U.S. patent application number 12/955854 was filed with the patent office on 2011-03-24 for press hardening die cooling device.
This patent application is currently assigned to HYUNDAI STEEL COMPANY. Invention is credited to Seungtaek Hong, Soonyong Kwon.
Application Number | 20110068519 12/955854 |
Document ID | / |
Family ID | 41570747 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110068519 |
Kind Code |
A1 |
Kwon; Soonyong ; et
al. |
March 24, 2011 |
PRESS HARDENING DIE COOLING DEVICE
Abstract
The present invention relates to an apparatus for a press
hardening die which has a structure improved to decrease cooling
rate of trimming portions in pressing a steel plate blank for
manufacturing a part for press hardening. A press hardening die
cooling device according to an embodiment of the present invention
includes: a press hardening die composed of upper and lower dies
equipped with cooling water suppliers therein to press a steel
plate blank from the top and the bottom; and a cooling water
temperature adjuster disposed between the cooling water suppliers
of the upper and lower dies and the contact surface of the steel
plate blank to adjust temperature of cooling water supplied to the
steel plate blank.
Inventors: |
Kwon; Soonyong; (Goyang-Si,
KR) ; Hong; Seungtaek; (Suwon-Si, KR) |
Assignee: |
HYUNDAI STEEL COMPANY
INCHEON
KR
|
Family ID: |
41570747 |
Appl. No.: |
12/955854 |
Filed: |
November 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/KR2009/004133 |
Jul 24, 2009 |
|
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12955854 |
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Current U.S.
Class: |
266/87 ; 266/259;
266/99 |
Current CPC
Class: |
B21D 37/16 20130101;
C21D 2221/00 20130101; B30B 15/064 20130101; C21D 1/673
20130101 |
Class at
Publication: |
266/87 ; 266/259;
266/99 |
International
Class: |
C21D 11/00 20060101
C21D011/00; C21D 1/673 20060101 C21D001/673 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2008 |
KR |
10-2008-0072979 |
Claims
1. A press hardening die cooling device, comprising: a press
hardening die including upper and lower die portions and configured
to press a steel plate blank; a plurality of cooling water
suppliers spaced apart from each other in the upper and lower die
portions and forming channels through which cooling water flows;
and a cooling water temperature adjuster configured to adjust
temperature of the cooling water supplied to the cooling water
suppliers.
2. The press hardening die cooling device according to claim 1,
wherein the cooling water temperature adjuster includes a
controller configured to operate such that cooling water is
supplied at a higher temperature to one of the plurality of cooling
water suppliers close to a trimming portion of the steel plate
blank than the other cooling water suppliers among the plurality of
cooling suppliers, and wherein the controller includes a heater
configured to heat the cooling water supplied to the cooling water
supplier close to the trimming portion.
3. The press hardening die cooling device according to claim 2,
wherein the controller configured to control the heater to maintain
the temperature of the cooling water supplied to the cooling water
supplier close to the trimming portion between 45 and 80.degree.
C.
4. The press hardening die cooling device according to claim 1,
further comprising a hole formed between the cooling water supplier
close to the trimming portion of the steel plate blank and a steel
plate blank contacting surface.
5. The press hardening die cooling device according to claim 1,
wherein the press hardening die is provided with an insulator.
6. The press hardening die cooling device according to claim 2,
further comprising temperature sensors disposed between the
trimming portion of the steel plate blank and the cooling water
supplier to sense temperature of the press hardening die, and
output sensed signals to the controller.
7. The press hardening die cooling device according to claim 1,
wherein the cooling water temperature adjuster configured to
control temperature of the cooling water such that the trimming
portion of the steel plate blank is changed into a mixed structure
of ferrite, pearlite, and bainite.
8. A press hardening die cooling device, comprising: a press
hardening die including upper and lower die portions provided with
insulators and configured to press a steel plate blank; a plurality
of cooling water suppliers spaced apart from each other in the
upper and lower die portions to be channels through which cooling
water flows; and a cooling water temperature adjuster configured to
adjust temperature of the cooling water supplied to the cooling
water suppliers using temperature sensors disposed in the press
hardening die.
9. A press hardening die cooling device, comprising: a press
hardening die and configured to press a steel plate blank; a
plurality of cooling water suppliers located in the press hardening
die, spaced apart from each other, and configured to form channels
through which cooling water flows; and a cooling temperature
adjuster configured to adjust the cooling rate of a trimming
portion of the steel plate blank such that the trimming portion is
cooled slower than other portion of the steel plate blank.
10. A press hardening die cooling device of claim 9, wherein at
least one of the plurality of cooling water suppliers close to the
trimming portion has a size smaller than the size of another
cooling water supplier.
11. A press hardening die cooling device of claim 9, wherein a
distance between at least one of the plurality of cooling water
suppliers close to the trimming portion and a steel blank contact
surface of the die is greater than a distance between another
cooling water supplier and a steel blank contact surface of the
die.
Description
TECHNICAL FIELD
[0001] The present invention relates to a press hardening die
cooling device, and more particularly, to a press hardening die
cooling device which has a structure improved for adjusting cooling
rate in order to adjust hardness of the surface structure of a
portion that is cut by trimming die of a steel plate blank.
BACKGROUND ART
[0002] In general, a method of manufacturing a high-strength
press-hardened product is to heat a steel material of which
hardenability is improved by adding B, Mo, and Cr etc. at a high
temperature, about 900.degree. C., above an Ac3 transformation
point to be completely changed into an austenite state, and then
hot-forming the steel plate at one time into a product shape with a
press die and rapidly cooling it into martensite structure.
[0003] As well known in the related art, a steel plate is easy to
form, because its ductility is increased when being heated at a
high temperature. Thus, the machinability of a steel plate
manufactured by press hardening is slightly better than that of
typical steel plates for machining and considerably better than
that of high-strength steel.
[0004] Further, a steel plate manufactured by press hardening has
very high strength (above 1,400 MPa) such that it is significantly
advantageous in terms of specific strength, obtained by dividing
yield strength by density, and thus can considerably contribute to
reducing weight of vehicles. Further, the steel plate manufactured
by press hardening is used to manufacture ultra high-strength parts
that are difficult to form, because there is little spring back
after machining.
[0005] It is required to heat a steel plate at about 900.degree. C.
or more for several minutes to transform the steel plate into an
austenite state in press hardening process, and this should be
automated for an efficient process.
[0006] Press hardening includes heating a blank before being
hardened from a wound steel plate coil in a furnace, and carrying
the blank into a press with a robot, and pressing it in the related
art.
[0007] The press includes upper and lower dies of a press hardening
die, cooling water is supplied to cooling water supplier for the
upper and lower dies to harden the surface structure of a steel
plate blank and cools the steel plate blank.
[0008] Steel plate blanks of the related art are cut into a middle
part which is substantially used for a part, and scraps which are
disposed at both sides and are substantially cut by a trimming die
in the post-machining.
[0009] However, the portion to be trimmed by a trimming die of the
related art is hardened by the cooling using a press die described
above. Thus, the trimming die is severely worn in trimming, and
accordingly machinability of the trimming is reduced, work loss is
caused by replacing the trimming die, and productivity
decreases.
DISCLOSURE
Technical Problem
[0010] In order to solve the above problems, the present invention
has been made in an effort to provide a press hardening die cooling
device that facilitates trimming a steel plate blank by applying
cooling processes to a part differently from the other part of the
blank, by using an improved structure of a press hardening die.
Technical Solution
[0011] In order to accomplish the above object, an embodiment of
the present invention provides a press hardening die cooling
device, which includes: a press hardening die including upper and
lower dies and pressing a steel plate blank; a plurality of cooling
water suppliers spaced apart from each other in the upper and lower
dies to be channels through which cooling water flows; and a
cooling water temperature adjuster configured to adjust temperature
of the cooling water supplied to the cooling water suppliers.
[0012] The cooling water temperature adjuster includes a controller
that operates such that cooling water is supplied at a higher
temperature to the cooling water suppliers close to trimming
portions of the steel plate blank than the other cooling water
suppliers in the cooling suppliers, and wherein the controller
includes a heater configured to heat the cooling water supplied to
the cooling water suppliers close to trimming portions.
[0013] The controller controls the heater to maintain the
temperature of the cooling water supplied to the cooling water
suppliers close to the trimming portions between 45 and 80.degree.
C.
[0014] Holes are formed between the cooling water suppliers close
to the trimming portions of the steel plate blank and the contact
surface of the steel plate blank.
[0015] The press hardening die is provided with insulators.
[0016] The press hardening die cooling device further includes
temperature sensors disposed between the trimming portions of the
steel plate blank and the cooling water supplier to sense
temperature of the press hardening die, and outputting sensed
signals to the controller.
[0017] The cooling water temperature adjuster controls temperature
of the cooling water such that the trimming portions of the steel
plate blank changes to a mixed structure of ferrite, pearlite, and
bainite.
[0018] Another embodiment of the present invention provides a press
hardening die cooling device, which includes: a press hardening die
including upper and lower dies provided with insulators therein and
pressing a steel plate blank; a plurality of cooling water
suppliers spaced apart from each other in the upper and lower dies
to be channels through which cooling water flows; and a cooling
water temperature adjuster adjusting temperature of the cooling
water supplied to the cooling water suppliers using temperature
sensors disposed in the press hardening die.
ADVANTAGEOUS EFFECTS
[0019] The present invention provides an apparatus for a press
hardening die which is improved to decrease cooling rate of
trimming portions in pressing a steel plate blank for manufacturing
a part for press hardening. According to the embodiments of the
present invention, it is possible to improve durability and
productivity by reducing wear of the trimming die, because it is
possible to prevent the trimming portion from changing to a
martensite structure having high hardness by decreasing cooling
rate by the cooling water suppliers in the upper and lower dies to
prevent the trimming portions from being rapidly cooled.
DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a view showing the configuration of a first
embodiment of a press hardening die cooling device according to the
present invention.
[0021] FIG. 2 is a perspective view showing a second embodiment of
the present invention.
[0022] FIG. 3 is a view showing the configuration of a third
embodiment of a press hardening die cooling device according to the
present invention.
[0023] FIG. 4 is a view showing the configuration of a fourth
embodiment of a press hardening die cooling device according to the
present invention.
[0024] FIG. 5 is a view showing the configuration of a fifth
embodiment of a press hardening die cooling device according to the
present invention.
[0025] FIG. 6 is a view showing the configuration of a sixth
embodiment of a press hardening die cooling device according to the
present invention.
[0026] FIG. 7 is a graph showing a cooling process to time of a
steel plate blank according to the present invention.
BEST MODE
[0027] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying
drawings.
[0028] Referring to FIG. 1, the first embodiment of a press
hardening die cooling device according to the present invention
includes: a press hardening die P composed of upper and lower dies
10 and 20 equipped with cooling water suppliers 12 and 22 therein
to press a steel plate blank S from the top and the bottom; and a
cooling water temperature adjuster disposed between the cooling
water suppliers 12 and 22 of the upper and lower dies 10 and 20 and
the contact surface of the steel plate blank S to adjust
temperature of cooling water supplied to the steel plate blank
S.
[0029] In detail, the cooling water temperature adjuster is
provided with a controller 100 for supplying cooling water at
different temperatures to the cooling water suppliers 12 and 22,
and the controller 100 includes a heater 150 for heating the
cooling water supplied to the cooling water suppliers 12 and 22
close to trimming portions T1.
[0030] The controller 100 controls the turning on/off of the heater
150 such that the temperature of the cooling water, which is
supplied to the cooling water suppliers 12 and 22 close to the
trimming portions T1, is maintained between 45 and 80.degree. C.
The other cooling suppliers 12 and 22 are supplied with cooling
water at a temperature between 10 and 25.degree. C. which is the
same as in the related art.
[0031] That is, controller 100 operates such that cooing water at
10 to 25.degree. C. is supplied to the cooling water suppliers 12
and 22 close to the middle portion of the steel plate blank S,
which will be a part, and cooling water at 45 to 80.degree. C.
heated by the heater 150 is supplied to the cooling water suppliers
12 and 22 close to the trimming portions T1 located at both
sides.
[0032] In this configuration, adjusting the temperature of the
cooling water between 45 and 80.degree. C. is for transforming the
structure of the trimming portions T1 in the steel plate blank S
into a mixed structure with ferrite, pearlite, and bainite, which
has excellent toughness and ductility, as compared with a
martensite structure.
[0033] The operation of the present invention having this
configuration is described hereafter.
[0034] A press hardening die cooling device according to the
present invention controls cooling rate of the cooling water
suppliers 12 and 22 during the press hardening of the steel plate
blank heated at 900.degree. C. or more through a furnace and
carried into the press hardening die P using a robot in order to
manufacture a press-hardened product such that heat conduction rate
of the trimming portions T1 interfacing each scrap and the middle
portion which will be a product is different from the other
portions of the steel plate blank S.
[0035] For this configuration, the some cooling air suppliers 12
and 22 which are close to the trimming portions T1 among the
cooling water suppliers 12 and 22 disposed in the upper and lower
dies 10 and 20 of the press hardening die P are supplied with
cooling water at a higher temperature than the other portions such
that the cooling rate becomes lower at the trimming portions T1
than the other portions to be trimmed, and accordingly,
hardenability can be more decreased than the other portions of the
steel plate blank S.
[0036] Therefore, the trimming portions T1 have lower cooling rate
than the other portions of the steel plate blank S in pressing, and
thus, the structures become having lower hardness than the other
portions.
[0037] Thereafter, the other portions of the steel plate blank S
except for the portions T1 to be trimmed in trimming process are
change into a martensite structure having high hardness, whereas
the trimming portions are changed into a ferrite+pearlite+bainite
structure, which has lower hardness and better machinability than
the martensite structure.
[0038] In this case, hardenability of the trimming portions T1 is
variable in accordance with cooling water temperature, and for
example, there is a relationship that the cooling rate decreases
when the cooling water temperature increases and the cooling rate
increases when the cooling water temperature decreases.
[0039] Hereinafter, repeated description for the components that
are the same as those in the above embodiment is not provided and
they are given the same reference numeral, in describing the other
embodiments of the present invention.
[0040] On the other hand, FIG. 2 is a view showing a second
embodiment of the present invention, in which holes 210 are formed
through the upper and lower dies, between the cooling water
suppliers 12 and 22 close to the trimming portions T1 and the
contact surface of the steel plate blank S.
[0041] The holes are formed to change the trimming portions T1 of
the steel plate blank S into a mixed structure with
ferrite+pearlite+bainite by reducing the rate of heat conduction to
the cooling water suppliers 12 and 22, as described above.
[0042] That is, heat transferred from the cooling water suppliers
12 and 22 is conducted to the trimming portions T1 through the
holes 210 such that cooling performance of the cooling water
decreases at the portions than the other portions and the trimming
portions T1 of the steel plate blank S are prevented from being
rapidly cooled.
[0043] In this configuration, although the holes 210 are formed at
both of the upper and lower dies 10 and 20, the hole may be formed
only at the upper die or the lower die.
[0044] Further, it is preferable that the hole 210 has a
rectangular or a circular cross section to decrease heat transfer
efficiency.
[0045] FIG. 3 is a view showing the configuration of a third
embodiment of the present invention. In addition to the
configurations of the embodiments described above insulators 300
are vertically disposed in the upper and lower dies 10 and 20 of
the press hardening die P.
[0046] The insulators 300 are vertically arranged to divide the
upper and lower dies of the press hardening die P around the
trimming portions T1.
[0047] This is for making the temperature of the cooling water
supplied to the trimming portions T1 of the steel plate blank S
different from the temperature of the cooling water supplied to the
other portions.
[0048] That is, since the press hardening die P is divided into the
middle portion and both sides by the insulators 300, it is possible
to provide different cooling performance to each portion of the
steel plate blank by supplying cooling water of the cooling water
suppliers 12 and 22 with different temperatures.
[0049] FIG. 4 is a view showing the configuration of a fourth
embodiment of the present invention, which includes the components
of the embodiments described above and further includes temperature
sensors 155 that are disposed in the press hardening die P to sense
the internal temperature of the die and outputs sensed signals to
the controller 100.
[0050] The temperature sensors 155 sense the temperature of the die
in real time such that the heater 150 heats the cooling water and
that temperature of specific portions is increased or maintained
when the temperature of the die is decreased under temperature set
in advance in the controller 100.
[0051] FIG. 5 is a view showing the configuration of a fifth
embodiment of the present invention, in which the diameter of the
cooling water suppliers 12 and 22 close to the trimming portions T1
is set smaller than the diameter of the other cooling water
suppliers 12 and 22.
[0052] Further, FIG. 6 is a view showing the configuration of a
sixth embodiment of the present invention, in which the cooling
water suppliers 12 and 22 close to the trimming portions T1 at both
sides in the press hardening die P are dispose further from the
contact surface of the steel plate blank than the other cooling
water suppliers 12 and 22.
[0053] That is, the cooling water suppliers 12 close to the
trimming portions T1 in the upper die are disposed at a level
higher than the other water suppliers 12 in the upper die, while
the water suppliers 22 close to the trimming portions T1 in the
lower die are disposed at a level lower than the other water
suppliers 22, in the figure.
[0054] Therefore, the fifth and sixth embodiments of the present
invention show that it is possible to make cooling performance of
each portion of the steel plate blank different without making
temperature of the supplied cooling water different.
[0055] That is, the embodiments of the present invention can
prevent the trimming portions from changing to the martensite
structure having high hardness by preventing the trimming portions
T1 of the steel plate blanks S from being rapidly cooled by way of
making the cooling rate of portions different using the cooling
water suppliers 12 and 22 in the upper and lower dies 10 and 20
when pressing the steel plate blanks S.
[0056] Therefore, as shown in FIG. 7, temperature distribution of
the steel plate blank S after the pressing is shown, in which the
section A shows cooling rate at the middle portion of the steel
plate blanks S and the section B shows cooling rate to time at the
trimming portions T1. The cooling rates of the portions are
different in the steel plate blank S. Accordingly, the structure
corresponding to the section A is cooled at a rate of 17 to
24.degree. C. per second from 950.degree. C. to 800.degree. C. and
then hardened by rapid cooling into the martensite structure, and
the structure corresponding to the section B is slowly cooled from
800.degree. C. into the mixed structure.)
* * * * *