Heating a flat metal rolling stock

Abstract

A flat metal rolling stock (2) extends transversely to a longitudinal direction (x), from a left to a right rolling stock edge (3, 4). By means of a first inductive heating device (5), the left rolling stock edge (3) is heated more intensely than the right rolling stock edge (4), and by means of a second inductive heating device (6), the right rolling stock edge (4) is heated more intensely than the left rolling stock edge (3). During the heating of the two rolling stock edges (3, 4), characteristic variables (K1, K2) are recorded which are characteristic of the heating of the respective rolling stock edge (3, 4). The characteristic variables (K1, K2) are fed to a control device (8), which determines a control command (P1, P2) based on the ratio (k) or the difference (δK) between the two characteristic variables (K1, K2). Based on the control command (P1, P2), a lateral position of at least one of the two heating devices (5, 6) relative to the rolling stock edge (3, 4) that is heated more intensely by the particular heating device (5, 6) is adjusted. The control command (P1, P2) is determined by the control device (8) in such a way that the ratio (k) of the two characteristic variables (K1, K2) is brought closer to a setpoint ratio (k*) or the difference (δK) between the two characteristic variables (K1, K2) is brought closer to a setpoint difference (δK*). The setpoint ratio (k*) or the setpoint difference (δK*) can be re-specified to the control device (8) directly or indirectly by an operator (15) at any time.

Description

[0001] Description

[0002] Title of the invention

[0003] Heating of a flat rolled metal stock

[0004] field of technology

[0005] The present invention is based on a heating method for a flat rolled metal product which extends transversely to a longitudinal direction from a left to a right rolled product edge,

[0006] - whereby the left edge of the rolling stock is heated more strongly than the right edge of the rolling stock by means of a first inductive heating device and the right edge of the rolling stock is heated more strongly than the left edge of the rolling stock by means of a second inductive heating device,

[0007] - during the heating of the two rolling stock edges, parameters are recorded which are characteristic for the heating of the respective rolling stock edge,

[0008] - the parameters are fed to a control device, which determines a control command based on the ratio or the difference between the two parameters, on the basis of which a lateral positioning of at least one of the two heating devices is adjusted relative to the edge of the rolling stock which is heated more strongly by the respective heating device,

[0009] - wherein the control command is determined by the control device in such a way that the ratio of the two parameters is approximated to a target ratio or the difference between the two parameters is approximated to a target difference.

[0010] The present invention further relates to a heating device for a flat rolled metal product which extends transversely to a longitudinal direction from a left to a right rolled product edge,

[0011] - wherein the heating device comprises a first inductive heating device by means of which the left edge of the rolling stock can be heated more than the right edge of the rolling stock,

[0012] - wherein the heating device has a second inductive heating device by means of which the right edge of the rolling stock can be heated more than the left edge of the rolling stock.

[0013] - wherein the heating device comprises detection devices by means of which parameters can be detected during the heating of the two rolling stock edges which are characteristic of the heating of the respective rolling stock edge,

[0014] - wherein the heating device comprises a control device which is connected to the detection devices for receiving the characteristic values ​​and from which a control command can be determined on the basis of the ratio or the difference between the two characteristic values, on the basis of which a lateral positioning of at least one of the two heating devices can be adjusted relative to the edge of the rolling stock which is heated more intensively by the respective heating device,

[0015] - wherein the control device determines the control command in such a way that the ratio of the two parameters is approximated to a target ratio or the difference between the two parameters is approximated to a target difference.

[0016] State of the art

[0017] Such a heating method and the associated heating device are known from JP H11 172 325 A.

[0018] Summary of the invention

[0019] A hot metal rolling stock that is to be rolled - for example a slab - should have as uniform a temperature as possible immediately before rolling. This applies both in the longitudinal direction of the flat rolled stock and transversely to it. However, the two edges of the flat rolled stock in particular cool down more quickly than the central area of ​​the flat rolled stock, which is located between the two edges. Therefore, before the flat rolled stock is rolled, induction heating devices are often used to heat the two edges of the flat rolled stock. The heating devices induce eddy currents in the respective edge area. The resulting heating depends on both the power and the position of the respective heating device, in particular on the distance of the respective heating device from the respective edge of the rolled stock.In general, the electrical energy introduced into the flat rolling stock in the area of ​​the respective rolling stock edge decreases drastically with increasing distance of the respective heating device from the respective rolling stock edge.

[0020] As a rule, the flat rolled stock exhibits a symmetrical temperature profile before heating with the heating devices. Therefore, while the left and right edges of the rolled stock are cooler than the central area of ​​the flat rolled stock between the two edges, they are equally warm. Therefore, both edges should be heated by the same amount to achieve a symmetrical temperature profile. If the two edges have different temperatures, the temperature difference should generally be compensated.

[0021] Because the efficiency of each heating device depends on the distance from the respective rolling stock edge, it is therefore extremely important, in the case of a symmetrical temperature profile, to adjust the two heating devices symmetrically to the rolling stock, i.e., so that the first inductive heating device is the same distance from the left rolling stock edge as the second inductive heating device is from the right rolling stock edge. Although the flat rolling stock can be centered through the usual lateral guidance of the flat rolling stock, minor deviations may still occur due to environmental influences, tolerances, and other inaccuracies.

[0022] In the current technology, the heating devices are manually positioned before heating and are not readjusted during heating. Any errors in the positioning of the heating devices are therefore no longer corrected during heating. Correction can only be made later when another flat rolled product is heated.

[0023] Furthermore, the temperature profile of the rolled stock may already be asymmetrical before heating by the heating devices. In this case, the asymmetry should be compensated as much as possible.

[0024] The object of the present invention is to create possibilities by means of which the heating devices can be positioned in an automated manner, even during the heating of the flat rolling stock, in such a way that the heating of the two rolling stock edges takes place in a defined manner.

[0025] The object is achieved by a heating method having the features of claim 1. Advantageous embodiments of the heating method are the subject of dependent claims 2 to 7.

[0026] According to the invention, a heating method of the type mentioned above is designed in such a way that the target ratio or target difference of the control device can be redefined directly or indirectly by an operator at any time. This allows the operator to intervene in the heating process at any time, if necessary.

[0027] Often, the target ratio will have the value 1 or the target difference will have the value 0. In individual cases, however, a target ratio other than 1 or a target difference other than 0 can also be specified. For example, it is possible to record the temperatures of the two rolling stock edges before heating. In particular, a model, a function, a characteristic curve, or a characteristic curve family can be stored in the control device so that the control device can determine the corresponding target value (ratio or difference) from the temperatures recorded before heating.

[0028] In the case of indirect specification, for example, a conversion device can be arranged upstream of the control device, to which a temperature ratio or temperature difference is specified. In this case, the conversion device determines the target ratio or target difference based on the temperature ratio or temperature difference and specifies the target ratio or target difference to the control device. The conversion device can, for example, have an internal characteristic curve or a model. In any case, however, the conversion device carries out the conversion. In the simplest case, the temperature ratio is 1 or the temperature difference is 0. In this case, the conversion is trivial (target ratio = 1 or target difference = 0).

[0029] This ensures that both rolled stock edges are heated as desired, even during heating of the flat rolled stock—i.e., while the associated heating device is in operation. If the target ratio is 1 or the target difference is 0, both heating devices heat both rolled stock edges to the same extent. If the target ratio is a value other than 1 or the target difference is a value other than 0, both heating devices heat both rolled stock edges to different extents.

[0030] The degree to which the first or second heating device exerts a greater influence on the respective rolling stock edge can be adjusted as needed. In extreme cases, the two heating devices act exclusively on the left or right rolling stock edge, respectively. However, it is also possible for the first heating device to exert a greater influence on the first rolling stock edge but also to a certain extent on the second rolling stock edge, and conversely, for the second heating device to exert a greater influence on the second rolling stock edge but also to a certain extent on the first rolling stock edge.

[0031] The respective parameter can be the temperature itself or be characteristic of the temperature. In this case, the temperatures of the two rolling stock edges can be specifically adjusted to each other, for example, by equalizing them.

[0032] Above all, the respective parameter can be characteristic of the extent to which the respective rolling stock edge is heated. In this case, the temperature changes of the two rolling stock edges can be specifically coordinated, for example, by setting them to the same values. For example, the proportion of electrical energy introduced into the flat rolling stock by a respective heating device in the area of ​​the respective rolling stock edge during a specific period of time can be recorded – either absolutely or relatively. The setting of an electrical power level also corresponds to this.

[0033] Preferably, the lateral positioning of both heating devices is adjusted in the same direction based on the actuating command, in particular by the same amount. This configuration has proven to be particularly efficient in practice. Adjusting both heating devices in the same direction means, for example, that if the first heating device is moved a certain distance to the left, the second heating device is also moved to the left. So, for example, if the first heating device moves away from the left edge of the rolling stock, the second heating device simultaneously approaches the right edge of the rolling stock. If the displacement occurs by the same distance, the displacement is also carried out by the same amount, for example to the left.

[0034] The two heating devices can be moved as required using a common positioning device or using two separate positioning devices whose control is coordinated accordingly.

[0035] Typically, the flat rolled stock is conveyed longitudinally during heating. In this case, the detection devices used to record the parameters can be arranged offset longitudinally from the heating devices, so that sections of the flat rolled stock pass the heating devices first and only then the detection devices. This allows the parameters to be characteristic, in particular, for the temperature of the respective rolled stock edge of the respective section after heating. The associated detection devices can therefore be designed as temperature measuring devices, for example, as pyrometers.

[0036] The design of the detection devices as temperature measuring devices has the advantage that the temperatures at the left and right edges of the rolling stock can be adjusted to a predetermined ratio or a predetermined difference by heating, regardless of the values ​​the temperatures at the left and right edges of the rolling stock had before heating.

[0037] Alternatively, it is possible for the parameters to be characteristic of the temperature change of a particular section of the flat rolled stock. This configuration can be implemented regardless of whether the flat rolled stock is conveyed in the longitudinal direction during heating or not. Recording such parameters is often simpler and can be implemented with less effort.

[0038] For example, the parameters can be electrical operating variables of the heating devices occurring during operation of the respective heating device or variables derived from the electrical operating variables. The operating variables can be, in particular, the voltage drop across the respective heating device and / or the current flowing through the respective heating device. The derived variables can be, in particular, the phase shift between current and voltage and variables derived therefrom, for example, the power introduced into the rolling stock by the respective heating device, the inductance of the respective heating device, and / or the resonant frequency of an oscillating circuit formed by a capacitor and the effective inductance of the respective heating device.These values ​​are characteristic because they arise dynamically in connection with the flat rolled material and therefore allow conclusions to be drawn about the positioning of the respective heating device relative to the respective rolled material edge.

[0039] In a preferred embodiment, the two heating devices are of identical design, connected in series, and powered by a common power supply. The respective characteristic value in this case can be the voltage drop across the respective heating device. This embodiment is easy to implement and operates very robustly.

[0040] In another simple embodiment, the two heating devices are of the same design and are each powered by their own energy supply device.

[0041] The object is further achieved by a heating device having the features of claim 8. Advantageous embodiments of the heating device are the subject of dependent claims 9 to 13.

[0042] According to the invention, a heating device of the type mentioned at the outset is designed in that the control device has an input via which the target ratio or the target difference can be re-specified to the control device directly or indirectly at any time by an operator.

[0043] The resulting advantages correspond to those of the heating process.

[0044] Advantageous designs are also possible for the heating device. These advantageous designs and the resulting advantages correspond to those of the heating process.

[0045] Short description of the drawings

[0046] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in conjunction with the drawings.

[0047] FIG 1 a heating device from above,

[0048] FIG 2 shows a modification of the heating device of FIG 1 from above, FIG 3 shows a structure of a heating device,

[0049] FIG 4 a flow chart,

[0050] FIG 5 another flowchart,

[0051] FIG 6 is a block diagram of a heating device,

[0052] FIG 7 shows a first modification of the block diagram of FIG 6,

[0053] FIG 8 shows a second modification of the block diagram of FIG 6,

[0054] FIG 9 is a block diagram of another heating device and

[0055] FIG 10 is a block diagram of another heating device.

[0056] Description of the embodiments

[0057] FIG. 1 schematically shows a top view of a heating device 1. In the heating device 1, a flat rolled stock 2 made of metal (in particular steel) is to be at least partially heated. The rolled stock 2 extends in a longitudinal direction x. The rolled stock 2 will later be rolled in the longitudinal direction x. Transverse to the longitudinal direction x, the rolled stock 2 extends in a transverse direction y from a left rolled stock edge 3 to a right rolled stock edge 4.

[0058] The heating device 1 has a first heating device 5 and a second heating device 6. The flat rolled stock 2 can be heated by both heating devices 5, 6.

[0059] However, the heating of the flat rolled stock 2 by the respective heating devices 5, 6 is not uniform in the transverse direction y. In particular, the left rolled stock edge 3 is heated more strongly by the first inductive heating device 5 than the right rolled stock edge 4. With the second inductive heating device 6, the situation is reversed. Often, the respective rolled stock edge 3, 4 is even heated exclusively by the respective heating device 5, 6. In this case, the heating devices 5, 6 are designed as edge heaters. The heating devices 5, 6 are designed as inductive heating devices. This is evident from the schematic representation of coils around the heating devices 5, 6 and the indication of corresponding voltages U1, U2 and currents I1, I2 in FIG. 1.

[0060] In many cases, the rolling stock 2 is conveyed in the longitudinal direction x during heating. This is indicated in FIG. 1 by a corresponding arrow 7.

[0061] FIG. 1 shows a minimal configuration in which a single pair of heating devices 5, 6 is present. However, the heating device 1 could also have several such pairs, as shown in FIG. 2.

[0062] FIG 3 shows a schematic view of the design of the heating device 1 according to the invention. FIG 4 shows the associated mode of operation in the form of a flow chart. According to FIG 4, a control device 8 begins in a step S1 by controlling the heating devices 5, 6. The heating devices 5, 6 are thereby activated so that they heat the rolling stock 2 (or a section of the flat rolling stock 2 which extends in the longitudinal direction x over a partial area of ​​the rolling stock 2). During the heating of the two rolling stock edges 3, 4, characteristic variables K1, K2 are recorded by recording devices 9, 10. The characteristic variables K1, K2 are characteristic of the heating of the respective rolling stock edge 3, 4 by the respective heating device 5, 6. Possible specific characteristic variables K1, K2 will be explained later. The recording devices 9, 10 feed the recorded characteristic variables K1, K2 to the control device 8. The control device 8 receives the parameters K1, K2 in a step S2.In a step S3, the control device 8 then determines the ratio k = K1 / K2 of the two characteristic variables K1, K2. In a step S4, the control device 8 determines (at least) one actuating command P1, P2 based on the ratio k. According to the representation of step S4 in FIG 4, the actuating command or the two actuating commands P1, P2 are determined by the control device 8 in such a way that the ratio k is approximated to a target ratio k*. In accordance with the determined actuating command P1, P2, a lateral positioning of at least one of the two heating devices 5, 6 relative to the rolling stock edge 3, 4 which is heated more intensively by the respective heating device 5, 6 is to be adjusted. In a step S5, the control device 8 therefore outputs the determined actuating command P1, P2 to a corresponding positioning device 11, 12.

[0063] In step S6, the control device 8 checks whether the heating of the rolling stock 2 has been completed or should be terminated. If and as long as this is not the case, the control device 8 returns to step S2. Otherwise, the control device 8 proceeds to step S7. In step S7, the control device 8 terminates the control of the heating devices 5, 6. This deactivates the heating devices 5, 6, so that they no longer heat the rolling stock 2.

[0064] It is possible that, within the scope of step S5, only the positioning of either one or the other heating device 5, 6 is adjusted. As a rule, however, the positions of both heating devices 5, 6 are adjusted. On the one hand, this can be achieved by, as indicated in FIG 3, the two heating devices 5, 6 each being adjusted by a separate positioning device 11, 12 and a separate positioning command P1, P2 being determined for each of the two positioning devices 11, 12. Alternatively, the heating devices 5, 6 can also be adjusted by a common positioning device. For example, the two heating devices 5, 6 can be arranged on a single cross member and the cross member can be moved laterally so that with the lateral displacement of the cross member, both heating devices 5, 6 are automatically moved laterally as well.As a rule, the lateral positioning of both heating devices 5, 6 is adjusted based on the control command P1, P2. Preferably, the adjustment takes place in the same direction and by the same amount, as shown in FIG. 3. Thus, if—for example—the first heating device 5, as indicated by arrow 13 for the first heating device, is adjusted.

[0065] 5 is shifted by 1 cm to the left, the second heating device 6 is simultaneously shifted by 1 cm to the left, as indicated by the arrow 13 for the second heating device 6. As a result, the first heating device 5 is moved away from the left-hand edge 3 of the rolling stock and the second heating device 6 is moved closer to the right-hand edge 4 of the rolling stock. Analogous embodiments also apply to shifts by a different amount and also to shifts in the opposite direction. However, it is also possible to adjust the lateral positioning of only one of the two heating devices 5, 6 or to adjust the lateral positioning of the two heating devices 5, 6 to different amounts.

[0066] Above, the ratio k of the two parameters K1, K2 was determined and approximated to a corresponding target ratio k*. As an alternative to the ratio k of the two parameters K1, K2, a difference ÖK between the two parameters K1, K2 could also be calculated, as shown in FIG. 5, i.e., ÖK = K1-K2, and the difference ÖK could be approximated to a target difference ÖK*. Otherwise, FIG. 5 corresponds to FIG. 4.

[0067] According to the invention, the control device 8 has an input 14 as shown in FIG. 3. Via the input 14, the target ratio k* (alternatively: the target difference ÖK*) can be re-specified to the control device 8 at any time by an operator 15, directly or indirectly.

[0068] In the following, in conjunction with the other FIGS, various concrete embodiments are explained which can be realized within the scope of the present invention.

[0069] In many of these embodiments, the parameters K1, K2 are characteristic of the temperature change of a respective section of the flat rolled stock 2. This can apply in particular if the parameters K1, K2 are electrical operating parameters of the heating devices 5,

[0070] 6, which occur during operation of the respective heating device 5, 6. The electrical operating variables of the heating device 5, 6 can in particular be the voltage U1, U2, which drops across the respective heating device 5, 6, or the current I1, I2, which flows through the respective heating device 5, 6. Alternatively, the characteristic variables K1, K2 can be variables which are derived from the electrical operating variables. The derivation is generally carried out by the detection devices 9, 10. For example, according to the illustration in FIG 6, the two heating devices 5, 6 can be of identical design, connected in series and fed by a common energy supply device 16. The energy input into the rolling stock 2 by the respective heating device 5, 6 is - regardless of the specific wiring of the heating device in 5, 6 - proportional to the power and thus the product of the respective voltage U1, U2 and the respective current I1, I2.Since the currents I1, I2 are necessarily equal due to the series connection, the energy input is proportional to the voltage U1, U2. This makes it possible to use precisely this voltage U1, U2 (in the general case: the power) as the respective characteristic value K1, K2.

[0071] As long as the basic condition is maintained, that is, that the two heating devices 5, 6 are of identical design, that the two heating devices 5, 6 are connected in series, and that the two heating devices 5, 6 are fed from a common power supply device 16, the fact that the energy input is proportional to the voltage U1, U2 applies, even if the heating devices 5, 6 comprise a series connection of coils as shown in FIG. 7 or a parallel connection of coils as shown in FIG. 8. This also applies to combinations of a series connection and a parallel connection.

[0072] In the embodiment according to FIG 9, the parameters K1, K2 are also characteristic of the temperature change of a respective section of the flat rolled stock 2. Furthermore, here too, the parameters K1, K2 are electrical operating parameters of the heating devices 5, 6 that occur during operation of the respective heating device 5, 6, or parameters that are derived from the electrical operating parameters. Finally, in the embodiment according to FIG 9, the two heating devices 5, 6 are also of identical design. In contrast to the embodiments of FIGS. 6 to 8, however, the two heating devices 5, 6 in the embodiment according to FIG 9 are each fed by their own energy supply device 17, 18.

[0073] In the case of the design according to FIG 9, the parameters K1 and K2 are particularly suitable:

[0074] - The voltage of the respective power supply device 17, 18; in the embodiment according to FIG 9, this voltage is identical to the voltage U1, U2 dropping across the respective heating device 5, 6.

[0075] - The current I1, I2 flowing through the respective heating device 5, 6.

[0076] - The effective inductance of the respective heating device 5, 6; the effective inductance is determined not only by the respective heating device 5, 6, but also by its interaction with the rolling stock 2 in the area of ​​the respective rolling stock edge 3, 4. - The power introduced into the rolling stock 2, determined by the respective voltage U1, U2, the respective current I1, I2 and, if applicable, a respective phase shift between the respective voltage U1, U2 and the respective current I1, I2.

[0077] - The resonance frequency of an oscillating circuit formed by the respective heating device 5, 6 in conjunction with a respective capacitance.

[0078] To determine the resonance frequency, for example, a respective phase shift between the voltage U1, U2 dropping across the respective heating device 5, 6 and the current I1, I2 flowing through the respective heating device 5, 6 can be determined and a respective operating frequency of the respective heating device 5, 6 can be adjusted until the phase shift has a value of 0.

[0079] From the resonant frequency, in turn, one can calculate the effective inductance of the respective heating device 5, 6. From the effective inductance, the position of the respective heating device 5, 6 relative to the respective rolling stock edge 3, 4 can be determined. For a precise determination, the temperature of the respective heating device may also be required because the ohmic resistance is temperature-dependent. The temperature, in turn, can depend on the applied power. Here, too, a model, a function, a characteristic curve, or a characteristic curve family can be stored in the control device 8 to determine the position.

[0080] Finally, FIG 10 shows a further embodiment. In this embodiment, the detection devices 9, 10 are offset in the longitudinal direction x relative to the heating devices 5, 6. For the proper functioning of the heating device 1 of FIG 10, it is therefore essential that the flat rolled stock 2 is conveyed in the longitudinal direction x during heating. Conveying occurs in such a way that sections of the flat rolled stock 2 first pass the heating devices 5, 6 and only then the detection devices 9, 10. In the case of the embodiment according to FIG 10, the parameters K1, K2 can be directly characteristic of the temperature T1, T2 of the respective rolled stock edge 3, 4 of the respective section after heating.

[0081] The present invention has many advantages. In particular, it is possible to adjust the heating of the two rolled stock edges 3, 4 according to the desired specification (defined by the target ratio k* or the target difference ÖK* of the parameters K1, K2) and, if necessary, to adjust it even during ongoing operation of the heating device 1. Quality problems and instabilities during subsequent rolling can be avoided. This applies particularly to the rolling of the rolled stock 2 into an ultra-thin strip (strip thickness 1 mm and less). The operator 15 is relieved of the workload. If the heating device 1 has several pairs of heating devices 5, 6 as shown in FIG. 2, a non-parallel adjustment of the heating devices 5, 6 relative to the rolled stock edges 3, 4 can also be detected.

[0082] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0083] List of reference symbols

[0084] 1 heating device

[0085] 2 Rolled goods

[0086] 3, 4 rolled stock edges

[0087] 5, 6 Heating devices

[0088] 7, 13 arrows

[0089] 8 Control device

[0090] 9, 10 Recording device

[0091] 11 , 12 Positioning device

[0092] 14 Entrance

[0093] 15 operators

[0094] 16 to 18 energy supply facilities

[0095] 11 , I2 currents k, k* ratios K1 , K2 parameters P1 , P2 control commands

[0096] S1 to S7 steps

[0097] T1 , T2 temperatures

[0098] U1 , U2 voltages x longitudinal direction y transverse direction

[0099] ÖK, ÖK' differences

Claims

Claims 1. Heating method for a flat rolled stock (2) made of metal, which extends transversely to a longitudinal direction (x) from a left to a right rolled stock edge (3, 4), - wherein the left rolling stock edge (3) is heated more strongly than the right rolling stock edge (4) by means of a first inductive heating device (5) and the right rolling stock edge (4) is heated more strongly than the left rolling stock edge (3) by means of a second inductive heating device (6), - during the heating of the two rolling stock edges (3, 4), parameters (K1, K2) are recorded which are characteristic of the heating of the respective rolling stock edge (3, 4), - wherein the parameters (K1, K2) are fed to a control device (8) which determines a control command (P1, P2) based on the ratio (k) or the difference (ÖK) of the two parameters (K1, K2), on the basis of which control command a lateral positioning of at least one of the two heating devices (5, 6) relative to that rolling stock edge (3, 4) which is heated more strongly by the respective heating device (5, 6) is adjusted, - wherein the control command (P1, P2) is determined by the control device (8) in such a way that the ratio (k) of the two characteristic variables (K1, K2) is approximated to a target ratio (k*) or the difference (ÖK) of the two characteristic variables (K1, K2) is approximated to a target difference (ÖK*), characterized in that the target ratio (k*) or the target difference (ÖK*) of the control device (8) can be re-specified directly or indirectly at any time by an operator (15).

2. Heating method according to claim 1, characterized in that the lateral positioning of both heating devices (5, 6) is adjusted in the same direction, in particular by the same amount, on the basis of the setting command (P1, P2).

3. Heating method according to claim 1 or 2, characterized in that the flat rolling stock (2) is conveyed in the longitudinal direction (x) during heating, that detection devices (9, 10) by means of which the characteristic variables (K1, K2) are detected are arranged offset in the longitudinal direction (x) with respect to the heating devices (5, 6), so that sections of the flat rolling stock (2) first pass the heating devices (5, 6) and only then the detection devices (9, 10), and that the characteristic variables (K1, K2) are characteristic of the temperature (T1, T2) of the respective rolling stock edge (3, 4) of the respective section after heating.

4. Heating method according to claim 1 or 2, characterized in that the parameters (K1, K2) are characteristic of the temperature change of a respective section of the flat rolling stock (2).

5. Heating method according to claim 4, characterized in that the characteristic variables (K1, K2) are electrical operating variables (U1, U2, I1, I2) of the heating devices (5, 6) occurring during operation of the respective heating device (5, 6) or variables derived from the electrical operating variables (U1, U2, I1, I2).

6. Heating method according to claim 5, characterized in that the two heating devices (5, 6) are of identical design, are connected in series and are fed by a common energy supply device (16) and that the respective characteristic value (K1, K2) is the voltage (U1, U2) which drops across the respective heating device (5, 6).

7. Heating method according to claim 5, characterized in that the two heating devices (5, 6) are of identical design and are each fed by a separate energy supply device (17, 18).

8. Heating device for a flat rolled stock (2) made of metal, which extends transversely to a longitudinal direction (x) from a left to a right rolled stock edge (3, 4), - wherein the heating device comprises a first inductive heating device (5) by means of which the left rolling stock edge (3) can be heated more strongly than the right rolling stock edge (4), - wherein the heating device comprises a second inductive heating device (6) by means of which the right rolling stock edge (4) can be heated more strongly than the left rolling stock edge (3), - wherein the heating device comprises detection devices (9, 10) by means of which parameters (K1, K2) can be detected during the heating of the two rolling stock edges (3, 4), which parameters are characteristic of the heating of the respective rolling stock edge (3, 4), - wherein the heating device comprises a control device (8) which is connected to the detection devices (9, 10) for receiving the characteristic variables (K1, K2) and from which a control command (P1, P2) can be determined on the basis of the ratio (k) or the difference (ÖK) of the two characteristic variables (K1, K2), on the basis of which a lateral positioning of at least one of the two heating devices (5, 6) relative to the rolling stock edge (3, 4) which is heated more strongly by the respective heating device (5, 6) can be tracked, - wherein the control device (8) determines the actuating command (P1, P2) in such a way that the ratio (k) of the two characteristic variables (K1, K2) is approximated to a target ratio (k*) or the difference (ÖK) of the two characteristic variables (K1, K2) is approximated to a target difference (ÖK*), characterized in that the control device (8) has an input (14) via which the target ratio (k*) or the target difference (ÖK*) can be newly specified to the control device (8) by an operator (15) directly or indirectly at any time.

9. Heating device according to claim 7 or 8, characterized in that the two heating devices (5, 6) are adjusted by the control device (8) in the same direction on the basis of the actuating command (P1, P2), in particular by the same amount.

10. Heating device according to claim 7, 8 or 9, characterized in that the flat rolling stock (2) is conveyed in the longitudinal direction (x) during heating, that the detection devices (9, 10) are arranged offset in the longitudinal direction (x) with respect to the heating devices (5, 6) so that sections of the flat rolling stock (2) first pass the heating devices (5, 6) and only then the detection devices (9, 10), and that the parameters (K1, K2) are characteristic of the temperature (T1, T2) of the respective rolling stock edge (3, 4) of the respective section after heating.

11. Heating device according to claim 7, 8 or 9, characterized in that the detection devices (9, 10) detect as characteristic variables (K1, K2) electrical operating variables (U1, U2, I1, I2) of the heating devices (5, 6) occurring during operation of the respective heating device (5, 6) or derive the characteristic variables (K1, K2) from detected electrical operating variables (U1, U2, I1, I2).

12. Heating device according to claim 11, characterized in that the two heating devices (5, 6) are of identical design, are connected in series and are fed by a common energy supply device (16) and that the respective characteristic value (K1, K2) is the voltage (U1, U2) which drops across the respective heating device (5, 6).

13. Heating device according to claim 11, characterized that the two heating devices (5, 6) are of identical design and are each fed by a separate energy supply device (17, 18).

Images