Method for evaluating hydrogen embrittlement sensitivity of pipeline steel welded joint in hydrogen environment
By combining slow tensile testing with hydrogen permeation, samples were directly taken from the welded pipeline and divided into different types of specimens. The combination of high-pressure hydrogen permeation and slow tensile testing solved the problem of the difficulty in effectively evaluating the hydrogen embrittlement sensitivity of pipeline steel welds in the existing technology, and achieved accurate quantification of hydrogen embrittlement performance and process improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2026-03-31
AI Technical Summary
Existing slow tensile testing methods are difficult to effectively evaluate the hydrogen embrittlement susceptibility of pipeline steel welds, especially in thermal simulation methods where there are large differences in microstructure. Furthermore, the notched tensile test specimens have high processing requirements and high data dispersion, leading to increased testing costs and reduced efficiency.
The hydrogen embrittlement sensitivity index was calculated by combining slow tensile testing with hydrogen permeation method. Samples were directly taken from the pipeline after welding and divided into different types. The hydrogen embrittlement sensitivity index was calculated by combining high-pressure hydrogen permeation test, air slow tensile test and high-pressure hydrogen environment slow tensile test. The hydrogen embrittlement performance of the welded joint was quantified by utilizing the microstructure and hydrogen adsorption characteristics of the welded joint.
It improves the accuracy and efficiency of hydrogen embrittlement sensitivity assessment, can quantify the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment, and guides welding process improvement and welding material selection.
Smart Images
Figure FT_1 
Figure FT_2 
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to a method for evaluating the hydrogen embrittlement sensitivity of pipeline steel welded joints in a hydrogen environment, belonging to the technical field of hydrogen embrittlement evaluation of metallic materials. Background Technology
[0002] The entire lifecycle of a hydrogen energy system includes hydrogen production, storage, transportation, and utilization. Hydrogen storage and transportation, connecting upstream production and downstream end-users, is a crucial link. Hydrogen storage and transportation containers and pipelines operate under high pressure and high-purity hydrogen environments for extended periods, which can easily lead to reduced local plasticity, accelerated crack propagation, and decreased durability, resulting in hydrogen-induced cracking, hydrogen embrittlement, or fatigue damage. Solving the problem of high-pressure hydrogen embrittlement in materials is a prerequisite for the safe use of high-pressure hydrogen storage containers. While various conventional material mechanical property methods can generally be used for hydrogen embrittlement testing, the test methods listed in Table 1 below are more common and are also the test methods required by relevant standards or specifications.
[0003] Table 1: Test methods required by the standard
[0004]
[0005] Hydrogen embrittlement testing methods for metallic materials can be broadly classified into two categories: one category is used for preliminary material screening to quickly evaluate whether a material is suitable for manufacturing hydrogen-exposed components, such as disc tests and hydrogen-induced cracking stress intensity factor threshold tests; the other category is used for in-situ testing of material mechanical properties to provide performance data for the design of hydrogen-exposed components or material suitability assessment, such as slow strain rate tensile tests. Slow tensile testing, as an important means of evaluating hydrogen embrittlement, is a key evaluation method in major high-pressure hydrogen embrittlement standards. Studying the correlation between strain and hydrogen embrittlement using slow tensile testing is crucial for evaluating hydrogen embrittlement under high-pressure hydrogen conditions. In pipeline steel applications, the hydrogen embrittlement sensitivity of welds is much higher than that of the base metal; therefore, employing appropriate methods to evaluate weld hydrogen embrittlement sensitivity is paramount. Existing slow tensile testing methods generally employ the following approaches: the first uses thermal simulation to prepare simulated weld composition samples, and then uses these samples to create other standard samples for hydrogen embrittlement evaluation and screening; the second directly samples the weld joint using notched slow tensile specimens, with the notch placed at the weld. Both of these methods are insufficient to effectively represent the hydrogen embrittlement sensitivity of welds. First, there are still significant differences between thermal simulation testing methods and actual welding processes. In particular, welded joints have a mixed microstructure of the weld zone and heat-affected zone, and actual thermal simulation methods can only simulate one of these microstructures. Furthermore, during actual tensile testing, the base metal interacts with the weld, and since the thermal simulation sample has a single microstructure and does not include the base metal, there are substantial differences between the hydrogen embrittlement evaluation and actual conditions. Second, using notched tensile specimens requires extremely precise notch machining. Literature research indicates that different types of pipeline steel require different notch stress concentration factors; otherwise, significant differences in hydrogen embrittlement performance will occur. In addition, notched specimens also face the problem of high data dispersion, requiring multiple tests to select appropriate data, which increases testing costs and reduces efficiency. Summary of the Invention
[0006] The technical problem to be solved by this invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment by using slow tensile testing combined with hydrogen permeation and other methods, thereby improving the accuracy and efficiency of hydrogen embrittlement sensitivity assessment. This method not only provides experimental evaluation of the hydrogen embrittlement correlation of welded joints of steel used in pipelines and hydrogen storage tanks in a hydrogen environment, but is also applicable to other metallic materials in hydrogen-containing or hydrogen-doped environments. Using this invention, the hydrogen embrittlement performance of welded joints with different welding processes can be obtained, and combined with actual service conditions, it can provide support for improving welding processes.
[0007] The technical problem it aims to solve can be addressed through the following technical solutions.
[0008] A method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment includes the following steps:
[0009] (1) Sample preparation
[0010] Take samples directly from the welded pipeline, ensuring the weld joint is centered on the sample;
[0011] The test specimens are divided into three types. The first type is hydrogen permeation test specimens, which are divided into two categories: welded specimens with the weld in the center of the specimen and base material specimens. The second type is full welded slow tensile test specimens with the entire gauge length consisting of welds. The third type is welded slow tensile test specimens with welds, which are processed according to the ASTM G 142-98 test standard and have the weld in the center of the gauge length.
[0012] (2) The steady-state hydrogen permeation current I of the welded area and the base material in the first type of sample was obtained by high-pressure hydrogen permeation test. w with I b The hydrogen adsorption concentration C on the surface of the welded sample and the base material was obtained. w With C b ;
[0013] (3) Calculate the area ratio K of the weld seam in the test area to the entire test area in step (2);
[0014] (4) Calculate the influence coefficient Y of the welded joint in the gaseous environment using the following formula:
[0015] Y = (I w -I b ) / (K*P)
[0016] Where P is the H2 pressure in the hydrogen permeation test;
[0017] (5) Calculate the reduction of area R of the full weld slow tensile specimen through air slow tensile test. air ;
[0018] (6) Calculate the reduction of area R of the welded slow-tension specimen by means of a slow tensile test under high pressure hydrogen environment. H The slow stretching rate is consistent with that in step (5);
[0019] (7) Calculation and evaluation of hydrogen embrittlement sensitivity:
[0020] Calculate the hydrogen embrittlement sensitivity index: EI = (R air -R H )*C w *100 / (R air *C b );
[0021] An EI of 0-15 indicates no risk of hydrogen embrittlement; an EI of 16-30 indicates a slight risk of hydrogen embrittlement; an EI of 31-50 indicates a moderate risk of hydrogen embrittlement; and an EI greater than 50 indicates a severe risk of hydrogen embrittlement.
[0022] Furthermore, in step (5), a slow tensile testing machine is used to conduct a slow tensile test according to standard ASTM G129. The slow tensile rate of the full weld slow tensile test specimen is controlled at 5*10. -7 —1*10 -5 / s, until the sample breaks, the reduction of area R is measured and calculated. air .
[0023] Furthermore, steps (5) and (6) also include processing the sample before the slow tensile test in a hydrogen environment until the roughness Ra of the gauge length section of the sample is greater than 64.
[0024] Furthermore, step (6) also includes the following pretreatment sub-steps, referencing ASTM G 129, before starting the slow tensile test:
[0025] 1) Purge the autoclave with high-purity nitrogen until the oxygen and other impurity gases in the environment are reduced to below 0.005%;
[0026] 2) Introduce hydrogen gas until the pressure reaches the simulated operating pressure P. H ;
[0027] 3) Before the test, let the sample stand in a high-pressure hydrogen environment for a sufficient time to ensure that hydrogen atoms are fully adsorbed on the sample surface;
[0028] 4) Introduce steam and mix in impurity water until the volume of impurity water reaches the impurity water content calculated by the following formula:
[0029] V = 5000 * Y / T S +20
[0030] Where V is the volume ratio of impurity water in the hydrogen environment (unit: ppm); T S The tensile strength of the test material (unit: MPa).
[0031] Furthermore, it also includes a step to confirm the validity of the test results in step (6), wherein the condition for confirmation of validity is that the fracture location is at the weld joint.
[0032] Furthermore, if the test result of step (6) is confirmed to be invalid, repeat the pretreatment sub-step and step (6), and in sub-step (4), increase the impurity water content on the original basis by an increase of J = 1200 / Ts + 12 until the test is valid.
[0033] Furthermore, in step (1), the sampling location is one-quarter of the way along the pipe wall thickness.
[0034] Furthermore, it also includes the steps of surface treatment of the hydrogen permeation sample and removal of hydrogen permeation sample surface residue.
[0035] Furthermore, the surface treatment includes polishing and cleaning; the polishing is to polish the hydrogen-permeable sample to 2000# using sandpaper; the cleaning is to perform ultrasonic cleaning with alcohol on the polished sample.
[0036] Furthermore, the hydrogen permeation sample surface was polarized using an electrochemical testing method, with a polarization current of 0.5 mA / cm. 2 -2mA / cm 2 The polarization time is 5-20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
[0037] Furthermore, in step (2), the hydrogen permeation test is carried out using a dual electrolysis cell.
[0038] Furthermore, step (3) also includes a step of etching the hydrogen permeation sample with weld seam after the test in step (3) with nitric acid alcohol before calculating the area ratio K.
[0039] This invention addresses the hydrogen embrittlement resistance of welded joints in pipeline steel under hydrogen conditions. Utilizing the microstructure of welded joints and the characteristics of hydrogen adsorption and absorption in a hydrogen environment, combined with theoretical calculations and dynamic slow tensile tests, it develops a test method suitable for evaluating hydrogen embrittlement in welded joints under hydrogen conditions. This invention can quantify the hydrogen embrittlement performance of pipeline steel welded joints in hydrogen environments, and it is also applicable to evaluating welded joints of other metallic materials under hydrogen conditions. Furthermore, this invention can also evaluate the impact of different welding processes and welding materials on the hydrogen resistance of welded joints, guiding improvements in welding processes and the selection of suitable welding materials. Attached Figure Description
[0040] Figure 1 This is a schematic diagram of the test sample; the left and right parts of the diagram are the front and side views of the sample, respectively.
[0041] Figure 2 This is a schematic diagram of a slow-tension specimen; where, Figure 2 a is a schematic diagram of a sample subjected to slow tensile testing of the entire weld seam. Figure 2 b is a schematic diagram of a slow-stretch sample with a weld. Detailed Implementation
[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0043] This invention provides a method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment. The specific operation steps are as follows:
[0044] 1. Sample taking:
[0045] Samples should be taken directly from the welded pipeline, ensuring the weld joint is centered on the sample. Figure 1As shown, the sampling size is 150*50*20mm, and the sampling location is one-quarter of the way along the pipe wall thickness.
[0046] 2. Sample preparation:
[0047] The specimens are divided into three types. The first type is a hydrogen permeation specimen with a size of φ30mm*1.5mm, which is divided into two categories: specimens with weld (the weld is located in the center of the specimen) and base metal specimens. The second type is a full-weld slow tensile specimen (the entire gauge length is a weld), see [link to relevant documentation]. Figure 2 a; The third type is a slow tensile test specimen with a weld, which is processed according to the ASTM G 142-98 test standard, ensuring that the weld is centered in the gauge length. See [link to relevant documentation]. Figure 2 b.
[0048] 3. Surface treatment:
[0049] The hydrogen-permeable sample was sanded to 2000# using sandpaper, and the slowly stretched sample was ultrasonically cleaned with alcohol for 20 minutes. The sample was then dried and stored in a dry environment for later use.
[0050] 4. Surface polarization:
[0051] To eliminate surface residues and improve experimental accuracy, the hydrogen-permeable sample surface was polarized using an electrochemical method before the experiment, with a polarization current of 0.5 mA / cm. 2 -2mA / cm 2 The polarization time is 5-20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
[0052] 5. High-pressure hydrogen permeation test:
[0053] The hydrogen permeation test was conducted using a high-pressure hydrogen permeation testing apparatus in a dual-electrolysis cell. A 0.1 mol / L NaOH solution was added to the hydrogen measurement cell, and the open-circuit potential of the sample was measured using an electrochemical workstation for 3600 s. Afterwards, the test surface of the sample was polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, and the curve of the anolyte current changing over time was recorded using the electrochemical workstation. When the background current fell below 100 nA, 0.2 MPa–10 MPa H2 was introduced into the cathodic electrolysis cell, and the start time of hydrogen injection was recorded to obtain the hydrogen permeation curve. The steady-state hydrogen permeation current I0 for both the welded and base metal samples (i.e., the two types of samples in the first type) was obtained. w with I b The hydrogen adsorption concentration C on the corresponding expanded surface of the welded sample and the base material was calculated. w With C b .
[0054] 6. Welded joint area ratio:
[0055] The hydrogen permeation specimen with weld seam after the test in step 5 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld joint size was observed and measured using a metallographic microscope, and the area ratio (i.e., the area ratio of the weld seam in the test area to the entire test area) K was calculated.
[0056] 7. Calculation of the influence coefficient of welded joints:
[0057] Because the presence of welded joints causes differences in hydrogen permeation between the base material and the welded sample, the degree of difference depends on the proportion of welded joints. Through multiple rounds of testing and summarization, this invention clarifies the calculation method for the welded joint influence coefficient Y in a gaseous environment: Y = (I w -I b ) / (K*P), where P is the H2 pressure in the hydrogen permeation test.
[0058] 8. Slow air stretching:
[0059] Slow tensile testing was conducted using a slow tensile testing machine, referring to the standard ASTM G129. Full-weld slow tensile specimens were used, and the slow tensile rate was 5 x 10⁻⁶. -7 —1*10 -5 / s (strain expression method) until the sample fractures, and the reduction of area R is measured and calculated. air .
[0060] 9. Sample preparation before slow tensile testing in a hydrogen atmosphere:
[0061] Material surface roughness has a significant impact on hydrogen adsorption, absorption, and dissolution, thus affecting the hydrogen embrittlement performance of the material. Appropriately increasing the surface roughness of the sample can help improve the difference in hydrogen embrittlement performance of materials under other environments. Through experiments and calculations, before the test, the gauge length of the slow-tensioned samples (for all slow-tensioned samples, including those with and without welds) was polished with 1000 grit sandpaper to a roughness Ra>64. This increases the hydrogen adsorption points and improves the hydrogen adsorption concentration on the sample surface, solving the problem that the hydrogen embrittlement effect is not significant under low-concentration hydrogen environments, making it impossible to effectively compare hydrogen embrittlement performance and improving the difference in test results.
[0062] 10. Calculation of impurity water content:
[0063] The addition of impurity water in a hydrogen atmosphere effectively verifies the hydrogen resistance of welded joints. The hydrogen embrittlement resistance of materials is influenced by both the environment and the inherent mechanical properties of the material. This invention, combining these two aspects, and through experimental verification, yields a method for calculating the amount of impurity water added: V = 5000 * Y / T S +20, where T S Y is the tensile strength of the test material (in MPa), Y is the influence coefficient of the welded joint calculated in step 7, and V is the volume ratio of impurity water in the hydrogen environment (in ppm).
[0064] 11. Slow tensile test under high pressure hydrogen environment:
[0065] The test method follows the standard ASTM G 129. Before the test, the autoclave was purged with high-purity nitrogen until the oxygen and other impurities in the environment were reduced to below 0.005%. Hydrogen gas was then introduced until the pressure reached the simulated operating pressure P. H Before the test, the sample was placed in a high-pressure hydrogen environment for more than 24 hours to ensure that hydrogen atoms were fully adsorbed on the sample surface, thus achieving the best hydrogen permeation effect. Then, water vapor was introduced, and impurity water was added to achieve the volume of impurity water V calculated in step 10. Immediately afterwards, a slow tensile test was conducted on a welded sample. The slow tensile rate was the same as that in step 8. After the test, the reduction of area R was recorded. H .
[0066] 12. Confirmation of result validity:
[0067] To ensure the validity of the test results and to effectively evaluate the hydrogen embrittlement performance of the welded joint, after the dynamic slow tensile test, the area around the fracture test was etched with 5% nitric acid alcohol for 10 seconds. Then, the fracture location was observed with a metallographic microscope. If the fracture location was at the welded joint, the test was considered valid; otherwise, the test was invalid. If invalid, the test could be repeated according to step 11, while increasing the impurity water content by J = 1200 / Ts + 12, until the test was valid.
[0068] 13. Calculation and evaluation of hydrogen embrittlement sensitivity:
[0069] If the test is effective, the hydrogen embrittlement susceptibility of the welded joint is evaluated using the results of two slow tensile tests. The hydrogen embrittlement susceptibility index EI = (R... air -R H )*C w *100 / (R air *C b An EI value between 0 and 15 indicates no risk of hydrogen embrittlement; an EI value between 16 and 30 indicates a slight risk of hydrogen embrittlement; an EI value between 31 and 50 indicates a moderate risk of hydrogen embrittlement; and an EI value greater than 50 indicates a severe risk of hydrogen embrittlement.
[0070] The following are more specific examples.
[0071] Example 1
[0072] This embodiment uses X52 as the base material and employs a manual welding process at a welding speed of 17 cm / min and a welding voltage of 22 V. The specific operating steps of the method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment provided in this embodiment are as follows:
[0073] 1. Sample taking:
[0074] Reference Figure 1 Samples should be taken directly from the welded pipeline, ensuring that the weld joint is in the center of the sample. The sample size is 150*50*20mm, and the sampling location is one-quarter of the way along the pipe wall thickness.
[0075] 2. Sample preparation:
[0076] The test specimens are divided into three types. The first type is a hydrogen permeation specimen with a size of φ30mm*1.5mm, which is divided into a sample with weld (the weld is located in the center of the sample) and a base material sample. The second type is a slow tensile test specimen with a full weld (the entire gauge length is a weld, see [reference]). Figure 2 a) The third type is a slow tensile test specimen with a weld, which is processed according to the ASTM G 142-98 test standard, ensuring that the weld is centered in the gauge length. See [link to relevant documentation]. Figure 2 b.
[0077] 3. Surface treatment:
[0078] The hydrogen-permeable sample was sanded to 2000# using sandpaper, and the slowly stretched sample was ultrasonically cleaned with alcohol for 20 minutes. The sample was then dried and stored in a dry environment for later use.
[0079] 4. Surface polarization:
[0080] To eliminate surface residues and improve experimental accuracy, the hydrogen-permeable sample surface was polarized using an electrochemical method before the experiment, with a polarization current of 0.5 mA / cm. 2 The polarization time is 20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
[0081] 5. High-pressure hydrogen permeation test:
[0082] The hydrogen permeation test was conducted using a high-pressure hydrogen permeation testing apparatus in a dual-electrolysis cell. A 0.1 mol / L NaOH solution was added to the hydrogen measurement cell, and the open-circuit potential of the sample was measured using an electrochemical workstation for 3600 s. Afterwards, the test surface of the sample was polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, and the curve of the anolyte current changing over time was recorded using the electrochemical workstation. When the background current fell below 100 nA, 0.2 MPa–10 MPa H2 was introduced into the cathodic electrolysis cell, and the start time of hydrogen injection was recorded to obtain the hydrogen permeation curve. The steady-state hydrogen permeation current I0 for both the welded and base metal samples (i.e., the two types of samples in the first type) was obtained. w with I b The hydrogen adsorption concentration C on the corresponding expanded surface of the welded sample and the base material was calculated. w With C b .
[0083] 6. Welded joint area ratio:
[0084] The hydrogen permeation specimen with weld seam after the test in step 5 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld joint size was observed and measured using a metallographic microscope, and the area ratio (i.e., the area ratio of the weld seam in the test area to the entire test area) K was calculated.
[0085] 7. Calculation of the influence coefficient of welded joints:
[0086] Because the presence of welded joints causes differences in hydrogen permeation between the base material and the welded sample, the degree of difference depends on the proportion of welded joints. Through multiple rounds of testing and summarization, this invention clarifies the calculation method for the welded joint influence coefficient Y in a gaseous environment: Y = (I w -I b ) / (K*P), where P is the H2 pressure in the hydrogen permeation test.
[0087] 8. Slow air stretching:
[0088] Using a slow tensile testing machine, slow tensile tests were conducted according to the standard ASTM G129. Full weld seam slow tensile specimens were selected, and the slow tensile rate was 1*10⁻⁶. -5 / s, until the sample breaks, and the reduction of area R is measured and calculated. air .
[0089] 9. Sample preparation before slow tensile testing in a hydrogen atmosphere:
[0090] Before the test, the gauge length of the slow tensile specimen was sanded with 1000 grit sandpaper for 5 rounds to ensure that the roughness Ra>64, thereby improving the difference in test results.
[0091] 10. Calculation of impurity water content:
[0092] In an experimental hydrogen environment, steam is introduced to introduce impurity water. The method for calculating the amount of impurity water introduced is: V = 5000 * Y / T S +20, where T S V represents the tensile strength of the test material, and V is the volume ratio of impurity water in the hydrogen environment (in ppm).
[0093] 11. Slow tensile test under high pressure hydrogen environment:
[0094] The test method followed ASTM G129. Before the test, the autoclave was purged with high-purity nitrogen for 2 hours, followed by the introduction of hydrogen gas until the hydrogen pressure reached 6 MPa. The sample was then allowed to stand in the high-pressure hydrogen environment for 24 hours before the test. Water vapor was then introduced, and impurity water was added until the volume of impurity water reached the amount V calculated in step 10. Immediately afterwards, a slow tensile test was conducted. The specimen was a welded slow tensile specimen, and the slow tensile rate was the same as that in step 8. The reduction of area R was recorded after the test. H .
[0095] 12. Confirmation of result validity:
[0096] To ensure the validity of the test results and to effectively evaluate the hydrogen embrittlement performance of the welded joint, after the dynamic slow tensile test, the periphery of the fracture test was etched with 5% nitric acid alcohol for 10 seconds. The fracture location was then observed using a metallographic microscope. If the fracture location was at the welded joint, the test was considered valid; otherwise, the test was invalid. If invalid, the test could be repeated according to step 11, while increasing the impurity water content by 20 ppm until the test was valid. After the test, the periphery of the fractured slow tensile specimen was etched with 5% nitric acid alcohol, and then observed using a metallographic microscope. If the fracture location was found at the welded joint, the test was confirmed to be valid.
[0097] 13. Calculation and evaluation of hydrogen embrittlement sensitivity:
[0098] The hydrogen embrittlement susceptibility of welded joints was evaluated using the results of two slow tensile tests. The hydrogen embrittlement susceptibility index EI = (R air -R H )*C w *100 / (R air *C b The calculated EI is 28.61, indicating a slight risk of hydrogen embrittlement.
[0099] Table 2 below shows the relevant parameter values involved in this embodiment.
[0100] Table 2:
[0101] <![CDATA[I w / uA]]> <![CDATA[I b / uA]]> Cw / ppm Cb / ppm K P / MPa Y V / ppm Ts / MPa <![CDATA[R air / ％ ]]> <![CDATA[R H / ％ ]]> Validity EI 0.934 0.802 0.094 0.075 0.163 6 0.135 21.22 554 79.95 61.7 yes 28.61
[0102] Example 2
[0103] This embodiment uses X52 as the base material and employs a fully automated welding process with a welding speed of 40 cm / min, a welding voltage of 26 V, and a welding current of 248 A. The specific operating steps of the method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment provided in this embodiment are as follows:
[0104] 1. Sample taking:
[0105] Samples should be taken directly from the welded pipeline, ensuring the weld joint is centered on the sample. Figure 1 As shown, the sampling size is 150*50*20mm, and the sampling location is one-quarter of the way along the pipe wall thickness.
[0106] 2. Sample preparation:
[0107] The test specimens are divided into three types. The first type is a hydrogen permeation specimen with a size of φ30mm*1.5mm, which is divided into a sample with weld (the weld is located in the center of the sample) and a base material sample. The second type is a slow tensile test specimen with a full weld (the entire gauge length is a weld, see [reference]). Figure 2 a) The third type is a slow tensile test specimen with a weld, which is processed according to the ASTM G 142-98 test standard, ensuring that the weld is centered in the gauge length. See [link to relevant documentation]. Figure 2 b.
[0108] 3. Surface treatment:
[0109] The hydrogen-permeable sample was sanded to 2000# using sandpaper, and the slowly stretched sample was ultrasonically cleaned with alcohol for 20 minutes. The sample was then dried and stored in a dry environment for later use.
[0110] 4. Surface polarization:
[0111] To eliminate surface residues and improve experimental accuracy, the hydrogen-permeable sample surface was polarized using an electrochemical method before the experiment, with a polarization current of 1.5 mA / cm. 2 The polarization time is 8 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
[0112] 5. High-pressure hydrogen permeation test:
[0113] The hydrogen permeation test was conducted using a high-pressure hydrogen permeation testing apparatus in a dual-electrolysis cell. A 0.1 mol / L NaOH solution was added to the hydrogen measurement cell, and the open-circuit potential of the sample was measured using an electrochemical workstation for 3600 s. Afterwards, the test surface of the sample was polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, and the curve of the anolyte current changing over time was recorded using the electrochemical workstation. When the background current fell below 100 nA, 0.2 MPa–10 MPa H2 was introduced into the cathodic electrolysis cell, and the start time of hydrogen injection was recorded to obtain the hydrogen permeation curve. The steady-state hydrogen permeation current I0 for both the welded and base metal samples (i.e., the two types of samples in the first type) was obtained. w with I b The hydrogen adsorption concentration C on the corresponding expanded surface of the welded sample and the base material was calculated. w With C b .
[0114] 6. Welded joint area ratio:
[0115] The hydrogen permeation specimen with weld seam after the test in step 5 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld joint size was observed and measured using a metallographic microscope, and the area ratio (i.e., the area ratio of the weld seam in the test area to the entire test area) K was calculated.
[0116] 7. Calculation of the influence coefficient of welded joints:
[0117] Because the presence of welded joints causes differences in hydrogen permeation between the base material and the welded sample, the degree of difference depends on the proportion of welded joints. Through multiple rounds of testing and summarization, this invention clarifies the calculation method for the welded joint influence coefficient Y in a gaseous environment: Y = (I w -I b ) / (K*P), where P is the H2 pressure in the hydrogen permeation test.
[0118] 8. Slow air stretching:
[0119] Slow tensile testing was conducted using a slow tensile testing machine, referring to the standard ASTM G129. The slow tensile specimens were full-weld slow tensile test samples, with a slow tensile rate of 1*10⁻⁶. -5 / s, until the sample breaks, and the reduction of area R is measured and calculated. air .
[0120] 9. Sample preparation before slow tensile testing in a hydrogen atmosphere:
[0121] Before the test, the gauge length of the slow tensile specimen was sanded with 1000 grit sandpaper for 7 rounds to ensure that the roughness Ra>64, thereby improving the difference in test results.
[0122] 10. Calculation of impurity water content:
[0123] In an experimental hydrogen environment, steam is introduced to introduce impurity water. The method for calculating the amount of impurity water introduced is: V = 5000 * Y / T S +20, where T S V represents the tensile strength of the test material, and V is the volume ratio of impurity water in the hydrogen environment (in ppm).
[0124] 11. Slow tensile test under high pressure hydrogen environment:
[0125] The test method follows the standard ASTM G129. Before the test, the autoclave was purged with high-purity nitrogen for 2 hours, followed by the introduction of hydrogen gas until the hydrogen pressure reached 4 MPa. The sample was then allowed to stand in the high-pressure hydrogen environment for 24 hours before the test. Water vapor was then introduced, and impurity water was added until the volume of impurity water reached the amount V calculated in step 10. Immediately afterwards, a slow tensile test was conducted. The slow tensile specimen used was a welded specimen, and the slow tensile rate was the same as that in step 8. After the test, the reduction of area R was recorded. H .
[0126] 12. Confirmation of result validity:
[0127] The effectiveness of the test was confirmed by observation of the fractured samples after the test was completed.
[0128] 13. Calculation and evaluation of hydrogen embrittlement sensitivity:
[0129] The hydrogen embrittlement susceptibility of welded joints was evaluated using the results of two slow tensile tests. The hydrogen embrittlement susceptibility index EI = (R air -R H )*C w *100 / (R air *C b The calculated hydrogen embrittlement index (EI) is 25.6, indicating a mild risk of hydrogen embrittlement.
[0130] Table 3 below shows the relevant parameter values involved in this embodiment.
[0131] Table 3:
[0132] <![CDATA[I w / uA]]> <![CDATA[I b / uA]]> Cw / ppm Cb / ppm K P / MPa Y V / ppm Ts / MPa <![CDATA[R air / ％ ]]> <![CDATA[R H / ％ ]]> Validity EI 0.313 0.226 0.04 0.03 0.108 4 0.201 21.82 554 79.95 64.6 yes 25.6
[0133] Example 3
[0134] This embodiment uses X52 as the base material and employs a fully automated welding process with a welding speed of 37 cm / min, a welding voltage of 25 V, and a welding current of 256 A. The specific operating steps of the method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment provided in this embodiment are as follows:
[0135] 1. Sample taking:
[0136] Samples should be taken directly from the welded pipeline, ensuring the weld joint is centered on the sample. Figure 1 As shown, the sampling size is 150*50*20mm, and the sampling location is one-quarter of the thickness direction.
[0137] 2. Sample preparation:
[0138] The test specimens are divided into three types. The first type is a hydrogen permeation specimen with a size of φ30mm*1.5mm, which is divided into a sample with weld (the weld is located in the center of the sample) and a base material sample. The second type is a slow tensile test specimen with a full weld (the entire gauge length is a weld, see [reference]). Figure 2 a) The third type is a slow tensile test specimen with a weld, which is processed according to the ASTM G 142-98 test standard, ensuring that the weld is centered in the gauge length. See [link to relevant documentation]. Figure 2 b.
[0139] 3. Surface treatment:
[0140] The hydrogen-permeable sample was sanded to 2000# using sandpaper, and the slowly stretched sample was ultrasonically cleaned with alcohol for 20 minutes. The sample was then dried and stored in a dry environment for later use.
[0141] 4. Surface polarization:
[0142] To eliminate surface residues and improve experimental accuracy, the hydrogen-permeable sample surface was polarized using an electrochemical method before the experiment, with a polarization current of 2 mA / cm. 2 The polarization time is 7 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
[0143] 5. High-pressure hydrogen permeation test:
[0144] The hydrogen permeation test was conducted using a high-pressure hydrogen permeation testing apparatus in a dual-electrolysis cell. A 0.1 mol / L NaOH solution was added to the hydrogen measurement cell, and the open-circuit potential of the sample was measured using an electrochemical workstation for 3600 s. Afterwards, the test surface of the sample was polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, and the curve of the anolyte current changing over time was recorded using the electrochemical workstation. When the background current fell below 100 nA, 0.2 MPa–10 MPa H2 was introduced into the cathodic electrolysis cell, and the start time of hydrogen injection was recorded to obtain the hydrogen permeation curve. The steady-state hydrogen permeation current I0 for both the welded and base metal samples (i.e., the two types of samples in the first type) was obtained. w with I b The hydrogen adsorption concentration C on the corresponding expanded surface of the welded sample and the base material was calculated. w With C b .
[0145] 6. Welded joint area ratio:
[0146] The hydrogen permeation specimen with weld seam after the test in step 5 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld joint size was observed and measured using a metallographic microscope, and the area ratio (i.e., the area ratio of the weld seam in the test area to the entire test area) K was calculated.
[0147] 7. Calculation of the influence coefficient of welded joints:
[0148] Because the presence of welded joints causes differences in hydrogen permeation between the base material and the welded sample, the degree of difference depends on the proportion of welded joints. Through multiple rounds of testing and summarization, this invention clarifies the calculation method for the welded joint influence coefficient Y in a gaseous environment: Y = (I w -I b ) / (K*P), where P is the H2 pressure in the hydrogen permeation test.
[0149] 8. Slow air stretching:
[0150] Slow tensile testing was conducted using a slow tensile testing machine, referring to the standard ASTM G129. The slow tensile specimens were full-weld slow tensile test samples, with a slow tensile rate of 1*10⁻⁶. -5 / s, until the sample breaks, and the reduction of area R is measured and calculated. air .
[0151] 9. Sample preparation before slow tensile testing in a hydrogen atmosphere:
[0152] Before the test, the gauge length of the slow tensile specimen was sanded with 1000 grit sandpaper for 10 rounds to ensure that the roughness Ra>64, thereby improving the difference in test results.
[0153] 10. Calculation of impurity water content:
[0154] The addition of impurity water in a hydrogen atmosphere effectively verifies the hydrogen resistance of welded joints. The hydrogen embrittlement resistance of materials is influenced by both the environment and the inherent mechanical properties of the material. This invention, combining these two aspects, and through experimental verification, yields a method for calculating the amount of impurity water added: V = 5000 * Y / T S +20, where T S V represents the tensile strength of the test material, and V is the volume ratio of impurity water in the hydrogen environment (in ppm).
[0155] 11. Slow tensile test under high pressure hydrogen environment:
[0156] The test method followed ASTM G129. Before the test, the autoclave was purged with high-purity nitrogen for 2 hours, followed by the introduction of hydrogen gas until the hydrogen pressure reached 20 MPa. The sample was then allowed to stand in the high-pressure hydrogen environment for 24 hours before the test. Water vapor was then introduced, and impurity water was added until the volume of impurity water reached the amount V calculated in step 10. Immediately afterwards, a slow tensile test was conducted at the same rate as in step 8. The reduction of area R was recorded after the test. H .
[0157] 12. Confirmation of result validity:
[0158] The effectiveness of the test was confirmed by observation of the fractured samples after the test was completed.
[0159] 13. Calculation and evaluation of hydrogen embrittlement sensitivity:
[0160] If the test is valid, the hydrogen embrittlement susceptibility of the welded joint is evaluated using the results of two slow tensile tests. The hydrogen embrittlement susceptibility index EI = (R... air -R H )*C w *100 / (R air *C b The calculated hydrogen embrittlement index (EI) is 61.02, indicating a severe risk of hydrogen embrittlement.
[0161] Table 4 below shows the relevant parameter values involved in this embodiment.
[0162] Table 4:
[0163] <![CDATA[I w / uA]]> <![CDATA[I b / uA]]> Cw / ppm Cb / ppm K P / MPa Y V / ppm Ts / MPa <![CDATA[R air / ％ ]]> <![CDATA[R H / ％ ]]> Validity EI 0.395 0.143 0.045 0.035 0.12 20 0.105 20.94 554 79.95 42 yes 61.02
Claims
1. A method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment, characterized in that, Includes the following steps: (1) Sample preparation Take samples directly from the welded pipeline, ensuring the weld joint is centered on the sample; The test specimens are divided into three types. The first type is hydrogen permeation test specimens, which are divided into two categories: welded specimens with the weld in the center of the specimen and base material specimens. The second type is full welded slow tensile test specimens with the entire gauge length consisting of welds. The third type is welded slow tensile test specimens with welds, which are processed according to the ASTM G 142-98 test standard and have the weld in the center of the gauge length. (2) The steady-state hydrogen permeation current I of the welded area and the base material in the first type of sample was obtained by high-pressure hydrogen permeation test. w with I b The hydrogen adsorption concentration C on the surface of the welded sample and the base material was obtained. w With C b ; (3) Calculate the area ratio K of the weld seam in the test area to the entire test area in step (2); (4) Calculate the influence coefficient Y of the welded joint in the gaseous environment using the following formula: Y=(I w -I b ) / (K*P) Where P is the H2 pressure in the hydrogen permeation test; (5) Calculate the reduction of area R of the full weld slow tensile specimen through air slow tensile test. air ; (6) Calculate the reduction of area R of the welded slow-tension specimen by means of a slow tensile test under high pressure hydrogen environment. H The slow stretching rate is consistent with that in step (5); (7) Calculation and evaluation of hydrogen embrittlement sensitivity: Calculate the hydrogen embrittlement sensitivity index: EI = (R air -R H )*C w *100 / (R air *C b ); An EI of 0-15 indicates no risk of hydrogen embrittlement; an EI of 16-30 indicates a slight risk of hydrogen embrittlement; an EI of 31-50 indicates a moderate risk of hydrogen embrittlement; and an EI greater than 50 indicates a severe risk of hydrogen embrittlement.
2. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, In step (5), a slow tensile testing machine is used to conduct a slow tensile test according to standard ASTM G 129. The slow tensile rate of the full weld slow tensile test specimen is controlled at 5*10. -7 —1*10 -5 / s, until the sample breaks, the reduction of area R is measured and calculated. air .
3. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, Steps (5) and (6) also include processing the sample before the slow tensile test in a hydrogen environment until the roughness Ra of the gauge length section of the sample is greater than 64.
4. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, Step (6) also includes the following pretreatment sub-steps, referencing ASTM G 129, before starting the slow tensile test: 1) Purge the autoclave with high-purity nitrogen until the oxygen and other impurity gases in the environment are reduced to below 0.005%; 2) Introduce hydrogen gas until the pressure reaches the simulated operating pressure P. H ; 3) Before the test, let the sample stand in a high-pressure hydrogen environment for a sufficient time to ensure that hydrogen atoms are fully adsorbed on the sample surface; 4) Introduce steam and mix in impurity water until the volume of impurity water reaches the impurity water content calculated by the following formula: V=5000*Y / T S +20 Where V is the volume ratio of impurity water in the hydrogen environment (unit: ppm); T S The tensile strength of the test material (unit: MPa).
5. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 4, characterized in that, It also includes a step to confirm the validity of the test results in step (6), wherein the condition for confirmation of validity is that the fracture location is at the weld joint.
6. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment according to claim 5, characterized in that, If the test result of step (6) is confirmed to be invalid, repeat the pretreatment sub-step and step (6), and in sub-step (4), increase the impurity water content on the original basis by an increase of J = 1200 / Ts + 12 until the test is valid.
7. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, In step (1), the sampling location is one-quarter of the way along the pipe wall thickness.
8. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, It also includes the steps of surface treatment of hydrogen-permeable samples and removal of hydrogen-permeable sample surface residues.
9. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints in a hydrogen environment according to claim 8, characterized in that, The surface treatment includes polishing and cleaning; the polishing is to polish the hydrogen-permeable sample to 2000# using sandpaper; the cleaning is to perform ultrasonic cleaning of the polished sample with alcohol.
10. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 8, characterized in that, The surface of the hydrogen-permeable sample was polarized using an electrochemical test method, with a polarization current of 0.5 mA / cm. 2 -2mA / cm 2 The polarization time is 5-20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.
11. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, In step (2), the hydrogen permeation test is carried out using a dual electrolysis cell.
12. The method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints under hydrogen environment according to claim 1, characterized in that, Step (3) also includes a step of etching the hydrogen-permeable sample with weld seam after the test in step (3) using nitric acid alcohol before calculating the area ratio K.