Method and device for predicting service life of P91 pipe fitting containing soft area

Abstract

The invention provides a life prediction method and device for a soft area-containing P91 pipe fitting, and the method comprises the steps: firstly, accurately obtaining the soft area range of the pipe fitting through hardness detection, accurately obtaining the depth value of the soft area and the mechanical properties of the allowable stress value of a soft area material through a micro-damage sampling test, the operation is easy, and the economic loss caused by pipe cutting sampling is avoided. And secondly, the stress redistribution state of the soft area caused by creep relaxation can be accurately obtained through two-stage numerical simulation, the concept of creep relaxation allowable time is defined according to a strength theory, and then the residual life of the soft area when the soft area reaches a yield condition is determined, so that rapid and accurate prediction of the residual life of the P91 pipe fitting containing the soft area is realized. Whether the pipe fitting needs to be replaced or not and when the pipe fitting needs to be replaced can be more accurately determined through the residual life of the soft area, and economic losses caused by blind pipe replacement are avoided.

Description

Technical Field

[0001] The present application relates to the technical field of pipe component life prediction, and in particular to a method and device for predicting the life of P91 pipe components with soft zones. Background Art

[0002] Due to its excellent high-temperature creep strength and good welding performance, P91 steel has been widely used in high-temperature and high-pressure components such as main steam pipes, high-temperature reheat steam pipes, and high-temperature headers in thermal power plants. However, under long-term operation conditions of high temperature and high pressure, P91 steel inevitably undergoes creep damage, thereby affecting its structural integrity and operation reliability. Creep failure is the main failure mode of high-temperature components made of P91 steel. In recent years, through hardness inspection, it has been found that many P91 thick-walled pipe components in power plants have low hardness even though the operation time is far from the end of their service life. In some units, low hardness has occurred just a few thousand hours after commissioning or even before commissioning. Low-hardness P91 has become a relatively common phenomenon both at home and abroad. Regarding the problem of low hardness of P91 pipe components, there have been many related studies at home and abroad. The Electric Power Research Institute (EPRI) of the United States first described this phenomenon of low hardness in 2011 and defined the low-hardness area as the soft zone (Soft-Zone). A large number of literature studies have shown that when the hardness value of P91 pipe components is relatively low, its mechanical properties decline significantly, and the remaining life will be significantly shortened, even only thousands of hours left, which will bring great potential safety hazards to the safe operation of the unit.

[0003] Currently, when many power plants find low hardness in P91 pipe components during maintenance, they often feel at a loss. They either directly replace the pipes or carry out life assessment work. However, on the one hand, when directly replacing pipe components, power plants generally have insufficient spare parts, and the cycle of reordering and manufacturing is relatively long, which will seriously affect the power generation time of the unit and the economy is poor. More importantly, this method is a bit blind. The main reason for the low hardness of P91 pipe components is improper heat treatment process during manufacturing, welding, and heat treatment. The hardness reduction caused by this improper heat treatment often has a certain depth. When the depth is relatively shallow, P91 thick-walled pipe components still have reliable safety performance within a certain service life, and directly replacing the pipe components will cause unnecessary waste. On the other hand, existing life prediction methods need to cut pipe samples according to traditional test methods, that is, cut a pipe section sufficient to complete performance tests from the pipe component, and conduct long-term creep rupture tests to obtain relevant test data. This method has a relatively long test cycle, which will also affect the power generation time of the unit, the economy is not high, and the test conditions cannot accurately simulate the complex working conditions of the pipe component operation.

[0004] Therefore, how to conveniently and accurately predict the remaining life of P91 pipe components with soft zones to ensure the reliability of their safe operation is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a method and device for predicting the life of P91 pipe fittings with soft zones, which can quickly and accurately predict the remaining life of P91 pipe fittings with soft zones, without the need for on-site pipe cutting, is easy to operate, and can avoid economic losses caused by blind pipe replacement or pipe cutting for sampling.

[0006] An embodiment of this application provides a method for predicting the life of P91 pipe fittings with soft zones. The life prediction method includes:

[0007] Conduct surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting;

[0008] Conduct micro-damage sampling tests within the soft zone range of the target pipe fitting to determine the soft zone depth value and the allowable stress value of the soft zone material of the target pipe fitting;

[0009] Establish a finite element model of the target pipe fitting based on the pipe fitting parameters, the soft zone range, and the soft zone depth value of the target pipe fitting;

[0010] Conduct numerical simulation in the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting;

[0011] Determine whether the soft zone meets the strength check condition in the elastic stage based on the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material;

[0012] If it meets the condition, conduct numerical simulation in the creep stage on the finite element model, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage; where the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state that meets the strength check condition due to stress redistribution occurring during the creep stage;

[0013] Determine the remaining life of the soft zone of the target pipe fitting based on the allowable creep relaxation time.

[0014] Further, conducting surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting includes:

[0015] Select position points on the surface of the target pipe fitting in a grid pattern, and conduct surface hardness detection on each position point;

[0016] If the hardness value of any position point is less than the preset hardness threshold, determine that this position point is a soft zone position point;

[0017] Determine the soft zone range of the target pipe fitting according to the detected multiple soft zone position points.

[0018] Further, conduct a micro-damage sampling test within the soft zone range of the target pipe fitting to determine the soft zone depth value and the allowable stress value of the soft zone material, including:

[0019] Conduct a small punch sampling test on the target position points within the soft zone range of the target pipe fitting, take out a small punch specimen, and perform surface hardness detection on the target position points after sampling;

[0020] If the surface hardness detection result shows that the target position point meets the hardness condition corresponding to the soft zone, conduct a small punch sampling test on the target position point again until the surface hardness detection result shows that the target position point does not meet the hardness condition corresponding to the soft zone, and then determine the soft zone depth value according to the depth value corresponding to the target position point;

[0021] Conduct a tensile test on each obtained small punch specimen respectively to determine the yield strength of each small punch specimen;

[0022] Determine the allowable stress value of the soft zone material according to the yield strength corresponding to each small punch specimen.

[0023] Further, the surface hardness detection for any position point includes:

[0024] Use a Leeb hardness tester and a Brinell hardness tester to detect the surface hardness of the same area on the target pipe fitting respectively, and obtain the Leeb hardness value and the Brinell hardness value of this area;

[0025] Determine the hardness calibration deviation as the difference between the Leeb hardness value and the Brinell hardness value of this area;

[0026] Use a Leeb hardness tester to conduct surface hardness detection on any position point, and determine the hardness value after calibration of this position point as the sum of the Leeb hardness value of this position point and the hardness calibration deviation.

[0027] Further, determine whether the soft zone meets the strength calibration condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material, including:

[0028] Compare the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material;

[0029] If the maximum principal stress value corresponding to the soft zone depth value is less than the allowable stress value of the soft zone material, determine that the soft zone meets the strength calibration condition in the elastic stage.

[0030] Further, perform a numerical simulation of the creep stage on the finite element model, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage, including:

[0031] Take the maximum principal stress on the inner wall of the target pipe fitting as the initial loading stress, select a creep numerical model, and perform a numerical simulation of the creep stage on the finite element model to obtain the inner wall stress redistribution process occurring during the creep stage; wherein, the maximum principal stress on the inner wall is obtained through the numerical simulation of the elastic stage;

[0032] According to the soft zone depth value, determine the change of the maximum principal stress value corresponding to the depth where the soft zone depth value is located from the inner wall stress redistribution process;

[0033] When the difference between the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material is less than a preset threshold, determine that the soft zone reaches a critical state that meets the strength check condition, and obtain the allowable creep relaxation time.

[0034] Further, determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time, including:

[0035] Determine the difference between the allowable creep relaxation time and the unit operation time as the remaining life of the soft zone.

[0036] The embodiment of the present application also provides a life prediction device for a P91 pipe fitting with a soft zone, and the life prediction device includes:

[0037] A detection module, configured to perform surface hardness detection on a target pipe fitting to determine the soft zone range of the target pipe fitting;

[0038] A test module, configured to perform a micro-damage sampling test in the soft zone range of the target pipe fitting to determine the soft zone depth value and the allowable stress value of the soft zone material of the target pipe fitting;

[0039] A model establishment module, configured to establish a finite element model of the target pipe fitting according to the pipe fitting parameters, the soft zone range, and the soft zone depth value of the target pipe fitting;

[0040] A numerical simulation module, configured to perform a numerical simulation of the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting;

[0041] A judgment module, configured to determine whether the soft zone meets the strength check condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material;

[0042] The numerical simulation module is further configured to, when the strength check condition is satisfied, perform numerical simulation on the finite element model in the creep stage, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage; wherein, the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state that meets the strength check condition due to the stress redistribution occurring in the creep stage.

[0043] The determination module is configured to determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time.

[0044] An embodiment of the present application further provides an electronic device, including: a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the electronic device runs, the processor communicates with the memory through the bus. When the machine-readable instructions are executed by the processor, the steps of the life prediction method for the P91 pipe fitting with a soft zone as described above are executed.

[0045] An embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, the steps of the life prediction method for the P91 pipe fitting with a soft zone as described above are executed.

[0046] A life prediction method and device for a P91 pipe fitting with a soft zone provided by an embodiment of the present application. First, the soft zone range of the pipe fitting can be accurately obtained through hardness detection, and the mechanical properties such as the soft zone depth value and the allowable stress value of the soft zone material can be accurately obtained through a micro-damage sampling test. Among them, the micro-damage sampling test has little damage to the pipe fitting, does not require pipe cutting, is easy to operate, and avoids the economic loss caused by pipe cutting for sampling. Secondly, through two-stage numerical simulation, the stress redistribution state generated by the soft zone due to creep relaxation can be accurately obtained. According to the strength theory, the concept of the allowable creep relaxation time is defined, and then the remaining life of the soft zone when it reaches the yield condition is determined, so as to realize the rapid and accurate prediction of the remaining life of the P91 pipe fitting with a soft zone. Through the remaining life of the soft zone, it can be more accurately determined whether to replace the pipe fitting and when to replace the pipe fitting, avoiding the economic loss caused by blindly replacing the pipe.

[0047] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specific preferred embodiments are given in conjunction with the accompanying drawings and are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0049] Figure 1 It shows a flowchart of a method for predicting the life of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0050] Figure 2 It shows a schematic diagram of the distribution of the soft zone and sampling positions of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0051] Figure 3(a) shows a schematic cross-sectional view of a small punch specimen of the soft zone of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0052] Figure 3(b) shows a schematic longitudinal sectional view of the soft zone of a small punch specimen of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0053] Figure 3(c) is a schematic diagram of the maximum depth of the sampling position of the small punch of the soft zone of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0054] Figure 4 It shows a schematic diagram of a finite element model and a meshing effect diagram provided by an embodiment of the present application;

[0055] Figure 5 It shows an effect diagram after welding repair of the sampling position of the small punch of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0056] Figure 6 It shows a schematic structural diagram of a device for predicting the life of a P91 pipe fitting with a soft zone provided by an embodiment of the present application;

[0057] Figure 7 It shows a schematic structural diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only some of the embodiments of this application, rather than all of them. The components of the embodiments of this application usually described and illustrated in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, every other embodiment obtained by those skilled in the art without creative efforts belongs to the scope of protection of this application.

[0059] First, the applicable application scenarios of this application will be introduced. This application can be applied to the technical field of pipe component life prediction, and more specifically to the technical field of life assessment of P91 steel thick-walled pipe components in the power industry. It should be understood that the life prediction method provided in this application is not limited to steel pipes made of P91 material, and other steel pipes with similar properties are also applicable.

[0060] Through research, it has been found that due to its excellent high-temperature creep strength and good welding performance, P91 steel has been widely used in high-temperature and high-pressure components such as main steam pipes, high-temperature reheat steam pipes, and high-temperature headers in thermal power plants. However, under long-term high-temperature and high-pressure operating conditions, P91 steel inevitably undergoes creep damage, thereby affecting its structural integrity and operating reliability. Creep failure is the main failure mode of high-temperature components made of P91 steel. In recent years, through hardness inspection, it has been found that many P91 thick-walled pipe components in power plants have shown low hardness even though their operating time is far from the end of their service life. In some units, low hardness has occurred just a few thousand hours after startup or even before startup. Low-hardness P91 has become a relatively common phenomenon both at home and abroad. Regarding the problem of low hardness of P91 pipe components, there have been many relevant studies at home and abroad. The Electric Power Research Institute (EPRI) in the United States first described this phenomenon of low hardness in 2011 and defined the low-hardness area as the Soft-Zone. A large number of literature studies have shown that when the hardness value of P91 pipe components is relatively low, its various mechanical properties decline significantly, and the remaining life will be significantly shortened, even only thousands of hours left, which will pose a huge hidden danger to the safe operation of the unit.

[0061] At present, when many power plants find that P91 pipe fittings have low hardness during maintenance, they often seem helpless. They either replace the pipe directly or carry out life assessment. However, on the one hand, when directly replacing pipe fittings, the spare parts of the power plant are generally insufficient, and the re-ordering and production cycle is relatively long, which will seriously affect the power generation time of the unit and have poor economic efficiency. More importantly, this method is slightly blind. The reason for the low hardness of P91 pipe fittings is mainly due to improper heat treatment process during manufacturing, welding and heat treatment. The low hardness caused by improper heat treatment often has a certain depth. When the depth is shallow, P91 thick-walled pipe fittings still have reliable safety performance within a certain service life. Directly replacing pipe fittings will cause unnecessary waste. On the other hand, the existing life prediction method needs to cut the pipe sampling according to the traditional test method, that is, cut a pipe section from the pipe fitting that is sufficient to complete the performance test, and conduct a long creep endurance test to obtain relevant test data. The test cycle of this method is relatively long, which will also affect the power generation time of the unit, and the economy is not high. Moreover, the test conditions cannot accurately simulate the complex working conditions of the pipe fittings.

[0062] Therefore, how to conveniently and accurately predict the remaining life of P91 pipe fittings containing soft areas to ensure the reliability of their safe operation is a technical problem that needs to be solved urgently.

[0063] Based on this, an embodiment of the present application provides a life prediction method for P91 pipe fittings containing soft areas, so as to achieve rapid and accurate prediction of the remaining life of P91 pipe fittings containing soft areas. It does not require on-site pipe cutting, is easy to operate, and avoids economic losses caused by blind pipe replacement or pipe cutting for sampling.

[0064] In one embodiment, the target pipe fitting is a P91 thick-walled pipe fitting of the main steam pipeline of a power plant, with a specification of Ф311×41mm, a main steam pressure of 25.35MPa in the pipeline, a temperature of 570°C, and a unit operation time of 6100 hours. During a certain unit overhaul, a hardness test was performed using a hardness tester, and it was found that the parent material area of ​​the straight pipe section of the main steam pipeline had a low hardness phenomenon (for example, the hardness was lower than a preset threshold). According to the prior art, it is necessary to conduct a life assessment on the straight pipe section or directly replace the pipe, but the power plant has no spare parts for replacement, and the traditional life assessment work cycle is relatively long. Both solutions are not in line with the actual production of the power plant.

[0065] The reason why the pipe has low hardness is suspected to be due to improper heat treatment during installation. The soft zone should have a certain depth. If the soft zone depth is small, the pipe may still have the ability to continue to serve. The following will introduce the specific steps for life prediction for the target pipe.

[0066] See also Figure 1 and Figure 2 , Figure 1The flowchart of a method for predicting the service life of a P91 pipe fitting with a soft zone provided by an embodiment of the present application Figure 2 The schematic diagram of the soft zone and sampling position distribution of a P91 pipe fitting with a soft zone provided by an embodiment of the present application. As Figure 1 shown in, the service life prediction method provided by the embodiment of the present application includes:

[0067] S101. Perform surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting.

[0068] In this step, a hardness tester can be used to perform surface hardness detection on the thick-walled pipe fitting (1). According to the measured hardness values of some regions, it is determined that the target pipe fitting has a low hardness phenomenon, that is, there is a soft zone. Then, through a more refined grid detection, the soft zone range of the target pipe fitting is determined.

[0069] In a possible implementation manner, step S101 may include:

[0070] Select position points on the surface of the target pipe fitting in a grid manner, and perform surface hardness detection on each position point; if the hardness value of any position point is less than the preset hardness threshold, determine that this position point is a soft zone position point; according to the detected multiple soft zone position points, determine the soft zone range of the target pipe fitting.

[0071] As Figure 2 shown in, increase the position points of hardness detection on the surface of the target pipe fitting. The detection points are arranged in a "grid" pattern with an appropriate spacing, and can be appropriately set and adjusted according to the specification size of the thick-walled pipe fitting to ensure the accurate division of the low hardness area; determine the specific position of the soft zone position point (low hardness point, that is, the position point with a hardness value lower than the preset threshold) according to the measured hardness value of each position point; then, the outermost soft zone position points can be connected to confirm the normal zone range (1-1) and soft zone range (1-2) of the target pipe fitting.

[0072] In addition, performing surface hardness detection on any position point includes:

[0073] Respectively use a Leeb hardness tester and a Brinell hardness tester to detect the surface hardness of the same region on the target pipe fitting to obtain the Leeb hardness value and Brinell hardness value of this region; determine the hardness calibration deviation as the difference between the Leeb hardness value and Brinell hardness value of this region; use a Leeb hardness tester to perform surface hardness detection on any position point, and determine the hardness value after calibration of this position point as the sum of the Leeb hardness value of this position point and the hardness calibration deviation.

[0074] In one example, a portable Leeb hardness tester is used to detect the surface hardness of the target pipe fitting (1). It is found that the measured hardness value in some areas is about 125 HBHLD. Through a portable Brinell hardness tester for hardness verification, the measured hardness value in this area is about 145 HBW. Then the hardness verification deviation ΔHB = 20 HB.

[0075] Here, in the embodiment of the present application, considering that the Leeb hardness tester is simple to measure but has poor accuracy, while the Brinell hardness tester is cumbersome to measure but has high accuracy. Therefore, after obtaining the hardness verification deviation, the subsequent steps can only use the Leeb hardness tester to detect the surface hardness at any position point, and then use the obtained hardness verification deviation for verification to obtain a more accurate verified hardness value.

[0076] S102. Conduct a micro-damage sampling test in the soft area range of the target pipe fitting to determine the soft area depth value of the target pipe fitting and the allowable stress value of the soft area material.

[0077] Here, the micro-damage sampling test is a sampling test with minimal or almost no damage to the material. The volume of the sampled specimen is small, and the damage to the original part is small. For example, small punch sampling test, nano-indentation, etc. By conducting a micro-damage sampling test in the soft area range of the target pipe fitting and performing mechanical property analysis on the sampled specimen and the pipe fitting after sampling, the soft area depth value of the target pipe fitting and the allowable stress value of the soft area material can be determined.

[0078] In a possible implementation manner, step S102 may include:

[0079] On the one hand: Conduct a small punch sampling test on the target position point in the soft area range of the target pipe fitting, take out a small punch specimen, and detect the surface hardness of the target position point after sampling; if the surface hardness detection result shows that the target position point meets the hardness condition corresponding to the soft area, conduct a small punch sampling test on the target position point again until the surface hardness detection result shows that the target position point does not meet the hardness condition corresponding to the soft area, and then determine the soft area depth value according to the depth value corresponding to the target position point.

[0080] The following takes the small punch sampling test as an example for illustration. Please refer to FIGS. 3(a), (b), and (c). FIG. 3(a) is a cross-sectional schematic diagram of a small punch specimen in the soft area of a P91 pipe fitting with a soft area provided by the embodiment of the present application. FIG. 3(b) is a longitudinal sectional schematic diagram of a small punch specimen in the soft area of a P91 pipe fitting with a soft area provided by the embodiment of the present application. FIG. 3(c) is a schematic diagram of the maximum depth of the small punch sampling position in the soft area of a P91 pipe fitting with a soft area provided by the embodiment of the present application.

[0081] Continue to refer to Figure 2, the center position of the soft zone range (1 - 2) is the target position point (1 - 3) for small punch sampling. Multiple small punch samplings can be carried out along the radial direction of the pipe wall. The sampling method refers to the requirements specified in GB / T 29459.1. The small punch specimen (2) taken is a sheet specimen, with the specimen diameter d ≈ 10 mm and the thickness δ ≈ 0.5 mm.

[0082] After each small punch sampling test, the hardness of the bottom of the small punch sampling position (1 - 3) can be detected and verified in the aforementioned manner. In this embodiment, when a total of 10 small punch samplings are carried out, a portable Leeb hardness tester is used for hardness detection. The detection result is 160 HBHLD. Since the hardness verification deviation ΔHB = 20 HB, it can be confirmed that the hardness value after verification is 180 HBW, which is greater than the preset hardness threshold of 170 HBW. Therefore, it does not meet the hardness condition corresponding to the soft zone. At this time, the sampling can be ended, and the depth value corresponding to the target position point is determined according to the distance between the target position point and the surface, that is, the soft zone depth value h = 11 mm.

[0083] It should be noted here that using the depth of the small punch sampling position (1 - 3) to reflect the depth of the entire low - hardness area (1 - 2) is mainly considered for the following two aspects: First, as mentioned above, the reason for the low hardness is improper heat treatment. Then, the degree of influence of the entire low - hardness area (1 - 2) by this improper heat treatment process is basically the same. Therefore, the depth of the low hardness generated is also basically the same. Second, the small punch sampling position (1 - 3) is located at the center of the low - hardness area (1 - 2), which can better represent the influence degree of the entire area.

[0084] On the other hand: Tensile tests are carried out separately for each small punch specimen obtained to determine the yield strength of each small punch specimen; according to the yield strength corresponding to each small punch specimen, the allowable stress value of the soft zone material is determined.

[0085] Corresponding to the above example, 10 specimens (2) are respectively subjected to small punch tensile tests according to the small punch test method specified in GB / T 29459.2, and the yield strength corresponding to each small punch specimen in the soft zone (1 - 2) is obtained. The smallest yield strength among them is determined as the minimum yield strength of the material in the high - temperature tensile test, Relmin 570℃ = 107.85 MPa.

[0086] Furthermore, according to the regulations on the value - taking of allowable stress in GB / T 16507.1, in this embodiment, the allowable stress value [σ] of the material in the soft zone (1 - 2) of the target pipe fitting (1) 570℃ should be equal to Relmin 570℃ / 1.5, that is, [σ] 570℃ = 71.90 MPa.

[0087] S103. Establish a finite element model of the target pipe fitting according to the pipe fitting parameters of the target pipe fitting, the soft zone range, and the soft zone depth value.

[0088] In this step, an existing finite element analysis software can be used to establish a finite element model of the target pipe fitting and perform mesh generation according to the pipe fitting parameters (including specifications, dimensions, etc.), the soft zone range, and the soft zone depth value of the target pipe fitting.

[0089] Please refer to Figure 4 , Figure 4 which is a finite element model and a mesh generation effect diagram provided by an embodiment of the present application. In the embodiment of the present application, the mesh element type can adopt a standard eight-node hexahedron element. In order to ensure the accuracy of the local stress value and strain gradient of the simulation calculation, the mesh is refined. In addition, since the elastic properties (elastic modulus, Poisson's ratio) of the material are independent of hardness, the materials in the normal region (1-1) and the soft region (1-2) have the same material properties. Referring to relevant materials, it can be known that at 570 °C, the elastic modulus E of P91 steel is 1.745×10 5 MPa, and the Poisson's ratio υ is 0.3. Corresponding parameter settings are made in the finite element analysis software to establish a finite element model of the target pipe fitting.

[0090] S104. Perform a numerical simulation in the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting.

[0091] Here, finite element analysis (FEA) has the advantages and characteristics of convenient and fast operation and saving test time, and has been widely applied in engineering practice. Commonly used finite element analysis software mainly includes ANSYS, ADINA / COMSOL, and MSC, etc. It has a rich element library and can simulate any complex geometric structure, reflecting subtle structural phenomena and differences between phenomena. At the same time, the finite element analysis software has a very rich model library, including creep damage constitutive models and judgment criteria for material failure, etc. Therefore, the finite element analysis software can be used as a numerical simulation software to simulate complex structural mechanics problems and has advantages in solving nonlinear problems such as the creep behavior of metal materials.

[0092] In this step, the elastic stage is an instantaneous stage when the target pipe fitting is stressed. Corresponding to the above example, through numerical simulation, it can be known that the maximum principal stress on the inner wall of the target pipe fitting (1) is the largest, denoted as σ maxDi = 84.63 MPa; the maximum principal stress value corresponding to the small punch sampling position (1-3), that is, the soft zone depth value h, is σ maxh = 63.36 MPa.

[0093] S105. Determine whether the soft zone meets the strength check condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material.

[0094] In this step, the strength check condition can be defined according to the strength theory. Specifically, compare the maximum principal stress value corresponding to the soft zone depth value with the allowable stress value of the soft zone material. If the maximum principal stress value corresponding to the soft zone depth value is less than the allowable stress value of the soft zone material, it is determined that the soft zone meets the strength check condition. If the maximum principal stress corresponding to the soft zone depth value is greater than or equal to the allowable stress value of the soft zone material, it is determined that the soft zone does not meet the strength check condition.

[0095] Corresponding to the above example, the maximum principal stress value at the soft zone depth value h of the small punch sampling position (1 - 3) is lower than the yield strength of the soft zone (1 - 2) material, that is, σ maxh <[σ] 570℃ . This means that although there is a soft zone in the target pipe fitting, due to the relatively shallow depth of the soft zone, its stress state still meets the strength check condition, and the maximum principal stress does not exceed the yield strength.

[0096] S106. If it meets, perform numerical simulation of the creep stage on the finite element model, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage.

[0097] In this step, the creep stage refers to the stage in which the deformation of the material gradually increases with time under constant stress and temperature. During the creep stage, due to creep relaxation, the internal stress of the thick - wall pipe fitting will redistribute, and the maximum principal stress value corresponding to the soft zone depth value will also change. By performing numerical simulation of the creep stage on the finite element model, the change process of the stress can be simulated, and then the change of the maximum principal stress value corresponding to the soft zone depth value can be observed.

[0098] The concept of the allowable creep relaxation time refers to the maximum time that the material can safely withstand creep and stress relaxation without failure under specific temperature and stress conditions. For the convenience of numerical simulation calculation, in the embodiments of the present application, the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state that meets the strength check condition due to the stress redistribution occurring in the creep stage.

[0099] In a possible implementation manner, step S106 may include:

[0100] S1061. Take the maximum principal stress on the inner wall of the target pipe fitting as the initial loading stress, select a creep numerical model, perform numerical simulation of the creep stage on the finite element model, and obtain the inner wall stress redistribution process occurring during the creep stage.

[0101] In this step, the maximum principal stress of the inner wall is obtained through numerical simulation in the elastic stage. Corresponding to the above example, taking σ maxDi = 84.63 MPa as the initial loading stress, and selecting the typical Norton model for the creep model. Referring to relevant materials, the Norton formula of P91 material at 570 °C is expressed as follows:

[0102]

[0103] After that, the numerical simulation in the creep stage is started through finite element analysis software to obtain the process of redistribution of the inner wall stress occurring in the creep stage.

[0104] S1062. According to the soft zone depth value, determine the change of the maximum principal stress value corresponding to the depth where the soft zone depth value is located from the inner wall stress redistribution process.

[0105] In the process of numerical simulation, according to the soft zone depth value, the change of the maximum principal stress value σ maxh corresponding to the specified depth can be determined from the inner wall stress redistribution process obtained by real-time simulation.

[0106] S1063. When the difference between the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material is less than the preset threshold, determine that the soft zone reaches the critical state satisfying the strength checking condition, and obtain the creep relaxation allowable time.

[0107] When the maximum principal stress value σ maxh corresponding to the soft zone depth value approaches the allowable stress value [σ] 570℃ of the soft zone material, that is, when the difference between the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material is less than the preset threshold, determine that the soft zone reaches the critical state satisfying the strength checking condition (if the maximum principal stress value continues to increase, it will exceed the allowable stress value and the soft zone no longer satisfies the strength checking condition). At this time, the creep analysis time step of the numerical simulation stops, and the creep analysis duration at this time is the creep relaxation allowable time.

[0108] Corresponding to the above example, through numerical simulation, it is found that when the creep analysis time is 5.2231E+08 S (145086 h), the maximum principal stress value σ maxh at the depth h of the small punch sampling position (1-3) is 71.82 MPa. At this time, σ maxh ≈ [σ] 570℃ , according to the strength theory, at this time the soft zone has reached the strength checking condition, and record the creep relaxation allowable time t = 145086 h.

[0109] S107. Determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time.

[0110] In this step, the difference between the allowable creep relaxation time and the unit operation time can be determined as the remaining life of the soft zone. In the embodiment of the present application, the remaining life refers to the life when the soft zone (1-2) reaches the critical state that meets the strength check condition due to the stress redistribution caused by creep relaxation. The calculation result belongs to a conservative estimate. When the unit operation time t0 = 6100h, the remaining life t r = t - t0, that is, 138986h.

[0111] If the determined remaining life of the soft zone is long, the target pipe fitting can continue to be used to reduce unnecessary losses; if the determined remaining life of the soft zone is short, the pipe fitting can be selected for replacement, and spare parts can be prepared in advance with reference to the remaining life of the soft zone to avoid delaying production.

[0112] Furthermore, in the embodiment of the present application, the sampling position (1-3) of the small punch should also be repaired by welding. The effect after welding is as Figure 5 shown.

[0113] In addition, after it is determined in step S105 that the soft zone does not meet the strength check condition in the elastic stage, information such as the determined soft zone range and soft zone depth value can be submitted to manual for further comprehensive judgment to determine whether to replace the pipe or continue to serve.

[0114] A life prediction method for a P91 pipe fitting with a soft zone provided by the embodiment of the present application. First, the soft zone range of the pipe fitting can be accurately obtained through hardness detection, and the mechanical properties such as the soft zone depth value and the allowable stress value of the soft zone material can be accurately obtained through the micro-damage sampling test. Among them, the micro-damage sampling test has little damage to the pipe fitting, does not require pipe cutting, is easy to operate, and avoids the economic loss caused by pipe cutting for sampling. Secondly, through two-stage numerical simulation, the stress redistribution state generated by the soft zone due to creep relaxation can be accurately obtained, the concept of the allowable creep relaxation time is defined according to the strength theory, and then the remaining life of the soft zone when it reaches the yield condition is determined, so as to realize the rapid and accurate prediction of the remaining life of the P91 pipe fitting with a soft zone. Through the remaining life of the soft zone, it can be more accurately determined whether to replace the pipe fitting and when to replace the pipe fitting, avoiding the economic loss caused by blindly replacing the pipe.

[0115] Please refer to Figure 6 , Figure 6 which is the structural schematic diagram of a life prediction device for a P91 pipe fitting with a soft zone provided by the embodiment of the present application. As Figure 6 shown in, the life prediction device 600 includes:

[0116] The detection module 610 is used to perform surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting;

[0117] The test module 620 is used to perform a micro-damage sampling test within the soft zone range of the target pipe fitting to determine the soft zone depth value of the target pipe fitting and the allowable stress value of the soft zone material;

[0118] The model establishment module 630 is used to establish a finite element model of the target pipe fitting according to the pipe fitting parameters, the soft zone range, and the soft zone depth value of the target pipe fitting;

[0119] The numerical simulation module 640 is used to perform numerical simulation in the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting;

[0120] The judgment module 650 is used to determine whether the soft zone meets the strength check condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material;

[0121] The numerical simulation module 640 is further used to perform numerical simulation in the creep stage on the finite element model when the strength check condition is met, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage; wherein, the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state that meets the strength check condition due to the stress redistribution occurring in the creep stage;

[0122] The determination module 660 is used to determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time.

[0123] Furthermore, when the detection module 610 is used to perform surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting, the detection module 610 is used for:

[0124] Select position points on the surface of the target pipe fitting in a grid pattern and perform surface hardness detection on each position point;

[0125] If the hardness value of any position point is less than the preset hardness threshold, determine that this position point is a soft zone position point;

[0126] Determine the soft zone range of the target pipe fitting according to the detected multiple soft zone position points.

[0127] Furthermore, when the test module 620 is used to perform a micro-damage sampling test within the soft zone range of the target pipe fitting to determine the soft zone depth value of the target pipe fitting and the allowable stress value of the soft zone material, the test module 620 is used for:

[0128] Conduct a small punch sampling test on the target position point in the soft area range of the target pipe fitting, take out a small punch sample, and perform surface hardness detection on the target position point after sampling;

[0129] If the surface hardness detection result shows that the target position point meets the hardness condition corresponding to the soft area, conduct a small punch sampling test on the target position point again until the surface hardness detection result shows that the target position point does not meet the hardness condition corresponding to the soft area, and then determine the soft area depth value according to the depth value corresponding to the target position point;

[0130] Conduct a tensile test on each obtained small punch sample respectively to determine the yield strength of each small punch sample;

[0131] Determine the allowable stress value of the soft area material according to the yield strength corresponding to each small punch sample.

[0132] Further, when the detection module 610 is used to perform surface hardness detection on any position point, the detection module 610 is used for:

[0133] Detect the surface hardness of the same area on the target pipe fitting using a Leeb hardness tester and a Brinell hardness tester respectively to obtain the Leeb hardness value and the Brinell hardness value of this area;

[0134] Determine the hardness verification deviation as the difference between the Leeb hardness value and the Brinell hardness value of this area;

[0135] Use a Leeb hardness tester to perform surface hardness detection on any position point, and determine the hardness value after verification of this position point as the sum of the Leeb hardness value of this position point and the hardness verification deviation.

[0136] Further, when the judgment module 650 is used to determine whether the soft area meets the strength verification condition in the elastic stage according to the maximum principal stress value corresponding to the soft area depth value and the allowable stress value of the soft area material, the judgment module 650 is used for:

[0137] Compare the maximum principal stress value corresponding to the soft area depth value and the allowable stress value of the soft area material;

[0138] If the maximum principal stress value corresponding to the soft area depth value is less than the allowable stress value of the soft area material, determine that the soft area meets the strength verification condition in the elastic stage.

[0139] Further, when the numerical simulation module 640 is used to perform numerical simulation on the finite element model in the creep stage and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage, the numerical simulation module 640 is used for:

[0140] Taking the maximum principal stress on the inner wall of the target pipe fitting as the initial loading stress, selecting a creep numerical model, performing numerical simulation on the finite element model in the creep stage, and obtaining the inner wall stress redistribution process occurring during the creep stage; wherein, the maximum principal stress on the inner wall is obtained through numerical simulation in the elastic stage;

[0141] According to the soft zone depth value, determine the change of the maximum principal stress value corresponding to the depth where the soft zone depth value is located from the inner wall stress redistribution process;

[0142] When the difference between the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material is less than a preset threshold, determine that the soft zone reaches a critical state satisfying the strength check condition, and obtain the allowable creep relaxation time.

[0143] Further, when the determination module 660 is used to determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time, the determination module 660 is used for:

[0144] Determine the difference between the allowable creep relaxation time and the unit operation time as the remaining life of the soft zone.

[0145] Refer to Figure 7 , Figure 7 which is a schematic structural diagram of an electronic device provided by an embodiment of the present application. As Figure 7 shown in

[0146] the electronic device 700 includes a processor 710, a memory 720, and a bus 730. Figure 1 The memory 720 stores machine-readable instructions executable by the processor 710. When the electronic device 700 runs, the processor 710 communicates with the memory 720 through the bus 730. When the machine-readable instructions are executed by the processor 710, the steps of the life prediction method of the P91 pipe fitting with a soft zone in the method embodiment as described above can be executed. The specific implementation manner can refer to the method embodiment and will not be elaborated here.

[0147] An embodiment of the present application further provides a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is run by a processor, it can execute as described above Figure 1The steps of the method for predicting the lifespan of the pipe fitting with a soft zone P91 in the method embodiments shown can be specifically implemented as seen in the method embodiments and will not be elaborated here.

[0148] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described systems, devices, and units can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated here.

[0149] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division, and there can be other division methods in actual implementation. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some communication interfaces. The indirect coupling or communication connection of the devices or units can be in an electrical, mechanical, or other form.

[0150] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0151] In addition, in each embodiment of the present application, the functional units can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit.

[0152] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs that can store program codes.

[0153] Finally, it should be noted that the above-described embodiments are only specific implementation manners of the present application, used to illustrate the technical solutions of the present application, rather than limiting it. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any technician familiar with the technical field of the present application can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for predicting the service life of P91 pipe fittings with soft zones, characterized in that, The described life prediction method includes: Performing surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting; Conducting a micro-damage sampling test within the soft zone range of the target pipe fitting to determine the soft zone depth value of the target pipe fitting and the allowable stress value of the soft zone material; Establishing a finite element model of the target pipe fitting based on the pipe fitting parameters, the soft zone range, and the soft zone depth value of the target pipe fitting; Performing numerical simulation in the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting; Determining whether the soft zone meets the strength check condition in the elastic stage based on the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material; If it meets the condition, performing numerical simulation in the creep stage on the finite element model, and determining the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage; wherein, the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state that meets the strength check condition due to the stress redistribution occurring during the creep stage; Determining the remaining life of the soft zone of the target pipe fitting based on the allowable creep relaxation time.

2. The life prediction method according to claim 1, characterized in that Performing surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting, including: Selecting position points on the surface of the target pipe fitting in a grid pattern and performing surface hardness detection on each position point; If the hardness value of any position point is less than the preset hardness threshold, determining that this position point is a soft zone position point; Determining the soft zone range of the target pipe fitting based on the detected multiple soft zone position points.

3. The life prediction method according to claim 2, wherein Conducting a micro-damage sampling test within the soft zone range of the target pipe fitting to determine the soft zone depth value of the target pipe fitting and the allowable stress value of the soft zone material, including: Performing a small punch sampling test on a target position point within the soft zone range of the target pipe fitting, taking out a small punch specimen, and performing surface hardness detection on the target position point after sampling; If the result of the surface hardness detection is that the target position point meets the hardness condition corresponding to the soft zone, performing a small punch sampling test on the target position point again until the result of the surface hardness detection is that the target position point does not meet the hardness condition corresponding to the soft zone, and determining the soft zone depth value according to the depth value corresponding to the target position point; Conducting a tensile test on each obtained small punch specimen respectively to determine the yield strength of each small punch specimen; Determining the allowable stress value of the soft zone material based on the yield strength corresponding to each small punch specimen.

4. The life prediction method according to claim 2 or 3, characterized in that Performing surface hardness detection on any position point, including: Respectively using a Leeb hardness tester and a Brinell hardness tester to detect the surface hardness of the same area on the target pipe fitting to obtain the Leeb hardness value and the Brinell hardness value of this area; Determining the hardness check deviation as the difference between the Leeb hardness value and the Brinell hardness value of this area; Using a Leeb hardness tester to perform surface hardness detection on any position point, and determining the hardness value after check of this position point as the sum of the Leeb hardness value of this position point and the hardness check deviation.

5. The life prediction method according to claim 1, characterized in that Determine whether the soft zone meets the strength check condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material, including: Compare the maximum principal stress value corresponding to the soft zone depth value with the allowable stress value of the soft zone material; If the maximum principal stress value corresponding to the soft zone depth value is less than the allowable stress value of the soft zone material, it is determined that the soft zone meets the strength check condition in the elastic stage.

6. The life prediction method according to claim 1, wherein Conduct a numerical simulation of the creep stage on the finite element model, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage, including: Use the maximum principal stress on the inner wall of the target pipe fitting as the initial loading stress, select a creep numerical model, and conduct a numerical simulation of the creep stage on the finite element model to obtain the inner wall stress redistribution process occurring during the creep stage; wherein, the maximum principal stress on the inner wall is obtained through the numerical simulation of the elastic stage; According to the soft zone depth value, determine the change of the maximum principal stress value corresponding to the depth where the soft zone depth value is located from the inner wall stress redistribution process; When the difference between the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material is less than the preset threshold, it is determined that the soft zone reaches the critical state of meeting the strength check condition, and the allowable creep relaxation time is obtained.

7. The life prediction method according to claim 1, characterized in that Determine the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time, including: Determine the difference between the allowable creep relaxation time and the unit operation time as the remaining life of the soft zone.

8. A life prediction device for P91 pipe fittings with soft zones, characterized in that, The life prediction device includes: A detection module for performing surface hardness detection on the target pipe fitting to determine the soft zone range of the target pipe fitting; An experiment module for conducting a micro-damage sampling experiment in the soft zone range of the target pipe fitting to determine the soft zone depth value and the allowable stress value of the soft zone material of the target pipe fitting; A model establishment module for establishing a finite element model of the target pipe fitting according to the pipe fitting parameters, the soft zone range, and the soft zone depth value of the target pipe fitting; A numerical simulation module for performing a numerical simulation of the elastic stage on the finite element model to determine the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting; A judgment module for determining whether the soft zone meets the strength check condition in the elastic stage according to the maximum principal stress value corresponding to the soft zone depth value and the allowable stress value of the soft zone material; The numerical simulation module is further configured to, when the strength check condition is met, perform a numerical simulation of the creep stage on the finite element model, and determine the allowable creep relaxation time of the target pipe fitting by analyzing the change of the maximum principal stress value corresponding to the soft zone depth value in the target pipe fitting during the creep stage; wherein, the allowable creep relaxation time refers to the service time when the soft zone reaches the critical state of meeting the strength check condition due to the stress redistribution occurring during the creep stage; A determination module for determining the remaining life of the soft zone of the target pipe fitting according to the allowable creep relaxation time.

9. An electronic device, characterized in that, including: A processor, a memory, and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the memory through the bus, and when the machine-readable instructions are run by the processor, the steps of the life prediction method of the P91 pipe fitting with a soft zone as described in any one of claims 1 to 7 are executed.

10. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when the computer program is run by a processor, the steps of the life prediction method of the P91 pipe fitting with a soft zone as described in any one of claims 1 to 7 are executed.

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