JPH07178493A - Die for cold forging - Google Patents

Abstract

PURPOSE:To prevention of burrs in the forming, and to surely and easily avoid generation of cracks breakage, or the like in a die member. CONSTITUTION:A die is provided with a lower die 16 and an upper die 18, and the lower die 16 and the upper die 18 are provided with a split part 34 where one end side is arranged at the part corresponding to the inner end part of the outer circumference of the formed shape of a cavity 20, and the other end side is inclined outward to the press-fit direction of a punch 22, A first abutting surface 36 and a second abutting surface 38 are provided continuous to the other end part of this split part 34, and this constitution prevents the forming pressure from being applied in the vicinity of the first abutting surface 36 and the second abutting surface 38.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is directed to a first bonded structure.
The present invention relates to a cold forging die in which a material is disposed in a forging cavity formed in a die member and a second die member, and the material is subjected to cold forging under a press-fitting action of a pressing die.

[0002]

2. Description of the Related Art Generally, cold forging is to obtain a forged product having a predetermined shape by applying a pressing force to the material with a mold member at room temperature or below the recrystallization temperature of the material. It is widely used because of its advantages such as improved hardness and improved product accuracy and mass production.

Since cold forging is applied with a higher pressure than hot forging, durability is required. Therefore, usually, the upper die member and the lower die member made of steel or ultra high speed steel are joined to each other, and the material is placed in the forging cavity formed in the upper die member and the lower die member. The punch is press-fitted from above, and the material is cold forged.

By the way, the contact surfaces of the upper mold member and the lower mold member are set by the shape of the molded product so as to correspond to the inner end of the outer periphery of the molded shape. Therefore, the upper mold member and the lower mold member are easily separated from each other by the plastic flow of the material at the time of plastic working, and burrs are generated on the contact surfaces of these members, which causes deterioration of the quality of the molded product. Moreover, since the contact surfaces of the upper mold member and the lower mold member are end surfaces, respectively, a large compressive stress cannot be obtained in the vicinity of the contact surfaces. As a result, in the vicinity of the contact surface, the circumferential stress generated during molding cannot be countered, and there is a problem that radial cracks (vertical cracks) occur in the upper mold member or the lower mold member.

Therefore, as shown in FIG. 6, a lower die (lower die member) 2 has an R-shaped portion 4 corresponding to the bottom of the molded product.
Is provided, and a contact surface 8 between the lower die 2 and the upper die (upper die member) 6 is formed at the end of the R-shaped portion 4, whereby the flow of material moving from the bottom to the outer peripheral surface of the molded product. Has become possible.

[0006]

However, in the above-mentioned conventional technique, cracks 9 are generated in the circumferential direction due to the concentrated stress acting on the corner portion of the R-shaped portion 4 as the frequency of use increases. The problem has been pointed out. Moreover,
In the lower die 2 and the upper die 6, there is a problem that radial cracks occur near the contact surface 8 due to the circumferential stress generated during molding.

The present invention is intended to solve this kind of problem, and can prevent burrs from being generated during molding, and can reliably and easily prevent cracks or breaks from occurring in the mold member. An object is to provide a cold forging die that can be avoided.

[0008]

In order to achieve the above object, the present invention provides a forging cavity formed on a first mold member and a second mold member which are joined to each other, in which a material is arranged and pressed. A die for cold forging in which cold forging is performed on the material under the action of press-fitting a die, wherein the first die member and the second die member are inside the outer periphery of the forming shape of the forging cavity. A split portion is provided, one end side of which is disposed at a portion corresponding to the end portion and the other end side of which is inclined outward with respect to the press-fitting direction of the pressing die, and which is continuous with the other inclined end portion of the split portion. Then, a contact surface between the first mold member and the second mold member is provided.

Further, it is preferable that the divided portion has a gap from the one end side to the other end side.

Furthermore, the first die member has a first wall surface forming the forging cavity and extending toward the dividing portion, and the second die member forms the forging cavity. Second extending toward the dividing portion
An angle formed at the forging cavity side at a virtual intersection of the first wall surface and the second wall surface is an obtuse angle,
Moreover, it is preferable that an end of the second wall surface on the side of the divided portion extends from the virtual intersection to the side of the first mold member.

[0011]

In the cold forging die according to the present invention, the pressing die is pressed from the portion corresponding to the inner end of the outer shape of the forging cavity where the divided portion of the first die member and the second die member is located. It extends in a direction inclined outward with respect to the press-fitting direction of. Therefore, the divided portion is oriented in a direction substantially opposite to the plastic flow direction of the material at the time of forming, and it is possible to prevent burrs from being generated at the divided portion at the time of forming. Moreover, since the contact surfaces of the first mold member and the second mold member are continuously provided to the other inclined end portion of the divided portion, this contact surface is effectively separated from the molding surface for actual molding. The stress at the time of molding does not act in the vicinity of the contact surface. Therefore, it is possible to reliably prevent the first mold member and the second mold member from being cracked or broken, and it is possible to effectively use the mold for a long period of time.

Further, the gap provided from one end side to the other end side in the divided portion can effectively alleviate (absorb) the stress generated at the time of molding, and excessive stress is not partially concentrated. . Furthermore, since the angle formed between the wall surfaces of the first mold member and the second mold member is an obtuse angle, the plastic flow of the material is smoothly performed, and it is possible to reliably prevent burrs from occurring. Become.

[0013]

EXAMPLES Examples of a cold forging die according to the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a cold forging die according to the present embodiment. The die 10 is joined to a die holder 12 through a fastening means 14, and is placed on the die holder 12. A lower die (first die member) 16 and an upper die (second die member) 18 to be installed, a forging cavity 20 formed on the lower die 16 and the upper die 18, and a cavity 20 for this. A punch (pressing die) 22 for pressurizing the material W, and a knockout pin 24 for advancing and retracting the die holder 12 to push out a molded product are provided.

As shown in FIG. 2, the lower die 16 forms a cavity 20, and the first wall surface 2 is inclined toward the punch 22 with respect to the radial direction of the cavity 20.
Have six. The upper die 18 has a second wall surface 28 that forms the cavity 20 and extends in the axial direction of the punch 22 (direction of arrow A). As shown in FIG. 3, the second wall surface 28 extends further from the imaginary intersection P with the extension of the first wall surface 26 in the direction of arrow A by a length L. The angle α formed on the cavity 20 side is set to be an obtuse angle.

A first sloped surface portion 30 and a second sloped surface portion 32 are provided by bending from the ends of the first wall surface 26 and the second wall surface 28, respectively. The first sloped surface portion 30 and the second sloped surface portion 3 are provided.
The divided portion 34 is formed by 2. This dividing unit 34
One end is arranged at a portion corresponding to the inner end 20a on the outer periphery of the molded shape of the cavity 20, and the other end is punched 22.
Is inclined outward with respect to the press-fitting direction (direction of arrow A), and a predetermined gap C is provided from this one end side to the other end side (see FIG. 3).

The punch 22 is provided at the other end of the first inclined surface portion 30.
Is provided with a first contact surface 36 directed in the diametrical direction (arrow B direction), and the other end of the second inclined surface portion 32 is also directed in the arrow B direction and is attached to the first contact surface 36. A second contact surface 38 that contacts is formed.

Next, the operation of the cold forging die 10 thus constructed will be described.

First, as shown in FIG. 1, the material W is placed in the cavity 20 with the punch 22 placed in the raised position. Then, the punch 22 is lowered, and the cold forging process is performed on the material W through the punch 22, the lower die 16 and the upper die 18.

At this time, as shown in FIGS. 2 and 3, the material W plastically flows in the direction indicated by the arrow through the pressing force of the punch 22, the lower die 16 and the upper die 18. Therefore, in the present embodiment, the first slanted surface portion 30 and the second slanted surface portion 32 that form the dividing portion 34 are made of the material W.
Since it is directed in a direction substantially opposite to the plastic flow direction of No. 3, it is possible to surely prevent burrs from being generated in the divided portion 34 and to smoothly flow the material W. Is obtained.

Further, the first contact surface 36 of the lower die 16
The second contact surface 38 of the upper die 18 is provided continuously to the other inclined end portion of the dividing portion 34. Therefore, in the upper die 18, the distance H from the second contact surface 38 to the end portion of the second wall surface 28 that is actually used as the molding surface becomes considerably long, and cracks or cracks are generated in the upper die 18 during molding. It is possible to prevent the occurrence of cracks and the like.

That is, FIG. 4 shows a conventional upper die 6
FIG. 5 shows the distribution of the compressive stress in the circumferential direction after press fitting when using, while FIG. 5 shows the compression in the circumferential direction after press fitting when using the upper die 18 according to the present embodiment. The stress distribution is shown. Here, in the conventional upper die 6, the entire inner peripheral surface is the molding surface, and the compressive stress particularly near the die contact surface 6a is considerably weakened. Therefore, when the upper die 6 is used, this die contact surface 6a
Cracks and fractures tend to occur in the vicinity. On the other hand, in the upper die 18 of the present embodiment, the molding surface is in the range of the distance L ₀ excluding the second inclined surface portion 32, and sufficient compressive stress can be secured in this range, so It becomes possible to endure effectively. This prevents the upper die 18 from being cracked or broken and the mold 1
The effect that the whole 0 can be utilized efficiently over a long period of time is obtained.

Further, a predetermined gap C is provided between the first inclined surface portion 30 and the second inclined surface portion 32 forming the divided portion 34. Therefore, the stress acting on the lower die 16 at the time of molding is absorbed by the gap C and effectively relaxed, and the excessive stress is not partially concentrated on the lower die 16, and cracks or cracks are generated in the lower die 16. It is possible to avoid the occurrence of cracks and the like.

Furthermore, the first wall surface 26 and the second wall surface 28
The angle α formed by the second wall surface 28 becomes obtuse.
Extends below the virtual intersection P. Therefore, the material W
The molding work can be performed more smoothly and reliably, and the occurrence of burrs can be further reduced.

[0025]

According to the die for cold forging according to the present invention,
The divided portion of the first die member and the second die member extends from a portion corresponding to the inner end of the outer periphery of the forming shape of the forging cavity in a direction inclined outward with respect to the press-fitting direction of the pressing die. ing. For this reason, the divided portion is oriented in a direction substantially opposite to the plastic flow direction of the material at the time of molding, and it is possible to prevent burrs from being generated at the divided portion at the time of molding as much as possible. Liquidity can be maintained smoothly. Moreover, since the contact surfaces of the first mold member and the second mold member are continuously provided to the other inclined end portion of the divided portion, this contact surface is effectively separated from the molding surface for actual molding. The stress at the time of molding does not act in the vicinity of the contact surface. Therefore, it is possible to reliably prevent the first mold member and the second mold member from being cracked or broken, and it is possible to effectively use the mold for a long period of time.

Further, the gap provided from one end side to the other end side of the divided portion can effectively alleviate the stress generated at the time of molding, and excessive stress is not partially concentrated. Furthermore, since the angle formed between the wall surfaces of the first mold member and the second mold member is an obtuse angle, the plastic flow of the material can be performed more smoothly, and burrs can be reliably prevented. become.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of a cold forging die according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional explanatory view of a main part of the mold.

FIG. 3 is an enlarged explanatory view of a split portion and a contact surface that constitute the mold.

FIG. 4 is an explanatory diagram of compressive stress of a conventional upper die.

FIG. 5 is an explanatory diagram of compressive stress of the upper die according to the present embodiment.

FIG. 6 is a vertical cross-sectional explanatory view of a conventional mold.

[Explanation of symbols]

10 ... Mold 16 ... Lower die 18 ... Upper die 20 ... Cavity 22 ... Punch 26, 28 ... Wall surface 30, 32 ... Inclined surface part 34 ... Dividing part 36, 38 ... Contact surface

Claims (3)

[Claims] 1. A material is disposed in a forging cavity formed in a first mold member and a second mold member joined to each other,
A cold forging die that performs cold forging on the material under the press-fitting action of a pressing die, wherein the first die member and the second die member are inward of an outer periphery of a forming shape of the forging cavity. The one end side is arranged at a portion corresponding to the side end part, and the other end side is provided with a dividing part that is inclined outward with respect to the press-fitting direction of the pressing die, and the other end part of the dividing part that is inclined is provided. A die for cold forging, characterized in that contact surfaces of the first die member and the second die member are continuously provided. 2. The mold for cold forging according to claim 1, wherein the dividing portion has a gap from the one end side to the other end side. 3. The mold according to claim 1, wherein the first mold member has a first wall surface that forms the forging cavity and extends toward the dividing portion, and the second mold. The member has a second wall surface that forms the forging cavity and extends toward the dividing portion, and an angle formed on the forging cavity side at an imaginary intersection of the first wall surface and the second wall surface is A cold forging die, wherein the die has an obtuse angle and an end portion of the second wall surface on the side of the divided portion extends from the virtual intersection to the side of the first die member.