JP2024164297A - Forged products - Google Patents

Abstract

To improve the durability of a forged molding.SOLUTION: A forged molding 60 comprises: an outer peripheral part 62 formed into a cylindrical shape; a flange part 64 formed at the upper end of the outer peripheral part 62 and swelling to the radial outside of the outer peripheral part 62; a center part 66 formed inside the outer peripheral part 62; a recessed part 68A formed by a forging molding in the bottom surface of the center part 66; and a projected part 69 formed above the recessed part 68A in the center part 66 and larger in diameter than the recessed part 68A. The projected part 69 is provided with a free molding surface 69A formed not in contact with the forging molding.SELECTED DRAWING: Figure 3B

Description

The present invention relates to forged products.

The following Patent Document 1 describes a forging die for a rotor hub. An opening is formed in the part of this forging die where the flange portion of the rotor hub is formed. This opening allows a portion of the workpiece to escape to the outside during the forging process. This reduces the load applied from the forging die to the part of the workpiece that will become the flange portion, and suppresses the occurrence of residual strain in that part.

JP 2019-147172 A

The rotor hub forging die of the above-mentioned Patent Document 1 can suppress the occurrence of residual strain in the flange portion of the rotor hub. By suppressing the residual strain in the flange portion, it is possible to increase the smoothness of the disk mounting surface, which requires particularly high machining accuracy.

In this way, in forged products, it is preferable to suppress residual strain in appropriate locations depending on the application. On the other hand, during the forging process, the forging die is also subjected to a load due to a reaction force from the workpiece. For this reason, in addition to suppressing residual strain in the molded product, it is also necessary to improve the durability of the die.

Taking the above facts into consideration, the present invention aims to improve the durability of forging dies.

The forged product of the first embodiment has an outer circumferential portion formed in a cylindrical shape, a flange portion formed at the upper end of the outer circumferential portion and extending radially outward from the outer circumferential portion, a central portion formed inside the outer circumferential portion, a recess formed on the bottom surface of the central portion by a forging die, and a convex portion formed above the recess in the central portion and having a larger diameter than the recess, and the convex portion has a free forming surface formed without contacting the forging die.
In the second aspect of the forged product, the smoothness of the radially outer end face of the flange portion is higher than that of the free-form surface and is equal to that of the portion other than the free-form surface in the forged product of the first aspect.
A forged product of a third aspect is the forged product of the first aspect, in which a free forming surface is formed on a radially outer end face of the flange portion.
The forged product of the fourth aspect is the forged product of the first aspect, wherein a curved surface is formed between the side surface of the convex portion and the free forming surface.
A forged product of a fifth aspect is the forged product of the first or second aspect, wherein a through hole is formed from the recess through the free forming surface.

The forging die of the first embodiment has a first die with a cavity, a second die with a core that can sandwich and press a workpiece between the first die and the core by moving relatively toward the first die, a protrusion formed on the bottom surface of the cavity and protruding toward the core in the direction of movement of the first die or the second die, and an opening that is provided in the core in the direction of movement opposite the protrusion and forms a gap between the workpiece and the core when the first die and the second die are clamped together.

In the forging die of the first embodiment, a protrusion is formed on the bottom surface of the cavity, protruding toward the core in the direction of movement of the first or second die. Therefore, when the workpiece is sandwiched and pressed between the cavity and the core, the workpiece receives localized pressure from the protrusion. This causes the workpiece to deform toward the core.

On the other hand, an opening is provided in the portion of the core facing the protrusion of the cavity, facing the direction of movement of the first or second die. This opening is a portion that forms a gap between the workpiece when the first and second dies are clamped together. In other words, at least a portion of the portion of the workpiece that is pressed and deformed by the protrusion of the cavity does not come into contact with the core. This reduces the pressing force acting from the protrusion to the core via the workpiece. Also, the pressing force acting from the core to the cavity via the workpiece is reduced. This improves the durability of the forging die.

The second aspect of the forging die is the forging die of the first aspect, in which a step surface is provided on the side surface of the cavity along a direction intersecting the direction of movement, and the core is formed with a pressing surface that presses the workpiece between the step surface and the core.

In the forging die of the second embodiment, the workpiece is pressed by the step surface and pressing surface in the direction intersecting the movement direction of the first or second die. This causes the outer periphery of the workpiece to be upset forged. This makes it possible to make the metal structure in the outer periphery of the workpiece denser and increase its strength.

In addition, a flange can be formed on the outer periphery of the workpiece, projecting in a direction intersecting the direction of movement of the first or second die. This results in a higher material yield than when the flange is formed by machining alone.

The forging method of the third aspect is a forging method using a first die having a cavity and a second die having a core capable of pressing a workpiece between the cavity and the first die, and includes the steps of placing the workpiece in the cavity having a protrusion formed on the bottom surface thereof that protrudes in the direction of movement of the first die or the second die toward the core, and clamping the first die and the second die, which has an opening provided in the part of the core facing the protrusion and facing the direction of movement, to mold the workpiece, and forming a free forming surface by the gap formed between the workpiece and the core.

The forging die used in the forging method of the third embodiment has a protrusion formed on the bottom surface of the cavity that protrudes toward the core. Therefore, when the workpiece is sandwiched and pressed between the cavity and the core, the workpiece receives localized pressure from the protrusion. This causes the workpiece to deform toward the core.

In addition, a free forming surface is formed on the workpiece above the protrusion of the first die. In other words, at least a part of the part of the cavity that is pressed and deformed by the protrusion does not come into contact with the core. This reduces the pressing force acting from the protrusion to the core via the workpiece. Also, the pressing force acting from the core to the cavity via the workpiece is reduced. This improves the durability of the forging die.

The forged product of the fourth embodiment has an outer periphery formed in a cylindrical shape, a flange portion formed at the upper end of the outer periphery and extending radially outward from the outer periphery, a central portion formed inside the outer periphery, a recess formed on the bottom surface of the central portion, and a protrusion formed above the recess in the central portion, and the protrusion has a free forming surface.

In the fourth embodiment, the forged product has a recess formed in the bottom surface of the center. In other words, the bottom surface of the center is deformed by being pressed by the forging die.

On the other hand, above the recess in the center, a convex portion is formed as a free forming surface. In other words, the portion opposite the bottom surface pressed by the forging die is not pressed by the forging die. In other words, this portion is formed by free deformation without being pressed by the forging die. This reduces the pressing force acting from the molded product on the forging die during the forging process. This improves the durability of the forging die.

This invention makes it possible to improve the durability of forging dies.

FIG. 1 is an elevational view showing a forging die according to an embodiment of the present invention. 1B is a cross-sectional view taken along line BB in FIG. 1A. 1 is a cross-sectional elevation view showing a state in which a billet is placed in a cavity of a forging die according to an embodiment of the present invention. FIG. FIG. 2 is a cross-sectional elevation view showing a state in which the forging die according to the embodiment of the present invention is clamped to deform a billet. FIG. 11 is a cross-sectional elevation view showing a state in which the forging die according to the embodiment of the present invention is further clamped to deform the billet. FIG. 2 is an elevational view showing a forged product according to an embodiment of the present invention. This is a cross-sectional view of line BB in Figure 3A. 4 is a cross-sectional view showing an example of the shape of a free forming surface in a forged product according to an embodiment of the present invention. FIG. FIG. 4 is a cross-sectional view showing another example of the shape of a free forming surface in a forged product according to an embodiment of the present invention. 1 is an elevational view showing a rotor hub formed by cutting a forged product according to an embodiment of the present invention; This is a cross-sectional view taken along line BB in FIG. 5A.

The following describes the forging die, forging method, and forged product according to the embodiments of the present invention with reference to the drawings. Components indicated with the same reference numerals in each drawing are the same components. However, unless otherwise specified in the specification, each component is not limited to one, and may exist in multiples. Also, explanations of configurations and reference numerals that are duplicated in each drawing may be omitted. Note that the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications, such as omitting configurations or replacing them with different configurations, within the scope of the purpose of the present invention.

First, we will provide an overview of the "forging die," "forging method," and "forged product" according to an embodiment of the present invention.

Figures 1A and 1B show a "forging die 20 (hereinafter referred to as die 20)" according to an embodiment of the present invention. Using this die 20, a billet 50, which is the workpiece, is forged by the "forging method" shown in Figures 2A to 2C. This results in a "forged molded product 60 (hereinafter referred to as molded product 60)" shown in Figures 3A and 3B. The molded product 60 is an intermediate material for the rotor hub 10, which is the final molded product shown in Figure 5. The rotor hub 10 is formed by cutting the molded product 60.

<Rotor hub>
Prior to describing the die 20, the forging method, and the molded product 60 according to the embodiment of the present invention, the configuration of the rotor hub 10 will be described. The rotor hub 10 shown in Figures 5A and 5B is a cylindrical rotor that constitutes an outer rotor type spindle motor (not shown). The rotor hub 10 is made of a metal material such as stainless steel.

In the following description, the direction along the rotation axis O of the rotor hub 10 is referred to as the axial direction. The direction perpendicular to the rotation axis O is referred to as the radial direction, and the direction rotating around the rotation axis O is referred to as the circumferential direction.

The rotor hub 10 has an outer circumferential portion 12 formed in a cylindrical shape, a flange portion 14 formed at the upper end of the outer circumferential portion 12 and extending radially outward from the outer circumferential portion 12, and a central portion 16 formed on the inside of the outer circumferential portion 12.

Note that the "upper end" refers to the end at the top of the paper in FIG. 5B. This "upper end" does not necessarily coincide with the up-down direction of the rotor hub 10 when in use. The same applies to the "lower end" (the end at the bottom of the paper in FIG. 5B) described below.

The flange portion 14 is formed in a circular ring shape, projecting radially outward around the entire circumference of the upper end of the outer periphery portion 12. The central portion 16 is formed radially inward of the outer periphery portion 12, between the upper and lower ends of the outer periphery portion 12. The central portion 16 is formed with a protrusion 19 that protrudes toward the flange portion 14. The central portion 16 is also formed with a through hole 18. The through hole 18 is a round hole with the rotation axis O as its central axis, and penetrates from the bottom surface of the central portion 16 to the top surface of the protrusion 19.

The rotor hub 10 is used, for example, in an information recording and reproducing device. The rotor hub 10 is used with its outer periphery 12 fitted into a central hole Dh in a circular disk (magnetic recording medium) D. At this time, the edge of the hole Dh in the disk D is placed on the flange portion 14 (mounting surface 14A). When the information recording and reproducing device is operating, the rotor hub 10 is supported so as to be freely rotatable in the circumferential direction and rotates in the circumferential direction by the drive of a spindle motor (not shown).

<Forging dies>
As shown in FIGS. 1A and 1B , the mold 20 is configured to include a first mold 30 and a second mold 40 .

(Type 1)
The first die 30 is a fixed die that is used in a fixed state during forging. The first die 30 is formed with a cavity 30C, which is a recess in which a billet 50 (see FIG. 2A) is placed. The first die 30 is also formed with a bottom die 30A that forms a bottom surface 36 of the cavity 30C, and a side die 30B that forms a side surface 32 of the cavity 30C.

The bottom surface 36 of the cavity 30C is formed in a circular shape centered on an axis O along the movement direction of the second mold 40 (hereinafter referred to as the movement direction V). Correspondingly, the top surface of the bottom mold 30A is formed in a circular shape centered on the axis O, and the bottom mold 30A is formed in a cylindrical shape centered on the axis O.

In addition, protrusions 36A and 36B are formed on the bottom surface 36 of the cavity 30C, protruding along the movement direction V toward the second die 40. Protrusion 36A is a truncated cone-shaped protrusion with axis O as its central axis. Protrusion 36B is an annular protrusion that surrounds protrusion 36A. The height of protrusion 36A (the dimension along the movement direction V) is higher than the height of protrusion 36B. In other words, protrusion 36A is the tallest protrusion among the multiple protrusions formed on the bottom surface 36.

The side surface 32 of the cavity 30C has a first side surface 32A and a second side surface 32B. The first side surface 32A is the side surface closer to the bottom surface 36 of the cavity 30C, and its shape when viewed from a direction along the movement direction V is approximately the same as that of the bottom surface 36. The second side surface 32B is formed on the second mold 40 side when viewed from the first side surface 32A. Furthermore, the shape of the second side surface 32B when viewed from a direction along the movement direction V is a circle that is concentric with the first side surface 32A and has a larger diameter than the first side surface 32A.

In addition, in the cavity 30C, a step surface 34 is formed between the first side surface 32A and the second side surface 32B. The step surface 34 is a flat surface formed along a plane that is approximately perpendicular to the movement direction V.

(Type 2)
The second die 40 is a movable die that is used by being moved in a direction (movement direction V) approaching the first die 30 during forging (when clamping the die). Since the second die 40 is disposed above the first die 30, the second die 40 and the first die 30 may be referred to as the upper die and the lower die, respectively. Since the second die 40 is inserted into the cavity 30C of the first die 30, the second die 40 may be referred to as a core die or a core.

The second mold 40 is formed with a side surface 42, a pressing surface 44, a top surface 46, and a through hole 48.

The side surface 42 has a first side surface 42A and a second side surface 42B. The shape of the first side surface 42A when viewed from a direction along the movement direction V is a circle that is concentric with the first side surface 32A of the first die 30 and has a smaller diameter than the first side surface 32A. The first side surface 42A is formed closer to the bottom surface 36 of the cavity 30C than the second side surface 42B. The shape of the second side surface 42B when viewed from a direction along the movement direction V is substantially the same as the shape of the second side surface 32B of the first die 30.

As a result, the second mold 40 is moved with the first side 42A spaced apart from the first side 32A of the cavity 30C and the second side 42B in contact with the second side 32B of the cavity 30C.

The pressing surface 44 is a flat surface formed between the first side surface 42A and the second side surface 42B along a plane that is approximately perpendicular to the moving direction V. The pressing surface 44 is disposed opposite the step surface 34 of the cavity 30C.

The top surface 46 is a surface that intersects with the first side surface 42A and is positioned opposite the bottom surface 36 of the cavity 30C.

The through hole 48 is a circular hole that forms an opening in the top surface 46, and is provided along the movement direction V with the axis O as the central axis. In other words, the through hole 48 is provided at a position opposite the protrusion 36A. Also, when viewed from the direction along the movement direction, the inner diameter of the through hole 48 is larger than the outer diameter of the protrusion 36A.

<Forging method>
3A and 3B is forged using the above-described die 20. The molded product 60 can also be formed by hot forging, but in this specification, the case where the molded product 60 is formed by cold forging will be described.

To forge the molded product 60, first, as shown in FIG. 2A, a billet 50, which is the workpiece, is placed in the cavity 30C. The billet 50 is made of a metal material such as stainless steel. The billet 50 has a cylindrical shape, and the outer peripheral surface 50A is placed in contact with the first side surface 32A of the cavity 30C. Note that "in contact" includes a state in which a gap is formed between the outer peripheral surface 50A and the first side surface 32A large enough to allow the billet 50 to be attached and detached.

When the billet 50 is placed in the cavity 30C, the bottom surface 50B of the billet 50 is placed in contact with the top surface of the protrusion 36A formed on the bottom surface 36 of the cavity 30C. In this state, by moving the second die 40 in a direction approaching the first die 30, the top surface 46 of the second die 40 first comes into contact with the top surface 50C of the billet 50. As a result, the billet 50 is sandwiched between the second die 40 and the first die 30.

Next, as shown in FIG. 2B, the billet 50 is pressed (clamped) between the second die 40 and the first die 30. As a result, the bottom surface 50B of the billet 50 is deformed by being pressed by the protrusions 36A and 36B of the first die 30. As a result, a recess 58 is formed in the bottom surface 50B of the billet 50. The recesses 58 formed by being pressed by the protrusions 36A and 36B are referred to as recesses 58A and 58B, respectively.

Meanwhile, the top surface 50C of the billet 50 is also pressed by the top surface 46 of the second die 40 and deformed. This forms an outer periphery 52 in the billet 50, which is the portion sandwiched between the first side surface 32A of the first die 30 and the first side surface 42A of the second die 40.

In addition, the top surface 50C of the billet 50 is pressed from the top surface 46 of the second die 40, which has a through hole 48, and a convex portion 59 is formed in the billet 50, which is recessed into the through hole 48. The convex portion 59 is formed above the concave portion 58A. In addition, the side surface of the convex portion 59 contacts the inner peripheral surface of the through hole 48, while the top surface (the portion of the top surface 50C of the billet 50 that is located inside the through hole 48) does not contact the second die 40. In other words, the top surface of the convex portion 59 is a free forming surface (the free forming surface will be described later).

In this embodiment, the "gap formed between the workpiece and the core" in this invention refers to the gap formed between the convex portion 59 of the billet 50, which is the workpiece, and the second die 40, which is the core. Specifically, it refers to the space surrounded by the convex portion 59 and the portion of the inner wall of the through hole 48 formed in the second die 40 that does not come into contact with the convex portion 59.

As the second die 40 and the first die 30 continue to press the billet 50, the upper end of the outer periphery 52 comes into contact with the pressing surface 44 of the second die 40 and is pressed from the pressing surface 44. As a result, the upper end of the outer periphery 52 is deformed toward the outside in the radial direction of the outer periphery 52.

This deformed portion is pressed by the pressing surface 44 and the step surface 34 of the first die 30, forming a flange portion 54 as shown in FIG. 2C. The flange portion 54 is a portion that protrudes radially outward from the upper end of the outer periphery 52.

Through the above steps, a molded product 60 shown in Figures 3A and 3B is obtained.

<Forged products>
The molded product 60 is formed to include an outer periphery 62 , a flange portion 64 , a central portion 66 , a recessed portion 68 , and a protruding portion 69 .

The outer peripheral portion 62 corresponds to the outer peripheral portion 52 in the molded billet 50, and is formed in a cylindrical shape. In the example shown in Figures 3A and 3B, the outer peripheral surface and inner peripheral surface of the outer peripheral portion 62 are formed to be inclined with respect to the cylindrical axis direction, but the embodiment of the present invention is not limited to this. Depending on the shape of the mold used and the specifications of the spindle motor, either or both of these outer peripheral surfaces and inner peripheral surfaces may be shaped to be non-inclined (along the cylindrical axis direction).

The flange portion 64 corresponds to the flange portion 54 in the molded billet 50, and is formed at the upper end of the outer periphery 62 and extends radially outward from the outer periphery 62.

The central portion 66 corresponds to the inner portion of the outer periphery 52 in the formed billet 50, i.e., the inner portion of the outer periphery 62.

The recess 68 corresponds to the recess 58 in the molded billet 50, and is formed on the bottom surface of the central portion 66. Note that the recesses 68A and 68B in the recess 68 correspond to the recesses 58A and 58B in the recess 58, respectively.

The protrusion 69 corresponds to the protrusion 59 in the formed billet 50, and is formed above the recess 68 in the central portion 66. This protrusion 69 has a free forming surface 69A.

The "free forming surface" is a surface that is formed during the forging process without contacting the die 20. In this embodiment, it corresponds to the top surface of the protrusion 59 that is formed by recessing into the through hole 48 in the billet 50.

The free forming surface 69A has a rougher surface and is molded in a matte finish compared to the portion formed in contact with the mold 20. On the other hand, the portion formed in contact with the mold 20 has a higher smoothness compared to the free forming surface 69A. Also, the portion formed in contact with the mold 20 has a higher surface hardness compared to the free forming surface 69A.

This is because forging dies are generally made from hardened steel or cemented carbide by machining or electric discharge machining. Through these processes, the surface of the die is ground or lapped with free abrasive grains, resulting in a high degree of smoothness. The smoothness of the surface of this die 20 is transferred to the parts of the molded product 60 other than the free forming surface 69A.

Between the free forming surface 69A and the side surface 69B of the protrusion 69 in the molded product 60, a curved surface 69C that does not come into contact with the mold 20 is formed. The curved surface 69C has a radius of 0.01 mm or more.

Because the free-forming surface 69A is not pressed by the mold 20, the shape is not stable during molding. For this reason, the free-forming surface 69A may be formed flat as shown in FIG. 3B, or curved as shown in FIGS. 4A and 4B.

As one example, the free-forming surface 69A shown in FIG. 4A is shaped to follow the spherical surface R1 that protrudes upward from the convex portion 59. As another example, the free-forming surface 69A shown in FIG. 4B is shaped to follow the spherical surface R2 that recesses downward from the convex portion 59. The diameters of the spherical surfaces R1 and R2 are not particularly limited, but are formed to be at least larger than the radius r1 of the upper end of the side surface 69B of the convex portion 69.

<Cutting>
5A and 5B is obtained by cutting the molded product 60. The outer periphery 12, flange portions 14, central portion 16, and protruding portions 19 of the rotor hub 10 are formed by cutting the outer periphery 62, flange portions 64, central portion 66, and protruding portions 69 of the molded product 60. The through holes 18 of the rotor hub 10 are formed by cutting the recesses 68A of the molded product 60 to form through holes that penetrate to the free forming surface 69A.

<Action and Effects>

As shown in Figures 1A and 1B, in the mold 20 according to the embodiment of the present invention, a protrusion 36A is formed on the bottom surface 36 of the cavity 30C, protruding along the movement direction V of the second die 40 toward the second die 40, which is the core. Therefore, as shown in Figure 2B, when a billet 50 as the workpiece is sandwiched and pressed between the cavity 30C and the second die 40, the billet 50 receives localized pressure from the protrusion 36A. This causes the billet 50 to deform toward the second die 40.

On the other hand, a through hole 48 is provided as an opening in the moving direction V of the second die 40 in the portion of the second die 40 facing the protrusion 36A of the cavity 30C. This through hole 48 is a portion that forms a gap between the billet 50 when the first die 30 and the second die 40 are clamped together. In other words, at least a portion of the portion of the billet 50 that is deformed by being pressed by the protrusion 36A of the cavity 30C (i.e., the free forming surface 69A of the molded product 60) does not come into contact with the second die 40.

This reduces the pressing force acting on the second die from the protrusion 36A via the billet 50. Also, the pressing force acting on the first die 30 from the second die 40 via the billet 50 is reduced. This improves the durability of the die 20 and extends its lifespan.

In addition, in the die 20 according to the embodiment of the present invention, as shown in FIG. 2C, the billet 50 is pressed by the step surface 34 and the pressing surface 44 in a direction intersecting (substantially perpendicular to) the moving direction V of the second die 40. As a result, the outer periphery 52 of the billet 50 is upset forged. This makes it possible to make the metal structure in the outer periphery 52 of the billet 50 denser and increase its strength.

Here, a flange portion 54 is formed on the outer periphery 52 of the billet 50 by pressing it against the step surface 34 and the pressing surface 44. This flange portion 54 corresponds to the flange portion 14 in the rotor hub 10, which is the final molded product. As mentioned above, the disk D is placed on this flange portion 14, so high-precision machining is required.

On the other hand, the central portion of the billet 50 is provided with a portion that does not come into contact with the second die 40, and is allowed to deform freely. This allows the flange portion 54 (i.e., the flange portion 64 of the molded product and the flange portion 14 of the rotor hub 10) to be machined with high precision, while allowing the free forming surface 69A of the molded product 60 to absorb any variation in the volume of the billet 50.

In addition, a flange portion 54 that protrudes in a direction intersecting the moving direction V of the second die 40 can be formed on the outer periphery 52 of the billet 50. This results in a higher material yield than when the flange portion 54 is formed by machining alone.

The flange portion 54 is formed by the billet 50 being pressed by the step surface 34 and the pressing surface 44, and being deformed in a direction intersecting (approximately perpendicular to) the moving direction V of the second die 40. That is, the outer peripheral portion 52 of the billet 50 is deformed in a direction intersecting the moving direction V, thereby reducing the internal stress that occurs. Therefore, the pressing force applied to the die 20 is unlikely to become large.

In contrast, the central portion, which is the inner portion of the outer periphery 52, is less likely to deform in a direction intersecting the moving direction V. For this reason, if the through hole 48 were not formed in the second die 40, a large internal stress would be generated in the portion above the recess 58 in the center of the billet 50. In this case, a large pressing force may be applied to the die 20.

<Other embodiments>
In this embodiment, the first mold 30 is a fixed type and the second mold 40 is a movable type, but the embodiment of the present invention is not limited to this. For example, the first mold 30 may be a movable type and the second mold 40 may be a fixed type. In this case, the above-mentioned "movement direction V of the second mold 40" and "movement direction V" should be read as the movement direction V of the first mold 30.

In addition, in this embodiment, the through hole 48 is formed in the top surface 46 of the second die 40, but the embodiment of the present invention is not limited to this. As long as an opening is formed in the top surface 46, a bottomed hole can be formed instead of the through hole 48. In this case, the "gap formed between the workpiece and the core" in this invention refers to the space sandwiched between the convex portion 59 and the bottom of the hole formed in the second die 40.

In addition, the second mold 40 has a portion with a top surface 46 and a portion with a pressing surface 44 formed integrally, but the embodiment of the present invention is not limited to this. For example, the second mold 40 may be formed by dividing the portion with the top surface 46 and the portion with the pressing surface 44, as shown by the two-dot chain line S1 in FIG. 1B, and each portion may be moved independently.

In other words, the forging process is not limited to a single step, but each part of the molded product 60 may be forged in multiple steps. For example, the outer periphery 62 and the flange portion 64 of the molded product 60 may be forged separately.

Although the second mold 40 shown in FIG. 1B is entirely a core, the embodiment of the present invention is not limited to this. For example, the second mold in the present invention may include a holding mechanism for holding the illustrated second mold 40.

In addition, in this embodiment, the second side 32B is formed on the side mold 30B of the first mold 30, but the embodiment of the present invention is not limited to this. For example, as shown by the two-dot chain line S2 in FIG. 1B, the step surface 34 may be formed as the upper surface of the side mold 30B. In this case, the second side surface 32B is not formed. Therefore, the billet 50 pressed by the step surface 34 and the pressing surface 44 is freely deformed in a direction intersecting (approximately perpendicular to) the moving direction V of the second mold 40. The flange portion 54 formed in this way does not press the side mold 30B. This makes it possible to reduce the pressing force acting from the flange portion 54 to the second mold 40.

20 Forging die 30 First die 30C Cavity 34 Step surface 36 Bottom surface 36A Protrusion 40 Second die (core)
44 Pressing surface 48 Through hole (opening)
50 Billet (workpiece)
62 Outer periphery 64 Flange portion 66 Central portion 68A Concave portion 69 Convex portion 69A Free forming surface V Movement direction

Claims (5)

An outer periphery formed in a cylindrical shape;
a flange portion formed at an upper end of the outer circumferential portion and extending radially outward from the outer circumferential portion;
A central portion formed inside the outer periphery;
a recess formed on a bottom surface of the central portion by a forging die;
a protrusion formed above the recess in the central portion and having a diameter larger than that of the recess;
having
The protrusion has a free forming surface formed without contact with the forging die. The smoothness of the radially outer end surface of the flange portion is higher than that of the free forming surface and is equal to that of the portion other than the free forming surface.
The forged product according to claim 1. A free forming surface is formed on the radially outer end surface of the flange portion.
The forged product according to claim 1. A curved surface is formed between the side surface of the protrusion and the free forming surface.
The forged product according to claim 1. A through hole is formed from the recess through the free forming surface.
The forged product according to claim 1 or 2.