a phenol resin, arid modified products of those resins. In
the case \vhere zirconia powder is used, a solvent resin in which any of various
20 solvents is used as the solvent may be used in addition to the above-mentioned
water-based resin.
[0049]
Examples of the crosslinking agent include a zirconium carbonate
compound, an organic titaniutli conlpound, an oxazoline polymer, a water-soluble
25 epoxy compound, a water-soluble melamine resin, a water-dispersible blocked
isocyanate, and a wates-based aziridine comnpound.
[OOSO]
Furtliel; examples of the other component that is preferably further
contained in the surface treatment layer according to the present embodiment include
30 one or more selected horn zirconia, lantlianuin oxide, cerium oxide, and neodymium
oxide.
[0051]
When zirconia, lanthanum oxide, cerium oxide, or neodymium oxide
~nentioned above is contained in the surface treatment layer, during heating, zircotiia,
lanthanum oxide, cerium oxide, or neodymium oxide in the surface treatment layer
5 rnakes harmless an A1 oxide that is present before hot pressing and is formed during
hot pressing. Thereby, the formation of zinc oxide during hot pressing is
accelerated; thus, phosphate treatability after hot pressing is enhanced, and coating
film adhesiveness is improved. Althoogh details of the fact that an Al oxide is
made harmless during heating by zirconia, lanthanum oxide, cerium oxide, or
10 neodymium oxide are unkno\vn, it is presumed that zirconia, lanthanum oxide,
cerium oxide, or tieodymiuni oxide dissolves an A1 oxide formed on the surface of
the steel sheet, thereby Zn, which is relatively easy to oxide after Al, is oxidized
during hot pressing, and consequently the production of zinc oxide (ZnO), which is
excellent in chemical convertibility, is accelerated. To obtain this effect niore
15 esciently, the particle size of the oxide mentioned above is preferably more than or
equal to 5 nm and less than or equal to 500 nm.
[0052]
The amount of the one or more selected from zirconia, lantharium oxide,
ceriutn oxide, and neodymium oxide contained in the surface treatment layer is
20 preferably in the range of more than or equal to 0.2 &n2 and less than or equal to 2
g/m2 per one surface. When the amount of the one or more selected from zirconia,
lanthanum oxide, ceri~ium oxide, and neodymium oxide contained in the surface
treatment layer is less than 0.2 dm2 per one surface, suflicient zirconia, lanthanum
oxide, ceriutn oxide, and neodymiu~n oxide are not present after hot pressing;
25 consequently, the effect of making harmless an A1 oxide of the plated sorface is
reduced, and it may be difficult to sufficiently ensure coating adhesiveness after hot
pressing. On the other hand, when the amount of zirconia etc. contained in the
surface treatment layer is more than 2 g/m2 per one surface, the cost of the Zn-based
plated steel sheet according to the present embodiment is increased, and it is
30 presumed that the cohesive force of the surface treatment layer is weakened and a
coating film that is formed on the surface treatment layer after hot pressing is likely
to peel off.
[0053]
The content of the one or more selected from zirconia, lanthanum oxide,
cerium oxide, and neodymium oxide in the surface treatment layer is preferably more
5 than or equal to 0.4 g/m2 and less than or equal to 1.5 g/~np2e r one surface.
[0054]
Typical examples of the treatment liquid containing zirconia, lanthanum
oxide, cerium oxide, and neodymiutn oxide include a zirconia sol, a lanthanum oxide
sol, a cerium oxide sol, and a neodymium oxide sol, and specific examples of the
10 con~tnercially available product include NanoUse (registered trademark) series
manufactul.ed by Nissan Chemical Industries, Ltd. and Ceramase series
manufactured by Taki Chemical Co., Ltd.
[OOSS]
Further, examples of the other component that is prefel-ably further
15 contained in the surface treatment layer according to the present embodiment include
magnesium oxide, calcium oxide, or zinc oxide.
[0056]
When the surface treatment layer contains the above-mentioned magnesium
oxide, calcium oxide, or zinc oxide, those oxides are present on the outer layer of the
20 surface treatment layer after hot pressing; and thus, phospllate treatability is
improved. As a reason for the improvement in phosphate treatability, it is presumed
that the chemical conversion reaction with a phosphate is accelerated by magtlesium
oxide being dissolved in the phosphate treatment liquid. To obtain this effect tnore
efficiently, the particle size of each of the above-mentioned magnesium oxide,
25 calcium oxide, atid zinc oxide is preferably more than or equal to 5 nm and less than
or equal to 100 nm, and more preferably tnore than or equal to 10 nln and less than or
equal to 50 nm.
[0057]
In the case where the surface treatment layer contains magnesium oxide,
30 calcium oxide, or zinc oxide, the content tl~ereofi s preferably in the range of more
than or equal to 0.2 g/m2 and less than or equal to 5 g/n12 per one surface, and more
preferably more than or equal to 0.4 g/m2 and less than or equal to 2.5 g/m2 per one
surface. In the case where the content of nlagnesium oxide, calcium oxide, or zinc
oxide is less than 0.2 g/m2 per one surface, since those oxides are not sufficiently
present after hot pressing, it may be difficult to exhibit satisfactory phosphate
5 treatability. On the other hand, in the case where the content of magnesium oxide,
calcium oxide, or zinc oxide exceeds 5 &n2per one surface, the cost of the 211-based
plated steel sheet according to the present embodiment is increased, and it is
presun~ed that the cohesive force of the surface treatment layer is weakened and a
coating fill11 that is formed on the surface treatment layer after hot pressing is likely
10 to peel off.
[0058]
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
compounds, one or more V-containing compounds, one or more Cu-containing
15 compounds, one or more Al-containing compounds, one or more Si-containing
compounds, and one or more Cr-containing compounds described in detail below in
the range of a predetermined content.
[0059]
The P-containing compouud is a compound containing phospho~us as a
20 constituent element. Examples of the P-containing colnpound include compounds
such as phosphoric acid, phosphorous acid, pliosphonic acid, phosphonous acid,
phosphinic acid, phosphinous acid, a phosphine oxide, and pl~osphine, an ionic
compound containing any of these compounds as an anion, and the like. All these
P-containing compounds are comrnercially available as reagents or products, and can
25 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
treatment liquid, and exist, in the surface treatrnent layer, in a state of being dispersed
as solid.
[0060]
30 The V-containing compound is a compound containing vanadium as a
constituent element. Examples of the V-containit~g compound include vanadium
oxides such as vanadium pentoxide, metavanadic acid-based compounds such as
ammonium metavauadate, 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
5 compounds exist in a state of being dissolved in a treatment liquid or in a state of
being dispersed as powder in a treattnent 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 e~nbodimentp referably
10 contains one or more cotnpounds selected from one or more P-containing compounds
and one or niore V-containing co~npoundsm entioned above individually in the range
of more than or equal to 0.0 g/m2 and less than or equal to 0.01 g/n12 per one surface
on a P and V basis.
[0062]
15 One or more compounds selected from one or more P-containing
compounds and one or more V-containing compounds mentioned above are oxidized
into an oxide during hot pressing, and the oxide exists locally at the interface
between the 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
20 the content of the one or more compounds selected fsom one or Inore P-containing
compounds and one or more V-containing conipounds contained is individually in
the range of more than or equal to 0.0 g/m2 and less than or equal to 0.01 g/n? per
one surface 011 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
25 adhesiveness between the Zn-based plating layer and the surface treatment layer after
hot pressing is further improved.
[0063]
I11 the case where the content of the one or Inore selected fiom one or tnore
P-containing compounds and one or more V-containing compounds in the surface
30 treatment layer exceeds 0.01 g/~n2p er one surface, the thickness of the oxide layer
that is formed during hot pressing and has weak cohesive force is increased;
consequently, the adhesiveness between the Za-based plating layer and the surface
treatment layer is reduced, and as a resuIt also adhesiveness after electrodeposition
coating is reduced. From the viewpoint of the adhesiveness between the Zn-based
plating layer and the surface treattnent layer after hot pressing, the content of the one
6 or Inore compounds selected fiom one or more P-containing compounds and one or
more V-containing compounds in the surface treatment layer is more preferably
individually more than or equal to 0.0 g/m2 and less than or equal to 0.003 dm2 per
one surface on a P and V basis.
[0064]
10 The Cu-containing compound is a cotnpoutld containing copper as a
constituent element. Examples of the Cu-co~ltainiug cotnpound include metal Cu,
copper oxide, various organic copper compounds, various inorganic copper
compounds, and various copper complexes. Those Cu-containing compoutlds are
commercially available as reagents or products, and can be easily obtained. Those
15 Cu-containing compounds exist in a state of being dissolved in a treatment liquid or
in a state of being dispersed as powder in a treattnent liquid, and exist, in the surface
treatn~eutla yer, in a state of being dispersed as solid.
[0065]
The surface treatment layer according to the present embodiment preferably
20 contains one or more cotnpounds selected from one or more Cu-containing
compounds ~nentiolied 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.
[0066]
One or more cotnpounds selected from one or more Cu-containing
25 compounds mentioned above are oxidized into an oxide during hot pressing, and the
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 colnpoutlds is in the range of more than or equal to 0.0 g/m2
30 and less than or equal to 0.02 g/m2 per one surface on a Cu 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 Zn-based plating layer and the
surface treatment layer after hot pressing is fulther improved.
100671
In the case where the content of tlie one or more selected fiom one or Inore
5 Ca-containing compounds in tlie ssuface treatment layer exceeds 0.02 g/n12 per one
surface, the thickness of the oxide layer that is formed during hot pressing and has
weak cohesive force is increased; consequently, the adhesiveness between the Znbased
plating layer and the surface treatment layer is reduced, and as a result, also
adhesiveness after electrodeposition coating is reduced. In addition, since Cu is an
10 element nobler than Fe, which is a main component of the ground steel sheet, also
the corrosion resistauce tends to decrease. From the viewpoint of the adhesiveness
between the 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 more than or equal to
15 0.0 g/m2 and less than or equal to 0.005 g/m2 per one surface on a Cn basis.
[0068]
The Al-containing compound is a compound containing alutninutn as a
constituent element. Examples of the Al-containing compound include metal Al,
aluminum oxide, aluminum hydroxide, an ionic co~npound containing an aluminum
20 ion as a cation, and the like. Those Al-containing compounds are commercially
available as reagents or products, and can be easily obtained. Tliose 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
layer, in a state of being dispersed as solid.
25 [0069]
The Si-containing cornpound is a con~pound containing silicon as a
constituent element. Exainples of the Si-containing conlpound include Si simple
substance, silica (silicon oxide), organic silane, a silicone resin used also as a binder
resin, and other Si-containing compounds. All these Si-containing compounds are
30 connnercially available as reagents or products, and can be easily obtained. These
Si-containing compounds exist in a state of being dissolved in a treatment liquid or in
a state of beir~g dispersed as powder in a treatment liquid, and exist, in the surface
treatment layer, in a state of being dispersed as solid.
[0070]
The surface treatment layer according to the present embodiment preferably
5 contains one or more compounds selected from one or more Al-containing
compounds and one or more Si-containing compounds like the above individually in
the range of more than or equal to 0.0 g / ~ a~nd~ l2es s than or equal to 0.005 g/m2p er
one surface on an A1 and Si basis.
[0071]
10 One or more colnpounds selected from one or more Al-containing
con~pounds and one or more Si-containing compour~ds like the above are oxidized
into an oxide during hot pressing, and the oxide concentrates 011 the surface of the
surface treatment layer. Since the amount of the one or more conlpounds selected
from one or more Al-cot~taining cornpounds and one or more Si-containing
15 compou~~dcosn tained is individually in the range of more than or equal to 0.0 g/m2
and less than or equal to 0.005 g/m2 per one surface on an Al and Si basis, the
existence ratio of the oxides containing A1 or Si that are formed on the surface of the
surface treatment layer during hot pressing is reduced, and the adhesivel~ess between
the surface treatment layer and the electrodeposition coating film after hot pressing is
20 further improved.
[0072]
111 the case where the content of the one or more selected from one or more
Al-containing conlpounds and one or Inore Si-containing compounds in the surface
treatment layer is more than 0.005 g/~np2er one surface, the existence ratio of the
25 oxides containing A1 or Si that are formed during hot pressing is increased. These
oxides containing A1 or Si inhibit the formation of a chemical conversion treatment
coatiug film, and reduce the adhesiveness behveen the surface treatment layer and
the electrodeposition coating film after hot pressiug; therefore, when the existence
ratio of the oxides containing A1 or Si that are formed during hot pressing is
30 increased, the adhesiveness between the surface treatment layer and the
electrodeposition coating film is reduced. From the viewpoint of the adhesiveness
between the surface treatment layer and the electrodcposition coating film after hot
pressing (that is, post-coating adhesiveuess), the amount of the one or more
cot~~pounsdesl ected from one or more Al-containing cotnpounds and one or more Sicontaining
compounds contained in the surface treatment layer is more preferably
2 5 individually more than or equal to 0.0 g/m2 atid less than or equal to 0.002 gltn per
one surface on an Al and Si basis.
[0073]
The Cr-containing cotnpound is a compound containing chsomium as a
constituent element. Exatllples of the Cr-containing cotnpound include metal Cr,
10 chron~iutnc ompounds having various valences, and an ionic cotilpound 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 tseattnent liquid or in a state of
beitig dispersed as powder in a treatment liquid, and exist, in the surface treatment
layer, in a state of being dispersed as solid.
15 (00741
The Cr-containing cotnpoutld varies in performance and properties in
accordance with the valence, and many hexavalent clxomiun~ compounds are
harmful. In view of the current tendency of attention to envirorunental protection
being strongly required, the surface treatment layer according to the present
20 embodiment preferably contains as little arnount of Cr-containing cotnpoulids
mentioned above as possible, and is more preferably chsotniutn-free.
[0075]
From tlte view point mentioned above, the surface treatment layer according
to the present embodiment preferably cotltai~iso ne or more compounds selected from
25 Cr-containing cornpounds like the above in the range of more than or equal to 0.0
g/m2 and less thart or equal to 0.01 &'m2 per one surface on an Cr basis, and is more
preferably chromiutn-free.
[0076]
The surface treatment layer may contain pigments such as carbon black and
30 titania, various anti-corrosive particles used for coated steel sheets, and the like as
long as the effect of the present invetltion based on containing one or Inore oxides
selected frotn titanium oxide, nickel oxide, and tin(1V) oxide is not inhibited. Also
it1 this case, the surface treatment layer co~~taitnhse one or more oxides selected from
titanium oxide, nickel oxide, and tin(1V) oxide in the range of more than or equal to
0.2 g/m2 and less than or equal to 2 g/m2 per one surface.
5 [0077]
As the method for forming the surface treatment layer, a treatment liquid
containing one or more oxides selected frotn titanium oxide, nickel oxide, and
tin(1V) oxide may be applied to the surface of a zinc-plated steel sheet, and d~ying
and baking may be pel-formed.
10 [0078]
The coating tnethod is not limited to a specific method, arid examples
include a method in which a ground steel sheet is dipped in a treatment liquid or a
treatment liquid is sprayed to the surface of a ground steel sheet, and then the
attached amount is controlled by a roll or gas splaying so as to obtain a prescribed
15 attached amount, and a method of coating using a roll coater or a bar coater.
[0079]
The metliod of dlying and baking is not limited to a specific method, either,
as long as it is a method that cat1 volatilize a dispersion medium (n~ainly water).
Here, if heating is performed at an excessively high temperature, it is feared that the
20 uniformity of tlie surface treatment layer will be reduced; conversely, if heating is
performed at an excessively low temperature, it is feared that productivity will be
reduced. Thus, to produce a surface treatment layer having excellent characteristics
stably and efficiently, the surface treatment layer after coating is preferably heated at
a temperature of approximately 80°C to 150°C for approximately 5 seconds to 20
25 seconds.
[OOSO]
The formation of the surface treatment layer is preferably performed in-line
in the production line of tlie plated steel sheet because this is economical; but the
surface treatment layer may be formed also in another line, or may be formed after
30 blanking for molding is performed.
roo8 11
Here, the content of the one or inore oxides selected from titanium oxide,
nickel oxide, and tin(1V) oxide in the surface treatment layer can be measured by a
known method; for example, the fact that the various compounds are the one or more
oxides selected from titanium oxide, nickel oxide, and tin(1V) oxide is checked
5 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. Also,
the content of other oxides that are preferably contained in the surface treatment
layer, and the content of the above-tnentioned one or more P-containing cotnpounds,
10 V-containing compounds, Cu-containing compounds, Al-containing con~pounds, Sicontaining
compounds, and Cr-containing compounds contained in the surface
treatment layer can be measured by a similar method.
[0082]
4. Regarding hot pressing procesQ
15 In the case where the hot pressing method is used for a hot-dip Zn-based
plated steel sheet like that described above, the hot-dip Zn-based plated steel sheet is
heated to a prescribed temperature, and is then press-molded. In the case of the hotdip
Zn-based plated steel sheet according to the present embodiment, heating is
usually perfomled to 700 to 1000°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 important that the lower limit of the
heating temperature be the ACJ point or more. Ln the case of the present invention,
also the case where a two-phase region of 111ai-tensitelferrite is formed after rapid
cooling is included, and therefore the heating temperature is preferably 700 to
25 1000°C as described above.
[0083]
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 fi~rnace or a gas furnace, flame heating,
30 energizatiori heating, high-frequency heating, and induction heating, and the
atmosphere during heating is not particularly limited; as a heating inethod to obtain
the effect of the present invention sig~lificantly, energization heating, induction
lieating, and tlie like, which are rapid heating, are preferably used.
[0084]
In the hot pressing method by slow heating, the radiation heating of a
5 heating furnace is used. First, the hot-dip Zn-based plated steel sheet according to
the present e~nbodinie~tihta t is used as a steel sheet for hot pressing is placed in a
heating furnace (a gas furnace, an electric furnace, or the like). Tlie steel slieet for
hot pressing is heated at 700 to 1000°C in the heating furnace, arid is, depending on
the condition, kept at this heating temnperatulre (soaking). Thereby, molten Zn in the
10 hot-dip Zn-based plating layer is combined with Fe and forms a solid phase (Fe-Zn
solid solutio~ip hase). After the molten Zn in tlie hot-dip Zn-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 Zn-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.
[OOSS]
Alternatively, the Zn-based plated steel sheet may be heated to 700 to
1000°C while no keeping time is provided or the keeping time is set to a short time,
20 and the steel sheet may be taken out of the heating furnace. In this case, after the
steel slieet is heated to 700 to 1000°C, cooling is performed without applying stress
to the steel sheet by press ~noldingo r the like until Zn in the Zn-based plating layer is
combined with Fe and fornis a solid phase (Fe-Zn solid solutio~pi hase or ZnFe alloy
phase). Specifically, cooling is performed until at least the temperature of the steel
25 sheet becomes lower than or equal to 782OC. After tlie cooling, as described below,
cooling is perfornied while the steel sheet is pressed using a inold. [0086]
Also in hot pressing by rapid heating, similarly, the Zn-based plated steel
sheet according to tlie present embodiment that is used as a steel sheet for hot
pressing is rapidly heated to 700 to 1000°C. The rapid heating is performed by, for
30 example, e~iergizationh eating or induction heating. The average heating rate in this
case is 2O0Clsecond or more. In the case of rapid heating, after tlie Zn-based plated
steel sheet hot-dip Zn-based plated steel sheet is heated to 700 to 100O0C, cooling is
performed \vithout applying stress to the steel sheet by press molding or the like until
Zn in the Zn-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
5 at least the tenlperature of the steel sheet becomes lower than or equal to 782OC.
After the cooling, as described below, cooling is performed while the steel sheet is
pressed using a mold.
[0087]
The taken-out steel sheet is pressed using a mold. When pressing the steel
10 sheet, the steel sheet is cooled by the mold. A cooling tnediutn (for example, water
or the like) is circulated through tl~em old, 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.
[OOSS]
15 The hot pressed steel material produced using the Zn-based plated steel
sheet having the surface treatment layer according to the present embodiment can
exhibit satisfactory post-coating adhesiveness, because even if chemical conversion
treatment after hot pressing is insuttlcient due to influences of treatment time,
concentration, temperature, and the like, one or tnore oxides selected from titanium
20 oxide, nickel oxide, and tin(1V) formed on the surface of the steel sleet exhibit
excellent adhesiveness with the electrodeposition coating film.
[Examples]
[0089]
The action and effect of the Zn-based plated steel sheet according to an
25 embodiment of the present invention will no\v be described still tilore specifically
with reference to Examples. Examples shown below are only examples of the Znbased
plated steel sheet according to the present invention, and the Zn-based plated
steel sheet according to the present invention is not limited to Examples below.
[0090]
30
In the following, first, pieces of molten steel having the chemical
compositions shown in Table 1 below were produced. After that, the produced
pieces of molten steel were used to produce slabs by the continuous casting method.
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 performed to produce
5 a cold rolled steel sheet; thus, steel sheets of steel #1 to #S having the chemical
cornpositions described in Table 1 were prepared. As shown it1 Table 1, the sheet
thicknesses of the steel sheets of all the steel types were 1.6 nnn.

[0092]
iZn-based plating layer>
The steel sheets of steel #I to #8 were subjected to hot-dip galvanizing
5 treatment, and were then subjected to alloying treatment. With the maxitnum
temperature in each alloying treatment set to 530°C, heating was performed for
approximately 30 seconds; and then cooling was perfornled 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
10 (GI) was produced without performing alloying treatment.
[0093]
Further, steel #I was subjected to various types of hot-dip galvanizing using
three types of plating baths of tnolten Zn-55%AI, molten Zn-6%AI-3%Mg, and
molten Zn-lI%Al-3%Mg-0.2%Si, and hot-dip zinc-based plated steel sheets A1 to
15 A3 were produced.
[0094]
Al: molten Zn-55%A1
A2: molten Zn-6%A1-3%Mg
A3: molten Zn-1 l%Al-3%Mg-0.2%Si
20 [0095]
In addition, steel #1 was subjected to various types of Zn-based plating of
Zn electroplating, Zn-Ni electroplating, and Zn-Co electroplating.
[0096]
Note that, as a specific plating operation in the case of using electroplating,
25 electrolysis treatment was performed in an electrolyte solution containing Zn ions,
using the steel sheet, as a negative electrode, and a counter electrode. The amount
of plating attached to the steel sheet was controlled by the composition of the
electrolyte solution, the curlent density, and the electrolysis time.
[0097]
30 A4: Zn electroplating
A5: Zn-Ni electroplating
A6: Zn-Co electroplating
[0098]
In the eight types of Zn-based plating processes lnentioned above, the
amourit of the Zn-based plating layer attached was equally set to 60 g/m2 per one
5 surface.
[0099]

Subsequently, in order to prepare a chemical solution having the
compositions shown in Table 2 in a solid content ratio, the following oxides and
10 chemical agents were blended using water. The obtained treatment liquid was
applied with a bar coater, and drying was performed using an oven under conditions
for keeping a maximum peak temperature of 100°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 ihe liquid and the count of the bar coater so that the
15 total amount of attached nonvolatile content in the treatment liquid might be the
numerical value shown in Table 3. In Table 2 below; the solid content concentration
of each co~nponent is written as the ratio of the nonvolatile content of each
component, such as "oxide A," to the nonvolatile content of the entire treatment
liquid (unit: mass%).
20 [OIOO]
The components (symbols) in Table 2 are as follows.
As described later, also a treatment liquid containing alumina (sol) was
investigated as granular substances other than titanium oxide, nickel oxide, and
tin(1V) oxide; in this case, alumina is denoted by "oxide A". Similarly, zirconia,
25 lanthanum oxide, cerium oxide, and neodymium oxide are denoted by "oxide B", and
magnesium oxide, calciutn oxide, and zinc oxide are denoted by "oxide C".
[OlOl]
(Oxide A) titanium oxide, nickel oxide, tin(1V) oxide, and alu~nina
TPA: titania powder (manufactured by IoLiTec GmbH), particle size: 10 to
30 30 nm (catalog value)
TPB: titania powder (TITANIX JA-1, manufactured by Tayca Corporation),
particle size: 180 nnl (catalog value)
Ti: titania sol (titania sol TKS-203, manufactured by Tayca Corporation),
particle size: 6 nm (catalog value)
Ni: nickel oxide (nickel oxide, manufactured by IoLiTec GmbH), particle
5 siz:e 20 nm
NP: nickel oxide (nickel oxide, manufactured by Japan Pure Chemical Co.,
Ltd.), particle size: approximately 7 ptn
Sn: tin(IV) oxide sol (Ceramase C-10, manufactured by Taki Chemical Co.,
Ltd.), particle size: 10 ntn
10 SP: tin(N) oxide (tin oxide, manufactul.ed by IoLiTec GmbH), particle size:
10 to 20 111n
AZ: an alumina sol (alumina sol 200, manufactured by Nissan Chemical
Industries, Ltd.), particle size: approximately 10 nm
[O 1021
(Oxide B) zirconia, lanthanum oxide, cerium oxide, and neodymium oxide
ZA: a zirconia sol (NanoUse (registered trademark) ZR-30AL,
manufactured by Nissan Chemical Industries, Ltd.), particle size: 70 to 110 ilm
(catalog value)
La: a lanthanum oxide sol (Biral La-CIO, rna~lufactured by Taki Chemical
20 Co., Ltd.), particle size: 40 tun (catalog value)
Ce: a cerium oxide sol (Needlal P-10, manufactured by Taki Chemical Co.,
Ltd.), particle size: 20 nm (catalog value)
Nd: a neody~niom oxide sol (Biral Nd-CIO, manufactured by Taki Cl~emical
Co., Ltd.), particle size: 40 nrn (catalog value)
25 [0103]
(Oxide C) tnagnesium oxide, calcium oxide, and zinc oxide
Mg: mag~lesiut~oxl ide (ma~lufacturedb y IoLiTec GmbH), particle size: 35
Inn (catalog value)
Ca: calcium oxide (manufactured by Kalito Chemical Co.,Inc.)
30 *Used after being dispersed in resin-added water and pulverizing pigment
with a ball mill.
Zn: zinc oxide (manufactured by IoLiTec GmbH), particle size: 20 11111
(catalog value)
[0 1041
(iii) Resin
5 A: a urethane-based resin emulsion (Superflex (registered trademark) 150,
manufactured by DKS Co. Ltd.)
B: a urethane-based resin emulsion (Superflex (registered tradernark) E-
2000, manufactured by DKS Co. Ltd.)
C: a polyester resin enlulsion (Vylonal (registered trademark) MD1480,
10 manufactured by Toyobo Co., Ltd.)
[0105]
(iv) Crosslinking agent
M: a melamine resin (Cyme1 (registered trademark) 325, manufactured by
Mitsui Cytec Ltd.)
15 Z: ammonium zirco~lium cabonate (an ammonium zirconium carbonate
solution, manufactured by Kishida Chemical Co.,Ltd.)
S: a silane coupling agent (Sila-Ace S5 10, tnanufactured by Nichibi Trading
Co.,LTD.) (a Si-containing compound)
[OI 061
20 (v) Pigment
CB: carbon black (Ivlitsubishi (registered trademark) carbon black #1000,
manufactured by Mitsubishi Chemical Corporation)
T: titanium oxide (titanium oxide R-930, manufactured by Isllihara Sangyo
Kaisha, Ltd.), particle size: 250 nm (catalog value)
25 "T" titanium oxide described herein is a pigment with a particle size of 200
to 400 nm mainly used for a white pigment or the like in a coating material, and
cannot achieve performance obtained by oxide B because the particle size is larger
than that of (oxide A).
PA: condensed Al phosphate (condensed aluminum phosphate, K-White
30 ZFlSOW, manufactured by Tayca Corporation) (a P and Al-containing compound)
PZ: zinc phosphite (NP-530, manufactured by Toho Ganryo Co., Ltd.) (a Pcontaining
compound)
Sil: silica particles (Sylomask 02, manufactured by Fuji Silysia Chemical
Ltd.) (a Si-containing compound)
Si2: colloidal silica (Snowtex 0, manufactured by Nissan Chemical
5 Industries, Ltd.) (a Si-containing comnpound)
Al: an alumina sol (AS-200, manufactured by Nissan Chemical Industries,
Ltd.) (an Al-containing compound)
V: potassium vanadate (a general reagent) (a V-containing compound)
Cr: Cr(V1) oxide (a general reagent) (a Cr-containing compoumld)
Cu: copper(I1) oxide (a general reagent) (a Cu-containing compouud)
Oxide A Oxide B Oxide C Resin Crossiinking agent Pigment etc.
I Notes
Concentration Concentration Concentration Concentration I Concentration Concentration y e I (mass%) I 'yPe I (mass%) I Type I (mass%) I Type / (mass% I Type 1 (mass9 I ----
Table 2-2
[0109]
(Table 41

[OlIl]
[Table 61
[0112]
[Table 71
[0113]

After the formation process of the surface treatment layer, the steel sheet of
each test number was subjected to hot press heating by hvo types of heating systems
5 of furnace heating and energization heating, and thus hot pressing was performed.
In the furnace heating, the atmosphere in the filmace was set to 910°C and the airfuel
ratio was set to 1.1, and the steel sheet was taken out of the furnace immediately
after the temperature of the steel sheet reached 900°C. In the energization heating,
heating \\as performed at 870°C, with the heating rate set to 85"CIsecond and
10 42.5"CIsecond. In the following, the results of energizatiotl heating, which is
heating of a shorter time than furnace heating, are shown in Table 3, and the results
by furnace heating are shown in Table 4.
[0114]
After the hot press heating, cooling was performed until the temperature of
15 the steel sheet became 650°C. After the cooling, the steel sheet was sandwiched by
a flat sheet mold equipped with a water cooling jacket, and thus a hot pressed steel
lnaterial (steel sheet) was produced. Cooling was performed up to approximately
360°C, \vhich 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 coolitig rate had
20 been low during the hot pressing, and thus quenching was performed.
[0115]

[Phosphate treatability evaluation test]
The sheet-like hot pressed steel material of each of the test numbers
25 described in Table 3 and Table 4 below was subjected to surface conditioning at
room temperature for 20 seconds using a surface conditioning treatment agent,
Prepalene X (product name) manufactured by Nihon Parkerizing Co.,Ltd. Fuither,
phosphate treatment was performed using a zinc phosphate treatment liquid, Palbond
3020 (product name) manufactured by Nihon Parkerizing Co.,Ltd. The sheet-like
30 hot pressed steel material was dipped in the treattnent liquid for 10 seconds or 30
seconds, while it is normally 120 seconds, with the temperature of the treattnent
liquid set to 43OC, and then water washing and dtying were performed. The reason
for making the time for dipping the material in the treatment liquid shorter than the
ordinary time for dipping the material in the treatment liquid is to imitate the
situation in which attached amount of phosphate treatment to be performed after that
5 on the hot-dip Zn-based plated steel sheet is not sufficient.
[0116]
Random 5 visual fields (125 pm x 90 ptn) of the surface of the hot pressed
steel material after phosphate treatment were obset-ved with a scanning electron
microscope (SEM) at a mag~iification of 1000 times, and back scattered electron
10 images (BSE images) were obtained. In the back scattered electron image, the
observation area was displayed as an image by the gray scale. In the back scattered
electron image, the contrast is different between a portion where a phosphate coating
film that is a chemical con\~ersion coating film is formed and a portion where a
phosphate coating filrn is not formed. Thus, the numerical range X1 of the
15 lightness (a plurality of levels of gradation) of a portion where a phosphate coating
film was not fornled was detennined in advance by a SEM and an energy dispersive
X-ray spectrometer (EDS).
[0117]
In the back scattered electron image of each visual field, the area A1 of an
20 area showing the contrast of the numerical range X1 was found by image processing.
Then, the transparent area ratio TR (YO) of each visual field was found on the basis of
Formula (1) below.
[0118]
TR=(Al/AO)xlOO (1)
25 [0119]
Here, in Formula (1) above, A0 represents the total area of the visual field
(11,250 pm2). The average of the transparer~t area ratios TR (%) of the 5 visual
fields was defined as the transparent area ratio (%) of the hot pressed steel material
of the test number.
30 [0120]
"Mu in the "Phosphate treatability" section in Table 3 and Table 4 means that
the transparent area ratio was more tlian or equal to 30%. "L" tneans that the
transparent area ratio was more than or equal to 25% and less than 30%. "K" means
that the transparent area ratio was more than or equal to 20% and less than 25%.
"J" means that the transparent area ratio was more than or equal to 15% and less than
5 20%. "I" means that the transparent area ratio was more than or equal to 13% and
less than 15%. "H" means that the transparent area ratio was more than or equal to
11% and less than 13%. "G" means that the transparent area ratio was more than or
equal to 10% and less than 11%. "F" means that the transparent area ratio was Inore
than or equal to 18% and less than 10%. "E" means that the transparent area ratio
10 was more than or equal to 6% and less than 8%. "D" means that the transparent
area ratio wvas more than or equal to 5% and less than 6%. "C" means that the
transparent area ratio was more tlian or equal to 2.5% and less than 5%. "B" means
that the transparent area ratio was more than or equal to 1% and less than 2.5%.
"A" means that the tlansparent area ratio wvas less than 1%. The case of "I," "H,"
15 "G," "F," "E," "D,"" C," "B,"o r "A" in the transparency evaluation was assessed as
excellent in phosphate treatability.
[0121]
[FF chemical conversion treatability evaluation test]
Further, instead of the phosphate treatability, treatment using an aqueous
20 solution containing Zr ions andlor Ti ions, and fluorine and containing 100 to 1000
ppm of free fluoride ions (hereinafter, referred to as FF chemical conversion
treatment liquid) was performed.
[O 1 221
The FF chemical conversion treatment liquid mentioned above dissolves
25 free fluorine (hereinafter, abbreviated as FF), an A1 oxide coating film, and a Zn
oxide coating film. Therefore, while dissolving part or the whole of the A1 oxide
coating film and the Zn oxide coating film, FF etches the Zn-containing layer formed
in the hot stanlping process. As a result, a chemical conversion treatment layer
made of an oxide of Zr and/ Ti, or a mixture of an oxide and a fluoride of Zr andl Ti
30 (hereinafter, referred to as a specific chemical conversion treatment layer) is formed.
When the FF concentration is controlled so that the Al oxide coating film and the Zn
oxide coating film can be etched, the A1 oxide coating fill11 and the Zn oxide coating
film are etched, and the specific chemical conversion treatment layer is formed.
[0123]
To obtain the FF chemical conversion treatment liquid, H&F6
5 (hexafluorozirconic acid) and HzTiF6 (hexafluorotitanic acid) were put in a container
so that the metal concentration might be a prescribed value, and were diluted with
ion-exchanged water. After that, hydrofluoric acid and a sodium hydroxide aqueous
solution were put in the container, and adjustlnent was made so that the fluorine
concentration and the free fluorine concentration in the solution might be prescribed
10 values. The free fluorine concentration was measured using a connnercially
available concentration measuring device. After the adjustment, the container was
adjusted to a fixed volume with ion-exchanged water; thus, an FF chemical
conversion treatment liquid was prepared.
[0 1241
15 Regarding the FF chemical conversion treatment, as pre-treatment, dipping
degreasing was performed at 45°C for 2 minutes using an alkaline degreasing agent
(EC90, tnanufactured by Nippon Paint Co., Ltd.). After that, dipping was
performed in the FF chemical conversion treatment liquids shown in Table 6 below
at 40°C for 10 seconds or 30 seconds, while it is nornlally 120 seconds, and thus
20 chemical conversion treatment was performed. After the che~nical conversion
treatment, the test piece was washed with water and dried. The reason for ~naking
the time for dipping the material in the treatment liquid shorter than the ordinary time
for dipping the material in the treatment liquid is to imitate the situation in which
attached amount of FF che~nicalc onversion treatment to be performed after that on
25 the hot-dip Zn-based plated steel sheet is not sufficient.
[0125]
To investigate the chemical conversion treatability of the specific chemical
conversion treatment layer of the resulting test material, the amount of Zr or Ti
attached \4'as measured by fluorescent X-ray analysis; the case where the
30 measurement value of the attached amount was 10 to 100 mg/1n2 was classified as
"A," and the case where the measurement value of the attached amount was less than
10 tng/ln2 or more than 100 mg/m2 was classified as "B"; the obtained results are
collectively shown in Table 5. Note that, for a system containing zirconia, the
attached amount before performing Zr-based FF treatment was measured by
fluorescent X-ray analysis in advance, and the value obtained by subtracting the
5 amount of Zr attached before the chemical conversion treatment from the amount of
Zr attached after the treatment was set as the attached a~nount of FF chemical
conversion treatment. The method and the evaluation criterion of the coating
adhesiveness evaluation test and the cycle corl.osion test perfor~iled on the resulting
test material are similar to those of the coating adhesiveness evaluation test and the
10 cycle corrosion test performed on the test material on which the phosphate coating
film inentiorled above was formed. Note that since the present invention exlubits
satisfactory adl~esivenesse ven in the case where the chemical conversion treatability
is insufficient, the FF chemical conversion treatability is not a necessary propertj:
and a result of a system having low FF chemical conversion treatability in which the
15 FF chernical conversion treatability is "B", which is a gist of the present invention, is
also shown as an index exhibiting satisfacto~ya dhesiveness.
[O 1261
[Coating adhesiveness evaluatio~tie st]
After the phosphate treatment or the FF chemical cotiversioti treatment
20 described above was performed, the sheet-like hot pressed steel material of each test
number was coated with a cationic electrodepositioi~c oating material tnanufactured
by Nippon Paint Co., Ltd. by electrodeposition with slope energization at a voltage
of 160 V, and baking coating was performed at a baking tenlperature of 170°C for 20
minutes. The average of filin thicknesses of the coating material after
25 eIectrodeposition coating was 10 prn in all the test numbers.
[O 1271
After the electrodepositio~c~o ating, the hot pressed steel material was
dipped in a 5% NaCl aqueous solution having a temperature of 50°C for 500 hours.
After the dipping, a polyester tape was adhered to the whole of an area of 60 mm x
30 120 nun (area A10 = 60 nun x 120 nlm = 7200 mm2) of the test surface. After that,
the tape was ripped off. Tlie area A2 (nn11~) of the coating film peeled off by the
ripping-off of the tape was found, and the rate of coating peeling (YO) was found on
the basis of Formula (2).
[0128]
Rate of coatingpeeling=(A2/AlO)xlOO (2)
5 [0129]
"Mu of the "Coating film adhesiveness" section in Tables 3 to 5 means that
the rate of coating peeling was more than or equal to 50.0%. "L" means that the
rate of coating peeling was more than or equal to 35% and less than 50%. "K"
means that the rate of coating peeling was more than or equal to 20% and less than
10 35%. "J" means that the rate of coating peeling was more than or equal to 10% and
less than 20%. "I" means that the rate of coating peeling was more than or equal to
8% and less than 10%. "H" means that the rate of coating peeling was more than or
equal to 6% and less than 8%. "G" means that the rate of coating peeling was more
than or equal to 5% and less than 6%. "F" means that the rate of coating peeling
15 was more than or equal to 4% and less than 5%. "E" means that the rate of coating
peeling was more than or equal to 3% and less than 4%. "D" means that the rate of
coating peeling was more than or equal to 2.5% and less than 3%. "C" means that
the rate of coating peeling was more than or equal to 1.3% arid less than 2.5%. "B"
tneans that the rate of coating peeling was more than or equal to 0.5% and less than
20 1.3%. "A" means that the rate of coating peeling was less than 0.5%. The case of
"I," "H," "G," "F," "E," "D," "C," "B," or "A" in the coating adhesiveness evaluation
was assessed as excellent in coating adhesiveness.
[0130]
[Cycle corrosion test]
25 A gap was provided to the coating of the evaluation surface with a cutter
(load: 500 gf; I gf being approxinlately 9.8 x 10.' N), and a cycle col~osionte st of
the following cycle conditions was performed 180 cycles.
[0131]
- Cycle conditions
30 A cycle corrosion test was performed in which a procedure of two hours of
salt water spraying (SST; 5% NaC1; atmosphere: 3S°C), then two hours of drying
(6OoC), and then four liours of wetting (50°C; RH: 98%) was taken as one cycle.
[0132]
After that, the presence or absence of a blister of the coating film occurrilig
in an area of an approximately 1 cm width from the cut portion was observed.
5 "E" of the "Corrosion resistance" section in Tables 3 to 5 means that a
coating blister of more than or equal to 3.0 nun occurred. "D" nieans that a coating
blister of more than or equal to 2.0 mm and less than 3.0 mm occurred. "C" means
that a coating blister of more than or equal to 1.0 mtn and less than 2.0 mm occurred.
"B" nieans that a minute coating blister of more than or equal to 0.5 mn and less
10 than 1 mm occurred. "A" rneans that a very minute coating blister of less than 0.5
mm occurred. The case of "C," "B," or "A" in the cycle corrosion test was assessed
as excellent in corrosion resistance.
[0133]
[Table 81
[0134]
[Table 91

[0136]
[Table 1 I]

[0138]
[Table 131

[0 1401
[Table 151
[0141]
[Table 161
Table 6
I I I I
Zr-based FF chemical
conversion treatment
liquid
[0 1 421
5 Further, to verify the ir~fluence given by a P-contailling compoutld, a Vcontaining
compound, a Cu-containing compound an Al-containing con~pounda, Sicontaining
compound, and a Cr-containing colnpound present it1 the surface
treatment layer, plated steel sheets for hot pressing were produced using the
treatment liquids shown in No. 97 to No. 164 of Table 2. At this time, each of the
10 treatlnent liquids shown in No. 97 to No. 164 of Table 2 was applied with a bar
coater, and was dried using an oven under conditions for keeping a ~naximum peak
temperature of 100°C for 8 seconds. The alnount of the treatment liquid attached
was adjusted by the dilution of the liquid and the count of the bar coater so that the
total alnount of the attached nonvolatile conter~itn the treatmel~tl iquid might be the
H,ZrF,
Ti-based
FF chemical conversion
treatment liquid
15 nunlerical value shown it1 Table 7.
[0143]
After the formation process of the surface treatment layel; the steel sheet of
H,TiF,
each test number was subjected to hot press heating by an energization heating
system, and thus hot pressing was perfonned. At this time, heating was performed
20 at 870°C, with the heating rate set to 8S°C/sccond and 42.S0Clsecond.
[0144]
After the hot press heating, cooli~lgw as perfor~nedu ntil the ternperatuse of
tlie steel sheet became 650°C. After the cooling, the steel sheet was sandwiched by
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 approxiliiately
36OoC, which is the martensite transformation starting point, so as to ensure a
5 cooling rate of 50°C/seco~id or more even in a portion wliere the cooling rate had
been low during the hot pressing, and thus quenching was perforlned.
[0145]
The sheet-like hot pressed steel material of each of the test numbers
described in Table 7 below was subjected to surface conditioning at room
10 temperature for 20 seconds using a surface conditioning treatment agent, Prepalene
X (product t~arne)m anufactured by Nihon Parkerizing Co.,Ltd. Further, phosphate
treatment was performed using a zinc phosphate treatment liquid, Palbond 3020
(product name) manufactured by Nihon Parkerizing Co.,Ltd. The sheet-like hot
pressed steel material was dipped in the treatment liquid for 30 seconds, with the
15 temperature of the treatment liquid set to 43OC, and then water washing and drying
were performed. After that, a phosphate treatability evaluation test was performed
in a similar lnanner to the case shown in Table 3.
[0146]
Furthel; the sl~eet-likeh ot pressed steel material of each of the test numbers
20 described in Table 7 below was subjected to a coating adhesiveness evaluation test
and a cycle corrosion test in a similar manner to the case shown it1 Table 3. The
method and the evaluation criterion of each test are similar to those of the case
shown in Table 3.

[0148]
[Table 181
[0149]
As is clear from Tables 3 to S and Table 7 above, it is shown that the zincbased
plated steel sheet according to the present invention has excellent coating film
adhesiveness after hot pressing even in tlie case where the chemical conversion
5 treatment to be performed thereafter is not sufficient.
[OlSO]
The preferled enlbodiment(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.

CLAIMS
Claim 1
A zinc-based plated steel sheet comprising:
a zinc-based plated steel sheet that is a base metal; and
5 a surface treatment layer formed on at least one surface of the zinc-based
plated steel sheet, wherein
the surface treatnlent layer contains one or more oxides selected fiom
titanium oxide, nickel oxide, and tin(1V) oxide each having a pasticle size of more
than or equal to 2 nm and less than or equal to 100 nrn, in a range of more than or
10 equal to 0.2 dm2 and less than or equal to 2 g h ~p~er2 o ne surface.
Claim 2
The zinc-based plated steel sheet according to claim 1, wherein
the surface treatment layer fiuther contains at least one of one or more
15 phosphorus-containing compounds, one or more vanadium-containing compounds,
one or more copper-containing conlpounds, one or more aluminum-containing
compounds, one or more silicon-containing compounds, or one or morechromiuincontaining
compounds in the following range as a content per one surface,
the one or more phosphorus-containing compounds: Inore than or equal to
20 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/n12 on a V basis,
the one or Inore copper-containing compounds: more than or equal to 0.0
dm2 and less than or equal to 0.02 g/m2 on a Cu basis,
25 the one or more aluminum-containing compounds: lnore than or equal to 0.0
g/ii12 and less than or equal to 0.005 &n2 on an A1 basis,
the one or more silicon-containing conlpounds: more than or equal to 0.0
g/n12 and less than or equal to 0.005 g/m2 on a Si basis, and %..
the one or more chromium-containing compounds: more than or equal to 0.0
30 g/m2 and less than or equal to 0.01 g/m2 on a Cr basis.
Claim 3
The zinc-based plated steel sheet according to claim 1 or 2, wherein
the particle size of each of the one or more oxides selected horn titanium
oxide, nickel oxide, and tin(1V) oxide is m6re than or equal to 5 nm and less than or
5 equal to 50 nm.
Claim 4
The zinc-based plated steel sheet according to any one of claims 1 to 3,
wherein
10 the content of the one or more oxides selected hom titanium oxide, nickel
oxide, and tin(1V) oxide is more than or equal to 0.4 g/rn2 and less than or equal to
1.5 g/m2 per one surface.
Claim 5
15 The zinc-based plated steel sheet according to any one of claims 1 to 4,
wherein
the one or more oxides are titanium oxide.
Claim 6
20 The zinc-based plated steel sheet according to any one of claims 1 to 5,
wherein
the zinc-based plated steel sheet is a zinc-based plated steel sheet for hot
pressing..