Hydrogen embrittlement evaluation test method for metal welding area

Abstract

The invention discloses a hydrogen embrittlement evaluation test method for a metal welding area. The hydrogen embrittlement evaluation test method comprises the steps that 1, sampling is conducted from the welding area and base metal; 2, processing the sample into a hydrogen permeation sample with a welding seam and a base material sample; 3, performing surface treatment on the sample; 4, plating nickel on the hydrogen permeation sample; 5, removing residues on the surface of the sample; 6, obtaining the steady-state hydrogen permeation current Ib and Iw of the base metal and the welding area corresponding to the two samples, and the hydrogen permeability psi b and psi w corresponding to the base metal and the sample with the welding seam; 7, calculating the area ratio k of the weld joints in the test area in the whole test area in the step 6; 8, calculating the adsorption hydrogen concentration psi q = (psi w-psi b) / k + psi b; 9, calculating a hydrogen embrittlement risk index E = (psi q-psi b) * Ib * 100% / (psi q * Iw) based on the hydrogen permeability; and 10, evaluating the hydrogen embrittlement sensitivity of the welding area: if the E is 0-12%, the welding area has no hydrogen embrittlement risk, if the E is 12-24%, the welding area has low hydrogen embrittlement risk, if the E is 24-55%, the welding area has moderate hydrogen embrittlement risk, and if the E is more than 55%, the welding area has serious hydrogen embrittlement risk.

Description

Technical Field

[0001] This invention relates to the field of hydrogen embrittlement evaluation technology for metallic materials, and specifically to a test method for evaluating hydrogen embrittlement in the welded area of ​​a metal welded joint. Background Technology

[0002] Hydrogen energy, as a clean energy source, is widely available and boasts advantages such as high energy conversion efficiency, zero pollution, zero emissions, storability, and renewability. It represents a crucial direction for energy transformation and upgrading, with enormous market potential. 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 critical link. Long-term operation of hydrogen storage and transportation containers and pipelines in high-pressure, high-purity hydrogen environments can easily lead to reduced local plasticity, accelerated crack propagation, decreased durability, and problems such as 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 mentioned 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] However, due to the narrow and complex microstructure of welded joints, conventional sampling contains various microstructures, making the above-mentioned hydrogen embrittlement evaluation methods unsuitable for evaluating welded joints. Currently, the main methods for evaluating welded joints are as follows: First, thermal simulation methods are used to prepare samples of different microstructures in the weld heat-affected zone (HAZ) at a large scale, and then these samples are used for hydrogen embrittlement evaluation and screening. Second, samples are directly taken from the weld, using notched slow-tension specimens with the notch placed at the weld. Both of these methods are difficult to effectively represent the hydrogen embrittlement sensitivity of the HAZ. First, the sampling methods using thermal simulation differ significantly from the actual welding process, especially regarding the mixed microstructure of the HAZ. Actual thermal simulation methods can only simulate one microstructure and cannot represent the actual welded joint (including the weld, HAZ, and base metal). Therefore, there is a significant difference between the hydrogen embrittlement evaluation and the actual situation. Second, using notched tensile specimens requires extremely high precision in notch processing. Literature research indicates that different types of pipeline steel require different notch stress concentration factors; otherwise, significant differences in hydrogen embrittlement performance will occur. Furthermore, notched specimens also face the problem of high data dispersion, requiring multiple experiments to select appropriate data, which increases experimental 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 test method for evaluating hydrogen embrittlement in metal welded areas, capable of analyzing the correlation between hydrogen embrittlement and welded joints of steel used in pipelines and hydrogen storage tanks under hydrogen conditions. This method for testing the hydrogen resistance of welded joints combines hydrogen permeation testing with calculation to evaluate the hydrogen embrittlement performance of welded joints, improving the accuracy and efficiency of hydrogen embrittlement sensitivity assessment. This method is also applicable to other metallic materials under hydrogen conditions. Using the method of this invention, the hydrogen embrittlement performance of welded joints with different welding processes can be obtained, guiding welding process improvement and providing support for the safety assessment of metallic materials under hydrogen conditions.

[0007] The technical problem it aims to solve can be addressed through the following technical solutions.

[0008] A test method for evaluating hydrogen embrittlement in welded metal areas includes the following steps:

[0009] (1) Sample taking

[0010] Samples were taken from the welding area or the base material, respectively.

[0011] (2) Sample processing

[0012] After sampling, the samples are processed into hydrogen permeation samples, one type being hydrogen permeation samples with weld seams, and the other being base material samples.

[0013] (3) Surface treatment of the sample;

[0014] (4) Nickel plating is performed on one side of the hydrogen permeation sample;

[0015] (5) Remove any residue from the sample surface;

[0016] (6) Obtain the steady-state hydrogen permeation current I of the base material and weld area corresponding to the two samples through hydrogen permeation test. b and I w And the hydrogen permeability ψ of the base material and the welded sample. b and ψ w ;

[0017] (7) Calculate the ratio k of the weld seam in the test area to the total area of ​​the test area in step (6);

[0018] (8) Calculate the hydrogen adsorption concentration ψ in the weld area using the following formula. q :

[0019] ψ q =(ψ w -ψ b ) / k+ψ b ;

[0020] (9) Calculate the hydrogen embrittlement sensitivity of the weld area using the following formula:

[0021] E=(ψ q -ψ b )*I b* 100% / (ψ) q *I w )

[0022] Where E is the hydrogen embrittlement risk index based on hydrogen permeability, and the higher the value, the greater the risk;

[0023] (10) Evaluation of hydrogen embrittlement sensitivity in the welded area:

[0024] If the hydrogen embrittlement sensitivity index E obtained in step (9) is in the range of 0-12%, then the welded area has no risk of hydrogen embrittlement; if E is in the range of 12%-24%, then the welded area has a low risk of hydrogen embrittlement; if E is in the range of 24%-55%, then the welded area has a moderate risk of hydrogen embrittlement; and if E is above 55%, then the welded area has a severe risk of hydrogen embrittlement.

[0025] Furthermore, in step (1), when taking samples, the sampling location for samples with welds is one-half to one-quarter of the pipe wall thickness.

[0026] Furthermore, for hydrogen permeation specimens with welds, the weld is located in the middle of the specimen.

[0027] Furthermore, the surface treatment in step (3) includes polishing and cleaning. Even further, the polishing is to use sandpaper to polish the hydrogen permeation sample obtained in step (2) step by step to 1000#-2000#; the cleaning is to perform ultrasonic cleaning of the polished sample with alcohol.

[0028] Furthermore, in step (4), the prepared nickel plating solution is a Watts bath with the composition of 250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4; the nickel plating current is 1-30 mA / cm. 2 The time is 1-30 minutes.

[0029] Furthermore, in step (5), surface polarization is used to remove residues from the sample surface. Even further, when using an electrochemical testing method to polarize the hydrogen-permeable sample surface, the polarization current is 0.2 mA / cm². 2 -5mA / cm 2 The polarization time is 1-20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.

[0030] Furthermore, in step (6), the hydrogen permeation test is conducted using a dual electrolysis cell.

[0031] Furthermore, step (7) also includes a step of etching the hydrogen permeation sample with weld seam after the test in step (6) with nitric acid alcohol before calculating the area ratio k.

[0032] This invention, starting from the characteristics and actual conditions of welded joints, develops a method for evaluating the hydrogen resistance of welded joints using computational derivation combined with relevant experimental methods, solving the current challenge of evaluating the hydrogen resistance of welded joints. Compared with methods such as thermal simulation sample preparation and regional sampling, this method is closer to reality, allowing for direct experimental evaluation of welded joints with reliable and more accurate results. This method can support welding process development and performance improvement, reduce the risk of hydrogen embrittlement in welded joints, and enhance the safety of pipeline steel during service. Furthermore, it can be used in academic research to study the cracking mechanism of welded joints in conjunction with other analytical methods. This method is not only applicable to pipeline steel welded joints but also to welded joints of other metallic materials. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the sample collection location;

[0034] Figure 2 This is a schematic diagram of a hydrogen permeation sample, where, Figure 2 a is a schematic diagram of a hydrogen permeation sample with a welded joint. Figure 2 b is a schematic diagram of the hydrogen permeation sample of the parent material;

[0035] Figure 3 This is a schematic diagram of electrochemical hydrogen permeation. Detailed Implementation

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] This invention provides a test method for evaluating hydrogen embrittlement in welded metal areas, the main operations of which are as follows:

[0038] 1. Sample taking:

[0039] Samples should be taken directly from the welded joints of the pipeline steel, such as... Figure 1 As shown, the sampling locations are in two places (see...). Figure 1 (The two boxes in the middle) are for two types of samples. One is for the welded joint sample, where the welded joint should be in the exact center of the sample. The sample size is 60*40*5mm, and the sampling location is between one-half and one-quarter of the pipe wall thickness. The other is for the base material sample, which should be taken from the base material away from the weld location, along the circumferential direction.

[0040] 2. Sample preparation:

[0041] Reference Figure 2After sampling, the samples were processed into hydrogen permeation samples, shaped like a ping-pong paddle with dimensions of φ35mm*1.5mm (in fact, the paddle face in the picture is divided into samples, and the handle is for easy gripping). There are two types of samples: one is a hydrogen permeation sample of a welded joint, with the weld seam located in the middle of the sample (see...). Figure 2 a) Another type is the parent material (see Figure 2 b) Process 5 of each type of sample.

[0042] 3. Sample surface treatment:

[0043] The processed hydrogen permeation sample was polished step by step to 1000#-2000# using sandpaper, then sonicated with alcohol for 5-20 minutes, and dried before use.

[0044] 4. Surface coating:

[0045] A nickel plating solution was prepared using a Watts bath (250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4). Nickel plating was then performed on the hydrogen-permeable sample side using a plating current of 1-30 mA / cm². 2 The time is 1-30 minutes.

[0046] 5. Surface polarization:

[0047] To eliminate surface residues and improve experimental accuracy, the surface of the hydrogen-permeable sample was polarized using an electrochemical method before the experiment, with a polarization current of 0.2 mA / cm. 2 -5mA / cm 2 The polarization time is 1-20 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.

[0048] 6. The hydrogen permeation test was conducted using a dual electrolytic cell. The dual electrolytic cell was set up according to... Figure 3 The hydrogen release electrolysis cell terminal connection is shown. Sufficient 0.1 mol / L NaOH solution is injected into the cell. The open-circuit potential of the sample is measured using an electrochemical workstation for 3600 s. Afterwards, the test surface of the sample is polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential. A cathode current of 0.5–10 mA is applied to the hydrogen charging side, and the curve of the anolyte current changing over time is recorded using the electrochemical workstation. Using the experimental curves, the steady-state hydrogen permeation currents of the base material and the weld area are obtained as I0 and I0, respectively. b I w (i.e., the base material and the welded sample correspond to I respectively) b and I w ), and combined with relevant formulas, the corresponding hydrogen permeability ψ of the base material and the welded sample were obtained as follows: b ψw The experiment was repeated 3 times, and the difference in the measurement results was within 12%. The average value was taken.

[0049] 7. Measure the area ratio of the welding area (weld and heat-affected zone):

[0050] The hydrogen permeation specimen with weld seam after the test in step 6 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld area size was observed and measured using a metallographic microscope, and the area ratio (i.e., the ratio of the weld seam area to the total area of ​​the test area) k was calculated.

[0051] 8. Calculation of hydrogen permeability at the weld:

[0052] Compared to the base metal sample, the welded sample exhibits higher hydrogen embrittlement sensitivity in the welded area. Therefore, the difference in hydrogen permeation between the base metal and welded samples can be attributed to the welded area. Since hydrogen diffusion follows the first law of diffusion, the adsorbed hydrogen concentration in the welded area can be estimated by measuring the area occupied by the welded region and the adsorbed hydrogen concentration in the base metal. Through measurement and derivation, the adsorbed hydrogen concentration ψ in the welded region is... q The calculation formula is ψ q =(ψ w -ψ b ) / k+ψ b .

[0053] 9. Calculation of hydrogen embrittlement sensitivity in the welded area:

[0054] Based on the different adsorbed hydrogen permeability, hydrogen embrittlement sensitivity analysis can be performed, and the specific formula is E=(ψ q -ψ b )*I b* 100% / (ψ) q *I w E is the hydrogen embrittlement risk index based on hydrogen permeability; the higher the value, the greater the risk.

[0055] 10. Evaluation of hydrogen embrittlement sensitivity in the welded area:

[0056] Through experimental research and demonstration, it was found that if the hydrogen embrittlement sensitivity index E is in the range of 0-12%, the welded area has no risk of hydrogen embrittlement; if E is in the range of 12%-24%, the welded area has a low risk of hydrogen embrittlement; if E is in the range of 24%-55%, the welded area has a moderate risk of hydrogen embrittlement; and if E is above 55%, the welded area has a severe risk of hydrogen embrittlement.

[0057] The following are more specific examples.

[0058] Example 1

[0059] This embodiment uses X52 as the base material and employs a manual welding process with a welding heat input of 1.4–2.5 KJ / mm. The method provided in this embodiment for evaluating the hydrogen embrittlement performance of welded joints in pipeline steel is as follows:

[0060] 1. Sample taking:

[0061] Samples should be taken directly from the welded joint of the pipeline steel. There are two sampling locations: one is the weld joint sample, where the weld joint should be centered on the sample. Figure 1 As shown, the sampling size is 60*40*5mm, and the sampling location is between one-half and one-quarter of the pipe wall thickness. Another method is to use a base material sample, which is taken from the base material away from the welding location, along the circumferential direction.

[0062] 2. Sample preparation:

[0063] After sampling, the samples were processed into hydrogen permeation specimens, shaped like ping-pong paddles with dimensions of φ35mm*1.5mm. Two types of specimens were used: one was a hydrogen permeation specimen of a welded joint, with the weld seam located in the center of the specimen (see...). Figure 2 a) Another type is the parent material (see Figure 2 b) Process 5 of each type of sample.

[0064] 3. Sample surface treatment:

[0065] The processed hydrogen permeation sample was polished step by step to 1200# using sandpaper, then ultrasonicated with alcohol for 5-20 minutes, and dried before use.

[0066] 4. Surface coating:

[0067] A nickel plating solution was prepared as a Watts bath (250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4). Nickel plating was then performed on the hydrogen-permeable sample side using a plating current of 3 mA / cm². 2 The time is 5 minutes.

[0068] 5. Surface polarization:

[0069] 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 10 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.

[0070] 6. The hydrogen permeation test was conducted using a dual electrolytic cell. The dual electrolytic cell was set up according to... Figure 3The hydrogen release electrolysis cell terminal connection is shown. Sufficient 0.1 mol / L NaOH solution is injected into the cell. The open-circuit potential of the sample is measured using an electrochemical workstation for 3600 s. Afterwards, the sample's test surface is polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, with a cathode current of 1 mA. The curve of the anolyte current changing over time is recorded using the electrochemical workstation. Using the experimental curve, the steady-state hydrogen permeation current I in the base material and weld area is obtained. b I w And obtain the corresponding hydrogen permeability ψ by combining relevant formulas. b ψ w The experiment was repeated 3 times, and the difference in the measurement results was within 12%. The average value was taken.

[0071] 7. Measure the area ratio of the welding area (weld and heat-affected zone):

[0072] The hydrogen permeation specimen with weld seam after the test in step 6 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld area size was observed and measured using a metallographic microscope, and the area ratio k of the weld seam in the test area to the entire test area was calculated.

[0073] 8. Calculation of hydrogen permeability at the weld:

[0074] Compared to the base metal sample, the welded sample exhibits higher hydrogen embrittlement sensitivity in the welded area. Therefore, the difference in hydrogen permeation between the base metal and welded samples can be attributed to the welded area. Since hydrogen diffusion follows the first law of diffusion, the adsorbed hydrogen concentration in the welded area can be estimated by measuring the area occupied by the welded region and the adsorbed hydrogen concentration in the base metal. Through measurement and derivation, the adsorbed hydrogen concentration ψ in the welded region is... q The calculation formula is ψ q =(ψ w -ψ b ) / k+ψ b .

[0075] 9. Calculation of hydrogen embrittlement sensitivity in the welded area:

[0076] Based on the different adsorbed hydrogen permeability, hydrogen embrittlement sensitivity analysis can be performed, and the specific formula is E=(ψ q -ψ b )*I b* 100% / (ψ) q *I w E is the hydrogen embrittlement risk index based on hydrogen permeability; the higher the value, the greater the risk.

[0077] 10. Evaluation of hydrogen embrittlement sensitivity in the welded area:

[0078] Based on calculations using relevant parameters, E is 44.94%, falling within the 24%-55% range. Therefore, the welded area has a moderate risk of hydrogen embrittlement.

[0079] Table 2 below shows the relevant parameter values ​​involved in this embodiment.

[0080] Table 2:

[0081]

[0082] Example 2

[0083] This embodiment uses X52 as the base material and employs a manual welding process with a welding heat input of 0.5–0.8 KJ / mm. The specific operating steps of the method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints provided in this embodiment are as follows:

[0084] 1. Sample taking:

[0085] Samples should be taken directly from the welded joint of the pipeline steel. There are two sampling locations: one is the weld joint sample, where the weld joint should be centered on the sample. Figure 1 As shown, the sampling size is 60*40*5mm, and the sampling location is between one-half and one-quarter of the pipe wall thickness. Another method is to use a base material sample, which is taken from the base material away from the welding location, along the circumferential direction. The sampling locations are as follows... Figure 1 As shown.

[0086] 2. Sample preparation:

[0087] After sampling, the samples were processed into hydrogen permeation specimens, shaped like ping-pong paddles with dimensions of φ35mm*1.5mm. Two types of specimens were used: one was a hydrogen permeation sample of a welded joint, with the weld seam located in the center of the sample; the other was the base material, as detailed below. Figure 2 As shown in the figure, the racket face represents two different samples, while the handle is designed for easy gripping. Five of each sample were processed.

[0088] 3. Sample surface treatment:

[0089] The processed hydrogen permeation sample was polished step by step to 1500# using sandpaper, then ultrasonicated with alcohol for 10 minutes, and dried before use.

[0090] 4. Surface coating:

[0091] A nickel plating solution was prepared as a Watts bath (250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4). Nickel plating was then performed on the hydrogen-permeable sample side using a plating current of 5 mA / cm². 2 The time is 10 minutes.

[0092] 5. Surface polarization:

[0093] 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 10 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.

[0094] 6. The hydrogen permeation test was conducted using a dual electrolytic cell. The dual electrolytic cell was set up according to... Figure 3 The hydrogen release electrolysis cell terminal connection is shown. Sufficient 0.1 mol / L NaOH solution is injected into the cell. The open-circuit potential of the sample is measured using an electrochemical workstation for 3600 s. Afterwards, the sample's test surface is polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, with a cathode current of 0.5 mA. The curve of the anolyte current changing over time is recorded using the electrochemical workstation. Using the experimental curve, the steady-state hydrogen permeation current I in the base material and weld area is obtained. b I w And obtain the corresponding hydrogen permeability ψ by combining relevant formulas. b ψ w The experiment was repeated 3 times, and the difference in the measurement results was within 12%. The average value was taken.

[0095] 7. Measure the area ratio of the welding area (weld and heat-affected zone):

[0096] The hydrogen permeation specimen with weld seam after the test in step 6 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld area size was observed and measured using a metallographic microscope, and the area ratio k of the weld seam in the test area to the entire test area was calculated.

[0097] 8. Calculation of hydrogen permeability at the weld:

[0098] Compared to the base metal sample, the welded sample exhibits higher hydrogen embrittlement sensitivity in the welded area. Therefore, the difference in hydrogen permeation between the base metal and welded samples can be attributed to the welded area. Since hydrogen diffusion follows the first law of diffusion, the adsorbed hydrogen concentration in the welded area can be estimated by measuring the area occupied by the welded region and the adsorbed hydrogen concentration in the base metal. Through measurement and derivation, the adsorbed hydrogen concentration ψ in the welded region is... q The calculation formula is ψ q =(ψ w -ψ b ) / k+ψ b .

[0099] 9. Calculation of hydrogen embrittlement sensitivity in the welded area:

[0100] Based on the different adsorbed hydrogen permeability, hydrogen embrittlement sensitivity analysis can be performed, and the specific formula is E=(ψq -ψ b )*I b* 100% / (ψ) q *I w E is the hydrogen embrittlement risk index based on hydrogen permeability; the higher the value, the greater the risk.

[0101] 10. Evaluation of hydrogen embrittlement sensitivity in the welded area:

[0102] Based on calculations using relevant parameters, E is 39.74%, falling within the 24%-55% range. Therefore, the welded area has a moderate risk of hydrogen embrittlement.

[0103] Table 3 below shows the relevant parameter values ​​involved in this embodiment.

[0104] Table 3:

[0105]

[0106] Example 3

[0107] This embodiment uses X52 as the base material and employs a manual welding process with a welding heat input of 0.9–1.1 KJ / mm. The specific operating steps of the method for evaluating the hydrogen embrittlement performance of pipeline steel welded joints provided in this embodiment are as follows:

[0108] 1. Sample taking:

[0109] Samples should be taken directly from the welded joint of the pipeline steel. There are two sampling locations: one is the weld joint sample, where the weld joint should be centered on the sample. Figure 1 As shown, the sampling size is 60*40*5mm, and the sampling location is between one-half and one-quarter of the pipe wall thickness. Another method is to use a base material sample, which is taken from the base material away from the welding location, along the circumferential direction. The sampling locations are as follows... Figure 1 As shown.

[0110] 2. Sample preparation:

[0111] After sampling, the samples were processed into hydrogen permeation specimens, shaped like ping-pong paddles with dimensions of φ35mm*1.5mm. Two types of specimens were used: one was a hydrogen permeation sample of a welded joint, with the weld seam located in the center of the sample; the other was the base material, as detailed below. Figure 2 As shown in the figure, the racket face represents two different samples, while the handle is designed for easy gripping. Five of each sample were processed.

[0112] 3. Sample surface treatment:

[0113] The processed hydrogen permeation sample was polished step by step to 2000# using sandpaper, then ultrasonicated with alcohol for 15 minutes, and dried before use.

[0114] 4. Surface coating:

[0115] A nickel plating solution was prepared as a Watts bath (250 g / L NiSO4·7H2O + 45 g / L NiCl2·6H2O + 40 g / L H3BO4). Nickel plating was then performed on the hydrogen-permeable sample side using a plating current of 3 mA / cm². 2 The time is 15 minutes.

[0116] 5. Surface polarization:

[0117] 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 mA / cm. 2 The polarization time is 10 minutes. After polarization is complete, rinse with alcohol and dry immediately for later use.

[0118] 6. The hydrogen permeation test was conducted using a dual electrolytic cell. The dual electrolytic cell was set up according to... Figure 3 The hydrogen release electrolysis cell terminal connection is shown. Sufficient 0.1 mol / L NaOH solution is injected into the cell. The open-circuit potential of the sample is measured using an electrochemical workstation for 3600 s. Afterwards, the sample's test surface is polarized at a potential of +250–300 mV vs. SCE relative to the open-circuit potential, with a cathode current of 0.8 mA. The curve of the anolyte current changing over time is recorded using the electrochemical workstation. Using the experimental curve, the steady-state hydrogen permeation current I in the base material and weld area is obtained. b I w And obtain the corresponding hydrogen permeability ψ by combining relevant formulas. b ψ w The experiment was repeated 3 times, and the difference in the measurement results was within 12%. The average value was taken.

[0119] 7. Measure the area ratio of the welding area (weld and heat-affected zone):

[0120] The hydrogen permeation specimen with weld seam after the test in step 6 was etched with 5% nitric acid alcohol for 20 seconds. Then, the weld area size was observed and measured using a metallographic microscope, and the area ratio k of the weld seam in the test area to the entire test area was calculated.

[0121] 8. Calculation of hydrogen permeability at the weld:

[0122] Compared to the base metal sample, the welded sample exhibits higher hydrogen embrittlement sensitivity in the welded area. Therefore, the difference in hydrogen permeation between the base metal and welded samples can be attributed to the welded area. Since hydrogen diffusion follows the first law of diffusion, the adsorbed hydrogen concentration in the welded area can be estimated by measuring the area occupied by the welded region and the adsorbed hydrogen concentration in the base metal. Through measurement and derivation, the adsorbed hydrogen concentration ψ in the welded region is...q The calculation formula is ψ q =(ψ w -ψ b ) / k+ψ b .

[0123] 9. Calculation of hydrogen embrittlement sensitivity in the welded area:

[0124] Based on the different adsorbed hydrogen permeability, hydrogen embrittlement sensitivity analysis can be performed, and the specific formula is E=(ψ q -ψ b )*I b* 100% / (ψ) q *I w E is the hydrogen embrittlement risk index based on hydrogen permeability; the higher the value, the greater the risk.

[0125] 10. Evaluation of hydrogen embrittlement sensitivity in the welded area:

[0126] Calculations based on relevant parameters show that E is 22.77%, which falls within the 12%-24% range. Therefore, the welded area has a slight risk of hydrogen embrittlement.

[0127] Table 4 below shows the relevant parameter values ​​involved in this embodiment.

[0128] Table 4:

[0129]

Claims

1. A method for evaluating hydrogen embrittlement of a metal welding zone, characterized by, The method comprises the following steps: (1) sampling of test pieces sampling from the welding area and the base material respectively; (2) processing of test pieces processing the test pieces after sampling into hydrogen permeation test pieces, one of which is a hydrogen permeation test piece with a weld, and the other of which is a base material test piece; (3) surface treatment of test pieces; (4) nickel plating on one side of the hydrogen permeation test piece; (5) removal of surface residues of test pieces; (6) Steady-state hydrogen permeation currents I of the base metal and the welding zone corresponding to the two samples are obtained by the hydrogen permeation test b and I w , and hydrogen permeation rates ψ of the base metal and the sample with weld corresponding to the two samples b and ψ w ; (7) calculating the area ratio k of the weld in the test area to the whole test area in step (6); (8) The absorbed hydrogen concentration ψ in the weld zone is calculated by the following equation q : ψ q = (ψ w - ψ b ) / k + ψ b ; (9) calculating the hydrogen embrittlement susceptibility of the welding area according to the following formula: E = (ψ q - ψ b ) * I b * 100% / (ψ q * I w ) wherein E is a hydrogen embrittlement risk index based on the hydrogen permeation rate, and the higher the value, the greater the risk; (10) evaluation of the hydrogen embrittlement susceptibility of the welding area: if the hydrogen embrittlement susceptibility index E obtained in step (9) is in the range of 0-12%, the welding area has no hydrogen embrittlement risk, if the index E is in the range of 12%-24%, the welding area has low hydrogen embrittlement risk, if the index E is in the range of 24%-55%, the welding area has moderate hydrogen embrittlement risk, and if the index E is in the range of more than 55%, the welding area has serious hydrogen embrittlement risk.

2. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, In step (1), when sampling the test pieces, the sampling position of the test piece with a weld is at one-half to one-fourth of the thickness of the pipe wall.

3. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, For the hydrogen permeation test piece with a weld, the weld is located in the middle position of the test piece.

4. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, The surface treatment in step (3) comprises polishing and cleaning.

5. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 4, characterized by, The polishing is to polish the hydrogen permeation test piece obtained in step (2) to 1000#-2000# by using sandpaper; and the cleaning is to clean the polished test piece by alcohol ultrasonic cleaning.

6. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, In step (4), the prepared nickel plating solution is a Watts bath having components of NiSO4-7H2O + NiCl2-6H2O + H3BO4; the nickel plating current is 1-30 mA / cm2, and the time is 1-30 minutes. 2 , time is 1-30 minutes.

7. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, In step (5), surface polarization is used to remove the surface residues of the test piece.

8. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 7, characterized by, The polarization current is 0.2 mA / cm 2 -5 mA / cm 2 The polarization time is 1-20 min, and the sample is immediately washed with alcohol and dried after polarization.

9. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, In step (6), the hydrogen permeation test is performed by using a double electrolytic cell.

10. The hydrogen embrittlement evaluation test method for a metal welding zone according to claim 1, characterized by, In step (7), before calculating the area ratio k, nitric acid alcohol is used to erode the hydrogen permeation test piece with a weld after the test in step (6).

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