JPS61119636A - Electrode wire for electric spark machining and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an electrode wire for electric spark machining having a high rate of electric spark machining by using a Cu-SrB6 alloy contg. a specified amount of SrB6 of a specified particle size or below. CONSTITUTION:SrB6 is added to Cu powder by 0.1-5wt%, and they are mechanically mixed to form particles of Cu contg. uniformly dispersed SrB6 of <=1mum particle size. The particles are reduced and compacted, and the green compact is hot extruded and cold drawn to obtain an electrode wire for electric spark machining. Electrolytic Cu powder of 100 mesh is generally used as the Cu powder.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to an electrode wire for electric discharge machining, particularly to an electrode wire for wire-cut electric discharge machining.

<Conventional technology> Electrical discharge machining involves applying an intermittent high voltage (pulse voltage) between the electrodes to generate transient electrical discharges (spark discharges) one after another.
As a result, the electrode, which becomes the workpiece, is consumed and processed.

One type of electrical discharge machining is wire-cut electrical discharge machining, which is a processing method that uses a metal wire as an electrode and operates it like a jig saw to cut out a required shape. In recent years, with the development of numerical control (NC) technology as a means of controlling machine tools, wire-cut electric discharge machining has rapidly developed in fields such as press cutting dies and narrow slit machining. .

Wire-cut electrical discharge machining is particularly suitable for continuous machining of workpieces such as press molds that have complex and precise shapes.

In this electrical discharge machining, the finished surface condition and dimensional accuracy of the workpiece are required to be good, the electrode wire does not adhere to the workpiece, and the machining speed is high.

In particular, if the efficiency of electrical discharge that occurs between the electrode wire operated like a jig saw and the workpiece is improved, the machining speed can be increased and highly accurate machining with a good finished surface condition can be achieved.

For this reason, various materials for the electrode wire have been studied, and hard copper wire, 65/35 brass wire, tungsten wire, etc. have been used for conventional electrode wires.

However, all of these wires have poor processing speeds, and in particular, hard copper wire and 65/35 brass wire have the disadvantage of a large amount of adhesion to the workpiece, and tungsten wire has the disadvantage of being expensive.

Attempts have been made to add various additive elements to improve the processing speed of 65/35 brass wire, but to date, no examples have shown sufficient effects.

SrB6 has a small work function and was thought to improve discharge characteristics, but there was no way to use SrBB itself as a wire material for wire cutting.

In other words, the conventional manufacturing method for a composite agent is Cu powder and Sr.
This is because the manufacturing method involves mixing B6 powder and sintering it as is. According to this manufacturing method, the dispersion of Cu and SrB6 is not uniform, and the SrB6 particles are large, so when wire is drawn into a thin wire. This may cause disconnection of Cu-SrB.
It was not practical as a wire material for wire-cut electrodes made of 6 alloy.

<Problems to be Solved by the Invention> An object of the present invention is to eliminate such drawbacks and provide an electrode wire for electrical discharge machining with a high electrical discharge machining speed and a method for manufacturing the same.

<Brief explanation of the invention> Such objects are achieved by the following invention.

That is, in the first invention, SrB6 having a particle size of 1 to 5. This is an electrode wire for electric discharge machining, characterized in that it is made of a Cu-SrB6 alloy containing Owt%.

The second invention is 0.1 to 5. Owt% of SrB6 powder and Cu powder (remainder) are mechanically mixed (mechanical alloying) to form Cu powder with a particle size of 1 #Lm or less.

This method of manufacturing an electrode wire for electric discharge machining is characterized in that particles in which SrB6 is homogeneously dispersed are prepared, and the particles are reduced, compacted, hot extruded, and then cold drawn.

Means for Solving the Problem> The present invention provides SrB6 with a particle size of IILm or less in a form of 0.1 to 5
The present invention aims to provide an electrode wire for electric discharge machining made of a SrB6-Cu alloy containing 0 wt%, and will be described in detail below along with a manufacturing method thereof.

The Cu powder used in the present invention may be produced by any method, and generally 100 mesh electrolytic Cu powder is used.
Use powder.

The SrB6 powder mixed with this Cu powder is for reducing the work function and increasing the discharge efficiency, and is 0.1 to 5. Owt% is added.

When SrB6 is less than 0.1 wt%, the amount of SrBa(7) added is small, the discharge characteristics are not improved, and the increase in machining speed, which is an effect of the present invention, is not observed.

SrB6 is 5. If it exceeds Owt%, the addition amount is too large and SrB6 aggregates are likely to be formed, and the wire diameter is 0.2■■φ.
It becomes impossible to draw even a thin wire.

The Cu and SrB6 powder mixture in proportions as mentioned above is
In particular, mechanical mixing is carried out for atomization of SrB6 and homogeneous mixing of Cu and SrB6.

For this mixing operation, it is preferable to use a mechanical dry mixer called an attriter shown in FIG.

In Fig. 1, l is a pot, 2 is an Ar gas inlet, 3 is an Ar gas outlet, 4 is an agitator arm, 5 is a shaft,
6 is a ball, and 7 and 8 are the cooling water inlet and outlet of the water jacket 9, respectively.

It goes without saying that the attritor is not limited to the above-mentioned attritor, and a conventional mechanical mixer such as a vibrating ball mill or a centrifugal ball mill may be used.

What is important is that in this mixing operation, SrB in Cu
6 becomes fine particles with a particle size of 14 m or less and is mixed homogeneously,
It becomes a state similar to a kind of alloy.

The reason why the grain size of SrB6 is limited to 1IL11 or less is that if the grain size exceeds the diameter lIL11, the SrB6 grain size will be too large and uniform discharge will not occur, making it impossible to increase the machining speed. be. Furthermore, the uniform dispersion of fine SrBa makes it difficult for dislocations introduced by wire drawing to move, thereby increasing the strength of the wire.

Next, as described above, S with a particle size of one body layer or less is added to Cu.
The dispersion mixture in which rBH is homogeneously dispersed is granulated into particles having a particle size that can be easily processed later by wire drawing.

The particle size of this dispersed mixture is not particularly limited, but
Generally, it is granulated to about 16 to 60 meshes.

The particles thus obtained are subjected to a conventional wire drawing process, an example of which will be described below, or by other suitable wire drawing processes to obtain an electrode wire for electrical discharge machining.

(1) Reduction Reduction is carried out at 350-800°C for 2 hours in a hydrogen stream.

(2) After powder reduction, temperature 350~Booo℃, pressure 5~100Kg/
The powder is compacted into a billet of the required size in an Ar atmosphere with a volume of 2.

(3) The billet obtained by hot extrusion is heated to 1,500 to 900 in an Ar atmosphere.
After heating to a temperature of 300-600°C, the container is extruded into a desired shape such as a round bar.

Regarding extrusion processing, in addition to normal hot extrusion, the particles obtained by mixing are fed into a continuous extruder called a conform, which combines a rotating wheel and a shoe, and extruded, followed by wire drawing. good.

(4) Wire drawing The obtained round bar-like extruded wire is subjected to cold wire drawing.
For example, the wire is drawn into a thin wire of 1.8 mm diameter, then intermediate annealing is performed at 200 to SOO℃ for 2 hours in a N2 atmosphere, and the wire is further drawn to a wire of, for example, 0.2 mta diameter. .

EXAMPLE 1150 mesh electrolytic Cu powder and -350 mesh SrB6 powder were placed in the dry mixer called 7 Tritor mentioned above and mixed at a rotational speed of 30 rpm for 5 hours.

Here, the internal volume of the attritor pot is 5 cm, the pole diameter is 3/8 inch, the pole material is SUJ 2, and the pole weight is 17.5 kg.The pot is water-cooled, and the atmosphere during mixing is Ar. It was an air current.

The compositions of the raw materials in the mixer were varied as shown in Table 2.

After 5 hours of mixing, the Cu powder and SrB6 powder were completely mechanically mixed, and as a result of examining the cross section of the particles with a 400x optical microscope, the particle size of the SrB6 particles was less than 1 l. Ta. Further, the particle size of the mixed particles was 1007791 or more.

After reducing the mixed particles in a hydrogen stream at 800°C for 1 hour, the temperature was 500°C and the pressure was 100Kg/+w+w2.
It was compacted into a billet with a diameter of 30 mm and a length of 80 mm in an Ar atmosphere. After heating this billet to 900°C in an Ar atmosphere, the diameter of the billet was 71°C at a container temperature of 500°C.
It was extruded into a round bar of 1Ilφ. This round bar was cold-drawn to form S amφ, intermediately annealed in N2 at 400°C for 1 hour, and further wire-drawn to form a diameter of 0-2m5+.
It was made into a line of φ.

Using the various electrode wires thus obtained, electrical discharge machining experiments were conducted under the electrical discharge machining conditions shown in Table 1.

Table 2 summarizes the extrusion results, wire drawing results, and electrical discharge machining results.

Note that the electrical discharge machining results are shown by comparing the machining speed with that when Cu wire is used.

As is clear from Table 2, the examples of the present invention all exhibit good extrudability and wire drawability, and the processing speed is also C.
This is a large increase compared to the U-line.

In contrast, those containing 0.05 wt% SrB6 (
In Comparative Example 8), the extrudability and wire drawability were good, but the improvement in processing speed was not remarkable, and 8.0 wt% Sr
In the case containing B6 (Comparative Example 9), the processing speed was improved, but the extrudability was poor, and wire breakage occurred frequently during wire drawing.
It cannot be processed into wire rods.

In addition, as another comparative example, a Cu-3wt%SrB6 alloy was manufactured by the conventional casting method (
Comparative Example 1O), in which SrB6 wrapped in copper foil was added to molten Cu and stirred to produce M. This cast billet was heated to 900°C and then hot extruded at a container temperature of 500°C. The extruded rod with a diameter of 7 mm was processed to a diameter of 0.2 mm in the same process as in the example described above.

However, the extruded material was partially cracked and broke frequently during wire drawing, so it could not be used for processing experiments.

When the disconnected part is observed with an optical microscope, it has a diameter of about 50 to 100 mm.
Six giant SrB grains of ILs+ were observed.

<Effect of the invention> As in the unreleased product, S with a particle size of 1 μm or less is contained in Cu.
rB6 from 0.1 to 5. Owt% homogeneously dispersed Cu-
Electrical discharge machining electrode wire made of SrB6 alloy provides many advantages as described below.

Since the particle size of SrB6 added to Cu is as fine as 1 size or less, wire breakage during wire drawing processes such as extrusion and wire drawing was eliminated, and the 1 yield was improved.

Similarly, the processing speed when used as an electrode wire was significantly improved (approximately twice that of copper wire).

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an attritor used for mechanical mixing. Explanation of symbols 1...Pot, 2...Ar gas inlet, 3...Ar
Gas outlet, 4... Agitator arm, 5... Shaft, 6... Pole, 7... Cooling water inlet, 8... Cooling water outlet, 9... Water jacket FIG, 1

Claims (2)

[Claims] (1) 0.1 to 5.0 SrB_6 with a particle size of 1 μm or less
An electrode wire for electrical discharge machining, characterized in that it is made of a Cu-SrB_6 alloy containing wt%. (2) 0.1 to 5.0 wt% SrB_6 powder and Cu powder (remainder) are mechanically mixed to produce particles in which SrB_6 with a particle size of 1 μm or less is uniformly dispersed in Cu, and these particles are reduced. A method for manufacturing an electrode wire for electric discharge machining, which comprises cold wire drawing after powder compaction and hot extrusion.