QUENCHING DEVICE AND QUENCHING METHOD

Abstract

A quenching device is described that includes at least one chamber that can be filled with quenching gas and that has a blower wheel for circulating quenching gas, in particular a quenching chamber and/or a flow channel, a drive motor, situated outside the chamber, for driving the blower being allocated to the blower wheel. The drive motor is coupled to the blower wheel so as to transmit torque via a coupling that operates in contactless fashion. Also described is a related quenching method.

Description

FIELD OF THE INVENTION

The present invention relates to a quenching device for quenching material that is to be quenched, in particular metallic workpieces, using quenching gas, as well as a quenching method for quenching material that is to be quenched, in particular metallic workpieces, using quenching gas.

BACKGROUND INFORMATION

In order to produce defined material properties, such as a high degree of hardness or sufficient resistance to wear, workpieces, usually made of metal, are subjected to thermal treatment. The most important factor in determining the result of this treatment is the speed with which the workpieces are cooled after having been heated. It is known to use water, oil, or quenching gas for the quenching process necessary for this purpose. The main advantage of using quenching gases instead of quenching liquids is that the material being quenched does not have to be cleaned after quenching, and that a higher degree of quenching homogeneity can be achieved in the batch.

A quenching device used for a quenching process as discussed above is discussed for example in EP 1 154 024 B1. The foregoing device has a chamber that can be flooded with quenching gas, formed by a quenching chamber for accommodating the material that is to be quenched and by a flow channel for the formation of a quenching gas flow circuit. The quenching chamber is loaded and unloaded not while flooded with quenching gas, but rather, as a rule, under vacuum. In the known quenching device, in order to form a quenching gas flow a blower wheel is situated in the flow channel that is driven by an electric motor that is situated outside the chamber that can be flooded with quenching gas. Because a motor shaft of the drive motor passes through an outer wall of the flow channel, a large constructive outlay is necessary in order to achieve a hermetic seal of the chamber that can be flooded with quenching gas.

In alternative known quenching devices, the drive motor is situated, together with the blower wheel, inside the chamber that can be flooded with quenching gas, in order to avoid leakages. Here there is the problem that the drive motor cannot be started in a vacuum, because otherwise electrical flashovers (arcs) could arise in the winding of the drive motor that could destroy the drive motor. This is problematic to the extent that the powerful blowers required in order to increase the quenching rate require long start-up times, relative to the actual quenching duration, to reach their nominal rotational speed. Because the drive motor cannot be started during the loading of the quenching chamber under a vacuum atmosphere, but rather has to take place after this chamber has been flooded with quenching gas, the overall start-up time is added to the actual quenching duration, which has a negative effect on the cycle rate that is to be achieved.

The described disadvantage results overall in a slower quenching of the material compared to quenching using liquids, because with the use of liquids the maximum quenching intensity is available immediately after the immersion of a batch that is to be quenched in the liquid bath. In quenching devices having drive motors situated inside the chamber that is to be flooded, the reduced quenching speed affects not only the cycle time, but also, due to the prolonged quenching duration, the quality of the workpiece joining, and thus also the properties of the components.

SUMMARY OF THE INVENTION

The exemplary embodiments and/or exemplary methods of the present invention are based on an object of providing a quenching device in which leakage problems are avoided and in which a starting of the powerful drive motor for the blower is possible even before the flooding of the chamber with quenching gas, in particular when there is a vacuum in the chamber. In addition, an object of the exemplary embodiments and/or exemplary methods of the present invention is to indicate a method that enables operation of the blower drive motor independent of the atmosphere in the chamber in which the blower wheel is situated.

With regard to the quenching device, this object is achieved by the features described herein, and with regard to the method the object is achieved by the features also described herein. Advantageous developments of the exemplary embodiments and/or exemplary methods of the present invention are indicated further herein. The scope of the exemplary embodiments and/or exemplary methods of the present invention include all combinations of at least two features disclosed in the entire disclosure of the present application, including the description and/or the Figures.

The exemplary embodiments and/or exemplary methods of the present invention recognize that operation of the drive motor (which may be fashioned as a standard electric motor) for the at least one blower wheel independent of the atmosphere and pressure conditions in the chamber accommodating the blower wheel is possible only if the drive motor is situated outside this chamber. Because in the prior art the motor shaft of the drive motor passes through the wall of the chamber, problems with leakage are necessarily present in the prior art. In order to avoid this problem, the exemplary embodiments and/or exemplary methods of the present invention provides that the drive motor be coupled to the blower wheel not mechanically, as in the prior art, but rather in contactless fashion. In other words, the drive motor and the blower wheel are provided with a coupling that is fashioned such that this coupling is capable of transmitting, without contact, a torque from the drive motor to the blower wheel. In this way, it is not necessary for mechanical components of the drive train to pass through the wall of the chamber, thus avoiding leakage problems.

The situation of the drive motor outside the chamber that can be flooded with quenching gas and in which a vacuum may be produced additionally makes it possible to start up the powerful drive motor before the chamber is flooded with quenching gas, which may be early enough that the drive motor has already reached its nominal rotational speed at the beginning of the actual quenching process, i.e., as a rule, when the chamber is completely flooded with quenching gas. A further advantage of the quenching device designed in this way is that it is not necessary to use specially sealed motors; rather, comparatively inexpensive standard electric motors may be used. A specific embodiment of the quenching device quite particularly may be used in which the coupling by which a drive torque can be transmitted from the drive motor to the blower wheel is fashioned as a magnetic coupling capable of transmitting torque through the wall of the chamber.

A specific embodiment may be particularly provided in which the magnetic coupling has a first rotor connected mechanically to the drive motor, which may be to a motor shaft of the drive motor, and has a second rotor drivable in contactless fashion by the first rotor and connected mechanically to the blower wheel, the second rotor together with the blower wheel being situated in the chamber that can be flooded with quenching gas.

According to a first alternative, the rotor coupled mechanically to the drive motor is an inner rotor surrounded radially outwardly by the second rotor driven in contactless fashion, the inner rotor being set into rotational movement by the rotationally moved magnetic field.

The converse variant may also be realized. Here, the second rotor, i.e. the rotor driven in contactless fashion, is an inner rotor surrounded radially outwardly by the first rotor (outer rotor). The latter specific embodiment is a particular variant.

In a development of the exemplary embodiments and/or exemplary methods of the present invention, it is advantageously provided that the blower wheel is situated immediately in the quenching chamber, i.e. in the chamber that is immediately to be loaded with material to be quenched. In an alternative specific embodiment, the blower is situated in a flow channel that is connected in terms of flow to the quenching chamber. The provision of a flow channel is optional; i.e., a specific embodiment of the quenching device as a quenching cell not having a flow channel may also be realized; i.e., a specific embodiment in which the quenching gas is circulated exclusively in the quenching cell by the blower.

A specific embodiment of the quenching device may particularly be used in which this device has a flooding arrangement for flooding the chamber having the blower wheel with quenching gas. Particularly, the flooding arrangement may include a gas supply line that opens into the chamber, the supply line being fed by a pressure tank filled with quenching gas.

It may be further provided that an evacuating arrangement may be provided for evacuating the quenching device. These evacuating arrangement may be configured such that low pressure compared to the surrounding environment can be produced in the quenching chamber; i.e., a vacuum can be produced in the chamber.

Quite particularly, a heat exchanger may be situated in the chamber having the blower wheel, said heat exchanger being charged with the quenching gas circulated by the blower wheel and removing heat from this gas in a targeted manner.

The present invention is also directed to a method for quenching material to be quenched, in particular metallic workpieces, with quenching gas using a quenching device, which may be a quenching device as described above. In the method, the blower wheel is used to accelerate the quenching gas in order to realize a good heat transmission between the material being quenched and the quenching gas. The core of the method of the present invention is that the blower wheel is driven by the drive motor in contactless fashion, in particular using a magnetic coupling. This specific embodiment makes it possible to transmit the torque through a wall and thus to situate the drive motor outside the chamber in which the blower wheel is situated.

It may be quite particularly provided that the drive motor is already started and/or operated while the chamber is not (yet) flooded with quenching gas. Given the use of a standard drive motor that is not sealed, this is possible only if the drive motor is not situated in the flooded chamber.

Further advantages, features, and details of the present invention result from the following description of the exemplary embodiments, and on the basis of the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a possible design of a quenching device.

DETAILED DESCRIPTION

FIG. 1 shows a possible specific embodiment of a quenching device 1. In the depicted exemplary embodiment, quenching device 1 has a single chamber 2 that can be flooded with quenching gas. A floodable chamber in the form of a flow channel as shown in EP 1154 024 B1 does not exist here, but can be provided if needed.

Chamber 2 has a loading door 3 that can be sealed in pressure-tight fashion, through which chamber 2 (here the quenching chamber) can be loaded with material 4 that is to be quenched. For this purpose, material 4 that is to be quenched, which in the depicted exemplary embodiment is made up of steel workpieces, is placed on a charging rack 5 that, using suitable transport devices, can be transported into chamber 2 under a vacuum atmosphere and then transported out of said chamber after the quenching process.

An oven (not shown) for the preliminary heat treatment of quenching material 4 is standardly situated in front of loading door 3.

A quenching gas supply line 6 opens into chamber 2, via which quenching gas can be conducted into chamber 2 from a pressure gas container 7. In order to flood chamber 2 with the quenching gas, it is necessary merely to open a valve 8, which may be automatically.

The pressure in chamber 2 after the flooding with quenching gas may be up to approximately 20 bar.

Inside chamber 2, a blower wheel 9 (fan wheel) is mounted so as to be capable of rotation, blower wheel 9 being situated on the end of a shaft 10 that on its opposite end bears a second rotor 11 (here an inner rotor) of a magnetic coupling 12. Shaft 10 extends with second rotor 11 into a protuberance 13 of chamber 2 that is surrounded radially outwardly by a first rotor 14 (here an outer rotor) of magnetic coupling 12. First rotor 14 is situated at a (radial) distance from second rotor 11, and, when drive motor 15 is running, transmits a torque in contactless fashion through wall 16 of chamber 2, or, more precisely, through wall 16 of protuberance 13 of chamber 2, to second rotor 11, which consequently rotates along with the first rotor, setting blower wheel 9 into rotational movement. First rotor 14 is seated in rotationally fixed fashion on the end of a motor shaft 17 of drive motor 15, which is fashioned as a standard electric motor. It is essential that drive motor 15 be situated outside wall 16 of chamber 2, i.e. which may be in a normal air atmosphere, so that drive motor 15 can be operated independent of the atmosphere and internal pressure in the chamber.

FIG. 1 also shows that a heat exchanger 18 is situated inside chamber 2 that withdraws heat from quenching gas not circulated by blower wheel 9.

In the following, a particular quenching process is described in detail. First, loading door 3 is opened and charging rack 5, with material 4 that is to be quenched, is introduced into chamber 2, in which there may be a vacuum. The drive motor 15 may be started already during this loading. After loading door 3 is closed, chamber 2 is flooded with quenching gas via quenching gas supply line 6 until the quenching pressure is reached. Drive motor 15 and, as a consequence, blower wheel 9 have already reached their nominal rotational speed by the end of the flooding process, so that immediately after the termination of the flooding process the full quenching intensity is available. After a predetermined quenching time, the quenching gas is either released to the surrounding environment or is conveyed back into pressure gas container 7 via a compressor (not shown), and loading door 3 is removed in order to remove charging rack 5 with the quenched material 4. A vacuum may then be produced in chamber 2.

Claims

1-10. (canceled)

11. A quenching device, comprising:

at least one chamber, which is fillable with a quenching gas and which has a blower wheel for circulating the quenching gas, wherein the at least one chamber includes at least one of a quenching chamber and a flow channel; and

a drive motor, which is situated outside the chamber, for driving the blower being allocated to the blower wheel;

wherein the drive motor is coupled to the blower wheel so as to transmit torque via a coupling that operates in contactless fashion.

12. The quenching device of claim 11, wherein the coupling includes a magnetic coupling.

13. The quenching device of claim 12, wherein the magnetic coupling includes a first rotor connected mechanically to the drive motor and a second rotor, which is drivable in contactless fashion by the first rotor and which is mechanically connected to the blower wheel.

14. The quenching device of claim 13, wherein the first rotor includes an outer rotor, radially outwardly surrounding the second rotor, which is fashioned as an inner rotor.

15. The quenching device of claim 13, wherein the second rotor includes an outer rotor, radially outwardly surrounding the first rotor, which includes an inner rotor.

16. The quenching device of claim 11, wherein material to be quenched is situatable in the chamber having the blower wheel.

17. The quenching device of claim 11, further comprising:

a flodding arrangement to flood the chamber with quenching gas.

18. The quenching device of claim 11, wherein a heat exchanger is situated in the chamber.

19. A method for quenching material to be quenched with quenching gas, the method comprising:

circulating quenching gas, using a quenching device, with a blower wheel driven by a drive motor, wherein the blower wheel is driven by the drive motor in contactless fashion;

wherein the quenching device, includes at least one chamber, which is fillable with the quenching gas and which includes the blower wheel for circulating the quenching gas, wherein the at least one chamber includes at least one of a quenching chamber and a flow channel, and the drive motor, which is situated outside the chamber, for driving the blower being allocated to the blower wheel.

20. The method of claim 19, wherein the drive motor is at least one of started up and operated while the chamber is not yet flooded with quenching gas.

21. The method of claim 19, wherein the quenching material includes a metallic workpiece.