Method and installation for inductively heating flat objects

Abstract

A method and an installation for inductively heating flat objects that are transported in a feed direction. The installation has at least one transverse field inductor device which extends transversely to the feed direction over the width of the flat object and has a longitudinal axis running parallel to the transverse axis of the flat object. The transverse field inductor device is positioned such that the longitudinal axis extends in a vertical plane obliquely with respect to the transverse axis of the flat object. With the method it is possible to vary the distance between the flat object and the inductor device and thus the temperature distribution over the transverse profile of the flat object so that the flat object is heated homogeneously.

Claims

1. A method for inductively heating a flat object transported in a feed direction (V) with a transverse field inductor device, which extends transversely with respect to the feed direction (V) over the width of the flat object and has a longitudinal axis running parallel to a transverse axis (Q) of the flat object, and another transverse field inductor device, which extends transversely with respect to the feed direction (V) over the width of the flat object and has a longitudinal axis running parallel to the transverse axis (Q) of the flat object, wherein the transverse field inductor device comprises at least two conductors, which are not rotatable about longitudinal axes thereof and run in the transverse axis (Q) of the flat object and through which an alternating current flows in series, the transverse field inductor device and the another transverse field inductor device being arranged on opposite sides of the flat object; the method comprising: transporting the flat object in the feed direction; positioning the transverse field inductor device relative to the flat object and relative to the another transverse field inductor device so that a longitudinal axis (L) of the transverse field inductor device is oriented obliquely to the transverse axis (Q) of the flat object in a vertical plane; and inductively heating the flat object with the transverse field inductor device while the transverse field inductor device is oriented obliquely to the transverse axis (Q) of the flat object in the vertical plane.

2. The method as claimed in claim 1, wherein a temperature of the flat object is measured upstream and/or downstream of the transverse field inductor device in the feed direction (V), and oblique setting of the transverse field inductor device is carried out in accordance therewith.

3. The method as claimed in claim 2, wherein a temperature profile is measured over the width of the flat object.

4. The method as claimed in claim 2, wherein the power applied to the transverse field inductor device is determined in accordance with the measured temperature or the measured temperature profile and is set by an alternating current source.

5. The method as claimed in claim 1, wherein the oblique setting of the transverse field inductor device is carried out hydraulically, pneumatically or electromechanically.

6. The method as claimed in claim 1, wherein the at least one transverse field inductor device is shifted transversely with respect to the feed direction (V).

7. The method as claimed in claim 6, wherein the transverse field inductor device is shifted transversely with respect to the feed direction (V) relative to the another transverse field inductor device.

8. The method as claimed in claim 6, wherein the transverse field inductor device is shifted transversely with respect to the feed direction (V) in accordance with the temperature measurement of the flat object upstream and/or downstream of the transverse field inductor device.

9. The method as claimed in claim 2, wherein oblique setting and transverse positioning of the transverse field inductor device are carried out in accordance with the temperature measurement of the flat object upstream and/or downstream of the transverse field inductor device in the feed direction (V).

10. The method as claimed in claim 1, wherein the flat object is hot rolled after the inductive heating and a flatness and/or a profile of the hot-rolled flat object are/is measured, and wherein oblique setting and/or transverse positioning of a transverse field inductor device are/is carried out in accordance with the measured flatness and/or profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described properties, features and advantages of this invention and the manner in which these are achieved will become more clearly and distinctly comprehensible in conjunction with the following description of an exemplary embodiment, which is explained in greater detail in conjunction with the drawings. In the drawings:

(2) FIG. 1 shows a diagram depicting the induced current density as a function of the distance between the transverse field inductor device and the material of the flat object;

(3) FIG. 2 shows a schematic cross section through a first embodiment of an installation for inductively heating flat objects;

(4) FIG. 3 shows a schematic cross section through a second embodiment of an installation for inductively heating flat objects;

(5) FIG. 4 shows a schematic cross section through a third embodiment of an installation for inductively heating flat objects;

(6) FIG. 5 shows a plan view of an installation for inductively heating flat objects in a hot-rolling mill; and

(7) FIG. 6 shows a diagram of an installation for inductively heating flat objects in a hot-rolling mill.

DESCRIPTION OF THE EMBODIMENTS

(8) FIG. 1 shows a diagram depicting the induced current density as a function of the distance between the coil of a transverse field inductor device and the flat object. In this case, the normalized current density is indicated on the ordinate, while the normalized distance is shown on the abscissa. It can clearly be seen that the current density decreases with increasing distance.

(9) The installation shown schematically in FIG. 2 for inductively heating flat objects which can be transported in a feed direction has an upper transverse field inductor device 2 and a lower transverse field inductor device 3, which are illustrated here only schematically in each case as bars. The two devices 2, 3 have induction coils, which are supplied with alternating current via electric cables 9, 10 in order to generate corresponding eddy currents that cause heating of the flat object 1 arranged between the two transverse field inductor devices 2, 3. Here, the flat object 1 is a steel strip to be heated, which passes through the installation in a direction perpendicular to the plane of the drawing.

(10) The two transverse field inductor devices 2, 3 are wider than the flat object 1 and are each mounted on a frame 5 of the installation so as to be vertically adjustable by means of two positioning devices 4 designed as hydraulic cylinders or electric linear drives. The installation can be moved in the transverse direction, i.e. perpendicularly to the longitudinal axis of the flat object 1, by means of rollers 6 on a base 8 provided with rails. A corresponding drive device is illustrated at 7.

(11) The installation is provided with a positioning device for the two transverse field inductor devices 2, 3, which comprises the positioning devices 4 illustrated. Each inductor device 2, 3 is therefore provided with two positioning devices 4, which bring about raising or lowering of the inductor devices 2, 3 in their transverse end regions. In the embodiment illustrated in FIG. 1, the lower inductor device 3 extends parallel to the flat object 1 and at a distance therefrom, while the upper inductor device 2 is arranged obliquely thereto. The oblique setting of inductor device 2 is achieved by actuating the positioning device 4 illustrated on the left in FIG. 1, which has raised inductor device 2 somewhat in this region, with the result that its distance from the flat object 1 increases.

(12) This oblique setting or raising of inductor device 2 has the purpose of increasing the distance of the inductor device 2 from the flat object 1 and thereby varying the heating of the latter in this region compared to the heating in the other transverse end region. As a result of the greater distance, therefore, the flat object is heated less in this end region than in the opposite end region, thus making it possible, for example, to achieve a greater uniformity of the temperature profile in the transverse direction of the flat object 1.

(13) In particular, the installation functions in such a way that a measuring device (not shown here) is arranged upstream of the passage through the installation, said device measuring a temperature profile in the transverse direction of the flat object 1. The corresponding signal from the measuring device is fed to a control device (not shown), which uses this to determine a temperature and position model and controls, on the one hand, the alternating current source for the two inductor devices 2, 3 and, on the other hand, the two positioning devices 4 of the upper inductor device 2. The two inductor devices 2, 3 and the positioning devices 4 are therefore controlled in such a way that a homogeneous temperature distribution results over the transverse profile of the flat object 1.

(14) FIG. 3 shows an embodiment of an installation in which, in addition to the oblique setting of the inductor devices 2, 3, shifting of the installation in the transverse direction relative to the flat object 1 is possible. The two positions of the inductor devices 2, 3, which are shifted to the right, are illustrated in dotted lines in the figure. For this purpose, the housing of the installation is shifted to the right in the figure by means of rollers 6 arranged on the underside of the associated frame 5, the shifted position being illustrated by dashed lines. After the shift, the flat object 1 is therefore no longer situated centrally with respect to the two inductor devices 2, 3 but is shifted to the left relative to these.

(15) Moreover, the installation is provided with a device for the oblique setting of the two inductor devices 2, 3. In this case, both the upper and the lower inductor device 2, 3 have been moved somewhat upward and downward by means of the positioning devices 4 illustrated on the left-hand side of the figure, resulting in a corresponding oblique setting. In the left-hand transverse end region of the flat object 1, therefore, the distance from the respective inductor device 2, 3 is greater than in the right-hand transverse end region thereof.

(16) In this embodiment too, a measuring device (not shown) is provided upstream of the passage through the installation, said measuring device measuring a transverse temperature profile of the flat object 1 and transmitting a corresponding signal to an associated control device (likewise not shown). This control device then controls both the alternating current source for the application of energy to the two inductor devices 2, 3 and the positioning device for the oblique setting of the inductor devices 2, 3 and the device for shifting them transversely. The position and temperature model generated by the control device is therefore implemented by actuating the three above-mentioned devices, resulting in a substantially homogeneous transverse temperature profile for the flat object 1 at the outlet of the installation.

(17) FIG. 4 illustrates an installation for inductively heating flat objects 1. In contrast to FIG. 4, the upper and lower transverse field inductor devices 2, 3 can be moved independently of one another in the transverse direction of the flat object by means of drive devices 7. The temperature profile can thereby be set independently from the upper and lower sides of the flat object 1. In addition, it is possible to shift the entire frame 5 by means of a further drive device 7. This can be advantageous in order to be able to move the induction modules quickly away from the flat object 1 in the event of a cobble. As illustrated, the upper and lower transverse field inductor devices 2, 3 can be both set obliquely separately with respect to the transverse axis of the flat object 1 and shifted separately in the transverse direction. It is, of course, possible to provide only the transverse shifting of a transverse field inductor device. In this case too, a relative shift of the transverse field inductor devices can be achieved.

(18) FIG. 5 shows schematically a plan view of an installation for inductive heating with a single induction module having an upper and lower transverse field inductor device 2, 3, only the upper transverse field inductor device 2 being visible. Each inductor device 2, 3 has eight conductors 30, which are aligned in the transverse direction Q of the flat object 1 and, for example, forms four windings. Of course, it is possible to provide more than four, e.g. 20, windings. The inductor devices 2, 3 can be positioned obliquely to the transverse axis of the flat object by means of two positioning devices 4 each. Oblique setting is carried out by an open-loop or closed-loop control device 23, which calculates the oblique setting in accordance with a temperature profile of the flat object 1 (see the temperature measuring device 22 upstream or downstream of the induction module), a setpoint value for the profile and/or flatness 41 and the actual value for the profile and/or flatness of the hot-rolled flat object (see the measuring unit 40). The open-loop or closed-loop device 23 is connected to the positioning devices 4 for oblique setting, the drive device 7 for the transverse shifting of the frame 5 and the alternating current source 24. By means of the alternating current source 24, it is possible to set the current intensity and optionally also the frequency of the alternating current flowing through the conductors 30. After the flat object has been heated, the flat object is descaled by the descaling device 21 and then hot rolled in succession by a plurality of hot-rolling stands 20.

(19) Finally, FIG. 6 shows schematically a front view of an installation for inductive heating with five induction modules 2, 3, a temperature measuring device 22 for measuring a temperature profile, a descaling device 21, three hot-rolling stands 20 and a measuring unit 40 for profile and/or flatness. In this case, an open-loop or closed-loop control device 23 sets the oblique setting and, if appropriate, also a transverse shift of the transverse field inductor devices 2, 3 in accordance with the measured profile and/or flatness and with the temperature profile. The hot-rolling stands 20 can be an intermediate or finishing train in a combined casting/rolling installation in which a hot-rolled finished strip is produced from molten steel, preferably in continuous operation.

(20) Although the invention has been illustrated and described more specifically in detail by means of the preferred exemplary embodiments, the invention is not restricted by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without exceeding the scope of protection of the invention.

LIST OF REFERENCE SIGNS

(21) 1 flat object 2 upper transverse field inductor device 3 lower transverse field inductor device 4 positioning device 5 frame 6 roller 7 drive device 8 base 9, 10 electric cable 20 hot-rolling stand 21 descaling device 22 temperature measuring device 23 open-loop or closed-loop control device 24 alternating current source 30 conductor 40 measuring unit for profile and flatness 41 setpoint value for profile and flatness L longitudinal axis of the transverse field inductor device Q transverse axis of the flat object V feed direction of the flat object