Die for forging, forging method, and forged product

Abstract

The forging die of the present invention has: a first die having a cavity; a second die having a core capable of sandwiching and pressing a work material between the cavity by moving toward the first die in opposition; a protrusion formed on the bottom surface of the cavity, protruding toward the core and in the moving direction of the first die or the second die; and an opening portion provided in the portion of the core facing the protrusion in the moving direction, forming a gap between the work material and the core in the state where the first die and the second die are closed.

Description

Technical Field

[0001] This disclosure relates to forging dies, forging methods, and forged products. Background Technology

[0002] Japanese Patent Application Publication No. 2019-147172 discloses a forging die for a rotor hub. An opening is formed in the portion of the rotor hub flange that is formed in this forging die. During forging, a portion of the workpiece can escape outward through this opening. This reduces the load applied from the forging die to the flange portion that becomes the workpiece, and suppresses residual strain in that portion.

[0003] According to the forging die for the rotor hub disclosed in Japanese Patent Application Publication No. 2019-147172, residual strain can be suppressed in the flange portion of the rotor hub. By suppressing the residual strain in the flange portion, the smoothness of the disc mounting surface, which requires particularly high machining accuracy, can be improved.

[0004] Thus, in forged products, it is preferable to suppress residual strain in appropriate areas according to their intended use. On the other hand, during forging, the forging die is also subjected to load due to the reaction force from the workpiece. Therefore, in addition to suppressing residual strain in the formed product, it is also necessary to improve the durability of the die. Summary of the Invention

[0005] This disclosure takes into account the above facts to improve the durability of forging dies.

[0006] The forging die of the first embodiment includes: a first die having a cavity; a second die having a core capable of clamping and pressing a work-bearing material between itself and the cavity by moving relative to the first die; a protrusion formed on the bottom surface of the cavity, protruding toward the core and along the moving direction of the first die or the second die; and an opening in the core, the portion of which faces the protrusion and is provided toward the moving direction, forming a gap between the work-bearing material and the core when the first die and the second die are closed.

[0007] In the first type of forging die, a protrusion is formed on the bottom surface of the cavity, projecting toward the core in the direction of movement of the first or second die. Therefore, when the workpiece is clamped between the cavity and the core and pressed, the workpiece is subjected to localized pressure from the protrusion. Consequently, the workpiece deforms toward the core.

[0008] On the other hand, an opening is provided in the portion of the core facing the protrusion of the cavity, in the direction of movement of the first or second die. This opening forms a gap between itself and the work-processed material when the first and second dies are closed. That is, at least a portion of the part of the work-processed material from which the protrusion of the cavity is deformed by being pushed does not contact the core. This reduces the pushing force exerted on the core by the protrusion through the work-processed material. In addition, it reduces the pushing force exerted on the cavity by the core through the work-processed material. Therefore, the durability of the forging die can be improved.

[0009] In the forging die of the second type, in the forging die of the first type, a stepped surface is provided on the side of the cavity along a direction intersecting the moving direction, and a pressing surface is formed on the core to press the workpiece between the core and the stepped surface.

[0010] In the forging die of the second type, the workpiece is pressed by a stepped surface and a pressing surface that intersect the moving direction of the first or second die. Therefore, the outer periphery of the workpiece is upset. This allows the metal structure of the outer periphery of the workpiece to become denser, increasing its strength.

[0011] Furthermore, a flange extending in a direction intersecting the moving direction of the first or second die can be formed on the outer periphery of the material being processed. Therefore, the material yield is higher compared to forming the flange solely through cutting.

[0012] The third forging method utilizes a first mold having a cavity and a second mold having a core with a workpiece sandwiched between the cavity and capable of being pushed, wherein the method includes: a step of placing the workpiece into the cavity, the cavity having a protrusion formed on its bottom surface facing the core and protruding along the movement direction of the first mold or the second mold; and a step of closing the first mold and the second mold to form the workpiece, and forming a free-forming surface through the gap formed between the workpiece and the core, wherein the portion of the second mold in the core opposite to the protrusion has an opening facing the movement direction.

[0013] In a forging die used in a third-party forging method, a protrusion is formed on the bottom surface of the cavity, pointing towards the core. Therefore, when the workpiece is clamped between the cavity and the core and pressed, the workpiece is subjected to localized pressure from the protrusion. This causes the workpiece to deform towards the core.

[0014] Furthermore, a free-forming surface is formed on the work-bearing material above the protrusion of the first die. That is, at least a portion of the part deformed by the protrusion from the cavity does not contact the core. This reduces the pushing force exerted by the protrusion on the core through the work-bearing material. Additionally, it reduces the pushing force exerted by the core on the cavity through the work-bearing material. Therefore, the durability of the forging die can be improved.

[0015] The forged article of the fourth type has: an outer periphery that is cylindrical; a flange that is formed at the upper end of the outer periphery and extends radially outward from the outer periphery; a central portion that is formed on the inner side of the outer periphery; a recess that is formed on the bottom surface of the central portion; and a convex portion that is formed on the central portion above the recess, the convex portion having a free-formable surface.

[0016] The forged product of the fourth method has a concave portion formed on the bottom surface of the central part. That is, the bottom surface of the central part is deformed by being pushed by a forging die.

[0017] On the other hand, a protrusion is formed above the concave portion in the center, serving as a free-forming surface. That is, the portion opposite to the bottom surface that is pressed by the forging die is not pressed by the forging die. In other words, this portion is formed freely by deformation without being pressed from the forging die. Therefore, during forging, the pushing force acting on the forging die from the formed product is reduced. Consequently, the durability of the forging die can be improved.

[0018] According to this disclosure, the durability of forging dies can be improved. Attached Figure Description

[0019] The embodiments disclosed herein are described in detail with reference to the following drawings.

[0020] Figure 1A This is a front view of the forging die according to the embodiments of this disclosure.

[0021] Figure 1B yes Figure 1A BB line cross-section diagram.

[0022] Figure 2A This is a front cross-sectional view showing the state in which the cavity of the forging die according to the embodiments of this disclosure is configured with a blank.

[0023] Figure 2B This is a front cross-sectional view showing the state of the billet deformed by the closing of the forging die according to the embodiments of this disclosure.

[0024] Figure 2C This is a front cross-sectional view showing the state of the billet deformed by further closing the forging die according to the embodiments of this disclosure.

[0025] Figure 3A This is a front view showing the forged article according to the embodiments of this disclosure.

[0026] Figure 3B yes Figure 3A BB line cross-section diagram.

[0027] Figure 4A This is a cross-sectional view showing an example of the shape of the free-forming surface of a forged article according to an embodiment of the present disclosure.

[0028] Figure 4B This is a cross-sectional view showing another example of the shape of the free-forming surface of the forged article according to the embodiments of this disclosure.

[0029] Figure 5A This is a front view showing a rotor hub formed by cutting a forged product according to an embodiment of the present disclosure.

[0030] Figure 5B yes Figure 5A BB line cross-section diagram. Detailed Implementation

[0031] Hereinafter, the forging die, forging method, and forged product according to the embodiments of this disclosure will be described with reference to the accompanying drawings. Structural elements indicated by the same reference numerals in the various drawings refer to the same structural element. However, unless otherwise specified in the description, there may be multiple structural elements, not just one. Furthermore, descriptions of structures and symbols repeated in the various drawings may be omitted. Moreover, this disclosure is not limited to the following embodiments; it may be implemented by adding appropriate modifications, such as omitting structures or replacing them with different structures, within the scope of the purpose of this disclosure.

[0032] First, a general overview of the "forging die", "forging method" and "forged product" involved in the embodiments of this disclosure will be provided.

[0033] exist Figure 1A , Figure 1B In the text, "20" refers to the "forging die 20" (hereinafter referred to as "die 20") as described in the embodiments of this disclosure. Using this die 20, through... Figures 2A to 2C The "forging method" shown describes forging the blank 50, which is the material to be processed. This results in the formation of... Figure 3A , Figure 3B The image shows a "forged product 60 (hereinafter referred to as shaped product 60)". Shaped product 60 is... Figure 5A The intermediate material shown is for the rotor hub 10, which is the final molded product. The rotor hub 10 is formed by machining the molded product 60.

[0034] <rotor hub>

[0035] Before describing the mold 20, forging method, and molded article 60 related to the embodiments of this disclosure, the structure of the rotor hub 10 will be described. Figure 5A , Figure 5B The rotor hub 10 shown is a cylindrical rotor constituting an external rotor type spindle motor (not shown). The rotor hub 10 is formed, for example, from a metal material such as stainless steel.

[0036] Furthermore, in the following description, the direction along the rotation axis O of the rotor hub 10 will be referred to as the "axial direction". In addition, the direction orthogonal to the rotation axis O will be referred to as the "radial direction", and the direction of rotation about the rotation axis O will be referred to as the "circumferential direction".

[0037] The rotor hub 10 includes: an outer peripheral portion 12, which is cylindrical; a flange portion 14, which is formed at the upper end of the outer peripheral portion 12 and extends radially outward from the outer peripheral portion 12; and a central portion 16, which is formed on the inner side of the outer peripheral portion 12.

[0038] In addition, "upper end" indicates Figure 5B The end facing upwards on the paper. This "direction facing upwards on the paper" may not necessarily be consistent with the vertical direction of the rotor hub 10 in its operational state. For the "lower end" described later... Figure 5B The same applies to the end of the paper (the part facing downwards).

[0039] The flange portion 14 extends radially outward around the upper end of the outer peripheral portion 12, forming a ring shape. The central portion 16 is formed radially inward between the upper and lower ends of the outer peripheral portion 12. A protrusion 19 protruding towards the flange portion 14 is formed in the central portion 16. Furthermore, a through hole 18 is formed in the central portion 16. The through hole 18 is a circular hole centered on the rotation axis O, extending from the bottom surface of the central portion 16 to the top surface of the protrusion 19.

[0040] Furthermore, the rotor hub 10 is used, for example, in an information recording and playback device. The rotor hub 10 is used with its outer periphery 12 fitted into the central hole Dh in the disc-shaped disk (magnetic recording medium) D. At this time, the edge portion (mounting surface 14A) of the hole Dh in the disk D is mounted on the flange portion 14. When the information recording and playback device is driven, the rotor hub 10, in a state of free rotation along the circumference, is driven circumferentially by a spindle motor (not shown).

[0041] <Forging Dies>

[0042] like Figure 1A , Figure 1B As shown, the mold 20 is composed of a first mold 30 and a second mold 40.

[0043] (First mock exam)

[0044] The first die 30 is a fixed die used in a fixed state during forging. A blank 50 (see reference) is formed on the first die 30. Figure 2A The recessed portion of the cavity is called cavity 30C. In addition, the first mold 30 is formed by having a bottom mold 30A that forms the bottom surface 36 of the cavity 30C and a side mold 30B that forms the side surface 32 of the cavity 30C.

[0045] The bottom surface 36 of cavity 30C is formed in a circle centered on axis O along the moving direction (hereinafter referred to as moving direction V) of the second mold 40. Correspondingly, the top surface of bottom mold 30A is formed in a circle centered on axis O, and bottom mold 30A is formed in a cylindrical shape with axis O as the central axis.

[0046] Additionally, on the bottom surface 36 of cavity 30C, protrusions 36A and 36B are formed, protruding toward the second mold 40 and along the movement direction V. Protrusion 36A is a frustum-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 greater than the height of protrusion 36B. In other words, protrusion 36A is the tallest of the multiple protrusions formed on the bottom surface 36.

[0047] The cavity 30C has a first side surface 32A and a second side surface 32B on its side surface 32. The first side surface 32A is the side surface of the cavity 30C near the bottom surface 36, and its shape, when viewed along the movement direction V, is approximately the same as that of the bottom surface 36. The second side surface 32B, when viewed from the first side surface 32A, is formed on the side of the second mold 40. Furthermore, the shape of the second side surface 32B, when viewed along the movement direction V, is a circle along the first side surface 32A with a diameter larger than that of the first side surface 32A.

[0048] Furthermore, for cavity 30C, a stepped surface 34 is formed between the first side surface 32A and the second side surface 32B. The stepped surface 34 is a flat surface formed along a plane that is approximately orthogonal to the direction of movement V.

[0049] (Second Mock Exam)

[0050] The second die 40 is a movable die used during forging (when the die is closed) to move in a direction (movement direction V) relative to the first die 30. Furthermore, the second die 40 is positioned above the first die 30, therefore the second die 40 and the first die 30 are sometimes referred to as the upper die and lower die, respectively. Additionally, the second die 40 is inserted into the cavity 30C of the first die 30, therefore the second die 40 is sometimes also referred to as the "core die" or "core".

[0051] The second mold 40 is formed by having a side surface 42, a pressing surface 44, a top surface 46, and a through hole 48.

[0052] Side 42 has a first side 42A and a second side 42B. The first side 42A, viewed from the direction of movement V, is a circle concentric with the first side 32A in the first mold 30, but with a diameter smaller than that of the first side 32A. The first side 42A is formed on the bottom surface 36 side of the cavity 30C, which is closer to the second side 42B than the second side 42B. The second side 42B, viewed from the direction of movement V, has a shape that is substantially the same as that of the second side 32B in the first mold 30.

[0053] Thus, the second module 40 operates in a state where the first side surface 42A is separated from the first side surface 32A of the cavity 30C, and the second side surface 42B is close to the second side surface 32B of the cavity 30C.

[0054] 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 orthogonal to the moving direction V. The pressing surface 44 is arranged opposite to the stepped surface 34 of the cavity 30C.

[0055] The top surface 46 is the surface that intersects with the first side surface 42A and is positioned opposite to the bottom surface 36 of the cavity 30C.

[0056] The through hole 48 is a circular hole with an opening formed on the top surface 46, and is positioned along the moving direction V with the shaft O as the central axis. That is, the through hole 48 is located opposite the protrusion 36A. In addition, when viewed from the direction of movement, the inner diameter of the through hole 48 is larger than the outer diameter of the protrusion 36A.

[0057] <Forging Methods>

[0058] Using the aforementioned mold 20, forging is performed as follows: Figure 3A , Figure 3B The molded article 60 shown. The molded article 60 can also be formed by hot rolling forging, but in this specification, the case of forming by cold rolling forging will be described.

[0059] When the forged product reaches 60, firstly as follows: Figure 2A As shown, a blank 50, which is the material to be processed, is disposed in cavity 30C. The blank 50 is formed of a metal material such as stainless steel. The blank 50 is cylindrical in shape, and its outer peripheral surface 50A is disposed in contact with the first side surface 32A in cavity 30C. Furthermore, "in contact" means that a gap is formed between the outer peripheral surface 50A and the first side surface 32A to a degree that allows the blank 50 to be loaded and unloaded.

[0060] With the blank 50 positioned in cavity 30C, the bottom surface 50B of the blank 50 is in contact with the top surface of the protrusion 36A formed on the bottom surface 36 of cavity 30C. In this state, by moving the second mold 40 closer to the first mold 30, the top surface 46 of the second mold 40 first contacts the top surface 50C of the blank 50. Thus, the blank 50 is clamped in by the second mold 40 and the first mold 30.

[0061] Next, as Figure 2B As shown, the blank 50 is pressed (closed) by the second mold 40 and the first mold 30. As a result, the bottom surface 50B of the blank 50 is deformed by being pressed from the protrusions 36A and 36B of the first mold 30. Consequently, a recess 58 is formed on the bottom surface 50B of the blank 50. Furthermore, the parts formed by pressing from the protrusions 36A and 36B into the recess 58 are respectively referred to as recesses 58A and 58B.

[0062] On the other hand, the top surface 50C of the blank 50 is also deformed by being pushed from the top surface 46 of the second mold 40. As a result, an outer peripheral portion 52 is formed in the blank 50, which is sandwiched between the first side surface 32A of the first mold 30 and the first side surface 42A of the second mold 40.

[0063] Furthermore, the top surface 50C of the blank 50 is pressed from the top surface 46, which has a through hole 48, in the second mold 40, thereby forming a protrusion 59 that is recessed into the through hole 48 in the blank 50. The protrusion 59 is formed above the recess 58A. In addition, the side surface of the protrusion 59 is in contact with the inner peripheral surface of the through hole 48, while the top surface (the portion of the top surface 50C of the blank 50 disposed inside the through hole 48) is not in contact with the second mold 40. In other words, the top surface of the protrusion 59 becomes a free-forming surface (the free-forming surface will be described later).

[0064] Furthermore, the "gap formed between the processed material and the core" in this disclosure refers to the gap formed between the protrusion 59 of the blank 50, which is the processed material, and the second mold 40, which is the core. Specifically, it refers to the space surrounded by the protrusion 59 and the portion of the inner wall of the through hole 48 formed in the second mold 40 that does not contact the protrusion 59.

[0065] When the blank 50 is continuously pressed by the second mold 40 and the first mold 30, the upper end of the outer peripheral portion 52 comes into contact with the pressing surface 44 of the second mold 40 and is pressed from the pressing surface 44. As a result, the upper end of the outer peripheral portion 52 deforms radially outward from the outer peripheral portion 52.

[0066] The deformed part is pressed by the pressing surface 44 and the stepped surface 34 of the first mold 30, thus... Figure 2C As shown, a flange portion 54 is formed. The flange portion 54 is the portion that extends radially outward from the upper end of the outer peripheral portion 52.

[0067] Through the above steps, we can obtain the following: Figure 3A , Figure 3B The molded part 60 shown.

[0068] <Forged Products>

[0069] The molded article 60 is formed having an outer peripheral portion 62, a flange portion 64, a central portion 66, a recessed portion 68, and a protruding portion 69.

[0070] The outer peripheral portion 62 is the portion of the formed blank 50 corresponding to the outer peripheral portion 52, forming a cylindrical shape. Furthermore, in Figure 3A , Figure 3B In the example shown, the outer and inner circumferential surfaces of the outer peripheral portion 62 are formed inclined relative to the cylinder axis, but the embodiments of this disclosure are not limited thereto. Depending on the shape of the mold used, and in conjunction with the specifications of the spindle motor, one or both of their outer and inner circumferential surfaces may also be non-inclined (along the cylinder axis).

[0071] The flange portion 64 is a portion of the formed blank 50 corresponding to the flange portion 54, formed at the upper end of the outer peripheral portion 62, and extending radially outward from the outer peripheral portion 62.

[0072] The central portion 66 is the portion of the formed blank 50 that corresponds to the inner portion of the outer peripheral portion 52, i.e., the inner portion of the outer peripheral portion 62.

[0073] Recess 68 is a portion of the formed blank 50 corresponding to recess 58, and is formed on the bottom surface of the central portion 66. Furthermore, recesses 68A and 68B in recess 68 correspond to recesses 58A and 58B in recess 58, respectively.

[0074] The protrusion 69 is a portion of the formed blank 50 corresponding to the protrusion 59, and is formed in the central portion 66 above the recess 68. The protrusion 69 has a free-formable surface 69A.

[0075] "Free-formed surface" refers to a surface that does not come into contact with the mold 20 during the forging process. In this embodiment, it corresponds to the top surface of the protrusion 59 formed in the blank 50 by being embedded inside the through hole 48.

[0076] Compared to the portion formed by contacting the mold 20, the free-formed surface 69A has a rougher, pear-skin-like surface. On the other hand, the portion formed by contacting the mold 20 has a higher smoothness compared to the free-formed surface 69A. Furthermore, the portion formed by contacting the mold 20 has a higher surface hardness compared to the free-formed surface 69A.

[0077] Here, forging dies are generally made from quenched steel or superhard alloys through machining or electrical discharge machining. Through these processes, the die surface becomes a ground and polished surface or a ground and polished surface composed of free abrasive particles, resulting in a high degree of smoothness. The surface smoothness of the die 20 is transferred to the portion of the molded article 60 other than the free forming surface 69A.

[0078] Between the free forming surface 69A of the protrusion 69 in the molded article 60 and the side surface 69B, a curved surface 69C is formed that does not contact the mold 20. The curved surface 69C has a radius of 0.01 mm or more.

[0079] Since the free-formed surface 69A is not pressed by the mold 20, its shape is not stable during molding. Therefore, the free-formed surface 69A exhibits the following characteristics: Figure 3B The situation where it forms flat as shown, or as... Figure 4A , Figure 4B As shown, it is formed in a curved shape.

[0080] As an example Figure 4A The freeform surface 69A shown is shaped along a spherical surface R1 protruding upwards from the protrusion 59. Additionally, as another example, Figure 4B The freeform surface 69A shown is shaped along a spherical surface R2 that is recessed downward from the protrusion 59. The diameters of the spherical surfaces R1 and R2 are not particularly limited, but they are formed to be at least larger than the radius r1 of the upper end of the side surface 69B of the protrusion 69.

[0081] <Cutting>

[0082] By cutting the molded part 60, the following is obtained: Figure 5A , Figure 5B The rotor hub 10 is shown. The outer peripheral portion 12, flange portion 14, central portion 16, and protrusion 19 of the rotor hub 10 are formed by cutting the outer peripheral portion 62, flange portion 64, central portion 66, and protrusion 69 of the molded article 60. In addition, the through hole 18 in the rotor hub 10 is formed by cutting the recess 68A in the molded article 60 to form a through hole that extends to the free forming surface 69A.

[0083] <Functions and Effects>

[0084] like Figure 1A , Figure 1B As shown, in the embodiments of this disclosure, the mold 20 has a protrusion 36A formed on the bottom surface 36 of the cavity 30C, facing the second mold 40 which serves as the core, and protruding along the moving direction V of the second mold 40. Therefore, as... Figure 2BAs shown, when the blank 50, which is the material to be processed, is clamped by the cavity 30C and the second mold 40 and pushed, the blank 50 is subjected to local pressure from the protrusion 36A. As a result, the blank 50 deforms toward the second mold 40.

[0085] On the other hand, in the second mold 40, a through hole 48, serving as an opening, is provided in the portion facing the protrusion 36A of the cavity 30C in the moving direction V of the second mold 40. This through hole 48 forms a gap between the first mold 30 and the blank 50 when the first mold 30 and the second mold 40 are closed. That is, at least a portion of the portion of the blank 50 that is deformed by being pushed from the protrusion 36A of the cavity 30C (i.e., the free forming surface 69A in the molded article 60) does not contact the second mold 40.

[0086] This reduces the pushing force exerted on the second mold from the protrusion 36A via the blank 50. Furthermore, it reduces the pushing force exerted on the first mold 30 from the second mold 40 via the blank 50. Therefore, the durability of the mold 20 can be improved, and its lifespan extended.

[0087] Furthermore, in the mold 20 involved in the embodiments of this disclosure, such as Figure 2C As shown, the blank 50 is pressed using a stepped surface 34 that intersects (approximately orthogonal to) the moving direction V of the second die 40 and a pressing surface 44. This results in the upsetting of the outer periphery 52 of the blank 50. Consequently, the metal structure of the outer periphery 52 of the blank 50 becomes denser, increasing its strength.

[0088] Here, a flange portion 54 is formed on the outer periphery 52 of the blank 50 by being pressed by the stepped surface 34 and the pressing surface 44. This flange portion 54 is the part of the rotor hub 10 that corresponds to the flange portion 14 in the final product. As described above, the disk D is placed on this flange portion 14, which requires high-precision machining.

[0089] On the other hand, the central portion of the blank 50 has a part that does not contact the second mold 40, allowing for free deformation. As a result, the flange portion 54 (i.e., the flange portion 64 of the molded article and the flange portion 14 of the rotor hub 10) can be machined with high precision, and the volume unevenness of the blank 50 can be absorbed by the free forming surface 69A of the molded article 60.

[0090] Furthermore, a flange portion 54 extending in a direction intersecting the moving direction V of the second mold 40 can be formed on the outer periphery 52 of the blank 50. Therefore, compared with the case where the flange portion 54 is formed only by cutting, the material yield is high.

[0091] Furthermore, the flange portion 54 is formed by deforming the blank 50, which is pressed by the stepped surface 34 and the pressing surface 44, in a direction intersecting (approximately orthogonal) the moving direction V of the second mold 40. That is, the outer periphery 52 of the blank 50 reduces the generated internal stress by deforming relative to the direction intersecting the moving direction V. Therefore, the pushing force applied to the mold 20 is difficult to increase.

[0092] In contrast, the central portion of the inner part of the outer periphery 52 is difficult to deform relative to the direction intersecting the movement direction V. Therefore, if the through hole 48 is not formed in the second mold 40, a large internal stress will be generated in the portion above the recess 58 in the center of the blank 50. In this case, there is a possibility that a large pushing force will be exerted on the mold 20.

[0093] <Other Implementation Methods>

[0094] In this embodiment, the first mold 30 is used as a fixed mold and the second mold 40 is used as a movable mold; however, the embodiments disclosed herein are not limited to this. For example, the first mold 30 may also be used as a movable mold and the second mold 40 as a fixed mold. In this case, the "moving direction V of the second mold 40" and "moving direction V" mentioned above may be replaced with the moving direction V of the first mold 30.

[0095] Furthermore, in this embodiment, a through hole 48 is formed on the top surface 46 of the second mold 40, but the embodiments of this disclosure are not limited to this. As long as an opening is formed on the top surface 46, a bottomed hole can also be formed instead of the through hole 48. In this case, the "gap formed between the processed material and the core" in this disclosure refers to the space held by the protrusion 59 and the bottom of the hole formed in the second mold 40.

[0096] Furthermore, for the second mold 40, the portion having the top surface 46 and the portion having the pressing surface 44 are integrally formed, but the embodiments of this disclosure are not limited thereto. For example, the second mold 40 may also be as follows: Figure 1B As shown by the double-dotted line S1, the part having the top surface 46 and the part having the pressing surface 44 are divided into two parts, and each part operates independently.

[0097] That is, the forging process is not limited to one time, and can be divided into multiple forging processes for different parts of the formed article 60. For example, the outer peripheral portion 62 and the flange portion 64 of the formed article 60 can be forged separately.

[0098] in addition, Figure 1B The second mold 40 shown in the figure is a core as a whole, but the embodiments of this disclosure are not limited to this. For example, the second mold in this disclosure may also have a holding mechanism for holding the second mold 40 shown in the figure.

[0099] Furthermore, in this embodiment, a second side surface 32B is formed in the side surface mold 30B of the first mold 30, but the embodiments of this disclosure are not limited to this. For example, it may also be as follows: Figure 1B As shown by the double-dotted line S2, the stepped surface 34 is formed as the upper surface of the side mold 30B. In this case, the second side surface 32B is not formed. Therefore, the blank 50, which is pressed by the stepped surface 34 and the pressing surface 44, deforms freely in a direction intersecting (approximately orthogonal) with the moving direction V of the second mold 40. The flange portion 54 formed thereby does not press against the side mold 30B. As a result, the pushing force exerted on the second mold 40 from the flange portion 54 can be reduced.

Claims

1. A die for forging, wherein, Having: a first mold provided with a cavity; a second mold provided with a core that sandwiches a work material between the cavity and is capable of pushing the work material by moving relatively toward the first mold; a protrusion formed on a bottom surface of the cavity, protruding toward the core and in a moving direction of the first mold or the second mold; and an opening portion provided in a portion of the core that faces the protrusion in the moving direction, forming a gap between the work material and the core in a state in which the first mold and the second mold are closed, a step surface is formed on a side surface of the cavity in a direction intersecting the moving direction, a pushing surface is formed on the core for pushing the work material between the step surface and the core, wherein the side surface of the cavity has a contact portion that is located outside the step surface and contacts a side surface of the core. Having:

2. A forging method using a first die having a cavity and a second die having a core sandwiching a workpiece between the cavity and the core and capable of being pushed. a step of arranging the work material toward the cavity, the cavity being formed with a protrusion on a bottom surface, the protrusion protruding toward the core and in a moving direction of the first mold or the second mold; a step of closing the first mold and the second mold to shape the work material, and forming a free-form surface through a gap formed between the work material and the core, the second mold having an opening portion provided in a portion of the core that faces the protrusion in the moving direction; a step of forming a step surface on a side surface of the cavity in a direction intersecting the moving direction, a pushing surface is formed on the core for pushing the work material between the step surface and the core, wherein the side surface of the cavity has a contact portion that is located outside the step surface and contacts a side surface of the core. Having: an outer peripheral portion formed in a cylindrical shape; 3. A forged shaped article, wherein, a flange portion formed on an upper end portion of the outer peripheral portion, extending to a radially outer side of the outer peripheral portion; a central portion formed on an inner side of the outer peripheral portion; a recess portion formed on a bottom surface of the central portion; and a protrusion portion formed on the central portion above the recess portion, the protrusion portion is provided with a free-form surface, the flange portion is not provided with a free-form surface. ​ ​

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