JP2017077569A - Forging method and forged object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to efficiently forge a forged object with a small load by use of plural partial molds and to smoothly execute forging work.SOLUTION: An upper die 11 is plural partial molds 12 which are so located in a circumferential direction as to surround a central axis 1L of a forged object 1, and the forged object 1, in which an annular groove part 2 with the central axis 1L as a center is formed on a region between the central axis 1L and an outer periphery 4, is located between the upper die 11 and a lower die 21 in such a manner that the groove part 2 is so made as to face the partial mold 12. At least one of the upper die 11 and the lower die 21 is rotated around the central axis 1L, a part of the partial mold 12 is brought into contact with a partial region 2a of the groove part 2, and while remaining a region 2b with which the partial mold 12 is not brought into contact in the groove part 2, the partial mold 12 is moved to the forged object 1 side without being brought into contact with a region surrounded by the groove part 2 of the forged object 1 thereby pressurizing the forged object 1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a forging method and a forged product, and more particularly, to a rotary forging method for rotationally forging using a partial die and a forged product used in the forging method.

  A so-called rotary forging method is known in which a forged object is intermittently pressurized with an upper die and a lower die while forging the disc-like forged object relative to the upper die or the lower die. Yes. In such a forging method by rotary forging, a technique for forging a forged object having a large outer diameter with a smaller load is required.

  For example, Patent Document 1 discloses a disk-shaped forging manufacturing apparatus that performs forging by pressing a forging by reciprocating linear motion of an upper metallurgy having a plurality of pressing surfaces. According to this technique, it is possible to reduce the area per one time pressed by the upper anvil, and it becomes possible to forge a forging having a relatively large outer diameter even with a manufacturing apparatus having a small capacity. In this method, as an upper anvil for pressing the forged object, a rectangular bar-shaped upper anvil having a length capable of pressing an area from the end of the forged object through the central axis to the end opposite to the end. Is used.

  In addition, as the partial mold, the area near the central axis of the to-be-forged object is not pressurized, and the part of the split mold that pressurizes from the area between the central axis of the to-be-forged object and the outer peripheral edge to the outer peripheral edge. The type is known. According to the partial mold of the split mold, it is possible to efficiently forge a forged object having a large outer diameter with a smaller load.

JP 2009-12059 A

  In the upper anvil described in Patent Document 1, it is possible to reduce the load applied to the forged product to some extent as compared with the case of using the full surface mold. However, when forging a forging object having a larger outer diameter, the method described in Patent Document 1 is not necessarily sufficient in the effect of reducing the load applied to the forging object.

  In addition, when the above-described split-type partial mold is used, the end portion of the partial mold is easy to bite into the forged object during pressurization. For this reason, after pressurizing with a partial die, there is a problem that it is difficult to separate the forged product and the partial die, and the subsequent forging process cannot be smoothly transferred.

  An object of the present invention is to efficiently forge a forged object with a small load using a plurality of partial molds and smoothly perform a forging process.

  A preferred embodiment of the forging method according to the present invention is a forging method in which a forging is disposed between an upper die and a lower die, and the forging is forged. At least one of the plurality of partial molds is disposed in a circumferential direction so as to surround the central axis of the to-be-forged material, and is formed on a ring centered on the central axis in a region between the central axis and the outer peripheral portion. The forged object in which the groove portion is formed is disposed between the upper die and the lower die with the groove portion facing the partial die, and at least one of the upper die or the lower die is placed on the workpiece. The partial mold is rotated while rotating around the central axis of the forging, with a part of the partial mold contacting a partial region of the groove, and a region where the partial mold does not contact is left in the groove. And move the forging object to the forging object side without contacting the area surrounded by the groove. Characterized in that pressurizing the 該被 forging.

  Moreover, as a preferable embodiment of the forged product according to the present invention, a groove on an annular ring centering on the central axis is formed in a region between the central axis and the outer peripheral portion. .

  According to the present invention, a forged product can be efficiently forged with a small load and a forging process can be smoothly performed using a plurality of partial dies.

3 is a plan view for explaining a forging method according to Embodiment 1. FIG. It is the sectional view on the AA line of FIG. It is sectional drawing which shows the structure of the to-be-forged object 1 arrange | positioned between the upper mold | type 11 and the lower mold | type 21 of a forge type | mold shown in FIG. It is sectional drawing which shows the state at the time of the pressurization of the to-be-forged thing 1 by the upper mold | type 11 and the lower mold | type 21 shown in FIG. It is sectional drawing which shows the structure of the forging 1P obtained by the forging method which concerns on Example 1. FIG. It is sectional drawing which shows the structure of the to-be-forged material 51 used in the forging method which concerns on Example 2. FIG. 6 is a diagram for explaining a forging method according to Example 2. FIG. It is sectional drawing which shows the state at the time of the pressurization of the forging 51 by the upper mold | type 31 and the lower mold | type 41 shown in FIG. It is sectional drawing which shows the structure of the forging 51P obtained by the forging method which concerns on Example 2. FIG. 6 is a diagram for explaining a forging method according to Example 3. FIG. It is sectional drawing which shows the state at the time of the pressurization of the to-be-forged material 101 by the upper mold | type 111 and the lower mold | type 121 shown in FIG. FIG. 10 is a view showing a modification of the forging method according to the third embodiment.

Below, the forging method which concerns on Example 1 of this invention is demonstrated.
FIG. 1 is a plan view for explaining a forging method according to the first embodiment, and FIG. 2 is a cross-sectional view taken along line AA in FIG.

  As shown in FIG. 1, a forging die 100 that performs rotary forging includes a lower die 21 that is a full die having a circular planar shape, and an upper die 11 that is disposed to face the lower die 21.

  As shown in FIG. 2, the lower die 21 is formed with a cored bar 22 that is a truncated cone-shaped convex portion in a region including the central axis 21 </ b> L. In the upper mold 11, a plurality of divided partial molds 12 (four partial molds in the drawing) are arranged in the circumferential direction so as to surround the central axis 21 </ b> L of the lower mold 21.

  First, the to-be-forged product 1 is disposed between the upper die 11 and the lower die 21. FIG. 2 shows the state of the upper die 11, the lower die 21 and the forged product 1 at this time. FIG. 3 is a cross-sectional view showing the configuration of the forged object 1 disposed between the upper die 11 and the lower die 21.

  As shown in FIG. 3, the to-be-forged object 1 has a substantially cylindrical shape as a whole, and has main surfaces on both sides thereof. On one main surface 1a of the to-be-forged object 1, an annular groove 2 centering on the center axis 1L of the to-be-forged object 1 is formed in a region between the central axis 1L and the outer peripheral part 4 thereof. . The groove portion 2 has a curved inner surface.

  Further, a central hole 3 is formed in the central region of the other main surface 1b of the forged article 1. The center hole 3 is formed as a truncated cone-shaped recess (a blind hole), and the center thereof is formed so as to coincide with the center axis 1 </ b> L that is the center axis of the groove 2. In the example illustrated in FIG. 3, the center hole 3 is formed as a recess in the forged article 1, but the center hole 3 may be formed as a through hole.

  As shown in FIG. 2, the center hole 3 of the to-be-forged object 1 is fitted to the cored bar 22 of the lower die 21. Thereby, the to-be-forged object 1 is fixed on the lower mold | type 21 in the state centered with respect to the upper mold | type 11, and the groove | channel 2 facing the partial mold | type 12 of the upper mold | type 11. FIG. Thereby, the some partial type | mold 12 which comprises the upper mold | type 11 will be in the state arrange | positioned in the circumferential direction so that the center axis | shaft 1L of the to-be-forged material 1 may be enclosed (refer FIG. 1).

  In the example shown in FIG. 2, the lower mold 21 has a core bar 22, but the lower mold 21 does not necessarily have the core bar 22. However, in the forging process described later, in order to prevent the center of the to-be-forged object 1 from deviating from the centers of the upper die 11 and the lower die 21, a lower die 21 having a cored bar 22 is used. Is good.

  FIG. 2 shows an example in which the core metal 22 is formed as a convex part in which a part of the lower mold 21 is raised. As the core metal 22, for example, a member separate from the lower mold 21 is shown. May be appropriately attached to the lower mold 21.

  Next, the upper die 11 is moved toward the forged object 1 to press the forged object 1 and forge it. The state of the upper die 11, the lower die 21, and the forged product 1 at this time is shown in FIG.

  As shown in FIGS. 2 and 4, each of the partial molds 12 of the upper mold 11 has a curved end portion 12 e installed on the side of the central axis 21 </ b> L of the lower mold 21 (the central axis 1 </ b> L of the forged object 1). ing. The curved surface shape of the end portion 12e is formed so as to project toward the central axis 21L side from the pressurizing surface 12a side that pressurizes the forged object 1 toward the opposite surface 12b side.

  When the workpiece 1 is pressed, a part of each partial die 12 formed in this way is brought into contact with a partial region in the groove 2 and the outer peripheral portion 4 of the workpiece 1 so that the partial die 12 is entirely Is moved in the direction of the workpiece 1. At this time, after appropriately adjusting the position of the end portion 12e of each partial mold 12 so that each partial mold 12 does not contact the region 5 surrounded by the groove 2 in the main surface 1a of the forged article 1, The partial die 12 that is the upper die 11 is moved to the forged object 1 side.

  In the groove portion 2, a part of the partial mold 12 is brought into contact with the outer peripheral side region 2 a, and the non-contact region 2 b where the partial die 12 is not brought into contact is left on the inner peripheral side of the groove portion 2. Then, the partial mold 12 is moved to the forged object 1 side.

  In the example shown in FIG. 2, the inner peripheral surface of the groove portion 2 is formed in a curved shape having a smaller radius of curvature on the inner peripheral side than on the outer peripheral side. For this reason, each partial die 12 is moved vertically from the position shown in FIG. 2 in the direction of the to-be-forged object 1 (vertical direction in FIG. 2), so that the contact region 2a of the partial die 12 and the non-contact region 2a are not in the groove portion 2. The to-be-forged object 1 can be pressurized in the state where the contact region 2b coexists (see FIG. 4).

  As the upper die 11 moves toward the to-be-forged object 1, an area on the outer peripheral side of the groove portion 2 of the to-be-forged object 1 is pressurized by the upper die 11, and the thickness at the pressurized portion is reduced. The outer diameter of the entire object 1 is increased.

Next, the upper die 11 is moved in a direction in which the upper die 11 is separated from the forged object 1.
As described above, each partial die 12 that is the upper die 11 is in contact with the region 2a on the outer peripheral side of the groove portion 2 with the non-contact region 2b remaining on the inner peripheral side of the groove portion 2, respectively. 1 is pressurized. As a result, the radial force acting on the workpiece 1 from each partial mold 12 is reduced, and the partial mold 12 is prevented from biting into the workpiece 1. Therefore, the upper die 11 can be easily separated from the forged object 1.

  After separating the upper die 11 from the workpiece 1, the upper die 11 is rotated by a predetermined angle around the central axis 1 </ b> L of the workpiece 1. Next, the upper die 11 after the rotation is moved again to the forging object 1 side in the same manner as described above, and the forging object 1 is pressurized.

  After repeating the series of operations described above a plurality of times, the upper die 11 is separated from the obtained forging 1P, and the forging 1P is taken out from the lower die 21. The structure of the forged product 1P obtained by the forging method according to Example 1 is shown in FIG.

  According to the forging method of Example 1, the forged product 1P shown in FIG. 5 can be obtained by forging with a small load. Further, the partial mold 12 is prevented from being bitten into the forged object 1 during pressurization, and the forging process can be performed smoothly.

  In the first embodiment, an example in which the inner peripheral surface of the groove portion 2 is formed in a curved shape is shown, but the inner peripheral surface of the groove portion 2 may be formed in a rectangular shape, for example. This shape is the same as in the second embodiment.

  Next, a forging method according to Example 2 will be described with reference to FIGS.

  Example 2 is an example in which partial molds are used for both the upper mold and the lower mold, and the to-be-forged object 51 having groove portions on both main surfaces is pressed from both sides by the upper mold and the lower mold. FIG. 6 is a cross-sectional view showing the configuration of the forged object 51.

  The to-be-forged object 51 has a main surface on both surfaces thereof, a groove portion 52 is formed on one main surface 51a, and a groove portion 53 is formed on the other main surface 51b. The groove parts 52 and 53 are each formed in an annular shape in the region between the central axis 51L of the forged article 51 and the outer peripheral part 54 with the central axis 51L of the forged article 51 as the center.

  FIG. 7 is a diagram for explaining the forging method according to the second embodiment. As shown in FIG. 7, in the forging die 200 that performs rotary forging, the upper die 31 is constituted by a plurality of divided partial portions 32, and the lower die 41 is constituted by a plurality of divided partial portions 42. Yes. The partial mold 32 and the partial mold 42 are respectively arranged in the circumferential direction so as to surround the common central axis 200L.

  The partial mold 32 and the partial mold 42 have the same shape as the partial mold 12 of the first embodiment. That is, the curved surface shapes of the end portion 32e of the partial mold 32 and the end portion 42e of the partial mold 42 are respectively directed from the pressing surfaces 32a and 42a that press the workpiece 51 to the opposite surfaces 32b and 42b. Accordingly, it is formed so as to protrude to the center axis 200L side.

  First, the forged object 51 is disposed between the upper die 31 and the lower die 41. The forged object 51 is disposed between the upper die 31 and the lower die 41 with the groove 52 facing the partial die 32 of the upper die 31 and the groove 53 facing the partial die 42 of the lower die 41. . The forged article 51 is disposed between the upper mold 31 and the lower mold 41 so that the central axis 51L of the forged article 51 is aligned with the central axis 200L of the partial mold 32 and the partial mold 42. Thereby, the plurality of partial molds 32 and the plurality of partial molds 42 are in a state of being arranged in the circumferential direction so as to surround the central axis 51 </ b> L of the forged object 51.

  Next, the upper mold 31 and the lower mold 41 are moved toward the forged object 51 to pressurize the forged object 51 and forge it. The state of the upper die 31, the lower die 41 and the forged product 51 at this time is shown in FIG.

  The positional relationship between the partial mold 32 of the upper mold 31 and the partial mold 42 of the lower mold 41 and the forged object 51 during pressurization is the same as the positional relationship between the upper mold 11 and the forged object 1 in Example 1. is there. That is, when the workpiece 51 is pressed, a part of the partial die 32 is brought into contact with a partial region in the groove 52 and the outer peripheral portion 54 of the workpiece 51, and a part of the partial die 42 is made to pass into the groove portion. The entire partial molds 32 and 42 are moved in the direction of the to-be-forged object 51 by bringing them into contact with a part of the region 53 and the outer peripheral portion 54 of the to-be-forged object 51. At this time, the end portions 32e and 42e of the surface of the to-be-forged object 51 have the end portions 32e and 42e so that the partial molds 32 and 42 do not contact the region 55 and the region 56 surrounded by the groove portion 53, respectively. After adjusting the position as appropriate, the partial dies 32 and 42 are moved to the forged object 51 side.

  Further, in the groove portion 52, a part of the partial mold 32 is brought into contact with the outer peripheral side region 52a, and the non-contact region 52b where the partial die 32 is not brought into contact is left on the inner peripheral side of the groove portion 52. Then, the partial mold 32 is moved to the forged object 51 side. Similarly, in the groove portion 53, a part of the partial mold 42 is brought into contact with the outer peripheral side region 53 a, and a non-contact region 53 b that does not contact the partial die 42 is left on the inner peripheral side of the groove portion 53. Then, the partial die 42 is moved to the forged object 51 side.

  Also in Example 2, the inner peripheral surfaces of the groove portions 52 and 53 have a curved shape, and the inner peripheral side is formed with a smaller radius of curvature than the outer peripheral side. For this reason, the partial molds 32 and 42 are moved vertically from the position shown in FIG. 7 in the direction of the to-be-forged object 51 (up and down direction in FIG. 7), respectively, so that the partial molds 32 and The to-be-forged object 51 can be pressurized in the state where the contact areas 52a and 53a of 42 and the non-contact areas 52b and 53b coexist.

  As the upper die 31 and the lower die 41 move toward the to-be-forged object 51, the outer peripheral region of the to-be-forged object 51 from the groove portions 52 and 53 is pressurized by the upper die 31 and the lower die 41. The thickness in the portion is reduced, and the outer diameter of the forged object 51 as a whole is increased.

  Next, the upper die 31 and the lower die 41 are moved in a direction in which they are separated from the forged object 51. Also in Example 2, the partial mold 32 and the partial mold 42 pressurize the forged object 51 in a state where the non-contact regions 52b and 53b remain in the groove portions 52 and 53, respectively. For this reason, the radial force acting on the forged object 51 from the partial mold 32 and the partial mold 42 is reduced, and the partial mold 32 and the respective partial molds 42 are prevented from biting into the forged object 51. ing. Therefore, the upper die 31 and the lower die 41 can be easily separated from the forged object 51.

  After separating the upper die 31 and the lower die 41 from the forged article 51, the upper die 31 and the lower die 41 are rotated by a predetermined angle about the central axis 51L of the forged article 51, that is, the central axis 200L. Next, the upper die 31 and the lower die 41 after rotation are moved again to the forged object 51 side in the same manner as described above, and the forged object 51 is pressurized.

  After repeating the series of operations described above a plurality of times, the upper die 31 and the lower die 41 are separated from the obtained forged product 51P, and the obtained forged product 51P is taken out from the upper die 31 and the lower die 41. . The structure of the forged product 51P obtained by the forging method according to Example 2 is shown in FIG.

  According to the forging method of the second embodiment, the forged object 51 is pressed from both sides by the partial mold 32 and the partial mold 42, and therefore the forged object 51 is forged with a smaller load than that of the first embodiment. be able to. Further, the partial mold 32 and the partial mold 42 are prevented from being bitten into the forged object 51 during pressurization, and the forging process can be performed smoothly.

  In the examples shown in FIGS. 7 and 8, the groove 52 and the groove 53 are formed with substantially the same diameter, but the groove 52 and the groove 53 are formed according to the shape of the target final product. May be formed with different diameters. However, from the viewpoint of ease of forging, it is better to form the groove 52 and the groove 53 with the same diameter.

Next, a forging method according to Example 3 will be described with reference to FIGS.
Example 3 describes the first forging process performed before the first example. That is, Example 3 uses the upper mold 111 described later as the first upper mold, and uses the lower mold 121 described later as the first lower mold, and intermediates the forged article 1 described in Example 1 to the middle. It is the 1st forge process for obtaining as a forging.

  In addition, the forging process of Example 1 becomes a forging process performed in the latter stage of Example 3. That is, Example 1 uses the upper die 11 as the second upper die, uses the lower die 21 as the second lower die, and forges the intermediate forged product obtained in Example 3 as the forged product. The second forging step is performed.

  The forging die 300 used in the third embodiment includes a lower die 121 that is a full surface die having a circular planar shape, and an upper die 111 that is a full surface die arranged to face the lower die 121. Similar to the lower mold 121, the upper mold 111 has a circular planar shape.

  The lower mold 121 has a protruding portion 122 formed in an annular shape. Moreover, the upper mold | type 111 has the convex part 112 formed in the center area | region. The upper mold 111 and the lower mold 121 are arranged so that the center of the convex portion 112 coincides with the central axis 122 </ b> L of the annular projecting portion 122.

  As shown in FIG. 10, first, a forging object 101 (hereinafter, the forging object 101 is referred to as a billet 101) is disposed on the lower die 121. The billet 101 is disposed in a region surrounded by the annular protrusion 122. As a result, the billet 101 is placed on the lower die 121 in a state where it is centered with respect to the convex portion 112 of the upper die 111.

  That is, the annular projecting portion 122 can be used for shape transfer with respect to the billet 101, which will be described later, and can be used for centering with respect to the upper mold 111 having the convex portion 112.

  From the viewpoint of centering the billet 101 with respect to the convex portion 112 of the upper mold 111, the inner peripheral diameter r1 of the annular ridge 122 is smaller in the difference from the diameter r2 of the outermost peripheral portion of the billet 101. Good. On the other hand, from the viewpoint of easy installation when the billet 101 is installed on the lower mold 121, the inner peripheral diameter r1 of the annular protrusion 122 is different from the diameter r2 of the outermost peripheral portion of the billet 101. Is better. For this reason, the inner peripheral diameter r1 of the protrusion 122 and the outermost diameter r2 of the billet 101 may be appropriately determined in consideration of the above points.

  As the billet 101, for example, a cylindrical body having an outermost diameter r <b> 2 smaller than the inner circumferential diameter r <b> 1 of the annular protrusion 122 by about 1 mm to 50 mm is installed on the lower mold 121.

  Next, the upper die 111 is moved in the direction of the billet 101, and the billet 101 is pressurized by the upper die 111 and forged. FIG. 11 shows a cross-sectional view of the upper mold 111, the lower mold 121, and the billet 101 at this time.

  As the upper die 111 moves to the billet 101 side, the entire billet 101 is pressed by the upper die 111 to lower the overall height, and the outer diameter of the billet 101 as a whole increases.

  At this time, the shape of the protrusion 122 is transferred to the billet 101 by the lower mold 121, the groove 2 (see FIGS. 2 and 3) is formed in the billet 101, and the convex 112 is formed by the upper mold 111. The shape is transferred, and the center hole 3 is formed in the billet 101. Thereby, the forged product 101P having the shape of the workpiece 1 is obtained.

  The billet 101 is installed on the lower die 121 in a state of being centered with respect to the convex portion 112 of the upper die 111 by an annular ridge 122. For this reason, the groove part 2 is formed in the billet 101 substantially concentrically with the center hole 3. That is, the groove portion 2 is formed so that the central axis thereof substantially coincides with the center of the central hole 3.

  10 shows an example in which the center hole 3 is formed in the billet 101. For example, when the obtained forged product 101P is forged as the forged product 1, the cored bar 22 (see FIG. 2). In the case of using the lower mold 21 that does not have (), a flat mold may be used as the upper mold 111 in FIGS.

  In addition, when forging 101P forged by the method demonstrated in Example 3 is forged by the method of Example 1 as to-be-forged object 1, whether the top and bottom of forging 101P obtained in Example 3 is replaced? Alternatively, the upper and lower relationships of the upper mold 11 and the lower mold 21 shown in FIGS. 2 and 4 may be switched.

  In the third embodiment, the method of forming the groove 2 and the center hole 3 in the billet 101 by forging has been described. However, the groove 2 and the center hole 3 are formed by a removal process such as machining. You may do it.

  In the third embodiment, an example in which the groove portion 2 is formed by pressing the protrusion 122 against the billet 101 while forging the billet 101 using the lower mold 121 having the protrusion 122 formed thereon is shown. However, as shown in FIG. 12, for example, the groove portion 2 is formed by using a forging die 400 having a second upper die 213 in which a ring-shaped member 212 is attached to a flat plate material 211, and the upper die 213 is billeted. You may make it carry out by pressing to 101.

DESCRIPTION OF SYMBOLS 1, 51 ... Forged material, 1a, 1b, 51a, 51b ... Main surface of forged material, 1L, 51L ... Center axis of forged material, 1P, 51P, 101P ... Forged material, 2, 52, 53 ... Groove 2a ... an outer peripheral region in the groove 2, 2b ... an inner peripheral region in the groove 2, 52a ... an outer peripheral region in the groove 52, 52b ... an inner peripheral region in the groove 52, 53a ... in the groove 53 Area on the outer peripheral side, 53b ... Area on the inner peripheral side of the groove part 53, 3 ... Center hole, 4, 54 ... Outer peripheral part of the forged article, 5, 55, 56 ... Area surrounded by the groove part 2, 11, 31, 111 ... Upper mold, 12, 32, 42 ... Partial mold, 12a, 32a, 42a ... Partial mold pressing surface, 12b, 32b, 42b ... Surface opposite to the partial mold pressing surface, 12e, 32e, 42e ... Partial End of mold, 21, 41, 121 ... lower mold, 21L ... central axis of lower mold 21, 22 ... cored bar, 10 , 200, 300, 400 ... forging die, 200L ... central axis of forging die 200, 101 ... billet, 112 ... convex portion of upper die 111, 122 ... protruding portion, 122L ... central axis of protruding portion 122, 211 ... Plate material 212 ... Ring-shaped member, 213 ... Upper mold, r1 ... Inner diameter of the protrusion 122, r2 ... Diameter of the outermost periphery of the billet 101

Claims (7)

A forging method in which a forging is arranged between an upper die and a lower die and the forging is forged,
At least one of the upper mold or the lower mold is a plurality of partial molds that are disposed in a circumferential direction around a central axis of the forged object,
In the region between the central axis and the outer peripheral part, the to-be-forged object in which a groove on the ring centering on the central axis is formed, the upper mold and the lower are placed with the groove facing the partial mold. Between the mold and
Rotate at least one of the upper mold or the lower mold around the central axis of the forged object,
The partial mold is surrounded by the groove portion of the to-be-forged material while a part of the partial die is brought into contact with a partial region of the groove portion and a region where the partial die does not contact is left in the groove portion. A forging method, wherein the forging is moved to the forging side without being brought into contact with the region, and the forging is pressurized.   The forging method according to claim 1, wherein the to-be-forged object in which an inner peripheral surface of the groove portion has a curved shape is disposed between the upper die and the lower die. The lower mold is a full face mold in which a convex portion is formed in a region including the central axis of the lower mold,
The upper mold is a plurality of partial molds arranged in a circumferential direction around the central axis of the lower mold,
The to-be-forged object in which a concave portion is formed in a region including the central axis of the groove portion on the main surface opposite to the groove forming surface, the concave portion is fitted to the convex portion of the lower mold, and the upper The forging method according to claim 1, wherein the forging method is arranged between a die and the lower die. Both the upper mold and the lower mold are the partial molds,
The forging method according to claim 1, wherein the groove portions are formed on both main surfaces of the forged object, and the forged object is disposed between the upper die and the lower die. A forging method in which a forging is arranged between an upper die and a lower die and the forging is forged,
As the upper mold, a first upper mold that is a full-surface mold having a convex portion in the central region is prepared,
As the lower mold, a first lower mold that is a full face mold having an annular ridge is prepared,
A first forging object is disposed between the first upper mold and the first lower mold, the center of the convex portion and the central axis of the protruding portion being aligned with each other; A first forging step of producing an intermediate forging in which a groove on an annular shape is formed by the protrusions by pressurizing the first forged object with one upper mold and the first lower mold;
As the upper mold and the lower mold, a second upper mold and a second lower mold, at least one of which is a plurality of partial molds arranged around the central axis of the intermediate forging, are prepared. And
The intermediate forging is disposed between the second upper mold and the second lower mold with the groove facing the partial mold;
Rotating at least one of the second upper die or the second lower die about the central axis of the intermediate forging,
The partial die is surrounded by the groove portion of the intermediate forging while a part of the partial die is brought into contact with a partial region of the groove portion and a region where the partial die does not contact is left in the groove portion. And a second forging step in which the intermediate forging is moved to the side of the intermediate forging without being brought into contact with the region, and the intermediate forging is pressurized.   A to-be-forged object, wherein a groove on an annular ring centering on the central axis is formed in a region between the central axis and the outer peripheral portion.   The forged product according to claim 6, wherein the groove is formed on both main surfaces.

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