JPS6123799A - Electrolytic polishing method of hollow niobium body - Google Patents

Abstract

PURPOSE:To polish smoothly and efficiently only the inside surface of a hollow niobium body by supplying continuously an electrolyte to the inside of the hollow body, rotating continuously the hollow body and conducting continuously electricity to the body thereby executing electrolysis. CONSTITUTION:The electrolyte 21 in a liquid storage tank 20 is introduced by a pump 18 via a flow rate regulating valve 17 into an Al cathode 7 and is supplied through the liquid blow-off hole 16 into the hollow niobium body 1. A motor 27 is started when the electrolyte 21 beings to overflow through an overflow hole 9. A power source 31 is turned on to impress voltage to the body 1 and polishing is started while said body 1 and rotary flanges 2a, 2b are rotated at a specified speed. The electrolytic current flows from the inside surface of the body 1 dipped in the electrolyte 21 to the cathode 7 when the voltage is impressed thereto. The current density and voltage are monitored by an ampere- hour meter 30 and a voltmeter 34 to maintain the current density always in a specified range. The gaseous hydrogen generated from the cathode 7 is discharged through discharge holes 8a, 8b to the outside.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for electrolytic polishing of niobium hollow bodies.
The following method is used to finish the inner surface of a niobium hollow body having openings at both ends (or one end) smooth and glossy by electrolytic polishing using an electrolytic solution consisting of 8O,F (fluorosulfuric acid) and H2O (water). is known (West German Siemens patent: Special Publication No. 55-39640). That is,
First, the niobium hollow body is made rotatable about an axis passing through its opening. Next, this is partially immersed in the electrolytic solution, and with the internal space of the hollow body above the liquid level communicating with the outside air through the opening, each part of the inner surface of the hollow body is sequentially electrolyzed by rotation of the hollow body. Allow it to be immersed in the liquid.

The cathode is then inserted into the hollow body through the opening and placed opposite the niobium hollow body in the electrolyte. Then, electrolysis is carried out at a constant voltage while generating an oscillating current by intermittent energization that repeats the application and interruption of voltage, and the niobium hollow body is stopped while voltage is being applied, and after the voltage is interrupted, the rotating shaft is By rotating the hollow body around the center, each part of the inner surface of the hollow body is evenly polished.

[Problem that the invention seeks to solve]

However, the above method had the following drawbacks.

(1) Although the niobium hollow body is rotated little by little after each cycle of intermittent energization, a slight level difference occurs on the inner surface of the niobium hollow body.

(2) Evaporation of HF from the liquid surface outside the niobium hollow body accelerates deterioration of the electrolytic solution.

(3) When removing the niobium hollow body in the electrolytic polishing method, it is necessary to take out the electrolytic solution, which is dangerous to handle, from the polishing solution tank, which reduces work efficiency.

The present invention has been made in view of the above circumstances, and is capable of polishing only the inner surface of a niobium hollow body to make it smooth and efficient.7. It is an object of the present invention to provide a method for electrolytic polishing of a niobium hollow body that can reduce loss due to evaporation of hydrogen chloride.

[Means for solving problems]

The present invention includes a niobium hollow body having an opening, and a drain hole provided at the opening of the hollow body to maintain a constant level of electrolyte in the hollow body, and an exhaust hole for contacting the outside air. It is equipped with a lid and a sealed liquid storage tank for supplying electrolyte to the hollow body, and the electrolyte is continuously supplied into the hollow body, and a constant current is supplied while the hollow body is continuously rotated at a constant speed. It is characterized by polishing the hollow body by electrolyzing the hollow body by applying electricity continuously at high density, thereby achieving the above object. [Function] According to the present invention, the niobium hollow body In addition to improving the structure of the peripheral parts of the body, the following effects are obtained by adopting constant current density, continuous current flow, etc.

(1) Since the hollow body is rotated at a constant speed while being energized, only the inner surface of the hollow body can be well polished without creating a step.

(2) Continuous energization reduces work time.

(3) By reducing the area where the electrolyte comes into contact with the outside air, evaporation of the fluorinated water wood () (F) can be reduced. Therefore, it is possible to prevent contamination of the workplace and to reduce the rate of deterioration of the electrolyte.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

1 in the figure is for example L = 320 s with both ends open.
Hxx160my Hs=500 Cage niobium hollow body (as shown in Figure 2). Both ends of this hollow body 1 rotate 7 runs -2)
m, 2b. This rotating flange 2m,
2b are bearings Ja and 3 each made of an insulator.
It is supported by frames 4a and 4b via b. The hollow body 1 and the rotating 7-lunges 2m and 2b can rotate via O-rings 6h and 6b for sliding the same rotating 7-lunges. The fixed 7 flange 5m, 5b holds a hollow aluminum (At) cathode 7 opposed to the hollow body 1, and has 8 exhaust holes.

8b, and has an overhole 70 for an electrolytic solution (described later), a drainage hole 10 in one fixed 7 run 5b.

In addition, 11th and llb in the figure are the exhaust holes 8 and lb.
Showing the gas venting hoses attached to each jb, 12
is fixed 7 ranzo 5b.

A temperature sensor is shown installed in the hollow body 1 through the rotating flange 2b. The fixed flange 5a.

6b are also fitted with O-rings 13 &, 13b, respectively, to seal the electrolyte.

The human-made cathode 7 has a bulge in the center and is shifted downward from the center of the rotation axis of the hollow body 1 in order to bring the distance from the equatorial part 15 of the hollow body 1 closer.

A liquid blowout hole 16 is provided in the center of the cathode 7 made of At. One end of the At cathode 7 is connected to a closed liquid storage tank 20 via a liquid feed pipe 19 with a flow rate regulating valve 17 and a liquid feed pump 18 interposed therebetween. This liquid storage tank 20 contains an electrolytic solution 2 . A temperature sensor f-22 and a cooler 23 are set in this electrolytic solution 21. The overflow hole 9 and the drain hole 10 of the fixed 7 flange 5b are as follows:
Each is connected to the reservoir goo by a drain 24,26. One drain pipe 25 is provided with a gate valve 26 .

A motor 27 is mounted on the pedestal 4a, and a gear 28 at the end of the motor 27 meshes with a gear mounted on one rotational 7 lange 21. The other rotary 7 flange 2b is in contact with a car & pump 29, which is connected via an integrating ammeter 30 to the positive side of the power source 3 via a cord 32. On the other hand, power supply 3
The negative side of 0 is connected to the ht# electrode 7 by a cord 33. Note that 34 in the figure indicates a voltmeter.

Next, the effect will be explained.

First, the electrolytic solution 2 in the liquid storage tank 2σ is discharged by the liquid feeding pump 18. Electrolyte 2 discharged from the liquid pump f1g
After the amount of liquid to be fed is adjusted by the flow rate adjustment valve 17,
The liquid is guided to the Al cathode 7, and the liquid blowing hole 16 of the Al cathode 7
niobium is supplied to the inside of the hollow body 1. Liquid feeding l776
Excess electrolyte 21 discharged from 18 is returned to liquid storage tank 2Q by flow rate adjustment valve 17.

The electrolytic solution 21 supplied into the niobium hollow body 1 fills the inside of the niobium hollow body 1, overflows when it reaches the overflow hole 9 of the fixed flange 5b, and returns to the liquid storage tank 20. In this way, the necessary amount of electrolytic solution 2 is replaced inside the niobium hollow body 1 while maintaining the liquid level 35 at all times.

In this way, when the electrolytic solution 21 starts to overflow from the overflow hole 9 of the fixed 7 flange 5b, the motor 27 is started and the two hollow bodies 1 and the rotating 7 langes 2h, 2b are
While rotating at a constant speed, the power source 31 is turned on and voltage is applied to start polishing. By applying a voltage, At
An electrolytic current flows toward the cathode 7. Integrating ammeter 30
and a voltmeter 34 monitors the current density and voltage to maintain the current density within a constant range at all times.

ho111! Hydrogen gas is generated from the hard pole 7, and this gas is passed through the gas venting hoses i1m and ilb from the exhaust holes IJ* and 8b attached to the fixed 7 runzos 5h and 5b, respectively.
It is then discharged to the outside. Further, when the electrolytic current flows, a large amount of heat is generated, but the temperature is controlled to be constant due to the circulation of the electrolytic solution 21 sent from the liquid sending pump 18. To do this, the inside of the liquid storage tank 20 must be checked by the temperature sensor 22.
In addition, the temperature of the electrolyte inside the υniobium hollow body 1 was monitored by the temperature sensor 12, and the temperature of the liquid inside the liquid storage tank 20 was set to a low value by the cooler 23. Further, although the electrolytic solution 21 inside the niobium hollow body 1 deteriorates due to electrolytic reactions, since the electrolytic solution 21 is constantly replaced, a good solution composition can be maintained for a long period of time.

When the integrated current value reaches a value corresponding to a predetermined polishing amount, the power supply 31 is turned off, and then the niobium hollow body 1 and the rotation 7 are turned off.
Stop the rotation of 2 cylinders 2h and 2b. And gate valve 3
1 is opened, and the electrolytic solution 21 is returned to the liquid storage tank 20 through the drain hole 1σ and the drain pipe 25.

However, in this example, the hollow body 1 shown in FIG. 2 was electrolytically polished under the conditions shown in Table 1 below.

Chapter 1 Table As a result, the following effects can be obtained.

(1) The polishing quality is below the level shown in Table 2 below.

Table 2 (2) By continuous energization, the polishing time was reduced to half of the conventional method. Specifically, when polishing by 120 μm, it took about 6 hours using the conventional method, but it took about 3 hours according to the present invention.

(3) Since the liquid storage tank 20 is airtight and the interior of the hollow body 1 is kept from contacting the outside air as much as possible, the electrolyte 2
1 has few parts that come in contact with the outside air, and fluoride, hydrohydric acid (HF)
There is no longer any contamination in the workplace caused by (no odor).

(4) Evaporation loss of HF was reduced to about 1/4. Specifically, when polishing 120 μm, the conventional method
While there was a loss of 14 ce/J, in the case of the present invention, it was 3.1 ce/J. However, the HF concentration is 46 typh, converted to hydrochloric acid.

〔Effect of the invention〕

As detailed above, according to the present invention, only the inner surface of the niobium hollow body can be polished smoothly and efficiently, and the loss due to evaporation of hydrogen fluoride can be reduced, and it can be applied to superconducting accelerating cavity rings. It is possible to provide a method for electropolishing a niobium hollow body.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for electropolishing a niobium hollow body according to an embodiment of the present invention, and FIG. 2 is a sectional view of the niobium hollow body. 1... Niobium hollow body, 2m, 2b... Rotation 7 lunge 1. ? a, Jb...slide bearing, 4m, 4b...frame, 5&, 5b...fixed 7 langes, 6*, 6b...
Sliding O-ring, 7... Aluminum cathode, 8m,
8b...Exhaust hole, 9...Overflow hole, 10.
・Drain hole, 11&, Ilb...Gas vent hose, X
i! , 22...Temperature sensor, 13! L, 1
3b...0 ring, 15...Equatorial portion, 16...Liquid outlet, 17...Flow rate adjustment valve, 18...Liquid feeding ponder, 19...Liquid feeding pipe, 20... Liquid storage tank, 21... Electrolyte, 23... Cooler, 24s xs... Drain pipe,
26... Gate valve, 27... Motor, 28... Gear, 29... Carden brush, 30... Integrating ammeter,
31... Power supply, 32° 33... Cord, 34...
Voltmeter, 35...liquid level.

Claims (1)

[Claims] a niobium hollow body having an opening, a lid provided at the opening of the hollow body and having a drain hole for keeping the liquid level of the electrolyte in the hollow body constant and an exhaust hole for contacting the outside air; Equipped with a sealed liquid storage tank that supplies electrolyte to the hollow body,
A niobium hollow body characterized in that an electrolytic solution is continuously supplied into the hollow body, and the hollow body is continuously rotated at a constant speed while electricity is continuously applied at a constant current density to perform electrolysis and polish the hollow body. electrolytic polishing method.