A manufacturing process of aluminum bar hot spinning forming automobile wheel hub and automobile wheel hub made by the same

Abstract

This invention discloses a manufacturing process for automotive wheel hubs using aluminum rod hot spinning and the corresponding automotive wheel hub, belonging to the field of automotive parts processing. Using solid aluminum alloy rods as raw materials, the process involves pre-treatment of blanking, uniform heating, upsetting pre-forming, pre-forging, high-intensity hot spinning with lubrication and online temperature control, composite heat treatment, precision machining, and surface treatment to produce the wheel hub. This invention employs integral plastic forming of aluminum rods, combined with pre-spinning isolation lubrication and a full-process water-cooling temperature control system, solving problems such as low density, easy cracking, uneven wall thickness, and high mold wear in traditional wheel hubs. Multiple plastic deformation processes refine the grains, forming continuous metal fiber streamlines, achieving a balance between lightweight, high strength, and high fatigue resistance. The forming is stable, with a high yield rate, enabling large-scale mass production of high-quality aluminum alloy wheel hubs. This invention also protects the integrated automotive wheel hub produced by this process.

Description

Technical Field

[0001] This invention relates to the field of automotive parts processing technology, specifically to a manufacturing process for automotive wheel hubs by hot spinning of aluminum rods and the automotive wheel hubs produced therefrom. Background Technology

[0002] Aluminum alloy wheels, with their advantages of light weight, excellent heat dissipation, beautiful appearance, and good corrosion resistance, have been widely used in various passenger and commercial vehicles. Currently, the mainstream processing techniques for aluminum alloy wheels are casting and casting-spinning. Wheels formed by pure casting are prone to inherent defects such as porosity, looseness, and shrinkage cavities, resulting in lower matrix density, poor overall mechanical strength and fatigue resistance. During long-term high-speed driving, these wheels are susceptible to deformation, vibration, and even cracking, posing safety hazards and compromising reliability.

[0003] The spinning process uses cast blanks as the base material and only strengthens the rim area by spinning, while the spokes remain cast. This results in significant shortcomings in overall mechanical properties and limited weight reduction, failing to meet the dual requirements of high-end vehicles for high strength and lightweight wheels. While traditional fully forged wheels offer excellent mechanical properties, their complex manufacturing process, high investment costs in large equipment, high energy consumption, low mass production efficiency, and high selling price make large-scale widespread application difficult.

[0004] In addition, the existing hot spinning forming process still has many defects in actual production: aluminum alloy blanks at high temperatures are prone to sticking and welding with the spinning wheel and mold, resulting in scratches, peeling, and nodules on the workpiece surface, which seriously affects the surface quality of the product; at the same time, repeated contact with high temperature can cause thermal shock and thermal fatigue damage to the tooling, resulting in rapid mold wear and short service life, which greatly increases production costs; and traditional processes cannot accurately control the spinning forming temperature, which can easily cause local overheating of the workpiece, leading to forming problems such as turbulent metal flow, coarse grains, uneven rim wall thickness, and workpiece collapse and cracking. The product qualification rate and production stability are poor, which restricts the large-scale production of high-quality lightweight aluminum alloy wheels. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for automotive wheel hubs by hot spinning of aluminum rods and the automotive wheel hubs produced therefrom, in order to solve the technical problems in the prior art, such as low density of wheel hub matrix, poor mechanical properties, many forming defects, large tooling losses, poor production stability, and the inability to achieve both lightweight and high strength.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0007] A process for manufacturing automotive wheel hubs by hot spin forming of aluminum rods includes the following steps:

[0008] S1. Raw material cutting: Select aluminum alloy rods as raw materials, saw them to prepare cylindrical blanks of a fixed length, leave a processing allowance of 5%-8%, remove oxide scale, oil stains and impurities from the surface of the blanks, and complete the pretreatment of the blanks.

[0009] S2. Uniform heating: The pretreated billet is sent to the heating equipment for heating and heat preservation. The heating temperature is controlled at 420-450℃, and the heat preservation time is 1-2 hours. The overall temperature difference of the billet is controlled to be ≤±5℃.

[0010] S3. Upsetting preforming: The heated billet is placed in a hydraulic forming equipment, and the billet is axially upset using a preheated mold to compress the billet height to 40%-50% of the original height, forming a round preform.

[0011] S4. Pre-forging: The round pre-blank is pre-forged as a whole to form the hub spokes, center hole and mounting hole prototype. The outer ring is formed into a thick-walled cup-shaped blank with spokes. The wall thickness of the rim part of the cup-shaped blank is controlled to be 15-25mm.

[0012] S5. High-power hot spinning forming: The pre-forged cup-shaped blank is reheated to 380-420℃ and clamped and fixed on the main shaft mold of the three-wheel high-power spinning machine; before spinning, a high-temperature resistant release agent is evenly sprayed on the working surfaces of the spinning wheels and spinning mold; during spinning, the main shaft drives the blank to rotate at high speed, and the three sets of spinning wheels are synchronously fed radially to continuously and forcefully compress the thick wall of the rim, reducing the rim wall thickness to 6-10mm and axially stretching it to the finished product design size; throughout the spinning process, the spinning wheels, mold and workpiece are continuously cooled by localized cooling water spray.

[0013] S6. Heat treatment strengthening: The spun wheel blank is subjected to a combination of solution quenching and artificial aging heat treatment. The solution temperature is 530-540℃, and after holding for 2-4 hours, it is water quenched. The aging temperature is 160-180℃, and after holding for 6-10 hours, it is air cooled to room temperature.

[0014] S7. Precision machining: Perform CNC precision machining on the heat-treated wheel blank, trim the end face, center hole, back of the spokes, bolt holes and tire bead seat structure, correct the deformation of spinning, and finally perform dynamic balancing.

[0015] S8. Surface treatment: The machined wheel hubs are pretreated by degreasing, deoxidizing, and passivating, followed by surface coating and protection treatment. After passing quality inspection, the finished car wheel hubs are obtained.

[0016] Preferably, in step S3, the hydraulic forming equipment is an 800-1000 ton hydraulic press, and the preheating temperature of the mold used for upsetting is 250-300℃.

[0017] Preferably, in step S4, the pre-forging is performed using a press with a capacity of 2500 tons or more, and the preheating temperature of the pre-forging die is 420±10℃.

[0018] Preferably, in step S5, the spindle speed of the high-power spinning machine is 500-1500 rpm, the single-roller extrusion pressure is 20-30 tons, and the preheating temperature of the spinning die is 250-300℃; the release agent is a high-temperature resistant water-based release agent for aluminum.

[0019] Preferably, in step S5, the cooling water is continuously sprayed to keep the workpiece spinning temperature stable within the plastic forming range of 380-420℃.

[0020] Preferably, the aluminum alloy bar is made of 6061-T6 or 6082 forged aluminum alloy.

[0021] Preferably, in step S7, the positional error of the wheel hub assembly surface after machining is ≤0.1mm, and the single balance amount after dynamic balancing correction is ≤5g.

[0022] In addition, the present invention also provides an automobile wheel hub manufactured by the aluminum rod hot spinning forming automobile wheel hub manufacturing process described in any of the above technical solutions.

[0023] In this car wheel hub, the rim has continuous plastic deformation metal fiber streamlines that extend in the circumferential direction, and the spokes and rim are made of the same aluminum alloy integrally, with no casting pores, porosity and shrinkage defects inside.

[0024] Preferably, the rim wall thickness of the car wheel hub is 6-10mm, the positional error of the assembly surface is ≤0.1mm, and the single dynamic balancing amount is ≤5g.

[0025] Preferably, the car wheel hub is made of 6061-T6 or 6082 aluminum alloy and strengthened by solution treatment and aging heat treatment. The metallographic structure of the rim is a fine-grained strengthened structure with a grain size finer than that of the casting structure. Beneficial effects

[0026] This invention uses solid aluminum bars as raw materials and undergoes upsetting pre-forming and integral pre-forging double reshaping and densification treatment to completely eliminate the porosity, looseness, and shrinkage defects inherent in the casting process. The internal structure of the billet is uniform and dense, overcoming the drawbacks of traditional casting-spinning wheel spokes with a cast structure. The overall matrix mechanical properties are uniform and consistent. Combined with powerful hot spinning and large plastic deformation, the metal grains are refined and the fiber flow lines are continuous and regular. The tensile strength, yield strength, and fatigue resistance of the wheel hub are significantly improved compared to traditional casting and casting-spinning wheel hubs. At the same time, it achieves wheel rim lightweighting, with a weight reduction effect of 15%-30%, balancing the requirements of lightweight and high strength.

[0027] This invention innovatively employs a high-temperature resistant release agent spraying process before spinning, forming a stable lubricating and isolating layer at the high-temperature contact interface between the tooling and the workpiece. This effectively solves the industry problem of adhesion and welding between aluminum alloy blanks and spinning wheels and molds under high-temperature and high-pressure spinning conditions, avoiding defects such as workpiece surface scratches, peeling, and nodules, and significantly improving product surface quality. Simultaneously, it reduces frictional resistance, decreases equipment operating load and energy consumption, slows down tooling thermal wear and erosion, effectively extends the service life of spinning wheels and molds, and reduces production consumables and equipment maintenance costs.

[0028] This invention features an online cooling water spray temperature control process throughout the spinning process, which can accurately lock the optimal plastic forming temperature range for aluminum alloys. This effectively avoids forming defects such as coarse grains, disordered metal flow, uneven rim wall thickness, workpiece collapse, and cracking caused by local overheating of the workpiece. It significantly improves the dimensional accuracy of the wheel hub, such as roundness and coaxiality, and significantly enhances the product qualification rate and production stability, making it suitable for industrial mass production.

[0029] This invention features a tightly integrated process with precise control over temperature, pressure, speed, and dimensional parameters at each stage. The process boasts high stability and reproducibility. Compared to traditional forging processes, it offers lower equipment investment and production costs. Compared to casting and casting-spinning processes, it delivers superior product performance, effectively balancing product performance and production costs. This enables the large-scale production of high-quality, lightweight automotive wheels. Furthermore, automotive wheels produced using this process exhibit continuous plastic deformation of metal fiber flow lines, absence of internal casting defects, uniform wall thickness, and excellent mechanical properties, indicating broad market application prospects. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the overall process of hot spinning of aluminum rods to form automotive wheel hubs according to the present invention.

[0031] Appendix Figure 1 The process flow is as follows: raw material blanking → billet pretreatment → uniform heating → upsetting preforming → pre-forging → high-strength hot spinning forming (release agent spraying + cooling water spraying temperature control) → heat treatment strengthening → precision machining → dynamic balance correction → surface treatment → finished product quality inspection and warehousing. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] In this embodiment, 18-inch passenger car wheel hubs are manufactured using 6061-T6 aluminum alloy bars. The specific process steps are as follows.

[0034] Raw material pretreatment: Select qualified 6061-T6 aluminum alloy bars, cut them into fixed-length cylindrical blanks according to the wheel hub specifications, leave a 6% machining allowance, remove the surface oxide scale by grinding, remove surface oil and impurities by ultrasonic cleaning, and dry for later use.

[0035] Uniform heating: The pretreated billet is placed in an electric heating furnace, heated to 430℃, and held for 1.5 hours. The overall temperature difference of the billet is strictly controlled to be ≤±5℃ to ensure uniform temperature inside and outside the billet.

[0036] Upsetting preforming: A 900-ton hydraulic press is used to preheat the mold to 280°C and axially upset the heated billet to compress the billet height to 45% of the original size, forming a round preform with uniform structure.

[0037] Pre-forging: Using a 2800-ton press, the pre-forging die is preheated to 420℃ to pre-forge the round pre-bill as a whole, forming the wheel hub spokes, center hole and bolt hole prototype, to obtain a thick-walled cup-shaped blank with spokes, and controlling the wall thickness of the rim part to be 20mm.

[0038] High-pressure hot spinning forming: The pre-forged cup-shaped billet is reheated to 400℃ and clamped and fixed on the main spindle mold of a three-roller high-pressure spinning machine; a special high-temperature resistant water-based release agent for aluminum is evenly sprayed on the working surfaces of the rollers and spinning mold; the spindle speed of the spinning machine is set to 1000rpm, the extrusion force of a single roller is 25 tons, and the mold preheating temperature is 280℃; through the synchronous radial feed of three sets of rollers, the thick wall of the rim is continuously and forcefully extruded, and the wall thickness of the rim is uniformly reduced to 8mm, while axially stretched to the designed width of the finished product; cooling water is continuously sprayed throughout the spinning process to keep the workpiece processing temperature stable at 380-420℃.

[0039] Heat treatment strengthening: The spun wheel blank is sent into a heat treatment furnace, where it is solution-treated at 535℃ for 3 hours, then rapidly water-quenched, and then aged at 170℃ for 8 hours. It is then naturally air-cooled to room temperature to complete the matrix strengthening.

[0040] Precision machining and dynamic balancing: After heat treatment, the wheel hub is precision machined by CNC machining to repair the end face, center hole, back of the spokes, bolt holes and bead seat, ensuring that the positional error of the assembly surface is ≤0.1mm; after machining, dynamic balancing is performed to control the single balancing amount to ≤5g.

[0041] Surface treatment and quality inspection: The machined wheel hubs are pretreated by degreasing, washing, deoxidation and passivation. The surface is coated by electrostatic powder coating. After completion, dimensional inspection, air tightness test and salt spray test are carried out. The finished car wheel hubs are obtained after passing the quality inspection.

[0042] Testing revealed that the automotive wheel hub rim produced in this embodiment has continuous plastic deformation metal fiber streamlines extending along the circumference. The spokes and rim are made of the same aluminum alloy integrally, with no casting porosity, looseness, or shrinkage defects inside. The rim wall thickness is 8mm, the positional error of the assembly surface is ≤0.1mm, the single dynamic balancing amount is ≤5g, and the tensile strength, yield strength, and fatigue life are significantly better than those of traditional cast and spun wheel hubs.

Claims

1. A manufacturing process for automotive wheel hubs by hot spinning of aluminum rods and the automotive wheel hubs produced therefrom, characterized in that, Includes the following steps: S1. Raw material cutting: Select aluminum alloy bars as raw materials, saw them to prepare cylindrical blanks of a fixed length, leave a 5%-8% machining allowance, remove oxide scale, oil and impurities from the surface of the blank, and complete the pretreatment of the blank. S2. Uniform heating: The pre-treated billet is sent into the heating equipment for heating and heat preservation. The heating temperature is controlled at 420-450℃, the heat preservation time is 1-2 hours, and the overall temperature difference of the billet is controlled to be ≤±5℃. S3. Upsetting preforming: The heated billet is placed in a hydraulic forming equipment, and the billet is axially upset using a preheated mold to compress the billet height to 40%-50% of the original height, forming a round preform. S4. Pre-forging: The round pre-blank is pre-forged as a whole to form the hub spokes, center hole and mounting hole prototype. The outer ring is formed into a thick-walled cup-shaped blank with spokes. The wall thickness of the rim part of the cup-shaped blank is controlled to be 15-25mm. S5. High-Intensity Hot Spinning: The pre-forged cup-shaped blank is reheated to 380-420℃ and clamped onto the main shaft mold of a three-roller high-intensity spinning machine. Before spinning, a high-temperature release agent is evenly sprayed onto the working surfaces of the rollers and the spinning mold. During spinning, the main shaft drives the blank to rotate at high speed, and the three sets of rollers feed radially synchronously, continuously and forcefully extruding the thick wall of the rim to reduce the rim wall thickness to 6-10mm and axially stretching it to the finished product design dimensions. Throughout the spinning process, the rollers, mold, and workpiece are continuously and locally cooled by cooling water spray. S6. Heat treatment strengthening: The spun wheel blank is subjected to a combination of solution quenching and artificial aging heat treatment. The solution temperature is 530-540℃, and after holding for 2-4 hours, it is water quenched. The aging temperature is 160-180℃, and after holding for 6-10 hours, it is air cooled to room temperature. S7. Precision machining: Perform CNC precision machining on the heat-treated wheel hub blank, trim the end face, center hole, back of the spokes, bolt holes and tire bead seat structure, correct the deformation of spinning, and finally perform dynamic balancing. S8. Surface treatment: The machined wheel hubs are pretreated by degreasing, deoxidizing, and passivating, followed by surface coating and protection treatment. After passing quality inspection, the finished car wheel hubs are obtained.

2. The aluminum rod hot spin forming process for manufacturing automobile wheel hubs according to claim 1, and the automobile wheel hubs produced therefrom, are characterized in that, In step S3, the hydraulic forming equipment is an 800-1000 ton hydraulic press, and the preheating temperature of the mold used for upsetting is 250-300℃.

3. The manufacturing process for an aluminum rod hot spin forming automobile wheel hub according to claim 1, and the automobile wheel hub produced therefrom, is characterized in that... In step S4, the pre-forging process uses a press with a capacity of 2500 tons or more, and the preheating temperature of the pre-forging die is 420±10℃.

4. The manufacturing process for an aluminum rod hot spin forming automobile wheel hub according to claim 1, and the automobile wheel hub produced therefrom, is characterized in that... In step S5, the spindle speed of the high-power spinning machine is 500-1500 rpm, the extrusion pressure of a single spinning wheel is 20-30 tons, and the preheating temperature of the spinning die is 250-300℃; the release agent is a high-temperature resistant water-based release agent for aluminum.

5. The manufacturing process for an aluminum rod hot spin forming automobile wheel hub according to claim 1, and the automobile wheel hub produced therefrom, characterized in that, In step S5, the cooling water is continuously sprayed to keep the workpiece spinning temperature stable within the plastic forming range of 380-420℃.

6. The manufacturing process for an aluminum rod hot spin forming automobile wheel hub according to claim 1, and the automobile wheel hub produced therefrom, is characterized in that, The aluminum alloy bar is made of 6061-T6 or 6082 forged aluminum alloy.

7. The manufacturing process for an aluminum rod hot spin forming automobile wheel hub according to claim 1, and the automobile wheel hub produced therefrom, is characterized in that, In step S7, the positional error of the wheel hub assembly surface after machining is ≤0.1mm, and the single balance amount after dynamic balancing correction is ≤5g.

8. An automobile wheel hub manufactured by the hot spinning forming process of aluminum rods as described in any one of claims 1-7.

9. The automobile wheel hub according to claim 8, characterized in that, Its rim has continuous plastic deformation metal fiber streamlines that extend continuously along the circumference. The spokes and rim are made of the same aluminum alloy as a whole, and there are no casting pores, porosity and shrinkage defects inside.

10. The automobile wheel hub according to claim 8, characterized in that, Its rim wall thickness is 6-10mm, the positional error of the assembly surface is ≤0.1mm, and the single dynamic balancing amount is ≤5g.

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