U.S. patent application number 12/702367 was filed with the patent office on 2010-09-02 for method for producing a molded sheet metal part from an as-rolled, non-hardenable aluminum alloy.
Invention is credited to Jochen Dorr, Rafael Garcia Gomez, Markus Pellmann.
Application Number | 20100218860 12/702367 |
Document ID | / |
Family ID | 42338593 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100218860 |
Kind Code |
A1 |
Dorr; Jochen ; et
al. |
September 2, 2010 |
Method for producing a molded sheet metal part from an as-rolled,
non-hardenable aluminum alloy
Abstract
Method for producing an open molded sheet metal part from a
non-hardenable aluminum alloy that has the following steps: a) a
sheet is prepared that is made of a non-hardenable aluminum alloy,
the temper of which is H12, H14, H16, H18, H19, H22, H24, H26, H28,
H32, H34, H36 or H38 according to European Standard EN 515:1993 and
that in addition to aluminum includes at least magnesium and where
necessary manganese; b) the aluminum is heated at least locally to
a temperature between 200.degree. C. and 350.degree. C. within a
period of 1 to 60 seconds; c) the heated sheet is placed in a cold
forming die of a forming press and the sheet is formed, creating a
molded sheet metal part.
Inventors: |
Dorr; Jochen; (Bad Driburg,
DE) ; Gomez; Rafael Garcia; (Paderborn, DE) ;
Pellmann; Markus; (Sassenberg, DE) |
Correspondence
Address: |
PRICE HENEVELD COOPER DEWITT & LITTON, LLP
695 KENMOOR, S.E., P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Family ID: |
42338593 |
Appl. No.: |
12/702367 |
Filed: |
February 9, 2010 |
Current U.S.
Class: |
148/695 |
Current CPC
Class: |
C21D 7/02 20130101; C21D
1/34 20130101; C21D 8/04 20130101; C22F 1/04 20130101; C21D 2221/00
20130101; C21D 9/46 20130101 |
Class at
Publication: |
148/695 |
International
Class: |
C22F 1/04 20060101
C22F001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2009 |
DE |
102009008282.4 |
Claims
1. Method for producing an open molded sheet metal part from an
as-rolled, non-hardenable aluminum alloy that has the following
steps: a) preparing a sheet that is made of a non-hardenable
aluminum alloy, the temper of which is H12, H14, H16, H18, H19,
H22, H24, H26, H28, H32, H34, H36 or H38 according to European
Standard EN 515:1993 and that in addition to aluminum includes at
least magnesium and where necessary manganese; b) heating the
aluminum at least locally to a temperature between 200.degree. C.
and 350.degree. C. within a period of 1 to 60 seconds; c) placing
the heated sheet in a cold forming die of a forming press and
forming the sheet, creating a molded sheet metal part.
2. Method in accordance with claim 1, characterized in that the
sheet is heated to a temperature between 200.degree. C. and
240.degree. C. in a period of 1 to 10 seconds.
3. Method in accordance with claim 2, characterized in that the
sheet is heated to different temperatures by area prior to
forming.
4. Method in accordance with claim 3, characterized in that the
sheet is heated resistively, conductively, or capacitively.
5. Method in accordance with claim 3, characterized in that areas
of the sheet are heated for different lengths of time.
6. Method in accordance with claim 5, characterized in that the
sheet is heated resistively, conductively, or capacitively.
7. Method in accordance with claim 6, characterized in that the
forming die has a cavity that has at least one area that is
heated.
8. Method in accordance with claim 2, characterized in that areas
of the sheet are heated for different lengths of time.
9. Method in accordance with claim 8, characterized in that the
sheet is heated resistively, conductively, or capacitively.
10. Method in accordance with claim 2, characterized in that the
sheet is heated resistively, conductively, or capacitively.
11. Method in accordance with claim 2, characterized in that the
forming die has a cavity with at least one area that is heated.
12. Method in accordance with claim I, characterized in that the
sheet is heated to different temperatures by area prior to
forming.
13. Method in accordance with claim 12, characterized in that areas
of the sheet are heated for different lengths of time.
14. Method in accordance with claim 13, characterized in that the
sheet is heated resistively, conductively, or capacitively.
15. Method in accordance with claim 12, characterized in that the
sheet is heated resistively, conductively, or capacitively.
16. Method in accordance with claim 12, characterized in that the
forming die has a cavity with at least one area that is heated.
17. Method in accordance with claim 1, characterized in that areas
of the sheet are heated for different lengths of time.
18. Method in accordance with claim 17, characterized in that the
sheet is heated resistively, conductively, or capacitively.
19. Method in accordance with claim 1, characterized in that the
sheet is heated resistively, conductively, or capacitively.
20. Method in accordance with claim 1, characterized in that the
forming die has a cavity with at least one area that is heated.
Description
CLAIM OF PRIORITY
[0001] Applicants hereby claim the priority benefits under the
provisions of 35 U.S.C. .sctn.119, basing said claim of priority on
German Patent Application Serial No. 102009008282.4, filed Feb. 10,
2009.
FIELD OF THE INVENTION
[0002] The invention relates to a method for producing a molded
sheet metal part from an as-rolled, non-hardenable aluminum
alloy.
BACKGROUND OF THE INVENTION
[0003] Producing highly-stressed vehicle components from aluminum
sheet is known. Primarily hardenable alloys are used for this.
Normally production consists of pre-forming the low-strength
aluminum sheet and then aging it to obtain increased strength.
[0004] Forming is the only way to increase the strength of those
aluminum alloys in which an increase in hardness cannot be attained
using a thermal treatment (natural or artificial aging). In order
to be able to produce complex geometries from sheets of these
alloys, as well, they are generally shaped in a soft temper, like
the hardenable alloys. This means that these non-hardenable
aluminum alloys are for instance soft-annealed in advance.
[0005] It is a disadvantage that the strength of pressed parts that
are produced by shaping these soft-annealed, non-hardenable
aluminum alloys increases considerably only in areas that have
undergone significant shaping. The result is that there is
relatively limited potential in lightweight design for using shaped
parts that are made of the inexpensive, non-hardenable aluminum
alloys. This is also the reason that non-hardenable aluminum alloys
are used predominantly as thick-walled components in the chassis.
Non-hardenable aluminum alloys are generally distinguished by very
good resistance to corrosion. In addition, they are frequently used
in components that are not subject to high stress, but in
applications in which the focus is not specifically on lightweight
design.
[0006] There must be an effort to save weight in all components in
order to satisfy current and future requirements for motor vehicles
to optimize weight. This applies to components made of
non-hardenable aluminum alloys, as well. These aluminum alloys are
available as high-strength and higher-strength sheets that are
produced by cold rolling or by cold rolling with partial annealing.
However, in the past it has not been possible to produce complex
components from these commercially readily available semi-finished
products, even though this would be very attractive economically
due to the potential weight reduction and savings in materials.
SUMMARY OF THE INVENTION
[0007] The underlying object of the invention is therefore to
provide an option for producing a high-strength component that is
complex in terms of shaping from sheets that comprise as-roiled,
non-hardenable aluminum alloys.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0008] This object is attained in a method having the features of
patent claim 1. One essential step of the invention is that the
temperature range at which the sheet is to be heated is less than
300.degree. C., in particular is less than 250.degree. C. This is
because of the fact that most of the strength is lost after heating
in the furnace when conventional heating methods to temperatures of
about 300.degree. C. are used. However, it has been found that both
the recrystallization and the recovery of the structure are a
function of a temperature threshold. Therefore the invention
provides that an as-rolled, non-hardenable aluminum sheet is heated
at an extremely high speed. The sheet temper is H12, H14, H16, H18,
H19, H22, H24, H26, H28, H32, H34, H36 or H38 according to European
Standard EN515:1993, the disclosure of which is included herein by
reference. In addition to aluminum, the sheet includes at least
magnesium and where necessary manganese as alloy components. Then
the sheet is shaped so rapidly in a cold shaping tool that most of
the strength is retained in the entire component. To this end the
sheet must be heated at least locally to a temperature between
200.degree. C. and 250.degree. C., preferably 240.degree. C.,
within a period of 1 to 60 seconds. This heating period is
preferably significantly shorter and is especially a period of 1 to
10 seconds.
[0009] European Standard EN 515 establishes how to designate basic
tempers for aluminum semi-finished products. The letter H means
strain hardened. This designation applies for products that are
subjected to cold deformation or a combination of cold deformation
and recovery annealing and stabilization after soft annealing (or
after hot forming) to assure the established mechanical properties.
Two digits follow the letter H; the first identifies the type of
thermal treatment, and the second identifies the degree of strain
hardening.
[0010] Cold deformation includes plastic deformation of a metal at
a temperature and speed that leads to strain hardening. Strain
hardening is the change in the metal structure due to cold
deformation, which leads to increased strength and hardness,
reducing formability.
[0011] H1x means only cold-worked products that are strain
hardened, without additional thermal treatment, to attain the
desired strength.
[0012] H2x means cold-worked and partially annealed. It applies to
products that are strain hardened beyond the desired final strength
and then are reduced in strength to the desired strength level by
partial annealing.
[0013] H3x means cold-worked and stabilized and applies to
strain-hardened products whose mechanical properties are stabilized
either by a low temperature thermal treatment or as a result of
heat introduced during fabrication. Stabilization improves
formability in general. This designation applies only to alloys
that lose strength without stabilization by being stored at room
temperature.
[0014] The second digit after the H indicates the final degree of
strain hardening, which is characterized by the minimum value of
the tensile strength. The number 8 is associated with the hardest
tempers that are normally produced. The number 9 identifies tempers
whose minimum tensile strength is about 10 MPa or more above the
H8x tempers. The numbers 2, 4, and 6 identify intermediate tempers.
Consequently, H12 means strain hardened--1/4 hard, H14 means strain
hardened--1/2 hard, H16 means strain hardened--3/4 hard, and H18
means strain hardened--4/4 hard (fully hardened). Therefore strain
hardened and partially annealed materials are categorized in
tempers H22/24/26/28 and strain hardened and stabilized materials
are categorized in tempers H32/34/36/38. Overall, therefore, sheets
that are as-rolled and thus have been strain-hardened by rolling
should be used.
[0015] The advantage of the invention is that a relatively complex
component can be fabricated that is made of an as-rolled,
non-hardenable aluminum alloy and that has high strength overall or
in parts. What is particularly noteworthy is that the parts that
have high strength do not depend on the forming and the degree of
forming. The result is an alternative fabrication compared to
hardenable alloys that are associated with high production costs
due to lengthy thermal treatment for up to 24 hours.
[0016] In the context of this invention, an open molded sheet metal
part is an element manufactured from a sheet metal plate using
molding, that is, from an essentially flat start condition. The
starting material has been strain hardened by rolling to a specific
target value. An open molded sheet metal part in the context of the
invention is not a hollow profile.
[0017] In the framework of the invention, the as-rolled,
non-hardenable aluminum sheet should preferably be completely
heated and formed. However, partial thermal forming, in which
different areas of the sheet metal are heated to different
temperatures, is also possible. It is also possible for the sheet
metal to have areas that have been heated for different lengths of
time, whether to attain different target temperatures or to use the
length of heating time to influence the local deformation
properties of the sheet metal, and thus its tensile strengths.
[0018] The sheet metal can preferably be heated resistively,
conductively, or capacitively.
[0019] With the inventive method it is also possible to create
components that should have high strength only in certain areas, it
being possible for the components to have a lower strength in other
areas, with improved strain values at the same time. The goal
pursued is to create a component that is in general better than a
completely hard component. It will especially have better
properties in terms of deformation behavior in an accident, whether
with respect to energy absorption or savings in weight.
[0020] In the framework of the invention it is also possible to
continue heating the sheet by area for different lengths of time
and to different temperatures during the forming process. To this
end the forming die can have a cavity with at least one area that
is heated. Locations in the die that are to be heated alternatively
or additionally can also be provided cooled areas. The heated areas
in the forming die provide the opportunity to keep the die at a
higher temperature within an additional period in that a specific
area is first heated continuously for a longer period.
[0021] In multi-stage forming, it is also possible to provide
cavities that are partially heated in additional die steps. In the
same manner, in a process step that follows the forming it is
possible to have temporally extended heating using an oven that is
active at times or using an inductor. However, it is considered
useful to have the extended heating time or higher temperature
prior to the forming and not following the forming.
* * * * *