EP1059363B2 - Method for process integrated heat treatment - Google Patents

Abstract

Production of cold-formed components made of a hardenable aluminum material comprises producing an aluminum strip or sheet, positioning the strip or sheet, heat treating, and cold forming. Cold forming is carried out shortly after heat treatment. Preferred Process: The heat treatment is carried out by calcining and quenching the aluminum strip or sheet. The aluminum strip or sheet has a width of up to 1000 mm.

Description

The invention relates to a method for producing cold-formed components made of a hardenable aluminum material, in which a process-integrated heat treatment is carried out. Curable aluminum materials, such as Al-Mg-Cu, Al-Mg-Si, Al-Zn-Mg, Al-Cu-Mg or comparable alloys, are preferably used for the production of cold-formed, in particular deep-drawn components. In this case, curable alloys have particular advantages with respect to the achievable by heat strength strengths. For example, body parts such as hoods, doors, etc., which have been made of an Al-Cu-Mg or Al-Mg-Si alloy, have been found to be useful in the automotive field. The strength of the components produced from these alloys can be increased, for example, by the heat applied when applying a baking finish ("bake hardening").

Conventionally, an aluminum strip produced by successive hot and cold rolling of a cast aluminum slab is used to produce cold-worked aluminum components. Depending on the respective state of the aluminum strip desired by the end user, a heat treatment is carried out downstream of the rolling process, which comprises annealing the strip in the continuous furnace.

Such a method is for example in the German patent application DE 196 19 034 A1 been described. In this known method, the aluminum strip is annealed prior to its transformation into a component in order to improve the formability of the aluminum material. The heat treatment in question is preferably carried out by means of an inductively operating heating device. With such a device can be in a relatively short time large amounts of heat in the glowing material bring.

In connection with the processing of non-hardenable aluminum alloys, it is from the German patent application DE AS 1 087 815 also known, soft annealed from the aluminum strip in question cut blanks before they are formed into moldings.

The different delivery conditions of aluminum strips are, for example, in aluminum headquarters: aluminum pocketbook, aluminum-Verlag Dusseldorf, 1974, p. 989 et seq.

The furnaces used for carrying out generic methods for the production of components made of thermosetting aluminum alloys must be designed so that they can be annealed bands of different width and thickness. On the one hand, this entails high investment costs in the construction and operation of such furnaces. On the other hand, in practice, the problem is not only to glow wide, thin bands, but also narrow bands with a greater thickness. This makes it difficult to design a continuous furnace, taking into account the desired capacity utilization, to cope with any heating task.

The described production of the aluminum strip usually takes place in a rolling mill. The processor, in which the component to be produced is produced from the aluminum material by cold forming, receives aluminum strips or sheets from the rolling mill. Subsequently, this material is usually stored at the processor for a certain time before it is fed to cold forming. The bearing has the function of a buffer, which ensures that there is always a sufficient amount of material available for processing.

A problem with the storage of aluminum strips made of hardenable materials of the type described above is that with strips leaving the mill in the annealed and quenched state, this state is not stable. Thus, immediately after the completion of the heat treatment, a process called "cold curing" sets in, in the course of which fine, metastable material phases are formed in increasing amounts, by which the deformability of the material is impaired. Therefore, aluminum strips must be cold-worked within certain time limits, for example at the latest after three months, but ideally within 14 days, after their production. After this time, the bands harden so much that their trouble-free processing is no longer guaranteed. The limited durability of the aluminum strips introduces logistical problems for the processor and the danger that, in the event of a breakdown, larger quantities of the aluminum tapes kept in stock become unusable.

The invention has for its object to provide a method for producing cold-formed components made of hardenable aluminum materials, in which the processability of the aluminum strip used is independent of the storage time.

This object is achieved by a method for producing cold-formed components made of a hardenable aluminum material with the features of claim 1. The heat treatment usually includes annealing and quenching the aluminum strip or sheet.

In contrast to the conventional procedure, the invention provides for the heat treatment of the aluminum strips to be carried out only after storage shortly before the cold forming. Since, according to the invention, there is only a small amount of time between the heat treatment and the cold forming, the process of cold curing can no longer be used to any appreciable extent. The aluminum strip is thus in its entry into the cold forming in an optimal deformation for the structure state, in which it has a low yield strength, a favorable yield ratio and high elongation values.

Another essential advantage of the invention is that it is no longer necessary to subject the rolled aluminum strip before its storage in the warehouse of the processor of a comprehensive annealing. Thus, the investments of considerable height required for the conventional procedure can be saved for the construction and operation of the furnaces used for annealing. Instead, small, compact and thus inexpensive devices for heat treatment at the processor can be set up. These devices can be easily optimized with regard to the respective heating task. The processor is thus independent of shelf life and can consume the required aluminum strip at any time according to the actual needs. Capacity bottlenecks or insufficient capacity utilization of the devices used to process the aluminum strips or sheets can be avoided.

At the same time, a starting material is available for the production of the end products, which is in an optimal state with regard to its processibility. In this way, not only the investment and operating costs are reduced by the inventive method in the processing of aluminum strips or aluminum sheets and significantly improved utilization efficiency, but also the quality of the products produced.

Particularly suitable is the inventive method for the production of components made of aluminum strip, which has a small width and a greater thickness in relation to the width. Especially such bands can be effectively heat treated in inexpensive manufacturable and operable devices, the respective heating devices, unlike conventionally used furnaces can be easily adapted to the specific task. As a result, the procedure according to the invention, particularly in the processing of narrow, thicker strips, has particularly significant cost advantages over the conventional production of such aluminum strips. Thus, with the method according to the invention, preferably ribbons with a width of up to 1000 mm and a thickness of more than 3 mm can be processed.

Another particular advantage of the invention in connection with the processing of thick, narrow aluminum bands is that the facilities used for the heating of these bands can be designed without special effort so that a safe heating of each heated aluminum strip is guaranteed. This leads to a further improvement in the quality of the finished products produced from the thick strips.

A particularly advantageous embodiment of the invention is characterized in that the heating takes place inductively during annealing. Devices in which an inductive heating of the processed material is carried out by the action of an electromagnetic field, make it possible to heat the strip to be heated within a short time to the required annealing temperature. In this case, both the duration and the temperature development can be controlled exactly, so that an optimal treatment result is achieved. For this reason, inductively operating heating devices are particularly suitable for the heat treatment of narrow and thick tapes in which a proper heating of the material is required, which is to ensure in conventional furnaces used only with difficulty.

Of course, it is also conceivable to heat the bands before cold working, for example, in ovens operated with gas or other fuels. This is indicated, for example, when the structural conditions make it difficult to install the components required for the inductive heating, such as coils, converters, etc.

In many applications, it is useful to cut the aluminum strip to blanks before it is fed to cold forming. In such a case, it is favorable if the assembly takes place at a central location, from which the blanks are passed on to the devices for cold forming, and if the heat treatment of the aluminum strip is carried out immediately before entry into the finishing device. By this measure, the cost of the heat treatment can be reduced. At the same time passing between the cutting and the cold forming time is so short that the adjusting itself in this time, undesirable cold curing reaches only a small extent and on the result of cold forming has no significant influence.

It is to minimize the time that passes between the heat treatment and the cold forming According to a further embodiment of the invention, it is advantageous if the heat treatment takes place in the catchment area of the device used for cold forming. With this procedure, it is ensured that the aluminum strip or the blank made therefrom passes into cold forming in the best possible state for further processing. Particularly suitable for the realization of these measures are due to their small size inductively operating heating devices.

Fig. 1

einen Verfahrensablauf bei der Herstellung eines tiefgezogenen Bauteils;

Fig. 2

einen Verfahrensablauf bei gleichzeitiger Herstellung mehrerer tiefgezogener Bauteile auf verschiedenen Mehrstufenpressen.

The invention will be explained in more detail with reference to a drawing illustrating two embodiments. In a schematic representation:

Fig. 1

a process flow in the manufacture of a deep-drawn component;

Fig. 2

a process sequence with simultaneous production of several deep-drawn components on different multi-stage presses.

An aluminum strip 1 of small width and large thickness produced from a hardenable alloy is produced in a rolling mill 2 in a conventional manner by rolling from a slab. The aluminum strip 1, which has been wound into coils 3, leaves the rolling mill 2 without first being subjected to a final heat treatment, such as solution heat treatment and quenching in a continuous furnace.

The coils 3 are delivered to a processor 4, which may be, for example, a factory for the production of body components, and stored in its bearing 5. From the bearing 5, the coils 3 are removed if necessary and transferred to a production line 6.

The production line 6 comprises a uncoiling device 7, a heat treatment device 8, a blank punch press 9 and a multi-stage press 10. As devices for cold forming u.a. in addition to multi-stage presses, i. Forming presses, e.g. Also Rollprofilieranlagen in question. The heat treatment device 8 is arranged in the catchment area 9a of the board punch press 9. It comprises a device 8a, not shown here in detail, for inductive heating and a quenching device 8b, likewise not shown in detail. In the heating device 8a, an over the width of the material to be heated extending, not shown induction coil is arranged, which generates an electromagnetic field that causes the heating of each located in the sphere of action of the coil Guts.

The taken from the bearing 5 coils 3 are placed in the uncoiler 7. From this, the coiled aluminum strip 1 of the heat treatment device 8 is supplied. The section of the aluminum strip 1 located in the heat treatment device 8 is first brought to the solution annealing temperature by the inductively operating heating device 8a for a short time, for example 2 to 3 seconds. Subsequently, the relevant heated to annealing temperature portion of the aluminum strip 1 is quenched in the quenching device 8b. The thus heat-treated portion of the aluminum strip 1 then passes into the blank punch press 9, which punches from the strip blanks 11. The blanks 11 are then fed to the multi-stage press 10.

In the multi-stage press 10, the annealed and quenched blanks 11 are cold formed into body components 12. Due to the small spatial distance between the heat treatment device 8, the blank punch press 9 and the multi-stage press 10, the time passing between the heat treatment and the cold working in the multi-stage press 10 is short. Therefore, the blanks 11 have on their entry into the multi-stage press 10 an optimal in terms of formability their structural state.

At the in Fig. 2 1, a production line 20 comprises an uncoiling device 21, a heat treatment device 22, a blank punch press 23 and a plurality of multi-stage presses 24, 25, 26, 27, 28, 29.

The heat treatment device 22 is arranged in the draw-in region 23 a of the blank punch press 23. It includes like those in Fig. 1 illustrated heat treatment device 9 a not shown here in detail means 22a for inductive heating and also not shown in detail quenching device 22b.

In the Abhaspeleinrichtung 21 is wound to a coil 30, consisting of a hardenable alloy aluminum strip 31 given previously as in the embodiment according to Fig. 1 produced in a rolling mill and stored at the processor in a warehouse. From the unwinding device 21, the aluminum strip 31 is fed into the heat treatment device 22 in which it is briefly heated by the heating device 22a to solution annealing temperature and then quenched by the quenching device 22b. The thus heat-treated, an optimum state for cold forming state having aluminum strip 31 then passes into the board punch press 23, in which 31 blanks 33 are punched from the aluminum strip. From the blank punch press 23, the blanks 33 reach the multi-stage presses 24-29, in which they are cold-formed into multi-stage body parts.

LIST OF REFERENCE NUMBERS

1

aluminum tape

2

rolling mill

3

coils

4

processors

5

camp

6

production line

7

Abhaspeleinrichtung

8th

Heat treatment facility

8a

Device for inductive heating

8b

quenching

9

Platinum punch press

10

Multistage press

10a

Catchment area of the multi-stage press 10

11

blanks

12

body component

20

production line

21

Abhaspeleinrichtung

22

Heat treatment facility

22a

Device for inductive heating

22b

quenching

23

Platinum punch press

23a

Feed area of the board punching press 23

24,25,26,27,28,29

Multi-station presses

30

coil

31

aluminum tape

33

blanks

Claims (9)

1. A method of producing cold-formed components (12) from a heat treatable aluminum material, comprising the following steps:

   - producing an aluminum strip (1) by rolling a slab without a subsequent heat treatment,

   - subsequent intermediate storing the aluminum strip (1) by coiling the aluminium strip onto a coil and storing of the coil,

   - subsequent applying the coil to a production line comprising a coiling unit, a heat treatment unit, a blank punch press and a cold forming unit,

   - heat treating the aluminum strip (1),

   - cold forming the aluminum strip (1),

   wherein the heat treatment occurs at a time close to the cold forming.
2. The method according to Claim 1,
   characterized in that the heat treatment includes annealing and quenching of the aluminum strip (1).
3. The method according to Claim 2,
   characterized in that the heating during the annealing is performed inductively.
4. The method according to one of the preceding claims,
   characterized in that the aluminum strip (1) is tailored into blanks (11) before it is furnished to the cold forming.
5. The method according to Claim 4, characterized in that the blanks (11) are tailored before the heat treatment.
6. The method according to Claim 4,
   characterized in that the tailoring is performed at a central location, from which the blanks (11) are relayed to the devices for cold forming, and the heat treatment of the aluminum strip (1) is performed immediately before the entrance into the tailoring device (8).
7. The method according to one of Claims 1 to 5,
   characterized in that the heat treatment is performed in the entering region of the device (10) used for the cold forming.
8. The method according to one of the preceding claims,
   characterized in that the aluminum strip (1) has a width of up to 10 00 mm.
9. The method according to one of the preceding claims,
   characterized in that the aluminum strip (1) has a thickness of over 3 mm.

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