JP2002192290A - Die for forgoing and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce manufacturing cost by making a structure of a die simple, simplify press fitting work, and prevent the occurrence of galling, buckling or the like resulting from an excessive load in press fitting. SOLUTION: After hardening the whole of a single ring body 16 made up of alloy steel, induction hardening treatment is applied to the inner peripheral surface of the ring body 16, thereby forming a induction hardened part 18 whose hardness is HRC 45-60 and hardened layer is about 5-15 mm deep. A die made up of super hard steel is press fitted to the ring body 16 in which the induction hardened part 18 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forging die and a method for manufacturing a forging die in which a cavity is filled with a forging material and forging is performed under a pressing action on the forging material.

[0002]

2. Description of the Related Art Conventionally, there has been known a die for forging a forging material into a predetermined shape by loading a forging material into a cavity and applying a pressing force to the forging material via a punch. ing.

[0003] Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 5-136537 discloses a mold for cold forming. As shown in FIG. 5, this cold forming mold is
An upper mold 2 and a lower mold 3 made of cemented steel and having a cavity 1 formed therein; a first shrink fit ring body 4 shrink-fitted on the outer peripheral surfaces of the upper mold 2 and the lower mold 3; and the first shrink fit It is constituted by a plurality of members including a second shrink-fit ring body 5 further shrink-fitted on the outer peripheral surface of the ring body 4.

When a pressing force is applied to a forging material (not shown), a tensile stress and a compressive stress are applied to members constituting a cold-forming die. To prevent expansion, the first and second shrink-fit ring bodies 4, 5 are provided with a predetermined interference.

That is, in order to maintain the life of the mold due to the tensile stress and the compressive stress during forging, multiple ring bodies 4, 5 consisting of double and triple are press-fitted or shrink-fitted to form an upper mold 2 and a lower mold. By assembling with No. 3, a die for forging is formed.

[0006]

In the cold forming mold according to the prior art, the outer peripheral surfaces of the upper and lower dies into which the first shrink fit ring body is press-fitted, and the upper and lower dies. The first and second shrink-fit ring bodies respectively fitted to the mold are machined with respect to the press-fit surfaces of the ring bodies, respectively.
Further, after finishing the heat treatment, a polishing finish process is performed, and an integrated finish process and a surface polishing process are performed on the assembled assembly which is press-fitted to each other, thereby obtaining a finished cold-forming mold.

As described above, in the cold forming mold according to the prior art, various processes such as machining, heat treatment, and polishing finishing are performed on the upper and lower dies and the first and second shrink-fit rings. It is necessary to maintain the high precision, press-fit each and assemble them, and then perform an integral finishing process and a surface polishing process on the assembly.

[0008] Therefore, since the cold forming mold according to the prior art is completed through various manufacturing steps, there is a problem that the manufacturing cost increases due to a large number of steps.

Further, when press-fitting the first and second shrink-fitting ring bodies into the upper mold and the lower mold, the first and second shrink-fitting ring bodies are press-fitted by a large pressing force.
If the press-fitting work becomes complicated and the processing accuracy is poor, excessive load applied at the time of press-fitting may cause galling, buckling, etc. Has the disadvantage of adversely affecting

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described disadvantages, and simplifies the structure of a mold to reduce the manufacturing cost, simplifies the press-fitting operation, and furthermore, due to an excessive load at the time of press-fitting, it is possible to prevent a galling. It is an object of the present invention to provide a forging mold capable of preventing occurrence of buckling and the like, and a method of manufacturing the same.

[0011]

In order to achieve the above-mentioned object, the present invention provides a forging metal for forming a forged product by applying a pressing force to a forging material loaded in a cavity. In the mold, a die made of a metal material of cemented carbide, the cavity is formed, and a single ring body made of a metal material of a structural alloy steel and pressed into the outer peripheral surface of the die, After the entire ring body is quenched, the ring body is subjected to high-frequency quenching on the inner wall surface on which the outer peripheral surface of the die is press-fitted, and has a predetermined hardened layer. A part is provided.

In this case, it is preferable that the induction hardened portion has a hardness of HRC 45 to 60 and a hardened layer having a depth of about 5 mm to 15 mm.

Further, the present invention provides a method of manufacturing a forging die for forming a forged product by applying a pressing force to a forging material loaded in a cavity. After quenching the entire ring,
The inner peripheral surface of the ring body is subjected to induction hardening treatment to form an induction hardened portion having a hardness of HRC 45 to 60 and a hardened layer having a depth of about 5 mm to 15 mm. The forging die is assembled integrally by press-fitting a die made of cemented steel into the ring body having the portion formed therein.

According to the present invention, the rigidity and toughness can be improved by forming a double hardened layer composed of a hardened layer and an induction hardened layer on the press-fitting surface of a single ring body fitted to the die. Thus, a forging die having substantially the same rigidity and toughness as a forging die to which a double or triple ring body according to the prior art is externally fitted can be obtained.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a forging die and a method for manufacturing the same according to the present invention.

In FIG. 1, reference numeral 10 denotes a forging die manufactured by the method for manufacturing a forging die according to the embodiment of the present invention.

The forging die 10 is press-fitted into a die 14 having a cavity 12 (see FIG. 3) corresponding to a predetermined product shape (for example, a differential gear) and an outer peripheral surface of the die 14. And a ring body 16. In this case, the die 14 is formed of, for example, a metal material such as cemented steel, and the ring body 16 is
It is preferable to be formed of a metal material such as structural alloy steel.

The entire inner wall surface of the ring body 16 which is press-fitted in contact with the outer peripheral surface of the die 14 has a hardness of HRC 45 to 60 and a hardened layer having a depth of about 5 mm to 15 mm. 18 are preferably formed.

In this case, if the hardness of the induction hardened portion 18 is less than HRC45, there is a problem that the stress generated by the pressing force of a punch (not shown) is insufficient and the life of the mold is adversely affected. Is HRC60
If the ratio exceeds the limit, there is a problem that quenching cracking or insufficient toughness adversely affects the life of the mold.

If the depth of the hardened layer of the induction hardened portion 18 is less than about 5 mm, there is a problem that the strength is insufficient and the mold is adversely affected. On the other hand, the depth of the hardened layer is about 15 mm. If it exceeds, quenching becomes difficult.

Next, an embodiment of a forging die according to the present invention will be described below. Structural alloy steel (S
(NCM439) was subjected to a so-called hardening treatment to form a hardened hardened layer. The hardness of the hardened hardened layer was HRC41. further,
Using a high-frequency heating device (not shown), high-frequency quenching is performed only on the inner peripheral surface (press-fit portion) of the ring body on which the quench-hardened layer is formed, and a hardened layer having a hardness of HRC55 is obtained. The induction hardened part 18 having a length of about 10 mm was formed.

As shown in FIG. 2, the forging die 10 is integrally formed by press-fitting the die 14 into the hole of the ring body 16 thus formed.

As a result of forming a differential gear using the integrated forging die 10, the conventional die life was about 15,000, but the forging die according to the present embodiment was used. In No. 10, it was possible to increase the number to about 18,000 pieces, and it was found that the durability was equal to or longer than the conventional mold life.

In the present embodiment, a die 14 made of a metal material of cemented carbide and having a cavity surface, and a single ring body 16 pressed into the die 14 constitute a forging die 10. ing. In other words, in the present embodiment, the die 14 and one ring body 16 functioning as a single backup ring for the die 14
By forming a double hardened layer (induction hardened portion 18) composed of a hardened layer and an induction hardened layer on the press-fit surface of the ring body 16, both rigidity and toughness are achieved. And double or triple according to the prior art
A forging die 10 having substantially the same rigidity and toughness as the forging die to which the heavy ring body is fitted is obtained.

Therefore, it is sufficient to press-fit one ring body into the die without externally fitting a plurality of ring bodies as in the prior art, so that the number of parts can be reduced and the manufacturing cost can be reduced.

Further, in the present embodiment, it is not necessary to perform heat treatment, machining, and finishing such as polishing on a plurality of ring bodies, and heat treatment including induction hardening on one ring body 16 is not required. Since a finishing process such as machining or polishing may be performed, the manufacturing process is simplified, and the manufacturing cost can be further reduced.

Further, since only one ring body 16 is press-fitted into the die 14, the press-fitting operation is simplified, and the time required for the assembling process can be shortened to simplify the operation.

Further, by forming the high frequency hardened portion 18 on the inner peripheral surface of the ring body 16 which is press-fitted on the outer peripheral surface of the die 14, the occurrence of galling, buckling, etc. due to an excessive load at the time of press-fitting. Can be prevented.

Next, FIG. 4 shows a comparison result of the circumferential stress affecting the life of the forging die (not shown) according to the comparative example and the forging die 10 according to the present embodiment. Shown in

FIG. 4 shows a forging die according to a comparative example having a double ring system of an inner ring and an outer ring.
As shown by the broken line in the middle, a very large compressive stress is applied to the die, and the compressive stress is maintained at a high state even during molding, and particularly, a high tensile stress is applied to the outer ring.

On the other hand, in the forging die 10 according to the present embodiment, as shown by the solid line in FIG. 4, the rigidity and toughness of the backup ring are high at a position separated from the center by a predetermined distance. Therefore, it is understood that the circumferential stress is substantially uniform, and that there is sufficient durability.

[0032]

According to the present invention, the following effects can be obtained.

That is, by press-fitting a single ring into the die, the structure of the forging die can be simplified and the manufacturing cost can be reduced.

Further, by forming an induction hardened portion on the inner peripheral surface of the ring body pressed into the outer peripheral surface of the die,
It is possible to simplify the press-fitting operation and to prevent occurrence of galling, buckling, and the like due to an excessive load at the time of press-fitting.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a forging die manufactured by a method for manufacturing a forging die according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of the forging die of FIG. 1;

FIG. 3 is a plan view of the forging die apparatus as viewed from the direction of arrow A in FIG. 1;

FIG. 4 is an explanatory diagram comparing circumferential stresses of a forging die according to the present embodiment and a forging die according to a comparative example.

FIG. 5 is a longitudinal sectional view of a cold forming mold according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Forging die 12 ... Cavity 14 ... Die 16 ... Ring body 18 ... Induction hardening part

Claims (3)

[Claims] A forging die for forming a forged product by applying a pressing force to a forging material loaded in a cavity, wherein the cavity is formed of a metal material of cemented carbide. And a single ring body made of a metal material of structural alloy steel and pressed into the outer peripheral surface of the die, wherein the entire ring body is hardened in the ring body. A die for forging, wherein an induction hardening process is performed on an inner wall surface into which the outer peripheral surface of the die is press-fitted, and an induction hardened portion having a predetermined hardened layer is provided. 2. The forging die according to claim 1, wherein the induction hardened portion has a hardness of 45-60 HRC.
And a hardened layer having a depth of about 5 mm to 15 mm. 3. A method for manufacturing a forging die for forming a forged product by applying a pressing force to a forging material loaded in a cavity, the method comprising the steps of: After quenching, the inner peripheral surface of the ring body is subjected to induction hardening treatment to form an induction hardened portion having a hardness of HRC 45 to 60 and a depth of a hardened layer of about 5 to 15 mm. And, for the ring body on which the induction hardened part is formed,
A method for manufacturing a die for forging, characterized in that a die for forging is integrally assembled by press-fitting a die made of cemented steel.