JPS6259255B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is a position-sensitive X-ray detector (hereinafter simply referred to as
The present invention relates to a method of measuring the texture of a rolled metal sheet using PSPC (abbreviated as PSPC) while the steel sheet is running on a production line. In general, the texture of metal materials, especially steel sheets, is an important element that determines its workability, magnetic properties, etc. Conventionally, texture has been measured on small test pieces taken from a material off-line, in other words, after leaving the production line, and this has been treated as a representative value for the material. On the other hand, this invention deals with rolling metal plates, that is, plate materials (including strip materials, the same shall apply hereinafter) while running on a production line.
The plate surface is directly irradiated with characteristic X-rays, the diffraction By determining the strength and calculating the ratio with the random strength, the density distribution of crystal grains with crystal axes parallel to the normal direction of the sheet surface (hereinafter simply referred to as axial density distribution) can be determined, especially during the production line of metal rolled sheets. In other words, online
In addition, we have newly developed a method for quickly and easily measuring texture on-line.Random strength here refers to the above-mentioned metal rolling of a so-called disorderly oriented sample consisting of a homogeneous metal plate with no crystal grain orientation. This is the diffraction intensity from the crystal lattice plane corresponding to the plate. Common practical materials are polycrystalline, and each grain of a polycrystalline sample has a distinct orientation.
However, when looking at the sample as a whole statistically, it is possible to represent the sample orientation with a specific orientation, although there are differences in degree. Therefore, to measure the texture of a polycrystalline sample, it is necessary to determine the crystal orientation as its preferred orientation and quantify the degree of aggregation. First, determining the crystal orientation is to find the angular relationship between the coordinate system fixed to the sample and the coordinate system fixed to the crystal. Orthogonal coordinates are often set in the plate width direction (hereinafter abbreviated as RD), the plate width direction (abbreviated as TD), and the plate surface normal direction (abbreviated as ND), while a coordinate system fixed to the crystal is an example of iron. Normally, orthogonal coordinates are set in the three crystal axis directions of [100], [010], and [001]. Next, the degree of aggregation in the preferred orientation can be quantified by the ratio of the diffraction intensity from a certain crystal plane of the sample to the random intensity from the same crystal plane. Now, there are two ways to display the collective structure: (1) Fix the sample coordinate system and find out in what direction and with what density the poles of a certain crystal plane, for example {hkl}, that is, the intersection of the crystal plane normal and the projection sphere, are distributed on the stereo projection diagram. How to show if you are there. (2) A method in which the crystal coordinate system is fixed and the density of crystal axes parallel to the ND in any direction of the sample is displayed in this coordinate system. The former (1) is called the {hkl} plane (positive) pole figure or polar density distribution map, and the latter (2) is called the ND axis density distribution or reverse or inverted pole figure. Now, X-ray diffraction is usually used to measure texture. Generally, a crystal is defined as a solid in which atoms are arranged periodically in three-dimensional space to form a spatial lattice. All the lattice points of these spatial lattices can be arranged on a group of mutually parallel and equidistant planes called lattice planes, and regardless of their position in space, only the orientation of the lattice planes is a so-called mirror. Displayed as an index (Miller index). The interval between adjacent planes of a group of planes {hkl) in Miller index representation is called the lattice spacing, and this is d _hkl . In cubic crystals (such as iron), there is a relationship between the Miller index and d _hkl . a: There is a relationship called a lattice constant. Now, the X-ray with wavelength: λ is incident on the lattice surface with Miller index (hkl) at an angle of incidence: θ (90° to the normal to the surface).
Let us consider the case of incidence at angle θ). Diffraction occurs if X-rays scattered by atoms traveling in a direction forming an angle of 2θ with respect to the incident X-ray, that is, in the direction of the diffraction angle, satisfy the following conditions. That is, nλ=2d _hkl・sinθ...(2) As equation (2) is known as Bragg's law, n is the reflection order, a positive integer greater than or equal to 1, and sinθ≦1.
Takes successively larger values within the range. Normally, the texture is measured by a diffraction method using characteristic X-rays, and since these characteristic X-rays have a sharp intensity at a certain wavelength position, the value of λ in equation (2) is a constant value. In order to obtain diffraction, θ must be made variable. In reality, diffracted X-rays are detected and counted using a diffractometer, which is a type of X-ray spectrometer, but by scanning the diffractometer with a goniometer, θ can be varied to satisfy equation (2). The diffraction angle position: θ _hkl is determined, and the diffraction intensity at that position is measured. As a result, when creating a positive pole figure on the {hkl} plane, since θ _hkl is constant, the diffractometer is fixed at this angular position, so angular scanning is not performed, but the sample stage is used to scan each point on the stereo projection sphere. In order to measure the value, it is necessary to perform a complicated rotational movement, and on the other hand, when creating an inverse pole figure, a simple method is used by Jetter et al. that is created from the diffraction intensities of about 15 crystal faces that can be directly measured. Although there are a precise method proposed previously and a method of calculating from a three-dimensional crystal orientation distribution function, a simple method is usually used and satisfies practical requirements. However, in either case, it takes a considerable amount of time to measure the texture, so online measurement has traditionally been impossible. By the way, metal materials, especially iron crystals, exhibit anisotropy in various properties depending on their orientation.
Regarding magnetic anisotropy, the {100} axis direction is the axis of easy magnetization, and therefore unidirectional silicon steel sheets are manufactured to increase the degree of integration in this direction with respect to RD. In addition, the r value, which is a measure of deep drawing, has a close relationship with the texture of the material, and with regard to ND <111>
The higher the degree of integration in the direction, the higher the r value and the better the deep drawability. In this way, even for steel sheets as practical polycrystalline products, manufacturing methods that actively utilize anisotropy have become common sense. The determination was only performed off-line by X-ray diffraction on a sample taken from a portion of the steel plate as described above. The present invention attempts to improve the conventional drawbacks by determining the texture online and in real time, thereby greatly contributing to product grading, quality control, and quality assurance. In this invention, a parallel beam of characteristic X-rays is transmitted over a certain angular range on a circular arc centered on the center of the X-ray irradiation area on the sample surface within a plane that includes the irradiation optical path and is perpendicular to the sample surface. A rotating X-ray source irradiates the sample, and diffracted X-rays from each crystal lattice plane in the sample are reflected on the side opposite to the irradiation side with respect to the normal to the plate surface at the center of the X-ray irradiation area. In addition, by detecting it with a PSPC arranged along an arc concentric with the circular arc and analyzing its waveform, it becomes possible to calculate the diffracted X-ray intensity from the polycrystal lattice plane in a short time. By the way, X-ray diffraction using a crystal utilizes the fact that it is expressed by Bragg's conditional expression (2) as mentioned above, and uses the angular dispersion method, that is, the conventional method of measuring the diffraction angle (θ) mainly using characteristic X-rays. , especially when trying to use it for online texture measurement, as an example, as shown in Figure 1 a.
It is conceivable to measure the ND axis density distribution map using a simple method. However, when using this type of angular dispersion method, as is clear from the figure, it is necessary to set up multiple X-ray tubes and the same number of detectors to point at the same measurement point, making the equipment complex and expensive. Not only that, but from an implementation standpoint, there were extremely many restrictions on the number and types of lattice planes that could be measured, making it virtually impossible to create something usable. For example, when measuring the texture of a normal steel plate, it is necessary to measure the ND axis density for the (110), (200), (211) and (222) planes at a minimum, and here M _p - K = The diffraction angle (θ) when using characteristic X-rays is θ ₍₁₁₀₎ ≒ 10.1, respectively.
゜, θ ₍₂₀₀₎ ≒14.1゜, θ ₍₂₁₁₎ ≒17.7゜ and θ _(2
22) ≒25.5°, but even if we assume an optical system with a relatively long X-ray path with a distance of about 200 mm between the center of the measurement point on the sample and the X-ray tube (or detector), The center distances of the X-ray tube (or detector) are 15 mm, 12 mm, and 27 mm, respectively, making implementation impossible. When C _p -K characteristic X-rays are used to solve this problem, the diffraction angle shifts toward a higher angle, making it impossible to measure lattice planes with a spacing of 0.895 Å or less. Furthermore, when C _r -K characteristic X-rays are used, the diffraction angle shifts to a higher angle side, and it is impossible to measure the diffraction angle below 1.15 Å. Also, in both cases, ND
<222> Measuring axial density is virtually impossible. In addition, when using the angular dispersion method online, there is a drawback that the influence of sample position fluctuations is large. That is, in online measurements, even if the fluctuations in the X-ray pass line are suppressed to a sufficiently small level, sufficient accuracy cannot be obtained. As a result of intensive studies to resolve these fatal drawbacks of conventional methods, PSPC was developed for the detection of diffracted X-rays.
The above disadvantages are advantageously solved by using
For the first time, it has become possible to easily measure texture online. PSPC uses a single core wire as an anode, and generates an "electron avalanche" due to the diffracted X-rays at the point where the diffracted X-rays are incident on the core wire, and the induced charges generated on the cathode surface surrounding the core wire are e.g. It is a detector that ultimately locates the incident position of the diffracted X-rays from the time when the induced charge flows into the delay line connected to the cathode and reaches both ends of the delay line. This method is called "PSPC using delay line readout".
Although the other methods have different readout formats, their purpose is to precisely locate the incident position of diffracted X-rays on the core line by some means. In this invention, on the circumferential locus on which the diffractometer was scanned in the conventional angular dispersion method,
PSPC that divides multiple angular regions according to the diffraction angle position determined by the lattice plane of the measurement object, or a curved or broken line that can sufficiently cover the range from the minimum angle to the maximum angle of the diffraction line to be detected. Place the PSPC with a single detection surface. Furthermore, when measuring the ND <hkl> axis density distribution map of a ferritic single-phase steel plate according to the present invention, the lattice spacing d is d ₍₄₂₀₎ ≒ 0.64 Å to d _(110
) = Diffraction X from crystal lattice planes in the range of 2.02 Å
It is sufficient to be able to measure the line. For example, when the M _p -K line is used as the characteristic X-ray, the Bragg angle range is θ ₍₁₁₀₎ = 10.13° to _{θ (420)} = 3.73°, and measurements are made at seven locations during this period. Although the necessary number of X-ray tubes may be installed at predetermined angular positions, usually the X-ray tubes are scanned continuously or in steps within a fixed angular range. In this specification, continuous or step scanning of the X-ray tube refers to rotating the X-ray tube continuously or intermittently over a certain angle range along an arc centered on the center of the irradiation area on the sample surface. Say something. Furthermore, the present invention is not limited to the case where the measurement sample is a single phase, such as a single ferrite phase or austenite phase in steel, but even when both phases are mixed, the ND<hkl> axis of each phase A density distribution map can be obtained. The case where a steel plate in this two-phase ferrite-austenite mixed state is used as a test object will be described below as a representative example. Now, the optical system of this invention is specifically shown in FIG. An example of this is when a PSPC with a single curved detection anode is used as a detector. Since this optical system determines the ND<hkl> axis density distribution, the position of the X-ray source and the detection position are always symmetrical with respect to the normal to the sample surface. As is clear from the figure, even when the X-ray tube is scanned continuously or in steps within a predetermined angle range, the curved shape remains.
By using PSPC, all diffracted X-rays can be detected with a single optical system, which greatly simplifies the structure of the head section. Note that there are cases where it is impossible to measure the low angle side of the diffraction angle θ due to the actual arrangement of the measuring device, but in this case, 2
The use of different types of characteristic X-rays is effective. That is, Table 1 shows the lattice spacing (d _hkl ) when both M _p -K〓 and C _p -K〓 characteristic X-rays are used.
As shown in the relationship between and diffraction angle (θ),
M _p -K〓Measure from austenite (220) plane to ferrite (420) plane with characteristic X-ray, C _p -K
Measure from the austenite (111) plane to the ferrite (211) plane using the 〓 line. Then, the intensity of both measurement systems is corrected based on the diffraction intensity from the austenite (220) plane or the ferrite (211) plane, which is measured overlappingly.

[Table] According to the above method, for the M _O tube, there are 10 measurement points in the scanning angle range: 15° to 35°, and for the C _P tube, the measurement points are in the scanning angle range: 20° to 55°. :
It will be 6 points. Further, unlike the diffract meter method, there is no need to scan the X-ray tube and detector in synchronization, so the structure is simplified and maintenance is easy, making it very advantageous as an on-line device. Furthermore, when multiple detectors were placed at diffraction angle positions, the measurement angle positions became discrete;
This invention uses a solid-state detector, such as a curved PSPC, which is sufficiently segmented and is considered to be suitable for practical use, so it is easy to detect adjacent diffraction lines and separate them into elementary waveforms by subsequent waveform separation processing. Ru. Note that when using multiple characteristic X-rays, multiple PSPCs are not necessarily required, and multiple X-ray tubes can be scanned continuously or step-scanned on the same trajectory with time differences. , the only
PSPC allows measurement of the entire range of diffraction X-rays. From the diffraction intensities from the seven diffraction planes of the ferrite phase or the seven diffraction planes of the austenite phase measured in this way, a simple method is used to calculate ND<hkl.
> Find the axial density. In other words, a set of crystal lattice planes is obtained from the diffraction intensity of a random group obtained just before or after measurement, or the diffraction intensity of a random sample stored in advance, and the diffraction intensity from each crystal lattice plane of the corresponding measurement sample. It calculates the degree. Here, the random strength is determined as follows. The sum of the diffraction intensities from the seven crystal planes of each phase usually accounts for the majority of the sum of the diffraction intensities of each phase. Therefore, from the diffraction intensity ratio of each crystal lattice plane of a random sample using this measuring device, a value of the device-specific intensity ratio is determined, and the diffraction intensities are added for each phase for the ferrite phase and austenite phase, and then this addition is performed. If the intensity is proportionally distributed to each crystal plane of each phase according to the above intensity ratio, this becomes a random intensity for each crystal plane. By comparing this random intensity value with the intensity value of the corresponding sample diffraction surface, the axial density value for the diffraction surface is determined. According to this method, a practically accurate axial density can be quickly obtained even from the diffraction intensity when the sample is not a single phase, such as in the case of a ferrite-austenite two-phase mixed sample. Generally, in a two-phase mixed sample, such as the above-mentioned ferrite-austenite two-phase mixed sample, the diffraction waveforms from both phases, such as the ferrite phase (222) plane and the austenite phase (331) plane, are shown in Figure 3. Although there is an overlap of
This is easily separated into elementary waveforms by using, for example, fast Fourier analysis in the electronic calculator 5 connected at the subsequent stage. The integrated intensity is then calculated for each diffraction surface. Further, in this invention, since the incident X-rays are in the form of a parallel beam and consideration is given to the slit system, the present invention is not affected much by variations in the sample position. In other words, (1) an incidence-detection slit system that detects diffracted X-rays with an aperture width narrower than the incident line width, and (2) contrary to (1), a system that detects diffracted X-rays with an aperture width wider than the incident line width. A slit system, etc., is used. Furthermore, when using a position-sensitive X-ray detector, it is often possible to obtain a better quality diffraction profile by not using a detection slit at all, and when not using a detection slit at all, the detector becomes less sensitive to sample position fluctuations. Therefore, it is more convenient as an online measurement method. As described above, in this invention, in order to quickly and easily measure each diffraction X-ray in the measurement area,
ND using a simple method that conventionally required more than 30 minutes
Axial density distribution maps can be measured in a short time including signal processing, and it can be said that a practical method for online measurement of texture has been established. A more detailed explanation of specific embodiments will be given below. FIG. 4 is an example of a measurement system for online real-time measurement of the texture of a steel plate 7 that is supported by a plurality of suitable rollers 8 and is traveling.
The figure shows the specific structure of the head section 1. The tube current and tube voltage are transmitted from the X-ray generator 2 to the spectroscopic chamber 1.
-0 is supplied to the X-ray tube 1-1 housed in.
The spectroscopic chamber 1-0 houses the X-ray tube 1-1 and the subsequent slit 1-2 system PSPC 1-3, and is designed to protect them from heat, dust, and corrosive atmosphere from the surroundings. cut off Furthermore, it is more desirable to provide the X-ray passageway with a vacuum atmosphere in order to reduce the attenuation of the X-rays in the passageway. The head section 1 includes a spectroscopic chamber 1-0, a vacuum pump, a heat-resistant water-cooled tube (not shown), etc., and has an internal explosion-proof structure as required, which is suitable for use during annealing in an atmosphere containing hydrogen gas, etc. This method is used for measuring the texture of steel sheets. The characteristic X-rays generated from the X-ray tube 1-1 pass through the incident solar slit (or incident collimator) 1-2 and the filter foil 1-2' that cuts off the K-rays, and form a parallel beam, whose parallel components are reflected by the plate material. 7 at an angle θ. Among the incident parallel X-rays, the diffracted X-rays that satisfy Bragg's equation are
The diffraction
Detected by PSPC1-3. If the lower Bragg angle cannot be detected due to the structure of the measuring device, a plurality of characteristic X-rays with different wavelengths are used as described above. Diffraction It is sent to computer 5. At this time, in the case of the FT measurement method, that is, the method of integrating diffracted X-rays at a predetermined angular position for a certain period of time, the counted value after the integration is transferred to the signal processing system. The count signal processed digitally or the data A/D converted at an appropriate time is used to smooth the waveform using an appropriate method such as the moving average method in the electronic computer 5 to obtain the background, and then calculates the background from the original waveform. The background is removed to obtain only the diffraction lines, and the diffraction profile is subjected to an appropriate integral operation such as window integration to calculate the diffraction X-ray intensity for each crystal lattice plane. After performing these waveform numerical processings, the axial density of each crystal lattice plane is calculated by comparing it with the diffraction intensity of the corresponding crystal lattice plane of the random sample obtained by the method described above. In Figure 4, 4 is traverse, and head 1
is driven in the width direction of the sample, and if necessary, the TD
It is provided to measure the texture of. The effects of this invention can be summarized as follows according to the field of application. (1) Since PSPC is used as a detector, it is possible to eliminate the dead zone that occurs in the conventional method in which multiple detectors are placed at diffraction angle positions, and in practice it is possible to continuously adjust diffraction angle positions. It can be taken. Furthermore, since PSPC is a fixed-position detector, there is no need to synchronize the movement of both the X-ray source and the detector, and the diffraction angle can always be determined independently. (2) Since a parallel beam optical system is used, the tolerance range for sample position fluctuation is large, which is extremely advantageous for online measurements. (3) For ordinary plate-shaped BCC metals, it is extremely easy to measure the diffraction intensity from a minimum of five crystal lattice planes: (200), (211), (110), (310), and (222). This has made it possible, for example, to estimate various properties of steel sheets online, and perform quality control and grade classification. (4) The field of application of this invention is not limited to steel plates, but can also be applied to general BCC metals, FCC metals, and two-phase alloy metals containing both.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the optical system in the conventional angular dispersion method, Fig. 2 is an explanatory diagram of the optical system of the present invention using a curved PSPC, and Fig. 3 is a diffraction waveform in a ferrite-austenite two-phase mixed sample. FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5 is an explanatory diagram showing the structure of the head section. 1...Head part, 1-0...Spectroscopy chamber, 1-1...
...X-ray tube, 1-2...Incidence solar slit, 1-
2'...Filter foil, 1-3...PSPC, 2...
X-ray generator, 3...Control unit, 4...Traverse drive control unit, 5...Electronic computer, 7...Plate material, 8
……roller.

Claims (1)

[Claims] 1. When measuring the texture of a rolled metal plate while the rolled metal plate is running on a production line, a parallel beam of characteristic The rolled metal plate is irradiated from an X-ray source that rotates over a certain angle range on an arc centered on the center of the X-ray irradiation area on the surface of the rolled metal plate, and A position sensitive type X in which the diffracted X-rays from each crystal lattice plane are arranged along an arc on the side opposite to the irradiation side with respect to the plate surface normal at the center of the X-ray irradiation area and concentric with the above-mentioned arc. The intensity of the diffracted X-rays from each crystal lattice plane is measured by detecting the diffracted X-rays with a radiation detector and analyzing the waveform of the obtained diffracted X-rays. Analyze the sample in the same way, measure the diffraction X-ray intensity from each crystal lattice plane corresponding to the rolled metal plate, and compare the two to determine the crystal axis parallel to the normal direction of the plate surface of the rolled metal plate. A method for measuring the texture of a rolled metal plate during running on a production line, the method comprising determining the density distribution of crystal grains having the following properties.