Evaluation Method for the Effect of Coupled Hydrogen and Anodic Dissolution on Stress Corrosion Cracking of Pipeline Steel

Abstract

The present invention relates to a method for evaluating the effect of hydrogen and anodic dissolution coupling on stress corrosion cracking of pipeline steel, comprising: (1) performing slow strain rate tensile tests in an acidic environment and a nitrogen environment respectively to determine the degree of damage caused by the acidic environment to the mechanical properties of the pipeline steel sample; (2) performing potentiodynamic polarization curve tests on the pipeline steel sample using slow rate scanning and fast rate scanning respectively to determine the potential range of the stress corrosion sensitive area; (3) performing constant potential slow tensile tests on the pipeline steel sample in an acidic environment at the starting potential of anodic dissolution alone and the starting potential of hydrogen-induced cracking alone to determine the degree of damage caused by anodic dissolution and hydrogen-induced cracking to the mechanical properties of the pipeline steel; (4) determining the degree of influence of anodic dissolution and hydrogen coupling on the stress corrosion cracking of the pipeline steel sample in the acidic environment and the contribution ratio of stress corrosion cracking. The present invention can accurately and quickly evaluate the stress corrosion resistance of pipeline steel.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline steel stress corrosion performance detection, and in particular to a method for evaluating the influence of coupling of hydrogen and anodic dissolution in an acidic environment on pipeline steel stress corrosion cracking. Background Art

[0002] Stress corrosion cracking refers to the phenomenon that metal materials under tensile stress produce delayed cracking or delayed fracture in certain specific media due to the synergistic effect of corrosive media and stress. It is one of the most common and most harmful forms of corrosion failure. In recent years, with the exploration and development of ultra-deep, ultra-high temperature, and ultra-high corrosion harsh environment oil and gas wells, the working environment of oil and gas wells generally has "high temperature, high pressure, high H2S, high Cl - Due to the complex and harsh working conditions and special operating processes, the steel used in ground transportation pipelines faces severe challenges. Especially in the long-distance, high-temperature and high-pressure oil and gas transportation process, pipeline steel often suffers from stress corrosion cracking failure, which seriously affects the normal production and operation of oil and gas fields.

[0003] In sulfur-containing acidic wells, pipeline steel is subject to the combined effects of tension and corrosion, ultimately leading to stress corrosion cracking. The main mechanisms are anodic dissolution, hydrogen-induced cracking, and a combination of anodic dissolution and hydrogen-induced cracking. In other words, pipeline steel fractures are typically the result of anodic dissolution alone, hydrogen-induced cracking alone, or the combined effects of the two.

[0004] At present, stress corrosion sensitivity is generally used to evaluate the degree of stress corrosion cracking of pipeline steel. The stress corrosion sensitivity of pipeline steel consists of three parts: one is caused by anodic dissolution, the second is caused by hydrogen-induced cracking caused by hydrogen entering the interior of the specimen, and the third is caused by the coupling effect of hydrogen-induced cracking and anodic dissolution. Usually, the stress corrosion sensitivity of pipeline steel is obtained by slow strain rate tensile test in the experiment. The test result is the sum of the stress corrosion sensitivity composed of the above three parts, but the actual contribution of any one part cannot be obtained. Especially in acidic environment, the stress corrosion cracking of pipeline steel is not only caused by hydrogen-induced cracking and anodic dissolution alone, but also by the coupling effect of the two. That is, the coupling of hydrogen-induced cracking and anodic dissolution has a certain contribution rate to the stress corrosion cracking of pipeline steel.

[0005] Constant strain, constant load, and slow strain rate tensile (SSRT) methods are commonly used domestically and internationally to study the stress corrosion resistance of pipeline steel. However, the constant strain and constant load methods can only provide failure or non-failure information when evaluating specimens. They cannot quantitatively evaluate the specimen's sulfidation stress corrosion resistance, nor can they provide stress corrosion sensitivity data. Other experimental methods must be combined, resulting in extended test cycles or the need to purchase new equipment, and high test costs.

[0006] The slow strain rate tensile method is a commonly used test method to study the stress corrosion resistance of pipeline steel. The specimen is stretched at a slow and constant strain rate on a testing machine until it breaks. The stress corrosion sensitivity is evaluated based on the tensile performance data. The stress corrosion sensitivity index is defined as: =(Ψ0-Ψ1) / Ψ0, where Ψ0 is the sample's reduction of area, yield strength or elongation, and fracture time in nitrogen, and Ψ1 is the sample's reduction of area, yield strength or elongation, and fracture time in the ambient medium. The test uses an acidic aqueous solution as the test solution and evaluates the stress corrosion performance of pipeline steel at a constant rate. The stress corrosion sensitivity result obtained is the overall stress corrosion sensitivity, and the specific contribution of a particular component cannot be determined. Summary of the Invention

[0007] The present invention provides a method for evaluating the effect of the coupling of hydrogen and anodic dissolution on the stress corrosion cracking of pipeline steel. By accurately calculating the contribution rate of hydrogen-induced cracking and the contribution rate of anodic dissolution alone, the influence of anodic dissolution and hydrogen coupling on the stress corrosion cracking of pipeline steel is further calculated, thereby achieving the purpose of accurately and quickly evaluating the stress corrosion resistance of pipeline steel.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The evaluation method of the effect of coupling of hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel includes the following steps:

[0010] (1) Slow strain rate tensile tests were conducted in acidic and nitrogen environments, respectively, to obtain stress-strain curves of pipeline steel specimens in the two environments, determine the degree of damage to the mechanical properties of pipeline steel specimens in the acidic environment, and obtain the corresponding stress corrosion cracking sensitivity factor;

[0011] (2) The pipeline steel samples were subjected to potentiodynamic polarization curve tests using slow rate scanning and fast rate scanning to determine the potential range of the stress corrosion sensitive area and the maximum corrosion potential V s V is the starting potential for anodic dissolution alone, the minimum value of the corrosion potential f is the starting potential of hydrogen-induced cracking alone, Vs~V f The corrosion potential range between 10 and 15 is the potential range of the coupling effect of hydrogen-induced cracking and anodic dissolution;

[0012] (3) Conduct a constant potential slow tensile test on the pipeline steel specimens in an acidic environment at the starting potential of anodic dissolution alone and the starting potential of hydrogen-induced cracking alone, record the test results and stress-strain curves, determine the degree of damage to the mechanical properties of the pipeline steel caused by anodic dissolution and hydrogen-induced cracking, and obtain the corresponding stress corrosion cracking sensitivity factor;

[0013] (4) By comparing the stress-strain curves and test results of nitrogen environment, acidic environment and constant potential slow tensile test, the influence degree of the coupling effect of anodic dissolution and hydrogen in acidic environment on the stress corrosion cracking of pipeline steel specimens and the contribution ratio of stress corrosion cracking were determined.

[0014] The acidic environment is a sodium chloride solution containing sulfur with a mass concentration of 5% and a pH value of 2≤≤6; wherein the sulfur is gaseous sulfur, solid sulfur, or a mixture of one gaseous sulfur and one solid sulfur, the gaseous sulfur includes H2S and SOx, and the solid sulfur includes Na2S and CH4N2S.

[0015] The damage degree of the mechanical properties of the pipeline steel sample in the acidic environment is determined by taking the tensile performance parameters of the pipeline steel sample in the nitrogen environment as a benchmark and combining the tensile performance parameters in the acidic environment to determine the stress corrosion cracking sensitivity of the pipeline steel sample in the acidic environment. The specific process is as follows:

[0016] Based on the cross-sectional area of ​​the pipeline steel specimen before and after stretching, the cross-sectional shrinkage Ψ of the pipeline steel specimen is calculated using formula (1);

[0017] Ψ=(S0-S1) / S0×100%------(1);

[0018] In formula (1), S0 is the cross-sectional area of ​​the standard moment section before the specimen breaks, and S1 is the cross-sectional area of ​​the standard moment section after the specimen breaks;

[0019] Based on the section reduction rate Ψ of pipeline steel samples in nitrogen environment a , Sectional shrinkage of pipeline steel samples in acidic environment Ψ b , use formula (2) to calculate the stress corrosion cracking sensitivity factor of the sample in acidic environment , here The influence of anodic dissolution, hydrogen-induced cracking, and the coupling effect of the two on stress corrosion cracking of samples in acidic environment;

[0020] .

[0021] The slow strain rate tensile test is first carried out according to 1×10 -4 The strain rate was quickly preloaded to 80% of the yield strength of the pipeline steel sample at a strain rate of 5×10 -6The loading was started at a strain rate of mm / s.

[0022] During the potentiodynamic polarization curve test, the test solution is a NaCl solution with a mass concentration of 5%, a three-electrode system is adopted, the auxiliary electrode is a platinum mesh, the reference electrode is a saturated calomel electrode, the fast rate scanning speed is 1000-1200mV / min, and the slow rate scanning speed is 5-10mV / min.

[0023] The constant potential slow tensile test is a slow strain rate tensile test under a constant potential. The preloading method and strain rate during the constant potential slow tensile test are the same as those of the slow strain rate tensile test.

[0024] The specific process of step (4) is as follows:

[0025] The cross-sectional shrinkage of the pipeline steel sample during the constant potential slow tensile test was calculated according to formula (1). Based on the cross-sectional shrinkage of the pipeline steel sample in the nitrogen environment and formula (2), the stress corrosion cracking sensitivity factor of the pipeline steel sample under the starting potential of anodic dissolution alone was calculated. , Stress corrosion cracking sensitivity factor of pipeline steel specimens under the initiation potential of hydrogen-induced cracking alone The influence of anodic dissolution and hydrogen coupling on stress corrosion cracking of pipeline steel specimens in acidic environment was calculated by formula (3): c ;

[0026] ;

[0027] In formula (3), parameter a=|(V f -V s ) / V s |.

[0028] The test solutions used in the potentiodynamic polarization curve test, slow strain rate tensile test and constant potential slow tensile test were all deoxygenated with high-purity nitrogen.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention combines an electrochemical workstation with a slow strain rate stretching device. The potential range of the stress corrosion sensitive region is determined by fast and slow sweeping potential polarization curves. The stress corrosion cracking sensitivity factors of anodic dissolution and hydrogen-induced cracking are tested by slow strain rate stretching tests under constant potential. The contribution rate of the coupled effect of the two to the stress corrosion cracking of pipeline steel is further calculated.

[0031] 2) This method simulates the actual service environment of pipeline steel, first calculating the stress corrosion cracking sensitivity factor, then further analyzing the stress corrosion performance of pipeline steel and clarifying the stress corrosion mechanism, providing a theoretical basis for improving the SCC resistance of pipeline steel.

[0032] 3) By evaluating the effect of the coupling of hydrogen and anodic dissolution in an acidic environment on the stress corrosion cracking of pipeline steel, the stress corrosion performance and service life of pipeline steel in actual service environment can be predicted, ensuring the safety and stability of oil and gas field exploitation and pipeline transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the slow tensile test specimen according to an embodiment of the present invention.

[0034] Figure 2 This is the fast and slow sweep potential polarization curve of the pipeline steel sample in the embodiment of the present invention in a NaCl solution with a mass concentration of 5%.

[0035] Figure 3 These are stress-strain curves of pipeline steel samples in an embodiment of the present invention under nitrogen environment, acidic environment, hydrogen-induced cracking potential, and anodic dissolution potential. DETAILED DESCRIPTION

[0036] The method for evaluating the effect of coupled hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to the present invention comprises the following steps:

[0037] (1) Slow strain rate tensile tests were conducted in acidic and nitrogen environments, respectively, to obtain stress-strain curves of pipeline steel specimens in the two environments, determine the degree of damage to the mechanical properties of pipeline steel specimens in the acidic environment, and obtain the corresponding stress corrosion cracking sensitivity factor;

[0038] (2) The pipeline steel samples were subjected to potentiodynamic polarization curve tests using slow rate scanning and fast rate scanning to determine the potential range of the stress corrosion sensitive area and the maximum corrosion potential V s V is the starting potential for anodic dissolution alone, the minimum value of the corrosion potential f is the starting potential of hydrogen-induced cracking alone, Vs~V f The corrosion potential range between 10 and 15 is the potential range of the coupling effect of hydrogen-induced cracking and anodic dissolution;

[0039] (3) Conduct a constant potential slow tensile test on the pipeline steel specimens in an acidic environment at the starting potential of anodic dissolution alone and the starting potential of hydrogen-induced cracking alone, record the test results and stress-strain curves, determine the degree of damage to the mechanical properties of the pipeline steel caused by anodic dissolution and hydrogen-induced cracking, and obtain the corresponding stress corrosion cracking sensitivity factor;

[0040] (4) By comparing the stress-strain curves and test results of nitrogen environment, acidic environment and constant potential slow tensile test, the influence degree of the coupling effect of anodic dissolution and hydrogen in acidic environment on the stress corrosion cracking of pipeline steel specimens and the contribution ratio of stress corrosion cracking were determined.

[0041] The acidic environment is a sodium chloride solution containing sulfur with a mass concentration of 5% and a pH value of 2≤≤6; wherein the sulfur is gaseous sulfur, solid sulfur, or a mixture of one gaseous sulfur and one solid sulfur, the gaseous sulfur includes H2S and SOx, and the solid sulfur includes Na2S and CH4N2S.

[0042] The damage degree of the mechanical properties of the pipeline steel sample in the acidic environment is determined by taking the tensile performance parameters of the pipeline steel sample in the nitrogen environment as a benchmark and combining the tensile performance parameters in the acidic environment to determine the stress corrosion cracking sensitivity of the pipeline steel sample in the acidic environment. The specific process is as follows:

[0043] Based on the cross-sectional area of ​​the pipeline steel specimen before and after stretching, the cross-sectional shrinkage Ψ of the pipeline steel specimen is calculated using formula (1);

[0044] Ψ=(S0-S1) / S0×100%------(1);

[0045] In formula (1), S0 is the cross-sectional area of ​​the standard moment section before the specimen breaks, and S1 is the cross-sectional area of ​​the standard moment section after the specimen breaks;

[0046] Based on the section reduction rate Ψ of pipeline steel samples in nitrogen environment a , Sectional shrinkage of pipeline steel samples in acidic environment Ψ b , use formula (2) to calculate the stress corrosion cracking sensitivity factor of the sample in acidic environment , here The influence of anodic dissolution, hydrogen-induced cracking, and the coupling effect of the two on stress corrosion cracking of samples in acidic environment;

[0047] .

[0048] The slow strain rate tensile test is first carried out according to 1×10 -4 The strain rate was quickly preloaded to 80% of the yield strength of the pipeline steel sample at a strain rate of 5×10 -6 The loading was started at a strain rate of mm / s.

[0049] During the potentiodynamic polarization curve test, the test solution is a NaCl solution with a mass concentration of 5%, a three-electrode system is adopted, the auxiliary electrode is a platinum mesh, the reference electrode is a saturated calomel electrode, the fast rate scanning speed is 1000-1200mV / min, and the slow rate scanning speed is 5-10mV / min.

[0050] The constant potential slow tensile test is a slow strain rate tensile test under a constant potential. The preloading method and strain rate during the constant potential slow tensile test are the same as those of the slow strain rate tensile test.

[0051] The specific process of step (4) is as follows:

[0052] The cross-sectional shrinkage of the pipeline steel sample during the constant potential slow tensile test was calculated according to formula (1). Based on the cross-sectional shrinkage of the pipeline steel sample in the nitrogen environment and formula (2), the stress corrosion cracking sensitivity factor of the pipeline steel sample under the starting potential of anodic dissolution alone was calculated. , Stress corrosion cracking sensitivity factor of pipeline steel specimens under the initiation potential of hydrogen-induced cracking alone The influence of anodic dissolution and hydrogen coupling on stress corrosion cracking of pipeline steel specimens in acidic environment was calculated by formula (3): c ;

[0053] ;

[0054] In formula (3), parameter a=|(V f -V s ) / V s |.

[0055] The test solutions used in the potentiodynamic polarization curve test, slow strain rate tensile test and constant potential slow tensile test were all deoxygenated with high-purity nitrogen.

[0056] The following examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0057] Example:

[0058] In this embodiment, the evaluation process of the effect of the coupling of hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel in an acidic environment is as follows:

[0059] First, a slow strain rate tensile (SSRT) test was conducted on pipeline steel samples in acidic and nitrogen environments using a CORTEST slow strain rate tensile testing machine. The dimensions of the tensile samples are shown in Figure 2. Figure 1 Before the test, the pipeline steel sample was # After polishing with sandpaper, clean it with acetone and anhydrous ethanol respectively, blow dry with cold air and set aside. After installing the pipeline steel sample, apply a load of 200kgf to eliminate the gap between the reduction gear and the fixture. -4The strain rate was quickly preloaded to 80% of the yield strength of the pipeline steel sample at a strain rate of 1600 ± 10 kgf. After stabilization, the sample was loaded at 5 × 10 -6 The slow tensile test was carried out at a strain rate of mm / s until the pipeline steel sample was broken. The stress-strain curves and mechanical property parameters of the pipeline steel samples in acidic environment and nitrogen environment were recorded respectively. The cross-sectional shrinkage of the pipeline steel samples in acidic environment and nitrogen environment were calculated according to formula (1). In this embodiment, the values ​​of the above two cross-sectional shrinkages were 8.06% and 73.76% respectively. The stress corrosion cracking sensitivity factor of the pipeline steel sample in acidic environment was calculated according to formula (2), and the result was The sensitivity factor is the total impact of anodic dissolution (AD), cathodic reaction hydrogen permeation (i.e., hydrogen embrittlement, HE), and the coupling effect of the two on the stress corrosion cracking (SSC) of pipeline steel specimens in an acidic environment. It is the total stress corrosion cracking sensitivity in an acidic environment and characterizes the stress corrosion cracking sensitivity of pipeline steel specimens in an acidic environment.

[0060] Secondly, in a NaCl solution with a mass concentration of 5%, an electrochemical workstation was used to perform slow rate scanning and fast rate scanning potentiodynamic polarization curve tests on the pipeline steel sample, such as Figure 2 As shown, determine V s The value is -694mV (relative to saturated calomel electrode SCE, the same below), determine V f The value is -744mV, and the potential between -744mV and -694mV is the mixed action area of ​​anodic dissolution and hydrogen-induced cracking.

[0061] Again, in V s Potential and V f The pipeline steel samples were subjected to constant potential slow tensile tests under different potentials, and the test results and stress-strain curves were recorded to determine the damage degree of anodic dissolution and hydrogen-induced cracking on the mechanical properties of the pipeline steel samples, and to obtain the corresponding stress corrosion cracking sensitivity factor. The specific process is as follows:

[0062] a. The corrosion medium of the constant potential slow tensile test is a NaCl solution with a mass concentration of 5%. A high temperature and high pressure reference electrode is used, and the cathode hydrogen charging potential is set to -744mV. First, according to 1×10 -4 The strain rate was quickly preloaded to 80% of the yield strength of the pipeline steel sample at a strain rate of 1600±10kgf, and then the strain rate was adjusted to 5×10 -6 The strain rate was tested at a constant mm / s until the pipeline steel sample was broken, and the stress-strain curve and mechanical properties were recorded. The starting potential V of nitrogen environment and hydrogen-induced cracking alone were compared. fBased on the slow tensile test results and mechanical property parameters under the cathode hydrogen charging potential, the cross-sectional shrinkage of the pipeline steel sample under the cathode hydrogen charging potential is calculated to be 18.04%. Based on the cross-sectional shrinkage of the pipeline steel sample under the nitrogen environment and formula (2), the damage degree of the mechanical properties of the pipeline steel sample caused by hydrogen embrittlement caused by hydrogen penetration under the cathode hydrogen charging potential in the acidic environment is calculated, that is, the stress corrosion cracking sensitivity factor .

[0063] b. Change the cathode hydrogen charging potential set in step a to the anodic dissolution starting potential of -694mV, and repeat step a. Compare the nitrogen environment and the anodic dissolution starting potential V s Based on the slow tensile test results and mechanical property parameters under anodic polarization, the cross-sectional shrinkage of the pipeline steel sample under anodic polarization is calculated to be 56.19% according to formula (1). Based on the cross-sectional shrinkage of the pipeline steel sample in nitrogen environment and formula (2), the damage degree of the mechanical properties of the pipeline steel sample caused by anodic dissolution in acidic environment is calculated, that is, the stress corrosion cracking sensitivity factor .

[0064] c. The influence of the coupling effect of hydrogen and anodic dissolution on the stress corrosion cracking of pipeline steel specimens in an acidic environment is calculated by formula (3) to be Cc=0.75%.

[0065] It can be seen from this that in this embodiment, the stress corrosion cracking process of the pipeline steel specimen in an acidic environment is controlled by both anodic dissolution and hydrogen. The contribution of hydrogen-induced cracking caused by hydrogen penetration is very large, while the contribution of anodic dissolution is very small. As a result, the contribution rate of the coupled effect of the two to the stress corrosion cracking of the pipeline steel specimen is relatively small, only 0.75%.

[0066] In the above embodiment, the pipeline steel sample is X65S sulfur-resistant pipeline steel, and the acidic environment is a 5% NaCl solution (pH=3) with hydrogen sulfide introduced. The slow tensile specimens used in steps a and b are parallel specimens taken from the same coil after processing. The stress-strain curves of the pipeline steel sample in this embodiment under nitrogen environment, acidic environment, hydrogen-induced cracking onset potential alone, and anodic dissolution onset potential alone are shown in Figure 2. Figure 3 shown.

[0067] The test data of other embodiments are shown in the following table:

[0068]

[0069] It can be seen that the NaCl solution with a mass concentration of 5% sodium sulfide (pH=4) and the NaCl solution with a mass concentration of 5% thiourea (pH=6) under these two acidic environments The contribution of hydrogen-induced cracking caused by hydrogen penetration is very large, while the contribution of anodic dissolution is very small, which makes the contribution of the coupling effect of the two to the stress corrosion cracking of pipeline steel samples very small.

[0070] In NaCl solution (pH=2) containing 5% SO2, the stress corrosion sensitivity of pipeline steel samples is It is generally believed that pipeline steel will not suffer from stress corrosion cracking and has no tendency of hydrogen-induced cracking. At this time, the influence of the acidic environment on the stress corrosion cracking of pipeline steel can be regarded as entirely caused by anodic dissolution, that is, the coupling influence degree Cc is 0.

[0071] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for evaluating the effect of coupling of hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel, characterized in that: The steps include: (1) Slow strain rate tensile tests were conducted in acidic and nitrogen environments, respectively, to obtain stress-strain curves of pipeline steel specimens in the two environments, determine the degree of damage to the mechanical properties of pipeline steel specimens in the acidic environment, and obtain the corresponding stress corrosion cracking sensitivity factor; (2) The pipeline steel samples were subjected to potentiodynamic polarization curve tests using slow rate scanning and fast rate scanning to determine the potential range of the stress corrosion sensitive area and the maximum corrosion potential V s V is the starting potential for anodic dissolution alone, the minimum value of the corrosion potential f is the starting potential of hydrogen-induced cracking alone, Vs~V f The corrosion potential range between 10 and 15 is the potential range of the coupling effect of hydrogen-induced cracking and anodic dissolution; (3) Conduct a constant potential slow tensile test on the pipeline steel specimens in an acidic environment at the starting potential of anodic dissolution alone and the starting potential of hydrogen-induced cracking alone, record the test results and stress-strain curves, determine the degree of damage to the mechanical properties of the pipeline steel caused by anodic dissolution and hydrogen-induced cracking, and obtain the corresponding stress corrosion cracking sensitivity factor; The damage degree of the acidic environment on the mechanical properties of the pipeline steel sample is determined by taking the tensile performance parameters of the pipeline steel sample in the nitrogen environment as a benchmark and combining the tensile performance parameters in the acidic environment to determine the stress corrosion cracking sensitivity of the pipeline steel sample in the acidic environment; The specific process is as follows: Based on the cross-sectional area of ​​the pipeline steel specimen before and after stretching, the cross-sectional shrinkage Ψ of the pipeline steel specimen is calculated using formula (1); Ψ=(S0-S1) / S0×100%------(1) In formula (1), S0 is the cross-sectional area of ​​the standard moment section before the specimen breaks, and S1 is the cross-sectional area of ​​the standard moment section after the specimen breaks; Based on the section reduction rate Ψ of pipeline steel samples in nitrogen environment a , Sectional shrinkage of pipeline steel samples in acidic environment Ψ b , the stress corrosion cracking sensitivity factor η of the sample in acidic environment is calculated using formula (2) Ψ , where η Ψ The influence of anodic dissolution, hydrogen-induced cracking, and the coupling effect of the two on stress corrosion cracking of samples in acidic environment; or Ψ =(Ψ a -P b ) / Ψ a ×100%------(2); (4) By comparing the stress-strain curves and test results of nitrogen environment, acidic environment and constant potential slow tensile test, the influence degree of the coupling effect of anodic dissolution and hydrogen in acidic environment on the stress corrosion cracking of pipeline steel specimens and the contribution ratio of stress corrosion cracking are determined; the specific process is as follows: The cross-sectional shrinkage of the pipeline steel sample during the constant potential slow tensile test was calculated according to formula (1). Based on the cross-sectional shrinkage of the pipeline steel sample in the nitrogen environment and formula (2), the stress corrosion cracking sensitivity factor η of the pipeline steel sample under the starting potential of anodic dissolution alone was calculated. A , stress corrosion cracking sensitivity factor η of pipeline steel specimens under the initiation potential of hydrogen-induced cracking alone H The influence of anodic dissolution and hydrogen coupling on stress corrosion cracking of pipeline steel samples in acidic environment was calculated by formula (3): c ; C c =(1+a)×(1-(η H +n A )) / or Ψ ×100%------(3) In formula (3), parameter a=|(V f -V s ) / V s |.

2. The method for evaluating the effect of coupled hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to claim 1, characterized in that: The acidic environment is a sodium chloride solution containing sulfur with a mass concentration of 5% and a pH value of 2≤≤6; wherein the sulfur is gaseous sulfur, solid sulfur, or a mixture of one gaseous sulfur and one solid sulfur, the gaseous sulfur includes H2S and SOx, and the solid sulfur includes Na2S and CH4N2S.

3. The method for evaluating the effect of coupled hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to claim 1, characterized in that: The slow strain rate tensile test is first carried out according to 1×10 -4 The strain rate was quickly preloaded to 80% of the yield strength of the pipeline steel sample at a strain rate of 5×10 -6 The loading was started at a strain rate of mm / s.

4. The method for evaluating the effect of coupled hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to claim 1, characterized in that: During the potentiodynamic polarization curve test, the test solution is a NaCl solution with a mass concentration of 5%, a three-electrode system is adopted, the auxiliary electrode is a platinum mesh, the reference electrode is a saturated calomel electrode, the fast rate scanning speed is 1000-1200mV / min, and the slow rate scanning speed is 5-10mV / min.

5. The method for evaluating the effect of coupling of hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to claim 1, characterized in that: The constant potential slow tensile test is a slow strain rate tensile test under a constant potential. The preloading method and strain rate during the constant potential slow tensile test are the same as those of the slow strain rate tensile test.

6. The method for evaluating the effect of coupled hydrogen and anodic dissolution on stress corrosion cracking of pipeline steel according to claim 1, characterized in that: The test solutions used in the potentiodynamic polarization curve test, slow strain rate tensile test and constant potential slow tensile test were all deoxygenated with high-purity nitrogen.

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