EP0274335A2 - Induction for the inductive reheating of metallurgical products - Google Patents

Abstract

The inductor, used for the inductive reheating of metallurgical products, is of the inductor type with a C-shaped magnetic yoke intended to overlap the product to be reheated and whose free ends form magnetic coiled poles facing each other. The cylinder head has two pole branches 24, 25 and two intermediate links 26, 27, hinged together by one of their ends and each hinged respectively to a pole leg by its other end, the three joints 3 thus formed being of parallel axes. This inductor is intended for reheating products which may have different thicknesses, in particular of products in movement during their rolling.

Description

The present invention relates to an inductor for the inductive heating of metallurgical products. In particular, but not exclusively, the invention applies to the reheating of the edges of the blanks of the flat products in movement during their rolling on a strip train.

Different types of inductors have been developed for these applications, and, in particular, inductors with magnetic yokes in the shape of a "C" are known, in the opening of which passes the product to be heated (edges of strips or wires and bars), the free ends of the cylinder head facing each other and advantageously serving as a support for the windings of the excitation electric current conductor, so as to form wound magnetic poles of opposite polarities: FR-A-2 489 645 - (EDF); FR-A-2 555 353 - (CEM) or EP-A-0 170 556 - (EDF).

Another inductor of this type is also described in document FR-A-2583 249.

In this document is described a C inductor articulated around an axis so as to allow the separation of the two ends of the C, to facilitate the positioning of the inductor on the edge of the flat product, and above all to prevent the ends of the laminated strip, which commonly have a large curvature (ski), do not strike either of the poles of the inductor. For this purpose, one of the branches of the inductor is controlled to tilt backwards by pivoting around the articulation axis, which increases the air gap and frees a larger passage section for the product.

One of the important characteristics of this inductor resides in the particular design of the articulation intended to ensure the best possible transmission of the magnetic flux by limiting the heating of the cylinder head at the level of the articulation.

This inductor already has appreciable advantages, but it does not allow correct heating of products of dimensions, and in particular of various thicknesses. Indeed, the inventors have discovered that, if we tried to re heating, by means of articulated C inductors, products of thickness different from that for which these inductors were initially designed, by varying the spacing of the branches of C, the results were not satisfactory and the heating efficiency was going down.

The purpose of the present invention is to solve this type of drawback, by proposing an inductor whose air gap can be adapted to a wide range of products of different thickness, thus making it possible to obtain maximum heating efficiency while ensuring homogeneous heating.

To this end, the subject of the invention is an inductor for the localized heating of metallurgical products such as strips, wires or bars, in particular for the heating of the edges of blanks of flat products in movement during their rolling, of the type to C-shaped magnetic yoke, comprising two polar branches hinged relative to each other to allow the air gap to be modified, the free ends of each branch carrying excitation windings and forming magnetic poles of opposite polarities and facing each other, inductor characterized in that, in order to be able to maintain a determined relative orientation of the poles, in particular their coaxiality, for different air gaps, the cylinder head further comprises two intermediate links connected to each other at one of their ends by a articulation and articulated each respectively on one or the other of said polar branches of the breech by their other end, the three articula tions thus formed having parallel axes of rotation.

Thanks to the inductor according to the invention, it is possible to ensure maximum heating efficiency and symmetry of the heating profile. Indeed, the efficiency tends to decrease if the air gap or the air gaps of the magnetic circuit constituted by the cylinder head and the products to be heated, increase.

The inventors discovered that, when a C-type inductor, with only one joint, was used, the air gaps could not be kept at their minimum value. better yield than in the case where the pole faces were parallel to the surfaces of the heated product, and therefore generally parallel to each other. It follows that, when the inductor has only one articulation, there is only one thickness of product which ensures maximum efficiency of the device. For other product thicknesses, the pole faces will be inclined relative to the corresponding surfaces of the product, which implies an increase in the air gaps.

Furthermore, the inventors have also discovered that in the case of reheating bars (of circular section for example), if the polar faces of the inductor are not parallel, the temperature profile inside the product is asymmetrical, that is to say that the temperature is higher in the part of the product located where the faces are closest.

Thanks to the three joints of the inductor according to the invention, it is easy to position and maintain the polar faces parallel to one another, even if the thickness of the products varies.

As a corollary, one can also adjust the position and the orientation of each pole according to products of particular section, or according to a determined heating profile (reheating of edges of flat products or bars of polygonal section, for example , or modifications of a preexisting temperature profile).

We see that the primary advantage offered by the invention is the flexibility of use of the inductor articulated in three points, which, thanks to the variable geometry of its cylinder head, makes it possible to solve practically all the problems of reheating of flat products. or long products of regular shape section, of course remaining within the limits determined by the dimensions of the different parts of the inductor. It will be noted in this regard that, by replacing the rods with longer rods, it is possible to increase the range of thicknesses of the products which can be reheated, without that it is necessary to replace the pole branches of the "C" and the windings which they carry at their free ends.

Other characteristics and advantages will appear on reading the following description of a particular embodiment of the inductor according to the invention.

• - la figure 1 est une vue schématique de l'inducteur à trois articulations ;
• - la figure 2 est une vue en coupe montrant un mode préféré de réalisation d'une articulation (ici, articulation entre les deux biellettes) ;
• - la figure 3 représente schématiquement différentes configurations et utilisations de l'inducteur selon la forme et la taille des produits à traiter.

Reference is made to the accompanying drawings in which:

• - Figure 1 is a schematic view of the inductor with three joints;
• - Figure 2 is a sectional view showing a preferred embodiment of a joint (here, joint between the two links);
• - Figure 3 shows schematically different configurations and uses of the inductor according to the shape and size of the products to be treated.

In Figure 1 is shown an inductor 2 in the reheating position of the edge of a steel plate 1 before rolling. The plate 1 is inserted between the two poles 21 and 22 of opposite signs of the inductor 2. The yoke 23 consists of an upper pole branch 24, a lower pole branch 25 and two intermediate links 26 and 27. The rods are connected to each other by one end by means of an articulation 3. A similar articulation 3 ′, 3 "connects the other end of each rod respectively to one or the other of the pole branches 24, 25, with the end of these opposite the poles.

The polar branches, like the links, consist of a laminated sheet of ferromagnetic sheets 26a, 27a, as can be seen in FIG. 2. Therefore, the branches and links generally have a section of rectangular shape, but d other sections could be envisaged (for example substantially circular section, in particular at the level of the poles 21, 22 of the inductor).

The magnetic poles 21, 22 of the inductor are formed by the free ends of the two branches 24, 25 directed towards one another, the end faces of the poles or polar faces 4, 5 being opposite one the other.

The conductive windings 31, 32, supplied with electric current from an alternative voltage source not shown, are provided directly on the poles 21 and 22, to avoid losses of magnetic flux and ensure maximum efficiency.

As has already been specified, an important advantage of the inductor articulated in three points according to the invention, is to make it possible to minimize the space between pole and product by keeping the pole faces parallel to the surfaces of the product.

In the case of a product having a beveled section, it is possible to envisage making the polar ends also in a bevel, of corresponding slope, in order to preserve the coaxiality of the conductive windings wound on the poles. It is easily understood that, in this case, the windings are more distant from the product because of their obliquity with respect to the surface of said product.

This distance being unfavorable to the transmission of the flux, and therefore to the heating efficiency, it is preferable to produce the end surfaces of the poles, or pole faces 4, 5, perpendicular to the axis of the windings and therefore of the poles. This is all the more justified since the treated products generally have a simple geometry section and, in particular, have parallel faces, which leads to having polar faces parallel to each other, at the same time as a coaxiality of the poles.

Figure 2 is a view of the joint 3 of the two links 26 and 27 therebetween, the other two joints 3 'and 3 "being produced in a similar manner.

The two rods pivot on one another along an axis of rotation 8. The laminates 26a and 27a, the sheets of which are placed in planes perpendicular to the axis 8 of the joint 3, are clamped between attached flanges 26b and 27b which maintain the joint. To this end, two half-shafts - or pivots - 8a, 8b, which do not cross the laminates, but which are aligned on the axis 8 on either side of said laminates, are hooped in the flanges 26b forming a chappe. The half-shafts 8a, 8b carry bearings 9 whose outer cage is hooped in the flanges 27b. When the assembly is carried out, the flanges 26b come astride the flanges 27b at the joint, so that only a small functional clearance 10 remains between the laminates facing each other, causing a flow of magnetic leaks as small as possible. .

FIG. 3 schematically represents several possible configurations and uses with the same inductor according to the invention.

In a) the inductor is used for reheating the edges of a thick flat product. In b), it is used in the same way on a thinner product. We see that in both cases the pole faces 4, 5 remain parallel to the surfaces of the product 1, and also parallel to each other. The axes of the articulations of the upper 24 and lower 25 pole branches move towards one another in a translatory movement on a trajectory parallel to the common axis of the poles; the links 26, 27 form scissors which close when the branches come together.

Diagrams c) and d) represent the same configuration as a) and b), but applied to bars of circular section.

Diagram e) represents a particular arrangement specifically adapted to the reheating of an edge 1a of a flat product 1. From this diagram clearly emerges the flexibility of use of the device and its adaptability to very diverse uses. It is observed, in fact, that the lower pole branch 25 is maintained in a position such that the lower pole face 5 is parallel to the large face of the product, while the upper pole branch 24 is angularly offset towards the small face of the product, so that the upper pole is directly and only opposite the upper edge 1a of the edge of the product.

Diagram f) represents yet another configuration which the inductor articulated at three points can take, here adapted to the reheating of the upper and lower edges of the product.

Other configurations are of course possible. The only limits for using a C inductor according to the invention are linked to space constraints. Indeed, even if, from a magnetic point of view, nothing prevents the design of polar branches and long rods, without significant loss of flow thanks to the particular design of the joints, it will be easily understood that long rods are not justified if the treated products are generally thin or of small section.

It is also possible to envisage an automatic positioning of the poles of the inductor as a function of the section of the product to be reheated, in particular of its thickness, or even as a function of the heating profile detected upstream or downstream of the reheating installation using inductors of this type.

The displacement of the poles can be controlled continuously by mechanical, electrical actuation means or jacks, for example means such as those described in the document FR-A-2583249 already cited. Likewise, the position of the inductor assembly relative to the rolling line can be adapted to the width of the product.

In the drawing of Figure 1, there is shown schematically a relative positioning control system of the poles. The two ends of a jack 13 are respectively articulated on the two links 26, 27. Another jack 13 'is articulated on the one hand on a rigid support 11 linked to the lower branch 25, and on the other hand on a guide 12, the slide of which is fixed to the upper branch 24.

The two jacks are connected to an actuator 14 slaved to a control unit 15 to which various sensors are connected, such as a position sensor (connection shown schematically by line 16 on line 1). Other sensors can also intervene for example to take the temperature into account.

It is important to note that the different pole position adjustments can be made continuously, without manual intervention, and even, thanks to the articulation system previously described, during operation, without interrupting the supply of the pole coils, or appreciably modifying the characteristics of the magnetic circuit.

According to a particular embodiment of the inductor, there may also be provided means for guiding the pole branches, lower or upper, so that the wound poles are kept coaxial whatever the degree of opening of the inductor.

Claims (3)

1) Inductor for localized reheating of metallurgical products such as strips, wires or bars, in particular for reheating the edges of blanks of flat products in movement during their rolling, inductor of the magnetic yoke type in the shape of a "C" , comprising two pole branches (24, 25) articulated relative to each other to allow the air gap to be modified, the free ends of the C constituting wound magnetic poles (21, 22) of opposite polarities and facing each other , inductor characterized in that, in order to be able to maintain a determined relative orientation of the poles (21, 22), in particular their coaxiality, for different air gaps, the magnetic yoke (23) is further formed by two links (26, 27) connected together, at one of their ends, by a joint (3) and articulated each respectively by their other end on one or the other of said pole branches (24, 25), the three joints (3, 3 ', 3 ") so for mées being axes of rotation parallel to each other. 2) Inductor according to claim 1, characterized in that the pole branches (24, 25) and the rods (26, 27) of the magnetic yoke are each formed by a laminate (26a, 27a) of ferromagnetic sheets carrying two lateral flanges (26b, 27b) in which are housed two pivots (8a, 8b) on either side of the laminates and coaxial with each axis (8) of the joints (3), and in that a functional play (10) of form semi-cylindrical is provided at each joint (3) between the laminates (26a, 27a) opposite. 3) Inductor according to claim 1, characterized in that the pole faces (4, 5) are perpendicular to the axes of the poles (21, 22).

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