JP2009091607A - Method for coating inner wall surface of converter with slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for coating the inner wall surface of a converter with slag, which enables refractory in the periphery of a tapping hole to be effectively repaired, at which the inner wall surface is especially severely worn, while shortening a period of time for stopping the operation of the converter in order to repair the refractory as much as possible. <P>SOLUTION: The method for coating the inner wall surface of the converter with slag includes: a step (A) of lowering the temperature of the slag 16 to 1,150 to 1,400°C by swinging the converter 10 several times, in which the steel has been tapped out and the slag 16 remains; and a step (B) of forming a coating of the slag 16 on the surface of the refractory 13 which is arranged in the inner wall surface of the converter 10, while discharging the slag 16 from the tapping hole 12 provided in an upper side of a side part of the converter 10 by tilting the converter 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for coating slag on the inner wall of a converter, and more specifically, slag, which is a by-product of converter refining, is coated on the surface of a refractory disposed on the inner wall of the converter. The present invention relates to a slag coating method for an inner wall surface of a converter for protecting an object.

As a method for repairing refractories disposed on the inner wall of a converter that has been worn out by blowing operation, a slag coating method is generally used in which slag, which is a by-product of converter refining, is coated on the surface of the refractory. ing. The slag coating method can be carried out in a relatively short time without completely stopping the converter operation, and the refractory replacement interval on the inner wall surface of the converter can be lengthened. It is effective in improving
For example, in Patent Document 1, a solidified material that causes a decomposition endothermic reaction is added to the molten slag remaining in the converter after the steel is produced in the converter operation, and a coating action such as spraying or tilting the converter is performed. Thus, a method of slag coating the converter inner wall surface is disclosed.
Further, in Patent Document 2, the molten slag remaining in the converter is supplied from the bottom tuyeres provided at the bottom of the converter to the inner wall surface of the converter where the inert gas mixed with the gas generating substance is blown. A slag coating method is disclosed.

Japanese Patent Laid-Open No. 9-209022 JP 59-93816

However, in the slag coating method on the converter inner wall surface described in Patent Document 1, it takes a long time until the solidified material is uniformly dissolved and dispersed in the molten slag, and the coating action such as spraying or tilting the converter In this case, it is difficult to form a coating having a sufficient thickness in the vicinity of the steel hole having the largest wear. Moreover, since the coating formed in the vicinity of the steel hole is multi-layered, the peeling strength of the coating is lowered, and high durability cannot be obtained.
Also, in the slag coating method on the converter inner wall surface described in Patent Document 2, it is difficult to form a coating having a sufficient thickness in the vicinity of the most worn out steel hole, and in the vicinity of the steel hole. Since the coating formed in the multilayer is multi-layered, the peel strength of the coating is lowered and high durability cannot be obtained.

The present invention has been made in view of such circumstances, and effective repair for refractories in the vicinity of a steel outlet hole where wear is particularly severe while shortening the time to stop the operation of the converter as much as possible for repair of refractories. An object of the present invention is to provide a method for coating slag on the inner wall of a converter that makes it possible.

The slag coating method for the inner wall surface of the converter according to the present invention that meets the above-mentioned object includes the step A of lowering the temperature of the slag by swinging the converter in which the slag remains after the steel is output a plurality of times, and the converter Inclining and forming the coating of the slag on the surface of the refractory disposed on the inner wall surface of the converter while discharging the slag from the steel outlet hole provided on the upper side of the converter Have

In the slag coating method for the converter inner wall surface according to the present invention, in the step A, the temperature of the slag is preferably lowered to 1150 ° C to 1400 ° C.

In the slag coating method for a converter inner wall surface according to the present invention, it is preferable that the number of oscillations of the converter is 2 to 5 times.

In the slag coating method for a converter inner wall surface according to the present invention, it is preferable that an inner diameter of the steel outlet hole is 140 to 300 mm.

In the slag coating method for a converter inner wall surface according to the present invention, before the converter is swung in the step A, the particle diameter is 10 to 50 mm, and 6 to 30% by mass of the slag remaining in the converter. The basic carbonate mass may be added.

In the slag coating method for a converter inner wall surface according to the present invention, in the step B, it is preferable that the slag is discharged from the steel outlet hole for 5 to 120 seconds.

In the slag coating method of the converter inner wall surface according to claim 1, repairing the refractory disposed on the converter inner wall surface in a series of converter operation steps from steel tapping to waste. Therefore, the time to stop the operation of the converter for repairing refractories can be shortened.
Further, by reducing the temperature of the slag in the process A, the viscosity of the slag is increased and easily adhered to the inner wall surface of the converter, and then the coating is formed while discharging the slag from the steel outlet hole in the process B. In particular, it is possible to form a slag coating having a sufficient thickness in the vicinity of a steel hole that is heavily worn. Therefore, it is possible to lengthen the interval for exchanging the refractories on the inner wall surface of the converter, which can contribute to improvement of the operation efficiency of the converter and reduction of the operation cost.

In particular, in the slag coating method for the converter inner wall surface according to claim 2, the temperature of the slag is lowered to 1150 ° C. to 1400 ° C., so that the viscosity can be increased while ensuring the fluidity of the slag. Therefore, a coating having a sufficient thickness can be formed.

In the slag coating method for the converter inner wall surface according to claim 3, since the number of oscillations of the converter is 2 to 5 times, the temperature of the slag can be lowered by the minimum oscillation of the converter. .

In the slag coating method of the converter inner wall surface according to claim 4, since the inner diameter of the steel outlet hole is 140 to 300 mm, it is necessary and sufficient for the slag to solidify in the vicinity of the steel outlet hole to form a coating. By ensuring the residence time, a uniform coating having a sufficient thickness can be formed.

In the slag coating method of the converter inner wall surface according to claim 5, the basic carbonate lump added before the converter is swung in step A reduces the slag temperature by a decomposition endothermic reaction and generates a reaction. Since the oxide which is a thing plays the role of a fireproof aggregate, the durability of a coating can be improved.

In the slag coating method of the converter inner wall surface according to claim 6, since the slag is discharged from the steel outlet hole for 5 to 120 seconds in Step B, a sufficient thickness is obtained without reducing the operation efficiency of the converter. This coating can be formed in the vicinity of the exit hole.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a schematic explanatory diagram of a converter to which a slag coating method for a converter inner wall surface according to an embodiment of the present invention is applied, and FIG. 2 is an explanatory diagram of a series of cycles for swinging the converter. FIG. 3 is a partial schematic view of the vicinity of the steel exit hole for explaining the convex deposit formed in the vicinity of the steel exit hole.

As shown in FIG. 1, a converter 10 applied to a method for coating a slag on the inner wall surface of a converter according to an embodiment of the present invention is a barrel-shaped reactor used for refining pig iron to produce steel. Thus, it is swingably supported around a trunnion shaft (not shown). During normal refining, the converter 10 is used in an upright state, but it can be tilted around the trunnion shaft in either direction during hot metal injection, molten steel removal, slag discharge, etc. .
A furnace port 11 is provided at the top of the converter 10. Injection of hot metal, discharge of slag after completion of refining, and injection of oxygen from an upper blowing lance (not shown) are performed from the furnace port 11.
A steel outlet hole 12 is provided on the upper side of the converter 10 so as to face downward when the converter 10 is tilted in one direction. The outer wall of the converter 10 is made of steel, and a refractory 13 having heat resistance and impact resistance is disposed on the inner wall surface. A tuyere 14 for blowing inert gas or the like is provided at the bottom of the converter 10.
Further, a cylindrical steel exit hole sleeve 15 made of a refractory is attached to the steel exit hole 12.

Manufacturing of steel using the converter 10 is performed as follows.
Hot metal is poured into the converter 10 and a slag raw material mainly containing calcium carbonate or lime is added. When high-pressure oxygen is blown into the lance and stirred, the oxygen reacts with impurities such as carbon, silicon, phosphorus, and manganese in the hot metal (oxidation reaction), and high heat is generated. At this time, since the high-temperature molten iron flows vigorously in the converter 10, the refractory 13 is worn out.
Among the oxidation products, carbon monoxide is removed as a gas, and oxidation products such as silicon and phosphorus are combined with the slag raw material to form slag and removed from the molten iron. In this way, impurities are removed and molten steel is produced.
After finishing the refining, the converter 10 is tilted so that the steel output hole 12 faces downward, and the molten steel is taken out from the steel output hole 12 (steel output). At this time, friction occurs between the molten steel flowing at high speed and the refractory 13 disposed in the vicinity of the steel outlet hole 12, so that the wear of the refractory 13 is particularly remarkable in the vicinity of the steel outlet hole 12. is there.

The slag coating method for the converter inner wall surface according to the present embodiment includes a step A in which the converter 10 in which the slag 16 (see FIG. 2) remains after the steelmaking is swung a plurality of times to lower the temperature of the slag 16. The process B includes the step B of forming the slag coating on the surface of the refractory 13 disposed on the inner wall surface of the converter 10 while the converter 10 is tilted and the slag 16 is discharged from the steel outlet hole 12.
Hereinafter, step A and step B will be described in detail.

In step A, the temperature of the slag 16 is adjusted by swinging the converter 10 in which the slag 16 remains after steelmaking a plurality of times and bringing the slag 16 into contact with the inner wall surface of the upper part of the converter 10 having a relatively low temperature. Reduce.
There is no restriction | limiting in particular in the method for making the slag 16 remain in the converter 10 at the time of steel extraction, Although arbitrary methods can be used, For example, a slag ball is used. The slag ball is made of a heat-resistant material having a specific gravity larger than that of the slag 16 and smaller than that of the molten steel, and has a spherical shape whose diameter is larger than the inner diameter of the outgoing steel hole 12. While the molten steel is being discharged from the exit steel hole 12, the slag ball is located in the vicinity of the interface between the molten steel and the slag 16 having a smaller specific gravity that floats on the molten steel, but the discharge of the molten steel is completed. Then, the slag ball having a specific gravity larger than that of the slag 16 sinks in the slag 16 and closes the steel outlet hole 12 from the inside, so that the slag 16 is not discharged from the steel outlet hole 12 and remains in the converter 10. .
In this way, after the converter 10 in which the slag 16 remains at the time of steel output is once erected, the converter 10 is swung around the trunnion shaft to lower the temperature of the slag 16. The slag 16 immediately after the completion of steel production is poor in viscosity at a high temperature (for example, about 1700 ° C.) and does not form a coating by adhering to the surface of the refractory 13 as it is, so the temperature is lowered by swinging the converter 10. It is necessary to increase the viscosity.

The temperature of the slag 16 is lowered to 1150 to 1400 ° C. Since the viscosity is too low when the temperature of the slag 16 is higher than 1400 ° C., it is difficult to form a coating having a sufficient thickness on the surface of the refractory 13. On the contrary, when the temperature of the slag 16 is lower than 1150 ° C., the viscosity of the slag 16 increases too much, so that the fluidity is lowered, and it is difficult to form a coating having a sufficient thickness on the surface of the refractory 13. .

The swing of the converter 10 means that a series of cycles consisting of (A), (B), (C), and (D) shown in FIG. The number of repetitions of this cycle is called the number of oscillations.
(A) The converter 10 in an upright state is rotated around the trunnion shaft so that the steel outlet hole 12 faces upward.
(B) The converter 10 with the steel output hole 12 facing upward is rotated around the trunnion shaft in the direction opposite to that of (A) to be brought into an upright state again.
(C) The converter 10 in an upright state is rotated around the trunnion shaft in the direction opposite to (A), and the converter 10 is tilted so that no slag is discharged from the steel outlet hole 12.
(D) The converter 10 with the steel output hole 12 facing downward is rotated around the trunnion shaft in the same direction as (A), and is brought into an upright state again.

In addition, in order to shorten the time required for the slag coating of the converter inner wall surface, it is preferable to continuously execute the series of cycles including (A) to (D) without stopping the converter 10 in the middle. . Further, the rotation speed of the converter 10 and the inclination angle of the converter 10 in (A) and (C) may always be a constant value, but depending on the amount of slag 16 remaining in the converter 10 and the like. May be determined as appropriate.

The number of oscillations of the converter 10 necessary for lowering the slag temperature to the above range is uniquely determined for reasons such as variations in the amount of slag remaining in the converter 10 after steelmaking. In general, it is preferably 2 times or more and 5 times or less. When the number of swings is 0 or 1, a sufficient slag cooling effect due to the swing cannot be obtained. On the contrary, when the number of oscillations is 6 times or more, the difference between the slag and the inner wall temperature of the converter 10 becomes small, and the amount of increase in the cooling effect accompanying the increase in the number of oscillations is saturated.

The number of oscillations of the converter 10 may be determined according to the amount and temperature of the slag 16 remaining in the converter 10 after steel output. This is because when the amount of residual slag 16 is small, the amount of stored heat is also small, so that a sufficient cooling effect can be obtained with a smaller number of oscillations. For example, when the amount of remaining slag is less than 40 tons, the number of swings may be two, and when the amount of remaining slag is 40 tons or more, the number of swings may be five.
Thus, by optimizing the number of oscillations according to the amount of slag 16 remaining in the converter 10, slag coating can be performed in the minimum necessary time.

In the last swing (for example, the fifth swing when the number of swings is 5), (D) is not executed in the series of cycles, and after executing (C), Opening the steel hole 12 with the steel hole 12 facing downward (if necessary, the tilt angle of the converter 10 may be changed) and starting the process B for coating while discharging the slag 16 May be. By doing so, it is possible to save the time required for the converter 10 to be returned to the upright state and then tilted again.

Before starting the oscillation of the converter 10, a basic carbonate lump is charged into the converter 10. Examples of basic carbonates that can be used include carbonates such as alkali metals and alkaline earth metals. Specific examples thereof include magnesium carbonate (MgCO ₃ ), calcium carbonate (CaCO ₃ ), raw dolomite (MgCO ₃ · CaCO ₃ ), and raw dolomite is preferable from the viewpoint of cost.

When these basic carbonates are put into the converter 10, a decarboxylation reaction is caused by furnace heat, and oxides and carbon dioxide are generated. Since the decarboxylation reaction is an endothermic reaction, the temperature of the slag can be reduced by, for example, 50 to 60 ° C. Therefore, by introducing the basic carbonate lump, the cooling efficiency of the slag can be increased and the number of oscillations of the converter 10 can be reduced.
In addition, since oxides such as CaO and MgO produced by the decarboxylation reaction have a high melting point of 2000 ° C. or higher, they also act as an aggregate that increases the strength of the slag coating formed on the surface of the refractory 13. Yes.

In addition, as an aggregate, although it is thought that the thing which made the waste material (magcarbon brick block; MgO-C) of a converter brick into a block shape is excellent in cost, for example, since it does not contain carbonate ion, it is basic. Cooling effect is inferior compared to carbonate. In addition, since magcarbon bricks have low wettability to slag, the aggregates of slag coating cannot be fully effective, and the aggregates fall off compared to when using basic carbonates such as raw dolomite. Likely to happen.

The average particle size of the basic carbonate block is 10 mm or more and 50 mm or less.
When the average particle size is less than 10 mm, the durability of the generated oxide as an aggregate is insufficient. On the contrary, when the average particle diameter exceeds 50 mm, the particle diameter of the generated oxide is too large compared to the thickness of the slag coating formed on the surface of the refractory 13, so that the coating easily falls off. Become.

The input amount of the basic carbonate lump is 6% by mass to 30% by mass with respect to the mass of the slag 16 remaining in the converter 10, and is preferably 10% by mass to 20% by mass. When the input amount of the basic carbonate lump is less than 6% by mass of the mass of the slag 16, the effect of improving the durability of the slag coating as an aggregate is insufficient. Conversely, if the amount of basic carbonate block input exceeds 30% by mass of the slag 16, the ratio of aggregate (oxide) contained in the slag becomes too high, and a uniform coating without irregularities is formed. It becomes difficult. In particular, as shown in FIG. 3, when a convex deposit 17 is formed in the vicinity of the steel exit hole 12, residual hot water (molten steel that is not discharged at the time of steel output) 18 is generated, which causes a decrease in the yield of molten steel. Become.

In the process B, the slag coating is formed on the surface of the refractory 13 disposed on the inner wall surface of the converter 10 while the converter 10 is tilted and the slag 16 is discharged (hole rejection) from the steel outlet hole 12. To do. Note that the slag 16 remaining in the converter 10 after being discharged from the steel outlet hole 12 is discharged from the furnace port 11.
By discharging the slag 16 whose temperature has been lowered in the process A not from the furnace port 11 but from the steel outlet hole 12, it is effectively applied to the surface of the refractory 13 disposed in the vicinity of the steel outlet hole 12 with high wear. Slag coating can be performed.

In order to form a slag coating having a sufficient thickness on the surface of the refractory 13 near the exit steel hole 12, the slag is secured in the vicinity of the exit steel hole 12 so as to ensure a sufficient residence time for the slag 16 to solidify. It is necessary to adjust the flow rate. In order to satisfy such a requirement, the inner diameter of the outgoing steel hole 12 (specifically, the inner diameter of the outgoing steel hole sleeve 15) is set to 140 mmφ or more and 300 mmφ or less. When the inner diameter of the outgoing steel hole 12 is less than 140 mmφ, the flow rate of the slag is reduced and, as shown in FIG. 3, the convex deposit 17 is likely to be formed in the vicinity of the outgoing steel hole 12. The yield of molten steel tends to decrease due to the occurrence of. On the other hand, if the inner diameter of the outgoing steel hole 12 exceeds 300 mmφ, the flow rate of the slag increases, so that it becomes difficult to ensure the thickness of the coating, resulting in a decrease in durability.

In order to perform the slag coating, the time for discharging the slag from the steel outlet hole 12 (hereinafter referred to as “hole evacuation time”) is set to 5 seconds or more and 120 seconds or less. If the hole evacuation time is less than 5 seconds, the thickness of the slag coating formed is insufficient, and the protective effect of the refractory 13 by the coating is insufficient. On the other hand, when the hole removal time exceeds 120 seconds, the influence of a decrease in operation efficiency due to an increase in the non-operation time of the converter 10 becomes significant. Moreover, since the residence time of the slag in the vicinity of the outgoing steel hole 12 becomes too long and, as shown in FIG. 3, a convex deposit 17 is easily formed in the vicinity of the outgoing steel hole 12, the remaining hot water 18 is generated. As a result, the yield of molten steel tends to decrease.

Next, examples carried out for confirming the effects of the present invention will be described.
FIG. 4 is a graph showing the relationship between the remaining thickness of the refractory and the number of times of steel extraction when hole removal is performed and when hole removal is not performed, and FIG. 5 is the relationship between the average slag temperature and the wear rate of the refractory FIG. 6 is a graph showing the relationship between the number of oscillations of the converter and the slag temperature when the residual slag amount is 20 t and 40 t, and FIG. 7 is a graph showing the relationship between the inner diameter of the outlet steel hole sleeve and the wear rate of the refractory. Graph showing the relationship, FIG. 8 is a graph showing the relationship between the addition ratio of raw dolomite or magcarbon brick mass and the refractory wear rate, FIG. 9 is a graph showing the relationship between the hole evacuation time and the refractory wear rate, FIG. 10 is a graph showing a comparison of converter non-operation time when hole removal is performed and when hole removal is not performed.

Experimental (Test Operation) Conditions A 350 t converter was used in the implementation of the example.
Since the inner diameter of the outgoing steel hole sleeve increases as the number of outgoing steels increases and wear increases, the measured value of the outgoing steel hole sleeve measured at the first outgoing steel in each experiment was used as a representative value. .
The experimental operation is as shown below.
After completing the refining of steel in the converter and the steel output from the outlet hole, the slag remained in the converter and, if necessary, a predetermined amount of raw dolomite was added (specific addition The amount is explained in the section of each experiment). Then, after the converter was rocked a predetermined number of times (the specific number of times of rocking will be explained in the section of each experiment), the slag was discharged from the converter steel outlet hole for a predetermined time (hole removal) (specifically The hole removal time is explained in the section of each experiment). In addition, the implementation ratio ((number of times slag was discharged from the steel outlet holes) / (total number of steel outlets)) was unified to 50% during the test operation.
Thereafter, the slag remaining in the converter was entirely discharged from the furnace port by tilting the converter.

Measurement of slag temperature Using a radiation thermometer, the temperature of slag immediately after discharging from the steel outlet hole or furnace port was measured. Therefore, the measured value of the slag temperature is considered to be approximately equal to the temperature of the slag in the converter.

Measurement of Wear Rate of Refractory Using a laser profile meter, the thickness (residual thickness) of the refractory at the same site in the vicinity of the steel exit hole was measured each time steel was extracted 30 to 50 times. The wear rate (mm / ch) of the refractory per unit steel output was determined from the slope of the graph in which the remaining thickness was plotted against the steel output (ch: abbreviation for charge).

Experiment 1: Relationship between presence or absence of slag coating and wear rate of refractory 10 to 12% by mass with respect to slag remaining in the converter after refining of the steel in the converter and completion of steel output from the steel outlet hole Of raw dolomite. When the amount of slag remaining in the converter is 40t or more, the converter is swung four times when the amount of slag remaining in the converter is less than 40t, and the slag temperature is reduced to 1400 ° C or less twice. Reduced. After removing the hole for 10 seconds (the inner diameter of the steel hole sleeve is 220 to 280 mmφ), the slag remaining in the converter is discharged from the furnace port by tilting the converter, and after oscillating the converter, In the case where the entire amount was discharged from the furnace port without hole removal, the wear rates of the refractories near the steel outlet holes were compared.

FIG. 4 shows the relationship between the remaining thickness of the refractory and the number of times of steel extraction when the hole evacuation is performed (indicated by ●) and when the hole evacuation is not performed (indicated by ▲). The wear rates of the refractory when the hole removal is performed and when the hole removal is not performed are 0.2 mm / ch and 0.5 mm / ch, respectively. From the above results, it can be seen that the slag coating on the refractory in the vicinity of the steel outlet hole reduces the wear rate to about 40% when the slag coating is not performed. In addition, in the case where hole evacuation was not performed, when the steel was removed approximately 1400 times, the refractory was worn out and it was necessary to stop the operation and repair the refractory. In some cases, the operation can be continuously performed 3000 times or more without temporarily stopping the operation for repairing the refractory.
From these results, the effect of the slag coating on the refractory near the steel hole was confirmed.

Experiment 2: Relationship between slag temperature and refractory wear rate at the time of hole removal 10% of slag remaining in the converter after refining of the steel in the converter and completion of steel output from the outlet hole ˜12% by weight of raw dolomite was added. Thereafter, the converter was swung twice, and the slag was discharged for 10 seconds from the steel outlet hole (the inner diameter of the steel outlet hole sleeve was 220 mmφ), and the temperature was measured using a radiation thermometer. All the slag remaining in the converter was discharged from the furnace port by tilting the converter. Further, every 30 to 50 ch, the remaining thickness of the refractory near the exit hole was measured using a laser profile meter to determine the wear rate. Thereafter, the slag remaining in the converter was entirely discharged from the furnace port by tilting the converter.
The experiment was performed several tens to several hundreds for each different raw material lot.

FIG. 5 shows the relationship between the average slag temperature and the refractory wear rate. From the vicinity of the slag temperature exceeding 1400 ° C., the wear rate increases as the slag temperature rises. At about 1500 ° C., the wear rate when the slag coating is not performed (0.5 mm / ch) is almost the same. It can be seen that the values are the same. From the above results, it is considered that when the temperature of the slag exceeds 1400 ° C., the effect of the slag coating decreases, and at 1500 ° C., the viscosity decreases and almost no coating is formed.
From these results, it was confirmed that the temperature of the slag needs to be reduced to 1400 ° C. or lower in order to have a sufficient durability.

Experiment 3: Relationship between the number of oscillations of the converter and the slag temperature After completing the refining of the steel in the converter and the steel output from the outlet hole, 10-12 mass% of the slag remaining in the converter Raw dolomite was charged, slag was discharged from a steel outlet hole (the inner diameter of the steel outlet hole sleeve was 220 mmφ) for 5 seconds, and the temperature was measured using a radiation thermometer. Thereafter, each time the converter was swung once, the slag was discharged from the steel outlet hole (the inner diameter of the steel outlet hole sleeve was 220 mmφ) for 5 seconds, and the temperature was measured using a radiation thermometer. After rocking 6 times, the slag remaining in the converter was discharged from the furnace port by tilting the converter.

FIG. 6 shows the relationship between the number of oscillations of the converter and the slag temperature when the residual slag amount is 20 t and 40 t. In any case, in order to reduce the temperature of the slag to about 1400 ° C., one swing is not sufficient, and it is necessary to swing the converter at least twice, and the number of swings is It can be seen that when the number of times exceeds five, the temperature of the slag hardly decreases.
From these results, it was confirmed that it is preferable to swing the converter 2 to 5 times in order to reduce the temperature of the slag to 1400 ° C. or less without greatly reducing the operation efficiency.

Experiment 4: Relationship between the inner diameter of the steel exit hole and the wear rate of the refractory 10 to 12 mass with respect to the slag remaining in the converter after the refining of the steel in the converter and the steel exit from the exit hole are completed. % Raw dolomite. When the amount of slag remaining in the converter is 40t or more, the converter is swung four times when the amount of slag remaining in the converter is less than 40t, and the slag temperature is reduced to 1400 ° C or less twice. Reduced. After evacuating the hole for 10 seconds (the inner diameter of the steel outlet sleeve 160 to 330 mmφ), the slag remaining in the converter was discharged from the furnace port by inclining the converter. Every 30 to 50 ch, the remaining thickness of the refractory in the vicinity of the steel hole was measured using a laser profile meter to determine the wear rate.

FIG. 7 shows the relationship between the inner diameter of the steel exit hole sleeve and the wear rate of the refractory. When the inner diameter of the steel hole sleeve exceeds 300 mmφ, the wear rate increases almost linearly, but the flow rate of the slag increases, and the residence time necessary to form the coating cannot be secured. It is believed that there is.
From the above results, it was confirmed that in order to form a highly durable slag coating on the refractory in the vicinity of the steel exit hole, it is preferable that the inner diameter of the steel exit hole (sleeve) be 300 mmφ or less.

Experiment 5: Relationship between the amount of raw dolomite added and the refractory wear rate 0 to 40 mass relative to the slag remaining in the converter after the refining of the steel in the converter and completion of the steel output from the outlet hole % Of raw dolomite and, for comparison, 6 to 30% by mass of a magcarbon brick block was added to the slag remaining in the converter. When the amount of slag remaining in the converter is 40t or more, the converter is swung four times when the amount of slag remaining in the converter is less than 40t, and the slag temperature is reduced to 1400 ° C or less twice. Reduced. After evacuating the hole for 10 seconds (the inner diameter of the steel outlet hole sleeve was 220 mmφ), the slag remaining in the converter was discharged from the furnace port by inclining the converter. Every 30 to 50 ch, the remaining thickness of the refractory in the vicinity of the steel hole was measured using a laser profile meter to determine the wear rate.

Relationship between the addition rate of raw dolomite (indicated by ●) and magcarbon brick mass (indicated by ■) (ratio of the mass of raw dolomite and magcarbon brick mass to the mass of slag remaining in the converter) and the refractory wear rate Is shown in FIG. With increasing raw dolomite addition rate, the refractory wear rate decreased. Moreover, when the addition ratio of raw dolomite was 6 mass% or more, it was found that the wear rate was 0.25 mm / ch or less, and sufficient durability was obtained. When the addition ratio of raw dolomite exceeded 12% by mass, the amount of decrease in the wear rate was saturated, and no significant improvement in the wear rate accompanying the increase in the addition ratio was observed. Furthermore, when the addition ratio of raw dolomite exceeded 30% by mass, convex deposits causing residual hot water were observed in the vicinity of the tapped holes.
From the above results, in order to form a highly durable slag coating on the refractory in the vicinity of the steel hole, it is preferable to introduce raw dolomite of 6 to 30% by mass of the slag remaining in the converter. confirmed.

When a magcarbon brick block was added instead of raw dolomite, a slight improvement was seen in the wear rate of the refractory, but the effect was small compared to raw dolomite.

Experiment 6: Relationship between hole removal time and wear rate of refractory 10 to 12% by mass with respect to slag remaining in the converter after the refining of the steel in the converter and completion of steel output from the outlet hole Of raw dolomite. When the amount of slag remaining in the converter is 40t or more, the converter is swung four times when the amount of slag remaining in the converter is less than 40t, and the slag temperature is reduced to 1400 ° C or less twice. Reduced. After evacuation for 1 to 180 seconds (the inner diameter of the steel hole sleeve was 220 to 280 mmφ), the slag remaining in the converter was discharged from the furnace port by inclining the converter. Every 30 to 50 ch, the remaining thickness of the refractory in the vicinity of the steel hole was measured using a laser profile meter to determine the wear rate.

FIG. 9 shows the relationship between the hole removal time and the wear rate of the refractory. When the hole evacuation time is 1 to 2 seconds, the wear rate is not sufficiently reduced, whereas when the hole evacuation time is 5 seconds or more, the wear rate is reduced to about 0.2 mm / ch. It can be seen that it has sufficient durability.
Moreover, the comparison of the non-operation time of the converter in the case where it does and does not perform hole evacuation is shown in FIG. Even if the hole evacuation time exceeds 120 seconds, the wear rate is slightly reduced, and improvement in durability is confirmed. However, if the hole evacuation time is excessively long, as shown in FIG. The non-operating time of the converter increases due to the implementation of evacuation. Considering these results and the operating efficiency of the converter, the hole evacuation time is preferably 120 seconds or less.
From the above results, in order to form a highly durable slag coating on the refractory in the vicinity of the steel outlet hole, it was confirmed that it is preferable to carry out the hole removal for 5 to 120 seconds.

It is explanatory drawing which shows the cross section of the converter to which the slag coating method of the converter inner wall surface which concerns on one embodiment of this invention is applied. It is explanatory drawing of a series of cycles which rocks the converter. It is a partial schematic diagram in the vicinity of a steel outlet hole for explaining convex deposits formed in the vicinity of the steel outlet hole. It is a graph which shows the relationship between the remaining thickness of a refractory, and the number of times of steel extraction when hole evacuation is performed and when hole evacuation is not performed. It is a graph which shows the relationship between average slag temperature and the wear rate of a refractory. It is a graph which shows the relationship between the frequency | count of rocking | fluctuation of a converter, and slag temperature in case residual slag amount is 20t and 40t. It is a graph which shows the relationship between the internal diameter of a steel exit hole sleeve, and the wear rate of a refractory. It is a graph which shows the relationship between the addition rate of raw dolomite or a mag-carbon brick block, and the wear rate of a refractory. It is a graph which shows the relationship between hole removal time and the wear rate of a refractory. It is a graph which shows the comparison of the non-operation time of a converter in the case where it does not perform hole excretion and it does not.

Explanation of symbols

10: Converter, 11: Furnace, 12: Outgoing steel hole, 13: Refractory material, 14: Tuyere, 15: Outgoing steel hole sleeve, 16: Slag, 17: Convex deposit, 18: Residual hot water

Claims (6)

From step A, the converter in which the slag remains after rocking is swung several times to lower the temperature of the slag, and the converter is tilted, from the steel outlet hole provided on the upper side of the converter. And a step B of forming a coating of the slag on the surface of the refractory disposed on the inner wall surface of the converter while discharging the slag. The slag coating method for an inner wall surface of a converter according to claim 1, wherein the temperature of the slag is lowered to 1150 ° C to 1400 ° C in the step A. 3. The slag coating method for a converter inner wall surface according to claim 1, wherein the number of oscillations of the converter is 2 to 5 times. 4. . 4. The slag coating method for a converter inner wall surface according to claim 1, wherein an inner diameter of the steel outlet hole is 140 to 300 mm. 5. In the slag coating method of the converter inner wall surface of any one of Claims 1-4, before making the said converter rock | fluctuate by the said process A, a particle size is 10-50 mm and in the said converter. A slag coating method for an inner wall surface of a converter, wherein 6-30% by mass of a basic carbonate lump of residual slag is added. In the slag coating method of the converter inner wall surface of any one of Claims 1-5, in the said process B, discharge | emission of the said slag from the said steel outlet hole is performed for 5-120 seconds, The rolling characterized by the above-mentioned. Slag coating method for furnace inner wall.

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