JPH08300066A - Production of die - Google Patents

Abstract

PURPOSE: To produce a long life die having high wear resistance by removing the softened layer generated at surface of working face of die produced with bobbing-heat treatment or by making deep work hardening layer. CONSTITUTION: Electro-discharge machining, shot peening or shot peening + electro-discharge machining is executed on the work face of die produced by bobbing-heat treatment by the use of a general tool steel such as hot die steel, high speed tool steel, etc. The softened layer existed on surface layer of bobbing formed face having complicated shape is removed by electro-discharge machining, etc., because very deep work hardened layer is obtained by finish working of shot peening, shot peening + electro-discharge machining, etc., the die life of all warm and hot forging is extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a long-life die using tool steel such as cold die steel, hot die steel, and high speed steel.

[0002]

2. Description of the Related Art When heat-treating a die manufactured by hobbing, it is difficult to finish the work surface, leaving a decarburized layer, or the residual strain causes the surface structure to become coarse, resulting in a low surface hardness. There are many. Especially for complex type elegance such as gear type, since mechanical finishing is not possible, it is usually used as it is, or soft nitriding treatment, C
Surface effect treatment is performed by VD, PVD, or the like. However, when used in this state, the surface of the mold is often sagged, or the desired effect cannot be obtained because the effective cured layer of the surface treatment is shallow.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a die manufactured by hobbing using hot die steel, tool steel such as high-speed steel, and finishing by machining by electric discharge machining, The present invention proposes a method of manufacturing a long-life mold that removes softening layers and irregularities on the mold work surface to prevent sagging. Hobbing molding-shot peening after heat treatment, or electrical discharge machining after shot peening,
The present invention proposes a method of manufacturing a die having a further long life by performing a finishing process by machining to form a deep work-hardened layer.

[0004]

The mold surface (work surface) molded by hobbing has a problem that a coarse structure appears on the surface layer due to strain concentration on the decarburized layer or the surface layer. Generally, it is difficult to machine and finish the hobbing surface in terms of the shape of the mold to be hobbed. Further, there are cases where the softened layer cannot be removed sufficiently by only chemical surface treatment.

According to the present invention, a deep effective work hardened layer is produced by removing a softening layer existing on a work surface after hobbing-heat treatment by electric discharge machining or by finish processing by shot peening or shot peening + electric discharge machining. This makes it possible to extend the life of the mold.

FIG. 1 shows the hardness distribution near the surface layer when JIS-SKD62 is manufactured by warm hobbing (850 ° C.).

A softened layer due to decarburization can be confirmed up to a depth of about 200 μm from the surface. Further, in the case of forming by cold hobbing, it is often confirmed that the structure near the surface layer is coarsened by subsequent quenching.

Such a softening layer is difficult to remove by machining or the like when hobbing a complex shaped product.

In FIG. 2, JIS-SKD62 was hobbed (extruded backward) at 600 ° C., and then tempered twice at 575 ° C. for 60 minutes. The mold was shot peened with HRC62-0.2 mm hard balls for 60 seconds. The hardness distribution of the thing is shown. The measurement was performed on the side of the machined surface.

It can be confirmed from FIG. 2 that the effective hardened layer is usually about several tens of microns in the soft nitriding treatment, whereas it is possible to obtain a very deep hardened layer in the shot peening.

However, the shot peening process causes the surface of the mold to become slightly rough, so the mold life may not be extended as expected unless some surface treatment is applied.

FIG. 3 shows the relationship between the number of heat cracks and surface finishing treatment, which is one of the items for evaluating die life in hot forging. By the way, the die is JIS-SKD.
62 was manufactured by warm hobbing at 600 ° C., quenched (1030 ° C. × 30 min) -tempered (575 ° C. × 1)
After 80 min), only (1) shot blasting,
(2) Shot blast + electric discharge machining, (3) shot peening, (4) shot peening + lathe machining. The forging temperature was 1000 ° C., and the heat crack measurement location was at the portion of the drawing where the load was applied most.

From the results shown in FIG. 3, the effects of removing the surface softening layer, shot peening, or shot peening + surface finishing can be confirmed.

【Example】

In order to further clarify the present invention, the detailed description of the embodiments will be given below. Table 1 shows JIS-SKD62-bevel gear type warm hobbing (forging temperature 600 ° C.)-Quenching (1030 ° C. × 30 minutes / oil cooling) -tempering (600 ° C.
After 90 minutes / AC 2 times), the actual machine test results when each surface treatment was performed are shown. The surface treatment is (A)
These are shot blasting, (B) shot blasting + electric discharge machining, (C) shot peening, and (D) shot peening + electric discharge machining.

[0015]

[Table 1]

From the results shown in Table 1, it can be confirmed that the surface hardness is higher and the mold life is extended when the surface is finished.

It can be confirmed that the die life is extended by performing electrical discharge finishing, shot peening, or shot peening + electrical discharge finishing on the work surface of the die made by hobbing as in the above embodiments.

The embodiment of the present invention has been described in detail above, but this is merely an example, and the present invention can be implemented in a mode in which various modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the invention. .

EFFECT OF THE INVENTION By the method of manufacturing a mold according to the present invention,
Hobbing-Since the softened layer on the mold surface generated after heat treatment can be completely removed, the mold life can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a hardness distribution near a surface after warm hobbing.

FIG. 2 is a diagram showing a hardness distribution when shot peening is performed after hobbing.

FIG. 3 is a diagram showing the relationship between the surface finishing treatment of the mold and the number of heat cracks.

Claims (3)

[Claims] 1. A tool life, such as hot die steel and high-speed steel, is improved by subjecting a work surface of a die manufactured by hobbing to electrical discharge machining or machining. Manufacturing method. 2. A manufacturing method for improving the life of a mold by subjecting a work surface of a mold manufactured by hobbing to shot peening using tool steel such as hot die steel and high speed steel. 3. A workpiece surface of a die manufactured by hobbing using tool steel such as hot die steel and high speed steel is subjected to shot peening and then electrical discharge machining or machining finishing. A manufacturing method for improving the life of a mold.