EP2511639B1 - Rotary hearth furnace - Google Patents

Rotary hearth furnace Download PDF

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Publication number
EP2511639B1
EP2511639B1 EP11162322.9A EP11162322A EP2511639B1 EP 2511639 B1 EP2511639 B1 EP 2511639B1 EP 11162322 A EP11162322 A EP 11162322A EP 2511639 B1 EP2511639 B1 EP 2511639B1
Authority
EP
European Patent Office
Prior art keywords
rotary hearth
workpieces
heating device
furnace
furnace chamber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Not-in-force
Application number
EP11162322.9A
Other languages
German (de)
French (fr)
Other versions
EP2511639A1 (en
Inventor
Alfons Gockel
Dominikus Dr. Schröder
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
LOI Thermprocess GmbH
Original Assignee
LOI Thermprocess GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by LOI Thermprocess GmbH filed Critical LOI Thermprocess GmbH
Priority to EP11162322.9A priority Critical patent/EP2511639B1/en
Priority to ES11162322T priority patent/ES2531314T3/en
Priority to PL11162322T priority patent/PL2511639T3/en
Priority to US13/407,532 priority patent/US20120264074A1/en
Priority to CA2771921A priority patent/CA2771921A1/en
Priority to MX2012004060A priority patent/MX2012004060A/en
Priority to BRBR102012008643-3A priority patent/BR102012008643A2/en
Publication of EP2511639A1 publication Critical patent/EP2511639A1/en
Application granted granted Critical
Publication of EP2511639B1 publication Critical patent/EP2511639B1/en
Not-in-force legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
    • F27B9/16—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a circular or arcuate path
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0037—Rotary furnaces with vertical axis; Furnaces with rotating floor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B9/36—Arrangements of heating devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system

Definitions

  • the invention is directed to a rotary hearth furnace in ring type for heat treatment of workpieces
  • a rotary hearth furnace in ring type for heat treatment of workpieces
  • an outer and inner wall defining a furnace chamber having at least one treatment zone, at least one heating device heating the furnace chamber, an annular rotary hearth and a rotary drive driving the rotary hearth, the outer wall at least one closable opening for loading and / or unloading of the furnace chamber, wherein a plurality of racks for receiving or supporting workpieces on the annular rotary hearth are arranged circumferentially, wherein a respective frame is provided with receiving elements, the frame in at least two horizontal planes to the one above the other split arranged receiving workpieces, wherein at least one workpiece is receivable in each horizontal plane.
  • a workpiece such as boron-alloyed tempering steels (22MnB5)
  • a heat treatment such as heating / austenitization.
  • the heat treatment before the press-hardening of workpieces, such as coated and uncoated steel blanks (eg boron-alloyed tempering steels) has hitherto been carried out in a roller hearth furnace using ceramic conveyor rollers for transporting the steel blanks through the furnace space.
  • a reaction between the then liquid Al-Si coating of the steel blanks and the rollers is formed.
  • the forming metal / metal oxide mixtures infiltrate into the rollers and damage them until they break.
  • heat treatments can also be carried out in a rotary hearth furnace, which is characterized by its space-saving design distinguishes.
  • the workpieces or steel blanks are not transported via rollers during the heat treatment, but introduced through an opening in the furnace chamber and deposited for heat treatment on appropriately trained and arranged in the furnace chamber on the rotary hearth racks.
  • a rotary hearth furnace of the type referred to input is for example from the DE 10 2007 048 041 A1 and from the US 3,545,733 A known, in which a plurality of workpieces with respect to the circumference of the rotary hearth furnace are arranged radially one behind the other on a respective frame. Furthermore, in order to provide an identical throughput compared to roller hearth furnaces, it is known to design racks or charging racks in such a way that a plurality of workpieces for heat treatment can be arranged in several superimposed horizontal planes or rack planes in one rack.
  • the invention is therefore an object of the invention to provide a solution in a rotary hearth furnace of the type designated a solution that in a structurally simple way and cost extremely extremely uniform heating in the oven room with heat treated workpieces allows, under production and operating conditions favorable conditions.
  • this object is achieved in that at least one of the two horizontal planes of a respective frame at least one held in the respective horizontal planes workpieces heating additional heater is arranged, wherein the at least one additional heater is an electrically operated heater, which is at least a busbar extending below the rotary hearth is electrically connected.
  • the invention provides a possibility with which workpieces can be treated with heat in a structurally simple manner and inexpensively in large series with high throughput.
  • the frame allows the inclusion of multiple workpieces, the workpieces are held both side by side and one above the other by a respective frame.
  • at least one additional heating device which heats the workpieces held in the corresponding horizontal planes at least between two horizontal planes of a frame, a uniform heating of the workpieces for a minimum residence time of the workpieces in the furnace chamber is ensured.
  • the residence time of the workpieces in the furnace chamber thus depends primarily on the nature of the materials to be treated and is not dependent on possibly an unfavorable arrangement of individual workpieces with respect to the primary heating device.
  • a respective frame may consist of struts, fired shaped bodies or fired profiles and / or comprise a grid per horizontal plane for receiving workpieces. Due to the intended use of a respective frame at high temperatures in the furnace chamber, it is advantageous if a respective frame made of silicon carbide (SiC) or made of heat-resistant steel.
  • SiC silicon carbide
  • the additional heating device may be connected to the frame via ceramic insulators based on aluminum oxide (Al 2 O 3 ) or zirconium oxide (ZrO 2 ).
  • the additional heater may be part of the arranged on the rotary hearth frame or alternatively be arranged and mounted on a separate holder on the rotary hearth between two frame levels.
  • the control or regulation of at least one, provided for a frame auxiliary heating is independent or separate from the control or regulation of the primary heater in the furnace chamber, which may be in the form of several radiant tubes or direct heating, which vertically or horizontally in the furnace chamber can be arranged running.
  • the at least one additional heating device is designed as a flat, extending between the horizontal planes element.
  • the at least one additional heater provided per frame between two horizontal receiving areas or surfaces is formed to cover the receiving areas, so that the heat radiation of the additional heater both on the underside of the arranged above the additional heater workpieces as well as on the top of the additional heater below arranged workpieces is aligned and this can heat.
  • the auxiliary heater may extend only over a core or center surface of the adjacent workpieces so that only the core region of the workpieces is heated by the auxiliary heater.
  • the invention provides in a further embodiment that below the lowest horizontal plane of a respective frame, a further additional heating device is arranged, which is formed as a flat, extending between the lowest horizontal plane and the rotary hearth element to to compensate for the heat losses of the bottom of the oven cavity.
  • a particularly efficient heating of the workpieces on horizontal planes, which are not directly irradiated by the heater is characterized in an embodiment of the invention possible that the heating power of the at least one additional heating device for a corresponding horizontal plane, in the vicinity of which it extends, can increase concentrically from outside to inside. While the outer portions of the workpieces of the horizontal planes arranged between the lowermost and uppermost horizontal planes can obtain a part of the heat radiation of the primary heater, this thermal radiation does not reach the center region of the rack or charging frame, in particular if they are plate-shaped workpieces , Therefore, efficient and inexpensive heating of these central areas can be made possible if the auxiliary heater is designed so that the central areas can be heated more than the outer areas.
  • thermocouple for temperature control of the additional heater is associated with a respective additional heater or a Schuungsstellvous with a recipe.
  • a thermocouple the performance of a respective additional heating device can be adjusted not only as a function of the treatment zone, but in particular on the power required for uniform heating.
  • the use of a recipe, which is a collection of values of functional and / or procedural related parameters, to specify the Schuungsstelliere or power control of Rajsammlungvorraum offers the possibility of a largely automated and reproducible heat treatment process.
  • the at least one closable opening for loading and / or unloading of the furnace chamber is designed as a vertically movable slot door through which workpieces for a corresponding horizontal plane of the frame in the furnace chamber can be introduced or be discharged from the furnace room.
  • An inventive rotary hearth furnace 1 in ring type comprising an outer wall 2 and an inner wall 3, which are fixed and made of refractory masonry.
  • a fixed ceiling wall 4 which is fixedly connected to the outer and inner walls 2 and 3, and a ring-shaped and rotatably driven by a rotary drive not shown rotary hearth 5, which is supported on support rollers 26, define an annular furnace chamber 6.
  • the furnace chamber 6 is divided into different treatment zones, wherein individual zones can be formed by means of not shown, installed on the rotary hearth 5, insulated intermediate walls can be separated from each other.
  • the rotary hearth furnace 1 shown schematically has a loading zone 7, three heating zones 8, 9 and 10, three holding zones 11, 12 and 13, and a removal zone 14.
  • a closable opening is provided in the outer wall 2, through which the introduction of individual workpieces 15 into the oven interior 6 takes place by means of a manipulator 19a.
  • a frame 16 for receiving or supporting the workpieces 15 is provided in each zone.
  • the workpieces 15 are plate-shaped, which in the specific case are steel blanks. In this case, by a respective frame 16, which in the FIGS.
  • each four workpieces 15 received in a horizontal plane 17, wherein the workpieces 15 are arranged radially from the inside to the outside.
  • the racks 16 are arranged circumferentially or around the circumference of the annular rotary hearth 5 on this and remain constantly in the oven chamber 6. In the heating zones 8, 9, 10, the heating of the workpieces 15 takes place, for which purpose a trained in the form of several Strahltropicrohren Heating device 18 is provided.
  • the workpieces After the workpieces have passed the heating zones 8, 9, 10, they pass into the so-called holding zones 11, 12, 13, in which a temperature compensation takes place in the workpieces 15. After passing through the holding zone 13, the workpieces 15 are then arranged in a removal zone 14, where they are removed by means of a manipulator 19b from an opening in the outer wall 2 of the rotary hearth furnace 1 from the furnace chamber 6 and then provided centered for transfer to the press.
  • the manipulator 19b may be such that all workpieces 15 of a horizontal plane are simultaneously conveyed out of the furnace chamber 6.
  • a respective frame 16 has a plurality of horizontal planes 17 and 17a, 17b, 17c, 17d, so that workpieces 15 can be held or supported not only next to each other, but also one above the other by a frame 16.
  • a respective frame made of struts, fired moldings or burned profiles and / or include a grid per horizontal plane for receiving workpieces
  • the frame 16 may be formed as a four-legged frame with vertical supports and corresponding, connecting the vertical supports and the horizontal planes forming horizontal struts , Due to the high temperatures prevailing in the furnace chamber 6, the racks 16 are preferably made of silicon carbide or of a heat-resistant steel or other ceramic material.
  • a respective frame 16 has receiving elements 21, which can either be adapted to the shape of the workpiece 15 to be supported or supported, or can have a shape designed for universal support of differently shaped workpieces 15.
  • the individual horizontal planes 17a, 17b, 17c, 17d defined by the corresponding receiving elements 21, which are formed in this exemplary embodiment as horizontal struts 22 extending from respective vertical struts 23 and on which the workpieces 15 side by side and lying over one another are deductible.
  • the horizontal struts 22 thus provide laser-supporting support or support elements Supporting the respective longitudinal ends of the workpieces 15.
  • a respective frame 16 is selected only by way of example and a respective frame 16 may have a different structure, as long as corresponding receiving elements 21 are provided which allow a horizontal and vertical recording of workpieces, wherein the receiving elements 21, the frame 16 in at least two horizontal planes 17a, 17b, 17c, 17d for superimposed arranged receiving workpieces 15 split. In this case, at least one workpiece 15 in each frame plane or horizontal plane 17a, 17b, 17c, 17d can be accommodated.
  • a respective frame 16 at least one additional heater 24a is arranged.
  • the radiation of the radiant heating pipes designed as a heater 18 acts only in the lateral areas of the workpieces, wherein the bottom and the ceiling of the oven chamber 6 are formed such that the heat radiation of the heater 18 is reflected and on the floor or to the ceiling directed surfaces of the lower and upper workpiece 15 passes.
  • the radiation does not reach the middle workpieces 15, so that their heating is greatly delayed compared to the lower and upper workpieces.
  • the invention provides the additional heater 24a, which is arranged between the two horizontal planes 17b and 17c and additionally heats the previously insufficiently heat-radiating surfaces of the workpieces 15 of the middle horizontal planes 17b and 17c.
  • the additional heating device 24a may be a part of the arranged on the rotary hearth 5 frame 16 or be introduced via a separate holder on the rotary hearth 5 between two horizontal planes 17b and 17c of the frame 16.
  • an additional heating device 24a as described above may also be additionally or alternatively arranged between the horizontal planes 17a and 17b and / or 17c and 17d in order to even out the heating of the workpieces 15. It is also conceivable that - as exemplified in the FIGS. 4 and 5 shown - below the lowest horizontal plane 17a of a respective frame 16, a further additional heating device 24b is arranged, which extends between the lowest horizontal plane 17a and the rotary hearth 5 as the bottom of the furnace chamber 6. The region of the rotary hearth 5 usually represents a heat sink, which can be counteracted by means of the auxiliary heater 24b.
  • the auxiliary heaters 24a and / or 24b may be connected to the frame 16 via ceramic insulators based on alumina (Al 2 O 3 ) or zirconium oxide (ZrO 2 ) and each formed as an electrically operated heating device with at least one below the rotary hearth 5 extending busbar 25 is electrically connected.
  • At least one of the two auxiliary heaters 24a, 24b for a respective frame 16 may be formed as a planar element, which covers the area of the workpieces 15 received by the frame 16 across the entire area. As a result, thermal radiation of the entire upper or lower side surface of a workpiece 15 is ensured by the additional heating device 24a, 24b.
  • the auxiliary heating device 24a, 24b In a planar design of the additional heating device 24a, 24b, it is then optionally possible to design the auxiliary heating device in such a way that the heating power of the additional heating device 24a, 24b can increase concentrically from outside to inside for a corresponding horizontal plane 17 in the immediate vicinity of which so that a rapid heating of the center of the workpiece 15 is ensured.
  • the auxiliary heaters 24a, 24b may be designed as Elektrowarehausl, wherein the inner portions of the Elektroutz Listel are arranged to increase the power closer to each other.
  • the additional heaters 24a, 24b or only the auxiliary heater 24a in dependence of are operated treatment zone, so that it is conceivable that, for example, the auxiliary heater 24a only in the heating zones 8, 9 and 10 or only in the holding zone 11, 12, 13 in operation to a temperature compensation in the workpieces 15 of the middle horizontal planes 17b and 17c to ensure.
  • a respective additional heating device 24a or 24b may be associated with a temperature control thermocouple, not shown in detail in the figures, so that the heating power of the auxiliary heater 24a or 24b is independent of the treatment zone and adjusted solely based on the actual heating of the workpiece 15.
  • the present invention is directed to a rotary hearth furnace 1 for heating coated and uncoated steel blanks prior to the hot working or press hardening step.
  • the steel blanks are charged as workpieces 15 in individual racks or receiving racks 16.
  • a separate loading and unloading device with manipulator 19a and 19b is arranged in front of the rotary hearth furnace 1, respectively.
  • the sampling device is additionally equipped with a centering unit for the heated steel blanks.
  • Each frame 16 has at least two horizontal planes 17, wherein each horizontal plane 17 can accommodate at least one workpiece 15.
  • the frame is made of silicon carbide (SiC), alternatively made of heat-resistant steel or a ceramic material.
  • the rotary hearth furnace 1 has a performance-adapted number of heating zones 8, 9, 10 and holding zones 11, 12, 13, each further a place for charging 7 and decharging 14.
  • a heater 18 for example, indirectly via vertically in the ceiling of the furnace chamber 6 built radiant tubes, for reasons of clarity, only for the heating zone 9, the heater 18 in drawing FIG. 1 are shown.
  • an auxiliary heater 24 a for example in the form of electrical Heating elements arranged.
  • the energy for example electric auxiliary heater 24a is tapped from one or more bus bars 25 below the rotary hearth 5.
  • the electrical supply for all auxiliary heaters 24a of the rotary hearth furnace 1 is centrally, whereas the respective additional heaters 24a can be controlled decentralized.
  • the respective auxiliary heaters 24a may be constructed so flat that the power can be increased concentrically towards the inside.
  • the power control or control is carried out either via a direct control function of the temperature in the vicinity of the workpiece 15, an indirect zone control variable or fixed prescriptions depending on the workpiece to be heated 15.
  • Energy or heat sink may be provided under the lowest horizontal position 17a of the frame 16, a further additional heating device 24b.
  • thermocouple The regulation to material target temperature of the workpiece 15 via at least one corresponding thermocouple, which is carried in the region of the corresponding additional heating device 24a and 24b.
  • the position of the thermocouple is chosen so that the thermocouple lies mainly in the radiation influence region of the workpiece 15 and the additional heater 24a or 24b.
  • the thermocouple controls only the power output of the electric auxiliary heater 24a or 24b, whereas the main or primary heater 18 is controlled by a control of the electric auxiliary heater 24a or 25b independent.
  • the corresponding closable opening for loading and / or unloading the furnace chamber 6 can be designed as a vertically movable slot door, through which the workpieces 15 for a corresponding horizontal plane 17 of the frame 16 can be introduced into the furnace chamber 6 or be discharged from the furnace chamber 6.
  • a pneumatic or electromotive slide opening in the Slit door is positioned for charging and decharging only one horizontal plane 17 in a rack 16 with a rack drive or alternatively a chain in front of the respective horizontal plane 17 of a respective rack 16.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Tunnel Furnaces (AREA)
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  • Muffle Furnaces And Rotary Kilns (AREA)

Description

Die Erfindung richtet sich auf einen Drehherdofen in Ringbauart zur Wärmebehandlung von Werkstücken, umfassend eine Außen- und Innenwand, die einen wenigstens eine Behandlungszone aufweisenden Ofenraum begrenzen, wenigstens eine den Ofenraum erwärmende Heizvorrichtung, einen ringförmigen Drehherd und einen den Drehherd antreibenden Drehantrieb, wobei die Außenwand zumindest eine verschließbare Öffnung zum Be- und/oder Entladen des Ofenraumes aufweist, wobei mehrere Gestelle zur Aufnahme oder Abstützung von Werkstücken auf dem ringförmigen Drehherd umfangsmäßig angeordnet sind, wobei ein jeweiliges Gestell mit Aufnahmeelementen versehen ist, die das Gestell in wenigstens zwei Horizontalebenen zur übereinanderliegend angeordneten Aufnahme von Werkstücken aufteilen, wobei zumindest ein Werkstück in jeder Horizontalebene aufnehmbar ist.The invention is directed to a rotary hearth furnace in ring type for heat treatment of workpieces comprising an outer and inner wall defining a furnace chamber having at least one treatment zone, at least one heating device heating the furnace chamber, an annular rotary hearth and a rotary drive driving the rotary hearth, the outer wall at least one closable opening for loading and / or unloading of the furnace chamber, wherein a plurality of racks for receiving or supporting workpieces on the annular rotary hearth are arranged circumferentially, wherein a respective frame is provided with receiving elements, the frame in at least two horizontal planes to the one above the other split arranged receiving workpieces, wherein at least one workpiece is receivable in each horizontal plane.

Zur Erzeugung von definierten Werkstückeigenschaften, wie beispielsweise einer hohen Härte und/oder einer hohen Zeitstandfestigkeit bzw. Streckgrenze, wird ein Werkstück, wie zum Beispiel borlegierte Vergütungsstähle (22MnB5), einer Wärmebehandlung, wie beispielsweise einer Erwärmung/Austenitisierung, unterzogen. Die Wärmebehandlung vor dem Presshärten von Werkstücken, wie beispielsweise von beschichteten und unbeschichteten Stahlplatinen (z.B. borlegierte Vergütungsstähle), erfolgt bislang in einem Rollenherdofen, wobei für den Transport der Stahlplatinen durch den Ofenraum keramische Förderrollen eingesetzt werden. Es hat sich allerdings gezeigt, dass beim Aufheizen der Stahlplatinen im Temperaturbereich zwischen 450°C und 750°C eine Reaktion zwischen der dann flüssigen Al-Si Beschichtung der Stahlplatinen und den Rollen entsteht. Die sich hier bildenden Metall-/Metalloxidmischungen infiltrieren in die Rollen und schädigen diese bis zum Bruch. Als Alternative zu einem Rollenherdofen können solche an Stahlplatinen vorzunehmenden Wärmebehandlungen auch in einem Drehherdofen durchgeführt werden, der sich durch seine platzsparende Bauweise auszeichnet. Bei diesem Ofentyp werden die Werkstücke bzw. Stahlplatinen während der Wärmebehandlung nicht über Rollen transportiert, sondern über eine Öffnung in den Ofenraum eingebracht und zur Wärmebehandlung auf entsprechend ausgebildete und im Ofenraum auf dem Drehherd angeordnete Gestelle abgesetzt. Ein Drehherdofen vom Eingangs bezeichneten Typ ist beispielsweise aus der DE 10 2007 048 041 A1 und aus der US 3,545,733 A bekannt, bei dem auf einem jeweiligen Gestell mehrere Werkstücke in Bezug auf den Umfang des Drehherdofens radial hintereinander liegend angeordnet sind. Um ferner eine im Vergleich zu Rollenherdöfen identische Durchsatzleistung vorzuweisen, ist es bekannt, Gestelle bzw. Chargiergestelle derart auszugestalten, dass in einem Gestell mehrere Werkstücke zur Wärmebehandlung in mehreren übereinanderliegenden Horizontalebenen bzw. Gestellebenen angeordnet werden können.To produce defined workpiece properties, such as high hardness and / or high creep strength, a workpiece, such as boron-alloyed tempering steels (22MnB5), is subjected to a heat treatment, such as heating / austenitization. The heat treatment before the press-hardening of workpieces, such as coated and uncoated steel blanks (eg boron-alloyed tempering steels), has hitherto been carried out in a roller hearth furnace using ceramic conveyor rollers for transporting the steel blanks through the furnace space. However, it has been shown that when heating the steel blanks in the temperature range between 450 ° C and 750 ° C, a reaction between the then liquid Al-Si coating of the steel blanks and the rollers is formed. The forming metal / metal oxide mixtures infiltrate into the rollers and damage them until they break. As an alternative to a roller hearth furnace to be carried out on steel blanks heat treatments can also be carried out in a rotary hearth furnace, which is characterized by its space-saving design distinguishes. In this type of furnace, the workpieces or steel blanks are not transported via rollers during the heat treatment, but introduced through an opening in the furnace chamber and deposited for heat treatment on appropriately trained and arranged in the furnace chamber on the rotary hearth racks. A rotary hearth furnace of the type referred to input is for example from the DE 10 2007 048 041 A1 and from the US 3,545,733 A known, in which a plurality of workpieces with respect to the circumference of the rotary hearth furnace are arranged radially one behind the other on a respective frame. Furthermore, in order to provide an identical throughput compared to roller hearth furnaces, it is known to design racks or charging racks in such a way that a plurality of workpieces for heat treatment can be arranged in several superimposed horizontal planes or rack planes in one rack.

Wie vorstehend erwähnt, ist zur Erzeugung von definierten Werkstückeigenschaften eine gleichmäßige und homogene Erwärmung der Werkstücke während der Wärmebehandlung erforderlich. Allerdings ist bei einer übereinanderliegenden Anordnung der mit Wärme zu behandelnden Werkstücke in mehreren Gestellebenen eine gleichmäßige Erwärmung der Werkstücke der mittleren Ebenen problematisch. Zwar strahlt die Wandung des Ofenraumes vollumfänglich die Wärme ab, die von der im Ofenraum angeordneten Heizvorrichtung abgegeben wird. Bei beispielsweise vier übereinanderliegend angeordneten Lagen von als Stahlplatinen ausgeführten Werkstücken ergibt sich jedoch das Problem, dass die reflektierte Wärmestrahlung die auf den mittleren Gestellebenen angeordneten Stahlplatinen nur unzureichend erreicht, so dass die Verweilzeit der Werkstücke im Ofenraum erhöht werden muss, damit auch die Werkstücke der mittleren Horizontal- bzw. Gestellebenen die gewünschte Erwärmung erfahren, was höhere Betriebs- und Produktionskosten nach sich zieht.As mentioned above, to produce defined workpiece characteristics, uniform and homogeneous heating of the workpieces during the heat treatment is required. However, in a superimposed arrangement of the workpieces to be heat treated in several frame levels uniform heating of the workpieces of the middle levels is problematic. Although the wall of the oven chamber radiates fully from the heat that is emitted by the arranged in the oven heater. In the case of, for example, four superimposed layers of workpieces designed as steel blanks, however, there is the problem that the reflected heat radiation insufficiently reaches the steel blanks arranged on the central frame planes, so that the residence time of the workpieces in the furnace chamber must be increased, so that the workpieces of the middle Horizontal or frame levels experience the desired warming, resulting in higher operating and production costs.

Der Erfindung liegt daher die Aufgabe zugrunde, bei einem Drehherdofen der Eingangs bezeichneten Art eine Lösung zu schaffen, die auf konstruktiv einfache Weise und kostengünstig eine extrem gleichmäßige Erwärmung der im Ofenraum mit Wärme zu behandelnden Werkstücke ermöglicht, und zwar unter fertigungs- und betriebstechnisch günstigen Voraussetzungen.The invention is therefore an object of the invention to provide a solution in a rotary hearth furnace of the type designated a solution that in a structurally simple way and cost extremely extremely uniform heating in the oven room with heat treated workpieces allows, under production and operating conditions favorable conditions.

Bei einem Drehherdofen der Eingangs bezeichneten Art wird diese Aufgabe erfindungsgemäß dadurch gelöst, dass zumindest zwischen zwei Horizontalebenen eines jeweiligen Gestells wenigstens eine die in den entsprechenden Horizontalebenen gehaltenen Werkstücke erwärmende Zusatzheizvorrichtung angeordnet ist, wobei die wenigstens eine Zusatzheizvorrichtung eine elektrisch betriebene Heizvorrichtung ist, die mit wenigstens einer unterhalb des Drehherds verlaufenden Stromschiene elektrisch verbunden ist.In a rotary hearth furnace of the type described input, this object is achieved in that at least one of the two horizontal planes of a respective frame at least one held in the respective horizontal planes workpieces heating additional heater is arranged, wherein the at least one additional heater is an electrically operated heater, which is at least a busbar extending below the rotary hearth is electrically connected.

Vorteilhafte und zweckmäßige Ausgestaltungen und Weiterbildungen der Erfindung ergeben sich aus den Unteransprüchen.Advantageous and expedient refinements and developments of the invention will become apparent from the dependent claims.

Durch die Erfindung wird eine Möglichkeit bereitgestellt, mit welcher auf konstruktiv einfache Weise und kostengünstig Werkstücke in Großserie bei hoher Durchsatzleistung mit Wärme behandelt werden können. Das Gestell ermöglicht die Aufnahme von mehreren Werkstücken, wobei die Werkstücke sowohl nebeneinander als auch übereinander liegend von einem jeweiligen Gestell gehalten werden. Dadurch, dass zumindest zwischen zwei Horizontalebenen eines Gestells wenigstens eine die in den entsprechenden Horizontalebenen gehaltenen Werkstücke erwärmende Zusatzheizvorrichtung angeordnet ist, ist eine gleichmäßige Erwärmung der Werkstücke für eine Mindestverweildauer der Werkstücke im Ofenraum sichergestellt. Die Verweildauer der Werkstücke im Ofenraum richtet sich somit in erster Linie an die Beschaffenheit der zu behandelnden Werkstoffe und ist nicht abhängig von ggf. einer ungünstigen Anordnung einzelner Werkstücke in Bezug auf die primäre Heizvorrichtung.The invention provides a possibility with which workpieces can be treated with heat in a structurally simple manner and inexpensively in large series with high throughput. The frame allows the inclusion of multiple workpieces, the workpieces are held both side by side and one above the other by a respective frame. By arranging at least one additional heating device which heats the workpieces held in the corresponding horizontal planes at least between two horizontal planes of a frame, a uniform heating of the workpieces for a minimum residence time of the workpieces in the furnace chamber is ensured. The residence time of the workpieces in the furnace chamber thus depends primarily on the nature of the materials to be treated and is not dependent on possibly an unfavorable arrangement of individual workpieces with respect to the primary heating device.

Ein jeweiliges Gestell kann aus Streben, gebrannten Formkörpern oder gebrannten Profilen bestehen und/oder ein Gitterrost pro Horizontalebene zur Aufnahme von Werkstücken umfassen. Aufgrund des Einsatzzweckes eines jeweiligen Gestells bei hohen Temperaturen im Ofenraum ist es vorteilhaft, wenn ein jeweiliges Gestell aus Siliziumkarbid (SiC) oder aus hitzebeständigem Stahl hergestellt ist.A respective frame may consist of struts, fired shaped bodies or fired profiles and / or comprise a grid per horizontal plane for receiving workpieces. Due to the intended use of a respective frame at high temperatures in the furnace chamber, it is advantageous if a respective frame made of silicon carbide (SiC) or made of heat-resistant steel.

Die Zusatzheizvorrichtung kann über keramische Isolatoren auf Basis von Aluminiumoxid (Al2O3) oder Zirkonoxid (ZrO2) mit dem Gestell verbunden sein. Somit kann die Zusatzheizvorrichtung Teil des auf dem Drehherd angeordneten Gestells sein oder alternativ über eine separate Halterung auf dem Drehherd zwischen zwei Gestellebenen angeordnet und angebracht sein.The additional heating device may be connected to the frame via ceramic insulators based on aluminum oxide (Al 2 O 3 ) or zirconium oxide (ZrO 2 ). Thus, the additional heater may be part of the arranged on the rotary hearth frame or alternatively be arranged and mounted on a separate holder on the rotary hearth between two frame levels.

Die Steuerung bzw. Regelung der zumindest einen, für ein Gestell vorgesehenen Zusatzheizung erfolgt unabhängig bzw. getrennt von der Steuerung bzw. Regelung der primären Heizvorrichtung im Ofenraum, die in Form von mehreren Strahlheizrohren oder als Direktbeheizung ausgebildet sein kann, die vertikal oder waagerecht im Ofenraum verlaufend angeordnet sein können.The control or regulation of at least one, provided for a frame auxiliary heating is independent or separate from the control or regulation of the primary heater in the furnace chamber, which may be in the form of several radiant tubes or direct heating, which vertically or horizontally in the furnace chamber can be arranged running.

Von besonderem Vorteil ist es, wenn die wenigstens eine Zusatzheizvorrichtung als flächiges, sich zwischen den Horizontalebenen erstreckendes Element ausgebildet ist. Mit anderen Worten ist die zumindest eine pro Gestell vorgesehene Zusatzheizung zwischen zwei horizontalen Aufnahmebereichen bzw. -flächen flächendeckend zu den Aufnahmebereichen ausgebildet, so dass die Wärmeabstrahlung der Zusatzheizvorrichtung sowohl auf die Unterseite der oberhalb der Zusatzheizvorrichtung angeordneten Werkstücke als auch auf die Oberseite der unterhalb der Zusatzheizvorrichtung angeordneten Werkstücke ausgerichtet ist und diese erwärmen kann. Alternativ kann sich die Zusatzheizvorrichtung nur über eine Kern- bzw. Zentrumsfläche der benachbarten Werkstücke erstrecken, so dass nur der Kernbereich der Werkstücke von der Zusatzheizvorrichtung erwärmt wird.It is particularly advantageous if the at least one additional heating device is designed as a flat, extending between the horizontal planes element. In other words, the at least one additional heater provided per frame between two horizontal receiving areas or surfaces is formed to cover the receiving areas, so that the heat radiation of the additional heater both on the underside of the arranged above the additional heater workpieces as well as on the top of the additional heater below arranged workpieces is aligned and this can heat. Alternatively, the auxiliary heater may extend only over a core or center surface of the adjacent workpieces so that only the core region of the workpieces is heated by the auxiliary heater.

Um den baulichen Aufwand des Drehherdofens gering zu halten, sieht die Erfindung in weiterer Ausgestaltung vor, dass unterhalb der untersten Horizontalebene eines jeweiligen Gestells eine weitere Zusatzheizvorrichtung angeordnet ist, die als flächiges, sich zwischen der untersten Horizontalebene und dem Drehherd erstreckendes Element ausgebildet ist, um die Wärmeverluste des Bodens des Ofenraumes zu kompensieren.In order to keep the structural complexity of the rotary hearth furnace low, the invention provides in a further embodiment that below the lowest horizontal plane of a respective frame, a further additional heating device is arranged, which is formed as a flat, extending between the lowest horizontal plane and the rotary hearth element to to compensate for the heat losses of the bottom of the oven cavity.

Eine besonders effiziente Erwärmung der Werkstücke auf Horizontalebenen, die nicht direkt von der Heizvorrichtung bestrahlt werden, ist in Ausgestaltung der Erfindung dadurch möglich, dass die Heizleistung der wenigstens einen Zusatzheizvorrichtung für eine entsprechende Horizontalebene, in deren Nähe sie sich erstreckt, konzentrisch von außen nach innen zunehmen kann. Während die Außenbereiche der Werkstücke der Horizontalebenen, die zwischen der untersten und obersten Horizontalebene angeordnet sind, einen Teil der Wärmestrahlung der primären Heizvorrichtung erlangen können, gelangt diese Wärmestrahlung nicht in den Mittenbereich des Gestells bzw. Chargiergestells, insbesondere wenn es sich um plattenförmig ausgebildete Werkstücke handelt. Daher kann eine effiziente und kostengünstige Erwärmung dieser zentralen Bereiche dadurch ermöglicht werden, wenn die Zusatzheizvorrichtung derart ausgebildet ist, dass die zentralen Bereiche stärker erwärmt werden können als die äußeren Bereiche.A particularly efficient heating of the workpieces on horizontal planes, which are not directly irradiated by the heater, is characterized in an embodiment of the invention possible that the heating power of the at least one additional heating device for a corresponding horizontal plane, in the vicinity of which it extends, can increase concentrically from outside to inside. While the outer portions of the workpieces of the horizontal planes arranged between the lowermost and uppermost horizontal planes can obtain a part of the heat radiation of the primary heater, this thermal radiation does not reach the center region of the rack or charging frame, in particular if they are plate-shaped workpieces , Therefore, efficient and inexpensive heating of these central areas can be made possible if the auxiliary heater is designed so that the central areas can be heated more than the outer areas.

Diesbezüglich ist es dann von Vorteil, wenn einer jeweiligen Zusatzheizvorrichtung wenigstens ein Thermoelement zur Temperaturregelung der Zusatzheizvorrichtung zugeordnet ist oder eine Heizungsstellgröße über ein Rezept vorgegeben ist. Bei Verwendung eines Thermoelements kann dadurch die Leistung einer jeweiligen Zusatzheizvorrichtung nicht nur in Abhängigkeit der Behandlungszone, sondern insbesondere an der zur einheitlichen Erwärmung erforderlichen Leistung eingestellt werden. Die Verwendung eines Rezepts, welches eine Wertesammlung von im funktionalen und/oder verfahrenstechnischen Zusammenhang stehenden Parametern ist, zur Vorgabe der Heizungsstellgröße bzw. Leistungssteuerung der Zusatzheizvorrichtung bietet die Möglichkeit eines weitestgehend automatisierten und reproduzierbaren Wärmebehandlungsprozesses.In this regard, it is advantageous if at least one thermocouple for temperature control of the additional heater is associated with a respective additional heater or a Heizungsstellgröße is specified via a recipe. When using a thermocouple, the performance of a respective additional heating device can be adjusted not only as a function of the treatment zone, but in particular on the power required for uniform heating. The use of a recipe, which is a collection of values of functional and / or procedural related parameters, to specify the Heizungsstellgröße or power control of Zusatzheizvorrichtung offers the possibility of a largely automated and reproducible heat treatment process.

Hinsichtlich einer Reduzierung der Wärmeverluste des Drehherdofens bei Be- und Entladung des Ofenraumes mit Werkstücken ist es besonders von Vorteil, wenn die zumindest eine verschließbare Öffnung zum Be- und/oder Entladen des Ofenraumes als vertikal verfahrbare Schlitztür ausgebildet ist, durch die hindurch Werkstücke für eine entsprechende Horizontalebene des Gestells in den Ofenraum einbringbar oder aus dem Ofenraum ausbringbar sind.With regard to a reduction of the heat losses of the rotary hearth furnace during loading and unloading of the furnace chamber with workpieces, it is particularly advantageous if the at least one closable opening for loading and / or unloading of the furnace chamber is designed as a vertically movable slot door through which workpieces for a corresponding horizontal plane of the frame in the furnace chamber can be introduced or be discharged from the furnace room.

Es versteht sich, dass die vorstehend genannten und nachstehend noch zu erläuternden Merkmale nicht nur in der jeweils angegebenen Kombination, sondern auch in anderen Kombinationen oder in Alleinstellung verwendbar sind, ohne den Rahmen der vorliegenden Erfindung zu verlassen. Der Rahmen der Erfindung ist nur durch die Ansprüche definiert.It is understood that the features mentioned above and those yet to be explained not only in the each combination specified, but also in other combinations or alone, without departing from the scope of the present invention. The scope of the invention is defined only by the claims.

Weitere Einzelheiten, Merkmale und Vorteile des Gegenstandes der Erfindung ergeben sich aus der nachfolgenden Beschreibung im Zusammenhang mit der Zeichnung, in der beispielhafte Ausführungsbeispiele der Erfindung dargestellt sind. In der Zeichnung zeigt:

  • Figur 1 eine schematische Draufsicht auf einen erfindungsgemäßen Drehherdofen,
  • Figur 2 eine schematische Schnittdarstellung des in Figur 1 gezeigten Drehherdofens in Seitenansicht,
  • Figur 3 ein vergrößerter Ausschnitt des in Figur 2 dargestellten Drehherdofens,
  • Figur 4 eine exemplarische Ausführung eines Gestells des Drehherdofens in Frontalansicht und
  • Figur 5 eine Seitenansicht des in Figur 4 dargestellten Gestells.
Further details, features and advantages of the subject matter of the invention will become apparent from the following description taken in conjunction with the drawings in which exemplary embodiments of the invention are shown. In the drawing shows:
  • FIG. 1 a schematic plan view of a rotary hearth furnace according to the invention,
  • FIG. 2 a schematic sectional view of the in FIG. 1 shown rotary hearth furnace in side view,
  • FIG. 3 an enlarged section of the in FIG. 2 illustrated rotary hearth furnace,
  • FIG. 4 an exemplary embodiment of a frame of the rotary hearth furnace in front view and
  • FIG. 5 a side view of the in FIG. 4 illustrated frame.

Ein erfindungsgemäßer Drehherdofen 1 in Ringbauart, der in Figur 1 in einer Draufsicht und in Figur 2 in einer seitlichen Schnittansicht dargestellt ist, umfasst eine Außenwand 2 und eine Innenwand 3, die feststehend sind und aus feuerfestem Mauerwerk bestehen. Eine feststehende Deckenwand 4, die mit der Außen- und Innenwand 2 und 3 fest verbunden ist, und ein ringförmig ausgebildeter und von einem nicht näher dargestellten Drehantrieb drehbar antreibbarer Drehherd 5, der auf Stützrollen 26 abgestützt ist, begrenzen einen ringförmigen Ofenraum 6. Der Ofenraum 6 ist in unterschiedliche Behandlungszonen eingeteilt, wobei einzelne Zonen mit Hilfe von nicht näher dargestellten, auf dem Drehherd 5 installierten, isolierten Zwischenwänden ausgebildet sein können, voneinander abgetrennt sein können. Der schematisch dargestellte Drehherdofen 1 weist eine Beladezone 7, drei Aufheizzonen 8, 9 und 10, drei Haltezonen 11, 12 und 13, und eine Entnahmezone 14 auf. In der Beladezone 7 ist in der Außenwand 2 eine verschließbare Öffnung vorgesehen, durch die hindurch mittels eines Manipulators 19a die Einbringung von einzelnen Werkstücken 15 in den Ofeninnenraum 6 erfolgt. Im Ofenraum 6 ist in jeder Zone ein Gestell 16 zur Aufnahme oder Abstützung der Werkstücke 15 vorgesehen. Wie aus den Figuren 1 und 2 ersichtlich ist, sind die Werkstücke 15 plattenförmig ausgebildet, wobei es sich in dem konkreten Fall um Stahlplatinen handelt. Dabei werden von einem jeweiligen Gestell 16, welches in den Figuren 2 bis 5 näher dargestellt ist, jeweils vier Werkstücke 15 in einer Horizontalebene 17 aufgenommen, wobei die Werkstücke 15 radial von innen nach außen liegend angeordnet sind. Denkbar ist selbstverständlich auch eine davon abweichende Anordnung der Werkstücke 15, wobei je nach Außenabmessung des mit Wärme zu behandelnden Werkstücks auch nur ein einziges Werkstück 15 in einer Gestellebene bzw. Horizontalebene 17 des Gestells 16 gehalten bzw. abgestützt sein kann. Die Gestelle 16 sind umfangsmäßig bzw. um den Umfang des ringförmigen Drehherds 5 auf diesem angeordnet und verbleiben ständig im Ofenraum 6. In den Aufheizzonen 8, 9, 10 erfolgt die Aufheizung der Werkstücke 15, wobei zu diesem Zweck eine in Form von mehreren Strahlheizrohren ausgebildete Heizvorrichtung 18 vorgesehen ist. Nachdem die Werkstücke die Aufheizzonen 8, 9, 10 passiert haben, gelangen sie in die sogenannten Haltezonen 11, 12, 13, in denen ein Temperaturausgleich in den Werkstücken 15 erfolgt. Nach Passieren der Haltezone 13 sind die Werkstücke 15 dann in einer Entnahmezone 14 angeordnet, wo sie mit Hilfe eines Manipulators 19b aus einer Öffnung in der Außenwand 2 des Drehherdofens 1 aus dem Ofenraum 6 entnommen und anschließend zur Übergabe an die Presse zentriert bereit gestellt werden. Dabei kann der Manipulator 19b so beschaffen sein, dass alle Werkstücke 15 einer Horizontalebene gleichzeitig aus dem Ofenraum 6 heraus befördert werden.An inventive rotary hearth furnace 1 in ring type, the in FIG. 1 in a plan view and in FIG. 2 in a lateral Sectional view, comprising an outer wall 2 and an inner wall 3, which are fixed and made of refractory masonry. A fixed ceiling wall 4, which is fixedly connected to the outer and inner walls 2 and 3, and a ring-shaped and rotatably driven by a rotary drive not shown rotary hearth 5, which is supported on support rollers 26, define an annular furnace chamber 6. The furnace chamber 6 is divided into different treatment zones, wherein individual zones can be formed by means of not shown, installed on the rotary hearth 5, insulated intermediate walls can be separated from each other. The rotary hearth furnace 1 shown schematically has a loading zone 7, three heating zones 8, 9 and 10, three holding zones 11, 12 and 13, and a removal zone 14. In the loading zone 7, a closable opening is provided in the outer wall 2, through which the introduction of individual workpieces 15 into the oven interior 6 takes place by means of a manipulator 19a. In the oven chamber 6, a frame 16 for receiving or supporting the workpieces 15 is provided in each zone. Like from the Figures 1 and 2 it can be seen, the workpieces 15 are plate-shaped, which in the specific case are steel blanks. In this case, by a respective frame 16, which in the FIGS. 2 to 5 is shown in more detail, each four workpieces 15 received in a horizontal plane 17, wherein the workpieces 15 are arranged radially from the inside to the outside. Of course, it is also conceivable deviating arrangement of the workpieces 15, and depending on the outer dimension of the workpiece to be treated with heat, only a single workpiece 15 can be held or supported in a frame plane or horizontal plane 17 of the frame 16. The racks 16 are arranged circumferentially or around the circumference of the annular rotary hearth 5 on this and remain constantly in the oven chamber 6. In the heating zones 8, 9, 10, the heating of the workpieces 15 takes place, for which purpose a trained in the form of several Strahlheizrohren Heating device 18 is provided. After the workpieces have passed the heating zones 8, 9, 10, they pass into the so-called holding zones 11, 12, 13, in which a temperature compensation takes place in the workpieces 15. After passing through the holding zone 13, the workpieces 15 are then arranged in a removal zone 14, where they are removed by means of a manipulator 19b from an opening in the outer wall 2 of the rotary hearth furnace 1 from the furnace chamber 6 and then provided centered for transfer to the press. In this case, the manipulator 19b may be such that all workpieces 15 of a horizontal plane are simultaneously conveyed out of the furnace chamber 6.

Wie insbesondere den Figuren 3 bis 5 zu entnehmen ist, weist ein jeweiliges Gestell 16 mehrere Horizontalebenen 17 bzw. 17a, 17b, 17c, 17d auf, damit Werkstücke 15 nicht nur nebeneinander, sondern auch übereinander liegend von einem Gestell 16 gehalten bzw. abgestützt werden können. Dabei kann ein jeweiliges Gestell aus Streben, gebrannten Formkörpern oder gebrannten Profilen bestehen und/oder ein Gitterrost pro Horizontalebene zur Aufnahme von Werkstücken umfassen, wobei das Gestell 16 als vierbeiniger Rahmen mit Vertikalstützen und entsprechenden, die Vertikalstützen verbindenden und die Horizontalebenen bildenden Horizontalstreben ausgebildet sein kann. Aufgrund der hohen Temperaturen, die im Ofenraum 6 vorherrschen, sind die Gestelle 16 vorzugsweise aus Siliziumkarbid oder aus einem hitzebeständigen Stahl oder aus einem sonstigen keramischen Material hergestellt.As in particular the FIGS. 3 to 5 can be seen, a respective frame 16 has a plurality of horizontal planes 17 and 17a, 17b, 17c, 17d, so that workpieces 15 can be held or supported not only next to each other, but also one above the other by a frame 16. In this case, a respective frame made of struts, fired moldings or burned profiles and / or include a grid per horizontal plane for receiving workpieces, the frame 16 may be formed as a four-legged frame with vertical supports and corresponding, connecting the vertical supports and the horizontal planes forming horizontal struts , Due to the high temperatures prevailing in the furnace chamber 6, the racks 16 are preferably made of silicon carbide or of a heat-resistant steel or other ceramic material.

Ein jeweiliges Gestell 16 weist Aufnahmeelemente 21 auf, die entweder an die Form des zu haltenden bzw. abzustützenden Werkstücks 15 angepasst sein können oder eine zur universellen Abstützung unterschiedlich geformter Werkstücke 15 ausgebildete Gestalt aufweisen können. Bei der in den Figuren 4 und 5 dargestellten Ausführungsform eines Gestells 16 werden die einzelnen Horizontalebenen 17a, 17b, 17c, 17d von den entsprechenden Aufnahmeelementen 21 definiert, die in dieser beispielhaften Ausführung als Horizontalstreben 22 ausgebildet sind, die sich von entsprechenden Vertikalstreben 23 aus erstrecken und auf denen die Werkstücke 15 nebeneinander und übereinander liegend absetzbar sind. Die Horizontalstreben 22 stellen somit lastragende Abstütz- bzw. Trägerelemente zur Abstützung der jeweiligen Längsenden der Werkstücke 15 dar. Es sei nochmals angemerkt, dass die in den Figuren 4 und 5 dargestellte Ausführung eines jeweiligen Gestells 16 nur exemplarisch gewählt ist und ein jeweiliges Gestell 16 einen davon abweichenden Aufbau aufweisen kann, solange entsprechende Aufnahmeelemente 21 vorgesehen sind, die eine horizontale und vertikale Aufnahme von Werkstücken ermöglichen, wobei die Aufnahmeelemente 21 das Gestell 16 in wenigstens zwei Horizontalebenen 17a, 17b, 17c, 17d zur übereinanderliegend angeordneten Aufnahme von Werkstücken 15 aufteilen. Dabei ist zumindest ein Werkstück 15 in jeder Gestellebene bzw. Horizontalebene 17a, 17b, 17c, 17d aufnehmbar.A respective frame 16 has receiving elements 21, which can either be adapted to the shape of the workpiece 15 to be supported or supported, or can have a shape designed for universal support of differently shaped workpieces 15. In the in the FIGS. 4 and 5 illustrated embodiment of a frame 16, the individual horizontal planes 17a, 17b, 17c, 17d defined by the corresponding receiving elements 21, which are formed in this exemplary embodiment as horizontal struts 22 extending from respective vertical struts 23 and on which the workpieces 15 side by side and lying over one another are deductible. The horizontal struts 22 thus provide laser-supporting support or support elements Supporting the respective longitudinal ends of the workpieces 15. It should be noted again that in the FIGS. 4 and 5 illustrated embodiment of a respective frame 16 is selected only by way of example and a respective frame 16 may have a different structure, as long as corresponding receiving elements 21 are provided which allow a horizontal and vertical recording of workpieces, wherein the receiving elements 21, the frame 16 in at least two horizontal planes 17a, 17b, 17c, 17d for superimposed arranged receiving workpieces 15 split. In this case, at least one workpiece 15 in each frame plane or horizontal plane 17a, 17b, 17c, 17d can be accommodated.

Erfindungsgemäß ist vorgesehen, dass zumindest zwischen zwei Horizontalebenen 17, in den Figuren 4 und 5 die Horizontalebenen 17b und 17c, eines jeweiligen Gestells 16 wenigstens eine Zusatzheizvorrichtung 24a angeordnet ist. Wie aus Figur 3 ersichtlich ist, wirkt die Strahlung der als Heizvorrichtung 18 ausgebildeten Strahlheizrohre nur in den seitlichen Bereichen der Werkstücke, wobei der Boden und die Decke des Ofenraumes 6 derart ausgebildet sind, dass die Wärmestrahlung der Heizvorrichtung 18 reflektiert wird und auf die zum Boden bzw. zur Decke gerichteten Flächen des unteren bzw. oberen Werkstücks 15 gelangt. Dadurch ist zwar eine Erwärmung des unteren Werkstückes 15 und des oberen Werkstückes 15 sichergestellt. Jedoch gelangt die Strahlung nicht an die mittleren Werkstücke 15, so dass sich deren Erwärmung im Vergleich zu dem unteren und oberen Werkstück stark verzögert. Um dies zu verhindern und die Erwärmung zeitlich zu vergleichmäßigen, sieht die Erfindung die Zusatzheizeinrichtung 24a vor, die zwischen den zwei Horizontalebenen 17b und 17c angeordnet ist und die zuvor nicht ausreichend wärmebestrahlten Flächen der Werkstücke 15 der mittleren Horizontalebenen 17b und 17c ergänzend erwärmt. Dabei kann die Zusatzheizvorrichtung 24a ein Teil des auf dem Drehherd 5 angeordneten Gestells 16 sein oder über eine separate Halterung auf dem Drehherd 5 zwischen zwei Horizontalebenen 17b und 17c des Gestells 16 eingebracht sein.According to the invention it is provided that at least between two horizontal planes 17, in the FIGS. 4 and 5 the horizontal planes 17b and 17c, a respective frame 16 at least one additional heater 24a is arranged. How out FIG. 3 it can be seen, the radiation of the radiant heating pipes designed as a heater 18 acts only in the lateral areas of the workpieces, wherein the bottom and the ceiling of the oven chamber 6 are formed such that the heat radiation of the heater 18 is reflected and on the floor or to the ceiling directed surfaces of the lower and upper workpiece 15 passes. As a result, although a heating of the lower workpiece 15 and the upper workpiece 15 is ensured. However, the radiation does not reach the middle workpieces 15, so that their heating is greatly delayed compared to the lower and upper workpieces. In order to prevent this and make the heating uniform in time, the invention provides the additional heater 24a, which is arranged between the two horizontal planes 17b and 17c and additionally heats the previously insufficiently heat-radiating surfaces of the workpieces 15 of the middle horizontal planes 17b and 17c. In this case, the additional heating device 24a may be a part of the arranged on the rotary hearth 5 frame 16 or be introduced via a separate holder on the rotary hearth 5 between two horizontal planes 17b and 17c of the frame 16.

Selbstverständlich kann eine wie vorstehend beschriebene Zusatzheizvorrichtung 24a auch zusätzlich oder alternativ zwischen den Horizontalebenen 17a und 17b und/oder 17c und 17d angeordnet sein, um die Erwärmung der Werkstücke 15 zu vergleichmäßigen. Denkbar ist es auch, dass - wie exemplarisch in den Figuren 4 und 5 dargestellt - unterhalb der untersten Horizontalebene 17a eines jeweiligen Gestells 16 eine weitere Zusatzheizvorrichtung 24b angeordnet ist, die sich zwischen der untersten Horizontalebene 17a und dem Drehherd 5 als Boden des Ofenraums 6 erstreckt. Der Bereich des Drehherds 5 stellt üblicherweise eine Wärmesenke dar, der mit Hilfe der Zusatzheizvorrichtung 24b entgegen gewirkt werden kann.Of course, an additional heating device 24a as described above may also be additionally or alternatively arranged between the horizontal planes 17a and 17b and / or 17c and 17d in order to even out the heating of the workpieces 15. It is also conceivable that - as exemplified in the FIGS. 4 and 5 shown - below the lowest horizontal plane 17a of a respective frame 16, a further additional heating device 24b is arranged, which extends between the lowest horizontal plane 17a and the rotary hearth 5 as the bottom of the furnace chamber 6. The region of the rotary hearth 5 usually represents a heat sink, which can be counteracted by means of the auxiliary heater 24b.

Die Zusatzheizvorrichtungen 24a und/oder 24b können über keramische Isolatoren auf Basis von Aluminiumoxid (Al2O3) oder Zirkonoxid (ZrO2) mit dem Gestell 16 verbunden sein und als jeweils eine elektrisch betriebene Heizvorrichtung ausgebildet sein, die mit wenigstens einer unterhalb des Drehherds 5 verlaufenden Stromschiene 25 elektrisch verbunden ist. Wenigstens eine der beiden Zusatzheizvorrichtungen 24a, 24b für ein jeweiliges Gestell 16 kann als flächiges Element ausgebildet sein, welches flächendeckend den Bereich der vom Gestell 16 aufgenommenen Werkstücke 15 überdeckt. Dadurch ist eine Wärmebestrahlung der gesamten oberen bzw. unteren Seitenfläche eines Werkstückes 15 durch die Zusatzheizvorrichtung 24a, 24b sichergestellt. Bei einer flächigen Ausbildung der Zusatzheizvorrichtung 24a, 24b ist es dann optional möglich, die Zusatzheizvorrichtung derart auszugestalten, dass die Heizleistung der Zusatzheizvorrichtung 24a, 24b für eine entsprechende Horizontalebene 17, in deren unmittelbarer Nähe sie sich erstreckt, konzentrisch von außen nach innen zunehmen kann, so dass auch eine rasche Erwärmung des Zentrums des Werkstücks 15 sichergestellt ist. Beispielsweise können die Zusatzheizvorrichtungen 24a, 24b als Elektroheizwendel ausgeführt sein, wobei die innenliegenden Abschnitte der Elektroheizwendel zur Leistungserhöhung enger aneinander liegend angeordnet sind. Dabei können die Zusatzheizvorrichtungen 24a, 24b oder nur die Zusatzheizvorrichtung 24a in Abhängigkeit der Behandlungszone betrieben werden, so dass es denkbar ist, dass beispielsweise die Zusatzheizvorrichtung 24a nur in den Aufheizzonen 8, 9 und 10 oder nur in den Haltezone 11, 12, 13 in Betrieb ist, um einen Temperaturausgleich in den Werkstücken 15 der mittleren Horizontalebenen 17b und 17c sicherzustellen. Alternativ kann einer jeweiligen Zusatzheizvorrichtung 24a oder 24b ein in den Figuren nicht näher dargestelltes Thermoelement zur Temperaturregelung zugeordnet sein, so dass die Heizleistung der Zusatzheizvorrichtung 24a oder 24b unabhängig von der Behandlungszone ist und allein auf Basis der tatsächlichen Erwärmung des Werkstücks 15 eingestellt wird.The auxiliary heaters 24a and / or 24b may be connected to the frame 16 via ceramic insulators based on alumina (Al 2 O 3 ) or zirconium oxide (ZrO 2 ) and each formed as an electrically operated heating device with at least one below the rotary hearth 5 extending busbar 25 is electrically connected. At least one of the two auxiliary heaters 24a, 24b for a respective frame 16 may be formed as a planar element, which covers the area of the workpieces 15 received by the frame 16 across the entire area. As a result, thermal radiation of the entire upper or lower side surface of a workpiece 15 is ensured by the additional heating device 24a, 24b. In a planar design of the additional heating device 24a, 24b, it is then optionally possible to design the auxiliary heating device in such a way that the heating power of the additional heating device 24a, 24b can increase concentrically from outside to inside for a corresponding horizontal plane 17 in the immediate vicinity of which so that a rapid heating of the center of the workpiece 15 is ensured. For example, the auxiliary heaters 24a, 24b may be designed as Elektroheizwendel, wherein the inner portions of the Elektroheizwendel are arranged to increase the power closer to each other. In this case, the additional heaters 24a, 24b or only the auxiliary heater 24a in dependence of Are operated treatment zone, so that it is conceivable that, for example, the auxiliary heater 24a only in the heating zones 8, 9 and 10 or only in the holding zone 11, 12, 13 in operation to a temperature compensation in the workpieces 15 of the middle horizontal planes 17b and 17c to ensure. Alternatively, a respective additional heating device 24a or 24b may be associated with a temperature control thermocouple, not shown in detail in the figures, so that the heating power of the auxiliary heater 24a or 24b is independent of the treatment zone and adjusted solely based on the actual heating of the workpiece 15.

Zusammenfassend richtet sich die vorliegende Erfindung auf einen Drehherdofen 1 zum Erwärmen von beschichteten und unbeschichteten Stahlplatinen vor dem Behandlungsschritt der Warmumformung bzw. des Presshärtens. Bei dem erfindungsgemäßen Drehherdofen 1 werden die Stahlplatinen als Werkstücke 15 in einzelne Gestelle bzw. Aufnahmegestelle 16 chargiert. Zu diesem Zweck ist vor dem Drehherdofen 1 jeweils eine separate Belade- und Entnahmevorrichtung mit Manipulator 19a bzw. 19b angeordnet. Die Entnahmevorrichtung ist zusätzlich mit einer Zentriereinheit für die erwärmten Stahlplatinen ausgestattet. Jedes Gestell 16 verfügt über zumindest zwei Horizontalebenen 17, wobei jede Horizontalebene 17 zumindest ein Werkstück 15 aufnehmen kann. Das Gestell ist aus Siliziumkarbid (SiC), alternativ aus warmfestem Stahl oder einem keramischen Werkstoff gefertigt. Der Drehherdofen 1 verfügt über eine leistungsangepasste Anzahl von Aufheizzonen 8, 9, 10 und Haltezonen 11, 12, 13, ferner je einen Platz zum Chargieren 7 bzw. Dechargieren 14. Die Beheizung des Ofenraumes 6 erfolgt über eine Heizvorrichtung 18 z.B. indirekt über senkrecht in der Decke des Ofenraumes 6 eingebaute Strahlheizrohre, wobei aus Gründen der Übersichtlichkeit lediglich für die Aufheizzone 9 die Heizvorrichtungen 18 zeichnerisch in Figur 1 dargestellt sind. Um eine möglichst genaue und homogene Temperaturverteilung in den Werkstücken 15 über alle Horizontalebenen 17 des Gestells 16 zu erreichen, wird zumindest zwischen zwei Horizontalebenen 17 des Gestells 16 eine Zusatzheizvorrichtung 24a, beispielsweise in Form elektrischer Heizelemente, angeordnet. Die Energie für die beispielsweise elektrische Zusatzheizvorrichtung 24a wird von einer oder mehreren Stromschienen 25 unterhalb vom Drehherd 5 abgegriffen. Dabei erfolgt die elektrische Versorgung für alle Zusatzheizvorrichtungen 24a des Drehherdofens 1 zentral, wohingegen die jeweiligen Zusatzheizvorrichtungen 24a dezentral geregelt werden können. Dabei können die jeweiligen Zusatzheizvorrichtungen 24a derart flächig aufgebaut sein, dass die Leistung konzentrisch nach innen hin erhöht werden kann. Die Leistungsregelung bzw. -steuerung erfolgt entweder über eine direkte Regelung in Abhängigkeit der Temperatur in näherer Umgebung des Werkstücks 15, über eine indirekte Zonenstellgröße oder über fest vorgegebene Rezepte in Abhängigkeit des zu erwärmenden Werkstücks 15. Zum Ausgleich der üblicherweise am Boden des Ofenraumes 6 befindlichen Energie- bzw. Wärmesenke kann auch unter der untersten Horizontallage 17a des Gestells 16 eine weitere Zusatzheizvorrichtung 24b vorgesehen sein. Die Regelung auf Material-Solltemperatur des Werkstücks 15 erfolgt über zumindest ein entsprechendes Thermoelement, das im Bereich der korrespondierenden Zusatzheizvorrichtung 24a bzw. 24b mitgeführt wird. Die Position des Thermoelements wird so gewählt, dass das Thermoelement hauptsächlich im Strahlungseinflussbereich des Werkstücks 15 und der Zusatzheizung 24a bzw. 24b liegt. Das Thermoelement regelt nur die Leistungsabgabe der elektrischen Zusatzheizvorrichtung 24a bzw. 24b, wohingegen die hauptsächliche bzw. primäre Heizvorrichtung 18 über eine von der elektrischen Zusatzheizvorrichtung 24a bzw. 25b unabhängigen Regelung erfolgt.In summary, the present invention is directed to a rotary hearth furnace 1 for heating coated and uncoated steel blanks prior to the hot working or press hardening step. In the rotary hearth furnace 1 according to the invention, the steel blanks are charged as workpieces 15 in individual racks or receiving racks 16. For this purpose, a separate loading and unloading device with manipulator 19a and 19b is arranged in front of the rotary hearth furnace 1, respectively. The sampling device is additionally equipped with a centering unit for the heated steel blanks. Each frame 16 has at least two horizontal planes 17, wherein each horizontal plane 17 can accommodate at least one workpiece 15. The frame is made of silicon carbide (SiC), alternatively made of heat-resistant steel or a ceramic material. The rotary hearth furnace 1 has a performance-adapted number of heating zones 8, 9, 10 and holding zones 11, 12, 13, each further a place for charging 7 and decharging 14. The heating of the oven chamber 6 via a heater 18, for example, indirectly via vertically in the ceiling of the furnace chamber 6 built radiant tubes, for reasons of clarity, only for the heating zone 9, the heater 18 in drawing FIG. 1 are shown. In order to achieve the most accurate and homogeneous temperature distribution in the workpieces 15 over all horizontal planes 17 of the frame 16, at least between two horizontal planes 17 of the frame 16 is an auxiliary heater 24 a, for example in the form of electrical Heating elements arranged. The energy for example electric auxiliary heater 24a is tapped from one or more bus bars 25 below the rotary hearth 5. The electrical supply for all auxiliary heaters 24a of the rotary hearth furnace 1 is centrally, whereas the respective additional heaters 24a can be controlled decentralized. In this case, the respective auxiliary heaters 24a may be constructed so flat that the power can be increased concentrically towards the inside. The power control or control is carried out either via a direct control function of the temperature in the vicinity of the workpiece 15, an indirect zone control variable or fixed prescriptions depending on the workpiece to be heated 15. To compensate for the usually located at the bottom of the oven chamber 6 Energy or heat sink may be provided under the lowest horizontal position 17a of the frame 16, a further additional heating device 24b. The regulation to material target temperature of the workpiece 15 via at least one corresponding thermocouple, which is carried in the region of the corresponding additional heating device 24a and 24b. The position of the thermocouple is chosen so that the thermocouple lies mainly in the radiation influence region of the workpiece 15 and the additional heater 24a or 24b. The thermocouple controls only the power output of the electric auxiliary heater 24a or 24b, whereas the main or primary heater 18 is controlled by a control of the electric auxiliary heater 24a or 25b independent.

Mit Bezug auf die Beladezone 7 und die Entnahmezone 14 sei angemerkt, dass die entsprechende verschließbare Öffnung zum Be- und/oder Entladen des Ofenraumes 6 als vertikal verfahrbare Schlitztür ausgebildet sein kann, durch die hindurch die Werkstücke 15 für eine entsprechende Horizontalebene 17 des Gestells 16 in den Ofenraum 6 einbringbar oder aus dem Ofenraum 6 ausbringbar sind. Die mit einem pneumatischen oder elektromotorischen Schieber zu verschließende Öffnung in der Schlitztür wird für das Chargieren und Dechargieren von nur einer Horizontalebene 17 in einem Gestell 16 mit einem Zahnstangen-Antrieb oder alternativ einer Kette vor der jeweiligen Horizontalebene 17 eines jeweiligen Gestells 16 positioniert.With reference to the loading zone 7 and the removal zone 14, it should be noted that the corresponding closable opening for loading and / or unloading the furnace chamber 6 can be designed as a vertically movable slot door, through which the workpieces 15 for a corresponding horizontal plane 17 of the frame 16 can be introduced into the furnace chamber 6 or be discharged from the furnace chamber 6. To be closed with a pneumatic or electromotive slide opening in the Slit door is positioned for charging and decharging only one horizontal plane 17 in a rack 16 with a rack drive or alternatively a chain in front of the respective horizontal plane 17 of a respective rack 16.

Claims (7)

  1. A rotary hearth furnace (1) of annular design for the heat treatment of workpieces (15), comprising an outer wall and an inner wall (2, 3) that define a furnace chamber (6) with at least one treatment zone (8, 9, 10, 11, 12, 13), at least one heating device (18) that heats the furnace chamber (6), an annular rotary hearth (5) and a rotary drive that drives the rotary hearth (5),
    wherein several racks (16) are provided in the furnace chamber (6) and circumferentially arranged on the annular rotary hearth (5) in order to accommodate or support workpieces (15) introduced into the furnace chamber (6),
    wherein the outer wall (2) features at least one closable opening for loading and/or unloading the furnace chamber (6),
    wherein a respective rack (16) is provided with receptacle elements (21) that divide the rack (16) into at least two horizontal planes (17, 17a, 17b, 17c, 17d) such that workpieces (15) can be accommodated on top of one another, and wherein at least one workpiece (15) can be accommodated in each horizontal plane (17, 17a, 17b, 17c, 17d),
    characterized in that
    at least one auxiliary heating device (24a) is arranged at least between two horizontal planes (17, 17a, 17b, 17c, 17d) of a respective rack (16) and heats the workpieces (15) held in the corresponding horizontal planes (17, 17a, 17b, 17c, 17d), wherein the at least one auxiliary heating device (24a) consists of an electrically operated heating device that is electrically connected to at least one conductor rail (25) extending underneath the rotary hearth (5).
  2. The rotary hearth furnace (1) according to Claim 1, characterized in that a respective rack (16) is made of silicon carbide or of heat-resistant steel.
  3. The rotary hearth furnace (1) according to one of the preceding claims, characterized in that the at least one auxiliary heating device (24a) is realized in the form of a flat element extending between the horizontal planes (17a, 17b, 17c, 17d).
  4. The rotary hearth furnace (1) according to one of the preceding claims, characterized in that an additional auxiliary heating device (24b) is arranged underneath the lowermost horizontal plane (17a) of a respective rack (16) and realized in the form of a flat element extending between the lowermost horizontal plane (17a) and the rotary hearth (5).
  5. The rotary hearth furnace (1) according to Claim 3 or 4, characterized in that the heating power of the at least one auxiliary heating device (24a, 24b) for a corresponding horizontal plane (17a, 17b, 17c, 17d), in the vicinity of which it extends, may increase concentrically from the outside toward the inside.
  6. The rotary hearth furnace (1) according to one of the preceding claims, characterized in that at least one thermocouple is assigned to a respective auxiliary heating device (24a, 24b) in order to control the temperature of the auxiliary heating device (24a, 24b) or a heater control value is predefined by means of a recipe.
  7. The rotary hearth furnace (1) according to one of the preceding claims, characterized in that the at least one closable opening for loading and/or unloading the furnace chamber (5) is realized in the form of a vertically displaceable slot door, through which workpieces for a corresponding horizontal plane (17a, 17b, 17c, 17d) of the rack (16) can be introduced into the furnace chamber (6) or removed from the furnace chamber (6).
EP11162322.9A 2011-04-13 2011-04-13 Rotary hearth furnace Not-in-force EP2511639B1 (en)

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EP11162322.9A EP2511639B1 (en) 2011-04-13 2011-04-13 Rotary hearth furnace
ES11162322T ES2531314T3 (en) 2011-04-13 2011-04-13 Rotating hearth furnace
PL11162322T PL2511639T3 (en) 2011-04-13 2011-04-13 Rotary hearth furnace
US13/407,532 US20120264074A1 (en) 2011-04-13 2012-02-28 Rotary hearth furnace
CA2771921A CA2771921A1 (en) 2011-04-13 2012-03-16 Rotary hearth furnace
MX2012004060A MX2012004060A (en) 2011-04-13 2012-04-04 Rotary hearth furnace.
BRBR102012008643-3A BR102012008643A2 (en) 2011-04-13 2012-04-12 rotary oven

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WO2019016428A1 (en) 2017-07-21 2019-01-24 Outotec (Finland) Oy Rotary bed-type electric furnace
DE102018103145A1 (en) 2018-02-13 2019-08-14 Ebner Industrieofenbau Gmbh Arrangement with several temperature control stations for heat treatment of components and their handling
CN209792358U (en) * 2019-01-29 2019-12-17 苏州普热斯勒先进成型技术有限公司 hot stamping production line without oxidation heating
DE102019120831A1 (en) * 2019-08-01 2021-02-04 Technische Universität Darmstadt Batch holder, nitriding furnace and heat treatment system
EP3868902B1 (en) * 2020-02-21 2022-09-21 C.R.F. Società Consortile per Azioni Method for moulding a sheet into a component of complex shape having areas with different mechanical properties, particularly a motor-vehicle component, and kiln for heating a sheet prior to a forming step.
EP3868901B1 (en) * 2020-02-21 2022-09-21 C.R.F. Società Consortile per Azioni Method for moulding a sheet into a component of complex shape having areas with different mechanical properties, particularly a motor-vehicle component, and kiln for heating a sheet prior to a forming step.
CN114322541B (en) * 2021-12-10 2024-06-11 肇庆北新建材有限公司 Rotary kiln

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CA2771921A1 (en) 2012-10-13
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EP2511639A1 (en) 2012-10-17
MX2012004060A (en) 2012-10-25
BR102012008643A2 (en) 2013-06-11

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