EP3108019B1 - Method for conductively heating sheet metal in pairs, and heating device for carrying out said method - Google Patents
Method for conductively heating sheet metal in pairs, and heating device for carrying out said method Download PDFInfo
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- EP3108019B1 EP3108019B1 EP15705981.7A EP15705981A EP3108019B1 EP 3108019 B1 EP3108019 B1 EP 3108019B1 EP 15705981 A EP15705981 A EP 15705981A EP 3108019 B1 EP3108019 B1 EP 3108019B1
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- sheet
- conductive heating
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/40—Direct resistance heating
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/0004—Devices wherein the heating current flows through the material to be heated
Definitions
- the invention relates to a method for conductive heating of a sheet, wherein the sheet or at least one conductive area of the sheet to be heated has an outer contour, which is not rectangular, according to claim 1.
- the invention also relates to a conductive heating device for performing a method for conductive heating of a sheet according to claim 10.
- the invention relates to the field of metalworking, in particular the production of parts made of sheet metal, such as. B. vehicle body panels.
- the production of such sheet metal parts is z. B. on production lines, such. B. extrusion lines.
- Such production lines usually have forming facilities and trimming equipment and optionally facilities for performing other methods, such. B. shape property changes, coating, press hardening, etc., which are connected to each other in terms of process technology.
- components made of high-strength or vorfestem material to be produced are made of high-strength or fungem material to be produced.
- a sheet In press hardening, a sheet is heated to a temperature of about 950 ° C and cooled during molding.
- a martensitic structure By targeted cooling (hardening) during press hardening via cooled pressing tools, a martensitic structure can be created that leads to the desired material properties, eg. B. to a tensile strength of more than 1,500 MPa strains in the range of> 5%.
- a disadvantage of such heating processes are the relatively long heating times, at the conventional heating z. B. occur in roller hearth furnaces. As a result of the long heating times, a scale formation on the material (burnup of material), which is also disadvantageous.
- coatings are applied to the component surfaces in accordance with the prior art, which diffuse into the component during the heating of the furnace. The production of coatings is associated with additional effort and costs.
- An alternative to conventional, relatively long-lasting heating is the heating of a sheet by a conductive heating process.
- the sheet is heated by applying an electric current through the resulting current heat.
- a typical warm-up process can be carried out in less than 10 seconds, which has the advantage that no appreciable scale layers can form in the short time, which in turn has the advantage that no scale protection coatings are required.
- a conductive heating process of metal sheets is e.g. B. in the DE 10 2006 037 637 A1 described.
- the invention is therefore based on the object to provide a method for conductive heating of a sheet, wherein the sheet or at least one conductively heated region of the sheet has an outer contour, which is not rectangular, with the still a uniform heating of the area to be heated can be achieved.
- the sheet is called in the terminology of the expert also board and the non-rectangular board blank is called form board. Furthermore, a suitable for this purpose conductive heating device should be specified.
- the invention has the advantage that a tailored to the outer contour of the sheet or the area to be heated sheet metal arrangement of power supply and current dissipation electrodes is provided, which are arranged piecewise separated along the outer contour and are acted upon by electrically separate electrical energy sources : So can z.
- the outer contour of the area to be heated in individual turn rectangular surface portions or at least substantially rectangular surface portions are divided and created for each surface section a customized power supply and Stromableitungselektrode with which exactly this area is acted upon by the desired current density.
- a further pair of power supply and current dissipation electrodes can be arranged and via a second electrical Power source with a matched voltage or a matched current are applied, so that the same current density is generated as in the adjacent area previously mentioned.
- the entire area to be heated can be subdivided into substantially rectangular area sections, and the same current density can be generated in each area section.
- transverse currents between the surface sections are avoided, which in turn prevents undefined heating results. Due to the resistance conditions, the current density inevitably sets in and basically can not be forced homogeneously.
- the conductive heating process with its advantages can thus be made universally usable for any shaped metal sheets.
- the sheet can be regarded as a resistor in which the current supplied via the electrodes flows.
- sheets can be brought almost without scale to the desired temperature.
- the heating process can be performed in a period of 10 seconds or less.
- the heating time can be determined by the size of the power supply. Basically, the more current is passed through the sheet, the faster the heating can be performed.
- a sheet is every sheet of electrically conductive metal in question, such. B. steel, aluminum and magnesium sheets.
- the sheet has it in one advantageous development of the invention to a constant material thickness, at least before it is further processed after the conductive heating process and thereby optionally transformed.
- a current supply electrode serves to introduce electrical current from the electrical energy source into the metal sheet.
- a current dissipation electrode serves to drain the current from the sheet back to the source of electrical energy.
- the electrical energy sources are dimensioned such that the same current densities are introduced from the power supply electrodes in the sheet over all pairs of associated power supply and Stromableitungselektroden and derived from the sheet via the Stromableitungselektroden.
- the number of current supply electrodes used may be equal to or different from the number of current discharge electrodes used. With the same number, it is advantageous if in each case one current supply electrode and one current discharge electrode form a pair of such electrodes, which are each connected to the same electrical energy source. It is also possible, for. B. electrically connect two power supply electrodes to each other or electrically connect two Stromableitungselektroden together. The non-interconnected electrodes are then connected to different electrical energy sources with different voltage, so that in turn equal current densities can be generated in adjacent surface areas in the sheet.
- the electrically separate electrical sources must be electrically separated from each other at least at one of its terminals (plus or minus).
- the plurality of energy sources are not connected to each other and not grounded.
- the potential of the adjacent energy sources "floats" at the contact line, similar to multiple spot welds operated simultaneously on a vehicle body.
- the "swim" is a well-known term from the resistance welding technique.
- the area to be conductively heated can be divided into substantially rectangular area sections.
- the region to be heated conductively can also be divided into trapezoidal surface sections or substantially trapezoidal surface sections.
- a combination is also advantageous, ie a division of the region to be heated conductively into rectangular and / or trapezoidal surface sections.
- a pair of sheets is electrically interconnected by a plurality of electrically insulated from each other, side by side along a transition region from one to the other sheet in their respective trapezoidal surface portions arranged transfer electrodes. By correspondingly opposing arrangements of one sheet with respect to the other sheet can be created in this way with respect.
- the two connected by means of the transition electrodes trapezoidal surface sections turn a total rectangular surface section, connected to the one side at least one power supply electrode and at the other side at least one current dissipation electrode can be.
- the flexibility and applicability of the method according to the invention is further increased. It is advantageous, trapezoidal surface portions of the sheets with the same or mirror-symmetrical outer To connect contour with each other via the transition electrodes.
- trapezoidal surface portions of the same sheet can be electrically connected to each other in pairs via the transfer electrodes to electrically behave then like a rectangular surface section.
- the trapezoidal surface portions are suitable to divide, in particular with equal angles bevelled sides.
- one, several or all current supply and current discharge electrodes are each formed as elongated electrodes extending with their largest dimension over a portion of the outer contour of the conductive region to be heated, each of which is connected to an electrical lead only at one end are connected to the electrical energy source.
- a pair of current supply and current discharge electrodes are connected at diagonally opposite ends to the electrical energy source.
- one, several or all of the power supply, Stromableitungs- and / or transmission electrodes are formed as cooled with a cooling medium electrodes. So can be used as a cooling medium z. B. be passed through a hollow channel of the respective electrode cooling water.
- the cooling of the electrodes has the advantage that they do not heat undesirable and a heating-related change in resistance of the electrodes is avoided.
- a further advantage is that the adjacent sheet is cooled by the cooled electrodes, so that by appropriate arrangement of the electrodes to desired, not to be heated areas of the sheet heating and a concomitant hardening can be avoided. This in turn has the advantage that by the location and arrangement of the electrodes z. B. cutting areas in the subsequent processing of the component, i.
- edge trimming can be done with conventional tools, eg. B. by the very economical applicable shear cutting. A more elaborate Hartbezel is not required. Also, for joining the component in later welding processes, it is favorable to have non-hardened edge regions. Curing can be done by a subsequent press hardening process.
- the conductive heating is carried out by means of direct current.
- This has the advantage compared to alternating current that electrical losses and other adverse effects can be excluded by existing inductors and capacitances in the system. It also generates no reactive power.
- the existing electrical power can be used completely in the form of active power. By eliminating inductive losses line cross sections and electrical energy sources, eg. As transformers are smaller. In addition, energy is saved.
- the electrical energy sources can, for. B. three-phase can be supplied from the three-phase network. Also, the calculation and design of the entire system, in particular the electrodes and their arrangement is simplified, because you can work with the simpler, applicable to direct current electrical engineering laws.
- the conductive heating device can be realized comparatively easily and inexpensively.
- one, several or all current supply, Stromableitungs- and / or transfer electrodes are moved away from each other during the conductive heating process in order to stretch the sheet.
- a heating-related expansion of the heated area of the sheet during the heating process can be compensated.
- a parallel conductor is connected to this electrode for supplying current to a current supply electrode, for transferring energy from or to a transfer electrode and / or for current discharge from a current discharge electrode, which runs parallel to the current lines flowing therein over part of the sheet to be heated is conducted electrically isolated over the sheet metal against the sheet.
- the parallel conductor may in particular be guided on an edge region of a rectangular or trapezoidal surface section to be heated.
- one, several or all parallel conductors are designed as conductors cooled with a cooling medium.
- a conductive heating device according to claim 10.
- the advantages mentioned above with regard to the method for conductive heating can likewise be realized.
- the conductive heating device is set up to carry out a method of the type described above.
- the electrical energy sources may be formed as DC sources.
- the conductive heating device has a stretching device which is set up to stretch the sheet at least in the conductive heated area during the heating process is.
- the stretching apparatus may in particular be adapted to move certain current supply, current discharge and / or transfer electrodes away from one another during the conductive heating process.
- the electrode arrangement of the conductive heating device has transfer electrodes for current transfer between two sheets simultaneously heated in the conductive heating device.
- a method of conductively heating a sheet e.g. Example, be arranged such that the sheet to be heated is placed in the conductive heating device, then electrodes of the conductive heating device are pressed onto the sheet and then the electrical current flow through the sheet is switched via the electrodes to perform the conductive heating, and after sufficient heating the electrodes are removed from the sheet again, it being advantageous to first turn off the flow of current.
- the sheet can then continue in the heated state be processed, for. B. be brought by pressing in a desired shape.
- an electrical energy source z. B. have a welding rectifier. In this way, the required direct current in the desired height of several thousand amps can be provided in a simple and cost-effective manner.
- the current supply, Stromableitungs- and / or transfer electrodes can, for. B. made of copper or alloyed copper, z. B. CuCoBe or CuBe 2 . Especially with the latter alloys, very hard, robust electrodes can be provided.
- the mentioned parallel conductors can be made of the same material or another material. For the electrical insulation of the parallel conductors, these z. B. have on the surface of a plasma-sprayed ceramic layer.
- the conductive heating process can be carried out heat-encapsulated according to an advantageous embodiment of the invention.
- the sheets are characterized by an external heat encapsulation, for. B. a thermal insulation of the conductive heating device, thermally shielded from the environment.
- B. a thermal insulation of the conductive heating device, thermally shielded from the environment.
- the FIG. 1 shows in plan view a cut into a specific shape sheet 1, the z. B. is cut out of a steel coil. It is a shell component for a B-pillar of a motor vehicle before forming in a press.
- the metal sheet 1 is first subdivided into substantially rectangular surface sections 2, 4 and a substantially trapezoidal surface section 3.
- electrodes of an electrode arrangement of a conductive heating device are made tailor-made, which are then connected to the sheet 1 for carrying out the conductive heating process.
- the area section 3 In order to further optimize the manufacturing process in the case of non-rectangular area sections which result from the subdivision explained above, in this case the area section 3, according to the invention two sheets 1 are simultaneously heated in the conductive heating device.
- the two sheets are preferably next as in FIG. 2 shown arranged and created the required electrodes accordingly.
- the FIG. 3 shows the in FIG. 2 illustrated sheets 1, according to FIG. 3
- the conductive heating device 10 comprises the aforementioned custom-made electrode assembly, the power supply electrodes 11, 12, 13, 14, 15, power dissipation electrodes 16, 17, 18, 19, 20 and transfer electrodes 31 has.
- At the rectangular surface portions 2, 4 of the sheets 1 are respective pairs of each of a power supply electrode and a power dissipation electrode, as in FIG FIG.
- the transfer electrodes 31 are electrically isolated from each other, e.g. B. by being arranged as metal blocks with a certain distance from each other. In this way will be out of the two trapezoidal surface sections 3, a uniform electrical rectangular area between the electrodes 12, 19 created.
- the transfer electrodes 31 may, for. B. at a width of 20 mm at a distance of 5 mm from each other. In order to ensure a uniform spacing of the transfer electrodes from each other, they can, for. B. be mounted on an insulating plate and pressed as a one-piece transfer electrode assembly on the sheets 1. In an industrial implementation, e.g. all electrodes are mounted on a large base plate, with installation e.g. in a hydraulic press.
- FIG. 4 shows a further conductive heating device 10, which is adapted to not heat the respective surface portions 4 of the sheets 1.
- the electrodes 14 and 17 are not connected directly to their respective electrical energy source 22 and 25, but over along the direction of current flow in the respective sheet guided parallel conductor 26, 27 by the parallel conductors 26, 27 can continue a parallel course of the streamlines in the adjacent surface portions 3 are ensured to the transfer electrodes 31, which would not be ensured without the parallel electrodes 26, 27.
- the parallel electrodes 26, 27 can be cooled, which has the further advantage that the cooling is also transferred to the sheet 1 and thus unwanted heat transfer from the heated surface portions of the sheet can be prevented in the non-heated surface portions 4.
- the transmission electrodes 31 may be formed as cooled electrodes.
- the FIG. 5 shows an example of a cooled electrode on the basis of the parallel conductor 27. In the longitudinal direction through the respective electrode extends a bore 28, which forms a cooling channel. Through the cooling channel can coolant, z. As cooling water, are passed. If the electrode is designed as a parallel conductor 26, 27, this is formed insulated on the outer surface, ie there is no electrical contact with the sheet 1. In the remaining electrodes 11, 12, 13, 14, 15, 16, 17, 18, 19 , 20, 31 of course, the electrical contact with the sheet 1 is necessary.
- the FIG. 5 shows an example of a cooled electrode on the basis of the parallel conductor 27. In the longitudinal direction through the respective electrode extends a bore 28, which forms a cooling channel. Through the cooling channel can coolant, z. As cooling water, are passed. If the electrode is designed as a parallel conductor 26, 27, this is formed insulated on the outer surface, ie there is no electrical contact with the sheet 1. In the remaining electrodes 11, 12, 13, 14, 15, 16,
- FIG. 5 shows by means of two parallel conductor 27 by way of example a paired arrangement above and below the sheet 1.
- the arranged below the plate 1 parallel conductor 27 is based on a thrust bearing 32 against a contact force F, which is exerted on the above the plate 1 arranged parallel conductor 27.
- FIG. 6 shows a further embodiment of a conductive heating device 10, which, except for the differences explained below of the device 10 according to FIG. 4 equivalent.
- the conductive heating device is adapted with regard to the formation of the parallel conductors 26, 27 and the transmission electrodes 21 by forming these not as linearly extending electrodes, but according to the desired ones , are angled to be heated surface areas.
- the current supply electrode 12 and the current discharge electrode 19 are accordingly compared to FIG. 4 something shortened trained.
- the sheets 1 can also be different than before in the FIGS. 2 to 6 be arranged represented, for. B. as in the FIG. 7 specified.
- the rectangular surface sections 2 and 4 are as described above with the current supply electrodes and the current collector electrodes and the associated connected to electrical energy sources.
- trapezoidal surface portions 3 results in comparison to the embodiments described above, the difference that to maintain the same current densities and thus the same heating behavior for connecting the surface portions 3 between the sheets 1 not juxtaposed transfer electrodes are provided, but as shown arranged crosswise Transfer electrodes 31, so that by the transfer electrodes 31 results in a spider-like construction.
- the transfer electrodes 31 are still electrically isolated from each other, z. B. by the electrodes are passed past each other in different height levels or are designed as electrically insulated cable. As a result, homogeneous resistance ratios can be realized analogous to rectangular sheets.
- An advantage of this embodiment is the saving of two energy sources, since the rectangular surface sections 2, 4 of the board can be connected as a series circuit to a power source.
- the surface portions 2 are connected in series with the power source 22.
- the electrodes 14, 16 can be connected together or combined to form an electrode.
- the surface portions 4 are connected in series with the power source 24.
- the electrodes 15, 17 can be connected together or combined to form an electrode.
- connection points of the connection lines of the energy sources to the electrodes are as far apart as possible and the current discharge points as possible further apart.
- FIG. 8 shows an advantageous embodiment of an electrode 80, which can be used as Stromzu effets-, Stromableitungs- and / or transfer electrode.
- the electrode 80 in turn has a bore 28 which forms a cooling channel.
- the in the illustration according to FIG. 8 The upwardly facing surface of the electrode 80, which is the contact surface of the electrode with the sheet, is formed unevenly with a certain structure. In the illustrated embodiment, a comb-like structure is created by 81 grooves 82 are formed between elevations. By such an uneven surface, which is brought into contact with the sheet to be heated, isolated hotspots can be selectively avoided, ie places where there is an above-average heating of the sheet.
- hotspots have been considered to be disadvantageous and attempts have been made to avoid them because they have the disadvantage that the sheet is heated uncontrollably in such places.
- a positive temperature coefficient of the sheet also increases with the heating of the specific electrical resistance at such locations of the sheet, so that a kind of avalanche effect occurs because the hotspot areas heat comparatively quickly and come at the points of highest temperature to damage the sheet can (burn).
- the conductive heating device according to the invention is further developed by forming at least one current supply, current dissipation and / or transition electrode as an electrode 80 with an uneven structured contact surface.
- the contact surface of the electrode is a surface that is electrically brought into direct contact with the sheet.
- the uneven structured contact surface of the electrode can be realized, for example, by providing a plurality of rectangular electrode edges, as in US Pat FIG. 8 shown. Instead of the illustrated linear pattern, the uneven structured contact surface may also be formed by punctiform elevations on the surface.
- the surface structure of the contact surface may be a regular or irregular structure.
- the method according to the invention is thus further developed in that the conductive heating of the sheet takes place via an uneven structured contact surface of at least one current supply, current discharge and / or transition electrode.
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Description
Die Erfindung betrifft ein Verfahren zum konduktiven Erwärmen eines Blechs, wobei das Blech oder zumindest ein konduktiv zu erwärmender Bereich des Blechs eine äußere Kontur hat, die nicht rechteckförmig ist, gemäß dem Anspruch 1. Die Erfindung betrifft außerdem eine konduktive Erwärmungseinrichtung zur Durchführung eines Verfahrens zum konduktiven Erwärmen eines Blechs gemäß dem Anspruch 10.The invention relates to a method for conductive heating of a sheet, wherein the sheet or at least one conductive area of the sheet to be heated has an outer contour, which is not rectangular, according to
Allgemein betrifft die Erfindung das Gebiet der Metallbearbeitung, insbesondere der Herstellung von Teilen aus Blech, wie z. B. Fahrzeug-Karosserieteile. Die Fertigung solcher Blech-Formteile erfolgt z. B. auf Fertigungsstraßen, wie z. B. Serienpressstraßen. Solche Fertigungsstraßen weisen üblicherweise Umformeinrichtungen und Beschneideinrichtungen sowie gegebenenfalls Einrichtungen zur Durchführung weiterer Verfahren, wie z. B. Formeigenschaftsänderungen, Beschichtung, Presshärtung etc. auf, die prozesstechnisch miteinander verbunden sind. In vielen Fällen sollen dabei Bauteile aus hoch- bzw. höchsfestem Material hergestellt werden.In general, the invention relates to the field of metalworking, in particular the production of parts made of sheet metal, such as. B. vehicle body panels. The production of such sheet metal parts is z. B. on production lines, such. B. extrusion lines. Such production lines usually have forming facilities and trimming equipment and optionally facilities for performing other methods, such. B. shape property changes, coating, press hardening, etc., which are connected to each other in terms of process technology. In many cases, components made of high-strength or hochsfestem material to be produced.
Beim Presshärten wird ein Blech auf eine Temperatur von ca. 950°C erwärmt und während der Formgebung abgekühlt. Durch gezielte Abkühlung (Härten) während des Presshärtens über gekühlte Presswerkzeuge kann ein martensitisches Gefüge geschaffen werden, dass zu den gewünschten Werkstoffeigenschaften führt, z. B. zu einer Zugfestigkeit von über 1.500 MPa Dehnungen im Bereich von >5 %. Nachteilig bei solchen Erwärmungsprozessen sind die relativ langen Erwärmungszeiten, die bei der konventionellen Erwärmung z. B. in Rollenherdöfen auftreten. Als Folge der langen Erwärmungszeiten kommt es zu einer Zunderbildung am Material (Abbrand von Material), was ebenfalls nachteilig ist. Um dem entgegenzuwirken, werden dem Stand der Technik folgend Beschichtungen auf den Bauteiloberflächen aufgebracht, die während der Ofenerwärmung in das Bauteil hinein diffundieren. Die Herstellung der Beschichtungen ist mit zusätzlichem Aufwand und Kosten verbunden.In press hardening, a sheet is heated to a temperature of about 950 ° C and cooled during molding. By targeted cooling (hardening) during press hardening via cooled pressing tools, a martensitic structure can be created that leads to the desired material properties, eg. B. to a tensile strength of more than 1,500 MPa strains in the range of> 5%. A disadvantage of such heating processes are the relatively long heating times, at the conventional heating z. B. occur in roller hearth furnaces. As a result of the long heating times, a scale formation on the material (burnup of material), which is also disadvantageous. In order to counteract this, coatings are applied to the component surfaces in accordance with the prior art, which diffuse into the component during the heating of the furnace. The production of coatings is associated with additional effort and costs.
Eine Alternative zur konventionellen, relativ lange dauernden Erwärmung ist die Erwärmung eines Blechs durch einen konduktiven Erwärmungsprozess. Dabei wird das Blech durch Anlegen eines elektrischen Stroms durch die dabei entstehende Stromwärme erwärmt. Bei entsprechend großen elektrischen Strömen kann ein typischer Aufwärmprozess in weniger als 10 Sekunden durchgeführt werden, was den Vorteil hat, dass sich in der kurzen Zeit keine nennenswerten Zunderschichten bilden können, was wiederum den Vorteil hat, dass keine Zunderschutzbeschichtungen erforderlich sind. Ein konduktiver Erwärmungsprozess von Metallblechen ist z. B. in der
Die Vorschläge aus dem Stand der Technik sind bisher in der Praxis nur sehr begrenzt anwendbar, weil sie sich nur für Erwärmungsprozesse von nahezu rechteckigen Bauteilen oder rechteckigen Teilbereichen von Bauteilen eignen. Viele in der Praxis zu fertigende Bauteile, z. B. Karosseriebauteile bei Kraftfahrzeugen, weisen jedoch nicht diese ideale Rechteckform des zu erwärmenden Blechs oder eines zu erwärmenden Bereichs des Blechs auf. Vielmehr sind viele Bauteile unregelmäßig geformt. Bei Anwendung der Vorschläge aus dem Stand der Technik wäre eine ungleichmäßige Erwärmung des Bauteils die Folge, was wiederum nicht zu den gewünschten Fertigungsergebnissen führt.The proposals from the prior art have hitherto been applicable in practice only to a very limited extent, because they are only suitable for heating processes of nearly rectangular components or rectangular partial regions of components. Many components to be manufactured in practice, eg. As body parts in motor vehicles, but do not have this ideal rectangular shape of the sheet to be heated or a portion of the sheet to be heated. Rather, many components are irregular shaped. When applying the proposals of the prior art, uneven heating of the component would result, which in turn does not lead to the desired manufacturing results.
Aus der
Der Erfindung liegt daher die Aufgabe zu Grunde, ein Verfahren zum konduktiven Erwärmen eines Blechs anzugeben, wobei das Blech oder zumindest ein konduktiv zu erwärmender Bereich des Blechs eine äußere Kontur hat, die nicht rechteckförmig ist, mit dem dennoch eine gleichmäßige Erwärmung des zu erwärmenden Bereichs erzielt werden kann. Das Blech heißt in der Terminologie des Fachmanns auch Platine und der nicht-rechteckige Platinenzuschnitt heißt Formplatine. Ferner soll eine hierfür geeignete konduktive Erwärmungseinrichtung angegeben werden.The invention is therefore based on the object to provide a method for conductive heating of a sheet, wherein the sheet or at least one conductively heated region of the sheet has an outer contour, which is not rectangular, with the still a uniform heating of the area to be heated can be achieved. The sheet is called in the terminology of the expert also board and the non-rectangular board blank is called form board. Furthermore, a suitable for this purpose conductive heating device should be specified.
Diese Aufgabe wird durch ein Verfahren zum konduktiven Erwärmen eines Blechs gemäß Anspruch 1 gelöst. Die Erfindung hat den Vorteil, dass eine an die äußere Kontur des Blechs bzw. des zu erwärmenden Bereichs des Blechs maßgeschneidert angepasste Anordnung von Stromzuleitungs- und Stromableitungselektroden geschaffen wird, die stückweise getrennt entlang der äußeren Kontur angeordnet werden und von elektrisch getrennten elektrischen Energiequellen beaufschlagt werden: So kann z. B. die äußere Kontur des zu erwärmenden Bereichs in einzelne wiederum rechteckige Flächenabschnitte oder zumindest im Wesentlichen rechteckige Flächenabschnitte aufgeteilt werden und für jeden Flächenabschnitt eine angepasste Stromzuleitungs- und Stromableitungselektrode geschaffen werden, mit denen genau dieser Bereich mit der gewünschten Stromdichte beaufschlagt wird. In einem benachbarten, ebenfalls im Wesentlichen rechteckförmig definierten Flächenabschnitt kann ein weiteres Paar von Stromzuleitungs- und Stromableitungselektroden angeordnet werden und über eine zweite elektrische Energiequelle mit einer angepassten Spannung oder einem angepassten Strom beaufschlagt werden, sodass die gleiche Stromdichte erzeugt wird wie in dem benachbarten, zuvor angegebenen Flächenabschnitt. Auf diese Weise kann der gesamte zu erwärmende Bereich in im Wesentlichen rechteckige Flächenabschnitte unterteilt werden und in jedem Flächenabschnitt die gleiche Stromdichte erzeugt werden. Durch Erzeugung der gleichen Stromdichten in allen Flächenabschnitten werden Querströme zwischen den Flächenabschnitten vermieden und damit wiederum undefinierte Erwärmungsergebnisse verhindert. Die Stromdichte stellt sich aufgrund der Widerstandsverhältnisse zwangsläufig ein und kann grundsätzlich nicht homogen erzwungen werden. Nur eine homogene Stromdichte erwirkt aber homogene Erwärmung, da immer die gleiche Leistung pro Fläche umgesetzt wird. Hier wird der Ansatz verfolgt, die Widerstandsverhältnisse in der Formplatine durch die beschriebene Art und Weise so einzustellen, dass homogene Stromdichten resultieren. Auf diese Weise kann eine gleichmäßige konduktive Erwärmung auch eines unregelmäßig geformten Blechs oder eines unregelmäßig geformten zu erwärmenden Bereichs des Blechs realisiert werden. Durch die Erfindung kann somit der konduktive Erwärmungsprozess mit seinen Vorteilen universell für beliebig geformte Bleche einsetzbar gemacht werden. Zur Erzeugung nahezu gleicher, homogener Stromdichten kann dabei das Blech als Widerstand angesehen werden, in dem der über die Elektroden zugeführte Strom fließt.This object is achieved by a method for conductive heating of a sheet according to
Mit der Erfindung können Bleche nahezu zunderfrei auf die gewünschte Temperatur gebracht werden. Der Erwärmungsprozess kann in einem Zeitraum von 10 Sekunden oder weniger durchgeführt werden. Die Erwärmungsdauer kann dabei durch die Größe der Stromzufuhr festgelegt werden. Grundsätzlich gilt, je mehr Strom durch das Blech geführt wird, desto schneller kann die Erwärmung durchgeführt werden.With the invention sheets can be brought almost without scale to the desired temperature. The heating process can be performed in a period of 10 seconds or less. The heating time can be determined by the size of the power supply. Basically, the more current is passed through the sheet, the faster the heating can be performed.
Als Blech kommt jedes Blech aus elektrisch leitfähigem Metall in Frage, wie z. B. Stahl-, Aluminium- und Magnesiumbleche. Das Blech weist dabei in einer vorteilhaften Weiterbildung der Erfindung eine gleichbleibende Materialdicke auf, zumindest bevor es nach dem konduktiven Erwärmungsprozess weiter bearbeitet wird und dabei gegebenenfalls umgeformt wird.As a sheet is every sheet of electrically conductive metal in question, such. B. steel, aluminum and magnesium sheets. The sheet has it in one advantageous development of the invention to a constant material thickness, at least before it is further processed after the conductive heating process and thereby optionally transformed.
Eine Stromzuleitungselektrode dient dabei zum Einleiten elektrischen Stroms von der elektrischen Energiequelle in das Blech. Eine Stromableitungselektrode dient zum Ableiten des Stroms von dem Blech zurück zur elektrischen Energiequelle. Gemäß einer vorteilhaften Weiterbildung der Erfindung sind die elektrischen Energiequellen derart dimensioniert, dass über alle Paare von einander zugeordneten Stromzuleitungs- und Stromableitungselektroden gleiche Stromdichten von den Stromzuleitungselektroden in das Blech eingeleitet und über die Stromableitungselektroden von dem Blech abgeleitet werden.A current supply electrode serves to introduce electrical current from the electrical energy source into the metal sheet. A current dissipation electrode serves to drain the current from the sheet back to the source of electrical energy. According to an advantageous embodiment of the invention, the electrical energy sources are dimensioned such that the same current densities are introduced from the power supply electrodes in the sheet over all pairs of associated power supply and Stromableitungselektroden and derived from the sheet via the Stromableitungselektroden.
Die Anzahl der verwendeten Stromzuleitungselektroden kann gleich oder ungleich der Anzahl der verwendeten Stromableitungselektroden sein. Bei gleicher Anzahl ist es vorteilhaft, wenn jeweils eine Stromzuleitungselektrode und eine Stromableitungselektrode ein Paar solcher Elektroden, die jeweils an dieselbe elektrische Energiequelle angeschlossen sind, bilden. Es ist auch möglich, z. B. zwei Stromzuleitungselektroden elektrisch miteinander zu verbinden oder zwei Stromableitungselektroden elektrisch miteinander zu verbinden. Die jeweils nicht miteinander verbundenen Elektroden sind dann an verschiedene elektrische Energiequellen mit unterschiedlicher Spannung verbunden, sodass wiederum gleiche Stromdichten in benachbarten Flächenbereichen in dem Blech erzeugt werden können.The number of current supply electrodes used may be equal to or different from the number of current discharge electrodes used. With the same number, it is advantageous if in each case one current supply electrode and one current discharge electrode form a pair of such electrodes, which are each connected to the same electrical energy source. It is also possible, for. B. electrically connect two power supply electrodes to each other or electrically connect two Stromableitungselektroden together. The non-interconnected electrodes are then connected to different electrical energy sources with different voltage, so that in turn equal current densities can be generated in adjacent surface areas in the sheet.
Die voneinander elektrisch getrennten elektrischen Energiequellen müssen dabei zumindest an einem ihrer Anschlüsse (Plus oder Minus) voneinander elektrisch getrennt sein. In einer vorteilhaften Weiterbildung der Erfindung sind die mehreren Energiequellen untereinander nicht verbunden und nicht geerdet. Hierdurch "schwimmt" sich das Potential der benachbarten Energiequellen an der Berührungslinie ein, ähnlich wie bei mehreren gleichzeitig betriebenen Punktschweißungen an einer Fahrzeugkarosserie. Das "Einschwimmen" ist ein bekannter Begriff aus der Widerstandsschweißtechnik.The electrically separate electrical sources must be electrically separated from each other at least at one of its terminals (plus or minus). In an advantageous embodiment of the invention, the plurality of energy sources are not connected to each other and not grounded. As a result, the potential of the adjacent energy sources "floats" at the contact line, similar to multiple spot welds operated simultaneously on a vehicle body. The "swim" is a well-known term from the resistance welding technique.
Zur Sicherstellung der gleichen Stromdichten in dem Blech ist es ferner vorteilhaft, wenn zwischen einem Paar von einander zugeordneten Stromableitungs- und Stromzuleitungselektroden keine andere Elektrode angeordnet wird, über die dem Blech von einer weiteren elektrischen Energiequelle Strom zugeleitet oder von dem Blech Strom zu einer weiteren elektrischen Energiequelle abgeleitet wird. Hierdurch werden Unregelmäßigkeiten in der gewünschten gleichen Stromdichte in dem Blech vermieden.To ensure the same current densities in the sheet, it is also advantageous if between a pair of associated Stromableitungs- and power supply electrodes, no other electrode is arranged, fed to the sheet of electricity from another electric power source or from the sheet of electricity to another electrical Energy source is derived. As a result, irregularities in the desired same current density in the sheet are avoided.
Wie erwähnt, kann der konduktiv zu erwärmende Bereich in im Wesentlichen rechteckige Flächenabschnitte aufgeteilt werden. Der konduktiv zu erwärmende Bereich kann auch in trapezförmige Flächenabschnitte oder im Wesentlichen trapezförmige Flächenabschnitte aufgeteilt werden. Auch eine Kombination ist vorteilhaft, d.h. eine Aufteilung des konduktiv zu erwärmenden Bereichs in rechteckige und/oder trapezförmige Flächenabschnitte. Zur Erreichung gleicher Stromdichten in trapezförmigen Flächenabschnitten wird gemäß der Erfindung ein Paar von Blechen durch mehrere elektrisch gegeneinander isolierte, nebeneinander entlang eines Übergangsbereichs von einem zum anderen Blech in deren jeweils trapezförmigen Flächenabschnitten angeordneten Übertragungselektroden miteinander elektrisch verbunden. Durch entsprechend gegensätzliche Anordnungen des einen Blechs gegenüber dem anderen Blech kann auf diese Weise bzgl. der zwei mittels der Übergangselektroden verbundenen trapezförmigen Flächenabschnitte wiederum ein insgesamt rechteckförmiger Flächenabschnitt geschaffen werden, an den an einer Seite wenigstens eine Stromzuleitungselektrode und an der anderen Seite wenigstens eine Stromableitungselektrode angeschlossen werden kann. Auf diese Weise wird die Flexibilität und Anwendbarkeit des erfindungsgemäßen Verfahrens weiter erhöht. Vorteilhaft ist es dabei, trapezförmige Flächenabschnitte der Bleche mit gleicher oder spiegelsymmetrischer äußerer Kontur miteinander über die Übergangselektroden zu verbinden.As mentioned, the area to be conductively heated can be divided into substantially rectangular area sections. The region to be heated conductively can also be divided into trapezoidal surface sections or substantially trapezoidal surface sections. A combination is also advantageous, ie a division of the region to be heated conductively into rectangular and / or trapezoidal surface sections. In order to achieve the same current densities in trapezoidal surface portions, a pair of sheets is electrically interconnected by a plurality of electrically insulated from each other, side by side along a transition region from one to the other sheet in their respective trapezoidal surface portions arranged transfer electrodes. By correspondingly opposing arrangements of one sheet with respect to the other sheet can be created in this way with respect. The two connected by means of the transition electrodes trapezoidal surface sections turn a total rectangular surface section, connected to the one side at least one power supply electrode and at the other side at least one current dissipation electrode can be. In this way, the flexibility and applicability of the method according to the invention is further increased. It is advantageous, trapezoidal surface portions of the sheets with the same or mirror-symmetrical outer To connect contour with each other via the transition electrodes.
Gemäß einer vorteilhaften Weiterbildung der Erfindung können auch trapezförmige Flächenabschnitte desselben Blechs paarweise elektrisch miteinander über die Übertragungselektroden miteinander elektrisch verbunden werden, um sich elektrisch dann wie ein rechteckförmiger Flächenabschnitt zu verhalten. Hierzu sind die trapezförmigen Flächenabschnitte geeignet einzuteilen, insbesondere mit gleichen Winkeln abgeschrägter Seiten.According to an advantageous embodiment of the invention, trapezoidal surface portions of the same sheet can be electrically connected to each other in pairs via the transfer electrodes to electrically behave then like a rectangular surface section. For this purpose, the trapezoidal surface portions are suitable to divide, in particular with equal angles bevelled sides.
Im Ergebnis können somit auch bei trapezförmigen Flächenabschnitten auf diese Weise homogene Widerstandsverhältnisse analog zu rechteckförmigen Blechen realisiert werden.As a result, even with trapezoidal surface sections in this way homogeneous resistance ratios can be realized analogous to rectangular sheets.
Gemäß der Lehre der Erfindung werden damit vielfältig kompliziert geformte Bleche auf eine Rechteckform bzw. eine Kombination von Rechteckformen zurückgeführt, sodass mit geringem operativem Aufwand gleiche Stromdichten erzeugt werden können.According to the teachings of the invention, a variety of complicated shaped sheets are thus attributed to a rectangular shape or a combination of rectangular shapes, so that the same current densities can be generated with little operational effort.
Gemäß einer vorteilhaften Weiterbildung der Erfindung sind eine, mehrere oder alle Stromzuleitungs- und Stromableitungselektroden jeweils als längliche, sich mit ihrer größten Abmessung über einen Abschnitt der äußeren Kontur des konduktiv zu erwärmenden Bereichs erstreckende Elektroden ausgebildet, die jeweils nur an einem Ende mit einer elektrischen Zuleitung mit der elektrischen Energiequelle verbunden sind. Dies hat den Vorteil, dass die elektrische Energie an einer definierten Stelle der Elektrode eingespeist bzw. abgeführt wird. Dies vereinfacht die Berechnung und Auslegung der erforderlichen Elektroden.According to an advantageous development of the invention, one, several or all current supply and current discharge electrodes are each formed as elongated electrodes extending with their largest dimension over a portion of the outer contour of the conductive region to be heated, each of which is connected to an electrical lead only at one end are connected to the electrical energy source. This has the advantage that the electrical energy is fed or removed at a defined point of the electrode. This simplifies the calculation and design of the required electrodes.
Gemäß einer vorteilhaften Weiterbildung der Erfindung wird ein Paar von Stromzuleitungs- und Stromableitungselektroden an diagonal gegenüberliegenden Enden mit der elektrischen Energiequelle verbunden. Dies hat den Vorteil, dass sich für jede Stromlinie des durch das Blech fließenden Stroms derselbe Gesamtwiderstand ergibt, da jeweils ein mehr oder weniger großer Anteil der Stromzuleitungs- und Stromableitungselektrode durchflossen werden muss und diese Anteile für jede Stromlinie in Summe immer denselben Wert ergeben. Auch hierdurch kann das Ziel einer gewünschten gleichen Stromdichte in dem Blech gefördert werden. Es gilt:
Gemäß einer vorteilhaften Weiterbildung der Erfindung sind eine, mehrere oder alle Stromzuleitungs-, Stromableitungs- und/oder Übertragungselektroden als mit einem Kühlmedium gekühlte Elektroden ausgebildet. So kann als Kühlmedium z. B. durch einen Hohlkanal der jeweiligen Elektrode Kühlwasser geleitet werden. Die Kühlung der Elektroden hat den Vorteil, dass sich diese nicht unerwünscht erhitzen und eine erwärmungsbedingte Widerstandsänderung der Elektroden vermieden wird. Ein weiterer Vorteil ist, dass durch die gekühlten Elektroden auch das angrenzende Blech gekühlt wird, sodass durch entsprechende Anordnung der Elektroden an gewünschten, nicht zu erwärmenden Bereichen des Blechs eine Erwärmung und eine damit einhergehende Härtung vermieden werden kann. Dies hat wiederum den Vorteil, dass durch die Lage und Anordnung der Elektroden z. B. Schnittbereiche bei der späteren Weiterverarbeitung des Bauteils, d.h. des Blechs nach der Umformung, definiert werden können, die nicht gehärtet sind. Auf diese Weise kann ein Randbeschneiden mit konventionellen Werkzeugen erfolgen, z. B. durch das sehr wirtschaftlich anwendbare Scherschneiden. Ein aufwendigeres Hartbeschneiden ist nicht erforderlich. Auch für ein Fügen des Bauteils in späteren Schweißprozessen ist es günstig, nicht gehärtete Randbereiche zu haben. Eine Härtung kann durch einen anschließenden Presshärteprozess erfolgen.According to an advantageous embodiment of the invention, one, several or all of the power supply, Stromableitungs- and / or transmission electrodes are formed as cooled with a cooling medium electrodes. So can be used as a cooling medium z. B. be passed through a hollow channel of the respective electrode cooling water. The cooling of the electrodes has the advantage that they do not heat undesirable and a heating-related change in resistance of the electrodes is avoided. A further advantage is that the adjacent sheet is cooled by the cooled electrodes, so that by appropriate arrangement of the electrodes to desired, not to be heated areas of the sheet heating and a concomitant hardening can be avoided. This in turn has the advantage that by the location and arrangement of the electrodes z. B. cutting areas in the subsequent processing of the component, i. of the sheet after forming, can be defined, which are not hardened. In this way, edge trimming can be done with conventional tools, eg. B. by the very economical applicable shear cutting. A more elaborate Hartbeschneiden is not required. Also, for joining the component in later welding processes, it is favorable to have non-hardened edge regions. Curing can be done by a subsequent press hardening process.
Gemäß einer vorteilhaften Weiterbildung der Erfindung wird die konduktive Erwärmung mittels Gleichstrom durchgeführt. Dies hat im Vergleich zu Wechselstrom den Vorteil, dass elektrische Verluste und sonstige nachteilige Effekte durch im System vorhandene Induktivitäten und Kapazitäten ausgeschlossen werden können. Es wird dadurch auch keine Blindleistung erzeugt. Die vorhandene elektrische Leistung kann vollständig in Form von Wirkleistung genutzt werden. Durch den Entfall induktiver Verluste können Leitungsquerschnitte und elektrische Energiequellen, z. B. Transformatoren, kleiner dimensioniert werden. Zudem wird Energie gespart. Die elektrischen Energiequellen können z. B. dreiphasig aus dem Drehstromnetz versorgt werden. Auch die Berechnung und Auslegung des gesamten Systems, insbesondere der Elektroden und deren Anordnung, vereinfacht sich, weil mit den einfacheren, für Gleichstrom geltenden elektrotechnischen Gesetzmäßigkeiten gearbeitet werden kann.According to an advantageous embodiment of the invention, the conductive heating is carried out by means of direct current. This has the advantage compared to alternating current that electrical losses and other adverse effects can be excluded by existing inductors and capacitances in the system. It also generates no reactive power. The existing electrical power can be used completely in the form of active power. By eliminating inductive losses line cross sections and electrical energy sources, eg. As transformers are smaller. In addition, energy is saved. The electrical energy sources can, for. B. three-phase can be supplied from the three-phase network. Also, the calculation and design of the entire system, in particular the electrodes and their arrangement is simplified, because you can work with the simpler, applicable to direct current electrical engineering laws.
Durch die Erfindung kann auf komplizierte Steuerungen für die Erzeugung gleichmäßiger Stromdichten im Blech verzichtet werden. Hierdurch kann die konduktive Erwärmungseinrichtung vergleichsweise einfach und kostengünstig realisiert werden.By the invention can be dispensed with complicated controls for the generation of uniform current densities in the sheet. As a result, the conductive heating device can be realized comparatively easily and inexpensively.
Gemäß einer vorteilhaften Weiterbildung der Erfindung werden eine, mehrere oder alle Stromzuleitungs-, Stromableitungs- und/oder Übertragungselektroden während des konduktiven Erwärmungsprozesses voneinander fortbewegt, um das Blech zu strecken. Hierdurch kann eine erwärmungsbedingte Ausdehnung des erwärmten Bereichs des Blechs während des Erwärmungsprozesses kompensiert werden.According to an advantageous embodiment of the invention, one, several or all current supply, Stromableitungs- and / or transfer electrodes are moved away from each other during the conductive heating process in order to stretch the sheet. As a result, a heating-related expansion of the heated area of the sheet during the heating process can be compensated.
Gemäß einer vorteilhaften Weiterbildung der Erfindung wird zur Stromzuführung zu einer Stromzuleitungselektrode, zur Stromübertragung von oder zu einer Übertragungselektrode und/oder zur Stromableitung von einer Stromableitungselektrode ein Parallelleiter an diese Elektrode angeschlossen, der über einen Teil des zu erwärmenden Blechs parallel zu den Stromlinien darin fließender Ströme gegenüber dem Blech elektrisch isoliert über das Blech geführt wird. Der Parallelleiter kann insbesondere an einem Randbereich eines zu erwärmenden rechteckigen oder trapezförmigen Flächenabschnitts geführt sein.According to an advantageous development of the invention, a parallel conductor is connected to this electrode for supplying current to a current supply electrode, for transferring energy from or to a transfer electrode and / or for current discharge from a current discharge electrode, which runs parallel to the current lines flowing therein over part of the sheet to be heated is conducted electrically isolated over the sheet metal against the sheet. The parallel conductor may in particular be guided on an edge region of a rectangular or trapezoidal surface section to be heated.
Dies hat den Vorteil, dass durch entsprechende Anordnung eines solchen Parallelleiters bestimmte Bereiche des Blechs von einer Erwärmung ausgeschlossen werden können und zugleich die Stromlinien in einem dem Parallelleiter benachbarten zu erwärmenden Flächenabschnitt in der gewünschten Richtung geführt werden können. Insbesondere kann ein unerwünschter Stromfluss durch den nicht zu erwärmenden Bereich des Blechs durch Stromverdrängungseffekte (Abstoßung von parallel angeordneten stromdurchflossenen Leitern) vermieden werden. Die Feldlinien stoßen sich ebenfalls ab. Auf diese Weise können z. B. sogenannte Tailored Tempered Blanks hergestellt werden, d. h. Bleche, die nur in bestimmten, gewünschten Bereichen gehärtet sind und in anderen Bereichen ungehärtet bleiben. Dies ist z. B. bei Fahrzeugkarosserieteilen zum Erzeugen eines bestimmten Verformungsverhaltens im Crashfall gewünscht. Der Parallelleiter muss elektrisch isoliert sein, aber nicht unbedingt thermisch. Auf diese Weise kann der Parallelleiter eine erwünschte Kühlung des Blechs bewirken.This has the advantage that by appropriate arrangement of such a parallel conductor certain areas of the sheet can be excluded from heating and at the same time the streamlines can be performed in a direction adjacent to the parallel conductor to be heated surface portion in the desired direction. In particular, unwanted current flow through the area of the sheet which is not to be heated can be avoided by means of current displacement effects (repulsion of conductors arranged in parallel current-carrying). The field lines are also repelled. In this way, for. B. so-called tailored tempered blanks are made, d. H. Sheets that are only hardened in certain desired areas and remain uncured in other areas. This is z. B. desired in vehicle body parts for generating a certain deformation behavior in the event of a crash. The parallel conductor must be electrically isolated, but not necessarily thermally. In this way, the parallel conductor can cause a desired cooling of the sheet.
Gemäß einer vorteilhaften Weiterbildung der Erfindung sind eine, mehrere oder alle Parallelleiter als mit einem Kühlmedium gekühlte Leiter ausgebildet.According to an advantageous development of the invention, one, several or all parallel conductors are designed as conductors cooled with a cooling medium.
Die eingangs genannte Aufgabe wird außerdem durch eine konduktive Erwärmungseinrichtung gemäß Anspruch 10 gelöst. Mit der konduktiven Erwärmungseinrichtung sowie den nachfolgend genannten weiteren Ausgestaltungen der konduktiven Erwärmungseinrichtung können ebenfalls die zuvor bezüglich des Verfahrens zum konduktiven Erwärmen genannten Vorteile realisiert werden.The aforementioned object is also achieved by a conductive heating device according to
Gemäß einer vorteilhaften Weiterbildung der Erfindung ist die konduktive Erwärmungseinrichtung zur Durchführung eines Verfahrens der zuvor beschriebenen Art eingerichtet. So können z. B. die elektrischen Energiequellen als Gleichstromquellen ausgebildet sein.According to an advantageous development of the invention, the conductive heating device is set up to carry out a method of the type described above. So z. B. the electrical energy sources may be formed as DC sources.
Gemäß einer vorteilhaften Weiterbildung der Erfindung weist die konduktive Erwärmungseinrichtung eine Streckvorrichtung auf, die zum Strecken des Blechs zummindest in dem konduktiv erwärmten Bereich während des Erwärmungsprozesses eingerichtet ist. Die Streckvorrichtung kann insbesondere dazu eingerichtet sein, während des konduktiven Erwärmungsprozesses bestimmte Stromzuleitungs-, Stromableitungs- und/oder Übertragungselektroden voneinander fortzubewegen.According to an advantageous development of the invention, the conductive heating device has a stretching device which is set up to stretch the sheet at least in the conductive heated area during the heating process is. The stretching apparatus may in particular be adapted to move certain current supply, current discharge and / or transfer electrodes away from one another during the conductive heating process.
Gemäß der Erfindung weist die Elektrodenanordnung der konduktiven Erwärmungseinrichtung Übertragungselektroden zur Stromübertragung zwischen zwei in der konduktiven Erwärmungseinrichtung gleichzeitig erwärmten Blechen auf.According to the invention, the electrode arrangement of the conductive heating device has transfer electrodes for current transfer between two sheets simultaneously heated in the conductive heating device.
Unter Anwendung der zuvor erläuterten konduktiven Erwärmungseinrichtung kann ein Verfahren zum konduktiven Erwärmen eines Blechs z. B. derart durchgeführt werden, dass das zu erwärmende Blech in der konduktiven Erwärmungseinrichtung angeordnet wird, dann Elektroden der konduktiven Erwärmungseinrichtung auf das Blech gepresst werden und dann der elektrische Stromfluss durch das Blech über die Elektroden eingeschaltet wird, um die konduktive Erwärmung durchzuführen, und nach ausreichender Erwärmung die Elektroden wieder vom Blech entfernt werden, wobei es vorteilhaft ist, zuvor den Stromfluss abzuschalten. Das Blech kann dann im erwärmten Zustand weiter verarbeitet werden, z. B. durch Pressen in eine gewünschte Form gebracht werden.Using the conductive heating device explained above, a method of conductively heating a sheet, e.g. Example, be arranged such that the sheet to be heated is placed in the conductive heating device, then electrodes of the conductive heating device are pressed onto the sheet and then the electrical current flow through the sheet is switched via the electrodes to perform the conductive heating, and after sufficient heating the electrodes are removed from the sheet again, it being advantageous to first turn off the flow of current. The sheet can then continue in the heated state be processed, for. B. be brought by pressing in a desired shape.
Zur Bereitstellung des Gleichstroms kann eine elektrische Energiequelle z. B. einen Schweißgleichrichter aufweisen. Auf diese Weise kann auf einfache und kostengünstige Weise der erforderliche Gleichstrom in der gewünschten Höhe von mehreren Tausend Ampere bereitgestellt werden.To provide the direct current, an electrical energy source z. B. have a welding rectifier. In this way, the required direct current in the desired height of several thousand amps can be provided in a simple and cost-effective manner.
Die Stromzuleitungs-, Stromableitungs- und/oder Übertragungselektroden können z. B. aus Kupfer oder legiertem Kupfer hergestellt sein, z. B. aus CuCoBe oder CuBe2. Insbesondere mit den letztgenannten Legierungen können sehr harte, robuste Elektroden bereitgestellt werden. Die genannten Parallelleiter können aus demselben Material oder einem anderen Material hergestellt werden. Für die elektrische Isolation der Parallelleiter können diese z. B. an der Oberfläche eine plasmagespritzte Keramikschicht aufweisen.The current supply, Stromableitungs- and / or transfer electrodes can, for. B. made of copper or alloyed copper, z. B. CuCoBe or CuBe 2 . Especially with the latter alloys, very hard, robust electrodes can be provided. The mentioned parallel conductors can be made of the same material or another material. For the electrical insulation of the parallel conductors, these z. B. have on the surface of a plasma-sprayed ceramic layer.
Der konduktive Erwärmungsprozess kann gemäß einer vorteilhaften Weiterbildung der Erfindung wärmegekapselt durchgeführt werden. Dabei werden die Bleche durch eine äußere Wärmekapselung, z. B. eine Wärmeisolierung der konduktiven Erwärmungseinrichtung, thermisch von der Umgebung abgeschirmt. Hierdurch wird die Wärmestrahlung in die Umgebung reduziert und damit Kosten und Erwärmungszeit eingespart. Versuche haben gezeigt, dass einfache Wärmeabschirmplatten schon gute Vorteile bieten. Eine Isolierung wie im Ofenbau ist noch besser. Hierdurch können auch Umwelteinflüsse für den Erwärmungsprozess ausgeschlossen werden.The conductive heating process can be carried out heat-encapsulated according to an advantageous embodiment of the invention. The sheets are characterized by an external heat encapsulation, for. B. a thermal insulation of the conductive heating device, thermally shielded from the environment. As a result, the heat radiation is reduced in the environment and thus saves costs and heating time. Experiments have shown that simple Wärmeabschirmplatten already offer good benefits. An insulation as in the furnace is even better. As a result, environmental influences for the heating process can be excluded.
Die Erfindung wird nachfolgend anhand von Ausführungsbeispielen unter Verwendung von Zeichnungen näher erläutert.The invention will be explained in more detail by means of embodiments using drawings.
Es zeigen
Figur 1- ein Blech-Rohteil zur Herstellung einer B-Säule eines Kraftfahrzeugs und
- Figur 2
- zwei Blech-
Rohteile gemäß Figur 1 und Figur 3- eine konduktive Erwärmungseinrichtung sowie die zwei BlechRohteile gemäß
Figur 2 und Figur 4- eine weitere konduktive Erwärmungseinrichtung sowie die zwei Blech-Rohteile gemäß
Figur 2 und - Figur 5
- die Anordnung eines Parallelleiters auf einem Blech in Querschnittsdarstellung und
- Figur 6
- eine weitere konduktive Erwärmungseinrichtung sowie die zwei Blech-Rohteile gemäß
Figur 2 und - Figur 7
- eine weitere konduktive Erwärmungseinrichtung sowie die zwei Blech-Rohteile gemäß
Figur 2 und - Figur 8
- eine Ausführungsform einer Elektrode in perspektivischer Darstellung.
- FIG. 1
- a sheet blank for the production of a B-pillar of a motor vehicle and
- FIG. 2
- two sheet metal blanks according to
FIG. 1 and - FIG. 3
- a conductive heating device and the two BlechRohteile according to
FIG. 2 and - FIG. 4
- another conductive heating device and the two sheet blanks according to
FIG. 2 and - FIG. 5
- the arrangement of a parallel conductor on a sheet in cross-sectional view and
- FIG. 6
- another conductive heating device and the two sheet blanks according to
FIG. 2 and - FIG. 7
- another conductive heating device and the two sheet blanks according to
FIG. 2 and - FIG. 8
- an embodiment of an electrode in perspective view.
In den Figuren werden gleiche Bezugszeichen für einander entsprechende Elemente verwendet.In the figures, like reference numerals are used for corresponding elements.
Die
Zur weiteren Optimierung des Fertigungsprozesses im Fall von nicht-rechteckförmigen Flächenabschnitten, die sich aus der zuvor erläuterten Unterteilung ergeben, in diesem Fall dem Flächenabschnitt 3, werden gemäß der Erfindung zwei Bleche 1 gleichzeitig in der konduktiven Erwärmungseinrichtung erwärmt. Dafür werden die zwei Bleche vorzugsweise nächst wie in
Die
The
Die Übertragungselektroden 31 können z. B. bei einer Breite von 20 mm im Abstand von 5 mm voneinander entfernt angeordnet sein. Um eine gleichmäßige Beabstandung der Übertragungselektroden voneinander zu gewährleisten, können sie z. B. auf einer isolierenden Platte befestigt sein und als einstückige Übertragungselektroden-Anordnung auf die Bleche 1 gepresst werden. In einer Industrieumsetzung können z.B. alle Elektroden auf einer großen Grundplatte befestigt sein, mit Einbau z.B. in eine hydraulische Presse.The
In vielen Fällen sollen Bleche wie das Blech 1 gemäß
In einer vorteilhaften Ausgestaltung werden auch einige oder alle der übrigen Elektroden 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 gekühlt. Auch die Übertragungselektroden 31 können als gekühlte Elektroden ausgebildet sein. Die
Die
Die Bleche 1 können auch anders als zuvor in den
Ein Vorteil dieser Ausführungsform ist die Einsparung von zwei Energiequellen, da die rechteckförmigen Flächenabschnitte 2, 4 der Platine als Reihenschaltung an eine Energiequelle angeschlossen werden können. So sind die Flächenabschnitte 2 in Reihe mit der Energiequelle 22 verbunden. Die Elektroden 14, 16 können miteinander verbunden oder zu einer Elektrode vereint werden. Die Flächenabschnitte 4 sind in Reihe mit der Energiequelle 24 verbunden. Die Elektroden 15, 17 können miteinander verbunden oder zu einer Elektrode vereint werden.An advantage of this embodiment is the saving of two energy sources, since the
Wie erwähnt ist es vorteilhaft, ein Paar von Stromzuleitungs- und Stromableitungselektroden an diagonal gegenüberliegenden Enden mit der elektrischen Energiequelle zu verbinden. Wie zudem in den Figuren erkennbar ist, ist es zusätzlich vorteilhaft, die Anschlussstellen der Anschlussleitungen der Energiequellen an die Elektroden an einer Seite (links/rechts) des Blechs möglichst weit voneinander entfernt anzuordnen, so dass die Stromeinleitstellen möglichst weiter auseinander liegen und die Stromableitstellen möglichst weiter auseinander liegen.As mentioned, it is advantageous to connect a pair of power supply and drain electrodes at diagonally opposite ends to the source of electrical energy. As can also be seen in the figures, it is additionally advantageous to arrange the connection points of the connection lines of the energy sources to the electrodes on one side (left / right) of the sheet metal as far apart as possible so that the current introduction points are as far apart as possible and the current discharge points as possible further apart.
Die
Bisher wurden Hotspots als nachteilig angesehen und es wurde versucht, diese zu vermeiden, weil sie den Nachteil haben, dass das Blech an solchen Stellen unkontrolliert erwärmt wird. Bei positivem Temperaturkoeffizienten des Blechs erhöht sich zudem mit der Erwärmung der spezifische elektrische Widerstand an solchen Stellen des Blechs, so dass eine Art Lawineneffekt eintritt, da sich die Hotspot-Bereiche vergleichsweise schnell erwärmen und es an den Stellen der höchsten Temperatur zu Beschädigungen des Blechs kommen kann (Durchbrennen).So far, hotspots have been considered to be disadvantageous and attempts have been made to avoid them because they have the disadvantage that the sheet is heated uncontrollably in such places. With a positive temperature coefficient of the sheet also increases with the heating of the specific electrical resistance at such locations of the sheet, so that a kind of avalanche effect occurs because the hotspot areas heat comparatively quickly and come at the points of highest temperature to damage the sheet can (burn).
Demgemäß wird nach der hier beschriebenen neuen Lehre eine undefinierte bzw. vereinzelte Erzeugung von Hotspots vermieden. Stattdessen werden viele kleine Kontaktstellen nahe beieinander erzeugt, die dann für einen kontrollierten, reproduzierbaren Erwärmungsprozess und damit für einen Härtungsprozess des Blechs förderlich sind. Durch eine Kühlung der Elektrode kann dieser Effekt sogar noch verstärkt werden. Durch die Vielzahl kleiner Kontaktstellen kann eine Linie von "Mini-Hotspots" erzeugt werden, die die von der Kühlwirkung der Elektrode erzeugten Abkühlungen kompensiert.Accordingly, according to the new teaching described herein, an undefined or isolated generation of hotspots avoided. Instead, many small contact points are created close to each other, which are then conducive to a controlled, reproducible heating process and thus to a hardening process of the sheet. By cooling the electrode, this effect can even be enhanced. Due to the large number of small contact points, a line of "mini-hotspots" can be generated, which compensates for the cooling caused by the cooling effect of the electrode.
Dementsprechend wird die erfindungsgemäße konduktive Erwärmungseinrichtung weitergebildet, indem wenigstens eine Stromzuleitungs-, Stromableitungs- und/oder Übergangselektrode als Elektrode 80 mit einer unebenen strukturierten Kontaktoberfläche ausgebildet ist. Die Kontaktoberfläche der Elektrode ist eine Oberfläche, die elektrisch in direkten Kontakt mit dem Blech gebracht wird. Die unebene strukturierte Kontaktoberfläche der Elektrode kann z.B. durch Vorsehen einer Vielzahl rechtwinkliger Elektrodenkanten realisiert werden, wie in der
Das erfindungsgemäße Verfahren wird somit dahingehend weitergebildet, dass das konduktive Erwärmen des Blechs über eine unebene strukturierte Kontaktoberfläche wenigstens einer Stromzuleitungs-, Stromableitungs- und/oder Übergangselektrode erfolgt.The method according to the invention is thus further developed in that the conductive heating of the sheet takes place via an uneven structured contact surface of at least one current supply, current discharge and / or transition electrode.
Claims (13)
- Method for conductively heating a metal sheet (1), the metal sheet (1) or at least one region to be conductively heated of the metal sheet (1) that is having a non-rectangular outer contour, wherein an assembly of current-supplying and current-removing electrodes (11-20) adapted to the outer contour is formed, said electrodes being arranged separately from one another on its own along the outer contour and being connected to electrical energy sources (21-25) which are electrically insulated from one another and are dimensioned in such a way that, between all pairs of associated current-supplying and current-removing electrodes (11-20), essentially the same current densities are produced in the metal sheet (1) or the regions to be conductively heated, characterized in that metal sheets (1) each with at least one trapezoidal zone (3) of their region to be conductively heated are conductively heated in pairs, wherein a pair of metal sheets (1) are electrically connected to one another by a number of transfer electrodes (31) that are electrically insulated from one another and are arranged next one another along the transfer region from one metal sheet (1) to the other.
- Method according to Claim 1, characterized in that the non-rectangular outer contour of the region to be conductively heated is divided into essentially rectangular and/or trapezoidal zones (2, 3, 4) and, in a way corresponding to the division into the zones (2, 3, 4), an electrode assembly adapted thereto is provided, comprising at least current-supplying and current-removing electrodes (11-20) and, in the presence of at least one trapezoidal zone, transfer electrodes (31).
- Method according to one of the preceding claims, characterized in that one or more or all of the current-supplying and current-removing electrodes (11-20) are respectively formed as elongated electrodes extending with their greatest dimension over a portion of the outer contour of the region to be conductively heated, which are in each case only connected at one end (29, 30) by an electrical supply lead to the electrical energy source (21-25).
- Method according to one of the preceding claims, characterized in that a pair of current-supplying and current-removing electrodes (11-20) are connected to the electrical energy source (21-25) at diagonally opposite ends (29, 30).
- Method according to one of the preceding claims, characterized in that one or more or all of the current-supplying, current-removing and/or transfer electrodes (11-20, 31) are formed as electrodes that are cooled with a cooling medium.
- Method according to one of the preceding claims, characterized in that the conductive heating is carried out by means of direct current.
- Method according to one of the preceding claims, characterized in that one or more or all of the current-supplying, current-removing and/or transfer electrodes (11-20, 31) are moved away from one another during the conductive heating process, in order to stretch the metal sheet.
- Method according to one of the preceding claims, characterized in that, for supplying current to a current-supplying electrode (11-15), for transferring current from or to a transfer electrode (31) and/or for removing current from a current-removing electrode (16-20), a parallel conductor (26, 27) is connected to this electrode and, over part of the metal sheet (1) to be heated, is taken over the metal sheet (1) parallel to the flow lines of currents flowing therein while being electrically insulated from the metal sheet (1).
- Method according to one of the preceding claims, characterized in that, as a result of the contacting of the metal sheet, one or more or all of the current-supplying, current-removing and/or transfer electrodes (11-20, 31) cool a peripheral region in such a way that no heat treatment of the metal sheet takes place in the pressing region of the respective electrodes.
- Conductive heating device (10) for carrying out a method for conductively heating a metal sheet (1), the metal sheet (1) or at least one region to be conductively heated of the metal sheet (1) having a non-rectangular outer contour, wherein the conductive heating device (10) has an assembly of current-supplying and current-removing electrodes (11-20) adapted to the outer contour, said electrodes being arranged separately from one another on its own along the outer contour and being connected by means of separate electrical supply leads to electrical energy sources (21-25) which are electrically insulated from one another, wherein the electrical energy sources (21-25) are dimensioned in such a way that, between all pairs of associated current-supplying and current-removing electrodes (11-20), the same current densities are produced in the metal sheet (1), characterized in that the electrode assembly of the conductive heating device (10) has transfer electrodes (31) for transferring current between two metal sheets (1) simultaneously heated in the conductive heating direction (10).
- Conductive heating device according to Claim 10, characterized in that the conductive heating device (10) is designed for carrying out a method according to one of Claims 1 to 10.
- Conductive heating device according to Claim 10 or 11, characterized in that the electrical energy sources (21-25) are designed as direct current sources.
- Conductive heating device according to one of Claims 10 to 12, characterized in that the conductive heating device (10) has a stretching device, which is designed for stretching the metal sheet (1), at least in the conductively heated region, during the heating process.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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DE102014102033.2A DE102014102033B4 (en) | 2014-02-18 | 2014-02-18 | Method for conductive heating of a sheet and heating device therefor |
PCT/EP2015/053382 WO2015124604A1 (en) | 2014-02-18 | 2015-02-18 | Method for conductively heating sheet metal, and heating device for carrying out said method |
Publications (2)
Publication Number | Publication Date |
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EP3108019A1 EP3108019A1 (en) | 2016-12-28 |
EP3108019B1 true EP3108019B1 (en) | 2018-12-26 |
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EP15705981.7A Active EP3108019B1 (en) | 2014-02-18 | 2015-02-18 | Method for conductively heating sheet metal in pairs, and heating device for carrying out said method |
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EP (1) | EP3108019B1 (en) |
JP (1) | JP6679595B2 (en) |
DE (1) | DE102014102033B4 (en) |
WO (1) | WO2015124604A1 (en) |
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DE102017104494B4 (en) | 2017-03-03 | 2021-10-21 | Gottfried Wilhelm Leibniz Universität Hannover | Process for forming a sheet metal and manufacturing plant with conductive heating device |
EP3589756B1 (en) | 2017-03-03 | 2024-05-15 | Gottfried Wilhelm Leibniz Universität Hannover | Method for forming a sheet metal and manufacturing system with conductive heating device |
DE102017110221A1 (en) * | 2017-05-11 | 2018-11-15 | Gottfried Wilhelm Leibniz Universität Hannover | Process for heat treatment of a component and plant therefor |
DE102020125946A1 (en) | 2020-10-05 | 2022-04-07 | HEGGEMANN Aktiengesellschaft | Process for processing an electrically conductive sheet metal blank |
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US4404047A (en) * | 1980-12-10 | 1983-09-13 | Lasalle Steel Company | Process for the improved heat treatment of steels using direct electrical resistance heating |
GB8324643D0 (en) * | 1983-09-14 | 1983-10-19 | British Steel Corp | Production of grain orientated steel |
DE19527827C2 (en) * | 1995-07-29 | 1998-02-12 | Kuka Schweissanlagen & Roboter | Method and device for generating electrical heat |
DE10238972B4 (en) * | 2002-08-20 | 2004-07-15 | C.D. Wälzholz Produktionsgesellschaft mbH | Method and device for the continuous tempering of strip steel and correspondingly produced strip steel |
DE10339119B3 (en) * | 2003-08-22 | 2005-03-17 | Benteler Automobiltechnik Gmbh | Method of making hardened steel structural component, involves cutting panel from coil, heating, hardening and cold-forming to form structural component |
DE102005018974B4 (en) * | 2004-04-29 | 2015-04-09 | Kuka Systems Gmbh | Method and device for heating electrically conductive uncoated or coated circuit boards |
US7714253B2 (en) * | 2006-03-16 | 2010-05-11 | Noble Advanced Technologies, Inc. | Method and apparatus for the uniform resistance heating of articles |
DE102006037637A1 (en) * | 2006-08-10 | 2008-02-14 | Müller Weingarten AG | Procedures for heating of metal sheets for hot deformation, comprises inserting work pieces by means of a transport device into a forming tool and heating the work pieces during the transportation procedure by a heating device |
DE102008051471B4 (en) * | 2008-09-30 | 2012-01-26 | Elisabeth Braun | Method for heating sheet metal parts |
DE102009016027A1 (en) * | 2009-04-02 | 2010-10-07 | Volkswagen Ag | Method for producing a component, in particular a body part, and production line for carrying out the method |
CN102575310B (en) * | 2009-10-16 | 2013-11-20 | 丰田自动车株式会社 | Energization heating method and energization heating device |
DE102014101891A1 (en) * | 2014-02-14 | 2015-08-20 | Thyssenkrupp Ag | System for warming up workpieces |
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2014
- 2014-02-18 DE DE102014102033.2A patent/DE102014102033B4/en not_active Expired - Fee Related
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2015
- 2015-02-18 WO PCT/EP2015/053382 patent/WO2015124604A1/en active Application Filing
- 2015-02-18 EP EP15705981.7A patent/EP3108019B1/en active Active
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