Preparation method of regenerated aluminum profile extrusion die with uniformly distributed stress

Abstract

The invention discloses a method for preparing a regenerated aluminum profile extrusion die with uniform stress distribution, and relates to the field of regenerated aluminum profile extrusion dies, the method comprises the following steps: S1, base material preparation: mixing 92-94% of W6Mo5Cr4V2 high-speed steel, 5-7% of Cu-Ni alloy, 0.5-1% of rare earth element Ce and 0.5-1% of carbide WC according to the mass ratio, S2, gradient heat treatment: sequentially preheating, quenching and tempering a base material blank; s3, bionic design and processing of a mold cavity: designing the mold cavity by adopting a bionic honeycomb structure according to the sectional dimension of the regenerated aluminum profile, accurately controlling the temperature, the heating rate and the heat preservation time of each stage by setting a gradient heat treatment process of two-stage preheating, rapid quenching and three-time tempering, and accurately cooling by adopting high-purity nitrogen, so that the mold cavity is formed; the effects of eliminating the residual stress in the base material and optimizing the structure uniformity are achieved, and internal stress accumulation caused by the imperfect heat treatment process is avoided.

Description

Technical Field

[0001] This invention relates to the field of recycled aluminum profile extrusion dies, and particularly to a method for preparing a recycled aluminum profile extrusion die with uniform stress distribution. Background Technology

[0002] With the increasing global demand for resource recycling, the recycled aluminum industry, leveraging its core advantages of "energy saving, consumption reduction, and emission reduction," continues to expand its application scale in fields such as automotive lightweighting, building structure upgrading, and rail transit equipment manufacturing. Extrusion molding, as the core process in recycled aluminum profile production, directly determines the quality and production efficiency of the profiles. The performance of the extrusion die, as a key tool in this process, is paramount—the die must not only withstand the high temperature and pressure during the recycled aluminum extrusion process but also resist the intense friction between the molten aluminum and the cavity surface, as well as the cyclical alternating stress; the working conditions are extremely harsh.

[0003] However, existing technologies for manufacturing extrusion dies for recycled aluminum profiles have several shortcomings, leading to uneven stress distribution in the dies and becoming a core bottleneck restricting production stability and economy. First, at the die substrate design level, traditional technologies often use single-component high-speed steel (such as W6Mo5Cr4V2) or hot-work die steel (such as H13). Although these materials have certain high-temperature strength, they have two major defects: one is poor thermal conductivity, with the temperature difference between the die cavity surface and the core reaching 80-100℃ during extrusion, easily forming a significant thermal stress gradient; the other is an imbalance between toughness and fatigue resistance, under long-term alternating stress, microcracks are easily generated in weak parts such as die corners and ribs, and the cracks propagate rapidly, eventually leading to macroscopic cracking.

[0004] Therefore, it is necessary to propose a method for preparing extrusion dies for recycled aluminum profiles with uniform stress distribution to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a recycled aluminum profile extrusion die with uniform stress distribution, in order to solve the problems of poor thermal conductivity of traditional dies, large temperature difference between the die cavity surface and core during extrusion, which easily leads to significant thermal stress gradient; secondly, imbalance between toughness and fatigue resistance, under long-term alternating stress, microcracks are easily generated in weak parts such as die corners and ribs, and the cracks propagate rapidly, eventually leading to macroscopic cracking.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a recycled aluminum profile extrusion die with uniform stress distribution, comprising the following steps: S1. Substrate preparation: Mix 92%–94% W6Mo5Cr4V2 high-speed steel, 5%–7% Cu-Ni alloy, 0.5%–1% rare earth element Ce, and 0.5%–1% carbide WC by mass ratio, wherein the mass ratio of Cu to Ni in the Cu-Ni alloy is 7:3. Put the mixed raw materials into a vacuum induction melting furnace and melt at 1550–1600℃ for 2–2.5 hours. During the melting process, the vacuum degree is controlled at ≤30Pa. Then, directional solidification technology is used to solidify the melted raw materials into a mold substrate blank at a cooling rate of 5–8℃ / min. The hardness of the substrate blank is controlled at 28–32HRC. S2. Gradient heat treatment: The substrate blank is preheated, quenched and tempered in sequence. Preheating: First, maintain the temperature at 650-680℃ for 1-1.5 hours, then raise the temperature to 850-880℃ at a rate of 10-15℃ / min, and maintain the temperature at this temperature for 2-3 hours. Quenching: Heat to 1180-1220℃ at a set rate, hold at this temperature for 1.5-2 hours, and then cool to below 200℃ using nitrogen cooling at a cooling rate of 50-60℃ / s. Tempering: The quenched substrate blank is placed at 560-580℃ and held for 2-2.5 hours, then cooled to room temperature in the furnace. This tempering operation is repeated 3 times, and the final substrate hardness is controlled at 62-65HRC. S3. Bionic Design and Processing of Cavities: Based on the cross-sectional dimensions of recycled aluminum profiles, a bionic honeycomb structure is used to design the mold cavity. The wall thickness difference of the designed cavity is ≤0.8mm, and an arc transition of R3-R5mm is set at the corner of the cavity. The cavity is machined using a five-axis linkage machining center. During the machining process, the spindle speed is controlled at 8000-10000 r / min and the feed rate is controlled at 150-200 mm / min. Laser inspection is used after machining is completed. S4. Surface strengthening treatment: The mold cavity is sequentially subjected to sandblasting, plasma spraying, sealing treatment and aging treatment. Sandblasting treatment: 120-150 mesh white corundum sand is used to sandblast the surface of the mold cavity at a pressure of 0.4-0.6MPa. After treatment, the surface roughness Ra of the mold cavity is controlled at 1.2-1.5μm. Plasma spraying: Plasma spraying is performed on the surface of the mold cavity after sandblasting. The spraying material is Al2O3-TiO2 mixed powder, in which the mass ratio of Al2O3 to TiO2 is 85:15. The spraying power is controlled at 35-40kW, the spraying distance is controlled at 100-120mm, and the coating thickness formed after spraying is 50-80μm. Sealing treatment: The coating is sealed with an epoxy resin sealing agent with a solid content of ≥95%, and cured at 80-100℃ for 1-1.5h. Aging treatment: After the sealing treatment is completed, the mold is subjected to overall aging treatment, which is carried out at 180-200℃ for 4-5 hours, and then cooled to room temperature in the furnace. The final surface hardness of the mold is ≥850HV.

[0007] Preferably, the stirring rate of the vacuum induction melting furnace in the substrate preparation step is controlled at 300-350 r / min to ensure uniform alloy composition; after melting, the content deviation of W, Mo, Cr and V elements is detected by a spectrometer and is ≤ ±0.1%.

[0008] Preferably, the nitrogen used in the quenching and cooling process during the gradient heat treatment step has a purity of ≥99.99%, and the temperature difference between different parts of the mold during the cooling process is controlled within ±10℃ to avoid internal stress caused by excessive temperature difference.

[0009] Preferably, in the biomimetic design and processing steps of the cavity, the width of the cavity ribs of the biomimetic honeycomb structure is 2-3mm, the rib spacing is 5-8mm, and the connection angle between the ribs and the cavity wall is 120°, so as to improve the stability of the cavity structure and the stress dispersion ability.

[0010] Preferably, before plasma spraying in the surface strengthening treatment step, the mold cavity surface is subjected to ultrasonic cleaning with alcohol, with the cleaning power controlled at 300-400W and the cleaning time controlled at 15-20min, in order to remove surface oil and impurities and ensure that the coating adhesion is ≥50MPa.

[0011] Preferably, a water-cooled copper mold is used for directional solidification in the substrate preparation step, and the grain size of the mold substrate blank is controlled at 5-10μm to avoid stress concentration caused by coarse grains.

[0012] Preferably, in the cavity biomimetic design and processing steps, the five-axis linkage machining center uses diamond tools with a hardness ≥90HRC, and the cutting fluid with a cooling rate ≥80℃ / min is used for cooling during the processing to prevent the mold surface from overheating and causing oxidation or microcracks.

[0013] Preferably, during the sandblasting process, the spraying angle of the white corundum abrasive is controlled at 45-60°, and the spraying path is moved in a reciprocating and uniform manner to ensure uniform sandblasting in all areas of the mold cavity surface and avoid surface roughness differences caused by excessive or insufficient sandblasting in certain areas.

[0014] Preferably, in the preheating stage of the gradient heat treatment step, after the temperature is raised to 850-880℃, the temperature of the substrate blank during the heat preservation process needs to be checked. The temperature of different areas of the substrate blank is recorded every 30 minutes to ensure that the temperature deviation of each area is ≤±5℃, so as to ensure that the substrate structure transformation is uniform.

[0015] Preferably, after the sealing process is completed in the surface strengthening treatment step, the surface of the mold cavity needs to be inspected for appearance and porosity. The appearance inspection is carried out by visual inspection combined with a magnifying glass to ensure that the coating has no missing seals or bubbling.

[0016] The technical effects and advantages of this invention are as follows: 1. By setting a multi-component synergistically reinforced mold substrate, optimizing the ratio of W6Mo5Cr4V2 high-speed steel, Cu-Ni alloy, rare earth element Ce and carbide WC, and simultaneously employing vacuum induction melting and water-cooled copper mold directional solidification technology, the high-temperature strength, toughness and thermal conductivity of the substrate are improved, avoiding stress concentration caused by material property imbalance.

[0017] 2. By setting up a gradient heat treatment process of "two-stage preheating - rapid quenching - three-stage tempering", the temperature, heating rate and holding time of each stage are precisely controlled. At the same time, high-purity nitrogen is used for precise cooling to achieve the effect of eliminating residual stress inside the substrate and optimizing the uniformity of the structure, thus avoiding the accumulation of internal stress caused by imperfect heat treatment process.

[0018] 3. By setting up a cavity with a biomimetic honeycomb structure, the cavity wall thickness difference, corner arc transition, and rib distribution and connection angle are optimized. At the same time, a five-axis linkage machining center and high-precision laser detection are used to disperse local stress in the mold, improve the stability of the cavity structure and the machining accuracy, and avoid local high stress areas caused by unreasonable cavity design.

[0019] 4. By setting up a surface strengthening process of "sandblasting-plasma spraying-sealing-aging", Al2O3-TiO2 mixed powder is selected for plasma spraying, combined with epoxy resin sealing and low temperature aging treatment, the surface hardness, wear resistance and coating adhesion of the mold are improved, while eliminating residual stress generated during the surface treatment process, and avoiding coating peeling or cracking.

[0020] 5. By setting up a stress control strategy for the entire process, stress is controlled in a coordinated manner at each stage from substrate solidification, heat treatment, cavity machining to surface treatment, so as to achieve the effect of uniform stress transfer from the substrate to the surface of the mold, fundamentally solving the problems of mold cracking and deformation, and ensuring the structural stability of the mold during use.

[0021] 6. By setting process parameters compatible with existing equipment, the cavity design and substrate composition can be adjusted according to recycled aluminum profiles with different cross-sections, without the need for large-scale replacement of core equipment, thereby improving process adaptability and compatibility, and facilitating promotion and application by enterprises of different sizes.

[0022] 7. By setting a highly wear-resistant surface coating and a low-porosity sealing treatment, the consumption of lubricating grease during mold use is reduced, the maintenance cycle is extended, and the failed mold can be reused by recoating the surface, thereby reducing mold maintenance costs and improving material utilization. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the steps of the method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to the present invention. Detailed Implementation

[0024] This invention provides, for example Figure 1 The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution is shown. To address the problems of imbalance between strength and toughness and poor thermal conductivity of traditional substrates, a substrate design with multi-component synergistic reinforcement is adopted.

[0025] S1. Optimized preparation of mold substrate The raw materials are precisely proportioned by mass: 92%~94% W6Mo5Cr4V2 high-speed steel (providing basic high-temperature strength), 5%~7% Cu-Ni alloy (Cu:Ni=7:3, improving thermal conductivity, with the thermal conductivity coefficient increased to 40-45W / (m·K)), 0.5%~1% rare earth element Ce (refining grains and improving the uniformity of the structure), and 0.5%~1% carbide WC (enhancing wear resistance and fatigue resistance).

[0026] The raw materials are placed in a vacuum induction melting furnace, and after being evacuated to ≤30Pa, the temperature is raised to 1550-1600℃ and melted for 2-2.5 hours. During the melting process, the mixture is stirred at a rate of 300-350 r / min to ensure uniform alloy composition. After melting, the content of W, Mo, Cr, and V elements is tested using a spectrometer, and the deviation is ≤±0.1%. After melting, a water-cooled copper mold directional solidification technology is used to solidify the mold base blank at a cooling rate of 5-8℃ / min. The grain size of the base material is controlled to be 5-10μm to avoid grain boundary stress concentration caused by coarse grains. The hardness of the final base blank is controlled at 28-32HRC to reserve a suitable hardness range for subsequent processing and heat treatment.

[0027] S2, gradient heat treatment process To eliminate residual stress inside the substrate and achieve gradient optimization of microstructure and properties, a gradient heat treatment process of "two-stage preheating - rapid quenching - three-stage tempering" is adopted.

[0028] Two-stage preheating: First, hold at 650-680℃ for 1-1.5 hours to remove residual moisture and gases from the substrate, reducing oxidation and decarburization during quenching. Then, heat to 850-880℃ at a rate of 10-15℃ / min and hold at this temperature for 2-3 hours to allow the substrate microstructure to fully transform into austenite, preparing it for subsequent quenching and avoiding uneven microstructure transformation caused by single-stage preheating. After heating to 850-880℃ during the preheating stage, the temperature of the substrate blank needs to be monitored during the holding process. Record the temperature of different areas of the substrate blank every 30 minutes to ensure that the temperature deviation of each area is ≤±5℃, guaranteeing uniform microstructure transformation.

[0029] Precision quenching: The preheated substrate is heated to 1180-1220℃ (at which austenitization is sufficient and grain growth is not obvious), and held for 1.5-2 hours; nitrogen gas with a purity of ≥99.99% is used for cooling, and the cooling rate is controlled at 50-60℃ / s to quickly cool to below 200℃, promoting martensitic transformation and improving the hardness of the substrate; during the cooling process, multiple temperature sensors are used to monitor in real time to ensure that the temperature difference between different parts of the mold is ≤±10℃, and to prevent thermal stress caused by uneven cooling.

[0030] Three tempering processes: Hold at 560-580℃ for 2-2.5 hours, cool to room temperature in the furnace, and repeat tempering 3 times. The first tempering eliminates quenching internal stress (residual stress is reduced by 40% to 50%), the second tempering refines the martensitic structure, and the third tempering stabilizes the structure and properties, ultimately controlling the hardness of the substrate at 62-65 HRC, ensuring both high-temperature strength and good toughness (impact toughness ≥18 J / cm²).

[0031] Cavity biomimetic design and precision machining S3. Drawing inspiration from the stress dispersion characteristics of honeycomb structures, the mold cavity is designed with biomimetic optimization. Based on the cross-sectional dimensions of recycled aluminum profiles (such as 300mm×80mm for automotive door frames, 400mm×100mm for building curtain wall profiles, and 500mm×120mm for rail transit profiles), the cavity wall thickness difference is designed to be ≤0.8mm to ensure coordinated deformation of various parts of the mold under stress. R3-R5mm rounded transitions are set at the corners of the cavity to reduce the stress concentration factor to below 1.2. The cavity ribs are distributed in a honeycomb pattern, with a rib width of 2-3mm, a rib spacing of 5-8mm, and a connection angle of 120° between the ribs and the cavity wall. A triangular stabilizing structure is used to enhance the rib support strength and disperse local stress.

[0032] The cavity is machined using a five-axis linkage machining center with diamond tools of hardness ≥90HRC. The spindle speed is controlled at 8000-10000 r / min and the feed rate at 150-200 mm / min to ensure machining accuracy. During machining, a water-based cutting fluid with a cooling rate ≥80℃ / min is used to avoid overheating of the mold surface, which could lead to oxidation or microcracks. After machining, the cavity dimensions are checked using a laser interferometer (accuracy ±0.005 mm), and the surface roughness Ra of the cavity is controlled at 1.2-1.5 μm by sandpaper polishing (400-600 grit) to reduce stress concentration caused by microscopic defects on the surface.

[0033] S4, Surface Strengthening and Stress Relief The surface treatment process of "sandblasting-coating-sealing-aging" is used to improve the surface performance of the mold and eliminate residual stress.

[0034] Sandblasting pretreatment: Use 120-150 mesh white corundum abrasive, apply 0.4-0.6 MPa pressure and spray angle of 45-60° to the mold cavity surface. The spray path should be reciprocating and moving evenly to ensure uniform sandblasting in all areas of the mold cavity surface and avoid surface roughness differences caused by excessive or insufficient sandblasting in some areas. After sandblasting, the surface roughness Ra of the mold cavity should be controlled at 1.2-1.5 μm, and a uniform rough structure should be formed on the surface to enhance the adhesion of subsequent coatings. After sandblasting, use alcohol ultrasonic cleaning (power 300-400W, time 15-20min) to thoroughly remove surface impurities.

[0035] Plasma spraying: Al2O3-TiO2 mixed powder is selected (mass ratio: Al2O3-TiO2 ... 3： TiO2=85:15), Al2O3 provides high hardness (≥1800HV), and TiO2 improves the coating toughness (fracture toughness ≥4MPa·m¹ / ²); control the spraying power to 35-40kW, the spraying distance to 100-120mm, and the spraying rate to 5-8mm / s to form a uniform coating with a thickness of 50-80μm. The coating adhesion is ≥50MPa when tested by cross-cut test.

[0036] Sealing treatment: Use epoxy resin sealing agent with a solid content ≥95% to cover the coating surface by dip coating, and cure at 80-100℃ for 1-1.5h to fill the coating pores; after the sealing treatment is completed, the surface of the mold cavity needs to be inspected for appearance and porosity. The appearance inspection is carried out by visual inspection combined with a magnifying glass (magnification of 10-20 times) to ensure that there are no incomplete sealing or bubbling phenomena in the coating; the porosity test is carried out by the impregnation method, and the test results must meet the requirement that the coating porosity is ≤1% to prevent the aluminum melt from penetrating into the interior of the coating and generating corrosion stress during the subsequent extrusion process.

[0037] Overall aging treatment: After sealing, place the mold in an aging furnace and keep it at 180-200℃ for 4-5 hours. Then cool it to room temperature with the furnace. Low-temperature aging further eliminates the residual stress generated during cavity processing and surface spraying (residual stress is reduced to ≤100MPa), ensuring that the overall stress distribution of the mold is uniform and the stress distribution standard deviation is ≤35MPa.

[0038] This invention achieves uniform stress transfer from the substrate to the surface of the mold through the synergistic effects of substrate composition optimization, gradient heat treatment, biomimetic cavity design, and surface strengthening. Testing shows that the maximum stress value during mold operation is ≤450MPa, a reduction of 25%–35% compared to traditional molds (600-700MPa); the stress distribution standard deviation is ≤35MPa, far lower than the ≥80MPa level of traditional molds, effectively eliminating localized stress concentration and fundamentally solving the problems of mold cracking and deformation. For example, when applied to the extrusion of recycled aluminum profiles for automotive door frames, the stress concentration coefficient at the mold corners drops from the traditional 3.0 to below 1.2, the probability of microcrack formation is reduced by more than 90%, and the uniformity of stress distribution is significantly improved.

[0039] The multi-component synergistically reinforced substrate (hardness 62-65HRC, impact toughness ≥18J / cm²) possesses excellent high-temperature strength and toughness. Combined with the high wear resistance of the Al₂O₃-TiO₂ coating (surface hardness ≥850HV, adhesion ≥50MPa), the service life of the mold is increased to over 8000 cycles, which is 60% to 167% longer than that of traditional molds (3000-5000 cycles). Based on a production cost of 50,000 yuan per mold set and a profit of 200 yuan per extruded profile, a single mold set can increase profits by 600,000 to 1,000,000 yuan, significantly reducing enterprise production costs and greatly extending the mold's service life.

[0040] Bionic cavity design (wall thickness difference ≤0.8mm, corner radius R3-R5mm) and precision machining (dimensional accuracy ±0.005mm) ensure uniform profile cross-sectional dimensions, avoiding dimensional deviations caused by mold deformation. The low roughness (Ra1.2-1.5μm) and high wear resistance of the surface-strengthening coating reduce surface scratches, increasing the surface quality pass rate from the traditional 85%–90% to over 99%. Simultaneously, uniform mold stress distribution stabilizes extrusion process parameters, reducing the fluctuation range of profile mechanical properties—the tensile strength fluctuation of 6061 series recycled aluminum profiles decreases from ±15MPa to ±5MPa, meeting the requirements of high-end manufacturing for consistent profile quality and improving the quality stability of recycled aluminum profiles.

[0041] The substrate is prepared using vacuum induction melting (vacuum degree ≤30Pa), which reduces the emission of harmful gases (such as SO2, NO) during the melting process. xEmissions are reduced by more than 95%; surface treatment uses plasma spraying instead of chrome plating, avoiding pollution from heavy metals such as hexavalent chromium, and meeting the environmental protection requirements of the "National Hazardous Waste List". Simultaneously, the synergistic process of gradient heat treatment and surface treatment shortens the mold preparation cycle from the traditional 15-20 days to 10-12 days, increasing production efficiency by 25% to 33%. This meets the mold needs of large-scale production by recycled aluminum profile enterprises, and the mold preparation process is green and efficient.

[0042] The process boasts strong compatibility and adaptability: The method of this invention allows for adjustment of the cavity biomimetic design parameters (such as rib spacing and wall thickness difference) according to different cross-sectional types of recycled aluminum profiles (e.g., building curtain wall profiles, rail transit profiles), without requiring replacement of core equipment. The substrate composition and heat treatment process can be flexibly optimized for mold dimensions—for example, when preparing large molds (weight ≥ 50 kg), the Cu-Ni alloy content can be appropriately increased to 7% to enhance thermal conductivity and prevent overheating of the mold core. Furthermore, the process is compatible with existing mold production equipment (e.g., vacuum induction melting furnaces, five-axis machining centers), requiring only 300,000-400,000 RMB for equipment modification, with a modification cycle of 20-25 days, facilitating rapid adoption by small and medium-sized enterprises.

[0043] Reduced mold maintenance costs: The high wear resistance of the Al2O3-TiO2 surface coating (wear rate ≤0.005mm / thousand cycles) and the sealing treatment (porosity ≤1%) reduce lubricant consumption during mold use (lubricant usage reduced by 40%–50%); the uniform stress distribution of the mold extends the maintenance cycle from once every 2000 cycles to once every 4000 cycles, shortening maintenance time by more than 60% and reducing maintenance costs by 35%–45%. Simultaneously, the mold failure mode changes from traditional cracking failure to normal wear failure; failed molds can be reused through surface recoating, increasing mold material utilization by 50%–60%.

[0044] Example 1 This embodiment focuses on the extrusion die for 6061 series recycled aluminum automotive door frame profiles (cross-section size 300mm×80mm). The specific steps are as follows: Substrate preparation: 92% W6Mo5Cr4V2 high-speed steel, 7% Cu-Ni alloy (Cu:Ni=7:3), 0.5% Ce, and 0.5% WC were mixed in a vacuum induction melting furnace (vacuum degree 30Pa) and melted at 1550℃ for 2 hours with a stirring rate of 300 r / min. A water-cooled copper mold was used for directional solidification (cooling rate 5℃ / min) to prepare the substrate blank. The grain size was measured to be 10 μm, and the hardness was 28 HRC. Spectroscopic analysis showed that the content of W, Mo, Cr, and V elements deviated by ±0.1%.

[0045] Gradient heat treatment: ① Preheating: Hold at 650℃ for 1 hour, then heat to 850℃ and hold for 2 hours (heating rate 10℃ / min). Record the temperature every 30 minutes during the holding process. The temperature deviation of each area should be ≤±5℃. ② Quenching: Hold at 1180℃ for 1.5 hours, then cool with 99.99% nitrogen (rate 50℃ / s) to below 200℃. The temperature difference of each part of the mold should be ±10℃. ③ Tempering: Hold at 560℃ for 2 hours, then cool with the furnace. Repeat 3 times. The final hardness is 62HRC.

[0046] Cavity biomimetic design and machining: The cavity wall thickness difference is designed to be 0.8mm, the corner radius is 3mm, the rib width is 2mm, the spacing is 5mm, and the connection angle is 120°; machining is performed on a five-axis machining center (diamond tool hardness 90HRC), with a spindle speed of 8000r / min, a feed rate of 150mm / min, and water-based cutting fluid (cooling rate 80℃ / min); laser inspection dimensional accuracy is ±0.005mm, and the polished surface is Ra1.5μm.

[0047] Surface strengthening treatment: ① Sandblasting: 120-mesh white corundum sand, 0.4MPa pressure, 45° spray angle, reciprocating spray, Ra1.5μm; ultrasonic cleaning with alcohol (300W, 15min); ② Plasma spraying: Al2O3-TiO2 (85:15) powder, 35kW power, 100mm distance, coating thickness 50μm, adhesion 50MPa; ③ Sealing: epoxy resin sealing agent (95% solid content), cured at 80℃ for 1h, visual inspection shows no leakage or bubbling, porosity ≤1%; ④ Aging: heat preservation at 180℃ for 4h, followed by furnace cooling.

[0048] Test results: Maximum mold stress 450MPa, stress distribution standard deviation 35MPa, service life 8000 cycles; dimensional accuracy of extruded profile ±0.1mm, surface qualification rate 99%.

[0049] Example 2 This embodiment focuses on the extrusion die for 6061 series recycled aluminum automotive door frame profiles (same as in Embodiment 1), with the following parameter adjustments: Substrate preparation: mass ratio of 92.5% W6Mo5Cr4V2, 6.5% Cu-Ni, 0.6% Ce, and 0.4% WC; melting temperature 1560℃, time 2.1h, stirring 310r / min; directional solidification cooling rate 6℃ / min, grain size 8μm, hardness 29HRC; elemental deviation ±0.08%.

[0050] Gradient heat treatment: ① Preheating: 660℃ for 1.2h, 860℃ for 2.2h (12℃ / min), temperature deviation during the holding process ≤±5℃; ② Quenching: 1190℃ for 1.6h, nitrogen cooling rate 52℃ / s, temperature difference ±8℃; ③ Tempering: 565℃ for 2.2h, 3 times, hardness 63HRC.

[0051] Cavity machining: wall thickness difference 0.7mm, corner radius R3.5mm, rib width 2.2mm, spacing 6mm; machining center speed 8500r / min, feed 160mm / min, cutting fluid cooling rate 85℃ / min, polished surface Ra1.4μm.

[0052] Surface strengthening: ① Sandblasting with 130-mesh sand, 0.45MPa pressure, 50° spray angle, Ra 1.4μm; cleaning at 320W for 16min; ② Spraying at 36kW power and 105mm distance, coating thickness 55μm, adhesion 52MPa; ③ Sealing and curing at 90℃ for 1.1h, appearance and porosity tests passed; ④ Aging at 185℃ for 4.2h.

[0053] Test results: maximum stress 440MPa, standard deviation 33MPa, life 8200 cycles; profile dimensional accuracy ±0.09mm, pass rate 99.2%.

[0054] Example 3 This embodiment focuses on the extrusion die for 6061 series recycled aluminum automotive door frame profiles (same as in Embodiment 1), with the following parameter adjustments: Substrate preparation: 93% W6Mo5Cr4V2, 6% Cu-Ni, 0.7% Ce, 0.3% WC; melting at 1570℃ for 2.2h, stirring at 320r / min; solidification rate at 7℃ / min, grain size at 7μm, hardness at 30HRC; elemental deviation ±0.07%.

[0055] Heat treatment: ① Preheating 670℃ / 1.3h, 870℃ / 2.5h (13℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1200℃ / 1.7h, cooling rate 55℃ / s, temperature difference ±7℃; ③ Tempering 570℃ / 2.3h, 3 times, hardness 64HRC.

[0056] Cavity: wall thickness difference 0.6mm, R4mm, ribs 2.5mm / 7mm; machining speed 9000r / min, feed 170mm / min, cooling rate 90℃ / min, Ra1.3μm.

[0057] Surface treatment: ① Sandblasting 140 mesh / 0.5MPa pressure, 55° spray angle, Ra1.3μm; cleaning 350W / 17min; ② Spraying 37kW / 110mm, coating 60μm, adhesion 53MPa; ③ Sealing 95℃ / 1.2h, qualified; ④ Aging 190℃ / 4.5h.

[0058] Test results: maximum stress 430MPa, standard deviation 31MPa, life 8500 cycles; profile accuracy ±0.08mm, pass rate 99.3%.

[0059] Example 4 This embodiment focuses on the extrusion die for 6061 series recycled aluminum automotive door frame profiles (same as in Embodiment 1), with the following parameter adjustments: Substrate: 93.5% W6Mo5Cr4V2, 5.5% Cu-Ni, 0.8% Ce, 0.2% WC; Melting at 1580℃ for 2.3h, stirring at 330r / min; solidification rate at 7℃ / min, grain size at 6μm, hardness at 31HRC; elemental deviation ±0.06%.

[0060] Heat treatment: ① Preheating 675℃ / 1.4h, 875℃ / 2.7h (14℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1210℃ / 1.8h, cooling rate 58℃ / s, temperature difference ±6℃; ③ Tempering 575℃ / 2.4h, 3 times, hardness 64.5HRC.

[0061] Cavity: wall thickness difference 0.5mm, R4.5mm, ribs 2.8mm / 7.5mm; machining speed 9500r / min, feed 180mm / min, cooling rate 95℃ / min, Ra1.25μm.

[0062] Surface treatment: ① Sandblasting 145 mesh / 0.55MPa pressure, 58° spray angle, Ra1.25μm; cleaning 380W / 18min; ② Spraying 38kW / 115mm, coating 70μm, adhesion 54MPa; ③ Sealing 98℃ / 1.4h, qualified; ④ Aging 195℃ / 4.7h.

[0063] Test results: maximum stress 420MPa, standard deviation 29MPa, life 8800 cycles; profile accuracy ±0.07mm, pass rate 99.4%.

[0064] Example 5 This embodiment focuses on the extrusion die for 6061 series recycled aluminum automotive door frame profiles (same as in Embodiment 1), with the following parameter adjustments: Substrate: 94%W6Mo5Cr4V2, 5%Cu-Ni, 1%Ce, 1%WC; Melting at 1600℃ for 2.5h, stirring at 350r / min; Solidification rate at 8℃ / min, grain size 5μm, hardness 32HRC; Elemental deviation ±0.05%.

[0065] Heat treatment: ① Preheating 680℃ / 1.5h, 880℃ / 3h (15℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1220℃ / 2h, cooling rate 60℃ / s, temperature difference ±5℃; ③ Tempering 580℃ / 2.5h, 3 times, hardness 65HRC.

[0066] Cavity: wall thickness difference 0.4mm, R5mm, ribs 3mm / 8mm; machining speed 10000r / min, feed 200mm / min, cooling rate 100℃ / min, Ra1.2μm.

[0067] Surface treatment: ① Sandblasting 150 mesh / 0.6MPa pressure, 60° spray angle, Ra1.2μm; cleaning 400W / 20min; ② Spraying 40kW / 120mm, coating 80μm, adhesion 55MPa; ③ Sealing 100℃ / 1.5h, qualified; ④ Aging 200℃ / 5h.

[0068] Test results: maximum stress 400MPa, standard deviation 25MPa, life 9000 cycles; profile accuracy ±0.06mm, pass rate 99.5%.

[0069] Example 6 This embodiment focuses on the extrusion die for 6082 series recycled aluminum building curtain wall profiles (cross-section size 400mm×100mm), with the following parameters: Substrate preparation: 92% W6Mo5Cr4V2, 7% Cu-Ni, 0.5% Ce, 0.5% WC; melting at 1550℃ / 2h, stirring at 300r / min; directional solidification at 5℃ / min, grain size 10μm, hardness 28HRC; elemental deviation ±0.1%.

[0070] Gradient heat treatment: ① Preheating 650℃ / 1h, 850℃ / 2h (10℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1180℃ / 1.5h, nitrogen cooling 50℃ / s, temperature difference ±10℃; ③ Tempering 560℃ / 2h, 3 times, hardness 62HRC.

[0071] Cavity design: wall thickness difference 0.8mm, corner R3mm, ribs 2mm / 5mm; machining speed 8000r / min, feed 150mm / min, cooling 80℃ / min, Ra1.5μm.

[0072] Surface strengthening: ① Sandblasting 120 mesh / 0.4MPa pressure, 45° spray angle, cleaning 300W / 15min; ② Spraying 35kW / 100mm, coating 50μm; ③ Sealing 80℃ / 1h, inspection qualified; ④ Aging 180℃ / 4h.

[0073] Test results: Maximum stress 450MPa, standard deviation 35MPa, life 8000 cycles; profile bending degree ≤0.5mm / m, surface qualification rate 99%.

[0074] Example 7 This embodiment focuses on the extrusion die for 6082 series recycled aluminum building curtain wall profiles (same as in embodiment 6), with the following parameter adjustments: Substrate: 92.5% W6Mo5Cr4V2, 6.5% Cu-Ni, 0.6% Ce, 0.4% WC; Melting at 1560℃ for 2.1h, stirring at 310r / min; directional solidification at 6℃ / min, grain size 8μm, hardness 29HRC; elemental deviation ±0.08%.

[0075] Gradient heat treatment: ① Preheating 660℃ / 1.2h, 860℃ / 2.2h (12℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1190℃ / 1.6h, nitrogen cooling 52℃ / s, temperature difference ±8℃; ③ Tempering 565℃ / 2.2h, 3 times, hardness 63HRC.

[0076] Cavity machining: wall thickness difference 0.7mm, corner R3.5mm, ribs 2.2mm / 6mm; machining speed 8500r / min, feed 160mm / min, cutting fluid cooling 85℃ / min, polished Ra1.4μm.

[0077] Surface strengthening: ① Sandblasting 130 mesh / 0.45MPa pressure, 50° spray angle, Ra1.4μm; cleaning 320W / 16min; ② Spraying 36kW / 105mm, coating 55μm, adhesion 52MPa; ③ Sealing 90℃ / 1.1h, inspection qualified; ④ Aging 185℃ / 4.2h.

[0078] Test results: Maximum stress 440MPa, standard deviation 33MPa, life 8200 cycles; profile bending degree ≤0.45mm / m, pass rate 99.2%.

[0079] Example 8 This embodiment focuses on the extrusion die for 6082 series recycled aluminum building curtain wall profiles (same as in embodiment 6), with the following parameter adjustments: Substrate: 93%W6Mo5Cr4V2, 6%Cu-Ni, 0.7%Ce, 0.3%WC; Melting at 1570℃ for 2.2h, stirring at 320r / min; Solidification at 7℃ / min, grain size 7μm, hardness 30HRC; elemental deviation ±0.07%.

[0080] Heat treatment: ① Preheating 670℃ / 1.3h, 870℃ / 2.5h (13℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1200℃ / 1.7h, cooling 55℃ / s, temperature difference ±7℃; ③ Tempering 570℃ / 2.3h, 3 times, hardness 64HRC.

[0081] Cavity: wall thickness difference 0.6mm, R4mm, ribs 2.5mm / 7mm; machining speed 9000r / min, feed 170mm / min, cooling 90℃ / min, Ra1.3μm.

[0082] Surface treatment: ① Sandblasting 140 mesh / 0.5MPa pressure, 55° spray angle, Ra1.3μm; cleaning 350W / 17min; ② Spraying 37kW / 110mm, coating 60μm, adhesion 53MPa; ③ Sealing 95℃ / 1.2h, qualified; ④ Aging 190℃ / 4.5h.

[0083] Test results: Maximum stress 430MPa, standard deviation 31MPa, life 8500 cycles; profile bending degree ≤0.4mm / m, pass rate 99.3%.

[0084] Example 9 This embodiment focuses on the extrusion die for 6082 series recycled aluminum building curtain wall profiles (same as in embodiment 6), with the following parameter adjustments: Substrate: 93.5% W6Mo5Cr4V2, 5.5% Cu-Ni, 0.8% Ce, 0.2% WC; Melting at 1580℃ for 2.3h, stirring at 330r / min; Solidification at 7℃ / min, grain size 6μm, hardness 31HRC; elemental deviation ±0.06%.

[0085] Heat treatment: ① Preheating 675℃ / 1.4h, 875℃ / 2.7h (14℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1210℃ / 1.8h, cooling 58℃ / s, temperature difference ±6℃; ③ Tempering 575℃ / 2.4h, 3 times, hardness 64.5HRC.

[0086] Cavity: wall thickness difference 0.5mm, R4.5mm, ribs 2.8mm / 7.5mm; machining speed 9500r / min, feed 180mm / min, cooling 95℃ / min, Ra1.25μm.

[0087] Surface treatment: ① Sandblasting 145 mesh / 0.55MPa pressure, 58° spray angle, Ra1.25μm; cleaning 380W / 18min; ② Spraying 38kW / 115mm, coating 70μm, adhesion 54MPa; ③ Sealing 98℃ / 1.4h, qualified; ④ Aging 195℃ / 4.7h.

[0088] Test results: Maximum stress 420MPa, standard deviation 29MPa, life 8800 cycles; profile bending degree ≤0.35mm / m, pass rate 99.4%.

[0089] Example 10 This embodiment focuses on the extrusion die for 6082 series recycled aluminum building curtain wall profiles (same as in embodiment 6), with the following parameter adjustments: Substrate: 94%W6Mo5Cr4V2, 5%Cu-Ni, 1%Ce, 1%WC; Melting at 1600℃ for 2.5h, stirring at 350r / min; Solidification at 8℃ / min, grain size 5μm, hardness 32HRC; elemental deviation ±0.05%.

[0090] Heat treatment: ① Preheating 680℃ / 1.5h, 880℃ / 3h (15℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1220℃ / 2h, cooling 60℃ / s, temperature difference ±5℃; ③ Tempering 580℃ / 2.5h, 3 times, hardness 65HRC.

[0091] Cavity: wall thickness difference 0.4mm, R5mm, ribs 3mm / 8mm; machining speed 10000r / min, feed 200mm / min, cooling 100℃ / min, Ra1.2μm.

[0092] Surface treatment: ① Sandblasting 150 mesh / 0.6MPa pressure, 60° spray angle, Ra1.2μm; cleaning 400W / 20min; ② Spraying 40kW / 120mm, coating 80μm, adhesion 55MPa; ③ Sealing 100℃ / 1.5h, qualified; ④ Aging 200℃ / 5h.

[0093] Test results: Maximum stress 400MPa, standard deviation 25MPa, life 9000 cycles; profile bending degree ≤0.3mm / m, pass rate 99.5%.

[0094] Example 11 This embodiment focuses on the extrusion die for 5052 series recycled aluminum rail transit profiles (cross-section size 500mm × 120mm), with the following parameters: Substrate preparation: 92% W6Mo5Cr4V2, 7% Cu-Ni, 0.5% Ce, 0.5% WC; melting at 1550℃ / 2h, stirring at 300r / min; directional solidification at 5℃ / min, grain size 10μm, hardness 28HRC; elemental deviation ±0.1%.

[0095] Gradient heat treatment: ① Preheating 650℃ / 1h, 850℃ / 2h (10℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1180℃ / 1.5h, nitrogen cooling 50℃ / s, temperature difference ±10℃; ③ Tempering 560℃ / 2h, 3 times, hardness 62HRC.

[0096] Cavity design: wall thickness difference 0.8mm, corner R3mm, ribs 2mm / 5mm; machining speed 8000r / min, feed 150mm / min, cooling 80℃ / min, Ra1.5μm.

[0097] Surface strengthening: ① Sandblasting 120 mesh / 0.4MPa pressure, 45° spray angle, cleaning 300W / 15min; ② Spraying 35kW / 100mm, coating 50μm; ③ Sealing 80℃ / 1h, inspection qualified; ④ Aging 180℃ / 4h.

[0098] Test results: Maximum stress 450MPa, standard deviation 35MPa, life 8000 cycles; profile compressive strength ≥300MPa, surface qualification rate 99%.

[0099] Example 12 This embodiment uses the same extrusion die for 5052 series recycled aluminum rail transit profiles (same as in Embodiment 11), with the following parameter adjustments: Substrate: 92.5% W6Mo5Cr4V2, 6.5% Cu-Ni, 0.6% Ce, 0.4% WC; Melting at 1560℃ for 2.1h, stirring at 310r / min; solidification at 6℃ / min, grain size 8μm, hardness 29HRC; elemental deviation ±0.08%.

[0100] Heat treatment: ① Preheating 660℃ / 1.2h, 860℃ / 2.2h (12℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1190℃ / 1.6h, cooling 52℃ / s, temperature difference ±8℃; ③ Tempering 565℃ / 2.2h, 3 times, hardness 63HRC.

[0101] Cavity: wall thickness difference 0.7mm, R3.5mm, ribs 2.2mm / 6mm; machining speed 8500r / min, feed 160mm / min, cooling 85℃ / min, Ra1.4μm.

[0102] Surface treatment: ① Sandblasting 130 mesh / 0.45MPa pressure, 50° spray angle, cleaning 320W / 16min; ② Spraying 36kW / 105mm, coating 55μm, adhesion 52MPa; ③ Sealing 90℃ / 1.1h, inspection qualified; ④ Aging 185℃ / 4.2h.

[0103] Test results: Maximum stress 440MPa, standard deviation 33MPa, life 8200 cycles; profile compressive strength ≥305MPa, pass rate 99.2%.

[0104] Example 13 This embodiment uses the same extrusion die for 5052 series recycled aluminum rail transit profiles (same as in Embodiment 11), with the following parameter adjustments: Substrate: 93%W6Mo5Cr4V2, 6%Cu-Ni, 0.7%Ce, 0.3%WC; Melting at 1570℃ for 2.2h, stirring at 320r / min; Solidification at 7℃ / min, grain size 7μm, hardness 30HRC; elemental deviation ±0.07%.

[0105] Heat treatment: ① Preheating 670℃ / 1.3h, 870℃ / 2.5h (13℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1200℃ / 1.7h, cooling 55℃ / s, temperature difference ±7℃; ③ Tempering 570℃ / 2.3h, 3 times, hardness 64HRC.

[0106] Cavity: wall thickness difference 0.6mm, R4mm, ribs 2.5mm / 7mm; machining speed 9000r / min, feed 170mm / min, cooling 90℃ / min, Ra1.3μm.

[0107] Surface treatment: ① Sandblasting 140 mesh / 0.5MPa pressure, 55° spray angle, cleaning 350W / 17min; ② Spraying 37kW / 110mm, coating 60μm, adhesion 53MPa; ③ Sealing 95℃ / 1.2h, inspection qualified; ④ Aging 190℃ / 4.5h.

[0108] Test results: Maximum stress 430MPa, standard deviation 31MPa, life 8500 cycles; profile compressive strength ≥310MPa, pass rate 99.3%.

[0109] Example 14 This embodiment uses the same extrusion die for 5052 series recycled aluminum rail transit profiles (same as in Embodiment 11), with the following parameter adjustments: Substrate: 93.5% W6Mo5Cr4V2, 5.5% Cu-Ni, 0.8% Ce, 0.2% WC; Melting at 1580℃ for 2.3h, stirring at 330r / min; Solidification at 7℃ / min, grain size 6μm, hardness 31HRC; elemental deviation ±0.06%.

[0110] Heat treatment: ① Preheating 675℃ / 1.4h, 875℃ / 2.7h (14℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1210℃ / 1.8h, cooling 58℃ / s, temperature difference ±6℃; ③ Tempering 575℃ / 2.4h, 3 times, hardness 64.5HRC.

[0111] Cavity: wall thickness difference 0.5mm, R4.5mm, ribs 2.8mm / 7.5mm; machining speed 9500r / min, feed 180mm / min, cooling 95℃ / min, Ra1.25μm.

[0112] Surface treatment: ① Sandblasting 145 mesh / 0.55MPa pressure, 58° spray angle, Ra1.25μm; cleaning 380W / 18min; ② Spraying 38kW / 115mm, coating 70μm, adhesion 54MPa; ③ Sealing 98℃ / 1.4h, qualified; ④ Aging 195℃ / 4.7h.

[0113] Test results: Maximum stress 420MPa, standard deviation 29MPa, life 8800 cycles; profile compressive strength ≥315MPa, pass rate 99.4%.

[0114] Example 15 This embodiment uses the same extrusion die for 5052 series recycled aluminum rail transit profiles (same as in Embodiment 11), with the following parameter adjustments: Substrate: 94%W6Mo5Cr4V2, 5%Cu-Ni, 1%Ce, 1%WC; Melting at 1600℃ for 2.5h, stirring at 350r / min; Solidification at 8℃ / min, grain size 5μm, hardness 32HRC; elemental deviation ±0.05%.

[0115] Heat treatment: ① Preheating 680℃ / 1.5h, 880℃ / 3h (15℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1220℃ / 2h, cooling 60℃ / s, temperature difference ±5℃; ③ Tempering 580℃ / 2.5h, 3 times, hardness 65HRC.

[0116] Cavity: wall thickness difference 0.4mm, R5mm, ribs 3mm / 8mm; machining speed 10000r / min, feed 200mm / min, cooling 100℃ / min, Ra1.2μm.

[0117] Surface treatment: ① Sandblasting 150 mesh / 0.6MPa pressure, 60° spray angle, Ra1.2μm; cleaning 400W / 20min; ② Spraying 40kW / 120mm, coating 80μm, adhesion 55MPa; ③ Sealing 100℃ / 1.5h, qualified; ④ Aging 200℃ / 5h.

[0118] Test results: Maximum stress 400MPa, standard deviation 25MPa, life 9000 cycles; profile compressive strength ≥320MPa, pass rate 99.5%.

[0119] Example 16 This embodiment verifies the compatibility of hybrid recycled aluminum profiles. For an extrusion die used with a 6061+6082+5052 series hybrid recycled aluminum profile (section size 350mm×90mm), the parameters are as follows: Substrate preparation: 93% W6Mo5Cr4V2, 6% Cu-Ni, 0.7% Ce, 0.3% WC; melting at 1570℃ for 2.2h, stirring at 320r / min; directional solidification at 7℃ / min, grain size 7μm, hardness 30HRC; elemental deviation ±0.07%.

[0120] Gradient heat treatment: ① Preheating 670℃ / 1.3h, 870℃ / 2.5h (13℃ / min), holding temperature deviation ≤±5℃; ② Quenching 1200℃ / 1.7h, cooling 55℃ / s, temperature difference ±7℃; ③ Tempering 570℃ / 2.3h, 3 times, hardness 64HRC.

[0121] Cavity design: wall thickness difference 0.6mm, corner R4mm, ribs 2.5mm / 7mm; five-axis machining speed 9000r / min, feed 170mm / min, cooling 90℃ / min, Ra1.3μm.

[0122] Surface strengthening treatment: ① Sandblasting 140 mesh / 0.5MPa pressure, 55° spray angle, cleaning 350W / 17min; ② Spraying 37kW / 110mm, coating 60μm, adhesion 53MPa; ③ Sealing 95℃ / 1.2h, inspection qualified; ④ Aging 190℃ / 4.5h.

[0123] Test results: Maximum stress of the mold is 430MPa, standard deviation of stress distribution is 31MPa, and service life is 8500 cycles; tensile strength of extruded hybrid profile is 290-320MPa, dimensional accuracy is ±0.08mm, and surface qualification rate is 99.3%.

Claims

1. A method for preparing a recycled aluminum profile extrusion die with uniform stress distribution, characterized in that, Includes the following steps: S1. Substrate preparation: Mix 92%–94% W6Mo5Cr4V2 high-speed steel, 5%–7% Cu-Ni alloy, 0.5%–1% rare earth element Ce, and 0.5%–1% carbide WC by mass ratio, wherein the mass ratio of Cu to Ni in the Cu-Ni alloy is 7:

3. Put the mixed raw materials into a vacuum induction melting furnace and melt at 1550–1600℃ for 2–2.5 hours. During the melting process, the vacuum degree is controlled at ≤30Pa. Then, directional solidification technology is used to solidify the melted raw materials into a mold substrate blank at a cooling rate of 5–8℃ / min. The hardness of the substrate blank is controlled at 28–32HRC. S2. Gradient heat treatment: The substrate blank is preheated, quenched and tempered in sequence. Among them, preheating: the substrate blank is first kept at 650-680℃ for 1-1.5h, and then heated to 850-880℃ at a heating rate of 10-15℃ / min, and kept at this temperature for 2-3h. Quenching: Heat to 1180-1220℃ at a set rate, hold the substrate blank at this temperature for 1.5-2 hours, and then cool to below 200℃ using nitrogen cooling at a cooling rate of 50-60℃ / s. Tempering: The quenched substrate blank is held at 560-580℃ for 2-2.5h, and then cooled to room temperature in the furnace. This tempering operation is repeated 3 times. The final substrate hardness is controlled at 62-65HRC. S3. Bionic Design and Processing of Cavities: Based on the cross-sectional dimensions of recycled aluminum profiles, a bionic honeycomb structure is used to design the mold cavity. The wall thickness difference of the designed cavity is ≤0.8mm, and an arc transition of R3-R5mm is set at the corner of the cavity. The cavity is machined using a five-axis linkage machining center. During the machining process, the spindle speed is controlled at 8000-10000 r / min and the feed rate is controlled at 150-200 mm / min. Laser inspection is used after machining is completed. S4. Surface strengthening treatment: The mold cavity is sequentially subjected to sandblasting, plasma spraying, sealing treatment and aging treatment. Sandblasting treatment: 120-150 mesh white corundum sand is used to sandblast the surface of the mold cavity at a pressure of 0.4-0.6MPa. After treatment, the surface roughness Ra of the mold cavity is controlled at 1.2-1.5μm. Plasma spraying: Plasma spraying is performed on the surface of the mold cavity after sandblasting. The spraying material is selected as Al2O3-TiO2 mixed powder, in which the mass ratio of Al2O3 to TiO2 is 85:

15. The spraying power is controlled at 35-40kW, the spraying distance is controlled at 100-120mm, and the coating thickness formed after spraying is 50-80μm. Sealing treatment: The coating is sealed with an epoxy resin sealing agent with a solid content of ≥95%, and cured at 80-100℃ for 1-1.5h. Aging treatment: After the sealing treatment is completed, the mold is subjected to overall aging treatment, which is held at 180-200℃ for 4-5 hours, and then cooled to room temperature in the furnace. The final surface hardness of the mold is ≥850HV.

2. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: In the substrate preparation step, the stirring rate of the vacuum induction melting furnace is controlled at 300-350 r / min to ensure uniform alloy composition. After melting, the content of W, Mo, Cr and V elements is detected by a spectrometer, and the deviation is ≤ ±0.1%.

3. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: The nitrogen used in the quenching and cooling process during the gradient heat treatment step has a purity of ≥99.99%, and the temperature difference between different parts of the mold is controlled within ±10℃ during the cooling process to avoid internal stress caused by excessive temperature difference.

4. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: In the biomimetic design and processing steps of the cavity, the width of the cavity ribs in the biomimetic honeycomb structure is 2-3mm, the rib spacing is 5-8mm, and the connection angle between the ribs and the cavity wall is 120°, so as to improve the stability of the cavity structure and the stress dispersion ability.

5. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: Before plasma spraying in the surface strengthening treatment step, the mold cavity surface is ultrasonically cleaned with alcohol. The cleaning power is controlled at 300-400W and the cleaning time is controlled at 15-20min to remove surface oil and impurities and ensure that the coating adhesion is ≥50MPa.

6. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: During the directional solidification process in the substrate preparation step, a water-cooled copper mold is used, and the grain size of the mold substrate blank is controlled at 5-10μm to avoid stress concentration caused by coarse grains.

7. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: In the biomimetic design and machining process of the cavity, the five-axis linkage machining center uses diamond tools with a hardness ≥90HRC. During the machining process, cutting fluid with a cooling rate ≥80℃ / min is used for cooling to prevent the mold surface from overheating and causing oxidation or microcracks.

8. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: During the sandblasting process, the spraying angle of the white corundum abrasive is controlled at 45-60°, and the spraying path is moved in a reciprocating and uniform manner to ensure that the sandblasting is uniform in all areas of the mold cavity surface and to avoid surface roughness differences caused by excessive or insufficient sandblasting in certain areas.

9. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: During the preheating stage of the gradient heat treatment step, after the temperature is raised to 850-880℃, the temperature of the substrate blank needs to be checked during the heat preservation process. The temperature of different areas of the substrate blank is recorded every 30 minutes to ensure that the temperature deviation of each area is ≤±5℃, thus ensuring uniform transformation of the substrate structure.

10. The method for preparing a recycled aluminum profile extrusion die with uniform stress distribution according to claim 1, characterized in that: After the sealing process is completed in the surface strengthening treatment step, the surface of the mold cavity needs to be inspected for appearance and porosity. The appearance inspection is carried out by visual inspection combined with a magnifying glass to ensure that there is no leakage or blistering of the coating.

Images