JPH02208563A - Steel evaluating apparatus - Google Patents

Abstract

PURPOSE:To evaluate the configuration of a deposited material and to make it possible to provide a practical apparatus for delivery inspection by providing a means for inputting the image of an enclosure from a microscope, a point-sequence taking-out means, a virtual-grain-boundary computing means, and a dispersion judging means. CONSTITUTION:An image inputting means performs the binary coding of the image signal of an enclosure from a scanning type electron microscope 1 or an optical microscope and inputs the signal into an image memory 4 of a computer. A point-sequence taking-out means 5 obtains the center of gravity of the enclosure from the image signal which is inputted into the memory 4 after the binary colding of the enclosure. Only the signal indicating the enclosure whose center of gravity approaches by a specified distance is selected, and the linear point sequence is taken out. The linear point-sequence signal which is taken out with the means 5 is sent into a virtual-grain- boundary computing means 7. The virtual grain boundary is computed from the enclosure for every point sequence. Then, a judging means 8 computes the distance to the center of the enclosure from the virtual grain boundary for every linear point sequence. It is judged that the materials having the small dispersion have weak stress resistance and corrosion cracking and that the materials having the large dispersion have the strong stress resistance and corrosion cracking.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a steel material that improves stress corrosion cracking resistance by discontinuously precipitating inclusion particles (hereinafter simply referred to as particles) at grain boundaries. This invention relates to an apparatus for evaluating the precipitation status of.

[Conventional technology]

In recent years, for example, ALLOY 690 (30% Cr-6
Techniques have been developed to control and precipitate inclusions at grain boundaries through heat treatment, such as grain boundary strengthening heat treatment (0%N1-9%Fe), to improve crackability along grain boundaries. Precipitation control through this heat treatment is delicately related to ingredients, furnace temperature, etc., and it is necessary to inspect the precipitation results at the time of shipment.

In this test, after polishing the sample material, a transmission microscope is used to focus on each particle and irradiate it with an electron beam.The electron beam is diffracted by the crystal lattice and a striped crystal image is obtained. The direction of the crystals was measured, and the grain boundary precipitation state was examined based on the variation in the direction of precipitation.

(Problem to be solved by the invention) However, in the above inspection, only the direction of one precipitated particle can be obtained by one measurement, and for quality evaluation, 5'OO
There was a problem in that it required ~2000 direction measurements, which required too many man-hours and was not practical for shipping inspection.

The present invention has been made in view of the above circumstances, and its purpose is to provide an evaluation rIH value of steel materials that can be easily inspected with a small number of man-hours.

[Means to solve the problem]

The present invention provides a method for evaluating steel materials that improves stress corrosion cracking resistance by precipitating inclusions discontinuously at grain boundaries. A point sequence extracting means for extracting a Ia dot sequence, a virtual grain boundary calculating means for calculating a virtual grain boundary from the point sequence, and a dispersion determining means for calculating and determining the dispersion of the precipitation position of point inclusions from the virtual grain boundary. This is a steel evaluation device characterized by comprising:

[For production]

As described above, the steel evaluation apparatus of the present invention includes an image input means, a point sequence extraction means, a virtual grain boundary calculation means, and a variation determination means. The image input means is configured to binarize an inclusion image signal from a scanning electron microscope or an optical microscope and input it into the image memory of the computer.

The point sequence extracting means binarizes the inclusion, determines the center of gravity of the inclusion from the image signal input to the image memory, selects only those whose center of gravity is close to each other by a predetermined distance, and extracts a linear point sequence.

Next, the linear point sequence signal extracted by the point sequence extraction means is sent to the virtual grain boundary calculation means, and a virtual grain boundary is calculated from inclusions for each point sequence.

Next, the dispersion determining means calculates the distance from the virtual grain boundary to the center of the inclusion for each linear point sequence, and calculates and determines the dispersion. From this, it is determined that those with small variations have weak stress corrosion abrasion resistance, and those with large variations are strong.

〔Example〕

The present invention will be explained below based on the drawings. FIG. 1 is a schematic diagram showing a steel evaluation apparatus of the present invention.

In the figure (1) is a scanning electron microscope. The details are shown in Figure 2. FIG. 2 is a schematic diagram of a scanning electron microscope ifi (1) with a magnification of 5000 times or more, in which a specimen (2), which is a polished sample material, is cut out below.

The sample (2) is irradiated with an electron beam, the electron beam is diffracted by a crystal lattice, and the electron beam is detected by an electron beam tube (3). The detected signal is binarized and input to the image memory (4). Only particles are extracted from the data input to the image memory (4). Since the lattice constants of crystal particles and particles are different, the particles are separated from the base and appear as an image.

Next, the point sequence extraction means will be explained. The image memory (
The signal from 4) is sent to the point sequence extraction mechanism shown by Find the center of gravity ratio l1l). This state will be explained with reference to FIG. First, if you choose the closest particle, 1...2...
・3...... However, if the distance does not exceed a certain distance, it is determined that the point sequence ends there. When a group of three or more particles is formed, a1 is directly calculated from the first to last particles (for example, 1 and 11). Next, the legs d2 to d8 of the perpendicular line from each particle to 1 are calculated. The longest d+ is found from among these, and if it is greater than a certain value, the particle group is cut at the corresponding particle. In the example, when straight line 1 is obtained from 1 and 11, d6 is the longest.

If this is da>dl1mth, then 1 to 6 are extracted as a straight line point sequence. The extracted particles are excluded, and the remaining particles are extracted in the same manner. In the example, 1~6.7-10.11~
14 three columns are extracted.

Next, the virtual grain boundary calculation means will be explained. point sequence extraction v
The signal from the R structure (5) is sent to the virtual grain boundary calculation mechanism (2) shown in Figure 1.
). A method for calculating virtual grain boundaries will be explained in more detail based on FIG. 4.

Since it is unknown where the actual grain boundary passes through the precipitate, the circumscribed rectangle of each particle (6) is determined, and the coordinates of four points in contact with this rectangle are determined. The circumscribed rectangle here is X, Y
In the rectangular coordinate system, it is a rectangle that is bordered by straight lines parallel to the X and Y axes, respectively. Each point sequence (Xil, Yil) corresponding to the four sides, (Xi2. Yi2
), (Xi3. Yi3), and (Xi4°Yi4) to find a straight line or quadratic approximate curve. These four glands are virtual grain boundaries.

Next, the variation determining means will be explained. The signal from the virtual grain boundary calculation mechanism (2) is sent to the variation determination mechanism shown in (8) in FIG. 1, and the vertical distances from the center of gravity of each particle to the four virtual grain boundaries are determined, and the standard deviation is determined. Select the virtual grain boundary with the smallest standard deviation among the four virtual grain boundaries, use it as the grain boundary, and find its (σmin): a min > ao : B typecrmi
It is determined that n≦aO: A type. The A type mentioned here is shown in Figure 5 (a>
As shown in Figure 5, the particles (6) are coherently precipitated on one side and have weak stress corrosion cracking resistance.
As shown in b), the particles (6) are coherently precipitated on both sides and have strong stress corrosion cracking resistance. For reference, see Figure 5 (
C) shows a case where particles are precipitated in a non-coherent manner; in this case, stress corrosion cracking resistance is extremely weak. In the wE4 diagram, IiL becomes σmin, and in this case A type
It is. The reason why virtual grain boundaries are determined using this method is that precipitated particles are thought to occur at grain boundaries, so the gland closest to each precipitated particle is assumed to be a grain boundary.

This is done for each point sequence, and the judgment for the entire loft is made for each t
Evaluation is performed using the following formula based on the ratio of the length of the point sequence determined to ype.

ΣJ2ai Then, depending on whether the value of R is larger or smaller than the reference value RO, it is determined that R≧RO: A type R<RO: n type.

As above, the whole is A type % B ty
Pe, A type Pe is determined to have weak stress corrosion cracking resistance, and B type is determined to be strong.

Incidentally, in the embodiments of the present invention, the case where a scanning electron microscope was used to obtain a crystal image of a sample was explained, but the same effect can be obtained even if an optical microscope or an image sensor is used to receive an image input signal. Of course, this can be obtained.

〔Effect of the invention〕

The steel evaluation apparatus of the present invention can quantitatively evaluate the form of precipitates using images, and the number of man-hours can be significantly reduced, so it can be put to practical use as a shipping inspection, and has the excellent effect of ensuring quality assurance.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the steel evaluation device of the present invention, Fig. 2 is a schematic diagram of a scanning electron microscope, Fig. 3 is a diagram for explaining the point sequence extraction method, and tJ4 diagram is a virtual grain boundary calculation method. FIG. 5 is a diagram schematically showing the precipitation situation of particles, in which (a) shows an example of coherent precipitation on one side, (b) shows an example of coherent precipitation on both sides, and (C) shows an example of coherent precipitation on both sides. ) is an example of non-coherent precipitation. 1... Scanning electron microscope 2... Sample 3... Electron beam picture tube 4... Image memory 5... Point sequence extraction mechanism 6... Particle 7... Virtual grain boundary calculation mechanism 8.
・・Variation determination mechanism (a and Cb) CC)

Claims (1)

[Claims] In an evaluation method for steel materials that improves stress corrosion cracking resistance by precipitating inclusions discontinuously at grain boundaries, an image input means for inputting images of inclusions from a microscope and a linear dot sequence are extracted from the inclusion images. A virtual grain boundary calculating means calculates virtual grain boundaries from the point sequence, and a variation determining means calculates and determines variations in precipitation positions of point-like inclusions from the virtual grain boundaries. Characteristic steel evaluation equipment.