EP0163906B1 - Method and vacuum furnace for heat treatment a charge - Google Patents

Method and vacuum furnace for heat treatment a charge Download PDF

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Publication number
EP0163906B1
EP0163906B1 EP85104965A EP85104965A EP0163906B1 EP 0163906 B1 EP0163906 B1 EP 0163906B1 EP 85104965 A EP85104965 A EP 85104965A EP 85104965 A EP85104965 A EP 85104965A EP 0163906 B1 EP0163906 B1 EP 0163906B1
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EP
European Patent Office
Prior art keywords
heating chamber
gas
heating
load
charge
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Expired
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EP85104965A
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German (de)
French (fr)
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EP0163906A2 (en
EP0163906A3 (en
Inventor
Peter Schmetz
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Schmetz GmbH and Co KG
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Schmetz GmbH and Co KG
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Priority to AT85104965T priority Critical patent/ATE37201T1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
    • 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
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B2005/062—Cooling elements
    • F27B2005/064—Cooling elements disposed in the furnace, around the chamber, e.g. coils
    • 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
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/14—Arrangements of heating devices
    • F27B2005/143—Heating rods disposed in the chamber
    • 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
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • F27B2005/161—Gas inflow or outflow
    • F27B2005/162—Gas inflow or outflow through closable or non-closable openings of the chamber walls
    • 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
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • F27B2005/166—Means to circulate the atmosphere
    • F27B2005/167—Means to circulate the atmosphere the atmosphere being recirculated through the treatment chamber by a turbine

Definitions

  • the invention relates to a method for the heat treatment of a batch of metallic workpieces or a single workpiece in a vacuum oven to temperatures above approximately 750 ° C. with a closable and evacuable container and a heating chamber for receiving the batch.
  • the invention further relates to a vacuum furnace for carrying out the method.
  • the heat treatment of a batch takes place, e.g. the bright annealing of metallic workpieces in a lockable glow pot under protective gas in two stages.
  • a first stage - below the radiation temperature of about 500 ° C - the batch is heated by inert gas circulation and in a subsequent second stage the heat transfer to the batch is essentially only effected by radiation (with the circulation device switched off).
  • the furnace used here is a so-called hot-wall furnace, in which the glow pot (recipient) that receives the material to be treated is exposed to the full process temperature.
  • protective gas is accordingly also used in the second treatment stage, in which the material to be treated is heated by radiation.
  • the object of the invention is to improve and further develop a process for the heat treatment of a batch in a vacuum furnace to temperatures above approximately 750 ° C. in such a way that not only faster heating with a view to increasing the economy, but also at the same time a more uniform heating of the batch can be achieved.
  • this object is achieved in that the container is evacuated after the batch has been inserted and flooded with protective gas, and the batch is heated and the gas is circulated within the heating chamber up to the maximum permissible working temperature of the circulating device of approx 750 ° C. is heated and that the container is then evacuated and the batch is heated under vacuum, essentially by radiant heat, to a desired final temperature for the heat treatment.
  • the batch is heated in a first stage by hot gas circulation, i.e. essentially by convection heat up to a working temperature permissible for the circulation device, and in an immediately subsequent second stage under vacuum essentially by radiation to the desired final temperature.
  • hot gas circulation i.e. essentially by convection heat up to a working temperature permissible for the circulation device
  • second stage under vacuum essentially by radiation to the desired final temperature.
  • the circulating device is suitably protected against the effects of the higher temperatures.
  • the object of the invention is also to provide a vacuum furnace suitable for carrying out this method.
  • the invention is based on a known vacuum furnace with a lockable steel container and an internal heating chamber for receiving the batch, with a radiation heating device located within the heating chamber and with a gas blower and a gas guide device for generating a circulating flow through the heating chamber, in the wall of which a opening which can be closed by a slide with a thermal insulation layer is contained.
  • Such a vacuum furnace is known for example from DE-B 1 259919.
  • a fixed fan is arranged outside the heating chamber, which faces a closable opening in the heating chamber wall.
  • the material to be treated is only heated by radiation when the opening is closed.
  • the blower is only used to cool or quench the material to be treated after it has warmed up.
  • a vacuum oven which is suitable for carrying out the method according to the invention contains a gas blower which, according to the invention, is mounted so that it can be moved back and forth between a working and a rest position in such a way that its fan in the working position with the slide open through the opening into the interior of the heating chamber protrudes, on the other hand lies in the rest position outside the heating chamber.
  • the vacuum furnace When carrying out a heat treatment, the vacuum furnace is flooded with protective gas in the first treatment stage. This is circulated with the help of the fan of the gas blower protruding into the heating chamber and the gas guiding device in the heating chamber in such a way that the thermal energy given off by the heating elements is also transferred convectively to the batch to be heated in addition to radiation. After the maximum permissible working temperature of the fan has been reached, it is moved out of the heating chamber and the opening is closed by a slide. Thereafter, in the second treatment stage, the batch can be emitted under radiation by radiation desired final temperature can be further heated.
  • a vacuum shaft furnace with vertical loading was chosen for the description of an exemplary embodiment.
  • This furnace consists of a cylindrical lower part 1, which stands on the floor with a support structure 2, and an upper part 3, which is detachably connected to the lower part 1 in the parting plane 4.
  • a hood 5 is attached to the upper part 3 on the upper side by means of a flange connection.
  • a lifting and swiveling device 6 is provided which rests on the floor with one foot and is connected to the lower part 1 on its side wall.
  • Lower part 1 and upper part 3 consist of sheet steel and form a vacuum-tight container in the operating position.
  • a likewise cylindrical heating chamber 7 is arranged in the interior of this container, the walls of which are equipped with a thermal insulation layer 8.
  • the bottom 9 of the heating chamber 7 can be lowered. It rests on the ends of piston rods of lifting cylinders 10 which are fastened in the bottom of the lower furnace part 1. With the aid of the lifting cylinders, the base 9 can be moved from the closed position into an open position and vice versa, as is shown in the two half-cuts in FIG. 1.
  • a support grate 12 is provided in the interior of the heating chamber 7, which is supported on the bottom of the lower part 1 by means of a support structure 13 consisting essentially of vertical supports.
  • a support structure 13 consisting essentially of vertical supports.
  • openings are contained in which the vertical supports of the support structure 13 are slidably guided.
  • cooling tubes 14 are arranged, for example in the form of a spiral made of finned tubes.
  • heating elements 15 e.g. electric resistance heating elements.
  • a gas guiding device 16 is provided in the interior of the heating chamber 7 and is located in the space between the heating elements 15 and the charge 11. This gas guiding device is guided upwards like a hood to the center, a central opening 17 being left free.
  • a fan motor 18 which carries an impeller 19 at the end of the motor shaft projecting downwards.
  • the fan motor 18 is attached to the free end of a piston rod of a lifting cylinder 20 and can be lowered with the aid of this lifting cylinder from an upper rest position into a lower operating position and vice versa.
  • an opening 21 of approximately the same size is contained in the upper ceiling of the heating chamber, through which the impeller 19 can penetrate into the interior of the heating chamber 7.
  • a circular plug 23 with a corresponding thermal barrier coating is fastened to the piston rod of the lifting cylinder 20 via a linkage 22 and closes the opening 21 of the heating chamber 7 in the operating position of the fan motor 18.
  • a cooling disk 24 is provided for the shaft of the fan motor 18 on the back of the plug 23, which is also attached to the linkage 22.
  • a slide 25 is provided which, like the wall of the heating chamber 7, is equipped with a thermal barrier coating. This slide 25 can be moved back and forth from the operating position shown in FIG. 2 into a lateral rest position. For this purpose, a laterally projecting nozzle 26 is formed on the upper part 3.
  • the described vacuum shaft furnace is used for the heat treatment of a batch as follows:
  • the left half section in Fig. Shows the operating state for heating with gas circulation up to a temperature of about 750 ° C.
  • the fan motor 18 assumes the lower operating position, in which the fan 19 is located at the opening 17 of the gas guiding device 16.
  • the protective gas inside the heating chamber is placed in a circulating flow from the interior of the gas guiding device 16 upwards into the space between the gas guiding device 16 and the wall of the heating chamber 7, the gas flow being heated at the heating elements 15 and again at the lower end of the space Inside the gas guide device 16 occurs.
  • the fan motor 18 is moved back into the rest position shown in FIG.
  • the opening 21 of the heating chamber 7 is closed with the slide 25.
  • the batch 11 is quenched with inert gas or under vacuum essentially by radiant heat to the desired final temperature, e.g. 1,150 ° C, heated.
  • the subsequent cooling takes place again with gas circulation.
  • the slide 25 is opened and the fan motor 18 is lowered into the intermediate position shown in the right half section of FIG. 1.
  • the bottom 9 of the heating chamber 7 is dealt down lowers, as is also shown in the right half section of FIG. 1.
  • the gas is now again ventilated with the help of the fan 19 into a circulation flow upwards out of the heating chamber 7 into the space between the heating chamber 7 and the lower part 1 past the cooling tubes 14 and here into the interior of the heating chamber 7 set back.

Abstract

A method and vacuum furnace for heat-treating a charge. Pursuant to the method, after the charge is placed in the receiving vessel, the latter is evacuated and flooded with inert gas. Subsequently, the charge is heated to the maximum permissible operating temperature of the circulation device by heating and gas circulation. Thereafter, the charge is heated to the desired end temperature by static inert gas or under vacuum, and essentially by radiation heat. The vacuum furnace may include a steel vessel which can be closed off, and which contains an inner heating chamber for receiving the charge. A heating device is provided within the heating chamber, and a fan and a gas guiding arrangement are provided for producing a gas circulation through the heating chamber. In the second phase, in which the heating is effected by radiant heat, the heating chamber can be closed off, accompanied by disconnection of the fan. For this purpose, an opening is provided in the wall of the heating chamber. This opening can be closed off by a sliding plug.

Description

Die Erfindung betrifft ein Verfahren zur Wärmebehandlung einer Charge aus metallischen Werkstücken oder einem einzigen Werkstück in einem Vakuumofen auf Temperaturen oberhalb von ca. 750°C mit einem verschliessbaren und evakuierbaren Behälter und einer Heizkammer zur Aufnahme der Charge. Weiter betrifft die Erfindung einen Vakuumofen zur Durchführung des Verfahrens.The invention relates to a method for the heat treatment of a batch of metallic workpieces or a single workpiece in a vacuum oven to temperatures above approximately 750 ° C. with a closable and evacuable container and a heating chamber for receiving the batch. The invention further relates to a vacuum furnace for carrying out the method.

Beim Erwärmen einer Charge im Vakuum erfolgt die Wärmeübertragung vom Beginn der Behandlung bis zum Erreichen der gewünschten Endtemperatur fast ausschliesslich durch Strahlung. Die übertragbare Energie ist dabei abhängig von der Höhe der Temperatur. In der Praxis bedeutet dies, dass die Erwärmung bis etwa 750°C sehr langsam abläuft. Ausserdem treten Schatteneffekte auf, die eine angestrebte gleichmässige Erwärmung der Charge erschweren.When a batch is heated in a vacuum, the heat transfer from the start of the treatment until the desired final temperature is reached is almost exclusively by radiation. The transferable energy depends on the temperature. In practice, this means that the heating takes place very slowly up to about 750 ° C. In addition, there are shadow effects that make it difficult to heat the batch uniformly.

Nach einem in der DE-C 877 153 beschriebenen Verfahren erfolgt die Wärmebehandlung einer Charge, z.B. das Blankglühen von metallischen Werkstücken, in einem verschliessbaren Glühtopf unter Schutzgas in zwei Stufen. Dabei wird in einer ersten Stufe - unterhalb der Strahlungstemperatur von etwa 500°C - die Charge durch Schutzgasumwälzung aufgeheizt und in einer anschliessenden zweiten Stufe die Wärmeübertragung auf die Charge im wesentlichen nur noch durch Strahlung (bei abgeschalteter Umwälzeinrichtung) bewirkt. Der hierbei benutzte Ofen ist ein sogenannter Heisswandofen, bei dem der Glühtopf (Rezipient), der das Behandlungsgut aufnimmt, der vollen Prozesstemperatur ausgesetzt ist. Bei dem beschriebenen Verfahren zum Betrieb von Glühöfen wird dementsprechend auch in der zweiten Behandlungsstufe, in der das Behandlungsgut durch Strahlung erwärmt wird, mit Schutzgas gearbeitet.According to a process described in DE-C 877 153, the heat treatment of a batch takes place, e.g. the bright annealing of metallic workpieces in a lockable glow pot under protective gas in two stages. In a first stage - below the radiation temperature of about 500 ° C - the batch is heated by inert gas circulation and in a subsequent second stage the heat transfer to the batch is essentially only effected by radiation (with the circulation device switched off). The furnace used here is a so-called hot-wall furnace, in which the glow pot (recipient) that receives the material to be treated is exposed to the full process temperature. In the described method for operating annealing furnaces, protective gas is accordingly also used in the second treatment stage, in which the material to be treated is heated by radiation.

Die Aufgabe der Erfindung besteht darin, ein Verfahren zur Wärmebehandlung einer Charge in einem Vakuumofen auf Temperaturen oberhalb von ca. 750°C dahingehend zu verbessern und weiter zu entwickeln, dass nicht nur eine schnellere Erwärmung im Hinblick auf eine Steigerung der Wirtschaftlichkeit, sondern zugleich auch eine gleichmässigere Erwärmung der Charge erzielbar ist.The object of the invention is to improve and further develop a process for the heat treatment of a batch in a vacuum furnace to temperatures above approximately 750 ° C. in such a way that not only faster heating with a view to increasing the economy, but also at the same time a more uniform heating of the batch can be achieved.

Diese Aufgabe wird ausgehend von einem Verfahren der eingangs beschriebenen Art erfindungsgemäss dadurch gelöst, dass der Behälter nach dem Einsetzen der Charge evakuiert und mit Schutzgas geflutet wird, dass die Charge durch Heizen und Gasumwälzung innerhalb der Heizkammer bis auf die maximal zulässige Arbeitstemperatur der Umwälzeinrichtung von ca. 750°C erwärmt wird und dass anschliessend der Behälter evakuiert und die Charge unter Vakuum im wesentlichen durch Strahlungswärme auf eine gewünschte Endtemperatur der Wärmebehandlung erwärmt wird.Based on a method of the type described in the introduction, this object is achieved in that the container is evacuated after the batch has been inserted and flooded with protective gas, and the batch is heated and the gas is circulated within the heating chamber up to the maximum permissible working temperature of the circulating device of approx 750 ° C. is heated and that the container is then evacuated and the batch is heated under vacuum, essentially by radiant heat, to a desired final temperature for the heat treatment.

Nach diesem Verfahren erfolgt das Erwärmen der Charge in einer ersten Stufe durch Heissgasumwälzen, also im wesentlichen durch Konvektionswärme bis zu einer für die Umwälzeinrichtung zulässigen Arbeitstemperatur und in einer unmittelbar anschliessenden zweiten Stufe unter Vakuum im wesentlichen durch Strahlung bis zur gewünschten Endtemperatur. Vor Beginn der zweiten Stufe wird die Umwälzeinrichtung auf geeignete Art gegen die Einwirkung der höheren Temperaturen geschützt. Ein solches Verfahren ermöglicht eine insgesamt schnellere und gleichmässigere Erwärmung einer Charge als nach den herkömmlichen Verfahren.According to this method, the batch is heated in a first stage by hot gas circulation, i.e. essentially by convection heat up to a working temperature permissible for the circulation device, and in an immediately subsequent second stage under vacuum essentially by radiation to the desired final temperature. Before the second stage begins, the circulating device is suitably protected against the effects of the higher temperatures. Such a method enables a batch to be heated more quickly and more uniformly than in the conventional method.

Aufgabe der Erfindung ist es auch, einen für die Durchführung dieses Verfahrens geeigneten Vakuumofen bereitzustellen. Die Erfindung geht dabei aus von einem bekannten Vakuumofen mit einem verschliessbaren Stahlbehälter und einer inneren Heizkammer zur Aufnahme der Charge, mit einer innerhalb der Heizkammer befindlichen Strahlungs-Heizeinrichtung und mit einem Gasgebläse sowie einer Gasleiteinrichtung zur Erzeugung einer Umwälzströmung durch die Heizkammer, in deren Wandung eine durch einen Schieber mit Wärmedämmschicht verschliessbare Öffnung enthalten ist.The object of the invention is also to provide a vacuum furnace suitable for carrying out this method. The invention is based on a known vacuum furnace with a lockable steel container and an internal heating chamber for receiving the batch, with a radiation heating device located within the heating chamber and with a gas blower and a gas guide device for generating a circulating flow through the heating chamber, in the wall of which a opening which can be closed by a slide with a thermal insulation layer is contained.

Ein solcher Vakuumofen ist beispielsweise aus der DE-B 1 259919 bekannt. Bei diesem Vakuumofen ist ausserhalb der Heizkammer ein feststehendes Gebläse angeordnet, welches einer verschliessbaren Öffnung in der Heizkammerwand gegenübersteht. Das Erwärmen des Behandlungsgutes erfolgt bei geschlossener Öffnung ausschliesslich durch Strahlung. Das Gebläse wird hierbei erst nach abgeschlossener Erwärmung zum Kühlen bzw. Abschrecken des Behandlungsgutes eingesetzt.Such a vacuum furnace is known for example from DE-B 1 259919. In this vacuum oven, a fixed fan is arranged outside the heating chamber, which faces a closable opening in the heating chamber wall. The material to be treated is only heated by radiation when the opening is closed. The blower is only used to cool or quench the material to be treated after it has warmed up.

Ein Vakuumofen, der zur Durchführung des erfindungsgemässen Verfahrens geeignet ist, enthält ein Gasgebläse, welches erfindungsgemäss zwischen einer Arbeits- und einer Ruhestellung derart hin- und herbewegbar gelagert ist, dass sein Ventilator in der Arbeitsstellung bei geöffnetem Schieber durch die Öffnung in das Innere der Heizkammer hineinragt, dagegen in der Ruhestellung ausserhalb der Heizkammer liegt.A vacuum oven which is suitable for carrying out the method according to the invention contains a gas blower which, according to the invention, is mounted so that it can be moved back and forth between a working and a rest position in such a way that its fan in the working position with the slide open through the opening into the interior of the heating chamber protrudes, on the other hand lies in the rest position outside the heating chamber.

Eine vorteilhafte Weiterbildung dieses Vakuumofens besteht darin, dass auf der motorseitigen Rückseite des Ventilators ein zum Verschliessen der Öffnung dienender Stopfen mit integrierter Wärmedämmschicht angebracht ist.An advantageous further development of this vacuum furnace consists in that a plug with an integrated thermal insulation layer serving to close the opening is attached to the motor-side rear side of the fan.

Bei der Ausführung einer Wärmebehandlung ist der Vakuumofen in der ersten Behandlungsstufe mit Schutzgas geflutet. Dieses wird mit Hilfe des in die Heizkammer hineinragenden Ventilators des Gasgebläses und der Gasleiteinrichtung in der Heizkammer derart umgewälzt, dass die von den Heizelementen abgegebene Wärmeenergie ausser durch Strahlung auch konvektiv auf die zu erwärmende Charge übertragen wird. Nach Erreichen der maximal zulässigen Arbeitstemperatur des Ventilators wird dieser aus der Heizkammer herausgefahren und die Öffnung durch einen Schieber verschlossen. Danach kann in der zweiten Behandlungsstufe die Charge unter Vakuum durch Strahlung auf die gewünschte Endtemperatur weiter erwärmt werden.When carrying out a heat treatment, the vacuum furnace is flooded with protective gas in the first treatment stage. This is circulated with the help of the fan of the gas blower protruding into the heating chamber and the gas guiding device in the heating chamber in such a way that the thermal energy given off by the heating elements is also transferred convectively to the batch to be heated in addition to radiation. After the maximum permissible working temperature of the fan has been reached, it is moved out of the heating chamber and the opening is closed by a slide. Thereafter, in the second treatment stage, the batch can be emitted under radiation by radiation desired final temperature can be further heated.

Die Erfindung wird nachstehend an einem in der Zeichnung schematisch dargestellten Vakuumschachtofen näher erläutert.The invention is explained in more detail below on a vacuum shaft furnace shown schematically in the drawing.

Es zeigen:

  • Fig. 1 einen senkrechten Schnitt des Vakuumschachtofens, bei dem im linken Halbschnitt die Betriebsstellung «Heizen mit Gasumwälzung» und im rechten Halbschnitt die Betriebsstellung «Kühlen mit Gasumwälzung» dargestellt ist, und
  • Fig. einen senkrechten Schnitt des Vakuumschachtofens entsprechend der Betriebsstellung «Heizen unter Ausschluss des Gasgebläses».
Show it:
  • Fig. 1 is a vertical section of the vacuum shaft furnace, in which the operating position «heating with gas circulation» and the operating position «cooling with gas circulation» is shown in the left half section, and
  • Fig. A vertical section of the vacuum shaft furnace according to the operating position "heating with the gas blower excluded".

Für die Beschreibung eines Ausführungsbeispieles wurde ein Vakuumschachtofen mit vertikaler Beschickung gewählt. Dieser Ofen besteht aus einem zylindrischen Unterteil 1, der mit einer Trägerkonstruktion 2 auf dem Boden steht, und einem Oberteil 3, der in der Trennebene 4 mit dem Unterteil 1 lösbar verbunden ist. Am Oberteil 3 ist auf der Oberseite eine Haube 5 mittels einer Flanschverbindung befestigt. Für das Abheben des Oberteils 3 vom Unterteil 1 und das seitliche Ausschwenken ist eine Heb- und Schwenkeinrichtung 6 vorgesehen, die mit einem Fuss auf dem Boden ruht und mit dem Unterteil 1 an dessen Seitenwand verbunden ist.A vacuum shaft furnace with vertical loading was chosen for the description of an exemplary embodiment. This furnace consists of a cylindrical lower part 1, which stands on the floor with a support structure 2, and an upper part 3, which is detachably connected to the lower part 1 in the parting plane 4. A hood 5 is attached to the upper part 3 on the upper side by means of a flange connection. For the lifting of the upper part 3 from the lower part 1 and the lateral pivoting out, a lifting and swiveling device 6 is provided which rests on the floor with one foot and is connected to the lower part 1 on its side wall.

Unterteil 1 und Oberteil 3 bestehen aus Stahlblech und bilden in der Betriebsstellung einen vakuumdicht abgeschlossenen Behälter. Im Innern dieses Behälters ist eine ebenfalls zylindrische Heizkammer 7 angeordnet, deren Wandungen mit einer Wärmedämmschicht 8 ausgestattet sind. Der Boden 9 der Heizkammer 7 ist absenkbar. Er ruht auf den Enden von Kolbenstangen von Hubzylindern 10, die im Boden des Ofenunterteils 1 befestigt sind. Mit Hilfe der Hubzylinder kann der Boden 9 aus der Schliessstellung in eine Offenstellung und umgekehrt bewegt werden, wie es in den beiden Halbschnitten in Fig. 1 dargestellt ist.Lower part 1 and upper part 3 consist of sheet steel and form a vacuum-tight container in the operating position. A likewise cylindrical heating chamber 7 is arranged in the interior of this container, the walls of which are equipped with a thermal insulation layer 8. The bottom 9 of the heating chamber 7 can be lowered. It rests on the ends of piston rods of lifting cylinders 10 which are fastened in the bottom of the lower furnace part 1. With the aid of the lifting cylinders, the base 9 can be moved from the closed position into an open position and vice versa, as is shown in the two half-cuts in FIG. 1.

Für das Auflegen der Charge 11, die in der Zeichnung durch ein Rechteck angedeutet ist, ist im Innern der Heizkammer 7 ein Auflagerost 12 vorgesehen, der mit Hilfe einer im wesentlichen aus senkrechten Stützen bestehenden Tragkonstruktion 13 am Boden des Unterteils 1 abgestützt ist. In dem heb- und senkbaren Boden 9 der Heizkammer 7 sind Öffnungen enthalten, in denen die senkrechten Stützen der Tragkonstruktion 13 gleitend geführt sind.For placing the batch 11, which is indicated in the drawing by a rectangle, a support grate 12 is provided in the interior of the heating chamber 7, which is supported on the bottom of the lower part 1 by means of a support structure 13 consisting essentially of vertical supports. In the lifting and lowering bottom 9 of the heating chamber 7 openings are contained in which the vertical supports of the support structure 13 are slidably guided.

In dem Zwischenraum zwischen dem Unterteil 1 und der Heizkammer 7 sind Kühlrohre 14, beispielsweise in Form einer Wendel aus Rippenrohren angeordnet. Im Innern der Heizkammer 7 befinden sich nahe der inneren Mantelfläche Heizelemente 15, z.B. elektrische Widerstandsheizelemente. Weiter ist im Innern der Heizkammer 7 eine Gasleiteinrichtung 16 vorgesehen, die sich im Zwischenraum zwischen den Heizelementen 15 und der Charge 11 befindet. Diese Gasleiteinrichtung ist nach oben haubenartig zur Mitte geführt, wobei eine zentrale Öffnung 17 freigelassen ist.In the space between the lower part 1 and the heating chamber 7, cooling tubes 14 are arranged, for example in the form of a spiral made of finned tubes. Inside the heating chamber 7 there are heating elements 15, e.g. electric resistance heating elements. Furthermore, a gas guiding device 16 is provided in the interior of the heating chamber 7 and is located in the space between the heating elements 15 and the charge 11. This gas guiding device is guided upwards like a hood to the center, a central opening 17 being left free.

Innerhalb der oberen Haube 5 befindet sich ein Ventilatormotor 18, der am Ende der nach unten ragenden Motorwelle ein Flügelrad 19 trägt. Der Ventilatormotor 18 ist am freien Ende einer Kolbenstange eines Hubzylinders 20 befestigt und mit Hilfe dieses Hubzylinders aus einer oberen Ruhestellung in eine untere Betriebsstellung absenkbar und umgekehrt. Ebenso wie in der Gasleiteinrichtung 16 ist in der oberen Decke der Heizkammer eine etwa gleich grosse Öffnung 21 enthalten, durch die das Flügelrad 19 in das Innere der Heizkammer 7 eindringen kann. Über ein Gestänge 22 ist an der Kolbenstange des Hubzylinders 20 ein kreisrunder Stopfen 23 mit entsprechender Wärmedämmschicht befestigt, der in der Betriebsstellung des Ventilatormotors 18 die Öffnung 21 der Heizkammer 7 verschliesst. Weiter ist auf der Rückseite des Stopfens 23 eine Kühlscheibe 24 für die Welle des Ventilatormotors 18 vorgesehen, der ebenfalls am Gestänge 22 befestigt ist.Inside the upper hood 5 there is a fan motor 18 which carries an impeller 19 at the end of the motor shaft projecting downwards. The fan motor 18 is attached to the free end of a piston rod of a lifting cylinder 20 and can be lowered with the aid of this lifting cylinder from an upper rest position into a lower operating position and vice versa. Just as in the gas guiding device 16, an opening 21 of approximately the same size is contained in the upper ceiling of the heating chamber, through which the impeller 19 can penetrate into the interior of the heating chamber 7. A circular plug 23 with a corresponding thermal barrier coating is fastened to the piston rod of the lifting cylinder 20 via a linkage 22 and closes the opening 21 of the heating chamber 7 in the operating position of the fan motor 18. Furthermore, a cooling disk 24 is provided for the shaft of the fan motor 18 on the back of the plug 23, which is also attached to the linkage 22.

Für das Verschliessen der Heizkammer in der Betriebsphase, in der der Ventilatormotor 18 die Ruhestellung einnimmt, ist ein Schieber 25 vorgesehen, der wie die Wandung der Heizkammer 7 mit einer Wärmedämmschicht ausgestattet ist. Dieser Schieber 25 ist aus der in Fig. 2 dargestellten Einsatzstellung in eine seitliche Ruhestellung hin- und her bewegbar. Zu diesem Zweck ist am Oberteil 3 ein seitlich vorstehender Stutzen 26 angeformt.For closing the heating chamber in the operating phase, in which the fan motor 18 assumes the rest position, a slide 25 is provided which, like the wall of the heating chamber 7, is equipped with a thermal barrier coating. This slide 25 can be moved back and forth from the operating position shown in FIG. 2 into a lateral rest position. For this purpose, a laterally projecting nozzle 26 is formed on the upper part 3.

Für die Wärmebehandlung einer Charge wird der beschriebene Vakuumschachtofen wie folgt eingesetzt:The described vacuum shaft furnace is used for the heat treatment of a batch as follows:

Der linke Halbschnitt in Fig. zeigt den Betriebszustand für das Heizen mit Gasumwälzung bis zu einer Temperatur von etwa 750°C. Der Ventilatormotor 18 nimmt die untere Betriebsstellung ein, in der der Ventilator 19 in Höhe der Öffnung 17 der Gasleiteinrichtung 16 sich befindet. Das im Innern der Heizkammer befindliche Schutzgas wird in eine Umwälzströmung aus dem Innenraum der Gasleiteinrichtung 16 nach oben in den Zwischenraum zwischen Gasleiteinrichtung 16 und Wandung der Heizkammer 7 versetzt, wobei der Gasstrom an den Heizelementen 15 erwärmt wird und am unteren Ende des Zwischenraumes erneut in das Innere der Gasleiteinrichtung 16 eintritt. Wenn die für den Ventilator 19 maximal zulässige Temperatur erreicht ist, wird der Ventilatormotor 18 in die in Fig. dargestellte Ruhestellung zurückbewegt. Mit dem Schieber 25 wird die Öffnung 21 der Heizkammer 7 verschlossen. In dieser Phase wird die Charge 11 mit ruhendem Schutzgas oder unter Vakuum im wesentlichen durch Strahlungswärme bis zur gewünschten Endtemperatur, z.B. 1.150°C, erwärmt.The left half section in Fig. Shows the operating state for heating with gas circulation up to a temperature of about 750 ° C. The fan motor 18 assumes the lower operating position, in which the fan 19 is located at the opening 17 of the gas guiding device 16. The protective gas inside the heating chamber is placed in a circulating flow from the interior of the gas guiding device 16 upwards into the space between the gas guiding device 16 and the wall of the heating chamber 7, the gas flow being heated at the heating elements 15 and again at the lower end of the space Inside the gas guide device 16 occurs. When the maximum permissible temperature for the fan 19 is reached, the fan motor 18 is moved back into the rest position shown in FIG. The opening 21 of the heating chamber 7 is closed with the slide 25. In this phase the batch 11 is quenched with inert gas or under vacuum essentially by radiant heat to the desired final temperature, e.g. 1,150 ° C, heated.

Das nachfolgende Kühlen erfolgt wiederum mit Gasumwälzung. Zu diesem Zweck wird der Schieber 25 geöffnet und der Ventilatormotor 18 in die im rechten Halbschnitt der Fig. 1 dargestellte Zwischenstellung abgesenkt. Weiter wird der Boden 9 der Heizkammer 7 nach unten abgesenkt, wie es ebenfalls im rechten Halbschnitt der Fig. 1 dargestellt ist. In Verbindung mit der Gasleiteinrichtung 16 wird nun das Gas mit Hilfe des Ventilators 19 erneut in eine Umwälzströmung nach oben aus der Heizkammer 7 heraus in den Zwischenraum zwischen Heizkammer 7 und Unterteil 1 an den Kühlrohren 14 vorbei nach unten und hier in das Innere der Heizkammer 7 zurückversetzt.The subsequent cooling takes place again with gas circulation. For this purpose, the slide 25 is opened and the fan motor 18 is lowered into the intermediate position shown in the right half section of FIG. 1. The bottom 9 of the heating chamber 7 is abge down lowers, as is also shown in the right half section of FIG. 1. In connection with the gas guide device 16, the gas is now again ventilated with the help of the fan 19 into a circulation flow upwards out of the heating chamber 7 into the space between the heating chamber 7 and the lower part 1 past the cooling tubes 14 and here into the interior of the heating chamber 7 set back.

Claims (3)

1. Process for the heat treatment of a load of metallic workpieces or a single workpiece in a vacuum furnace at temperatures above approximately 750°C, with a closable and evacuatable container and a heating chamber for accepting the load, characterized in that the container is evacuated and flooded with protective gas after the load is inserted, that the load is heated to the maximum permitted operating temperature of the circulation device by heating and gas circulation inside the heating chamber, and that the container is then evacuated and the load is heated to a desired final heat treatment temperature mainly by radiation heat.
2. Vacuum furnace for carrying out the process as claimed in Claim 1, with a closable steel container and an inner heating chamber for accepting the load, with a radiation-heating device which is situated inside the heating chamber, and with a gas blower and also a gas-conveying device for creating a circulating flow through the heating chamber, in the wall of which there is contained an orifice which can be closed by a slide valve with a heat-insulating layer, characterized in that the gas blower (18 and 19) is mounted so as to be movable to and fro between a working position and a resting position, in such a way that its ventilator (19), when the slide valve (25) is opened, projects through the orifice (21) into the interior of the heating chamber (7) in the working position, but is situated outside the heating chamber (7) in the resting position.
3. Vacuum furnace as claimed in Claim 2, characterized in that a plug (23) with an integrated heat-insulating layer which serves to close the orifice (21) is fixed to the rear of the ventilator (19) on the side where the motor is located.
EP85104965A 1984-05-08 1985-04-24 Method and vacuum furnace for heat treatment a charge Expired EP0163906B1 (en)

Priority Applications (1)

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AT85104965T ATE37201T1 (en) 1984-05-08 1985-04-24 PROCESS AND VACUUM FURNACE FOR THE HEAT TREATMENT OF A BATCH.

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DE3416902 1984-05-08
DE19843416902 DE3416902A1 (en) 1984-05-08 1984-05-08 METHOD AND VACUUM OVEN FOR HEAT TREATING A BATCH

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EP0163906A2 EP0163906A2 (en) 1985-12-11
EP0163906A3 EP0163906A3 (en) 1986-08-20
EP0163906B1 true EP0163906B1 (en) 1988-09-14

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EP (1) EP0163906B1 (en)
AT (1) ATE37201T1 (en)
DE (2) DE3416902A1 (en)

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Also Published As

Publication number Publication date
DE3416902A1 (en) 1985-11-14
US4709904A (en) 1987-12-01
DE3564965D1 (en) 1988-10-20
EP0163906A2 (en) 1985-12-11
EP0163906A3 (en) 1986-08-20
ATE37201T1 (en) 1988-09-15
US4612064A (en) 1986-09-16

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