RU2247625C1 - Method for acting upon chemical composition of melt steel before continuous casting process and during such process and crater formation preventing apparatus for performing the method - Google Patents

Abstract

FIELD: metallurgy, namely processes for billet continuous casting.

SUBSTANCE: method comprises steps of preparing melt steel in main vessel, then pouring it through discharge opening to intermediate vessel and from intermediate vessel at least to one mold. When steel is in main vessel and during stages of pouring steel into one of said vessels elements changing properties of steel together with inert or neutral gas are added to steel. At least during one stage of pouring steel, said elements together with gas are fed through hollow stopper made as one piece with apparatus preventing crater formation while changing position of stopper relative to discharge opening. At lower position lower end working part of stopper is arranged in steel flow leaving respective vessel. In hollow stopper pressure of supplied gas is kept slightly higher or equal to steel pressure acting upon lower end working part of stopper. Continuous casting is also realized through apparatus preventing crater formation.

EFFECT: production of small lots of high quality billets of different chemical composition due to uniform rational feed of alloying elements and(or) killing agents together with gas in melt steel, controlled casting rate, elimination of slag penetration to intermediate vessel and mold.

4 cl, 11 dwg, 7 ex

Description

The invention relates to metallurgy, but more to the production of billets in the steel industry by continuous casting.

In recent years, the technical problem of the operational organization of production in ferrous metallurgy, oriented toward mass production, of small batches of billets with increased demand in the market has become more and more acute. The existence of this problem and the search for its solutions was noted in a review of the journal “News of the iron and steel abroad” (JSC “Chermetinformatsiya”, “Steelmaking on the threshold of the third millennium”, Appendix No. 7 to this journal, 2000, p. 38).

Thus, in large metallurgy, focused on the mass production of steel billets by continuous casting, the technical problem arose of changing the chemical composition of steel as it is cast and on this basis obtaining small batches of billets (little party in big metallurgy, "LP in BM", t .e. “small batches in large metallurgy”).

When searching for a technical solution to the actual problem under consideration, it is taken into account that the continuous casting process includes preparing steel for casting and two stages of steel transfusion: from a steel ladle to an intermediate ladle and from the latter to a mold. At each of these operations, the chemical composition of steel can be influenced and the technical solution to the problem is to find such a set of techniques that would ensure good results while maintaining the continuity of the casting process. At the same time, good results are understood as ensuring high quality of the obtained blanks at minimal cost.

A known method of treating liquid steel with gas in the process of continuous casting, comprising casting steel with an inert or neutral gas in a steel stream through a hollow stopper under a pressure equal to the metal pressure in the stream (see, for example, RF patent No. 1838037, 22 D 11 / 10, published in BI No. 32 of 08.30.93).

This method has inherent disadvantages that impede its highly efficient use for influencing the chemical composition of steel before and during continuous casting:

- firstly, the method does not provide for the supply of alloying elements and / or deoxidizing agents to steel, which excludes a change in the chemical composition of the steel;

- secondly, the adoption of a gas supply condition under pressure equal to the steel pressure in the jet is not unambiguous (the latter will become clear when considering this proposal) to ensure good quality of the obtained workpieces.

There is a method of preparing steel for casting, including the supply of alloying elements and / or deoxidizers from above into the steel ladle tank (see, for example, V.I. Yavoysky et al. “Steel metallurgy”: Textbook for high schools. M: Metallurgy, 1983, pp. .268).

This method, widely used in ferrous metallurgy, has significant disadvantages:

- firstly, the problem of influencing the chemical composition of steel in the entire volume of the ladle capacity is solved, which excludes the organization of the production of small batches of steel billets in large metallurgy, when the mass of steel in the ladle can reach 300 tons;

- secondly, only a part of the deoxidant supplied to the liquid steel (aluminum, calcium, rare-earth metals, rare earth metals, etc.) is involved in the steel deoxidation process; a significant part of the deoxidizer evaporates (burns out);

- thirdly, the implementation of the method essentially precedes the process of continuous casting and the method cannot be applied in the process of casting itself.

A known method of influencing the chemical composition of liquid steel before and during continuous casting, including the preparation of molten steel in the main tank and its continuous casting, which consists in the transfusion of steel through the outlet from the main tank to the intermediate tank and from the intermediate tank to at least one mold, the supply to the steel of elements that change its properties when it is in the main container and during at least one of the transfusions (see, for example, US 4632368A, B22D 11/118, 11/14, 12/30/1986).

This known method, according to the essential features, is closest to the proposed one, therefore it is adopted as a prototype.

The known method has the following significant disadvantages that impede its successful application for the operational solution of the problem of production of small batches of steel billets in large metallurgy:

- firstly, the supply of alloying elements and / or deoxidizers directly into the glass, connecting the containers with steel, cannot provide the desired quality of the obtained billets for chemical composition. This is due to the fact that it is not possible to reliably determine and control the speed of steel flow in the glass and the pressure that forms during this process, which, moreover, continuously changes as the steel is cast. As a result, the possibility of uniform supply of these elements to steel is excluded;

- secondly, the problem of uniform distribution of input elements in the volume of liquid steel in the mold, which also reduces the quality of the workpieces, has not been solved;

- thirdly, in the preparation of steel for casting, significant losses of deoxidizing agents have already been noted.

The proposed method of influencing the chemical composition of liquid steel before and during the continuous casting process is free from these disadvantages. It optimally solves the problem of uniform and economical supply of alloying elements and / or deoxidizers together with an inert / neutral gas to liquid steel, including in the mold.

The technical result is the rapid production of high-quality steel in the production of small batches of billets in large metallurgy, thus solving technological possibilities by ensuring the receipt of billets of different chemical composition.

This technical result is obtained due to the fact that in the known method of influencing the chemical composition of liquid steel before and during the continuous casting process, which includes preparing the molten steel in the main vessel and subsequent transfusion of steel through the outlet from the main vessel to the intermediate vessel and from the intermediate vessel to at least one mold, feeding elements into the steel that change its properties when it is in the main tank and in the process of at least one of these transfusions, according to the invention, the supply of the indicated elements to the liquid steel during at least one of the transfusions is carried out together with an inert or neutral gas through a hollow stopper made with the possibility of vertical movement, while the lower end working part of the stopper is moved relative to the outlet from the upper to the lower position in the lower position, the lower end working part of the stopper is placed in a stream of steel leaving the corresponding container, and pressure is maintained in the hollow stopper along the supplied gas is somewhat greater than or equal to the pressure of the steel on the lower end working part of the stopper.

The supply of the indicated elements to liquid steel together with an inert or neutral gas during at least one of the overflows is carried out through a hollow stopper, which is integral with the anti-funnel device.

In addition, in the process of preparing liquid steel for continuous casting, these elements are supplied to the main tank together with an inert or neutral gas through a hollow false stopper.

For the effective implementation of the proposed method, it is important to ensure a uniform distribution of the elements supplied to the steel in the volume of liquid steel in the mold. Usually for this, the main part of the steel stream is twisted in a limited volume of the mold.

An anti-funnel-forming device is known that contains a bottom, side walls with through side holes and an assembly section that is integral with the side walls and forms the outlet of the device, while the device is installed in the bottom of the tank for casting steel with slag and is located opposite the outlet of the tank with the bottom up ( see, for example, WO 02/076658 A1, B 22 D 43/00, 03/10/2002).

The specified anti-funnel device by essential features is closest to the proposed, therefore, taken as a prototype.

The main disadvantage of the known device is the inability to use it with a stopper that regulates the process of casting liquid steel from the tank.

The proposed anti-funnel device is free from this drawback. It provides for the possibility of using the device in conjunction with a stopper that controls the rate of pouring liquid metal from the tank.

The technical result is the complete exclusion of funnel formation during casting of steel and ingress of slag into the intermediate ladle and mold during continuous casting of steel.

This is achieved by the fact that in the known anti-funnel forming device comprising a bottom, side walls with through side openings and an assembly section that is integral with the side walls and forming the outlet of the device, the device is installed in the bottom of the tank for casting steel with slag and is located opposite the outlet upside down, according to the invention it is provided with outer side walls installed with a gap with the inner side walls, while the height of the outer side walls enshe height of the inner walls, and a bottom configured for mounting a hollow stopper central through hole with walls defining a hollow appendix coaxial with the outlet opening of the container and extending beyond the slag located in the vessel, with the inner diameter of ridge exceeds the diameter of the outlet of the container.

For the effective implementation of the proposed method, it is essential to solve the technical problem of guaranteeing the supply of alloying elements to an appropriate container and ensuring uniform distribution of the alloying elements supplied to the liquid steel in the volume of steel in the mold prior to the start of crystallization of steel, which is carried out using the known design of a hollow stopper and using a deaf immersion nozzle at the site of transfusion of steel from the capacity of the intermediate ladle into the mold, providing x conversion of kinetic energy within the moving glass steel in its rotational movement in the mold.

By the combination of the above methods and devices for their implementation, they are supplied to liquid steel before (in the main vessel, a steel ladle) and during continuous casting of alloying elements that change the properties of cast steel, thereby solving the urgent problem of producing small batches of steel billets in large ferrous metallurgy (little party in big metallurgy, “LР in ВМ”).

The proposed method of feeding into liquid steel before and during the continuous casting of elements that change the properties of cast steel, and an anti-funnel-forming device for its implementation are explained in schematic drawings.

Figure 1 shows a General diagram of the implementation of the method of feeding into liquid steel elements that change its chemical composition;

figure 2 - the relative position of the anti-funnel device and the hollow stopper;

figure 3 - the relative position of the hollow stopper, anti-funnel device and submersible deepwater nozzle in the area of continuous casting: intermediate tank - mold;

figure 4 is a section along aa in figure 3;

figure 5 - the device of the lower part of the submersible deep-sea glass and its location relative to the mold, as well as the movement of liquid steel provided by this glass in the mold;

in Fig.6 - the specifics of the supply to liquid steel during its transfusion from one tank to another of alloying elements or deoxidants and an inert or neutral gas when the lower end part of the hollow stopper is located above the main stream of steel leaving the corresponding tank, and at the pressure of the gas supplied to hollow stopper at the level of pressure of liquid steel on the lower end working part of the hollow stopper;

in Fig.7 - the same as in Fig. 6, but at a gas feed pressure in the hollow stopper below the pressure level of the molten steel on the lower end working portion of the hollow stopper;

on Fig - the same as on fig. 6, but at a gas supply pressure in the hollow stopper above the pressure level of the liquid steel on the lower end working part of the hollow stopper;

Fig.9 - the supply of liquid steel alloying elements and / or deoxidizers and inert or neutral gas during the transfusion of steel through the outlet from one container to another when using a hollow stopper located in the lower position;

figure 10 is a hollow stopper;

figure 11 is a diagram of a laboratory setup (cold model), which assessed the effectiveness of the methods for implementing the proposed method.

The continuous casting machine (CCM) contains (Fig. 1) a steel ladle 1, an intermediate ladle 2 and a mold 3 (the number of molds can vary from one to several). The capacity of the steel ladle is filled with steel 4, the capacity of the intermediate ladle is filled with steel 5 and the mold capacity (within the crystallized steel - meniscus of liquid steel) is filled with steel 6. The capacity of the steel ladle is equipped with an outlet 7. Slag 8, 9 and 10 are located above the liquid steel in steel bucket 1, in the intermediate bucket 2 and in the mold 3. The component of the bucket 2 is an anti-funnel-forming device 11. For at least one of these anti-funnel-forming devices, the component is tsya hollow retainer 12 - for ladle 1 and 13 - to the tundish 2. The hollow stopper may be false, for example in the ladle and perform only those functions which are provided by the present method. In this case, a slide gate is used. The hollow stopper is equipped with a vertical movement mechanism (in Fig. 1, the vertical movement of the stopper is shown by arrows). The cavity of the applied hollow stopper is connected by a pipeline or pipelines 14 to a container or containers 15 filled with (filled) powder or powders containing alloying elements and / or deoxidizing agents. At the same time, deoxidizers are preferred (but, strictly speaking, not necessary) for steelmaking, alloying elements are mainly for the intermediate ladle.

The number of containers 15 and pipelines 14 is determined by the number of alloying elements and deoxidizers supplied to the steel. The final combination of these elements in one container, common for this hollow stopper, is possible. But the more accurate the dosage of alloying elements introduced into the steel, the more preferable is their individual supply to the hollow stopper.

An inert or neutral gas is supplied to each container 15 through the pipe 16, the flow rate of which is determined by the device 17, and the pressure by the device 18; the consumption of alloying elements and deoxidizing agent is controlled by the dispenser 19 for each container personally. The anti-funnel device 11 with the side openings 20 (FIG. 2) is located upside down 21 and the neck 22 (mounting portion) down, opposite to the outlet 23 of the corresponding container with a recess in the bottom material 24 of the container. In the bottom 21 of the anti-funnel forming device (FIGS. 2 and 3), a central hole 25 is made, into which the hollow stopper 13 (for the intermediate bucket) enters with the possibility of vertical movement relative to the bottom 21, which is an integral part of this device. The wall 26 of the opening 25 is raised from the bottom 21 of the anti-funnel-forming device with the formation of a process 27 (Fig. 1), so that the upper part of the process 27 extends beyond the slag 9 (see Fig. 1; the latter mainly relates to the operation of the tundish). In the bottom 21 also anti-funnel device made evaporation holes 28 (Fig.3). The hollow stopper 12 (13) comprises a body 29 (FIG. 10), an upper end portion for securing the stopper 30, and another (lower) end working portion 31; the distance between the lower end working surface of the stopper and the surface of the outlet 23 determines the casting speed of the molten steel. The end working part of the hollow stopper during its operation is its lower part. This lower part of the hollow stopper ends with the process 32 (Fig.2, 3, 9-10), which in the lower position of the stopper enters the outlet 23 (Fig.2, 3, 9). The process 32 is coaxial with the body of the stopper 29 and is made with a through central hole 33 that is integral with the central hole 34 in the body 29 of the hollow stopper. The anti-funnel device 11 in FIG. 1 can also be made without a shoot 27 and a central hole 25 in the bottom 21 (FIG. 1). In this case, the casting of steel from the intermediate tank to the corresponding mold is carried out without adding these elements to liquid steel, i.e. liquid steel is poured having a chemical composition in the volume of the intermediate tank. The casting of liquid metal can be carried out without a glass (figure 1). Thus, the Central outlet 7 and 23 (respectively, the main tank is a bucket, an intermediate tank is an intermediate bucket), passing into the dispenser glass 35 (Figs. 2 and 3), can be the final part of the corresponding tank, from which the liquid steel enters another capacity (figure 1, shown by a dotted line). However, it is preferable that the dispensing cup 35 is connected to a submersible cup 36 (FIGS. 3 and 5 and FIG. 1), which is made deaf-flowing (FIGS. 3 and 5), containing at the bottom part output channels 37 fan-shaped around the cup perimeter (FIG. 3 -5) with the displacement of their longitudinal axes relative to the longitudinal axis of the glass (figure 4). On a deep-sea submersible glass 36 with fan-shaped channels 37, on its lower end part, a dome in the form of a skirt 38 is fixed, the lower edge of which and the lower surface of the output channels 37 of the deep-sea glass 36 are interconnected. The deep-sea immersion nozzle 36 has a central opening 39 in the bottom (Figs. 3-5), the area of which is approximately ≈ 0.25 of the sum of the cross-sectional areas of the outlet channels 37. The outer diameter D of the skirt 38 is selected on the basis of the impossibility of the outer surface of the skirt coming into contact with a crystallized steel crust 40 (Fig. 5). The skirt 38 in its main part has a cylindrical inner working surface 41, the most developed taking into account the noted restrictions on the outer surface (figure 4). The use of a mold 3 with extensions 42 is preferred (FIG. 5, dotted). The Roman numerals I-VII in FIG. 5 show typical trajectories of the majority of the flow of molten steel coming from the intermediate vessel 2 into the mold 3 through a deep-dipped immersion nozzle 36 and fan-shaped channels 37. The Roman numerals I ′ - III ′ in FIG. 5 shows typical motion paths of a smaller part of a stream of molten steel coming from an intermediate vessel (scoop) 2 into the mold 3 through a deep-sea immersion nozzle 36 and a central hole 39 in the bottom of this nozzle. The entry into the liquid metal of alloying elements and / or deoxidizers 43 and neutral or inert gas bubbles 44 (FIGS. 6-9) depends on the ratio of the pressures of the supplied inert or neutral gas p _r and the steel pressure p _c on the lower end working part of the process 32 of the hollow stopper 13. The specificity of this admission in the absence on the hollow stopper 13 of the appendix 32 is shown in Fig.6-8. In a laboratory setup (FIG. 11), in addition to those shown in FIG. 1-10 devices and structures used a funnel 45, a metering valve 46, sensors for measuring the resistance (concentration) of the solution 47, microammeters 48, a solution of KCl 49 and water 50.

The method of supplying to molten steel before and during its continuous casting of elements that change the properties of cast steel is as follows.

Take into account the determining influence on the process of entry into liquid steel (of the introduced elements changing the ratio of the gas pressure p _g supplied to the steel through the hollow stopper together with the introduced

in steel elements, and steel pressure on the lower end working part of the hollow stopper p _s (Fig.6-9).

Moreover, at the bottom of the vessel 24, the dependence of p _c on the depth of steel in the vessel has the form:

p _с1 = ρ _{с •} h _c + ρ _{ш •} h _ш, (1)

where ρ _c is the density of steel; ρ _W - the density of the slag; h _W - the height of the slag in the tank; h _with - the value of the height of the steel in the tank.

Since the value of h _c decreases as the steel is cast, the value of p _c1 also decreases.

The same dependence when the lower end working part 32 of the hollow stop is located in the area of the steel flow (i.e., below the bottom of the tank 24) leaving the tank has the form

where V is the speed of flow of steel around the lower end of the working part 32 of the hollow stopper at the exit level of the hole 33 from the body of the hollow stopper 29. The value of V varies depending on p _{c1 the} location of the lower end working part 32 (end face of the working part 31) of the stopper relative to the bottom 24 of the tank (Fig.6-9), which in turn are determined by the speed of drawing the workpiece from the mold (mold), i.e. casting speed.

For highly efficient supply of alloying elements, deoxidizing agents, etc. to the molten steel leaving the tank, it is necessary to fulfill at least the ratio

p _g ≅ p _c . (3)

To a large extent, a slight excess of p _g over p _s and the location of the end face of the end working part 31 of the body of the hollow stop 29 are necessary in the stream of molten steel leaving the tank.

In the case of p _g <p _s (Fig. 6) and the location of the end face of the end working part 31 of the hollow stopper outside or at the beginning of the flow of liquid steel leaving the tank, the liquid steel of the corresponding capacity rises into the stopper cavity to a height at which p _g = p _s Thus, when these conditions are realized, there is no entry of elements 43 introduced into the steel.

Therefore, when implementing the present method, the condition p _g <p _s is satisfied at the level of the end face of the end working part 31 of the hollow stopper, and if this ratio takes place, the steel transfusion process is stopped.

Thus, when implementing the present method, before and during the continuous casting of steel in the hollow stopper, the pressure of the inert or neutral gas supplied is slightly greater than or equal to the pressure of the steel on the lower end working part 31 of the hollow stopper, while the alloying elements and / or deoxidizers are fed into the steel together with inert or neutral gas.

In the case of p _g > p _s (Fig. 7), the elements 43 and gas bubbles 44 supplied to the steel after rising from the cavity of the working end part of the stopper 31 rise up, the more so, the greater the excess of p _g over p _s . As a result, alloying elements and / or deoxidants introduced into the steel are captured by gas 44 and carried into the bulk of the liquid steel in the vessel. First of all, these substances enter the capacity of the anti-funnel device (if used) and, if the continuous casting process is not stopped, then into the capacity of the bucket 2 or steel ladle 1 (Fig. 1). Basically, the indicated ratio p _g > p _{c is} guided by acting on the chemical composition of steel 4 in steel ladle 1 (Fig. 1) before it begins to be cast, i.e. when they carry out the refinement of steel before casting. In this case, the end face of the end working part 31 of the stopper is raised to a level or slightly higher than the bottom level of the tank 24 (i.e., it is removed from the zone of action of the steel flow leaving the tank), a false stopper 13 and a slide gate are used.

In the case of p _g ≅ p _s (Fig. 8) (and some excess) when the end face of the end working part 31 of the stopper is in the stream of liquid steel leaving the vessel, the elements introduced into the steel completely enter the stream of steel leaving the corresponding vessel. The indicated ratio is guided by a change in the chemical composition of steel during its transfusion from one container to another, i.e. mainly when transfusing steel 5 from an intermediate ladle 2 into a crystallizer (molds) 3.

For guaranteed fulfillment of condition (3) and its effective implementation when feeding elements into molten steel, a hollow stopper having a process 32 of the end working part 31 of the hollow stopper is used before and during its continuous pouring from one container to another. At the same time, the process 32 is coaxial with the body of the hollow stopper 29 and has a through central hole unified with it (Fig. 10).

Using the described hollow stopper, condition (3) is guaranteed to be satisfied (see Fig. 9), and when the stopper 13 is raised to a level where the end section of the appendix 32 is raised to the level (and slightly higher) of the bottom 24 of the tank, the elements supplied to the steel from the cavity 34 of the hollow stopper 13 into a container with liquid metal (analogy with Fig. 7 and materials for this figure).

The alloying elements and / or deoxidants necessary for the implementation of the method are supplied to the container (s) 15 in the form of a powder. As these elements pass through the cavity of the stopper 12 (for steel ladle 1) or 13 (for the intermediate ladle 2) immersed in liquid steel, some of them having a low melting point (for example, Al, Ca, etc.) melt the elements are ultimately fed into the steel in a liquid state. Moreover, in the process of implementing this method provide significant savings of deoxidants entering the steel, due to the lack of contact with air.

Before continuous casting (before installing steel ladle 1 on the continuous casting machine), steel 4 with slag 8 (Fig. 1) is poured into the steel ladle 1 tank and by supplying alloying elements and deoxidizers, often together, and mainly with argon (may be nitrogen) through a hollow stopper 12 carry out the refinement of steel 4 to the main chemical composition. In this case, a false hollow stopper 12 and a slide gate (not conventionally shown in FIG. 1) are used. The main chemical composition of steel is steel, which dominates the program of orders for steel billets received from continuous casting machines (comprising 50 ... 100% of the order portfolio). Alloying elements and deoxidizing agents (deoxidizing agent) are supplied to the hollow stopper 12 from the container (s) 15 (Fig. 1) through the pipe (s) 14. Through these same pipes argon is supplied to the hollow stopper, which is supplied through the pipe 17 to each container 15. The argon pressure p _g in the cavity of the stopper 12 is set higher than the pressure of steel p _s on the lower working part of the stopper 12, more precisely, on the end face of the process 32. The hollow stopper 12 is installed in the capacity of the steel ladle 1 at a distance of 50 ... 100 mm (or less) of the end face of the process 32 from the bottom of the bucket. The installation of the hollow stopper is carried out using, for example, hydraulic cylinders (in Fig. 1, the hydraulic cylinders and the mechanism for moving the stopper are not conventionally shown, since they do not change the essence of the method). The argon flow rate is controlled by the device 17, the flow rate of alloying elements and deoxidizing agents is controlled by the dispenser (s) 19. In the course of these operations, the steel shutter 1 slide gate is closed.

At the end of the process of finishing the steel to the basic chemical composition, the steel ladle 1, filled with steel 4 and slag 8, is fed to the continuous casting machine.

In the steel ladle 1 installed on the CCM with steel 4 of the main chemical composition and slag 8, the hollow stopper 12, more precisely the butt of the process 32, is located at a depth guaranteeing that this end is in the zone of the steel flow, which is transfused into the intermediate ladle 2 through the outlet 7 A false hollow stopper 12 and a slide mechanism for closing (opening) the outlet opening are used (not shown in the drawings, since it does not affect the essence of the implemented method).

In the absence of a slide mechanism in the steel ladle, the hollow stopper 12 in the steel ladle 1 installed on the continuous casting machine is lowered until its end part 31 comes into contact with the surface of the outlet and the described position of the end face 32 is provided before the steel casting begins. Naturally, in this case, the ingredients are fed into molten steel in order to change its chemical composition of the steel when steel is transferred from the steel ladle to the intermediate ladle, fulfilling condition (3), i.e. p _g ≅ p _s

In steel ladle 1, an anti-funnel device is used (or not used). The use of such a device does not complicate the initial location of the hollow stopper 12 opposite to the outlet 23.

In the intermediate bucket 2, a hollow stopper 13 is used (stoppers - according to the number of outlet openings corresponding to the number of molds). The cavity of each stopper 13 is connected to its complex of containers 15 with elements introduced into the steel and supply of argon (nitrogen) to the containers. In all molds 3 caster set the seed (in the drawings, the seed is not conventionally shown, since it does not determine the nature of the implemented method). Carry out the installation of the stoppers 13 in the intermediate bucket 2 so that the outlet openings 23 are closed. In this state, the continuous casting machine is ready for continuous casting of steel with exposure to its chemical composition during the specified casting.

Carry out continuous casting of steel with an effect on its chemical composition during casting, which is realized by arranging the hollow stopper 12 for the steel ladle (stopper or stoppers 13 for the intermediate ladle) in such a way that the lower end working part 32 of the stoppers is installed in the area of the steel flow leaving appropriate capacity (see Fig.9). The impact on the chemical composition of the steel is carried out by feeding elements introduced into it from the steel from the containers 15 together with argon (nitrogen) into the cavity of the hollow stoppers. The feed is carried out when the considered ratio p _g ≅ p _{s is} fulfilled. The fulfillment of this ratio is ensured by arranging the lower end working part of the hollow stopper (end face of the appendix 32) in the stream of steel leaving the corresponding container (steel ladle 1 or bucket 2).

Thus, during the transfusion of steel from one tank to another, it is supplied together with an inert or neutral gas with all the necessary and sufficient elements for a given change in the chemical composition of the steel, while creating a supply gas pressure p _g at the level of steel pressure p _s per end of the process 32 of the corresponding stopper 12 (13), which is located in the area of the flow of steel leaving the corresponding container.

Depending on the portfolio of orders for manufactured billets, they carry out various options for influencing the chemical composition of steel before and during the continuous casting process.

Option 1. Before casting steel by performing the described techniques in steel ladle 1 form steel of the same chemical composition. During the transfusion of steel from steel ladle 1 into the intermediate ladle 2, the chemical composition is adjusted by feeding alloying elements together with argon (may be nitrogen) into the hollow stopper 12 and from it into steel. The implementation of option 1 greatly simplifies the operation of lapping steel, making it the same (quasi-identical) for CCM.

Option 2. In the process of casting steel by performing the described operations in the stream of steel leaving the steel ladle 1, serves the main part of the input elements. As a result, in the intermediate bucket 2, steel of intermediate chemical composition is obtained. When pouring steel from blast furnace 2 into the mold 3, the rest of the alloying elements are fed into the stream of steel leaving the blast furnace 2, clarifying the chemical composition (and, accordingly, the properties) of the obtained steel billets. If there are several molds into which steel from the ladle is continuously poured, the specified refinement of the chemical composition is performed for one or for a number of molds. The latter depends on the portfolio of orders.

An integral part of the method for influencing the chemical composition of steel is the use of an anti-funnel-forming device 11 and its definite relative position with the hollow stopper 13 and the latter relative to the surface of the outlet 23 in the tank (FIGS. 2 and 3).

In the tundish, an anti-funnel-forming device is used, made in the form of a jug with holes 20 in the side walls (Fig. 2), with its bottom 21 upward and its neck 22 downward opposite to the outlet 23 and with the recess of the mounting section into the bottom material 24 of the corresponding capacity. To exit the slag (9, respectively), which got into the device through the holes 20 when filling the tank, evaporation holes 28 are made in the bottom 21. The anti-funnel-forming device is made with a single bottom 21 and two side walls with a gap between them and with holes 20 in the inner side wall, while the outer side wall is shorter than the inner. In the center at the bottom 21 of the device, a hole 25 is made with walls 26, into which a hollow stopper 13 is provided, equipped with a device for vertical movement of the stopper (see Figs. 2 and 3). The side walls 26 are continued and form a process 27, the height of which eliminates the ingress of slag 9 into the anti-funnel-forming device (see figure 1).

For steel ladle 1, the anti-funnel-forming device can be made in the form of a known float of refractory material, the density of which is greater than the density of slag, but less than the density of liquid steel. In this case, there is also a hole in the center of the anti-funnel device (float) into which a hollow stopper with a drive is inserted for its vertical movement.

The hollow stopper, along with the use of an anti-funnel device to perform the described operations, eliminates the phenomenon of funnel formation. Thus, the hollow stopper is integral with the anti-funnel device used (FIGS. 2 and 3).

In those continuous casting machines where steel is poured from the intermediate ladle 3 into the crystallizer 3 without using an immersion nozzle (shown in dashed in Fig. 1), the above operations complete the supply to the molten steel before and during its continuous casting of elements that change the properties of being cast into billets steel.

части потока переливаемой стали, поступающей в кристаллизатор. Для реализации этого приема применяют глуходонный погружной стакан 36 (фиг.3 и 4), содержащий в нижней части выполненные веерообразно по периметру стакана выходные каналы 37 со смещением их продольных осей относительно продольной оси стакана (фиг.4). На этот погружной стакан 36, на его нижнюю часть, выше выходных каналов 37, закрепляют купол в форме юбки 38. Юбка 38 может иметь цилиндрическую форму с наружным диаметром D меньше расстояния между закристаллизовавшимся слоем стали 40 на уровне нижнего края юбки (фиг.5). Может быть также применена юбка 38 конической формы, в которой очертания внутренней и наружной поверхностей выполнены коническими с меньшим диаметром у нижнего края юбки, так что расстояние между наружной поверхностью юбки и внутренней поверхностью закристаллизовавшейся стали 40 сохраняют примерно одинаковым на длине юбки.When using a submersible deep-sea cup 36 (Figs. 3–5) at the overflow section of steel 5 from the intermediate ladle 2 to the crystallizer 3, the effectiveness of the above set of operations for influencing the chemical composition of steel and, accordingly, the properties of the resulting workpieces is enhanced by twisting

part of the overflow steel stream entering the mold. To implement this technique, a deep-sea submersible nozzle 36 is used (FIGS. 3 and 4), comprising output channels 37 fan-shaped along the circumference of the nozzle in the lower part with a shift of their longitudinal axes relative to the longitudinal axis of the nozzle (FIG. 4). A dome in the form of a skirt 38 is fixed to this immersion cup 36, to its lower part, above the outlet channels 37. The skirt 38 may have a cylindrical shape with an outer diameter D less than the distance between the crystallized layer of steel 40 at the level of the lower edge of the skirt (Fig. 5) . A conical-shaped skirt 38 can also be used in which the outlines of the inner and outer surfaces are made conical with a smaller diameter at the lower edge of the skirt, so that the distance between the outer surface of the skirt and the inner surface of the crystallized steel 40 is kept approximately the same along the length of the skirt.

In addition, in the bottom of the deep-sea submersible nozzle 36, an axial hole 39 is formed. The cross-sectional area of this hole is approximately 0.25 of the sum of the cross-sectional areas of the output channels 37.

A deep-sea immersion nozzle 36 is used and the kinetic energy of the steel 5 moving inside the nozzle is used to rotate the molten steel in the mold 3. The skirt 38 eliminates the impact of the steel jets leaving the nozzle 36 through the fan-shaped outlet channels 37 into the crystallizing steel 40, thereby preventing the possibility of breakthrough by molten steel crystallized crust 40. The location of the lower edge of the skirt 38 between the level of the lower surface of the bottom of the glass 36 and the lower surface of the output channels 37 minimize the observed rapid quenching the resulting rotation of the steel in the skirt 38 due to friction between the layers of steel after they enter the bulk of the mold.

In this case, the steel flow 5 (FIG. 5) is twisted by the output channels 37 due to the impact of the jets of steel leaving the channels 37 into the cylindrical surface of the skirt 38. The steel flows are formed in the skirt 38 and out along the paths of type I-VII in FIG. 5. In this way, a large part of the flow of steel 5 is screwed into the mold 3 through the cup 36, at the beginning in the mold volume limited by the skirt 38, then in this state the steel enters the mold bulk.

The use of a skirt 38 with a conical surface enhances the effect of steel rotation in the mold due to, firstly, a decrease in the cross section of the rotating steel flow emerging from the skirt, and secondly, to a constant gap between the outer surface of the skirt 38 and the crystallized steel sheath 40.

To better mix the steel in the center of the mold and reduce, on this basis, segregation phenomena in the center of the cast billet, a smaller part of the steel flow from the cup 36 enters the mold 3 through the central hole 39 and moves along the paths similar to I ′ -III ′ in the mold in FIG. 5 . This additionally ensures homogenization of the chemical composition of the steel in the mold.

The rotation of the steel in the mold has an undesirable effect on the meniscus of steel. The maximum elimination of this influence is provided by the use of extensions 42 in the molds.

When implementing the described method at continuous casting machines, devices and methods are used that prevent contact of the cast steel with the ambient air, ensure the safety of the processes of preparation, storage and transportation of bulk materials introduced into steel.

The implementation of this method involves solving the problems of desulfurization of steel, its dephosphorization, non-oxidation, nitriding (or nitrogen removal), carburization, alloying with various elements, removal of non-metallic inclusions, etc., i.e. a set of actions that ensure a change in the chemical composition of steel during its casting along with quality improvement.

When implementing this method, observe the known recommendations for safety when working with bulk materials:

- do not allow the possibility of local concentration of fine fractions;

- exclude access to an open flame, sparks or spray of liquid metal;

- exclude the possibility of electrostatic discharges;

- do not allow moisture during storage and during transportation of bulk materials by gas, etc.

Particular attention is paid to these recommendations when feeding Al, Mg, CaSi and CaC ₂ ; in these cases, only Ar is used as the gas.

When implementing this method, it is taken into account that a number of powder materials with a particle size <0.2 mm (and even 0.5 mm) tend to form explosive mixtures.

Thus, the implementation of this method is impossible without strict adherence to well-known rules and experience gained in working with bulk materials, the use and observance of which guarantee the safety of the method.

The implementation of this method involves working with the following materials in powder form:

1) for desulfurization: CaSi, CaC ₂ , CaCN ₂ , CaAl, CaMg, CaSiMg, Mg and others. In this case, for slagging reactions, combinations are possible: CaO - CaF ₂ ; CaO - Al ₂ O ₃ ; CaO - Al ₂ O ₃ - CaF ₂ ; CaO - Al; CaO — CaF ₂ —Al; CaO - CaF ₂ - CaSi; CaO - Mg; CaO - Mg; CaO - CaF ₂ - Mg; CaO and others;

2) for deoxidation (deoxidation): CaSi; CaSiBa; CaSiMn; CaSiMnAl; CaSiMgFe; Al et al .;

3) for sulfur modification: CaSi; SiZr et al .;

4) for dephosphorization: CaO - CaF ₂ - Fe ₂ O ₃ in the form of a mixture;

5) for decontamination: FeZr; SiZr et al .;

6) for alloying: Si with FeSi75; N with CaCN ₂ (≈ 55% CaCN ₂ ; 33% CaO; 12% C).

With graphite powder:

B with B ₂ O ₃ ;

Ni with nickel oxides;

Mo with molybdenum oxides.

For a number of powders, for economic reasons, fractions are used:

CaSi - up to 0.6 mm;

CaC ₂ -0.1 ... 0.6 mm;

CaMg - 0.1 ... 1.5 mm.

The combination of the described techniques and the used fractions of the elements introduced into the steel during the implementation of the variants (and their combinations) of the present method of influencing the chemical composition of the steel before and during the continuous casting process solve the important technical problem of producing small batches of billets in large metallurgy at continuous casting machines , “LР in ВМ”), designed for mass production of blanks. The economic efficiency of solving this problem is manifested in the prompt satisfaction of customer requests without creating excessive stocks of stocks in warehouses, in accelerating the turnover of invested funds.

Example 1. On a cold model (Fig. 11) containing an intermediate bucket 2, a crystallizer 3 (square), an anti-funnel device 11 with a hollow stopper 13 with a process 32 passing through its center, a submersible deaf glass 35 with an inner ⌀ 35 mm and a skirt 38 (and without it) with fan-shaped openings 37, resistance sensors 47 (platinum, with an area of 20 mm ² and a distance between them of 17 mm), microammeters 48, studied the supply of a 6% solution of KCl (49), poured into a funnel 45, for the chemical composition of water 50 , poured into the container 2 and through the holes 20, a glass-dosed p 35, holes 34 and 37 and a skirt 38, poured into a square container 3 and from it to the drain.

38 l of water 50 was poured into tank 2, 600 cm ^{3 of a} 6% KCl solution was poured into a funnel 45 with the ultimate goal of having a solution of 0.1% KCl in water in tank 3.

At the beginning, by lifting the stopper 13 (lifting the plug 31) with the dispensing valve 46 open, the container 3 (crystallizer) was filled with water and KCl solution and, at the moment the container 3 was completely filled, the plug was opened in the bottom of the container. Thus, the KCl solution entered the tank 3, the level of the water solution in which was kept constant.

Microammeters 47 recorded the obtained values of the concentration of the KCl solution in water at the level of 0.1% KCl in three places of measurement. The outflow time was 1'5 "... 1 ′ 10".

The main mixing of water with a 50 and 6% KCl solution to obtain a calculated solution of 0.1% KCl occurred along the path of movement of these components along the dispenser glass 35 and the glass 36. The use of a skirt 38 further improved the mixing of KCl and water by about 25 ... 28% .

In 40 measurements, the maximum deviation from the calculated concentration of KCl in the solution, equal to 0.1% KCl, was obtained at a level of ± 0.005% or less.

Example 2. There is an order for billets made of steel with chemical composition A (symbol) and chemical composition B, the ratio between which is, for example, 80% steel A and 20% steel B of the volume of steel ladle. There is an insignificant difference in chemical composition between steels A and B, while steel B contains a greater number of alloying elements. To complete the order there is a continuous casting machine equipped with one mold. The blanks have the same cross section.

The steel obtained at the steelmaking unit using the described set of techniques of the proposed method is brought in the steel ladle (ladle furnace) to the chemical composition of steel A and the steel ladle with steel A is fed to the casting machine for continuous casting.

Without changing the chemical composition of the steel, 80% of the volume of the steel ladle is casted. By the end of the casting of this volume of steel, the flow of steel from the steel ladle into the intermediate ladle is temporarily stopped. Moreover, thanks to extensions 42 support a stable process of crystallization of steel A in the mold. Carry out the maximum, but not complete emptying of the tundish. The use of an anti-funnel-forming device 11 eliminates the formation of a funnel and the entry of slag from the tundish into the mold.

After the indicated emptying of the intermediate ladle from the main part of steel A, the intermediate ladle is accelerated to be filled with steel B, while steel B is obtained by introducing the necessary elements together with argon into steel A through the hollow stopper of the steel ladle according to the techniques described in the proposed method. The lower end of the stopper (process 32) of the steel ladle when converting steel A to steel B is located in the area of the flow of steel leaving the steel ladle. The rest carry out the operations described in the description of the method.

In essence, the casting process is carried out with the effect on the chemical composition of the steel before casting and during the transfusion of steel from a steel ladle into an intermediate ladle.

Part of the workpiece with a transition chemical composition between steels A and B after continuous casting machine is cut.

Example 3. There is an order similar to example 2, but steel B in chemical composition differs significantly from steel A and contains a larger number of alloying elements. Casting is carried out on continuous casting machine with one mold. Until the start of the casting of steel B, the set of operations described in example 2 is repeated.

When switching to casting steel of chemical composition B and obtaining billets from it, the main effect on the chemical composition of steel is carried out at the stage of steel transfusion from the steel ladle to the intermediate ladle by supplying the main alloying elements necessary for changing the chemical composition of steel from A to B. through steel hollow stopper of the steel ladle.

The final chemical composition of steel B is provided by affecting the chemical composition of steel at the stage of steel transfusion from the intermediate ladle to the mold. At this stage of steel transfusion, alloying elements are fed into the steel, sufficient to change the chemical composition of the steel from A to B.

The impact on the chemical composition of steel when pouring it from a steel ladle to an intermediate ladle and from the latter to a mold is carried out using the methods of the present method.

Part of the workpiece with a transition chemical composition between steels A and B after continuous casting machine is cut.

Example 4. The production of preforms according to example 2 is carried out on a continuous casting machine with two molds.

In the steel ladle, analogously to example 2, steel A of the main chemical composition is obtained and the steel ladle is fed to the continuous casting machine.

In the process of continuous casting at the beginning, both crystallizers are used to produce steel A workpieces, then, after casting 60% of the volume of the steel ladle, steel A is continued to be poured from one of the molds, steel B is fed into the other mold, and the chemical composition is affected at the stage of transfusion of steel from the intermediate ladle into this mold.

The productivity of continuous casting machines in the implementation of example 4 in comparison with example 2 is almost doubled. After crystallization, part of the preform with a transition chemical composition between steels A and B is cut out.

Example 5. The production of preforms according to example 2 is carried out on a continuous casting machine with two molds.

In the steel ladle, analogously to example 2, steel A of the main chemical composition is obtained and the steel ladle is fed to the continuous casting machine.

During casting, at the beginning 60% of the volume of the steel ladle is poured through one of the molds and billets are made of steel A. Then, from 40% of the remaining volume of steel being poured into the pit, 20% of the steel is poured into a working mold, and 20% of the steel is poured into another mold. acting on the chemical composition of the steel at the stage of its transfusion into another mold in accordance with the methods of the present method, obtaining steel B from this mold.

Before the casting of steel B and in its process take into account the transition moment necessary to start casting steel chemical composition B.

Provide the production of steels of different cross sections from steels A and B.

Example 6. Carry out the production of preforms according to example 2. In contrast to example 2, the transfusion of steel from the ladle into the mold with the effect on its chemical composition is carried out using a deaf submersible nozzle of the described construction. As a result, the main part of the steel stream is twisted in a limited volume of the mold and in this state, steel B enters the main volume of the mold. The implementation of the latter operations improves the distribution of alloying elements over the volume of steel B in the mold and affect the formation of dendrites of the crystallizing crust of steel. This improves the quality of steel B.

Example 7. There is an order for billets made of steels A, B and C, the ratio between the supply volumes of which is x, y and z% of the volume Q of the steel ladle, respectively, while, for example, x> y> z. The casting is carried out on a continuous casting machine with three molds. Steel A contains the smallest number and number of alloying elements, steel B contains the largest number and number of alloying elements.

The steel obtained in the steelmaking unit is poured into a steel ladle. In the steel ladle using the described set of techniques, chemical composition steel A is obtained and the steel ladle is fed to the continuous casting machine.

In the casting process, through one of the molds, billets of steel A are obtained without affecting the chemical composition of the steel. In the process of transfusion,% of the volume of steel A from the intermediate ladle to another mold affects the chemical composition of steel, transferring it from steel A to steel B. In the process of transfusion, z% of the volume of steel A from the intermediate ladle to the third crystallizer affects the chemical composition of steel, transferring it is from steel A to steel B. As production of x billets from steel A, for billets from steel B and z of billets from steel B, the casting process in the corresponding mold is stopped.

Thus, simultaneously with a continuous casting machine, x · Q billets of steel A are obtained from the same steel ladle with steel of volume Q, y · Q are billets of steel B and z · Q are billets of steel B. The cross section of the resulting billets of different chemical composition may be different (or the same) .

Claims (3)

1. The method of influencing the chemical composition of liquid steel before and during continuous casting, including the preparation of molten steel in the main tank and its subsequent transfusion through the outlet into the intermediate tank, and from the intermediate tank into at least one mold, feeding into steel elements that change its properties when it is in the main tank and in the process of at least one of the transfusions, characterized in that in the process of at least one of the transfusions in molten steel the elements are fed together with an inert or neutral gas through a hollow stopper integrally with the anti-funnel device, arranged for vertical movement, while the lower end working part of the stopper is moved relative to the outlet from the upper to the lower position, and in the lower position the lower end working part of the stopper placed in a stream of steel leaving the appropriate container, and in the hollow stopper, the pressure of the supplied gas is kept somewhat greater or equal steel pressure on the lower end working part of the stopper. 2. The method according to claim 1, characterized in that in the process of preparing molten steel, these elements are fed into the main tank together with an inert or neutral gas through a hollow false stopper. 3. An anti-funnel-forming device for influencing the chemical composition of molten steel before and during continuous casting, comprising a bottom, side walls with through side holes and an installation section that is integral with the side walls and forms the outlet of the device, while the device is installed in the bottom of the tank for casting metal with slag and is located opposite to the outlet of the tank upside down, characterized in that it is provided with outer side walls installed with a gap with an inner side walls, while the height of the outer side walls is less than the height of the inner side walls, and the bottom has a central through hole for installing a hollow stopper with walls forming a hollow process, coaxial with the outlet of the vessel and extending beyond the slag located in the vessel, while the inner diameter of the process exceeds the diameter of the outlet of the tank.

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