JPH10300692A - Method and device for measuring assembly organization of metal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an assembly organization in the direction of a plate thickness accurately and quickly by scanning a plurality of layers that are in parallel with the surface of a metal material with electron beams and calculating the crystal orientation distribution (ODF) strength in a specific orientation from crystal orientation data for each layer being obtained from the diffraction pattern of reflection electron beams. SOLUTION: A sample 1 is cut from a metal material S and is divided into a plurality of layers 21-2N that are in parallel with a rolled surface over the measurement depth of the assembly organization of the metal material S. Then, while the sample 1 is moved automatically at a constant interval, electron beams are applied to an electron beam irradiation point 4 within a specific range for each of the layers 21-2N, an electron beam rear scattering pattern(EBSP) is detected by a two-dimensional screen detector that is installed in a reflection electronic diffraction cone being generated at each irradiation point 4. Then, the EBSP is analyzed for obtaining the crystal orientation of each crystal particle and the crystal orientation file for each layer is created, thus specifying an ODF function at an arbitrary position from the surface of the metal material S. Then, ODF strength at a specific orientation is calculated by the ODF function.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a texture of a metal material, and more particularly to a method for accurately and quickly measuring a change in a texture of a metal material such as steel in the thickness direction. And an apparatus for the same.

[0002]

2. Description of the Related Art Since the texture of a metal material, particularly steel, has a great influence on the workability and magnetic properties of the steel material, its control is important for quality improvement. For steel materials,
The origin of the texture is in the slab structure, and in slabs, $ 10
Columnar crystals developed so that the 0 ° plane was parallel to the slab surface, and equiaxed crystals with relatively random orientations developed in the center near the surface, but changed due to shear stress applied during rolling. The final product texture is formed. At that time, since the shear stress at the time of rolling is not uniform in the thickness direction, the texture changes in a complicated manner in the thickness direction. Therefore, it is necessary to check and properly control the texture not only in the final product but also in the manufacturing process. For example, in a unidirectional silicon steel sheet, the change in the thickness direction of the texture is positively utilized for improving the properties of the product, and the secondary recrystallized grains (110) [001] which greatly affect the magnetic properties are obtained.
In order to improve the degree of integration in the orientation, {111} <1 in the portion of the sheet thickness of 1/10 to 1/5 in the cold-rolled sheet before final annealing.
12> The texture is controlled to develop the texture of the orientation. On the other hand, in the cold-rolled steel sheet for deep drawing, in order to improve the plastic strain ratio (average r value, Rankford value), a {111} orientation texture must be uniformly generated in the thickness direction. In order to prevent ridging of ferritic stainless steel sheets, a (110) [001] recrystallized structure is developed deep under the steel sheet surface, and a {100} <011> oriented texture is developed in the central layer. It is important to control

In order to control the texture in the thickness direction,
A means for simply and accurately measuring the texture change in the thickness direction is indispensable. Therefore, conventionally, a method of analyzing the crystal orientation distribution function (hereinafter referred to as ODF function) from the inverted pole figure intensity (inverse intensity) or the positive pole figure by the X-ray diffraction method has been adopted, but the change in the plate thickness direction is measured. to do so,
It is necessary to measure multiple specimens by cutting the specimen in the thickness direction from the surface, or to repeat the measurement and grinding of the texture at a specific position on the plate surface. The repetition took time and was inefficient.

In order to measure the change of texture in the thickness direction in a non-destructive manner without performing such a complicated operation, the present inventors have proposed that the penetration depth of the X-ray into the sample decreases as the wavelength becomes shorter. Paying attention to becoming deeper,
In Japanese Patent Publication No. 99, a symmetrical reflection scan is performed using an energy dispersive X-ray diffractometer equipped with a semiconductor detector and a multi-wave height analyzer, and a differential analysis is sequentially performed on a plurality of diffraction patterns whose X-ray penetration depths are sequentially changed from the surface. Go to
A method of finding the inverse strength at a specific depth was proposed. On the other hand, in Japanese Patent Application Laid-Open No. 7-63709, a conventional angle-dispersion type X-ray diffractometer has a solar slit and a slit position with respect to the X-ray optical axis such that the X-rays are parallel to the incident side and the light receiving side, respectively. There is also disclosed a method in which a movable slit for scanning in the vertical direction is attached, and a diffraction pattern is measured while continuously changing the slit position, thereby measuring a change in the inverse intensity in the thickness direction. However, in all of these methods, although the measurement itself is very simple, the measurable plate thickness depth is X
The fundamental problem is that the measurement depth is limited to several tens of μm, which is the penetration depth of the ray, and the deeper the depth from the sample surface, the more the intensity of the diffracted X-rays decays exponentially. was there. In addition, as a simple means to evaluate the texture in the thickness direction, there is a method of estimating from the etch pits on the sample surface.However, it is only possible to roughly estimate the crystal orientation. Not suitable.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, the present invention makes it possible to accurately and rapidly change the texture of a metal material such as steel, including changes in the direction perpendicular to the surface, for example, in the thickness direction. It is an object of the present invention to propose a method and an apparatus for performing measurement.

[0006]

As shown in FIG. 2, when the electron beam 11 is irradiated on the surface of the sample 1 inclined at 45 to 85 ° with respect to the electron beam 11, the electron beam irradiation position is changed together with the secondary electrons. A large amount of backscattered electrons are generated from a region having a radius of about several tens nm to about 0.1 μm at the center, and when the backscattered electrons pass through the inside of the sample, a backscattered electron diffraction cone 12 diffracted by the crystal lattice of the sample is formed. . A two-dimensional screen detector 13 for reflected electrons is placed in the diffraction cone 12. A diffraction pattern called an electron beam backscattering pattern (EBSP) is obtained on this detector. This diffraction pattern is similar to a kick pattern observed with a transmission electron microscope or an electron beam channeling pattern observed with a scanning electron microscope. And Steel, 70 (1984) S565, "Method for Analyzing Crystal Orientation from Electron Beam Channeling Pattern", ie, any three sets of (hk
l) The line pair is binarized by the image processing device and intersected (hk
By using 1) a method of determining the crystal orientation from the intersection angle of the lines and the coordinates of the intersection, the orientation of the crystal grains at the electron beam irradiation position can be measured. The inventor of the present invention can determine the crystal orientation at that depth by performing such a measurement on a section of the metal material in a layer having an arbitrary depth from the surface of the material, and scan the crystal over a certain range at that depth. The orientation was measured for a large number of crystal grains while performing the measurement. I. Wright et al.
own of computer-assist
ed Microscopy, 5 (1993) p207
It has been found that the ODF function can be determined by performing the processing described in the above section, and the present invention has been completed.

Accordingly, the present invention provides a method for measuring the texture of a metal material, in which the cross section of the metal material is divided into a plurality of layers parallel to the surface of the material over the measurement depth of the texture. Each layer is scanned while being irradiated with an electron beam, and a diffraction pattern formed by diffracting a reflected electron beam is sequentially analyzed for crystal grains present on the scanning line to obtain a series of crystal orientation data for each layer. The data of the above is stored in correspondence with the layer subjected to the scanning, and a crystal orientation file for each layer is created, and the crystal orientation data for each layer is analyzed over the layer or a plurality of layers to specify an ODF function, Said O
The DF function is used to calculate the ODF intensity in a specific direction for each of the layers or for a plurality of layers from the DF function. A micro-domain crystal orientation analysis device, a plurality of layer-by-layer crystal orientation files that accumulate crystal orientation analysis data obtained by scanning corresponding to the scanning lines, and crystal orientation data stored in the layer-by-layer crystal orientation file An ODF analyzer for analyzing and specifying an ODF function;
The apparatus comprises a specific azimuth ODF intensity calculating device for calculating the ODF intensity in a specific azimuth based on the DF function, and a display unit for displaying the specific azimuth ODF intensity in correspondence with the scanning line position.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.
As shown in FIG. 1A, a sample 1 is cut out of a metal material S. Generally, a cross section perpendicular to the rolling direction (RD) is defined as an electron beam irradiation surface 2 to be used for measurement. This is because, in the cross section, a correct measurement result can be obtained without being affected by the texture caused by the fiber structure parallel to the rolling direction generated when the metal is rolled. However, if necessary, a plane parallel to the rolling direction can be used as the irradiation plane. As shown in FIG. 1B, the irradiation surface has a plurality of arbitrary number N of layers (21, 22, 23,..., 2) over the measurement depth of the texture.
N). The division is performed so as to form a layer parallel to the surface (generally, a rolling surface) of a metal material, for example, a steel plate, so that an electron beam can be scanned at each depth from the material surface. In this case, the measuring depth of the texture and the number of measuring layers, N, are determined by the requirements of the material to be measured. However, if the distance between the layers is too small, there is a relationship with the crystal grain size, but this results in duplicate measurement, which impairs the work efficiency. Therefore, it is preferable to provide an interval of 1 μm or more. When the product shape is a wire, the measurement layer can be formed in an arc shape along the surface shape.

Electron beam scanning is performed on the irradiation surface 2 of the sample 1 for each of the above layers, and the crystal grains existing on the scanning lines 3 are sequentially measured for crystal grain orientation. That is, as shown in FIG. 2, the sample is fixed on an XY sample stage 14 which can automatically move the sample at regular intervals in the XY directions, and the sample is moved by the stage control unit 15 for each of the layers. An electron beam is irradiated to an electron beam irradiation point 4 within a predetermined range. The scanning range is preferably set to a range of 100 times or more the average particle size along the plate surface (rolled surface). If the range is too small, in the subsequent analysis of the ODF function by the series expansion method or the like, it is not possible to secure the same level of resolution as in the case where the plate surface is measured by the conventional X-ray analysis method. It is preferable to set the range to include the crystal grains.

The electron beam irradiation is preferably performed at regular intervals on the scanning line 3 as shown in FIG. The spacing is determined by the size of the crystal grains, the required precision, and the like, but is preferably equal to or less than the average crystal grain size of the layer and equal to or more than 1 μm. The reason why the average crystal grain size is set to be equal to or smaller than that is that if the crystal orientation measurement is performed at a coarser interval than this, crystal grains that do not affect the orientation measurement increase, and the ODF accuracy decreases,
The reason why the minimum pitch is set to 1 μm or more is that even if the crystal orientation is measured at finer intervals than this, it takes a long time, but the ODF is required.
This is because it does not lead to the improvement of the function analysis accuracy. The reflected electron diffraction cone 12 generated at each electron beam irradiation point 4 is passed through a two-dimensional screen detector 13 to form an EBSP.
This is analyzed by an image analysis computer 18 controlled by a detector control unit 16 and an image digitizer 17, so that each irradiation point 4
Is calculated.

The above measurement was performed for each layer (21, 22,... 2).
Since each measurement point (irradiation point 4) is performed successively for each N), a series of crystal orientation data on crystal grains existing on the electron beam irradiation point 4 over the scanning range can be obtained. The series of measurement data is stored in the storage device of the data analysis computer 30 in association with the scanned layer, and a layer-by-layer crystal orientation file 32 is created. For example, a series of crystal orientation data obtained by sequentially analyzing the orientation of a layer immediately below the surface of the material, that is, the measurement result of the first layer is stored as a first layer crystal orientation file, and then stored in the thickness direction. The measurement result of the layer at a position at a predetermined depth is stored as a second layer crystal orientation file. This operation is repeated to create a crystal orientation file up to the Nth layer.

The data stored in the N files for the first to Nth layers obtained by repeating the measurement over the desired range in the plate thickness direction as described above is analyzed by the analyzer, and the ODF function is specified. Is done. The ODF function may be created for each of the above-described files for each layer, or may be created as an ODF function for an integrated file created by connecting files having an arbitrary surface depth range. In the latter case, evaluation is performed as an analysis result at the average depth position of the connected files.

Since the ODF function at an arbitrary position from the surface of the material has been specified as described above, the ODF intensity in a specific direction is calculated using the ODF function. The calculation is performed by designating a specific direction by an Euler angle with respect to the ODF function at an arbitrary position from the material surface. If the results are plotted in the plate thickness direction, it is possible to know the distribution state of crystal grains in a specific orientation in the plate thickness direction. For example, if the plots are sequentially plotted from the first layer to the Nth layer, the texture changes in the thickness direction.

In the measurement of the texture of the metal material of the present invention, a micro-domain crystal orientation analyzer 10 having an XY movement stage that scans a cross section of the metal material while irradiating it with an electron beam is used. A computer 30 that accumulates and analyzes a series of data measured by the device may be used. In the case of steel, EBSP is used for crystal orientation measurement. The recrystallized structure of steel materials may be as fine as 5 μm or less in average grain size. The minimum beam convergence diameter is as large as 10 μm, which is of course the case for X-ray diffraction, and the minimum measurement area even for electron channeling patterns and Kossel patterns. Is 5 μm, which is larger than the crystal grain size, and orientation analysis cannot be performed in some cases. On the other hand, in the EBSP, the diameter of the minimum measurement area is 0.5 to 1 μm at the same sample current as the channel pattern or Kossel pattern of the electron beam, and if the sample current is set slightly lower, the crystal orientation measurement limit becomes 0. .1 μm, and the crystal orientation of the recrystallized structure of a steel material having a fine structure can be analyzed. The beam spot preferably has a diameter of 1 μm or less, and it has been confirmed by actual measurement that if the beam current is used at 1 × 10 ⁻⁹ A or less, it is possible to measure the orientation of crystal grains having a particle size of 1 μm. .

A computer 30 for analyzing the measurement results obtained by the micro-domain crystal orientation analysis apparatus 10 stores a plurality of orientation analysis data obtained as a result of scanning by the above-described apparatus corresponding to the scanned layers. It has an orientation file 32. The stratified orientation file 32 is obtained by sequentially accumulating orientation analysis data obtained by irradiating a scanning line with an electron beam, and storing data corresponding to the same plane on the surface of the material sample, for example, in association with the same address. It is configured such that integration can be performed over a certain range of depth directions.

The ODF function analyzer 3 analyzes the data stored in the file 32 to calculate the ODF intensity.
3. It has an ODF intensity calculator 34. The ODF analyzer 33 stores the data stored in the layer-by-layer crystal orientation file 32 into the layers (21, 22,.
N) Each program has a program for analyzing the data. If necessary, a plurality of files can be integrated for analysis, and an ODF function file 36 for storing analysis results can be provided. The ODF intensity calculation device 34 is a calculation device that receives an input of a specific azimuth and calculates the intensity of a specific azimuth on each measurement surface. The display unit 35 receives the above calculation result and displays the ODF intensity in a specific direction in correspondence with the distance from the rolling surface of the sample.
RT and the like. The data analysis computer 30 has an input unit 37 and an output unit 38.

[0017]

EXAMPLE For measuring the texture in the thickness direction of a steel sheet having a thickness of 1 mm and an average grain size of 20 μm, the conventional step-cutting method requires 5 minutes in a total of 6 steps from the surface to the central layer in 100 μm steps. × 6 = 30 minutes, the time required for 5 times of step cutting was 30 minutes × 5 = 150 minutes, which required a total of 180 minutes. Using the method of the present invention, the measurement range is 20 μm × 1
It is sufficient to measure the orientation in 5 μm steps at 00, and the time required for the orientation measurement and analysis per measurement point is 1.5 seconds. It was possible to measure the texture in the sheet thickness direction in a short time of 1/3 × 2000/5 × 6 = 60 minutes, which is 1/3 of the conventional method.

[0018]

As described above, according to the present invention,
An excellent effect is obtained in that the texture change of the metal material in the thickness direction can be easily and accurately measured quickly.

[Brief description of the drawings]

FIG. 1 is a sketch showing the relationship between a sample and a material used for orientation measurement according to the present invention. (A) shows the relationship between the metal material and the sample and the electron beam irradiation surface, and (b) shows how to set the scanning line and the electron beam irradiation point in the electron beam irradiation surface.

FIG. 2 is a conceptual diagram showing a configuration of a micro-domain crystal orientation analyzer used in the present invention.

FIG. 3 is a conceptual diagram showing a configuration of a data analysis computer used in the present invention.

[Description of Signs] 1: Sample 2: Electron beam irradiation surface 3: Scanning line 4: Electron beam irradiation point 10: Micro-domain crystal orientation analyzer 11: Electron beam 12: Reflection electron diffraction cone 30: Computer for data analysis 31: Control device 32: Layer-by-layer file Crystal orientation file 33: ODF function analyzer 34: Specific orientation ODF intensity calculator 35: Display unit 36: Metal material

Claims (3)

[Claims] 1. A section of a metal material is divided into a plurality of layers parallel to the surface of the material over a measurement depth of a texture, and each of the divided layers is scanned while being irradiated with an electron beam, and a reflected electron beam is scanned. A series of crystal orientation data is obtained for each layer by sequentially analyzing the diffraction pattern formed by diffracting the crystal grains present on the scanning line, and the series of crystal orientation data is made to correspond to the layer subjected to the scanning. To generate a crystal orientation file for each layer, and analyze a series of crystal orientation analysis data accumulated in the crystal orientation file for each layer and analyze the data for each layer or for a plurality of layers.
A method for measuring a texture of a metal material, comprising: identifying a DF function; and calculating an ODF intensity in a specific direction from the ODF function for each of the layers or over a plurality of layers. 2. An EBSP is used for measuring a crystal orientation, an electron beam irradiation scanning range is 100 times or more of an average crystal grain size of a crystal present in a measurement layer, and an irradiation pitch is 1 μm on a scanning line.
The method for measuring a texture of a metal material according to claim 1, wherein the metal material has an average crystal grain size of at least m. 3. A micro-area crystal orientation analysis apparatus using an EBSP having an XY movement stage that scans a cross section of a metal material while irradiating an electron beam, and scans a series of crystal orientation data obtained by scanning. A plurality of layer-by-layer crystal orientation files stored corresponding to the position; an ODF function analyzer that analyzes the crystal orientation data stored in the layer-by-layer crystal orientation file to determine an ODF function; A collection device of a specific azimuth ODF intensity calculating device for calculating the ODF intensity of a specific azimuth, and a display unit for displaying the specific azimuth ODF intensity as a specific ODF intensity-scanning line positional relationship diagram in correspondence with a scanning line position. Tissue measuring device.