Device for inductively heating at least one workpiece and method for inductively heating at least one workpiece

Abstract

The 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 shell (6); at least one inductor device (8) arranged in the furnace shell (6), wherein the inductor device (8) is arranged at least partially in an inductor region (10) of the furnace shell (6); at least one heating zone (14) for receiving a process gas, the heating zone (14) being arranged in the furnace shell (6); and an insulating material (12) for insulating, in particular thermally insulating, the inductor region (10) and the heating region (14). The invention further relates to a method for induction heating of at least one workpiece.

Description

Technical Field

[0001] The invention relates to a device for inductively heating at least one workpiece, in particular a substantially strip-shaped workpiece, comprising: at least one furnace housing; at least one inductor arrangement arranged in the furnace housing, wherein the inductor arrangement is at least partially arranged in an inductor region of the furnace housing; at least one heating region for receiving process gas, the heating region being arranged in the furnace housing; and an insulating material for insulating, in particular thermally insulating, the inductor region and the heating region. The invention also relates to a method for inductively heating at least one workpiece, in particular by means of the above-mentioned device. Background Art

[0002] Induction heating devices are known in the prior art, for example, they may be referred to as continuous tunnel furnaces or electric induction tunnel furnaces. These devices can be used to inductively heat a workpiece. Induction heating methods generally refer to methods of heating the surface of a material to be heated, in particular a steel material surface, by means of an electromagnetic field induced into the workpiece.

[0003] In this method, the furnace can be filled with process gas, but the process gas should not escape from the furnace to the atmosphere around the furnace. This is because if the process gas escapes from the furnace, it will not only pollute the air around the continuous tunnel furnace, but also an explosive reaction of the process gas will occur.

[0004] Therefore, conventional continuous tunnel furnaces usually have a substantially airtight furnace path, which is airtightly connected to a connecting pipe upstream and downstream of the heating section. Here, the inductor device can surround the workpiece, or it can be arranged above and / or below at least one workpiece.

[0005] However, a problem with this design is that the material usually used for the gas-tight insulation is at least partially made of metal, which, when the inductor device is used, also heats up in a similar manner to the at least one workpiece, which is not acceptable.

[0006] EP 2 577 201 B1 discloses an electric induction tunnel furnace having a gas-tight barrier chamber surrounding a gas-tight tunnel region, wherein a gas-tight insulating surface or a gas-tight insulating material is arranged between the tunnel region and the barrier chamber. In order to prevent an exchange of barrier gas in the barrier chamber with process gas in the tunnel region, the electric induction tunnel furnace also has a barrier gas regulator.

[0007] However, in practice, the problem arises when providing such a gas-tight insulating surface: the gas-tight material is either a metallic material, which has problems with the penetration of magnetic fields or is only possible with high energy losses, or can only be achieved with temperature-critical polymer materials. Another disadvantage is that if the pressure difference between the barrier chamber and the tunnel area is large, large forces will be exerted on the insulating surface, which can endanger the integrity of the insulating surface. In addition, a large amount of construction is necessary to achieve a gas-tight connection to the connecting pipe. Summary of the invention

[0008] Based on the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a device and a method for inductively heating at least one workpiece, which can achieve reliable and safe operation of the device or the method in a structurally simple manner.

[0009] According to a first aspect of the invention, the above-mentioned technical problem is solved in the above-mentioned device in that the insulating material is designed in such a way that there is a flow connection between the inductor area and the heating area.

[0010] By providing a flow connection between the inductor region and the heating region, a flow exchange of the medium arranged in the inductor region and the medium arranged in the heating region can be achieved. In particular, the respective media are gases or gas mixtures located in the furnace housing.

[0011] For example, it has proven to be advantageous to flush the entire furnace housing with an inert gas, such as nitrogen or a nitrogen mixture, before starting the operation of the device for inductively heating at least one workpiece and then to fill the furnace housing with the process gas used during the operation of the device, such as hydrogen or a hydrogen mixture. In this way, residual air or residual oxygen in the inductor region can be reliably avoided during the operation of the device for inductively heating at least one workpiece, thereby ensuring a reliable operation of the at least one inductor arrangement.

[0012] The flow connection between the inductor region and the heating region means in particular that the gaseous medium can flow along a pressure gradient from the inductor region to the heating region or vice versa. The insulating material is preferably designed to be essentially thermally stable, so that even at high temperatures, the properties of the insulating material do not substantially change. It is also preferred that the heating region is designed as an essentially tunnel-shaped furnace.

[0013] In a preferred embodiment of the invention, the insulating material has at least one through-opening for the flow connection of the inductor region and the heating region. By providing the through-opening in the insulating material, a flow connection can be provided between the inductor region and the heating region in a structurally advantageous manner.

[0014] The at least one through-opening preferably has a diameter of at least 1 mm and / or a width of at least 1 mm. 2 Furthermore, the at least one through-opening is preferably formed to be substantially circular.

[0015] According to a preferred design of the present invention, at least one through-opening can be at least partially closed by at least one baffle, so that the exchange of gas or gas mixture between the inductor area and the heating area can be regulated.

[0016] A preferred embodiment of the invention is characterized in that the insulating material is designed as an at least partially permeable material for the flow connection between the inductor region and the heating region. By designing the insulating material as an at least partially permeable material, an advantageous, substantially uniform flow connection can be provided over substantially the entire area of ​​the insulating material. The permeable material is preferably particularly permeable to gas, so that process gas and / or housing gas can flow along the pressure gradient from the inductor region into the heating region and vice versa.

[0017] In another preferred embodiment of the invention, the insulating material comprises a fabric, in particular a fabric made of high-temperature fibers. By providing a fabric, a permeable material can be provided for the flow-technical connection of the inductor region and the heating region. The fabric is preferably a fabric made of high-temperature fibers, since these fibers are suitable for the temperatures occurring inside the furnace housing, in particular inside the heating region. The high-temperature fibers can be, for example, silicate glass fibers.

[0018] Another preferred embodiment of the invention is characterized in that the inductor region has at least one inlet for feeding the housing gas, and the control device regulates the feeding of the housing gas into the inductor region so that a pressure gradient is generated from the housing gas in the inductor region in the direction of the process gas in the heating region. Since the pressure of the housing gas arranged in the inductor region is higher than the pressure of the process gas arranged in the heating region, it is possible to reliably prevent the process gas from penetrating into the inductor region from the heating region. In this way, hot process gas can be prevented from entering the inductor region. The inlet can also be used to fill the heating region with process gas. For example, the process gas and the housing gas can also be essentially the same gas and / or a gas mixture. For example, the temperatures of the housing gas and the process gas can each be different, the temperature of the housing gas preferably being lower than the temperature of the process gas.

[0019] The process gas is in particular a flammable gas, in particular a flammable gas mixture, in particular when mixed with oxygen. For example, the process gas can be a hydrogen and / or nitrogen mixture or pure hydrogen. Thus, by providing a pressure gradient, it is prevented that the process gas flows from the heating area into the inductor area or the furnace environment and mixes with oxygen, thereby producing a flammable gas mixture. The housing gas is preferably an inert gas, such as nitrogen or a nitrogen mixture.

[0020] The pressure gradient also enables a substantially constant flow of the housing gas in the direction of the heating region, so that the sensor region can be purged continuously. The temperature of the process gas is preferably higher than the temperature of the housing gas. For example, the composition of the process gas is identical to that of the housing gas. Alternatively, the composition of the process gas is different from that of the housing gas. The process gas is in particular a hydrogen mixture and / or a nitrogen mixture or pure hydrogen, while the housing gas is an inert gas, preferably nitrogen or a nitrogen mixture.

[0021] In a further preferred embodiment of the invention, the inductor region has at least one outlet. By providing an outlet, when the apparatus for inductively heating at least one workpiece is started up, the furnace housing including the inductor region and the heating region can first be purged with a substantially inert gas, for example housing gas, which is introduced via the at least one inlet and discharged via the at least one outlet. In this way, the furnace interior can be freed from ambient air. During operation of the apparatus for inductively heating at least one workpiece, the at least one outlet is preferably closed.

[0022] Another preferred embodiment of the invention is characterized in that the device further comprises at least one measuring device for measuring the pressure in the sensor region and / or the pressure in the heating region and / or the pressure difference between the sensor region and the heating region. By providing at least one measuring device, the regulation of the control device for feeding the housing gas into the sensor region can be improved. In particular, the heating region containing the process gas can also be purged with the housing gas, thereby reducing the temperature in the heating region and reducing the probability of ignition overall.

[0023] Furthermore, another embodiment of the invention is characterized in that the device comprises at least one flow measuring device for measuring the flow of the supplied housing gas and / or the device further comprises at least one dew point measuring device for measuring the dew point of the gas mixture arranged in the sensor region and / or the dew point of the gas mixture arranged in the process region. By providing at least one such measuring device, the regulation of the control device for feeding the housing gas into the sensor region can be improved.

[0024] In a further preferred embodiment of the invention, the control device regulates the feeding of the housing gas into the inductor region in such a way that the housing gas in the inductor region forms a pressure gradient with respect to the ambient air around the furnace housing. This also prevents hot and possibly flammable process gases from passing from the heating region through the inductor region into the furnace environment outside the furnace housing.

[0025] Another 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 the substantially elongated extension of the heating zone. By providing such a transport device, substantially uniform heating can be provided over the entire length of the workpiece. For example, the speed of the workpiece to be moved can be variably adjusted by the transport device, thereby changing the thermal treatment of the workpiece.

[0026] In another preferred embodiment, a thermal insulation device is provided between the insulating material and the heating region. In addition to the existing insulating material, the thermal insulation device can further thermally isolate the sensor region from the heating region. The thermal insulation device is preferably formed similarly to the insulating material, so that there is still a flow connection between the sensor region and the heating region via the separating surface and the thermal insulation device. The thermal insulation device can also be formed by the insulating material alone.

[0027] According to a second aspect of the invention, the above technical problem is solved in a method for inductively heating at least one workpiece, in particular by means of the above-mentioned device, the method comprising the following steps:

[0028] - guiding the workpiece to be heated along the heating zone of the furnace housing which is filled with process gas;

[0029] - heating the workpiece by means of at least one inductor device arranged in an inductor region filled with housing gas;

[0030] - establishing a flow connection between the induction region and the heating region, in particular by means of an insulating material arranged between the induction region and the heating region; and

[0031] - A housing gas is fed into the inductor region so that a pressure gradient is formed between the housing gas in the inductor region and the process gas in the heating region.

[0032] In this case, the housing gas can be fed temporarily or permanently into the inductor region, for example. The housing gas is advantageously fed into the inductor region in such a way that a gas exchange can only take place in the direction of the heating region, so that essentially no process gas can enter the inductor region from the heating region. Further advantages associated with the method are explained in conjunction with the above-described device.

[0033] In one embodiment of the invention, the amount of housing gas to be fed in is determined as a function of the pressure difference between the inductor region and the heating region and / or the amount of housing gas to be fed in is determined as a function of the housing gas flow rate between the inductor region and the heating region, in particular as a function of the housing gas volume flow rate. This allows the amount of gas or gas mixture to be fed in to be reliably controlled.

[0034] In another embodiment of the invention, the housing gas is fed into the sensor region such that the temperature, in particular the average temperature, of the housing gas in the sensor region is lower than the temperature, in particular the average temperature, of the protective gas in the heating region. This further reduces the probability of ignition of the gas that may enter the sensor region.

[0035] Another preferred embodiment of the invention is characterized in that before the workpiece to be heated is guided along the heating zone of the furnace housing, the inductor region and the heating zone are first purged with housing gas; process gas is then fed into the heating zone; and preferably further housing gas is subsequently fed into the inductor region. This procedure can in particular ensure that no critical residual air concentrations are present in the furnace environment before the plant is put into operation. In particular, any condensation that may form, preferably on the inductor arrangement, can also be avoided.

[0036] Another advantageous embodiment of the invention is characterized in that the gas mixture fed into the sensor region is obtained in such a way that the housing gas dew point in the sensor region is shifted to a lower temperature than the process gas dew point in the process region and / or the housing gas dew point in the sensor region is monitored substantially continuously and the housing gas is subsequently fed in as a function of the dew point. In this way, the fed-in gas mixture can be reliably controlled. The temperature of the gas mixture entering the sensor region is preferably lower than the temperature of the process gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] More advantageous exemplary embodiments of various aspects of the present invention can be found in the detailed description of some exemplary embodiments of the present invention below, in particular in conjunction with the accompanying drawings. However, the drawings of the present application are only for illustrative purposes and are not used to determine the scope of protection of the present invention. The drawings are not necessarily drawn to scale and are intended only to exemplarily reflect the general concept of the present invention. In particular, the features contained in the drawings should never be interpreted as constituting an essential part of the present invention.

[0038] In the figure

[0039] Figure 1 a schematic diagram showing a first embodiment of the device according to the invention; and

[0040] Figure 2 A schematic diagram of a second embodiment of the device according to the invention is shown. DETAILED DESCRIPTION

[0041] In the following description of the various embodiments of the present invention, parts and elements having the same function and the same operation mode are all denoted by the same reference numerals even though the parts and elements in the various embodiments may differ in size or shape.

[0042] Figure 1 A first embodiment of a device 2 for inductively heating at least one strip-shaped workpiece 4 is shown. The device 2 comprises a furnace housing 6 and an inductor arrangement 8 arranged inside the furnace housing 6. The inductor arrangement 8 can completely surround the strip-shaped workpiece 4.

[0043] The inductor device 8 is arranged in an inductor region 10 which is separated from a heating region 14 by an insulating material 12, in particular a thermal insulating material. In addition to the insulating material 12, a thermal insulation device 16 is provided between the insulating material 12 and the heating region 14, wherein the insulating material 12 and the thermal insulation device 16 are designed in such a way that there is a flow connection between the inductor region 10 and the heating region 14.

[0044] For this purpose, the insulating material 12 has at least one through-opening 18 for fluidic connection of the induction region 10 and the heating region 14. Furthermore, the insulating material 12 is designed as an at least partially permeable material, so that fluidic exchange between the induction region 10 and the heating region 14 can also take place away from the through-opening 18.

[0045] The inductor region 10 has an inlet 20 for supplying a gas mixture, in particular a shell gas, to the inductor region 10. In addition, a control device 22 is provided at the inlet 20 for regulating the feed amount of the shell gas into the inductor region 10 so that a pressure gradient exists from the shell gas arranged in the inductor region 10 to the process gas arranged in the heating region 14. In this way, it is possible to prevent the process gas in the heating region 14 from flowing to the outside of the inductor region 10 or the furnace shell.

[0046] 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 housing gas, during startup of the device 2.

[0047] Furthermore, the device has a measuring device 26 in the inductor region 10, a measuring device 28 in the heating region 14 and a further measuring device 30 outside the furnace housing. For example, the measuring devices 26, 28 and 30 can be used to measure the pressure present in the inductor region 10, the heating region 14 and / or the ambient air. The measuring devices 26 and 28 can also be used to measure the dew point of the gas or gas mixture present in the inductor region 10 and / or the heating region 14. The control device 22 can also have a measuring device for measuring the flow rate of the supplied housing gas.

[0048] Figure 2 A schematic side view of a second embodiment of a device 2 according to the invention is shown. Figure 1 In the embodiment of the device 2 shown, the insulating material 12 is designed as a thermal insulation and has a plurality of through-openings 18 for establishing a flow connection between the inductor region 10 and the heating region 14. At the start of the heating process, the air in the furnace housing 6 can be driven out through the inlet 20, for example with inert gas. The inductor region 10 and the heating region 14 can thus be purged. This prevents the process gas subsequently introduced into the inductor region 10 and the heating region 14 from reacting with the residual air in the furnace housing 6.

[0049] Description of Reference Numerals

[0050] 2 Equipment

[0051] 4 Workpiece

[0052] 6 Furnace shell

[0053] 8 Sensor device

[0054] 10 Sensor area

[0055] 12 Isolation materials

[0056] 14 Heating Zones

[0057] 16. Thermal insulation

[0058] 18 Through opening

[0059] 20 Entrance

[0060] 22 Control Devices

[0061] 24 Exit

[0062] 26 Measuring device for sensor area

[0063] 28 Measuring device for heating area

[0064] 30. Measuring device 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 shell (6); at least one inductor device (8) arranged in the furnace housing (6), wherein the inductor device (8) is at least partially arranged in an inductor region (10) of the furnace housing (6); at least one heating area (14) for receiving process gas, the heating area (14) being arranged in the furnace shell (6); as well as Insulating material (12) for isolating, in particular thermally isolating, the sensor region (10) and the heating region (14); It is characterized in that The insulating material (12) is formed in such a way that a flow connection exists between the inductor region (10) and the heating region (14).

2. The device according to claim 1, It is characterized in that The insulating material (12) has at least one through-opening (18) for the flow connection between the inductor region (10) and the heating region (14).

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

4. The device according to any one of claims 1 to 3, It is characterized in that - The insulating material (12) comprises a fabric, in particular a high temperature fiber fabric.

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

6. The device according to claim 5, It is characterized in that The sensor region (10) has at least one outlet (24).

7. The device according to any one of claims 5 or 6, It is characterized in that The device further comprises at least one measuring device (26, 28) for measuring the pressure in the sensor region (10) and / or the pressure in the heating region (14) and / or the pressure difference between the sensor region and the heating region.

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

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

10. The device according to any one of claims 5 to 9, It is characterized in that The control device (22) further regulates the feeding of the housing gas into the inductor region (10) such that a pressure gradient is generated from the housing gas in the inductor region (10) to the ambient air around the furnace shell (6).

11. The device according to any one of claims 1 to 10, It is characterized in that The device further comprises transport means for transporting the workpiece to be inductively heated substantially longitudinally along the substantially elongated extension of the heating zone.

12. The device according to any one of claims 1 to 11, It is characterized in that - A thermal insulation device (16) is provided between the insulating material (12) and the heating area (14).

13. Method for inductively heating at least one workpiece, in particular by means of a device according to any one of claims 1 to 12, the method comprising the following steps: - guiding the workpiece to be heated along the heating zone of the furnace housing which is filled with process gas; - heating the workpiece by means of at least one inductor device arranged in an inductor region filled with housing gas; - establishing a flow connection between the induction region and the heating region, in particular by means of an insulating material arranged between the induction region and the heating region; as well as - A housing gas is fed into the inductor region, so that a pressure gradient forms in the inductor region of the housing gas in the direction of the process gas in the heating region.

14. The method according to claim 13, It is characterized in that - the amount of housing gas to be fed in is determined as a function of the pressure difference existing between the inductor area and the heating area, and / or the amount of housing gas to be fed in is determined as a function of the housing gas flow between the inductor region and the heating region, in particular as a function of the housing gas volume flow, and / or The housing gas is fed into the inductor region such 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 protective gas in the heating region.

15. The method according to claim 13 or 14, It is characterized in that - before guiding the workpiece to be heated along the heating zone of the furnace shell, firstly the inductor area and the heating zone are purged with shell gas; - The process gas is then fed into the heating zone; Preferably, further housing gas is subsequently fed into the region of the inductor.

16. The method according to any one of claims 13 to 15, It is characterized in that - obtaining a gas mixture fed into the sensor region such that the housing gas dew point in the sensor region is shifted towards a lower temperature than the process gas dew point in the process region, and / or - The housing gas dew point in the sensor area is essentially continuously monitored and the housing gas is subsequently fed in depending on the dew point.

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