JP5370126B2 - Sinter analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and quantitatively evaluate the crystal structure of a crystal phase comprised in a sintered ore for a blast furnace raw material. <P>SOLUTION: The crystal structure of a calcium ferrite compound phase comprised in a sintered ore is decided, and, with the existing numbers of the Ca atoms and the Fe atoms present in the range at which the distance from the Fe atoms is &gt;0.067 nm to 0.6 nm as N<SB>Ca</SB>and N<SB>Fe</SB>, a correlation coefficient CFC defined by a ratio=N<SB>Ca</SB>/(N<SB>Ca</SB>+N<SB>Fe</SB>) is derived. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention is suitable for use in analyzing the crystal structure of the binder phase of various brands of iron ore used in the production of sintered ore for blast furnace raw materials.

  In general, sintered ore for blast furnace raw materials is manufactured through granulation and firing processes using iron ore powder, limestone, or the like as raw materials. That is, first, iron ore powder, sieving powder, auxiliary materials (limestone, serpentine, etc.), coke breeze, anthracite, return mineral, etc. are mixed, granulated with a primary mixer and secondary mixer, and granulated. Pseudo particles in which fine powder having a particle size of less than 1 mm adheres around a core particle having a diameter of 1 mm or more (a portion where the fine powder adheres are referred to as “adhered powder portion”) are manufactured. Thereafter, the pseudo particles are charged into a sintering machine to form a sintering bed, and then a fuel such as powdered coke on the surface of the sintering bed is ignited and burned while passing downward to sinter the sintered raw material. To do. Thereby, the sintered ore for blast furnace raw materials is manufactured.

In the firing process, the sintered raw material is heated by the combustion heat of the fuel, and its temperature rises to a maximum of nearly 1400 ° C. Usually, at around 1200 ° C, the initial melt (CaO-Fe ₂ O ₃ ) starts to form from the adhering powder part of the pseudoparticles. After this, when the temperature rises above around 1200 ° C, The initial melt penetrates into the sintered raw material, dissolves the required ore components, generates more melt, and finally forms the binder phase of the sintered ore. The amount of the binder phase, the degree of spreading, and / or the bonding mode greatly affect the quality of the sintered ore and the yield.

Conventionally, as a method for evaluating the binder phase, a method of estimating the amount of the binder phase from the raw material composition of the sintered ore using an equilibrium diagram (see, for example, Patent Document 1), or a cross-sectional structure of the sintered ore is used. There is a method (for example, refer to Patent Document 2) for evaluating the tissue morphology by observing with an optical microscope or the like.
However, even if the amount and structure of the binder phase are similar, the properties of sintered ore, such as strength and reducibility, often differ greatly, and a new evaluation method is required to improve the sintering process. It was.
In general, there is a technique using X-rays in a solid structural analysis method including sintered ore (see, for example, Non-Patent Documents 1 and 2).

JP 2002-129247 A JP 2003-82417 A

Kikuta, "X-ray diffraction / scattering technology" (The University of Tokyo Press, 1992) Edited by Yasuo Udagawa "X-ray absorption fine structure" (Japan Society for Publication Press, 1993)

  The present invention has been made in view of the above problems, and an object thereof is to enable simple and quantitative evaluation of the crystal structure of the binder phase contained in the sintered ore for blast furnace raw material. .

The present inventors examined the atomic arrangement of the calcium ferrite compound phase (hereinafter referred to as CF phase), which is the main binder phase of the sintered ore, and various properties of the sintered ore. As a result, the present inventors have found that the atomic arrangement of the CF phase, in particular, the atomic correlation between Fe and Ca is important.
CaFe ₂ O ₄ , which is a Ca-Fe-O oxide corresponding to the vicinity of the typical raw material mixture ratio used in the actual sinter production process in the Ca-Fe-O ternary equilibrium diagram in the atmosphere The crystal structure of the phase and the Ca ₂ Fe ₉ O ₁₃ phase is shown in FIG. Specifically, FIG. 1A shows the CaFe ₂ O ₄ phase, and FIG. 1B shows the Ca ₂ Fe ₉ O ₁₃ phase. Further, in FIG. 1, a white circle represents O, a hatched circle represents Ca, and a black circle represents Fe. As shown in FIG. 1, the CaFe ₂ O ₄ phase and the Ca ₂ Fe ₉ O ₁₃ phase are units in which O (oxygen) is coordinated around Fe and Ca (hereinafter, Fe-O unit and Ca-O, respectively). Units) are arranged, and the difference between the two structures lies in how the units are arranged. That is, the unit ratio obtained from the number of Fe-O units and the number of Ca-O units existing around the Fe-O unit (= number of Ca-O units / (number of Fe-O units + Ca-O It can be seen that the number of units)) is larger in the CaFe ₂ O ₄ phase than in the Ca ₂ Fe ₉ O ₁₃ phase. That is, the CaFe ₂ O ₄ phase is closer to the Fe—O unit and the Ca—O unit than the Ca ₂ Fe ₉ O ₁₃ phase.

  However, the CF phase in the sintered ore actually produced has the same crystal structure as the stable phase predicted from the Ca-Fe-O ternary equilibrium diagram in the atmosphere as described above. Not exclusively. This is because the conditions (temperature, concentration of constituent elements in the local material, gas atmosphere, etc.) in which the CF phase is formed in the sintering process are not constant for a long time but greatly change in a short time. For example, in a region where the diameter of the region is about several millimeters, the time during which the temperature of 1200 ° C. or higher is maintained is several tens of seconds or less. Therefore, diffusion occurs only on the surface between different particles, and the concentration of the constituent elements in the material in the local region is greatly different from the blending ratio of the raw materials. Furthermore, as the coke burns, the oxygen concentration in the local region is lower than the oxygen concentration in the atmosphere.

Therefore, as has been done conventionally, in the method of estimating the amount of the binder phase from the raw material composition of the sintered ore using an equilibrium diagram, the value may not be estimated correctly. In addition, in the conventional method of evaluating the structure of the sintered ore by observing the cross-sectional structure of the sintered ore with an optical microscope or the like, a plurality of CF phases contained in the binder phase cannot be distinguished, and the same structure However, various properties of the sintered ore (for example, mechanical strength and reducibility) are different.
Crystal growth is highly dependent on the environment around the atom. Therefore, if this environment is different, there will be a difference in the phenomenon of diffusion, melting, solidification, etc. that accompanies the temperature rise and fall, and the structure of the iron ore that will ultimately be produced will vary greatly. As a result, the strength and reducibility of iron ore are greatly different. In essence, the chemical structural environment is important, and as an indicator, the present inventors have found that the atomic correlation between Fe and Ca is important.

The present invention made under the above knowledge is as follows.
(1) Based on the crystal structure determination step for determining the crystal structure of the calcium ferrite compound phase contained in the sintered ore, and the crystal structure of the calcium ferrite compound phase, from the Fe atoms contained in the calcium ferrite compound phase An atomic number deriving step for deriving the number of Ca atoms and Fe atoms existing in a range of 0.067 nm to 0.6 nm or less, and a Ca atom existing in a range of 0.067 nm to 0.6 nm or less from the Fe atom The correlation index CFC (Calcium Ferrite) for evaluating the crystallographic characteristics of the binder phase in the sintered ore, defined by the following formula (A), where N _Ca and N _Fe are present as N _Ca and N _Fe , respectively. And a correlation index deriving step for deriving a correlation).
CFC = N _Ca / (N _Ca + N _Fe ) (A)
(2) In the correlation index derivation step, a correlation index CFC is obtained for each of the plurality of calcium ferrite compound phases, and each correlation index CFC is multiplied by a molar fraction of each of the plurality of calcium ferrite compound phases. Then, the correlation index CFC of the entire plurality of calcium ferrite compound phases is determined, and the sintered ore analysis method according to (1),
(3) It has a measurement step of measuring the calcium ferrite compound phase contained in the sintered ore by X-ray diffraction method, and the crystal structure determination step is based on the result measured by the X-ray diffraction method, The method for analyzing a sinter according to (1) or (2), wherein a crystal structure of a calcium ferrite compound phase contained in the sinter is determined.
(4) A radial distribution function determining step of determining a radial distribution function around Fe atoms contained in the calcium ferrite compound phase contained in the sintered ore by an XAFS method, and the crystal structure determining step includes: The method for analyzing sinter according to (1) or (2), wherein a crystal structure of a calcium ferrite compound phase contained in the sinter is determined based on the radial distribution function.

  According to the present invention, it is possible to easily and quantitatively evaluate the crystal structure of the binder phase contained in the sintered ore for blast furnace raw material. As a result, it is possible to evaluate in consideration of the atomic arrangement of the calcium ferrite compound phase in the crystal phase, and it is possible to evaluate highly related to various properties of the sintered ore. Furthermore, in the present invention, it is possible to cope with manufacturing conditions peculiar to the sintering process, and it is also applicable to a phase having no standard substance in the database. The present invention is an effective evaluation method for the development of sintered ore corresponding to deterioration and diversification of raw materials, environment resistance and high efficiency, and has great industrial significance.

It is a diagram showing the crystal structure of CaFe ₂ O ₄ phase and Ca ₂ Fe ₉ O ₁₃ phase. It is a figure which shows the X-ray-diffraction figure of the iron ore of the mixing | blending 3 in an Example. It is a figure which shows the investigation result of the atomic type, the distance from Fe atom, and an average number of the compounding example 1 in an Example. It is a figure which shows the radial distribution function calculated | required from the XAFS spectrum of the iron ore of the mixing | blending 2 in an Example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the evaluation method of sintered ore according to the present embodiment, the crystal structure of the calcium ferrite compound phase contained in the sintered ore is determined, and the following index: Correlation index CFC (Calcium Ferrite Correlation) of Fe atom and Ca atom, What is necessary is just to evaluate the crystal structure of a sintered ore. As used herein, “determining the crystal structure of the calcium ferrite compound phase” means at least obtaining information on the atomic correlation between Fe atoms and Ca atoms with respect to the arrangement of atoms constituting the calcium ferrite compound phase. Means. That is, the evaluation method of the sintered ore according to the present embodiment can be implemented regardless of the crystallinity of the calcium ferrite compound phase. When the crystallinity of the calcium ferrite compound phase is high, the structure of the unit cell of the crystal can be determined. On the other hand, when the crystallinity of the calcium ferrite compound phase is low, that is, when the calcium ferrite compound phase contains an amorphous component, it is theoretically difficult to determine the structure of the unit cell of the crystal. However, it is possible to determine information regarding the atomic correlation of the constituent atoms. Therefore, the evaluation method of the sintered ore according to the present embodiment can be implemented even when the crystallinity of the calcium ferrite compound phase is low.

After determining the crystal structure of the calcium ferrite compound phase, for each Fe atom present in the calcium ferrite compound phase, the distance r from the Fe atom is in the range of 0.067 nm to 0.6 nm or less. The ratio (= N _Ca / (N _Ca + N _Fe )) when the number of existence (number of atoms) is N _Ca and N _Fe is obtained for all Fe atoms present in the calcium ferrite compound phase, and Let the average be the correlation index CFC.
As an index indicating the arrangement of Fe-O units and Ca-O units, the ratio when the number of Ca and Fe atoms present in a certain range of distance r from Fe atoms is N _Ca and N _Fe , respectively. If the correlation index CFC which is (= N _Ca / (N _Ca + N _Fe )) is used, the CF phase contained in the binder phase can be simply and essentially evaluated. This means that the correlation between Fe and Ca atoms is a simple evaluation of how close the Fe-O unit and Ca-O unit exist, that is, the interaction (spatial arrangement) between the two units. It is because it is an index that can be done. As a result, the correlation index CFC is a useful evaluation method that is highly related to various properties (for example, mechanical strength and reducibility) of the sintered ore that are developed as a result of the interaction between the two units.

  When the correlation index CFC is used, the conventional problem that the CF phase that does not correspond to the equilibrium diagram or the crystal structure database cannot be evaluated can be solved. Furthermore, when many types of CF phases are mixed in the binder phase or the crystallinity of some of the phases is poor, it is possible to solve the problem that the evaluation by the diffraction method or the like is difficult. . The correlation index CFC is an index that continuously changes in accordance with the crystal structure of the bonded phase. Unlike the conventional two-way selective discontinuous evaluation method for determining whether a specific CF phase exists, It is possible to clearly evaluate slight differences in the crystal structure of the phases.

Here, the reason why the distance r from the Fe atom is limited to a range of more than 0.067 nm and not more than 0.6 nm when obtaining the correlation index CFC will be described.
The size of the Fe atom in the crystal differs depending on the valence, and Fe (II) has a radius of about 0.082 nm and Fe (III) has a size of about 0.067 nm. Therefore, no other atom can exist in the region where the distance r from the Fe atom is 0.067 nm or less. Therefore, the distance r from the Fe atom was set to more than 0.067 nm. When evaluating the atomic correlation between Fe and Ca, the correlation between the directly adjacent Fe—O unit and Ca—O unit is important. Therefore, the upper limit of the distance r from the Fe atom is larger than the distance from the Fe atom to the first proximity unit (unit closest to the Fe atom), and the second proximity unit (Fe 1 next to the first proximity unit). It is desirable that the distance is smaller than the distance to the unit close to the atom. The distance between the Fe atom and O (oxygen) adjacent to the Fe atom is about 0.20 to 0.21 nm, and the distance between the Ca atom and O (oxygen) adjacent to the Ca atom is about 0.24 nm. Alternatively, 0.6 nm, which is more than twice the distance of Ca—O and not more than 3 times, was used as a guide, and the distance r from the Fe atom was made 0.6 nm or less.

The correlation index CFC is specifically determined by quantitatively analyzing phenomena such as X-ray, electron beam, neutron, and ion scattering of a plurality of phases constituting the CF phase contained in the sintered ore. Do.
(First determination method of correlation index CFC)
First, taking as an example a method for obtaining a correlation index CFC by measuring a plurality of phases constituting a CF phase contained in a sintered ore by an X-ray diffraction method and determining a crystal structure of each phase. Described below.
When the X-ray diffraction method is used, the arrangement of atoms in the material can be evaluated, and the space group of the crystal and the position of the constituent atoms in the unit cell can be determined (see, for example, Chapter 1 of Non-Patent Document 1). A specific method will be described below, but the present invention is not limited to this. About the sample extract | collected from the sintered ore, the powder diffraction pattern is measured by an X-ray diffractometer. From the result, the crystal structure of the CF phase contained in the sintered ore is determined.

  The crystal structure of the CF phase is determined by calculating the diffraction pattern based on the crystal model constructed with reference to the structural data in the crystal database and past report examples, and the measured diffraction pattern and the diffraction pattern based on the crystal model. This is done by changing the crystal model so that the difference between the two is small. In this embodiment, the computer (information processing apparatus) determines the crystal structure of the CF phase by parameter fitting. That is, the computer inputs and stores the structural model (initial value) obtained by the user empirically. After that, when the computer inputs X-ray diffraction patterns of a plurality of phases constituting the CF phase contained in the sintered ore, the X-ray diffraction pattern based on the structural model (initial value thereof) is input. The crystal structure of the CF phase is derived on the basis of the parameters of the structural model when the X-ray figures coincide with each other.

When the crystal structure of the CF phase contained in the sintered ore is determined as described above, in the crystal structure, the Ca atom and the Fe atom existing in the range where the distance r from the Fe atom is greater than 0.067 nm and less than or equal to 0.6 nm. The ratio (= N _Ca / (N _Ca + N _Fe )) where N _Ca and N _Fe are respectively present is calculated as the correlation index CFC. When there are a plurality of CF phases, an average of correlation indices CFC obtained for all Fe atoms contained in one CF phase is taken (correlation indices CFC are obtained for each of the plurality of CF phases), The correlation index CFC of all the CF phases may be obtained by adding the correlation index CFC multiplied by the mole fraction of each CF phase. In the present embodiment, the computer performs such arithmetic processing.

(Second method for determining correlation index CFC)
Next, as another method for concretely determining the correlation index CFC, the radial distribution function around the Fe atom contained in the CF phase contained in the sintered ore is determined by the XAFS method, whereby the correlation index CFC is determined. The method for obtaining is described below.
The XAFS (X-ray Absorption Fine-structures) method is one of X-ray absorption spectrum methods. When the absorptance of a material is measured while increasing the energy of X-rays, the absorptance of the material decreases corresponding to the increase in energy of X-rays. However, the absorption at a specific X-ray energy (absorption edge energy) is reduced. The rate increases rapidly. Some of the photoelectrons generated by the absorption of X-rays are reflected as structural information on the amount of X-ray absorption by scattering and interference by a plurality of atoms. That is, if the amount of X-ray absorption near the absorption edge energy of a specific atom is monitored, information on the atomic arrangement (radial distribution function) around that atom can be obtained (see, for example, Non-Patent Document 2). A specific method will be described below, but the present invention is not limited to this.

  First, a sample collected from sintered ore is irradiated with X-rays having energy near the absorption edge energy of Fe and transmitted therethrough. The intensity of X-rays before and after transmission is measured, and the degree of X-ray absorption by the sample is measured from the ratio. This measurement is performed by changing the energy of X-rays. For the obtained X-ray absorption spectrum (XAFS spectrum), a vibration component from which the background is removed is obtained, and a radial distribution function around the Fe atom is obtained from a Fourier transform related to the distance. The energy of X-rays is proportional to the reciprocal of the wavelength of X-rays, and a correlation with atoms close to Fe atoms can be obtained by Fourier transforming this vibration period. In the present embodiment, when an X-ray absorption spectrum is input, the computer performs such calculation processing.

Each peak of the radial distribution function corresponds to the abundance ratio (coordination number) of Fe, Ca, and O. Therefore, in the radial distribution function, the number of Ca atoms and Fe atoms (number of atoms) is determined from the ratio of the peaks corresponding to Fe and Ca that exist in the range where the distance r from the Fe atom is greater than 0.067 nm and less than or equal to 0.6 nm. ) As N _Ca and N _Fe , respectively, the ratio (= N _Ca / (N _Ca + N _Fe )) is obtained as the correlation index CFC. When the peaks corresponding to Fe and Ca partially overlap, the peak corresponding to Fe and Ca is calculated by the crystal structure model assuming the distance and coordination number, and the distance of the crystal structure model when it matches the actual measurement And the coordination number.

The embodiment of the present invention described above can be realized by a computer executing a program. Further, a means for supplying the program to the computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium for transmitting such a program may be applied as an embodiment of the present invention. it can. A program product such as a computer-readable recording medium that records the program can also be applied as an embodiment of the present invention. The programs, computer-readable recording media, transmission media, and program products are included in the scope of the present invention.
In addition, the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

Example 1
The raw materials for sintering shown in Table 1 were blended in the proportions shown in Table 1. At this time, the ratio of other auxiliary materials such as limestone, serpentine, and silica was adjusted so that the ratio (ratio) of SiO ₂ , CaO / SiO ₂ , and MgO in the sintered ore was not greatly changed. The sintering raw material thus adjusted was sintered in a sintering pot test to produce a sintered ore, and the cold strength was measured. The cold strength was determined from the mass ratio of particles having a particle size of 10 mm or more after dropping a block (for example, a diameter of about 10 to 30 cm) of sintered ore from a height of 2 m.

  The obtained sintered ore was pulverized and the crystal structure was determined using an X-ray diffraction method. Using Cu Ka line as the source, X-ray diffractometer, 2θ = 5 to 120 ° (π / 36 to 2π / 3 rad), Δ2θ = 0.04 ° (π / 4500 rad), holding time for each step = 10 seconds The measurement was carried out. In order to determine the crystal structure of the CF phase, the diffraction pattern is calculated based on the crystal model constructed with reference to the structure data of the crystal database and past reports, and the measured diffraction pattern and the crystal model are used. This was carried out by changing the crystal model so that the difference from the diffraction pattern was small. In FIG. 2, the measured data and calculated value of the X-ray diffraction pattern of the sintered ore of the composition 3 are shown.

When the crystal structure of the CF phase is determined, in the crystal structure, the number of Ca atoms and Fe atoms existing in the range where the distance r from the Fe atom is more than 0.067 nm and 0.6 nm or less (number of atoms) is expressed as N _Ca , ratio when the N _Fe a _{(= N Ca / (N Ca} + N Fe)) was determined as the correlation index CFC. The results are shown in Table 2.

Taking the case of formulation 1 as an example, a more detailed method for determining correlation index CFC will be described.
As a result of measurement of the X-ray diffraction pattern, the sintered ore of Formulation 1 is a phase having a crystal structure close to [A phase] = CaFe ₂ O ₄ phase and a crystal close to [B phase] Ca ₂ Fe ₉ O ₁₃ phase. It was comprised from the two phases of the phase which has a structure, and the ratio became [A phase] = 31.5 mass% and [B phase] = 68.5 mass%. For each of [A phase] and [B phase], the type, distance, and average number of elements present around the Fe atom were determined. [Phase A] had two types of Fe atoms. FIG. 3 shows the survey results of the types of atoms (atomic species), the distance from the Fe atoms, and the average number of existing (average number) around one type of Fe atom. With respect to these elements present around the Fe atoms, the existence numbers (number of atoms) of Ca atoms and Fe atoms existing in the range where the distance r from the Fe atom is more than 0.067 nm and 0.6 nm or less were obtained. The same was done for another type of Fe atom. Further, in the same procedure for [B phase], the number of Ca atoms and Fe atoms existing in the range where the distance r from the Fe atom is more than 0.067 nm and not more than 0.6 nm for the elements present around the Fe atom. (Number of atoms) was determined. For each of [A phase] and [B phase], the ratio (N _Ca / (N _Ca + N _Fe )) was determined as the correlation index CFC of each phase. Then, the correlation index CFC of [A phase] and [B phase] is multiplied by the respective mole fraction calculated from [A phase] = 31.5 mass% and [B phase] = 68.5 mass%. The overall correlation index CFC was determined.

(Example 2)
Using the same sample as in Example 1 (see Table 1), the crystal structure of the CF phase was determined by the XAFS method. The sintered ore obtained as described above was pulverized, and the XAFS spectrum was measured by the transmission method. Using a synchrotron X-ray as a radiation source, the sample is irradiated with X-rays with different energy by spectroscopic analysis with X-rays, and the intensity of X-rays before and after transmission is measured in an ion chamber. XAFS spectrum was obtained. For the obtained XAFS spectrum, the vibration component from which the background was removed was obtained, and the radial distribution function around the Fe atom was obtained from the Fourier transform related to the distance. Each peak of the radial distribution function corresponds to the abundance ratio (coordination number) of Fe, Ca, and O. Since the binder phase and Fe ₂ O ₃ phase coexist in the sample, the radial distribution function of the binder phase is subtracted from the contribution to the radial distribution function from the Fe ₂ O ₃ phase with a known crystal structure. Got. In addition, when the peaks corresponding to Fe and Ca partially overlap in the binder phase, the peak corresponding to Fe and Ca is calculated by the crystal structure model assuming the distance and the coordination number. The distance and coordination number of the crystal structure model were adopted. Then, in the radial distribution function, the number of Ca atoms and Fe atoms (from the ratio of peaks corresponding to Fe atoms and Ca atoms existing in a range where the distance r from the Fe atom is greater than 0.067 nm and less than or equal to 0.6 nm ( The correlation index CFC was determined from the ratio (= N _Ca / (N _Ca + N _Fe )) where the number of atoms was N _Ca and N _Fe , respectively. In FIG. 4, the measurement example of the radial distribution function g (r) calculated | required from the XAFS spectrum of the iron ore of the mixing | blending 2 is shown.

(Comparative Example 1)
Using the same sample as in Example 1, the binder phase was observed with an optical microscope. After the sample was embedded in the resin and the cross section was polished, the ratio of the binder phase was measured with an optical microscope.
(Comparative Example 2)
Using the same sample as in Example 1, the amount of the binder phase was estimated using an equilibrium diagram. The composition of the sample was determined from instrumental analysis and chemical analysis, and the ratio of the binder phase was estimated from the Ca-Fe-O ternary phase diagram.

As described above, the effects of this example were clearly shown from the results of the examples and comparative examples. That is, it is clear when the correlation with the cold strength is examined. In the index obtained in the example, there is a correlation between the correlation index CFC and the cold strength, and the correlation index CFC is a value corresponding to the difference in the characteristics (cold strength) of the sample. On the other hand, the ratio of the binder phase and the amount of binder phase obtained in the comparative example are not correlated with the cold strength, and the correspondence with the cold strength cannot be found. The reason why this difference appears is described below.
In the bonded phase of this sample, two to three types of CF phases having different crystal structures and compositions were confirmed. Since the crystal structure of each phase is different, a difference occurs in the phenomenon such as diffusion, melting, and solidification accompanying the temperature increase and decrease, and the effect (contribution rate) on the cold strength in the binder phase is different. Since the correlation index CFC is an index based on the atomic arrangement of each phase, it is possible to correctly estimate the effect (contribution rate) of each phase, and a good correlation with the macro characteristics (cold strength) that is the result of such a combined effect. showed that. As described above, the present inventors have found a correlation index CFC for extracting essential features of atomic arrangement, and the correlation index CFC can quantitatively evaluate a composite effect based on scientific rationality. Therefore, by using the correlation index CFC, the crystal structure of the binder phase contained in the sinter for blast furnace raw material can be evaluated easily and quantitatively.

On the other hand, in the conventional method (Comparative Example 1), the CF phase having a different crystal structure and composition is not distinguished, and the ratio of the binder phase is measured as an indicator only from the form. This ratio is considered to have no correlation with the macro characteristics (cold strength).
In the conventional method (Comparative Example 2), the amount of the binder phase was estimated from the average composition of the entire sintered ore from the Ca-Fe-O ternary equilibrium diagram. However, in the sintering process, the conditions under which the CF phase is formed (temperature, constituent element concentration in the local material, gas atmosphere) are not in an equilibrium state over the entire sample in a very short time. Therefore, the composition of the binder phase is usually greatly different from the average composition of the entire sintered ore. Therefore, it is considered that the index obtained by the method for estimating the amount of the binder phase by the conventional method (Comparative Example 2) did not show a correlation with the macro characteristic (cold strength).

Claims (4)

A crystal structure determination step for determining the crystal structure of the calcium ferrite compound phase contained in the sintered ore;
Based on the crystal structure of the calcium ferrite compound phase, the number of atoms for deriving the number of Ca atoms and Fe atoms existing in the range of more than 0.067 nm and not more than 0.6 nm from the Fe atom contained in the calcium ferrite compound phase A derivation process;
The sintered ore defined by the following formula (A), where the numbers of Ca atoms and Fe atoms existing in the range of more than 0.067 nm and less than or equal to 0.6 nm are N _Ca and N _Fe , respectively. And a correlation index deriving step for deriving a correlation index CFC (Calcium Ferrite Correlation) for evaluating crystallographic characteristics of the binder phase therein.
CFC = N _Ca / (N _Ca + N _Fe ) (A)   The correlation index deriving step obtains a correlation index CFC for each of the plurality of calcium ferrite compound phases, and adds each correlation index CFC multiplied by the mole fraction of each of the plurality of calcium ferrite compound phases. The sinter analysis method according to claim 1, wherein the correlation index CFC of all of the plurality of calcium ferrite compound phases is determined. Having a measurement step of measuring the calcium ferrite compound phase contained in the sintered ore by an X-ray diffraction method,
The crystal structure determination step determines a crystal structure of a calcium ferrite compound phase contained in the sintered ore based on a result measured by the X-ray diffraction method. The sinter analysis method described. A radial distribution function determining step of determining a radial distribution function around Fe atoms contained in the calcium ferrite compound phase contained in the sintered ore by an XAFS method;
The sintered ore according to claim 1 or 2, wherein the crystal structure determining step determines a crystal structure of a calcium ferrite compound phase contained in the sintered ore based on the radial distribution function. analysis method.

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