JP2006138003A - Method for treating molten iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating molten iron having good thermal efficiency with which melting quantity of iron scraps can be made more than that of the conventional method, when molten steel is produced by applying each molten iron pre-treatment of desiliconizing treatment, dephosphorizing treatment and desulfurizing treatment to the molten iron tapped off from a blast furnace. <P>SOLUTION: The iron scraps 7 are beforehand charged into a molten iron carrying vessel 1 of empty after discharging the molten iron, and the molten iron 5 tapped off from the blast furnace, is received with this molten iron carrying vessel, and after receiving the molten iron, only oxygen gas or oxygen-containing gas is supplied, and silicon concentration in the molten steel at the completing time of the desiliconizing treatment, is made to be in the range of ≥0.10 mass% to apply the desiliconizing treatment. In this case, it is desirable to make slag generated by the desiliconizing treatment flow-out from the molten iron carrying vessel by tilting the molten iron carrying vessel during desiliconizing treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermally efficient hot metal treatment method, and more specifically, hot metal capable of increasing the amount of iron scrap melted and obtaining more molten steel even with the same composition and temperature. It is related with the processing method.

  In recent years, hot metal discharged from a blast furnace is often subjected to desiliconization treatment, desulfurization treatment and dephosphorization treatment called hot metal pretreatment before being refined in a converter. Initially, these hot metal pretreatments were carried out for steels that require low sulfidation and low phosphatization from the standpoint of steel quality. Recently, however, productivity improvement in converters, and Mn ore in converters have been improved. As a means of reducing the total cost of the steelmaking process in the steelmaking integrated steelworks, the hot metal pretreatment has been applied to almost all the hot metal that is produced due to the cost reduction effect by reduction. Here, the desiliconization process is a process performed prior to the dephosphorization process in order to efficiently perform the dephosphorization process because the dephosphorization reaction is inhibited when the silicon content of the hot metal is high.

  This desiliconization treatment is performed by blowing or blowing a solid oxygen source such as iron ore or mill scale or a gaseous oxygen source such as oxygen gas or oxygen-containing gas into the hot metal flowing in the blast furnace casting bed or the hot metal transfer container, Silicon in the hot metal is oxidized by oxygen in these oxygen sources, and the generated oxide is removed as slag. When a solid oxygen source is used, the sensible heat to raise the temperature of the solid oxygen source itself and the heat of decomposition of iron oxide, which is the solid oxygen source, are necessary. On the other hand, when a gaseous oxygen source is used, an exothermic reaction occurs due to the oxidation heat of silicon.

  From the viewpoint of effectively utilizing the heat of reaction caused by the desiliconization treatment, Patent Documents 1 and 2 disclose a method in which oxygen gas is positively used as an oxygen source used for the desiliconization treatment. Patent Document 1 proposes a hot metal treatment method in which converter slag is added to the hot metal flowing down the blast furnace casting floor and oxygen gas is blown at the same time to perform desiliconization, and then dephosphorization and desulfurization are performed. In Reference 2, iron scrap is added to the hot metal discharged from the blast furnace, then desiliconization is performed using oxygen gas, slag generated by the desiliconization is removed, and then dephosphorization is performed. Has proposed.

  In Patent Document 3, Patent Document 4 and Patent Document 5, the ratio of the oxygen gas used as an oxygen source in the desiliconization treatment and the addition time of the solid oxygen source and the addition timing are adjusted to a predetermined range, and the desiliconization is efficiently performed. A desiliconization treatment method in which the reaction is advanced is disclosed. In particular, in Patent Document 5, in the desiliconization treatment performed in a ladle-type hot metal transport container, the silicon concentration in the hot metal is 0.10% by mass or less for the purpose of suppressing the decarburization reaction of hot metal and suppressing the formation of slag. In this region, a silicon removal method is proposed in which the supply rate of the oxygen source is reduced and only oxygen gas is used as the oxygen source.

On the other hand, as a method for melting a metal such as iron scrap in the hot metal pretreatment process, for example, Patent Document 6 discloses a metal recovered from slag generated by a hot metal pretreatment as a desiliconized metal or a desulfurized metal. And the dephosphorized ingots are separated into three types, and one of the three types of ingots is placed in an empty hot metal transfer container after the hot metal is charged into the converter, and the hot metal transfer container A method is disclosed in which the hot metal discharged from the blast furnace is received to melt the metal, and then the hot metal is desulfurized and dephosphorized.
Japanese Patent Publication No.58-27322 Japanese Patent Laid-Open No. 5-148525 Japanese Patent Publication No.57-54524 JP 58-27916 A JP 2001-316711 A JP-A-8-193210

By the way, suppression of CO ₂ gas emission from the iron and steel industry has been screamed, and a thermally highly efficient technique is also required in the hot metal treatment process. The use of iron scrap in the hot metal treatment process does not require reduction heat reduction compared to the case of producing hot metal from iron ore, and the expansion of the use of iron scrap is extremely advantageous thermally. However, when melting iron scrap with hot metal that is lower than the melting temperature of iron scrap, the melting rate of iron scrap is slow, and in order to expand the use of iron scrap while maintaining the same productivity as before It is necessary to increase the thermal margin in the hot metal treatment process, for example, by forcibly increasing the temperature of the hot metal, or by maintaining a high concentration of components that serve as heat sources such as carbon and silicon in the hot metal.

  When the above prior art is verified from this viewpoint, each of the above prior arts has the following problems. That is, in patent document 1, converter slag and oxygen gas are used together as an oxygen source, and it is disadvantageous to use converter slag (solid oxygen source) as an oxygen source from a thermal viewpoint. In addition, oxygen gas is used in the desiliconization treatment in the blast furnace casting floor, and there is a problem that wear of refractories such as hot metal and tilting iron is promoted. Patent Document 2 does not disclose a specific method related to the addition of iron scrap or a desiliconization treatment method, and the conditions for performing a thermally highly efficient desiliconization treatment are unclear. Moreover, since iron scrap is added to the hot metal after brewing, the preheating effect of the iron scrap due to the heat of the hot metal transfer container is not expected, and it cannot be said that the thermal efficiency is high.

  In Patent Document 3, Patent Document 4, and Patent Document 5, an oxygen gas and a solid oxygen source such as iron oxide are used in combination as an oxygen source to optimize the ratio or addition timing of both, as described above. In order to ensure a thermal margin, a gaseous oxygen source such as oxygen gas is more advantageous than a solid oxygen source, and there is a problem in terms of securing a thermal margin. Moreover, in order to improve the thermal efficiency from hot metal preliminary treatment to converter refining, it is necessary to suppress the decarburization reaction in the desiliconization treatment, but Patent Documents 3 to 5 do not consider this point.

Furthermore, the slag produced by the desiliconization treatment is mainly composed of SiO ₂ and must be eliminated because it hinders the reaction rate of the dephosphorization treatment and desulfurization treatment in the subsequent steps. If this waste disposal process is prolonged, it will bring about a decrease in the hot metal temperature and the like, and a technique for waste removal quickly and efficiently is desired. However, in Patent Documents 1 to 5, conventional methods such as a dragger scraping method are used. It takes a long time to evacuate and is not highly efficient.

  In Patent Document 6, there is a problem that it is necessary to separate and store the bullion generated in the hot metal preliminary treatment process, and it is costly to place and store. In addition, slag is inevitably attached to the bullion generated in the hot metal pretreatment process, and there is a pickup of phosphorus and sulfur from the slag, so it is necessary to change the pretreatment method according to the bullion used. In addition, there is a problem that complicated work is forced, and there is also a problem that a load of slag removal increases due to an increase in the amount of slag to be generated.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to apply hot metal pretreatments such as desiliconization treatment, dephosphorization treatment, and desulfurization treatment to the hot metal discharged from the blast furnace, and to convert the hot metal to the hot metal. When melting molten steel by decarburizing and refining in a furnace, it is possible to use iron scrap generated with any history, and it is possible to increase the melting amount of iron scrap compared to the conventional one It is to provide a thermally efficient hot metal treatment method.

  The inventors of the present invention have conducted intensive studies and studies to solve the above problems. The following describes the results of research and examination.

  In a series of hot metal processing steps including receiving, desiliconization, dephosphorization, and desulfurization, desiliconization is first performed after receiving. If the added iron scrap remains undissolved after the desiliconization treatment, the dephosphorization treatment or desulfurization treatment performed after the desiliconization treatment is sufficiently performed, for example, due to the high phosphorus concentration or sulfur concentration of the iron scrap. There is a possibility that it will not be performed. Therefore, it was found that it was necessary to melt the iron scrap by the end of the desiliconization process. In addition, after iron is received in the hot metal transport container, iron scrap is charged into the hot metal in the hot metal transport container, so that the heat of the hot metal transport container cannot be used effectively. It was decided that the empty hot metal transfer container after discharging into a container or a converter was charged in advance before receiving.

  Based on the results of this study, an iron scrap was placed in the hot metal transfer container. In the test, a 300-ton capacity topped car was used as the hot metal transfer container, and 6 tons of iron scrap was charged into the topped car before receiving from the blast furnace, and after receiving, the hot metal contained in the topped car was injected via an injection lance. Then, desiliconization treatment was performed by blowing oxygen gas. The injection lance used was a lance having a double pipe structure, in which oxygen gas was blown from the inner pipe and nitrogen gas for lance cooling was blown from the outer pipe. Nitrogen gas also functions as a stirring gas. Table 1 shows the test conditions and the average value of 10 charge test results.

  The silicon concentration in the hot metal decreased from 0.25% by mass to 0.16% by mass by the desiliconization treatment. After the silicon removal treatment, there was no unmelted iron scrap added, and the hot metal temperature was almost the same before and after the silicon removal treatment. From the heat balance calculation based on these results, it has been found that it is thermally advantageous by 20 to 30% as compared with the case of melting iron scrap in a conventional converter. It was also confirmed that the refractory life of the topped car was not adversely affected.

  Moreover, the iron scrap previously charged into the topped car was preheated to 700-800 degreeC. The topped car has a small opening area and is superior in heat retention as a hot metal transfer container compared to ladle-type hot metal ladle etc., but heat radiation to the outside is mainly performed by the iron skin of the topped car body, The amount of heat release is determined by the temperature of the refractory that contacts the iron skin. Therefore, when iron scrap is put in place, the iron scrap is preheated by the refractory lining the topped car, so that the temperature of the refractory lining the topped car is lowered and heat radiation to the outside of the container is reduced. This is also one of the reasons why the thermal efficiency is better than the converter.

  A test was also performed in which the oxygen gas flow rate was not changed, the oxygen gas blowing time was changed to 5 to 20 minutes, and the silicon concentration in the hot metal at the end of the desiliconization process was changed. The result of investigating the amount of decarburization of the hot metal at that time is shown in FIG. Here, the decarburization amount is a value obtained by subtracting the carbon concentration in the hot metal after the desiliconization treatment from the carbon concentration in the hot metal before the desiliconization treatment. As shown in FIG. 1, it was found that the decarburization reaction of the hot metal becomes remarkable when the desiliconization process is performed until the silicon concentration in the hot metal after the desiliconization process becomes less than 0.10% by mass. The progress of the hot metal decarburization reaction is disadvantageous because it leads to a heat loss outside the system due to a rise in exhaust gas temperature in addition to a decrease in sensible heat of the hot metal. Therefore, in the present invention, the silicon removal treatment is terminated when the silicon concentration in the hot metal is 0.10 mass or more.

Slag generated in the desiliconization process (referred to as “desiliconization slag”) is mainly composed of SiO ₂ , and it is necessary not to bring it into the dephosphorization process and desulfurization process in the subsequent steps. Silica removal slag is highly viscous, and it takes a long time to remove it with a dragger. Therefore, in the present invention, the topped car was tilted by 5 ° to 10 ° during the desiliconization process to try to cause the slag to flow out. As a result, it was confirmed that 70% by mass or more of the generated slag was discharged. Moreover, it turned out that the hot metal mass mixed in the slag which flows out is 5 mass% or less with respect to the mass of slag.

  The present invention has been made on the basis of the above examination results. In the hot metal processing method according to the first invention, iron scrap is placed in an empty hot metal transfer container after the hot metal is discharged, and the hot metal transfer container After receiving the hot metal from the blast furnace, supply only the oxygen gas or oxygen-containing gas as the oxygen source to the hot metal in the hot metal transport container, and the silicon concentration in the hot metal at the end of the desiliconization process The desiliconization treatment is performed within the range of 0.10% by mass or more.

  The hot metal processing method according to the second invention is characterized in that, in the first invention, the hot metal transport container is tilted during the desiliconization process, and the slag generated by the desiliconization process is caused to flow out of the hot metal transport container. To do.

  The hot metal processing method according to a third aspect of the present invention is characterized in that, in the first or second aspect, the hot metal transfer container is a topped car.

According to the present invention, not only the sensible heat of hot metal but also the heat retained in the hot metal transfer container and the heat of oxidation reaction by the gaseous oxygen source of silicon contained in the hot metal are used to melt iron scrap. It is possible to dissolve iron scrap quickly and efficiently. As a result, commercialization of iron scrap is promoted, and even when hot metal having the same composition and the same temperature is used, high crude steel productivity can be ensured as compared with the prior art. Further, since the desiliconization process is performed by tilting the hot metal transfer container, the slag mainly composed of SiO ₂ generated by the desiliconization process can be efficiently discharged, and the dephosphorization process and the desulfurization process are the subsequent processes of the desiliconization process. In processing, it becomes possible to reduce the usage-amount of quicklime as a slagging agent, and can reduce the amount of slag generation.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. As a hot metal transport container for receiving the hot metal discharged from the blast furnace and transporting the received hot metal, a topped car, a ladle type hot metal ladle or the like is usually used. Among these, the topped car has a smaller opening (referred to as a “furnace port”) area with respect to the toped car body and is thermally advantageous compared to hot metal ladle, etc. Therefore, here, the topped car was used as a hot metal transport container. This will be explained with an example. FIG. 2 is a schematic cross-sectional view showing a state in which the desiliconization process is performed on the hot metal contained in the topped car.

  Before the hot metal 5 discharged from a blast furnace (not shown) is received by the topped car 1, the iron scrap 7 is placed inside the topped car body 2 constituting the topped car 1. From the viewpoint of efficiently transferring the heat of the refractory lining of the topped car body 2 to the iron scrap 7, the hot metal 5 received last time is discharged to other processing containers and holding containers. Although it is preferable to set it immediately after it becomes empty, it may be just before receiving the hot metal 5. The amount of iron scrap 7 charged into the topped car 1 is 10% by mass with respect to the total mass of the mass of the hot metal 5 to be received and the mass of the iron scrap 7 to be added in order not to reduce the temperature of the hot metal 5 excessively. Hereinafter, it is more preferable that the content be 5% by mass or less. In this case, iron scrap 7 of any composition can be used, and any size of iron scrap can be used as long as it can be charged from the furnace port 3 installed in the topped car body 2. 7 can also be used.

  After the iron scrap 7 is charged, the topped car 1 is placed at a predetermined position directly below the blast furnace casting floor, and the hot metal 5 discharged from the blast furnace is received. Part of the iron scrap 7 is melted by the sensible heat of the hot metal 5 received. When a predetermined amount of hot metal 5 is received, the topped car 1 is transported to a desiliconization treatment site where an injection lance 4 is installed.

  In the present invention, the desiliconization process is performed using only a gaseous oxygen source as an oxygen source. The gaseous oxygen source refers to both oxygen gas and oxygen-containing gas such as air or oxygen-enriched air. Here, the oxygen gas is pure oxygen in the industry, and includes a gas containing 5% by volume or less of impurities such as nitrogen gas. In the present invention, either oxygen gas or oxygen-containing gas may be used. In particular, when a gaseous oxygen source is blown into the hot metal 5 and supplied, for example, nitrogen gas in the oxygen-containing gas functions as a stirring gas, so there is no significant difference between the oxygen-containing gas and the oxygen gas. May be used. However, when supplying by blowing up toward the surface of the hot metal 5, if an oxygen-containing gas such as air is used, the reaction time is generally longer than that in the case of using oxygen gas. Therefore, it is preferable to use oxygen gas rather than oxygen-containing gas because the heat dissipation amount is increased. Solid oxygen sources mainly composed of iron oxide such as iron ore and mill scale require sensible heat to raise the temperature of the solid oxygen source itself and heat of decomposition of iron oxide, which is a solid oxygen source, and Since it is disadvantageous, it is not used in the present invention.

As described above, it is preferable to stir the hot metal 5 in order to accelerate the desiliconization process and promote the dissolution of the iron scrap 7, and therefore, in this embodiment, as shown in FIG. Oxygen gas is blown into the hot metal 5 through an injection lance 4 inserted into the topped car body 2 from the furnace port 3 and supplied. The injection lance 4 shown in FIG. 2 has a double tube structure (not shown) of an inner tube and an outer tube, in which oxygen gas is blown from the inner tube, and lance cooling of nitrogen gas, propane gas, Ar gas, etc. from the outer tube. Desiliconize while blowing gas. The lance cooling gas also functions as a stirring gas. Oxygen in the oxygen gas reacts with silicon in the hot metal to form SiO ₂ and the desiliconization process proceeds. Slag produced by desiliconization treatment is mainly formed of a SiO _2, in order to adjust the slag basicity to (CaO / SiO _2), containing CaO such as lime during desiliconization pretreatment or treatment You may add a faux-making agent.

  The injection lance 4 described above has a double-pipe structure. However, the injection lance 4 may be a single-pipe lance, and an oxygen-containing gas such as a mixed gas of oxygen gas and Ar gas or air may be blown into the injection lance 4. Gases other than the blown oxygen gas function as a stirring gas and a lance cooling gas. Further, two injection lances may be used to efficiently blow in the longitudinal direction of the topped car 1. Further, it may be supplied by spraying on the surface of the hot metal 5 from an upper spray lance or the like without blowing it into the hot metal 5.

  As the desiliconization process progresses, the silicon concentration of the hot metal 5 decreases. In the present invention, in order to suppress the decarburization reaction during the desiliconization process, that is, from the viewpoint of increasing the heat margin in the converter decarburization refining in the subsequent step, the silicon concentration of the hot metal 5 is 0.10% by mass or more. The silicon removal process ends. However, if the desiliconization process is terminated in a state where the silicon concentration of the hot metal 5 is too high, not only the melting of the iron scrap 7 does not proceed, but also the purpose of the desiliconization process itself is not achieved. It is preferable to carry out desiliconization treatment until That is, it is preferable to finish the desiliconization process when the silicon concentration of the hot metal 5 is 0.10 to 0.17 mass%.

The slag produced by the desiliconization treatment is mainly composed of SiO ₂ and inhibits the respective reactions in the dephosphorization treatment and the desulfurization treatment in the next step. Therefore, it is necessary to remove this slag from the hot metal 5 before the dephosphorization process and the desulfurization process in the next step. Conventionally, the slag in the container has been removed by a dragger or the like, but it is necessary to provide a separate draining time, which causes a long processing time for the hot metal processing. In other words, the heat dissipation time from the hot metal 5 is increased, which is not preferable from the viewpoint of thermal efficiency.

  Therefore, in the present invention, in order to shorten the evacuation time, as shown in FIG. 3, the topped car body 2 is inclined with respect to the vertical line during the desiliconization process, and the generated slag 6 is removed from the furnace port 3 to the pit 8. Spill into. FIG. 3 is a schematic view in which the topped car body 2 is tilted and the slag 6 flows out during the desiliconization process. The inclination angle θ with respect to the vertical line depends on the mass of the hot metal 5 accommodated in the topped car body 2, but about 5 ° to 10 ° is sufficient in a normal case. The point is that only the slag 6 flows out and the molten iron 5 does not flow out. Of course, the slag 6 cannot be completely discharged only by tilting the topped car body 2. Therefore, the slag 6 is separately removed by a dragger or the like after the desiliconization process. The slag 6 discharged to the pit 8 is disposed of by an appropriate processing facility such as an excavator 9. By tilting the topped car main body 2 and causing the slag 6 to flow out, even if a bullion to which the slag is inevitably attached is used, the load of removal is not increased.

  When the desiliconization process is completed, the hot metal 5 is subjected to the dephosphorization process and desulfurization process of the next step, and then charged into a converter (not shown) and subjected to decarburization refining with oxygen gas to obtain molten steel. . The dephosphorization treatment and the desulfurization treatment may be carried out either in the topped car 1 that has received the hot metal from the blast furnace, or after being transferred from the topped car 1 to another transport container or processing container. It does not matter which order comes first. However, after the dephosphorization treatment and the desulfurization treatment are completed, it is necessary to remove the generated slag with a dragger or the like. The dephosphorization treatment and the desulfurization treatment method do not need to use a special method, and may be performed by a publicly known and commonly used method.

  As described above, according to the present invention, the hot metal 5 discharged from the blast furnace is received by the hot metal transfer container such as the topped car 1 or the hot metal ladle, and the received hot metal 5 is subjected to desiliconization treatment and dephosphorization. In order to receive the hot metal 5 discharged from the blast furnace and transport the received hot metal 5 in a series of processes in which the hot metal is decarburized and refined by a converter and the molten steel is melted in a series of processes. Before receiving the hot metal 5 from the blast furnace, the iron scrap 7 is put in the hot metal transport container, and the iron scrap 7 placed in the hot metal transport container is subjected to heat of the hot metal transport container, sensible heat of the hot metal 5 received, and Since the iron scrap 7 is melted using the oxidation heat of silicon in the silicon removal treatment performed in the received hot metal transport container, the iron scrap 7 can be melted quickly and efficiently.

  Generally, iron scrap is often added at the time of decarburization and refining in the converter because of the large amount of heat generated during refining. However, if the amount of iron scrap added increases, the iron scrap charging time increases and iron scrap melting This leads to an increase in time, and productivity decreases even in converter decarburization refining. In addition, from the viewpoint of suppressing the wear of the converter lining refractories when charging iron scrap, the shape of the iron scrap to be used may be limited, and in some cases the amount of iron scrap charged cannot be increased. . In the present invention, the amount of iron scrap used in converter decarburization refining is maintained at a conventional level, and by adding iron scrap in the hot metal treatment process, it is possible to use iron scrap that exceeds the conventional level in the total amount. . In other words, even when hot metal having the same composition and the same temperature is used, it is possible to produce more molten steel than in the past.

  Examples of the present invention will be described below. The hot metal discharged from the blast furnace is received by a topped car, and the hot metal contained in the topped car is first subjected to desiliconization treatment, then dephosphorized, and then the hot metal is transferred from the topped car to the charging pan. The present invention was carried out in the process of performing desulfurization treatment in the ladle, charging the molten iron into a converter, performing decarburization refining, and melting molten steel (referred to as “example of the present invention”). The topped car used in the example of the present invention has a capacity of 300 tons and has the ability to receive hot metal equivalent to one charge of converter decarburization refining.

  The inventive example was carried out as follows. That is, 6 tons of iron scrap was charged into the empty topped car after the hot metal was transferred from the topped car to the charging pan, and 300 tons of hot metal discharged from the blast furnace was received with this topped car. After receiving, as in the method shown in FIGS. 2 and 3, the slag generated by injecting oxygen gas and nitrogen gas from the injection lance having a double-pipe structure and tilting the topped car body during processing is generated. Desiliconization treatment was carried out while allowing it to flow out. After desiliconization treatment, exhaust with a dragger, and after exhaustion, oxygen gas is blown into the hot metal, and iron ore powder as a solid oxygen source and quick lime powder as a dephosphorizing agent are blown into the hot metal to perform dephosphorization treatment. Carried out. After the dephosphorization treatment, the hot metal was transferred from the topped car to the charging pan, and was discharged with a dragger in the charging pan, and then desulfurization processing was performed by a mechanical stirring method using a desulfurizing agent mainly composed of quicklime. After the desulfurization treatment, the generated slag was discharged, the hot metal was charged into the converter, and decarburization refining was performed. In the converter, 15 tons of iron scrap was charged and decarburized and refined.

  For comparison, when the hot metal was processed by a conventional method (referred to as “conventional example”), the same desiliconization treatment as in the present invention example was performed, but the iron scrap was not placed in the topped car. The case (denoted as “Comparative Example”) was also carried out. FIG. 4 shows process flows of the present invention example, the conventional example, and the comparative example.

  In the conventional example, the steel is received with a topped car where iron scrap is not placed, and the received hot metal is dephosphorized with a toped car without desiliconization, and the dephosphorized hot metal is transferred to a charging pan and desulfurized. Then, 15 tons of iron scrap was charged in the converter and decarburization refining of the hot metal was performed. Also, in the comparative example, it was received by a topped car where iron scrap was not placed, and the received hot metal was subjected to desiliconization treatment, further subjected to dephosphorization treatment, and this hot metal was transferred to a charging pan and subjected to desulfurization treatment. After that, 21 tons of iron scrap was charged in the converter and decarburization of the hot metal was performed. In the inventive example and the comparative example, the total amount of iron scrap charged was matched. The dephosphorization treatment, desulfurization treatment, and converter decarburization refining in the conventional example and the comparative example were carried out in the same manner as in the present invention example.

  Then, in the present invention example, the conventional example, and the comparative example, the molten steel components after the converter decarburization refining, the obtained molten steel amount, the total unit of quick lime from the hot metal treatment to the converter decarburization refining are investigated and compared. did. Table 2 shows the operation conditions and operation results in comparison with the present invention example, the conventional example, and the comparative example.

  From the survey results, the following was found. That is, in the example of the present invention, compared with the conventional example, the desiliconization process using oxygen gas was performed, and the preheating effect by placing the iron scrap in the topped car, the iron scrap ratio was 2.5%. Only a minute thermal advantage was obtained. In addition, for the comparative example, a thermal advantage of only 1.4% in terms of the iron scrap ratio is obtained due to the preheating effect by placing the iron scrap in the topped car and the iron yield difference in the topped car and the converter. It was. Here, temperature evaluation was performed based on the molten steel mass and converter end point temperature conversion (assuming that an iron scrap ratio of 1% corresponds to a temperature of 17 ° C.). As described above, in the present invention example, it was confirmed that the condition is thermally advantageous as compared with the conventional example and the comparative example, and more molten steel can be produced from the hot metal having the same composition and the same temperature.

  In addition, by removing the slag by tilting the topped car body during the desiliconization process, the desiliconization slag can be removed in a short time. As a result, it was possible to reduce the basic unit of quick lime by 4 to 5 kg / t in the dephosphorization processing step as a subsequent step.

It is a figure which shows the decarburization amount of hot metal when the silicon concentration in hot metal at the time of completion | finish of a desiliconization process is changed. It is a schematic sectional drawing which shows a mode that the desiliconization process is implemented with respect to the hot metal accommodated in the topped car. It is the schematic which tilts a topped car during a desiliconization process and flows out slag. It is a figure which shows the process flow of the example of this invention, a prior art example, and a comparative example.

Explanation of symbols

1 Topped Car 2 Topped Car Body 3 Furnace 4 Injection Lance 5 Hot Metal 6 Slag 7 Iron Scrap 8 Pit 9 Excavator θ Inclination Angle

Claims (3)

  Iron scrap is placed in an empty hot metal transfer container after discharging the hot metal, and the hot metal discharged from the blast furnace is received in the hot metal transfer container. After receiving, the hot metal in the hot metal transfer container is supplied with oxygen as an oxygen source. A method for treating hot metal, wherein only the gas or oxygen-containing gas is supplied to carry out the desiliconization treatment so that the silicon concentration in the hot metal at the end of the desiliconization treatment is within a range of 0.10% by mass or more.   2. The hot metal processing method according to claim 1, wherein the hot metal transport container is tilted during the desiliconization process, and the slag generated by the desiliconization process is caused to flow out of the hot metal transport container.   The hot metal processing container according to claim 1, wherein the hot metal transport container is a topped car.

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