JPS642895B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for measuring the texture of a rolled metal plate. In general, the texture of metal materials, especially steel sheets, is an important element that determines its workability, magnetic properties, etc. In the past, excellent products have been developed by devising manufacturing processes and ingredients to actively utilize various properties based on the texture, but it is difficult to control the quality and grade the products. requires accurate measurements of texture. By the way, texture measurements are generally carried out off-line, in other words, away from the production line, using small test pieces taken from the material, but conventional measurement methods require a long time, which poses problems in terms of work efficiency. It was hot. For this reason, there was a demand for the development of a rapid and highly accurate measurement method. This invention meets the above-mentioned needs by irradiating a rolled metal plate with continuous X-rays at a constant angle of incidence in a plane including the normal to the plate surface, and detecting the diffracted X-rays from the rolled metal plate.
The rays are detected by a semiconductor detector fixed at a predetermined diffraction angle position, and this is analyzed especially by the energy dispersion method to determine the diffracted X-ray intensity from each crystal lattice plane. This method has been newly developed to quickly and easily measure the texture of a rolled metal plate that is left still by comparing it with the standard diffraction X-ray intensity for each crystal lattice plane determined from a theoretical formula. 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, measuring the texture of a polycrystalline sample means determining its preferred crystal orientation and quantifying 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. Usually, 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 lattice plane of the sample to the random intensity from the same crystal lattice plane. Now, there are two ways to display the collective structure: In other words, (1) Fix the sample coordinate system, and determine in what directions 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. (2) A method of fixing the crystal coordinate system and displaying the density of crystal axes parallel to the ND in any direction of the sample in that coordinate system.For the former (1), { hkl} plane (positive) pole figure or polar density distribution diagram, the latter (2) is called an ND//axis density distribution diagram or a 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 called (hkl) planes 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 . There is a relationship. Now, the X-ray with wavelength: λ is incident on the lattice surface with Miller index (hkl) at an angle of incidence of 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 is known as Bragg's law, n is the reflection order, and takes successively larger values in the range of sinθ≦1. 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. With this, when creating a {hkl} plane positive pole figure,
Since θ _hKL is constant, the diffractometer is fixed at this angular position and no angular scanning is performed, but the sample stage must perform complex rotational movements to measure the value at each point on the stereo projection sphere. There is,
On the other hand, when creating an inverse pole figure, it is possible to directly measure
There are a simple method in which about 15 crystal planes are created from diffraction intensity, a precise method proposed by Jetter et al., and a method in which calculation is performed from a three-dimensional crystal orientation distribution function, but the simple method is usually the most commonly used method. , the practical requirements are met in this way. 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 so as 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 processing, has a close relationship with the texture of the material and is related 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 knowledge. Therefore, rapid and highly accurate measurement of the texture of steel sheets greatly contributes to product grading, quality control, and quality assurance. However, conventionally used methods for measuring texture require a long time for measurement, as described above, and also have the disadvantage that accuracy decreases because the volume that contributes to diffraction changes as the diffraction angle changes. Now, let us consider the case of creating an inverse pole figure using the simple method according to the conventional method. For example, for α-iron (ferrite), in descending order of crystal plane spacing, (110), (200), ..., (640)
Until now, determining the axial density of 13 diffraction grating surfaces (excluding overlapping gratings) required more than an hour of measurement time for a single sample. I mean,
To scan while holding the x-ray tube and detector in an angular position that satisfies Bragg's law, move the detector 1°/
It had to be driven over an angular range of about 120° at an angular velocity of min. At this time, it usually took about 2 hours even if the angular range where no diffraction lines were present was fast-forwarded. For example, to detect diffracted X-rays from the (110) and (640) planes using Mo-Kα rays,
The diffraction angles are θ = 10.10° and θ = 63.0°, respectively, and when the same slit system is used, the irradiation area and penetration depth are different, so the volume that contributes to the diffraction intensity changes significantly. This invention solves the above-mentioned conventional drawbacks by irradiating a sample with continuous X-rays instead of characteristic This makes it possible to analyze the diffraction intensity from each diffraction crystal lattice plane in a short time by energy-analyzing the detected diffraction X-rays according to the energy dispersion method described below. In this energy dispersion method, especially continuous (white)
The crystal lattice spacing d _hKL is determined by measuring the energy value (hc/λ) of reflected X-rays from the crystal at an appropriate diffraction angle using X-rays. In other words, there is a relationship between energy (E) and wavelength (λ): λhc/E...(3) where h: Planck's constant c: speed of light, so the above equation (2) and this (3) ), the required lattice spacing d _hKL is d _hKL = hc/2sinθ・1/E (4). By the way, the energy range of X-rays used for diffraction mainly depends on the detection efficiency and energy resolution of the detector, the maximum voltage of the X-ray generator, etc., but is usually in the range of about 5 to 45 KeV. An appropriate diffraction angle is selected according to the lattice spacing of the measurement sample so that the main peak to be measured is in the range of about 10 to 35 KeV. Now, FIG. 1 specifically shows an optical system of the present invention according to the energy dispersion method. As is clear from the figure, all the diffraction lines can be measured simultaneously with a single optical system with fixed incident angles and diffraction angles (θ), which greatly simplifies the structure of the head section, and also makes it possible to measure all the diffraction lines simultaneously. Since the diffraction angle θ can be arbitrarily selected for the diffraction surface according to the purpose, the X-ray incident angle (or diffraction angle) when using a constant width slit, which has been a problem in the past, can be
There is no difference in the irradiated area on the sample surface due to a change in the diffraction X-ray intensity, and therefore, no matter what minute region in the sample is targeted, a diffracted X-ray intensity corresponding to the sample position can be obtained. Also, the fact that the incident angle θ is constant means that the absorption effect,
The penetration depth may also be assumed to be constant for each diffraction grating surface, and in practice, the diffraction intensity can be obtained under constant diffraction conditions for each grating surface. Tables 1(a) and 2 are based on the above method and show the energy levels and their distributions ( The degree of overlap) was carefully examined.
Further, Table 1(b) shows the relationship between each diffraction grating surface in Table 1(a) and the energy value E using an energy level scale. In the figure, black triangles indicate diffraction surfaces that can be measured individually, and white circles indicate that multiple surfaces overlap.

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Claims (1)

[Scope of Claims] 1. When measuring the texture of a rolled metal plate under static conditions, continuous X-rays are irradiated onto the rolled plate at a constant angle of incidence, and the diffracted X-rays from the rolled metal plate are measured. is detected by a semiconductor detector fixed at a predetermined diffraction angle position, and the diffracted X-rays are analyzed by the energy dispersion method to measure the diffracted X-ray intensity for each crystal lattice plane. By adding the diffraction X-ray intensities and proportionally distributing this added intensity according to the relative intensity ratio of each crystal lattice plane obtained from the following theoretical formula, the standard diffraction X-ray intensity for each crystal lattice plane is calculated. Find the diffraction X of the rolled metal plate in each crystal lattice plane.
1. A method for measuring the texture of a rolled metal sheet, comprising determining the texture of the rolled metal sheet by comparing line intensity and standard diffraction X-ray intensity. Note RI(i)=I(i)/ΣI(i) I(i)=K・1/v ²・F ²・P・(L)・e ^-2M・V・
A(θ) where RI(i): Relative intensity ratio I(i): Theoretical intensity of any diffraction surface K: Constant independent of the amount and type of sample v: Volume of unit cell F: Structure factor P: Multiply Severeness factor (L): Lorentzian bias factor e ^-2M : Temperature factor V: Volume of sample irradiated with X-rays and contributing to diffraction A(θ): Absorption factor