APPARATUS FOR HEATING METAL PRODUCTS

Apparatus for heating metal products, able to heat by electromagnetic induction at least one metal product positioned in a heating chamber and mobile in a direction of feed, in which said heating apparatus comprises one or more heating coils positioned in a ring around said heating chamber and said metal product to be heated; said one or more heating coils are positioned substantially transversely to the direction of feed of the metal product and are able to generate a magnetic field having a direction substantially parallel or coincident to the direction of feed of the product to be heated and directed in the same direction as said direction of feed of the product to be heated; said heating apparatus also comprises at least one heat shield positioned between said one or more heating coils and the metal product to be heated; said heat shield comprises walls provided with blocks of thermal and electric insulating material and positioned around the metal product to be heated and also comprises cooling pipes positioned in said walls and configured to allow the flow of at least one cooling fluid.

FIELD OF APPLICATION

The present invention concerns a heating apparatus for metal products used in the iron and steel field, for example, in casting plants, in rolling plants, combinations thereof or other plants in which it is necessary to heat a metal product on each occasion. The heating apparatus uses electromagnetic induction to heat metal products.

By way of non-restrictive example, the metal or semi-finished metal products in question can be slabs, billets, blooms, or suchlike with a round, square, rectangular or similar cross section.

BACKGROUND OF THE INVENTION

In the production of metal products, such as slabs, billets, blooms or other similar products, it is known that the products are heated, or kept at a predefined temperature, in order to obtain a metal product free of cracks and having the desired characteristics on each occasion.

This can be achieved by suitable induction heating apparatuses which, on the basis of the magnetic field they generate on each occasion and, in particular, by means of the electric currents induced in the metal product, allow to heat part of the section of the metal product due to the Joule effect.

Induction heating apparatuses exist, that is so-called Longitudinal Flux Heaters (LFH), in which the induction coils, or windings, surround a chamber in which the metal product to be heated is made to transit, so that the magnetic field generated is parallel to the metal product to be heated and directed in the direction of movement of the metal product to be heated along the heating apparatus.

LFH heating apparatuses are particularly suitable for heating long metal products having a round, square or rectangular cross-section.

In such heating apparatuses, normally the coils are incorporated in a structure made of refractory material, for example cement, and are cooled by means of a series of pipes in which cooling water flows.

The cement faces the chamber in which the metal product to be heated passes and very high temperatures can be reached in the chamber, even up to 1100° C., while the coils, which are normally located a few centimeters away from the surface of the chamber, being cooled, are subjected to a maximum temperature of about 100° C.

The temperature difference between the surface of the heating chamber and the zone where the cooled coils are found is therefore very high and this leads to uncontrollable thermal expansions inside the coating material of the chamber, causing harmful phenomena such as cracks, fissures or other, which propagate in the heating apparatus and become increasingly deeper as time goes by, until the heating apparatus becomes unusable.

This problem is all the more accentuated the greater the size of the heating apparatus in terms of width, for example if metal products such as slabs or suchlike are heated, or in terms of length, for example if metal products such as billets or suchlike are heated.

The incorporation of the coils in the cement also means that it is difficult to subject the coils to maintenance operations and moreover they can also suffer damage as a result of the presence of cracks or breaks in the refractory material in which they are incorporated.

Furthermore, the refractory material can also deteriorate and break as a result of mechanical vibrations, as well as the temperature difference that generates phenomena of thermal expansion as described above.

There is therefore a need to improve a heating apparatus for metal products that can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to provide a heating apparatus for metal products, in particular an apparatus of the LFH type, which is able to withstand high temperatures and phenomena of thermal expansion, thus ensuring efficient thermal protection both for the structure of the heating apparatus and also for the induction coils.

Another purpose of the present invention is to provide a heating apparatus for metal products which allows to significantly reduce the temperature of the elements located behind the heating chamber, that is, the heating coils, supports or other.

Another purpose of the present invention is to provide a heating apparatus for metal products which allows to reduce heat losses by irradiation, thus improving the overall efficiency of inductive heating, thanks in particular to its high thermal resistance.

Another purpose of the present invention is to provide a heating apparatus for metal products that is efficient, highly flexible and can adapt to different heating needs.

Another purpose of the present invention is to provide a heating apparatus for metal products in which, thanks to the use of at least one heat shield, a thermal decoupling is performed between the inside and the outside of the heating chamber, that is, between the zone where the metal product is heated and the zone where the cooled induction coils are taken.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claim, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

According to the above purposes, one purpose of the invention is a heating apparatus for metal products, able to heat by electromagnetic induction at least one metal product positioned in a heating chamber and mobile along a direction of feed; the heating apparatus comprises one or more heating coils positioned in a ring around the heating chamber and the metal product to be heated; the one or more heating coils are positioned substantially transversely to the direction of feed of the metal product and are able to generate a magnetic field having a direction substantially parallel or coincident to the direction of feed of the product to be heated and directed in the same direction as the direction of feed of the product to be heated; the heating apparatus also comprises at least one heat shield positioned between the one or more heating coils and the metal product to be heated; the heat shield comprises walls provided with blocks of thermal and electric insulating material and positioned around the metal product to be heated and also comprises cooling pipes positioned in the walls and configured to allow the flow of at least one cooling fluid.

The present heating apparatus, provided with a heat shield and able to generate a magnetic field having a direction substantially parallel or coincident to the direction of feed of the metal product to be heated and directed in the same direction as the direction of feed of the product to be heated, advantageously allows to obtain an effective thermal protection, substantially through 360°, that is, in all the zones of the apparatus which surround the metal product to be heated and therefore disposed radially with respect thereto, it allows to reduce, significantly and in every direction, the surface temperature of elements disposed behind the same, therefore for example the heating coils, it allows to reduce the heat losses through irradiation, thus improving the overall efficiency of the heating by induction thanks to the high thermal resistance of the heat shield, and furthermore it is only affected in a limited way, or not affected at all, by harmful phenomena due to thermal expansions.

According to another aspect of the invention, the blocks with which the walls are provided can be positioned reciprocally adjacent and a free space can be left between them to allow for suitable thermal expansion of the heat shield.

In some embodiments, the walls of the heat shield can comprise at least one plate made of thermal and electric insulating material on which the blocks and the cooling pipes are positioned.

In some embodiments, the heat shield can have a substantially square or rectangular cross section and can be formed by at least two walls independent of each other.

According to other aspects of the invention, the heat shield can comprise one or two pairs of opposite and parallel walls and connection elements independent of the walls and positioned in correspondence with corner zones defined between the opposite lateral walls.

According to other characteristics of the invention, between the blocks of the walls compartments can be made to house the cooling pipes or cooling coils, wherein the compartments preferably comprise at least two opposite arched lateral walls.

In some embodiments, the heating apparatus can comprise a plurality of heating coils located in sequence and aligned in the direction of feed and in the direction of the magnetic field produced.

Each of the heating coils can comprise its own connection elements, which can be coupled by means of suitable removable attachment means with a support that runs along the heating apparatus.

In some embodiments, the one or more heating coils are made by a single solid copper element.

In other embodiments, the one or more heating coils can be made by one or more layers of adjacent Litz-type conductors, that is, conductors formed by multiple conductor strands, electrically insulated one from the other, interwoven or not, and contained inside a sheath.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the various embodiments of the present invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

Before describing these embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings. The present description can provide other embodiments and can be obtained or executed in various other ways. We must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative.

With reference to the attached drawings, a heating apparatus10according to the present invention is able to heat by electromagnetic induction at least one metal product11positioned in a heating chamber12and mobile in a direction of feed X1, see for exampleFIG. 1.

In particular, the metal product11shown can be an elongated metal product such as a bloom or a billet, having a square or rectangular cross section. However, the metal product11which moves in the direction of feed X1could also be a slab, a wire rod or other.

The heating apparatus10comprises one or more heating coils13, see alsoFIG. 5, able to heat the metal product11by electromagnetic induction.

The one or more heating coils13are positioned in a ring around the heating chamber12and therefore around the metal product11to be heated.

The one or more heating coils13are positioned substantially transversely with respect to the direction of feed X1and are able to generate a magnetic field having a direction M1substantially parallel or coincident to the direction of feed X1, as shown for example inFIG. 1. The magnetic field is also directed in the same direction as the direction of feed X1.

The heating apparatus10comprises at least one heat shield14positioned between the one or more heating coils13and the metal product11to be heated.

The heat shield14comprises walls15provided with blocks16made of thermal and electric insulating material and cooling pipes17positioned in the walls15. A suitable cooling fluid will be sent in the cooling pipes17, such as water or other. In particular, the walls15are formed by the blocks16, located suitably adjacent.

The heat shield14has a high electromagnetic efficiency, is totally transparent from the electromagnetic point of view to the longitudinal magnetic flow in the direction M1, with losses of less than 0.1% of the total heating power. The heat shield allows to reduce heat losses through irradiation, thus improving the overall heating efficiency by induction, thanks to its high thermal resistance. In particular, the heat shield14ensures thermal protection in all directions of the heating chamber12and therefore of the heating apparatus10, therefore a protection through 360°. Thus the temperature from the inside to the outside of the heating chamber12is drastically reduced in every direction.

The blocks16, see also the enlargements ofFIG. 2aandFIG. 4, are located reciprocally adjacent and a certain free space S is left between them, in order to compensate for the thermal expansions that occur in the heating apparatus10. The amplitude of the free space S can naturally be chosen according to the project, based for example on the type of heating apparatus10in which the heat shield14is installed.

The heat shield14, see for exampleFIG. 2, can have a square or rectangular cross section. The heat shield14is formed by at least two walls15independent of each other.

In the embodiment shown by way of non-restrictive example, four walls15independent of each other are shown.

The heat shield14can have one or two pairs of opposite and parallel walls15and connection elements18positioned in correspondence with the corners of the heating chamber and the corners of the walls. The connection elements18will be provided with a certain inclination with respect to the walls15of the heat shield14.

The blocks16are disposed adjacent and a compartment19,19′ to house at least one cooling pipe17is made between them, see also the enlargement inFIG. 2a, or part of a cooling coil20, formed by the cooling pipes17, seeFIG. 4.

The blocks16can be for example small bricks, tiles or suchlike and can be made of refractory material.

The compartment19,19′ is delimited by lateral walls21defined between the blocks16and have an arched shape, so as to house the cooling pipes17or the cooling coil20in a more stable manner.

The walls15of the heat shield14also comprise a plate22made of electrical and thermal insulation material. The cooling pipes17and the blocks16are positioned on the plate22.

The plate22with the cooling pipes17and the blocks16disposed adjacent can also be housed in a support23, for example in the form of a profiled element or suchlike, made of thermally and electrically insulating material.

FIG. 3shows the present heating apparatus10in which one of the heating coils13has been removed in order to highlight the cooling pipes17. The cooling pipes17will be provided with suitable connectors24to connect with a hydraulic circuit to supply a cooling fluid.

FIG. 5shows a lateral view of the present heating apparatus10in which a plurality of heating coils13are provided in sequence, for example four heating coils13. The possibility of providing several heating coils13disposed in sequence gives the present heating apparatus greater modularity and possibility of adapting to specific heating needs, as well as allowing the possibility of making heating devices of a certain length.

The heating coils13are then put in sequence and aligned in the direction of feed X1and produce a magnetic field in direction M1.

Each of the heating coils13is independent of the other and therefore can easily be replaced with another heating coil13. In fact, each of the heating coils13comprises its own connection elements25, which can be coupled by means of suitable removable attachment means26, such as bolts, pins or suchlike, with a support27which runs along the heating apparatus10, for example on the upper part of the heating apparatus10.

The heating coils13can be made by a single solid copper element. The solid copper element is hollow inside and is provided with a cooling circuit. The heating coils13in a single solid copper element can be used in particular for low operating frequencies, typically less than or equal to about 1000 Hz. The solid copper element could have any cross section, for example square, rectangular, round or other.

The heating coils13could also be made by conductors of the “Litz” type, that is, conductors formed by multiple conductor strands, electrically insulated from one another, interwoven or not, and contained inside a sheath.

The heating coil13can be formed by one or more layers of conductors of the Litz type, located adjacent to each other. In this case too, the heating coils13will be provided with their own cooling circuit. Litz-type conductors allow to significantly reduce losses due to the skin effect and proximity effect, thus leading to an improvement in the overall heating efficiency of the heating apparatus10. Heating coils13with Litz-type conductors can be used in particular for medium operating frequencies, typically comprised between 1000 and 10000 Hz.

As we have seen, the present heating apparatus10, provided with a heat shield14and able to generate a magnetic field having a direction M1substantially parallel or coincident to the direction of feed X1of the metal product11to be heated and directed therein toward the direction of feed of the product to be heated, advantageously allows to obtain an effective thermal protection substantially through 360°, that is, in all the zones of the apparatus which surround the metal product11to be heated and therefore disposed radially with respect thereto, it allows to decrease, significantly and in every direction, the surface temperature of elements disposed behind it, therefore for example the heating coils13, and it allows to reduce heat losses through irradiation, thus improving the overall efficiency of the heating by induction thanks to the high thermal resistance of the heat shield14, and also it is only affected in a limited way, or not affected at all, by harmful phenomena due to thermal expansions.

Advantageously, moreover, the present heating apparatus10allows to obtain, thanks to the use of at least one heat shield14, a thermal decoupling between the inside and the outside of the heating chamber12, therefore between the heating zone of the metal product and the zone where the cooled heating coils13are positioned.

It is clear that modifications and/or additions of parts may be made to the heating apparatus as described heretofore, without departing from the field and scope of the present invention.

In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.