RU2804206C1 - Device for heating steel products - Google Patents

Abstract

FIELD: heat treatment.

SUBSTANCE: apparatus (10) for heating steel products (100) contains a direct-heating radiation furnace containing a path for supplying steel products (100), which extends between input end (110) and output end (111) for steel products (100), the inlet in accordance with the said input end (110) to ensure entry of the said steel products (100) into the said furnace (11) and outlet (150) in accordance with the said output end (111) to ensure output of the said steel products (110) from the said furnace (11), means for supplying fuel, means for supplying combustibles, including oxygen, and burners (40, 41) capable of controlling combustion of fuel and combustibles. At the same time, the said means for supplying fuel and the said means for supplying combustibles are configured to supply fuel and combustibles in such a way that oxygen is in a substoichiometric or stoichiometric proportion with respect to fuel in at least one part of the said apparatus (10), and the said outlet (150) is provided with sealing device (152) including stuffing box (153) configured to interact with closing door (151) of the said outlet (150) and inert gas barrier means (155) configured to prevent air from entering the said furnace (11).

EFFECT: creating an apparatus for heating steel products, which reduces formation of scale when the products are heated.

16 cl, 16 dwg

Description

FIELD OF APPLICATION OF THE INVENTION

The present invention relates to a method and apparatus for the production of steel products, in particular, for carrying out heat treatment when heating steel products in general, and not just blanks.

The steel products to which the invention relates can be either flat or long.

By long products we usually mean blanks or blooms intended for the production of steel bars, rods, profiles and pipes.

By steel products we mean metal or non-metal products, such as alloys. The invention makes it possible to minimize, if not eliminate, the scale content present on the products when leaving the furnace, essentially to a "scale-free" state.

BACKGROUND OF THE ART

Rolling plants used in the steel industry are traditionally associated with reheating furnaces, the role of which is to raise the temperature of billets, for example coming from continuous casting, to a set point suitable for plastic deformation, for sending, for example, to rolling. The blanks can be flat products, such as slabs, or long products, such as billets or blooms.

In order for steel products to quickly reach a temperature suitable for plastic deformation, various heating methods can be used, based on as many different physical principles. Among them, the most common are convection, irradiation and induction.

Convection is a heat exchange phenomenon in which heat flow is exchanged through a heating fluid flowing around a product. Heat flow is directly proportional to the temperature difference, or temperature delta, between the heating medium and the surface of the steel product.

On the contrary, irradiation provides that the heat flux is exchanged not by contact, but by irradiation between the hot surface and the surface of the heated steel product. The heat flow is directly proportional to the temperature delta between the radiating surface (hot) and the surface of the metal product, but in this delta both temperatures increase to the fourth power, according to the Stefan-Boltzmann law.

Induction involves the generation of currents within the product itself, caused by the magnetic field in which it is immersed. These internal currents help heat the product.

Due to performance requirements, heat transfer phenomena and electrical energy expended, irradiation is the physical principle most used in industry.

Heating by irradiation is achieved by surfaces that are kept very hot by electrical resistances, or by flames that burn fuel in the presence of a fuel. The products of combustion, which are typically CO, CO2, H2, H2O, O2 and possible impurities present in the fuel itself, have such a high enthalpy content that they constitute an "irradiation" agent towards the cold surface.

In general, fuel contains molecular oxygen O2. Heating devices are known that, to control the heating temperature and combustion coefficient inside the furnace, use hoses to supply pure molecular oxygen, the use of which allows better control of the amount of oxygen actually present in various parts of the furnace (RU2733614, publ. 10/05/2020, US6183246, publ. 02/06/2001). One of the disadvantages of using pure oxygen is that it is expensive to produce, store and manage. In addition, it is not always available and/or suitable for use in all metallurgical plants.

Ordinary air can be used as an alternative to oxygen, but this has the disadvantage that it is difficult to accurately control the amount of oxygen in the furnace due to ambient air that can enter the furnace and change combustion parameters.

Returning to the principle of irradiation, two different methods of application can be distinguished: direct heating by irradiation, in which contact is allowed between the combustion products and the surface of the products; and indirect heating by irradiation, in which contact between combustion products and the surface of products is prevented.

Among the known types of heating furnaces, the most common are furnaces with direct and continuous irradiation during combustion; in such ovens, the products pass through an almost perfectly closed environment to ensure continuous heating of the products (patent US5143558, published 09/01/1992).

This type of furnace is widely used because it achieves the best performance compared to other types of furnaces and allows for mass production.

Typically, the heating furnace includes, sequentially in the workpiece feeding direction, an initial preheating zone, an intermediate heating zone, and a temperature maintenance zone.

The preheat zone can be extended to approximately half the length between the oven entry point and the oven exit point. The temperature inside the kiln, usually above 700°C, rises between the inlet and outlet of the kiln.

In fig. Figure 1 shows a graph of one example of the progress of changes in the temperature of the workpiece in the furnace. In the example shown, the oven is 20 meters long. Curve T1 denotes the temperature set inside the furnace, and curves T2, T3 and T4 represent, respectively, the internal temperature of the workpiece taken at a point near the core (axis), the external temperature of the workpiece taken at a point near the top or bottom surface, and the average temperature of the workpiece . Curve D represents the temperature difference between the outer surface and the core of the workpiece.

As can be seen, the oven temperature starts at just over 700°C at the oven inlet and gradually increases until about halfway through the oven. From there to the exit zone (right of the graph), the temperature remains high but almost constant, with minimal fluctuations. Meanwhile, the temperature difference between the core and the outside of the workpiece gradually decreases until it reaches almost zero value (curve D).

As the closest solution, a furnace for heating metal material (patent EP2891859, publ. 07/08/2015) was selected, containing a dark zone and at least one heating zone located downstream from the dark zone, the heating zone is equipped with at least , one burner, wherein said dark zone is located upstream of all fuel supply points in the industrial furnace and the furnace is designed in such a way that combustion gases circulate countercurrently in the industrial furnace and pass through at least one heating zone and then through the dark zone zone. The dark zone is connected to at least one oxidizer supply tube. In this case, the means for supplying oxygen and fuel are configured in such a way that the ratio of the actual ratio of oxygen to fuel and the stoichiometric ratio of oxygen to fuel during combustion in at least one of said heating zones is less than one.

One of the disadvantages of known thermal heating furnaces is the formation of a surface layer of undesirable material on the surface of products, usually called scale, or calamine.

Scale consists of iron oxides of varying chemical composition, usually including FeO, Fe3O4 and Fe2O3. Their formation occurs as a result of contact of product surfaces with fuel combustion products.

Scale is formed, in part, due to the residence time of steel billets or blooms in an oxidizing and high-temperature environment. In fact, it has been confirmed that its formation increases exponentially with the time the workpieces remain under these conditions.

The formation of a surface layer of scale is problematic, as it is a source of surface defects that are rolled, as well as considerable economic losses.

To prevent surface defects from appearing in a metal product, it is common to remove the scale layer using high-pressure water cleaners or brush systems. The removed scale ends up as waste, resulting in loss of material, which in turn reduces the weight of the workpieces, which reduces the productivity of the steel conversion or processing operation.

Therefore, there is a need to improve the method of heating metal blanks and the corresponding device, which can overcome at least one of the disadvantages of the prior art.

In particular, one of the objectives of the present invention is to improve a method for heating products made of iron and steel, for example, but not only steel, which can dramatically reduce the formation of scale on the surface of steel products, reducing it by at least 50% and even to negligible values ( "no scale").

Another object of the present invention is to improve a heating method that allows mass production of steel products.

It is yet another object to provide an apparatus enabling the above-described method to be carried out.

Another goal is to provide a device that allows the use of air as fuel and at the same time allows precise control of the amount of combustible air - and therefore combustion oxygen - present inside the furnace.

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 the independent claims. Dependent claims describe other characteristics of the present invention or variations of the main inventive idea.

In accordance with the above objectives, a method and apparatus for thermally heating steel products, such as billets, metal and non-metal products, will be described below.

In accordance with some embodiments, the thermal heating method involves controlling/regulating the internal atmosphere of the furnace to reduce the amount of oxygen present in various zones of the furnace.

The method also advantageously involves feeding at least one steel product, such as a billet, through a thermal heating apparatus and monitoring/regulating, while accelerating the heating of the heated product, the level of oxygen in the atmosphere within the apparatus. Preferably, the steel product is supplied along a supply path that extends between the inlet and outlet ends.

Advantageously, the method involves, at least while accelerating the heating of the heated portion, supplying fuel and fuel containing oxygen to the apparatus and causing combustion of the fuel and fuel using a plurality of burners located inside the apparatus.

In some embodiments, in at least one zone of the apparatus, fuel is supplied such that oxygen is in a stoichiometric or substoichiometric proportion to the fuel.

By substoichiometric oxygen we mean an amount less than that strictly necessary for complete combustion. In this way, the presence of residual oxygen during combustion is limited or even eliminated in accordance with the above-mentioned zone inside the apparatus.

Preferably, at least a first part and a second part are defined inside the apparatus, arranged sequentially along the direction of supply of products, the temperature of the second part being higher than the temperature of the first part. According to the invention, it is advantageous that the supply of fuel with a stoichiometric or substoichiometric amount of oxygen occurs in accordance with the second part.

Preferably, the method also involves monitoring the amount of oxygen present inside the apparatus.

According to some embodiments, the method involves burning, in a first part of the apparatus, residual fuel not consumed in the second part.

Preferably, the steel products fed into the device have a transverse dimension of from 100 to 250 mm. More preferably, the transverse dimension is greater than 190 mm. The above products preferably have a round or square cross-section.

According to one aspect of the invention, an apparatus for thermally heating steel products includes a furnace within which a product supply path is defined extending between an inlet and outlet end of the furnace.

The furnace includes an inlet for entering the furnace to be heated steel products and an outlet for exiting the furnace, as well as means for supplying fuel.

The inlet and outlet holes are arranged in accordance with the corresponding inlet and outlet ends.

The furnace also includes means for supplying oxygen-containing fuel, such as ordinary air, and burners capable of activating the combustion reaction of the fuel and fuel. Advantageously, the fuel supply means and the fuel supply means are configured to supply the fuel and fuel such that oxygen is in a substoichiometric or stoichiometric proportion to the fuel in at least one portion of the apparatus.

The oxygen in the mixture can be in a proportion equal to about 2-3%, as is normally present in air, or even in a higher proportion obtained through O2 enrichment methods.

The outlet opening is preferably provided with a sealing device including at least one seal configured to cooperate with a door covering the outlet opening, and inert gas barrier means configured to prevent air from entering the oven.

In accordance with some embodiments of the invention, the inert gas protection means includes at least one chamber defined by the edge of the outlet and at least one opening for supplying inert gas to the outlet. To do this, the chamber opening is oriented towards the furnace outlet.

Preferably, the sealing device also includes water sealing means located around the outlet, more preferably around the inert gas protection means.

Preferably, the furnace is internally divided into a first part and a second part, arranged sequentially along the path for supplying steel products. More preferably, the fuel supply means and the fuel supply means are configured to supply the fuel and fuel such that oxygen is in a substoichiometric or stoichiometric proportion with respect to the fuel in accordance with the second part.

In some embodiments, the first portion and the second portion are in turn divided into two zones.

In particular, the first part includes an inlet zone or loading zone that extends from the inlet end, and a preheating zone that extends from the end of the inlet zone to the beginning of the second part. The second part is in turn divided into a heating zone following the preheating zone, and an equalization zone that extends between the heating zone and the outlet end.

According to some embodiments of the invention, the heating device also includes an afterburning device configured to inject fuel into the heating device, preferably into a first portion of the furnace where the temperature is lower. Thus, the afterburning device allows the chemical combustion reaction (not completed in the end leveling zone) to be completed by injecting fuel (to burn the unburned fuel mixed with the residues of unfinished combustion coming from the said zone) and transfer the combustion residues (now completed) to the first part apparatus.

Preferably, the afterburning device includes one or more nozzles located in the first part of the combustion chamber and configured to inject a combustible substance therein.

According to some embodiments of the invention, the apparatus includes a heated food discharge station located outside the oven in accordance with the outlet end and configured to discharge heated products from the oven.

Preferably, the discharge station includes one or more conveyor devices partially inserted within the oven to transport heated products through an exit door. These conveyor devices are controlled by mechanical elements located outside the oven. For this reason, the conveyor devices are equipped with a suitable sealing device, including water sealing means and inert gas protection means, and located in accordance with the hole made in the end wall of the furnace.

Preferably, the waterproofing means are inserted within the through hole and configured to seal it, and the inert gas protection means are located immediately outside the through hole and are effectively positioned coaxially with the waterproofing means.

In some embodiments, the discharge station also includes one or more transfer devices equipped with corresponding transfer elements partially inserted within the oven and configured to transfer heated products from the feed plane to the conveyor devices. These transmission elements are also equipped with mechanical control elements located outside the oven.

Preferably, the transfer devices include at least one transfer element movably located inside the container and partially inserted into the oven; the container is preferably directly connected to the furnace and is filled with water and inert gas to prevent air from entering the furnace, and is in air communication with the interior of the furnace to allow the transfer element to enter therein.

In some embodiments, the oven includes a top wall, also referred to as a top roof, formed by a plurality of modules connected to each other by plates connected to two successive modules by rods, and includes an internal closing element in each hollow space present between two successive modules to seal the hollow spaces hermetically.

Advantageously, the top arch also includes a plurality of strip-shaped packages, each of which is placed between the inner cover member and one or more corresponding plates.

In accordance with some embodiments of the invention, the furnace includes, in accordance with the bottom wall of the furnace, also called the hearth, one or more evacuation funnels, the upper end of which is located inside the furnace. These hoppers are designed to collect scale that could potentially be present as it is separated from the steel product en route to the conveyor elements to exit the furnace. Therefore, to prevent air from entering from these hoppers, they are also equipped with a sealing device that can prevent air from entering the oven.

In particular, each hopper includes a lower channel, to the end of which is attached a plate and a corresponding sealing element consisting of a stuffing box and a closing element attached to the outer surface of the lower channel and closing the stuffing box.

Preferably, each bin includes an internal member attached to an outer surface of a lower channel within the closure member and configured to press the package against the closure member.

The combination of the sealing elements described above and appropriate design and functional measures allows the inside of the furnace to be sealed from the outside, ensuring that the entry or exit of unwanted air is minimized, and therefore allowing control of the oxygen present to be obtained with maximum precision and precise stoichiometric ratios. This minimizes, almost completely eliminating, the formation of scale on the surface of metal products.

BRIEF DESCRIPTION OF THE DRAWINGS

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

- fig. 1 - possible graph of the temperature of the workpiece inside a 20 m long furnace;

- fig. 2 is a longitudinal section through a device for heating steel products according to the invention, taken along plane II-II of FIG. 3;

- fig. 2a is a longitudinal section through a detail of the device of FIG. 2 taken along plane A-A of FIG. 3;

- fig. 3 is a plan view of the apparatus of FIG. 2;

- fig. 4 is a partial perspective schematic view of the device of FIG. 2;

- fig. 5 - three-dimensional view of the conveyor device of the unloading zone;

- fig. 6 is a longitudinal section through part of the conveyor device of FIG. 5;

- fig. 7 - three-dimensional view of the transfer device of the unloading zone;

- fig. 8 and 9 are three-dimensional views and sections of a part of the transfer device of FIG. 7 in two different operating stages;

- fig. 10 - three-dimensional view of the furnace outlet;

- fig. 11 is a partially sectioned and three-dimensional view of the detail of FIG. 10;

- fig. 12 and 13 are side views of two parts of the furnace support area;

- fig. 14 - three-dimensional view of the evacuation funnel of the device;

- fig. 15 is a partially cut away enlarged view of a detail of the evacuation funnel of FIG. 14; And

- fig. 16A-D are schematic views of billet feeding modes into the furnace.

To facilitate understanding, like reference numerals are used to denote like general elements throughout the drawings where possible. It is understood that elements and characteristics of one embodiment of the invention may be conveniently included in other embodiments of the invention without further explanation.

DETAILED DESCRIPTION OF SOME IMPLEMENTATION OPTIONS

We will now consider in detail possible embodiments of the invention, one or more non-limiting examples of which are shown in the accompanying drawings. The phraseology and terminology used herein are also intended to provide non-limiting examples.

In fig. 2 and 3 show a device 10 for heating steel products 100 such as castings, typically steel billets.

In the following, for simplicity, we will refer to the tickets 100, or blooms, as the products processed in the apparatus 10, but this reference is made by way of example only.

The apparatus 10 contains a furnace 11, preferably with direct combustion and radiation and with continuous feed. The oven 11 has an inlet end 110 and an outlet end 111 opposite the inlet end 110, according to which a loading station 12 or loading station and an unloading station 13 or unloading station are respectively located, respectively configured to load tickets 100 into the oven 11 according to with the inlet end 110 and for unloading the heated tickets 100 from the oven 11 in accordance with the outlet end 111.

Within the furnace 11, a straight billet supply path 100 is defined, extending between the inlet end 110 and the outlet end 111, along which the billets respectively enter and exit the furnace 11.

The inlet 110 and outlet 111 ends are defined by the respective end walls 112, 113 of the furnace 11, which also has two side walls 114, 115, each of which is connected to two end walls 112, 113, as well as an upper wall 116, also called the roof, and a lower wall 117, also called the bottom. These walls 112-117 help to delimit the internal volume of the furnace, in which the heating of the tickets 100 occurs, and in which the path for supplying the tickets 100 is located.

The supply path is defined on a horizontal plane P located at an intermediate height within the furnace 11 (FIG. 2) between the top wall 116 and the bottom wall 117, preferably at approximately half the height of the furnace 11.

The tickets 100 are placed in special receptacles 200, commonly referred to as seats, which move in a substantially continuous manner between the input end 110 and the output end 111.

Advantageously, the oven 11 includes an inlet port located in correspondence with the inlet end 110, more preferably in accordance with the side wall 114, 115 of the oven 11.

The oven 11 is internally divided into a first part 20 and a second part 30, which are arranged in this order along the supply path. The first part 20 starts from the inlet end 110 and is set to the first temperature T1 to preheat the tickets 100 to gradually increase their temperature. For this reason, the first part 20 of the oven 11 is also called a preheating zone. For example, the temperature T1 in the first part 20 ranges between approximately 700 and 1000-1100°C, depending on the steel to be heated.

The second part 30 is located between the first part 20 and the outlet end 111 and is set to a second temperature T2 higher than the first temperature T1 (Fig. 1). The temperature T2, typically exceeding 1000° C., is such that it heats the billets 100 to such an extent that they become plastically deformable.

As can be seen from Fig. 2, the first portion 20 defines an inlet zone 21, or feed zone, adjacent the inlet end 110 of the furnace 10. Following the inlet zone 21 is a preheat zone 22, also included in the first portion 20 of the furnace 11.

Preferably, the second part 30 is also divided into two zones, a heating zone 31, which immediately follows the preheating zone 22, and an equalization zone 32 located between the heating zone 31 and the outlet end 13 of the furnace 11.

In the example shown in FIG. 2 and 4, the heating zone 31 is divided into an upper half heating zone 31A and a lower half heating zone 31B located below the upper half heating zone 31A.

Likewise, the alignment zone 32 is divided approximately in half into an upper alignment area 32A and a lower alignment area 32B.

This division of the heating zone 31 and the leveling zone 32 is preferably materialized by the billet supply plane P 100. It follows that the preheating zone 22 is also divided into an upper preheating zone 22A and a lower preheating zone 22B (FIGS. 2 and 3).

The heating zone 31 has a temperature T2 higher than the maximum temperature T1 of the preheating zone 22 and is designed to heat the billet 100 to the point of deformation for subsequent rolling. The equalizing zone 32, with a temperature T2 even higher than in the heating zone 31, is designed to equalize the temperature of the steel between the inside of the workpiece and its surface.

The temperature inside the furnace 11 gradually and continuously increases along the straight feed path, starting from, for example, 700° C. in accordance with the inlet end 110 until reaching a temperature of the order of 1000° C. at the end of the first part 20. In the second part 30, the temperature T2 is maintained substantially , at the same high level or slightly higher than the temperature obtained at the end of the preheating zone 22, so as to increase the temperature of the workpiece both at its surface and inside. For example, the temperature T2 in the second part may be of the order of 1100°C.

It should be noted that the temperature inside the oven 11 is regulated so as not to overheat the surface of the workpieces to the detriment of the uniformity of the crust-core.

The zones 21, 22, 31, 32 defined above preferably have known dimensions and volumes, which allows their physical parameters to be effectively controlled during the operation of the thermal heating apparatus 10, in particular the temperature and concentration of fuel and fuel present therein.

In the example shown, the first portion 20 and the second portion 30 are substantially the same length. The entrance zone 21 has a height preferably less than the height of the other zones 22, 31, 32, all three of which have the same height.

Preferably, the boundary between the first part 20 and the second part 30 is materialized by an inner edge 23 that projects from the upper wall of the furnace 11. This upper inner edge 23 may have a height such that its lower end is at the same height of the upper wall in the inlet area 21.

The apparatus 10 also includes within it combustion elements 40, or burners, distributed among the various zones 21, 22, 31, 32 previously defined. The burners 40 are connected to a fuel source, for example methane, and a fuel source, which preferably contains oxygen, in particular air, by suitable fuel supply means and fuel supply means, for example pipes.

In the example shown in FIG. 2, the apparatus includes a plurality of burners 40, referred to as side burners, located in the side walls 114, 115 of the furnace 11, and at least one burner 41, referred to as a front burner, located in correspondence with the outlet end 111. More preferably, the furnace 11 includes a plurality of front burners. burners 41, for example eight, regularly distributed between the side walls 114, 115 so as to uniformly heat the upper leveling half-zone 32A.

It should be noted that the burners 40 are located in the preheating zone 22, in the heating zone 31 and in the leveling zone 32. As an example, it can be provided that on each of the side walls 114, 115 of the furnace there are four burners 40 located in the preheating zone 22 and in heating zone 31, and only two burners 40 in the leveling zone 32.

In the last zone 32, side burners 40 are preferably located only in the lower leveling half-zone 32B, due to the presence of front burners 41 in the upper leveling half-zone 32A.

The burners 40, 41 used in the furnace 11 are effectively characterized in that they can operate in any condition with any amount of fuel.

In particular, the relationship LAMBDA = Areal/Atheoretical is defined, in which Areal is the amount of fuel actually supplied, and Atheoretical is the amount of fuel, which corresponds to the exact amount of oxygen necessary and sufficient to complete the corresponding combustion reactions, namely:

C + O2 = CO2 + 33910 kJ/kg

2 H2 + O2 = 2 H2O + 143000 kJ/kg

S + O2 = SO2 + 8800 kJ/kg

If LAMBDA is equal to 1, then combustion occurs at the exact theoretical amount of oxygen. The burners 40 can operate with either a LAMBDA less than 1 or a LAMBDA greater than 1.

The apparatus 10 also includes fuel supply means for supplying fuel from a suitable source to the burners 40, 41 and fuel supply means for supplying fuel from a suitable source to the burners 40, 41.

Preferably, the fuel supply means and the fuel supply means are configured to supply fuel in excess relative to the fuel in accordance with the second part 30. Thus, during combustion, complete consumption of fuel and therefore oxygen occurs, allowing heating and maintaining the temperature of the workpieces, preventing the formation of scale on steel products (“scale-free” products).

In the present invention, scale is reduced by at least 50% compared to known solutions, even to negligible values.

For example, it may be provided that the fuel supply means and the fuel supply means are configured to supply excess fuel so as to have a substoichiometric oxygen presence in the leveling zone 32, and to have a substoichiometric or stoichiometric oxygen presence in the heating zone 31.

By stoichiometric fraction in the context of this description we mean that the amount of oxygen introduced is exactly equal to the amount suitable for burning that particular amount of fuel (this corresponds to LAMBDA = 1).

Likewise, by substoichiometric fraction it is meant that the amount of oxygen supplied is less than the amount required to burn the supplied fuel (this corresponds to LAMBDA < 1). In other words, when air is supplied in substoichiometric proportions, the combustion reaction theoretically results in complete consumption of oxygen while not completely consuming fuel.

In contrast, the fuel and fuel supply means are preferably configured to supply excess fuel (LAMBDA > 1) to the first portion 20 of the furnace 11.

It is also advantageous to provide that the device 10 be equipped with an additional fuel injection circuit, also called an afterburning system, configured to complete the combustion of fuel transferred (without combustion) from the second part 30 of the furnace 11 (where the fuel is supplied in a substoichiometric proportion) to the first part 20 (where fuel is supplied in excess). Thus, excess fuel in the second part 30 is burned in the first part 20, and the combustion reaction is used to transfer heat to the steel blanks.

This position allows you to optimize fuel consumption. The afterburning circuit includes nozzles 50 located in the first part 20 of the furnace 11, obviously inside the latter. According to some embodiments of the invention, the circuit also includes a monitoring device configured to verify that fuel has been consumed.

Advantageously, it is possible to provide nozzles 50 on the upper inner edge 23, more preferably on the surface of the upper inner edge 23 facing the first part 20 of the furnace 11 to directly inject fuel therein, avoiding injection into the second part 30 of the furnace (FIG. 2).

In the example shown, the afterburning circuit is capable of controlling the consumption of excess fuel in the upper zone 22A of the preheat zone 22. To further optimize fuel consumption, other nozzles 50 (not shown) may be provided in the lower zone of the first furnace portion 20, preferably in the lower zone 22B. preheating 22.

For example, a second inner edge may be provided, which may be similar to the inner edge 23 of the top wall, but located on the bottom wall. The lower half-zone nozzles 22B may be effectively positioned on this lower inner edge and face the preheating zone 22. The presence of the lower inner edge also allows the separation between the first portion 20 of the oven 11 and the second portion 30 to be further defined.

Preferably, the monitoring device is configured to measure the presence of oxygen, and possibly carbon monoxide CO, in the inlet zone 21. To do this, the monitoring device may include a laser spectrometer 51, one or more oxygen probes 52 for determining free oxygen, and one or more sampling probes CO samples The spectrometer 51 and the probe 52 for determining free oxygen are preferably located in the inlet zone 21.

The oven 10 also preferably includes oxygen sensors capable of monitoring the presence and concentration of oxygen within the oven 11. Preferably, the oven includes at least one sensor in each of the inlet 21, preheat 22, heat 31, and equalization zones 32.

Advantageously, the sensors are configured to continuously monitor the presence of oxygen. More preferably, they are of the optical type, such as laser.

Preferably, the oven 11 also includes a smoke exhaust system configured to exhaust smoke from inside the oven 11 to the outside. More preferably, a smoke exhaust system, which is known and therefore not described further herein, is located in the first part 20 of the furnace 11.

According to some embodiments of the invention, the device 10 may also include a plurality of probes 70 coupled to the furnace 11 to detect the presence and/or concentration of other chemical compounds therein, such as, for example, carbon monoxide CO, carbon dioxide CO ₂ , hydrogen H ₂ and /or methane CH ₄ .

In the example shown, apparatus 10 includes four probes 70 in each of the preheating 22, heating 31, and leveling zones 32 of the oven 11. Preferably, the probes 70 are located in the side walls 114, 115 of the oven 11 (FIGS. 2 and 4). More preferably, they are arranged in pairs, with two components of one pair located in one respective side wall 114, 115 and facing each other.

Even more preferably, two pairs of each of preheating zones 21, heating 31 and leveling 32 are located one above the other, that is, vertically aligned. For example, in the heating zones 31 and leveling 32, it may be provided that one pair of probes 70 is located in the upper half zone 31A, 32A, and the other in the lower half zone 31B, 32B.

The oven 10 also preferably includes thermometers located in various areas of the oven to determine the temperature accordingly.

According to some embodiments, the oven 11 is also equipped with laser sensors positioned so that the straightness of the billets 100 and their progress status in the oven can be monitored.

It should be noted that all of the above sensors can be effectively connected to the oven without making holes in its walls or ensuring they are properly sealed in order to minimize the risk of air getting inside the oven.

Advantageously, the apparatus 10 also includes a number of measures aimed at improving the gas seal in order to prevent loss of fuel and/or fuel, but also and especially the entry of unwanted air into the furnace. In this way, it is possible to regulate the composition of the atmosphere within the various zones 21, 22, 31, 32 of the furnace 11 with greater precision. These measures are essentially present in all zones of the furnace 11 that separate the internal volume of the furnace 11 from the external, especially in relation to the hottest part of the furnace , that is, the second part 30. For example, the oven 11 may include doors with improved sealing.

In the example shown in FIG. 2 and 3, a loading station 12 is located outside the inlet end wall 112. The loading station 12, in turn, includes a plurality of conveyor devices 120, each of which consists of a roller 121 located inside the oven 11 and a corresponding motor 122 located outside ovens. The roller 121 and the motor 122 are connected by a shaft 123, which passes through a corresponding through hole 124 made in the end wall 112 of the furnace 11 (Fig. 2a).

Likewise, the unloading station 13 is located outside the exit end wall 113 and includes conveyor devices 130 provided for transporting the tickets 100 from the oven 11, and transfer devices 140 for transferring the tickets 100 from the feed plane P to the conveyor devices 130.

The conveyor devices 130 (FIGS. 5 and 6) are similar to the conveyor devices 120 of the loading station 12 and consist of a roller 131 located within the oven 11 during use, and a motor 132 for driving it, the roller 131 and the motor 132 being mutually connected by a shaft 133, rotating inside a fixed bushing 133a. The sleeve 133a passes through a through hole formed in the outlet end wall 113 so that the motor 132 remains outside the furnace 11.

Each conveyor device 130 of the unloading station 13 is provided with a sealing device 134 located around the sleeve 133a and located outside the oven during use. The sealing device 134 includes a fastening collar 135 attached around the sleeve 133a and configured to be secured in a through hole of the outlet end wall 113 of the furnace 11 so as to seal it. The fastening collar 135 provides an inner chamber 136 in which water is present as an insulating agent. It should be noted that the inner chamber 136 has a diameter smaller than the diameter of the fastening collar 135 and is configured to be inserted within the through hole of the outlet end wall 113.

The conveyor device 130 also includes a support ring 137 positioned between the mounting ring 135 and the motor 132 and provided with a pair of seals 137a, such as rubber or the like. Between the fastening ring 135 and the support ring 137 there is a bellows sleeve 138 located around and spaced from the sleeve 133a so as to form a cylindrical chamber 138a. A cylindrical chamber 138a, sealed at both the fastening ring 135 and the support ring 137, is connected to an opening 139 through which an inert gas, such as nitrogen or argon, is supplied. The cylindrical chamber 138a, which extends to the fastening ring 135, allows for improved sealing in accordance with the fastening ring 135, making up for any loss of sealing at the junction between the fastening ring 135 and the sleeve 133a.

In the example shown, the feeding zone conveyor devices 120 are not provided with the same sealing device described above, but it is obvious that they can be provided, in order to benefit from optimized control of the amount of air also inside the first part 20 of the oven 11.

The unloading station 13 also includes a pair of transfer devices 140 (FIG. 7), each of which consists of two transfer elements 141 configured to insert into the oven 11 and move the tickets 100. The transfer elements 141 are designed as levers provided with a corresponding seat 141a for section of the billet 100 (FIGS. 7 and 8) and integrated with corresponding supports 141b perpendicular to them (FIGS. 8 and 9). Specifically, in the inactive position (FIG. 8), the bracket 141 is oriented horizontally and the support 141b is oriented vertically downward.

Each transfer element 141 is enclosed in a corresponding hermetically sealed containing box 142 having an end opening 142a for passage of the bracket 141 and a bottom opening 142b for passage of the support 141b. The end opening 142a is designed to be attached to the outlet end wall 113 of the furnace 11, thereby sealing it tightly. The lower opening 142b, on the other hand, is left open and has an elongated shape in the longitudinal direction relative to the containing box 142 to allow the support 141b to move back and forth, and is limited by four walls 142c that extend vertically inside the containing box 142 (FIGS. 8 and 9). ).

The transmission mechanism 141 also includes a clamp housing 143 attached to a cuboid-shaped support 141b and enclosed within a containing box 142. Specifically, the clamp housing 143 is completely open on its lower side and is located around four walls 142c defining a lower opening 142b holding box 142.

The containment box 142 is partially filled with liquid water, at a level in any case lower than the height of the walls 142c defining the lower opening 142b, but high enough so that the lower edge of the clamp housing 143 is always submerged, regardless of its position, for example, the inactive position (Fig. 8), in which the lever 141 is not raised, or the lifting position (Fig. 9), in which the lever is advanced so that its end is inside the furnace 11 and is raised. The remainder of the interior of the containment box 142 is filled with an inert gas such as nitrogen or argon.

The combination of the walls 142c, the clamp housing 143, and the water level inside the containment box 142 allows air that passes through the lower opening 142b in the clamp housing 143 to be blocked. Additionally, if air were to pass between the bottom edge of the housing 143 and the water body, it would be blocked by the inert gas filling the remainder of the containing box 142.

In fig. 10 and 11 show an outlet 150 of the oven 11 through which heated billets 100 are discharged. The outlet 150 is effectively located at the end of the side wall 114 of the oven 11, in close proximity to the outlet end 113.

The discharge opening 150 is provided with a closing door 151 that can be driven between a closed position in which it is in contact with the discharge opening 150 to seal it (FIG. 11) and an open position in which it is removed from the discharge opening 150 (Fig. 10). The discharge opening 150 is surrounded by a sealing device 152, which includes a seal 153 located on the outer surface of the discharge opening 150 so as to engage the closing door 151 when it is in the closed position. This creates a first seal that prevents the passage of air.

The sealing device 152 also includes a first inner chamber 154 located behind and extending beyond the package with respect to the outlet 150. The first inner chamber 154 is filled with water as a sealing fluid. There is also a pair of side chambers 155 located immediately on each side of the outlet 150, between it and the first inner chamber 154 (Fig. 11). These side chambers 155 are designed to be filled with an inert gas, such as nitrogen or argon, and each has a corresponding vertical linear opening 156 oriented towards the discharge opening 150 so as to blow the inert gas towards the relief opening 150, thereby creating a barrier of inert gas to prevent air from entering when the closing door 151 is in the opening position. Thus, the chambers 155 act as barrier means.

In a preferred solution, another element that improves the sealing of the furnace 11 is provided in the upper wall 116, which consists of a plurality of modules 116a oriented transversely relative to the furnace 11 and assembled in series using ties 160, connected to each other using connecting plates 161. FIG. 12 shows the assembly detail of the module 116a to the transverse and longitudinal beam 118 of the top wall 116. The plate used is bent into an L-shape so as to be attached to both the beam 118, in accordance with its side surface, and to the module 116a, by means of thrust 160 corresponding to its upper surface.

To seal this area in which openings are formed between the edge of the module and the plate 161, for example, an internal closure member 162 provided with an edge 163 extending perpendicularly and configured to be sealed in the space between the edge of the module 116a and the plate 161 is provided. In addition The inner cover 162 is also provided with a flat-shaped padding 164, preferably made of fibre.

Likewise, corresponding to the transverse joints between two successive modules 116a (FIG. 13), a T-shaped inner cover 162 is inserted between the two modules, i.e. having two side edges 163, and two fiber packings 164a, one of which is attached to the bottom surfaces of two successive modules 116a, and the other is clamped between the inner cover element 162 and a plate 161 located above the space between the two modules 116a. This plate 160 is spatially centered so as to partially overlap both modules 116a so that it can be secured to both of them by means of respective tie rods 160 (FIG. 13).

It should be noted that the top wall 116 has two side pads 164 and the same number of internal cover elements 162, which extend along the corresponding side beam 118, as well as a plurality of transverse pads 164 and the same number of side cover elements 162 located in accordance with the joints between two consecutive modules 116a. Thus, all openings between the modules and the side beams are closed.

Finally, to improve the seal against the bottom wall 117, sealing elements have been inserted into the dross collection funnels 170, which constitute the main air access point in this area of the furnace 11.

Such funnels 170 include a lower channel 171 having a substantially cylindrical shape, which can be selectively closed by a closing member 172 movable between a position in which the lower channel 171 is open and a position in which the lower channel 171 is closed (FIGS. 14 and 15). .

Each funnel 170 consists of a plate 173 attached to the bottom opening of the bottom channel 171 and a sealing member 174 that seals the joint between the bottom channel 171 and the plate 173 to prevent air from passing through that area. In particular, the sealing element 174 consists of a rectangular cross-section seal ring 175 that rests on the plate 172, and a cover ring 176 attached to the outside of the lower channel 171 in accordance with its lower edge (Fig. 15). This closure ring 176 has an inverted L-shape with its vertical portion located outside the gland with respect to the lower bore 171. The closure ring 176 is also provided with an inner member 177 attached to the outer wall of the lower bore 171 and extending horizontally to press against the inner surface O-ring 175 to provide a seal between cover ring 176 and packing 173.

The combination of elements described above makes it possible to control the amount of air inside the furnace 11 with almost absolute precision, since unwanted and uncontrolled entry of air from outside the furnace is prevented. This air control makes it possible to guarantee the functionality of the process and almost completely prevent the formation of scale on the 100 billets, thanks to the precise control of the amount of air inside the furnace. It is therefore possible to supply normal air to the furnace so that oxygen is present in a substoichiometric amount in the second part of the furnace 11 without the risk of undesirable additional air supply.

Thus, the convenience of using air as a fuel is ensured and at the same time precision control of the amount of oxygen present inside the furnace 11 is achieved.

To control all of its components, the furnace 10 includes a centralized control system (not shown in the drawings), which receives the results of parameters determined using sensors and probes, and allows you to regulate the flow of fuel and fuel supplied to the furnace 10.

The operating mode of the heating device 10 described above is as follows.

Billets 100 are continuously fed along a straight feed path into the oven 10, previously brought to operating condition, that is, with the operating temperature set in various zones. The temperature setting is carried out depending on the composition of the steel of the billets 100, as well as their sizes and is regulated so as not to overheat the surface of the billets.

To provide heating within the furnace 11, a controlled supply of fuel and fuel is provided to the burners 40, which provide combustion, thereby generating the desired heat.

Advantageously, in the second furnace part 30, in which the temperature T2 is higher than in the first part 20, fuel and fuel are supplied in such a way that oxygen is in a stoichiometric and/or substoichiometric ratio with respect to the fuel. Thus, during combustion all the oxygen is consumed. In the absence of oxygen in the second part 30 of the furnace 10, the formation of scale on the surface of the billets (which can be called "no scale") is prevented, reducing it by at least 50% to negligible values.

It is possible to provide differential control of the supply of fuel to the zones of the furnace 10, for example, so that oxygen is in a substoichiometric proportion in the equalization zone, and in a substoichiometric or stoichiometric proportion in the heating zone.

The supply of fuel in a substoichiometric proportion ensures that part of the fuel located in the second part 30 does not burn. This residual part of the fuel, together with the combustion smoke, is directed to the first part 20 of the furnace 10, where the smoke exhaust system is located.

According to some embodiments, in the first portion 20 of the furnace 10, fuel and fuel are supplied so as to have an excess of oxygen. This excess oxygen can be supplied via an afterburning circuit.

In fact, the afterburning circuit is provided to inject the required combustible substance in accordance with the first part 20 to complete the combustion of the unburned fuel in the second part 30. Thus, the residual fuel is supplied with the fuel necessary to complete the combustion, preventing the emission of unburned products.

To ensure proper distribution of fuel inside the apparatus 10, the presence and concentration of oxygen is constantly monitored using laser oxygen sensors 51.

According to some embodiments of the invention, a gas-air control loop is provided within the furnace 11 in which the flow of fuel and fuel is monitored and regulated, for example, by a centralized control system, to maintain the ratio of fuel and fuel at a desired level in each of the zones of inlet 21, preheat 22, heating 31 and leveling 32.

In accordance with some embodiments of the invention, constant monitoring of the final quality of heating is also provided, taking into account variations in the speed of movement of steel billets within the furnace 11. In particular, constant monitoring of the concentration of fuel and fuel, as well as the temperature within the various zones 21, 22, can be ensured. 31, 32 furnace 11. In case the parameters do not correspond to the predetermined quality level of the steel billets, it is possible to intervene by appropriately changing one or more such parameters and/or the speed of advance of the steel billets.

Control, as stated above, is carried out by the furnace control system using the control device 52.

In accordance with other embodiments of the invention, it may be provided that the control system implements the function of controlling the residence time of the steel workpieces inside the furnace 11.

This control function can be implemented in two different modes, which are a variable residence time mode and a constant residence time mode, which takes into account the idle time when advancing the steel workpieces 100.

Variable residence time control ensures that the furnace 11 is always fully loaded, that is, that all seats 200 are loaded with the corresponding workpiece 100 (as in FIG. 2).

When stops occur in the progress of seats 200, the steel billets 100 located in the furnace 11 accumulate residence time in the furnace, with the result that, when unloading from the furnace, the total residence time exceeds the optimal residence time determined by the design (meaning the optimal time for based on design calculations).

The variable residence time mode corresponds to the control mode already known in the industry.

The constant residence time control mode aims to ensure that the heating time of each workpiece is as constant as possible, regardless of the average hourly productivity, and at the same time as close as possible to the optimal time based on the design calculation.

Maintaining the heating time is preferably achieved using a loading pattern that can provide unloaded seats 200, that is, without the steel blank 100.

As shown in FIG. 16A-D, the loading pattern of the seats 200 is varied by increasing the distance between the workpieces, alternating empty seats 200 with loaded seats 200. The loading pattern can be adapted based on the characteristics of the resulting workpiece 100.

With regard to the total loading of the furnace 11, loading classes can be distinguished that correspond to corresponding loading percentages of the seats 200, in accordance with the characteristics of the final product.

In fig. 16A shows a 50% load class where only half of the seats 200 are loaded with workpieces 100. In this case, the loaded seat 200 is alternated with an empty seat 200.

A 66% load class as shown in FIG. 1 may also be provided. 16B, in which two loaded seats 200 alternate with one empty seat 200. This pattern is repeated as seats 200 advance.

Another load class shown in FIG. 16C, ensures loading at 70%. This load class can be achieved by cycling through ten 200 locations, two loaded 200 locations, one empty 200 location, two loaded 200 locations, one empty 200 location, three loaded 200 locations, and finally one empty 200 location. In other words, two 200 seats from three, two 200 seats from three and three 200 seats from four are loaded, completing the cycle of ten 200 seats.

In fig. 16D shows a fourth loading class that involves loading 90% of seats 200. The loading pattern involves loading nine consecutive seats 200 and leaving one empty.

In accordance with other embodiments, consideration of programmed pauses in rolling may also be provided. These rolling pauses can be controlled so as not to increase the residence time of the billets 100 in the furnace, for example by anticipating a loading interruption, knowing the expected downtime.

The idle time determines, depending on the operating speed of the load that will be processed at the end of the programmed rolling pause, the number of places 200 that must remain empty so that the operation of the furnace 11 remains constant during the entire pause time.

However, we want to point out that these voids created during loading will result in the same amount of voids during unloading, and therefore there will be no blanks 100 ready for rolling. This makes it possible to carry out the necessary work to replace cylinders at the rolling mill without changing the residence time of the workpieces 100 in the furnace.

The number of 200 seats that must remain empty can be summed up using the following formula: (n° empty seats) = (idle time) / (rate of charge loading into the furnace at the end of the pause). The idle time and the charge loading rate at the end of the pause are information that must be known for proper control of the furnace 10.

It is understood that changes and/or additions to parts or steps may be made to the previously described method and apparatus 10 without departing from the scope and scope of the present invention as defined in the claims.

In the following claims, parenthetical references are intended to facilitate reading only: they are not to be construed as limiting factors with respect to the scope of protection claimed in specific claims.

Claims (16)

1. An apparatus (10) for heating steel products (100), including a direct irradiation heating furnace having inside a path for supplying steel products (100) that extends between an inlet end (110) and an outlet end (111) of the steel products (100) , an inlet hole in accordance with said inlet end (110) to allow said steel products (100) to enter said furnace (11), and an outlet hole (150) in accordance with said outlet end (111) to allow said steel products to exit (110 ) from said furnace (11), means for supplying fuel, means for supplying fuel including oxygen, and burners (40, 41) capable of controlling the combustion of fuel and fuel, characterized in that said means for supplying fuel and said means for supplying fuels are configured to supply fuel and fuel such that oxygen is in a substoichiometric or stoichiometric proportion with respect to the fuel in at least one part of said apparatus (10), and that said outlet (150) is provided with a sealing device (152 ) including a seal (153) configured to cooperate with a closing door (151) of said outlet (150), and inert gas barrier means (155) configured to prevent air from entering said oven (11). 2. Apparatus (10) according to claim 1, characterized in that said means (155) for protection against inert gas include at least one chamber (155) defined by the edge of said outlet opening (150), and in that it includes at least one hole for supplying said inert gas to said outlet (150). 3. Apparatus (10) according to claim 1 or 2, characterized in that said sealing device (152) also includes means (154) for isolating water located around said outlet opening (150). 4. Apparatus (10) according to any of the previous paragraphs, characterized in that it includes an unloading station (12) located outside the furnace (11) in accordance with the specified outlet end (111), and in that this unloading station (12) includes one or more conveyor devices (130) partially inserted inside the furnace (11) for transporting steel products (100) through said outlet opening (150), and in that said one or more conveyor devices (130) are each provided with a corresponding sealing a device (134), including means for isolating water (136) and means for protecting against inert gas (138, 139), and located in accordance with the through hole of the end wall (113) of the specified furnace (11). 5. Apparatus (10) according to claim 4, characterized in that said water isolating means (136) is inserted inside said through hole and configured to seal it, and in that said inert gas protection means (138, 139) are located immediately outside said through hole and coaxial with said water isolating means (136). 6. Apparatus (10) according to claim 4 or 5, characterized in that said unloading station (12) includes one or more transfer devices (140) for transferring said steel products (100) from said supply path to said conveyor devices (130 ), and in that each of said transfer devices (140) includes at least one transfer element (141) movably located inside a containing box (142) and partially inserted inside said oven (11), said box (142) is directly connected with said furnace (11) and filled with liquid water and inert gas to prevent air from entering into said furnace (11) and in air communication with the interior of said furnace (11) to allow said transmission element (141) to enter said furnace ( eleven). 7. Apparatus (10) according to any of the previous paragraphs, characterized in that the oven (11) includes an upper wall (116) formed by a plurality of modules (116a) connected to each other by means of plates (161) connected to each of two consecutive modules (116a) by means of tie rods (160), and in that it includes an internal closing element (162) in each hollow space between two successive modules (116a) to seal the hollow spaces. 8. Apparatus (10) according to claim 7, characterized in that the upper wall (116) also includes a plurality of strip-shaped packings (164), each of which is located between the inner closure element (162) and one or more corresponding plates (161 ). 9. Apparatus (10) according to any of the previous paragraphs, characterized in that the oven (11) includes a lower wall (117) through which funnels (170) are inserted, each of which has a lower channel (171) at the end of which a plate is attached (173), and in that each funnel (170) includes a corresponding sealing element (174) consisting of a gland (175) and a closing element (176) attached to the outer surface of the lower channel (171) and surrounding the gland (175). 10. Apparatus (10) according to claim 9, characterized in that each of said funnels (170) also includes an internal element (177) attached to the outer surface of said lower channel (171) within said closing element (176) and configured to pressing said seal (175) against said closing member (176). 11. Apparatus (10) according to any of the previous paragraphs, characterized in that it includes a furnace (11) internally divided into a first part (20) and a second part (30) located sequentially along the path of supply of steel products (100), while the temperature (T2) in the second part (30) is higher than the temperature (T1) in the first part (20), and wherein the fuel supply means and the fuel supply means are configured to supply the fuel and fuel such that oxygen is at substoichiometric or stoichiometric proportion with respect to the fuel in accordance with said second part (30). 12. Apparatus (10) according to claim 11, characterized in that the first part (20) includes an inlet zone (21) that extends from the inlet end (110), and a preheating zone (22) that extends from the end the specified entrance zone (21) before the beginning of the second part (30), and the fact that the second part (30) includes a heating zone (31) following the specified preheating zone (22), and an equalization zone (32), which extends between said heating zone (31) and the outlet end (111). 13. Apparatus (10) according to claim 11 or 12, characterized in that it includes an afterburning device that promotes complete combustion in the first part (20) of fuel residues not burned in the second part (30) of the furnace (10). 14. Apparatus (10) according to claim 13, characterized in that the afterburning device includes one or more nozzles (50) located in the first part (20) of the furnace (10) and configured to inject fuel there. 15. Apparatus (10) according to claim 14, characterized in that the nozzles (50) of the afterburning device are located on the upper inner edge (23) separating the first part (20) from the second part (30), and/or on the lower inner edge , separating the first part (20) from the second part (30). 16. Apparatus (10) according to any of the previous paragraphs, characterized in that the starting material is air, and the oxygen in the starting material is in a proportion equal to about 2-3%, or in a greater proportion obtained using oxygen enrichment methods (O ₂ ).