A crescent part for angle adjustment of a car seat and a cold heading manufacturing method thereof

Abstract

The application belongs to the technical field of mechanical manufacturing process, and discloses a crescent part for angle adjustment of an automobile seat and a cold upsetting preparation method thereof, the preparation method comprising: precise pretreatment of raw materials; multi-station progressive cold upsetting forming based on in-service thermodynamic coupling control, dynamic control of die temperature at 130 DEG C-145 DEG C, adoption of high-performance dies, subsequent temperature control heat treatment, and final finishing and protection. The application realizes improvement of production efficiency and reduction of cost through multi-aspect collaborative improvement of a process scheme, obtains a crescent part with high precision, high density, high strength, high wear resistance, hard outside and tough inside, eliminates dependence on an intermediate annealing process, and better solves the deficiencies of the existing process in efficiency, energy consumption, continuity, and product performance including strength, toughness, wear resistance, dimensional accuracy, etc.

Description

Technical Field

[0001] This invention belongs to the field of mechanical manufacturing technology, specifically relating to a crescent-shaped component for adjusting the angle of an automobile seat and its cold heading preparation method. Background Technology

[0002] In the modern automotive industry, seats, as the core interface for interaction between occupants and the vehicle, have become key indicators for measuring overall vehicle quality in terms of safety, comfort, and functional integration. The automotive seat angle adjuster, as the core assembly for precisely adjusting the seat back posture, directly impacts user experience and driving safety in terms of smooth operation, reliability, and durability. This type of adjustment mechanism contains a series of precisely matched transmission components. Among them, the crescent-shaped component used to achieve eccentric transmission, due to its irregular geometry and the complex stress it bears in the transmission chain, has a decisive influence on the performance, cost control, and mass production efficiency of the entire adjuster assembly.

[0003] Currently, the industry has mainly developed two mainstream technical paths for manufacturing such high-strength, irregularly shaped critical components: one is multi-pass hot-cold composite forging, and the other is powder metallurgy forming. Specifically, the multi-pass forging process, especially the solution represented by double upsetting, is based on the technical logic of balancing forming efficiency and final accuracy through step-by-step deformation. This process usually begins with the initial cold upsetting and trimming of metal raw materials with a large wire diameter to form a blank. During this process, due to the intense plastic deformation, the internal lattice of the metal material undergoes slippage and distortion, resulting in significant work hardening, which leads to increased material hardness and decreased plasticity. In order to enable subsequent fine shaping and avoid defects such as microcracks in the second upsetting, an intermediate annealing process must be introduced. Through annealing heat treatment, the grains that have become coarse due to work hardening are refined, internal stress is eliminated, and the plasticity of the material is restored, enabling it to withstand the next stage of shaping processing, and finally forging it into a crescent-shaped component that meets the dimensional accuracy requirements. The advantage of this process route lies in its ability to fully utilize forging technology, ensuring that the product achieves a dense internal structure and continuous metal flow lines, thus possessing excellent mechanical strength and toughness. Powder metallurgy, on the other hand, involves pressing metal powder or mixtures into shape within a mold, followed by high-temperature sintering to achieve metallurgical bonding between powder particles, forming a part with the desired shape and properties. This process exhibits a significant advantage in near-net-shape forming in terms of material utilization, greatly reducing subsequent machining operations, and therefore is attractive in terms of cost control.

[0004] However, as the automotive industry places increasingly stringent demands on component performance thresholds, cost-effectiveness, and production cycle time, some inherent characteristics of the two mainstream technical solutions mentioned above are gradually revealing deep-seated contradictions and limitations when facing new challenges. For the secondary upsetting process, the core contradiction lies not only in the numerous steps and low efficiency, but also in the inherent discontinuity of its process flow and the resulting systemic costs. Cold work hardening and intermediate annealing are essentially a pair of co-existing processes that "create problems" and "solve problems." To achieve the final complex configuration, intense plastic deformation is unavoidable, but this inevitably leads to the deterioration of material processing performance; and to correct this deterioration, a high-energy-consuming and long-cycle annealing heat treatment process must be introduced. The existence of the annealing process not only physically interrupts the continuous operation of cold upsetting, introducing additional material transfer, secondary loading and unloading, and other auxiliary time, but also fundamentally increases heat consumption and equipment footprint costs. This "harden first, soften then shape" process cycle is an additional cost incurred to overcome the inherent side effects of the process itself, essentially representing an internal drain on process efficiency. On the other hand, while powder metallurgy avoids the aforementioned contradictions, it introduces new and more fatal performance compromises. The reason lies in the fact that the sintering process cannot completely eliminate the microscopic porosity between powder particles, resulting in the final product's density typically falling short of that of forgings of the same composition, and its internal microstructure uniformity also being poor. This inherent microstructural defect directly translates into insufficient macroscopic performance, manifesting as significantly lower product strength, especially fatigue strength and impact toughness, compared to forgings. Furthermore, the volume shrinkage and deformation during sintering are difficult to control precisely, posing a challenge to dimensional accuracy. More importantly, its surface hardness and wear resistance, even after subsequent treatment, cannot reach the high standards achieved by forgings after carburizing heat treatment. For crescent-shaped components subjected to contact stress and frictional wear during long-term high-frequency adjustment, this is a direct weakness affecting their service life.

[0005] Therefore, those skilled in the art face a pressing technical dilemma: existing manufacturing processes either sacrifice process continuity and economy by employing secondary upsetting to ensure final mechanical properties, or sacrifice the core strength and wear resistance of the product by employing powder metallurgy to pursue process simplification and material utilization. Overcoming this technical bottleneck and developing a process preparation method that combines the high strength and high density characteristics of forgings with an efficient, continuous, and low-cost production model to produce complex-shaped and high-performance crescent-shaped components for automotive seat angle adjustment in a one-step molding process has become a key challenge driving the advancement of related component manufacturing technologies. Summary of the Invention

[0006] The technical problem this invention aims to solve is to overcome the fundamental contradiction between mechanical performance and production efficiency inherent in the existing process routes for manufacturing crescent-shaped parts of automotive seat angle adjusters. Specifically, it aims to address the problems of discontinuous process, high energy consumption, and low efficiency caused by the introduction of intermediate annealing in traditional secondary upsetting processes. Simultaneously, it aims to avoid the performance defects of powder metallurgy processes, such as insufficient strength, toughness, wear resistance, and dimensional accuracy, caused by the inherent microporous structure of the powder metallurgy process.

[0007] To achieve the above-mentioned objectives, this invention provides a crescent-shaped component for adjusting the angle of an automobile seat and its cold heading preparation method. By systematically and integratedly designing the material rheological behavior during the pretreatment of raw materials, the continuous progressive forming process at multiple stations, and the coordinated control of the mold system and process parameters, the invention achieves net or near-net-shape forming of high-precision, high-performance crescent-shaped components from wire rods on a single cold heading machine. This completely eliminates the dependence on intermediate annealing processes and organically combines the inherent high density and continuous metal flow lines of forgings with a continuous, high-cycle production mode.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A cold heading method for preparing a crescent-shaped component for adjusting the angle of an automobile seat includes the following steps in chronological order:

[0010] S1: Precision pretreatment of raw materials, spheroidizing annealing is performed on low carbon alloy structural steel that is initially coiled wire to reduce its hardness and improve its plasticity, and then the wire is surface treated to form a composite lubricating layer.

[0011] S2: Multi-station progressive cold heading based on in-service thermodynamic coupling control. On a multi-station automatic cold heading machine, the wire that has been pretreated in step S1 is progressively plastically deformed through at least two consecutive forming stations without intermediate annealing process, so as to form a predetermined shape of crescent part.

[0012] S3: Subsequent temperature-controlled heat treatment;

[0013] S4: Final finishing and protective treatment.

[0014] A crescent-shaped component for adjusting the angle of an automobile seat, prepared using the aforementioned cold heading method.

[0015] The beneficial effects of the present invention include at least the following:

[0016] 1. This invention constructs a completely new, efficient, and continuous cold heading process path through systematic integration and innovation of material pretreatment, multi-station progressive forming, in-service thermodynamic coupling control system, high-performance mold technology, and subsequent heat treatment. It not only retains and enhances the high strength and high density performance advantages of forging, but also fundamentally eliminates the efficiency bottleneck and energy waste caused by the "work hardening-annealing softening" cycle in traditional processes. It achieves one-time precision forming of complex irregular-shaped parts on a single machine, significantly improving production efficiency, reducing manufacturing costs, and ensuring high consistency and reliability of product performance, thus effectively solving the technical dilemmas described in the background section.

[0017] 2. The mold temperature dynamic control adopted in this invention is 130℃-145℃, which can optimally balance material flowability and work hardening inhibition within this range; at the same time, through the synergistic effect of the mold coating (WC / C functional layer) and the temperature control system, surface cracks caused by lack of annealing are avoided (see fatigue life data in Example 1). Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main process of the preparation method in the embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the six-station progressive cold heading process in an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the composition and process of the in-service thermodynamic coupling control system in an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the main structure of the crescent-shaped component in an embodiment of the present invention;

[0022] Figure 5 This is a three-dimensional structural diagram of the crescent-shaped component in an embodiment of the present invention.

[0023] Figure label:

[0024] 1. Center hole; 3. Rounded corners; 4. Overall width of the body; 5. Overall length of the body. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, a cold-forging method for preparing a crescent-shaped component for adjusting the angle of an automobile seat, provided by this invention, will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit its scope of protection. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0026] Reference Figure 1 The overall process flow diagram of the present invention shown, and Figure 2 The multi-station progressive forming process shown in this invention provides an efficient, continuous, and precise cold heading method for manufacturing crescent-shaped automotive seat angle adjuster parts with complex geometries and stringent performance requirements. The core of this method lies in the systematic integration of deep pretreatment of raw materials, multi-station continuous forming based on in-service thermodynamic coupling control, the application of a high-performance mold system, and subsequent precision heat treatment. This achieves one-time, automated production from wire rod to near-net-shape high-precision forgings, fundamentally eliminating the reliance on interrupted intermediate annealing processes in traditional processes. Example 1

[0027] In one specific embodiment, the cold heading preparation method for the crescent-shaped component for adjusting the angle of an automobile seat according to the present invention is described in chronological order, outlining its complete technical implementation path; see appendix. Figure 4-5 The crescent-shaped component prepared according to this embodiment of the invention includes a crescent-shaped body. One end of the body is narrow, and the other end is wide. The wide end has an arc-shaped recess. The upper and lower ends of the body are flat, and the joints between the surfaces are rounded corners 3. Specifically, the body has a central hole 1 with a radius R of 3 mm, the rounded corner 3 with a radius R of 3 mm, the overall width 4 of the body is 7 ± 0.01 mm, the overall length 5 of the body is 38 ± 0.01 mm, the thickness of the body is 4 mm ± 0.01 mm, and its surface hardness is 58-62 HRC.

[0028] The first step, step S1, is the precision pretreatment of the raw materials. In this embodiment, low-carbon alloy structural steel of grade 20CrMnTi is selected as the original coiled wire, which arrives in the hot-rolled state with an original diameter of Φ20.0 mm. In order to give this material excellent forming performance under subsequent extreme plastic deformation conditions and to suppress the excessive accumulation of work hardening, a series of precision pretreatments are required.

[0029] First, spheroidizing annealing is performed on the entire coil of wire. The coiled wire is placed in a continuous mesh belt furnace for processing. To prevent oxidation and decarburization at high temperatures, a protective atmosphere composed of a mixture of nitrogen and hydrogen is introduced into the furnace, with nitrogen accounting for 95% by volume and hydrogen accounting for 5% by volume. The dew point of the atmosphere in the furnace is monitored in real time using a dew point meter to ensure that it is stable below -40°C. The annealing process curve is set as follows: the wire is fed into the heating zone at a preset mesh belt speed and heated uniformly to 760°C within 15 minutes. This temperature is approximately 25°C above the austenite transformation point Ac1 line of this steel grade, which falls within the critical heating range of hypoeutectoid steel. The wire is held at this temperature for 5 hours to ensure that the lamellar pearlite and network cementite in the original microstructure are fully dissolved and transformed into fine carbide particles dispersed in the austenite matrix. After the heat treatment, the wire rod enters the slow cooling zone with the conveyor belt, where it undergoes furnace cooling at a strictly controlled rate of 20°C per hour until the temperature drops below 500°C. At this point, the carbides have fully spheroidized and stabilized. Subsequently, the wire rod leaves the slow cooling zone and enters the cooling sleeve, where it is naturally cooled to room temperature in ambient air. After this spheroidizing annealing treatment, metallographic examination of the wire rod samples reveals a microstructure consisting of finely granular cementite uniformly dispersed in a ferrite matrix, with a spheroidization level of 3-4. Simultaneously, the macroscopic hardness is measured using a Brinell hardness tester, and the value stabilizes at around 145 HBW, a significant decrease compared to the original hot-rolled state of 220 HBW. The elongation increases from 18% to over 30%, providing ideal initial microstructure conditions for subsequent large-deformation multi-station cold heading without intermediate annealing.

[0030] After spheroidizing annealing, the wire undergoes surface treatment to form a composite lubricating film that plays a crucial role in subsequent high-pressure forming. This process is completed on a continuous surface treatment line. The wire first passes through an acid pickling tank containing a 15% hydrochloric acid solution, maintained at 40°C, to thoroughly remove surface oxide scale. After pickling, the wire is rinsed with high-pressure water to remove residual acid and salt, and then enters a neutralization tank for neutralization. Next, the cleaned wire enters a phosphating tank. The phosphating solution is a zinc phosphate solution containing zinc nitrate, zinc dihydrogen phosphate, and various accelerators, with the tank temperature precisely controlled at 75°C ± 2°C. The wire is immersed in the phosphating tank for 12 minutes, during which a uniform, dense non-metallic phosphate film is formed on its surface through a chemical reaction. The thickness of the phosphate film, measured by a film thickness gauge, is 10 μm, with a film weight of 10 g / m². This phosphate coating not only provides rust prevention, but more importantly, its microporous structure offers an excellent physical adsorption carrier for subsequent lubricants. During molding, it acts as a robust isolation layer, preventing direct contact between the metal substrate and the mold. After phosphate treatment, the wire is washed again and then undergoes the final lubrication process: saponification. The wire with the phosphate coating (10 μm thick) is immersed in a saponification solution maintained at 85°C. This solution is a 10% sodium stearate aqueous solution. Through physical adsorption and chemical reaction, a firmly bonded white metallic soap lubricating film is formed in the micropores and on the surface of the phosphate coating. After drying, this composite lubricating layer exhibits an extremely low coefficient of friction and extremely high compressive strength, ensuring its integrity even under subsequent cold heading pressures up to 2000 MPa. This significantly reduces forming force and minimizes mold wear and adhesion.

[0031] The second step, execution step S2: multi-station progressive cold heading based on in-service thermodynamic coupling control. The Φ20.0 mm wire, after precision pretreatment, is fed into a six-station horizontal automatic cold heading machine, such as the German HATEBUR AMP 30 S model or a domestically equivalent Z47-24 model. One of the core components of this invention, the in-service thermodynamic coupling control system, has been integrated into this equipment. This system implements precise, dynamic, closed-loop temperature control for the forming dies at the second to sixth stations.

[0032] Reference Figure 3The schematic diagram shows that this in-service thermodynamic coupling control system consists of several precisely coordinated components. First, within the concave and convex molds at each critical workstation, a three-dimensional mesh cooling / heating channel conformally to the mold cavity surface is integrally formed using selective laser melting (SLM) additive manufacturing technology (the three-dimensional mesh cooling can be selectively laser melted). This conformal channel design allows the heat exchange medium to be maximally close to the mold's working surface, resulting in a thermal response speed and heat transfer efficiency far exceeding that of traditional drilled straight channels. Second, an independent industrial-grade mold temperature controller serves as the temperature-controlled fluid circulation unit, integrating a high-power heater and a high-efficiency refrigeration compressor. It is connected to the conformal channels of all molds via high-pressure resistant hoses, forming a closed loop. The circulating medium in the loop is a synthetic ester-based heat transfer oil with high thermal stability and high thermal conductivity, operating in a temperature range of -20℃ to 350℃. Third, a multi-point distributed sensing system is deployed at each workstation. In critical areas of the die and punch at each controlled station, such as stress concentration points or areas with the most severe heat accumulation, 1.5 mm diameter K-type armored thermocouples are embedded 3 mm deep from the working surface to monitor the internal temperature of the die body in real time, with a temperature measurement accuracy of ±0.5℃. Simultaneously, a non-contact infrared thermometer with a spectral response range of 8-14 μm and a response time of less than 100 milliseconds is installed at the exit of the material conveying path at each station to instantly capture the peak surface temperature of the workpiece immediately after it leaves the die. All sensor signals are fed into a Siemens S7-1500 series programmable logic controller (PLC) as the central processing and control unit. The PLC runs a proportional-integral-derivative (PID) control algorithm based on predictive fuzzy logic. This algorithm not only provides feedback adjustment based on the deviation between the current die temperature and the set value, but also uses parameters such as the cold heading machine's operating cycle and the forming load detected by the punching force sensor as feedforward signals to predict upcoming changes in heat load, thereby compensating for adjustments in advance. Finally, a high-speed response electronically controlled proportional valve, controlled by a PLC, is installed in the pipeline from the mold temperature controller to each mold station as a precision actuator. It can accurately adjust the flow rate of heat transfer oil to each mold with a millisecond-level response speed.

[0033] Before cold heading production begins, the system first activates the heating mode to preheat and stabilize all dies at stations two through six at a target temperature of 140°C. The control window is set to 140°C ± 5°C. After production begins, the metal wire is sheared and enters the second station. During the subsequent intense plastic deformation, a large amount of deformation heat is generated, causing the workpiece temperature to rise instantly to 250°C-300°C. This heat is rapidly transferred to the die. When the thermocouple of a die detects that the temperature is about to exceed the upper limit of 145°C, the PLC immediately instructs the corresponding proportional valve to increase its opening, increasing the flow rate of the cooling oil. This quickly and accurately removes the excess heat, causing the die temperature to drop back to the set range. Conversely, if the die temperature falls below the lower limit of 135°C due to a brief shutdown or other reasons, the system automatically reduces the cooling flow rate or switches to heating mode. Through this high-frequency, dynamic, feedforward, and feedback-based closed-loop control, the temperature of each die at each station is always locked within an extremely narrow and optimized process window. This "quasi-isothermal" cold forming environment ensures constant forming conditions, thereby guaranteeing a high degree of consistency in the dimensions and performance of each product in continuous production. Simultaneously, maintaining a mold temperature of 140°C moderately reduces the rheological stress of the 20CrMnTi steel, improving the material's filling ability within complex cavities and effectively preventing surface microcracks caused by low-temperature brittleness. More importantly, by actively controlling the heat transfer rate, it slows the rate of heat loss from the workpiece's interior due to severe deformation to the mold, ensuring that the workpiece's internal structure is in a temperature-dependent state conducive to dislocation dynamic recovery at the moment of deformation. This effectively suppresses the rapid accumulation of work hardening, allowing the material to withstand continuous large deformations in subsequent stages without intermediate annealing softening. This constitutes the core mechanism enabling the realization of the process path of this invention.

[0034] To support the aforementioned extreme forming conditions, the mold system used in step S2 is also specially designed and manufactured. All core mold components that come into direct contact with the workpiece, including the die liners, punches, and punching pins at each station, are made of ultrafine-grained tungsten-cobalt cemented carbide (WC-Co) of grade K40UF. In this grade of cemented carbide, the mass fraction of the binder phase cobalt (Co) is 12%, the average grain size of tungsten carbide (WC) is controlled at 0.5 μm, and internal micropores are eliminated through hot isostatic pressing (HIP) process, thus giving it both a compressive strength exceeding 6000 MPa and excellent fracture toughness. On the cemented carbide substrate, a composite nano-coating with a total thickness of approximately 4 μm is prepared using multi-arc ion plating physical vapor deposition (PVD) technology. The coating has a multi-layer structure, consisting of the following layers from the inside out: a 0.5 μm thick titanium nitride (TiN) underlayer, which enhances the ion bombardment effect by applying a high bias voltage, ensuring a strong metallurgical bond between the coating and the cemented carbide substrate; a 2.0 μm thick titanium aluminum nitride (TiAlN) transition layer, with an aluminum content gradient along the thickness direction, providing excellent high-temperature hardness and oxidation resistance; and a 1.5 μm thick WC / C (diamond-like tungsten carbide) functional layer as the outermost working layer. Under high-pressure contact conditions with 20CrMnTi steel, this WC / C coating exhibits a dynamic friction coefficient below 0.08 and extremely high chemical inertness, effectively preventing "cold welding" or adhesive wear between the workpiece material and the mold, ensuring smooth demolding of parts after each stamping and achieving a smooth surface.

[0035] With the support of this high-performance equipment and mold system, the specific six-station progressive cold heading process is as follows:

[0036] Sub-step S2.1, First Station: Precision Shearing and Initial Upsetting. Precision-prepared Φ20.0 mm wire is fed into the shearing station with extremely high length accuracy via a servo motor-driven roller feeding mechanism. This station employs a closed shearing mechanism consisting of a shearing die and a shearing punch. Their cutting edges are precision-ground, and the radial clearance between them is set to 0.15 mm, or 0.75% of the wire diameter. Based on the precise volume of the final crescent-shaped part, including the volume of subsequent punching waste and material density, the shearing length is set to 35.0 mm. The closed shearing ensures that both end faces of the blank are flat, with a perpendicularity to the axis of less than 0.5°, and effectively suppresses shearing collapse and burr formation. The sheared blank is precisely gripped by a transfer claw and fed into the adjacent squaring station for a slight upsetting, making its end faces even flatter and providing a more regular cylindrical preform for subsequent forming.

[0037] Sub-step S2.2, Second Station: Asymmetric Preforming. The cylindrical preform is transferred to the second station. The concave cavity of this station is an asymmetric structure designed based on the mass distribution of the final part, using the finite element analysis software DEFORM-3D for topology optimization. Its cross-sectional shape is approximately kidney-shaped or bean-shaped. The preform undergoes a stamping process at this station, being upset into a kidney-shaped intermediate billet with preliminary mass offset. The purpose of this step is to perform controlled and non-uniform redistribution of the metal, allowing the material to actively flow along a preset path to the two distal thin-walled regions of the final crescent shape during subsequent forming. This lays the foundation for final filling, effectively prevents forming defects such as folding and underfilling, and begins to construct the metal streamline prototype of the crescent part.

[0038] Sub-step S2.3, Third Station: Closed-loop Extrusion Molding of the Main Cavity. The kidney-shaped intermediate billet is transferred to the third station, i.e., the main forming station. This station adopts a fully closed-loop forging structure, consisting of a main die and a forming punch. When the forming punch is pressed into the main die at extremely high speed and pressure, the kidney-shaped intermediate billet undergoes intense plastic flow within the fully constrained space, filling every corner of the main die cavity with a precise crescent shape. During this process, the metal is forced to flow intensely around the cavity contour, and its internal grains are elongated and flattened, forming dense and continuous fibrous metal flow lines that are highly conformal to the shape of the part. This flow line distribution endows the part with excellent mechanical properties, especially fatigue resistance.

[0039] Step 4: Final Finishing and Protective Treatment. After heat treatment, the parts will have a thin layer of tempered oxide and oil residue on their surface, requiring final finishing. The parts are batched into a 300-liter three-dimensional vibratory polishing machine, with 10mm brown corundum pyramid-shaped abrasive stones and a weakly acidic polishing agent added, and subjected to 3 hours of vibratory polishing. This process effectively removes the heat-treated oxide scale, eliminates all microburrs, and improves the surface roughness of all parts to Ra 0.6μm. After finishing, the parts are sent to a multi-tank ultrasonic cleaning machine, sequentially passing through an alkaline degreasing tank at 60℃, a hot rinsing tank, a pure water rinsing tank, and a hot air drying channel to thoroughly remove any residual abrasive and oil residue. Finally, the completely clean and dried parts are immersed in rust-preventive oil for sealing, forming a uniform and dense protective oil film on their surface. After passing inspection, they are packaged and stored for assembly.

[0040] Example

[0041] The crescent-shaped component for adjusting the angle of a car seat and its cold heading preparation method provided in this embodiment are further optimizations based on Embodiment 1. The preparation method specifically includes the following steps:

[0042] Step S1: Precision pretreatment of raw materials

[0043] Step S1 includes spheroidizing annealing, surface phosphating, and lubrication of the initial coiled wire. Low-carbon alloy structural steel of grade 20CrMnTi or 20CrMo is selected as the original coiled wire with an original diameter of Φ18mm to Φ22mm. First, the coiled wire is subjected to spheroidizing annealing. The specific process is as follows: the wire is placed in a pit-type resistance furnace or a continuous mesh belt furnace and heated to a temperature range of 20°C to 30°C above the Ac1 line, i.e., 750°C to 770°C, under a protective atmosphere. The temperature is held for 4 to 6 hours, and then furnace-cooled at a cooling rate of 15°C to 25°C per hour until it is cooled to below 500°C and then air-cooled. This spheroidizing annealing treatment aims to transform the lamellar pearlite structure in the steel into spherical or granular carbides dispersed in a ferrite matrix, thereby reducing the material's original hardness to 130-160 HBW and significantly improving its plastic deformation capacity and cold forming performance. This provides a raw microstructure with excellent work hardening inhibition for subsequent large-deformation cold heading processes. After spheroidizing annealing, the wire undergoes surface treatment, which includes pickling to remove scale, phosphating, and saponification lubrication. The wire is sequentially passed through a pickling tank to remove surface oxide scale, washed with water, and then immersed in a phosphating tank at a temperature of 60°C to 80°C for 10 to 15 minutes, forming a dense non-metallic phosphate film with a thickness of 8μm to 12μm on its surface. This phosphating film serves as a carrier layer for subsequent lubricants and also acts as a barrier between the mold and the substrate during high-pressure forming. Subsequently, the wire with the phosphate coating is immersed in a sodium stearate saponification solution at a temperature of 70°C to 90°C and a concentration of 8% to 12% for lubrication treatment, forming a strong metal soap lubricating film. This composite lubricating layer can withstand extremely high contact stress without cracking during subsequent multi-station cold heading processes, effectively reducing forming force, minimizing mold wear, and ensuring smooth and uniform flow of metal material within the mold cavity.

[0044] Step S2: Multi-station progressive cold heading based on in-service thermodynamic coupling control;

[0045] Step S2 is performed continuously on a horizontal multi-station automatic cold heading machine. This equipment integrates an in-service thermodynamic coupling control system, which decomposes the complex geometry of the crescent-shaped part into a series of continuous, progressive plastic deformation steps, which are completed sequentially through at least four core forming stations without interrupting material transport. The in-service thermodynamic coupling control system is one of the core technical features of this invention. Its purpose is to perform precise and dynamic closed-loop control of the temperature of the molds and workpieces during deformation at each station, thereby actively managing the work hardening behavior and rheological properties of the material.

[0046] Specifically, the multi-station progressive cold heading process includes the following sub-steps:

[0047] Sub-step S2.1: Precision Shearing and Initial Upsetting. The pre-treated wire is precisely fed into the first station, the shearing station, via a servo motor-driven roller feeding mechanism. The shearing station employs a closed shearing mechanism consisting of a shearing die and a shearing punch. The blade clearance is set to 0.5% to 1.0% of the wire diameter to ensure a smooth sheared surface with a perpendicularity of less than 0.5°, effectively suppressing shearing collapse and burr formation. The length of the blank obtained from shearing is precisely calculated based on the final volume of the crescent-shaped part. After shearing, the blank is transferred to the adjacent initial upsetting station. At this station, the blank is axially pressurized for the first upsetting, forming a cylindrical preform with a diameter larger than the original wire diameter and a shortened height. The purpose of this step is to eliminate shear stress and provide a uniformly structured and dimensionally regular initial shape for subsequent asymmetric forming.

[0048] Sub-step S2.2: Asymmetric preforming. The cylindrical preform is transferred to the second station, namely the asymmetric preforming station. The mold cavity of this station has a non-axisymmetric structure. Through a single stamping, the cylindrical preform is upset into an intermediate billet with a kidney-shaped or bean-shaped cross-section. This step is a key transition to achieve the final crescent shape. Its core purpose is to redistribute the metal in a guided and uneven manner according to the mass distribution of the final part. Through the precisely designed kidney-shaped mold cavity, the material can fill the thin-walled area at the far end of the mold according to the preset path during subsequent forming, avoiding defects such as folding and underfilling, and initially constructing the metal streamline prototype of the crescent part.

[0049] Sub-step S2.4: Precision Pressing and Contour Finishing. The initially formed crescent-shaped part is transferred to the fourth station, the precision pressing station. The main purpose of this station is to achieve final precision control over the key dimensions, flatness, and surface quality of the part. Through a very small reduction, the upper and lower planes of the crescent-shaped part are precision pressed to ensure that its thickness meets the final tolerance requirements and achieves extremely high flatness. Simultaneously, the mold cavity edges at this station are designed with small rounded corners or fillets, which, while precision pressing, simultaneously finishes the finishing of burrs on the outer contour of the part and forms rounded corners, improving assembly performance and safety in use.

[0050] Throughout the continuous process of sub-steps S2.1 to S2.4, the in-service thermodynamic coupling control system operates continuously. This system specifically consists of the following parts:

[0051] a) Built-in heat management channels in the mold: Complex three-dimensional mesh cooling / heating channels are pre-machined inside the concave and convex molds in the second, third and fourth stations.

[0052] b) Temperature-controlled fluid circulation unit: An independent industrial integrated cooling and heating unit, connected to the thermal management channels of all molds through pipelines to form a closed-loop circulation circuit. The circulation medium uses synthetic ester heat transfer oil with high thermal stability and high thermal conductivity.

[0053] c) Multi-point distributed sensing system: K-type armored thermocouples are embedded in the critical areas of the die and punch at each controlled station to monitor the internal temperature of the die body in real time. At the same time, a non-contact infrared thermometer is installed at the material outlet of each station to measure the surface temperature of the workpiece that has just left the die.

[0054] d) Central Processing and Control Unit: An industrial-grade programmable logic controller (PLC) receives real-time temperature signals from all thermocouples and infrared thermometers. The PLC internally runs an advanced proportional-integral-derivative (PID) control algorithm based on predictive fuzzy logic.

[0055] e) Precision actuator: A high-speed response electro-pneumatic proportional valve controlled by a PLC is installed in the pipeline of the temperature-controlled fluid circulation unit.

[0056] The operation of this in-service thermodynamic coupling control system is as follows: Before the cold heading process begins, the system preheats the mold and stabilizes it within the target temperature range of 130°C to 145°C. After cold heading begins, the large amount of heat generated by the plastic deformation of the metal is transferred to the mold, causing the mold temperature to rise. The PLC monitors in real time that the mold temperature exceeds the set upper threshold and immediately instructs the electronically controlled proportional valve to increase the flow rate of the cooling oil, quickly removing the excess heat and causing the mold temperature to drop. Conversely, if the mold temperature falls below the lower threshold due to shutdown or other reasons, the system switches to heating mode or reduces the cooling flow rate. Through this high-frequency, precise dynamic adjustment, the mold temperature is always locked within an extremely narrow and optimized process window. This "isothermal" or "quasi-isothermal" cold forming environment brings fundamental technological advantages: First, the constant mold temperature ensures the absolute stability of forming conditions, thereby guaranteeing a high degree of consistency in the size and performance of each product; second, maintaining a mold temperature above 130°C moderately reduces the rheological stress of the metal material, promotes the material's filling capacity, and effectively avoids surface cracking caused by low-temperature brittleness; most importantly, by controlling the heat transfer rate, it prevents the rapid dissipation of heat generated by the severe deformation inside the workpiece, keeping the workpiece in a warm state at the moment of deformation, promoting the dynamic recovery process of dislocations, and effectively suppressing the rapid accumulation of work hardening. Thus, without intermediate annealing, the material can still withstand the large deformation of subsequent steps, which fundamentally solves the inherent contradiction of traditional cold heading processes.

[0057] Furthermore, to support the aforementioned extreme forming conditions, the mold system used in step S2 has also undergone special design. All core mold components that come into direct contact with the workpiece, such as the die liners, punches, and punching pins at each station, are made of ultra-fine grained tungsten-cobalt cemented carbide (WC-Co), with a cobalt (Co) mass fraction of 12% to 15% and an average tungsten carbide (WC) grain size of 0.4 μm to 0.6 μm, to achieve extremely high compressive strength and fracture toughness. On the cemented carbide substrate, a composite nano-coating is prepared using multi-arc ion plating physical vapor deposition (PVD) technology. The coating structure, from the inside out, consists of: a TiN underlayer (enhancing the adhesion between the coating and the substrate), a TiAlN transition layer (providing high-temperature hardness and oxidation resistance), and an outermost WC / C (diamond-like tungsten carbide) functional layer. The WC / C coating has an extremely low coefficient of friction (<0.1) and excellent anti-adhesive wear properties, which can effectively prevent the workpiece material from "cold welding" with the mold under high pressure, ensuring that the parts can be demolded smoothly and obtain a smooth surface.

[0058] Step S3: Subsequent temperature-controlled heat treatment;

[0059] The crescent-shaped parts coming off the cold heading machine, while possessing their final shape and high density, still exhibit significant residual forming stress, and their hardness and wear resistance do not yet meet final usage requirements. Therefore, subsequent temperature-controlled heat treatment is necessary. This step includes a low-temperature stress-relieving annealing and a carburizing, quenching, and tempering process.

[0060] First, the parts are loaded into a vacuum heat treatment furnace in batches for low-temperature stress-relief annealing. They are held at 200°C to 250°C for 2 to 3 hours, then cooled in the furnace. This step aims to effectively eliminate most of the macroscopic residual stress generated during cold forming, improving the dimensional stability and fatigue resistance of the parts, without significantly reducing their hardness and strength. Subsequently, gas carburizing, quenching, and low-temperature tempering are performed. The stress-relieved parts are placed in a continuous gas carburizing furnace, and under an endothermic atmosphere and with propane or natural gas dripping, strong carburizing and diffusion are carried out at 920°C to 940°C, controlling the carburized layer depth to 0.6 mm to 0.8 mm. After carburizing, the parts are directly oil-quenched without intermediate cooling, with the quenching oil temperature controlled at 60°C to 80°C. Immediately after quenching, a low-temperature tempering treatment is performed at 180°C to 200°C for 2.5 to 3.5 hours. After this complete carburizing heat treatment, the surface of the crescent-shaped component acquires a layer of high-hardness martensite and dispersed carbides, with a surface hardness of 58-62 HRC. The core, however, remains a low-carbon martensite and small amount of ferrite, possessing good strength and toughness, with a core hardness controlled at 35-42 HRC. This gradient performance structure, with its hard exterior and tough interior, is key to ensuring the crescent-shaped component exhibits excellent wear resistance under high contact stress while also withstanding impact loads.

[0061] Step S4: Final finishing and protective treatment.

[0062] After heat treatment, the surface of the parts will have a thin oxide layer and oil stains, and there may be slight deviations in size and surface roughness. Therefore, final finishing is required. The parts are placed in a three-dimensional vibratory polishing machine, with brown corundum or ceramic abrasive stones and a brightener added, and vibratory polishing is performed for 2 to 4 hours. This process effectively removes the heat-treated oxide scale, eliminates microburrs, and further improves the surface roughness to a level of Ra 0.4μm to 0.8μm. After finishing, the parts are cleaned in multiple tanks using an ultrasonic cleaner, successively going through degreasing, rinsing, and pure water washing to thoroughly remove residual abrasive and oil stains from the surface. Finally, the clean and dry parts are immersed in rust-preventive oil for sealing, forming a uniform protective oil film for assembly.

[0063] Comparative Example 1

[0064] To further illustrate the advantages of the preparation method of the present invention, a comparative example is provided of a crescent-shaped part manufactured using a traditional two-stage upsetting process.

[0065] This traditional process uses the exact same raw material as in Example 1, namely 20CrMnTi coiled wire with a diameter of Φ20.0 mm, and performs the same spheroidizing annealing and initial phosphating saponification treatment. The treated wire is then fed into a conventional four-station cold heading machine without an in-service thermodynamic control system. The process steps are as follows: First station: shearing and blanking, with the same billet size as in Example 1. Second station: first upsetting to form a cylindrical preform. Third station: asymmetric preforming, upsetting the preform into a kidney-shaped intermediate billet. After this step, due to the lack of a mold temperature control system to regulate the work hardening behavior of the material, the kidney-shaped intermediate billet undergoes severe deformation, resulting in a sharp increase in hardness to over 260 HBW and a significant decrease in plasticity. If the final closed forming in the fourth station is performed directly, incomplete filling is likely due to poor material flowability, or surface cracking due to plasticity depletion, leading to an extremely high scrap rate. Therefore, the production process must be interrupted. All kidney-shaped intermediate billets produced at the third station are collected and subjected to an intermediate annealing process. These billets are then fed into a pit-type resistance furnace and heated to 680°C under a protective atmosphere for recrystallization annealing, held for 4 hours to eliminate work hardening and restore their plasticity. This annealing process is not only time-consuming but also requires a large amount of energy. After intermediate annealing, because the high-temperature treatment will damage the original phosphating lubricating layer, all intermediate billets must undergo a secondary surface treatment, namely, re-pickling, phosphating, and saponification. After the secondary surface treatment, these softened intermediate billets are reloaded to a subsequent station on another press or cold heading machine for final closed-loop forming, punching, and precision pressing. After all forming processes are completed, the same subsequent temperature-controlled heat treatment step S3 and final finishing and protective treatment step S4 as in Example 1 are performed.

[0066] Performance Comparison

[0067] The crescent-shaped parts prepared in Example 1 and Comparative Example 1 were subjected to performance tests, and the key production indicators of the two process routes were compared. The results are summarized in the table below:

[0068] The quantitative data comparison in the table above clearly demonstrates that the crescent-shaped component for adjusting the angle of automotive seats and its cold-forging preparation method provided by this invention, through multifaceted synergistic improvements, particularly the introduction of an in-service thermodynamic coupling control system, successfully constructs a continuous, efficient, and energy-saving production path. Compared to traditional secondary upsetting processes, this invention exhibits overwhelming advantages in production efficiency, energy consumption, die life, product precision, and final mechanical properties, effectively solving the technical challenges faced in existing technologies. This invention not only achieves high-quality, low-cost manufacturing of the complex crescent-shaped component but also provides a novel paradigm with universal guiding significance for the cold forming technology of similar complex, irregularly shaped precision forgings.

[0069] The crescent-shaped component for adjusting the angle of an automobile seat and its cold heading preparation method provided in the above embodiments of the present invention are mainly aimed at solving the shortcomings of existing processes in terms of efficiency, energy consumption, continuity, and product performance, including strength, toughness, wear resistance, and dimensional accuracy. They can improve production efficiency, reduce costs, and obtain crescent-shaped components with high precision, high density, high strength, high wear resistance, and hardness on the outside and toughness on the inside, while eliminating the dependence on intermediate annealing processes.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cold heading method for preparing a crescent-shaped component for adjusting the angle of an automobile seat, characterized in that, Includes the following steps: S1: Precision pretreatment of raw materials, spheroidizing annealing is performed on low carbon alloy structural steel that is initially coiled wire to reduce its hardness and improve its plasticity, and then the wire is surface treated to form a composite lubricating layer. S2: Based on in-service thermodynamic coupling control, multi-station progressive cold heading is performed on a multi-station automatic cold heading machine. The wire pretreated in step S1 is progressively plastically deformed through at least two consecutive forming stations without intermediate annealing to form a predetermined shape for a crescent-shaped part; specifically: S2.1: Precision cutting and initial upsetting: The pre-treated wire is precisely cut into blanks of a predetermined length, and the blanks are initially upset axially to form a cylindrical preform. S2.2: Asymmetric preforming, the cylindrical preform is upset at a second station with an asymmetric mold cavity to form an intermediate blank with a kidney-shaped cross section and uneven mass distribution, thereby providing pre-guided material distribution for the final crescent-shaped filling; S2.3: Closed-cavity extrusion molding of the main cavity, the kidney-shaped intermediate billet is forged in a closed die at the third station with a crescent-shaped die cavity, so that the metal material completely fills the die cavity and forms a preliminary crescent part shape with continuous metal flow lines conforming to the shape of the part. S2.4: Precision pressing and contour trimming. The crescent-shaped part is precision pressed in the fourth station to control its final thickness and flatness, and the outer contour of the part is trimmed at the same time. During the execution of step S2, an in-service thermodynamic coupling control system is used to monitor and dynamically control the temperature of the mold in at least two forming stations in real time. The temperature of the mold is actively maintained within a preset target temperature range that is higher than room temperature. This is to adjust the material rheological behavior of the workpiece during the intense plastic deformation process and actively manage its work hardening accumulation rate, thereby ensuring that continuous large deformation forming is completed without intermediate annealing. The in-service thermodynamic coupling control system comprises: a mold-embedded thermal management channel, which is a three-dimensional mesh channel for circulating temperature-controlled fluid, pre-machined inside the concave mold and / or convex mold of the forming station in the multi-station automatic cold heading machine. The temperature-controlled fluid circulation unit is an industrial integrated heating and cooling machine connected to the thermal management channel to form a closed-loop circulation circuit, used to provide precise heating or cooling for the temperature-controlled fluid in the circuit; the multi-point distributed sensing system includes thermocouples embedded in the key areas of the die and / or punch for real-time monitoring of the internal temperature of the die body, and a non-contact infrared thermometer set at the station outlet for measuring the demolding surface temperature of the workpiece; The central processing and control unit is a programmable logic controller (PLC) that receives all real-time temperature signals output by the sensing system. The PLC runs a proportional-integral-derivative (PID) control algorithm based on predictive fuzzy logic, which generates control commands based on the deviation between the real-time temperature and the set value, combined with the cold heading process parameters. And a precision actuator, which is a high-speed response electronically controlled proportional valve installed in the pipeline of the temperature-controlled fluid circulation unit and driven by the control command of the PLC, for precisely adjusting the flow rate of the temperature-controlled fluid to each mold thermal management channel; Before the cold heading process begins, the mold is preheated and stabilized in the target temperature range of 130°C to 145°C by the temperature-controlled fluid circulation unit. During the cold heading process, the central processing and control unit dynamically changes the flow rate and / or temperature of the temperature-controlled fluid by adjusting the precision actuator based on the real-time temperature feedback from the sensing system, thereby locking the temperature fluctuation range of the mold within ±5°C of the target temperature range to achieve a quasi-isothermal forming environment. S3: Subsequent temperature-controlled heat treatment, specifically including: First, the crescent-shaped part formed by cold heading undergoes a low-temperature stress-relief annealing process, holding it at 200°C to 250°C for 2 to 3 hours to eliminate macroscopic residual stress generated during cold forming and improve the dimensional stability of the part. Subsequently, the stress-relieved part undergoes a complete carburizing, quenching, and tempering treatment. Specifically, this carburizing, quenching, and tempering treatment involves gas carburizing the part at 920°C to 940°C, controlling the effective carburized layer depth to 0.6 mm to 0.8 mm. After carburizing, it is directly oil-quenched. After quenching, it undergoes a low-temperature tempering treatment at 180°C to 200°C. After this heat treatment, the crescent-shaped part forms a performance gradient structure with an outer hardness and an inner toughness, with a surface hardness of 58-62 HRC and a core hardness controlled at 35-42 HRC. S4: Final finishing and protective treatment.

2. The cold heading preparation method for the crescent-shaped component for adjusting the angle of an automobile seat according to claim 1, characterized in that, The surface treatment of the wire in step S1 specifically includes: phosphating the wire surface to generate a dense non-metallic phosphate film as a lubricating support layer; and performing saponification lubrication treatment on the phosphate film to form a strong metallic soap lubricating film; the phosphate film and the metallic soap lubricating film together constitute the composite lubricating layer to provide continuous and effective lubrication and isolation under the high pressure conditions of subsequent cold forging.

3. The cold heading preparation method for the crescent-shaped component for adjusting the angle of an automobile seat according to claim 1, characterized in that, After the main cavity closed extrusion molding in S2.3 and before the precision pressing in S2.4, a synchronous punching sub-step is also included: using a punching pin integrated in the center of a forming punch, the central area of ​​the initially formed crescent part is reverse extruded and punched to form the central hole of the crescent part; by utilizing the radial metal flow during the punching process, the metal flow lines around the central hole wall are strengthened and densified, thereby improving the fatigue strength and shear resistance of the peri-hole area.

4. The cold heading preparation method for the crescent-shaped component for adjusting the angle of an automobile seat according to claim 1, characterized in that, The core components of the mold used in the multi-station automatic cold heading machine that are in direct contact with the workpiece include the inner lining of the die cavity, the punch and the punching pin of each station. The base material is made of tungsten cobalt cemented carbide WC-Co with ultra-fine grains, wherein the mass ratio of cobalt is 12% to 15% and the average grain size of tungsten carbide is 0.4μm to 0.6μm. A composite nano-coating is prepared on the surface of the cemented carbide substrate by physical vapor deposition. The coating structure, from the inside out, consists of: a TiN underlayer for enhancing the adhesion between the coating and the substrate; and a TiAlN transition layer for providing high-temperature hardness and oxidation resistance. And a WC / C functional layer with extremely low friction coefficient and anti-adhesive wear properties.

5. The cold heading method for preparing the crescent-shaped component for adjusting the angle of an automobile seat according to claim 1, characterized in that, Step S4 specifically includes: The heat-treated parts are placed in a three-dimensional vibratory polishing machine, and abrasive stones and brighteners are added for vibratory grinding and polishing to remove heat-treated oxide scale, eliminate microburrs, and improve surface roughness to a level of Ra 0.4μm to 0.8μm. Subsequently, the polished parts are subjected to multi-tank ultrasonic cleaning to thoroughly remove surface residues. Finally, the clean and dry parts are immersed in rust-preventive oil for sealing and protection.

6. A crescent-shaped component for adjusting the angle of an automobile seat, prepared by the cold heading method according to any one of claims 1 to 5.

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