JP2007225450A - Life estimation method of low-alloy steel used under high-temperature and high-pressure condition, life estimation device, life estimation program and program housing medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately estimate the low-alloy steel life of a structure used under a high-temperature and high-pressure condition. <P>SOLUTION: In the metal tissue photograph of a sample of low-alloy steel sampled from an actual machine in operation, executed are: a linear approximation step of approximating a curved line constituting a crystal grain boundary to a straight line; a damage degree calculation step of calculating the deflection degree of crystal particles; and a life judging step of judging the life of the low-alloy steel from the calculated index value with reference to a use time-index value curve showing the relation between the index value preliminarily calculated with respect to the low-alloy steel and a use time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for predicting the life of a low alloy steel in a structure operated at high temperature and high pressure, such as a boiler for thermal power generation.

  In structures such as thermal power plants and chemical plants that are used for a long time under high temperature and high pressure, creep due to constant stress occurs during operation, and the constituent materials deteriorate. Therefore, it is important to accurately determine material deterioration due to creep, predict the remaining life based on this, and systematically extend the life of the plant by performing partial replacement and repair systematically. It has become to. And in order to predict the remaining life of a structure, there exists a method of evaluating a damage degree based on the change of the metal structure of the low alloy steel which comprises a structure, or predicting the lifetime of a structure.

In the damage evaluation method described in Patent Document 1, the angle between the major axis direction of the crystal grain and the stress direction in the structure is measured for each metal crystal grain included in the sample taken out from the structure. Find the standard deviation for. The degree of deflection of the crystal grains in the stress direction in the major axis direction is determined based on the obtained standard deviation, and the degree of deflection is used as the degree of damage. Further, in the damage evaluation method described in Patent Document 2, the degree of deterioration is determined based on the state of occurrence of voids generated at crystal grain boundaries. Non-Patent Document 1 describes details of various life evaluation methods.
JP-A-11-142399 JP-A-6-50966 Realize Co., Ltd., “Aging and Life Prediction of Thermal / Nuclear and Chemical Plant Equipment / Structural Materials”, published on April 30, 1994, p329-335

  In the evaluation method described in Patent Document 1, since a person recognizes the major axis direction of crystal grains, the degree of damage that should be originally obtained as objective numerical data depends on the subjectivity of the measurer. Also, the criteria for determining the long axis of crystal grains having a complicated shape are ambiguous, and even if the damage degree is automatically calculated by applying image processing by a computer, the calculated value itself lacks reliability. Therefore, the prediction accuracy of the lifetime is lowered. Moreover, although the evaluation method described in Patent Document 2 is based on the premise that voids are generated at the crystal grain boundaries due to deterioration, the voids may not be generated depending on the material, temperature, and stress conditions. In addition, the generation of voids due to deterioration is limited to materials with low intragranular ductility such as stainless steel and high Cr steel, and materials with high intragranular ductility, such as low alloy steel for boilers, may progress. Void is unlikely to occur. Thus, voids due to deterioration may not occur, and in that case, the evaluation method described in Patent Document 2 cannot be applied.

  The present invention has been made in view of the above problems, and based on objective data, evaluates the degree of damage of low-alloy steel in structures such as boilers that are used under high temperature and high pressure with higher accuracy, and ensures accurate life. It aims to provide a method for predicting. Another object of the present invention is to provide an apparatus for predicting the life of a low alloy steel based on the method, and a computer program for causing a computer to function as the apparatus.

In order to achieve the above object, the present invention is a method for predicting the life until a low alloy steel constituting a structure such as a boiler that is operated under high temperature and high pressure is broken,
In a replica obtained by transferring the metal structure or metal structure of the low alloy steel, a linear approximation step for approximating a curve constituting a grain boundary to a straight line;
A damage degree calculating step for calculating a predetermined index value representing the degree of deflection of the grain boundary based on the approximated straight line;
A life determination step for determining a life from the calculated index value with reference to a usage time-index value curve indicating a relationship between the index value and the usage time obtained in advance for the low alloy steel;
It is characterized by including.

Further, the present invention is a method for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure such as a boiler breaks,
In the replica having transferred the metal structure or metal structure of the low alloy steel, a stress method specifying step for setting a stress direction,
In the replica that has transferred the metal structure or metal structure, a linear approximation step that approximates a curve constituting a crystal grain boundary,
For the approximated straight line, a straight line feature acquisition step for acquiring straight line feature information including a length and an angle with respect to the set stress direction;
Based on the straight line feature information, a straight line extracting step of extracting a straight line within a predetermined angle with respect to the set stress direction and obtaining a length of each extracted straight line;
A damage degree calculating step of calculating a predetermined index value representing a degree of deflection of a grain boundary based on the length of all the approximated straight lines and the length of each of the extracted straight lines;
A life determination step of determining a life from the calculated index value with reference to a usage time-index value curve showing a relationship between the usage time and the index value obtained in advance for the low alloy steel,
It is characterized by including.

  In the present application, “long linearity” of a grain boundary means a property indicating a degree of how long a crystal grain boundary can be approximated by a plurality of straight lines. That is, when the grain boundary is approximated by a plurality of straight lines, the “long linearity” is so high that it can be approximated by a longer straight line. When the damage increases, the grain boundaries deform, but those with increased damage can approximate the grain boundaries in the stress direction with a longer straight line and have higher long linearity than those with less damage. . That is, when creep damage progresses, the crystal grain boundary extends in the same direction as the stress direction and becomes linear, and the long linearity increases.

  In the damage degree calculating step of the present invention, a ratio between the total length of all approximated straight lines and the total length of straight lines extracted in the straight line extracting step may be calculated as the index value. . Alternatively, the ratio between the average value of the approximated lengths of all straight lines and the average value of the lengths of the straight lines extracted in the straight line extraction step may be calculated as the index value.

Further, the present invention is a method for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure such as a boiler breaks,
In a replica obtained by transferring the metal structure or metal structure of the low alloy steel, a linear approximation step for approximating a curve constituting a grain boundary to a straight line;
Obtaining the number of approximated straight lines and the length of each straight line;
A damage degree calculating step for calculating a predetermined index value representing the long linearity of the grain boundary based on the number of the straight lines and the length of each straight line;
A life determination step for determining a life from the calculated index value with reference to a usage time-index value curve indicating a relationship between the index value and the usage time obtained in advance for the low alloy steel;
It is characterized by including.
In this case, the index value may be an average value of the lengths of the approximated straight lines.

In each of the above methods of the present invention, the usage time-index value curve is
Obtaining the index value of a sample taken from the structure for which the operating time Ta has elapsed;
Performing an accelerated aging test until the sample reaches the end of its life;
Obtaining the index value of the sample at any time during the accelerated degradation test;
Obtaining a time Tb until the lifetime is reached in the accelerated deterioration test on the sample;
Based on the times Ta and Tb, and the temperature and stress in the accelerated deterioration test, converting the acquisition time of the index value into a usage time in an actual machine;
It is good also as producing by the step which calculates | requires the relationship between the said converted usage time and the acquired parameter | index value as said usage time-index value curve.

In addition, an apparatus for predicting a lifetime until a low alloy steel constituting a structure operated under high temperature and high pressure, such as a boiler, according to the present invention breaks,
An apparatus for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure, such as a boiler, breaks,
Image conversion means for converting the metal structure and replica of the low alloy steel into image data;
Grain boundary extraction means for processing the image data and extracting a curve constituting the crystal grain boundary of the metal structure;
Straight line approximating means for processing the image data and approximating the crystal grain boundary curve to a straight line;
Based on the approximated straight line, a damage degree calculating means for calculating a predetermined index value representing the long linearity of the grain boundary,
A usage time-index value curve storage means for storing a usage time-index value curve indicating the relationship between the index value and the usage time determined in advance for the low alloy steel;
Life determination means for determining a life from the calculated index value with reference to the usage time-index value curve.

  According to the method for predicting the life of low alloy steel according to the present invention, it is possible to accurately evaluate the deterioration state of a structure made of a low alloy used under high temperature and high pressure, and to predict the remaining life of the structure with high accuracy. it can.

=== Life prediction based on grain boundaries ===
As is well known, in a low alloy steel constituting a structure used under high temperature and high pressure such as a boiler, as the deterioration progresses, crystal grains in the metal structure are deflected in the stress direction. The present invention evaluates the degree of damage (damage degree) based on the degree of crystal grain boundary and long linearity, and predicts the remaining life. Although there are conventional methods for predicting the life of low alloy steels based on the state of crystal grain deflection, the present invention is based on the degree of crystal grain boundary deflection and grain boundary long linearity (that is, the degree of damage to the material) in the metal structure. ) Is obtained based on objective information, and the lifetime is determined based on the index value.

  The concept of the said index value in the lifetime prediction method of the low alloy steel of this invention was shown in FIGS. 1-3. First, a metal piece or replica taken from the inside of a structure is used as a sample, and the metal structure of the sample is visualized by a micrograph or the like (FIG. 1). In FIG. 1, the boundary (crystal grain boundary) 3 that borders the crystal grain 2 in the metal structure is shown by a white line. Next, the stress direction 4 is set in the photograph 1, and the grain boundary 3 of each crystal grain 2 is approximated by a polygon. FIG. 2 is a diagram in which all crystal grains 2 in FIG. 1 are approximated to a polygon 5, and the stress direction 4 is indicated by an arrow. In FIG. 2, the polygon 5 corresponding to the crystal grain 2 indicated by the white line in FIG. 1 is indicated by a thick line.

  FIG. 3 shows an enlarged view of crystal grains approximated by a polygon. All the crystal grains 2 in FIG. 1 are approximated to a polygon 5, and as shown in FIG. 3, the length d of each side (straight line) 7 of the polygon 5 and the angle θ with respect to the stress direction are obtained. Based on the information (hereinafter referred to as linear characteristic information) consisting of the length d and the angle θ, the index value representing the degree of deflection or long linearity of the crystal grain boundary is calculated.

  In the present embodiment, life prediction is performed based on a feature in the metal structure of the crystal grain boundary 3 that can be reliably specified by a micrograph or the like. For this reason, it is possible to eliminate any subjective index that has been conventionally specified in an ambiguous manner, such as the major axis direction of the crystal grains 2. In addition, contour enhancement and linear approximation of curves are well-established technologies in the field of computer image processing, and provide objectivity, accuracy, reliability, and affinity for automation when measuring damage. . Of course, even if the grain boundary 3 is linearly approximated by human subjectivity, the accuracy is far higher than when the major axis of the crystal grain 2 is determined.

=== Damage ===
In order to predict the remaining life of an actual machine, it is necessary to specify the current damage level in the actual machine and to specify at which point in the life the damage level is. FIG. 4 shows an outline of the damage degree evaluation method in the life prediction method of the present embodiment. The straight lines on each side obtained by approximating the crystal grains in the metal structure to a polygon are inclined substantially uniformly with respect to the stress direction in the initial state (A). As the deterioration proceeds, the shape of the crystal grains 2 is generally deflected in the stress direction 4 as is well known. Therefore, as compared with the initial state, the straight line portion deflected in the stress direction 4 is relatively increased (B). Then, the deterioration further proceeds (C, D), and finally breaks.

  In the present embodiment, the degree of damage of the low alloy steel is not the inclination of the major axis direction of the crystal grains 2 but the linear feature information (the length d and the stress direction) of each side (straight line) 7 of the crystal grains approximated by a polygon. Is evaluated based on the degree of deflection of the crystal grains. Then, in order to quantitatively evaluate the states (A) to (D) in FIG. 4, a straight line (straight line within a predetermined angle) within a predetermined angle range from the stress direction 4 is extracted, and the length of the straight line portion is calculated. The index value indicating the degree of deflection or long linearity is calculated based on the length of the straight line (omnidirectional straight line) in all angle ranges.

In the present embodiment, (1) the ratio between the total length of straight lines within a predetermined angle and the total length of omnidirectional straight lines as an index value K representing the degree of deflection of crystal grain boundaries based on the straight line angle. Or (2) The ratio of the average length of straight lines within a predetermined angle and the average length of straight lines in all directions is used.

Further, in this embodiment, as another index value that does not use the angle of the straight line, the number of straight lines when the grain boundary is approximated by a straight line as long as possible and the length of each approximate straight line are obtained, and the length of all approximate straight lines is obtained. A method is also proposed in which a value obtained by dividing the total by the number of straight lines (that is, the average length of the approximate straight lines) is used as an index value indicating the long linearity of the grain boundaries. That is, (3) the average length of the approximate straight line of the crystal grain boundary is used as the index value K not based on the angle of the straight line.

  As described above, in this embodiment, any one of (1) to (3) is set as an index value K representing the long linearity of the crystal grain boundary or the degree of deflection of the crystal grain boundary and the long linearity of the crystal grain boundary. A value of index value K at several points in time from the initial state of alloy steel to fracture is obtained, and based on this, a curve representing the relationship between the use time until the service life and index value K (hereinafter referred to as use) A time-index value curve) is set in advance. Then, the index value K obtained by measuring the sample collected from the actual machine is compared with this usage time-index value curve to identify the time point in the usage time-index value curve of the actual machine. Predict life.

=== Creating time-index value curve ===
In order to identify the deterioration state of the low alloy steel in the actual machine as the deterioration gradually progresses from the initial state, a usage time-index value curve indicating the correspondence between the life and the deterioration state is obtained in advance. There is a need. In this embodiment, the usage time-index value curve is obtained by an accelerated deterioration test.

  Although this accelerated deterioration test may be performed on a new test piece, in the present embodiment, a test piece is collected from a part of an actual machine that has been judged to be at the end of its life and discarded. It is obtained by conducting an accelerated deterioration test. This is because there is a possibility that the actual deterioration mode in the actual machine can be faithfully reproduced rather than performing an accelerated deterioration test that deteriorates the test piece under severe conditions compared to the actual machine from the initial state using a new test piece. Because there is. Therefore, specimens were collected from the actual machine parts that were judged to be at the end of their life and discarded, and then subjected to an acceleration test to maximize the deterioration of the actual machine and minimize the effects of acceleration. Thereby, it is possible to obtain a usage time-index value curve that more accurately reflects the deterioration tendency in the actual machine.

  Specifically, in order to obtain the usage time-index value curve, the time point when the test piece is taken out and the above-described index value of the test piece obtained in a timely manner during the accelerated deterioration test are correlated and plotted. When the test piece breaks, it is extended so as to convert the accelerated time (compressed time) from sampling to breakage into real time, and the change characteristic of the index value with respect to the actual operating time of the real machine is acquired. The time axis can be extended by the well-known Larson-Miller parameter based on the conditions (stress / temperature) used for the acceleration test. When the total life is normalized to 1, the specimen was collected. It is possible to specify the point in time with respect to the total life by the ratio, and it is possible to obtain a usage time-index value curve in the remaining life from the time when the test piece is collected. Then, by multiplying the operation time of the test piece in the actual machine at the start of the accelerated deterioration test by the ratio to the life, the life and remaining life can be obtained in real time.

FIGS. 5 to 10 show examples of usage time-index value curves obtained by the accelerated deterioration test.
5 to 7 are usage time-index value curves for the index value K of (1) above. That is, FIG. 5 to FIG. 7 show the total extension of the straight lines that are the sides of the polygonal approximated crystal grains within ± 5 degrees, ± 15 degrees, and ± 30 degrees with respect to the stress direction. Usage time-index value curve 7a in which the ratio _{dθ = x} / D of _{dθ = 5} , _{dθ = 15} , _{dθ = 30} and the total extension D for all the lines is associated with the time series until the lifetime. (X is 5, 15, 30).

8 to 10 are usage time-index value curves for the index value K in (2) above. That is, FIGS. 8 to 10 show the average length davg _{θ = x} (x = 5, 15, 30) for straight lines within ± 5 degrees, ± 15 °, and ± 30 ° with respect to the stress direction, respectively. The usage time-index value curve 7b in which the ratio davg _{θ = x} / Davg to the average length Davg for all the straight lines is associated with the time series until the lifetime is shown. Since the absolute time of the life varies depending on the sample, the time axis is normalized by the total life time tr, and the horizontal axis is indicated by t / tr.

  FIG. 11 is a usage time-index value curve for the index value K in (3) above. That is, FIG. 11 shows the usage time-index value curve 7c in which the average length Davg for all the straight lines that are each piece of the crystal grain boundary approximated to the polygon is associated with the time series until the lifetime.

As can be seen from FIGS. 5 to 11, the index value K of each of the usage time-index value curves (7a, 7b, 7c) based on dθ _{= x} / D, davg _{θ = x} / Davg, and Davg Time dependence is seen, and after a certain period of time, the shape of the usage time-index value curve (7a, 7b, 7c) goes from the state 9 substantially parallel to the time axis 8 to the bent state 10 and gradually increases the degree of damage. Eventually, the fracture state 11 is reached.

=== Life prediction ===
Once the usage time-index value curve has been obtained as described above, a sample of the metal structure at the site to be evaluated for damage degree during periodic inspection of the actual machine, etc. is collected with a replica, etc. The index value is calculated based on the length of each straight line and the angle with respect to the stress direction, and the damage level and the actual operation time are recorded in association with each other.

  At the beginning of actual operation, the index value does not change, but when the operation time becomes longer to some extent, the same tendency as the bent portion 10 in the usage time-index value curve (7a, 7b, 7c) is observed. Seen in the characteristics. Then, if the characteristic curve of the actual machine and the usage time-index value curve (7a, 7b, 7c) are overlapped with each other, each measurement point in the actual machine is associated with the time series of the life cycle. As described above, since the time axis of the usage time-index value curve is expressed as a ratio to the life Tr, if the operating elapsed time t at the time of sampling from the actual machine is multiplied by the ratio, the total of the actual machine If the life time tr is known and the operation elapsed time t at the time of sampling is subtracted from the total life time tr, the remaining life time can be obtained.

  Further, in the low alloy steel, the crystal grains are deflected to some extent even in the initial state, and the straight line 6 is not averaged in all directions and the index value in the initial state is biased. Therefore, the entire usage time-index value curve is shifted up and down so that the index value in the initial state becomes a predetermined value (for example, 1.0), and the sample collected from the actual machine that is the object of life prediction is also the initial value. Correction is made by multiplying the correction coefficient so that the state index value becomes the predetermined value. After that, when the sample is collected and the index value is evaluated, the index value is multiplied by the correction coefficient. In this way, the influence of crystal grain deflection in the initial state can be eliminated.

=== Damage evaluation device ===
The method of predicting the life of the low alloy steel of the above embodiment includes the identification of grain boundaries, linear approximation of curves bordering the grain boundaries, calculation of the damage degree based on the length of each approximated curve and the angle to the stress method, actual machine Are composed of the steps of collating the damage degree / operating elapsed time characteristic with the usage time-index value curve. It is easy to process these steps automatically by a computer. Below, the apparatus (life prediction apparatus) which estimates the lifetime of a low alloy steel automatically based on the method of the said embodiment is mentioned as specific embodiment of this invention.

  As the hardware of the prediction device, a general-purpose computer such as a personal computer can be adopted, and the device can be configured by execution of a program installed in the computer or peripheral equipment attached to the computer. For example, a scanner for taking a micrograph as image data, an external storage for recording usage time-index value curves and various programs, a user interface such as a monitor and a keyboard as peripheral devices, and a program installed in a computer includes these peripheral devices And processing information input from peripheral devices and users and information stored in an external storage, thereby causing the computer to function as a life prediction apparatus.

  FIG. 12 is a flow of information processing in an example of the life prediction apparatus. This process is performed by the computer reading and executing a program stored in a storage medium such as a hard disk.

  First, a photograph of a sample metallographic structure is read by a scanner and converted into image data of a predetermined format (s1). If a CCD camera or the like is installed in the eyepiece optical system of the microscope instead of the procedure of converting the photographed photograph into image data using a scanner, the electrical signal from the CCD camera corresponding to the optical image of the microscope is converted to A / It may be a procedure for obtaining image data by performing D conversion.

  Next, the stress direction is set by user input (s2). For example, an appropriate setting method may be employed such as drawing and setting a straight line on the screen by an operation input from the user interface in a state where the image data of the metal structure is displayed on the monitor. By this stress direction setting process, the stress direction for all crystal grains included in the image data of the metal structure is set. Then, by performing a known contour extraction process on the image data, a grain boundary curve constituting the crystal grain is extracted, and the grain boundary curve is approximated to a straight line (s3, s4).

  As a straight line approximation method, for example, in a captured image of a crystal structure, among pixels forming a grain boundary, pixels overlapping on a straight line having a predetermined line width may be processed as being on the same straight line. . FIG. 13 shows a conceptual diagram of the processing. In the image processing, the crystal grain boundary 3 in the photographed image is composed of pixels (A). Here, if a straight line is drawn with the line width of the grain boundary curve, the length of the straight line becomes extremely short. Therefore, a straight line having a predetermined number of pixel widths is drawn, and all the pixels included in the width of the straight line are considered to be on the same straight line. For example, in order to extract a straight line component that forms an angle of 90 ° with respect to the stress direction, the horizontal direction of the photographed image is set to the stress direction 4 and a straight line having a line width of a predetermined pixel (for example, four pixels) is horizontal. Align with the direction. Then, 4 pixels × 4 pixels are taken as 1 dot, and a series of 2 dots or more in the vertical direction is extracted as a straight line 6. If the number of dots of the extracted straight line 6 is defined as the length, the length of the straight line 6 that makes ± 90 ° with respect to the stress direction can be acquired (B). Similarly, if the grain boundary 3 is approximated by a wide straight line that coincides with the stress direction 4, a straight line 6 that forms an angle of 0 ° (180 °) with the stress direction can be extracted (C). For the crystal grain boundaries that are inclined with respect to the stress direction, the straight line extraction process may be performed in the same manner as described above by inclining the dot arrangement direction by the same angle as the inclination angle of the crystal grain boundaries. In this way, the crystal grain boundary 3 is approximated to the straight line 6 by a wide straight line extending in various angular directions with respect to the stress direction 4.

  If all the crystal grains 2 are approximated to the polygon 5, the straight line feature information (length d, angle θ) of each side (straight line) 6 of the polygon 5 is acquired (s5), and the length d and angle are obtained. Based on θ, the index value K of (1), (2) or (3) is calculated (s6). Then, the actual operating time of the sample that is the origin of the calculation of the index value K, the contents of the sample (information of the collected actual machine, the sampling location of the sample, the collection date and time) and identification information are received by user input, and these user input information And the index value K are recorded in the storage device as sample information (s7). Also, sample information about the same actual machine recorded in the past is acquired, the operating time characteristic of the index value K in the actual machine is obtained, and this characteristic is collated with the usage time-index value curve stored in advance in the storage device (s8). . And if similarities are found in both characteristic curves, the similar curve parts are overlapped to identify at what point in the life cycle the actual machine is in the life cycle, and the standardized life is The remaining life is calculated in conformity with the operation elapsed time and displayed / printed on the user interface or output to the external storage as a file (s9 → s10, s11). If there is no similarity, the process is terminated (s9 → end), and the index value K is obtained again at the next sample collection to determine the similarity.

  In this way, the index value until now is taken in parallel with taking the sample from the same part in the same structure regularly or in time and storing the index value K and the elapsed operation time in association with each other. The operating elapsed time characteristics of the are compared with the usage time-index value curve.

It is the photograph which image | photographed the metal structure of the low metal steel which the life prediction method of this invention makes object. It is the schematic when the crystal grain in the said metal structure approximates a polygon. It is explanatory drawing about the parameter | index which shows the deflection | deviation state of the said metal grain. It is a conceptual diagram of the lifetime prediction method in embodiment of this invention. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is an example of the usage time-index value curve prepared with the lifetime prediction method in the said embodiment. It is a flowchart of the information processing in the apparatus which estimates the lifetime of a low alloy steel based on the lifetime prediction method of this invention. It is a conceptual diagram of the straight line approximation process included in the said information processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal structure photograph 2 Crystal grain 3 Grain boundary 4 Stress direction 5 Polygon 6 Straight line 7a, 7b Usage time-index value curve

Claims (14)

A method for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure such as a boiler breaks,
In a replica obtained by transferring the metal structure or metal structure of the low alloy steel, a linear approximation step for approximating a curve constituting a grain boundary to a straight line;
A damage degree calculating step for calculating a predetermined index value representing the long linearity of the grain boundary based on the approximated straight line;
A life determination step of determining a life from the calculated index value with reference to a usage time-index value curve showing a relationship between the usage time and the index value obtained in advance for the low alloy steel,
The life prediction method of the low alloy steel characterized by including this. A method for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure such as a boiler breaks,
In the replica having transferred the metal structure or metal structure of the low alloy steel, a stress method specifying step for setting a stress direction,
In the replica that has transferred the metal structure or metal structure, a linear approximation step that approximates a curve constituting a crystal grain boundary,
For the approximated straight line, a straight line feature acquisition step for acquiring straight line feature information including a length and an angle with respect to the set stress direction;
Based on the straight line feature information, a straight line extracting step of extracting a straight line within a predetermined angle with respect to the set stress direction and obtaining a length of each extracted straight line;
A damage degree calculating step for calculating a predetermined index value representing a degree of deflection and long linearity of a grain boundary based on the length of all the approximated straight lines and the length of each of the extracted straight lines;
A life determination step of determining a life from the calculated index value with reference to a usage time-index value curve showing a relationship between the usage time and the index value obtained in advance for the low alloy steel,
The life prediction method of the low alloy steel characterized by including this.   3. The damage degree calculation step according to claim 2, wherein a ratio between the total length of all approximated straight lines and the total length of straight lines extracted in the straight line extraction step is calculated as the index value. Characteristic method for predicting the life of low alloy steel.   3. The damage degree calculation step according to claim 2, wherein a ratio between an average value of the approximated straight line lengths and an average value of the straight line lengths extracted in the straight line extraction step is calculated as the index value. A method for predicting the life of a low alloy steel under high temperature and pressure. A method for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure such as a boiler breaks,
In a replica obtained by transferring the metal structure or metal structure of the low alloy steel, a linear approximation step for approximating a curve constituting a grain boundary to a straight line;
Obtaining the number of approximated straight lines and the length of each straight line;
A damage degree calculating step for calculating a predetermined index value representing the long linearity of the grain boundary based on the number of the straight lines and the length of each straight line;
A life determination step for determining a life from the calculated index value with reference to a usage time-index value curve indicating a relationship between the index value and the usage time obtained in advance for the low alloy steel;
The life prediction method of the low alloy steel characterized by including this.   6. The method for predicting the life of a low alloy steel according to claim 5, wherein the index value is an average length per one of the approximated straight lines. The use time-index value curve according to any one of claims 1 to 6,
Obtaining the index value of a sample taken from the structure for which the operating time Ta has elapsed;
Performing an accelerated aging test until the low alloy steel reaches the end of its life;
Obtaining the index value of the low alloy steel at any time during the accelerated deterioration test;
Obtaining a time Tb until reaching the life in the accelerated deterioration test in the low alloy steel;
Based on the times Ta and Tb, and the temperature and stress in the accelerated deterioration test, converting the acquisition time of the index value into a usage time in an actual machine;
A method for predicting the life of a low alloy steel, comprising: obtaining a relationship between the converted usage time and the acquired index value as the usage time-index value curve. An apparatus for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure, such as a boiler, breaks,
Image conversion means for converting the replica of the metal structure of the low alloy steel and the metal structure into image data;
Grain boundary extraction means for processing the image data and extracting a curve constituting the crystal grain boundary of the metal structure;
Straight line approximating means for processing the image data and approximating the crystal grain boundary curve to a straight line;
Based on the approximated straight line, a damage degree calculating means for calculating a predetermined index value representing the long linearity of the grain boundary,
Usage time-index value curve storage means for storing a usage time-index value curve indicating the relationship between the usage time and the index value determined in advance for the low alloy steel;
With reference to the usage time-index value curve, a life determination means for determining a life from the calculated index value;
A device for predicting the life of a low alloy steel characterized by comprising: An apparatus for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure, such as a boiler, breaks,
Image conversion means for converting the replica of the metal structure of the low alloy steel and the metal structure into image data;
Direction setting means for setting a stress direction in image data of a replica obtained by transferring the metal structure or metal structure;
Grain boundary extraction means for processing the image data and extracting a curve constituting the crystal grain boundary of the metal structure;
Straight line approximating means for processing the image data and approximating the crystal grain boundary curve to a straight line;
Straight line feature acquisition means for acquiring straight line feature information including a length and an angle with respect to the set stress direction for the approximated straight line;
Based on the straight line feature information, a specific straight line feature acquisition unit that extracts straight lines within a predetermined angle with respect to the set stress direction and acquires the length of each of the extracted straight lines;
Damage that calculates a predetermined index value representing the degree of deflection of the grain boundary and the long linearity of the grain boundary based on the length of all the approximated straight lines and the length of the straight line within the predetermined angle Degree calculation means;
A usage time-index value curve storage means for storing a usage time-index value curve indicating the relationship between the index value and the usage time determined in advance for the low alloy steel;
With reference to the use time-index value curve stored in the use time-index value curve storage means, a life determination means for judging the life of the low alloy steel from the calculated index value;
A result output means for outputting information on the determined life,
An apparatus for predicting the life of a low alloy steel, comprising: An apparatus for predicting the life until a low alloy steel constituting a structure operated under high temperature and high pressure, such as a boiler, breaks,
Image conversion means for converting the replica of the metal structure of the low alloy steel and the metal structure into image data;
Grain boundary extraction means for processing the image data and extracting a curve constituting the crystal grain boundary of the metal structure;
Straight line approximating means for processing the image data and approximating the crystal grain boundary curve to a straight line;
Straight line feature acquisition means for acquiring the number of approximated straight lines and the length of each straight line;
Damage degree calculating means for calculating a predetermined index value representing the long linearity of the grain boundary based on the number of the straight lines and the length of each straight line;
Usage time-index value curve storage means for storing a usage time-index value curve indicating the relationship between the usage time and the index value determined in advance for the low alloy steel;
With reference to the use time-index value curve stored in the use time-index value curve storage means, a life determination means for judging the life of the low alloy steel from the calculated index value;
A result output means for outputting information on the determined life,
An apparatus for predicting the life of a low alloy steel, comprising: A computer program that is installed in a computer and causes the computer to predict the life until the low alloy steel constituting the structure that operates under high temperature and high pressure such as a boiler breaks,
Converting the metal structure of the low alloy steel and a replica obtained by transferring the metal structure into image data;
Processing the image data to extract a curve constituting a grain boundary of the metal structure;
Processing the image data to approximate the grain boundary curve to a straight line;
Calculating a predetermined index value representing the long linearity of the grain boundary based on the approximated straight line;
Determining a life from the calculated index value with reference to a usage time-index value curve showing a relationship between the index value and the usage time obtained in advance for the low alloy steel;
A device for predicting the life of a low alloy steel, characterized in that the computer is executed. A computer program that is installed in a computer and causes the computer to predict the life until the low alloy steel constituting the structure that operates under high temperature and high pressure such as a boiler breaks,
Converting the metal structure of the low alloy steel and a replica obtained by transferring the metal structure into image data;
Setting a stress direction in image data of a replica obtained by transferring the metal structure or metal structure;
Processing the image data to extract a curve constituting a grain boundary of the metal structure;
Processing the image data to approximate the grain boundary curve to a straight line;
Obtaining linear feature information including a length and an angle with respect to the set stress direction for the approximated straight line;
Extracting a straight line within a predetermined angle with respect to the set stress direction based on the straight line feature information, and obtaining a length of each extracted straight line;
Calculating a predetermined index value representing the degree of deflection and long linearity of the grain boundary based on the length of all the approximate straight lines and the length of the straight line within the predetermined angle;
A step of determining a life of the low alloy steel from the calculated index value with reference to a usage time-index value curve indicating a relationship between the index value and the life obtained in advance for the low alloy steel;
Outputting information about the determined life,
A computer-executable program for predicting the life of low alloy steel. A computer program that is installed in a computer and causes the computer to predict the life until the low alloy steel constituting the structure that operates under high temperature and high pressure such as a boiler breaks,
Converting the metal structure of the low alloy steel and a replica obtained by transferring the metal structure into image data;
Processing the image data to extract a curve constituting a grain boundary of the metal structure;
Processing the image data to approximate the grain boundary curve to a straight line;
Obtaining the number of approximated straight lines and the length of each straight line;
Calculating a predetermined index value representing the long linearity of the grain boundary based on the number of the straight lines and the length of each straight line;
Determining a life of the low alloy steel from the calculated index value with reference to a usage time-index value curve indicating a relationship between the index value and the usage time obtained in advance for the low alloy steel;
Outputting information about the determined life,
Is a program for predicting the life of a low alloy steel. The program storage medium which recorded the lifetime prediction program in any one of Claims 11-13.