Slag coating method

Abstract

The present invention provides a slag coating method that can enhance the effect of suppressing damage to the bricks at the bottom of a converter furnace without blocking the tuyeres at the bottom of the furnace. [Solution] The bottom of the converter 1 is coated with a coating material 50 which is accumulated at the bottom of the furnace 6 and contains slag with a liquid phase ratio of 70% to 80%, while gas is supplied from the tuyeres 15 at the bottom of the furnace 6.

Description

[Technical Field]

[0001] The present invention relates to a slag coating method for coating the bottom of a converter with slag. [Background technology]

[0002] A method for coating the bottom of a converter with slag is known (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 63-50411 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the method described in Patent Document 1, the bottom of the converter is coated with slag, and then oxygen is blown onto the bottom tuyeres under high-temperature conditions to remove the slag adhering to the tuyeres. On the other hand, Patent Document 1 does not disclose a slag coating method that can enhance the effect of suppressing damage to the bottom of the converter during operation.

[0005] The present invention aims to provide a slag coating method that can enhance the effect of suppressing damage to the bricks at the bottom of a converter furnace without blocking the tuyeres at the bottom of the furnace. [Means for solving the problem]

[0006] The present invention is summarized in the following slag coating method.

[0007] (1) A slag coating method comprising: a coating material accumulated at the bottom of a converter, which contains slag and has a liquid phase ratio of 70% to 80%, and a gas supply from a tuyer at the bottom of the converter, while coating the bottom of the converter with the coating material.

[0008] (2) 1 m on the upper surface of the coating material 2 The slag coating method according to (1), wherein the coating material is agitated by supplying gas at a rate of 80 kW to 110 kW per unit from a lance installed above the bottom of the furnace.

[0009] (3) The gas from the lance is flowed at a rate of 45 kNm 3 / hr~48kNm 3 The slag coating method according to (2), wherein the slag is supplied to the coating material at a rate of / hr for 90 to 180 seconds.

[0010] (4) The slag coating method according to any one of (1) to (3) above, wherein the gas is an inert gas.

[0011] (5) The converter comprises a fixed furnace bottom and a replaceable furnace bottom that includes the tuyeres of the furnace bottom and is replaceable with respect to the fixed furnace bottom, A slag coating method for a converter according to any one of (1) to (4) above, wherein the coating material is coated so as to fill the step difference between the upper surface of the fixed furnace bottom and the upper surface of the replaceable furnace bottom. [Effects of the Invention]

[0012] According to the present invention, a slag coating method can be realized that enhances the effect of suppressing damage to the bricks at the bottom of the converter furnace without blocking the tuyeres at the bottom of the furnace furnace. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view of a converter in which a slag coating method according to one embodiment of the present invention is carried out. [Figure 2] Figure 2 is a magnified view of the area around the bottom of the furnace shown in Figure 1. [Figure 3] Figure 3 shows an example of a slag coating method at the bottom of the furnace. [Figure 4]FIG. 4 is a graph showing the relationship between the slag temperature and the liquid phase fraction of the coating material. [Figure 5] FIG. 5 is a graph showing the relationship between the impact energy of the upward blowing gas on the coating material and the splash height when splash occurs in the coating material due to the upward blowing gas. [Figure 6] FIG. 6 is a diagram for explaining the slag coating when the wear bricks at the bottom of the fixed furnace are worn out and the wear bricks at the bottom of the converter furnace are replaced.

Mode for Carrying Out the Invention

[0014] <Background Leading to the Present Invention> The bottom of a converter for steelmaking is paved with bricks, and these bricks receive molten steel. Also, a tuyere for gas blowing may be installed at the bottom of the converter. When, for example, room temperature gas is blown from the tuyere, the high-temperature bricks around the tuyere are cooled, and as a result, the bricks around the tuyere are damaged by thermal spalling. Therefore, the bottom bricks are more damaged than the bricks other than the bottom of the furnace. Also, when the operation rate of the converter (the number of times of processing molten steel per day) is low, the amount of heat stored in the converter is small, so the scrap (iron source) remaining unmolten in the converter remains at the bottom of the furnace and adheres in a form covering the entire bottom of the furnace together with the slag. As a result, the gas from the tuyere passes between the bottom bricks and the scrap - slag (by - product), cooling the entire surface of the bottom bricks, and thus the entire bottom bricks are greatly worn out. Here, there is a converter in which the central part of the bottom can be exchanged with other parts of the bottom. In such a converter, when the damage to the bottom bricks becomes large, the life of the bottom can be extended by exchanging the bricks in the replaceable part of the bottom with new bricks. However, in this case, since the non - replaceable part (fixed hearth) of the bottom is damaged, a step occurs between the replaceable part and the non - replaceable part (fixed hearth) of the bottom. That is, the newly replaced bricks protrude into the converter with respect to the worn non - replaceable bricks. The protruding part of the new bricks is exposed to molten steel to a large extent, so the progress of damage becomes fast and the life becomes short.

[0015] Under the above premises, the inventor of the present application has conducted intensive research and conceived a method of improving the durability of bricks by preventing scrap slag from adhering to the tuyere at the bottom of the furnace and protecting the surface of the hearth bricks. The present invention is particularly effective as a method for efficiently filling and repairing the step between the replaceable furnace bottom and the fixed furnace bottom.

[0016] <Embodiment> Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a schematic cross-sectional view of a converter 1 in which a slag coating method according to an embodiment of the present invention is implemented. FIG. 2 is an enlarged view of the periphery of the furnace bottom 6 in FIG. 1. In FIG. 1, an example is illustrated in which both the fixed brick portion 20 of the fixed furnace bottom 12 and the replaceable brick portion 30 of the replaceable furnace bottom 11 of the converter 1 are in a new state.

[0018] As shown in FIGS. 1 and 2, the converter 1 is used, for example, to refine (e.g., decarburize) hot metal taken out from a blast furnace. The converter 1 may be used as an electric furnace that melts iron scrap by electric energy. In the present embodiment, unless otherwise specified, the description will be based on the case where the converter 1 is in a standing posture (the posture during refining). In the case of a converter for refining hot metal from a blast furnace, the weight of hot metal per charge (one-time refining) is, for example, about 250 tons or so. In the case of an electric furnace, the weight of hot metal per charge is, for example, about 100 tons or so.

[0019] The converter 1 has an iron shell 2, and a permanent brick 4 and a wear brick 5 installed over substantially the entire inner surface of the iron shell 2.

[0020] The iron shell 2 is a hollow metal member. The upper end portion of the iron shell 2 is open, and the lower end portion of the iron shell 2 is closed.

[0021] The permanent brick 4 is disposed adjacent to the iron shell 2, and the wear brick 5 is disposed inside the converter 1 with respect to the permanent brick 4.

[0022] The permer bricks 4 are, for example, MgO bricks and are formed in block shape. Numerous permer bricks 4 are arranged on the inner surface of the iron shell 2 along the circumferential and vertical directions of the converter 1.

[0023] The wear bricks 5 are bricks that are directly exposed to molten iron, such as MgO-C bricks, and are formed in block form. Numerous wear bricks 5 are arranged on the inner surface of the permer bricks 4. The wear bricks 5 are arranged along the circumferential and vertical directions, similar to the permer bricks 4.

[0024] The converter 1 having the above configuration includes a furnace bottom 6, a straight cylinder 7 positioned above the furnace bottom 6, and a tapered inclined portion 8 extending upward from the straight cylinder 7 and decreasing in diameter as it moves away from the straight cylinder 7.

[0025] The furnace bottom 6 has a replaceable furnace bottom 11 installed in the center of the furnace bottom 6 and a fixed furnace bottom 12 formed around the replaceable furnace bottom 11.

[0026] The fixed furnace bottom 12 has a fixed iron shell 2a and a fixed brick section 20.

[0027] The fixed iron shell 2a is a part of the iron shell 2 and is positioned to cover the bottom of the molten iron storage space 14 inside the converter 1. The fixed iron shell 2a is formed integrally with the iron shell 2 in the straight section 7. The fixed brick section 20 is installed on the fixed iron shell 2a.

[0028] The fixed brick section 20 has a two-layer brick structure composed of permer bricks 4 and wear bricks 5 (5a) arranged at the furnace bottom 6. The wear bricks 5a of the fixed brick section 20 are flat brick members, and for example, a large number of them are arranged vertically. Of the fixed brick section 20, the upper surface 20a facing the inside of the converter 1 is composed of wear bricks 5a. The upper surface 20a is formed in a curved shape that is concave downward toward the center 6a of the furnace bottom 6.

[0029] The fixed iron shell 2a and fixed brick section 20 are not located on the central side of the furnace bottom 6, but surround the replaceable furnace bottom 11. The boundary 9 between the fixed furnace bottom 12 and the straight cylinder section 7 can be exemplified by a portion where the angle between the upper surface 20a of the furnace bottom 6 and the horizontal plane is approximately 30° to 45°.

[0030] The replaceable furnace bottom 11 is the portion including the center 6a of the furnace bottom 6, and has a diameter of, for example, 1 m to several m. The replaceable furnace bottom 11 is replaceable with the fixed furnace bottom 12.

[0031] The replacement furnace bottom 11 includes a replacement iron shell 2b and a replacement brick section 30.

[0032] The replacement iron shell 2b is a separate component from the fixed iron shell 2a and is positioned to work together with the replacement iron shell 2b to seal the bottom of the molten iron storage space 14. The replacement brick section 30 is installed on top of the replacement iron shell 2a.

[0033] The replacement brick section 30 has a two-layer brick structure composed of permer bricks 4 and wear bricks 5 (5b) arranged in the furnace bottom 6. The wear bricks 5 of the replacement brick section 30 are flat brick members, and are arranged in large numbers, for example, in a vertical orientation. Of the replacement brick section 30, the upper surface 30a facing the inside of the converter 1 is composed of wear bricks 5b. The upper surface 30a works in cooperation with the upper surface 20a of the fixed furnace bottom 20 to form a curved shape that is recessed downward toward the center of the furnace bottom 6.

[0034] The bottom of the furnace 11 is provided with tuyeres 15 from the bottom of the furnace 6. The tuyeres 15 are metal tubes that extend from the outside to the inside of the converter 1, through which gas from a gas supply source (not shown) passes and supplies this gas to the molten iron storage space 14. The tuyeres 15 penetrate the replacement iron shell 2b, the permer bricks 4 and the wear bricks 5b, and open to the upper surface 30a of the bottom of the furnace 30. Multiple tuyeres 15 are provided in the bottom of the furnace 11 (for example, a total of four, one at each of the four corners of the rectangle in plan view), and are spaced apart from each other. In the figure, two tuyeres 15 are shown. The inner diameter of each tuyere 15 is, for example, 38 mm to 45 mm, but is not limited to the inner diameter shown in this example.

[0035] An amorphous refractory material 16 is filled between the replaceable furnace bottom 11 and the fixed furnace bottom 12. The amorphous refractory material 16 has a composition in which a bonding agent is mixed with a powdered material. An example of the amorphous refractory material 16 is a composition containing approximately 80% by weight of MgO and approximately 6% by weight of C.

[0036] The amorphous refractory material 16 has a first portion 16a that fills the space between the inner surface of the fixed furnace bottom 12 and the outer surface of the replaceable furnace bottom 11. The first portion 16a only needs to be able to fill the space between the inner surface of the fixed furnace bottom 12 and the outer surface of the replaceable furnace bottom 11, and its specific shape is not limited.

[0037] A slag coating layer 18 is formed on the wear bricks 5a and 5b of the furnace bottom 6. The slag coating layer 18 covers the entire upper surface 30a of the replaceable furnace bottom 11 and also covers at least a portion of the upper surface 20a of the fixed furnace bottom 12 (all or all of the fixed furnace bottom 12 except for the outer periphery 20b).

[0038] The slag coating layer 18 is formed by coating the furnace bottom 6 with a coating material containing slag, which is the residue after molten steel is tapped from the converter 1. The slag coating layer 18 mainly consists of CaO and SiO2, and also contains Fe, MgO, Al2O3, S, P2O5, and MnO. The upper surface 18a of the slag coating layer 18 is a smooth, curved surface that is recessed toward the exchange furnace bottom 11. The slag coating layer 18 does not cover the opening 15a of the tuyere 15, and an opening 18b is formed in the slag coating layer 18 above the opening 15a of the tuyere 15, through which gas from the tuyere 15 is supplied to the molten iron storage space 14. The maximum thickness of the slag coating layer 18 is, for example, about 200 mm to 300 mm, but is not limited to this example thickness.

[0039] The straight section 7 comprises an iron shell 2 in the straight section 7, permer bricks 4 arranged on the inner surface of the iron shell 2, and wear bricks 5 arranged on the inner surface side of the permer bricks 4.

[0040] A lance 19 is inserted into the molten iron storage space 14 within the converter 1, and a gas for refining the molten steel in the converter 1 is supplied to it. The lance 19 is a cylindrical member having a predetermined outer diameter and is connected to a gas supply source (not shown). Refining gas and inert gas are supplied from an opening 19a formed at the lower end of the lance 19. The lance 19 is configured to be switchable between a state where it is removed from the converter 1 and a state where a portion of it is inserted into the converter 1.

[0041] <An example of a slag coating method> Next, a slag coating method for forming the slag coating layer 18 will be described. The slag coating is performed after molten steel has been tapped from the converter 1 and the slag remains in place.

[0042] In this embodiment, a slag coating is applied to the upper surfaces of the bricks 5a and 5b at the furnace bottom 6 in order to protect the wear bricks 5 and amorphous refractories 16 at the furnace bottom 6. In this embodiment, in order to prevent the tuyeres 15 at the furnace bottom 6 from becoming clogged during slag coating, and to ensure that the wear bricks 5a and 5b at the furnace bottom 6 are reliably protected by the slag coating layer 18, the slag temperature is adjusted by adjusting the amount of slag and the flow rate of the gas from the lance 19 (hereinafter also referred to as the top-blown gas), and the scattering range is set by adjusting the impact energy of the top-blown gas.

[0043] The reason for the above-mentioned settings is that, conventionally, when repairing the furnace bottom by slag coating, there was a problem in that a large amount of slag adhered to the furnace bottom 6, causing the tuyeres 15 to clog. The reasons why slag adheres to the tuyeres 15 of the furnace bottom 6 include: (i) the slag remaining on the furnace bottom 6 is cooled and solidified by the cooling caused by the upward-blowing gas during slag coating and the gas from the tuyeres 15 (hereinafter also referred to as bottom-blowing gas); and (ii) when slag coating is applied to the furnace bottom, a large amount of slag covers the tuyeres 15, solidifies, and clogs the tuyeres 15.

[0044] Therefore, in this embodiment, as shown in Figures 3 and 4, the bottom of the converter 1 is coated with a coating material 50 which contains slag and has a liquid phase ratio of 70% to 80%, while gas is supplied from the tuyeres 15 of the bottom of the converter 6 as shown by arrow F. Figure 3 is a diagram showing an example of a slag coating method at the bottom of the converter 6. Figure 4 is a graph showing the relationship between the slag temperature and the liquid phase ratio of the coating material 50. Figure 4 shows a graph when nitrogen gas, which is an inert gas, is injected as the top blowing gas and the bottom wiping gas.

[0045] Slag coating is performed by agitating the slag coating material 50 at the bottom of the furnace 6 while cooling the slag coating material 50. Specifically, it is performed under the following conditions.

[0046] <Conditions for slag coating> (liquid phase ratio) The coating material 50 may consist of slag, which is the residue after tapping molten steel from the converter 1, or a predetermined amount of a solidifying agent such as dolomite may be added to the slag. If the liquidity ratio of the coating material 50 is less than 70%, it is difficult to ensure sufficient fluidity of the coating material 50 with respect to at least one of the amorphous refractory material 16 at the bottom of the furnace 6, the wear bricks 5a in the fixed brick section 20, and the wear bricks 5b in the replacement brick section 30. Therefore, it is difficult to form a slag coating layer 18 over a wider area of ​​the bottom of the furnace 6. Also, if the liquidity ratio of the coating material 50 exceeds 80%, the fluidity of the coating material 50 becomes too high, and the retention of the coating material 50 near the outer circumference 20b of the bottom of the furnace 6 is insufficient, making it difficult to ensure a sufficient thickness of the slag coating layer 18. By controlling the flow rate of the top-blown gas, in particular, among the top-blown and bottom-blown gases, the coating material 50 is cooled so that its liquid phase ratio is 70% to 80%. As shown in Figure 4, when the liquid phase ratio exceeds 80% and is in the range of 95%, the coating material 50 is easily scattered by the top-blown gas, making it difficult for the slag coating layer 18 to form due to the solidification of the coating material 50. Also, when the liquid phase ratio is 95% to 100%, although scattering of the coating material 50 by the top-blown gas is not observed, the fluidity is too high, making it difficult for the slag coating layer 18 to form due to the solidification of the coating material 50.

[0047] (Conditions for upward-blowing gas) During slag coating, apply 1 m to the upper surface 50a of the coating material 50. 2It is preferable to agitate the coating material 50 by supplying gas at an energy of 80 kW to 110 kW per unit area from a lance 19 installed above the furnace bottom 6. The energy (kW) at this time can be called the impact energy, which refers to the average impact energy per unit area in the region where the gas is injected. It is preferable that the upward-blowing gas from the lance 19 is an inert gas. Examples of inert gases include nitrogen and carbon dioxide. It is preferable that the temperature of the upward-blowing gas be at room temperature in order to reduce the cost of slag coating.

[0048] Figure 5 is a graph showing the relationship between the impact energy of the upward-blowing gas onto the coating material 50 and the splash height when a splash occurs on the coating material 50 due to the upward-blowing gas. In Figure 5, the measured results are shown with triangles, and the trend line is shown with a straight line. As shown in Figure 5, when the impact energy is 1 m 2 With a power output of 80 kW or more per unit, sufficient stirring energy is provided to the coating material 50, allowing it to be thoroughly stirred to the point where splashing occurs. Furthermore, the impact energy is 1 m 2 By keeping the power output below 110 kW, the splash height can be reduced to approximately 1 meter or less. As a result, it is possible to suppress the coating material 50 from adhering to the wear bricks 5 of the straight section 7 due to the splash, which would reduce the thickness of the slag coating layer 18 at the bottom of the furnace 6.

[0049] The upward-blowing gas from Lance 19 has a flow rate of 45 kNm 3 / hr~48kNm 3It is preferably supplied to the coating material 50 for 90 to 180 seconds at / hr. The flow rate in this case indicates the momentum (mass × velocity) of the upward blowing gas, and does not indicate the thermal energy of the upward blowing gas. By setting the flow rate of the upward blowing gas to be not less than the above lower limit, the upward blowing gas with a collision energy of 80 kw or more as described above can be supplied to the coating material 50, and the coating material 50 can be surely stirred to surely form the slag coating layer 18. Further, by setting the flow rate of the upward blowing gas to be not more than the above upper limit, the upward blowing gas with a collision energy of 110 kw or less as described above can be supplied to the coating material 50, and it is possible to suppress the splash height of the coating material 50 from becoming too high. Therefore, by suppressing the adhesion of the coating material 50 to the straight body part 7, a slag coating layer 18 with a sufficient thickness can be formed on the furnace bottom 6.

[0050] During slag coating, the pressure of the upward blowing gas from the lance 19 is 3.7 kg / m 2 ~4.0 kg / m 2 which is preferably the case. By setting the pressure of the upward blowing gas to be not less than the above lower limit value, it is possible to suppress the coating material 50 blown up by the upward blowing gas from entering the lance 19. Further, by setting the pressure of the upward blowing gas to be not more than the above upper limit value, it is possible to suppress the coating material 50 blown up by the upward blowing gas from adhering to the wear bricks 5 of the straight body part 7 and the thickness of the slag coating layer 18 on the furnace bottom 6 from becoming small.

[0051] As shown in FIG. 4, when the flow rate of the upward blowing gas from the lance 19 is within the above range, by continuously injecting the upward blowing gas into the coating material 50 for 90 seconds or more, the coating material 50 can be cooled until the liquid phase ratio of the coating material 50 becomes 80% or less. Further, by setting the injection time of the upward blowing gas to be 180 seconds or less, the liquid phase ratio of the coating material 50 can be made 70% or more. Thus, by setting the injection time of the upward blowing gas within the above range, slag coating can be performed in a state where the coating material 50 is cooled so that the liquid phase ratio becomes 70% to 80%, and further, the slag coating layer 18 can be formed by solidification of the coating material 50.

[0052] The unsolidified coating material 50 is discharged from the opening of the inclined section 8 by tilting the converter 1 after the gas is injected.

[0053] In this embodiment, during slag coating, the upward-blowing gas from the lance 19 does not directly hit the coating material 50 on the center 6a of the furnace bottom 6, for example, but is injected towards the area excluding the circular region in a plan view near the center 6a. The region 25 to which the gas from the lance 19 is injected at this time has the shape shown in Figure 3, with the outer and inner circumferences of the region 25 being roughly conical. It is preferable that the upward-blowing gas is blown directly onto at least 50% or more, for example, 50% to 60%, of the upper surface 50a of the coating material 50. By directly injecting the upward-blowing gas from the lance 19 over a sufficient area of ​​the upper surface 50a of the coating material 50 in this way, the coating material 50 can be sufficiently stirred to form a slag coating layer 18 with a more uniform density and sufficient thickness.

[0054] The height h from the wear brick 5 at the bottom 11 of the replacement furnace to the lance 19 is preferably set to, for example, 2800 mm to 4000 mm. By setting the height above the lower limit, the upward-blowing gas can be injected onto the coating material 50 over a sufficiently wide area. Conversely, by setting the height below the upper limit, it is possible to prevent the upward-blowing gas from getting too close to the straight section 7. Therefore, it is possible to prevent splashes of the coating material 50 from adhering to the straight section 7 due to the upward-blowing gas. It is preferable that the injection angle θ1 of the upward-blowing gas from the lance 19 is about 20°, in order to supply the upward-blowing gas to the coating material 50 over a sufficiently wide area. Furthermore, regarding the upward-blowing gas from the lance 19, if the upward-blowing gas is not supplied in a conical shape downward from the lance 19 in a range of about θ2 = 10°, it is possible to suppress the generation of unwanted splashes near the center 6a of the furnace bottom 6. In this case, if the upward-blowing gas from the lance 19 is supplied to the coating material 50 while avoiding the area directly above the tuyere 15, it is possible to suppress the solidification of the coating material 50 so that it blocks the tuyere 15. Note that in Figure 3, the injection angles θ1 and θ2 are exaggerated and shown larger than their actual values.

[0055] (Conditions for bottom-blowing gas) Gas should be supplied from the tuyere 15 so that it does not become blocked during slag coating. Preferably, the gas used is an inert gas. Examples of inert gases include nitrogen and carbon dioxide. The temperature of the inert gas from the tuyere 15 should be room temperature, which is preferable for reducing the cost of slag coating. The flow rate of the bottom-blowing gas from the tuyere 15 should be 600 kNm³. 3 / hr~1600kNm 3 / hr (flow rate at atmospheric pressure and 0°C) can be used as an example, for instance, 800 kNm 3 Set to / hr. Bottom-blowing gas flow rate to 600kNm 3 By setting the flow rate to 1600 kNm³ or more, a sufficient flow rate can be secured to prevent the tuyeres 15 from becoming clogged with the coating material 50. 3By keeping the rate below / hr, excessive consumption of bottom-blowing gas can be suppressed.

[0056] (Amount of slag) In the slag coating method of this embodiment, it is preferable that the amount of slag in the coating material 50 be less than the amount of slag produced by refining. By performing slag coating with a relatively small amount of slag after a portion of the slag produced during refining has been discharged from the converter 1, a slag coating layer 18 of appropriate thickness can be formed on the furnace bottom 6. The ratio of the amount of slag used for slag coating to the amount of slag produced during refining is, for example, 30% to 70%, and preferably 50%.

[0057] The above are the conditions for slag coating.

[0058] It is preferable to perform slag coating every few dozen charges, as this ensures that the slag coating layer 18 is adequately maintained.

[0059] By performing slag coating every few dozen charges, even if the slag coating layer 18 is worn down during smelting in the converter 1, it is possible to prevent the wear bricks 5 from being exposed from the slag coating layer 18 and directly exposed to the molten steel by the wear bricks 5a and 5b at the bottom of the furnace 6.

[0060] In addition, the replacement furnace bottom 11 may be removed from the fixed furnace bottom 12, and the worn ware bricks 5a of the fixed furnace bottom 12 may be replaced with new ones. In this case, as shown in Figure 6, which illustrates the slag coating when the ware bricks 5b of the replacement furnace bottom 11 are replaced while the ware bricks 5a of the fixed furnace bottom 12 are worn, the ware bricks 5b of the replacement furnace bottom 11 are new and thick. On the other hand, the ware bricks 5a of the fixed furnace bottom 12 remain worn and thinner, creating a step (step portion 26) between the ware bricks 5a and 5b. The second portion 16b of the amorphous refractory material 16 is then positioned to fill the step between the ware bricks 5a and 5b. The second portion 16b is positioned on the upper surface 20a of the fixed furnace bottom 12. For example, the second portion 16b forms a smooth, curved upper surface that is recessed toward the replacement furnace bottom 11. However, after several tens of charges of smelting following the placement of the second portion 16b, the amorphous refractory material 16 on the wear bricks 5a and 5b may have disappeared due to the molten steel. Even when the second portion 16b of the amorphous refractory material 16 on the wear bricks 5a and 5b has disappeared in this manner, a slag coating layer 18 can be formed with a coating material 50 having a liquid phase ratio of 70% to 80%, as in this embodiment.

[0061] In other words, the coating material 50 can be applied to fill the step (step portion 26) between the upper surface 20a of the fixed furnace bottom 12 and the upper surface 30a of the replaceable furnace bottom 11. In this case, the fluidity of the coating material 50 can be increased, so a slag coating layer 18 of sufficient density can be formed around the step portion 26. With such a slag coating layer 18, damage to the slag coating layer 18 can be suppressed even during the refining of tens to hundreds of tons of molten iron, and the protective effect of the slag coating layer 18 on the wear bricks 5a and 5b can be more reliably demonstrated. Thus, the slag coating method of this embodiment is particularly suitable for a converter 1 in which a part of the furnace bottom 6 is replaceable.

[0062] As described above, according to this embodiment, slag coating is possible without clogging the tuyere 15 by supplying gas from the tuyere 15 of the furnace bottom 6 to the coating material 50 which is accumulated in the furnace bottom 6 of the converter 1 and has a liquid phase ratio of 70% to 80%, while coating the wear bricks 5a and 5b of the furnace bottom 6 with the coating material 50.

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. The present invention can be modified in various ways as long as they are described in the claims.

[0064] In the above embodiment, the coating material 50 was prepared for slag coating by controlling the upward-blowing gas from the lance 19. However, this is not required. For example, a solidifying agent such as dolomite may be sufficiently added to the slag at the bottom of the furnace 6 to create a coating material with a viscosity higher than that of the slag, and the coating material 50 may be appropriately cooled by a method other than upward-blowing gas until the liquid phase ratio reaches 70% to 80%, and then the coating may be performed.

[0065] Furthermore, in the above-described embodiment, a configuration was described in which the replaceable furnace bottom 11 is replaceable with the fixed furnace bottom 12 in the furnace bottom 6. However, this is not required, and the entire furnace bottom 6 may be non-replaceable (the furnace bottom 6 may be formed from a fixed furnace bottom). [Industrial applicability]

[0066] This invention can be applied as a slag coating method. [Explanation of Symbols]

[0067] 1 Converter 6 Furnace bottom 11 Exchange furnace bottom 12 Fixed furnace bottom 15 Tuyere 19 Lance 20a Upper surface of the fixed furnace bottom 30a Upper surface of the bottom of the replacement furnace 50 Coating Materials 50a Top surface of coating material

Claims

1. A slag coating method comprising coating the bottom of a converter with a coating material that contains slag and has a liquid phase ratio of 70% to 80%, while supplying gas from a tuyer at the bottom of the converter.

2. 1 m on the upper surface of the aforementioned coating material ２ The slag coating method according to claim 1, wherein the coating material is agitated by supplying gas at a rate of 80 kW to 110 kW per unit from a lance installed above the bottom of the furnace.

3. The gas from the lance is supplied at a flow rate of 45 kNm ３ / hr ~ 48kNm ３ The slag coating method according to claim 2, wherein the slag is supplied to the coating material at a rate of / hr for 90 to 180 seconds.

4. The slag coating method according to claim 1, wherein the gas is an inert gas.

5. The converter comprises a fixed furnace bottom and a replaceable furnace bottom that includes the tuyeres of the furnace bottom and is replaceable with respect to the fixed furnace bottom. A method for coating a converter with slag according to any one of claims 1 to 4, comprising coating the coating material so as to fill the step difference between the upper surface of the fixed furnace bottom and the upper surface of the replaceable furnace bottom.

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