JP2007248390A - Breakage life evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance life prediction precision and practical usability, when evaluating a breakage life, by inspecting a change in a surface texture of an evaluating object, using an EBSP method. <P>SOLUTION: This breakage life evaluation device is provided with an electron beam irradiating means for irradiating a sample of the evaluating object with an electron beam, while scanned, a photographing means for photographing an electron backscattered analytical image formed by backscattering the electron beam emitted to the sample, an image processing means for generating a crystal grain boundary distribution in a prescribed area of the sample, by image-processing the electron backscattered analytical image, an average crystal grain size calculating means for calculating an average crystal grain size, based on the crystal grain boundary distribution, a breakage life determination means for determining the breakage life of the evaluating object, based on a characteristic curve for indicating a correlation between the average crystal grain size and the breakage life of the evaluating object, and based on the average crystal grain size calculated by the average crystal grain size calculating means, and an output means for outputting a determination result of the breakage life. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fracture life evaluation apparatus.

  Metal parts exposed to high temperatures and high stresses such as boiler tubes and gas turbine engine rotor blades may be subject to fatigue failure or creep failure due to aging. Therefore, accurately and quantitatively predicting the fracture life of such metal parts is very important in planning the timing of inspection and replacement of the metal parts.

  Conventionally, as a method for quantitatively evaluating the creep rupture life, a replica of the surface structure of a metal part is collected at each elapse of a predetermined use time, and the remaining life is checked by examining the temporal change of the surface structure. When the creep failure life is predicted based on the prediction method or the Larson-Miller curve, and the usage time of the metal part reaches the predicted creep failure life, voids generated in the inspection area of the metal part (void) A method for predicting the remaining life based on a characteristic curve indicating the relationship between the void area ratio and the lifetime consumption rate obtained by experiments in advance is known.

However, for example, in the case of a metal part made of a high Cr material such as modified 9Cr-1Mo steel, the change in surface texture due to creep as described above is very fine. There is a problem that the change cannot be inspected and voids are generated inside the metal part but not on the surface. In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 2005-24389 discloses an EBSP (Electron Back Scatter Diffraction Pattern) method for measuring an average crystal orientation difference for specific crystal grains in a metal part. A technique for predicting the remaining life based on a characteristic curve (see FIG. 7) showing the relationship between the average crystal orientation difference and the life consumption rate under a creep environment obtained in advance by experiments is disclosed.
In particular, a weld heat-affected zone occurs at the weld between the base metal and the welded joint, and creep rupture is generally considered to occur at this weld heat-affected zone. Therefore, the evaluation method was not examined.
JP 2005-24389 A

 By the way, when the average crystal orientation difference is measured using the EBSP method as in the above-described prior art, various measurement conditions such as the polishing state of the sample surface, the degree of vacuum of the chamber provided in the measurement apparatus, the vibration of the measurement apparatus, etc. Due to this variation, the measured value of the average crystal orientation difference greatly fluctuates, and it is difficult to ensure reproducibility. Therefore, in order to ensure the reproducibility of the average crystal orientation difference, it is necessary to perform the measurement at a facility comparable to the laboratory, and it is difficult to deal with at the field level and the practicality is poor.

 In the prediction of the creep rupture life using the characteristic curve showing the relationship between the average crystal orientation difference and the life consumption rate shown in FIG. 7, the most important information is the property after the life consumption rate of 40%. However, as can be seen from FIG. 7, there is almost no temporal change in the average crystal orientation difference between the lifetime consumption rates of 40% to 60%, and there is a large change between about 60% and 80%, but about 80%. There is only a gradual change between% and 100%. Therefore, there is a problem that the response to changes in the measured average crystal orientation difference is poor and the life prediction accuracy is low.

 The present invention has been made in view of the above-described circumstances, and in the case of evaluating the fracture life by inspecting the change in the surface texture of the evaluation object using the EBSP method, the life prediction accuracy and practicality are improved. With the goal.

  In order to achieve the above object, in the present invention, as a first solving means related to a fracture life evaluation apparatus, an electron beam irradiation means for irradiating a sample of an evaluation object while scanning an electron beam, and irradiating the sample A photographing means for photographing an electron backscattering analysis image formed by the backscattering of the electron beam, and a crystal in a predetermined region of the sample by image processing the electron backscattering analysis image photographed by the photographing means. Image processing means for generating a grain boundary distribution, average crystal grain size calculating means for calculating an average crystal grain size based on the crystal grain boundary distribution, and the average crystal grain size and the evaluation object obtained in advance. Based on a characteristic curve indicating a relationship with the fracture life and the average crystal grain size calculated by the average crystal grain size calculation unit, a fracture life determination unit that determines the fracture life of the evaluation object, and the breakdown lifespan And an output means for outputting the judgment result of the breakdown lifetime by constant means, to adopt a means of.

According to the present invention, as the second solving means relating to the fracture life evaluation apparatus, in the first solving means, the image processing means includes a grain boundary having a crystal orientation difference of 15 ° or more in a predetermined region of the sample. A distribution is generated, the average crystal grain size calculating means calculates the average crystal grain size based on a grain boundary distribution having a crystal orientation difference of 15 ° or more, and the fracture life determining means is obtained in advance.
A characteristic curve showing the relationship between the average crystal grain size obtained based on the grain boundary distribution with the crystal orientation difference of 15 ° or more and the fracture life of the evaluation object, and the average crystal grain size calculating means The fracture life of the evaluation object is determined based on the average crystal grain size.

Further, in the present invention, as the third solving means relating to the fracture life evaluation apparatus, in the first or second solving means, the evaluation object is a welded joint portion of a high Cr material. Do

Further, in the present invention, as a fourth solving means related to the fracture life evaluation apparatus, in any one of the above-mentioned first to third solving means, the breaking life determination means determines the average crystal grain size and the above-mentioned obtained in advance. Determining the creep rupture life of the evaluation object based on a characteristic curve showing a relationship with the creep rupture life of the evaluation object and the average crystal grain size calculated by the average crystal grain size calculating means. Features.

  According to the present invention, in the case where the fracture life is evaluated by inspecting the change in the surface texture of the evaluation object using the EBSP method, the fracture life is based on the average crystal grain size having a large temporal change with respect to the life consumption rate. Therefore, it is possible to predict the fracture life of the evaluation object with higher accuracy than in the past. In addition, the average crystal grain size as described above is reproducibility independent of variations in various measurement conditions such as the polishing state of the sample surface, the degree of vacuum of the chamber provided in the fracture life prediction device, and the vibration of the fracture life prediction device. Therefore, it is possible to cope with at the field level and improve the practicality.

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a fracture life evaluation apparatus according to an embodiment of the present invention. As shown in this figure, this fracture life evaluation apparatus includes a PC (Personal Computer) 1, a SEM (Scanning Electron Microscope) control unit 2, an electron beam irradiation unit 3, a vacuum chamber 4, a sample stage 5, and a stage control unit 6. The camera 7 and the camera control unit 8 are configured. Moreover, the code | symbol X is a section | slice of the welded joint part (evaluation object) of the boiler pipe which consists of improved 9Cr-1Mo steel (high Cr system material), for example, In the boiler pipe actually used as piping of a plant, The sample was taken from the inspection target area of the welded joint where there was a risk of creep fracture.

  As shown in FIG. 1, the PC 1 includes an image processing unit 1b, an average crystal grain size calculation unit 1c, and a control unit 1a having a fracture life determination unit 1d therein, a storage unit 1e, and a display unit 1f (output means). ing. The control unit 1a is based on an EBSP method control program stored in advance in the storage unit 1e. The image processing unit 1b, the average crystal grain size calculation unit 1c, the fracture life determination unit 1d, the SEM control unit 2, and the stage control The unit 6 and the camera control unit 8 are controlled.

  Under the control of the control unit 1a, the image processing unit 1b performs image processing on an image signal input from the camera control unit 8, that is, an electronic backscatter analysis image taken by the camera 7, based on the EBSP method, The crystal orientation of the position (irradiation point) irradiated with the electron beam in the predetermined region is determined, and the crystal orientation obtained for each irradiation point on the sample X irradiated with the electron beam on the scan is The information is sequentially stored in the storage unit 1e together with the position information of the irradiation points. Furthermore, the image processing unit 1b, based on the position information of each irradiation point stored in the storage unit 1e and the crystal orientation corresponding to the position information, the distribution of crystal grain boundaries having a crystal orientation difference of 15 ° or more. Data is generated, and the grain boundary distribution data is output to the average crystal grain size calculator 1c.

  The average crystal grain size calculation unit 1c calculates the average crystal grain size of crystal grains existing in a predetermined region of the sample X based on the crystal grain boundary distribution data under the control of the control unit 1a. An average crystal grain size signal indicating the diameter is output to the fracture life determination unit 1d.

 Under the control of the control unit 1a, the fracture life determination unit 1d determines the average crystal grain size signal and the average crystal grain size and the creep rupture life of the welded joint of the boiler tube, which are stored in advance in the storage unit 1e. The creep rupture life of the welded joint portion of the boiler pipe is determined based on characteristic curve (hereinafter referred to as remaining life curve) data indicating the relationship. More specifically, as shown in FIG. 2, the remaining life curve shows the relationship between the average crystal grain size and the lifetime consumption rate, and the fracture life determination unit 1d includes the average crystal grain size calculation unit 1c. The remaining life display for determining the remaining life until creep rupture and displaying the remaining life on the display unit 1f based on the average crystal grain size calculated in step 1 and the remaining life curve of FIG. The signal is output to the display unit 1f. In addition, the said remaining life curve is calculated | required in advance from the creep fracture test using the welded joint part of the boiler pipe which consists of improved 9Cr-1Mo steel.

 The storage unit 1e stores in advance a control program for the EBSP method executed by the control unit 1a, other system programs, and the like, and a sample X irradiated with an electron beam on the scan in response to a request from the image processing unit 1b. The crystal orientation obtained for each irradiation point is stored together with the position information of each irradiation point. Further, the storage unit 1e stores in advance the remaining life curve data shown in FIG. 2, and outputs the remaining life curve data to the failure life determination unit 1d in response to a request from the failure life determination unit 1d. The display unit 1f is, for example, a liquid crystal monitor, and displays the remaining life until the welded joint portion of the boiler tube reaches creep failure based on the remaining life display signal input from the failure life determination unit 1d.

 The SEM control unit 2 controls the electron beam irradiation operation of the electron beam irradiation unit 3 under the control of the control unit 1 a in the PC 1. More specifically, the SEM control unit 2 controls electron beam irradiation energy, irradiation timing, scanning direction, and the like. The electron beam irradiation unit 3 includes an electron gun 3a, an electron lens 3b, an objective lens 3c, and a scanning coil 3d. The electron gun 3a emits an electron beam to the electron lens 3b with a predetermined acceleration voltage under the control of the SEM control unit 2. The electron lens 3b converges the electron beam incident from the electron gun 3a and emits it to the objective lens 3c. The objective lens 3c irradiates the irradiation point on the sample X with the electron beam so that the electron beam incident from the electron lens 3b is focused on the sample X. A scanning coil 3d is provided between the electron lens 3b and the objective lens 3c, and the scanning coil 3d changes the incident direction of the electron beam to the objective lens 3c under the control of the SEM control unit 2. As a result, the electron beam is irradiated onto the sample X in a scanning manner.

  The vacuum chamber 4 is a chamber connected directly below the electron beam irradiation unit 3 and capable of lowering the internal atmospheric pressure to a high vacuum state by a vacuum pump (not shown), and includes a sample stage 5 and a camera 7 inside. The sample stage 5 is a disk-shaped stage on which the sample X is placed, and is provided inside the vacuum chamber 4 so as to be driven in a 5-axis direction by a 5-axis control motor (not shown). Here, the five axes indicate the XYZ direction, the R direction (that is, the rotation direction of the sample stage 5), and the T direction (that is, the tilt direction of the sample stage 5). The stage control unit 6 performs drive control of the sample stage 5 (specifically, a 5-axis control motor) under the control of the control unit 1a in the PC 1. That is, the stage control unit 6 controls the tilt angle, rotation angle, and XYZ coordinates of the sample stage 5 by controlling the drive of the 5-axis control motor.

  The camera 7 is, for example, a high-sensitivity CCD (Charge Coupled Devices) camera or the like, and is provided substantially perpendicular to the irradiation direction of the electron beam inside the vacuum chamber 4, and an electron is applied to the sample X under the control of the camera control unit 8. An electron backscatter analysis image generated by the irradiation of the line is taken, and an image signal indicating the electron backscatter analysis image is output to the camera control unit 8. The camera control unit 8 controls the photographing timing, exposure time, focusing, and the like of the camera 7 under the control of the control unit 1a in the PC 1, and outputs an image signal input from the camera 7 to the image processing unit 1b. To do.

  Since the present fracture life prediction apparatus can use a conventional SEM apparatus, the illustration is omitted, but secondary electrons generated by irradiating the sample X with an electron beam are detected, and the amount of generation of the secondary electrons is detected. Is converted into a luminance signal, and a secondary electron detector that outputs the signal to the controller 1a of the PC 1 is provided inside the vacuum chamber 4, and the controller 1a is based on the luminance signal input from the secondary electron detector. The SEM image is displayed on the display unit 1f.

  Next, a breakdown life prediction processing procedure using the breakdown life prediction apparatus configured as described above will be described below with reference to the flowchart of FIG.

First, for a welded joint portion of a boiler tube for which a predetermined usage time has elapsed, a section of a region to be inspected that may cause a creep failure, that is, a sample X is collected (step S1).
Here, the inspection object area of the welded joint will be described. For example, as shown in FIG. 4, when welding is performed on a boiler tube made of improved 9Cr-1Mo steel, a weld heat affected zone (HAZ: Heat Affected Zone) is formed on the welded portion between the base material 10 and the welded joint portion 11. ) 12 is generated. In general, it is known that creep fracture occurs in the fine grain region 13 formed in the HAZ 12. Such a fine grain region 13 is a region in which normalized martensite crystal grains and tempered martensite crystal grains are mixed to form a fine structure, and creep voids are likely to occur. In the present embodiment, the region to be inspected is the fine particle region 13, and the sample X is collected from the fine particle region 13. In conducting an actual test, a sample X is taken from the HAZ 12 that is exposed from the outside of the boiler tube to the surface portion, and evaluation is performed.

  Subsequently, the sample X is processed (step S2). Here, the processing of the sample X is performed by first cutting the sample X into a size that can be set on the sample stage 5 and then polishing or electrolytic polishing the surface of the sample X.

  Next, the sample X that has been processed as described above is placed on the sample stage 5 (step S3). Specifically, the vacuum pump is operated to return the inside of the vacuum chamber 4 to atmospheric pressure, the sample X is attached to the sample insertion rod, and the sample is inserted from a sample inlet (not shown) provided in the vacuum chamber 4. The rod is inserted, and the sample X is set on the sample stage 5. When the installation of the sample X is completed, the sample insertion rod is removed and the vacuum pump is operated to lower the internal pressure of the vacuum chamber 4 to a predetermined pressure (high vacuum).

  Subsequently, the irradiation start position of the electron beam is determined (step S4). In this case, the SEM function of the present fracture life prediction apparatus is used. That is, the electron beam irradiation unit 3 irradiates the sample X with the electron beam, and determines a desired irradiation start position while confirming the SEM image displayed on the display unit 1 f of the PC 1. Here, the sample stage 5 is tilted to about 70 ° with respect to the horizontal by operating the 5-axis control motor. In the present embodiment, the electron beam irradiation region on the sample X is set to a range of 20 μm × 20 μm, and the electron beam is irradiated at a pitch of 0.2 μm.

  Then, after determining the electron beam irradiation start position, the control program for the EBSP method is activated in the PC 1 to start the electron beam irradiation (step S5). The PC 1 (specifically, the control unit 1a) controls the SEM control unit 2 and the camera control unit 8 based on a control program for the EBSP method, and the electron beam is 0.2 μm pitch in the electron beam irradiation area by the control. The electron backscattering analysis image generated by the irradiation is captured by the camera 7 for each irradiation point.

 The camera 7 sequentially outputs an image signal indicating an electronic backscattering analysis image taken for each irradiation point to the image processing unit 1b via the camera control unit 8. The image processing unit 1b processes the image signal input as described above, that is, the electron backscatter analysis image based on the EBSP method, determines the crystal orientation for each irradiation point, and applies the crystal orientation to each irradiation. The information is sequentially stored in the storage unit 1e together with the point position information (step S6). The size of the electron beam irradiation region and the scanning pitch amount can be arbitrarily set.

  When the determination of the crystal orientation at all the irradiation points in the electron beam irradiation region is completed in step S6, the image processing unit 1b acquires the position information and the crystal orientation of each irradiation point stored in the storage unit 1e, and Based on the position information and the crystal orientation, distribution data of crystal grain boundaries having a crystal orientation difference of 15 ° or more is generated in the electron beam irradiation region, and the crystal grain boundary distribution data is output to the average crystal grain size calculation unit 1c. (Step S7).

  FIG. 5 shows an example of the grain boundary distribution data. FIG. 5A shows grain boundary distribution data obtained from the initial state, that is, the sample X of the welded joint portion of an unused boiler tube. FIG. 5 (b) shows grain boundary distribution data obtained from the sample X of the welded joint portion of the boiler tube after the usage time corresponding to 60% of the life consumption rate, that is, 60% of the creep rupture life. FIG.5 (c) is the grain boundary distribution data obtained from the sample X of the welded joint part of the boiler pipe after a creep fracture, ie, 100% lifetime consumption rate. As shown in these figures, under the creep environment, the crystal grains in the fine grain region 13 become larger with time. That is, it can be seen that there is a correlation between the change in crystal grain size and the creep rupture life.

  The average crystal grain size calculation unit 1c calculates a crystal grain size (average equivalent diameter) for each crystal grain in the electron beam irradiation region based on the above-described crystal grain boundary distribution data, and averages these to obtain an average crystal The particle size is calculated (step S8). Then, the average crystal grain size calculation unit 1c outputs an average crystal grain size signal indicating the average crystal grain size to the fracture life determination unit 1d.

 The failure life determination unit 1d determines the remaining life until creep failure based on the average crystal grain size signal and the remaining life curve data shown in FIG. 2 stored in the storage unit 1e (step S9). ). More specifically, for example, when the average crystal grain size calculated by the average crystal grain size calculating unit 1c is 4 μm, it can be seen from the remaining life curve of FIG. 2 that the lifetime consumption rate is about 65%. . That is, the remaining life of the welded joint portion of the boiler pipe until creep rupture is determined to be 45% of the creep rupture life.

 The breakdown life determination unit 1d outputs a remaining life display signal for displaying the remaining life determined as described above on the display unit 1f. The display unit 1f displays the remaining life until the welded joint portion of the boiler pipe undergoes creep failure based on the remaining life display signal input from the failure life determination unit 1d (step S10).

 As described above, the average crystal grain size is calculated from the grain boundary distribution data having a crystal orientation difference of 15 ° or more, and the remaining life is quantitatively determined from the remaining life curve indicating the relationship between the average crystal grain size and the creep fracture life. Can be determined. Hereinafter, the reason for obtaining crystal grain boundary distribution data having a crystal orientation difference of 15 ° or more in this embodiment will be described.

  FIG. 6 shows a crystal orientation difference of 3 ° or more (reference numeral 20), 10 ° or more (reference numeral 21), or 15 ° or more (reference numeral 22) obtained from a creep fracture test using a boiler tube made of modified 9Cr-1Mo steel. ), Experimental data of a remaining life curve obtained for each grain boundary distribution of 30 ° or more (reference numeral 23). As shown in this figure, when the crystal orientation difference is 15 ° or more, the change of the average crystal grain size after the life consumption rate of 40%, which is particularly necessary information, is the largest, that is, the life against the change of the average crystal grain size. It can be seen that the consumption rate is responsive and the life prediction accuracy is the highest.

 Therefore, according to the present embodiment, when the fracture life is evaluated by inspecting the change in the surface texture of the evaluation object using the EBSP method, the remaining life of the evaluation object, that is, with a higher accuracy than in the past, It is possible to predict the creep rupture life. In addition, the average crystal grain size as described above is reproducibility independent of variations in various measurement conditions such as the polishing state of the sample surface, the degree of vacuum of the chamber provided in the fracture life prediction device, and the vibration of the fracture life prediction device. Therefore, it is possible to cope with at the field level and improve the practicality.

  In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.

(1) In the above embodiment, a boiler tube made of improved 9Cr-1Mo steel has been exemplified and described as an evaluation object. However, the present invention is not limited to this, and any metal part made of another high Cr material may be used. The invention is applicable. Moreover, even if it is a material other than a high Cr system material, if the material has a fine structure that cannot be confirmed by the EBSP method and the crystal grain size changes with the progress of creep fracture, The invention is applicable.

(2) In the above embodiment, the average crystal grain size was calculated from the grain boundary distribution with a crystal orientation difference of 15 ° or more. However, the present invention is not limited to this, and other conditions shown in FIG. Above, 10 ° or more, 30 ° or more) may be used. When these conditions are used, the prediction accuracy of the remaining life slightly decreases, but when compared with the conventional case, as shown in FIG. 6, the change in the average crystal grain size after the life consumption rate of 40% is large. This can contribute to improvement in accuracy.
If the crystal orientation difference is within 62.8 °, it may be used. This 62.8 ° is the maximum angle θmax in performing the EBSP method, and is obtained from the following equation (1) in the Mackenzie plot showing the tendency of the orientation relation between the cubic crystals in the EBSP method.
θmax = cos ⁻¹ {(2 + √2) / 4} = 62.8 ° (1)

(3) In the above embodiment, the case where the fracture life due to creep is predicted has been described. However, the present invention is not limited to this, and has a fine structure that cannot be confirmed unless the EBSP method is used. The present invention can be applied to any cause of destruction having a characteristic that the particle size changes.

1 is a schematic configuration diagram of a fracture life prediction apparatus according to an embodiment of the present invention. It is a remaining life curve used with the fracture life prediction apparatus which concerns on one Embodiment of this invention. It is a flowchart figure which shows the fracture life prediction procedure which concerns on one Embodiment of this invention. It is explanatory drawing of the evaluation target object which concerns on one Embodiment of this invention. It is an example of the grain boundary distribution obtained by the fracture life prediction apparatus according to an embodiment of the present invention. It is an experimental data of the remaining life curve corresponding to the various conditions which concern on one Embodiment of this invention. It is a characteristic curve which shows the relationship between the average crystal orientation difference used by a prior art, and a lifetime consumption rate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... PC (Personal Computer), 1a ... Control part, 1b ... Image processing part, 1c ... Average crystal grain size calculation part, 1d ... Destruction life judgment part, 1e ... Storage part, 1f ... Display part, 2 ... SEM (Scanning) Electron Microscope) control unit, 3 ... electron beam irradiation unit, 4 ... vacuum chamber, 5 ... sample stage, 6 ... stage control unit, 7 ... camera, 8 ... camera control unit, X ... sample

Claims (4)

An electron beam irradiation means for irradiating the sample of the evaluation object while scanning the electron beam;
Imaging means for photographing an electron backscattering analysis image formed by backscattering the electron beam irradiated on the sample;
Image processing means for generating a grain boundary distribution in a predetermined region of the sample by image processing an electron backscattering analysis image photographed by the photographing means;
An average crystal grain size calculating means for calculating an average crystal grain size based on the crystal grain boundary distribution;
Based on the characteristic curve indicating the relationship between the average crystal grain size and the fracture life of the evaluation object obtained in advance, and the average crystal grain size calculated by the average crystal grain size calculating means, the evaluation A destructive life judging means for judging the destructive life of the object;
A failure life evaluation apparatus comprising: output means for outputting a result of determination of the destruction life by the destruction life determination means. The image processing means generates a crystal grain boundary distribution having a crystal orientation difference of 15 ° or more in a predetermined region of the sample,
The average crystal grain size calculating means calculates an average crystal grain size based on a grain boundary distribution in which the crystal orientation difference is 15 ° or more,
The fracture life determination means is a characteristic curve showing a relationship between an average crystal grain size obtained based on a grain boundary distribution having a crystal orientation difference of 15 ° or more and a fracture life of the evaluation object, which is obtained in advance. ,
2. The fracture life evaluation apparatus according to claim 1, wherein the fracture life of the evaluation object is determined based on the average crystal grain size calculated by the average crystal grain size calculation means. The fracture life evaluation apparatus according to claim 1 or 2, wherein the evaluation object is a welded joint portion of a high Cr material. The fracture life determination means includes a characteristic curve indicating a relationship between the average crystal grain size and the creep fracture life of the evaluation object obtained in advance, and an average crystal grain calculated by the average crystal grain size calculation means. The fracture life evaluation apparatus according to any one of claims 1 to 3, wherein a creep fracture life of the evaluation object is determined based on a diameter.

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