A method for acceptance of manufacturing defects in a high-temperature service welded component

Abstract

The present application relates to the technical field of safety evaluation or nondestructive testing acceptance of welding structure containing defects, and provides a manufacturing defect acceptance method of high-temperature service welding component, which comprises the following steps: calibrating parameters of a creep constitutive model by testing the creep performance of a defect-free material / structure; performing regular processing on the defects, and constructing a finite element model of the structure containing defects by using a finite element tool; obtaining the creep life under different defects by controlling the defect variables, performing normalization processing on the creep life under different defect characteristics, and obtaining a mapping relationship between the defect characteristics and the creep life by regression analysis; determining the defect diameter acceptance limit value under a specific plate thickness, and passing the acceptance if the defect diameter is within the acceptance limit value. The acceptance limit value of the structure containing defects is determined by the weakening degree of the creep life, the safety operation of the structure during the service period is determined, theoretical support is provided for the nondestructive testing acceptance of nuclear power or chemical equipment containing defects, and the acceptance limit value of the structure containing defects is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of safety evaluation or nondestructive testing acceptance of high-temperature service equipment such as nuclear power and petroleum chemical industry containing defects, and particularly relates to a manufacturing defect acceptance method of high-temperature service welding component. BACKGROUND

[0002] The fourth generation nuclear island equipment represented by fast reactors has key components that are long-term served in extreme environments such as high temperature and high stress, and faces severe creep failure challenges. At the same time, with the development of large-scale nuclear power units, welding as a core manufacturing process is difficult to completely avoid the generation of defects such as pores, inclusions and incomplete fusion when manufacturing super-large size complex structures, and these defects will significantly reduce the performance of the joint and are a potential threat to the structure failure.

[0003] Currently, the selection and development of acceptance standards for high-temperature components containing defects still rely on international standards such as ASME and RCC, but these standards are based on foreign material system and process basis. In recent years, China's welding technology has made breakthroughs in inverter welding machines, laser welding and high-end welding materials, and the welding process level has also steadily improved. Existing nondestructive testing technologies are also developing rapidly, such as intelligent precise identification, micro-nano scale detection, multi-source fusion imaging and cross-scale quantitative evaluation technologies have made breakthroughs, and the defect detection scale and precision are gradually optimized. If the foreign defect acceptance method of ASME and the like is continued to be used, the applicability of the defect acceptance criteria and the accuracy of the defect acceptance results are both lack of verification. Therefore, it is urgent to establish a defect acceptance standard and evaluation method with independent intellectual property rights in line with the characteristics of China's nuclear power equipment to ensure the safe and reliable operation of nuclear power equipment.

[0004] The defect acceptance limit in existing standards such as ASME BPVC Section XI is only for in-service components, and for defects exceeding the limit, the fracture mechanics method is usually used for evaluation, which causes great conservatism, resulting in material waste and increased maintenance cost. In addition, the influence of creep is not considered in the defect safety evaluation process, often leading to overly conservative or unsafe evaluation results, and thus causing unplanned shutdown or potentially catastrophic accidents. Existing research such as BS 7910: 2019 Appendix P attempts to introduce the creep fracture mechanics parameter C* integral, but it is only applicable to the steady-state creep stage, and no quantitative correlation between defect geometry and remaining life is established. The complexity of the morphology of the welding defects and the nonlinear evolution of the material creep damage in actual engineering limit the applicability of existing methods in key structures such as nuclear island main welds and hydrogen reactors. More importantly, the existing non-destructive testing acceptance limit does not consider the correlation between defect characteristics and life, and establishing such a mapping relationship is crucial for judging the safety of manufacturing defects and then carrying out manufacturing defect acceptance. Existing research has shown that the size, shape, orientation, and other geometric characteristics of defects significantly affect the fatigue life of materials; and the type of defect also affects the degradation mechanism of material performance and the life of the component. Therefore, the existing standards lack a pre-service acceptance method for high-temperature service components with defects, and the existing evaluation method for high-temperature components with defects is not accurate and cannot directly establish a mapping relationship between defect characteristics and creep life.

[0005] Therefore, there is an urgent need for a defect acceptance method based on "defect characteristics-creep life" to determine the defect acceptance limit. SUMMARY

[0006] To solve the above technical problems, the present application provides a manufacturing defect acceptance method for high-temperature service welded components, which comprises:

[0007] Step (1) calibrate the parameters of the creep constitutive model by testing the creep performance of the defect-free material / structure;

[0008] Step (2) regularize the defect and use finite element tools to build a finite element model of the structure containing the defect;

[0009] Step (3) based on the finite element model of the structure containing the defect, control the defect variable to obtain the creep life under different defects, normalize the creep life t under different defect characteristics to obtain the weakening degree of the creep life t , and perform regression analysis to obtain the mapping relationship between the defect characteristics and the creep life;

[0010] Step (4) determine the defect diameter acceptance limit under a specific plate thickness T based on the mapping relationship between the defect characteristics and the creep life , if the defect diameter acceptance limit The inside is accepted by acceptance.

[0011] Further, the specific steps of step (1) are:

[0012] The sample is cut from the defect-free material / structure by wire cutting technology to minimize processing residual stress and surface damage; by high temperature / room temperature creep tensile test on the sample, the creep life and steady-state creep rate of the sample under different stress conditions are obtained, and the creep curve and strain rate curve under different stress are obtained,

[0013] The creep constitutive model includes:

[0014] The creep strain rate equation is: exp (Formula 1)

[0015] Wherein, is the creep strain rate tensor;

[0016] is the damage parameter, (Formula 2);

[0017] , is a material-related parameter; A and n are material constants; n reflects the stress sensitivity, the greater n, the more significant the influence of stress on creep strain rate; is the equivalent stress; p is the creep constitutive model parameter, and e represents the exponential function with e as the base;

[0018] Assume that the damage variable parameter of the material / structure in the creep steady-state stage =0, at this time exp(0)=1, (Formula 1) is simplified and logarithm is taken as:

[0019] (Formula 3)

[0020] According to the test data, the material constants A and n in (Formula 3) are fitted:

[0021] Integrate (Formula 2), take the initial time =0, and the initial damage parameter =0, to obtain the damage evolution equation:

[0022] (Formula 4)

[0023] The creep life of the defect-free structure is simulated as:

[0024] (Formula 5)

[0025] ​Taking logarithm of (formula 5) and fitting material parameters M, p according to uniaxial creep rupture data, (formula 4) is brought into (formula 2) to obtain a creep strain-time curve, the expression of which is as follows:

[0026] (formula 6)

[0027] The most suitable q value under each stress level is determined by (formula 6), and constants A, n, and are obtained.

[0028] Further, the content of the step (2) of regularizing the defects includes: the size of a single defect is the size of a rectangle or a square completely containing the area of the defect, and the shape of the defect is equivalent to an ellipse or a circle.

[0029] When analyzing the influence of different defect sizes, the ratio D / T of the diameter of the defect to the thickness of the plate is taken as a parameter for describing the size of the defect; when analyzing the influence of different defect positions, the ratio L / T of the defect position to the thickness of the plate is taken as a parameter for describing the position of the defect; when analyzing the influence of different defect shapes, the ratio a / c of the long axis of the defect to the short axis is taken as a parameter for describing the shape of the defect; and when analyzing the influence of different defect types, the ratio E d / E m of the elastic modulus of the defect to the elastic modulus of the base material is taken as a parameter for describing the type of the defect.

[0030] Further, in the step (2), the power-law model in the finite element analysis software is taken as the creep constitutive model, and a finite element model of the structure containing defects is constructed according to the calibrated creep constitutive parameters and a self-defined subroutine defining the coupling relationship between the damage evolution equation and the creep constitutive. The self-defined subroutine accurately describes the progressive damage behavior of the material / structure under high temperature conditions.

[0031] Further, the self-defined subroutine is developed by using Fortran language.

[0032] The self-defined subroutine detects the load state. If the unit bears pure hydrostatic pressure (the stress deviator is a zero matrix), it is determined that no creep deformation occurs and the subsequent calculation is terminated, so as to avoid numerical singularity. When a non-hydrostatic pressure load is detected, the creep strain increment is calculated based on the stress deviator, and the damage parameter is updated by coupling the damage evolution equation, and finally the quantitative prediction of the creep life is realized through the cumulative damage parameter, which not only ensures the numerical stability, but also realizes the continuous calculation process from stress analysis to life evaluation.

[0033] In the simulation process, when the damage variable of a specific Gaussian integral point on the outer surface of the sample reaches the critical threshold Dmax and reaches the damage critical value, the total time at this time is considered as the creep life.

[0034] Further, the step (3) is specifically as follows:

[0035] In the study of the influence of defect size, the defect is idealized as a sphere, the defect type is selected as a pore defect, and multiple models are established for analysis by taking the ratio of defect diameter to plate thickness D / T, wherein the plate thickness T is kept unchanged, the defect is placed at the geometric center position, and the creep life of the structure containing the defect is solved;

[0036] In the study of the influence of defect position, the defect is idealized as a sphere, the defect type is selected as a pore defect, and multiple models are established for analysis by taking the ratio of defect position to plate thickness L / T, wherein the plate thickness T is kept unchanged, the defect diameter is kept consistent, and the creep life of the structure containing the defect is solved;

[0037] In the study of the influence of defect shape, the defect is idealized as an ellipsoid and placed at the geometric center of the unit body, multiple models are established for analysis by taking the ratio of defect long axis to short axis a / c, wherein the ellipsoid short axis c is kept unchanged and the long axis size a is changed, and the creep life of the structure containing the defect is solved;

[0038] Further, the step (3) is specifically as follows:

[0039] The creep life t under different defect characteristics is normalized to obtain the weakening degree of the creep life t , and the expression is:

[0040]

[0041] , wherein is the creep life of the defect-free structure obtained by finite element / experiment; t is the creep life of the structure containing the defect; h , and g are coefficients;

[0042] is the ratio of the defect elastic modulus to the matrix elastic modulus calculated by test;

[0043] is the ratio of the defect diameter to the plate thickness calculated by test;

[0044] is the ratio of the defect position to the plate thickness calculated by test;

[0045] is the ratio of the defect long axis to the short axis calculated by test;

[0046] Through regression analysis of the creep life under different defect characteristics, the following is obtained: h , andg If the value of the defect characteristic is less than the value of the defect acceptance limit, then the mapping relationship between the defect characteristic and the creep life is:

[0047] .

[0048] The present application has the following beneficial effects:

[0049] (1) The present application determines the defect acceptance limit under a specific plate thickness based on the mapping relationship between the defect characteristic and the creep life. The acceptance limit of the defect-containing structure is determined by the degree of weakening of the creep life, so as to determine whether the structure is safe during service, thereby providing theoretical and technical support for non-destructive testing acceptance of nuclear power or chemical defect-containing equipment, and realizing optimization of the acceptance limit of the defect-containing structure;

[0050] (2) The present application overcomes the shortcomings of the existing non-destructive testing acceptance standard in China, and can quickly determine whether the defect is safe according to the defect acceptance limit, thereby improving the acceptance efficiency of the defect-containing structure and ensuring the long-term service safety of the defect-containing structure;

[0051] (3) The present application can be applied to optimize the non-destructive testing acceptance standard of the defect-containing structure, and has important significance for establishing a self-defect acceptance standard and design evaluation system that meets the characteristics of nuclear power equipment in China. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 is the acceptance flowchart of the present application.

[0053] Figure 2 is the result graph of the influence law of the defect characteristic (size) on the creep life and the parameter normalization processing in the present application.

[0054] Figure 3 is the result graph of the influence law of the defect characteristic (position) on the creep life and the parameter normalization processing in the present application.

[0055] Figure 4 is the result graph of the influence law of the defect characteristic (shape: aspect ratio) on the creep life and the parameter normalization processing in the present application.

[0056] Figure 5 is the result graph of the mapping relationship between the defect characteristic (size) and the creep life obtained by regression analysis in the present application.

[0057] Figure 6 is the defect diameter acceptance limit under a specific plate thickness T determined based on the mapping relationship between the defect characteristic and the creep life is a schematic view. DETAILED DESCRIPTION

[0058] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. However, these embodiments are not intended to limit the present invention. Any similar structures and similar variations of the present invention should be included in the protection scope of the present invention. The commas in the present invention all indicate the relationship between and. The English letters in the present invention are case-sensitive.

[0059] This embodiment uses 316H stainless steel, a typical material for nuclear power equipment, as an example to illustrate the manufacturing defect acceptance method of this scheme.

[0060] like Figure 1 As shown, the defect acceptance method includes:

[0061] S1, the parameters of the creep constitutive model are calibrated by testing the creep performance of defect-free materials / structures (316H stainless steel);

[0062] Wire cutting technology was used to cut samples from 316H stainless steel to minimize residual stress and surface damage during processing. High-temperature / room-temperature creep tensile tests were conducted on 316H material / structures according to the national standard GB / T 2039-2024 "Metallic Materials - Uniaxial Tensile Creep Test Method". The test was carried out under a constant temperature of 580℃, with tensile loads of 180 MPa, 190 MPa and 200 MPa applied respectively. The creep life and steady-state creep rate of the samples under different stress conditions were obtained, and creep curves and strain rate curves under different stresses were acquired.

[0063] Creep constitutive models include:

[0064] Creep strain rate equation: exp (Equation 1)

[0065] in, For creep strain rate tensor;

[0066] For damage parameters, (Equation 2);

[0067] , These are material-related parameters; A and n are material constants; n reflects the degree of stress sensitivity, and the larger n is, the more significant the effect of stress on creep strain rate. It is the equivalent stress; its value can be taken as the stress load applied in the creep test. p Here are the parameters for the creep constitutive model, and e represents an exponential function with base e.

[0068] Assuming the damage parameters of the material / structure during the creep steady-state stage =0, at this time exp(0) =1, and the logarithm of (Equation 1) after simplification is:

[0069] (Equation 3)

[0070] The material constants A are fitted based on experimental data using equation (3).

[0071] Integrating (Equation 2), taking the initial time... =0, initial damage parameter =0, the damage evolution equation is obtained as follows:

[0072] (Equation 4)

[0073] Simulating the creep life of a defect-free structure for:

[0074] (Equation 5)

[0075] Taking the logarithm of (Equation 5), and fitting the material parameters M and p based on the uniaxial creep fracture data, substituting (Equation 4) into (Equation 2) yields the creep strain-time curve, the expression of which is:

[0076] (Equation 6)

[0077] The optimal q value for each stress level is determined using Equation 6, and the constants A, n, and ... are obtained. and ;

[0078] S2, the defects are regularized and a finite element model of the structure with defects is constructed using finite element tools;

[0079] The content of the standardization of defects includes: the size of a single defect is the size of a rectangle or square that completely contains the area of ​​the defect, and the shape of the defect is equivalent to an ellipse or a circle;

[0080] When analyzing the influence of different defect sizes, the ratio of defect diameter to plate thickness (D / T) is used as a parameter describing defect size; when analyzing the influence of different defect locations, the ratio of defect location to plate thickness (L / T) is used as a parameter describing defect location; when analyzing the influence of different defect shapes, the ratio of defect major axis to minor axis (a / c) is used as a parameter describing defect shape; when analyzing the influence of defect type, the ratio of defect elastic modulus to base material elastic modulus (E) is used as a parameter. d / E m As a parameter describing the type of defect;

[0081] The power law model in the finite element analysis software is taken as the creep constitutive model, and a finite element model of the structure containing defects is constructed according to the calibrated creep constitutive parameters and a self-defined subroutine coupling the damage evolution equation and the creep constitutive model, wherein the self-defined subroutine accurately describes the progressive damage behavior of the material / structure under high-temperature conditions;

[0082] The self-defined subroutine is developed by using Fortran language; the self-defined subroutine detects the load state, and if the unit bears pure hydrostatic pressure (the stress deviator is a zero matrix), it is determined that no creep deformation occurs and the subsequent calculation is terminated, so as to avoid numerical singularity; when a non-hydrostatic pressure load is detected, the creep strain increment is calculated based on the stress deviator, and the damage evolution equation is coupled to update the damage parameter, and finally the quantitative prediction of the creep life is realized through the cumulative damage parameter, which not only ensures the numerical stability, but also realizes the continuous calculation process from stress analysis to life evaluation.

[0083] In the simulation process, when the damage variable of a specific Gaussian integral point on the outer surface of the sample reaches a critical threshold When the damage reaches the critical value, the total time at this time is regarded as the creep life.

[0084] S3, based on the finite element model of the structure containing defects, the creep life under different defects is obtained by controlling the defect variable, the creep life t under different defect characteristics is normalized to obtain the weakening degree t of the creep life , and regression analysis is performed to obtain the mapping relationship between the defect characteristics and the creep life;

[0085] In the study of the influence of the defect size, the defect is idealized as a sphere, the defect type is selected as a pore defect, D / T=0.02, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.50 are taken respectively, nine models are established for analysis, wherein the plate thickness T is kept unchanged at 20 mm, the defect is placed at the geometric center position, and the influence law result graph of the defect characteristics (size) on the creep life is as shown in Figure 2 When t =1, the defect size D=0 (no defect); when t =0.9, the defect size D=6 mm, and for a 20 mm thick plate, the critical defect size considered by ASME and other specifications is about 6 mm.

[0086] In the study of the influence of the defect position, the defect is idealized as a sphere, the defect type is selected as a pore defect, L / T=0.20, 0.25, 0.30, 0.40, 0.50 are taken respectively, five models are established for analysis, wherein the plate thickness T is kept unchanged at 20 mm, and the defect diameter D is kept unchanged at 6 mm, and the influence law result graph of the defect characteristics (position) on the creep life is as shown in Figure 3shown; under the premise of t / tr≥0.9, it is considered that the porosity defects less than 6 mm (in line with the limit value of ASME specification) have no effect on the creep performance. From Figure 3 It can be seen that the internal defect position has little effect on the creep life for creep. In the figure, tr' is the creep life corresponding to the 6 mm spherical defect.

[0087] In the study of the effect of defect shape, the defect is idealized as an ellipsoid and placed at the geometric center of the unit body, a / c=1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, seven models are established for analysis, at this time the short axis of the ellipse c is kept unchanged at 3 mm, 1 mm, the long axis size a is changed, the influence law of defect characteristics (shape) on creep life is shown in the figure Figure 4 As the aspect ratio of the defect increases, the creep life decreases, when a / c tends to infinity (i.e. plane crack), the creep life is the lowest, which is consistent with the fact that plane crack defects are not allowed in ASME and other specifications, under the premise of t / tr≥0.9 (tr is the creep life of the defect-free component), it is considered that the defects with aspect ratio less than 1 (6 mm round display) are in line with the requirements. From Figure 4 It can be seen that when c=1 mm, a / c=3, the ratio of structure life to defect-free structure life is 0.99, which is approximately no effect. Under the premise of short half axis c=1 mm, the defect length can be increased to 20 mm, at this time the life is only 0.95 of the life of the defect-free component, which shows that the defect is sensitive to the size factor.

[0088] To simplify the calculation of the mapping relationship between defect characteristics and creep life, simple linear regression can be used, if high-precision relationship such as nonlinear mapping relationship is needed, professional mathematical methods can be used to obtain;

[0089] As Figure 5As shown, the model is constructed using 47 groups of observation values, and regression statistics is performed, wherein the regression coefficient reflects the "marginal effect" of the independent variable on the dependent variable, and the creep life statistics is used to test the significance of the regression coefficient; the coefficient significance determines whether the independent variable is "statistically significant" (usually P < 0.05 is the significant standard), and the 95% confidence interval is used to determine the reasonable range of the coefficient. The regression statistics shows that the regression coefficient of the intercept term is 1.1195, the coefficient significance is 1.63E-14, which is much smaller than 0.05, the creep life statistics is 11.46431, which is extremely large and statistically extremely significant, and the 95% confidence interval [0.9224, 1.3166] does not contain 0, verifying the significance; the type (Ed / Em) term has a regression coefficient of 0.0035 (Ed / Em increases by 1 unit on average, and the creep life increases by 0.0035), the coefficient significance is 0.0300, which is less than 0.05, the creep life statistics is 2.246258, and the 95% confidence interval [0.0004, 0.0067] does not contain 0, supporting the significance, indicating that Ed / Em has a significant positive effect on the creep life; the size (D / T) term has a regression coefficient of -1.0406 (D / T increases by 1 unit on average, and the creep life decreases by 1.0406), the coefficient significance is 6.28E-14, the absolute value of the creep life statistics is extremely large and statistically extremely significant, the 95% confidence interval [-1.2317, -0.8494] is all negative, verifying the negative effect, indicating that D / T has a significant negative effect on the dependent variable; the position (L / T) term has a regression coefficient of 0.07798 (L / T increases by 1 unit on average, and the creep life increases by 0.078), the coefficient significance is 0.6912, which is much larger than 0.05, the creep life statistics is 0.399968, which is not statistically significant, and the 95% confidence interval [-0.3155, 0.4714] contains 0, further verifying the insignificance, indicating that L / T has no significant effect on the dependent variable; the shape (a / c) term has a regression coefficient of 0.0279 (a / c increases by 1 unit on average, and the creep life increases by 0.0279), the coefficient significance is 0.00039, which is less than 0.05, the creep life statistics is 3.856283, which is statistically significant, and the 95% confidence interval [0.0133, 0.0425] does not contain 0, supporting the significance, indicating that a / c has a significant positive effect on the dependent variable; at the coefficient level, the intercept is significantly non-zero; the type, size, and shape have a significant effect on the creep life, and the type and shape are positive, while the size is negative; the position has no significant effect.

[0090] The creep life t is normalized under different defect characteristics to obtain the weakening degree of the creep life t The expression is:

[0091]

[0092] wherein, t is the creep life of the structure with defects; t is the creep life of the defect-free structure obtained by finite element / experiment; h and g are coefficients;

[0093] is the ratio of the elastic modulus of the defect to the elastic modulus of the base metal calculated by experimental test;

[0094] is the ratio of the diameter of the defect to the thickness of the plate calculated by experimental test;

[0095] is the ratio of the defect location to the thickness of the plate calculated by experimental test;

[0096] is the ratio of the long axis to the short axis of the defect calculated by experimental test; by regression analysis of the creep life under different defect characteristics, and the mapping relationship between the defect characteristics and the creep life is:

[0097] t / = (Equation 8).

[0098] S4, determine the defect diameter acceptance limit under a specific plate thickness T based on the mapping relationship between the defect characteristics and the creep life Analysis shows that the defect type and shape are negatively related to the life, the defect location has no significant effect on the life, and the aspect ratio a / c of the circular defect is the largest, up to 3, so a circular pore located at the geometric center is selected for study, i.e. E d / E m = 0, L / T = 0.5, a / c = 3, and T = 20 mm. Ideally, the defect weakening t / = 1 can be considered to have no effect on the creep life, and the critical size can be calculated by substituting (Equation 8) to be 4.66 mm. In fact, the presence of defects will affect the stress field of the component and have an effect on the life, so it is difficult for t / to reach 1.0. If t / ≥ 0.9, it is considered that the defect has no effect on the creep performance, and according to the above recalculation, the critical size can be obtained to be 6.57 mm, as shown in Figure 6 From the perspective of defect acceptance limit optimization, a larger defect acceptance size can be obtained by using the weakening degree.

[0099] ​​​​The present application determines the defect acceptance limit of a specific plate thickness based on the mapping relationship between defect characteristics and creep life. The acceptance limit of the structure containing defects is determined by the degree of creep life weakening, so as to determine whether the structure is safe during service, provide theoretical and technical support for nondestructive testing acceptance of nuclear power or chemical equipment containing defects, and realize the optimization of the acceptance limit of the structure containing defects.

[0100] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic creative principles involved. Such additional variations and modifications should be considered as within the scope of the application as described in the claims that follow.

Claims

1. A method for accepting manufacturing defects in welded components used in high-temperature service, characterized in that, The defect acceptance method includes: Step (1) The parameters of the creep constitutive model are calibrated by testing the creep performance of defect-free materials / structures; Step (2) Regularize the defects and use the finite element tool to construct a finite element model of the structure with defects; Step (3) Based on the finite element model of the defective structure, the creep life under different defects is obtained by controlling the defect variables. The creep life t under different defect characteristics is normalized to obtain the degree of reduction of creep life t / t. r And to conduct regression analysis to obtain the mapping relationship between defect characteristics and creep life; When studying the influence of defect size, the defect is idealized as a sphere, and the defect type is selected as porosity defect. Multiple models are established for analysis by taking the ratio of diameter to plate thickness D / T of different defects. The plate thickness T is kept constant, and the defect is placed at the geometric center position to solve the creep life of the structure with defects. When studying the influence of defect location, the defect is idealized as a sphere and the defect type is selected as porosity defect. Multiple models are established for analysis based on the ratio of defect location to plate thickness L / T. The plate thickness T is kept constant and the defect diameter is kept consistent. The creep life of the structure with defects is then calculated. When studying the influence of defect shape, the defect is idealized as an ellipsoid and placed at the geometric center of the unit. Multiple models are established and analyzed by taking different ratios of the major axis to the minor axis a / c of ​​the defect. At this time, the minor axis c of the ellipse is kept constant, and the major axis dimension a is changed to solve the creep life of the structure containing the defect. The specific steps are as follows: Normalizing the creep lifetime t under different defect characteristics yields the degree of creep lifetime reduction t / t. r Its expression is: t / t r =h+b*Ed / Em 测 +f*D / T 测 +d*L / T 测 +g*a / c 测 ; Among them, t r t represents the creep life of the defect-free structure obtained by finite element method / experiment; t represents the creep life of the structure with defects; h, b, f, d, and g are all coefficients. Ed / Em 测 This is the ratio of the elastic modulus of the defect, calculated from experimental testing, to the elastic modulus of the parent material. D / T 测 The ratio of the defect diameter to the plate thickness, calculated from experimental testing. L / T 测 This is the ratio of the defect location to the plate thickness, calculated from experimental testing. a / c 测 This is the ratio of the major axis to the minor axis of the defect, calculated from experimental testing. By performing regression analysis on creep life under different defect characteristics, the values ​​of h, b, f, d, and g were obtained. The mapping relationship between defect characteristics and creep life is as follows: t / t r =h+b*Ed / Em+f*D / T+d*L / T+g*a / c; Step (4) Determine the acceptance limit value D of the defect diameter for a specific plate thickness T based on the mapping relationship between defect characteristics and creep life. 限 If the defect diameter acceptance limit D 限 If it passes inspection, then it is accepted.

2. The method for accepting manufacturing defects in high-temperature service welded components according to claim 1, characterized in that, The specific steps of step (1) are as follows: Specimens were cut from defect-free materials / structures using wire cutting technology. High-temperature / room-temperature creep tensile tests were then conducted on the specimens to obtain their creep life and steady-state creep rate under different stress conditions. Creep curves and strain rate curves under different stresses were also obtained. Creep constitutive models include: Creep strain rate equation: in, For creep strain rate tensor; D 损 For damage parameters, M and q are material-related parameters; A and n are material constants; σ eq It is the equivalent stress; p is the parameter of the creep constitutive model, and e represents an exponential function with base e; Assuming the material / structure has a damage parameter D during the creep steady-state stage 损 =0, at this time exp(0) = 1, and the simplified logarithm of (Equation 1) is: The material constants A and n are fitted based on the experimental data using equation (3); Integrating Equation 2, taking the initial time t0 = 0 and the initial parameter D 损 =0, the damage evolution equation is obtained as follows: Simulated creep life t of a defect-free structure r for: Taking the logarithm of (Equation 5), and fitting the material parameters M and p based on the uniaxial creep fracture data, substituting (Equation 4) into (Equation 2) yields the creep strain-time curve, the expression of which is: The optimal q value for each stress level is determined using Equation 6, and the constants A, n, and D are obtained. 损 and p.

3. The method for accepting manufacturing defects in high-temperature service welded components according to claim 1, characterized in that, The content of the standardization process for defects in step (2) includes: the size of a single defect is the size of a rectangle or square that completely contains the defect area, and the shape of the defect is equivalent to an ellipse or a circle; When analyzing the influence of different defect sizes, the ratio of defect diameter to plate thickness (D / T) is used as a parameter describing defect size; when analyzing the influence of different defect locations, the ratio of defect location to plate thickness (L / T) is used as a parameter describing defect location; when analyzing the influence of different defect shapes, the ratio of defect major axis to minor axis (a / c) is used as a parameter describing defect shape; when analyzing the influence of defect type, the ratio of defect elastic modulus to base material elastic modulus (E) is used as a parameter. d / E m As a parameter describing the type of defect.

4. The method for accepting manufacturing defects in high-temperature service welded components according to claim 1, characterized in that, In step (2), the power law model in the finite element analysis software is used as the creep constitutive model. Based on the calibrated creep constitutive parameters and the custom subroutine that defines the coupling relationship between the damage evolution equation and the creep constitutive model, a finite element model of the defective structure is constructed.

5. The method for accepting manufacturing defects in high-temperature service welded components according to claim 4, characterized in that, The custom subroutine was developed using the Fortran language; A custom subroutine detects the load state. If the element is subjected to pure hydrostatic pressure, it is determined that no creep deformation will occur and the subsequent calculation will be terminated to avoid numerical singularity. When a non-hydrostatic pressure load is detected, the creep strain increment is calculated based on the stress skewness, and the damage parameters are updated by coupling the damage evolution equation. Finally, the creep life is quantitatively predicted by accumulating the damage parameters.

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