EP2439289B1 - Method and furnace for treating workpieces - Google Patents

Method and furnace for treating workpieces Download PDF

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Publication number
EP2439289B1
EP2439289B1 EP10186516.0A EP10186516A EP2439289B1 EP 2439289 B1 EP2439289 B1 EP 2439289B1 EP 10186516 A EP10186516 A EP 10186516A EP 2439289 B1 EP2439289 B1 EP 2439289B1
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EP
European Patent Office
Prior art keywords
workpiece
contact surfaces
heating unit
pressure pistons
contact
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.)
Active
Application number
EP10186516.0A
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German (de)
French (fr)
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EP2439289A1 (en
Inventor
Rolf-Josef Schwartz
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.)
Schwartz GmbH
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Schwartz 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
Priority to ES10186516.0T priority Critical patent/ES2609328T3/en
Application filed by Schwartz GmbH filed Critical Schwartz GmbH
Priority to EP10186516.0A priority patent/EP2439289B1/en
Priority to PL10186516T priority patent/PL2439289T3/en
Priority to JP2013532132A priority patent/JP6158086B2/en
Priority to PCT/EP2011/066959 priority patent/WO2012045647A1/en
Priority to KR1020137011576A priority patent/KR101869576B1/en
Priority to BR112013008194A priority patent/BR112013008194A2/en
Priority to US13/877,807 priority patent/US9840748B2/en
Priority to MX2013003767A priority patent/MX356552B/en
Priority to CN201180048353.3A priority patent/CN103270178B/en
Publication of EP2439289A1 publication Critical patent/EP2439289A1/en
Application granted granted Critical
Publication of EP2439289B1 publication Critical patent/EP2439289B1/en
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D37/00—Tools as parts of machines covered by this subclass
    • 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
    • C21D1/52—Methods of heating with flames
    • 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
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • 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
    • F27B17/00—Furnaces of a kind not covered by any preceding group
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets

Definitions

  • the invention relates to a method for treating at least one workpiece in a furnace, in which the workpiece is heated in a furnace chamber of the furnace by at least two heating units, wherein the workpiece has a first workpiece side and a second workpiece side, and wherein a first heating unit, the first workpiece side of the workpiece and a second heating unit heats the second workpiece side of the workpiece.
  • the invention further relates to a corresponding furnace for carrying out the method.
  • molded components In the field of production and treatment of molded components, it is customary to produce molded components specifically with desired material properties. For example, in the automotive industry, components such as control arms, B-pillars, or automotive bumpers are cured by complete heating followed by quenching. To do this, components made of steel must be heated at least to the austenitic temperature so that martensite forms during rapid cooling. By contrast, light metal components are heated to a softening temperature. In various applications, in particular the automotive technology, it is advantageous if molded components have different material properties in different areas. For example, it may be provided that a component in one area should have high strength, while in another area it should have a higher ductility in relation to it. This is achieved for example by a different heating of the individual areas.
  • the component is heated between two heated tools in the form of plates.
  • this method has the disadvantage that due to the required size of the plates after a short period of operation surface deformations and cracks in the plates arise because at each cycle, the allowable elastic deformation of the plates is exceeded by thermal deformation. The service lives of the tools are thus very low, so that this method is very expensive due to the high wear of the tools.
  • the known methods are therefore in particular not suitable for producing molded parts which partially in a middle region, for example in the area of the lock case in a B-pillar have a different structure than in the rest of the molded part, and at the same time given the requirements in the automotive industry to the Process reliability and the resulting quality standards, allowing the heating with very high heat transfer coefficients and therefore allow low operating costs and lowest primary energy consumption and high wear of the tools used is avoided.
  • the US patent US 3,461,709 discloses a hydraulic press installed in a furnace for plastically deforming and / or stress relieving metallic workpieces having a top plate and a bottom plate. Both plates are heated directly by integrated electric heating elements and are vertically movable. Each plate of the press has a corresponding contact surface, which is placed in direct contact with the treated workpiece by the vertical movement of the two plates. The contact surfaces are each divided in half. The workpiece is heated on both sides by direct contact with the vertically moving halves of the contact surfaces of the heating units.
  • the document D2 describes a deep-drawing press, which has an upper and a lower punch. On the stamp heated upper and lower sides of a tool are clamped. Between the top and bottom of the tool can be clamped by moving the press a metallic workpiece. Heatable punches also dive through the tool, which can plastically deform the clamped workpiece by a vertical movement in this area.
  • the object of the invention is therefore to provide a method for treating workpieces, which allows the formation of such different material and process properties while maintaining quality standards and at low cost.
  • An object of the invention is further to provide a corresponding furnace for carrying out the method.
  • the invention comprises a method of treating at least one workpiece in an oven, wherein the workpiece is heated in a furnace chamber of the furnace by at least two heating units, the workpiece having a first workpiece side and a second workpiece side.
  • a first heating unit heats the first workpiece side of the workpiece
  • a second heating unit heats the second workpiece side of the workpiece.
  • the two heating units each associated with a workpiece, and each heating unit comprises at least two plunger with heated contact surfaces, which are arranged side by side and with the same orientation.
  • the workpiece is heated by making contact between the first workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the first heating unit, and also making contact between the second workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the second heating unit.
  • the invention is based on the essential finding that the heating of a workpiece via contact heating with a large continuous contact surface is disadvantageous because such a contact surface due to the temperature conditions in Use is exposed to strong thermal changes in shape, which allows only a certain number of strokes.
  • a heating unit consisting of at least two pressure punches with smaller contact surfaces, however, this negative effect can be avoided and a method can be provided, with which the requirements can be fulfilled permanently.
  • two plungers per heating unit are the minimum requirement, but more than two plungers have proved to be even more advantageous.
  • the contact surfaces of the plunger of a heating unit are in contact with the workpiece in each case in different planes, whereby uneven workpieces with elevations and / or depressions can be contacted.
  • At least two of the plungers are vertically moved prior to heating the workpiece, from a position without contact between their contact surfaces and the workpiece sides of the workpiece in a position with contact between their contact surfaces and the workpiece sides the workpiece are moved.
  • the workpiece is placed horizontally in the oven chamber, and the workpiece is placed with the lower workpiece side on the contact surfaces of the plunger of the lower heating unit.
  • the upper heater unit plungers are then moved vertically down until there is contact between the contact surfaces of the upper heater unit plungers and the upper workpiece side, while the position of the lower heater unit plungers is not changed.
  • a charging device for charging the furnace with workpieces, which has at least one charging element on which the workpiece rests with its lower side of the workpiece, it can be provided that those pressure pistons of the lower heating unit are moved vertically downwards, which are located in the region of the charging element , And that the workpiece is then stored with the lower side of the workpiece on the contact surfaces of the other plunger of the lower heating unit.
  • the previously vertically moved down plungers are then again moved vertically up to their contact surfaces contact the lower workpiece side of the workpiece, and the plunger of the upper heating unit are moved vertically down until their contact surfaces make contact with the upper side of the workpiece.
  • the contact surfaces of the plunger are heated to different temperatures, which allows the heating of areas in the workpiece to different temperatures.
  • the contact surface of at least one pressure stamp is cooled.
  • the invention further comprises an oven for treating at least one workpiece comprising at least one oven chamber and at least two heating units for heating the workpiece in the oven chamber, the workpiece having a first workpiece side and a second workpiece side and the at least two heating units being arranged a first workpiece side of the workpiece is heatable by the respective first heating unit and the second workpiece side of the workpiece by the respective second heating unit, wherein each heating unit comprises at least two plungers and the contact surfaces of the plunger of a heating unit lie in different planes when contacting the workpiece.
  • the at least two heating units are each assigned to a workpiece, and each heating unit comprises at least two pressure stamps with heatable contact surfaces which are arranged next to one another and with the same orientation.
  • the workpiece is heatable in the oven chamber by making contact between the first workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the first heating unit, and also making contact between the second workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the second heating unit becomes.
  • At least two of the plungers are vertically movable, means being provided to move these plungers from a position without contact between their contact surfaces and the workpiece sides of the workpiece to a position with contact between their contact surfaces and the workpiece sides of the workpiece.
  • the contact surfaces of a plurality of pressure stamps arranged in rows and columns of a heating unit each form a heating surface whose dimensions correspond at least to the contours of the workpiece, wherein the contact surfaces of the pressure stamp of a heating unit in contact with the workpiece in each case a level or in different levels can be arranged.
  • the heating surface formed by the plunger of a heating unit thus one side of a workpiece can be contacted almost completely, but it can also be provided that at uneven workpiece surfaces with elevations and / or depressions only all horizontal surfaces are contacted, the contact surfaces of Plunging a heating unit to be positioned in different levels to achieve this.
  • the contact surfaces of the plunger are honeycomb-shaped, as this form has proved due to the largest inner surface with the smallest external length while avoiding unheated areas as an advantageous form.
  • the contact surfaces of the plunger of the first heating unit are arranged offset to the contact surfaces of the plunger of the second heating unit, whereby a uniform heating of the workpiece is achieved while avoiding unheated gaps between the contact surfaces.
  • the contact surfaces of the plunger can be heated to different temperatures, which increases the flexibility of the furnace in use, since different areas of a workpiece can be heated to different temperatures. It is also advantageous if at least one plunger is coolable. In a particular embodiment of the invention, the contact surface of at least one plunger is therefore selectively both heated and cooled.
  • At least two of the plungers of a heating unit may be selectively vertically movable.
  • Fig. 1 shows an embodiment of a furnace 10 according to the invention with two heating units 15 and 16 consisting of a plurality of pressure punches, wherein only the essential features of the furnace are shown.
  • the oven details can be selected by a skilled person in the usual way.
  • furnace 10 is an oven with a furnace chamber 11, in which at least one workpiece 20 is introduced for heating.
  • the oven 10 may be a station in a series of processing stations, wherein the oven 10 takes over the heating or at least a portion of the heating.
  • the furnace 10 preferably has a furnace body 14, into which the furnace chamber 11 is inserted with a feed opening 12 and an opposite removal opening 13, so that the furnace 10 can be charged from one side with a workpiece to be heated, while an already heated Workpiece is removed on the other side. A heated workpiece can then, for example, be transferred directly to a press after removal or held in a heat channel until it is processed at the next station.
  • the oven 10 does not necessarily have to have two openings, but may also comprise only one opening for loading and unloading.
  • the feed opening 12 and the removal opening 13 can be temporarily closed by oven flaps, and in the oven chamber 11 so a certain gas atmosphere can be generated.
  • only one workpiece 20 is heated over the length of the oven 10, so that no workpieces are arranged one behind the other, but this is not mandatory, if appropriate loading and unloading devices are present, which allow the simultaneous heating of several workpieces. But it is also possible to arrange over the width of the furnace 10 several workpieces side by side to heat them at the same time, or to operate several ovens 10 side by side to reduce the cycle time for subsequent stations.
  • a feeder 40 which is used in front of the oven 10, while behind the oven 10, a removal device 50 is used to remove heated workpieces from the oven 10.
  • both devices have a loading or removal element in the form of a fork, with which workpieces can be received.
  • the feeder 40 then has, for example, two forks 41 and 42, while the removal device 50 has two forks 51 and 52.
  • Both the charging device 40 and the removal device 50 are preferably designed so that they can move horizontally, so that they can pick up a workpiece 20 on the forks and move into the opened furnace chamber 11 or pick up a workpiece 20 in the furnace 10 and exit it.
  • the forks can also be designed to be vertically movable.
  • a loading and unloading device but also any other means in the form of robots or conveyor belts or combinations thereof may be used.
  • the oven chamber 11 preferably extends horizontally in the oven 10 so that the two heating units 15 and 16 are above and below the workpiece 20 when placed in the oven 10.
  • a first workpiece side 21 faces upward and can be heated by the upper heating unit 15 while the opposite workpiece side 22 is heated by the lower heating unit 16.
  • Each of the heating units 15 and 16 consists of at least two pressure punches, the distal end surfaces are heated. Such a contact surface is located on the workpiece 20 side facing a punch.
  • the plunger of both heating units are brought into contact with the workpiece 20, so that the workpiece 20 is heated by contact heating.
  • a heating unit according to the invention consists of at least two separate plungers with respective contact surfaces. However, these plungers and thus their contact surfaces are arranged so close together and aligned in the same direction that results in a heating surface, which is approximately continuous. If the workpiece 20 is plate-shaped and is introduced horizontally into the oven, the contact surfaces of the plunger thus also extend horizontally.
  • the distance between the individual contact surfaces of a heating unit is small, with distances of approximately 0.5 mm have proved advantageous, which can be considered in the context of this invention as approximately continuous heating surface.
  • the diameter of the contact surfaces is in the order of about 50 to 150 mm.
  • the actual size of the contact surfaces can be calculated from the thermal expansion of the stamp material used and the permissible elastic deformation and the desired life of the plunger.
  • a heating unit consists of more than two pressure punches, so that seen from above several rows and columns are formed from pressure punches to from their contact surfaces an approximately continuous heating surface form, with which a workpiece can be contacted and so heated.
  • a heating unit consists of more than two pressure punches, so that seen from above several rows and columns are formed from pressure punches to from their contact surfaces an approximately continuous heating surface form, with which a workpiece can be contacted and so heated.
  • the front row of the lower heating unit 16 comprises six pressure punches, since these are arranged in their horizontal position offset from the pressure punches of the upper heating unit 15, wherein the two right pressure punches are again identified by the reference numerals 32 and 33.
  • the contact surfaces of the plunger are honeycomb-shaped and arranged in a heating unit offset from one another so that they form an approximately continuous heating surface.
  • the hexagonal honeycomb shape has the advantage that, similar to a honeycomb, it has the largest inner surface with the smallest external length while avoiding unheated areas, and thus a surface can be filled and parqueted completely. Other geometries of the contact surfaces can also be displayed.
  • a heating surface in the context of this invention is to be understood not only an area formed by contact surfaces of the plunger, which are all in one plane, but the contact surfaces can also be located in different levels. Although the contact surfaces are then all the same orientation - ie, they all extend horizontally - but their vertical position may be different be. This can occur when plunger and thus their contact surfaces are moved vertically different. Projected onto one level, the contact surfaces then form a continuous heating surface, but this heating surface is offset in height.
  • This may still be referred to as a heating surface in the context of the invention, since the contact surfaces can heat, for example, an uneven surface of a workpiece with elevations and / or depressions. Although not horizontally extending surface sections then have no contact with the plunger, but this can possibly be accepted or may even be desirable.
  • the contact surfaces of the plunger of the two heating units 15 and 16 in the furnace chamber 11 are brought into contact with the workpiece 20, so that the workpiece 20 is heated over both sides of the workpiece 21 and 22.
  • at least two of the plunger are designed to be vertically movable. This can be at least the upper pressure stamp, which are designed to be vertically movable, while the lower plunger fixed.
  • a workpiece can be placed on the contact surfaces of the lower plunger after the upper plunger were previously moved upwards. As soon as the workpiece rests, the upper plungers are moved down until they come into contact with the workpiece.
  • At least the upper plunger can be made resilient, so that they can be further lowered vertically after contact with the workpiece in order to apply a spring pressure on the top of the workpiece can.
  • Which pressure stamp movable and which are resilient depends in accordance with the design and execution of the furnace 10, which in turn depends for example on the design of the workpieces.
  • the individual plunger can be controlled separately, so that a uniform contact of all contact surfaces can be achieved to the workpiece, even if the workpiece has elevations and / or depressions.
  • Selective control of individual plungers is also advantageous if the outlines of the workpieces to be heated change, so that the shape of the required heating surface, ie the selection of the applied plunger is to be varied.
  • thermal fluid can be used, for example, monatomic gases such as helium or hydrogen. These gases are characterized by a very high thermal conductivity and thus serve as a good heat conductor in the press nips between the contact surfaces of the plunger and the surfaces of the workpiece 20th
  • the movable plungers are relieved of pressure in a selectable clock frequency and then loaded again.
  • the workpiece 20 can expand accordingly during the heating, so that a high quality of the treated workpieces can be achieved.
  • the furnace 10 For feeding the furnace 10 with workpieces 20, various methods can be used and the furnace 10 is designed accordingly.
  • the width of a heating surface formed by the lower pressure pistons eg, 32, 33, 34
  • this workpiece 20 is transferred from the charging device 40 into the oven chamber 11 can be moved, it is picked up by two forks 41 and 42 and can then be stored in the oven chamber 11 on the lower pressure dies 32, 33 and 34.
  • those plungers can be moved vertically downwards, in the region of which the forks 41 and 42 are located. This is schematically in the supervision of Fig.
  • the oven chamber 11 may be formed so that there is otherwise room for the loading and unloading device 40, 50 to bring the workpiece 20 into position between the upper and lower dies.
  • the workpiece 20 may also be slid horizontally into the oven chamber 11 until it reaches a mark on which the workpiece 20 is aligned to be positioned between the dies of the two heating units. If feeders are used which can place and pick up a workpiece 20 directly on the lower plungers, no further precautions in the oven 10 may be necessary.
  • heat transfer coefficients of> 2,000W / m 2 / K can be achieved, which also different Heating and cooling strategies are possible. It can be implemented cycle times of about 6 seconds, with two ovens can be positioned side by side.
  • the workpiece may first be fully heated to or above austenite temperature with all of the plungers, after which certain areas are then cooled by individual plungers back to a temperature below the austenitic temperature.
  • Last embodiment may require that individual plunger are both heatable, as well as designed to cool. In both cases, these selected plungers are arranged to be in the areas where a different temperature is to be set. In order to obtain certain shapes of these areas, the contact surfaces of these plungers may also have corresponding other outlines than the other plunger.
  • Both the temperature control and the vertical movement of the plunger is preferably carried out by a central control unit of the furnace, which is freely programmable.
  • the plunger itself can be heated by gas or electrically, with an electric heating, for example, can be done inductively via a resistor.
  • Fig. 4 shows a possible embodiment of a lower plunger 32 having an upper contact surface 35.
  • the plunger 32 is cylindrical and is heated by gas burners inside. These gas burners are equipped for example with heat exchangers, which use the heat of the outflowing combustion gas to preheat the incoming gases.
  • the burners are preferably equipped in each plunger with a thermocouple and an external control technology, which ensures, for example, an auto-ignition temperature of about 800 ° C.
  • a thermocouple and an external control technology, which ensures, for example, an auto-ignition temperature of about 800 ° C.
  • one or more separate, intrinsically safe gas burners are provided in the oven chamber 11, which preheat the oven 10 to the autoignition temperature of the plunger. After this ignition process, the furnace chamber 11 can be acted upon with conditioned gas, since the combustion chamber is gas-tight in each plunger separated therefrom.
  • inert gas or dried air can be used to prevent H 2 -Versprödung.
  • different materials can be used for the plungers and in particular for their contact surfaces.
  • hot working steels which can be used as alloyed tool steels for applications in which the surface temperature in use can reach up to 400.degree. C. are suitable.
  • the alloying elements are coordinated so that the hot-work tool steels have sufficient hardness and strength, high heat resistance, hot hardness and wear resistance even at elevated temperatures. So they are suitable as a material for contact surfaces, which are used for heating workpieces up to 400 ° C. This is the case, for example, for light metals, such as aluminum or magnesium workpieces, which are typically heated to temperatures in the range of 230 ° C to 250 ° C.
  • SiC silicon carbide

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Tunnel Furnaces (AREA)
  • Heat Treatment Of Articles (AREA)
  • Furnace Details (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Press Drives And Press Lines (AREA)

Description

Die Erfindung betrifft ein Verfahren zum Behandeln wenigstens eines Werkstücks in einem Ofen, bei dem das Werkstück in einer Ofenkammer des Ofens von wenigstens zwei Heizeinheiten erwärmt wird, wobei das Werkstück eine erste Werkstückseite und eine zweite Werkstückseite aufweist, und wobei eine erste Heizeinheit die erste Werkstückseite des Werkstücks und eine zweite Heizeinheit die zweite Werkstückseite des Werkstücks erwärmt.The invention relates to a method for treating at least one workpiece in a furnace, in which the workpiece is heated in a furnace chamber of the furnace by at least two heating units, wherein the workpiece has a first workpiece side and a second workpiece side, and wherein a first heating unit, the first workpiece side of the workpiece and a second heating unit heats the second workpiece side of the workpiece.

Die Erfindung betrifft ferner einen entsprechenden Ofen zur Durchführung des Verfahrens.The invention further relates to a corresponding furnace for carrying out the method.

Im Bereich der Fertigung und Behandlung von Formbauteilen ist es üblich, Formbauteile gezielt mit gewünschten Werkstoffeigenschaften herzustellen. Beispielsweise werden in der Automobilindustrie Bauteile wie Querlenker, B-Säulen oder Stoßfänger für Kraftfahrzeuge durch eine vollständige Erwärmung mit einer anschließenden Abschreckung gehärtet. Dazu müssen Bauteile aus Stahl mindestens bis zur Austenittemperatur erwärmt werden, damit sich bei der raschen Abkühlung Martensit bildet. Bauteile aus Leichtmetall hingegen werden bis zu einer Erweichungstemperatur erwärmt. In verschiedenen Anwendungsfällen insbesondere der Kraftfahrzeugtechnik ist es vorteilhaft, wenn Formbauteile in verschiedenen Bereichen unterschiedliche Werkstoffeigenschaften aufweisen. Beispielsweise kann es vorgesehen sein, dass ein Bauteil in einem Bereich eine hohe Festigkeit, in einem anderen Bereich hingegen eine im Verhältnis dazu höhere Duktilität aufweisen soll. Dies wird beispielsweise durch eine unterschiedliche Erwärmung der einzelnen Bereiche erreicht.In the field of production and treatment of molded components, it is customary to produce molded components specifically with desired material properties. For example, in the automotive industry, components such as control arms, B-pillars, or automotive bumpers are cured by complete heating followed by quenching. To do this, components made of steel must be heated at least to the austenitic temperature so that martensite forms during rapid cooling. By contrast, light metal components are heated to a softening temperature. In various applications, in particular the automotive technology, it is advantageous if molded components have different material properties in different areas. For example, it may be provided that a component in one area should have high strength, while in another area it should have a higher ductility in relation to it. This is achieved for example by a different heating of the individual areas.

Um große Produktionsmengen derartiger Formbauteile zu erwärmen, sind heute elektrisch betriebene Öfen bekannt, wobei zur Erwärmung eines Werkstücks beispielsweise ein Wirbelstrom im Werkstück induziert wird. Bei Konduktionsöfen wird dagegen ein elektrischer Strom direkt durch das Formbauteil geleitet.In order to heat large production quantities of such mold components, today electrically operated ovens are known, wherein for heating a workpiece, for example an eddy current is induced in the workpiece. In Konduktionsöfen, however, an electric current is passed directly through the mold component.

Hierbei sind Durchlauföfen jedoch selbst bei mehrlagiger Ausführung aufgrund der vergleichsweise niedrigen Wärmeübergangszahl (WÜZ) von max. 125 W/m2/K sehr lang und verbrauchen aufgrund der dadurch bedingten großen Oberfläche viel Energie. Bei Mehrkammeröfen werden die Bauteile zwar übereinander angeordnet, aber da diese Öfen ebenfalls eine niedrige WÜZ haben, sind sie dennoch groß und haben den Nachteil eines hohen Energieverbrauchs.Here, however, continuous furnaces are even with multi-layer design due to the relatively low heat transfer coefficient (WÜZ) of max. 125 W / m 2 / K very long and consume a lot of energy due to the resulting large surface area. In multi-chamber ovens, the components are indeed stacked, but since these ovens also have a low WÜZ, they are still large and have the disadvantage of high energy consumption.

Mit der direkten Induktionserwärmung lässt sich eine WÜZ von bis zu 5.000 W/m2/K erreichen. Da die induktive Ankoppelung jedoch bei magnetischen Eisenwerkstoffen oberhalb des Curiepunktes gravierend abfällt und der induzierte Stromfluss aufgrund der erforderlichen Platinengeometrie - welche Löcher und Querschnittserweiterungen sowie -verengungen haben kann - sehr unterschiedlich ausfällt, erfolgt die Erwärmung sehr ungleichmäßig. Zur Vergleichmäßigung ist deshalb danach noch ein gewöhnlicher Ofen nötig. Diese umständliche Anordnung stellt sich nicht als sinnvoll dar, es sei denn, es handelt sich um sehr einfache Geometrien, welche praktisch in diesem Bereich nicht vorkommen. Darüber hinaus ist die Induktionserwärmung sowohl von den Investitionskosten als auch von den Betriebskosten aufgrund der erforderlichen Sekundärenergie und der nötigen Spulenkühlung sehr teuer.With the direct induction heating a WÜZ of up to 5,000 W / m 2 / K can be achieved. However, since inductive coupling is seriously reduced in magnetic iron materials above the Curie point and the induced current flow is very different due to the required board geometry - which may have holes and cross-sectional extensions and constrictions - the heating is very uneven. To even out a normal stove is then necessary after. This cumbersome arrangement does not make sense, unless it concerns very simple geometries, which practically do not occur in this area. In addition, induction heating is very expensive in terms of both capital cost and operating costs due to the required secondary energy and coil cooling required.

Ähnliche Nachteile gelten für die Konduktiverwärmung, wobei die Betriebskosten niedriger sind, da zumindest die Spulenkühlung entfällt. Jedoch wird für ein Werkstück mehr Blech verbraucht, da die Elekrodenanschlüsse Kontaktlaschen erfordern. Darüber hinaus decken die beiden letztgenannten Verfahren nicht die Notwendigkeit der unterschiedlichen Gefüge ab, welche dann in einem weiteren Prozessschritt herbeigeführt werden müssen.Similar disadvantages apply to the Konduktivenwärmung, the operating costs are lower, since at least the coil cooling is eliminated. However, more sheet metal is consumed for a workpiece since the electrode terminals require contact tabs. In addition, the two latter methods do not cover the need for different structures, which then have to be brought about in a further process step.

Bei einem anderen Verfahren wird das Bauteil zwischen zwei beheizten Werkzeugen in Form von Platten erwärmt. Dieses Verfahren hat jedoch den Nachteil, dass durch die erforderliche Größe der Platten nach kurzer Betriebszeit Oberflächenverformungen und Risse in den Platten entstehen, da bei jedem Zyklus die zulässige elastische Verformung der Platten durch thermische Formänderung überschritten wird. Die Standzeiten der Werkzeuge sind somit sehr niedrig, sodass dieses Verfahren aufgrund des hohen Verschleißes der Werkzeuge sehr kostenintensiv ist.In another method, the component is heated between two heated tools in the form of plates. However, this method has the disadvantage that due to the required size of the plates after a short period of operation surface deformations and cracks in the plates arise because at each cycle, the allowable elastic deformation of the plates is exceeded by thermal deformation. The service lives of the tools are thus very low, so that this method is very expensive due to the high wear of the tools.

Die bekannten Verfahren sind somit insbesondere nicht dafür geeignet, Formteile zu erzeugen, die partiell in einem mittleren Bereich, beispielsweise im Bereich des Schlosskastens in einer B-Säule ein anderes Gefüge aufweisen als im übrigen Formteil, und die gleichzeitig den im Kraftfahrzeugbau gegebenen Anforderungen an die Prozesssicherheit und den sich daraus ergebenden Qualitätsstandards genügen, wobei sie die Erwärmung mit sehr hohen Wärmeübergangszahlen erlauben und daher niedrige Betriebskosten und geringsten Primärenergieverbrauch gestatten und wobei ein hoher Verschleiß der verwendeten Werkzeugen vermieden wird.The known methods are therefore in particular not suitable for producing molded parts which partially in a middle region, for example in the area of the lock case in a B-pillar have a different structure than in the rest of the molded part, and at the same time given the requirements in the automotive industry to the Process reliability and the resulting quality standards, allowing the heating with very high heat transfer coefficients and therefore allow low operating costs and lowest primary energy consumption and high wear of the tools used is avoided.

Das US-amerikanische Patent US 3,461,709 offenbart eine in einen Ofen installierte hydraulische Presse zur plastischen Verformung und/oder Spannungsabbau metallischen Werkstücke, die eine obere Platte sowie eine untere Platte aufweist. Beide Platten werden direkt durch integrierte elektrische Heizelemente erwärmt und sind vertikal bewegbar. Jede Platte der Presse weist eine entsprechende Kontaktfläche auf, die durch die vertikale Bewegung der beiden Platten in direkter Kontakt mit dem behandelten Werkstück gesetzt wird. Die Kontaktflächen sind jeweils in zwei Hälften geteilt. Das Werkstück wird beiderseitig durch direkten Kontakt mit den sich vertikal bewegenden Hälften der Kontaktoberflächen der Heizeinheiten erwärmt.The US patent US 3,461,709 discloses a hydraulic press installed in a furnace for plastically deforming and / or stress relieving metallic workpieces having a top plate and a bottom plate. Both plates are heated directly by integrated electric heating elements and are vertically movable. Each plate of the press has a corresponding contact surface, which is placed in direct contact with the treated workpiece by the vertical movement of the two plates. The contact surfaces are each divided in half. The workpiece is heated on both sides by direct contact with the vertically moving halves of the contact surfaces of the heating units.

Die Druckschrift D2 beschreibt eine Tiefziehpresse, die einen Ober- und einen Unterstempel aufweist. Auf die Stempel sind beheizbare Ober- und Unterseiten eines Werkzeugs aufgespannt. Zwischen die Ober- und Unterseite des Werkzeug kann durch Zufahren der Presse ein metallisches Werkstück eingespannt werden. Durch das Werkzeug tauchen ebenfalls beheizbare Stempel hindurch, die das eingespannte Werkstück durch eine Vertikalbewegung in diesem Bereich plastisch verformen können.The document D2 describes a deep-drawing press, which has an upper and a lower punch. On the stamp heated upper and lower sides of a tool are clamped. Between the top and bottom of the tool can be clamped by moving the press a metallic workpiece. Heatable punches also dive through the tool, which can plastically deform the clamped workpiece by a vertical movement in this area.

Aufgabe der Erfindung ist es daher, ein Verfahren zum Behandeln von Werkstücken bereitzustellen, das die Ausbildung solcher unterschiedlicher Werkstoff- und Prozesseigenschaften bei gleichzeitiger Einhaltung der Qualitätsstandards sowie bei niedrigen Kosten ermöglicht.The object of the invention is therefore to provide a method for treating workpieces, which allows the formation of such different material and process properties while maintaining quality standards and at low cost.

Eine Aufgabe der Erfindung ist es ferner, einen entsprechenden Ofen zur Durchführung des Verfahrens bereitzustellen.An object of the invention is further to provide a corresponding furnace for carrying out the method.

Diese Aufgabe wird gelöst durch ein Verfahren mit den Merkmalen des unabhängigen Anspruchs 1. Vorteilhafte Weiterbildungen des Verfahrens ergeben sich aus den Unteransprüchen 2-7. Die Aufgabe wird ferner durch einen Ofen nach Anspruch 8 gelöst. Ausführungsformen des Ofens ergeben sich aus den Unteransprüchen 9-15.This object is achieved by a method having the features of independent claim 1. Advantageous developments of the method will become apparent from the dependent claims 2-7. The object is further achieved by an oven according to claim 8. Embodiments of the furnace will become apparent from the dependent claims 9-15.

Die Erfindung umfasst ein Verfahren zum Behandeln wenigstens eines Werkstücks in einem Ofen, bei dem das Werkstück in einer Ofenkammer des Ofens von wenigstens zwei Heizeinheiten erwärmt wird, wobei das Werkstück eine erste Werkstückseite und eine zweite Werkstückseite aufweist. Eine erste Heizeinheit erwärmt dabei die erste Werkstückseite des Werkstücks, und eine zweite Heizeinheit erwärmt die zweite Werkstückseite des Werkstücks. Erfindungsgemäß ist den beiden Heizeinheiten jeweils ein Werkstück zugeordnet, und jede Heizeinheit umfasst wenigstens zwei Druckstempel mit beheizten Kontaktflächen, die nebeneinander und mit der gleichen Ausrichtung angeordnet sind. Das Werkstück wird erwärmt, indem zwischen der ersten Werkstückseite des Werkstücks und den Kontaktflächen der wenigstens zwei Druckstempel der ersten Heizeinheit Kontakt hergestellt wird, und indem zwischen der zweiten Werkstückseite des Werkstücks und den Kontaktflächen der wenigstens zwei Druckstempel der zweiten Heizeinheit ebenfalls Kontakt hergestellt wird.The invention comprises a method of treating at least one workpiece in an oven, wherein the workpiece is heated in a furnace chamber of the furnace by at least two heating units, the workpiece having a first workpiece side and a second workpiece side. A first heating unit heats the first workpiece side of the workpiece, and a second heating unit heats the second workpiece side of the workpiece. According to the invention, the two heating units each associated with a workpiece, and each heating unit comprises at least two plunger with heated contact surfaces, which are arranged side by side and with the same orientation. The workpiece is heated by making contact between the first workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the first heating unit, and also making contact between the second workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the second heating unit.

Durch diese Kontakterwärmung können Wärmeübergangszahlen von >2.000W/m2/K erreicht werden, wobei der Erfindung dabei die wesentliche Erkenntnis zugrunde liegt, dass die Erwärmung eines Werkstückes über Kontakterwärmung mit einer großen durchgehenden Kontaktfläche nachteilig ist, da eine solche Kontaktfläche aufgrund der Temperaturbedingungen im Einsatz starken thermischen Formveränderungen ausgesetzt ist, welche nur eine bestimmte Anzahl von Hüben erlaubt. Durch eine Heizeinheit bestehend aus wenigstens zwei Druckstempeln mit kleineren Kontaktflächen kann dieser negative Effekt jedoch vermieden und ein Verfahren bereitgestellt werden, mit dem sich die gestellten Anforderungen dauerhaft erfüllen lassen. Dabei sind je nach Größe des Werkstücks zwei Druckstempel pro Heizeinheit das Mindesterfordernis, mehr als zwei Druckstempel haben sich jedoch als noch vorteilhafter erwiesen.By this contact heat transfer rates of> 2.000W / m 2 / K can be achieved, the invention is based on the essential finding that the heating of a workpiece via contact heating with a large continuous contact surface is disadvantageous because such a contact surface due to the temperature conditions in Use is exposed to strong thermal changes in shape, which allows only a certain number of strokes. By a heating unit consisting of at least two pressure punches with smaller contact surfaces, however, this negative effect can be avoided and a method can be provided, with which the requirements can be fulfilled permanently. Depending on the size of the workpiece, two plungers per heating unit are the minimum requirement, but more than two plungers have proved to be even more advantageous.

Vorzugsweise liegen die Kontaktflächen der Druckstempel einer Heizeinheit bei Kontakt mit dem Werkstück jeweils in unterschiedlichen Ebenen, wodurch auch unebene Werkstücke mit Erhöhungen und/oder Vertiefungen kontaktiert werden können.Preferably, the contact surfaces of the plunger of a heating unit are in contact with the workpiece in each case in different planes, whereby uneven workpieces with elevations and / or depressions can be contacted.

Um ein Werkstück in einen Ofen einbringen zu können, werden vor der Erwärmung des Werkstücks vorzugsweise wenigstens zwei der Druckstempel vertikal bewegt, wobei sie aus einer Position ohne Kontakt zwischen ihren Kontaktflächen und den Werkstückseiten des Werkstücks in eine Position mit Kontakt zwischen ihren Kontaktflächen und den Werkstückseiten des Werkstücks verfahren werden.To be able to introduce a workpiece into an oven, preferably at least two of the plungers are vertically moved prior to heating the workpiece, from a position without contact between their contact surfaces and the workpiece sides of the workpiece in a position with contact between their contact surfaces and the workpiece sides the workpiece are moved.

Insbesondere wird das Werkstück horizontal in die Ofenkammer eingebracht, und das Werkstück wird mit der unteren Werkstückseite auf den Kontaktflächen der Druckstempel der unteren Heizeinheit abgelegt. Die Druckstempel der oberen Heizeinheit werden dann vertikal nach unten verfahren, bis Kontakt zwischen den Kontaktflächen der Druckstempel der oberen Heizeinheit und der oberen Werkstückseite besteht, während die Lage der Druckstempel der unteren Heizeinheit nicht verändert wird.In particular, the workpiece is placed horizontally in the oven chamber, and the workpiece is placed with the lower workpiece side on the contact surfaces of the plunger of the lower heating unit. The upper heater unit plungers are then moved vertically down until there is contact between the contact surfaces of the upper heater unit plungers and the upper workpiece side, while the position of the lower heater unit plungers is not changed.

Wird zur Beschickung des Ofens mit Werkstücken eine Beschickungsvorrichtung eingesetzt, welche wenigstens ein Beschickungselement aufweist, auf dem das Werkstück mit seiner unteren Werkstückseite aufliegt, kann vorgesehen sein, dass diejenigen Druckstempel der unteren Heizeinheit vertikal nach unten verfahren werden, die sich im Bereich des Beschickungselementes befinden, und dass das Werkstück anschließend mit der unteren Werkstückseite auf den Kontaktflächen der anderen Druckstempel der unteren Heizeinheit abgelegt wird. Die zuvor vertikal nach unten verfahrenen Druckstempel werden daraufhin wieder vertikal nach oben verfahren, bis ihre Kontaktflächen Kontakt zur unteren Werkstückseite des Werkstücks haben, und die Druckstempel der oberen Heizeinheit werden vertikal nach unten verfahren, bis ihre Kontaktflächen Kontakt zu der oberen Werkstückseite haben. Durch diese Vorgehensweise ist es möglich, dass bei der Beschickung ausreichend Raum für die Beschickungsvorrichtung in der Ofenkammer gegeben ist.If a charging device is used for charging the furnace with workpieces, which has at least one charging element on which the workpiece rests with its lower side of the workpiece, it can be provided that those pressure pistons of the lower heating unit are moved vertically downwards, which are located in the region of the charging element , And that the workpiece is then stored with the lower side of the workpiece on the contact surfaces of the other plunger of the lower heating unit. The previously vertically moved down plungers are then again moved vertically up to their contact surfaces contact the lower workpiece side of the workpiece, and the plunger of the upper heating unit are moved vertically down until their contact surfaces make contact with the upper side of the workpiece. By doing so, it is possible that there is sufficient space for the charging device in the furnace chamber during charging.

Da weder die Oberflächen der Werkstückseiten des Werkstücks noch die Kontaktflächen der Druckstempel fertigungstechnisch bedingt völlig eben sind, sodass der direkte Kontakt zwischen den Kontaktflächen der Druckstempel und den Werkstückseiten des Werkstücks bereichsweise unterbrochen sein kann, wird zur Verbesserung des Wärmeübergangs ein Wärmefluid in den Pressspalt zwischen den Werkstückseiten des Werkstücks und den Kontaktflächen der Druckstempel eingebracht. Die Zuführung des Wärmefluids in den jeweiligen Pressspalt zwischen den beiden Werkstückseiten des Werkstücks und den Kontaktflächen der Druckstempel erfolgt dabei über Mittel, die in die Druckstempel integriert sind.Since neither the surfaces of the workpiece sides of the workpiece nor the contact surfaces of the plunger manufacturing reasons are completely flat, so that the direct contact between the contact surfaces of the plunger and the workpiece sides of the workpiece can be partially interrupted, to improve the heat transfer, a heat fluid in the press nip between the Workpieces sides of the workpiece and the contact surfaces of the plunger introduced. The supply of the thermal fluid in the respective press nip between the two sides of the workpiece workpiece and the contact surfaces of the plunger takes place via means that are integrated into the plunger.

Vorzugsweise werden die Kontaktflächen der Druckstempel auf unterschiedliche Temperaturen beheizt, was die Erwärmung von Bereichen im Werkstück auf unterschiedliche Temperaturen ermöglicht. Insbesondere wird die Kontaktfläche wenigstens eines Druckstempels gekühlt.Preferably, the contact surfaces of the plunger are heated to different temperatures, which allows the heating of areas in the workpiece to different temperatures. In particular, the contact surface of at least one pressure stamp is cooled.

Von der Erfindung umfasst ist ferner ein Ofen zum Behandeln wenigstens eines Werkstücks, umfassend wenigstens eine Ofenkammer und wenigstens zwei Heizeinheiten zum Erwärmen des Werkstücks in der Ofenkammer, wobei das Werkstück eine erste Werkstückseite und eine zweite Werkstückseite aufweist und die wenigstens zwei Heizeinheiten so angeordnet sind, dass eine erste Werkstückseite des Werkstücks von der jeweiligen ersten Heizeinheit und die zweite Werkstückseite des Werkstücks von der jeweiligen zweiten Heizeinheit erwärmbar ist, wobei jede Heizeinheit wenigstens zwei Druckstempel umfasst und die Kontaktflächen der Druckstempel einer Heizeinheit bei Kontakt mit dem Werkstück jeweils in unterschiedlichen Ebenen liegen. Erfindungsgemäß sind die wenigstens zwei Heizeinheiten jeweils einem Werkstück zugeordnet, und jede Heizeinheit umfasst wenigstens zwei Druckstempel mit beheizbaren Kontaktflächen, die nebeneinander und mit der gleichen Ausrichtung angeordnet sind. Das Werkstück ist in der Ofenkammer erwärmbar, indem zwischen der ersten Werkstückseite des Werkstücks und den Kontaktflächen der wenigstens zwei Druckstempel der ersten Heizeinheit Kontakt hergestellt wird, und indem zwischen der zweiten Werkstückseite des Werkstücks und den Kontaktflächen der wenigstens zwei Druckstempel der zweiten Heizeinheit ebenfalls Kontakt hergestellt wird.The invention further comprises an oven for treating at least one workpiece comprising at least one oven chamber and at least two heating units for heating the workpiece in the oven chamber, the workpiece having a first workpiece side and a second workpiece side and the at least two heating units being arranged a first workpiece side of the workpiece is heatable by the respective first heating unit and the second workpiece side of the workpiece by the respective second heating unit, wherein each heating unit comprises at least two plungers and the contact surfaces of the plunger of a heating unit lie in different planes when contacting the workpiece. According to the invention, the at least two heating units are each assigned to a workpiece, and each heating unit comprises at least two pressure stamps with heatable contact surfaces which are arranged next to one another and with the same orientation. The workpiece is heatable in the oven chamber by making contact between the first workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the first heating unit, and also making contact between the second workpiece side of the workpiece and the contact surfaces of the at least two pressure stamps of the second heating unit becomes.

Vorzugsweise sind wenigstens zwei der Druckstempel vertikal bewegbar, wobei Mittel vorgesehen sind, um diese Druckstempel aus einer Position ohne Kontakt zwischen ihren Kontaktflächen und den Werkstückseiten des Werkstücks in eine Position mit Kontakt zwischen ihren Kontaktflächen und den Werkstückseiten des Werkstücks zu verfahren.Preferably, at least two of the plungers are vertically movable, means being provided to move these plungers from a position without contact between their contact surfaces and the workpiece sides of the workpiece to a position with contact between their contact surfaces and the workpiece sides of the workpiece.

Zweckmäßigerweise bilden die Kontaktflächen von mehreren in Reihen und Spalten angeordneten Druckstempeln einer Heizeinheit jeweils eine Heizfläche, deren Abmessungen wenigstens den Umrissen des Werkstücks entspricht, wobei die Kontaktflächen der Druckstempel einer Heizeinheit bei Kontakt mit dem Werkstück jeweils in
einer Ebene oder in unterschiedlichen Ebenen angeordnet werden können. Mit der durch die Druckstempel einer Heizeinheit gebildeten Heizfläche kann somit eine Seite eines Werkstücks annähernd vollständig kontaktiert werden, wobei es jedoch auch vorgesehen sein kann, dass bei unebenen Werkstückoberflächen mit Erhöhungen und/oder Vertiefungen nur alle horizontal liegenden Flächen kontaktiert werden, wobei die Kontaktflächen der Druckstempel einer Heizeinheit in unterschiedlichen Ebenen positioniert werden, um dies zu erreichen.Expediently, the contact surfaces of a plurality of pressure stamps arranged in rows and columns of a heating unit each form a heating surface whose dimensions correspond at least to the contours of the workpiece, wherein the contact surfaces of the pressure stamp of a heating unit in contact with the workpiece in each case
a level or in different levels can be arranged. With the heating surface formed by the plunger of a heating unit thus one side of a workpiece can be contacted almost completely, but it can also be provided that at uneven workpiece surfaces with elevations and / or depressions only all horizontal surfaces are contacted, the contact surfaces of Plunging a heating unit to be positioned in different levels to achieve this.

In einem Ausführungsbeispiel der Erfindung sind die Kontaktflächen der Druckstempel wabenförmig ausgebildet, da sich diese Form aufgrund der größten Innenfläche bei geringster Außenlänge unter Vermeidung von unbeheizten Bereichen als vorteilhafte Form erwiesen hat. Vorzugsweise sind die Kontaktflächen der Druckstempel der ersten Heizeinheit versetzt zu den Kontaktflächen der Druckstempel der zweiten Heizeinheit angeordnet, wodurch eine gleichmäßige Erwärmung des Werkstücks unter Vermeidung von unbeheizten Spalten zwischen den Kontaktflächen erreicht wird.In one embodiment of the invention, the contact surfaces of the plunger are honeycomb-shaped, as this form has proved due to the largest inner surface with the smallest external length while avoiding unheated areas as an advantageous form. Preferably, the contact surfaces of the plunger of the first heating unit are arranged offset to the contact surfaces of the plunger of the second heating unit, whereby a uniform heating of the workpiece is achieved while avoiding unheated gaps between the contact surfaces.

In einem Ausführungsbeispiel der Erfindung sind die Kontaktflächen der Druckstempel auf unterschiedliche Temperaturen beheizbar, was die Flexibilität des Ofens im Einsatz erhöht, da unterschiedliche Bereiche eines Werkstücks so auf unterschiedliche Temperaturen erwärmbar sind. Vorteilhaft ist dabei ferner, wenn wenigstens ein Druckstempel kühlbar ist. In einem besonderen Ausführungsbeispiel der Erfindung ist die Kontaktfläche wenigstens eines Druckstempels daher selektiv sowohl beheizbar als auch kühlbar.In one embodiment of the invention, the contact surfaces of the plunger can be heated to different temperatures, which increases the flexibility of the furnace in use, since different areas of a workpiece can be heated to different temperatures. It is also advantageous if at least one plunger is coolable. In a particular embodiment of the invention, the contact surface of at least one plunger is therefore selectively both heated and cooled.

Um die Flexibilität des Ofens zu erhöhen, können wenigstens zwei der Druckstempel einer Heizeinheit selektiv vertikal bewegbar ausgeführt sein.In order to increase the flexibility of the furnace, at least two of the plungers of a heating unit may be selectively vertically movable.

Die zuvor genannten und weitere Vorteile, Besonderheiten und zweckmäßige Weiterbildungen der Erfindung werden auch anhand der Ausführungsbeispiele deutlich, die nachfolgend unter Bezugnahme auf die Figuren beschrieben werden.The above and other advantages, features and expedient developments of the invention will become apparent from the embodiments, which are described below with reference to the figures.

Von den Figuren zeigt:

Fig. 1
ein Ausführungsbeispiel eines erfindungsgemäßen Ofens mit zwei Heizeinheiten bestehend aus mehreren Druckstempeln in einer schematischen Seitenansicht;
Fig. 2
einen Ofen gemäß Fig. 1 in einer schematischen Aufsicht mit einer Beschickungsvorrichtung vordem Ofen;
Fig. 3
einen Ofen gemäß Fig. 1 in einer schematischen Aufsicht beim Einbringen eines Werkstücks durch eine Beschickungsvorrichtung gemäß einem möglichen Verfahren; und
Fig. 4
ein Ausführungsbeispiel eines Druckstempels.
From the figures shows:
Fig. 1
an embodiment of a furnace according to the invention with two heating units consisting of several pressure punches in a schematic side view;
Fig. 2
an oven according to Fig. 1 in a schematic plan view with a charging device in front of the furnace;
Fig. 3
an oven according to Fig. 1 in a schematic plan view when introducing a workpiece by a loading device according to a possible method; and
Fig. 4
an embodiment of a printing stamp.

Fig. 1 zeigt ein Ausführungsbeispiel eines erfindungsgemäßen Ofens 10 mit zwei Heizeinheiten 15 und 16 bestehend aus mehreren Druckstempeln, wobei lediglich die wesentlichen Merkmale des Ofens dargestellt sind. Die Ofendetails können von einem Fachmann auf übliche Weise gewählt werden. Bei dem in Fig. 1 dargestellten Ofen 10 handelt es sich um einen Ofen mit einer Ofenkammer 11, in welche wenigstens ein Werkstück 20 für die Erwärmung eingebracht wird. Der Ofen 10 kann dabei eine Station in einer Reihe von Bearbeitungsstationen sein, wobei der Ofen 10 die Erwärmung oder zumindest einen Teil der Erwärmung übernimmt. Daher weist der Ofen 10 vorzugsweise einen Ofenkörper 14 auf, in den die Ofenkammer 11 mit einer Beschickungsöffnung 12 und einer gegenüber liegenden Entnahmeöffnung 13 eingebracht ist, so dass der Ofen 10 von einer Seite mit einem zu erwärmenden Werkstück beschickt werden kann, während ein bereits erwärmtes Werkstück auf der anderen Seite entnommen wird. Ein erwärmtes Werkstück kann nach der Entnahme dann beispielsweise direkt einer Presse übergeben oder auch in einem Wärmekanal gehalten werden, bis es an der nächsten Station bearbeitet wird. Der Ofen 10 muss dabei jedoch nicht zwingend zwei Öffnungen aufweisen, sondern kann auch nur eine Öffnung zum Beschicken und Entnehmen umfassen. Fig. 1 shows an embodiment of a furnace 10 according to the invention with two heating units 15 and 16 consisting of a plurality of pressure punches, wherein only the essential features of the furnace are shown. The oven details can be selected by a skilled person in the usual way. At the in Fig. 1 shown furnace 10 is an oven with a furnace chamber 11, in which at least one workpiece 20 is introduced for heating. The oven 10 may be a station in a series of processing stations, wherein the oven 10 takes over the heating or at least a portion of the heating. Therefore, the furnace 10 preferably has a furnace body 14, into which the furnace chamber 11 is inserted with a feed opening 12 and an opposite removal opening 13, so that the furnace 10 can be charged from one side with a workpiece to be heated, while an already heated Workpiece is removed on the other side. A heated workpiece can then, for example, be transferred directly to a press after removal or held in a heat channel until it is processed at the next station. However, the oven 10 does not necessarily have to have two openings, but may also comprise only one opening for loading and unloading.

Die Beschickungsöffnung 12 und die Entnahmeöffnung 13 können durch Ofenklappen temporär verschlossen werden, und in der Ofenkammer 11 kann so eine bestimmte Gasatmosphäre erzeugt werden.The feed opening 12 and the removal opening 13 can be temporarily closed by oven flaps, and in the oven chamber 11 so a certain gas atmosphere can be generated.

Vorzugsweise wird über die Länge des Ofens 10 jeweils nur ein Werkstück 20 erwärmt, so dass keine Werkstücke hintereinander angeordnet werden, was aber keine zwingende Vorgabe ist, falls entsprechende Beschickungs- und Entnahmevorrichtungen vorliegen, welche die gleichzeitige Erwärmung von mehreren Werkstücken ermöglichen. Möglich ist es aber auch, über die Breite des Ofens 10 mehrere Werkstücke nebeneinander anzuordnen, um sie gleichzeitig zu erwärmen, oder mehrere Öfen 10 nebeneinander zu betreiben, um die Taktzeit für nachfolgende Stationen zu verringern.Preferably, only one workpiece 20 is heated over the length of the oven 10, so that no workpieces are arranged one behind the other, but this is not mandatory, if appropriate loading and unloading devices are present, which allow the simultaneous heating of several workpieces. But it is also possible to arrange over the width of the furnace 10 several workpieces side by side to heat them at the same time, or to operate several ovens 10 side by side to reduce the cycle time for subsequent stations.

Um den Ofen 10 mit Werkstücken zu beschicken, ist beispielsweise eine Beschickungsvorrichtung 40 vorgesehen, die vor dem Ofen 10 eingesetzt wird, während hinter dem Ofen 10 eine Entnahmevorrichtung 50 dazu verwendet wird, um erwärmte Werkstücke aus dem Ofen 10 zu entnehmen. Beide Vorrichtungen weisen dazu beispielsweise ein Beschickungs- bzw. Entnahmeelement in Form einer Gabel auf, mit dem Werkstücke aufgenommen werden können. Die Beschickungsvorrichtung 40 weist dann beispielsweise zwei Gabelzinken 41 und 42 auf, während die Entnahmevorrichtung 50 zwei Gabelzinken 51 und 52 aufweist. Sowohl die Beschickungsvorrichtung 40 als auch die Entnahmevorrichtung 50 sind vorzugsweise horizontal verfahrbar ausgestaltet, sodass sie ein Werkstück 20 auf den Gabeln aufnehmen und in die geöffnete Ofenkammer 11 verfahren können bzw. ein Werkstück 20 im Ofen 10 aufnehmen und aus diesem herausfahren können. Ergänzend können die Gabelzinken auch vertikal verfahrbar ausgeführt sein. Als Beschickungs- und Entnahmevorrichtung können aber auch jegliche andere Einrichtungen in Form von Robotern oder Transportbändern bzw. Kombinationen davon eingesetzt werden. Alternativ besteht auch die Möglichkeit, dass für Beschickung und Entnahme des Werkstücks 20 nur eine einzelne Vorrichtung vorgesehen ist, die vor dem Ofen 10 eingesetzt wird und die das Werkstück 20 in den Ofen 10 einlegt und aus diesem auch wieder entnimmt.To feed the oven 10 with workpieces, for example, a feeder 40 is provided, which is used in front of the oven 10, while behind the oven 10, a removal device 50 is used to remove heated workpieces from the oven 10. For example, both devices have a loading or removal element in the form of a fork, with which workpieces can be received. The feeder 40 then has, for example, two forks 41 and 42, while the removal device 50 has two forks 51 and 52. Both the charging device 40 and the removal device 50 are preferably designed so that they can move horizontally, so that they can pick up a workpiece 20 on the forks and move into the opened furnace chamber 11 or pick up a workpiece 20 in the furnace 10 and exit it. In addition, the forks can also be designed to be vertically movable. As a loading and unloading device but also any other means in the form of robots or conveyor belts or combinations thereof may be used. Alternatively, there is also the possibility that for loading and unloading of the workpiece 20 only a single device is provided, which is used in front of the furnace 10 and which inserts the workpiece 20 into the furnace 10 and removes it again.

Die Ofenkammer 11 erstreckt sich vorzugsweise horizontal im Ofen 10, sodass sich die beiden Heizeinheiten 15 und 16 oberhalb und unterhalb des Werkstücks 20 befinden, wenn es in den Ofen 10 eingebracht ist. Somit weist eine erste Werkstückseite 21 nach oben und kann von der oberen Heizeinheit 15 erwärmt werden, während die gegenüber liegende Werkstückseite 22 von der unteren Heizeinheit 16 erwärmt wird.The oven chamber 11 preferably extends horizontally in the oven 10 so that the two heating units 15 and 16 are above and below the workpiece 20 when placed in the oven 10. Thus, a first workpiece side 21 faces upward and can be heated by the upper heating unit 15 while the opposite workpiece side 22 is heated by the lower heating unit 16.

Jede der Heizeinheiten 15 und 16 besteht dabei aus wenigstens zwei Druckstempeln, deren distale Endflächen beheizbar sind. Eine solche Kontaktfläche befindet sich dabei an der dem Werkstück 20 zugewandten Seite eines Druckstempels. Für die Erwärmung werden die Druckstempel beider Heizeinheiten in Kontakt mit dem Werkstück 20 gebracht, sodass das Werkstück 20 durch Kontakterwärmung erwärmt wird. Im Gegensatz zu einer Lösung mit einem einzelnen großen Druckstempel pro Heizeinheit setzt sich eine Heizeinheit erfindungsgemäß aus wenigstens zwei getrennten Druckstempeln mit jeweiligen Kontaktflächen zusammen. Diese Druckstempel und damit ihre Kontaktflächen sind jedoch so nah nebeneinander angeordnet und in die gleiche Richtung ausgerichtet, dass sich eine Heizfläche ergibt, die annähernd durchgehend ist. Ist das Werkstück 20 plattenförmig und wird horizontal in den Ofen eingebracht, verlaufen die Kontaktflächen der Druckstempel somit ebenfalls horizontal. Der Abstand zwischen den einzelnen Kontaktflächen einer Heizeinheit ist dabei gering, wobei sich Abstände von näherungsweise 0,5 mm als vorteilhaft erwiesen haben, was im Sinne dieser Erfindung als annähernd durchgehende Heizfläche angesehen werden kann. Der Durchmesser der Kontaktflächen liegt in der Größenordnung von ca. 50 bis 150 mm. Die tatsächliche Größe der Kontaktflächen kann dabei aus der Wärmeausdehnung des verwendeten Stempel materials sowie der zulässigen elastischen Verformung und der gewünschten Lebensdauer der Druckstempel errechnet werden.Each of the heating units 15 and 16 consists of at least two pressure punches, the distal end surfaces are heated. Such a contact surface is located on the workpiece 20 side facing a punch. For heating, the plunger of both heating units are brought into contact with the workpiece 20, so that the workpiece 20 is heated by contact heating. In contrast to a solution with a single large plunger per heating unit, a heating unit according to the invention consists of at least two separate plungers with respective contact surfaces. However, these plungers and thus their contact surfaces are arranged so close together and aligned in the same direction that results in a heating surface, which is approximately continuous. If the workpiece 20 is plate-shaped and is introduced horizontally into the oven, the contact surfaces of the plunger thus also extend horizontally. The distance between the individual contact surfaces of a heating unit is small, with distances of approximately 0.5 mm have proved advantageous, which can be considered in the context of this invention as approximately continuous heating surface. The diameter of the contact surfaces is in the order of about 50 to 150 mm. The actual size of the contact surfaces can be calculated from the thermal expansion of the stamp material used and the permissible elastic deformation and the desired life of the plunger.

Vorzugsweise besteht eine Heizeinheit jedoch aus mehr als zwei Druckstempeln, sodass von oben gesehen mehrere Reihen und Spalten aus Druckstempeln gebildet werden, um aus deren Kontaktflächen eine annähernd durchgehende Heizfläche zu bilden, mit der ein Werkstück kontaktiert und so erwärmt werden kann. In der Seitenansicht der Fig. 1 sind beispielsweise in der vorderen Reihe der oberen Heizeinheit 15 fünf Druckstempel vorgesehen, von denen die beiden rechten Druckstempel beispielhaft mit den Bezugsziffern 30 und 31 gekennzeichnet sind. Die vordere Reihe der unteren Heizeinheit 16 umfasst dagegen sechs Druckstempel, da diese in ihrer horizontalen Lage versetzt zu den Druckstempeln der oberen Heizeinheit 15 angeordnet sind, wobei die beiden rechten Druckstempel wiederum beispielhaft mit den Bezugsziffern 32 und 33 gekennzeichnet sind. Durch die versetzte Anordnung kann eine möglichst gleichmäßige Erwärmung des Werkstücks erreicht werden. Würden die Druckstempel nicht versetzt zueinander angeordnet, könnten sich hingegen in den Bereichen zwischen den Kontaktflächen nachteilige Temperaturgefälle ausbilden. Durch eine versetzte Anordnung wird jedoch ein Spalt zwischen den oberen Druckstempels stets durch einen unteren Druckstempel erwärmt und umgekehrt, sodass sich eine gleichmäßige Erwärmung ergibt.Preferably, however, a heating unit consists of more than two pressure punches, so that seen from above several rows and columns are formed from pressure punches to from their contact surfaces an approximately continuous heating surface form, with which a workpiece can be contacted and so heated. In the side view of Fig. 1 For example, five plungers are provided in the front row of the upper heating unit 15, of which the two right plungers are identified by the reference numerals 30 and 31 by way of example. In contrast, the front row of the lower heating unit 16 comprises six pressure punches, since these are arranged in their horizontal position offset from the pressure punches of the upper heating unit 15, wherein the two right pressure punches are again identified by the reference numerals 32 and 33. Due to the staggered arrangement as uniform as possible heating of the workpiece can be achieved. If the plungers were not arranged offset to one another, however, disadvantageous temperature gradients could form in the areas between the contact surfaces. By a staggered arrangement, however, a gap between the upper plunger is always heated by a lower plunger and vice versa, so that there is a uniform heating.

Vorzugsweise sind die Kontaktflächen der Druckstempel wabenförmig ausgebildet und in einer Heizeinheit so versetzt zueinander angeordnet, dass sie eine annährend durchgehende Heizfläche bilden. Die sechseckige Wabenform bringt den Vorteil mit sich, dass sie ähnlich einer Bienenwabe die größte Innenfläche bei geringster Außenlänge unter Vermeidung von unbeheizten Bereichen aufweist und dass damit eine Fläche lückenlos gefüllt und parkettiert werden kann. Andere Geometrien der Kontaktflächen können aber auch dargestellt werden.Preferably, the contact surfaces of the plunger are honeycomb-shaped and arranged in a heating unit offset from one another so that they form an approximately continuous heating surface. The hexagonal honeycomb shape has the advantage that, similar to a honeycomb, it has the largest inner surface with the smallest external length while avoiding unheated areas, and thus a surface can be filled and parqueted completely. Other geometries of the contact surfaces can also be displayed.

Diese wabenförmige Form ist der Aufsicht in der Fig. 2 zu entnehmen, wobei hier durch die unteren Druckstempel eine rechteckige Heizfläche gebildet wird. Die Heizfläche kann jedoch auch andere Formen annehmen und beispielsweise an die Umrisse der zu erwärmenden Werkstücke angepasst sein. Dabei ist unter einer Heizfläche im Sinne dieser Erfindung nicht nur eine Fläche zu verstehen, die durch Kontaktflächen der Druckstempel gebildet wird, die sich alle in einer Ebene befinden, sondern die Kontaktflächen können sich auch in unterschiedlichen Ebenen befinden. Die Kontaktflächen sind dann zwar alle gleich ausgerichtet - d.h. zweckmäßigerweise erstrecken sie sich alle horizontal - aber ihre vertikale Position kann verschieden sein. Dies kann eintreten, wenn Druckstempel und damit ihre Kontaktflächen unterschiedlich vertikal verfahren werden. Auf eine Ebene projiziert bilden die Kontaktflächen dann zwar eine durchgehende Heizfläche, diese Heizfläche ist aber in der Höhe versetzt. Dies kann im Sinne der Erfindung dennoch als Heizfläche bezeichnet werden, da die Kontaktflächen so beispielsweise eine unebene Oberfläche eines Werkstücks mit Erhöhungen und/oder Vertiefungen erwärmen können. Sich nicht horizontal erstreckende Oberflächenabschnitte haben dann zwar keinen Kontakt zu den Druckstempeln, aber dies kann gegebenenfalls in Kauf genommen werden bzw. kann sogar erwünscht sein.This honeycomb shape is the top view in the Fig. 2 can be seen, in which case a rectangular heating surface is formed by the lower plunger. However, the heating surface may take other forms and be adapted for example to the contours of the workpieces to be heated. Here, a heating surface in the context of this invention is to be understood not only an area formed by contact surfaces of the plunger, which are all in one plane, but the contact surfaces can also be located in different levels. Although the contact surfaces are then all the same orientation - ie, they all extend horizontally - but their vertical position may be different be. This can occur when plunger and thus their contact surfaces are moved vertically different. Projected onto one level, the contact surfaces then form a continuous heating surface, but this heating surface is offset in height. This may still be referred to as a heating surface in the context of the invention, since the contact surfaces can heat, for example, an uneven surface of a workpiece with elevations and / or depressions. Although not horizontally extending surface sections then have no contact with the plunger, but this can possibly be accepted or may even be desirable.

Wie wiederum aus der Fig. 1 ersichtlich, werden die Kontaktflächen der Druckstempel der beiden Heizeinheiten 15 und 16 in der Ofenkammer 11 mit dem Werkstück 20 in Kontakt gebracht, sodass das Werkstück 20 über beide Werkstückseiten 21 und 22 erwärmt wird. Um die Kontaktflächen der Druckstempel mit dem Werkstück 20 in Kontakt zu bringen, sind wenigstens zwei der Druckstempel vertikal verfahrbar ausgestaltet. Dabei kann es sich wenigstens um die oberen Druckstempel handeln, die vertikal verfahrbar ausgestaltet sind, während die unteren Druckstempel feststehen. So kann ein Werkstück auf den Kontaktflächen der unteren Druckstempel abgelegt werden, nachdem die oberen Druckstempel zuvor nach oben verfahren wurden. Sobald das Werkstück aufliegt, werden die oberen Druckstempel nach unten verfahren, bis sie Kontakt zum Werkstück haben. Dabei können wenigstens die oberen Druckstempel federnd ausgeführt sein, so dass sie nach Kontakt mit dem Werkstück weiter vertikal abgesenkt werden können, um einen Federdruck auf die Oberseite des Werkstücks aufbringen zu können. Welche Druckstempel verfahrbar und welche federnd ausgeführt sind, hängt dabei entsprechend von der Ausgestaltung und Ausführung des Ofens 10 ab, die wiederum beispielweise von der Ausgestaltung der Werkstücke abhängt.As again from the Fig. 1 As can be seen, the contact surfaces of the plunger of the two heating units 15 and 16 in the furnace chamber 11 are brought into contact with the workpiece 20, so that the workpiece 20 is heated over both sides of the workpiece 21 and 22. In order to bring the contact surfaces of the plunger with the workpiece 20 into contact, at least two of the plunger are designed to be vertically movable. This can be at least the upper pressure stamp, which are designed to be vertically movable, while the lower plunger fixed. Thus, a workpiece can be placed on the contact surfaces of the lower plunger after the upper plunger were previously moved upwards. As soon as the workpiece rests, the upper plungers are moved down until they come into contact with the workpiece. In this case, at least the upper plunger can be made resilient, so that they can be further lowered vertically after contact with the workpiece in order to apply a spring pressure on the top of the workpiece can. Which pressure stamp movable and which are resilient, depends in accordance with the design and execution of the furnace 10, which in turn depends for example on the design of the workpieces.

Es kann dabei vorgesehen sein, dass die einzelnen Druckstempel getrennt voneinander angesteuert werden können, sodass ein gleichmäßiger Kontakt aller Kontaktflächen zum Werkstück erreicht werden kann, auch wenn das Werkstück Erhebungen und/oder Vertiefungen aufweist. Eine selektive Ansteuerung einzelner Druckstempel ist auch dann vorteilhaft, wenn sich die Umrisse der zu erwärmenden Werkstücke ändern, sodass die Form der erforderlichen Heizfläche, d.h. die Auswahl der eingesetzten Druckstempel variiert werden soll. Hierbei kann es auch vorteilhaft sein, dass einzelne Kontaktflächen insbesondere in den Außenbereichen spezielle Formen haben, um bei einer wechselnden Auswahl von Druckstempeln möglichst alle erforderlichen Heizflächenformate erzeugen zu können.It can be provided that the individual plunger can be controlled separately, so that a uniform contact of all contact surfaces can be achieved to the workpiece, even if the workpiece has elevations and / or depressions. Selective control of individual plungers is also advantageous if the outlines of the workpieces to be heated change, so that the shape of the required heating surface, ie the selection of the applied plunger is to be varied. In this case, it may also be advantageous for individual contact surfaces to have special shapes, particularly in the outer regions, in order to be able to generate as many heating surface formats as possible with a changing selection of pressure punches.

Da sowohl die Oberflächen des Werkstücks 20 als auch die Kontaktflächen der Druckstempel jedoch fertigungstechnisch bedingte, kleinste Unebenheiten aufweisen können, bilden sich trotz des Kontaktes zwischen Werkstück 20 und Druckstempeln kleine Pressspalte zwischen den Oberflächen des Werkstücks 20 und den Kontaktflächen der Druckstempel aus, die einen vollständigen Kontaktschluss verhindern. Zur Verbesserung des Wärmeübergangs sind deshalb dünne Leitungen in die Druckstempel integriert, über die ein Wärmeleitfluid in die entstehenden Pressspalte geleitet werden kann. Als Wärmefluid verwendet werden können beispielsweise einatomige Gase wie Helium oder auch Wasserstoff. Diese Gase zeichnen sich durch eine sehr hohe thermische Leitfähigkeit aus und dienen somit als ein guter Wärmeleiter in den Pressspalten zwischen den Kontaktflächen der Druckstempel und den Oberflächen des Werkstücks 20.However, since both the surfaces of the workpiece 20 as well as the contact surfaces of the plunger production-related, may have the smallest bumps, form despite the contact between the workpiece 20 and stamping small press nips between the surfaces of the workpiece 20 and the contact surfaces of the plunger from a complete Prevent contact closure. To improve the heat transfer therefore thin lines are integrated into the plunger, via a heat conducting fluid can be passed into the resulting nip. As thermal fluid can be used, for example, monatomic gases such as helium or hydrogen. These gases are characterized by a very high thermal conductivity and thus serve as a good heat conductor in the press nips between the contact surfaces of the plunger and the surfaces of the workpiece 20th

Damit die lineare Wärmeausdehnung des Werkstücks 20 während des Erwärmens im Ofen 10 möglich wird, kann in dem Verfahren vorgesehen sein, dass die verfahrbaren Druckstempel in einer wählbaren Taktfrequenz druckentlastet und anschließend wieder belastet werden. In den Phasen der Druckentlastung kann sich das Werkstück 20 während der Erwärmung entsprechend ausdehnen, sodass eine hohe Qualität der behandelten Werkstücke erreicht werden kann.In order that the linear thermal expansion of the workpiece 20 during heating in the oven 10 is possible, it can be provided in the method that the movable plungers are relieved of pressure in a selectable clock frequency and then loaded again. In the phases of the pressure relief, the workpiece 20 can expand accordingly during the heating, so that a high quality of the treated workpieces can be achieved.

Zur Beschickung des Ofens 10 mit Werkstücken 20 können verschiedene Verfahren eingesetzt werden und der Ofen 10 ist jeweils entsprechend ausgeführt. Wie aus der Fig. 2 ersichtlich, entspricht die Breite einer durch die unteren Druckstempel (z.B. 32, 33, 34) gebildeten Heizfläche etwa der Breite des zu erwärmenden Werkstücks 20. Damit dieses Werkstück 20 von der Beschickungsvorrichtung 40 in die Ofenkammer 11 verfahren werden kann, wird es von zwei Gabelzinken 41 und 42 aufgenommen und kann dann in der Ofenkammer 11 auf den unteren Druckstempeln 32, 33 und 34 abgelegt werden. Damit dies erfolgen kann, ist es in einem Ausführungsbeispiel der Erfindung vorgesehen, dass sich diejenigen Druckstempel vertikal nach unten bewegen lassen, in deren Bereich sich die Gabelzinken 41 und 42 befinden. Dies ist schematisch in der Aufsicht der Fig. 3 dargestellt, bei der die schwarz gekennzeichneten Druckstempel 32, 33 und 34 gegenüber den verbleibenden Druckstempeln dieser unteren Heizeinheit 16 vertikal nach unten abgesenkt wurden. So besteht ausreichend Platz, um das Werkstück 20 mit den Gabelzinken 41 und 42 oberhalb der verbleibenden Druckstempel zu positionieren und auf diesen abzulegen, indem die Gabelzinken nach unten verfahren werden. Anschließend können die Gabelzinken 41 und 42 unter dem Werkstück 20 weggezogen werden, sodass es auf den Kontaktflächen der unteren Druckstempel aufliegt und Kontakt zu diesen hat. Danach können die zuvor nach oben verfahrenen oberen Druckstempel 30 und 31 herab gefahren werden, bis auch sie Kontakt zum Werkstück 20 haben, wobei es erforderlich ist, dass die Heizflächen ohne größere Lücken wieder geschlossen sind, damit die Erwärmung völlig gleichmäßig erfolgen kann. Nach der Erwärmung kann die Entnahme des Werkstücks 20 durch die Entnahmevorrichtung 50 mit den Gabelzinken 51 und 52 anlog in umgekehrter Reihenfolge der Schritte erfolgen.For feeding the furnace 10 with workpieces 20, various methods can be used and the furnace 10 is designed accordingly. Like from the Fig. 2 As can be seen, the width of a heating surface formed by the lower pressure pistons (eg, 32, 33, 34) is approximately equal to the width of the workpiece to be heated 20. Thus, this workpiece 20 is transferred from the charging device 40 into the oven chamber 11 can be moved, it is picked up by two forks 41 and 42 and can then be stored in the oven chamber 11 on the lower pressure dies 32, 33 and 34. In order for this to be possible, it is provided in one embodiment of the invention that those plungers can be moved vertically downwards, in the region of which the forks 41 and 42 are located. This is schematically in the supervision of Fig. 3 shown in which the black marked plunger 32, 33 and 34 were lowered relative to the remaining pressure punches of this lower heating unit 16 vertically downwards. Thus, there is sufficient space to position the workpiece 20 with the forks 41 and 42 above the remaining plunger and store on this by the forks are moved down. Subsequently, the forks 41 and 42 can be pulled away under the workpiece 20 so that it rests on the contact surfaces of the lower plunger and has contact with them. Thereafter, the previously moved upwards upper plunger 30 and 31 can be moved down until they also have contact with the workpiece 20, wherein it is necessary that the heating surfaces are closed again without large gaps, so that the heating can be completely uniform. After heating, the removal of the workpiece 20 by the removal device 50 with the forks 51 and 52 anlog in the reverse order of the steps take place.

Alternativ kann die Ofenkammer 11 so ausgebildet sein, dass anderweitig Raum für die Beschickungs- und Entnahmevorrichtung 40, 50 besteht, um das Werkstück 20 in eine Position zwischen den oberen und unteren Druckstempeln zu bringen. Beispielsweise kann das Werkstück 20 auch horizontal in die Ofenkammer 11 geschoben werden, bis es eine Markierung erreicht, an der das Werkstück 20 so ausgerichtet ist, dass es zwischen den Druckstempeln der beiden Heizeinheiten positioniert ist. Falls Beschickungsvorrichtungen eingesetzt werden, welche ein Werkstück 20 direkt auf den unteren Druckstempeln ablegen und von diesen aufnehmen können, sind gegebenenfalls keine weiteren Vorkehrungen im Ofen 10 zu treffen.Alternatively, the oven chamber 11 may be formed so that there is otherwise room for the loading and unloading device 40, 50 to bring the workpiece 20 into position between the upper and lower dies. For example, the workpiece 20 may also be slid horizontally into the oven chamber 11 until it reaches a mark on which the workpiece 20 is aligned to be positioned between the dies of the two heating units. If feeders are used which can place and pick up a workpiece 20 directly on the lower plungers, no further precautions in the oven 10 may be necessary.

Durch den Kontakt der beheizten Druckstempel mit dem Werkstück 20 können Wärmeübergangszahlen von >2.000W/m2/K erreicht werden, wodurch auch unterschiedliche Aufheiz- und Kühlstrategien möglich sind. Es lassen sich Taktzeiten von etwa 6 Sekunden realisieren, wobei auch zwei Öfen nebeneinander positioniert werden können.By the contact of the heated plunger with the workpiece 20 heat transfer coefficients of> 2,000W / m 2 / K can be achieved, which also different Heating and cooling strategies are possible. It can be implemented cycle times of about 6 seconds, with two ovens can be positioned side by side.

Insbesondere ist es auch möglich, unterschiedliche Bereiche eines Werkstücks auf unterschiedliche Temperaturen zu erwärmen. Dies ist beispielsweise erforderlich, wenn sich in unterschiedlichen Bereichen des Werkstücks unterschiedliche Gefüge einstellen sollen, was durch die Erwärmung auf oder unterhalb der Austenittemperatur erfolgen kann. Dies kann mit der Erfindung dadurch erreicht werden, dass wenigstens einige der Druckstempel auf unterschiedliche Temperaturen beheizbar sind oder einzelne Druckstempel sogar kühlbar sind. So kann in einem Ausführungsbeispiel der Erfindung eine partielle Erwärmung in einem definierten Bereich des Werkstückes mittels eines oder mehrerer dieser Druckstempel auf eine Temperatur unterhalb der Austenitbildung erfolgen, während andere definierte Bereiche auf oder über Austenittemperatur erwärmt werden. Um diesen Zustand zu erreichen, können bestimmte Bereiche mit voll beheizten Druckstempeln auf Austenittemperatur erwärmt werden, während andere Bereiche mit weniger beheizten Druckstempeln auf eine Temperatur unterhalb der Austenittemperatur erwärmt werden. Alternativ kann das Werkstück zuerst mit allen Druckstempeln vollständig auf oder über Austenittemperatur erwärmt werden, woraufhin bestimmte Bereiche anschließend von einzelnen Druckstempeln zurück auf eine Temperatur unterhalb der Austenittemperatur gekühlt werden. Letzte Ausführungsform kann voraussetzen, dass einzelne Druckstempel sowohl beheizbar, als auch kühlbar ausgeführt sind. In beiden Fällen sind diese ausgewählten Druckstempel so angeordnet, dass sie sich in den Bereichen befinden, in denen eine andere Temperatur eingestellt werden soll. Um bestimmte Formen dieser Bereiche zu erhalten, können die Kontaktflächen dieser Druckstempel auch entsprechende andere Umrisse haben als die übrigen Druckstempel.In particular, it is also possible to heat different areas of a workpiece to different temperatures. This is necessary, for example, if different microstructures are to be set in different areas of the workpiece, which can be done by heating at or below the austenitic temperature. This can be achieved with the invention in that at least some of the plunger can be heated to different temperatures or individual plunger are even coolable. Thus, in one embodiment of the invention, a partial heating in a defined region of the workpiece by means of one or more of these plunger to a temperature below austenite, while other defined areas are heated to or above austenite temperature. To achieve this condition, certain areas of fully heated plungers may be heated to austenitic temperature while other areas of less heated plungers are heated to a temperature below the austenitic temperature. Alternatively, the workpiece may first be fully heated to or above austenite temperature with all of the plungers, after which certain areas are then cooled by individual plungers back to a temperature below the austenitic temperature. Last embodiment may require that individual plunger are both heatable, as well as designed to cool. In both cases, these selected plungers are arranged to be in the areas where a different temperature is to be set. In order to obtain certain shapes of these areas, the contact surfaces of these plungers may also have corresponding other outlines than the other plunger.

Sowohl die Temperatursteuerung als auch die vertikale Bewegung der Druckstempel erfolgt vorzugsweise durch eine zentrale Steuerungseinheit des Ofens, die frei programmierbar ist.Both the temperature control and the vertical movement of the plunger is preferably carried out by a central control unit of the furnace, which is freely programmable.

Die Druckstempel selbst können durch Gas oder auch elektrisch beheizt werden, wobei eine elektrische Beheizung beispielsweise induktiv über einen Widerstand erfolgen kann. Fig. 4 zeigt eine mögliche Ausführungsform eines unteren Druckstempels 32 mit einer oberen Kontaktfläche 35. Der Druckstempel 32 ist zylinderförmig ausgeführt und wird durch Gasbrenner im Inneren beheizt. Diese Gasbrenner sind beispielsweise mit Wärmetauschern ausgestattet, welche die Wärme des abströmenden Verbrennungsgases zur Vorwärmung der zuströmenden Gase nutzten.The plunger itself can be heated by gas or electrically, with an electric heating, for example, can be done inductively via a resistor. Fig. 4 shows a possible embodiment of a lower plunger 32 having an upper contact surface 35. The plunger 32 is cylindrical and is heated by gas burners inside. These gas burners are equipped for example with heat exchangers, which use the heat of the outflowing combustion gas to preheat the incoming gases.

Damit eine schnelle Temperaturregelung möglich ist, sind die Brenner vorzugsweise in jedem Druckstempel mit einem Thermoelement und einer außen liegenden Regeltechnik ausgestattet, welche z.B. eine Selbstzündtemperatur von ca. 800°C sicherstellt. Zum sicheren Start der Einrichtung sind in der Ofenkammer 11 ein oder mehrere separate, eigensichere Gasbrenner vorgesehen, welche den Ofen 10 bis zur Selbstzündtemperatur der Druckstempel vorheizen. Nach diesem Zündprozess kann die Ofenkammer 11 mit konditioniertem Gas beaufschlagt werden, da der Brennraum in jedem Druckstempel gasdicht davon getrennt ist. In der Ofenkammer kann dann beispielsweise Schutzgas oder getrocknete Luft zur Vermeidung einer H2-Versprödung eingesetzt werden.In order to allow rapid temperature control, the burners are preferably equipped in each plunger with a thermocouple and an external control technology, which ensures, for example, an auto-ignition temperature of about 800 ° C. To safely start the device, one or more separate, intrinsically safe gas burners are provided in the oven chamber 11, which preheat the oven 10 to the autoignition temperature of the plunger. After this ignition process, the furnace chamber 11 can be acted upon with conditioned gas, since the combustion chamber is gas-tight in each plunger separated therefrom. In the oven chamber, for example, inert gas or dried air can be used to prevent H 2 -Versprödung.

Für die Druckstempel und insbesondere für ihre Kontaktflächen können je nach Anwendungsfall verschiedene Materialien eingesetzt werden. Geeignet sind beispielsweise Warmarbeitsstähle, die als legierte Werkzeugstähle für Verwendungszwecke eingesetzt werden können, bei denen die Oberflächentemperatur im Einsatz bis zu 400°C betragen kann. Die Legierungselemente sind dabei so aufeinander abgestimmt, dass die Warmarbeitsstähle ausreichende Härte und Festigkeit, hohe Warmfestigkeit, Warmhärte und Verschleißwiderstand auch bei erhöhter Temperatur besitzen. Sie sind also als Material für Kontaktflächen geeignet, die zum Erwärmen von Werkstücken bis zu 400°C eingesetzt werden. Dies ist beispielsweise für Leichtmetalle wie Aluminium- oder Magnesiumwerkstücke der Fall, die typischerweise auf Temperaturen im Bereich von 230°C bis 250°C erwärmt werden.Depending on the application, different materials can be used for the plungers and in particular for their contact surfaces. For example, hot working steels which can be used as alloyed tool steels for applications in which the surface temperature in use can reach up to 400.degree. C. are suitable. The alloying elements are coordinated so that the hot-work tool steels have sufficient hardness and strength, high heat resistance, hot hardness and wear resistance even at elevated temperatures. So they are suitable as a material for contact surfaces, which are used for heating workpieces up to 400 ° C. This is the case, for example, for light metals, such as aluminum or magnesium workpieces, which are typically heated to temperatures in the range of 230 ° C to 250 ° C.

Für die Erwärmung von Werkstücken auf höhere Temperaturen im Bereich von 900°C, wie es beispielsweise für Borstähle der Fall ist, sind Warmarbeitsstähle für die Druckstempel und ihre Kontaktflächen nicht mehr geeignet, sodass für diesen Anwendungsbereich beispielsweise Keramiken eingesetzt werden können. Vorteilhaft hat sich hierfür insbesondere der Werkstoff Siliziumcarbid (SiC) erwiesen. Wird der Werkstoff SiC mit dem typischerweise sehr hohen Wärmeleitwert gewählt, hat dies den Vorteil, dass die im Inneren des Druckstempels bereitgestellte Wärmeenergie ausreichend schnell durch die Stempelwand/Kontaktfläche fließt und an das Werkstück übertragen werden kann.For the heating of workpieces to higher temperatures in the range of 900 ° C, as is the case for boron steels, hot working steels are no longer suitable for the pressure punches and their contact surfaces, so that, for example, ceramics can be used for this application. The material silicon carbide (SiC) has proven to be advantageous in particular for this purpose. If the material SiC is selected with the typically very high thermal conductivity, this has the advantage that the heat energy provided in the interior of the pressure stamp flows through the stamp wall / contact surface sufficiently quickly and can be transmitted to the workpiece.

Bezugszeichenliste:LIST OF REFERENCE NUMBERS

1010
Ofenoven
1111
Ofenkammerfurnace chamber
1212
Beschickungsöffnungloading port
1313
Entnahmeöffnungremoval opening
1414
Ofenkörperfurnace body
15,1615.16
Heizeinheitheating unit
2020
Werkstückworkpiece
2121
Erste Werkstückseite, OberseiteFirst workpiece side, top side
2222
Zweite Werkstückseite, UnterseiteSecond side of the workpiece, underside
30,3130.31
Oberer DruckstempelUpper plunger
32,33,3432,33,34
Unterer DruckstempelLower pressure stamp
3535
Kontaktflächecontact area
4040
Beschickungsvorrichtungloader
41,4241.42
Beschickungselement, GabelzinkenLoading element, forks
5050
Entnahmevorrichtungremoval device
51,5251.52
Entnahmeelement, GabelzinkenRemoval element, forks

Claims (13)

  1. A method for the treatment of at least one workpiece (20) in a furnace (10), in which method the workpiece (20) is heated up in a chamber (11) of the furnace (10) by at least two heating units (15; 16), said workpiece having a first side (21) and a second side (22), and whereby a first heating unit (15) heats up the first side (21) of the workpiece (20) and a second heating unit (16) heats up the second side (22) of the workpiece (20), whereby each heating unit (15; 16) comprises at least two pressure pistons (30; 31; 32; 33; 34) and, when the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) of a heating unit make contact with the workpiece (20), these contact surfaces are each arranged in different planes,
    characterized in that
    the heating units (15; 16) are each associated with a workpiece (20), and the at least two pressure pistons (30; 31; 32; 33; 34) of each heating unit (15; 16) have heated contact surfaces that are arranged next to each other and with the same orientation, and in that the workpiece (20) is heated up in that contact is made between the first side (21) of the workpiece (20) and the contact surfaces of the at least two pressure pistons (30; 31) of the first heating unit (15), and in that contact is likewise made between the second side (22) of the workpiece (20) and the contact surfaces of the at least two pressure pistons (32; 33; 34) of the second heating unit (16), whereby the contact surfaces of the pressure pistons (30; 31) of the first heating unit (15) are arranged offset with respect to the contact surfaces of the pressure pistons (32; 33; 34) of the second heating unit (16).
  2. The method according to claim 1,
    characterized in that,
    before the workpiece (20) is heated up, at least two of the pressure pistons (30; 31; 32; 33; 34) are moved vertically, whereby they are moved out of a position without contact between their contact surfaces and the sides (21; 22) of the workpiece (20) into a position with contact between their contact surfaces and the sides (21; 22) of the workpiece (20).
  3. The method according to claim 2,
    characterized in that
    the workpiece (20) is placed horizontally into the furnace chamber (11) and the bottom (22) of the workpiece is laid onto the contact surfaces of the pressure pistons (32; 33; 34) of the lower heating unit (16), and in that the pressure pistons (30; 31) of the upper heating unit (15) are then moved vertically downward, until contact is made between the contact surfaces of the pressure pistons (30; 31) of the upper heating unit (15) and the top (21) of the workpiece, while the position of the pressure pistons (32; 33; 34) of the lower heating unit (16) is not changed.
  4. The method according to claim 3,
    characterized in that
    the workpiece (20) is placed into the furnace chamber (11) by means of a charging device (40), whereby the charging device (40) has at least one charging element (41; 42) on which the bottom (22) of the workpiece (20) rests, and in that the pressure pistons (32; 33; 34) of the lower heating unit (16) that are located in the area of the charging element (41; 42) are moved vertically downward, and in that the bottom (22) of the workpiece (20) is subsequently placed onto the contact surfaces of the other pressure pistons of the lower heating unit (16), and in that the pressure pistons (32; 33; 34) that had previously been moved vertically downward are then moved vertically upward until their contact surfaces make contact with the bottom (22) of the workpiece (20), and in that the pressure pistons (30; 31) of the upper heating unit (15) are moved vertically downward until their contact surfaces make contact with the top (21) of the workpiece.
  5. The method according to one or more of claims 1 to 4,
    characterized in that
    a thermal fluid is fed into a pressure gap between the sides (21; 22) of the workpiece (20) and the contact surfaces of the pressure pistons (30; 31; 32; 33; 34), whereby the thermal fluid is fed into the pressure gap by means of mechanisms that are integrated into the pressure pistons (30; 31; 32; 33; 34).
  6. The method according to one or more of claims 1 to 5,
    characterized in that
    the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) are heated up to different temperatures, and in that the contact surface of at least one pressure piston (30; 31; 32; 33; 34) is cooled.
  7. A furnace for the treatment of at least one workpiece (20), comprising at least one furnace chamber and at least two heating units (15; 16) for heating up the workpiece (20) in the furnace chamber (11), said workpiece having a first side (21) and a second side (22), and the at least two heating units (15; 16) are arranged in such a way that a first side (21) of the workpiece (20) is heated up by the first heating unit (15), and the second side (22) of the workpiece (20) can be heated up by the second heating unit (16), whereby each heating unit (15; 16) comprises at least two pressure pistons (30; 31; 32; 33; 34) and, when the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) of a heating unit make contact with the workpiece (20), these contact surfaces are each arranged in different planes,
    characterized in that
    the at least two heating units (15; 16) are each associated with a workpiece (20), and each heating unit (15; 16) comprises at least two pressure pistons (30; 31; 32; 33; 34) with heatable contact surfaces that are arranged next to each other and with the same orientation, and in that the workpiece (20) can be heated up in the furnace chamber (11) in that contact is made between the first side (21) of the workpiece (20) and the contact surfaces of the at least two pressure pistons (30; 31) of the first heating unit (15), and in that contact is likewise made between the second side (22) of the workpiece (20) and the contact surfaces of the at least two pressure pistons (32; 33) of the second heating unit (16), whereby the contact surfaces of the pressure pistons (30; 31) of the first heating unit (15) are arranged offset with respect to the contact surfaces of the pressure pistons (32; 33; 34) of the second heating unit (16).
  8. The furnace according to claim 7,
    characterized in that
    at least two of the pressure pistons (30; 31; 32; 33; 34) can be moved vertically, whereby means are provided to move these pressure pistons (30; 31; 32; 33; 34) out of a position without contact between their contact surfaces and the sides (21; 22) of the workpiece (20), into a position with contact between their contact surfaces and the sides (21; 22) of the workpiece (20).
  9. The furnace according to one of claims 7 and 8,
    characterized in that
    the contact surfaces of several pressure pistons (30; 31; 32; 33; 34) of a heating unit (15; 16) arranged in rows and columns each form a heating surface whose dimensions correspond to at least the contours of the workpiece (20), whereby, when the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) of a heating unit (15; 16) make contact with the workpiece (20), these contact surfaces can each be arranged in one plane or in different planes.
  10. The furnace according to one of claims 7 to 9,
    characterized in that
    the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) have a honeycomb configuration.
  11. The furnace according to one or more of claims 7 to 10,
    characterized in that
    the contact surfaces of the pressure pistons (30; 31; 32; 33; 34) can be heated up to different temperatures.
  12. The furnace according to one or more of claims 7 to 11,
    characterized in that
    the contact surface of at least one pressure piston (30; 31; 32; 33; 34) can be heated or cooled selectively.
  13. The furnace according to one or more of claims 8 to 12,
    characterized in that
    at least two of the pressure pistons (30; 31; 32; 33; 34) of a heating unit (15; 16) can be moved vertically selectively.
EP10186516.0A 2010-10-05 2010-10-05 Method and furnace for treating workpieces Active EP2439289B1 (en)

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EP10186516.0A EP2439289B1 (en) 2010-10-05 2010-10-05 Method and furnace for treating workpieces
PL10186516T PL2439289T3 (en) 2010-10-05 2010-10-05 Method and furnace for treating workpieces
ES10186516.0T ES2609328T3 (en) 2010-10-05 2010-10-05 Procedure and oven to treat work pieces
PCT/EP2011/066959 WO2012045647A1 (en) 2010-10-05 2011-09-29 Process and furnace for treating workpieces
KR1020137011576A KR101869576B1 (en) 2010-10-05 2011-09-29 Process and furnace for treating workpieces
BR112013008194A BR112013008194A2 (en) 2010-10-05 2011-09-29 process and oven for treating at least one piece in an oven
JP2013532132A JP6158086B2 (en) 2010-10-05 2011-09-29 Work processing method and furnace
US13/877,807 US9840748B2 (en) 2010-10-05 2011-09-29 Process and furnace for treating workpieces
MX2013003767A MX356552B (en) 2010-10-05 2011-09-29 Process and furnace for treating workpieces.
CN201180048353.3A CN103270178B (en) 2010-10-05 2011-09-29 Process and furnace for treating workpieces

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DE102022130365A1 (en) * 2022-11-16 2024-05-16 Sms Group Gmbh Heat treatment equipment, process and use

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US20130196275A1 (en) 2013-08-01
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MX356552B (en) 2018-06-04
WO2012045647A1 (en) 2012-04-12
ES2609328T3 (en) 2017-04-19
CN103270178A (en) 2013-08-28
JP2013542324A (en) 2013-11-21
CN103270178B (en) 2015-01-07
BR112013008194A2 (en) 2016-06-21
EP2439289A1 (en) 2012-04-11
PL2439289T3 (en) 2017-06-30
US9840748B2 (en) 2017-12-12
MX2013003767A (en) 2013-12-16

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