Solid-state repairing method for defects of ultrathin-wall component

Abstract

The invention belongs to the technical field of friction stir deposition additive repair, and particularly relates to a solid-state repair method for defects of an ultrathin-wall component. Comprising the steps that a to-be-repaired ultra-thin-wall component defect area is pretreated; the thickness of the ultra-thin wall component is smaller than or equal to 4 mm. The metal bar is put into an induction heating coil for induction heating, so that the metal bar reaches an unmelted softened state; the softened metal bar is rotated at the rotating speed of 100-1000 rpm, stirring friction repair is conducted on the defect area at the feeding speed of 5-50 mm / min, and defect filling and densification are completed; and liquid spraying or gas spraying cooling is conducted on the repaired area. By means of the method, high-quality material regeneration and performance recovery of the difficult-to-repair area can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of additive repair technology of friction stir deposition, specifically relating to a solid-state repair method for defects in ultrathin-walled components. Background Technology

[0002] With the continuous development of the equipment manufacturing and automotive industries, the service life of molds and structural components is constantly being extended, and surface defects and damage are becoming increasingly prominent. Taking steel molds commonly used in the automotive field as an example, during long-term service and high-load cyclic use, defects such as cracks, wear, and corner collapse are easily generated on the mold surface, seriously affecting its dimensional accuracy and service performance. In addition, for some thin-walled structural components (such as engine casings and gearbox housings), defects such as porosity, inclusions, and scratches are difficult to avoid during casting, machining, or assembly. Directly replacing the entire component would not only be costly and time-consuming, but would also result in material waste, which does not meet the current requirements of energy conservation, emission reduction, and sustainable development in the manufacturing industry.

[0003] To address the aforementioned issues, defect repair technology has become a key research and engineering application area in recent years. Traditional repair methods include melting-based processes such as welding, laser cladding, and laser additive manufacturing. These methods share the common characteristic of using a high-energy heat source to locally melt and solidify the metal, achieving material replenishment and bonding. However, due to the large heat input and rapid cooling rate of welding, problems such as hot cracking, porosity, and coarsening of the microstructure are easily generated during the solidification process of the molten pool. These defects not only weaken the strength and toughness of the repaired area but may also prevent the mechanical properties of the repaired component from returning to their original level, limiting its further application in high-performance manufacturing.

[0004] In recent years, with the development of solid-state additive manufacturing technology, a novel technology derived from friction stir welding (FSW)—additive friction stir deposition (AFSD)—has been proposed. This process utilizes a high-speed rotating tool to achieve plastic flow and deposition of materials under solid conditions, eliminating the need for melting. This significantly reduces heat input and avoids the hot cracking and porosity problems common in traditional melting methods, making it a highly efficient and low-thermal-affected solid-state repair and additive manufacturing method. In recent years, researchers have attempted to apply AFSD technology to the surface repair and remanufacturing of lightweight alloy components such as aluminum and magnesium alloys.

[0005] However, a prominent problem with existing AFSD technology in the field of defect repair is the excessive process force. The upsetting force in the AFSD process is usually measured in tons (often exceeding 3 tons). When used for defect repair of thin-walled structural parts, it can easily lead to workpiece bending, deformation, or instability, thereby affecting the dimensional accuracy and mechanical properties of the component. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a solid-state repair method for defects in ultrathin-walled components that can achieve high-quality material regeneration and performance restoration in areas that are difficult to repair.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a solid-state repair method for defects in ultrathin-walled components, comprising: Pre-treatment is performed on the defective area of ​​the ultrathin-walled component to be repaired; the thickness of the ultrathin-walled component is less than or equal to 4 mm. The metal rod is placed in an induction heating coil for induction heating, so that the metal rod reaches a softened state before melting. The softened metal rod is rotated at a speed of 100-1000 rpm and subjected to stirring friction repair in the defect area at a feed rate of 5-50 mm / min to complete defect filling and densification. The repaired area is cooled by liquid spraying or air spraying.

[0008] In one embodiment, during friction stir repair, the repair temperature is 0.6-0.9 times the melting point of the metal rod.

[0009] In one embodiment, cooling the repaired area includes cooling during the friction stir repair process or cooling after the repair is completed.

[0010] In one embodiment, the cooling medium for the cooling process is one or more of compressed air, liquid carbon dioxide, liquid nitrogen, or water.

[0011] In one embodiment, the cooling rate during the cooling process is greater than 50°C / min.

[0012] In one embodiment, a robotic arm is used to hold a metal rod and place it into an induction heating coil for induction heating, and then the robotic arm is used to hold the metal rod for stirring and friction repair.

[0013] In one embodiment, the metal rod is made of aluminum alloy, magnesium alloy, or copper alloy.

[0014] In one embodiment, the metal rod is made of aluminum alloy, and the repair temperature is 500±10℃.

[0015] In one embodiment, the pretreatment involves cleaning the defective area of ​​the ultrathin-walled component to be repaired, removing the surface oxide layer, oil, and impurities.

[0016] Beneficial Effects: In the aforementioned solid-state repair method for defects in ultrathin-walled components, the metal rod is pre-softened to a plastic state (unmelted softened state) by induction heating before friction stirring, significantly reducing its rheological stress. The softened rod acts as a "moving preheater," resulting in a more uniform temperature distribution along the repair path, which is beneficial for obtaining a repair zone with consistent microstructure and properties, and reducing residual stress concentration caused by uneven temperature. Good fluidity reduces the risk of tunneling, trenching, or incomplete welding due to insufficient material flow during friction stirring repair. Since neither the metal rod nor the substrate reaches its melting point, metallurgical defects such as porosity, hot cracking, component segregation, and coarse grains caused by fusion welding are avoided. The repair zone has a dense microstructure, with properties close to or even exceeding those of the substrate. Furthermore, during subsequent rotation at 100-1000 rpm and feeding at 5-50 mm / min, only relatively small axial pressure is required for the material to smoothly fill the defects. This is crucial for ultrathin-walled components, as excessive axial pressure generated by existing friction stirring repair techniques can easily lead to bulging or direct crushing of the thin-walled back side. The heat required for friction stir repair comes partly from the heat carried by the pre-softened bar itself and partly from the secondary heat generated by the friction stir. This avoids the localized instantaneous high temperature peaks caused by the stirring head acting as a concentrated heat source in traditional FSW, reduces the heat-affected zone, results in a smoother overall heat input, a narrower heat-affected zone (HAZ) around the repaired area, and a less severe deterioration of the microstructure properties. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a solid-state repair method for defects in an ultrathin-walled component according to one embodiment. Figure 2 This is a schematic diagram of the structure of a robotic arm according to one embodiment; Figure 3 This is a schematic diagram of an induction heating coil structure according to one embodiment; Figure 4 This is a schematic diagram of the repair results for Comparative Example 1; Figure 5 This is a schematic diagram of the repair result in Example 1; Figure 6 This is a schematic diagram of the repair results in Example 2. Detailed Implementation

[0019] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0022] Please see Figure 1-6 A solid-state repair method for defects in ultrathin-walled components, comprising: S10. Pre-treat the defective area of ​​the ultra-thin-walled component to be repaired; the thickness of the ultra-thin-walled component is less than or equal to 4 mm. Specifically, pretreatment involves cleaning the defective area of ​​the component to be repaired, removing surface oxide layers, oil stains, and impurities to ensure a clean and smooth repair interface, providing good bonding conditions for subsequent repair. For ultra-thin-walled components with a thickness of 4mm or less, the forging force during the AFSD process (often exceeding 3 tons) is typically measured in tons and is therefore unsuitable for repairing defects in ultra-thin-walled components.

[0023] S20. Place the metal rod into the induction heating coil for induction heating, so that the metal rod reaches a softened state before melting. Preferably, a robotic arm holds the metal rod and places it into an induction heating coil for induction heating, causing the rod to soften without melting. The softened state without melting refers to the state where the metal rod is below its solidus temperature but has undergone significant plastic softening. In this state, the material has high plastic fluidity and completely avoids defects such as porosity and hot cracks that may result from melting.

[0024] In one embodiment, a robotic arm grips a metal rod and places it into an induction heating coil for induction heating, followed by friction stirring repair. During the process of the robotic arm removing the metal rod from the induction coil and positioning it at the repair starting point, its spatial position, orientation, and movement speed are precisely controlled. This minimizes heat loss, positioning deviations, and angular offsets that may occur during manual transfer or simple fixture handling. Because the transfer process is rapid and controllable, the pre-softened metal rod enters the repair zone with minimal temperature drop, ensuring that the rod temperature remains strictly within the ideal plasticity window of 0.6-0.9 Tm at the start of stirring, thus optimizing material flowability. Tm represents the melting point temperature of the metal rod. The robotic arm can integrate force sensors and vision / temperature monitoring to achieve "constant pressure control" or "adaptive speed control." When a change in resistance in the repair zone is detected, the feed speed or rotation speed is adjusted in real time to maintain stable heat input and material flow.

[0025] The metal rod is made of aluminum alloy, magnesium alloy, or copper alloy. Preferably, the metal rod is made of aluminum alloy, and the repair temperature is 500±10℃.

[0026] S30. The softened metal rod is rotated at a speed of 100-1000 rpm and subjected to stirring friction repair in the defect area at a feed speed of 5-50 mm / min to complete the defect filling and densification. Specifically, in one embodiment, during friction stir repair, the repair temperature is 0.6-0.9 times the melting point of the metal rod. Under the combined effect of the temperature (0.6-0.9 Tm) and the intense plastic deformation caused by stirring, the original microstructure in the repair area undergoes dynamic recrystallization, forming new, fine equiaxed grains. The equiaxed grain structure makes the properties of the repair area more uniform in all directions. The recrystallization process can "heal" micro-defects, making the microstructure of the repair area denser. In this temperature range, the pre-softened metal rod exhibits extremely high strain rate sensitivity under friction stir shear, and its flow behavior is close to a superplastic state. The material can flow smoothly like a viscous fluid and completely fill every tiny corner of the defect, including the root and irregularly shaped areas, achieving repair without dead angles. The oxide film and contaminants on the defect surface are completely broken down, allowing fresh metal to come into close contact under high temperature and pressure, forming an atomic-scale metallurgical bond.

[0027] S40. Cool the repaired area with liquid spray or air spray.

[0028] Liquid or gas jet cooling is employed to achieve rapid cooling. Rapid cooling effectively "locks in" the fine, uniform dynamically recrystallized grains formed during the friction stir process, preventing excessive growth and thus preserving or even enhancing the strength, hardness, and toughness of the repaired area (fine-grain strengthening). For certain alloys (such as some aluminum alloys), a faster cooling rate can suppress the precipitation of unfavorable second phases or form more favorable metastable phases, optimizing overall performance. Specifically, in one embodiment, the cooling of the repaired area includes cooling during the friction stir repair process or cooling after repair to avoid microstructure coarsening and excessive formation of intermetallic compounds. The cooling medium during the cooling process is one or more of compressed air, liquid carbon dioxide, liquid nitrogen, or water. Preferably, the cooling rate during the cooling process is greater than 50°C / min to ensure the refinement of the repair layer microstructure and interface quality.

[0029] Comparative Example 1 Using conventional AFSD technology, a 3 mm thick thin-walled 6061 aluminum alloy sheet was repaired. The sheet had blind holes with a diameter of 15 mm and a depth of approximately 2 mm. The repair parameters were: spindle speed 400 RPM and feed rate 15 mm / min. The results are as follows: Figure 4 As shown, the circles represent the defect locations, and the substrate shows obvious deformation at the defect locations after repair.

[0030] Example 1 Using the method described in this application, a 3 mm thick thin-walled 6061 aluminum alloy plate was repaired. First, the 6061 aluminum alloy was placed inside an induction heating coil and induction heated to 500°C. The thin-walled plate had blind holes with a diameter of 15 mm and a depth of approximately 2 mm. The repair parameters were: spindle speed 400 RPM and feed rate 15 mm / min. The results are as follows: Figure 5 As shown, the circle represents the defect location, and the substrate did not deform after repair.

[0031] Example 2 Using the method described in this application, a 3.5 mm thick thin-walled 6061 aluminum alloy sheet was repaired. The sheet had blind holes with a diameter of 15 mm and a depth of approximately 2 mm. The repair parameters were: spindle speed 400 RPM and feed rate 15 mm / min. The results are as follows. Figure 6 As shown, the circle represents the defect location, and the substrate did not deform after repair.

[0032] The above are merely preferred embodiments of the present invention. It should be noted that the present invention is not limited to the above embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A solid-state repair method for defects in ultrathin-walled components, characterized in that, include: Pre-treatment is performed on the defective areas of the ultra-thin-walled component to be repaired; The thickness of the ultrathin-walled component is less than or equal to 4 mm; The metal rod is placed in an induction heating coil for induction heating, so that the metal rod reaches a softened state before melting. The softened metal rod is rotated at a speed of 100-1000 rpm and subjected to stirring friction repair in the defect area at a feed rate of 5-50 mm / min to complete defect filling and densification. The repaired area is cooled by liquid spraying or air spraying.

2. The solid-state repair method for defects in ultrathin-walled components according to claim 1, characterized in that, During friction stir repair, the repair temperature is 0.6-0.9 times the melting point of the metal rod.

3. The solid-state repair method for defects in ultrathin-walled components according to claim 2, characterized in that, Cooling the repaired area includes cooling during the friction stir repair process or cooling after the repair is completed.

4. The solid-state repair method for defects in ultrathin-walled components according to claim 3, characterized in that, The cooling medium in the cooling process is one or more of compressed air, liquid carbon dioxide, liquid nitrogen, or water.

5. The solid-state repair method for defects in ultrathin-walled components according to claim 3, characterized in that, The cooling rate during the cooling process is greater than 50℃ / min.

6. The solid-state repair method for defects in ultrathin-walled components according to claim 1, characterized in that, A robotic arm is used to hold a metal rod and place it into an induction heating coil for induction heating. The robotic arm is then used to hold the metal rod for stirring and friction repair.

7. The solid-state repair method for defects in ultrathin-walled components according to claim 1, characterized in that, The metal rod is made of aluminum alloy, magnesium alloy or copper alloy.

8. The solid-state repair method for defects in ultrathin-walled components according to claim 7, characterized in that, The metal rod is made of aluminum alloy, and the repair temperature is 500±10℃.

9. The solid-state repair method for defects in ultrathin-walled components according to claim 1, characterized in that, The pretreatment involves cleaning the defective area of ​​the ultrathin-walled component to be repaired, removing the surface oxide layer, oil, and impurities.

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