Metal plastic deformation damage repairing method based on high-frequency electric pulse

Abstract

The invention discloses a metal plastic deformation damage repair method based on high-frequency electric pulse, which comprises the following steps: S1, carrying out flaw detection on early damage of a damaged metal component, and determining a plastic deformation damage position in the metal component; s2, the damaged metal component is fixed to a pulse current processing device, and the damaged metal component and the exciting electrode are fastened through a clamp; s3, compressing the exciting electrode and the damaged metal component by using a high-temperature-resistant mica plate; and S4, pulse current signals are applied to the two ends of the damaged part, pulse current processing parameters are determined according to the size of the damaged metal component, and the damaged part is repaired through the determined pulse current parameters. According to the method, the problems of plasticity and toughness reduction, stress concentration, mechanical property reduction and the like caused by generation and accumulation of tiny plastic deformation of the material are effectively solved through pulse current repair, and meanwhile, the mechanical properties such as tensile strength of the material can be improved. And in-situ operation can be directly carried out by utilizing the electric pulse device, so that the material damage repair efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material damage repair, and specifically relates to an in-situ repair method for metal plastic deformation damage based on high-frequency electric pulses. Background Art

[0002] During the use of metal materials, tiny plastic deformations will occur, which will lead to hidden damages such as microstructural degradation and local stress concentration. These damages gradually accumulate during the service life of the components, and eventually lead to a decrease in the mechanical properties of the materials, a significant reduction in ductility, damage, cracking and other problems, which will reduce the service life of the components and even cause failure and damage of the components in severe cases. In some key application fields, such as aerospace and automotive industries, serious safety hazards and economic losses may occur. If the hidden damage of metal materials can be repaired and their mechanical properties and machinability can be restored, it can not only avoid catastrophic consequences, but also have great engineering significance for the life extension and remanufacturing of metal materials.

[0003] At present, the most common damage repair technology is heat treatment. Through the annealing process, the heat treatment method rearranges the crystal structure of the material, restores the plastic toughness and mechanical properties of the material, and thus reduces the tendency of internal damage to expand. However, the heat treatment method has high requirements for equipment and component size, and has limited effect on more serious damage. It requires strict control of temperature and time, otherwise it will lead to a decline in material performance. Summary of the invention

[0004] Metal components will produce tiny plastic deformations during service and after being subjected to cyclic loads. The accumulated tiny plastic deformation damage causes the plastic toughness of the material to decrease, and stress concentration occurs in the tiny plastic deformation area, and residual tensile stress accumulates. Finally, cracks occur inside the material, causing the component to crack. In view of the above problems, the purpose of the present invention is to propose a metal plastic deformation damage repair method based on high-frequency electric pulses, which can repair the plastic deformation damage of conductive metal materials, effectively solve the problems of decreased plastic toughness, decreased mechanical properties, stress concentration, etc., and inhibit the generation of defects in the subsequent service process.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A method for repairing metal plastic deformation damage based on high-frequency electric pulses comprises the following steps: S1: Perform flaw detection on damaged metal components, detect early damage to materials, and determine the location of plastic deformation damage in metal components; S2: Fix the damaged metal component to be inspected on the pulse current processing device, and use a clamp to fasten the damaged metal component to the excitation electrode; S3: Use a high temperature resistant mica plate to press the excitation electrode and the damaged metal component; S4: applying a pulse current signal to both ends of the damaged part, determining pulse current processing parameters according to the size of the damaged metal component, and repairing the damaged part using the determined pulse current parameters.

[0006] Furthermore, in step S1, non-destructive testing techniques such as non-linear ultrasonic testing are used to detect damaged metal components.

[0007] Furthermore, in step S2, the excitation electrodes are fixed at both ends of the damaged part of the damaged metal component to reduce the distance between the two electrodes and reduce the resistance when the current flows in the conductor.

[0008] Furthermore, in step S3, the excitation electrode and the component are pressed tightly with a high temperature resistant mica plate to avoid arcing. Pressing the excitation electrode and the component tightly can also make the electrode and the component contact better, increase their contact area, and reduce the resistance during current transmission. In addition, the high temperature resistant mica plate is used to take electrical isolation measures to ensure good electrical insulation performance and ensure the safety of pulse current use.

[0009] Furthermore, the pulse current processing parameters in step S4 include current density, current frequency and power-on processing time, which are three key parameters.

[0010] Furthermore, the pulse current is a rectangular DC pulse current with a current density of 50-150 A / mm 2 The frequency is 400-800 Hz, the pulse width of each pulse current is 100μs, the time interval between adjacent pulses is 1.25-2.5 ms, the entire processing time of the electric pulse treatment process is 1-3 min, and the damaged area is repaired using determined pulse current parameters.

[0011] Compared with the prior art, the present invention aims to solve the problem that plastic deformation during service causes the material ductility to decrease and stress concentration to occur, thus causing the service life of metal components to decrease. Plastic deformation of materials will lead to uneven fatigue performance, strength and ductility, and will also cause stress concentration, accelerate the generation of cracks and the cracking behavior of materials.

[0012] Compared with the prior art, the present invention is not aimed at repairing the crack damage that has already occurred, but at repairing the brittle damage caused by the plastic deformation of the metal, realizing the recovery of its ductility and machinability after the brittle damage, restoring the plastic toughness of the material, facilitating the subsequent reprocessing and strengthening of the workpiece in service, and improving the reuse rate of the damaged material. The present invention effectively solves the problems of decreased plastic toughness, stress concentration, decreased mechanical properties, etc. caused by the generation and accumulation of tiny plastic deformations of the material. At the same time, the use of pulse current repair can also improve the mechanical properties of the material, such as tensile strength. The electric pulse device can be used to directly perform in-situ operations, which improves the efficiency of material damage repair.

[0013] A comparison of the material microstructures before and after repair shows that when the pulse current passes through the damaged location, the thermal effect and electron wind effect not only promote the healing of micro defects and recrystallization of grains, but also eliminate the stress concentration of the material, reduce the residual tensile stress level of the damaged sample, and enhance the tensile strength of the material, effectively improving the mechanical properties, reprocessing performance and service life of the damaged metal materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The schematic diagram of the structure of an example of the in-situ restoration device for metal hidden damage of the present invention is shown in the figure: 1 is a high-frequency pulse power supply, 2 is an excitation electrode, 3 is a wire, 4 is an output electrode, and 5 is a damaged part; Figure 2 This is a comparison chart of the tensile strength of AZ91D magnesium alloy after plastic deformation treatment in step (1) of Example 1 after different treatment processes; Figure 3 This is a comparison chart of the elongation of AZ91D magnesium alloy after plastic deformation treatment in step (1) of Example 1 and after different treatment processes. DETAILED DESCRIPTION

[0015] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0016] The purpose of the present invention is to propose an in-situ repair method and device for metal hidden damage based on high-frequency electric pulses, which can realize in-situ repair of plastic deformation damage of conductive metal materials. Metal components will undergo tiny plastic deformations due to the effect of cyclic stress during service. The accumulation of tiny plastic deformations will cause stress concentration and decreased plastic toughness of the components, reduce mechanical properties, and cause changes in the microstructure of the metal material, making the components prone to cracks, and ultimately causing the components to crack, reducing their service life. The present invention effectively solves the problems of decreased plastic toughness, stress concentration, and decreased mechanical properties caused by the generation and accumulation of tiny plastic deformations. At the same time, the use of pulse current repair can also improve the mechanical properties of the material, such as tensile strength. The electric pulse device can be used to directly perform in-situ operations, improving the efficiency of material damage repair.

[0017] A magnesium alloy tensile specimen was prepared and placed on a tensile machine for a pre-stretching test. The specimen was stretched at a stretching speed of 0.005 mm / s to an elongation of 12%. At this time, the material was stretched to the plastic stage, and plastic deformation damage was introduced. The plastic deformation was irreversible, and the residual elongation of the damaged specimen was obtained. The residual elongation at this time was 13.76% from Comparative Example 2. At this time, the elongation of the damaged specimen was greatly reduced, and the toughness was seriously reduced.

[0018] First, the prepared damaged sample was subjected to nonlinear ultrasonic nondestructive testing to find the location of microstructural deterioration, and the residual stress value of the damaged part was measured by X-ray diffraction method. Nonlinear ultrasonic nondestructive testing and X-ray diffraction methods are non-destructive and highly accurate, and will not introduce additional damage to the test sample.

[0019] Secondly, fasten the damaged specimen to the pulse current device, such as Figure 1 The present invention is a schematic diagram of a device for repairing metal plastic damage by using high-frequency electric pulse processing. The electric pulse repair technology outputs a pulse current signal through a high-frequency pulse power supply 1. The pulse current is injected into the damaged part 5 through a wire 3 via an excitation electrode 2 and an output electrode 4. The output electrode 4 is connected to both ends of the damaged part 5. The output electrode 4 should be fixed at both ends of the damaged part to reduce the distance between the two electrodes, so that the pulse current has the shortest path, reduces the resistance when the current flows in the conductor, and consumes the least energy.

[0020] Next, use high-temperature resistant mica plates to press the excitation electrodes and components to avoid arcing, take electrical isolation measures, and ensure good electrical insulation performance.

[0021] Subsequently, a rectangular DC pulse current signal is applied to both ends of the damaged part, and the pulse current treatment parameters are determined according to the size of the damaged component, among which current density, current frequency and power-on treatment time are three key parameters.

[0022] After the pulse current treatment, nonlinear ultrasonic nondestructive testing and X-ray diffractometer were used to measure the microstructure and residual stress value of the repaired sample to check the degree of completion of the repair.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and in combination with specific embodiments. Embodiment 1:

[0024] Preparation process of alloy 1 1) Plastic deformation damage pretreatment loading treatment The wire-cut AZ91D magnesium alloy specimens after grinding and polishing were placed in the in-situ testing system and stretched to an elongation of 12%. After loading, the specimens showed tensile plastic deformation damage but did not fail, and the damaged specimens were cleaned.

[0025] 2) Pulse current processing The cleaned AZ91D sample was fixed on the copper electrode, and an electric signal was applied to both ends of the damaged part of the sample for pulse current treatment. The current density of the applied current signal was 60A / mm 2 , pulse width of 100μs, frequency of 400Hz, and treatment time of 1min. The mechanical properties of the treated AZ91D specimens were tested, and the residual elongation after repair was 19.15%, the total elongation increased to 31.15%, and the tensile strength was 285.64Mpa. Embodiment 2:

[0026] Preparation process of alloy 2 1) Plastic deformation damage pretreatment loading treatment The wire-cut AZ91D magnesium alloy specimens after grinding and polishing were placed in the in-situ testing system and stretched to an elongation of 12%. After loading, the specimens showed tensile plastic deformation damage but did not fail, and the damaged specimens were cleaned.

[0027] 2) Pulse current processing The cleaned AZ91D sample was fixed on the copper electrode, and an electric signal was applied to both ends of the damaged part of the sample for pulse current treatment. The current density of the applied current signal was 80A / mm 2 , pulse width is 100μs, frequency is 400Hz, and treatment time is 2min. The mechanical properties of the treated AZ91D specimens were tested, and the residual elongation after repair was 23.08%, the total elongation increased to 35.08%, and the tensile strength was 279.87Mpa. Embodiment 3:

[0028] Preparation process of alloy 3 1) Plastic deformation damage pretreatment loading treatment The wire-cut AZ91D magnesium alloy specimens after grinding and polishing were placed in the in-situ testing system and stretched to an elongation of 12%. After loading, the specimens showed tensile plastic deformation damage but did not fail, and the damaged specimens were cleaned.

[0029] 2) Pulse current processing The cleaned AZ91D sample was fixed on the copper electrode, and an electric signal was applied to both ends of the damaged part of the sample for pulse current treatment. The current density of the applied current signal was 120A / mm 2 , pulse width is 100μs, frequency is 800Hz, and treatment time is 3min. The mechanical properties of the treated AZ91D sample were tested, and the residual elongation after repair was 29.01%, the total elongation increased to 41.01%, and the tensile strength was 274.49Mpa. Comparative Example 1:

[0030] Original sample preparation process 1) Mechanical properties test of original specimen The wire-cut AZ91D magnesium alloy specimens after grinding and polishing were placed in the in-situ testing system for tensile testing. The total elongation was 27.20% and the tensile strength was 269.99 MPa.

[0031] Its total elongation is much lower than the lowest total elongation (31.15%) in the embodiment, and its tensile strength is close to the lowest tensile strength (274.49Mpa) in the embodiment. It can be seen that the present invention can repair the plastic deformation damage better under the condition of saving a lot of time and energy cost through the synergistic effect of various process parameters of electric pulse, so that the total elongation of the material is improved, and the tensile strength reaches the requirement of not less than the original sample. Comparative Example 2:

[0032] 1) Plastic deformation damage pretreatment and loading treatment The wire-cut AZ91D magnesium alloy specimens after grinding and polishing were placed in the in-situ testing system and stretched to an elongation of 12%. After loading, the specimens showed tensile plastic deformation damage but did not fail, and the damaged specimens were cleaned.

[0033] 2) Mechanical properties test The cleaned AZ91D sample was placed in the in-situ testing system for another tensile test, and the residual elongation was 13.76%, the total elongation was 25.76%, and the tensile strength was 277.16 MPa. The elongation was less than the minimum elongation of the sample obtained by the present invention, and the total elongation was less than the minimum total elongation of 31.15% of the sample obtained by the present invention. The tensile strength was also close to the minimum tensile strength of 274.49 MPa obtained by the present invention, which shows that the present invention can effectively repair the damaged area.

[0034] In summary, the present invention uses high pulse current to repair plastic deformation damage. The high-frequency pulse current passes through the damaged part, and the continuous electron wind force and Joule heat act on the damaged part, causing the local temperature to rise, repairing the defects and improving the distribution state. At the same time, the thermal effect of the current only acts locally and will not affect other undamaged area tissues. The pulse current not only promotes the healing of micro-defects and the recrystallization of grains, but also eliminates the stress concentration of the material, reduces the residual tensile stress level of the damaged sample, and strengthens the tensile strength of the material. Finally, the mechanical properties of the metal material are repaired, the stress concentration caused by plastic deformation is eliminated, and the service life is extended.

[0035] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for repairing metal plastic deformation damage based on high-frequency electric pulses, characterized in that: The steps include: S1: Perform flaw detection on damaged metal components, detect early damage to materials, and determine the location of plastic deformation damage in metal components; S2: Fix the damaged metal component to be inspected on the pulse current processing device, and use a clamp to fasten the damaged metal component to the excitation electrode; S3: Use a high temperature resistant mica plate to press the excitation electrode and the damaged metal component; S4: applying a pulse current signal to both ends of the damaged part, determining pulse current processing parameters according to the size of the damaged metal component, and repairing the damaged part using the determined pulse current parameters.

2. The method for repairing metal plastic deformation damage based on high-frequency electric pulse according to claim 1, characterized in that: In step S1, nonlinear ultrasonic detection technology is used to detect damaged metal components.

3. The method for repairing metal plastic deformation damage based on high-frequency electric pulse according to claim 1, characterized in that: In step S2, the excitation electrodes are fixed at both ends of the damaged part of the damaged metal component to reduce the distance between the two electrodes and reduce the resistance when the current flows in the conductor.

4. The method for repairing metal plastic deformation damage based on high-frequency electric pulse according to claim 1, characterized in that: The pulse current processing parameters in step S4 include current density, current frequency and power-on processing time.

5. The method for repairing metal plastic deformation damage based on high-frequency electric pulse according to claim 4, characterized in that: The pulse current of the action is a rectangular DC pulse current with a current density of 50-150 A / mm 2 , frequency is 400-800 Hz, the pulse width of each pulse current is 100 μs, the time interval between adjacent pulses is 1.25-2.5 ms, and the entire processing time of the electric pulse treatment process is 1-3 min.

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