EP1229137B1 - Installation and process for the transport of metallic workpieces and installation for the heat treatment of metallic workpieces - Google Patents

Abstract

The arrangement has a heat-insulated transport chamber (10) to hold work pieces (20). The chamber is moved horizontally and designed to be vacuum-tight, and evacuated of air to create vacuum to protect work pieces from environmental influences. The chamber has a heating unit for heating a treatment chamber. The transport chamber has removable thermal insulation made of steel. A vacuum pump evacuates the air from the transport chamber. Independent claims are also included for the following: (a) a system for heat treating metallic work pieces; and (b) a method of transporting metallic work pieces during a heat treatment process.

Description

The invention relates to a device for transporting metal workpieces, in particular during a heat treatment, which is provided with a heat-insulated transport chamber for receiving the workpieces, means for loading and unloading of the workpieces and a transport chamber moving chassis. The invention further relates to a plant for heat treatment of metallic workpieces, which has at least two treatment chambers in which the workpieces are heat-treatable. Moreover, the invention has to do with a method for transporting metal workpieces during a heat treatment in which the workpieces are transported in a heat-insulated transport chamber between at least two treatment chambers, in which the workpieces are heat-treatable.

To produce defined workpiece properties, such as high hardness or wear resistance, metallic workpieces are usually subjected to a thermal or thermochemical heat treatment. The result of the heat treatment is a modified material structure, which gives the workpieces the required properties. Of particular influence on the treatment result is in addition to the general process parameters pressure, temperature and treatment time, the atmosphere in which the heat treatment is carried out. A number of procedures are known in which the workpieces are exposed to different atmospheres to achieve the desired treatment result. The workpieces are successively fed to several treatment chambers of a heat treatment plant. The individual treatment chambers are for this purpose usually by a transfer lock, which protects the workpieces during transport against environmental influences, which would adversely affect the previously achieved treatment result, connected to each other. For this purpose, the transfer lock can be acted upon either with a protective gas atmosphere, as known, for example, from DE-A-43 16 841, or can be evacuated, as proposed in FR-A-2 771 754.

Such transfer locks are associated with the disadvantage that they allow a variable design of the procedure of the heat treatment system at best to a limited extent. In addition, the expansion of the heat treatment plant, even with a modular design, as is known from FR-A-2 771 754, not without a relatively high effort to realize. From an economic point of view, it is also extremely unsatisfactory that maintenance work on individual treatment chambers and in particular on the transport carriage in the transfer lock can only be carried out when the temporary temporary shutdown of the entire heat treatment installation is accepted.

From US-A-5 567 381 a heat treatment plant is also known which comprises a vacuum furnace, a lock and a mobile transport chamber. The transport chamber can be coupled via the lock to the vacuum furnace. The heat-insulated to the outside and provided with a hermetically sealed door transport chamber also has a heater for heating the workpieces and a conveyor for loading and unloading of the workpieces. In order to transfer the workpieces heated in the vacuum furnace to a certain temperature into a further treatment chamber, such as a quenching chamber, the transport chamber is coupled to the lock and preheated. Subsequently, both the lock and the transport chamber with an inert gas flooded to a pressure greater than the ambient pressure, to prevent air from entering the lock or the transport chamber from the outside. The workpieces in the vacuum furnace are then cooled to the temperature prevailing in the transport chamber, and the vacuum furnace is also flooded with inert gas. After the same pressure level is reached in the vacuum furnace and in the lock or transport chamber, the door of the vacuum furnace is opened and the workpieces by means of the conveyor of the transport chamber in this loaded.

With the transport chamber described above, it is thus possible to transport workpieces in the heated state from one treatment chamber to the next and thereby exposing them to an atmosphere of inert gas, which prevents unwanted oxidation of the workpieces. Although the heat treatment plant according to US Pat. No. 5,567,381 thus offers greater flexibility than the heat treatment plants with a stationary transfer lock discussed above, it has the disadvantage that, when the transport chamber is coupled to the vacuum furnace, both the transport chamber and the lock as well the vacuum furnace is flooded with the inert gas. Apart from the fact that this requires a not inconsiderable expense for the provision of the inert gas, the inert gas proves to be a hindrance to subject the workpieces during transport to another treatment chamber of a continued heat treatment. Because the change in the furnace atmosphere associated with the inevitable flooding of the vacuum furnace with inert gas not only requires the completion of the heat treatment process step taking place in the vacuum furnace, but is inevitably associated with a cooling of the workpieces, as long as the inert gas is not preheated. The latter is noticeable in a particularly disadvantageous manner in a heat treatment in the high temperature range, in which no appreciable temperature fluctuations are allowed in the rule.

Finally, from FR-A-2 782 156 a device for transporting metal workpieces is known which with a Transport chamber for receiving the workpieces, means for loading and unloading of the workpieces and a transport chamber moving chassis is provided, the transport chamber is horizontally movable, vacuum-tight and evacuated on a workpieces from environmental influences protective vacuum and a horizontal Batchbe- and -dladungsvorrichtung contains. In this prior art device, it is disadvantageous that the transport chamber is not formed thermally insulated. Thus, the temperature within the transport chamber of the device known from FR-A-2 782 156 can not be kept constant, so that it can disadvantageously lead to undesirable temperature drops within the transport chamber. Thus, the previously known from FR-A-2,782,156 device is not suitable for the transport of during a heat treatment before Termperaturschwankungen to be protected workpieces.

The invention is based on the invention to provide an apparatus and method for transporting metallic workpieces and a plant for heat treatment of these workpieces, which allow a comparatively flexible and efficient way transporting the workpieces between multiple treatment chambers during a heat treatment.

On the device side, this object is achieved by a device for transporting metallic workpieces, in particular during a heat treatment, with a heat-insulated transport chamber for receiving the workpieces, means for loading and unloading the workpieces and a chassis moving the transport chamber, wherein the transport chamber can be moved horizontally formed vacuum-tight and on the workpieces from environmental influences evacuating vacuum is evacuated and includes a horizontal batch loading and unloading, the transport chamber is heated, and wherein the transport chamber is provided with a replaceable thermal insulation, which is made of steel.

A device designed in this way offers a flexible transport of the workpieces during a heat treatment compared to the stationary transfer locks known in the prior art. Thus, for example, individual treatment chambers of a heat treatment plant for maintenance or repair work can be excluded from the process cycle without the other treatment chambers being affected as a result. The extension of an existing heat treatment plant to additional treatment chambers is possible with the device according to the invention without much effort.

In addition, such a device recognizes the fact that a much more efficient process can be achieved if, instead of floating with inert gas, a vacuum is generated in the transport chamber to the workpieces against unwanted environmental influences, such as by the supply of Oxygen-related oxidation, to protect. In contrast to the mobile transport chamber according to US Pat. No. 5,567,381, it is thus possible with the device according to the invention to continue the heat treatment during the transport of the workpieces to a next treatment chamber in the transport chamber, without a noticeable temperature change occurring. In addition to the thus caused, economically advantageous time savings, the device according to the invention is therefore also characterized by the fact that it is particularly suitable for heat treatment processes that take place in the high temperature range.

It is particularly advantageous if the device is provided with a vacuum pump for evacuating the transport chamber. This offers the advantage that the device is self-sufficient with respect to the evacuation of the transport chamber and thus independent of the respective type of treatment chambers. It can therefore for example dock both to vacuum or atmospheric furnaces and to cooling chambers. Furthermore, the provision of a vacuum pump that the transport chamber can be evacuated even during transport. This comes into play, for example, when loading the Workpieces from a processing chamber into the transport chamber, the atmosphere in the processing chamber is allowed to expand into the transport chamber to continue the heat treatment in this atmosphere during transport until just before reaching the next treatment chamber.

Another advantage is to heat the transport chamber. Although the transport chamber already counteracts due to their thermal insulation temperature drop of the workpieces, which is usually sufficient for short transport routes, it may be necessary in cases of heat treatment at high temperatures to keep the workpieces by an additional heat to the desired temperature. According to the invention the transport chamber is provided with a replaceable thermal insulation, which is made of steel. Such, for example made of a chromium-nickel steel insulation can be freely exchanged for repair and maintenance purposes. It also has the advantage that due to their low heat storage, the temperature of the transport chamber changed within a few minutes, that can be adapted to the different temperatures of several treatment chambers.

In a particularly useful development of the device according to the invention, the transport chamber is provided with a hermetically closing loading door, which can be actuated by a drive to ensure an automatic docking of the transport chamber to a treatment chamber. With regard to an accident that occurs again and again in operational practice, it may also be advantageous to additionally provide the transport chamber with a hermetically closing installation door. For example, by means of an external Hubladegeräts the transport chamber can thus be unloaded regardless of the possibly not freely accessible loading door through the mounting door.

A highly advantageous embodiment of the device according to the invention is also given when transport chamber and chassis are relatively movable. Because this makes it easy possible to largely decouple the trajectory to be traveled by the device of the arrangement of the individual treatment chambers and thus to take the best possible account of the respective operating conditions. As particularly suitable in this context, it has been shown to arrange the transport chamber horizontally pivotable or in a horizontal and / or vertical direction to move rectilinearly on the chassis. The latter variant is used, for example, when several treatment chambers are arranged vertically one above the other.

Furthermore, in view of effortless docking of the transport chamber to treatment chambers whose loading sides are oriented differently in space, it may alternatively or additionally be useful to form the landing gear so as to allow the device to be turned on the spot. For instance, in the case of treatment chambers arranged on both sides of a heat treatment line with respect to their loading side, it is sufficient in this case to provide the transport chamber in an economically favorable manner with only one loading door. Advantageously, the suspension is depending on the operational requirement rail-bound or freely steered by embedded in the ground induction loops. In order to achieve a convenient loading of the workpieces from a treatment chamber in the transport chamber or vice versa, it has also proven to be, if the means for loading and unloading of the workpieces have a loading fork, which is horizontally and vertically movable.

To achieve the above object is proposed in a system for heat treatment of metallic workpieces with the features mentioned that the system has a device according to one of claims 1 to 8, which can be coupled by means of an evacuable lock to the treatment chamber.

Such a heat treatment system makes use of the advantages resulting in connection with the previously described device for transporting metallic workpieces. By providing the lock is thereby ensured that the workpieces from environmental influences protected between a treatment chamber and the transport chamber can be shipped. The heat treatment plant according to the invention is characterized by great flexibility in terms of the transport of the workpieces between the individual treatment chambers, which also allows a relatively high throughput and thus achieve an efficient process in economic terms.

In order to ensure a compact and relatively lightweight design of the transport chamber, it is expedient to arrange the lock stationary on the treatment chamber. This has the consequence that a lock is to be provided on each treatment chamber. In general, however, the lock can also be designed as an integrated part of the transport chamber or even mobile. Although the latter embodiment is associated with a higher design effort, but offers about when the heat treatment plant has a large number of treatment chambers, each with long residence times of the workpieces, so that a mobile lock can be used in time unproblematically for several treatment chambers ,

It is also expedient if the lock is separately evacuated, so that it is independent of the type of the respective treatment chamber, such as vacuum oven or atmospheric oven to operate. In addition, it is possible in this way, the lock already during the transport of the transport chamber to the corresponding treatment chamber evacuate to ensure the fastest possible procedure. Depending on the application, however, it is also conceivable that the lock is evacuated by a vacuum pump arranged on the transport chamber. In a particularly advantageous embodiment of the system according to the invention, the lock has a drive, through which the loading door of the transport chamber can be actuated. This contributes to a particularly lightweight design of the transport chamber and thus at a relatively low cost for the promotion of workpieces between the individual treatment chambers. In view of the greatest possible variability in the design of the heat treatment, the treatment chamber is expediently a vacuum furnace, an atmospheric furnace or a cooling chamber.

In procedural terms, the solution to the above problem in a method having the features mentioned is characterized in that the vacuum-tight transport chamber is evacuated to a workpieces from environmental influences protective vacuum and the workpieces are transported in this vacuum from one treatment chamber to the next.

The transport of the workpieces in an evacuated to a predetermined vacuum transport chamber has been found to be extremely advantageous, especially for the transport of heated to a relatively high temperature, for example, 1000 ° C workpieces. In contrast to the known in the prior art transport of the workpieces in an atmosphere of inert gas can be avoided in this way namely often unwanted temperature drop. In a further development of the method according to the invention is further proposed to couple the transport chamber by means of a lock to the respective treatment chamber to use the advantages described above. Finally, it is proposed to evacuate the lock separately to ensure a rapid coupling of the transport chamber.

Fig. 1a

eine schematische Seitenansicht einer Vorrichtung zum Transportieren metallischer Werkstücke;

Fig. 1 b

einen Schnitt gemäß der Linie Ib-Ib in Fig. 1 und

Fig. 2

eine schematische Darstellung einer Anlage zur Wärmebehandlung metallischer Werkstücke mit einer der Vorrichtung nach den Fig. 1a und 1b ähnlichen Transportvorrichtung.

Details and further advantages of the subject matter of the present invention will become apparent from the following description of a preferred embodiment. In the accompanying drawings show in detail:

Fig. 1a

a schematic side view of an apparatus for transporting metallic workpieces;

Fig. 1 b

a section along the line Ib-Ib in Fig. 1 and

Fig. 2

a schematic representation of a plant for heat treatment of metallic workpieces with a device of the Fig. 1a and 1b similar transport device.

The device shown in Fig. 1a for transporting metallic workpieces 20 has a heat-insulated to the outside and vacuum-tight, cylindrical transport chamber 10 for receiving the assembled into a batch of workpieces 20 and a transport chamber 10 moving chassis 30. The device is also provided with means 40 for loading and unloading the workpieces 20, which have a horizontally movable pawl 41. By an electromechanical drive, the pawl 41 can move by means of a forward and retractable print chain 43 in the horizontal direction, the leadership of the empty strand is made in a vertically arranged receptacle 42. In this way, it is ensured that all Startbeziehungsweise braking operations with respect to a reliable transport of the workpieces 20 from the transport chamber 10 into a treatment chamber 50 or vice versa soft run.

As can be seen mainly in Fig. 1b, the transport chamber 10 has a flange 11 for a vacuum pump, not shown. By means of the vacuum pump mounted on the chassis 30, it is possible to evacuate the interior of the transport chamber 10 to a final pressure of about 0.1 mbar (= 10 Pa) and at a leak rate of about 0.003 mbar l / s at this pressure level hold. Accordingly, it is ensured that located in the transport chamber 10, heat treated workpieces 20 ago Environmental factors, such as an undesirable oxidation inducing oxygen supply, are protected.

In order to avoid a noticeable drop in temperature of the workpieces 20 previously heated in a treatment chamber 50, the transport chamber 10 is provided with an exchangeable thermal insulation 12 of, for example, chromium-nickel steel and additionally has heating elements 14 connected to a current feedthrough 13. The heating elements 14 allow heating of the empty transport chamber 10 to about 1000 ° C in the shortest possible time at a control temperature of about ± 5 ° C.

On its front side, the transport chamber 10 is provided with a hermetically closing loading door 15, which can be raised in the vertical direction by a drive 16, which in the present case is hydraulically movable, depending on the application, but also electrically or pneumatically actuated. When opening or closing, the loading door 15 moves in a double-walled portal 17, on whose side facing away from the transport chamber 10 coupling means 18 are arranged. With the aid of the coupling means 18, the transport chamber 10 can be vacuum-tight dock to a lock 60 only hinted.

The provided with wheels 31 chassis 30 of the device is driven by a driven by means of an inverter and thus soft starting or braking gear motor. The positioning speed of about ± 1 mm permitting travel speed of the freely traveling in all directions and rotating on the ground chassis 30 is only between 0.01 m / s and 0.03 m / s, so that additional protective measures, such as a Grid arrangement are dispensable. At the front and rear end of the chassis 30, however, safety devices are provided to trigger an emergency stop when hitting an obstacle. On the chassis 30 rails 32 are also arranged, through which the transport chamber 10 is movable relative to the chassis 30 over a distance of about 200 mm. The transport chamber 10 is moved by a hydraulic cylinder, not shown.

With the above-described apparatus for transporting metal workpieces 20, batches having a dimension of 600 mm x 900 mm x 600 mm and a maximum weight of 600 kg - but also batches of 900 mm x 1200 mm x 900 mm and 1000 kg and also even larger and smaller - with temperatures of up to about 1100 ° C flexible and efficient transport between several treatment chambers 50 a system for heat treatment of metallic workpieces 20. In the illustration of FIG. 2 such a system is shown. The treatment chambers 70 arranged vis-à-vis on either side of one of the devices described above with slight modifications are designed as a vacuum preheating chamber 50a, vacuum carburizing chambers 50b, diffusion chambers 50c and gas quenching chamber 50d, or oil or salt bath quenching chamber.

In order to transport the untreated workpieces 20 initially introduced into the vacuum preheating chamber 50a via a conveyor belt or a roller conveyor 51 into the treatment chambers 50 corresponding to the respective heat treatment, the transporting chamber 10 of the transport device 70 is moved over the lock 60 which is stationarily arranged in front of each treatment chamber 50 coupled to the vacuum preheat chamber 50a. For loading the transport chamber 10 with the workpieces 20, the lock 60 and the transport chamber 10 is evacuated. Then, the doors of the vacuum preheating chamber 50a and the lock 60 and the loading door 15 of the transport chamber 10 are opened and the workpieces 20 are transported by means of the loading fork 41 into the transport chamber 10. After the loading door 15 is closed again, the transport chamber 10 is transported to one of the vacuum carburizing chambers 50b. The thermal insulation 13 and the heating elements 14 thereby ensure that the workpieces 20 experience no temperature loss. After reaching the position of the corresponding carburizing 50 b opens a second door of the loading door 15 opposite the rails 71 linearly movable transport device 70, and the workpieces 20 are about the standing on this treatment chamber 50 Lock 60 moved by means of the loading fork 41 in the carburizing 50b.

During further transport of the workpieces 20 in approximately one of the diffusion chambers 50c or the gas quenching chamber 50d, the sequence described above is repeated in a corresponding manner. The respective separately evacuated designed locks 60 help that the workpieces 20 can be transported between treatment chambers 50 without much loss of time, such as the carburizing 50b and the diffusion chambers 50c, accommodate different atmospheres, while ensuring that the workpieces 20 in which they are transported against environmental influences protective vacuum inside the transport chamber 10. Finally, the workpieces 20 leave the gas quenching chamber 50d via a conveyor belt 52 which, depending on the type of heat treatment, conveys the workpieces 20 to a tempering furnace 53 and to a cooling tunnel 54 adjoining this.

The above-described, only one loading door 15 having and thus structurally simpler to be designed device for transporting metallic workpieces 20 could also be used in the last discussed heat treatment plant. The reason for this is that the chassis 30 of this device is designed such that the transport chamber 10 is rotatable in place, allowing the opposite treatment chambers 50 can dock easily.

LIST OF REFERENCE NUMBERS

10

transport chamber

11

flange

12

insulation

13

power supply

14

heating element

15

loading door

16

drive

17

portal

18

coupling means

20

workpieces

30

landing gear

31

wheel

32

rail

40

Means for loading and unloading

41

pawl

42

admission

43

pressure chain

50

treatment chamber

50a

Vacuum preheating

50b

Vacuum carburizing

50c

diffusion chamber

50d

Gas quenching chamber

51

Conveyor belt / roller track

52

Conveyor belt / roller track

53

tempering furnace

54

cooling tunnel

60

lock

70

transport device

71

rail

Claims (16)

1. Apparatus for transporting metal workpieces (20), in particular during a heat treatment process, with a heat-insulated transport chamber (10) to hold the workpieces (20), means (40) for loading and unloading the workpieces (20) and a transport assembly (30) for moving the transport chamber (10), wherein the transport chamber (10) can be moved horizontally, is designed to be vacuum-tight and can be evacuated to create a vacuum for protection of the workpieces (20) against environmental influences, and also contains a horizontal batch loading and unloading device, wherein the transport chamber (10) can be heated and wherein the transport chamber (10) is provided with a replaceable thermal insulation (12) which is made from steel.
2. Apparatus as claimed in Claim 1, characterised by a vacuum pump for evacuation of the transport chamber (10).
3. Apparatus as claimed in Claim 1 or 2, characterised in that the transport chamber (10) is provided with a hermetically sealing loading door (15) which can be actuated by a drive means (16).
4. Apparatus as claimed in Claim 3, characterised in that the transport chamber (10) is provided with a hermetically sealing assembly door.
5. Apparatus as claimed in any one of Claims 1 to 4, characterised in that the transport chamber (10) and the transport assembly (30) can be moved relative to one another.
6. Apparatus as claimed in Claim 5, characterised in that the transport chamber (10) is disposed on the transport assembly (30) so that it can pivot horizontally or can move in a straight line in a horizontal and/or vertical direction.
7. Apparatus as claimed in any one of Claims 1 to 6, characterised in that the transport assembly (30) can rotate in place.
8. Apparatus as claimed in any one of Claims 1 to 7, characterised in that the transport assembly (30) is rail-mounted or can be steered by induction loops embedded in the base or can be steered freely.
9. A system for heat treatment of metal workpieces (20) with at least two treatment chambers (50) for horizontally receiving batches, in which the workpieces (20) can be heat treated, with an apparatus according to any one of Claims 1 to 8 which can be coupled to the treatment chamber (50) by means of a gate valve (60) which can be evacuated.
10. Installation as claimed in Claim 9, characterised in that the gate valve (60) is disposed stationary on the treatment chamber (50).
11. Installation as claimed in Claim 9 or 10, characterised in that the gate valve (60) can be evacuated separately.
12. Installation as claimed in any one of Claims 9 to 11, characterised in that the gate valve (60) has a drive means by which the loading door (15) of the transport chamber (10) can be actuated.
13. Installation as claimed in any one of Claims 9 to 12, characterised in that the treatment chamber (50) is a vacuum furnace, an atmospheric furnace or a cooling chamber.
14. Method of transporting metal workpieces (20) during a heat treatment process, in which the workpieces (20) are transported in a heat-insulated horizontally movable transport chamber (10) as defined in Claim 1 between at least two treatment chambers (50) which can be loaded horizontally and in which the workpieces (20) can be heat treated, characterised in that the transport chamber (10) which is designed to be vacuum-tight is evacuated to create a vacuum which protects the workpieces (20) against environmental influences, and the workpieces (20) are transported in this vacuum from one treatment chamber (50) to the next and in the course of this are held at the treatment temperature without any significant drop in temperature.
15. Method as claimed in Claim 14, characterised in that the transport chamber (10) is coupled by means of a gate valve (60) to the respective treatment chamber (50).
16. Method as claimed in Claim 15, characterised in that the gate valve (60) is evacuated separately.

Images