Circulating soaking device for stress corrosion test and control method thereof

Abstract

The invention discloses a circulating soaking device for a stress corrosion test and a control method thereof, and relates to the technical field of metal corrosion, a soaking solution box is used for containing a corrosion solution, and the lower end of an action assembly is used for being connected with a stress corrosion sample and can drive the stress corrosion sample to be completely soaked in or separated from the corrosion solution in the soaking solution box; the PH sensor is used for stretching into the soaking solution box and detecting the PH value of a corrosion solution in the soaking solution box, the PH sensor is electrically connected with the controller, and the non-contact liquid level monitoring element is used for detecting the liquid level height when the stress corrosion sample is completely separated from the corrosion solution in the soaking solution box and transmitting liquid level height information to the controller; and the controller controls whether to supplement distilled water or purified water into the soaking solution tank or not according to the liquid level height information detected by the non-contact liquid level monitoring element. According to the invention, the cyclic soaking of the stress corrosion sample can be accurately controlled, and the liquid level height of the corrosion solution or the corrosive concentration can be controlled to be kept in a test error range.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion technology, and in particular to a circulating immersion device for stress corrosion testing and its control method. Background Technology

[0002] In marine steel structure engineering and the application of seamless gas cylinders for diving, the ebb and flow of tides, wave action, and periodic diving processes all cause cyclic corrosion damage to metal components. Prolonged cyclic corrosion can lead to intergranular corrosion and failure, resulting in economic losses and safety hazards. Therefore, such metal products or engineering components often require rigorous evaluation and testing of their resistance to cyclic immersion corrosion before being put into use to meet technical specifications.

[0003] Cyclic immersion corrosion testing involves alternating immersion of metal specimens in a liquid corrosive medium and exposure to air under stress-loaded and unstressed conditions. This method is particularly suitable for evaluating the service performance of materials under cyclic corrosion environments. Typically, this type of test first applies a predetermined load or deformation to the specimen using clamping fixtures, followed by reciprocating cyclic immersion corrosion tests to increase the corrosion rate and shorten the test cycle. Nevertheless, the overall test cycle for this type of corrosion testing is often still quite long.

[0004] For example, the national standard GB / T 11640-2021 specifies that when simulating seawater stress corrosion of the stress-bearing ring component of seamless aluminum alloy gas cylinders, the ring needs to be immersed in the corrosive solution for 10 minutes, then removed and exposed to air for 50 minutes, and this cycle needs to be repeated for 30 days. Furthermore, this long-term cyclic corrosion process leads to severe evaporation of the corrosive solution, increasing the concentration of corrosive substances and thus reducing the accuracy of the test results.

[0005] Therefore, this type of test requires a fully automated testing device that can accurately control the cyclic immersion of stress corrosion samples and keep the liquid level of the corrosion solution or the concentration of corrosion products within the test error range. However, such equipment is lacking in the current technology. Summary of the Invention

[0006] The purpose of this invention is to provide a circulating immersion device and its control method for stress corrosion testing, so as to solve the problems existing in the prior art. It can not only achieve precise control of the circulating immersion of stress corrosion samples, but also control the liquid level of the corrosion solution or the concentration of corrosion products to be kept within the test error range.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a circulating immersion device for stress corrosion testing, comprising a frame platform, an immersion solution tank located below the platform surface, and an actuating component, a pH sensor, a non-contact liquid level monitoring element, and a controller mounted on the frame platform. The immersion solution tank is used to hold a corrosive solution. The lower end of the actuating component is used to connect to the stress corrosion sample and can drive the stress corrosion sample to be completely immersed in or detached from the corrosive solution in the immersion solution tank. The pH sensor is used to extend into the immersion solution tank and detect the pH value of the corrosive solution in the immersion solution tank, and the pH sensor is electrically connected to the controller. The non-contact liquid level monitoring element is used to detect the liquid level height when the stress corrosion sample is completely detached from the corrosive solution in the immersion solution tank and transmits the liquid level height information to the controller. The controller controls whether to add distilled water or purified water to the immersion solution tank based on the liquid level height information detected by the non-contact liquid level monitoring element.

[0008] Preferably, the actuation component includes a lifting driver, a lifting rod, and a lifting bracket. The lifting driver is mounted on the frame platform. The lower end of the lifting rod can pass through the surface of the frame platform and be connected to the lifting bracket. The lower end of the lifting bracket can be detachably connected to a plurality of stress corrosion samples. The lifting driver is connected to the lifting rod and can drive the lifting rod and stress corrosion samples to rise and fall.

[0009] Preferably, the lifting driver includes a drive motor and a drive gear, with the output shaft of the drive motor coaxially connected to the drive gear; one side of the lifting rod is rack-shaped, and the drive gear can mesh with the lifting rod and drive the lifting rod to rise and fall.

[0010] Preferably, the upper end of the lifting rod is provided with an upper limit switch, the lower end of the lifting rod is provided with a lower limit switch, the drive motor is electrically connected to the controller, and when the drive gear drives the lifting rod, when the drive gear contacts the upper limit switch or the lower limit switch, the upper limit switch or the lower limit switch transmits a signal to the controller, and causes the controller to control the drive motor to stop working.

[0011] Preferably, the lifting rod is made of stainless steel.

[0012] Preferably, the non-contact liquid level monitoring element is a radar liquid level gauge, and the measuring end face of the radar liquid level gauge is directly facing the corrosive solution in the immersion solution tank, and the accuracy of the radar liquid level gauge is not less than 2mm.

[0013] Preferably, it also includes a water supply tank, a water supply pipe, and a water solenoid valve. The water supply tank is installed on the platform of the frame and is used to hold distilled water or purified water. The lower end of the water supply tank is connected to the upper end of the water supply pipe. The water solenoid valve is installed on the water supply pipe, and the lower end of the water supply pipe extends into the soaking solution tank. The water solenoid valve is electrically connected to the controller.

[0014] Preferably, the controller is equipped with parameter setting buttons, a display screen and a PLC programming interface. The display screen can display the liquid level height information monitored by the non-contact liquid level monitoring element and the pH value information monitored by the pH sensor in real time.

[0015] Preferably, the system also includes an alarm, which is electrically connected to the controller. When the pH sensor detects that the pH value is lower or higher than a set value, it can transmit a signal to the controller, which then controls the alarm to sound.

[0016] The present invention also provides a control method for a cyclic immersion device for stress corrosion testing based on any one of the above technical solutions, comprising the following steps: S1. Fix the stress corrosion specimen: Use a soft line or metal wire that does not react with the corrosive solution to suspend the stress corrosion specimen with stress clamp and fix it to the bottom of the specimen support. S2. Setting the corrosive solution level: Prepare the corrosive solution according to the test requirements and fill it into the immersion solution tank until the level of the corrosive solution reaches the set position. Measure the level of the corrosive solution using a non-contact level monitoring element. Set the low and high limits of the corrosive solution level based on the PLC. When the corrosive solution level reaches the low limit, open the water solenoid valve; when the corrosive solution level reaches the high limit, close the water solenoid valve. Set the pH reference range of the corrosive solution based on the PLC. Activate the alarm switch when the pH value is lower than the minimum value or higher than the maximum value of the reference range. S3. Setting the lifting rod stroke: Based on the PLC, set the rising and falling positions of the lifting rod, the cycle duration and the lifting speed parameters, start the equipment, complete one cycle of immersion corrosion simulation, and ensure that the stress corrosion sample is completely immersed in the corrosion solution when the lifting rod is in the falling position, and completely removed from the corrosion solution when the lifting rod is in the rising position. S4. Corrosion solution level control communication signal setting: When the stress corrosion sample is out of the corrosion solution, the non-contact level monitoring element and the water solenoid valve are set to the communication enabled state based on the PLC. When the stress corrosion sample is immersed in the corrosion solution, the non-contact level monitoring element and the water solenoid valve are set to the communication disabled state based on the PLC. The water supply tank is filled with distilled water or pure water and is used to replenish the solution when the non-contact level monitoring element detects that the liquid level of the corrosion solution is lower than the set position. S5. Start the equipment controller and conduct a cyclic immersion corrosion test until the corrosion test is completed.

[0017] The present invention achieves the following technical effects compared to the prior art: The present invention provides a circulating immersion device and control method for stress corrosion testing, comprising a frame platform, an immersion solution tank located below the platform surface, and an actuating component, a pH sensor, a non-contact liquid level monitoring element, and a controller mounted on the frame platform. The immersion solution tank holds the corrosive solution. The lower end of the actuating component is connected to the stress corrosion sample and can completely immerse or detach the sample from the corrosive solution in the tank, achieving circulating immersion of the stress corrosion sample. The pH sensor extends into the immersion solution tank to detect the pH value of the corrosive solution and is electrically connected to the controller. The non-contact liquid level monitoring element detects the liquid level height when the stress corrosion sample is completely detached from the corrosive solution in the tank and transmits the liquid level height information to the controller. The controller then uses the liquid level height information detected by the non-contact liquid level monitoring element to... The system controls whether distilled or purified water is added to the immersion solution tank, thereby intermittently monitoring the liquid level of the corrosion solution using a non-contact level monitoring element. Specifically, the non-contact level monitoring element is in monitoring mode when the stress corrosion sample leaves the corrosion solution, and stops monitoring when the sample is immersed. When the liquid level detected by the non-contact level monitoring element reaches the low limit, the immersion solution tank is automatically replenished with water; when the liquid level detected by the non-contact level monitoring element reaches the high limit, water replenishment stops. Throughout this process, liquid level monitoring and automatic water replenishment are performed under the same conditions, avoiding the influence of liquid level fluctuations caused by the stress corrosion sample immersing in or leaving the corrosion solution. This facilitates precise control of the liquid level and concentration of the corrosion solution, keeping them within the experimental error range. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of the circulating immersion device used for stress corrosion testing in Example 1; Figure 2 This is a control system diagram of the circulating immersion device used in the stress corrosion test in Example 1; Figure 3 This is a schematic diagram illustrating the principle of controlling the corrosion liquid level height during corrosion testing using the circulating immersion device in Example 1. In the figure: 1-Frame platform, 2-Lifting drive, 3-Lifting rod, 301-Upper limit switch, 302-Lower limit switch, 4-Sample holder, 5-Immersion solution tank, 6-Water supply tank, 7-Radar level gauge, 8-Water solenoid valve, 9-PH sensor, 10-Alarm, 11-Controller, 12-Stress corrosion sample. Detailed Implementation

[0020] 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.

[0021] The purpose of this invention is to provide a circulating immersion device and its control method for stress corrosion testing, so as to solve the problems existing in the prior art. It can not only achieve precise control of the circulating immersion of stress corrosion samples, but also control the liquid level of the corrosion solution or the concentration of corrosion products to be kept within the test error range.

[0022] 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.

[0023] Example 1 For example, 1- Figure 2As shown, this embodiment provides a circulating immersion device for stress corrosion testing, including a frame platform 1, an immersion solution tank 5 located below the platform surface of the frame platform 1, and an actuating component, a pH sensor 9, a non-contact liquid level monitoring element, and a controller 11 installed on the frame platform 1. The immersion solution tank 5 is used to hold the corrosive solution. The lower end of the actuating component is used to connect to the stress corrosion sample 12 and can drive the stress corrosion sample 12 to be completely immersed or removed from the corrosive solution in the immersion solution tank 5, realizing the circulating immersion of the stress corrosion sample 12. The pH sensor 9 is used to extend into the immersion solution tank 5 and detect the pH value of the corrosive solution in the immersion solution tank 5, and the pH sensor 9 is electrically connected to the controller 11. The non-contact liquid level monitoring element is used to detect the liquid level height when the stress corrosion sample 12 is completely removed from the corrosive solution in the immersion solution tank 5, and transmits the liquid level height information to the controller 11. The controller 11 detects the liquid level height based on the non-contact liquid level monitoring element. The measured liquid level information controls whether distilled or purified water is added to the immersion solution tank 5. This allows the liquid level of the corrosive solution to be monitored intermittently by a non-contact liquid level monitoring element. Specifically, the non-contact liquid level monitoring element is in monitoring mode when the stress corrosion sample 12 leaves the corrosive solution, and stops monitoring when the stress corrosion sample 12 is immersed in the corrosive solution. When the liquid level detected by the non-contact liquid level monitoring element reaches the low limit, the immersion solution tank 5 automatically replenishes water. When the liquid level detected by the non-contact liquid level monitoring element reaches the high limit, the water replenishment in the immersion solution tank 5 terminates. During this process, the liquid level monitoring and automatic water replenishment are carried out under the same conditions, avoiding the influence of liquid level fluctuations caused by the stress corrosion sample 12 being immersed in or removed from the corrosive solution. This facilitates the precise control of the liquid level and concentration of the corrosive solution, keeping them within the experimental error range.

[0024] Specifically, the actuation components include a lifting driver 2, a lifting rod 3, and a lifting bracket. The lifting driver 2 is mounted on the frame platform 1. The lower end of the lifting rod 3 can pass through the table surface of the frame platform 1 and be connected to the lifting bracket. The lower end of the lifting bracket can be detachably connected to several stress corrosion samples 12. The lifting driver 2 is connected to the lifting rod 3 and can drive the lifting rod 3 and the stress corrosion samples 12 to rise and fall.

[0025] The lifting drive 2 includes a drive motor and a drive gear. The output shaft of the drive motor is coaxially connected to the drive gear, and the drive motor drives the drive gear to rotate. One side of the lifting rod 3 is rack-shaped, and the drive gear can mesh with the lifting rod 3. As the drive gear rotates, it drives the lifting rod 3 to rise and fall, so as to realize the periodic up and down movement of the lifting rod 3 and the stress corrosion sample 12 to complete the cyclic immersion corrosion test.

[0026] The upper end of the lifting rod 3 is provided with an upper limit switch 301, and the lower end of the lifting rod 3 is provided with a lower limit switch 302. The drive motor is electrically connected to the controller 11. When the drive gear drives the lifting rod 3, when the drive gear contacts the upper limit switch 301 or the lower limit switch 302, the upper limit switch 301 or the lower limit switch 302 transmits a signal to the controller 11, and causes the controller 11 to control the drive motor to stop working, so as to prevent the drive gear from disengaging from the lifting rod 3.

[0027] The lifting rod 3 is made of stainless steel.

[0028] The non-contact liquid level monitoring element is a radar level gauge 7. Using the radar level gauge 7 to monitor the liquid level avoids the corrosion and sensitivity reduction caused by the long-term exposure of the immersion level gauge to the corrosive solution during use, thereby reducing the failure rate of liquid level control and improving the service life of the equipment. The measuring end face of the radar level gauge 7 is directly facing the corrosive solution in the immersion solution tank 5, and the accuracy of the radar level gauge 7 is not less than 2mm.

[0029] This embodiment also includes a water supply tank 6, a water supply pipe, and a water solenoid valve 8. The water solenoid valve 8 is driven to open and close by a solenoid valve driver. The water supply tank 6 is installed on the platform of the frame 1 and is used to hold distilled water or pure water to replenish the water in the corrosion solution in the immersion solution tank 5 to prevent excessive evaporation. As a preferred embodiment, the corrosion solution in the immersion solution tank 5 is a mixture of water and non-volatile or non-volatile substances such as sodium chloride / sulfuric acid.

[0030] As a preferred embodiment, the height difference between the high and low limits of the corrosive solution is no more than 10 mm, and the total depth of the corrosive solution is no less than 500 mm. This ensures that the total volume change rate during automatic water replenishment of the corrosive solution is no more than 2%, reduces the change in the concentration of corrosive substances in the corrosive solution, and improves the accuracy of the results of the cyclic immersion corrosion experiment.

[0031] As a preferred embodiment, the immersion solution tank 5 has a depth of not less than 600 mm, and the immersion solution tank 5 is made of a material such as glass or PE that does not react with the corrosive solution.

[0032] In a preferred embodiment, the pH reference range of the corrosive solution during the cyclic corrosion test is controlled to be no higher than 0.05. When the pH value detected by the pH sensor 9 exceeds this reference range, the alarm 10 is triggered, indicating that the concentration of corrosive substances in the corrosive solution has decreased due to participation in the reaction or excessive evaporation. Furthermore, when the experimenter learns that the alarm 10 has been triggered due to a decrease in the concentration of the corrosive solution, the corrosive solution should be replaced or corrosive agent added to meet the required concentration. In practical applications, the concentration of the corrosive solution is controlled by both the liquid level and the pH value. The liquid level and pH value of the corrosive solution in the immersion tank 5 are monitored in real time and displayed on the screen of the controller 11, providing an interface for manual assessment of the corrosive solution concentration.

[0033] The lower end of the water supply tank 6 is connected to the upper end of the water supply pipe. The water solenoid valve 8 is installed on the water supply pipe, and the lower end of the water supply pipe extends into the soaking solution tank 5. The water solenoid valve 8 is electrically connected to the controller 11.

[0034] The controller 11 is equipped with parameter setting buttons, a display screen and a PLC programming interface. The display screen can display the liquid level height information monitored by the non-contact liquid level monitoring element and the pH value information monitored by the pH sensor 9 in real time, which is convenient for experimental personnel to observe.

[0035] This embodiment also includes an alarm 10, which is electrically connected to the controller 11. When the pH sensor 9 detects that the pH value is lower or higher than the set value, it can transmit a signal to the controller 11 and cause the controller 11 to control the alarm 10 to sound an alarm.

[0036] The working principle of the circulating immersion device for stress corrosion testing in this embodiment for controlling the corrosion liquid level during corrosion testing is as follows: When the lifting rod 3 is in the lowered position, the stress corrosion sample 12 is immersed in the corrosive solution. At this time, the communication between the radar level gauge 7 and the water solenoid valve 8 is closed, the radar level gauge 7 stops monitoring the liquid level depth, and the water solenoid valve 8 is closed. When the lifting rod 3 is in the raised position, the stress corrosion sample 12 is removed from the corrosive solution and exposed to the air. At this time, the communication between the radar level gauge 7 and the water solenoid valve 8 is opened, and the radar level gauge 7 monitors the liquid level of the corrosive solution. When the radar level gauge 7 detects that the liquid level of the corrosive solution has reached the low limit, the controller 11 drives the water solenoid valve 8 to open, and the immersion solution tank 5 is automatically replenished with water. When the radar level gauge 7 detects that the liquid level of the corrosive solution has reached the high limit, the controller 11 deactivates the actuator of the water solenoid valve 8, drives the water solenoid valve 8 to close, and the replenishment of the immersion solution tank 5 is terminated.

[0037] This embodiment, through the above design, has a simple overall working principle and an automatic liquid replenishment function to compensate for the excessive evaporation of water in the corrosive solution caused by excessively long test cycles. It is suitable for long-cycle cyclic immersion corrosion tests of stress corrosion specimen 12 to evaluate the service performance of materials in cyclic corrosion environments.

[0038] Example 2 This embodiment provides a control method based on the cyclic immersion device for stress corrosion testing in Embodiment 1, including the following steps: S1. Fix the stress corrosion specimen 12. Use a soft line or metal wire that does not react with the corrosive solution to suspend the stress corrosion specimen 12 with stress clamps and fix it to the bottom of the specimen support 4. S2. Setting the corrosive solution level: Prepare the corrosive solution according to the test requirements and fill it into the immersion solution tank 5 until the level of the corrosive solution reaches the set position. Measure the level of the corrosive solution using a non-contact level monitoring element. Set the low and high limits of the corrosive solution level based on the PLC. When the corrosive solution level reaches the low limit, open the water solenoid valve 8. When the corrosive solution level reaches the high limit, close the water solenoid valve 8. Set the pH reference range of the corrosive solution based on the PLC. Set the alarm switch 10 to activate when the pH value is lower than the minimum value or higher than the maximum value of the reference range. S3. Setting the stroke of lifting rod 3: Based on the PLC, set the rising and falling positions, cycle duration and lifting speed parameters of lifting rod 3, start the equipment, complete one cycle of immersion corrosion simulation, and ensure that the stress corrosion sample 12 is completely immersed in the corrosion solution when the lifting rod 3 is in the falling position, and the stress corrosion sample 12 is completely removed from the corrosion solution when the lifting rod 3 is in the rising position. S4. Corrosion solution level control communication signal setting: When the stress corrosion sample 12 is in the state of being removed from the corrosion solution, the non-contact level monitoring element and the water solenoid valve 8 are set to the communication enabled state based on the PLC. When the stress corrosion sample 12 is in the state of being immersed in the corrosion solution, the non-contact level monitoring element and the water solenoid valve 8 are set to the communication closed state based on the PLC. The water supply tank 6 is filled with distilled water or pure water and is used to replenish the water when the non-contact level monitoring element detects that the liquid level of the corrosion solution is lower than the set position. S5. Start the equipment controller 11 to conduct a cyclic immersion corrosion test until the corrosion test is completed.

[0039] Example 3 This embodiment is a specific application of the control method in Embodiment 2 to control the cyclic immersion device for stress corrosion testing in Embodiment 1. This embodiment takes the stress corrosion sensitivity test of a seamless aluminum alloy gas cylinder as an example, and the specific process of the test is as follows: Stress corrosion testing was conducted according to the national standard GB / T 11640-2021. Seamless aluminum alloy gas cylinders were cut into C-shaped specimens, and the C-shaped stress rings were pressurized using bolts, nuts, and insulating sleeves to prepare standard C-shaped stress corrosion specimen 12. Sodium chloride aqueous solution was used as the corrosion solution, with a ratio of 3.5 ± 0.1 parts sodium chloride dissolved in 96.5 parts water. The pH value of the freshly prepared solution should be in the range of 6.4 to 7.2. The cyclic immersion corrosion conditions were as follows: the stress corrosion specimen 12 was immersed in the corrosion solution for 10 minutes, then removed from the corrosion solution and exposed to air for 5 minutes, and this cycle was repeated for 30 days. After preparing the stress corrosion sample 12 and the corrosion solution, pour the corrosion solution into the immersion solution tank 5, and control the corrosion solution depth at 500mm. Use the radar level gauge 7 to measure the distance between the corrosion liquid surface and the signal receiving end of the radar level gauge 7, and denote it as D. Use the controller 11, based on the PLC, to set the high limit of the corrosion liquid surface when the distance between the corrosion liquid surface and the signal receiving end of the radar level gauge 7 is D-5mm, and the low limit of the corrosion liquid surface when the distance between the corrosion liquid surface and the signal receiving end of the radar level gauge 7 is D+5mm. Set the water solenoid valve 8 to open when the corrosion liquid surface reaches the low limit, and set the water solenoid valve 8 to close when the corrosion liquid surface reaches the high limit. Set the alarm 10 to be activated when the pH value is lower than 6.4 or higher than 7.2. Use a PE wire to tie the bolts on the stress corrosion specimen 12, and fix the other end of the PE wire to the specimen holder 4; use the controller 11 to control the lifting rod 3 to descend, and stop descending when the stress corrosion specimen 12 is completely immersed 50mm below the surface of the corrosion solution, and set this height as the descending position of the lifting rod 3; use the controller 11 to control the lifting rod 3 to rise, and stop rising when the stress corrosion specimen 12 is completely removed 50mm from the corrosion solution, and set this height as the rising position of the lifting rod 3. The lifting rod 3 is set to stay in the lowering position for 10 minutes, then raised; the lifting rod 3 is set to stay in the rising position for 50 minutes, then lowered again, thus forming a cyclic lifting condition; the radar level gauge 7 communication is set to be enabled when the lifting rod 3 is in the rising position, and the radar level gauge 7 communication is set to be disabled when the lifting rod 3 is in the lowering position. Add distilled water to the water supply tank 6, then activate the controller 11 for automatic control and conduct a cyclic immersion test; after the cyclic immersion test is completed, turn off and clean the cyclic immersion device; remove the stress corrosion sample 12 for subsequent testing.

[0040] 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 circulating immersion device for stress corrosion testing, characterized in that: The device includes a frame platform, an immersion solution tank located below the platform surface, and an actuating component, a pH sensor, a non-contact liquid level monitoring element, and a controller mounted on the frame platform. The immersion solution tank is used to hold a corrosive solution. The lower end of the actuating component is used to connect a stress corrosion sample and can drive the stress corrosion sample to be completely immersed in or detached from the corrosive solution in the immersion solution tank. The pH sensor is used to extend into the immersion solution tank and detect the pH value of the corrosive solution in the immersion solution tank, and the pH sensor is electrically connected to the controller. The non-contact liquid level monitoring element is used to detect the liquid level height when the stress corrosion sample is completely detached from the corrosive solution in the immersion solution tank and transmits the liquid level height information to the controller. The controller controls whether to add distilled water or purified water to the immersion solution tank based on the liquid level height information detected by the non-contact liquid level monitoring element.

2. The circulating immersion device for stress corrosion testing according to claim 1, characterized in that: The actuation component includes a lifting driver, a lifting rod, and a lifting bracket. The lifting driver is mounted on the frame platform. The lower end of the lifting rod can pass through the surface of the frame platform and is connected to the lifting bracket. The lower end of the lifting bracket can be detachably connected to several stress corrosion samples. The lifting driver is connected to the lifting rod and can drive the lifting rod and stress corrosion samples to rise and fall.

3. The circulating immersion device for stress corrosion testing according to claim 2, characterized in that: The lifting drive includes a drive motor and a drive gear, with the output shaft of the drive motor coaxially connected to the drive gear; one side of the lifting rod is rack-shaped, and the drive gear can mesh with the lifting rod and drive the lifting rod to rise and fall.

4. The circulating immersion apparatus for stress corrosion testing according to claim 3, characterized in that: The upper end of the lifting rod is provided with an upper limit switch, and the lower end of the lifting rod is provided with a lower limit switch. The drive motor is electrically connected to the controller. When the drive gear drives the lifting rod, when the drive gear contacts the upper limit switch or the lower limit switch, the upper limit switch or the lower limit switch transmits a signal to the controller, and the controller controls the drive motor to stop working.

5. The circulating immersion apparatus for stress corrosion testing according to claim 2, characterized in that: The lifting rod is made of stainless steel.

6. The circulating immersion apparatus for stress corrosion testing according to claim 1, characterized in that: The non-contact liquid level monitoring element is a radar liquid level gauge, and the measuring end face of the radar liquid level gauge is facing the corrosive solution in the immersion solution tank. The accuracy of the radar liquid level gauge is not less than 2mm.

7. The circulating immersion apparatus for stress corrosion testing according to claim 1, characterized in that: It also includes a water supply tank, a water supply pipe, and a water solenoid valve. The water supply tank is installed on the platform of the frame and is used to hold distilled water or purified water. The lower end of the water supply tank is connected to the upper end of the water supply pipe. The water solenoid valve is installed on the water supply pipe and the lower end of the water supply pipe extends into the soaking solution tank. The water solenoid valve is electrically connected to the controller.

8. The circulating immersion apparatus for stress corrosion testing according to claim 1, characterized in that: The controller is equipped with parameter setting buttons, a display screen and a PLC programming interface. The display screen can display the liquid level height information detected by the non-contact liquid level monitoring element and the pH value information detected by the pH sensor in real time.

9. The circulating immersion apparatus for stress corrosion testing according to claim 1, characterized in that: It also includes an alarm, which is electrically connected to the controller. When the pH sensor detects that the pH value is lower or higher than the set value, it can transmit a signal to the controller, and the controller can then control the alarm to sound.

10. A control method for a circulating immersion apparatus for stress corrosion testing based on any one of claims 1-9, characterized in that: Includes the following steps: S1. Fix the stress corrosion specimen: Use a soft line or metal wire that does not react with the corrosive solution to suspend the stress corrosion specimen with stress clamp and fix it to the bottom of the specimen support. S2. Setting the corrosive solution level: Prepare the corrosive solution according to the test requirements and fill it into the immersion solution tank until the level of the corrosive solution reaches the set position. Measure the level of the corrosive solution using a non-contact level monitoring element. Set the low and high limits of the corrosive solution level based on the PLC. When the corrosive solution level reaches the low limit, open the water solenoid valve; when the corrosive solution level reaches the high limit, close the water solenoid valve. Set the pH reference range of the corrosive solution based on the PLC. Activate the alarm switch when the pH value is lower than the minimum value or higher than the maximum value of the reference range. S3. Setting the lifting rod stroke: Based on the PLC, set the rising and falling positions of the lifting rod, the cycle duration and the lifting speed parameters, start the equipment, complete one cycle of immersion corrosion simulation, and ensure that the stress corrosion sample is completely immersed in the corrosion solution when the lifting rod is in the falling position, and completely removed from the corrosion solution when the lifting rod is in the rising position. S4. Corrosion solution level control communication signal setting: When the stress corrosion sample is out of the corrosion solution, the non-contact level monitoring element and the water solenoid valve are set to the communication enabled state based on the PLC. When the stress corrosion sample is immersed in the corrosion solution, the non-contact level monitoring element and the water solenoid valve are set to the communication disabled state based on the PLC. The water supply tank is filled with distilled water or pure water and is used to replenish the solution when the non-contact level monitoring element detects that the liquid level of the corrosion solution is lower than the set position. S5. Start the equipment controller and conduct a cyclic immersion corrosion test until the corrosion test is completed.

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