JP7156099B2 - Manufacturing method of circular material - Google Patents

Description

The present invention relates to a method for manufacturing circular members.

Circular materials typified by railroad wheels, gears and rings are manufactured, for example, as follows.

First, a cylindrical material (billet) is heated. An intermediate product (rough forging) is manufactured by performing a rough forming process on the heated cylindrical material. In the rough forming process, forging is performed once or multiple times. Finish rolling, finish forging, and the like are performed on the rough forging to manufacture a circular material. If necessary, heat treatment and machining are performed on the circular material after the finish forging.

Such a circular member often has an H-shaped cross section along the central axis of the circular member. When upsetting a circular material having an H-shaped cross section, it is necessary to greatly deform the cylindrical material, so that the material does not flow to every corner of the die, which may result in undercut forging. If the volume of the cylindrical material is increased in order to suppress the lack of thickness in the rough forging, a large amount of burrs will be generated after forming the rough forging, and the yield will decrease.

For example, Japanese Utility Model Laid-Open No. 50-117137 (Patent Document 1) discloses a method for suppressing the lack of thickness in a forged product. For example, Japanese Utility Model Publication No. 7-44350 (Patent Document 2) discloses a method for suppressing a decrease in the yield of forged products.

In Patent Document 1, upset forging is performed using a die including an upper die, a lower die, and a guide ring. A guide ring surrounds the cylindrical material and is attached to the lower die via a coil spring. When the upper die presses down on the cylindrical material, the cylindrical material deforms in its radial direction. A radially deformed cylindrical blank hits the guide ring. After that, the guide ring unites with the upper die and reaches the bottom dead center. At this time, since the cylindrical material is in contact with the guide ring, when the guide ring descends, the area of the cylindrical material in contact with the guide ring also descends due to friction. Patent Literature 1 describes that this suppresses underfilling of the corner region formed by the lower mold and the guide ring.

In Patent Document 2, upset forging is performed using an upper die including an inner punch and an outer punch, and a lower die. The outer punch surrounds the circular blank and is attached to the inner punch via a disc spring. When forging is started, the outer punch hits the lower die first, and the cylindrical material is confined in the closed space formed by the upper and lower dies. In this state, the inner punch pushes down the cylindrical material. When the cylindrical material deforms, the internal pressure of the closed space increases, and when the internal pressure exceeds a predetermined value, the pressure causes the outer punch to rise, releasing the closed state of the cylindrical material. Therefore, the cylindrical material is forged while forming burrs. Patent document 2 states that this prevents unnecessary burrs from being formed in the initial stage of molding, thereby improving the yield, and that burrs are formed in the final stage of molding, thereby suppressing underfilling.

Japanese Utility Model Laid-Open No. 50-117137 Japanese Utility Model Publication No. 7-44350

However, in the method of Patent Document 1, even if it is possible to suppress the lack of thickness in one corner region (the corner region formed by the lower mold and the guide ring) of the forging having an H-shaped cross section, the other corner region (the upper It is difficult to suppress underfilling of the corner area formed by the mold and the guide ring). Similarly, in the method of Patent Document 2, it is difficult to suppress underfilling in the corner region formed by the inner punch and the outer punch, that is, the corner region above the mold.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a circular material that can suppress underfilling and decrease in yield.

The method for manufacturing a circular member according to this embodiment is a method for manufacturing a circular member from a columnar raw material including a central portion and an edge portion having an outer peripheral surface. A method for manufacturing a circular member includes a step of radially deforming the columnar blank by compressing the central portion of the columnar blank, a step of constraining the radial deformation of the columnar blank that is being radially deformed, and a step of restricting the radial deformation of the columnar blank. After the step of constraining the radial deformation, the step of rolling down the central portion of the cylindrical material and rolling down the edge portion of the cylindrical raw material at a rolling speed lower than the rolling speed of the central portion, and after the step of rolling down the edge portion. , and rolling down the central portion and the edge portion of the cylindrical blank at the same rolling speed.

According to the manufacturing method of the circular member of the present embodiment, it is possible to suppress insufficient thickness and suppress a decrease in yield.

FIG. 1 is a cross-sectional view of a circular material forging apparatus according to a first embodiment. FIG. 2 is a cross-sectional view showing the central portion rolling-down process of the first embodiment. FIG. 3 is a cross-sectional view showing the restraining process of the first embodiment. FIG. 4 is a cross-sectional view showing forging according to a general manufacturing method. FIG. 5 is a cross-sectional view showing the initial stage of the different speed reduction process of the first embodiment. FIG. 6 is a cross-sectional view showing the final stage of the different speed reduction process of the first embodiment. FIG. 7 is a cross-sectional view showing the same speed reduction process of the first embodiment. FIG. 8 is a cross-sectional view showing the boundary between the first upper die and the second upper die in the forging apparatus of the first embodiment. FIG. 9 is a cross-sectional view showing the boundary between the first upper mold and the second upper mold, which is different from FIG. FIG. 10 is a cross-sectional view of the forging device of the second embodiment. FIG. 11 is a cross-sectional view showing a state after the restraining step in the manufacturing method of the second embodiment. FIG. 12 is a cross-sectional view showing a pressurizing step in the manufacturing method of the second embodiment. FIG. 13 is a cross-sectional view showing a state in which the first upper die and the second upper die have reached the bottom dead center in the manufacturing method of the second embodiment.

(1) A method for manufacturing a circular member according to the present embodiment is a method for manufacturing a circular member from a columnar raw material including a central portion and an edge portion having an outer peripheral surface. A method for manufacturing a circular member includes a step of radially deforming the columnar blank by compressing the central portion of the columnar blank, a step of constraining the radial deformation of the columnar blank that is being radially deformed, and a step of restricting the radial deformation of the columnar blank. After the step of constraining the radial deformation, the step of further reducing the central portion of the cylindrical material and reducing the edge portion of the cylindrical material at a reduction speed lower than the reduction speed of the central portion, and the step of reducing the edge portion. Afterwards, a step of rolling down the central portion and the edge portion of the columnar blank at the same rolling speed.

In upset forging a circular material with an H-shaped cross-section, it is often difficult to fill the die with the material. In particular, the molding of the region above the radial end (edge) of the H-shaped cross section is highly difficult because it is necessary to flow the material against the pressing direction of the upper die. In this regard, in the manufacturing method of the present embodiment, in the upsetting forging (forming of rough ground) of the cylindrical material, the rolling speed at the edge of the cylindrical raw material is slower than the rolling speed at the central portion. As a result, the edges are pushed upward relative to the central portion. As a result, a rough forging ground in which underfilling in the region above the edge is suppressed is obtained, so underfilling in the circular material subjected to finishing rolling or the like later is also suppressed. In addition, in general upsetting forging, it is usually necessary to increase the volume of the cylindrical material in order to suppress underfilling above the edge. However, according to the manufacturing method of the present embodiment, the lack of thickness in the region above the edge is suppressed, so it is not necessary to increase the volume of the cylindrical material. That is, a decrease in yield is suppressed.

(2) The manufacturing method of (1) further includes a first upper mold and a side wall portion facing the outer peripheral surface of the cylindrical material, which is arranged radially outside of the cylindrical material relative to the first upper mold. placing the cylindrical material in a forging device including a second upper die slidable in a rolling direction with respect to the first upper die, and a lower die facing the first upper die and the second upper die; preferable. In this case, in the step of radially deforming the columnar blank, the first upper die presses down the central portion of the columnar blank. In the step of constraining the radial deformation of the columnar blank, the side wall portion of the second upper die contacts the outer peripheral surface of the columnar blank to constrain the radial deformation of the columnar blank. In the step of rolling down the central part of the cylindrical material and rolling down the edge of the cylindrical material at a rolling speed lower than the rolling speed of the central part, the second upper mold is rolled down at a lowering speed than the lowering speed of the first upper mold. presses down on the edge of the cylindrical blank.

The manufacturing method of this embodiment uses a divided upper mold. This makes it possible to make the rolling speed at the edges slower than the rolling speed at the center.

(3) In the manufacturing method of (2) above, in the step of rolling down the central portion and the edge portion of the cylindrical material at the same rolling speed, the first upper mold preferably reaches the bottom dead center at the same time as the second upper mold. .

If the first upper die reaches the bottom dead center first, a gap is formed between the second upper die and the lower die when the first upper die reaches the bottom dead center. Therefore, the material may flow out from the gap between the second upper mold and the lower mold, excessive burrs may occur, and the yield may decrease. If the second upper die reaches the bottom dead center first, the edge of the cylindrical blank is not pushed down after the second upper die reaches the bottom dead center. Therefore, it is difficult for the material to flow at the edge of the cylindrical material, and there is a possibility that the edge will be underfilled. On the other hand, if the first upper die reaches the bottom dead center at the same time as the second upper die, it is easy to maintain a balance between filling the edge of the cylindrical blank with the material and suppressing a decrease in yield.

(4) The manufacturing method of (1) to (3) preferably further comprises a step of applying pressure to the edge of the cylindrical material in a direction opposite to the pressing direction after the step of radially deforming the cylindrical material.

According to such a manufacturing method, after the cylindrical blank is deformed in the radial direction, the downward flow of the material at the edge of the cylindrical blank is restricted. As a result, the material of the columnar raw material that was about to flow downward can easily flow upward, further suppressing the lack of thickness in the region above the edge.

(5) The manufacturing method of (2) or (3) further includes, after the step of radially deforming the columnar blank, applying pressure to the edge of the columnar blank in a direction opposite to the rolling direction. The mold includes a first lower mold, and a second lower mold arranged outside the first lower mold in the radial direction of the cylindrical material and attached to the first lower mold via an elastic member, In the step of pressing the edge of the cylindrical material in the direction opposite to the rolling direction, it is preferable that the second lower mold presses the edge of the cylindrical material.

According to such a manufacturing method, the lower mold is divided, and the second lower mold in contact with the edge of the cylindrical material can suppress the downward flow of the material at the edge, and the area above the edge can be suppressed. Undercutting is suppressed.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same reference numerals are given to the same or corresponding parts in the drawings, and the description thereof will not be repeated. First, a forging apparatus used in the method for manufacturing a circular member according to the first embodiment will be described. In addition, the forging apparatus of the first embodiment is used in a rough land forming process for manufacturing a forged rough land.

[First embodiment]
[Forging device 1]
FIG. 1 is a cross-sectional view of a forging device 1 of the first embodiment. Since the forging device has an axially symmetrical shape, FIG. Referring to FIG. 1 , forging apparatus 1 includes a first upper die 2 , a second upper die 3 and a lower die 4 . The forging device 1 performs upsetting forging on a cylinder material.

The first upper mold 2 faces the central portion 6 of the columnar blank 5 . The central portion of the columnar blank 5 means a region with a predetermined radius from the central axis of the columnar blank 5 and does not include the edge 7 and the outer peripheral surface 9 of the columnar blank 5 . The first upper die 2 has a shape corresponding to the central portion of the rough forging after molding. The first upper mold 2 is attached to a bolster plate (not shown).

The second upper mold 3 is arranged radially outside the cylindrical material 5 relative to the first upper mold 2 . The second upper mold 3 has a shape corresponding to the edge of the rough forging after molding. The edge of the forging rough means the area radially outward of the center of the forging rough and includes the outer peripheral surface. Further, the edge of the rough forging area corresponds to the edge 7 and the outer peripheral surface 9 of the cylindrical material 5 .

The second upper mold 3 is suspended from the first upper mold 2 . That is, the second upper mold 3 is not attached to the first upper mold 2 via an elastic member such as a spring, and only its own weight is applied to the second upper mold 3 . The second upper die 3 is freely slidable by a predetermined distance in the pressing direction with respect to the first upper die 2 . For example, by providing key grooves in the first upper mold 2 and the second upper mold 3, the second upper mold 3 can be slid. The forging device 1 is provided with a stopper (not shown) for restricting the sliding of the second upper die 3 . Also, the second upper mold 3 includes a side wall portion 8 facing the outer peripheral surface 9 of the cylindrical material 5 . The side wall portion 8 facing the outer peripheral surface 9 means that the side wall portion 8 faces the outer peripheral surface 9 during upset forging.

The forging device 1 includes a ram (not shown). The ram can move the bolster plate in the downward direction. That is, the ram can raise or lower the first upper mold 2 and the second upper mold 3 . With such a configuration, as will be described later, when the first upper mold 2 descends after the columnar material 5 contacts the side wall portion 8 of the second upper mold 3, the second upper mold 3 moves toward the first upper mold. 2 is relatively higher.

The lower mold 4 faces the first upper mold 2 and the second upper mold 3 . The lower die 4 has a shape corresponding to the central portion and edge portions of the rough forging after molding.

[Production method]
Next, a method for manufacturing a circular member according to the first embodiment will be described. The manufacturing method of the circular member of the first embodiment includes a central portion reduction process, a restraining process, a different speed reduction process, and a same speed reduction process. The forging apparatus 1 of the first embodiment described above is used in the method for manufacturing a circular member of the first embodiment.

Referring to FIG. 1, first, a cylinder material 5 is prepared. The material of the cylindrical material 5 is steel, for example. The size of the cylindrical material 5 is not particularly limited. The size of the cylindrical material 5 is appropriately set according to the size of the rough forging (or circular material) to be manufactured.

Next, the cylindrical material 5 is heated in a heating furnace. The heating furnace is, for example, a gas atmosphere heating furnace or an induction heater. The heating temperature of the cylindrical material 5 is not particularly limited. The heating temperature is appropriately set according to the material of the cylindrical material 5, the amount of processing, and the like.

Subsequently, the heated cylindrical material 5 is placed on the lower die 4 of the forging apparatus 1 as shown in FIG. Then, the central portion reduction step is performed. The cylindrical material 5 may be preformed before the central portion reduction process is performed (first rough-field forming process). As a result, the volume of the cylindrical raw material 5 is appropriately distributed, and a decrease in yield is suppressed.

[Central part reduction process]
FIG. 2 is a cross-sectional view showing the central portion rolling-down process of the first embodiment. Referring to FIG. 2, in the center reduction step, the ram lowers the bolster plate. As a result, the first upper mold 2 and the second upper mold 3 suspended from the first upper mold 2 are lowered. In the center part pressing step, the first upper die 2 presses down the center part 6 of the cylindrical material 5 , and the second upper die 3 does not press down the cylindrical material 5 . When the central portion 6 of the cylindrical material 5 is pressed down, the cylindrical material 5 is deformed radially outward.

[Restraint process]
FIG. 3 is a cross-sectional view showing the restraining process of the first embodiment. Referring to FIG. 3, pressing down of the central portion 6 of the cylindrical material by the first upper die 2 is continued even in the restraining step. The side wall portion 8 of the second upper mold 3 that has descended together with the first upper mold 2 is present on the radially outer side of the cylindrical material 5 that is deformed by the pressing of the central portion 6 . Therefore, as the pressing of the central portion 6 by the first upper mold 2 progresses, the outer peripheral surface 9 of the deformed columnar material 5 hits the side wall portion 8 of the second upper mold 3 . As a result, radial deformation of the cylindrical material 5 is restrained.

FIG. 4 is a cross-sectional view showing forging according to a general manufacturing method. Referring to FIG. 4, there is one upper die 100 in general forging. In this case, when the cylindrical material 5 deforms radially outward and the edge 7 hits the side wall 102 of the upper die 100, the edge 7 is dragged downward (toward the lower die 101) by the side wall 102. Therefore, the corner area A1 above the edge 7 (upper die 100 side) is less likely to be filled with the material, and the produced circular material is likely to be underfilled.

On the other hand, in the manufacturing method of the first embodiment, the downward drag of the edge portion 7 of the cylindrical material 5 is suppressed in the step of different speed reduction as described below. This point will be described in detail below.

[Different speed reduction process]
FIG. 5 is a cross-sectional view showing the initial stage of the different speed reduction process of the first embodiment. Referring to FIG. 5 , after restraining the radial deformation of the cylindrical material 5 in the restraining step, the first upper die 2 further presses down the central portion 6 of the cylindrical material 5 . As a result, the cylindrical material 5 tries to deform in the radial direction, but the radial deformation of the cylindrical material 5 is restrained by the side wall portion 8 . The second upper mold 3 is suspended from the first upper mold 2 as described above. Further, the side wall portion 8 of the second upper mold 3 is slightly inclined because it has a draft angle. Therefore, the second upper mold 3 rises relative to the first upper mold 2 due to the force applied to the side wall portion 8 by the radially deforming cylindrical material 5 . Therefore, the lowering speed of the second upper mold 3 is slower than the lowering speed of the first upper mold 2 . In other words, the rolling speed of the edge portion 7 of the cylindrical blank is lower than the rolling speed of the central portion 6 . In this specification, the term "reduction" means that the shape of the cylindrical material is changed by the mold. Therefore, since the shape of the edge portion 7 of the cylindrical material 5 changes due to the rise (sliding) of the second upper mold 3 with respect to the first upper mold 2, this change in shape is also included in the reduction.

As the second upper mold 3 rises with respect to the first upper mold 2 , the material that has flowed to the edge 7 also rises relative to the first upper mold 2 . As a result, the corner area A1 formed by the first upper mold 2 and the second upper mold 3 is easily filled with the material, and the area above the edge of the circular product (the first upper mold 2 and the second upper mold 3) The area corresponding to the corner area A1 formed by the mold 3) is suppressed from being underfilled. Such a manufacturing method of the first embodiment is particularly effective when the volume of the region above the edge of the circular member having the H-shaped cross section is larger than the volume of the region below the edge.

FIG. 6 is a cross-sectional view showing the final stage of the different speed reduction process of the first embodiment. Referring to FIG. 6, as described above, the second upper mold 3 moves up relative to the first upper mold 2 at a predetermined distance. The predetermined distance is appropriately set according to the shape of the circular material to be manufactured. When the lifting of the second upper mold 3 with respect to the first upper mold 2 is completed, the differential speed reduction step is completed.

[Same speed reduction process]
FIG. 7 is a cross-sectional view showing the same speed reduction process of the first embodiment. Referring to FIG. 7, the same speed reduction process is performed after the different speed reduction process. After the second upper mold 3 finishes rising relative to the first upper mold 2, the bolster plate is further lowered. In this case, since the second upper mold 3 does not slide with respect to the first upper mold 2 , the second upper mold 3 descends together with the first upper mold 2 . That is, in the same-speed reduction step, the reduction speed of the cylindrical material 5 by the first upper mold 2 is the same as the reduction speed of the second upper mold 3 . That is, the center portion 6 of the columnar blank 5 is pressed down by the first upper die 2, and the edge portion 7 of the columnar blank 5 is pressed down by the second upper die 3 at the same pressing speed as the center portion 6. After that, the first upper mold 2 and the second upper mold 3 reach the bottom dead center. When the first upper die 2 and the second upper die 3 reach the bottom dead center, a forging rough ground is obtained.

In the same speed reduction process, the material pushed out by the reduction of the first upper mold 2 and flowed to the edge 7 is reduced downward toward the edge 7 by the second upper mold 3 . This also facilitates filling of the area A2 below the edge of the forging rough with an H-shaped cross-section.

Well-known finish processing is applied to the manufactured forged rough ground, and a circular material (product) is obtained. For example, a rolling mill is used to perform finish rolling on the rough forging. After finish rolling, finish forging is performed to produce a circular material.

Here, in the same speed reduction step, it is preferable that the first upper die 2 and the second upper die 3 reach the bottom dead center at the same time. If the first upper die 2 reaches the bottom dead center first, a gap is formed between the second upper die 3 and the lower die 4 when the first upper die 2 reaches the bottom dead center. After the first upper die 2 reaches the bottom dead center, the central portion 6 of the cylindrical blank 5 is not pushed down. Therefore, the material is not pushed out toward the edge 7 by the first upper mold 2 . As a result, there is a possibility that underfill may occur at the edges. Moreover, if the size of the cylindrical material 5 is sufficiently large, the material may flow out from the gap between the second upper mold 3 and the lower mold 4, resulting in excessive burrs. Therefore, the yield may decrease. On the other hand, if the second upper die 3 reaches the bottom dead center first, the edge 7 of the columnar blank 5 is not pressed down after the second upper die 3 reaches the bottom dead center. Therefore, it is difficult to fill the edge portion 7 with the material, and there is a possibility that a shortage of material may occur. If the first upper die 2 reaches the bottom dead center at the same time as the second upper die 3, it is easy to maintain a balance between filling the edge of the cylindrical blank with the material and suppressing a decrease in yield.

FIG. 8 is a cross-sectional view showing the boundary between the first upper die and the second upper die in the forging apparatus of the first embodiment. Referring to FIG. 8, the boundary between the first upper mold 2 and the second upper mold 3, that is, the dividing position of the upper mold is at a position that coincides with the boundary between the central portion 6 and the edge portion 7 of the columnar blank 5. It is preferable to have A radially outer corner 10 of the corner region formed by the first upper mold 2 and the second upper mold 3 is present on the extension of the material flow direction. However, the radially inner corner 11 is not in the direction of material flow, but is at a negative angle.

When the boundary position between the first upper mold 2 and the second upper mold 3 coincides with the boundary between the central portion 6 and the edge portion 7 of the cylindrical material 5, the central portion 6 of the cylindrical material 5 is pressed down. It does not come into contact with the first upper mold 2 and the second upper mold 3 until a certain amount of time has passed since then. Therefore, since the edge portion 7 does not come into contact with the die early, the rolling progresses while the fluidity of the material is high, and the radially inner corner 11 is likely to be filled with the material.

However, the manufacturing method of this embodiment is not limited to the case where the boundary position between the first upper mold 2 and the second upper mold 3 coincides with the boundary between the center portion 6 and the edge portion 7 of the cylindrical material. Since the fluidity changes depending on the heating temperature, material composition, etc., even if the boundary between the first upper mold 2 and the second upper mold 3 does not coincide with the boundary between the central part 6 and the edge part 7 of the cylindrical material, the radial direction This is because in some cases the inner corners 11 can be filled with material. For example, as shown in FIG. 9, the boundary between the first upper mold 2 and the second upper mold 3 may be located at a position corresponding to the outer peripheral surface 9 of the cylindrical material 5 (rough forging).

[Second embodiment]
Next, a method for manufacturing a circular member according to the second embodiment will be described. Only points different from the first embodiment will be described below, and descriptions of the same points as the first embodiment will be omitted. First, the forging apparatus of 2nd Embodiment is demonstrated.

[Forging equipment]
FIG. 10 is a cross-sectional view of the forging device 1 of the second embodiment. Referring to FIG. 10, lower die 4 of forging apparatus 1 includes a first lower die 4A and a second lower die 4B.

The first lower mold 4A has a shape corresponding to the central portion of the rough forging after forming.

The second lower mold 4B is arranged outside the first lower mold 4A in the radial direction of the cylindrical material 5 . The second lower die 4B has a shape corresponding to the edge of the rough forging after molding. The second lower mold 4B is connected to the first lower mold 4A via an elastic member 12. As shown in FIG. The elastic member 12 supports the second lower mold 4B so as to be vertically movable. Elastic member 12 is, for example, a spring, a hydraulic device, or the like. Before pressing down the cylindrical material 5, the upper surface of the second lower mold 4B is located below the upper surface of the first lower mold 4A.

[Production method]
Next, a method for manufacturing a circular member according to the second embodiment will be described. The method for manufacturing a circular material according to the second embodiment uses the forging apparatus 1 according to the second embodiment described above. The manufacturing method of the circular member of the second embodiment includes a pressurizing step in addition to the manufacturing method of the first embodiment. A method for manufacturing a circular member according to the second embodiment will be described below with reference to FIGS. 11 to 13. FIG.

[Pressurization process]
Referring to FIG. 11, in the manufacturing method of the second embodiment, as in the first embodiment, first, a central part pressing step of pressing down the central part 6 of the cylindrical material 5, the outer peripheral surface of the edge part 7 of the cylindrical material 5 is A constraining step is performed to constrain radial deformation of 9 .

After the constraint step, the side wall portion 8 of the second upper mold 3 constrains the radially outward deformation of the cylindrical material 5. Therefore, when the central portion 6 of the cylindrical material 5 is further pressed down by the first upper mold 2, , the material flows vertically at the edge 7 . When the material flows in the vertical direction, the lower surface of the edge portion 7 comes into contact with the second lower mold 4B because the second lower mold 4B is arranged below the edge portion 7 .

Referring to FIG. 12, after the lower surface of the edge portion 7 comes into contact with the second lower die 4B, when the first upper die 2 presses down the central portion 6 of the cylindrical material 5, the material moves vertically at the edge portion 7. Although it tries to flow, the downward flow of the material is suppressed by the second lower mold 4B. As a result, the material of the edge portion 7 of the columnar blank 5, which was about to move downward, now flows upward. The upward flow of the material at the edge 7 also causes the second upper mold 3 to slide relative to the first upper mold 2 . When the first upper mold 2 is further lowered from this state, the upward sliding of the second upper mold 3 is completed (the different speed reduction step is completed), and the first upper mold 2 and the second upper mold 3 are the same. The column material 5 is rolled down at a downward speed (the same speed rolling process is performed).

When the first upper mold 2 and the second upper mold 3 press down the cylindrical material 5 at the same descending speed, the material flows downward at the edge 7 of the cylindrical material 5, pushing the second lower mold 4B downward. Moving. At this time, since the second lower mold 4B is supported by the elastic member 12, the second lower mold 4B applies an upward force to the edge 7 of the cylindrical material 5. As shown in FIG. In this state, the first upper mold 2 and the second upper mold 3 reach the bottom dead center as shown in FIG.

As described above, according to the method of manufacturing the circular member of the second embodiment, the second lower mold 4B suppresses the downward flow of the material at the edge 7 of the columnar blank 5 . Further, even after the second upper die 3 has finished sliding, the pressing action of the second lower die 4B supported by the contracting elastic member 12 applies an upward force to the edge 7 of the cylindrical material 5. continue. Therefore, the material of the edge portion 7 of the columnar material 5 can easily flow upward, and the lack of thickness in the area above the edge portion of the circular material, which is the product, is further suppressed.

In addition, the corner region formed by the first lower mold 4A, the second lower mold 4B and the second upper mold 3 is pressed upward by the second lower mold 4B against the edge 7 of the cylindrical material 5. Since the molding can be performed early, the lack of thickness in the region below the edge of the circular product, which is the product, is also suppressed.

In the second embodiment described above, the case where the upward sliding of the second upper mold 3 ends after the lower surface of the edge portion 7 of the cylindrical material 5 comes into contact with the second lower mold 4B has been described. However, the lower surface of the edge portion 7 of the cylindrical blank 5 may contact the second lower mold 4B after the upward sliding of the second upper mold 3 is completed. In short, the pressurizing process may be performed after the central portion reduction process, and the timing thereof may be appropriately set.

The method for manufacturing the circular member according to the present embodiment has been described above. In addition, the present invention is not limited to the above embodiments, and it goes without saying that various modifications are possible without departing from the scope of the present invention.

For example, in each of the above-described embodiments, the case of manufacturing a circular material by hot forging has been described, but the method for manufacturing a circular material of the present invention is not limited to this, and when manufacturing a circular material by cold forging can also be applied. In this case, the heating step in each of the above-described embodiments is omitted.

1: forging device 2: first upper die 3: second upper die 4: lower die 5: cylindrical material 6: central part 7: edge part 8: side wall part 9: outer peripheral surface

Claims (5)

A method of manufacturing a circular member from a cylindrical blank including a central portion and an edge portion having an outer peripheral surface, the method comprising:
pressing down the central portion of the cylindrical material to radially deform the cylindrical material;
constraining the radial deformation of the radially deforming cylindrical blank;
After the step of constraining the radial deformation of the columnar blank, the step of further rolling down the central portion of the columnar blank and rolling down the edge portion of the columnar blank at a lower rolling speed than the rolling speed of the central portion. When,
A method for manufacturing a circular material, comprising: after the step of rolling down the edge portion, rolling down the center portion and the edge portion of the cylindrical material at the same rolling speed. A method for manufacturing a circular member according to claim 1, further comprising:
a first upper mold;
A second upper die which includes a side wall portion facing the outer peripheral surface of the cylindrical blank, is arranged radially outside the cylindrical blank relative to the first upper die, and is slidable in the rolling direction with respect to the first upper die. type and
placing the cylindrical material in a forging device including a lower die facing the first upper die and the second upper die;
In the step of radially deforming the cylindrical material, the first upper die presses down the central portion of the cylindrical material,
In the step of constraining radial deformation of the columnar blank, the side wall portion of the second upper mold is in contact with the outer peripheral surface of the columnar blank to constrain the radial deformation of the columnar blank;
In the step of rolling down the center portion of the cylindrical material and rolling down the edge portion of the cylindrical material at a rolling speed lower than the rolling speed of the central portion, the first upper die is rolled down at a lowering speed than the lowering speed of the first upper die. 2. A method for manufacturing a circular material, in which the upper die presses down the edge of the cylindrical material. A method for manufacturing a circular member according to claim 2,
In the step of rolling down the central portion and the edge portion of the cylindrical material at the same rolling speed, the first upper die reaches the bottom dead center at the same time as the second upper die. The method for manufacturing a circular member according to any one of claims 1 to 3, further comprising:
A method for manufacturing a circular member, comprising a step of applying pressure to the edge portion of the columnar blank in a direction opposite to a pressing direction after the step of radially deforming the columnar blank. A method for manufacturing a circular member according to claim 2 or 3, further comprising:
After the step of radially deforming the cylindrical material, a step of pressing the edge of the cylindrical material in a direction opposite to the rolling direction,
The lower die of the forging device includes a first lower die and a second lower die arranged outside the first lower die in the radial direction of the cylindrical material and attached to the first lower die via an elastic member. including a lower mold;
In the step of pressing the edge of the cylindrical material in a direction opposite to the rolling direction, the second lower mold presses the edge of the cylindrical material.

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