Method and system for improving pipeline tensile strain capacity and girth weld joint reliability

Abstract

The present invention relates to the technical field of pipeline mechanical property testing, and in particular to a method and system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints. The method and system use testing methods such as hardness cloud diagrams, Charpy impact tests, and wide plate tensile tests to test the performance of pipelines containing girth weld joints, thereby ensuring the reliability of the girth weld joints and ensuring that the tensile failure mode of the pipeline is the yield failure of the pipeline base material of the girth weld joint or the ductile tear failure at the girth weld joint, thereby improving the tensile strain capacity of pipelines such as natural gas pipelines, reducing the risk of low-stress brittle fracture of girth weld joints under geological disaster conditions, and ensuring the safe operation of the pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline mechanical property testing, and in particular to a method and system for improving pipeline tensile strain capacity and girth welding joint reliability. Background Art

[0002] The failure mode of the girth weld of the natural gas pipeline can be divided into the failure of the weld joint under the tensile load and the failure of the steel pipe parent material at the far end of the weld according to the failure location. The deformation capacity of the steel pipe parent material is much greater than that of the weld. When the steel pipe parent material at the far end of the weld fails under the tensile load, the deformation at the girth weld is small, and the deformation is mainly concentrated on the parent material at the far end of the weld, so the tensile strain of the pipeline is high. For the failure mode of the girth weld, it can be divided into the necking failure of the girth weld joint and the crack propagation failure at the girth weld joint. The former is caused by the low tensile performance of the weld joint, the deformation is mainly concentrated on the weld, and the tensile strain is low. The tensile strain in the latter mainly depends on the fracture mode. When the fracture process is brittle or ductile-brittle mixed type, the crack propagation resistance is low and the tensile strain capacity of the pipeline is poor. When the fracture process is ductile tearing, the crack propagation resistance is high and the tensile strain capacity of the pipeline is good.

[0003] The existing natural gas pipeline welding process specifications only put forward some requirements for the performance of pipeline joints, and cannot guarantee that the failure mode of the pipeline is the far-end yielding type of the weld and the ductile tearing type failure of the heat-affected zone of the weld. Therefore, the failure probability of the pipeline due to the low tensile strain value is high, which has a greater risk. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for improving the tensile strain capacity of pipelines and the reliability of girth welding joints in view of the deficiencies of the prior art.

[0005] The technical solution of a method for improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention is as follows:

[0006] Performing hardness tests on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld, drawing a hardness cloud map, and judging whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result;

[0007] Performing a Charpy impact test on the girth weld joint at the lowest service temperature, and judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result, thereby obtaining a second judgment result;

[0008] When at least one of the first judgment result and the second judgment result is no, optimizing the welding process of the girth weld joint until both the first judgment result and the second judgment result are yes;

[0009] When both the first judgment result and the second judgment result are yes, a wide plate tensile test is performed on the pipeline, and whether the tensile strain of the pipeline is reliable is judged according to the wide plate tensile test result to obtain a third judgment result. When the third judgment result is yes, the current welding process is determined as the target welding process to perform welding. When the third judgment result is no, the welding process of the girth weld joint is continuously optimized until the third judgment result is yes.

[0010] The beneficial effects of the method of improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention are as follows:

[0011] The performance of pipelines containing girth welds is tested using testing methods such as hardness cloud maps, Charpy impact tests, and wide plate tensile tests. This can ensure the reliability of girth welds and ensure that the tensile failure mode of the pipeline is the yield failure of the pipeline base material of the girth weld or the ductile tearing failure at the girth weld. This improves the tensile strain capacity of pipelines such as natural gas pipelines, reduces the risk of low-stress brittle fracture of girth welds under geological disaster conditions, and ensures the safe operation of the pipeline.

[0012] On the basis of the above scheme, the method of improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention can also be improved as follows.

[0013] Further, judging whether the hardness of the girth weld joint is reliable according to the hardness cloud diagram to obtain a first judgment result includes:

[0014] According to the hardness cloud map, the hardness values ​​of each first preset position of the weld are counted and averaged to obtain a first average value; according to the hardness cloud map, the hardness values ​​of each second preset position of the heat-affected zone of the weld are counted and averaged to obtain a second average value; according to the hardness cloud map, the hardness values ​​of each third preset position of the distal pipeline base material are counted and averaged to obtain a third average value, wherein the distal pipeline base material refers to: a pipeline base material on the pipeline and the distance between the distal pipeline base material and the weld is greater than a preset distance threshold;

[0015] It is determined whether the first average value and the second average value are both greater than the third average value to obtain the first determination result.

[0016] Further, judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result to obtain a second judgment result includes:

[0017] The Charpy impact test result is compared with a preset ductile-brittle transition curve to determine whether the Charpy impact test result is on an upper platform of the ductile-brittle transition, thereby obtaining the second determination result.

[0018] Furthermore, it also includes:

[0019] A Charpy impact test is performed on the preset ring weld joint at each preset temperature to obtain the fracture shear area of ​​the preset ring weld joint corresponding to each preset temperature, and the preset ductile-brittle transition curve is drawn according to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset ring weld joint.

[0020] Furthermore, the pipeline is a natural gas pipeline.

[0021] The technical solution of a system for improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention is as follows:

[0022] It includes a hardness test module, a toughness test module, a first optimization module, a tensile test module and a second optimization module;

[0023] The hardness test module is used to: perform hardness testing on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld, draw a hardness cloud map, and judge whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result;

[0024] The toughness test module is used to: perform a Charpy impact test on the girth weld joint at the lowest service temperature, and determine whether the toughness of the girth weld joint is reliable according to the Charpy impact test result to obtain a second determination result;

[0025] The first optimization module is used to: when at least one of the first judgment result and the second judgment result is no, optimize the welding process of the girth welding joint until both the first judgment result and the second judgment result are yes;

[0026] The tensile test module is used to: when the first judgment result and the second judgment result are both yes, perform a wide plate tensile test on the pipeline, judge whether the tensile strain of the pipeline is reliable according to the wide plate tensile test result, and obtain a third judgment result; when the third judgment result is yes, determine the current welding process as the target welding process to perform welding;

[0027] The second optimization module is used to: when the third judgment result is no, continue to optimize the welding process of the girth weld joint until the third judgment result is yes.

[0028] The beneficial effects of the system for improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention are as follows:

[0029] The performance of pipelines containing girth welds is tested using testing methods such as hardness cloud maps, Charpy impact tests, and wide plate tensile tests. This can ensure the reliability of girth welds and ensure that the tensile failure mode of the pipeline is the yield failure of the pipeline base material of the girth weld or the ductile tearing failure at the girth weld. This improves the tensile strain capacity of pipelines such as natural gas pipelines, reduces the risk of low-stress brittle fracture of girth welds under geological disaster conditions, and ensures the safe operation of the pipeline.

[0030] On the basis of the above scheme, the system for improving the tensile strain capacity of pipelines and the reliability of girth welding joints of the present invention can also be improved as follows.

[0031] Further, the hardness test module is used for:

[0032] According to the hardness cloud map, the hardness values ​​of each first preset position of the weld are counted and averaged to obtain a first average value; according to the hardness cloud map, the hardness values ​​of each second preset position of the heat-affected zone of the weld are counted and averaged to obtain a second average value; according to the hardness cloud map, the hardness values ​​of each third preset position of the distal pipeline base material are counted and averaged to obtain a third average value, wherein the distal pipeline base material refers to: a pipeline base material on the pipeline and the distance between the distal pipeline base material and the weld is greater than a preset distance threshold;

[0033] It is determined whether the first average value and the second average value are both greater than the third average value to obtain the first determination result.

[0034] Further, the toughness test module is specifically used for:

[0035] The Charpy impact test result is compared with a preset ductile-brittle transition curve to determine whether the Charpy impact test result is on an upper platform of the ductile-brittle transition, thereby obtaining the second determination result.

[0036] Furthermore, it also includes a building block, wherein the building block is used to:

[0037] A Charpy impact test is performed on the preset ring weld joint at each preset temperature to obtain the fracture shear area of ​​the preset ring weld joint corresponding to each preset temperature, and the preset ductile-brittle transition curve is drawn according to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset ring weld joint.

[0038] Furthermore, the pipeline is a natural gas pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic flow chart of a method for improving the tensile strain capacity of a pipeline and the reliability of a girth weld joint according to an embodiment of the present invention;

[0040] Figure 2 The present invention is a schematic structural diagram of a system for improving the tensile strain capacity of pipelines and the reliability of girth welding joints according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] like Figure 1 As shown, a method for improving the tensile strain capacity of a pipeline and the reliability of a girth weld joint according to an embodiment of the present invention comprises the following steps:

[0042] S1. Hardness test:

[0043] Performing hardness tests on the weld of the girth weld joint of the pipeline and the pipe base material adjacent to the weld, drawing a hardness cloud map, and judging whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result;

[0044] The hardness test is performed on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld to obtain the hardness value of each position of the girth weld joint, and a hardness cloud diagram is drawn accordingly.

[0045] S2. Charpy impact test:

[0046] Performing a Charpy impact test on the girth weld joint at the lowest service temperature, judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result, and obtaining a second judgment result;

[0047] Among them, the minimum service temperature can be set according to actual conditions, such as determining the minimum service temperature according to the working environment of the pipeline.

[0048] Among them, the Charpy impact test is: the fracture shear area of ​​the girth weld joint corresponding to the lowest service temperature.

[0049] S3. When at least one of the first judgment result and the second judgment result is negative, perform optimization:

[0050] When at least one of the first judgment result and the second judgment result is no, optimizing the welding process of the girth welding joint until both the first judgment result and the second judgment result are yes;

[0051] S4, wide plate tensile test;

[0052] When both the first judgment result and the second judgment result are yes, a wide plate tensile test is performed on the pipeline, and whether the tensile strain of the pipeline is reliable is judged according to the wide plate tensile test result to obtain a third judgment result. When the third judgment result is yes, the current welding process is determined as the target welding process to perform welding;

[0053] Among them, the specific process of judging whether the tensile strain of the pipeline is reliable based on the results of the wide plate tensile test is as follows:

[0054] According to the wide plate tensile test results, check whether the girth weld joint is broken at the weld. If so, the third judgment result is unreliable and the welding process needs to be optimized. If not, the third judgment result is reliable.

[0055] S5. When the third judgment result is no, continue to optimize:

[0056] When the third judgment result is no, the welding process of the girth weld joint continues to be optimized until the third judgment result is yes.

[0057] Optimizing the welding process includes changing welding materials, adjusting welding current, etc.

[0058] The performance of pipelines containing girth welds is tested using testing methods such as hardness cloud maps, Charpy impact tests, and wide plate tensile tests. This can ensure the reliability of girth welds and ensure that the tensile failure mode of the pipeline is the yield failure of the pipeline base material of the girth weld or the ductile tearing failure at the girth weld. This improves the tensile strain capacity of pipelines such as natural gas pipelines, reduces the risk of low-stress brittle fracture of girth welds under geological disaster conditions, and ensures the safe operation of the pipeline.

[0059] Optionally, in the above technical solution, in S1, judging whether the hardness of the girth weld joint is reliable according to the hardness cloud diagram to obtain a first judgment result includes:

[0060] S10. According to the hardness cloud map, the hardness value of each first preset position of the weld is counted and averaged to obtain a first average value. According to the hardness cloud map, the hardness value of each second preset position of the heat affected zone of the weld is counted and averaged to obtain a second average value. According to the hardness cloud map, the hardness value of each third preset position of the remote pipe base material is counted and averaged to obtain a third average value. The remote pipe base material refers to: the pipe base material on the pipe and the distance between the pipe and the weld is not less than a preset distance threshold.

[0061] The distribution and quantity of all first preset positions are adjusted according to actual conditions, and the distribution and quantity of each second preset position can also be adjusted according to actual conditions.

[0062] The preset distance threshold is the length of the outer diameter of the pipeline, and can also be set according to actual conditions.

[0063] S11. Determine whether the first average value and the second average value are both greater than the third average value, and obtain a first determination result.

[0064] Optionally, in the above technical solution, in S2, judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result, and obtaining a second judgment result includes:

[0065] S20, comparing the Charpy impact test result with the preset ductile-brittle transition curve, judging whether the Charpy impact test result is on the upper platform of the ductile-brittle transition, and obtaining a second judgment result. Specifically:

[0066] If the Charpy impact test result is on the upper platform of the ductile-brittle transition, the second judgment result is reliable. If the Charpy impact test result is not on the upper platform of the ductile-brittle transition, the second judgment result is unreliable and the welding process needs to be optimized.

[0067] Optionally, in the above technical solution, it also includes:

[0068] S020, performing a Charpy impact test on the preset girth weld joint at each preset temperature to obtain the fracture shear area of ​​the preset girth weld joint corresponding to each preset temperature, and drawing a preset ductile-brittle transition curve according to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset girth weld joint. The horizontal axis of the preset ductile-brittle transition curve corresponds to the temperature, and the vertical axis of the preset ductile-brittle transition curve corresponds to the fracture shear area.

[0069] Optionally, in the above technical solution, the pipeline is a natural gas pipeline.

[0070] In the above embodiments, although the steps are numbered S1, S2, etc., these are only specific embodiments given in the present application. Those skilled in the art may adjust the execution order of S1, S2, etc. according to actual conditions, which is also within the scope of protection of the present invention. It can be understood that in some embodiments, some or all of the above embodiments may be included.

[0071] like Figure 2 As shown, a system 200 for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to an embodiment of the present invention includes a hardness test module 210, a toughness test module 220, a first optimization module 230, a tensile test module 240, and a second optimization module 250;

[0072] The hardness test module 210 is used to: perform hardness tests on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld, draw a hardness cloud map, and judge whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result;

[0073] The toughness test module 220 is used to: perform a Charpy impact test on the girth weld joint at the lowest service temperature, and determine whether the toughness of the girth weld joint is reliable according to the Charpy impact test result to obtain a second determination result;

[0074] The first optimization module is used for 230: when at least one of the first judgment result and the second judgment result is no, optimizing the welding process of the girth welding joint until both the first judgment result and the second judgment result are yes;

[0075] The tensile test module 240 is used to: when the first judgment result and the second judgment result are both yes, perform a wide plate tensile test on the pipeline, judge whether the tensile strain of the pipeline is reliable according to the wide plate tensile test result, and obtain a third judgment result; when the third judgment result is yes, determine the current welding process as the target welding process to perform welding;

[0076] The second optimization module 250 is used to: when the third judgment result is no, continue to optimize the welding process of the girth weld joint until the third judgment result is yes.

[0077] The performance of pipelines containing girth welds is tested using testing methods such as hardness cloud maps, Charpy impact tests, and wide plate tensile tests. This can ensure the reliability of girth welds and ensure that the tensile failure mode of the pipeline is the yield failure of the pipeline base material of the girth weld or the ductile tearing failure at the girth weld. This improves the tensile strain capacity of pipelines such as natural gas pipelines, reduces the risk of low-stress brittle fracture of girth welds under geological disaster conditions, and ensures the safe operation of the pipeline.

[0078] Optionally, in the above technical solution, the hardness test module 210 is used to:

[0079] According to the hardness cloud map, the hardness value of each first preset position of the weld is counted and averaged to obtain a first average value; according to the hardness cloud map, the hardness value of each second preset position of the heat affected zone of the weld is counted and averaged to obtain a second average value; according to the hardness cloud map, the hardness value of each third preset position of the remote pipe parent material is counted and averaged to obtain a third average value, and the remote pipe parent material refers to: the pipe parent material on the pipe and the distance between the pipe and the weld is greater than the preset distance threshold;

[0080] It is determined whether the first average value and the second average value are both greater than the third average value to obtain a first determination result.

[0081] Optionally, in the above technical solution, the toughness test module 220 is specifically used for:

[0082] The Charpy impact test result is compared with a preset ductile-brittle transition curve to determine whether the Charpy impact test result is on the ductile-brittle transition upper platform, thereby obtaining a second determination result.

[0083] Optionally, in the above technical solution, a building module is further included, and the building module is used to:

[0084] A Charpy impact test is performed on the preset ring weld joint at each preset temperature to obtain the fracture shear area of ​​the preset ring weld joint corresponding to each preset temperature. According to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset ring weld joint, a preset ductile-brittle transition curve is drawn.

[0085] Optionally, in the above technical solution, the pipeline is a natural gas pipeline.

[0086] The above-mentioned parameters in the system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints of the present invention and the steps for each unit module to achieve corresponding functions can refer to the parameters and steps in the embodiment of a method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints mentioned above, and will not be repeated here.

[0087] In the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0089] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints, characterized in that: include: Performing hardness tests on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld, drawing a hardness cloud map, and judging whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result; Performing a Charpy impact test on the girth weld joint at the lowest service temperature, and judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result, thereby obtaining a second judgment result; When at least one of the first judgment result and the second judgment result is no, optimizing the welding process of the girth weld joint until both the first judgment result and the second judgment result are yes; When both the first judgment result and the second judgment result are yes, a wide plate tensile test is performed on the pipeline, and whether the tensile strain of the pipeline is reliable is judged according to the wide plate tensile test result to obtain a third judgment result. When the third judgment result is yes, the current welding process is determined as the target welding process to perform welding. When the third judgment result is no, the welding process of the girth weld joint is continuously optimized until the third judgment result is yes.

2. A method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 1, characterized in that: The step of judging whether the hardness of the girth weld joint is reliable according to the hardness cloud diagram to obtain a first judgment result includes: According to the hardness cloud map, the hardness values ​​of each first preset position of the weld are counted and averaged to obtain a first average value; according to the hardness cloud map, the hardness values ​​of each second preset position of the heat-affected zone of the weld are counted and averaged to obtain a second average value; according to the hardness cloud map, the hardness values ​​of each third preset position of the distal pipeline base material are counted and averaged to obtain a third average value, wherein the distal pipeline base material refers to: a pipeline base material on the pipeline and the distance between the distal pipeline base material and the weld is greater than a preset distance threshold; It is determined whether the first average value and the second average value are both greater than the third average value to obtain the first determination result.

3. A method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 1, characterized in that: The method of judging whether the toughness of the girth weld joint is reliable according to the Charpy impact test result to obtain a second judgment result includes: The Charpy impact test result is compared with a preset ductile-brittle transition curve to determine whether the Charpy impact test result is on an upper platform of the ductile-brittle transition, thereby obtaining the second determination result.

4. A method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 3, characterized in that: Also includes: A Charpy impact test is performed on the preset ring weld joint at each preset temperature to obtain the fracture shear area of ​​the preset ring weld joint corresponding to each preset temperature, and the preset ductile-brittle transition curve is drawn according to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset ring weld joint.

5. A method for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to any one of claims 1 to 4, characterized in that: The pipeline is a natural gas pipeline.

6. A system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints, characterized in that: It includes a hardness test module, a toughness test module, a first optimization module, a tensile test module and a second optimization module; The hardness test module is used to: perform hardness testing on the weld of the girth weld joint of the pipeline and the pipeline base material adjacent to the weld, draw a hardness cloud map, and judge whether the hardness of the girth weld joint is reliable according to the hardness cloud map to obtain a first judgment result; The toughness test module is used to: perform a Charpy impact test on the girth weld joint at the lowest service temperature, and determine whether the toughness of the girth weld joint is reliable according to the Charpy impact test result to obtain a second determination result; The first optimization module is used to: when at least one of the first judgment result and the second judgment result is no, optimize the welding process of the girth welding joint until both the first judgment result and the second judgment result are yes; The tensile test module is used to: when the first judgment result and the second judgment result are both yes, perform a wide plate tensile test on the pipeline, judge whether the tensile strain of the pipeline is reliable according to the wide plate tensile test result, and obtain a third judgment result; when the third judgment result is yes, determine the current welding process as the target welding process to perform welding; The second optimization module is used to: when the third judgment result is no, continue to optimize the welding process of the girth weld joint until the third judgment result is yes.

7. A system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 6, characterized in that: The hardness test module is used for: According to the hardness cloud map, the hardness values ​​of each first preset position of the weld are counted and averaged to obtain a first average value; according to the hardness cloud map, the hardness values ​​of each second preset position of the heat-affected zone of the weld are counted and averaged to obtain a second average value; according to the hardness cloud map, the hardness values ​​of each third preset position of the distal pipeline base material are counted and averaged to obtain a third average value, wherein the distal pipeline base material refers to: a pipeline base material on the pipeline and the distance between the distal pipeline base material and the weld is greater than a preset distance threshold; It is determined whether the first average value and the second average value are both greater than the third average value to obtain the first determination result.

8. A system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 6, characterized in that: The toughness test module is specifically used for: The Charpy impact test result is compared with a preset ductile-brittle transition curve to determine whether the Charpy impact test result is on an upper platform of the ductile-brittle transition, thereby obtaining the second determination result.

9. A system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to claim 8, characterized in that: Also included are building blocks for: A Charpy impact test is performed on the preset ring weld joint at each preset temperature to obtain the fracture shear area of ​​the preset ring weld joint corresponding to each preset temperature, and the preset ductile-brittle transition curve is drawn according to the corresponding relationship between each preset temperature and the fracture shear area of ​​the preset ring weld joint.

10. A system for improving the tensile strain capacity of pipelines and the reliability of girth weld joints according to any one of claims 6 to 9, characterized in that: The pipeline is a natural gas pipeline.

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