US20170072447A1

US20170072447A1 - Moulding Tool for Producing Hot-Formed Components

Info

Publication number: US20170072447A1
Application number: US15/358,430
Authority: US
Inventors: Juergen Becker
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2014-07-18
Filing date: 2016-11-22
Publication date: 2017-03-16
Also published as: WO2016008720A1; DE102014214027A1; CN106232255B; EP3169462B1; CN106232255A; EP3169462A1

Abstract

A molding tool is provided for producing hot-formed components, in particular moulded sheet metal parts consisting of steel, aluminium, magnesium or a combination thereof. The tool has a lower tool part and an upper tool part which are displaceable relative to one another and have corresponding active areas for forming the component. At least some sections of at least the active area of one tool part can be cooled and the molding tool is provided with at least one descaling device.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No. PCT/EP2015/064853, filed Jun. 30, 2015, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2014 214 027.7, filed Jul. 18, 2014, the entire disclosures of which are herein expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a molding tool for producing hot-formed components.
In current automotive engineering, the comfort for vehicle occupants is improving increasingly, as a result of the use of special equipment. This includes many electromechanical components such as sensors, motors, actuators, and serves to facilitate the task of driving for the driver. However, the vehicle weight is also increasing at the same time as the growth in comfort. In order to counteract this, attempts are made in the prior art to configure the structural components of the vehicle body with a reduced weight.
The structural components of the vehicle body are not only involved decisively in the stability of the vehicle, but rather also play a decisive role in the safety in the event of a crash. In order to solve this conflict of objectives between a reduction in the component weight of structural components with simultaneous retention or realization of high mechanical properties, it has been proven in the past to produce structural components by means of hot forming. Hot-forming processes are also described in the literature as hot stamping or press hardening.
Two methods which are different in principle are known for producing hot-stamped components, in particular for producing vehicle body components. In the case of the direct hot-forming method, first of all a plate is heated in a furnace to a temperature above the austenitizing temperature of the steel and is subsequently simultaneously reshaped and cooled, that is to say hot-stamped. In the direct hot-forming process, first a component made from steel which has been finally formed and cut to size, is produced from a plate by way of cold-forming. This component is then heated in a heating system to a temperature above the austenitizing temperature of the steel and is subsequently hot-stamped in a tool by way of rapid cooling. In both hot-forming methods, the plate or a component made from steel which has already been finally formed and cut to size is reshaped thermomechanically in the tool following the heating to the austenitizing temperature. The thermomechanical reshaping takes place at a temperature above the austenitizing end temperature Ac3 (approximately 830° C.), preferably between 900 and 1100° C. The cooling of the reshaped workpieces takes place by use of a cooling unit which is situated in a closed tool body. As a result, components can be produced with particularly high mechanical properties, in particular with high strengths.
German Patent document DE 19723655 B4 discloses a method for producing sheet steel products by way of heating of a measured steel sheet, hot forming of the steel sheet in a tool pair, hardening of the product which is formed by way of rapid cooling from an austenitic temperature while it continues to be held in the tool pair, and subsequent machining of the product.
Scale formation occurs on the surface of the component as a result of the thermal reaction between the furnace atmosphere and the material of the component which can be coated or uncoated. The scale formation can already occur in the furnace or subsequent to the furnace. A protective gas atmosphere in the furnace also cannot prevent the scale formation, but rather can merely reduce it within certain limits. In the hot-forming tool, the scale deposits lead to severe wear of the tool, specifically of the inserts with integrated cooling systems which are involved in the shaping of the component. This leads to it being repeatedly necessary to stop the hot-forming plant during the process, in order to remove the scale deposits from the tool cavities of the hot-forming tool by way of compressed air or dry ice. There is a risk here of contaminating the entire plant and impairing the health of the employees.
A further disadvantage of the contamination by way of scale deposits is to be seen in the partially greatly abrasive wear of the forming tool inserts. In serious cases, the contamination can be so pronounced that the tools are subjected to a cleaning operation after every pressing operation, for example by way of spraying with compressed air or dry ice. Depending on the degree of wear, the inserts are additionally milled or built up by welding, in order to obtain the original contour shape again. Since the cooling lines of the cooling system run below the active surface at a small spacing, this overhaul work cannot be repeated as often as desired. The inserts have to be replaced completely after a certain service life. This is firstly very expensive and secondly not sustainable.
Proceeding from this prior art, the object of the present invention is to provide a molding tool for producing hot-formed components, in particular vehicle components made from sheet metal, with a high service life.
This and other objects are achieved according to the invention by a molding tool for producing hot-formed components, in particular shaped sheet metal parts made from steel, aluminum, magnesium or a combination thereof, having a tool lower part and a tool upper part which can be moved relative to one another and which are configured with corresponding active faces for shaping the component. At least the active face of a tool part is configured such that it can be cooled at least in sections. Furthermore, the forming tool can include at least one descaling device. Scale and scale dust are removed directly at the point of origin or immediately before the hot forming from the heated sheet metal part by way of the descaling device. This avoids a situation where deposits are formed in the forming tool or on its active faces.
In a first embodiment, the descaling device can be configured as an extraction and ejection device. Via specially constructed blower/intake nozzles, an air flow is generated which is deflected in the direction of the sheet metal part. When the air flow strikes the sheet metal part, the scale is swirled up and is separated from the sheet metal part. The scale which has been swirled up is extracted by way of a second air flow which is likewise generated by the descaling device. As an option, the extracted scale can subsequently be fed to recycling plants, big bags, briquetting presses, skips or the like. A particularly sustainable production process can be realized as a result.
According to a second embodiment, the descaling device can be configured as an air curtain. Air curtains are also known as air doors and function on the basis of a combination of ejecting and extracting.
According to a third embodiment, the descaling device can also be configured as a dry ice cleaning system which is integrated into the tool. The sheet metal part can be sprayed by means of dry ice with the aid of a robot or another mechanical mount, in order to remove scale.
In both embodiments, the descaling device can be arranged in front of the molding tool in the introduction direction of the component. This affords the advantage that the scale is removed even before the introduction of the sheet metal part into the hot-forming tool, and thus the risk of contamination of the molding tool is minimized.
Furthermore, the molding tool can also include a plurality of descaling devices which are arranged around the active face of the tool. According to this embodiment, ejection and extraction takes place at a plurality of locations of the molding tool. The descaling devices are positioned around the molding tool in the circumferential direction. As a result, the sheet metal part can be freed from scale formation from a plurality of sides at the same time. Furthermore, the descaling devices can also be directed directly onto the molding tool, with the result that the flows which are generated in this way act directly on the active surface of the molding tool halves. If a transmission of scale from the sheet metal part to the molding tool has taken place, the scale can be removed again in this way and the molding tool can be cleaned as a result.
In all described embodiments, the descaling device can be arranged on the tool upper part on the tool lower part or on both tool parts.
Moreover, the descaling device may be capable of being operated intermittently, said descaling device being switched off at least in a completely closed state of the molding tool and being switched on in a completely open state of the molding tool. In this way, the blowing and extracting are actuated in such a way that energy-consuming cleaning is also carried out only when the sheet metal part or the active face of the molding tool can be reached by the flows. The sustainability of the production process is advantageously increased as a result.
The descaling device can be switched on after every forming operation or after a predefined number of forming operations. This affords the advantage that deposits by way of scale can be counteracted in a preventive manner.
As an alternative, the descaling device can be activated in a manner which is dependent on the tool state. The ejection and extraction of the scale can be controlled in accordance with the degree of tool contamination by scale. The degree of contamination can be detected via a camera system of the tool.
Furthermore, air channels can be provided in at least one tool part, via which air channels air can be applied to the active surface of the tool part. The fine air channels can assist the ejection operation, with the result that a particularly thorough removal of scale can be ensured.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view through a molding tool, according to a first embodiment of the invention.

FIG. 2 is a diagrammatic sectional view through a molding tool, according to a first embodiment of the invention, in which air channels are arranged in the tool halves.

FIG. 3 is a diagrammtic plan view of a tool lower part.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a molding tool 10 which can be used in presses for hot-forming sheet metal plates to form sheet metal components 17. The molding tool 10 has a lower tool half 12 u which is seated on a base plate 11. The lower molding tool half 12 u interacts with an upper molding tool half 12 o. The mutually facing active faces of the upper molding tool half 12 o and the lower molding tool half 12 u are of corresponding configuration, with the result that they act as a die and a punch of a pressing tool. In the example which is shown in FIG. 1, the tool half 12 o is configured as a punch and the tool half 12 u is configured as a die. Without departing from the scope of the invention, the upper and the lower molding tool halves can be swapped in terms of their arrangement, with the result that the upper tool acts as a die and the lower tool acts as a punch. The upper tool half 12 o and the lower tool half 12 u can be moved relative to one another. The molding tool halves 12 o, 12 u which are shown in FIG. 1 can be moved apart from one another and together again. A sheet metal piece or a sheet metal plate is caught between the molding tool halves when the molding tool halves are moved together, and is enclosed and reshaped by the active faces. The state which is shown in FIG. 1 corresponds to an open position of the tool halves 12 u, 12 o during a reshaping operation, in which the component 17 is completed and can be removed from the molding tool 10.
A cooling system which has a plurality of cooling channels or cooling lines 14 is integrated into the insert 13. The insert 13 is provided in the lower molding tool half 12 u. The use of inserts 13 of this type affords the advantage, firstly, that different component contours can be stamped with one lower molding tool 12 u, by it being possible for the insert 13 to be exchanged in accordance with the desired component shape. The cooling lines 14 run substantially parallel to the surface of the component 17 and, therefore, also substantially parallel to the active face of the molding tool halves 12 u, 12 o. The cooling lines 14 therefore follow the component surface at a certain spacing in the insert 13 of the lower molding tool half 12 u. Targeted cooling of the component 17 in the region of the cooling channels 14 is made possible by way of the cooling channels, with the result that a structure is realized in the component in said region, with high mechanical strengths.
Descaling devices 18, 18′ are provided on the tool halves 12 u, 12 o, in each case one descaling device 18′ being arranged on the tool upper part 12 o and one descaling device 18 being arranged on the tool lower part 12 u. Both descaling devices are connected via a common line 19. Compressed air can be fed in via said line, which compressed air is then sprayed onto the component 17 or the sheet metal part which has not yet been reshaped. At the same time, the detached scale dust is collected via a further air flow and is extracted by way of the descaling device. The air which is contaminated with scale dust is discharged via the line 19 and possibly fed to a recycling plant. As can be seen from FIG. 1, the descaling device is situated in front of the molding tool in the introduction direction of the sheet metal part. In FIG. 1, the sheet metal part is introduced from the left into the hot-forming tool and is therefore cleaned of scale before the introduction between the tool halves 12 u, 12 o. If one of the descaling devices 18, 18′ is configured as an air curtain, it can run over the entire length of the sheet metal part, with the result that the sheet metal part is cleaned completely of scale when the sheet metal part is introduced.
FIG. 2 shows a molding tool with an analogous construction to that shown in FIG. 1. In addition, the molding tool halves 12 u, 12 o have air lines 15 which are connected fluidically to a distributor or connector system 16. In this way, compressed air is introduced via the connector system 16 and is distributed to the air lines 15. At the upper end of the air channels 15 in FIG. 1, outlets or openings are provided, from which the compressed air flows into the region between the molding tool halves 12 u and 12 o. The air lines 15 can be produced in any desired grid pattern and with any desired diameter, and assist the action of the descaling device 18, 18′. FIG. 2 shows a closed position of the molding tool 10. In this state, the sheet metal part 17 is hardened. The descaling device 18 is switched off.
In the figures, merely the lower tool half 12 u is provided with cooling channels 14, air channels 15 being provided in the tool upper part 12 o and the tool lower part 12 u. In further embodiments of the invention, as an alternative, the arrangement of the cooling system, that is to say the connector system 16 and the cooling channels 15, can also be arranged merely in one of the tool halves 12 u, 12 o. In a further alternative embodiment, cooling channels 14 can be provided both in the upper tool half 12 o and in the lower tool half 12 u.
FIG. 3 shows a plan view of a tool lower part 12 u of the molding tool 10. Here, by way of example, the active face is configured as a B-pillar. As an alternative, the active face can also be configured in the shape of other vehicle components or vehicle structural components. In FIG. 3, the descaling devices 18 according to a second embodiment of the invention are configured as individual extraction and ejection devices and are arranged substantially around the active face of the tool lower part 12 u. The descaling devices 18 are connected via a common feed and discharge line system 19. The air channels 15 which are described in relation to the embodiment which is shown in FIG. 2 can also be provided in the embodiment according to FIG. 3.
In the following text, the advantages of the invention are to be listed in summary. With the aid of the descaling device, an optimum plant availability can be ensured by way of an operating environment which is virtually free from scale and scale dust. In addition, an improvement in occupational safety is achieved and the health burden on the employees is reduced. A time and cost saving results from the fact that scale residues do not have to be removed manually by employees. This is accompanied by an increase in the plant speed as a result of the integrated extraction of the scale residues. On the component side, an improvement in quality can be realized by way of high quality assurance. On the tool side, the service lives of the machining tools can be extended considerably (cooling inserts) as a result of the minimization of the internal dust loading. On account of the extraction system which is then installed directly within the production line, the measuring instruments (thermographic camera systems) are no longer contaminated, and substantially more precise measurements can therefore be carried out during the production, which ultimately results in a considerable improvement in quality. The machine down times can be reduced considerably on account of the cleaning cycles which lie further apart.

LIST OF DESIGNATIONS

10 Molding tool
11 Tool base plate
12 u Tool lower part
12 o Tool upper part
13 Tool insert
14 Cooling lines
15 Air channels
16 Feed system
17 Component
18 Descaling device
19 Line system

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

What is claimed is:

1. A molding tool for producing a hot-formed component, comprising:

a tool lower part and a tool upper part which are movable relative to one another and which are configured with corresponding active faces for shaping the component, wherein

at least an active face of one of the tool parts is configured so as to be cooled at least in sections; and

at least one descaling device for the molding tool.

2. The molding tool according to claim 1, wherein the component is a shaped sheet metal part made from steel, aluminum, magnesium or a combination thereof

3. The molding tool according to claim 1, wherein the descaling device is configured as an extraction and ejection device.

4. The molding tool according to claim 1, wherein the descaling device is configured as an air curtain.

5. The molding tool according to claim 3, wherein the descaling device is also configured as an air curtain.

6. The molding tool according to claim 1, wherein the descaling device is arranged in front of the molding tool in an introduction direction of the component.

7. The molding tool according to claim 3, wherein the descaling device is arranged in front of the molding tool in an introduction direction of the component.

8. The molding tool according to claim 1, wherein the molding tool comprises a plurality of descaling devices which are arranged around the active face of the tool.

9. The molding tool according to claim 1, wherein the descaling device is arranged on the tool upper part, on the tool lower part or on both tool parts.

10. The molding tool according to claim 1, wherein the descaling device is operatable intermittently, said descaling device being switched off at least in a completely closed state of the molding tool and being switched on in a completely open state of the molding tool.

11. The molding tool according to claim 10, wherein the descaling device is switched on after every forming operation or after a predefined number of forming operations.

12. The molding tool according to claim 11, wherein the descaling device is activated in a manner which is dependent on a state of the molding tool.

13. The molding tool according to claim 1, wherein air channels are provided in at least one tool part, via which air channels air is appliable to the active face of the tool part.