EP0716152A1 - Process for heat treating workpieces - Google Patents

Process for heat treating workpieces Download PDF

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Publication number
EP0716152A1
EP0716152A1 EP95119203A EP95119203A EP0716152A1 EP 0716152 A1 EP0716152 A1 EP 0716152A1 EP 95119203 A EP95119203 A EP 95119203A EP 95119203 A EP95119203 A EP 95119203A EP 0716152 A1 EP0716152 A1 EP 0716152A1
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EP
European Patent Office
Prior art keywords
workpieces
convection gas
workpiece
industrial furnace
temperature
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.)
Withdrawn
Application number
EP95119203A
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German (de)
French (fr)
Inventor
Wolfgang Kühne
Dominik Dr. Schröder
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schmitz and Apelt LOI Industrieofenanlagen GmbH
Original Assignee
Schmitz and Apelt LOI Industrieofenanlagen GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Schmitz and Apelt LOI Industrieofenanlagen GmbH filed Critical Schmitz and Apelt LOI Industrieofenanlagen GmbH
Publication of EP0716152A1 publication Critical patent/EP0716152A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
    • F27B9/20—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path tunnel furnace
    • 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
    • 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
    • C21D9/0006—Details, accessories not peculiar to any of the following furnaces
    • 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
    • C21D9/005—Furnaces in which the charge is moving up or down
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B9/36—Arrangements of heating devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B9/36—Arrangements of heating devices
    • F27B2009/3607—Heaters located above the track of the charge
    • F27B2009/3615—Burner in the ceiling directed vertically downwards

Definitions

  • the invention relates to a generic method for the heat treatment of workpieces.
  • the invention further relates to an industrial furnace for carrying out the method.
  • the workpieces can be semi-finished or pre-material, such as.
  • B. press pin sections or finished products for the automotive industry such as axle beams, cylinder heads, wheels, steering knuckles or gearbox.
  • the workpieces which in most cases are thin-walled, are usually transported through the industrial furnace in baskets or other charging aids.
  • the workpieces are heated in the heating zone by convection, in which the furnace atmosphere is circulated, lengthways or crosswise in the furnace.
  • the furnace atmosphere is either heated directly using an open burner or indirectly using radiant tubes or electrical heating registers.
  • Alternative methods for coupling the heat via heat exchangers from parallel processes are also possible and have already been tried and tested.
  • the temperature of the circulated furnace atmosphere may only be approx. 20 ° C above the temperature of the workpieces to avoid thermal stress. Heating up the workpieces is therefore relatively time-consuming. For example, the heating of workpieces that are to be heat-treated between 530 and 580 ° C. takes between 90 and 180 minutes depending on the shape and shape of the workpiece, in particular depending on the wall thickness. Heating massive bolt sections requires maximum heating times. Differences in heating times are also due to the way the workpieces are packed in baskets. As a result, there are different quality results that are not reproducible.
  • the object of the invention is to provide a remedy here and to provide an economically usable possibility of increasing the quality of the results.
  • the method according to the invention is characterized in that the workpieces are transported individually or next to one another in rows through the industrial furnace and that each workpiece in the heating zone is supplied directly by at least one radiation source by thermal radiation and by at least one convection gas stream which surrounds the radiation source , is heated to the heat treatment temperature.
  • the radiation source is a burner or an electrically heated radiation element. Since the power of the radiation source and the convection gas flow can be controlled separately, it is possible to optimize the energy input into each workpiece precisely.
  • the workpieces are heated by means of high temperature differences, the heating temperature always being chosen so that there is no partial melting of the surface of the workpiece and that the heat treatment temperature is also defined with the highest possible gradients between the material to be treated and the furnace atmosphere.
  • This solution has the advantage that a significant increase in the quality of the workpieces and a better reproducibility of the results are achieved.
  • the operating costs are reduced by eliminating the charging aids, such as transport containers.
  • the convection gas flow is guided in a ring around the radiation source.
  • the convection gas flow can arise from recirculated exhaust gas and / or preferably preheated air.
  • a preferred development is that the ratio of heat radiation and convection gas flow is set depending on the difference between the actual temperature of the workpiece and the target heat treatment temperature, such that the convection gas flow is greater, the smaller the difference between Actual and target temperature of the workpiece.
  • the heating gradient is therefore large at the beginning of the heating zone. The smaller the distance between the actual temperature of the workpiece and the target temperature, the greater the proportion of the convection gas flow, so that the heating gradient is low at the end of the heating zone.
  • the temperature of the workpiece is preferably measured and the power of the burner flame and / or the size of the volume of the convection gas stream is regulated as a function of the measured value.
  • the regulation can be done programmatically with the help of a computer.
  • a special embodiment of the invention consists in that the temperature of the workpiece is measured at a reference point via contact elements.
  • the workpieces are convectively heated during transport through the holding zone and then individually cooled in a cooling basin. This ensures that there are always the same cooling gradients and thus the same quality results.
  • the invention also provides an industrial furnace for the heat treatment of workpieces, in particular cast aluminum parts, the industrial furnace having a heating and holding zone and a transport device for the workpieces.
  • the transport device is designed such that the workpieces can be transported individually or in rows next to one another.
  • At least one radiation source which is surrounded by an outlet opening for a convection gas stream, is arranged in the heating zone in such a way that the heat radiation and the convection gas stream act directly on each workpiece.
  • the radiation source is a burner or an electrically heated radiation element.
  • a plurality of radiation sources can preferably be arranged in groups in the heating zone.
  • the radiation sources can be arranged in the heating zone depending on the shape of the workpiece.
  • the radiation source can be arranged vertically so that the workpieces are heated from above. In the case of high parts, it is advantageous to heat the parts by means of a radiation source arranged on the side. There can also be two facing each other Radiation sources are used so that the workpiece is heated from two sides.
  • each zone can also have its own transport device.
  • the transport device can, for. B. be designed as a conveyor belt or conveyor chain.
  • the industrial furnace is also characterized by a control device that program-controlled controls the output of each burner and each convection gas flow depending on the temperature of the workpieces.
  • the transport device is deflected in the holding zone in such a way that the workpieces pass through the holding zone essentially horizontally, the workpieces being heated by means of a directed convection gas flow.
  • This results in a considerable reduction in the overall length, which saves space.
  • the directional convection gas flows achieve an even temperature distribution.
  • the downsizing of the furnace system results in energy savings due to the reduction in surface losses. Further energy is saved due to the individual part treatment in the holding zone.
  • the holding time can be shortened because tolerance and safety surcharges can be dispensed with.
  • the industrial furnace has a tunnel-like heating zone 1 and a holding zone 2.
  • the workpieces 3 are transported individually or in rows next to one another by means of a conveyor belt 4.
  • the workpieces 3 are fixed on the conveyor belt 4 in a manner not shown.
  • a plurality of radiation sources in the form of burners 5 are arranged in the heating zone 1 in such a way that the flames heat each workpiece directly from above.
  • the workpiece 3 shows another arrangement of the burners in the heating zone in a sectional view over time.
  • the workpiece 3 is heated by laterally attached burners, the arrangement of which is adapted to the shape of the workpiece.
  • each burner is concentrically surrounded by an annular outlet opening 6 for a convection gas flow.
  • the convection gas is circulated.
  • the recirculation of the convection gas flow varies between 0 and 100%.
  • the burner output is high and the convection gas volume is low.
  • the convection gas volume is large and the burner output is low.
  • the temperature of the workpieces is measured via a contact element (not shown) at a reference point of the workpiece.
  • the heating power of the burner and the volume of the convection gas flow are controlled, with the aid of a program control, not shown.
  • the workpieces After the workpieces have been heated to the target temperature in 10 to 45 minutes, the workpieces are transferred from the heating zone to holding zone 2. During transport through the holding zone 2, the temperature differences in the workpiece resulting from empty losses in the heating zone 1 are compensated for by convective heating.
  • a fan 7 in conjunction with baffles 8 ensures a downward flow of the convection gas heated by the heating devices 9.
  • the baffles 8 cause a partial reversal of the direction of flow of the convection gas, so that a uniform temperature distribution in the holding zone is supported.
  • the holding zone is designed as a so-called paternoster oven. This results in a considerable reduction in the overall length, which saves space.
  • the downsizing of the furnace system results in energy savings due to the reduction in surface losses.
  • the holding time can be shortened because tolerance and safety surcharges can be dispensed with.
  • the workpieces After passing through the holding zone 2, the workpieces are individually cooled in a cooling basin 7. This ensures that there are always the same cooling gradients and thus the same quality results.

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

Abstract

In a heat treatment process, partic. for Al castings, casting are individually or successively transported in series through an industrial furnace, each workpiece being heated directly to the heat treatment temp. in a heating zone by at least one radiation source and by at least one convection gas stream which surrounds the radiation source, pref. in a ring shape. Convection gas stream pref. comprises recirculated waste gas and/or pref. preheated air. Also claimed in an industrial furnace with heating and holding zones (1,2) and a transporting device (4) for conveying workpieces, with radiation source (5), pref. several sources in gps., surrounded by outlet for the convection gas stream.

Description

Die Erfindung betrifft ein gattungsgemäßes Verfahren zur Wärmebehandlung von Werkstücken. Ferner betrifft die Erfindung einen Industrieofen zur Durchführung des Verfahrens.The invention relates to a generic method for the heat treatment of workpieces. The invention further relates to an industrial furnace for carrying out the method.

Bei den Werkstücken kann es sich um Halbzeuge oder Vormaterial, wie z. B. Preßbolzenabschnitte oder um Fertigprodukte für die Automobilindustrie wie Achsträger, Zylinderköpfe, Räder, Achsschenkel oder Getriebegehäuse handeln.The workpieces can be semi-finished or pre-material, such as. B. press pin sections or finished products for the automotive industry such as axle beams, cylinder heads, wheels, steering knuckles or gearbox.

Die in den meisten Fällen dünnwandigen Werkstücke werden üblicherweise in Körben oder anderen Chargierhilfsmitteln durch den Industrieofen transportiert. Die Aufheizung der Werkstücke in der Aufheizzone erfolgt in der Praxis durch Konvektion, indem die Ofenatmosphäre, längs oder quer im Ofen umgewälzt wird. Die Ofenatmosphäre wird entweder direkt mittels offener Brenner erwärmt oder indirekt mittel Strahlrohren oder elektrischen Heizregistern. Alternative Verfahren zur Einkopplung der Wärme über Wärmetauscher aus parallelen Prozessen sind ebenfalls möglich und bereits erprobt.The workpieces, which in most cases are thin-walled, are usually transported through the industrial furnace in baskets or other charging aids. In practice, the workpieces are heated in the heating zone by convection, in which the furnace atmosphere is circulated, lengthways or crosswise in the furnace. The furnace atmosphere is either heated directly using an open burner or indirectly using radiant tubes or electrical heating registers. Alternative methods for coupling the heat via heat exchangers from parallel processes are also possible and have already been tried and tested.

Die Temperatur der umgewälzten Ofenatmosphäre darf nur ca. 20 °C über der Temperatur der Werkstücke liegen, um Wärmespannung zu vermeiden. Das Aufheizen der Werkstücke ist daher relativ zeitaufwendig. Beispielsweise dauert das Aufheizen von Werkstücken, die zwischen 530 und 580 °C wärmebehandelt werden sollen, zwischen 90 bis 180 Minuten je nach Form und Gestalt des Werkstückes, insbesondere in Abhängigkeit von der Wandstärke. Das Aufheizen von massiven Bolzenabschnitten erfordert maximale Aufheizzeiten. Unterschiede in den Aufheizzeiten werden auch bedingt durch die Art der Packung der Werkstücke in Körben. Folglich kommt es zu unterschiedlichen Qualitätsergebnissen, die nicht reproduzierbar sind.The temperature of the circulated furnace atmosphere may only be approx. 20 ° C above the temperature of the workpieces to avoid thermal stress. Heating up the workpieces is therefore relatively time-consuming. For example, the heating of workpieces that are to be heat-treated between 530 and 580 ° C. takes between 90 and 180 minutes depending on the shape and shape of the workpiece, in particular depending on the wall thickness. Heating massive bolt sections requires maximum heating times. Differences in heating times are also due to the way the workpieces are packed in baskets. As a result, there are different quality results that are not reproducible.

Demgemäß liegt der Erfindung die Aufgabe zugrunde, hier Abhilfe vorzusehen und eine wirtschaftlich einsetzbare Möglichkeit zu schaffen, die Qualität der Ergebnisse zu steigern.Accordingly, the object of the invention is to provide a remedy here and to provide an economically usable possibility of increasing the quality of the results.

Zur Lösung dieser Aufgabe ist das Verfahren nach der Erfindung dadurch gekennzeichnet, daß die Werkstücke einzeln oder nebeneinander in Reihen durch den Industrieofen transportiert werden und daß jedes Werkstück in der Aufheizzone direkt von mindestens einer Strahlungsquelle durch Wärmestrahlung und durch mindestens einen Konvenktionsgasstrom, der die Strahlungsquelle umgibt, auf die Wärmebehandlungstemperatur erwärmt wird.To achieve this object, the method according to the invention is characterized in that the workpieces are transported individually or next to one another in rows through the industrial furnace and that each workpiece in the heating zone is supplied directly by at least one radiation source by thermal radiation and by at least one convection gas stream which surrounds the radiation source , is heated to the heat treatment temperature.

Bei der Strahlungsquelle handelt es sich um einen Brenner oder ein elektrisch beheiztes Strahlungselement. Da die Leistung der Strahlungsquelle und des Konvektionsgasstromes getrennt gesteuert werden können, ist es möglich, den Energieeintrag in jedes Werkstück genau zu optimieren.The radiation source is a burner or an electrically heated radiation element. Since the power of the radiation source and the convection gas flow can be controlled separately, it is possible to optimize the energy input into each workpiece precisely.

Die Werkstücke werden mittels hoher Temperaturdifferenzen erwärmt, wobei die Aufheiztemperatur immer so gewählt wird, daß es nicht zum partiellen Anschmelzen der Oberfläche des Werkstückes kommt und daß ferner die Wärmebehandlungstemperatur definiert mit höchst möglichsten Gradienten zwischen Behandlungsgut und Ofenatmospäre angefahren wird.The workpieces are heated by means of high temperature differences, the heating temperature always being chosen so that there is no partial melting of the surface of the workpiece and that the heat treatment temperature is also defined with the highest possible gradients between the material to be treated and the furnace atmosphere.

Diese Lösung hat den Vorteil, daß eine deutliche Steigerung der Qualität der Werkstücke und eine bessere Reproduzierbarkeit der Ergebnisse erreicht werden. Außerdem werden die Betriebskosten reduziert durch Wegfall der Chargierhilfsmittel, wie Transportbehälter.This solution has the advantage that a significant increase in the quality of the workpieces and a better reproducibility of the results are achieved. In addition, the operating costs are reduced by eliminating the charging aids, such as transport containers.

Da insgesamt die Durchlaufzeiten stark verkürzt werden konnten, sind die Betriebsabläufe sehr flexibel.Since the overall throughput times were greatly reduced, the operational processes are very flexible.

Eine besonders vorteilhafte Weiterbildung steht darin, daß der Konvektionsgasstrom ringförmig um die Strahlungsquelle geführt wird. Der Konvektionsgasstrom kann aus rezirkuliertem Abgas und/oder vorzugsweise vorgewärmter Luft entstehen.A particularly advantageous development is that the convection gas flow is guided in a ring around the radiation source. The convection gas flow can arise from recirculated exhaust gas and / or preferably preheated air.

Eine bevorzugte Weiterbildung besteht darin, daß das Verhältnis von Wärmestrahlung und Konvektionsgasstrom in Abhängigkeit von der Differenz zwischen der Ist-Temperatur des Werkstückes und der Soll-Wärmebehandlungstemperatur eingestellt wird, derart, daß der Konvektionsgasstrom um so größer ist, je kleiner die Differenz zwischen Ist- und Solltemperatur des Werkstückes ist. Am Anfang der Aufheizzone ist daher der Aufheizgradient groß. Je geringer der Abstand der Isttemperatur des Werkstückes von der Solltemperatur wird, desto größer wird der Anteil des Konvektionsgasstromes, so daß am Ende der Aufheizzone der Aufheizgradient gering ist.A preferred development is that the ratio of heat radiation and convection gas flow is set depending on the difference between the actual temperature of the workpiece and the target heat treatment temperature, such that the convection gas flow is greater, the smaller the difference between Actual and target temperature of the workpiece. The heating gradient is therefore large at the beginning of the heating zone. The smaller the distance between the actual temperature of the workpiece and the target temperature, the greater the proportion of the convection gas flow, so that the heating gradient is low at the end of the heating zone.

Vorzugsweise wird die Temperatur des Werkstückes gemessen und in Abhängigkeit vom Meßwert die Leistung der Brennerflamme und/oder die Größe des Volumens des Konvektionsgasstromes geregelt. Die Regelung kann programmgesteuert mit Hilfe eines Rechners erfolgen.The temperature of the workpiece is preferably measured and the power of the burner flame and / or the size of the volume of the convection gas stream is regulated as a function of the measured value. The regulation can be done programmatically with the help of a computer.

Eine besondere Ausgestaltung der Erfindung besteht darin, daß die Temperatur des Werkstückes an einem Referenzpunkt über Kontaktelemente gemessen wird.A special embodiment of the invention consists in that the temperature of the workpiece is measured at a reference point via contact elements.

In Weiterbildung der Erfindung werden die Werkstücke beim Transport durch die Haltezone konvektiv beheizt und anschließend in einem Abkühlbecken einzeln abgekühlt. Damit ist sichergestellt, daß es stets zu gleichen Abkühlgradienten und damit zu gleichen Qualitätsergebnissen kommt.In a development of the invention, the workpieces are convectively heated during transport through the holding zone and then individually cooled in a cooling basin. This ensures that there are always the same cooling gradients and thus the same quality results.

Die Erfindung schafft ferner einen Industrieofen zur Wärmebehandlung von Werkstücken, insbesondere Aluminium-Gußteilen, wobei der Industrieofen eine Aufheiz- und eine Haltezone und eine Transporteinrichtung für die Werkstücke aufweist. Erfindungsgemäß ist die Transporteinrichtung derart ausgebildet, daß die Werkstücke einzeln oder in Reihen nebeneinander transportierbar sind. In der Aufheizzone ist mindestens eine Strahlungsquelle, die von einer Austrittsöffnung für einen Konvektionsgasstrom umgeben ist, derart angeordnet, daß die Wärmestrahlung und der Konvektionsgasstrom jedes Werkstück direkt beaufschlagen.The invention also provides an industrial furnace for the heat treatment of workpieces, in particular cast aluminum parts, the industrial furnace having a heating and holding zone and a transport device for the workpieces. According to the invention, the transport device is designed such that the workpieces can be transported individually or in rows next to one another. At least one radiation source, which is surrounded by an outlet opening for a convection gas stream, is arranged in the heating zone in such a way that the heat radiation and the convection gas stream act directly on each workpiece.

Bei der Strahlungsquelle handelt es sich um einen Brenner oder ein elektrisch beheiztes Strahlungselement. In der Aufheizzone können vorzugsweise mehrere Strahlungsquellen in Gruppen angeordnet sein.The radiation source is a burner or an electrically heated radiation element. A plurality of radiation sources can preferably be arranged in groups in the heating zone.

Die Anordnung der Strahlungsquellen in der Aufheizzone kann in Abhängigkeit von der Form des Werkstückes erfolgen.The radiation sources can be arranged in the heating zone depending on the shape of the workpiece.

Die Strahlungsquelle kann senkrecht angeordnet sein, so daß die Werkstücke von oben erwärmt werden. Bei hohen Teilen ist es günstig, die Teile durch eine seitlich angeordnete Strahlungsquelle zu erwärmen. Es können auch zwei sich gegenüberstehende Strahlungsquellen eingesetzt werden, so daß das Werkstück von zwei Seiten beheizt wird.The radiation source can be arranged vertically so that the workpieces are heated from above. In the case of high parts, it is advantageous to heat the parts by means of a radiation source arranged on the side. There can also be two facing each other Radiation sources are used so that the workpiece is heated from two sides.

Im Rahmen der Erfindung kann auch jede Zone eine eigene Transporteinrichtung aufweisen. Die Transporteinrichtung kann z. B. als Förderband oder Förderkette ausgebildet sein.Within the scope of the invention, each zone can also have its own transport device. The transport device can, for. B. be designed as a conveyor belt or conveyor chain.

Der Industrieofen ist ferner gekennzeichnet durch eine Regelungseinrichtung, die programmgesteuert die Leistung jedes Brenners und jedes Konvektionsgasstromes in Abhängigkeit von der Temperatur der Werkstücke regelt.The industrial furnace is also characterized by a control device that program-controlled controls the output of each burner and each convection gas flow depending on the temperature of the workpieces.

Bei einer bevorzugten Ausführungsform wird in der Haltezone die Transporteinrichtung derart umgelenkt, daß die Werkstücke im wesentlichen horizontal die Haltezone durchlaufen, wobei die Werkstücke mittels gerichteter Konvektionsgasströmung beheizt werden. Dadurch ergibt sich eine erhebliche Reduktion der Baulänge, wodurch Platz eingespart wird. Durch die gerichteten Konvektionsgasströmungen wird eine gleichmäßige Temperaturverteilung erreicht. Außerdem ergeben sich durch die Verkleinerung der Ofenanlage Energieersparnisse aufgrund der Reduzierung der Oberflächenverluste. Weitere Energie wird eingespart aufgrund der Einzelteilbehandlung in der Haltezone. Die Haltezeit kann verkürzt werden, weil auf Toleranz und Sicherheitszuschläge verzichtet werden kann.In a preferred embodiment, the transport device is deflected in the holding zone in such a way that the workpieces pass through the holding zone essentially horizontally, the workpieces being heated by means of a directed convection gas flow. This results in a considerable reduction in the overall length, which saves space. The directional convection gas flows achieve an even temperature distribution. In addition, the downsizing of the furnace system results in energy savings due to the reduction in surface losses. Further energy is saved due to the individual part treatment in the holding zone. The holding time can be shortened because tolerance and safety surcharges can be dispensed with.

Die Erfindung wird im folgenden anhand eines bevorzugten Ausführungsbeispiels eines erfindungsgemäßen Industrieofens in Zusammenhang mit der Zeichnung näher erläutert.The invention is explained below with reference to a preferred embodiment of an industrial furnace according to the invention in connection with the drawing.

Die Zeichnung zeigt in:

Fig. 1
eine schematische Darstellung eines Industrieofens im Längsschnitt;
Fig. 2
eine schematische Darstellung der Aufheizzone des Industrieofens nach Fig. 1;
Fig. 3
eine andere Anordnung der Brenner in der Aufheizzone.
The drawing shows in:
Fig. 1
a schematic representation of an industrial furnace in longitudinal section;
Fig. 2
a schematic representation of the heating zone of the industrial furnace according to Fig. 1;
Fig. 3
another arrangement of the burners in the heating zone.

Es handelt sich beim Ausführungsbeispiel nach Fig. 1 und 2 um einen Wärmebehandlungsofen zum Lösungsglühen für Aluminium-Gußteile. Der Industrieofen weist eine tunnelartige Aufheizzone 1 und eine Haltezone 2 auf. Die Werkstücke 3 werden mittels eines Förderbandes 4 einzeln oder in Reihen nebeneinander transportiert. Die Werkstücke 3 sind dabei auf nicht dargestellte Art und Weise auf dem Förderband 4 fixiert.1 and 2 is a heat treatment furnace for solution annealing for aluminum castings. The industrial furnace has a tunnel-like heating zone 1 and a holding zone 2. The workpieces 3 are transported individually or in rows next to one another by means of a conveyor belt 4. The workpieces 3 are fixed on the conveyor belt 4 in a manner not shown.

In der Aufheizzone 1 sind mehrere Strahlungsquellen in Form von Brennern 5 derart angeordnet, daß die Flammen jedes Werkstück von oben direkt erwärmen.A plurality of radiation sources in the form of burners 5 are arranged in the heating zone 1 in such a way that the flames heat each workpiece directly from above.

In Fig. 3 zeigt in einer zeitlichen Schnittdarstellung eine andere Anordnung der Brenner in der Aufheizzone. Die Beheizung des Werkstückes 3 erfolgt durch seitlich angebrachte Brenner, deren Anordnung an die Form des Werkstückes angepaßt ist.3 shows another arrangement of the burners in the heating zone in a sectional view over time. The workpiece 3 is heated by laterally attached burners, the arrangement of which is adapted to the shape of the workpiece.

Wie in Fig. 2 dargestellt, ist jeder Brenner konzentrisch von einer ringförmigen Austrittsöffnung 6 für einen Konvektionsgasstrom umgeben.As shown in Fig. 2, each burner is concentrically surrounded by an annular outlet opening 6 for a convection gas flow.

Das Konvektionsgas wird im Kreislauf gefahren. Die Rezirkulation des Konvektionsgasstromes variiert zwischen 0 und 100 %.The convection gas is circulated. The recirculation of the convection gas flow varies between 0 and 100%.

Am Anfang der Aufheizzone, in der die Werkstücke noch kalt sind, ist die Brennerleistung groß und das Konvektionsgas-Volumen gering. Am Ende der Aufheizzone 1, wenn die Werkstücke die Solltemperatur fast erreicht haben, ist das Konvektionsgas-Volumen groß und die Brennerleistung gering.At the beginning of the heating zone, in which the workpieces are still cold, the burner output is high and the convection gas volume is low. At the end of heating zone 1, when the workpieces have almost reached the target temperature, the convection gas volume is large and the burner output is low.

Die Temperatur der Werkstücke wird über ein nicht dargestelltes Kontaktelement an einem Referenzpunkt des Werkstückes gemessen. In Abhängigkeit vom Meßwert wird die Heizleistung des Brenners und das Volumen des Konvektionsgasstromes gesteuert, und zwar mit Hilfe einer nicht dargestellten Programmsteuerung.The temperature of the workpieces is measured via a contact element (not shown) at a reference point of the workpiece. Depending on the measured value, the heating power of the burner and the volume of the convection gas flow are controlled, with the aid of a program control, not shown.

Nach Aufheizung der Werkstücke in 10 bis 45 Minuten auf Solltemperatur werden die Werkstücke aus der Aufheizzone in die Haltezone 2 übergeben. Beim Transport durch die Haltezone 2 werden die durch Leerverluste der Aufheizzone 1 entstehenden Temperaturdifferenzen im Werkstück durch konvektive Beheizung ausgeglichen. Ein Ventilator 7 sorgt in Verbindung mit Leitblechen 8 für eine abwärts gerichtete Strömung des durch die Beheizungseinrichtungen 9 erhitzten Konvektionsgases. Die Leitbleche 8 bewirken eine teilweise Umkehr der Strömungsrichtung des Konvektionsgases, so daß eine gleichmäßige Temperaturverteilung in der Haltezone unterstützt wird. Die Haltezone ist als sogenannter Paternosterofen ausgeführt. Dadurch ergibt sich eine erhebliche Reduzierung der Baulänge, wodurch Platz eingespart wird. Außerdem ergeben sich durch die Verkleinerung der Ofenanlage Energieersparnisse aufgrund der Reduzierung der Oberflächenverluste.After the workpieces have been heated to the target temperature in 10 to 45 minutes, the workpieces are transferred from the heating zone to holding zone 2. During transport through the holding zone 2, the temperature differences in the workpiece resulting from empty losses in the heating zone 1 are compensated for by convective heating. A fan 7 in conjunction with baffles 8 ensures a downward flow of the convection gas heated by the heating devices 9. The baffles 8 cause a partial reversal of the direction of flow of the convection gas, so that a uniform temperature distribution in the holding zone is supported. The holding zone is designed as a so-called paternoster oven. This results in a considerable reduction in the overall length, which saves space. In addition, the downsizing of the furnace system results in energy savings due to the reduction in surface losses.

Weitere Energie wird eingespart aufgrund der Einzelteilbehandlung in der Haltezone. Die Haltezeit kann verkürzt werden, weil auf Toleranz und Sicherheitzuschläge verzichtet werden kann.Further energy is saved due to the individual part treatment in the holding zone. The holding time can be shortened because tolerance and safety surcharges can be dispensed with.

Nach Durchlaufen der Haltezone 2 werden die Werkstücke in einem Abkühlbecken 7 einzeln abgekühlt. Dadurch ist sichergestellt, daß es stets zu gleichen Abkühlgradienten und damit zu gleichen Qualitätsergebnissen kommt.After passing through the holding zone 2, the workpieces are individually cooled in a cooling basin 7. This ensures that there are always the same cooling gradients and thus the same quality results.

Claims (12)

Verfahren zur Wärmebehandlung von Werkstücken, insbesondere Aluminium-Gußteilen, die durch einen Industrieofen mit einer Aufheizzone und einer Haltezone transportiert und anschließend abgekühlt werden
dadurch gekennzeichnet,
daß die Werkstücke einzeln oder nebeneinander in Reihen durch den Industrieofen transportiert werden und
daß jedes Werkstück in der Aufheizzone direkt von mindestens eine Strahlungsquelle durch Wärmestrahlung und durch mindestens einen Konvektionsgasstrom, der die Strahlungsquelle umgibt, auf die Wärmebehandlungstemperatur erwärmt wird.Process for the heat treatment of workpieces, in particular cast aluminum parts, which are transported through an industrial furnace with a heating zone and a holding zone and then cooled
characterized,
that the workpieces are transported individually or side by side in rows through the industrial furnace and
that each workpiece in the heating zone is directly heated to the heat treatment temperature by at least one radiation source by thermal radiation and by at least one convection gas stream which surrounds the radiation source. Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
daß der Konvektionsgasstrom ringförmig um die Strahlungsquelle geführt wird.Method according to claim 1,
characterized,
that the convection gas flow is guided in a ring around the radiation source. Verfahren nach einem der Ansprüche 1 bis 2
dadurch gekennzeichnet,
daß der Konvektionsgasstrom aus rezirkuliertem Abgas und/oder vorzugsweise vorgewärmter Luft besteht.Method according to one of claims 1 to 2
characterized,
that the convection gas stream consists of recirculated exhaust gas and / or preferably preheated air. Verfahren nach einem der Ansprüche 1 bis 3
dadurch gekennzeichnet,
daß das Verhältnis von Wärmestrahlung und Konvektionsgasstrom in Abhängigkeit von der Differenz zwischen der Isttemperatur des Werkstückes und der Soll-Wärmebehandlungstemperatur eingestellt wird, derart, daß der Konvektionsgasstrom um so größer ist je kleiner die Differenz zwischen Ist- und Solltemperatur des Werkstückes ist.Method according to one of claims 1 to 3
characterized,
that the ratio of heat radiation and convection gas flow is set depending on the difference between the actual temperature of the workpiece and the target heat treatment temperature, such that the convection gas flow is greater, the smaller the difference between the actual and target temperature of the workpiece. Verfahren nach einem der Ansprüche 1 bis 4
dadurch gekennzeichnet,
daß die Temperatur des Werkstückes gemessen und in Abhängigkeit vom Meßwert die Leistung der Brennerflamme und/oder die Größe des Volumens des Konvektionsgasstromes geregelt wird.Method according to one of claims 1 to 4
characterized,
that the temperature of the workpiece is measured and the output of the burner flame and / or the size of the volume of the convection gas stream is regulated as a function of the measured value. Verfahren nach Anspruch 5,
dadurch gekennzeichnet,
daß die Temperatur des Werkstückes an einem Referenzpunkt über Kontaktelemente gemessen wird.Method according to claim 5,
characterized,
that the temperature of the workpiece is measured at a reference point via contact elements. Verfahren nach einem der Ansprüche 1 bis 6
dadurch gekennzeichnet,
daß die Werkstücke beim Transport durch die Haltezone konvektiv beheizt werden und anschließend in einem Abkühlbecken einzeln abgekühlt werden.Method according to one of claims 1 to 6
characterized,
that the workpieces are convectively heated during transport through the holding zone and then individually cooled in a cooling basin. Industrieofen zur Wärmebehandlung von Werkstücken (3), insbesondere Aluminium-Gußteilen, wobei der Industrieofen eine Aufheiz- und eine Haltezone (1,2) und eine Transporteinrichtung (4) für die Werkstücke (3) aufweist dadurch gekennzeichnet,
daß die Transporteinrichtung (4) derart ausgebildet ist, daß die Werkstücke (3) einzeln oder in Reihen nebeneinander transportierbar sind und daß in der Aufheizzone (1) mindestens eine Strahlungsquelle (5), die von einer Austrittsöffnung für einen Konvektionsgasstrom umgeben ist, derart angeordnet ist, daß die Wärmestrahlung und der Konvektionsgasstrom jedes Werkstück direkt beaufschlagen.Industrial furnace for the heat treatment of workpieces (3), in particular cast aluminum parts, the industrial furnace having a heating and holding zone (1, 2) and a transport device (4) for the workpieces (3),
that the transport device (4) is designed such that the workpieces (3) can be transported individually or in rows next to one another and that in the heating zone (1) at least one radiation source (5), which is surrounded by an outlet opening for a convection gas stream, is arranged in such a way is that the heat radiation and the convection gas flow act directly on each workpiece. Industrieofen nach Anspruch 8,
dadurch gekennzeichnet,
daß in der Aufheizzone (1) mehrere Strahlungsquellen (5) in Gruppen angeordnet sind.Industrial furnace according to claim 8,
characterized,
that several radiation sources (5) are arranged in groups in the heating zone (1). Industrieofen nach einem der Ansprüche 8 bis 9,
dadurch gekennzeichnet,
daß die Anordnung der Strahlungsquellen (5) in der Aufheizzone (1) in Abhängigkeit von der Form des Werkstückes (3) erfolgt.Industrial furnace according to one of claims 8 to 9,
characterized,
that the arrangement of the radiation sources (5) in the heating zone (1) is dependent on the shape of the workpiece (3). Industrieofen nach einem der Ansprüche 8 bis 10,
gekennzeichnet durch ein Regeleinrichtung, die Prozeßrechner-gestützt die Leistung jedes Brenners (5) und jedes Konvektionsgasstromes in Abhängigkeit von der Temperatur der Werkstücke regelt.Industrial furnace according to one of claims 8 to 10,
characterized by a control device, which supports the power of each burner (5) and each convection gas flow as a function of the temperature of the workpieces. Industrieofen nach einem der Ansprüche 8 bis 11,
dadurch gekennzeichnet,
daß in der Haltezone (2) die Transporteinrichtung (4) derart umgelenkt wird, daß die Werkstücke (3) im wesentlichen horizontal die Haltezone (2) durchlaufen, wobei die Werkstücke (3) mittels gerichteter Konvektionsgasströmungen beheizt werden.Industrial furnace according to one of claims 8 to 11,
characterized,
that the transport device (4) is deflected in the holding zone (2) in such a way that the workpieces (3) pass through the holding zone (2) essentially horizontally, the workpieces (3) being heated by means of directed convection gas flows.
EP95119203A 1994-12-08 1995-12-06 Process for heat treating workpieces Withdrawn EP0716152A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4443692 1994-12-08
DE4443692 1994-12-08

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