JP5326591B2 - Hot metal manufacturing method using steel scrap as iron source - Google Patents

Description

  The present invention relates to a method for producing hot metal for high-grade steel using steel scrap (iron-based scrap) as a main iron source, and in particular, a quality problem when producing high-grade steel using steel scrap. The present invention relates to a method for producing hot metal for high-grade steel from steel scrap by removing copper in the steel scrap.

The iron source used in the steelmaking process is mainly hot metal obtained by reducing iron ore in a blast furnace, but with the aging of steel scraps, buildings and machinery products generated in the processing process of steel materials A considerable amount of steel scrap is also used. The production of hot metal in the blast furnace requires a great deal of energy to reduce and melt iron ore, whereas steel scrap requires only heat of melting, and when steel scrap is used in the steelmaking process, There is an advantage that the amount of energy used for reducing heat of iron ore can be reduced. Therefore, from the viewpoint of energy saving and prevention of global warming by reducing CO _2, it is desired to promote the use of steel scrap.

By the way, when recycling steel scraps, trump elements represented by copper and tin accompanying these steel scraps are inevitably mixed in the molten iron in the process of steel scrap melting. The trump element is a component that impairs the properties of steel and must be kept below a certain concentration. For this reason, it has been difficult to use low-grade steel scraps that may contain copper or tin as an iron source for producing high-grade steel. However, considering the recent increase in steel scrap generation and the demand for increased use of steel scrap to reduce CO ₂ generation, it is necessary to promote recycling of lower steel scrap.

  As a practical technology for using the current low-grade steel scrap, the steel scrap is physically decomposed and harmful parts are separated by methods such as human power and magnetic separation. There is no effective method other than blending in a raw material containing almost no carbon and using it within a range where there is no problem in the material properties of the steel material. With such a method, it is impossible to recycle a large amount of scrap steel from used cars, etc., and it is sufficient as a technology for removing copper in steel scrap corresponding to the era of the large amount of scrap scrap expected in the future. Cannot be a good solution.

On the other hand, the principle invention described below is known about the copper removal method after mixing in molten iron. That is, the basic technical knowledge of contacting the copper-containing high carbon molten iron with the FeS-Na ₂ S-based flux and separating and removing the copper component in the molten iron as Cu ₂ S is disclosed in Non-Patent Document 1 and Non-Patent Document. 2 is reported. This technique proposes a wider applicability to the above-described physical removal method as a copper removal technique. However, this method has a problem that the sulfur (S) component is mixed into the molten iron from a sulfur-containing flux such as a Na ₂ S-based flux, and the sulfur concentration in the molten iron increases. In addition, the distribution ratio, which is the ratio of the Cu concentration in the slag formed on the molten iron by melting the sulfur-containing flux and the Cu concentration in the molten iron, is about 30 at most, giving sufficient stirring to the slag and the distribution ratio It is necessary to prevent the deterioration.

As a decoppering treatment method based on this fundamental technical knowledge, Patent Document 1 discloses that a copper-containing high-carbon molten iron is obtained by carburizing and melting copper-containing steel scrap, and then contacting with a flux mainly composed of Na ₂ S. A method is disclosed in which the copper component in molten iron is separated and removed in the Na ₂ S flux as Cu ₂ S by reacting.

  However, Patent Document 1 does not disclose any desulfurization of high carbon molten iron after copper removal. Moreover, although the copper removal treatment is performed by stirring the hot metal and slag by blowing Ar gas from the bottom of the reaction vessel (hot metal ladle), stirring of the slag is insufficient. In order to compensate for this, it is equipped with an electric heating device for maintaining a reaction temperature of 1200 to 1500 ° C., and uses a covered reaction vessel for cutting off the contact with the atmosphere. It is not an established technology.

Japanese Patent Laid-Open No. 4-198431

Masato Imai, iron and steel, vol.74 (1988) No.4. p. 640 Oshio et al., Iron and Steel, vol.77 (1991) No.4. p. 504

  The present invention has been made in view of the above circumstances, and the object thereof is to use copper-containing steel scrap as an iron source, and to remove copper in hot metal resulting from copper in the steel scrap with a sulfur-containing flux. When manufacturing hot metal for high-grade steel, the copper in the hot metal can be efficiently removed without requiring a large facility, and the sulfur-containing flux after the copper removal treatment can be removed from the reaction vessel. A method for producing hot metal using steel scrap as an iron source, which can prevent the copper contained in the flux from returning to the hot metal and efficiently remove sulfur brought into the hot metal by the sulfur-containing flux. Is to provide.

  The method for producing hot metal using steel scraps as an iron source according to the first invention for solving the above-mentioned problem is obtained by adding sulfur to the hot metal accommodated in a reaction vessel produced by carburizing and dissolving copper-containing steel scraps. The contained flux is added, the copper in the molten iron is absorbed into the flux to remove the copper in the molten iron, and then the CaO-containing substance is introduced into the reaction vessel without discharging the sulfur-containing flux containing this copper. And the sulfur-containing flux is solidified by heat absorption by the CaO-containing substance.

  According to a second aspect of the present invention, there is provided a hot metal manufacturing method using steel scrap as an iron source. In the first aspect of the present invention, after the sulfur-containing flux is solidified by heat absorption by the CaO-containing material, the added CaO-containing material is used as the hot metal. And the sulfur in the molten iron is removed.

  According to a third aspect of the present invention, there is provided a hot metal manufacturing method using steel scrap as an iron source. In the first aspect, after the sulfur-containing flux is solidified by heat absorption by the CaO-containing substance, the CaO-containing substance is further reacted with the reaction. It is added to the container, and the added CaO-containing material is stirred with hot metal to remove sulfur in the hot metal.

According to a fourth aspect of the present invention, there is provided a hot metal manufacturing method using steel scrap as an iron source. In any one of the first to third aspects of the present invention, a material containing Na ₂ CO ₃ as a main component as a starting material for the sulfur-containing flux. And an iron-sulfur alloy.

  According to a fifth aspect of the present invention, there is provided a hot metal manufacturing method using steel scrap as an iron source. In any one of the first to fourth aspects of the invention, the copper removal process of the hot metal is performed with a mechanical stirring type refining apparatus. To do.

  According to a sixth aspect of the present invention, there is provided a hot metal manufacturing method using steel scraps as an iron source, in any one of the first to fifth aspects, the hot metal is formed by using a vertical furnace in which a carbon material bed is formed. It is characterized by carburizing and dissolving copper-containing steel scraps.

  According to the present invention, copper in hot metal produced by carburizing and dissolving copper-containing steel scrap is separated and removed by the sulfur-containing flux. The copper that has been difficult to separate can be separated and removed efficiently, and the CaO-containing material is added to the sulfur-containing flux in the reaction vessel without discharging the sulfur-containing flux that has absorbed copper. Since the sulfur-containing flux is solidified by sensible heat to stabilize the copper in the sulfur-containing flux, the same desulfurization process for removing sulfur brought into the hot metal by the sulfur-containing flux is performed next. It is possible to continue in the reaction vessel, improving the productivity by eliminating the need to remove the sulfur-containing flux and preventing the temperature of the hot metal from being lowered. Less from chromatic steel scrap of copper and sulfur hot metal can be efficiently produced, as a result, be available copper-containing steel scraps as an iron source of high-grade steel, the use of lower steel scrap is promoted.

  Hereinafter, the present invention will be specifically described.

When the hot metal for steelmaking containing carbon is produced by carburizing and dissolving copper-containing steel scrap, almost all of the copper in the steel scrap is dissolved in the hot metal. In the present invention, as a means for removing the copper (referred to as “copper removal treatment”), the sulfur-containing flux is brought into contact with the hot metal, and the copper in the hot metal is separated and removed into the sulfur-containing flux as copper sulfide (Cu ₂ S). . As the sulfur-containing flux, those containing an alkali metal or alkaline earth metal sulfide as a main component are suitable. In order to increase the sulfur content in the sulfur-containing flux, FeS (iron sulfide) may be mixed. Particularly suitable is a flux mainly composed of Na ₂ S. In the case of a flux mainly composed of Na ₂ S, if Na ₂ CO ₃ (soda ash) widely used industrially is used as the Na source, and an iron-sulfur alloy (ferrosulfur) is used as the sulfur source, This is advantageous in terms of cost. As the composition of the sulfur-containing flux, it is desirable that the molar fraction of Na ₂ S in the flux is 0.2 or more from the viewpoint of efficient copper removal. There is no particular upper limit for the molar fraction of Na ₂ S in the flux, and a desired copper removal reaction can be expected as long as it is 0.2 or more.

  Since copper removal with a sulfur-containing flux is a process with a low distribution ratio (ratio of Cu concentration in the flux and Cu concentration in the molten iron), the sulfur-containing flux should be added in order to sufficiently proceed with copper removal. Therefore, it is necessary to promote the mass transfer on the slag side formed in the reaction vessel. For this purpose, it is important to also stir the slag layer. In particular, in the present invention, the copper removal treatment is performed in the hot metal stage, the hot metal temperature range (1200 to 1400 ° C.) is lower than the molten steel temperature range (1550 to 1700 ° C.), and the slag fluidity is also low. Slag agitation is important.

  As a method of simultaneously stirring the molten iron and the slag present on the molten iron, the stirring slag is blown from the injection lance immersed in the molten iron in the reaction vessel or the tuyere installed at the bottom of the reaction vessel, and the slag and molten iron are stirred. Although a method (referred to as “gas stirring method”) can also be employed, in the present invention, it is preferable to perform a copper removal treatment using a mechanical stirring type refining apparatus because good stirring can be obtained. As a mechanical stirring type refining apparatus, stirring using an impeller (also referred to as “stirring blade”) is typical. In other words, the impeller is immersed in the hot metal contained in a ladle-shaped reaction vessel, and the impeller is rotated about the axis of rotation to forcibly stir the hot metal and the sulfur-containing flux added on the hot metal. Is the method. In the mechanical stirring type refining apparatus, the sulfur-containing flux charged on the hot metal is sufficiently entrained in the hot metal, and the hot metal and the sulfur-containing flux are sufficiently stirred. On the other hand, in the gas stirring method disclosed in Patent Document 1, the slag is not easily caught in the hot metal, and stirring is insufficient.

  Further, a method of blowing a powdery sulfur-containing flux into the hot metal together with the conveying gas from an injection lance immersed in the hot metal, so-called flux blowing method, is also a preferable processing method. In this case, the powdered sulfur-containing flux blown into the hot metal is in direct contact with the hot metal, and new unreacted sulfur-containing flux is continuously in contact with the hot metal, facilitating mass transfer on the slag side. The effect equivalent to the case where it is made to develop is exhibited, and the reaction between the hot metal and the sulfur-containing flux is promoted. Further, since the carrier gas also functions as a stirring gas, although the stirring strength is not as high as that of the mechanical stirring type refining apparatus, the hot metal and the hot metal slag are stirred.

  In the copper removal treatment, an inert gas such as Ar gas or a reducing gas such as propane may be supplied onto the hot metal bath surface in order to prevent air from entering the atmosphere.

  In the present invention, the temperature of the hot metal before the copper removal treatment, that is, the hot metal for steelmaking containing carbon produced by carburizing and melting the copper-containing steel scrap is 1200 ° C. or higher and 1500 ° C. or lower, desirably 1250 ° C. or higher and 1350 ° It is preferable that it is below ℃. If the hot metal temperature is less than 1200 ° C., there is a concern about solidification and solidification of the flux and the hot metal itself due to the low temperature. In particular, considering the temperature guarantee in the subsequent desulfurization process and converter decarburization process, it is desirable to set the temperature to 1250 ° C. or higher. On the other hand, at 1500 ° C. or higher, the evaporation of flux due to high temperature cannot be ignored. That is, in order to suppress the evaporation of the sulfur-containing flux and efficiently perform the copper removal reaction, the hot metal temperature is preferably as low as possible. Therefore, for the efficient copper removal reaction, the hot metal temperature is more preferably 1400 ° C. or less. Is preferably 1350 ° C. or lower.

  The carbon concentration in the hot metal before the copper removal treatment is preferably 2% by mass or more. It is known that the reaction in which the copper in the hot metal becomes copper sulfide proceeds more thermodynamically as the carbon concentration in the hot metal increases, and if the carbon concentration in the hot metal before the copper removal treatment is less than 2% by mass, In addition to the fact that the copper sulfide formation reaction does not occur sufficiently, the liquidus temperature of the hot metal rises, and adhesion of hot metal to the container wall becomes a problem. The upper limit of the carbon concentration is not particularly required, but it is preferably up to about 5.5% by mass in consideration of reduction of the amount of carbon material used. Even if excessive carburizing is performed, only graphite is deposited on the hot metal surface, and the contribution to the copper removal reaction is small. Furthermore, the copper concentration in the hot metal before the copper removal treatment is preferably 0.1% by mass or more and 1.0% by mass or less. When the copper concentration in the hot metal before the copper removal treatment exceeds 1.0% by mass, the amount of the sulfur-containing flux necessary for removing copper becomes excessive, and the practical load is large. On the other hand, when it is less than 0.1% by mass, it can be dealt with by, for example, diluting with a hot metal having a low copper content without performing a copper removal treatment.

  Further, the sulfur concentration of the hot metal before the copper removal treatment is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more. If the sulfur concentration of the hot metal before the copper removal treatment is less than 0.01% by mass, the amount of sulfur dissolved from the sulfur-containing flux into the hot metal becomes excessive, and the use efficiency of the sulfur-containing flux is lowered, which is not economical. The upper limit of the sulfur concentration does not need to be specified in particular, but if it is too high, the desulfurization treatment in the next step will be hindered, so it is preferably 0.5% by mass or less.

  As the hot metal components other than those described above before the copper removal treatment, for example, the silicon concentration is preferably 0.5% by mass or less and the manganese concentration is preferably 0.5% by mass or less. When these concentrations are exceeded, silicon oxide and manganese oxide generated by oxidation of these components during the copper removal treatment are transferred to slag to increase the amount of slag, making slag treatment difficult, as well as silicon oxide and manganese oxide. May inhibit the copper removal reaction of the sulfur-containing flux.

  In addition, the hot metal for steelmaking manufactured by carburizing and melting copper-containing steel scrap is mixed with hot metal discharged from the blast furnace (hereinafter referred to as “blast furnace hot metal”) as necessary to dilute the copper concentration. Thereafter, copper contained in the mixed hot metal may be removed using a sulfur-containing flux.

  As a process for producing hot metal containing carbon by carburizing and dissolving copper-containing steel scrap, there are a method using an electric furnace, a method using a converter, a method using a vertical furnace, etc. A method using a vertical furnace in which a charcoal bed is formed is preferable because energy efficiency is higher than that of a converter or a converter.

  Here, a vertical furnace with a charcoal bed formed inside is a steel containing copper-containing steel scraps and coke from the upper part of the vertical furnace and, if necessary, a slagging agent, and is provided at the lower part of the vertical furnace. The coke is burned by blowing air, oxygen-enriched air, oxygen gas, hot air, etc. from the heated tuyere, and the copper-containing steel scrap and iron making agent are melted by the combustion heat of the coke, and the hot metal is melted from the tap at the bottom of the furnace. And an apparatus for taking out molten slag. In this case, only the coke is filled in the range from the furnace bottom to a certain height above the tuyere, and this is burned to melt the copper-containing steel scrap charged in the upper part of the coke. The coke that fills the bottom of the furnace is called a “charcoal bed”, and the charcoal bed burns and wears out. To compensate for this, the coke is charged from the top of the furnace body. The molten iron produced by melting the copper-containing steel scraps flows down the coke gap and is carburized by the coke to produce hot metal.

  When hot metal is produced using such a vertical furnace in which a carbon material bed is formed, the sulfur concentration in the hot metal is generally higher than that in blast furnace hot metal. Taking advantage of this high sulfur concentration, copper removal with a sulfur-containing flux can be advantageously advanced. Since the sulfur concentration in the hot metal is high, there is little movement of sulfur from the sulfur-containing flux into the hot metal, and the utilization efficiency of the sulfur-containing flux can be increased.

  Along with the above copper removal treatment, sulfur in the sulfur-containing flux inevitably moves into the hot metal, so that the sulfur concentration in the hot metal increases. Accordingly, when the hot metal is decopperized using the sulfur-containing flux, after the decoppering process, a desulfurization process for removing sulfur in the hot metal is required. In the present invention, the desulfurization treatment is performed without discharging the sulfur-containing flux used in the decopperization treatment from the reaction vessel for the purpose of improving productivity and preventing the hot metal temperature from decreasing. Carry out in the same reaction vessel as the performed reaction vessel.

  In that case, if the sulfur-containing flux used in the decopperization process remains in a molten state, a reaction ("recovered copper reaction") occurs in which the copper absorbed in the sulfur-containing flux returns to the hot metal during the desulfurization process. There is a fear. In order to prevent this copper recovery reaction, in the present invention, a CaO-containing material at room temperature is added as a coolant to a reaction vessel containing the sulfur-containing flux used in the copper removal treatment, and heat absorption by the CaO-containing material is performed. To solidify the sulfur-containing flux. By solidifying the sulfur-containing flux, the copper in the sulfur-containing flux is stabilized and the copper recovery reaction in the desulfurization process is suppressed.

In the present invention, the reason for using a CaO-containing substance as a coolant is that CaO-containing substances such as quick lime (CaO), limestone (CaCO ₃ ), and dolomite (MgCO ₃ · CaCO ₃ ) are inexpensive and, By functioning as a desulfurization agent. That is, this is because the CaO-containing material is added to solidify the sulfur-containing flux, and the hot metal desulfurization treatment is performed with the added CaO-containing material. As a CaO hatching accelerator, a material obtained by adding several to tens of mass% of fluorite, alumina or the like to quicklime is defined as a CaO-containing substance in the present invention.

  The hot metal desulfurization treatment may be started simultaneously with the addition of the CaO-containing material, or may be started after the addition of the CaO-containing material and after the sulfur-containing flux is solidified, and the CaO-containing material for cooling. After adding, a CaO-containing substance as a desulfurizing agent may be further added before starting.

  The addition amount of the CaO-containing substance added as the coolant and the desulfurizing agent is preferably 0.10 kg or more per 1 kg of the sulfur-containing flux used in the copper removal treatment. If the CaO-containing material to be added is less than this, the sulfur-containing flux is not sufficiently solidified, and a copper recovery reaction may occur during the desulfurization treatment, which may increase the copper concentration in the hot metal. Regarding the amount of CaO-containing material added, operating restrictions such as the sulfur concentration in the hot metal after the copper removal treatment, the sulfur concentration in the hot metal after the desulfurization treatment, the hot metal temperature, and the size of the scouring reaction vessel Although it is determined as appropriate depending on the conditions, the upper limit is preferably 1 kg or less per 1 kg of the sulfur-containing flux used in the copper removal treatment from the viewpoint of processing cost.

  The hot metal desulfurization treatment can be performed by any of a known mechanical stirring type refining apparatus, a gas stirring method, etc., but a high desulfurization rate can be obtained even when an inexpensive CaO-containing substance is used as a desulfurizing agent. Therefore, it is preferable to use a mechanical stirring type refining apparatus. When the copper removal treatment is performed with a mechanical stirring type refining device, the sulfur-containing flux used in the copper removal treatment can be desulfurized with the same mechanical stirring type refining device without discharging from the reaction vessel, High productivity can be obtained.

  When carrying out desulfurization treatment, the blast furnace hot metal may be mixed with the hot metal subjected to decoppering treatment to dilute the sulfur concentration, and then the mixed hot metal may be subjected to desulfurization treatment. Blast furnace hot metal may be mixed with the hot metal.

After the desulfurization treatment, it is necessary to remove the slag in the reaction vessel (a mixture of solidified sulfur-containing flux and desulfurization agent) from the reaction vessel. If this slag is not removed and it is subjected to the converter decarburization refining or preliminary dephosphorization process in the next step, the converter decarburization refining and preliminary dephosphorization process are oxidation refining, and copper sulfide ( Cu ₂ S) decomposes and returns to the molten steel or hot metal, not only the copper concentration in the molten steel or hot metal increases, but also the sulfur in the desulfurizing agent returns to the molten steel or hot metal, and the sulfur concentration in the molten steel or hot metal This is because a molten steel with low copper and sulfur cannot be obtained. The slag removal operation may be any of a method using a known slag dragger, a method using a slag suction machine, a method of discharging the slag in the container by inclining the hot metal container, and is suitable for the equipment situation possessed by each steelworks You can select the one you want.

  As described above, according to the present invention, the copper in the hot metal is separated and removed by the sulfur-containing flux, so that it is difficult to separate by the method of separating and removing the steel scraps by magnetic separation after physically decomposing the steel scrap. Copper can be separated efficiently, and the sulfur-containing flux is solidified by adding a CaO-containing material to the sulfur-containing flux in the reaction vessel without discharging the sulfur-containing flux that has absorbed the copper, and the sulfur-containing flux is solidified. Since the copper in the inside is stabilized, it is possible to carry out hot metal decopperization and desulfurization treatment in the same reaction vessel, improving the productivity and eliminating the need to remove the sulfur-containing flux. Therefore, it is possible to efficiently produce hot metal containing less copper and sulfur from copper-containing steel scrap.

Using a vertical furnace with a charcoal bed formed inside, copper-containing steel scraps are melted to produce hot metal for steel making, and this hot metal is received in the hot metal ladle. First, FeS- was added to a flux mainly composed of Na ₂ S subjected to a copper removal treatment, after the copper removal treatment was carried out 3 times a test for the desulfurization process by adding quicklime (test No.1~3). Both the copper removal treatment and the desulfurization treatment used a mechanical stirring type refining apparatus.

In both tests No. 1 to No. 3, about 5 tons of the hot metal for steel making was charged into the hot metal ladle, and in a mechanical stirring type refining apparatus, flux containing FeS—Na ₂ S as a main component (in the flux) The Na ₂ S molar fraction of 0.4) was put on the hot metal, the impeller covered with the refractory was immersed in the hot metal, and the impeller was rotated to stir the hot metal and the flux. In any test, 200 kg of flux containing FeS—Na ₂ S as a main component was introduced per ton of hot metal.

After the copper removal treatment, test No. 1 was conducted in such a manner that the flux mainly composed of FeS-Na ₂ S was not discharged from the hot metal ladle while the impeller of the mechanical stirring type refining apparatus was immersed in the hot metal, and this flux was 1 kg. 0.10 kg of quick lime is charged into the hot metal ladle to solidify the flux, and when 1 minute has passed since the quick lime is charged, the impeller starts to rotate and is maintained at a predetermined rotational speed. The desulfurization process was carried out without charging.

In test No. 2, after the copper removal treatment, the impeller was lifted from the hot metal, the hot metal ladle containing the hot metal was moved from the mechanical stirring type refining apparatus to the slagging station, and FeS-Na ₂ S was mainly used using a slag dragger. The component flux is discharged from the hot metal ladle, and then the hot metal ladle containing the hot metal is returned to the mechanical stirring type refining device, and the impeller is again immersed in the hot metal and then rotated, and from the time when the predetermined rotational speed is reached. Then, 25 kg of quick lime per ton of hot metal was continuously charged into the hot metal ladle and subjected to desulfurization treatment.

In test No. 3, after removing the copper, the flux mainly composed of FeS-Na ₂ S was not discharged from the hot metal ladle while the impeller of the mechanical stirring type refining apparatus was immersed in the hot metal, and per 1 kg of flux. 0.09 kg of quicklime is charged into the hot metal ladle, and when 1 minute has passed since the quicklime is charged, the impeller starts rotating, and is maintained at a predetermined rotational speed, and desulfurization treatment is performed without newly adding quicklime. Carried out. In Test No. 3, the amount of quicklime added was small, and a part of the flux mainly composed of FeS—Na ₂ S was solidified, but most remained in a molten state.

  In each of Test Nos. 1 to 3, the hot metal concentration before the copper removal treatment was 0.33% by mass, the sulfur concentration was 0.10% by mass, and the hot metal temperature was 1350 ° C. Table 1 shows the transition of copper concentration and sulfur concentration in hot metal and the transition of hot metal temperature in Test Nos. 1-3. In the remarks column of Table 1, tests within the scope of the present invention are displayed as “examples of the present invention”, and other tests are displayed as “comparative examples”.

As shown in Table 1, the test No. 1 in which quick lime was added and the flux mainly composed of FeS-Na ₂ S was solidified after the copper removal treatment was performed mainly using FeS-Na ₂ S using a slag dragger. Similar to test No. 2 in which the flux as a component was discharged, it was confirmed that the copper concentration in the hot metal was reduced and no copper was generated during the desulfurization treatment. In addition, in test No. 1, the flux used in the copper removal treatment was not discharged, so the hot metal temperature after the desulfurization treatment could be maintained at 25 ° C. higher than in test No. 2. It can be seen that the thermal margin after the process is remarkably improved.

On the other hand, in test No. 3 in which the amount of quick lime charged is small and the flux mainly composed of FeS-Na ₂ S cannot be sufficiently solidified, recovery copper is generated during the desulfurization treatment, and the effect of the decopperization treatment. Was confirmed to decrease. It was also confirmed that the desulfurization rate was low.

  In Test No. 1, as in Test No. 2, it is possible to obtain hot metal that has both a low copper concentration and a low sulfur concentration, which can be used without any problem as hot metal for high-grade steel, and the thermal margin after the next step. It has been found that the degree can be maintained higher than test No. 2.

Claims (6)

  A sulfur-containing flux is added to the hot metal contained in the reaction vessel, which is produced by carburizing and dissolving copper-containing steel scrap, and the copper in the hot metal is absorbed by the flux to remove the copper in the hot metal, and then A steel scrap characterized by adding a CaO-containing substance into the reaction vessel without discharging the sulfur-containing flux containing copper and solidifying the sulfur-containing flux by heat absorption by the CaO-containing substance. Hot metal manufacturing method using iron as an iron source.   The steel scrap according to claim 1, wherein after the sulfur-containing flux is solidified by heat absorption by the CaO-containing material, the added CaO-containing material is stirred with hot metal to remove sulfur in the hot metal. Hot metal manufacturing method using iron as an iron source.   After the sulfur-containing flux is solidified by heat absorption by the CaO-containing material, a CaO-containing material is further added to the reaction vessel, and the added CaO-containing material is stirred with hot metal to remove sulfur in the hot metal. A hot metal production method using the steel scrap according to claim 1 as an iron source. The steel scrap according to any one of claims 1 to 3, wherein a material mainly composed of Na ₂ CO ₃ and an iron-sulfur alloy are used as a starting material for the sulfur-containing flux. Hot metal manufacturing method using iron as an iron source.   The method for producing hot metal using steel scrap as an iron source according to any one of claims 1 to 4, wherein the copper removal treatment of the hot metal is performed with a mechanical stirring type refining apparatus.   The hot metal is obtained by carburizing and melting the copper-containing steel scrap using a vertical furnace in which a carbon material bed is formed. A method for producing hot metal using the described steel scrap as an iron source.