Apparatus and method for refining liquid metals

Abstract

An apparatus (10) for smelting liquid metal (L) includes a ladle (11) for containing the liquid metal (L), having an open top (12) and at least one porous plug (13) on its bottom wall (14), a removable lid (19, 23), a gas injection line (21) connected to the at least one porous plug (13), and a control unit (27).

Description

Technical Field

[0001] The present invention relates to an apparatus and method for refining liquid metal in a ladle downstream of an electric arc furnace (EAF) and in the context of secondary steel refining that occurs prior to continuous casting. This refining apparatus and method are particularly aimed at controlling the injection of an inert gas into the liquid metal so as to determine the desired agitation while being able to insert alloying elements to obtain the desired chemical composition and facilitating the removal of inclusions and impurities.

Background Art

[0002] In the area of secondary refining processes, it is known to perform refining treatment directly in a ladle, particularly for the production of so-called specialty application steels.

[0003] In particular, this treatment is carried out in a ladle furnace equipped with a lid that is lowered via an electrode to heat the liquid metal bath, and, if possible, in the next step, also in a vacuum degassing device equipped with a chamber that can be hermetically sealed with the lid and in which the ladle is placed before a vacuum is generated inside.

[0004] Refining treatment often includes deoxidation, alloying, desulfurization, vacuum degassing, removal of inclusions, etc., and sufficient homogenization of the liquid metal in terms of both chemical composition and temperature is required.

[0005] Homogenization is usually reliably carried out by continuous agitation by injecting an inert gas such as argon or nitrogen through a submerged lance or a porous plug installed at the bottom of the ladle and connected to a gas injection line, aiming to continuously agitate the liquid metal bath and make the solid and / or gaseous inclusions and impurities contained therein float to the surface.

[0006] Good agitation control is essential to maximizing productivity and metal quality. However, defining the optimal gas flow rate is extremely difficult. This is because it depends not only on the type of secondary treatment applied, but also on the frequent occurrence of injection system malfunctions, such as porous plugs and blockages in the gas injection lines.

[0007] Agitation efficiency depends on many parameters, including cleaning of the porous plug between ladle cycles, the durability of the porous plug, and the durability of the refractory material. Although most gas injection lines are equipped with independent pressure sensors and flow meters, their measurements do not adequately reflect the actual agitation of the molten metal in the ladle.

[0008] In particular, in the case of vacuum degassing equipment, due to the extremely harsh and smoky environment, high temperatures, and the impossibility of direct visual inspection of the process, on-site technicians use systems to indirectly measure the agitation state of the liquid metal, such as systems that measure mechanical vibrations of the ladle or acoustic radiation from turbulent agitation, or systems that detect images using optical cameras or infrared telescopes.

[0009] The most promising solution at present involves using a telephoto camera mounted on the lid of the ladle to detect an image of the free surface of the liquid metal tank.

[0010] However, especially in vacuum degassing systems, processing is carried out at a pressure lower than atmospheric pressure, and the foaming action caused by gas injection significantly raises the surface level of the liquid metal. This surface level is usually formed by a slag layer, and sometimes by bubbles, which can overflow and cause water to flood the containment chamber.

[0011] This foaming generates high-temperature smoke, slag, and liquid metal droplets reaching approximately 1700°C, affecting the structure and function of the telephoto camera itself and hindering accurate, long-term image detection.

[0012] Therefore, the analysis performed on images is unreliable and only shows what is happening during the process, so it is rarely used to guide the process.

[0013] Therefore, it is necessary to perfect apparatus and methods for refining liquid metals that can overcome at least one of the shortcomings of current technology.

[0014] To achieve this, it is necessary to solve the technical problem of precisely and uniformly controlling the stirring and homogenization of the liquid metal throughout the entire refining process, especially during the processes that occur in the ladle furnace, and above all, during the processes that occur in the vacuum degassing unit, which is completely isolated from the outside and therefore cannot be visually inspected to see what is happening inside.

[0015] In particular, one of the objectives of the present invention is to provide a liquid metal refining apparatus and method that can essentially continuously monitor the stirring state of the liquid metal, or at predetermined time intervals, regardless of the extremely aggressive environment present inside the apparatus (to varying degrees, such as strong vacuum, high temperature, presence of smoke, and splashing of liquid metal).

[0016] Another object of the present invention is to provide an apparatus for smelting liquid metal, which provides information on the operating state of a ladle or porous plug in a gas injection line by monitoring the stirring of the liquid metal.

[0017] Another object of the present invention is to provide an apparatus for smelting liquid metal, which provides indicators for controlling the pressure and flow rate of inert gas blown through the porous plug of the ladle by monitoring the stirring of the liquid metal.

[0018] The applicant has invented, tested, and embodied the present invention to overcome the shortcomings of the prior art and to achieve these and other objectives and advantages. [Overview of the Initiative]

[0019] The present invention is described and characterized by the independent claims. Dependent claims describe other features of the present invention or variations of the principal inventive idea.

[0020] To achieve the above objectives, and to solve the technical problems disclosed above in a novel and original way, and to achieve considerable advantages compared to the prior art, the apparatus for refining liquid metal according to the present invention includes a ladle for containing the liquid metal, having an open top and at least one porous plug on its bottom wall, a removable lid, a gas injection line connected to the at least one porous plug, and a control unit.

[0021] According to one aspect of the present invention, the apparatus includes an observation unit mounted on the lid, comprising a support assembly associated with at least one IR (infrared) telephoto camera connected to the control unit to detect and transmit a sequence of thermographic images of the free surface of the liquid metal, at least one protective lens directly facing the open top, and an intermediate lens positioned between the at least one infrared telephoto camera and the at least one protective lens.

[0022] By doing this, it is possible to detect a sequence of thermographic images continuously or at pre-set time intervals, even if the smelting environment is thermally and chemically aggressive. In fact, thanks to the presence of dual lenses, the IR telephoto camera is always protected not only from heat but also from slag and metal splatters that hit it.

[0023] According to another aspect of the present invention, an observation aperture is created on the support assembly that defines the detection direction in which the at least one IR telephoto camera, the intermediate lens, and in any case the at least one protective lens are aligned.

[0024] According to another aspect of the present invention, the at least one protective lens is selectively movable between an operating position corresponding to the observation aperture and a non-operating cleaning position away from the observation aperture. Thus, the at least one protective lens can be cleaned, and its transparency can be automatically restored before, after, and during the ongoing process.

[0025] According to another aspect of the present invention, the observation unit includes a selector member rotatably associated with the support assembly, around which the at least one protective lens is mounted. The rotation of the selector member advantageously allows for the automatic positioning of the lens between the working position and the at least one non-working cleaning position based on the ongoing refining process or a program that depends on specific input from an operator.

[0026] According to another aspect of the present invention, at least one cover element may also be mounted around the selector member to cover the observation aperture. Having a cover element that selectively closes the observation aperture makes it possible to prevent the most sensitive components, such as protective lenses, intermediate lenses, and IR telephoto cameras, from being subjected to thermochemical and thermomechanical attacks that can become very aggressive at some stages of the refining process.

[0027] According to another aspect of the present invention, the support assembly includes a pair of plates through which the observation aperture is made, the plates being related to each other and having a shape that defines a hollow space in which the selector member is housed, isolated from the outside. In this way, the selector member, which rotatably supports the at least one protective lens and the at least one cover element, is protected from the ladle environment.

[0028] According to another aspect of the present invention, the observation unit is arranged within the hollow space and includes cleaning means that cooperate with the at least one protective lens when the at least one protective lens is in the at least one non-operating cleaning position. Advantageously, the cleaning means can automatically, quickly and reliably restore the transparency of the at least one measurement lens, if necessary, without interrupting the ongoing process or subsequent processes.

[0029] According to another aspect of the present invention, the control unit has a plurality of commands for the movement of the at least one protective lens in one or more operating modes that depend on the refining process being performed. For this reason, according to the plurality of steps of the process, the at least one protective lens can remain in its position for a predetermined time, be cleaned, or be alternated with at least one cover element.

[0030] According to another aspect of the present invention, the observation unit advantageously includes a plurality of different protective lenses. By having a predetermined number of protective lenses, it is possible to at least extend the life of each protective lens that is used for a more limited period of time.

[0031] According to some embodiments of the present invention, the device is a pot furnace provided with electrodes, and the lid can be arranged in cooperation with the upper aperture and provided corresponding to the through aperture for the electrodes.

[0032] According to some embodiments of the present invention, the device is a vacuum degassing device and includes a vacuum chamber having a container with an upper aperture, in which the pot is arranged, and the lid can be hermetically coupled to the container.

[0033] Some embodiments of the present invention relate to a method for smelting a liquid metal, comprising the steps of preparing a ladle for containing the liquid metal, having an open top and at least one porous plug on its bottom wall; temporarily placing a removable lid on the open top; blowing an inert gas into the ladle through the at least one porous plug via a gas injection line; and controlling at least the gas injection line using a control unit.

[0034] According to one aspect of the present invention, the method includes monitoring the free surface of the liquid metal by means of an observation unit mounted on the lid, wherein at least one infrared telephoto camera connected to the control unit detects and transmits a sequence of thermographic images of the free surface of the liquid metal through at least one protective lens directly facing the open top and an intermediate lens positioned between the at least one infrared telephoto camera and the at least one protective lens.

[0035] According to another aspect of the present invention, the method includes positioning the at least one protective lens alternately between an operating position corresponding to an observation aperture that defines a detection direction in which the at least one infrared telephoto camera and the intermediate lens are also aligned, and a non-operating cleaning position that is away from the observation aperture.

[0036] According to another aspect of the present invention, the method includes positioning a cover element in place of the at least one protective lens at the operating position.

[0037] According to another aspect of the present invention, the method includes positioning each of the plurality of protective lenses alternately between the operating position and the non-operating cleaning position.

[0038] According to another aspect of the present invention, monitoring of the liquid metal on the free surface occurs continuously or discontinuously using the same protective lens. This is particularly advantageous in that the analysis of the thermographic images is more correlated, uniform, and statistically consistent.

[0039] According to one modification, monitoring of the liquid metal on the free surface is performed discontinuously using distinctly distinguished protective lenses. This mode of managing the protective lenses allows for an extension of the service life of the protective lenses themselves and is particularly usable in cases of aggressive environments.

[0040] According to another aspect of the present invention, the control unit executes an identification algorithm in each frame of the sequence of thermographic images to identify at least one exposed region in which the liquid metal is exposed to the surface layer of the slag and a covered region in which the layer of slag completely covers the liquid metal.

[0041] According to another aspect of the present invention, the identification of the at least one exposed region and the covered region is performed by estimating the order of temperature of the regions. Estimating the order of magnitude rather than the exact temperature simplifies the identification algorithm and allows for faster and more efficient analysis.

[0042] According to another aspect of the present invention, the control unit processes both geometric and thermal information on the exposed and covered regions to determine the stirring state of the liquid metal and the gas injection efficiency, and to adjust the gas supply flow rate, and combines the information with the pressure and flow rate values ​​of the gas passing through the at least one porous plug.

[0043] According to another aspect of the present invention, the control unit compares the geometric information and / or thermal information on one or more of the exposed regions and combines these with the pressure and flow rate values ​​of the gas passing through the corresponding porous plug in order to determine the injection efficiency of the porous plug.

[0044] In this way, not only can the process be controlled continuously and instantaneously, but it also becomes possible to program maintenance plans for porous plugs, contributing to a reduction in production costs.

[0045] These and other aspects, features and advantages of the present invention will become apparent from the following description of some embodiments shown as non-limiting examples with reference to the accompanying drawings. [Brief explanation of the drawing]

[0046] [Figure 1] This is a schematic diagram of an apparatus for liquid metal refining according to the present invention. [Figure 2] This is a schematic diagram of another apparatus for liquid metal refining according to the present invention. [Figure 3] These are cross-sectional views of the observation unit present in the apparatus shown in Figures 1 and 2. [Figure 4] These are cross-sectional views of the observation unit present in the apparatus shown in Figures 1 and 2. [Figure 5] These are cross-sectional views of the observation unit present in the apparatus shown in Figures 1 and 2. [Modes for carrying out the invention]

[0047] It is important to clarify that the terminology and reference numerals used herein, as well as the numerals in the accompanying drawings, have the sole function of better illustrating and describing the invention, since the scope of protection is defined by the claims, and that their function is to provide non-limiting examples of the invention itself.

[0048] For ease of understanding, the same reference numerals are used whenever possible to identify identical common elements within the drawings. It should be understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further explanation.

[0049] Referring to Figures 1 and 2, according to the present invention, the apparatus 10 for refining liquid metal L contained in a ladle 11 can typically be used to remove inclusions and impurities from the liquid metal L and to insert alloying elements to obtain a desired chemical composition.

[0050] The ladle 11 is a bucket-shaped container lined with refractory material, and is configured to contain liquid metal L produced in a furnace such as an electric arc furnace (EAF), and to transport it to a downstream ladle furnace 10b (see Figure 2) and possibly a vacuum degassing unit 10a (see Figure 1) for refining, and finally to be sent to continuous casting.

[0051] The ladle 11 is provided with an open top 12 and at least one porous plug 13 (usually two or three) that penetrates the bottom wall 14 of the ladle 11, and preferably an inert gas is blown through it to determine the agitation of the contained liquid metal L.

[0052] The liquid metal L in the ladle 11 is covered with a layer of slag S that protects the metal bath during the refining process up to continuous casting, and at the end of continuous casting, the layer of slag S remains at the bottom of the ladle 11 and is subsequently removed.

[0053] The performance of at least one porous plug 13 is monitored through a sensor 15 capable of detecting the flow rate and / or pressure value of the gas flow passing through at least one porous plug 13.

[0054] The porous plug 13 has a structure that allows pressurized gas to pass from the outside towards the inside of the ladle 11, but prevents leakage of the liquid metal L.

[0055] Those skilled in the art will understand that, as an alternative to the porous plug 13, a lance, nozzle, or other distributing element capable of blowing gas into a bath of liquid metal L to determine its agitation can be provided.

[0056] Referring to Figures 1 and 2, the ladle 11 preferably comprises two porous plugs 13 positioned at dispersed locations relative to the center of the bottom wall 14. In this case, each porous plug 13 is preferably monitored by a separate and independent sensor 15.

[0057] In other embodiments, the number of porous plugs 13 is generally two or three, but may be more or fewer.

[0058] The apparatus 10 is either a vacuum degassing apparatus 10a (see Figure 1) or a ladle furnace 10b (see Figure 2). In the following description, elements common to both embodiments will be given the same reference numerals.

[0059] Referring to Figure 1, the vacuum degassing apparatus 10a is formed by a vacuum chamber 16 having a container 17 with an upper aperture 18 in which a ladle 11 is placed, and a lid 19 that can be airtightly connected to the container 17.

[0060] The vacuum degassing apparatus 10a comprises, or is connected to, a vacuum pump system 20, which typically consists of a mechanical pump or a vapor ejector.

[0061] The vacuum degassing device 10a also includes a gas injection line 21 configured to supply, preferably, an inert gas to at least one porous plug 13. If there are two porous plugs 13, the gas injection line 21 can branch into two independent segments along which sensors 15 are located.

[0062] Referring to Figure 2, the ladle furnace 10b comprises a lid 23 positioned to cover the open upper part 12 of the ladle 11 and provided with one or more through-apers 24, a support structure 25 having electrodes 26 that can be moved through the through-apers to be housed inside the ladle 11, and its own gas injection line 21 having the above-described features.

[0063] The apparatus 10 also includes a control unit 27 configured to control the operation of the apparatus 10, whether it is a vacuum degassing apparatus 10a or a ladle furnace 10b.

[0064] The control unit 27 is operably connected to the gas injection line 21, the sensor 15, the vacuum pump system 20 (in the case of the vacuum degassing device 10a), and the moving means of the support structure 25 (in the case of the ladle furnace 10b). The apparatus 10 also includes a series of additional sensors and measuring instruments used to control the refining process, which are not described or illustrated herein.

[0065] The device 10 also includes an infrared observation unit 30 associated with the covers 19, 23 which are operably connected to the control unit 27.

[0066] The observation unit 30 is installed on top of the lids 19 and 23. Preferably, the observation unit 30 is installed in accordance with a structure or opening that is pre-fabricated, already provided but not in use, used for maintenance and / or inspection purposes, or temporarily created.

[0067] Referring to Figures 3 to 5, the observation unit 30 is connected to the control unit 27 and comprises a support assembly 31 associated with at least one IR telephoto camera 32 that detects and transmits a series of thermographic images of the free surface of the liquid metal L, at least one protective lens 33 that faces directly the open top 12 of the ladle 11, in particular the free surface of the liquid metal L, during use, and an intermediate lens 34 positioned between the IR telephoto camera 32 and the protective lens 33.

[0068] At least one protective lens 33 and intermediate lens 34 feature a specific transparency index, allowing the IR telephoto camera 32 to observe the free surface of the liquid metal L as clearly as possible.

[0069] The "free surface" of the liquid metal L refers to the surface of the bath of liquid metal L contained in the ladle 11, which may be defined by the surface layer of slag S, or it may be defined by the region of liquid metal L that escapes from the layer of slag S due to agitation generated by the blown gas.

[0070] The protective lens 33 and the intermediate lens 34 are preferably not part of the IR telephoto camera 32, that is, they are separate and independent components both with respect to the IR telephoto camera 32 and to each other.

[0071] The IR telephoto camera 32 is a thermal telephoto camera or an infrared thermal imaging camera. In one modification, an optical telephoto camera may be provided in addition to the IR telephoto camera 32.

[0072] The support assembly 31 is formed by a pair of plates 35, 36 that are related to each other and are shaped to define a hollow space 37 in which at least one protective lens 33 is housed.

[0073] Plates 35 and 36 have a substantially circular planar shape. However, those skilled in the art should understand that the shape of plates 35 and 36 is not limited to the circular shape shown in Figures 3 to 5.

[0074] The pair of plates 35 and 36 consists of a first plate, or upper plate 35, and a second plate, or lower plate 36, and when in use, it faces the ladle 11, in particular the open upper part 12.

[0075] The hollow space 37 is defined by the inner lower surface 35a of the upper plate 35 and the inner upper surface 36a of the lower plate 36, respectively, and laterally by the inner circumferential surfaces of one or the other plate 35,36.

[0076] In the examples shown in Figures 3 to 5, the inner circumferential surface is the inner circumferential surface 36c of the lower plate 36.

[0077] The upper plate 35 and the lower plate 36 are preferably removably joined to each other by known types of connecting elements such as bolts, pins, or tabs.

[0078] An observation aperture 38 is created on the support assembly 31 that passes through both plates 35 and 36 along the axis or along the detection direction X.

[0079] The detection direction X is preferably perpendicular to the plates 35 and 36, particularly their upper and lower surfaces.

[0080] The observation aperture 38 is preferably formed in the peripheral region of plates 35 and 36 with respect to the central point of plates 35 and 36.

[0081] The element 51, which is attached to the lower plate 36, can be associated with the observation aperture 38. The element 51 is substantially conical and preferably has a narrowest portion that is positioned in correspondence with the observation aperture 38.

[0082] The IR telephoto camera 32 is mounted on the upper plate 35 in accordance with the observation aperture 38. The IR telephoto camera 32 is mounted on the upper plate 35 in accordance with the external upper surface 35b, which is opposite the internal lower surface 35a.

[0083] Optionally, the connecting flange, which is part of the support assembly 31, may be located between the upper plate 35 and the IR telephoto camera 32.

[0084] The observation unit 30 may include a shell 39 in which an IR telephoto camera 32 is housed. The shell 39 fully accommodates the IR telephoto camera 32 and is optionally detachably connected to an upper plate 35 via means of a connecting flange.

[0085] The shell 39 can be advantageously defined by channels, tubes, coils, or other similar elements and may be equipped with cooling means 40 through which a cooled fluid, such as water, air, or air mist, flows.

[0086] The lens of the IR telephoto camera 32 can be equipped with its own compressed air and / or inert gas cooling and cleaning system.

[0087] A seat portion 41 is formed on the cross-section of the observation aperture 38 to accommodate the intermediate lens 34.

[0088] The intermediate lens 34 can be held in place by a blocking ring and gasket, or other similar temporary retaining elements.

[0089] The seat portion 41 is preferably formed on the upper plate 35. This simplifies maintenance and replacement of the intermediate lens 34 because the upper plate 35 is more accessible than the lower plate 36. Alternatively, the seat portion 41 can also be formed on the lower plate 36.

[0090] The observation unit 30 includes a selector member 42 with at least one protective lens 33 attached to its periphery. The selector member 42 is housed within a hollow space 37.

[0091] At least one protective lens 33 can be selectively positioned between an operating position corresponding to the observation aperture 38 and at least one non-operating position that is away from the observation aperture 38. Such a non-operating position can be a cleaning or parking non-operating position.

[0092] According to some embodiments, a plurality of protective lenses 33, specifically N different protective lenses 33, are mounted around the selector member 42. The number N of protective lenses 33 may range from 1 to 20, for example, 12.

[0093] In this case, one of the protective lenses 33 can be positioned in the operating position, and at least one of the other protective lenses 33 is in a cleaning or parking non-operating position.

[0094] According to possible embodiments, at least one cover element 43 can be mounted around the selector member 42 to selectively cover the observation aperture 38. The cover element 43 can be made of a metallic material (e.g., steel), such as a lens, disc, or plate. Alternatively, the cover element 43 may be defined by a physical part of the selector disc 46.

[0095] The cover element 43 is configured to protect the intermediate lens 34 by acting as a physical barrier during the most critical stages of the refining process when positioned in the operational location. More specifically, the cover element 43 protects the intermediate lens 34 and the IR telephoto camera 32 from the combined action of slag and liquid metal L splatter, which causes very aggressive thermochemical and thermomechanical attacks during several stages of the refining process.

[0096] The selector member 42 is rotatably associated with the support assembly 31 by a drive shaft 44 that passes through the upper plate 35 and is operably connected to the drive member 45. In other words, the selector member 42 is a rotating carousel to which a protective lens 33 and at least one cover element 43 are attached.

[0097] The drive shaft 44 has a rotation axis R that is substantially parallel to the detection axis X.

[0098] The drive member 45 is part of the observation unit 30 and is preferably attached to the upper plate 35.

[0099] The drive member 45 is connected to the control unit 27 to transmit the angular position of the selector member 42 and to receive command signals to rotate the selector member 42, for example, by means of an encoder.

[0100] The selector member 42 includes a selector disc 46, which has at least one housing 47 that passes through the body of the selector disc 46 and is adapted to house at least one protective lens 33.

[0101] The selector member 42 may also include at least one additional housing 47 designed to accommodate at least one cover element 43.

[0102] Referring to Figure 4, the selector disc 46 is provided with multiple housings 47 that support and house separate protective lenses 33.

[0103] Advantageously, the number of housings 47 provided on the selector disc 46 is equal to the sum of the number of protective lenses 33 and the number of cover elements 43.

[0104] According to one possible embodiment, the housings 47 can be arranged in a continuous manner with respect to a circular configuration.

[0105] The housings 47 can be arranged at equal angular intervals, or they can be created at uneven angular distances.

[0106] According to possible modifications, the protective lens 33 may be single and have an annular shape defined by two concentric circles of different radii to form a transparent protective strip. Alternatively, multiple protective lenses 33, for example having a circular shape, may be incorporated into a single annular component. The housing 47 has a corresponding annular shape.

[0107] The selector disc 46 is keyed to the drive shaft 44 and rotated around the rotation axis R in such a way that at least one protective lens 33 is positioned in an operational position, i.e., a position corresponding to the observation aperture 38. Thus, the protective lens 33 is aligned with both the intermediate lens 34 and the IR telephoto camera 32 in the detection direction X and faces the open top 12 of the ladle 11 through the observation aperture 38.

[0108] If there are multiple protective lenses 33, each can be positioned in the operating position at the same time. The other protective lenses 33 are in corresponding non-operating positions within the hollow space 37 and are shielded from the ladle environment by a lower plate 36 that acts as a protective barrier.

[0109] The selector disk 46 can also be rotated to position at least one cover element 43 in a working position that covers the observation aperture 38.

[0110] The observation unit 30 is located within a hollow space 37 and includes a cleaning means 48 that cooperates with at least one protective lens 33 when at least one protective lens 33 is in at least one non-operational cleaning position.

[0111] The cleaning means 48 faces at least one protective lens 33 to mechanically remove any metal particles and slag that may have accumulated on the surface of at least one protective lens 33 and to restore at least some of its transparency.

[0112] If the observation unit 30 has multiple separate protective lenses 33, the cleaning means 48 alternately interferes with each protective lens 33 while moving to a non-operational cleaning position.

[0113] The cleaning means 48 is attached to the lower plate 36 at a position different from the position where the observation aperture 38 is provided. In one embodiment, the cleaning means 48 may be positioned directly opposite the observation aperture 38.

[0114] Referring to Figures 3 and 5, the mounting aperture 49 is created through the lower plate 36 to position the cleaning means 48 which is attached to the support plate 50.

[0115] The support plate 50 is removably secured to the lower plate 36 by known types of connecting elements such as bolts, pins, tabs, grippers, and clamps.

[0116] According to another embodiment, the cleaning means 48 can be directly attached to the inner upper surface 36a of the lower plate 36.

[0117] The cleaning means 48 is basically composed of a brush element consisting of a support to which a metal wire is attached. The relative movement between at least one protective lens 33 and the metal wire allows for determining a rubbing action to clean at least one protective lens 33.

[0118] In one modified example, the cleaning means 48 may also include, or may only include, a spray element configured to inject a fluid, liquid, gas, or two-phase fluid by pressure applied to at least one protective lens 33.

[0119] Cleaning of at least one protective lens 33 can be achieved by rotating the selector disc 46 clockwise and / or counterclockwise a certain number of times around the rotation axis R.

[0120] Cleaning can be performed on a single protective lens 33 or on all protective lenses 33. The rotation speed for cleaning all protective lenses 33 or each individual protective lens 33 is a controllable parameter managed by the control unit 27 based on the ongoing refining process or specific input from the operator.

[0121] The positioning of at least one protective lens 33 is performed according to one or more operational logics that depend on a particular application, namely whether it is a vacuum degassing unit 10a or a ladle furnace 10b, or a particular step in the refining process being carried out in the vacuum degassing unit 10a or the ladle furnace 10b.

[0122] These operational logics can be stored within the control unit 27.

[0123] In the first operating mode, the same protective lens 33 is used throughout the smelting process performed in the same ladle 11. This protective lens 33 can be maintained in the operating position throughout all steps of the smelting process (continuous detection), or it can be periodically cleaned and returned to the operating position (interval detection). This first operating mode is advantageous in that it can uniformly detect the thermal image sequence of the free surface of the liquid metal L. In fact, the fact that using the same protective lens 33 prevents "noise" from occurring in the analysis of the thermal image sequence will be explained in more detail below.

[0124] According to the second operating mode, the observation unit 30 is equipped with a plurality of individual protective lenses 33, and each protective lens 33 is sequentially moved to an operating position while the smelting process is being carried out on the same ladle 11. In this case, at least two protective lenses 33 alternately move between an operating position and a non-operating position, which may be a parking position or a cleaning position.

[0125] A complete or partial washing cycle can be provided before, after, or during one or more steps of the purification process.

[0126] Referring to Figures 1 and 2, the observation unit 30 is mounted on the lids 19 and 23 in such a position that the IR telephoto camera 32 can at least frame the area of ​​the free surface of the liquid metal L above the corresponding area of ​​the bottom wall 14 of the ladle 11 where at least one porous plug 13 is present.

[0127] Advantageously, the IR telephoto camera 32 can capture the entire free surface of the liquid metal L within the frame.

[0128] The IR telephoto camera 32 can detect and measure at least one temperature value for at least one point, set of points, or region contained in each frame of the thermographic image sequence. By "point," we mean a single pixel in one image within the image sequence.

[0129] The correct detection of the sequence of thermographic images by the IR telephoto camera 32 is, firstly, due to the presence of a dual lens, namely a protective lens 33 and an intermediate lens 34, and secondly, due to the presence of a selector member 42 that allows for the efficient maintenance of the protective lens 33 by moving at least one of the protective lenses 33 according to the aforementioned operating mode or according to other operating modes provided for a particular refining process.

[0130] The control unit 27 comprises an internal storage module 27a, a processor 27b, and a communication module 27c. As an alternative modification, the control unit 27 can connect to one or more external databases.

[0131] The recognition algorithm ALG, installed in the memory module 27a and executed by the processor 27b, can identify, in each frame of a sequence of thermographic images, an exposed region A where the liquid metal L is exposed to the slag layer S, known to those skilled in the art as the "open eye," and a covered region B where the slag layer S completely covers the underlying liquid metal L.

[0132] Exposed area A can be detected because it emits different radiation than covered area B. For example, the radiation can differ when the temperature is different but the emissivity is the same, when the temperature is the same but the emissivity is different, and when both the temperature and emissivity are different.

[0133] If there are two porous plugs 13, two separate exposed regions A may be visible. In some cases, the two separate exposed regions A may intersect and merge into one larger region, but in either case, its contour can be defined and traced by one or the other porous plug 13.

[0134] Exposed region A is a thermal hotspot region, and covered region B is a thermal coldspot region. For example, exposed region A can be characterized by temperatures in the range of approximately 1500°C, and covered region B can be characterized by temperatures in the range of approximately 1000°C to 1100°C.

[0135] The ALG identification algorithm can distinguish at least exposed region A and covered region B by estimating the order of temperature in regions A and B. In fact, in applications of the present invention, it is not necessary to obtain precise values; it is sufficient to know that the temperature of exposed region A is approximately 600-800°C higher than that of covered region B.

[0136] The exposed area A formed on top of each of the porous plugs 13 provided in the ladle 11 is determined by the flow rate of the blown gas, and it is possible that a higher (lower) pressure and / or flow rate of the blown gas will result in a larger (smaller) exposed area A.

[0137] The thermographic image sequence detected by the IR telephoto camera 32 is transmitted to the control unit 27 and processed so as to generate both thermal information, such as the temperature and / or emissivity of the exposed area A and the covered area B, along with geometric information, such as the surface size of at least one exposed area A and the covered area B.

[0138] The surface size and temperature of at least one exposed region A are directly correlated with the pressure and / or injection flow rate of the inert gas passing through at least one porous plug 13.

[0139] Measurements of the injection pressure and flow rate of the inert gas can be stored in a database contained in the memory module 27a.

[0140] The control unit 27 can determine the stirring state of the liquid metal in the ladle 11 and the efficiency of gas injection by combining the information obtained by processing a series of thermographic images detected by the IR telephoto camera 32 with the aforementioned pressure and flow rate values.

[0141] The control unit 27 can also use hierarchically recorded flow rate and pressure values ​​related to previous processes in combination with the thermographic measurements performed.

[0142] The information generated by the control unit 27 is converted by means of the communication module 27c into corresponding control signals that are sent to components of the apparatus 10 to control the ongoing process. These components include the vacuum pump system 20, the gas injection line 21, the electrode 26, and one or more other components of the apparatus 10 that are not described or illustrated herein.

[0143] Multiple control signals may include, for example, one control signal for controlling the position of electrode 26, the power of electrode 26 (in the case of ladle furnace 10b), or the pressure / depressurization of vacuum chamber 16 (in the case of vacuum degassing device 10a), and the injection pressure and flow rate of gas through at least one porous plug 13 (in the case of ladle furnace 10b and vacuum degassing device 10a).

[0144] This allows for control of the stirring of the liquid metal L contained in the ladle 11 and instantaneous evaluation of the operating state of at least one porous plug 13. This enables automatic optimization of the stirring of the liquid metal L and control of its operation based on the current state of at least one porous plug 13. Furthermore, it becomes possible to program a predictive maintenance plan for one or more porous plugs 13, contributing to a reduction in production costs.

[0145] It is evident that modifications and / or additions to parts of the apparatus 10 and the method described above can be made without departing from the field and scope of the invention as defined in the claims.

[0146] Although the present invention has been described with reference to several specific examples, it will also be apparent to those skilled in the art that many other equivalent forms of apparatus and methods for refining liquid metals can be reliably realized, having the features described in the claims and therefore being entirely within the protected field defined by the claims.

[0147] In the following claims, the sole purpose of the references in parentheses is for readability and should not be considered as limiting factors relating to the field of protection defined by the same claims.

Claims

1. Apparatus (10) for refining liquid metal (L), A ladle (11) for containing the liquid metal (L) comprises an open top (12) and at least one porous plug (13) on its bottom wall (14), Removable lids (19, 23), A gas injection line (21) connected to the at least one porous plug (13), Includes a control unit (27), An observation unit (30) is attached to the aforementioned lid (19, 23), At least one infrared telephoto camera (32) connected to the control unit (27) to detect and transmit a sequence of thermographic images of the free surface of the liquid metal (L), At least one protective lens (33) that directly faces the open upper part (12), Apparatus (10) comprising an observation unit (30) having an intermediate lens (34) positioned between the at least one infrared telephoto camera (32) and the at least one protective lens (33), and a support assembly (31) associated therewith.

2. The apparatus (10) according to claim 1, characterized in that an observation aperture (38) is created on the support assembly (31) which defines a detection direction (X) in which the at least one infrared telephoto camera (32), the intermediate lens (34), and in any case the at least one protective lens (33) are aligned.

3. The apparatus (10) according to claim 2, characterized in that the at least one protective lens (33) is selectively movable between an operating position corresponding to the observation aperture (38) and a non-operating cleaning position that is moved away from the observation aperture (38).

4. The apparatus (10) according to any one of claims 1 to 3, wherein the observation unit (30) is rotatably associated with the support assembly (31) and includes a selector member (42) on which the at least one protective lens (33) is mounted.

5. The apparatus (10) according to claim 4, characterized in that at least one cover element (43) is also attached around the selector member (42) so as to cover the observation aperture (38).

6. The apparatus (10) according to claim 4 or 5, wherein the support assembly (31) includes a pair of plates (35, 36) through which the observation aperture (38) is made, the plates being related to each other and having a shape that defines a hollow space (37) in which the selector member (42) is housed, isolated from the outside.

7. The apparatus (10) according to claim 6, wherein the observation unit (30) is disposed within the hollow space (37) and includes cleaning means (48) that cooperate with the at least one protective lens (33) when the at least one protective lens (33) is in the at least one non-operational cleaning position.

8. The apparatus (10) according to any one of claims 1 to 7, wherein the control unit (27) has a plurality of commands for the movement of the at least one protective lens (33) in one or more operating modes depending on the refining process being performed.

9. The apparatus (10) according to any one of claims 1 to 8, characterized in that the observation unit (30) includes a plurality of different protective lenses (33).

10. The apparatus (10) is a ladle furnace (10b) equipped with electrodes (26), The cover (23) is characterized in that it is arranged in cooperation with the upper aperture (12) and is provided corresponding to the through aperture (24) for the electrode (26), The apparatus (10) according to claim 1.

11. The aforementioned apparatus (10) is a vacuum degassing apparatus (10a), A vacuum chamber (16) having a container (17) with an upper aperture (18), wherein the ladle (11) is placed inside the vacuum chamber (16) and the lid (19) can be airtightly coupled to the container (17), characterized in that The apparatus (10) according to claim 1.

12. A method for refining liquid metal (L), A ladle (11) for containing the liquid metal (L) is prepared, comprising an open top (12) and at least one porous plug (13) on its bottom wall (14). A removable cover (19, 23) is temporarily placed on the open upper part (12). The gas injection line (21) blows an inert gas into the ladle (11) through the at least one porous plug (13), This includes controlling at least the gas injection line (21) using a control unit (27), The method includes monitoring the free surface of the liquid metal (L) by means of an observation unit (30) mounted on the lid (19, 23), A method characterized in that at least one infrared telephoto camera (32) connected to the control unit (27) detects and transmits a sequence of thermographic images of the free surface of the liquid metal (L) through at least one protective lens (33) directly facing the open top (12) and an intermediate lens (34) positioned between the at least one infrared telephoto camera (32) and the at least one protective lens (33).

13. The method according to claim 12, characterized in that the at least one protective lens (33) is alternately positioned between an operating position corresponding to an observation aperture (38) that defines a detection direction (X) in which the at least one infrared telephoto camera (32) and the intermediate lens (34) are also aligned, and a non-operating cleaning position that is away from the observation aperture (38).

14. The method according to claim 13, characterized in that a cover element (43) is placed in the operating position instead of the at least one protective lens (33).

15. The method according to claim 13 or claim 14, wherein each of the plurality of protective lenses (33) is alternately positioned between the operating position and the non-operating cleaning position.

16. The method according to any one of claims 12 to 15, characterized in that monitoring of the liquid metal (L) on the free surface occurs continuously or discontinuously using the same protective lens (33).

17. The method according to any one of claims 12 to 15, characterized in that monitoring of the liquid metal (L) on the free surface occurs discontinuously using differently distinguished protective lenses (33).

18. The method according to any one of claims 12 to 17, characterized in that the control unit (27) executes a recognition algorithm (ALG) in each frame of the sequence of the thermographic image to identify at least one exposed region (A) in which the liquid metal (L) is exposed to the surface layer of the slag (S) and a covered region (B) in which the layer of the slag (S) completely covers the liquid metal (L).

19. The method according to claim 18, characterized in that the identification of the at least one exposed region (A) and the covered region (B) is performed by estimating the temperature order of the regions (A, B).

20. The method according to claim 18 or 19, characterized in that the control unit (27) processes both geometric information and thermal information on the exposed area (A) and the covered area (B) in order to determine the stirring state of the liquid metal (L) and the injection efficiency of the gas, and to adjust the supply flow rate of the gas, and combines the information with the pressure and flow rate values ​​of the gas passing through the at least one porous plug (13).

21. The method according to claim 12, characterized in that the control unit (27) compares the geometric information and / or the thermal information on one or more of the exposed regions (A) to determine the injection efficiency of the porous plug (13), and combines these with the pressure and flow rate values ​​of the gas passing through the corresponding porous plug (13).

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