Method and system for rapidly judging hydrogen embrittlement critical instability content of pipeline steel

Abstract

The invention belongs to the technical field of pipeline material safety monitoring, and relates to a pipeline steel hydrogen embrittlement critical instability content rapid determination method and system.The method comprises the steps that simulated hydrogen charging is conducted on multiple sets of notch samples and non-notch samples with the same diffusion thickness under the same condition, and the hydrogen charging duration of each set of notch samples and non-notch samples is different; measuring to obtain the hydrogen content of the unnotched sample after hydrogen charging and the yield energy density and the fracture energy density of the notched sample after hydrogen charging; based on the hydrogen contents of the multiple groups of unnotched samples and the yield energy density and the fracture energy density of the notched samples, fitting out performance relationships between different hydrogen contents and the yield energy and the fracture energy; and determining the actual hydrogen embrittlement critical instability point based on the performance relationship. The method is short in test period and rapid in data acquisition, and the hydrogen embrittlement critical instability point and the corresponding risk interval of the pipeline steel can be rapidly and accurately judged.

Description

Technical Field

[0001] The present application belongs to the technical field of pipeline material safety monitoring, and more specifically, relates to a method and system for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel. Background Art

[0002] Currently, hydrogen pipeline safety testing primarily uses leak detection to generate alerts, which is a post-destruction test. However, damage detection for hydrogen pipelines does have a traceable path; detecting the hydrogen content in the pipeline can prevent damage. However, this typically requires extensive testing to establish an empirical relationship curve between hydrogen concentration and hydrogen damage, and then determine the critical instability hydrogen concentration for pipeline steel as a warning parameter. This results in long testing cycles, high costs, and inadequate data updates. Furthermore, there is a mismatch between experimental and test data. Traditional methods utilize electrochemical hydrogen charging to impart a high surface hydrogen concentration to the pipeline. However, this excessive hydrogen content differs from actual operating conditions in a gas phase environment, making it difficult to accurately determine the critical instability concentration for hydrogen embrittlement in pipeline steel and to provide timely and efficient warnings of pipeline risks. Summary of the Invention

[0003] In response to the defects of the existing technology, the purpose of this application is to provide a method and system for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel, aiming to solve the problem that the existing hydrogen pipeline safety early warning method is difficult to quickly determine the critical instability hydrogen concentration risk range of pipeline steel.

[0004] To achieve the above objectives, in a first aspect, the present application provides a method for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel, comprising: S1 simulates hydrogen charging of multiple groups of notched specimens and unnotched specimens with the same diffusion thickness under the same conditions, and the hydrogen charging time of each group of notched specimens and unnotched specimens is different; and measures the hydrogen content of the unnotched specimens after hydrogen charging and the yield energy density and fracture energy density of the notched specimens; S2 fitting the performance relationships between different hydrogen contents and yield energy and fracture energy based on the hydrogen contents of the unnotched specimens and the yield energy density and fracture energy density of the notched specimens; S3 determines the actual hydrogen embrittlement critical instability point based on the performance relationship.

[0005] Furthermore, in step S1, each group of notched specimens and unnotched specimens are placed in an environment of 70° C. to 200° C. for simulated hydrogen charging.

[0006] Furthermore, in step S1, the yield energy density and fracture energy density of the notched specimen after hydrogen charging are obtained using the following expressions:

[0007] in, Ui represents the yield energy density, represents the yield strain obtained from the hydrogen compatibility test;

[0008] Among them, U f represents the fracture energy density, represents the fracture strain obtained in the hydrogen compatibility test.

[0009] Furthermore, in step S2, based on the hydrogen content of the plurality of groups of unnotched specimens and the yield energy density and fracture energy density of the notched specimens, the performance relationship between different hydrogen contents and yield energies is fitted using the following formula: Y1=A1+B1X+C1X 2 +D1X 3 +E1X 4 , Among them, X is the hydrogen content, Y1 is the yield energy density, A1, B1, C1, D1 and E1 are different coefficient fitting parameters; The performance relationship between different hydrogen contents and fracture energy is fitted using the following formula: Y2=A2+B2X+C2X 2 +D2X 3 +E2X 4 , Among them, X is the hydrogen content, Y2 is the yield energy density, and A2, B2, C2, D2 and E2 are different coefficient fitting parameters.

[0010] Furthermore, when fitting the performance relationship between different hydrogen contents and yield energy, it is required that each risk interval on the fitting curve has at least two data points, and there are at least two risk intervals with a coefficient of determination R 2 >0.95.

[0011] Furthermore, in step S3, the method for determining the actual hydrogen embrittlement critical instability point based on the performance relationship is: S301 determines a first hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and yield energies; and determines a second hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and fracture energies; S302 selects the minimum value between the first hydrogen embrittlement critical instability point and the second hydrogen embrittlement critical instability point as the actual hydrogen embrittlement critical instability point.

[0012] Furthermore, after step S3, the risk interval is divided based on the actual hydrogen embrittlement critical instability point, wherein: the drop point on the fitting curve corresponding to the actual hydrogen embrittlement critical instability point is obtained, and the numerical interval less than the drop point is defined as an absolute safety interval; the numerical interval between the drop point and the actual hydrogen embrittlement critical instability point is defined as a relatively safe interval; the numerical interval between the actual hydrogen embrittlement critical instability point and 25% hydrogen embrittlement hydrogen content is defined as a general risk interval, and the numerical interval exceeding 25% hydrogen embrittlement hydrogen content is defined as a dangerous risk interval.

[0013] According to a second aspect of the present application, a system for implementing any of the aforementioned methods for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel is provided, comprising: The simulated hydrogen charging module is used to simulate hydrogen charging of multiple groups of notched specimens and unnotched specimens with the same diffusion thickness under the same conditions; A hydrogen content measurement module, used to measure the hydrogen content of the unnotched sample after hydrogen filling; An energy density acquisition module, used to measure and obtain the yield energy density and fracture energy density of the notched sample after hydrogen filling; A performance relationship fitting module is configured to fit the performance relationships between different hydrogen contents and yield energy and fracture energy based on the hydrogen contents of the unnotched specimens and the yield energy density and fracture energy density of the notched specimens; The actual hydrogen embrittlement critical instability point determination module is used to determine the actual hydrogen embrittlement critical instability point based on the performance relationship.

[0014] Furthermore, it also includes a risk area division module for dividing the risk interval based on the actual hydrogen embrittlement critical instability point.

[0015] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: (1) This application only requires a small amount of sample and can establish the precise relationship between hydrogen concentration and sample failure energy (fracture energy, yield energy) in a relatively short time, so as to quickly determine the critical instability hydrogen concentration risk range of pipeline steel. It has the advantages of short test cycle, fast data acquisition, economic efficiency, and simple operation. It can be effectively used for pipeline safety early warning and risk management in actual engineering and has a broad application prospect.

[0017] (2) This application uses comparative hydrogen charging experiments on notched and unnotched specimens, combined with dual-parameter fitting (polynomial regression) of yield energy and fracture energy density, to accurately capture the critical transition point from plastic deformation to brittle fracture. Compared with traditional methods that rely on a single mechanical indicator (such as elongation), this method can more sensitively reflect the nonlinear relationship between hydrogen concentration and material properties, and is particularly suitable for the complex service environment of high-strength pipeline steel.

[0018] (3) This application calculates yield energy and fracture energy by integrating the stress-strain curve, converting hydrogen embrittlement sensitivity into the attenuation of energy dissipation capacity. This method more intuitively reflects the cumulative effect of hydrogen-induced damage than traditional fracture toughness tests (such as KIC) and is suitable for thin-walled specimens or samples of non-standard size.

[0019] (4) This application compares the critical instability points of yield energy (reflecting initial plastic damage) and fracture energy (reflecting final fracture resistance) and selects their minimum value as the final criterion, which can provide early warning of hydrogen embrittlement risks. For example, when the yield energy drops sharply before the fracture energy, it indicates that the material has entered the metastable damage stage although it has not yet broken, which is particularly important for pipeline safety monitoring. In addition, the data point distribution is required to have an R²>0.95 during fitting to ensure the statistical reliability of the critical value judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel provided in Example 1 of the present application; Figure 2 is a schematic diagram of a stress-strain curve provided in Example 1 of the present application; Figure 3 This is a schematic diagram of the relationship between the fitting performance of different hydrogen contents and the corresponding yield energy and fracture energy provided in Example 1 of the present application; Figure 4 This is a schematic diagram of risk interval division provided in Example 1 of the present application; Figure 5 This is a flow chart of a method for monitoring the safety risk of a 1#X65 steel material pipeline in an air environment provided in Example 2 of the present application; Figure 6 This is a schematic diagram of the cumulative change of hydrogen charging of the sample provided in Example 2 of the present application; Figure 7 This is a schematic diagram of the fitting performance relationship between different hydrogen contents and corresponding yield energy and fracture energy provided in Example 2 of the present application; Figure 8 This is a schematic diagram of step current data provided in Example 2 of the present application; Figure 9 This is a schematic diagram of the fitting performance relationship between different hydrogen contents and corresponding yield energy and fracture energy provided in Example 3 of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0022] The term "and / or" as used herein describes an association between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. The symbol " / " as used herein indicates that the related objects are in an "or" relationship, for example, A / B means either A or B.

[0023] The terms "first" and "second" in this specification and claims are used to distinguish different objects rather than to describe a specific order of objects. For example, "first response message" and "second response message" are used to distinguish different response messages rather than to describe a specific order of response messages.

[0024] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more, for example, multiple processing units means two or more processing units, etc.; multiple elements means two or more elements, etc.

[0026] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0027] Example 1 This embodiment provides a method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel. Figure 1 As shown, the following steps are included: S1 simulates hydrogen charging of multiple groups of notched and unnotched specimens with the same diffusion thickness under the same conditions, with different hydrogen charging times for each group of notched and unnotched specimens. The hydrogen content of the unnotched specimens after hydrogen charging is measured, and the yield energy density and fracture energy density of the notched specimens after hydrogen charging are obtained using the hydrogen compatibility test method. S2 is based on the hydrogen content of multiple groups of unnotched specimens and the yield energy density and fracture energy density of notched specimens, and the performance relationship between different hydrogen contents and yield energy and fracture energy is fitted; S3 determines the actual critical instability point of hydrogen embrittlement based on performance relationships.

[0028] Specifically, multiple groups of identical slow strain tensile specimens with V-notches (i.e., notched specimens) were prepared. The notched specimens met the standards of GB / T34542.2-2018 "Test Methods for Compatibility of Metallic Materials with the Environment" to simulate the local damage of pipeline steel caused by stress concentration under service conditions. At the same time, multiple groups of unnotched specimens with equivalent diffusion thickness to the notched specimens were prepared, with dimensions of approximately 8×8×Xcm. 3 , where the thickness X is 1 / 2 of the width of the notch of the notch specimen. In this embodiment, the width of the notch of the notch specimen is 3 mm, so X is 1.5 mm.

[0029] In step S1, each set of notched and unnotched specimens is placed in an environment of 70°C to 200°C for simulated hydrogen charging. If the temperature exceeds 200°C, a phase change may occur. The hydrogen charging time for each set of specimens is varied. Specifically, each set of specimens is subjected to a high-pressure hydrogen charging treatment for a certain period of time to simulate the diffusion and infiltration of hydrogen during actual service. One side of an unnotched specimen with an equivalent diffusion thickness is nickel-plated or shielded, leaving the opposite side exposed to the hydrogen environment for hydrogen charging.

[0030] The hydrogen content in the unnotched sample was then measured using TDS (Thermal Desorption Spectrometry). During the measurement, the temperature gradient of the unnotched sample was increased from room temperature to about 450°C. Above 450°C, irreversible hydrogen and hydrides are present and do not participate in the hydrogen embrittlement process, so they cannot be heated above 450°C.

[0031] In step S1, the yield energy density and fracture energy density are obtained using a hydrogen compatibility test method. Since the hydrogen compatibility test method is a conventional test method in the field, it will not be described here. Specifically, the yield energy density is calculated using the following formula: (1) in, U i represents the yield energy density, represents the yield strain obtained by the hydrogen compatibility test method; (2) Among them, U f represents the fracture energy density, Represents the fracture strain obtained by the hydrogen compatibility test method.

[0032] In the aforementioned step S2, based on the hydrogen content of multiple groups of unnotched specimens and the yield energy density and fracture energy density of notched specimens, the performance relationship between different hydrogen contents and yield energies is fitted using the following formula: Y1=A1+B1X+C1X 2 +D1X 3 +E1X 4 (3) Among them, X is the hydrogen content, Y1 is the yield energy density, A1, B1, C1, D1 and E1 are different coefficient fitting parameters; The performance relationship between different hydrogen contents and fracture energy is fitted using the following formula: Y2=A2+B2X+C2X 2 +D2X 3 +E2X 4 (4) Among them, X is the hydrogen content, Y2 is the yield energy density, A2, B2, C2, D2 and E2 are different coefficient fitting parameters; Specifically, when fitting the performance relationship between different hydrogen contents and yield energy, it is required that each risk interval on the fitting curve has at least two data points, and there are at least two risk intervals of the fitting data with a determination coefficient R 2 (COD)>0.95. The performance relationship diagram is shown in the figure below. Figure 3 As shown, there are three stages: the first stage is a slow decline or basically unchanged; the second stage is a rapid decline; and the third stage is an increase in hydrogen content while the hydrogen sensitivity remains basically unchanged.

[0033] In the aforementioned step S3, the method for determining the actual hydrogen embrittlement critical instability point based on the performance relationship is: S301 determines a first hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and yield energies; and determines a second hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and fracture energies; S302 selects the minimum value between the first hydrogen embrittlement critical instability point and the second hydrogen embrittlement critical instability point as the actual hydrogen embrittlement critical instability point.

[0034] After step S3, the risk interval is further divided based on the actual hydrogen embrittlement critical instability point, such as Figure 4 As shown, where: the drop point on the fitting curve corresponding to the actual hydrogen embrittlement critical instability point is obtained, and the numerical interval less than the drop point is defined as the absolute safety interval; the numerical interval between the drop point and the actual hydrogen embrittlement critical instability point is defined as the relative safety interval; the numerical interval between the actual hydrogen embrittlement critical instability point and the 25% hydrogen content for hydrogen embrittlement is defined as the general risk interval, and the numerical interval exceeding the 25% hydrogen content for hydrogen embrittlement is defined as the dangerous risk interval. That is, the absolute safety period is the stable period concentration, the relative safety interval is the concentration before the actual hydrogen embrittlement critical instability point, and the general risk interval is the hydrogen content corresponding to the actual hydrogen embrittlement critical instability point <C H The range of hydrogen content that causes hydrogen embrittlement is less than 25%.

[0035] The actual hydrogen embrittlement critical instability point obtained above is the inner wall hydrogen content. The outer wall hydrogen potential is obtained in the hydrogen probe monitoring at the engineering site. Therefore, it is also necessary to convert the outer wall hydrogen potential to the inner wall hydrogen unit.

[0036] The hydrogen content is expressed in wppm (parts per million by mass). First, convert it to concentration units (such as mol / m³) using the following formula: (5) Among them, M H is the molar mass of hydrogen, M H =0.001008kg / mol, is the material density.

[0037] The relationship between the outer wall hydrogen potential and the inner wall hydrogen concentration is: (6) The aforementioned hydrogen diffusion process follows Fick's first law: (7) in, is the flux ( ), D is the diffusion coefficient ( ), is the concentration gradient ( ).

[0038] For steady-state diffusion, assuming that the pipe wall thickness is L, the thickness of the unnotched specimen for TDS test is X, and the hydrogen concentration measured by TDS is the concentration of the inner wall of the pipe, then the hydrogen concentration is C inner Linearly descend to the outer wall C outer , at this time the inner wall C inner The hydrogen concentration represents the hydrogen concentration of the inner wall of the pipe with a thickness of L-1 / 2X, so the outer wall flux J outer It can be expressed as: (8) Since the outer wall is exposed to a non-hydrogen environment, when all hydrogen atoms are converted into electric current, C outer ≈0 , so the formula can be simplified to: (9) The stable current is: (10) in, F is the Faraday constant (C / mol), I To monitor the current (A), STo monitor density.

[0039] The calculation formula for the theoretical current density is: (11) in, i is the theoretical current density (A / cm²); the theoretical current density can also be calculated using formula (6).

[0040] Considering the influence of temperature on the diffusion coefficient, it is also necessary to perform engineering calibration on the diffusion coefficient. Diffusion coefficient Varies with temperature, so adjust according to the Arrhenius relation: (12) in, D 0 is the initial diffusion coefficient, Q is the activation energy, R is the gas constant, T is the absolute temperature.

[0041] Pipeline risk monitoring uses a step test principle. Normally, the polarization overpotential is 0V. A step potential (>0.25V) is applied every 10 hours and maintained for 300 seconds to allow hydrogen atoms accumulated in the pipeline's outer wall to diffuse outward and fully oxidize. The theoretical current density equation is corrected using the step current to obtain the critical monitoring warning potential.

[0042] Example 2 This embodiment provides a method for monitoring the safety risk of a 1#X65 steel pipe in an air environment. The specific process is as follows: Figure 5 shown.

[0043] First, multiple groups of notched specimens with a size of 8 mm*8 mm*1.5 mm and multiple groups of unnotched specimens (i.e., sheet-shaped square specimens) with equivalent hydrogen thickness corresponding to the notched specimens were prepared according to the method of Example 1.

[0044] Then, multiple groups of samples were charged with hydrogen in the gas phase at 100°C and 10 MPa, and the charging time of each group of samples was different, such as Figure 6 As shown in the figure, after 49 days of hydrogen charging, the accumulation of hydrogen tends to be stable and close to saturation.

[0045] TDS was then used to measure the effective hydrogen accumulation (i.e., hydrogen content data) of each group of unnotched specimens. Slow strain tensile testing was used to obtain fracture / yield energy density data for notched specimens at different hydrogen contents, as shown in Table 1 below: Table 1 Hydrogen content-fracture energy density / yield energy density in air environment

[0046] Then, the data in Table 1 were fitted according to formula (3) and formula (4) in Example 1 to obtain the following: Figure 7 The performance relationship between different hydrogen contents and yield energy density and fracture energy density is shown in the fitting curve diagram (i.e. failure curve diagram), where R 2 The (COD) value is > 0.98, which meets the design requirements of this application, and there are more than three data points in the first and second stages.

[0047] Determine the actual critical instability point for hydrogen embrittlement and divide the risk range: Multiple instability points are found through the intersection of the slopes of the first and second stages, and the critical instability hydrogen concentration is determined from these instability points. The stable period concentrations of the fracture energy density and yield energy density are 0.213wppm (drop point 1) and 0.224wppm (drop point 2), respectively. The smaller value between the two is taken as the actual stable period concentration value, that is, the actual stable period concentration value is 0.213wppm. In the figure, the instability point concentrations of the fracture energy density and yield energy density are 0.270wppm and 0.268wppm, respectively. The smaller value between the two is taken as the actual critical instability point for hydrogen embrittlement, that is, the actual critical instability point for hydrogen embrittlement is 0.268wppm.

[0048] Therefore, when the pipeline operates in an air environment, the absolute safe range of hydrogen content is less than 0.213wppm, the relative safe range is 0.213wppm~0.268wppm, and the general risk range is 0.268wppm~0.317wppm. When operating in an air environment, even if the hydrogen content in the pipeline is high, the risk of hydrogen embrittlement is very small.

[0049] The hydrogen content of the inner and outer walls of the pipeline steel is then converted to the current data. The hydrogen flux is converted to the corresponding hydrogen concentration according to the following formula: (13) in, C wppm is the hydrogen flux, M H =0.001008kg / mol, ρ is the material density (7850 ), that is, the hydrogen concentration of 1 mol / m³ corresponds to approximately 0.1284 wppm, and the calculation yields: Drop point: 0.213wppm=1.673×10 -6 mol / cm³; Instability point: 0.268wppm=2.104×10 - 6mol / cm³; Saturation point: 0.317wppm=2.491×10 -6 mol / cm³; In this embodiment, the Faraday constant is: The thickness of the monitoring pipe is 16 mm. The diffusion coefficient D in the 25°C environment is 1.4×10 -6 cm 2 / s.

[0050] The theoretical current densities corresponding to the drop point, instability point, and saturation point calculated using the theoretical current density calculation formula (6) or (11) in Example 1 are 1.458×10 -8 A / cm², 1.834×10 -8 A / cm², 2.170×10 -8 A / cm².

[0051] The theoretical current density needs to be corrected with the experimental detection value. In this embodiment, the detection device based on the dual-battery principle uses a step potential for detection.

[0052] like Figure 8 The figure shows the change in step current data. The initial hydrogen content is 0.079wppm. After 21 days of high-temperature hydrogen charging, the hydrogen content is 0.263wppm. The current density corresponding to the initial hydrogen content is higher than the current density after 21 days of pre-charging. After the actual detection potential interval is 10 hours, the hydrogen atoms on the surface of the pipeline are released with a step voltage of 0.25V, and the actual current density is measured. The calculation formula for the actual current density is: (14) is the starting time of the potential step, is the potential step stop moment, i ( t ) is the current density at a certain moment during the potential jump, The interval is 10 hours. i a The actual current density is shown in Table 2 below, which shows the theoretical surface current density and actual current density obtained under different hydrogen concentrations: Table 2 Theoretical surface current density and actual current density

[0053] There are differences in pipe thickness and diffusion coefficient between the theoretical surface current density and the actual surface current. According to the formula, there should be a linear relationship between the two. The fitted linear correction equation is: (15) in, k i is the correction factor for thickness and diffusion coefficient, k i =0.154; b is the ideal crystal current,b =3.96×10 -9 A / cm²; the corrected actual surface current i a =0.154 i +3.96×10 -9 .

[0054] The drop point, instability point and saturation point correspond to the theoretical potential 1.458×10 -8 A / cm², 1.834×10 -8 A / cm², 2.170×10 -8 Substitute A / cm² into the aforementioned linear correction equation (15) and solve for the monitoring critical potential corresponding to the drop point, instability point and saturation point respectively:

[0055] Table 3 below shows the critical range of hydrogen embrittlement monitoring current under non-hydrogen operating conditions obtained in this embodiment: Table 3 Critical range of hydrogen embrittlement monitoring current

[0056] Example 3 The risk situation of the 2#X65 steel material pipeline in a 10MPa hydrogen environment was monitored according to the method described in Example 1.

[0057] First, multiple sets of notched specimens measuring 8 x 8 x 1.5 mm were prepared, along with corresponding sets of unnotched specimens (i.e., square-shaped sheet specimens). Each set of specimens was charged with hydrogen in the vapor phase at 100°C and 10 MPa in air, with each charging time varying. TDS was then used to measure the effective hydrogen accumulation in each unnotched specimen. After 49 days of charging, hydrogen accumulation stabilized, approaching saturation.

[0058] The fracture energy density / yield energy density data corresponding to different hydrogen contents were also obtained by slow strain stretching, as shown in Table 4: Table 4 Hydrogen content in air environment - fracture energy density / yield energy density

[0059] According to formula (3) and formula (4) in Example 1, the fracture energy density and yield energy density (i.e., failure energy density in the figure) under different hydrogen contents were fitted to obtain the following: Figure 9 The graph shown.

[0060] Figure 9 In the figure, the 25% energy damage line intersects with the fitting curve, so there is a dangerous risk range in the 10MPa hydrogen environment. On the two fitting curves: The hydrogen content of drop point 1 is 0.131wppm, which is less than the hydrogen content of drop point 2, 0.199wppm. Therefore, the actual drop point is selected as 0.131wppm. The theoretical current density calculated by formula (14) is 8.967×10 -9 A / cm²; The hydrogen content at instability point 1 is 0.163wppm, which is less than the hydrogen content at instability point 2, which is 0.241wppm. Therefore, the actual instability point (the actual hydrogen embrittlement critical instability point) is determined to be 0.163wppm. The theoretical current density calculated using formula (14) is 1.116×10 -8 A / cm²; The hydrogen content of high-risk point 1 is 0.196wppm, which is less than the hydrogen content of high-risk point 2, which is 0.307wppm. The actual high-risk point is 0.196wppm. The theoretical current density calculated by formula (14) is 1.341×10 -8 A / cm².

[0061] The three calculated theoretical current densities were substituted into the linear correction equation (15) in Example 2 to obtain the actual surface currents: 5.341×10 -8 A / cm²、5.678×10 -8 A / cm² and 6.025×10 -8 A / cm². Therefore, the critical range of hydrogen embrittlement monitoring current under 10MPa operating environment is shown in Table 5 below: Table 5 Critical range of hydrogen embrittlement monitoring current

[0062] In practical applications, by monitoring the above-mentioned critical current range, it is possible to quickly and accurately determine whether the hydrogen pipeline is at risk of damage.

[0063] The following describes the system for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel provided by the present application. The system for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel described below and the method for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel described above can be referenced to each other.

[0064] The system for rapid determination of critical instability content of hydrogen embrittlement in pipeline steel includes: The simulated hydrogen charging module is used to simulate hydrogen charging of multiple groups of notched specimens and unnotched specimens with the same diffusion thickness under the same conditions; A hydrogen content measurement module is used to measure the hydrogen content of a sample without a gap after hydrogen filling; Energy density acquisition module, used to measure the yield energy density and fracture energy density of the notched specimen after hydrogen filling; The performance relationship fitting module fits the performance relationship between different hydrogen contents and yield energy and fracture energy based on the hydrogen content of multiple groups of unnotched specimens and the yield energy density and fracture energy density of notched specimens; The actual hydrogen embrittlement critical instability point determination module is used to determine the actual hydrogen embrittlement critical instability point based on the performance relationship.

[0065] In other embodiments, a risk area division module is further included, and the risk area division module is used to divide the risk interval based on the actual hydrogen embrittlement critical instability point.

[0066] In summary, this application only requires a small amount of sample to efficiently establish a precise relationship between hydrogen concentration and sample failure energy (fracture work, yield energy), and uses this precise relationship to quickly determine the critical instability hydrogen concentration risk range of pipeline steel. It has the advantages of short test cycle, rapid data acquisition, cost-effectiveness, and simple operation. It can be effectively used for pipeline safety early warning and risk management in actual projects and has a broad application prospect.

[0067] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0068] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0069] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the two are connected to each other and the relative position relationship after the connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after the connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after the connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0070] In addition, in the embodiments of the present application, the mathematical concepts mentioned include symmetry, equality, parallelism, and perpendicularity. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense. A small amount of deviation is allowed, and it is possible to be approximately symmetric, approximately equal, approximately parallel, or approximately perpendicular. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0071] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel, characterized in that: include: S1 simulates hydrogen charging of multiple groups of notched specimens and unnotched specimens with the same diffusion thickness under the same conditions, and the hydrogen charging time of each group of notched specimens and unnotched specimens is different; the hydrogen content of the unnotched specimens after hydrogen charging and the yield energy density and fracture energy density of the notched specimens after hydrogen charging are measured; S2 fitting the performance relationships between different hydrogen contents and yield energy and fracture energy based on the hydrogen contents of the unnotched specimens and the yield energy density and fracture energy density of the notched specimens; S3 determines the actual hydrogen embrittlement critical instability point based on the performance relationship.

2. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 1, characterized in that: In step S1, each group of notched specimens and unnotched specimens are placed in an environment of 70° C. to 200° C. for simulated hydrogen charging.

3. The method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 1, characterized in that: In step S1, the yield energy density and fracture energy density of the notched specimen after hydrogen charging are obtained using the following expressions: in, U i represents the yield energy density, represents the yield strain obtained from the hydrogen compatibility test; Among them, U f represents the fracture energy density, represents the fracture strain obtained in the hydrogen compatibility test.

4. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 1, characterized in that: In step S2, based on the hydrogen content of the plurality of groups of unnotched specimens and the yield energy density and fracture energy density of the notched specimens, the performance relationship between different hydrogen contents and yield energies is fitted using the following formula: Y1=A1+B1X+C1X 2 +D1X 3 +E1X 4 , Among them, X is the hydrogen content, Y1 is the yield energy density, A1, B1, C1, D1 and E1 are different coefficient fitting parameters; The performance relationship between different hydrogen contents and fracture energy is fitted using the following formula: <h2 style=";text-align:left;direction:ltr">Y2=A2+B2X+C2X<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +D2X<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +E2X<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> , Among them, X is the hydrogen content, Y2 is the yield energy density, and A2, B2, C2, D2 and E2 are different coefficient fitting parameters.

5. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 4, characterized in that: When fitting the performance relationship between different hydrogen contents and yield energy, it is required that each risk interval on the fitting curve has at least two data points, and there are at least two risk intervals with the determination coefficient R 2 >0.

95.

6. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 1, characterized in that: In step S3, the method for determining the actual hydrogen embrittlement critical instability point based on the performance relationship is: S301 determines a first hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and yield energies; and determines a second hydrogen embrittlement critical instability point based on a performance relationship between different hydrogen contents and fracture energies; S302 selects the minimum value between the first hydrogen embrittlement critical instability point and the second hydrogen embrittlement critical instability point as the actual hydrogen embrittlement critical instability point.

7. A method for quickly determining the critical instability content of hydrogen embrittlement in pipeline steel according to claim 1, characterized in that: After step S3, the risk interval is further divided based on the actual hydrogen embrittlement critical instability point, wherein: the drop point on the fitting curve corresponding to the actual hydrogen embrittlement critical instability point is obtained, and the numerical interval less than the drop point is defined as an absolute safety interval; the numerical interval between the drop point and the actual hydrogen embrittlement critical instability point is defined as a relatively safe interval; the numerical interval between the actual hydrogen embrittlement critical instability point and 25% hydrogen embrittlement hydrogen content is defined as a general risk interval, and the numerical interval exceeding 25% hydrogen embrittlement hydrogen content is defined as a dangerous risk interval.

8. A system for implementing the method for rapidly determining the critical instability content of hydrogen embrittlement in pipeline steel according to any one of claims 1 to 7, characterized in that: include: The simulated hydrogen charging module is used to simulate hydrogen charging of multiple groups of notched specimens and unnotched specimens with the same diffusion thickness under the same conditions; A hydrogen content measurement module, used to measure the hydrogen content of the unnotched sample after hydrogen filling; An energy density acquisition module, used to measure and obtain the yield energy density and fracture energy density of the notched sample after hydrogen filling; A performance relationship fitting module is configured to fit the performance relationships between different hydrogen contents and yield energy and fracture energy based on the hydrogen contents of the unnotched specimens and the yield energy density and fracture energy density of the notched specimens; The actual hydrogen embrittlement critical instability point determination module is used to determine the actual hydrogen embrittlement critical instability point based on the performance relationship.

9. The system according to claim 8, wherein It also includes a risk area division module for dividing the risk interval based on the actual hydrogen embrittlement critical instability point.

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