JPS6039494B2 - Electrical discharge machining method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining method and its equipment, and particularly to an electric discharge machining method and apparatus suitable for machining materials with high melting points and high machinability.

Electrical discharge machining is a process in which a part of the workpiece is locally melted by electrical discharge heat, and the melted and liquefied part is blown away by pressure shock waves generated in the machining fluid and removed from the surface of the workpiece. Since it is nothing but heat processing, it is possible to process high melting point materials such as metals such as Ta, W, Ti, Si, Mo, alloys, carbides, and chambers that are difficult to mechanically grind or cut. Needless to say, it has been extremely difficult to process the metals, alloys, etc., which have high melting points and generally have high viscosity in the molten state, compared to, for example, ordinary iron-based materials.

The present invention has been made with the above-mentioned viewpoints in mind, and
The purpose is to provide a novel electric discharge machining method and apparatus that can process these scale-processable materials at high speed.

Therefore, the gist of the present invention is to perform electrical discharge machining while blowing a halogen compound gas into the machining fluid, and to generate an electrical discharge while the halogen compound and the workpiece are in contact with each other. The purpose is to halogenate the surface material of the workpiece to lower its melting point, and then remove this low melting point halide by natural vaporization or electrical discharge machining.

Therefore, in order to increase the machining speed in normal electrical discharge machining, colloidal crabstone (CaF) is added to the oil-based or water-based machining fluid.
2) (Japanese Patent Publication No. 31-1050) and technology of mixing Br into oil-based machining fluid (Japanese Patent Publication No. 40-52)
No. P) is publicly known.

However, these known techniques have the disadvantage that halogens easily create anions, and therefore, when halogens are present, the cations generated in the discharge gap disappear, and the time required for the insulation in the machining gap to be restored is greatly shortened. The idea was to add halogen to the machining fluid to increase the repetition frequency of machining pulses and increase the machining speed.

When using this machining fluid containing CaF2 or Br,
When machining steel etc., it is true that the off-time of the pulse can be slightly shortened and the machining speed can be increased, but with these machining fluids, high melting point materials such as Ta, W, Ti, Si or Mo, It was still difficult to process.

The reason is that the removal amount of these high melting point materials per unit discharge pulse is extremely small, so even if halogen addition can shorten the deionization time, it will essentially reduce the machining speed. This is because the process is not accelerated, and with conventionally known processing fluids of this type, halogenation of the surface of the workpiece does not occur, as occurs when the method of the present invention is carried out. On the other hand, in the present invention, a large amount of a gaseous halogen compound is mixed into the machining fluid in the working state, and electrical discharge machining is performed, thereby converting the surface material of the workpiece into a low melting point halogen compound in the first step. This is then removed by natural vaporization or secondary electrical discharge machining to perform the desired processing. It is a processing method. The details of the present invention will be explained below with reference to the drawings and examples.

The drawing is an explanatory view showing the main parts of an embodiment of the electric discharge machining apparatus according to the present invention. Electrode, 3 is electrode holder, 4 is processing tank, 5 and 6
7 is a lid body that airtightly closes the processing tank 4; 7 is a workpiece;
8 is a machining fluid, 9 is a power source for machining, 10 is a switching element, 11 is a pulse oscillator, 12 is a machining fluid pump, 13 is a filter, 14 is a compressor, 15 is a cooler, 16 is a gas separator, 17 is a reverse A stop valve, 18 is a tetrafluoromethane tank, 19 is a pressure relief valve, 20 is a gas-liquid mixing valve, and 21 is a line blender.

The illustrated processing example is a workpiece 7 made of titanium material.
This is an example of drilling process for.

The workpiece 7 is installed in the processing tank 4, and the electrode 2 is attached to the main shaft 1 via the electrode holder 3, and its tip is inserted into the tortoise electrode insertion hole provided in the center of the processing tank lid 6. 6a and is inserted into the processing tank 4. Further, in this embodiment, the electrode 2 is a cylindrical electrode for drilling,
Machining fluid 8 is forcibly supplied into the machining gap from the center hole 2a.

The electrode 2 is given a machining feed downward in the figure at a desired speed, and the pulse oscillator 11 oscillates pulses having a predetermined period and duty factor.
Therefore, the switching element 10 is controlled to open and close, and the workpiece 7 is subjected to electrical discharge machining. In this embodiment, the machining fluid 8 is a known machining fluid such as water or kerosene mixed with tetrafluoromethane CF4 in the form of fine bubbles.

Therefore, the machining fluid 8 in the machining tank 4 during machining is transferred to the pump 1.
2, processed waste etc. are removed by a filter 13, and then sent to a mixing valve 20}, where the CF4 is supplied from a tetrafluoromethane tank 18 and reduced to an appropriate pressure by a pressure concession valve 19. After being mixed with gas and vigorously condensed by the line blender 21, it is fed into the processing gap through the inside of the electrode holder 3 and the electrode 2,
It flows back into the processing tank 4.

Inside the machining tank 4, the CF4 bubbles float together with various gases generated during electrical discharge machining, and are separated from the liquid phase such as water or kerosene.

This free gas is sucked and compressed by a compressor 14, cooled and liquefied by a cooler 15, separated from other gases such as carbon dioxide, CO2, and other discharge decomposition gases by a gas separator 16, and recovered in a tetrafluoromethane tank 18. be done. In this way, when titanium material is machined, when a discharge occurs on the surface of the workpiece, the discharge point is filled with titanium tetrafluoride T.
Generated by iF4.

The boiling point of this TiF4 is 284oC, and this value is
The boiling point of itself is 3000 qo or more, the melting point is about 1800 qo
This value is much lower than that, and if a discharge occurs in the vicinity later, it will easily vaporize and be removed from the surface of the workpiece. W, M by the same process
o Other high melting point materials can also be processed.

Table 1 shows the melting points of these materials and the boiling and melting points of their chlorides. From the values shown in Table 1, it is clear that in the case of W, Mo, Si, etc., fluorides are naturally vaporized after being formed and removed from the processed surface.

Moreover, from this table, it is clear that not only fluoridation but also chloride processing is effective.

In addition to those listed in Table 1, it is known that there are various unstable* compounds and chlorides.

When the method of the present invention is carried out, these fluorides and chlorides are also produced intermediately, but these do not interfere with the processing in any way. First, in the method of the present invention, the halogen compound that can be used may be heated to gasify or vaporize it, or cooled to partially vaporize it, but it is preferable to use it as a gas at room temperature. In addition to this, the material itself, as well as its discharge decomposition gas, are low in toxicity and pose no danger of explosion or combustion.
It is necessary that the material be easy to process, inexpensive, and easily available, and from these points of view, CC
13F, CC12F2, CCIF3, CF4, CHC1
It is recommended to use 2F, CC12FCCIF2, or CH3CI or a cocompetitive mixture thereof.

Next, various samples were processed using a processing solution in which kerosene and CF4 were mixed at a standard state volume ratio of 1:1 and a processing solution containing only kerosene, and the results shown in Table 2 were obtained. . The processing conditions were as follows.

〔Processing conditions〕

Electrode material WC Processing pulse lp; 10 peaks A Ton; 8 Buddha S Ding.

H;4〆S processing liquid supply amount 0.9/mjn (watch flow rate)
Table 2 loss Ta, 60Wt%; W, 30Wt%; Ni, 1
Here, method 1 of the present invention uses a processing fluid containing kerosene and CF4;
The case is shown in which 10% of the gas was added in the standard state volume ratio.

The reason for adding inert gas is to reduce the partial pressure of the workpiece fluoride gas in the processing gap and promote this vaporization separation.
In the excellent work example of o, a considerable processing promotion effect is observed. Note that the above inert gas includes N2, C0
2. K-jaku etc. can also be used. Since the present invention is constructed as described above, it is possible to process these high melting point materials at a speed approximately 3 to 8 times higher than that of known methods. Note that the configuration of the present invention is not limited to the above embodiments, and includes, for example, the mixing ratio of the gaseous halogen compound and kerosene or water, the addition of an inert gas such as argon gas, and the introduction of the halogen compound gas into the processing gap. The supply method, the recovery treatment method for halogen compound gas, etc. can be freely changed in design depending on the dimensions, shape, purpose of processing, etc. of the processing machine and electrode, and the present invention encompasses all of them. It is.

[Brief explanation of the drawing]

The drawing is an explanatory view showing a main part of an embodiment of an electric discharge machining apparatus according to the present invention. 1...Main shaft, 2...Electrode, 4...Processing tank, 5, 6...Lid, 7...Workpiece, 8... Machining fluid, 12... Machining fluid pump,
13... Filter, 14... Compressor, 15... Cooler, 16... Gas separator,
18...Tetrafluoromethane tank, 20...
... Gas-liquid mixing valve, 21 ... Line blender.

Claims (1)

[Claims] 1. An electrical discharge machining method for materials with high melting points that are difficult to machine, characterized by performing electrical discharge machining while injecting a halogen compound, which is in a gas phase at least in working conditions, into the machining fluid. The above electrical discharge machining method. 2 Halogen compounds are CCl_3F, CCl_2F_
2, CClF_3, CF_4, CHCl_2F, CHC
IF_2, CCl_2FCClF_2 and CH_3Cl
The electrical discharge machining method according to claim 1, wherein the electrical discharge machining method is at least one halogen compound or a mixture of two or more halogen compounds selected from the group consisting of. 3. A machining tank that is hermetically closed and configured to accommodate a machining electrode, a workpiece, and a desired machining fluid, and to perform electric discharge machining therein, and a gas phase at least in working conditions. A storage tank for storing a halogen compound, and a processing liquid in the processing tank is extracted to the outside of the processing tank, and the halogen compound stored in the storage tank is mixed with this as a gas phase, and the mixture is poured into the processing tank again. Return processing fluid circulation, halogen compound addition device, extraction of free gas in the processing tank to the outside of the processing tank, pressurization and/or
or a halogen compound recovery device that separates the halogen compound from other exhaust gases by cooling and recovers the halogen compound in the storage tank.