A simulation and evaluation method and device for the corrosion resistance of a metal in a frozen soil environment

Abstract

The present invention relates to a method and device for simulating and evaluating the corrosion resistance of metals in a frozen soil environment, belonging to the technical field of evaluating the corrosion resistance of metal materials, and solves the problem that there is no reliable evaluation and preliminary screening technology for the corrosion resistance of metals in a frozen soil environment in the prior art, and thus it is impossible to predict the corrosion resistance of metal materials in a frozen soil environment. The present invention provides a simulation and evaluation method, which pre-configures a simulated corrosion solution and sets a temperature curve, and evaluates the corrosion performance of metal materials in a frozen soil environment by the method of full immersion corrosion. The method is used in cooperation with a dedicated device, and can simulate the corrosion behavior of metal materials in a frozen soil environment in a laboratory scenario, and can preliminarily evaluate and compare the corrosion resistance of different types of metal materials in a frozen soil environment, providing support for the selection and research and development of metal materials for equipment or construction in a frozen soil environment.

Description

Technical Field

[0001] The present invention relates to the technical field of evaluating the corrosion resistance of metal materials, and particularly to a method and device for simulating and evaluating the corrosion resistance of metals in a frozen soil environment. Background Art

[0002] With the economic development of China, the development of the western region has become the focus of the next stage. Economic development is inseparable from infrastructure construction. Therefore, highway construction in the alpine regions of the west has also been put on the agenda. Compared with the eastern regions of China, due to the high altitude and low temperature in the western regions, there are a large number of frozen soil layers, making the road foundation construction conditions extremely harsh, and the construction and maintenance of high-grade highways extremely difficult.

[0003] To solve the problems of highway construction and service life in frozen soil areas, by changing the construction method and optimizing the structure to enhance the strength, the stability of the road foundation is increased, uneven settlement of the road is reduced and avoided, the service life is extended, the maintenance volume is reduced, and the comprehensive cost of the whole life cycle of the road is reduced. Inevitably, the amount of steel used in the road structure will increase, mainly including the following categories: guardrails, road signs, and some other auxiliary facilities for maintaining road driving safety; steel bars, steel pipes, steel plates, etc. for road foundation construction; steel plates, profiles, steel cables, etc. for bridge construction.

[0004] In addition to the steel used for frozen soil highways, the equipment set in the frozen soil environment based on scientific research or other special needs is also gradually increasing; for example, high-end equipment for environmental monitoring, seismic wave monitoring, geological exploration or other special purposes, especially high-end equipment that needs to be buried or semi-buried underground, also requires specific material selection according to environmental conditions.

[0005] Corrosion is an important factor leading to the failure of steel. The corrosion resistance of steel determines the amount of material used and the maintenance and replacement cycle. Generally speaking, materials with poor corrosion resistance will consider a sufficient margin during design, increase the amount of material used, and increase the construction cost; for replaceable components, materials with poor corrosion resistance will shorten the service time and increase the replacement frequency, thus increasing the maintenance cost. Therefore, screening suitable materials according to regional conditions, correctly evaluating the corrosion resistance of materials, predicting the service life, and comprehensively considering the manufacturing cost, construction cost, and maintenance cost of materials are effective methods to reduce the comprehensive cost of the whole life cycle of metal materials in the frozen soil environment.

[0006] However, at present, there is still a blank for the method of simulating and evaluating the corrosion behavior of metal materials in the frozen soil environment. Therefore, it is necessary to develop a method for simulating and evaluating the corrosion resistance of metals in the frozen soil environment to provide support for the selection and research and development of metal materials in the subsequent frozen soil environment. Summary of the Invention

[0007] In view of the above analysis, the embodiments of the present invention aim to provide a method and device for simulating and evaluating the corrosion resistance of metals in a frozen soil environment, so as to solve the problem that there is no reliable evaluation and preliminary screening technology for the corrosion resistance of metals in a frozen soil environment in the prior art, and thus it is impossible to predict the corrosion resistance of metal materials in a frozen soil environment.

[0008] The present invention provides a method for simulating and evaluating the corrosion resistance of metals in a frozen soil environment, specifically including the following steps:

[0009] S1: Make a metal sample of a certain specification from the metal to be tested, weigh the metal sample and record it;

[0010] S2: Configure a simulated corrosion solution and completely immerse the metal sample in the simulated corrosion solution, put the container containing the simulated corrosion solution into a closed simulation chamber and perform pre-temperature adjustment;

[0011] S3: Preset a temperature curve in advance, and introduce a circulating gas with controllable temperature into the closed simulation chamber to adjust the temperature in the simulation chamber and start timing, so that the temperature in the chamber changes according to the preset temperature curve;

[0012] S4: After reaching the preset detection time, take out the corroded metal sample, clean it to remove the surface corrosion part, and calculate the corrosion amount through the weight difference before and after;

[0013] The simulated corrosion solution contains NaCl, Na2SO4 and MgCl2;

[0014] The temperature in the simulation chamber is -70°C to 80°C, and changes according to the preset temperature curve. The temperature curve takes 24 hours as a cycle, and the single detection time is 1 to 30 days.

[0015] Specifically, the specific composition of the simulated corrosion solution is by mass percentage: Na2SO4 0.06 to 1%, MgCl2 0.05 to 0.1%, NaCl 3 to 5%, and the rest is deionized water; the pH value of the simulated corrosion solution is 6 to 8.

[0016] Further, when simulating a stable low-temperature frozen soil environment or a permafrost environment, the temperature curve is set to a constant temperature, and the constant temperature is the same as the preset initial temperature; the temperature range is -70°C to -10°C, the temperature remains constant during the simulation process, and the temperature fluctuation ≤ 1°C; the detection time is 1 to 30 days.

[0017] Further, when simulating an alternating low-temperature frozen soil environment, the temperature curve range is between -40°C and 5°C;

[0018] The temperature change cycle is carried out in the same proportion as the temperature change cycle of the simulated environment, and the heating and cooling rates are consistent with the actual temperature curve of the simulated environment; the preset initial temperature is the highest temperature in the temperature curve range.

[0019] The alternating low-temperature frozen soil environment is divided into frozen environment simulation and gradually thawing environment simulation. When simulating the gradually thawing environment, the highest temperature is not lower than the freezing point of the corresponding real environment.

[0020] It should be noted that when simulating the frozen environment in the frozen soil area in the northern part of the Mohe Basin in Northeast China, the temperature range is -40°C to -20°C, and the preset initial temperature is -20°C.

[0021] The first stage: the target temperature is -40 ± 1°C, the cooling rate is 0.5 to 10°C / hour, and after reaching the target temperature, keep warm for a total of 15h.

[0022] The second stage: the target temperature is -20 ± 1°C, the heating rate is 0.5 to 5°C / hour, and after reaching the target temperature, keep warm for a total of 9h.

[0023] Taking 24h as a cycle, the total detection time is 1 to 30 days.

[0024] Specifically, when simulating the short-term frozen soil environment, the temperature curve range is between -5°C and 20°C, and the preset initial temperature is 20°C.

[0025] The first stage: the target temperature is -5 ± 1°C, the cooling rate is 0.5 to 3°C / hour, and after reaching the target temperature, keep warm for a total of 12 to 16h.

[0026] The second stage: the target temperature is 20 ± 1°C, the heating rate is 0.5 to 5°C / hour, and after reaching the target temperature, keep warm for a total of 8 to 12h.

[0027] The first stage and the second stage together are 24h.

[0028] Taking 24h as a cycle, the total detection time is 1 to 30 days.

[0029] Specifically, the specific operation of pre-temperature adjustment in step S2 is: close the simulation chamber 2 to start temperature adjustment, and when the simulated corrosion solution and metal specimens reach the preset initial temperature, proceed to the next step; the pre-temperature adjustment time is 0.5 to 2h, and the purpose is to avoid too large a difference between the target temperature and the initial temperature, which may cause the temperature of the simulated corrosion solution and metal specimens not to reach the preset temperature curve.

[0030] Specifically, the main components of the circulating gas are nitrogen and oxygen, and their ratio and pressure are set according to the atmospheric conditions of the simulated environment.

[0031] The present invention also provides a device for implementing the simulation evaluation method. The device includes a temperature control module 1 and a simulation test module, and the two parts are independent of each other and have no physical connection relationship;

[0032] The temperature control module 1 includes a heat exchange medium circulation system composed of a radiator 13, a four-way reversing valve 11, a first heat exchanger 16, a second expansion valve 151, and a first expansion valve 141 connected in sequence. The four-way reversing valve 11 is also connected to a compressor 12; the first expansion valve 141 is provided with a parallel first check valve 142; the second expansion valve 151 is provided with a parallel second check valve 152;

[0033] The simulation test module includes a closed simulation chamber 2. Inside the simulation chamber, a second heat exchanger 21, a circulation fan 22, a specimen pool 23, and a sensor 25 are arranged. The second heat exchanger 21, the specimen pool 23, and the circulation fan 22 are arranged in sequence to form an annular air path. The sensor 25 is arranged in the upper middle part of the specimen pool 23. The simulation chamber is provided with an exhaust hole, and a negative pressure filter 24 is arranged at the exhaust hole;

[0034] The first heat exchanger 16 and the second heat exchanger 21 are installed close to each other to achieve contactless heat exchange.

[0035] Specifically, the specimen pool 23 is provided with a supporting reagent tank for containing a simulated corrosion solution, and the reagent tank is provided with fins.

[0036] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0037] 1. The simulation evaluation method for the corrosion resistance of metals in frozen soil environments provided by the present invention can preliminarily simulate the corrosion behavior of metals in frozen soil environments in a laboratory scenario, can preliminarily compare and screen the corrosion resistance of different metal materials in frozen soil environments, and can also provide support for the subsequent development of metal materials; the simulated corrosion process is relatively close to the real corrosion process and has strong reference.

[0038] Frozen soil in geology refers to various rocks and soils below 0°C and containing ice. Generally, it can be divided into short-term frozen soil (several hours, several days or even half a month), seasonal frozen soil (half a month to several months), and permafrost (more than several years). Frozen soil is a soil medium extremely sensitive to temperature, containing abundant underground ice, and there is a certain amount of unfrozen water in frozen soil. Therefore, frozen soil has rheological properties, and its long-term strength is far lower than the instantaneous strength characteristics; and with temperature changes, frozen soil continuously changes between frost heaving and thaw settlement, having a great impact on the safety of structures in frozen soil areas.

[0039] The temperature conditions in permafrost regions vary greatly. Taking the Qinghai-Tibet Plateau as an example: the average temperature in the hottest month is 6 - 18°C; in the northwest, nearly 1 / 4 of the area is in the alpine frigid zone of the plateau, with an altitude above 5000 meters, the average annual temperature is -10 - -4°C, and the average temperature in the hottest month is less than 6°C; in the central and western parts, nearly 1 / 4 of the area is in the subalpine zone of the plateau, with an altitude mostly between 4500 - 5000 meters. The average annual temperature is below 0°C, and the average temperature in the hottest month is 6 - 10°C. And Genhe City, Hulunbuir, Inner Mongolia, known as the "cold pole of China", has an average temperature of -5.3°C. The highest temperature of 34°C in 2024 occurred in July, and the lowest temperature of -45°C occurred in January. The historically recorded extreme minimum temperature is -58°C. Due to the large temperature span, the surface permafrost is in a state of freeze-thaw alternation, and the permafrost depth changes with the seasons, bringing great problems to road safety.

[0040] The hydrogeological conditions in permafrost regions are very different from those in plain areas. Taking the salt lake area as an example, affected by the warm and humid climate of the Qinghai-Tibet Plateau, it is gradually desalinated. The downstream Qingshui River has changed from slightly saline water to brine due to the influence of the salt lake discharge; the hydrochemical types of perennial surface water such as salt lakes and Qingshui River and their shallow groundwater are all of the Cl·SO4-Na type, with evaporation crystallization as the dominant role, while the hydrochemical type of the northern river water is HCO3 - Mg·Ca. Its shallow groundwater is similar to the ion composition of the deep groundwater of the Qingshui River, and the overall water quality is weakly alkaline, with the pH value fluctuating between 7.8 - 8.5 in different seasons. The main cations in the water are Ca 2+ 、Mg 2+ dominant, and the main anions are Cl - 、SO4 2- 、HCO3 - dominant. Among them, the Cl - ion concentration is 40 - 190mg / l, the SO4 2- ion concentration is 8 - 25mg / l, and the HCO3 - ion concentration is 190 - 480mg / l, which varies with seasons. The chemical composition of the water is mainly affected by rock weathering and dissolution. The principal component and correlation analysis show that in the salt lake area, Na + 、K + 、Cl - 、Mg 2+ and SO4 2- mainly come from evaporite rocks such as rock salt and magnesium sulfate, and Ca 2+ 、HCO3 - mainly come from silicate rocks such as dolomite and anorthite.

[0041] Due to Cl - 、SO4 2- 、HCO3 -Plasma will corrode metals, so the corrosion resistance requirements of these ions need to be considered when using steel for highway construction in this area; among them, Cl - 、SO4 2- It contributes more to metal corrosion.

[0042] Based on the above-mentioned specific environmental factors, the present invention appropriately simplifies some minor influencing factors while restoring the real environmental corrosion mechanism as much as possible, and strives to simulate and evaluate the metal corrosion behavior in the frozen soil environment through simplified simulation conditions and operation processes.

[0043] Since the method of the present invention is mainly aimed at metal materials buried or semi-buried under frozen soil, a simulated corrosion solution and full immersion method are selected to perform corrosion simulation;

[0044] By preparing a simulated corrosion solution containing NaCl, Na2SO4 and MgCl2, the corrosion behavior of cations and anions that play a major role in metal corrosion in the actual environment is simulated on metal materials;

[0045] By setting the temperature range and temperature curve, the temperature changes in the real environment are simulated. In the real environment, the temperature changes generally change in a "natural day" cycle, so the temperature curve takes 24 hours as a cycle;

[0046] In addition, since metal materials are actually buried or semi-buried underground, the impact of atmospheric corrosion is relatively small, and its impact is ignored in the present invention; however, oxygen in the atmosphere has an important impact on metal corrosion in the soil. It not only participates in the metal oxidation reaction, but also acts as an electron acceptor in the corrosion process, accelerating the occurrence and development of corrosion. The corrosion rate of oxygen on metals increases with increasing temperature and concentration, and the presence of water will also accelerate the corrosion rate of metals. In order to restore the air pressure conditions of the frozen soil environment as much as possible (generally speaking, frozen soil environments are mostly plateaus with lower air pressure) and atmospheric components, the present invention can adjust the composition and air pressure of the circulating gas to make the simulated corrosion process as close to the actual situation as possible;

[0047] It is worth emphasizing that existing full immersion corrosion simulation experiments generally ignore the regulation of gas atmosphere. However, since frozen areas are often located at high altitudes or high latitudes, the air pressure and air composition ratio are significantly different from those in plains or low altitude areas. Therefore, the influence of air / atmosphere must be considered when simulating the corrosion resistance of metal materials in frozen soil environments.

[0048] The evaluation method provided by the present invention can preliminarily simulate the corrosion behavior of metal materials in a frozen soil environment, and can preliminarily evaluate and compare the corrosion resistance of different types of metal materials in a frozen soil environment, providing support for the selection and development of metal materials for equipment or construction in a frozen soil environment.

[0049] 2. According to the environmental characteristics of the specific region being simulated, the present invention can further adjust the temperature curve, and thus achieve targeted simulation of permafrost environment, alternating low-temperature frozen soil environment, and short-term frozen soil environment; it can adjust the composition of the simulated corrosion solution according to the hydrological information of the specific region, adjust the concentration of each component, and add appropriate other components or even sand and gravel, etc., so as to achieve targeted reduction and simulation of the metal corrosion behavior in the specific region, and the evaluation results are more accurate and targeted.

[0050] 3. The present invention provides a supporting device for the above evaluation method. The device includes two parts: a temperature control module and a simulation test module. The two parts are independent of each other and have no physical connection relationship.

[0051] The temperature control module adopts the reverse Carnot cycle and controls the temperature of the simulation test module by changing the heat flow direction. The first heat exchanger is placed in the environment and can exchange heat with the atmosphere; the first heat exchanger adopts an isolation design to exchange heat with the simulation test module (mainly referring to the second heat exchanger), so as to achieve temperature control of the simulation test module on the premise of avoiding corrosive gases in the temperature control module.

[0052] When refrigeration is required, the heat pump makes the heat flow from the second heat exchanger to the first heat exchanger; after the temperature of the second heat exchanger decreases, it absorbs heat from the closed simulation chamber circulation system, resulting in a decrease in its temperature; after the first heat exchanger obtains heat, its temperature rises, and the heat is dissipated into the surrounding atmosphere. When heating is required, the heat pump reverses, and the heat flows from the first heat exchanger to the second heat exchanger. At this time, the temperature of the first heat exchanger decreases and absorbs heat from the surrounding atmosphere; after the second heat exchanger obtains heat, its temperature rises and releases heat to the simulation chamber circulation system to increase its temperature. The second heat exchanger is provided with an electric heater itself, and when the heat in the surrounding environment is insufficient, it can be assisted by the heater to heat up quickly to increase the temperature of the simulation chamber.

[0053] Since the corrosion reagent has a certain volatility, it makes the circulating gas contain certain corrosive components. The closed simulation chamber in the simulation test module is designed to be closed and made of corrosion-resistant materials, and a protective layer is attached to its outer surface; to protect the internal equipment and the surrounding environment, the temperature control module and the simulation test module adopt an isolation design, and the two exchange heat through a heat exchange system to avoid the influence of the simulated gas on the temperature control module.

[0054] The above device can perfectly adapt to and meet the implementation requirements of the evaluation method provided by the present invention, and thus achieve a preliminary simulation of the corrosion behavior of metals in the frozen soil environment in a laboratory scenario, and can preliminarily compare and screen the corrosion resistance of different metal materials in the frozen soil environment, and can also provide support for the subsequent development of metal materials.

[0055] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combined solutions. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification, or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained from the content specifically pointed out in the specification and the drawings. Description of the Drawings

[0056] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs denote the same components.

[0057] Figure 1 It is a schematic diagram of the device (refrigeration mode) for implementing the simulation evaluation method;

[0058] Figure 2 It is a schematic diagram of the temperature control module (heating mode);

[0059] Figure 3 It is a schematic diagram of the reagent tank.

[0060] Reference Signs:

[0061] 1. Temperature control module; 11. Four-way reversing valve; 12. Compressor; 13. Radiator; 141. First expansion valve; 142. First check valve; 151. Second expansion valve; 152. Second check valve; 16. First heat exchanger; 2. Closed simulation chamber; 21. Second heat exchanger; 22. Circulation fan; 23. Specimen pool; 24. Negative pressure filter; 25. Sensor. Detailed Embodiments

[0062] The following will specifically describe the preferred embodiments of the present invention with reference to the drawings. The drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, and are not used to limit the scope of the present invention.

[0063] The frozen soil state is unstable due to the influence of the surrounding environmental temperature and can be roughly divided into the following three types:

[0064] When the temperature is relatively low, the water in the frozen soil solidifies into ice, and other components in the frozen soil combine with the ice to form a relatively stable solid. At this time, the surrounding environment of the steel is relatively stable. However, the pressure change caused by expansion during the solidification process has a certain impact on the steel, and at the same time, the friction change caused by expansion has a negative impact on the external protective layer of the metal. When the temperature rises, the strength of the solidified ice in the frozen soil decreases with the increase in temperature, and melting occurs when the temperature is higher than the freezing point of water. Since the thermal resistance of the metal is much smaller than that of the soil, the frozen soil around the metal will change first during the heating process, and the water and the substances contained in the water transform from a solid state to an ionic state. At this time, the corrosion effect on the metal increases with the increase in ion concentration. When the environmental temperature further increases, the frozen soil completely melts into a flowing state, and the corrosion caused by the environment is the strongest at this time.

[0065] Since the corrosion situation changes with the environment, it is difficult to obtain the corrosion rate at different stages through simple calculations. Therefore, a set of devices and methods capable of simulating the changes in the frozen soil environment are needed for simulation evaluation, and the corrosion amount is quantitatively evaluated.

[0066] The present invention provides a method for simulating and evaluating the corrosion resistance of metals in a frozen soil environment, which specifically includes the following steps:

[0067] S1: Fabricate a metal sample piece of a certain specification from the metal to be tested, weigh the metal sample piece and record it;

[0068] S2: Configure a simulated corrosion solution and completely immerse the metal sample piece in the simulated corrosion solution. Place the container containing the simulated corrosion solution in a closed simulation chamber and perform pre-temperature adjustment;

[0069] S3: Preset a temperature curve in advance, and introduce a circulating gas with controllable temperature into the closed simulation chamber to adjust the temperature in the simulation chamber and start timing, so that the temperature in the chamber changes according to the preset temperature curve;

[0070] S4: After reaching the preset detection time, take out the corroded metal sample piece, clean it to remove the surface corrosion part, and calculate the corrosion amount through the weight difference before and after;

[0071] The described simulation evaluation method can preliminarily simulate the corrosion behavior of metals in a frozen soil environment in a laboratory scenario, can preliminarily compare and screen the corrosion resistance of different metal materials in a frozen soil environment, and can also provide support for the subsequent development of metal materials;

[0072] There are many factors that affect the corrosion resistance of metals. It is generally believed that the corrosion system is composed of materials and the environment. The factors that affect corrosion can be basically divided into internal factors related to the material and external factors related to the medium environment. By simulating external environmental factors and using accelerated or simulated corrosion methods to study the corrosion of materials in specific environments, it is helpful to evaluate the corrosion resistance of materials and is helpful for the final application of the product. Under the premise of restoring the corrosion mechanism of the real environment as much as possible, the present invention appropriately simplifies some minor influencing factors, and strives to simulate and evaluate the corrosion behavior of metals in frozen soil environments through simplified simulation conditions and operating procedures. The simulated corrosion process is close to the real corrosion process and has strong reference value.

[0073] Preferably, the metal sample can be in two shapes, and the specific specifications are as follows:

[0074] Plate specimen: Overall dimensions: length l × width b × thickness h;

[0075] Circular specimen: Overall dimensions: diameter φ×thickness h;

[0076] l, b, φ≤100mm, h is 2~5mm, and the surface area of each sample is ≥10cm 2 The shape and size of the specimen depend on the original conditions of the test material and the test container used. Specimens with large surface area per unit mass and small ratio of side to total area should be used as much as possible. In general, the area perpendicular to the rolling or forging direction shall not be greater than half of the total area of the specimen, but the specimen should not be too large. Specimens of other shapes and sizes may also be used depending on the purpose of the test. The specimen is suspended in the solution by hanging.

[0077] The simulated corrosion solution contains NaCl, Na2SO4 and MgCl2;

[0078] The temperature in the simulation chamber is -70°C to 80°C, and changes according to a preset temperature curve. The temperature curve has a cycle of 24 hours, and a single detection time is 1 to 30 days, for example 1, 2, 3, 5, 10, 15, 20, 25, 30 days.

[0079] Since the method of the present invention is mainly aimed at metal materials buried or semi-buried under frozen soil, a simulated corrosion solution and full immersion method are selected to perform corrosion simulation;

[0080] By preparing a simulated corrosion solution containing NaCl, Na2SO4 and MgCl2, the corrosion behavior of cations and anions that play a major role in metal corrosion in the actual environment is simulated on metal materials;

[0081] By setting the temperature range and temperature curve, the temperature range completely covers the temperature fluctuation range in the real environment. The temperature curve simulates the temperature change in the real environment. And since in the real environment, the temperature change generally takes the "natural day" as a cycle, the temperature curve has a cycle of 24 hours.

[0082] In addition, since in actual situations, metal materials are buried or semi-buried underground, the influence of atmospheric corrosion is relatively small, so this influence is omitted in the present invention. However, oxygen in the atmosphere has an important influence on the corrosion of metals in soil. It not only participates in the metal oxidation reaction but also acts as an electron acceptor during the corrosion process, accelerating the occurrence and development of corrosion. The corrosion rate of metals by oxygen increases with the increase of temperature and concentration, and the presence of water will also accelerate the corrosion rate of metals. In order to restore as much as possible the air pressure conditions (generally, the permafrost environment is mostly in high plateaus with relatively low air pressure) and atmospheric components of the permafrost environment, the present invention can adjust the composition and air pressure of the circulating gas to make the simulated corrosion process as close to the actual situation as possible.

[0083] Specifically, the specific composition of the simulated corrosion solution is by mass percentage: 0.06 - 1% of Na2SO4, 0.05 - 0.1% of MgCl2, 3 - 5% of NaCl, and the rest is deionized water; the pH value of the simulated corrosion solution is 6 - 8. There are significant differences in the hydrographic conditions between permafrost regions and plain areas. Taking the salt lake area as an example, it is gradually desalinated under the influence of the warm and humid climate of the Qinghai-Tibet Plateau. The downstream Qingshui River has changed from slightly saline water to salt water due to the influence of the salt lake discharge; the hydrochemical types of perennial surface waters such as salt lakes and Qingshui River and their shallow groundwater are all of the Cl·SO4-Na type, with evaporation and crystallization as the dominant role, while the hydrochemical type of the northern river water is HCO3-Mg·Ca, and the ion composition of its shallow groundwater is similar to that of the deep groundwater of the Qingshui River, and the overall water quality is weakly alkaline, and the PH value fluctuates between 7.8 - 8.5 with different seasons. The main cations in the water are Ca 2+ and Mg 2+ , and the main anions are Cl - , SO4 2- , HCO3 - . Among them, the Cl - ion concentration is 40 - 190 mg / l, the SO4 2- ion concentration is 8 - 25 mg / l, and the HCO3 - ion concentration is 190 - 480 mg / l, which varies with different seasons. The chemical composition of water is mainly affected by rock weathering and dissolution. The principal component and correlation analysis show that Na + , K + , Cl - , Mg 2+ and SO4 2- in the salt lake area mainly come from evaporite rocks such as rock salt and magnesium sulfate, and Ca2+ , HCO3 - mainly comes from silicate rocks such as dolomite and anorthite. Since Cl - , SO4 2- , HCO3 - ions can all cause corrosion to metals, the corrosion resistance requirements for these several ions need to be considered when using steel for highway construction in this area; among them, Cl - , SO4 2- contribute more to metal corrosion. Through theoretical analysis and experimental verification, the above-mentioned simulated corrosion solution composition can basically reproduce the metal corrosion situation in the frozen soil environment.

[0084] It should be noted that since the corrosion experiment takes a long time, when an accelerated experiment is needed, the concentration of the reagent needs to be increased accordingly, and the environmental temperature needs to be appropriately increased to speed up the reaction rate. The adjustment period of the temperature control curve needs to be synchronously adjusted according to the acceleration ratio. When the alternating freezing and thawing affect the corrosion rate, the purpose of accelerating corrosion is achieved by shortening the heating / cooling time and increasing the number of cycles.

[0085] Furthermore, to simulate the influence of physical damage on the surface of metal materials caused by freeze-thaw on corrosion, a part of sandy soil components can be added to the simulated solution, and the specimen is inserted into the sandy soil and completely covered by the simulated corrosion solution to simulate the additional wear caused by the change of soil freezing volume in the alternating environment. Among them, the corrosion situation of the metal specimen part buried in the sandy soil will be closer to the corrosion situation in the real environment.

[0086] Furthermore, when simulating a stable low-temperature frozen soil environment or a permafrost environment, the temperature curve is set to a constant temperature, and the constant temperature is the same as the preset initial temperature; the temperature range is -70°C to -10°C, such as -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C. During the simulation process, the temperature remains constant, and the temperature fluctuation ≤ 1°C; the detection time is 1 to 30 days, such as 1, 2, 3, 5, 10, 15, 20, 25, 30 days.

[0087] It should be noted that the above simulation mode is applicable to areas where the annual / monthly temperature change is small and the environmental temperature is significantly lower than the freezing point all year round.

[0088] Furthermore, when simulating an alternating low-temperature frozen soil environment, the temperature curve range is between -40°C and 5°C;

[0089] The temperature change period is carried out in the same ratio as the temperature change period of the simulated environment, and the heating and cooling rates are consistent with the actual temperature curve of the simulated environment; the preset initial temperature is the highest temperature of the temperature curve range;

[0090] The alternating low-temperature frozen soil environment is divided into frozen environment simulation and thawing environment simulation. When simulating the thawing environment, the highest temperature is not lower than the freezing point of the corresponding real environment.

[0091] It should be noted that the above simulation mode is applicable to areas with large annual / monthly temperature changes. The environmental temperature may be lower than the freezing point all year round or may be higher than the freezing point for a short time. This simulation mode mainly aims at the fact that when frozen soil is in a frozen state, with large temperature changes in the temperature range, the properties of chemical corrosion and physical corrosion (expansion or contraction) will also change, thus generating a comprehensive and unpredictable corrosion on metal materials.

[0092] Specifically, taking the frozen environment simulation of the frozen soil area in the northern part of the Mohe Basin in Northeast China as an example, the temperature range is set to -40°C to -20°C, and the preset initial temperature is -20°C;

[0093] The first stage: the target temperature is -40±1°C, the cooling rate is 0.5 to 10°C / hour, and after reaching the target temperature, keep warm for a total of 15h;

[0094] The second stage: the target temperature is -20±1°C, the heating rate is 0.5 to 5°C / hour, and after reaching the target temperature, keep warm for a total of 9h;

[0095] Taking 24h as a cycle, the total detection time is 1 to 30 days, such as 1, 2, 3, 5, 10, 15, 20, 25, 30 days.

[0096] Specifically, the above temperature range, heating and cooling rates, and heating and cooling time are determined according to the local specific meteorological conditions and hydrological conditions, generally taking the monthly average value or extreme value, such as the monthly highest temperature (obtained from the daily average value), the average daily sunshine time of this month (obtained from the daily average value), the monthly lowest temperature (obtained from the daily average value), etc.

[0097] Specifically, when simulating the short-term frozen soil environment, the temperature curve range is between -5°C and 20°C, and the preset initial temperature is 20°C;

[0098] The first stage: the target temperature is -5±1°C, the cooling rate is 0.5 to 3°C / hour, and after reaching the target temperature, keep warm for a total of 12 to 16h;

[0099] The second stage: the target temperature is 20±1°C, the heating rate is 0.5 to 5°C / hour, and after reaching the target temperature, keep warm for a total of 8 to 12h;

[0100] The first stage and the second stage total 24h;

[0101] Taking 24h as a cycle, the total detection time is 1 to 30 days, such as 1, 2, 3, 5, 10, 15, 20, 25, 30 days.

[0102] Specifically, since the short-term frozen soil environment is relatively mild, if there is no special need, the above general temperature curve can be used for corrosion simulation, and the simulation evaluation results still have high reliability and reference value.

[0103] It should be noted that whether it is the simulation of the alternating low-temperature frozen soil environment or the short-term frozen soil environment, the cooling and heating rates are variable. The specific cooling and heating rates can be changed according to the actual temperature curve of the simulated environment, such as slow first and then fast, fast first and then slow, etc.

[0104] Specifically, the specific operation of pre-temperature adjustment in step S2 is: start temperature adjustment with the simulation chamber closed, and proceed to the next step when the simulated corrosion solution and the metal sample reach the preset initial temperature; the pre-temperature adjustment time is 0.5 - 2h, aiming to avoid too large a difference between the target temperature and the initial temperature, so as to prevent the temperature of the simulated corrosion solution and the metal sample from not reaching the preset temperature curve.

[0105] Specifically, the main components of the circulating gas are nitrogen and oxygen, and their ratio and pressure are set according to the atmospheric conditions of the simulated environment. For example, nitrogen:oxygen (volume ratio) = 7 - 8:3 - 2, and the pressure is 50 - 100 kPa.

[0106] Since in actual situations, metal materials are buried or semi-buried underground, the influence of atmospheric corrosion is relatively small, so this influence is omitted in the present invention; however, oxygen in the atmosphere has an important influence on the corrosion of metals in soil. It not only participates in the metal oxidation reaction but also acts as an electron acceptor during the corrosion process, accelerating the occurrence and development of corrosion. The corrosion rate of metals by oxygen increases with the increase of temperature and concentration, and the presence of water will also accelerate the corrosion rate of metals. In order to restore as much as possible the air pressure conditions (generally, the frozen soil environment is mostly on the plateau with relatively low air pressure) and atmospheric components of the frozen soil environment, the present invention can adjust the composition and air pressure of the circulating gas to make the simulated corrosion process as close to the actual situation as possible.

[0107] The present invention also provides a device (as shown in Figure 1 ) for implementing the above simulation evaluation method. The device includes two parts: a temperature control module 1 and a simulation test module. The two parts are independent of each other and have no physical connection relationship;

[0108] The temperature control module 1 includes a heat transfer medium circulation system composed of a radiator 13, a four-way reversing valve 11, a first heat exchanger 16, a second expansion valve 151, and a first expansion valve 141 connected in sequence. The four-way reversing valve 11 is also connected to a compressor 12; the first expansion valve 141 is provided with a parallel first check valve 142; the second expansion valve 151 is provided with a parallel second check valve 152;

[0109] The simulation test module includes a closed simulation chamber 2. Inside the simulation chamber, there are a second heat exchanger 21, a circulation fan 22, a specimen cell 23, and a sensor 25. The second heat exchanger 21, the specimen cell 23, and the circulation fan 22 are arranged in sequence to form an annular air path. It should be noted that there is no physical connection between the components arranged in sequence here, but they are only arranged in sequence on the gas circulation path / annular closed path to achieve temperature control of the closed simulation chamber 2. The sensor 25 is arranged in the upper middle part of the specimen cell 23. The simulation chamber is provided with an exhaust hole, and a negative pressure filter 24 is arranged at the exhaust hole;

[0110] The first heat exchanger 16 is closely installed with the second heat exchanger 21 to achieve contactless heat exchange.

[0111] The temperature control module 1 adopts the reverse Carnot cycle and controls the temperature of the simulation test module by changing the heat flow direction. The first heat exchanger 16 is placed in the environment and can exchange heat with the atmosphere; the first heat exchanger 16 adopts an isolation design to exchange heat with the simulation test module (mainly referring to the second heat exchanger 21).

[0112] When refrigeration is required, the heat pump makes the heat flow from the second heat exchanger 21 to the first heat exchanger 16; after the temperature of the second heat exchanger 21 decreases, it absorbs heat from the circulation system of the closed simulation chamber 2, resulting in a decrease in its temperature; after the first heat exchanger 16 obtains heat, its temperature rises, and it dissipates the heat to the surrounding atmosphere. When heating is required, the heat pump reverses, and the heat flows from the first heat exchanger 16 to the second heat exchanger 21. At this time, the temperature of the first heat exchanger 16 decreases, and it absorbs heat from the surrounding atmosphere; after the second heat exchanger 21 obtains heat, its temperature rises, and it releases heat to the simulation chamber circulation system to increase its temperature. The second heat exchanger 21 is provided with an electric heater itself, and when the surrounding environmental heat is insufficient, it can be assisted by the heater to heat up quickly to increase the temperature of the simulation chamber;

[0113] The simulation test module adopts an air-cooled design and simulates the environment around the specimen by changing the temperature and circulation speed of the circulating air. Since the simulated corrosion solution has a certain volatility, it makes the circulating gas contain a certain amount of corrosive components. The closed simulation chamber 2 adopts a corrosion-resistant design to ensure its service life; the simulation chamber is provided with sensors 25 such as temperature, humidity, and pressure to detect the current environmental state; the gas components of the circulation system are mainly nitrogen and oxygen, and their ratio and pressure are set according to the atmospheric conditions of the simulated environment;

[0114] To protect the internal equipment and the surrounding environment, the temperature control module 1 and the simulation test module adopt an isolation design, and the two exchange heat through a heat exchange system to avoid the influence of the simulated gas on the temperature control module 1.

[0115] Specifically, the sample cell 23 is provided with a supporting reagent tank for containing the simulated corrosion solution, and the reagent tank is provided with fins. To improve the heat exchange effect, fins are arranged on the outer side of the reagent tank along the gas flow direction, which can increase the heat exchange area with the gas and enable the reagent in the reagent tank to reach the predetermined temperature faster.

[0116] Specifically, the operation process / principle of the temperature control of the temperature control module 1 is as follows:

[0117] The components inside the temperature control module 1 are connected by pipelines, and the inside of the pipelines is a heat exchange medium. When refrigeration is required, the heat exchange medium enters from the inlet of the compressor 12, is compressed and changes from a gas to a liquid, and at the same time releases heat through the radiator 13. The heat exchange medium in the liquid state passes through the first one-way valve 142 and the second expansion valve 151 and then evaporates from a liquid to a gas due to the pressure reduction, and at the same time absorbs heat through the heat exchanger.

[0118] The first heat exchanger 16 of the temperature control module 1 is installed close to the second heat exchanger 21. Since the heat is transferred to the first heat exchanger 16, the temperature of the gas passing through the second heat exchanger 21 drops, achieving the purpose of refrigeration. The refrigerated gas is pressurized by the circulation fan and then enters the space where the sample cell 23 is located to cool it down and simulate the low-temperature environment of frozen soil (see Figure 1 ).

[0119] When it is necessary to simulate the thawing process of frozen soil, the four-way valve is reversed. The heat exchange medium passes through the compressor 12 and then changes from a gas to a liquid and enters the first heat exchanger 16, while releasing heat. The heat exchange medium that has become a liquid passes through the second one-way valve 152 and the first expansion valve 141 and then becomes a gas due to the pressure reduction, and then exchanges heat with the outside air through the radiator 13 and returns to the compressor 12 through the four-way valve to complete the cycle. The heating process of the temperature control system (see Figure 2 ).

[0120] Refrigeration and heating are completely completed by the heat pump system. A sensor 25 is arranged in the closed simulation chamber 2, which can control the refrigeration and heating amounts according to the current temperature to make the environment in the chamber meet the detection requirements.

[0121] An isolation design is adopted between the temperature control module 1 and the simulation test module (closed simulation chamber 2), and the gases of the two are not connected to avoid the corrosive gas generated by the volatilization of the reagent in the sample cell 23 from affecting the equipment; the simulation chamber adopts a closed design and is also provided with a negative pressure filter 24, which can extract and purify the gas in the chamber when the sample is put in and taken out and then discharge it to avoid environmental pollution caused by the direct discharge of corrosive gas.

[0122] Example / Application Example

[0123] Adopt as Figure 1The device shown is used to conduct corrosion simulation evaluations on four types of steel samples to be tested, namely Q235 steel, Q460 steel, Q690 steel, and Ni-Cr-Mo-V low-alloy high-strength steel.

[0124] Permafrost environment test group

[0125] Specimen size: 50mm×40mm×3mm;

[0126] Solution composition: 0.08% Na2SO4, 0.06% MgCl2, 4% NaCl, and the rest is deionized water;

[0127] Sand addition amount: 100g / L (calculated based on the total volume of the simulated corrosion solution);

[0128] Temperature curve: -40±1°C;

[0129] Cyclic gas parameters: Nitrogen: Oxygen (volume ratio) = 8:2, gas pressure 75kPa;

[0130] The detection time is 72h, with a total of 3 temperature cycles, each temperature cycle being 24h. After the corrosion, the metal specimens are taken out and cleaned to remove the corroded part on the surface. The corrosion amount is calculated based on the weight difference before and after. The corrosion rate calculation formula is as follows:

[0131]

[0132] X---------Specimen corrosion rate, mm / a

[0133] W1--------Specimen weight before the test, g

[0134] W2--------Specimen weight after the test, g

[0135] 87600----Calculation constant

[0136] A---------Specimen surface area, cm 2

[0137] T----------Test time, h

[0138] D---------Specimen material density, g / cm 3

[0139] Table 1 Summary of simulated corrosion results of each sample in the permafrost environment

[0140]

[0141] Alternating low-temperature environment test group

[0142] Specimen size: 50mm×40mm×3mm;

[0143] Solution composition: 0.06% Na2SO4, 0.1% MgCl2, 3.5% NaCl, and the rest is deionized water;

[0144] Sand addition amount: 80 g / L (calculated based on the total volume of the simulated corrosion solution);

[0145] Temperature curve: The temperature range is set to -20°C to 5°C, and the preset initial temperature is 5°C;

[0146] First stage: The target temperature is -20 ± 1°C, the cooling rate is 0.5 - 3°C / hour, and after reaching the target temperature, keep warm for a total of 15 hours;

[0147] Second stage: The target temperature is 5 ± 1°C, the heating rate is 0.5 - 2°C / hour, and after reaching the target temperature, keep warm for a total of 9 hours;

[0148] Circulating gas parameters: Nitrogen: Oxygen (volume ratio) = 7:3, gas pressure 60 kPa;

[0149] The detection time is 3 days (72 hours), with a total of 3 temperature cycles, and each temperature cycle is 24 hours. Take out the corroded metal sample pieces, clean the surface corrosion part, and calculate the corrosion amount through the weight difference before and after.

[0150] Table 2 Summary table of simulated corrosion results of each sample in the alternating low-temperature environment

[0151]

[0152] Short-term frozen soil environment test group

[0153] Specimen size: 50 mm × 40 mm × 3 mm;

[0154] Solution composition: 0.1% Na2SO4, 0.05% MgCl2, 5% NaCl, and the rest is deionized water;

[0155] Sand addition amount: 150 g / L (calculated based on the total volume of the simulated corrosion solution);

[0156] Temperature curve: The temperature range is set to -5°C to 20°C, and the preset initial temperature is 20°C;

[0157] First stage: The target temperature is -5 ± 1°C, the cooling rate is 0.5 - 2°C / hour, and after reaching the target temperature, keep warm for a total of 14 hours;

[0158] Second stage: The target temperature is 20 ± 1°C, the heating rate is 0.5 - 3°C / hour, and after reaching the target temperature, keep warm for a total of 10 hours;

[0159] Recirculating gas parameters: nitrogen: oxygen (volume ratio) = 7.5:2.5, gas pressure 95 kPa;

[0160] The detection time was 3 days (72 h), with a total of 3 temperature cycles, each temperature cycle being 24 h. The corroded metal specimens were taken out and cleaned to remove the corroded parts on the surface, and the corrosion amount was calculated from the weight difference before and after.

[0161] Table 3 Summary table of simulated corrosion results of each sample in short-term frozen soil environment

[0162]

[0163] It can be seen from the results of each experiment that the corrosion rate is positively correlated with the temperature, and the higher the temperature, the higher the corrosion rate. A high corrosion rate requires the steel structure parts to have sufficient design redundancy, or to select corrosion-resistant structure parts. Considering the material cost, when the corrosion rate is low in a low-temperature environment, materials with lower prices can be selected for replacement under the condition of meeting the service life.

[0164] Taking the above test results as an example, when the material is placed in the permafrost environment, calculated according to a service life of 20 years, materials 1-2 (Q460 steel) or 1-3 (Q690 steel) can be selected according to the strength, and the thickness surplus ≥ 3 mm is sufficient. For the short-term frozen soil environment, since the corrosion rates of 2-1 to 2-3 are relatively fast, material 2-4 (Ni-Cr-Mo-V low-alloy high-strength steel) is selected, and a thickness surplus ≥ 0.75 mm is sufficient to meet the 20-year service requirements. Material Q235 steel is not generally recommended because of its poor corrosion resistance and its own strength, and its price is not much different from that of Q460 steel and Q690 steel. After comparison with the coupons buried in the field in the Qinghai-Tibet Plateau, the annual corrosion rate error is not more than 5%, which can meet the needs of predicting and preliminarily screening the corrosion resistance of metal materials in the frozen soil environment.

[0165] As described above, only the specific preferred embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A simulation and evaluation method for the corrosion resistance of a metal in a frozen soil environment, characterized in that Specifically, it includes the following steps: S1: Make a metal sample of a certain specification from the metal to be tested, weigh the metal sample and record it; S2: Prepare a simulated corrosion solution and completely immerse the metal sample in the simulated corrosion solution. Place the container containing the simulated corrosion solution into the closed simulation chamber (2) and perform pre-temperature adjustment; S3: Preset a temperature curve in advance, and introduce a circulating gas with controllable temperature into the closed simulation chamber (2) to adjust the temperature in the simulation chamber and start timing, so that the temperature in the chamber changes according to the preset temperature curve; Among them, the circulating gas is nitrogen and oxygen, and its ratio and pressure are set according to the atmospheric conditions of the simulated environment; By volume ratio, nitrogen: oxygen = 7 - 8:3 - 2, and the pressure is 50 - 100 kpa; S4: After reaching the preset detection time, take out the corroded metal sample, clean it to remove the surface corroded part, and calculate the corrosion amount through the weight difference before and after; The method is aimed at metal materials buried or semi-buried under frozen soil, and a simulated corrosion solution and a fully immersed method are selected for corrosion simulation; The simulated corrosion solution contains NaCl, Na2SO4 and MgCl2; The specific composition of the simulated corrosion solution is by mass percentage: Na2SO4 0.06 - 1%, MgCl2 0.05 - 0.1%, NaCl 3 - 5%, and the rest is deionized water; the pH value of the simulated corrosion solution is 6 - 8; The temperature in the simulation chamber is -70°C to 80°C, and it changes according to the preset temperature curve. The temperature curve has a cycle of 24 hours, and the single detection time is 1 - 30 days; The frozen soil environment is a high-altitude frozen soil environment.

2. The simulation evaluation method according to claim 1, wherein When simulating a stable low-temperature frozen soil environment or a permafrost environment, the temperature curve is set to a constant temperature, and the constant temperature is the same as the preset initial temperature; the temperature range is -70°C to -10°C, the temperature remains constant during the simulation process, and the temperature fluctuation ≤ 1°C; the detection time is 1 - 30 days; this simulation mode is applicable to areas where the annual / monthly temperature change is small and the ambient temperature is significantly lower than the freezing point all year round.

3. The simulation evaluation method according to claim 1, characterized in that When simulating an alternating low-temperature frozen soil environment, the temperature curve range is between -40°C and 5°C; The temperature change cycle is carried out in the same ratio as the temperature change cycle of the simulated environment, and the heating and cooling rates are consistent with the actual temperature curve of the simulated environment; the preset initial temperature is the highest temperature of the temperature curve range; The alternating low-temperature frozen soil environment is divided into a freezing environment simulation and a thawing environment simulation. When simulating the thawing environment, the highest temperature is not lower than the freezing point of the corresponding real environment; This simulation mode is applicable to areas where the annual / monthly temperature change is large, and the ambient temperature is lower than the freezing point all year round or higher than the freezing point for a short time.

4. The simulation evaluation method according to claim 1, characterized in that When simulating a short-term frozen soil environment, the temperature curve range is between -5°C and 20°C, and the preset initial temperature is 20°C; The first stage: the target temperature is -5 ± 1°C, the cooling rate is 0.5 - 3°C / hour, and after reaching the target temperature, keep it warm for a total of 12 - 16 hours; The second stage: the target temperature is 20 ± 1°C, the heating rate is 0.5 - 5°C / hour, and after reaching the target temperature, keep it warm for a total of 8 - 12 hours; The first stage and the second stage together last for 24 hours; Taking 24 hours as a cycle, the total detection time is 1 to 30 days; The short-term frozen soil environment is relatively mild, and the above-mentioned general temperature curve is used for corrosion simulation.

5. The simulation evaluation method according to claim 1, wherein When simulating the frozen soil in the northern part of the Mohe Basin in Northeast China, the temperature range is set to -40°C to -20°C, and the preset initial temperature is -20°C; The first stage: the target temperature is -40 ± 1°C, the temperature reduction rate is 0.5 to 10°C per hour, and after reaching the target temperature, heat preservation is carried out for a total of 15 hours; The second stage: the target temperature is -20 ± 1°C, the temperature increase rate is 0.5 to 5°C per hour, and after reaching the target temperature, heat preservation is carried out for a total of 9 hours; Taking 24 hours as a cycle, the total detection time is 1 to 30 days.

6. The simulation evaluation method according to claim 1, wherein The specific operation of pre-temperature adjustment in step S2 is: start temperature adjustment with the simulation chamber (2) closed, and proceed to the next step when the simulated corrosion solution and the metal specimen reach the preset initial temperature; the pre-temperature adjustment time is 0.5 to 2 hours.

7. An apparatus for implementing the simulation evaluation method according to any one of claims 1 to 6, characterized in that: The apparatus includes two parts, a temperature control module (1) and a simulation test module; The temperature control module (1) includes a heat transfer medium circulation system composed of a radiator (13), a four-way reversing valve (11), a first heat exchanger (16), a second expansion valve (151), and a first expansion valve (141) connected in sequence, and the four-way reversing valve (11) is also connected to a compressor (12); a first one-way valve (142) is provided in parallel with the first expansion valve (141); a second one-way valve (152) is provided in parallel with the second expansion valve (151); The simulation test module includes a closed simulation chamber (2), and a second heat exchanger (21), a circulation fan (22), a specimen pool (23), and a sensor (25) are arranged inside the simulation chamber. The second heat exchanger (21), the specimen pool (23), and the circulation fan (22) are arranged in sequence to form an annular air path. The sensor (25) is arranged in the upper middle part of the specimen pool (23), and the simulation chamber is provided with an exhaust hole, and a negative pressure filter (24) is arranged at the exhaust hole; The first heat exchanger (16) and the second heat exchanger (21) are installed close to each other to achieve contactless heat transfer.

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