JPH11123444A - Manufacture of extruding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove pore and microcrack generated by electric discharge machining and to prolong the die life by removing an affected layer by electric discharging which is formed on the machined surface by grinding after cutting a master disk for dies into a required shape by electric discharge machining. SOLUTION: The core 21 of a male die 4 is cut out from the master disk consisting of WC-Co of 3 mm in thickness, for example, into the required shape by wire cut electric discharge machining. After the wire cut electric discharge machining, by grinding between hollow forming parts 24, 24 with emery paper #600 which is slenderly cut for 10 min, the affected layer by electric discharging which is formed on the machined surface is removed. It is not necessary to execute grinding on the whole of the machined surface by electric discharging and executed to the fragile part where stress at the time of extrusion is concentrated. For example, in a combined die 2, the root of joint in the hollow forming part 24 of the core 21 of the male die 4 is ground. Because the thickness of the affected layer by electric discharging is the order of several to several tens mm, the depth of grinding is taken as the same order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion die suitably used for extrusion molding of a hollow material, and relates to a method for producing an extrusion die capable of suppressing cracks and extending the life.

[0002]

2. Description of the Related Art For example, when a flat porous tube (1) as shown in FIG. 1 is manufactured by extrusion molding, generally, a male mold for forming a hollow portion (1a) in the tube and a tube of the tube are used. A combination die is used which is combined with a female mold for forming an outer peripheral portion. And furthermore, the manufacture of a small and elaborate flat perforated tube used as a tube for a heat exchanger facilitates the manufacture of a miniaturized die,
In order to reduce the cost of replacing the dies due to wear and the like, a combination of a male die and a core that forms the hollow portion (1a) of the tube (1) and a holding die that holds the core. Dice are used.

In the combination die (2) illustrated in FIGS. 2 and 3, the female die (3) has an elliptical flat forming hole (11) for forming the outer periphery of the flat porous tube (1). Welding for joining and welding extruded materials which are arranged adjacent to the rear part of the female main body mold (12) having the core part and the female main body mold (12) and have passed through the male mold (4). It comprises a welding chamber forming mold (14) for forming the chamber (13) and a cylindrical housing mold (15) for housing both the molds (12) and (14).

[0004] In the male mold (4), (21) is a core, (22) is a core holding mold, and (23) is a lid.

As shown in FIG. 3, the core (21) has a flat shape, and a plurality of hollow forming portions (24) (24) for forming the hollow portion (1a) of the flat porous tube (1) at its tip. Are formed in a comb shape, and a support protrusion (25) projecting in the width direction is formed at a base end portion.

The core holding die (22) is provided with a bridge (26) in such a manner as to cross an extruded material conducting hole (not shown) in the axis of the core. This is an integrally molded mold divided into (not shown). And
The bridge (25) has a flat core holding hole (2) for holding the core (21) in a mode penetrating the bridge (25) in the extrusion direction.
7) is provided. The core holding hole (27) has a support step (28) (28) formed at a base end thereof, and the projecting portion (2) of the core (21) when the core (21) is inserted and arranged.
5) and (25) are to be supported by the bearing steps (28) and (28).

[0007] The rear end face of the bridge (26) of the core holding mold (22) is retracted into the mold (22), and the lid (23) is fitted therein. A lid fitting recess (29) is formed.

By the way, as the material of the core (21), a cemented carbide or the like is used in order to secure wear resistance and durability.
It is common to cut and manufacture a flat hard master into a required shape. Moreover, since it is an elaborate and small die, the comb-shaped hollow molded part (24) is cut out by electric discharge machining such as wire electric discharge machining with high machining accuracy.

[0009]

However, in the above-mentioned combination die (2), there is a problem that the die (2) is liable to be broken at the base of the tip forming portion (24) of the core (21). This is because the discharge-altered layer formed on the machined surface during electric discharge machining is a layer containing many pores and microcracks, so that the core material surface does not have the original material strength of the super hard and the stress during extrusion is concentrated It is presumed that it will be broken at the base of the joint. Also, if there is a discharge alteration layer, the superhardness is easily eluted during caustic cleaning after use of the die, which also causes a decrease in the strength of the core.

The present invention has been made in view of such technical background,
An object of the present invention is to provide a method for manufacturing an extrusion die that can be extended in life while being formed by electric discharge machining.

[0011]

In order to achieve the above object, a method for manufacturing an extrusion die according to the present invention is to cut a die master into a required shape by electric discharge machining, and then form a discharge-altered layer formed on a machining surface. Is removed by polishing.

The material of the die to which the method of the present invention can be applied is not limited as long as it is usually used as a die material and can be cut by electric discharge machining, and examples thereof include various cemented carbides and various die steels.

In the electric discharge machining, the kind of the electrode to be used is not limited, such as a wire cutting method or a graphite method. But,
In particular, the wire cutting method is suitable for the production of precise small dies because the processing accuracy is excellent.

Further, it is not always necessary to apply the polishing to the entire electric discharge machined surface, but by applying the polishing to a portion where the stress at the time of extrusion is likely to be broken due to concentration, the life of the extrusion die can be extended. For example, in the combination die (2) shown in FIGS. 2 and 3, it is possible to extend the life of the die by polishing the base of the hollow molded portion (24) of the core (21) of the male die (4). it can. The polishing method is not particularly limited, and examples thereof include polishing with emery paper, polishing with a diamond tool, gum polishing, shot blast using fine glass beads, and polishing with an ultrasonic tool. Since the polishing depth is about several μm to several tens of μm, the thickness of the discharge altered layer formed by electric discharge machining,
The same level.

According to the method of the present invention, the discharge-altered layer having a reduced strength generated by electric discharge machining is removed, so that the original strength of the material is exhibited on the die surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A combination die (2) shown in FIGS.
, A core (21) of a male type (4) was manufactured. The core was cut into a required shape from a 3 mm-thick master made of WC-Co by wire-cut electric discharge machining.

In the embodiment, after the wire cut electric discharge machining, the hollow formed portions (24) and (24) are polished for 10 minutes using 600 # emery paper having a long and thin cut to remove the discharge altered layer formed on the machined surface. did. On the other hand, in the comparative example,
No polishing treatment was performed on the core of the same shape after wire cut electric discharge machining.

Next, these cores are assembled in a combination die, and a flat porous tube (1) shown in FIG. 1 is extruded using A1100 aluminum. The sex was evaluated. As a result, the core of the example could extrude 5000 kg in three extrusions, whereas the comparative example in which the discharge-altered layer was left could extrude only 700 kg in one extrusion. .

As in this embodiment, if the polishing is performed at least at the base of the hollow molded portion of the core where stress during extrusion is concentrated, the durability of the die can be improved. By polishing other parts and the female mold, the extrusion die can be made harder to break and the durability can be improved.

[0020]

As described above, the method for manufacturing an extrusion die according to the present invention is to cut a die master into a required shape by electric discharge machining, and then remove the discharge-altered layer formed on the machining surface by polishing. Therefore, pores and microcracks generated by electric discharge machining are removed, the original strength of the die material is developed, and the life of the die can be extended.

[Brief description of the drawings]

FIG. 1 is a perspective view of a flat perforated tube.

FIG. 2 is a cross-sectional view of a combination die for extruding a hollow material.

FIG. 3 is a perspective view of a core incorporated in the male die of the combination die of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Flat perforated tube 2 ... Combination die 3 ... Female type 4 ... Male type 21 ... Core

Claims (1)

[Claims] 1. A method for manufacturing an extrusion die, comprising cutting a die master into a required shape by electric discharge machining, and removing a discharge-altered layer formed on a machining surface by polishing.