Precise cold heading forming process for special-shaped hardware

Abstract

The invention discloses a precise cold heading forming process for special-shaped hardware. The precise cold heading forming process comprises the five steps of precise blank pretreatment, graded cold heading forming, intermediate stress elimination, precise finishing calibration and finished product full-dimension detection. The consistency of blanks is guaranteed through customized lubricating liquid and precise cleaning and drying; stable forming is realized by adopting a gradually-changed cavity mold and collaborative progressive cold heading parameters; internal stress is uniformly eliminated through low-temperature aging treatment; the size precision is improved through finishing calibration of composite positioning and real-time adjustment; and laser detection, visual detection and mechanical property detection ensure the quality of finished products. The forming precision, the surface quality and the mechanical property stability of the special-shaped hardware are effectively improved, the special-shaped hardware forming device is suitable for various special-shaped structures and size ranges, the yield of finished products is high, the forming efficiency is high, and the production cost is reduced.

Description

A precision cold heading process for irregularly shaped hardware parts Technical Field

[0001] This invention relates to the field of hardware forming technology, specifically a precision cold heading forming process for irregularly shaped hardware parts. Background Technology

[0002] Due to their unique structural advantages, irregularly shaped hardware parts are widely used in various fields such as machinery manufacturing, automotive parts, and electronic equipment. The market demands increasingly stringent requirements for their dimensional accuracy, surface quality, and mechanical properties. Currently, the cold heading process for irregularly shaped hardware parts still has many shortcomings, making it difficult to meet the needs of precision production: The lack of standardized control in blank pretreatment, and inaccurate material selection, cleaning, drying, and lubrication treatments, easily lead to uneven blank deformation and surface defects; graded cold heading forming often uses single-station or non-gradual molds, resulting in unreasonable deformation distribution and problems such as internal stress and cracking; the lack of precise parameter control in stress relief and finishing calibration stages leads to large dimensional tolerances and substandard surface roughness in the formed products; at the same time, existing processes have poor adaptability, making it difficult to efficiently form different types and sizes of irregularly shaped hardware parts, resulting in a low finished product qualification rate. Therefore, developing a precision cold heading process for irregularly shaped hardware parts that can achieve accurate pretreatment, stable graded forming, uniform stress relief, and high-precision calibration has become a pressing technical challenge for the industry. Summary of the Invention

[0003] In order to overcome the shortcomings of existing technical solutions, the present invention provides a precision cold heading process for irregularly shaped hardware parts, which can effectively solve the problems raised in the background art.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A precision cold heading process for irregularly shaped hardware parts includes the following steps:

[0006] Step S1: Precise pretreatment of billet: Select metal billets that meet the preset material and size requirements, and perform rust removal, ultrasonic cleaning, vacuum drying, and special lubrication treatment in sequence to obtain pretreated billets; the special lubrication treatment uses a customized lubricant, and after lubrication, a uniform and dense lubrication layer is formed on the surface of the billet, with the thickness of the lubrication layer controlled between 0.01-0.03mm;

[0007] Step S2: Graded cold heading: The pre-treated billet is fed into a multi-station cold heading machine and passes through three consecutive stations: rough heading, semi-finish heading, and finish heading. Each station uses a special mold adapted to irregular contours, and the mold cavities of adjacent stations have a gradual transition. The gradual contour matches the deformation trajectory of the billet at each stage. Among them, the deformation of the billet is controlled at 30%-50% in rough heading, 15%-25% in semi-finish heading, and 5%-15% in finish heading. The cold heading pressure, temperature, and speed of each station are set in a coordinated and progressive manner.

[0008] Step S3: Intermediate stress relief: The billet after precision upsetting is sent to a low-temperature aging treatment equipment for low-temperature aging treatment to eliminate the internal stress generated during cold upsetting and avoid subsequent deformation. The internal stress value of the billet after treatment is ≤50MPa.

[0009] Step S4: Precision finishing and calibration: The aging-treated billet is fed into an integrated finishing mold to precisely calibrate the irregular contour and dimensional accuracy of the billet, ensuring that the dimensional tolerance of the billet is controlled within ±0.005-±0.01mm and the surface roughness is ≤Ra0.08μm;

[0010] Step S5: Finished product inspection and processing: The finished blanks are cleaned, dried and inspected in all dimensions in sequence. Products with dimensional deviations, surface defects and mechanical properties that do not meet the requirements are removed to obtain finished irregular-shaped hardware parts.

[0011] The comprehensive inspection includes dimensional inspection, surface defect inspection, and mechanical property inspection. The hardness of the finished irregular-shaped hardware parts is HRC25-35, and the tensile strength is ≥600MPa.

[0012] As a further description of the above technical solution, in step S1, the customized lubricant is composed of the following components in parts by weight: 60-80 parts base oil, 5-10 parts extreme pressure agent, 3-5 parts rust inhibitor, and 1-2 parts defoamer. The extreme pressure agent is isobutylene sulfide, the rust inhibitor is sodium petroleum sulfonate, and the defoamer is an organosilicon defoamer.

[0013] The ultrasonic cleaning frequency is 40-60kHz, the cleaning time is 10-15min, the vacuum drying temperature is 80-100℃, the drying time is 20-30min, and the surface moisture content of the blank after drying is ≤0.1%.

[0014] As a further description of the above technical solution, in step S2, the temperature of rough upsetting is 200-350℃, the pressure is 800-1200MPa, and the speed is 10-20mm / s; the temperature of semi-finish upsetting is 150-250℃, the pressure is 1000-1400MPa, and the speed is 7-15mm / s; and the temperature of finish upsetting is 100-200℃, the pressure is 1200-1600MPa, and the speed is 5-10mm / s.

[0015] The inner wall of the cavity of each cold heading die is provided with a wear-resistant lubricating layer with a thickness of 0.005-0.015mm and made of titanium nitride.

[0016] As a further description of the above technical solution, in step S2, a synchronous conveying mechanism is provided between each station of the multi-station cold heading equipment. The synchronous conveying mechanism adopts a flexible clamping structure, and the clamping force can be adaptively adjusted according to the size of the billet, with an adjustment range of 20-50N. The conveying speed is synchronized with the cold heading speed of each station, and the synchronization error is ≤±0.5mm / s, ensuring that the billet does not shift or deform during the conveying process, and that there are no scratches on the surface of the billet during the conveying process.

[0017] As a further description of the above technical solution, in step S2, the precision upsetting mold includes an upper mold and a lower mold. After the cavities of the upper mold and the lower mold are closed, they are precisely matched with the contour of the target irregular hardware part, and the matching error is ≤ ±0.003mm.

[0018] The bottom of the lower mold cavity is equipped with an elastic ejection mechanism. The ejection force of the elastic ejection mechanism is 50-100N, and the ejection speed is synchronized with the fine upsetting speed. After ejection, the gap between the blank and the inner wall of the cavity is ≤0.002mm, which avoids damage to the blank surface and dimensional deviation during demolding.

[0019] As a further description of the above technical solution, in step S3, the temperature of the low-temperature aging treatment is 150-250℃, the holding time is 2-4h, the cooling rate is 5-10℃ / min, and a combination of natural cooling and forced cooling is adopted. After cooling to room temperature, the billet is taken out. The low-temperature aging treatment equipment is equipped with a temperature uniformity control system with a temperature uniformity error ≤ ±5℃ to ensure uniform stress relief in all parts of the billet.

[0020] As a further description of the above technical solution, in step S4, the positioning structure of the finishing mold adopts a combination of pin hole positioning and contour positioning, with a positioning accuracy of ≤ ±0.002mm; the clamping structure adopts a flexible clamping pad made of polyurethane, with a clamping force of 30-60N, and the blank has no clamping marks after clamping; the finishing pressure is 600-800MPa, the finishing time is 10-20s, the blank size is monitored in real time during the finishing process, and the finishing pressure is automatically adjusted according to the size deviation, with an adjustment accuracy of ≤ ±5MPa.

[0021] As a further description of the above technical solution, in step S1, the metal billet is one of carbon steel, alloy steel or stainless steel, the diameter tolerance of the billet is controlled within ±0.01-±0.02mm, the length tolerance is controlled within ±0.02-±0.03mm, the surface roughness of the billet is ≤Ra0.2μm, and there are no defects such as cracks, inclusions, or oxide scale.

[0022] As a further description of the above technical solution, in step S5, the size detection adopts a laser detection device with a detection accuracy of ≤±0.001mm and a detection efficiency of 10-15 pieces / min; the surface defect detection adopts a vision inspection system, which can identify defects such as scratches, dents, and protrusions with a size ≥0.005mm through high-definition imaging and image recognition technology; the mechanical property detection adopts a hardness tester and a tensile strength testing machine, with a pass rate ≥99%.

[0023] As a further description of the above technical solution, the irregular hardware includes non-circular cross-section hardware and irregular hardware with protrusions or grooves. The ratio of the maximum cross-sectional dimension to the minimum cross-sectional dimension of the irregular hardware is 2-5:1. The process is applicable to the forming of irregular hardware with a diameter of 5-50mm and a length of 10-100mm, and the forming efficiency is 8-12 pieces / min.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The precision cold heading process for irregularly shaped hardware parts of the present invention has at least one of the following beneficial effects during use:

[0026] This process effectively addresses the technical pain points of existing cold heading processes for irregularly shaped metal parts, such as low precision, high defect rate, and poor adaptability, thereby improving forming quality and production efficiency. Through standardized blank pretreatment, strict control over material, dimensions, and cleaning / lubrication requirements reduces forming fluctuations and minimizes friction loss and mold wear. The graded cold heading process uses a gradually changing cavity mold and coordinated progressive parameters to match the blank deformation trajectory, avoiding cracking and dimensional deviations caused by large one-time deformation, ensuring forming stability. Intermediate low-temperature aging treatment uniformly eliminates internal stress, preventing subsequent deformation and improving the consistency of product dimensions and mechanical properties. Precise finishing calibration combined with full-dimensional inspection significantly improves product dimensional accuracy and surface quality, ensuring that the finished product meets mechanical property standards. This process is adaptable to the forming of various irregularly shaped metal parts, balancing precision and efficiency, effectively improving the finished product qualification rate, reducing production costs, and extending mold life. Attached Figure Description

[0027] Figure 1 is a process flow diagram of a precision cold heading process for irregularly shaped hardware parts according to the present invention.

[0028] Figure 2 is a flowchart of the precise pretreatment process of blanks for a precision cold heading process of irregularly shaped hardware parts according to the present invention.

[0029] Figure 3 is a flowchart of the graded cold heading process of a precision cold heading process for irregularly shaped hardware parts according to the present invention.

[0030] Figure 4 is a flow chart of the lubricating oil treatment process for a precision cold heading process of irregularly shaped hardware parts according to the present invention.

[0031] Figure 5 is a flowchart of the cold heading mold transfer process at the workstation in the precision cold heading forming process of irregularly shaped hardware parts according to the present invention.

[0032] Figure 6 is a flowchart of the intermediate stress relief process in the precision cold heading process of irregularly shaped hardware parts according to the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] As shown in Figures 1-6, this invention provides a precision cold heading process for irregularly shaped hardware parts, comprising the following steps:

[0035] Step S1: Precise pretreatment of billet: Select metal billets that meet the preset material and size requirements, and perform rust removal, ultrasonic cleaning, vacuum drying, and special lubrication treatment in sequence to obtain pretreated billets; the special lubrication treatment uses a customized lubricant, and after lubrication, a uniform and dense lubrication layer is formed on the surface of the billet, with the thickness of the lubrication layer controlled between 0.01-0.03mm;

[0036] Carbon steel, alloy steel, and stainless steel billets are selected, and diameter tolerances (±0.01-±0.02mm), length tolerances (±0.02-±0.03mm), and surface roughness (≤Ra0.2μm) are strictly controlled to ensure the consistency of the initial billets and lay a stable foundation for subsequent forming. Rust removal and ultrasonic cleaning (40-60kHz, 10-15min) remove oxide scale and impurities, followed by vacuum drying (80-100℃, 20-30min, moisture content ≤0.1%) to thoroughly remove moisture and prevent defects such as porosity and cracks during forming. A customized lubricant (60-80 parts base oil + 5-10 parts sulfurized isobutylene extreme pressure agent + 3-5 parts sodium petroleum sulfonate rust inhibitor + 1-2 parts silicone defoamer) is used to form a uniform lubricating layer of 0.01-0.03mm on the billet surface. Among them, the extreme pressure agent forms a protective film under high pressure to reduce mold wear, the rust inhibitor prevents the billet from rusting, and the defoamer avoids the lubricant bubbles from affecting the lubrication uniformity, ultimately reducing the cold heading friction resistance and improving the billet deformation uniformity.

[0037] Step S2: Graded cold heading: The pre-treated billet is fed into a multi-station cold heading machine and passes through three consecutive stations: rough heading, semi-finish heading, and finish heading. Each station uses a special mold adapted to irregular contours, and the mold cavities of adjacent stations have a gradual transition. The gradual contour matches the deformation trajectory of the billet at each stage. Among them, the deformation of the billet is controlled at 30%-50% in rough heading, 15%-25% in semi-finish heading, and 5%-15% in finish heading. The cold heading pressure, temperature, and speed of each station are set in a coordinated and progressive manner.

[0038] The billet is gradually deformed by using a gradually changing cavity mold with three consecutive stations: rough upsetting, semi-finish upsetting, and finish upsetting (the cavity contour matches the deformation trajectory of the billet).

[0039] Rough upsetting (deformation 30%-50%, temperature 200-350℃, pressure 800-1200MPa, speed 10-20mm / s): Initially shapes the contour, using a larger deformation to reduce pressure in subsequent stages. Semi-finish upsetting (deformation 15%-25%, temperature 150-250℃, pressure 1000-1400MPa, speed 7-15mm / s): Refines the contour, preparing for finish upsetting. Finish upsetting (deformation 5%-15%, temperature 100-200℃, pressure 1200-1600MPa, speed 5-10mm / s): Small deformation combined with high pressure and low speed precisely shapes the target contour.

[0040] Step S3: Intermediate stress relief: The billet after precision upsetting is sent to a low-temperature aging treatment equipment for low-temperature aging treatment to eliminate the internal stress generated during cold upsetting and avoid subsequent deformation. The internal stress value of the billet after treatment is ≤50MPa.

[0041] Cold heading plastic deformation can generate internal stress in the billet, which, if residual, can easily lead to subsequent deformation or cracking. Low-temperature aging treatment (holding at 150-250℃ for 2-4 hours, cooling rate 5-10℃ / min, a combination of natural and forced cooling) utilizes atomic diffusion and dislocation movement to relax internal stress, reducing the internal stress value to ≤50MPa. The equipment's temperature uniformity control system (error ≤±5℃) ensures uniform stress elimination across all parts of the billet, preventing localized residual stress from causing failure.

[0042] Step S4: Precision finishing and calibration: The aging-treated billet is fed into an integrated finishing mold to precisely calibrate the irregular contour and dimensional accuracy of the billet, ensuring that the dimensional tolerance of the billet is controlled within ±0.005-±0.01mm and the surface roughness is ≤Ra0.08μm;

[0043] The synchronous conveying mechanism between each station adopts flexible clamping (force 20-50N adaptive adjustment), and the conveying speed is synchronized with the cold heading speed (error ≤ ±0.5mm / s) to ensure that the billet is free from displacement, deformation and scratches; the titanium nitride wear-resistant lubricating layer (0.005-0.015mm) on the inner wall of the mold cavity reduces wear, and the elastic ejection mechanism of the lower mold (ejection force 50-100N, ejection speed synchronized with fine heading) avoids demolding damage.

[0044] Step S5: Finished product inspection and processing: The finished blanks are cleaned, dried and inspected in all dimensions in sequence. Products with dimensional deviations, surface defects and mechanical properties that do not meet the requirements are removed to obtain finished irregular-shaped hardware parts.

[0045] Combined with a polyurethane flexible clamping pad (clamping force 30-60N, no clamping marks), precise positioning of the blank is achieved; finishing pressure 600-800MPa, time 10-20s, real-time monitoring of dimensions and automatic adjustment of pressure (adjustment accuracy ≤±5MPa), calibration of irregular contours and dimensions, so that the tolerance is controlled within ±0.005-±0.01mm and the surface roughness ≤Ra0.08μm.

[0046] The comprehensive inspection includes dimensional inspection, surface defect inspection, and mechanical property inspection. The hardness of the finished irregular-shaped hardware parts is HRC25-35, and the tensile strength is ≥600MPa.

[0047] After cleaning and drying, products are screened from all dimensions through laser size inspection (accuracy ≤ ±0.001mm, efficiency 10-15 pieces / min), visual surface defect inspection (identifying scratches / dents ≥0.005mm), and mechanical property testing (hardness HRC25-35, tensile strength ≥600MPa), eliminating defective parts and ensuring a finished product qualification rate of ≥99%.

[0048] This embodiment precisely selects initial blanks to reduce fluctuations in subsequent molding; multi-stage cleaning effectively eliminates impurities and moisture, avoiding molding defects; customized lubricant and precise lubrication layer control significantly reduce friction and mold wear. Three-stage gradual cold heading matches the blank deformation trajectory, avoiding cracking and dimensional deviations caused by large one-time deformation, thus improving molding stability. Low-temperature aging treatment precisely eliminates internal stress, preventing subsequent deformation or cracking; temperature uniformity control ensures uniform stress elimination, improving product dimensional stability and mechanical property consistency, and reducing the risk of failure during use. Real-time monitoring and automatic pressure adjustment precisely calibrate the contour, meeting the precision requirements of irregularly shaped hardware parts.

[0049] Furthermore, in step S1, the customized lubricant is composed of the following components in parts by weight: 60-80 parts base oil, 5-10 parts extreme pressure agent, 3-5 parts rust inhibitor, and 1-2 parts defoamer. The extreme pressure agent is isobutylene sulfide, the rust inhibitor is sodium petroleum sulfonate, and the defoamer is an organosilicon defoamer.

[0050] This embodiment uses a base oil (60-80 parts) as the lubricating base to ensure the fluidity and adhesion of the lubricant; it is combined with isobutylene sulfide as an extreme pressure agent (5-10 parts), which can form a dense chemical protective film on the contact surface between the billet and the mold under the high pressure of cold heading, resisting the wear caused by high pressure friction; sodium petroleum sulfonate (3-5 parts) as a rust inhibitor can form an adsorption film on the surface of the billet, isolating air and moisture, and preventing rust from occurring on the billet after pretreatment and before cold heading; organosilicon defoamer (1-2 parts) can quickly eliminate the air bubbles generated during the stirring and application of the lubricant, avoiding uneven lubrication layer on the surface of the billet caused by air bubbles, ensuring full coverage of lubrication effect without dead corners, and finally forming a uniform and dense lubrication layer with a thickness of 0.01-0.03mm on the surface of the billet.

[0051] The ultrasonic cleaning frequency is 40-60kHz, the cleaning time is 10-15min, the vacuum drying temperature is 80-100℃, the drying time is 20-30min, and the surface moisture content of the blank after drying is ≤0.1%.

[0052] Ultrasonic cleaning uses a frequency of 40-60kHz, utilizing the cavitation effect generated by ultrasonic waves propagating in the cleaning solution to quickly remove oxide scale, oil, and impurities from the surface of the billet. A cleaning time of 10-15 minutes ensures thorough removal of impurities while avoiding damage to the billet surface caused by excessively long cleaning times. Vacuum drying uses a low-temperature drying temperature of 80-100℃. In a vacuum environment, the resistance to moisture evaporation is reduced, accelerating the drying speed. A drying time of 20-30 minutes ensures that the moisture inside the billet is completely extracted, controlling the surface moisture content of the billet after drying to ≤0.1%, thus avoiding defects such as pores and cracks caused by residual moisture during subsequent cold heading.

[0053] The customized lubricant has strong compatibility, and the components work synergistically to solve the problem of friction and wear between the billet and the mold under high pressure during cold heading, extend the service life of the mold, effectively prevent the billet from rusting, avoid air bubbles affecting the uniformity of lubrication, improve the stability of billet deformation, and provide a guarantee for subsequent high-precision forming.

[0054] The precise matching of parameters between ultrasonic cleaning and vacuum drying can thoroughly remove impurities and moisture from the surface of the billet, while avoiding any impact on the surface quality and dimensional accuracy of the billet during the cleaning and drying process. This ensures that the surface of the billet is clean, dry, and undamaged after pretreatment, with the moisture content controlled within a reasonable range, effectively reducing the defect rate in subsequent cold heading.

[0055] To further clarify, in step S2, the temperature for rough upsetting is 200-350℃, the pressure is 800-1200MPa, and the speed is 10-20mm / s; the temperature for semi-finish upsetting is 150-250℃, the pressure is 1000-1400MPa, and the speed is 7-15mm / s; and the temperature for finish upsetting is 100-200℃, the pressure is 1200-1600MPa, and the speed is 5-10mm / s.

[0056] Rough upsetting uses a relatively high temperature of 200-350℃, a medium pressure of 800-1200MPa, and a relatively high speed of 10-20mm / s, combined with a relatively large deformation amount of 30%-50%, to quickly shape the approximate outline of the billet. The higher temperature reduces the resistance to plastic deformation of the billet, thus reducing the risk of billet cracking. Semi-finish upsetting uses a medium temperature of 150-250℃, a relatively high pressure of 1000-1400MPa, and a medium speed of 7-15mm / s. The process involves three stages: First, a medium deformation of 15%-25% refines the blank profile, gradually correcting dimensional deviations generated during rough upsetting and paving the way for finish upsetting. Second, a lower temperature of 100-200℃, a high pressure of 1200-1600MPa, and a slower speed of 5-10mm / s, combined with a small deformation of 5%-15%, are used. High pressure precisely controls the blank profile, while the slow speed ensures uniform deformation, ultimately resulting in a compliant irregular shape. This gradual decrease in temperature, pressure, and speed, along with the gradual reduction in deformation, creates a synergistic progression, matching the deformation characteristics of the blank at each stage and preventing damage caused by large, one-time deformation. This effectively avoids defects such as blank cracking and dimensional deviations caused by large, one-time deformation, improving the forming accuracy and surface quality of irregularly shaped hardware parts while reducing equipment load during cold upsetting.

[0057] The inner wall of the cavity of each cold heading die is provided with a wear-resistant lubricating layer with a thickness of 0.005-0.015mm and made of titanium nitride.

[0058] The inner walls of the cold heading dies at each station are lined with a wear-resistant and lubricating layer of titanium nitride, with a thickness controlled between 0.005-0.015 mm. Titanium nitride possesses high strength, high wear resistance, and excellent lubrication properties, reducing the coefficient of friction between the blank and the die cavity wall, lowering frictional resistance during cold heading, and preventing die cavity wear. This ensures the stability of the die cavity profile and guarantees the consistency of the blank's dimensional forming. This significantly improves the die's wear resistance and service life, reduces die replacement frequency, lowers production costs, and further enhances the uniformity of blank deformation by reducing frictional resistance, preventing dimensional deviations caused by die wear and ensuring consistency in mass production.

[0059] Furthermore, in step S2, a synchronous conveying mechanism is provided between each station of the multi-station cold heading equipment. The synchronous conveying mechanism adopts a flexible clamping structure, and the clamping force can be adaptively adjusted according to the size of the billet, with an adjustment range of 20-50N. The conveying speed is synchronized with the cold heading speed of each station, with a synchronization error of ≤±0.5mm / s, ensuring that the billet does not shift or deform during the conveying process, and that there are no scratches on the surface of the billet during the conveying process.

[0060] Furthermore, in step S2, the precision upsetting mold includes an upper mold and a lower mold. After the cavities of the upper mold and the lower mold are closed, they are precisely matched with the contour of the target irregular-shaped hardware part, with a matching error of ≤ ±0.003mm.

[0061] The mold for precision upsetting is divided into an upper mold and a lower mold. After the upper mold and the lower mold cavity are closed, they are precisely matched with the contour of the target irregular hardware part. The matching error is controlled within ±0.003mm, ensuring that the blank can completely fit the cavity contour during the precision upsetting process. The contour of the formed blank is highly consistent with the target product, reducing dimensional deviation.

[0062] The bottom of the lower mold cavity is equipped with an elastic ejection mechanism. The ejection force of the elastic ejection mechanism is 50-100N, and the ejection speed is synchronized with the fine upsetting speed. After ejection, the gap between the blank and the inner wall of the cavity is ≤0.002mm, which avoids damage to the blank surface and dimensional deviation during demolding.

[0063] The bottom of the lower mold cavity is equipped with an elastic ejection mechanism. The ejection force is controlled at 50-100N, and the ejection speed is precisely synchronized with the precision upsetting speed. After the precision upsetting is completed, the elastic ejection mechanism slowly ejects the blank from the cavity. After ejection, the gap between the blank and the inner wall of the cavity is ≤0.002mm, which avoids scratches and deformation of the blank surface caused by excessive ejection force or excessive ejection speed, or damage caused by the blank getting stuck in the cavity due to uneven ejection.

[0064] Furthermore, in step S3, the temperature of the low-temperature aging treatment is 150-250℃, the holding time is 2-4h, the cooling rate is 5-10℃ / min, and a combination of natural cooling and forced cooling is used. After cooling to room temperature, the billet is taken out. The low-temperature aging treatment equipment is equipped with a temperature uniformity control system with a temperature uniformity error ≤ ±5℃ to ensure uniform stress relief in all parts of the billet.

[0065] After precision upsetting, the billet is sent to a low-temperature aging treatment device and held at a low temperature of 150-250℃ for 2-4 hours. Under low temperature conditions, the atoms inside the billet diffuse slowly, and the dislocation movement tends to be gentle, thereby relaxing the internal stress generated during the cold upsetting plastic deformation process. The cooling process adopts a combination of natural cooling and forced cooling, and the cooling rate is controlled at 5-10℃ / min to avoid the generation of new internal stress inside the billet due to excessive cooling rate, ensuring that the internal stress is completely eliminated, and finally the internal stress value of the treated billet is ≤50MPa.

[0066] The low-temperature aging treatment equipment is equipped with a temperature uniformity control system to control the temperature uniformity error within ±5℃, ensuring that the temperature in all areas of the equipment is consistent. This allows all parts of the billet to be heated and cooled evenly, avoiding uneven stress elimination caused by local temperature deviations and ensuring that the stress values ​​in all parts of the billet meet the requirements.

[0067] Furthermore, in step S4, the positioning structure of the finishing mold adopts a combination of pin hole positioning and contour positioning, with a positioning accuracy of ≤ ±0.002mm; the clamping structure uses a flexible clamping pad made of polyurethane, with a clamping force of 30-60N, and the blank has no clamping marks after clamping; the finishing pressure is 600-800MPa, the finishing time is 10-20s, the blank size is monitored in real time during the finishing process, and the finishing pressure is automatically adjusted according to the size deviation, with an adjustment accuracy of ≤ ±5MPa.

[0068] The positioning structure of the finishing mold adopts a composite positioning method that combines pin hole positioning and contour positioning. The positioning accuracy is controlled within ±0.002mm. Pin hole positioning ensures that the reference position of the blank in the mold is accurate, while contour positioning further conforms to the irregular contour of the blank. The dual positioning works together to prevent the blank from shifting during the finishing process and ensure the accuracy of finishing calibration.

[0069] The clamping structure uses a flexible clamping pad made of polyurethane. Polyurethane is soft and tough, and the clamping force is controlled at 30-60N. This provides sufficient clamping force to ensure that the billet does not loosen or shift during the finishing process, while also avoiding clamping marks on the billet surface, thus achieving non-destructive clamping of the billet.

[0070] The quantitative control and real-time adjustment function of finishing parameters can dynamically adjust the finishing pressure according to the actual size deviation of the blank, ensuring the consistency of finishing effect and meeting the size requirements of precision irregular hardware parts; at the same time, it reduces human adjustment error and improves the efficiency and quality stability of the finishing process.

[0071] Furthermore, in step S1, the metal billet is one of carbon steel, alloy steel or stainless steel, and the diameter tolerance of the billet is controlled within ±0.01-±0.02mm, and the length tolerance is controlled within ±0.02-±0.03mm; the surface roughness of the billet is ≤Ra0.2μm, and there are no defects such as cracks, inclusions, or oxide scale.

[0072] Based on the usage requirements of irregularly shaped hardware parts, one of carbon steel, alloy steel or stainless steel is selected as the metal blank. All three materials have good plasticity and strength, which can adapt to the plastic deformation requirements of cold heading, and at the same time meet the mechanical performance requirements of the finished hardware parts.

[0073] Furthermore, in step S5, the dimensional inspection uses a laser inspection device with an accuracy of ≤±0.001mm and an efficiency of 10-15 pieces / min; the surface defect inspection uses a vision inspection system, which, through high-definition imaging and image recognition technology, can identify defects such as scratches, dents, and protrusions with a size ≥0.005mm; the mechanical property inspection uses a hardness tester and a tensile strength testing machine, with a pass rate ≥99%.

[0074] Laser inspection equipment is used for dimensional inspection. Laser inspection is characterized by high precision and high efficiency, with an accuracy of ≤±0.001mm. It can accurately detect irregular contours and dimensional deviations of blanks, with an inspection efficiency of 10-15 pieces / min, meeting the inspection needs of mass production and quickly screening out products that do not meet dimensional standards. This avoids omissions and errors associated with manual inspection, ensuring that the surface quality of finished products meets standards.

[0075] Furthermore, the irregularly shaped hardware includes non-circular cross-section hardware and irregularly shaped hardware with protrusions or grooves. The ratio of the maximum cross-sectional dimension to the minimum cross-sectional dimension of the irregularly shaped hardware is 2-5:1. The process is applicable to the forming of irregularly shaped hardware with a diameter of 5-50mm and a length of 10-100mm, with a forming efficiency of 8-12 pieces / min.

[0076] For non-circular cross-section hardware parts and irregular hardware parts with protrusions or grooves, a composite positioning structure of graded cold heading gradient cavity molds and finishing molds is used to adapt to the forming requirements of their irregular contours. It is compatible with various types of irregular hardware parts, covering common irregular hardware parts such as non-circular cross-sections and parts with concave and convex structures, and adapts to a wide range of cross-sectional size ratios, significantly improving the versatility and applicability of the process and expanding its application scope.

[0077] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A precision cold heading process for irregularly shaped hardware parts, characterized in that, Includes the following steps: Step S1: Precise Pre-treatment of Billet: Select metal billets that meet the preset material and size requirements, and sequentially perform rust removal, ultrasonic cleaning, vacuum drying, and special lubrication treatment to obtain pre-treated billets. The special lubrication treatment uses a customized lubricant, and after lubrication, a uniform and dense lubricating layer is formed on the surface of the billet, with the thickness of the lubricating layer controlled between 0.01-0.03mm. Step S2: Graded Cold Heading: The pre-treated billet is fed into a multi-station cold heading equipment, and sequentially passes through three continuous stations: rough heading, semi-finish heading, and finish heading. Each station uses a special mold adapted to irregular contours, and the mold cavities of adjacent stations have a gradual transition, with the gradual contour matching the deformation trajectory of the billet at each stage. Among them, rough heading controls the deformation of the billet. The amount of cold heading is 30%-50%, the deformation amount of semi-finishing is controlled at 15%-25%, and the deformation amount of finishing is controlled at 5%-15%. The cold heading pressure, temperature and speed of each station are set in a coordinated and progressive manner; Step S3: Intermediate stress elimination: The blank after finishing is sent to a low temperature aging treatment equipment for low temperature aging treatment to eliminate the internal stress generated during the cold heading process and avoid subsequent deformation. The internal stress value of the blank after treatment is ≤50MPa; Step S4: Precision finishing calibration: The blank after aging treatment is sent to an integrated finishing mold to precisely calibrate the irregular contour and dimensional accuracy of the blank, ensuring that the dimensional tolerance of the blank is controlled within ±0.005-±0.01mm and the surface roughness is ≤Ra0.08μm; Step S5: Finished product inspection and processing: The finished blanks are cleaned, dried and inspected in all dimensions in sequence. Products with dimensional deviations, surface defects and mechanical properties that do not meet the requirements are removed to obtain finished irregular-shaped hardware parts. The all-dimensional inspection includes dimensional inspection, surface defect inspection and mechanical property inspection. The hardness of the finished irregular-shaped hardware parts is HRC25-35 and the tensile strength is ≥600MPa.

2. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S1, the customized lubricant is composed of the following components in parts by weight: 60-80 parts base oil, 5-10 parts extreme pressure agent, 3-5 parts rust inhibitor, and 1-2 parts defoamer. The extreme pressure agent is isobutylene sulfide, the rust inhibitor is sodium petroleum sulfonate, and the defoamer is an organosilicon defoamer. The ultrasonic cleaning frequency is 40-60 kHz, the cleaning time is 10-15 min, the vacuum drying temperature is 80-100℃, the drying time is 20-30 min, and the surface moisture content of the blank after drying is ≤0.1%.

3. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S2, the temperature for rough upsetting is 200-350℃, the pressure is 800-1200MPa, and the speed is 10-20mm / s; the temperature for semi-finish upsetting is 150-250℃, the pressure is 1000-1400MPa, and the speed is 7-15mm / s; the temperature for finish upsetting is 100-200℃, the pressure is 1200-1600MPa, and the speed is 5-10mm / s. The inner wall of the cavity of each cold upsetting die is provided with a wear-resistant lubricating layer with a thickness of 0.005-0.015mm and made of titanium nitride.

4. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S2, a synchronous conveying mechanism is provided between each station of the multi-station cold heading equipment. The synchronous conveying mechanism adopts a flexible clamping structure, and the clamping force can be adaptively adjusted according to the size of the billet, with an adjustment range of 20-50N. The conveying speed is synchronized with the cold heading speed of each station, with a synchronization error of ≤±0.5mm / s, ensuring that the billet does not shift or deform during the conveying process, and that there are no scratches on the surface of the billet during the conveying process.

5. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S2, the precision upsetting mold includes an upper mold and a lower mold. After the upper mold and the lower mold cavity are closed, they are precisely matched with the contour of the target irregular hardware part, with a matching error of ≤ ±0.003mm. The bottom of the lower mold cavity is provided with an elastic ejection mechanism. The ejection force of the elastic ejection mechanism is 50-100N, and the ejection speed is synchronized with the precision upsetting speed. After ejection, the gap between the blank and the inner wall of the cavity is ≤0.002mm, so as to avoid damage to the blank surface and dimensional deviation during demolding.

6. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S3, the temperature of the low-temperature aging treatment is 150-250℃, the holding time is 2-4h, the cooling rate is 5-10℃ / min, and a combination of natural cooling and forced cooling is adopted. After cooling to room temperature, the billet is taken out. The low-temperature aging treatment equipment is equipped with a temperature uniformity control system with a temperature uniformity error ≤±5℃ to ensure uniform stress relief in all parts of the billet.

7. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S4, the positioning structure of the finishing mold adopts a combination of pin hole positioning and contour positioning, with a positioning accuracy of ≤ ±0.002mm; the clamping structure adopts a flexible clamping pad made of polyurethane, with a clamping force of 30-60N, and no clamping marks on the blank after clamping; the finishing pressure is 600-800MPa, the finishing time is 10-20s, the blank size is monitored in real time during the finishing process, and the finishing pressure is automatically adjusted according to the size deviation, with an adjustment accuracy of ≤ ±5MPa.

8. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S1, the metal billet is one of carbon steel, alloy steel or stainless steel, and the diameter tolerance of the billet is controlled within ±0.01-±0.02mm, and the length tolerance is controlled within ±0.02-±0.03mm; the surface roughness of the billet is ≤Ra0.2μm, and there are no defects such as cracks, inclusions, or oxide scale.

9. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: In step S5, the dimensional inspection uses a laser inspection device with an accuracy of ≤±0.001mm and an inspection efficiency of 10-15 pieces / min; the surface defect inspection uses a vision inspection system, which uses high-definition imaging and image recognition technology to identify defects such as scratches, dents, and protrusions with a size ≥0.005mm; the mechanical property inspection uses a hardness tester and a tensile strength testing machine, with a pass rate ≥99%.

10. The precision cold heading process for irregularly shaped hardware parts according to claim 1, characterized in that: The irregularly shaped hardware includes non-circular cross-section hardware and irregularly shaped hardware with protrusions or grooves. The ratio of the maximum cross-sectional dimension to the minimum cross-sectional dimension of the irregularly shaped hardware is 2-5:

1. The process is applicable to the forming of irregularly shaped hardware with a diameter of 5-50mm and a length of 10-100mm, with a forming efficiency of 8-12 pieces / min.

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