WO2024113103A1 - Smelting apparatus for clean and homogenized extra-large steel ingot, and use method - Google Patents

Abstract

Disclosed in the present invention are a smelting apparatus for a clean and homogenized extra-large steel ingot, and a method. The smelting apparatus comprises base metal chambers, a vacuum smelting chamber, and an electroslag furnace; the base metal chambers are located directly above the vacuum smelting chamber; the vacuum smelting chamber is located directly above the electroslag furnace; a plurality of induction heating crucibles disposed side by side at the same height are arranged in the vacuum melting chamber. The use method for the smelting apparatus comprises the following steps: (1) the plurality of induction heating crucibles in the vacuum smelting chamber are sequentially and periodically filled with base metal steel ingots and melt same into molten steel; and (2) each crucible sequentially, periodically and slowly pours the molten steel into a crystallizer of the electroslag furnace, thereby supplying continuous and stable molten steel into the crystallizer, and an extra-large electroslag ingot is obtained under the cooling of the crystallizer. As the molten steel is always in vacuum and the air is isolated, the ultra-cleanness of the electroslag ingot is realized. According to the present invention, an ultra-clean and homogenized extra-large electroslag ingot weighting 100 tons or more can be obtained, so that the defect that ultra-clean and homogenized extra-large electroslag ingots cannot be produced in major engineering is overcome.

Description

A smelting device for clean homogenized extra-large steel ingot and its use method Technical Field

The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a smelting device and method for clean homogenized extra-large steel ingots.

Background technique

With the rapid development of my country's industry, the demand for ultra-clean, homogenized, and extra-large steel ingots in the fields of national defense, aerospace, energy and power is increasing. As an important method for producing high-quality and extra-large steel ingots, electroslag remelting occupies an important position in the smelting of high-quality special steel. The main reason is that the steel ingots obtained by electroslag remelting have high cleanliness, fine non-metallic inclusions, good central segregation, and dense structure. The traditional method of smelting extra-large steel ingots is to use the parent steel ingot as a consumable electrode, use double arms to alternately melt several parent steel ingots, and melt extra-large electroslag ingots in an ingot extraction electroslag furnace. However, during the period when the double arms exchange the parent steel ingots, the crystallizer is in contact with air, resulting in the appearance of oxide scale on the surface of the parent steel ingot and the phenomenon of hydrogen absorption by the slag, which causes the phenomenon of oxygen and hydrogen increase in the electroslag ingot, and it is impossible to obtain ultra-clean electroslag ingots; and there is a current interruption, which easily causes defects such as slag inclusion and shrinkage in the electroslag ingot at this part, and it is impossible to ensure the homogenization of the electroslag ingot during the period of exchanging the parent steel ingot. In summary, when a super-large electroslag ingot is obtained by exchanging several parent steel ingots through double-arms, the surface oxidation of the parent steel ingot increases the oxygen content and inclusion level in the electroslag ingot, and the water vapor in the air enters the crystallizer, which easily increases the hydrogenation of the electroslag ingot. When the parent steel ingot is exchanged, defects such as slag inclusions and shrinkage cavities appear in the corresponding electroslag ingot. The small-diameter parent steel ingot easily leads to serious center segregation of the electroslag ingot, affecting the performance of the final product. The traditional double-arm electroslag remelting method cannot obtain ultra-clean, homogenized, low-segregation, and super-large electroslag ingots. In response to this problem, it is urgent to develop a new set of electroslag remelting devices and methods to produce ultra-clean, homogenized, low-segregation, and super-large electroslag ingots to meet the needs of major projects in my country.

technical problem

The technical problem to be solved by the present invention is that the existing smelting of extra-large electroslag ingots has the problems of low cleanliness and poor homogenization, and provides a new type of electroslag furnace steelmaking device and method, which can produce ultra-clean, homogenized, low-segregation, extra-large electroslag ingots; extra-large steel ingots refer to steel ingots with a diameter greater than 120 cm, a height greater than 400 cm, and a weight greater than 50 tons. Preferably, extra-large steel ingots refer to steel ingots with a diameter of 120-220 cm, a height of 400-800 cm, and a weight of 50-250 tons.

Technical Solutions

In order to solve the above technical problems, the present invention provides a smelting device for clean homogenized extra-large steel ingots, comprising n mother material chambers, a vacuum smelting chamber, and an electroslag furnace; the mother material chamber is provided with a mother material lifting rod and a mother material grabber, and a mother material chamber vacuum valve is provided on the side wall; the vacuum smelting chamber is provided with n induction heating crucibles and a funnel guide groove, and a smelting chamber vacuum valve is provided on the side wall; the electroslag furnace includes a conductive crystallizer; the mother material chamber is connected to the vacuum smelting chamber, and a movable sealing plate is provided at the connection point; the induction heating crucible, the funnel guide groove, and the conductive crystallizer are arranged in sequence up and down; n≥2, preferably 2.

In the above technical scheme, the parent material chamber, vacuum melting chamber and electroslag furnace are arranged in sequence from top to bottom. Preferably, the parent material chamber is located directly above the vacuum melting chamber, and the vacuum melting chamber is located directly above the electroslag furnace; the bottom of the parent material chamber is connected to the vacuum melting chamber, and the top of the conductive crystallizer is sealed and connected to the bottom of the vacuum melting chamber, so that the entire melting device is connected. After evacuation, the interior of the melting device is a vacuum environment; a sealing plate is provided at the connection between the bottom of the parent material chamber and the vacuum melting chamber to separate the parent material chamber from the vacuum melting chamber. When the parent material chamber is not vacuum, the sealing plate blocks the vacuum melting chamber and still maintains a vacuum; the top of the conductive crystallizer is sealed and connected to the vacuum melting chamber to avoid vacuum breaking caused by the external environment. As common sense, the parent material chamber and the vacuum melting chamber are connected to the vacuum pump through vacuum valves, respectively, so that they can be evacuated.

In the above technical scheme, a mother material grabber is provided at the bottom of the mother material lifting rod. The mother material grabber is an existing product, which is used to grab and release the steel ingot; the induction heating crucible is located directly below the mother material grabber. After the steel ingot is grabbed, it can be lowered into the induction heating crucible through the lifting rod to be melted; the guide groove is located below the induction heating crucible, which can receive the molten steel liquid in the induction heating crucible; the guide groove is located above the conductive crystallizer, which can inject the molten steel liquid into the conductive crystallizer; there is no special restriction on the specific positional relationship between the induction heating crucible, the guide groove and the conductive crystallizer opening, as long as the above functions can be achieved.

In the above technical solution, a plurality of induction heating crucibles are arranged in the vacuum melting chamber. The induction heating crucible itself and its use are existing technologies, and its installation in the vacuum melting chamber is also conventional technology. For example, the induction heating crucible used for melting the steel ingot is installed on the rotating shaft of the motor, and the molten steel can be poured out. There are n parent material chambers corresponding to the n induction heating crucibles, one-to-one, and the n induction heating crucibles can pour the molten steel into the funnel guide trough respectively; the guide trough is a funnel-shaped crucible with an open bottom or other device that can receive the molten steel and guide it into the conductive crystallizer.

The vacuum melting chamber of the present invention is provided with a plurality of induction heating crucibles and a guide groove, and the plurality of induction heating crucibles can guide the molten steel into the guide groove; preferably, the guide groove is a funnel, which can not only use the large opening to receive the molten steel of a plurality of crucibles, but also reduce the cost. Preferably, the plurality of induction heating crucibles are placed side by side. Furthermore, the induction heating crucibles in the vacuum melting chamber are placed side by side at the same height: each induction heating crucible is periodically loaded and melted with a parent material steel ingot in turn, and the molten steel is poured into the electroslag furnace crystallizer through the funnel by tilting the crucible alternately in turn, so as to provide a continuous and stable molten steel for the electroslag furnace crystallizer.

In the above technical scheme, a ceramic net is provided at the opening of the conductive crystallizer, and an electromagnetic stirring device is provided outside the opening of the conductive crystallizer; preferably, the aperture of the ceramic net is 6mm to 9mm. The conductive crystallizer itself is an existing product, which is a pull-out type. The entire conductive crystallizer consists of an upper conductive crystallization part, a lower water-cooled crystallization part and an external power supply circuit. It is conventionally provided with a liquid slag inlet, and forms a conventional electroslag furnace with a pull-out bottom water tank. The improvement of the present invention is that a ceramic net and an electromagnetic stirring device are provided at the connection between the vacuum melting chamber and the electroslag furnace. As common sense, the upper conductive crystallization part and the lower water-cooled crystallization part cooperate to form a crystallizer, an insulating plate is provided between the upper conductive crystallization part and the lower water-cooled crystallization part, the lower water-cooled crystallization part is provided on the installation platform, and a pull-out bottom water tank is provided below the installation platform. The pull-out bottom water tank is controlled by the pull-out moving assembly, and an AC power supply and a high-voltage switch are also provided between the pull-out bottom water tank and the upper conductive crystallization part. Further, a liquid level detection sensor is provided on the electroslag furnace to measure the height of the molten steel liquid level.

The parent steel ingot is placed in the crucible of the vacuum melting chamber through the parent steel chamber. After each parent steel ingot is loaded, the parent steel chamber is evacuated to prevent air from entering the vacuum melting chamber through the parent steel chamber, thereby ensuring that the vacuum melting chamber and the crystallizer are always in a vacuum or inert gas protection state, avoiding direct contact between the molten steel and the air, thereby improving the cleanliness of the molten steel and obtaining an ultra-clean electroslag ingot. Further, the casting rate of the molten steel is controlled by adjusting the inclination angle of the induction heating crucible, and each induction heating crucible alternately casts the molten steel in turn to provide continuous and stable molten steel for the electroslag furnace crystallizer. The casting rate of the crucible in the vacuum melting chamber matches the solidification rate of the ingot of the electroslag furnace, so that the electroslag ingot is continuously solidified, and the growth of the electroslag ingot is achieved through the ingot extraction device. Consistent with the existing method, the conductive heating method of the ingot extraction type electroslag furnace is an AC power supply-conductive crystallization part-liquid slag-metal molten pool-electroslag ingot-bottom water tank-high voltage switch-AC power supply power supply circuit, and the slag generates a large amount of Joule heat, so that the slag is in a high-temperature molten state.

Furthermore, the vacuum melting chamber and the electroslag furnace crystallizer are sealed and connected, and are provided with a ceramic net and an electromagnetic stirring device. After the molten steel passes through the ceramic net, it is dispersed into metal droplets. During the descent, the metal droplets are stirred and broken by the electromagnetic stirring device, and further decomposed into dispersed fine metal droplets, which eventually fall into the electroslag furnace crystallizer at the bottom, pass through the liquid slag pool, and solidify into electroslag ingots under the cooling of the crystallizer.

The present invention discloses a method for preparing a clean homogenized extra-large steel ingot by using the above-mentioned smelting device for a clean homogenized extra-large steel ingot, comprising the following steps: (1) loading the parent material steel ingot into each induction heating crucible in a vacuum melting chamber through a parent material chamber, evacuating the parent material chamber and the vacuum melting chamber, and then induction heating and melting the parent materials in each induction heating crucible to convert them into molten steel; (2) tilting the first induction heating crucible, allowing the molten steel to flow into an electroslag furnace crystallizer through a funnel guide groove, and then returning the first induction heating crucible; at the same time, tilting the second induction heating crucible, allowing the molten steel to flow into the electroslag furnace crystallizer through the funnel guide groove, and then returning the second induction heating crucible. ; The subsequent induction heating crucibles are subjected to the same operation in sequence; (3) the sealing plate is closed, the first parent material ingot is placed in the parent material chamber, and after the parent material chamber is evacuated, the sealing plate is opened, the parent material in the parent material chamber is placed in the first induction heating crucible that has been returned to the right position, and the parent material ingot in the crucible is heated and melted; when the second induction heating crucible is returned to the right position, the first induction heating crucible is tilted, the molten steel flows into the electroslag furnace crystallizer, and at the same time, the parent material in the second parent material chamber is placed in the second induction heating crucible that has been returned to the right position, and the parent material ingot in the crucible is heated and melted; the subsequent induction heating crucibles are subjected to the same operation in sequence; step (3) is repeated to obtain a clean, homogenized, extra-large steel ingot.

As common sense, after the ingot-drawing bottom water tank and the crystallizer of the electroslag furnace are sealed, liquid slag is poured in through the slag feeding port, and the high-voltage switch is closed at the same time, forming a power supply circuit of AC power supply-conductive crystallizer-liquid slag-bottom water tank-AC power supply. The Joule heat generated by the liquid slag will keep itself warm and heat it; the crystallizer will draw ingots to maintain the slag liquid level. This is a conventional method in this field. After the parent material chamber and vacuum melting chamber are evacuated, the electroslag furnace crystallizer is naturally vacuumed.

Specifically, when a plurality of induction heating crucibles are placed side by side at the same height in a vacuum melting chamber, taking two of them as an example, the guide groove is a funnel, and the method for using the above-mentioned device comprises the following steps: (1) loading a mother steel ingot into each induction heating crucible in the vacuum melting chamber, evacuating the mother material chamber and the vacuum melting chamber, and then the sealing plate is opened, and then the mother steel ingots in each crucible are induction heated and melted to become molten steel; (2) tilting the first crucible, the molten steel flows into the electroslag furnace crystallizer through the funnel, and then the crucible is returned to the center; at the same time, tilting the second crucible, the molten steel flows into the electroslag furnace crystallizer through the funnel, and then the crucible is returned to the center; (3) closing the sealing plate, and the mother steel ingots are placed in the vacuum melting chamber; The mother material steel ingot is placed in the mother material chamber, and after the mother material chamber is evacuated, the sealing plate at the bottom of the mother material chamber is opened, and the mother material steel ingot in the mother material chamber is placed in the first induction heating crucible that is returned to the right position, and the mother material steel ingot in the crucible is heated and melted; when the second crucible is returned to the right position, the first crucible is tilted, and the molten steel flows into the electroslag furnace crystallizer through the funnel, and then the crucible is returned to the right position; at the same time, the mother material steel ingot in the mother material chamber is placed in the second induction heating crucible that is returned to the right position, and the mother material steel ingot in the crucible is heated and melted; when the first crucible is returned to the right position, the second crucible is tilted, and the molten steel flows into the electroslag furnace crystallizer through the funnel, and then the crucible is returned to the right position; step (3) is repeated to obtain an extra-large electroslag ingot.

The present invention places a parent material steel ingot into a parent material chamber at the top of a first crucible, and after the parent material chamber is evacuated, the sealing plate at the bottom of the parent material chamber is opened, and the parent material steel ingot in the parent material chamber is placed in a first induction heating crucible. As an objective condition, a small amount of molten steel will remain in the crucible, which fills the gap between the parent material steel ingot and the crucible, and the parent material steel ingot is induction heated and melted. While the first crucible is returning to the right position, the second crucible is tilted, wherein the molten steel continues to slowly flow into the electroslag furnace crystallizer, and then returns to the right position; at the same time, the parent material steel ingot is placed into the parent material chamber at the top of the second crucible, and after the parent material chamber is evacuated, the sealing plate at the bottom of the parent material chamber is opened, and the parent material steel ingot in the parent material chamber is placed in the second induction heating crucible, wherein the small amount of molten steel remaining fills the gap between the parent material steel ingot and the crucible, and then the parent material steel ingot is induction heated and melted. While the second crucible is returning to the right position, the first crucible is tilted to continue to cast molten steel into the electroslag furnace crystallizer, ensuring that there is always continuous molten steel cast into the electroslag furnace crystallizer. The two mother material chambers periodically provide mother material steel ingots to the two crucibles respectively. The two crucibles periodically melt the mother material steel ingots and periodically and alternately provide continuous and stable molten steel to the electroslag furnace crystallizer, ensuring that there is continuous and stable molten steel in the electroslag furnace crystallizer. This cycle repeats itself over and over again. The molten steel solidifies into electroslag ingots under cooling of the crystallizer, and the electroslag ingots are drawn out. The solidification rate of the molten steel in the electroslag furnace crystallizer matches the casting rate of the molten steel in the crucible, and the slag liquid level position is stabilized by the drawing method of the electroslag ingot, and finally an extra-large electroslag ingot is obtained.

In the above technical scheme, the mother material chamber periodically and alternately provides mother material steel ingots to the crucible, the crucible periodically and alternately melts the mother material steel ingots, and periodically and alternately provides continuous and stable molten steel to the electroslag furnace crystallizer, ensuring that there is continuous and stable molten steel in the electroslag furnace crystallizer, and this cycle is repeated to obtain an extra-large electroslag ingot under the cooling of the crystallizer.

Furthermore, the parent material ingot is periodically placed in the parent material chamber, and the two crucibles periodically melt the parent material ingot into molten steel, and periodically and alternately provide continuous and stable molten steel to the electroslag furnace. A funnel-shaped guide groove is set below the two crucibles. After passing through the funnel-shaped guide groove, the molten steel enters the ceramic mesh below, and after passing through the ceramic mesh and the electromagnetic stirring and crushing molten steel device area, dispersed fine metal droplets are formed, passing through the liquid slag pool in the crystallizer, and finally solidified into electroslag ingots under the cooling of the crystallizer. The flow rate of the molten steel is controlled by tilting the crucible during the smelting process.

Beneficial Effects

In order to reduce the center segregation of the electroslag ingot, the diameter of the parent steel ingot is guaranteed to have a certain safety gap with the crystallizer. The larger the diameter of the parent steel ingot, the more conducive it is to reduce the center segregation of the electroslag ingot: for example, for electroslag ingots with a diameter of more than 180 cm, the diameter of the parent steel ingot is required to be greater than 150 cm, but the current technology is almost unable to produce parent steel ingots with a diameter greater than 150 cm. At present, no parent steel ingots with a diameter of more than 120 cm and a weight greater than 50 tons have been found in production or in the literature. When a small-diameter parent steel ingot is used, the center segregation of the extra-large electroslag ingot is serious, which ultimately reduces the product performance of the forged material. Under the existing technology, there is no ladle or steelmaking furnace that can melt a whole ingot weighing more than 50 tons. The existing electroslag remelting production process of double-arm exchange of parent steel ingots is used to prepare extra-large steel ingots, but during the exchange period, the crystallizer is in contact with air, so that the surface of the parent steel ingot is exposed to oxide scale and slag absorbs hydrogen, resulting in oxygen and hydrogen increase in the electroslag ingot, and it is impossible to obtain an ultra-clean electroslag ingot; and there is a current interruption, which easily causes defects such as slag inclusion and shrinkage in the electroslag ingot at this part, and it is impossible to ensure the homogenization of the electroslag ingot during the exchange period of the parent steel ingot. The present invention solves the problems that have always existed but cannot be solved in the prior art, and achieves the following beneficial effects: 1. The present invention obtains an ultra-clean, homogenized, low-segregation, extra-large electroslag ingot; the steelmaking method of using a parent material chamber-vacuum melting chamber with multiple crucibles to periodically provide molten steel-obtaining continuous and stable molten steel in the electroslag furnace crystallizer-cooling and solidifying the electroslag furnace crystallizer into an electroslag ingot provides continuous and stable molten steel for the electroslag furnace crystallizer, and the molten steel is always under vacuum protection and isolated from the air, realizing vacuum degassing and ultra-clean smelting of the molten steel.

2. The present invention has low requirements on the diameter of the parent steel ingot: the traditional electroslag furnace requires that the diameter of the parent steel ingot is large, while ensuring a certain safety gap with the crystallizer. The larger the diameter, the more conducive it is to reducing the central segregation of the electroslag ingot; however, the preparation of parent steel ingots with large cross-sections is extremely difficult and costly, and the shrinkage cavity in the center of the ingot is very serious. According to the prior art, parent steel ingots with a diameter greater than 1.2 meters and more than 50 tons cannot be prepared. The present invention places the parent steel ingot into an induction heating crucible, and uses a steel retention operation to fill the gap between the parent steel ingot and the crucible. By adjusting the amount of steel retained, the induction heating melting of parent steel ingots of different specifications can be achieved. Therefore, only commercially available continuous casting billets that are smaller than the inner diameter of the induction heating crucible are required, which significantly reduces the diameter requirement of the parent steel ingot.

3. The present invention realizes a closed loop of directly producing electroslag ingots from high-quality scrap steel: when the steel products used by customers are scrapped, the high-quality scrap steel can be directly put into multiple induction heating crucibles in the vacuum melting chamber to be melted into molten steel, providing continuous and stable molten steel for the electroslag furnace crystallizer, which is cooled and solidified into high-quality electroslag ingots, forming a production closed loop of re-melting of high-quality scrap steel - preparation of high-quality electroslag ingots - hot processing, heat treatment - high-quality forging products - scrapping of forging products - remelting of high-quality forging scrap steel and returning to the furnace for smelting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a smelting device for clean homogenized extra-large steel ingots according to Example 1.

FIG. 2 is a schematic diagram of the connection between the motor and the induction heating crucible.

FIG. 3 is a schematic diagram of the sealing plate installation.

FIG. 4 is a schematic diagram of the use status of the first embodiment.

Explanation of the numbers in the figure: parent material chamber 1, left parent material chamber 11, right parent material chamber 12, parent material lifting rod 13, parent material grabber 14, parent material ingot 15, vacuum valve 16, vacuum valve 17, vacuum melting chamber 2, left induction heating crucible 21, crucible rotating motor 211, right induction heating crucible 22, funnel guide groove 23, vacuum valve 24, molten steel 25, movable sealing plate 26, sealing plate handle 261, support roller 262, rope 263, rotor 264, electroslag furnace 3, vacuum pump 4, upper conductive crystallization part 31, lower water-cooled crystallization part 32, liquid slag addition port 33, insulating plate 34, ingot-drawing bottom water tank 35, liquid level detection sensor 36, ceramic net 37, electromagnetic stirring device 38, slag 5, metal molten pool 6, electroslag ingot 7.

FIG. 5 shows the grain morphology of the electroslag ingot forging material according to the first application example.

Embodiments of the present invention

The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. The specific components and specific connection methods of the components involved in the present invention are conventional methods, such as the installation and control of the induction heating crucible, the installation and control of the vacuum valve, the installation and control of the parent material grabber, etc. The specific electroslag remelting process is also a conventional technology; the ceramic net and the electromagnetic stirring device are existing products that can produce electromagnetic stirring on the molten steel; the positional relationship of the present invention is the positional relationship during actual production. In the prior art, when preparing extra-large steel ingots (greater than 100 tons) by electroslag remelting, due to the limitation of the parent material ingot, only one parent material can be replaced after melting, and there are problems such as contact with air and power failure, which greatly affects the performance of the extra-large steel ingot. The present invention solves the problems that the prior art has been unable to solve, and creatively proposes a smelting device for clean and homogenized extra-large steel ingots composed of a parent material chamber, a vacuum melting chamber, and an electroslag furnace, which maintains continuous electroslag remelting and a vacuum environment, and can prepare extra-large steel ingots of more than 50 tons, 100 tons, or even 200 tons.

The present invention discloses a smelting device and a method for using a clean homogenized extra-large steel ingot composed of a parent material chamber, a vacuum melting chamber, and an electroslag furnace. A plurality of induction heating crucibles are placed in the vacuum melting chamber, which can realize the production of ultra-clean, homogenized extra-large electroslag ingots. The orientation relationship is that the parent material chamber is located directly above the vacuum melting chamber, and the vacuum melting chamber is located directly above the electroslag furnace. A plurality of induction heating crucibles are arranged in the vacuum melting chamber, and the crucibles can be placed side by side at the same height. The inclination angle of the crucible is used to control the rate at which the molten steel flows into the electroslag furnace crystallizer. The device and process enable ultra-clean, continuous and stable molten steel to be obtained in the electroslag furnace crystallizer. At the same time, the conductive mode of AC power supply-upper conductive crystallization part-liquid slag-metal molten pool-electroslag ingot-bottom water tank-high voltage switch-AC power supply is adopted to make the metal molten pool in the electroslag furnace shallow and flat, which is conducive to reducing the central segregation of the electroslag ingot, and achieves the purpose of obtaining ultra-clean, homogenized, low-segregation, extra-large electroslag ingots. The induction heating crucible in the vacuum melting chamber adopts the operation of retaining liquid steel each time it returns to the center after tapping steel, so that after the parent material steel ingot in the parent material chamber is loaded into the upper induction heating crucible, the remaining liquid steel can fill the gap between the parent material steel ingot and the crucible, ensuring the efficient operation of the induction coil and the rapid melting of the parent material steel ingot. The specific operation of retaining liquid steel is a conventional technology, and there is no special restriction on the amount of retained liquid, as long as the liquid steel continues to flow into the crystallizer and does not overflow when the parent material is melted. When the induction heating crucible in the vacuum melting chamber melts the parent material steel ingot for the first time, the gap between the crucible and the parent material steel ingot is filled with broken steel chips of the same material as the parent material steel ingot, to promote induction heating and melting of the parent material steel ingot in the crucible. The rate of pouring molten steel into the electroslag furnace crystallizer v (kg/hour) = D × inner diameter of the crystallizer (mm), where D is 0.7~0.8; the temperature of pouring molten steel into the electroslag furnace crystallizer is 1600~1630℃; the total mass of slag in the electroslag furnace crystallizer m (kg) = C × inner diameter of the crystallizer × inner diameter of the crystallizer (cm), where C is 0.03~0.04.

The existing technology adopts the electroslag remelting method of exchanging the parent steel ingot. When exchanging the parent steel ingot, there are always problems such as the current interruption of the electroslag furnace, the change of the atmosphere in the electroslag furnace crystallizer, and the slag inclusion when exchanging the parent steel ingot. The new device and steelmaking method composed of the parent material chamber, vacuum melting chamber, and electroslag furnace developed by the present invention obtains ultra-clean, homogenized, low-segregation, and extra-large electroslag ingots, which meet the needs of major projects in my country.

Embodiment one .

The present embodiment adopts a steelmaking device having a vacuum melting chamber with a parent material chamber and an electroslag furnace, as shown in FIGS. 1-3 , the smelting device for clean homogenized extra-large steel ingots comprises a parent material chamber 1, a vacuum melting chamber 2 and an electroslag furnace 3 arranged in sequence from top to bottom, wherein the parent material chambers are a left parent material chamber 11 and a right parent material chamber 12; the same parts in the figures are marked only once, which does not affect the understanding of those skilled in the art.

The left and right parent material chambers are both provided with parent material lifting rods 13 and parent material grabbers 14, and are conventionally provided with chamber doors for parent material transportation. The parent material steel ingots 15 are grabbed and lifted by the parent material lifting rods and parent material grabbers; the left and right parent material chamber side walls are respectively provided with vacuum valves 16 and 17, and then the vacuum pump can evacuate the parent material chambers respectively.

The vacuum melting chamber is provided with a left induction heating crucible 21 and a right induction heating crucible 22, and a funnel guide groove 23, which correspond to the left and right parent material chambers respectively. The two crucibles are respectively installed on the motor shaft to realize the pouring of molten steel. FIG2 takes the left induction heating crucible 21 as an example, which is installed on the motor shaft 211. The motor and its installation and control are conventional technologies; the funnel guide groove is located below the two crucibles, which is used to receive the molten steel in the two crucibles and guide it into the crystallizer; a vacuum valve 24 is provided on the side wall of the vacuum melting chamber, and then a vacuum pump can evacuate the melting chamber.

The electroslag furnace comprises an upper conductive crystallization part 31 and a lower water-cooled crystallization part 32, which cooperate to form a crystallizer. A liquid slag inlet 33 is provided on the outer side of the opening. An insulating plate 34 is provided between the upper conductive crystallization part and the lower water-cooled crystallization part. The upper conductive crystallization part forms a power supply circuit and heats the liquid slag. The lower water-cooled crystallization part is used for electroslag ingot forming, and a steel and copper composite structure can be adopted. The lower water-cooled crystallization part is arranged on an installation platform, and an ingot-drawing bottom water tank 35 is arranged below the installation platform. An AC power supply and a high-voltage switch are also arranged between the ingot-drawing bottom water tank and the upper conductive crystallization part. When the high-voltage switch is closed, a power supply circuit of AC power supply-upper conductive crystallization part-liquid slag-metal molten pool-electroslag ingot-bottom water tank-high-voltage switch-AC power supply is formed to achieve the purpose of heating and keeping the slag warm. A liquid level detection sensor 36 is provided on the electroslag furnace. By accurately detecting the liquid level position of the molten steel in the crystallizer, a reasonable ingot-drawing method is determined to ensure the stability of the slag liquid level position. The above is the conventional structure and control of the electroslag furnace.

Furthermore, a ceramic mesh 37 is provided at the opening of the crystallizer, and an electromagnetic stirring device 38 is provided on the outside.

The parent material chamber, vacuum melting chamber and electroslag furnace are arranged in sequence from top to bottom; the bottom of the parent material chamber is connected with the vacuum melting chamber, and a movable sealing plate 26 is provided at the connection point; the top of the conductive crystallizer is sealed and connected with the bottom of the vacuum melting chamber; the induction heating crucible, the funnel guide groove and the conductive crystallizer are arranged in sequence from top to bottom, the induction heating crucible is located directly below the parent material grabber, and the two induction heating crucibles can pour molten steel into the funnel guide groove respectively; a ceramic net is provided at the opening of the conductive crystallizer; an electromagnetic stirring device is provided outside the opening of the conductive crystallizer. The movable sealing plate provided at the connection between the bottom of the parent material chamber and the vacuum melting chamber is opened and closed to realize the connection or isolation between the bottom of the parent material chamber and the vacuum melting chamber. The installation and use of the movable sealing plate are conventional techniques, as long as the effect of the present invention is achieved, as shown in FIG3 , one end of the sealing plate is installed on the wall of the connection through a hinge, and the other end is provided with a handle 261, and sealing strips are provided around. When sealing is required, the sealing plate is pulled up by the handle, and the sealing plate can be fixed at the connection by the friction force of the sealing strip, and can be released when it is needed to be opened. Specifically, it is a conventional technique, such as using a rope 263 to connect the handle at one end and the rotating wheel 264 at the other end, and a supporting roller 262 is provided in the middle to support, so as to realize the rotation of the rotating wheel. The rope is retracted and released to control the closing or opening of the sealing plate. The rotation of the wheel is a conventional technology and can be achieved by a motor. In this embodiment, the handle is on the left and the loose-leaf is on the right, and the sealing plate is opened downward. When the wheel rotates clockwise, the rope is retracted and the sealing plate is pulled up to close the sealing plate. When the wheel rotates counterclockwise, the rope is loosened and the sealing plate is opened into the vacuum melting chamber. When the sealing plate is opened, the parent material chamber is connected to the vacuum melting chamber, and the whole is a vacuum environment. When the sealing plate is closed, the parent material chamber is separated from the vacuum melting chamber, the parent material chamber is a non-vacuum environment, and the vacuum melting chamber is a vacuum environment. The specific connection structure of the movable sealing plate is a conventional technology, and other methods can also be used in existing production, as long as the sealing plate can be opened and closed.

The parent material steel ingot is placed in the left induction heating crucible by using the parent material lifting rod. The left induction heating crucible heats the parent material steel ingot through the external induction coil and melts it into molten steel. The motor is started, and the rotating shaft drives the crucible to rotate so that the molten steel is evenly poured into the lower funnel-shaped guide groove. The casting speed of the molten steel is adjusted by adjusting the inclination angle of the crucible. The molten steel is dispersed into a number of metal droplets after passing through the guide groove and the ceramic net, and is broken into dispersed metal droplets by the electromagnetic stirring device. The droplets pass through the liquid slag pool to form a metal molten pool, and are solidified into an electroslag ingot under the coordinated cooling of the upper conductive crystallization part and the lower water-cooled crystallization part. After the molten steel in the left crucible is poured, the molten steel in the right crucible is poured. The whole process is safe, reliable and has excellent controllability.

The present invention adopts an induction heating crucible to melt the parent steel ingot, shortening the high-end special steel smelting process to the left parent steel chamber - the left induction heating crucible - the right parent steel chamber - the right induction heating crucible periodically alternately melts the parent steel ingot and casts the molten steel - the electroslag furnace production line; the conventional vacuum pump 4 is used to evacuate the vacuum valves 16, 17, 24 simultaneously or separately, and the whole process is isolated from the air, which can avoid the secondary oxidation of the molten steel and perform vacuum degassing on the molten steel; in the electroslag furnace, the molten steel is chemically refined again, and at the same time, its top-down heat conduction mode makes the metal molten pool shallow and flat, which helps the electroslag ingot to obtain a good crystal structure and reduce the center segregation. The production of ultra-clean, homogenized, low-segregation, and extra-large electroslag ingots is realized. In addition, the size of the parent steel ingot in the device only needs to be smaller than the inner diameter of the crucible, and the preparation of the parent steel ingot is extremely simple, and a general continuous casting billet can be used; the height requirement of the plant can also be reduced, the production cost is reduced, and the process is simpler.

Application Example 1.

Referring to FIG. 4 , the base steel ingot 15 is a commercially available stainless steel continuous casting billet with a diameter of 0.5 m and a length of 1.3 m, and the base steel ingot usage is 50 pieces; the inner diameter of the crystallizer of the electroslag furnace is 180 cm, and the solidification rate of the molten steel in the electroslag furnace is controlled at 1320±15 kg/h; the composition of the liquid slag is fluorite: lime: alumina: silicon oxide = 50: 21: 21: 8, mass ratio, and the total mass of the liquid slag is 1000 kg; the temperature of the molten steel in the induction heating crucible during pouring is 1600°C; the two induction heating crucibles have the same structure, with an inner diameter of 0.6 m and a height of 1.3 m; the crucibles both have a weighing function, which is common sense.

After the ingot-drawing bottom water tank and the crystallizer in the electroslag furnace are sealed, the liquid slag is added into the crystallizer through the slag adding port, and the power supply circuit of AC power supply-upper conductive crystallization part-liquid slag-bottom water tank-high voltage switch-AC power supply is turned on to achieve the purpose of heating and insulating the liquid slag 5.

Two parent material steel ingots are placed in the left induction heating crucible and the right induction heating crucible respectively, and the gap between the crucible and the parent material steel ingot is filled with stainless steel chips of the same material. After the two parent material chambers and the vacuum melting chamber are evacuated, the parent material steel ingots in the induction heating crucibles are melted into molten steel 25 in sequence, and the weight of the molten steel is about 2.5 tons; the left crucible is dumped first, the molten steel flows into the guide groove, and the molten steel is broken into dispersed fine metal droplets through the ceramic net and the electromagnetic stirring device, and finally passes through the slag pool to reach the metal molten pool 6, and solidifies into an electroslag ingot 7 under the cooling of the upper conductive crystallization part and the lower water-cooled crystallization part; during the casting process of the left crucible, the sealing plate is closed, the third parent material steel ingot is placed in the left parent material chamber, and the vacuum valve is opened to evacuate.

When the electroslag furnace steelmaking is carried out for about 1.5 hours, there is about 0.5 tons of molten steel left in the left crucible. The crucible is straightened and the right crucible is dumped at the same time. The molten steel flows into the guide groove and finally enters the electroslag furnace crystallizer to solidify into an electroslag ingot. After the left crucible is straightened, the sealing plate of the mother material chamber is opened, and the mother material ingot is placed into the left induction heating crucible through the mother material lifting rod and the mother material grabber. The remaining molten steel fills the gap between the mother material ingot and the crucible, thereby improving the heating efficiency of the induction coil. The heating coil heats the mother material ingot and melts it into molten steel within 1.5 hours. The subsequent odd mother materials are operated in the same way.

When the electroslag furnace steelmaking has been going on for about 3 hours, there is about 0.5 tons of molten steel left in the right crucible. The crucible is straightened and the left crucible is dumped at the same time. The molten steel flows into the diversion trough and finally enters the electroslag furnace crystallizer to solidify into an electroslag ingot. After the right crucible is straightened, the fourth parent material steel ingot is placed into the right crucible through the right parent material chamber and melted into molten steel within 1.5 hours. The same operation is performed for subsequent even-numbered parent materials.

The process is repeated over and over again, with the mother material chamber and crucible on the left side and the mother material chamber and crucible on the right side periodically placing the mother material ingot and melting the mother material ingot into 2 tons of molten steel for 1.5 hours. The mother material ingot is continuously heated and melted by two induction heating crucibles on the left and right sides, and the molten steel is cast alternately at a constant rate to ensure that a continuous and stable molten steel is always provided at a steel output rate of 1320±15 kg/hour. The molten steel is then cast into the crystallizer of the electroslag furnace 3 through the guide groove 23 and the ceramic net 37, so that the electroslag remelting continues; the solidification rate of the electroslag ingot of the electroslag furnace matches the pouring rate of the molten steel, so as to achieve the effect of continuously transporting the molten steel into the crystallizer of the electroslag furnace, and finally produce a 100-ton extra-large electroslag ingot with a diameter of 180 cm and a height of more than 5 meters. Specifically, the liquid level detection sensor detects the liquid level in real time, and drives the formed electroslag ingot to move downward through the ingot-pulling bottom water tank to achieve the purpose of ingot pulling. A molten metal pool will form at the interface between the top of the electroslag ingot and the liquid slag pool. The constructed power supply circuit keeps the slag in a high-temperature molten state. When the ingot is pulled out, the liquid level detection signal is used to ensure that the slag liquid level position in the crystallizer is constant. The ingot pulling can be automatically adjusted by PLC, which is a conventional technology.

After forging and heat treatment, 100 tons of electroslag ingots were sampled, and the oxygen content in the steel was 0.001% and the hydrogen content was less than 0.0001%; the grades of the four types of inclusions A, B, C, and D of the 100 tons of electroslag ingots are shown in Table 1; after the sample was ground and polished and electrolytically corroded by nitric acid solution, the grain size was rated by the comparison method according to ASTM E112-13 (2021), and the grain size grade of the sample was 8.5, as shown in Figure 5; the room temperature tensile strength of the final product was 630MPa; according to JIS Z 2284-1998 standard, the sample was processed into an impact sample with a thickness of 25mm, a width of 50mm, and an initial crack length of 26.5mm, and the sample was impacted in a liquid helium (4.2 K) environment, and the impact energy was measured to be 115J; the corrosion current of the sample was measured to be 2.40× ^10-7 A/ ^cm2 , and the lower the corrosion current value, the better the corrosion resistance of the sample.

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The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. The increase in the number of induction heating crucibles and charging bins, the replacement or transformation of the molten steel participating in the power supply circuit conduction, and the rotation and diversion of the molten steel by the ceramic mesh made by the technicians in this technical field on the basis of the present invention are all within the protection scope of the present invention.

Comparative Example 1.

When the prior art uses a double-arm electroslag furnace to exchange parent steel ingots to produce large-sized electroslag ingots, the cross-sectional diameter of the parent steel ingot is required to be very large. For example, when producing an extra-large electroslag ingot with a cross-sectional diameter of 1.8 meters, the cross-sectional diameter of the parent steel ingot is required to reach 1.4 meters or more to improve the depth of the metal molten pool and reduce the central segregation of the electroslag ingot. This is extremely difficult to produce a parent steel ingot with a cross-sectional diameter of 1.4 meters. The use of parent steel ingots with smaller cross-sectional diameters will seriously worsen the central segregation of the electroslag ingot. The use of die-cast ingots with small cross-sectional areas needs to be forged and roughened before use, which easily leads to forging and roughening cracking of the steel ingot, and the yield rate is extremely low. At the same time, the cross-sectional diameter after forging and roughening cannot meet the parent steel ingot size requirements for the production of extra-large electroslag ingots, and large-tonnage forging machines are also extremely rare on the market. In addition, during the period of time when the double-arm electroslag furnace exchanges the parent steel ingot, the electroslag furnace is in a current interruption state, which is easy to cause slag inclusion and pores, which undoubtedly reduces the performance of the electroslag ingot at this location and makes it impossible to achieve homogenization of the electroslag ingot; at the same time, during the period of exchanging the parent steel ingot, the electroslag furnace crystallizer is in an air atmosphere, which is easily affected by the oxygen and water vapor in the air, causing the electroslag ingot to increase oxygen and hydrogen, and deteriorating the product performance of the electroslag ingot. The device of the present invention alternately melts small-diameter parent steel ingots into molten steel through multiple induction heating crucibles, and the molten steel is alternately poured into the electroslag furnace crystallizer. Only small-diameter parent steel ingots are needed, thereby avoiding the defects of using large-diameter parent steel ingots, and also avoiding the serious problem of electroslag ingot center segregation when the diameter of the parent steel ingot is too different from the diameter of the electroslag ingot. At the same time, the entire electroslag remelting process is carried out in a vacuum and is not interrupted, which solves the problems that the prior art has always wanted to solve, such as vacuum breaking and interruption, but cannot solve.

As shown in CN202671630U (its or similar structures are devices with good application effects in existing production), a double-arm electroslag furnace is used to exchange parent steel ingots to produce extra-large electroslag ingots. Conventional steelmaking-refining-mold casting is used to produce 8 stainless steel mold-cast ingots with a cross-sectional diameter of 72 cm and a length of 6 meters. After heating and forging roughing, 2 mold-cast ingots are scrapped due to cracking during forging roughing, and finally 5 parent steel ingots with a cross-sectional diameter of 100 cm and a length of 3.2 meters are obtained. The inner diameter of the electroslag furnace crystallizer is 180 cm, and the solidification rate of the molten steel in the electroslag furnace is controlled at 1320±15 kg/h; the pre-melted slag composition is fluorite: lime: alumina: silicon oxide = 50: 21: 21: 8, and the total mass is 1000 kg; the electroslag furnace arm has a weighing function to determine the melting rate of electroslag remelting.

Using conventional technology, a double-arm atmosphere-protected electroslag furnace was used to alternately melt five parent steel ingots under the action of the double arms, and finally a 100-ton electroslag ingot with a diameter of 1.8 meters and a height of more than 5 meters was produced. During the electroslag remelting process, the double arms opened the atmosphere protection cover when exchanging the parent steel ingots, and the parent steel ingots were exchanged. During the period of exchanging the parent steel ingots, a large amount of air entered the crystallizer, causing the electroslag ingots to increase in oxygen and hydrogen; in addition, due to the large difference between the diameter of the parent steel ingot and the diameter of the electroslag ingot, the filling ratio was less than the normal electroslag furnace parameter requirements, resulting in severe center segregation.

100 tons of electroslag ingots produced were sampled after forging and heat treatment, and the oxygen content and hydrogen content in the steel were 0.0045% and 0.0007% respectively; the grades of A, B, C, and D inclusions of the 100 tons of electroslag ingots are shown in Table 2; after the sample was ground and polished and electrolytically corroded by nitric acid solution, the grain size was rated by the comparison method according to ASTM E112-13 (2021), and the grain size grade of the sample was 6; the room temperature tensile strength of the final finished product was 400 MPa; according to JIS Z 2284-1998 standard, the sample was processed into an impact sample with a thickness of 25 mm, a width of 50 mm, and an initial crack length of 26.5 mm, and the sample was impacted in a liquid helium (4.2 K) environment, and the impact energy was measured to be 72 J; the corrosion current of the sample was measured to be 1.37×10 ^-7 A/cm ² , and the corrosion current value was significantly lower than that of the sample in Application Example 1. In summary, the inclusion content, grain size, tensile strength, impact energy and corrosion resistance of the sample in Application Example 1 are obviously inferior to the performance indicators of the sample in Application Example 1.

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Embodiment 2.

On the basis of the first application example, the ceramic mesh and the electromagnetic stirring device are removed, and the rest remain unchanged. The same electroslag remelting stainless steel was carried out, and the 100 tons of electroslag ingots finally produced were sampled after forging and heat treatment, and the oxygen content in the steel was 0.0020% and the hydrogen content was 0.0002%; the grades of the four types of inclusions A, B, C, and D of the 100 tons of electroslag ingot are shown in Table 3; after the sample was ground and polished and electrolytically corroded by nitric acid solution, the grain size was rated by the comparison method according to ASTM E112-13 (2021), and the grain size grade of the sample was 7.5; the room temperature tensile strength of the final product was 580MPa; according to JIS Z 2284-1998 standard, the sample was processed into an impact sample with a thickness of 25mm, a width of 50mm, and an initial crack length of 26.5mm, and the sample was impacted in a liquid helium (4.2 K) environment, and the impact energy was measured to be 105J; the corrosion current of the sample was measured to be 2.25× ^10-7 A/ ^cm2 .

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The inclusion content, grain size, tensile strength, impact energy, and corrosion resistance of the sample in Example 2 are slightly worse than those in Example 1, but are significantly better than the performance indicators of the sample in the comparative example.

In the prior art, whether it is consumable electrode type electroslag remelting or refined steel liquid type electroslag remelting, for electroslag remelting of extra-large steel ingots (more than 50 tons), it is necessary to replace the raw materials during the remelting process. Even if it is short, it will cause problems such as contact with air and power failure, which has a great impact on the performance of the extra-large steel ingot. The present invention solves the problem that the prior art has been unable to solve, and creatively proposes a smelting device for clean and homogenized extra-large steel ingots composed of a parent material chamber, a vacuum melting chamber, and an electroslag furnace. The electroslag remelting is continuous and the vacuum environment is maintained, and extra-large steel ingots of more than 50 tons or even more than 150 tons can be prepared. The device of the present invention can produce extra-large steel ingots with a diameter of 120 to 220 cm, a height of 400 to 800 cm, and a weight of 50 to 250 tons. In addition, it also has the advantages of small workshop area, low workshop building height requirement, low production and investment cost, excellent product quality, and the ability to directly induction melt and cool and solidify high-quality scrap parts into electroslag ingots to form a production closed loop for the reuse of high-quality scrap steel.

Claims (10)

1. A smelting device for clean homogenized extra-large steel ingots, characterized in that it comprises n mother material chambers, a vacuum smelting chamber, and an electroslag furnace; the mother material chamber is provided with a mother material lifting rod and a mother material grabber, and a mother material chamber vacuum valve is provided on the side wall; the vacuum smelting chamber is provided with n induction heating crucibles and a funnel guide groove, and a vacuum melting chamber vacuum valve is provided on the side wall; the electroslag furnace comprises a conductive crystallizer; the mother material chamber is connected with the vacuum smelting chamber, and a movable sealing plate is provided at the connection point; the induction heating crucible, the funnel guide groove, and the conductive crystallizer are arranged in sequence up and down; n≥2.
2. The smelting device for clean homogenized extra-large steel ingots according to claim 1 is characterized in that the parent material chamber, the vacuum melting chamber, and the electroslag furnace are arranged in sequence from top to bottom; the bottom of the parent material chamber is connected to the vacuum melting chamber, and the top of the conductive crystallizer is sealed and connected to the bottom of the vacuum melting chamber.
3. According to the smelting device of clean homogenized extra-large steel ingots as described in claim 1, it is characterized in that the induction heating crucible is located directly below the parent material grabber; a ceramic mesh is provided at the opening of the conductive crystallizer; and an electromagnetic stirring device is provided outside the opening of the conductive crystallizer.
4. The smelting device for clean homogenized extra-large steel ingots according to claim 1 is characterized in that n induction heating crucibles can pour molten steel into the funnel guide groove respectively.
5. The smelting device for clean homogenized extra-large steel ingots according to claim 4 is characterized in that n induction heating crucibles are arranged side by side.
6. Application of the smelting device for clean homogenized extra-large steel ingots as described in claim 1 in the preparation of clean homogenized extra-large steel ingots.
7. The method for preparing a clean homogenized extra-large steel ingot by using the smelting device for a clean homogenized extra-large steel ingot according to claim 1 is characterized in that it comprises the following steps:

   (1) loading a base material steel ingot into each induction heating crucible in a vacuum melting chamber through a base material chamber, evacuating the base material chamber and the vacuum melting chamber, and then induction heating and melting the base materials in each induction heating crucible to form molten steel;

   (2) The first induction heating crucible is tilted, and the molten steel flows into the electroslag furnace crystallizer through the funnel guide groove, and then the first induction heating crucible is returned to the right position; at the same time, the second induction heating crucible is tilted, and the molten steel flows into the electroslag furnace crystallizer through the funnel guide groove, and then the second induction heating crucible is returned to the right position; the subsequent induction heating crucibles are sequentially subjected to the same operation;

   (3) Close the sealing plate, place the first parent material ingot into the parent material chamber, evacuate the parent material chamber, open the sealing plate, place the parent material in the parent material chamber into the first induction heating crucible that has returned to the right position, and heat and melt the parent material ingot in the crucible; when the second induction heating crucible returns to the right position, tilt the first induction heating crucible, and allow the molten steel to flow into the electroslag furnace crystallizer. At the same time, place the parent material in the second parent material chamber into the second induction heating crucible that has returned to the right position, and heat and melt the parent material ingot in the crucible; perform the same operation on subsequent induction heating crucibles in sequence;

   Repeat step (3) to obtain a clean, homogenized extra-large steel ingot.
8. The method for preparing a clean, homogenized extra-large steel ingot according to claim 7 is characterized in that the molten steel flows from the funnel guide groove through a ceramic mesh and electromagnetic stirring treatment, and continuously flows into the electroslag furnace crystallizer.
9. A clean, homogenized extra-large steel ingot prepared according to the method for preparing a clean, homogenized extra-large steel ingot according to claim 7.
10. The use of the clean homogenized extra-large steel ingot as described in claim 9 in the preparation of extra-large steel products.