Hydrogen embrittlement test device and method for simulating underwater wave flow scouring

Abstract

The invention discloses a hydrogen embrittlement test device and method for simulating underwater wave flow scouring. The device comprises a washing system, a slow stretching system and an electrochemical system, the washing system comprises a box body, an upper fixing plate, a lower fixing plate, a vertical rod group, a fluid monitoring probe, a fluid data acquisition system, a medium mixing tank, a proportioning pump and a flow meter, and the slow stretching system comprises a slow stretching testing machine. The electrochemical system comprises a graphite electrode, a salt bridge, a saturated calomel electrode and an electrochemical workstation. The use method comprises the following steps: fixing a sample on a slow tensile testing machine, conveying seawater with target mud and sand content at a certain flow rate, externally adding direct current cathode protection current to an electrochemical workstation to inhibit uniform corrosion of the sample, recording pure scouring loss Ww of the sample, pre-charging hydrogen into the samples with the same steel grade and the same specification, carrying out a slow tensile test, and recording total loss W of the sample, the contribution rate of scouring and hydrogen embrittlement is represented, and the hydrogen embrittlement sensitivity is evaluated according to the percentage reduction of area.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, and in particular to a hydrogen embrittlement test apparatus and method for simulating underwater wave erosion. Background Technology

[0002] Offshore platforms are the infrastructure for near-shore oil and gas resource development. Built on the continental shelf, these platforms are subjected to intense erosion from waves, currents, and sediment, making them prone to structural failure and posing significant risks to their stability and normal operation. Furthermore, the loss of life and property caused by failure during long-term service is incalculable, and the resulting environmental pollution is extremely severe.

[0003] With the development of electric arc additive manufacturing technology, its application scope is becoming increasingly wide. Due to its advantages such as high material utilization efficiency, low cost, and high production efficiency, electric arc additive manufacturing is particularly suitable for manufacturing risers, horizontal pipes, and support structures for offshore platforms, and its application prospects are broad. For additive manufacturing products used in marine industrial environments, they need to possess high corrosion resistance, such as resistance to seawater corrosion, erosion corrosion, and hydrogen embrittlement.

[0004] Investigations revealed that the construction of the platform riser altered the original ocean current patterns in the area, making the surrounding water flow highly complex. Secondary flows formed in front of the piles, creating vortices around them, which increased scouring intensity and caused severe scouring of the riser system. Furthermore, the scouring altered the stress state at the pile tops, increasing the equivalent pile length, affecting the lateral stiffness and internal forces of the structure, and consequently impacting the stability of the platform.

[0005] Furthermore, arc additive manufacturing technology inevitably introduces a certain amount of hydrogen. The introduction of hydrogen degrades the properties of steel; under external loads, hydrogen reduces the steel's plasticity, causing hysteresis fracture and leading to hydrogen embrittlement. Therefore, the probability of corrosion failure in offshore platform riser systems increases dramatically under the combined effects of wave erosion and hydrogen embrittlement.

[0006] The published invention, “A test instrument and test method for simulating fatigue load and dynamic water scouring” (publication number CN106644788B), belongs to the field of road material testing technology. The dynamic water scouring involved refers to the water film covering the road surface and the erosion effect of de-icing salt melting on the road surface, and does not involve the problem of seawater wave scouring.

[0007] The disclosed "A test device for concrete scour under load and environmental coupling" (publication number CN216386650U) relates to the scour fatigue test of concrete engineering structures in a simulated ocean wave environment, but does not involve wave scour or hydrogen embrittlement sensitivity issues.

[0008] In summary, the aforementioned disclosed patents do not address the issue of testing the performance of offshore platform riser systems under the combined effects of wave erosion and hydrogen embrittlement, and cannot construct the wave morphology of the offshore platform riser environment. Therefore, establishing a hydrogen embrittlement test device and method for simulating underwater wave erosion is of practical significance. It is beneficial for identifying potential safety hazards in existing systems, which is of great importance for reducing platform maintenance costs and ensuring the safety of life and property. Furthermore, it can provide technical information for further optimization of material selection, thereby improving the safety factor of offshore platforms in service. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a hydrogen embrittlement test device and method for simulating underwater wave and current erosion, to test and evaluate the corrosion resistance of materials for riser structural components of offshore platforms, and to provide a basis for safety evaluation and material selection optimization of offshore platform riser systems.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A hydrogen embrittlement test apparatus for simulating underwater wave erosion includes an erosion system, a slow tensile system, and an electrochemical system. The erosion system includes a chamber, an upper fixed plate, a lower fixed plate, a group of upright rods, a fluid monitoring probe, a fluid data acquisition system, a medium mixing tank, a dispensing pump, and a flow meter. The slow tensile system includes a slow tensile testing machine. The electrochemical system includes an electrochemical workstation, a graphite electrode, a salt bridge, and a saturated calomel electrode.

[0012] The housing is equipped with upper and lower fixed plates, forming a wave-current scouring space. Several mounting holes are symmetrically arranged on the upper and lower fixed plates. A vertical rod is installed between the upper and lower fixed plates through these holes. The medium mixing tank, dispensing pump, flow meter, fluid data acquisition system, and housing are sequentially connected in a loop via pipelines. A fluid monitoring probe is horizontally mounted circumferentially on the vertical rod and connected to the fluid data acquisition system. The scouring system simulates the wave-current scouring environment of the riser system, constructing horseshoe-shaped vortices and erosion vortices, providing conditions for simulating the wave-current morphology of a marine platform riser system in service. The slow-tension system includes a slow-tension testing machine. The specimen is connected to the slow-tension testing machine via upper and lower clamps, enabling hydrogen embrittlement sensitivity testing of metallic materials under slow-rate conditions. The electrochemical system includes an electrochemical workstation, a graphite electrode, a salt bridge, and a saturated calomel auxiliary electrode, employing a three-electrode system. The working electrode is the sample, the auxiliary electrode is the graphite electrode, and the reference electrode is the saturated calomel electrode. The salt bridge reduces and stabilizes the liquid junction potential. The electrochemical system applies an external cathode current to the sample through the electrochemical workstation to achieve cathodic protection of the metallic material and the pre-hydrogen charging process of the sample.

[0013] Furthermore, there should be no fewer than 14 upright rods, evenly distributed around the sample.

[0014] Furthermore, the vertical and horizontal distances between adjacent uprights are equal.

[0015] Furthermore, the upright rod is a cylinder made of polytetrafluoroethylene or plexiglass, and the diameter of the upright rod is between 1 and 3 times the diameter of the sample clamping section.

[0016] Under the impact of fluid, the group of upright rods causes horseshoe-shaped vortices and erosion vortices to form around the sample, which transforms the advection fluid into vortex fluid, thus drastically increasing the scouring depth and scouring range, thereby simulating local scouring corrosion.

[0017] Furthermore, the sample is a circular sample with a surface roughness of less than 0.8 μm and a consistent surface finish to eliminate stress concentration; the transition section has a tangential transition arc to smoothly connect the clamping section and the parallel section to eliminate stress concentration.

[0018] Furthermore, the height of the wave current scouring space in the scouring system box, i.e. the height between the upper fixed plate and the lower fixed plate, is greater than the sum of the lengths of the transition section and the parallel section of the tensile specimen, and the distance between the outer vertical rod and the box wall is ≥0.7m.

[0019] Furthermore, the number of fluid monitoring probes is ≥4; the fluid monitoring probes are evenly set at the same horizontal position as the group of upright rods, and the fluid flow velocity and direction data are collected by the fluid data system to draw a fluid waveform diagram. The horizontal position of the fluid monitoring probes is the midpoint of the sample.

[0020] Furthermore, the flushing seawater is mixed with a simulated fluid medium in a medium mixing tank, stirred evenly, and then pumped into the tank via a dispensing pump. The seawater then flows out of the tank and is sent back to the medium mixing tank for recycling. The simulated fluid medium is seawater, simulated seawater solution, or seawater containing mud and sand, with a sand and gravel concentration not exceeding 50%.

[0021] A hydrogen embrittlement test method for simulating underwater wave and current erosion includes the following steps:

[0022] Step 1: Adjust the two test parameters, namely the distance between the uprights and the fluid velocity entering the chamber, to simulate the target wave flow pattern. The distance between the uprights and the fluid velocity entering the chamber are key parameters for constructing the wave flow pattern. The method for determining these test parameters is as follows: A uniformly mixed simulated fluid medium is delivered into the chamber using a dispensing pump. The fluid velocity and direction are monitored using a fluid monitoring probe, and data is collected every 15 minutes. Fluid waveforms are obtained through a fluid data system to determine whether horseshoe vortices and erosion vortices are formed. If not, the distance between the uprights or the fluid velocity entering the chamber is adjusted until the target wave flow pattern is formed. The determined upright distance is then used to simulate fatigue test parameters for underwater wave erosion.

[0023] Step 2: Fix the sample onto the slow tensile testing machine using the upper and lower clamps. Prepare seawater with the target mud and sand content in the mixing tank. Transport the target simulated fluid medium into the chamber at the flow rate determined in Step 1. Use an electrochemical workstation with an external DC cathodic protection current to suppress uniform corrosion of the sample. Use a graphite electrode as the anode, the sample as the cathode, and a saturated calomel electrode as the reference electrode. Remove corrosion products from the sample surface, dehydrate with alcohol, and dry with cold air. Weigh the sample and record the pure erosion loss Ww.

[0024] Step 3: Apply a constant current to pre-charge hydrogen onto samples of the same steel grade and specifications using an electrochemical workstation;

[0025] Step 4: Install the pre-hydrogen-charged sample on the slow tensile testing machine. Flow the simulated fluid medium into the chamber at the rate determined in Step 1. Perform a slow tensile test on the pre-hydrogen-charged sample at the target tensile rate. Stop the experiment when the sample fractures. Remove corrosion products from the sample surface, dehydrate with alcohol, and dry with cold air. Weigh the sample and record the total loss W.

[0026] Step 5: The acceleration increment ΔW due to hydrogen embrittlement on scouring can be obtained through W-Ww, i.e., ΔW = W-Ww. The contribution rate of the interaction between erosion and hydrogen embrittlement during the service process of materials is characterized, thereby evaluating the corrosion resistance of the metal material itself, arc additive manufacturing components or welded joints under the synergistic effect of wave erosion and hydrogen embrittlement; the hydrogen embrittlement sensitivity is evaluated by the reduction of area.

[0027] The service wave current scours the tensile specimen in a vortex pattern. The impact force generated by the multiphase scour angle can be divided into horizontal and vertical components. Therefore, the specimen subjected to axial force in the tensile test also experiences non-axial impact force. The horizontal component has a cutting effect on the scour surface; at small scour angles, the horizontal component is stronger, and this horizontal cutting mechanism is the main cause of material loss. The vertical component generates impact; at large scour angles, the vertical component is stronger, with solid particles impacting the material surface. Some particles impact to form impact pits and surrounding protruding lips; others impact the metal surface, forming microcracks. Thus, the vortex-shaped wave current impact force has a significant effect on tensile specimens subjected to axial force. The hydrogen embrittlement sensitivity test of the specimen in the wave current scour environment can be used to test the hydrogen embrittlement performance of the metal material itself, arc additive manufacturing components, or welded joints, achieving hydrogen embrittlement sensitivity testing in a simulated wave current scour environment for offshore platform riser systems.

[0028] The fluid entering the tank has a flow rate ≥0.5m / s.

[0029] The applied cathodic protection current method utilizes an electrochemical workstation with an external DC power supply and an auxiliary anode graphite electrode to direct current to the sample being protected. This reduces the surface cathodic potential to the metal's natural corrosion potential in a simulated medium solution, at which point the surface corrosion current drops to zero or near zero, thus providing protection. In this experiment, the pure corrosion rate component during the scouring corrosion process is eliminated, thereby obtaining the rate component of the interaction between scouring and hydrogen embrittlement.

[0030] Preferably, the electrochemical workstation applies an external DC cathodic protection current, with the cathodic protection current range being 0.002–0.010 A / m. 2 .

[0031] Preferably, the sample is pre-charged with hydrogen by applying a cathode current through an electrochemical workstation. The hydrogen charging solution is 0.1–0.5 mol / L NaOH and 0.5–2 g / L thiourea, and the hydrogen charging current density is 0.05–10 A / m. 2 The hydrogen charging time is 0.5 to 100 hours.

[0032] Preferably, the tensile rate of the slow tensile testing machine is 10. -5 ~10 -8 mm / s.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention provides a hydrogen embrittlement testing apparatus for simulating underwater wave current erosion, comprising an erosion system, a slow tensile system, and an electrochemical system. In the erosion system, two parameters—the spacing between the uprights and the fluid velocity entering the chamber—are determined using fluid data acquisition and fluid waveform plotting. Horseshoe-shaped vortices and erosion vortices are constructed by adjusting the number and spacing of the uprights and the fluid velocity to simulate an underwater wave current erosion environment. In the slow tensile system, the mechanical properties of metallic materials are tested. The electrochemical system applies a cathode current to the sample via an electrochemical workstation, achieving cathodic protection of the metallic material and a pre-hydrogen charging process for the sample.

[0035] 2. This invention provides cathodic protection for metallic materials by applying an external current, and performs erosion corrosion tests on the metallic materials under cathodic protection.

[0036] 3. This invention enables a hydrogen-charged slow tensile test in a wave-current scouring environment, thereby testing the hydrogen embrittlement sensitivity of materials used in marine platform riser structures.

[0037] 4. This device investigated the corrosion behavior of offshore platform structural components under conditions of coexisting wave erosion and hydrogen embrittlement. This study characterizes the contribution of the interaction between erosion and hydrogen embrittlement during material service, thereby evaluating the corrosion resistance of materials under the synergistic effects of wave erosion and hydrogen embrittlement, and exploring the mechanism of this synergistic effect. Its advantages include providing a method for evaluating corrosion performance under the combined effects of wave erosion and hydrogen embrittlement, offering product performance information for the development and performance improvement of marine engineering metal materials, identifying potential safety hazards in existing systems, providing technical information for further material selection optimization, and ultimately improving the safety factor of offshore platforms. Furthermore, it facilitates the observation of material failure states, helps identify severely failed areas, and provides valuable information for subsequent protective measures. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the hydrogen embrittlement test device for simulating underwater wave erosion according to the present invention.

[0039] Figure 2 AA section view

[0040] Figure 3 Fluid wave flow diagram

[0041] In the figure: 1 is the box body; 2 is the upper fixing plate; 3 is the lower fixing plate; 4 is the upright rod; 5 is the upper and lower end clamps; 6 is the slow tensile testing machine; 7 is the graphite electrode; 8 is the salt bridge; 9 is the saturated calomel electrode; 10 is the electrochemical workstation; 11 is the fluid monitoring probe; 12 is the fluid data acquisition system; 13 is the dispensing pump; 14 is the flow meter; 15 is the medium mixing tank; 16 is the sample. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The following description of an exemplary embodiment of the experimental apparatus and method is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0043] This invention provides a hydrogen embrittlement testing apparatus and method for simulating underwater wave current scouring, which is a testing apparatus and method for testing the hydrogen embrittlement risk of metallic materials during scouring under specific wave current morphology. The testing apparatus of this invention can simulate the changes in factors such as the morphology, velocity, sand content, solid particle size, and corrosive medium of the wave current fluid in service with a marine platform riser system, constructing a scouring system under service conditions for marine engineering components, and then measuring the hydrogen embrittlement sensitivity of the metallic materials themselves, arc additive manufacturing structures, or welded joints.

[0044] like Figure 1 As shown, a hydrogen embrittlement test apparatus for simulating underwater wave erosion includes an erosion system, a slow stretching system, and an electrochemical system.

[0045] The flushing system includes a housing 1, an upper fixed plate 2, a lower fixed plate 3, a vertical rod 4, a fluid monitoring probe 11, a fluid data acquisition system 12, a dispensing pump 13, a flow meter 14, and a media mixing tank 15; the slow tensile system includes a slow tensile testing machine 6; and the electrochemical system includes a graphite electrode 7, a salt bridge 8, a saturated calomel electrode 9, and an electrochemical workstation 10.

[0046] Several mounting holes are symmetrically arranged on the upper fixing plate 2 and the lower fixing plate 3. The upright rod 4 is installed between the upper fixing plate 2 and the lower fixing plate 3 through the mounting holes. The specimen 16 is fixed on the slow tensile testing machine 6 by the upper and lower end clamps 5. The space between the upper fixing plate 2 and the lower fixing plate 3 is the wave scouring space, and its height is greater than the length of the specimen transition section and the parallel section.

[0047] As a preferred embodiment, the sample 16 is a circular sample with a surface roughness of less than 0.8 μm and a consistent surface finish.

[0048] In a preferred embodiment, there are no fewer than 14 upright rods in group 4.

[0049] In a preferred embodiment, the vertical and horizontal distances between adjacent uprights 4 are equal.

[0050] In a preferred embodiment, the upright rod 4 is cylindrical, made of polytetrafluoroethylene or plexiglass, and its diameter is 1 to 3 times the diameter of the clamping section of the sample 15. Under the action of the wave current, the upright rod 4 causes horseshoe-shaped vortices and erosion vortices to form around the sample 15, which deforms the advection wave current, causing a sharp increase in both the scouring depth and the scouring range, thereby realizing a simulated corrosion test of the riser system of an offshore platform.

[0051] A fluid monitoring probe 11 is horizontally positioned circumferentially at the midpoint of the vertical rod 4. The fluid monitoring probe 11 is connected to the fluid data acquisition system 12. The fluid monitoring probe 11 monitors the flow rate and direction of the fluid and collects data every 15 minutes. The fluid data acquisition system 12 collects the above data and generates a fluid waveform diagram to determine whether the fluid forms horseshoe vortices and erosion vortices.

[0052] The media mixing tank 15, the dispensing pump 13, the flow meter 14, the fluid data acquisition system 12, and the housing 1 are connected in sequence to form a loop via pipelines. The media mixing tank 15 provides a homogeneous single-phase or multiphase fluid. The dispensing pump 13 provides the fluid at the target flow rate, which is measured by the flow meter 14. The fluid flows from the media mixing tank 15 to the housing 1 via the dispensing pump 13, and the flushing fluid flows back to the media mixing tank 15 for continuous flushing.

[0053] In a preferred embodiment, the media mixing tank 15 is equipped with a stirrer to uniformly mix seawater, simulated seawater solution, or seawater containing mud and sand. The media mixing tank 15 stores the test fluid, with a sand and gravel concentration not exceeding 50%.

[0054] An electrochemical workstation 10 applied an external cathode current to sample 16. A three-electrode system was used, with sample 16 as the working electrode, graphite electrode 7 as the auxiliary electrode, and saturated calomel electrode 9 as the reference electrode.

[0055] A method of using a hydrogen embrittlement device for simulating underwater wave erosion includes:

[0056] Step 1: Adjust the test parameters of the spacing of the uprights 4 and the fluid flow velocity entering the chamber 1 to simulate the target wave flow pattern;

[0057] Step 2: Fix the sample 16 onto the slow tensile testing machine 6 using the upper and lower clamps 5. Prepare seawater with the target mud and sand content in the medium mixing tank 15. Transport the target simulated fluid medium into the chamber 1 at the flow rate determined in Step 1. Apply an external DC cathodic protection current using the electrochemical workstation 10 to suppress uniform corrosion of the sample 16. Use the graphite electrode 7 as the anode, the sample 16 as the cathode, and the saturated calomel electrode 9 as the reference electrode. Remove the corrosion products from the surface of the sample 16, dehydrate it with alcohol, and dry it with cold air. Weigh the sample and record the pure erosion loss Ww of the sample 16.

[0058] Step 3: Apply a constant current to pre-charge hydrogen onto samples of the same steel grade and specifications using an electrochemical workstation 10;

[0059] Step 4: Install the pre-hydrogen-charged sample 16 on the slow tensile testing machine 6. Transport the simulated fluid medium to the chamber 1 at the flow rate determined in Step 1. Conduct a slow tensile test on the pre-hydrogen-charged sample 16 at the target tensile rate. The test stops when the sample 16 fractures. Remove the corrosion products from the surface of the sample 16, dehydrate it with alcohol, and dry it with cold air. Weigh the sample and record the total loss W of the sample 16.

[0060] Step 5: The acceleration increment ΔW due to hydrogen embrittlement on scouring can be obtained through W-Ww, i.e., ΔW = W-Ww. Characterize the contribution of scouring and hydrogen embrittlement interaction during material service; evaluate hydrogen embrittlement sensitivity by reduction of area.

[0061] As a preferred embodiment, the method for determining the test parameters of the spacing of the uprights 4 and the flow rate of the fluid entering the chamber 1 is as follows: a uniformly mixed simulated fluid medium is delivered to the chamber 1 by a dispensing pump 13, and the fluid flow rate and direction are monitored by a fluid monitoring probe 11, with data collected every 15 minutes; the fluid waveform is obtained by a fluid data acquisition system 12 to determine whether the fluid forms horseshoe vortices and erosion vortices. If not, the spacing of the uprights 4 and the flow rate of the fluid entering the chamber 1 are adjusted until the target wave flow shape is formed.

[0062] In a preferred embodiment, the fluid entering the tank has a flow rate ≥0.5m / s.

[0063] The external cathodic protection current method utilizes an external DC power supply and an auxiliary anode graphite electrode from an electrochemical workstation to direct current to the sample being protected. The surface cathodic potential of the sample is reduced to the natural corrosion potential of the metal in the simulated medium solution. At this point, the corrosion current on the metal surface drops to zero or close to zero, thereby achieving a protective effect.

[0064] In a preferred embodiment, an external DC cathodic protection current is applied to the electrochemical workstation 10 to suppress uniform corrosion of the sample 16. The cathodic protection current ranges from 0.002 to 0.01 A / m. 2 .

[0065] In a preferred embodiment, the slow tensile testing machine 6 has a tensile rate of 10. -5 ~10 -8 mm / s.

[0066] In a preferred embodiment, sample 16 is pre-charged with hydrogen by applying a cathode current through an electrochemical workstation 10. The hydrogen charging solution consists of 0.1–0.5 mol / L NaOH and 0.5–2 g / L thiourea, and the hydrogen charging current density is 0.05–10 A / m. 2 The hydrogen charging time is 0.5 to 100 hours.

[0067] Example 1

[0068] Taking E690 steel as an example, combined with the attached... Figure 1 , 2 Sections 3 and 4 further illustrate the present invention.

[0069] Step 1: The hydrogen embrittlement test apparatus for simulating underwater wave erosion is designed with 14 vertical rods. Initially, the distance between the outermost rod and the tank wall is set to 1m, the spacing between the rods is 100mm, and the fluid velocity entering the tank is 1m / s. The fluid velocity and direction are monitored using a fluid monitoring probe, and the fluid waveform is plotted using a fluid data acquisition system. (See attached diagram.) Figure 3It can be seen that the fluid flow pattern is horseshoe vortex and erosion vortex. Therefore, the distance between the outer rod and the box wall is determined to be 1m, the fluid velocity entering the box is 1m / s, the distance between the rods is 100mm, the rods and the sample are fixed to the upper and lower fixing plates at a distance of 100mm, and the height of the wave scouring space is 45cm.

[0070] Step 2: Using a standard Ф6.35mm E690 steel circular tensile test specimen, fix the specimen onto the slow tensile testing machine using the upper and lower clamps. A uniformly mixed mixture of seawater and silt (10% silt content) is prepared in the mixing tank and pumped into the test chamber at a rate of 1 m / s. An electrochemical workstation with external DC cathodic protection and a current density of 0.005 A / m is used. 2 After cleaning the sample, dehydrating it with alcohol, and drying it with cold air, weigh it and record the pure erosion loss Ww as 0.04g.

[0071] Step 3: Pre-charge another 6.35mm E690 steel sample (US standard) with hydrogen using an electrochemical workstation. The hydrogen charging solution consisted of 0.2 mol / L NaOH and 1 g / L thiourea, and the hydrogen charging current density was 3.0 A / cm². 2 The hydrogen charging time is 48 hours.

[0072] Step 4: Install the pre-hydrogen-charged sample on the slow tensile testing machine. The medium mixing tank contains a uniformly mixed mixture of seawater and silt (10% silt content), which is pumped into the chamber at a speed of 1 m / s using a dispensing pump. Simultaneously, the pre-hydrogen-charged sample undergoes a 10-minute tensile test. -6 The slow tensile test at a tensile rate of mm / s resulted in specimen fracture, and the test was stopped. Corrosion products on the specimen surface were removed, the specimen was rinsed with deionized water, dehydrated with alcohol, and dried with cold air. The specimen was then weighed, and the total loss W was recorded as 0.18 g.

[0073] Step 5: Obtain the acceleration increment of hydrogen embrittlement on erosion, ΔW = W - Ww = 0.18g - 0.04g = 0.14g. This value characterizes the contribution rate of the interaction between erosion and hydrogen embrittlement during the service process of the material, and thus evaluates the corrosion resistance of the material under the synergistic effect of wave erosion and hydrogen embrittlement; the sample has a cross-sectional area reduction rate of 9.1%.

[0074] Example 2

[0075] Taking X52 steel as an example, combined with the attached... Figure 1 and 2 The present invention will be further described below.

[0076] Step 1: The hydrogen embrittlement test apparatus for simulating underwater wave erosion is designed with 24 support rods. Initially, the distance between the outer support rods and the tank wall is set to 1m, the distance between the support rods is 150mm, and the fluid velocity entering the tank is 1.2m / s. The fluid velocity and direction are monitored using a fluid monitoring probe, and the fluid waveform is plotted using a fluid data acquisition system. Under these conditions, the fluid flow pattern exhibits horseshoe vortices and erosion vortices. Therefore, the distance between the outer support rods and the tank wall is determined to be 1m, the fluid velocity entering the tank is 1.2m / s, the distance between the support rods is 150mm, and the support rods and the sample are fixed to the upper and lower fixing plates at a distance of 150mm. The wave erosion space height is 45cm.

[0077] Step 2: Using a standard Ф6.35mm x 52mm tensile circular specimen, fix the specimen to the slow tensile testing machine using the upper and lower clamps. A uniformly mixed mixture of seawater and silt (20% silt content) is prepared in the mixing tank and pumped into the chamber at a rate of 1.2 m / s. An electrochemical workstation with external DC cathodic protection and a current density of 0.01 A / m is used. 2 After cleaning the sample, dehydrating it with alcohol, and drying it with cold air, weigh it and record the pure erosion loss Ww as 0.12g.

[0078] Step 3: Pre-charge another US standard Ф6.35mm x 52 steel sample with hydrogen using an electrochemical workstation. The hydrogen charging solution consisted of 0.2 mol / L NaOH and 0.5 g / L thiourea, and the hydrogen charging current density was 1.0 A / cm². 2 The hydrogen charging time is 50 hours.

[0079] Step 4: Install the pre-hydrogen-charged sample on the slow tensile testing machine. The medium mixing tank contains a uniformly mixed mixture of seawater and silt (20% silt content), which is pumped into the chamber at a speed of 1.2 m / s using a dispensing pump. Simultaneously, the pre-hydrogen-charged sample undergoes a 10-minute tensile test. -6 The slow tensile test at a tensile rate of mm / s resulted in specimen fracture, and the test was stopped. Corrosion products on the specimen surface were removed, the specimen was rinsed with deionized water, dehydrated with alcohol, and dried with cold air. The specimen was then weighed, and the total loss W was recorded as 0.41 g.

[0080] Step 5: Obtain the acceleration increment of hydrogen embrittlement on erosion, ΔW = W - Ww = 0.41g - 0.12g = 0.29g. This value characterizes the contribution rate of the interaction between erosion and hydrogen embrittlement during the service process of the material, and thus evaluates the corrosion resistance of the material under the synergistic effect of wave erosion and hydrogen embrittlement; the sample has a cross-sectional area reduction rate of 22%.

[0081] Example 3

[0082] Taking Q460 steel as an example, combined with the attached... Figure 1 and 2The present invention will be further described below.

[0083] Step 1: The hydrogen embrittlement test apparatus for simulating underwater wave erosion is designed with 34 support rods. Initially, the distance between the outer support rods and the tank wall is set to 1m, the distance between the support rods is 80mm, and the fluid velocity entering the tank is 2m / s. The fluid velocity and direction are monitored using a fluid monitoring probe, and the fluid waveform is plotted using a fluid data acquisition system. Under these conditions, the fluid flow pattern exhibits horseshoe vortices and erosion vortices. Therefore, the distance between the outer support rods and the tank wall is determined to be 1m, the fluid velocity entering the tank is 2m / s, the distance between the support rods is 80mm, and the support rods and the sample are fixed to the upper and lower fixing plates at 80mm intervals. The wave erosion space height is 45cm.

[0084] Step 2: Using a standard Ф6.35mm Q460 steel circular tensile test specimen, fix the specimen onto the slow tensile testing machine using the upper and lower clamps. A uniformly mixed mixture of seawater and silt (30% silt content) is prepared in the mixing tank and pumped into the test chamber at a rate of 2 m / s. An electrochemical workstation with external DC cathodic protection and a current density of 0.007 A / m is used. 2 After cleaning the sample, dehydrating it with alcohol, and drying it with cold air, weigh it and record the pure erosion loss Ww as 0.2g.

[0085] Step 3: Pre-charge another US standard Ф6.35mm Q460 steel sample with hydrogen using an electrochemical workstation. The hydrogen charging solution was 0.5mol / L NaOH and 1g / L thiourea, and the hydrogen charging current density was 0.5A / cm². 2 The hydrogen charging time is 72 hours.

[0086] Step 4: Install the pre-hydrogen-charged sample on the slow tensile testing machine. The medium mixing tank contains a uniformly mixed mixture of seawater and silt (30% silt content), which is pumped into the chamber at a speed of 2 m / s using a dispensing pump. Simultaneously, the pre-hydrogen-charged sample undergoes a 10-minute tensile test. -8 The slow tensile test at a tensile rate of mm / s resulted in specimen fracture, and the test was stopped. Corrosion products on the specimen surface were removed, the specimen was rinsed with deionized water, dehydrated with alcohol, and dried with cold air. The specimen was then weighed, and the total loss W was recorded as 0.59 g.

[0087] Step 5: Obtain the acceleration increment of hydrogen embrittlement on erosion, ΔW = W - Ww = 0.59g - 0.2g = 0.39g. This value characterizes the contribution rate of the interaction between erosion and hydrogen embrittlement during the service process of the material, and thus evaluates the corrosion resistance of the material under the synergistic effect of wave erosion and hydrogen embrittlement; the sample has a cross-sectional area reduction rate of 37.2%.

[0088] Based on the above results, it can be concluded that the device of the present invention can test the contribution rate of the interaction between wave erosion and hydrogen embrittlement of riser structural components and the sensitivity to hydrogen embrittlement in a simulated wave-current erosion environment of a marine platform riser system. It realistically and accurately simulates the service environment of a marine platform riser system, and the obtained corrosion resistance results can be used to assess the safety of structural components and explore the mechanism of the synergistic effect of wave erosion and hydrogen embrittlement on materials.

Claims

1. A hydrogen embrittlement test apparatus for simulating underwater wave erosion, characterized in that: The system includes a flushing system, a slow-tensioning system, and an electrochemical system. The flushing system simulates the wave-current scouring environment of the riser system of an offshore platform, constructing horseshoe-shaped vortices and erosion vortices. The flushing system includes a box (1), an upper fixed plate (2), a lower fixed plate (3), a group of uprights (4), a fluid monitoring probe (11), a fluid data acquisition system (12), a medium mixing tank (15), a dispensing pump (13), and a flow meter (14). The slow-tensioning system includes a slow-tensioning testing machine (6). The electrochemical system includes an electrochemical workstation (10), a graphite electrode (7), a salt bridge (8), and a saturated calomel electrode (9). The box (1) is equipped with an upper fixed plate (2) and a lower fixed plate (3). The space formed by the upper fixed plate (2) and the lower fixed plate (3) is the wave-current scouring space. A number of mounting holes are symmetrically arranged. The upright rod (4) is installed between the upper fixing plate (2) and the lower fixing plate (3) through the mounting holes. The medium mixing tank (15), the dispensing pump (13), the flow meter (14), the fluid data acquisition system (12) and the box (1) are connected in sequence to form a loop through the pipes. The upright rod (4) is horizontally arranged with a fluid monitoring probe (11) in the circumference. The fluid monitoring probe (11) is connected to the fluid data acquisition system (12). The sample (16) is connected to the slow tensile testing machine (6) through the upper and lower end clamps (5). The electrochemical workstation (10) applies a cathode current to the sample (16) and adopts a three-electrode system. The working electrode is the sample (16), the auxiliary electrode is the graphite electrode (7), and the reference electrode is the saturated calomel electrode (9).

2. The hydrogen embrittlement test apparatus for simulating underwater wave erosion according to claim 1, characterized in that, The group of upright rods (4) shall have no less than 14 rods; the vertical and horizontal distances between adjacent upright rods (4) shall be equal; the upright rods (4) shall be cylindrical and made of polytetrafluoroethylene or plexiglass, and the diameter of the upright rods (4) shall be 1 to 3 times the diameter of the clamping section of the sample (16).

3. The hydrogen embrittlement test apparatus for simulating underwater wave and current erosion according to claim 1, characterized in that, The sample (16) is a circular sample with a surface roughness of less than 0.8 μm.

4. The hydrogen embrittlement test apparatus for simulating underwater wave and current erosion according to claim 1, characterized in that, The height of the wave current scouring space in the scouring system box (1) is greater than the sum of the lengths of the transition section and the parallel section of the tensile specimen, and the distance between the outer layer upright (4) and the box wall is ≥0.7m.

5. The fatigue testing apparatus for simulating underwater wave and current erosion according to claim 1, characterized in that, The horizontal position of the fluid monitoring probe (11) is the midpoint of the sample (16), and the number of circumferential fluid monitoring probes (11) on the upright rod (4) is ≥4.

6. A method of using the hydrogen embrittlement test apparatus for simulating underwater wave erosion as described in any one of claims 1-5, characterized in that, Step 1: Determine the two test parameters: the spacing of the uprights (4) and the flow rate of the fluid entering the chamber (1); Step 2: Fix the sample (16) on the slow tensile testing machine (6) using the upper and lower end clamps (5). Prepare the target mud and sand content seawater in the medium mixing tank (15). Transport the target simulated fluid medium to the box (1) at the flow rate determined in Step 1. Use the electrochemical workstation (10) to apply DC cathodic protection current to suppress uniform corrosion of the sample (16), remove the corrosion products on the surface of the sample (16), dehydrate with alcohol and dry with cold air, weigh, and record the pure scouring loss Ww of the sample (16). Step 3: Apply a constant current to pre-charge hydrogen onto samples of the same steel grade and specifications using an electrochemical workstation (10); Step 4: Install the pre-hydrogen-charged sample (16) on the slow tensile testing machine (6), and transport the above-mentioned simulated fluid medium to the chamber (1) at the flow rate determined in Step 1. Conduct a slow tensile test on the pre-hydrogen-charged sample (16) at the target tensile rate. When the sample (16) breaks, the experiment is stopped. Remove the corrosion products on the surface of the sample (16), dehydrate it with alcohol and dry it with cold air, weigh it, and record the total loss W of the sample (16). Step 5: Obtain the acceleration increment ΔW of hydrogen embrittlement on scouring through W-Ww, and then... The contribution rate of scouring and hydrogen embrittlement interaction to the service life of materials is characterized, and the hydrogen embrittlement sensitivity is evaluated by the reduction of area.

7. The hydrogen embrittlement test method for simulating underwater wave current erosion according to claim 6, characterized in that, The method for determining the test parameters of the spacing of the uprights (4) and the flow rate of the fluid entering the chamber (1) is as follows: a uniformly mixed simulated fluid medium is transported to the chamber (1) by a dispensing pump (13), and the fluid flow rate and direction are monitored by a fluid monitoring probe (11). Data is collected every 15 minutes, and the fluid waveform is obtained by a fluid data acquisition system (12). It is determined whether the fluid forms a horseshoe vortex and an erosion vortex. If not, the spacing of the uprights (4) and the flow rate of the fluid entering the chamber (1) are adjusted until the target wave flow shape is formed.

8. The hydrogen embrittlement test method for simulating underwater wave current erosion according to claim 6, characterized in that, The electrochemical workstation (10) applies an external DC cathodic protection current to suppress uniform corrosion of the sample (16). The cathodic protection current ranges from 0.002 to 0.01 A / m. 2 .

9. The hydrogen embrittlement test method for simulating underwater wave and current erosion according to claim 6, characterized in that, The sample (16) is pre-charged with hydrogen by applying a cathode current through an electrochemical workstation (10). The specific process parameters are: hydrogen charging solution of 0.1-0.5 mol / L NaOH and 0.5-2 g / L thiourea, and hydrogen charging current density of 0.05-10 A / m. 2 The hydrogen charging time is 0.5 to 100 hours.

10. The hydrogen embrittlement test method for simulating underwater wave current erosion according to claim 6, characterized in that, The slow tensile testing machine (6) has a tensile rate of 10. -5 ~10 -8 mm / s.

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