Anti-deformation engineering mechanical structural part and forming method thereof

Abstract

The invention belongs to the technical field of machining, and particularly relates to an anti-deformation engineering mechanical structural component and a forming method thereof.The forming method comprises the steps that S1, a base material is selected and cut into a blank with the preset size, and after the blank is subjected to pre-oil treatment, the blank is machined through cold press forming to obtain a preliminary configuration; s2, the preformed blank is heated to 420-450 DEG C, heat preservation is conducted for 20-30 min, the blank is put into a mold with a subarea gradient cooling channel, and a dynamic pressure mode of prepressing, main pressing and pressure maintaining is adopted; a densified formed part is obtained; s3, heating the densified molded part to 460-480 DEG C, preserving heat for 1.5-2 hours, cooling the molded part to 200-220 DEG C along with a furnace when the internal stress value of the molded part is reduced to 120-150 MPa, adjusting the heat preservation time according to the real-time stress, and quickly cooling the molded part to room temperature in a manner of combining air cooling and water mist cooling; and S4, the size of the formed part is corrected, a bionic hollow grid reinforcing structure is machined on a key stress part, and finally the anti-deformation mountain bike structural part is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical processing, and particularly relates to an anti-deformation engineering mechanical structural member and a forming method thereof. BACKGROUND

[0002] The core structural members (such as front forks, frames, cranks) of mountain bikes need to bear high-frequency impact loads and cyclic stresses under off-road working conditions, and the anti-deformation performance thereof directly determines the riding safety and service life. In the prior art, the forming process of the structural members of mountain bikes mainly includes two types: Metal base structural members: the "extrusion forming + welding assembly" process is generally adopted, and there are inherent defects: the welding joint is easy to form a heat-affected zone, and thermal cracks and stress concentration are generated, and the joint strength is only 70% to 85% of that of the base material; the internal extrusion blank is easy to leave defects such as porosity, and the compactness is insufficient, resulting in limited anti-deformation ability. Some improved schemes adopt the traditional isothermal die forging process, but the constant pressure and uniform cooling mode cannot adapt to the forming requirements of different wall thickness regions of the structural members, and the thick wall region is easy to accumulate internal stress due to rapid cooling, and the thin wall region is easy to cause insufficient densification due to insufficient pressure.

[0003] Carbon fiber reinforced epoxy resin composite material structural members: mainly adopt the "pre-impregnated cloth layering + air bag integrated forming" process, which relies on preset layering direction to control fiber orientation, and the deviation of fiber orientation and actual stress direction of complex stress nodes (such as frame five-way joints) often exceeds 10°, resulting in local weak strength; and the fiber orientation cannot be dynamically adjusted during the forming process, the production efficiency is low, and the forming quality stability of complex structures is poor.

[0004] The traditional reinforcing structure is designed as a solid or simple hollow structure, and there is a contradiction that "lightweight and anti-deformation performance cannot be achieved simultaneously", the solid structure is too heavy, and the simple hollow structure has insufficient bending and torsional deformation resistance. Therefore, an anti-deformation engineering mechanical structural member and a forming method thereof are improved and designed. SUMMARY

[0005] In view of the above deficiencies in the prior art, the present application provides an anti-deformation engineering mechanical structural member and a forming method thereof to solve the problems in the background art.

[0006] In order to solve the above technical problems, the present application adopts the following technical scheme: A forming method of an anti-deformation engineering mechanical structural member, comprising the following steps: S1. Pre-forming treatment: selecting a high-strength base material, cutting it into a blank of a predetermined size, and after surface rust removal and oil removal treatment of the blank, cold pressing pre-forming is adopted to obtain a preliminary configuration, and the preliminary configuration is adapted to the shape of the target structural member of the mountain bike; S2. Dynamic pressure-gradient cooling synergistic isothermal die forming: after preforming the blank, heat it to 420-450℃ and keep it for 20-30 min, put it into a precision die with built-in partitioned gradient cooling channels and titanium nitride coating on the surface of the cavity, and use the dynamic pressure mode of "pre-pressing-main pressing-holding": first apply a pre-pressing of 500-600 MPa for 10-15 s to make the blank adhere to the die cavity, then increase the main pressure to 800-1000 MPa for 15-25 s to realize densification, and finally reduce the holding pressure to 600-700 MPa for 5-8 s to eliminate local stress; at the same time, gradient temperature cooling liquid is supplied to the partitioned cooling channels of the die: 30-35℃ cooling liquid is supplied to the thick wall area of the structure, and 45-50℃ cooling liquid is supplied to the thin wall area, controlling the difference in cooling rate of different areas of the blank to be ≤2℃ / min, to obtain a densified formed part; S3. Stress self-adaptive staged heat treatment: use a heat treatment furnace with built-in infrared stress sensors, first heat the densified formed part to 460-480℃ and keep it for 1.5-2h, monitor the internal stress of the formed part in real time through the sensor, when the stress value decreases to 120-150 MPa, cool it to 200-220℃ in the furnace and adjust the holding time according to the real-time stress (if the stress is >100 MPa, extend the holding time to 40-45 min, if the stress is ≤100 MPa, keep it for 30-35 min), then use a combination of air cooling and water mist cooling to quickly cool it to room temperature to eliminate residual stress of the formed part; S4. Bionic topological precision post-processing: use CNC machining to correct the size of the formed part, with a machining accuracy of ±0.02mm; process bionic hollow grid reinforcement structure on key stress areas (such as front fork legs and frame five-way junction), which includes micro-hollow cavities with a diameter of 1-2mm and cross support ribs with an included angle of 60°, the overall thickness of the reinforcement structure is 1.2-1.5 times the thickness of the main body of the structure, and the cross support ribs are consistent with the stress direction of the structure, finally obtaining an anti-deformation mountain bike structure.

[0007] Further, the high-strength substrate is 7075 aluminum alloy.

[0008] Further, the mold parting surface in step S2 is provided with a stepped exhaust groove, which includes a main exhaust section with a width of 0.1-0.2mm and a depth of 0.3-0.5mm, and an auxiliary exhaust section with a width of 0.05-0.08mm and a depth of 0.1-0.2mm, the main exhaust section and the auxiliary exhaust section are connected at an angle of 30° to avoid gas wrapping defects during blank forming.

[0009] Further, the combination of air cooling and water mist cooling in step S3 is as follows: 10-12 m / s air cooling is used in the initial cooling stage (the temperature of the formed part is 200-150 DEG C), 12-15 m / s air cooling plus 5-8 um particle size water mist cooling is used in the middle cooling stage (150-80 DEG C), and air cooling is restored in the late cooling stage (80 DEG C to room temperature) to avoid surface cracking caused by rapid cooling.

[0010] Further, the micro hollow cavity of the bionic hollow grid reinforcing structure in step S4 is filled with nano-sized alumina ceramic particles (particle size 50-100 nm), and the filling amount is 30%-40% of the volume of the hollow cavity, so that the wear resistance and impact resistance of the structure are improved.

[0011] Further, the structure is a mountain bike front fork, frame or crank, the grain size inside the structure is ≤50 um (metal base material) or the fiber orientation deviation is ≤5 DEG (carbon fiber base material), the residual stress is ≤60 MPa, the bending deformation under a load of 2000 N is ≤0.12 mm, and the torsional deformation under a torsional load of 1500 N is ≤0.08 mm.

[0012] Further, the surface of the structure is provided with a micro-arc oxidation ceramic coating, the coating thickness is 8-12 um, the hardness is ≥1200 HV, and the corrosion resistance and scratch resistance are improved.

[0013] Compared with the prior art, the present application has the following beneficial effects: 1. The dynamic pressure mode of "pre-pressing-main pressing-pressure maintaining" adapts to the plasticity requirements of the blank in different forming stages, and the partition gradient cooling balances the uneven cooling rate caused by the wall thickness difference, so that the density of the metal base material is improved from 99.2% in the prior art to 99.8%, and stress concentration is effectively avoided. Stress self-adaptive staged heat treatment: real-time monitoring by an infrared stress sensor combined with parameter self-adaptive adjustment, the residual stress control precision is improved from ±20 MPa in the prior art to ±5 MPa, and the final residual stress is ≤60 MPa, which is reduced by more than 30% compared with the traditional process; 2. Bionic hollow grid reinforcing structure: imitating the topological design of bird bones, the micro hollow cavity realizes weight reduction of 10%-15%, the 60 DEG cross support rib strengthens the deformation resistance in the stress direction, the bending deformation under a load of 2000 N is ≤0.12 mm, which is improved by 20% compared with the traditional structure; 3. The main and auxiliary exhaust sections are cooperatively exhausted to avoid gas wrapping defects, and the surface defect rate of the formed part is reduced by 40%. Nano ceramic particle filling: the wear resistance and impact resistance of the bionic structure are improved, and the impact test life is prolonged from 300,000 times to 400,000 times. Micro-arc oxidation ceramic coating: hardness ≥1200 HV, corrosion resistance and scratch resistance are improved by more than 2 times compared with the uncoated structure. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 This is a flowchart of a method for forming anti-deformation engineering mechanical structural components according to the present invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0017] A method for forming a deformation-resistant engineering machinery structural component includes the following steps: S1. Pre-forming process: Select a high-strength substrate, cut it into blanks of a preset size, and after surface rust removal and degreasing treatment, use cold pressing to pre-form a preliminary shape. The preliminary shape is adapted to the shape of the target structural component of the mountain bike. S2. Dynamic Pressure-Gradient Cooling Coordinated Isothermal Forging: The pre-formed billet is heated to 420-450℃ and held for 20-30 minutes. It is then placed in a precision mold with built-in partitioned gradient cooling channels and a titanium nitride coating on the cavity surface. A dynamic pressure mode of "pre-pressure-main pressure-holding" is adopted: first, a pre-pressure of 500-600MPa is applied for 10-15 seconds to make the billet fit the mold cavity, then the main pressure is increased to 800-1000MPa for 15-25 seconds to achieve densification, and finally the pressure is reduced to 600-700MPa and held for 5-8 seconds to eliminate local stress. At the same time, gradient temperature coolant is introduced into the partitioned cooling channels of the mold: 30-35℃ coolant is introduced into the thick-walled area channel of the structural part, and 45-50℃ coolant is introduced into the thin-walled area channel. The cooling rate difference between different areas of the billet is controlled to be ≤2℃ / min to obtain a densified formed part. The critical temperature range for plastic deformation of the selected substrate (taking 7075 aluminum alloy as an example) is 400-480℃, of which 420-450℃ is the overlapping range of dynamic recrystallization and optimal plasticity: if the temperature is too low (<420℃): the material plasticity is insufficient, cracks are easily generated during die forging, and higher pressure is required to deform, increasing die wear. Excessive temperature (>450℃): The material is prone to overheating, resulting in coarse grains and reduced final strength. Furthermore, aluminum alloys are prone to oxidation above 480℃, forming oxide scale that affects forming quality. The design of holding the temperature for 20-30 minutes is to ensure uniform internal temperature of the billet (temperature difference ≤5℃) and avoid uneven deformation caused by local temperature differences. If the holding time is too short (<20 minutes), the core of the billet will not be fully heated, and "hard spots" are likely to occur during die forging. If it is too long (>30 minutes), it will increase energy consumption and may lead to accelerated surface oxidation.

[0018] The core of the dynamic pressure mode is to "adjust the pressure according to the mechanical state of the billet at different forming stages," precisely matching the plastic flow law of the material: Pre-compression stage (500-600MPa, 10-15s): Achieving a tight fit between the billet and the cavity. The pre-compression pressure needs to be sufficient to overcome the initial plastic resistance of the billet, allowing it to quickly fill the corner details of the mold cavity (such as the curvature of the fork, the irregular structure of the frame), but it cannot be too high—if the pressure > 600MPa, it may cause premature excessive deformation in thin-walled areas (such as wrinkles); if the pressure < 500MPa, the fit will be insufficient, and air bubbles or unfilled areas are easily formed during subsequent main compression. The 10-15s time design is to give the billet sufficient flow time to ensure complete fit of complex cavities. Main compression stage (800-1000MPa, 15-25s): Achieving material densification and eliminating internal defects. Main compression is the core stage of densification: the yield strength of 7075 aluminum alloy decreases significantly at high temperatures (approximately 1 / 3 of that at room temperature at 420℃). Pressure of 800-1000MPa forces the closure of internal defects such as porosity and pores in the billet (increasing density from 95%-97% in the extruded state to over 99.5%). The time is set at 15-25s because the closure of defects in thick-walled areas (such as fork legs) requires more time—too short (<15s) results in incomplete densification, while too long (>25s) may lead to localized thinning of the material due to excessive plastic flow (thin-walled area risk).

[0019] The coordination between the cooling system and dynamic pressure is key to solving the problem of uneven molding quality in areas with different wall thicknesses. The core logic is to "synchronously control the temperature gradient during pressure application, allowing the material to release stress in a plastic state": Thick-walled areas (30-35℃ coolant) and their coordination with the main pressure stage: Thick-walled areas (such as fork legs and frame bottom brackets) have large volumes and slow heat dissipation. Insufficient cooling will result in the material remaining in a high-temperature plastic state after the main pressure, easily generating internal stress due to uneven shrinkage during subsequent cooling. A low-temperature coolant of 30-35℃ can accelerate heat dissipation in thick-walled areas, reducing their temperature to 380-400℃ at the end of the main pressure (while still maintaining a certain degree of plasticity). Combined with the pressure during the holding stage, this allows the material to release stress through controlled shrinkage. Thin-walled areas (45-50℃ coolant) and their coordination with the pre-pressure / main pressure stage: Thin-walled areas (such as fork tubes and frame top tubes) dissipate heat quickly. If cooling is too rapid (e.g., using 30℃ coolant), the material will lose its plasticity due to a sudden temperature drop before the main pressure, leading to cracking during the main pressure. A high-temperature coolant of 45-50℃ can slow down heat dissipation, ensuring that the thin-walled area maintains a high plastic temperature of 400-420℃ throughout the pre-pressing and main-pressing densification stages, guaranteeing that the pressure can smoothly drive material flow. Simultaneously, the higher coolant temperature reduces the cooling rate difference between the thin-walled and thick-walled areas (controlled to ≤2℃ / min), preventing thermal stress caused by excessive temperature differences. The timing of the cooling rate and pressure stages is matched as follows: Pre-pressing stage (10-15s): The cooling system starts synchronously. At this time, the billet has just come into contact with the mold, and heat dissipation is mainly through conduction from the mold, with gradient cooling initially establishing the temperature field; Main-pressing stage (15-25s): The cooling rate reaches its peak (approximately 5-6℃ / min for thick-walled areas and 3-4℃ / min for thin-walled areas), achieving "densification while controlling temperature" in conjunction with high pressure; Holding pressure stage (5-8s): The cooling rate slows down, ensuring that the material still has plastic buffer when stress is released, preventing embrittlement and cracking.

[0020] The channel routing follows the cavity contour (e.g., the channel in a fork mold bends with the curvature of the fork foot and fork tube), ensuring that the coolant can directly act on the corresponding wall thickness area; the channel diameter design of 8-10mm ensures flow rate (meeting the cooling rate requirements) without weakening the mold strength due to excessive diameter (the mold needs to withstand 1000MPa high pressure, and excessively large channels will lead to local stress concentration). The titanium nitride coating (hardness ≥2000HV) on the cavity surface has two main functions: reducing the coefficient of friction (from 0.3 to 0.15), reducing the risk of adhesion between the billet and the mold, and ensuring that the billet can smoothly fit the cavity during the pre-pressing stage (avoiding local deformation lag caused by frictional resistance); improving the mold's wear resistance (extending life by 3-5 times), adapting to repeated friction under high pressure during the main pressing stage, while the coating's high temperature resistance (can withstand above 600℃) ensures stable performance at forging temperatures of 420-450℃.

[0021] The four elements of isothermal forging (staged deformation control), gradient cooling (balanced temperature field), heating parameters (ensuring plasticity), and mold structure (stabilizing the forming environment) form a closed loop: heating provides the "plastic basis" for pressure, pressure provides the "densification prerequisite" for cooling, cooling provides the "temperature conditions" for stress control after pressure, and the mold structure provides the "stabilizing carrier" for all three. Ultimately, the following results are achieved: metal substrate density ≥99.8%, residual stress ≤60MPa, and bending deformation ≤0.12mm under 2000N load. This represents a 20% to 30% performance improvement over traditional isothermal forging (constant pressure + uniform cooling), completely solving the industry pain points of "porosity in thick-walled areas, cracking in thin-walled areas, and excessive overall stress".

[0022] The division between thick-walled and thin-walled channels is based entirely on the design wall thickness distribution of the target structural component. Thick-walled channels are for areas on the mold corresponding to structural components with "larger wall thickness, slower heat dissipation, and requiring rapid cooling," and are used to introduce low-temperature coolant at 30-35℃. Thin-walled channels are for areas on the mold corresponding to structural components with "smaller wall thickness, faster heat dissipation, and requiring slow cooling," and are used to introduce high-temperature coolant at 45-50℃. The core purpose is to balance the cooling rate of different wall thickness areas (difference ≤2℃ / min) through the temperature difference of the coolant, avoiding stress concentration or molding defects caused by heat accumulation in thick-walled areas and overcooling in thin-walled areas. For mountain bike forks, thick-walled areas are those with a wall thickness ≥6mm (such as fork legs and the connection to the frame), and thin-walled areas are those with a wall thickness ≤4mm (such as the fork tube body). Transition areas with a wall thickness between 4 and 6mm, such as the transition between the fork legs and the fork tube, are connected to thick-walled channels according to the principle of "matching the nearest available channel." For mountain bike frames, the thick-walled areas are those with a wall thickness ≥ 5mm (such as the bottom bracket and lower section of the seat tube), the thin-walled areas are those with a wall thickness ≤ 3mm (such as the top tube and middle section of the down tube), and the transition areas with a wall thickness between 3 and 5mm are matched according to the "wall thickness ratio." Areas ≥ 4mm are connected to the thick-walled area channels. For mountain bike cranks, the thick-walled areas are those with a wall thickness ≥ 8mm (such as around the crank pin holes), the thin-walled areas are those with a wall thickness ≤ 5mm (such as the crank stem body), and the transition areas with a wall thickness between 5 and 8mm are directly connected to the thick-walled area channels. The above thresholds can be adjusted according to the mechanical design of specific structural components, but it is necessary to ensure that "the wall thickness of the thick-walled area is ≥ 1.5 times the wall thickness of the thin-walled area" to ensure significant differences in cooling requirements. Due to the need for enhanced cooling, the thick-walled area channels have a denser channel spacing (15-20mm) and run closely to the cavity contour to ensure sufficient heat exchange between the coolant and the thick-walled area; the thin-walled area channels have a wider channel spacing (25-30mm) and can be appropriately simplified to avoid over-cooling.

[0023] S3. Stress-Adaptive Graded Heat Treatment: A heat treatment furnace with built-in infrared stress sensors is used to first heat the densified molded part to 460-480℃ and hold it for 1.5-2 hours. The internal stress of the molded part is monitored in real time by the sensor. When the stress value drops to 120-150MPa, it is cooled to 200-220℃ in the furnace and the holding time is adjusted according to the real-time stress (the holding time is extended to 40-45 minutes when the stress is >100MPa, and 30-35 minutes when the stress is ≤100MPa). Then, it is rapidly cooled to room temperature by a combination of air cooling and water mist cooling to eliminate residual molding stress. Traditional graded heat treatment relies on preset fixed parameters (such as a fixed holding time of 2 hours), which cannot perceive the actual residual stress distribution of individual molded parts. After die forging, the residual stress difference between different structural parts (fork / frame / crank), and even different areas of the same part, can reach 50-80 MPa (the stress in thick-walled areas is usually 30% higher than that in thin-walled areas). Sensors, through infrared thermal imaging combined with stress wave detection, can accurately identify the internal stress value of the molded part (error ≤ 5 MPa), avoiding the blindness of "setting parameters based on experience". It forms a closed-loop control with subsequent temperature, holding time, and cooling method to ensure "more stress release when the stress is high and stable strength when the stress is low", which is a key prerequisite for achieving residual stress ≤ 60 MPa.

[0024] Heating temperature (460-480℃) and holding time (1.5-2h) create conditions for stress release. This temperature and time setting simultaneously meets the two major requirements of "stress release" and "solid solution strengthening of materials" and forms a connection with the die forging process: The recrystallization temperature of the selected 7075 aluminum alloy is 380-400℃, and 460-480℃ is its optimal overlap range of "stress release + solid solution strengthening": When the temperature is ≥460℃, the work hardening caused by die forging inside the formed part can be effectively eliminated, the atomic diffusion ability is enhanced, and the residual stress (usually 200-300MPa after die forging) can be reduced rapidly; When the temperature is ≤480℃, excessive grain growth can be avoided (grain size controlled ≤50μm), while ensuring that the strengthening phase (MgZn2) in the aluminum alloy is fully dissolved in the matrix, laying the foundation for subsequent aging strengthening. The purpose of holding the temperature for 1.5 to 2 hours is to achieve a uniform temperature field and initial stress relief. After forging, there is a temperature gradient inside the formed part (the temperature in the thick-walled area may be 20-30℃ higher than that in the thin-walled area). Holding for 1.5 to 2 hours can first achieve "temperature homogenization" (temperature difference ≤ 5℃), avoiding uneven stress release due to local temperature differences. At the same time, this duration can reduce the initial residual stress from 200-300MPa to 120-150MPa (sensor monitoring threshold), laying the groundwork for subsequent "targeted holding". If the holding time is too short (<1.5h), the stress will not drop to the threshold before cooling, which may lead to stress freezing. If it is too long (>2h), the grains will become coarse, reducing the material strength (tensile strength may decrease by 8% to 10%).

[0025] The stress threshold (120-150MPa) is coordinated with furnace cooling to 200-220℃ to avoid the generation of new stress. When the sensor detects that the stress has dropped to 120-150MPa, furnace cooling to 200-220℃ is initiated. This step is the key link between "stress release and prevention of new stress". The stress threshold is set based on the fact that 120-150MPa is the critical stress for "safe cooling". If the stress is >150MPa and cooling is performed directly, the molded part will generate new thermal stress due to stress superposition during cooling and shrinkage (which may add 30-40MPa). If the stress is <120MPa and cooling is performed, the production cycle will be extended and overheating may cause the strengthening phase to precipitate prematurely, affecting the subsequent strength.

[0026] The synergy of furnace cooling and target temperature (200-220℃) with the slow furnace cooling rate (5-8℃ / min), far lower than the air cooling rate (15-20℃ / min), avoids uneven thermal expansion and contraction caused by excessively rapid cooling, ensuring that stress is continuously released during slow contraction. 200-220℃ is the aging temperature range of 7075 aluminum alloy. Cooling to this temperature and then holding it at that temperature can not only continue to release stress, but also allow the dissolved strengthening phase (MgZn2) in the matrix to precipitate uniformly, forming a fine and dispersed second phase, which improves the material's hardness and resistance to deformation—achieving simultaneous "stress release" and "strength improvement".

[0027] When the sensor detects that the initial stress at 200-220℃ is >100MPa (indicating that the residual stress is still high, such as in thick-walled areas or complex structures), the holding time is extended to 40-45 minutes: through longer atomic diffusion, the residual stress is further released to ≤80MPa before entering the cooling stage; when the stress is ≤100MPa (indicating that the stress release is sufficient, such as in thin-walled areas or simple structures), the holding time is only 30-35 minutes: to avoid excessive holding time leading to excessive or large precipitation of strengthening phase, which affects the material's toughness (elongation may decrease by 15%); the essence is "allocating the holding time as needed" to ensure that the molded parts under different stress states can achieve "residual stress ≤60MPa" without sacrificing strength and toughness.

[0028] The core design principle of the cooling stage is to "avoid new stress caused by uneven cooling rate while fixing the strengthening phase" and to precisely match the stress state after the previous heat preservation: initial cooling stage (200-150℃): 10-12m / s air cooling. At this time, the molded part is still in the late stage of aging and the strengthening phase is not yet completely stable. The air cooling rate is moderate (cooling down about 10℃ / min), which can avoid "insufficient precipitation of strengthening phase" caused by rapid cooling, and at the same time allow the residual stress to continue to be released during slow cooling (the stress can be reduced by another 10-15MPa during this stage). Mid-cooling stage (150-80℃): 12-15 m / s air cooling + 5-8 μm water mist cooling. Below 150℃, the strengthening phase is basically stable, and the cooling rate needs to be accelerated to "fix the strengthening effect" (prevent the strengthening phase from growing). Water mist cooling can absorb heat through water vapor evaporation, increasing the cooling rate to 15-18℃ / min. At the same time, the 5-8 μm fine water mist can evenly cover the surface, preventing excessively rapid local cooling. Increasing the air velocity to 12-15 m / s can quickly remove the heat after water mist evaporation, ensuring cooling uniformity and preventing thermal stress caused by excessive temperature difference between the surface and the core. Late-cooling stage (80-room temperature): Resuming air cooling. Below 80℃, the shrinkage rate of the molded part slows down. Resuming gentle air cooling (10-12 m / s) can avoid "excessive cooling" caused by water mist cooling (such as excessively rapid cooling to room temperature may add 20 MPa stress), ensuring that the final residual stress is stable at ≤60 MPa.

[0029] Each design point is not isolated, but rather deeply integrated with the forging process and subsequent processing: Integration with the forging process: After forging, the densely formed part (density ≥99.8%) exhibits significant internal stress concentration. Heating at 460-480℃ precisely targets the work hardening and residual stress generated during forging, preventing stress accumulation; Coordination of temperature transfer and cooling: The temperature curve of heating – holding – segmented cooling (460-480℃ → 200-220℃ → room temperature) conforms to the heat treatment rules of 7075 aluminum alloy, while ensuring stress release always occurs within the "plastic buffer zone," preventing embrittlement and cracking.

[0030] S4. Biomimetic Topology Precision Post-Processing: CNC machining is used to correct the dimensions of the molded parts, and the machining accuracy is controlled within ±0.02mm; biomimetic hollow mesh reinforcement structures are processed for key stress-bearing parts (such as the fork legs and frame bottom brackets). This structure includes micro hollow cavities with a diameter of 1-2mm and cross support ribs with an included angle of 60°. The overall thickness of the reinforcement structure is 1.2-1.5 times the thickness of the main body of the structural part, and the cross support ribs are consistent with the stress direction of the structural part, ultimately obtaining a deformation-resistant mountain bike structural part.

[0031] Example 1 Existing aluminum alloy front fork welding processes suffer from low joint strength, uneven cooling in traditional die forging, high residual stress, and bulky reinforced structures. This invention addresses these issues by employing a forming method that synergistically improves both deformation resistance and lightweight design. The invention provides a forming method for a deformation-resistant engineering machinery structural component, specifically for forming a 075 aluminum alloy mountain bike front fork. The specific steps are as follows: Step S1: Pre-forming process Select 20mm thick 7075 aluminum alloy sheet, cut it into 300mm×80mm blanks, clean and degrease and remove rust with ultrasonic cleaning, spray the surface with 6μm thick nano release agent, cold press pre-form it into a fork prototype, and leave a 6mm die forging allowance.

[0032] Step S2: Dynamic pressure-gradient cooling coordinated isothermal forging The billet is placed in a heating furnace and held at 430℃ for 25 minutes. It is then transferred to a precision mold with built-in partitioned cooling channels (the cavity surface is coated with titanium nitride, and the parting surface is equipped with stepped venting grooves). Dynamic pressure parameters: 550MPa pre-press for 12s → 900MPa main pressure for 20s → 650MPa holding pressure for 6s. Gradient cooling: 32℃ coolant is introduced into the thick-walled area of ​​the fork leg (8-10mm), and 48℃ coolant is introduced into the thin-walled area of ​​the fork tube (3-5mm). The cooling rate difference is controlled at 1.5℃ / min to obtain a densely formed part.

[0033] Step S3: Stress-adaptive graded heat treatment The molded part was placed in a heat treatment furnace with a built-in infrared stress sensor and held at 470℃ for 1.8 hours. The sensor detected that the stress dropped from 280MPa to 135MPa. The part was then cooled to 210℃. Since the real-time stress was 135MPa > 100MPa, the holding time was extended to 42 minutes, and the stress dropped to 75MPa. The part was then cooled in stages: 200-150℃ (11m / s air cooling) → 150-80℃ (14m / s air cooling + 7μm water mist) → 80℃ to room temperature (11m / s air cooling). The final residual stress was 58MPa.

[0034] Step S4: Precision post-processing of biomimetic topology CNC machining corrects dimensions with precision controlled within ±0.015mm; biomimetic hollow mesh structure is machined in the key stress area of ​​the fork: hollow cavity diameter 1.5mm, cross support rib thickness 1mm, included angle 60°, cavity filled with 60nm alumina ceramic particles (filling amount 35%); surface micro-arc oxidation treatment is applied to form a 10μm ceramic coating with a hardness of 1250HV.

[0035] (3) Test results and technical effects The fork has an internal grain size of 38μm, a density of 99.8%, a residual stress of 58MPa, a bending deformation of 0.09mm under a vertical load of 2000N, a torsional deformation of 0.06mm under a torsional load of 1500N, a weight reduction of 12% compared to traditional solid reinforced rib forks, and no deformation after 400,000 repeated impact tests. Its service life is 1.5 times longer than existing technologies.

[0036] Example 2: Specific steps for forming the crank of a 7075 aluminum alloy mountain bike; (1) Specific steps Pre-forming process: 7075 aluminum alloy blank is cut into 150mm×60mm, cold-pressed into crank prototype, with a 5mm die forging allowance.

[0037] Forging process: Hold at 440℃ for 22 min, apply dynamic pressure of 580MPa for 14 s, apply main pressure of 950MPa for 18 s, and hold pressure of 680MPa for 7 s; introduce 34℃ coolant into the thick-walled area (6 mm) and 46℃ coolant into the thin-walled area (2.5 mm).

[0038] Heat treatment: Hold at 475℃ for 1.7h, and after the stress drops to 145MPa, hold at 215℃ for 44min. After segmented cooling, the residual stress is 57MPa.

[0039] Post-processing: CNC machining accuracy ±0.018mm, biomimetic hollow mesh structure is machined around the crank pin hole, without ceramic particle filling.

[0040] (2) Test results With a grain size of 45μm, residual stress of 57MPa, bending deformation of 0.11mm under 2000N load, and torsional deformation of 0.08mm under 1500N load, it meets the performance indicators of claim 6. Compared with traditional welded cranks, it reduces weight by 10% and increases strength by 45%.

[0041] Example 3: Addressing the problems of large fiber orientation deviations, unstable molding quality of complex structures, and high residual stress in existing carbon fiber frames, this invention employs a carbon fiber adaptation scheme to improve mechanical performance matching. The specific steps for molding a carbon fiber reinforced epoxy resin mountain bike frame are as follows: Step 1: Pre-forming process Toray T700 carbon fiber prepreg was selected and cut into 28 pieces of different shapes according to the frame structure. The pieces were laid in layers with fiber directions of 0°, ±45° and 90° and cold-pressed to preform the frame segments (stem tube, top tube and bottom tube).

[0042] Step 2: Fiber Orientation Dynamic Calibration Integrated Molding The preformed blank is placed outside the double nylon duct mold core (the mold core has a built-in 180mT adjustable magnetic field generator). After the mold is placed in, 220psi pressure gas is introduced into the duct. The calibration component is activated to guide the carbon fiber to be oriented along the axial direction of the frame riser and the radial direction of the five-way connector. The mold is heated to 145℃ and held for 45 minutes. After curing, the duct is extracted to obtain a dense molded part.

[0043] Step 3: Stress-adaptive graded heat treatment The molded part was placed in a heat treatment furnace and held at 465℃ for 1.6 hours. The stress monitored by the sensor decreased from 220MPa to 140MPa. It was then cooled to 205℃ in the furnace. Since the real-time stress was 140MPa > 100MPa, it was held for 43 minutes, and the stress decreased to 62MPa. The part was then cooled in stages: 200-150℃ (10m / s air cooling) → 150-80℃ (13m / s air cooling + 6μm water mist) → 80℃ to room temperature (10m / s air cooling).

[0044] Step 4: Precision post-processing of biomimetic topology The interface dimensions are machined and trimmed with CNC precision of ±0.02mm; the key stress area of ​​the frame bottom bracket is machined with a biomimetic hollow mesh structure (hollow cavity diameter 1.2mm, cross support rib angle 60°), and the cavity is filled with 50nm alumina ceramic particles (filling amount 32%).

[0045] (3) Test results and technical effects The frame has a fiber orientation deviation of 3.2°, a residual stress of 59MPa, a bending deformation of 0.10mm under a load of 2000N, a torsional deformation of 0.07mm under a load of 1500N, and a density of 1.6g / cm³. Compared with the traditional air-bag molded frame, the frame has a 28% higher torsional strength, a 30% higher molding efficiency, and a higher quality pass rate for complex structure molding from 85% to 98%.

[0046] The above are merely embodiments of the present invention. The circuits, electronic components, and modules involved are all prior art, fully achievable by those skilled in the art, and require no further explanation. The scope of protection in this application does not involve improvements to the software and methods. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the application.

Claims

1. A method for forming a deformation-resistant engineering machinery structural component, used for processing mountain bike structural components, characterized in that: Includes the following steps: S1. Select a base material, cut it into blanks of a preset size, pre-oil the blanks, and then cold-press the blanks to obtain a preliminary shape. The preliminary shape is adapted to the shape of the target structural component of the mountain bike. S2. Heat the preformed blank to 420-450℃ and hold it for 20-30 minutes. Place it into a mold with partitioned gradient cooling channels and a titanium nitride coating on the cavity surface. Use a dynamic pressure mode of pre-pressing-main pressing-holding pressure. At the same time, introduce gradient temperature coolant into the partitioned cooling channels of the mold to control the cooling rate of different areas of the blank and obtain a dense molded part. S3. First, heat the densified molded part to 460-480℃ and hold it for 1.5-2 hours. When the internal stress value of the molded part drops to 120-150MPa, cool it with the furnace to 200-220℃ and adjust the holding time according to the real-time stress. Then, use a combination of air cooling and water mist cooling to quickly cool it to room temperature. S4. The dimensions of the molded parts are corrected, and a biomimetic hollow mesh reinforcement structure is processed on the key stress parts to finally obtain the deformation-resistant mountain bike structural parts.

2. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: In step S2, the step of introducing gradient temperature coolant into the mold partition cooling channels specifically includes: introducing 30-35℃ coolant into the thick-walled area channel of the structural component and 45-50℃ coolant into the thin-walled area channel.

3. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: In step S3, adjusting the heat preservation time according to the real-time stress specifically includes: extending the heat preservation to 40-45 minutes when the internal stress value of the molded part is >100MPa, and maintaining the heat preservation for 30-35 minutes when the internal stress value of the molded part is ≤100MPa.

4. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: In step S4, the biomimetic hollow mesh reinforcement structure includes a micro hollow cavity with a diameter of 1 to 2 mm and cross support ribs with an included angle of 60°. The overall thickness of the reinforcement structure is 1.2 to 1.5 times the thickness of the main body of the structural component, and the cross support ribs are aligned with the force direction of the structural component.

5. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: The micro-hollow cavity of the biomimetic hollow grid reinforced structure is filled with nano-sized alumina ceramic particles, with a filling amount of 30% to 40% of the cavity volume.

6. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: In step 3, the combination of air cooling and water mist cooling is as follows: when the temperature of the molded part is 200-150℃ in the initial stage of cooling, air cooling with a wind speed of 10-12m / s is used; when the temperature of the molded part is 150-80℃ in the middle stage of cooling, cooling is combined with a wind speed of 12-15m / s and water mist with a particle size of 5-8μm; when the temperature of the molded part is 80℃ to room temperature in the later stage of cooling, air cooling is restored.

7. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: In step S2, the mold parting surface is provided with a stepped venting groove. The venting groove includes a main venting section with a width of 0.1 to 0.2 mm and a depth of 0.3 to 0.5 mm, and an auxiliary venting section with a width of 0.05 to 0.08 mm and a depth of 0.1 to 0.2 mm. The main venting section and the auxiliary venting section are connected at a 30° angle.

8. The forming method for a deformation-resistant engineering machinery structural component as described in claim 1, characterized in that: The pre-pressure-main pressure-holding dynamic pressure mode includes: first applying a pre-pressure of 500-600MPa for 10-15s to make the billet fit the mold cavity, then raising the main pressure to 800-1000MPa for 15-25s to achieve densification, and finally lowering the pressure to 600-700MPa for 5-8s to eliminate local stress.

9. A method for forming a deformation-resistant engineering machinery structural component as described in any one of claims 1-8, characterized in that: The structural components are mountain bike forks, frames, or cranks.

10. The forming method of a deformation-resistant engineering machinery structural component as described in claim 9, characterized in that: The surface of the structural component is provided with a micro-arc oxidation ceramic coating with a coating thickness of 8-12μm.

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