EP0621904B1 - Device for heat-treating metal workpieces - Google Patents

Abstract

The description relates to a device for heat-treating metal workpieces having at least two furnace units (12, 14) of which at least the first one (12) has a plurality of individual chambers (13), each of which can be closed by gastight doors (61). A workpiece charge can be directly fed into each individual chamber (13) as desired and, after heat treatment with individually controllable parameters (temperature, duration and atmosphere) removed for subsequent heat treatment in the next furnace unit (14). The installation is made particularly flexible by the modular division of the furnace units (12, 14) into individual chambers (13, 15, 16) which can be individually controlled.

Description

• mindestens einer ersten, über gasdichte Türen verschließbaren Ofeneinheit zur Durchführung eines ersten Wärmebehandlungsschrittes;
• mindestens einer zweiten, nachfolgenden, über gasdichte Türen verschließbaren ofeneinheit zur Durchführung eines zweiten Wärmebehandlungsschrittes;
• wobei die Werkstücke in der ersten Ofeneinheit und in der zweiten Ofeneinheit für jede Werkstückcharge hinsichtlich Temperatur, Verweildauer und Atnosphäre individuell behandelbar sind;
• einer Zuführungseinrichtung zur taktweisen Zuführung von Werkstücken zu der mindestens einen ersten Ofeneinheit, wobei die Zuführungseinrichtung eine gasverlustarme Beschickungseinheit sowie daran angeschlossen gasdichte erste Führungsmittel umfaßt; und
• zweiten gasdichten Fördermitteln zum Transportieren der Werkstücke nach der jeweils gewünschten Verweildauer von der mindestens einen ersten ofeneinheit zu der mindestens einen zweiten Ofeneinheit.

The invention relates to a device for the heat treatment of metallic workpieces

• at least one first furnace unit, closable via gas-tight doors, for carrying out a first heat treatment step;
• at least one second, subsequent furnace unit, which can be closed via gas-tight doors, for carrying out a second heat treatment step;
• wherein the workpieces in the first furnace unit and in the second furnace unit can be treated individually for each workpiece batch with regard to temperature, residence time and atmosphere;
• a feed device for the intermittent feed of workpieces to the at least one first furnace unit, the feed device comprising a gas loss-free feed unit and gas-tight first guide means connected thereto; and
• second gas-tight conveying means for transporting the workpieces from the at least one first furnace unit to the at least one second furnace unit according to the desired residence time.

A device of the type mentioned above is known from document EP-A-0 209 408.

Industrial heat treatment plants are operated as continuously or intermittently as possible to achieve a high throughput. In addition to continuously operating conveyor belt furnaces, intermittent piercing furnaces have become known, which are used in particular in piercing gas carburizing plants. Conventional push-through systems are mainly set up in a rectangular shape, so that a closed circuit is created.

Systems of this type are designed for high throughput, but have the disadvantage that, as a result of the cyclical circulating operation, adaptation measures have to be carried out when switching between different batches. In some cases, empty grates have to be driven or the furnace system has to be run empty before other parts can be processed.

In addition, two- and three-lane push-through systems were developed to enable intermittent operation with different cycle times. However, a multi-lane design leads to a lower uniformity of the heat treatment.

In addition, push-through systems have the fundamental disadvantage that a certain minimum utilization is required for economical operation, since empty gratings have to be driven if the utilization is not complete.

In order to allow a higher flexibility of the heat treatment, in particular with a lower throughput, rotary hearth furnaces were combined with upstream and downstream piercing or pulling furnaces. While the carburizing is usually carried out in the one- or two-stage rotary hearth area, the heating and diffusing mostly takes place in the piercing or pulling yards.

Such an oven system is known from DE 34 41 338 A1. Here, the workpieces are heated in an impact furnace under protective gas and then transferred via an intermediate door into the connected carburizing chamber, which is designed as a rotary rotary furnace that can be rotated in cycles. After different carburizing times controlled in cycles, the individual batches can be transferred via an intermediate door to a subsequent diffusion chamber, which is also designed as a cyclically operated rotary cycle furnace. From the diffusion chamber, the batches pass through an intermediate door into a compensation chamber which is designed as an impact furnace.

With such a system, the carburizing time of the individual batches can be controlled differently, so that different workpieces can be heat treated or different case hardening depths can be achieved.

However, with such a system, all batches located in a rotary hearth area can only be heat-treated at a predetermined temperature in each case under a specific atmosphere. Individual grate locations must also be partially emptied in order to maintain the specified treatment parameters for the other batches.

In the device according to the aforementioned document EP-A-0 209 408, the workpieces are fed in batches via a horizontally running conveyor belt. At the end of the conveyor belt, the batches are placed on a table which conveys the batches vertically upwards through the bottom of a loading unit which is open at the bottom. After moving the batch into the loading unit, the bottom is closed by means of a gas-tight door. The batches then pass through another horizontal one Conveyor on a second lifting table, where they are placed on a lower cover of a first vertical shaft furnace. The batches are then moved from below into the first vertical shaft furnace by means of a piston-cylinder unit, so that it is sealed gas-tight after the batch has been moved in. The batches are then treated in the first vertical shaft furnace at a low temperature.

After this first heat treatment step, the batches are lowered again and then reach the bottom of a second vertical shaft furnace of a similar design by means of the same horizontal conveying device. The batches are then raised again so that the second vertical shaft furnace is closed and the batch can be subjected to a second heat treatment step at high temperature.

After this second heat treatment step has been completed, the batches are then lowered again and are moved in the same plane by means of a further horizontal conveyor in a direction angled by 90 ° through a lock door into an output lock. From this discharge lock, the batches are brought down into a quenching bath by means of a basket elevator and then discharged horizontally on the lower level.

In this known device, the conveyor devices between the inlet of the loading unit and the outlet of the conveyor, which is angled by 90 °, are designed to be gas-tight by means of gas-tight closable doors.

The invention is therefore based on the object of providing a device for the heat treatment of metallic workpieces which ensures the greatest possible flexibility.

• daß die mindestens eine erste Ofeneinheit eine Mehrzahl von Einzelkammern aufweist, die jeweils mit einer Einlaß- und mit einer Auslaßtür versehen sind, wobei Temperatur, Verweildauer und Atmosphäre für jede Wierkstückcharge einer jeden Einzelkammer individuell steuerbar sind;
• das die ersten Fördermittel als Einlauf-Transferschleuse an die Einlaßtüren der Einzelkammern angeschlossen sind, um Werkstückchargen wahlweise direkt zuzuführen;
• daß die zweiten Fördermittel als Zwischen-Transferschleuse eingangsseitig an die Auslaßtüren der Einzelkammern angeschlossen sind, um Werkstückchargen wahlweise direkt abzuführen, und ausgangsseitig mit der mindestens einen zweiten Ofeneinheit in Verbindung stehen; und
• daß die Beschickungseinheit als vakuum-Einlaufschleuse ausgebildet ist.

According to the present invention, this object is achieved in that

• in that the at least one first furnace unit has a plurality of individual chambers, each of which is provided with an inlet and an outlet door, the temperature, residence time and atmosphere for each batch of workpieces in each individual chamber being individually controllable;
• that the first funding is connected as an inlet transfer lock to the inlet doors of the individual chambers in order to feed batches of workpieces directly;
• that the second conveying means are connected as an intermediate transfer lock on the input side to the outlet doors of the individual chambers, in order to optionally remove workpiece batches directly, and are connected on the output side to the at least one second furnace unit; and
• that the loading unit is designed as a vacuum inlet lock.

A major advantage of this structure is that the heat treatment parameters for each individual batch can be freely selected for each individual chamber, i.e. Temperature, dwell time and atmosphere can be controlled individually for each individual batch. Such a structure can be used particularly advantageously for flexible gas carburizing for smaller heat treatment batches.

Because the heat treatment parameters pressure, temperature and residence time can be controlled separately for each individual batch, heat treatments can be carried out with particularly high precision for high-quality parts. This possibility is further improved in that a diffusion calculation with real data can be carried out for each individual batch.

Since each individual chamber can be closed via gas-tight doors and the temperature and residence time can be individually controlled, different heat treatment processes can be carried out in the individual chambers at the same time. For example, gas carburizing, carbonitriding, quenching and tempering, nitrocarburizing, etc. can be carried out in various individual chambers as part of a cyclical operation. This means that even small batches can be processed economically.

Since individual chambers can be put out of operation individually, a high level of economy is guaranteed even if the system is not fully utilized. In addition, maintenance work can be carried out on certain individual chambers while the remaining individual chambers are being operated.

Another advantage of the device according to the invention is that empty gratings are not required, which ensures particularly economical operation with widely varying utilization and minimizes wear.

According to the invention, the batch transport can be carried out at the starting point of each batch (cold batch before the start of the heat treatment) to the exit point of the batch from a quenching unit or a cooling lock under a protective gas atmosphere, preferably in an oxidation-free protective gas atmosphere.

The invention also has the advantage that the system can be filled with particularly short cycle times, which is particularly advantageous in the case of different heat treatment parameters for individual batches, for example to achieve different case hardening depths.

In a further development of the invention, the intermediate transfer lock is also equipped with a vacuum inlet lock.

This results in the possibility of injecting repair batches for special heat treatment or injecting batches that are only intended to be hardened.

In a further embodiment of the invention, at least one downstream furnace unit has a plurality of individual chambers, each of which can be closed via gas-tight doors, the temperature, residence time and atmosphere for each individual chamber being individually controllable.

This measure has the advantage that an optimized intermediate or final heat treatment can be carried out for each batch, since the temperature, residence time and atmosphere can be freely selected.

In an expedient embodiment, an intermediate treatment chamber is provided for this purpose, which can be connected to a subsequent final treatment chamber via a gas-tight door.

Additional units can optionally be connected to the intermediate or final treatment chamber, preferably an outlet lock with a quenching bath for oil, salt or polymer quenching, a single removal device with a hardening press and after-cooling device for hardening sensitive workpieces, a high-pressure gas quenching unit or a gas cooling lock.

In any case, the system can be expanded to include additional individual chambers due to the modular structure, the other system parts, such as quenching baths, transfer locks and the like, being able to be retained.

The entire system can of course be supplemented with other system components, e.g. Washing devices, tempering ovens with cooling section and the like ..

If a high-pressure gas quenching system is connected to the final treatment chamber, the cooling gas from the high-pressure quenching chamber can advantageously be used for the inert gas admission to the intermediate transfer lock, the inlet transfer lock and / or the vacuum inlet lock.

It is obvious that the modular construction of the furnace units from individual chambers, for each of which the heat treatment parameters temperature, residence time and atmosphere can be freely selected, enables a large number of different system configurations.

It goes without saying that the features mentioned above and those yet to be explained below do not only apply to specified combination, but also in other combinations or alone, without departing from the scope of the present invention.

Fig. 1

ein erstes Ausführungsbeispiel der erfindungsgemäßen Vorrichtung in schematischer Darstellung,

Fig. 2

ein zweites Ausführungsbeispiel der Erfindung in schematischer Darstellung und

Fig. 3

ein drittes Ausführungsbeispiel der Erfindung in schematischer Darstellung.

Preferred embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it:

Fig. 1

a first embodiment of the device according to the invention in a schematic representation,

Fig. 2

a second embodiment of the invention in a schematic representation and

Fig. 3

a third embodiment of the invention in a schematic representation.

Fig. 1 shows a first embodiment of the invention, which is generally designated by the number 10.

A first furnace unit 12 is divided into three identical individual chambers 13, each of which can be closed via gas-tight inlet doors and outlet doors 21. Another furnace unit 14 has an intermediate treatment chamber 15 with a gas-tight entrance door, which can be connected to a final treatment chamber 16 via a gas-tight connecting door. For each individual chamber 13 of the first furnace unit 12, as well as for the intermediate treatment chamber 15 and the final treatment chamber 16, the heat treatment parameters temperature, residence time and gas atmosphere can be controlled individually.

An inlet transfer lock 18 is provided for loading the first furnace unit 12, into which individual gratings with batches of workpieces can be inserted via a vacuum inlet lock 23. A grate transport wagon 30 can be moved in the inlet transfer lock 18 via a gastight drag chain circulating drive 28. A servomotor with positioning control is used for the drive, which enables the grate transport carriage 30 to be positioned in front of the outlet of the vacuum inlet lock 23 or in front of the entrance of each individual chamber 13 of the furnace unit 12.

For pushing the grids out of the vacuum inlet lock 23 into the inlet transfer lock 18 or for inserting them from the inlet transfer lock 18 through an open inlet door into a single chamber 13 and for later pushing them out of the single chamber through an opened outlet door, there is a transverse push device 26 intended.

The first furnace unit 12 and the intermediate treatment chamber 15 of the subsequent furnace unit 14 are connected via an intermediate transfer lock 19. The intermediate transfer lock 19 is not heated and is provided with internal insulation for radiation protection. To transport the grids, a grate transport carriage 29 is again provided, which can be moved and positioned within the intermediate transfer lock 19 via a gas-tight grate transport carriage drive 27.

Both the inlet transfer lock 18 and the intermediate transfer lock 19 are exposed to protective gas. Workpiece batches can be fed to each of the individual chambers 13 via the inlet vacuum lock 23 and the inlet transfer lock 18 and after an individually controlled heat treatment (temperature, atmosphere and residence time) via the intermediate transfer lock 19 by means of the grate transport carriage 29 in front of the following one Intermediate treatment chamber 15 are transported under protective gas. From here, the grate can be inserted into the intermediate treatment chamber 15 via the cross joint device with the inlet door open. After the intermediate heat treatment with any temperature and gas atmosphere that can be selected, the grate can be pushed further into the final treatment chamber 16 via a further cross joint device with the intermediate door open.

A quench bath 31 for oil or salt quenching is connected to the final treatment chamber 16 via a gas-tight outlet door, with a downstream outlet lock, from which the workpiece batches can be removed after leaving the hardening bath.

A further vacuum inlet lock 24 is connected to the intermediate transfer lock 19, via which individual workpiece batches can be fed directly to the intermediate treatment chamber 15 by bypassing the first furnace unit 12 for repair purposes or for exclusive hardening via the intermediate transfer lock 19.

The individual workpiece batches are moved by means of a loading carriage 39 over a transfer path 43 to a connecting channel 25, from which they can each be moved into the first vacuum lock 23 or the second vacuum lock 24 by means of a transverse impact drive.

The individual workpiece batches can be stored in a storage path 41 via a loading / unloading lifting table 42 and can be transferred from this into the loading carriage 39. The workpiece batches can be loaded by means of the loading carriage 39 to other components of the system, to low-temperature cells 37a, 37b to a washing device 36 or to a surface storage 40 for intermediate storage.

A further exemplary embodiment of the invention is designated as a whole by the number 50 in FIG. 2.

In this case, two furnace units 52a, 52b are provided for high-temperature treatment, each of which is divided into three identical individual chambers 53, which can be closed via gas-tight inlet and outlet doors 61. The temperature, gas atmosphere and dwell time of workpiece batches can be freely configured for each individual chamber 53.

In order to load the six individual chambers 53, an inlet transfer lock 58 is again provided in the manner previously described with reference to FIG. 1, which individual grates with batches of workpieces can be fed via a vacuum inlet lock 63. A grate transport carriage 70 is provided in the inlet transfer lock 58, which can be positioned as desired via a gas-tight drag chain circulating drive 68 relative to the outlet of the vacuum inlet lock 63 or relative to the inlet doors 61 of the individual chambers 53. For pushing the grate between the individual components of the system, that is to say, for example, for pushing a grate into a single chamber 53 and for subsequent pushing out, transverse push devices 66 are again provided.

For the subsequent treatment of the workpiece batches, two further furnace units 54a, 54b are provided, each of which has an intermediate treatment chamber 55a or 55b and a final treatment chamber 56a or 56b. Here too are each the individual chambers can be closed via gas-tight doors 61 and the heat treatment parameters temperature, residence time and gas atmosphere can be freely selected.

The intermediate treatment chambers 55a and 55b are connected to an intermediate transfer lock 59 via gas-tight inlet doors. The non-heated intermediate transfer lock 59 is in turn provided with internal insulation as radiation protection and is designed to be gas-tight for the application of protective gas. To move the grate between the individual chambers 53 and the intermediate treatment chambers 55a and 55b, a grate transport carriage 69 is provided, which can be moved in a targeted manner by a gas-tight drag chain circulating drive 67 with a servo motor and positioning control in order to expel a grate from a single chamber 53 into the intermediate To enable transfer lock 59 or pushing into one of the two intermediate treatment chambers 55a, 55b. The inlet transfer lock 58 and the intermediate transfer lock 59 are completely exposed to protective gas.

The final treatment chamber 56a of the first subsequent furnace unit 54a is connected via a slotted sliding door 73 to an individual removal device 72, via which sensitive workpieces can be transferred to a hardening press 74 with after-cooling device for hardening without distortion. The first final treatment chamber 56a is also connected via a gas-tight door to a quench bath 71a, for quenching in an oil or salt bath with a downstream outlet lock.

The second intermediate treatment chamber 55b has a gas-tight outlet door, via which workpiece batches can be transferred to a high-pressure gas quenching device 75. The workpiece batches can alternatively from the second intermediate treatment chamber 55b via a gas-tight intermediate door to the final treatment chamber 56b, which in turn is connected via a gas-tight outlet door to a quench bath 71b for oil or salt with a downstream outlet lock.

For loading and removing individual batches of workpieces, a loading trolley 79 is again provided, which can be moved via a transfer path 83 to the individual components or to their connecting lines. With the loading trolley 79, other system components, such as two surface storage units 80a, 80b, two starting furnaces with a cooling section 85a, 85b, two washing devices 76a, 76b and a loading / unloading lifting table 81 can also be started up.

Another exemplary embodiment of the invention is designated as a whole by the number 90 in FIG. 3.

A total of four furnace units 92a, 92b, 92c, 92d of identical construction are provided, each of which is divided into four identical individual chambers 93, which can be closed via inlet doors or outlet doors 101. The heat treatment parameters temperature, gas atmosphere and residence time can be controlled individually for each individual chamber 93.

In each case two of the oven units 92a, 92b and 92c, 92d are arranged on both sides of an intermediate transfer lock 99, so that a total of eight individual chambers 93 are located opposite each other on both sides of the intermediate transfer lock 99.

An inlet transfer lock 98b and 98a is provided for loading two furnace units 92a, 92b and 92c, 92d, respectively.

Grates with workpiece batches are fed into the inlet transfer locks 98a and 98b via a vacuum inlet lock 103a and 103b, respectively. The inlet transfer locks 98a, 98b and the intermediate transfer lock 99 are designed to be gas-tight and subjected to protective gas. The intermediate transfer lock 99 is not heated and is provided with internal insulation as radiation protection. For the transportation of the grates within the inlet transfer locks 98a, 98b and the intermediate transfer lock 99, grate transport carriages 110a, 110b and 109 are provided, each via a gas-tight grate transport carriage drive 108a, 108b and 107 within the inlet transfer locks 98a, 98b and within the intermediate transfer lock 99 can be moved and positioned.

Transverse joint devices 106 are in turn provided for transporting the grids between the individual components of the system.

The intermediate transfer lock 99 is connected to a subsequent furnace unit 94 which has an intermediate treatment chamber 95 and a final treatment chamber 96 separated therefrom via a gas-tight door. The workpiece grates are pushed in from the intermediate transfer lock 99 after the gas-tight inlet door has been opened via the cross joint device and, after an intermediate treatment step, are pushed into the final treatment chamber 96 in order to carry out a further heat treatment step.

Both in the intermediate treatment chamber 95 and in the final treatment chamber 96, the heat treatment parameters temperature, atmosphere and residence time can in turn be controlled separately for each individual workpiece batch.

From the final treatment chamber 96, the workpiece batches can either be removed from a single removal device 112 via a slot sliding door 113 and transferred to a hardening press 114 with aftercooling device, or removed via an outlet gas cooling lock 111 and cooled without pressure.

For further aftertreatment of the workpiece batches after leaving the aftercooling device after completion of the hardening process, an aftertreatment unit 124 with a conveyor belt transport device is provided, which comprises a washing unit, a drying unit, a starting unit and a downstream air cooling unit.

A reloading manipulator 125 with position control is used to handle the workpieces during the individual removal and for transfer to the hardening press 114.

Another reloading manipulator 125 with position control is provided for handling the workpieces in the loading and unloading area 122.

Two loading carriages 119a, 119b are provided for feeding or removing the workpieces, which can be moved on a transfer path 123. From the loading trolley 119b, the grids with the workpiece batches each reach the vacuum inlet locks 103a and 103b via a connecting channel 126.

Other components of the system, such as surface storage 120 and a further washing device 116, can be reached via the loading trolleys 119a and 119b.

Claims (10)

1. Device for heat-treating metal workpieces having

   - at least one first furnace unit (12; 52a, 52b; 92a to 92d) that can be closed by gas-tight doors (21; 61; 101), for carrying out a first heat-treatment step;

   - at least one second downstream furnace unit (14; 54a, 54b; 94) that can be closed by gas-tight doors (61; 73; 101, 113), for carrying out a second heat-treatment step;

   - the first furnace unit (12; 52a, 52b; 92a to 92d) and the second furnace unit (14; 54a, 54b; 94) being adapted for individual treatment of the workpieces of each workpiece charge, with respect to temperature, dwelling time and atmosphere;

   - a feeding device (23, 39, 43; 63, 79, 83; 103a, 103b, 119a, 119b, 123) for feeding workpieces in cycle-controlled manner to the at least one first furnace unit (12; 52a, 52b; 92a to 92d), the feeding device (23, 39, 43; 63, 79, 83; 103a, 103b, 119a, 119b, 123) comprising a loading unit having low gas losses and, connected therewith, gas-tight first conveyor means (18; 58; 98a, 98b); and

   - second gas-tight conveyor means (19; 59; 99) for transporting the workpieces at the end of the respective desired dwelling time from the at least one first furnace unit (12; 52a, 52b; 92a to 92d) to the at least one second furnace unit (14; 54a, 54b; 94).

   wherein

   - the at least one first furnace unit (12; 52a, 52b; 92a to 92d) comprises a plurality of individual chambers (13; 53; 93), each provided with an inlet and an outlet door (21; 61; 101), the temperature, dwelling time and atmosphere being individually controllable for each workpiece charge of each individual chamber (13; 53; 93);

   - the first conveyor means are connected, as entry transfer lock (18; 58; 98a, 98b), with the inlet doors (21) of the individual chambers (13; 53, 93), in order to enable workpiece charges to be directly fed-in, if desired;

   - the second conveyor means are connected on the inlet side, as intermediate transfer lock (19; 59; 99), to the outlet doors (21) of the individual chambers (13; 53; 93) in order to enable the workpiece charges to be directly carried off, if desired, while on their outlet end they are connected with the at least one second furnace unit (14; 54a, 54b; 94); and

   - the loading unit is designed as a vacuum entry lock (23; 63; 103a, 103b).
2. Device according to claim 1, wherein each individual chamber (13; 53; 93) is preceded by a cross-pusher means (26; 66; 106) for loading and unloading.
3. Device according to claim 1 or 2, wherein the intermediate transfer lock (19) can be connected with a further vacuum entry lock (24).
4. Device according to any of claims 1 to 3, wherein at least one second furnace unit (14; 54a, 54b; 94) comprises a plurality of individual chambers (15, 16; 55a, 55b, 56a, 56b; 95, 96), each of which can be closed by gas-tight doors (61; 73; 101, 113) and can be individually controlled with respect to temperature, dwelling time and atmosphere.
5. Device according to claim 4, wherein an intermediate treatment chamber (15; 55a, 55b; 95) is provided in the at least one second furnace unit (14; 54a, 54b; 94), which can be connected with a downstream final treatment chamber (16; 56a, 56b; 96) via a gas-tight door (21; 61; 101).
6. Device according to claim 5, wherein the final treatment chamber (16; 56a, 56b; 96) can be connected with a quenching bath (31; 71a, 71b) with discharge lock (111).
7. Device according to any of claims 4 to 6, wherein the second furnace unit (54a, 94) can be connected with a single-unit unloading device (52, 112) with hardening press and re-cooling system (74; 114) for delicate workpieces.
8. Device according to any of claims 4 to 7, wherein the downstream furnace unit (54b) can be connected with a high-pressure gas quenching system (75).
9. Device according to claim 8, wherein cooling gas is fed into the high-pressure gas quenching system (75) of the intermediate transfer lock (59), the entry transfer lock (58) and/or the vacuum entry lock (63).
10. Device according to any of the preceding claims, wherein the downstream furnace unit (94) can be connected with a gas cooling lock (111).

Images