JPS59104237A - Forming method of rough material for forging - Google Patents

Abstract

PURPOSE:To prevent die cracking and to improve the accuracy in forming by setting the shape of a rough material so as to form a gap between both side parts in the central part of the rough material for forging and a die surface and relieving the initial plastic deformation generated near the mating surface of the top and bottom dies. CONSTITUTION:A required gap (e) is formed between the outside peripheral surface of a rough material 6 for forging and the die surface near the mating surface of a top die 1 and a bottom die 2, and the rough material 6 having the shape resembling approximately to the shape of the die surface is forged. Such material 6 is inserted between the die 1 and the die 2 which are positioned oppositely to each other and are formed with depressed parts. The material 6 is then formed under pressure by the die 1 and the die 2. The moment relating to die cracking is thus generated in the final stage of forming, whereby the deformation of the dies 1, 2 is minimized, the die cracking is prevented as far as possible and the accuracy in forming is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forging rough material for forming a rough material into a uniform forging die material as a pre-step for forging the rack shaft in the manufacturing process of a rank shaft in a power steering device, for example. This relates to a method of forming materials.

Conventionally, in order to form this type of raw material for forging into a substantially uniform die shape, for example, as shown in FIG. Recesses (Ia) facing each other in (1) and lower mold (2)
, (2a) are formed respectively, and these upper and lower molds (1),
(2), the rough material for forging (
3) Transport all the parts and use the upper and lower molds (1) and (2) to roughen them (3).
) is clamped and pressure-molded to form a mold material (4) as shown in Figure 6.
’).

In such a conventional method for forming the forging material (3), the forging material (3) carried between the upper and lower dies (11, (2)
8) is the concave portion (1a) of the upper and lower molds (1) and (2) as described above.

Since the mold surface shape is almost the same as that formed by (2a), when the upper and lower molds (1) and (2) are clamped, the joint opening between these upper and lower molds (1) and (2) As shown in Fig. 2, in the vicinity of the upper and lower molds (1), large moments (restrictions occur and these moments) (M) are concentrated in both directions before obtaining the molded material (4'). .

Concave portions (1a) and (2a) near the mating portion of (2)
) Due to the load applied to the inner wall, the concave part (2a) of the lower mold (2)
) This resulted in mold cracking at the bottom. For this reason,
In the conventional molding method, this mold side i''L is prevented by increasing the mold strength of the upper and lower molds (1) and (2) and applying pressing force from the outside to the peripheral side of the mold. Reinforcement measures must be taken to maintain a predetermined pressure in the molded portion, resulting in a high waste of energy.

In view of the above-mentioned drawbacks, the present invention provides a rough forging material having a shape substantially similar to the mold surface shape defined by both of these concave portions, between an upper die and a lower die in which concave portions facing each other are formed. In the method for forming a forging raw material in which a uniform forging material is obtained by press-forming the raw material using the upper mold and the lower mold, A method for forming a raw material for forging, characterized in that a required gap is formed in advance between the upper and lower mold surfaces near the mating openings to prevent mold cracking when pressurized. This is what we are trying to provide.

Hereinafter, an embodiment in which the present invention is applied to a rack shaft of a power steering device will be described. As a finished product, this rack shaft is forged as a rack shaft (5) having rack teeth (4) at the top as shown in Figure 5, but this method is performed as a pre-process to this forging process. As shown in FIGS. 3 and 4, the above-mentioned recesses (1a) and (2a) formed in the upper and lower molds (1) and (2) have a unique circumferential shape as described below. All of the rough material for forging (6) is brought in and pressure-formed.

As is not particularly clear in Fig. 6, this forged raw material (6) basically has an actual volume of the upper and lower molds <1).
+ Although it is set to match the mold surface volume at the time of joining (2), the flat top part (6a) where the rack teeth (4) are to be formed is ) is formed in a vertically elongated shape with the bottom surface of the concave portion (1a) of the upper die (1) in contact with the bottom surface of the concave portion (1a). Then, this raw material for forging (
Both sides and the lower surface of 6) are composed of two linear parts (6b) and (6c) sequentially connected to the top part (6a), and a semicircular part (6d) further connected to this, and this semicircular part The shaped part (2) is centered at a center point (0') eccentrically downward from the recess center point fO) of the recessed part (2a) in the lower mold <2) K, and the radius of the recessed part (2a) (R□ ) smaller radius (
R2) is formed as a circular arc-shaped portion. Therefore, when carrying the raw material for forging (6) with such a circumferential shape between the upper and lower molds (1) and (2), a crescent-shaped, i.e., upper and lower mold (1) )
, (2) A gap (e) is formed that gradually narrows upward and downward with the mating surface as the center.

Therefore, the raw material for forging (6) having the above structure is used in the upper and lower molds (1
) l (2) When press forming by inserting between
, The largest lateral plastic deformation occurs near the joint opening in (2), but since JN is the largest between this part and the mold surface, the moment that occurs in this part and leads to the mold cracking described above is is adjusted so that it occurs at the final stage of molding, making it possible to prevent mold cracking as much as possible. Therefore, it is possible to save the energy equivalent to the force required to suppress the mold peripheral surface in the conventional mold, and to improve molding accuracy by minimizing the deformation of the upper and lower molds (1> + (2)). becomes.

As described above, according to the present invention, it is possible to provide a method for forming a raw material for forging, which can prevent mold cracking during forming and improve forming accuracy.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a conventional method for forming a rough material for forging, Fig. 2 is a sectional view similar to Fig. 1, and shows a state in which the coarse material for forging is carried into the upper and lower dies, and Fig. 3 is a perspective view of the present invention. FIG. 4 is a cross-sectional view similar to FIG. 2, showing a method for forming a raw material for forging according to an embodiment, and FIG. 4 shows a state of the raw material for forging in FIG. FIG. 5 is a perspective view showing a rank shaft with rank teeth formed as a final forged product, and FIG. 6 is a sectional view showing a state in which the upper and lower dies are joined together in an embodiment according to the present invention. It is. (1): Upper mold (2) Second lower mold (6): Rough material for forging (e) Two gaps? -11.] Figure 2 1n Figure 3 City 5 Figure 6 Cause

Claims (2)

[Claims] (1) A forging material having a shape almost similar to the mold surface shape defined by both of these concave portions is inserted between an upper die and a lower die in which concave portions facing each other at C are formed. , in a method for forming a rough material for forging in which a uniform forging die material is obtained by pressure-forming the coarse phase with the upper die and the lower die, the shape of the coarse phase is adjusted by adjusting the shape of the coarse phase by aligning the outer circumferential surface of the coarse phase with the upper and lower dies. A method for forming a raw material for forging, characterized in that a required gap is formed in advance between the mold surface near the mouth and mold cracking during pressurization is prevented. (2) The method for forming a raw material for forging according to claim 1, characterized in that the gap is gradually reduced along the bottom direction of the concave portion of the upper and lower dies.