JPH09257665A - Fluorescent x-ray spectrometer and method for evaluating cleanliness of metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly carry out evaluation by providing a driver for rotating a sample on a base plate, a holder for transmitting the rotary drive force to a sample by a friction by holding the sample, a rotary shaft support plate, and a rotation control circuit board. SOLUTION: Components are mounted on a base plate 1, and installed in a sample chamber together with the plate 1. An X-ray emitting opening 7 is provided at the center of the plate 1, a cold crucible melting sample 5 is sandwiched between sample holders 10, and fixed by a retaining spring 9. When a switch 4 is closed and power is supplied from a power source 6, a driver 2 is operated, and the sample 5 is rotated by the rotary drive force maintained constant at the number of revolutions by a reduction gear 3 via the friction between the sample 5 and the holder 10. A rotary shaft support plate 8 supports the rotary shaft. A delay circuit is assembled on a circuit board 11 instead of continuous rotation, thereby making it possible to intermittently rotate at a predetermined angle at each predetermined set time. Thus, nonmetal inclusion in the metal can be rapidly analyzed and evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rapidly evaluating the amount and composition of impurity particles in a metal.

[0002]

2. Description of the Related Art The case of steel will be described as an example of metal. Impurity particles present in the steel, for example, in the case of aluminum-killed steel, alumina-based inclusions generated by the reaction of oxygen in the steel with added aluminum, slag-based inclusions such as lime and silica resulting from steelmaking slag. Products, powder-type inclusions, etc. due to the mold lubricant during continuous casting are
Since the intermediate product or the product when rolled and formed into a material such as a wire rod leads to defects such as scratches and breakage, evaluation is added by various methods, and measures such as scrapping defective materials are taken.

On the other hand, if a defect is found in a product, the material has undergone various processes, and if the material is discarded, it leads to a deterioration in the manufacturing cost. . In particular, since the presence of inclusions is determined at the stage of refining and solidifying a metal, various evaluation techniques have been conventionally tried.

Among metals, as a technique for evaluating inclusions in steel, total oxygen (T
[O]) method, a slime method by electrolytic extraction used for evaluating large inclusions, a microscope method for magnifying and observing a cross section of a metal to evaluate inclusions, an electron beam melting method (EB), etc. Exists as. However, these techniques are generally limited in the types of inclusions and diameters to be investigated due to the characteristics of each method, it takes time to evaluate, the evaluation sample does not sufficiently represent the quality of the intermediate product, or the sample There was a problem that the inclusions were altered during preparation.

Compared with the above-mentioned respective techniques, the metal fragments are floated and melted by the cold crucible flotation melting method, the inclusions in the metal fragments are discharged to the surface of the molten material for a certain period of time, and the solidified sample (hereinafter, cold crucible In the method of measuring inclusions on the surface (called dissolution sample), there are few restrictions on the type and diameter of inclusions that can be evaluated, the evaluation amount is sufficient to represent intermediate quality, and overheating during dissolution is small. Therefore, there is an advantage that the quality of inclusions is small. For example, “Evaluation of alloy cleanness in su-perclean
materials ”KCMills, PNQuested.RFBrooks, DMH
The article of ayes, TURKDOGANSYMPSIUM PROCEEDINGS 105-11 (1994) describes a method of observing surface inclusions of a cold crucible dissolution sample by SEM. However, there is a problem that the SEM observation is inferior in speed.

As an inexpensive and rapid evaluation method, an evaluation method of directly analyzing by an energy dispersive X-ray fluorescence analysis method is disclosed in Japanese Patent Application No. 7-054810. In this example,
Primary X-rays are irradiated onto the area of about 13 mm in diameter on the upper part of the sample, and the impurity particles distributed in an island shape on this irradiation surface are collectively analyzed in a few minutes quickly. In the case of energy dispersive X-ray fluorescence analysis, measurement is possible even if the measurement surface is slightly curved or non-smooth. However, it is difficult to accumulate the entire amount of the impurity particles within such a limited range, and in reality, there is a considerable amount of distribution on the side surface. Therefore, for accurate evaluation, it is necessary to analyze not only one measurement surface but also two or more measurement surfaces, and as a result, there is a problem that speediness is impaired.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the problems of evaluation time and accuracy in the above-mentioned evaluation method of directly analyzing the surface of a cold crucible dissolved sample by energy dispersive X-ray fluorescence analysis, and improves product quality. It is intended to provide a method capable of quickly evaluating the quality of a corresponding intermediate product.

[0008]

In order to achieve the above object, the present invention (1) continuously rotates a sample in a closed sample chamber at a constant rotation speed. Or it is a sample rotation device that rotates a fixed angle intermittently at a constant time interval, and a driving device for obtaining the driving force to rotate the sample on the base plate and the sample is sandwiched and held, and the rotational driving force is rubbed. Sample for fluorescent X-ray analysis, comprising a pair of sample holders for transmitting the sample to the sample by means of a rotary shaft, a rotary shaft support plate for supporting the rotary shaft, and a circuit board for controlling the rotary operation. The first gist is that it is a rotating device, and (2) the surface of the sample is irradiated with X-rays, and the generated fluorescent X-rays are detected by an energy dispersive spectroscope.
In a fluorescent X-ray analyzer for measuring the abundance of each element on the sample surface from the line intensity, the sample rotating device described in the first summary is housed in the sample chamber, and 1 The second gist is that the apparatus for fluorescent X-ray analysis is arranged so that the next X-ray is irradiated, and (3) the metal piece is levitated for a certain period of time by the cold crucible levitating and melting apparatus. The impurity particles present in the metal pieces that have been melted and are present in the metal piece are discharged to the surface of the melt, and the solidified sample surface is subjected to fluorescence X using an energy dispersive spectrometer
In the method for evaluating the cleanliness of metals, in which the amount of elements constituting impurity particles is measured by direct analysis by a line analysis method, and the amount of impurities is identified, in a sample rotation device installed in a sample chamber of an X-ray fluorescence analyzer. And measure the fluorescent X-ray while continuously rotating the sample at a constant rotation speed in the sample chamber, or after measuring for a certain period of time in a stationary state, rotating the sample at a certain angle and then standing still to measure different measurements of the same sample. The third gist is that it is a metal cleanliness evaluation method characterized by repeating the operation of measuring the surface any number of times. Furthermore, (4) levitation melting of metal pieces for a certain period of time using a cold crucible levitation melting device. After discharging the impurity particles present in the metal piece to the surface of the melt, the applied voltage is reduced at a constant rate to impure the band-shaped region with a constant width on the sample surface. A metal cleanliness evaluation method in which particles are accumulated and the sample surface is directly analyzed by a fluorescent X-ray analysis method using an energy dispersive spectroscope. Place a sample and measure it while continuously rotating it at a constant rotation speed, or after measuring for a certain time in a stationary state, rotate the sample by a certain angle and then stand still, and measure different bands of impurity particles in the same sample. The fourth gist is a metal cleanliness evaluation method characterized by measuring the amount of elements constituting impurity particles by repeating the operation of measuring the surface any number of times and identifying the amount of impurities. Is.

In a cold crucible levitation melting apparatus, a metal sample to be evaluated for cleanliness is placed in a water-cooled crucible, and when an electric current is applied to the coil, the electromagnetic force generated melts the metal sample and levitates in the water-cooled crucible. . Therefore, there is no contamination due to contact with the crucible. In general, inclusions have a lower specific gravity than molten metal and interfacial tension exists between inclusions and molten metal, so that inclusions are discharged to the surface of the float. In the case of a steel sample, the temperature during melting is relatively low, such as the melting point of about a dozen and a dozen degrees. Therefore,
In addition to alumina-based inclusions, various inclusions such as slag-based and powder-based inclusions can be evaluated in a form similar to that existing in the base material.

Although the cold crucible dissolution sample depends on the crucible shape, it is generally obtained as a rotating body substantially symmetrical about the central vertical axis. If the inclusions discharged to the surface can be accumulated on the upper part of the sample within a certain range by controlling the applied voltage to the coil, this part should be irradiated with primary X-rays and analyzed collectively. You can However, even in such a case, it has been found that, in reality, a considerable amount of inclusions is also analyzed on the side surface, and it is not possible to accurately grasp the total amount of inclusions by analyzing only one upper part.

In particular, in the analysis of inclusions distributed on the side surface,
No matter how the orientation of the sample is devised, there will always be a portion that is shaded by the primary X-rays, so it becomes necessary to change the orientation of the sample and perform multipoint measurement. It is necessary to draw a vacuum in the sample chamber of the X-ray fluorescence analyzer in order to prevent attenuation of X-rays due to air absorption. Therefore, every time the direction of the sample is changed, the vacuum in the sample chamber must be broken and the vacuum must be evacuated again, which requires time and effort.

In the present invention, since the apparatus for rotating the sample is housed in the sample chamber of the energy dispersive X-ray fluorescence analyzer, it is possible to continuously analyze the entire circumference of the side surface of the sample without breaking the vacuum of the sample chamber. The evaluation time can be dramatically reduced. By the means described above, the evaluation of inclusions distributed on the side surface of the sample can be significantly accelerated. However, for further speeding up, the present inventors tried to collect all the inclusions in the sample on the side surface of the sample surface. As a result, it was possible to prepare a sample in which inclusions were accumulated in a strip shape on the side surface of the sample by lowering the voltage applied to the coil at a constant rate when solidifying after cold-creasable levitation melting. In the sample manufactured in this manner, there is no distribution of inclusions on the upper part of the sample, and most of the inclusions are accumulated on the side surface of the sample. Therefore, by analyzing the entire side surface while rotating this sample in the sample chamber of the X-ray fluorescence analyzer, the total amount of inclusions existing in the sample can be evaluated in a shorter time. It was.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a sample rotating device in a sample chamber of a fluorescent X-ray analyzer used in the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of the sample rotator seen from above, and FIG. 2 is a side view. Each component is mounted on the base plate 1 and is installed in the sample chamber together with the base plate. An opening 7 for irradiating the sample with X-rays is provided in the center of the base plate 1. The cold crucible dissolution sample 5 is sandwiched between the sample holders 10. At this time, the sample is fixed by the pressing spring 9. When the switch 4 is turned on, electric power is supplied from the power source 6, the driving device 2 operates, and the rotational driving force at a constant rotation speed by the speed reducer 3 is transmitted to the sample through friction between the sample holder 10 and the sample 5. And rotate the sample. The rotation shaft is supported by the rotation shaft support plate 8 to ensure rotation around a constant rotation shaft. Another operation mode of this rotating device is
It is realized through a delay circuit incorporated on the circuit board 11. That is, when the switch 4 is put into this operation mode after fixing the sample, the sample is rotated by a predetermined angle, for example, 90 ° and stopped after a preset time, for example, 100 seconds, and the same operation is repeated 100 seconds later.

In this sample rotating device, the sample holder 10
Is preferably made of a material such as rubber in order to ensure sufficient friction with the sample. To further increase friction,
This rubber may be processed such as having a groove. By adopting such a sample holding and rotary drive force transmission method, a spherical sample weighing about 100 g and having a diameter of about 300 mm can be held without processing the sample, and the measurement surface on the side surface of the sample can be shielded against X-rays. It is possible to rotate without doing.

FIG. 3 is a block diagram of an X-ray fluorescence analyzer in which the sample rotating device of FIG. 1 is housed in a sample chamber. The cold crucible dissolution sample 5 is held between the sample holders 10 of the sample rotation device housed in the sample chamber 13, the door 14 of the sample chamber is closed, the sample chamber is evacuated to a vacuum for a certain time, and then the fluorescent X-ray analysis is started. To do. Here, the primary X generated from the X-ray tube 15.
The line is irradiated on the sample surface through the opening 7 provided in the base plate 1. The sample peripheral surface around the rotation axis is sequentially measured as the sample rotates. The X-ray tube 15 and the detector 16 are shown in FIG.
In, it is also possible to arrange in the direction perpendicular to the paper surface.

Next, a method for evaluating the cleanliness of a metal sample using a sample rotating device will be described in detail. When the sample is continuously rotated, the fluorescent X-ray intensity of each element measured for a fixed analysis time is integrated, and the concentration of each inclusion on the sample surface is calculated based on these numerical values. Also, when the sample is rotated intermittently, the sample is analyzed for a certain period of time in a stationary state, the fluorescent X-ray intensity of each element is integrated, and based on these values, each inclusion on one measurement surface of the sample surface Then, after the sample is rotated by a certain angle and stands still, the analysis is similarly started to calculate the concentration of each inclusion on the other measurement surface in the sample surface. By repeating this operation, the entire inclusion accumulation zone is analyzed, and the concentration of each inclusion is calculated by numerical processing such as averaging the concentration of the inclusions obtained by the analysis of each measurement surface.

As described above, the concentration of inclusions obtained in each case has a certain correlation with the amount of inclusions present in the original sample obtained by the chemical analysis by extracting the inclusions by electrolysis. I confirmed that there is. Therefore, the concentration of inclusions directly obtained by the fluorescent X-ray analysis is an index of the amount of each inclusion contained in the metal sample by using this correlation as a calibration curve. The smaller the abundance index of inclusions, the higher the cleanliness of the metal. That is, the abundance index of the inclusions represents the cleanliness of the metal.

[0018]

【Example】

[Example 1] During continuous casting of low-carbon steel, a cast sample was taken from the molten steel in the turn dish, and a rectangular parallelepiped sample having a weight of about 100 g was cut out and melted under an atmospheric pressure Ar atmosphere using a cold crucible device. After the dissolution, the mixture was held for 5 minutes, the inclusions were discharged, and then solidified. The surface of the cold crucible dissolved sample was analyzed by X-ray fluorescence analysis. Primary X-ray intensity is 1
The measurement was performed with μA × 50 kV, irradiation diameter of 20 mm and irradiation time of 90 seconds. The abundance index of alumina, silicate, calcia, etc. in the sample was determined from the fluorescent X-ray intensity of Al, Si, Ca, etc.

The cold crucible dissolution sample was fixed between the sample holders 10 of the sample rotating device shown in FIG. 1 so as to be rotatable about the central axis, and was rotated at a rotation speed of 6 rpm under the above conditions. The results of fluorescent X-ray analysis are shown in Table 1.
Raised. Table 1 also shows, as a comparative example, the results of performing measurements in a stationary state one by one by changing the orientation of the sample without using the sample rotating device. As seen in this comparative example, the distribution of inclusions varies significantly depending on the measurement surface,
It can be seen that correct results cannot be obtained unless the entire circumference of the side surface of the sample is evaluated. The results according to the present invention substantially match the average values of the measured values on the four surfaces of the comparative example, indicating that they are applicable as an index of the amount of inclusions. On the other hand, according to the present invention, the evaluation time per sample can be about 3 minutes, and about 1/4 of the speed of the comparative example can be achieved. Even when the four-sided measurement of the comparative example is performed using the intermittent rotation mode of the sample rotation device of the present invention, the evaluation time can be shortened by about 40%.

[0020]

[Table 1]

[Embodiment 2] Next, a sample collected from a turn dish was dissolved in a cold crucible in the same manner as described above, and after the dissolution, it was held for 5 minutes, and then the applied voltage was set to 4
The sample coagulated by gradually lowering over a period of time was subjected to fluorescent X-ray analysis using a sample rotating device while rotating at a rotation speed of 6 rpm. Moreover, the amount of spherical inclusions (calcia inclusions) was measured by a total oxygen (T [O]) analysis and a slime method using a sample taken from the latest cut-out sample for cold crucible in a cast sample. Alumina content index and T [O] obtained by fluorescent X-ray analysis
4 and the relationship between the calcia amount index obtained by X-ray fluorescence analysis and the amount of spherical inclusions by the slime method are shown in FIG. In the case of the steel type used in this example, T
[O] is an amount that correlates with the amount of alumina-based inclusions.
The amount of spherical inclusions by the slime method represents the amount of calcia-based inclusions.

As can be seen from FIG. 4, a good correlation was observed between the alumina content index obtained in the present invention and T [O]. Further, it can be seen from FIG. 5 that the calcia amount index obtained in the present invention has a good correlation with the amount of spherical inclusions by the slime method. From the above, it can be seen that according to the present invention, an index indicating the amount of inclusions classified by type, such as alumina-based or calcia-based (slag-based), can be obtained. According to the evaluation method of the present invention, inclusions can be evaluated in about 12 minutes by combining cold crucible flotation dissolution and fluorescent X-ray analysis.

[Embodiment 3] Samples were taken at a constant time interval in the vicinity of a nozzle where molten steel flows into a turn dish from a pan, and the time transition of alumina and calcia content indexes obtained by the above-described evaluation method of the present invention is shown. 6 shows. FIG.
According to the present invention, as can be seen in, it is possible to quickly detect the degree of contamination of molten steel, including the outflow of ladle slag when the amount of residual hot water in the pot is low, and therefore casting based on this can be performed. It can predict the cleanliness of a piece and implement proper operation management.

[0024]

As described above, the use of the method of the present invention makes it possible to quickly and inexpensively analyze and evaluate nonmetallic inclusions in metals while maintaining good representativeness and correlation with products. It becomes possible. The rapid evaluation of inclusions according to the present invention can be applied, for example, as a management index for steelmaking operations, as a quality assurance when an intermediate product is sent to a lower process, or as an evaluation index when developing / introducing a new process. Is.

[Brief description of drawings]

FIG. 1 is a plan view of a sample rotation device as viewed from above.

FIG. 2 is a side view of a sample rotation device.

FIG. 3 is an energy dispersive X-ray fluorescence analyzer in which a sample rotating device is housed in a sample chamber.

FIG. 4 is a diagram showing a correlation between an alumina analysis result and a total oxygen concentration according to the present invention.

FIG. 5 is a diagram showing a correlation between the results of calcia analysis according to the present invention and the results of slime analysis.

FIG. 6 is a diagram showing the time course of the amount of inclusions in the molten steel in the turn dish obtained by the present invention.

[Explanation of symbols]

 1: Base plate 2: Drive device 3: Reducer 4: Switch 5: Cold crucible melting sample 6: Power supply 7: Opening 8: Rotating shaft support plate 9: Pressing spring 10: Sample holder 11: Circuit board 12: Impurity Particle accumulation unit 13: Sample chamber 14: Sample chamber door 15: X-ray tube 16: Detector 17: Data processing device

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[Procedure amendment]

[Submission date] October 1, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

In this sample rotating device, the sample holder 10
Is preferably made of a material such as rubber in order to ensure sufficient friction with the sample. To further increase friction,
This rubber may be processed such as having a groove. By adopting such a sample holding and rotational driving force transmission method, a spherical sample weighing about 100 g and having a diameter of about 30 mm can be held without processing the sample, and the measurement surface on the side surface of the sample can be kept on X-axis.
It is possible to rotate without blocking the line.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Takeuchi 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division

Claims (4)

[Claims] 1. A sample rotation device for continuously rotating a sample in a closed sample chamber at a constant rotation speed or intermittently rotating at a constant time interval for a constant angle, which drive the sample to rotate on a base plate. A driving device for obtaining a force, a pair of sample holders for sandwiching and holding the sample and transmitting the rotational driving force to the sample by friction, a rotating shaft support plate for supporting the rotating shaft, and a rotation A sample rotating device for X-ray fluorescence analysis, comprising a circuit board for controlling the operation. 2. The surface of the sample is irradiated with X-rays, the generated fluorescent X-rays are detected by an energy dispersive spectroscope, and the abundance of each element on the sample surface is measured from the fluorescent X-ray intensity of the energy peculiar to the element. An X-ray fluorescence analyzer for use in
An apparatus for fluorescent X-ray analysis, characterized in that the sample rotating device according to (1) is housed in a sample chamber and is arranged so that the sample peripheral surface around the rotation axis is irradiated with primary X-rays. 3. A cold crucible flotation / melting apparatus float-melts a metal piece for a certain period of time, discharges impurity particles present in the metal piece to the surface of the melt, and solidifies the sample surface to an energy dispersive spectroscope. In a method for evaluating the cleanliness of metals, in which the amount of elements constituting impurity particles is measured by direct analysis by a fluorescent X-ray analysis method using, a sample installed in a sample chamber of an X-ray fluorescence analyzer Hold the sample in a rotating device and measure the fluorescent X-ray while continuously rotating the sample at a constant rotation speed in the sample chamber, or after measuring for a certain period of time in a stationary state, rotate the sample by a certain angle and then stand still A method for evaluating the cleanliness of a metal, which comprises repeating an operation of measuring different measurement surfaces of a sample any number of times. 4. A cold crucible levitation melting apparatus is used to float and melt a metal piece for a certain period of time, discharge impurity particles present in the metal piece to the surface of the melt, and then reduce the applied voltage at a constant speed. A method for evaluating the cleanliness of metals, in which impurity particles are accumulated in a band-shaped region having a certain width on the sample surface, and the sample surface is directly analyzed by a fluorescent X-ray analysis method using an energy dispersive spectrometer, The sample is arranged so that the band-shaped region is irradiated with the primary X-ray, and the measurement is performed while continuously rotating at a constant rotation speed, or after the measurement is performed in a stationary state for a certain period of time, the sample is rotated by a certain angle and then stopped. The feature is that the amount of elements that make up the impurity particles is measured and the amount of impurities is identified by repeating the operation of measuring different measurement planes in strip-shaped regions where the impurity particles of the same sample are accumulated. Method for assessing cleanliness of metals to be collected.