WO2014102919A1

WO2014102919A1 - System and method for evaluating state of processed surface

Info

Publication number: WO2014102919A1
Application number: PCT/JP2012/083549
Authority: WO
Inventors: ユウ王
Original assignee: 株式会社日立製作所
Priority date: 2012-12-26
Filing date: 2012-12-26
Publication date: 2014-07-03
Also published as: JPWO2014102919A1; TWI515426B; JP5989135B2; TW201435337A

Abstract

The purpose of the present invention is to provide a system and a method capable of non-destructively evaluating the state of a processed surface of an object to be measured, even for aggregate structures and coarse crystalline materials that have anisotropic X-ray diffraction, such as weld metal. The means for achieving this is characterized by: finding a two-dimensional X-ray diffraction parameter, said two-dimensional X-ray diffraction parameter being the definite integral of the value of subtracting, from the full width of an X-ray intensity curve at half maximum in the radial direction relative to the center of the incident X-ray of the two-dimensional X-ray diffraction spots, the full width at half maximum owing to the device, over the entire circumference of a central angle for the center of the incident X-ray; and evaluating the state of a processed surface of the object to be measured from the relation of the two-dimensional X-ray diffraction parameter found in advance and at least one physical quantity from among either plastic deformity or hardness.

Description

Surface processing state evaluation system and evaluation method

The present invention relates to a surface processing state evaluation system and evaluation method, and more particularly, to a non-destructive evaluation system and evaluation method using an X-ray diffraction phenomenon.

The surface of the structure generally retains plastic strain and increases hardness due to processing history such as grinding and polishing. The plastic strain and hardness are used when evaluating the surface processing state of a structure as an index reflecting the degree of processing. In particular, in the case of a structure operating in a stress corrosion environment, it is known that the higher the degree of surface processing, the higher the susceptibility to stress corrosion cracking (SCC). In addition, it is suggested that the plastic deformation zone and surface fine crystal structure formed by surface processing may be the starting point and the propagation path of SCC.

¡Non-destructive methods are required when measuring the surface processing of actual machine structures and large parts. The X-ray diffraction method is applied to various material evaluations such as crystal structure analysis, component analysis, and residual stress measurement as a non-destructive measurement method. X-ray diffractometry means that when incident X-rays strike a regularly arranged lattice plane of atoms inside a crystal material, the reflected X-ray is reflected when the optical path difference between different lattice planes is exactly an integral multiple of the X-ray wavelength. This is a method that uses the phenomenon that the lines interfere with each other and strengthen each other.

In Patent Document 1, in the evaluation of delayed fracture resistance of a steel sheet molded article, a steel sheet molded article is obtained by using a relationship in which the amount of hydrogen is associated with the distortion of crystal grains in the structure of the steel material when delayed fracture occurs. A technique for performing a delayed fracture hydrogen amount estimation step for estimating the amount of hydrogen that causes delayed fracture in the evaluation site by obtaining the amount of hydrogen corresponding to the strain of the crystal grains in the structure of the evaluation site is described. In the evaluation of crystal grain strain, the local difference parameter KAM (Kernel Average Misorientation) of electron backscattering diffraction (EBSD) and the half width of the X-ray diffraction peak are used. KAM is an average value of misorientation between a certain measurement point and a measurement point adjacent thereto. The half width is a difference between diffraction angles at two points at a level half the maximum value of the X-ray diffraction intensity.

Patent Document 2 describes a method of inspecting hardness from the half value of the X-ray diffraction intensity curve of the measurement object based on the relationship between the half value and hardness of the X-ray diffraction intensity curve.

In Patent Document 3, as a method of non-destructively inspecting mechanical parts for fatigue damage, a monochromatic thin bundle X-ray is irradiated two-dimensionally and continuously on the surface of a machine part, and an X-ray diffraction intensity signal is used. A technique is described in which the half-value width of each diffracted X-ray is measured, and the fatigue damage at the measurement location is evaluated using a diffracted X-ray half-width-fatigue damage reference diagram.

JP 2011-033600 A Japanese Patent No. 2615064 Japanese Patent Publication No. 07-046081

Since the surface processing degree of the structure affects stress corrosion cracking, etc., it is required to evaluate the surface processing degree. For example, some devices and methods for evaluating the surface processing state of a structure by measuring the hardness by utilizing the phenomenon that the hardness increases by work hardening have been proposed. If a contact-type portable hardness tester is used, it is possible to measure the actual machine. However, since the diamond indenter is pushed into the measurement surface at the time of measurement, the plastic strain is further increased by measurement at the measurement location. Further, considering that SCC is mainly generated at the surface starting point, the indentation remaining on the measurement surface after the hardness measurement is not preferable from the viewpoint of preventing SCC.

In Patent Document 1, the EBSD method is used. However, since the EBSD method is a destructive analysis method, it cannot be applied when a non-destructive method such as an actual machine structure or a manufactured part is required.

Patent Document 2 describes a method of inspecting the hardness from the half value of the X-ray diffraction intensity curve of the measurement object, based on the relationship between the half value and the hardness of the X-ray diffraction intensity curve. According to the configuration of the apparatus and the embodiment, the evaluation method uses only the half width on the one-dimensional X-ray diffraction intensity line profile. Further, the relationship between the X-ray half width and the surface plastic strain is not discussed.

In Patent Document 3, as a method for non-destructively inspecting mechanical parts for fatigue damage, a monochromatic thin bundle X-ray is irradiated two-dimensionally and continuously on the surface of the machine part, and each of the X-ray diffraction intensity signals is used. Although the technology to measure the half width of diffracted X-rays and evaluate fatigue damage is described, it can be applied to textures and coarse crystal materials with direction dependency of X-ray diffraction intensity such as weld metal It's not a good technique. Further, the relationship between the diffracted X-ray half width and the plastic strain or hardness of the surface is not discussed.

In any of the above Patent Documents 1 to 3, since the half width of the X-ray diffraction intensity curve or the spread of diffraction spots is a one-dimensional parameter, it depends on the direction of the X-ray diffraction intensity as in a weld metal. In the case of a textured structure or a coarse crystal material, there are cases where it cannot be applied or there is a problem that the variation varies depending on the measurement location.
Accordingly, the present invention provides a system capable of nondestructively evaluating the surface processing state of a measurement object even in a texture or coarse crystal material having a direction dependency of X-ray diffraction intensity such as a weld metal, and It aims to provide a method.

In the present invention, the value obtained by subtracting the half width by the apparatus from the half width of the X-ray intensity curve in the radial direction with respect to the X-ray incident center of the two-dimensional X-ray diffraction spot, and the center angle with respect to the X-ray incident center The surface of the object to be measured is obtained from the relationship between the two-dimensional X-ray diffraction parameter obtained in advance and at least one physical quantity of plastic strain or hardness. The processing state is evaluated.

According to the present invention, it is possible to provide a system and method capable of non-destructively evaluating the surface processing state even for a measurement object having the direction dependency of the X-ray diffraction intensity.

Schematic which shows the structure of the plastic strain and hardness evaluation system by this invention. The block diagram which shows the structure of the evaluation system of the plastic strain and hardness by this invention. The flowchart of the method of evaluating the plastic strain and hardness of a measurement object nondestructively. The schematic diagram which shows the optical system at the time of measuring the half value width B of the radial direction with respect to the incident center of two-dimensional X-ray diffraction. The schematic diagram which shows an optical system when measuring a position. Schematic diagram of a standard powder diffraction ring recorded on a two-dimensional X-ray diffractometer The schematic diagram which shows the optical system at the time of using an imaging plate detector. The schematic diagram which shows the method of calculating | requiring the half value width B and the diffraction intensity peak position by the "half value width method". The schematic diagram which shows the calculation method of the two-dimensional X-ray-diffraction parameter w. The schematic diagram which shows the optical system in the case of arrange | positioning a X-ray incident center and a two-dimensional X-ray detector asymmetrically. The schematic diagram which shows the analysis method by the representative photograph of 2D X-ray diffraction currently recorded on the imaging plate, and an image processing algorithm. The correlation diagram which shows the relationship between the two-dimensional X-ray-diffraction parameter w and the plastic distortion | strain (epsilon) _P. The correlation diagram which shows the relationship between the two-dimensional X-ray-diffraction parameter w and Vickers hardness HV. The master diagram which shows the relationship between the two-dimensional X-ray-diffraction parameter w of the weld metal plate material measured by the method of this invention, and the plastic distortion | strain (epsilon) _P. The master diagram which shows the relationship between the two-dimensional X-ray-diffraction parameter w of the weld metal plate material measured by the method of this invention in an Example, and Vickers hardness HV. The measurement result which shows the hardness dependence of the SCC progress rate of the welding heat affected zone of SUS316 published in the nonpatent literature 2.

In the present invention, a master diagram obtained by functionalizing the relationship between the two-dimensional X-ray diffraction parameter and plastic strain or hardness is prepared in advance, and the plastic strain or hardness is determined nondestructively using this master diagram as an evaluation criterion. Propose system and method to evaluate.

That is, in the present invention, a two-dimensional X-ray is obtained by constructing a plastic strain introduced by a uniaxial tensile test of a metal material test piece, or a functional relationship between hardness and a two-dimensional X-ray diffraction parameter obtained from the test piece. Create a master diagram showing the relationship between diffraction parameters and plastic strain or hardness. The two-dimensional X-ray diffraction parameter w is defined by Equation (1).

That is, the value obtained by subtracting the half-value width B ₀ by the apparatus from the half-value width B of the X-ray intensity curve in the radial direction with respect to the X-ray incident center at the two-dimensional X-ray diffraction spot, and the center angle with respect to the X-ray incident center The definite integral over the whole circumference range is defined as a two-dimensional X-ray diffraction parameter w.

When actually measuring an object to be measured, the X-ray diffraction parameters obtained from the surface of the object to be measured are plotted on this master diagram, so that the plastic strain or hardness of the surface of the object to be measured is nondestructive. Evaluation becomes possible.

Hereinafter, Example 1 of the present invention will be described in detail. In the following description, the correspondence between the two-dimensional X-ray diffraction parameter w and the plastic strain or hardness is approximated by the least square method and expressed as a function. However, in the present invention, the approximation method is not limited to the least square method, and an arbitrary approximation method can be used. Further, the hardness is applicable not only to Vickers hardness (HV) but also to other defined hardnesses such as Brinell hardness (HBS, HBW) and Rockwell hardness (HRC, HRB). The function representing the correspondence between the two-dimensional X-ray diffraction parameter w and the plastic strain or hardness is not limited to that shown in the following description. These correspondences can be expressed in an arbitrary function form. When these correspondences cannot be formulated, the correspondence is represented by the point sequence data (the function is represented by the point sequence data). In this case, plastic strain or hardness can be evaluated using a correlation diagram or a master diagram showing these correspondences. In this specification, the correspondence represented by the data of the point sequence is also referred to as “function”.

FIG. 1 (a) is a schematic diagram showing the configuration of a plastic strain or hardness evaluation system according to the present invention. The plastic strain evaluation system according to the present invention includes an X-ray diffraction apparatus 100, an image analysis apparatus 110 that performs image processing and numerical calculation, and two-dimensional X-ray diffraction parameters w of various materials and plastic strain or hardness. A database 120 constructed with a master diagram representing the relationship is provided.

The X-ray diffractometer 100 includes an X-ray tube 101 and a two-dimensional X-ray detector 102, and X-rays are incident on the surface of the measurement object 104 and diffracted two-dimensional X-ray diffraction spots are converted into two-dimensional X-rays. Record in line detector 102.

The image analysis apparatus 110 measures the X-ray diffraction intensity half-value width B and the central angle α in the radial direction with respect to the X-ray incident center O point from the two-dimensional X-ray diffraction spots obtained on the surface of the measurement object 104. A one-dimensional X-ray diffraction intensity line profile in a certain radial direction is obtained as an X-ray diffraction intensity curve 111.

Based on the master diagram corresponding to the material of the measurement object 104 in the database 120 constructed with the master diagram representing the relationship between the two-dimensional X-ray diffraction parameter w of various materials and the plastic strain or hardness, From the two-dimensional X-ray diffraction parameter w obtained by substituting the half-value width B, the central angle α, and the X-ray diffraction intensity half-value width B ₀ by the apparatus into the equation (1), the plastic strain or hardness of the measurement object 104 To evaluate.

FIG. 1B is a block diagram showing the configuration of a plastic strain or hardness evaluation system according to the present invention. The image analysis apparatus 110 includes an X-ray incidence center calculation unit 112 that obtains the X-ray incidence center position from the result of the X-ray measurement apparatus 100, and an X-ray diffraction intensity / center angle that obtains a half-value width and a center angle of the X-ray diffraction intensity. A calculation unit 113, a two-dimensional X-ray diffraction parameter calculation unit 114 for obtaining a two-dimensional X-ray diffraction parameter defined by Equation (1), a master diagram representing a relationship between the two-dimensional X-ray diffraction parameter w and plastic strain or hardness Are provided with a master diagram creation unit 115 and a plastic strain / hardness calculation unit 116. Further, an input device 118 such as a keyboard and a display device 119 for displaying the results are also provided.

FIG. 2 is a flowchart of a method for nondestructively evaluating the plastic strain of the surface processed layer of the measurement object in the embodiment of the present invention. This flow diagram is divided into two parts: “Create Master Diagram” and “Actual Measurement”. In “Create Master Diagram”, create a master diagram, and in “Actual Measurement”, use the X-ray diffraction parameters obtained by the X-ray diffraction method and the created master diagram to determine the plasticity of the measurement object. Evaluate strain. There are a plurality of methods for creating a master diagram, and FIG. 2 shows one of them. Hereinafter, the method illustrated in FIG. 2 will be described as “a procedure for creating a master diagram”.
1． Procedure for Creating Master Diagram A procedure for functionalizing the correlation between the two-dimensional X-ray diffraction parameter w and plastic strain or hardness will be described as a procedure for creating a master diagram. The master diagram is a function of the correlation between the two-dimensional X-ray diffraction parameter w and plastic strain or hardness. Therefore, a master diagram is created by obtaining the relationship between the two-dimensional X-ray diffraction parameter w and plastic strain or hardness.
(1) Measurement of half-value width B ₀ by the apparatus The half-value width of the diffraction intensity of X-rays is a parameter that reflects lattice distortion, particle size, etc. Components that are affected by the system are also included. Therefore, it is necessary to separate the half-value width B ₀ by the apparatus from the actually measured half-value width B. In order to measure the half-value width B ₀ by the apparatus, the half-value width of the diffraction intensity is set to B ₀ by the apparatus using a measurement object in an unstrained state. However, since the measured value of B ₀ is affected by the divergence angle of incident X-rays, the measured value depends on the irradiation region size φ and the irradiation distance l. The half width B ₀ by the apparatus must be measured at the same irradiation area size φ and irradiation distance l as when the half width B of the measurement object is actually measured. In consideration of versatility, it is preferable to measure the half width B ₀ by the apparatus in advance with a plurality of irradiation region sizes φ and irradiation distances l.

In addition, the optical system schematic diagram at the time of measuring the half width B in FIG. 3 is shown. X-ray tube 1 for irradiating X-rays, two-dimensional X-ray detector 2 for detecting diffracted X-rays, measurement object 4, incident X-rays 6, diffracted X-rays 7 and two-dimensional diffraction spots 8 of the measurement object The relationship is as shown in FIG. In the present invention, since the central angle α of the discontinuous diffraction spots is detected as a parameter, the upper limit of the number of crystals that are surrounded by the irradiation region and contributes to diffraction and the crystal orientation are required. It is desirable that the number of crystals that are surrounded by the irradiation region and contribute to diffraction is adjusted to several hundred or less by adjusting the irradiation region size φ in accordance with the crystal grain size and crystal orientation of the actual material. In general, it is recommended that the irradiation area size is 2 mm or less. In consideration of the X-ray intensity and the X-ray absorption ability of the material, the X-ray irradiation distance 1 is preferably set to 10 to 30 mm. In the case of a general metal, the penetration depth of incident X-rays is about 10 μm. However, the X-ray diffraction intensity is affected by absorption by the material. Further, since absorption by the material depends on the penetration path length, the X-ray diffraction intensity varies depending on a slight difference in the penetration path length. For this reason, in the circumferential direction of the two-dimensional X-ray diffraction ring, in order to make the penetration path length inside the material corresponding to the X-ray diffraction intensity of all diffraction points constant, the incident X-ray 6 is perpendicular to the surface of the measurement object. And diffracted X-rays 7 must be obtained. However, measurement is possible even when X-rays are not incident vertically, but in that case, correction of the X-ray diffraction intensity is necessary.
FIG. 4 is a schematic diagram of an optical system when the position of the incident center O point is measured. In order to obtain the position of the incident center O point, a standard powder sample 5 in an unstrained state is used. Using the diffraction phenomenon from the crystal that satisfies the Bragg condition, the diffraction angle θ corresponding to the diffractive surface interval d is determined from the relationship shown in Equation (2). Therefore, in the case of the standard powder sample, the diffraction angle 2θ ₀ is known from the X-ray wavelength λ and the appropriate diffraction surface interval d of the standard powder sample.

FIG. 5 shows a schematic diagram of the two-dimensional diffraction ring 9 of the standard powder sample recorded in the two-dimensional X-ray diffractometer. In the two-dimensional diffraction ring 9 of the standard powder sample, a plurality of maximum luminance points can be detected, and an approximate circle can be determined by the least square method indicated by a white line in the figure. If the center O of the approximate circle is the incident center, the radius R _P can be measured.

Here, as a detector for recording the diffraction angle and diffraction intensity of diffracted X-rays, a two-dimensional position-sensitive proportional counter (PSPC) or imaging plate (IP) is used. A detector in which a representative photostimulable phosphor is applied to a two-dimensional X-ray detector is used. This is because a wide range of diffraction information can be acquired in a short time.

The two-dimensional position sensitive proportional counter is an X-ray detector that can determine the X-ray receiving position on the detection surface. It is not necessary to scan the detector when measuring the diffraction intensity curve. Further, the X-ray energy can be converted into an electric signal, and the X-ray diffraction intensity can be measured two-dimensionally by the image processing circuit.

The imaging plate is a film coated with a photostimulable luminescent material (BaFX: Eu2 +, X = Br, I). When the imaging plate is irradiated with X-rays, a kind of metastable colored center is formed in the phosphor. Thereafter, when the phosphor is irradiated with laser light by the reading device, the X-ray energy stored in the phosphor is emitted as fluorescence. X-ray information recorded on the fluorescent screen can be read by scanning the laser on the fluorescent screen two-dimensionally and measuring the generated fluorescence as a time-series signal with a photomultiplier tube. The imaging plate can be used repeatedly because the colored center is erased when exposed to visible light.

In the case of a position-sensitive two-dimensional X-ray detector, the detector and the X-ray tube are fixed. Therefore, if the coordinates of the incident center O point are determined in one initial measurement, the standard powder will be used again during the actual measurement. It is not necessary to obtain the incident center O point using. On the other hand, in the case of an imaging plate detector that needs to be replaced for each measurement, the diffraction center of the standard powder sample is recorded on the same imaging plate as the object to be measured and the coordinates of the incident center O point are measured. There is a need to.

FIG. 6 shows an optical system when the imaging plate two-dimensional X-ray detector 3 is used. By irradiating twice with X-rays, the diffraction rings of the standard powder sample and the measurement object are recorded on the same imaging plate.

Since the X-ray diffraction intensity I-line profile in the radial direction with respect to the incident center O point recorded on the two-dimensional X-ray detector is relative to the distance s, the half-value width B of the diffraction angle is obtained by Equation (3). As shown, the distance coordinate s must be converted to a diffraction angle 2θ coordinate.

The half-value width B is determined by subtracting the background from the X-ray diffraction intensity profile curve with respect to the diffraction angle 2θ coordinate and performing function approximation of the X-ray diffraction intensity curve. The half-value width B is obtained by a known “half-value width method” or “function approximation method”.

Fig. 7 shows the "half-value width method". In the X-ray diffraction intensity profile curve obtained by the measurement, a half-value width B is a difference between diffraction angles at two points that are directly at a half level of the maximum value of the X-ray diffraction intensity.

In the case of the “function approximation method”, function approximation is performed on the X-ray diffraction intensity profile curve obtained by measurement, and then the half width B is obtained. For function approximation, any one of known Gaussian curves, Lorentz curves, and pseudo-Voigt functions may be used.

An X-ray diffraction intensity curve I _G approximated by a Gaussian curve is expressed by Expression (4). At this time, the integral width B ′ (a value obtained by dividing the integral intensity by the peak intensity) can also be obtained by Expression (5). Here, J is the integrated intensity, the 2 [Theta] _[psi is the peak position.

An X-ray diffraction intensity curve I _L approximated by a Lorentz curve is expressed by Expression (6). At this time, the integral width B ′ is obtained by Expression (7). Here, J is the integrated intensity, the 2 [Theta] _[psi is the peak position.

An X-ray diffraction intensity curve I _V approximated by a pseudo-Voigt function is expressed by Expression (8) using I _G and I _L. Here, η indicates a Gaussian degree.

Further, the width S _R of the diffraction intensity profile shown in FIG. 5 generally has a simple relationship represented by the equation (9).

That is, the integration width B ′ or the diffraction intensity profile width S _R is also used as an alternative parameter for the half-value width B, which is a variable of the two-dimensional X-ray diffraction parameter w shown in Expression (1).

According to the above method, the half width B ₀ by the apparatus can be measured by using a standard powder in an unstrained state.
(2) Introduction of plastic strain by tensile test In order to consider the validity of the tensile test, it is preferable that the conditions of the preparation of the test piece and the tensile test comply with the provisions of JIS Z2241 (1998). Moreover, in order to consider the variation of a test piece, several test pieces are manufactured from the same material, and a strain gauge is installed in each test piece. On the other hand, plastic strain is introduced by a tensile test, and the residual strain ε _P after unloading is measured by the output of the strain gauge. Furthermore, the Vickers hardness HV of each test piece is measured. In general, in the case of a metal material, the hardness increases as the plastic strain increases. This is assumed to be work hardening.
The processing history of the specimen surface also affects the X-ray diffraction parameters. For this reason, when using this method, it is preferable to perform a tensile test after removing the surface layer by several tens to several hundreds of μm by electrolytic polishing or the like.

In the high plastic strain range, the unevenness of the specimen surface and the high dislocation density affect the X-ray diffraction intensity. Therefore, in general, in the range where the plastic strain is small, the change in the half width B and the central angle α of the diffraction spot is High sensitivity to plastic strain. Therefore, it is desirable to set the interval between plastic strains to be relatively fine at a level with a small plastic strain, rather than at a large level. For example, plastic strain is introduced into the test piece at intervals of 1 to 2% when the plastic strain is 0 to 10%, and at intervals of 4 to 5% when 10 to 20%. However, since the plastic strain range varies depending on the material properties, it is necessary to set the plastic strain interval according to the actual material. In addition, in order to detect a change in the central angle α of a remarkable diffraction spot, the present invention can be applied to plastic strain evaluation of a textured material or a coarse crystal material with high sensitivity of the central angle α of the diffraction spot due to plastic strain. desirable. In the present application, the texture material refers to a material having directionality in crystal growth, such as a weld metal or casting, and the coarse crystal material refers to a material having a grain boundary of 20 μm or more.
(3) Calculation of two-dimensional X-ray diffraction parameter w 1 FIG. 8 shows a calculation method of the two-dimensional X-ray diffraction parameter w. The method for measuring the half-value width B in the drawing is the same as the method for measuring the half-value width B ₀ using the above-described apparatus. In order to measure the central angle α of the diffraction spots, it is necessary to designate both end ranges in the circumferential direction of each diffraction spot. In general, a range obtained by subtracting the background from the diffraction intensity may be used as the diffraction spot range. However, when a clear diffraction intensity such as a weld metal cannot be obtained, for example, “intensity of 25% or more of the maximum intensity” The range of the diffraction spots can be specified by performing filtering on the diffraction intensity such as “use a spot having a diffraction spot”.

In FIG. 8, assuming that the central angle α _i of each diffraction spot is sufficiently small and the half-value width B _i in the radial direction of each diffraction spot, the two-dimensional X-ray diffraction parameter w can be calculated by Expression (10).

(4) Functionalization of two-dimensional X-ray diffraction parameters and plastic strain or hardness By functional approximation of two-dimensional X-ray diffraction parameters w obtained for each plastic strain ε _P , ε _P = f (w) is functionalized. Do. Based on this function ε _P = f (w), a master diagram w-ε _P representing the relationship between the X-ray diffraction parameter and the plastic strain ε _P can be created.

Similarly, HV = g (w) is functionalized by function approximation in the Vickers hardness HV and the two-dimensional X-ray diffraction parameter w after introducing each plastic strain ε _P. Based on this function HV = g (w), a master diagram w-HV representing the relationship between the X-ray diffraction parameters and the Vickers hardness HV can be created.
2. Evaluation of plastic strain or hardness (actual measurement)
By plotting the two-dimensional X-ray diffraction parameter w obtained by measuring the measurement object on the master diagram w-ε _P or the master diagram w-HV, the plastic strain ε _P or HV of the measurement object is obtained. It is possible to evaluate non-destructively.
(1) Two-dimensional X-ray diffraction is measured on the surface of the measurement object.
(2) The half-value width B and the central angle α are measured from the two-dimensional X-ray diffraction spots by an image processing program, and w is obtained from the equation (1).
(3) By plotting the obtained two-dimensional X-ray diffraction parameter w on the master diagram w-ε _P or master diagram w-HV of the same material of the measurement object, the plasticity of the surface processed layer of the measurement object It is possible to estimate the strain ε _P or the Vickers hardness HV nondestructively.
3. Evaluation System 3.1 Two-dimensional X-ray Detector A position-sensitive two-dimensional X-ray detector or two-dimensional detection using an imaging plate can be used as the two-dimensional X-ray detector of this system.

In the case of a position-sensitive two-dimensional X-ray detector, the detector and the X-ray tube are fixed, so the coordinates of the incident center O point can be determined by one initial measurement using an unstrained standard powder sample. If it is determined, there is no need to measure a standard powder sample in an unstrained state again when actually measuring.

A two-dimensional X-ray detector using an imaging plate is cheaper and easier to manufacture than a position-sensitive two-dimensional X-ray detector, but if it has a replaceable structure, it is standard on the same imaging plate as the measurement object each time. It is necessary to record the diffraction ring of the powder sample and measure the coordinates of the incident center O point.

In addition, the X-ray incident center and the two-dimensional X-ray detector are arranged asymmetrically so that only a part of the two-dimensional X-ray diffraction ring can be measured according to the geometric conditions of the actual measurement environment (for example, a narrow place). It is also possible to use the asymmetric type two-dimensional X-ray detector 10 which comprises. However, in this case, when using the master diagram w-ε _P or w-HV obtained in the whole circumference central angle range 2π, the actually measured two-dimensional X-ray diffraction parameter w is changed to It is necessary to correct by dividing the integral range of the central angle α of the diffraction spots by the ratio of the entire peripheral central angle range 2π. For example, in the case of FIG. 9, since the integration range of the central angle α of the diffraction spot of the measurement object is π, when plotting on the master diagram obtained in the entire circumference central angle range 2π, Correct by 2 times.
3.2 Image Processing Algorithm In order to realize highly accurate measurement, it is necessary to measure the half-value width B in as many radial directions as possible within the integration range of the central angle α of the diffraction spots. For example, the half-value width B corresponding to the minute center angle at intervals of 1 (deg) is measured for α. An image processing algorithm for efficiently calculating such a large amount of measurement is required. Also, a filtering function is desirable for X-ray diffraction intensity in order to remove background.
4). Practicality In the present invention, the degree of surface processing is evaluated nondestructively by measuring the plastic strain or hardness of a measurement object using a two-dimensional X-ray diffraction parameter. Therefore, this evaluation method can be applied to actual structures and finished products that cannot be sampled due to destruction. Also, the plastic strain or hardness can be evaluated simply by substituting the measured two-dimensional X-ray diffraction parameter into a function representing the relationship between the two-dimensional X-ray diffraction parameter prepared in advance as an evaluation criterion and the plastic strain or hardness. For this reason, prompt evaluation of the degree of surface processing at the measurement location is expected, and it can be used for mass measurement in consideration of variations in mass-produced products.

Further, as the degree of surface processing increases, application of the material having higher SCC generation sensitivity (for example, non-sensitized austenitic stainless steel such as SUS316L) to the SCC generation sensitivity evaluation is also expected.

In Example 2, plastic strain and hardness were measured on a measurement object of a Ni-based weld metal DNiCrFe-1J (JIS Z 3224) on which a grinder was applied.

As a master diagram, a plurality of tensile test pieces were manufactured from the Ni-base weld metal DNiCrFe-1J. In order to remove the remaining surface processed layer by the surface finishing, the surface was polished by electrolytic polishing to a depth of 50 μm and then subjected to stress relaxation heat treatment at 870 ° C. for 2 hours. The tensile test is performed according to the standard of JIS Z 2241 (1998), and is 0%, 0.5%, 1.0%, 1.8%, 3.8%, 6.0%, 10.0% 14.7%, 19.8%, 24.8% and 29.6% of plastic strain ε _P were introduced, respectively. After the tensile test, the Vickers Vickers hardness HV was measured with a hardness measuring machine. The load for hardness measurement is 1 kgf, and the load time is 20 sec. Table 1 shows the value of Vickers hardness HV in each test piece.

FIG. 6 shows a schematic diagram of the measurement optical system. An imaging plate was used for the two-dimensional X-ray detector. X-ray irradiation region φ = 1 mm, irradiation distance 1 = 20 mm, and irradiation time were 10 min. The X-ray tube is Mn, and the output is 17 kV and 1.5 mA. Using the characteristic X-ray wavelength of Mn_Kα, λ is 2.10314 × 10 ⁻¹⁰ m. The diffraction surface of the Ni-based alloy is the (311) plane, and the theoretical value 2θ _Ψ = 163.575 (deg) of the peak of the diffraction angle. The imaging plate after the irradiation test was read with an X-ray diffraction pattern using an image analysis apparatus Typhoon FLA9000 manufactured by GE Healthcare Japan. The resolution is 25 μm / Pixel. In order to obtain the X-ray incident center O point, Cu powder subjected to complete annealing was applied as a standard powder sample to the surface of a tensile test piece, and a two-dimensional diffraction ring was recorded on the same imaging plate as the tensile test piece. The Cu powder has a (311) plane and a diffraction angle peak position 2θ ₀ = 149.518 (deg).

First, the half width B ₀ by the apparatus was measured using a test piece with ε _P = 0%. The half width B ₀ is 2.27 (deg).

Next, a two-dimensional X-ray diffraction parameter w of each test piece is obtained. As a representative example, FIG. 10A shows a two-dimensional X-ray diffraction ring of a test piece with ε _P = 0% and ε _P = 6.0% (intensity is inverted). Since the weld metal has a texture and coarse crystals, discontinuous two-dimensional X-ray diffraction appears. FIG. 10B shows an analysis method using an image processing algorithm. The maximum luminance point is detected in the two-dimensional X-ray diffraction ring of the Cu powder, and an approximate circle of the two-dimensional X-ray diffraction ring of the Cu powder by the least square method by the image processing algorithm (black broken line in FIG. 10B) And the center O of this approximate circle was taken as the X-ray incident center. The full width at half maximum B in the radial direction was determined by the above-described method in the entire circumferential range of 0 to 360 (deg) with the central angle α with respect to the point O being 1 (deg). In order to subtract the background from the diffraction intensity, filtering was performed on the diffraction intensity so that a portion having an intensity of 25% or more of the maximum intensity was an analysis range. A solid white line in FIG. 10B indicates the maximum luminance position P in the analysis range extracted by filtering. The total diffraction spot central angle α in the analysis range is 62 (deg) for the test piece with ε _P = 0%, but 154 (deg) for the test piece with ε _P = 6.0%. As the plastic strain increases, the increase in the central angle is noticeable. From the above analysis, w is calculated by Equation (11). Here, B _α is the half width in the radial direction at the central angle α. n is a determination coefficient, and is defined as n = 1 when within the analysis range, and n = 0 when outside the analysis range. The calculated unit of w is deg ² .

FIG. 11 and FIG. 12 show correlation diagrams of the two-dimensional X-ray diffraction parameter w, the plastic strain ε _P and the Vickers hardness HV measured in this example, respectively. A function representing the relationship between the two-dimensional X-ray diffraction parameter w and the plastic strain ε _P was approximated to ε _P = 0.0014w ² −0.0468w + 0.8836 by the least square method. A function representing the relationship between the two-dimensional X-ray diffraction parameter w and the Vickers hardness HV was approximated to HV = 0.024 w ² + 0.2866w + 211.07 by the least square method. The above function is a master diagram.

After creating the master diagram, actual measurement was carried out using a weld metal sheet made of the same material as the test piece, using the object to be measured. The weld metal sheet was subjected to stress relaxation heat treatment and cold rolled at a rolling rate of 10%. The surface Vickers hardness HV = 268 (N / mm ² ) after cold rolling.

In the welded metal sheet, the result of measuring the two-dimensional X-ray diffraction parameter w by the method described above is w = 102 (deg ² ).

Figure 13 is a master diagram of w and plastic strain epsilon _P, the relationship of the two-dimensional X-ray diffraction parameters w and plastic strain epsilon _P is represented by ε _P = 0.0014w ² -0.0468w + 0.8836 . From FIG. 13, the plastic strain ε _P = 10.7% with respect to w = 102 (deg ² ), which was evaluated at a value close to a rolling rate of 10%.

FIG. 14 is a master diagram of w and the Vickers hardness HV, and the relationship between the two-dimensional X-ray diffraction parameter w and the Vickers hardness HV is represented by HV = 0.024 w ² + 0.2866w + 211.07. Than 14, a w = 102 Vickers hardness HV = 265 for ^{(deg 2) (N / mm} 2), could be evaluated by a value close to the measured value of HV = 268.

From the above measurement results, the effectiveness of the nondestructive plastic strain and hardness evaluation system and evaluation method according to the present invention could be shown.

In addition, according to conventional research, a tendency that a high degree of material surface processing in a stress corrosion environment promotes SCC generation sensitivity and progress rate is recognized. The hardness dependence of the SCC progress rate of the welding heat affected zone of the austenitic stainless steel SUS316 published in FIG. Cold-rolled SUS316 shows a tendency for the SCC progress rate to increase as the hardness increases, suggesting that the SCC characteristics of the material can be evaluated using the hardness or the cold working rate as a parameter. From the above research results, if the cold rolling rate, plastic strain or hardness is used as the SCC evaluation parameters, the plastic strain and hardness evaluation system and evaluation method according to the present invention is an actual structure that cannot be sampled by fracture. Or as a part of the evaluation of the susceptibility to the occurrence of stress corrosion cracking (SCC) in a stress corrosion environment.

DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... Two-dimensional X-ray detector 3 ... Imaging plate two-dimensional X-ray detector 4 ... Measurement object 5 ... Standard powder sample 6 ... Incident X-ray 7 ... Diffraction X-ray 8 ... Measurement object Two-dimensional diffraction spot 9 ... Two-dimensional diffraction ring 10 of standard powder sample ... Asymmetric type two-dimensional X-ray detector 100 ... X-ray diffraction apparatus 101 ... X-ray tube 102 ... Two-dimensional X-ray detector 104 ... Measurement object 110 Image analyzer 111 X-ray diffraction intensity curve 112 X-ray incident center calculation unit 113 X-ray diffraction intensity / center angle calculation unit 114 Two-dimensional X-ray diffraction parameter calculation unit 115 Master diagram creation unit 116 Plasticity Strain / hardness calculation unit 118 ... input device 119 ... display device 120 ... database w constructed by master diagram ... two-dimensional X-ray diffraction parameter ε _P ... plastic strain HV ... Vickers hardness I ... X-ray diffraction intensity O ... X-ray incident center position s ... Center with respect to the incident center position O at the distance R _P ... radius l ... X-ray irradiation distance alpha ... two-dimensional diffraction rings of the approximate circle of a two-dimensional diffraction rings standard powder sample on the radial direction with respect to the incident center position O in the two-dimensional diffraction rings Angle B ... Half-value width B '... Integration width S _R ... Radial width P of the two-dimensional X-ray diffraction ring P ... Maximum intensity position in the X-ray diffraction intensity curve ψ ... Diffraction plane normal and sample surface normal Angle 2θ ... Diffraction angle 2θ _ψ X-ray diffraction intensity peak position 2θ ₀ ... Diffraction angle d of standard powder sample ... Diffraction plane lattice spacing

Claims

An X-ray irradiation apparatus for injecting X-rays onto the surface of the measurement object;
A two-dimensional X-ray detector for detecting the diffracted X-ray;
A storage device having data on the relationship between a two-dimensional X-ray diffraction parameter determined in advance and at least one physical quantity of plastic strain or hardness;
The image analysis apparatus obtains an X-ray diffraction intensity curve from the X-ray diffraction angle and diffraction intensity detected by the two-dimensional X-ray detector, and X-rays in the radial direction with respect to the X-ray incident center of the two-dimensional X-ray diffraction spot A two-dimensional X-ray that obtains a definite integral over the entire circumference of the half-width of the intensity curve after subtracting the half-width by the apparatus and the central angle with respect to the X-ray incident center as a two-dimensional X-ray diffraction parameter A line diffraction parameter calculation unit;
An evaluation system for a surface processing state, comprising: a calculation unit that obtains at least one physical quantity of plastic strain and hardness from a two-dimensional X-ray diffraction parameter of the measurement object.
In the surface processing state evaluation system according to claim 1,
The two-dimensional X-ray detector is an imaging plate using a stimulable phosphor,
A surface processing state evaluation system, characterized in that a standard sample powder is adhered to the surface of the measurement object.
In the surface processing state evaluation system according to claim 1,
The two-dimensional X-ray detector is a position sensitive detector.
Make X-rays incident on the surface of the measurement object,
Record the diffracted X-rays on a flat-plate X-ray detector,
The total perimeter of the value obtained by subtracting the half width by the device from the half width of the X-ray intensity curve in the radial direction with respect to the X-ray incident center at the two-dimensional X-ray diffraction spot and the center angle with respect to the X-ray incident center Find the definite integral over the range as a two-dimensional X-ray diffraction parameter,
Using the relationship between the two-dimensional X-ray diffraction parameter and at least one physical quantity of plastic strain or hardness, the measured value of the two-dimensional X-ray diffraction parameter is used to determine at least one of plastic strain or hardness. A method for evaluating a surface processing state, wherein one physical quantity is evaluated.
In the evaluation method of the surface processing state of Claim 4,
The two-dimensional X-ray detector is an imaging plate using a photostimulable phosphor. A standard sample powder is attached to the surface of a measurement object, and an X-ray incident center and irradiation distance are obtained from a diffraction ring of the standard sample powder. A method for evaluating a surface processing state characterized by the following.
In the evaluation method of the surface processing state of Claim 4,
The two-dimensional X-ray detector is a position sensitive detector.
Using the surface processing state evaluation system according to claim 1,
A stress corrosion cracking susceptibility evaluation method for a non-sensitized material, wherein at least one physical quantity of plastic strain or hardness is used as an evaluation standard for SCC sensitivity.