RU2831628C1 - Device for heating of steel products - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: device (10) for heating steel articles (200), which are blooms or workpieces, comprises heating chamber (13), which is located between inlet (11) and outlet (12), inside which inlet zone (A), intermediate zone (B) and outlet zone (C) are successively defined, wherein inlet zone (A) is made with possibility of heating to maximum temperature of 1000 °C, intermediate zone (B) to maximum temperature of 1100 °C, and outlet zone (C) to maximum temperature of 1150 °C, plane of movement (P) in said heating chamber (13), defined by alternation of fixed support elements (14) and movable support elements (15), resting respectively on fixed bearing elements (16) and movable bearing elements (17), and extraction (18, 20), equipped with corresponding feed and extraction rollers (19, 21), respectively connected to said inlet and outlet (11, 12), heating and/or combustion elements (43) located both above and below said advancement plane (P). Fixed and movable support elements (14, 15), fixed and movable bearing elements (16, 17) and feeding and extraction rollers (19, 21) are made from metal superalloys containing at least a combination of nickel and cobalt in amount of 30% to 60%, and chromium, from 24% to 35%, wherein said superalloy also contains a combination of additional components from 5% to 50%, where said additional components are selected from W, Nb, Ti, C, Si, Al and Mn, wherein fixed and movable support elements (14, 15), fixed and movable bearing elements (16, 17) and feed and extraction rollers (19, 21) are made from different metal superalloys within specified ratios and in accordance with zones (A, B, C) heating chamber (13), in which they are located, to ensure different operating temperatures, wherein content of nickel and chromium in said metal superalloys increases in direction from inlet zone (A) to outlet zone (C), and the cooling system inside heating chamber (13) of device (10) is made without using a liquid.

EFFECT: eliminating the need to use liquid cooling systems and reducing harmful emissions into the atmosphere.

13 cl, 11 dwg

Description

FIELD OF APPLICATION OF THE INVENTION

The embodiments described herein relate to a device for heating steel articles, such as metallic or non-metallic articles, such as those made of an alloy.

The invention relates in particular to semi-finished steel products, such as blanks or blooms, which are subsequently sent for rolling.

BACKGROUND OF THE INVENTION

Furnaces are known for heating steel products such as blooms or billets, used to raise the temperature of metal semi-finished products to a value suitable for rolling.

Traditional heating furnaces are equipped with water cooling systems for the structural elements subject to high loads during heating and usually have a heating chamber in which steel products are continuously or periodically moved between an inlet and an outlet, in accordance with which there are appropriate roller tracks for loading and removing products, as well as possible loading and unloading machines.

The heating chamber has a plane of advancement, which, depending on the case, can be made in different ways. In furnaces with movable longitudinal elements, better known as walking beam furnaces, the plane of advancement is determined by alternating fixed beams and movable beams located parallel to the length of the plane of advancement.

There are also furnaces without water cooling systems, in which, however, the material being processed consists of pipes, so the products are significantly lighter than blooms or blanks, and heating and heat treatment are carried out at much lower temperatures.

In such tube furnaces, given the lower heating requirements, the burners are provided only above the so-called "pass-through line", since the tubes, being light and having a hollow circular cross-section, are designed to rotate as they advance so that heating at not very high temperatures occurs uniformly over their entire surface.

On the contrary, considering that the blanks or blooms are heavier products and have a square/rectangular/polygonal/full round cross-section, they cannot be rotated during movement, so the heating and heat treatment temperatures must be much higher.

Examples of such furnaces, mainly for pipes, are described in documents GB 1473645, DE3339585 and WO 2012/052960.

In particular, document GB 1473645 describes a furnace for tempering steel tubes which has movable longitudinal members shaped to accommodate the tubes, which, as mentioned above, rotate as they advance. Burners are located on only one upper wall of the furnace.

Document DE3339585 also relates to a furnace for heating pipes, special profiles, etc., in which the burners are located on the top wall of the furnace only in the heating chamber where the pipes are located, while additional burners are provided in side chambers distinct and separated from the heating chamber.

Document WO 2012/052960 describes a conveyor with movable longitudinal elements and a furnace for heat treatment of metallurgical products, which contains said conveyor. This document does not consider or solve the problem of heating these products, but only the problem of their movement.

When processing pipes, the heating process occurs in a controlled manner, since heating serves to produce a change in the crystalline structure that determines the mechanical characteristics of the pipe itself.

On the contrary, when heating blanks and blooms, the goal is not to change the crystalline structure, but only to heat the metal products in order to bring them to a temperature suitable for subsequent processing.

In the known furnaces, metal products are placed on beams, transverse to their longitudinal development.

Fixed beams are connected to a fixed support frame, and movable beams are connected to one or more movable support frames to ensure correct feeding of products.

The support frames, in particular the beams and their supporting elements, as well as the roller track section, since they are located inside the heating chamber, are subject to strong thermal and mechanical loads due to the heating parameters required during the processing of blanks and blooms.

Typically, given the high temperatures inside the furnace, which can range from 600°C to 1250°C, and the heavy weight of the metal parts being processed, traditional bloom and billet reheat furnaces require a water cooling system to ensure that the components inside the chamber maintain adequate mechanical properties and do not deform or break.

Such deformations and destructions are especially dangerous and harmful given the high mechanical loads that the supporting elements must withstand, given the weight of blooms and blanks, which significantly exceeds, for example, the weight of pipes.

On the other hand, cooling the components increases heat removal from the inside of the chamber, which leads to the need for greater thermal energy input by the burners to achieve the required temperatures. The increase in the amount of thermal energy is directly related to higher fuel consumption, higher operating costs and increased emissions of gases such as CO ₂ , NO _{x ,} etc.

EP 2 678 458 describes an alloy particularly suitable for use in furnace construction, in particular in furnaces in which there is no real movement of the products and the heating process takes place in an intermittent manner. In such furnaces there are no mechanical loads on the structure due to the combination of the weight and movement of the products and the high temperatures. Consequently, this material is not suitable for walking beam furnaces for heating steel products such as blooms or billets that move within the furnace.

Another problem associated with water cooling of these components is that the water forms a black streak, known as "beam track", on the lower outer surface of the billets and blooms, in line with the beams being cooled. To reduce this phenomenon, traditional walking beam furnaces use devices known as "riders", which reduce the problem but do not eliminate it, which becomes very critical, especially for subsequent rolling operations.

One of the advantages of traditional walking beam furnaces is that they have a limited length due to the fact that much higher temperatures can be reached inside them, and therefore the residence time of the workpieces in the furnace is reduced. However, the high temperature causes a large amount of scale to form on the surface of the workpieces themselves. The scale formed during removal ends up in the waste, causing material losses, which in turn entails a reduction in the weight of the semi-finished products at the expense of productivity, i.e. the yield of the steel conversion or processing operation.

Therefore, there is a need to improve a device for heating steel products that would overcome at least one of the disadvantages of the prior art.

In particular, one of the objects of the present invention is to provide a heating device that does not have the disadvantages associated with the use of a liquid cooling system.

Another object of the present invention is to provide a heating device with a reduced impact on the environment, especially with respect to gas emissions into the atmosphere.

Another object of the present invention is to provide a heating device that has lower operating and maintenance costs than conventional devices.

Another object of the present invention is to provide a device that has a particularly compact vertical development to simplify construction work during initial installation.

Another object of the present invention is to obtain a heated article with a uniform temperature gradient, without cold zones or spots.

The applicant has developed, tested and implemented the present invention to overcome the disadvantages of the prior art and to achieve these and other objects and advantages.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is set out and characterized in an independent claim. The dependent claims describe other features of the present invention or variations of the basic idea of the invention.

In accordance with the above objectives, a device for heating steel products such as blooms and blanks, which goes beyond the state of the art and eliminates the disadvantages present therein, comprises:

- a heating chamber located between the input and output, within which at least one input zone, an intermediate zone and an output zone are successively defined,

- a plane of advancement defined inside the heating chamber by alternating fixed support elements and movable support elements located parallel to the development along the length of the device and supported respectively by a plurality of fixed supporting elements and movable supporting elements,

- means for feeding and extracting metal products, provided with corresponding feed and extract rollers, respectively connected to the input and output ends,

- heating and/or combustion elements, such as burners, located both above and below the plane of advance.

According to the first aspect, the fixed and movable support elements, the fixed and movable bearing elements, as well as the feed and extract rollers are made of a metallic superalloy containing at least a total percentage of nickel and cobalt in an amount from about 30% to about 60%, and chromium - from about 24% to about 35%.

Thanks to the special metal superalloy used for the production of fixed and movable support elements, fixed and movable load-bearing elements, as well as feed and extract rollers, there is no need for their liquid cooling, which is always required in traditional furnaces for heating blooms or blanks.

Thus, the device according to the present invention does not have liquid, in particular water, cooling systems inside the heating chamber.

In another preferred solution, the metallic superalloy comprises nickel in an amount of from about 40% to about 50%, chromium in an amount of from about 25% to about 35%, and cobalt in combination with one or more additional elements in an amount of no more than 10%, wherein the superalloy also comprises a combination of additional components from 5% to 50%.

According to another aspect, the fixed and movable support elements, the fixed and movable carrier elements, and the feed and extract rollers are respectively made of different metal superalloys in accordance with the zones of the heating chamber in which they are located and the resulting different operating temperatures. In this case, the different metal superalloys used have at least a nickel and chromium content that increases from the input zone to the output zone.

According to another aspect, the fixed and movable support elements, the fixed and movable carrier elements and the feed rollers, located at least in the input zone, are made of a first metallic superalloy.

The fixed and movable support elements, as well as the fixed and movable load-bearing elements located in the intermediate zone, are made of a second metallic superalloy, different from the first.

The fixed and movable support elements, the fixed and movable bearing elements and the extraction rollers located in the output zone are made of a third metallic superalloy, different from the first and second.

All three metal superalloys, the first, second and third, are characterized by a nickel and chromium content of not less than 50% and not more than 90% of their composition.

The first metallic superalloy has a total nickel and chromium content lower than the second metallic superalloy, and the second metallic superalloy has a total nickel and chromium content lower than the third metallic superalloy.

As already mentioned, this solution allows to completely abandon traditional water cooling, since the metal superalloys used allow the structural elements inside the heating chamber to withstand the temperature without the use of liquid cooling systems, while guaranteeing the necessary structural strength.

Thus, the overall efficiency of the device is increased and the corresponding emissions into the atmosphere are reduced. The quality and uniformity of heating of the products is also higher, since contact with the supporting elements does not lead to the formation of traces and residues due to the temperature difference between the mutually located surfaces.

Differentiation of materials according to the different zones of the heating chamber allows optimizing the characteristics of the components under load, finding a compromise between investment costs and the required thermal resistance. In fact, the different zones have correspondingly different operating temperatures, which, combined with the weight of the metal products, require that all supporting and moving elements have certain thermal-mechanical density characteristics.

According to another aspect, the movable bearing elements are made through the lower wall of the heating chamber and are fixed on a single support frame located under the lower wall and connected to the means of movement. Preferably, the presence of a single support frame limits the space required for its movement, which allows for a more compact device.

According to another aspect, the device comprises a side inlet and a side outlet, both of which are connected to a corresponding closing unit provided with a door and a corresponding movement mechanism, preferably of the pantograph type.

According to another aspect, the closing unit as described above comprises a plurality of inert gas supply devices associated with the inlet and outlet openings to create a gas barrier that prevents contamination of the atmosphere of the heating chamber by external air, limiting the supply of oxygen from the outside and, therefore, the formation of flocs, and also prevents the release of harmful gases from the furnace, such as, for example, CO and NO _x .

According to another aspect, the feed and extract rollers are located inside the heating chamber, are made through and are cantilevered on the corresponding front and rear end walls of the heating chamber. The feed and extract means comprise a plurality of additional inert gas supply devices, designed with the possibility of creating an aerodynamic seal for the feed and extract rollers. These precautions, by limiting the oxygen supply to the furnace, make it possible to reduce the formation of flakes and the release of harmful gases from the furnace.

According to one aspect, the device comprises, inside the chamber, in accordance with the input and output, respectively, a loading device and an unloading device for placing steel products from the feed rollers onto the advance plane and from the advance plane onto the extracting rollers.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given by way of non-limiting example with reference to the accompanying drawings, in which:

- Fig. 1 is a schematic side view of a device for heating steel products in accordance with some embodiments described herein;

- Fig.2 - section along line II-II in Fig.1;

- Fig.3 - section along line III-III in Fig.1;

- Fig. 4 - front view of the closing unit;

- Fig. 5 - side view of Fig. 4;

- Fig. 6 - schematic view of the feed or extraction means;

- Fig. 7-9 - schematic side views of an installation for the production of steel products, which contains a heating device according to Fig. 1-6;

- Fig. 10 - a variant of a device for heating steel products in accordance with some embodiments described herein;

- Fig. 11 is a section along line XI-XI in Fig. 10.

For ease of understanding, the same reference numbers have been used to identify identical common elements throughout the drawings where possible. It should be understood that elements and features of one embodiment may be included in other embodiments without further explanation.

DETAILED DESCRIPTION OF SOME IMPLEMENTATION OPTIONS

The following is a detailed discussion of possible embodiments of the present invention, one or more examples of which are shown in the accompanying drawings, by way of non-limiting example. The phraseology and terminology used herein is also intended to provide non-limiting examples.

Fig. 1 shows a device 10 for heating steel products 200, which may be casting semi-finished products, typically steel blooms or blanks.

The steel products 200 under consideration have a solid cross-section of a square, rectangular, polygonal, round shape. In addition, each steel product 200 can have a weight of about 0.5 tons to about 5 tons, preferably from about 0.5 tons to about 2.5 tons.

For the sake of simplicity in further presentation of the material, we will refer to the 200 blanks only as an example.

The device 10 is a furnace with fixed and movable rods or longitudinal elements, also known as a walking beam furnace.

The furnace 10 comprises a heating chamber 13, which is located between the inlet 11 and the outlet 12 of the furnace 10 (Fig. 1). Inside the heating chamber 13, an inlet zone or recovery zone A, an intermediate zone or preheating zone B and an outlet zone or heating and equalization zone C are successively defined, characterized by different operating temperatures.

The inlet zone A may have a maximum temperature of about 1000°C, the intermediate zone B may have a maximum temperature of about 1100°C, and the outlet zone C may have a maximum temperature of about 1150°C.

In particular, in Fig. 2-3, inside the heating chamber 13 there is a plane of advancement P, determined by the alternation of fixed support elements 14 and movable support elements 15, which are located parallel to the development along the length of the furnace 10.

The support elements 14 and 15 support the blanks 200 and at the same time ensure their step-by-step advancement between the input 11 and the output 12.

Fixed support elements 14 and movable support elements 15 rest respectively on fixed load-bearing elements 16 and movable load-bearing elements 17.

By way of example only, the fixed 14 and movable 15 support elements may consist of beams or longitudinal elements made in the shape of the letter "I", whereas the fixed 16 and movable 17 load-bearing elements may consist of round pipes.

The fixed 14 and movable 15 support elements have a corresponding support surface for the blanks 200, which is essentially flat, that is, without any shaping, with a shape that coincides with the shape of the cross-section of the blanks 200.

However, solutions cannot be excluded in which this surface may have concavities, in the case where the steel products have, for example, a circular cross-section.

The furnace 10 comprises feed means 18, connected to the inlet 11 and provided with feed rollers 19, and extraction means 20, connected to the outlet 12 and provided with extraction rollers 21, for moving each workpiece 200 respectively into and out of the heating chamber 13.

According to one aspect, the fixed and movable support elements 14, 15, the fixed and movable bearing elements 16, 17 and the feed and extract rollers 19, 21 are made of a metallic superalloy containing at least a combination of nickel and cobalt in an amount of from about 30% to about 60%, and chromium - from about 24% to about 35%.

The superalloy also contains a combination of additional chemical components or elements in amounts ranging from about 5% to about 50%.

Such a combination of additional chemical components may advantageously depend on the position in which the fixed and movable support elements 14, 15, the fixed and movable carrier elements 16, 17 and the feeding and extracting rollers 19, 21 are located inside the furnace 10. In another preferred embodiment, the metallic superalloy contains from about 40% to about 50% nickel, from about 25% to about 35% chromium and a maximum of 10% cobalt in combination with one or more additional elements. In this case, the superalloy contains a combination of additional components from 5% to 35%.

In another embodiment of the present invention, the fixed and movable support elements 14, 15, the fixed and movable bearing elements 16, 17 and the feed and extract rollers 19, 21 are made of different metallic superalloys in accordance with the zones of the device 10 in which they are located. In this case, the metallic superalloys have a content of at least nickel and chromium, which increases from the input zone A to the output zone C.

According to one embodiment, the fixed and movable support elements 14, 15, the fixed and movable bearing elements 16, 17 and the feed rollers 19 located in the input zone A are made of the first metal superalloy M1.

Fixed and movable support elements 14, 15, fixed and movable load-bearing elements 16, 17, located in the intermediate zone B, are made of the second metal superalloy M2.

Fixed and movable support elements 14, 15, fixed and movable bearing elements 16, 17 and extraction rollers 21, located in the output zone C, are made of the third metal superalloy M3.

Metallic superalloys M1, M2 and M3 contain nickel and chromium as the main components, at least 70% and up to 90% of their composition. In this case, the superalloy contains a combination of additional components in an amount of 10% to 30%.

Additional chemical components that complement the chemical composition of the superalloy may include aluminum, iron, tantalum, zirconium, vanadium, magnesium, calcium, carbon, boron, phosphorus, molybdenum, and tungsten. Other components may include, but are not limited to, titanium, silicon, niobium, manganese, and cobalt.

The first metallic superalloy M1 has a total nickel and chromium content lower than the second metallic superalloy M2, and the second metallic superalloy M2 has a total nickel and chromium content lower than the third metallic superalloy M3.

The production of components inside the heating chamber from metal superalloys M1, M2, M3 allows to significantly simplify the arrangement of the furnace 10, since in this case there is no need for a liquid cooling system to cool the components. In addition, the absence of cooling allows to maintain a more uniform temperature in the chamber, which directly affects both the quality of the heated products and the fuel consumption, as well as the emissions of gases into the atmosphere.

In addition, the absence of liquid cooling eliminates the problem of beam marks, since the zones in which the 200 blanks are located in each case have the same temperature as the latter.

Metal superalloys M1, M2, M3 are particularly resistant to loads occurring at high temperatures. This is especially necessary in the area of heating blanks 200, which are particularly heavy and, due to their structure, require high heating temperatures and/or a long residence time inside the heating chamber 13.

According to some embodiments, the first metallic superalloy M1 comprises Ni+Co in an amount of 30-40%, Cr in an amount of 24-30%, W+Nb+Ti in an amount of 1-5%, and C+Si+Mn in an amount of 1-4%. In this case, the superalloy comprises a combination of additional components from 21% to 44%.

The second metal superalloy M2 contains Ni in the amount of 40-50%, Cr in the amount of 25-35%, W+Co in the amount of maximum 10%, C in the amount of maximum 1%, Si+Al in the amount of maximum 3% and Mn in the amount of maximum 3%. In this case, the superalloy contains a combination of additional components in the amount of no more than 35%.

The third metal superalloy M3 contains Ni+Co in the amount of 45-60%, Cr in the amount of 25-35%, W in the amount of 8-16% and C+Si+Al in the amount of 1-4%. In this case, the superalloy contains a combination of additional components in the amount of no more than 21%.

Such differentiation in the composition of the superalloys makes it possible to adapt the thermal-mechanical characteristics of the materials in accordance with the temperatures present in the various zones of the heating chamber 13, taking into account the economic aspect. In fact, the solution of the present invention optimizes the compromise between the thermal resistance and the efficiency of the materials used in terms of tooling and maintenance costs, taking into account the increase in the cost of the superalloys as their thermal resistance characteristics increase. The materials thus defined also support the large weight of the blanks 200, which becomes even more significant when high temperatures are applied to the supporting components.

According to some embodiments, a feed path for blanks 200 is defined inside the chamber 13, which runs rectilinearly in the plane of advancement P between the inlet 11 and the outlet 12, according to which the blanks 200 respectively enter and exit the furnace 10.

The heating chamber 13 is limited by an upper wall 22 and an opposite lower wall 23, first and second end walls 24 and 25 and two side walls 26, 27, essentially parallel to each other.

The walls, as indicated above, can be covered with plates of refractory material 28 to limit heat loss to the outside (Fig. 1).

The plane of advancement P is horizontal and is located at an intermediate height between the upper wall 22 and the lower wall 23. The plane of advancement P is essentially parallel to the lower wall 23 and has a slightly smaller extent than the extent of the latter.

According to some embodiments, zones A, B and C may be defined by the geometry between the upper wall 22 and the lower wall 23. In particular, the upper wall 22 may have sections that are more or less distant from the lower wall 23, defining zones that have a larger or smaller cross-section for the passage of air.

The fixed supporting elements 16 are orthogonally attached to the bottom wall 23 and are aligned in the longitudinal direction in groups to support the corresponding fixed supporting element 14.

The movable supporting elements 17 are made through in the lower wall 23, aligned in the longitudinal direction in groups to support the corresponding movable support element 15 and secured to a single support frame 29 located under the lower wall 23 and connected to the moving means 30. The presence of a single support frame 29 makes it possible to limit the volume of the technical compartment under the furnace 10 and, therefore, to simplify and limit the costs of construction work required for the assembly/installation of the furnace 10.

However, it is possible that the support frame 29 may be divided into two or more independent structures.

In the lower wall 23, for each movable supporting element 17, an opening 38 is provided, having a longitudinal development, coordinated with a given step of advancement-retraction. Each opening 38 can be sealed by means of a through sealing element 39, which interacts with the inner surface and with the opposite outer surface of the lower wall 23.

The moving means 30 are designed with the possibility of a combined movement of advancing-lifting and lowering-retracting the support frame 29.

In particular, in Fig. 1-3, the moving means 30 comprise two groups or rows, each of which consists of four aligned moving units 31, located on the installation plane of the furnace 10 and located below the support frame 29, which rests on them.

Each movement unit 31 may comprise a connecting rod 32 which can be selectively driven to move the support frame 29.

The moving units 31 can be driven independently of each other or, as in the case described here, one moving unit 31 from each group can be driven and synchronously direct the movement of all the others.

Therefore, some of the moving units 31 are connected to corresponding electromechanical devices for moving the connecting rods 32, wherein the electromechanical devices are driven by a hydraulic or electric cylinder.

The furnace 10 comprises an inlet opening 33 located in correspondence with the inlet end 11, more preferably in correspondence with the side wall 26 or 27, and an outlet opening 34 located in correspondence with the outlet end 12, the outlet opening 34 is also more preferably located in correspondence with the side wall 26 or 27.

The corresponding closing units 35 are connected to the inlet opening 33 and the outlet opening 34.

Each closing unit 35 comprises a door 36 and a pantograph type mechanism 37 for moving the door 36.

The closing unit 35 may comprise a plurality of devices 42 for supplying inert gas, such as nitrogen, arranged along the perimeter of the opening 34, 35 and configured to create a gas barrier preventing the release of hot air together with gas, such as CO, to the outside of the furnace 10 and the entry of air from outside. In this way, the risk of contamination of operators and the environment is limited, and the formation of scale is reduced.

According to some embodiments, the feed rollers 19 and the extraction rollers 21 are located inside the heating chamber 13 and are located respectively through the front end wall 24 and the rear end wall 25 and cantilevered from them with corresponding axes of rotation parallel to the direction of advancement of the blanks 200 inside the furnace 10.

Rollers 19, 20 define a corresponding roller path located on both sides of the opening 33, 34 of the furnace 10.

Rollers 19, 20 are supported by rotating shafts 41, driven individually or in groups by one or more drive devices 40.

The part of each rotating shaft 41 outside the heating chamber 13 is protected by a metal box 42, which extends to the flange for connection with the wall 24, 25 of the furnace 10.

The feeding means 18 and the extraction means 20 comprise a plurality of additional devices 44 for feeding an inert gas, such as nitrogen, designed to feed the gas into the metal box 42 to create a barrier preventing the hot air from escaping outside the furnace 10 and the air from entering from outside, which could pollute the atmosphere of the heating chamber 13 and also increase the amount of scale formed on the surface of the workpieces.

The combination of specific materials selected for the internal components of the furnace and the nitrogen seals described above allows for a significant reduction in furnace 10 consumption, emissions of polluting gases such as _CO2 and _NOx , and operating costs, as well as an increase in its efficiency.

According to possible embodiments, the furnace 10 may contain inside the chamber 13, in accordance with the input 11 and output 12, respectively, a loading device and an unloading device for placing the blanks 200 from the feed rollers 19 onto the advance plane P and from the advance plane P onto the extraction rollers 21.

In particular, the loading device is designed with the possibility of removing the workpiece 200 from the internal feed rollers 19 and placing it on the first support elements 14, 15, while the unloading device is designed with the possibility of removing the workpiece 200 from the last position in the furnace 10 and placing it on the internal extraction rollers 21.

The loading and unloading devices may be connected to corresponding devices for supplying inert gas to create an aerodynamic seal in accordance with the slots made on the walls of the furnace 10 for the entry of the gripping and movable elements of such devices.

The furnace 10 comprises, inside the heating chamber 13, a plurality of heating and/or combustion elements or burners 43 distributed between different zones. The burners 43 are connected to a fuel source, for example methane, and to a fuel source, preferably containing oxygen, for example air, by means of suitable fuel supply means and fuel supply means, for example pipes.

According to some embodiments, the control and regulation of the supply of fuel and propellant inside the chamber 13 can be carried out in such a way that the propellant is in a sub-stoichiometric or stoichiometric proportion with respect to the propellant, as described in the Italian patent application No. 102020000013285 in the name of the same applicants.

The burners 43 are arranged in groups, each group containing a plurality of burners 43 aligned transversely with respect to the longitudinal development of the furnace 10.

Burners 43 are connected to the upper wall 22, to the rear end wall 25 and, if possible, to the lower wall 23.

Burners 43 are located both above and below the plane of advancement P. Such an arrangement of burners 43 allows to limit the length of furnace 10 and to obtain uniform heating of blanks 200, which, as was said earlier, do not rotate around their own axis during movement due to their weight.

However, other arrangement options are also possible.

In particular, in Fig. 1-3, the first group of burners 43 is connected to the lower wall 23 of the intermediate zone B, the second group of burners 43 is connected to the upper wall 22, again in the intermediate zone B, and two additional groups are located on the rear end wall 25, parallel to and on both sides of the plane of advancement P in the outlet zone C.

Thus, the furnace 10 according to the present invention has free side walls 26, 27, i.e. it is not equipped with burners 43.

According to some embodiments shown in Figs. 7-9, the furnace 10 is installed within the installation 100 for producing steel products.

The 100 installation can be made in different configurations depending on the requirements and the type of energy (gas, electricity) available and/or more convenient in the country of installation.

In the first configuration shown in Fig. 7, the installation 100 comprises in the following order a casting line 110, a furnace 10 and a rolling line 111. In this case, the furnace 10 receives the blanks 200 directly from the continuous casting line at a temperature of about 850°C and heats them to a temperature of about 1050°C so that they have an initial rolling temperature of about 950°C-1000°C. This makes it possible to limit the length of the furnace 10, given that the inlet temperature is already high, and to reduce the number of burners 43, which in this case are located only on the upper wall 22 of the intermediate zone B and in the outlet zone C.

This application is an alternative to the use of an induction furnace and is used when it is necessary to level the draft of a workpiece 200, for example, made of carbon steel, with a reduced thermal interval between the surface and the core. In addition, the furnace 10 allows for a buffer in case of interruption of the subsequent rolling process due to accidents or replacement of cylinders.

In the second configuration shown in Fig. 8, the installation 100 comprises a semi-finished product warehouse 112, where the blanks 200 are at an ambient temperature of about 20°C. The furnace 10, located downstream, is followed by an induction furnace 113 and a rolling line 111. In this case, the size of the furnace 10 makes it possible to bring the temperature of the blanks 200 from an inlet temperature of about 20°C to an outlet temperature of about 850-950°C. In this way, the formation of scale, which begins to form at a temperature of about 750°C, is significantly reduced, and gas consumption and, consequently, emissions are significantly reduced.

The induction furnace 113 heats the blanks 200 to an initial rolling temperature of approximately 1150-1250°C. The furnace 10 of the second configuration of the installation 100 has already been described with reference to Figs. 1-3.

In the third configuration shown in Fig. 9, the installation 100 comprises a semi-finished product warehouse 112, where the blanks 200 are at an ambient temperature of about 20°C. The size of the furnace 10 located downstream allows the blanks 200 to be brought from an inlet temperature of about 20°C to an outlet temperature of about 1050°C, so that they have an initial rolling temperature of about 950-1000°C at the inlet to the rolling line 111. The furnace 10 of the third configuration of the installation 100 is longer than the furnaces 100 of the previous solutions, and has a longer heating zone B, equipped with a large number of burners 43, both on the lower wall 23 and on the upper wall 22.

According to one embodiment shown in Fig. 10-11, the furnace 10 comprises inside the heating chamber 13 another plane of advancement P’, located downstream from the plane of advancement P in the direction of advancement of the blanks 200.

The other plane of advancement P' is of the walking beam type so that the furnace 10 is of the walking beam type in the first sector, which comprises the entry zone A, the intermediate zone B and the exit zone C, which in this case becomes the intermediate exit zone, and in the second sector, where the final exit zone D is defined, it is of the walking beam type. In the latter sector, higher heating temperatures are permitted compared to those provided for in the first sector.

Both sectors are characterized by the absence of cooling systems for the elements that make up the corresponding planes of advancement P, P’.

Similar to the plane of advancement P, another plane of advancement P’ is also determined by the alternation of additional fixed support elements 45 and additional movable support elements 46, located parallel to the development along the length of the furnace 10 (Fig. 11).

The additional fixed 45 and movable 46 support elements may consist of corresponding refractory plates, which as a whole form a substantially continuous plane.

The movable support elements 46 are secured in a known manner, essentially similar to that described earlier, to the same support frame 29, so that the movement of the workpieces 200 occurs in a uniform and coordinated manner between the first and second sectors.

In the embodiment shown in Fig. 10-11, the support frame 29 comprises a lower frame, or lifting frame, 29a, which provides lifting, and an upper frame, or translational frame, 29b, which provides translational movement of the movable support elements 15, 46.

The upper frame 29b is supported on the lower frame 29a in a sliding manner.

The lower frame 29a moves up/down thanks to the moving means 30, which comprise one or more inclined planes 47, one or more rolling bodies 48, pivotally fixed on the lower frame and sliding along the inclined plane, and one or more pistons 49, fixed on the lower frame 29a and at fixed attachment points.

The rolling elements 48 are arranged in pairs in such a way that one of them slides along an inclined plane and the other slides to support the upper frame 29b.

The upper frame 29b moves with the possibility of sliding in a horizontal direction along the lower frame 29a thanks to the moving means 30, which contain one or more additional pistons 51, fixed on the upper frame 29b and at fixed attachment points.

It should be understood that modifications and/or additions to the details of the apparatus for heating steel articles as described above may be made without departing from the scope and scope of the present invention as defined by the claims.

In the following claims, the sole purpose of the references in brackets is to facilitate reading: they should not be construed as limiting factors with respect to the scope of protection claimed in specific claims.

Claims (21)

1. A device (10) for heating steel products (200), which are blooms or blanks, comprising: - a heating chamber (13), which is located between the input (11) and the output (12), inside which the input zone (A), the intermediate zone (B) and the output zone (C) are successively defined, wherein the input zone (A) is designed with the possibility of heating to a maximum temperature of 1000°C, the intermediate zone (B) to a maximum temperature of 1100°C, and the output zone (C) to a maximum temperature of 1150°C, - the plane of advancement (P) in the said heating chamber (13), determined by the alternation of fixed support elements (14) and movable support elements (15), resting respectively on fixed supporting elements (16) and movable supporting elements (17), - feeding and extraction means (18, 20) equipped with corresponding feeding and extraction rollers (19, 21), respectively connected to the specified input and output (11, 12), - heating and/or combustion elements (43) located both above and below the specified plane of advancement (P), fixed and movable support elements (14, 15), fixed and movable bearing elements (16, 17) and feed and extract rollers (19, 21) are made of metallic superalloys containing at least a combination of nickel and cobalt in an amount of from 30 to 60%, and chromium - from 24 to 35%, wherein said superalloy also contains a combination of additional components from 5 to 50%, where said additional components are selected from W, Nb, Ti, C, Si, Al and Mn, wherein the fixed and movable support elements (14, 15), the fixed and movable bearing elements (16, 17) and the feed and extract rollers (19, 21) are made of different metallic superalloys within the specified ratios and in accordance with the zones (A, B, C) of the heating chamber (13) in which they are located, to ensure different operating temperatures, wherein the content of nickel and chromium in the specified metallic superalloys increases in the direction from the input zone (A) to the output zone (C), Moreover, the cooling system inside the heating chamber (13) of the device (10) is made without the use of liquid. 2. The device (10) according to claim 1, characterized in that said metallic superalloy contains 40-50% nickel, 25-35% chromium and 1-10% cobalt in combination with one or more additional components in an amount of 5-35%. 3. The device (10) according to claim 1 or 2, characterized in that the fixed and movable support elements (14, 15), fixed and movable bearing elements (16, 17) and feed rollers (19) located in the specified input zone (A) are made of a first metallic superalloy (M1), the fixed and movable support elements (21, 22), as well as the fixed and movable bearing elements (16, 17) located in the specified intermediate zone (B) are made of a second metallic superalloy (M2), while the fixed and movable support elements (21, 22), fixed and movable bearing elements (16, 17) and extraction rollers (21) located in the specified output zone (C) are made of a third metallic superalloy (M3), wherein the specified first metallic superalloy (M1) has a total nickel and chromium content lower than the second metallic superalloy (M2), and the second metallic superalloy (M2) has a lower nickel and chromium content than the third metallic superalloy (M3). 4. The device (10) according to item 3, characterized in that said first metallic superalloy (M1) contains Ni+Co in an amount of 30-40%, Cr in an amount of 24-30%, W+Nb+Ti in an amount of 1-5% and C+Si+Mn in an amount of 1-4%, while said superalloy also contains a combination of additional components in an amount of 21-44%. 5. The device (10) according to claim 3, characterized in that said second metallic superalloy (M2) contains Ni in an amount of 40-50%, Cr in an amount of 25-35%, W+Co in an amount of 0-10%, C in an amount of 0-1%, Si+Al in an amount of 0-3% and Mn in an amount of 0-3%, wherein said superalloy also contains a combination of additional components in an amount of 0-35%. 6. The device (10) according to item 3, characterized in that said third metallic superalloy (M3) contains Ni+Co in an amount of 45-60%, Cr in an amount of 25-35%, W in an amount of 8-16% and C+Si+Al in an amount of 1-4%, while said superalloy also contains a combination of additional components in an amount of 0-21%. 7. A device (10) according to any of the above points, characterized in that said movable supporting elements (17) are made through the bottom wall (23) of said heating chamber (13) and are secured to a single support frame (29) located under said bottom wall (23) and connected to the moving means (30). 8. The device (10) according to item 7, characterized in that said moving means (30) comprise moving units (31), each of which is provided with a connecting rod (32) designed to ensure the correct movement of said support frame (29), and electromechanical devices designed to enable direct or indirect movement of said connecting rods (32). 9. A device (10) according to any of the above claims, characterized in that it comprises a side inlet (33) and a side outlet (34), both of which are connected to a corresponding closing unit (35) provided with a door (36) and a pantograph-type mechanism (37) for moving said door (36). 10. The device (10) according to claim 9, characterized in that said closing unit (35) contains devices for supplying inert gas (42) connected to said inlet and outlet openings (34, 35) and designed with the possibility of creating a gas barrier that prevents contamination of the atmosphere of the heating chamber (13) by external air and prevents the release of harmful gases from the heating chamber (13) itself. 11. A device (10) according to any of the above points, characterized in that said feed and extract rollers (19, 21) are located inside said heating chamber (13), are made through and are cantilevered on the corresponding front and rear end walls (24, 25) of said heating chamber (13), wherein said feed and extract means (18, 20) contain additional inert gas feed devices (44), designed with the possibility of creating an aerodynamic seal for the feed and extract rollers (19, 21). 12. A device (10) according to any of the above points, characterized in that it comprises, inside said chamber (13), in accordance with said inlet (11) and outlet (12), respectively, a loading device and an unloading device for placing said steel products (200) from said feed rollers (19) onto said advance plane (P) and from said advance plane (P) onto said extraction rollers (21). 13. A device (10) according to any of the above points, characterized in that it comprises an additional plane of advancement (P') located in said heating chamber (13) downstream from said plane of advancement (P) in the direction of advancement of said products (200), defined by alternating additional fixed support elements (45) and additional movable support elements (46), consisting of corresponding refractory plates.