EP0699243A1

EP0699243A1 - Thermal treatment device for metallic workpieces

Info

Publication number: EP0699243A1
Application number: EP94917626A
Authority: EP
Inventors: Helmut Egger
Original assignee: Aichelin GmbH Germany
Current assignee: Aichelin GmbH Germany
Priority date: 1993-05-19
Filing date: 1994-05-12
Publication date: 1996-03-06
Anticipated expiration: 2014-05-12
Also published as: DE4316841A1; EP0699243B1; ATE152183T1; WO1994026940A1; DE59402542D1

Abstract

A thermal treatment device for metallic workpieces has a plurality of furnace modules (12, 14, 16, 18, 20) in which a protective gas atmosphere may be established and which are interconnected by at least one intermediate transfer sluice (22) in which a protective gas atmosphere may also be established. An arrangement (28) for transporting the grates (24) in a protective gas atmosphere is provided within the intermediate transfer sluice (22). The furnace modules (12-20) are designed as pusher type furnace modules with grates (24) for transporting the workpieces (26). By interconnecting the furnace modules (12-20) through a gas-tight intermediate transfer sluice and at the same time by designing the furnace modules as pusher type furnace modules, the whole installation is made very flexible and has a high throughput.

Description

Device for the heat treatment of metallic workpieces

The invention relates to a device for the heat treatment of metallic workpieces, with a plurality of furnace modules which can be exposed to a protective gas atmosphere and are connected to one another via at least one intermediate transfer lock which can be subjected to protective gas, and the intermediate transfer locks a transport device for transporting the grids having.

Such a device is known from EP 0 209 408 AI. The known device has a low-temperature furnace module, a high-temperature furnace module and an intermediate transfer lock in order to be able to transport workpieces under a protective gas atmosphere between the individual modules. The known device can be used very flexibly, since the gas atmosphere, treatment duration and temperature can be selected individually in the individual modules, but is only suitable for small throughputs.

From EP 0 296 102 AI a further device for the heat treatment of metallic workpieces is known, in which two furnace modules, which each have different individual chambers arranged one behind the other, are arranged one above the other. Here, too, heat treatment of the workpieces is provided in a protective gas atmosphere.

However, heat treatment in the two furnace modules arranged one above the other cannot be combined with one another at will, since the lifting device for transporting the workpieces between the two modules arranged one above the other does not allow transport under a protective gas atmosphere. Furthermore, this device also has the disadvantage that it is only suitable for relatively low throughputs.

From the international patent application PCT / DE 92 100019, which is however not previously published, a device for the heat treatment of metallic workpieces is also known, which has at least two furnace modules, of which at least one furnace module has a plurality of individual chambers, each of which can be closed via gas-tight doors . At least one intermediate transfer lock is provided for transport between the individual oven modules, which enables the workpieces to be transported under an inert gas atmosphere.

A modular arrangement of the furnace units into individual chambers, each of which can be individually controlled, results in a particularly high flexibility of the system, however such a system can only be used for small to medium throughputs.

The invention is therefore based on the object of providing a device for the heat treatment of metallic workpieces which guarantees the greatest possible flexibility and is also suitable for higher throughputs.

This object is achieved in that in a device of the type mentioned at least one furnace module is designed as a push-through furnace module with grids for the transport of workpieces.

According to the invention, a plurality of furnace modules which can be exposed to a protective gas atmosphere are connected to one another via at least one intermediate transfer lock which can be subjected to a protective gas atmosphere, and at least one furnace module is designed as a push-through furnace module with grids for transporting the workpieces. This configuration of at least one furnace module, preferably all furnace modules, as a push-through furnace module enables a significantly higher throughput of the overall system to be achieved, while a high degree of flexibility is ensured as a result of the transport between the individual furnace modules via a protective gas-charged intermediate transfer lock.

In an advantageous development of the invention, the intermediate transfer lock is coupled to at least one vacuum inlet lock for loading workpieces.

This measure has the advantage that the system can be filled with particularly short cycle times, which is particularly evident in the case of different heat treatment parameters individual oven modules has an advantageous effect. Via the vacuum inlet lock, each individual oven module can be quickly loaded via the at least one intermediate transfer lock, and there is also the possibility of quickly removing repair batches.

In a further embodiment of the invention, the intermediate transfer lock has at least one grate transport carriage with a gas-tight drive.

This measure has the advantage that a largely wear-free transport of the grids between the individual furnace modules is possible under protective gas.

In an expedient development of the invention, the drive can be designed as a positionable drag chain circulating drive.

In a preferred development of the invention, the intermediate transfer lock is designed as an unheated, heat-insulated lock tunnel.

In this way, heating of the intermediate transfer lock can be dispensed with, while the workpieces can be transported between the individual furnace modules under protective gas without excessive heat loss.

In an advantageous embodiment of the invention, a cross-joint device for loading and unloading is provided in front of at least one oven module, preferably in front of each oven module.

In this way, the individual batches can easily be moved from the grate transport trolley out of the intermediate transfer lock Are moved into the individual oven modules or are moved from the oven modules onto a further grate transport carriage to another oven module or to another unit.

In a further embodiment of the invention, at least one furnace module has a plurality of individual chambers, which can each be closed by means of gas-tight doors, the temperature, dwell time and atmosphere being freely selectable.

This measure has the advantage that different heat treatments can be carried out in succession in the furnace module divided into several individual chambers without first having to be transported to another furnace module. Rather, the sliding transport of the grates from single chamber to single chamber ensures quick transport.

In a further embodiment of the invention, at least one oven module has two slides arranged below the grids, which are supported on one another, the upper slider being able to be raised relative to the lower slider in order to lift the grids off the furnace floor, and the two slides in the raised position are displaceable together for the sport of the gratings.

This known from DE 41 32 197 AI lifting furnace conveyor ensures wear-free transport of the grates through the furnace module. As a result of the lower wear, lighter grates can be used at the same time, which increases the economy. Furthermore, this measure has the advantage that the furnace module can also be driven completely empty without the need for empty gratings, which would lead to unnecessary wear and energy consumption. The combination according to the invention of such a practically wear-free drive with different furnace modules, which are connected to one another via at least one gas-tight intermediate transfer lock, on the one hand achieves extremely high flexibility of the overall system and on the other hand also enables high throughput rates. Because variable module cycle times are possible within a wide range for each furnace module, and even multiple passes through a furnace module are made possible via the intermediate transfer lock, practically all conceivable case hardening depths can be achieved and at the same time run in the overall system. By means of an infinitely adjustable or repeatedly repeatable conveying stroke per charging cycle, a variable furnace occupancy can be achieved in each furnace module, which further increases the flexibility of the overall system.

Although a grate transport carriage with a gas-tight drive, for example a drag chain circulating drive, can be provided between the individual furnace modules for transporting the workpiece grates in the intermediate transfer lock, in a further preferred alternative embodiment a lifting furnace conveyor can also be provided within the intermediate transfer lock the aforementioned manner.

In a further preferred embodiment of the invention, support elements are provided between the two slides of the lifting furnace conveyor, which enable a combined movement of at least the upper slider in the horizontal direction and in the vertical direction.

In a preferred embodiment of this embodiment, the support elements are designed as mutually parallel inclined planes of the upper slide or lower slide. This measure has the advantage that the transport mechanism is extremely simple, since only a translational movement is required in order to raise and lower the upper slide relative to the lower slide and to move both slides and thus the grids forward. When using inclined planes as support elements, there is frictional contact of the guide surfaces with a relative movement of the slide, but the frictional forces are limited to the guide surfaces, which can be designed accordingly. In contrast, the grates themselves are moved largely wear-free against the furnace floor.

In a further preferred embodiment of the invention, the throughput time of at least one oven module is variable independently of the other oven modules.

As a result, the highest possible flexibility of the overall system is achieved, with preferably all furnace modules being variable independently of the other furnace modules.

If, for example, a control cycle of ten minutes is set for the entire device on the loading and unloading side, variable module cycle times of ten, twenty, thirty, forty and sixty minutes can be provided for each furnace module. In connection with internally possible different throughput variants and including multiple throughputs through a furnace module, various possible uses can be achieved, namely one use as a single-purpose system with, for example, a single case depth but with a very high total throughput, or use as a multi-purpose system, for example at the same time with different case hardnesses, and finally also as a multi-purpose system, for example when driving with more than three different ones Case hardening depths and various hardening and tempering processes with short throughputs.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.

Further features and advantages of the invention result from the following description of a preferred exemplary embodiment with reference to the drawing. Show it:

1 shows an exemplary embodiment of the device according to the invention in a schematic representation;

2 shows an enlarged schematic illustration of the grate transport drive within an oven module and

Fig. 3 shows the grate transport drive according to FIG. 2 after moving the upper slide and lifting the grids.

A device according to the invention is generally designated by the number 10 in FIG. 1.

The device 10 has a total of five furnace modules, all of which are designed as push-through furnace modules. The first furnace module 12 and the second furnace module 14 are provided, for example, for heating and carburizing, while the third furnace module 16 and the fourth furnace module 18 are used for carburizing and the fifth furnace module 20 can be used for the final diffusion. The individual furnace modules 12, 14, 16, 18, 20 are connected to one another via an intermediate transfer lock 22, in which the workpieces 26 or the grids 24 can be transported under a protective gas atmosphere. All of the furnace modules 12, 14, 16, 18, 20 and the intermediate transfer lock 22 are therefore largely gas-tight in order to enable treatment or transport under protective gas. It goes without saying that treatment or transport under vacuum could of course also be provided in an alternative manner, provided that this is advantageous in individual cases.

In the example shown, the loading takes place via a loading trolley 54 through a connecting channel 56 via a vacuum inlet lock 30, from which the grids 24 reach the intermediate transfer lock 22 via a transverse pushing device 58. Within the intermediate transfer lock 22, a transport device 28 with a plurality of grate transport carriages 32 can be moved and positioned as desired via a drag chain circulating drive. It goes without saying that any other types of drive for transporting the grids 24 can also be provided within the intermediate transfer lock 22, provided that these meet the respective requirements.

For the transportation of the grids between the intermediate transfer lock 22, the vacuum inlet lock 30, the inlet side and the outlet side of the furnace modules 12, 14, 16, 18, 20 and a dip-oil quenching bath 34 arranged downstream of the fifth furnace module 20, transverse push devices 58 are respectively provided, which are indicated only schematically with their transverse impact drive 59.

The first four oven modules 12 to 18 can each accommodate nine grids 24 in a row, while the fifth oven module 20 can hold one grate in its first single chamber 19 and two grids in its second single chamber 21. The furnace modules 12 to 20 are each connected via gas-tight doors 60 to the intermediate transfer lock 28 or the upstream vacuum inlet lock 30 or the downstream immersion oil quenching bath 34. The two individual chambers 19, 21 of the fifth furnace module 20 are separated from one another via a gas-tight door 62, so that the temperature, gas atmosphere and, within certain limits, the dwell time of the workpieces in both individual chambers 19, 21 can be freely selected.

Finally, the immersion oil quenching bath 34 is followed by a cleaning system 36.

The intermediate transfer lock 22 is designed as an unheated, heat-insulated lock tunnel, so that the workpieces can be transported without major heat losses within the intermediate transfer lock 22 without additional heating of the intermediate transfer lock 22.

A buffer memory 64 is also provided for holding workpieces before or after the heat treatment.

A lifting furnace conveyor device according to DE 41 32 197 A1 is provided for transporting the grids 24 within the first four furnace modules 12 to 18, to which express reference is made here with regard to details of the drive.

FIGS. 2 and 3 are provided only for the purpose of a basic explanation of this transport device 38. While the gratings 24 are placed on the furnace floor 44 in the basic position according to FIG. 2, they are lifted off the furnace floor 44 according to FIG. 3 for advancement.

The transport device 38 has a lower slide 40 and an upper slide 42, which are arranged below the grids 24 and wherein the upper slide 42 is supported on the lower slide 40.

According to FIGS. 2 and 3, parallel guide surfaces in the form of inclined planes 46, 48 are provided on the lower slide 40 and on the upper slide 42. The inclined planes 46, 48 are connected by bearing surfaces 50, 52 of the upper slide 42 and of the lower slide 40 parallel to the furnace floor 44, so that both slides 40, 42 have a sawtooth shape in longitudinal section according to FIGS. The upper slide 42 and the lower slide 40 are divided into individual modules which are arranged one behind the other in the transport direction 54. FIG. 2 shows the basic position in which the two slides 40, 42 lie flat on one another and the grids 24 are on the furnace floor 44.

In Fig. 3, the upper slide 42 has been moved in relation to the lower slide 40 in the transport direction 54, whereby the upper slide 42 has been raised by shifting its inclined plane 46 with respect to the inclined plane 48 of the lower slide 40 with respect to the latter until both parallel to the furnace floor 44 Support surfaces 50, 52 rest on one another. In this position, both slides 40, 42 can be moved forward together by a translation movement in the transport direction 54 in order to transport the gratings 24. Thereafter, the upper slide 42 is again relatively displaced relative to the lower slide 40 until the two slides are immediately adjacent to one another can rest and be moved back into the starting position while the grids 24 rest on the furnace floor 44. As already mentioned, reference is made to DE 41 32 197 AI for further details.

The device according to the invention is subordinated to a charging cycle of ten minutes on the loading and unloading side.

Variable module cycle times can be set in each case within the oven modules 12 to 20, specifically ten, twenty, thirty, forty and sixty minutes.

The connection of the individual oven modules 12 to 20 via the gas-tight intermediate transfer lock 22 also enables the first four oven modules 12 to 18 to be run through several times. Furthermore, a variable furnace occupancy between zero and nine grids per furnace module is possible within the first four furnace modules 12 to 18 per loading cycle.

These possible combinations result in extremely high system flexibility, and at the same time individual furnace modules can also be at least partially put out of operation in order to enable economical operation of the device according to the invention even with reduced throughput. In addition, depending on the desired mode of operation, a high throughput can also be achieved with flexibility of the device according to the invention. The device according to the invention can thus advantageously also be used in large-scale production.

As a result of the preferred lifting furnace conveyor, at least within the first four furnace modules 12 to 18, a largely wear-free transport of the gratings is achieved, so that these can be made lighter and can have a larger base area than grates in conventional push-through systems, so that in addition the overall throughput of the device according to the invention is improved.

It goes without saying that the exemplary embodiment according to FIG. 1 shows only one possible of many alternatives, and that the system can be varied as desired with regard to the structure and the number of individual oven modules, that other additional components, such as quenching baths and the like, are used can be that further intermediate transfer locks can be provided, that additional inlet transfer locks or also further vacuum inlet locks can be provided.

Claims

1. Device for the heat treatment of metallic workpieces, with a plurality of furnace modules (12, 14, 16, 18, 20) which can be exposed to a protective gas atmosphere and are connected to one another via at least one intermediate transfer lock (22) which can be subjected to a protective gas atmosphere, and wherein the intermediate transfer lock (22) has a transport device (28) for transporting the grids (24), characterized in that at least one furnace module as a push-through furnace module (12, 14, 16, 18, 20, 22) with grates (24) for Transport of the workpieces (26) is formed.

2. Device according to claim 1, characterized in that the intermediate transfer lock (22) is coupled to at least one vacuum inlet lock (30) for loading workpieces (24).

3. Apparatus according to claim 1 or 2, characterized in that the intermediate transfer lock (22) has at least one grate transport carriage (32) with a gas-tight drive.

4. Device according to one or more of the preceding claims, characterized in that the intermediate transfer lock (22) is designed as an unheated, heat-insulated lock tunnel.

5. The device according to one or more of the preceding claims, characterized in that in front of at least one furnace module (12, 14, 16, 18, 20) a transverse pushing device (58) is provided for loading and unloading.

6. The device according to one or more of the preceding claims, characterized in that at least one oven module (20) has a plurality of individual chambers (19, 21), each of which can be closed via gas-tight doors (60, 62), the temperature, residence time and atmosphere in each case are freely selectable.

7. The device according to one or more of the preceding claims, characterized in that at least one furnace module (12, 14, 16, 18, 20) has two slides (40, 42) arranged below the gratings (24), which are supported on one another, that the upper slide (42) can be raised relative to the lower slide (40) in order to lift the grids (24) off the furnace floor (44), and that the two slides (40, 42) together in the raised position for transporting the grates ( 24) are displaceable.

8. The device according to claim 7, characterized in that between the slides (40, 42) support elements (46, 48) are provided which allow a combined movement of at least the upper slide (42) in the horizontal direction and in the vertical direction.

9. The device according to claim 8, characterized in that the support elements as mutually parallel inclined planes (46, 48) of the upper slide (42) and the lower slide (40) are formed.

10. The device according to one or more of the preceding claims, characterized in that the throughput time of at least one oven module (12, 14, 16, 18, 20) is variable independently of the other oven modules (12, 14, 16, 18, 20).