JP5109408B2 - Oxygen gas blowing lance for refining and method of desiliconization of hot metal - Google Patents

Description

  The present invention relates to an oxygen gas blowing lance for blowing oxygen gas into molten metal in order to refine the molten metal, and a hot metal desiliconization method using the oxygen gas blowing lance.

  In recent years, hot metal dephosphorization has been widely carried out in converters, hot metal pans or kneading vehicles (also called “torpedo cars”) for the purpose of reducing phosphorus content accompanying the upgrading of steel materials or rationalizing the steel making process. Yes. Moreover, in order to perform this dephosphorization process efficiently, the desiliconization process which removes the silicon in a hot metal beforehand is also performed before the dephosphorization process. Since phosphorus and silicon in the hot metal are removed by an oxidation reaction, the dephosphorization process and desiliconization process of the hot metal supply oxygen source such as oxygen gas or iron oxide to the hot metal, and phosphorus or silicon in the hot metal is supplied by the oxygen source. Is removed by oxidation. At that time, a flux such as quicklime is also added to increase the reaction efficiency or adjust the composition of the slag to be generated.

  Methods for supplying oxygen gas to hot metal in hot metal dephosphorization and desiliconization are roughly classified into two types. One method is a method in which oxygen gas is blown toward the hot metal bath surface from a non-contact upper blowing lance or the like, a so-called top blowing method (referred to as “top blowing acid method”). The other method is a method in which oxygen gas is directly blown into the hot metal from a blow lance immersed in the hot metal or a tuyere provided at the bottom of the reaction vessel (referred to as “blow acid feeding method”). Each method has its own characteristics, and in the case of the blow-in acid transfer method, there are advantages such as high oxygen gas addition efficiency and improved stirring power, while the heat load of the immersion part is large and the service life is long. There are problems such as limited number of times. On the other hand, in the case of the top blowing acid method, there is an advantage that the heat load to the top blowing lance is small and it can be used for a long period of time, but the addition efficiency of oxygen gas is low and the stirring power cannot be obtained. There are problems such as.

  When supplying oxygen gas, whether to use the top-blowing acid method or the blow-in acid method is determined in consideration of the above-mentioned features. For example, as in the case of a chaotic vehicle, the shape of the processing vessel Therefore, the top blowing acid method has poor reaction efficiency, and the blowing acid method may have to be adopted. In the case of a kneading vehicle, the shape of the container is difficult to stir and mix, and in addition to that, the number of openings is small with respect to the capacity of the molten iron, and the desired reaction efficiency cannot be obtained by the top blowing acid method.

As described above, since the blow lance used in the blow acid method has a high wear of the immersion part, means for improving this has been proposed. For example, in Patent Document 1, in a blowing lance composed of a tip portion immersed in molten metal and a holder portion that holds the tip portion, the tip portion has a single tube structure, and the entire surface thereof is calorized, Furthermore, a technique for preventing the blown lance tip from being melted by covering the outer periphery with a refractory is disclosed. Further, in Patent Document 2, the blowing lance has a double pipe structure with a refractory coated on the outer periphery, a refining agent and oxygen gas are blown from the inner pipe, and a hydrocarbon-based gas is blown from the outer pipe. A technique for preventing melting of the tip of the blowing lance is disclosed. The technique of Patent Document 2 is a technique in which a hydrocarbon-based gas is decomposed when heated and absorbs heat when it is decomposed, so that the end of the blowing lance is cooled using this endotherm.
Japanese Utility Model Publication No. 6-6447 JP 58-22212 A

  However, the above prior art has the following problems. That is, when oxygen gas is blown into the molten metal together with the refining agent, as in Patent Document 1, in the technique in which the immersion portion is a calorized pipe and the periphery thereof is covered with a refractory, iron oxide is supplied as an oxygen source to be supplied. The upper limit of the oxygen gas ratio, that is, the ratio of the oxygen gas supply amount to the total oxygen gas supply amount (iron oxide (converted to oxygen gas) + oxygen gas) is 20 to 30%. When the oxygen gas ratio is increased, the heat generation is intense and the single tube structure cannot withstand. In order to effectively use the heat generated by the oxidation reaction, the oxygen gas ratio is preferably 100%, but this technique does not have sufficient durability against the blowing of oxygen gas alone.

  Further, in the method disclosed in Patent Document 2, the tip of the blowing lance is cooled by the decomposition heat absorption of the hydrocarbon gas, but the endothermic effect due to the decomposition of the hydrocarbon gas is caused by the extreme tip, that is, the blowing portion. It is the main and does not contribute to the cooling of the refractory coated on the blowing lance. Therefore, although it is necessary to ensure the durability of the refractory itself, Patent Document 2 does not specifically disclose the composition of the refractory.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to provide a high durability in an oxygen gas blowing lance for blowing oxygen gas into molten metal such as hot metal, which is used many times as compared with the prior art. It is possible to provide an oxygen gas blowing lance that contributes to the reduction of manufacturing costs, and to provide a hot metal desiliconization method using the blowing lance.

An oxygen gas blowing lance for refining according to the first invention for solving the above-mentioned problem is an oxygen gas blowing lance for blowing oxygen gas into a molten metal, and is a double pipe structure comprising an inner tube and an outer tube. , and the oxygen gas is blown from the inner tube, from the gap between the inner tube and the outer tube is blown a hydrocarbon-based gas is blown on the outer circumference of the outer tube of the lance tip, the MgO 5 to 30 wt% Al ₂ O ₃ —MgO-based amorphous refractory contained is coated, and Al ₂ O ₃ —SiO containing 10 to 40 mass% of SiO ₂ is formed on the outer periphery of the outer tube of the blown lance body portion following this tip portion. ₂ type amorphous refractory is coated, and the boundary between the Al ₂ O ₃ —MgO type amorphous refractory coating layer and the Al ₂ O ₃ —SiO ₂ type refractory coating layer is L In the letter-shaped lance, the bent part and the molten metal surface position of the molten metal In a T-shaped lance and a Y-shaped lance, the distance from the center of the lance to the tip of the lance is d, and the position of the molten metal surface is 2 × d away from the tip of the lance. It is comprised so that it may be located between .

Further, desiliconization treatment method of hot metal according to the second invention, the refining oxygen gas injection lance as described in the first invention is immersed in the hot metal, the oxygen gas into the molten iron from the inner tube of the blowing lance In addition to blowing, hydrocarbon gas is blown from the gap between the inner pipe and the outer pipe to oxidize and remove silicon in the hot metal.

According to the present invention, the oxygen gas injection lance for injecting oxygen gas into the molten metal has a double tube structure, and the hydrocarbon gas is allowed to flow through the outer tube of the double tube structure, and the endothermic reaction due to the decomposition of the hydrocarbon gas is performed. Oxygen gas blowing lance is used to cool, and the outer surface of at least the tip is coated with an Al ₂ O ₃ —MgO amorphous refractory containing 5 to 30% by mass of MgO, which has excellent melt damage to molten metal. Therefore, the wear rate of the oxygen gas blowing lance can be greatly reduced as compared with the conventional case. As a result, the oxygen gas used for the refining reaction can be added with the same blowing lance over a long period of time by a method that can improve the stirring power with high efficiency. In particular, by using the oxygen gas blowing lance of the present invention in the hot metal desiliconization treatment, it is possible to effectively use the heat generated by the desiliconization reaction.

  Hereinafter, the present invention will be specifically described.

  The present inventors have made it possible to extend the life of the gas blowing lance in the desiliconization process of the hot metal performed by immersing the oxygen gas blowing lance in the hot metal contained in the kneading wheel and blowing oxygen gas from the gas blowing lance into the hot metal. Researched and studied.

  As a result, it has been found that if the outer surface of the oxygen gas blowing lance is made of metal, the erosion caused by hot metal cannot be suppressed. Moreover, even if the outer surface was calorized as in Patent Document 1, it was found that the effect was small when oxygen gas was blown in a large amount because the wear was significant. In other words, in order to improve the durability of the oxygen gas blowing lance, it has been found that it is necessary to form a refractory coating layer at least on the outer surface of the portion immersed in the hot metal.

  In addition, when the immersion part in the hot metal is a single pipe structure, even if it is covered with a refractory, the durability is poor. Therefore, at least a double pipe structure is used, and a hydrocarbon-based gas for cooling is provided between the inner pipe and the outer pipe. I found it necessary to flow. This is because it has been confirmed that at least the pole tip of the oxygen gas blowing lance is cooled by the endothermic reaction when the hydrocarbon-based gas is decomposed, thereby suppressing the melting of the pole tip.

However, these measures alone did not provide the intended durability, and therefore, the used blowing lances were investigated to investigate the causes that hindered the extension of the service life. From the results of the investigation, two types of wear patterns were observed as the wear pattern of the blown lance immersion part: molten metal and slag, and physically spalling.

  As a result of further investigation, regarding the erosion damage at the tip of the lance, the cooling effect of the hydrocarbon gas has hardly been obtained except at the tip of the pole, and the portion of the refractory covered with the oxygen gas blowing lance has the highest erosion damage. Was not the extreme tip, but was found to be a site slightly away from the tip where the cooling effect of the hydrocarbon gas could not be obtained. From this knowledge, it was found that in order to improve the durability of the oxygen gas blowing lance, it is necessary to reduce the melting rate of the refractory itself covering at least the most severely damaged site. In other words, it has been found that it is necessary to use a refractory that has excellent resistance to erosion against hot metal.

  Therefore, a test was conducted to optimize the refractory material. The test was conducted with an oxygen gas blowing lance used for desiliconization of hot metal contained in a kneading wheel. 1 and 2 are schematic cross-sectional views of each oxygen gas blowing lance used in the test, and FIG. 3 shows a situation where the hot metal contained in the kneading vehicle is desiliconized.

  FIG. 1 is a schematic cross-sectional view of an oxygen gas blowing lance according to the present invention, FIG. 2 is a schematic cross-sectional view of another oxygen gas blowing lance according to the present invention, and in FIGS. A blow lance, 2 is an inner pipe, 3 is an outer pipe, and 4 is a refractory coating layer made of an irregular refractory. In the oxygen gas blowing lance 1 shown in FIG. 2, the refractory coating layer 4 is divided into a tip refractory coating layer 4A on the tip side and a trunk refractory coating layer 4B on the trunk side, which are different from each other. Things are used. Other structures are the same in both cases. Reference numeral 7 in FIG. 2 denotes a bent portion which is a boundary portion between the tip portion and the trunk portion of the oxygen gas blowing lance. Oxygen gas (a refining agent if necessary) flows through the inner pipe 2, hydrocarbon gas flows through the gap between the inner pipe 2 and the outer pipe 3, and oxygen gas and hydrocarbon gas are supplied with an oxygen gas blowing lance. 1 is blown into the hot metal from the tip 1A.

  In FIG. 3, 5 is a kneading wheel and 6 is a hot metal. The tip 1A of the oxygen gas blowing lance 1 shown in FIG. 1 or 2 is immersed in the hot metal 6 accommodated in the kneading wheel 5, and the inner tube 2 shows a state in which oxygen gas is blown from 2 and hydrocarbon gas is blown from the gap between the inner tube 2 and the outer tube 3 to perform desiliconization treatment on the molten iron 6.

In this hot metal desiliconization treatment, the compositions of the refractory coating layer 4 or the tip refractory coating layer 4A and the trunk refractory coating layer 4B were changed, and the durability of the oxygen gas blowing lance 1 was investigated. In the test, oxygen gas was blown into the hot metal 6 of about 300 tons accommodated in the kneading wheel 5 at a flow rate of 30 Nm ³ / min from the inner tube 2, and 2 to 5 Nm ³ from the gap between the inner tube 2 and the outer tube ^3. Propane gas was blown at a flow rate of / min for desiliconization treatment. Nm ³ indicates the volume converted to the volume in the standard state in the unit m ³ . The inner tube 2 and the outer tube 3 were stainless steel tubes. Table 1 shows the test conditions in this desiliconization treatment.

As the refractory coating layer 4 of the oxygen gas blowing lance 1 shown in FIG. 1, Al ₂ O ₃ —SiO ₂ type castable (Al ₂ O ₃ -20 mass% SiO ₂ ), Al ₂ O ₃ —MgO type castable, Tested. In the Al ₂ O ₃ —MgO-based castable, the MgO content is changed to _3, 5, 10, 20, 30, 40, 50, 70 mass%, and the MgO content affecting the wear rate of the refractory coating layer 4 is changed. The impact was investigated.

Further, as the tip refractory coating layer 4A in the oxygen gas blowing lance 1 shown in FIG. 2, Al ₂ O ₃ -7 mass% MgO castable, and as the trunk refractory coating layer 4B, Al ₂ O ₃ -20 mass% SiO. ₂ Using castable, the boundary between the tip refractory coating layer 4A and the trunk refractory coating layer 4B is the molten metal surface position, the bent portion 7, and the intermediate point between the molten metal surface position and the bent portion 7 (middle) ). The hot metal surface of the hot metal is not the slag surface but the hot metal surface of the hot metal itself. The test results are shown in Table 2.

As shown in Table 2, when the whole is Al ₂ O ₃ -20 mass% SiO ₂ castable (test No. 1), the wear rate per charge is 200 mm (hereinafter referred to as “mm / ch”). However, the wear rate was 15 mm / ch or less in the Al ₂ O ₃ —MgO castable in which 5 to 30% by mass of MgO was blended. However, even in the case of Al ₂ O ₃ —MgO castable, it was found that when MgO was less than 5% by mass, the wear rate was high and the effect of MgO was small. On the other hand, even in the case of Al ₂ O ₃ —MgO-based castable, when MgO exceeds 30% by mass, the Young's modulus of the refractory increases, so that cracking of the refractory coating layer 4 becomes remarkable, and the spalling is performed. It has been found that the improvement of the service life cannot be expected due to the progress of cracking due to.

From these results, Al ₂ O ₃ —MgO-based amorphous refractory containing 5 to 30% by mass of MgO is optimal as the refractory coating layer 4, and oxygen gas can be obtained by using this amorphous refractory. It has been found that the durability of the blowing lance 1 is improved.

The best results were obtained when an Al ₂ O ₃ —MgO amorphous refractory was used on the tip side and an Al ₂ O ₃ —SiO ₂ amorphous refractory was used on the body side. (Test Nos. 10 to 12), and the wear rate was lower and better than when the whole was coated with an Al ₂ O ₃ —MgO amorphous refractory. This is considered to be due to the following reason. Compared to the Al ₂ O ₃ —MgO amorphous refractories in the above-mentioned proper range, Al ₂ O ₃ —SiO ₂ amorphous refractories are basically superior in spalling resistance, It is effective against the added thermal shock. For this reason, it is considered that the durability of the oxygen gas blowing lance 1 is further improved by using the Al ₂ O ₃ —SiO ₂ system refractory as the body portion.

In addition, the inventors have also tested Al ₂ O ₃ —Cr ₂ O ₃ system, Al ₂ O ₃ —ZrO ₂ system, and SiO ₂ —ZrO ₂ system alone or in combination. The improvement effect was not obtained.

The present invention is based on these test results, and a refining oxygen gas blowing lance 1 according to the present invention has a double-pipe structure comprising an inner tube 2 and an outer tube 3, as shown in FIGS. Oxygen gas (and a refining agent if necessary) is blown from the inner pipe 2, hydrocarbon gas is blown from the gap between the inner pipe 2 and the outer pipe 3, and the outer circumference of the outer pipe 3 is MgO. whether the Al ₂ O ₃ -MgO based monolithic refractory containing 5 to 30 mass% is coated, or as shown in FIG. 2, the tip portion is covered with Al ₂ O ₃ -MgO based monolithic refractory The remaining body is covered with an Al ₂ O ₃ —SiO ₂ amorphous refractory.

In the case of the oxygen gas blowing lance 1 shown in FIG. 2, the Al ₂ O ₃ —MgO-based amorphous refractory on the tip side is also used with 5 to 30% by mass of MgO. Further, as the Al ₂ O ₃ —SiO ₂ amorphous refractory, it is effective to contain 10 to 40% by mass of SiO ₂ . From the viewpoint of spalling resistance, it is preferable that the trunk portion refractory coating layer 4B covers at least a portion of the hot metal surface of the hot metal. The tip portion refractory coating layer 4A preferably covers a sufficient range from the viewpoint of resistance to melting, and preferably covers at least the bent portion 7 in the oxygen gas blowing lance 1 having the shape shown in FIG. That is, in the oxygen gas blowing lance 1 of FIG. 2, the boundary between the tip refractory coating layer 4A and the trunk refractory coating layer 4B is preferably located between the bent portion 7 and the molten metal surface position of the hot metal. .

In addition, it is preferable that 4 A of front-end | tip refractory coating layers and the trunk | drum refractory coating layer 4B transfer continuously in a boundary part. This creates a mold around the outer tube 3, in coating the oxygen gas injection lance 1 by pouring castable refractory can be easily realized by changing the refractory material in the middle.

The Al ₂ O ₃ —MgO-based amorphous refractory and the Al ₂ O ₃ —SiO ₂ -based amorphous refractory used in the present invention have no problem in containing impurities of about 7% by mass or less. Further, in any of the embodiment of FIG. 1 and FIG. 2, from the viewpoint of spalling resistance, the content of MgO in Al ₂ O ₃ -MgO based monolithic refractory in is most preferably 5 to 10 wt%. The thickness of the refractory layer is preferably about 25 mm or more.

The refining oxygen gas blowing lance 1 according to the present invention is applicable to any refining as long as it is a refining performed by supplying a refining agent together with oxygen gas or oxygen gas into the molten metal. It is optimal to apply as oxygen gas supply means in hot metal desiliconization. The slag produced by the hot metal desiliconization treatment is mainly composed of SiO ₂ , and used in the present invention as the refractory coating layer 4 or the tip refractory coating layer 4A, Al ₂ O containing 5 to 30% by mass of MgO. _{This is because the 3-} MgO-based amorphous refractory is excellent in resistance to erosion with respect to slag mainly composed of SiO ₂ . Here, the refining agent is a flux of iron oxide, quick lime, limestone, or the like that serves as an oxygen source.

Further, the oxygen gas blowing lance 1 according to the present invention, applications in particular, such as desiliconization process in torpedo cars, large amounts of oxygen-flow (e.g., 10 Nm ³ / min or more, preferably of 15 Nm ³ / min or more) to advance the process by It is suitable for.

  When performing desiliconization treatment of the hot metal 6 using the oxygen gas blowing lance 1 for refining according to the present invention, oxygen gas is blown from the inner tube 2 in the same manner as the above test, and the inner tube 2 and the outer tube 3 The desiliconization process is performed by blowing a hydrocarbon-based gas from the gap between the two, and at that time, other oxygen gas supply means such as oxygen gas addition by a non-immersion type upper blowing lance may be used in combination. Further, in the refining oxygen gas blowing lance 1 shown in FIG. 1 or FIG. 2, the inner tube 2 and the outer tube 3 do not branch up to the tip 1A, but the inner tube 2 and the outer tube 3 branch near the tip. It may be T-shaped or Y-shaped. As an example of the T-shaped oxygen gas blowing lance 1, FIG. 4 shows another aspect of the oxygen gas blowing lance of the present invention. In FIG. 4, reference numeral 1C is the center of the lance opening, and the meanings of the other signs are the same as in FIG. 2, and the usage is the same as that of the lance shown in FIG. It is. In the oxygen gas blowing lance 1 shown in FIG. 4, in order to sufficiently suppress melting damage, the tip refractory coating layer 4A is positioned twice the distance d from the lance opening center 1C to the tip of the lance. It is preferable to coat at least. That is, the boundary between the tip refractory coating layer 4A and the trunk refractory coating layer 4B is preferably located between the position 2d from the lance tip and the molten metal surface position. The same applies to the Y-shaped lance. The refining oxygen gas blowing lance 1 shown in FIGS. 1 and 2 is referred to as an “L-shaped lance” with respect to the T-shaped lance and the Y-time lance.

Further, the inner tube 2 and the outer tube 3 do not need to be stainless steel tubes, and there is no problem even if they are, for example, carbon steel tubes. Further, when the flow rate of the oxygen gas blown from the inner pipe 2 is reduced, an inert gas such as nitrogen gas or Ar gas may be mixed with the oxygen gas, or an oxygen-containing gas such as oxygen-rich air is used as appropriate. May be. What is necessary is just to determine an oxygen concentration suitably from the amount of oxygen required. When the flow rate of the hydrocarbon gas blown from the outer tube 3 is reduced in accordance with the change in the flow rate of the oxygen gas blown from the inner tube 2, an inert gas such as nitrogen gas or Ar gas is mixed with the hydrocarbon gas. May be. As a standard of the amount of the hydrocarbon gas, it is preferable that the amount of the oxygen gas supplied from the inner pipe 2 is about 5 to 20% by volume. As hydrocarbon gas, propane (C ₃ H ₈ ), methane (CH ₄ ), ethane (C ₂ H ₆ ), butane (C ₄ H ₁₀ ), etc. are thermally decomposed at a relatively low temperature and have a large decomposition endotherm. Easy to use in steelmaking process.

By means of the refining oxygen gas blowing lance 1 according to the present invention, oxygen gas is blown into the hot metal from one refining oxygen gas blowing lance 1 over a long period of time without using equipment such as a converter bottom blowing tuyere. It becomes possible. Moreover, it is possible to create a heat margin by blowing oxygen gas. As a result, it can be used as heat for melting iron scrap, contributing to a reduction in the amount of CO ₂ generated during the manufacture of steel materials. Further, since the life of the oxygen gas blowing lance 1 is extended, there are advantages that the frequency of lance replacement work is reduced and that the immersion depth can always be kept large.

  Using the L-shaped oxygen gas blowing lance shown in FIG. 1 and FIG. 2 and the T-shaped oxygen gas blowing lance shown in FIG. 4, the hot metal contained in the kneading wheel is desiliconized (example of the present invention). 1-4). L-shaped lances were used in Invention Examples 1 to 3, and T-shaped lances were used in Invention Example 4. In Invention Examples 1 to 3 using an L-shaped lance, as shown in FIG. 3 described above, an oxygen gas blowing lance is immersed obliquely with respect to the hot metal bath surface, and Example 4 using a T-shaped lance. In this case, an oxygen gas blowing lance was immersed perpendicularly to the hot metal.

The refractory coating layer of the oxygen gas blowing lance was constructed as a single layer of Al ₂ O ₃ -10 mass% MgO castable in the present invention example 1, and in the present invention example 2, from the tip to the hot metal surface of Al ₂ O. _3-7 wt% MgO castables, the above the hot metal bath level and applied by Al ₂ O ₃ -20 wt% SiO ₂ castable, invention sample 3, Al ₂ O ₃ -7 weight% MgO and to the bending portion from the distal end Castable, from the bent portion to the upper end was constructed with Al ₂ O ₃ -20 mass% SiO ₂ castable, and in Example 4 of the present invention, the Al ₂ O ₃ -7 mass% MgO castable, molten iron surface from the tip to the molten metal surface more upwards and applied by Al ₂ O ₃ -20 wt% SiO ₂ castable. In the silicon removal treatment, propane gas was blown from the gap between the inner tube and the outer tube while blowing oxygen gas from the inner tube, and a total of 39 to 46 charges of silicon removal treatment was performed.

For comparison, the Al ₂ O ₃ -50 wt% MgO desiliconization treatment using oxygen gas injection lance that applying a refractory coating layer of a single layer of castable also performed a total of 32 charge (Comparative Example 1). Comparative Example 1 was carried out under the same conditions as in Invention Examples 1 to 4 except that the refractory material of the refractory coating layer was changed. In addition, a total of 33 desiliconization treatments using an oxygen gas blowing lance in which the refractory coating layer was constructed as a single layer of Al ₂ O ₃ -20 mass% SiO ₂ castable were performed (Comparative Example 2). In Comparative Example 2, without using oxygen gas as an oxygen source, iron oxide (iron ore) was blown from the inner pipe using nitrogen gas as a carrier gas, and nitrogen gas was blown from the gap between the inner pipe and the outer pipe. Infused. The amount of oxygen in the iron oxide was adjusted so that 1 kg of iron oxide was equivalent to 0.15 Nm ³ of oxygen gas based on the chemical analysis value, and the acid feeding rate was constant.

  In the inventive examples 1 to 4, the comparative example 1 and the comparative example 2, the life of the oxygen gas blowing lance and the hot metal temperature were comparatively evaluated. Table 3 shows test conditions and test results.

  In Example 1 of the present invention, the average lance life was 6.5 charges per lance (hereinafter referred to as “ch / piece”), but in Comparative Example 1, 2.5 ch / piece, and in Comparative Example 2, It was 4.1 ch / book, and the superiority of the present invention example could be confirmed. Further, in the present invention example 2, it was 7.5 ch / line, and in the present invention example 3 it was 7.7 ch / line, and the lance life was further improved by using the composite coating. In Example 4 of the present invention using a T-shaped lance, the lance life was further improved by providing a composite coating and a T-shape at 10.0 ch / line. Further, by using oxygen gas as an oxygen source, 0.01% by mass of silicon in the hot metal was oxidized and removed in the desiliconization process, and an increase in hot metal temperature of about 3 ° C. was observed. In Comparative Example 2 in which iron oxide was used as the oxygen source, it was confirmed that the sensible heat of the iron oxide used was deprived of heat, and the hot metal temperature did not increase but decreased.

It is a schematic sectional drawing of the oxygen gas blowing lance which concerns on this invention. It is a schematic sectional drawing of another oxygen gas blowing lance which concerns on this invention. It is a figure which shows the condition which desiliconizes the hot metal accommodated in the kneading vehicle using the oxygen gas blowing lance which concerns on this invention. It is a schematic sectional drawing of another oxygen gas blowing lance which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxygen gas blowing lance 2 Inner pipe 3 Outer pipe 4 Refractory coating layer 4A Tip part refractory coating layer 4B Trunk refractory coating layer 5 Chaotic wheel 6 Hot metal 7 Bending part

Claims (2)

An oxygen gas blowing lance for blowing oxygen gas into the molten metal,
It is a double tube structure consisting of an inner tube and an outer tube, oxygen gas is blown from the inner tube, and hydrocarbon gas is blown from the gap between the inner tube and the outer tube,
The outer periphery of the outer tube of the blowing lance tip, Al ₂ O ₃ -MgO based monolithic refractory containing MgO 5 to 30% by weight is coated, the outer periphery of the outer tube of the blowing lance barrel following the tip portion Is coated with an Al ₂ O ₃ —SiO ₂ amorphous refractory containing 10 to 40% by mass of SiO ₂ ,
In the L-shaped lance, the boundary between the coating layer of the Al ₂ O ₃ —MgO-based amorphous refractory and the coating layer of the Al ₂ O ₃ —SiO ₂ -based refractory has a bent portion and the molten metal. In the T-shaped lance and the Y-shaped lance, the distance from the center of the lance opening to the tip of the lance is d. An oxygen gas blowing lance for refining, characterized in that the lance is configured to be located between the hot water surface position of the steel. The smelting oxygen gas blowing lance according to claim 1 is immersed in the hot metal, oxygen gas is blown into the hot metal from the inner pipe of the blowing lance, and hydrocarbon gas is introduced from the gap between the inner pipe and the outer pipe. A method for removing silicon from hot metal, which comprises blowing and removing silicon in the hot metal by oxidation.

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