HOT FORMING LINE FOR PRODUCING HOT FORMED AND PRESS HARDENED STEEL SHEET PRODUCTS

Abstract

A hot forming line for producing hot formed and press hardened steel sheet products, in particular motor vehicle parts includes a heating device and a forming device, wherein the heating device has a temperature treatment station with an upper tool and a lower tool and the temperature treatment station has a temperature source for heating, wherein exchangeable temperature treatment plates are arrangeable on the upper and/or the lower tool and the temperature source is constructed as inductor, and the temperature treatment plates can be heated by the inductor.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2012 110 650.9, filed Nov. 7, 2012, 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 hot forming line producing hot formed and press hardened steel sheet products.

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.

It is known from state-of-the-art to produce motor vehicle bodies from metallic materials. For this in particular steel materials but also lightweight metal materials are used. In recent years high-strength and ultra-high-strength steels were used as steel materials, which have at least portions of high hardness or ductile properties so that the strength and also the crash performance of a motor vehicle body is increased while at the same time saving weight.

Thus a tempering method is known for example from DE 10 2010 004 081 B3 for producing steel sheet blanks with at least two structural regions of different ductility. For this, a blank is first homogenously heated in a furnace to a temperature and then further heated at least in sub-regions to a temperature above the austenizing temperature (AC3). Subsequent thereto, the blank is closed-die press formed and quench hardened

It would be desirable and advantageous to provide an improved device with which it is possible to produce sheet metal parts having regions of different strength properties, wherein the device requires low energy and low acquisition costs and can be flexibly used in a broad range of applications.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a hot forming line for producing hot formed and press hardened steel sheet products, in particular motor vehicle parts, includes a heating device formed as a temperature treatment station with an upper tool and a lower tool, exchangeable temperature treatment plates arranged on the upper tool and/or the lower tool; and a temperature source constructed as an inductor for heating the temperature treatment plates

According to the invention it is thus possible to heat a metallic part preferably a blank, by means of the temperature treatment plates, which metallic part is inserted in the temperature treatment station. The temperature treatment plates are arranged on the upper tool and/or the lower tool so that heat is transferred from the temperature treatment plate to the metallic part to be heated via conductive heat transfer i.e., by heat conduction. In order for the temperature treatment plates themselves to be brought to a temperature, which is higher than the ambient temperature, inductors are arranged in/or on the lower tool and/or the upper tool. By means of these inductors it is possible due to inductive heating to heat the temperature treatment plates themselves. According to the invention the temperature treatment plates can thus be exchanged to heat different parts on the upper tool and/or the lower tool.

In particular, the temperature treatment plates can be exchanged in case of wear and/or retrofitting. It is also possible however that the temperature treatment plates are exchangeable in such a manner that they can be adjusted to the different requirements of heating. Thus it is for example possible to configure the temperature treatment plates so that they contact the metal part to be heated, in particular the blank, only in regions thereby only heating regions of the metal blank.

According to another advantageous feature of the invention, the temperature treatment plates themselves can be configured flat for temperature treatment of the sheet metal blank. This enables in particular to heat a sheet-metal blank by means of the temperature treatment plates. As an alternative however it is also possible that the temperature treatment plates are configured three-dimensional, wherein between the temperature treatment plates a hollow space remains in the in the temperature treatment station when the temperature treatment station is closed. The sheet-metal blank is then located in this hollow space. Within the scope of the invention the term three-dimensionally configured means that the temperature treatment plates have in particular a three-dimensionally extending surface or contact surface.

According to another advantageous feature of the invention, at least one inductor is arranged in the upper tool or the lower tool, wherein the inductor of the upper tool heats the temperature treatment plate of the upper tool and the inductor of the lower tool heats the temperature treatment plate of the lower tool, wherein the temperature treatment plates can preferably be heated to a temperature of more than 1000° C. by means of the inductors. With this it is possible within the scope of the invention that at least regions of an inserted metal part in particular a sheet-metal blank which is preferably formed from a steel material can be heated to a temperature above austenizing temperature. However, it is also possible within the scope of the invention to set a temperature of the temperature treatment plate by means of the inductors in a targeted manner, which then correspondingly heats the sheet-metal blank and/or the metallic part. For example it is thus possible within the framework of the invention to set the temperature in a targeted manner, which heats the sheet-metal blank to AC1. However, it is also possible within the scope of the invention to set the temperature of the sheet-metal blank such that the sheet metal blank can be heated to a desired temperature between 200° to 1200° C. In particular it is possible by selecting the temperature treatment plates and/or by arranging the inductors and/or by means of closed loop or open loop control of the inductors to heat regions of a sheet metal blank, which is inserted the temperature treatment station to different temperatures.

According to another advantageous feature of the invention the inductor can have essentially the same surface distribution as the temperature treatment plate, which is associated with the inductor. Within the framework of the invention, multiple induction loops and/or induction coils are thus for example distributed on the upper tool and/or lower tool or are integrated in the upper tool and/or product so as to essentially cover the same region as the associated temperature treatment plate.

According to another advantageous feature of the invention, the inductor can be distributed across the surface so as to be configured smaller than the associated temperature treatment plate. In the following only a surface region, which corresponds to the inductor is heated. The remaining surface regions of the temperature treatment plate are initially not heated in a targeted manner by the inductor. In this case however heat is conducted from the heated surface region to the not heated surface region of the temperature treatment plate, which however is negligible in the context of the invention in particular in the case of short time heating between one second and up to 10 minutes.

According to another advantageous feature of the invention, different voltages can be applied to different regions of the inductor, which is arranged on the upper tool and/or lower tool to thereby generate different temperatures in different regions on the temperature treatment plates. This is realized for example in that different inductor loops are installed inside the lower tool and/or upper tool, wherein different regions of the inductor loops can be controlled independent of each other.

Further preferably it is possible within the framework of the invention for heating regions to different temperatures to use temperature treatment plates which are formed from multiple parts. The at least two different parts of the temperature treatment plate then differ in their respective heat conducting properties and/or material properties. Thus, when the temperature treatment plate has two regions of different heat conducting properties it is possible to heat the temperature treatment plate to an essentially uniform temperature by inductive heating, however due to the different heat conducting properties heat is transferred in the two regions of the temperature treatment plate differently to the sheet metal blank to be heated, which in turn results in the sheet metal blank being heated differently in different regions.

According to another advantageous feature of the invention the temperature treatment plate can have regions of different material properties. This makes it possible that while the temperature treatment plate is under uniform influence of the inductor, these different regions are heated differently due to the different material properties. As a result, when the temperature treatment plate contacts the sheet metal blank, different regions of the sheet metal blank are then also heated to different temperatures.

According to another advantageous feature of the invention, regions of a first type and regions of a second type are treated with different temperatures in the same sheet metal blank, wherein the regions of the first type are in direct contact with the temperature treatment plate themselves when the temperature treatment station is closed and in the regions of the second type a space is formed between the surface of the sheet metal blank and the temperature treatment plate, which space is in particular formed as an air gap. As an alternative it is also possible that in the region of the second type an insulating material is arranged between the surface of the sheet metal blank and the temperature treatment plate. The air gap and/or the insulating material thus results in decreased heat conduction from the temperature treatment plate to the sheet metal blank so that different regions of the sheet metal blank are heated to different temperatures.

The previously mentioned different embodiments of the temperature treatment plates and/or the sectional heating of the temperature treatment plates can also be combined in any desired manner within the scope of the invention, with the associated advantages. It is an important advantage of the invention that at least two different regions can be treated with different temperatures in the same blank. It is also possible to expose in particular small local surfaces to temperature treatment with the temperature treatment plates according to the invention. Especially preferably, it is possible to temperate in the region of flanges or passages, in particular at regions that border at the flanges or the passages.

Subsequent to the heating of the sheet metal blank, the sheet metal blank is transferred to a forming tool, where it is hot formed and preferably subsequently press hardened.

According to another advantageous feature of the invention, a furnace can be arranged in the hot forming line upstream of the temperature treatment station and the metal parts or the sheet metal blanks can be pre-heated in the furnace to a temperature. For example it is possible to heat the part homogenously in the furnace to AC1 temperature and then to heat regions above AC3 point by the temperature treatment station. In particular this heating process can be carried out with the temperature treatment station particularly cost efficiently because the inductive heating only requires a small energy input.

According to another advantageous feature of the invention, the temperature treatment plate on the lower tool can have spacers, wherein the blank or the metallic part that is placed on the temperature treatment plate can be supported by the spacer so that it is held at a distance to the surface of the temperature treatment plate. In particular this arrangement is formed in the region of the second type so that here a lower heating occurs than in the region of the first type.

According to another advantageous feature of the invention, the temperature treatment plates can have a coating, in particular a scale resisting coating. This achieves that during the entire production process an almost constant production quality is maintained because the temperature treatment plates essentially do not become contaminated due to the scale resisting coating and with this the same heating of the different blanks, sheet metal blanks and/or metallic parts can be carried out over the entire production. Particularly preferably, the coating is also heat resistant and/or wear resistant.

According to another advantageous feature of the invention, the temperature treatment plate can be coupled form fittingly to the upper tool and/or the lower tool, preferably via bolts. This enables a coupling so that the bolts can also be unscrewed again and/or are configured as quick closures, so that the temperature treatment plates in case of a different dimensioning and/or wear can be easily exchanged while requiring only short mounting times.

According to another advantageous feature of the invention, the temperature treatment plates can further be configured to have a convex curvature, which is formed in the hollow space of the temperature treatment station. Thus a central region of the temperature treatment plate protrudes into the hollow space opposite the regions of the temperature treatment plates, which flatten towards the sides. This achieves that when the temperature treatment station is closed the central region initially rests against the blank and when further closing and/or pressing the temperature treatment station, the border regions also successively rest against the sheet metal blank to be heated. Within the scope of the invention a full surface contact is thereby created between the temperature treatment plate and the surface of the sheet metal blank to be heated. According to the invention it is again possible due to the inductive heating of the temperature treatment plate itself to compensate displacements of up to a few millimeters that are caused thereby, because the temperature treatment plate itself is contactlessly heated via the inductive heating.

The invention also includes a method for producing a hot formed and press hardened motor vehicle part with a hot forming line according to at least claim 1, wherein the method is characterized by the following method steps:

• • heating a blank to a temperature below AC3,
  • transferring the blank into a temperature treatment station,
  • heating regions of a first type in the temperature treatment station by means of conductive heating to above AC3,
  • holding region of a second type at a temperature below AC3,
  • transferring the sheet metal blank into a forming tool, hot forming and press hardening.

According to another advantageous feature of the invention, the blank may not already heated to below AC3 before the transfer into the temperature treatment station but to below AC1 temperature. Regions of the second type are then held in the temperature treatment station at a temperature below the AC-1 point. An important advantage of the method according to the invention is in particular the possibility to set the temperature on the sheet metal blank and/or the metallic part to be heated in a targeted manner while at the same tie using a small amount of energy due to the inductive heating of the temperature treatment plate, wherein then again the temperature treatment plate heats the part to be heated by means of conduction.

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 temperature treatment station according to the invention with different temperature treatment plates, wherein the temperature treatment plates have different regions;

FIG. 2 shows the temperature treatment station with only partially arranged inductor and

FIG. 3 shows a top view onto a temperature treatment plate according to the invention with placed on blank.

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 temperature treatment station 1 according to the invention, wherein the temperature treatment station 1 has an upper tool 2 and a lower tool 3. The upper tool 2 and/or the lower tool 3 are movable in the movement direction B, so that between the temperature treatment plate 4 of the upper tool 2 and a temperature treatment plate 5 of the lower tool 3 a hollow space 6 remains. A sheet metal blank 7 can be inserted into the hollow space 6, wherein the sheet metal blank 7 can then be heated by the temperature treatment plates 4, 5 by means of conductive heating to a predetermined temperature.

In order to heat the temperature treatment plate 5 itself, inductors 8 are provided on the lower tool 3 and on the upper tool 2 in the form of inductor loops 9. By means of the inductors 8 the temperature treatment plates 4, 5 themselves can then be heated to a desired temperature, wherein heat is then conducted from the temperature treatment plates 4, 5 into the sheet metal blank 7 when the temperature treatment plates 4, 5 contact the sheet metal blank 7. Consequently, the sheet metal blank 7 itself can be heated up to the temperature of the temperature treatment plate 4, 5 depending on the time for which the sheet metal blank 7 stays between the upper tool 2 and the lower tool 3.

FIG. 1 also shows that the temperature treatment plate 4 of the upper tool 2 and the temperature treatment plate 5 of the lower tool 3 are constructed two-part. The first part 10 is made of a different material than a second part 11. The first part 10 is for example a material of the temperature treatment plate 4, 5 which has a good heat conducting property and the second part 11 is a material which relative to the second part 10 is less heat conducting. Within the scope of the invention the second part 11 can also be configured as insulating material, for example a ceramic or other insulating material can be used. This allows the sheet metal blank 7 to be heated to different temperatures.

FIG. 2 shows an analogous embodiment, wherein as shown on the right hand image plane no inductors 8 are provided above the second part 11 of the temperature treatment plate 4, 5.

FIG. 3 shows a top view onto a lower tool 3 onto which a sheet metal blank 7 is placed, whose contour is shown. It can be recognized that the temperature treatment plate 5 does not extend over the complete region of the lower tool 3 but has outer dimensions so as to only partially rest against the outer geometry of the sheet metal blank 7. This reduces the energy input for heating the sheet metal blank 7 to a necessary minimal amount. It can also be well recognized that an induction loop 9 is only formed in the region of the first part 10 of the temperature treatment plate 4, 5, whereas the second part 11 of the temperature treatment plate 4, 5 does not have an inductor. The inductor loop 9 itself is distributed above the first part 10 so that also here an adjustment of the induction loop 9 to the outer dimensions of the first part 10 of the temperature treatment plate 5 is formed, which again leads to energy savings.

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

1. A hot forming line for producing hot formed and press hardened steel sheet products, in particular motor vehicle parts, comprising:

a heating device, said heating device comprising a temperature treatment station with an upper tool and a lower tool;

exchangeable temperature treatment plates arranged on the upper tool and/or the lower tool; and

an inductor for heating the temperature treatment plates.

2. The hot forming line of claim 1, wherein the temperature treatment plates are configured flat for temperature treatment of a sheet metal blank.

3. The hot forming line of claim 1, wherein the temperature treatment plates are configured three-dimensional wherein a hollow space remains between the temperature treatment plates when the temperature treatment station is closed.

4. The hot forming line of claim 1, further comprising two said inductor, wherein one the two conductors is arranged in the upper tool and the other one of the two inductors is arranged in the bottom tool, said one of the inductors heating the upper tool, said other conductor heating the bottom tool, wherein the temperature treatment plates are heatable to above 1000° C.

5. The hot forming line of claim 1, wherein a surface distribution of the inductor essentially corresponds to a surface of one of the temperature treatment plates associated with the inductor.

6. The hot forming line of claim 1, wherein the inductor is smaller than one of the temperature treatment plates associated with the inductor, wherein at least regions the one of the temperature treatment plates are heated by the inductor.

7. The hot forming line of claim 1, wherein the inductor is constructed so that different voltages can be applied at different regions of the inductor thereby causing different regions of the temperature treatment plates to attain different temperatures

8. The hot forming line of claim 1, wherein the temperature treatment plate is constructed from at least two parts, said at least two parts having different heat conducting properties and/or different material properties.

9. The hot forming line of claim 1, wherein the temperature treatment plates are constructed to establish different temperatures in first and second regions of the sheet metal blank, wherein the first regions are in direct contact with the temperature treatment plates when the temperature treatment station is closed, and wherein a space is formed in the second regions between a surface of the sheet metal blank and the temperature treatment plates.

10. The hot forming line of claim 1, wherein the temperature treatment plates are constructed to establish different temperatures in first and second regions of the sheet metal blank, wherein the first regions are in direct contact with the temperature treatment plates when the temperature treatment station is closed, and wherein an insulating material is arranged in the temperature treatment plates in the second regions.

11. The hot forming line of claim 1, further comprising a furnace arranged upstream of the temperature treatment station for pre-heating the metal parts or the sheet metal blank to a temperature.

12. The hot forming line of claim 9, wherein at least the temperature treatment plate on the lower tool has spacers, wherein the sheet metal blank or the metal part placed on the temperature treatment plate is supported by the spacer.

13. The hot forming line of claim 12, wherein the wherein the sheet metal blank or the metal is supported in the second regions.

14. The hot forming line of claim 1, wherein the temperature treatment plates have a coating.

15. The hot forming line of claim 14, wherein the coating is a scale resisting coating.

17. The hot forming line of claim 1, wherein the temperature treatment plates are coupled form fittingly on the upper tool and/or the lower tool.

18. The hot forming line of claim 1, wherein the temperature treatment plates are coupled on the upper and/or the lower tool via bolts.

19. A method for producing a hot formed and press hardened motor vehicle part with the hot forming line according to claim 1, comprising:

heating a sheet metal blank to a temperature below AC3;

transferring the sheet metal blank into the temperature treatment station

heating first regions of the sheet metal blank in the temperature treatment station by means of condicutive heating to above AC3;

holding second regions of the sheet metal blank at a temperature below AC3; and

transferring the sheet metal blank into a forming tool;

forming and press hardening the sheet metal blank.

20. The method of claim 19, wherein the sheet metal blank is heated to below AC1, wherein the second region is held in the temperature treatment station at below AC1.