A method for evaluating the air tightness reliability of a seam-welded structure based on electrochemical parameters

Abstract

The purpose of this invention is to provide a method for evaluating the airtight reliability of welded structures based on electrochemical parameters. This method takes the weld zone and its interface region of the welded structure as the evaluation object, and combines the correlation between interface state changes and airtight performance degradation under corrosive environments. By analyzing and processing electrochemical parameters that reflect the corrosion behavior and structural state changes of the weld interface, an evaluation criterion for characterizing the airtight reliability of the welded structure is constructed. Furthermore, the processed electrochemical characteristic information is compared with preset evaluation standards or thresholds to determine the airtight reliability level and potential failure risk of the welded structure. This method can provide a reference for failure risk prediction, quality control, and maintenance decisions of welded structures in corrosive environments, and has the characteristics of simple evaluation process, strong applicability, and high engineering application value.

Description

Technical Field

[0001] This invention belongs to the technical field of welded structure reliability evaluation, specifically relating to a method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters. It is applicable to the quantitative evaluation of the airtight reliability of seam welded structures under corrosive environments and the determination of failure risk. Background Technology

[0002] Seam-welded structures, due to their continuous welds and high forming efficiency, are widely used in sealed containers, heat exchangers, pressure pipelines, and aerospace applications. Their airtightness is a crucial indicator of structural safety and service reliability. In practical applications, seam-welded structures typically operate in complex environments for extended periods, subjected to the combined effects of humidity, salt spray, and temperature cycling. This makes the weld and its interface areas susceptible to electrochemical corrosion, adversely affecting the structure's airtightness. Under corrosive conditions, the weld interface area of ​​seam-welded structures often becomes a corrosion-sensitive region due to factors such as uneven microstructure, residual stress concentration, and welding defects. As the corrosion process progresses, micropores and microcracks may gradually form at the weld interface. Under certain conditions, these defects can evolve into gas leakage channels, leading to a gradual deterioration of the airtightness of the seam-welded structure and even airtight failure. Therefore, effectively evaluating the airtight reliability of seam-welded structures under corrosion is a pressing issue in current engineering applications.

[0003] Currently, the main methods for testing the airtightness of welded structures include helium mass spectrometry leak detection, pressure holding method, and pressure decay method. These methods typically focus on detecting the current airtightness of the structure, and are post-event testing methods, making it difficult to assess the reliability of the structure before airtightness failure occurs. Furthermore, these methods often require specific operating conditions and cannot reflect the impact of corrosion processes on the long-term evolution of airtightness, thus limiting their ability to predict airtightness failure risks. On the other hand, electrochemical testing methods, as an important tool for studying the corrosion behavior of metallic materials, have been widely used in the field of material corrosion resistance evaluation. By measuring parameters such as corrosion potential, corrosion current density, polarization resistance, and electrochemical impedance, the corrosion state of materials in specific environments can be effectively characterized. However, existing research mostly focuses on the corrosion resistance analysis of the material bulk or individual welded joints, and a systematic evaluation method that directly correlates electrochemical parameters with the airtightness reliability of welded structures has not yet been developed.

[0004] Existing technologies generally lack a standardized and procedural evaluation method to convert electrochemical test results into hermetic reliability levels or failure risk assessments for welded structures. This results in low utilization efficiency of electrochemical test data in engineering applications, making it difficult to provide direct evidence for safety assessments and maintenance decisions for welded structures. It is necessary to propose a hermetic reliability evaluation method for welded structures based on electrochemical parameters. By establishing a correspondence between electrochemical parameters and hermetic reliability, this method can enable early judgment of hermetic failure risks in welded structures, thereby overcoming the shortcomings of existing technologies in hermetic reliability evaluation of welded structures. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the airtight reliability of welded structures based on electrochemical parameters. By subjecting the welded structure to accelerated corrosion treatment and conducting electrochemical tests, electrochemical characteristic parameters characterizing the corrosion state of the weld interface are extracted, and a correspondence between electrochemical parameters and airtight reliability is established, thereby achieving quantitative evaluation of the airtight reliability of welded structures and determination of failure risk.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] Step 1: Prepare a seam welded structure specimen with a continuous weld seam;

[0008] Step 2: Perform accelerated corrosion treatment on the welded structure specimens to simulate the corrosion process in the service environment;

[0009] Step 3: Establish an electrochemical testing system for the weld interface region;

[0010] Step 4: Perform electrochemical tests on the weld interface area to obtain electrochemical parameters;

[0011] Step 5: Process the electrochemical parameters to construct comprehensive electrochemical characteristic parameters;

[0012] Step 6: Determine the airtight reliability level of the seam weld structure based on comprehensive electrochemical characteristic parameters and output the evaluation results.

[0013] Furthermore, the specific method for preparing the aforementioned seam weld structure specimen is as follows:

[0014] (1) The metal material to be evaluated is welded using a parallel seam welding process to prepare a seam welded structure specimen with a continuous weld. The specimen includes the weld area and its interface area, wherein the weld interface area is the key area for subsequent electrochemical testing.

[0015] (2) To ensure the repeatability of the test results, the welded structure specimen should be cleaned after preparation to remove residual oil and impurities from the welding process.

[0016] Furthermore, the specific method for the corrosion acceleration test is as follows:

[0017] (1) The welded structure sample obtained in step one is placed in a salt spray corrosion chamber for accelerated corrosion treatment.

[0018] (2) Control the corrosion time and environmental parameters to simulate the corrosion process of the welded structure under actual service conditions.

[0019] Furthermore, the specific method for establishing the aforementioned electrochemical testing system is as follows:

[0020] (1) The electrochemical testing system adopts a three-electrode system, which consists of the weld interface region of the welded structure sample as the working electrode, a saturated calomel electrode or silver / silver chloride electrode as the reference electrode, and a platinum electrode or graphite electrode as the counter electrode.

[0021] (2) The electrochemical test medium is a 3.5wt% NaCl aqueous solution that simulates a corrosive environment, and the solution temperature is controlled at 25±1℃.

[0022] Furthermore, the specific method for extracting the electrochemical characteristic parameters is as follows:

[0023] (1) The electrochemical tests include potential polarization tests and electrochemical impedance spectroscopy tests.

[0024] (2) First measure the open circuit potential, and then conduct subsequent tests after the potential stabilizes for 600–1200s.

[0025] (3) The scanning range of the potentiodynamic polarization test is ±0.5V (relative to the open circuit potential), and the scanning rate is 0.5–1.0mV / s, which is used to obtain the corrosion potential and corrosion current density.

[0026] (4) The frequency range for electrochemical impedance spectroscopy testing is 10⁻²Hz–10⁻¹⁰. 5 Hz, with an AC disturbance amplitude of 5–10mV, is used to obtain charge transfer resistance and interface impedance parameters.

[0027] Furthermore, the specific method for processing the electrochemical parameters is as follows:

[0028] (1) Normalize the parameters such as corrosion current density, polarization resistance and charge transfer resistance so that their values ​​are in the range of 0–1.

[0029] (2) The comprehensive electrochemical characteristic parameters described are the weighted sum of multiple normalized electrochemical parameters, wherein the weight of each parameter is set according to experimental statistical results or engineering experience.

[0030] Furthermore, the specific method for determining the airtightness reliability level and outputting the evaluation results is as follows:

[0031] (1) Compare the comprehensive electrochemical characteristic parameters obtained in step five with the preset threshold, and determine the airtight reliability level of the welded structure based on the comparison results, wherein:

[0032] ① When the comprehensive electrochemical characteristic parameters are within the first threshold range, the seam weld structure is determined to have high airtight reliability;

[0033] ② When the comprehensive electrochemical characteristic parameters are within the second threshold range, the seam weld structure is judged to have moderate airtight reliability;

[0034] ③ When the comprehensive electrochemical characteristic parameters exceed the third threshold range, the welded structure is judged to have a risk of airtight failure.

[0035] (2) Output the airtightness reliability level and the corresponding failure risk information in text, table or graphic form.

[0036] V. Beneficial Effects

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. This invention evaluates the airtight reliability of seam welded structures through electrochemical parameters, enabling early detection of airtight failure risks;

[0039] 2. The method described in this invention has clear steps, is easy to operate, and has good repeatability and engineering applicability;

[0040] 3. This invention can complete the evaluation without damaging the welded structure, and is applicable to the airtight reliability assessment of various welded structures. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the parallel seam welding sample preparation according to the present invention.

[0042] Figure 2 This is a schematic flowchart of the gas tightness reliability evaluation method for seam welded structures based on electrochemical parameters described in this invention.

[0043] Figure 3 This is a schematic diagram of the seam weld structure and electrochemical testing area of ​​the present invention;

[0044] Figure 4 This is the equivalent circuit test model of the cover plate and weld interface before and after corrosion of the present invention. Detailed Implementation

[0045] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments. The following embodiments will help those skilled in the art to better understand the invention.

[0046] Step one: In this embodiment, a seam-welded structure specimen with a continuous weld seam is prepared using a typical metallic material. The specimen substrate is a Kovar alloy with a plate thickness of 0.5 mm. Parallel seam welding is employed, with a welding current of 5 kA, a welding speed of 1.5 m / min, and an electrode pressure of 0.3 MPa, thereby forming a continuous and dense weld seam structure. The resulting seam-welded structure specimen includes a weld metal zone, a heat-affected zone, and a weld interface region, with the weld interface region being the focus of subsequent evaluation. After specimen preparation, the specimen surface is ultrasonically cleaned sequentially with anhydrous ethanol and deionized water for 5–10 min, followed by natural drying at room temperature to remove surface oil and impurities, ensuring the stability and repeatability of the test results.

[0047] Step two involves placing the cleaned welded structure sample in an accelerated corrosion environment to simulate its corrosion process under actual service conditions. In this embodiment, the corrosion environment is a neutral salt spray environment, using a 3.5 wt% sodium chloride aqueous solution. The salt spray chamber temperature is controlled at 35 ± 2 °C, and the salt spray deposition rate is controlled at 1.0–2.0 mL / (80 cm²·h). Corrosion times are set to 24 h, 48 h, and 72 h, respectively, to induce different degrees of electrochemical corrosion evolution in the weld interface area.

[0048] Step three: After the corrosion treatment is completed, the sample is allowed to air dry naturally, followed by electrochemical testing of the weld interface area. The electrochemical test uses a three-electrode system, where the working electrode is the weld interface area of ​​the welded structure sample, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum electrode. The test medium is a 3.5 wt% sodium chloride aqueous solution, and the solution temperature is controlled at 25±1℃.

[0049] Step four: During the test, the open-circuit potential of the sample is first measured, and the stabilization time of the open-circuit potential is set to 900 s. When the potential fluctuation is less than ±5 mV, the system is considered to have reached a stable state. Subsequently, a potentiodynamic polarization test is performed, with the scanning potential range set to ±0.5V relative to the open-circuit potential and the scanning rate set to 0.5 mV / s, to obtain the corrosion potential and corrosion current density of the weld interface region.

[0050] Step 5: After completing the potentiodynamic polarization test, perform electrochemical impedance spectroscopy (EIS) on the same region. The frequency range for the EIS test is set from 10⁻²Hz to 10⁻²Hz. 5 The AC disturbance signal amplitude is 10mV at Hz. By fitting impedance spectrum data, the interfacial charge transfer resistance, polarization resistance, and related impedance parameters are obtained to characterize the corrosion state of the weld interface region.

[0051] Step Six: After obtaining the aforementioned electrochemical parameters, the corrosion current density, polarization resistance, and charge transfer resistance are normalized to unify their numerical range to the 0–1 interval. Subsequently, based on the experimental statistical results, each normalized parameter is assigned a corresponding weight, and a weighted summation method is used to construct a comprehensive electrochemical characteristic parameter, which is used to characterize the overall corrosion degree and defect evolution level of the weld interface. Further, the comprehensive electrochemical characteristic parameter is compared with a pre-set airtightness reliability evaluation threshold. In this embodiment, when the comprehensive electrochemical characteristic parameter is less than 0.3, the welded structure is determined to have high airtightness reliability; when the comprehensive electrochemical characteristic parameter is in the 0.3–0.6 range, the welded structure is determined to have medium airtightness reliability; when the comprehensive electrochemical characteristic parameter is greater than 0.6, the welded structure is determined to have a high risk of airtightness failure. The airtightness reliability evaluation results and corresponding failure risk levels are output in textual description or graphical form, providing a basis for evaluating the airtightness performance and predicting the failure risk of welded structures in corrosive environments.

Claims

1. The technical solution adopted in this invention is a method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters, characterized in that... Includes the following steps: Step 1: Prepare a seam welded structure specimen with a continuous weld, wherein the specimen includes the weld zone and its interface region; Step two: The welded structure sample is placed in a preset corrosion environment for accelerated corrosion treatment to simulate the corrosion process of the welded structure under service conditions. Step 3: After the corrosion treatment is completed, electrochemical tests are performed on the weld interface area of ​​the welded structure sample to obtain electrochemical parameters characterizing the corrosion state of the weld interface. Step four: Process the electrochemical parameters to construct comprehensive electrochemical characteristic parameters that characterize the corrosion state of the weld interface; Step 5: Compare the comprehensive electrochemical characteristic parameters with preset thresholds, and determine the airtight reliability level of the seam weld structure based on the comparison results. Step 6: Output the airtightness reliability evaluation results of the seam weld structure and the corresponding failure risk level.

2. The method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters according to claim 1, characterized in that, The preset corrosion environment includes one or more of the following: salt spray environment, humid heat environment, or temperature cycling environment.

3. The method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters according to claim 1, characterized in that, The electrochemical test uses a three-electrode system, where the working electrode is the weld interface region of the seam welded structure sample.

4. The method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters according to claim 1, characterized in that, The electrochemical parameters include one or more of the following parameters: corrosion potential, corrosion current density, polarization resistance, and electrochemical impedance.

5. The method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters according to claim 1, characterized in that, The electrochemical parameters are normalized or standardized to construct the comprehensive electrochemical characteristic parameters.

6. The method for evaluating the airtight reliability of seam welded structures based on electrochemical parameters according to claim 1, characterized in that, Based on the correspondence between the comprehensive electrochemical characteristic parameters and the preset threshold, the airtight reliability of the seam welded structure is divided into high airtight reliability, medium airtight reliability, and low airtight reliability or failure risk state.

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