JPH115137A - Manufacturing method of forging with hollow shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a forging with a Y-shaped part; wherein a durable life of a cope for finish forging is prolonged and the stroke of finishing forging is shortened. Also, the number of the interruptions of manufacture is reduced. SOLUTION: In the first preforging process of a roughly finished member 3 with a shaft part 31, a yoke part 32 and a shallow hole 33, the yoke part 32 is processed into the shape of a finished product. In the second preforging process of the roughly finished member, the second roughly finished member 4 with an extended shaft part 41 which holds a deep hole 43 is formed by extruding the shaft part 31. In the finishing forging process, the yoke part 42 is processed finally to obtain a forging with the hollow shaft by inserting a finishing punch into the deep hole 43, wherein the punch's end does not reach the bottom of the deep hole 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forged product having a hollow shaft having a forked U-shaped, forked V-shaped or cup-shaped yoke, such as a sleeve yoke or a steering yoke, and a shaft with a hole. And a method for producing the same.

[0002]

2. Description of the Related Art The prior art will be described below using a sleeve yoke as an example. (1) Forging Method for Extending Shaft by Forward Extrusion Molding Conventionally, in the process of forging a sleeve yoke, first, a round bar material is forged and a first rough ground material 3 as shown in FIG.
To manufacture. The first waste material 3 includes a shaft 31 and a shaft 3
1. A fork U-shaped yoke 32 provided at one end of
And a shallow hole 33 formed in the crotch portion of the yoke portion 32 in the axial direction.
And

Then, in the step shown in FIG. 11, the first waste material 3 is forged to obtain a second waste material 4 as shown in FIG. In this step, as shown in FIG.
The yoke portion is finish-formed while the shaft portion 31 of the first waste material 3 in the hot state is inserted into the cavity of the forging die, and the punch type C3P is pushed into the shallow hole 33 to thereby form the shallow hole 3.
3 is deformed deeply, and the shaft 31 is extended in the pushing direction (the direction of the arrow in FIG. 11). By this step, FIG.
A second rough ground material 4 having an extension shaft portion 41 having a deep hole 43 as shown in FIG. 2 is obtained. Thereafter, a sleeve yoke is manufactured by removing burrs on the outer periphery of the yoke portion and penetrating the deep hole 43 near the end of the upper air extension shaft portion 41.

However, in this forging method, when the punch type C3P is pushed into the shallow hole 33 and the shaft portion 31 is stretched by elongation, the shaft portion 31 is stretched by a tensile force depending on forging conditions.
In some cases, necking and tearing occurred. Therefore, there is a problem that the forging line of the extension shaft portion 41 is also broken, which is disadvantageous in securing the strength of the sleeve yoke.

Further, in the conventional forging method, a punch type C3
When the P is inserted into the shallow hole 33, if there is a misalignment between the shallow hole 33 and the shaft portion 31, uneven thickness is promoted at the time of forming the deep hole, and a bending force is applied to the punch type C3P, and the punch type C3
There was a problem that P broke. Therefore, in this forging method, there is a limit to the depth of the deep hole 43 in an attempt to reduce uneven thickness of the extension shaft portion 41 and breakage of the punch die, and when the length of the extension shaft portion 41 is increased, as shown in FIG. Thus, it is necessary to provide the reverse hole 44 on the opposite side of the deep hole 43 as well.

(2) Forging method for extending the shaft portion by backward extrusion molding As a forging method which has solved the above-mentioned problems, Japanese Patent Laid-Open No. 2-18 / 1990
There is a forging method as shown in Japanese Patent No. 7230. That is, in the step of deeply deforming the shallow hole 33 by the punch type C3P and at the same time elongating the shaft portion 31, as shown in FIG. 13, the yoke portion 32 of the first rough ground material 3 is unconstrained, and the lower die C3L is closed. The end 3 of the shaft 31 by the cavity (recess)
13b, the punch C3P is pushed into the shallow hole 33, and at the same time, the material of the shaft portion 31 is opened in the cavity opening direction of the lower mold (the direction opposite to the pushing direction of the punch C3P, the direction of the arrow in FIG. 13). This is a forging method of extruding backward to ()).

According to the present forging method, the material of the shaft portion 31 is extruded from the bottom of the cavity of the lower mold C3L toward the opening, whereby the shaft portion 31 is extended. For this reason, in the present method, the problem of tearing of the extension shaft portion 41 and uneven thickness does not occur. Then, after the shallow hole 33 is deeply deformed and the shaft portion 31 is extended, as shown in FIG. 14, the point of finishing and forging the second rough ground material 4 is the same as the forging method by the forward extrusion molding described above.

[0008]

As shown in FIG. 14, a finish die used for finish forging the second rough ground material 4 is a finish die C5U for finish-forming a yoke portion and the like.
And a finishing punch portion C5P for preventing deformation of the deep hole 43 and finish forming the inside of the deep hole 43. And usually, FIG.
As shown in FIG. 4, the finishing punch portion C5P is a finishing die C5U.
And reaches the bottom of the deep hole 43 during insertion.

However, the finish punch portion C5P receives a compressive force as a reaction force from the bottom of the deep hole 43 and a bending force as a reaction force from a side portion of the deep hole 43 at the time of finish forging. . For this reason, the finishing punch portion C4P is
Stress concentrates on the base protruding from 5U, and the life of the finishing punch portion C5P and the finishing die C5U is shortened.

Recently, the length of the extension shaft portion 41 of the product (sleeve yoke) has been increased in order to improve the transmission torque, and the length of the finished punch type C5P has been increased accordingly. Therefore, the stress applied to the finishing punch C5P and the finishing die C5U by bending and compression is further increased, and as a result, cracks and breakage are increased.

Furthermore, if the length of the finishing punch portion C5P is long, the finishing punch portion C5P and the finishing die C5L for installing the second waste material 4 and taking out the finishing forged material 5 after finishing forging are provided. The gap between them becomes small, and it becomes difficult to take out the above-mentioned installation and finish forged material 5. On the other hand, the finish punch portion C5P is pulled out from the deep hole 53 of the finish forged material 5,
A long-stroke forging machine (a so-called long-stroke-type press) that can create a large gap and can be lifted with a sufficient interval that does not interfere with the finished forging material 5 is required. For this reason, a general-purpose forging machine cannot be used. Also,
Finishing punch portion C inserted into deep hole 43 of second waste material 4
Since the length 5P is long, the finish punch portion C5P sticks in the deep hole 53 after the finish forging, so that the die cannot be removed, and the production work is temporarily interrupted (so-called "choco stop").

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of extending the life of an upper die used in finish forging, shortening the stroke required for finish forging, and further reducing the manufacturing time. An object of the present invention is to provide a method for manufacturing a forged product having a hollow shaft, which can reduce temporary interruption.

[0013]

According to the first aspect of the present invention,
A method for manufacturing a forged product having a hollow shaft, comprising the following steps. First, in a first wasteland material manufacturing process, a first wasteland material having a shaft portion, a yoke portion provided at one end of the shaft portion, and a shallow hole provided axially in a crotch portion of the yoke portion is provided. obtain. In this step, the shape of the yoke is processed to a product shape when the yoke is formed. Here, the “axial direction” refers to the longitudinal direction of the shaft portion. “Processing to a product shape” refers to roughly processing a shape to a finished shape excluding a rounded portion, a flash rounded portion, or the like at a corner portion processed in a finishing process.

Thereafter, in the second rough ground material manufacturing process, the shaft portion of the first rough ground material is inserted into a rough ground recess provided in a rough underground mold, so that the tip and the outer periphery of the shaft portion are substantially restrained. The yoke portion of the first rough ground material is unconstrained, and a punch is pressed into the shallow hole in the axial direction to deform the shallow hole deeply. An extension shaft having a deep hole is formed by extruding the shaft portion backward in the opening direction of the wasteland concave portion and extending the shaft portion so that the shaft portion having a shallow hole of the first wasteland material is an extension shaft portion having a deep hole. To obtain a second wasteland material.

Next, in the finish forging step, the distal end and the side outer periphery of the elongated shaft are substantially restrained by inserting the elongated shaft of the second rough ground material into a finishing recess provided in a finishing die. While inserting a finishing punch having a cross-sectional shape in which the inner wall of the deep hole of the extension shaft portion is in a substantially restrained state and having a length not reaching the bottom of the deep hole into the deep hole, a finishing die and a finishing The yoke is finished with a lower die to obtain a finished forged product having a hollow shaft.

The invention according to claim 2 includes the first rough ground material manufacturing step, the second rough ground material manufacturing step, and a finish forging step, and further includes the deep hole after the finish forging step. And a shaft hole penetrating step of penetrating at an end of the elongated shaft portion.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a method for manufacturing a forged product according to the present invention is applied to a sleeve yoke will be described below with reference to FIGS. (1) Production of Intermediate Material First, a round bar 1 having a diameter of about 60 mm and a length of about 80 mm shown in FIG. 4 was used, and the round bar 1 was upset and forged to form a shaft 21 and a large diameter shown in FIG. The intermediate member 2 including the head 22 is obtained. In this step, as in the prior art, the shaft portion is extruded forward, and the volume distribution of the yoke portion and the shaft portion is performed. The material of the round bar 1 is, for example, carbon steel, alloy steel, or the like. However, the material to be processed in the present invention can be appropriately selected and may be any material that can be forged.

(2) Manufacture of first waste material Next, the intermediate material 2 is forged in a hot state to obtain a first waste material 3 as shown in FIG. The first waste material 3 includes a shaft portion 31.
And a thick-walled yoke portion 32 provided at an end 31a of the shaft portion 31 and forming a bifurcated U-shape, and a shallow hole 33 formed in the crotch portion of the yoke portion 32 in the axial direction. In addition, the shallow hole 33 of the first waste material 3 has a role of guiding the insertion of the punch type D3P in the second waste material manufacturing process. Also, this shallow hole 3
The hole depth of No. 3 is set so as to be formed deeper than the upper surface of the lower die D3L during the backward extrusion in the second waste material manufacturing process.

In this step, when the yoke portion 32 is formed, the shape of the yoke portion 32 is roughly processed to a finished shape except for corner rounds and flash rounds. In other words, conventionally, in this step, the shallow hole drilling of the shaft portion and the rough shaping of the yoke portion are performed.
Forming is performed up to the roughly finished shape of 2.

In this step, since the shape of the yoke portion 32 is roughly processed to a finished shape, in the finish forging process described later, the finishing process is performed without greatly deforming the second rough ground material. be able to. Here, in the present embodiment, the dimension L1 from the end face of the other end 31b of the shaft section 31 to the intermediate position of the yoke section 32 is about 125.6 mm (124 mm to 127 mm), and the width dimension L2 of the yoke section 32 is It is around 76 mm (74 mm to 78 mm).

(3) Manufacture of the second rough ground material (second rough ground material manufacturing step) Next, in the second rough ground material manufacturing step, as shown in FIGS. Is inserted into the cavity D3L1 of the lower mold D3L, and the end 31 of the shaft portion 31 of the crude material 3 is inserted.
b is brought into contact with the bottom mold surface D3La of the lower mold D3L and restrained. At this time, the outer peripheral surface 31d of the shaft portion 31 is the lower mold D3.
It faces the side mold surface D3Lb of L via a predetermined clearance.

The yoke portion 32 of the first rough ground material 3
As shown in FIG. 1, there is no contact with any of the mold surfaces, and the mold is in an unconstrained state. The lower mold D3L in this step corresponds to the “rough underground mold” described in the claims,
The cavity D3L1 corresponds to a “landscape recess”.

In this state, the pressing device is operated to insert the punch type D3P into the shallow hole 33 of the first waste material 3 in a hot state.
Is forcibly pushed in the depth direction of the shallow hole 33. As a result,
The outer peripheral surface 31d of the shaft portion 31 surrounding the shallow hole 33 is extruded and pressed against the side mold surface D3Lb of the lower mold D3L, and the shallow hole 33 is deeply deformed.

Further, the material of the shaft portion 31 surrounding the punch D3P is pushed backward in the cavity D3L1 in a direction opposite to the pushing direction of the punch D3P, that is, in the direction of the arrow shown in FIG. In this case, since the end surface of the other end portion 31b of the shaft portion 31 is constrained by the bottom die surface D3La of the lower die D3L, the pushing amount of the punch die D3P is opposite to the pushing direction of the punch die D3P. It substantially corresponds to the backward extrusion amount pushed backward in the direction. The punch type D3P in this step corresponds to the “punch type” described in the claims.

As a result, as shown in FIG. 2, the shaft portion 31 extends in the longitudinal direction and surrounds the outer surface of the punch type D3P from the outside, and as a result, has a deep hole 43 as shown in FIG. The second waste material 4 having the extension shaft portion 41 is obtained. still,
In the second rough ground material 4 shown in FIG. 7, a dimension L4 between the end surface of the end portion 41 b of the extension shaft portion 41 and an intermediate position between the yoke portion 42.
Is about 145.1 mm (144 mm to 147 mm), and the width L5 of the yoke part 42 is about 76 mm (74 m).
m to 78 mm).

In this step, the yoke portion 3 of the first waste material 3
Since the punch-type D3P is pushed into the shallow hole 33 and the material of the shaft 31 is pushed backward while the 2 is in an unconstrained state, no tensile force acts on the shaft 31. In addition, it is possible to avoid the occurrence of necking and tearing when forming the extension shaft portion 41. Further, the strength of the product is also improved because the forging line of the extension shaft portion 41 flows uniformly in the axial direction.

Also, in this step, when the punch type D3P is pushed into the shallow hole 33 and the material of the shaft portion 31 is extruded backward, a method is adopted in which the yoke portion 32 is in an unconstrained state. The rear extrusion part can escape to the rear,
The backward extrusion phenomenon can be effectively performed. Therefore,
It is possible to prevent an excessive load from acting on the punch type D3P at the time of backward extrusion, and to reduce or avoid the eccentricity of the punch type D3P at the time of backward extrusion. For this reason, it is advantageous in suppressing uneven thickness of the extension shaft portion 41 of the second rough ground material 4.

FIG. 9 is a side view of the punch type D3P. As shown in FIG. 9, the punch type D3P has a collar portion D3P1.
And a large diameter portion D3P2, a conical portion D3P3, and a rod portion D3P4. At the tip of the rod D3P4, a rod D3
A bulge D3P protruding from the end of the trunk D3P4a of P4
4b is formed. In addition, the bulging portion D3P4b is the second
The outer diameter is set smaller than the rod portion D3P4 in order to prevent sticking and seizure to the second waste material at the time of forging the waste material.

(4) Finish Forging Step After the above-mentioned second waste material manufacturing step is completed, a finish forging step as shown in FIG. 3 is performed. In the finish forging step, as shown in FIG. 3, the extension shaft portion 41 of the second rough ground material 4 is inserted into the cavity D5L1 of the finishing die D5L, and the end portion 41b thereof.
Is constrained by the bottom die surface D5Lb of the finishing die D5L. Then, in this state, the finishing die D5U is brought close to the finishing die D5L, and the yoke portion 42 of the second rough ground material 4 is restrained by the yoke upper die surface D5Ua and the yoke lower die surface D5La.
The finishing punch type D5P is inserted into the deep hole 53. that time,
The tip D5Pa of the finishing punch type D5P does not reach the bottom of the deep hole 53.

According to this step, the yoke portion 4 of the second waste material 4
2 and the extension shaft portion 41 are finish forged, and the dimensions of the yoke portion 42 and the extension shaft portion 41 are adjusted to predetermined values.
2 and the forged material 5 of the elongated portion 51 is formed. That is,
In this step, the yoke portion is formed by coining and the shaft portion is sized. This step corresponds to the “finish forging step” described in the claims. The finishing die D5L in this step corresponds to the “finishing die” described in the claims, and the cavity D5L1 corresponds to the “finishing recess”. The finish forging upper die D5U corresponds to the “finish finish die”, and the finish punch die D5P corresponds to the “finish punch”.

In the forging process of the present embodiment, the shape of the yoke is almost finished to a finished state in the manufacturing process of forming the yoke of the first rough ground material 3. For this reason, in the final finishing step, only the finishing processing such as the corner rounding or the flash rounding needs to be performed, and the second rough ground material 4 is not greatly deformed in the finishing processing. Therefore, at the time of finishing, the deformation due to the processing does not reach the vicinity of the distal end of the deep hole 53 of the second rough ground material 4, and it is necessary to constrain the inner surface of the deep hole 53 to the distal end (bottom) with the finishing punch D5P. There is no one. For this reason, the finish punch type D5P sufficiently achieves its purpose even if the tip does not reach the bottom of the deep hole 53.

In this step, since the tip D5Pa of the finished punch D5P does not reach the bottom of the deep hole 53, the finished punch D5P is directly subjected to a reaction force from the bottom during stamping. And does not receive compressive force from the tip. Further, since the length is shorter than the case where the tip reaches the bottom of the deep hole 53, it is less susceptible to bending stress and compressive stress at the time of pushing. Furthermore, deep hole 5
Since the length of the finishing punch D5P pushed into the inside 3 is short, the possibility that the finishing punch D5P sticks to the deep hole 53 can be eliminated.

In this embodiment, the length of the finishing punch D4P is 25 mm shorter than the hole depth.
The length of the finishing punch D5P need only be such that it does not reach the bottom of the deep hole 53, and may be even shorter as long as deformation in the deep hole 53 can be prevented. Also, if the shape of the product is difficult to process, it is assumed that some deformation processing is performed in this process,
This can be solved by making the length of the finishing punch type D4P closer to the bottom of the deep hole 43.

(5) Subsequent Processing Step After the finishing step, a shaft hole is formed in the end portion 51b of the elongated shaft portion 51 of the finished forged material 5 shown in FIG. Then, as shown in FIG. 8, a spline is formed at the peripheral portion of the deep hole 63 by machining thereafter, and the molded product 6 having the yoke portion 62 and the extension shaft portion 61 is obtained.

(6) Effect of the Forging Process of the Present Embodiment As described above, in the forging method of the present embodiment, when the forging method is inserted into the deep hole 43 of the second rough ground material 4, the tip is located at the bottom of the deep hole 43. Since the finishing punch type D5P which cannot be reached is employed, a strong compressive force does not act on the finishing punch type D5P from the tip as in the related art. Further, since the length of the finishing punch D5P is short, the compressive force, bending force, and the like acting on the finishing punch D5P when the punch is pressed into the deep hole 43 can be reduced. For this reason, the finishing punch D5U to the finishing punch D
The stress and the like acting on the portion where the 5P protrudes (the respective portions of the finishing die D5U and the finishing punch D5P) can be reduced.

Accordingly, it is possible to reduce breakage of the finished punch D5P and cracking of the finished D5U, and to prolong the life of the finished punch D5P and the finished D5U. Specifically, the finish punch D5P and the finish die D5U which have been exchanged in the past 2000 times have been replaced by 60
Can be used more than 00 times.

Further, since the finishing punch D5P is short, the stamping load is small and the contact area is small, so that the finishing punch D5P pushed into the deep hole 53 is
No more sticking. Therefore, finishing punch D
Temporary interruption of the work due to the deep hole 53 sticking to 5P (so-called "choco stop") can be eliminated.

Further, in the forging method of this embodiment, since the finishing punch D5P is short, the second waste material 4 is easily installed in the cavity D5L1 of the finishing D5L without being hindered by the finishing punch D5P. And can be easily taken out after processing. That is, in the forging process as in the present embodiment, the work (product) becomes longer (higher) in the later process. Therefore, in the final process (finish forging process), the length of the finishing punch facing the work is shortened and the gap between them is increased, so that a larger work can be installed and taken out, and the entire forging process can be performed. Can expand the manufacturing range (size of the work).

Further, in the forging process, the holes of the shaft portion and the extension shaft portion do not penetrate, and the deep hole of the extension shaft portion is made to penetrate after the forging process. Is possible. Therefore, by performing the rearward extrusion when the shaft portion is extended, the shaft portion can be extended without necking or tearing.
It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention according to the purpose and application. In the above-described embodiment, the present invention is applied to a sleeve yoke. However, the present invention is not limited to this, and it goes without saying that the present invention may be applied to the manufacture of a forged product having a hollow shaft such as a steering yoke.

[0040]

According to the method of manufacturing a forged product having a hollow shaft according to the present invention, the shape of the yoke is processed in advance to a finished shape, and in the finish forging step, the yoke reaches the bottom of the deep hole. Since a finishing punch that is not used is used, no strong compressive force or bending force acts on the finishing punch, and the life of the finishing punch and the finishing die can be extended. Further, since the finishing punch is short, the deep hole does not stick to the finishing punch pushed into the deep hole, and a temporary interruption of work (so-called choke stop) can be eliminated.

Since the finishing punch is short, the second waste material can be easily installed in the finishing recess of the finishing type.
It can be easily removed after processing. In addition, since the finishing punch is short, the stroke required for installing the second rough ground material in the finishing die in the forging machine and taking out the finished forged product after finishing forging can be shortened. A forged product having a long extension shaft, which has been difficult to produce, can be manufactured using a general-purpose forging machine.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a punch die is pushed into a shallow hole of a first rough ground material.

FIG. 2 is a cross-sectional view showing a state in which a material of a shaft is being pushed backward.

FIG. 3 is a sectional view showing a finish forging process.

FIG. 4 is a perspective view of a round bar.

FIG. 5 is a perspective view of an intermediate member.

FIG. 6 is a cross-sectional view of a first waste material.

FIG. 7 is a sectional view of a second waste material.

FIG. 8 is a sectional view of the yoke after machining.

FIG. 9 is a side view of a punch type.

FIG. 10 is a sectional view showing a conventional process.

FIG. 11 is a cross-sectional view showing a conventional process.

FIG. 12 is a sectional view showing a conventional process.

FIG. 13 is a cross-sectional view showing a conventional process.

FIG. 14 is a cross-sectional view showing a conventional process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Round bar material, 2; Intermediate material, 21; Shaft part, 22; Large diameter head, 3; First rough ground material, 31; Shaft part, 31a; End of shaft part 31, 31b; End portion, 31d; side outer peripheral surface of shaft portion 31, 32; yoke portion, 33; shallow hole, 4; finish forged material, 41; extension shaft portion, 41b; end portion of extension shaft portion 41, 4
2, yoke portion, 43; deep hole, 44; reverse hole, 5; finish casting, 51; extension shaft portion, 52; yoke portion, D3P; punch type, D3P1: collar portion, D3P2; large diameter portion, D3P3;
Conical part, D3P4; rod part, D3P4a; trunk, D3P4
b; bulging portion, D3L; lower die, D3L1; cavity (recess), D3La; bottom die surface of lower die D3L, D3Lb: side die surface of lower die D3L, D4U: finishing die, D4Ua: yoke upper die surface. D5P: Finishing punch type, D5Pa: Tip of finishing punch type D4P, D5L: Finishing vertical type, D5L1: Cavity (finish recess), D5La: Yoke lower mold surface, D5L
b: Bottom surface of finishing D5L, C3P: Punch type, C3
L: rough underground type, C4U: rough ground type, C4P: finishing punch portion, C4L: lower die, L1: dimension from the end face of end 31b to the intermediate position of yoke portion 32, L2: width dimension of yoke portion 32, L4: a dimension from the end face of the end 41b to an intermediate position between the yoke 42, and L5: a width of the yoke 42.

Continued on the front page (72) Inventor Shinji Takeda 1 Wanowari, Arao-cho, Tokai City, Aichi Prefecture Inside Aichi Steel Corporation

Claims (2)

[Claims] In the step of obtaining a first rough ground material having a shaft portion, a yoke portion provided at one end of the shaft portion, and a shallow hole provided in a crotch portion of the yoke portion in an axial direction. A first rough land material manufacturing step of processing the shape of the yoke part to a finished shape at the time of forming the yoke part, and thereafter, inserting the shaft part of the first rough ground material into a rough ground recess provided in a rough ground type The tip and the outer periphery of the shaft portion are made substantially constrained, the yoke portion of the first rough ground material is made unconstrained, and a punch die is pressed into the shallow hole in the axial direction, thereby forming the shallow hole. At the same time, the material of the shaft portion is extruded backward in the opening direction of the wasteland recess, the shaft portion is extended, and the shaft portion having the shallow hole of the first wasteland material is extended with the deep hole. A second wasteland material manufacturing process for obtaining a second wasteland material having an elongated shaft portion having a deep hole by using the shaft portion; Next, by inserting the extension shaft portion of the second rough ground material into a finishing recess provided in a finishing up / down mold, the distal end and the side outer periphery of the extension shaft portion are substantially restrained, and the deep hole of the extension shaft portion is formed. The yoke portion is finished by a finishing die and a finishing die while inserting a finishing punch having a cross-sectional shape in which the inner wall is substantially in a restrained state and having a length not reaching the bottom of the deep hole into the deep hole. A forging process having a hollow shaft for processing to obtain a forged product having a yoke portion. 2. A process for producing a first waste material, a second waste material production process, and a finish forging process, and further comprising, after the finish forging process, forming the deep hole into an end of the extension shaft portion. A method of manufacturing a forged product having a hollow shaft, the method comprising: