Intermediate pouring device (embodiments)

Abstract

FIELD: metallurgy.SUBSTANCE: intermediate pouring device comprises a metal flask with a refractory ceramic trough (2) placed inside it. The trough (2) comprises one or at least two isolated channels (3), in each of which at least two filter elements (4, 5) are installed in series, which are foam ceramic filters. At least one drain cup (7) is installed at the bottom of the trough. The trough is made curved at an angle of 80-100°, which allows to increase the filtration efficiency by reducing the melt speed in front of the second filter and to reduce the dirt load on it. The bottom of the trough is made with a slope of 0.5-5° in the direction of melt flow, which ensures optimal melt flow rate. The filter elements are installed at an angle of 45-135° to the horizontal axis of the device, which allows increasing the area of their surfaces in contact with the melt and preventing premature flow cessation due to clogging of the filter cells.EFFECT: quality of the resulting parts is improved by increasing the purity of the melt in terms of non-metallic inclusions.10 cl, 4 dwg

Description

[0001] The invention relates to the field of metallurgy, namely, to the production of heat-resistant and corrosion-resistant alloys and steels by induction melting in crucible furnaces, in particular, to an intermediate pouring device designed to receive the melt from a melting crucible or ladle during melt pouring, filter it from non-metallic inclusions, and supply the melt to a casting mold. The invention can be used for the manufacture of charge blanks, ingots, shaped castings, blanks for obtaining powders (granules) intended for the subsequent production of gas turbine engine parts by casting methods (blades with polycrystalline, directional and single-crystal structure, flaps, swirl devices, diffusers and other castings), metal pressure processing (disks, shafts, welded housings, sheets, etc.), additive technologies, and granule production technologies.

[0002] Metallurgical and procurement technologies are closely linked, forming a sequential production cycle. Metallurgical technologies are the first stage, the purpose of which is to obtain an alloy of a given chemical composition with a minimum impurity content and high purity of non-metallic inclusions from the initial charge materials (pure metals, master alloys, ferroalloys, and scrap). The alloy is most often produced as charge blanks or ingots, the shape and size of which are determined by the requirements of a specific procurement technology. Induction melting in crucible furnaces produces a wide range of alloys, from mass-produced to specialty alloys. For example, vacuum induction furnaces are used to smelt high-alloy and chemically active alloys, including heat-resistant and corrosion-resistant nickel and cobalt alloys, special steels (high-alloy stainless steel, high-speed tool steel, bearing steel, etc.), high-purity aluminum alloys, and others.Carbon and low-alloy steels, cast irons, aluminum and copper alloys are smelted in open induction furnaces.

[0003] To melt an alloy, the charge materials are loaded into the crucible of an induction furnace and a current is applied to the inductor, creating a magnetic field inside the inductor. The magnetic field creates eddy currents in the charge materials, causing them to heat up and melt.

[0004] When melting in open induction furnaces, slag-forming materials are added to the crucible. Their composition depends on the chemical composition of the alloy being smelted. Slag-forming materials protect the melt from contact with atmospheric oxygen, preventing oxidation. For example, for steel smelting, lime, fluorspar, and magnesite are most often used. They are added after the melt appears but before the charge is completely melted. Before alloying and deoxidation, the primary slag is removed to prevent rephosphorization, and a new slag is added.

[0005] In the production of high-quality and special steels (stainless, tool, heat-resistant), secondary metallurgy is widely used after induction melting to ensure ultra-low sulfur, phosphorus, nitrogen, and oxygen contents and to remove non-metallic inclusions from the melt. Various secondary metallurgy methods are used for this purpose, including inert gas purging, vacuum treatment, and synthetic slag treatment. Depending on the steel's intended use, either a full range of these methods or a combination of several may be used. Secondary metallurgy is performed in steel-pouring ladles, where the melt is poured from the crucible of an induction furnace.

[0006] The smelting of critical alloys, such as heat-resistant and corrosion-resistant nickel and cobalt alloys, is carried out in vacuum induction furnaces. Melting (from loading the charge materials to pouring the melt into molds and solidifying the metal) is carried out in a vacuum with continuous operation of vacuum pumps. Slag and secondary melt processing are not used.

[0007] However, when smelting high-purity steels in vacuum induction furnaces, such as low-carbon and carbon-free steels, high-strength structural and corrosion-resistant steels, slags can also be used to improve the efficiency of refining the melt from sulfur, oxygen, and reduce the content of non-metallic inclusions.

[0008] Pouring of the melt into casting molds, such as ingot molds, can be carried out either directly from the crucible, or the melt can first be poured into a tundish for its secondary treatment and / or transport of the melt to the mold installation location and subsequent pouring from the ladle.

[0009] Pouring of alloys smelted in open induction furnaces can be carried out both in air and in an inert environment.

[0010] Preparation technologies (casting, pressure processing, powder metallurgy, additive manufacturing, granule production technologies, and combined methods) are the next stage of the production cycle and ensure the production of semi-finished products (castings, stampings, products manufactured using additive technologies, granule metallurgy, etc.) of the required shape and size, as close as possible to the finished product, from raw material blanks or ingots. In some cases, semi-finished products must also meet certain additional requirements, such as having a specified macrostructure and a limited number and size of maximum permissible defects in the form of non-metallic inclusions, detected by visual inspection and non-destructive testing methods (luminescence method (LUM), X-ray testing, and ultrasonic testing).

[0011] Casting technologies involve loading a charge (the required alloy grade) into a melting crucible, most often in the form of a charge blank of a specified mass, heating and melting it, superheating it above the liquidus temperature and holding the melt at this temperature for a specified time, bringing the melt to the specified temperature, and pouring the melt into a mold. Solidification of the melt and formation of the casting occurs in the mold. If necessary, pouring into molds can be accomplished using a spout, kettle (siphon) ladle, or a stopper ladle.

[0012] Remelting is typically performed in open or vacuum induction melting and pouring furnaces. Similar to melting alloys in metallurgical induction furnaces, remelting can be performed either in air with the use of slag or in a vacuum, with or without the use of slag. Casting can be performed in a vacuum, in a protective atmosphere, or in air.

[0013] When smelting alloys in induction furnaces, after melting the charge materials, the molten metal is typically subjected to high-temperature refining, heating it to 150-300°C above the liquidus temperature of the alloy and holding it at this temperature to remove impurities of oxygen, nitrogen, and some non-ferrous metals. During charge melting and high-temperature refining, most of the gases introduced with the charge—hydrogen, oxygen, and nitrogen—are removed from the melt. However, the oxygen and nitrogen content of the melt may remain elevated even after high-temperature refining, especially when waste is used as charge materials. To reduce the oxygen content, active elements with a high affinity for oxygen, such as carbon, aluminum, calcium, magnesium, cerium, lanthanum, and others, can be added to the melt.Some elements can simultaneously act as alloying elements (carbon, aluminum), microalloying elements (cerium, lanthanum), or refining additives (calcium, magnesium). As a result, oxygen dissolved in the melt reacts with these elements, forming oxides. Of all the elements listed above, only carbon forms gaseous oxides (CO or CO2), which are removed from the melt; the remaining elements form solid or liquid oxides that remain in the melt.

[0014] Some of the listed elements are complex refining additives. For example, cerium, lanthanum, and magnesium are also effective desulfurizers, binding sulfur dissolved in the melt into solid refractory compounds, thereby minimizing the negative impact of sulfur on the mechanical properties of alloys.

[0015] It should also be noted that during prolonged holding of the melt in a ceramic crucible, especially at high temperatures, interaction of the active elements included in the melted alloy with the crucible material may occur, as a result of which the alloy may be additionally contaminated with non-metallic inclusions, as well as elements restored from the lining (silicon, aluminum, etc.) (Voskoboinikov V.G., Kudrin V.A., Yakushev A.M. General metallurgy: textbook for universities / 6th ed. revised and enlarged. - M .: ITC "Akademkniga", 2002).

[0016] One of the most important requirements for steels, heat-resistant and corrosion-resistant alloys based on nickel, cobalt, and iron is high purity in terms of the content of harmful impurities, primarily oxygen, nitrogen, and sulfur.

[0017] For example, in nickel-based alloys, sulfur is present in compounds with alloying elements, which can be located both at grain boundaries and within grains. Under high temperature and stress conditions, sulfur accelerates the coagulation of the strengthening γ'-phase, leading to a reduction in the long-term strength, ductility, and fatigue.

[0018] Nitrogen in heat-resistant alloys forms nitrides and carbonitrides, which act as stress concentrators and a source of crack initiation, thereby reducing the ultimate tensile strength, ductility, and strength. In wrought alloys, these precipitates lead to a decrease in process ductility and cracking of the material during deformation.

[0019] Oxygen in steels and heat-resistant alloys forms non-metallic inclusions in the form of oxides with the active components of the alloy, which are sources of crack initiation and reduce the mechanical properties and service life of parts made from such alloys.

[0020] Thus, the search for effective technological solutions aimed at removing non-metallic inclusions (oxide, nitride, sulfide, etc.) from alloys, formed during the neutralization of harmful impurities, as well as those introduced with charge materials, is an extremely pressing issue. Reducing the content of non-metallic inclusions in both charge blanks and castings improves the mechanical and other properties of parts produced from alloys.

[0021] One of the effective ways to reduce the contamination of alloys with non-metallic inclusions is to filter the melts during their pouring into molds through porous ceramic filters.

[0022] Traditional methods of removing inclusions from melts, such as the use of slag collectors, do not always ensure the production of inclusion-free products, especially when using waste.

[0023] In recent decades, highly porous ceramics made of refractory oxides, such as aluminum, magnesium, and zirconium oxides, have been widely used to filter molten metals. These ceramics exhibit high chemical inertness to molten metals, as well as strength and thermal stability. The ceramic structure is a spatial framework with open porosity, with pore cells ranging in size from 2 to 5 mm. This multidimensional pore structure, unlike the one-dimensional channels of pressed and extruded filters, ensures a tortuous flow of molten metal, significantly increasing filtration capacity. Labyrinth pores initially retain large non-metallic inclusions exceeding the pore diameter, which settle on the filter surface and form a layer of inclusions in front of the filter, which begins to retain inclusions of smaller sizes (V.G. Babashov, N.M. Varrik, T.A. Karaseva. POROUS CERAMICS FOR FILTRATION OF METAL MELTS AND HOT GASES (review).Scientific and technical journal "TRUDY VIAM", No. 8.2020).

[0024] Most often, inclusions in steels and heat-resistant alloys are oxide inclusions and films. Inclusions can range in size from a few to hundreds of microns (µm), while oxide films can reach several millimeters. Even inclusions of a few microns in size prevent the production of thin parts under high deformation rates.

[0025] In addition to their filtering effect, foamed ceramic filters improve melt flowability. It has been noted that passing through a foam ceramic filter (FCF) reduces the content of gases dissolved in the melt, which also positively impacts the alloy's properties. Furthermore, when pouring the melt in air, foam ceramic filters help prevent the formation of secondary oxides by reducing the turbulence of the flow passing through the filter. Pouring turbulence must be reduced when casting any alloys, and especially when casting alloys prone to oxidation. When pouring in air, turbulence promotes air entrapment, which leads to the formation and growth of oxide inclusions in the melt due to the interaction of the alloy's active components with air.A ceramic foam filter reduces the flow rate by repeatedly changing the direction of melt flow within the filter pores, which helps entrapped air escape from the melt (Master's thesis "Aluminum Melt Filtration Unit with a Capacity of 20 to 45 Tons per Hour with Combined Heating." K.A. Baykova. Federal State Autonomous Educational Institution of Higher Professional Education "SIBERIAN FEDERAL UNIVERSITY." Polytechnic Institute of Electrical Engineering and Electrotechnology. 2016). The use of ceramic foam filters also significantly reduces turbulence and melt flow rate during casting. This ensures a laminar flow of the melt in the filter pores, which prevents the metal flow from washing away non-metallic inclusions deposited on the filter surface into the casting (MECHANISM OF REMOVING SULFUR AND PHOSPHORUS FROM U8 STEEL BY FILTRATION OF THE MELT THROUGH FOAM CERAMICS. E.A. Stoyakina, A.G.Degtyareva. Polytechnic youth magazine. 2017. No. 12).

[0026] A pouring ladle for receiving and filtering molten metals is known. It has an opening at the bottom for draining the melt after passing through a filtering device. A removable ceramic filter is installed across virtually the entire surface of the ladle. It is positioned horizontally, with its through-holes oriented primarily vertically, coinciding with the direction of melt flow through the ladle (EP 0726115 A1, 14.08.1996). Such pouring ladles, also known as crucible ladles, are used in both continuous and intermittent pouring of molten metal. It is known that such ladles can be used to remove non-metallic inclusions, particularly slag, from the melt. According to the invention, the horizontally positioned filter provides a larger effective surface area.Furthermore, according to the invention, the filter has passage openings arranged predominantly vertically, which corresponds to the direction of melt flow, allowing the molten metal to pass through the filter more quickly under the force of gravity. Thus, the invention allows for very rapid filtration in the pouring ladle, eliminating the relatively long settling time of the molten metal in the ladle.

[0027] A disadvantage of this solution is the relatively high contamination of the finished metal with non-metallic inclusions. The high melt velocity in the filter allows for filtration of only large non-metallic inclusions, while relatively small inclusions are washed off the filter surface by the melt flow and enter the mold along with the melt. Furthermore, the proposed solution poses the risk of damage to the filter installed in the ladle during the initial pouring period due to the energy of the falling melt stream.

[0028] Also known is a ladle for continuously casting metal, comprising a cavity containing an inlet portion designed to receive a flow of molten metal, an outlet portion with an outlet opening designed to release molten metal into a mold, and a filtration system separating the inlet and outlet portions across the entire width of the ladle cavity (US 2024253111 A1, 01.08.2024). The filtration system consists of a filter module containing a filter block provided with expanding channels, and a wall module extending across the entire width of the cavity, with one or more openings. The invention effectively removes most inclusions and other non-metallic particles, regardless of their size, from the molten metal flowing through the ladle from the inlet to the outlet opening, and at the same time ensures a high level of safety, eliminating the risk of melt overflowing over the edges of the ladle due to a malfunction of the filtration system.

[0029] A disadvantage of the presented solution is the relatively low melt filtration efficiency. As the melt moves in the ladle, not all of it can pass through the filter block with its channels, which is where non-metallic inclusions are actually retained, especially in cases of high inclusion contamination. This will lead to channel blockage, and the melt, along with the inclusions, will bypass the filter block and move toward the outlet, resulting in non-metallic inclusions being present in the finished metal. Furthermore, the expanding channels used in the filter block, unlike, for example, cylindrical channels, do not reliably retain inclusions trapped within them, which can be carried out of the block by the melt flow and contaminate the finished metal.

[0030] Also known is an intermediate ladle for continuous casting, provided with an internal cavity, containing a pouring pipe and sequentially arranged filter elements designed to remove slag (CN 223588317 U, 11 / 25 / 2025).

[0031] The disadvantage of this solution is the use of filter elements instead of ceramic foam filters, which prevents the melt from being filtered of small non-metallic inclusions and the production of high-purity finished metal. It should also be noted that this ladle design is extremely difficult to use in vacuum furnaces unless the furnace was originally designed with this type of ladle in mind. The presence of hydraulic cylinders and additional systems to support their operation (tanks, oil pumps, valves, and other components) located within the furnace space requires significant structural modifications to the vacuum induction furnace, which virtually eliminates the use of this device.

[0032] The closest analogue of the proposed invention is a device for filtering metal melts, comprising a first filter made of a porous filter medium and a second filter installed in the direction of melt flow (RU 2237733 C2, 10.10.2004). Use of the described device and method allows for increased purification of metal melts using simple filter systems.

[0033] A disadvantage of this solution is the horizontally positioned ceramic foam filter in the melt filtering device. This design feature can lead to partial or complete filter failure, given that until the first filter chamber is completely filled with melt (i.e., until the filter is completely immersed in the melt), the melt on the filter will exert significant bending stress on it, especially when casting steels or heat-resistant alloys, the melt density of which typically ranges from 7500 to 8500 kg / m3.3 Accordingly, if the filter is partially destroyed, the melt will become additionally contaminated with the filter material, and if it is completely destroyed, filtration will be carried out only by the second filter, which will significantly reduce the efficiency of melt filtration from non-metallic inclusions.

[0034] It should also be noted that this device has an upper housing, meaning it is a closed structure, which significantly complicates or even makes it impossible to preheat the ceramic foam filter. This can lead to premature cessation of melt flow during casting, before the crucible is completely emptied, due to solidification of the melt in the filter channels.

[0035] In addition, the use of a bulk filter placed in the second filter chamber of the device for filtering steels and heat-resistant alloys requires preheating this type of filter to temperatures at least close to the alloy solidus temperatures, i.e., about 1300-1500°C and higher, which is extremely difficult to implement in practice.

[0036] The problem solved by the proposed solutions is to improve the quality of the cast metal.

[0037] The technical result provided by the proposed solutions is an increase in the purity of steels, heat-resistant and corrosion-resistant alloys in terms of the content of non-metallic inclusions due to improved melt filtration efficiency, which leads to an increase in the quality of parts obtained from such steels and alloys.

[0038] The intermediate casting device comprises a metal flask containing a refractory ceramic trough, forming a channel in which at least two filter elements are installed in series. A pouring nozzle is installed at the bottom of the trough. The trough is curved at an angle of 80-100°, the bottom of the trough is inclined from 0.5 to 5° in the direction of melt flow, the filter elements are installed at an angle of 45° to 135° to the horizontal axis of the device, and foam ceramic filters are used as filter elements.

[0039] The ratio of the turning radius of the gutter along the centerline to the width of the gutter is preferably ~1.

[0040] The refractory ceramic trough is preferably molded in a metal flask.

[0041] It is preferable to install filters perpendicular to the horizontal axis of the device.

[0042] The vertical walls of the channel are provided with grooves for installing and fixing filters.

[0043] It is preferable to use foam ceramic filters of different porosity, with the filter of greater porosity installed first in the direction of melt flow, and the filter of lesser porosity installed second.

[0044] It is possible to use filters of the same porosity.

[0045] It is preferable that the width of the channel in the melt receiving area be at least 1.2 times the width of the pouring spout of the melting crucible, spout or teapot (siphon) ladle, or at least 1.2 times the diameter of the opening of the nozzle in the case of pouring the melt from a stopper ladle.

[0046] It is preferable that the thickness of the ceramic foam filters be at least 15mm.

[0047] The intermediate casting device according to the second embodiment includes a metal flask containing a refractory ceramic trough containing at least two isolated channels, each of which contains at least two filter elements installed in series, and at least one pouring nozzle installed in the bottom of the trough. The trough is curved, with the bending angle being 80-100°, the bottom of the trough is inclined from 0.5 to 5° in the direction of melt flow, the filter elements are installed at an angle of 45° to 135° to the horizontal axis of the device, and foam ceramic filters are used as filter elements.

[0048] The drain cup has two holes, each of which is located in the corresponding channel of the gutter.

[0049] Also, a separate drain cup can be located in each channel of the ceramic gutter.

[0050] The ratio of the turning radius of the gutter along the center line to the width of the gutter is preferably ~1.

[0051] The refractory ceramic trough is preferably molded in a metal flask.

[0052] It is preferable to install filters perpendicular to the horizontal axis of the device.

[0053] The vertical walls of the channels are provided with grooves for installing and fixing filters.

[0054] It is preferable to use foam ceramic filters of different porosity, with the filter of greater porosity installed first in the direction of melt flow, and the filter of lesser porosity installed second.

[0055] It is possible to use filters of the same porosity.

[0056] It is preferable that the width of each channel in the melt receiving area be at least 1.2 times the width of the pouring spout of the melting crucible, spout or teapot (siphon) ladle, or at least 1.2 times the diameter of the opening of the nozzle in the case of pouring the melt from a stopper ladle.

[0057] It is preferable that the thickness of the foam ceramic filters be at least 15mm.

[0058] The curved, L-shaped chute is designed to reduce melt velocity and turbulence before the second filter. This allows for higher filtration efficiency by reducing melt velocity before the filter and reducing dirt load on the main filter element (second filter). For this purpose, the second filter is located downstream of the bend in the direction of melt flow. The loss of melt flow velocity during a turn (due to hydraulic resistance) depends on the local resistance coefficient (ξ), which is determined by the turning angle, the type of turn (smooth or abrupt), and other factors, such as melt viscosity, channel surface quality, and melt temperature. The magnitude of pressure loss due to hydraulic resistance can be estimated, for example, using the Weisbach formula:

[0059] Δh=ξ*V 2 / 2g, where

[0060] Δh - pressure loss due to hydraulic resistance, m;

[0061] ξ - local resistance coefficient (loss coefficient);

[0062] V - average flow velocity after hydraulic resistance, m / s;

[0063] g - acceleration of gravity, m / s 2 .

[0064] For example, with a smooth turn, for angles of 30°, 45°, 60° and 90°, the local resistance coefficient (ξ) takes on the values ​​of 0.067, 0.1, 0.133 and 0.2, respectively, i.e. with an increase in the angle of turn, all other things being equal, the value of ξ increases and, consequently, the pressure loss.

[0065] Turning the chute at an angle of 80° to 100° creates significant hydraulic resistance due to the abrupt change in the direction of the melt flow, which leads to the formation of eddies and the emergence of centrifugal forces that tend to press the flow against the outer wall of the chute, causing additional friction against the walls of the channel, as a result of which the flow rate after the turn is noticeably reduced.

[0066] Thus, a bending angle of up to 80° does not provide a sufficient reduction in the melt flow rate, and a bending angle of more than 100° leads to excessive braking of the melt flow and, as a result, to a more noticeable decrease in its temperature, which can lead to a premature stop of the melt in the device before the crucible is completely emptied.

[0067] The local resistance coefficient (loss coefficient) (ξ) additionally depends on the channel geometry, including the nature of the turn—rounded (smooth) or sharp (undouble-edged). To assess the smoothness of a turn, the ratio of the turning radius along the centerline (R) to the channel width (b) is used. For a rounded turn, the ratio R / b ~ 1, the coefficient ξ is taken as 1.0, and in the case of a sharp turn with an R / b ratio from 3.0 to 4.0, the coefficient ξ takes values ​​from 0.5 to 0.3. Thus, it is preferable to use a rounded turn of the trough when turning the melt flow by 90° with a ratio of R / b ~ 1, since the implementation of sharp turns can lead to an excessively large loss of flow velocity, and, as a consequence, to a significant cooling of the melt, which can cause a premature stop of the melt before the crucible is completely emptied.

[0068] The use of a ceramic trough molded into a flask prevents melt leakage through the trough walls if cracks form. It also provides thermal insulation for the flask during both preheating of the trough and during its heating by the melt during pouring, as well as its subsequent cooling after pouring. To achieve this, the gaps between the flask walls and the ceramic trough are filled with loose refractory material. Molding can be performed using any convenient method: manually, on a vibrating table, with rammers, hand vibrators, etc.In addition, the placement of the chute in a metal flask makes it possible to transport the device to the installation site of casting molds for pouring the melt in the case of its use for open induction furnaces, as well as for moving, loading the device into a vacuum induction furnace for pouring the melt and removing the device upon completion using lifting devices, as well as moving it within the furnace space.

[0069] The presence of grooves in the intermediate casting device ensures easy installation and replacement of filters after casting, minimizing the amount of maintenance work at the filter installation sites when reusing the device. Fixing the filters in the grooves eliminates gaps between the filters, vertical walls, and the bottom of the trough, ensuring that the entire volume of flowing melt passes through the filters, which, in turn, prevents mixing of filtered and unfiltered melt during the filtration process.

[0070] Filters positioned at an angle of 45° to 135° to the horizontal axis of the device significantly increases the filter surface area in contact with the melt, preventing premature melt flow stoppage due to clogging of the filter cells by inclusions. Positioning filters at angles less than 45° and greater than 135° to the horizontal axis of the device significantly increases the local resistance coefficient due to an increased melt flow rotation angle as it moves through the filter channels. This causes a decrease in melt velocity and, consequently, a decrease in its temperature, thereby increasing the risk of premature melt flow stoppage.In addition, the placement of filters at angles to the horizontal axis of the device that differ from the values ​​specified above complicates the design of molds for the production of ceramic gutters and may increase the rejection of gutters during their production, which leads to an increase in the cost of gutters and negatively affects economic indicators.

[0071] As the melt passes through the filter, the melt flow rate decreases and the flow switches from turbulent to laminar, resulting in non-metallic inclusions not being washed out of the filter pores.

[0072] Using a coarse filter first in the melt flow direction, and a fine filter second, significantly reduces the likelihood of the fine filter becoming clogged with large particles, which could lead to premature melt flow shutdown. This solution also improves the efficiency of melt removal from small particles by allowing the use of fine filters with significantly smaller mesh sizes.

[0073] When using filters of the same porosity, the degree of purity of the melt also increases due to the reduction of its speed after passing through the first filter, which helps to increase the filtration efficiency of the second filter.

[0074] This solution is suitable for alloys with low fluidity, such as corrosion-resistant nickel- and cobalt-based alloys with chromium content exceeding 15% (wt.), especially when using a significant proportion of waste. The increased chromium content results in a relatively high melt viscosity, which causes pressure losses both when turning at an angle of 80-100° and when passing through each of the two filters. This is significantly higher than, for example, when filtering heat-resistant nickel- and cobalt-based alloys with chromium content in the range of 5-10% (wt.). On the one hand, this circumstance leads to an excessive slowdown in the melt flow rate when using coarse and fine filters, which does not always guarantee the pouring of the entire volume of melt in the crucible until it is completely empty due to the premature stopping of the melt flow while moving along the trough channel due to the solidification of the melt in the pores of the filters.On the other hand, high viscosity allows for a sufficient reduction in melt velocity using only two coarse filters of equal porosity, ensuring high alloy purity in terms of non-metallic inclusion content. The first filter filters out large inclusions, while the second filters out small non-metallic inclusions and film. The use of foam ceramic filters as filter elements reduces melt velocity, which in turn promotes laminar flow. Furthermore, these filters offer significant mechanical strength and are easily installed in the grooves of metallurgical distribution systems, whereas pressed filters do not provide sufficient reduction in linear flow velocity. While this filter separates the melt into small parallel streams of metal, the deceleration effect is insufficient.Woven (mesh) filters only filter large slag particles, but they do not filter out slag and do not sufficiently reduce flow velocity, which does not facilitate the transition from turbulent to laminar melt flow. Therefore, only the use of ceramic foam filters in the proposed invention ensures both the required degree of melt purity and the necessary reduction in flow velocity, as well as high processability.

[0075] The porosity of ceramic foam filters is traditionally measured in pores per square inch (ppi). The difference between filters with different porosity is quite large, making it impossible to achieve the required degree of melt purification using a single filter. Preliminary refining and converting the melt flow to laminar flow can be achieved using filters with a porosity of 5-10 ppi; however, filters with this porosity do not allow for the removal of films from the melt. For film removal, it is advisable to use filters with a porosity of 15 ppi or higher. However, using only one filter with a porosity of 15 ppi or higher for melt filtration can lead to premature clogging of the filter pores, an excessive reduction in the melt flow rate, and a complete stop of the melt flow before the crucible is completely emptied.This circumstance dictates the feasibility of using two sequentially arranged foam ceramic filters of varying porosity: the first filter element removes large particles and reduces flow velocity, while the second filter provides fine purification of the pre-cleaned and retarded melt. The first filter, which has a relatively coarse porosity (typically around 5 ppi, less commonly 10 ppi, depending on the melt's fluidity), is installed to reduce melt velocity and remove large slag particles present in the melt. This reduces the dirt load on the second filter and facilitates a transition from turbulent to laminar melt flow before entering the second filter. This, in turn, ensures deeper refining of the melt in the second filter, removing film and small non-metallic inclusions that become entangled in the filter's pores and, due to their low flow rates, are not washed out, remaining in the second filter.

[0076] The gradual penetration of the melt through the filter causes the leading edge of the melt to lose temperature, which reduces its fluidity. This is critical, as there is a high risk of the melt solidifying in the filter channels, preventing further flow through the filter, if the casting temperature is insufficient, if the melt cools excessively during the casting process, or if the pressure (hydraulic head) is too low.

[0077] The pouring temperature for each alloy grade is selected depending on the capacity of the melting crucible, the liquidus temperature and fluidity of the alloy, the thermophysical characteristics of the material of the intermediate pouring device and its design characteristics (the total length and width of the channels, the angle of the channel bends, the diameter of the drain hole of the cup, the roughness of the surfaces in contact with the melt, etc.), the temperature of the device together with the filters before pouring, the nature of filling the molds (individual or collective pouring), the use of additional elements for pouring, for example, ceramic bowls for collective pouring.

[0078] One of the most important parameters determining the cooling rate of the melt relative to the pouring temperature during its flow in the intermediate device is the channel width, as it limits the amount of radiant heat loss from the melt surface to the surrounding space (for open furnaces) or into the furnace chamber (for vacuum furnaces) and convective heat loss into the bottom of the ceramic trough, all other things being equal. Obviously, the smaller the channel width, the lower the melt's heat loss and the higher its fluidity. At the same time, the channel width in the jet reception zone is directly related to the width of the pouring spout of the melting crucible, the spout, teapot (siphon) ladle, or the diameter of the stopper ladle opening and cannot be less than this value, otherwise the melt stream will not completely enter the device channel.Furthermore, as the molten stream falls from the crucible or ladle before entering the casting device, an increase in stream diameter is typically observed due to the velocity gradient across its cross-section. The authors experimentally determined that using a device with a channel width of at least 1.2 times the width of the crucible or ladle pouring spout or the diameter of the stopper ladle nozzle opening, with a jet drop height of up to 1.0 m, ensures guaranteed entry of the molten stream into the casting device over a wide range of casting speeds for steels and heat-resistant alloys used in casting production, taking into account errors in mold installation and the position of the casting device relative to the crucible or ladle. The specified height of the melt jet fall corresponds to the moment the melt begins to flow out from the pouring spout of a rotating crucible, a spout or teapot (siphon) ladle, or from the glass of a stop ladle for most industrial furnaces with a crucible capacity of 300 to 1500 kg of steel.

[0079] After receiving the molten stream from the crucible or ladle, its further flow through the tundish channel occurs under the influence of hydrostatic pressure, the magnitude of which is determined, among other things, by the channel slope. For technological reasons, certain sections of the trough bottom (where filters and the cup are installed) may be horizontal, meaning the trough bottom in these areas is flat. However, to ensure hydrostatic pressure, the overall slope of the trough bottom and, consequently, the channel is determined by the overall slope of the trough bottom and, consequently, the channel. The overall slope of the trough bottom and, consequently, the channel is defined as the angle of inclination of a straight line drawn through the two most distant points lying on the same centerline of the channel to a straight line drawn through either of these two points, lying in a horizontal plane. The authors have found that, for steels and heat-resistant alloys, the optimal slope ranges from 0.5 to 5°.With a channel slope of less than 0.5°, the melt flow rate significantly decreases, leading to melt stagnation in the casting device. This increases heat loss from the melt, reduces its fluidity, and increases the risk of premature melt shutdown before the crucible is completely empty due to melt solidification in the filter pores. Furthermore, this leads to a significant mass of melt residue in the device after casting, reducing production efficiency.

[0080] With a slope exceeding 5°, the melt flow velocity increases sharply, increasing flow turbulence. This reduces the effectiveness of melt filtration, removing non-metallic inclusions due to their leaching from the filter pores. As a result, some inclusions end up in the mold. Furthermore, with such a slope, the weight of the ceramic trough increases due to the increased thickness of the base, increasing the rejection rate, leading to higher product costs.

[0081] To ensure effective filtration, the thickness of foam ceramic filters should be at least 15 mm. Using filters thinner than 15 mm reduces their mechanical strength, which can lead to their destruction under the force of the jet. Furthermore, the degree of removal of non-metallic inclusions from the melt using filters of such thin thickness will be insufficient. Using filters thicker than 45 mm increases the hydraulic resistance to melt flow, significantly reducing its velocity, temperature, and, consequently, fluidity. Consequently, the risk of premature melt shutdown before the crucible is completely empty increases. The preferred filter thickness is 25 to 40 mm.

[0082] Before use, the intermediate casting device, together with the filter trough installed within it, should be heated to a temperature of at least 500°C to reduce heat loss from the melt when it contacts the device surfaces and prevent premature melt flow interruption during casting. Heating of the device is carried out either in a gas stand or in a furnace preheater, if such a unit is included in the equipment.

[0083] Selecting the above parameters within the recommended ranges eliminates problems with premature melt flow stoppages associated with melt solidification in the filter pores. However, if the dirt holding capacity of even one filter in the tundish's filtration section is lower than the amount of non-metallic inclusions in the melt, filtration may stop due to blockage and / or significant narrowing of the filter channels. Furthermore, an unacceptable reduction in melt flow through the filter may occur, resulting in the actual flow rate being lower than required for uniform mold filling. This, in turn, can significantly degrade the surface quality of cast blanks and lead to defects such as unmelted surfaces, welds, wrinkling, and the like.For this reason, it is necessary to select the optimal combination of filters not only taking into account the characteristics of each alloy grade, primarily fluidity, but also taking into account the predicted contamination of the alloy depending on the type and proportion of waste used, as well as the grades of fresh charge materials.

[0084] A drain cup with a calibrated hole is used to drain the melt, filtered from non-metallic inclusions, either into a ceramic bowl through which the melt is supplied to the molds, or directly into the sprue mold, depending on the pouring scheme (collective filling or individual).

[0085] Fig. 1 shows a general view of the proposed device containing one channel,

[0086] Fig. 2 shows a general view of the proposed device containing two channels,

[0087] Fig. 3 shows the movement of the melt through individual elements of the casting equipment, including its flow from the rotating melting crucible, for a collective mold casting scheme,

[0088] Fig. 4 shows the movement of the melt through individual elements of the casting equipment, including its flow from the rotating melting crucible, for an individual mold casting scheme.

[0089] The proposed tundish (also known as a tundish, trough, or pouring trough) in the first embodiment consists of a metal flask 1, typically made of high-quality structural carbon steels, such as grade 20 steel. The flask material must provide the required strength at the operating temperature, taking into account the weight of the trough, the refractory backfill, and the weight of the melt contained in the trough. It must also have good machinability and weldability, be free from temper embrittlement, and be readily available and inexpensive. A curved refractory ceramic trough 2 is located inside the flask 1. The trough bending angle ranges from 80 to 100°, forming an L-shape. The ceramic trough 2 forms a channel 3 for the melt flow. The ceramic trough 2 can be made of any refractory material that is chemically inert with respect to the melt.In addition to being chemically inert to the melt, the ceramic material must have high heat resistance and sufficient mechanical strength at melt pouring temperatures, be free of polymorphic transformations upon heating and cooling, be non-gassing, ensure high geometric dimensional accuracy, and be cost-effective. Refractory oxide ceramics, such as fused alumina, zircon, fused quartz, and chamotte, meet these requirements.

[0090] Filters 4 and 5 are installed in channel 3 of trough 2. Grooves 6 are provided in the vertical walls of channel 3 for installing and securing the filters. Positioning the filters using these grooves 6 allows for quick filter replacement. Filters 4 and 5 are secured in grooves 6 using a mixture consisting of a loose refractory material (e.g., corundum, magnesite, or fireclay) and a binder (e.g., liquid glass or ethyl silicate), mixed in a ratio that allows for the use of this mixture.

[0091] The proposed intermediate pouring device according to the first variant (Fig. 1.3) is intended for the use of a collective scheme for pouring melt into molds (simultaneous filling of several molds with melt at once), in which the melt from the intermediate pouring device first enters the ceramic bowl 9, and then, through openings made in the bottom of the bowl 9, communicating with the openings of the casting molds 10, enters the molds 10.

[0092] A hole is made in the bottom of trough 2, in which a pouring cup 7 is installed. This cup has an opening through which the filtered melt is poured into ceramic bowl 9, which is installed above molds 10 for collective casting. Molds such as ingot molds, chill molds, ceramic molds, etc. can be used as molds.

[0093] Ceramic trough 2 with filters 4, 5 and drain cup 7 installed is installed in metal flask 1, centering it relative to the walls of flask 1 to ensure a uniform gap around the perimeter. The gaps between the walls of flask 1 and ceramic trough 2 are filled with loose refractory material, such as corundum, magnesite, quartz, chamotte, periclase, or a mixture thereof, and compacted manually; using electric or pneumatic rammers; or on a vibrating table to prevent cracks from forming and opening in the ceramic and prevent melt leaks. Before use, the device is heated in a gas stand or directly by electric heaters in a vacuum furnace to a temperature of at least 500°C.

[0094] The metal melt ready for pouring is poured into channel 3 of the ceramic trough 2 installed in the metal flask 1, for which purpose the intermediate pouring device is moved using the movement mechanism to the position where pouring begins.

[0095] The melt may be received from a melting crucible, a spout or teapot (siphon) ladle, or a stopper ladle. After receiving the melt by the device (for example, from a rotating crucible 8, as shown in Fig. 3), the melt flows through channel 3 of the ceramic trough 2 of the proposed device. Inside channel 3, filters 4 and 5 are installed in series along the direction of melt flow. It is preferable to use coarse filters 4 and fine filters 5. A foam ceramic filter with a porosity of 5-10 ppi is used as a coarse filter 4, and a foam ceramic filter with a porosity of 15-30 ppi is used as a fine filter 5. The choice of the porosity degree of each filter is determined by the alloy grade (melt fluidity) and the predicted degree of its contamination.As the melt flows, it sequentially passes through the pores of filters positioned at an angle of 45 to 135° to the horizontal axis of the device. This traps non-metallic inclusions contained in the melt on the filter pore walls. Melt filtration involves not only mechanical filtration but also adsorption mechanisms. Adhesion forces arise between the filter material and certain non-metallic particles due to intermolecular interactions. An opening with a drain cup 7 is located in the bottom of a ceramic trough 2, in the part furthest from the melt receiving point of the device. Drain cup 7 is also made of a ceramic refractory material, the requirements for which are similar to those for ceramic trough 2. Drain cup 7 is secured in the trough opening in the same manner as the filters in grooves 6.

[0096] After entering channel 3 of the intermediate casting device, the melt, under the action of hydrostatic pressure due to the melt level (the height of the melt in the trough) and the existing slope in channel 3 of the ceramic trough 2, corresponding to the slope of the bottom of trough 2, begins to flow towards the pouring nozzle 7. A turn of trough 2 and, accordingly, channel 3, by an angle of 80-100° creates significant hydraulic resistance due to an abrupt change in the direction of the melt flow, which leads to the formation of eddies and the emergence of centrifugal forces that tend to press the flow against the outer wall of the trough, causing additional friction against the channel walls, as a result of which the flow velocity after the turn is noticeably reduced. Passing the melt through the pores of the foam ceramic filter 4 leads to an even further decrease in the melt velocity and a change in the turbulent flow of the melt to laminar. Large non-metallic inclusions are also retained in filter 4.The slowed and pre-cleaned melt passes through the pores of filter 5, which retains smaller non-metallic inclusions and films not captured by the first filter. The laminar flow of the melt is maintained, ensuring uniform pouring of the melt into the molds. After passing through the second filter 5, the melt, filtered from non-metallic inclusions, enters through the opening of the pouring cup 7 into the ceramic bowl 9, where it is then fed into the molds. After all the molds located below the ceramic bowl 9 have been filled with melt, the furnace's turntable 11 rotates to the position for pouring the molds into the next ceramic bowl 9. Pouring continues until the melt in the melting crucible 8 is completely empty.

[0097] The proposed intermediate casting device according to the second embodiment (Fig. 2, 4) consists of a metal flask 1, inside which a refractory ceramic trough 2 of a curved shape is placed. The bending angle of the trough is from 80 to 100°, forming an L-shape of the trough. The ceramic trough 2 forms several isolated channels 3 for the melt flow, i.e., the melt from one channel 3 cannot flow into the adjacent channel 3. The ceramic trough 2 can be made of any refractory material that is chemically inert with respect to the melt. The ceramic material, in addition to being chemically inert with respect to the melt, must have high heat resistance and sufficient mechanical strength at the melt pouring temperatures, not have polymorphic transformations during heating and cooling, be non-gas-forming, ensure high dimensional accuracy, and also meet economic considerations.In particular, ceramics made from refractory oxides, such as electrocorundum, zircon, fused quartz, and chamotte, meet the specified requirements.

[0098] Filters 4 and 5 are installed in each channel 3 of trough 2. Grooves 6 are provided in the vertical walls of channels 3 for installing and securing the filters. Filters 4 and 5 are secured in grooves 6 using a mixture consisting of a loose refractory material (e.g., corundum, magnesite, or fireclay) and a binder (e.g., liquid glass or ethyl silicate), mixed in a ratio that allows for the application of this mixture.

[0099] The proposed intermediate casting device according to the second embodiment is intended for the use of an individual melt pouring scheme into molds (each mold is filled with melt separately), in which the melt from the intermediate casting device is poured directly into the casting molds one by one (Fig. 4). In this case, as a rule, the molds are located in cassettes designed for their installation and fixation (the cassette is not shown in Fig. 4).

[0100] At the bottom of the trough 2, there is an opening in which a pouring cup 7 is installed with openings, each of which is located in the corresponding channel 3. In the case of installing 3 individual pouring cups 7 in each channel, an individual opening is made at the bottom of the trough 2 in each channel for placing the corresponding cup 7. Through the openings, the filtered melt is poured directly into the casting molds 10. Molds, chill molds, ceramic molds, etc. can be used as molds.

[0101] Ceramic trough 2 with filters 4, 5 and drain cup(s) 7 installed is installed in metal flask 1, centering it relative to the walls of flask 1 to ensure a uniform gap around the perimeter. The gaps between the walls of flask 1 and ceramic trough 2 are filled with loose refractory material, such as magnesite, quartz, chamotte, periclase, or a mixture thereof, and compacted manually; using electric or pneumatic rammers, or on a vibrating table, to prevent cracks from forming and opening in the ceramic and prevent melt leaks. Before use, the device is heated in a gas stand or directly by electric heaters in a vacuum furnace to a temperature of at least 500°C.

[0102] The melt may be received from a melting crucible, a spout or teapot (siphon) ladle, or a stopper ladle. After receiving the melt by the device (for example, from a rotating crucible 8, as shown in Fig. 4), the melt flows through one of the channels 3 of the ceramic trough 2 of the proposed device. Inside each channel 3, filters 4 and 5 are installed in series along the direction of melt flow. It is preferable to use coarse filters 4 and fine filters 5. A foam ceramic filter with a porosity of 5-10 ppi is used as a coarse filter 4, and a foam ceramic filter with a porosity of 15-30 ppi is used as a fine filter 5. The choice of the porosity degree of each filter is determined by the fluidity of the alloy and the predicted degree of its contamination.As the melt flows, it sequentially passes through the pores of filters positioned at an angle of 45 to 135° to the horizontal axis of the device. This traps non-metallic inclusions contained in the melt on the filter pore walls. Melt filtration involves not only mechanical filtration but also adsorption mechanisms. Adhesion between the filter material and the non-metallic particles arises due to intermolecular forces. The opening with the drain cup 7 is located in the bottom of the ceramic trough 2, in the part furthest from the melt receiving point of the device. The drain cup 7 is also made of a ceramic refractory material, the requirements for which are similar to those of the ceramic trough 2. The drain cup 7 is secured in the trough using a refractory mixture, similar to the fixation of the filters in the grooves.

[0103] When using a multi-channel ceramic trough, the molten metal from the rotary melting crucible 8 or ladle is sequentially poured into channels 3 and 3 ' ceramic trough 2 installed in metal flask 1, for which the device is moved using a movement mechanism to the position where pouring begins.

[0104] After entering each of the intermediate casting device channels 3 and 3', the melt begins to flow toward the pouring nozzle 7 under the action of hydrostatic pressure due to the melt level (melt height in the trough) and the existing slope in channels 3 of the ceramic trough 2, corresponding to the slope of the trough 2 bottom. Turning the trough at an angle of 80-100° creates significant hydraulic resistance due to the abrupt change in the direction of the melt flow, which leads to the formation of vortices and the emergence of centrifugal forces that tend to press the flow against the outer wall of the trough, causing additional friction against the channel walls, as a result of which the flow velocity after the turn is noticeably reduced. Passing the melt through the pores of the foam ceramic filter 4 leads to an even further decrease in the melt velocity and a change in the turbulent melt flow to laminar. Large non-metallic inclusions are also retained in the filter 4.The slowed and pre-cleaned melt passes through the pores of filter 5, which retains smaller non-metallic inclusions and films that were not retained by the first filter 4. The laminar nature of the melt flow is maintained, which ensures uniform pouring of the melt into the molds. After passing the second filter 5, the melt, filtered from non-metallic inclusions, enters directly into mold 10 through the opening of pouring cup 7. After filling one casting mold 10 with melt, rotary table 11 of the furnace is rotated to the position for pouring the next mold. After pouring all the molds, which are filled from one channel 3 and emptying said channel 3 of trough 2, the pouring device is moved within the furnace space or at the mold pouring location to a position intended for pouring the melt from crucible 8 or from the ladle into the next channel 3' and pouring it into the molds corresponding to this channel.Pouring continues until the crucible 8 or ladle is completely empty.

[0105] The proposed device can be used in both metallurgical and procurement technologies.

[0106] The proposed intermediate casting device, in any of its variants, minimizes heat loss and utilizes two-stage filtration to improve melt filtration efficiency, resulting in higher metal purity in terms of non-metallic inclusion content. Achieving this effect is only possible with the full complement of essential features of the claimed solutions, as eliminating even one element will not achieve the required degree of alloy purity.

Claims

1. An intermediate pouring device comprising a metal flask, inside which a refractory ceramic trough is placed, forming a channel in which at least two filter elements are installed in series, and a drain cup is installed at the bottom of the trough, characterized in that the gutter is made curved, and the bending angle is 80-100°, the bottom of the trough is made with a slope of 0.5 to 5° in the direction of the melt flow, the filter elements are installed at an angle of 45 to 135° to the horizontal axis of the device, Foam ceramic filters are used as filter elements.

2. An intermediate pouring device according to claim 1, characterized in that the ratio of the turning radius of the chute along the centerline to the width of the chute is preferably ~1.

3. An intermediate pouring device according to paragraph 1, characterized in that the width of the channel in the melt receiving zone is not less than 1.2 times the width of the pouring spout of the melting crucible, spout or teapot siphon ladle, or not less than 1.2 times the diameter of the stopper ladle cup.

4. An intermediate filling device according to paragraph 1, characterized in that the thickness of the foam ceramic filters is at least 15 mm.

5. An intermediate pouring device comprising a metal flask, inside which is placed a refractory ceramic trough containing at least two isolated channels, in each of which at least two filter elements are installed in series, and at least one drain cup is installed in the bottom of the trough, characterized in that: the gutter is made curved, and the bending angle is 80-100°, the bottom of the trough is made with a slope of 0.5 to 5° in the direction of the melt flow, the filter elements are installed at an angle of 45 to 135° to the horizontal axis of the device, Foam ceramic filters are used as filter elements.

6. An intermediate pouring device according to paragraph 5, characterized in that two openings are made in the pouring cup, each of which is located in the corresponding channel of the gutter.

7. An intermediate pouring device according to paragraph 5, characterized in that a separate pouring cup is located in each channel of the ceramic trough.

8. An intermediate pouring device according to claim 5, characterized in that the ratio of the turning radius of the chute along the centerline to the width of the chute is preferably ~1.

9. An intermediate pouring device according to paragraph 5, characterized in that the width of each channel in the melt receiving zone is not less than 1.2 times the width of the pouring spout of the melting crucible, spout or teapot siphon ladle, or not less than 1.2 times the diameter of the stopper ladle cup.

10. An intermediate filling device according to paragraph 5, characterized in that the thickness of the foam ceramic filters is at least 15 mm.

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