A concave blank design for high-performance forged bearing steel balls

Abstract

This invention relates to a concave billet design for high-performance forged bearing steel balls, belonging to the field of steel ball forging. This invention addresses the problems of excessive protrusion of streamlines at the poles and flash of existing billet processes, making it difficult to control flash dimensions, and also solves the difficulty of applying the pre-forging followed by final forging process to large-scale industrial production. This invention changes the original cylindrical billet to a concave cylindrical billet with frustum-shaped grooves at both ends. The method includes: 1. Billet design; 2. Billet processing; 3. Hot forging. This invention is used for forging high-performance bearing steel ball billets.

Description

Technical Field

[0001] This invention belongs to the field of steel ball parts forging. Background Technology

[0002] Bearing steel balls, as fundamental mechanical components, are widely used in various fields such as automobiles, high-speed rail, wind power, precision machine tools, and aerospace. Ball blank forming, as the central step in steel ball manufacturing, has a significant impact on the microstructure and streamline distribution of the steel ball. Current processes use simple cylindrical blanks, which, while convenient for machining, cannot control the size of the flash, leading to excessive flash; nor can they control the metal streamlines of the blank, resulting in extensive exposure of streamlines at the annular and polar regions. Steel ball failure typically occurs in these streamline-exposed areas, and large areas of streamline exposure severely affect the service life of the steel ball.

[0003] Besides the forging process mentioned above, another process involves pre-forging followed by final forging for bearing steel balls. This process can control and reduce the excessive protrusion of the streamlines and the excessive size of the flash at both stages to some extent. However, this process adds an extra step, changing from one-step to two-step forming, which greatly affects the factory's production efficiency. Furthermore, during the two-step forging process, the billet is easily misplaced, and the billet temperature is difficult to control, thus affecting the microstructure of the ball billet. Summary of the Invention

[0004] This invention aims to solve the problems of excessive protrusion of streamlines at the poles and flash of the ball blank produced by existing processes, and the inability to control the flash size. It also aims to solve the problem that the process of pre-forging followed by final forging is difficult to apply to mass industrial production. Therefore, it provides a concave blank design for high-performance forged bearing steel balls.

[0005] A concave blank design for a high-performance forged bearing steel ball is carried out according to the following steps:

[0006] I. Billet Design:

[0007] The design is based on a cylindrical blank, which is a concave cylindrical blank; the concave cylindrical blank has frustum-shaped grooves at both ends.

[0008] Let the length of the concave cylindrical blank be L1 and the diameter be d; let the chamfer of the upper and lower end faces of the concave cylindrical blank be c;

[0009] Let the angle between the inclined surface of the frustum-shaped groove of the concave cylindrical billet and the end face of the billet be the concave angle θ, where θ is 20 degrees to 40 degrees.

[0010] Let the distance between the bottom surfaces of the frustum-shaped grooves at both ends of the concave cylindrical blank be the length L2 of the concave part, where L2 is 82% to 92% of L1;

[0011] Let the angle between the bottom surface of the frustum-shaped groove and the inclined surface of the concave cylindrical blank be a fillet, and let the radius of the fillet be R, where R is 5% to 8% of d;

[0012] II. Blank processing:

[0013] A round bar with diameter d is cut to obtain a cylindrical segment with length L1, ensuring that the segment length is within the tolerance range. Then, the upper and lower end faces are chamfered. Two identical frustum-shaped grooves with an inner concave angle θ are machined on the upper and lower end faces, ensuring that the length L2 of the concave part is within the tolerance range. The included angle between the bottom surface of the frustum-shaped groove and the inclined surface is machined into a fillet with a radius of R to obtain the designed blank.

[0014] The mass of the blank in the design is equal to the mass of the steel ball blank prepared in step three;

[0015] III. Hot Forging:

[0016] The designed billet is heated to 800℃~1150℃ and held at that temperature to obtain the heated billet; the pressing amount of the press is set to ensure that the flash height of the steel ball billet is less than 2.6% of the diameter of the steel ball billet; the heated billet is quickly transferred to the cavity of the spherical mold for hot forging to obtain the steel ball billet, thus completing the design of the concave billet for high-performance forged bearing steel balls.

[0017] The beneficial effects of this invention are:

[0018] This invention ensures high production efficiency and quality in large-scale industrial production without altering the original forging process of the steel ball (one-step hot forging). Simultaneously, it changes the shape and size of the billet, transforming it into a cylinder with frustum-shaped grooves at both ends. The concavity of the upper and lower end faces of the billet promotes metal flow towards the polar holes during hot forging, further reducing the area of ​​the streamline outcrop region and decreasing the angle between the metal streamlines in the streamline outcrop region and the surface of the billet, thereby optimizing the streamline distribution in the polar regions.

[0019] This invention ensures high production efficiency and quality in large-scale industrial production without altering the original forging process of steel balls (one-step hot forging). Simultaneously, it changes the shape and size of the billet, thereby altering the flow direction of metal filling during the hot forging process, avoiding the slow metal flow velocity and excessive metal flow lines that occur at the poles in the original process. It also mitigates the tendency for flash to form first in the original process, effectively reducing flash size; the flash height of the bearing steel ball billet can be controlled within 2.6% of the billet diameter.

[0020] This invention ensures high production efficiency and quality in large-scale industrial production without altering the original forging process of the steel ball (one-step hot forging). Simultaneously, it significantly reduces flash size, improves the streamline protrusion at both ends of the resulting ball blank, maintains better forging streamlines in the steel ball blank, greatly enhances the fatigue resistance of the bearing steel ball blank, and extends its service life.

[0021] This invention relates to the design of a concave blank for a high-performance forged bearing steel ball. Attached Figure Description

[0022] Figure 1 The flowchart is shown in the diagram for the design of the concave blank of the high-performance forged bearing steel ball of the present invention. (a) is the blank processing in step two, (b) is the hot forging in step three, and (c) is the preparation of the steel ball blank in step three.

[0023] Figure 2 This is a schematic diagram of the blank dimensions designed in step one of the present invention. L1 is the length of the concave cylindrical blank, d is the diameter of the concave cylindrical blank, c is the chamfer of the upper and lower end faces of the concave cylindrical blank, c1 is the angle of chamfer c, h is the height of chamfer c, θ is the concave angle, L2 is the length of the concave part, and R is the radius of the fillet.

[0024] Figure 3 This is a physical drawing of the blank obtained in step two of Example 1;

[0025] Figure 4 The spherical mold described in step three of Example 1 is shown in (a) as a three-dimensional schematic diagram of the mold and (b) as a physical image of the mold.

[0026] Figure 5 This is a photograph of the steel ball blank prepared in step three of Example 1;

[0027] Figure 6 This is a schematic diagram of the metal flow line changes in the concave blank design of the high-performance forged bearing steel ball in Example 1. (a) is the blank designed in step 2, and (b) is the steel ball blank prepared in step 3.

[0028] Figure 7 To compare the actual and streamlined schematic diagrams of the steel ball billet prepared by the forging process without changing the billet shape in Experiment 1, (a) shows the actual flow line morphology, and (b) shows the simulated streamline morphology. A is the exposed area, and B is the flash.

[0029] Figure 8 To compare the actual and streamlined schematic diagrams of the steel ball billets prepared by the two-step forming process of pre-forging followed by final forging in Experiment 2, (a) shows the actual streamlined morphology, and (b) shows the simulated streamlined morphology. A is the exposed area, and B is the flash.

[0030] Figure 9The following is a schematic diagram of the actual steel ball blank prepared in step three of Example 1 and its streamline. (a) shows the actual streamline morphology, and (b) shows the simulated streamline morphology. A is the exposed area, and B is the flash. Detailed Implementation

[0031] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0032] Specific implementation method one: Combining Figures 1 to 2 Specifically, the concave blank design for a high-performance forged bearing steel ball described in this embodiment is carried out according to the following steps:

[0033] I. Billet Design:

[0034] The design is based on a cylindrical blank, which is a concave cylindrical blank; the concave cylindrical blank has frustum-shaped grooves at both ends.

[0035] Let the length of the concave cylindrical blank be L1 and the diameter be d; let the chamfer of the upper and lower end faces of the concave cylindrical blank be c;

[0036] Let the angle between the inclined surface of the frustum-shaped groove of the concave cylindrical billet and the end face of the billet be the concave angle θ, where θ is 20 degrees to 40 degrees.

[0037] Let the distance between the bottom surfaces of the frustum-shaped grooves at both ends of the concave cylindrical blank be the length L2 of the concave part, where L2 is 82% to 92% of L1;

[0038] Let the angle between the bottom surface of the frustum-shaped groove and the inclined surface of the concave cylindrical blank be a fillet, and let the radius of the fillet be R, where R is 5% to 8% of d;

[0039] II. Blank processing:

[0040] A round bar with diameter d is cut to obtain a cylindrical segment with length L1, ensuring that the segment length is within the tolerance range. Then, the upper and lower end faces are chamfered. Two identical frustum-shaped grooves with an inner concave angle θ are machined on the upper and lower end faces, ensuring that the length L2 of the concave part is within the tolerance range. The included angle between the bottom surface of the frustum-shaped groove and the inclined surface is machined into a fillet with a radius of R to obtain the designed blank.

[0041] The mass of the blank in the design is equal to the mass of the steel ball blank prepared in step three;

[0042] III. Hot Forging:

[0043] The designed billet is heated to 800℃~1150℃ and held at that temperature to obtain the heated billet; the pressing amount of the press is set to ensure that the flash height of the steel ball billet is less than 2.6% of the diameter of the steel ball billet; the heated billet is quickly transferred to the cavity of the spherical mold for hot forging to obtain the steel ball billet, thus completing the design of the concave billet for high-performance forged bearing steel balls.

[0044] The angle θ mentioned in step one is 20 to 40 degrees. The purpose is to ensure that the outer metal flows towards the center during the hot forging process at both ends of the billet. If θ is too small, the improvement in the flow direction of metal filling is not obvious, and a large number of flow lines will still appear at the metal poles. If θ is too large, the groove part of the billet is too deep, resulting in obvious metal folding.

[0045] The L2 mentioned in step one is 82% to 92% of L1. The purpose is to address the folding phenomenon caused by the outer metal flow velocity being much greater than the central metal flow velocity, where the groove becomes deeper closer to the center of the billet. During hot forging, if L2 is too small, the improvement in the flow direction of metal filling is not significant, and the improvement in the metal flow line emergence phenomenon is not obvious; if L2 is too large, the center of the groove in the billet becomes too deep, resulting in severe metal folding.

[0046] In step one, c1 is 45 degrees. When the material segment is placed, the side of c contacts the inner wall of the hot forging spherical cavity, and h is 0.5mm to 1mm. On the one hand, this ensures that the bar can be stably placed in the lower die cavity during the hot forging process. On the other hand, it reduces stress concentration in the chamfer area and prevents metal cracking.

[0047] The purpose of R being 5% to 8% of d in step one is to prevent the metal at the contact point between the concave frustum sidewall and the bottom platform from folding.

[0048] In step three, during hot forging, the frustum-shaped grooves on the billet alter the flow direction of the metal filling during the hot forging process. The metal preferentially fills the spherical mold cavity before forming flash. The grooves on the upper and lower end faces of the billet cause the external metal at both ends to flow towards the center under the action of the spherical cavity, reducing the phenomenon of metal flow lines protruding at the two poles.

[0049] Step 3, hot forging, yields steel ball blanks with smaller flash size and less metal flow line exposure at both poles.

[0050] The beneficial effects of this embodiment are:

[0051] This implementation method, without altering the original forging process of the steel ball (one-step hot forging), ensures production efficiency and quality in large-scale industrial production. Simultaneously, it changes the shape and size of the billet, transforming it into a cylinder with frustum-shaped grooves at both ends. The concavity of the upper and lower end faces of the billet promotes metal flow towards the polar holes during hot forging, further reducing the area of ​​the streamline outcrop region and decreasing the angle between the metal streamlines in the streamline outcrop region and the surface of the billet, thereby optimizing the streamline distribution in the polar regions.

[0052] This implementation method, without altering the original forging process of the steel ball (one-step hot forging), ensures production efficiency and quality in large-scale industrial production. Simultaneously, it changes the shape and size of the billet, thereby altering the flow direction of the metal filling during the hot forging process, avoiding the slow metal flow velocity and excessive metal flow lines that occur at the poles in the original process. It also mitigates the tendency for flash to form first in the original process, effectively reducing flash size; the flash height of the bearing steel ball billet can be controlled within 2.6% of the billet diameter.

[0053] This implementation method, without altering the original forging process of the steel ball (one-step hot forging), ensures production efficiency and quality in large-scale industrial production. Simultaneously, it significantly reduces flash size, improves the streamline protrusion at both ends of the resulting ball blank, maintains better forging streamlines in the steel ball blank, greatly enhances the fatigue resistance of the bearing steel ball blank, and extends its service life.

[0054] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the length of the cylindrical material segment in step two is L1±a, where a is 0.1mm. Everything else is the same as in Specific Implementation Method One.

[0055] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the material of the round bar mentioned in step two is bearing steel. Everything else is the same as in Specific Implementation Method One or Two.

[0056] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the length of the concave portion mentioned in step two is L2±b, where b is 0.05mm. Everything else is the same as in Specific Implementation Methods One to Three.

[0057] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the angle c1 of the chamfer c in step one is 30 degrees to 60 degrees, and the height h of the chamfer c is not less than 0.5 mm. Everything else is the same as in Specific Implementation Methods One to Four.

[0058] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the height-to-diameter ratio of the concave cylindrical blank described in step one is (1.6 to 2.4):1. Everything else is the same as in Specific Implementation Methods One to Five.

[0059] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: in step three, the designed billet is heated to 800℃~1150℃ and held at that temperature for 20min~80min. Everything else is the same as Specific Implementation Methods One to Six.

[0060] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that, in step three, under the condition that the overall furnace transfer time does not exceed 35 seconds, the heated billet is quickly transferred to the spherical mold cavity for hot forging. Everything else is the same as in Specific Implementation Methods One to Seven.

[0061] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the spherical mold cavity described in step three is spherical. Everything else is the same as Specific Implementation Methods One to Eight.

[0062] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the diameter of the polar hole in the spherical mold is 20% to 30% of the diameter of the spherical blank; the fillet diameter between the polar hole and the cavity of the spherical mold is 1 / 5 to 1 / 6 of the diameter of the polar hole; and the diameter of the spherical blank is not less than 10 mm. Everything else is the same as in Specific Implementation Methods One to Nine.

[0063] The beneficial effects of the present invention are verified using the following embodiments:

[0064] Example 1:

[0065] A concave blank design for a high-performance forged bearing steel ball is carried out according to the following steps:

[0066] I. Billet Design:

[0067] The design is based on a cylindrical blank, which is a concave cylindrical blank; the concave cylindrical blank has frustum-shaped grooves at both ends.

[0068] Let the length of the concave cylindrical blank be L1 = 35.7 mm, the diameter be d = 16 mm, and the height-to-diameter ratio be 2.23:1; let the chamfer of the upper and lower end faces of the concave cylindrical blank be c, the angle c1 of the chamfer c be 45 degrees, and the height h of the chamfer c be 0.5 mm.

[0069] Let the angle between the inclined surface of the frustum-shaped groove of the concave cylindrical billet and the end face of the billet be the concave angle θ, where θ is 30 degrees;

[0070] Let the distance between the bottom surfaces of the frustum-shaped grooves at both ends of the concave cylindrical blank be L2 = 32.8 mm, and L2 be 92% of L1;

[0071] Let the angle between the bottom surface of the frustum-shaped groove and the inclined surface of the concave cylindrical blank be a fillet, with a fillet radius of R = 1 mm, where R is 6.3% of d;

[0072] II. Blank processing:

[0073] A round bar with diameter d is cut to obtain a cylindrical segment with length L1, ensuring that the segment length is within the tolerance range. Then, the upper and lower end faces are chamfered. Two identical frustum-shaped grooves with an inner concave angle θ are machined on the upper and lower end faces, ensuring that the length L2 of the concave part is within the tolerance range. The included angle between the bottom surface of the frustum-shaped groove and the inclined surface is machined into a fillet with a radius of R to obtain the designed blank.

[0074] The designed billet mass is equal to the mass of the steel ball billet prepared in step three, specifically 56.64g;

[0075] III. Hot Forging:

[0076] The designed billet is heated to 930℃ and held for 30 minutes to obtain the heated billet; the pressing amount of the press is set to ensure that the flash height of the steel ball billet is less than 0.40mm; under the condition that the transfer time of a single billet is 5s and the transfer time of the whole furnace is 32s, the heated billet is quickly transferred to the cavity of the spherical mold for hot forging to obtain the steel ball billet, thus completing the design of the concave billet for high-performance forged bearing steel balls;

[0077] In step three, five billets are produced per furnace, and the diameter of the steel ball billet is 23.6 mm.

[0078] In step two, the length of the cylindrical material segment is L1±a, where a is 0.1mm.

[0079] The round bar material mentioned in step two is bearing steel 8Cr4Mo4V.

[0080] The length of the concave portion mentioned in step two is L2±b, where b is 0.05mm.

[0081] The spherical mold cavity mentioned in step three is spherical. The diameter of the extreme hole of the spherical mold is 6mm; the radius of the fillet between the extreme hole of the spherical mold and the cavity of the spherical mold is 1mm; the metal filling condition is judged by observing the two extreme dimensions of the forged steel ball blank and whether flash is generated.

[0082] The purpose of θ being 30 degrees and L2 being 32.8 mm in step one is to ensure that the metal on the outer side of the core at both ends of the billet has a radial inward flow tendency during hot forging, thereby reducing the phenomenon of streamlines protruding at the two poles; slowing down the tendency of metal to first form flash and then fill the cavity, thereby reducing flash, ensuring that the missing volume of the core at both ends of the billet is appropriate, and finally the metal fills the entire ball cavity without metal folding.

[0083] Figure 3 This is a physical drawing of the blank obtained in step two of Example 1;

[0084] Figure 4 The spherical mold described in step three of Example 1 is shown in (a) as a three-dimensional schematic diagram of the mold and (b) as a physical image of the mold.

[0085] Figure 5 This is a photograph of the steel ball blank prepared in step three of Example 1;

[0086] Figure 6 The diagram shows the metal flow line changes of the concave billet design for the high-performance forged bearing steel ball in Example 1. (a) is the designed billet obtained in step 2, and (b) is the steel ball billet prepared in step 3. As can be seen from the figure, after the original bar stock is processed, the core of the upper and lower end faces lacks metal. After hot forging, the metal on the outer side of the upper and lower end faces flows radially inward, and the flow lines show a closed trend, which greatly reduces the flow line protrusion at the two poles.

[0087] Comparative Experiment 1: This comparative experiment differs from Example 1 in that the machining of the frustum-shaped groove in steps one and two is omitted. After cutting the round bar, a cylindrical section with a diameter of 16.5 mm and a length of 34.17 mm is obtained, ensuring that the length of the section is within the tolerance range. This cylindrical blank is then hot-forged into a spherical blank. Everything else is the same as in Example 1.

[0088] Comparative Experiment 2: This comparative experiment differs from Example 1 in that the processing of the frustum-shaped groove in steps 1 and 2 is omitted. The round bar is cut to obtain a cylindrical segment with a diameter of 16.5 mm and a length of 34.2 mm, ensuring the segment length is within tolerance. Then, the upper and lower end faces are chamfered with a chamfer height of 0.5 mm to obtain the processed billet. A pre-forging step is added, changing the process to pre-forging followed by final forging. The pre-forging process specifically involves setting the pre-forging reduction of the press, pre-forging to obtain a pre-forged billet, and then performing final forging on the pre-forged billet according to step 3 of Example 1. The cone angle in the conical pre-forging die cavity is 50°. The reduction during the pre-forging process is 28% of the height of the processed segment. Everything else is the same as in Example 1.

[0089] Figure 7 To compare the actual and streamlined schematic diagrams of the steel ball billet prepared by the forging process without changing the billet shape in Experiment 1, (a) shows the actual flow line morphology, and (b) shows the simulated streamline morphology. A is the exposed area, and B is the flash. Figure 8 To compare the actual and streamlined schematic diagrams of the steel ball billets prepared by the two-step forming process of pre-forging followed by final forging in Experiment 2, (a) shows the actual streamlined morphology, and (b) shows the simulated streamlined morphology. A is the exposed area, and B is the flash. Figure 9The figures show the actual steel ball billet prepared in step three of Example 1 and its streamlines. (a) shows the actual streamline morphology, and (b) shows the simulated streamline morphology. A represents the exposed area, and B represents the flash. As can be seen from the figures, by changing the forging method of the billet shape, the exposed area of ​​the streamlines in the two polar regions of the billet is reduced by 65%, and the angle between the streamlines in the exposed area and the surface of the billet is reduced. Simultaneously, the flash size (less than 0.40 mm) is significantly reduced, with almost no flash, and the metal streamlines are basically distributed along the surface of the billet. Furthermore, this process does not affect the factory's production efficiency, is less prone to problems such as misalignment and temperature discrepancies, and can be applied to large-scale industrial production.

Claims

1. A high performance forged bearing steel ball's inner concave type blank design characterized by It is done in the following steps: I. Billet Design: The design is based on a cylindrical blank, which is a concave cylindrical blank; the concave cylindrical blank has frustum-shaped grooves at both ends. Let the length of the concave cylindrical blank be L1 and the diameter be d; let the chamfer of the upper and lower end faces of the concave cylindrical blank be c; Let the angle between the inclined surface of the frustum-shaped groove of the concave cylindrical billet and the end face of the billet be the concave angle θ, where θ is 20 degrees to 40 degrees. Let the distance between the bottom surfaces of the frustum-shaped grooves at both ends of the concave cylindrical blank be the length L2 of the concave part, where L2 is 82% to 92% of L1; Let the angle between the bottom surface of the frustum-shaped groove and the inclined surface of the concave cylindrical blank be a fillet, and let the radius of the fillet be R, where R is 5% to 8% of d; II. Blank processing: A round bar with diameter d is cut to obtain a cylindrical segment with length L1, ensuring that the segment length is within the tolerance range. Then, the upper and lower end faces are chamfered. Two identical frustum-shaped grooves with an inner concave angle θ are machined on the upper and lower end faces, ensuring that the length L2 of the concave part is within the tolerance range. The included angle between the bottom surface of the frustum-shaped groove and the inclined surface is machined into a fillet with a radius of R to obtain the designed blank. The mass of the blank in the design is equal to the mass of the steel ball blank prepared in step three; III. Hot Forging: The designed billet is heated to 800℃~1150℃ and held at that temperature to obtain the heated billet; the pressing amount of the press is set to ensure that the flash height of the steel ball billet is less than 2.6% of the diameter of the steel ball billet; the heated billet is quickly transferred to the cavity of the spherical mold for hot forging to obtain the steel ball billet, thus completing the design of the concave billet for high-performance forged bearing steel balls.

2. A concave type blank design for high performance forged bearing steel balls as claimed in claim 1, wherein In step two, the length of the cylindrical material segment is L1±a, where a is 0.1mm.

3. A concave type blank design for high performance forged bearing steel balls as claimed in claim 1, wherein The round bar material mentioned in step two is bearing steel.

4. A concave type blank design for high performance forged bearing steel balls as claimed in claim 1, wherein The length of the concave portion mentioned in step two is L2±b, where b is 0.05mm.

5. The concave blank design for a high-performance forged bearing steel ball according to claim 1, characterized in that... In step one, the chamfer angle c1 is 30 degrees to 60 degrees, and the chamfer height h is not less than 0.5 mm.

6. The concave blank design for a high-performance forged bearing steel ball according to claim 1, characterized in that... The height-to-diameter ratio of the concave cylindrical blank mentioned in step one is (1.6~2.4):

1.

7. The concave blank design for a high-performance forged bearing steel ball according to claim 1, characterized in that... In step three, the designed billet is heated to 800℃~1150℃ and held for 20min~80min.

8. The concave blank design for a high-performance forged bearing steel ball according to claim 1, characterized in that... In step three, under the condition that the transfer time of the whole furnace is no more than 35 seconds, the heated billet is quickly transferred to the cavity of the spherical mold for hot forging.

9. The concave blank design for a high-performance forged bearing steel ball according to claim 1, characterized in that... The spherical mold cavity mentioned in step three is spherical.

10. The concave blank design for a high-performance forged bearing steel ball according to claim 9, characterized in that... The diameter of the polar hole in the spherical mold is 20% to 30% of the diameter of the spherical blank; the fillet diameter between the polar hole and the cavity of the spherical mold is 1 / 5 to 1 / 6 of the diameter of the polar hole; and the diameter of the spherical blank is not less than 10 mm.

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