METHOD AND MOLD FOR COLD EXTRUSION FORMING OF WHEEL HUB

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International Patent Application No. PCT/CN2023/107373 with an international filing date of Jul. 14, 2023, designating the United States, now pending, further claims foreign priority benefits to Chinese Patent Application No. 202310642088.6 filed Jun. 1, 2023. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, MA 02142.

BACKGROUND

The disclosure relates to the field of cold extrusion technology, and more particularly, to a method and a mold for cold extrusion forming of a wheel hub.

Wheel hubs are presently manufactured using a variety of techniques. Predominant among these are casting, forging, and a combined forging and spinning process.

Casting methods involve pouring a molten alloy into a mold under gravitational or low pressure to form a hub blank. This is typically followed by various machining and surface finishing operations to produce a final part. While casting offers benefits such as relatively low cost and high production rates, it suffers from several inherent drawbacks. These include, but are not limited to, the formation of gas porosity, relatively low material density, and poor surface finish in the as-cast part. These defects consequently lead to inferior comprehensive mechanical properties in the final product. Furthermore, traditional casting processes often raise environmental concerns.

Forging methods generally involve applying pressure to a metal blank using forging equipment to plastically deform the material into a desired preform shape. The rim section is often subsequently formed via a spinning operation. Conventional forging is typically performed with the workpiece in a heated or hot condition, which can produce parts with enhanced reliability. However, this hot forging process presents significant disadvantages: it requires a high-temperature operating environment with associated safety hazards, exhibits low material utilization leading to substantial waste, involves numerous processing steps, and incurs excessive costs for subsequent machining.

Moreover, a common structural feature in existing wheel hub designs is a rim portion having a diameter smaller than that of the spoke region. This configuration creates a junction area that is particularly susceptible to defects during forming, such as entrapped foreign material, inadequate bonding, folding, and crack formation.

SUMMARY

To overcome issues in existing wheel hub casting processes such as susceptibility to gas porosity, low density, poor surface finish, inferior comprehensive mechanical properties, and insufficient environmental friendliness, the disclosure provides a method for cold extrusion forming of a wheel hub. The method can significantly reduce environmental pollution from forging production, lower operational hazards, improve raw material utilization, reduce material waste, and decrease subsequent processing costs. Furthermore, by employing a structural design where the flange is larger than the spoke in diameter, the method effectively avoids defects such as cracking, wrinkling, peeling, and inclusion of foreign matter at the flange region during the forming of the spoke.

Specifically, the disclosure provides a method for forming a wheel hub through cold extrusion, the method comprising:

• • S1: placing a round cake of forgeable metal material into a first die set, and extruding, via a cold extrusion process by the first die set, the round cake of forgeable metal material to form a cylindrical blank which is U-shaped and comprises an opening facing downward, wherein an upper portion of the cylindrical blank forms a spoke and a lower portion of the cylindrical blank forms a rim, and a diameter of a flange of the cylindrical blank is greater than a diameter of the rim of the cylindrical blank, and removing the cylindrical blank from the first die set;
  • S2: placing the cylindrical blank into a second die set, and extruding, via a cold extrusion process by the second die set, the cylindrical blank to obtain a secondary blank having a desired spoke shape, forming spoke recesses by extrusion on both upper and lower sides of a center of the spoke of the secondary blank, forming an extruded step on an outer wall of the flange of the secondary blank, and removing the secondary blank from the second die set; and
  • S3: inverting the secondary blank 180 degrees and placing into a third die set, preliminarily forming, via a cold extrusion process by the third die set, the rim of the secondary blank to cause the rim to assume a flared shape, and then cold extruding and bending outward a top end of the rim, thereby obtaining a finished wheel hub.

Compared with existing technologies, the method extrudes the forgeable metal material through the first die set to obtain the cylindrical blank comprising the protruding flange shape, then forms the spoke shape through cold extrusion via the second die set, and subsequently forms the rim shape through cold extrusion via the third die set. This method utilizes die-based cold extrusion of raw material throughout the entire process to obtain the finished wheel hub, achieving extremely high material utilization and a high product qualification rate. Moreover, production is conducted under ambient temperature conditions, making it safe and environmentally friendly. The produced wheel hubs exhibit good consistency and high comprehensive mechanical performance.

• • 1. Compared with casting methods, the method for cold extrusion forming of a wheel hub provided in this disclosure produces wheel hubs with higher density and significantly improved structural strength. Wheel hubs produced by casting methods typically have a rough surface and require further machining, whereas wheel hubs produced by the cold extrusion method of this disclosure exhibit superior surface finish, usually achieving a surface roughness of 0.4 or better, eliminating the need for further machining, while also offering higher structural strength and better quality.
  • 2. Since forging methods cannot directly forge the spoke shape, they result in significant raw material waste. The method for cold extrusion forming of a wheel hub provided in this disclosure can substantially save raw materials. Furthermore, this method omits the step of milling the spoke shape from a wheel hub blank using machining equipment, thereby saving equipment and labor costs. Additionally, the wheel hub produced by the cold extrusion method of this disclosure does not disrupt the grain flow lines of the raw material, enabling better structural strength and mechanical properties, and avoids defects such as cracks, pores, folds, or non-metallic inclusions.
  • 3. The method extrudes the forgeable metal material through the first die set to obtain a cylindrical blank comprising a protruding flange shape. The cylindrical blank with the protruding flange shape facilitates the subsequent formation of the spoke shape and helps prevent issues such as cracking, wrinkling, peeling, and inclusion of foreign matter at the flange location during the step of forming the spoke shape. The wheel hub produced by the cold extrusion method of this disclosure exhibits smoother grain flow lines, high structural strength, good integrity, and superior overall mechanical performance.
  • 4. The product of this disclosure involves fewer production steps. The wheel hub completed through the three extrusion steps requires only minor finishing operations to finalize the process, effectively improving production efficiency and saving workforce and material resources.

In a class of this embodiment, a ratio of the diameter of the flange to the diameter of the rim of the cylindrical blank is between 1.09 and 1.15. By reasonably setting the sizes of the diameter of the flange and the diameter of the rim, the possibility of unreasonable grain flow at the flange during the second processing step can be effectively reduced, thereby enhancing the overall strength of the finished product and providing significant practical value.

The disclosure further provides a mold for forming a wheel hub through cold extrusion, the mold comprising: a first die set for extruding a round cake blank to form a cylindrical blank; a second die set for extruding the cylindrical blank to form a secondary blank; and a third die set for extruding the secondary blank to form a finished wheel hub. The first die set comprises a first upper die, a first lower die, a first ejector pin, and a first forming sleeve; the first forming sleeve is hollow and comprises a first wheel hub forming cavity; the first upper die and the first lower die are configured to cooperate to simultaneously apply a cold extrusion force inward to form the round cake blank into the cylindrical blank having a contour that conforms to a protruding shape of the flange, such that a diameter of the flange of the cylindrical blank is greater than a diameter of a rim of the cylindrical blank; and the first ejector pin is configured to eject the cylindrical blank from the first die set. By designing the diameter of the flange of the cylindrical blank greater than the diameter of its rim, the method can thereby prevent issues such as cracking, wrinkling, peeling, and inclusion of foreign matter at the flange location during the step of forming the spoke shape. This results in the produced wheel hub exhibiting smoother grain flow lines, high structural strength, good integrity, and superior overall mechanical performance.

In a class of this embodiment, an annular inclined surface is circumferentially disposed on an inner peripheral wall of the first forming sleeve, and is inclined inward from top to bottom. The annular inclined surface facilitates better forming of the spoke and further aids in achieving the configuration where the diameter of the flange of the cylindrical blank is greater than the diameter of its rim. Consequently, it helps prevent issues such as cracking, wrinkling, peeling, and inclusion of foreign matter at the flange location during the step of forming the spoke shape. This results in the produced wheel hub exhibiting smoother grain flow lines, high structural strength, good integrity, and superior overall mechanical performance.

In a class of this embodiment, a first annular recess is circumferentially disposed on an outer peripheral wall of the first lower die; a first rim forming cavity is formed between the first annular recess and the first wheel hub forming cavity; the first upper die and the first lower die are configured to be simultaneously driven to apply an extrusion force, such that, in a combined state of the first upper die and the first lower die, a cylindrical cavity having a contour that conforms to a shape of the flange is formed therein; the first ejector pin is movably connected to the first lower die, and during ejection, the first ejector pin is configured to move upward through the first lower die to push against the cylindrical blank. The first upper die and the first lower die cooperate to form the cylindrical blank through a cold extrusion process, and the first ejector pin facilitates the ejection of the cylindrical blank, thereby enabling convenient transfer of the cylindrical blank to the next processing step.

In a class of this embodiment, the second die set comprises a second upper die, a second lower die, a second ejector pin, and a second forming sleeve; the second forming sleeve is hollow and comprises a second wheel hub forming cavity; the second upper die and the second lower die are configured to cooperate to apply a cold extrusion force, thereby forming the cylindrical blank into a secondary blank having a desired spoke shape.

In a class of this embodiment, an annular step surface is circumferentially disposed on an inner peripheral wall of the second forming sleeve, and is inclined inward from top to bottom. The annular step surface facilitates better extrusion of the spoke at the step region, thereby aiding in shaping the spoke and improving its strength and aesthetics.

In a class of this embodiment, a bottom surface of the second upper die comprises a plurality of protruding ribs corresponding to a shape of the spoke; a top surface of the second lower die comprises a plurality of grooved surfaces matching the protruding ribs; a second annular recess is circumferentially disposed on an outer peripheral wall of the second lower die; a second rim forming cavity is formed between the second annular recess and the second wheel hub forming cavity; a top of the second ejector pin comprises an ejector pin head; the second upper die, the second lower die, and the second ejector pin are configured to cooperate to press the cylindrical blank into the secondary blank comprising the spoke shape. Pressing down the second upper die facilitates cold extrusion forming of the spoke.

In a class of this embodiment, the third die set comprises: an inner upper die, an outer upper die, a third lower die, at least two sliders respectively disposed on two sides of the third die set, and a third ejector pin; the secondary blank is placed on the third lower die and is secured by the at least two sliders; the outer upper die is fitted over the inner upper die; the inner upper die is first configured to press down to preliminarily form the rim; then the outer upper die is configured to press down to cold extrude and form a top end of the rim, ultimately yielding a finished wheel hub; the third ejector pin is movably connected to a central portion of the third lower die; during ejection, the third ejector pin is configured to move upward through the third lower die to push against the finished wheel hub, thereby ejecting the finished wheel hub.

In a class of this embodiment, a top surface of the third lower die comprises a support surface corresponding to a shape of the spoke; a lower portion of each slider comprises a first step surface matching a shape of the annular step surface; an upper portion of each slider comprises a second step surface inclined inward from top to bottom; a top of the second step surface forms a rim end forming groove, and the second step surface is configured to cooperate with the rim; an outer peripheral wall of the inner upper die is circumferentially provided with a rim mating surface inclined inward from top to bottom; a bottom surface of the inner upper die comprises a spoke forming cavity surface identical to that in the top surface of the second lower die; the outer upper die is fitted over the inner upper die and is located at an upper portion of the inner upper die; a bottom of the outer upper die is circumferentially provided with an annular rim end forming recess; the outer upper die is configured to press down such that the rim end forming recess presses onto the rim end forming groove; and the rim end forming groove and the rim end forming recess are configured to cooperate to extrude and shape an end portion of the rim; the third ejector pin is movably connected to a central portion of the third lower die; and during ejection, the third ejector pin is configured to move upward through the third lower die to push against the finished wheel hub. By inverting and placing the secondary blank onto the third die set, and through the extrusion cooperation between the inner upper die and the third lower die, the rim is more easily shaped and flared outward, thereby enhancing the connection strength and performance.

In summary, the following advantages are associated with the method of the disclosure. The wheel hub has higher density and significantly improved structural strength. The surface finish of the wheel hub is superior, typically achieving a surface roughness of 0.4 or better, eliminating the need for further machining, while also providing higher structural strength and better quality. Producing the wheel hub can substantially save raw materials and also omits the step of milling the spoke shape from the wheel hub blank using machining equipment, thereby saving equipment and labor costs. The process does not disrupt the grain flow lines of the raw material, resulting in better structural strength and mechanical properties, and avoids defects such as cracks, pores, folds, or non-metallic inclusions. The wheel hub exhibits smoother grain flow lines, high structural strength, good integrity, and superior overall mechanical performance. The production process involves fewer steps; the wheel hub completed in three extrusion steps requires only minor finishing operations, effectively improving production efficiency and saving workforce and material resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for cold extrusion forming of a wheel hub according to one embodiment of the disclosure;

FIG. 2 is a schematic diagram of a first die set used in a first step of a method for cold extrusion forming of a wheel hub according to one embodiment of the disclosure;

FIG. 3 is a plan view of a cylindrical blank (with flange larger than rim) according to the present invention;

FIG. 4 is a perspective view of a cylindrical blank (with flange larger than rim) according to one embodiment of the disclosure;

FIG. 5 is a schematic diagram of a second die set used in a second step of a method for cold extrusion forming of a wheel hub according to one embodiment of the disclosure;

FIG. 6 is a schematic diagram of a third die set used in a third step of a method for cold extrusion forming of a wheel hub according to one embodiment of the disclosure;

FIG. 7 is an exploded view of a third die set used in a third step of a method for cold extrusion forming of a wheel hub according to one embodiment of the disclosure;

FIG. 8 is a front view of a finished wheel hub according to one embodiment of the disclosure;

FIG. 9 is a cross-sectional view of a conventional cylindrical blank (with flange smaller than rim) (Prior Art); and

FIG. 10 is a schematic diagram showing grain flow formation during the forming of a spoke in a conventional extrusion process (Prior Art).

In the drawings, the following reference numbers are used: 1. Cylindrical blank; 101. Flange; 102. Spoke; 103. Rim; 110. First Upper Die; 120. First Lower Die; 130. First Ejector Pin; 140. First Forming Sleeve; 150. Annular Inclined Surface; 170. First Annular Groove; 180. First Rim Forming Cavity; 2. Secondary Blank; 210. Second Upper Die; 2101. Protruding Rib; 220. Second Lower Die; 2201. Grooved Surface; 2202. Second Annular Groove; 2203. Second Rim Forming Cavity; 230. Second Ejector Pin; 2301. Ejector Pin Head; 240. Second Forming sleeve; 250. Annular Step Surface; 3. Finished Wheel Hub; 310. Inner Upper Die; 3101. Rim Mating Surface; 320. Third Lower Die; 3201. Support Surface; 330. Slider; 3301. First Step Surface; 3302. Second Step Surface; 340. Third Ejector Pin; 350. Outer Upper Die; 3501. Rim End Forming Recess; 3502. Rim End Forming Groove.

DETAILED DESCRIPTION

To further illustrate the disclosure, embodiments detailing a method and a mold for cold extrusion forming of a wheel hub are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

It should be noted that, while functional modules are divided in the system schematic diagrams and a logical order is shown in the flowcharts, in some cases, the steps shown or described may be executed in an order different from the module division in the system or the sequence in the flowchart. The terms “first”, “second”, etc., in the description, the claims, and the above-mentioned drawings are used to distinguish similar objects and are not necessarily intended to describe a specific order or sequence.

Existing wheel hubs are as shown in FIG. 9 and FIG. 10. The flange 101 of the wheel hub is smaller than its spoke 102, which can lead to defects such as easy inclusion of foreign matter, poor adhesion, folding, or cracks in the transition area.

The disclosure provides a method for manufacturing a wheel hub through cold extrusion processing, which can improve the product yield rate. Production is carried out under room temperature conditions, offering significantly enhanced safety compared to high-temperature environments.

As shown in FIG. 1 to FIG. 8, the method for manufacturing a wheel hub through cold extrusion processing comprises the following steps:

• • S1. Forming a cylindrical blank 1: A round cake of forgeable metal material is placed into a first die set. Through a cold extrusion process, the first die set extrudes the round cake of forgeable metal material to form a cylindrical blank 1, which is U-shaped with its opening facing downward. The upper portion of the cylindrical blank 1 forms a spoke 102, and the lower portion of the cylindrical blank 1 forms a rim 103. The diameter of a flange 101 of the cylindrical blank 1 is greater than the diameter of the rim 103 of the cylindrical blank 1. Finally, the cylindrical blank 1 is removed from the first die set. The first die set comprises a first upper die 110, a first lower die 120, a first ejector pin 130 and a first forming sleeve 140. The first forming sleeve 140 is hollow so that its hollow portion forms a first wheel hub forming cavity. The first upper die 110 and the first lower die 120 cooperate to simultaneously apply a cold extrusion force inward, thereby forming the cylindrical blank 1 having a contour that conforms to a protruding shape of the flange 101, and the diameter of the flange 101 is greater than the diameter of the rim 103. Subsequently, the cylindrical blank 1 is ejected from the first die set by the first ejector pin 130.
  • S2. Forming a secondary blank 2: The cylindrical blank 1 is placed into a second die set. The second die set extrudes the cylindrical blank 1 via a cold extrusion process to obtain a secondary blank 2 having a contour that conforms to a desired shape of the spoke 102. The cold extrusion forms spoke recesses on both upper and lower sides of the center of the spoke 102 of the secondary blank 2 and forms an extruded step on the outer wall of the flange 101 of the secondary blank 2. The formed secondary blank 2 is then removed from the second die set. The second die set comprises a second upper die 210, a second lower die 220, a second ejector pin 230, and a second forming sleeve 240. The second forming sleeve 240 is hollow so that its hollow portion forms a second wheel hub forming cavity. The second upper die 210 and the second lower die 220 cooperate to apply a cold extrusion force, thereby forming the secondary blank 2 having a contour that conforms to a desired shape of the spoke 102.
  • S3. Forming a wheel hub: The secondary blank 2 is turned over 180 degrees and placed into a third die set. The third die set first preliminarily shapes the rim 103 of the secondary blank 2 via a cold extrusion process, causing the rim 103 to assume a flared shape. Subsequently, the top end of the rim 103 is cold extruded and bent outward to complete the forming, ultimately obtaining a finished wheel hub 3 with a final rim 103 shape. The third die set comprises: an inner upper die 310, an outer upper die 350, a third lower die 320, and at least two sliders 330 respectively disposed on both sides of the third die set. The secondary blank 2 is placed on the third lower die 320 and is secured by the at least two sliders 330. The outer upper die 350 is fitted over the inner upper die 310. First, the inner upper die 310 presses down to preliminarily form the rim 103. Then, the outer upper die 350 presses down to cold extrude and form an end portion of the rim 103, ultimately yielding the finished wheel hub 3.

As shown in FIGS. 9 and 10, in the related art, the diameter of the flange 101 of the extruded cylindrical blank 1 is equal to or less than the diameter of the rim 103. In this approach, during the step of forming the spoke 102 in a desired shape, it is prone to occur that the outer ring of the second die set presses against the inner ring at the top of the wheel hub when extruding the wheel hub. This causes the spoke 102 to be extruded toward the flange 101, resulting in a thinner region at the flange 101 and, consequently, leading to folding of the metal material at the flange 101 during extrusion. In the related art, the grain flow lines of the extruded spoke 102 converge, disrupting the overall flow lines of the product. Defects such as foreign material inclusion, poor bonding, folding, and cracking are likely to occur in the convergence area, resulting in low structural strength and poor durability of the product. In contrast, by designing the diameter of the flange 101 of the cylindrical blank 1 greater than the diameter of the rim 103, even if the spoke 102 is extruded toward the flange 101, it will not affect the junction between the spoke 102 and the flange 101, thereby preserving the overall structural strength.

Optionally, the implementation steps for forming the wheel hub by cold extrusion are as follows:

As shown in FIGS. 2 to 4, first, a forgeable metal material of a corresponding mass is selected based on the size and shape of a desired wheel hub. The forgeable metal material is placed vertically into a first die set. The first die set comprises a first upper die 110 and a first lower die 120. The first lower die 120 and the first upper die 110 simultaneously apply an extrusion force inward. In their combined state, they extrude the material to form a cylindrical cavity having a contour corresponding to the shape of the flange 101 of the wheel hub. In conventional practice, during extrusion with the first lower die 120 and the first upper die 110, typically only the first upper die 110 performs the pressing action, while the first lower die 120 remains stationary. This leads to a higher tonnage requirement for the first upper die 110. In contrast, the present disclosure, by employing simultaneous extrusion action from both the upper and lower dies, imposes a lower tonnage requirement on the first upper die 110. Furthermore, the simultaneous extrusion by both the first lower die 120 and the first upper die 110 on the wheel hub material achieves a superior forming effect. The forgeable metal material is extruded using the first lower die 120 and the first upper die 110 to obtain a cylindrical blank 1 having a shape matching the contour of the rim 101. The diameter of the flange 101 of the cylindrical blank 1 is greater than the diameter of its rim 103. Processing a blank with a larger flange 101 is beneficial for subsequently forming the shape of the spoke 102 in later steps. The larger diameter of the flange 101 reduces the likelihood of issues such as grain flow line convergence, weak bonding, folding, and cracking at the edges, thereby enhancing the mechanical strength of the product.

As shown in FIG. 2, in the first die set of the wheel hub mold, an annular inclined surface 150 is circumferentially disposed on the inner peripheral wall of the first forming sleeve 140. This annular inclined surface 150 is inclined inward from top to bottom. The annular inclined surface 150 facilitates better forming of the spoke 102, and further aids in achieving the configuration where the diameter of the flange 101 of the cylindrical blank 1 is greater than the diameter of its rim 103. Consequently, it helps prevent issues such as cracking, wrinkling, peeling, and foreign material inclusion at the flange location during the step of forming the spoke 102 shape. This results in a wheel hub with smoother grain flow lines, higher structural strength, better integrity, and superior overall mechanical properties.

As shown in FIG. 2, a first annular recess 170 is circumferentially disposed on the outer peripheral wall of the first lower die 120. A first rim forming cavity 180 is formed between the first annular recess 170 and the first wheel hub forming cavity. A cylindrical cavity having a contour corresponding to the shape of the flange 101 of the wheel hub is formed inside the first upper die 110 and the first lower die 120 when they are in a combined state. The first ejector pin 130 is movably connected to the first lower die 120. During ejection, the first ejector pin 130 moves upward through the first lower die 120 to push against the cylindrical blank 1. The cylindrical blank 1 is formed by the cooperation of the first upper die 110 and the first lower die 120 in a cold extrusion process. The first ejector pin 130 facilitates the ejection of the cylindrical blank 1, thereby making it convenient to transfer the cylindrical blank 1 to the next processing step.

Through the first step, the forgeable metal material is extruded by the first die set to obtain the cylindrical blank 1 which incorporates the shape of the protruding flange 101. The cylindrical blank 1 with the protruding flange 101 facilitates the subsequent shaping of the spoke 102. This configuration helps prevent issues such as cracking, wrinkling, peeling, and foreign material inclusion at the flange 101 location during the step of shaping the spoke 102. The method for manufacturing a wheel hub through cold extrusion according to the disclosure results in the wheel hub with smoother grain flow lines, higher structural strength, better integrity, and superior overall mechanical properties.

As shown in FIG. 5, in the second step, the cylindrical blank 1 is placed into the second lower die 220 of the second die set. The bottom of the second upper die 210 of the second die set comprises a plurality of protruding ribs 2101 corresponding to a shape of the spoke 102. The shape of the die can be flexibly changed according to the shape of the spoke 102. The second upper die 210 and the second lower die 220 are used to extrude the cylindrical blank 1 to obtain the secondary blank 2 which incorporates the shape of the spoke 102. The secondary blank 2 formed in a single operation exhibits smoother grain flow lines and higher structural strength, avoiding defects such as convergence of material flow lines.

In the second die set of the wheel hub mold, an annular step surface 250 is circumferentially disposed on the inner peripheral wall of the second forming sleeve 240. The annular step surface 250 is inclined inward from top to bottom. The annular step surface 250 facilitates better extrusion of the spoke 102 at the step region, thereby aiding in better shaping of the spoke 102, improving the strength and aesthetics of the spoke. A bottom surface of the second upper die 210 comprises protruding ribs 2101 corresponding to the shape of the spoke 102. A top surface of the second lower die 220 comprises a plurality of grooved surfaces 2201 matching the protruding ribs 2101. A second annular recess 2202 is circumferentially disposed on an outer peripheral wall of the second lower die 220. A second rim forming cavity 2203 is formed between the second annular recess 2202 and the second wheel hub forming cavity. A top of the second ejector pin 230 comprises an ejector pin head 2301. The second upper die 210, the second lower die 220, and the second ejector pin 230 are configured to cooperate to press the cylindrical blank 1 into the secondary blank 2 which incorporates the shape of the spoke 102. Pressing down with the second upper die 210 facilitates the cold extrusion forming of the spoke 102.

As shown in FIGS. 6 to 7, in the third step, since the basic shape of the wheel hub is already formed at the formation stage of the secondary blank 2, only the shape of the rim 103 needs to be processed in the third stage. The secondary blank 2 is placed on the third lower die 320 and secured by the two sliders 330 disposed on both sides of the third die set. The outer upper die 350 is fitted over the inner upper die 310. First, the inner upper die 310 presses down to preliminarily form the rim 103. Then, the outer upper die 350 presses down to cold extrude and form an end portion of the rim 103, ultimately yielding the finished wheel hub 3 with the final shaped rim 103. Furthermore, after obtaining the finished wheel hub 3 with the formed rim 103, minor finishing operations such as deburring and drilling bolt holes, as well as surface coating, are performed.

In the process of forging wheel hubs, conventional forming methods typically involve spin forming followed by turning. In the process of casting wheel hubs, the top portion of the rim often suffers from insufficient density and low strength, making it prone to fracture. In contrast, through the two-step extrusion approach of the disclosure, the inner upper die 310 first preliminarily forms the lower portion of the rim 103 as a whole. Subsequently, the outer upper die 350 extrudes and shapes the top end of the rim 103. This method allows for the application of different pressure values in the two steps, facilitating better shaping of the top end of the rim 103 while also ensuring the integrity and meeting the precision requirements of the rim 103.

As shown in FIGS. 6 to 8, in the third die set of the wheel hub mold, a top surface of the third lower die 320 comprises a support surface 3201 corresponding to the shape of the spoke 102. A lower portion of each slider 330 comprises a first step surface 3301 matching the shape of the annular step surface 250. An upper portion of each slider 330 comprises a second step surface 3302 which is inclined inward from top to bottom. A top of the second step surface 3302 contacts a rim end forming recess 3501, and the second step surface 3302 cooperates with the rim 103. An outer peripheral wall of the inner upper die 310 is circumferentially provided with a rim mating surface 3101 which is inclined inward from top to bottom. A bottom surface of the inner upper die 310 comprises a spoke forming cavity surface identical to that in the top surface of the second lower die 220. The outer upper die 350 is fitted over the inner upper die 310 and is located at an upper portion of the inner upper die 310. A bottom of the outer upper die 350 is circumferentially provided with an annular rim end forming recess 3501. Pressing down the outer upper die 350 causes the rim end forming recess 3501 to press onto a rim end forming groove 3502 disposed on the second step surface. The cooperation between the rim end forming recess 3501 and the rim end forming groove 3502 extrudes and shapes the end portion of the rim 103. By inverting and placing the secondary blank 2 onto the third die set, and through the extrusion cooperation between the inner upper die 310 and the third lower die 320, the rim 103 is more easily shaped and flared outward, thereby enhancing connection strength and performance. The third die set further comprises a third ejector pin 340. The third ejector pin 340 is movably connected to a central portion of the third lower die 320. During ejection, the third ejector pin 340 moves upward through the third lower die 320 to push against the finished wheel hub 3. The movable third ejector pin 340 facilitates the ejection of the finished wheel hub 3.

The forgeable metal material used is typically 6061 aluminum alloy or 6082 aluminum alloy. Aluminum alloy is a commonly used material for wheel hubs, offering advantages such as high structural strength. With its low density, the produced wheel hub is lightweight and maintains high structural strength, which is beneficial for the lightweight production of vehicles. Of course, other alloy materials, such as forgeable alloy materials meeting the requirements for wheel hubs, may also be used.

As shown in FIGS. 6 and 7, the number of the sliders 330 is optionally two. The cross-section of each slider 330 is semi-annular. Through the combination of the two sliders 330 and their cooperation with the third lower die 320, the secondary blank 2 can be securely held. The extrusion by the two sliders 330 and the inner upper die 310 can then yield the finished wheel hub 3 with the shaped rim 103. The number of the sliders 330 may also be three or more. The secondary blank 2 is fixed on the third lower die 320 through the cooperation of the three sliders 330. Since both the sliders 330 and the inner upper die 310 have the contour of the rim 103, applying cold extrusion to the secondary blank 2 via the inner upper die 310 produces the finished wheel hub 3 with the shaped rim 103. The configuration using three sliders 330 can shorten the formation of the stroke of each slider, thereby improving production efficiency.

The ratio of the diameter of the flange 101 to the diameter of the rim 103 of the cylindrical blank 1 is between 1.09 and 1.15. This ratio may be 1.09 or 1.15. By reasonably setting the sizes of the diameter of the flange 101 and the diameter of the rim 103, the possibility of unreasonable grain flow at the flange 101 during the second processing step can be effectively reduced, thereby enhancing the overall strength of the finished product and providing significant practical value.

The method for manufacturing a wheel hub through cold extrusion provided in this embodiment requires only three cold extrusion operations performed on the forgeable alloy material at room temperature to obtain the finished wheel hub 3. Compared to conventional casting processes or forging combined with spin forming processes, the method for manufacturing a wheel hub through cold extrusion can significantly improve the efficiency of wheel hub production. Production under ambient temperature conditions is safe and environmentally friendly, substantially saves raw material, reduces process steps, lowers costs, enhances quality, achieves technological innovation in wheel hub production, and possesses high economic value.

The disclosure further provides an electronic device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor. When executed by the processor, the computer program implements the method for manufacturing a wheel hub through cold extrusion as described above. The processor and the memory may be connected via a bus or other means. The memory, as a non-transitory computer-readable storage medium, may be used for storing non-transitory software programs and non-transitory computer-executable programs. Furthermore, the memory may comprise high-speed random access memory, and may also comprise non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory may optionally comprise memory remotely located relative to the processor. Such remote memory may be connected to the processor via a network. Examples of the aforementioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

In summary, the following advantages are associated with the method of the disclosure. The wheel hub has higher density and significantly improved structural strength. The surface finish of the wheel hub is superior, typically achieving a surface roughness of 0.4 or better, eliminating the need for further machining, while also providing higher structural strength and better quality. Producing the wheel hub can substantially save raw materials and also omits the step of milling the spoke shape from the wheel hub blank using machining equipment, thereby saving equipment and labor costs. The process does not disrupt the grain flow lines of the raw material, resulting in better structural strength and mechanical properties, and avoids defects such as cracks, pores, folds, or non-metallic inclusions. The wheel hub exhibits smoother grain flow lines, high structural strength, good integrity, and superior overall mechanical performance. The production process involves fewer steps; the wheel hub completed in three extrusion steps requires only minor finishing operations, effectively improving production efficiency and saving workforce and material resources.

While the exemplary embodiments of the disclosure have been described in detail above, the invention is not limited to these specific implementations. Those skilled in the art may make various equivalent modifications or substitutions without departing from the spirit of the disclosure. All such equivalent modifications or substitutions shall fall within the scope defined by the appended claims of the disclosure, such as using the method or apparatus provided in this disclosure for warm forging or hot forging.

It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.