U.S. patent application number 16/061893 was filed with the patent office on 2018-12-20 for zinc-based plated steel sheet having post-treated coating formed thereon and post-treatment method therefor.
The applicant listed for this patent is POSCO. Invention is credited to Yeon-Ho KIM, Yong-Woon KIM, Yung-Keun KIM, Young-Jun PARK.
Application Number | 20180363119 16/061893 |
Document ID | / |
Family ID | 57835470 |
Filed Date | 2018-12-20 |
United States Patent
Application |
20180363119 |
Kind Code |
A1 |
KIM; Yeon-Ho ; et
al. |
December 20, 2018 |
ZINC-BASED PLATED STEEL SHEET HAVING POST-TREATED COATING FORMED
THEREON AND POST-TREATMENT METHOD THEREFOR
Abstract
Provided is a zinc-based plated steel sheet having a
post-treated coating filmed thereon including: a steel sheet; a
zinc plated layer formed on the steel sheet; and a post-treated
coating formed on the plated layer, wherein the atomic ratio (O/M)
of oxygen (O) to metals (M) contained in the post-treated coating
is greater than 2 and less than 20, and a method for post-treating
a zinc-based plated steel sheet. According to this, the zinc-based
plated steel sheet having the post-treated coating formed thereon
has the effects excellent in lubricity, weldability, adhesiveness,
film-removing property and paintability. As the method of
post-treating a zinc-based plated steel sheet of the present
invention employs a simple coating method irrespective of the kind
of plating layer, the process is simple and economical and the
process operation cost is low.
Inventors: |
KIM; Yeon-Ho; (Gwangyang-si,
KR) ; KIM; Yung-Keun; (Gwangyang-si, KR) ;
PARK; Young-Jun; (Gwangyang-si, KR) ; KIM;
Yong-Woon; (Gwangyang-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POSCO |
Pohang-si |
|
KR |
|
|
Family ID: |
57835470 |
Appl. No.: |
16/061893 |
Filed: |
December 21, 2016 |
PCT Filed: |
December 21, 2016 |
PCT NO: |
PCT/KR2016/015002 |
371 Date: |
June 13, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 2/06 20130101; C23C
22/40 20130101; C23C 22/74 20130101; C23C 18/00 20130101; C23C 2/40
20130101; C23C 2/26 20130101 |
International
Class: |
C23C 2/26 20060101
C23C002/26; C23C 2/06 20060101 C23C002/06; C23C 2/40 20060101
C23C002/40; C23C 22/40 20060101 C23C022/40 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2015 |
KR |
10-2015-0183679 |
Claims
1. A zinc-based plated steel sheet having a post-treatment coating,
the zinc-based plated steel sheet comprising: a steel sheet; a
zinc-based plating layer formed on the steel sheet; and a
post-treatment coating formed on the plating layer, wherein the
post-treatment coating includes metal oxide salt and an organic
compound, and an atomic ratio (O/M) of oxygen (O) to metals (M)
included in the post-treatment coating is greater than 2 and
smaller than 20.
2. The zinc-based plated steel sheet of claim 1, wherein the
post-treatment coating includes a coating upper portion and a
coating lower portion, an atomic ratio (O/M) of oxygen and metal of
the coating upper portion is greater than 5, and an atomic ratio
(O/M) of oxygen and metal of the coating lower portion is less than
5.
3. The zinc-based plated steel sheet of claim 2, wherein an atomic
ratio (O/M) of oxygen and metal of the coating upper portion is
greater than 3.2, and an atomic ratio (O/M) of oxygen and metal of
the coating lower portion is less than 3.2.
4. The zinc-based plated steel sheet of claim 2, wherein a
thickness of the coating lower portion is 1/4 to 3/4 of the total
thickness of the post-treatment coating.
5. The zinc-based plated steel sheet of claim 1, wherein the metal
oxide salt further includes one or more selected from the group
consisting of molybdenum (Mo), boron (B), silicon (Si), titanium
(Ti), and zirconium (Zr).
6. A method for post-treating a zinc-based plated steel sheet, the
method comprising: applying a post-treatment coating solution to a
zinc-based plated steel sheet and drying the same to form a
post-treatment coating, wherein an atomic ratio (O/M) of oxygen (O)
to metals (M) included in the post-treatment coating is greater
than 2 and smaller than 20.
7. The method of claim 6, wherein the post-treatment coating
includes a coating upper portion and a coating lower portion, an
atomic ratio (O/M) of oxygen and metal of the coating upper portion
is greater than 5, and an atomic ratio (O/M) of oxygen and metal of
the coating lower portion is less than 5.
8. The method of claim 7, wherein a thickness of the coating lower
portion is 1/4 to 3/4 of the total thickness of the post-treatment
coating.
9. The method of claim 6, wherein the post-treatment coating
solution has pH ranging from 3.0 to 7.0.
10. The method of claim 6, wherein the post-treatment coating has a
coating weight ranging from 100 to 1000 mg/m.sup.2.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a zinc-based plated steel
sheet having a post-treatment coating formed thereon and a
post-treatment method thereof.
BACKGROUND ART
[0002] A zinc-based plated steel sheet used for an automobile panel
is inexpensive, has excellent corrosion resistance, has a fine
surface appearance, and usage thereof is increasing for automobile
interior and exterior panels. During an automobile manufacturing
process, a plated steel sheet is sequentially subjected to a
pressing process, an assembling process such as welding and
bonding, a debinding process, a phosphating process, and a painting
process, and here, a zinc plated steel sheet is required to have
physical properties such as lubricity, weldability, adhesiveness,
decoatability, paintability, and the like.
[0003] The zinc-based plated steel sheet has different physical
properties according to compositions of a plating layer formed on
the steel sheet and manufacturing methods and inferior physical
properties are required to be complemented. For example, in the
case of a hot-dip galvanized steel sheet (GI) and an
electrolytically galvanized steel sheet (EG), a soft plating layer
is eliminated during pressing involving high-pressure and
high-speed friction and fused to a bead part, or the like, of a
die. This causes defects such as scratches and dents on a surface
of the steel sheet. In particular, a plating layer composed of pure
zinc, such as a hot dip galvanized steel sheet (GI), has a low
melting point and the plating layer component is fused to and
oxidized on an electrode surface due to a trace amount of aluminum
(Al) contained therein during a welding process to form a
non-conductive contaminant to degrade continuous welding
points.
[0004] Further, in the case of the galvannealed steel sheet (GA),
lubrication characteristics are insufficient during pressing due to
a high coefficient of friction, and a powdering phenomenon in which
a material itself is fractured or a hard plating layer is chipped
off occurs. In addition, the zinc alloy plated steel sheet in which
a trace amount of aluminum (Al) or magnesium (Mg) is included in a
plating layer has excellent press formability but has low
adhesiveness due to a stable metal oxide present in an extreme
surface layer or has low continuous welding points during welding
due to an alloy phase having a low melting point.
[0005] In order to solve the problems, a surface of the zinc-based
plated steel sheet used as an automobile plate is required to be
post-treatment, and thus, it is necessary to improve inferior
physical properties.
[0006] Techniques regarding a post-treatment include a technique of
forming a phosphate layer on a surface of a zinc plating layer
(Korean Patent Laid-Open Publication No. 2001-0074527) and a
technique of forming a metal oxide layer (Japanese Patent Laid-Open
Publication No. JP-2014-185381). However, the technology of forming
the phosphate layer requires processes such as surface
conditioning, phosphate treatment, washing, drying, and the like,
and requires considerable facility space and solution management at
the time of an actual operation. Also, since it is a treatment
method depending on reactivity with a plating layer, solution
compositions must be changed according to types of the zinc-based
plated steel sheet. Further, since the technique of forming a metal
oxide layer is limited by metal components of a plating layer, it
cannot be applied to every zinc-based plated steel sheet.
DISCLOSURE
Technical Problem
[0007] An aspect of the present disclosure is to provide a
zinc-based plated steel sheet having excellent lubricity,
weldability, adhesiveness, decoatability, and paintability, which
are physical properties required for a sheet material for
automobiles.
[0008] An aspect of the present disclosure is to provide a method
for post-treating a zinc-based plated steel sheet through a simple
and low-priced process.
Technical Solution
[0009] According to an aspect of the present disclosure, a
zinc-based plated steel sheet having a post-treatment coating
includes: a steel sheet; a zinc-based plating layer formed on the
steel sheet; and a post-treatment coating formed on the plating
layer, wherein the post-treatment coating includes metal oxide salt
and an organic compound and an atomic ratio (O/M) of oxygen (O) to
metals (M) included in the post-treatment coating is greater than 2
and smaller than 20.
[0010] The post-treatment coating includes a coating upper portion
and a coating lower portion, an atomic ratio (O/M) of oxygen and
metal of the coating upper portion may be greater than 5, and an
atomic ratio (O/M) of oxygen and metal of the coating lower portion
may be less than 5.
[0011] An atomic ratio (O/M) of oxygen and metal of the coating
upper portion may be greater than 3.2, and an atomic ratio (O/M) of
oxygen and metal of the coating lower portion may be less than
3.2.
[0012] A thickness of the coating lower portion may be 1/4 to 3/4
of the total thickness of the post-treatment coating.
[0013] The metal oxide salt may further include one or more
selected from the group consisting of molybdenum (Mo), boron (B),
silicon (Si), titanium (Ti), and zirconium (Zr).
[0014] According to another aspect of the present disclosure, a
method for post-treating a zinc-based plated steel sheet includes:
applying a post-treatment coating solution to a zinc-based plated
steel sheet and drying the same to form a post-treatment coating,
wherein an atomic ratio (O/M) of oxygen (O) to metals (M) included
in the post-treatment coating is greater than 2 and smaller than
20.
[0015] The post-treatment coating includes a coating upper portion
and a coating lower portion, an atomic ratio (O/M) of oxygen and
metal of the coating upper portion may be greater than 5, and an
atomic ratio (O/M) of oxygen and metal of the coating lower portion
may be less than 5.
[0016] A thickness of the coating lower portion may be 1/4 to 3/4
of the total thickness of the post-treatment coating. The
post-treatment coating solution may have pH ranging from 3.0 to
7.0.
[0017] The post-treatment coating may have a coating weight ranging
from 100 to 1000 mg/m.sup.2.
Advantageous Effects
[0018] As set forth above, the zinc-based plated steel sheet having
a post-treatment coating formed thereon according to an exemplary
embodiment in the present disclosure has excellent lubricity,
weldability, adhesiveness, decoatability, and paintability.
[0019] In addition, since the method of post-treating a zinc-based
plated steel sheet according to the present disclosure employs a
simple coating method regardless of kind of a plating layer, the
process is simple and cost for a process operation is low,
obtaining economical efficiency.
Best Mode for Invention
[0020] Hereinafter, preferred exemplary embodiments of the present
disclosure will be described with reference to various exemplary
embodiments. However, the exemplary embodiments of the present
disclosure may be modified to have various other forms, and the
scope of the present disclosure is not limited to the exemplary
embodiments described below.
[0021] The present disclosure relates to a zinc-based plated steel
sheet having a post-treatment coating formed thereon and a
post-treatment method thereof, and specifically, may provide a
zinc-based plated steel sheet having a post-treatment coating,
which includes a steel sheet, a zinc-based plating layer formed on
the steel sheet, and a post-treatment coating formed on the plating
layer, wherein the post-treatment coating includes metal oxide salt
and an organic compound and an atomic ratio (O/M) of oxygen (O) to
metals (M) included in the post-treatment coating is greater than 2
and smaller than 20.
[0022] The zinc-based plated steel sheet having the post-treatment
coating of the present disclosure has excellent effects on
lubricity, weldability, adhesiveness, decoatablity, and
paintability, which are physical properties required for sheet
material of automobiles.
[0023] During an automobile manufacturing process, an automobile
sheet material sequentially undergoes a pressing process, an
assembling process such as welding and bonding, a debinding
process, a phosphating process, and a painting process, and here,
the automobile sheet material is required to have physical
properties such as lubricity, weldability, adhesiveness,
decoatability, paintability, and the like. If lubricity is
insufficient during the pressing process, powdering phenomenon in
which a material itself is fractured or a hard plating layer is
chipped off may occur. If weldability is insufficient during the
assembling process, a welding electrode may be contaminated during
welding to reduce an electrode life and continuous welding points,
and if adhesiveness is insufficient, delamination may occur during
tensile testing. Also, if decoatability is insufficient during the
debinding process, the post-treatment coating may not be
sufficiently removed to cause a defect during a phosphating
treatment and a painting process and degrade paintability.
[0024] In order to improve lubricity, weldability, adhesiveness,
decoatability, and paintability, which are physical properties
required for an automobile manufacturing process, the zinc-based
plated steel sheet of the present disclosure may include a
post-treatment coating formed on a plating layer and the
post-treatment coating may include metal oxide salt and an organic
compound. Furthermore, an atomic ratio (O/M) of oxygen (O) to
metals (M) contained in the post-treatment coating may be
controlled to be greater than 2 and less than 20.
[0025] The atomic ratio (O/M) of oxygen (O) to metals (M) in the
post-treatment coating is an average value per unit depth of
nanometer scale using by X-ray photoelectron spectroscopy (XPS)
after debinding the zinc-based plated steel sheet on which the
post-treatment coating is formed thereon by acetone.
[0026] The content of oxygen contained in the post-treatment
coating is an important condition for determining the physical
properties of the zinc-based plated steel sheet. In particular,
preferably, an atomic ratio (O/M) of oxygen (O) to metals (M)
included in the post-treatment coating is preferably greater than 2
and less than 20, and more preferably, greater than 2 and less than
10.
[0027] If the atomic ratio (O/M) of the oxygen (O) and the metal
(M) is 2 or less, the oxygen content in the post-treatment coating
is excessively small so that a fraction of the metal oxide salt
imparting lubricity between a press die and the steel sheet is too
low to ensure lubricity, causing the plating layer to be eliminated
or the material of the steel sheet to be fractured during pressing
of the steel sheet. In addition, since the fraction of the metal
oxide salt having a high melting point is lowered, contamination of
an electrode is increased in the welding process to lower the
electrode life and the continuous welding points, making it
difficult to ensure weldability. In addition, bonding sites using
oxygen as a medium such as oxo-ligand and hydroxyl group are
insufficient to lower adhesiveness ensuring bonding strength
between the zinc-based plated steel sheet and an adhesive.
[0028] Meanwhile, if the atomic ratio (O/M) of oxygen (O) to metals
(M) is 20 or greater, the content of oxygen in the post-treatment
coating may be excessively large. In particular, the fraction of
bonding sites such as oxo-ligand or hydroxyl group may be increased
to degrade decoatability. As a result, the post-treatment coating
may not be sufficiently removed to cause a defect during a
phosphating process and painting process and degrade
paintability.
[0029] The post-treatment coating of the present disclosure may be
divided into a coating upper portion and a coating lower portion.
Preferably, an atomic ratio (O/M) of oxygen (O) to metals (M) of
the coating upper portion is 5 or greater, and that of the coating
lower portion is less than 5. More preferably, the atomic ratio
(O/M) of oxygen (O) to metals (M) of the coating upper portion is
3.2 or greater, and that of the coating lower portion is less than
3.2.
[0030] In the present disclosure, the atomic ratio (O/M) of oxygen
(O) to metals (M) of the coating upper portion may be controlled to
have the oxygen content of 5 or greater. Accordingly, a surface
layer of the zinc-based plated steel sheet of the present
disclosure may have a high fraction of metal oxide salt to obtain
excellent lubricity and weldability, and since bonding sites such
as oxo-ligand and hydroxyl group are concentrated on the surface
layer, affinity with an adhesive during the assembling process may
be increased to ensure bonding strength.
[0031] Further, in the present disclosure, the atomic ratio (O/M)
of oxygen (O) to metals (M) in the coating lower portion may be
controlled to have the oxygen content of 5 or less. Accordingly,
the coating lower portion may smoothly induce the decoatability of
the post-treatment coating during a debinding process performed
before the painting process, and thus, a defect is prevented during
the phosphating process and the painting process, the follow-up
processes, to ensure paintability, and corrosion resistance may be
ensured due to the excellent paintability.
[0032] Meanwhile, a thickness of the coating lower portion may be
1/4 to 3/4 of a total thickness of the post-treatment coating,
preferably, 1/3 to 2/3. If the thickness of the coating lower
portion is less than 1/4 of the total thickness of the
post-treatment coating, the share of the coating lower portion
having excellent decoatability may be so low to cause a defect
during a phosphating treatment or electrodeposition coating, and if
the thickness of the coating lower portion exceeds 3/4, it may be
difficult to ensure bonding strength of the adhesive due to
shortage of adherence.
[0033] Preferably, the metal oxide salt included in the
post-treatment coating further includes at least one selected from
the group consisting of molybdenum (Mo), boron (B), silicon (Si),
titanium (Ti), and zirconium (Zr). Also, the post-treatment coating
may be a post-treatment coating including phosphor (P) alone or may
be a post-treatment coating including the metal oxide salt together
with phosphor (P).
[0034] Meanwhile, the organic compound may not be limited as long
as it is an organic compound containing a hydroxyl group (--OH).
For example, the organic compound may be an organic compound
including a function group such as a hydroxyl group, a carbonyl
group, and the like. Further, for example, the organic compound may
be a compound including polyvinyl acetate (PVAc), polyvinyl alcohol
(PVA), polyacrylic acid (PAA), polyvinyl butyral (PVB),
polyethylene glycol (PEG), and the like.
[0035] According to an exemplary embodiment of the present
disclosure, there is provided a method of post-treating a
zinc-based plated steel sheet, including applying a post-treatment
coating solution to a zinc-based plated steel sheet and drying the
same to form a post-treatment coating, wherein an atomic ratio
(O/M) of oxygen (O) to metals (M) included in the post-treatment
coating is greater than 2 and smaller than 20.
[0036] A coating method for post-treating the zinc-based plated
steel sheet may include a dry coating method such as physical vapor
deposition (PVD) or chemical vapor deposition (CVD), a powder spray
coating method such as thermal spraying, a solution coating method
such as roll coating, and the like. In the present disclosure, the
post-treatment is performed by the solution coating method in which
a post-treatment coating solution is simply applied to the plating
layer regardless of type of the plating layer, and thus, the
process is simple and cost for the process operation is low, which
is economical.
[0037] The post-treatment coating formed by applying the
post-treatment coating solution to the plating layer and drying the
same preferably has an atomic ratio (O/M) of oxygen (O) to metals
(M) greater than 2 and less than 20. The reason for controlling the
atomic ratio to such a range is as described above.
[0038] The post-treatment coating of the present disclosure may be
divided into an upper coating layer and a lower coating layer.
Preferably, an atomic ratio (O/M) of oxygen and metal of the
coating upper portion is 5 or greater and an atomic ratio (O/M) of
oxygen and metal of the coating lower portion is less than 5. In
addition, more preferably, an atomic ratio (O/M) of oxygen and
metal of the coating upper portion is 3.2 or greater and an atomic
ratio (O/M) of oxygen and metal of the coating lower portion is
less than 3.2. A thickness of the coating lower portion may be 1/4
to 3/4 of the total thickness of the post-treatment coating, and
preferably, 1/3 to 2/3. The reasons for controlling the atomic
ratio of the coating upper portion and the coating lower portion to
such a range and the reason for controlling the thickness of the
coating lower portion are as described above.
[0039] Preferably, the metal oxide salt included in the
post-treatment coating further includes at least one selected from
the group consisting of molybdenum (Mo), boron (B), silicon (Si),
titanium (Ti), and zirconium (Zr). As the metal oxide salt
contained in the post-treatment coating solution, a solution in
which metal oxide salt is colloidally dispersed or a solution in
which metal oxide salt is dissolved in the form of an oxide may be
used.
[0040] Meanwhile, the organic compound is not limited as long as it
is an organic compound containing a hydroxyl group (--OH). For
example, the organic compound may be an organic compound including
a function group such as a hydroxyl group, a carbonyl group, and
the like. Further, for example, the organic compound may be a
compound including polyvinyl acetate (PVAc), polyvinyl alcohol
(PVA), polyacrylic acid (PAA), polyvinyl butyral (PVB),
polyethylene glycol (PEG), and the like.
[0041] The pH of the post-treatment coating solution is not limited
but it preferably ranges from 3.0 to 7.0 in order to prevent the
plating layer from being dissolved and to form a stable
coating.
Mode for Invention
[0042] Hereinafter, the present disclosure will be described more
specifically through specific embodiments. The following
embodiments are provided to help understanding of the present
disclosure and the scope of the present disclosure is not limited
thereto.
EXAMPLES
Inventive Example 1
[0043] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 1 wt % of Mo and 0.2 wt % of B, 0.3 wt % of PEG, and the
balance being water was applied to the steel sheet by a bar coating
method and then a post-treatment coating having a coating weight of
300 mg/m.sup.2 was formed under a condition of PMT 100.degree.
C.
Inventive Example 2
[0044] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 1 wt % of Mo and 0.5 wt % of B, 0.5 wt % of PEG, and the
balance being water was applied to the steel sheet by a bar coating
method and then a post-treatment coating having a coating weight of
300 mg/m.sup.2 was formed under a condition of PMT 100.degree.
C.
Inventive Example 3
[0045] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 1 wt % of Mo and 1 wt % of B, 1 wt % of PEG, and the
balance being water was applied to the steel sheet by a bar coating
method and then a post-treatment coating having a coating weight of
300 mg/m.sup.2 was formed under a condition of PMT 100.degree.
C.
Inventive Example 4
[0046] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 0.5 wt % of Mo and 1 wt % of B, 1.5 wt % of PEG, and the
balance being water was applied to the steel sheet by a bar coating
method and then a post-treatment coating having a coating weight of
300 mg/m.sup.2 was formed under a condition of PMT 100.degree.
C.
Comparative Example 1
[0047] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared, and a post-treatment coating was not formed on
the steel sheet.
Comparative Example 2
[0048] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 1 wt % of Mo, 0.1 wt % of PEG, and the balance being
water was applied to the steel sheet by a bar coating method and
then a post-treatment coating having a coating weight of 300
mg/m.sup.2 was formed under a condition of PMT 100.degree. C.
Comparative Example 3
[0049] A zinc-based steel sheet having a thickness of 0.8 mm, an
elongation of 36% to 37%, and a plating amount of 40 g/m.sup.2 and
including a plating layer in which Al is 2.5%, Mg is 3% and Zn is
94.5% was prepared. A coating solution containing metal oxide salt
containing 1 wt % of Mo and 0.5 wt % of B, 3 wt % of PEG, and the
balance being water was applied to the steel sheet by a bar coating
method and then a post-treatment coating having a coating weight of
300 mg/m.sup.2 was formed under a condition of PMT 100.degree.
C.
[0050] The atomic ratios (O/M) of oxygen (O) to metals (M) in the
post-treatment coatings of Inventive Examples 1 to 4 and
Comparative Examples 1 to 3 were measured and shown in Table 1. The
atomic ratio is an average value per unit depth of nanometer scale
using an X-ray photoelectron spectroscopy (XPS) method after
acetone-debinding the zinc-based plated steel sheet on which the
post-treatment coating is formed. A boundary between an upper
portion and a lower portion was half of a total thickness. In order
to evaluate physical properties according to the atomic ratio (O/M)
conditions of oxygen (O) to metals (M), processibility, adhesion
and decoatability were evaluated and the results are shown in Table
1.
[0051] <Evaluation of Processibility>
[0052] A cup drawing test was carried out to evaluate
processibility. In the cup drawing test, a tester including a mold
and a punch was used. Testing was performed, while increasing a
blank holding force (BHF), and a BHG value immediately before
material fracture occurred was determined as a maximum BHF value
and written in Table 1. As the maximum BHF value is higher,
workability is better. Detailed conditions of the cup drawing test
carried out in this example are as follows.
[0053] .asterisk-pseud.Detailed Conditions of Cup Drawing Test
[0054] Punch diameter: 50 mm
[0055] Punch edge radius: 6 mm
[0056] Die diameter: 52.25 mm
[0057] Punch movement rate: 230 mm/min
[0058] Post-treatment coating was in contact with mold and testing
was performed after applying washing oil to surface of the
post-treatment coating
[0059] <Evaluation of Adhesion>
[0060] For an adhesion test, two 25 mm.times.100 mm samples were
manufactured, and after washing oil was applied to the samples, the
samples were erected and left as is for one day. Thereafter, a
mastic sealer adhesive was applied with a size of 25 mm
(width).times.25 mm (length).times.3 mm (height) to an inner side
by 10 mm from the end of one sample and the other sample was folded
thereon, which were then cured at 170.degree. C. for 20 minutes.
Thereafter, adhesion shear strength of the upper and lower samples
was measured and the results thereof are shown in Table 1. The
shear strength was measured at a speed of 50 mm/min and a measured
maximum shear force was divided by an adhesion area of 6.25
cm.sup.2.
[0061] <Evaluation of Decoatability>
[0062] For a decoatability test, a material was stirred and dipped
at 50 to 55.degree. C. for 2 minutes using a degreasing solution
used in an automobile manufacturing process and subsequently
washed, and an amount of coating remaining on a surface of the
material was measured, a decoating rate to a coating weight of the
coating before degreasing was calculated by percentage and shown in
Table 1. For the remaining amount of coating, a coating layer
having a predetermined area was dissolved with an acid solution,
and the content of molybdenum of the solution was analyzed
quantitatively with inductively coupled plasma (ICP) to calculate a
remaining amount per area.
TABLE-US-00001 TABLE 1 O/M* of O/M of entire lower post- post-
Bonding treatment treatment Maximum strength Decoating
Classification coating coating BHF (ton) (kgf/cm.sup.2) rate (%)
Inventive 3.2 1.9 10 4.0 97 Example 1 Inventive 7.2 2.4 12 5.2 95
Example 2 Inventive 10.1 3.1 14 5.5 96 Example 3 Inventive 19.2 4.7
13 5.5 95 Example 4 Comparative Not -- 7 0.5 -- example 1 treated
Comparative 1.8 1.5 8 1.1 98 example 2 Comparative 25.3 6.2 14 5.3
87 example 3 *O/M is an atomic ratio of oxygen (O) to metals
(M)
[0063] As shown in Table 1, it can be seen that, in Inventive
Examples 1 to 6 in which the post-treatment coating was formed, the
maximum BHF value and the bonding strength were significantly
higher than those in Comparative Example 1 in which post-treatment
was not performed, and thus, Inventive Examples 1 to 6 have
excellent processibility and adhesiveness as physical properties
that may be used as a sheet material of automobiles.
[0064] It was also confirmed that Inventive Examples 1 to 6 in
which the atomic ratio (O/M) of oxygen (O) to metals (M) is greater
than 2 and less than 20 had a decoating rate of 95% or greater,
exhibiting excellent decoatability. However, in Comparative Example
2 in which the atomic ratio (O/M) of oxygen (O) to metals (M) is 2
or less, processibility and adhesiveness are inferior and, in
Comparative Example 3 in which the atomic ratio (O/M) of oxygen (O)
to metals (M) is 20 or greater, processibility and adhesiveness
were good but has an inferior decoating rate because the decoating
rate is 87% or less.
[0065] While exemplary embodiments of the present disclosure have
been shown and described above, it will be apparent to those
skilled in the art that modifications and variations could be made
without departing from the scope of the present disclosure as
defined by the appended claims.
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