Testing device for testing crack stress corrosion

Abstract

The invention belongs to the technical field of gap stress corrosion testing, and particularly relates to a testing device for testing gap stress corrosion, which comprises a square steel plate, an inner tube is hermetically welded on the top of the square steel plate, an outer tube is sleeved on the outer surface of the inner tube, the outer tube and the inner tube are concentrically welded on the square steel plate, and the inner tube is sleeved on the outer tube. A gap is formed between the inner pipe and the outer pipe, and an electric heating pipe spiral section and an electric heating pipe linear section are inserted into the inner pipe; according to the device designed by the invention, the crack stress corrosion working condition can be fully simulated, after different materials are tested, the microscopic and macroscopic structures of the surface of the pipe wall are detected to present different forms, which indicates that the stress corrosion resistance of different materials under the simulated working condition is different, and the stress corrosion resistance of the different materials under the simulated working condition is greatly improved. Therefore, an important basis is provided for design and model selection of key parts of various devices, and the positive effects of reducing the failure rate of the devices, improving the reliability of the devices and prolonging the service life of the devices are further achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of crevice stress corrosion testing, in particular to a testing device for testing crevice stress corrosion. Background Art

[0002] Crevice corrosion is common in all industries, and material failure and equipment accidents caused by crevice corrosion are not uncommon. Most of the existing devices and standards are used to test the electrochemical corrosion or chemical corrosion between the crevice environment material and the medium by measuring the potential change and corrosion product composition of the material corrosion process. There is no test device that can test the stress corrosion effect on the material caused by the change of physical properties of the medium in the confined space.

[0003] The existing Chinese patent application number CN202410661363.3 discloses a high-throughput test device for evaluating crevice corrosion resistance, including an experimental part and a data test part. The experimental part is mainly composed of a test box, a test chamber, a transition chamber and a chamber cover, and the data test part is composed of a three-electrode system, connecting wires and an electrochemical workstation. When the present invention is used, multiple groups of tests can be carried out simultaneously, the gap width gradient changes and is controllable, and the current and potential changes in the corrosion progress of each group of samples can be synchronously monitored, providing an effective test method for efficiently evaluating the crevice corrosion performance of materials such as stainless steel and titanium alloys.

[0004] The existing device usually consists of a support base, a force plate and a loading nut. The gap between the sample and the stress corrosion test specimen is maintained by a fixing clamp, and the gap distance is adjusted using a loading nut. The sample to be tested is connected to the corrosion test system with wires to collect corrosion potential and current for testing electrochemical corrosion or chemical corrosion between the gaps. It is not possible to test crevice stress corrosion, especially stress corrosion caused by different physical parameters of the medium and materials.

[0005] To this end, the present invention provides a test device for testing crevice stress corrosion. Summary of the invention

[0006] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a test device for testing crevice stress corrosion described in the present invention comprises a square steel plate, an inner tube is seal-welded on the top of the square steel plate, an outer tube is sleeved on the outer surface of the inner tube, the outer tube and the inner tube are concentrically welded on the square steel plate, a gap is provided between the inner tube and the outer tube, a spiral section of an electric heating tube and a straight section of the electric heating tube are inserted in the inner tube, a surface of the outer tube is sleeved with thermal insulation cotton, and the thermal insulation cotton is fixedly mounted on the square steel plate; a temperature sensor is fixedly mounted on the surface of the outer tube, a temperature patrol meter is arranged on the square steel plate, the temperature sensor and the temperature patrol meter are electrically connected, and the temperature patrol meter and the straight section of the electric heating tube are electrically connected through a wire.

[0008] Furthermore, a medium liquid level and a solid-liquid boundary line are set on the surface of the outer tube, and the medium liquid level is above the solid-liquid boundary line.

[0009] Furthermore, the temperature sensor is a temperature-sensing thermocouple, and the temperature inspection instrument is a temperature control PLC.

[0010] Furthermore, the gap between the inner tube and the outer tube is controlled by the diameter and the wall thickness.

[0011] Furthermore, the height of the spiral section of the electric heating tube is consistent with the height of the thermal insulation cotton, and the straight section of the electric heating tube is located on the solid-liquid dividing line.

[0012] Furthermore, a funnel is fixedly mounted on the top of the outer tube, and the funnel is aligned with the gap between the outer tube and the inner tube.

[0013] Furthermore, the gap between the outer tube and the inner tube is uniform, and the temperature sensor is located 5 cm above the square steel plate.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The test device for testing crevice stress corrosion described in the present invention starts the heat source to melt all the medium in the gap between the inner tube and the outer tube. When the liquid level does not reach the medium level, it is replenished through the funnel. When the device is tested normally, the temperature sensor detects the temperature of the medium. When the temperature set by the temperature patrol meter is higher than the melting temperature of the medium, the spiral section of the electric heating tube is powered off, the device dissipates heat, and the medium solidifies from liquid to solid. When the temperature drops to the solidification temperature of the medium, the spiral section of the electric heating tube is powered on, the device heats up, and the medium melts from solid to liquid. In order to eliminate the ratio error and ensure sufficient phase change of the medium in the gap between the tubes, the heat source shutdown temperature is set to be ten degrees Celsius above the melting temperature of the medium, and the heat source startup temperature is ten degrees Celsius below the solidification temperature of the medium. The medium above the solid-liquid dividing line does not undergo phase change. The device designed by the present invention can fully simulate the crevice stress corrosion working condition. After the test and detection of different materials, the microscopic and macroscopic structures of the pipe wall surface present very different forms, indicating that different materials have different abilities to resist stress corrosion under the simulated working condition, thereby providing an important basis for the design and selection of key components of various equipment, thereby further playing a positive role in reducing equipment failure rate, improving equipment reliability and extending equipment service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings.

[0017] Figure 1 It is a schematic diagram of the cross-sectional structure of the thermal insulation cotton in the present invention.

[0018] In the figure: 1. square steel plate; 2. spiral section of electric heating tube; 3. thermal insulation cotton; 4. outer tube; 5. inner tube; 6. wire; 7. funnel; 8. medium liquid level; 9. straight section of electric heating tube; 10. solid-liquid dividing line; 11. temperature patrol meter; 12. temperature sensor. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0020] like Figure 1As shown, a test device for testing crevice stress corrosion described in an embodiment of the present invention includes a square steel plate 1, an inner tube 5 is seal-welded on the top of the square steel plate 1, an outer tube 4 is sleeved on the outer surface of the inner tube 5, the outer tube 4 and the inner tube 5 are concentrically welded on the square steel plate 1, a gap is provided between the inner tube 5 and the outer tube 4, an electric heating tube spiral section 2 and an electric heating tube straight section 9 are inserted in the inner tube 5, the surface of the outer tube 4 is sleeved with thermal insulation cotton 3, and the thermal insulation cotton 3 is fixedly installed on the square steel plate 1; a temperature sensor 12 is fixedly installed on the surface of the outer tube 4, a temperature patrol meter 11 is provided on the square steel plate 1, the temperature sensor 12 and the temperature patrol meter 11 are electrically connected, and the temperature patrol meter 11 and the electric heating tube straight section 9 are electrically connected through a wire 6.

[0021] Specifically, a medium liquid level 8 and a solid-liquid dividing line 10 are set on the surface of the outer tube 4, and the medium liquid level 8 is above the solid-liquid dividing line 10. The temperature sensor 12 is a temperature-sensing thermocouple, and the temperature patrol meter 11 is a temperature control PLC. The gap between the inner tube 5 and the outer tube 4 is controlled by the diameter and wall thickness. The height of the spiral section 2 of the electric heating tube is consistent with the height of the insulation cotton 3, and the straight section 9 of the electric heating tube is on the solid-liquid dividing line 10. A funnel 7 is fixedly installed on the top of the outer tube 4, and the funnel 7 is aligned with the gap between the outer tube 4 and the inner tube 5. The gap between the outer tube 4 and the inner tube 5 is uniform, and the temperature sensor 12 is 5 cm above the square steel plate 1.

[0022] When working, first place the square steel plate 1 on a flat, heat-resistant platform to ensure the stability of the device. Next, pour the weighed solid medium particles into the gap between the inner tube 5 and the outer tube 4 through the funnel 7. During the process, knock the tube wall appropriately so that the granular medium fills the gap between the tubes as much as possible. Then start the heat source to melt the medium in the gap between the inner tube 5 and the outer tube 4. When the liquid level does not reach the medium liquid level 8, it is replenished through the funnel 7. When the device is tested normally, the temperature sensor 12 detects the medium temperature. When the temperature of the temperature patrol meter 11 is set to a temperature higher than the melting temperature of the medium, the electric heating tube spiral section 2 is powered off, the device dissipates heat, and the medium solidifies from liquid to solid. When the temperature drops to the solidification temperature of the medium, the electric heating tube spiral section 2 is powered on, the device heats, and the medium melts from solid to liquid. In order to eliminate the ratio error and ensure that the medium in the gap between the tubes is fully phase-changed, the heat source shutdown temperature is set to be ten degrees Celsius above the melting temperature of the medium, and the heat source opening temperature is ten degrees Celsius below the solidification temperature of the medium. The medium above the solid-liquid boundary line 10 does not undergo phase change. Repeat the above steps to the specified number of times to complete the test.

[0023] It should be noted that the material of the inner tube 5 in the above design operation steps can be replaced, and then the inner tube 5 of different materials can be tested to obtain the required experimental data.

[0024] The device designed in the present invention can fully simulate the crevice stress corrosion working condition. After the test and detection of different materials, the microscopic and macroscopic structures of the pipe wall surface present very different forms, indicating that different materials have different abilities to resist stress corrosion under the simulated working condition, thereby providing an important basis for the design and selection of key components of various equipment, thereby further playing a positive role in reducing equipment failure rate, improving equipment reliability and extending equipment service life.

[0025] Working principle: First, pour the weighed solid medium particles into the gap between the inner tube 5 and the outer tube 4 through the funnel 7. During the process, knock the tube wall appropriately so that the granular medium fills the gap between the tubes as much as possible. Then start the heat source to melt the medium in the gap between the inner tube 5 and the outer tube 4. When the liquid level does not reach the medium level 8, it is replenished through the funnel 7. When the device is tested normally, the temperature sensor 12 detects the temperature of the medium. When the temperature set by the temperature inspection instrument 11 is higher than the melting temperature of the medium, the electric heating tube spiral section 2 is powered off, the device dissipates heat, and the medium solidifies from liquid to solid. When the temperature drops to the solidification temperature of the medium, the electric heating tube spiral section 2 is powered on, the device heats up, and the medium melts from solid to liquid. In order to eliminate the ratio error and ensure that the medium in the gap between the tubes is fully phase-changed, the heat source shutdown temperature is set to be ten degrees Celsius above the melting temperature of the medium, and the heat source opening temperature is ten degrees Celsius below the solidification temperature of the medium. The medium above the solid-liquid dividing line 10 does not undergo phase change. Repeat the above steps to the specified number of times to complete the test.

[0026] The above-mentioned front, back, left, right, top and bottom are all based on the figures in the specification. Figure 1 As a benchmark, according to the person's observation perspective, the side of the device facing the observer is defined as the front, the left side of the observer is defined as the left, and so on.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present invention.

[0028] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A test device for testing crevice stress corrosion, characterized in that: It comprises a square steel plate (1), the top of the square steel plate (1) is sealed with an inner tube (5), the outer surface of the inner tube (5) is sleeved with an outer tube (4), the outer tube (4) and the inner tube (5) are concentrically welded to the square steel plate (1), there is a gap between the inner tube (5) and the outer tube (4), the inner tube (5) is inserted with a spiral section (2) of an electric heating tube and a straight section (9) of an electric heating tube, the surface of the outer tube (4) is sleeved with heat-insulating cotton (3), and the heat-insulating cotton (3) is fixedly mounted on the square steel plate (1); A temperature sensor (12) is fixedly mounted on the surface of the outer tube (4); a temperature patrol meter (11) is arranged on the square steel plate (1); the temperature sensor (12) and the temperature patrol meter (11) are electrically connected; and the temperature patrol meter (11) and the straight section (9) of the electric heating tube are electrically connected via a wire (6).

2. A test device for testing crevice stress corrosion according to claim 1, characterized in that: A medium liquid level (8) and a solid-liquid boundary line (10) are arranged on the surface of the outer tube (4), and the medium liquid level (8) is above the solid-liquid boundary line (10).

3. A test device for testing crevice stress corrosion according to claim 1, characterized in that: The temperature sensor (12) is a temperature-sensing thermocouple, and the temperature inspection instrument (11) is a temperature control PLC.

4. A test device for testing crevice stress corrosion according to claim 1, characterized in that: The gap between the inner tube (5) and the outer tube (4) is controlled by the diameter and the wall thickness.

5. The test device for testing crevice stress corrosion according to claim 1, characterized in that: The height of the spiral section (2) of the electric heating tube is consistent with the height of the thermal insulation cotton (3), and the straight section (9) of the electric heating tube is located on the solid-liquid boundary line (10).

6. A test device for testing crevice stress corrosion according to claim 1, characterized in that: A funnel (7) is fixedly mounted on the top of the outer tube (4), and the funnel (7) is aligned with the gap between the outer tube (4) and the inner tube (5).

7. A test device for testing crevice stress corrosion according to claim 1, characterized in that: The gap between the outer tube (4) and the inner tube (5) is uniform, and the temperature sensor (12) is located 5 cm above the square steel plate (1).

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