US20140224388A1

US20140224388A1 - Heat treatment line and method for operating the heat treatment line

Info

Publication number: US20140224388A1
Application number: US14/180,106
Authority: US
Inventors: Georg Frost; Werner Morgenroth
Original assignee: Benteler Automobiltechnik GmbH
Current assignee: Benteler Automobiltechnik GmbH
Priority date: 2013-02-14
Filing date: 2014-02-13
Publication date: 2014-08-14
Also published as: EP2767599A1; CN103993137A; EP2767599B1; ES2845558T3; DE102013101489B3

Abstract

A heat treatment line for producing a heat treated metal component includes a heating station, which heats the metal component to a component temperature above the austenizing temperature, and a temperature treatment station, wherein the temperature treatment station has an internal temperature which essentially corresponds to the temperature of the metal component.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Ser. No. 10 2013 101 489.5, filed Feb. 14, 2013, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
This application claims the priority of European Patent Application, Serial No. 13 186 929.9, filed Oct. 1, 2013, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a heat treatment line and a method for operating the heat treatment line.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
In motor vehicle construction it is known for producing vehicle body components and structural components of motor vehicles to produce the components as formed sheet metal components from a steel alloy. For this, a sheet metal blank is formed into a formed sheet metal component in a forming press.
It is further known to produce these formed sheet metal parts from high strength or ultra-high strength steel alloys, wherein the mechanical resistance, in particular the strength and the ductility properties, are significantly increased compared to components made of conventional steel.
For producing hardened, formed sheet metal components, the hot forming and press hardening technology has been standardized for many years, wherein a sheet metal blank, which is heated to austenizing temperature, is inserted into a forming tool, hot formed in this forming tool and at the same time quenched in the forming tool and thereby hardened.
For hardening components it is further possible to first form the component, subsequently heat the component to above austenzing temperature and thereafter take up the component again and cool the component in a quenching station at such a fast rate that the microstructure of the component is hardened. Such a device is for example known from DE 102 009 051 157 B4.
From this, chamber furnaces are known which can be space effectively arranged in a mounting hall. Such a chamber furnace has however a limited capacity so that it can essentially only take up one component at a time. When now the further processing is interrupted, for example when a manipulator for loading the chamber furnace has failed, this leads to halts in the production process so that the components may remain in the chamber furnace for a longer period of time. The chamber furnaces are heated to above austenizing temperature and therefore require high energy consumption for operating the furnace itself.
It would therefore be desirable and advantageous to provide a possibility to heat treat metal components more efficiently, while requiring a small space in an assembly hall, and wherein fluctuations in production are compensated and energy consumption is optimized.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a heat treatment One for producing a heat treated, in particular pre-coated metal component, includes a heating station which heats at least regions of the metal component to a component temperature above austenizing temperature; and a temperature treatment station, the temperature treatment station having at least in regions an internal temperature which essentially corresponds to the component temperature of the metal component.
According to the invention a heating station is thus provided in the heat treatment line, which may preferably be configured as chamber furnace, alternatively also as rotary kiln or continuous furnace. In the heating station the component is heated to the desired component temperature. This component temperature is particularly preferably above the austenizing temperature and is thus between 800° C. and 1000° C., in particular between 850° C. and 950° C. This austenizing temperature is established at least in regions of the component with the heat treatment line according to the invention. The remaining regions of the component then remain at a temperature below the austenizing temperature. The internal temperature of the heating station is to be set above this temperature. When a particularly fast heating time of the metal component is to be achieved, the internal temperature of the heating station is to be set significantly above the component temperature. The temperature inside the heating station is thus preferably between 950° C. to 1300° C., in particular 1100° C. to 1200° C.
Relative to the component temperature, the internal temperature of the heating station is to be selected so as to be in particular 5 to 30% above the component temperature, preferably 10 to 25% above the component temperature. The heating station can in particular be configured as furnace with a burner.
The components thus heated to component temperature are then removed from the heating station and according to the invention transferred into a temperature treatment station. The temperature treatment station is configured as intermediate station, in order to maintain the temperature established in the component itself at least in regions. Also in the temperature treatment station itself the component temperature is then held at least in regions, whereas the non-heated regions are correspondingly below the component temperature. Here it is possible that an internal temperature which corresponds to the component temperature itself is preferably present in the temperature treatment station. As an alternative thereto it is possible that an internal temperature exists in the temperature treatment, which is set slightly above, in particular between 0 and 10%, particularly preferably between 1 and 5%, above the component temperature. It is thus possible to maintain the component temperature inside the temperature treatment station for a longer period of time. A component, which may not be fully austenized inside the material due to production fluctuations is further maintained at component temperature in the temperature treatment station so that a complete austenization occurs as a result of heat conduction inside the component itself. Due to the fact that the internal temperature of the temperature treatment station is selected so as to be not higher, in particular not significantly higher, than the component temperature itself, the temperature treatment station can be operated with lower energy costs compared to the heating station.
When fluctuations in production occur during further processing downstream of the temperature treatment station or already at the heating station, for example as a result of failure of a heating station or failure of a manipulator for transferring the components between individual stations, it is possible to build up a buffer of metal components to be heated with the temperature treatment station according to the invention. This buffer makes it possible that the entire production does not necessarily have to be halted. Thus, maintenance work can be carried out, wherein the metal components located inside the temperature treatment station allow production to continue. For this, between 40 and 60% of the possible components to be received are always located inside the temperature treatment station during normal production. This ensures that in case of a failure of the production line downstream of the temperature treatment station, components can initially still be transferred from the heating station into the temperature treatment station. When the production line fails upstream of the temperature treatments station, components are still initially stored in the temperature treatment station for further production.
For this, the temperature treatment station is particularly preferably constructed as continuous furnace. The advantage compared to the state-of-the-art is however that different from conventional continuous furnaces, the temperature treatment station does not have to have lengths of several dozen meters, so that the component is heated to a temperature by the continuous furnace over the time period in which it is to be transported, but is only held at the temperature. It is thus possible to configure the temperature treatment station to be only a few meters long. Within the scope of the invention, it is also possible in the continuous furnace to maintain the component temperature to be generated only in regions in the temperature treatment station, for example by means of sealing walls or the like. It is also possible within the scope of the invention, for example by means of corresponding covering elements, in particular in the form of cooling plates and/or shielding plates, to prevent some regions to reach a temperature above austenizing temperature. Within the scope of the invention, the temperature treatment station and the heating station are suited to subject only regions of the metal components to temperature treatment.
Within the context of the invention a metal component means a blank, wherein the metal component can be treated with the heat treatment line according to the invention also as already three-dimensionally formed metal component. Further particularly preferably pre-coated materials for example a blank with a metallic coating can also be used.
As an alternative thereto it is also possible within the scope of the invention that the temperature treatment station itself is constructed as chamber furnace, wherein multiple chamber furnaces are arranged on top of each other and/or adjacent each other. It is then possible by using a manipulator, in particular in the form of an industrial robot, to load the multiple chamber furnaces in the temperature treatment station or to remove the components that are temperature treated in the multiple chamber furnaces. Also in the chamber furnace or in the rotary kiln described below it is again possible to bring only regions of the component to the desired component temperature. Also in this case it is again possible, for example by means of covering elements in the form of cooling plates or by means of intermediate walls, sealing walls or an insulation, to cool other regions or to keep other regions colder than the component temperature.
Further preferably, the temperature treatment station is constructed as rotary kiln. This again offers the advantage that the rotary kiln can be loaded by means of only one manipulator. The rotary kiln is in particular constructed so that it has multiple receiving possibilities for receiving metal components on top of each other and also radially circumferentially adjacent each other. A respective empty chamber of the temperature treatment station can then be loaded by the manipulator.
Further preferably, it is then provided in the heat treatment according to the invention that a cooling station is arranged downstream of the temperature treatment station. The components heated to above austenizing temperature are removed from the temperature treatments station and then quench hardened in the cooling station. This can for example be realized by means of a sprinkler or shower, so that the component is guided through a sprayed-on cooling medium. As an alternative it is also possible that the cooling station is configured as dip bath, wherein the component is removed and dipped into the cooling station. In this case the material of the microstructure of the component undergoes such a change that the austenitic microstructure is transformed into an essentially martensitic microstructure. Within the scope of the invention, the cooling station can also be a hot forming and press-hardening tool. The correspondingly heat treated component is then transferred out of the temperature treatment station into the hot forming tool where it is hot formed and subsequently press hardened. In particular when only regions of the component are austenized, press hardening also only occurs in the austenized regions, wherein in contrast to this, the regions, which were not temperature treated are not completely austenized and thus also not completely hardened. These regions have a rather ductile component property.
According to another advantageous aspect of the invention, a method for operating the heat treatment line according to the aforementioned features includes establishing an internal temperature of the heat treatment station above the component temperature of the metal component; introducing the metal component into the heating station; heating at least regions of the metal component in the heat treatment station to a component temperature above austenizing temperature; and introducing the metal component into the in the temperature treatment station.
Preferably an internal temperature is set in the heat treatment station which is between 1000° C. and 1300° C., in particular between 1100° C. and 1200° C. and the internal temperature of the temperature treatment station is between 800° C. and 1000° C., preferably between 850° C. and 950° C.
According to another advantageous aspect of the invention, the temperature treatment station is used as a buffer in order to compensate downtime and/or production halts at the heating station and/or at the cooling station.
Within the scope of the invention it is in particular possible to heat treat at least regions of a metal component with a metallic pre-coating so that at least in regions an intermetallic phase is generated.
According to the invention, a particularly advantageous embodiment of the method is to remove the metal component from the heating station at an actual temperature of the component of 700° C. to 1100° C., preferably 800° C. to 1000° C., in particular 850° C. to 950° C., and to subsequently post heat at least regions of the metal component in the temperature treatment station to above austenizing temperature, in particular to the component temperature, particularly preferably to at least 900° C. It is also possible to then heat the entire component in the downstream temperature treatment station to above 900° C. This results in an overall shortened run time to realize the pre-coated metal component on the corresponding heat treatment line when producing an at least regionally homogenous intermetallic alloy coating. For example, an aluminum-silicone coating is used as metallic pre-coating on the metal component to be heat treated, in particular to be hot formed and press hardened. Within the scope of the invention the time of the heating phase can further be shortened when a metal component with a pre-alloyed metallic pre-coating is produced. Pre-alloyed means that a heat treatment with diffusion processes between steel substrate and the elements of the metallic coating is already carried out prior to the heating station, in particular at the steel producer.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 shows a heat treatment line according to the invention with a temperature treatment station in the form of a roller conveyor furnace and

FIG. 2 shows a heat treatment line according to the invention with a temperature treatment station in the form of a rotary kiln.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Turning now to the drawing, and in particular to FIG. 1, there is shown a heat treatment line 1 according to the invention for producing heat treated metal components. The heat treatment line 1 has a heating station 2 in the form of three adjacently arranged chamber furnaces 3 and a temperature treatment station 4 arranged downstream of the heat treatment station 2. The temperature treatment station 4 itself is constructed as roller conveyor furnace 5, so that the roller conveyor furnace 5 has a receiving side 6 with a not further shown receiving opening and a retrieval side 7 with a not further shown retrieval opening. Following the temperature treatment station 4 is a cooling station 8 for example in the form of a dip bath. Between the individual stations a respective industrial robot 9 is used which transfers the not further shown metal components between the individual stations.
FIG. 2 shows an alternative embodiment wherein the heat treatment line 1 again has a heating station 2 in which the chamber furnaces are arranged adjacent one another. The temperature treatment station 4 itself is constructed in the form of a rotary kiln 10 which can be freely rotated in the rotation direction D in order to transfer the individual components via an industrial robot 9 from the heating station 2 into the rotary kiln and after a defined incubation time in the rotary kiln 10 to remove the components from the rotary kiln 10 and feed the components to the cooling station 8.
While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention, The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein:

Claims

What is claimed is:

1. A heat treatment line for producing a heat treated, in particular pre-coated metal component, comprising:

a heating station which heats at least regions of the metal component to a component temperature above austenizing temperature; and

a temperature treatment station, said temperature treatment station having at least in regions an internal temperature which essentially corresponds to the component temperature of the metal component.

2. The heat treatment line of claim 1, wherein the temperature treatment station is constructed as continuous furnace, in particular the continuous furnace has at least in regions the internal temperature of the temperature treatment station.

3. The heat treatment line of claim 1, wherein the temperature treatment station is constructed as chamber furnace.

4. The heat treatment line of claim 3, further comprising multiple said multiple chamber furnace arranged on top of each other and/or adjacent each other.

5. The heat treatment line of claim 3, wherein the chamber furnace at least in regions has the internal temperature of the temperature treatment station.

6. The heat treatment line of claim 1, wherein the temperature treatment station is constructed as rotary kiln.

7. The heat treatment line of claim 1, further comprising a cooling station arranged upstream of the temperature treatment station,

8. The heat treatment line of claim 7, wherein the cooling station is constructed as hot forming and press hardening tool.

9. The heat treatment line of claim 8, wherein the cooling station is constructed as dip bath.

10. The heat treatment line of claim 7, further comprising a manipulator for transferring the metal component between the heating station, the heat treatment station and the cooling station.

11. The heat treatment line of claim 10, wherein the manipulator is constructed as an industrial robot.

12. A method for operating the heat treatment line of claim 1, comprising:

establishing an internal temperature of the heating station above the component temperature of the metal component;

introducing the metal component into the heating station;

heating at least regions of the metal component in the heating station to a component temperature above austenizing temperature; and

introducing the metal component into the temperature treatment station.

13. The method of claim 12, wherein the internal temperature of the heating station is set between 1000° C. and 1300° C. and the internal temperature of the temperature treatment station is set between 800° C. and 1000° C.

14. The method of claim 12, wherein the internal temperature of the heating station is set between 1100° C. and 1200° C., and the internal temperature of the temperature treatment station is set between 850° C. and 950° C.

15. The method of claim 8, wherein the temperature treatment station is used as buffer to compensate down times and/or production halts at the heating station and/or the cooling station.

16. The method of claim 8, wherein a pre-coated metal component with a metallic pre-coating is heat treated for generating an at least regional intermetallic phase.

17. The method of claim 12, wherein the metal component is removed from the heating station when reaching an actual temperature of the metal component of 700° C. to 1100° C. and transferred into the temperature treatment station, and wherein at least regions of the metal component are post heated in the temperature treatment station to the component temperature, in particular to at least 900° C.

18. The method of claim 12, wherein the metal component is removed from the heating station when reaching an actual temperature of the metal component of 800° C. to 1000° C.

19. The method of claim 12, wherein the metal component is removed from the heating station when reaching an actual temperature of the metal component 850° C. to 950° C.