Method and device for prolonging operation life of welding joint of high-temperature pipeline of thermal power plant

Abstract

The invention discloses a method and a device for prolonging the service life of a high-temperature pipeline welding joint of a thermal power plant, belongs to the technical field of heat-resistant steel welding, and solves the problem of creep life loss caused by mismatching of two-side performances during welding of a new high-temperature pipeline and an old high-temperature pipeline. According to the actual performance difference of a new P92 pipeline and an old P92 pipeline, a new P92 pipeline welding joint high-temperature creep calculation model and an old P92 pipeline welding joint high-temperature creep calculation model in an asymmetric groove form are designed, the operation life of the high-temperature pipeline welding joint under different groove angles is calculated, and the maximum operation life of the high-temperature pipeline welding joint and the optimal groove angle of the high-temperature pipeline welding joint are obtained; therefore, the stress states of heat affected zones on the two sides of the new and old P92 pipeline welding joints are adjusted, creep strain concentration of the old pipe side in the high-temperature operation process of the welding joints is improved, and compared with a traditional technology that new and old pipes are welded in a symmetrical mode, the high-temperature operation life of the new and old pipeline welding joints is effectively prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of heat-resistant steel welding, and relates to a method and a device for improving the service life of high-temperature pipeline welding joints in a thermal power plant. Background Art

[0002] The high-temperature pipeline components of thermal power plants are all connected in the form of welding, and the number of welded joints is very large. The welding quality needs to be strictly controlled during the welding process, and physical and chemical tests and non-destructive tests need to be carried out after welding to ensure that there are no abnormal performance and excessive defects in the welded joints. However, despite strict control measures for supervision, as the operation time increases, various problems still exist in the operation of welded joints. In regular inspections, P91 and P92 pipeline welding joints have problems such as abnormal physical and chemical properties (manifested as high or low joint hardness, unqualified microstructure), defects in welds (such as cracks, slag inclusions, etc. in welds) and cracking in the heat-affected zone (such as the generation of IV-type cracks). When the problem is more serious and only a small range of repair welding cannot solve it, it is necessary to cut off the old pipe of the abnormal part as a whole, replace it with a new pipe, and re-weld it to achieve the welding of new and old pipes. Under the existing technology, this kind of pipeline welding adopts symmetrical beveling on both sides for welding.

[0003] After operation, the performance of high-temperature pipelines will gradually deteriorate, and the degree of deterioration is closely related to the operation time. Therefore, a new pipe in the supply state is replaced in the middle of the old pipeline that has been in operation for a long time, and the welding is carried out by symmetrical beveling on both sides. Due to the obvious difference in the performance of the parent materials on both sides of the welded joint, the creep strain will be concentrated in the heat-affected zone on one side of the old pipe under long-term operation under high temperature and stress conditions, resulting in a decrease in the creep rupture life of the welded joint and a reduction in the operation life of the pipeline.

[0004] For example, the invention patent with application publication number CN116050228B discloses a creep life prediction method for P92 main steam pipe welded joints, which takes into account the reduction of creep life caused by microstructural degradation during the creep process, and incorporates the life assessment of P92 steel welded joints, making up for the shortcomings of traditional life prediction methods in terms of microstructural evolution. However, although there have been relevant studies in the industry on predicting the creep life of high-temperature pipeline welded joints, there has been no proposal on how to solve the problem of creep life loss caused by the mismatch of performance on both sides of the new and old pipes when welding high-temperature pipelines. How to adjust the stress state of the heat-affected zones on both sides of the new and old pipes and improve the operating life of the new and old pipe welded joints is a problem that needs to be overcome urgently. Summary of the invention

[0005] The technical solution of the present invention is used to solve the problem of creep life loss caused by performance mismatch between the two sides when welding a new pipe and an old pipe of a high-temperature pipeline.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] A method for improving the service life of high-temperature pipeline welding joints in a thermal power plant comprises the following steps:

[0008] Step S1, grouping P92 steel pipe samples under different conditions, testing the creep properties of P92 steel base material, weld and heat affected zone under different conditions through thermal simulation test and creep test, and calculating creep performance parameters through creep constitutive equation;

[0009] Step S2, selecting a conventional groove form and groove angle of the pipeline welding joint according to the pipe wall thickness of the P92 steel pipe;

[0010] Step S3, according to the service time of the P92 steel pipe, creep performance parameters of the P92 steel base material, weld and heat-affected zone under the corresponding state are selected from step S1, and high-temperature creep calculation models of new and old P92 pipeline welded joints with conventional symmetrical groove form and asymmetrical groove form are established respectively, and the service life of the high-temperature pipeline welded joint under different groove angles is calculated to obtain the maximum service life of the high-temperature pipeline welded joint and the optimal groove angle of the high-temperature pipeline welded joint;

[0011] Step S4, based on the optimal groove angle of the high-temperature pipeline welding joint, groove processing is performed on both sides of the new and old P92 pipeline welding joints;

[0012] Step S5, performing conventional welding and post-weld heat treatment on the processed new and old P92 pipes;

[0013] Step S6, the excess height of the weld surface of the high-temperature pipeline welding joint is removed by mechanical processing to keep the weld flush with the parent material or a smooth transition.

[0014] Furthermore, the grouping of P92 steel pipe samples under different conditions described in step S1 is specifically as follows: steel pipe samples with different service times are selected and divided into five intervals: no service, service time less than 40,000 hours, service time 40,000 to 80,000 hours, service time 80,000 to 120,000 hours, and service time greater than 120,000 hours.

[0015] Furthermore, the heat affected zone in step S1 includes a coarse grain zone and a fine grain zone.

[0016] Furthermore, the creep performance parameters calculated by the creep constitutive equation in step S1 are specifically:

[0017] The expression of the creep constitutive equation is as follows:

[0018]

[0019] In the formula, represents creep rate, B represents material constant, n represents stress exponent, and σ represents creep stress;

[0020] The creep performance parameters include material constant B and stress exponent n.

[0021] Furthermore, the P92 steel base material sample in step S1 is obtained through the main steam pipeline of the supercritical unit actually in service, the weld seam sample is obtained by surfacing welding of the actual welding material, and the heat affected zone sample is obtained by thermal simulation test of the P92 steel base material.

[0022] Furthermore, step S3 includes the following steps:

[0023] S31, determine the creep performance parameters of the old pipe side according to the service time of the P92 steel pipe that actually needs to be partially replaced;

[0024] S32, based on the outer diameter and wall thickness of the P92 steel pipe, the high temperature creep calculation model of the new and old P92 pipe welding joints was established in the form of conventional symmetrical grooves and the cells were divided;

[0025] S33, assigning material properties to the base material, weld, coarse grain area and fine grain area of ​​the calculation model respectively; the material properties include elastic modulus, Poisson's ratio, static load mechanical performance parameters and creep performance parameters;

[0026] S34, setting boundary conditions and load conditions of the calculation model; the boundary conditions include temperature and structural constraints, and the load conditions include tensile loads;

[0027] S35, setting calculation model parameters and performing finite element calculation of high temperature creep process; the calculation model parameters include calculation step length, total time and result parameters;

[0028] S36, obtaining an equivalent creep strain cloud diagram of the welded joint according to the finite element calculation results, analyzing the maximum creep strain position of the heat affected zone, intercepting the strain-time relationship curve at the position, and calculating the service life of the high-temperature pipeline welded joint in the conventional symmetrical groove form;

[0029] S37, taking the weld cross-sectional area unchanged as the control condition, adjusting the groove angles on both sides of the weld joint, establishing a high-temperature creep calculation model of the new and old P92 pipeline weld joints in the form of asymmetric grooves and performing cell division, and repeatedly executing S33-S36 to calculate the service life of the high-temperature pipeline weld joint in the form of asymmetric grooves;

[0030] S38, adjusting the groove angles on both sides of the new and old P92 pipes, traversing different groove angles and calculating the service life of the high-temperature pipe welding joint under different groove angles, obtaining the maximum service life of the high-temperature pipe welding joint, and using the corresponding groove angle as the optimal groove angle of the high-temperature pipe welding joint.

[0031] Furthermore, the service life of the high-temperature pipeline welded joint in step S3 is the time required for the maximum creep strain of the heat-affected zone to reach 0.2.

[0032] Furthermore, the groove processing in step S4 is performed by mechanical processing, and the oil stains within 15 mm of the groove and both sides are cleaned before welding.

[0033] Furthermore, the conventional welding in step S5 uses argon tungsten arc welding for base laying, and arc welding or submerged arc welding for filling and covering.

[0034] The present invention also provides a device for improving the service life of high-temperature pipeline welding joints in thermal power plants, comprising a creep performance parameter calculation module, a groove selection module, an service life calculation module, a groove processing module, a welding processing module and a weld processing module;

[0035] The creep performance parameter calculation module is used to group P92 steel pipe samples under different states, test the creep performance of P92 steel base material, weld and heat affected zone under different states through thermal simulation test and creep test, and calculate the creep performance parameters through creep constitutive equation;

[0036] The groove selection module is used to select the conventional groove form and groove angle of the pipeline welding joint according to the pipeline wall thickness of the P92 steel pipe;

[0037] The service life calculation module is used to select creep performance parameters of P92 steel base material, weld and heat affected zone under corresponding conditions from the creep performance parameter calculation module according to the service time of P92 steel pipe, respectively establish high temperature creep calculation models of new and old P92 pipeline welding joints with conventional symmetrical groove form and asymmetrical groove form, calculate the service life of high temperature pipeline welding joints under different groove angles, and obtain the maximum service life of high temperature pipeline welding joints and the optimal groove angle of high temperature pipeline welding joints;

[0038] The groove processing module is used to perform groove processing on both sides of the new and old P92 pipe welding joints based on the optimal groove angle of the high-temperature pipe welding joint;

[0039] The welding processing module is used to perform conventional welding and post-weld heat treatment on the processed new and old P92 pipes;

[0040] The weld processing module is used to remove the excess height of the weld surface of the high-temperature pipeline welding joint by mechanical processing to keep the weld flush with the parent material or a smooth transition.

[0041] The advantages of the present invention are:

[0042] According to the actual performance difference between the new and old P92 pipelines, the present invention designs a high-temperature creep calculation model for the new and old P92 pipeline welding joints with asymmetric grooves, calculates the service life of the high-temperature pipeline welding joints under different groove angles, and obtains the maximum service life of the high-temperature pipeline welding joint and the optimal high-temperature pipeline welding joint groove angle, so as to adjust the stress state of the heat-affected zones on both sides of the new and old P92 pipeline welding joints, and improve the creep strain concentration on the old pipe side during the high-temperature operation of the welding joint. Compared with the traditional technology of welding new and old pipes in a symmetrical form, the present invention effectively improves the high-temperature service life of the new and old pipeline welding joints. At the same time, the present invention does not need to increase the amount of weld metal and welding process, and does not require additional processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a method for improving the service life of a high-temperature pipeline welding joint in a thermal power plant according to a first embodiment of the present invention;

[0044] Figure 2 is a curve diagram of creep of the fine grain region of P92 steel under different stresses at 650° C. according to Example 1 of the present invention;

[0045] Figure 3 This is a flow chart of obtaining the optimal groove angle of the high-temperature pipeline welding joint in step S38 of the first embodiment of the present invention;

[0046] Figure 4 Schematic diagram of the groove shape and groove angle of the welding joint according to the first embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of performing cell division in a finite element calculation model according to the first embodiment of the present invention;

[0048] Figure 6 It is a schematic diagram of the finite element calculation results of the asymmetric groove new and old pipe welding joints in the first embodiment of the present invention during the high temperature creep process under the conditions of 650° C. and 80 MPa. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0051] Embodiment 1

[0052] like Figure 1 Specifically, a method for improving the service life of a high-temperature pipeline welding joint of a thermal power plant is disclosed, comprising the following steps:

[0053] Step S1, grouping P92 steel pipe samples under different states, testing the creep properties of P92 steel base material, weld and heat affected zone under different states through thermal simulation test and creep test, and calculating the creep performance parameters through creep constitutive equation.

[0054] Since the P92 steel pipe samples exist in different states according to the length of service time, this embodiment selects steel pipe samples with different service times and divides them into five intervals: no service, service time less than 40,000 hours, service time 40,000 to 80,000 hours, service time 80,000 to 120,000 hours, and service time greater than 120,000 hours.

[0055] The heat affected zone includes a coarse grain zone and a fine grain zone. In this embodiment, a large block coarse grain heat affected zone (coarse grain zone) and a fine grain heat affected zone (fine grain zone) specimen are obtained through a thermal simulation test, and a large block weld specimen is obtained through welding of welding materials. Creep specimens are cut from each group of P92 steel base metal, weld and heat affected zone, and high temperature creep tests are carried out to obtain the creep curve of each group of specimens. Figure 2 For example, Figure 2 This is the creep curve of the fine grain area of ​​P92 steel under different stresses at 650°C. It can be seen that the creep curve can represent the relationship between creep strain and time under certain temperature and stress.

[0056] The creep performance parameters include material constant B and stress exponent n. In this embodiment, the creep performance parameters are expressed by the creep constitutive equation, and the creep constitutive equation is expressed as follows:

[0057]

[0058] In the formula, represents the creep rate, represents the derivative of creep strain with time, B represents the material constant, n represents the stress exponent, σ represents the creep stress. The purpose of calculating the creep constitutive equation is to determine the creep rate through tests under various creep stresses σ. Relationship with creep stress σ.

[0059] In this embodiment, the creep rate can be obtained based on the creep curve. Different creep stresses σ are given during the test. Therefore, the creep curves under different creep stresses σ can be used to calculate the material constant B and stress exponent n according to the creep constitutive equation, expressing the relationship between creep stress σ and creep rate. relationship.

[0060] Furthermore, in the present embodiment, each group of P92 steel base materials is obtained through the main steam pipeline of the supercritical unit actually in service, the weld seam sample is obtained through surfacing forming of the actual welding material, and the heat affected zone sample is obtained through thermal simulation test for each group of P92 steel base materials.

[0061] Specifically, taking a power plant as an example, a weld of a P92 pipeline with a service time of more than 70,000 hours in the power plant had an excessive defect. After partial pipe cutting, a new P92 pipeline short section was replaced, involving two butt welding joints of the new and old P92 steel pipes. The pipeline specifications By obtaining P92 steel pipe samples with different service times, weld samples were prepared by surfacing welding with welding materials, and the coarse grain zone and fine grain zone samples were tested by thermal simulation. The creep properties of each group of P92 steel base material, weld and heat affected zone were tested by high temperature creep test. The creep performance parameters of each group of samples at 650℃ were calculated according to the creep constitutive equation and are shown in Table 1 below:

[0062] Table 1 Creep performance parameters of each group of samples at 650℃

[0063]

[0064] Step S2, selecting a conventional groove form and groove angle of the pipeline welding joint according to the pipeline wall thickness of the P92 steel pipe.

[0065] Furthermore, the groove form and groove angle need to be selected according to the pipe wall thickness of the P92 steel pipe that actually needs to be partially replaced, with reference to the power standard DL / 869-2021 "Technical Regulations for Welding of Thermal Power Plants".

[0066] Specifically, in this embodiment, a U-shaped groove is selected for a weld of a P92 pipeline of a power plant with a service time of more than 70,000 hours, and the groove angle of the U-shaped groove is 10-15°.

[0067] Step S3, according to the service time of the P92 steel pipe, the creep performance parameters of the P92 steel base material, weld and heat affected zone under the corresponding state are selected from step S1, and high-temperature creep calculation models of new and old P92 pipeline welded joints with conventional symmetrical groove forms and asymmetrical groove forms are established respectively, and the service life of the high-temperature pipeline welded joints under different groove angles is calculated to obtain the maximum service life of the high-temperature pipeline welded joint and the optimal groove angle of the high-temperature pipeline welded joint.

[0068] Specifically, step S3 includes the following steps:

[0069] S31, determine the creep performance parameters of the old pipe side according to the service time of the P92 steel pipe that actually needs to be partially replaced.

[0070] S32, according to the outer diameter and wall thickness of the P92 steel pipe, a high temperature creep calculation model of the new and old P92 pipeline welding joints is established in a conventional symmetrical groove form and cell division is performed; the high temperature creep calculation model is a two-dimensional finite element calculation model.

[0071] like Figure 4 As shown, in this embodiment, the P92 steel pipe that actually needs to be partially replaced selects a U-shaped groove form, which means that the welding joint of the new and old P92 pipes is a U-shaped groove, which is a conventional symmetrical groove form. At this time, the groove angles of the welding joints of the new and old P92 pipes are the same, that is, the new pipe groove angle α = the old pipe groove angle β.

[0072] Figure 5 The figure is a schematic diagram of cell division for a two-dimensional finite element calculation model. Specifically, the cells are quadrilateral cells.

[0073] S33, assigning material properties to the base material, weld, coarse grain area and fine grain area of ​​the calculation model respectively, wherein the material properties include elastic modulus, Poisson's ratio, static load mechanical performance parameters and creep performance parameters;

[0074] Specifically, the creep performance parameters are selected by the creep performance parameters of the P92 steel base material, weld and heat-affected zone in the corresponding state in step S1, and the creep constitutive equation is established by using the subroutine to assign the corresponding material constant B and stress exponent n to the P92 steel base material, weld and heat-affected zone. The elastic modulus is used to describe the stiffness of the P92 steel pipe within the elastic deformation range, the Poisson's ratio is used to describe the ratio of the transverse and longitudinal deformation of the P92 steel pipe when stretched or compressed, and the static load mechanical performance parameters include yield strength and ultimate strength, which can describe the mechanical behavior of the material under static load.

[0075] S34, setting boundary conditions and load conditions of the calculation model; the boundary conditions include temperature and structural constraints, and the load conditions include tensile loads.

[0076] In this embodiment, by providing initialization parameters for the boundary conditions and load conditions of the calculation model, an external environment is provided for the operation of the calculation model.

[0077] S35, setting calculation model parameters and performing finite element calculation of the high temperature creep process; the calculation model parameters include calculation step length, total time and result parameters.

[0078] In this embodiment, the parameters of the high-temperature creep calculation model are initialized and finite element calculation is performed through steps S33-S35. The parameters of each part of the calculation model are clearly given, providing the necessary basis for the subsequent calculation of the high-temperature operating life of the welded joint and the result analysis.

[0079] S36, obtaining an equivalent creep strain cloud diagram of the welded joint according to the finite element calculation results, analyzing the maximum creep strain position of the heat affected zone, intercepting the strain-time relationship curve at the position, and calculating the service life of the high-temperature pipeline welded joint in the conventional symmetrical groove form;

[0080] Specifically, for high-temperature pressure-bearing pipelines, the weld joint is usually judged to be failed when the creep strain reaches 0.2 in the steady state. Therefore, in this embodiment, the time required for the maximum creep strain in the heat-affected zone strain-time relationship curve to reach 0.2 is used as the high-temperature creep life, that is, the operating life of the high-temperature pipeline weld joint.

[0081] S37, taking the weld cross-sectional area unchanged (weld volume unchanged) as the control condition, adjusting the groove angles on both sides of the weld joint, establishing a high-temperature creep calculation model of the new and old P92 pipeline weld joints in the form of asymmetric grooves and performing cell division, and repeatedly executing S33-S36 to calculate the service life of the high-temperature pipeline weld joint in the form of asymmetric grooves;

[0082] like Figure 6 As shown, in this embodiment, the cross-sectional area of ​​the weld remains unchanged (the volume of the weld metal remains unchanged) is used as the control condition, and the groove angles on both sides of the weld joint are adjusted to make the groove angle α of the new pipe ≠ the groove angle β of the old pipe, and the creep evolution process of the new and old P92 pipe weld joints with asymmetric grooves is simulated to obtain the service life of the high-temperature pipeline weld joint under different groove angle conditions.

[0083] S38, adjusting the groove angles on both sides of the new and old P92 pipes, traversing different groove angles and calculating the service life of the high-temperature pipe welding joint under different groove angles, obtaining the maximum service life of the high-temperature pipe welding joint, and using the corresponding groove angle as the optimal groove angle of the high-temperature pipe welding joint.

[0084] Specifically, with the single-side groove angle of 0° as the boundary (i.e., no groove is opened on one side), the groove angle is increased or decreased by about 2.5° each time, different groove angles are traversed and the service life of the high-temperature pipeline welding joint under different groove angles is calculated until one traversal calculation is completed, or the groove angle corresponding to the current maximum service life of the high-temperature pipeline welding joint obtained exceeds 30% of the conventional symmetrical groove angle, the traversal calculation is terminated.

[0085] This embodiment selects the third group of creep performance parameters according to the P92 pipeline of a power plant with a service time of more than 70,000 hours in step S1. First, a finite element calculation model is constructed according to the conventional symmetrical groove form with a groove angle of 10° on both sides of the new and old P92 pipelines. The cross-sectional area of ​​the weld when the groove angle on both sides of the new and old P92 pipelines is 10° is used as the constraint condition for controlling the change of the groove angle on both sides of the new and old P92 pipelines. The service life of the high-temperature pipeline welded joint is calculated based on the time required for the maximum variable creep strain of each region of the welded joint to reach 0.2 at 650°C; the groove angles on both sides of the new and old P92 pipelines are adjusted, different groove angles are traversed and the service life of the high-temperature pipeline welded joint under different groove angles is calculated, and the maximum service life of the high-temperature pipeline welded joint is obtained. The corresponding groove angle is used as the optimal groove angle of the high-temperature pipeline welded joint as shown in Table 2 below:

[0086] Table 2 Data table of service life of high temperature pipeline welding joints calculated by asymmetric groove at 650℃

[0087]

[0088]

[0089] It can be seen from the above table that when the new pipe groove angle α is 5° and the old pipe groove angle β is 15°, the maximum operating life of the high-temperature pipe welding joint of the P92 pipeline in a power plant with a service time of more than 70,000 hours at 650°C is 1806 hours.

[0090] Step S4, based on the optimal high-temperature pipeline welding joint groove angle, groove processing is performed on both sides of the new and old P92 pipeline welding joints.

[0091] Furthermore, the groove processing should be carried out by mechanical processing, and the oil stains within 15mm of the groove and both sides should be cleaned before welding.

[0092] Step S5, performing conventional welding and post-weld heat treatment on the processed new and old P92 pipes.

[0093] Specifically, the conventional welding uses tungsten inert gas arc welding for base laying, and arc welding or submerged arc welding for filling and covering. The specific welding process can refer to the provisions of DL / T 869-2021 "Technical Regulations for Welding of Thermal Power Plants".

[0094] Step S6, the excess height of the weld surface of the high-temperature pipeline welding joint is removed by mechanical processing to keep the weld flush with the parent material or a smooth transition.

[0095] This embodiment also provides comparative welded joints. By sampling and performing creep tests, the maximum service life of high-temperature pipeline welded joints and the optimal groove angle of high-temperature pipeline welded joints of Comparative Example 1 and Comparative Example 2 are calculated, as shown in Table 3 below:

[0096] Table 3 Comparison of service life of welded joints under different joint groove angles and different creep stresses

[0097]

[0098] It can be seen from the above table that the service life of the high-temperature pipeline welded joints manufactured according to this embodiment at 80 MPa and 100 MPa at 650°C is significantly higher than that of the control example, which significantly improves the service life of the high-temperature pipeline welded joints.

[0099] According to the actual performance difference between the new and old P92 pipelines, this embodiment designs a high-temperature creep calculation model for the new and old P92 pipeline welded joints with asymmetric grooves, calculates the service life of the high-temperature pipeline welded joints under different groove angles, and obtains the maximum service life of the high-temperature pipeline welded joint and the optimal groove angle of the high-temperature pipeline welded joint. In this way, the stress state of the heat-affected zones on both sides of the new and old P92 pipeline welded joints is adjusted, and the creep strain concentration on the old pipe side during the high-temperature operation of the welded joint is improved. Compared with the traditional technology of welding new and old pipes in a symmetrical form, this embodiment effectively improves the high-temperature service life of the new and old pipeline welded joints. At the same time, this embodiment does not require additional weld metal consumption and welding procedures, and does not require additional processing costs.

[0100] The present invention also provides a device for improving the service life of high-temperature pipeline welding joints in thermal power plants, comprising a creep performance parameter calculation module, a groove selection module, an service life calculation module, a groove processing module, a welding processing module and a weld processing module;

[0101] The creep performance parameter calculation module is used to group P92 steel pipe samples under different states, test the creep performance of P92 steel base material, weld and heat affected zone under different states through thermal simulation test and creep test, and calculate the creep performance parameters through creep constitutive equation;

[0102] The groove selection module is used to select the conventional groove form and groove angle of the pipeline welding joint according to the pipeline wall thickness of the P92 steel pipe;

[0103] The service life calculation module is used to select creep performance parameters of P92 steel base material, weld and heat affected zone under corresponding conditions from the creep performance parameter calculation module according to the service time of P92 steel pipe, respectively establish high temperature creep calculation models of new and old P92 pipeline welding joints with conventional symmetrical groove form and asymmetrical groove form, calculate the service life of high temperature pipeline welding joints under different groove angles, and obtain the maximum service life of high temperature pipeline welding joints and the optimal groove angle of high temperature pipeline welding joints;

[0104] The groove processing module is used to perform groove processing on both sides of the new and old P92 pipe welding joints based on the optimal groove angle of the high-temperature pipe welding joint;

[0105] The welding processing module is used to perform conventional welding and post-weld heat treatment on the processed new and old P92 pipes;

[0106] The weld processing module is used to remove the excess height of the weld surface of the high-temperature pipeline welding joint by mechanical processing to keep the weld flush with the parent material or a smooth transition.

[0107] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants, characterized in that: The following steps are involved: Step S1, grouping P92 steel pipe samples under different conditions, testing the creep properties of P92 steel base material, weld and heat affected zone under different conditions through thermal simulation test and creep test, and calculating creep performance parameters through creep constitutive equation; Step S2, selecting a conventional groove form and groove angle of the pipeline welding joint according to the pipe wall thickness of the P92 steel pipe; Step S3, according to the service time of the P92 steel pipe, creep performance parameters of the P92 steel base material, weld and heat-affected zone under the corresponding state are selected from step S1, and high-temperature creep calculation models of new and old P92 pipeline welded joints with conventional symmetrical groove form and asymmetrical groove form are established respectively, and the service life of the high-temperature pipeline welded joint under different groove angles is calculated to obtain the maximum service life of the high-temperature pipeline welded joint and the optimal groove angle of the high-temperature pipeline welded joint; Step S4, based on the optimal high-temperature pipeline welding joint groove angle, groove processing is performed on both sides of the new and old P92 pipeline welding joints; Step S5, performing conventional welding and post-weld heat treatment on the processed new and old P92 pipes; Step S6, the excess height of the weld surface of the high-temperature pipeline welding joint is removed by mechanical processing to keep the weld flush with the parent material or a smooth transition.

2. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The grouping of the P92 steel pipe samples under different conditions described in step S1 is specifically as follows: steel pipe samples with different service times are selected and divided into five intervals: no service, service time less than 40,000 hours, service time 40,000 to 80,000 hours, service time 80,000 to 120,000 hours, and service time greater than 120,000 hours.

3. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The heat affected zone in step S1 includes a coarse grain zone and a fine grain zone.

4. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 3, characterized in that: The creep performance parameters calculated by the creep constitutive equation in step S1 are specifically: The expression of the creep constitutive equation is as follows: In the formula, represents creep rate, B represents material constant, n represents stress exponent, and σ represents creep stress; The creep performance parameters include material constant B and stress exponent n.

5. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The P92 steel base material sample in step S1 is obtained through the main steam pipeline of the supercritical unit actually in service, the weld seam sample is obtained by surfacing welding of the actual welding material, and the heat affected zone sample is obtained by thermal simulation test of the P92 steel base material.

6. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The step S3 comprises the following steps: S31, determine the creep performance parameters of the old pipe side according to the service time of the P92 steel pipe that actually needs to be partially replaced; S32, according to the specifications of P92 steel pipe, the high temperature creep calculation model of new and old P92 pipe welding joints is established in the form of conventional symmetrical groove and cell division is performed; S33, assigning material properties to the base material, weld and heat-affected zone of the calculation model respectively; the material properties include elastic modulus, Poisson's ratio, static load mechanical performance parameters and creep performance parameters; S34, setting boundary conditions and load conditions of the calculation model; the boundary conditions include temperature and structural constraints, and the load conditions include tensile loads; S35, setting calculation model parameters and performing finite element calculation of high temperature creep process; the calculation model parameters include calculation step length, total time and result parameters; S36, obtaining an equivalent creep strain cloud diagram of the welded joint according to the finite element calculation results, analyzing the maximum creep strain position of the heat affected zone, intercepting the strain-time relationship curve at the position, and calculating the service life of the high-temperature pipeline welded joint in the conventional symmetrical groove form; S37, taking the weld cross-sectional area unchanged as the control condition, adjusting the groove angles on both sides of the weld joint, establishing a high-temperature creep calculation model of the new and old P92 pipeline weld joints in the form of asymmetric grooves and performing cell division, and repeatedly executing S33-S36 to calculate the service life of the high-temperature pipeline weld joint in the form of asymmetric grooves; S38, adjusting the groove angles on both sides of the new and old P92 pipes, traversing different groove angles and calculating the service life of the high-temperature pipe welding joint under different groove angles, obtaining the maximum service life of the high-temperature pipe welding joint, and using the corresponding groove angle as the optimal groove angle of the high-temperature pipe welding joint.

7. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 6, characterized in that: The service life of the high-temperature pipeline welding joint in step S3 is the time required for the maximum creep strain of the heat-affected zone to reach 0.

2.

8. The method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The groove processing described in step S4 is carried out by mechanical processing, and the oil stains within 15 mm range of the groove and both sides are cleaned before welding.

9. A method for improving the service life of high-temperature pipeline welding joints in thermal power plants according to claim 1, characterized in that: The conventional welding in step S5 uses argon tungsten arc welding for base application, and arc welding or submerged arc welding for filling and covering.

10. A device for improving the service life of high-temperature pipeline welding joints in thermal power plants, characterized in that: It includes creep performance parameter calculation module, groove selection module, service life calculation module, groove processing module, welding processing module and weld processing module; The creep performance parameter calculation module is used to group P92 steel pipe samples under different states, test the creep performance of P92 steel base material, weld and heat affected zone under different states through thermal simulation test and creep test, and calculate the creep performance parameters through creep constitutive equation; The groove selection module is used to select the conventional groove form and groove angle of the pipeline welding joint according to the pipeline wall thickness of the P92 steel pipe; The service life calculation module is used to select creep performance parameters of P92 steel base material, weld and heat affected zone under corresponding conditions from the creep performance parameter calculation module according to the service time of P92 steel pipe, respectively establish high temperature creep calculation models of new and old P92 pipeline welding joints with conventional symmetrical groove form and asymmetrical groove form, calculate the service life of high temperature pipeline welding joints under different groove angles, and obtain the maximum service life of high temperature pipeline welding joints and the optimal groove angle of high temperature pipeline welding joints; The groove processing module is used to perform groove processing on both sides of the new and old P92 pipe welding joints based on the optimal groove angle of the high-temperature pipe welding joint; The welding processing module is used to perform conventional welding and post-weld heat treatment on the processed new and old P92 pipes; The weld processing module is used to remove the excess height of the weld surface of the high-temperature pipeline welding joint by mechanical processing to keep the weld flush with the parent material or a smooth transition.

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