JPH0669648B2 - Electrolytic grinding method for Ti, Zr, Nb, Ta or their alloys - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic grinding method for surface finishing of Ti, Zr, Nb, Ta or their alloys.

[Prior Art] For example, in a boiling water reactor, a long rectangular tube made of Zr alloy called a channel box is used to equalize the flow of cooling water. When processed and manufactured from an alloy plate, a scratch having a depth of several tens of μm may occur.

If such large scratches remain, they will reduce the commercial value of the product and will have an adverse effect under the conditions of use, so they will be shipped or transferred to the next step in the state where they are completely removed.

Conventionally, mechanical abrasion is used to remove these scratches, but it requires a large grinding allowance because it has a slightly uneven and complicated shape. In addition, since pickling with nitric hydrofluoric acid is performed in order to smooth the surface, if hydrofluoric acid remains on the surface, there is a problem that a product defect occurs in the next step.

From such a background, there is a demand for a method of performing a surface finish that enables uniform grinding even for a product having a complicated shape and does not cause surface contamination.

By the way, as a technique that meets the above-mentioned demand, there is an electrolytic grinding method.

However, metals such as Ti, Zr, Nb, Ta and their alloys produce an anodic oxide film on the surface when electrolytically ground by a general method, and because this is an extremely strong film, anodic current does not flow, Electrolytic grinding is practically impossible.

In order to avoid this, a means for adding a film-disrupting substance such as fluorine or chlorine to the electrolytic bath can be considered, but as mentioned above, hydrofluoric acid or hydrochloric acid remains on the ground surface, which causes a product defect.

Therefore, as a means for solving this problem, attention has been paid to a so-called composite electrolytic polishing method, and a technique for applying this has been developed.

That is, it is a technique disclosed in Japanese Examined Patent Publication No. 57-47759, which is a means for pressing a non-woven fabric containing abrasive grains against the object to be ground and performing electrolytic grinding while giving a relative speed between the object to be ground and the non-woven fabric. .

A schematic diagram of an apparatus for carrying out this electrolytic grinding means is shown in FIG.

In this device, the object to be ground installed on the copper plate is moved along with the movement of the movable table, and the electrolytic solution is supplied from the inside to the tip. And electrolytically grinding while pressing the nonwoven fabric at the tip end against the surface of the grinding body.

When the Zr alloy was electrolytically ground by changing the electrolytic voltage and the non-woven fabric pressing surface pressure by using the above-mentioned device, when the electrolytic voltage was set to 15 [V] or more as shown in FIG. It turned out that electrolytic grinding of "/ min" is also possible.

According to this method, a neutral salt aqueous solution such as NaNO ₃ can be used in the electrolytic bath, and since it does not substantially contain fluorine or chlorine, it is possible to achieve the surface finish without causing the above-mentioned product defects. become.

[Problems to be Solved by the Invention] However, if the electrolytic voltage is set to 15 [V] or more in order to secure a sufficient productivity and obtain a sufficient grinding amount as described above, When an anodic oxide film is formed on the non-contact part of the non-woven fabric (non-grinding part) and the electrode part is moved, the light reflection state between the part where the anodic oxide film is generated and other parts is different, and as a result, the light There is a problem that interference occurs and an interference color is generated on the surface after grinding.

In addition, I looked at Zr alloy, but this problem is Zr and Ti, Nb, Ta
Alternatively, the same applies to those alloys.

When the interference color is generated in this way, the commercial value is remarkably reduced, and it is desired to remove it.

Therefore, the present invention has been made for the purpose of providing a method for effectively removing this interference color.

[Means for Solving Problems] The present invention provides a grinding method in which a non-woven fabric containing abrasive grains is pressed against an object to be ground and electrolysis is performed while a relative speed is applied between the object to be ground and the non-woven fabric. After performing the first electrolytic grinding with an electrolysis speed of several tens of μm / min or more by applying an interelectrode voltage of [V] or more, further applying an interelectrode voltage of 6 [V] or less to perform anodization. A second electrolytic grinding for removing the anodized film generated in the first electrolytic grinding step without forming a film is performed, and Ti, Zr, Nb, Ta or alloys thereof are characterized. The present invention relates to an electrolytic grinding method.

[Operation] The present invention employs a grinding method in which a non-woven fabric containing abrasive grains is pressed against an object to be ground and electrolysis is performed while a relative speed is applied between the object to be ground and the non-woven fabric. Zr, N
a first step of electrolytically grinding the surface of b, Ta or an alloy thereof by applying an inter-electrode voltage of 15 [V] or higher;
It comprises a second step of applying an inter-electrode voltage of [V] or less to perform electrolytic grinding.

The first step is several tens of μm that are initially present in the workpiece.
This is a process for removing scratches on the surface.

However, in this first step of electrolytic grinding, an anodic oxide film is formed on the part of the non-woven fabric that is not in contact with the object to be ground (non-ground part). It may cause interference color.

Therefore, in the second step, the voltage between the electrodes is reduced to carry out electrolytic grinding to remove the portion where the anodic oxide film is formed. That is, the second step is a step of eliminating the cause of the interference color.

Therefore, by adopting the electrolytic grinding method of the present invention,
It is possible to efficiently remove scratches of several tens of μm originally present in the non-ground body without causing interference color on the surface after grinding.

[Examples] Using the apparatus shown in FIG. 1, electrolytic grinding was performed on Ti, Zr, Nb, Ta or their alloys, and the amount of grinding and the presence or absence of interference color were examined. In this experiment, the inter-electrode voltage was set to 15 for the traveling path of the electrode coated with the non-woven fabric.
[V] or higher, and the voltage between contacts is 6 on the return trip.
It was set to [V] or less.

The results are summarized in Table 1.

As is clear from the table, according to the embodiment of the present invention, it is possible to grind several tens of μm and the surface of the non-ground body after grinding has a metallic luster, but there is no interference color. .

On the other hand, when the electrodes are made to travel with the interelectrode voltage set to 15 [V] or higher according to the conventional method, interference colors are all generated. For Zr alloy, the voltage between electrodes is 5 [V]
However, the amount of grinding was insufficient, and the purpose of removing scratches of several tens of μm could not be achieved even if there was no interference color, and it cannot be used from the original purpose.

[Advantages of the Invention] As described above, in the present invention, in electrolytic grinding in the surface finishing of Ti, Zr, Nb, Ta or their alloys, the interference color of the surface caused by grinding is removed while securing a large grinding amount. Made it possible.

This improves the commercial value of the material used for the channel box and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electrolytic grinding experimental apparatus, and FIG. 2 is a graph showing the amount of grinding under each condition, with the horizontal axis representing the electrolytic voltage and the vertical axis representing the contact pressure of the nonwoven fabric.

Front page continuation (72) Inventor Nobuo Takaoka 991-287 Kitano, Noguchi-cho, Kakogawa-shi, Hyogo Prefecture (72) Inventor Kinji Uemura 2-6-1 Nakajima, Takasago-shi, Hyogo Prefecture (72) Sumio Takahashi Tamachi, Akashi-shi, Hyogo Prefecture 1-chome 12-14 (72) Inventor Fukuo Fujikawa 947-1 Okubo-cho, Okubo-cho, Akashi-shi, Hyogo Prefecture (72) Inventor Masaharu Morishita 1107-2 Okubo-cho, Okubo-cho, Akashi-shi, Hyogo (56) References JP 60- 186318 (JP, A) JPK 57-47759 (JP, B2) "Special processing" Toshikazu Sato Published by Yokendo (May 20, 1985)

Claims (1)

[Claims] 1. A grinding method in which a nonwoven fabric containing abrasive grains is pressed against an object to be ground and electrolysis is performed while a relative speed is applied between the object to be ground and the nonwoven fabric. First, an inter-electrode voltage of 15 [V] or more is applied. After performing the first electrolytic grinding with an electrolysis rate of several tens of μm / min or more, an inter-electrode voltage of 6 [V] or less is further applied, without forming an anodized film, and A method for electrolytically grinding Ti, Zr, Nb, Ta or their alloys, which comprises performing second electrolytic grinding to remove an anodized film generated in the first electrolytic grinding step.