KR20180119664A - Method of analysis of slag and refining method of molten iron - Google Patents

Abstract

A slag analysis method capable of quickly and accurately measuring the composition of slag generated by refining molten iron is provided. A method of analyzing slag according to the present invention is a method of analyzing slag produced by refining molten iron, comprising the steps of: crushing a slag sample taken from slag; measuring a particle size distribution of slag particles passing through the sieve Having a 10% particle diameter (D ₁₀ ) of not less than 0.1 mm and a 90% particle diameter (D ₉₀ ) of not more than 2.0 mm in a cumulative particle size distribution curve represented by a mass percentage as a curved line of a right- A step of filling the measurement container with the collected slag particles; a step of measuring the fluorescent X-ray intensity from the filled slag particle group; a step of quantitatively analyzing the composition of the slag from the measured fluorescent X- .

Description

Method of analysis of slag and refining method of molten iron

The present invention relates to a method of analyzing slag for quickly and precisely measuring the composition of slag generated by refining of molten iron and a method of analyzing slag based on the analysis results of composition by this analysis method, To the refining method of molten iron. Here, molten iron means molten iron or molten steel, and when molten iron or molten steel is clearly distinguished, molten iron is referred to as molten iron or molten steel.

BACKGROUND ART [0002] In recent years, a variety of pre-treatment techniques for molten iron and decarbonization technology for molten iron are being developed in consideration of environmental considerations such as carbon dioxide gas emission regulations and the need to combine high productivity. Among these, as one of the new preliminary iron processing techniques, there is a technique in which one of the converter type refining furnaces is used to carry out degassing treatment and tallining treatment of a charcoal, and a char iron preliminary treatment Technology has been proposed.

For example, in Patent Document 1, first, the amount of the CaO-based antistatic agent is adjusted so that the basicity (basicity = (mass% CaO) / (mass% SiO ₂ )) of the slag falls within the range of 0.3 to 1.3, The slag generated in the furnace (the slag generated by the degassing process is referred to as " demineralized slag ") is discharged from the furnace, and then the slag produced in the furnace is discharged , A CaO pre-treatment agent is added to perform a talline treatment of the molten iron remaining in the furnace.

However, in general, since the basicity of slag during the degassing treatment is changed by SiO ₂ produced by the denitrification treatment, in Patent Document 1, the basicity of the slag is out of the above range, There is a possibility that discharge becomes difficult. Further, in Patent Document 1, slag is discharged after tallin processing, and even if it is small, molten iron remains in the furnace, and this molten iron is also discharged together with the slag, resulting in reduction of the iron yield.

Also, with regard to the decarburization treatment for dissolving molten steel from molten iron, there has been proposed a treatment technique in which a single transfer type refining furnace is used to carry out the tallane treatment and the decarburization treatment of molten iron continuously with the disposal step in between.

For example, in Patent Document 2, a single converter type refining furnace is used. First, a molten iron is subjected to a tallin process, then the slag generated by tilting the furnace body is discharged, and thereafter, Is subjected to decarburization treatment. After introducing the molten steel from the converter type refining furnace, the following charge iron is charged into the converter refining furnace while the slag generated by the decarburization treatment is remained, and the following charge tallining and decarburization treatment , A refining technique to be carried out in the above-described order has been proposed. According to Patent Document 2, by intentionally leaving the slag after the decarburization treatment, it is possible to realize reduction of the CaO-based antifouling agent, improvement of the iron yield, lowering of the temperature of the tallin treatment, and lowering of the slag in the tallin treatment. Discharges carried out between two refinements in one converter type refining disclosed in Patent Document 1 and Patent Document 2 are also referred to as "intermediate disposal" and "intermediate disposal process".

However, in Patent Documents 1 and 2, only the slag in the furnace is discharged by tilting the furnace-type refining furnace in the intermediate depositing step, and only by tilting the furnace-type refining furnace, depending on the composition of the slag , The slag can not be sufficiently discharged. Therefore, in Patent Documents 1 and 2, undesirable phenomena such as blooming may occur due to the influence of the slag remaining in the converter-type refining furnace. Here, "bouling" refers to a phenomenon in which phosphorus (P ₂ O ₅ ) contained in the slag is reduced and phosphorus in the phosphorus oxide shifts to molten iron or molten steel, thereby increasing the phosphorus concentration of molten iron or molten steel.

In such a background, Patent Document 3 discloses a method in which, when a single converter type refining furnace is used to carry out a tallin process, an intermediate disposing process, and a decarburization process, , An inert gas is blown from a wick installed on the furnace belly of a converter type refining furnace and the slag is discharged to the furnace side by an inert gas while being discharged.

Patent Document 4 discloses that when one of the converter type refining furnaces is used to leave a part of the slag produced by the talline processing of the molten iron and to carry out the next talline processing of the molten iron, A technique of previously measuring the relationship between the tilting angle of the converter type refining furnace and the residual amount of slag for the purpose of causing a predetermined amount to remain in the furnace and tilting the furnace body based on the result of this measurement to leave a predetermined amount of slag Has been proposed.

By the way, the knowledge of the composition of the slag has been widely practiced in quantitative analysis using the intensity of fluorescent X-rays conventionally under conditions that are indispensable when refining molten iron. The method of quantifying the slag composition using this fluorescent X-ray analysis method is as follows. A part of the slag is collected and the collected slag is returned to the analysis room to prepare it as an analytical sample. Thereafter, the prepared analytical sample is irradiated with X-ray (primary X-ray) The intensity of a line (secondary X-ray) is measured for each element, and the content of each element is obtained from the measurement value of fluorescent X-ray intensity using a calibration line for each element prepared in advance.

In fluorescence X-ray analysis, in order to quantify with high accuracy, it is necessary to make the measurement surface of the sample for analysis smooth. As a method for preparing the analytical sample for this purpose, three methods of glass bead method, briquetting method and direct method are mainly performed.

The glass bead method is a method in which slag collected is melted with a flux such as Na ₂ B ₄ O ₇ or Li ₂ B ₄ O ₇ to be vitrified and vitrified to be used as an analytical sample. The analytical sample by the glass bead method is rich in homogeneity and can be analyzed with high precision. However, since it takes a long time of about 1 hour until the analysis value is determined, feedback on the operation can not be performed.

The briquetting method is a method of preparing a sample by mixing the pulverized slag with a small amount of an organic binder such as starch or cellulose, and press-molding it into a disk. The analysis by the briquetting method is advantageous in that the sample preparation time can be shortened to about half, though it is lower than the analytical precision, compared with the glass bead method.

Patent Literature 5 discloses that in order to shorten the analysis time without lowering the analysis accuracy in the briquetting method, the slurry is made into ultrafine particles with an average particle size of 10 μm or less by using a jet mill, and the ultrafine particles are dispersed in a binder- And a method of analyzing by pressure molding is proposed. In the example of Patent Document 5, the mean analysis time is 10 minutes.

In the direct method, it is possible to perform analysis for a short time of about several minutes by providing the sampled slag sample piece to the fluorescent X-ray analysis method as it is. However, in the fluorescent X-ray analysis method, a smooth measurement surface is required. Therefore, in order to obtain a smooth measurement surface, Patent Document 6 and Patent Document 7 disclose a technique in which a sampler is pressed in a molten slag, There is proposed a method of sampling a slag sample piece having a smooth surface.

Japanese Patent Application Laid-Open No. 10-152714 Japanese Unexamined Patent Publication No. 4-72007 Japanese Unexamined Patent Publication No. 5-140627 Japanese Unexamined Patent Publication No. 6-200311 Japanese Laid-Open Patent Publication No. 11-23496 Japanese Patent Application Laid-Open No. 9-166589 Japanese Laid-Open Patent Publication No. 11-304675

The present inventors have found that when a converter type refining furnace in which a part of slag is remained is used to refine the next step of molten iron left in the furnace or to refine the molten iron charged after the newly charged molten iron in the furnace is used (Mass% CaO) / (mass% SiO ₂ ) of the slag was not easy to control in the refining of the next process or the next refining of the charge. In short, it was confirmed that it is not easy to add a proper amount of CaO-based magenta agent. In general, by controlling the basicity of the slag to about 1.20, it is possible to carry out a suitable talline treatment for the molten iron, but adding the necessary amount of the CaO-based antifoaming agent leads to an increase in cost.

That is, in the refining method of the molten iron proposed so far, it is necessary to suppress the addition amount of the coagulant such as the CaO-based magma agent to the minimum necessary amount in order to further reduce the cost. In order to realize this, it is necessary to accurately grasp the composition and the residual amount of the slag in the furnace before adding the coagulant. For example, in the case of Patent Document 1, in the case of adding a CaO-based magenta agent after discharging after decalcification, it is necessary to grasp the basicity of the slag remaining in the furnace and the residual amount of the slag in order to calculate an appropriate amount of the CaO-based magenta agent .

In Patent Document 4, although a predetermined amount of slag is left in the furnace, the residual amount of slag is obtained from the relationship between the tilting angle and the amount of residual slag when no molten iron is present in the furnace. In the case where molten iron exists in the furnace as in the intermediate discharge process of Patent Document 1 or Patent Document 2, even when the technique of Patent Document 4 is used, the residual amount of slag in the furnace can be accurately I can not grasp.

On the other hand, as a method for accurately evaluating the composition of the residual slag in the furnace, the method disclosed in Patent Document 5 needs to carry out pulverization up to a level at which press molding is possible. Therefore, preparation of analytical samples It is difficult to complete. In the methods disclosed in Patent Documents 6 and 7, since the slag is quenched, segregation is likely to occur in the analytical sample and there is a problem in the analytical accuracy. As described above, no detailed description is found in the past patent documents including Patent Documents 1 to 7 regarding the method of accurately analyzing the composition of the residual slag in the furnace.

Thus, a method of predicting slag composition by calculation is generally carried out. However, in the case of the calculation method in which the refining of the next step or the subsequent refining of the molten iron is carried out with some or all of the produced slag remaining in the furnace, the expected slag composition and the amount of slag The accuracy is lowered. Therefore, the difference between the actual slag composition and the calculated value becomes large, and there is a possibility that it is difficult to continuously carry out the preliminary processing for molten iron.

In addition to the basicity, the needs to know the composition of the slag promptly spread over many aspects. For example, the MgO concentration in the slag is closely related to the refractory life of the furnace body. This is because if the MgO concentration in the slag is excessively low, the damage of the furnace wall refractory becomes remarkable. On the other hand, if the concentration of MgO in the slag is excessively high, it is not preferable in that the waste slag is used for a roadbed material or the like, which may cause expansion or the like. Therefore, the concentration of MgO in the slag is within an appropriate range, and analysis of the slag composition rapidly is desired. If the MgO concentration in the slag can be evaluated quickly in the refining step, the life of the furnace body can be prolonged by controlling the MgO concentration appropriately, and in the case where the furnace body is biased toward the high concentration side, It is possible to increase the productivity through separation.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method of analyzing slag which can quickly and accurately measure the composition of slag generated by the refining of molten iron, And a method of refining molten iron to determine an appropriate amount of the additive based on the result of analysis by an analytical method.

The gist of the present invention to solve the above problems is as follows.

[1] As a method for analyzing slag produced by refining molten iron,

A step of crushing the slag sample taken from the slag,

The particle size distribution of the slag particles passing through the sieve from the pulverized slag particles is set to zero and the 10% particle size (D ₁₀ ) in the cumulative particle size distribution curve represented by the mass percentage as a curved line in the upward direction is 0.1 mm or more , A step of collecting slag particles having a 90% particle diameter (D ₉₀ ) of 2.0 mm or less,

A step of filling the measurement container with the collected slag particles,

Measuring the fluorescent X-ray intensity from the charged group of slag particles,

And a step of quantitatively analyzing the composition of the slag from the measured fluorescent X-ray intensity.

[2] The method for analyzing slag according to [1], wherein in the step of measuring the fluorescent X-ray intensity, the fluorescent X-ray intensity of two or more kinds of elements containing calcium (Ca) and silicon (Si) is measured.

[3] Refining of the next step of molten iron remaining in the converter-type refining furnace while part of the slag generated by refining the molten iron in the converter refining furnace remains in the converter refining furnace, A refining method of molten iron which performs refining of molten iron following charging using a newly charged molten iron in a converter type refining furnace,

The composition of the slag generated by the refining of molten iron was quantitatively analyzed by the slag analysis method described in [1] or [2] above,

In the refining of the next step of the molten iron remaining in the furnace or the refining of the molten iron charged in the furnace newly charged in the furnace, which is carried out in the converter-type refining furnace in which the slag is remained, Wherein the amount of the additive to be added is determined before and / or during the refining of the molten iron.

[4] The refining of the molten iron is carried out by using a single converter type refining furnace to carry out a plurality of refining processes with respect to the molten iron, and a part of the molten iron and the slag are refined in the refining furnace And then discharging the remaining portion of the slag,

The composition of the slag is analyzed at the time of discharging the remaining portion of the slag,

And the amount of the additive agent to be added in the refining step of the next step is determined based on the result of the analysis.

 [5] The refining of the molten iron is a refining in which a furnace is preliminarily treated using one converter type refining furnace,

 A preliminary treatment of the molten iron is carried out in which molten iron after the preliminary treatment is spouted while part or all of the generated slag is remained in the refining furnace and the molten iron is newly charged into the furnace to carry out the next preliminary treatment,

 When the part or all of the slag is left in the reflux furnace, the composition of the remaining slag is analyzed,

 The method for refining molten iron according to [3], wherein the amount of the additive agent to be added in the following preliminary processing is determined on the basis of the analysis result.

[6] a degassing process for degassing the molten iron leaving the furnace,

An intermediate discharging step of discharging the demineralized slag generated in the demineralizing treatment step in the transfer refining furnace while the molten iron after the demineralization treatment is left in the converter refining furnace;

A tallining process for tallining the molten iron remaining in the converter refining furnace,

And a tapping step of tapping the talline-treated molten iron from the converter-type refining furnace,

There is provided a refining method of molten iron in which a single converter refining furnace is used to carry out the above steps in the above-described order to preliminarily process molten iron,

During the intermediate disposal process, the composition of the demineralized slag is quantitatively analyzed by the slag analysis method described in [2] above,

Based on the analysis result, the basicity ((mass% CaO) / (mass% SiO ₂ )) of the degassed slag was obtained,

Wherein the amount of the additive to be added in the talline processing step is determined based on the obtained basicity ((mass% CaO) / (mass% SiO ₂ )).

[7] A method for refining molten iron according to any one of [3] to [6], wherein the above-mentioned conditioning agent is a CaO-based anticorrosion agent.

[8] A method for producing a magnetic recording medium, comprising the steps of:

The analysis results of the slag include the MgO content in the slag,

The method for refining molten iron according to any one of [3] to [7], wherein an addition amount of the MgO based antiscaling agent is determined on the basis of an analysis result of the slag.

[9] An iron oxide-based antistatic agent is used as a part of the above-

The analysis results of the slag include the iron oxide content in the slag,

The method for refining molten iron according to any one of [3] to [8], wherein the amount of the iron oxide based anticorrosive agent to be added is determined based on the analysis result of the slag.

According to the present invention, slurry particles having a 10% particle diameter (D ₁₀ ) of 0.1 mm or more and a 90% particle diameter (D ₉₀ ) of 2.0 mm or less in the cumulative particle size distribution curve are filled in a measurement container. Since it is used as a sample for analysis in the fluorescent X-ray analysis method, it is possible to quickly and accurately quantitatively analyze the composition of slag produced by refining molten iron. It is also possible to refine the next step of the molten iron or to remove the following amount of the molten iron after the refining of the molten iron with the use of the converter type refining furnace while the part or all of the slag generated by refining the molten iron remains in the converter- When the refining is carried out, it is possible to determine the appropriate addition amount of the coagulant by determining the addition amount of the coagulant based on the analysis result of the slag analysis method according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between the particle diameter of slag particles and measured slag basicity. Fig.
2 is a graph showing a comparison of the basicity of the desulfurized slag obtained by the slag analysis method according to the present invention and the basicity of the desulfurized slag obtained from the analytical value of the analytical sample prepared by the briquetting method.
Fig. 3 is a graph showing the phosphorus concentration in the molten iron spiked in the molten iron receiving vessel after the tallin treatment in Comparative Example 1 and Comparative Example 1. Fig.

In order to solve the above problems, the inventors of the present invention have studied the shortening of the analysis time of the slag and intentionally left the slag produced by the refining of the molten iron, The present invention relates to a process for refining a molten wire including a process for utilizing the molten iron for refining the molten iron. As a result, as a means for solving the above problem, a method of quickly quantitatively analyzing the composition of slag produced by refining of molten iron at the meteorological side of a converter type refining furnace has been found. Here, " intentionally retaining the slag " means that the tilting angle of the converter-type refining furnace is adjusted without inverting the inverting refining furnace so that the furnace of the converter refining furnace is directly underneath The slag is discharged to leave the slag in the furnace.

That is, for example, as disclosed in Patent Document 1, after the completion of the degassing treatment in the molten iron preliminary treatment, there is an intermediate discharging step of discharging the slag from the furnace by tilting the converging-type refining furnace. It is possible to analyze the composition of the slag within the time of the intermediate disposing process by collecting the slag in the furnace or during the disposal or after disposing and analyzing it on the basis of the furnace of the converter type refining furnace, And found that the analysis results can be applied to the talline process of the next process.

Hereinafter, the present invention will be described in detail. First, a method of analyzing the slag composition will be described.

Among the slag compositions, the basicity ((mass% CaO) / (mass% SiO ₂ )) of the slag greatly influences the slag viscosity and tallin efficiency during refining, and thus the analysis needs are large. It is possible to quickly and quantitatively evaluate the basicity of the slag in the furnace of the converter type refining furnace, and thus the industrial significance is large in that it is possible to carry out efficient talline treatment or the like after minimizing the amount of the additive additive agent .

In order to quantitatively evaluate the basicity of the slag, it is necessary to quantitatively analyze the CaO content and SiO ₂ content of the slag. Typically, calcium (Ca) and silicon (Si) exist in the form of oxides (CaO and SiO ₂ ) in the slag at the time of disposal, and other forms other than oxides of calcium and silicon are present in the slag at the time of disposal . In other words, when quantifying elemental composition of calcium and silicon in the slag, it is possible to quantitatively analyze the CaO content and SiO ₂ content of the slag. From this viewpoint, fluorescent X-ray analysis is preferable as a method for quantitative analysis of slag. In addition, the fluorescent X-ray analysis method is excellent in stability, operability, and promptness, and from this point as well, it is preferable as an analyzing means on a substrate side of a converter type refining furnace or the like.

The fluorescent X-ray analysis apparatus, as a detection system, has an energy dispersion type and a wavelength dispersion type, and the slag composition can be measured in any of the methods. The energy dispersive type detector does not need to scan the spectroscopic crystal like the wavelength dispersive type detector, so that the measurement can be performed in a shorter time. Therefore, from the viewpoint of quickness of measurement time, it is more preferable that the detection system is energy dispersive. Further, in consideration of the analysis on the side of the converter-type refining furnace, it is preferable to use a fluorescent X-ray analyzer having a simple structure such as a portable type that does not use cooling water or liquid nitrogen.

The element to be analyzed is preferably composed of two or more kinds of elements containing calcium and silicon which are essential for the evaluation of the basicity. Examples of elements to be analyzed other than calcium and silicon include magnesium (Mg), iron (Fe) (Ti), manganese (Mn), phosphorus (P), and sulfur (S).

In order to evaluate the basicity of the slag, it is necessary to measure the content of CaO and the content of SiO ₂ in the slag. In the case of analysis by fluorescent X-ray analysis, in order to cancel the influence of the coexisting element, a calibration curve is prepared in advance by using a standard slag sample made of a component system equivalent to the target slag, and a quantitative value of calcium, silicon, It can be determined by the CaO content and SiO ₂ content in the slag (hereinafter referred to as "calibration method"). In addition, X-rays also in the absorption coefficient and the first X and from the physical constants based on the theory of strength of expression fundamental parameter method to conduct a quantitative determination of such line intensity distribution, it is possible to obtain the CaO content and SiO ₂ content in the slag, the evaluation of the basicity Is possible. In the present invention, both the calibration curve method and the fundamental parameter method can be used.

Next, a method for preparing a sample for analysis will be described.

Since a large amount of gas is generated during the refining process such as the degassing treatment process or the talline process of the molten iron, the collected slag sample pieces are porous and have many voids. Therefore, even if the surface of the slag is smoothed by polishing or the like in order to adopt the direct method, microscopic holes are present in some places, and the basicity based on the analysis value obtained by analyzing the sampled sample greatly differs depending on the measurement position . In addition, there is also a problem that the measured value becomes expensive because of the basicity determined by the direct method. This is considered to be because the fluorescent X-ray intensity from silicon belonging to the soft X-ray region is attenuated by the air existing in the gap of the slag sample piece, and thus the apparent basicity is increased.

The present inventors have studied to prevent attenuation of the fluorescent X-ray intensity of silicon by air existing in the pores of the slag sample piece. To do so, the inventors of the present invention have found out that the slag particles can be made to have such a size that the attenuation of the fluorescent X- It was considered that pulverization was necessary, and the experiment was conducted.

In the examination experiment, the slag sample pieces were roughly pulverized, and then the pulverized material was classified into a sieve, and the effect of the slag particle diameter on the measured basicity was examined. Classification,

(1) A method for producing slag particles,

(2) having a particle diameter of 9.5 mm or more,

(3) having a particle diameter of 4.8 mm or more and less than 9.5 mm,

(4) having a particle diameter of 2.0 mm or more and less than 4.8 mm,

(5) having a particle diameter of 1.2 mm or more and less than 2.0 mm,

(6) having a grain size of 0.1 mm or more and less than 1.2 mm,

.

Here, for example, when the particle diameter of the slag particles is 0.1 mm or more, the particles passing through the sieve having a mesh size of 2.0 mm means that the particles remain in the sieve having a mesh size of 0.1 mm and the particle diameter of the slag particles is less than 2.0 mm . In short, the particle size of the slag particles is a particle size determined by classification by sieves.

Each of the classified slag particle groups was filled in a measuring container of a cylindrical shape (chalet image) having an inner diameter of 90 mm as a sample for analysis, and a group of slag particles in the measuring container was subjected to a hand-held fluorescent X- DELTA), the intensity of calcium and silicon fluorescent X-rays (secondary X-ray) from the sample for analysis was measured, and the slag basicity was calculated using the fundamental parameter method Respectively. The output of the X-ray source was a tube voltage of 50 kV and a tube current of 0.2 mA, and the fluorescence X-ray counting time per point was 25 seconds. The measurement score was 6 points for each analytical sample, and the deviation (standard deviation) of the measured values was also evaluated.

It is sufficient that the thickness of the group of slag particles in the measuring container is such that the bottom portion of the measuring container is completely invisible. There is also a case where the surface of the group of slag particles is inclined or in the form of an acid upon filling of the measuring container. In such a case, vibration is applied to the measuring container to make it flat, It is sufficient to secure a portion that makes contact with the X-ray irradiated portion of the fluorescent X-ray analyzer without gap. In other words, there is no restriction on the charging method as long as a portion for making contact with the X-ray irradiated portion of the hand-held fluorescent X-ray analyzer without gaps can be ensured.

As a comparison, a sample for analysis was prepared using the briquetting method and the glass bead method (process analysis method), and the basicity of slag was measured under the same conditions as above.

Fig. 1 shows the measurement results of slag basicity of each analytical sample. As shown in Fig. 1, the slag has a basicity of about 1.20 in all of the analytical samples prepared by the briquetting method and the glass bead method, and the basicity of the slag provided in the test is about 1.20. On the contrary, the measured value of the slag basicity of the sample for analysis is about 2.40, which decreases with decreasing particle size of the slag particles, and when the particle size of the slag particles is 0.1 mm or more and less than 1.2 mm or 1.2 Mm or more and less than 2.0 mm, a basicity almost equal to that of the analytical sample prepared by the briquetting method and the glass bead method was obtained. In addition, with respect to the deviation of the measured value of the basicity, when the particle diameter is less than 0.1 mm and less than 1.2 mm and the particle diameter is not less than 1.2 mm and less than 2.0 mm, the standard deviation sigma, %).

From the above experiments, it was found that by adjusting the particle diameter of the slag particles to about 2.0 mm or less, the decline of the fluorescent X-ray intensity of the silicon by the gap can be reduced to a negligible level and the analytical accuracy is improved, Or the analytical value obtained by the glass bead method.

Further, in order to investigate the influence of the slag particles having a particle diameter larger than 2.0 mm, the following experiment was conducted.

The same slag was pulverized and classified by slag granulation,

(1) The particle size distribution of the slag particles passing through the sieve is defined as 100% particle size (the cumulative mass percentage is 100%) in the cumulative particle size distribution curve represented by the percentage of the mass, particle size as will be described also as "D _100"), that is, the sample (sample a particle size of the cumulative mass percentage of the following body being 100% 2.0 ㎜) which,

(95% particle diameter, 95% particle diameter, also referred to as " D ₉₅ ") in the cumulative particle size distribution curve represented by the mass percentage, that is, the cumulative mass percentage below the body is 95% A sample (sample B) having a particle diameter of 2.0 mm,

(Also referred to as " D _{90 &} quot ;, with a particle size at which the cumulative mass percentage is 90%), that is, the cumulative mass percentage under the sieve is 90 % (Sample C) having a particle diameter of 2.0 mm,

85% particle diameter (particle diameter with 85% cumulative mass percentage, also referred to as " D ₈₅ ") in a cumulative particle size distribution curve represented by the mass percentage, that is, a cumulative mass percentage below the body is 85% A sample (sample D) having a particle diameter of 2.0 mm,

(Also referred to as " D _{80 &} quot ;, with a particle size at which the cumulative mass percentage is 80%) in a cumulative particle size distribution curve represented by a mass percentage, that is, a cumulative mass percentage below the body is 80 % (Sample E) having a particle diameter of 2.0 mm,

Were prepared.

Each prepared slag particle group was filled in a measuring container of a cylindrical shape (chiral image) having an inner diameter of 90 mm in the same manner as the above-mentioned experiment, and the slag was measured for its basicity by a hand-held fluorescent X-ray analyzer (6 points of measurement).

Table 1 shows the measurement results of the basicity.

The basicity of the slag measured by the glass bead method was 1.18, and the analytical values of the samples A, B, C and D were substantially equal to the basicity measured by the glass bead method. In the sample E, the measured basicity was 1.24, which was slightly higher than the glass bead method. Regarding the analytical accuracy, in the samples A, B and C, the standard deviation sigma was all 0.05 or less, while in the samples D and E, the standard deviation sigma was approximately 0.1.

This result shows that, in the sample D, although the average value of the basicity by the six-point analysis is close to the analytical value by the glass bead method, the deviation of the analysis value is large and the correct basicity may not always be obtained. Further, in the sample E, the measured basicity is high in price relative to the glass bead method and large in deviation, indicating that it is not suitable for analyzing the basicity.

For this reason, all of the samples D and E contain 15 mass% or more of slag particles larger than 2.0 mm in the analytical sample. As a result, voids and irregularities generated by the slag particles larger than 2.0 mm It is thought that it is affecting. In other words, in order to measure the basicity with good accuracy and also, it is shown that the slag sample to be measured for basicity should not contain slag particles of 2.0 mm or more in a range exceeding 10% by mass. That is, it was found that the slag sample for measuring the basicity needs to have a 90% particle size, that is, a D ₉₀ of 2.0 mm or less.

As described above, by adjusting the particle diameter of the slag particles, the attenuation of the fluorescent X-ray intensity of silicon by the void can be reduced to a negligible level, the analysis accuracy is improved, and the analyzed value of the basicity is improved by the brittle method or the glass bead method It becomes clear that the obtained analytical value becomes almost equal to the obtained analytical value. It was possible to measure the basicity of the slag in a short period of time of about 30 seconds or so in addition to the analysis time after grinding and classification of the slag particles to obtain the analytical sample.

As long as the slag can be crushed by the above-mentioned particle diameter, there is no restriction on the crushing method. For example, by controlling the gap width of the crusher to an appropriate set value and pulverizing the crushed material, slag particles having a particle size satisfying D ₉₀ 2.0 2.0 mm Can be obtained.

As described above, by setting the slag sample to D ₉₀ 2.0 2.0 mm, good results almost equivalent to those obtained by the briquetting method and the glass bead method can be obtained. As a result of further studies, When the content is increased, the analytical precision tends to be lowered. The reason for this is that the obtained sample is uneven as a mixture of the fine-particle-like slag and the granular slag, that is, in a portion where the ratio of the granular slag is large and the ratio of the fine-particle slag is large, It is thought that it is by thing having.

Moreover, the fine-particle-like slag particles having a particle size of about 0.1 mm or less fly easily and the handling of the sample becomes troublesome, and it takes time for the operation, which is not preferable when applied to rapid analysis. Thus, the following experiment was conducted to investigate the influence of the fine powdery slag particles.

The same slag was pulverized and classified by slag granulation,

(1), a sample of D ₉₀ = 2.0 mm (sample I)

(Sample 2), D ₉₀ = 2.0 mm and D ₅ = 0.1 mm (sample II)

(3), D ₉₀ = 2.0 mm and D ₁₀ = 0.1 mm (Sample III),

(Sample 4), D ₉₀ = 2.0 mm and D ₁₅ = 0.1 mm (sample IV)

(5), D ₉₀ = 2.0 mm and D ₂₀ = 0.1 mm (sample V)

(6): a sample of D ₁₀₀ = 0.1 mm (sample VI),

Were prepared.

Each slag particle group was packed in a cylindrical container (chiral phase) measuring 90 mm in inner diameter in the same manner as the above-described experiment, and used as a sample for analysis. The slag basicity was determined by a handheld fluorescent X-ray analyzer Point).

Table 2 shows the measurement results of the basicity.

As shown in Table 2, in all the analytical samples, the measured basicity was in good agreement with the basicity measured by the glass bead method. However, in the sample IV and the sample V, the standard deviation sigma indicating the analytical precision exceeded 0.05, and it was found that the sample deviates from the other samples. On the other hand, in the sample VI, both the accuracy and the accuracy of the analysis were excellent, but it was necessary for about 7 minutes to prepare the sample with a sample of D ₁₀₀ = 0.1 mm. In addition, the treatment of the sample was troublesome, and it took 12 minutes or more until the completion of the measurement of the basicity, due to operational troubles such as the attachment of the fine slag to the measurement site of the fluorescent X-ray analyzer.

These results indicate that if the slag particle size of 0.1 mm or less is more than 10%, the analysis accuracy may be lowered. In addition, if the slag particles are all made to have a fine particle size of 0.1 mm or less, Respectively. From the above, it was found that the slag sample for measuring the basicity needs to have a D ₁₀ of 0.1 mm or more.

From the above experimental results, it was found that the slag sample for measuring the basicity had a D ₁₀ ? 0.1 mm and a D ₉₀ ? 2.0 mm.

For example, when a sieve having a mesh size of 0.1 mm and a sieve having a mesh size of 2.0 mm are passed through a sieve having a mesh size of 2.0 mm and passed through a sieve having a mesh size of 0.1 mm Is used as a sample for analysis, it is possible to obtain an analytical sample having a desired particle size of 2.0 mm or less and having fine particle-free particles removed. Further, at that time, by using a sieve having a mesh size of 2.0 mm and a sieve having a mesh size of 0.1 mm in a superimposed manner, the operation time required for classification is sufficiently shortened, which is preferable for rapid analysis.

Hereinafter, one embodiment of the present invention including a refining step for preliminarily treating molten iron with the intermediate disposing step therebetween will be described.

In the molten iron preliminary treatment in which the degreasing treatment and the talline treatment are carried out with the intermediate disposing process in between, the composition and mass of the slag remaining in the furnace at the time before the talline treatment are grasped is determined in order to determine the amount of the appropriate CaO- It is necessary to put it. CaO-based bulking agents for controlling the CaO content in the slag are formed from CaO, limestone (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ), dolomite (MgO-CaO) And decarburized slag (also referred to as " converter material ").

Therefore, in one embodiment of the present invention, in order to quickly analyze the slag composition, the slag is collected during the intermediate discharge process from the end of the degassing process, and the collected slag is discharged from the furnace of the furnace type refining furnace into a simple sample preparation To obtain slag particles satisfying D ₁₀ ≥ 0.1 mm and D ₉₀ ≤ 2.0 mm. Thereafter, the collected slag particles are charged in a measuring container to be used as an analytical sample, and the composition of the slag is quantitatively analyzed by fluorescent X-ray analysis, and the basicity of the slag is measured from this analytical value.

More specifically, a degasification treatment step of degasifying a molten iron wire out of a blast furnace by using one converter type refining furnace, and a step of regenerating the molten metal iron powder produced by the degasification treatment step in a state where the molten iron after the degassing treatment is remained in the refining furnace A tallining process for talling the molten iron remaining in the converter refining furnace; a tallining process for talleting the molten tallane-treated molten iron from the converter refining furnace; In which the composition of the pre-formed slag is quantitatively analyzed by the above-described slag analysis method according to the present invention, and based on the analysis result, the pre- To obtain the basicity of the degassed slag.

In other words, after performing the conventional degasification treatment in which the CaO system bulking agent and gaseous oxygen or iron oxide are supplied as an oxygen source to the charcoal in the converter type refining furnace, the converter type refining furnace is disposed on the side opposite to that at the time of tapping, In short, the converter type refining furnace is tilted on the opposite side of the side where the tapping tunnel is installed, and the slag is discharged (intermediate discharge) through the nog. During this intermediate disposal process, an analysis of the slag composition is performed.

The slag sample piece to be provided to the sample for analysis is not particularly limited as long as it can be collected during the intermediate disposal process from the end of the degumming treatment. Examples of the method of collecting the slag sample pieces include a method of collecting the slag from the furnace that has been tilted at the time of intermediate disposal, a method of collecting the slag from the furnace at the time of intermediate disposal, And a method of sampling the slag from the slag.

Measurement of the basicity of a talgyu slag collected is, in gicheuk of a converter type refining, and imports the fluorescent X-ray analyzer, crusher, sieve, and measuring container, by performing a coarse ground particles and the sample prepared on the spot, D ₁₀ ≥ 0.1 mm Further, slag particles satisfying D ₉₀ & amp _; le; 2.0 mm are collected. The collected slag particles are charged in a measurement container and used as an analytical sample. The fluorescent X-ray intensity of two or more elements containing calcium and silicon from the analytical sample is measured. Subsequently, the slag composition is quantitatively determined using the calibration curve method or the fundamental parameter method, and the basicity of the slag is calculated.

It is possible to quantitatively analyze the slag from the sampling of the slag sample to the basicity measurement, including the sample preparation of crude grinding, in about 1 minute per point of one analytical sample. The method of analyzing slag according to the present invention is advantageous in that the deviation is small, so it is sufficient to perform analysis at one point for one analytical sample. Needless to say, it is possible to analyze a plurality of points with respect to one analytical sample and use their average value, but the necessity is low because the analysis time is long.

2 is a graph showing a comparison of the basicity of the demineralized slag obtained by the slag analysis method according to the present invention and the basicity of the demineralized slag obtained from the analytical value of the analytical sample prepared by the briquetting method conducted in the analysis room. As shown in Fig. 2, it can be confirmed that there is a good linear relationship between them. The details of FIG. 2 will be described later.

In the talline processing step subsequent to the intermediate disposal step, the basicity of the demineralized slag and the residual amount of slag in the converter-type refining furnace obtained by the analysis method according to the present invention are used so that the slag basicity required for the tallin processing of the molten iron in the furnace , The amount of the CaO-based antistatic agent to be added is calculated, and based on the calculation result, the CaO-based antistatic agent is added to the furnace to carry out the tallin processing. The amount of residual slag in the converter type refinery is calculated as the difference between the estimated mass value of the slag in the furnace before the intermediate disposal and the slag discharge amount estimated from the mass measurement value of the slag receiving container containing the slag discharged by the intermediate disposal.

As for the talline treatment process, a conventional tallane treatment process is carried out by supplying gaseous oxygen or iron oxide as an oxygen source into a furnace. The target value of the slag basicity is set from the phosphorus concentration of the molten iron before the tallin treatment, the molten iron temperature, the target value of the phosphorus concentration of the molten iron after the tallin treatment, and the like, and the composition analysis of the demineralized slag Based on the result and the amount of residual slag in the furnace, the addition amount of the CaO based antistatic agent is determined based on the mass balance. It is also possible to collect slag before the talline treatment in each charge and then prepare samples for analysis by the glass bead method or the briquetting method and confirm the composition of this sample for analysis by an analysis method such as fluorescent X- It is possible to confirm to what extent the basicity of the slag before the tallin treatment is.

The molten iron after the tallin treatment is tilted by a converter type refining furnace and is poured into the molten iron receiving vessel from the outflow port provided in the converter type refining furnace. On the other hand, the slag after the tallin processing (the slag generated in the tallin processing step is referred to as "tallin slag" ) Is left in the converter-type refining furnace. Thereafter, a new char iron line (char iron used in the next charger) is charged into the converter refining furnace, and the next charger charger is started. After the next charge, since the slag of the former charge remains in the converter type refining furnace, the degasification treatment can be carried out even without adding the CaO based anticorrosive agent. However, when the basicity of the slag is lowered, a CaO-based antistatic agent is added.

As is apparent from the above description, according to the embodiment of the present invention including the refining process for preliminarily treating molten iron through the intermediate disposing process, the slag basicity in the intermediate disposing process can be grasped with good precision, , It is possible to determine the addition amount of the CaO-based magenta agent suitable for the talline treatment. As a result, it is possible to minimize the addition amount of the CaO-based antistatic agent, and it is possible to carry out the preliminary treatment of molten iron at a low cost without lowering the productivity.

In the above description, the case of the iron preliminary treatment in which the degreasing treatment and the tallin treatment are carried out with the intermediate disposing step in between has been described. However, even when the molten steel is dissolved from the iron wire, , The present invention is applicable.

That is, a CaO-based scavenger and an oxygen source are supplied to a converter-type scouring furnace to perform a talline treatment on a charcoal in the converter-type scouring furnace (also called a "decalignant treatment" And the discharge is carried out. In this intermediate disposal step, the slag analysis method according to the present invention is applied to analyze the slag composition. As for the decarburization treatment process in the next step, a decarburization treatment method conventionally performed is carried out by supplying a CaO-based magenta powder and an oxygen source to the furnace. The target value of the slag basicity is set from the molten steel temperature after the decarburization treatment and the target value of the phosphorus concentration of the molten steel and the like and the analysis result of the component of the talline slag measured by applying the slag analysis method according to the present invention, From the amount of residual slag estimated from the mass measurement of the slag receiving vessel containing the talline slag, the amount of CaO-based scavenger added is determined based on the mass balance.

After the decarburization treatment, the generated molten steel is tilted in a converter type refining furnace, the molten steel is introduced into a molten steel receiving container from a tapping hole provided in a converter refining furnace, and a part or all of the decarburized slag (decarburization slag) ≪ / RTI > Thereafter, a new charcoal line (char iron used in the next charge) is charged into the converter refining furnace, and the next talline charge process is started.

It is also clear that components other than calcium (Ca) and silicon (Si) in the slag can be analyzed by the same procedure. For example, by controlling and controlling the MgO content in the slag, It can be prepared as slag having an appropriate composition with little expansion. The reason why the furnace body life affects the content of MgO in the slag is that the built-in refractory of the converter type refining furnace is formed of the MgO refractory, and when the MgO content in the slag is lowered, the MgO leaching occurs from the MgO refractory, , And the lifetime of the MgO-based refractory is lowered. Therefore, in the talline treatment and decarburization treatment of the molten iron using the converter type refining furnace, MgO-based fugitive agent is used as a part of the coagulant. Examples of the MgO-based bulking agent for controlling the content of MgO in the slag include dolomite, a crushed product of MgO-based bricks, and magnesia clinker.

Further, in the talline treatment of the molten iron, the talline treatment can be performed efficiently by measuring and controlling the FeO _x content in the slag. In the talline treatment of molten iron, FeO _x in the slag contributes to the oxidation of phosphorus in the molten iron and the commodification of the slag. For efficient tallin treatment, it is preferable that 5 to 15 mass% of FeO _x exist in the slag. Therefore, in the talline treatment of a molten iron using a converter-type refining furnace, an iron oxide-based antifoaming agent is used as a part of the anticorrosive agent. Examples of the iron oxide scavenger for controlling the content of FeO _{x in the} slag include iron ore powder, sintered powder as a mixture of iron ore and quicklime, and dust dust in a steelmaking process. Further, FeO _x refers to all of iron oxides such as FeO and Fe ₂ O ₃ .

The slag analysis method according to the present invention is also applicable to the refining process in which the slag is intentionally left in the refining furnace and the remaining slag is utilized for the next charge.

For example, when one of the converter type refining furnaces is used to repeatedly perform the talline processing (including the degassing and tallining processing) of the molten iron, or the one molten steel is decarburized using one converter type refining furnace In the case where the molten iron is refined in the next refining furnace by newly charging molten iron while at least part of the slag remains in the furnace after the molten iron is poured . This is carried out in order to utilize the talline function remaining in the treated slag for the next talline treatment and decarburization treatment of the following charcoal. In this case, the slag analysis method of the present invention is applied to analyze and evaluate the slag component after the treatment to evaluate the talliness or the like of the slag to adjust the residual amount of the slag or the following amount of the additive for refining Or the like.

Example 1

In the preliminary treatment for the charcoal using the one degassing treatment, the intermediate discharge, and the tallin treatment in this order using one converter type refining furnace having a capacity of 250 tons, Subsequently, the degassed slag was collected from the converter-type refining furnace. Each of the obtained slag was divided into two, and one of them was provided to the slag analysis method (the present invention method) related to the present invention, and the other was provided to the conventional slag analysis method (conventional method) conducted as the process analysis. With the present invention method and the conventional method, it was compared with the basicity of the slag talgyu ((mass% CaO) / (SiO ₂ mass%)). In the method of the present invention, all steps from preparation to analysis of analytical samples were carried out at the metering side of the converter type refining furnace.

The preparation method of the sample for analysis and the analysis conditions in the method of the present invention are as follows.

[Analytical Sample Preparation Method]: The slag was pulverized with a jaw crusher set to a grinding grain size of 2.0 mm, and classified into a sieve having a mesh size of 0.1 mm and a mesh size of 2.0 mm to obtain a grain size of 0.1 mm to 2.0 mm And the group of slag particles thus collected were charged in a measurement container to prepare a sample for analysis.

[Analysis conditions]: X-rays were irradiated at an output of 50 kV and 0.2 mA using an energy dispersive hand-held fluorescent X-ray analyzer (Olympus-manufactured DELTA). The measurement score was one point for each analytical sample, and calcium and silicon were used as elements to be analyzed. Calcium and silicon were quantitatively determined by the fundamental parameter method.

On the other hand, the preparation method and the analysis conditions of the analytical sample in the conventional method are as follows.

[Analytical sample preparation method]: A sample for analysis was prepared by the briquetting method. Specifically, the slag was pulverized to a particle diameter of 75 탆 or less, and the pulverized slag was filled in a dedicated metal vessel (diameter: 40 mm, thickness: 5 mm) and pressure-molded.

[Analysis conditions]: X-rays were irradiated with an output of 50 kV and 50 mA using a wavelength dispersive X-ray fluorescence spectrometer (Rigaku Simultix). The measurement score was one point for each analytical sample, and calcium and silicon were used as elements to be analyzed. Calcium and silicon were determined by the calibration curve method.

2 is a graph showing the basicity of the desulfurized slag obtained by the method of the present invention and the conventional method. When the accuracy of the method of the present invention was evaluated by an error (standard deviation sigma d of deviations) from the conventional method, sigma d = 0.04, and it was confirmed that there was a good linear relationship between them as shown in Fig. When the analysis time per sample was compared, it was one minute in the method of the present invention and 25 minutes in the conventional method.

From these results, it can be confirmed that the composition analysis of the slag can be accurately and quickly performed by applying the slag analysis method according to the present invention.

Example 2

When the pre-treatment is carried out on the molten iron by carrying out the degreasing treatment, the intermediate discharging treatment and the talline treatment in this order using one converter type refining furnace having a capacity of 250 tons, the slag analysis method according to the present invention is used, (Refining 1 of the present invention) for determining the addition amount of the CaO based anticorrosive agent based on the analysis result of the slag composition. Specifically, the slag composition after the degassing treatment was analyzed at the time of the intermediate discharge, and the basicity ((mass% CaO) / (mass% SiO ₂ )) of the slag after the degreasing treatment was determined based on the result of analysis of the slag composition. Based on the obtained basicity, the addition amount of the CaO-based bulking agent in the talline processing in the next step was calculated, and the calculated amount of the CaO-based bulking agent was added. The method of analyzing the slag composition at the time of the intermediate disposal was carried out under the same conditions as the method of the present invention of [Example 1] from preparation to analysis of analytical samples.

Apart from this, the basicity of the slag after the degumming treatment is estimated by calculation, without analyzing the slag composition after the degasification treatment, and the addition amount of the CaO-based scavenger in the tallining treatment in the next step is calculated based on the estimated basicity (Comparative Example 1) in which the calculated amount of the CaO based antioxidant was added.

With respect to both of Inventive Example 1 and Comparative Example 1, the target value (upper limit value) of the phosphorus concentration at the end of the talline processing was 0.030 mass%, and the slag after the tallin treatment was left in the furnace without being discharged, (N = 1 to 100) of a series of preliminary treatments of a series of charcoal, in which a charcoal charge was charged, followed by decalcification treatment, and then a tallin treatment was carried out with an intermediate charge disposed therebetween.

In the decalcification process, the amount of the decarburized slag was adjusted so that the calculated value (calculated basicity) of the basicity of the slag after the denitrification treatment was 1.20, using decarburized slag as the CaO-based magma. When the calculated basicity can secure the above-mentioned target value (1.20) without adding decarburized slag, the decarburization treatment is carried out without adding decarburized slag. The oxygen source was supplied according to the silicon concentration in the molten iron.

The basicity of the degassed slag was calculated by the equation (1) in the comparative example 1, and calculated by the equation (2) in the inventive example 1.

In the equations (1) and (2), the symbols are as follows.

B _{c, Si 1} (n): Calculation of slag at the end of deagglomeration in the pre-treatment of the n-th base,

_{Bc, P1} (n-1): Calculation of slag at the end of the talline treatment of the pre-treatment of the n-1th charge

W _{S, P1} (n-1): calculation at the end of the talline processing of the pre-processing of the (n-1) th charge slag mass (t)

W _{SL, Si1} (n): The addition amount (t) of decarburized slag in the decarburization treatment step of the pre-

X _Si1 (n): Silicon concentration (mass%) in the molten iron before the degreasing treatment in the pre-treatment of the nth charge,

W _HM1 (n): the molar mass (t) before the degreasing treatment in the pre-

B _{m and Si 1} (n): the slag after completion of the degassing treatment in the pre-treatment of the n-th charge, the basicity obtained by the slag analysis method according to the present invention

(% By mass) determined by the slag analysis method according to the present invention of the slag after completion of the degassing treatment in the pretreatment of the n-th storage tank (% CaO) _{m and Si1} (n)

(% SiO _{2) m, Si1} (n): n in the slag after the end talgyu up processing of the second pre-processing, the SiO ₂ concentration (% by weight) amount by the slag analysis method according to the invention

α ₁ : Sum of the average values of the mass ratios of CaO and SiO _{2 in} the slag after the tallin treatment

β ₁ : average value of the mass ratio of CaO in the decarburization slag added during the degassing treatment

γ ₁ : the average value of the mass ratio of SiO ₂ in the decarburization slag added during the degassing treatment

In the second embodiment,? ₁ = 0.6,? ₁ = 0.4, and? ₁ = 0.1. In addition, B _{c, P1} (n-1) and W _S, in the pretreatment of about described later, at 1 up to the calculation method of _P1 (n-1), B _{c, P1} (0) is 0 (zero) And W _{S, P 1} (0) = 0.

The slag mass at the completion of the degassing treatment was calculated by using the equation (3) in Comparative Example 1, and calculated by using the equation (4) in the present invention.

In Equation (3) and Equation (4), the symbols are as follows.

W _{S, Si 1} (n): Calculation at the end of deagglomeration of the pre-treatment of the n-th charge The slag mass (t)

隆₁ : Sum of the average values of the mass ratios of CaO and SiO _{2 in} the slag after degreasing treatment

The codes described in the expressions (1) and (2) other than the above are the same as those described above. In the second embodiment,? ₁ = 0.5.

In the intermediate disposal step, the intermediate disposal was carried out while confirming the weighing value of the slag to be discharged so that the disposal amount to the calculated slag mass (W _{S, Si1} (n)) at the end of the denitrification treatment was 50 mass% or more. The weighing of the slag discharged was carried out by using a weighing machine provided on a moving truck carrying a container for receiving the slag.

Here, in the case of the intermediate scatters, when it is desired to reduce the residual amount of slag in the furnace and to increase the tilting angle of the converter-type scouring furnace in order to obtain a large dispatching rate, or when the forming of the descaling slag is low, Is mixed into the slag and discharged to some extent from the furnace. In this case, the amount of charcoal emissions is not necessarily constant. However, in most cases, it has been confirmed that the mass ratio of molten iron incorporated into the degassed slag is relatively low and stable. Therefore, even if the mass ratio of the pig iron obtained from the analytical sample of the discharged degassed slag is used as a representative value and the mass of the discharged degassed slag is calculated based on the weighed value of the effluent, there is no problem in most cases. Thus, in Example 2, 0.9 times the value of the weight of the effluent in the intermediate scraping was calculated as the slag mass (= W _{O, Si 1} (n)) discharged after the decarburization treatment.

In the talline treatment process, calcium oxide was used as a CaO-based magma tanning agent and the amount of calcium oxide used was adjusted so that the calculated basicity of slag after talline treatment was 2.00 or more. The amount of gaseous oxygen used was set to a certain amount in any charge.

The calculated basicity of the slag (talline slag) after the talline treatment was calculated by using the equation (5) in Comparative Example 1, and calculated by using the equation (6) in the Inventive Example 1.

In Equation (5) and Equation (6), the symbols are as follows.

B _{c, P 1} (n): Calculation of slag after talline treatment of pre-treatment of n charge

W _{O, Si 1} (n): Slag mass (t) discharged after degreasing treatment in the pre-

W _{CaO and P1} (n): the addition amount (t) of the quicklime in the taline treatment step of the pre-

The codes described in the expressions (1) to (4) other than the above are the same as those described above.

The calculated slag mass at the end of the tallane treatment was calculated using the equation (7) in Comparative Example 1, and calculated using the equation (8) in the Inventive Example 1.

In the equations (7) and (8), W _{S and P 1} (n) are calculated slag masses (t) at the end of the tulle processing of the n th preliminary processing. The codes described in the other formulas (1) to (6) are as described above.

After boiling the molten iron after the talline treatment, the molten slag was not discharged, and the total amount of the molten slag remaining in the furnace was transferred to the next charge.

Thus, the phosphorus concentration of the molten iron after the talline treatment was compared in Example 1 and Comparative Example 1.

Fig. 3 shows the phosphorus concentration in the molten iron spouted in the molten iron receiving vessel after the tallin treatment of Inventive Example 1 and Comparative Example 1. Fig. For example, a value of "0 to 5" on the horizontal axis in FIG. 3 indicates "0 or more and less than 5", and other values are the same.

As shown in Fig. 3, in Comparative Example 1 in which the added amount of burnt lime was determined based on the composition of the prescaled slag estimated by calculation, in Example 1 of the present invention, the phosphorus concentration of the molten iron after the tallin treatment exceeded 0.050 mass% . As a result, the phosphorus concentration of the molten iron solder according to the present invention 1 was 0.028% by mass, which was significantly lower than that of Comparative Example 1 by 0.035% by mass.

When the basicity of the slag is not within the appropriate range in the tallin treatment process, the talline treatment does not proceed appropriately and the phosphorus concentration of the molten iron after the tallin treatment becomes higher than the target value. That is, in Comparative Example 1, there is a possibility that the calculated basic slag basicity deviates from the actual slag basicity.

On the other hand, in Example 1 of the present invention, the slag basicity of the tallin process is controlled based on the actual value of the slag basicity, so that the addition amount of the CaO-based magenta agent to make the slag basicity within the optimum range can be obtained with little or no excess. Thus, it is considered that the phosphorus concentration of the molten iron after the tallin treatment is reduced.

The above equations (1) to (8) are equations that correspond to the operating conditions such as the subsidiary materials used in [Example 2], but by changing their calculation equations in consideration of the material balance in other operating conditions, It is possible to calculate it.

Example 3

A refining method for performing preliminary treatment on a molten iron by performing degreasing treatment, intermediate discharging treatment and tallin treatment in this order using one converter type refining furnace having a capacity of 250 tons, characterized in that, after the degreasing treatment and after the tallining treatment, The residual degassing slag is utilized for the talline treatment in the next step and the remaining talline slag is used for the subsequent degassing treatment of the charcoal, , The refining method using the slag analysis method according to the present invention was carried out.

Specifically, the composition of the demineralized slag remaining in the furnace at the time of the intermediate impregnation was analyzed, and the amount of the CaO-based anticorrosive agent (burnt lime) in the tallin treatment was determined based on the composition analysis value, and the tallin treatment was carried out. Next, the basicity of the talline slag is estimated based on the addition amount of the CaO-based anticorrosive (quicklime), and the addition amount of the CaO-based anticorrosive agent (decarburization slag) is determined before the next decarburization treatment based on the estimated basicity of the talline slag And refining was carried out to add decarburized slag.

In other words, the slag basicity ((mass% CaO) / (mass% SiO ₂ )) after the degreasing treatment was determined by analyzing the composition of the degassed slag at the time of the intermediate disposal, and based on the slag basicity, After the prediction, the total amount of the slag after the tallin treatment was left in the furnace, and the addition amount of the decarburized slag was adjusted so that the basicity of the slag after the next degassing treatment was 1.2. The oxygen source was supplied according to the silicon concentration of the molten iron.

As described above, when the preliminary treatment of the molten iron is repeatedly carried out while adjusting the addition amount of the decarburized slag based on the measured value of the basicity of the demineralized slag (Example 2 of the present invention) and the analysis of the demineralized slag (Comparative Example 2) was repeatedly carried out based on the basicity of the pre-determined slag obtained by calculation, and the basicity of the slag after the degreasing treatment was compared with each other. Inventive Example 2 and Comparative Example 2 were carried out in eight consecutive pieces each.

In the second example of the present invention, the method of analyzing the slag composition at the time of the intermediate disposal was carried out under the same conditions as the method of the present invention of [Example 1], from preparation to analysis of the analytical sample. In Inventive Example 2 and Comparative Example 2, various parameters shown in Equations (1) to (8) used in [Example 2] were used as needed.

Table 3 shows the slag basicity after the degreasing treatment when the degreasing treatment, the intermediate disposal, and the talline treatment were repeatedly carried out.

In the present invention 2, the basicity of the demineralized slag is 1.21 as an average value of 8 charges, and falls within a range of ± 0.05 with respect to 1.20 of the target in all cases, and the slag basicity is controlled with good precision of less than 3% It was possible. On the other hand, in Comparative Example 2, the average value of the 8-charge degassed slag basicity was 1.27, which was slightly higher, and the relative standard deviation was 6% or more, so that the deviation of the slag basicity after the degreasing treatment was larger than that of Inventive Example 2.

The reason for this is as follows. In Example 2 of the present invention, the addition amount of the CaO-based anticorrosive agent (quicklime) was determined based on the measured value of the basic slag basicity at the time of the intermediate discharge, and the talline treatment was carried out. I think it is because it was. On the contrary, in Comparative Example 2, for example, the calculated basicity of talline slag is different from the actual basicity, and as a result, there is a possibility that the decarburized slag to be added as the CaO-based antistatic agent before the next degrada- tion treatment is excessive.

From the above results, according to the present invention, it was confirmed that refining can be carried out more efficiently in the next degreasing step.

Claims (9)

As a method for analyzing slag produced by refining molten iron,
A step of crushing the slag sample taken from the slag,
The particle size distribution of the slag particles passing through the sieve from the pulverized slag particles is set to zero and the 10% particle size (D ₁₀ ) in the cumulative particle size distribution curve represented by the mass percentage as a curved line in the upward direction is 0.1 mm or more , A step of collecting slag particles having a 90% particle diameter (D ₉₀ ) of 2.0 mm or less,
A step of filling the measurement container with the collected slag particles,
Measuring the fluorescent X-ray intensity from the charged group of slag particles,
And a step of quantitatively analyzing the composition of the slag from the measured fluorescent X-ray intensity. The method according to claim 1,
The fluorescent X-ray intensity of the two or more elements containing calcium (Ca) and silicon (Si) is measured in the step of measuring the fluorescent X-ray intensity. Refining of the next step of molten iron remaining in the converter refining furnace or part of refining of the converter refining furnace with the part of the slag generated by the refining of the molten iron in the converter refining furnace remaining in the converter refining furnace The present invention relates to a refining method of molten iron which performs refining of molten iron following charging using a newly charged molten iron into a furnace,
The composition of the slag generated by the refining of molten iron is quantitatively analyzed by the analysis method of slag described in the item 1 or 2,
In the refining of the next step of the molten iron remaining in the furnace or the refining of the molten iron charged in the furnace newly charged in the furnace, which is carried out in the converter-type refining furnace in which the slag is remained, Wherein the amount of the additive to be added is determined before and / or during the refining of the molten iron. The method of claim 3,
The refining of the molten iron is carried out by using a single converter type refining furnace to carry out a plurality of refining processes with respect to the molten iron and to cause a part of the molten iron and the slag to remain in the refining furnace And discharging the remaining portion of the slag,
The composition of the slag is analyzed at the time of discharging the remaining portion of the slag,
And the amount of the additive agent added in the refining step of the next step is determined based on the result of the analysis. The method of claim 3,
The refining of the molten iron is a refining in which preliminary treatment is performed on molten iron using one converter type refining furnace,
A preliminary treatment of the molten iron is carried out in which molten iron after the preliminary treatment is spouted while part or all of the generated slag is remained in the refining furnace and the molten iron is newly charged into the furnace to carry out the next preliminary treatment,
When the part or all of the slag is left in the reflux furnace, the composition of the remaining slag is analyzed,
And determining the amount of the additive agent to be added in the following preliminary processing based on the analysis result. A degassing step of degassing the molten iron leaving the furnace,
An intermediate discharging step of discharging the demineralized slag generated in the demineralizing treatment step in the transfer refining furnace while the molten iron after the demineralization treatment is left in the converter refining furnace;
A tallining process for tallining the molten iron remaining in the converter refining furnace,
And a tapping step of tapping the talline-treated molten iron from the converter-type refining furnace,
There is provided a refining method of molten iron in which a single converter refining furnace is used to carry out the above steps in the above-described order to preliminarily process molten iron,
During the intermediate disposal step, the composition of the demineralized slag is quantitatively analyzed by the slag analysis method described in the second paragraph,
Based on the analysis result, the basicity ((mass% CaO) / (mass% SiO ₂ )) of the degassed slag was obtained,
Wherein the amount of the additive to be added in the talline processing step is determined based on the obtained basicity ((mass% CaO) / (mass% SiO ₂ )). 7. The method according to any one of claims 3 to 6,
Wherein the conditioning agent is a CaO based anticorrosive agent. 8. The method according to any one of claims 3 to 7,
An MgO-based magentic agent is used as a part of the above-
The analysis results of the slag include the MgO content in the slag,
And the amount of the MgO-based magenta agent to be added is determined based on the analysis result of the slag. 9. The method according to any one of claims 3 to 8,
An iron oxide based anticorrosive agent is used as a part of the above-
The analysis results of the slag include the iron oxide content in the slag,
And the amount of the iron oxide based magenta agent to be added is determined based on the analysis result of the slag.

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