JP6685260B2 - Method for refining molten iron and method for analyzing composition of slag - Google Patents

Description

  The present invention relates to a method for refining molten iron for producing hot metal or molten steel from hot metal as a raw material, and a composition analysis method and composition analysis apparatus for high-temperature substances used at that time, and more specifically, a composition of slag produced in refining molten iron. Quantitative analysis of the slag, leaving a portion of the slag whose composition has been clarified in the converter-type smelting furnace in the state where the slag remains in the next step of refining molten iron or refining molten iron for the next charge. The present invention relates to a refining method performed in a converter-type refining furnace, and a composition analysis method and a composition analysis apparatus capable of accurately quantitatively analyzing the composition of a high temperature substance such as slag used at that time. Here, the molten iron means molten pig iron or molten steel.

  In recent years, various hot metal pretreatment techniques and hot metal decarburization treatment techniques have been developed due to the need to balance environmental considerations such as carbon dioxide gas emission regulations and high productivity. Under these circumstances, one of the novel hot metal pretreatment technologies is to continuously perform hot metal desiliconization treatment and dephosphorization treatment using a single converter-type refining furnace with an intermediate slag process interposed therebetween. Processing techniques have been proposed.

For example, in Patent Document 1, first, the basic amount of slag ((mass% CaO) / (mass% SiO ₂ )) is added in an amount of CaO-based solvent such that it falls within the range of 0.3 to 1.3. After performing the desiliconization treatment in the converter-type refining furnace, tilt the converter-type refining furnace to discharge the slag generated in the furnace from the furnace mouth, and then add the CaO-based solvent medium. There has been proposed a hot metal pretreatment technique for dephosphorizing the hot metal left in the furnace.

However, in general, since the basicity of slag during desiliconization varies depending on the SiO ₂ generated by the desiliconization, in Patent Document 1, the basicity of slag deviates from the above range and the intermediate discharge It may happen that it becomes difficult to discharge the slag at the slag. Further, in Patent Document 1, the slag is discharged after the dephosphorization treatment, and although the amount is small, the hot metal remains in the furnace, and this hot metal is also discharged together with the slag, resulting in a decrease in iron yield.

  Further, also regarding decarburization treatment for producing molten steel from molten pig iron, a treatment for continuously performing dephosphorization treatment and decarburization treatment of molten pig iron by using one converter-type refining furnace with an intermediate slag step interposed therebetween. Technology is proposed.

  For example, in Patent Document 2, using one converter-type refining furnace, first, dephosphorization treatment of hot metal is performed, then the slag generated by tilting the furnace body is discharged, and then left in the furnace. After decarburizing the molten hot metal and tapping the molten steel from the converter-type refining furnace, the molten iron of the next charge is transferred to the converter-type refining furnace while leaving the slag generated by the decarburizing treatment. A refining technique has been proposed in which the molten iron is charged and then subjected to the dephosphorization treatment and the decarburization treatment of the next charge in the above order. According to Patent Document 2, by intentionally leaving the slag after the decarburization treatment, reduction of CaO-based medium solvent, improvement of iron yield, lowering of temperature in dephosphorization treatment and low basicity of slag are realized. I am going to do it.

However, in Patent Documents 1 and 2, the slag in the furnace is discharged by tilting the converter-type refining furnace in the slag removal process. However, if the converter-type refining furnace is tilted, the slag is removed. It cannot be fully discharged. Therefore, in Patent Literature 1 and Patent Literature 2, an undesirable phenomenon such as phosphorus reversion may occur due to the influence of the slag remaining in the converter-type refining furnace. The "Fukurin" decomposes phosphorus oxides that had been present (P ₂ O ₅₎ is in the slag moves to hot metal and molten steel, a phenomenon in which the phosphorus concentration of the molten iron and molten steel rises. Further, the slag that is performed between two refining processes in one converter-type smelting process as disclosed in Patent Document 1 and Patent Document 2 is also called “intermediate slag” or “intermediate slag process”.

  Against such a background, in Patent Document 3, one converter-type refining furnace is used, and when performing the dephosphorization process, the slag process, and the decarburization process, the slag in the slag process in the middle is sufficiently For the purpose of carrying out, in the slag process, a technology is proposed in which inert gas is blown from the tuyere installed in the furnace side of the converter-type refining furnace and the slag is discharged while being moved to the furnace mouth side by the inert gas. Has been done.

  In Patent Document 4, when one converter-type refining furnace is used and a part of the slag produced by the dephosphorization treatment is left to perform the dephosphorization treatment of the hot metal of the next charge, it is produced by the dephosphorization treatment. For the purpose of leaving a predetermined amount of slag in the furnace, the relationship between the tilt angle of the converter-type refining furnace and the residual amount of slag was measured in advance, and the furnace body was tilted based on this measurement result. Techniques for leaving a predetermined amount of slag have been proposed.

Further, in Patent Document 5, when performing desiliconization treatment and dephosphorization treatment of hot metal using one converter-type refining furnace continuously with an intermediate slag process interposed, a desiliconization treatment is performed. In order to prevent re-phosphorization, a technique has been proposed in which the composition of slag during desiliconization treatment is controlled so as not to be in the SiO ₂ saturation region.

JP, 10-152714, A JP-A-4-72007 JP-A-5-140627 JP-A-6-200311 JP, 2013-227664, A

When the present inventors perform refining of the next step of molten iron or refining of molten iron of the next charge by using a converter type refining furnace in which a part of the slag remains, the refining of the next step or the next charge In refining, confirm that it is not easy to adjust the basicity of slag ((mass% CaO) / (mass% SiO ₂ )), that is, it is not easy to add an appropriate amount of CaO-based solvent. There is. Generally, by controlling the basicity of the slag to about 1.20, it is possible to perform an appropriate dephosphorization treatment on the hot metal, but it is not possible to add more than the necessary amount of CaO-based solvent. It leads to cost increase.

  That is, in the methods for refining molten iron that have been proposed so far, it is necessary to suppress the addition amount of the slag forming agent such as CaO-based solvent to the necessary minimum amount in order to further reduce the cost. In order to realize this, it is necessary to accurately grasp the composition and residual amount of slag in the furnace before adding the slag-forming agent.

  For example, in Patent Document 1, when a CaO-based solvent is added after the slag after desiliconization, in order to calculate an appropriate CaO-based solvent addition amount, the basicity of the slag remaining in the furnace and It is necessary to know the residual amount of slag, but it is difficult to measure both accurately.

  In Patent Document 4, a predetermined amount of slag is left in the furnace, but the slag residual amount is obtained from the relationship between the tilt angle and the slag residual amount when there is no molten pig iron in the furnace. When hot metal is present in the furnace, as in the slag process in the middle of Patent Document 2, the amount of hot metal in the furnace itself changes, so even if the technique of Patent Document 4 is used, the slag in the furnace is It is not possible to accurately grasp the residual amount.

  Further, regarding the method for accurately evaluating the composition of the residual slag in the furnace, no detailed description is found in the past patent documents including Patent Documents 1 to 5. When trying to know the slag composition, a method of actually collecting a part of the slag and analyzing it on the machine side or after transporting it to the analysis room is conceivable, but in either method, the CaO-based solvent added It is unlikely that they will be quick enough to estimate and put in quantities.

  Therefore, a method of estimating the slag composition by calculation is generally used. However, in the case of the method by calculation, the estimated slag composition and the estimated slag composition can be obtained by repeatedly performing the refining of the next step or refining the molten iron of the next charge while leaving a part or all of the generated slag in the furnace. The accuracy of slag amount gradually decreases. For this reason, the difference between the actual slag composition and the calculated value becomes large, and depending on the situation, it may be difficult to continuously perform the hot metal pretreatment.

  In addition to the basicity, there is a wide variety of needs to quickly know the slag composition. For example, the MgO concentration in slag is closely related to the refractory life of the furnace body. This is because if the MgO concentration in the slag is too low, the damage to the furnace wall refractory becomes significant, but if the MgO concentration in the slag is too high, when the waste slag is used as a roadbed material, etc. It is not preferable because it may cause swelling.

  Therefore, the MgO concentration in the slag has an appropriate range, and rapid analysis of the slag composition is desired. If the MgO concentration in the slag can be quickly evaluated in the refining process, not only can the life of the furnace be extended by appropriately controlling the MgO concentration, but also if it swings to the high concentration side, slag that can be used as a material It is possible to improve productivity through sorting with and.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a converter-type refining furnace in which a part of the slag generated in the refining of molten iron remains in the converter-type refining furnace. When performing refining of molten iron in the next step of molten iron or refining of molten iron for the next charge, the slag components remaining in the furnace are measured quickly and with high accuracy, and appropriate production is performed based on this measurement result. It is to provide a method for refining molten iron, which determines the addition amount of a slag agent, and can quantitatively analyze the composition of a high temperature substance such as slag with high accuracy without collecting an analysis sample from the high temperature substance. It is an object of the present invention to provide a composition analysis method and composition analysis apparatus for a high-temperature substance.

The gist of the present invention for solving the above problems is as follows.
[1] Molten iron left in the converter-type refining furnace or the above-mentioned converter with slag generated in refining of molten iron in the converter-type refining furnace, with a part of the slag remaining in the converter-type refining furnace When refining the hot metal newly charged into the furnace-type refining furnace, the components of the slag generated in the refining of molten iron, quantitative analysis without collecting an analytical sample from the slag, based on the component analysis results, Performed in the converter type refining furnace with slag remaining, before refining in the next step refining of molten iron left in the furnace or refining of molten iron of the next charge using hot metal newly charged in the furnace and And / or a method of refining molten iron, characterized in that the amount of a slag forming agent added during refining is determined.
[2] The analysis of the components of the slag is performed by converging laser light on the surface of the slag, and at least two kinds containing at least calcium (Ca) and silicon (Si) in plasma generated by condensing the laser light. Refining the molten iron according to the above [1], which comprises measuring the luminescence intensity of the element and evaluating the basicity of the slag based on the measured luminescence intensity and / or the luminescence intensity ratio. Method.
[3] The analysis of the components of the slag is performed by converging a laser beam on the surface of the slag, and at least two kinds containing at least calcium (Ca) and silicon (Si) in plasma generated by condensing the laser beam. [1] or [2] above, which comprises: measuring the luminescence intensity of the element, and evaluating the composition of the slag based on the measured luminescence intensity and / or the luminescence intensity ratio. Method for refining molten iron.
[4] A laser beam is focused on the surface of the slag in the converter-type refining furnace, the slag being discharged from the converter-type refining furnace, or the slag in the slag storage container after discharge, and the plasma is slag surface. The method for refining molten iron according to the above [2] or [3], characterized in that
[5] The refining of the molten iron is a pretreatment of the hot metal in which a plurality of refining steps are performed by using one converter-type refining furnace, and a part of the hot metal and slag is transferred to the converter during the plurality of refining steps. While remaining in the mold smelting furnace, discharging the rest of the slag, in performing the pretreatment on the hot metal, when discharging the remaining portion of the slag, analyze the components of the slag, based on the component analysis results The method for refining molten iron according to any one of the above [1] to [4], characterized in that the amount of the slag forming agent added in the subsequent refining step is determined.
[6] The pretreatment of the molten pig iron includes a desiliconization treatment step and a dephosphorization treatment step, and between the desiliconization treatment step and the dephosphorization treatment step, a part of the molten pig iron and slag is transferred to the converter-type refining furnace. Characteristically, when discharging the rest of the slag, the components of the slag are analyzed while remaining, and the amount of the slag-forming agent to be added in the dephosphorization treatment step is determined based on the component analysis result. The method for refining molten iron according to the above [5].
[7] The refining of the molten iron is a pretreatment of the hot metal, and a part or all of the slag generated by the dephosphorization treatment of the hot metal of the precharge in the converter type refining furnace is left in the converter type refining furnace. As it is, the hot metal of the next charge is charged into the converter-type refining furnace, and the pretreatment of the hot metal of the next charge is carried out. Any one of the above-mentioned [1] to [6] Method for refining hot metal described.
[8] A dephosphorization treatment step in which one converter-type refining furnace is used, and a CaO-based solvent medium and an oxygen source are supplied into the converter-type refining furnace to dephosphorize the hot metal in the converter-type refining furnace. , Tilting the converter-type refining furnace, and discharging the rest of the slag while leaving a part of the hot metal after the dephosphorization treatment step and the slag generated in the dephosphorization treatment step in the converter-type refining furnace And an intermediate slag step for performing decarburization of molten iron by supplying a CaO-based medium solvent and an oxygen source into the converter-type refining furnace to decarburize the hot metal remaining in the converter-type refining furnace to form molten steel. A slag in the intermediate slag process in treating the molten steel after the decarburization treatment step is performed in this order in the steelmaking step of tapping the molten steel from the converter-type refining furnace to produce molten steel from the hot metal. When discharging the rest of the, the components of the slag are analyzed, and based on the results of the component analysis, the decarburizing and refining process is performed. Concrete and determines the amount of slag agent, the above-mentioned [1] to molten iron method refining according to any one of the above [4] to be added to have.
[9] A part or all of the slag generated in the decarburizing treatment step of the molten iron of the previous charge in the converter-type refining furnace is left in the converter-type refining furnace while the molten iron of the next charge is added to the converter. The method for refining molten iron according to the above [8], characterized in that the molten iron is charged into a mold-type refining furnace, and the subsequent hot metal dephosphorization treatment step is performed.
[10] Part of the slag generated in the decarburization treatment step in which a CaO-based solvent medium and an oxygen source are supplied into the converter-type refining furnace to decarburize the hot metal in the converter-type refining furnace to produce molten steel Or, while leaving the whole in the converter-type refining furnace, when charging the next charge of hot metal into the converter-type refining furnace for refining, the components of the slag generated in the decarburization treatment step are analyzed. The amount of the slag forming agent to be added in refining the molten iron of the next charge is determined based on the result of the component analysis, according to any one of the above [1] to [4]. Method of refining molten iron.
[11] A part or all of the slag generated in the dephosphorization treatment step in which a CaO-based solvent and an oxygen source are supplied into the converter-type refining furnace to dephosphorize the hot metal in the converter-type refining furnace. While remaining in the converter-type refining furnace, injecting the next charge of hot metal into the converter-type refining furnace to perform dephosphorization treatment on the hot metal, analyze the components of the slag generated in the dephosphorization treatment step The amount of the slag forming agent to be added in refining molten iron of the next charge is determined based on the component analysis result. [1] to [6] above. Method for refining molten iron.
[12] The above-mentioned [1] to any one of the above-mentioned [11], wherein the slag-forming agent whose addition amount is determined based on the result of the component analysis of the slag is a CaO-based solvent medium. Method for refining molten iron.
[13] The slag component analysis result includes the MgO content in the slag, and the slag-forming agent that determines the addition amount based on the slag component analysis result contains an MgO-based solvent. The method for refining molten iron according to any one of [1] to [12] above.
[14] The slag component analysis result includes the iron oxide content in the slag, and the slag-forming agent that determines the addition amount based on the slag component analysis result includes an iron oxide-based solvent medium. The method for refining molten iron according to any one of [1] to [13] above.
[15] Molten iron left in the converter-type smelting furnace or the slag generated by refining molten iron in the converter-type smelting furnace, with some of the slag remaining in the converter-type smelting furnace At the time of refining the hot metal newly charged in the furnace-type refining furnace, a laser beam is focused on the surface of the slag generated by the refining of molten iron, and at least iron (Fe ) Is measured, the iron oxide content of the slag is quantitatively analyzed based on the measured emission intensity, based on the analysis result, in the converter-type refining furnace with slag remaining. Performing, characterized by controlling the iron oxide content of the slag in the refining of the next step of the molten iron left in the furnace or the refining of the molten iron of the next charge using the hot metal newly charged in the furnace, Method of refining molten iron.
[16] The molten iron refining is molten iron refining in which a primary blowing process and a secondary blowing process are performed using one converter-type refining furnace, and the primary blowing process and the secondary blowing process are performed. In between, while leaving a part of the molten iron and slag in the converter-type refining furnace, discharging the rest of the slag, in refining the molten iron left in the converter-type refining furnace, in the slag When discharging the rest, quantitatively analyze the iron oxide content by focusing the laser light on the surface of the slag generated in the primary blowing step, based on the quantitative analysis result of the iron oxide content, two. The method for refining molten iron according to the above [15], characterized in that the iron oxide content of the slag in the next blowing step is controlled.
[17] The molten iron refining is molten iron refining in which a primary blowing process and a secondary blowing process are performed using one converter-type refining furnace, and the primary blowing process and the secondary blowing process are performed. In between, a part of the molten iron and slag is discharged to the converter type refining furnace while the remaining part of the slag is discharged, and a refining method for refining the molten iron left in the converter type refining furnace is continued. When applying the hot metal having two or more charges, the slag produced in the secondary blowing step of the pre-charged hot metal in the converter type refining furnace is partially or wholly left in the converter type refining furnace as follows. Charge hot metal into the converter-type refining furnace, when performing the primary blowing step of the next charge hot metal, laser light on the surface of the slag generated in the secondary blowing step of the hot metal of the previous charge To analyze the iron oxide content quantitatively, and based on the results of the quantitative analysis of the iron oxide content. Te, and controlling the iron oxide content of the slag in the primary blowing process of the next charge molten iron, molten iron method refining according to the above [15] or the [16].
[18] When controlling the iron oxide content of slag in the primary blowing step or the secondary blowing step, the supply rate of gaseous oxygen, the lance height of the upper blowing lance for supplying gaseous oxygen, the bottom The molten iron refining method according to the above [16] or [17], characterized in that the iron oxide content is controlled by adjusting one or more conditions of the flow rate of the blowing gas.
[19] Any of the above [16] to [18], wherein the primary blowing step is hot metal desiliconization treatment and the secondary blowing step is hot metal dephosphorization treatment. 2. The method for refining molten iron according to item 1.
[20] The above-mentioned [16], wherein the primary blowing step is a dephosphorization treatment of the hot metal, and the secondary blowing step is a decarburization treatment of decarburizing the hot metal to obtain molten steel. To the molten iron refining method according to any one of [18] above.
[21] The molten iron refining is molten iron refining in which a primary blowing process and a secondary blowing process are performed by using one converter-type refining furnace, and the primary blowing process and the secondary blowing process are performed. In between, while leaving a part of the molten iron and slag in the converter type refining furnace, discharging the rest of the slag, a refining method for refining the molten iron left in the converter type refining furnace, continuous, In applying the molten iron of 2 charges or more, the slag generated in the secondary blowing step of the previously charged molten iron in the converter-type refining furnace was left in the converter-type refining furnace without being discharged to the outside of the furnace. As it is, the hot metal of the next charge is charged into the converter-type refining furnace, and when performing the primary blowing process of the hot metal of the next charge, before and after the secondary blowing process of the hot metal of the previous charge, Quantitative analysis of the components, quantitative analysis of the components of the slag before and after the secondary blowing process Based on the result and the amount of the slag forming agent in the secondary blowing step to obtain the amount of slag after the secondary blowing step, the obtained slag amount of slag in the primary blowing step of the hot metal of the next charge The method for refining molten iron according to any one of the above [1] to [20], which is used for control.
[22] A method for quantitatively analyzing the components of the slag collects laser light on the surface of the slag, measures the emission intensity of an element in plasma generated as the laser beam is collected, and measures the measured emission intensity and And / or a method for quantitatively analyzing the components of the slag based on the emission intensity ratio, and measuring a distance between a condenser lens for condensing the laser light on the surface of the slag and a slag surface for condensing the laser light. However, the position of the condenser lens is adjusted so that the distance between the condenser lens and the surface of the slag is a predetermined value, any one of the above [1] to [21]. Refining method of molten iron described in.
[23] A laser beam is focused on the surface of an object to be analyzed at a high temperature of 800 ° C. or higher, and the emission intensity of an element in plasma generated by the concentration of the laser beam is measured, and the measured emission intensity and / or A composition analysis method of a high temperature substance for evaluating a composition of an analysis object based on a light emission intensity ratio, wherein a predetermined distance is provided from an optical axis of a condenser lens for condensing the laser light, and An image pickup device whose relative position is fixed with respect to the object picks up an image of the emission of the laser beam on the surface of the object to be analyzed, and the emission of the laser beam collected by the imager at the point of collection. The composition analysis method for a high-temperature substance, characterized in that the position of the condenser lens is adjusted so that the distance between the condenser lens and the surface of the slag has a predetermined value, based on the position information.
[24] A laser beam is focused on the surface of an object to be analyzed at a high temperature of 800 ° C. or higher, and the emission intensity of an element in plasma generated with the concentration of the laser beam is measured, and the measured emission intensity and / or A composition analyzer for a high-temperature substance that evaluates the composition of the analyte based on the emission intensity ratio, wherein the laser light is movable in the direction of the optical axis of the condenser lens with respect to the analyte. A condensing lens for condensing, and a surface of the analysis object, which is arranged at a position separated from the optical axis of the condensing lens by a predetermined distance and fixed relative to the condensing lens. An image pickup device for picking up the light emission of the laser beam at the focus position, and the focusing lens and the slag surface based on the position information of the light emission of the focus position of the laser light sampled by the image pickup device. The distance to and is set to a predetermined value It characterized by having a a mechanism for adjusting the position of the focusing lens, the composition analyzer hot material.

  According to the method for refining molten iron according to the present invention, while leaving a part of the slag generated in the refining of molten iron in the converter-type refining furnace, using this converter-type refining furnace, the next step of the molten iron When refining or refining the molten iron of the next charge, the components of the slag remaining in the furnace are quantitatively analyzed quickly and with high accuracy without collecting an analytical sample from the slag. Therefore, it is possible to determine an appropriate addition amount of the slag forming agent or a blowing condition for appropriately controlling the production amount of iron oxide.

  Further, according to the composition analysis method and composition analysis apparatus for a high-temperature substance according to the present invention, it is possible to accurately quantitatively analyze the composition of a high-temperature substance such as slag without collecting an analysis sample from the high-temperature substance. .

It is a figure which shows the peak intensity of the spectrum when the slag A with low basicity and the slag B with high basicity are evaluated by each emission line of the iron of wavelength 271nm, the silicon of 288nm, and the calcium of 318nm. It is a schematic diagram showing an example of composition of a slag ingredient analysis system based on a LIBS method. It is a figure which shows the relationship between the slag basicity calculated | required by the LIBS method, and the slag basicity calculated | required by the fluorescent X-ray analysis method.

  In order to solve the above problems, the inventors include a step of intentionally leaving the slag generated by the refining of molten iron, and utilizing the remaining slag in the refining of the next step or the refining of the molten iron of the next charge. The characteristics and environment of the hot metal refining process were scrutinized. As a result, the inventors of the present invention have conceived as a means for solving the above problems, a method of rapidly quantitatively analyzing the slag composition by non-contact spectroscopic measurement without collecting the slag in the furnace or at the time of slag. Here, "to intentionally leave the slag" means that the slag is left inside the furnace by adjusting the tilt angle of the furnace body without performing the slag operation that inverts the furnace body with the furnace mouth facing downward. However, this also includes the case where the slag is solidified to adhere and remain on the inner wall of the furnace body and is used as a slag agent for refining the next charge. However, this does not include the case where slag is attached for the purpose of protecting the inner wall of the furnace body and at least a part of the slag remains attached for two or more charges.

  That is, for example, as disclosed in Patent Document 1, after the desiliconization treatment in the hot metal pretreatment, there is a slag process of tilting the converter-type refining furnace to discharge the slag from the furnace opening. We found that slag can be observed relatively easily during the slag process. During refining, it is difficult to analyze the slag, which is the object of measurement, by non-contact spectroscopic measurement because of the interference of flames due to the combustion of carbon monoxide gas and large amounts of dust, but before and after the slag treatment process. Is suitable for non-contact spectroscopic measurement without generation of flame or dust.

Among the slag compositions, the basicity of the slag ((mass% CaO) / (mass% SiO ₂ )) has a great influence on the slag viscosity and dephosphorization efficiency during refining, so there is a great need for analysis. The basicity of slag can be quickly and quantitatively evaluated on-site without taking a sample from the slag. Since it can be processed, it has great industrial significance.

In order to quantitatively evaluate the basicity of the slag, it is necessary to quantitatively analyze the CaO content and the SiO ₂ content of the slag. Usually, calcium (Ca) and silicon (Si) exist in the form of oxides in the slag during slag, and no other form other than oxides of calcium and silicon exists in the slag during slag. Therefore, in the case of analysis using a light emission method, the CaO content and the SiO ₂ content of the slag can be quantitatively analyzed by quantifying the elemental compositions of calcium and silicon.

For example, by using Laser Induced Breakdown Spectroscopy (“LIBS method”) suitable for analysis from a remote location, calcium and silicon in slag can be easily excited and emitted, and the basicity of the slag can be increased. It becomes possible to quantitatively evaluate. That is, using the LIBS method, the laser light is focused on the surface of the slag, the emission intensity of calcium and silicon in the plasma generated with the concentration of the laser beam is measured, and the measured emission intensity and / or emission intensity is measured. It becomes possible to grasp the basicity of the slag by quantitatively analyzing the CaO content and the SiO ₂ content of the slag based on the ratio.

  When the slag sampled from the inside of the furnace was cooled to room temperature and analyzed by the LIBS method, clear spectra of calcium and silicon could be confirmed in the visible region that could be easily detected by a small spectroscope. Further, as a result of analyzing a sample having a known stoichiometric ratio, it was confirmed that the peak intensity of the spectrum changes depending on the contents of calcium and silicon in the sample. In actual slag, various coexisting elements exist in addition to calcium and silicon. Therefore, depending on the situation, it may be necessary to prepare a calibration curve in consideration of coexisting element correction in advance and calculate the slag basicity.

  In FIG. 1, a slag A having a low basicity (basicity = 0.80) and a slag B having a high basicity (basicity = 4.00) are used as iron (Fe) having a wavelength of 271 nm and silicon (Si) having a wavelength of 288 nm. ), And the peak intensity of the spectrum when evaluated by each emission line of calcium (Ca) of 318 nm. As shown in FIG. 1, it can be seen that in slag A and slag B, spectra with sufficient peak intensities can be detected.

On the other hand, MgO and FeO _x in the slag are also required to be analyzed because the productivity can be improved if the content rates can be controlled. The MgO content and the FeO _x content in the slag can be quantified as well as CaO and SiO ₂ by using the LIBS method. In addition, P ₂ O ₅ in the slag can be quantitatively analyzed by using the LIBS method similarly to CaO and SiO ₂ . Note that FeO _x refers to all iron oxides such as FeO and Fe ₂ O ₃ .

  Regarding the application of the LIBS method to slag analysis, some references have been recognized in the past, but when applied to the steelmaking process, it is necessary to quantify the slag composition using an appropriate means. The inventors of the present invention recognize that there are roughly two problems in order to obtain a method that can be put to practical use, based on the results of past studies.

  Specifically, they are (A) discrimination between molten iron and slag, and (B) evaluation of slag composition (absolute value). Problem (A) is an analysis point at which laser light is focused, and in the actual manufacturing process, only slag does not always exist, and therefore, it is necessary to identify when the analysis point is molten iron. Regarding the problem (B), the primary information obtained by the LIBS analysis is the emission intensity, and it is necessary to use a reliable calibration curve in order to convert this into the concentration. However, in the actual measurement at the manufacturing site, if the same measurement conditions as when the calibration curve was created cannot be guaranteed, it will be difficult to convert the concentration to an accurate concentration using the calibration curve.

The present inventors have come up with the following method as a proposal that can solve the problems (A) and (B) and can be applied to an actual manufacturing site. In order to simplify the description, the case of slag analysis of a ternary system of CaO, SiO ₂ , and FeO _x will be described below.

First, prepare several kinds of slag to be used as standard samples with known contents, which have close to the composition range of the slag to be analyzed, the concentration of oxide to be analyzed is changed, and the conditions for actual on-site analysis are set. Perform LIBS analysis of the slag prepared as a standard sample in a state as close as possible. Next, a tentative calibration curve is created from the emission intensity of each element and the previously analyzed contents, and the emission intensity I (X) ₀ per unit concentration of each oxide is determined. Here, X represents the metal element in each metal oxide.

For example, when the emission intensity obtained by LIBS analysis is 5000 cps for the slag containing 40% by mass of CaO, the emission intensity I (Ca) ₀ per unit concentration of CaO is calculated as 125 cps /% by mass. Similarly, the emission intensity I (Si) ₀ per unit concentration of SiO ₂ and the emission intensity I (Fe) ₀ per unit concentration of FeO _x are also obtained. The emission intensities I (Ca), I (Si), and I (Fe) of the respective elements obtained when the slag analysis was actually carried out on-site were taken as I (Ca) ₀ , I (Si) ₀ , and I ( By dividing by Fe) ₀ , the temporary concentrations (% CaO) ′, (% SiO ₂ ) ′, and (% FeO _x ) ′ of each oxide are calculated and obtained. The total of the temporary concentrations of the obtained oxides is generally not 100% by mass due to the difference between the measurement conditions at the time of creating the calibration curve and the actual slag analysis, but the total is 100% by mass. The actual content can be calculated by converting it into That is, in the case of CaO, "(% CaO) '× 100 / {(% CaO)' + (% SiO ₂ ) '+ (% FeO _x )'}" is the actual CaO concentration in the slag (mass%) Can be asked as

As oxides contained in the slag, other oxides such as Al ₂ O ₃ , TiO ₂ , MgO, MnO, and P ₂ O ₅ are considered. If the same method as the above is carried out so as to cover all, it becomes possible to perform quantitative analysis by expanding to a multi-component slag other than the above-mentioned three-component system. Moreover, it is desirable to prepare a standard sample containing an element expected in the field, and it is possible to perform a highly accurate analysis by preparing a sample having a composition close to the actual slag. Depending on the element, the emission intensity per unit concentration may change if the concentrations of coexisting components change greatly, so it is also effective to divide the concentration range and prepare standard samples for quantitative analysis. It is a means. Further, it is considered that the temperature of the slag on the molten iron is 1000 ° C. or higher at the actual analysis site, which may be different from the case where the LIBS emission intensity of each element is analyzed at room temperature. Therefore, even when the standard sample is analyzed in advance and the emission intensity per unit concentration is calculated, it is desirable to prepare a heating furnace or the like and perform the analysis in a state close to the slag temperature at which the analysis is actually performed.

Here, when it is important to know the composition ratio of a specific element like slag basicity, it does not matter so much, but in the analysis of MgO and FeO _x , it is important to know the content itself, not the composition ratio. In many cases, it is necessary to distinguish between slag and molten iron (problem (A)) when FeO _x is analyzed.

  Several methods can be considered as means for doing this. For example, a method in which the intensity of radiant light is different between molten iron and slag is used, and the radiant light intensity at the analysis point is separately measured and discriminated. . As a simpler method, it is possible to distinguish between the light emission corresponding to the slag and the light emission corresponding to the molten iron by using the emission intensity of the component contained in the slag in a large amount and hardly contained in the molten iron. . This method can be preferably used, for example, for the Ca emission intensity when analyzing the slag basicity. The threshold value is set in advance by the emission intensity of Ca, and the case where the emission intensity equal to or higher than the threshold value is obtained can be identified as the emission intensity corresponding to the slag. In the case of LIBS analysis, the laser focusing region is on the order of several tens of μm, and it is unlikely that molten iron and slag are mixed in the analysis region. However, even if both are mixed, it can be determined as an abnormal value by determining both the emission intensities of Ca and Fe based on the threshold value.

  Fe is also present in the slag as FeO, but since the difference in the emission intensity from the molten iron is large, it is possible to discriminate the mixture of the molten iron and the slag with high accuracy by combining with the emission intensity of Ca, and exclude from the slag analysis. It is possible. Usually, the pulse laser used in the LIBS analysis has a frequency of several tens Hz, and even if the light emission due to the analysis of the non-slag component that occurs at low frequency is removed, information having statistical accuracy can be obtained in a short time of several seconds to several tens seconds. Obtainable.

  Further, when analyzing Ca (CaO) or Mg (MgO) that is concentrated in slag and hardly exists in molten iron, the distinction between slag and molten iron does not matter, but slags such as Si, Mn, and P and molten iron In the case of elements that can be contained in both of the above, it is necessary to determine whether the light emission source is slag or molten iron. This can be realized by a method of distinguishing the light emission corresponding to the slag and the light emission corresponding to the molten iron, or by utilizing the difference in luminance between the slag and the molten iron at the same temperature. In addition, it is possible to use a method of directly observing the laser irradiation position by installing a camera or the like and determining whether the laser irradiation position is slag, hot metal, or molten steel.

As an alternative to the basicity of slag ((mass% CaO) / (mass% SiO ₂ )), by using ({(mass% CaO) + (mass% MgO)} / (mass% SiO ₂ )), It is possible to manage furnace refractories and expandability of slag. Also, as an alternative to the basicity of slag, by using ((mass% CaO) / {(mass% SiO ₂ ) + (mass% P ₂ O ₅ )}), it is possible to know the dephosphorization capacity of the slag. You can

  Hereinafter, one embodiment of the present invention, which is conceived from the above technical idea, including a refining step of performing a pretreatment of molten pig iron with an intermediate slag sandwich, and a refining step of producing molten steel from molten pig iron with an intermediate slag pile An embodiment of the present invention including the above will be described.

  In the hot metal pretreatment that performs desiliconization treatment and dephosphorization treatment with an intermediate slag sandwiched between them, in order to determine the proper addition amount of CaO-based medium solvent without excess or deficiency, in the furnace before the dephosphorization treatment It is necessary to know the composition and amount of residual slag. As the CaO-based solvent for controlling the CaO content in the slag, decarburizing slag (“converter slag”, “decarburizing furnace”, “decarburizing furnace”) produced during decarburizing treatment of quicklime, limestone, slaked lime, dolomite, and hot metal is used. Also referred to as "slag").

  Conventionally, as a method for analyzing the composition of slag, for example, slag is collected after the completion of desiliconization, the collected slag is sent to an analysis room, and the slag composition is analyzed using an analyzer such as a fluorescent X-ray analysis method. A method is being considered. However, in this method, since the slag is subjected to the analysis after the sample preparation, it takes a lot of time until the composition of the slag is determined, and the addition amount of the CaO-based solvent in the dephosphorization treatment is determined. Is not in time. As a result, when the CaO-based solvent is added more than necessary, or conversely, the amount of CaO-based solvent added is insufficient, the slag basicity is lowered, and the dephosphorization ability is lowered, resulting in a sufficient Dephosphorization could not be performed frequently, or it took time to reach a predetermined phosphorus (P) concentration.

  In one embodiment of the present invention, which includes a refining process in which hot metal is pretreated with an intermediate slag sandwiched between the slag compositions, the slag composition is quantitatively analyzed without collecting the slag in order to quickly analyze the slag composition. Specifically, using one converter-type refining furnace, a desiliconizing step of desiliconizing the hot metal tapped from the blast furnace, and leaving the desiliconized hot metal in the converter-type refining furnace In this state, an intermediate slag process for discharging the desiliconization slag generated in the desiliconization process from the converter-type refining furnace, and a dephosphorization process for dephosphorizing the hot metal remaining in the converter-type refining furnace. In the method of pretreatment of molten pig iron, in which a phosphorus treatment step and a tapping step of tapping the dephosphorized molten pig iron from the converter-type refining furnace are performed in this order, laser light is focused on the slag surface during intermediate slag Thus, the slag composition and the slag basicity are quantitatively evaluated by irradiating the laser light and measuring the light intensity according to each element in the plasma generated by the irradiation of the laser light.

  That is, the conventional desiliconization treatment is performed by supplying CaO-based medium solvent, and gaseous oxygen (also called "gaseous acid") or iron oxide as an oxygen source to the hot metal in the converter-type refining furnace. After that, the furnace is tilted to the side opposite to that at the time of tapping, that is, the side opposite to the side where the tap hole is installed, and slag is discharged (intermediate sludge) through the furnace port. In this intermediate sludge process, the slag composition is directly quantitatively analyzed by the LIBS method. For example, it is possible to analyze the composition of the slag by irradiating the slag with a laser immediately before, during, or after the slag is discharged from the converter-type refining furnace to the slag container. Hereinafter, an example of a method for suitably analyzing the slag composition using the LIBS method will be described.

  FIG. 2 is a schematic diagram showing a configuration example of a slag component analysis system based on the LIBS method. In FIG. 2, reference numeral 1 is a converter-type refining furnace, 2 is a furnace mouth, 3 is a bottom blowing tuyere, 4 is hot metal, 5 is slag, 6 is a laser light generator, 7 is a condenser lens, and 8 is laser light. , 9 is a light receiving part, 10 is an optical fiber, 11 is a spectrophotometer, 12 is a computing computer, 13 is an image pickup device, and 14 is a slag container.

For example, at the time of intermediate slag after desiliconization, the converter-type smelting furnace 1 is tilted so that the slag 5 existing on the hot metal 4 is placed directly below the converter-type smelting furnace 1 from the furnace port 2. It is discharged into the container 14. At that time, the laser light 8 generated by the laser light generator 6 is condensed on the surface of the slag 5 being discharged through the condenser lens 7, and plasma is generated on the surface of the slag 5. The light of the plasma is observed by the light receiving unit 9, and the light receiving unit 9 guides the observed light of the plasma to the spectroscope / photometer 11 via the optical fiber 10. The spectroscope / photometer 11 measures the emission intensity of two or more kinds of elements containing at least calcium and silicon from the received plasma light, and based on the measured emission intensity and / or the emission intensity ratio, CaO of slag. Quantitatively analyze the content and the SiO ₂ content. The quantitative analysis result is transmitted to and stored in the computing computer 12.

  In FIG. 2, the laser light 8 is focused on the surface of the slag 5 being discharged from the converter-type refining furnace 1 to analyze the components of the slag 5, but as long as it is in the intermediate discharge, The laser beam 8 may be focused on the surface of the slag 5 in the converter-type refining furnace or the surface of the slag 5 in the discharged slag container 14 to analyze the components of the slag 5.

  From the viewpoint of protecting the laser light generator 6 and the light receiving portion 9 from radiant heat and splash, the greater the distance from the slag 5 to be analyzed, the more advantageous it is. It is disadvantageous in terms of measurement sensitivity. Therefore, it is desirable to generate plasma on the slag surface by laser irradiation / focusing from a distance of 1 to 10 m away from the slag in the slag.

  The light of the plasma is received by the light receiving unit 9 arranged in the immediate vicinity of the laser light generator 6, and then guided to the spectroscope / photometer 11 set at a position 10 to 15 m away. It is preferable that the laser light generator 6 and the light receiving portion 9 are provided with heat resistance protection and then are arranged at appropriate places, and dust is prevented by spraying an inert gas from the vicinity.

  Here, regarding the irradiation of laser light, a laser light generator is placed at a location away from the converter-type refining furnace, the laser light is guided to the vicinity of the measurement part through an optical fiber, and the laser light is condensed using optical parts.・ You can irradiate. Further, as far as the spectroscopic / photometric system is a system that can obtain appropriate sensitivity, the spectroscopic / photometric system may be arranged at a sufficiently distant place in order to avoid thermal influence in the vicinity of the converter-type refining furnace.

  Since the actual position of the slag surface is not always constant, it is desirable to provide an optical device capable of sequentially detecting and correcting the condensing point. That is, as the device, the condensing lens 7 for condensing the laser light is combined with the light receiving portion 9 (light receiving lens) for measuring the emission of plasma and the imaging device 13 for measuring the emission position of plasma. The measuring device is integrally configured as a tip portion, and at least the tip portion is provided with a mechanism (not shown) that is movable in the direction of the optical axis of the condenser lens 7 with respect to the slag surface. In this case, not only the tip portion, but the entire device may be moved on a support frame (not shown).

  Here, the image pickup device 13 for measuring the light emission position of the plasma is separated from the optical axis of the condenser lens 7 by a predetermined distance, and is set at a position fixed relative to the condenser lens 7. According to the principle of triangulation, the distance between the tip of the measuring device such as the condenser lens 7 and the slag surface can be calculated based on the position information of the plasma emission collected by the imaging device 13, and the calculation computer 12 or the like can be used. It can be calculated using The driving device (not shown) at the tip of the measuring device is controlled by using the computing computer 12 or the like so that the calculated distance between the condensing lens and the slag surface becomes a predetermined value. Adjust the position of.

  By doing this, even if the position of the slag surface changes, by moving the tip of the measuring device to follow it, fluctuations in plasma generation efficiency and plasma emission detection sensitivity are suppressed. Then, the measurement can be performed under a relatively constant condition, the analysis accuracy is improved, and the labor can be saved by automating the measurement.

  In addition, in the above, the case where the molten slag discharged at the time of intermediate slag was analyzed was described, but the above-described measuring device and measuring method are not limited to this case, and the position of the high-temperature substance to be analyzed varies. It is useful in cases where the At this time, if the temperature of the substance to be analyzed is low, a commercially available laser rangefinder or the like can be used to measure the distance between the condenser lens 7 and the substance to be analyzed, but at a high temperature of 800 ° C. or higher, It is difficult to detect the light emitting position with high accuracy unless such a high energy density laser beam for plasma generation is used. Further, when the analysis is continued for a long period of time, it is preferable that the state of the apparatus can be regularly checked.

  The spectroscope / photometer 11 analyzes each component of the slag based on the measured light intensity of each element based on a calibration curve prepared in advance.

  FIG. 3 is a diagram showing the relationship between the slag basicity obtained by the LIBS method and the slag basicity obtained by the fluorescent X-ray analysis method. As shown in FIG. 3, it was confirmed that there was a good linear relationship between the two. That is, it is understood that by applying the LIBS method, the basicity of the slag can be evaluated with substantially the same accuracy and precision as the method performed in the step analysis such as the fluorescent X-ray analysis method.

  After that, the amount of CaO-based solvent added in the dephosphorization process in the next step was determined based on the slag basicity determined by the LIBS method and the residual slag amount in the furnace to dephosphorize the hot metal remaining in the furnace. The slag basicity required for the treatment is determined, and the determined addition amount of the CaO-based medium solvent is added to the furnace to carry out the dephosphorization treatment step. The residual slag amount in the furnace is the difference between the slag discharge amount estimated from the mass measurement value of the slag storage container storing the slag discharged by the intermediate slag and the estimated slag mass in the furnace before the intermediate slag. Calculate as

  Regarding the dephosphorization treatment step, there is no need to change from the conventional dephosphorization treatment method in which gaseous oxygen or iron oxide is supplied into the furnace as an oxygen source, and the phosphorus concentration of the hot metal and the molten iron temperature before the dephosphorization treatment The dephosphorization treatment may be performed in a pattern that is predetermined based on the target value of the phosphorus concentration of the hot metal after the dephosphorization treatment. By collecting the slag before dephosphorization treatment at each charge and confirming the composition later by an analysis method such as X-ray fluorescence analysis, it was found that the basicity of the slag before the dephosphorization treatment was actual. You can check if.

  After the dephosphorization treatment, the hot metal is tilted in the converter-type refining furnace and tapped into the hot-metal container through the tap hole installed in the converter-type refining furnace. A part or all of the slag generated in step (referred to as "dephosphorization slag") is left in the converter-type refining furnace. After that, new hot metal (hot metal used in the next charge) is charged into the converter-type refining furnace, and desiliconization of the hot metal of the next charge is started. After the next charge, since the slag from the previous charge remains in the converter-type refining furnace, it is possible to perform desiliconization without adding CaO-based solvent, but the slag basicity is low. In that case, a CaO-based solvent is added.

  As is clear from the above description, according to an embodiment of the present invention including a refining step of preliminarily treating the hot metal with the intermediate slag sandwiched, it is possible to accurately grasp the slag basicity in the intermediate slag, This makes it possible to determine the addition amount of the CaO-based medium solvent that is suitable for the dephosphorization treatment, and to minimize the addition amount of the CaO-based medium solvent. As a result, it is possible to perform hot metal pretreatment at low cost without lowering productivity.

  In the above description, the case of the hot metal pretreatment for performing the desiliconization treatment and the dephosphorization treatment with the intermediate slag sandwiched between them is explained. The accuracy of slag composition control can be improved by applying the method.

  Further, even when molten steel is produced from molten pig iron, the present invention can be applied by the following procedure similar to the above-mentioned molten pig iron pretreatment.

  That is, a CaO-based solvent and an oxygen source are supplied into the converter-type refining furnace to perform dephosphorization treatment (also desiliconization treatment) on the hot metal in the converter-type refining furnace, and then the converter-type refining furnace. Tilt the smelting furnace and perform intermediate slag. In this intermediate sludge process, the slag composition is directly measured by the LIBS method. Regarding the decarburization process in the next step, there is no need to change from the conventional decarburization process performed by supplying CaO-based medium solvent and oxygen source into the furnace, the molten steel temperature after treatment and the phosphorus concentration of the molten steel. The target value of slag basicity is set from the target value of slag, and it is estimated from the component analysis result of the slag measured by the LIBS method and the mass measurement value of the slag storage container that stores the slag discharged in the intermediate slag. From the amount of residual slag, the amount of CaO-based solvent added is determined based on the mass balance.

  After the decarburization treatment, the produced molten steel is tilted in the converter-type refining furnace and tapped into the molten-steel container from the tap hole installed in the converter-type refining furnace, and the slag after decarburization treatment (decarburization slag ) Is partially or entirely left in the converter type refining furnace. After that, new hot metal (hot metal used in the next charge) is charged into the converter-type refining furnace, and the dephosphorization process of the hot metal of the next charge is started.

In addition, it is clear that other components in the slag can be analyzed by the same procedure. For example, by measuring and controlling the MgO content in the slag, the life of the furnace body can be extended and the expansion as a roadbed material can be achieved. It can be prepared into a slag with a small amount and a proper composition. The reason that the life of the furnace affects the MgO content in the slag is that the refractory lining refractory furnace is made of MgO-based refractory, and if the MgO content in the slag decreases, This is because MgO is eluted from the MgO-based refractory, which is a substance, and the life of the MgO-based refractory is shortened. Examples of the MgO-based solvent for controlling the MgO content in the slag include dolomite (MgCO ₃ —CaCO ₃ ), crushed products of MgO-based bricks, and magnesia clinker.

Further, by measuring and controlling the FeO _x content in the slag, an efficient dephosphorization treatment can be performed. In the dephosphorization treatment, FeO _x in the slag contributes to the oxidation of phosphorus in the hot metal and the slag slag formation. For efficient dephosphorization treatment, 5 to 15% by mass of FeO _{x in the} slag is used. Is desired to exist. Examples of the iron oxide-based solvent for controlling the FeO _x content in the slag include iron ore powder, sintered ore powder that is a mixture of iron ore and quick lime, and dust collection dust in the iron making process.

  Further, the iron oxide content in the slag is controlled by the supply rate of gaseous oxygen (also referred to as “acid transport rate”) and the lance height of the upper blowing lance for supplying gaseous oxygen (the lance height is a stationary state. It is also effective to adjust any one kind or two or more kinds of the distance between the molten iron bath surface in the furnace and the tip of the lance) and the flow rate of the gas for bottom blowing for stirring. For example, when the content of iron oxide in the desiliconization slag is as low as less than 5% by mass, the lance height is increased in the next dephosphorization process as compared with the conditions of the normal dephosphorization process. It is desired to increase the iron oxide content by reducing the flow rate of bottom-blown gas. Further, when the iron oxide content in the desiliconization slag is as high as more than 25% by mass, the lance height is decreased in the next dephosphorization step as compared with the conditions of the normal dephosphorization step. In addition, it is desirable to reduce the iron oxide content by increasing the bottom blown gas flow rate.

  The content of iron oxide in the desiliconized slag is desirably high to promote dephosphorization, but is desirably low to prevent melting loss of the refractory. Considering the above, it is desirable to control the iron oxide content in the desiliconized slag to be 5% by mass or more and 25% by mass or less. In the refining method in which the dephosphorization slag of the previous charge is left in the furnace and the hot metal of the next charge is desiliconized, the iron oxide content in the desiliconized slag can be controlled by the dephosphorization process of the previous charge. It is necessary to measure the iron oxide content in the resulting dephosphorized slag. By using the measured value of the iron oxide content in the dephosphorization slag by the LIBS method, the supply amount of gaseous oxygen and the amount of the iron oxide-based solvent used in the desiliconization treatment can be adjusted to determine the iron oxide content in the desiliconization slag. Can be controlled.

  If the iron oxide content in the dephosphorization slag of the previous charge was higher than the sum of the supply amount of gaseous oxygen and the amount of the iron oxide-based medium solvent used, the desiliconization treatment lance of the charge was By lowering the height and increasing the bottom blown gas flow rate, iron oxide production can be suppressed and the iron oxide content in the desiliconized slag can be reduced. On the contrary, if the iron oxide content in the dephosphorization slag of the previous charge was lower than the sum of the supply amount of gaseous oxygen and the amount of the iron oxide medium solvent used, the desiliconization treatment of the charge was performed. By increasing the lance height and decreasing the bottom blowing flow rate, the generation of iron oxide can be promoted and the iron oxide content in the desiliconized slag can be increased.

  The iron oxide content in the desiliconized slag can be controlled by the above method. In the method of controlling the iron oxide content in the slag described above, the iron oxide content in the slag before the refining treatment needs to be quickly measured, and the slag analysis by the LIBS method described above is applied.

  Further, even when the iron oxide content is estimated from the oxygen balance in the furnace, by analyzing the iron oxide content in the slag before refining treatment by the LIBS method, the work efficiency can be improved without sacrificing the work efficiency. The estimation accuracy of the iron oxide content in the slag is improved. A method for calculating the iron oxide content from the oxygen balance in the furnace is described in, for example, Publication 1 (Publication 1; JP2013-136831A).

In Publication 1, the amount of unknown oxygen in the furnace is obtained by subtracting the amount of oxygen discharged into the slag and the amount outside the furnace from the total amount of oxygen sources supplied to the furnace. The amount of oxygen discharged into the slag is calculated assuming changes in the Si, Mn, and P concentrations. The amount of oxygen discharged outside the furnace is calculated from the exhaust gas flow rate and the CO and CO ₂ concentrations in the exhaust gas. Assuming that the unknown oxygen amount in the furnace thus obtained is consumed for the combustion of molten iron, the iron oxide production amount is calculated. The iron oxide content concentration in the slag can be obtained by dividing the iron oxide production amount by the slag amount calculated as the sum of the amounts of the input auxiliary material and the produced oxide.

  However, in the method described in Publication 1, since the amount of the residual slag in the furnace in the previous step and the iron oxide content concentration are not taken into consideration, the slag composition measured by the LIBS method indicates that It is necessary to calculate the amount and the iron oxide content concentration, and use this as a starting point to calculate the iron oxide content concentration.

With this calculation, even if a part or the whole amount of the slag generated in the previous step is left in the furnace, the FeO _x content in the slag can be sequentially calculated. Then, the FeO _x content in the slag calculated in this way is controlled by adjusting at least one of the supply rate of gaseous oxygen, the lance height of the top blowing lance, and the bottom blowing gas flow rate. . During the desiliconization blowing, it is desirable to control the FeO _x content in the slag to be 5 to 25% by mass, and during the dephosphorization blowing, the FeO _x content in the slag is 5 to 15% by mass. It is desirable to control it during the period.

  In the above description, a hot metal pretreatment method in which a primary blowing step for performing desiliconization processing and a secondary blowing step for performing dephosphorization processing are continuously performed with an intermediate slag step interposed therebetween, or this hot metal In the pretreatment method, the hot metal for the next charge is treated while leaving at least a part of the slag after the secondary blowing step in which the pre-charge dephosphorization process is carried out without being discharged in the furnace. In the above pretreatment method, the method of accurately controlling the iron oxide content in the slag during blowing by using the measurement of the iron oxide content in the slag by the LIBS method has been described.

  However, the embodiment of the present invention is not limited to this. For example, the primary blowing step is a dephosphorization treatment of hot metal (in this case, desiliconization treatment is also included in the same primary blowing step), and the secondary blowing step The same can be applied to the case where is a decarburization treatment for decarburizing hot metal to obtain molten steel. In that case, the iron oxide content in the slag in each blowing step can be accurately controlled, and the effect of improving the efficiency of the refining agent, improving the accuracy of blowing control, and improving the iron yield or the ferroalloy yield can be obtained. It will be possible.

  INDUSTRIAL APPLICABILITY The present invention is also applicable to a refining process in which slag is intentionally left and the remaining slag is utilized for the next hot metal treatment of the charge.

  For example, when performing dephosphorization treatment (including desiliconization and dephosphorization treatment) of hot metal using one converter-type refining furnace, or decarburizing the hot metal using one converter-type refining furnace. When repeatedly performing decarburization treatment to make molten steel, in order to utilize the dephosphorization ability remaining in the slag after the treatment for the dephosphorization treatment and decarburization treatment of the hot metal of the next charge, after tapping (steel tapping), While leaving at least a part of the slag in the furnace, the molten iron of the next charge may be smelted by newly charging the molten iron into the converter-type smelting furnace. In this case, the slag component after the treatment is analyzed and evaluated by using the LIBS method to evaluate the dephosphorization ability of the slag and adjust the residual amount of the slag, or for refining the next charge. It is possible to adjust the addition amount of the slag forming agent.

  In this case, the laser light may be focused on the surface of the slag in the furnace of the converter-type refining furnace tilted during tapping, and the components of the slag may be analyzed. When discharging, the laser light may be focused on the surface of the slag being discharged or the surface of the slag in the slag container after discharging.

  Further, in the refining of molten iron in which the primary blowing process and the secondary blowing process are performed using one converter-type refining furnace, one of molten iron and slag is removed between the primary blowing process and the secondary blowing process. Part is left in the converter-type refining furnace, the rest of the slag is discharged, and the refining method of refining the molten iron remaining in the converter-type refining furnace is applied to the continuous hot metal of 2 charges or more. In the furnace-type refining furnace, the slag generated in the secondary blowing process of the pre-charged hot metal remains in the converter-type refining furnace without being discharged to the outside of the furnace, and the next-charged hot metal is converted into the converter-type refining. In order to efficiently carry out each primary blowing and each secondary blowing when charging the furnace and carrying out the method of performing the primary blowing step of the hot metal of the next charge, in order to efficiently carry out each primary blowing and each secondary blowing, It is desirable to accurately estimate the amount of slag remaining in the furnace. At this time, the increase / decrease in the amount of slag and the change in the slag component based on the components of the hot metal charged and the refining agent charged into the furnace can be evaluated to some extent accurately, but the evaluation of the amount of slag discharged in the intermediate slag Is likely to include a relatively large error.

  This is a considerable amount that is unavoidable to be mixed into the slag when the slag mass discharged from the furnace to the slag storage container 14 by the intermediate slag is weighed by the weighing device installed on the truck arranged under the furnace. This is due to the fact that the amount of molten pig iron is unknown and that the weighing device may not be maintained in a normal state due to the accumulation of a large amount of dust. The error in the estimated value of slag discharge in this intermediate slag is due to the estimation of the slag amount and slag composition in the subsequent secondary blowing process, and the slag amount in the primary and secondary blowing processes after the next charge and This may cause an error in the estimation of the slag composition, and the error may gradually be accumulated by repeating the refining method as described above.

  When the rapid analysis of the slag composition is used as in the present invention, it is possible to estimate the amount of slag remaining in the furnace without depending on the measured value of the amount of slag, as shown below. It is possible to improve the refining efficiency by reducing the factors of the error in the estimation of the slag amount and the slag composition described above.

  This is a quantitative analysis of the components of the slag before and after the secondary blowing process of the hot metal of the pre-charge, the quantitative analysis results of the components of the slag before and after the secondary blowing process and of the slag forming agent in the secondary blowing process. It is realized by obtaining the slag amount after the secondary blowing process based on the amount used and using the obtained slag amount for controlling the slag in the primary blowing process of the hot metal of the next charge. At this time, the quantitative analysis method of the slag component before and after the secondary blowing step is not necessarily limited to the LIBS method, but the method for analyzing the slag after the secondary blowing step is particularly rapid. Therefore, it is desirable to apply the LIBS method.

That is, assuming that the amounts of slag before and after the secondary blowing process are W _{S, 2i} and W _{S, 2f} , respectively, the following two equations shown in the following equations (1) and (2) are established, and these equations are combined. The slag amount W _{S, 2f} after the secondary blowing process can be obtained by solving the above.

W _{S, 2i} × (% CaO) _{m, 2i} / 100 + W _{CaO, 2} = W _{S, 2f} × (% CaO) _{m, 2f} / 100… (1)
W _{S, 2i} × (% SiO ₂ ) _{m, 2i} / 100 + W _SiO2,2 + W _HM × (X _{Si, 2i} -X _{Si, 2f} ) × (60/28) / 100 = W _{S, 2f} × ( % SiO ₂ ) _{m, 2f} / 100… (2)
However, in the formulas (1) and (2), each symbol is as follows.

W _{S, 2i} : Mass of slag before the secondary blowing process (t)
W _{S, 2f} : Mass of slag after secondary blowing process (t)
W _{CaO, 2} : Mass of CaO (t) in the slag forming agent added in the secondary blowing process
W _SiO2,2 : SiO ₂ mass (t) in the slag forming agent added in the secondary blowing step
W _HM : Hot metal mass (t) before the secondary blowing process
(% CaO) _{m, 2i} : Measured CaO concentration of slag before the secondary blowing process (% by mass)
(% CaO) _{m, 2f} : Measured CaO concentration of slag after the secondary blowing process (mass%)
(% SiO ₂ ) _{m, 2i} : Measured SiO ₂ concentration in the slag before the secondary blowing process (mass%)
(% SiO ₂ ) _{m, 2f} : Measured SiO ₂ concentration of slag after the secondary blowing process (mass%)
X _{Si, 2i} : Silicon concentration in the hot metal before the secondary blowing process (mass%)
X _{Si, 2f} : Silicon concentration (mass%) of the hot metal after the secondary blowing process
Based on the slag amount W _{S, 2f} after the secondary blowing process obtained above, the slag amount and the slag composition in the primary blowing process of the hot metal of the next charge are estimated, and based on this, the production in the primary blowing process is performed. The target slag composition can be efficiently adjusted by adjusting the addition amount of the slag agent or by adjusting the blowing conditions for appropriately controlling the production amount of iron oxide.

[Test 1]
When performing pretreatment on the hot metal by using one converter-type refining furnace with a capacity of 330 tons, desiliconization treatment (primary smelting), intermediate slag and dephosphorization treatment (secondary smelting) in this order Further, the slag composition was measured at the time of intermediate slag using the LIBS method with the apparatus having the configuration shown in FIG. At this time, the tip of the measuring device in which the condensing lens 7, the light receiving unit 9 and the imaging device 13 are integrally configured so that the distance between the condensing lens and the slag surface to be measured is almost the focal length of the condensing lens. The position is configured to be automatically adjusted in the direction of the optical axis of the condensing lens based on the measurement image of the condensing position by the imaging device 13. Based on the slag component analysis result, the amount of CaO-based solvent added in the subsequent dephosphorization treatment was calculated, and hot metal pretreatment (invention example) performed by adding the calculated amount of CaO-based solvent and The hot metal pretreatment (comparative example) according to the conventional method in which the slag composition was not measured after the silicidation was continuously carried out by 10 charges each.

  The target value of the phosphorus concentration in the hot metal at the end of the dephosphorization treatment was 0.030% by mass. In each of the present invention example and the comparative example, the slag after the dephosphorization treatment of the previous charge was left in the furnace without being discharged, and the molten iron of the next charge was charged, and the molten iron was removed with the intermediate slag sandwiched. The pretreatment of the hot metal, which was subjected to silicidation and dephosphorization, was repeated. In addition, iron scrap was added as an iron source during the desiliconization treatment.

In the desiliconization process, decarburized slag is used as the CaO-based solvent, and the calculated value (calculated basicity) of the basicity ((mass% CaO) / (mass% SiO ₂ )) of the slag after the desiliconization treatment is The amount of decarburized slag used was adjusted so that the target value was 1.20. When the calculated basicity of 1.20, which is the target value, can be secured without using decarburizing slag, desiliconization treatment was performed without using decarburizing slag. The oxygen source was supplied according to the silicon concentration in the hot metal.

  The basicity of the slag after desiliconization (desiliconized slag) was calculated by the formula (3) in the comparative example and by the formula (4) in the example of the present invention.

B _{c, Si1} (n) = [W _{S, P1} (n-1) × α ₁ × B _{c, P1} (n-1) / {B _{c, P1} (n-1) +1} + W _{SL, Si1} (n) × β ₁ ] /
[W _{S, P1} (n-1) × α ₁ / {B _{c, P1} (n-1) +1} + W _{SL, Si1} (n) × γ ₁
+ (X _Si1 (n) / 100) × W _HM1 (n) × _60/28 ]… (3)
B _{m, Si1} (n) = (% CaO) _{m, Si1} (n) / (% SiO ₂ ) _{m, Si1} (n)… (4)
However, in the expressions (3) and (4), each symbol is as follows.

B _{c, Si1} (n): Calculated basicity of slag at the end of desiliconization in the pretreatment of the nth charge
B _{c, P1} (n-1): Calculated basicity of the slag at the end of the dephosphorization treatment of the n-1th charge pretreatment
W _{S, P1} (n-1): Calculated slag mass (t) at the end of dephosphorization in the pretreatment of the n-1th charge
W _{SL, Si1} (n): Addition amount of decarburizing slag in the desiliconization process of the pretreatment of the nth charge (t)
X _Si1 (n): Silicon concentration (% by mass) in the hot metal before desiliconization in the pretreatment of the nth charge
W _HM1 (n): _Hot metal mass (t) before desiliconization in the pretreatment of the nth charge
B _{m, Si1} (n): Measured value of slag basicity by LIBS method of slag after completion of desiliconization of pretreatment of nth charge
(% CaO) _{m, Si1} (n): CaO concentration (mass%) measured by the LIBS method of the slag after the completion of the desiliconization treatment in the pretreatment of the nth charge
(% SiO ₂ ) _{m, Si1} (n): SiO ₂ concentration (mass%) measured by the LIBS method of the slag after the completion of the siliconization treatment of the pretreatment of the nth charge
α ₁ : Sum of average values of mass ratio of CaO and SiO _{2 in} slag after dephosphorization treatment β ₁ : Average value of mass ratio of CaO in decarburized slag added during desiliconization treatment and dephosphorization treatment γ ₁ : Average value of mass ratio of SiO _{2 in} decarburization slag added during desiliconization treatment and dephosphorization treatment. In this example, α ₁ = 0.6, β ₁ = 0.4, γ ₁ = 0 It was set to 1. Further, the calculation method of B _{c, P1} (n-1) and W _{S, P1} (n-1) will be described later, but in the first charge pretreatment, B _{c, P1} (0) is 0 (zero). ) Is not a constant and W _{S, P1} (0) = 0.

  The slag amount at the end of the desiliconization treatment was calculated using the equation (5) in the comparative example, and was calculated using the equation (6) in the example of the present invention.

W _{S, Si1} (n) = (W _{S, P1} (n-1) × α ₁ + W _{SL, Si1} (n) × (β ₁ + γ ₁ ) + X _Si1 (n) /
100 × W _HM1 (n) × _60/28 } / δ ₁ … (5)
W _{S, Si1} (n) = (W _{S, P1} (n-1) × α ₁ + W _{SL, Si1} (n) × (β ₁ + γ ₁ ) + X _Si1 (n) / 100 × W _HM1 (n ) × 60/28} /
{((% CaO) _{m, Si1} (n) + (% SiO ₂ ) _{m, Si1} (n)) / 100}… (6)
However, in the expressions (5) and (6), each symbol is as follows.

W _{S, Si1} (n): Calculated slag mass (t) at the end of desiliconization in the pretreatment of the nth charge
δ ₁ : Sum of average values of mass ratio of CaO and SiO _{2 in} slag after desiliconization The symbols explained in the equations (3) and (4) other than the above are as described above. In this example, δ ₁ = 0.5.

The above formulas (3) to (6) are premised on operating conditions such that the silicon content in the hot metal after desiliconization is almost 0 (zero). In the operation that leaves the silicon content in the hot metal as X _Si1 (n) in each formula, instead of the silicon concentration in the hot metal before desiliconization, the silicon concentration in the hot metal before and after desiliconization is used. The measured value or estimated value of the change may be used.

  In the intermediate slag process, the moving trolley for loading the slag storage container that stores the slag to be discharged is used so that the amount of slag to the calculated slag mass after desiliconization is 50% by mass or more of the target value. The measurement was performed while confirming the weighed value of the installed slag container by the scale.

Here, in the middle slag, the tilting angle of the converter-type smelting furnace is increased by trying to obtain a large slag speed or by reducing the residual amount of slag in the furnace when the formation of desiliconization slag is low. When the value is increased, the hot metal mixed in the slag together with the desiliconized slag is discharged to some extent from the furnace port. In this case, the amount of hot metal discharged is not always constant. However, in many cases, the mass ratio of the hot metal mixed in the desiliconization slag is relatively low and at a stable level as compared with the case of mixing in the slag after dephosphorization treatment (dephosphorization slag). Therefore, using the mass ratio of pig iron obtained from the discharged desiliconized slag sample as a representative value and calculating the mass of the discharged desiliconized slag based on the measured value of the discharged materials, in many cases Is no problem. Therefore, in this example, 0.9 times the weighed value of the discharged matter in the intermediate discharged matter was calculated as the slag mass (= W _{O, Si1} (n)) discharged after the desiliconization treatment.

In the dephosphorization treatment step, quicklime and decarburized slag are used as the CaO-based medium solvent, of which the addition amount of quicklime is set to a predetermined amount (= 2 ton) for any charge, and the calculated base of the slag after the dephosphorization treatment is used. The amount of decarburized slag used was adjusted so that the degree became 2.00 or more of the target value. If the calculated basicity was 2.00 or more of the target value without using decarburizing slag, dephosphorization treatment was performed without using decarburizing slag. The amount of gaseous oxygen (gaseous acid) used was set to a predetermined amount (2600 Nm ³ ) in any charge.

  The calculated basicity of the slag after the dephosphorization treatment (dephosphorized slag) was calculated using the formula (7) in the comparative example and the formula (8) in the example of the present invention.

B _{c, P1} (n) = [{W _{S, Si1} (n) -W _{O, Si1} (n)} × δ ₁ × B _{c, Si1} (n) / {B _{c, Si1} (n) +1} + W _{SL, P1} (n) × β ₁ +
W _{CaO, P1} (n)] / [{W _{S, Si1} (n) -W _{O, Si1} (n)} × δ ₁ / {B _{c, Si1} (n) +1} + W _{SL, P1} (n) × γ ₁ ] ... (7)
B _{c, P1} (n) = [{W _{S, Si1} (n) -W _{O, Si1} (n)} × (% CaO) _{m, Si1} (n) / 100 + W _{SL, P1} (n) × β ₁ + W _{CaO, P1} (n)] /
[{W _{S, Si1} (n) -W _{O, Si1} (n)} × (% SiO ₂ ) _{m, Si1} (n) / 100 + W _{SL, P1} (n) × γ ₁ ]… (8)
However, in the expressions (7) and (8), each symbol is as follows.

B _{c, P1} (n): Calculated basicity of slag after dephosphorization in the pretreatment of the nth charge
W _{O, Si1} (n): Mass of slag (t) discharged after desiliconization in the pretreatment of the nth charge
W _{SL, P1} (n): Addition amount (t) of decarburizing slag in the dephosphorization process of n-charge pretreatment
W _{CaO, P1} (n): Amount of quicklime added (t) in the dephosphorization process of the pretreatment of the nth charge
The symbols explained in the expressions (3) to (6) other than the above are as described above.

  The calculated slag mass at the end of the dephosphorization treatment was calculated using formula (9) in the comparative example and formula (10) in the present invention example.

W _{S, P1} (n) = [{W _{S, Si1} (n) -W _{O, Si1} (n)} × δ ₁ + W _{SL, P1} (n) × (β ₁ + γ ₁ ) + W _{CaO, P1} (n)] / α ₁ … (9)
W _{S, P1} (n) = [{W _{S, Si1} (n) -W _{O, Si1} (n)} × {(% CaO) _{m, Si1} (n) + (% SiO ₂ ) _{m, Si1} (n) } / 100 +
W _{SL, P1} (n) × (β ₁ + γ ₁ ) + W _{CaO, P1} (n)] / α ₁ … (10)
However, in the equations (9) and (10), W _{S, P1} (n) is the calculated slag mass (t) at the end of the dephosphorization treatment in the pretreatment of the nth charge. The other symbols described in the expressions (3) to (8) are as described above.

  After tapping the hot metal after the dephosphorization treatment, the dephosphorization slag was not discharged and the entire amount was left in the furnace and carried over to the next charge.

  Table 1 shows the refining results in the comparative example and the present invention example. In Table 1, among the basicities of each slag, the value shown as basicity (LIBS value) is a value measured by the LIBS method, while the value shown as basicity (sample analysis value) is a small amount collected. This is based on the analysis value of the slag component obtained by crushing the slag sample of No. 1 and dissolving it with an acid to analyze an aqueous solution sample by ICP emission spectroscopy. Since the basicity (sample analysis value) requires a long time for analysis, it is difficult to use this analysis result as data for adjusting refining conditions of the charge or the next charge.

  In the comparative example, the accuracy of estimating the basicity of the slag after the desiliconization treatment was low, and the slag basicity was largely deviated from the target value of 1.20. In addition, it is considered that the estimation error of the amount of desiliconized slag is also large, and the basicity (sample analysis value) of the slag after the dephosphorization treatment greatly varies from the target value of 2.00. As a result, a charge was generated in which the phosphorus concentration after the dephosphorization treatment was higher than the target 0.030 mass%.

On the other hand, in the example of the present invention, the basicity of the desiliconized slag was accurately measured by measuring the basicity by the LIBS method. Specifically, the measured value of the basicity (B _{m, Si1} (n)) of desiliconized slag at the time of intermediate slag has an error of standard deviation of about 0.03, and the basicity that is the actual basicity (sample Analysis value). Further, the variation of the basicity (sample analysis value) of the desiliconized slag from the target value (1.20) was also significantly reduced as compared with the comparative example in Table 1. It is considered that this is because the accuracy of estimating the composition and amount of the precharged dephosphorization slag remaining in the furnace was improved. Furthermore, since the (mass% CaO) and (mass% SiO ₂ ) of the slag after the desiliconization treatment can be quantitatively analyzed, it is considered that the estimation accuracy of the residual amount of the desiliconized slag is also improved.

  As a result, the basicity of the slag after the dephosphorization treatment can be controlled to a value close to the target value, which reduces the phosphorus concentration of the hot metal after the dephosphorization treatment to 0.030 mass% or less of the target value for all charges. We were able to.

  The hot metal after the pretreatment according to the comparative example and the example of the present invention was charged into a converter and decarburized to produce molten steel. As a result, the hot metal subjected to the pretreatment by applying the present invention has a reduced phosphorus concentration in the hot metal before decarburization treatment as compared with the hot metal subjected to the pretreatment by applying the conventional method. Since the amount of CaO-based solvent used can be reduced and the manganese yield can be improved, and the amount of manganese ferroalloy used can be reduced, the manufacturing cost can be reduced.

  The above formulas (3) to (10) are calculation formulas corresponding to the operating conditions such as the auxiliary raw materials used in [Test 1]. However, even under other operating conditions, the material balance is taken into consideration. The same calculation can be performed by changing the calculation formula.

[Test 2]
Using one converter-type refining furnace with a capacity of 330 tons, dephosphorization treatment (primary smelting), intermediate slag, decarburization treatment (secondary smelting) are carried out in this order to produce molten steel from molten pig iron. At that time, the apparatus having the configuration shown in FIG. 2 was used to measure the slag composition at the time of intermediate slag using the LIBS method, and based on the slag component analysis results, the addition amount of the CaO-based solvent in the subsequent decarburization treatment was determined. Calculated, a refining method of molten iron performed by adding a calculated amount of CaO-based solvent (invention example), and a refining method of molten iron by a conventional method that does not measure the slag composition after dephosphorization treatment (comparative example) , 5 charges each were continuously carried out. In the dephosphorization process of primary blowing, the desiliconization process is also performed at the same time.

  The target values of the phosphorus concentration in the molten steel at the end of the decarburization treatment were both 0.020 mass%. In each of the present invention example and the comparative example, the slag after the decarburizing treatment of the previous charge was not left in the furnace but left in the furnace, the hot metal used for the next charge was charged, and the intermediate slag was sandwiched to remove the slag. The molten iron refining method of performing phosphorus treatment and decarburization treatment was repeatedly performed. Further, iron scrap was added as an iron source during the dephosphorization treatment.

In the dephosphorization treatment step, the amount of quicklime or silica stone added was adjusted so that the calculated value (calculated basicity) of the basicity of slag ((mass% CaO) / (mass% SiO ₂ )) was 1.60, which is the target value. I adjusted it so that. When the calculated basicity was 1.60 which is the target value without using quicklime and silica stone, dephosphorization treatment was performed without using quicklime and silica stone. The amount of gaseous oxygen (gaseous acid) used was supplied according to the silicon concentration in the hot metal.

  The basicity of the slag after the dephosphorization treatment was calculated by the formula (11) in the comparative example and by the formula (12) in the example of the present invention.

B _{c, P2} (n) = [W _{S, C2} (n-1) × ε ₂ × B _{c, C2} (n-1) / {B _{c, C2} (n-1) +1} + W _{CaO, P2} (n)] /
[W _{S, C2} (n-1) × ε ₂ / {B _{c, C2} (n-1) +1} + {X _Si2 (n) / 100} × W _HM2 (n) × _60/28
+ W _{SiO2, P2} (n)]… (11)
B _{m, P2} (n) = (% CaO) _{m, P2} (n) / (% SiO ₂ ) _{m, P2} (n)… (12)
However, in the expressions (11) and (12), each symbol is as follows.

B _{c, P2} (n): Calculated basicity of slag at the end of dephosphorization treatment for refining nth charge
B _{c, C2} (n-1): Calculated basicity of slag at the end of decarburization in the n-1th charge refining
W _{S, C2} (n-1): Calculated slag mass (t) at the end of decarburization in the n-1th charge refining
W _{CaO, P2} (n): Addition amount of quicklime (t) in the dephosphorization process of refining of nth charge
W _{SiO2, P2} (n): Addition amount of silica stone (t) in the dephosphorization process of refining of nth charge
X _Si2 (n): Silicon concentration (mass%) in the hot metal before dephosphorization treatment for refining the nth charge
W _HM2 (n): _Hot metal amount (t) before dephosphorization treatment for n-charge refining
B _{m, P2} (n): Measured value of slag basicity by LIBS method of slag after completion of dephosphorization treatment for refining of nth charge
(% CaO) _{m, P2} (n): CaO concentration (mass%) measured by the LIBS method of the slag after dephosphorization treatment for refining the nth charge
(% SiO ₂ ) _{m, P2} (n): SiO ₂ concentration (mass%) measured by the LIBS method of the slag after dephosphorization treatment for refining the nth charge
ε ₂ : Sum of average values of mass ratios of CaO and SiO _{2 in} the slag after decarburization treatment In this example, ε ₂ = 0.5. The calculation method of B _{c, C2} (n-1) and W _{S, C2} (n-1) will be described later, but in the refining of the first charge, B _{c, C2} (0) is 0 (zero). And W _{S, C2} (0) = 0.

  The slag mass at the end of the dephosphorization treatment was calculated using the equation (13) in the conventional method, and was calculated using the equation (14) in the example of the present invention.

W _{S, P2} (n) = [W _{S, C2} (n-1) × ε ₂ + {X _Si2 (n) / 100} × W _HM2 (n) × _60/28 + W _{CaO, P2} (n) +
W _{SiO2, P2} (n)] / α ₂ … (13)
W _{S, P2} (n) = [W _{S, C2} (n-1) × ε ₂ + {X _Si2 (n) / 100} × W _HM2 (n) × _60/28 + W _{CaO, P2} (n) + W _{SiO2, P2} (n)] /
[{(% CaO) _{m, P2} (n) + (% SiO ₂ ) _{m, P2} (n)} / 100] (14)
However, in the expressions (13) and (14), each symbol is as follows.

W _{S, P2} (n): Calculated slag mass (t) at the end of dephosphorization treatment for n-th charge refining
α ₂ : Sum of average values of mass ratio of CaO and SiO _{2 in} slag after dephosphorization treatment The symbols explained in the equations (11) and (12) other than the above are as described above. In this example, α ₂ = 0.6.

  In the intermediate slag process, the moving trolley for loading the slag storage container that stores the slag to be discharged is used so that the amount of slag to the calculated slag mass after dephosphorization treatment is 50% by mass or more of the target value. The measurement was performed while confirming the weighed value of the installed slag container by the scale.

Here, in the intermediate slag after the dephosphorization treatment, the mass ratio of the hot metal mixed in the slag is higher and the variation is larger than in the case of the intermediate slag after the desiliconization treatment described above. Therefore, in this example, the average value of the mass ratio of the pig iron in the plurality of samples collected from the discharged dephosphorization slag is determined as the mass ratio of the hot metal mixed in the dephosphorization slag, and the intermediate discharge based on this value. The mass ratio of dephosphorized slag in the slag discharge was set. Specifically, 0.8 times the weighed value of the discharged matter in the intermediate discharged matter was calculated as the mass of the discharged dephosphorized slag (= W _{O, P2} (n)).

  In the decarburization process, the amount of quicklime used is adjusted so that the calculated value of the basicity of the slag after decarburization (calculated basicity) becomes the target value set according to the target molten steel temperature at the end of the decarburization process. It was adjusted. All the decarburized slag was left in the furnace, and the hot metal used in the next charge was charged to refine the next charge.

  The calculated basicity of the decarburized slag (decarburized slag) was calculated by using the equation (15) in the comparative example, and by using the equation (16) in the example of the present invention.

B _{c, C2} (n) = [{W _{S, P2} (n) -W _{O, P2} (n)} × α ₂ × B _{c, P2} (n) / {B _{c, P2} (n) +1} + W _{CaO, C2} (n)] /
[{W _{S, P2} (n) -W _{O, P2} (n)} × α ₂ / {B _{c, P2} (n) +1}]… (15)
B _{c, C2} (n) = [{W _{S, P2} (n) -W _{O, P2} (n)} × {(% CaO) _{m, P2} (n) / 100} + W _{CaO, C2} (n)] /
[{W _{S, P2} (n) -W _{O, P2} (n)} × (% SiO ₂ ) _{m, P2} (n) / 100]… (16)
However, in the expressions (15) and (16), each symbol is as follows.

B _{c, C2} (n): Calculated basicity of slag after decarburization in refining of nth charge
W _{O, P2} (n): Mass of slag (t) discharged after dephosphorization treatment for refining nth charge
W _{CaO, C2} (n): Amount of quicklime added in decarburization process of refining of nth charge (t)
The symbols explained in the equations (11) to (14) other than the above are as described above.

  The calculated mass of the slag at the end of the decarburization treatment was calculated using the formula (17) in the comparative example and the formula (18) in the example of the present invention.

W _{S, C2} (n) = [{W _{S, P2} (n) -W _{O, P2} (n)} × α ₂ + W _{CaO, C2} (n)] / ε ₂ … (17)
W _{S, C2} (n) = [{W _{S, P2} (n) -W _{O, P2} (n)} × {(% CaO) _{m, P2} (n) + (% SiO ₂ ) _{m, P2} (n) } / 100
+ W _{CaO, C2} (n)] / ε ₂ … (18)
However, in the equations (17) and (18), W _{S, C2} (n) is the calculated slag mass (t) at the end of the decarburizing treatment of the nth charge refining. The other symbols explained in the equations (11) to (16) are as described above.

  After tapping the decarburized molten steel, the decarburized slag was not discharged and the entire amount was left in the furnace and carried over to the next charge.

  Table 2 shows the refining results in the comparative example and the present invention example. In Table 2, among the basicities of each slag, the value shown as basicity (LIBS value) is a value measured by the LIBS method, and the value shown as basicity (sample analysis value) is a small amount of collected slag sample. Is pulverized and dissolved in acid to prepare an aqueous solution sample, which is based on the analysis value of the slag component obtained by analyzing by ICP emission spectroscopy.

  In the comparative example, the estimation accuracy of the basicity of the dephosphorization slag was low, and the basicity (sample analysis value) was greatly varied from the target value of 1.60. In addition, the estimation error of the amount of slag after dephosphorization is considered to be large, and the basicity (sample analysis value) of the slag after decarburization greatly varied from the target value.

  That is, when the basicity (sample analysis value) of the slag after dephosphorization treatment is lower than the calculated basicity, that is, the target value of 1.60, the basicity (sample analysis value) of the slag after decarburization treatment is the target value. As a result, the phosphorus concentration of the molten steel after completion of the decarburization treatment was higher than the target of 0.020 mass%, and a charge exceeding the phosphorus specification upper limit was generated. On the other hand, when the basicity (sample analysis value) of the slag after dephosphorization treatment is higher than the calculated basicity, that is, the target value of 1.60, the basicity of the slag in decarburization treatment (sample analysis value) is higher than the target value. Although it will be higher, the slag slag will deteriorate and the fluidity will decrease, and the phosphorus distribution ratio of the decarburized slag may decrease. Therefore, the phosphorus concentration of the molten steel after the refining may be higher than the target value of 0.020 mass%.

On the other hand, in the example of the present invention, by quantitatively analyzing (mass% CaO) and (mass% SiO ₂ ) of the slag at the end of the dephosphorization treatment, the basicity of the slag at the end of the dephosphorization treatment can be accurately measured. I was able to figure it out. Specifically, the measured value of slag basicity (B _{m, P2} (n)) at the end of the dephosphorization treatment was in agreement with the basicity (sample analysis value) with an error of about 0.03 standard deviation. Further, the variation from the target value (1.60) of the slag basicity (sample analysis value) at the end of the dephosphorization treatment was also significantly reduced as compared with the comparative example in Table 2. It is considered that this is because the estimation accuracy of the composition and amount of precharged decarburized slag left in the furnace was improved. Furthermore, since the (mass% CaO) and (mass% SiO ₂ ) of the slag after the dephosphorization treatment can be quantitatively analyzed, it is considered that the estimation accuracy of the residual amount of the dephosphorization slag is also improved.

  As a result, it is possible to control the basicity of the actual slag at a value close to the target value even in the decarburization treatment, and as a result, the phosphorus concentration of the molten steel after the decarburization treatment is 0.020 mass% or less of the target in all charges. Could be reduced to

  The molten steel produced by the comparative example and the example of the present invention, after adjusting the components and temperature by further deoxidizing in a secondary refining equipment, continuously cast to produce a slab, this slab is a usual method By hot rolling to produce a steel product. In the present invention example, the phosphorus concentration of the hot metal before decarburization treatment was reduced as compared with the comparative example, so that it was possible to reduce the amount of CaO-based medium solvent used in the converter and to improve the manganese yield. Since the usage amount of was also reduced, it was possible to reduce the manufacturing cost.

  The above formulas (11) to (18) are calculation formulas corresponding to the operating conditions such as the auxiliary raw materials used in [Test 2]. However, even under other operating conditions, the mass balance is taken into consideration. The same calculation can be performed by changing the calculation formula.

1 Converter-type refining furnace 2 Furnace mouth 3 Bottom blowing tuyere 4 Hot metal 5 Slag 6 Laser light generator 7 Condensing lens 8 Laser light 9 Light receiving part 10 Optical fiber 11 Spectrometer / photometer 12 Calculation computer 13 Imaging device 14 Slag Container

Claims (23)

Molten iron left in the converter-type refining furnace or slag generated in refining molten iron in the converter-type refining furnace while leaving part of the slag in the converter-type refining furnace When refining the hot metal newly charged into the furnace,
The components of the slag generated in the refining of molten iron, in quantitative analysis without collecting an analytical sample from the slag, the laser light is focused on the surface of the analysis target containing the slag and the molten iron , laser light The luminescence intensity of two or more elements containing at least calcium in the plasma generated by condensing the light is measured, and the luminescence intensity of calcium is used to identify whether the luminescence corresponds to slag or the molten iron. , Quantitative analysis of the components of the slag based on the emission intensity of each element of the luminescence corresponding to the identified slag, based on the component analysis results, performed in the converter-type refining furnace left slag, Determine the amount of smelting agent to be added before and / or during refining in the next step of refining the molten iron remaining in the furnace or refining the molten metal of the next charge using the hot metal newly charged in the furnace And wherein the door, molten iron method of refining. In the quantitative analysis of the components of the slag, two or more elements containing at least calcium (Ca) and silicon (Si) in plasma generated by converging laser light on the surface of the slag are collected. 2. The method for refining molten iron according to claim 1, further comprising: measuring the luminescence intensity of the slag and evaluating the basicity of the slag based on the measured luminescence intensity and / or the luminescence intensity ratio. In the quantitative analysis of the components of the slag, two or more elements containing at least calcium (Ca) and silicon (Si) in plasma generated by converging laser light on the surface of the slag are collected. The refining of molten iron according to claim 1 or 2, further comprising: measuring the luminescence intensity of the slag and evaluating the composition of the slag based on the measured luminescence intensity and / or the luminescence intensity ratio. Method.   The laser light is focused on the surface of the slag in the converter-type refining furnace, the slag being discharged from the converter-type refining furnace or the slag in the slag storage container after being discharged, and the plasma is generated on the slag surface. The method for refining molten iron according to claim 2 or 3, characterized in that. The refining of the molten iron is a pretreatment of the hot metal in which a plurality of refining steps are performed by using one converter-type refining furnace, and a part of the hot metal and slag is partially converted into the converter-type refining furnace between the plurality of refining steps. The remaining part of the slag is discharged, and when the hot metal is subjected to the pretreatment, when the remaining part of the slag is discharged, the components of the slag are quantitatively analyzed, and based on the result of the component analysis, The method for refining molten iron according to any one of claims 1 to 4, wherein the amount of the slag-forming agent added in the refining step of the step is determined. The pretreatment of the hot metal includes a desiliconization treatment step and a dephosphorization treatment step, and between the desiliconization treatment step and the dephosphorization treatment step, a part of the molten pig iron and slag was left in the converter-type refining furnace. As it is, when discharging the remainder of the slag, quantitatively analyze the components of the slag, based on the result of the component analysis, to determine the amount of the slag forming agent to be added in the dephosphorization treatment step, The method for refining molten iron according to claim 5.   The refining of the molten iron is a pretreatment of the hot metal, and a part or all of the slag generated in the dephosphorization treatment of the hot metal in the converter-type refining furnace is left in the converter-type refining furnace as follows. 7. Molten iron refining according to any one of claims 1 to 6, characterized in that the molten iron with a charge of 1 is charged into the converter-type refining furnace to perform a pretreatment of the molten iron with the next charge. Method. A dephosphorization treatment step of dephosphorizing the hot metal in the converter-type refining furnace by using one converter-type refining furnace and supplying a CaO-based solvent medium and an oxygen source into the converter-type refining furnace; Tilt the furnace type refining furnace to discharge the hot metal after the dephosphorization step and part of the slag generated in the dephosphorization step while leaving the remaining part of the slag in the intermediate refining furnace. A slag process, and a decarburizing treatment process of molten iron to supply molten CaO-based solvent and an oxygen source into the converter-type refining furnace to decarburize the hot metal remaining in the converter-type refining furnace into molten steel. The molten steel after the decarburization treatment step is tapped from the converter-type refining furnace to produce a molten steel from molten pig iron in this order, and the remaining portion of the slag in the intermediate slag step is removed. when discharging, the components of the slag was quantitatively analyzed, based on the component analysis results, you the decarburization step And determining the amount of slag agent added Te, molten iron method refining according to any one of claims 1 to 4.   While leaving a part or all of the slag generated in the decarburization treatment step of the molten iron of the previous charge in the converter-type refining furnace, the molten iron of the next charge is left in the converter-type refining furnace and the converter-type refining furnace 9. The method for refining molten iron according to claim 8, further comprising the step of: A part or all of the slag generated in the decarburization treatment step in which a CaO-based solvent and an oxygen source are supplied into the converter-type refining furnace to decarburize the hot metal in the converter-type refining furnace to form molten steel While being left in the converter-type refining furnace, when the converter-type refining furnace is charged with the next charge of hot metal for refining, the components of the slag generated in the decarburization treatment step are quantitatively analyzed, and The amount of the slag forming agent to be added in refining the molten iron of the next charge is determined based on the component analysis result, any one of claims 1 to 4, claim 8 and claim 9 The method for refining molten iron according to the item. Part or all of the slag generated in the dephosphorization treatment step in which a CaO-based solvent and an oxygen source are supplied into the converter-type refining furnace to dephosphorize the hot metal in the converter-type refining furnace While remaining in the smelting furnace, when the molten iron of the next charge is charged into the converter-type smelting furnace to perform dephosphorization treatment on the hot metal, quantitatively analyze the components of the slag generated in the dephosphorization treatment step, The refining of molten iron according to any one of claims 1 to 6, wherein the amount of the slag-forming agent to be added in the refining of molten iron for the next charge is determined based on the result of the component analysis. Method.   The refining method for molten iron according to any one of claims 1 to 11, wherein the slag-forming agent whose addition amount is determined based on a result of component analysis of the slag is a CaO-based solvent medium. .   The slag component analysis result includes the MgO content in the slag, and the slag-forming agent that determines the addition amount based on the slag component analysis result contains a MgO-based solvent. A method for refining molten iron according to any one of claims 1 to 12.   The slag component analysis result includes the iron oxide content in the slag, the slag-forming agent for determining the addition amount based on the slag component analysis result contains an iron oxide-based solvent medium, The method for refining molten iron according to any one of claims 1 to 13. Molten iron left in the converter-type refining furnace or slag generated in refining molten iron in the converter-type refining furnace while leaving part of the slag in the converter-type refining furnace When refining the hot metal newly charged into the furnace,
Two types containing at least calcium and iron (Fe) in plasma generated by condensing laser light on the surface of an analysis target containing the slag and the molten iron produced by refining molten iron The luminescence intensity of the above elements is measured, and at least the luminescence intensity of calcium is used to identify whether the luminescence corresponds to slag or the luminescence corresponding to molten iron, and the luminescence intensity of each element of the luminescence corresponding to the identified slag. Quantitative analysis of iron oxide content of the slag based on the measurement results of,
Based on the analysis result, performed in the converter type refining furnace in which slag is left, refining in the next step of the molten iron left in the furnace or the next charge using the hot metal newly charged in the furnace A method for refining molten iron, which comprises controlling the iron oxide content of slag in the refining of molten iron.   The molten iron refining is molten iron refining in which the primary blowing step and the secondary blowing step are performed using one converter-type refining furnace, and between the primary blowing step and the secondary blowing step. , While leaving a part of the molten iron and slag in the converter-type refining furnace, discharging the remaining part of the slag, in refining the molten iron left in the converter-type refining furnace, discharging the remaining part of the slag When doing, quantitatively analyze the iron oxide content by focusing the laser light on the surface of the slag generated in the primary blowing step, based on the quantitative analysis result of the iron oxide content, the secondary blowing The method for refining molten iron according to claim 15, wherein the iron oxide content of the slag in the step is controlled.   The molten iron refining is molten iron refining in which the primary blowing step and the secondary blowing step are performed using one converter-type refining furnace, and between the primary blowing step and the secondary blowing step. A refining method in which a part of the molten iron and a part of the slag are left in the converter-type refining furnace and the remaining part of the slag is discharged, and the molten iron left in the converter-type refining furnace is refined by a continuous charge of 2 or more charges. When applying to the hot metal of the above, while leaving a part or all of the slag generated in the secondary blowing step of the pre-charged hot metal in the converter-type refining furnace in the converter-type refining furnace, Is charged into the converter-type refining furnace, and when performing the primary blowing step of the hot metal of the next charge, the laser light is focused on the surface of the slag generated in the secondary blowing step of the hot metal of the previous charge. And quantitatively analyze the iron oxide content, and based on the quantitative analysis result of the iron oxide content, And controlling the iron oxide content of the slag in the primary blowing process of the charge of molten iron, molten iron method refining of claim 15 or claim 16.   When controlling the iron oxide content of the slag in the primary blowing step or the secondary blowing step, the supply rate of gaseous oxygen, the lance height of the top blowing lance for supplying gaseous oxygen, the bottom blowing gas flow rate The method for refining molten iron according to claim 16 or 17, characterized in that the iron oxide content is controlled by adjusting the conditions of one or more of the above.   19. The hot metal desiliconization process in the primary blowing process, and the hot metal dephosphorization process in the secondary blowing process, according to any one of claims 16 to 18. Method for refining molten iron.   19. The method according to claim 16, wherein the primary blowing step is a dephosphorization treatment of molten pig iron, and the secondary blowing step is a decarburization treatment of decarburizing the molten pig iron to obtain molten steel. The method for refining molten iron according to any one of 1. The molten iron refining is molten iron refining in which the primary blowing step and the secondary blowing step are performed using one converter-type refining furnace, and between the primary blowing step and the secondary blowing step. , A part of molten iron and slag are left in the converter-type refining furnace, the remaining part of the slag is discharged, and the refining method of refining the molten iron left in the converter-type refining furnace is continuously charged by 2 charges. In applying the above hot metal, the slag generated in the secondary blowing step of the pre-charged hot metal in the converter-type refining furnace, while being left in the converter-type refining furnace without being discharged to the outside, When charging the molten iron of the above charge into the converter-type refining furnace and performing the primary blowing process of the molten iron of the next charge, the components of the slag are quantified before and after the secondary blowing process of the molten iron of the previous charge. Analyze, and the quantitative analysis results of the components of the slag before and after the secondary blowing process The amount of slag after the secondary blowing step is calculated based on the amount of the slag forming agent used in the secondary blowing step, and the obtained slag amount is used for controlling the slag in the primary blowing step of the hot metal of the next charge. The method for refining molten iron according to any one of claims 1 to 4 and claims 15 to 20, characterized in that it is utilized.   A method for quantitatively analyzing the components of the slag, in which a laser beam is focused on the surface of the slag, the emission intensity of an element in plasma generated by the concentration of the laser beam is measured, and the measured emission intensity and / or emission is measured. Including a method for quantitatively analyzing the components of the slag based on the intensity ratio, measuring the distance between the condensing lens for condensing the laser light on the surface of the slag and the slag surface for condensing the laser light, The molten iron according to any one of claims 1 to 21, wherein the position of the condenser lens is adjusted so that the distance between the condenser lens and the slag surface has a predetermined value. Refining method. Laser light is focused on the surface of the analysis target containing slag and molten iron at a temperature of 800 ° C. or higher, and the emission intensity of the element in the plasma generated by the concentration of the laser light is measured, and the measured emission intensity is measured. And / or a slag composition analysis method for analyzing the composition of the slag based on the emission intensity ratio,
The luminescence intensity of two or more elements containing at least calcium in the plasma is measured, and the luminescence intensity of calcium is used to identify whether the luminescence corresponds to slag or the luminescence corresponding to molten iron. A slag composition analysis method, which comprises quantitatively analyzing the composition of the slag based on the emission intensity of each element of the corresponding luminescence.