EP0355520B1 - Method of heat treating workpieces - Google Patents
Method of heat treating workpieces Download PDFInfo
- Publication number
- EP0355520B1 EP0355520B1 EP89114350A EP89114350A EP0355520B1 EP 0355520 B1 EP0355520 B1 EP 0355520B1 EP 89114350 A EP89114350 A EP 89114350A EP 89114350 A EP89114350 A EP 89114350A EP 0355520 B1 EP0355520 B1 EP 0355520B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- furnace
- treatment
- gas
- flow
- treatment gas
- 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.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000011282 treatment Methods 0.000 claims abstract description 64
- 238000001816 cooling Methods 0.000 claims description 25
- 238000007669 thermal treatment Methods 0.000 claims 1
- 238000007664 blowing Methods 0.000 abstract description 25
- 238000010438 heat treatment Methods 0.000 abstract description 12
- 239000000919 ceramic Substances 0.000 abstract description 2
- 239000002184 metal Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 57
- 238000002347 injection Methods 0.000 description 7
- 239000007924 injection Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 5
- 238000000137 annealing Methods 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000012495 reaction gas Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- UBAZGMLMVVQSCD-UHFFFAOYSA-N carbon dioxide;molecular oxygen Chemical compound O=O.O=C=O UBAZGMLMVVQSCD-UHFFFAOYSA-N 0.000 description 1
- 238000005255 carburizing Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- 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
- C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
-
- 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
- C21D9/0056—Furnaces through which the charge is moved in a horizontal straight path
-
- 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
- F27B9/3005—Details, accessories, or equipment peculiar to furnaces of these types arrangements for circulating gases
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D7/00—Forming, maintaining, or circulating atmospheres in heating chambers
- F27D7/02—Supplying steam, vapour, gases, or liquids
Definitions
- the invention relates to a method for the heat treatment of workpieces under a treatment gas atmosphere in a continuous furnace with an inlet, treatment and cooling zone, in which treatment gas is fed into one or more furnace zones comprising the cooling zone with the usual, low pressure and also a part of the Treatment gas directed in the cooling zone and injected at a higher pressure and thus a certain gas flow is produced in the interior of the furnace.
- heat treatment processes for metallic workpieces under a wide variety of treatment gas atmospheres are known. Examples of these are carburizing, hardening, nitriding and annealing processes e.g. among endogas, exogas, methanol and ammonia cracked gas and gases that are delivered ready to use and can be removed from storage tanks (e.g. nitrogen, hydrogen).
- Heat treatment methods under treatment gas for ceramic workpieces in continuous furnaces are also known, e.g. the burning of such workpieces.
- the treatment gas atmospheres can be divided into protective gas atmospheres and reaction gas atmospheres.
- Protective gases have the task of protecting the materials to be treated from undesired influences during heat treatment, for example from reactions with the oxygen, carbon dioxide or water vapor contained in the air, while desired reactions with the material to be treated are brought about in reaction gas atmospheres.
- the treatment gases are generally introduced into the heat treatment devices or furnaces at a plurality of points with a pressure slightly above atmospheric pressure (approximately between 0.01 and 0.2 mbar) and a low flow rate.
- the feed quantities and the feed points are selected so that a treatment gas atmosphere which is of sufficient quality for the respective treatment is established throughout the device and leak losses are compensated for.
- there is no deliberately chosen preferred flow direction of the introduced treatment gas but rather a flow results that depends on the particular furnace design, the flow essentially from one or more feed points to one or more main outflow points, e.g. the furnace entrance and exit.
- a heat treatment method for a continuous furnace is known from EP-B1 75 438, for example, in which curtains or flap-like closures at the furnace outlet and a suitable introduction rate of the treatment gas into the various furnace regions and in particular also in the cooling zone cause a flow in the direction of the furnace inlet becomes.
- a portion of the treatment gas to be supplied to the cooling zone be introduced into it in an appropriately directed manner, and thus to support the desired flow formation.
- EP-B1 75 438 using a series of measures, a very specific gas flow pattern directed towards the furnace entrance is set in a continuous furnace, which primarily serves to reduce the amount of treatment gas required for a heat treatment.
- This object is achieved with a method as described at the outset, in addition to which the gas which is blown in in the direction of the cooling zone is blown in at the higher pressure of 1 to 20 bar gauge pressure in the form of one or more blowing jets, and the amount of gas blown in is 5 to 35% of that the low pressure supplied to the furnace, makes up the amount of gas and - solely because of this - a treatment gas flow is produced in the entire furnace either in or against the direction of flow of the workpieces to be treated.
- the proportion of injection of the treatment gas which is blown in at the higher pressure which is preferably only 5 to 20% of the amount of gas supplied at the low pressure, is blown in at an excess pressure of 2 to 6 bar.
- This procedure can be carried out manually or automatically with an electronic control unit.
- a blowing device particularly suitable for carrying out the invention essentially consists of a straight, elongated tube, one end of which is closed except for one or more gas outlet openings with the desired orientation and which can be connected to a treatment gas supply via the other end.
- a straight, elongated tube in contrast to curved or diameter-varying shapes, can simply be inserted into an opening in the furnace wall and mounted therein.
- the tubular injection device is designed to be rotatable about its longitudinal axis at least by 180 ° at least in the region of the gas outlet opening (s).
- FIG. 3 shows a blowing device suitable for carrying out the invention. It essentially consists of a straight tube 15 which is closed on one side and in which at the closed end there is a gas outlet opening 16 with an orientation perpendicular to the tube axis.
- This blowing device can be easily installed through an opening in the furnace wall, for example as shown below in connection with FIGS. 1 and 2.
- FIG. 1 and 2 each show a continuous furnace 1 with inlet zone 2, treatment zone 3, cooling zone 4, furnace inlet 5 and furnace outlet 6.
- Treatment gas is fed to the continuous furnace 1 via the lines 11, 12, 13, 14 and the blowing devices 7, 8, the blowing devices 7 or 7 and 8 being connected to a treatment gas supply via a valve 9 or a three-way valve 10.
- an arrow 17 indicates the direction in which workpieces to be treated cross the continuous furnace.
- treatment gas would be supplied to the furnace via lines 11, 12, 13, 14 in an amount such that an atmosphere of the desired quality would arise in all furnace zones 2, 3, 4. Overall, this would result in a furnace gas flow such that protective or reaction gas introduced into the treatment zone would flow off both to the furnace inlet and to the furnace outlet.
- the shielding gas quantities introduced into the inlet and outlet zones would also leave the furnace through the furnace opening nearby. In this way, one would essentially obtain a two-part flow from the middle of the furnace to the furnace inlet and outlet.
- part of the treatment gas is blown into the cooling zone of the furnace system with the aid of blowing device 7.
- the blowing device 7 is arranged approximately in the central part of the cooling zone 4 and, in the case shown, is aligned against the direction of flow of the objects to be treated.
- Treatment gas is also supplied on both sides of the blowing device 7 with supply lines 13, 14 to the cooling zone 4. Due to the directed blowing with high pressure, i.e. pressure between 1 and 20 bar, preferably between 2 and 6 bar, the gas surrounding the blowing nozzle is entrained and so there is initially a flow in the cooling zone which flows to the treatment zone 3, whereby on Oven outlet 6 even a small proportion of the outside air is sucked in.
- this flow orientation results in a type of stowage area, in which treatment gas flowing out of the treatment zone and flowing with the flow from the cooling zone 4 runs against one another. Overall, this essentially prevents treatment gas from flowing out of the treatment zone 3 into the cooling zone 4. This has the result that excess treatment gas flows out of the treatment zone 3 essentially towards the inlet zone 2, which in turn creates a gas flow there opposite to the direction of flow towards the furnace inlet 5.
- These flow conditions are indicated by the arrows shown in Figure 1.
- a furnace gas flow similar to that described below in connection with FIG. 2, can be generated in the direction of flow of the objects to be treated.
- FIG. 2 shows a continuous furnace 1 with two blowing devices 7, 8 which can be switched alternately via the three-way valve 10 and only one further feed line 14 for treatment gas into the cooling zone 4.
- the blowing device 7 If the blowing device 7 is switched on, a furnace gas flow against the direction of flow is generated in a manner similar to that just described. If a furnace train is to be generated in the direction of flow, treatment gas is blown in the direction of the furnace exit into the cooling zone with the blowing device 8 arranged in the first third of the cooling zone 4 following the treatment zone 3, which in turn applies the entire atmosphere in the cooling zone to this flow direction and wherein in addition - with this arrangement of the injection nozzle 8 - treatment gas is already sucked out of the treatment zone 3.
- the aim with regard to heat treatments under treatment gas is to deliberately avoid the inevitable ingress of air components into the furnace - which is known to be reduced by a high throughput of treatment gas through the furnace to be approved on one side on the side that is harmless to the heat treatment material. This is achieved through the directional flow.
- significant savings in treatment gas are possible compared to the conventional process, since the furnace atmosphere can still be produced in all furnace areas with the necessary purity using a smaller amount of gas. This is an essential effect of the method according to the invention.
- the amount of the injected treatment gas is between 3 and 35%, preferably between 5 and 20%, of the amount that is supplied to the heat treatment device in a conventional manner with the lower pressure.
- An example of a treatment in which the method according to the invention can be used with a furnace train directed against the direction of flow is the annealing of nickel-copper alloys, because the penetration of air, particularly oxygen, into the materials due to the high corrosion resistance of these materials the cooling zone does not deteriorate the annealing result.
- the annealing of steel should be mentioned, in which it is possible to work with a furnace train directed in the direction of travel, since a certain degree of contamination from the air, in particular based on carbon dioxide, is tolerable for steel in the entrance area of the treatment furnace.
- a favorable, practical embodiment of the invention is obtained by two parallel-arranged blowing devices of the type described above, partially aligned with respect to their blow-out direction, as shown in FIG.
- injection devices which are rotatable about their axis
- an oblique injection of treatment gas directed at different angles to the direction of flow is possible.
- the method according to the invention can also be used to influence a flow that occurs from the beginning in a treatment furnace.
- a flow that occurs from the beginning in a treatment furnace For example, in an oven system due to unfavorable drafts in the hall surrounding the oven system, the use of the method according to the invention, even in a controlled version with an oven draft sensor and a correspondingly adjustable injection pressure, is a suitable way of generating a desired oven draft.
- the method according to the invention can be used in many heat treatments in an economically and / or technically advantageous manner.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (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)
- Furnace Details (AREA)
- Heat Treatments In General, Especially Conveying And Cooling (AREA)
- Heat Treatment Of Articles (AREA)
- Tunnel Furnaces (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
Description
Die Erfindung bezieht sich auf ein Verfahren zur Wärmebehandlung von Werkstücken unter Behandlungsgasatmosphäre in einem Durchlaufofen mit Einlauf-, Behandlungs- und Kühlzone, bei dem Behandlungsgas in eine oder mehrere, die Kühlzone umfassende, Ofenzonen mit üblichem, niedrigem Druck zugeführt wird und außerdem ein Teil des Behandlungsgases in der Kühlzone gerichtet und mit einem höheren Druck eingeblasen und damit in Verbindung eine bestimmte Gasströmung im Ofeninnenraum hergestellt wird.The invention relates to a method for the heat treatment of workpieces under a treatment gas atmosphere in a continuous furnace with an inlet, treatment and cooling zone, in which treatment gas is fed into one or more furnace zones comprising the cooling zone with the usual, low pressure and also a part of the Treatment gas directed in the cooling zone and injected at a higher pressure and thus a certain gas flow is produced in the interior of the furnace.
Es sind beispielsweise vielerlei Wärmebehandlungsverfahren für metallische Werkstücke unter verschiedensten Behandlungsgasatmosphären bekannt. Beispiele hierfür sind Aufkohl-, Härte-, Nitrier- und Glühverfahren z.B. unter Endogas, Exogas, Methanol- und Ammoniakspaltgas und Gasen, die verbrauchsfertig geliefert aus Speicherbehältern entnehmbar sind (z.B. Stickstoff, Wasserstoff). Ebenso sind Wärmebehandlungsverfahren unter Behandlungsgas für keramische Werkstücke in Durchlauföfen bekannt, z.B. das Brennen derartiger Werkstücke.For example, a variety of heat treatment processes for metallic workpieces under a wide variety of treatment gas atmospheres are known. Examples of these are carburizing, hardening, nitriding and annealing processes e.g. among endogas, exogas, methanol and ammonia cracked gas and gases that are delivered ready to use and can be removed from storage tanks (e.g. nitrogen, hydrogen). Heat treatment methods under treatment gas for ceramic workpieces in continuous furnaces are also known, e.g. the burning of such workpieces.
Die Behandlungsgasatmosphären lassen sich dabei in Schutzgasatmosphären und Reaktionsgasatmosphären einteilen. Schutzgase haben die Aufgabe, die zu behandelnden Werkstoffe bei der Wärmebehandlung vor unerwünschten Einflüssen zu schützen, z.B. vor Reaktionen mit dem in der Luft enthaltenen Sauerstoff, Kohlendioxid oder Wasserdampf, während mit Reaktionsgasatmosphären gewünschte Reaktionen mit dem zu behandelnden Werkstoff herbeigeführt werden.The treatment gas atmospheres can be divided into protective gas atmospheres and reaction gas atmospheres. Protective gases have the task of protecting the materials to be treated from undesired influences during heat treatment, for example from reactions with the oxygen, carbon dioxide or water vapor contained in the air, while desired reactions with the material to be treated are brought about in reaction gas atmospheres.
Die Behandlungsgase werden bei den heute bekannten Verfahren in der Regel an mehreren Stellen mit geringfügig über dem Atmosphärendruck liegenden Druck (etwa zwischen 0.01 und 0.2 mbar) und niedriger Strömungsgeschwindigkeit in die Wärmebehandlungseinrichtungen bzw. -öfen eingeführt. Dabei werden die Einspeisemengen und die Einspeisestellen so gewählt, daß sich überall in der Einrichtung eine qualitativ für die jeweilige Behandlung ausreichende Behandlungsgasatmosphäre einstellt und Leckverluste ausgeglichen werden. Im Regelfall besteht dabei keine absichtlich gewählte Vorzugsstromrichtung des eingeleiteten Behandlungsgases, sondern es ergibt sich ein Strom, der von der jeweiligen Ofenausgestaltung abhängt, wobei der Strom im wesentlichen von einer oder mehreren Einspeisestellen zu einer oder mehreren Hauptausflußstellen, z.B. dem Ofenein- und -ausgang, verläuft.In the processes known today, the treatment gases are generally introduced into the heat treatment devices or furnaces at a plurality of points with a pressure slightly above atmospheric pressure (approximately between 0.01 and 0.2 mbar) and a low flow rate. The feed quantities and the feed points are selected so that a treatment gas atmosphere which is of sufficient quality for the respective treatment is established throughout the device and leak losses are compensated for. As a rule, there is no deliberately chosen preferred flow direction of the introduced treatment gas, but rather a flow results that depends on the particular furnace design, the flow essentially from one or more feed points to one or more main outflow points, e.g. the furnace entrance and exit.
Andererseits ist z.B. aus der EP-B1 75 438 ein Wärmebehandlungsverfahren für einen Durchlaufofen bekannt, bei dem durch vorhang- oder klappenartige Verschlüsse am Ofenausgang und eine geeignete Einführungsrate des Behandlungsgases in die verschiedenen Ofenbereiche und insbesondere auch in den Kühlzone eine Strömung in Richtung des Ofeneingangs bewirkt wird. In ausgeführten Gestaltungsvarianten dieses Verfahrens wird zudem angeregt, einen Anteil des der Kühlzone zuzuführenden Behandlungsgases mit einem Injektor entsprechend gerichtet in diese einzuführen, und so die gewünschte Strömungsausbildung zu unterstützen. Gemäß der EP-B1 75 438 wird also unter Aufwendung einer Reihe von Maßnahmen ein ganz spezifisches, zum Ofeneintritt hin gerichtetes Gasströmungsmuster in einem Durchlaufofen eingestellt, das vor allem dazu dient, die notwendige Menge an Behandlungsgas für eine Wärmebehandlung zu reduzieren.On the other hand, a heat treatment method for a continuous furnace is known from EP-B1 75 438, for example, in which curtains or flap-like closures at the furnace outlet and a suitable introduction rate of the treatment gas into the various furnace regions and in particular also in the cooling zone cause a flow in the direction of the furnace inlet becomes. In the embodiment variants of this method, it is also suggested that a portion of the treatment gas to be supplied to the cooling zone be introduced into it in an appropriately directed manner, and thus to support the desired flow formation. According to EP-B1 75 438, using a series of measures, a very specific gas flow pattern directed towards the furnace entrance is set in a continuous furnace, which primarily serves to reduce the amount of treatment gas required for a heat treatment.
Grundsätzlich ist es aber wünschenswert, die Gasströmung in einem Durchlaufofen, je nach Anforderung bei der durchzuführenden Behandlung, beeinflussen oder bestimmen zu können. Darin besteht auch die Aufgabenstellung der vorliegenden Erfindung.In principle, however, it is desirable to be able to influence or determine the gas flow in a continuous furnace, depending on the requirements for the treatment to be carried out. This is also the object of the present invention.
Diese Aufgabe wird mit einem wie eingangs beschriebenen Verfahren gelöst, wobei zudem das in der Kühlzone gerichtet eingeblasene Gas mit dem höheren Druck von 1 bis 20 bar Überdruck in Form eines oder mehrerer Blasstrahlen eingeblasen wird und die so eingeblasene Gasmenge 5 bis 35 % der, mit dem niedrigen Druck dem Ofen zugeführten, Gasmenge ausmacht und - allein dadurch - eine Behandlungsgasströmung im gesamten Ofen wahlweise in oder gegen die Durchlaufrichtung der zu behandelnden Werkstücke hergestellt wird.This object is achieved with a method as described at the outset, in addition to which the gas which is blown in in the direction of the cooling zone is blown in at the higher pressure of 1 to 20 bar gauge pressure in the form of one or more blowing jets, and the amount of gas blown in is 5 to 35% of that the low pressure supplied to the furnace, makes up the amount of gas and - solely because of this - a treatment gas flow is produced in the entire furnace either in or against the direction of flow of the workpieces to be treated.
In besonders vorteilhafter Weise wird beim erfindungsgemäßen Verfahren der Einblas-Anteil des mit dem höheren Druck eingeblasenen Behandlungsgases, der vorzugsweise nur 5 bis 20 % der mit dem niedrigen Druck zugeführten Gasmenge beträgt, mit einem Überdruck von 2 bis 6 bar eingeblasen.In a particularly advantageous manner, in the method according to the invention, the proportion of injection of the treatment gas which is blown in at the higher pressure, which is preferably only 5 to 20% of the amount of gas supplied at the low pressure, is blown in at an excess pressure of 2 to 6 bar.
Diese Drucke sind einerseits problemlos verfügbar und andrerseits zur Erzeugung der gewünschten Strömungen geeignet.On the one hand, these prints are readily available and, on the other hand, they are suitable for generating the desired flows.
Besonders vorteilhaft wird das erfindungsgemäße Verfahren derart ausgestaltet, daß die Behandlungsgasströmung (= Ofenzug) mit einem Ofenzugsensor gemessen und der Einblasdruck des Behandlungsgases entsprechend diesem Meßwert und dem gewünschten Ofenzug eingestellt wird. Diese Vorgehensweise kann manuell oder in automtischer Weise mit einer elektronischen Regeleinheit ausgeführt werden.The method according to the invention is particularly advantageously designed such that the treatment gas flow (= furnace draft) is measured with a furnace draft sensor and the injection pressure of the treatment gas is adjusted in accordance with this measured value and the desired furnace draft. This procedure can be carried out manually or automatically with an electronic control unit.
Eine zur Ausführung der Erfindung besonders geeignete Einblasvorrichtung besteht im wesentlichen aus einer geraden, länglichen Röhre, deren eines Ende bis auf eine oder mehrere Gasauslaßöffnungen mit gewünschter Ausrichtung verschlossen ist und die über das andere Ende mit einer Behandlungsgasversorgung verbindbar ist.A blowing device particularly suitable for carrying out the invention essentially consists of a straight, elongated tube, one end of which is closed except for one or more gas outlet openings with the desired orientation and which can be connected to a treatment gas supply via the other end.
Eine gerade, längliche Röhre kann im Gegensatz zu krummen oder im Durchmesser variierenden Formen einfach in eine in der Ofenwand angebrachte Öffnung eingeführt und darin montiert werden.A straight, elongated tube, in contrast to curved or diameter-varying shapes, can simply be inserted into an opening in the furnace wall and mounted therein.
In einer vorteilhaften Ausgestaltung ist die rohrartige Einblasvorrichtung zumindest im Bereich der Gasauslaßöffnung(en) um ihre Längsachse mindestens um 180 ° drehbar ausgestaltet. Dadurch kann mit einer Einblasvorrichtung eine Strömung in oder eine Strömung gegen die Durchlaufrichtung in einem Durchlaufofen erzeugt werden.In an advantageous embodiment, the tubular injection device is designed to be rotatable about its longitudinal axis at least by 180 ° at least in the region of the gas outlet opening (s). As a result, a flow into or a flow against the direction of flow can be generated in a continuous furnace using a blowing device.
Anhand der folgenden schematischen Zeichnungen soll das erfindungsgemäße Verfahren mit dazugehörigen Vorrichtungen beispielhaft näher erläutert und eine geeignete Einblasvorrichtung genauer beschrieben werden.On the basis of the following schematic drawings, the method according to the invention with associated devices will be explained in more detail by way of example and a suitable blowing device will be described in more detail.
Es zeigen:
Figur 1- einen Durchlaufofen mit einer in der Kühlzone angebrachten Einblasvorrichtung,
Figur 2- einen Durchlaufofen mit zwei Einblasvorrichtungen in der Kühlzone,
Figur 3- eine Einblasvorrichtung,
- Figur 4:
- eine günstige Anordnung zweier drehbarer Einblasvorrichtungen.
- Figure 1
- a continuous furnace with a blowing device installed in the cooling zone,
- Figure 2
- a continuous furnace with two blowing devices in the cooling zone,
- Figure 3
- a blowing device,
- Figure 4:
- a favorable arrangement of two rotatable blowing devices.
Figur 3 zeigt eine zur Durchführung der Erfindung geeignete Einblasvorrichtung. Sie besteht im wesentlichen aus einer geraden, einseitig verschlossenen Röhre 15, bei der sich am verschlossenen Ende am Umfang eine Gasauslaß-Öffnung 16 mit zur Rohrachse senkrechter Ausrichtung befindet. Diese Einblasvorrichtung kann durch eine Öffnung in der Ofenwand einfach installiert werden, beispielsweise wie im folgenden in Zusammenhang mit Figuren 1 und 2 gezeigt.FIG. 3 shows a blowing device suitable for carrying out the invention. It essentially consists of a
In den Figuren 1 und 2 ist jeweils ein Durchaufofen 1 mit Einlaufzone 2, Behandlungszone 3, Kühlzone 4, Ofeneingang 5 und Ofenausgang 6 gezeigt. Behandlungsgas wird dem Durchlaufofen 1 über die Leitungen 11, 12, 13, 14 und die Einblasvorrichtungen 7, 8 zugeführt, wobei die Einblasvorrichtungen 7 bzw. 7 und 8 über ein Ventil 9 bzw. über ein Dreiwegeventil 10 mit einer Behandlungsgasversorgung verbunden sind. Ein Pfeil 17 gibt schließlich die Richtung an, in der zu behandelnde Werkstücke den Durchlaufofen durchqueren.1 and 2 each show a
Würde der gezeigte Durchlaufofen 1 in konventioneller Weise betrieben, so würde dem Ofen über die Leitungen 11, 12, 13, 14 Behandlungsgas in einer Menge zugeführt, daß sich in allen Ofenzonen 2, 3, 4 eine Atmosphäre gewünschter Qualität einstellen würde. Insgesamt ergäbe sich dabei etwa eine Ofengasströmung derart, daß in die Behandlungszone eingeführtes Schutz- oder auch Reaktionsgas sowohl zum Ofeneingang als auch zum Ofenausgang hin abfließen würde. Die in die Einlaufzone und Auslaufzone eingeführten Schutzgasmengen würden den Ofen dabei ebenfalls über die jeweils in der Nähe liegende Ofenöffnung verlassen. Man erhielte so also insgesamt im wesentlichen eine zweigeteilte Strömung von der Ofenmitte hin zum Ofenein- und -ausgang.If the
Erfindungsgemäß dagegen, wird, wie beispielsweise in Figur 1 gezeigt, ein Teil des Behandlungsgases mit Hilfe von Einblasvorrichtung 7 in die Kühlzone der Ofenanlage gerichtet eingeblasen. Die Einblasvorrichtung 7 ist etwa im mittleren Teil der Kühlzone 4 angeordnet und im gezeichneten Fall gegen die Durchlaufrichtung der zu behandelnden Gegenstände ausgerichtet. Behandlungsgas wird außerdem beidseitig der Einblasvorrichtung 7 mit Zufuhrleitungen 13, 14 der Kühlzone 4 zugeführt. Durch das gerichtete Einblasen mit hohem Druck, also Drucken zwischen 1 und 20 bar, vorzugsweise zwischen 2 und 6 bar, wird das die Einblasdüse umgebende Gas mitgerissen und es ergibt sich so zunächst in der Kühlzone eine Strömung die zur Behandlungszone 3 hin fließt, wobei am Ofenausgang 6 sogar ein geringer Anteil der außen anliegenden Luft eingesaugt wird. Zur Behandlungszone hin ergibt sich durch diese Strömungsausrichtung eine Art Staubereich, in dem aus der Behandlungszone ausfließendes und mit der Strömung aus der Kühlzone 4 fließendes Behandlungsgas gegeneinander anlaufen. Ingesamt wird dadurch im wesentlichen ein Ausfließen von Behandlungsgas aus der Behandlungszone 3 in die Kühlzone 4 verhindert. Dies hat zur Folge, daß Überschußbehandlungsgas aus der Behandlungszone 3 im wesentlichen zur Einlaufzone 2 hin abfließt, wodurch dort wiederum eine Gasströmung entgegengesetzt zur Durchlaufrichtung hin zum Ofeneingang 5 entsteht. Diese Strömungsverhältnisse sind durch die in Figur 1 dargestellten Pfeile angedeutet.In contrast, according to the invention, as shown in FIG. 1, for example, part of the treatment gas is blown into the cooling zone of the furnace system with the aid of blowing
Durch Drehen der Einblasvorrichtung um 180 ° kann dagegen eine Ofengasströmung, ähnlich wie im folgenden in Zusammenhang mit Figur 2 beschrieben, in Durchlaufrichtung der zu behandelnden Gegenstände erzeugt werden.By rotating the blowing device through 180 °, on the other hand, a furnace gas flow, similar to that described below in connection with FIG. 2, can be generated in the direction of flow of the objects to be treated.
In Figur 2 ist ein Durchlaufofen 1 mit zwei über das Dreiwegeventil 10 wechselweise schaltbaren Einblasvorrichtungen 7, 8 und nur einer weiteren Zufuhrleitung 14 für Behandlungsgas in die Kühlzone 4 dargestellt. Ist die Einblasvorrichtung 7 ein geschaltet, wird eine Ofengasströmung gegen die Durchlaufrichtung ähnlich wie eben beschrieben erzeugt. Soll ein Ofenzug in Durchlaufrichtung erzeugt werden, wird mit der im ersten Drittel der Kühlzone 4 im Anschluß an die Behandlungszone 3 angeordneten Einblasvorrichtung 8 Behandlungsgas in Richtung des Ofenausganges in die Kühlzone eingeblasen, wodurch wiederum die gesamte Atmosphäre in der Kühlzone mit dieser Strömungsrichtung beaufschlagt wird und wobei darüber hinaus - bei dieser Anordnung der Einblasdüse 8 - bereits Behandlungsgas aus der Behandlungszone 3 angesaugt wird. Daraus ergibt sich ein bevorzugtes Ausströmen des überschüssigen Behandlungsgases aus der Behandlungszone in die Kühlzone, während praktisch kein Behandlungsgas aus der Behandlungszone in die Einlaufzone 2 fließt und sogar das der Einlaufzone zugeführte Behandlungsgas eine überwiegende Strömung in die Behandlungszone hinein erhält. Wiederum sind die Strömungsverhältnisse in dieser Betriebssituation in der Figur durch Pfeile angedeutet.FIG. 2 shows a
Insgesamt ist festzustellen, daß je nach Ausrichtung der Einblasvorrichtung eine in die entsprechende Richtung stabile Ofenströmung erzeugt werden kann. Zielrichtung dabei im Hinblick auf Wärmebehandlungen unter Behandlungsgas ist, den grundsätzlich nicht zu vermeidenden Einbruch von Luftbestandteilen in den Ofen - der bekanntermaßen durch einen hohen Durchsatz von Behandlungsgas durch den Ofen verringert werden kann - absichtlich einseitig auf der für das Wärmebehandlungsgut unschädlicheren Seite zuzulassen. Dies wird durch die gerichtete Strömung erreicht. Damit einhergehend sind wesentliche Einsparungen an Behandlungsgas im Vergleich zum konventionellen Verfahren möglich, da mit geringerer Gasmenge trotzdem in allen Ofenbereichen die Ofenatmosphäre in notwendiger Reinheit hergestellt werden kann. Dies ist einen wesentlicher Effekt des erfindungsgemäßen Verfahrens. Die Menge des eingeblasenen Behandlungsgases liegt dabei zwischen 3 und 35 %, vorzugsweise zwischen 5 und 20 %, der Menge, die der Wärmebehandlungseinrichtung auf konventionelle Art mit dem niedrigeren Druck zugeführt wird.Overall, it should be noted that, depending on the orientation of the blowing device, a stable furnace flow can be generated in the corresponding direction. The aim with regard to heat treatments under treatment gas is to deliberately avoid the inevitable ingress of air components into the furnace - which is known to be reduced by a high throughput of treatment gas through the furnace to be approved on one side on the side that is harmless to the heat treatment material. This is achieved through the directional flow. Along with this, significant savings in treatment gas are possible compared to the conventional process, since the furnace atmosphere can still be produced in all furnace areas with the necessary purity using a smaller amount of gas. This is an essential effect of the method according to the invention. The amount of the injected treatment gas is between 3 and 35%, preferably between 5 and 20%, of the amount that is supplied to the heat treatment device in a conventional manner with the lower pressure.
Als Beispiel für eine Behandlung, bei dem das erfindungsgemäße Verfahren mit einem gegen die Durchlaufrichtung gerichteten Ofenzug angewendet werden kann, ist das Glühen von Nickel-Kupfer-Legierungen zu nennen, da wegen der hohen Korrosionsbeständigkeit dieser Werkstoffe das Eindringen von Luftanteilen, insbesondere Sauerstoff, in die Kühlzone zu keiner Verschlechterung des Glühergebnisses führt.An example of a treatment in which the method according to the invention can be used with a furnace train directed against the direction of flow is the annealing of nickel-copper alloys, because the penetration of air, particularly oxygen, into the materials due to the high corrosion resistance of these materials the cooling zone does not deteriorate the annealing result.
Als weiteres Beispiel sei das Glühen von Stahl erwähnt, bei dem mit einem in Durchlaufrichtung gerichteten Ofenzug gearbeitet werden kann, da für Stahl im Eingangsbereich des Behandlungsofen ein gewisses Maß an Verunreinigungen aus der Luft, insbesondere bezogen auf Kohlendioxid, tolerierbar ist.As a further example, the annealing of steel should be mentioned, in which it is possible to work with a furnace train directed in the direction of travel, since a certain degree of contamination from the air, in particular based on carbon dioxide, is tolerable for steel in the entrance area of the treatment furnace.
Eine günstige, praktische Ausgestaltung der Erfindung erhält man durch zwei parallel angeordnete, bezüglich ihrer Ausblasrichtung teilweise gegeneinander ausgerichtete Einblasvorrichtungen der obenbeschriebenen Bauart, wie sie in Figur 4 gezeigt ist. Mit dieser Anordnung von Einblasvorrichtungen, die um ihre Achse drehbar sind, ist ein schräges, in verschiedenen Winkeln zur Durchlaufrichtung gerichtetes Einblasen von Behandlungsgas möglich. Durch geeignet koordinierte, insbesondere in gleicher Schräge bezüglich der Durchlaufrichtung ausgerichtete Orientierung der beiden Einblasvorrichtungen sind so ebenfalls Strömungen in oder gegen die Durchlaufrichtung in sehr effizienter Weise erzeugbar.A favorable, practical embodiment of the invention is obtained by two parallel-arranged blowing devices of the type described above, partially aligned with respect to their blow-out direction, as shown in FIG. With this arrangement of injection devices, which are rotatable about their axis, an oblique injection of treatment gas directed at different angles to the direction of flow is possible. By suitably coordinated orientation of the two blowing devices, in particular oriented in the same incline with respect to the direction of flow, flows in or against the direction of flow can also be generated in a very efficient manner.
Mit dem erfindungsgemäßen Verfahren kann schließlich auch Einfluß auf eine in einem Behandlungsofen von vorne herein auftretende Strömung genommen werden. Herrscht z.B. in einer Ofenanlage aufgrund ungünstiger Luftzugverhältnisse in der die Ofenanlage umgebenden Halle eine unerwünschte Strömung, so ist die Anwendung des erfindungsgemäßen Verfahrens möglicherweise sogar in geregelter Version mit Ofenzugsensor und entsprechend regelbarem Einblasdruck eine geeignete Möglichkeit, einen gewünschten Ofenzug zu erzeugen.Finally, the method according to the invention can also be used to influence a flow that occurs from the beginning in a treatment furnace. For example, in an oven system due to unfavorable drafts in the hall surrounding the oven system, the use of the method according to the invention, even in a controlled version with an oven draft sensor and a correspondingly adjustable injection pressure, is a suitable way of generating a desired oven draft.
Zusammenfassend kann festgestellt werden, daß das erfindungsgemäße Verfahren bei vielen Wärmebehandlungen in ökonomisch und/oder produktionstechnisch vorteilhafter Weise eingesetzt werden kann.In summary, it can be stated that the method according to the invention can be used in many heat treatments in an economically and / or technically advantageous manner.
Claims (5)
- A process for the thermal treatment of workpieces in a treatment gas atmosphere in a continuous furnace with an inlet zone, treatment zone and cooling zone, wherein treatment gas is supplied at a normal, low pressure into one or more furnace zones including the cooling zone and additionally a part of the treatment gas is blown into the cooling zone directionally and at a higher pressure and in association therewith a specified gas flow is established in the interior of the furnace, wherein the quantity of gas blown into the cooling zone directionally and at the higher pressure of 1 to 20 bar excess pressure in the form of one or more blow jets amounts to 5 to 35% of the quantity of gas supplied to the furnace at the low pressure, and solely by this means a treatment gas flow is established in the entire furnace optionally in or opposed to the direction of passage of the workpieces to be treated.
- A process as claimed in Claim 1, characterised in that 5 to 20% of the quantity of gas supplied at the low pressure is blown in at the higher pressure.
- A process as claimed in one of Claims 1 or 2, characterised in that the proportion of the treatment gas blown in at the higher pressure is blown in at an excess pressure of 2 to 6 bar.
- A process as claimed in one of Claims 1 to 3, characterised in that the treatment gas flow is measured by a furnace draught sensor and the blow-in pressure is adjusted in accordance with this measured value and the desired furnace draught.
- A process as claimed in one of Claims 1 to 4, characterised in that in the case of a plurality of independent blow jets, the blow-in treatment gas is blown-in in coordination but obliquely to the direction of passage whereby the desired gas flow is established in or opposed to the direction of passage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT89114350T ATE104360T1 (en) | 1988-08-18 | 1989-08-03 | METHODS OF HEAT TREATMENT OF WORKPIECES. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3828134A DE3828134A1 (en) | 1988-08-18 | 1988-08-18 | METHOD FOR THE HEAT TREATMENT OF WORKPIECES |
| DE3828134 | 1988-08-18 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0355520A2 EP0355520A2 (en) | 1990-02-28 |
| EP0355520A3 EP0355520A3 (en) | 1990-04-18 |
| EP0355520B1 true EP0355520B1 (en) | 1994-04-13 |
Family
ID=6361156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP89114350A Expired - Lifetime EP0355520B1 (en) | 1988-08-18 | 1989-08-03 | Method of heat treating workpieces |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0355520B1 (en) |
| AT (1) | ATE104360T1 (en) |
| DE (2) | DE3828134A1 (en) |
| ZA (1) | ZA896284B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4121277C2 (en) * | 1991-06-27 | 2000-08-03 | Ald Vacuum Techn Ag | Device and method for the automatic monitoring of operational safety and for controlling the process sequence in a vacuum heat treatment furnace |
| DE69918548T2 (en) * | 1999-08-18 | 2005-08-25 | Patherm SA. | Apparatus for continuous heat treatment of metallic workpieces, individually or in groups |
| DE10347312B3 (en) * | 2003-10-08 | 2005-04-14 | Air Liquide Deutschland Gmbh | Process for the heat treatment of iron materials |
| PL1842931T3 (en) * | 2006-04-04 | 2014-07-31 | Linde Ag | Method for heat treatment |
| DE102006015739A1 (en) * | 2006-04-04 | 2007-10-11 | Linde Ag | Process for heat treatment |
| BRPI0702253B1 (en) | 2006-04-04 | 2020-02-04 | Linde Ag | heat treatment process of parts in a heat treatment oven |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE617319C (en) * | 1931-05-02 | 1935-08-16 | Benno Schilde Maschb Akt Ges | Procedure and device for bright annealing |
| US3415503A (en) * | 1967-08-18 | 1968-12-10 | Btu Eng Corp | Conditioned atmosphere furnace muffle |
| DE2601658C3 (en) * | 1976-01-17 | 1978-11-30 | Fa. J.F. Mahler, 7300 Esslingen | Cooling device for a continuous furnace open on the inlet and outlet side for the heat treatment of workpieces |
| DE2844843C2 (en) * | 1978-10-14 | 1985-09-12 | Ipsen Industries International Gmbh, 4190 Kleve | Industrial furnace for the heat treatment of metallic workpieces |
| JPS57192215A (en) * | 1981-05-21 | 1982-11-26 | Ishikawajima Harima Heavy Ind Co Ltd | Metal-heating oven |
| GB2108156B (en) * | 1981-09-19 | 1986-01-15 | British Oxygen Co Ltd | Heat treatment of metals |
| DE3208574A1 (en) * | 1982-03-10 | 1983-09-22 | Schmetz Industrieofenbau und Vakuum-Hartlöttechnik KG, 5750 Menden | Vacuum shaft furnace |
| DE3736501C1 (en) * | 1987-10-28 | 1988-06-09 | Degussa | Process for the heat treatment of metallic workpieces |
-
1988
- 1988-08-18 DE DE3828134A patent/DE3828134A1/en not_active Ceased
-
1989
- 1989-08-03 DE DE58907441T patent/DE58907441D1/en not_active Expired - Fee Related
- 1989-08-03 EP EP89114350A patent/EP0355520B1/en not_active Expired - Lifetime
- 1989-08-03 AT AT89114350T patent/ATE104360T1/en not_active IP Right Cessation
- 1989-08-17 ZA ZA896284A patent/ZA896284B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0355520A3 (en) | 1990-04-18 |
| ZA896284B (en) | 1990-04-25 |
| ATE104360T1 (en) | 1994-04-15 |
| EP0355520A2 (en) | 1990-02-28 |
| DE58907441D1 (en) | 1994-05-19 |
| DE3828134A1 (en) | 1990-02-22 |
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