EP1154024B1 - Process and device for heat treating metallic workpieces - Google Patents

Abstract

Process for heat treating metallic workpieces (20) comprises passing a quenching gas around the workpieces using guide channels (30). An Independent claim is also included for a device for heat treating metallic workpieces (20) comprising a quenching chamber (10), in which the workpieces are cooled using a quenching gas via guide channels (30). Preferred Features: The guide channels are reverse drawn before heating over the workpieces placed in a stack. The channels have a length which corresponds to the height of the workpieces.

Description

The invention relates to a method and an apparatus for heat treatment metallic workpieces or from several one above the other in the vertical direction arranged metal workpieces formed workpiece stack with a Cross section of the workpieces or the workpiece stack projecting. Longitudinal extent.

To create defined workpiece properties, such as a high one Hardness or sufficient wear resistance, become metallic workpieces subjected to a heat treatment. The result of the heat treatment is one Change in the material structure, for example a conversion of the cubic face-centered γ-lattice of carbon-rich austenite lamellas in the cubic body-centered α-lattice of ferrite lamellas. Of particular influence on that In addition to the temperature and the initial structure, the treatment results are The speed at which the heated workpieces are cooled and the type of the quenching agent used for this. Find as a deterrent - after order of increasing ruggedness - primarily gas, oil or water application.

In order to achieve approximately the same quenching intensity with gas quenching as with oil or water quenching, a relatively high gas velocity is required. For this purpose, it is known to provide nozzles with which correspondingly high gas velocities and thus generally sufficient heat transfer coefficients of more than 1000 W / m ² K can be achieved. A device provided with nozzles for quenching metallic workpieces is disclosed, for example, in EP 0 796 920 A1 or DE-U-94 00 222.3.

This is a nozzle field consisting of an interchangeable nozzle Device having a nozzle plate made possible by a rotating or pivotable arrangement of the nozzle plate and / or the workpieces supporting rust is a relative movement of the nozzle field and workpieces thus a relatively uniform application of the latter, but has the disadvantage that the gas flow hits the workpieces diffusely and turbulently. This causes the surface of the workpieces to be cooled unevenly, causing Tensions occur that can result in warping or even cracks. In front especially for workpieces with a climbing shape, such as shafts, or those that when stacking a batch can be stacked outstanding, like For example, rolling bearing rings or gears, a warping in particularly noticeable and leads due to the usually small tolerances such workpieces not seldom become one in economic terms unsatisfactory committee.

A method as well as a treatment device for cooling high heated metal components with different mass distribution is above it also known from WO 00/18972. One is provided for this purpose Cooling chamber into which the metal component is to be introduced for cooling. The entire cooling chamber is then flooded with cooling gas, as a result of which Cooling of the metal component can be achieved. To be even Cooling of components with uneven mass distribution to achieve can, it is provided that those areas of the cooled Metal component, which have a particularly high mass distribution, from separately enclosures to be arranged. These housings will be as well as the cooling chamber charged with a cooling gas as a result of which it to intensify cooling of the areas surrounded by the enclosures of the component in contrast to those areas of the component that do not pass through a housing to be arranged separately is coming. Is achieved this results in a uniform cooling despite different mass distribution of the entire component. This method is particularly to be used for Cooling of gas turbine blades, for the purpose of uniform cooling both the foot area and the head area of the gas turbine blade in each case is surrounded by a separate enclosure.

In order to control the gas flow more systematically, it is admittedly in the state of the art known to provide baffles with which, for example, also the Allow workpiece surface to be pressurized with quenching gas, otherwise in a flow shadow; Such a measure is satisfactory though not. Because in addition to the comparatively high effort, the baffles align according to the respective workpiece geometry, prevent the Baffles not that when the gas flow hits the workpieces Turbulence occurs, which is about the cooling of a batch affect neighboring workpieces and thus cause distortion.

The invention has for its object to provide a method and an apparatus for the heat treatment of metallic workpieces, with which a low-warpage gas quenching can be achieved even with workpieces of climbing or stacking shape.

According to the invention the above object is the method, solved by a method for heat treatment of metal workpieces or of a plurality formed in the height direction superposed metallic workpieces workpiece stacks having a cross-section of the workpieces or the workpiece stacks superior longitudinal extension, in which, after a previous heating of the workpieces or the workpiece stacks in a quenching chamber are cooled with a quenching gas, the workpieces or the stack of workpieces in each case by means of trained guide channels which have a closed lateral surface and completely enclose the workpieces or the stack of workpieces along the flow direction of the quenching gas, with quenching gas in a flow parallel in the direction of the longitudinal extent of the Workpieces or stack of workpieces are flowed around, the quenching gas by means of a flow to the quenching chamber connected flow channel is guided in a closed flow circuit.

Such a procedure adopts the knowledge that a low distortion cooling of the workpieces can then be achieved with quenching gas, if the individual or stacked workpieces are one batch to be cooled are separated from one another by guide channels. Because in this way a gas flow results in the guide channels flows around the entire workpiece surface parallel to the workpiece axis and Uniform cooling, unaffected by neighboring workpieces causes.

It is useful if the guide channels before heating over the individual or stacked workpieces. On in this way, the guide channels together with the workpieces of the Subjected to heat treatment. Although such a measure Requires guide channels made of a suitable heat-resistant material this has the advantage that the guide channels on these are still cold inverted and inserted in conventional quenching chambers or the workpieces can be quenched in the heat treatment furnace.

Alternatively, the guide channels in the quenching chamber can be attached to the individual or stacked and previously heated workpieces be arranged to obstruct the heating of the workpieces excluded. It is particularly advantageous here that the guide channels in the Quenching chamber, for example electromotive, hydraulic or pneumatic, from one or two sides, preferably from above and / or below to approach the workpieces, so that even with limited space the Quenching chamber a handling appropriate operation is ensured.

To achieve the above object is also proposed an apparatus for heat treatment of metal workpieces or of several superimposed in height direction arranged metallic workpieces formed workpiece stacks having a cross-section of the workpieces or the workpiece stacks superior longitudinal extension, with a quenching chamber, in which the workpieces or the workpiece stacks with a Quenching gas can be cooled, and a flow channel connected to the quenching chamber in terms of flow to form a closed flow circuit for the quenching gas, guide channels, which have a closed outer surface and the workpieces or the workpiece stacks along the flow direction, are provided for targeted flow around the workpieces or workpiece stacks with quenching gas completely enclose the quenching gas to form a flow in the longitudinal direction of the workpieces or workpiece stack eat.

This can be done with a device designed in this way Perform the inventive method. Because of the closed The surface of the guide channels are the workpieces along the Flow direction of the quenching gas completely enclosed and by the workpieces of the batch to be cooled that are adjacent to them. this has with the result that a largely laminar, in the guide channels neighboring workpieces unaffected gas flow, which the Workpieces cool down intensively and evenly.

It is particularly advantageous if the guide channels have a length the at least the height of the individual or stacked on top of each other Workpieces. Because in this way the impact of the Gas flow on the workpieces inevitable swirling of the Quench gas channeled, so that an impairment of the flow neighboring workpieces is omitted. As particularly advantageous in this regard has been found to measure the length of the guide channels so that the Height of the individual or stacked workpieces around the half the diameter or width of the workpieces is exceeded.

In a further advantageous embodiment of the device according to the invention is the shape of the guide channels cylindrical, preferably with a circular, square or polygonal cross section, or to the geometry of the Workpieces to be cooled adapted to make a simple and inexpensive production and on the other hand by a narrow distance conditional between the inner surface of the guide channels and the workpieces high gas velocity to ensure intense deterrence.

With a view to easy handling, it is also expedient that Guide channels to connect to each other to form a channel system joint placement of the guide channels on the individual or in stacks arranged workpieces results. This mainly comes into play if according to a further advantageous development of the invention Device the guide channels adjustable, preferably by electric motor, hydraulically or pneumatically, are arranged in the quenching chamber, for example in the form of a lowerable on the workpieces from above Canal system. The guide channels are advantageously interchangeable, to ensure adaptation to different workpiece geometries.

In a further development of the invention it is also proposed that the Quenching chamber has an inlet for the quenching gas, which seals the guide channels. This has the advantage that the Quench chamber supplied gas flow only in the guide channels and not past the workpiece batch or between the individual Guide channels flows. In addition, this becomes too Flow volume reduced to a minimum, with the result that a high Maintain gas velocity and thus a high quenching intensity is achieved. Finally, it is proposed that the guide channels consist of one heat-resistant material, preferably steel, iron or nickel alloys, exist, for example, before the heat treatment of the To put workpieces on them.

Fig. 1

eine schematische Darstellung einer Abschreckkammer bei einem hochgefahrenen Kanalsystem;

Fig. 2

eine schematische Darstellung der Abschreckkammer gemäß Fig. 1 bei auf Werkstücke abgesenktem Kanalsystem;

Fig. 3

eine schematische Seitenansicht des aus miteinander verbundenen Führungskanälen bestehenden Kanalsystems gemäß Fig. 2;

Fig. 3a

eine schematische Draufsicht des Kanalsystems gemäß Fig. 3;

Fig.4

eine schematische Seitenansicht einzelner, auf die Werkstücke aufgesetzter Führungskanäle und

Fig. 4a

eine schematische Draufsicht der Führungskanäle gemäß Fig. 4.

Details and further advantages of the subject matter of the present invention result from the following description of preferred exemplary embodiments. The accompanying drawings illustrate in detail:

Fig. 1

a schematic representation of a quenching chamber in a raised channel system;

Fig. 2

2 shows a schematic illustration of the quenching chamber according to FIG. 1 with the duct system lowered onto workpieces;

Fig. 3

a schematic side view of the channel system consisting of interconnected guide channels according to FIG. 2;

Fig. 3a

a schematic plan view of the channel system according to FIG. 3;

Figure 4

is a schematic side view of individual, placed on the workpieces guide channels and

Fig. 4a

3 shows a schematic top view of the guide channels according to FIG. 4.

The quenching chamber 10 shown in FIGS. 1 and 2 is part of a device for the heat treatment of metallic workpieces 20 and for example at the end a roller hearth furnace. The quenching chamber 10 can be such be designed so that they both with vacuum and with atmospheric or Overpressure can be operated. In the quenching chamber 10 there is an after workpieces 20 carrying grate 11 to be cooled prior to heating, which is a vertical circulation of a quench gas in the quench chamber 10 allows. A motor 12 is used to circulate the quenching gas driven fan 13 arranged below the grate 11. Except for Quenching chamber 10 becomes the quenching gas in the direction indicated by an arrow in FIG. 1 and 2 shown flow direction passed through a gas channel 14. upper and below the quenching chamber 10 there are also flaps 15 which prevent circulation of the quenching gas until the fan 13 its has reached the necessary number of revolutions.

When the flaps 15 are open, a cycle results in which the Quench gas from fan 13 through gas duct 14 into the quench chamber 10 and over the workpieces 20 and one in the flow direction in front of the fan 13 arranged heat exchanger 16, which cools the quenching gas again, flows back to the fan 13.

In order to achieve a targeted flow around the workpieces 20, Guide channels 30 provided from a heat-resistant material, the one Have closed outer surface and the workpieces 20 along the Enclose the flow direction of the quench gas. The guide channels 30 can through a coherent, grid-like channel system 31 be formed, in which the guide channels 30 are connected to each other, such as is shown in particular in FIGS. 3 and 3a. Alternatively, the Guide channels 30 also as individual hollow cylinders 32, 33 with, for example circular or square cross section. such Embodiments can be seen in FIGS. 4 and 4a. The length of the Guide channels 30 is dimensioned so that the height of the individual or to stack superimposed workpieces 20 is exceeded by the distance a, such as 3 and 4 can be seen. The distance a corresponds to half Diameter or width of the workpieces 20.

The guide channels 30 can either be inserted into the workpiece 20 Quenching chamber 10 can be placed on the workpieces 20, for example already when assembling the batch, or only in the quenching chamber 10. The latter is illustrated in FIGS. 1 and 2. The as a coherent Channel system 31 formed guide channels 30 are in this case Hydraulic cylinders 34 arranged vertically adjustable in the quenching chamber 10, as indicated by the double arrow in FIGS. 1 and 2. In this way it is possible after the workpieces 20 have been introduced into the quenching chamber 10 to place the channel system 31 on the workpieces 20 from above. Around Taking into account batches with different geometry of the workpieces 20, the channel system 31 is interchangeable on the hydraulic cylinders 34 attached. In the upper part of the quenching chamber 10 there is also an inlet 35 provided that the channel system 31 relative to the interior of the Quench chamber 10 seals, so that in quench chamber 10 circulating quench gas flows exclusively through the guide channels 30 and does not flow outside of the workpiece batch.

The device described above is particularly suitable Workpieces 20 with a climbing or towering shape, such as Shafts or stacked bearing rings, effective and free from distortion deter. The reason for this is that caused by the guide channels 30 high speed and laminar flow of quench gas. Through the height-adjustable arrangement of the channel system 31 is also a handling and process-oriented process management ensured. Last but not least, the Possibility to provide differently designed guide channels 30, and the Mainly interchangeable arrangement of the channel system 31 for this purpose an adaptation to different workpiece shapes and sizes achieved without that complex retrofitting work would be necessary.

LIST OF REFERENCE NUMBERS

10

quenching

11

rust

12

engine

13

fan

14

gas channel

15

flap

16

heat exchangers

20

workpiece

30

guide channel

31

channel system

32

hollow cylinder

33

hollow cylinder

34

hydraulic cylinders

35

inlet

a

distance

Claims (13)

1. Process for heat treating metallic workpieces (20) or workpiece stacks formed from a plurality of metallic workpieces, which are superimposed in the vertical direction, and having a longitudinal extent which projects beyond the cross section of the workpieces (20) or the workpiece stacks, in which the workpieces (20) or the workpiece stacks are cooled in a quenching chamber (10) with a quenching gas following previous heating, wherein quenching gas specifically flows around the workpieces (20) or the workpiece stacks in a flow parallel to the direction of the longitudinal extent of the workpieces (20) or workpiece stacks in each case by means of formed guide ducts (30) which have a closed circumferential surface and completely enclose the workpieces (20) or the workpiece stacks along the flow direction of the quenching gas, wherein the quenching gas is routed in a closed flow circuit by means of a flow duct (14) connected in terms of flow to the quenching chamber (10).
2. Process according to Claim 1, characterised in that the guide ducts (30) are placed over the individual or stacked workpieces (20) prior to heating.
3. Process according to Claim 1, characterised in that the guide ducts (30) are disposed in the quenching chamber (10) at the individual or stacked and previously heated workpieces (20).
4. Process according to Claim 2, characterised in that the guide ducts (30) in the quenching chamber (10) are brought up to the workpieces (20) or workpiece stacks from one or two sides, preferably from above and/or below.
5. Device for heat treating metallic workpieces (20) or workpiece stacks formed from a plurality of metallic workpieces, which are superimposed in the vertical direction, and having a longitudinal extent which projects beyond the cross section of the workpieces (20) or the workpiece stacks, with a quenching chamber (10), in which the workpieces (20) or the workpiece stacks can be cooled with a quenching gas, and a flow duct (14), connected in terms of flow to the quenching chamber (10), for forming a closed flow circuit for the quenching gas, wherein respective guide ducts (30) are provided in order for quenching gas to flow specifically around the workpieces (20) or workpiece stacks, these guide ducts having a closed circumferential surface and completely enclosing the workpieces (20) or the workpiece stacks along the flow direction of the quenching gas in order to form a flow in the longitudinal direction of the workpieces (20) or workpiece stacks.
6. Device according to Claim 5, characterised in that the guide ducts (30) are of a length which corresponds at least to the height of the individual or stacked workpieces (20).
7. Device according to Claim 6, characterised in that the length of the guide ducts (30) projects beyond the height of the individual or stacked workpieces (20) by half the diameter or width of the workpieces (20).
8. Device according to any one of Claims 5 to 7, characterised in that the shape of the guide ducts (30) is cylindrical, preferably with a circular (32), square (33) or polygonal cross section, or is adapted to the geometry of the workpieces (20) or workpiece stacks which are to be cooled.
9. Device according to any one of Claims 5 to 8, characterised in that the guide ducts (30) are connected together to form a duct system (31).
10. Device according to any one of Claims 5 to 9, characterised in that the guide ducts (30) are disposed in the quenching chamber (10) in an adjustable manner, preferably by electromotive, hydraulic or pneumatic means.
11. Device according to Claim 10, characterised in that the guide ducts (30) are interchangeable.
12. Device according to any one of Claims 5 to 11, characterised in that the quenching chamber (10) comprises an inlet (35) for the quenching gas which tightly adjoins the guide ducts (30).
13. Device according to any one of Claims 5 to 12, characterised in that the guide ducts (30) consist of a heat-resistant material, preferably steel, iron alloys or nickel alloys.

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