RU2250809C2 - Method for casting metal and apparatus for performing the same - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method comprises steps of filling vessel with metal together with slag; immersing refractory member into melt metal; emptying vessel through casting opening. Refractory member embraces body of stopper and it has specific dimensions in plan view. Refractory member is arranged with possibility of free vertical motion relative to stopper. At process of emptying vessel, refractory member vertically moves over casting opening. When casting process is terminated, refractory member self-descends until contact with bottom of vessel. Stopper is descended until contact with casting opening. Size of refractory member exceeds by several times diameter of casting opening.

EFFECT: prevention of funnel formation at end of casting and elimination of slag immersion in metal.

9 cl, 24 dwg

Description

The invention relates to the casting of liquid metal in metallurgy, in particular to the continuous casting of steel from a ladle, including intermediate, in ferrous metallurgy.

In the process of, for example, continuous casting of steel, a steel pouring ladle is used, from which liquid metal is fed into the intermediate ladle, from which steel in turn enters the mold and crystallizes into the billet (continuously cast slab, bloom, round billet). Casting of steel from the ladle is usually carried out through a casting hole (there may be several in the ladle) located at the bottom of the ladle.

To prevent oxidation and to slow down the cooling of steel, slag is formed in these ladles, which is significantly lower in density than the density of liquid steel, and therefore is on top of the liquid metal. Thus, the presence of slag is a prerequisite for casting steel.

During the casting process, it is highly desirable to exclude the ingress of slag from the casting ladle into the intermediate ladle and from the latter into the mold, since in these cases the likelihood of slag entering the finished workpiece increases, which leads to its rejection.

The inevitability of mass ingress of slag from the casting ladle into the intermediate ladle and from it into the workpiece increases many times at the end of the pouring of molten metal from the corresponding ladle and is due to the phenomenon of funnel formation (vortex), which leads to a sharp increase in the slag pulling into the funnel. Since vortex belongs to unstable natural phenomena, it is not possible to predict the moment and conditions of its occurrence and, therefore, to cut off slag from the metal in the ladle at the end of its casting. The latter makes it necessary to leave a significant part of the metal in the ladle and thereby increase the expenditure coefficient in the production of continuously cast billets, and worsen the technical and economic indicators of production.

The described phenomena are also fully inherent in casting steel from a ladle into molds, however, this method of casting steel is not analyzed in detail here because of its decreasing use in metallurgy, although the technical proposal considered below is fully applicable to this method of casting metal.

These phenomena also occur in the manufacture of shaped castings made of steel and cast iron by pouring molten metal from a steel ladle through an outlet in its bottom and usually result in rejects of 1-2 finished castings obtained by the latter.

Thus, the solution of the technical problem of cutting off slag from metal at the end of casting metal from the ladle is very relevant in the processes of casting steel into molds, continuous casting of steel at the continuous casting machine and in foundry, as it can significantly reduce the loss of steel during its subsequent crystallization.

A known method of casting steel, including the cut-off of slag in the ladle during casting of metal (see US patent No. 4936553 from 06.26.90). The method involves reducing the amount of slag leaving the metal through a pouring hole in the bottom of the bucket equipped with a slide gate.

The method includes introducing into the liquid metal bucket several pieces of irregularly shaped refractories. The density of these pieces of refractory material is greater than the density of the slag and less than the density of the liquid metal. Thus, these pieces of refractory material are located at the slag-metal interface, and at the end of the casting, thanks to the vortex, they rush to the casting hole and partially overlap it. Further ingress of slag into the metal is finally suppressed with a slide gate.

The disadvantages of this method include, firstly, only a partial overlap of the ingress of slag into the metal; secondly, the inability to implement the method in the presence of several casting holes in the bottom, for example, a casting or tundish; thirdly, essentially uncontrollability of the process of getting slag into the metal at the stage of vortex appearance.

A known method of casting steel, which includes cutting off slag from metal in ladles with a stopper by closing the stopper with a stopper (see, for example, V.I. Yavoysky et al. "Metallurgy of steel". M .: Metallurgy, 1983, p.341 -342).

The disadvantages of this method include, firstly, the inability to determine the volume of metal and slag in the bucket and, accordingly, to separate the slag from the metal; secondly, the application of the method does not prevent the appearance of vortex, but it appears when a significant portion of the metal is still in the bucket.

There is a known method of casting steel, the basis of which is the use of a system that automatically shows the degree of release of the intermediate ladle from steel and prevents the ingress of slag together with metal into the continuous casting machine (see, for example, “Ferrous metals”, November – December 1998, p. 41-45). In turn, the basis of this system is the use of a residual steel detector. The disadvantages of the method include the lack of its basis of measures to prevent the appearance of vortex. The latter makes it necessary to leave a significant amount of steel in the bucket: up to 150 mm in height of the bucket (instead of 450 mm without a detector), which is quite significant in mass production.

A known method of casting steel, comprising filling metal with a container equipped with at least one controlled stopper, placing with deepening in the metal of the refractory, supplying metal from this container through at least one casting hole provided in its bottom. At the end of the casting of the metal, the surface of the refractory, as indicated in the known method, reaches the surface of the casting hole, closes it and the flow of metal and slag from the tank automatically stops. Then the refractory is additionally pressed by the stopper and the container (ladle) is prepared for the next heat [see, for example, RF patent No. 21115510, B 22 D 41/08 of 05/10/94]. In this case, a refractory of the correct form with a flat working surface is used. In addition, the refractory is made of a material having a density higher than the density of the slag and lower than the density of the liquid metal.

The closest analogue to the metal casting method is a casting method, which includes filling a container with a stopper with metal, which stops casting the metal, placing a refractory into the metal, emptying the container through the casting hole provided in the bottom of the container, and self-moving the refractory vertically above the casting hole during casting ( US 4968007, C 21 V 7/24, 11/06/1990).

The known method has the following disadvantages:

1. The method does not provide for the exclusion of the appearance of vortex, and therefore, is not prevented from slag drawing in the metal at the stage before the end of the casting of the metal.

2. In a ladle with several casting holes (for example, in some cases, casting from a steel casting and from an intermediate ladle), it is not possible to guarantee the implementation of the method due to the unpredictable behavior in this case of several refractories floating in the metal.

3. At the end of the casting, when the casting hole is blocked by refractory material, a significant part of the metal remains in the ladle, because due to vortex and the appearance of a pulling force noticeably exceeding the buoyancy force, the thickness of the metal remaining in the ladle can be about 1.5 ... 2 times the height of the refractory.

The proposed method of casting metal is free from these disadvantages. In it, first of all, the appearance of vortex is prevented, thereby eliminating the drawdown of slag into the metal before the end of the casting of the metal. In addition, the amount of metal remaining in the ladle at the end of the metal casting is minimized, thereby improving the technical and economic performance of the metal casting process. The application of the method is also possible in a bucket with several casting holes.

These technical results are achieved due to the fact that in the method of casting metal, which includes filling the tank with metal with slag having a stopper, which stops casting the metal, immersion in the metal of the refractory covering the stopper, emptying the tank through the filling hole provided in the bottom of the tank, self-movement refractory during casting vertically above the pouring hole, self-movement of the refractory is carried out regardless of the movement of the stopper, while at all stages eniya refractory its upper surface projects above the slag surface.

In addition, at the end of the casting, after the refractory is self-lowering until it contacts the surface of the bottom of the container, the stopper is lowered to contact the casting hole, and the surface of the bottom of the container in contact with the refractory is protruded along the perimeter of the filling hole.

A device for casting a metal is known, containing a container, a stopper located opposite to the hole with the possibility of forced vertical movement [see, for example, Strugovshchikov D.P. Steel casting. M .: Metallurgizdat, 1961, p.29-31, fig. 12].

The closest analogue of the claimed device is a metal casting device containing a container having a pouring hole in the bottom, a stopper with a vertical movement opposing to this hole, a refractory covering the stopper body and having in plan characteristic dimensions exceeding the diameter of the casting hole (US 4968007, C 21 V 7/24, November 6, 1990).

A significant disadvantage of the known device is the inability to suppress the appearance of vortex and thereby eliminate the ingress of slag into the metal in the initial stages of the end of the casting. Thus, the use of the known device does not allow to completely cut off the slag from the metal at the end of the casting of the metal, which leads to increased losses of metal in the marriage, to increase the expenditure coefficient.

The proposed device for casting metal is free from these disadvantages. The use of its design allows to prevent the appearance of vortex, in addition to minimize the remaining metal in the tank (ladle) at the time of casting and the slag is cut off from the metal. Together, the above allows us to generally reduce the loss of metal when it is transferred from a liquid state to finished billets.

These technical results are achieved due to the fact that in the device for implementing the method of casting metal, containing a container having at least one casting hole in the bottom, an opposing stopper with a vertical movement mechanism, a refractory covering the stopper body and having in terms of characteristic linear dimensions several times the diameter of the pouring hole, according to the proposal, the refractory is installed with the possibility of free vertical movement of the relative but a stopper.

In addition, the device is equipped with a sleeve of graphite placed on the inner surface of the refractory.

The metal casting method and the device for its implementation can prevent the appearance of vortex itself as the metal level in the tank (ladle) decreases and, thus, eliminate the slag being drawn into the metal at the early and final stages of the end of its casting. In addition, there is minimal metal left in the ladle at the time of casting. At the same time, the tasks of filling the tank with metal, the beginning of casting and its implementation in the established mode are simultaneously solved. Ultimately, metal losses in the production of billets are generally reduced, thereby improving the technical and economic performance of the casting process.

The metal casting method and the device for its implementation are illustrated by schematic drawings on the example of casting steel from the CCM ladle. However, the essential features of the method and device for its implementation fully relate to the casting of steel from the casting ladle. They also apply to casting steel from a ladle into molds, as well as to casting shaped castings from steel and cast iron.

The drawings show several options used in the proposal of techniques and their technical implementation. Figure 1-4 shows the sequence of implementation of the casting method, when the refractory self-moves vertically regardless of the movement of the stopper. The bucket is shown, in the bottom of which a recess is made in the area of the location of the casting hole. The presence of this deepening enhances, as will be shown below, the effect of reducing metal losses, but does not significantly affect the implementation of the main operations of the method. Therefore, in the following figures, the absence of a depression in the bottom of the bucket indicates that it either does not exist, or it does not matter for explaining the method. Figure 5 and 6 enlarged shows the position of the metal, slag, stopper and refractory, shown in figure 3 (respectively figure 5) and figure 6 (respectively figure 4).

In Fig.7 shows the implementation of the casting method for the example of using an intermediate ladle with several recesses in the bottom of the bucket and with several casting holes (Fig.7 shows two recesses in the bottom of the bucket and two casting holes), Fig.8 is a section BB Fig.7 and Fig.9 is a section aa in Fig.7.

Figure 10-13 shows embodiments of the refractory in plan in the form of a circle: cylinder (figure 10); truncated cone (11); spherical layer (Fig.12) and barrels (Fig.13). On Fig-23 shows embodiments of the refractory in the form of a polyhedron: a direct prism (hexagon in Fig.14 and in plan in Fig.15); truncated pyramid (Fig. 16 and in plan of Fig. 17); truncated tetrahedron (Fig. 18 and in the plan of Fig. 19); the obelisk (Fig. 20 and in the plan of Fig. 21), a rectangular parallelepiped (Fig. 22 and in the plan of Fig. 23). The embodiments of the refractory shown in FIGS. 10-23 indicate that the execution of the refractory in plan can have an arbitrary shape determined by the conditions of manufacture and use.

24 are curves showing the influence of the gap (area F _Щ ) between the refractory and the bottom of the bucket on the duration of metal outflow (curve 1) and the influence of the characteristic linear size of the refractory in terms of d _c on the same metal casting parameter (curve 2) F ₀ , τ ₀ and d ₀ - for the case of free outflow of metal.

The bucket (for example, intermediate) 1 is equipped with a stopper 2 (Fig.1-16). The stopper 2 can be covered by a refractory 3, which is equipped with the ability to move freely relative to the stopper. The stopper 2 is equipped with a controlled vertical movement mechanism 4, an integral part of which is the balancing mechanism 5 of the stopper 2 and refractory 3, made, for example, in the form of a counterweight connected through a block system to the stopper 2. Refractory 3 is mainly made of refractory material having a density of 3 , 1 ... 4 g / cm ³ at a liquid steel density of 6.9 ... 7.0 g / cm ³ and a slag density of 2.6 ... 3.0 g / cm ³ . In the case of casting a metal of a different density and the formation of slags of a different density, the refractory material is selected with a density lying between the densities of the liquid metal and slag. The housing 6 of the bucket 1 inside is lined with refractory brick 7. The bottom of the bucket can be almost flat, without recesses. But preferably, a recess 8 is made in the bottom of the bucket 1, in which a casting hole 9 with an inner diameter d _{0 is located} (the number of casting holes and the number of recesses in the bucket are the same and can range from 1 to 6 ... 8 or more). The dimensions of the recess 8 in the bottom of the bucket and the dimensions of the refractory 3 are interconnected. The dimensions of the refractory 3 and the diameter d _{0 of the} pouring hole 9 are also interconnected. The liquid metal in the ladle 1 is designated 10, slag 11. The bottom of the bucket in all figures is indicated by 12.

Refractory 3, as already noted, may have an arbitrary shape in plan, but preference is given to its regular shape, moreover, in the form of a round body. Refractory 3 can also be used as a polyhedron. A cylinder-shaped refractory has a thickness h _c and a characteristic linear dimension (in plan) is a diameter d _c . The refractory in the form of a round straight truncated cone has a thickness h _c and a characteristic linear dimension (in plan) is the diameter d _{c of the} base of the cone. The refractory in the form of a spherical layer (Fig. 19) has a thickness h _c and a characteristic linear dimension (in plan) is the diameter d _c , the larger of the two diameters characterizing this body. A barrel-shaped refractory characterizes the thickness h _c and the largest diameter d _c . A product in the form of a polyhedron - a right prism has a thickness h _c and the characteristic linear dimension in a plane _with, in _c and d _c. A product in the form of a truncated pyramid has a thickness h _c and the characteristic large linear dimensions in terms of a _c, a _c and d _c. The refractory in the form of a truncated tetrahedron has a thickness h _c and characteristic linear dimensions in terms of a _c and d _c . The obelisk-shaped refractory has a thickness h _c and characteristic linear dimensions in terms of d _c , in _c and d _c . A product in the form of a rectangular parallelepiped has a thickness h _c and the characteristic linear dimension in a plane _with, in _c and d _c. Taking refractories of the correct form as a basis facilitates their manufacture. The shape of the refractory in the plan is determined, firstly, by its manufacture, and secondly, solved by the technical task during the implementation of the method: preventing the appearance of vortex and eliminating the ingress of slag into the metal when the ladle is empty. For example, the shapes of the refractory in FIGS. 20 and 22 are preferable for the rectangular shape of the bucket, and for FIGS. 10-18 for the practically cubic or cylindrical shape of the bucket (naturally, with a corresponding slope of the side walls).

When implementing the method, a refractory with an arbitrary figure in the plan is also used (Fig. Not shown, because the shape of the figure in the plan can be different). The use of a refractory with an arbitrary figure in the plan is preferred when, along with the noted technical problems, additional ones are solved. For example, to prevent the formation of a rectangular bucket in the bottom areas, in its corners of stagnant zones. In this case, the figure of the refractory is developed in this direction.

The bottom of the bucket 12, as already noted, can be made flat. However, this design of the bucket increases the amount of metal remaining in the ladle at the end of casting, when the flow of metal from the ladle is blocked. The design of the bottom of the bucket with recesses in which the casting holes are located minimizes the amount of metal remaining in the bucket. The noted correlation of the dimensions of the recess 8 in the bottom of the bucket aims to minimize the amount of metal remaining in the bucket and consists in the following. The height of the recess h _y in the bottom of the bucket is always less than or sometimes equal to the thickness of the refractory h _c , i.e. for all refractory designs, the inequality h _y <h _c holds. When using a stopper plug 3 with a refractory in the form of a round body (Figs. 10-13), along with the inequality h _y <h _{c, the} diameter of the recess d _y in the bucket exceeds the characteristic linear dimension in terms of refractory, i.e. refractory diameter d _c . Thus, the inequality d _y > d _c in Figs. 1-4 is guaranteed to be fulfilled for all embodiments of the refractories in the form of a round body (Figs. 10-13). When using refractories in the form of a polyhedron (Figs. 14-23), along with the inequality h _y <h _{c, the} characteristic linear dimensions in terms of the recess in the bucket also exceed the characteristic linear dimensions in terms of the refractory shown in Figs. 15, 17, 19, 21 and 23. In this case, in the case of the stopper 2 being rotatable relative to its longitudinal axis during vertical movement, the diameter of the recess d _y in the bucket exceeds the maximum characteristic linear dimension in terms of refractory, which is the diameter d _{c of the} described circle, i.e. the inequality d _y > d _c holds, d _c is the diameter of the circle that describes the base of the corresponding figure of the refractory. In the case of stopper 2 with guides that exclude the possibility of its rotation about its longitudinal axis during its vertical movement, the outline in terms of the recess in the bucket repeats the outline in terms of the refractory used in excess of its characteristic linear dimensions.

When implementing the technical proposal, preference is given to the implementation of the stopper 2 with guides that exclude its rotation in the process of its vertical movement. This design, firstly, guarantees a good joint of the refractory 3 and the recess 8 in all cases of their work; secondly, it minimizes the amount of metal remaining in the ladle at the time of cutting off its outflow at the end of the casting. This design of the stopper enhances the effect of the use of refractory in terms of preventing the formation of vortex.

In the case of the bottom 12 of the bucket 1 with recesses for a better solution of the problem, the bottom 12 of the bucket 1 can be made with a slope towards the recess 8 in the transverse and longitudinal directions of the bucket. Moreover, for ladles with two or more casting holes 9, the bottom 12 of the bucket 1 is made with a single longitudinal and single transverse slopes.

The stopper 2 in its lower part can end with a stopper plug 13 extending beyond the refractory 3. The materials of Fig. 10 on an enlarged scale illustrate the solution in this case of the technical problem of cutting off the flow of metal with slag from the ladle at the end of its emptying: the stopper plug 13 closes the pouring hole 9, while refractory 3 prevents the appearance of vortex. The bottom of the bucket 12 may be flat or have recesses 8.

At the same time, when assigning the magnitude of the protrusion h _{in the} stopper plug 13 from the refractory 3, it is taken into account that the size h in FIG. 10 between the bottom 12 of the bucket and the lower surface of the refractory 3 should be approximately 5 ... 10 mm and is specified by the practice. With a gap h of less than 5 mm, the probability of the refractory 3 touching the bottom of the bucket and not closing it with a stopper 3 of the hole 9 increases. With a gap h = 20 ... ∞30 mm, the likelihood of vortex forming in the molten metal at the final part of the casting and drawing slag 11 into the metal increases 10. In this case, the gap h-10 ... 20 mm is accepted as a safety net, taking into account the operation of the bucket, its parts and assemblies in real conditions of metal casting.

The technical proposal provides a movable connection of the refractory 3 relative to the stopper 2. In this case, the refractory 3 has the ability to self-move relative to the body of the stopper 2. An important position of this design is the guaranteed excess of the upper surface of the refractory 3 above the level of slag 11 at all stages of self-movement of the refractory. This requirement is due to the need to prevent slag from entering the gap between the stopper 2 and the refractory 3 and, accordingly, into the metal 10 leaving the bucket.

When performing the articulation of the refractory 3 and the stopper 2 in the form presented and described in FIGS. 5-10 and 16, the likelihood of liquid metal 10 getting into the gap between the stopper 2 and the refractory 3, in which there is an increased heat sink, is also taken into account. There is a real possibility of the solidification of the metal in this gap with the formation of so-called dots, the formation due to this fixed connection of the refractory 3 with the stopper 2 at an indefinite length of the stopper 2.

This problem is solved in the present technical proposal by making the inner cavity of the refractory 3 made of graphite 14. Graphite 14 forms cast iron with steel 10 (naturally in very small quantities), which has a noticeably lower melting point and thus prevents the formation of dots.

When performing the articulation of the refractory 3 and the stopper 2 in the form shown and described in FIGS. 1-4, the load 15, which controls the amount of penetration of A _m into the metal 10 of the refractory 3, is located directly above the refractory.

In some cases, especially when casting high-quality grades of steel, a projection 16 is made at the bottom 12 of the ladle, which covers the outlet 9 and in all respects (area, linear dimensions in plan) approximately corresponds to refractory 3.

When assigning the dimensions of the refractories and their location relative to the bottom of the bucket, it is recommended to use the data of Fig. 24, where it is indicated (except already indicated): F _u is the area of the gap between the refractory and the bottom of the bucket, F ₀ is the area of the hole 9, τ ₁ is the duration of the outflow of metal from bucket through the hole 9 when using the stopper 9 and refractory 3 at the ratios shown in Fig.24, τ ₀ - the same, in the absence of stopper 2 in the bucket (which is practically the same as the data if there is a stopper 2 in the bucket, but installed at a height of more 30 mm).

The metal casting method is as follows.

Before filling the bucket 1 with liquid metal 10 and pointing the slag 11 with a stopper 2 with mechanism 4, the refractory 3 is pressed with force P to the bottom of the recess 8 in the bottom 12 of the bucket. The stopper 2 with refractory 3 allows, when performing this operation, to cut off the casting hole 9 from the metal 10 and thereby eliminate the outflow of metal from the ladle 1 during its filling.

After the bucket 1 is filled with metal 10 and the slag 11 is full by mechanism 4, the stopper 2 with refractory 3 is lifted, thereby stopping the stopper 2 from the bottom 12 of the bucket 1 (or from the bottom of the recess 8, if any) or in the presence of a counterweight ( counterload), provide the stopper with refractory the ability to self-install in the metal that has filled the bucket. Self-determination occurs under the action of a buoyant force and ends with a certain depth of h _m refractory 3 in metal 10, i.e. stopper with refractory become a float type.

The depth value h _{m of the} refractory 3 is pre-adjusted by changing the counterweight of the mechanism 5 taking into account the weight of the stopper 2 and the refractory 3. Strictly speaking, the principle of regulating the value h _{m of the} depth of the refractory 3 in the metal does not matter when implementing this method, it is important to have a mechanism for regulating the specified depth h _m Those. the implementation of the present method involves along with the controlled movement of the stopper 2 using mechanism 4, the possibility of self-movement of the stopper 2 with refractory 3 in the form of a float that tracks the level of metal 10 in the bucket 1 with a well-defined penetration of h _u into the metal of the refractory 3. It is advisable to use refractory 3 of material with a density higher than the density of the slag and lower than the density of the metal, because this additionally facilitates the said preliminary regulation of the depth of h _{m of the} refractory 3 in the metal, but basically the said regulation is carried out by the indicated selection of the counterweight value in the mechanism 5 (or another mechanism that solves this problem).

The depth value h _{m of the} refractory 3 in the metal is controlled within 0 <h _u <h _y , where h _y is the height of the metal 10 left in the ladle 1 at the end of the casting process.

In this case, they are guided by the following provisions: 1. With a decrease in the value of I _s , and especially when its value approaches zero (where 0 is equivalent to the absence of penetration of the refractory 3 into metal 10 and the finding of its lower surface on the metal-10 interface, slag 11), sharply the likelihood of slag entering the pouring hole 9 increases, but at the same time, the volume of metal 10 remaining in the ladle 1 at the end of the casting is minimized.

2. With an increase in the value of h _m , the guarantee of the slag 11 being cut off from the metal 10 substantially increases by the end of the metal 10 emptying of the ladle 1, but at the same time, the volume of metal 10 remaining in the ladle 1 at the end of the casting also increases significantly.

Experimentally (in cold model) is obtained that in case of execution in the bottom 8, the height h _y recesses bucket decision value of penetration h _m refractory 3 metal 10 equal to the depth h _y recess 8 in the ladle occurs guaranteed clipping slag 11 from the metal 10 ( In the model, tinted vegetable oil was used as slag 11, metal 10 imitated water), while the volume of metal remaining in the ladle at the end of the casting is almost equal to the gap formed between the refractory 3 and the walls of the recess 8 in the bottom 12 of the ladle 1, t. e. in this case, the minimum possible amount of metal remains in the bucket 1.

Ultimately, the value of the penetration h _{u of the} refractory 3 into the metal 10 is selected empirically, taking into account the real ratios of the linear dimensions of the refractory 3, its height h _c , the density of the material of the refractory, the densities of the metal and slag; a significant influence on the choice of size h _{m is} proved by the diameter of the casting hole d ₀ , which largely determines the rate of outflow of metal 10 from the ladle 1, and the force attracting the refractory 3 to the bottom of the bucket (to the bottom of the recess 8) at the end of the casting of metal from the ladle. However, in the process of this selection, the values of h _u basically do not go beyond the already agreed limits 0 <h _u <h _y , where h _y in the case of the bottom of the bucket with a recess 8 is the value of this recess.

The position of the refractory 3 and stopper 2 changes during the casting of the metal, since they self-move vertically (like a float) with a change in the level of metal 10 in the ladle 1, i.e. refractory 3 and stopper 2 "track" the change in the level of metal 10 in the bucket 1.

The latter contributes to the fact that with the beginning of the emptying of the bucket 1 from the metal 10, the stopper 2 and the refractory 3 self-lower vertically towards the outlet 9 (towards the recess 8 if it is present in the bottom 12 of the bucket 1).

Moreover, due to the fact that the linear dimensions in terms of refractory 3 are several times greater than the diameter d _{Q of the} pouring hole as the metal level in the ladle decreases, they completely eliminate the appearance of vortex (funnel formation) in the metal and slag, thereby preventing slag from being drawn into the metal by all intermediate stages of emptying the bucket 1 from the metal 10.

At the time of the pouring of metal 10 from the ladle 1, the lower flat surface (working surface) of the refractory 3 (in the cases shown in Figs. 1-4, 11-13) reaches the flat working surface of the bottom 12 of the recess 8 and automatically cuts off the ingress of slag 11 into the casting hole 9 (figure 4).

Automatic slag 11 is cut off from falling into the pouring hole 9 because the refractory is buried in the metal by a value of h _u > 0. Due to this, the part covering the casting hole will always close the casting hole 9 until slag 11 approaches it. Moreover, if the bottom of the bucket is made with a recess 8, this overlapping of the casting hole occurs when the minimum amount of metal 10 is in the bucket. During the casting of metal 10 from the tank 1, at an intermediate stage of casting, it is possible to close the pouring hole 9 with a stopper 2 with refractory 3 from the mechanism 4 and thereby cut off the outflow of metal 10 from the tank 1.

As already noted, with the described design of the refractory 3 and stopper 2 and their operation during metal casting, slag is excluded from entering the gap between the refractory 3 and stopper 3. However, the metal 10 will naturally be in this gap, and it may freeze due to intensive removal heat to the stopper. To prevent this hardening, a graphite sleeve 14 is placed in the refractory. Graphite reacts with hot steel to form cast iron, the melting point of which is significantly lower than steel. This solves the problem of self-movement of the refractory vertically above the casting hole at all stages of the emptying of the bucket.

When casting high-quality steels, it is necessary to exclude as much as possible the ingress of ladle and refractory materials into the steel. The latter is solved by raising level 16 of the bottom 12 of the bucket 1 in the area of the casting hole 9.

Thus, in all considered cases of the implementation of the technical proposal, the refractory is self-moving vertically above the casting hole, while a certain depth of the refractory in the metal is preliminarily provided.

When implementing this method in matters of choosing the size of the refractory are additionally guided by the following considerations.

The height of the refractory 3 is assumed to be greater than the height h _{y of the} metal left in the bucket, i.e. h _c > h _y The magnitude of the specified excess is determined by the design of the bucket, stopper and their component parts. To implement the present method, the magnitude of this excess is not of fundamental importance when the stopper 2 - refractory 3 compound is movable, when the upper surface of the refractory must exceed the level of slag 11.

In all cases, the performance of the refractory 3 and the recess 8 in the bottom 12 of the bucket 1, the characteristic linear dimensions in terms of the recess exceed the characteristic linear dimensions in terms of the refractory.

There are two versions of the marked excess of linear dimensions.

1. The cross-sectional area of the recess 8 significantly exceeds the cross-sectional area of the working surface of the refractory 3 (refractory figures in plan). The use of this option reduces the amount of contaminants entering the mold with the last portions of the pouring metal. However, this increases the amount of metal remaining in the ladle after the end of the metal casting.

2. The cross-sectional area of the recess slightly exceeds the cross-sectional area of the working surface of the refractory.

3. In this case, they have effects opposite to the first option.

The choice of the embodiment of the ratios of the characteristic linear dimensions in terms of the recess 8 and the refractory is carried out, focusing on the cost of the poured metal, its cleanliness and the quality of preparation of the bucket for work (level of contamination of the bottom of the bucket, including due to its wear).

In the case of the execution of the joint of the refractory 3 and the recess 8 in the bottom of the bucket in the device of the stopper 2 and mechanism 4, it is necessary to provide guides that exclude the rotation of the stopper during its vertical movement. In General, in the design of the stopper 2, the presence of guides that exclude its rotation during its vertical movement is desirable in other cases of operation, especially when using refractories with an arbitrary figure in plan.

When implementing this method of casting metal, the bottom 12 of the bucket 1 is preferably performed with a bias towards the recesses 8 in the transverse and longitudinal directions (with an angle of inclination of 2 ... 3 °). This embodiment of the bottom 12 of the bucket 1 maximally contributes to the runoff of metal 10 towards the recess 8, i.e. minimize the amount of metal remaining in the ladle at the time of the end of the casting of metal.

For ladles with two or more casting holes, the bottom of the tank 12 is made with a single longitudinal and uniform transverse slope, thereby further reducing the amount of metal remaining in the ladle at the end of the casting: the slag will be cut off to the metal in the lowest located recess 8 ( 11 is the leftmost), to which the remnants of the metal 10 flow.

From the essence of the implementation of the present method of casting metal, the equality of the number of recesses 8 in the ladle 1 to the number of casting holes 9 in it follows.

The proposed method of casting metal and a device for its implementation can minimize metal loss at all stages of its casting: from a casting ladle to an intermediate ladle, from the latter to a mold. The marked reduction in metal losses is ensured by preventing the occurrence of vortex (funnel formation) when the metal flows out of the ladle through the hole (s) in its bottom, as well as by reliably cutting off the ingress of slag into the metal at the last moments of the ladle leaving metal. Thus, metal losses during the production of billets are reduced, technical and economic indicators of the metal casting process are improved.

Claims (9)

1. A method of casting metal, including filling the tank with metal with slag having a stopper, which stops casting the metal, placing the refractory covering the stopper by immersion in metal, emptying the container through the casting hole provided in the bottom of the tank, self-moving the refractory during casting vertically above the casting hole, characterized in that the self-movement of the refractory is carried out regardless of the movement of the stopper, while at all stages of the movement of the refractory its upper surface is a protrusion is above the slag surface. 2. The method of casting metal according to claim 1, characterized in that by the end of the casting after self-lowering of the refractory to contact with the surface of the bottom of the tank, the stopper is lowered to contact the casting hole. 3. The method of casting metal according to claim 2, characterized in that the surface of the bottom of the container in contact with the refractory is performed with a protrusion along the perimeter of the casting hole. 4. A device for casting metal, containing a container having at least one casting hole in the bottom, an opposed stopper with a vertical movement mechanism, a refractory covering the stopper body and having in the plan characteristic linear dimensions several times larger the diameter of the casting hole, characterized in that the refractory is installed with the possibility of free vertical movement relative to the stopper. 5. The device according to claim 4, characterized in that it is equipped with a sleeve of graphite placed on the inner surface of the refractory. 6. The device according to claim 4, characterized in that along the perimeter of the pouring hole the bottom of the tank is made with a protrusion, while the protrusion of the bottom is approximately equal to the area of the refractory, and the outline of the protrusion is the same as the outline of the refractory. 7. The device according to claim 4, characterized in that the refractory is made in the form of a direct prism. 8. The device according to claim 4, characterized in that the refractory is made in the form of a truncated pyramid. 9. The device according to claim 4, characterized in that the refractory is made in the form of a rectangular parallelepiped.

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