JP2011208172A - Decarburize-refining method in converter using iron-scrap as iron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decarburize-refining method in a converter, in which when producing molten steel by decarburize-refining molten iron with the converter by using iron-scrap as a part of the iron-source, copper contained in the iron scrap can efficiently be removed.SOLUTION: In the decarburize-refining method in the converter, using the iron-scrap as the iron-source, when the molten steel is produced from the molten iron while performing the decarburize-refining by supplying oxygen gas into the molten iron 2 accommodated in the converter 4, the iron-scraps 10 subjected to a shredder-treatment, and to wind power classification and/or magnetic classification after the shredder-treatment, are continuously or intermittently charged and added into the converter during the decarburize-refining.

Description

  The present invention relates to a converter decarburizing and refining method using iron scrap as an iron source, and more specifically, when melting steel from molten iron using iron scrap as a part of the iron source in a converter. The present invention relates to a method for removing copper contained in scrap.

The iron source used in the steelmaking process of the integrated steelworks is mainly hot metal obtained by reducing iron ore in a blast furnace, but iron scrap generated in the processing process of steel materials, buildings, machinery products and A considerable amount of iron scrap generated with the aging of electrical products is also used. In the production of iron and steel products, the production of hot metal in a blast furnace requires a great deal of energy to reduce and melt iron ore, whereas iron scrap requires only heat of melting. When used, there is an advantage that the amount of energy used for reducing heat of iron ore can be reduced. Therefore, not only effective use of iron scrap generated in large quantities but also promotion of the use of iron scrap is desired from the viewpoint of energy saving and prevention of global warming by reducing CO ₂ .

  By the way, when iron scrap is recycled, a trump element typified by copper accompanying the iron scrap is inevitably mixed into the hot metal and molten steel in the melting process of the iron scrap. Since copper has a low affinity for oxygen in molten iron and its vapor pressure is not so high compared to iron, it is difficult to remove copper from hot metal and molten steel in the normal steelmaking process. Copper is a component that impairs the properties of steel and must be kept below a certain concentration. For this reason, conventionally, it has been difficult to use low-grade iron scrap that may contain copper as an iron source for producing high-grade steel.

However, in view of the recent increase in the amount of iron scrap generated and the demand for increased use of iron scrap for reducing CO ₂ generation, it is necessary to promote recycling even for low-grade iron scrap.

  Accordingly, means for removing copper from molten iron have been studied and several proposals have been made. For example, in Patent Document 1, one or more oxidizing agents of oxygen, carbon dioxide, water vapor, iron oxide, manganese oxide and chromium oxide are introduced into molten iron placed under a high vacuum of 10 torr or less. A method for evaporating and removing copper and tin contained in molten iron by adding and decarburizing molten iron has been proposed. This method is a method of evaporating and removing copper and tin by utilizing a difference in vapor pressure between molten iron and copper and tin in the molten iron.

Patent Document 2 discloses that after adjusting the oxygen content of molten steel containing 0.05% by mass or more of copper and tin to 0.010% by mass or more, the molten steel is maintained in a vacuum atmosphere of 2 torr or less. A method for removing copper and tin therein has been proposed. In this method, an oxide such as Cu ₂ O or SnO having a higher evaporation rate than the metal state is generated on the surface of the molten steel, and the oxide is evaporated in a high vacuum atmosphere to remove copper and tin in the molten iron. It is a method.

  However, all of the above methods are not sufficient for removing copper from molten iron from the viewpoint of more efficiently using a large amount of iron scrap, and are difficult to adapt to industrial scale equipment. Currently.

JP-A-61-149414 JP 7-216435 A

  In recent years, the demand for quality characteristics of steel products has become more severe, and the demand for reducing the concentration of trump elements such as copper in steel has also increased. However, on the other hand, in the steel scrap market, as the amount of iron scrap stockpile increases in Japan, the concentration of trump elements in so-called “scrap waste” is increasing, ensuring the quality of steel products. It is a very difficult situation to do.

  The present invention has been made in view of such circumstances, and the object of the present invention is to use iron scrap as a part of the iron source, demetallize the hot metal in a converter and smelt the molten steel. It is an object of the present invention to provide a converter decarburization refining method that can efficiently remove copper contained in iron scrap.

  In order to solve the above problems, a converter decarburization refining method using iron scrap as an iron source according to the present invention performs decarburization refining by supplying oxygen gas to hot metal accommodated in the converter, and from molten iron to molten steel When melting the steel, the shredder process and the steel scrap that has been subjected to wind sorting and / or magnetic sorting after the shredder process are continuously charged or added to the converter during the decarburization refining. It is characterized by that.

  According to the present invention, at the time of decarburization and refining of hot metal in a converter, the shredder treatment and the iron scrap that has been subjected to wind sorting and / or magnetic sorting after the shredder treatment are continuously or intermittently placed in the furnace. Since it adds and adds, the evaporation removal of the copper mixed in the said iron scrap is accelerated | stimulated, and the raise of the copper concentration in molten steel is suppressed. As a result, not only can iron scrap be used in large quantities, but it can also be used at low cost as an iron source for high-grade steel materials, and its practical significance is extremely great.

It is a schematic sectional drawing which shows one example of the top bottom blowing type converter equipment used when implementing this invention.

  Hereinafter, the present invention will be specifically described. The present inventors have used a means for efficiently removing copper contained in iron scrap when iron scrap is used in combination with hot metal as an iron source, and decarburizing and refining the hot metal in a converter to produce molten steel. I studied and studied.

  In a converter, after decarburization and refining, the empty furnace body is tilted, and iron scrap is charged into the furnace through a scrap shooter. After iron scrap is charged, the hot metal is furnaced through a charging pan. After that, the furnace body is returned to a vertical position, an oxygen blowing lance is inserted into the furnace, oxygen gas is supplied through the oxygen blowing lance (referred to as “oxygen blowing”), and hot metal is removed. We are conducting charcoal refining. The charged iron scrap is melted during decarburization refining by the combustion heat of carbon in the hot metal and oxygen gas from the top blown oxygen lance. At that time, there is a flow due to gas stirring from the bottom of the furnace, but basically, iron scrap has a larger specific gravity than hot metal, so it drifts below the hot metal, and with the progress of oxygen blowing It is believed that the temperature of the iron scrap surface rises and gradually dissolves from the surface of the iron scrap. At this time, the copper accompanying the iron scrap comes into contact with the hot metal from the time when the hot metal is charged into the furnace, so the copper has a melting point lower than that of the hot metal, so the copper is introduced from an early stage after the hot metal is charged. The copper concentration in the molten steel increases.

  Copper in iron scrap may be dissolved in steel. However, in the case of pressed scraps that are used on used automobiles, the copper wire is wound around the surface of the iron scrap or the copper wire is iron scrap. Many are mixed inside. Accordingly, it was confirmed that about 40% of the copper contained in the iron scrap can be removed by shredding the iron scrap collected from the city with a shredder machine and then performing wind sorting and / or magnetic sorting. However, some copper wires still remain mixed in the shredded iron scrap, and even if shredded iron scrap is used, in the case of the conventional decarburization refining method described above, the copper concentration of the molten steel Confirmed to rise.

  Then, after shredding, the means which removes the copper which mixes in the iron scrap (henceforth "shredder waste") collect | recovered by performing wind sorting and / or magnetic sorting was examined. As a result, the shredder scrap is moved to a location where the oxygen gas jet from the top blown oxygen lance collides with the hot metal bath surface during decarburization and refining in the converter (this location is called “fire point”) or near the fire point. As a result, it was found that the hot spot was a high temperature of 1700 ° C. or higher, so that evaporation and removal of copper mixed in the shredder scrap can be expected. Shredder scraps can be charged into the furnace from a scrap shooter, such as normal on-site generated iron scrap (in-house scrap) and iron scrap collected from the city (city scrap), but the size is small. It is also possible to charge into the furnace from an auxiliary raw material charging device comprising a hopper and a chute installed on the converter furnace.

  In accordance with the above findings, a test was conducted in which shredder scraps were continuously or intermittently thrown into the furnace during oxygen blowing. As a result, by adding shredder scraps continuously or intermittently during decarburization refining, the sensible heat of iron scrap is temporally dispersed as compared with the case where it is added all at once before the start of oxygen blowing. Therefore, the hot metal temperature at the initial stage of decarburization and refining does not decrease, the dissolution rate of shredder scraps can be increased, and continuously or intermittently added from above, There are a lot of shredder scraps falling near the fire point due to the oxygen gas supplied from, and high activity copper just before or immediately after melting that was mixed in the shredder scraps was exposed to the high temperature atmosphere of the fire point It was confirmed that it was easily removed by evaporation.

  The present invention, which is based on the above knowledge, supplies oxygen gas to the hot metal accommodated in the converter, performs decarburization refining, and when producing molten steel from the hot metal, the shredder process, and after the shredder process Iron scrap that has been subjected to wind sorting and / or magnetic sorting is added or added to the converter continuously or intermittently during the decarburization refining, and the copper mixed in the iron scrap is removed by evaporation. To do.

  Next, a specific implementation method of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of the top-bottom blowing type converter equipment used in carrying out the present invention.

  As shown in FIG. 1, the converter equipment 1 contains a hot metal 2 inside thereof and a converter main body 4 for performing decarburization refining of the hot metal 2, and is inserted into the converter main body 4. The upper blown oxygen lance 7 for supplying oxygen gas to the inside of the converter main body 4 that can move in the direction and the furnace port of the converter main body 4 are covered, and the gas generated from the converter main body 4 is collected by a dust collector ( A hood 8 for introduction into a not-shown), a hopper 12 for containing quicklime 9 as a koji making agent, a hopper 13 for containing shredder waste 10, a hopper 12 and a hopper 13, Addition device 16 for conveying quick lime 9 cut out from the hopper 12 and shredder scrap 10 cut out from the hopper 13 and adding it to the inside of the converter main body 4, connected to the addition device 16, and added through the hood 8 By device 16 It includes a chute 17 for introducing the quicklime 9 and shredder scrap 10 which is added Te inside the Tenro body 4. The hopper 12 is provided with a cutting device 14 for adjusting the amount of quicklime 9 added, and the hopper 13 is provided with a cutting device 15 for adjusting the amount of shredder waste 10 added. Further, the converter main body 4 is provided with a plurality of bottom blowing tuyere 6 for blowing a stirring gas such as nitrogen gas or Ar gas at the bottom thereof, and obtained by decarburization refining at the upper part of the side wall. A steel outlet 5 is provided for discharging the molten steel. Furthermore, the converter equipment 1 is provided with a scrap shooter 11 for supplying other iron scraps or alloy auxiliary materials including the shredder scrap 10 into the converter main body 4. The scrap shooter 11 is lifted and moved by a crane and is inclined to supply iron scrap or the like to the inside of the converter main body 4, but the crane is omitted in FIG. 1.

  First, the converter main body 4 is inclined to the side where the scrap shooter 11 is installed, and large-sized iron scrap such as crop scrap of continuous cast slab is charged into the converter main body 4 via the scrap shooter 11. . Since the chemical components of the in-house waste generated in the steelworks such as crop waste are known, the trump elements such as copper are not mixed. In addition, when there is much compounding quantity of the shredder waste 10 and iron scraps other than shredder waste cannot be mix | blended, charging of iron scraps other than shredder waste, such as crop waste, is stopped. In addition, the present invention is basically based on charging the shredder scrap 10 into the converter main body 4 during decarburization refining, but a part of the shredder scrap 10 to be blended is passed through the scrap shooter 11 before decarburization refining. It is also possible to charge the converter main body 4. However, since the pick-up amount of the copper concentration of the hot metal 2 is determined by the copper concentration and the blending amount of the shredder scrap 10, the amount of the shredder scrap 10 to be charged before decarburization refining takes into account the pick-up amount of the copper concentration. Must be set.

  After charging iron scrap such as crop scrap into the converter main body 4, the hot metal 2 is put into the converter main body 4 through the charging pan (not shown) while the converter main body 4 is inclined. After charging and the molten iron 2 is charged, the converter main body 4 is erected.

  Next, oxygen gas is directed from the top blowing oxygen lance 7 toward the bath surface of the hot metal 2 while blowing a non-oxidizing gas such as nitrogen gas or a rare gas such as Ar gas from the bottom blowing tuyere 6 into the hot metal 2 as a stirring gas. To start decarburization refining. Decarburization and refining progresses when oxygen gas reacts with the carbon in the hot metal. Before or after the supply of oxygen gas from the top blown oxygen lance 7, quick lime 9 accommodated in the hopper 12 is charged into the converter main body 4 via the chute 17. The quicklime 9 hatches to form the slag 3.

  During this decarburization refining, the shredder scrap 10 accommodated in the hopper 13 is continuously or intermittently charged into the converter main body 4 via the chute 17. A part of the shredder scrap 10 that has been thrown in falls to the fire point and the vicinity of the fire point by the oxygen gas supplied from the top blowing oxygen lance 7, and the copper mixed in the shredder scrap 10 is exposed to a high-temperature atmosphere at the fire point. As the temperature rises, the copper with high activity evaporates and removes immediately before or immediately after the melting at which the temperature has risen. When a predetermined amount of shredder scrap 10 is charged and a predetermined amount of oxygen gas is supplied, the supply of oxygen gas is stopped and the decarburization refining is completed. The obtained molten steel is put into a ladle or the like through a tap outlet 5.

  As described above, according to the present invention, during the decarburization and refining of the hot metal 2 in the converter, the shredder treatment and the iron scrap subjected to the wind sorting and / or the magnetic sorting after the shredder treatment are continuously or intermittently performed. Thus, since it is added to the furnace, the evaporation removal of copper mixed in the iron scrap is promoted, and the increase of the copper concentration in the molten steel is suppressed.

  After the hot metal discharged from the blast furnace is received in the hot metal ladle, the hot metal in the hot metal ladle is desulfurized using a mechanical stirrer, and further, quick lime and oxygen gas are added and pre-dephosphorized. 1, molten iron was charged into a converter having a capacity of 300 tons and decarburization refining was performed in the converter using iron scrap as an iron source. As the iron scrap, shredder scraps subjected to magnetic sorting after the shredder treatment were used.

  The method of charging shredder scrap into the converter is as follows: (1) Start decarburization and refining by introducing hot metal into the converter, and enter the furnace from the hopper installed above the converter during decarburization and refining. A method of continuously charging shredder waste (example of the present invention) and (2) About half of the amount of shredder waste to be used is charged into the converter using a scrap shooter and then into the converter. A method (invention example) in which hot metal is charged, and the remaining shredder scraps of about half the amount during decarburization refining are continuously charged into the furnace from a hopper installed above the converter, (3) ) After the shredder scrap is charged into the converter using a scrap shooter, it is carried out in three ways: the normal method of charging hot metal into the converter (comparative example). The copper concentration of the molten steel after refining was compared.

  The balance of copper balance in the converter is calculated by calculating the copper concentration input to the converter from the analysis value of the copper concentration of the shredder scrap (0.22% by mass) and the analysis value of the copper concentration of hot metal. The output copper was the analysis value of the copper concentration of the molten steel after the end of oxygen blowing.

Decarburization and refining in the converter is performed by adding quick lime as a medium solvent from the furnace while blowing oxygen gas through the top blown oxygen lance, and as a stirring gas from the bottom blowing tuyere embedded in the furnace bottom. Nitrogen gas (Ar gas at the end) was blown in. Specifically, while adding oxygen gas from the top blowing oxygen lance to the hot metal at a supply rate of 3.0 Nm ³ / (min · t), nitrogen gas is added from the bottom blowing tuyere to 0.1 Nm ³ / (min · t ) Was blown at a feed rate (Ar gas for the final 2 minutes) and oxygen blowing was performed for 14 minutes. The amount of quicklime added was 8 kg / t, the hot metal temperature before decarburization refining was about 1300 ° C, and the molten steel temperature after refining was about 1650 ° C. Table 1 shows operating conditions and operating results. In addition, the copper removal rate shown in Table 1 is a percentage with respect to the copper concentration before decarburization refining of the difference of the copper concentration before and after decarburization refining.

  As is clear from Table 1, the comparative example is hardly decoppered, whereas in the present invention example in which the shredder scrap is introduced during the decarburization refining, it is decoppered and the target after the oxygen blowing is completed. A molten steel copper concentration of 0.05% by mass or less was obtained. It was also confirmed that a higher copper removal rate could be obtained by increasing the ratio of shredder scrap introduced during decarburization refining.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Hot metal 3 Slag 4 Converter body 5 Steel outlet 6 Bottom blow tuyere 7 Top blown oxygen lance 8 Hood 9 Quicklime 10 Shredder scrap 11 Scrap shooter 12 Hopper 13 Cutting device 15 Cutting device 16 Addition Device 17 Chute

Claims (1)

  Iron that has been subjected to decarburization and refining by supplying oxygen gas to the hot metal accommodated in the converter, and when the molten steel is melted from the hot metal, the shredder treatment and the wind sorting and / or magnetic force sorting after the shredder treatment A converter decarburization refining method using iron scrap as an iron source, wherein scrap is continuously charged or added to the converter continuously or intermittently during the decarburization refining.

Images