KR101647257B1 - Method for evaluating deterioration of materials - Google Patents

Abstract

The present invention relates to a method of evaluating deterioration of a material using ultrasonic waves, and more particularly, to a method of evaluating deterioration of a metallic material or the like constituting a part or an apparatus used in an environment at a high temperature for a long time by using an ultrasonic attenuation value ≪ / RTI >
The deterioration evaluation method provided by the present invention analyzes precipitates in isothermal aged metallic materials by using ultrasonic attenuation values, thereby making it possible to measure the degree of deterioration of materials constituting the materials without destroying equipment or parts used for a long time in a high- And can be evaluated in a simple way.

Description

[0001] The present invention relates to a method for evaluating deterioration of materials using ultrasound,

The present invention relates to a method of evaluating deterioration of a material using ultrasonic waves, and more particularly, to a method of evaluating deterioration of a metallic material or the like constituting a part or an apparatus used in an environment at a high temperature for a long time by using an ultrasonic attenuation value ≪ / RTI >

Austenitic stainless steels have excellent mechanical properties, and AISI 316L stainless steels, for example, are widely used in applications where they are exposed to high temperature environments such as thermal power plants for a long time.

On the other hand, creep damage is generated in parts used at high temperatures. Due to isothermal aging, the microstructure of the structural alloy continuously changes, thereby affecting the properties of the material. In addition, the long-term aging of the austenitic stainless steels may cause sigma precipitation in the material, which may result in a reduction in the hardness of the material.

Therefore, in recent years, studies on the microstructure change, sedimentation property and mechanical properties of a typical austenitic stainless steel have been conducted. However, these studies are limited to metal results only. For this reason, most researchers are evaluating cyclic tensile fatigue, bending fatigue specimens, corrosion damage samples, and thermal aging samples of damaged specimens through nondestructive testing. As a non-destructive test used for evaluating the deterioration of the metal as described above, ultrasonic wave analysis is widely used because it can analyze a minute structure change.

However, the methods of evaluating deterioration of metal materials so far have focused only on experimental results, and there is a limit to investigate and analyze only the relationship between ultrasound parameters and metallurgical results.

It is an object of the present invention to analyze precipitates in a metal material aged isothermally by using an ultrasonic attenuation value and thereby to precisely and effectively evaluate the degree of deterioration of a metal material constituting the material without destroying equipment or parts used at high temperatures for a long time Method.

Another object of the present invention is to derive the correlation between the attenuation value of ultrasonic waves and the degree of deterioration of the isothermal aged metallic material, and by making a database thereof, the degree of deterioration of the inspected object can be repeatedly evaluated.

According to an embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: (a) preparing two or more test specimens different in deterioration time;

(b) measuring an area fraction of the precipitate in the test specimen and deriving a change in the area fraction of the precipitate according to the deterioration time as a graph;

(c) measuring the ultrasound attenuation value by irradiating the test specimen with ultrasound waves to derive a change in ultrasound attenuation value according to the deterioration time as a graph; And

(d) deriving a graph of a correlation between the area fraction of the precipitate and the ultrasonic attenuation value through the graph obtained in the steps (b) and (c), and evaluating the deterioration of the material using ultrasonic waves .

(E) after the step (d), measuring the ultrasonic attenuation value by irradiating the ultrasonic wave to the inspected object; And

(f) evaluating the degree of deterioration of the inspected object by substituting the ultrasonic attenuation value of the inspected object obtained in the step (e) into the graph obtained from the step (d).

In the step (b), the measurement of the area fraction of the precipitate may be performed by measuring the fraction of the precipitate per unit area.

The area fraction of the precipitate can be measured using an image analyzer.

In the step (c), ultrasonic emission may be performed using a transducer.

The measurement of the ultrasonic attenuation value in the step (c)

Measuring the first bottom reflection signal reflected from the bottom of the test specimen by radiating ultrasonic waves to the test specimen; And

And irradiating ultrasonic waves to the test specimen to measure the reflected second sub-surface reflection signals in order from the opposite surface and the bottom surface of the test specimen.

And carrying the test specimen on a water-containing sedimentation tank prior to measuring the primary and secondary bottoms reflection signals.

The ultrasonic attenuation value can be measured from the following equation (1) using the measured first bottom reflection signal and the second bottom reflection signal.

(1) where α _s is the ultrasound attenuation value, V _BS1 (ω) is the value obtained by converting the primary bottom reflection signal that reaches the probe into the frequency domain, and V _BS2 (ω) the car bottom reflection signal is converted in frequency principal ^{_{value, D p (k p1 a 2}} / 2D bs2) , and ^{_{D p (k p1 a 2 /}} 2D bs2) are ultrasound spread correction, D _bs1 are tested from the transducer to emit an ultrasonic D _bs2 is the distance from the probe to the opposite side of the bottom of the test specimen, a is the diameter of the probe, k _p1 is the wave number in water, k ₂ is the wave number in the test specimen, R ₂₁ ^P is the reflection coefficient of ultrasound waves reflected from the test specimen in water, e ^ik2h2 is the propagation term of the ultrasonic wave in the test specimen, and h ₂ is the thickness of the test specimen.

The test specimen may be deteriorated for 5,000 to 30,000 hours.

The test specimen may be an austenitic stainless steel.

In this specification, the term "bottom surface of test specimen" means one surface of the test specimen contacting the bottom surface of the sedimentation tank when the test specimen is supported on the sedimentation tank.

In this specification, the term "opposite surface of the bottom of the test specimen" refers to the opposite surface opposite to one surface of the test specimen in contact with the bottom surface of the settling tank.

In the present specification, the term "primary bottom reflection signal" means a signal in which an ultrasonic wave is reflected from the bottom surface of the test specimen when the ultrasonic wave is radiated to the test specimen using the probe, and reaches the probe again. Reflected bottom signal "means a signal that is reflected from the bottom surface of the test specimen when the ultrasonic wave is radiated to the test specimen, reflected again from the opposite side of the bottom surface, reflected to the bottom surface side, .

In the present specification, the term "inspected object" may be all or a part of a device or part used for a long time at a high temperature for the purpose of knowing the deterioration level.

The deterioration evaluation method provided by the present invention analyzes precipitates in isothermal aged metallic materials by using ultrasonic attenuation values, thereby making it possible to measure the degree of deterioration of materials constituting the materials without destroying equipment or parts used for a long time in a high- And can be evaluated in a simple way.

FIG. 1 is a schematic diagram for measuring an ultrasound attenuation value according to an embodiment of the present invention. Referring to FIG.
FIG. 2 is a photograph of an AISI 316L stainless steel test specimen according to deterioration time in Example 1. FIG.
FIG. 3 is a photograph showing an optical microscope analysis of the change in the microstructure of the test specimen according to the deterioration time in Example 1. FIG.
Fig. 4 shows a photograph of a C-scan system used for measuring the ultrasound attenuation value in the embodiment 1. Fig.
5 is a graph showing changes in the area fraction of the precipitate with the deterioration time measured in Example 1. Fig.
6 is a graph showing a change in ultrasonic attenuation value according to the deterioration time measured in Example 1. Fig.
7 is a graph showing the correlation between the area fraction of the precipitate obtained in Example 1 and the ultrasonic attenuation value.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

The inventors of the present invention have found that when a metal material is exposed to a high temperature environment for a long time, a precipitate is formed in the metal material to change the attenuation value of the ultrasonic wave, leading to the present invention. That is, in the present invention, the degree of deterioration can be evaluated by measuring the ultrasound attenuation value of the inspected object by deriving a correlation between the precipitate in the metallic material and the attenuation value of the ultrasonic wave by making it into a data base.

Specifically, according to one embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: (a) preparing two or more test specimens different in deterioration time;

(b) measuring an area fraction of the precipitate in the test specimen and deriving a change in the area fraction of the precipitate according to the deterioration time as a graph;

(c) measuring the ultrasound attenuation value by irradiating the test specimen with ultrasound waves to derive a change in ultrasound attenuation value according to the deterioration time as a graph; And

(d) deriving a graph of the relationship between the area fraction of the precipitate and the attenuation value of the ultrasonic wave through the graph obtained in the steps (b) and (c).

In the present invention, the material of the test specimen is not particularly limited, but it is preferable to use the same material as the inspected object to be subjected to deterioration evaluation in order to improve the accuracy of the deterioration evaluation.

In general, the deterioration evaluation is aimed at metallic materials mainly used in equipment or parts used for a long time in a high-temperature environment. Therefore, it is more preferable to use a metal material as the test specimen described above. In recent years, The austenitic stainless steel is mainly used for equipment and parts used under environmental conditions, and the austenitic stainless steel can be used.

As described above, in the present invention, a step of preparing two or more test specimens having different deterioration times may be performed. The deterioration time of the test specimen is not particularly limited. For example, isothermal aging for 5,000 to 30,000 hours And preferably isothermal aging for 6,000 to 20,000 hours may be used.

However, in the present invention, the equivalent deterioration time can be calculated using the following formula (2).

Where T _eq is the equivalent deterioration time, t is the actual deterioration time, T _o is the equivalent deterioration temperature, T is the actual deterioration temperature, Q is the activation energy (for example, 172 KJ / mm 2 for AISI 316 steels, mol) and R is the gas constant (8.31 J / mol.K).

In addition, it is preferable to prepare two or more test specimens having different deterioration times. The number of test specimens is not particularly limited. However, in order to more precisely derive the correlation between the area fraction of the precipitates and the ultrasonic attenuation value due to deterioration, It is more preferable to prepare more than 10, and considering the economical point, it is possible to prepare 10 or less.

When the test specimen is prepared in this way, it is possible to measure the change of the area fraction of the precipitate in the test specimen with the deterioration time and the change of the ultrasonic attenuation value of the test specimen with the deterioration time.

That is, it is possible to measure the change of the ultrasonic attenuation value of the test specimen according to the deterioration time after measuring the change of the area fraction of the precipitate in the test specimen with the deterioration time, or to measure the change of the ultrasonic attenuation value of the test specimen with the deterioration time The change in the area fraction of the precipitate in the test specimen with the deterioration time can be measured first.

In the present invention, the method of measuring the area fraction of the precipitate in the test specimen as described above is not particularly limited. For example, the method can be performed by measuring the fraction of the precipitate per unit area using an image analyzer, Can represent the ratio of the area containing the sediment to the total area in%.

In the present invention, by measuring the area fraction of the precipitate by each test specimen, it is possible to derive the change in the area fraction of the precipitate according to the deterioration time of each test specimen.

In the present invention, the ultrasonic attenuation value of the test specimen may be measured by supporting the test specimen on a water holding tank. Measuring the first bottom reflection signal reflected from the bottom of the test specimen by radiating ultrasonic waves to the test specimen; And a step of radiating ultrasonic waves to the test specimen to measure the reflected second sub-surface reflection signals in order from the opposite surface and the bottom surface of the bottom surface and the bottom surface of the test specimen.

In the present invention, a method of radiating ultrasonic waves to a test specimen can be performed using, for example, a transducer, but is not limited thereto.

FIG. 1 is a schematic diagram for measuring an ultrasound attenuation value according to an embodiment of the present invention. Referring to FIG. 1 (a) shows a first bottom reflection signal. Ultrasonic waves 2 radiated from the transducer 1 to the test sample 10 are transmitted to the bottom surface 100 of the test sample 10, The ultrasonic wave 2 radiated from the probe 1 to the test specimen 10 is reflected by the test specimen 10 The light is reflected from the bottom surface 100 of the bottom surface 100 and then reflected by the bottom surface 100 and then reaches the probe 1. (C) shows signals measured with time by irradiating ultrasonic waves to the test specimen. In the case where the surface reflection signal 20, the first bottom reflection signal 30 and the second bottom reflection signal 40 are detected Can be seen.

In the present invention, the ultrasonic attenuation value can be more accurately measured through the following equation (1) using the first bottom reflection signal and the second bottom reflection signal among the signals measured as described above.

(1) where α _s is the ultrasound attenuation value, V _BS1 (ω) is the value obtained by converting the primary bottom reflection signal that reaches the probe into the frequency domain, and V _BS2 (ω) the car bottom reflection signal is converted in frequency principal ^{_{value, D p (k p1 a 2}} / 2D bs1) , and ^{_{D p (k p1 a 2 /}} 2D bs2) are ultrasound spread correction, D _bs1 are tested from the transducer to emit an ultrasonic D _bs2 is the distance from the probe to the opposite side of the bottom of the test specimen, a is the diameter of the probe, k _p1 is the wave number in water, k ₂ is the wave number of the test specimen (wavenumber ), R ₂₁ ^{P; P} is the reflection coefficient of ultrasound waves propagated in the test specimen, e ^ik2h2 is the propagation term of the ultrasonic wave in the test specimen, and h ₂ is the thickness of the test specimen.

In the present invention, the above equation (1) can be derived by the following calculation. First, V _BS1 (ω) and V _BS2 (ω) can be obtained by the following equations (3) and (4).

(The formulas (3) and (4 in), β (ω) is the system efficiency factor ^{_{(efficiency factor), T 12 P}} ; P is the rate at which the water is transmitted ultrasound in the test specimen (transmission coefficient), T ₂₁ ^{P; P} is in the test sample with water, the rate at which ultrasonic waves are transmitted (transmission coefficient), e ^ik1h1 the propagation period of ultrasonic waves in water (propagation term), e ^{- αwh1} the ultrasound attenuation in the water, e ^{- αsh2} the ultrasonic attenuation of the test specimen , a _W ultrasonic attenuation value of the water, h ₁ is the distance between the transducer and the test _{specimen, V bS1 (ω), V} bS2 (ω), e ik2h2, a S, h 2, D bs1, D bs2, k _{p1, a, k 2, R} 21 P; P, D p (k p1 a 2 / 2D bs1) , and ^{_{D p (k p1 a 2 /}} 2D bs2) are as defined in the formula (1)).

Here, the following equation (5) can be obtained by dividing the equation (3) by the equation (4), and the equation (6) below can be obtained.

(Where, in the formula (5) and (6), V _BS1 (ω), V _BS2 (ω), β (ω), T ₁₂ ^{P; P,} T ₂₁ ^{P; P,} R ₂₁ ^{P; P,} e ^{ik1h1, e ik2h2, e - αwh1} , e - αsh2, a S, a W, h 1 and h ₂ are as defined in the formula (3) and (4)).

In this case, D _bs1 and D _bs2 in the equation (6) can be expressed by the following equations (7) and (8).

In the above equations (7) and (8), h ₁ is the distance between the probe and the test specimen, h ₂ is the thickness of the test specimen, c ₁ is the ultrasonic sound velocity in water and c ₂ is the ultrasonic sound velocity in the test specimen do.)

In the present invention, the following formula (1) can be derived by summarizing the formula (6) with respect to? _S.

^{_{However, D p (k p1 a 2}} / 2D bs1) , and ^{_{D p (k p1 a 2 /}} 2D bs1) in the formula (1) can be calculated by the following formula (9) and (10) respectively.

(Note that the formula (9) and (10) in, D _p (k _p1 a ² / 2D _bs1), D _p (k _p1 a ² / 2D _bs2), D _bs1, D _bs2 , k _p1 and a are as defined in the above formulas (3) and (4).)

In the present invention, when the ultrasonic attenuation values of the respective test specimens are measured as described above, the change in the ultrasonic attenuation values according to the deterioration time of each test specimen can be derived as a graph.

In the present invention, when the graph of the change in the area fraction of the precipitate with the deterioration time and the graph of the change in the ultrasonic attenuation value according to the deterioration time are obtained, a graph of the correlation between the area fraction of the precipitate and the ultrasonic attenuation value is derived It can be converted into a database.

In the present invention, it is possible to evaluate the degree of deterioration of the inspected object to be subjected to the deterioration evaluation based on the database. Specifically, (e) measuring ultrasound attenuation values by irradiating the inspected object with ultrasound waves; And (f) substituting the ultrasonic attenuation value of the inspected object obtained in the step (e) into a graph of a correlation between the area fraction of the precipitate and the ultrasonic attenuation value, thereby calculating an area fraction of the precipitate in the inspected object So that the degree of deterioration can be evaluated.

In the present invention, as described above, the degree of deterioration of the inspected object to be subjected to the deterioration evaluation can be repeatedly evaluated by constructing a database on the correlation between the area fraction of the precipitate and the ultrasonic attenuation value using the test specimen, It is possible to evaluate the degree of deterioration more accurately and to appropriately adjust the replacement period of the apparatus or parts without destroying the apparatus.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

[Example 1]

1. Prepare test specimens for isothermal aged stainless steels

In order to evaluate the degree of deterioration of the isothermal aged stainless steels using ultrasonic attenuation values, AISI 316L stainless steel having the composition shown in the following Table 1 was subjected to aging at 750 ° C for 6,000 hours, 14,000 hours and 20,000 hours The aged test specimens were prepared and the photographs of the prepared test specimens are shown in FIG.

Furtherance C Si Mn P S Ni Cr Mo B N Al Cu Fe content
(weight%) 0.06 0.46 1.49 0.03 0.026 12.48 17.43 2.49 0.0008 0.019 0.025 0.15 Remainder

2. Observation of sediment in test specimen

The prepared test specimens were etched with glyceregia and Murakmi reagent, and the surface of each test specimen was observed with an optical microscope, and the photograph is shown in FIG. However, the glyceride in the etching solution used etches the precipitate, and the solution of the mask is etched in the sigma phase.

As shown in FIG. 3, it can be seen that the M ₂₃ C ₆ precipitate and the sigma phase are formed in each of the test specimens.

3. Graph of area fraction of sediment in test specimen with deterioration time

In order to quantify the precipitate in each test specimen, the area fraction (Af) and the diameter (D) of the precipitate per unit area of each test specimen were determined using an image analyzer and the results are shown in Table 2 below. FIG. 4 is a graph showing changes in the area fraction of the precipitate.

division Degradation time (hr) 6,000 14,000 20,000 precipitate Af (%) 8.67 10.37 11.31 D (탆) 0.88 0.95 1.11

As shown in Table 2 and FIG. 3, the area fraction and the size of the precipitate increase as the deterioration time increases.

4. Ultrasonic attenuation value of test specimen with deterioration time

In order to measure the ultrasonic attenuation value of the test specimen, the C-scan system equipment shown in FIG. 4 was used. The C-scan system includes a water immersion tank, a planar transducer (ultrasonic pulser / receiver) capable of emitting ultrasonic waves and having a center frequency of 10 and 20 MHz, And includes a controller and an acquisition system. At this time, the thickness of the test specimen is 10 cm, the distance between the probe and the test specimen is 5 cm, and the depth of the precipitation tank is 20 cm. The ultrasonic wave was radiated from the transducer at a frequency of 200 MHz to carry the test specimen to the settling tank, and the signal reflected from the surface of the test specimen, the primary bottom reflection signal reflected from the bottom surface, and the reflection signal from the bottom surface, After detecting the finally reflected second bottom reflection signal at the bottom, the ultrasonic attenuation value (? _S ) is calculated by substituting each coefficient in the following equation (1), and the change of the ultrasonic attenuation value according to the deterioration time is shown in FIG. Respectively.

(Note that the formula (1) α _s is the ultrasonic attenuation value at, V _BS1 (ω) is the first value obtained by converting the bottom surface of the reflected signal as a frequency lead, V _BS2 (ω) is the second to bottom reflection signals a frequency lead as by converting the ^{_{value, D p (k p1 a 2}} / 2D bs1) , and ^{_{D p (k p1 a 2 /}} 2D bs2) are ultrasound spread correction, D _bs1 the distance to the bottom surface of test specimen from the probe for emitting ultrasonic waves, D _bs2 the distance to the opposite side of the bottom surface of the test specimen from the probe, a is the diameter of the probe, k _p1 is a wave number in water (wave number), k ₂ is a wave number (wavenumber) of the test specimen, R ₂₁ ^{P; P} is when the test sample with water is conducted ultrasonic reflected reflection coefficient, e ^ik2h2 has ultrasonic wave propagation time period of the test specimen (propagation term), h ₂ means the test specimen thickness).

As shown in FIG. 5, as the deterioration time increases, the ultrasonic attenuation value of the test specimen increases.

5. Area of sediment in test specimen Fraction  ultrasonic wave Attenuation value  Derive Correlation Graph

Based on the graphs obtained in FIGS. 3 and 5, the area fraction of the precipitate in the test specimen is plotted on the x-axis and the ultrasonic attenuation value is plotted on the y-axis, and their correlation is shown graphically in FIG.

As shown in FIG. 6, as the area fraction of the precipitate in the test specimen increases, the attenuation value of the ultrasonic wave increases in a straight line form.

In the present invention, when a graph relating to the correlation between the area fraction of the sediment and the ultrasonic attenuation value is obtained by using the test specimen as described above, and the deterioration is to be evaluated later with respect to the inspected object, the ultrasonic attenuation value of the inspected object is measured The area fraction of the sediment can be confirmed and the degree of deterioration can be evaluated to judge whether or not the apparatus or parts are replaced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (10)

(a) preparing two or more test specimens having different deterioration times;
(b) measuring the area fraction of the precipitate per unit area of the test specimen using an image analyzer, and deriving a graph of the change in the area fraction of the precipitate with the deterioration time;
(c) measuring the ultrasound attenuation value by irradiating the test specimen with ultrasound waves to derive a change in ultrasound attenuation value according to the deterioration time as a graph; And
(d) deriving a graph of a correlation between the area fraction of the precipitate and the ultrasonic attenuation value through the graph obtained in the steps (b) and (c). The method according to claim 1,
(e) measuring ultrasound attenuation values by irradiating ultrasound waves on the inspected object; And
(f) evaluating the degree of deterioration of the inspected object by substituting the ultrasonic attenuation value of the inspected object obtained in the step (e) into the graph obtained from the step (d). Assessment Methods. delete delete The method according to claim 1,
Wherein the ultrasound emission in the step (c) is performed using a transducer. 6. The method of claim 5,
The measurement of the ultrasonic attenuation value in the step (c)
Measuring the first bottom reflection signal reflected from the bottom of the test specimen by radiating ultrasonic waves to the test specimen; And
And measuring the second reflected bottom signal reflected from the opposite surface and the bottom surface of the bottom and bottom of the test specimen by irradiating the test specimen with ultrasound waves. The method according to claim 6,
A method for evaluating deterioration of a material using ultrasonic waves, comprising the step of supporting a test specimen on a water-containing sedimentation tank before measuring the primary and secondary bottom reflection signals. 8. The method of claim 7,
Wherein the ultrasonic attenuation value is measured from the following formula (1) using the measured first and second bottom reflection signals.

(1) where α _s is the ultrasound attenuation value, V _BS1 (ω) is the value obtained by converting the primary bottom reflection signal that reaches the probe into the frequency domain, and V _BS2 (ω) the car bottom reflection signal is converted in frequency principal ^{_{value, D p (k p1 a 2}} / 2D bs1) , and ^{_{D p (k p1 a 2 /}} 2D bs2) are ultrasound spread correction, D _bs1 are tested from the transducer to emit an ultrasonic D _bs2 is the distance from the probe to the opposite side of the bottom of the test specimen, a is the diameter of the probe, k _p1 is the wave number in water, k ₂ is the wave number of the test specimen (wavenumber ), R ₂₁ ^{P; P} is the reflection coefficient of ultrasound waves propagated in the test specimen, e ^ik2h2 is the propagation term of the ultrasonic wave in the test specimen, and h ₂ is the thickness of the test specimen. The method according to claim 1,
Wherein the test specimen is deteriorated for 5,000 to 30,000 hours. The method according to claim 1,
Wherein said test specimen is an austenitic stainless steel material.

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