Patent Application
20240123486
The present application claims priority to European Application Number 22189765.5 filed Aug. 10, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present disclosure relates to a method for producing a motor vehicle component by hot-forming and hot-cutting.
A sheet metal plate made of a hardenable steel alloy is heated to a temperature above the Ac1 or Ac3 point. The plate which has been heated in this manner is then inserted in a forming tool and formed in the hot state. Subsequently, the forming tool is kept closed during a direct hot-forming process and rapidly cooled so that the formed plate is hardened. In this instance, tensile strengths of more than 1400 MPa are possible. The feature is that the hardened material structure is able to be mechanically reprocessed with great complexity. This great complexity involves, for example, an edge cut. The edge cut, in order to achieve a high level of precision of the component, is carried out in most cases after the forming method. The component precision is thereby precise with regard to the outer contour. However, the plate which has already been hardened is able to be processed with structural complexity and high abrasive wear of the tool which is problematic. Laser-cutting also leads to a high expenditure in the production or manufacture of the component. A cold cut on hardened components is not recommended as a result of the risk of (micro) cracks.
The problem of edge cutting is in some circumstances reinforced as another specific feature when the plates have different wall thicknesses, for example, with tailor welded blanks (TWB), which plates are welded together from different wall thicknesses or steel alloys. Weld seam overhangs, weld seam shrinkage (inward indentation) beyond the plate edge contour or also a plate offset between the two plates which are connected to each other are problematic and in some instances require trimming after the TWB are welded together.
An object of the present disclosure is to set out a possible method of producing a component by means of hot-forming in a cost-effective manner and at the same time increased precision.
The object mentioned above is achieved according to the disclosure with a method for producing a motor vehicle component by hot-forming and hot-cutting.
The method according to at least one embodiment of the disclosure is used to produce a motor vehicle component. The motor vehicle components are able to be, for example, a motor vehicle B-pillar, a motor vehicle pillar, a tunnel-like member, a bumper or bumper bracket, or the like. Flange-free reinforcement components which are at least partially U-shaped in cross section are also able to be produced, as such components are able to be used as insertion components or patches in order to reinforce the above-mentioned components internally or externally and to form a local dual metal sheet layer. They are produced by means of hot-forming and hot-cutting and optionally press-hardening in a combined tool.
All this is carried out in one press stroke.
The method according to at least one embodiment of the disclosure has the following method steps:
According to at least one embodiment of the disclosure, the plate which has been inserted is already guided through before the beginning of the forming operation or in the initial time of the forming operation and the cut is completed in this time period.
A vertical cutting movement is carried out exclusively at the edge cutting. The cutting tool itself is driven exclusively by means of the press stroke itself. There are no additional active drives exclusively for the cutting tool. There is also no wedge-like cross slide. A cut in a horizontal direction does not take place.
As a result of these measures according to at least one embodiment of the disclosure, components which are C-shaped or hat-shaped in cross section with high tolerance requirements are able to be produced. Components are also able to be produced from tailor welded blanks or plates having different regions with a different wall thickness. In this instance, no finishing cut has to be carried out as a tolerance cut. Insertion tolerances with respect to a separate pre-insertion in the hot-forming tool and a previously occurring simple plate cut are also dispensed with.
Forming components which are U-shaped or C-shaped in cross section are also able to be produced. Flange-free components which, as a result of the vertical orientation of the U-shaped or C-shaped members, would not be able to be cut in a press after the forming operation has been completed or only with a high degree of complexity.
The method makes provision for the plate to be inserted in the hot-forming tool at a temperature greater than 500° C., or greater than 550° C. The plate is also able to be inserted in the hot-forming tool at a temperature greater than Ac1 or greater than Ac3. Depending on the steel alloy used, the Ac temperature is greater than 700° C., the Ac3 temperature is greater than 900° C.
So that the plate is fixed in position, there is arranged on the upper tool a stamp which precedes the upper tool. The plate which is inserted in the hot-forming tool is placed on a lower molding jaw. The stamp is then lowered onto the plate and clamps the plate between the stamp and lower molding jaw in a state fixed in position. The hot-cutting operation is then carried out. This is able to be carried out before the beginning of the actual forming operation.
The hot-cutting operation is carried out as an at least partial to completely circumferential edge cut of the plate. To this end, an externally circumferential cutting tool is provided on the actual hot-forming tool. The edge cut is also able to be carried out completely in such a manner that initially a partially circumferential plate cut is carried out, before the plate is heated. During the hot-cutting operation in the local forming tool, the remaining edge cut is then carried out so that overall a completely circumferential edge cut is carried out. No subsequent edge cut is necessary. No lasering or hard-cutting is necessary.
The cutting tool is able to be arranged completely relative to the upper tool and lower tool. The cutting tool is also able to be integrated in the upper tool and/or the lower tool, in an upper molding jaw and/or in a lower molding jaw.
Alternatively to a complete edge cut prior to the beginning of the forming operation, the edge cut is also able to be carried out at a first time or first phase of the forming operation. The edge cut is carried out when the plate itself is still completely in a planar horizontal state or has a slight degree of forming. This is during a time period of less than 50%, less than 30%, or less than 20% of the forming progression.
In at least one embodiment of the disclosure, this time period is also able to be based on the overall press stroke which has been carried out by the upper tool and lower tool with respect to each other. The cutting operation is begun and terminated at least 20%, more than 30%, or more than 50% of the press stroke before the bottom dead center position is reached, with a completely closed forming tool. This means, in the case of 50%, that the edge cut is terminated when the upper tool is lowered onto the lower tool, with respect to the entire press stroke, that this stroke has progressed to a maximum of 50% and before the press stroke reaches the bottom dead center position of the forming tool.
Following the edge cut, the hot-forming operation is then carried out or terminated and an optional press-hardening takes place, when a hardenable steel alloy is used.
The edge cut severs the plate completely in terms of the wall thickness thereof.
The edge cut is carried out at a temperature of from 550° C. to 700° C. According to the disclosure, this temperature, depending on the steel alloy used, an optimum level of cutting capability of the steel and abrasive wear on the cutting tools is produced, also in the material structure which is produced at the cutting edge.
If the edge cut has been carried out, the cut plate which is intended to be formed is drawn into the interior of the mold hollow space which is produced. The members, which may be bent, of the motor vehicle component or formed component which is produced are able to extend in a vertically orientated manner so that where applicable no vertically orientated cut would be able to be carried out.
This is achieved according to the disclosure by a preceding edge cut in the horizontal state of the plate.
The edge cut is terminated at least 20 mm, more than 30 mm, more than 50 mm, more than 80 mm, and more than 100 mm before reaching the bottom dead center of the hot-forming tool.
In the context of this patent, the terms hot-forming tool and hot-cutting tool are also used for the forming and cutting tool.
Other advantages, features, properties, aspects of the present disclosure are set out in the following description.
They provide a simpler understanding of the disclosure. In the figures:
In the Figures, the same reference numerals are used for identical and similar components, even if a repeated listing is omitted for reasons of simplicity.
By further lowering, illustrated in
At the time of
In the case of
The foregoing description of some embodiments of the disclosure has been presented for purposes of illustration and description. The description is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. Various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22189765.5 | Aug 2022 | EP | regional |
