U.S. patent application number 14/594544 was filed with the patent office on 2016-03-24 for high temperature oxidation-resistant coated steel plate and hot stamping method thereof.
The applicant listed for this patent is CHINA STEEL CORPORATION. Invention is credited to SHEAU-HWA HSIEH, CHENG-EN HSU, CHING-KUO KUO, I-HSUANG LO, SHI-WEI WANG.
Application Number | 20160083814 14/594544 |
Document ID | / |
Family ID | 52432648 |
Filed Date | 2016-03-24 |
United States Patent
Application |
20160083814 |
Kind Code |
A1 |
HSIEH; SHEAU-HWA ; et
al. |
March 24, 2016 |
HIGH TEMPERATURE OXIDATION-RESISTANT COATED STEEL PLATE AND HOT
STAMPING METHOD THEREOF
Abstract
A high temperature oxidation-resistant coated steel plate
includes a steel base material and a high temperature
oxidation-resistant coating. The high temperature
oxidation-resistant coating is formed by coating a high temperature
oxidation-resistant paint onto the steel base material and baking
in an oven. The high temperature oxidation-resistant paint includes
a binder and a plurality of micron aluminum flakes. The binder has
a three-dimensional molecular structure of Al--O. The micron
aluminum flakes has a micron-sized thickness and a length ranging
from 5 to 30 .mu.m inclusive. The disclosure can enhance high
temperature oxidation-resistant ability and hot stamping
characteristics of the coated steel plate, and makes objects after
hot stamping have good spot weldability and coating
performance.
Inventors: |
HSIEH; SHEAU-HWA;
(KAOHSIUNG, TW) ; WANG; SHI-WEI; (KAOHSIUNG,
TW) ; HSU; CHENG-EN; (KAOHSIUNG, TW) ; KUO;
CHING-KUO; (KAOHSIUNG, TW) ; LO; I-HSUANG;
(KAOHSIUNG, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHINA STEEL CORPORATION |
KAOHSIUNG |
|
TW |
|
|
Family ID: |
52432648 |
Appl. No.: |
14/594544 |
Filed: |
January 12, 2015 |
Current U.S.
Class: |
428/562 ;
148/516; 428/546 |
Current CPC
Class: |
B21D 22/022 20130101;
C08K 2003/2227 20130101; C09D 1/00 20130101; C21D 9/46 20130101;
C22C 38/00 20130101; C23C 24/082 20130101; C21D 2211/008 20130101;
C09D 7/61 20180101; C09D 5/103 20130101; C09D 7/70 20180101; C09D
7/69 20180101; C08K 2003/0812 20130101; C21D 8/0247 20130101; C21D
8/00 20130101; C21D 1/673 20130101 |
International
Class: |
C21D 8/02 20060101
C21D008/02; C22C 38/00 20060101 C22C038/00; B21D 22/02 20060101
B21D022/02; C21D 9/46 20060101 C21D009/46 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2014 |
TW |
103131986 |
Claims
1. A high temperature oxidation-resistant coated steel plate,
comprising: a steel base material; and a high temperature
oxidation-resistant coating formed by coating a high temperature
oxidation-resistant paint onto the steel base material and baking
in an oven, wherein the high temperature oxidation-resistant paint
comprises a binder and a plurality of micron aluminum flakes, the
binder has a three-dimensional molecular structure of Al--O, and
the micron aluminum flakes has a micron-sized thickness and a
length ranging from 5 to 30 .mu.m inclusive.
2. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the steel base material is a manganese-boron steel
base material.
3. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the thickness of the high temperature
oxidation-resistant coating is between 2 and 10 .mu.m
inclusive.
4. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the weight of the micron aluminum flakes is 5-30%
of the total weight of the paint.
5. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the binder is made with a sol-gel method.
6. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the coating method of the high temperature
oxidation-resistant paint is selected from one of the following:
spraying, roller coating and dip coating.
7. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the baking temperature of the high temperature
oxidation-resistant coating is between 120 and 300.degree. C.
inclusive.
8. The high temperature oxidation-resistant coated steel plate of
claim 1, wherein the baking time of the high temperature
oxidation-resistant coating is between 36 and 90 seconds
inclusive.
9. A hot stamping method of the high temperature
oxidation-resistant coated steel plate, comprising: (a) providing
the high temperature oxidation-resistant coated steel plate as
claimed in claim 1; (b) heating the high temperature
oxidation-resistant coated steel plate to an austenitizing state;
and (c) transferring the high temperature oxidation-resistant
coated steel plate to a mold for hot stamping, to form an
object.
10. The hot stamping method of claim 9, wherein a tensile strength
of the high temperature oxidation-resistant coated steel plate of
the step (a) is 500 to 600 MPa inclusive.
11. The hot stamping method of claim 9, wherein the heating
temperature of the step (b) is 870 to 950.degree. C. inclusive.
12. The hot stamping method of claim 9, wherein the heating time of
the step (b) is 3 to 5 minutes inclusive.
13. The hot stamping method of claim 9, wherein the step (c)
further comprises performing pressure holding and quenching
treatment on the object at a cooling rate greater than 27.degree.
C. Is, so as to make the object to have a uniform martensite
organization.
14. The hot stamping method of claim 13, wherein a tensile strength
of the object is greater than 1400 MPa.
Description
FIELD
[0001] The disclosure relates to a steel plate and hot stamping
method thereof, more particular to a high temperature
oxidation-resistant coated steel plate and hot stamping method
thereof.
BACKGROUND
[0002] Hot stamping technologies in the automobile industry, due to
advantages such as excellent formability, good dimensional
stability, fewer forming steps and being capable of manufacturing
automotive structural parts with a tensile strength more than 1470
MPa, have become major application technologies of manufacturing
automotive metal plate parts at present. However, the temperature
may usually exceed 900.degree. C. during hot stamping, causing
serious high temperature rust scales on a surface of the steel
plate, so that a workpiece must be sandblasted after formation, so
as to remove the rust scales. In addition, the high temperature
rust scales on the surface of the steel plate may also cause
serious pollution and wear to hot stamping molds, which not only
cause trouble to production operations but also increase production
costs.
[0003] Although a conventional paint composed of aluminum powder,
silicone resins and silanes has been proposed, upon actual tests,
in addition to poor high temperature oxidation resistance of the
coating, the steel plate to which the coating is applied, after hot
stamping, may generate excessively thick alumina on its surface, so
that the electric resistance is too high to be spot-welded, and
thus the alumina should be removed through sandblasting. In
response to the procedure of sandblasting removal, the paint must
be added with an organic sacrificial component to protect the
aluminum powder, so as to avoid oxidation. However, during heat
treatment of the steel plate in the air, alumina and iron oxides
may still exist on the surface of the steel plate, and the alumina
and the iron oxides may cause high interface electric resistance,
so that a great amount of heat during spot welding is generated,
which easily causes expulsion. Meanwhile, in the case, the copper
electrode cap is easy to react with steels and cause bonding
between them. Also, because iron and aluminum oxides exist in the
weld nugget, mechanical properties of it is deteriorate.
[0004] On the basis of the foregoing analysis, the conventional
coating still has disadvantages of poor high temperature oxidation
resistance and spot weldability. Therefore, it is necessary to
provide a high temperature oxidation-resistant coated steel plate
and hot stamping method thereof, so as to solve the foregoing
deficiencies in the prior art.
SUMMARY OF THE INVENTION
[0005] In accordance with one aspect of the present disclosure, a
high temperature oxidation-resistant coated steel plate includes a
steel base material and a high temperature oxidation-resistant
coating. The high temperature oxidation-resistant coating is formed
by coating a high temperature oxidation-resistant paint onto the
steel base material and baking in an oven. The high temperature
oxidation-resistant paint includes a binder and a plurality of
micron aluminum flakes. The binder has a three-dimensional
molecular structure of Al--O. The micron aluminum flakes has a
micron-sized thickness and a length ranging from 5 to 30 .mu.m
inclusive.
[0006] In accordance with another aspect of the present disclosure,
a hot stamping method of a high temperature oxidation-resistant
coated steel plate includes steps in which a high temperature
oxidation-resistant coated steel plate is provided. The method
continues with step in which the high temperature
oxidation-resistant coated steel plate is heated to an
austenitizing state. The method continues with step in which the
high temperature oxidation-resistant coated steel plate is
transferred to a mold for hot stamping, to form an object.
[0007] In the present disclosure, a paint is formed with a binder
and micron aluminum flakes and applied to a steel base material to
form a high temperature oxidation-resistance coating. The coating
enhances the high temperature oxidation-resistance and hot stamping
characteristics of the coated steel plate, and makes objects after
hot stamping have good spot weldability and coating
performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Aspects of the present disclosure are understood from the
following detailed description when read with the accompanying
figures. It is emphasized that, in accordance with the standard
practice in the industry, various features are not drawn to scale.
In fact, the dimensions of the various features may be arbitrarily
increased or reduced for clarity of discussion.
[0009] FIG. 1 is a schematic structural view of a high temperature
oxidation-resistant coated steel plate according to the present
disclosure.
[0010] FIG. 2 is a flow diagram of a hot stamping method of a high
temperature oxidation-resistant coated steel plate according to the
present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0011] It is to be understood that the following disclosure
provides many different embodiments or examples, for implementing
different features of various embodiments. Specific examples of
components and arrangements are described below to simplify the
present disclosure. The present disclosure may, however, be
embodied in many different forms and should not be construed as
being limited to the embodiments set forth herein; rather, these
embodiments are provided so that this description will be thorough
and complete, and will fully convey the present disclosure to those
of ordinary skill in the art. It will be apparent, however, that
one or more embodiments may be practiced without these specific
details.
[0012] In addition, the present disclosure may repeat reference
numerals and/or letters in the various examples. This repetition is
for the purpose of simplicity and clarity and does not in itself
dictate a relationship between the various embodiments and/or
configurations discussed.
[0013] It will be understood that singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise.
[0014] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms; such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0015] FIG. 1 is a schematic structural view of a high temperature
oxidation-resistant coated steel plate according to the present
disclosure.
[0016] Referring to FIG. 1, the high temperature
oxidation-resistant coated steel plate 10 of the present disclosure
includes a steel base material 12 and a high temperature
oxidation-resistant coating 14. In some embodiments, the steel base
material 12 is a manganese-boron steel base material.
[0017] The high temperature oxidation-resistant coating 14 is
formed by coating a high temperature oxidation-resistant paint onto
the steel base material 12 and baking in an oven. In some
embodiments, the thickness of the high temperature
oxidation-resistant coating 14 needs to be controlled between 2 and
10 .mu.m inclusive, because high temperature oxidation resistance
of the coating will be reduced when the thickness is less than 2
.mu.m, and spot weldability of the steel plate will be worsened
when the thickness is greater than 10 .mu.m. In addition, in order
to enhance adhesion of the high temperature oxidation-resistant
coating 14, preferably, the baking temperature of the high
temperature oxidation-resistant coating 14 should be controlled
between 120 and 300.degree. C. inclusive, and the baking time
should be controlled between 36 and 90 seconds inclusive. Besides,
the coating method of the high temperature oxidation-resistant
paint is selected from one of the following: spraying, roller
coating and dip coating.
[0018] The high temperature oxidation-resistant paint includes a
binder and a plurality of micron aluminum flakes. In some
embodiments, the binder has a three-dimensional molecular structure
of Al--O, and the binder is made with a sol-gel method. The micron
aluminum flakes has a micron-sized thickness (about 0.5 to 1 .mu.m
thick) and a length ranging from 5 to 30 .mu.m inclusive, and
preferably, the weight of the micron aluminum flakes is 5-30% of
the total weight of the paint.
[0019] In some embodiments, the high temperature
oxidation-resistant coated steel plate 10 can adopt continuous
steel coil production or discontinuous blank production. If the
continuous steel coil production is adopted, the production process
can be: unwinding.fwdarw.alkali washing.fwdarw.drying.fwdarw.roller
coating or dip coating (two sides).fwdarw.baking.fwdarw.coiling. If
the discontinuous chip production is adopted, the production
process can be: blanking.fwdarw.alkali
washing.fwdarw.drying.fwdarw.spraying (one
side).fwdarw.baking.fwdarw.spraying (the other
side).fwdarw.baking.fwdarw.stacking and packing.
[0020] FIG. 2 is a flow diagram of a hot stamping method of a high
temperature oxidation-resistant coated steel plate according to the
present disclosure.
[0021] Referring to step S21 of FIG. 2 and FIG. 1, a high
temperature oxidation-resistant coated steel plate 10 is provided.
In the step, the high temperature oxidation-resistant coated steel
plate 10 includes a steel base material 12 and a high temperature
oxidation-resistant coating 14. The high temperature
oxidation-resistant coating 14 is formed by coating a high
temperature oxidation-resistant paint onto the steel base material
12 and baking in an oven. The high temperature oxidation-resistant
paint includes a binder and a plurality of micron aluminum flakes.
In some embodiments, the binder has a three-dimensional molecular
structure of Al--O, and the micron aluminum flakes has a
micron-sized thickness (about 0.5 to 1 .mu.m thick) and a length
ranging from 5 to 30 .mu.m inclusive.
[0022] In addition, in the step, a tensile strength of the high
temperature oxidation-resistant coated steel plate 10 is 500 to 600
MPa inclusive.
[0023] Referring to step S22 of FIG. 2 and FIG. 1, the high
temperature oxidation-resistant coated steel plate 10 is heated to
an austenitizing state. In the step, the heating temperature is 870
to 950.degree. C. inclusive, and the heating time is 3 to 5 minutes
inclusive.
[0024] Referring to step S23 of FIG. 2 and FIG. 1, the high
temperature oxidation-resistant coated steel plate 10 is
transferred to a mold (not shown) for hot stamping, to form an
object. The step includes: performing pressure holding and
quenching treatment on the object at a cooling rate greater than
27.degree. C./s, so as to make the object to have a uniform
martensite organization, thereby obtaining a tensile strength
greater than 1400 MPa.
[0025] In the present disclosure, the high temperature
oxidation-resistant paint is composed of the binder and the micron
aluminum flakes, and the high temperature oxidation-resistant paint
is applied to a high temperature oxidation-resistant coating 14
formed on a steel base material 12, which can enhance the high
temperature oxidation-resistance and hot stamping characteristics
of the coated steel plate 10, and makes objects after hot stamping
to have good spot weldability and coating performance.
[0026] The present disclosure is described in detail with the
following embodiments, but this does not mean that the present
disclosure is only limited to the content disclosed by the
embodiments.
Embodiment 1
[0027] A high temperature oxidation-resistant paint was prepared by
mixing binder and aluminum flakes. The weight of micron aluminum
flakes added to the paint was 30% of the total weight of the paint.
The length of the micron aluminum flakes was 5 to 10 .mu.m. An
appropriate amount of dispersing agent was added to make the micron
aluminum flakes mix uniformly and completely with binder to obtain
a solid content of 50 to 60 wt %.
[0028] The paint was coated onto a manganese-boron steel base
material through spraying. The thickness of the coating was 3.+-.1
.mu.m. After coating, the steel plate was baked in oven at
270.degree. C. for 48 seconds. The coated steel plate after baking
was placed in an air oven of 930.degree. C. for 5 minutes, and then
was quickly transferred to a mold for hot-stamping forming.
[0029] The cross-cut test (ASTM D3359) is performed on the coated
steel plate after baking, and the coating did not fall off at all
after tape was removed. It represented good coating adhesion
between steel plate and the coating. Similarly, the cross-cut test
was performed on the object after hot stamping, and the coating did
not fall off at all neither. In addition, a planar light source
resistance measurement module (Surface Resistance Meter,
Manufacturer/Model: Mitsubishi Chemical Analytech/Loresta-GP
MCP-T610) was used to measure the surface electric resistance of
the hot-stamping object with a four-point probe at a given current.
The surface electric resistance of the object was measured to be
less than 1.times.10.sup.-2.OMEGA.. Due to such low surface
electric resistance, the spot welding test result showed no
phenomenon of expulsion and no sign of spot welding electrode cap
bonding with the hot-stamping object, indicating that its welding
characteristics were identical with those of the bare steel. The
hot-stamping object could also be coated by electro-deposition
coating process. The tensile strength of the object after hot
stamping reached 1500 MPa.
Embodiment 2
[0030] A high temperature oxidation-resistant paint was prepared by
mixing binder and aluminum flakes. The weight of micron aluminum
flakes added to the paint was 15% of the total weight of the paint.
The length of the micron aluminum flakes was 5 to 10 .mu.m. An
appropriate amount of dispersing agent was added to make the micron
aluminum flakes mix uniformly and completely with binder to obtain
a solid content of 40 to 50 wt %.
[0031] The paint was coated onto a manganese-boron steel base
material through spraying. The thickness of the coating was 5.+-.1
.mu.m. After coating, the steel plate was baked in oven at
150.degree. C. for 36 seconds. The coated steel plate after baking
was placed in an air oven of 890.degree. C. for 5 minutes, and then
was quickly transferred to a mold for hot-stamping forming.
[0032] The cross-cut test (ASTM D3359) is performed on the coated
steel plate after baking, and the coating did not fall off at all
when the tape was removed. It represented good adhesion between
steel plate and the coating. Similarly, the cross-cut test was
performed on the object after hot stamping, and the coating did not
fall off at all neither when the tape was removed. In addition, a
planar light source resistance measurement module (Surface
Resistance Meter, Manufacturer/Model: Mitsubishi Chemical
Analytech/Loresta-GP MCP-T610) was used to measure the surface
electric resistance of the hot-stamping object with a four-point
probe at a given current. The surface electric resistance of the
object was measured to be less than 1.times.10.sup.-2.OMEGA.. Due
to such low surface electric resistance, the spot welding test
result showed no phenomenon of expulsion and no sign of spot
welding electrode cap bonding with the hot-stamping object,
indicating that its welding characteristics were identical with
those of the bare steel. The tensile strength of the object after
hot stamping reached 1500 MPa.
Embodiment 3
[0033] A high temperature oxidation-resistant paint was prepared by
mixing binder and aluminum flakes. The weight of micron aluminum
flakes added to the paint was 10% of the total weight of the paint.
The length of the micron aluminum flakes was 5 to 10 .mu.m. An
appropriate amount of dispersing agent was added to make the micron
aluminum flakes mix uniformly and completely with binder to obtain
a solid content of 35 to 45 wt %.
[0034] The paint was coated onto a manganese-boron steel base
material through spraying. The thickness of the coating was 9.+-.1
.mu.m. After coating, the steel plate was baked in oven at
300.degree. C. for 60 seconds. The coated steel plate after baking
was placed in an air oven of 870.degree. C. for 5 minutes, and then
was quickly transferred to a mold for hot-stamping forming.
[0035] The cross-cut test (ASTM D3359) is performed on the coated
steel plate after baking, and the coating did not fall off at all
after tape was removed. It represented good coating adhesion
between steel plate and the coating. Similarly, the cross-cut test
was performed on the object after hot stamping, and the coating did
not fall off at all neither. In addition, a planar light source
resistance measurement module (Surface Resistance Meter,
Manufacturer/Model: Mitsubishi Chemical Analytech/Loresta-GP
MCP-T610) was used to measure the surface electric resistance of
the hot-stamping object with a four-point probe at a given current.
The surface electric resistance of the object was measured to be
less than 1.times.10.sup.-2.OMEGA.. Due to such low surface
electric resistance, the spot welding test result showed no
phenomenon of expulsion and no sign of spot welding electrode cap
bonding with the hot-stamping object, indicating that its welding
characteristics were identical with those of the bare steel. The
hot-stamping object could also be coated by electro-deposition
coating process. The tensile strength of the object after hot
stamping reached 1480 MPa.
Embodiment 4
[0036] A high temperature oxidation-resistant paint was prepared by
mixing binder and aluminum flakes. The weight of micron aluminum
flakes added to the paint was 20% of the total weight of the paint.
The length of the micron aluminum flakes was 5 to 10 .mu.m. An
appropriate amount of dispersing agent was added to make the micron
aluminum flakes mix uniformly and completely with binder to obtain
a solid content of 45 to 55 wt %.
[0037] The cross-cut test (ASTM D3359) is performed on the coated
steel plate after baking, and the coating falled off partially
(about 5%) after tape was removed. It represented poor coating
adhesion between steel plate and the coating. Similarly, the
cross-cut test was performed on the object after hot stamping, and
the coating did not fall off. In addition, a planar light source
resistance measurement module (Surface Resistance Meter,
Manufacturer/Model: Mitsubishi Chemical Analytech/Loresta-GP
MCP-T610) was used to measure the surface electric resistance of
the hot-stamping object with a four-point probe at a given current.
The surface electric resistance of the object was measured to be
2.times.10.sup.-2.OMEGA., which indicates that the surface electric
resistance is high. Due to the high surface electric resistance,
spot welding test result showed slight expulsion and spot welding
electrode cap bonding with the hot-stamping object, indicating that
its welding characteristics were worse then those of the bare
steel. The hot-stamping object could be coated by
electro-deposition coating process.
Embodiment 5
[0038] A high temperature oxidation-resistant paint was prepared by
mixing binder and aluminum flakes. The weight of micron aluminum
flakes added to the paint was 5% of the total weight of the paint.
The length of the micron aluminum flakes was 5 to 10 .mu.m. An
appropriate amount of dispersing agent was added to make the micron
aluminum flakes mix uniformly and completely with binder to obtain
a solid content of 25 to 35 wt %.
[0039] The paint was coated onto a manganese-boron steel base
material through spraying. The thickness of the coating was 5.+-.1
.mu.m. After coating, the steel plate was baked in oven at
120.degree. C. for 90 seconds. The coated steel plate after baking
was placed in an air oven of 870.degree. C. for 5 minutes, and then
was quickly transferred to a mold for hot-stamping forming.
[0040] The cross-cut test (ASTM D3359) is performed on the coated
steel plate after baking, and the coating falled off partially
(about 5%) after tape was removed. It represented poor coating
adhesion between steel plate and the coating. Similarly, the
cross-cut test was performed on the object after hot stamping, and
the coating did not fall off. In addition, a planar light source
resistance measurement module (Surface Resistance Meter,
Manufacturer/Model: Mitsubishi Chemical Analytech/Loresta-GP
MCP-T610) was used to measure the surface electric resistance of
the hot-stamping object with a four-point probe at a given current.
The surface electric resistance of the object was measured to be
1.times.10.sup.-1.OMEGA., which indicates that the surface electric
resistance is high. Due to the high surface electric resistance,
spot welding test result showed slight expulsion and spot welding
electrode cap bonding with the hot-stamping object, indicating that
its welding characteristics were worse then those of the bare
steel. The reason for the high surface electric resistance was that
the weight of the added micron aluminum flakes was excessively low.
The hot-stamping object could be coated by electro-deposition
coating process.
[0041] Moreover, the scope of the present application is not
intended to be limited to the particular embodiments of the
process, machine, manufacture, and composition of matter, means,
methods and steps described in the specification. As those skilled
in the art will readily appreciate form the present disclosure,
processes, machines, manufacture, compositions of matter, means,
methods, or steps, presently existing or later to be developed,
that perform substantially the same function or achieve
substantially the same result as the corresponding embodiments
described herein may be utilized according to the present
disclosure.
[0042] Accordingly, the appended claims are intended to include
within their scope such processes, machines, manufacture, and
compositions of matter, means, methods or steps. In addition, each
claim constitutes a separate embodiment, and the combination of
various claims and embodiments are within the scope of the
invention.
* * * * *