Test method for rapidly and accurately charging hydrogen into high-strength steel

Abstract

The invention belongs to the field of metal material detection, and particularly relates to a hydrogen charging test method for a metal material. A test method for rapid and accurate hydrogen charging of high-strength steel comprises the following steps: by identifying independent variables (such as hydrogen charging current, time, solution volume, catalyst content, sample size, sample surface state and the like) in an electrochemical hydrogen charging test, screening out key variables which have obvious influence on the hydrogen charging amount and are easy to adjust, and determining the use range of the key variables; relative standard deviation (RSD) and standard samples with different contents are innovatively combined, so that the accuracy evaluation problem (RSD is required to be less than or equal to 8%) caused by the fact that the truth value of the hydrogen charging amount cannot be obtained is solved; by establishing a standard curve of the hydrogen charging amount and the key variable, rapid parameter locking of the specific hydrogen charging amount demand is realized. According to the method, the blank of high-strength steel hydrogen filling test accuracy evaluation is filled, and an accurate and efficient hydrogen filling technical support is provided for hydrogen embrittlement research.

Description

TECHNICAL FIELD

[0001] The application belongs to the experimental detection method of metal materials, and particularly relates to a hydrogen charging test method. BACKGROUND

[0002] High-strength steel is widely used in aerospace, petrochemical industry and other fields due to its excellent mechanical properties, but the hydrogen embrittlement phenomenon seriously restricts its service safety. Electrochemical hydrogen charging is a common means to introduce hydrogen into high-strength steel, and its principle is to produce hydrogen atoms through electrolytic reaction, and part of the hydrogen atoms enter the sample interior through adsorption and diffusion. However, the existing technology has the following problems: 1. The corresponding relationship between the hydrogen charging parameters (current, time, etc.) and the hydrogen charging amount is not clear, and it is difficult to quickly lock the test conditions of the target hydrogen charging amount; 2. The true value of the hydrogen charging amount (the true value is the real content of the measured component objectively existing in the sample) cannot be directly obtained, resulting in a lack of effective evaluation method for the accuracy of the test results; 3. The system error of the hydrogen measurement equipment may affect the reliability of the results, and there is a lack of standardized calibration process; 4. Factors such as sample surface state have not been systematically studied, resulting in poor test repeatability.

[0003] Although the existing patent literature (such as CN 113697768 A) relates to hydrogen charging control, it is not designed for the characteristics of high-strength steel materials, and the accuracy evaluation problem is not solved. The present application realizes the rapid and accurate hydrogen charging of high-strength steel by optimizing the hydrogen charging parameters and establishing a multi-dimensional evaluation system. SUMMARY

[0004] The present application is to solve the above problems, combine the accuracy of the hydrogen measurement equipment verified by the hydrogen standard sample with the precision of the hydrogen charging test results to jointly evaluate the accuracy of the hydrogen measurement results, and establish a standard hydrogen charging curve of hydrogen charging amount and independent variables to realize accurate hydrogen charging. It provides a basic guarantee for the research of high-strength steel hydrogen embrittlement.

[0005] The technical solution adopted by the present application to solve the above problems is: a test method for rapid and accurate hydrogen charging of high-strength steel, characterized in that it comprises the following steps: (1) identifying the independent variables in the electrochemical hydrogen charging test, the independent variables including hydrogen charging current, hydrogen charging time, electrolyte volume, catalyst content, sample size and sample surface state; (2) screening the independent variables to determine the key independent variables that significantly affect the dependent variable (hydrogen charging amount) and are easy to adjust in the test operation; (3) through multiple gradient tests, the specific use range of the key independent variables when the hydrogen charging amount changes from low to high is determined; (4) The precision of the hydrogen charging test results was evaluated using the relative standard deviation (RSD), where RSD ≤ 8%; (5) Select at least two standard samples with different hydrogen contents to verify the accuracy of the hydrogen measuring equipment, wherein the hydrogen contents of the standard samples cover the expected hydrogen filling amount range of the sample to be filled with hydrogen. (6) Use a calibrated hydrogen measurement device with acceptable accuracy to determine the hydrogen content of the hydrogen-filled sample; (7) Plot a standard curve based on the correspondence between key independent variables and hydrogen charge amount, and quickly lock the test conditions according to the target hydrogen charge amount; (8) The sample is pretreated to remove the surface oxide layer and oil stains. It is polished step by step with 180#-400# sandpaper until there is no coating or oxidation trace on the surface. After ultrasonic cleaning, a hydrogen charging test is performed.

[0006] As a preferred embodiment, in step (1), the initial range of the hydrogen charging current is 0.5-5 mA / cm², the hydrogen charging time is 12-120 h, the electrolyte volume is 100-500 mL, the catalyst content is 1-5 g / L, and the sample size is 5-10 mm in diameter and 20-50 mm in length.

[0007] As a preferred option, in step (2), the selection of independent variables adopts the control variable method, keeping other variables unchanged, changing only a single variable and repeating the experiment at least 3 times, judging the degree of influence of the variable by the coefficient of variation of hydrogen charge, and selecting variables with a coefficient of variation ≥15% as key independent variables.

[0008] As a preferred option, in step (3), the range of use of the key independent variable is determined by the hydrogen charging gradient test: when the hydrogen charging amount is 0.5-2ppm, the value range of the variable in this range is recorded; when the hydrogen charging amount is 2-5ppm, the value range of the corresponding variable is recorded, so as to ensure that the hydrogen charging amount and the variable have a monotonically linear relationship in each range.

[0009] As a preferred option, in step (4), the relative standard deviation is calculated based on the results of at least 10 repeated hydrogen charging tests, and the calculation formula is: RSD = (standard deviation / average value) × 100%, where the standard deviation is calculated by the Bessel formula.

[0010] As a preferred option, in step (5), the true value of the hydrogen content of the standard sample is known, including low content standard sample: 0.8-1.2 ppm and high content standard sample: 3.0-4.0 ppm. Each standard sample is measured no less than 12 times. When the deviation between the measured value of the standard sample and the true value is ≤5%, the accuracy of the hydrogen measuring equipment is determined to be up to standard.

[0011] As a preferred option, in step (7), the standard curve is plotted using the least squares method for linear fitting, with a goodness of fit R² ≥ 0.95. The key independent variables include hydrogen charging time and hydrogen charging current. The standard curve for hydrogen charging time is used for rapid parameter locking of 0.5-3 ppm hydrogen charging amount, and the standard curve for hydrogen charging current is used for rapid parameter locking of 3-5 ppm hydrogen charging amount.

[0012] As a preferred option, in step (8), anhydrous ethanol is used as the cleaning agent for ultrasonic cleaning, and the cleaning time is 3-10 min. After cleaning, the sample is dried under inert gas protection to avoid secondary oxidation.

[0013] As an alternative, step (9) is also included: monitoring the hydrogen escape rate of the sample after hydrogen charging, measuring the amount of hydrogen escape at different times by constant temperature heating method, verifying the stability of the hydrogen charging amount, and determining that the hydrogen charging effect is stable when the amount of hydrogen escape within 24 hours is ≤ 10% of the initial hydrogen charging amount.

[0014] Compared with the prior art, the advantages of the present invention are as follows: The core principle of this invention is to identify key independent variables affecting the hydrogen charging amount (such as charging current, time, etc.), screen and determine their effective range, establish a standard curve of "independent variable-hydrogen charging amount", and achieve rapid parameter matching of the target hydrogen charging amount; at the same time, it adopts a dual evaluation method of "relative standard deviation (RSD) + standard sample verification" to solve the problem of accuracy evaluation when the true value of hydrogen charging amount cannot be obtained.

[0015] Technical impact of the present invention: 1. The clarification of the influencing factors (independent variables) of the hydrogen charging test in this invention points the way for the rapid hydrogen charging of high-strength steel materials; the quantification of the independent variables of the hydrogen charging test provides a specific method for the rapid hydrogen charging of high-strength steel materials.

[0016] 2. This invention provides a method for effectively evaluating the accuracy of hydrogen charging test results, enabling operators to have a basis for judging the accuracy of test data and to trace the factors that cause errors. Most importantly, it fills the gap in the inability to evaluate hydrogen charging test results due to the ambiguity of the true value.

[0017] 3. This invention has conducted extensive experiments on the hydrogen charging and hydrogen measurement process, and has provided a detailed analysis and explanation of the influencing factors, providing valuable experience and data for those skilled in the art.

[0018] 4. This invention innovatively uses relative standard deviation, providing new ideas for researchers in many fields and having profound reference value. Attached Figure Description

[0019] Figure 1Schematic diagram of electrochemical hydrogen charging; Figure 2 This is a schematic diagram for measuring hydrogen by heating. Figure 3 Standard curves for hydrogen charging amount (ppm) and hydrogen charging time (h) of NM500 steel; Figure 4 Set the variables for the hydrogen charging test. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments described are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] This embodiment provides a rapid and accurate hydrogen charging test method, which involves the following: (1) Selecting standard samples Based on the existing hydrogen standard samples, two hydrogen standard samples with different high and low contents were selected. The principle for selecting the standard samples was that their hydrogen contents were close to those of the hydrogen-filled test sample. (2) Standard sample hydrogen determination test (the first step to ensure the accuracy of the test results) Twelve hydrogen determination tests were performed on two sets of standard samples, and the average value and relative standard deviation of each set of standard samples were calculated. This method was used to verify the accuracy of the hydrogen determination equipment. (3) Sampling of high-strength steel (determining the size of the sample) Samples were taken from the same location on the same steel plate, the decarburized oxide layer on the edge was removed, and the samples were processed into φ6*30 rod-shaped samples (the size of this sample was determined based on the size of the gauge length of the sample in the subsequent slow tensile test). The samples were then polished with 180# sandpaper to ensure that the surface was free of coating, oil, and oxidation before use. (4) Screening of process variables in hydrogen charging test Identify the influencing factors of the hydrogen charging process: hydrogen charging current, time and solution volume, and catalyst dosage, and specify the specific values ​​for each dependent variable; (5) Sample hydrogen charging test For the selected independent variables, including hydrogen charging current, time, solution volume, and catalyst, hydrogen charging tests were conducted by changing a single variable (three sets of values: low, medium, and high) while keeping other variables constant (selecting the intermediate value). This process required a total of 9 sets of tests, with 3 samples in each set being tested in parallel simultaneously (see...). Figure 1 A total of 27 samples were collected. The specific parameters for the 9 experimental groups were set as follows: I1T2C2R2, I2T2C2R2, I3T2C2R2, I2T1C2R2, I2T3C2R2, I2T2C1R2, I2T2C3R2, I2T2C2R1, and I2T2C2R3 (see...). Figure 4 ).

[0022] (6) Sample hydrogen determination process and data processing After hydrogen charging is completed, take the sample and place it into the quartz tube of the pre-calibrated hydrogen measurement device. Set the heating rate and the endpoint temperature, and start measuring hydrogen. The whole process should be controlled within 30 minutes. (7) Evaluate the accuracy of the hydrogen charging test (the second step to ensure the accuracy of the test results) With the hydrogen charging time fixed as the independent variable, such as 72 hours, the experiment was repeated 10 times under the same conditions. The relative standard deviation of the hydrogen charging amount in the 10 tests was calculated to evaluate the accuracy of the hydrogen charging test.

[0023] (8) Determine the independent and dependent variables of the standard curve. After the above process is completed, select an independent variable (e.g., hydrogen charging time), keep other conditions unchanged, and measure the amount of hydrogen charged in the samples at a series of different times; (9) Establish a standard curve for hydrogen charging of samples. Plot the dependent variable-independent variable relationship curve and establish a standard curve for hydrogen charging of the sample.

[0024] Taking the NM500 sample as an example, the following steps are used for the accurate hydrogen charging test: (1) Selecting standard samples Based on the existing hydrogen standards, two hydrogen standards with high and low contents (1.0 ppm and 3.55 ppm) were selected to be as close as possible to the hydrogen content of the hydrogen-filled test sample.

[0025] (2) Standard sample hydrogen determination test (the first step in evaluating the accuracy of hydrogen-filled samples) Using a temperature-rising hydrogen analyzer, 12 sets of hydrogen determination tests were conducted on two standard samples (1.0 / 3.55ppm) (Note: the relative standard deviation generally requires a sample size of not less than 10). The amount of hydrogen escaping from the standard samples in the range of room temperature to 900℃ was measured, and the average value and relative standard deviation of each set of standard samples were calculated. The accuracy of the hydrogen measuring equipment was verified by this method.

[0026] (3) Sampling of high-strength steel Using 12mm thick NM500 steel plates, samples were taken from the same location. After removing the decarburized oxide layer on the edges, several φ6*30mm samples were processed. The samples were polished with 180# sandpaper to ensure that the surface was free of plating, oil, and oxidation. After ultrasonic cleaning for 5 minutes, the samples were ready for use.

[0027] (4) Sample hydrogen charging test For the selected independent variables, including hydrogen charging current, time, solution volume, and catalyst, a single variable (three sets of values: low, medium, and high) was changed, while other variables remained unchanged (selecting the intermediate value). A total of nine sets of experiments were conducted, with three samples in each set being tested in parallel simultaneously. Figure 1A total of 27 samples were collected. The specific parameters for the 9 experimental groups were set as follows: I1T2C2R2, I2T2C2R2, I3T2C2R2, I2T1C2R2, I2T3C2R2, I2T2C1R2, I2T2C3R2, I2T2C2R1, and I2T2C2R3. (The rest of the text appears to be a continuation of the previous sentence and can be left as is.) Figure 4 .

[0028] (5) Standardization of hydrogen determination process and data processing for samples After hydrogen charging is completed, the sample is taken out, ultrasonically cleaned, and placed into the quartz tube of the pre-calibrated hydrogen measurement device. The heating rate and endpoint temperature are set, and hydrogen measurement begins. The entire process is controlled within 30 minutes.

[0029] (6) Determine the independent and dependent variables of the standard curve After the above process is completed, select the independent variable (hydrogen charging time) based on the results, fix the experimental conditions of other variables (hydrogen charging current 1 mA / cm2, hydrogen charging solution 250 mL, if the sample surface area changes, the solution volume will change accordingly, catalyst 3 g / L), and determine the hydrogen charging amount of the sample at a series of different times (12 / 24 / 36 / 42 / 48 / 72 / 96 h).

[0030] (7) Evaluate the accuracy of the hydrogen charging test. With the hydrogen charging time fixed as the independent variable, such as 72 hours, the experiment was repeated 10 times under the same conditions. The relative standard deviation of the hydrogen charging amount in the 10 tests was calculated to evaluate the accuracy of the hydrogen charging test.

[0031] (8) Establish a hydrogen charging standard curve for the sample. Plot the relationship curve between hydrogen charging amount and hydrogen charging time, and establish a standard curve for hydrogen charging of samples.

[0032] Taking NM500 high-strength steel as an example, the key parameters and ranges are as follows:

[0033] Taking NM500 high-strength steel as an example, the test data are as follows: Sample pretreatment: Take a 12mm thick steel plate, process it into a φ6×30mm sample, polish it with 180# sandpaper, ultrasonically clean it with anhydrous ethanol for 5 minutes, and dry it with nitrogen.

[0034] Standard calibration: Using 1.0 ppm and 3.55 ppm hydrogen standards, each was measured 12 times on a temperature-rising hydrogen analyzer (900℃, 10℃ / min). The average deviations were 3.2% and 4.5%, respectively, indicating that the equipment met the standards.

[0035] Variable screening: With the electrolyte volume fixed at 250 mL and the catalyst at 3 g / L, the current (1, 2, 3 mA / cm²) and time (24, 48, 72 h) were varied, with 3 parallel samples in each group. It was found that the current and time had a significant effect on the hydrogen charging capacity (CV = 18%-25%).

[0036] Range determined: When the current is 1-3 mA / cm², the hydrogen charging amount is linearly related to 2-5 ppm; when the time is 12-72 h, the hydrogen charging amount is linearly related to 0.5-3 ppm.

[0037] Standard curve plotting: The relationship between hydrogen charge (y) and time (t) obtained by fitting is: y = 0.042t + 0.08 (R² = 0.97), and the relationship between hydrogen charge (I) and current (I) is: y = 1.5I + 0.2 (R² = 0.96).

[0038] Accuracy verification: The 72-hour hydrogen charging test was repeated 10 times, with an average hydrogen charging amount of 2.98 ppm, RSD of 5.3% (≤8%), and a hydrogen escape amount of 0.21 ppm (≤10%) over 24 hours, indicating that the results are reliable.

[0039] Example of rapid hydrogen charging: The target hydrogen charging amount is 2ppm. The time curve shows t=45.7h, or the current curve shows I=1.2mA / cm². The deviation between the measured value and the target value is ≤6%.

[0040] The inventive significance of this invention is as follows: 1. It comprehensively and specifically clarifies the influencing factors of the hydrogen charging process, and systematically conducts experiments to screen independent variables and determine the optimal numerical settings; 2. Based on the experimental results, it selects the hydrogen charging time, which is easy to operate in the experiment, as the independent variable and completes the standard curve of the hydrogen charging experiment; 3. While using the relative standard deviation (RSD), which reflects the precision of the measurement results, to replace the error for accuracy evaluation, it also uses a standard sample with known true value to evaluate the accuracy of the equipment (TDS). The two work together to complete the accuracy evaluation of the hydrogen charging test results.

Claims

1. A test method for rapid and accurate hydrogen charging of high-strength steel, characterized in that, Includes the following steps: (1) Identify the independent variables in the electrochemical hydrogen charging test, including hydrogen charging current, hydrogen charging time, electrolyte volume, catalyst content, sample size and sample surface condition; (2) Screen the independent variables to identify the key independent variables that have a significant impact on the dependent variable (hydrogen charge) and are easy to adjust in the experimental operation; (3) Through multiple sets of gradient experiments, clarify the specific application range of the key independent variable when the hydrogen charging amount changes from low to high; (4) The precision of the hydrogen charging test results was evaluated using the relative standard deviation (RSD), where RSD ≤ 8%; (5) Select at least two standard samples with different hydrogen contents to verify the accuracy of the hydrogen measuring equipment, wherein the hydrogen contents of the standard samples cover the expected hydrogen filling amount range of the sample to be filled with hydrogen. (6) Use a calibrated hydrogen measurement device with acceptable accuracy to determine the hydrogen content of the hydrogen-filled sample; (7) Plot a standard curve based on the correspondence between key independent variables and hydrogen charge amount, and quickly lock the test conditions according to the target hydrogen charge amount; (8) The sample is pretreated to remove the surface oxide layer and oil stains. It is polished step by step with 180#-400# sandpaper until there is no coating or oxidation trace on the surface. After ultrasonic cleaning, a hydrogen charging test is performed.

2. The method according to claim 1, characterized in that, In step (1), the initial range of the hydrogen charging current is 0.5-5 mA / cm², the hydrogen charging time is 12-120 h, the electrolyte volume is 100-500 mL, the catalyst content is 1-5 g / L, and the sample size is 5-10 mm in diameter and 20-50 mm in length.

3. The method according to claim 1, characterized in that, In step (2), the independent variable is selected using the controlled variable method. Other variables are kept constant, only a single variable is changed and the experiment is repeated at least 3 times. The influence of the variable is judged by the coefficient of variation of the hydrogen charge, and the variable with a coefficient of variation ≥15% is selected as the key independent variable.

4. The method according to claim 1, characterized in that, In step (3), the range of use of the key independent variables is determined by the hydrogen charging gradient test: when the hydrogen charging amount is 0.5-2ppm, the value range of the variable in this range is recorded; when the hydrogen charging amount is 2-5ppm, the value range of the corresponding variable is recorded to ensure that the hydrogen charging amount and the variable have a monotonically linear relationship in each range.

5. The method according to claim 1, characterized in that, In step (4), the relative standard deviation is calculated based on the results of at least 10 repeated hydrogen charging tests. The calculation formula is: RSD = (standard deviation / average value) × 100%, where the standard deviation is calculated using the Bessel formula.

6. The method according to claim 1, characterized in that, In step (5), the true value of hydrogen content of the standard sample is known, including low content standard sample: 0.8-1.2 ppm and high content standard sample: 3.0-4.0 ppm. Each standard sample is measured no less than 12 times. When the deviation between the measured value of the standard sample and the true value is ≤5%, the accuracy of the hydrogen measuring equipment is determined to be up to standard.

7. The method according to claim 1, characterized in that, In step (7), the standard curve is plotted using the least squares method for linear fitting, with a goodness of fit R² ≥ 0.

95. The key independent variables include hydrogen charging time and hydrogen charging current. The standard curve for hydrogen charging time is used for rapid parameter locking of 0.5-3 ppm hydrogen charging amount, and the standard curve for hydrogen charging current is used for rapid parameter locking of 3-5 ppm hydrogen charging amount.

8. The method according to claim 1, characterized in that, In step (8), anhydrous ethanol is used as the cleaning agent for ultrasonic cleaning, and the cleaning time is 3-10 min. After cleaning, the sample is dried under inert gas protection to avoid secondary oxidation.

9. The method according to claim 1, characterized in that, The method also includes step (9): monitoring the hydrogen escape rate of the sample after hydrogen charging, measuring the amount of hydrogen escape at different times by constant temperature heating method, verifying the stability of the hydrogen charging amount, and determining that the hydrogen charging effect is stable when the amount of hydrogen escape within 24 hours is ≤ 10% of the initial hydrogen charging amount.

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