JP3381955B2 - Electrode material for wire electric discharge machining - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material for wire electric discharge machining.

[0002]

2. Description of the Related Art For example, wire electric discharge machining is a machining technique used for die machining of cemented carbide and die steel for molding semiconductor lead frames, motor cores and the like, and machining of various parts. In this processing, a tension is applied by a predetermined load, and an electric current is applied between the wire and the workpiece to form a predetermined shape. Conventionally, the electrode wire generally used for this wire electric discharge machining has a diameter of 0.1 to 0.1 mm.
0.3mm brass wire and copper wire are used.

In recent years, higher precision machining is required, and for this high precision machining, it is necessary to further reduce the wire diameter of the electrode wire for wire electric discharge machining. However, in the wire electric discharge machining electrode wire made of the brass wire or copper wire, strength, for example, tensile strength is insufficient due to thinning, and the wire breaks, which is not suitable for thinning for high-precision machining. It was

Therefore, instead of the conventional wire electric discharge machining electrode wire made of brass wire or copper wire, a wire electric discharge machining electrode wire using a doped tungsten wire or molybdenum wire to which potassium, aluminum, silicon or the like is added. Is used. By using these tungsten wires and molybdenum wires, the wire diameter of the electrode wire for wire electric discharge machining can be reduced to 25 to 100 μm, generally 30 to 70 μm, which enables high-precision machining.

[0005]

However, electric discharge machining such as wire electric discharge machining is becoming more and more sophisticated in order to process minute or highly accurate parts such as ultra-compact gears for micromachines in recent years. Precision processing is required,
Even for wire electric discharge machining electrode wires having a wire diameter of 25 to 100 μm, further thinning of the wire electric discharge machining electrode wire is required.

However, in the case of an extra-fine wire electric discharge machining electrode wire in which a tungsten wire or a molybdenum wire is further thinned, the wire rod is broken during connection, or local discharge occurs due to discharge with a work material during electric discharge machining. Disconnection due to excessive heating,
Furthermore, the electrical discharge machining speed could not be increased.

In view of the above circumstances, the present invention provides an electrode material for wire electric discharge machining, which has excellent electric discharge machinability in conventional wire electric discharge machining and also in highly accurate wire electric discharge machining.

[0008]

The first aspect of the electric discharge machining electrode material of the present invention is, in weight%, a wire diameter of more than 1% of rhenium and 45% or less, and the balance being substantially tungsten.
It is less than 25 μm .

Further, in the second invention by weight percent of the electrical discharge machining electrode material of the present invention, rhenium from 0.2 to 45%, one selected further potassium <br/> um, aluminum and silicon or 2 A wire having a wire diameter of less than 25 μm, which is composed of 100 ppm or less of elements of at least one kind, and the balance is substantially tungsten.
The components of the present invention will be described below.

In the first and second aspects of the present invention, the addition of rhenium (Re) improves the tensile strength of tungsten (W) and, depending on the amount added, secondary recrystallization. This is to raise the temperature.

As a result, a very fine wire, specifically a wire diameter of 25
When it is possible to obtain a wire EDM electrode wire of less than μm, when arranging this wire EDM electrode wire on each part of the wire EDM machine when attaching to the wire EDM machine at room temperature before machining Is easy to handle, and problems such as disconnection at the time of installation do not occur, and even during electrical discharge machining, even if local heating occurs due to electrical discharge with the work material due to the high secondary recrystallization temperature, No problems such as wire breakage during electrical discharge machining occur.

[0012] Here, if the amount of Re is too small, there is no effect of addition, and conversely, if the amount is too large, not only expensive Re is consumed, but also the formation of a hard and brittle δ phase, etc. In order to reduce the workability for obtaining the electrode material,
In the first invention, when Re alone is added to W, the amount thereof is more than 1% by weight and 45% by weight, and in the second invention, it is selected from potassium (K), aluminum (Al) and silicon (Si). When one or more of them are added together, the amount thereof is set to 0.2 to 45% by weight.
If too much is added, the tensile strength is improved but the recrystallization temperature is lowered. Therefore, the preferable amount is 0.2-2.
It is 6% by weight, and more preferably 1 to 10% by weight.

Next, in the second invention, one or more elements selected from K, Al and Si are added to Re in order to further raise the secondary recrystallization temperature. By increasing the secondary recrystallization temperature, it becomes possible to increase the machining energy such as current for wire electric discharge machining higher, and as a result, it becomes possible to increase the wire electric discharge machining speed. is there.

Here, if one or more elements selected from K, Al and Si are too much, the micro-pores due to these elements are large and a large amount are generated after sintering, so that the wire discharge occurs. When used as an electrode material for processing, the strength locally decreases and causes wire breakage. Therefore, the upper limit of the amount was set to 100 ppm. The preferable amount is 40 to 95
ppm, and more preferably 50 to 90 ppm.
Among the above K, Al and Si, K has a large effect for improving the secondary recrystallization temperature, so that the amount of K is preferably 50 to 80 ppm. Here, the amounts of K, Al and Si in the present invention are values calculated as individual components in the final product.

As described above, it becomes possible to further raise the secondary recrystallization temperature as compared with the case of adding Re alone, and by improving the tensile strength, there are problems such as disconnection at the time of mounting on a wire electric discharge machine. It does not occur, and problems such as disconnection during electric discharge machining do not occur. Furthermore, the current for electric discharge machining can be increased by increasing the recrystallization temperature, and the machining speed can also be increased. Here, the secondary recrystallization temperature is measured by the recrystallization temperature measuring method specified in JIS H4460.

The electrode material for electric discharge machining having the above composition is particularly used for the electric discharge machining electrode wire used for wire electric discharge machining, and among them, an extra fine wire for machining a minute or highly accurate part. It has a particularly excellent effect on the electric discharge machining electrode wire, specifically, the electric discharge machining electrode wire having a wire diameter of less than 25 μm.

The electric discharge machining electrode wire of the present invention is as follows:
Its tensile strength is 3770 N / mm ² at room temperature. (100
For the first time, it is possible to obtain extremely excellent tensile strength of gf / MG). Here, MG is a wire diameter measured by the weight per unit length of the wire, and specifically, the wire diameter 2
The wire diameter was determined by the weight per 00 mm. The electrode material for electric discharge machining of the present invention is manufactured, for example, by the following manufacturing method.

First, W powder, or K, Al and S
When i is added, for example, a tungsten oxide powder is mixed and dried in a mixed solution in which an aqueous potassium silicate solution, an aqueous potassium chloride solution and an aqueous aluminum chloride solution are appropriately combined, and then subjected to a doping treatment, followed by hydrogen reduction. To obtain W powder having K, Al and Si adsorbed,
Next, this powder is treated with a strong acid or a strong alkali and then washed with water to separate secondary particles in the powder into individual unit particles to obtain W powder to which K, Al and Si are added. Next, after mixing the W powder and the Re powder by a conventional method, the wire material intended in the present invention is obtained by molding, sintering, rolling and wire drawing.

Further, the straightness as an electrode wire for electric discharge machining used in the above-mentioned wire electric discharge machining is 960 by the natural hanging method.
mm or more / 1000 mm, preferably 980 mm or more / 100
It is preferably 0 mm, more preferably 990 mm or more / 1000 mm. This is because if the straightness is too poor, a problem such as twisting of the wire occurs, and a problem such as disconnection at the time of attachment to the wire electric discharge machine and further disconnection at the time of electric discharge machining occur. Here, the straightness according to the natural hanging method in the present invention is the distance between the ends when one end of a 1000 mm wire material is held and the other end is hung as a free end, and the greater the warp of the wire material, the greater The distance becomes smaller.

A method for making the straightness within the above range is, for example, to pass a wire rod through a furnace in a hydrogen atmosphere,
Straightness can be improved by applying reverse tension while heating to 0 ° C. Further, in the present invention,
By covering the electrode material for electric discharge machining with a material having a lower melting point than W, it becomes possible to further reduce the breakage during electric discharge machining.

This is because the coating material on the surface is melted and scattered by the local heating accompanied with the electric discharge during the electric discharge machining, and the heat is taken away, whereby the base material does not reach a high temperature as compared with the base material alone, and the strength is lowered. And, recrystallization embrittlement can be prevented. As the material having a lower melting point than W, Cu, N
The use of i, Zn, Au, Ag, etc. is preferred. Various coating methods such as a clad method and a plating method can be used as these coating methods.

[0022]

EXAMPLES When adding tungsten powder or K, Al and Si, for example, a tungsten oxide powder having a particle diameter of 5 μm is added to a mixed solution in which a predetermined amount of potassium silicate aqueous solution, potassium chloride aqueous solution and aluminum chloride aqueous solution are combined. Added and evaporated to dryness on a warm water bath. During the drying, it was occasionally stirred to prevent segregation. Average particle size 1 to 3 of the dried powder reduced with hydrogen to adsorb K, Al and Si
A tungsten powder of μm was obtained.

Next, each of these tungsten powder and tungsten powder having an average particle size of 1 to 3 μm, which adsorbs K, Al and Si, rhenium powder having an average particle size of 2 to 4 μm, and isoamyl acetate (reagent grade) are provided in predetermined amounts. It was housed in a pot made of stainless steel, and was pulverized and mixed for 4 hours using a ball of an ultra-hard tungsten alloy. Then, it was further crushed and passed through a 300 / mesh sieve. This powder was formed into a compact by an ordinary method, pre-sintered at 1200 ° C. for 15 minutes, and then subjected to electric current sintering in a hydrogen atmosphere to obtain a sintered body. The obtained sintered body was rolled and drawn by a conventional method to obtain wire rods having various wire diameters.

The composition of the wire obtained by the above-mentioned manufacturing method is as follows: sample 1: Re26 wt%, balance W sample 2: Re3 wt%, balance W sample 3: Re3 wt%, K50 ppm, Al5 ppm,
Si was 7 ppm and the balance was W 2. In addition, conventional doped W line (K60ppm, A
Using 15 ppm, Si 7 ppm, and the balance W), wire materials of various wire diameters (Sample 4 ) were obtained by the same manufacturing method as above.
The maximum tensile load of the wire rod having each wire diameter in the samples 1, 3 and 4 was measured. The result is shown in FIG.

As is apparent from FIG. 1, sample 1 and sample 3, which are the electric discharge machining electrode wires of the present invention, are superior to sample 4 of the conventional electric discharge machining electrode wire even in the fine wire diameter. It has a maximum tensile load.

Further, in each of the samples having a wire diameter of 10 μm in the above-mentioned embodiment, a sample whose straightness was changed to 900 mm / 1000 mm and 980 mm / 1000 mm was used, and a wire breakage and electric discharge machining at the time of attachment to a wire electric discharge machine were performed. The number of wire breakages was investigated, and the results are shown in Table 1. Also,
The secondary recrystallization temperature of each sample is also shown in Table 1.

Here, the number of wire breakages during electric discharge machining means that each sample having a wire diameter of 10 μm is subjected to wire electric discharge machining of a die steel as a work material by using a wire electric discharge machining electrode wire having a length of 1000 m. The number of breaks in the electric discharge machining electrode wire was measured. The wire traveling system during wire electric discharge machining was controlled to a constant tension (0.1 ± 0.01 N).

[0028]

[Table 1] As is clear from Table 1 above, the electrode wire for wire electric discharge machining of the present invention has a small number of wire breaks, and by improving the straightness, the number of wire breaks is further reduced.

Further, the sample 3 in which K, Al and Si are further added is the sample 2 in which these elements are not added.
Compared with the above, the recrystallization temperature was increased, and the number of wire breaks was also reduced, which is more excellent.

[0030]

According to the present invention, it is possible to provide an electrode material for wire electric discharge machining which has excellent electric discharge machinability in conventional electric discharge machining and further in high precision electric discharge machining.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a wire diameter of an electrode wire for wire electric discharge machining and a maximum tensile load in Examples and Comparative Examples.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Harumi Kinoshita 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside the Research Institute of Industrial Science, Toshiba Corporation (56) Reference JP-A-2-145214 (JP, A) 50-102999 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23H 7/08

Claims (3)

(57) [Claims] 1. A wire diameter of 25 .mu.m or less, wherein the weight percentage is more than 1% and less than or equal to 45% rhenium and the balance substantially tungsten.
Full electrode material for wire electric discharge machining. 2. Rhenium 0.2-45% by weight,
Potassium al, below aluminum and one or 100ppm of two or more elements selected from silicon, balance substantially Wye less than diameter 25μm of tungsten <br/> ya discharge machining electrode material. 3. The electrode material for wire electric discharge machining according to claim 1, which is formed by coating a material having a melting point lower than that of tungsten.