JPS6274529A - Electrolytic processing method - Google Patents

Abstract

PURPOSE:To enable non-shortcircuit and non-interruptive processing by adding a small amount of nitric acid etc. to an electrolytic liquid of neutral salt type of sodium nitrate to provide an acid solution, by re-dissolving the sludge produced during processing in said solution and thereby preventing affixation of sludge to the inside of electrode. CONSTITUTION:Sodium nitrate of neutral salt type at PH7 is put in a processing liquid supply tank 1, and after adjustment of its concentration, a valve 15 of a nitric acid tank 13 is opened, followed by automatic PH control with a PH meter 14, and a small amount of nitric acid is added to electrolytic liquid so that the PH of the electrolytic liquid in said supply tank 1 is adjusted to a PH between 1 and 3. If electrolytic processing is carried out by the use of this processing liquid, the sludge included in the processing liquid deposits once in the form of metal hydroxides M(OH)n, which will then be combined with hydrogen ions in the solution because the processing liquid is in acid atmosphere, to become metal ions again and be dissolved in the solution. Therefore, electrolytic processing with this liquid can be made without accumulation of deposited sludge over the pipe electrode, which allows omission of cleaning under processing to assure elimination of marks due to interruption of the processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for electrolytic machining of cooling holes in gas turbine and jet engine rotor and stationary blades and small-diameter deep holes in heat-resistant alloys and the like that cannot be drilled.

[Conventional technology]

For drilling cooling holes in gas turbine rotor and stationary blades.

Traditionally a neutral salt electrolyte? The electrolytic processing method used was adopted. This will be explained below with reference to the figures.

FIG. 2 shows a system diagram of a conventional electrolytic processing device.

The electrolytic solution is pumped from the machining fluid supply tank 1 by pump 2 and passes through three flow rate adjustment valves.

It enters the pipe of the pipe electrode 4. A plurality of pipe electrodes 4 are fed perpendicularly to a workpiece 6 attached to a processing machine main body 5 by a feeding mechanism 7, and a DC power supply 8 for one processing is provided.
Anode? Is there another cathode on workpiece 6? When coupled to the pipe electrode 4, processing from the surface of the workpiece 6 by elution is performed electrochemically and continuously. Note that the electrolytic solution flows back upwards as shown in the enlarged circle in FIG. 2 and is eluted from the upper surface of the workpiece 6. This electrolyte.

The sludge is separated by an electric centrifuge 9 and enters a settler/recipient 12 via a drainer/recipient 10 and a transfer pump lli. In the settling tank 12, is there sludge that was not removed by the centrifuge 9? The electrolyte is separated by gravity, and the supernatant electrolyte returns to the machining fluid supply tank 1, thereby completing an electrolyte circulation cycle.

3(a), (b), (c), and (d) show a gas turbine rotor blade 6 as an example of a workpiece 6.
In the cooling air hole 6by shown in B, 17 small-diameter deep cooling air holes 6b are simultaneously machined by the electrolytic machining apparatus.

FIG. 4 shows an example of the pipe electrode 4.

In this example, an electrode cap 4A is joined to a pipe electrode 4 having an outer diameter of 0.8 mm and an inner diameter of 0.5 mm.

[Problem that the invention seeks to solve]

However, when electrolytically machining the small-diameter deep cooling air holes 6b2 in the gas turbine rotor blade 6B, due to the relationship with the workpiece 6,
Since the pipe electrode 4 used is thin and long, it is difficult to maintain high machining fluid pressure and flow rate, and during machining, sludge (5ludFle:
(metal oxide) adheres and accumulates, clogging the inner surface of the pipe electrode 4.

If the machining continues as it is, the supply of electrolyte will be insufficient and the pipe electrode 4 and the workpiece 6 will be short-circuited.

The workpiece will be damaged. Electrolytic processing on the way for this? The current situation in the industry is that after the process is interrupted and the inner surface of the pipe electrode 4 is cleaned, electrolytic processing is performed again.

Does this mean production efficiency? Along with lowering.

When the machining is temporarily interrupted, stop marks are formed on the first workpiece 6, resulting in problems such as deterioration of the quality of the product.

[Means for solving problems]

Therefore, in the present invention, in order to prevent sludge from being deposited on the inner surface of the pipe electrode of the electrolytic processing equipment, we use nitric acid, which is currently used in the case. , add a small amount of nitric acid, etc. to make an acidic solution (PH: 1-3
), the sludge generated during machining is redissolved in the solution, thereby reducing the adhesion of sludge to the electrode circular surface. By preventing this, short-circuit-free machining can be achieved.

Eliminates the need to clean the inner surface of the electrode during processing.

This is designed to eliminate stoppage marks caused by interruptions in processing.

Therefore, this acidic electrolytic processing fluid? When electrolytic machining is performed using 1.1, the sludge in the machining fluid becomes a metal hydride (M(O
H)n: M is a metal atom) becomes a sludge and precipitates, but since the processing fluid is in an acidic atmosphere, it combines with hydrogen ions (H) in the solution, becomes metal ions (M) again, and enters the solution. dissolve.

This acidic electrolytic processing liquid? When used for electrolytic processing, there is no sludge build-up on the pipe electrode as described above, and the electrolytic effect remains the same as before.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrolytic processing apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing a small diameter deep hole electrolytic machining apparatus r according to the method of the present invention. Conventional example? Do the same parts have the same symbols compared to Figure 4? It is attached. This embodiment has a nitric acid tank 13. pH total 1
4. A nitric acid supply control valve 15 and a processing fluid supply tank internal pH value control device are additionally provided.

In this way, seven neutral salt-based sodium nitrate (Ba/・-value 7) was added to the processing liquid supply tank 1, and after the concentration was adjusted, 15 valves of the nitrate V tank 13 were opened, and the pH was adjusted to 14 in total. Perform automatic control 2 and add a small amount of nitric acid to the electrolyte? By adding, the p... value t of the electrolyte in the machining fluid supply tank 1
Adjust to 1-3. In the above embodiment, nitric acid was used to adjust the pH value of the electrolytic solution to 1 to 3, but sulfuric acid or tartaric acid may be used if necessary, such as hydrochloric acid.

〔Effect of the invention〕

By always adjusting the pH value of the electrolytic processing liquid to 1 to 3, the generation of sludge during electrolytic processing is prevented, so that sludge does not adhere to the inside of the pipe electrode. Therefore,
The present invention greatly contributes to the development of industry, such as thermal short-circuiting and non-stop machining of electrolytic machining equipment, and electrolytic drilling greatly contributes to improving productivity and quality in machining.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an electrolytic processing apparatus according to an embodiment of the present invention. FIG. 2 is a system diagram showing a conventional electrolytic processing apparatus. Fig. 3 is a diagram showing an example of a workpiece, in which Fig. 3(a) is a top view taken along the line aa in Fig. 3(b), Fig. 3(b) is a side view, and Fig. 3(b) is a side view. (C) is shown in Figure 3 (b)
Figure 3(d) is a bottom view of the arrow C-C of l, and Figure 3(a)
FIG. Further, FIG. 4 is a vertical [θ] sectional view showing an example of a pipe electrode. ■... Processing fluid supply tank, 4... Pipe electrode, 5...
...Processing machine body 16...Workpiece, 13...Nitric acid tank, 111...P-meter, 15...Nitric acid supply control valve.

Claims (1)

[Claims] In electrolytic processing methods that use neutral salt-based electrolytes such as sodium nitrate, an acid tank, a pH meter, and an acid supply control valve are added to conventional electrolytic processing equipment to control the electrolyte pH in the electrolyte supply tank. By detecting the pH value with the pH meter and automatically adjusting the amount of acid added from the acid tank with the acid supply control valve, the pH value of the electrolyte in the electrolyte supply tank is always kept between 1 and 1. An electrolytic processing method characterized by maintaining the temperature at 3.