Test apparatus and test method for fracture toughness of pipeline steel welded joints under corrosive environments

Abstract

This invention discloses a testing device and method for fracture toughness testing of welded joints in pipeline steel under corrosive environments, belonging to the technical field of fracture toughness testing equipment. It includes a test vessel unit and a testing unit. The test vessel unit comprises a test vessel body and a test vessel lid, the lid of which can close onto the opening of the test vessel body. The test vessel lid has an air inlet and an air outlet; the air inlet is used to connect to an air inlet pipe, and the air outlet is used to connect to an air outlet pipe. The testing unit includes a bending clamp assembly and a loading linear displacement measuring assembly. The bending clamp assembly is connected to the shaft of the testing machine and can be used to clamp the test specimen. Driven by the shaft of the testing machine, the bending clamp assembly can press down on the test specimen. The loading linear displacement measuring assembly is connected to a measuring point on the test specimen and is used to measure the linear displacement of the measuring point. This invention enables fracture toughness testing of welded joints under corrosive environments, ensuring the accuracy and safety of the test.

Description

Technical Field

[0001] This invention relates to the field of fracture toughness testing equipment, and in particular to a fracture toughness testing device and method for welded joints of pipeline steel under corrosive environments. Background Technology

[0002] In the oil and gas extraction, transportation, and refining industries, corrosive media containing hydrogen sulfide (H2S) and carbon dioxide (CO2) are widespread. The H2S / CO2 coexistence environment is highly corrosive, easily inducing uniform corrosion, pitting corrosion, and sulfide stress corrosion cracking in metallic materials, posing a serious threat to the structural integrity and service safety of pressure equipment and pipelines. Welded joints, as weak points in pipelines and pressure vessels, exhibit uneven microstructure and significant performance gradients, making them more prone to crack initiation and propagation under the coupled effects of corrosive environments and external loads.

[0003] Fracture toughness is an important mechanical property parameter characterizing the ability of materials and welded joints to resist crack propagation, and it is crucial for assessing the safety of structures under extreme service environments. However, most existing fracture toughness testing methods and devices are conducted in an air environment, making it difficult to simulate the coupled effects of H2S / CO2 corrosive media and mechanical loads.

[0004] Therefore, there is an urgent need in this field for a novel testing device and method for the fracture toughness of welded joints of pipeline steel under corrosive environments, in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a testing device and method for testing the fracture toughness of welded joints of pipeline steel in corrosive environments, so as to solve the problems existing in the prior art and improve the accuracy and safety of testing by conducting fracture toughness testing of welded joints in corrosive environments.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention discloses a fracture toughness testing device for welded joints of pipeline steel under corrosive conditions, comprising a test vessel unit and a testing unit, wherein the testing unit can be placed inside the test vessel unit; The test vessel unit includes a test vessel body and a test vessel lid. The test vessel body can be used to hold a test solution. The test vessel lid can be closed to the opening of the test vessel body. The test vessel lid is provided with an air inlet and an air outlet. The air inlet is used to connect to an air inlet pipe, which is used to introduce test gas into the test solution. The air outlet is used to connect to an air outlet pipe. The testing unit includes a bending fixture assembly and a loading linear displacement measuring assembly. The bending fixture assembly is connected to the shaft of the testing machine and can be used to clamp the test specimen. Under the drive of the shaft of the testing machine, the bending fixture assembly can press down on the test specimen. The loading linear displacement measuring assembly is connected to several measuring points on the test specimen and is used to measure the linear displacement of the measuring points.

[0007] Preferably, the bending fixture assembly includes two upper support rollers and one lower support roller. The two upper support rollers respectively contact the upper two sides of the test specimen, and the lower support roller contacts the lower center of the test specimen. The testing machine shaft can drive the upper support rollers to move up and down.

[0008] Preferably, the bending clamp assembly includes a fixed crossbeam and a support roller base, with the fixed crossbeam located above the support roller base; The upper end of the fixed crossbeam is connected to the shaft of the testing machine, and the lower end of the fixed crossbeam is connected to a support roller support. The support roller support is provided with a support roller limiting groove, and the upper support roller is located in the support roller limiting groove. The lower support roller is installed at the upper end of the support roller base.

[0009] Preferably, the length of the support roller limiting groove is greater than the diameter of the upper support roller, and the support roller support is connected to the upper support roller by a connecting spring.

[0010] Preferably, the support roller support is slidably connected to the fixed crossbeam, and the fixed crossbeam is provided with scale lines.

[0011] Preferably, the test specimen has a notch body, and the loading line displacement measuring component includes a notch displacement measuring component and a central axis displacement measuring component. The notch displacement measuring component is used to measure the displacement at the notch body, and the central axis displacement measuring component is used to measure the displacement at the central axis of the test specimen.

[0012] Preferably, the notch displacement measurement assembly includes a notch data acquisition unit, a notch displacement sensor, a notch extension rod, a notch measurement drive block, and two notch fixing rods. The upper end of the notch displacement sensor is connected to the notch data acquisition unit, and the lower end of the notch displacement sensor is connected to the notch extension rod. The notch measurement drive block is fixed on the notch extension rod. The two notch fixing rods are respectively fixed on both sides of the notch body, and the ends of the two notch fixing rods away from the notch body abut against the lower surface of the notch measurement drive block. The central axis displacement measurement assembly includes a central axis data acquisition unit, a central axis displacement sensor, a central axis extension rod, a central axis measurement drive block, and two central axis fixing rods. The upper end of the central axis displacement sensor is connected to the central axis data acquisition unit, and the lower end of the central axis displacement sensor is connected to the central axis extension rod. The central axis measurement drive block is fixed on the central axis displacement sensor. The two central axis fixing rods are respectively fixed on both sides of the central axis of the test specimen. The central axis measurement drive block has several drive block through holes, and the ends of the two central axis fixing rods away from the test specimen are respectively inserted into one of the drive block through holes.

[0013] Preferably, it also includes a heating furnace, into which the test vessel body can extend.

[0014] Preferably, it also includes a lifting device and a testing machine body, the lifting device being fixed to the testing machine body, and the lifting device being used to drive the heating furnace to move up and down; A tray body is placed at the opening of the test vessel body, and a tray notch is provided on the outer wall of the tray body. A tray baffle is fixed on the test machine body, and the shape of the tray baffle matches the shape of the tray notch.

[0015] This invention discloses a testing device for testing the fracture toughness of welded joints of pipeline steel under corrosive environments. The aforementioned testing device for testing the fracture toughness of welded joints of pipeline steel under corrosive environments includes the following steps: Step S1: Test specimen preparation and pretreatment. Test specimens are prepared from the welded joint of pipeline steel and fatigue cracks are pre-induced. The test specimens with pre-induced cracks are coated with an anti-corrosion coating on the surface of the specimens except for the notched body. After the anti-corrosion coating is cured, the test specimens are pre-immersed in the test solution. Step S2: Install the test specimen into the test unit; introduce the test solution into the test vessel body, and operate the lifting device to raise the heating furnace and the test vessel body and seal them together with the test vessel lid; Step S3: Establish a corrosive environment. After heating the test solution to the test temperature, nitrogen gas is introduced into the test vessel to remove dissolved oxygen. Then, the test gas is introduced until the test solution is saturated before starting the test. Step S4: Fracture toughness test. A load is applied to the test specimen at a fixed loading rate. The displacement measurement component collects displacement data in real time. The test ends when the force value reaches the expected value. Step S5: Data processing. After cooling the test specimen, the test specimen is broken by compression. The initial crack length a0 of the test specimen is measured, the loading line displacement q of the specimen is calculated, the force-displacement curve is plotted, and the fracture toughness J0 value is calculated.

[0016] The present invention achieves the following technical effects compared to the prior art: This invention utilizes a test vessel containing a test solution and the ability to add test gas to create a realistic corrosive environment. A test unit, equipped with a test specimen, is then immersed in the test solution to simulate the specimen's condition in a real environment. The test machine shaft, through a bending fixture assembly, applies force to the specimen, causing it to bend and deform. A load line displacement measurement assembly monitors the displacement of the load line in real time, and the fracture toughness of the specimen is calculated. Because the specimen remains immersed in the test solution throughout the process, the measurement results are more accurate. Furthermore, the sealed test vessel body and lid prevent gas leakage, ensuring the safety of the experiment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the fracture toughness testing device for pipeline steel welded joints under corrosive conditions, as shown in Example 1. Figure 2 This is an isometric view of the test unit in the fracture toughness testing device for pipeline steel welded joints under corrosive conditions, as shown in Example 1. Figure 3 This is a side view of the test unit in the fracture toughness testing device for pipeline steel welded joints under corrosive conditions, as shown in Example 1. Figure 4 This is a diagram showing the connection relationship between the test machine shaft and the fixed crossbeam in the fracture toughness testing device for pipeline steel welded joints under corrosive conditions, as shown in Example 1. Figure 5 This is a diagram showing the connection relationship between the heating furnace and the test vessel body in the fracture toughness testing device for pipeline steel welded joints under corrosive conditions, as shown in Example 1. Figure 6 This is a front view of the test specimen in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 3; Figure 7 This is a top view of the test specimen in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 3; Figure 8 This is a schematic diagram of the sampling of test specimens in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 3; Figure 9The figure shows the test results of the test method for the fracture toughness test device of pipeline steel welded joint under corrosive environment in Example 3; Figure 10 This is a front view of the test specimen in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 4; Figure 11 This is a top view of the test specimen in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 4; Figure 12 This is a schematic diagram of the sampling of test specimens in the test method of the fracture toughness test device for pipeline steel welded joints under corrosive environment in Example 4; Figure 13 The figure shows the test results of the test method for the fracture toughness test device of pipeline steel welded joint under corrosive environment in Example 4. In the diagram: 1-Test vessel body; 2-Test vessel cover; 201-Inlet pipe; 202-Outlet pipe; 3-Test machine shaft; 4-Test specimen; 401-Notch body; 5-Upper support roller; 6-Lower support roller; 7-Fixed crossbeam; 8-Support roller base; 9-Support roller support; 10-Connecting spring; 11-Notch displacement measurement assembly; 1101-Notch data acquisition unit; 1102-Notch displacement sensor; 1103-Notch extension rod; 1104-Notch measurement drive block; 1105 12-Central axis displacement measurement assembly; 1201-Central axis data acquisition unit; 1202-Central axis displacement sensor; 1203-Central axis extension rod; 1204-Central axis measurement drive block; 1205-Central axis fixing rod; 13-Heating furnace; 14-Testing machine body; 1401-Tray baffle; 15-Tray body; 1501-Tray notch; 1502-Tray handle; 16-Telescopic component; 17-Lifting base; 18-Reservoir lid fixing plate; 19-Rubber gasket. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide a testing device and method for testing the fracture toughness of welded joints of pipeline steel in corrosive environments, so as to solve the problems existing in the prior art and improve the accuracy and safety of testing by conducting fracture toughness testing of welded joints in corrosive environments.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1 like Figures 1-5 As shown, this embodiment provides a fracture toughness testing device for welded joints of pipeline steel under corrosive conditions, including a test vessel unit and a testing unit, wherein the testing unit can be placed inside the test vessel unit.

[0023] The test vessel unit includes a test vessel body 1 and a test vessel lid 2. The test vessel body 1 is made of materials including, but not limited to, glass. The test vessel body 1 is used to hold a test solution, which simulates the liquid composition of the material under real service conditions. The test vessel lid 2 closes to the opening of the test vessel body 1 and has an inlet and an outlet. The inlet connects to an inlet pipe 201, and the end of the inlet pipe 201 furthest from the inlet connects to a test gas source. The inlet pipe 201 is used to introduce test gas into the test solution. The reason for introducing test gas into the test solution is that some components cannot be simulated, such as the large amounts of hydrogen sulfide and carbon dioxide in crude oil extracted from the deep sea. Introducing gas is to simulate these components; therefore, the test gas includes, but is not limited to, H2S and / or CO2. The outlet connects to an outlet pipe 202, and the end of the outlet pipe 202 furthest from the outlet connects to an exhaust gas collection container. After the test, the exhaust gas in the collection container is treated uniformly.

[0024] The testing unit includes a bending fixture assembly and a loaded linear displacement measuring assembly. The bending fixture assembly is connected to the testing machine shaft 3, which is the output end of the testing machine body 14. The testing machine body 14 can be any commonly used laboratory testing machine; its specific type is not limited, as long as its output shaft can apply a downward force to the bending fixture assembly. The bending fixture assembly is used to clamp the test specimen 4, and driven by the testing machine shaft 3, it presses down on the test specimen 4, causing it to gradually bend under the downward pressure. The loaded linear displacement measuring assembly is connected to several measuring points on the test specimen 4 and is used to measure the linear displacement of these points.

[0025] In practical use, the required test solution is placed inside the test vessel body 1, and then the test unit containing the test specimen 4 is installed into the test vessel body 1. The test vessel lid 2 is closed to ensure a sealed internal environment. The required test gas is introduced into the test solution through the air inlet pipe 201, making the test solution a corrosive solution. The dissolved oxygen in the test solution is squeezed out by the introduction of nitrogen gas, and then the test gas is introduced. After the test solution is saturated, the testing machine shaft 3 is started. The testing machine shaft 3 moves downward and drives the test specimen 4 to bend through the bending fixture assembly. At this time, the test points on the test specimen 4 are offset, and the linear displacement of the test points is measured by the loading linear displacement measuring assembly. Finally, the fracture toughness of the test specimen 4 is calculated by the displacement.

[0026] In this embodiment, the bending fixture assembly uses a three-point bending method to press down on the test specimen 4 and bend it. Therefore, the bending fixture assembly includes two upper support rollers 5 and one lower support roller 6, both of which are made of ceramic. A notch body 401 is provided at the center of the upper surface of the test specimen 4, and the two upper support rollers 5 contact the upper two sides of the test specimen 4 respectively. The lower support roller 6 contacts the lower center of the test specimen 4, and the testing machine shaft 3 can drive the upper support rollers 5 to move up and down.

[0027] In actual use, the shaft 3 of the testing machine can drive the two upper support rollers 5 to move downwards simultaneously. When the upper support rollers 5 move downwards and contact the upper surface of the test specimen 4, the upper support rollers 5 will apply a downward squeezing force to both sides of the test specimen 4. Since the lower support roller 6 itself does not move and is always in contact with the lower center of the test specimen 4, that is, the lower support roller 6 applies an upward supporting force to the center of the test specimen 4. Therefore, the two upper support rollers 5 and the lower support roller 6 simultaneously apply three forces to the test specimen 4, causing the test specimen 4 to bend upwards in the middle and downwards at both ends.

[0028] In this embodiment, the bending fixture assembly includes a fixed crossbeam 7 and a support roller base 8. A kettle cover fixing plate 18 is fixed on the testing machine body 14. The test kettle cover 2 is fixed to the lower surface of the kettle cover fixing plate 18. The testing machine shaft 3 can simultaneously penetrate vertically through the kettle cover fixing plate 18 and the test kettle cover 2. The four corners of the lower surface of the kettle cover fixing plate 18 are respectively connected to the four corners of the support roller base 8 through a connecting column. The fixed crossbeam 7 is located above the support roller base 8.

[0029] The upper end of the fixed crossbeam 7 is fixedly connected to the end of the testing machine shaft 3, and the lower end of the fixed crossbeam 7 is connected to two support roller supports 9, which are respectively connected to the two sides of the lower end of the fixed crossbeam 7. The lower surface of the support roller support 9 is provided with a rectangular support roller limiting groove, and each upper support roller 5 is located in a corresponding support roller limiting groove.

[0030] The lower support roller 6 is rotatably mounted on the upper end of the support roller base 8.

[0031] When the shaft 3 of the testing machine moves downward, it will drive the support roller support 9 and the upper support roller 5 to move downward through the fixed crossbeam 7 until the upper support roller 5 abuts against the upper surface of the test specimen 4, while the position of the lower support roller 6 remains unchanged, thereby achieving the technical effect of the three-point bending test specimen 4.

[0032] In this embodiment, the length of the support roller limiting groove is greater than the diameter of the upper support roller 5, meaning that the upper support roller 5 can move left and right within the support roller limiting groove. The support roller support 9 is connected to the upper support roller 5 via a connecting spring 10. The advantage of this arrangement is that even if the upper support roller 5 can reciprocate, it will not disengage from the support roller limiting groove.

[0033] The reason for allowing the upper support roller 5 to move left and right within the support roller limiting groove is that under the downward pressure of the bending fixture assembly, the two sides of the test specimen 4 will tilt symmetrically, thus the contact point between the upper support roller 5 and the test specimen 4 will inevitably move spatially. Since the testing machine shaft 3 always applies a downward squeezing force to the upper support roller 5, there will be no relative movement between the upper support roller 5 and the test specimen 4. Therefore, driven by the movement of the test specimen 4, the upper support roller 5 will move within the support roller limiting groove.

[0034] In this embodiment, the fixed crossbeam 7 is provided with a transversely penetrating sliding groove. The cross-sectional shape of the sliding groove is trapezoidal. A trapezoidal block is fixed to the upper end of the support roller support 9 by bolts. The trapezoidal block on the support roller support 9 is slidably connected to the sliding groove on the fixed crossbeam 7. Its function is to adjust the actual position of the support roller support 9 as needed, thereby adjusting the contact position between the upper support roller 5 and the test specimen 4, so as to adapt to test specimens 4 of different sizes.

[0035] In addition, a tightening bolt can be added, which can pass through and be threaded to the support roller support 9. The end of the tightening bolt can abut against the inner wall of the sliding groove. After the support roller support 9 slides to the expected position in the sliding groove on the fixed crossbeam 7, the tightening bolt is tightened to fix the support roller support 9.

[0036] The fixed crossbeam 7 is equipped with scale lines, which facilitates the precise adjustment of the position of the support roller support 9.

[0037] In this embodiment, a notch body 401 is provided at the center of the upper surface of the test specimen 4. The loading line displacement measurement assembly includes a notch displacement measurement assembly 11 and a central axis displacement measurement assembly 12. The notch displacement measurement assembly 11 is used to measure the vertical displacement at the notch body 401, and the central axis displacement measurement assembly 12 is used to measure the vertical displacement at the central axis of the test specimen 4.

[0038] The measured value of the central axis displacement measuring component 12 is q1, and the measured data of the notch displacement measuring component 11 is q2. Then, the loaded linear displacement q is calculated using the formula q=q1-q2. The specific calculation process is as follows: In the formula, B is the thickness of test specimen 4, i.e. Figure 3 The length of test specimen 4 in the left and right directions, for test specimen 4 without side grooves, B N =B (some test specimen 4 will have non-penetrating grooves on its side surface); W is the width of test specimen 4, i.e. Figure 3 The length of the test specimen 4 in the vertical direction; S is the span, i.e., the center distance between the two upper support rollers 5; E is the elastic modulus; v is Poisson's ratio; U p To determine the plastic component of the area under the force and loading displacement curves, the Fq relationship needs to be plotted first, and then U can be calculated using Origin software. p The specific values ​​are: a0 is the initial crack length; g1 is the shape factor.

[0039] In this embodiment, as Figure 3 As shown, the notch displacement measurement assembly 11 includes a notch data acquisition unit 1101, a notch displacement sensor 1102, a notch extension rod 1103, a notch measurement drive block 1104, and two notch fixing rods 1105. The upper end of the notch displacement sensor 1102 is connected to the notch data acquisition unit 1101, and the detection data from the notch displacement sensor 1102 can be transmitted to the notch data acquisition unit 1101 in real time. The lower end of the notch displacement sensor 1102 is connected to the notch extension rod 1103 via a clamp. The notch measurement drive block 1104 is fixed to the notch extension rod 1103 via connecting bolts or pins; the notch measurement drive block 1104 is a rectangular block. The two notch fixing rods 1105 are respectively fixed to both sides of the notch body 401. The notch body 401 has internal threaded holes on both sides that match the notch fixing rods 1105, and one end of each notch fixing rod 1105 has an external thread, allowing the notch fixing rod 1105 to be threadedly connected to the test specimen 4. The ends of the two notch fixing rods 1105 away from the notch body 401 abut against the lower surface of the notch measuring drive block 1104. When the test specimen 4 bends, the two notch fixing rods 1105, being close to the middle position, will rotate upwards, thereby pushing the notch measuring drive block 1104 upwards. This, in turn, pushes the notch extension rod 1103 and the notch displacement sensor 1102 upwards. The notch displacement sensor 1102 is used to measure the upward displacement distance of the notch measuring point, i.e., q2 mentioned above.

[0040] Similarly, the central axis displacement measurement assembly 12 includes a central axis data acquisition unit 1201, a central axis displacement sensor 1202, a central axis extension rod 1203, a central axis measurement drive block 1204, and two central axis fixing rods 1205. The upper end of the central axis displacement sensor 1202 is connected to the central axis data acquisition unit 1201, and the detection data of the central axis displacement sensor 1202 can be transmitted to the central axis data acquisition unit 1201 in real time. The lower end of the central axis displacement sensor 1202 is connected to the central axis extension rod 1203 through a clamp. The central axis displacement sensor 1202 is fixed with the central axis measurement drive block 1204. The two central axis fixing rods 1205 are respectively fixed on both sides of the central axis of the test specimen 4. The central axis of the test specimen 4 is the middle horizontal line position of the test specimen 4, and the connection method is the same as that of the notch fixing rod 1105. The central axis fixing rods 1205 are also fixed to the corresponding internal threaded holes on the test specimen 4 by threads. Figure 2 As can be seen, the central axis measuring drive block 1204 is provided with several elongated drive block through holes. The ends of the two central axis fixing rods 1205 away from the test specimen 4 are respectively inserted into a corresponding drive block through hole. When the test specimen 4 moves due to bending, the central axis fixing rod 1205 will rotate and drive the central axis measuring drive block 1204 to move vertically, which will further drive the central axis extension rod 1203 and the central axis displacement sensor 1202 to move vertically. The central axis displacement sensor 1202 is used to count the vertical displacement of the central axis measuring point, i.e., q1 mentioned above.

[0041] from Figure 1 or Figure 2 It is easy to see that both the notch data acquisition device 1101 and the central axis data acquisition device 1201 are located above the lid fixing plate 18. Therefore, when the test vessel lid 2 is closed on the test vessel body 1, both the notch data acquisition device 1101 and the central axis data acquisition device 1201 are located outside the test vessel unit. The corrosive liquid inside the test vessel body 1 will not have any impact on the notch data acquisition device 1101 and the central axis data acquisition device 1201, thus ensuring the service life of the notch data acquisition device 1101 and the central axis data acquisition device 1201. The other components located inside the test vessel body 1 in the test unit (except for the upper support roller 5 and the lower support roller 6) are mostly made of corrosion-resistant materials, including, but not limited to, the existing C276 corrosion-resistant alloy (i.e., C276 nickel-based alloy).

[0042] The gap data acquisition unit 1101 and the central axis data acquisition unit 1201 are electrically connected to the back-end host, thereby transmitting data to the back-end host in real time for staff reference.

[0043] Both the notch displacement sensor 1102 and the central axis displacement sensor 1202 are existing LVDT displacement sensors, which can detect the displacement of the measurement point by their own displacement.

[0044] In this embodiment, a heating furnace 13 is also included. The heating furnace 13 is existing equipment, so its specific structure will not be described in detail here. The test vessel body 1 can extend into the heating furnace 13, and the heating furnace 13 can be used to heat the test vessel body 1, thereby simulating the temperature of a real corrosion environment.

[0045] In this embodiment, a lifting device and a testing machine body 14 are also included. The lifting device is fixed to the testing machine body 14 and is used to drive the heating furnace 13 to move up and down. Figure 1 As can be seen, the lifting device includes a telescopic component 16 and a lifting base 17. The telescopic component 16 is fixed to the frame of the testing machine body 14, and the telescopic end of the telescopic component 16 is fixedly connected to the lifting base 17. The lifting base 17 can be moved up and down by the telescopic action of the telescopic component 16.

[0046] Furthermore, the main body 14 of the testing machine is provided with four support columns, and the lifting base 17 is provided with sliding through holes that match the support columns. The support columns are slidably connected to the sliding through holes. The support columns can be used to limit the lifting base 17, so that the lifting base 17 can only move up and down under the extension and retraction of the telescopic member 16.

[0047] The telescopic component 16 includes, but is not limited to, existing telescopic devices such as electric push rods or hydraulic cylinders.

[0048] from Figure 1 and Figure 5 As can be seen, a tray body 15 is placed at the opening of the test vessel body 1. The tray body 15 has a circular structure, with its inner diameter smaller than the outer diameter of the opening of the test vessel body 1, and its outer diameter larger than the inner diameter of the opening of the heating furnace 13. Two tray notches 1501 and two tray handles 1502 are provided on the outer wall of the tray body 15. These two tray notches 1501 and two tray handles 1502 are staggered along the circumference of the outer wall of the tray body 15. The central angle between adjacent tray notches 1501 and tray handles 1502 is 90°. The two tray notches 1501 and two tray handles 1502 are positioned opposite each other. A tray baffle 1401 is fixed on each side of the test machine body 14, and the shape of the tray baffle 1401 matches the shape of the tray notches 1501.

[0049] When the test vessel lid 2 needs to be placed on the test vessel body 1, the lifting device moves the heating furnace 13 and the test vessel body 1 upwards. When the tray body 15 moves to the same height as the tray baffle 1401, the tray body 15 can continue to move upwards because the tray baffle 1401 and the tray notch 1501 cooperate. When the lower surface of the tray body 15 is higher than the upper surface of the tray baffle 1401, the operator uses the tray handle 1502 to rotate the tray body 15 by a certain angle (such as 90°, or other angles, as long as they are not 180° or multiples of 180°). At this time, there is no tray notch 1501 above the tray baffle 1401, so the tray body 15 itself can be locked on the upper surface of the tray baffle 1401. Since the inner diameter of the tray body is smaller than the outer diameter of the opening of the test vessel body 1, the tray body 15 itself can support the test vessel body 1. At this time, the upper opening of the test vessel body 1 is sealed with the test vessel lid 2. The advantage of this design is that the seal between the test vessel body 1 and the test vessel cover 2 can be achieved solely by the support of the tray baffle 1401, without the need for a lifting device for support and sealing, thus preventing the test vessel body 1 from breaking due to excessive force from the lifting device.

[0050] Furthermore, a rubber gasket 19 is provided at both the upper and lower ends of the opening edge of the test vessel body 1. The upper rubber gasket 19 is used to improve the sealing between the test vessel body 1 and the test vessel cover 2, and the lower rubber gasket 19 is used to achieve the sealing between the test vessel body 1 and the heating furnace 13.

[0051] Example 2 This embodiment provides a testing method for a fracture toughness testing device for welded joints of pipeline steel under corrosive environments. Based on the fracture toughness testing device for welded joints of pipeline steel under corrosive environments in Embodiment 1, the method includes the following steps: Step S1: Preparation and Pretreatment of Test Specimen 4. Test specimen 4 is prepared from the welded joint of the pipeline steel. Specifically, a single-sided notch bending (SENB) specimen can be prepared from the weld or heat-affected zone of the pipeline steel welded joint. Further, when the test object is the weld, test specimen 4 uses an NP notch, and the ratio of thickness B to width W of test specimen 4 is 1:2; when the test object is the heat-affected zone, test specimen 4 uses an NQ notch, and the ratio of thickness B to width W of test specimen 4 is 1:1. The thickness B of test specimen 4 is taken to be close to the wall thickness of the pipeline steel. Then, fatigue cracks are pre-induced by continuously applying a horizontal stress to test specimen 4. After the pre-cracked test specimen 4 is prepared, an anti-corrosion coating is applied to the surface except for the notch body 401. The anti-corrosion coating is an epoxy resin coating. After the anti-corrosion coating has cured, the test specimen 4 is placed in the test solution for pre-immersion, so that the test solution can fully penetrate into the notch body 401, but cannot penetrate into other surfaces of the test specimen 4. At this time, the pre-immersion solution is the test solution. Nitrogen gas is introduced before immersion to remove dissolved oxygen in the test solution. Test gas is continuously introduced during the immersion process, and the immersion time is at least 96 hours.

[0052] Step S2: Install test specimen 4. Install test specimen 4 into the test unit, that is, use the upper support roller 5 and the lower support roller 6 to fix test specimen 4, and use the lower support roller 6 to support the lower center position of test specimen 4. Introduce test solution into test vessel body 1, and operate the lifting device to raise the heating furnace 13 and test vessel body 1 and seal them with the test vessel cover 2.

[0053] Step S3: Establish the corrosive environment. After heating the test solution to the test temperature, nitrogen gas is introduced into the test vessel body 1 to remove dissolved oxygen. The end of the gas supply line furthest from the test vessel lid 2 can be connected to both the test gas source and the nitrogen source (including, but not limited to, a nitrogen cylinder) via a three-way valve. Of course, those skilled in the art can replace the nitrogen with other inert gases. The inert gas deoxygenation time should be at least 2 hours. Then, the test gas is introduced until the test solution is saturated, and the test begins. The test gas should be continuously introduced during the test until its completion.

[0054] Step S4: Fracture toughness test. The testing machine shaft 3 applies a load to the test specimen 4 at a fixed loading rate of 0.001~0.1 mm / min. The loading line displacement measurement component collects displacement data in real time. The test ends when the force value reaches the expected value, which can be the maximum value or other expected values.

[0055] Step S5: Data Processing. The test specimen 4 is broken by compression. The initial crack length a0 of the test specimen 4 is measured, and the loading displacement q of the specimen is calculated. Specifically, the value of q is obtained by the formula q = q1 - q2. Then, the force (F)-displacement (q) curve is plotted, and the fracture toughness J0 value is calculated. The specific calculation formula is as follows: In the formula, B is the thickness of test specimen 4, i.e. Figure 3 The length of test specimen 4 in the left and right directions, for test specimen 4B without side grooves. N =B (some test specimen 4 will have non-penetrating grooves on its side surface); W is the width of test specimen 4, i.e. Figure 3 The length of the test specimen 4 in the vertical direction; S is the span, i.e., the center distance between the two upper support rollers 5; E is the elastic modulus; v is Poisson's ratio; U p To determine the plastic component of the area under the force and loading displacement curves, the Fq relationship needs to be plotted first, and then U can be calculated using Origin software. p The specific values ​​are: a0 is the initial crack length; g1 is the shape factor.

[0056] Example 3 like Figures 6-9 As shown in the figure, this embodiment provides a test method for a fracture toughness testing device for welded joints of pipeline steel under corrosive environments, including the following steps: SENB (Self-Affected Zone) specimens were prepared from the welded joints of X65 / Inconel 625 bimetallic composite pipes with a diameter of 323.9 mm and a wall thickness of 12.7 ± 3 mm. Fracture toughness tests were conducted under H2S / CO2 corrosive conditions. Specimen 4 is shown in Figure 4. Figures 6-7As shown, the dimensions (width × thickness) of test specimen 4 are 14 × 14 mm. A notched body 401 is machined from the weld root upwards, with a length of 5 mm. The top of the notched body 401 is located at the fusion line. A fatigue crack of 2 mm length is pre-induced in air. After the crack pre-induction is completed, an epoxy resin anti-corrosion coating is applied to the surface of the unnotched body 401. After curing for 48 h, it is immersed in the test solution for pre-soaking for 96 h. The test solution is NACE™ 0177 B standard solution. Before immersion, nitrogen gas is purged for 1 h to remove dissolved oxygen from the solution. Then, a mixed gas of 20% H2S + 80% CO2 is continuously purged until the pre-soaking is completed. Test specimen 4 is removed and installed on the test unit. Sufficient prepared test solution is injected into the test vessel body 1, with the liquid level completely submerging test specimen 4. Nitrogen gas is purged into the test solution for 2 h to remove dissolved oxygen. Then, a mixed gas of 20% H2S + 80% CO2 is purged for 2 h before the fracture toughness test begins. The displacement rate of the testing machine body 14 was 0.00228 mm / min. During the test, the values ​​of q1 and q2 were read by the host computer and the Fq curve was plotted. The test was stopped when the force value dropped to 90% of the maximum force value. The test specimen 4 was removed and placed in dry ice or liquid nitrogen for 1 hour before being broken. The initial crack length a0 was measured using the nine-point method under a stereomicroscope, and the J0 value was calculated. Simultaneously, a heat-affected zone fracture toughness test was conducted in air using the fracture toughness testing device for pipeline steel welded joints under corrosive conditions provided in Example 1. The Fq curves for air and corrosive environments are shown below. Figure 7 As shown, the J0 value in the air environment (992.8 kJ / m) 2 Compared to ), the fracture toughness J0 (18.9 kJ / m) under corrosive conditions 2 () significantly reduced.

[0057] Example 4 like Figures 10-13 As shown in the figure, this embodiment provides a test method for a fracture toughness testing device for welded joints of pipeline steel under corrosive environments, including the following steps: SENB weld specimens were prepared from the welded joints of X65 / Inconel 625 bimetallic composite pipes with a diameter of 323.9 mm and a wall thickness of 12.7+3 mm. Fracture toughness tests were conducted under H2S / CO2 corrosive conditions. Specimen 4 is shown in Figure 4. Figures 10-12 As shown, the test specimen 4 (thickness × width) measures 12.5 × 25 mm, the notch body 401 is 10 mm long, and the pre-crack length is 2.5 mm. Other than this, the test conditions are the same as in Example 3. The test results are as follows: Figure 13 As shown, the test results under air conditions (538.1 kJ / m) 2Compared to the weld specimen, the fracture toughness in a corrosive environment (283.6 kJ / m) is significantly better. 2 The temperature dropped significantly. Because the weld is made of a corrosion-resistant alloy, the decrease was much smaller than that in the heat-affected zone.

[0058] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0059] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0060] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws) or a non-detachable fixed connection (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0061] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0062] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0063] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0064] It should also be noted that in the embodiments of this application, the same reference numerals are used to denote the same component or the same part.

[0065] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0066] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A device for testing the fracture toughness of welded joints of pipeline steel under corrosive environments, characterized in that: It includes a test vessel unit and a testing unit, wherein the testing unit can be placed inside the test vessel unit; The test vessel unit includes a test vessel body (1) and a test vessel lid (2). The test vessel body (1) can be used to hold a test solution. The test vessel lid (2) can be closed to the opening of the test vessel body (1). The test vessel lid (2) is provided with an air inlet and an air outlet. The air inlet is used to connect to an air inlet pipe (201). The air inlet pipe (201) is used to introduce test gas into the test solution. The air outlet is used to connect to an air outlet pipe (202). The testing unit includes a bending fixture assembly and a loading linear displacement measuring assembly. The bending fixture assembly is connected to the testing machine shaft (3) and can be used to clamp the test specimen (4). Under the drive of the testing machine shaft (3), the bending fixture assembly can press down on the test specimen (4). The loading linear displacement measuring assembly is connected to several measuring points on the test specimen (4) and is used to measure the linear displacement of the measuring points.

2. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 1, characterized in that: The bending fixture assembly includes two upper support rollers (5) and one lower support roller (6). The two upper support rollers (5) are in contact with the upper two sides of the test specimen (4) respectively, and the lower support roller (6) is in contact with the lower center of the test specimen (4). The test machine shaft (3) can drive the upper support rollers (5) to move up and down.

3. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 2, characterized in that: The bending clamp assembly includes a fixed crossbeam (7) and a support roller base (8), with the fixed crossbeam (7) located above the support roller base (8). The upper end of the fixed crossbeam (7) is connected to the shaft (3) of the testing machine, and the lower end of the fixed crossbeam (7) is connected to the support roller support (9). The support roller support (9) is provided with a support roller limiting groove, and the upper support roller (5) is located in the support roller limiting groove. The lower support roller (6) is installed on the upper end of the support roller base (8).

4. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 3, characterized in that: The length of the support roller limiting groove is greater than the diameter of the upper support roller (5), and the support roller support (9) is connected to the upper support roller (5) through a connecting spring (10).

5. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 3, characterized in that: The support roller support (9) is slidably connected to the fixed crossbeam (7), and the fixed crossbeam (7) is provided with scale lines.

6. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 1, characterized in that: The test specimen (4) is provided with a notch body (401). The loading line displacement measurement component includes a notch displacement measurement component (11) and a central axis displacement measurement component (12). The notch displacement measurement component (11) is used to measure the displacement at the notch body (401), and the central axis displacement measurement component (12) is used to measure the displacement at the central axis of the test specimen (4).

7. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 6, characterized in that: The notch displacement measurement assembly (11) includes a notch data acquisition unit (1101), a notch displacement sensor (1102), a notch extension rod (1103), a notch measurement drive block (1104), and two notch fixing rods (1105). The upper end of the notch displacement sensor (1102) is connected to the notch data acquisition unit (1101), and the lower end of the notch displacement sensor (1102) is connected to the notch extension rod (1103). The notch measurement drive block (1104) is fixed on the notch extension rod (1103). The two notch fixing rods (1105) are respectively fixed on both sides of the notch body (401), and the ends of the two notch fixing rods (1105) away from the notch body (401) abut against the lower surface of the notch measurement drive block (1104). The central axis displacement measurement assembly (12) includes a central axis data acquisition unit (1201), a central axis displacement sensor (1202), a central axis extension rod (1203), a central axis measurement drive block (1204), and two central axis fixing rods (1205). The upper end of the central axis displacement sensor (1202) is connected to the central axis data acquisition unit (1201), and the lower end of the central axis displacement sensor (1202) is connected to the central axis extension rod (1203). The central axis displacement sensor (1202) is fixed with the central axis measurement drive block (1204). The two central axis fixing rods (1205) are respectively fixed on both sides of the central axis of the test specimen (4). The central axis measurement drive block (1204) is provided with several drive block through holes. The ends of the two central axis fixing rods (1205) away from the test specimen (4) are respectively inserted into one of the drive block through holes.

8. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 1, characterized in that: It also includes a heating furnace (13), into which the test vessel body (1) can extend.

9. The fracture toughness testing device for pipeline steel welded joints under corrosive environments according to claim 8, characterized in that: It also includes a lifting device and a testing machine body (14). The lifting device is fixed on the testing machine body (14) and is used to drive the heating furnace (13) to move up and down. A tray body (15) is placed at the opening of the test vessel body (1). A tray notch (1501) is provided on the outer wall of the tray body (15). A tray baffle (1401) is fixed on the test machine body (14). The shape of the tray baffle (1401) matches the shape of the tray notch (1501).

10. A testing device for testing the fracture toughness of welded joints of pipeline steel under corrosive environments, characterized in that, The fracture toughness testing device for pipeline steel welded joints under corrosive conditions according to any one of claims 1-9 includes the following steps: Step S1: Preparation and pretreatment of test specimen (4): Test specimen (4) is prepared from the welded joint of pipeline steel and fatigue cracks are pre-formed; the test specimen (4) with pre-formed cracks is coated with anti-corrosion coating on the surface except for the notch body (401). After the anti-corrosion coating is cured, the test specimen (4) is placed in the test solution for pre-immersion. Step S2: Install the test specimen (4), install the test specimen (4) into the test unit; introduce the test solution into the test vessel body (1), operate the lifting device to raise the heating furnace (13) and the test vessel body (1) and seal them with the test vessel cover (2); Step S3: Establish a corrosive environment. After heating the test solution to the test temperature, nitrogen gas is introduced into the test vessel body (1) to remove dissolved oxygen. Then, test gas is introduced until the test solution is saturated and the test begins. Step S4: Fracture toughness test. Apply load to the test specimen (4) at a fixed loading rate. The displacement measurement component collects displacement data in real time. The test ends when the force value reaches the expected value. Step S5: Data processing. After cooling the test specimen (4), the test specimen (4) is broken by compression. The initial crack length a0 of the test specimen (4) is measured, the loading line displacement q of the specimen is calculated, the force-displacement curve is plotted, and the fracture toughness J0 value is calculated.

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