JP6874507B2 - Slag outflow prevention device - Google Patents

Description

The present invention relates to a slag outflow prevention device for preventing slag floating on the hot metal or molten steel from flowing out from the discharge hole when the hot metal or molten steel treated in the furnace is discharged from the converter. ..

When the dephosphorization treatment and decarburization treatment of hot metal are completed, the hot metal or molten steel in the furnace is provided in the side wall of the converter by tilting the converter. It is transferred to the pan through). However, slag is floating on hot metal or molten steel in the converter, and when the slag flows out from the discharge hole and enters the ladle, the dephosphorization treatment effect is substantially reduced, or steel. It reduces the quality of the. Therefore, it is necessary to take measures to prevent the outflow of slag at the stage when the tapping or steel is finished. Therefore, as one of the countermeasures, there is known a method of inserting a slag outflow prevention device (hereinafter referred to as darts) into the furnace at the final stage of tapping or steel ejection to close the discharge hole (for example). See Patent Document 1).

FIG. 3 is a vertical cross-sectional view of the inside of the converter at the final stage of steel output, showing a state in which the converter is in a substantially horizontal state and a small amount of molten steel remains in the converter. When the steel is ejected at the final stage, the darts 50 are put into the converter in order to prevent the slag 30 floating on the upper surface of the molten steel 20 from flowing out from the discharge hole 40 as shown in FIG.

FIG. 4 is an enlarged view of the periphery of the discharge hole 40 shown in FIG. As shown in FIG. 4, the darts 50 includes a head portion 50a and a guide portion 50b, and a gripping rod 50c is provided in the center above the head portion 50a. The gripping rod 50c is used, for example, when the darts 50 is charged into the converter by the charging equipment described in Patent Document 2. The darts 50 are charged into the furnace and dropped directly above the discharge hole 40 when the steel is discharged in the final stage and the amount of molten steel in the furnace is low. As shown in FIG. 4, the darts 50 are restricted from moving on the molten steel by the guide portion 50b entering the discharge hole 40. In this way, just before the molten steel in the furnace is exhausted, the head portion 50a covers the molten steel inlet portion of the discharge hole 40, and the outflow of the slag 30 is essentially prevented. Since the head portion 50a needs to be suspended at the interface between the molten steel and the slag, the head portion 50a is made of a material such that the specific gravity of the head portion 50a is a value between the specific gravity of the molten steel and the specific gravity of the slag. There is.

Japanese Unexamined Patent Publication No. 2003-96512 Jikkenhei 6-69259 Gazette

The refractory material 60 on the side with the discharge hole of the converter melts and becomes distorted as the number of operations of the converter is repeated. Then, it becomes difficult to stably suppress the slag outflow from the converter by darts. This is because the depletion of the refractory creates a large gap between the side with the discharge hole and the darts, from which a large amount of slag flows out. FIG. 5 is a diagram showing the state of the darts 50 when the steel removal is completed. As shown in FIG. 5, if the melting portion 70 is located on the discharge hole side, the darts 50 may be tilted and the slag 30 may flow out from the gap between the darts 50 and the discharge hole side.

In addition, the converter is used 2000 times or more, and the number of times it is used after the brick (refractory) on the side with the discharge hole is melted and becomes a distorted shape is overwhelmingly large. Therefore, there has been a strong demand for a means of suppressing the amount of slag flowing out from the discharge hole regardless of the number of operations of the converter.

In view of the above-mentioned problems, it is an object of the present invention to provide a slag outflow prevention device capable of suppressing the amount of slag flowing out from the discharge hole regardless of the number of operations of the converter.

The present inventor diligently studied a method for suppressing the outflow of slag from the discharge hole, and focused on a method for reducing the fluidity of the slag near the side where the slag enters the discharge hole. At the end of tapping or steel ejection, a phenomenon generally occurs in which the hot metal or molten steel discharged from the discharge hole forms a vortex and slag is caught in the vortex. At this time, if there is a darts head portion directly above the discharge hole, the presence of the head portion suppresses slag entrainment. However, if there is a melt-damaged part near the discharge hole entry side, the gap between the darts head and the discharge hole entry side becomes distorted, and the amount of slag that flows out due to the hot metal or molten steel flowing to the discharge hole increases. easy. Further, even after the head portion of the darts comes into contact with the inlet of the discharge hole, a gap remains in the melted portion at the inlet of the discharge hole, so that the slag continues to flow out from the gap. Therefore, it was found that if the fluidity of the slag existing around the darts is reduced, the amount of slag that is dragged by the hot metal or molten steel and flows out can be reduced even if there is a melting site near the discharge hole. ..

Specifically, together with darts, a high melting point substance that is dispersed as a solid phase in the slag to increase the apparent slag viscosity, a substance that thermally decomposes to cool the slag to increase the slag viscosity, or changes the composition of the slag. Allows the addition of substances that increase the viscosity of the slag. Examples of the above-mentioned substances include CaO, CaCO ₃ , MgO, MgCO ₃ , dolomite, brick scraps, converter slag and the like. The particle size of the substance is preferably 50 mm or less.

From the above, the present invention is as follows.
(1) Outflow prevention provided with at least a head portion for closing a discharge hole for discharging hot metal or molten steel and a guide portion for guiding the head portion to the discharge hole at the time of tapping or steel ejection of a converter. Around the tool, a substance that increases the viscosity or apparent viscosity of the slag is placed in a bag that can be torn by the time the slag begins to flow out and the substance can be added around the outflow prevention device. Slag outflow prevention device.
(2) The slag outflow prevention device according to (1) above, wherein the substance that increases the viscosity of the slag is a substance that changes the composition of the slag or a substance that cools the slag.
(3) The substance that increases the viscosity or apparent viscosity of the slag is one or more selected from the group consisting of _{CaO, CaCO 3} , MgO, MgCO _{3, dolomite, dolomite, and converter slag.} The slag outflow prevention device according to (1) or (2) above.
(4) The slag outflow prevention device according to any one of (1) to (3) above, wherein the maximum particle size of the substance that increases the viscosity or the apparent viscosity of the slag is 50 mm or less.

According to the present invention, it is possible to provide a slag outflow prevention device capable of suppressing the amount of slag flowing out from the discharge hole regardless of the number of operations of the converter.

It is a figure which shows an example of the slag outflow prevention device which concerns on this invention. It is a figure for demonstrating how to prevent the outflow of slag by using the slag outflow device which concerns on this invention. It is a figure for demonstrating how the darts fit in a discharge hole at the time of steel ejection. It is an enlarged view around the discharge hole at the time of steel ejection. It is a figure for demonstrating the outflow form of the slag when there is a melting site.

Hereinafter, the details of the present invention will be described with reference to the drawings. The present invention can be applied to both tapping after dephosphorization and steel removal after decarburization. Hereinafter, an example of application to steel output after decarburization treatment will be described as a representative.

When the slag outflow prevention device (hereinafter referred to as darts) of the present invention is introduced at the final stage of steel ejection (pig iron), the fluidity of the slag around the darts is reduced at the final stage of steel ejection (pig iron). By doing so, the amount of slag flowing out from the discharge hole is suppressed. As a method of reducing the fluidity of the slag, that is, increasing the viscosity, (1) a method of dispersing solid particles in the liquid phase slag, (2) a method of cooling the slag, and (3) changing the composition of the slag. There is a way.

(1) The method of dispersing solid particles in liquid phase slag is a method of adding and dispersing a substance having a high melting point that is difficult to dissolve in slag as solid phase particles to increase the apparent viscosity of the slag. It is known that the apparent viscosity increases when solid-phase particles are dispersed in liquid-phase slag. Possible solid-phase particles include MgO, dolomite, brick dust, converter slag, and the like.

(2) The method of cooling the slag is a method of increasing the viscosity of the slag itself by cooling the slag. In this method, the solid phase may crystallize in the slag during cooling to disperse the solid phase and the liquid phase, and the apparent viscosity described above may increase. As a cooling method, a method of adding a substance that undergoes an endothermic reaction that thermally decomposes and removes heat after being added to the slag can be considered. As such a substance, for example, CaCO ₃ , MgCO ₃ , dolomite and the like can be considered.

(3) The method of changing the composition of slag is a method of increasing the viscosity of the slag itself by adding a substance that dissolves in the slag and changing the composition of the slag. For example, when CaO is added, the (CaO) concentration _{in the slag is increased, the basicity (CaO / SiO 2} ratio) is increased, and the viscosity of the slag is increased.

As described above, a method of increasing the viscosity of the slag or the apparent viscosity can be considered. Therefore, the present inventors have found darts in which these substances can be attached in order to add these substances at the time of adding darts. For example, as shown in FIG. 1, a bag 1 containing a substance 2 for increasing the slag viscosity is attached to the darts 10. When the steel is ejected to the final stage and the amount of molten steel in the furnace is low, darts as shown in FIG. 1 are charged into the furnace and dropped directly above the discharge hole. Then, by the time the darts are dropped and the slag begins to flow out, the bag 1 is torn and the above substance is added to the slag around the darts and dispersed in the slag to increase the viscosity or the apparent viscosity of the slag. , The effect of suppressing slag outflow is fully exhibited. That is, as shown in FIG. 2, since the viscosity or the apparent viscosity of the slag 3 near the discharge hole increases, the slag will flow out even when the darts cannot sufficiently close the discharge hole due to the presence of the melted portion. It can be suppressed.

As described above, the main body of the darts 10 includes at least a head portion 10a and a guide portion 10b, but the head of the darts 10 so as to float on the hot metal (or molten steel) and finally block the inlet of the discharge hole. A material having a specific gravity smaller than that of hot metal (or molten steel) and larger than that of slag is used. As for the darts themselves, known ones may be used.

If a substance for increasing the viscosity of the slag or the apparent viscosity can be dropped together with the darts, it may be attached with an object other than a bag or a container. When a bag is used, for example, four bags are hung from the gripping rod 10c above the head portion 10a of the darts in four directions, and the above-mentioned substance is charged into the four bags. If such darts are dropped directly above the discharge hole, the above-mentioned effects can be easily and surely enjoyed. In addition to using a bag, a method of charging the above substance in an appropriate container and tying it to a gripping rod may also be used.

The material of the bag or container is not particularly limited as long as it is a material that does not melt or burn due to the heat generated from the molten steel and slag before dropping the darts into the molten steel from directly above the discharge hole. As the material of the bag or container, it is not damaged by melting or burning before dropping the darts, and it is just before the darts are dropped after being carried directly above the discharge hole, or the darts are dropped and molten steel. It is desirable that the material is such that the contents are added to the slag by tearing when it is located between the slag and the slag.
Specifically, it may be decided appropriately according to the time required to carry the darts to just above the discharge hole. If it is a bag, a flame-retardant / flame-retardant material, a thin wire mesh, etc. can be exemplified, and if it is a container, it can be used. For example, a thick cardboard or the like can be exemplified.

Examples of the substance that increases the viscosity (or apparent viscosity) of the slag include substances having at least one of the above-mentioned effects (1) to (3). Of course, there are substances that can simultaneously exert the above-mentioned effects (1) to (3), and the effect is greater. Dolomite and the like correspond to it. Further, two or more kinds of the above-mentioned substances may be mixed and used.

The maximum particle size of the substance is preferably 50 mm or less. However, if the proportion of the substance having a particle size of less than 5 mm is too large, the influence of the interfacial tension is strong, and the solid phase particles penetrate into the slag bath and are difficult to disperse. Therefore, the ratio (weight ratio) of the particle size of less than 5 mm is preferably 20% or less. On the other hand, when the maximum particle size is more than 50 mm and the amount of solid phase particles added is constant, the contact area with the slag is small, and it becomes difficult to dissolve in the slag and it becomes difficult to disperse.

The amount of the above-mentioned substance attached to the darts is preferably 0.07 to 1.0 kg / molten steel ton (or hot metal ton). If the amount of the above substance is less than the lower limit, the slag with increased viscosity cannot cover the area around the darts, which may reduce the effect. Further, if the amount of the above substance exceeds the upper limit, the effect is saturated, which is disadvantageous in terms of cost. More preferably, it is 0.2 to 0.7 kg / molten steel ton (or hot metal ton).

By adding the substance for increasing the slag viscosity together with the darts as described above, the amount of slag flowing out from the discharge hole can be suppressed regardless of the number of times of the converter, even with a small amount of solid phase grains. If it is applied to the pig iron after the dephosphorization treatment, the amount of phosphorus brought into the decarburization furnace after that can be reduced, and the amount of CaO added for dephosphorization in the decarburization furnace can be reduced. When applied to a decarburization furnace, the amount of lower oxides such as FeO flowing out to the ladle can be reduced, so that the load of secondary refining (deoxidation, desulfurization) can be significantly reduced. _{Furthermore, since the amount of Al 2} O ₃ system inclusions generated when FeO is reduced with Al can be reduced, the quality of steel products is improved.

Next, an example of the present invention will be described. The conditions in the examples are one condition example adopted for confirming the feasibility and effect of the present invention, and the present invention is described in this one condition example. It is not limited. The present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

(Example)
As an outflow prevention tool, the main composition of the head part is Cr ₂ O ₃ : 40%, Fe ₂ O ₃ : 25%, MgO: 10%, SiO ₂ : 10%, Al ₂ O ₃ : 10% in mass%. Yes, the main composition of the guide part was Al ₂ O ₃ : 70% and SiO ₂ : 20% darts.
On the other hand, 250 tons of hot metal was dephosphorized and smelted in a converter with 1500 or more operations. The slag after the dephosphorization was completed had a basicity (CaO / SiO ₂ ) of 1.3, 40 kg / hot metal ton, and the temperature of the hot metal after dephosphorization was 1350 ° C. After that, the furnace body was tilted to start tapping, and at the end of tapping, four corrugated cardboards in which 10 kg (0.04 kg / hot metal ton) of darts having a maximum particle size of 50 mm or less were charged into the darts having the above-mentioned composition. A dart was produced by tying the container to the four sides of the guide portion, and the dart was moved and dropped directly above the discharge hole while holding the gripping rod by the arm of the loading device. It takes 5 to 10 seconds to move the darts to just above the discharge hole after putting them in the converter, and it takes about 5 to 10 seconds from dropping the guide part of the darts into the hot metal to completing the ironing. It was one minute.
For the slag outflow amount, the outflow amount was calculated from the slag thickness in the ladle, and the amount was divided by the hot metal amount to obtain the slag outflow amount per ton of hot metal.
When the same experiment was performed 100 times, the average amount of slag outflow was 3 kg / hot metal ton.

(Comparison example)
As an outflow prevention tool, the main composition of the head part is Cr ₂ O ₃ : 40%, Fe ₂ O ₃ : 25%, MgO: 10%, SiO ₂ : 10%, Al ₂ O ₃ : 10% in mass%. Yes, the main composition of the guide part was Al ₂ O ₃ : 70% and SiO ₂ : 20% darts.
On the other hand, 250 tons of hot metal was dephosphorized and smelted in a converter with 1500 or more operations. The slag after the dephosphorization was completed had a basicity (CaO / SiO ₂ ) of 1.3, 40 kg / hot metal ton, and the temperature of the hot metal after dephosphorization was 1345 ° C. After that, the furnace body was tilted to start tapping, and at the end of tapping, the darts were moved and dropped directly above the discharge hole while holding the gripping rod of the darts having the above-mentioned composition with the arm of the loading device. .. It took about 1 minute from dropping the darts into the converter to completing the tapping.
For the slag outflow amount, the outflow amount was calculated from the slag thickness in the ladle, and the amount was divided by the hot metal amount to obtain the slag outflow amount per ton of hot metal.
When the same experiment was performed 100 times, the average amount of slag outflow was 6 kg / hot metal ton.

1 bag 2 substances 10 darts

Claims (4)

Around the outflow preventive tool provided with at least a head portion for closing the discharge hole for discharging the hot metal or molten steel and a guide portion for guiding the head portion to the discharge hole at the time of tapping or steel ejection of the converter. The slag outflow is characterized in that a substance that increases the viscosity or apparent viscosity of the slag is torn by the time the slag begins to flow out and the substance is placed in a bag that can be added around the outflow preventive device. Prevention device. The slag outflow prevention device according to claim 1, wherein the substance that increases the viscosity of the slag is a substance that changes the composition of the slag or a substance that cools the slag. The substance that increases the viscosity or apparent viscosity of the slag is one or more selected from the group consisting of _{CaO, CaCO 3} , MgO, MgCO _{3, dolomite, dolomite, and converter slag.} The slag outflow prevention device according to claim 1 or 2. The slag outflow prevention device according to any one of claims 1 to 3, wherein the maximum particle size of the substance that increases the viscosity or the apparent viscosity of the slag is 50 mm or less.

Images