EP0151700A2 - Industrial furnace, especially a multiple chamber vacuum furnace, for heat treating batches of metal workpieces - Google Patents

Abstract

An industrial furnace for heat-treating metallic workpieces has separate heating and cooling chambers. The latter uses a circulating cooling gas, the flow of which against or past the workpieces produces cooling or gas-quenching. The furnace may have another chamber for oil-quenching lying below the gas-cooling chamber. In order to enable the gas cooling to operate quickly and efficiently, a cooling box fed with air by ventilator fans is provided in the shape of a tunnel, with internal surfaces above and at both sides of the effective cooling space constituted by interchangeable nozzle plates (or blank plates if no nozzle openings are desired at the top or at the sides). The workpieces to be cooled rest on a platform which may be raised or lowered to adjust the distance from the top nozzle plate or lowered into an oil bath. The nozzle plates provide a choice of nozzle patterns for different articles or groups of articles to be cooled after heat treatment. The nozzle plates may have setbacks or protrusions in order to vary the spacing of the nozzle openings from the median plane of the cooling tunnel.

Description

The invention relates to an industrial furnace, in particular a multi-chamber vacuum furnace for the heat treatment of batches of metallic workpieces, with a heating chamber and a cooling chamber containing a cooling device acted upon with cooling gas, in which a heat-treated batch is flowed with cooling gas which is circulated via a heat exchanger, and optionally with a oil bath.

Industrial furnaces of this type are used to a large extent for hardening steel parts, in particular all types of parts made of tool steels, as well as for various cooling processes and other heat treatments of metal parts. An example of such an industrial furnace is described in DE-OS 26 08 850.

This three-chamber vacuum furnace, surrounded by a water-cooled, double-walled housing, has a heating chamber and two adjoining cooling chambers, one of which contains cooling means that act with cooling gas, while the other works with a quenching oil bath. The cooler direction in the first-mentioned cooling chamber has a cooling gas circulating device containing a fan, through which the circuit circulates via an outside of the housing arranged heat exchanger guided cooling gas, possibly with the aid of gas baffles, is moved around the heat-treated batch located in the cooling chamber in order to achieve rapid cooling of the batch. The gas circulation in the cooling chamber means that large amounts of gas have to be transported because of the relatively large gas passage cross sections and to generate the high speed of the cooling gas on the batch required for the rapid cooling of the batch already in the feed line between the fan and the batch as well high cooling gas velocities can be maintained in the return line from the batch to the heat exchanger and the fan, with the result that considerable pressure losses have to be accepted in the entire cooling gas circuit. These pressure losses either result in an increased power requirement of the fan drive, or else they result in an undesired reduction in the cooling gas speed prevailing in the area of the batch, given the drive power of the fan.

It is known that the cooling gas velocity required on the batch can be achieved with significantly lower amounts of cooling gas if the cooling gas comes into effect via nozzles which produce cooling air jets blowing on the batch. However, this gas cooling via nozzles harbors the risk of uneven cooling results within the batch. This was remedied in a single-chamber vacuum furnace with gas cooling device _L i, as described in AT-PS 370 869 tries to have the nozzles in the heating chamber mounted on gas supply pipes which are arranged parallel to the furnace axis and can be rotated about their axis. The one ends of the gas supply pipes protrude from the heating chamber, wherein they are connected to a fixed gas supply system via flexible hoses and connected to a drive for the pivoting movement.

In addition to the considerable design effort that the pivotably mounted gas supply pipes with their associated flexible connection devices and their drives require, this nozzle cooling device can only be adjusted to different batches to a limited extent. The charge can basically only be blown from opposite sides, because the cooling gas supply and drive devices are accommodated on the top of the heating channel. The blowing conditions required to achieve optimal cooling, however, vary depending on the particular shape and composition of the batch. It makes a difference whether a batch of cylindrical, standing parts or a batch consisting of one or more plate-shaped workpieces has to be cooled.

The object of the invention is therefore to provide an industrial furnace, in particular a multi-chamber To create a vacuum furnace with a cooling chamber containing a gas cooling device, in which an optimal adaptation of the flow conditions of the respective batch to be cooled to the conditions of this batch is possible with simple means, without the need for complex, expensive or difficult to operate facilities.

To achieve this object, the industrial furnace mentioned at the outset is characterized according to the invention in that the cooling device has nozzles which open into the cooling chamber and blow the batch with cooling gas, and that the nozzles which are arranged in a fixed manner in the cooling chamber are arranged interchangeably with changes in the blowing conditions of the batch.

In a preferred embodiment, the nozzles are designed to be interchangeable in groups, changing the nozzle arrangement (nozzle pattern) and / or the nozzle diameter and / or the nozzle spacing.

The new industrial furnace only allows high cooling gas speeds to be generated in the cooling chamber by appropriate selection of the nozzle arrangement, distribution and other characteristics on or within the batch to be cooled, where maximum cooling effect is required.

In this context, it is advisable if the distance of at least some nozzles from the batch is adjustable, as is also advantageous if at least some nozzles are arranged in an orientation resulting in an impingement flow and / or a parallel flow of the cooling gas on the batch. For a given cooling gas circulation capacity, the maximum cooling speed of the batch depends on the heat transfer values achieved. It is known that the gas inflow of the batch has a decisive influence on the degree of heat transfer cooling ^q as / Charne, with higher heat transfer values being achieved with impingement flow than with parallel flow, in which the cooling gas flows parallel to the workpiece surface. Other parameters for heat transfer include nozzle exit speed, nozzle diameter, nozzle distance from the batch, distance between the nozzles, average cooling gas temperatures and average batch temperatures.

The nozzles are advantageously arranged surrounding the batch on several sides in the cooling chamber, whereby particularly simple structural conditions result if the cooling device has a nozzle box arranged in the cooling chamber and loaded with cooling gas, in which at least one nozzle plate arranged opposite the batch is detachably inserted is. For this purpose, the nozzle box can have guide devices into which the nozzle plate can be inserted.

By simply exchanging the nozzle plates the above-described adaptation of the cooling device to the mentioned parameters for heat transfer can be achieved in a very simple manner. The individual, interchangeable nozzle plates can not only have different nozzle arrangements (nozzle patterns) and nozzle diameters etc., but it can also have, for example, a nozzle plate projecting into or out of the interior of the cooling chamber so that the distance between the nozzles and to change the batch according to the respective circumstances.

As a rule, the heat-treated batch will be surrounded by nozzles on several sides, for which purpose the nozzle box is expediently tunnel-shaped and is delimited on its inner wall by nozzle plates. At least one such nozzle plate can also be replaced by a gas-impermeable plate. In this way, an effective impingement flow can be achieved with plate-shaped workpieces by inserting nozzle plates laterally and a blind plate above the batch, so that the stationary workpiece can be optimally cooled from all sides. With a batch of cylindrical stationary tools, only parallel flow can be used as through-flow cooling, because cooling by means of impingement cooling is not possible due to the shape of the workpiece and the large number of workpieces. A nozzle plate are above these Durchströmkühlung and _B lindbleche to the inserted on both sides of the batch. The nozzle distance from the batch can then be optimized on each side by means of the nozzle plates already mentioned, with an area projecting into or out of the interior of the cooling chamber.

In order to be able to carry out the aforementioned arrangement of the nozzle plates in a simple manner, it is advantageous if the nozzle box is delimited on at least three inner sides by nozzle plates, two of which are arranged opposite one another and the third nozzle plate is arranged between the two other nozzle plates.

In the cooling chamber, a lifting or lowering device receiving the batch can also be provided, by means of which the batch can be brought at a predetermined distance from at least some of the nozzle orifices.

The nozzle box itself is expediently connected to the pressure side of at least one fan of a gas circulation device containing the heat exchanger. If the cooling chamber with the heating chamber is arranged in a common housing, the fan or the fans can be arranged on the housing radially at the front region of the cooling chamber.

Characterized in that in the nozzle box the nozzle plates are uniformly acted upon by cooling gas, there is an equal exit velocity at all nozzles of the respective nozzle plate, and thus ensures a uniform cooling effect on the entire loaded batch area. Such a uniform cooling effect is important for achieving a desired structural state in the batch to be cooled.

The cooling device is in the new ^p- Industri arranged not oven in the heating chamber, but in a separate cooling chamber. The cold batch environment in the cooling chamber not only exploits the convective heat transfer from the batch to the cooling gas, but also the heat dissipation by radiation, which helps in the upper temperature range in particular to increase the cooling effect. Compared to single-chamber vacuum furnaces there is the advantage that the heating chamber, the heating elements and the Char ^g enherd after the heat treatment in the critical cooling zone does not have to be cooled down together with the batch, so that the cooling performance achieved at the charge not by the discharge of the stored heat of the heating chamber is diminished. The cooling chamber separate from the heating chamber enables the described adaptability of the nozzle cooling device to the conditions of the respective batch, while on the other hand the heating chamber can be designed for optimum heating conditions regardless of the cooling of the batch required after the heat treatment.

• Fi^g. 1 einen Doppelkammer-Vakuumofen gemäß der Erfindung, im axialen Schnitt, in einer Seitenansicht,
• Fig. 2 den Doppelkammer-Vakuumofen nach Fig. 1, geschnitten längs der Linie II-II der Fig. 1, in einer Seitenansicht,
• Fig. 3 den Doppelkammer-Vakuumofen nach Fig. 1, geschnitten längs der Linie III-III der Fig. 1, in einer Seitenansicht,
• Fig. 4 den Doppelkammer-Vakuumofen nach Fig. 1, geschnitten längs der Linie IV-IV der Fig. 1, in einer Seitenansicht,
• Fig. 5 den Düsenkasten des Doppelkammer-Vakuumofens nach Fig. 3, in einer schematischen Seitenansicht, im Querschnitt, in einem anderen Maßstab, unter Veranschaulichung einer bestimmten Charge und einer bestimmten Düsenanordnung,
• Fig. 6 das an der oberhalb der Charge angeordnete Düsenblech der Anordnung nach Fig. 5, in einer Draufsicht,
• Fig. 7 den Düsenkasten nach Fig. 5, mit einer anderen Anordnung der Düsenbleche, in einer entsprechenden Darstellung,
• Fig. 8.ein oberhalb der Charge angeordnetes Düsenblech der Anordnung nach Fig. 7, in einer Draufsicht,
• Fig. 9 den Düsenkasten nach Fig. 7, in einer entsprechenden Darstellung,
• Fig.10 ein seitlich der Charge angeordnetes Düsenblech der Anordnung nach Fig. 9, in einer Draufsicht,
• Fig.11 den Düsenkasten nach Fig. 5, mit einer anderen Anordnung der Düsenbleche, in einer entsprechenden Darstellung,
• Fig.12 ein oberhalb der Charge angeordnetes Düsenblech der Anordnung nach Fig. 11, in einer Draufsicht,
• Fig.13 den Düsenkasten nach Fig. 5, beschickt mit einer anderen Charge, in einer entsprechenden Darstellung,
• Fig.14 einseitlich der Charge angeordnetes Düsenblech der Anordnung nach Fig. 13, in einer Draufsicht,
• Fig.15 den Düsenkasten nach Fig. 5, beschickt mit einer anderen Charge, in einer entsprechenden Darstellung,
• Fig.16.ein seitlich der Chargerangeordnetes Düsenblech der Anordnung nach Fig. 15, in einer Draufsicht,
• Fig.17 den Düsenkasten nach Fig. 5, mit einer anderen Anordnung der Düsenbleche, in einer entsprechenden Darstellung, und
• Fig. 18 das oberhalb der Charge angeordnete Düsenblech der Anordnung nach Fig.17 in einer Draufsicht.

In the drawing, an embodiment of the object of the invention is shown. Show it:

• Fi ^g . 1 shows a double-chamber vacuum furnace according to the invention, in axial section, in a side view,
• 2 shows the double-chamber vacuum furnace according to FIG. 1, cut along the line II-II of FIG. 1, in a side view,
• 3 shows the double-chamber vacuum furnace according to FIG. 1, cut along the line III-III of FIG. 1, in a side view,
• 4 shows the double-chamber vacuum furnace according to FIG. 1, cut along the line IV-IV of FIG. 1, in a side view,
• 5 shows the nozzle box of the double-chamber vacuum furnace according to FIG. 3, in a schematic side view, in cross section, on a different scale, illustrating a specific batch and a specific nozzle arrangement,
• 6 is a top view of the nozzle plate of the arrangement according to FIG. 5 arranged above the batch,
• 7, the nozzle box according to FIG. 5, with a different arrangement of the nozzle plates, in a corresponding representation,
• 8 shows a top view of a nozzle plate of the arrangement according to FIG. 7 arranged above the batch,
• 9, the nozzle box according to FIG. 7, in a corresponding representation,
• 10 shows a top view of a nozzle plate of the arrangement according to FIG. 9 arranged on the side of the charge,
• 11, the nozzle box according to FIG. 5, with a different arrangement of the nozzle plates, in a corresponding representation,
• 12 shows a top view of a nozzle plate of the arrangement according to FIG. 11,
• Fig. 13 the nozzle box according to Fig. 5, loaded with another batch, in a corresponding representation,
• 14 a nozzle plate of the arrangement according to FIG. 13 arranged on one side of the batch, in a top view,
• 15 shows the nozzle box according to FIG. 5, loaded with another batch, in a corresponding representation,
• 16 shows a top view of a nozzle plate of the arrangement according to FIG. 15 arranged on the side of the charger,
• Fig.17 the nozzle box according to Fig. 5, with a different arrangement of the nozzle plates, in a corresponding representation, and
• 18 shows a top view of the nozzle plate of the arrangement according to FIG. 17 arranged above the batch.

The double-chamber vacuum furnace shown in FIGS. 1 to 4 has a double-walled, water-cooled housing 1, in the rear part of which a heating chamber 2 and in the front part of which a cooling chamber 3 are accommodated. The essentially cylindrical housing 1 is closed on the front by a water-cooled double jacket door 4 which serves to load and unload the furnace, and which can be pivoted or pushed. On the rear side in the area behind the heating chamber 2, a double-walled swing door 5 is provided, which closes a housing opening available for assembly purposes. To the overall ^- housing 1 a double-walled, water-cooled vessel 6 on which is flanged to the housing 1 and an oil bath is in the, whose level is indicated at 7 closes below the cooling chamber. 3

In the front part of the cooling chamber 3, the housing 1 carries three radially projecting flanges 8 distributed around its circumference in the manner shown in FIG. 2, onto which double-walled, water-cooled hoods 9 are placed, each of which covers a fan drive unit 10 .

The heating chamber 2, which is essentially rectangular in cross section, is constructed in a lightweight steel construction and is lined with a multi-layer insulation made of high-quality ceramic fiber material and the purest graphite felt. On both sides and above the batch indicated at 11 large-area graphite heating elements 12 are arranged. This all-round arrangement of the graphite heating elements 12 ensures rapid and uniform heating of the batch 11. The current supply of the graphite heating elements 11 takes place via heating element connecting bolts 13 and one heating element connecting flange 14 in each case.

The batch 11 is located in the heating chamber 2 on a stove 15 which is designed to be raised and lowered for transport purposes. The end wall of the heating chamber 2 adjoining the cooling chamber 3 is closed by a horizontally movable heating chamber door 16.

Otherwise, the heating chamber 2 is optimally designed for the lowest possible storage heat and for heat treatment according to a preselected temperature program. Compared to single-chamber furnaces, neither the cooling gas flow and cooling gas speed nor other parameters for heat dissipation from the batch need to be taken into account.

The cooling chamber 3, which is arranged approximately coaxially to the heating chamber 2, contains a cooling device 17 which has a nozzle box 18 which is tunnel-shaped with an essentially U-shaped cross section and a heat-treated batch 11a to be cooled in the manner shown in FIG. 3 above and covering on both sides. The nozzle box 18 carries on the open inner sides pointing towards the batch 11a, paired side guide grooves 19, into the nozzle plates. 20, 20a or blind plates' 2 _{1 are} optionally interchangeably inserted, as will be explained with reference to FIGS. 5 to 18.

At its front end, the nozzle box 18 is directly connected to three fan housings 22, each of which contains a high-performance fan wheel 23 which sits directly on the shaft end of the associated drive motor 10, the vacuum-tight current feedthroughs of which are indicated at 24. The suction opening of each fan housing 22 is preceded laterally by two heat exchangers 25, which are supplied with cooling water via vacuum-tight feed and discharge ducts and to which gas guide plates 26 are assigned.

In the embodiment shown, three fan housings 22 and three associated fan units 10, 23 are provided. Embodiments are also conceivable in which only two fan housings 22 or also a single fan housing 22 are or are present.

The oil bath contained in the container 6 can be circulated evenly and vigorously by a hydraulic oil circulator 27, the speed of rotation of the oil circulator 27 being adjustable as required. An oil bath heater 28 is permitted it to bring the vacuum quenching oil to the desired temperature and to keep it at this temperature.

In the container 6, a lifting and lowering platform 29 is arranged, which allows a heat-treated batch 11a coming from the heating chamber 2 to be brought to a certain height in the cooling chamber 3 with respect to the nozzle box 18 - as will be explained in more detail below - or to immerse the batch 11a in the quenching oil contained in the container 6.

If the double-chamber vacuum furnace is designed without oil bath quenching, the container 6 with the oil bath contained therein is dispensed with.

When the door 4 is open, the double-chamber vacuum oven can be charged manually or automatically, the batch 11 being automatically moved into the open heating chamber 2. The heating chamber door 16 and the door 4 closing the loading opening are then closed, whereupon the vacuum furnace is evacuated. The batch 11 is then heat-treated in the heating chamber 2 according to a preselected temperature program. At the end of the heating cycle, the vacuum furnace is filled with inert gas under a maximum pressure of 6 bar abs. fumigated again. The fan drive motors 10 are switched on. The heating elements 12 are switched off and the batch 11 is moved into the cooling chamber 3, where it takes the place of the batch 11a and is quenched with cooling gas.

By appropriate actuation of the lifting and lowering platform 29, the charge in the cooling chamber 3 can be moved up to the nozzle plate 20 of the nozzle box 18 located above as required.

If the batch 11 is to be quenched in oil after the heat treatment in the heating chamber 2, it is lowered into the oil bath after it has left the heating chamber 2 by means of the lifting and lowering platform 29. If necessary, you can pre-cool briefly with inert gas before quenching the oil. The double chamber vacuum furnace is controlled automatically; the complete heat treatment cycle can be selected.

The nozzle box 18 is designed so that only low gas speeds occur in it, which on the one hand cause only small flow losses and on the other hand create the same pressure conditions at the nozzles of the nozzle plates 20, 20a, which lead to the same nozzle outlet speeds, which are the prerequisites for uniform cooling of the batch 11a are.

• Bei der Anordnung nach Fig. 5 besteht die abzuschreckende Charge 11a aus einer Anzahl schlanker, zylindrischer Werkzeuge, bspw. Spiralbohrer oder Fräser, mit 45 mm Durchmesser x 300 mm. Um den Verzug bei der Wärmebehandlung und der Abschreckung gering zu halten, werden die mit 30 bezeichneten zylindrischen Werkstücke stehend chargiert, wobei sie auf der Chargengrundfläche gleichmäßig verteilt sind. Die Chargengrundfläche entspricht der rechteckigen Umrißfläche des in Fig. 6 dargestellten Düsenbleches 20.

Since the nozzle plates 20, 20a are arranged interchangeably in the nozzle box 18 and, if appropriate, can be replaced by blind plates 21, the quenching conditions in the cooling chamber 3 can be optimally adapted to the shape and composition of each batch 11a. This is illustrated by way of example in FIGS. 5 to 18:

• 5 there is Batch 11a to be quenched from a number of slim, cylindrical tools, for example twist drills or milling cutters, with a diameter of 45 mm x 300 mm. In order to keep the distortion during heat treatment and quenching to a minimum, the cylindrical workpieces designated with 30 are charged standing, whereby they are evenly distributed on the base of the batch. The base area of the batch corresponds to the rectangular outline area of the nozzle plate 20 shown in FIG. 6.

Through-flow cooling with parallel flow is required for uniform and intensive gas quenching. For this purpose, a horizontal nozzle plate 20 is inserted into the nozzle box 18 above the charge 11a, while dummy plates 21 are attached to the side of the charge 11a. The nozzle plate 20 has uniformly distributed nozzle openings 35 (FIG. 6) over its entire surface. ensure a uniform and simultaneous cooling of all workpieces 30.

The distance between the nozzle openings 35 and the batch 11a has been optimized by lifting using the lifting and lowering platform 29. The overstroke is indicated at 32 in FIG. 5.

• Um die Wärmeübergabe durch Strahlung auf die runden kalten Kühlkammerwände voll ausnützen zu können, besteht die Charge 11a lediglich aus einem Werkstück 33 in Gestalt eines zylindrischen Dornes. Da dieser Dorn eine verhältnismäßig geringe Anströmfläche im Vergleich zu der durch die rechteckige Umrißfläche des Düsenbleches 20a der Fig. 8 gegebenen Chargengrundfläche aufweist, ist eine Kühlgasstromkonzentration im Bereich des zu kühlenden Werkstückes 33 notwendig, um maximale Kühlgeschwindigkeiten zu erzielen. Diese Forderung ist entweder durch Verringerung der Zahl der Düsenöffnungen 35 bei gleichzeitiger Erhöhung der Düsenaustrittsgeschwindigkeit oder bei gleichbleibender Düsenanzahl durch Verringerung des Düsenabstandes 36 (Fig. 8) zu erzielen.

Workpieces that occupy the entire available batch length must be loaded horizontally. This is illustrated in FIGS. 7, 8:

• To round the heat transfer by radiation To be able to take full advantage of cold cooling chamber walls, the batch 11a merely consists of a workpiece 33 in the form of a cylindrical mandrel. Since this mandrel has a relatively small inflow area in comparison to the batch base area given by the rectangular outline of the nozzle plate 20a of FIG. 8, a cooling gas flow concentration in the region of the workpiece 33 to be cooled is necessary in order to achieve maximum cooling speeds. This requirement can be achieved either by reducing the number of nozzle openings 35 while simultaneously increasing the nozzle outlet speed, or with a constant number of nozzles by reducing the nozzle spacing 36 (FIG. 8).

For the above considerations, a nozzle plate 20a is inserted in the nozzle box 18 above the charge 11a, which has a region 40 projecting into the interior of the cooling chamber 3, in which the nozzle openings 35 are arranged. The nozzle plate 20a thereby has a channel-like or box-like shape; the area containing the nozzle openings 35 is delimited on both sides by an unperforated area 41.

In addition, the workpiece has been brought through the hub 33 and Senkbühne 29 to the nozzle openings 35, as ^g at 32 in Fi. 7 is indicated.

The nozzle pattern in this case is that of Fig. 18 Obviously determined by nozzle holes 35 of the same diameter arranged in a rectangular pattern with the same height and side distances.

To the side of the workpiece 21, dummy plates 21 are inserted in the nozzle box 18 in order to prevent opposing cooling gas flows colliding against one another in the vicinity of the workpiece because this would substantially reduce the cooling gas velocity directly on the workpiece 33.

In the arrangement according to FIGS. 9, 10, the batch 11a consists of a heavy, compact tool, for example a cylindrical die, which in comparison to the batch base area given by the rectangular outline shape of the nozzle plate 20 (FIG. 10) has a small projecting inflow area having. The most effective cooling results from a combination of impingement cooling of the upper flat surface on the one hand and a parallel flow on the cylindrical lateral surface or the bores of the workpiece 33 on the other hand, while two blind plates 21 are inserted in the nozzle box 18 on the side of the workpiece 33.

As can be seen in FIG. 9, the nozzle pattern of the upper nozzle plate 20 is approximately diamond-shaped, again all the nozzle openings 35 having the same height and side distances 36.

To optimize the cooling effect, the workpiece 33 is moved to the upper nozzle plate 20 by means of the lifting and lowering platform 29 in the cooling chamber 3, as is indicated at 32.

• Die Düsenöffnungen 35 sind entsprechend den Stempeln 33 jeweils in rechteckigen Gruppen angeordnet, die durch gasundurchlässige Zwischenräume 34 voneinander getrennt sind. Der Seiten- und Höhenabstand 36 benachbarter Düsenöffnungen 35 ist wieder gleich.

11, 12, a batch 11a is illustrated, which consists of several cylindrical Stamp 33 exists. In the nozzle box 18 of the batch 11 a two dummy plates 21 inserted in this case laterally, while above the charge 11a, a nozzle plate is 20-see e ^g before, the nozzles image of Figure 12 is apparent.:

• The nozzle openings 35 are each arranged in rectangular groups corresponding to the stamps 33, which are separated from one another by gas-impermeable intermediate spaces 34. The side and height spacing 36 of adjacent nozzle openings 35 is the same again.

The batch 11a can be brought to the nozzle plate 20 through the lifting and lowering platform 29, as is indicated at 32 in FIG. 11; however, it is also conceivable to quench the charge 11a at a greater distance from the upper nozzle plate 20, which is illustrated in broken lines.

A typical example of a batch 11a quenched by intensive impingement cooling is illustrated in FIGS. 13, 14. Above the batch 11a consisting of two plate-shaped workpieces 33, for example in the form of a die-casting mold, a blind plate 21 is arranged in the nozzle box 18, while two nozzle plates 20a are provided to the side of the upright standing plate-shaped workpieces 33, which are shown in FIG. 13 Have a region 40 projecting into the cooling chamber 3, in which the nozzle openings 35 are arranged.

The plate-shaped workpieces 33 are vertical to avoid distortion in the upper temperature range during the dwell time in the heating chamber 2 in the vacuum oven. The nozzle openings 35 of the box-like nozzle plates 20a are brought close to the batch side surface, the nozzle openings 35 being arranged uniformly distributed over the entire batch side surface with the same height and side spacings 36 according to the nozzle image shown in FIG _'' To ensure workpieces 33.

In the arrangement according to FIGS. 15, 16, a single plate-shaped workpiece 33, for example in the form of a compression mold, is quenched in the cooling chamber 3, which - similar to FIG. 13 - with an overhead blind plate 21 and two lateral box or trough-like nozzle plates 20a is equipped.

• Die Düsenöffnungen 35, die gleichen Höhen- und. Seitenabstand 36 aufweisen, sind auf einen etwa der Chargenseitenfläche entsprechenden rechteckigen Bereich konzentriert, der von gasundurchlässigen Bereichen 41 umgeben ist. Durch die dadurch bedingte Verringerung der Zahl der Düsenöffnungen 35 ergibt sich eine Erhöhung der Düsenaustrittsgeschwindigkeit. Außerdem ist der Abstand der Düsenöffnungen 35 von der Werkstück- oder Chargenseitenfläche in beschriebener Weise durch Verwendung der Düsenbleche 20a optimiert. Die auf beiden Seiten auf das Werkstück aufgebrachte Prallstromströmung garantiert ein verzugsfreies und intensives Abkühlen der Charge 11a.

In order to achieve extreme optimization of the cooling conditions, the nozzle plates 20a are designed in the manner shown in FIG. 16 with a nozzle pattern which is matched to the side face of the batch:

• The nozzle openings 35, the same height and. Have side spacing 36 are concentrated on a rectangular area approximately corresponding to the batch side area, which is surrounded by gas-impermeable areas 41. Through the the resultant reduction in the number of nozzle openings 35 results in an increase in the nozzle outlet speed. In addition, the distance of the nozzle openings 35 from the workpiece or batch side surface is optimized in the described manner by using the nozzle plates 20a. The impingement flow applied to the workpiece on both sides guarantees a distortion-free and intensive cooling of the batch 11a.

Finally, FIGS. 17, 18 relate to the quenching of a batch 11a which consists of workpieces for which critical cooling speeds which are not too high are required and which, given their small wall thickness, can be cooled with parallel flow. For this purpose, a nozzle plate 20 is arranged in the nozzle box 18 above the batch 11a consisting of three workpieces 33, while dummy plates 21 are inserted on the side of the batch 11a.

The nozzle openings 35 - as can be seen from FIG. 17 - are again combined according to the three workpieces 33 into three adjacent, rectangularly delimited groups, between which gas-impermeable areas 41 are arranged.

The charge 11a is brought to the upper nozzle plate 20 through the lifting and lowering platform 29, as indicated at 32.

In the exemplary embodiments described above, nozzle openings 35 of the same diameter are provided in the nozzle plates 20, 20a in different nozzle patterns. In principle, it is of course also conceivable to vary the diameter of the nozzle openings 35 in accordance with the respective requirements and also to use differently shaped nozzle openings, for example in the form of slots, instead of cylindrical nozzle openings 35. It is also possible for the nozzle plates 20a to have an outwardly projecting area instead of a part 40 projecting into the cooling chamber 3, while for special cases the arrangement can also be such that a nozzle plate is present in the area of the batch base in order to to allow an inflow of charge 11a from below.

The drive motors 10 of the fans can be designed to be controllable in order to be able to select the cooling gas speed in the cooling chamber 3 in accordance with the requirements. The maximum cooling gas pressure is usually 2 bar abs. If necessary, it can also be higher.

With the new industrial furnace, 3 cooling intensities are achieved in the cooling chamber, which correspond to those of conventional and commercially available vacuum furnaces with high-pressure gas quenching. Conventional vacuum furnaces (predominantly single-chamber furnaces) must, for example, with 5 bar abs. Cooling gas pressure work in order to achieve a cooling effect comparable to that of the new industrial furnace in the cooling chamber 3 even at a cooling gas pressure of 2 bar abs. is obtained. The decisive advantage of the low cooling gas pressures that can be achieved in this way is a substantial saving of cooling gas (in particular nitrogen) during a heat treatment cycle, which means a correspondingly high cost saving. In addition, low cooling gas pressures allow the production of ^cost-g s system enclosures that are subject to any regulatory approval.

Claims (14)

1. industrial furnace, in particular a multi-chamber vacuum furnace for the heat treatment of batches of metallic workpieces, with a heating chamber and a cooling chamber containing a cooling device to which cooling gas is applied, in which a heat-treated batch with cooling gas circulated via a heat exchanger flows, and optionally with an oil bath, characterized in that the cooling device (17) has nozzles (35) opening into the cooling chamber (3) and blowing the charge (11a) with cooling gas, and in that the nozzles (35) which are arranged in a stationary manner in the cooling chamber (3), changing the Blowing conditions of the batch (11a) are optionally arranged interchangeably. 2. Industrial furnace according to claim 1, characterized in that the nozzles (35) are interchangeable in groups by changing the nozzle arrangement (nozzle pattern) and / or the nozzle diameter and / or the nozzle spacing (36). 3. Industrial furnace according to one of the preceding claims, characterized in that the distance between at least some nozzles (35) from the batch (11a) is adjustable. 4.Industrial furnace according to one of the preceding claims, characterized in that at least some nozzles (35) are arranged in an orientation resulting in an impingement flow and / or a parallel flow of the cooling gas on the charge (11a). 5.Industrial furnace according to one of the preceding claims, characterized in that the nozzles (35) the batch (11 a) are arranged on several sides surrounding. 6.Industrial furnace according to one of the preceding claims, characterized in that the cooling device (17) has a nozzle box (18) arranged in the cooling chamber (3) and loaded with cooling gas, into which at least one nozzle plate (20) arranged opposite the batch (11a) , 20a) is used releasably. 7. Industrial furnace according to claim 6, characterized in that the nozzle box (18) has guide devices (19) into which the nozzle plate (20, 20 a) can be inserted. 8. Industrial furnace according to one of claims 6 or 7, characterized in that the nozzle plate (20a) has a projecting into the interior of the cooling chamber (3) or recessed from this area (40). 9. Industrial furnace according to one of claims 6 to 8, characterized in that the nozzle box (18) is tunnel-shaped and is limited on its inner wall by nozzle plates (20, 20a). 10. Industrial furnace according to one of claims 6 to 9, characterized in that at least one nozzle plate (20, 20a) is replaced by a gas-impermeable blind plate (21). 11. Industrial furnace according to claim 6, characterized in that the
Nozzle box (18) is delimited on at least three inner sides by nozzle plates (20, 20a), two of which are located opposite one another and the third nozzle plate is arranged between the two other nozzle plates. 12. Industrial furnace according to one of the preceding claims, characterized in that in the cooling chamber (3) a batch (11a) receiving lifting or lowering device (29) is arranged, through which the batch (11a) at a predetermined distance from at least one Part of the nozzle orifices can be brought. 13. Industrial furnace according to one of claims 6 to 12, characterized in that the nozzle box (18) with the pressure side of at least one fan (10, 23) of the heat exchanger (25) containing gas circulation device is connected. 14. Industrial furnace according to claim 14, characterized in that the cooling chamber (3) with the heating chamber (2) is arranged in a common housing (1) and the fan or the fans on the housing (1) radially at the front region of the cooling chamber ( 3) is attached.

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