Method for recycling metal scraps

Abstract

The invention relates to the technical field of metal scrap recycling, in particular to a metal scrap recycling method. The invention discloses a method for recycling and reusing metal scraps, which comprises the following steps: carrying out magnetic separation, specific gravity separation and spectral analysis classification on copper scraps generated by machining, and combining size homogenization, ultrasonic purification and argon anti-oxidation pretreatment to obtain coarse-grain metal and fine-grain metal; after being subjected to high-energy ball milling and differential preheating activation, the fine-grain metal is mixed with the coarse-grain metal according to a certain proportion and plasticized, deposited and formed under argon protection, and then targeted stress relief annealing, pre-aging and shot blasting treatment are conducted to obtain the bimodal structure metal blank. Through graded pretreatment and bimodal structure design, the purity and reaction activity of the waste are improved, the problems of particle aggregation and interface bonding are solved, toughness synergy and stable performance of the regenerated material are achieved, and high-performance recovery of the copper waste is efficiently achieved.

Description

Technical Field

[0001] This invention relates to the field of metal waste recycling technology, and in particular to a method for recycling and reusing metal waste. Background Technology

[0002] With the rapid development of industrial production, the total amount of copper metal waste generated in the machining field continues to grow. The recycling and reuse of metal waste has become a key direction for resource circulation and environmental protection, and the demand for technologies that can manufacture items from waste scraps or metal particles is becoming increasingly urgent. However, existing metal waste recycling and reuse technologies still have many problems that need to be solved in practical applications, resulting in unstable performance of recycled materials and limited engineering application value.

[0003] Chinese Patent Publication No. CN115446318A discloses a plasticizing and recycling device and method for metal scrap. First, the metal scrap is pre-treated. Ordinary scrap is degreased with acetone and then air-dried. Easily oxidized materials require additional acid washing, followed by ethanol cleaning and air drying. Next, the equipment is started so that the tool head contacts and rotates, filling the pre-treated scrap into a storage hopper. A feeding device pushes the scrap into the hollow cavity of the rotating spindle. Then, the push rod is continuously squeezed, sending the scrap from the cavity to below the tool head. The tool head's rotation causes localized plasticizing deformation between the scrap and the substrate. Next, the substrate is moved, causing the scrap to plasticize and deposit along the moving direction. After a predetermined length is reached, the tool head moves upward, and the substrate moves in the opposite direction, achieving layer-by-layer, multi-pass plasticizing deposition. Finally, the deposition process is repeated until all scrap is deposited, ultimately obtaining a solidified metal plate. This patent only addresses oil stains and surface oxides with simple treatment, failing to classify and screen waste scrap according to its composition and grain size, and lacking a process for specifically removing impurities such as sulfur and phosphorus. Furthermore, it lacks pre-activation treatment under an inert atmosphere, resulting in few active sites on the surface of the metal waste scrap, low oxygen adsorption and desorption efficiency, and difficulty in improving purity and reactivity, thus failing to provide high-quality raw materials for subsequent plasticizing deposition. Material strengthening relies solely on microstructure refinement during plasticizing deformation, resulting in a single strengthening mechanism and limited potential for improving mechanical properties such as hardness, making it difficult to meet the needs of high-end engineering scenarios. Grain refinement is achieved solely through the mechanical action of plasticizing deformation, without employing efficient refinement technologies such as high-energy ball milling, failing to obtain micro / nano-scale fine grains, leading to particle agglomeration and uneven particle size distribution. The lack of preheating activation and other interface modification processes means that the bonding between waste scrap particles and between particles and the substrate is merely physical, failing to form atomic-level metallurgical bonding, resulting in low interfacial bonding strength, residual pores within the material, and difficulty in ensuring density. The single-modal microstructure formed by layer-by-layer plasticization deposition, without constructing a dual-modal system of "fine-grained strengthening - coarse-grained toughening," cannot balance strength and plasticity, exhibiting an inherent contradiction of "increased strength leading to decreased plasticity." This limits the impact toughness and plastic deformation capacity of the cured metal sheet, making it difficult to achieve synergistic optimization of strength and toughness. Furthermore, the recycling process, relying solely on plasticization deposition and layer-by-layer curing without multi-stage heat treatment processes such as stress-relief annealing and pre-aging, easily results in residual macroscopic stress within the formed metal sheet. Uneven precipitation of strengthening phases in the supersaturated solid solution also contributes to dimensional deformation and hardness decay during long-term use, making it difficult to guarantee fatigue resistance, service life, and operational stability.

[0004] Chinese patent CN113549772A discloses a method for the comprehensive recycling of valuable metals from copper-containing waste. The method involves first analyzing the copper-containing waste, then adding lime or quartz flux to form a mixed feedstock based on its composition. This feedstock is then added to a smelting furnace and heated to melt. A reducing agent and oxygen-enriched reducing process air are introduced, separating the reduction slag and molten black copper. The slag is then discharged. Next, an oxidation process air is introduced into the furnace to oxidize the more reactive metals in the molten black copper, forming crude copper melt, which is also discharged. The oxidized slag is retained for the next smelting cycle. The heat required for the oxidation process is partially or entirely derived from the exothermic reaction. However, this patent only analyzes the composition and gangue content of the copper-containing waste for feedstock preparation, without classifying and screening the waste according to grain size and particle size, thus failing to provide homogenized raw materials for subsequent processes. Furthermore, it lacks a specific process for removing harmful impurities such as sulfur and phosphorus, relying solely on flux to adjust the slag shape, resulting in limited impurity removal and impacting the quality of the recovered metal. The entire process relies on the melting, reduction, and oxidation processes of pyrometallurgical smelting, without employing high-energy ball milling or other grain refinement techniques, thus failing to achieve micro- and nano-scale fine-grained structures. No interface modification processes are involved; the molten metal is simply molten and cooled to form the ingot, without any interface bonding strengthening measures, and the issues of interface bonding strength and density remain unresolved. The core objective of the process is to recover crude copper and valuable metals, but no microstructure optimization design is implemented, and no synergistic strengthening system such as "fine-grain strengthening - coarse-grain toughening" is constructed. The final product is a crude copper ingot, achieving only metal recovery without considering the impact of microstructure on the material's mechanical properties, failing to balance comprehensive properties such as strength and plasticity. After the crude copper molten metal is discharged, it is only cooled by casting, without post-treatment processes such as stress-relief annealing and pre-aging, resulting in residual macroscopic stress easily remaining inside the formed copper ingot. The lack of a process to control the precipitation of strengthening phases fails to guarantee product dimensional stability, fatigue resistance, and operational stability, and the post-treatment process is incomplete.

[0005] In summary, current metal waste recycling technologies suffer from deficiencies in pretreatment precision, scientific fine-grain interface treatment, rational microstructure design, and post-processing integrity. These shortcomings result in recycled materials failing to meet practical application requirements in terms of purity, mechanical properties, and stability. Therefore, developing a systematic solution to address these issues and achieve efficient conversion and high-performance regeneration of copper waste is a critical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for recycling and reusing metal waste, specifically comprising the following steps: S001, the initial metal scraps are sorted, size homogenized, surface cleaned and anti-oxidized to obtain clean and anti-oxidized coarse-grained ordinary metal and clean and anti-oxidized fine-grained ordinary metal, which are referred to as pre-treated coarse-grained metal and pre-treated fine-grained metal. S002, the pretreated fine-grained metal is subjected to high-energy ball milling to obtain microcrystalline fine-grained powder, which is then subjected to preheating activation and spheroidization of precipitated phases to obtain a metal powder with a dual-mode microcrystalline fine-grained structure without control agent, denoted as modified metal fine-grained powder. S003, the modified fine-grained metal powder is mixed with the pretreated coarse-grained metal in a certain proportion to obtain an anti-oxidation dual-mode metal composite system, and plasticized deposition treatment is performed to obtain a regenerated dual-mode high-performance metal plate based on solid deposition forming. S004 involves stress-relief annealing and pre-aging treatment of a recycled dual-mode high-performance metal plate formed by solid-state deposition to obtain a dual-mode composite material blank with precipitated phase regulation. After shot blasting, a dual-mode metal blank is obtained.

[0007] In step S001, the initial metal scrap is copper produced by machining. The sorting and separation process involves first separating the metals using a 1000 Gs magnetic field to obtain a non-magnetic metal mixture. This mixture is then subjected to gravity separation at a 10 mm stroke, 200 strokes / min, and a 2° bed inclination angle to obtain a high-density mixture. Spectroscopic analysis reveals copper-based components, designated as ordinary metals. Size homogenization involves preliminary crushing of the sorted single-component metals using a jaw crusher, followed by screening and grading using a drum screen. The coarse-grained components have dimensions of 2–5 mm in length, 0.5–2 mm in width, and 0.5–1.5 mm in thickness, while the fine-grained components have dimensions of 0.1–0.5 mm in length. For surface purification and anti-secondary oxidation treatment of the ordinary metals, the process involves first ultrasonication at 50 °C and 250 W for 15 min using an acetone solution with a liquid-to-solid ratio of 2:1, followed by rinsing three times with deionized water, drying at 30 °C for 2 h, and then introducing 0.08 argon gas. Stored in sealed bags at MPa, clean and oxidation-resistant coarse and fine-grained common metals are obtained.

[0008] In step S002, the high-energy ball milling treatment involves adding 2 wt% zinc stearate, with a ball-to-material ratio of 60:1, ball milling at 300 r / min for 25 h under argon, followed by holding at 400 ℃ under argon for 2 h; the preheating activation and spheroidization treatment of the precipitated phase are carried out at 300 ℃ for 60 min.

[0009] In step S003, the mixing ratio of the modified fine-grained metal powder to the pretreated coarse-grained metal is 2:3, and the mixture is carried out under argon gas at 60 r / min for 30 min. The conditions for plasticizing deposition are as follows: under argon gas, the material is first pressed to a thickness of 2 mm at 2000 r / min, then reduced to 800 r / min and held for 30 s, with a feeding speed of 20 mm / min and a substrate moving speed of 10 mm / min.

[0010] In step S004, the stress-relief annealing and pre-aging treatment conditions are nitrogen gas, holding at 400 ℃ for 1 h, and cooling to room temperature in the furnace; the shot blasting treatment conditions are shot blasting at 0.4 MPa for 5 min.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a systematic graded pretreatment and preactivation process for metal waste and scrap, enhancing the reactivity and physical purity of the waste. By combining physical separation with chemical activation, the processing characteristics of metal waste and scrap are fundamentally improved. At the physical separation level, a multi-stage screening and grading technique is employed, based on differences in particle size distribution, to separate mixed waste into coarse and fine crystalline components. This provides a material basis for subsequent "dual-modal" structural design, as particles of different sizes exhibit drastically different behaviors during compaction and microstructure evolution. At the surface treatment level, the cavitation effect and microjets generated by alkaline solutions or organic solvents in an ultrasonic field are used to peel off organic contaminants and some inorganic salts adhering to the metal surface. The preactivation treatment is carried out under an inert atmosphere, using medium-temperature heat treatment to promote the desorption of adsorbed water on the metal surface, while simultaneously inducing the rearrangement and proliferation of dislocations within the crystal lattice, increasing the surface dangling bond density, and raising the surface energy and chemical barrier of the material, thus providing a strong thermodynamic driving force for subsequent processing. 2. This invention employs a synergistic approach of high-energy ball milling and interface engineering to process metal debris, solving the problems of agglomeration and interfacial bonding in fine-grained metals. High-energy ball milling utilizes prolonged and intense collisions, compression, and shearing between the grinding balls and the material to violently break the metal down to the micro-nano scale, increasing the specific surface area and grain boundary density, resulting in a fine-grain strengthening effect. Differentiated preheating and activation treatments are used to address the characteristics of different metals, utilizing thermal energy to induce atomic migration within the material, promoting the spheroidization transformation of brittle precipitates, reducing stress concentration, and improving the interfacial bonding strength and density. 3. This invention integrates metal waste and debris through a dual-modal structure method, achieving a synergistic improvement in the strength and toughness of recycled materials. Based on the composite strengthening mechanism and microstructure-coordinated deformation method in materials science, pretreated coarse-grained metal particles are mixed with fine-grained particles obtained through high-energy ball milling in a specific ratio. During the subsequent consolidation and forming process, a unique bimodal microstructure is formed. According to the Hall-Petch relationship, the fine-grained region contributes strength due to its abundant grain boundaries; simultaneously, the coarse-grained region, with its stronger dislocation storage capacity and more tortuous crack propagation path, primarily undertakes the function of plastic deformation. This synergistic mechanism of "fine-grained strengthening - coarse-grained toughening" overcomes the contradictory relationship between strength and toughness in traditional single-scale materials. In terms of forming process, solid-state deposition ensures the stable realization of the dual-modal structure by precisely controlling the strain rate and temperature field, while achieving high dimensional accuracy of the product, thus enhancing the engineering application value of metal waste. 4. This invention stabilizes the microstructure and properties of recycled materials prepared from metal scrap and debris through a multi-stage heat treatment process. By holding the material at temperatures below the recrystallization temperature, a recovery process occurs within the material, and atoms eliminate macroscopic residual stress through short-range diffusion, thereby improving dimensional stability and fatigue resistance. Prolonged holding at lower temperatures promotes the controlled precipitation of fine, uniformly distributed reinforcing phases within the supersaturated solid solution. These precipitated phases pin dislocations and grain boundaries, thereby improving the material's strength, hardness, and creep resistance. This ensures that the final product made from complex metal scrap and debris achieves reliable and consistent performance, guaranteeing the stability and practical value of the recycled materials' overall performance. Detailed Implementation

[0012] The present invention will be further described below with reference to specific embodiments. Example

[0013] A method for recycling and reusing metal scrap specifically includes the following steps: S001, 10000 g of initial metal scrap was separated by magnetic separation using a 1000 Gs magnetic field to obtain a non-magnetic metal mixture. This non-magnetic metal mixture was then subjected to gravity separation using a 10 mm stroke, 200 strokes / min, and a 2° bed inclination angle to obtain a high-density mixture. Spectroscopic analysis revealed copper as the base metal, designated as a common metal. The sorted single-component metals were then preliminarily crushed using a jaw crusher, followed by screening and grading using a drum screen. 6000 g of this mixture was first ultrasonically treated with 3000 mL acetone solution at 50 ℃ and 250 W for 15 min, then rinsed three times with deionized water, dried in a forced-air dryer at 30 ℃ for 2 h, and finally stored in a sealed bag under 0.08 MPa argon atmosphere to obtain clean, oxidation-resistant coarse-grained and fine-grained common metals. The initial metal scrap was copper produced by machining, and the coarse-grained components had dimensions of 2–5 mm in length, 0.5–2 mm in width, and 0.5–1.5 mm in thickness. mm, the size of the fine-grained component is 0.1~0.5 mm in length, clean and oxidation-resistant coarse-grained ordinary metal and clean and oxidation-resistant fine-grained ordinary metal are referred to as pretreated coarse-grained metal; S002, 50 g of zinc stearate was added to 2500 g of pretreated fine-grained metal at a ball-to-material ratio of 60:1. The mixture was ball-milled at 300 r / min for 25 h under argon, and then held at 400 ℃ under argon for 2 h to obtain microcrystalline fine-grained powder. The powder was then held at 300 ℃ for 60 min to obtain a metal powder with a dual-mode microcrystalline fine-grained structure without the control agent, which was denoted as modified metal fine-grained powder. S003, 2000 g of modified fine-grained metal powder and 3000 g of pretreated coarse-grained metal were mixed under argon gas at 60 r / min for 30 min to obtain an oxidation-resistant dual-mode metal composite system; under argon gas conditions, it was pressed to a thickness of 2 mm at 2000 r / min, then reduced to 800 r / min and held for 30 s, with a feeding speed of 20 mm / min and a substrate moving speed of 10 mm / min; thus, a regenerated dual-mode high-performance metal plate based on solid-state deposition was obtained. S004, a regenerated dual-mode high-performance metal plate based on solid-state deposition was heated at 400 ℃ for 1 h with nitrogen and then cooled to room temperature in the furnace to obtain a dual-mode composite material blank with precipitated phase control. The blank was shot-blasted at 0.4 MPa for 5 min to obtain a dual-mode metal blank, which was recorded as the test sample.

[0014] Comparative Example 1 A method for recycling and reusing metal waste lacking graded pretreatment specifically includes the following steps: The difference from the embodiment is: In S001, no size homogenization process is performed, and there is no division of coarse and fine grain components, resulting in a clean, oxidation-resistant single-grained ordinary metal. The raw material in S002 is a pretreated single-particle-size metal without distinction between coarse and fine crystal materials. After processing, it yields a single-mode metal powder with microcrystalline structure and no control agent. In S003, the coarse and fine crystal powder mixing step is not performed. Only 5000 g of metal powder with microcrystalline single mode is used to control the microcrystalline single mode to obtain a regenerated single mode high performance metal plate. In S004, the recycled single-mode high-performance metal plate is processed in the same way as in the example to obtain a single-mode microstructure metal blank, which is designated as control 1.

[0015] Comparative Example 2 A method for recycling and reusing metal waste lacking high-energy ball milling and interface engineering treatment specifically includes the following steps: The difference from the embodiment is: In S002, ordinary fine-grained metal powder without control agent is obtained by replacing high-energy ball milling with ordinary grinding at 150 r / min for 10 h, without preheating activation and spheroidization of precipitated phase. In S003, the control agent is replaced by ordinary fine-grained metal powder, and the modified fine-grained metal powder is replaced by ordinary fine-grained metal powder. The remaining steps are the same as in the example to obtain a recycled high-performance metal plate. In S004, the recycled high-performance metal plate is processed in the same way as in the example to obtain a common metal blank, which is designated as control 2. Step (S001) is the same as in the embodiment.

[0016] Comparative Example 3 A method for recycling and reusing metal scrap lacking a dual-modal structure specifically includes the following steps: The difference from the embodiment is: After sorting, size homogenization, surface cleaning and anti-oxidation treatment in S001, clean and anti-oxidation coarse-grained ordinary metal is obtained, which is denoted as pretreated coarse-grained metal. In S003, coarse and fine grains are not mixed. The pretreated coarse-grained metal is directly used for plastic deposition to obtain a regenerated single-grain high-performance metal plate. S002 is not performed; S004 is the same as in the example, and a metal blank with a single grain structure is obtained, which is designated as control 3.

[0017] Comparative Example 4 A method for recycling and reusing metal scrap lacking multi-stage heat treatment specifically includes the following steps: The difference from the embodiment is that in S004, stress-relief annealing and pre-aging treatment are not performed, but shot blasting is performed directly to obtain a bimodal metal billet without precipitate phase control, which is referred to as control product 4.

[0018] Experimental Example 1 This experimental example verifies the systematic graded pretreatment and preactivation effects of the test sample of the embodiment and control sample 1 of Comparative Example 1, specifically including the following steps: 1. Sample preparation The test sample and reference standard 1 were ground separately and passed through a 200-mesh sieve to obtain the sample.

[0019] 2. Purity determination Take 5 g of sample and detect impurity elements such as sulfur, phosphorus, and oxygen using an X-ray fluorescence spectrometer with an excitation voltage of 40 kV and an excitation current of 50 mA. The detection time is 30 s for each element. Each sample is in triplicate. Calculate the sum of the average mass fractions of impurity elements such as sulfur, phosphorus, and oxygen to obtain the purity. The results are shown in Table 1.

[0020] 3. Reactivity Test Take 1 g of sample, degas at 120 ℃ for 2 h, use nitrogen as adsorption gas, and determine the specific surface area according to the BET multi-point adsorption method. Each sample is in triplicate, and the average value is taken to obtain the specific surface area. The results are shown in Table 1.

[0021] 4. Verification of thermal activation effect Take 1 g of sample, degas at 170 ℃ for 2 h, and analyze it at 600 ℃ for 40 s using an oxygen, nitrogen and hydrogen analyzer. Each sample is repeated in triplicate, and the average value is taken to obtain the surface adsorbed oxygen content, which is recorded as the content before treatment. Take 1 g of sample and place it in a high-temperature furnace. Heat the sample from room temperature to 300 ℃ at 5 ℃ / min with argon gas and hold for 1 h. Cool the sample with the furnace and degas at 170 ℃ for 2 h. Analyze the sample at 600 ℃ for 40 s using an oxygen, nitrogen and hydrogen analyzer. Perform three replicates for each sample and take the average value to obtain the surface adsorbed oxygen content, which is recorded as the content after treatment. The oxygen content change rate was calculated based on the ratio of the difference between the content before and after treatment to the content before treatment. The measurement results are shown in Table 1.

[0022] Table 1. Results of purity determination, reactivity test, and thermal activation effect verification.

[0023] As can be seen from Table 1, the samples of the Example (with graded pretreatment) are superior to those of Comparative Example 1 (without graded pretreatment) in terms of core indicators. Graded pretreatment can improve the quality of metal waste recycling.

[0024] The purity of the Examples (99.1%) was higher than that of Comparative Example 1 (98.4%), indicating that the fractional pretreatment reduced residual impurities. The specific surface area of ​​the Examples (2.9 m² / g) was greater than that of Comparative Example 1 (2.3 m² / g), indicating stronger reactivity. The rate of change in oxygen content of the Examples (27.5%) was greater than that of Comparative Example 1 (19.8%), indicating better thermal activation.

[0025] In summary, graded pretreatment (separation of coarse and fine grain components and targeted treatment) can effectively improve the purity, reactivity, and thermal activation performance of recycled copper metal, and is a key step in improving the quality of copper metal waste recycling and reuse.

[0026] Experiment Example 2 This experimental example uses the test sample and control sample 2 (comparative example 2) of the embodiment to test hardness and wear resistance, specifically including the following steps: 1. Sample pretreatment Wipe the surface of the test sample and reference sample 2 with anhydrous ethanol, and dry them in a forced-air dryer at 30 ℃ for 1 h to obtain sample 1.

[0027] 2. Hardness Measurement Place sample 1 on a hardness tester, select 5 test points evenly on the surface of each sample, apply a 150 kg load, and record the hardness value of each test point. Each sample 3 is parallel, and the average value is taken. The test results are shown in Table 2.

[0028] 3. Wear resistance test Weigh sample 1 and record its mass before testing. Make three parallel samples and take the average value. Place the samples in a friction and wear tester and wear them for 60 min at 50 N and 200 r / min. Clean the wear debris on the sample surface with anhydrous ethanol, dry them, weigh them, and record the mass after testing. Take the average value. Calculate the wear mass based on the difference between the average mass before testing and the average mass after testing. Divide the difference by the load and time to calculate the wear rate. The test results are shown in Table 2.

[0029] Table 2. Results of Hardness and Wear Resistance Tests

[0030] As can be seen from Table 2, the copper-based sample of the example (treated with high-energy ball milling and interface engineering) is significantly better than that of Comparative Example 2 (which lacks this treatment) in terms of hardness and wear resistance. This treatment is the key to improving the mechanical properties of recycled metals.

[0031] The hardness of the example was 46.5 HRC, higher than that of Comparative Example 2 (39.5 HRC). The wear rate of the example was 5.3 × 10⁻⁶. -6 g / (N・min), lower than Comparative Example 2's 16.0 × 10⁻⁶ g / (N・min), -6 g / (N・min), enhanced wear resistance.

[0032] In summary, high-energy ball milling combined with interface engineering treatments (preheating activation, spheroidization of precipitates, etc.) can effectively optimize the internal structure of recycled metals, thereby improving material hardness, reducing wear rate, and significantly enhancing the mechanical properties and reliability of recycled metals.

[0033] Experimental Example 3 This experimental example verifies the effects of high-energy ball milling and interface engineering on the modified fine-grained metal powder and test sample of Example 1, and the ordinary fine-grained metal powder and control sample 2 of Comparative Example 2. Specifically, the following steps are included: 1. Sample pretreatment The modified fine-grained metal powder of the embodiment and the ordinary fine-grained metal powder of Comparative Example 2 were dried in a forced-air dryer at 30 °C for 2 h and then cooled to room temperature in a desiccator to obtain Sample 2. The test sample and reference sample 2 were cut into pieces 10 mm long, 10 mm wide and 5 mm thick. Their surfaces were wiped with anhydrous ethanol, dried at 30°C for 1 h, and cooled to room temperature in a desiccator to obtain sample 3.

[0034] 2. Fine-grained dispersion test Weigh 0.1 g of sample 2, add 10 mL of anhydrous ethanol, ultrasonically disperse at 250 W for 15 min, inject into a laser particle size analyzer, scan within a range of 0.1~100 μm and at a scanning speed of 2 ° / min, and record the D10, D50 and D90 particle size values ​​of the sample. Each sample is in triplicate, and the average value is taken. The span is calculated based on the ratio of the difference between the D90 and D10 particle sizes to the D50 particle size. The measurement results are shown in Table 3-1.

[0035] Table 3-1 Results of fine grain dispersibility test

[0036] As can be seen from Table 3-1, the modified fine-grained metal powder of the examples treated with high-energy ball milling and interface engineering has better fine-grained dispersion than the ordinary fine-grained metal powder of Comparative Example 2 without this treatment.

[0037] The span of the example is 1.057, which is much lower than that of Comparative Example 2 (1.813), indicating a significant improvement in dispersion uniformity.

[0038] In summary, high-energy ball milling combined with interface engineering treatments (such as adding zinc stearate and argon atmosphere insulation) can effectively reduce the span of fine-grained powders, resulting in a more uniform particle size distribution and significantly improved fine-grain dispersibility. This effect is consistently observed in copper-based powders, indicating that this treatment scheme has universal applicability for optimizing fine-grained dispersion of different matrix metals.

[0039] 3. Denseness test Weigh sample 3 and record it as the actual mass of the sample. Place it in a porosity tester with a test pressure of 0.1 MPa and nitrogen as the test medium. Test the actual volume of the sample and calculate the actual density. Make each sample 3 parallel and take the average value. Calculate the density based on the ratio of the actual density to the theoretical density. The test results are shown in Table 3-2.

[0040] Table 3-2 Results of Tightness Test

[0041] As can be seen from Table 3-2, the density of the copper-based metal blanks in the example (after high-energy ball milling and interface engineering treatment) exceeds that of Comparative Example 2 (which lacks this treatment). This treatment is the core process for improving the density of recycled metals.

[0042] The copper-based metal blanks in the examples all achieved a density of 99.9%, close to the theoretical density, with very few internal pores. In contrast, the copper-based metal blank in Comparative Example 2 had a density of only 89.4%, a difference of 10.5% from the examples, indicating a large number of internal pores and insufficient density.

[0043] In summary, high-energy ball milling combined with interface engineering treatments (such as adding zinc stearate, argon atmosphere insulation, and spheroidization of precipitates) can effectively optimize the formability of metal powders and reduce porosity defects generated during solid-state deposition. This process consistently improves the density of copper-based recycled metals, laying a structural foundation for the subsequent optimization of material mechanical properties (such as hardness and wear resistance).

[0044] Experiment Example 4 This experimental example verifies the synergistic effect of the dual-modal structure in terms of strength and toughness of the test sample of the embodiment, control sample 1 of Comparative Example 1, and control sample 3 of Comparative Example 3. The specific steps include: 1. Sample pretreatment Wipe the surfaces of the test sample, reference 1, and reference 3 with anhydrous ethanol, dry them at 30 ℃ for 1 h, and cool them to room temperature in a desiccator to obtain the sample.

[0045] 2. Determination of tensile strength and elongation after fracture The sample was placed in a universal testing machine and loaded at a rate of 3 mm / min until the sample broke. The tensile strength and elongation after fracture were recorded. Three parallel samples were used for each sample, and the average value was taken. The results are shown in Table 4.

[0046] 3. Charpy impact test The sample was cut and impacted perpendicular to the forming direction. The sample size was 10 mm × 10 mm × 55 mm, the notch depth was 2 mm, the angle was 45°, and the bottom radius of the notch was 0.25 mm. The sample was placed in an impact testing machine and subjected to an impact energy of 50 J. The impact energy was recorded. Three samples were made for each sample, and the average value was taken. The measurement results are shown in Table 4.

[0047] Table 4. Results of tensile strength and elongation after fracture, and Charpy impact test.

[0048] As can be seen from Table 4, the copper-based sample of the example (dual-mode structure) is superior to Comparative Example 1 (without graded pretreatment, single mode) and Comparative Example 3 (without dual-mode structure, single grain) in terms of tensile strength, elongation after fracture and impact energy. The dual-mode structure can achieve a synergistic improvement in the strength and toughness of recycled metals.

[0049] The tensile strength of the example (458.7 MPa) is higher than that of Comparative Example 1 (338.7 MPa) and Comparative Example 3 (391.6 MPa), showing a significant strength advantage.

[0050] Example 1 (27.7%) showed better elongation after fracture than Comparative Example 1 (16.7%) and Comparative Example 3 (21.7%), demonstrating superior plasticity.

[0051] The impact energy of Example 1 (40.7 J) is higher than that of Comparative Example 1 (19.2 J) and Comparative Example 3 (29.1 J), and the toughness is significantly improved.

[0052] In summary, the dual-modal structure (composite of coarse-grained metal and modified fine-grained powder) is the core of the synergistic effect of strength and toughness. The coarse-grained component ensures the material's plasticity (elongation after fracture), while the modified fine-grained component enhances the material's strength (tensile strength). The combination of the two overcomes the limitation of single-modal materials being "strong but brittle, tough but weak." Compared with schemes that lack graded pretreatment (Comparative Example 1) or directly eliminate the fine-grained component (Comparative Example 3), the dual-modal design of this embodiment can simultaneously optimize strength, plasticity, and toughness, and this effect is consistently demonstrated in copper-based recycled metals, verifying the versatility and reliability of the process.

[0053] Experimental Example 5 This experimental example demonstrates the stability effect of multi-stage heat treatment on the test sample of the embodiment and the control sample 4 of Comparative Example 4, specifically including the following steps: 1. Sample pretreatment Wipe the surfaces of the test sample and reference sample 4 with anhydrous ethanol, dry them at 30 ℃ for 1 h, and cool them to room temperature in a desiccator to obtain the sample.

[0054] 2. Residual stress test The sample was placed in a residual stress tester, and three test points were evenly selected on the sample surface. A chromium target was used, with a voltage of 30 kV and a speed of 20 mA. The scanning angle range was 140° to 160°. The residual stress was recorded. Three parallel samples were used for each sample, and the average value was taken. The measurement results are shown in Table 5.

[0055] 3. Tissue stability test Place the sample on a hardness tester, select 5 test points evenly on the surface of each sample, apply a 3 kg load, record the hardness value of each test point, make 3 parallel samples for each sample, and take the average value, which is the hardness before aging. The sample was placed in a 150 ℃ oven for 100 h and allowed to cool naturally to room temperature. The surface was wiped with anhydrous ethanol. Five measuring points were evenly selected on the surface of each sample. A 3 kg load was applied, and the hardness value of each measuring point was recorded. Three parallel samples were made for each sample, and the average value was taken as the hardness after aging. The hardness change rate was calculated based on the ratio of the difference between the hardness before and after aging to the hardness before aging. The measurement results are shown in Table 5.

[0056] 4. Fatigue resistance test Place the sample in a universal testing machine and apply a loading rate of 3 mm / min until the sample breaks. Record the tensile strength. Each sample is repeated in triplicate, and the average value is taken. The sample was placed on a fatigue testing machine with a cyclic load of 50% of the tensile strength, a stress ratio of 0.1, a loading frequency of 10 Hz, and a loading rate of 50 MPa / s. The number of cycles at the moment of fracture was measured, and the minimum number of cycles was taken. The results are shown in Table 5.

[0057] Table 5 Results of Residual Stress Test, Microstructure Stability Test, and Fatigue Resistance Test

[0058] As can be seen from Table 5, the copper-based sample of the example (after multi-stage heat treatment) is superior to Comparative Example 4 (without multi-stage heat treatment) in terms of residual stress control, microstructure stability and fatigue resistance. Multi-stage heat treatment is a key process for improving the overall service performance of recycled metals.

[0059] The residual stress of the example (40.0 MPa) was lower than that of Comparative Example 4 (65.0 MPa), indicating a significant stress relief effect.

[0060] The hardness change rate of the example was only 2.15%, which is much lower than that of Comparative Example 4 (9.89%), and the hardness is more stable during long-term use.

[0061] The minimum number of cycles in the example reached 98,000, which is higher than the 68,000 cycles in Comparative Example 4, and the fatigue life was significantly extended.

[0062] In summary, multi-stage heat treatment (stress-relief annealing and pre-aging treatment in a nitrogen atmosphere in S004) effectively eliminates residual stress generated during solid-state deposition and regulates the morphology and distribution of precipitated phases. This process not only improves the material's microstructure stability and reduces performance degradation during long-term service, but also enhances fatigue resistance by optimizing the internal stress state. This effect is consistently observed in copper-based dual-mode recycled metals, further verifying the important role of multi-stage heat treatment in improving the overall service reliability of materials.

[0063] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for recycling and reusing metal waste, characterized in that, The method for recycling and reusing the metal waste specifically includes the following steps: S001, the initial metal scraps are sorted, size homogenized, surface cleaned and anti-oxidized to obtain clean and anti-oxidized coarse-grained ordinary metal and clean and anti-oxidized fine-grained ordinary metal, which are referred to as pre-treated coarse-grained metal and pre-treated fine-grained metal, where the initial metal scraps are copper scraps generated by machining. S002, the pretreated fine-grained metal is subjected to high-energy ball milling to obtain microcrystalline fine-grained powder, which is then subjected to preheating activation and spheroidization of precipitated phases to obtain a metal powder with a dual-mode microcrystalline fine-grained structure without control agent, denoted as modified metal fine-grained powder. S003, the modified fine-grained metal powder is mixed with the pretreated coarse-grained metal in a certain proportion to obtain an anti-oxidation dual-mode metal composite system, and plasticized deposition treatment is performed to obtain a regenerated dual-mode high-performance metal plate based on solid deposition forming. S004 involves stress-relief annealing and pre-aging treatment of a recycled dual-mode high-performance metal plate formed by solid-state deposition to obtain a dual-mode composite material blank with precipitated phase regulation. After shot blasting, a dual-mode metal blank is obtained.

2. The method according to claim 1, characterized in that, The conditions for classification and sorting in step S001 are as follows: first, magnetic separation is performed to obtain a non-magnetic metal mixture; then, the non-magnetic metal mixture is separated by gravity separation to obtain a high-density mixture; finally, spectral analysis is performed to obtain copper-based metal, which is denoted as ordinary metal. The conditions for size homogenization are as follows: a jaw crusher is used to perform preliminary crushing of the single-component metals after classification and sorting, and then the metals are screened and graded by a drum screen.

3. The method according to claim 1, characterized in that, In step S002, the high-energy ball milling treatment involves adding 2 wt% zinc stearate, with a ball-to-material ratio of 60:1, ball milling at 300 r / min for 25 h under argon, followed by holding at 400 ℃ under argon for 2 h; the preheating activation and spheroidization treatment of the precipitated phase are carried out at 300 ℃ for 60 min.

4. The method according to claim 1, characterized in that, In step S003, the mixing ratio of the modified fine-grained metal powder to the pretreated coarse-grained metal is 2:3, and the mixture is carried out under argon gas at 60 r / min for 30 min.

5. The method according to claim 1, characterized in that, In step S004, the stress-relief annealing and pre-aging treatment conditions are nitrogen gas, holding at 400 ℃ for 1 h, and cooling to room temperature in the furnace; the shot blasting treatment conditions are shot blasting at 0.4 MPa for 5 min.

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