EP1685355B1 - Plant and method for the heat treatment of various workpieces - Google Patents

Abstract

The installation has a cyclically rotated rotary furnace (1) with outside and inside walls (3) and a rotary hearth delimiting the furnace chamber (4) with displaceable doors and charging openings. The hearth (1) is divided in the rotational direction into several defined first positions (8) for at least a first workpiece and second positions (12) for at least a second workpiece. The first and second positions alternate so that a treatment zone (6) extends between the openings (7,11) in the rotational direction. The number of positions in the treatment zone is a whole multiple of two and the length of one transport movement corresponds to the length of at least two positions. Independent claim describes method for operating installation wherein a workpiece is introduced into the furnace chamber on each cycle through each opening and at least one treatment zone extends between the openings in the direction of rotation in which heat exchange between first, second and possibly third workpieces takes place during the thermal treatment.

Description

The invention relates to a plant for heat treating workpieces with a cyclically rotatable rotary hearth furnace, which has an outer and an inner wall defining a furnace space, with doors that divide the furnace chamber into a plurality of treatment zones, with a first and a second closable opening to Be - or unloading, wherein the openings are arranged in the outer wall and wherein each opening is associated with a transport device for the workpieces and a quenching device. Furthermore, the invention relates to a method for operating the plant for heat treating workpieces.

Such a plant, which from the WO 03/081156 A1 is known and used for the hardening of workpieces, has two closable openings for loading and unloading in an outer wall. A first opening is a first quenching device in the form of a hardening press and a second opening is preceded by a second quenching device in the form of a quenching bath. The latter is connected by a lock directly to the rotary hearth furnace. The first opening is a first transport means in the form of a pusher and the second opening is associated with a second transport means in the form of a loading robot or manipulator.

The workpieces are heated in the rotary hearth furnace in several treatment zones, carburized and quenched in one of the quenching devices. Subsequently, the hardened workpieces are transported on a roller conveyor and enter a washer and a tempering furnace, in which the workpieces are released due to moderate heating of stress.

The rotary hearth furnace may be used for heating and carburizing first workpieces which are individually quenched in the first chill in the form of a hardening press. Alternatively, the rotary hearth furnace may be used for heating and carburizing second workpieces that are quenched freely in quench baths and packed into batches that may be stored on batch carriers, e.g. As gratings or in baskets or similar containers. The flexibility in terms of applications is therefore limited.

In addition, an embodiment of the known system has the disadvantage that the furnace chamber, which are located in the direction of rotation between the two openings, can not be used for the heat treatment.

The object of the invention is therefore to develop a system of the type mentioned in such a way that the simultaneous heat treatment of various workpieces is made possible.

This object is achieved by a system having the features of claim 1.

According to the invention, the installation is characterized in that the rotary hearth is divided in the direction of rotation into a plurality of defined first places for at least a first workpiece and second places for at least one second workpiece, wherein the first and second places alternate, that the first places are provided with internals , which are designed for heat storage, the heat capacity is at least 1.5 times the heat capacity of the first work, that extends between the openings in the direction of rotation at least one treatment zone, wherein the number of places in the treatment zone is a whole-part multiple of two and that Rotary hearth in the cyclical rotation about a delivery stroke to the length of at least two places in the direction of rotation is rotatable.

Each workpiece, which is introduced into the annular furnace chamber, passes through this completely and is removed through the same opening. The length of each treatment zone must be at least two places or an integer multiple of two, for example four, six or eight, for two different types of workpieces.

In this way, the simultaneous heat treatment of various workpieces in a single rotary hearth furnace is made possible and the furnace space is optimally utilized.

The first places are provided with internals, which are designed for heat storage. The heat capacity is at least 1.5 times the heat capacity of the first workpieces. If these fixtures remain permanently in the furnace chamber, they can store heat that can be delivered to the cold workpieces as soon as they are introduced into the furnace chamber. The fixtures thus serve as secondary heaters, which cause the workpieces are heated quickly and reduces the cycle time.

The object is achieved by an alternative system with the features of claim 2.

According to the invention, the system is characterized in that a third opening is arranged in the outer wall, wherein the third opening is associated with a transport device for the workpieces and a quenching device, wherein the rotary hearth in the direction of rotation in a plurality of defined first places for first workpieces, second places for second Workpieces and third places for third workpieces divided, with the first, second and third places alternate, that the first places (8) are provided with internals, which are designed for heat storage, whose heat capacity at least 1.5 times the heat capacity of the first workpieces is that extends between the openings in the direction of rotation at least one treatment zone, wherein the number of places in the treatment zone is a whole multiple of three, and that the rotary hearth in the cyclical rotation of a delivery stroke by the length of at least three places in Rotation is rotatable.

Preferably, the first places are provided with internals whose carbon activity is substantially equal to 1. The carbon availability is not reduced, because no carbon or soot precipitates on the heated internals.

It is particularly advantageous if the internals made of high temperature resistant ceramic, in particular SIC or carbon fiber amplifier ceramic. Ceramic has a low coefficient of expansion, so that the internals do not warp.

An advantageous development is that the internals are designed for mounting the workpieces.

The invention is further characterized in that the second and / or the third opening is assigned a quenching device in the form of a quenching bath, wherein the quenching bath by means of a heatable lock, which is designed for temporary storage of workpieces, which is designed for temporary storage of workpieces, directly connected to the rotary kiln. Finally, the invention offers the advantageous possibility that the quenching devices are followed by a common tempering furnace, each of which has a path for the first, second or optionally third workpieces.

The invention further provides a method, characterized in that at each cycle through each opening a workpiece is introduced into the furnace chamber and unloaded and that extends between the openings in the direction of rotation at least one treatment zone in which a heat exchange between the first, second during the heat treatment and possibly third workpieces takes place.

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

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

The drawing shows in

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

In the Fig. 1 schematically illustrated plant is used for case hardening, ie gas carburizing and hardening of various workpieces, such as crown wheels, which are quenched in a hardness press and drive bevel gears, which are quenched free in a quenching used.

The plant for heat treatment of workpieces has a rotary hearth furnace 1, which has a cyclically rotatable rotary hearth 2 and an outer and inner wall 3a, b, which delimit a furnace chamber 4, which is subdivided into a plurality of treatment zones 6a-d by means of vertically movable doors 5a-f ,

In the outer wall 3a there is a first closable opening 7 for loading and unloading of a plurality of first workpieces, in this case ring gears, which are quenched individually in a hardness press. The first opening 7 is associated with a first transporting device 9 in the form of a loading robot or manipulator, with the aid of which the first workpieces are transported into and out of the furnace chamber 4. The first opening 7 is preceded by a first quenching device 10 in the form of a hardening press in which the first workpieces are individually quenched.

In the outer wall 3a is spaced from the first opening 7, a second opening 1.1, for loading and unloading of second workpieces, here drive bevel gears. The second opening 11 is preceded by a second quenching device in the form of a quenching bath 13. The latter is connected by means of a lock 14 directly to the rotary hearth furnace 1. The second opening 11 is associated with a second transport device 15 in the form of a bumper. To the transport or. To shorten peak times, the lock 14 is heated and designed so that a batch or a rust can be stored in the lock. The second workpieces 12 are quenched freely in the quench bath and are packaged into batches which are stored on batch carriers, e.g. As gratings or in baskets or similar containers.

The rotary hearth 2 of the rotary hearth furnace 1 is cyclically rotatable intermittently. The rotary hearth moves only in one direction, in this case counterclockwise.

On the rotary hearth, first places 8 for a plurality of first workpieces and second places 12 for a plurality of second workpieces 12 alternate in the direction of rotation. Thus, the entire rotary hearth is divided into first 8 and second 12 places.

At each delivery stroke of the rotary hearth according to the invention two places, d. H. a first place 8 with first workpieces and a second place 12 with second workpieces moved on. The length of a delivery stroke thus corresponds to two places. This ensures that always arrive a first workpieces 8 in front of the first opening 7 and thus before the first quenching device and at the same time second workpieces 12 in front of the second opening 11 and accordingly before the second quenching device.

Each workpiece, which is introduced into the annular furnace chamber, passes through this completely and is removed through the same opening. The length of each treatment zone must be at least two places or an integer multiple of two, for example four or six, for two different types of workpieces.

If three different types of workpieces heat-treated at the same time, a third opening 20 must be present for loading and unloading. The length of each treatment zone must be at least three places or an integer multiple of three, for example six or nine.

The treatment zones 6a-d each have defined temperatures and treatment atmospheres. During the carburization process, the workpieces in the treatment zones are heated in a known manner, with a mass transfer taking place. Before removal, d. H. in the last treatment zone, the workpieces are cooled to the hardening temperature. In the last treatment zone, the carbon level contributes from 0.7% to 0.8% to achieve an edge carbon content in the workpieces at the same height.

It is particularly advantageous if the first places are provided with internals not shown in detail, which are designed for heat storage. The internals have a large heat storage mass and in relation to the first workpieces a large heat capacity and at the same time behave neutral towards the carbon-containing treatment atmosphere, d. H. that their carbon activity is substantially equal to 1. If these installations remain permanently in the furnace chamber, they can store heat that can be radiated to the cold workpieces as soon as they are introduced into the furnace chamber. The internals thus serve as a secondary radiator. The heating of the workpieces is shortened by the radiant heat. At the same time, the carbon availability is not reduced, because no carbon or soot can precipitate on the heated internals.

Preferably, the internals are made of high temperature resistant ceramic. The internals can also serve for the storage of workpieces. The internals are formed in this case as racks with several superposed trays for receiving workpieces. These racks form stackable modules that have closed walls and floors. On the racks, for example, the first workpieces are stored individually. The individual workpieces can also be located on support elements. These are, for example, gratings made of heat-resistant steel, on which the workpieces are loaded and unloaded. The individual modules form a single free-standing batch of batches so that the oven zones can be separated from each other by the intermediate doors. If the batches of batches are installed in niches in the furnace lining, there is a simple way of separating the furnace zones.

The workpieces, which are introduced through an opening in the furnace chamber, pass through this completely and are removed through the same opening. The length of each treatment zone must be at least two different types of workpieces two places or an integer multiple of two, for example four or six. If three different types of workpieces are heat-treated at the same time, the length of a treatment zone must be at least three places or an integer multiple of three, for example six or nine.

In the direction of rotation between the two openings 7 and 11 of the rotary hearth furnace 1 there is a treatment zone 6a. This acts as the first treatment zone for the first workpieces 8 and at the same time as the last treatment zone for the second workpieces 12, before the latter leave the furnace chamber through the opening 11.

In the treatment zone 6a, a heat exchange takes place between the various workpieces in the first and second places. Heat-storing fixtures on the squares for the first workpieces act as secondary heaters that emit heat. In this way, the simultaneous heat treatment of various workpieces in a single rotary hearth furnace is enabled, increases the cycle times and optimally utilized the furnace chamber.

After carburizing in the rotary hearth furnace, the workpieces are quenched in one of the quenching devices. After quenching, the workpieces are conveyed on roller conveyors 16a, b and pass into a respective washer 17a, b and a common tempering furnace 18, in which the first and the second workpieces are freed of stresses due to moderate heating.

According to the invention, the tempering furnace 18 each have a web 19a, b for the first and the second workpieces. The loading and unloading of the batches and the individual parts are sorted by the separate runways 16a, 16b.

In the context of the invention, three different workpieces can be heat-treated simultaneously. In this case, the length of a delivery stroke corresponds to three places to ensure that all workpieces arrive in front of the opening through which they entered the oven.

Claims (8)

1. Plant for the heat treatment of various workpieces, comprising a rotating hearth furnace (1), which is rotationally movable in a synchronized manner and has an outer wall and an inner wall (3a, 3b) and a rotating hearth which delimit a furnace chamber (4), comprising movable doors (5) which divide the furnace chamber into a plurality of treatment zones (6), comprising a first and a second closable opening (7, 11) for charging or discharging, wherein the openings are arranged in the outer wall (3a) and wherein each opening is assigned a conveying device for the workpieces and a quenching device (10, 13),
   characterized
   in that the rotating hearth (1) is divided in the direction of rotation into a plurality of defined first spaces (8) for at least one first workpiece and second spaces (12) for at least one second workpiece, where the first and second spaces (8, 12) alternate,
   in that the first spaces (8) are provided with internal fittings, which are designed for heat accumulation and the heat capacity of which is at least 1.5 times the heat capacity of the first workpieces,
   in that at least one treatment zone (6) extends between the openings (7, 11) in the direction of rotation, wherein the number of spaces (8, 12) in the treatment zone (6) is an integer multiple of two, and
   in that, during the synchronized rotation, the rotating hearth can be rotated by a delivery stroke by the length of at least two spaces (8, 12) in the direction of rotation.
2. Plant for the heat treatment of various workpieces,
   comprising a rotating hearth furnace (1), which is rotationally movable in a synchronized manner and has an outer wall and an inner wall (3a, b) and a rotating hearth which delimit a furnace chamber (4), comprising movable doors (5) which divide the furnace chamber into a plurality of treatment zones (6), comprising a first and a second closable opening (7, 11) for charging or discharging, wherein the openings are arranged in the outer wall (3a) and wherein each opening is assigned a conveying device for the workpieces and a quenching device (10, 13),
   characterized
   in that a third opening is arranged in the outer wall (3a), wherein the third opening is assigned a conveying device for the workpieces and a quenching device,
   in that the rotating hearth is divided in the direction of rotation into a plurality of defined first spaces (8) for first workpieces and second spaces (12) for second workpieces and also third spaces for third workpieces, where the first, second and third spaces (8, 12) alternate,
   in that the first spaces (8) are provided with internal fittings, which are designed for heat accumulation and the heat capacity of which is at least 1.5 times the heat capacity of the first workpieces,
   in that at least one treatment zone (6) extends between the openings (7, 11) in the direction of rotation, wherein the number of spaces (8, 12) in the treatment zone (6) is an integer multiple of three, and
   in that, during the synchronized rotation, the rotating hearth can be rotated by a delivery stroke by the length of at least three spaces (8, 12) in the direction of rotation.
3. Plant according to Claim 1 or 2,
   characterized in that the first spaces (8) are provided with internal fittings, the carbon activity of which is equal to 1.
4. Plant according to Claim 3,
   characterized in that the internal fittings consist of ceramic which is able to withstand high temperatures.
5. Plant according to one of Claims 1 to 4,
   characterized in that the internal fittings are designed for storage of the workpieces.
6. Plant according to one of Claims 1 to 5,
   characterized in that the second and/or the third opening (11) are/is assigned a quenching device (13) in the form of a quenching bath, which is connected directly to the rotating hearth furnace (1) by means of a heatable lock (14) designed for the intermediate storage of workpieces.
7. Plant according to one of Claims 1 to 6,
   characterized in that a common tempering furnace (18) is connected downstream from the quenching devices (10, 13) and has a track in each case for the first, second and possibly third workpieces.
8. Method for operating the plant according to one of Claims 1, 3 to 7 for the heat treatment of various workpieces,
   characterized in that a workpiece is introduced into the furnace chamber through each opening on each cycle and discharged, and in that at least one treatment zone extends between the openings in the direction of rotation, in which treatment zone heat is exchanged between first, second and possibly third workpieces during the heat treatment.

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