JPS62112744A - Electrode material for electric discharge machining in water - Google Patents

Abstract

PURPOSE:To obtain an electrode material capable of attaining a much hither rate of electric discharge machining than a conventional electrode by sintering a powder mixture consisting of Cu and C in a prescribed ratio by heating under pressure so as to give a specified density or above. CONSTITUTION:A powdery mixture is prepd. as starting material by uniformly mixing 85-97vol% Cu powder with 15-3vol% C powder. The starting material is sintered by heating under pressure so as to give a density corresponding to >=85% of the theoretical density. Thus, the desired electrode material is obtd. The starting material may be precompacted before the sintering. The electrode material can be used as an electrode as it is. It may be formed into an electrode as an end product as well by coining or other method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrode material for water discharge machining, and more particularly to a crushed material that is more suitable for water discharge machining than conventional electrodes.

[Conventional technology]

Conventionally, electric discharge machining has been carried out by placing a workpiece in a kerosene solution and using cast steel, graphite, copper-tungsten, or the like as an electrode. The kerosene in the machining fluid has the following effects: (1) cooling, (2) transporting machining debris, and (2) pyrographicite produced by decomposition of the machining fluid deposits on the electrode surface to reduce electrode wear.

Electric discharge machining using kerosene poses a risk of fire, and the kerosene machining fluid may contain acetylene, ethylene,
Since there are environmental problems due to the generation of gases such as methane, water has recently been used as a machining fluid in electric discharge machines.

[Problem that the invention seeks to solve]

When water is used as a machining fluid, water has a cooling effect on kerosene and a transporting effect on machining debris, but pyrographite does not precipitate on the surface of the electrode, making it difficult to use conventional electric discharge machining electrodes, especially cast JT steel materials, and graphite. etc. have the problem of being difficult to put to practical use due to their poor wear and tear.

In addition, copper tungsten has relatively low wear and tear, but large ones break during manufacturing, so there is a limit to the size, and the bulk specific gravity is ~76? /7, it is extremely heavy, difficult to process, and also costly.
Therefore, there has been a need for an electrode that is less abrasive even in water discharge machining and that solves the problems associated with copper-tungsten.

[Means for resolving intermittent points]

The present invention provides an electrode suitable for water release and processing, and the gist thereof is to use raw material powder consisting of 15 to 92 volumes of copper powder and 75 to 3 parts fR% of carbon powder at a theoretical density. !
The present invention relates to an electrode material for water discharge machining which is sintered under heat and pressure.

The present invention will be explained in detail below.

The copper powder used as a raw material may be any powdered copper, including atomized powder obtained by melting copper and then spraying it.
Electrolytic copper powder obtained by electrolysis, mechanically pulverized powder, etc. may be used, but electrolytic copper powder is preferable because of ease of sintering. Further, it is preferable that the copper powder has an average particle size of /~θμm.

Carbon powders include artificial and natural graphite, coke,
Any granular carbon such as raw coke, calcined coke, or carbon black may be used, but it is especially preferable to use raw coke with a volatile content of 2 to 70% by weight according to JIE M /77-2 that contains hydrogen atoms. is preferable because it increases the bonding strength after heat and pressure sintering, which will be described later. Carbon powder having an average particle diameter of 204 m or less, particularly 7 μm or less is suitable.

Copper powder? ! ~97 volume chi, preferably 97 volume chi, is mixed with carbon powder 15 to 3 volume chi, preferably 10 to 3 volume chi, and usually mixed and dispersed as uniformly as possible to obtain a raw material powder with a theoretical density. The desired electrode material is obtained by heating and pressurizing sintering to a temperature of rsgr or higher, preferably θg or higher. In addition, in the present invention, volumetric refers to the volume ratio based on the true volume obtained by dividing the weight used by the true specific gravity for each of copper powder and carbon powder, and also refers to the theoretical density. refers to a calculated value obtained by proportionally integrating the true specific gravity of copper and carbon powder, which are raw materials, based on their composition ratios.

Heat and pressure sintering can be carried out by any known method such as hot pressing or sintering as long as the theoretical density of the obtained sintered crystal is within the above value. The hot press method is preferred because it is easy. In this case, the normal surface pressure is θ~! θθ ship'ad, too~/
The φ-curing is carried out by raising the temperature to a temperature range of 100°C, preferably a range of 700 to 000°C.

The electrode material for water discharge machining of the present invention can be obtained by the above method, but the electrode material of the present invention is not limited to the electrode obtained as a final product only by the above-mentioned heating and pressure sintering. It also includes items that have been preformed or shaped before being tied. In addition, the obtained lightning pole material can be used as an electrode as it is, but it can also be further formed into a coining material to form an electrode as a final product.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example/ A mixed powder in which electrolytic copper powder with an average particle size of 10 μm and natural graphite powder with an average particle size of j μm were uniformly mixed and dispersed at a true volume ratio of 90 near 0 was mixed with a surface pressure of 2θ0 / ctA and a melting point of copper / θ/3℃
Heat and pressure sintering was performed by a hot press method at a lower temperature of 900° C. to obtain an electrode material with a specific gravity of 7 J t /all (theoretical density).

Use the obtained electrode material! The electrode has a discharge surface of -x sWM, a jet hole of 31 rFφ is drilled in the center, the workpiece is tool steel (SK-s), and the resistance is 1. ×70”Ω−
Jet-type water discharge machining using my own water with positive polarity, current r,
s A , Ton == J'μB.

Testing was carried out for 3θ minutes under the condition of Toff = 20μ days.

After the machining was completed, the machining speed and the wear rate calculated from the following equation were measured. The results are shown in Table 1.

Example 3 In Example/, instead of natural graphite powder, JISM rr
/2 raw coke with an average particle diameter of 09S μm and a volatile content of 1% was mixed with a volume ratio of electrolytic copper powder and raw coke of 90% each.
: 10 (Example 2) and 7:3 (Example 3). /y/crl (
9j% of theoretical density), specific gravity 7.9? /art (22% of theoretical density) was obtained.

Table 1 shows the results of water discharge machining of each single-pole electrode material under the same conditions as in Example.

Comparative Example/When commercially available cast copper material...O is used as the co-electrode material (Comparative Example/) and commercially available copper tungsten...
When 4P-...-OO was used (comparative example, 2), water discharge machining was performed under the same conditions as in Example.

The results are shown in Table 1.

Table 1 [Effects] According to the electrode material for water discharge machining of the present invention, the conventional! Much higher machining speeds than poles are achieved. The degree of wear is comparable to that of conventional copper tungsten electrodes, but compared to other mesh tungsten electrodes, the electrode material of the present invention has a density of about 1/-, so it is extremely lightweight and can be used as a large-sized electrode material. It has various effects such as easy manufacturing and easy processing of the electrode material itself, and is industrially excellent.

Claims (3)

[Claims] (1) An electrode material for water discharge machining, which is obtained by heat-pressing sintering raw material powder consisting of 85-97% by volume of copper powder and 15-3% by volume of carbon powder to 85% or more of the theoretical density. (2) The electrode material according to claim (1), wherein the carbon powder contains 2 to 10% by weight of volatile matter. (3) The electrode material according to claim (1) or (2), wherein the copper powder is electrolytic copper powder.