DEVICE FOR INDUCTION HEATING OF AT LEAST ONE WORKPIECE AND METHOD FOR INDUCTION HEATING OF AT LEAST ONE WORKPIECE - Patent application

Abstract

The present invention relates to a device for inductively heating at least one workpiece (4), in particular a substantially strip-shaped workpiece (4), comprising at least one furnace housing (6), at least one inductor arrangement (8) arranged in the furnace housing (6), at least partially in an inductor area (10) of the furnace housing (6), at least one heating area (14) for receiving a process gas, the heating area (14) arranged in the furnace housing (6), and a separating material (12) for separating, in particular for thermally separating, the inductor area (10) and the heating area (14).Furthermore, the present invention relates to a method for inductively heating at least one workpiece.

Description

[Technical field]

[0001] The invention relates to a device for induction heating of at least one workpiece, in particular a workpiece essentially in strip form, comprising at least one furnace housing, at least one inductor arrangement arranged in the furnace housing, at least partially in an inductor area of ​​the furnace housing, at least one heating area for receiving a process gas, the heating area arranged in the furnace housing, and a separating material for separating the inductor area and the heating area, in particular for thermal separation. The invention also relates to a method for induction heating of at least one workpiece, in particular using the aforementioned device. [Background technology]

[0002] Devices for induction heating are known from the prior art and may be called, for example, continuous tunnel furnaces or electric induction tunnel furnaces. Such devices may be used to inductively heat workpieces. The induction heating process is usually taken to be a process in which the surface of the material to be heated, in particular steel material, is heated by means of an electromagnetic field induced in the workpiece.

[0003] In such a process, the furnace tunnel may be filled with process gas, but the process gas must not escape from the furnace tunnel into the atmosphere surrounding the furnace tunnel, since this would not only pollute the air surrounding the continuous tunnel furnace, but also cause an explosive reaction of the process gas.

[0004] Thus, conventional continuous tunnel furnaces usually have an essentially gas-tight furnace tunnel, which is connected to gas-tight connecting ducts upstream and downstream of the heating section. An inductor arrangement may surround the workpieces or be arranged above and / or below at least one workpiece.

[0005] However, a problem with such arrangements is that the materials typically used for hermetic separation are made at least in part of metal, which would become unacceptably hot when the inductor arrangement is used in conjunction with at least one workpiece.

[0006] Patent Document 1 discloses an electric induction tunnel furnace having an airtight barrier chamber surrounding an airtight tunnel region, with an airtight separating surface or material being arranged between the tunnel region and the barrier chamber. In order to avoid exchange of the barrier gas arranged in the barrier chamber with the process gas arranged in the tunnel region, the electric induction tunnel furnace also has a barrier gas regulator.

[0007] However, when providing such an airtight separation surface, problems arise in practice in that the airtight material is metallic, i.e. problematic for the penetration of the magnetic field or such penetration can only be achieved with high energy losses, or in polymeric materials where temperature is critical. Another drawback is that when there is a high pressure difference between the barrier chamber and the tunnel area, large forces act on the separation surface, which forces can thereby jeopardize the integrity of the separation surface. In addition, an airtight connection to the connecting duct can only be achieved with a high level of design effort. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent No. 2 577 201(B1) Summary of the Invention [Means for solving the problem]

[0009] The present invention is therefore based on the aforementioned prior art and on the technical problem of providing a device and method for induction heating of at least one workpiece, which allows reliable and safe operation of the device or of the method in a structurally simple manner.

[0010] According to a first aspect of the invention, the aforementioned technical problem is solved in the aforementioned device, in that the separating material is designed such that there is a fluid connection between the inductor region and the heating region.

[0011] By providing a fluid connection between the inductor region and the heating region, a fluid exchange between a medium disposed in the inductor region and a medium disposed in the heating region can be provided, in particular the respective medium being a gas or a gas mixture located within the furnace housing.

[0012] For example, it has been found to be advantageous to flush the entire furnace housing with an inert housing gas, for example nitrogen or a nitrogen mixture, before starting the operation of the device for induction heating of at least one workpiece, and then fill it with the process gas used during the operation of said device, for example hydrogen or a hydrogen mixture. In this way, residual air or oxygen concentrations in the inductor area can be reliably avoided during the operation of the device for induction heating of at least one workpiece, and thus a reliable operation of the at least one inductor installation is ensured.

[0013] The fluid connection between the inductor region and the heating region means, in particular, that the gaseous medium can flow along the pressure gradient from the inductor region in the direction of the heating region or from the heating region in the direction of the inductor region. The separation material is preferably essentially thermally stable, so that the properties of the separation material do not essentially change even at high temperatures. Furthermore, the heating region is preferably essentially in the form of a tunnel-shaped furnace channel.

[0014] In a preferred embodiment of the present invention, the separation material has at least one through opening for fluid connection between the inductor region and the heating region. By providing a through opening in the separation material, the fluid connection between the inductor region and the heating region can be provided in a structurally favorable manner.

[0015] At least one through opening has a diameter of at least 1 mm and / or a width of at least 1 mm 2 Furthermore, it is preferred that the at least one through opening is essentially circular.

[0016] According to a preferred embodiment of the invention, the at least one through opening can be at least partially closed by at least one flap so that the exchange of gas or gas mixture between the inductor region and the heating region can be regulated.

[0017] A preferred embodiment of the invention is characterized in that the separation material is designed as an at least partially permeable material for fluidically connecting the inductor region and the heating region. With the design of the separation material as an at least partially permeable material, an advantageous essentially uniform fluid connection can be provided over essentially the entire area of ​​the separation material. The permeable material is preferably particularly gas-permeable so that the process gas and / or the housing gas can flow along the pressure gradient from the inductor region into the heating region or vice versa.

[0018] In a further preferred embodiment of the invention, the separating material comprises a fabric, in particular a fabric made of heat-resistant fibers. By providing a fabric, it is preferably possible to provide a permeable material for the fluid connection between the inductor region and the heating region. Advantageously, the fabric is a fabric made of heat-resistant fibers, since these fibers are suitable for the temperatures occurring inside the furnace housing, in particular inside the heating region. The heat-resistant fibers are, for example, silicate glass fibers.

[0019] A further preferred embodiment of the invention is characterized in that the inductor region has at least one inlet for supplying the housing gas, and that the control means regulate the supply of the housing gas into the inductor region such that there is a pressure gradient in the direction from the housing gas arranged in the inductor region to the process gas arranged in the heating region. Since the housing gas arranged in the inductor region has a higher pressure than the process gas arranged in the heating region, it can be reliably prevented that the process gas from the heating region can penetrate into the inductor region. This can prevent hot process gas from entering the inductor region. The inlet can also be used to fill the heating region with the process gas. For example, the process gas and the housing gas can be essentially the same gas and / or gas mixture. For example, the housing gas and the process gas can have different respective temperatures, the temperature of the housing gas being preferably lower than the temperature of the process gas.

[0020] In particular, the process gas is a highly flammable gas, especially when mixed with oxygen, and especially a highly flammable gas mixture. For example, the process gas may be a hydrogen and / or nitrogen mixture or pure hydrogen. Thus, the provision of a pressure gradient may prevent the process gas from flowing from the heating region into the inductor region or into the furnace environment, where it may mix with oxygen to produce a highly flammable gas mixture. The housing gas is preferably an inert gas, such as nitrogen or a nitrogen mixture.

[0021] The aforementioned pressure gradient also allows for an essentially constant flow of the housing gas in the direction of the heating region, i.e. the inductor region can be continuously purged. The temperature of the process gas is preferably higher than the temperature of the housing gas. For example, the process gas has the same composition as the housing gas. Alternatively, the process gas has a different composition than the housing gas. In particular, the process gas is a hydrogen and / or nitrogen mixture or pure hydrogen and the housing gas is an inert gas, preferably nitrogen or a nitrogen mixture.

[0022] In a further preferred embodiment of the invention, the inductor region has at least one outlet. By providing an outlet, when the device for induction heating of at least one workpiece is started, the furnace housing with the inductor region and the heating region can first be purged with a substantially inert gas, for example with a housing gas, which is introduced through the at least one inlet and discharged through the at least one outlet. This ensures that ambient air is purged from the interior of the oven. The at least one outlet is preferably closed during operation of the device for induction heating of at least one workpiece.

[0023] A further preferred embodiment of the invention is characterized in that the device further comprises at least one measuring means for measuring the pressure in the inductor region and / or in the heating region and / or the pressure difference between the inductor region and the heating region. The provision of at least one measuring means may allow for improved regulation of the control means for supplying the housing gas into the inductor region. In particular, since the heating region containing the process gas may also be purged with the housing gas, there is also a reduced temperature in the heating region and the overall probability of ignition may be reduced.

[0024] Furthermore, further embodiments of the invention are characterized in that the device comprises at least one flow measuring means for measuring the flow rate of the housing gas supplied and / or that the device further comprises at least one dew point measuring means for measuring the dew point of the gas mixture arranged in the inductor region and / or the dew point of the gas mixture arranged in the process region. The provision of at least one of the aforementioned measuring means may make it possible to improve the control of the control means for supplying the housing gas into the inductor region.

[0025] In a further preferred embodiment of the invention, the control means adjusts the supply of the housing gas into the inductor region such that there is a pressure gradient from the housing gas arranged in the inductor region towards the ambient air arranged around the furnace housing, whereby the passage of hot, possibly highly flammable process gas from the heating region through the inductor region into the furnace environment outside the furnace housing can also be prevented.

[0026] A further preferred embodiment of the invention is characterized in that the device further comprises a transport device for transporting the workpiece to be inductively heated substantially longitudinally along a substantially longitudinal extent of the heating zone. By providing such a transport device, an essentially uniform heating can be provided over the entire length of the workpiece. For example, the speed of the moved workpiece can be variably adjusted by means of the transport device, whereby, inter alia, the heat treatment of the workpiece can also be changed.

[0027] In another preferred embodiment, an insulating material is provided between the separating material and the heating region. In addition to the existing separating material, the insulating material allows for additional heat shielding of the inductor region from the heating region. The insulating material is preferably designed in the same way as the separating material, so that there is still a fluid connection between the inductor region and the heating region through the separating surface and the insulating material. The insulating material can also be formed by the separating material alone.

[0028] According to a second aspect of the present invention, the aforementioned technical problem is solved by a method for inductively heating at least one workpiece, in particular by means of a device as described above, the method comprising the following steps: - guiding the workpiece to be heated along a heating area of ​​a furnace housing filled with process gas; - heating the workpiece with at least one inductor arrangement arranged in an inductor region filled with a housing gas; - establishing a fluid connection between the inductor region and the heating region, in particular by means of an isolating material arranged between the inductor region and the heating region; - supplying a housing gas into the inductor region such that there is a pressure gradient in a direction from the housing gas disposed in the inductor region to the process gas disposed in the heating region; This is solved by including

[0029] The housing gas can be fed into the inductor region, for example, temporarily or constantly. In an advantageous manner, the housing gas is fed into the inductor region in such a way that only gas exchange can take place in the direction of the heating region, so that essentially no process gas can pass from the heating region into the inductor region. Further advantages described in connection with the method are described in connection with the aforementioned device.

[0030] In one embodiment of the present invention, the amount of housing gas supplied is determined as a function of the pressure difference existing between the inductor region and the heating region and / or the amount of housing gas supplied is determined as a function of the housing gas flow occurring between the inductor region and the heating region, in particular as a function of the volumetric flow rate of the housing gas, which allows reliable control of the amount of gas or gas mixture supplied.

[0031] In a further embodiment of the invention as described above, the housing gas is supplied into the inductor region such that the temperature, particularly the average temperature, of the housing gas in the inductor region is lower than the temperature, particularly the average temperature, of the shielding gas in the heating region, which may further reduce the probability of ignition of any gas that may enter the inductor region.

[0032] A further preferred embodiment of the invention is characterized in that before the workpiece to be heated is guided along the heating area of ​​the furnace housing, the inductor area and the heating area are first purged with housing gas, then process gas is fed into the heating area, and further housing gas is preferably fed into the inductor area thereafter. Such a procedure can in particular ensure that no significant residual air concentrations remain in the furnace environment before the device is put into operation. In particular, condensation formation that may preferably occur on the inductor equipment can also be avoided.

[0033] A further advantageous embodiment of the invention is characterized in that the gas mixture supplied into the inductor region is such that the dew point of the housing gas arranged in the inductor region is shifted towards lower temperatures compared to the dew point of the process gas arranged in the process region and / or the dew point of the housing gas arranged in the inductor region is essentially constantly monitored and the housing gas is supplied as a function of the dew point. In this way, a reliable control of the supplied gas mixture can be provided. The gas mixture supplied into the inductor region preferably has a lower temperature than the process gas.

[0034] Further advantageous exemplary embodiments of aspects of the present invention can be found in the following detailed description of some exemplary embodiments of the present invention, in particular in conjunction with the drawings. However, the drawings attached to this application are for the purpose of clarification only, and not for determining the scope of protection of the present invention. The attached drawings are not necessarily to scale, and are only intended to reflect the general idea of ​​the present invention by way of example. In particular, features contained in the drawings should in no way be interpreted as necessarily forming part of the present invention. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram of a first embodiment of a device according to the invention. [Diagram 2] FIG. 2 is a schematic diagram of a second embodiment of the device according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] In the following description of various embodiments according to the invention, parts and elements having the same function and the same manner of operation are provided with the same reference numerals, even if the dimensions or shapes of those parts and elements differ in the various embodiments.

[0037] 1 shows a first embodiment of a device 2 for inductively heating at least one strip-shaped workpiece 4. The device 2 comprises a furnace housing 6 and an inductor arrangement 8 arranged in the furnace housing 6. The inductor arrangement 8 can completely surround the strip-shaped workpiece 4.

[0038] The inductor arrangement 8 is arranged in an inductor region 10, whereby the inductor region 10 is in particular thermally separated from the heating region 14 by means of an isolation material 12. In addition to the isolation material 12, an insulation material 16 is provided between the isolation material 12 and the heating region 14, the isolation material 12 and the insulation material 16 being designed such that there is a fluid connection between the inductor region 10 and the heating region 14.

[0039] For this purpose, the separation material 12 has at least one through opening 18 for a fluid connection between the inductor region 10 and the heating region 14. In addition, the separation material 12 is designed as an at least partially permeable material, so that fluid exchange between the inductor region 10 and the heating region 14 can take place even away from the through opening 18.

[0040] The inductor region 10 has an inlet 20 for feeding a gas mixture, in particular a housing gas, into the inductor region 10. Furthermore, control means 22 are provided at the inlet 20 for regulating the feeding of the housing gas into the inductor region 10 in such a way that there is a pressure gradient from the housing gas arranged in the inductor region 10 towards the process gas arranged in the heating region 14. This makes it possible to avoid the process gas arranged in the heating region 14 flowing in the direction of the inductor region 10 or outside the furnace housing.

[0041] The inductor region 10 also has an outlet 24. By providing the outlet 24, the furnace housing 6 can be purged with a substantially inert gas, for example with a housing gas, when the device 2 is started up.

[0042] Furthermore, the device has a measuring means 26 in the inductor region 10, a measuring means 28 in the heating region 14 and a further measuring means 30 outside the furnace housing. The measuring means 26, 28, 30 can be designed, for example, to measure the pressure present in the inductor region 10, the heating region 14 and / or the ambient air. The measuring means 26, 28 can also be designed to measure the dew point of a gas or gas mixture present in the inductor region 10 and / or the heating region 14. The control means 22 can also have measuring means for measuring the flow rate of the supplied housing gas.

[0043] 2 shows a schematic side view of a second embodiment of the device 2 according to the invention. In contrast to the embodiment of the device 2 shown in FIG. 1, the separating material 12 is designed as a thermal insulator and has a through opening 18 for establishing a fluid connection between the inductor region 10 and the heating region 14. At the beginning of the heat treatment, the air arranged in the furnace housing 6 can be replaced, for example, by an inert gas using the inlet 20. Thus, the inductor region 10 and the heating region 14 can be purged. This can prevent the process gases that are later introduced into the inductor region 10 and the heating region 14 from reacting with the residual air concentration in the furnace housing 6. [Explanation of symbols]

[0044] 2 Devices 4 Workpiece 6 Furnace housing Equipped with 8 inductors 10 Inductor Area 12 Separation materials 14 Heating area 16 Insulation 18 Through opening 20 Entrance 22 Control Means 24 Exit 26 Measurement methods for inductor area 28 Measuring means for heating area 30 Measuring means for ambient air

Claims

1. A device for inductively heating at least one workpiece (4), in particular a substantially strip-shaped workpiece (4), comprising: at least one furnace housing (6), at least one inductor arrangement (8) arranged in said furnace housing (6), said inductor arrangement (8) being arranged at least partially in an inductor area (10) of said furnace housing (6); at least one heating area (14) for receiving a process gas, said heating area (14) being arranged inside said furnace housing (6); a separating material (12) for separating, in particular thermally, said inductor region (10) and said heating region (14); Equipped with the separating material (12) is designed so that there is a fluid connection between the inductor region (10) and the heating region (14); A device comprising:

2. said separating material (12) having at least one through opening (18) for said fluid connection between said inductor region (10) and said heating region (14); The device according to claim 1 , characterized in that

3. the separating material (12) is designed as an at least partially permeable material for the fluid connection between the inductor region (10) and the heating region (14); 3. The device according to claim 1 or 2, characterized in that

4. - said separating material (12) comprises a fabric, in particular a fabric made of heat-resistant fibers; The device according to any one of claims 1 to 3, characterized in that

5. - said inductor region (10) has at least one inlet (20) for supplying a housing gas; and - the control means (22) regulates the supply of the housing gas into the inductor region (10) so that there is a pressure gradient in the direction from the housing gas arranged in the inductor region (10) to the process gas arranged in the heating region (14); The device according to any one of claims 1 to 4, characterized in that

6. - said inductor region (10) has at least one outlet (24); The device according to claim 5 , characterized in that

7. said device further comprises at least one measuring means (26, 28) for measuring the pressure in said inductor region (10) and / or in said heating region (14) and / or the pressure difference between said inductor region and said heating region; 7. The device according to claim 5 or 6, characterized in that

8. said device further comprises at least one further measuring means (26, 30) for measuring the pressure in said inductor region (10) and / or in the surrounding air and / or the pressure difference between said inductor region and the surrounding air; The device according to any one of claims 5 to 7, characterized in that

9. - said device comprises at least one flow measuring means (22) for measuring the flow rate of said housing gas supplied, and / or the device further comprises at least one dew point measuring means (26, 28) for measuring the dew point of the gas mixture arranged in the inductor region (10) and / or the dew point of the gas mixture arranged in the process region (14); The device according to any one of claims 5 to 8, characterized in that

10. the control means (22) further regulates the supply of the housing gas into the inductor region (10) so that there is a pressure gradient from the housing gas located in the inductor region (10) towards the ambient air located around the furnace housing (6); The device according to any one of claims 5 to 9, characterized in that

11. said device further comprises a transport device for a substantially longitudinal transport of the inductively heated workpiece (4) along a substantially longitudinal extent of said heating zone (14); The device according to any one of claims 1 to 10, characterized in that

12. - a thermal insulation material (16) is provided between said separating material (12) and said heating area (14); The device according to any one of claims 1 to 11, characterized in that

13. A method for inductively heating at least one workpiece, in particular with a device according to any one of claims 1 to 12, comprising: - guiding the workpiece to be heated along a heating area of ​​a furnace housing filled with process gas; - heating said workpiece by means of at least one inductor arrangement arranged in an inductor region filled with a housing gas; establishing a fluid connection between the inductor region and the heating region, in particular by means of an isolating material arranged between the inductor region and the heating region; - supplying a housing gas into the inductor region such that there is a pressure gradient from the housing gas located in the inductor region towards the process gas located in the heating region; The method includes:

14. the amount of housing gas supplied is determined as a function of the pressure difference existing between the inductor region and the heating region, and / or the amount of housing gas supplied is determined as a function of the housing gas flow occurring between the inductor region and the heating region, in particular as a function of the volumetric flow rate of the housing gas, and / or the housing gas is fed into the inductor region in such a way that the temperature, in particular the average temperature, of the housing gas in the inductor region is lower than the temperature, in particular the average temperature, of the shielding gas in the heating region; The method according to claim 13, characterized in that

15. - before the workpiece to be heated is guided along the heating zone of the furnace housing, the inductor zone and the heating zone are first purged with the housing gas; - the process gas is then fed into the heating area, and Preferably further housing gas is then fed into the inductor region.

15. The method according to claim 13 or 14, characterized in that

16. the gas mixture supplied into the inductor region is such that the dew point of the housing gas located in the inductor region is shifted towards lower temperatures relative to the dew point of the process gas located in the process region, and / or the dew point of the housing gas arranged in the inductor region is essentially constantly monitored and the housing gas is supplied as a function of the dew point The method according to any one of claims 13 to 15, characterized in that

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