EP1488181B1 - Installation for the heat-treatment of parts - Google Patents

Abstract

Device for heat treating workpieces has an opening (16) for charging/discharging in the outer wall (2) of a rotary furnace (1) in a last treatment zone. The opening has a sluice (17). A quenching unit (18) formed as a quenching bath is connected to the furnace via a sluice. Preferred Features: The sluice is gas-tight. A further quenching unit (19) is connected to the furnace via the sluice and is formed as a quenching bath or as a gas quenching chamber. The temperature in the second quenching unit deviates from the temperature in the first quenching unit.

Description

The invention relates to a plant for the heat treatment of workpieces, comprising a cyclically rotary rotary hearth furnace having an outer and an inner wall defining a furnace space, which is divided by means of vertically movable doors in a heating zone and at least one treatment zone, wherein in the outer wall in the heating zone, a first closable opening for loading or unloading is arranged, with a first quenching device and with a transport device for transporting the workpieces in the rotary hearth furnace and from this into the first quenching device.

Such a plant is from the DE-C1-3427716 known. It is a system for hardening of individual parts with a rotary hearth furnace and a hardening press. The rotary hearth furnace has a lock-like loading or unloading zone, which is formed by means of both sides of the loading and unloading arranged vertically movable doors. From this loading or unloading the workpieces can be removed individually after opening the oven door using a loading and unloading robots and transferred to the hardness press.

There is a need to use the system more universal, d. H. Not only the heat treatment of individual parts, but also the heat treatment of whole batches, which are based on batch carriers, eg. B. rusting to allow. Whole batches of workpieces are usually quenched in a quench bath.

The cycle time, d. H. the time between loading and unloading a workpiece in or out of the rotary hearth furnace is relatively long in the known system, since a single opening is used both for loading and unloading. Therefore, there is also a need to minimize the cycle time.

The EP-A1-0 735 149 discloses a plant for heat treatment of workpiece batches under vacuum. A rotary kiln has in the outer wall a first opening with a door exclusively for loading and a second opening exclusively for unloading, the second opening being preceded by a sluice by means of which a cooling chamber or quenching chamber is connected to the rotary kiln. By means of the rotary kiln, the tool batches are transported to different treatment furnaces which are arranged outside on the circumference of the rotary kiln, for example a carburizing kiln chamber. To enter the To reach treatment furnaces, the workpieces from the turntable must be transported transversely to the direction of rotation in the treatment furnaces.

In the EP-A1-0 735 149 Although it is mentioned that tool batches can be treated simultaneously with different hardness conditions. However, this flexibility is achieved with a plant concept (vacuum furnaces, no subdivision of the rotary kiln into different treatment zones), which differs significantly from the generic plant concept.

The U.S.-A-4,496,312 discloses a plant with a rotary hearth furnace for heat treatment of workpieces. The rotary hearth furnace is divided by means of doors in a heating zone and a cooling zone. A first opening, preceded by a preheating chamber, serves exclusively to load the rotary hearth furnace, and a second opening, which is preceded by a cooling chamber, is used exclusively for unloading the workpieces. Thus, this system is not universally applicable.

The GB-A-1 181 924 discloses a plant for heat treating workpieces with two ovens each having an opening 106 for loading and an opening 108 for unloading.

The DE-C1-3 640 325 discloses a plant for heat treating workpieces in a carbonizing atmosphere. A Kohlungsofen is designed as a rotary kiln. The batches can be rotated for different lengths of time, resulting in different residence times for the batches. The carbonizing furnace is fed exclusively through a first opening and discharged through a second opening in a hardening furnace. The system concept differs significantly from the concept of the generic system

The invention has for its object to provide a system of the type mentioned, the universal use and the cycle time is low.

This object is achieved in a system of the type mentioned by the characterizing features of claim 1.

The rotary hearth furnace has two closable openings, both of which can be used for loading and unloading. The system of the invention is universally applicable. In addition, the cycle time can be minimized and thus the hourly throughput of workpieces can be increased.

The two openings are arranged side by side with a small circumferential distance, wherein the circumferential distance between the first and the second opening is preferably substantially 45 °. Depending on the space conditions in the individual case, the circumferential distance can also be up to 90 °.

In a preferred embodiment, the first opening is preceded by a lock for loading.

In an advantageous embodiment, the first opening is arranged vertically above the furnace chamber. The first opening is preceded in the vertical direction by a loading sluice, which is designed as a known per se elevator lock, with a transport device for the horizontal transport of the workpieces. Thus, the loading opening can be arranged relatively close or immediately adjacent to the removal opening. This has the advantage that the oven space available for the heat treatment can be optimally utilized.

Since the heat treatment usually takes place in a protective gas atmosphere or in a treatment atmosphere, both the lock and the optionally present loading lock are made gas-tight.

The locks have at least one lock door which extends substantially perpendicular to the opening in the outer wall. The lock door is thus located in a side wall of the lock. The quench bath, which is connected by means of the lock with the rotary hearth furnace, is accordingly arranged on a side wall of the lock.

Preferably, a further quenching device is connected to the rotary hearth furnace by means of the lock at the second opening. This may be a gas quenching chamber or another quench bath. Thus, the flexibility of the system is considerably increased because the quenching of the workpieces optionally at different Temperatures can be made. The two quenching devices are arranged on the opposite side walls of the lock.

Preferably, at least one opening is associated with a transport device in the form of a bumper. The batch is transported by means of the bumper in a simple manner in the removal lock and transferred from there into the subsequent to the removal lock quench. In the event that the first opening is provided with a loading lock, a bumper can also be used here. The workpieces, which are packed into batches in baskets or similar containers, are transported by means of the baffle device into the lock and transferred from there into the rotary hearth furnace.

Between the first opening and the second opening is one of the vertically movable doors, so that a zone separation takes place between the loading and unloading.

Preferably, at least one additional vertically movable door for changing the length of the heating and / or the treatment zone is present. The additional door can be used as needed for zone separation. All doors are individually controllable and thus individually movable.

In the phases in which the hearth of the rotary hearth furnace rotates, usually all doors are open, ie all doors are raised at the same time. In the motion-free phases, all doors that serve for zone separation are closed. If there is no need to make the zone separation by means of the additional door, this door is also open during the motion-free phases. If there is a need to use the additional door for zone separation and thus change the length of the heating or / or treatment zone, at least one of the doors that has been used for zone separation will be kept open during the motionless phases. In various heat treatment methods, the length of the heating zone and / or the treatment zone can thus be optimized as required.

An embodiment of the rotary hearth furnace is characterized in that the second closable loading and unloading opening in the outer wall, adjacent to the heating zone and spaced from the first loading and unloading opening is arranged and that the rotary hearth is rotatable in both directions.

This rotary hearth furnace offers the choice between two loading and unloading options. Both loading and unloading openings can be used both for loading and unloading. Both loading and unloading are adjacent to the heating zone, so that when each opening is charged ensures that the workpieces, after they have been introduced into the furnace chamber, get directly into the heating zone. It only has to be changed in accordance with the direction of rotation of the rotary hearth. This functionality of the rotary hearth furnace is significantly improved.

Preferably, the heating zone extends between the first and second loading and unloading over a range of substantially 90 °.

Advantageously, at least two treatment zones are provided, each of which adjoins the heating zone and which are differently adjustable with regard to treatment temperature and treatment atmosphere.

Since the heat treatment usually takes place in a protective gas atmosphere, the lock is accordingly preferably made gas-tight.

In a preferred embodiment, doors are provided on both sides immediately adjacent to the first loading and unloading opening, so that a loading and unloading zone is formed, which can be heated.

This system is particularly universally applicable, since a quenching device is provided at each opening. Each opening is used both for loading and unloading. Depending on the, through which of the two openings the workpieces get into the oven, the direction of rotation of the rotary hearth furnace is changed, so that the workpieces first reach the heating zone.

The invention will be explained in more detail below with reference to a preferred embodiment in conjunction with the drawings.

• Fig. 1 eine schematische Draufsicht auf eine erste Ausführungsform einer Anlage zur Wärmebehandlung;
• Fig. 2 eine schematische Draufsicht auf eine zweite Ausführungsform einer Anlage zur Wärmebehandlung.

The drawing shows in

• Fig. 1 is a schematic plan view of a first embodiment of a plant for heat treatment;
• Fig. 2 is a schematic plan view of a second embodiment of a plant for heat treatment.

The plant for the hardening of workpieces according to Fig. 1 comprises a rotary hearth furnace 1, the clockwise rotatable exclusively in one direction, in the clockwise direction. A fixed masonry outer wall 2 and an inner wall 3 of refractory masonry form with rotary hearth and a ceiling, not shown, an annular furnace chamber, not shown in the plan view. The furnace chamber is divided by means of doors 5a-5d into a heating zone 6 and three treatment zones 7, 8, 9, namely a first and a second diffusion / carbon zone 7, 9, and a carbon zone 8. The doors 5a-5d are vertically raised in a manner not shown. The workpieces are located on batch carriers 10 in the form of grates.

In the outer wall is located at the beginning of the heating zone 6, a first closable opening 11, which is preceded by a gas-tight lock 12 for loading. The opening 10 between the furnace chamber and lock 12 can be opened or closed in a known manner by means of an oven door. The lock 12 has a lock door 13 which substantially perpendicular to the opening 10 and which is alternately opened or closed for loading. Before loading, the batch carriers 10 are located with the workpieces in a pre-oxidation oven 14. The batch carriers 10 are inserted from the lock 12 into the oven space by means of a first push device 15. The batch carrier 10 arrive due to the rotation of the rotary hearth clockwise first in the heating zone 6 on and from the heating zone 6 in the treatment zones 7, 8 and 9. It is in the treatment zones to diffusion / carbon zones, in which the treatment temperatures and the treatment atmosphere are different adjustable. In the lock 12 and the load lock, the treatment atmosphere or a neutral gas, such as nitrogen may be located.

In the outer wall 2 is a second closable opening 16, which is preceded by a gas-tight lock 17 for unloading. Between the two openings 11 and 16 there is a circumferential distance of about 45 °. To the lock 17 are connected via not shown lock doors, which extend substantially perpendicular to the opening 16, both sides of a first Abschreckbad 18 and a second Abschreckbad 19 coupled, where different temperatures prevail.

The discharge of the individual batch carrier 10 with the workpieces at the end of the last treatment zone by means of a second pusher 20. The unloading takes place as well as the loading intermittently. The batch carrier 10, which has arrived at the end of the last treatment zone, after opening the second opening 16 by means of the pusher 20 in the lock 17 and from there either in one of the two quenching baths 18, 19 transported and quenched. Of course, the second opening 16 is closed again after each removal process.

Between the first opening 11 and the second opening 16 there is a vertically movable door 5d, so that the loading and unloading take place in different zones, namely the heating zone 7 and the last treatment zone 9.

Modifications are readily possible within the scope of the invention. Thus, the circumferential distance between the two openings may differ from 45 °. The circumferential distance should be as small as possible, but can be up to 90 ° for reasons of space. The second quenching device can be designed as a gas quenching chamber. Additional doors could be used to vary the length of the heating zone and / or the treatment zone.

Fig. 2 shows a rotary hearth furnace 21, which serves for heat treatment in the context of a process for hardening of workpieces 22, has a rotary hearth 23 which is cyclically rotatable in both directions. A fixed masonry outer wall 24 and an inner wall 25 of refractory masonry form with the rotary hearth 23 and a ceiling, not shown, an annular furnace chamber shown in plan view. The furnace chamber is divided by means of doors 26a-26e into a heating zone 27 and three treatment zones 28 to 30, namely a first and a second diffusion / carbon zone 28, 30 and a carbonization zone 29. The doors 26a-26d are vertically raised in a manner not shown.

In the outer wall there is a first opening 31 for loading and unloading, followed by doors 26a-26e on both sides, so that a loading and unloading zone 32 is formed. An oven door 33 closes the first opening 31.

The loading and unloading of individual workpieces is done by a loading and unloading robot 34. The loading takes place cyclically. The workpieces 22 which have been placed in the furnace chamber, after opening the door 26a due to the rotation of the rotary hearth counterclockwise in the heating zone 27. The workpieces 22 on the rotary hearth 23 are passed through the treatment zones 28, 29 and 30. In the diffusion / carbon zones 28, 30, the treatment temperature and the treatment atmosphere are differently adjustable. The first diffusion / carbon zone 28 is set up in this feed case so that the zone acts as a carbon zone. The second diffusion / carbonation zone 30, So the last treatment zone before removal acts as a diffusion zone, ie that the C-potential is lowered in the treatment atmosphere. The workpieces that have arrived in the loading and unloading zone 32 are removed individually after opening the oven door 33 and quenched in a hardening machine 35. Of course, the oven door 33 is closed again after each removal process.

In the outer wall 24, spaced from the first opening 31 for loading and unloading, arranged a second closable opening 36 for loading and unloading. Between the two loading and unloading openings 31, 36 extends over a range of about 90 °, the heating zone 27, which can be closed by means of a door 26b immediately behind the second opening 36 for loading and unloading. The two openings 31, 36 are thus in each case adjacent to the heating zone 27. The direction of rotation of the rotary hearth is selected as a function of which of the two loading and unloading openings 31, 36 is charged. In any case, the workpieces enter the heating zone after being charged.

At the second opening 36 for loading and unloading closes a lock 37 with a cooling bath 38 in the form of an oil bath. The workpieces 22, which are located on batch carriers in a known manner, are introduced into the furnace chamber in the second loading and unloading opening 36 and are transported on the rotary hearth 23 in a clockwise direction through the furnace chamber. In this charging case, the second diffusion / carbonization zone 30 is configured as a carbonation zone and the first diffusion / carbonization zone 28 as a diffusion zone.

Modifications are readily possible within the scope of the invention. Thus, the heating zone 27 may extend over a larger area of the furnace chamber.

Claims (17)

1. Plant for the heat treatment of workpieces, comprising a rotating hearth furnace (1; 21), which is rotationally movable in a synchronized manner and has an outer and an inner wall (2, 3; 23, 24), which walls delimit a furnace chamber divided by means of vertically movable doors (5a-d) into a heating zone (6) and at least one treatment zone (7-9; 27-30), a first closable opening (11; 31) for charging and discharging being disposed in the outer wall (2; 24) in the heating zone (6; 27), comprising a first quenching device (35) and comprising a conveying device (34) for conveying the workpieces into the rotating hearth furnace (1; 21) and from there into the first quenching device (35), characterized in that a second closable opening (16; 36) for charging and discharging is disposed in the outer wall (2; 24) in the last treatment zone (9; 28), and in that upstream of the second opening (16; 36) there is a lock (17), by means of which a second quenching device (18; 38) is connected to the rotating hearth furnace (1; 21).
2. Plant according to Claim 1, characterized in that the first opening (11, 31) and the second opening (16; 36) for charging or discharging are disposed one beside the other at a peripheral spacing of essentially 45°.
3. Plant according to Claim 1 or 2, characterized in that upstream of the first opening (11) for charging and discharging there is a charging lock (12).
4. Plant according to Claim 1, characterized in that the first opening (11) for charging and discharging is disposed perpendicularly above the furnace chamber, and in that upstream of the first opening in the vertical direction there is a charging lock (12), which is configured as an elevator lock.
5. Plant according to one of Claims 1 to 4, characterized in that the lock (17) and, where necessary, the charging lock (12) are of gas-tight construction.
6. Plant according to one of Claims 1 to 5, characterized in that the lock and, where necessary, the charging lock (12) have at least one lock door, which runs essentially at right angles to the opening (11, 16) in the outer wall.
7. Plant according to one of Claims 1 to 6, characterized in that the second quenching device (18, 38) is configured as a quenching bath.
8. Plant according to one of Claims 1 to 7, characterized in that, by means of the lock (17), a further quenching device (19) is connected to the rotating hearth furnace (1).
9. Plant according to Claim 8, characterized in that the further quenching device (19) is configured as a quenching bath or as a gas quenching chamber.
10. Plant according to Claim 8 or 9, characterized in that the temperature in the further quenching device (19) differs from the temperature in the quenching bath (18).
11. Plant according to one of Claims 1 to 10, characterized in that to at least one opening (11, 16) for charging or discharging there is assigned a conveying device (15, 20) in the form of a pushing mechanism.
12. Plant according to one of Claims 1 to 11, characterized in that at least one additional vertically movable door (5a-e) for changing the length of the heating and/or of the treatment zone is present, all doors being individually controllable.
13. Plant according to one of Claims 1 to 12, characterized in that one of the vertically movable doors (5a-e) is located between the first opening (11) and the second opening (16).
14. Plant according to Claim 1, characterized in that the second closable opening (36) for charging and discharging is disposed in the outer wall (24) adjacent to the heating zone (27) and at a distance from the first opening (31), and in that the rotating furnace (1) is rotatable in both directions.
15. Rotating hearth furnace according to Claim 14, characterized in that, between the first and the second opening (31, 36) for charging and discharging, the heating zone (27) extends over a range of essentially 90°.
16. Rotating hearth furnace according to Claim 14 or 15, characterized in that at least two treatment zones (28 to 30) are provided, which respectively adjoin the heating zone (27) and which are differently adjustable with respect to treatment temperature and treatment atmosphere.
17. Rotating hearth furnace according to one of Claims 14 to 16, characterized in that directly next to the opening (31) for charging and discharging, on both sides, doors (26a-26e) are provided, so that a charging and discharging zone (32) is formed.

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