A ball part plate-type cross wedge rolling die and forming method

Abstract

The application relates to the technical field of metal plastic forming processes, and provides a plate-type wedge cross rolling die for spherical parts and a forming method, the plate-type wedge cross rolling die for the spherical parts comprises an upper die and a lower die, the upper die and the lower die each comprise a plurality of pass semi-forming cavities arranged side by side, and adjacent semi-forming cavities are separated from each other through ridges; the upper die and the lower die are oppositely arranged, a complete forming cavity is formed by two corresponding semi-forming cavities which are separately arranged in the upper die and the lower die; and a plurality of forming cavities are used for wedge cross rolling of a metal round bar to obtain a plurality of spherical parts. The forming method comprises four steps of round bar feeding, die feeding and rolling forming, spherical forming and finishing, unloading and cutting of a connecting neck. The application has the advantages of simple structure, few production procedures, significantly improved production efficiency, high efficiency and material saving, can be used for mass production of spherical parts, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming technology, and in particular to a plate-type wedge cross rolling die and forming method for spherical parts. Background Technology

[0002] Spherical parts are used as grinding media in ball mills to grind various materials, such as metal ores, coal, gravel, and abrasive molding sand. These spherical parts range in diameter from 25 mm to 125 mm, with an annual demand of hundreds of thousands of tons. Spherical parts are also used in bearing balls, but traditional processes such as casting, forging, and cold heading are inefficient, have poor working environments, and require sophisticated equipment. While skew rolling, which has emerged in recent years, offers high production efficiency, the skew angle causes a radial deviation in the roll shape, and mold manufacturing presents challenges. Historically, skew-rolled steel balls were often used as grinding media in grinding mills, resulting in poor dimensional accuracy and surface defects such as pits, making them unsuitable for applications requiring high mechanical properties, such as bearing manufacturing. Therefore, a new near-net-shape spherical part production process is needed to meet the demand for high-volume, high-efficiency production of metal spherical parts with good mechanical properties and high dimensional accuracy, suitable for bearing manufacturing.

[0003] Plate wedge cross rolling, as a highly efficient metal forming process, is considered an important component of advanced manufacturing technology. Due to its numerous advantages, such as high production efficiency and high material utilization, it is now widely used in the market. Traditional wedge cross rolling forms parts using short bars, resulting in the loss of two stock heads per forming cycle, leading to low material utilization. Furthermore, plate wedge cross rolling, compared to skew rolling, avoids defects such as core porosity and damage in spherical parts produced by subjecting the ball's center to biaxial compressive stress and uniaxial tensile stress, resulting in higher forming quality. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plate wedge cross rolling die and forming method for spherical parts. By using plate wedge cross rolling to produce spherical parts, the spherical parts produced are guaranteed to have high dimensional accuracy and good mechanical properties. It inherits the characteristics of high material utilization and high production efficiency of skew rolling, and reduces the difficulties in manufacturing skew rolling dies. It has broad application prospects.

[0005] The present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a plate-type wedge cross rolling die for spherical parts, including an upper die and a lower die;

[0007] The upper and lower molds each include multiple semi-forming cavities arranged side by side, with adjacent semi-forming cavities separated by protruding ribs; the upper and lower molds are arranged opposite to each other, and two corresponding semi-forming cavities in the upper and lower molds form a complete forming cavity; the multiple forming cavities are used to obtain multiple spherical parts by wedge cross rolling of metal round bars in one operation.

[0008] In addition to any of the possible implementations described above, another implementation is provided in which the length of the semi-formed cavity in the middle pass is the longest, and decreases sequentially towards both sides.

[0009] In addition to any of the possible implementations described above, another implementation is provided in which the upper mold and the lower mold each include a forming section, a finishing section and an unloading section connected in sequence; the protrusion of the forming section gradually rises to a set height, the protrusion of the finishing section remains at a set height, and the protrusion of the unloading section gradually rises until the protrusions of the upper mold and the lower mold close tangentially to cut off the connecting neck between adjacent spherical parts.

[0010] In addition to any of the possible implementations described above, a further implementation is provided in which the size of the semi-forming chamber of the unloading section is slightly larger than the size of the semi-forming chamber of the finishing section, so as to complete the unloading of the spherical part after it has passed through the finishing section.

[0011] In addition to any of the possible implementations described above, a further implementation is provided in which the rear end of the unloading section of the lower mold is provided with a groove for receiving the formed spherical part. The part separates from the upper mold, and during the mold return process, contact between the upper mold and the ball is avoided, thus preventing any impact on the ball's shape and quality.

[0012] In addition to any of the possible implementations described above, another implementation is provided in which the front end of the forming section of the lower die is provided with a wedge fixing groove for defining the initial position of the metal bar stock during rolling.

[0013] In addition to any of the possible implementations described above, another implementation is provided in which the upper mold and the lower mold are both arranged horizontally; or the upper mold and the lower mold are both arranged vertically.

[0014] On the other hand, the present invention also provides a method for forming spherical parts by plate wedge cross rolling, the forming method using the above-mentioned spherical parts plate wedge cross rolling die, the forming method comprising:

[0015] S1. Feeding of metal round bar: Push the metal round bar along its axial direction to the set starting rolling position, which is located between the upper and lower dies;

[0016] S2. Die feed rolling forming: The upper and lower dies move horizontally towards each other. The protrusions of the semi-forming chambers of the upper and lower dies extrude the metal round bar. As the protrusions of the forming section of the die rise, the metal round bar is gradually formed into multiple balls with connecting necks by the complete forming chamber. The excess metal head is removed at both ends of the forming section of the die during rolling.

[0017] S3, Spherical Forming Finishing: The sphere with connecting neck is finished in the finishing section of the mold to refine the spherical contour;

[0018] S4. Unloading and cutting off the connecting neck: As the convex edge of the mold unloading section rises to tangential closure, the connecting neck between adjacent balls is cut off, separating them into multiple complete spherical parts.

[0019] In addition to any of the possible implementations described above, a further implementation is provided in which the forming method further includes:

[0020] S5. After being divided and unloaded, the spherical parts rotate and roll into the groove at the tail end of the lower mold, completing the recycling process.

[0021] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the lower die is provided with a wedge fixing groove at the starting rolling position to prevent the metal round bar from sliding out of the die.

[0022] In addition to any of the possible implementations described above, another implementation is provided in which the wedge fixing groove is an arc groove, for example, a 1 / 4 arc groove.

[0023] In addition to any of the possible implementations described above, another implementation is provided in which the forming method is used for thermoforming, warm forming, and cold forming processes, and the rolling diameter of the spherical parts ranges from φ3 to φ100 mm.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention employs plate wedge cross rolling to produce spherical parts, ensuring high dimensional accuracy and good mechanical properties of the formed spherical parts. It inherits the advantages of high material utilization and high production efficiency of skew rolling, while reducing the difficulty of skew rolling die manufacturing. Multiple spherical parts can be formed in one pass, resulting in high production efficiency. This invention has the advantages of significantly improving production efficiency, being easy to implement, and having low manufacturing costs. It can be used for mass production of spherical parts by plate wedge cross rolling and has broad application prospects. Attached Figure Description

[0026] Figure 1 The diagram shown is a structural schematic of a plate-type wedge cross-rolling die for spherical parts according to an embodiment of the present invention.

[0027] Figure 2The diagram shown is a schematic of the cross-rolling feed motion of the plate wedge for spherical parts in the embodiment. The upper and lower dies move toward each other at a speed v.

[0028] Figure 3 The diagram shown is a schematic of the mold forming chamber in the embodiment. The diagram shows the mold cavity structure, which includes a wedge tip fixing groove, a forming section, a finishing section, an unloading section, and a groove.

[0029] Figure 4 The diagram shown is a schematic of the wedge cross rolling forming process of the spherical parts in the embodiment. The height of the die protrusion increases in the inclined direction based on the widening angle. The rolled part relies on the friction between it and the die to roll into the die cavity in sequence to gradually complete the forming of the spherical parts.

[0030] Figure 5 As shown Figure 3 Schematic diagram of section AA.

[0031] Figure 6 As shown Figure 3 Schematic diagram of the BB section.

[0032] Figure 7 The diagram shown is a schematic of a ball-shaped part with a connecting neck in an embodiment.

[0033] In the diagram: 1-Upper mold; 2-Metal round bar; 3-Lower mold; 4-Wedge surface; 5-Wedge-in compensation arc groove. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated; they can be combined with each other to achieve better technical effects. In the accompanying drawings of the following embodiments, the same reference numerals appearing in each drawing represent the same features or components, which can be applied to different embodiments.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a wedge cross-rolling die for spherical parts, comprising an upper die 1 and a lower die 3. Both the upper die 1 and the lower die 3 include multiple semi-forming cavities arranged side by side, with adjacent semi-forming cavities separated by protruding ridges. The upper die 1 and the lower die 3 are arranged opposite to each other, and two corresponding semi-forming cavities in the upper die 1 and the lower die 3 form a complete forming cavity. The multiple forming cavities are used to cross-roll metal round bars 2 in one pass to obtain multiple spherical parts.

[0036] In one specific embodiment, both the upper mold 1 and the lower mold 3 include a forming section, a finishing section, and an unloading section. The protrusions of the forming section gradually rise to a set height, the protrusions of the finishing section remain at a set height, and the protrusions of the unloading section gradually rise until the protrusions of the upper mold 1 and the lower mold 3 tangentially close to cut off the connecting neck between adjacent spherical parts. The purpose of the finishing section is to finish the spherical contour of the rolled part before it is fully deformed after forming. To avoid the rolled part (metal round bar 2) being prematurely cut off in the forming section, the ratio of the height of the protrusions of the finishing section to the radius of the spherical part should preferably not exceed 80% to ensure the stability of the forming quality of the spherical part during the finishing process. This process is suitable for rolling diameters of spherical parts ranging from φ3 to φ100.

[0037] The mold plays two roles in the unloading section: First, the mold cavity (forming chamber) gradually expands outward to a reasonable range, causing the metal accumulated in the cavity to rebound uniformly on the spherical surface. Excess metal flows to the connecting neck and is cut off by the protruding ridge, completing the unloading of the rolled part. Second, it cuts off the metal at the connecting neck. The purpose of the unloading section is to prevent the rebound of the metal ball from affecting its quality and to separate the ball to obtain an ideal spherical part. The unloading section improves the surface quality of the spherical part. The metal in the cavity rebounds more uniformly during the unloading process, and the metal surface is round within the cavity. The surface quality of the spherical part is significantly improved compared to without an unloading section. Furthermore, according to finite element simulation results, the radial compressive stress gradually decreases during the outward expansion of the cavity cavity. After forming, the metal at the connecting neck of the spherical part is cut off by the protruding ridge, and the axial tensile stress disappears. The stress state at the center of the metal ball is under triaxial compression. Based on the improvement of the stress state during the unloading process, the core defects of the spherical part are reduced by 10-20%.

[0038] In one specific embodiment, the upper mold 1 and the lower mold 3 are both arranged in the horizontal direction; the two molds are parallel to each other and the gap at the highest point of the mold protrusion (located in the unloading section) is zero. The lower mold 3 has a wedge fixing groove. Compared with the upper mold 1, the lower mold 3 has an additional groove in the unloading section.

[0039] like Figure 2 As shown, the upper mold 1 and the lower mold 3 both move horizontally in a straight line at a speed V. During the movement, the metal round bar 2 rotates under the simultaneous action of the upper and lower half forming cavities, realizing continuous radial compression and axial extension deformation. The cavity extrudes the blank (metal round bar 2) to separate the metal, and finally forms the outline of the ball.

[0040] like Figure 3The diagram shows a semi-formed cavity of the lower mold 3. The metal bar 2 is recessed under the action of the wedge tip. The upper mold 1 and lower mold 3 move towards each other. The forming cavity extrudes the metal bar 2. Under the combined action of the forming angle and the widening angle, the metal bar 2 is gradually radially compressed at the connecting neck (the protrusion gradually increases in height), and axially extended under the push of the wedge surface, causing the metal to flow axially to the corresponding forming cavity. The forming sections sequentially shape the metal bar 2 to obtain the desired spherical part (with connecting neck) contour, as shown below. Figure 7 As shown; the height of the convex ridge in the finishing section remains constant, and the spherical part is finished as it rotates and moves forward in the forming chamber; the height of the convex ridge in the unloading section continues to increase, while the forming chamber expands slightly, and the connecting neck between the spherical parts is cut off during unloading.

[0041] like Figure 4 The diagram shows the wedge rolling process for forming spherical parts. The angle between the convex ridge and the horizontal is the widening angle, and the height of the convex ridge is related to the forming angle and the widening angle. In this embodiment of the invention, the forming of spherical parts is a sequential process. The die's central cavity wedges into the rolled piece (metal round bar 2). Relying on the friction between the die and the rolled piece, the inclined wedge surface 4 extrudes the metal outward, causing the metal to flow into the second cavity. Under the extrusion of the inclined wedge surface 4, the second spherical profile on the side is formed. The remaining metal ball forming process is as described above. The height of the convex ridge changes gradually, and the trend of the convex ridge change is consistent when the metal ball is wedge-shaped in each cavity. Therefore, the plastic flow of the rolled piece changes consistently during forming. To allow more metal to flow into the cavity and ensure the roundness of the metal spheres on both sides, a wedge-shaped compensating arc groove 5 is added in the early stage of forming. This stage consists of two arc grooves with the same radius. The bottom arc of the arc groove is connected by a straight line. The straight line segment varies from 0.1 to 2 mm. The variable hole design is achieved by connecting the variable straight line segment and the arc segment. This method solves the problem of inconsistent roundness of the metal spheres caused by the axial push of the inclined wedge surface to the metal transition.

[0042] This invention provides a method for forming spherical parts by plate wedge cross rolling. The forming method uses the aforementioned spherical part plate wedge cross rolling die, and the forming method includes:

[0043] S1. Feeding of metal round bar 2: Push the metal round bar 2 along its axial direction to the set starting rolling position, which is located between the upper die 1 and the lower die 3;

[0044] S2, Die feed rolling forming: The upper die 1 and the lower die 3 move horizontally towards each other. The protrusions of the semi-forming chambers of the upper die 1 and the lower die 3 extrude the metal round bar 2. As the protrusions of the forming section of the die rise, the metal round bar 2 is gradually formed into multiple balls with connecting necks by the complete forming chamber; the excess metal head is removed at both ends of the forming section of the die during rolling.

[0045] S3, Spherical Forming Finishing: The sphere with connecting neck is finished in the finishing section of the mold to refine the spherical contour;

[0046] S4. Unloading and cutting off the connecting neck: As the convex edge of the mold unloading section rises to tangential closure, the connecting neck between adjacent balls is cut off, separating them into multiple complete spherical parts.

[0047] The working principle of this invention is as follows:

[0048] After the metal round bar 2 is heated to a certain temperature, it is pushed to the center position of the wedge fixing groove. The upper and lower dies 1 and 3 move horizontally towards each other at a speed v. After the wedge tip wedges in, the metal round bar 2 flows into the cavity of the forming chamber. The metal round bar 2 enters the die track, and the wedge surface squeezes the metal to both sides, forming a sphere in the middle track. The metal squeezed by the wedge surface flows into the forming cavities on both sides of the middle spherical track. Driven by friction and the gradual increase of the edge height of the forming section, the two side forming cavities are spherically formed. The spherical forming principle of the remaining round bars is as above. In the forming section, the flow of metal is affected by the changes in the forming angle and widening angle of the die parameters. The schematic diagram of the die cross section in the finishing section is shown in BB. Figure 6 The forming cavity refines the contour of the formed metal round bar 2. The protruding edges on both sides of the mold reach the set position, the gaps at the protruding edges at both ends of the mold are eliminated, and the excess metal is completely cut off by the protruding edges of the finishing section and falls out of the mold; in the unloading section AA, (see...) Figure 5 The upper die 3 has an unloading gap at the protruding edge to facilitate uniform ball rebound. The protruding edge of the upper die 1 gradually rises, with the highest point of the protruding edge tangent to the plane of the protruding edge of the lower die 3. The upper die 1 cuts off the connecting neck of the rolled piece by the protruding edge, and the forming cavity of the die expands outward to a reasonable range, allowing the metal ball to rebound evenly and obtain stable rolled dimensions. The unloaded metal ball flows to... Figure 3 In the groove, the return motion of the two dies is used to avoid scraping the already formed sphere shape and affecting the surface quality of the sphere; after the metal round bar 3 is rolled into a metal sphere, the upper and lower dies 1 and 3 return to the initial rolling position for the next round of rolling.

[0049] The mold and method of this invention can be used to produce large-diameter spheres. A metal round bar 2 is pushed to a designated position in the wedge-shaped fixing groove. The wedge-shaped mold plate is fed at a constant speed and opposite speeds under the machine's push. The metal round bar 2 is extruded through the mold cavity, completing wedge forming, cavity finishing, unloading, and separation of the connecting neck and excess metal to obtain the desired spherical profile. After the sphere is formed, it falls into the groove of the lower mold and separates from the upper mold 1. The two plates return to their initial positions at a certain speed for the next rolling cycle. This invention has advantages such as simple structure, fewer production steps, significantly improved production efficiency, and high material saving. It can be used for mass production of spherical parts and has broad application prospects.

[0050] While several embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to these embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention.

Claims

1. A plate-type wedge cross-rolling die for spherical parts, characterized in that, The plate wedge cross rolling die for spherical parts includes an upper die and a lower die; Both the upper and lower molds include multiple semi-forming cavities arranged side by side, with adjacent semi-forming cavities separated by protruding ribs; the upper and lower molds are arranged opposite to each other, and two corresponding semi-forming cavities in the upper and lower molds form a complete forming chamber; the multiple forming chambers are used to obtain multiple spherical parts by wedge cross rolling of metal round bars in one operation. The upper mold and the lower mold each include a forming section, a finishing section and an unloading section connected in sequence; the protrusion of the forming section gradually rises to a set height, the protrusion of the finishing section remains at a set height, and the protrusion of the unloading section gradually rises until the protrusions of the upper mold and the lower mold close tangentially to cut off the connecting neck between adjacent spherical parts. In the early stage of forming, a wedge-shaped compensation arc groove is added. This stage consists of two arc grooves with the same radius. The bottom of the arc groove is connected by a straight arc, and the straight segment varies from 0.1 to 2 mm. The size of the semi-forming cavity in the unloading section is slightly larger than that in the finishing section, so as to complete the unloading of the spherical parts after they have passed through the finishing section. The lower mold has a groove at the rear end of the unloading section for receiving the formed spherical parts. The front end of the forming section of the lower die is provided with a wedge fixing groove for defining the initial position of the metal round bar during rolling.

2. The plate-type wedge cross-rolling die for spherical parts as described in claim 1, characterized in that, The upper mold and the lower mold are both arranged horizontally; or the upper mold and the lower mold are both arranged vertically.

3. A method for forming spherical parts by plate wedge cross rolling, characterized in that, The forming method uses the plate wedge cross-rolling die for spherical parts as described in any one of claims 1-2, and the forming method includes: S1. Feeding of metal round bar: Push the metal round bar along its axial direction to the set starting rolling position, which is located between the upper and lower dies; S2, Die feed rolling forming: The upper and lower dies move horizontally towards each other. The protrusions of the semi-forming cavities of the upper and lower dies extrude the metal round bar. As the protrusions of the forming section of the die rise, the metal round bar is gradually formed into multiple balls with connecting necks by the complete forming cavity. S3, Spherical Forming Finishing: The sphere with connecting neck is finished in the finishing section of the mold to refine the spherical contour; S4. Unloading and cutting off the connecting neck: As the convex edge of the mold unloading section rises to tangential closure, the connecting neck between adjacent balls is cut off, separating them into multiple complete spherical parts.

4. The method for forming spherical parts by plate wedge cross rolling as described in claim 3, characterized in that, The forming method further includes: S5. After being divided and unloaded, the spherical parts rotate and roll into the groove at the tail end of the lower mold, completing the recycling process.

5. The method for forming spherical parts by plate wedge cross rolling as described in claim 3, characterized in that, In step S1, the lower die is provided with a wedge fixing groove at the starting rolling position, and the wedge fixing groove is an arc groove.

6. The method for forming spherical parts by plate wedge cross rolling as described in any one of claims 3-5, characterized in that, The forming method is used for thermoforming, warm forming, and cold forming processes, and the rolling diameter range of spherical parts is φ3-φ100mm.

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