A slow tensile test method for pipeline steel in hydrogen environment

Abstract

The present invention relates to a slow tensile test method for pipeline steel in a hydrogen environment, belongs to the technical field of pipeline steel testing, and solves the problem that it is difficult to implement performance testing of pipeline steel in a high-pressure hydrogen environment in the prior art. The present invention includes steps S1: installing the pipeline steel of the test sample into a hydrogen environment box; step S2: hydrogenating the pipeline steel in the hydrogen environment box; step S3: connecting the hydrogenated pipeline steel to a slow tensile instrument to perform a slow tensile test. The present invention realizes the performance testing of pipeline steel under different hydrogen partial pressure conditions. During the test process, the pipeline steel is always in a hydrogen environment, thereby ensuring the accuracy of the test.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline steel testing, and in particular to a slow tensile test method for pipeline steel in a hydrogen environment. Background Art

[0002] Hydrogen energy has a wide range of sources. As a secondary energy source, hydrogen can be produced not only through the reforming of fossil energy such as coal, oil and natural gas, thermal cracking of biomass or microbial fermentation, but also from industrial by-product gases such as coking, chlor-alkali, steel and metallurgy. It can also be produced by electrolysis of water, especially when combined with renewable energy power generation. It not only achieves green and clean development throughout its life cycle, but also expands the utilization of renewable energy.

[0003] At present, my country's hydrogen storage and transportation mainly uses long-tube trailers to transport high-pressure gaseous hydrogen, supplemented by low-temperature liquid hydrogen and pipeline transportation, and develops in a coordinated manner. In the long run, the construction of hydrogen pipelines will accelerate the layout to achieve coordinated development of different market segments and regions. Pipeline transportation has a large volume, low energy consumption, and low marginal cost. It is an important way to achieve large-scale, long-distance gaseous hydrogen transportation, and it is also an inevitable trend in the development of hydrogen transportation.

[0004] High-pressure hydrogen can cause hydrogen damage to hydrogen transmission pipelines. Foreign countries generally improve safety by adopting lower steel grades, reducing hydrogen transmission pressure, and increasing wall thickness.

[0005] At present, the operating pressure of foreign hydrogen pipelines is usually 1.0-4.0MPa, and the steel grade is below X52. The steel grades of several hydrogen pipelines currently built in my country are L245 and 20# steel, and the hydrogen transmission pressure is all below 4MPa. Low steel grade and medium-low pressure hydrogen transmission is far from meeting the engineering needs of large-scale, long-distance pipeline hydrogen transmission in my country in the future. Therefore, it is urgent to study the hydrogen permeation behavior in high-grade steel pipes and welds, master the key factors affecting the mechanical properties of pipes and welds in hydrogen environments, develop high-grade steel hydrogen-resistant pipelines, ensure the safety of large-scale, long-distance medium-high pressure hydrogen transmission pipelines, and meet the engineering needs of my country's carbon emission reduction strategy for hydrogen energy.

[0006] Hydrogen embrittlement of metal materials refers to the phenomenon that after hydrogen enters the metal, the local hydrogen concentration reaches saturation, causing the metal's plasticity to decrease, cracks to be induced, or delayed fractures to occur. According to the source of hydrogen, hydrogen embrittlement can be divided into internal hydrogen embrittlement and environmental hydrogen embrittlement. The former refers to the absorption of excessive hydrogen by metal materials during smelting and processing processes such as pickling and electroplating, and the latter refers to the loss of performance caused by hydrogen entering the metal in an environment such as hydrogen sulfide, hydrogen, and water vapor. In a hydrogen environment, hydrogen will be adsorbed on the metal surface, dissolved in the metal, diffused, and enriched in specific parts. First, hydrogen molecules in the gas phase collide with the metal surface through irregular thermal motion, and remain on the metal surface through physical adsorption during the collision. Some of the adsorbed hydrogen molecules dissociate into atomic hydrogen under the action of activation energy and produce chemical adsorption on the metal surface. Due to the affinity, the dissociated hydrogen atoms enter the vacancies of the metal lattice or the gaps between metal atoms from the metal surface to form substitutional or interstitial solid solutions. As hydrogen atoms continue to enter, due to the effect of concentration gradient, hydrogen atoms diffuse in the gaps between metal atoms, causing the hydrogen in the metal matrix to reach a certain concentration.

[0007] The slow strain rate test is a fast test method for determining stress corrosion cracking or hydrogen-induced cracking performance. The sample is stretched slowly and uniformly on a constant strain rate machine (the sample is in a test solution or gas environment) until it breaks. After the test, the fracture morphology is analyzed using a scanning electron microscope. During the test, the load-elongation curve is measured, and many parameters reflecting stress corrosion or hydrogen embrittlement sensitivity can be analyzed from the curve. At present, most of the tests on hydrogen-induced cracking of pipeline steel use electrochemical pre-charging hydrogen test methods, which makes it difficult to perform performance tests on pipeline steel in a high-pressure hydrogen environment. Summary of the invention

[0008] In view of the above analysis, the present invention aims to provide a slow tensile test method for pipeline steel in a hydrogen environment, so as to solve the problem that it is difficult to perform performance testing on pipeline steel in a high-pressure hydrogen environment in the prior art.

[0009] The purpose of the present invention is mainly achieved through the following technical solutions:

[0010] A slow tensile test method for pipeline steel in a hydrogen environment comprises the following steps:

[0011] Step S1: installing the pipeline steel of the test sample into a hydrogen environment box;

[0012] Step S2: charging the pipeline steel in the hydrogen environment box with hydrogen;

[0013] Step S3: Connect the pipeline steel after hydrogen filling to a slow tensile tester to perform a slow tensile test.

[0014] Furthermore, in step S1, the pipeline steel installation process includes:

[0015] Step S11: Open the hydrogen environment box and put the pipeline steel to be tested into it;

[0016] Step S12: passing one end of the pipeline steel through the sealing cover and the other end through the bottom of the box;

[0017] Step S13: fasten the sealing cover to the box body by screws.

[0018] Furthermore, in step S2, the hydrogen charging process of the pipeline steel includes:

[0019] Step S21: replacing the internal gas of the box with high-purity nitrogen;

[0020] Step S22: filling the box with hydrogen of a predetermined pressure;

[0021] Specifically, the pressure of the gas inside the box 1 is monitored in real time by the pressure gauge 8 .

[0022] Step S23: Check the sealing performance of the hydrogen environment box and keep the pressure of the hydrogen environment box constant during the hydrogen filling test; specifically, let the hydrogen environment box stand for 20 minutes. If the pressure inside the box remains unchanged, it is considered that the sealing performance of the hydrogen environment box is good.

[0023] Step S24: To ensure that high-pressure hydrogen fully enters the sample working section through collision, adsorption, dissolution and diffusion, the sample must be pre-filled with hydrogen in a hydrogen environment box for more than 1 day.

[0024] Furthermore, in step S21, the high-purity nitrogen replacement step is repeated three times to ensure that the oxygen content in the box is lower than the explosion range of hydrogen.

[0025] Furthermore, in step S21, the high-purity nitrogen replacement process is as follows: nitrogen is injected into the box through the air inlet pipe, and the air outlet pipe is opened to discharge the gas inside the box.

[0026] Furthermore, in step S21, the volume of nitrogen gas injected into the box during the high-purity nitrogen replacement process is n times the volume of the box, where n is a natural number greater than 2.

[0027] Furthermore, in step S3, after the pipeline steel sample is pre-filled with hydrogen in a hydrogen environment box for 4 days, the pipeline steel and the hydrogen environment box are placed at both ends of a slow tensile tester through threaded connection to perform a tensile test.

[0028] A slow tensile test device for pipeline steel in a hydrogen environment is used to implement the above-mentioned slow tensile test method for pipeline steel in a hydrogen environment, comprising: a slow tensile tester and a hydrogen environment box; the hydrogen environment box comprises: a box body and a sealing cover; an air inlet pipe is arranged on the sealing cover; an air outlet pipe is arranged on the box body; high-pressure ball valves are installed on the air inlet pipe and the air outlet pipe, and the high-pressure ball valve is used to control the opening and closing of the air inlet pipe or the air outlet pipe;

[0029] A pipeline steel is arranged in the hydrogen environment box, and one end of the pipeline steel extends out of the surface of the sealing cover, and the other end of the pipeline steel extends out of the box body;

[0030] Threaded sections are provided at both ends of the pipeline steel and are connected to the slow tensile tester through the threaded sections.

[0031] Furthermore, a pressure gauge is installed on the hydrogen environment box to monitor the gas pressure in the box in real time.

[0032] Furthermore, an annular polytetrafluoroethylene liner is arranged inside the box.

[0033] Furthermore, the pipeline steel and the sealing cover are sealed by a sealing ring, and the pipeline steel and the box body are also sealed by a sealing ring.

[0034] Furthermore, a protruding sealing cylinder is arranged on the sealing cover, a sealing ring is installed in the sealing cylinder, and the sealing ring comprises a ring body and a protruding portion.

[0035] Furthermore, the ring body is a cylindrical structure, the inner surface of the ring body is in contact with the pipeline steel, and the outer surface of the ring body is in contact with the sealing cylinder.

[0036] Furthermore, a plurality of protrusions are arranged on the outside of the ring body, the protrusions protrude from the outer surface of the ring body, and can be snapped into the snap-fit ​​holes on the sealing cylinder.

[0037] The technical solution of the present invention can achieve at least one of the following effects:

[0038] 1. The slow tensile test device and test method of pipeline steel in a hydrogen environment of the present invention can examine the influence of different hydrogen partial pressures (up to 12 MPa) on hydrogen-induced cracking of pipeline steel, thereby providing a safe and reliable test method for studying the key factors affecting the mechanical properties of pipes and welds in a hydrogen environment.

[0039] 2. The present invention injects hydrogen of different pressures into the box through the air inlet pipe, monitors the hydrogen pressure through a pressure gauge, and performs a slow tensile test after hydrogen filling, so as to accurately obtain the mechanical properties of the pipeline steel under different hydrogen pressure conditions.

[0040] 3. The present invention connects the pipeline steel to the environmental box and extends both ends to connect with the tester, thereby ensuring that the pipeline steel is always in a hydrogen environment during the test process; the present invention pre-charges the pipeline steel with hydrogen through the environmental box before the tensile test, and during the tensile test, the pipeline steel is also always in a high-pressure hydrogen environment, thereby avoiding the impact on the test accuracy when the pipeline steel is out of the hydrogen pressure environment before testing, thereby ensuring the accuracy of the test results.

[0041] 4. The present invention provides an annular polytetrafluoroethylene liner in the hydrogen environment box. The polytetrafluoroethylene liner occupies most of the internal space of the hydrogen environment box, so that the total amount of hydrogen in the environment box is greatly reduced. After the polytetrafluoroethylene liner is added, the total amount of hydrogen in the environment box is reduced to less than one tenth of the original amount, reducing the risk of explosion caused by hydrogen leakage and improving the safety of the test process.

[0042] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0044] Figure 1 It is a structural schematic diagram of a slow tensile test device for pipeline steel in a hydrogen environment of the present invention;

[0045] Figure 2 for Figure 1 A partial enlarged view of the slow tensile test device in FIG.

[0046] Figure 3 It is a structural schematic diagram of the sealing ring of the slow tensile test device of the present invention;

[0047] Figure 4 A top view of the sealing ring of the slow tensile test device of the present invention;

[0048] Figure 5 It is a schematic diagram of a box body of the slow tensile test device of the present invention having a multi-layer structure;

[0049] Figure 6 for Figure 5 A schematic diagram of the structure of the fastening hoop of the middle box;

[0050] Figure 7 for Figure 5A diagram showing the matching state of the fastening hoop of the middle box and the box body;

[0051] Figure 8 for Figure 5 Exploded view of the box.

[0052] Reference numerals:

[0053] 1-box; 2-sealing cover; 3-PTFE lining; 4-inlet pipe; 5-outlet pipe; 6-bolt; 7-pipeline steel; 8-pressure gauge; 9-sealing ring; 10-first sealing ring; 11-second sealing ring; 12-screw;

[0054] 101-box body; 102-fastening hoop; 103-reinforcement tube; 102a-annular base; 102b-fastening hoop sheet;

[0055] 201-sealing cylinder;

[0056] 901- ring body; 902- protrusion. DETAILED DESCRIPTION

[0057] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0058] Example 1

[0059] A specific embodiment of the present invention provides a method for slow tensile testing of pipeline steel in a hydrogen environment, and a slow tensile testing device for pipeline steel in a hydrogen environment in Example 1 is used to perform a slow tensile testing, comprising the following steps:

[0060] Step S1: installing the pipeline steel 7 of the test sample into a hydrogen environment box;

[0061] Step S2: charging the pipeline steel 7 in the hydrogen environment box with hydrogen;

[0062] Step S3: Connect the hydrogen-filled pipeline steel 7 to a slow tensile tester to perform a slow tensile test.

[0063] In a specific implementation of the present invention, in step S1, the installation process of the pipeline steel 7 includes:

[0064] Step S11: Open the hydrogen environment box and put the pipeline steel 7 to be tested into it;

[0065] Step S12: one end of the pipeline steel 7 is passed through the sealing cover 2, and the other end is passed through the bottom of the box body 1;

[0066] Specifically, the two ends of the pipeline steel 7 are respectively sleeved in the sealing rings 9 on the sealing cover 2 and the box body 1. Figure 1 shown.

[0067] Step S13: fastening the sealing cover 2 to the box body 1 by means of screws 12 .

[0068] In a specific embodiment of the present invention, in step S2, the hydrogen charging process of the pipeline steel 7 includes:

[0069] Step S21: The internal gas of the box 1 is replaced with high-purity nitrogen to reduce the oxygen concentration and improve safety; the high-purity nitrogen replacement step is repeated 3 times to ensure that the oxygen content in the box 1 is lower than the explosion range of hydrogen;

[0070] Specifically, the high-purity nitrogen replacement process is: injecting nitrogen into the box 1 through the air inlet pipe 4, and opening the air outlet pipe 5 to discharge the gas inside the box 1. Furthermore, the volume of nitrogen injected into the box 1 during the high-purity nitrogen replacement process is n times the volume of the box 1, where n is a natural number greater than 2.

[0071] Step S22: filling the box 1 with hydrogen of a predetermined pressure; and monitoring the pressure of the gas inside the box 1 in real time through the pressure gauge 8.

[0072] Step S23: Check the sealing performance of the hydrogen environment box and keep the pressure of the hydrogen environment box constant during the hydrogen filling test; specifically, let the hydrogen environment box stand for 20 minutes. If the pressure in the box body 1 remains unchanged, it is considered that the sealing performance of the hydrogen environment box is good.

[0073] Step S24: To ensure that high-pressure hydrogen fully enters the sample working section through collision, adsorption, dissolution and diffusion, the sample must be pre-filled with hydrogen in a hydrogen environment box for more than 4 days.

[0074] In step S3, after the sample of pipeline steel 7 is pre-filled with hydrogen in the hydrogen environment box for 4 days, a support pad is inserted at the bottom of the hydrogen environment box, and the pipeline steel 7 and the hydrogen environment box are placed at both ends of the slow tensile tester through threaded connection to start the test. After the test is completed, the hydrogen in the box body 1 is emptied from the outlet through the outlet pipe 5.

[0075] Furthermore, when the slow tensile test is performed, both ends of the pipeline steel 7 are screwed to the tension end of the slow tensile tester through threads.

[0076] Furthermore, when the hydrogen pressure in the hydrogen environment box is increased to perform a tensile test, the box body 1 is reinforced by increasing the thickness of the box body 1 to ensure the structural strength of the hydrogen environment box;

[0077] Specifically, the reinforcement method of the box body 1 is:

[0078] First, the convex rib on the box body 101 is inserted into the groove on the inner side of the fastening hoop piece 102b of the fastening hoop 102, and then the fastening hoop 102 is moved axially so that the fastening hoop 102 is sleeved on the outside of the box body 101, as shown in FIG. Figure 7 shown.

[0079] Then, the reinforcing tube 103 is screwed onto the outside of the fastening hoop 102 by means of a thread, and the reinforcing tube 103 is sleeved onto the outside of the fastening hoop 102, as shown in FIG. Figure 5 As shown; the thickness of the box body 1 is increased, thereby strengthening the box body 1.

[0080] Example 2

[0081] A specific embodiment of the present invention discloses a slow tensile test device for pipeline steel in a hydrogen environment, such as Figure 1-Figure 8 As shown, it is used to implement the slow tensile test method in Example 1; the slow tensile test device for pipeline steel in a hydrogen environment includes: a slow tensile instrument and a hydrogen environment box.

[0082] The hydrogen environment box is used to simulate the hydrogen pressure environment; the metal sample for slow tensile test is placed, that is, the pipeline steel 7 is placed in the hydrogen environment box; the slow tensile tester is used to stretch the metal sample, that is, the pipeline steel 7 is stretched by the slow tensile tester. The slow tensile tester is an instrument for performing slow tensile test, which is an existing product and will not be described in detail in the present invention.

[0083] Furthermore, the air inlet pipe 4 is used to introduce gas into the hydrogen environment box.

[0084] Furthermore, the gas outlet pipe 5 is used to discharge the gas out of the hydrogen environment box.

[0085] like Figure 1-4 As shown, the hydrogen environment box includes: a box body 1, a sealing cover 2, an air inlet pipe 4 and an air outlet pipe 5.

[0086] Specifically, the box body 1 is a cylindrical structure, and the upper part of the box body 1 is sealed by a sealing cover 2; and an air inlet pipe 4 is arranged on the sealing cover 2, and the air inlet pipe 4 can be used to introduce hydrogen into the box body 1, and an air outlet pipe 5 is arranged at the bottom of the box body 1, and the air outlet pipe 5 is used to discharge the gas in the box body 1.

[0087] Specifically, the sealing cover 2 and the box body 1 are fastened together by bolts 6 ; and a sealing gasket is provided between the sealing cover 2 and the box body 1 for sealing.

[0088] Specifically, the pipeline steel 7 is arranged in the hydrogen environment box, and one end of the pipeline steel 7 extends out of the surface of the sealing cover 2 , and the other end of the pipeline steel 7 extends out of the box body 1 .

[0089] Furthermore, the box body 1 and the sealing cover 2 of the hydrogen environment box are made of austenitic stainless steel, and it is strictly forbidden to use ferritic stainless steel and high-strength low-alloy steel that are sensitive to hydrogen embrittlement.

[0090] Furthermore, both ends of the pipeline steel 7 are provided with threaded sections, and the two ends of the pipeline steel 7 are fixedly connected with the stretching end of the slow stretching instrument through threaded coupling; specifically, tensile force is applied to the two ends of the pipeline steel 7 by the slow stretching instrument to realize the slow stretching test of the pipeline steel in a high-pressure hydrogen environment.

[0091] like Figure 1 As shown, in a specific embodiment of the present invention, an annular polytetrafluoroethylene liner 3 is arranged inside the box body 1.

[0092] Specifically, the annular polytetrafluoroethylene liner 3 is placed in the box body 1 of the hydrogen environment box, and the annular polytetrafluoroethylene liner 3 is sleeved on the outside of the pipeline steel 7. The polytetrafluoroethylene liner 3 is in close contact with the sample (pipeline steel 7) in order to minimize the total amount of hydrogen in the environment box, thereby greatly improving the safety of the sample (pipeline steel 7).

[0093] like Figure 1 As shown, in a specific embodiment of the present invention, the hydrogen environment box is externally connected to a pressure gauge 8. Specifically, the pressure gauge 8 is arranged above the sealing cover 2 and communicated with the interior of the box body 1 for real-time monitoring of the pressure of the gas in the box body 1.

[0094] like Figure 1 As shown, in a specific embodiment of the present invention, a high-pressure ball valve is installed on both the air inlet pipe 4 and the air outlet pipe 5, and the high-pressure ball valve is used to control the opening and closing of the air inlet pipe 4 or the air outlet pipe 5.

[0095] like Figure 1 , Figure 2 As shown, sealing rings 9 are provided at the positions where the metal sample (pipeline steel 7) contacts the box body 1 and the sealing cover 2, and the hydrogen environment box is sealed by the sealing ring to prevent the escape of hydrogen.

[0096] Furthermore, the sealing ring 9 includes a ring body 901 and a protruding portion 902 .

[0097] Specifically, Figure 3 , Figure 4 As shown, the ring body 901 is a cylindrical structure, and the protrusion 902 is arranged on the outer surface of the ring body 901.

[0098] Correspondingly, a sealing cylinder 201 for installing the sealing ring 9 is provided in the middle of the sealing cover 2, and a snap-fitting hole corresponding to the protrusion 902 is provided on the surface of the sealing cylinder 201, and the sealing ring 9 is sleeved and installed inside the sealing cylinder 201. The inner surface of the ring body 901 of the sealing ring 9 is in contact with the outer surface of the pipeline steel 7, and the outer surface of the ring body 901 of the sealing ring 9 is in contact with the inner surface of the sealing cylinder 201, the protrusion 902 is in contact with the snap-fitting hole on the sealing cylinder 201, and the side surface of the protrusion 902 is in contact with the snap-fitting hole, and the top surface of the protrusion 902 is in contact with the gas of the box body 1.

[0099] Furthermore, if Figure 1 As shown, the pipeline steel 7 is arranged inside the sealing cylinder 201 and is sealed by the sealing ring 9.

[0100] When gas is injected into the box 1, the gas pressure will apply radial pressure between the sealing ring 9 and the pipeline steel 7 through the protrusion 902, so that the sealing ring 9 presses the pipeline steel 7, which can provide a good sealing effect when the pipeline steel 7 is subjected to a slow tensile test. Hydrogen is injected into the box 1 to simulate a hydrogen environment. When the hydrogen pressure in the box 1 is greater, the pressure applied by the gas to the top surface of the protrusion 902 (the outer surface exposed to the gas environment) is greater, that is, the greater the pressing force between the sealing ring 9 and the pipeline steel 7, achieving a self-locking seal and ensuring good airtightness of the environmental box.

[0101] Preferably, the sealing cylinder 201 and the sealing cover 2 are an integral structure, and the sealing ring 9 and the sealing cylinder 201 are fixed by bonding.

[0102] Preferably, the sealing ring 9 is made of elastic material, such as rubber.

[0103] Furthermore, if Figure 1 As shown, a sealing cylinder 201 is also provided at the bottom of the box body 1, and a sealing ring 9 is used to achieve sealing between the pipeline steel 7 and the box body 1. The sealing method between the bottom of the box body 1 and the pipeline steel 7 is the same as the sealing method between the sealing cover 2 and the pipeline steel 7.

[0104] In a specific implementation of the present invention, a sealing ring is further provided between the pipeline steel 7 and the hydrogen environment box, and the sealing ring is used to perform secondary sealing on the hydrogen environment box to improve the air tightness of the hydrogen environment box.

[0105] Specifically, the sealing ring includes a first sealing ring 10 and a second sealing ring 11 .

[0106] Specifically, the first sealing ring 10 is arranged above the sealing cover 2 and sleeved on the outside of the pipeline steel 7. The first sealing ring 10 is fastened and installed on the sealing cover 2 by screws 12, and the middle through hole of the first sealing ring 10 is in sealing contact with the pipeline steel 7, and the bottom surface of the first sealing ring 10 is in sealing contact with the upper surface of the sealing cover 2, so as to achieve sealing between the pipeline steel 7 and the sealing cover 2.

[0107] Specifically, the second sealing ring 11 is arranged below the box body 1 and sleeved on the outside of the pipeline steel 7. The second sealing ring 11 is fastened and installed on the box body 1 by screws 12, the upper surface of the second sealing ring 11 is in contact with the bottom surface of the box body 1, and the middle through hole of the second sealing ring 11 is in sealing contact with the pipeline steel 7, so as to realize the secondary sealing between the pipeline steel 7 and the box body 1.

[0108] Since the hydrogen environment box of the present invention is used to store high-pressure hydrogen, the box body 1 and the sealing cover 2 are required to have good structural strength. Therefore, the thickness of the box body 1 is designed according to the maximum use hydrogen pressure of the hydrogen environment box.

[0109] In a specific embodiment of the present invention, the box body 1 is an integral structure or a multi-layer structure.

[0110] Preferably, when the hydrogen pressure is very high, the thickness of the box body 1 is very thick. Since the box body 1 is made of metal, an excessive thickness of the box body 1 will result in excessive weight, making it difficult to move by manpower, which is not conducive to movement during use and placement of the pipeline steel 7. For ease of use, the box body 1 of the present invention is designed as a multi-layer structure.

[0111] Specifically, Figure 5 , Figure 8 As shown, the box body 1 includes: a box body main body 101 , a fastening hoop 102 and a reinforcement tube 103 .

[0112] Specifically, Figure 5-8 As shown, the outer surface of the box body 101 is a cylindrical arc surface, the fastening hoop 102 is sleeved on the outside of the box body 101, and the outer surface of the fastening hoop 102 is provided with threads, and the reinforcement tube 103 and the fastening hoop 102 are connected by threads.

[0113] Furthermore, the fastening hoop 102 includes an annular base 102a and an arc-shaped fastening hoop piece 102b. Figure 6 shown.

[0114] Furthermore, if Figure 6 As shown, the fastening hoop 102b is arranged on the outer edge of the annular base 102a and is perpendicular to the annular base 102a. The annular base 102a can fit with the bottom surface of the box body 101 to ensure the structural strength of the bottom; the fastening hoop 102b serves as a connecting piece to fasten the reinforcing tube 103 and the box body 101.

[0115] In order to facilitate the fastening connection between the box body 101, the fastening hoop 102 and the reinforcement tube 103, it is necessary to prevent the fastening hoop 102 and the box body 101 from rotating relative to each other when the reinforcement tube 103 is screwed. Furthermore, an axially extending rib is provided on the box body 101, and correspondingly, a groove matching the rib is provided on the inner side of the fastening hoop sheet 102b, such as Figure 7 As shown, when the fastening hoop 102 is sleeved on the outside of the box body 101, the convex rib is stuck in the groove. Since the convex rib and the groove are both axially extending linear structures, the fastening hoop 102 and the box body 101 can be effectively prevented from relative rotation.

[0116] Furthermore, a plurality of fastening hoop pieces 102b are evenly distributed circumferentially on the annular base 102a. Figure 7 As shown, when the fastening hoop 102 is sleeved on the box body 101 , the upper surface of the annular base 102a fits with the bottom surface of the box body 101 , and the smooth inner surface of the fastening hoop piece 102b fits with the box body 101 .

[0117] Furthermore, an outer surface of the fastening hoop piece 102b is provided with an outer thread, and an inner surface of the reinforcement tube 103 is provided with an inner thread; the fastening hoop 102 and the reinforcement tube 103 can be screwed together and sheathed into one body through the thread.

[0118] Preferably, the fastening hoop 102b is interference fit with the box body 101. When the box body 101, the fastening hoop 102 and the reinforcement tube 103 are sequentially sleeved, the reinforcement tube 103 can press the fastening hoop 102 onto the box body 101. Figure 5 shown.

[0119] During implementation, when the hydrogen filling pressure in the box body 1 is low, only the box body 101 is used as a hydrogen environment box. When the hydrogen environment pressure to be simulated is high, the box body 101 needs to be reinforced. At this time, a fastening hoop 102 is sleeved on the outside of the box body 101, such as Figure 7 Further, the outer part of the fastening hoop 102 is reinforced by a threaded sleeve 103, as shown in Figure 5 As shown; the thickness of the box body 1 is increased, thereby strengthening the box body 1.

[0120] Furthermore, a support pad is provided below the hydrogen environment box of the present invention, and the support pad is placed at the lower clamp of the slow stretching instrument to support the high-pressure environment box to prevent the environment box from shifting significantly.

[0121] Compared with the prior art, the technical solution provided by this embodiment has at least one of the following beneficial effects:

[0122] 1. The present invention can simulate the slow tensile test method of the actual working hydrogen environment (the maximum hydrogen partial pressure can reach 12MPa), and can more accurately and relatively safely simulate the influence of the actual working hydrogen environment on the performance of pipeline steel.

[0123] 2. The present invention injects hydrogen of different pressures into the box body 1 through the air inlet pipe 4, monitors the hydrogen pressure through the pressure gauge 8, and performs a slow tensile test after hydrogen filling, so as to accurately obtain the mechanical properties of the pipeline steel under different hydrogen pressure conditions.

[0124] 3. The slow tensile test device for pipeline steel in a hydrogen environment of the present invention is designed with a sealing ring 9 having a protruding portion, so that the greater the hydrogen pressure in the box 1, the greater the pressing force of the sealing ring on the pipeline steel 7, thereby avoiding hydrogen leakage in a high-pressure environment and ensuring the accuracy and safety of the test.

[0125] 4. The slow tensile test device for pipeline steel in a hydrogen environment of the present invention realizes the reinforcement of the box body 1 by sleeve-arranging a fastening hoop 102 and a reinforcement tube 103 on the outside of the box body 101. At the same time, the box body 1 can realize the hydrogen filling test under a high-pressure environment, thereby ensuring the stability of the environmental box and facilitating operation, thereby improving the work convenience of the tester.

[0126] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A slow tensile test method for pipeline steel in a hydrogen environment, characterized in that: The following steps are involved: Step S1: installing the pipeline steel (7) of the test sample into a hydrogen environment box; Step S2: charging the pipeline steel (7) in the hydrogen environment box with hydrogen; Step S3: connecting the hydrogen-filled pipeline steel (7) to a slow tensile tester to perform a slow tensile test; In step S1, the hydrogen environment box comprises: a box body (1) and a sealing cover (2); the installation process of the pipeline steel (7) comprises: Step S11: Open the hydrogen environment box and put the pipeline steel (7) to be tested into it; Step S12: one end of the pipeline steel (7) is passed through the sealing cover (2), and the other end is passed through the bottom of the box body (1); The two ends of the pipeline steel (7) are respectively sleeved in the sealing rings (9) on the sealing cover (2) and the box body (1); The sealing ring (9) comprises: a ring body (901) and a protruding portion (902); The ring body (901) is a cylindrical structure, and the protrusion (902) is arranged on the outer surface of the ring body (901); Correspondingly, a sealing cylinder (201) for mounting a sealing ring (9) is provided in the middle of the sealing cover (2); a snap-fitting hole corresponding to the protruding portion (902) is provided on the surface of the sealing cylinder (201); the sealing ring (9) is sleeved and mounted inside the sealing cylinder (201); the protruding portion (902) is snap-fitted into the snap-fitting hole on the sealing cylinder (201); When gas is injected into the box (1), the gas pressure will apply radial pressure between the sealing ring (9) and the pipeline steel (7) through the protrusion (902), so that the sealing ring (9) presses the pipeline steel (7); hydrogen is injected into the box (1) to simulate a hydrogen environment. When the hydrogen pressure in the box (1) is greater, the pressure applied by the gas to the top surface of the protrusion (902) is greater, that is, the pressing force between the sealing ring (9) and the pipeline steel (7) is greater, thereby achieving a self-locking seal; Step S13: fastening the sealing cover (2) and the box body (1) together by means of screws (12); In step S2, the hydrogen charging process of the pipeline steel (7) includes: Step S21: replacing the internal gas of the box (1) with high-purity nitrogen; Step S22: filling the box (1) with hydrogen at a predetermined pressure; Step S23: Check the sealing performance of the hydrogen environment box and keep the pressure of the hydrogen environment box constant during the hydrogen filling test; let the hydrogen environment box stand for 20 minutes. If the pressure in the box body (1) remains unchanged, it is considered that the sealing performance of the hydrogen environment box is good. Step S24: To ensure that the high-pressure hydrogen fully enters the sample working section through collision, adsorption, dissolution and diffusion, the sample must be pre-filled with hydrogen in a hydrogen environment box for more than 4 days; When the hydrogen pressure in the hydrogen environment box is increased to perform a tensile test, the box body (1) is reinforced by increasing the thickness of the box body (1) to ensure the structural strength of the hydrogen environment box; The box body (1) is reinforced in the following manner: The box body (1) comprises: a box body main body (101), a fastening hoop (102) and a reinforcement cylinder (103); The outer surface of the box body (101) is a cylindrical arc surface; the fastening hoop (102) is sleeved on the outside of the box body (101); the outer surface of the fastening hoop (102) is provided with a thread; the reinforcing tube (103) and the fastening hoop (102) are connected to each other via a thread; the fastening hoop (102) comprises an annular base (102a) and an arc-shaped fastening hoop sheet (102b); a plurality of fastening hoop sheets (102b) are evenly distributed circumferentially on the annular base (102a); an axially extending convex rib is provided on the box body (101); correspondingly, a groove cooperating with the convex rib is provided on the inner side surface of the fastening hoop sheet (102b); First, the convex rib on the box body (101) is inserted into the groove on the inner side of the fastening hoop sheet (102b) of the fastening hoop (102), and then the fastening hoop (102) is moved axially so that the fastening hoop (102) is sleeved on the outside of the box body (101); Then, a reinforcing tube (103) is screwed onto the outside of the fastening hoop (102) by means of a thread, and the reinforcing tube (103) is sleeved onto the outside of the fastening hoop (102), thereby increasing the thickness of the box body (1) and reinforcing the box body (1); An annular polytetrafluoroethylene liner (3) is arranged inside the box (1).

2. The slow tensile test method for pipeline steel in a hydrogen environment according to claim 1, characterized in that: In step S21, the high-purity nitrogen replacement step is repeated three times to ensure that the oxygen content in the box (1) is lower than the explosion range of hydrogen.

3. The slow tensile test method for pipeline steel in a hydrogen environment according to claim 2, characterized in that: In step S21, the high-purity nitrogen replacement process is as follows: nitrogen is injected into the box (1) through the air inlet pipe (4), and at the same time, the air outlet pipe (5) is opened to discharge the gas inside the box (1).

4. The slow tensile test method for pipeline steel in a hydrogen environment according to claim 3, characterized in that: In the step S21, the volume of nitrogen gas injected into the box (1) during the high-purity nitrogen replacement process is n times the volume of the box (1), where n is a natural number greater than 2.

5. The slow tensile test method for pipeline steel in a hydrogen environment according to claim 1, characterized in that: In step S3, after the sample of the pipeline steel (7) is pre-charged with hydrogen in a hydrogen environment box for 4 days, the pipeline steel (7) and the hydrogen environment box are placed at both ends of a slow tensile tester through threaded connection to perform a tensile test.

6. A slow tensile test device for pipeline steel in a hydrogen environment, used to implement the slow tensile test method for pipeline steel in a hydrogen environment according to any one of claims 1 to 5, characterized in that: include: Slow tensile tester and hydrogen environment chamber; The hydrogen environment box comprises: a box body (1) and a sealing cover (2); an air inlet pipe (4) is arranged on the sealing cover (2); an air outlet pipe (5) is arranged on the box body (1); high-pressure ball valves are installed on the air inlet pipe (4) and the air outlet pipe (5), and the high-pressure ball valves are used to control the opening and closing of the air inlet pipe (4) or the air outlet pipe (5); A pipeline steel (7) is arranged in the hydrogen environment box, and one end of the pipeline steel (7) extends out of the surface of the sealing cover (2), and the other end of the pipeline steel (7) extends out of the box body (1).

7. The slow tensile test device for pipeline steel in a hydrogen environment according to claim 6, characterized in that: A pressure gauge (8) is installed on the hydrogen environment box to monitor the gas pressure in the box body (1) in real time.

Images