JP2021178996A - Sintered ore structure evaluation method and sintered ore production method - Google Patents

Abstract

To propose a sintered ore structure evaluation method for readily evaluating the structure of a produced sintered ore and also propose a sintered ore production method for adjusting operation conditions of a sintering machine on the basis of the result of evaluation.SOLUTION: Any surface of a sintered ore is smoothened. A light-microscopic image of the smoothened surface is acquired, and a light-microscopic image of the smoothened surface having a translucent thin film added thereto is acquired. On the basis of the contrast between both light-microscopic images, an area ratio for each structure of the sintered ore is determined as a structural fraction.SELECTED DRAWING: Figure 1

Description

The present invention is a method for evaluating the structure of a sinter that evaluates the structure of the sinter by a simple method, and by optimizing the operating conditions of the sinter based on the evaluation results, the present invention provides a high-quality sinter. The present invention relates to a method for producing a sinter that can be produced.

Sintered ore is a mixture of multiple brands of powdered iron ore, auxiliary raw material powder such as limestone, silica stone, and serpentine, miscellaneous raw materials such as dust, scale, and return ore, and solid fuel such as powdered coke. It is produced by adding water to a sintering compound raw material, mixing and granulating it, and charging the obtained granulating raw material into a Dwightroid type (DL) sintering machine or the like and firing it. The above-mentioned sintering compounding raw material agglomerates with each other to form pseudo-particles by containing water during granulation, and the pseudo-granulated raw material for sintering is charged onto a pallet of a DL sintering machine during firing. Good air permeability can be ensured and smooth sintering can proceed.

By the way, in recent years, powdered iron ore, which is a raw material for sintering, has a remarkable tendency to be low in quality due to depletion of high quality iron ore, that is, an increase in slag component and micronization, which causes the quality of the sintered ore to deteriorate. It has become. In particular, there is a problem that an increase in the alumina component of iron ore increases the blast furnace slag ratio and causes an increase in the amount of reducing agent to be charged into the blast furnace. The sinter to be put into the blast furnace is required to have a low slag ratio, high reducibility and high strength from the viewpoint of reducing the _{cost of producing hot metal and reducing the amount of CO 2 generated.} From the viewpoint of operational stability of the blast furnace, it is also required to improve the product yield of the sinter (the ratio of the sinter having a particle size of 5 mm or more that can be put into the blast furnace). Therefore, in response to the adverse effects of lowering the quality of raw iron ore, the productivity of sinter is achieved by adjusting operating conditions such as the mixing ratio of raw materials, water content, sinter heat pattern, oxygen partial pressure in the atmosphere, and air permeability. It is necessary to take measures to improve quality and product yield without losing the product.

Sintered ore is composed of major mineral phases such as magnetite, hematite, calcium ferrite, and slag, and pores (sometimes referred to as voids), and its structural morphology is complicated. It is known that the reducibility, strength, and productivity of sinter are related to each other and are closely related to the structure morphology (Non-Patent Document 1). Non-Patent Document 2 discloses that the yield of sinter can be estimated using the strength and porosity of sinter obtained by the tablet firing test. Therefore, in order to improve the productivity, quality and product yield of sinter, it is important to evaluate the structural morphology of the manufactured sinter and appropriately adjust the manufacturing conditions based on the evaluation results. be.

As a method for evaluating the structure of sintered ore, quantitative analysis of the main mineral phase by powder X-ray diffraction, quantitative analysis of the structure by an optical microscope, an electron microscope, or an electron probe microanalyzer (EPMA), and a method using these in combination have been conventionally reported. There is. For example, in Patent Document 1, the boundary value of each constituent phase is determined from the brightness histogram in the texture image obtained by the optical microscope using the abundance ratio of each constituent phase obtained from the X-ray diffraction pattern, and the texture image is made to correspond to the constituent phase. The method of quaternizing is disclosed. Patent Document 2 discloses a method of correcting the mass ratio of each constituent phase obtained from the X-ray diffraction pattern by the average particle size and mass absorption coefficient of each constituent phase obtained from the characteristic X-ray mapping of the sinter. There is. On the other hand, Patent Document 3 discloses a method of obtaining an apparent density in a cross section of a sinter using microfocus X-ray CT and obtaining the content of each mineral phase from the apparent density.

Japanese Unexamined Patent Publication No. 2014-137344 Japanese Unexamined Patent Publication No. 2018-44855 Japanese Unexamined Patent Publication No. 2009-30104

Sasaki et al .: Iron and Steel, 68 (1982) p. 563. Oyama et al .: Iron and Steel, 82 (1996), p. 719.

However, the conventional structure evaluation technique for sinter has the following problems. For example, in the method of evaluating the structure from an image taken with an optical microscope or a scanning electron microscope (SEM), the structure is discriminated from a slight difference in contrast of the polished surface, so that the condition of the polished surface and the imaging conditions (light amount, acceleration voltage) are used. Etc.), and mineralogical knowledge and skill are required to discriminate the structure. In addition, the method of estimating the structure from the results of quantitative analysis of the structure by EPMA has a large number of quantitative elements, and when distinguishing between hematite and magnetite, it is necessary to correct with a small amount of oxide constituent elements such as Al and Mg. There is a problem that the quantitative work is complicated and it takes time to evaluate. Patent Documents 1 and 2 determine and correct threshold values such as contrast and brightness of the image by using the results of element mapping by X-ray diffraction and characteristic X-ray, but are complicated processes using a plurality of methods in combination. Therefore, there is a problem that it takes time to evaluate. Further, Patent Document 3 requires a powerful X-ray source of 150 kV or more, so that there is a problem that the equipment becomes large and cannot be carried out on the machine side of the sintering machine.

An object of the present invention is to propose a method for evaluating the structure of a sinter that quickly and easily evaluates the structure of the produced sinter, and to adjust the operating conditions of the sinter based on the evaluation result. It is to propose a method for producing ore.

Therefore, in the present invention, in order to solve the above-mentioned problems of the prior art and achieve the above object, the structure of the sinter is evaluated by a quicker and more objective index, and this is used as a sinter machine. We came to the conclusion that it is effective to sinter while feeding back to the operation of the above, and came to develop the present invention. That is, the inventors focused on the optical microscope from the viewpoint of convenience, and decided to use it by paying attention to the change in image contrast and color tone due to sample adjustment.

That is, in the present invention, an arbitrary surface of the sinter is smoothed to obtain an optical microscope image of the smoothed surface, and an optical microscope image of the surface after applying a light-transmitting thin film to the smoothed surface. Is obtained, and the area ratio of each structure of the sinter is obtained as the structure fraction based on the contrast between the two optical microscope images. This is a method for evaluating the structure of the sinter.

In the method for evaluating the structure of the sinter according to the present invention, which is configured as described above,
(1) The light-transmitting thin film is a carbon thin film.
(2) The structure of the sinter is hematite, magnetite, slag, and voids, and the balance is calcium ferrite.
(3) Among the structures of the sinter, the area ratios of hematite and magnetite are obtained from the contrast of the optical microscope image of the smoothed surface, and the area ratios of slags and voids are light on the smoothed surface. Obtaining from an optical microscope image of the surface after applying a transparent thin film,
Is considered to be a more preferable solution.

Further, the present invention is a granulated product obtained by adding water to a sintered compounded raw material, which is a compounded powdery substance containing iron ore, auxiliary raw materials, miscellaneous raw materials and solid fuel, and mixing and granulating the mixture. Certain pseudo-particles are sintered into a sinter, and the microstructural proportions of hematite, magnetite, slag, voids and calcium ferrite in the sinter are evaluated by the above-mentioned sinter texture evaluation method, and based on the evaluation results. It is a method for producing sinter, which is characterized by adjusting the production conditions of the sinter.

In the method for producing a sinter according to the present invention, which is configured as described above,
(1) The adjustment of the production conditions includes changing the mixing ratio of coke and / or lime.
Is considered to be a more preferable solution.

According to the sinter structure evaluation method of the present invention, the sinter structure can be quickly and easily evaluated, which can be reflected in the adjustment of operating conditions. As a result, the quality of the sinter is improved, and it is possible to reduce the production cost of the sinter and improve the productivity.

It is a photograph showing an example of an optical microscope image of a sintered ore, (a) is a photograph showing an optical microscope image of a sample as it is polished, and (b) is a photograph showing an optical microscope image of the same field of a sample after carbon deposition. Is. It is a figure which shows the variation of the strength (TI value) of the sinter of the invention example and the comparative example.

In developing the present invention, the inventors have diligently studied a method for quickly and accurately evaluating the microstructural fraction of each mineral phase of sinter and the morphology of some mineral phases. Focusing on the optical microscope from the viewpoint of convenience, we investigated the changes in image contrast and color tone due to sample adjustment in the same field of view. As a result, as shown in comparison with FIGS. 1 (a) and 1 (b), it was found that when carbon vapor deposition is applied to the observation surface (polished surface), the contrast and color tone are significantly changed as compared with the image before vapor deposition. rice field.

In order to clarify which mineral phase the image contrast and the color tone change correspond to, the element concentration was analyzed by the electron beam microanalyzer (EPMA). From the light microscope image of the sample as it is polished (FIG. 1 (a)), hematite, which is the main structure in the sinter, can be identified as the brightest contrast white region, and magnetite can be identified as the next brightest contrast light gray region. all right. Calcium ferrite, slag and voids have different contrasts (dark gray region and black region) from hematite and magnetite, but it was clearly difficult to classify each. On the other hand, from the optical microscope image (FIG. 1 (b)) of the sample subjected to carbon vapor deposition, the slag could be clearly distinguished from other tissues with the white region and the void as the black region. This is because the contrast of the slag changed from black to white due to carbon vapor deposition. From the above results, hematite and magnetite can be identified from the image of the sample as it is polished, slag and voids can be identified from the image after carbon deposition, and the rest can be calcium ferrite to identify all the main structures of the sinter. I understood.

The inventors considered the reason why the image contrast and color tone of the optical microscope were changed by carbon vapor deposition as follows. The reason why the contrast occurs in the optical microscope image of the sample while the sintered ore is being polished is that the light absorption / reflection characteristics differ depending on each mineral phase (black because all voids are absorbed), and a vapor deposition film should be attached. It is presumed that the incident light and reflected light of a specific wavelength are absorbed according to the vapor deposition type and the film thickness, the absorption / reflection spectrum of the slag changes, and the slag can be distinguished from the void. Further, since the thin-film film formed this time has a film thickness shorter than the wavelength of light, not only simple scattering absorption but also the state at the sample / thin-film film interface affects the scattering / absorption / reflection of light. Therefore, although the detailed mechanism is unknown, it is presumed that the contrast difference was formed by the change in the surface state depending on the mineral species due to carbon vapor deposition.

Hereinafter, embodiments of the present invention will be described in detail. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description.

The sinter discharged from the sinter is coarsely crushed with a crusher and introduced into a cooler for cooling. In order to collect sinter in an actual machine, it is not limited to collecting with a dedicated box-shaped sampler, but it may also be collected manually from the belt conveyor using a cassotte or the like, and it flows on the belt conveyor. It may be a method of collecting the sinter which is used by some means. For example, a robot arm may be used to continuously collect a part of the sinter flowing on the belt, or a sample container whose particle size has been selected for strength measurement may be continuously collected using the arm. It may be sorted and collected. Further, it may be a method of collecting the sample from the sample container by the operator's hand and performing it regularly and continuously. If tissue variability needs to be assessed, multiple samples are taken from the same lot.

In evaluating the structure of the sinter, the surface of the sinter sample, which is the observation surface, is first polished to a mirror surface. Since the sinter is amorphous and easily crumbles, it may be polished on a sample in which the sinter is pre-embedded in a resin.

Next, the surface of the polished sample is observed with an optical microscope. The optical microscope may be an ordinary metallurgical microscope. It is preferable to attach a camera or the like to the eyepiece position in order to take an image. It is preferable to adjust the observation magnification appropriately according to the size of the tissue so that the average information of the tissue can be obtained. Based on the contrast and color tone of the captured light microscope image, the white area is distinguished from hematite, the light gray area is distinguished from magnetite and others.

It is preferable to use an image processing device for specific identification. In the identification using the image processing device, the brightest contrast region and the next brightest contrast region are extracted so that hematite, magnetite and other contrasts are obtained, and the rest is divided into other regions. 3 Perform digitization. Further, quaternization may be performed in which the darkest region (black region) is also extracted. At this time, since the brightness of the image changes depending on the sample adjustment condition and the photographing condition, the contrast threshold value cannot be set to a constant value, but since the contrast difference of the tissue is clear, the contrast threshold value in each image. Is easy to set up.

In addition to the above, it is also possible to acquire a luminance profile after performing image processing, and identify each region by setting the peak with the highest luminance as hematite and the peak with the next highest luminance as magnetite. Further, in this case, since the contrast of the black region is clearly different from that of the surroundings, the black region may be inserted and image processing may be performed by quaternization. From the ternary or quaternized images obtained in this way, the area ratios of hematite and magnetite are obtained and used as the respective tissue fractions. Further, as shape parameters, the average circle equivalent diameter, the average ferret diameter, the average value of the aspect ratio, and the like can be obtained. It is also possible to use a polarizing filter or the like to further facilitate the identification of the tissue.

Next, a sample having a light-transmitting thin film on the polished surface is observed with an optical microscope. As the sample, a sample collected separately and polished to a mirror surface may be used, but it is preferable to continue to use the sample used in the above observation. The thin film is preferably a carbon thin film, and specifically, a carbon vapor-deposited film is preferable. The vapor deposition method may be a method of heating a vapor deposition source in vacuum for vapor deposition, or a method using a chemical reaction or ion sputtering, and is not particularly limited. The thickness of the thin film is preferably 1 nm or more and 50 nm or less. The film thickness can be controlled by the film thickness meter attached to the apparatus, but the relationship between the vapor deposition time and the film thickness may be obtained in advance and controlled by the time. The observation magnification is preferably the same as the observation before applying the thin film. Based on the contrast and color tone of the captured optical microscope image, the white area is distinguished from the slag, the black area from the void, and the others. For specific identification, it is preferable to use an image processing device to quantify the contrast between the slag and voids and other tissues. Since the brightness of the image changes depending on the sample adjustment conditions and the imaging conditions, the threshold value cannot be set to a constant value, but since the contrast of the tissue is clear, it is easy to set the threshold value in each image. Specifically, the brightest contrast region (white region) and the darkest contrast region (black region) are each extracted visually, and quantification is performed to divide the region into the other regions. Alternatively, after performing image processing, a luminance profile is acquired, the peak with the highest luminance is used as a slag, and the peak with the lowest luminance is used as a void, and other regions are determined. From the image quantified in this way, the area ratios of slag and voids are obtained and used as the respective tissue fractions. Further, as shape parameters, the average circle equivalent diameter, the average ferret diameter, the average value of the aspect ratio, and the like can be obtained.

The microstructural fraction of calcium ferrite is determined by the area ratio of hematite and magnetite obtained from the sample before thin film application, and the area ratio of the balance obtained by subtracting the area ratio of slag and voids obtained from the sample after thin film application. Here, the components (impurities) that are not classified into the above five are evaluated as calcium ferrite, but the problem is that the components are so small that they do not significantly affect the characteristics of the sinter. No. The observation region may be different before and after the thin film is applied, but it is preferable to use the same region in order to improve the evaluation accuracy of the tissue fraction.

On the other hand, the method for evaluating the structure of the sinter in the present invention is not limited to hematite, magnetite, slag, voids, and calcium ferrite, as long as the contrast can be identified by the optical microscope image obtained before or after the thin film is applied. By applying the method of the present invention, it is possible to obtain the tissue fraction as a new phase.

<Example 1>
Four types of sinters with different sinter conditions were prepared by a tablet test, and the microstructural fractions of each mineral phase and voids were measured. After the prepared sinter was roughly pulverized, an arbitrary sinter sample was embedded in a resin and mirror-polished to obtain an analysis sample.

(Comparative Example 1: EPMA)
Using EPMA (JXA-8100 manufactured by JEOL Ltd.) as a standard for the microstructure fraction, quantitative element mapping analysis of Fe, Ca, Al, Si, Mg and O of 400 μm × 300 μm was performed, and hematite, magnetite, calcium ferrite, The area ratio of slag and voids was determined. The analysis conditions are as follows.
Acceleration voltage: 20kV
Beam current value: 200nA
Number of measurement points: 200 x 150
Measurement interval: 2 μm
Beam system: 2 μm
Capture time / point: 1 sec
Quantitative method: ZAF

From the obtained quantitative mapping image, the mineral phase and voids were distinguished as follows. First, the region where the concentration of Fe was 95% or more in the atomic concentration ratio of the elements other than O and did not contain Ca and Si was determined to be the oxide phase of Fe (hematite or magnetite). At this time, trace amounts of Al and Mg were also detected in the oxide phase of Fe, so the oxide forms of these were assumed to be Al ₂ O ₃ and Mg O, respectively, and the oxygen content was based on the chemical quantitative composition. The O atom concentration distribution bonded only to Fe was obtained by subtracting it from the total oxygen content in the oxide phase of Fe. Regarding the atomic ratio of Fe and O thus obtained, it was determined that the Fe / O value of 0.70 or more was the magnetite phase and that the Fe / O value was less than 0.70 was the hematite phase. The calcium ferrite phase was an oxide region containing Fe, Ca, and Si other than the above. The slag was an oxide region mainly composed of calcium silicate containing Ca, Si: 10 to 30 at%, Al: 5 to 15 at%, Fe: 0 to 10 at%, and Mg: 0 to 5 at%. Since the voids are regions without these elements, the strength of each element was significantly reduced.

(Comparative example 2: Conventional method)
The sample was photographed with an optical microscope (manufactured by Nikon: ECLIPSE LV150N) at a magnification of 200 times as it was polished, and an optical microscope image of a region of 400 μm × 300 μm in the center of the sample was obtained. The area ratios of hematite, magnetite, calcium ferrite, slag and voids were determined for each of the acquired images.

(Invention Example: The present invention)
An optical microscope image was obtained from the sample as it was polished under the same conditions as in Comparative Example 2. Using image analysis software (Digital Micrograph), the brightest contrast region and the next brightest contrast region were extracted from the acquired image, and the area ratio of each region was defined as the area ratio of hematite and magnetite. Then, after carbon vapor deposition having a thickness of about 10 nm was applied to the sample after observation, an optical microscope image was acquired under the same conditions as in Comparative Example 2. The brightest contrast region and the darkest contrast region were extracted from the acquired image using the above image analysis software, and the area ratio of each region was defined as the area ratio of the slag and the void. The area ratio of calcium ferrite was obtained by subtracting the area ratio of hematite, magnetite, slag, and voids from 100%.

Here, in each of the invention examples and the comparative examples 1 and 2, the area ratios of each mineral phase and voids were measured for 10 fields of view by the above method, and the average value was taken as the tissue fraction. Table 1 below shows the evaluation results of the tissue fractions of Invention Examples and Comparative Examples 1 and 2.

From the differences of the present invention in Table 1, it was found that in the invention example, all of the four mineral phases and voids were almost the same within ± 2.5% with respect to Comparative Example 1 evaluated by EPMA. Further, the time required from the measurement to the acquisition of the tissue fraction was 0.5 h in the example of the present invention, which could be evaluated quickly, whereas in the comparative example 1, it took 10 hours. On the other hand, according to the difference between the conventional methods, in Comparative Example 2, magnetite and hematite were in agreement with Comparative Example 1 within ± 2.5%, whereas the structural fractions of calcium ferrite, slag, and voids were in Comparative Example. In many cases, it was confirmed that the difference from 1 was more than ± 2.5%.

<Example 2>
(Preparation of reference sample)
Two types of raw material ores A and B with the same particle size are mixed through a sieve in a mixing ratio of 7: 3, and lime is 1.0% and powdered coke is 5.0% of the raw material ore. Was added to make a sintered compounding raw material. Water was added to the sinter compounding raw material and mixed and granulated according to a conventional method to obtain pseudo-particles, and the pseudo-particles were sintered to prepare a sinter as a reference sample.

(Organizational evaluation)
After the reference sample (sintered ore) was roughly pulverized, 10 samples were arbitrarily selected from the pulverized sample. The selected sample was embedded in a resin, mirror-polished, and then subjected to microstructure evaluation. The microstructure evaluation was carried out under the same conditions as in the above-mentioned Invention Example and Comparative Example 2, and the average value of the area fractions of magnetite, hematite, calcium ferrite, slag and voids of the 10 samples was obtained and used as the microstructure fraction.

(Strength measurement)
As for the strength of the reference sample (sintered ore), the strength (TI value) was determined by the rotational strength test method according to the JIS M8712 method.

(Preparation of test sample)
Next, the raw material ores A and B were blended in a blending ratio of 3: 7, and coke breeze was added at a ratio of 5.0% to the raw material ore to prepare a sintered blended raw material. This sintered compound raw material was sintered under the same sintering conditions as the reference sample to prepare a test sample. Each tissue fraction of the test sample was determined by the above-mentioned invention example and comparative example 2, respectively. It is determined which of the criteria shown in the following (a) to (g) the obtained structural fraction corresponds to, and based on the determination, the blending ratio of the lime source and / or the coke breeze is adjusted, and then sintered again. The ore was made. It should be noted that X, Y, and Z described in the following (a) to (g) are defined by the formulas (1), (2), and (3), respectively. In addition, iron oxide in the formula indicates magnetite and / or hematite.

(A) When X ≧ 3 and Y ≦ −5 were satisfied, it was judged that the amount of heat was excessive, and the powder coke mixing ratio of the raw material powder was reduced by 0.10%.
(B) When only one of X ≧ 3 and Y ≦ −5 was satisfied, it was judged that the amount of heat was excessive, and the powder coke mixing ratio of the raw material powder was reduced by 0.05%.
(C) When -4 <X <3 and -5 <Y <5 were satisfied, it was judged to be equivalent to the reference sample, and the next sintering was carried out under the same conditions.
(D) When only one of X≤-4 or Y≥5 is satisfied and Z≤-6 is satisfied, it is judged that the amount of Ca is insufficient and the amount of heat is insufficient, and the mixing ratio of the lime source of the raw material powder is satisfied. Was increased by 0.5% and the coke breeze content was increased by 0.08%.
(E) If only either X ≦ -4 or Y ≧ 5 is satisfied and Z> -6 is satisfied, it is judged that the amount of heat is slightly insufficient, and the coke content of the raw material powder is increased by 0.04%. bottom.
(F) When X ≦ -4, Y ≧ 5, and Z ≦ -4 are satisfied, it is judged that the amount of Ca is insufficient and the amount of heat is insufficient, and the mixing ratio of the lime source of the raw material powder is increased by 1.0%. The powdered coke compounding ratio was increased by 0.10%.
(G) When X ≦ -4, Y ≧ 5, and Z> -4 were satisfied, it was judged that the amount of heat was slightly insufficient, and the coke content of the raw material powder was increased by 0.05%.

Based on the criteria shown in (a) to (g) above, sinter was produced by batch processing 20 times. The TI value of the obtained sinter was measured according to the JIS M8712 method, the difference from the TI value of the reference sample was obtained, and the standard deviation was taken as the variation in strength.

The variation in the strength of the sinter according to the method of the present invention is shown in FIG. 2 together with the conventional method (Comparative Example 2). In Comparative Example 2, the variation in strength was 1.7%, whereas in the example of the present invention, it was 0.7%, and the variation in strength could be improved.

In the method for evaluating the structure of sinter and the method for producing sinter according to the present invention, the sinter is manufactured while observing the sinter structure and reflecting the information based on the observation results in the operation of the sinter. Not limited to the method, it can be applied to the observation of other mineral structures and the manufacturing method of products based on the result.

Claims (6)

An optical microscope image of the smoothed surface is obtained by smoothing an arbitrary surface of the sintered ore, and an optical microscope image of the surface after applying a light-transmitting thin film to the smoothed surface is obtained. A method for evaluating the structure of a sintered ore, which comprises obtaining the area ratio of each structure of the sintered ore as a structure fraction based on the contrast of an optical microscope image. The method for evaluating the structure of a sinter according to claim 1, wherein the light-transmitting thin film is a carbon thin film. The method for evaluating the structure of sinter according to claim 1 or 2, wherein the structure of the sinter is hematite, magnetite, slag, and voids, and the balance is calcium ferrite. The area ratios of hematite and magnetite in the structure of the sinter are obtained from the contrast of the light microscope image of the smoothed surface, and the area ratios of slags and voids are light-transmitting to the smoothed surface. The method for evaluating the structure of a sinter according to any one of claims 1 to 3, wherein the sinter is obtained from an optical microscope image of the surface after the thin film is applied. Sintering made by blending powdery substances containing iron ore, auxiliary raw materials, miscellaneous raw materials and solid fuel Sintering of pseudo-particles, which are the obtained granulated products, are performed by adding water to the mixed raw material. The sinter is obtained, and the microstructure fraction of hematite, magnetite, slag, voids and calcium ferrite in the sinter is evaluated by the sinter texture evaluation method according to claim 3 or 4, and the evaluation result is obtained. A method for producing sinter, which comprises adjusting the production conditions of sinter based on the above. The method for producing a sinter according to claim 5, wherein the adjustment of the production conditions includes a change in the blending ratio of coke and / or lime.

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