Patent Application
20210260641
The invention relates to a method for producing a component having a bottom region, optionally a bottom-body transition region, optionally a body region, optionally a body-flange transition region and optionally a flange region, wherein a semifinished product made of a plastically deformable material is provided, wherein the semifinished product has a longitudinal extent and a transverse extent having a circumferential edge contour having a parting surface, wherein the semifinished product is processed in one or more stages in one or more tools to produce the component. Moreover, the invention relates to a tool for producing a component.
Cold-formed, e.g. deep-drawn components consisting of a metal sheet or blank, which is flat for example, usually require final edge trimming, during which excess regions of the formed component are cut off. In the case of flanged components, this is performed by one or more trimming tools, which partially or completely trim the flange from above or obliquely in a desired manner. In the case of flangeless components, trimming the body is significantly more complex because it generally has to be cut from the side with guidance via wedge-type slides. Trimming generally represents one or more separate operations, which require dedicated tool technology and a dedicated transfer system. Moreover, usage of material is often unfavorable as a result, and therefore further costs arise. This gives rise to very expensive and fault-prone manufacturing processes, especially for components with medium or small lot sizes, and these processes also cause an increase in the manufacturing costs of the components.
In general, the manufacture of high-strength components by means of hot forming or press hardening (likewise) involves the necessity of trimming, especially edge trimming of the components. This trimming establishes the necessary component tolerances of the component ends and of the flanges in a reliable process. A number of different technologies are available for trimming the components.
On the one hand, separate mechanical trimming can be performed on the hard component, which can have a hardness of >450 HV, wherein HV corresponds to the Vickers hardness and is determined in accordance with DIN EN ISO 6507-1:2005 to −4:2005, in which high cutting forces and, associated therewith, expensive, large-size, rigid tools are required. The tendency for high wear and the risk of local tool fractures in the case of mechanical trimming tools entail high maintenance costs.
On the other hand, hot or warm trimming integrated into the press hardening tool can be performed during or after forming. The fact that the component is in the soft, not yet hardened state and, as a result, only small cutting forces are required for trimming has an advantageous effect in this process. The challenge here is trimming waste management since hot forming presses generally do not have trimming waste wells and the trimming waste must thus be transported out of the tool with the component.
Moreover, separate laser cutting can be carried out on the hardened component, which is technically very attractive since almost any contours can be cut, irrespective of the hardness of the component. In comparison with mechanical trimming, however, manufacturing costs in large-scale production are quite high and are directly dependent on the necessary cutting length or the machining time in a laser cutting cell.
Since, as in cold forming, e.g. deep drawing, many process and material parameters, e.g. the blank and tool temperature but also the frictional forces, the sheet thickness and the material composition, may fluctuate in hot forming or press hardening, hardened components with an accurately repeatable and dimensionally accurate edge contour can be achieved only to a limited extent.
Owing to the disadvantages of the above methods, efforts are being made to minimize trimming on components or to reduce trimming lengths. Based on the existing process parameters, the manufacture of components in large-scale production with predetermined contour tolerance requirements is not possible or possible only in a complex and therefore expensive way. Given this background situation, there is still potential for improvement in respect of the production of components.
It is thus the underlying object of the invention to specify a method and a tool with which the production of components with an accurately repeatable and dimensionally accurate edge contour is possible, particularly in conjunction with a short process chain and a low susceptibility to faults.
According to a first teaching, this object is achieved by a method having the features of patent claim 1.
For the production of components, plastically deformable materials are used as a semifinished product, in particular metallic materials such as steel, aluminum, magnesium, but also thermoplastics or material composites, wherein the semifinished product has a longitudinal extent and a transverse extent having a circumferential edge contour having a parting surface.
A parting surface or parting surfaces is/are intended to mean the cut edge or cut edges of a semifinished product which, in turn, defines/define the circumferential edge contour of the semifinished product.
Precut blanks, in particular sheet-metal precut blanks which substantially form a two dimensional basic shape (development) of the subsequent three dimensionally shaped component, are referred to as shaped blanks. The semifinished product is provided as a shaped blank or precut blank, in particular sheet-metal precut blank.
The semifinished product is processed in one or more stages in one or more tools to produce a component. According to the invention, the parting surface is in contact with the tool at least temporarily, in particular during or after the processing of the semifinished product to produce the component, and at least in some section or sections.
The processing of the semifinished product to produce the component comprises shaping at least in some region or regions, upsetting at least in some region or regions, and/or elongation at least in some region or regions, which is carried out in one or more stages in one or more tools.
By virtue of the at least temporary contact of the parting surface with the tool, at least in some section or sections, in particular during or after the processing of the semifinished product to produce the component, a component with an accurately repeatable and dimensionally accurate edge contour is produced in that, in the end position of the tool, the material is converted or sized to give the desired geometry thereof, wherein thickening, but as far as possible no undulation, is permitted at least in some region or regions in the edge region close to the edge, in particular at least in some region or regions or in some section or sections in the longitudinal extent of the component to be produced. By virtue of the accurately repeatable and dimensionally accurate edge contour, edge trimming operations on the finished component can be eliminated or reduced. As a particular preference, there is contact with the tool, at least temporarily and at least in some section or sections, on two opposite parting surfaces of the component to be produced.
In particular, the opposite parting surfaces, of which there are preferably two, define two edges of the bottom region, of the optional body region or of the optional flange region, in particular along the longitudinal extent of the component to be produced.
The processing of the semifinished products to produce the components can take place in the cold state, in particular at room temperature, and also in the warm state, in particular at a temperature above room temperature, of the semifinished products. For example, semifinished products made from thermoplastics can be processed, in particular molded, while cold but also at temperatures above room temperature. For example, semifinished products made of metallic materials, in particular aluminum and magnesium, can be processed while cold. These are preferably heated to a temperature above 150° C., in particular above 200° C., before and/or during processing, preferably shaping. Semifinished products made of steel can also be processed, preferably shaped, while cold or hot. In particular, steels can be heated up to 700° C., e.g. up to 650° C., and then processed, in particular shaped, into components. As a particular preference, semifinished products made of steel are used, from which hardened components can be produced by means of processing.
According to one embodiment, a semifinished product made of a hardenable steel material with a carbon content of at least 0.15-% by weight, in particular of at least 0.22% by weight, preferably of at least 0.27% by weight, is provided for the production of a hardened component. The hardenable steel material can be a steel for quenching and tempering, in particular a C22, C35, C45, C55, C60, 42CrMo4 steel, a steel containing manganese, in particular a 16MnB5, 16MnCr5, 20MnB5, 22MnB5, 30MnB5, 36MnB5, 37MnB4, 37MnB5, 40MnB4 steel, a case-hardening steel, an air-hardening steel or a multi-layer steel material composite, e.g. one having two, preferably three, steel layers, of which at least one is hardenable. The use of tailored rolled blanks or tailored welded blanks is also possible. Depending on the composition of the hardenable steel material, corresponding parameters, e.g. the Ac1 temperature, Ac3 temperature, Ms-Start and other parameters for heat treatment or heating/cooling can be taken from “ZTU” diagrams.
The hardenable steel material can also be provided with an anticorrosion coating or anti-scale coating, preferably based on zinc and/or aluminum.
In the case of multi-layer steel material composites, the outer layers may preferably consist of a scale- and/or corrosion-resistant steel. Anti-scale protection offers advantages in processing, while anti-corrosion protection offers advantages in the application or use of the finished component. Stainless steels are preferably used as outer layers. As a result, lightweight construction targets are feasible in application or cost-optimized processing processes through more rapid heating of the semifinished products.
For the production of a hardened component, a semifinished product is provided which, on the one hand, is subjected in the form of a shaped blank to heat treatment at least in some region or regions, preferably fully to heat treatment, wherein the shaped blank is heated to a temperature, in particular above the Ac1 temperature, preferably above the Ac3 temperature, formed in one or more stages, and hardened at least in some region or regions by cooling (direct hot forming) or, on the other hand, the semifinished product is first of all cold-formed into a preform, the preform is subjected to heat treatment at least in some region or regions, preferably fully to heat treatment, wherein the preform is heated to a temperature, in particular above the Ac1 temperature, preferably above the Ac3 temperature, and is then hardened by cooling at least in some region or regions (indirect hot forming). Here, the Ac1 temperature corresponds to the temperature as a function of the composition of the hardenable steel material at which the microstructure is converted into austenite, or the Ac3 temperature corresponds to the temperature at which conversion fully into austenite is complete. A hardened microstructure can be produced at least in some region or regions of the component or in the entire component by cooling. The hardened microstructure is defined by a substantially martensitic and/or bainitic microstructure, wherein the percentage of martensite and/or bainite in the microstructure is at least 70% by area, in particular at least 80% by area, preferably at least 90% by area, particularly preferably 95% by area. The heating in at least some region or regions to at least one partial austenitization temperature (above the Ac1 temperature) is accomplished by suitable means, e.g. by means of inductors, furnaces, lasers, contact heating or burners.
The semifinished product made of a hardenable steel material can be fed as a shaped blank for direct hot forming or as a sheet-metal precut blank for indirect hot forming. Depending on the complexity of the component or sheet-metal component to be produced, additional trimming can be allowed for after the production of the preform in the case of indirect hot forming.
A cross section should be interpreted to mean a section or the extent substantially transversely to the longitudinal extent of the sheet-metal component produced or to be produced.
A hardened component having an accurately repeatable and dimensionally accurate edge contour is produced in that, in the end position of the tool, the material is converted or sized to give the desired geometry thereof, wherein thickening, but as far as possible no undulation, is permitted at least in some region or regions in the edge region close to the edge, in particular at least in some region or regions or in some section or sections in the longitudinal extent of the component to be produced. The thickening of the edge region takes place substantially in the still-hot and unhardened state, and therefore plastic deformation or massive deformation is possible without high press forces, thus making it possible to produce a hardened component with an accurately repeatable and dimensionally accurate edge contour which corresponds to the desired geometry within narrow tolerances. By virtue of the accurately repeatable and dimensionally accurate edge contour, edge trimming operations on the finished component can be eliminated or at least very largely reduced.
According to another embodiment, the semifinished product, in particular as a sheet-metal precut blank, is cold-formed to give a preform having a bottom region, a bottom-body transition region, a body region, optionally a body-flange transition region and optionally a flange region, wherein the geometry of the preform or individual preform regions differ, at least in some region or regions, from the geometry of the component or of individual component regions. In a first embodiment, the preform has a bottom region, a bottom-body transition region and a body region, wherein the preform is heated in a furnace, preferably in a continuous furnace, to at least Ac1 temperature, in particular fully to the Ac3 temperature, the heated preform is placed in an open tool for hardening, said tool preferably being actively cooled and comprising at least one female die and one punch, and the sheet-metal component produced is hardened, at least in some region or regions, through contact with the tool by closing the tool, wherein the punch and/or the female die act/acts to exert pressure, at least in some section or sections, on the parting surface of the body region, in particular along the longitudinal extent of the component produced or to be produced. In an alternative embodiment, the preform has a bottom region, a bottom-body transition region, a body region, a body-flange transition region and a flange region, wherein the preform is heated in a furnace, preferably in a continuous furnace to at least Ac1 temperature, in particular fully to the Ac3 temperature, the heated preform is placed in an open tool for hardening, said tool preferably being actively cooled and comprising at least one female die and one punch, and the sheet-metal component produced is hardened, at least in some region or regions, through contact with the tool by closing the tool, wherein the female die and/or the punch act/acts to exert pressure, at least in some section or sections, on the parting surface of the flange region, in particular along the longitudinal extent of the sheet-metal component produced or to be produced. According to a preferred embodiment, a punch consisting of a plurality of sub-punches is used, wherein, when the tool is closed for hardening, contact is established between a first sub-punch and the bottom region, the bottom-body transition region and the body region in a first step, and contact is established between a second sub-punch and the flange region in a second step. In the second step, the desired geometry of the edge contour of the sheet-metal component to the produced is established.
In a particularly preferred embodiment, a shaped blank, in particular a previously determined shaped blank, which is heated in a furnace, preferably in a continuous furnace, to at least Ac1 temperature, in particular fully to the Ac3 temperature, is used, after heating the shaped blank is placed in an open tool, said tool preferably being actively cooled and comprising at least one female die and one punch, is formed in one or more stages by shutting the tool, and the component produced is hardened, at least in some region or regions, through contact with the tool by (increasingly) closing the tool, wherein the punch and/or the female die act/acts to exert pressure, at least in some section or sections, on the parting surface of the body region, in particular along the longitudinal extent of the component to be produced, or the female die and/or the punch act/acts to exert pressure, at least in some section or sections, on the parting surface of the flange region, in particular along the longitudinal extent of the sheet-metal component to be produced, thus giving a dimensionally accurate edge contour which no longer has to be subsequently trimmed, or has to be subsequently trimmed only if required.
According to another embodiment, the tool for hardening has a female die region which is substantially vertically movable, in particular relative to the female die bearing surface, and/or a leading punch or punch region, which, after the placing of the heated shaped blank in the tool, fixes the shaped blank, together with the punch or punch region, with a clamping action, at least in the bottom region to be formed, until the tool is closed. It is thereby possible to ensure that the shaped blank can be guided and/or held in an accurate position in the tool during hot forming or until the conclusion of hardening. The female die region acts as an inner hold-down device.
According to another embodiment, the tool for hardening has an outer hold-down device, which, after the placing of the heated shaped blank in the tool, is lowered, preferably to a spaced position, before or after the coming together of the substantially vertically movable female die region and of the punch or punch region, to guide the shaped blank. Particularly when producing hardened components that have a flange region, a spaced hold-down device, which is heated or temperature-controlled when required, can guide the shaped blank edge, in particular, and thereby assist the hot forming process, wherein the spacing is chosen in such a way that the outer hold-down device has only slight contact with regions of the hot shaped blank, thereby also making it possible to substantially suppress premature cooling of the shaped blank edge due to contact with the (colder) outer hold-down device.
As a particular preference, the tool for hardening is closed before the last regions of the steel material in the tool fall below the Ms start temperature, thus making it possible to ensure for substantially all regions of the component that the desired shaping or sizing of the steel workpiece is complete before the phase transformation into martensite.
According to a second teaching, the object is achieved by a tool having the features of patent claim 10.
In particular, the tool, in particular for hardening, is part or a constituent part of a process line for producing a component having a bottom region, optionally a bottom-body transition region, optionally a body region, optionally a body-flange transition region and optionally a flange region consisting of a semifinished product, and, in particular, is suitable for carrying out the method according to the invention. The tool, in particular for hardening, comprises a female die and a punch, means for moving the punch and/or the female die, and optional means for cooling the tool.
According to the invention, the parting surface is in contact with the tool at least temporarily, in particular during or after the processing of the semifinished product to produce the component, and at least in some section or sections. The advantages of the method according to the invention also apply to the tool.
According to a first embodiment, the female die and/or the punch are/is configured in such a way that, at least in some section or sections, they/it act/s to exert pressure on the parting surface of the bottom region or of the body region or of the flange region, in particular along the longitudinal extent of the component to be produced. As a particular preference, the tool is suitable for hardening a semifinished product which consists of a hardenable steel material. However, the tool is also suitable for processing semifinished products made of aluminum, magnesium or thermoplastics and, in particular, is also embodied in such a way that it can be appropriately temperature-controlled if required.
According to one embodiment, the punch has a shoulder region for exerting pressure, at least in some section or sections, on the parting surface of the body region, in particular along the longitudinal extent of the component to be produced, and/or the female die has a shoulder region for exerting pressure, at least in some section or sections, on the parting surface of the bottom region or of the flange region, in particular along the longitudinal extent of the component to be produced. The action leads to thickening, at least in some region or regions, in particular along the longitudinal extent of the component, in particular in the edge region close to the edge of the bottom region or of the flange or body region or in the flange and/or body region and/or the body-flange transition region. As a particular preference here, the punch and/or the female die are designed in such a way, in particular in the sections in which the edge regions close to the edge may thicken, that there is more space available for plastic flow in order thereby to ensure that all regions of the component to be hardened have contact with the tool in the closed state of the tool, particularly during hardening.
According to another embodiment, the tool has at least one outer hold-down device, which is heatable if required, in particular for the supportive guidance of the shaped blank edge during hot forming.
According to another embodiment, the tool has a substantially vertically movable female die region, in particular for the clamping and positionally accurate fixing of the shaped blank together with the punch or punch region during hot forming or until the completion of hardening.
According to another embodiment, the punch consists of a plurality of sub-punches, which, in particular, are arranged in the working direction relative to one another and are preferably individually controllable or movable in order to produce a component, in particular a hardened component, with a flange region, in particular in several steps.
According to another embodiment, the punch is coupled to a punch holder, wherein the punch is arranged in such a way that it can be moved toward and away from the punch holder in the working direction. The punch is arranged mechanically spaced apart from the punch holder, e.g. by means of a spring element, or hydraulically by suitable means. This is advantageous, in particular, to enable fluctuating body lengths or body heights, for example, to be better compensated.
The invention is explained in greater detail below with reference to drawings.
Identical parts are provided with identical reference signs. In the drawings:
The following explanations show methods and tools for the production of a component, in particular a hardened component or sheet-metal component, wherein, in the simplest embodiment thereof and for the sake of illustration, the sheet-metal component to be produced has a symmetrical cross section along its longitudinal extent. Owing to the resulting symmetry (mirror symmetry on the axis of symmetry S), only partial sections of the right-hand side are shown. Of course, any cross-sectional shapes are conceivable, particularly in combination with cross-sections that vary along the longitudinal extent of the sheet-metal component to be produced and with curvatures in all directions.
A hardenable steel material is generally unwound from a coil (not illustrated), cut to length and made available to the further process as a blank (step A,
The heated preform (1′) is placed in an open tool (2) for hardening, which is actively cooled by suitable means, e.g. by means of cooling passages (2.X), which are supplied with a cooling fluid and are arranged or integrated in the tool (2), close to the contour surface, and comprises at least one female die (2.1) and one punch (2.2) (
Through the (increasing) closure of the tool (2), the preform (1′) is hardened, at least in some region or regions, by contact with the tool (2). The closure of the tool (2) takes place in several steps, wherein, in the first step, a first sub-punch (2.21) is moved into the female die (2.1) and contact is thereby established between the first sub-punch (2.21) and the bottom region (1′.1), the bottom-body transition region and the body region (1′.2) (
In a further example of indirect hot forming, the steps mentioned in connection with
The heated preform (1′) having a bottom region (1′.1), a bottom-body transition region and a body region (1′.2) is placed in an open tool (2), which is actively cooled by suitable means, e.g. by means of cooling passages (2.X), which are supplied with a cooling fluid and are arranged or integrated in the tool (2), close to the contour surface, and comprises a female die (2.1) and a punch (2.2) (
In another example of direct hot forming, a hardenable steel material is unwound from a coil (not illustrated), cut to length and made available to the further process as a blank, wherein, as a particular preference, the blank corresponds to a shaped blank (step A,
The heated preform (1′) is placed in an open tool (2) for hardening, which is actively cooled by suitable means, e.g. by means of cooling passages (2.X), which are supplied with a cooling fluid and are arranged or integrated in the tool (2), close to the contour surface, and comprises at least one female die (2.1), one punch (2.2) and one hold-down device (2.3), which is heatable if required (
Through the (increasing) closure of the tool (2), the shaped blank (1′) is first of all formed and then hardened, at least in some region or regions, by contact with the tool (2). The closure of the tool (2) takes place in several steps, wherein, in the first step, the hold-down device (2.3), which is heated if required, is lowered onto a spacer element (2.4) and held in order to provide supportive guidance for the shaped blank edge during hot forming. The spacer element (2.4) has the effect that only point contacts arise with the hot shaped blank (1′) and can also serve as a positioner for the placement of the hot shaped blank (1′). At the same time or at offset times, the female die region (2.11) and the punch (2.2) or punch region are moved relative to one another until they receive the shaped blank (1′) between them in a clamped manner (
In a further example of direct hot forming, the steps mentioned in connection with
The heated shaped blank (1′) is placed in an open tool (2) for hardening, which is actively cooled by suitable means, e.g. by means of cooling passages (2.X), which are supplied with a cooling fluid and are arranged or integrated in the tool (2), close to the contour surface, and comprises at least one female die (2.1), one punch (2.2) and one hold-down device (2.3), which is heated if required (
Through the closure of the tool (2), the shaped blank (1′) is first of all formed and then hardened, at least in some region or regions, by contact with the tool (2). The closure of the tool (2) takes place in several steps, wherein, in the first step, the hold-down device (2.3), which is heated if required, is lowered onto a spacer element (2.4) and held in order to provide supportive guidance for the shaped blank edge during hot forming. The spacer element (2.4) has the effect that only a few point contacts arise with the hot shaped blank (1′). At the same time or at offset times, the female die region (2.11) and the punch (2.2) or punch region are moved relative to one another until they receive the shaped blank (1′) between them in a clamped manner. The clamped region corresponds to the bottom region (1.1) to be formed on the sheet-metal component (1) to be produced. The punch (2.2) or punch region and the female die region (2.11) travel together with the clamped shaped blank (1′) into the female die (2.1), and a bottom-body transition region and a body region form as inward travel progresses (
In the sectional illustration of the tool (2) in
The invention is not restricted to the above-described embodiments and to the general description. In particular, all the features mentioned in relation to the method and in relation to the tool can be combined with one another. In the simplest embodiment, the component can be a substantially flat design and have only one bottom region and, in particular, can be thickened in the edge region close to the edge. Further embodiments of components having a bottom region, a bottom-body transition region, a body region, optionally a body-bottom transition region and optionally a flange region have been described. In addition to steel, which can be processed either cold or hot, other metals, such as aluminum, magnesium or other materials, e.g. thermoplastics, which can be processed especially in the cold or the hot state, can also be used. The preferably hardened sheet-metal component produced by the method according to the invention is used as a bodywork or chassis component in passenger cars, utility vehicles, commercial vehicles, heavy goods vehicles, special vehicles, buses, omnibuses, agricultural machines, construction machines, with or without an internal combustion engine and/or an electric drive, and trailers. Hardened sheet-metal components produced according to the invention can also be used in vehicle attachments, e.g. in assembled battery cases for electric or hybrid vehicles. Components produced according to the invention can also be used in applications that are not specific to vehicles.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/072244 | 9/5/2017 | WO | 00 |
