DE102021109678A1 - Press hardening plant for the heat treatment of metallic workpieces - Google Patents

Abstract

The invention relates to a press-hardening plant, with:- a hardening furnace designed as a continuous furnace and having a furnace inlet and a furnace outlet,- a hardening press for clamping a workpiece and for effecting a quenching process of the workpiece in the clamped state,- wherein in an intermediate area between a handling system is provided between the furnace exit and the hardening press and- a workpiece loading system is provided in an area adjacent to the furnace entrance,- the handling system and the workpiece loading system being connected to one another via a workpiece carrier return path that runs past the continuous furnace.

Description

The invention relates to a press-hardening system for the heat treatment of metallic workpieces, in particular transmission components, using a means for heating workpieces and a means for hardening workpieces as part of a quenching process.

Furthermore, the invention also relates to a press hardening system in which the means for heating the workpieces mentioned at the outset is designed as a hardening furnace for heating a workpiece to a defined target temperature. This press-hardening system includes a hardening press for carrying out a quenching procedure while the workpiece is under tension, as well as a control device for controlling the press-hardening system.

The heat treatment of metallic workpieces is known from the prior art. The well-known basic principle of heat treatment is that metallic workpieces are heated and then hardened by quenching.

In the heat treatment of numerous workpieces, for example in series production, etc., it is of great interest to obtain a consistent quality of the heat-treated workpieces, and therefore high reproduction accuracy, within the framework of a process that can be carried out with high efficiency.

In this context, the invention is based on the object of creating solutions by means of which a high degree of reproduction accuracy can be ensured with regard to the microstructure and the geometry of correspondingly heat-treated workpieces within the scope of a heat treatment that can be carried out in very short cycles.

• - einem Härteofen der als Durchlaufofen ausgeführt ist und einen Ofeneingang und einen Ofenausgang aufweist,
• - einer Härtepresse, zum Spannen eines Werkstücks und zur Bewerkstelligung eines Abschreckvorganges des Werkstücks in gespanntem Zustand,
• - wobei in einem Zwischenbereich zwischen dem Ofenausgang und der Härtepresse ein Handhabungssystem vorgesehen ist und
• - in einem dem Ofeneingang benachbarten Bereich ein Werkstückbeschickungssystem vorgesehen ist,
• - wobei das Handhabungssystem und das Werkstückbeschickungssystem über einen am Durchlaufofen vorbei geführten Werkstückträgerrückförderweg miteinander verbunden sind.

According to a first aspect of the present invention, this object is achieved by a press hardening plant with:

• - a hardening furnace that is designed as a continuous furnace and has a furnace inlet and a furnace outlet,
• - a hardening press, for clamping a workpiece and for effecting a quenching process of the workpiece in the clamped state,
• - a handling system being provided in an intermediate area between the furnace outlet and the hardening press, and
• - a workpiece loading system is provided in an area adjacent to the furnace entrance,
• - wherein the handling system and the workpiece loading system are connected to one another via a workpiece carrier return path guided past the continuous furnace.

This advantageously makes it possible, immediately after the workpieces have left the furnace outlet, to pick them up in an orientation defined by the respective workpiece carrier and insert them into the hardening press in this defined gripping state. The workpiece carrier that has become free in this way can be equipped again with a workpiece or a batch of workpieces with little cooling and a short handling time, or it can also first be fed to a processing system in which it is cooled and cleaned, in particular washed, and only loaded again in such a processed state . The continuous furnace and the workpiece carrier return path form a circulatory system via which heated workpieces are made available in a defined cycle sequence for transfer to the quenching press.

According to a particularly preferred embodiment of the invention, a cooling cell is preferably provided in the vicinity of the furnace entrance, and this cooling cell can be loaded with workpieces by integrating the workpiece loading system. The workpiece loading system can advantageously take over all workpiece handling tasks that have to be carried out in the spatial vicinity of the furnace entrance. In this case, the waiting times until the respective new introduction of a workpiece into the furnace entrance can be used in an advantageous manner for further activities of the workpiece loading system.

A particularly advantageous embodiment of the invention with regard to the shortest possible workpiece transfer path and efficient workpiece transfer of the workpieces to the hardening press preferably provides that the workpiece, after leaving the hardening furnace, is guided transversely to the direction of passage through the hardening furnace to the hardening press. This also results in a compact design of the press hardening system and the path running transversely to the throughput direction also makes it possible to convey the workpiece carriers back to the furnace entrance over a short distance. With this arrangement, the hardening furnace and the hardening press can then be advantageously coupled across the corner by the transfer system. With this corner coupling, the workpiece can be handled between the furnace outlet and the hardening press using a gripper arm be achieved mechanically, which realizes the main movement of the workpiece in the form of a pivoting movement. The pivot point of a corresponding arm is then preferably in the inner corner area of the track or in the area of the track pole or the track center of curvature.

According to a further particular aspect of the present invention, the press hardening plant is preferably constructed in such a way that the workpiece return path is formed by a workpiece return transfer system which extends along the hardening furnace between an output area of the hardening press and an input area of the hardening furnace. This workpiece return path can run parallel to the workpiece carrier return path. This results in an overall compact and structured structure of the press hardening system, in which the more complex units are each accessible from the outer edge area of the system, the longer workpiece and workpiece carrier transfer paths run parallel and the transverse movements of the workpieces and workpiece carriers can be used to separate and combine these structures will.

A particularly compact design of the press hardening system with short transfer paths for the workpieces and also for the workpiece carriers is preferably achieved according to a particular aspect of the present invention in that the workpiece return transfer system is connected to the hardening press on an output side of the hardening press running transversely to the longitudinal direction of the furnace. The workpieces can be passed through the hardening press "around the corner", so that the workpieces pass through the hardening press by being introduced into an input area of the same and removed via an output area facing away from it across the corner. This allows the workpiece to be brought into the hardening press and the workpiece removed from the hardening press within the framework of chronologically interlocking processes, since the input mechanism is not blocked by the output mechanism.

According to a further particular aspect of the present invention, the press hardening system is preferably designed in such a way that a post-cooling station, a washing station and/or a testing station can be loaded with workpieces via the workpiece return transfer system. The workpiece return transfer system acts as a universal conveying device embedded in the press hardening system, which enables a programmatically selected use of systems of the press hardening system that are attached to the workpiece return transfer system.

The test station can preferably be designed in such a way that workpieces located in the area of the test station can be removed from the press hardening system. This makes it possible to safely remove workpieces from the system and to subject them to more complex examinations, in particular manual metrological examinations. The workpieces that are possibly only temporarily ejected in this way can advantageously also be returned to the system via the test station, so that they can then be handled further automatically within the system.

According to a particular aspect of the present invention, the hardening system according to the invention is preferably operated in such a way that the removal of the workpieces from the hardening furnace and the insertion of the workpieces into the hardening press are chronologically coupled in terms of process. This results in high reproducibility of the thermal history of the workpieces up to the start of the quenching process.

The press hardening system according to the invention is used to carry out a method, also according to the invention, for the heat treatment of metallic workpieces, in particular transmission components, in which carburized metallic workpieces are introduced into a means for heating workpieces and heated therein, the means for heating workpieces being designed as a continuous furnace and wherein workpieces are introduced into the continuous furnace through a first opening device and are removed from the continuous furnace through a second opening device spaced apart from the first opening device, wherein after removal, workpieces are introduced into a means for hardening for hardening. The workpieces are conveyed through the continuous furnace via workpiece carriers. Outside of the continuous furnace, these workpiece carriers are conveyed back along it to the entrance area of the furnace.

The first opening device serves to release or close a furnace entrance area. The second opening device serves to open or close an oven output area. The method according to the invention comprises the steps of introducing the workpieces into the hardening furnace via the furnace entrance area and conveying the workpieces through a heating section of the hardening furnace to the furnace exit area. The method according to the invention is preferably carried out in such a way that at least one workpiece is heated in the heating section while at least one workpiece is kept warm in the output area. The method can also be processed in such a way that a workpiece is also preheated in the input area is accomplished. This allows the residence time in the heating section to be reduced.

Further, according to the method of the present invention, preferably, a negative pressure or a vacuum is set and maintained in the heating section while a workpiece is fed out from the furnace discharge section. For this purpose, the workpiece is guided through a lock device provided between the heating section and the furnace output area, and the pressure in the output area is alternately lowered and then brought back into line with the ambient pressure. The workpiece preheating in the input area can be limited to a temperature at which there is still no significant reaction of the workpiece surface with the gas atmosphere in the input area.

The method according to the invention is also preferably carried out in such a way that a pressure below the ambient pressure, in particular a vacuum, prevails in the heating section even during the introduction of a workpiece into the furnace entrance area. For this purpose, the workpiece is guided through a lock device located between the furnace entrance area and the heating section. The pressure in the furnace entrance area is also alternately lowered and adjusted to the ambient pressure. Direct communication between the heating section and the environment is avoided as part of the workpiece heating operation of the hardening system by coordinating the opening and closing of the locks and the opening devices.

The pressure control in the sections of the continuous furnace that can be sealed off selectively from one another, as well as the temperature control in these sections, is regulated or at least controlled in accordance with a coordinated process control.

• - das zumindest eine Mittel zum Erwärmen von Werkstücken als Durchlaufofen ausgebildet ist, durch welchen die Werkstücke in einer Durchlaufrichtung hindurchförderbar sind,
• - der Durchlaufofen einen Eingangsabschnitt, einen Heizabschnitt und einen Ausgangsabschnitt aufweist,
• - die Werkstücke über eine erste Öffnungseinrichtung in den Eingangsabschnitt einbringbar sind,
• - die Werkstücke über eine zweite Öffnungseinrichtung aus dem Ausgangsabschnitt ausbringbar sind,
• - der Ausgangsabschnitt eine Ausgabekammer umfasst und
• - die Ausgabekammer gegenüber dem Heizabschnitt und dem Mittel zum Härten des Werkstückes gesteuert verschließbar ist.

The device provided for carrying out this method comprises at least one means for heating workpieces and also at least one means for hardening workpieces, wherein:

• - the at least one means for heating workpieces is designed as a continuous furnace through which the workpieces can be conveyed in a direction of flow,
• - the continuous furnace has an input section, a heating section and an output section,
• - the workpieces can be introduced into the entry section via a first opening device,
• - the workpieces can be removed from the exit section via a second opening device,
• - the exit section comprises a delivery chamber and
• - the output chamber can be closed in a controlled manner in relation to the heating section and the means for hardening the workpiece.

This advantageously makes it possible to decouple the transfer of the workpieces into the quenching device from the introduction of the workpieces into the furnace and the furnace-internal transfer of the workpieces into the exit section and to coordinate them with the opening of the second opening device. In addition, the furnace acts as a transport system through which the components are heated as part of their transport to the entry area of the quenching agent. In a particularly advantageous manner, this results in a local offset of a cold zone in front of the furnace, which is used for the introduction of the workpiece, from a hot zone facing the means for hardening. This results in an elongation of an overall system formed including the device according to the invention.

The device according to the invention thus makes it possible to coordinate the sequential steps of heating and hardening with one another, as a result of which a consistent quality of the correspondingly heat-treated workpieces and thus high reproduction accuracy can be achieved.

The continuous furnace is preferably designed in such a way that it comprises at least one entry chamber, which forms the entry section. The input chamber and the output chamber are coupled to each other by a workpiece transport path passing through the heating section.

The workpieces are preferably conveyed through the continuous furnace in connection with workpiece carriers. The workpieces can be brought into the input chamber through the first opening device, preferably in conjunction with an associated workpiece carrier. The workpieces are preferably conveyed on the workpiece transport path by a transport mechanism. This transport mechanism can be designed in such a way that it conveys the workpieces in connection with the workpiece carriers. The workpieces can be removed from the output chamber through the second opening device. The workpiece carriers are preferably conveyed back to the input section. The heating section is preferably dimensioned such that several works in this heating section pieces can be arranged in successive stations. The workpieces can be conveyed through the heating section by successively advancing or trailing the workpiece carriers.

The input chamber and the output chamber are preferably designed in such a way that they each receive only one workpiece or a workpiece carrier with one or more workpieces arranged on it. The workpiece carriers can in particular be made of a ceramic or heat-resistant metallic material. The material carriers are handled automatically after they leave the output chamber. As part of this handling, they are cleaned in the form of blowing off, brushing and/or washing. It is possible to return the workpiece carriers to the input area of the continuous furnace in a temperature-controlled state and to bring the workpieces or the workpiece into the continuous furnace in connection with a workpiece carrier that has been preheated in a defined manner.

At least one further chamber is preferably provided. This further chamber preferably forms the heating section. The communication of the further chamber with the input chamber and/or with the output chamber can be established and interrupted in a switchable manner. For this purpose, doors, flaps or slide structures are preferably provided, which switchably separate the heating section from the input chamber upstream in the workpiece transport direction and the output chamber downstream in the workpiece transport direction.

According to a particular aspect of the present invention, the continuous furnace is preferably designed as a vacuum continuous furnace, with a negative pressure being able to be applied at least in the input chamber and/or in the output chamber and/or in the at least one further chamber, with the negative pressure preferably being able to be regulated in a chamber-specific manner.

Advantageously, at least one means is provided for interrupting communication, in particular for closing at least one section between the input chamber and output chamber and/or between the input chamber and the at least one additional chamber and/or between the at least one additional chamber and the output chamber. This means for interrupting the communication can be designed in particular as a flap, door, slider or bulkhead that can be brought selectively into a release position and into a closed position. The position of this means can be changed in an advantageous manner by electronically controlled actuating means.

According to a further aspect of the present invention, at least one means for setting at least one temperature of the continuous furnace, in particular a control unit, is preferably provided, by means of which the temperatures can be individually set chamber-specifically, preferably in the input chamber and in the output chamber.

The dispensing chamber can advantageously be provided with a heating device. This heating device is preferably operated via a control or regulating device. The output chamber can advantageously be operated in a controlled or regulated manner in such a way that it enables the workpiece located therein to be kept warm in a vacuum, preferably temperature-controlled. Furthermore, the dispensing chamber can be operated in such a way that it is kept warm at ambient pressure or reduced vacuum. Furthermore, the workpiece transfer from the output chamber to the hardening press can be handled in such a way that it takes place either in an atmospheric environment or in a vacuum.

The output chamber forms a lock system through which workpieces can be removed from the heating section without the vacuum in the heating section having to be broken for this purpose. The output chamber also functions as a warming section in which the workpieces can continue to be kept at a specified temperature level.

The pressure in the dispensing chamber can also preferably be adjusted in accordance with a control device. The dispensing chamber is separable from the heating section by a closure device. This closing device and the opening device are actuated at different times. In regular operation, the closing device is closed; it is preferably only temporarily opened to move a workpiece from the heating section into the output chamber. The opening device is also primarily closed and is only opened temporarily for the removal of a workpiece from the removal chamber. During regular operation of the hardening device, the opening device is only opened when the closing device is closed and the interior of the dispensing chamber is thus sealed off from the interior of the heating section. In the course of keeping the workpiece warm in the discharge chamber, the closing device pointing to the heating section and the opening device pointing outward are closed. In the open position, the closing device pointing towards the heating section provides a passage for the workpiece between the heating section and the dispensing chamber. In the closed position, the closing device blocks this workpiece passageway. The closure device atmospherically seals the heating section and the dispensing chamber from one another.

It is possible to set a negative pressure in the dispensing chamber for as long as possible and to equalize the pressure only shortly before the opening device is opened. This makes it possible to avoid the action of any non-inert gases on the workpiece and, in particular, avoid scaling.

The at least one means for hardening the workpieces is preferably designed in such a way that the workpieces introduced into it can be quenched by means of a fluid, preferably oil.

As an alternative to the measure mentioned above or also in combination with this, the at least one means for hardening the workpieces can also be designed in such a way that the workpieces introduced into it can be quenched by means of a gaseous medium.

According to a particular aspect of the present invention, the means for hardening is designed as a device in which the fluid provided for quenching the workpiece is actively brought to the workpiece. In this case, a channel system is created in the device in interaction with the workpiece and a structure enclosing it and/or dipping into it, and the quenching medium actively flows through this channel system. The flow is controlled in such a way that there is a defined heat dissipation from the zones of the workpiece that are flushed. The workpiece is preferably clamped and/or supported in the quenching device. Insofar as the workpiece is clamped, the workpiece is loaded in a state in which it assumes a desired geometry with the introduction of compressive forces.

The application of the quenching medium can be controlled in such a way that a defined energy discharge from the workpiece takes place, in which case the workpiece assumes a defined thermal expansion state. In this defined thermal state, the workpiece can be relieved or, in particular, mandrel structures can be moved out of the workpiece. After this change in the workpiece fixing, the quenching process can be continued in the quenching device, which can also be referred to as a means for hardening, or the workpiece can already be removed in this state from the hardening device, which can also be referred to as a means for hardening or quenching device and fed to another device, in which a further heat discharge from the workpiece takes place, which is defined in terms of its temporal characteristics.

The workpiece can be quenched in a clamped state at intervals. These intervals can be tailored to provide sequential reheating of selected and already quenched zones of the workpiece. The quenching medium can then be applied again to these reheated zones.

Different quenching media can be actively applied to the workpiece in chronological sequence or coordinated for different workpiece zones. It is thus possible, as part of a first quenching step, to apply a reactive quenching medium to the workpiece, which causes oxide removal or a layer-forming reaction with the workpiece. In a subsequent step, a quenching or reaction medium that differs in terms of its composition can then be applied to the workpiece.

The quenching device is designed in such a way that individual workpieces or groups of workpieces are subjected to a quenching treatment. The workpieces or the workpiece are held in a defined position in the quenching device. This position can be determined by receiving structures and/or by inserting the workpiece into the quenching device.

In addition to the automated introduction of the workpieces into the quenching device, it is also possible to automatically insert any matrices, fixtures, mandrels, housing bells or valve devices into the quenching device. The automated equipping of the quenching device with these auxiliary devices and the automated transfer of the workpiece into the quenching device enables the reproducible processing of the heat treatment of an individual workpiece while ensuring a required microstructure.

The system, ie the device according to the invention, comprising means for hardening and means for heating workpieces, is therefore suitable for the treatment of different workpieces in different batches, including batch 1 in a chronological sequence. Thus, the device according to the invention can also be a special allow high flexibility with regard to the number of workpieces to be treated and workpiece geometries.

The quenching device is designed in particular as a hardening press. The stamps provided for building up the pressing stress are preferably moved in the vertical direction. During the quenching process, the workpiece is preferably at or above the level at which it passed through the heating section of the continuous furnace or at which it was tapped from the discharge chamber. The quenching medium is thus brought to the fixed workpiece and not the workpiece to the quenching medium.

The device according to the invention preferably also comprises at least one handling device, by means of which workpieces can be transferred from the continuous furnace, preferably from the output chamber or from a storage device downstream of the output chamber, into the at least one means for hardening workpieces.

The device according to the invention forms part of an assembly which functions as a hardening cell. The hardening cell is preferably constructed in such a way that it covers those process steps that are necessary for hardening the components. These hardening process steps are austenitizing, quenching (preferably in oil), washing, deep freezing and tempering. The combination of austenitizing in vacuum and quenching in oil is accomplished within the hardening cell with the integration of an airlock acting as a holding chamber, which can be understood and referred to as a discharge chamber, a handling system and a hardening press.

Austenitizing is done by heating and holding in a vacuum. In this way, it is achieved in an advantageous manner that the process takes place with reduced release of particles and the workpiece surface is exposed to a reduced extent to reaction events. The workpieces are heated by passing them through a furnace designed as a continuous furnace, which is located between two lock devices. The workpieces are thus transported from an entry lock area through the furnace along a flow direction to an exit lock area. The opening of the sluice devices towards the inside of the furnace takes place only after a sufficient reduction in pressure in the respective sluice chamber.

The concept according to the invention makes it possible to subject individual parts or very small batches to a hardening treatment efficiently in a short time sequence. Due to the process management according to the invention, the transfer times incurred for moving the workpiece from the austenitizing furnace to the start of quenching can be maintained in a reproducible manner with high accuracy and can also be kept very short.

According to the concept of the invention, the discharge chamber forming the discharge area at the end of the furnace, in which the pressure is equalized to the ambient pressure, can be designed as a heatable chamber in which the heating can be continued in order to maintain the workpiece temperature reached in the continuous furnace or to set it in a defined manner.

It can also be possible that the dispensing chamber is designed as a heatable dispensing chamber that can be operated both at atmospheric pressure and in a vacuum.

By keeping the heated workpiece ready in a discharge chamber that is sealed off from the vacuum area of the continuous furnace, it is possible to coordinate the timing of the quenching process with the exit time of the workpiece from the discharge or pressure equalization chamber. The quenching process, which is monitored with regard to its timing, begins when the door of the output chamber, which acts as a pressure equalization chamber, is opened.

The workpiece transfer between the continuous austenitizing furnace and the hardening press is automated according to a particular aspect of the present invention. In this way, a programmatically defined and reproducible workpiece transfer between the continuous furnace and the press with regard to the workpiece transfer path and the temporal dynamics of the workpiece transfer can be ensured. The flaps, doors and bulkheads and/or locks at the beginning, at the end and inside the continuous furnace are opened in conjunction with a control device. The workpieces are heated in such a way that a defined heating over time in the oven and in the output area, i.e. the discharge or output chamber, results in high temperature stability. This can have a particularly advantageous effect on the consistent quality of heat-treated workpieces.

The quenching device is preferably designed as an oil quenching device, in particular in the form of a mandrel hardening press for quenching with oil. This advantageously ensures a controlled distortion behavior. As an alternative to this, or also in combination with this measure, quenching in gas can also take place. The system according to the invention can be designed in such a way that this is a combination of vacuum austenitizing with a gas quenching process in the hardening press.

Gas quenching can be carried out with or without support. In particular, it is possible to carry out targeted gas quenching in the hardening press using numerically controlled nozzles.

The workpiece is preferably clamped in the hardening press by inserting the workpiece into the press and driving a mandrel, preferably from below, into an oversized hole in the workpiece. The workpiece or component can be covered from above. For example, it may be possible for a hood to be lowered over the component from above. Subsequently, oil is again preferably pressed through this arrangement from below.

It may be possible for the oil flow to be controlled in such a way that all areas of the component or workpiece cool down evenly despite the different thicknesses. For this purpose, the press can advantageously control several, in particular two, different oil inflows. The hardening press offers channels that allow different fluid throughputs and these channels for supplying the quenching medium can be opened or closed individually in a time-controlled manner.

Advantageously, it can be possible that the mandrel is also designed in such a way that it includes oil channels.

After completion of the quenching process in the hardening press, the workpieces can be removed from the hardening press after sufficient cooling and subjected to a preferably multi-stage washing treatment.

It is also possible to carry out a first washing step inside the hardening press, in that a washing medium is passed through the channels for supplying the quenching medium by channel switching. This washing medium can be subjected to a separation treatment, by which washed-off quenching medium is separated.

This pre-cleaning, which is carried out within the hardening press, can also be carried out in connection with a gaseous medium.

The washed workpieces are preferably automatically transported to a preferably combined freezer/oven. The transformation of martensite is driven further by deep-freezing and the structure is strengthened. Subsequent tempering then removes residual internal stresses. After this thermal post-treatment, the workpiece treatment in this system is complete and the component can be output.

The hardening system according to the invention is preferably designed in the manner of a sealed, enclosed cell with a preferably elongated rectangular cross section. In one embodiment of the invention, the continuous furnace used according to the invention can extend in the longitudinal direction of this cell. The hardening press can be located in a longitudinal end area of this cell. The workpiece store can be located in the area of the longitudinal end area of the cell opposite the hardening press. A very compact cell can be provided in a particularly advantageous manner.

One embodiment can provide for a workpiece carrier circuit to take place inside the cell through the furnace and outside of the furnace back along it.

It is also possible to arrange the means for heating and the means for hardening in one cell such that a longitudinal extension of the output area of the means for heating, which is preferably designed as a continuous furnace, is arranged approximately parallel to a longitudinal extension of an insertion device of the means for heating. A very compact unit consisting of means for hardening and means for heating workpieces can thus be provided as part of a device for heat-treating workpieces.

A system can also be taken from the present disclosure, which comprises at least two, preferably several devices for the heat treatment of workpieces, in particular at least two, preferably several means for heating and means for hardening workpieces.

The heat treatment of the workpiece can be carried out as a so-called batch process. This batch process enables heat treatment as part of a single workpiece treatment as well as subsequent treatment of different single workpieces. In the hardening press, different quenching procedures specifically defined for the respective workpiece can be processed in direct succession.

According to a further aspect of the present invention, the hardening system is constructed in such a way that the workpieces are transported generically, above all through the austenitizing furnace, largely independently of the component size and geometry. For this purpose, the workpieces preferably guided through the continuous furnace via trays or can be guided through accordingly. In this way, several and even relatively small workpieces can be grouped and fed through the hardening plant, which is designed as a cell, for the processing of external orders.

The automated conveyance of the workpieces through the continuous furnace in connection with workpiece transport pallets or trays can be handled in such a way that the pallets or trays are transported back within the system from the output area of the continuous furnace to the input area of the same. For this purpose, the hardening system according to the invention preferably comprises a circulatory conveyor system for returning the pallets, trays or workpiece carriers. A wide variety of workpiece carriers can be stored in a carrier store.

It is also possible to bring the workpieces into the hardening plant in connection with workpiece carriers. It is also possible, after the workpieces have left the washing station, to put the workpieces back into the workpiece carriers intended for introduction into the continuous furnace, or to insert the workpiece carriers intended for the workpiece output. The workpiece handling within the system designed as a processing cell is preferably automated in all stations, monitored and documented by handling systems.

In the press hardening system according to the invention, components in the heating chamber are heated while components in the output chamber are kept warm. The system according to the invention thus enables a press hardening process to be carried out in which at least one workpiece is heated in the heating section, while at least one workpiece is kept warm in the output area or is brought to the hardening press.

The input chamber, the heating section and the output section comprise heating elements which can be controlled or regulated with regard to the heating power introduced into the oven as a result. Furthermore, means are provided in the input section, the heating section and the output section for detecting the temperatures in these sections. The heating section can form several zones in which different temperatures or heat outputs can be set. The respective chambers are preferably coupled to a vacuum pump with the involvement of electrically controllable valves. The input chamber and the output chamber can be coupled in terms of valves and lines in such a way that the negative pressure present in the corresponding chamber is used for gas extraction from a chamber with ambient pressure. Thus, before the output chamber is opened, it can be coupled to the input chamber via a line and a valve device, so that the negative pressure still prevailing in the output chamber is used to partially reduce the pressure in the input chamber that has just been loaded with a workpiece and is now closed. After this pressure reduction, which is advantageously implemented in terms of energy, the dispensing chamber can then be further aerated and opened at ambient pressure.

The process chamber is preferably equipped with three control zones. This ensures a particularly even working area. Also in this part of the furnace housing there are additional passages for reaching the measuring points for the TUS test. In this way, in particular, periodic checks of the workpieces can be carried out with little effort.

The heated output or discharge chamber is equipped with a separate control zone. This process chamber is flanged to the chamber of the heating section. The output chamber is also provided with passages to reach the measuring points.

The chamber parts, preferably all chamber parts, in particular the possibly unheated transfer chamber, are preferably equipped with vacuum and pressure measuring heads and enable the pressures to be monitored and recorded, with assignment to the respective workpiece.

The system's sensors enable automated, workpiece-specific process documentation. The hardening plant according to the invention combines a furnace designed as a continuous vacuum furnace with a discharge chamber with a stationary hardening press for austenitizing the components. The discharge chamber can be heated so that the components maintain a defined temperature level when the atmosphere changes.

The present invention also relates to the use of a press hardening system according to the invention for the heat treatment of metallic workpieces.

character list

• 1 eine Schemadarstellung zur Veranschaulichung des Aufbaus einer erfindungsgemäßen Vorrichtung zur Wärmebehandlung von Werkstücken unter Einsatz eines Durchlaufofens und einer Härtepresse;
• 2 eine weitere Schemadarstellung zur Veranschaulichung des Aufbaus einer als Härtezelle aufgebauten erfindungsgemäßen Härteanlage;
• 3 ein Flussdiagramm zur Veranschaulichung des nach Maßgabe einer Steuereinrichtung abgewickelten erfindungsgemäßen Ablaufs zur Wärmebehandlung von Werkstücken in der Vorrichtung nach 1;
• 4 eine Schemadarstellung zur Erläuterung der Einbettung des als Durchlaufofens gestalteten Ofens zwischen eine Eingangsschleusenkammer und eine Ausgangsschleusenkammer, sowie zwischen zwei Werkstücktransfersysteme.

Further details and features of the invention result from the following description of the invention in conjunction with the drawing. It shows:

• 1 a schematic representation to illustrate the structure of an inventive Device for the heat treatment of workpieces using a continuous furnace and a hardening press;
• 2 a further schematic diagram to illustrate the structure of a hardening system according to the invention constructed as a hardening cell;
• 3 1 shows a flowchart to illustrate the process according to the invention for the heat treatment of workpieces in the device, which is processed according to a control device 1 ;
• 4 a schematic representation to explain the embedding of the furnace designed as a continuous furnace between an inlet lock chamber and an outlet lock chamber, as well as between two workpiece transfer systems.

Detailed description of the figures

The representation after 1 illustrates the structure of a device according to the invention for the heat treatment of metallic workpieces, in particular transmission components.

The device according to the invention comprises at least one means TK for heating workpieces WP. In addition, the device also comprises at least one means PQ for hardening workpieces, the at least one means TK for heating workpieces WP being designed as a continuous furnace through which the workpieces WP travel in a continuous direction DTK, the continuous furnace having an input section TKI, a heating section TKH and an outlet section TKO, the workpieces being able to be introduced into the inlet section TKI via a first opening device 1, the workpieces being able to be removed from the outlet section TKO via a second opening device 2 and both the inlet section TKI and the outlet section TKO opposite the heating section TKH can be temporarily isolated.

This structure makes it possible to heat the components WP as part of their transfer to the quenching device PQ, with the transfer of the workpieces WP to the quenching device PQ being carried out by the introduction of the workpieces WP into the heating section TKH and the transfer of the workpieces WP within the furnace decoupled in time in the output section TKO and can be coordinated with the opening of the second opening device 2 .

The continuous furnace TK is designed here in such a way that it comprises at least one input chamber C1, which forms the input section TKI, and at least one output chamber C2, which forms the output section TKO, these two chambers C1, C2 being connected to one another through a heating section TKH extending workpiece transport path W are coupled. The workpieces WP can be brought into the input chamber C1 through the first opening device 1 . Furthermore, the workpieces WP can be removed from the output chamber C2 through the second opening device 2 .

In this exemplary embodiment, at least one further chamber C3 is provided, this further chamber C3 here forming the heating section TKH, through which the input chamber C1 communicates with the output chamber C2.

In the exemplary embodiment shown, the continuous furnace TK is designed as a vacuum continuous furnace, with a negative pressure being able to be applied at least in the input chamber C1 and/or in the output chamber C2 and/or in the at least one further chamber C3. This negative pressure can be regulated in a chamber-specific manner and is adjusted to ambient pressure before the openings 1, 2 are opened.

In the device according to the invention, a means 3 is provided for interrupting communication, in particular for closing at least one section between the first chamber C1 and the heating section TKH. Furthermore, a means 4 is provided between the second chamber C2 and the heating section TKH. These means 3, 4 for interrupting communication with the chamber C3 can be designed in particular as a flap, door, slider or bulkhead that can be brought into a release position and into a closed position. The position change of this means 3, 4 can be accomplished in an advantageous manner by electronically controlled actuators and / or actuators.

The device shown has at least one means 5 for setting at least one temperature of the continuous furnace TK, in particular a control unit CPU, by means of which the temperatures T1, T2, T3 are chamber-specific and individually, preferably in the output chamber C2 and in the at least third chamber C3 are individually adjustable.

The at least one means PQ for hardening the workpieces WP is designed here in such a way that the workpieces WP introduced into it can be quenched by means of a fluid, preferably oil or gas.

The inventive device includes a handling device TS by means of the workpieces WP from the continuous furnace TK, ie from the output chamber C2 or from a storage device downstream of the output chamber C2 into which at least one means PQ for hardening the workpieces WP can be transferred. The handling device TS can be formed by a robot arm or a portal system.

The control device CPU is used to control a heat treatment process of preferably metallic workpieces. As part of this heat treatment process, carburized workpieces are preferably introduced through a first opening device 1 into chambers C1, C2, C3 of a means TK for heating workpieces to a predetermined temperature and heated there. After heating, the workpieces WP are discharged from a discharge chamber C2 through a second opening device 2, which is different from the first opening device 1, and transported to a means for hardening workpieces and quenched thereby. The controller also controls the pressures in chambers C1, C2, C3. The controlled by the controller CPU procedure is in conjunction with 3 explained further.

The continuous furnace TK provides several heating zones Z1, Z2, Z3, AK. The continuous furnace TK provides several heating zones Z1, ZTK, AK. The heating zone of the heating section ZTK is subdivided into further zones Z2, Z3.

The temperature in these zones can be controlled according to the control unit CPU. The heating section TKH is constructed in such a way that it defines a number of heating zones Z2, Z3 in which different temperatures and heating outputs can be set to a sufficient extent. Both the input area TKI, the heating section TKH and the output area TKO are designed in such a way that these measuring points TUS provide for recording, monitoring and documenting the workpiece heating.

The pressures in chambers C1, C2, C3 are also measured and recorded.

The pressures in these chambers can be lowered to below ambient pressure via a vacuum pump VP. The chambers C1, C2, C3 are coupled to one another via a line system and electrically controllable valves provided therein. The chambers C1, C2, C3 can temporarily communicate with one another via the line system, so that in the context of partial ventilation of one chamber C1, C2, partial ventilation of the other chamber C2, C1 can be effected in phase opposition.

The representation after 2 shows one including the device 1 built and designed as a cell press hardening plant. This press hardening system includes a hardening furnace TK, an output lock/chamber TKO for outputting workpieces WP from the hardening furnace TK and a hardening press PQ for clamping a workpiece WP and for accomplishing a quenching process of the workpiece WP in the clamped state.

In the press hardening system shown, a handling system TS is provided in an intermediate area between the delivery chamber TKO, which functions as an output lock/chamber, and the hardening press PQ. This handling system TS is operated in such a way that a programmatically secured temporal temperature profile of the workpiece WP results for the movement of the workpiece WP from the output lock/chamber into the hardening press PQ.

In this exemplary embodiment, too, the hardening furnace TK is designed as a vacuum furnace for heating a workpiece WP in a low-oxygen environment. Furthermore, the TK hardening furnace is designed as a continuous furnace.

Within the meaning of the invention, a continuous furnace can also be referred to as a continuous furnace. A continuous furnace can accordingly be referred to as a continuous furnace.

The workpiece handling between the hardening furnace TK and the hardening press PQ is accomplished here in such a way that the workpiece WP, after exiting the opening device 2 of the output lock/chamber TKO, is guided through the hardening furnace TK to the hardening press PQ transversely to the flow direction DTK.

For this purpose, the TK hardening furnace and the PQ hardening press are linked across the corner by the TS transfer system with regard to workpiece travel. The transfer process of the workpieces from the WP from the output lock/chamber TKO of the hardening furnace TK to the hardening press PQ and the quenching process in the hardening press PQ take place at the same time in terms of process flow. The transfer of the workpiece from the output chamber TKO into the hardening press PQ is handled as a thermally relevant sub-step of the quenching process.

In an alternative configuration, it may be possible that the workpiece WP, after exiting the opening device 2 of the output lock/chamber TKO, is guided transversely to the flow direction DTK through the hardening furnace TK into the hardening press PQ.

In the press hardening system shown, a workpiece transfer system WPH1, WPH2 is provided, which extends along the hardening furnace TK between an output area of the hardening press PQ and an entry opening 1 of the entry lock TK1 of the hardening furnace TK. The workpiece transfer system WPH1, WPH2 includes several linked conveyor modules. A post-cooling station 6, a washing station 7 and/or a test station 8 can be loaded with workpieces via a first module of the workpiece transfer system WPH1. The respective workpiece can be returned to the input area 9 of the cell CW via a second module WPH2 of the workpiece transfer system. From there, the hardened and washed workpieces can be taken to the cooling cells 10...13. The press hardening system is designed in such a way that workpieces WP located in the area of the test station 8 can be removed from the press hardening system and preferably also used again.

The press-hardening system can be designed in such a way that the workpieces are press-hardened using a die device. This die device is used to hold the workpiece and to provide wall sections that support the workpiece. In the hardening press PQ, the quenching medium can be guided onto the workpiece in interaction with the die device, controlled by valve devices. If the workpiece is supported using a core or mandrel, it is possible to carry out the quenching process in such a way that the workpiece is not completely cooled. After this partial cooling, the supporting structures such as mandrels, cores or matrices can be removed from the workpiece, which is then still thermally expanded. Then there is further cooling. This can also take place outside of the hardening press, for example in a bath.

In the device after 1 , as well as in the press hardening plant 2 a handling system TS is provided. This handling system TS is arranged in an intermediate area between the output chamber TKO and the hardening press PQ. This handling system TS is operated in such a way that, for the transfer of the workpiece WP from the output chamber TKO into the hardening press PQ, there is a program-technically secured time sequence of movements for the transfer of the workpiece WP.

The handling system is configured in connection with a corresponding control device in such a way that the delivery process and the quenching process are linked in terms of time. The transfer process can be activated with a ready signal from the hardening press PQ or can only be initiated in a ready state PQ of the hardening press. Furthermore, a signal confirming the completion of the transfer process of the workpiece WP into the press PQ can start the press hardening process. The TS handling system is located in a CW hardening cell, which houses the TK hardening furnace and the PQ hardening press. The hardening cell CW is designed as a rectangular cuboid structure, the oven extends in the longitudinal direction of this cuboid structure. The hardening press PQ is located in a longitudinal end area.

The workpiece transfer process handled by the TS handling system is monitored and documented in terms of its timing. For this purpose, in particular the thermal time profile of the workpiece can be measured and recorded.

The representation after 2 also shows the overall structure of a hardening cell, with the hardening furnace TK, the hardening press PQ, a workpiece washing device 7 and the workpiece handling system TS for moving the workpieces from the hardening furnace TK into the hardening press PQ. The hardening cell CW includes a workpiece return system WPH for moving the workpieces WP from the hardening press PQ to an input and output area 9, 9a. The TK hardening furnace is designed as a continuous furnace. The WPH workpiece return system runs parallel to the TK hardening furnace. The workpiece washing device 7 is arranged in an intermediate area between the workpiece output area 9a and the hardening press PQ and can be loaded via the workpiece return system WPH.

The hardening furnace TK has an entry lock TKI and an exit lock TKO. A loading system LS is provided in a zone upstream of the entry lock TKI. The workpiece return system WPH1, WPH2 can be used to transfer workpieces between the PQ press and the LS loading system. A workpiece store WPB1, WPB2 is provided in an area of the hardening cell CW adjacent to the entry area or the entry lock TKI of the hardening furnace TK. Furthermore, a first cooling cell 10 is provided in an area of the hardening cell CW adjacent to the input area TKI of the hardening furnace TK. Additional cooling cells 11, 12, 13 are provided in an area of the hardening cell CW adjacent to the input area TKI of the hardening furnace TK. The workpiece store WPB1, WPB2 and/or the cooling cells 10, 11, 12, 13 can be reached via the loading system LS, so that workpieces WP can be removed from these modules by the loading system and introduced into these modules. The cooling cells 10..13 can also be equipped with heating devices be equipped so that a tempering process can also be carried out via these cells.

The hardening cell CW is enclosed by a cell wall CW2. The workpiece return system WPH is connected to an output lock/chamber 8 . A workpiece discharge from the hardening cell CW can be accomplished via this output lock/chamber 8 in order to carry out a workpiece test. Tested workpieces WP can also be returned to the system via the output lock/chamber, for example to be used in the cooling cell modules 10..13.

The operation of the hardening cell is controlled by a control device CPU (cf. 1 ) which is subdivided here, for example, into two modules CE, CP1 coupled with signals, whereby the module CE is used primarily for workpiece handling in the entrance area of the hardening furnace TK and the module CP1 controls the workpiece flow in the hardening furnace TK, the transfer system TS and the hardening press PQ. All control tasks relevant to the handling of the workpiece WP from entry into the hardening furnace TK to the end of the hardening process, including the temperature control of the hardening furnace TK, are thus coordinated by the control module CP1. The control module CP1 thus takes over the "hot handling" and the control module CE the "cold handling". The processes in "hot handling" are documented specifically for each workpiece. For "cold handling" there is only documentation with regard to the trouble-free handling process. The cold handling control processed via the CE module also includes the workpiece handling after exit from the PQ hardening press. Any data on thermal workpiece post-treatment, in particular cooling and renewed tempering, can be fed back to module CP1.

The representation after 3 shows schematically a control device CPU and a flowchart of a process executed by this control device CPU. The control device CPU controls the sequence of the method according to the invention for carrying out a press hardening process, in which workpieces are heated in a hardening furnace as part of a tempering step and quenched in a hardening press as part of a quenching step. The control device CPU is coupled here, for example, via a bus system with the switching elements of the controlled components of the hardening system. In the context of the present description, the term control used here also includes regulation; the control device can represent a control device in this respect, and adjust manipulated variables taking into account returned signals, in particular with regard to pressure, temperature, workpiece position and dynamically.

According to the system operating method processed by the control device CPU by configuring it, a workpiece WP is picked up by the handling device from the workpiece storage area WPB1 in step S1 and brought to an area upstream of the first opening device 1 . In step S2, in a system state in which the barrier wall 3 is closed, the pressure in the chamber C1 is adjusted to the ambient pressure. In step S3, the opening device 1 is opened. In step S4, the workpiece WP is introduced into the input chamber C1. In step S5, the opening device 1 is closed.

In step S6, the pressure in the chamber C1 is reduced to the internal pressure in the third chamber C3. In step S7, the barrier wall 3 is opened. In step S8, the workpiece is conveyed into the third chamber C3 in the throughput direction of the furnace TK. In step S9, the barrier wall 3 is closed.

In steps S10 to S15, the workpiece is conveyed through zones or stations of the furnace TK that follow in the throughput direction DTK and is heated in a defined manner in these zones. A defined negative pressure prevails in chamber C3, which is set and maintained via a control routine that is not described further here.

As soon as the workpiece WP is in a required thermal state in the last zone of the chamber C3 upstream of the barrier wall 4, the pressure in the output chamber C2 is lowered to the internal pressure of the chamber C3 in step S16. In step S17, the barrier wall 4 is opened and the workpiece WP is brought into the output chamber C2 forming the discharge section TKO. The barrier wall 4 is closed in step S18. In step S19, the pressure in the chamber C2 is increased to the atmospheric pressure level. The pressure increase can be accomplished by equalizing the pressure by introducing an inert gas into chamber C2. In step S20, the temperature in the discharge chamber C2 is adjusted to a workpiece holding temperature. In step S21 it is queried whether the transfer system TS and the hardening press PQ are in a ready state suitable for processing the quenching process.

In step S22, the quenching process is activated. For this purpose, the opening device 2 is opened in step Q1. In step Q2, the transfer system TS picks up the workpiece WP from the chamber C2 and transfers it on a defined path with a defined speed profile in the curing press PQ. In step Q3, the hardening press PQ clamps the workpiece used. In step Q4, the clamped workpiece is subjected to a quenching medium.

Steps Q1 to Q4 form a process step group that is processed in a time frame defined by the program. The release of the workpiece WP in the chamber C2 and the process of transferring the workpiece WP into the hardening press PQ form part of the quenching process, which is carried out in a parameterized manner specific to the workpiece. The handling system TS is operated in such a way that for the transfer of the workpiece WP from the output device TKO into the hardening press PQ, a program-technically secured temporal temperature profile of the workpiece WP as well as a program-technically secured temporal gas contacting of the workpiece WP results. The transfer process beginning with the opening of the opening device 2 can only be carried out in conjunction with a ready signal from the hardening press. In this respect, there is no waiting time or lengthening of the process time outside of the defined process.

Following the press hardening step sequence Q1...Q4, the hardening press PQ is opened in step S23 and the workpiece is removed from the hardening press PQ in step S24.

In step S25, the workpiece is inserted into a workpiece carrier and fed to a washing station in step S26.

After the system operation initiated according to the invention by the control device CPU, the opening device 2 is opened and the workpiece is picked up in the output area TKO of the hardening furnace when the workpiece has reached a defined thermal state and the transfer system and the hardening press are in a ready state. The process step group Q1..Q4 starts with the opening of the opening device 2 its course.

As part of the application of the medium to the workpiece WP in the hardening press PQ, in step Q4 the workpiece is exposed to a quenching medium in a way that is defined by the program and coordinated by means of adjusting means.

The heating of the workpieces as part of the passage through the hardening furnace AND is measured and recorded and documented for each workpiece.

The representation after 4 shows a press hardening system with a hardening furnace TK, which is designed as a continuous furnace and has a furnace inlet TKI and a furnace outlet TKO. The press hardening system also includes a hardening press PQ for clamping a workpiece and for effecting a quenching process of the workpiece in the clamped state. A handling system TS is provided in an intermediate area between the furnace outlet TKO and the hardening press PQ. Furthermore, a workpiece loading system LS is provided in an area adjacent to the furnace entrance TKI. The handling system TS and the workpiece loading system LS are connected to one another via a workpiece carrier return path DTR that runs past the continuous furnace TK.

The workpiece carriers are returned to the input area of the continuous furnace TK via the workpiece carrier return path DTR. The workpiece carriers pass through both the entry area of the continuous furnace TK and the output area of the continuous furnace TK zones in which a workpiece is handled by transfer systems that are formed in particular by a robot arm or a portal robot. The workpiece carrier conveyor path runs parallel to the continuous furnace. Again parallel to this workpiece carrier return path also runs in connection with 2 described workpiece conveyor path WPH from the exit from the hardening press PQ back to the cooling cells 10...13.

This makes it possible to use the TS handling system to pick up the workpiece carriers that have been brought out of the furnace outlet and bring them to the entrance of the hardening furnace TK.

It should be understood that the foregoing detailed description and drawings, while representing certain exemplary embodiments of the invention, are intended for purposes of illustration only and should not be construed as limiting the scope of the invention. Various modifications of the configurations described are possible without departing from the scope of the following claims and their range of equivalence. In particular, features of the exemplary embodiments that are not mentioned in the claims also emerge from this description and the figures. Such features may also occur in combinations other than those specifically disclosed herein. Therefore, the fact that several such features are mentioned together in the same sentence or in some other type of textual context does not justify the conclusion that they can only occur in the specifically disclosed combination. Instead, it can generally be assumed that from a number of such features, individual ones can also be omitted or modified, provided that this affects the functional capability of the invention is not called into question. The functions of the hardening system also represent process steps according to which the workpieces guided through the hardening system are treated.

Claims (10)

Press hardening plant, with: - a hardening furnace (TK) which is designed as a continuous furnace and has a furnace inlet (TKI) and a furnace outlet (TKO), - a hardening press (PQ) for clamping a workpiece (WP) and for effecting a quenching process of the workpiece (WP) in the clamped state, - a handling system (TS) being provided in an intermediate area between the furnace outlet (TKO) and the hardening press (PQ) and - a workpiece loading system (LS) is provided in an area adjacent to the furnace entrance (TKI), - wherein the handling system (TS) and the workpiece loading system (LS) are connected to one another via a workpiece carrier return path (DTR) which is guided past the continuous furnace. press hardening plant claim 1 , characterized in that a cooling cell (10, 11, 12, 13) is provided in the vicinity of the furnace entrance (TKI), and that this cooling cell (10, 11, 12, 13) can be loaded with workpieces by integrating the workpiece loading system (LS). . Press hardening plant according to at least one of Claims 1 or 2 , characterized in that the workpiece (WP) after leaving the hardening furnace (TK) is guided transversely to the direction of passage through the hardening furnace (TK) to the hardening press (PQ). Press hardening plant according to at least one of Claims 1 until 3 , characterized in that the hardening furnace (TK) and the hardening press (PQ) are coupled by the transfer system across the corner. Press hardening plant according to at least one of Claims 1 until 4 , characterized in that the workpiece return path is formed by a workpiece return transfer system that extends along the hardening furnace (TK) between an output area of the hardening press (PQ) and an input area of the hardening furnace (TK). Press hardening layer according to at least one of Claims 1 until 5 , characterized in that the workpiece return transfer system (WPH) connects to the hardening press (PQ) on an output side of the hardening press (PQ) running transversely to the longitudinal direction of the furnace. Press hardening layer according to at least one of Claims 1 until 6 , characterized in that an after-cooling station (6), a washing station (7) and/or a test station (8) can be loaded with workpieces (WP) via the workpiece return transfer system (WPH). press hardening plant claim 7 , characterized in that in the area of the test station (8) located therein workpieces (WP) can be removed from the press hardening system. Press hardening plant according to at least one of Claims 1 until 8th , characterized in that the removal of the workpieces (WP) from the hardening furnace (TK) and the insertion of the workpieces (WP) into the hardening press (PQ) are temporally coupled in terms of process. Using a press hardening plant according to at least one of the above Claims 1 until 9 for heat treatment of metallic workpieces.

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