JP6468264B2 - Operating method of hot metal holding furnace - Google Patents

Description

  The present invention relates to a method for operating a hot metal holding furnace equipped with an induction heating device that supplies hot metal as a raw material to a decarburization refining facility for producing molten steel, and more specifically, steel scrap such as ordinary steel and stainless steel. Is added to the hot metal in the hot metal holding furnace, the hot metal is heated by an induction heating device, the added steel scrap is melted in the hot metal, and the carbon concentration of the hot metal having a reduced carbon concentration is formed by melting the steel scrap. The present invention relates to a method for operating a hot metal holding furnace that can be increased.

  Conventionally, a hot metal holding furnace (also referred to as a “storage furnace”) is used to stably supply hot metal having a target composition, temperature and mass to a decarburization and refining facility for molten steel production such as a converter at the required timing. ) Is being used. Here, the hot metal held in the hot metal holding furnace includes blast furnace hot metal (also referred to as “normal hot metal”) used when melting ordinary steel and chromium-containing steel used when melting stainless steel. Hot metal is common. The “hot metal” in this specification refers to all hot metal such as blast furnace hot metal, chromium-containing hot metal, nickel-containing hot metal, cupola hot metal, and the like.

  For example, in Patent Document 1, a blast furnace hot metal subjected to hot metal pretreatment is charged into a hot metal holding furnace equipped with a heating means, the temperature and components of the blast furnace hot metal are adjusted in the hot metal holding furnace, and steel scrap Is added and melted to produce the simulated hot metal, and this simulated hot metal is supplied to the refining furnace (decarburization refining equipment), thereby realizing stable operation in the refining furnace and reducing the manufacturing cost. A method of operating a hot metal holding furnace equipped with a heating device that enables efficient production is disclosed.

  In Patent Document 2, a chromium-containing hot metal obtained by melting and reducing chromium oxide is held in a hot metal holding furnace equipped with a heating device, and then decarburized in a decarburization refining facility from the hot metal holding furnace. There has been proposed a method of producing a high chromium molten steel by discharging a necessary amount of chrome-containing molten iron to a decarburizing and refining facility in accordance with a refining schedule and decarburizing and refining in the decarburizing and refining facility. Patent Document 2 also proposes adding a solid metal raw material such as stainless steel scrap to the chromium-containing hot metal held in the hot metal holding furnace and melting the solid metal raw material in the hot metal holding furnace.

  By the way, steel scraps such as ordinary steel and stainless steel are scraps of steel products. Therefore, the carbon content of steel scraps is generally 0.01 to 0.1% by mass equivalent to that of steel products. It is much lower than the carbon content of hot metal such as blast furnace hot metal and chromium-containing hot metal. When a large amount of steel scrap is added to the hot metal held in the hot metal holding furnace, the carbon content of the hot metal formed by melting the steel scrap decreases, and the liquidus temperature of the hot metal formed (solidification start temperature) In addition, the solidus temperature (solidification completion temperature) is increased. For example, when 200 tons of steel scrap with a carbon content of 0.05% by mass is added to 900 ton of blast furnace hot metal with a carbon content of 4.5% by mass and dissolved in the blast furnace hot metal, the carbon content becomes 1100 tons of hot metal, which is 3.7% by mass, is produced. Since the carbon content decreases, the liquidus temperature of the hot metal produced by melting the steel scrap rises by about 60 ° C. relative to the liquidus temperature of the blast furnace hot metal before the steel scrap melts.

  The heating device provided in the hot metal holding furnace has a calorific value that prevents the temperature of the hot metal to be held from falling, and for the purpose of melting steel scrap, the heating value of the heating device is increased to increase the hot metal temperature. When the temperature is raised, the refractory constituting the hot metal holding furnace is extremely damaged. For these reasons, it has been difficult to raise the temperature of the hot metal held in the hot metal holding furnace until the steel scrap is sufficiently melted.

  That is, in Patent Document 1 and Patent Document 2, steel scrap such as ordinary steel and stainless steel is added to the hot metal holding furnace, and the added steel scrap is melted in the hot metal, but the amount of steel scrap added increases. In this case, the carbon content of the hot metal formed decreases, the liquidus temperature increases, and the amount of metal on the inner wall of the hot metal holding container that receives the hot metal discharged from the hot metal holding furnace increases. , You will be forced to the problem that the operation will be hindered. In order to avoid this problem, in Patent Document 1 and Patent Document 2, it is necessary to limit the amount of steel scrap added, and it is difficult to add a large amount of steel scrap.

  As a means for preventing such a problem when the carbon content in the hot metal is lowered, a solid carbon source is added to the hot metal in the hot metal holding furnace, and the solid carbon source is dissolved in the hot metal to dissolve in the hot metal. A method of increasing the carbon concentration, that is, a method of carburizing the hot metal in the hot metal holding furnace with a solid carbon source is conceivable.

  In fact, Patent Document 3 proposes an operation method of adding 0.5 kg or more of solid carbon source per ton of chrome-containing hot metal in the hot metal holding furnace for holding the chrome-containing hot metal in the method of operating the hot metal holding furnace. Yes. However, Patent Document 3 describes the effect of the addition of the solid carbon source as follows: “The added solid carbon source reacts with the oxygen gas in the atmospheric gas, and the oxygen potential of the chromium-containing hot metal bath surface decreases, so that the chromium in the chromium-containing hot metal At the same time, the slag in the holding furnace is heated by the heat generated by the oxidation reaction of the solid carbon source, and the viscosity of the slag is lowered to promote the discharge of slag at the time of tapping. The melting loss of the furnace refractory is reduced, and the life of the refractory is improved. "

JP 2004-218039 A JP 2003-155515 A JP 2007-224379 A

  As described above, in the hot metal holding furnace, the carbon content of the hot metal to be held may decrease due to melting of the added steel scrap or the like. In this case, the method of adding the solid carbon source proposed in Patent Document 3 to the hot metal in the hot metal holding furnace and carburizing the hot metal is considered to be optimal.

  However, the hot metal holding furnace does not have a sufficient stirring function to dissolve the added solid carbon source in the hot metal, and there is slag on the hot metal in the hot metal holding furnace. Contact between the solid carbon source and the hot metal is hindered. Therefore, most of the added solid carbon source burns on the slag, the yield of the added solid carbon source to the hot metal is low, and the endothermic amount due to dissolution of the solid carbon source is also large, so the solid carbon source It is extremely difficult to carburize the hot metal in the hot metal holding furnace. Another problem is that sulfur and phosphorus in the solid carbon source dissolve in the hot metal and the concentration of phosphorus and sulfur in the hot metal increases. Patent Document 3 also does not describe that the chromium-containing hot metal in the hot metal holding furnace is carburized by adding a solid carbon source.

  Moreover, new hot metal such as blast furnace hot metal produced in the blast furnace is successively inserted into the hot metal holding furnace because of its usage characteristics, and the carbon concentration and temperature of the hot metal held in the hot metal holding furnace are adjusted. Also, a method of raising the temperature by newly introduced hot metal can be considered.

  However, the blast furnace hot metal is usually subjected to hot metal pretreatment for dephosphorization and desulfurization. For example, when the blast furnace hot metal is subjected to dephosphorization treatment and desulfurization treatment to reduce the phosphorus content of the blast furnace hot metal to 0.020% by mass or less and the sulfur content to 0.010% by mass or less, the reaction with the refining agent The carbon concentration of the blast furnace hot metal is lowered to about 4.0% by mass or less, and the temperature is lowered to about 1250 ° C. or less by decarburization or endotherm by. When the blast furnace hot metal after such pretreatment is charged into a hot metal holding furnace equipped with a heating means, and steel scrap is charged and melted, it is formed by increasing the amount of steel scrap charged. There is a possibility that the melting rate of the steel scrap is lowered due to a decrease in the carbon content and temperature of the molten iron, and there is a possibility of causing an adverse effect due to the accumulation of the unmelted scrap in the molten iron holding furnace.

  In other words, the blast furnace hot metal is generally subjected to hot metal pretreatment of dephosphorization and desulfurization treatment, and in particular, in the case of blast furnace hot metal in which the phosphorus concentration is reduced by dephosphorization, the carbon concentration In addition, even if such a blast furnace hot metal is supplied to the hot metal holding furnace, it is difficult to sufficiently increase the carbon concentration of the hot metal having a reduced carbon concentration held in the hot metal holding furnace. .

  As described above, despite the desire to increase the carbon concentration of the hot metal held in the hot metal holding furnace, there is no conventional effective means, and the hot metal holding container that receives the hot metal discharged from the hot metal holding furnace. Operation has been forced to be hindered by the adhesion of bullion to the inner wall.

  The present invention has been made in view of the above circumstances, and the object is to add steel scrap to the hot metal in the hot metal holding furnace, and to heat the hot metal with an induction heating device provided in the hot metal holding furnace, An object of the present invention is to provide a method for operating a hot metal holding furnace capable of increasing the carbon concentration of the hot metal having a reduced carbon concentration, which is formed by melting the steel scrap, in melting the added steel scrap in the hot metal.

The gist of the present invention for solving the above problems is as follows.
[1] A method of operating a hot metal holding furnace equipped with an induction heating apparatus for supplying the hot metal held as a raw material to a decarburization refining facility for producing molten steel, the hot metal held in the hot metal holding furnace Steel scrap is added, and the hot metal is induction-heated with the induction heating device to melt the steel scrap in the hot metal, and then the steel scrap is melted, and a part of the hot metal in the hot metal holding furnace is melted in the hot metal holding furnace. The molten iron discharged from the reactor is charged into a converter reactor equipped with an upper blowing lance for sending acid, and carbonaceous material and gaseous oxygen are supplied to the hot metal contained in the converter reactor, While heating the hot metal in the converter reactor, the carbon content of the hot metal is increased, and then the hot metal in the converter reactor is discharged from the converter reactor, and the discharged hot metal is discharged into the hot metal holding furnace. And mixed with the hot metal in the hot metal holding furnace To, operating method of hot metal holding furnace.
[2] The hot metal held in the hot metal holding furnace is a chromium-containing hot metal obtained by melting treatment or smelting reduction treatment of a chromium source, and the steel scrap is stainless steel scrap, The operating method of the hot metal holding furnace as described in [1] above.
[3] A CaO-based medium solvent is added to the molten iron charged in the converter type reaction vessel, and a part of sulfur contained in the molten metal and the carbonaceous material is converted to the hatching of the CaO-based medium solvent. The hot metal holding furnace operating method according to the above [1] or [2], wherein the hot metal holding furnace is removed by slag formed in a converter type reaction vessel.
[4] In the converter-type reaction vessel, the hot metal is heated to a temperature of 1400 ° C. or higher, and the carbon content of the hot metal is increased to 4.0% by mass or more. [1] Or the operating method of the hot metal holding furnace of any one of said [3].

  According to the present invention, a part of the hot metal in the hot metal holding furnace is discharged from the hot metal holding furnace, the discharged hot metal is heated and carburized in the converter reactor, and the heated and carburized hot metal is supplied to the hot metal holding furnace. Since it is charged and mixed with the hot metal in the hot metal holding furnace, the carbon concentration of the hot metal held in the hot metal holding furnace can be increased efficiently, and thereby the carbon of the hot metal held in the hot metal holding furnace It is possible to prevent troubles caused by a decrease in concentration.

It is a schematic perspective view of an example of the hot metal holding furnace used when implementing this invention, and is a schematic perspective view shown in the cross section which cut a part of hot metal holding furnace.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of an example of a hot metal holding furnace used in carrying out the present invention, and shows a cross section of a part of the hot metal holding furnace.

  As shown in FIG. 1, the hot metal holding furnace 1 used in the present invention has a cylindrical shape, and a cylindrical outer shell is used as an iron shell 7, and a refractory 8 is applied to the inner side of the iron shell 7. The support mechanism (not shown) is supported so as to be rotatable about the axial direction of the cylindrical shape. In the hot metal holding furnace 1, an inlet 3 for receiving hot metal 6 from a hot metal transfer container (not shown) such as a hot metal ladle, charging steel scrap or alloy material, and the like are held. A hot water outlet 2 for discharging the hot metal 6 that has been discharged into a hot metal holding container (not shown) such as a charging pot is provided on the side wall. In addition, a groove-type induction heating device (hereinafter referred to as “groove-type induction heating device 5”) for induction heating of the held hot metal 6 is disposed at the lower part of the side wall of the hot metal holding furnace 1, while holding the hot metal. At the upper part of the side wall of the furnace 1, a hot metal 6 held in the hot metal holding furnace 1 and a sampling port 4 for collecting a sample from a slag (not shown) existing on the hot metal 6 are installed. When the hot metal is discharged from the hot metal holding furnace 1, the hot metal holding furnace 1 is tilted, and the hot metal 6 is discharged from the hot water outlet 2 into the hot metal holding container. In FIG. 1, only one grooved induction heating device 5 is installed, but two or more can be arranged. The groove type induction heating device 5 does not require a special device, and for example, a conventional groove type induction heating device disclosed in Japanese Patent Publication No. 50-25666 can be used.

  The hot metal 6 held in the hot metal holding furnace 1 is a blast furnace hot metal produced by reducing iron ore with coke in a blast furnace, or a melting furnace such as an electric furnace or induction heating furnace, and ferrochrome, stainless steel scrap. In a chrome-containing hot metal that has been melted and processed using a chromium source such as ordinary steel scrap and iron source such as cold iron, or in a converter-type smelting reduction furnace, chromium ore, ferrochrome, stainless steel Chromium-containing hot metal is generally produced by smelting reduction using a chromium source such as steel scrap and an iron source such as blast furnace hot metal, ordinary steel scrap, and cold iron as a main raw material.

  In particular, when the furnace capacity of the decarburization and refining equipment in the next process is larger than the furnace capacity of the melting furnace or smelting reduction furnace for melting chrome-containing hot metal, It is common to supply chromium hot metal to a single decarburization refining facility. In such a case, it is effective to use the hot metal holding furnace 1. In addition, the chromium containing hot metal in this specification is a hot metal containing 5 mass% or more of chromium and 2.5 mass% or more of carbon.

  Period until such hot metal 6 such as blast furnace hot metal or chromium-containing hot metal is charged into the hot metal holding furnace 1 through the charging port 3 and the supplied hot metal 6 is supplied to the decarburizing and refining equipment of the next process. Then, it is held in the hot metal holding furnace 1 while being heated by the groove type induction heating device 5. The hot metal holding furnace 1 holds the hot metal amount of several times to ten times as much as one charge of the decarburizing and refining equipment, while charging the hot metal 6 and supplying the hot metal 6 to the decarburizing and refining equipment of the next process. It is general that the operation is repeated so that the amount of molten iron is maintained at substantially the same level.

  While holding the hot metal 6 in the hot metal holding furnace 1, the steel scrap is added to the hot metal 6 in the hot metal holding furnace, the hot metal 6 is induction-heated by the grooved induction heating device 5, and the added steel scrap is put into the hot metal. Dissolve. As the steel scrap to be added, ordinary steel scrap is used when the hot metal 6 held in the hot metal holding furnace 1 is blast furnace hot metal, and stainless steel when the hot metal 6 held in the hot metal holding furnace 1 is chromium-containing hot metal. Use steel scrap. The reason for using ordinary steel scrap when the retained hot metal 6 is blast furnace hot metal is to prevent the alloy components from being mixed into ordinary steel produced from the blast furnace hot metal, while the retained hot metal 6 is retained. The reason for using stainless steel scrap in the case of chrome-containing hot metal is to increase or maintain the chromium concentration in the chrome-containing hot metal.

  The upper limit value of steel scrap added to the hot metal 6 accommodated in the hot metal holding furnace 1, that is, the upper limit value that can be added without causing unmelting of the steel scrap in the hot metal holding furnace is the groove type induction heating device 5. Depends on the supply power (heating capacity) to the hot metal holding furnace, the supply speed of the hot metal 6 supplied to the hot metal holding furnace, the carbon content and temperature of the hot metal 6, and the higher the supply power, the supply speed of hot metal, the carbon content and the temperature Large amounts of steel scrap can be added. Therefore, although the amount of steel scrap added cannot be generally specified, for example, in the hot metal holding furnace 1 provided with the 8 MW grooved induction heating device 5, the carbon concentration is 5.0 mass% and the temperature is 1400 ° C. Chromium-containing hot metal is supplied to the hot metal holding furnace 1 at an average supply rate of about 30 tons per hour, and the chrome-containing hot metal is discharged to the decarburization and refining equipment of the next process periodically while melting the stainless steel scrap. The present inventors have confirmed that about 420 kg of stainless steel scrap can be added per ton of chromium-containing hot metal supplied to the hot metal holding furnace 1 when the amount of hot metal in the range is maintained. In this case, the carbon concentration of the chromium-containing hot metal is diluted and falls to about 3.5% by mass.

  The steel scrap is added to the hot metal 6 in the hot metal holding furnace, the hot metal 6 is induction-heated by the groove type induction heating device 5, and the added steel scrap is dissolved in the hot metal 6, thereby forming the steel scrap by melting. The carbon content of the hot metal decreases. In this case, although heated by the grooved induction heating device 5, the temperature of the hot metal formed by melting the steel scrap also decreases.

  Therefore, a part of the hot metal having a reduced carbon content formed by melting steel scrap is discharged from the hot metal holding furnace 1 to the hot metal holding container, and the hot metal in the discharged hot metal holding container is supplied with an upper blowing lance for sending acid. The reactor is charged into a converter reactor (not shown). The converter type reaction vessel is provided with a bottom blowing tuyere for stirring the hot metal in the reaction vessel.

  While stirring the hot metal contained in the converter reactor with the stirring gas (nitrogen gas or rare gas) from the bottom blowing tuyere, supplying carbon material to the hot metal and supplying gaseous oxygen from the top blowing lance The carbon content of the hot metal is increased while heating the hot metal in the converter reactor. Specifically, it is preferable to perform carburization so that the carbon content of the hot metal is 4.0% by mass or more.

  The supply of gaseous oxygen in this case is not for decarburizing the hot metal, but for burning the carbon material added in the converter reactor and supplying heat to the hot metal in the converter reactor, Therefore, the supply amount of gaseous oxygen from the top blowing lance is limited according to the supply amount of the carbon material so that the hot metal in the converter reactor is not decarburized and the carburizing efficiency is not lowered. Specifically, it is desirable to limit the supply amount of gaseous oxygen to 70% or less of the amount of oxygen necessary to burn all the carbon in the supplied carbon material to CO, and the injection of gaseous oxygen from the top blowing lance Oxygen blowing is performed by so-called soft blow with a slow flow rate. Even when the hot metal contained in the converter reactor is chromium-containing hot metal, the oxidation loss of chromium remains at a level that does not cause a problem as long as the acid feeding conditions increase the carbon content of the hot metal.

  The hot metal in the converter reactor is stirred with the carbon material added in the converter reactor by the powerful stirring force of the stirring gas from the bottom blowing tuyere, melting the carbon material into the hot metal, That is, the carburization reaction proceeds. Moreover, the hot metal in the converter reactor is heated by the combustion heat generated by the combustion reaction between carbon and gaseous oxygen. That is, it is possible to efficiently raise the carbon content and temperature of the hot metal by supplying carbonaceous material and gaseous oxygen to the hot metal in the converter reactor and carrying out the carburizing and blowing.

  The hot metal whose carbon content and temperature are increased in the converter reactor is discharged from the converter reactor into the hot metal holding container, and the hot metal in the hot metal holding container is charged into the hot metal holding furnace 1 to form hot metal. Mix with the hot metal contained in the holding furnace 1. The hot metal contained in the hot metal holding furnace 1 is mixed with the hot metal whose carbon content and temperature are increased, so that the carbon concentration and temperature are increased.

  Thus, the hot metal in the hot metal holding furnace having an increased carbon content is supplied as a raw material to the decarburization refining equipment in accordance with the operation schedule of the decarburization refining equipment (not shown) for producing molten steel. Here, the decarburization refining equipment for producing molten steel includes a converter (melting of ordinary steel and stainless steel), an AOD furnace (melting of stainless steel), a VAD furnace (melting of stainless steel), and the like.

  In carburizing and blowing in a converter reactor, a CaO-based solvent is added to the converter-type reactor, and this CaO-based solvent is hatched to add desulfurizing slag into the converter-type reactor. Even if an inexpensive carbon material having a high sulfur content is used, a part of the sulfur contained in the hot metal and the carbon material is removed into the slag by a desulfurization reaction with CaO. Thereby, the raise of the sulfur concentration in hot metal can be suppressed, or the sulfur concentration in hot metal can be reduced.

  In order to advance such a desulfurization reaction positively, the temperature of the hot metal in the converter reactor is increased to 1400 ° C. or higher, and the addition of a hatching accelerator such as an alumina source causes the soot of the CaO-based solvent. Further, it is desirable to promote the reaction between the slag and the metal by gas agitation from the bottom blowing tuyere after stopping the supply of gaseous oxygen from the top blowing lance.

  In addition, as the carbon material to be added to the converter reactor, it is preferable to use a carbon material having a low phosphorus content such as anthracite coal in the case of chromium-containing hot metal that is difficult to be dephosphorized thereafter.

  As described above, according to the present invention, a part of the hot metal in the hot metal holding furnace is discharged from the hot metal holding furnace 1, the discharged hot metal is heated and carburized in the converter reactor, and heated and carburized. Since the molten iron is charged into the hot metal holding furnace 1 and mixed with the hot metal in the hot metal holding furnace, the carbon concentration of the hot metal held in the hot metal holding furnace can be increased efficiently. It is possible to prevent troubles caused by a decrease in the carbon concentration of the hot metal held in the steel.

[Example of the present invention]
The hot metal holding furnace shown in FIG. 1 is charged with about 700 tons of chromium-containing hot metal and an average of about 300 tons of stainless steel scrap per day, and the inside of the hot metal holding furnace is heated by an 8 MW channel type induction heating device. The chromium-containing hot metal was heated, the charged stainless steel scrap was melted in a hot metal holding furnace, and an average of about 1000 tons of chromium-containing hot metal was supplied to the decarburization and refining facility in the next step. The chromium-containing hot metal charged in the hot metal holding furnace is made by smelting reduction treatment of chromium ore.

  By this operation, in the hot metal holding furnace, carbon concentration: 3.5% by mass, silicon concentration; 0.01% by mass, manganese concentration; 0.10% by mass, phosphorus concentration; 0.030% by mass, sulfur concentration; An 840-ton chromium-containing hot metal with a temperature of 1380 ° C. and a chromium concentration of 13.0% by mass was formed.

140 tons of the 840-ton chromium-containing hot metal was discharged from the hot metal holding furnace into the hot metal holding container, and the discharged chromium-containing hot metal was charged into the top bottom blowing converter. 7.0 ton of anthracite (carbon pure content: 85% by mass, sulfur content: 0.5% by mass, phosphorus content; 0.002% by mass) as a carbonaceous material is charged into the top-bottom blow converter. Then, 0.5 ton of quick lime was charged and refined by supplying a total amount of 3000 Nm ³ of gaseous oxygen from the top blowing lance while blowing nitrogen gas as a stirring gas from the bottom blowing tuyere.

  After refining, the chrome-containing hot metal was poured into the hot metal holding container, resulting in 142 tons of chrome-containing hot metal having a carbon concentration of 5.5% by mass (other components are the same as before refining) and a temperature of 1450 ° C. It was. The carburized chromium-containing hot metal was charged into a holding furnace and mixed with 700 tons of chromium-containing hot metal held in the holding furnace. As a result, 842 tons of chromium-containing hot metal having a carbon concentration of 3.8% by mass (the other components are the same as those of the chromium-containing hot metal in the hot metal holding furnace) was obtained.

Treatment time: discharge of chrome-containing hot metal from hot metal holding furnace; 20 minutes, charging of chrome-containing hot metal into converter; 10 minutes, refining time; 10 minutes, hot water from converter; 10 minutes, hot metal holding furnace It was 20 minutes and the total was 70 minutes.
[Comparative example]
The hot metal holding furnace shown in FIG. 1 is charged with about 700 tons of chromium-containing hot metal and an average of about 300 tons of stainless steel scrap per day, and the inside of the hot metal holding furnace is heated by an 8 MW channel type induction heating device. The chromium-containing hot metal was heated, the charged stainless steel scrap was melted in a hot metal holding furnace, and an average of about 1000 tons of chromium-containing hot metal was supplied to the decarburization and refining facility in the next step. The chromium-containing hot metal charged in the hot metal holding furnace is made by smelting reduction treatment of chromium ore.

  By this operation, in the hot metal holding furnace, carbon concentration: 3.5% by mass, silicon concentration; 0.01% by mass, manganese concentration; 0.10% by mass, phosphorus concentration; 0.030% by mass, sulfur concentration; 840 tons of chromium-containing hot metal having a concentration of 0.010% by mass, a chromium concentration of 13.0% by mass and a temperature of 1380 ° C. was formed in the hot metal holding furnace.

  5% low phosphorus coke (pure carbon content: 85% by mass, sulfur content; 0.5% by mass, phosphorus content; 0.012% by mass) is added to the chromium-containing hot metal in the hot metal holding furnace through the charging port. 0.0 ton was added, and the chromium-containing hot metal in the hot metal holding furnace was heated and held with a grooved induction heating apparatus for 70 minutes corresponding to the total processing time of the present invention.

  After holding for 70 minutes, a sample for analysis was collected from the chromium-containing hot metal in the hot metal holding furnace, and the components of the chromium-containing hot metal were analyzed. As a result, the carbon concentration of the chromium-containing hot metal in the hot metal holding furnace was 3.6% by mass, and the sulfur concentration was 0.012% by mass (other components and temperatures were the same as those before holding for 70 minutes). In other words, the carbon concentration of the chromium-containing hot metal increased by 0.1% by mass, but the sulfur concentration of the chromium-containing hot metal increased by 0.002% by mass due to the sulfur contained in the low phosphorus coke.

[Contrast of inventive example and comparative example]
The amount of anthracite (carbon material) used in the examples of the present invention is 5.95 tons (7.0 × 0.85) in terms of pure carbon, and the carbon concentration of 840 tons of chromium-containing hot metal in the hot metal holding furnace is increased by 0.3% by mass. Thus, the carbonization yield of anthracite was 42% by mass. In contrast, in the comparative example, the amount of low phosphorus coke used (carbon material) is 4.25 tons (5.0 × 0.85) in terms of pure carbon, and the carbon concentration of 840 tons of chromium-containing hot metal in the hot metal holding furnace. Was increased by 0.1% by mass, and the carbonization yield of the low phosphorus coke was 20% by mass. In the comparative example, an increase in the sulfur concentration of the chromium-containing hot metal occurred.

  That is, it was confirmed that the carbon content of the chromium-containing hot metal can be efficiently increased by applying the present invention.

DESCRIPTION OF SYMBOLS 1 Hot metal holding furnace 2 Outlet 3 Charger 4 Sampling port 5 Induction heating device 6 Hot metal 7 Iron skin 8 Refractory

Claims (4)

A method of operating a hot metal holding furnace equipped with an induction heating device, supplying hot metal held as a raw material to a decarburization refining facility for producing molten steel,
Adding steel scrap to the hot metal held in the hot metal holding furnace, induction heating the hot metal with the induction heating device to dissolve the steel scrap in the hot metal,
Thereafter, a part of the hot metal in the hot metal holding furnace, in which the steel scrap is melted, is discharged from the hot metal holding furnace, and the discharged hot metal is charged into a converter type reaction vessel equipped with an upper blowing lance for acid feeding,
Supplying carbonaceous material and gaseous oxygen to the hot metal contained in the converter reactor, increasing the carbon content of the hot metal while heating the hot metal in the converter reactor,
Next, the hot metal in the converter type reaction vessel is discharged from the converter type reaction vessel, and the discharged hot metal is charged into the hot metal holding furnace and mixed with the hot metal in the hot metal holding furnace. Method of operating the holding furnace.   The hot metal held in the hot metal holding furnace is a chromium-containing hot metal obtained by melting treatment or smelting reduction treatment of a chromium source, and the steel scrap is stainless steel scrap. The operating method of the hot metal holding furnace described in 1.   A CaO-based solvent is added to the hot metal charged in the converter-type reaction vessel, and a part of sulfur contained in the hot metal and the carbonaceous material is converted into a converter by hatching the CaO-based solvent. The operation method of the hot metal holding furnace according to claim 1, wherein the hot metal holding furnace is removed in a slag formed in a reaction vessel.   In the converter type reaction vessel, the hot metal is heated to a temperature of 1400 ° C or higher, and the carbon content of the hot metal is increased to 4.0 mass% or more. The operating method of the hot metal holding furnace of any one of these.

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