U.S. patent application number 15/527333 was filed with the patent office on 2017-11-09 for method for hot or warm forming a workpiece and production plant for hot or warm forming a workpiece.
This patent application is currently assigned to ThyssenKrupp Steel Europe AG. The applicant listed for this patent is thyssenKrupp AG, ThyssenKrupp Steel Europe AG. Invention is credited to Janko Banik, Sascha Sikora.
Application Number | 20170321295 15/527333 |
Document ID | / |
Family ID | 54542226 |
Filed Date | 2017-11-09 |
United States Patent
Application |
20170321295 |
Kind Code |
A1 |
Banik; Janko ; et
al. |
November 9, 2017 |
METHOD FOR HOT OR WARM FORMING A WORKPIECE AND PRODUCTION PLANT FOR
HOT OR WARM FORMING A WORKPIECE
Abstract
A method for hot or warm forming a workpiece may comprise
providing the workpiece to be formed, at least partially
pretreating the workpiece, at least partially heating the workpiece
to a target temperature, and at least partially forming and/or
hardening the workpiece. Furthermore, the workpiece may be at least
partially cleaned in a cleaning step between the pretreating and
the heating of the workpiece. In some examples, at least partially
cleaning the workpiece may involve brushing the workpiece, using a
cleaning bath, or heating the workpiece with a first burner to a
cleaning temperature. Further, one or more burners used to heat or
clean the workpiece may be operated with a fuel gas and/or an
oxygen-containing gas.
Inventors: |
Banik; Janko; (Altena,
DE) ; Sikora; Sascha; (Lunen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ThyssenKrupp Steel Europe AG
thyssenKrupp AG |
Duisburg
Essen |
|
DE
DE |
|
|
Assignee: |
ThyssenKrupp Steel Europe
AG
Duisburg
DE
thyssenKrupp AG
Essen
DE
|
Family ID: |
54542226 |
Appl. No.: |
15/527333 |
Filed: |
November 5, 2015 |
PCT Filed: |
November 5, 2015 |
PCT NO: |
PCT/EP2015/075809 |
371 Date: |
May 17, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 1/18 20130101; C21D
1/72 20130101; C21D 9/46 20130101; C23C 22/73 20130101 |
International
Class: |
C21D 9/46 20060101
C21D009/46; C21D 1/18 20060101 C21D001/18; C21D 1/72 20060101
C21D001/72; C23C 22/73 20060101 C23C022/73 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2014 |
DE |
10 2014 116 950.6 |
Claims
1.-15. (canceled)
16. A method for hot or warm forming a workpiece, the method
comprising: providing the workpiece; at least partially pretreating
the workpiece; at least partially cleaning the workpiece that has
been at least partially pretreated; at least partially heating the
workpiece that has been at least partially cleaned to a target
temperature in a heating station; and at least partially forming
and/or hardening the workpiece.
17. The method of claim 16 wherein at least partially cleaning the
workpiece comprises at least partially treating the workpiece
chemically, mechanically, and/or thermally.
18. The method of claim 16 wherein at least partially cleaning the
workpiece comprises cleaning at least a portion of the workpiece in
a cleaning bath.
19. The method of claim 16 wherein at least partially cleaning the
workpiece comprises brushing the workpiece.
20. The method of claim 16 further comprising transporting the
workpiece as the workpiece is at least partially cleaned.
21. The method of claim 16 further comprising transporting the
workpiece from a cleaning station to the heating station after the
workpiece is at least partially cleaned and before the workpiece is
at least partially heated.
22. The method of claim 16 wherein at least partially cleaning the
workpiece comprises heating the workpiece with a first burner to a
cleaning temperature.
23. The method of claim 22 further comprising heating the workpiece
with a second burner to the target temperature.
24. The method of claim 23 wherein at least one of the first burner
or the second burner is operated with a fuel gas and an
oxygen-containing gas.
25. The method of claim 16 further comprising coating the workpiece
with at least one of a protective material or a corrosion
protection oil.
26. The method of claim 16 wherein at least partially forming
and/or hardening the workpiece comprises positioning the workpiece
in at least one of a forming die or a hardening die.
27. The method of claim 16 wherein the workpiece is a flat metal
sheet.
28. A production plant for hot or warm forming a workpiece by at
least partially pretreating the workpiece, at least partially
cleaning the workpiece that has been at least partially pretreated,
at least partially heating the workpiece that has been at least
partially cleaned to a target temperature, and at least partially
forming and/or hardening the workpiece, wherein the production
plant comprises: a cleaning station for at least partially cleaning
the workpiece; and a heating station for at least partially heating
the workpiece to the target temperature.
29. The production plant of claim 28 further comprising a conveying
mechanism.
30. The production plant of claim 28 wherein the cleaning station
is structurally separate from the heating station.
Description
PRIOR ART
[0001] The present invention concerns a method for hot or warm
forming of a workpiece and a production plant for hot or warm
forming of a workpiece.
[0002] In hot and warm forming, uncoated or coated materials are
generally used. To avoid corrosion during transport, a
semifabricated piece in the form of a coil or a sheet can be
provided partially, preferably entirely, with a corrosion
protection oil or with lubricants. In addition, a contamination
with dust or the like, especially in a coil or sheet warehouse, can
likewise hardly be avoided as a rule.
[0003] Caused by thermal processes which occur upon reaching the
desired temperature for the tempering process, a thermal
decomposition of the substances which have been deposited on the
semifabricated piece occurs. As a result of this thermal
decomposition, contaminants remain on the semifabricated piece,
which in turn reduce the quality of the fabricated semifabricated
piece. A mechanical cleaning, such as by shot blasting, cannot
always entirely remove the residues which occur, or it may in
particular impair semifabricated pieces which are coated.
Furthermore, large oil residues, such as those due to a large oil
film, may lead to an intensified hydrogen absorption in the
material during the processing of the semifinished piece. This may
result in material embrittlement on account of the high strength.
In the case of a micro-oiling, this behavior is not found, but then
no adequate corrosion protection can be assured.
DISCLOSURE OF THE INVENTION
[0004] One object of the present invention is to provide a method
for hot or warm forming of a workpiece with which the quality of
the piece fabricated by the hot or warm forming is further improved
beyond that of the prior art.
[0005] The present invention solves the object by a method for hot
or warm forming of a workpiece, comprising the following method
steps:
providing of the workpiece, at least partial pretreating of the
workpiece, at least partial heating of the workpiece to a target
temperature in a heating station and at least partial forming
and/or hardening of the workpiece, wherein the workpiece is at
least partially cleaned in a cleaning step between the pretreating
and the heating of the workpiece.
[0006] As compared to the prior art, the workpiece is cleaned after
the pretreating and before the heating for the forming and/or
hardening and in particular is thereby freed of residues which have
become deposited due to the pretreatment on the workpiece. In this
way, the quality of the part fabricated after the forming of the
workpiece is improved, since the likelihood of a depositing of
contaminants which form from the residues during the heating of the
workpiece and thus the likelihood of a permanent impairment of the
workpiece is reduced. Furthermore, other contaminations such as
dust can be removed from the workpiece in the cleaning step.
[0007] Preferably, it is provided that the cleaning step is done
immediately before the heating. It is furthermore preferably
provided that the workpiece as a finished part after the forming
and/or hardening is a structural or chassis part of a motor
vehicle. In particular, the workpiece is provided as a sheet metal
piece, especially a flat metal sheet (direct hot forming) or a
formed part having practically its final geometry (indirect hot
forming), and the pretreatment is at least part of the
manufacturing process for the sheet metal piece. Furthermore, it is
preferably provided that the partial region of the workpiece which
is supposed to be heated during the heating to the target
temperature, preferably the entire workpiece, is specifically
cleaned in the cleaning step. But it is also conceivable to clean
specifically those partial regions of the workpiece for which an
improved surface quality is desired on the finished part.
Advantageous embodiments and modifications of the invention will be
found in the dependent claims and in the specification making
reference to the drawings.
[0008] According to a further embodiment of the present invention,
it is provided that the workpiece in the cleaning step is at least
partially chemically, mechanically and/or thermally treated. The
chosen cleaning method is thereby preferably adapted to the
workpiece such that the cleaning leaves the properties of the
workpiece substantially unimpaired. In this way, one can
advantageously ensure that no steps are taken with the cleaning
step which endanger the quality of the subsequently fabricated
part.
[0009] According to a further embodiment of the present invention,
it is provided that the workpiece in the cleaning step is at least
partially cleaned in a cleaning bath. During this chemical
treatment of the workpiece, the contaminants are advantageously
bound in a liquid of the cleaning bath. It is conceivable that the
liquid in the cleaning bath will be exchanged by bringing the
liquid into the cleaning bath and draining it out once more, for
example it is pumped in a liquid circuit into the cleaning bath and
again pumped out from the cleaning bath. Thanks to the binding of
the contaminants to the liquid, it is advantageously prevented that
the contaminants spread via the air and become deposited for
example on plant parts. Furthermore, it is conceivable that the wet
workpiece will be dried, for example with hot air, before the
heating.
[0010] According to a further embodiment of the present invention,
it is provided that the workpiece is in the cleaning step brushed.
For this mechanical treatment in the cleaning step, it is
conceivable that the workpiece is brought into contact with the
brush and the workpiece is moved in the longitudinal direction,
while the brush extends substantially along the transverse
direction of the workpiece. In this way, the cleaning step can be
advantageously integrated in the transport of the workpiece to the
heating station, without the cleaning step occasioning any
significant delay in the hot or warm forming. It is also
conceivable that the brush or a system of brushes are arranged at
the entrance to the heating station and in this way the cleaning of
the workpiece is provided immediately before the heating.
Alternatively, it is conceivable that the workpiece is cleaned
manually. In manual cleaning with a brush, residues visible to the
naked eye can be advantageously removed without major additional
effort.
[0011] According to a further embodiment of the present invention,
it is provided that the workpiece in the cleaning step is heated by
a burner to a cleaning temperature. Preferably the workpiece is
heated by one or more burners, preferably on both sides, especially
all around and uniformly. It is conceivable that the burner is
moved during the heating along the transverse direction or the
longitudinal direction of the workpiece, preferably in oscillating
manner. Thanks to the heating already done during the cleaning of
the workpiece, relatively little heating energy is required to
attain the target temperature in the heating station. Preferably
the cleaning station with its burner is physically separate from
the heating station in order to prevent contaminants which are
present in the exhaust gases occurring during the heating to the
cleaning temperature from depositing on the plant parts during the
heating to the target temperature. But it is also conceivable that
the cleaning step is carried out in the heating station by the
burner responsible for the heating first heating the workpiece to
the cleaning temperature and then to the target temperature, the
target temperature being greater than the cleaning temperature. It
is preferably provided that the air surrounding the workpiece is
drawn off during the heating of the workpiece to a cleaning
temperature, for example by means of an exhaust hood, in order to
carry away the contaminants.
[0012] According to a further embodiment of the present invention,
it is provided that the workpiece is transported or moved during
the cleaning step. In this way, the cleaning step can be
advantageously integrated in the hot or warm forming of the
workpiece such that potential delays due to the cleaning step are
kept as short as possible. If the cleaning step involves a thermal
treatment, it is conceivable that the workpiece is moved by a
burner belt along the conveyance direction past a burner, with the
burner heating the workpiece as it moves past it. In particular,
the workpiece is moved with a conveying mechanism along a
conveyance direction and in this process it passes in succession
through the cleaning station, the heating station, and reaches the
forming and/or hardening die.
[0013] According to a further embodiment of the present invention,
it is provided that the workpiece is transported from a cleaning
station to a heating station between the cleaning step and the
heating step. In the case of thermal cleaning, it is preferably
provided that the transport path is covered in a shortest possible
time in order to prevent the workpiece from cooling down again. In
particular, it is conceivable that the conveying mechanism
comprises heating elements which ensure that the workpiece
basically maintains its cleaning temperature. Preferably, the
workpiece is transported such that the workpiece does not become
polluted or contaminated once more. In particular, the workpiece is
moved with a conveying mechanism along a conveyance direction and
thereby passes in succession through the cleaning station, the
heating station, and reaches the forming and/or hardening die.
[0014] According to a further embodiment of the present invention,
it is provided that the workpiece is heated during the heating for
the forming and/or hardening with an additional burner to the
target temperature. Preferably, the target temperature chosen is a
temperature between 600.degree. C. and 900.degree. C. If a
manganese-boron steel material is used preferably, it is preferably
provided that the target temperature is reached above AC3, in order
to transform the microstructure completely into austenite. If the
target temperature lies below AC3 and above AC1, a mixed
microstructure of austenite and ferrite is obtained. For example,
it is provided that the speed with which the workpiece is heated to
the cleaning temperature when using a burner is greater than the
speed with which the workpiece is heated to the target temperature,
especially when using a radiant furnace.
[0015] According to a further embodiment of the present invention,
it is provided that the workpiece is coated with a protective
material and/or in particular it is coated at least partially with
a corrosion protection oil in order to prevent corrosion during
transport.
[0016] According to a further embodiment of the present invention,
it is provided that the burner and/or the additional burner is
operated with a fuel gas and an oxygen-containing gas. Preferably,
the heating power of the burner and/or the additional burner is
adjusted by the mix ratio of the fuel gas and the oxygen-containing
gas. In particular, an oxygen content is used to establish the
maximum temperature in a burning flame of the burner and/or the
additional burner. It is provided for example that a technical
oxygen mixture is supplied to the additional burner wherein the
oxygen content is preferably greater than 70% or especially
preferably greater than 90%. Furthermore, it is provided that, in
order to reach the target temperature with a desired speed at which
the workpiece is heated, the distance between burner and workpiece,
the oxygen content, and/or a conveying speed of the workpiece being
transported along the conveyance direction are adjusted
accordingly.
[0017] According to a further embodiment of the present invention,
it is provided that the workpiece is arranged in a
forming/hardening die for the forming and/or hardening. Preferably,
the forming/hardening die is at least partially cooled and thereby
advantageously ensures, for example, a partial hardening of the
workpiece.
[0018] According to a further embodiment of the present invention,
it is provided that the workpiece used is a flat metal sheet. For
example, the workpiece is a workpiece fabricated substantially from
a manganese-boron steel, especially 22MnB5, or it is a flat metal
sheet with higher carbon content.
[0019] Another subject matter of the present invention is a
production plant for hot or warm forming of a workpiece, especially
for carrying out a method according to the invention, wherein the
production plant comprises a cleaning station for cleaning a
workpiece and a heating station for heating the cleaned
workpiece.
[0020] As compared to the prior art, the production plant according
to the invention has the advantage that, thanks to the cleaning
station, it can be ensured that possible residues from a
pretreatment of the workpiece are removed and thus the quantity of
potential contaminants which might impair the quality of the
subsequently fabricated part is reduced in advantageous manner.
[0021] According to a further embodiment of the present invention,
it is provided that the production plant comprises a conveying
mechanism. With the conveying mechanism, the workpiece can be
advantageously transported through the cleaning station and the
heating station to the forming/hardening die. It is conceivable
that the conveying mechanism comprises conveying rollers.
[0022] According to a further embodiment of the present invention,
it is provided that the cleaning station is structurally separate
from the heating station. In this way, it can be advantageously
ensured that the contaminants loosened by the heating of the
workpiece to the cleaning temperature are distributed through the
air and then become deposited on the plant parts of the heating
station.
[0023] Further details, features and benefits of the invention will
emerge from the drawings as well as the following specification of
preferred embodiments with the aid of the drawings. The drawings
only illustrate sample embodiments of the invention which do not
limit the notions of the invention.
BRIEF DESCRIPTION OF THE FIGURES
[0024] FIGS. 1a to 1d show a method for hot or warm forming of a
workpiece according to a sample embodiment of the present
invention.
EMBODIMENTS OF THE INVENTION
[0025] In the various figures, the same parts are always provided
with the same reference number and therefore as a rule will
respectively only be mentioned or designated once.
[0026] FIGS. 1a to 1d represent a method for hot or warm forming of
a workpiece 1 according to a sample embodiment of the present
invention. For example, this involves a structural or chassis part
of a motor vehicle, the workpiece 1 being provided as a
semifabricated part, especially in the form of a tailored rolled
blank or a metal sheet as shown in FIG. 1. The workpiece 1
consists, for example, of a material fabricated at least partially
from a boron-manganese steel, especially 22MnB5. Thanks to the hot
or warm forming, it is preferably provided that the workpiece 1 is
converted into its final form as a component part. In order not to
influence the properties and/or the form of the component
fabricated afterwards, the workpiece 1 is subjected to a
pretreatment. One example of such a pretreatment is the coating of
the workpiece 1 with a corrosion protection oil or with a lubricant
in order to prevent corrosion during the transport of the
workpiece. Another example of the pretreatment is the application
of a cutting oil to the workpiece 1 in order to facilitate a
possible cutting of the sheet to size in advance of the hot or warm
forming. Due to the pretreatment and other external circumstances,
residues remain behind on the workpiece 1, such as those of the
corrosion protection oil, the lubricant and/or the cutting oil.
Upon heating of the workpiece 1 required for the hot or warm
forming, these residues as contaminants would result in damage or
impairment of the finished part, for example in the form of a
material embrittlement. In order to avoid such impairment, it is
provided that the pretreated workpiece 1 is cleaned, preferably
directly before the heating of the workpiece 1 in a heating station
20, in a cleaning step. Preferably the cleaning step begins 60
seconds, preferably 20 seconds and especially preferably 5 seconds
before the heating of the workpiece 1.
[0027] As an example of a cleaning step, the embodiment in FIGS. 1a
to 1d shows in FIG. 1b a thermal treatment in a cleaning station
10. In the present embodiment, the cleaning station 10 comprises a
burner belt or roller conveyor 4, arranged underneath the workpiece
1 being delivered by the burner belt or roller conveyor 4.
Furthermore, the cleaning station 10 preferably comprises a burner
2, which is arranged above and/or beneath the transportable
workpiece 1. It is furthermore provided that the burner 2 heats the
workpiece 1 to a cleaning temperature. For this, the burner 2 is
operated in particular with a mixture of a burner gas and an
oxygen-containing gas. Furthermore, when using a burner 2 for
heating the workpiece 1 to the cleaning temperature, a burner flame
3 occurs which makes direct contact with the workpiece 1 in the
cleaning station 10, for example, or which is held at a distance
from the workpiece. In particular, the burner belt or roller
conveyor 4 has a recess 6 in one position so that the burner flame
3 can heat the workpiece 1 unhindered. Furthermore, it is provided
that the workpiece 1 is heated on both sides by one burner 2
apiece, in order to free as much of the surface of the workpiece 1
as possible from residues. It is conceivable that the burner 2 is
moved along a direction running perpendicular to a conveyance
direction of the burner belt or roller conveyor 4, preferably in
oscillating manner, in order to realize by this motion the heating
along a transverse dimension of the workpiece 1. In particular, it
is conceivable that the cleaning temperature is adjusted or
realized by the determination of a conveyance speed with which the
workpiece 1 is delivered by the burner belt or roller conveyor 4,
the determination of a distance of the burner 2 from the workpiece
1 and/or by the determination of an oxygen content of the
oxygen-containing gas mixed in with the fuel gas. Furthermore, it
is preferably provided that the burner flame 3 of the burner 2 in
the cleaning station 10 heats the workpiece 1 homogeneously, i.e.,
uniformly along the surface. Furthermore, it is conceivable that
the cleaning station 10 comprises an exhaust air system in order to
carry away the pollution gases arising during the thermal treatment
by the exhaust air system. In this way, it is possible to prevent
the pollutants contained in the pollution gas from being deposited
on the plant parts of the cleaning station 10. In order to further
prevent the pollutants contained in the pollution gas from being
deposited on plant parts which are situated for example in a
heating station 20, the cleaning station 10 in the depicted
embodiment is structurally separate from the heating station 20, as
shown in FIG. 1c.
[0028] FIG. 1c shows a heating station 20 in the form of a furnace
5, the workpiece 1 being arranged for the heating inside the
preferably enclosed furnace 5. In particular, it is provided that
the target temperature is greater than the cleaning temperature.
Furthermore, it is provided that the workpiece 1 is heated in the
heating station 20 with an additional burner or by radiant heating,
the additional burner being operated preferably with a mixture of a
fuel gas and an oxygen-containing gas. In particular, the
additional burner in the heating station 20 is operated with a
technical-grade oxygen whose oxygen content is preferably greater
than 75%, especially preferably greater than 90%. For example, the
heating in the heating station 20 can be used to adjust material
properties of the component fabricated afterwards. For example, the
workpiece 1 is specifically heated in at least a first region to a
temperature below AC3, especially below AC1, in order to avoid a
complete austenitization and/or at least in a second region to a
temperature above AC3, in order to bring about an austenitization.
It is also conceivable for the workpiece 1 to be precoated after
the cleaning step and before the heating in order to ensure by this
precoating the formation of an alloy layer on the surface of the
workpiece 1. Furthermore, it is provided that the cleaning station
10 is connected to the heating station 20 via a conveying mechanism
4. In particular, the cleaned workpiece 1 is delivered by the
conveying mechanism 4 to the furnace 5.
[0029] After the heating of the cleaned workpiece 1 it is provided
that the workpiece 1 is placed in a preferably cooled forming
and/or hardening die 30 and formed and/or hardened therein, as
shown in FIG. 1d. In particular, the forming and/or hardening die
30 comprises a mold which is adapted to the component to be
fabricated. Furthermore, it is conceivable that the conveying
mechanism delivers the workpiece 1 along the conveyance direction
in a production plant through the cleaning station 10 and the
heating station 20 to the forming and/or hardening die 30.
LIST OF REFERENCE NUMBERS
[0030] 1 Workpiece [0031] 2 Burner [0032] 3 Burner flame [0033] 4
Conveying mechanism, burner belt, roller conveyor [0034] 5 Furnace
[0035] 6 Recess [0036] 10 Cleaning station [0037] 20 Heating
station [0038] 30 Forming and/or hardening die
* * * * *