JPH06934B2 - Sintering degree measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a sintered product of a product obtained by sintering a powder or granular material, that is, for example, an iron ore sintered ore, an iron ore pellet, Cr, Mn. ,
Sinters and pellets of ores for alloys such as Ti and bricks,
This is a method of measuring the degree of bonding between powder particles of a sintered body such as a ceramic, that is, the degree of perfection of sintering (hereinafter referred to as the degree of sintering).

(Prior Art) When powder particles are heated to partially generate a melt, and the melt is used as a medium to combine or combine the particles, a sintered body generated by a so-called sintering reaction is used. Moreover, unsintered portions or insufficiently sintered portions are likely to be formed in the manufacturing process. Conventionally, the degree of bonding between these powder particles has been judged as a result of quality or yield, and there has been no method for directly measuring the degree of sintering, which is the object of the present invention, in particular, insufficient sintering. However, the quality or yield results depend on many factors other than sintering, such as the material quality of the raw materials and the components of the raw materials. When it fluctuates, it is difficult to trace back the cause, and it was necessary to make adjustments by relying on experience and intuition on a trial and error basis.

Therefore, the control itself in the production of the sintered body is also lacking in appropriateness, and the opportunity loss given to the sintering production process and the steps before and after that is large.

(Problems to be Solved by the Invention) As described above, the present invention utilizes the online and real measurement technology that has never existed in the prior art, so that the bonding between the powder particles of the sintered body, which does not exist in the past, can be achieved. The first purpose is to directly measure the degree of progress, that is, the degree of sintering of the sintered body.
Non-destructive, non-contact measurement of the sintered body, the progress of sintering,
A three-dimensional distribution is obtained for each of the firing-completed portion and the firing-incomplete portion, whereby the progress of sintering is precisely determined at each position, and in this way, the quality of the whole sintered body or the production related to the yield is improved. The second purpose is to accurately grasp the problematic part and perform accurate and prompt control.

(Means for Solving Problems) The present invention is configured as follows to achieve the above object. The transmission radiation intensity obtained by irradiating a given cross-section of the sintered body with radiation at a predetermined tube voltage and scanning the cross-section to detect the transmission radiation intensity from the periphery of the cross-section. While synthesizing the image of the cross section from
The CT value is calculated based on the radiation absorption coefficient obtained from the transmitted radiation intensity for each of the constituent pixels of the image, and the portion where the calculated CT value is a predetermined value or more is a sintered portion, and the portion where the calculated CT value is less than the predetermined value is unburned. It is a method of measuring the degree of sintering by dividing it as a joint and measuring the ratio of the number of divided constituent pixels.

Hereinafter, the basic components of the means of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross section 2 of a sintered body sample 1 such as a sinter or pellet.
FIG. 3 is an explanatory view showing a state in which the degree of sintering is measured by the method of the present invention using X-rays as radiation. 3 is a scanning surface of the high-voltage X-ray beam 8, 4a and 4b are the scanning start points, 5 is an X-ray irradiation device, a tube voltage of 100 to 420 KV (commercially available), and a tube current of 2 to 120 mA.
Used with a collimator of 1 mm or less. 6 is an X-ray detector, which may be a BGO (Bi and Ge oxide) semiconductor detector, a scintillation counter, a GM (Geiger-Muller) counter, or any other commonly used detector.

FIG. 2 shows an example of a mechanism for obtaining a cross-sectional image according to the present invention. Reference numeral 7 denotes an X-ray detector that directly measures the X-rays emitted from the X-ray irradiation device 5. Correct the change over time in the amount generated. Reference numeral 9 is an amplifier, 10 is an analog / digital converter, and 11 is an arithmetic and control unit, which comprises a buffer memory 12, a central arithmetic unit 13, a program store 14, a main memory 15, a reading unit 16 and the like. Reference numeral 17 is a digital / analog converter, 18 is an amplifier, and 19 is a display device.

In the present invention, in order to obtain a cross-sectional image of the cross section of the sample 1 of sinter and pellets, first, the X-ray irradiation device 5 and the X-ray irradiation device are used.
The line detector 6 and the X-ray beam 8 are adjusted so that the X-ray beam 8 passes through the predetermined cross section 2 of the sample 1. Therefore, the pair of the X-ray irradiator 5 and the X-ray detector 6 is moved along the scanning surface 3 starting from the scanning start points 4a and 4b, and the X-rays transmitted through the sample 1 by the X-ray detector 6 are moved during this movement. To detect. At this time, the X-ray detector 7 directly detects the X-rays from the X-ray irradiation device 5. These X
The detected values a and b of the line are inputted to the buffer memory 12 of the arithmetic and control unit 11 via the amplifier 9 and the analog / digital converter 10 as shown in FIG. 2, and the ratio between the detected values a and b is the scanning start point 4a, It is stored in correspondence with the moving distance of the X-ray detector 6 from 4b. That is, the intensity of the transmitted X-ray along the scanning direction is stored. Further, the intensity stored in the buffer memory 12 is arithmetically processed by the central arithmetic unit 13 so as to be back-projected onto the cross section 2 of the sample. For example, the third
As shown in FIG. 3A, the detected intensity 1 is uniformly distributed in proportion to the intensity 1 on the cross section along the direction perpendicular to the scanning direction S. The distributed value represents the light and shade of the image when the image is reproduced, and is displayed on the display device 19 in, for example, a 16-step gray scale.

In this way, when the first scanning of the cross section 2 is completed, the pair of the X-ray irradiation device 5 and the X-ray detector 6 is rotated around the sample 1 on the scanning surface 3, and the X-ray beam 8 is different from the previous one. Irradiate from another direction and perform the same scanning as the previous time. In this way, the X-ray beam 8 is irradiated to the cross section 2 of the sample 1 by changing the angle little by little (for example, by rotating by 6 °), and sequentially, FIG. 3 (a) (b) (c).
.. are obtained, the back projection images are superposed by arithmetic processing in the central processing unit 13, and the result is stored in the main memory 15. In the superposed images, as shown in FIG. 4, an iron oxide image G is formed at a position where a target substance (for example, iron oxide) F exists among the substances contained in the sample 1 of sinter and pellets. The image is composed of, for example, 512 × 512 pixels, and each pixel is displayed in 16 steps of gray scale as described above.
Pixels corresponding to the respective addresses are stored in the main memory 15 at the two-dimensionally arranged addresses. The size of one pixel is
It is 0.2 mm x 0.2 mm. The image stored in the main memory 15 is read by the reading device 16, and the digital-analog converter is used.
It is converted into an analog signal at 17 and further inputted to the display device 19 through the amplifier 18, and as a result, the image of the cross section 2 of the sample 1 is displayed. The arithmetic processing in the arithmetic and control unit 13 is executed according to the program read from the program store 14.

The present invention uses an X-ray beam with a tube voltage of 100 to 420 KV and a tube current of 2
It is characterized by using X-rays generated at ~ 120 mA, which are focused by a collimator with a diameter of 1 mm or less. The reason is as follows. First, the tube voltage and the tube current will be described. There are many variations in the components and defects of sinter and pellets, and it is not possible to make an overall judgment by examining only one sample. Empirically, it is necessary to put it in a bucket-shaped container having a size of 4 cm or more and 40 cm or less, examine its cross section, and obtain the average value of 3 to 500 samples. In order to be able to perform the transmission test within 10 minutes, it is necessary to increase the X-ray pressure. Tube voltage
The above conditions were satisfied when the voltage was 100 KV or higher. Of the X-ray generators currently on the market, the ones that are stable over time and can be used for such measuring devices are 42
Up to 0KV. In the X-ray generator, the tube voltage and the tube current value are related to each other and cannot be arbitrarily determined. The tube current corresponding to the tube voltage of 100 to 420 KV of the commercially available one is 2 to 120 mA. The X-ray generation system includes a continuous system and a pulse system, but both can be adopted.

Next, the collimator will be described. The collimator can be put to practical use in the analysis of sinter or pellets if it has a resolution of 1 mm or less. That is, it is known that the important mechanical strength in sinter or pellets is related to the microstructure, especially pores, and it is necessary to investigate the microstructure up to at least 1 mm. Therefore, it is necessary to measure with a resolution of 1 mm or less, so the diameter of the X-ray collimator should be at least 1 mm.
It is necessary to focus X-rays to 1 mm or less. However, if the resolution is lowered too much, it may take a long time to perform the measurement, which may not be a good idea. In the so-called first generation CT, one collimator is one source and one detector, so one collimator is sufficient, but in the second and subsequent CTs, two or more collimators are required.

As described above, the tomography method based on the test X-ray CT method has been described by taking the first-generation CT of the 1-ray source, 1-detector tube method as an example, but the so-called CT of the second, third, and fourth generations is used. It goes without saying that CT also falls within the scope of the present invention. That is, the X-ray beam is made into a narrow fan shape like the present medical CT and the X-ray transmission amount (transmitted radiation intensity) is measured using a plurality of detectors, or a wide fan-shaped X-ray and 300 or more pieces are used. A method of collecting transmission X-ray images of a sample from multiple directions only by rotating a X-ray source by combining a large number of detector rows, and further 60
For example, a method in which a large number of zero or more detectors are arranged on the entire circumference, only the X-ray source is rotated, and a transmission image of the sample is collected at once.

FIG. 5 is an example of a cross-sectional image of the internal structure of a sintered ore, which is a raw material for iron making, by radiation tomography used in the method of the present invention.
The cross section is schematically shown. The size of the cross section of the sample used was 4 cm x 5 cm, and the X-ray C used
The T device is a second-generation device that narrows narrow fan-shaped X-rays generated at a tube voltage of 420 KV and a tube current of 3 mA with eight collimators with a diameter of 1 mm or less. The scan time was 600 seconds, the image matrix was 240 × 240, and the detector was BGO. In FIG. 5, the portion A has a small X-ray transmission amount (transmitted radiation intensity), that is, a portion having a large radiation absorption coefficient (ratio between the absorbed radiation dose and the radiation dose from the radiation source) described later, It is iron oxide (hematite or magnetite).
In addition, the portion B has the smallest amount of X-ray transmission next to the portion A, that is, a portion having a large radiation absorption coefficient, and is calcium ferrite. Further, the portion C has a relatively large X-ray transmission amount, that is, a portion having a small absorption coefficient of radiation, and is a slag in which a non-sintered portion having a CT value <2000, which is particularly targeted for classification in the present invention, is inherent. . The portion D is a pore. Thus, according to the method of the present invention, the internal structure of the sintered ore can be clearly known in a non-destructive state.

In the present invention, the CT value for each of the constituent pixels of the cross-sectional image thus obtained is, for example, less than 2000 at a tube voltage of 420 KV,
The sintering degree is judged from the respective ratios by extracting the sintering incomplete portion based on the former and the sintering completed portion based on the latter by dividing the portions into 000 or more.

The CT value used in the present invention is a value obtained by using the following equation (1), but the CT value of the present invention is not limited to that obtained by this equation (1).

μ _s : Radiation absorption coefficient of sample μ _w : Radiation absorption coefficient of water K: Constant (usually K = 1000) This CT value increases as the density increases.

Speaking in relation to the composition of the sinter, the iron content has a high CT value, and the slag that has undergone melting, chemical reaction, and solidification also has a high CT value, both exceeding 2000.

However, there is a part of the slag where the CT value does not reach 2000, and according to the result of the investigation, the slag material and the chemical reaction agent, that is, the serpentine rock, the limestone, etc. that are the solvent cannot be completely melted. Was found to remain. That is C
A portion having a T value of 2000 or more is a sintering completed portion referred to in the present invention that does not cause deterioration of the quality of the sintered ore and yield, and is a portion where the solvent medium is melted and reacted, but the CT value is The portion which does not reach 2000 is a portion where the solvent medium is unmelted and unreacted in the unsintered portion of the present invention, which causes deterioration of the quality of the sintered ore and yield.

(Operation) Since the present invention is configured as described above, the progress of the degree of bonding between the powder particles of the sintered body, that is, the degree of sintering of the sintered body is non-destructive and non-contact at each position inside the sintered body. It can be measured and determined for each. This point will be described below with reference to the drawings.

The sintered body to be measured is sampled, and the product shape or part thereof is sampled and irradiated with radiation such as X-rays, γ-rays and neutrons. For sampling, for example, it is a large sintered body before it becomes a product for the first time after sizing, and in the case of a cake of iron ore sintered ore, a core like the one proposed in Japanese Utility Model Sho 56-13639 A core sample is taken from the sintered bed with a sampler and irradiated with radiation. The method of obtaining a cross-sectional image of a sintered body by irradiating with radiation can be performed according to the above-mentioned method disclosed in Japanese Patent Application No. 59-61104 by X-ray method.

The present invention enables a high-level quality analysis and quality evaluation of a sintered product by confirming the mineral composition and pores of the product in a non-destructive state. The proposed sintered body shows that firing has been completed,
In fact, as described above, it was found that the incompletely fired part is inherent and the incompletely fired part has different radiation transmission intensity.

This example will be described based on the results obtained with the core sample of the iron ore sintered cake.

When the CT value was calculated by taking the distribution of the X-ray transmission intensity in the cross section of the sintered body at 140 KV, 200 mA with X-ray irradiation and a pixel of 0.8 m / m × 0.8 m / m, the CT value of the completed firing part was 3400 or more. showed that. On the other hand, in the so-called incomplete firing portion where the progress of sintering is insufficient and the bonding between powder particles is only partially progressed, the CT of 1350 to 2850
Showed the value.

Therefore, when the number of pixels M in the firing completed portion and the number of pixels N in the firing incomplete portion are calculated in a coordinated manner and the calculation is performed by the following equation (2), the firing completion degree, that is, the degree of sintering is calculated. = Yield η can be calculated.

Further, 1-η can be used to find out the incomplete firing rate at which the bond between the powder particles is insufficient.

As is clear from the above description, the CT values described above are different even for the same irradiated object if the tube voltage is different. This relationship is the 7th
Shown in the figure. As is apparent from the figure, the CT value 2000 that separates the unsintered part and the completed part of the sintered body at the tube voltage of 420 KV changes to the value shown at the intersection of each voltage and the curve. Therefore, according to the present invention, the unsintered part and the completed part of the sintered body are discriminated by the value of the intersection with the curve obtained at each tube voltage.

(Example) (a) A core sample of an iron ore sintered cake was prepared according to Jitsuko 56-1363.
As proposed in Section 9, the 80 mmφ core sample from the surface layer to the lower layer of the obtained sintered bed was irradiated with X-rays, and the sintering degree was calculated according to the above equations (1) and (2). Was calculated. The result is I when it is a good standard sintering operation, and II when it is unstable and the product quality changes and the yield decreases by 2.3%. Yield 0.7
Table 1 shows the η values of each of the upper, middle, and lower layers, where III is the change in%.

Further, when the yield was decreased by the conventional method, the compounding ratio of the powder coke was increased by 0.07% for the purpose of increasing the amount of heat in all layers, and the result was defined as IV. The result is shown as V, which is an increase of 0.07% to the necessary upper layers.

As is clear from Table 1, in II, the η value of the upper layer is greatly reduced as compared with I in the standard state, and the tendency is similarly observed in III. This confirmation means that the existence of the present invention makes it possible to confirm the stratification for the first time.

Based on this stratified understanding, the difference between the action to the necessary part and the overaction to the whole is IV,
Looking at V, in IV which was over-action, the upper layer part was covered with heat shortage up to the standard state and η improved, but the lower layer part melted more than the sintering reaction rate due to excessive heat. So, this wraps a part of the raw material to produce the unsintered part,
On the contrary, η is getting worse.

On the other hand, the V of the present invention can obtain appropriate results with accurate and quick action, stable operation, improvement of quality of sintered body, improvement of yield, and drastic improvement of fuel consumption rate. Was seen.

Fig. 7 shows the yield of 77% of the lower layer sintered ore in the standard operating condition I (2)
The CT value distribution in the cross-sectional image of the sintered body consisting of the calculated value of the above formula (1), which is the basis of the calculation by the formula, is shown.

(B) Placing radiation on a brick with a thickness of 100 mm under a measuring device, continuously measuring cross-sectional images in the longitudinal direction (1) and measuring η by the formula (2), and η and strength. Was found to be inversely proportional. The low η part is concentrated at a specific place in the cross-sectional image of the low-strength brick, and this is because the charging packing density is 0.2 deviation from the average when charging the raw material at the time of brick molding into the formwork. It was also clarified by the X-ray irradiation method, and the deviation could be controlled and improved by adjusting the flow of raw material charging.

(Effects of the Invention) The present invention can measure the distribution of the signal state of sintering in a non-destructive and non-contact manner on a sintered body on a position-by-position basis inside the sintered body, and can measure the insufficient sintering portion. If necessary, the measurement results can be updated in real time promptly and accurately, and improvement actions can be taken accurately without opportunity loss, which is effective in improving the quality yield of sinter ore and reducing costs. Is extremely large.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an X-ray tomography method used in the present invention, FIG. 2 is a block diagram showing an example of an apparatus for carrying out the present invention, and FIG. 3 is an image backprojection method in the present invention. FIG. 4 is an explanatory view showing the principle of forming an image by the back projection method, and FIG. 5 is a tomographic photograph of a sinter obtained by the X-ray tomography method used in the method of the present invention. 6 and 6 are cross-sectional images of samples showing the degree of progress of bonding between powder particles of a sintered body according to the method of the present invention, that is, the degree of sintering. 7th
The figure shows the relationship between the tube voltage of the radiation source and the CT value of the object to be irradiated, showing the situation where the CT value of 2000 at a tube voltage of 420 KV changes with each tube voltage. 1: Sample, 2: Cross section, 3: Scan plane, 4, 4 ': Scan start point, 5: X-ray irradiation device, 6: X-ray detector, 7: X-ray detector, 8: X-ray beam.

Claims (2)

[Claims] 1. A method of irradiating a desired cross section of a sintered body with radiation at a predetermined tube voltage and scanning the cross section to detect transmitted radiation intensity from the periphery of the cross section. The cross-sectional image is synthesized from the transmitted radiation intensities obtained, and the CT value is calculated based on the radiation absorption coefficient obtained from the transmitted radiation intensity of each constituent pixel of the image.
A sintered body characterized by dividing a portion having a value equal to or more than a predetermined value as a sintered portion and a portion having a value less than the predetermined value as an unsintered portion, and measuring the degree of sintering by a ratio of the divided number of constituent pixels. Measuring method of sintering degree. 2. A CT value based on a radiation absorption coefficient obtained from the transmitted radiation intensity of the sintered body detected by setting a tube voltage of a radiation source for irradiating an arbitrary cross section of the sintered body to 420 KV. It is characterized in that a portion having a CT value of 2000 or more is defined as a sintered portion and a portion having a CT value of less than 2000 is classified as a non-sintered portion, and the degree of sintering is measured by the ratio of the divided number of constituent pixels. The method for measuring the degree of sintering of a sintered body according to claim 1.