JPH02298211A - Refining furnace and refining method - Google Patents

Abstract

PURPOSE:To prevent a decrease in the reaction efficiency of a refining furnace at the last stage of its service by providing a tuyere mounting part where a tuyere can be mounted when the lining refractory is eroded after repeated refinings below the tuyere of the furnace. CONSTITUTION:A tuyere 4 is provided in the side wall close to the bottom of a refining furnace 1, and a tuyere mounting part 5 where a tuyere can be mounted when the lining refractory 3 is eroded after repeated refinings is provided blow the tuyere 4. A tuyere brick 15 is tapered and slightly narrowed toward the inside of the furnace, and a closed hole 15a is furnished halfway to form the mounting part 5. A monolithic refractory such as MgO is packed in the closed hole 16 through a stainless steel pipe 13. As a result, when the molten metal surface is lowered due to the erosion of the lining refractory 3 after repeated refinings, a fresh tuyere is mounted in the mounting part 5, a decrease in the reaction efficiency from the start and to stage of service of the furnace is reduced, and productivity is drastically improved.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a refining furnace and a refining method used for refining molten metal. (Prior Art) Examples of methods that use one tuyere for refining molten metal include a converter refining method and an AOD refining method. For example, in the AOD refining method, inert gas such as argon or nitrogen is injected into the molten metal along with oxygen gas through tuyeres installed on the furnace wall, thereby reducing the 00 partial pressure and suppressing the oxidation loss of Cr. This method uses less low-carbon Fe-Cr than the electric furnace refining method, so it is particularly advantageous for producing low-carbon stainless steel. FIG. 4 illustrates the structure of a conventional refining furnace used in the AOD refining method, and this refining furnace 51 is provided with a lining refractory 53 inside a steel shell 52, and near the bottom of the furnace. A tuyere 54 is provided on the side wall of the furnace, and in some cases, a tuyere 55 is also provided at the bottom of the furnace. The tuyeres 54 are positioned at a height that exposes them to the outside surface during slag off. When the refining furnace 51 starts to be used, the furnace inner diameter is DI+
Although the hot water level height is H+ (=h+ +dt), by repeating refining using this refining furnace 51, structural spalling occurs in the altered layer due to penetration of slag on the outlet side of the molten metal 56. mechanical erosion caused by agitation of the molten metal around the tuyere and thermal shock damage (thermal spalling) due to temperature changes, and structural spalling and molten metal damage caused by slab penetration above the tuyere. This is because mechanical erosion due to agitation is likely to occur. The lining refractory 53 of the refining furnace 51 will gradually melt and damage, and at the end of the service life of the refining furnace 51, the furnace inner diameter will expand to D2 and the hot water level will change to H2 (=h2+d2). The state is as follows. (Problem to be Solved by the Invention) As described above, when the refining furnace 51 starts to be used, the furnace inner diameter is Dl.
, the melt surface height was Hl, but at the end of service, the furnace inner diameter expands to D2 and the melt surface height changes to H2, so at the beginning of use, the melt surface from the tuyere 54, At the end of service life, the height from the tuyere 54 to the hot water level L2 is hl, which is quite small, and at the beginning of use, the depth from the tuyere 54 to the bottom B1 is quite small. At the end of service life, the depth from the tuyere 54 to the furnace bottom B2 becomes quite large, dl.
The problem is that the stirring energy for the slag material is significantly reduced, the slag formation of the slag raw material is delayed, the reaction efficiency is reduced, the decarburization rate is reduced, and the Cr reduction time is increased, resulting in a decrease in productivity. Was. (Objective of the Invention) The present invention has been made in view of such conventional problems.
It is an object of the present invention to provide a smelting furnace and a smelting method in which the reduction in stirring energy for molten metal is smaller than in the past, and it is possible to prevent a decrease in reaction efficiency as much as possible and improve productivity. It is said that

[Structure of the invention]

(Means for Solving the Problems) A refining furnace according to the present invention is a refining furnace equipped with a tuyere for blowing gas into the molten metal during refining of the molten metal. (including the bottom part),
It is characterized by having a configuration including a tuyere attachment part to which a tuyere is attached when the lining refractory is eroded due to repeated refining, and in one embodiment, the tuyere attachment part is a blockage hole provided halfway. The refining method according to the present invention includes blowing gas into the molten metal through the tuyeres when refining the molten metal. The refining method is characterized by a structure in which the position of gas injection by the tuyere is lowered in response to erosion of the lining refractory due to repeated refining, and these structures solve the above-mentioned conventional problems. It is used as a means to achieve this goal. (Function of the invention) Since the smelting furnace and smelting method according to the present invention have the above-described configuration, the molten metal level decreases due to melting of the lining refractory due to repeated smelting. Since the position of gas injection by the tuyere is set to lower according to the lowering of the surface, ゛j#? After repeating 11 times, the height from the tuyere to the melt surface becomes larger than before, and the depth from the tuyere to the bottom of the furnace becomes shallower than before, so the stirring energy for the molten metal is reduced. The reduction is smaller than before, and the reduction in reaction efficiency from the start of use to the end of the life of the refining furnace is small, resulting in a significant improvement in productivity. (Embodiment) Fig. 1 shows a smelting furnace according to an embodiment of the present invention.This smelting furnace 1 is provided with a lining refractory 3 on the inside of an iron shell 2 and on a side wall near the bottom of the furnace. A tuyere 4 is provided, and a tuyere attachment part 5 is provided below the tuyere 4 to which the tuyere is attached when the lining refractory 3 is eroded due to repeated refining, and a molten metal 6 is accommodated in the furnace. It has a structure like this. FIG. 2 shows an enlarged view of the tuyere 4 and tuyere attachment part 5 in FIG. Inside, a copper inner pipe 12 and a stainless steel outer pipe 13 are provided concentrically, and 02+Ar gas or 02+N2 gas for refining is flowed inside the inner pipe 12, and between the inner pipe 12 and the outer pipe 13. The structure is such that cooling Ar gas is allowed to flow through it. In addition, the tuyere mounting part 5 is made of a tapered tuyere brick 15 that becomes slightly tapered toward the inside of the furnace, and a blockage hole 15a is provided halfway therein. It has a structure in which a monolithic refractory material 16 such as MgO is filled through a pipe 13. Therefore, if the molten metal 6 is repeatedly refined using the smelting furnace 1 having the structure shown in FIGS. Occurrence of spalling and molten metal around the tuyeres 6
Mechanical erosion due to stirring and thermal shock damage (thermal spalling) due to temperature changes, structural spalling due to slag penetration in the upper part of the tuyere, and mechanical erosion due to stirring of the molten metal 6. , the lining refractory 3 of the smelting furnace 1 will gradually melt away. Therefore, in this embodiment, the tuyere 4 of the smelting furnace 1, whose service life is conventionally 300 refining cycles, is For example, after 200 refining cycles, the lining refractory 3 will melt as shown by the solid line in Figure f53, and at this time the lower The depth of the blockage hole 15a is set so that the tip of the monolithic refractory 16 comes into contact with the molten metal 6 due to melting of the tuyere brick 15, and the stainless steel pipe 13 is inserted into the blockage hole 15a. It has a structure in which the monolithic refractory 16 is filled through the refractory 16. Therefore, after 200 refining cycles, the stainless steel pipe 13 and the monolithic refractory 16 are pulled out and removed as a single piece to prevent the penetration. A hole is formed, and a copper inner pipe (12
) and a stainless steel outer pipe (13) are installed concentrically to form a tuyere 11, and the copper inner pipe 12, the stainless steel outer pipe 13, and the tuyere that constituted the upper tuyere 4 were installed. The brick 11 was removed and a refractory brick 18 without hollow holes was installed in its place to seal it. Then, the next refining was started and the refining was carried out up to 300 times. As a result, after the position of the tuyere 4 shown in Fig. 1 became lower than the position of the tuyere 17 shown in Fig. 3, the height from the tuyere 17 to the hot water surface increased again. Therefore, the stirring energy for the molten metal 6 can be increased again, the decarburization rate increases, the Cri source opening time is shortened, and the reducing agent consumption rate is improved.
It was possible to increase the production efficiency in refining up to 00 times. In the above embodiment, two tuyere attachment parts 5 are provided on the furnace wall near the hearth bottom, but one tuyere attachment part 5 is provided at the hearth bottom and after refining a predetermined number of times, the tuyere attachment part 5 is installed on the furnace wall near the hearth bottom. By attaching a tuyere 17 to the furnace, it is also possible to blow in 02+ Ar gas for refining and Ar gas for cooling from the bottom of the furnace. Furthermore, the refining furnace and refining method according to the present invention are not limited to AOD operation suitable for refining stainless steel, but can be applied to refining in which gas is blown through tuyeres.

【Effect of the invention】

The smelting furnace according to the present invention has a configuration in which the tuyere is attached below the tuyere provided in the conventional smelting furnace, to which the tuyere is attached when the lining refractory is eroded due to repeated smelting, and the present invention In the refining method according to the above, the gas injection position by the tuyeres is lowered in response to the erosion of the lining refractory due to greening during refining. This makes it possible to secure a greater depth from the tuyere to the surface of the molten metal than before even when the temperature decreases, making it possible to utilize the stirring energy of the blown gas to a greater extent than before.1For example, in an AOD smelting furnace. In this method, it is possible to further improve the decarburization reaction efficiency, further shorten the opening time for CrQ, and further improve the reducing agent consumption rate. It is possible to improve the unit consumption, and by distributing the tuyeres used, it is possible to average out the significant melting damage around the tuyere, thereby further improving the life of the furnace. is possible,
This brings about the remarkable effect that it is possible to realize a reduction in refining costs.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a refining furnace showing one embodiment of the present invention;
Figure 2 is an explanatory cross-sectional view showing an enlarged view of the tuyere and tuyere attachment part of the refining furnace in Figure 1, and Figure 3 shows melting from the tuyere attached to the tuyere attachment part after the lining refractory has melted. A cross-sectional explanatory diagram of the smelting furnace when gas is started to be blown into the metal. Figure 4 is a cross-sectional diagram showing the state of erosion of the lining refractory of a conventional smelting furnace and the change in height from the tuyere to the surface of the molten metal. It is an explanatory diagram. 1... Refining furnace. 3... Lining refractory, 4... Tuyere. 5...Tyere mounting part. 6... Molten metal. Patent Applicant: Daido Steel Co., Ltd. Representative Patent Attorney Oshio Hazama Figure 1: Hatori = r@p Figure 4

Claims (3)

[Claims] (1) In a refining furnace equipped with a tuyere for blowing gas into the molten metal during refining the molten metal, below the tuyere,
A smelting furnace characterized by having a tuyere attachment part to which a tuyere is attached when a refractory lining is melted due to repeated smelting. (2) The refining furnace according to claim (1), wherein the tuyere mounting portion is formed of a tuyere brick in which a blockage hole provided halfway is filled with a monolithic refractory. . (3) In a refining method in which gas is blown into the molten metal through a tuyere when refining the molten metal, the position at which the gas is blown through the tuyere may be lowered in response to erosion of the lining refractory due to repeated refining. Characteristic refining method.