JPS5819411B2 - Electrolytic buffing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to an electrolytic puff polishing method for finishing an object to be polished, such as stainless steel, to a mirror surface.

Conventionally, when finishing stainless steel or the like to a mirror surface, a method has been used in which an object to be polished and an electrode are immersed facing each other in an electrolyte bath, and electrolytic polishing is performed.

However, this method chemically removes the anodic passivating oxide film that occurs on the surface to be polished and promotes electrolysis, so the polishing speed is slow and it can be applied to mirror finishing small items, but it is suitable for polishing large items. Not suitable for mirror finishing.

Furthermore, this method has various drawbacks, such as the fact that since the polishing process progresses over the entire surface to be polished, it is difficult to perform local correction polishing such as removing roll scratches and pinholes on the surface to be polished.

The present invention takes these points into consideration and provides a polishing method that can easily and economically perform mirror finishing and local correction polishing of a large-area object to be polished. Next, the present invention will be described in detail with reference to drawings showing embodiments thereof.

First, FIG. 1, which shows an example of a tool used in the polishing method of the present invention, will be described.

In the figure, 1 is a tool connected to a drive shaft and rotated by a drive device, 2 is a disc-shaped electrode formed at the bottom of tool 1, and 3 is an electrode that is glued with a cross-shaped part left on the bottom surface of the tool 1. The abrasive material 3 is an electrically insulating and water-permeable abrasive material such as a puff or abrasive cloth, and the exposed electrode surface and the abrasive material 3 are arranged alternately.

Reference numeral 4 denotes an electrically insulating adhesive, which adheres the abrasive material 3 to the electrode 2 and is applied to the circumferential surface of the electrode 2 and the circumferential surface of the tool 1 to form an insulating film 4'. Prevent leakage current from flowing out from the surface.

5 is a plurality of electrolyte outflow holes provided through the electrode 2; 6 is an electrolyte supply port that communicates with the outflow hole 5 and is formed in the upper center of the tool 1; From the provided electrolyte supply device, the electrolyte is supplied through the supply port 6 and the outflow hole 5 to the gap between the electrode 2 and the polished surface of the object to be polished, which is placed opposite the lower surface of the electrode 2.

Then, the cathode side and the anode side of a direct current or pulsed direct current power source are connected to the electrode 2 and the object to be polished, respectively.

During the polishing process, the object to be polished is placed on the lower surface of the electrode 2 of the tool 1, and DC power is applied to the electrode 2 and the object to be polished. By rotating while pressing the object to be polished, the metal of the object to be polished is anodicly dissolved by electrolysis, and the passivated oxide film formed on the surface to be polished is removed by being rubbed by the abrasive material 3, and selectively electrolyzed. It is possible to accelerate the polishing process and finish the surface to be polished into a mirror finish.

Next, experimental results of the polishing method of the present invention will be explained.

The diameter of the tool electrode is 150mmφ (electrode area 177cd)
, the area of the cross-shaped exposed electrode with no abrasive bonded 4
0cryf, the abrasive grains mixed in the electrolyte and used for polishing have an abrasive grain size of #=600 to #1500, a sodium nitrate (NaN03) aqueous solution is used as the electrolyte, and the voltage applied to the electrode and the object to be polished is DC 3 to 15V, gap between electrode and object to be polished to 0
．． 2 to 2.5 mm, stainless steel (SUS
An experiment was conducted regarding the finishing of 27).

That is, a 20% wt% aqueous solution of sodium nitrate is used as the electrolytic solution, and this electrolytic solution is supplied to the tool at a ratio of 3 to 51:7 ml yr, and the exposed electrode area is 4:1 with respect to the electrode area, with a pressing force of 0. Press the electrode against the surface to be polished at .2 to 0.4 kg/c4, and rotate the electrode at a circumferential speed of 150 to 300 m.
/min while sliding on the surface to be polished, with a constant machining gap of 1 mrn, and when the voltage applied to the electrode and the object to be polished is varied from 3 to 15 V DC, the surface to be polished Although a clean mirror surface can be obtained even when the applied voltage is 5 V or less, the current density is low and the processing speed is very slow, so it is not practical.

In addition, when the applied voltage exceeds 12V, the current density increases too much, causing oxides to adhere to the polished surface, increasing leakage current, and causing a lot of pitting around the machining area. , the polished surface becomes rough.

Therefore, the applied voltage for electrolytic puff polishing is 5 to 1
2V is appropriate.

Next, FIG. 2 shows the experimental results of the roughness of the polished surface with respect to the current density.

The figure shows the case where stainless steel (5TJS 27) with a surface roughness of 3 to 5 μRmax is used as the object to be polished, a 20% by weight aqueous solution of sodium nitrate is used as the electrolyte, and an applied voltage of 8 V is applied, and the solid line The polishing time is 1 minute,
The broken line indicates a polishing time of 1 minute or more.

As is clear from the figure, the current density is 2.5A.
/crtt or less, a clean mirror surface of 0.5 μRmax or less can be obtained.

However, when the current density is 0.5 to IA/cni, 3
~5 minutes of polishing time is required, and the current density is between 0.5 and 2
．． 5A/crA is optimal.

Note that even when the applied voltage is other than 81 cm, a clean mirror surface similar to that described above can be obtained as long as the current density is in the range of 05 to 2.5 A/crA.

On the other hand, the current density varies greatly depending on the conductive dust in the electrolyte, the applied voltage, and the machining gap.

Therefore, the properties of the surface to be polished were investigated when the machining gap was varied in the range of 0.2 to 2.5 mm.

As a result, when the machining gap is 0.5 mm or less, the ability to follow the undulations of the surface to be polished is poor, and unevenness is likely to occur on the surface to be polished.

In addition, it is difficult to position the electrode and the object to be polished, and there is a high risk of short circuit (and the selection of the thickness of the abrasive material is also difficult).

In addition, if the machining gap is wide, it is necessary to increase the applied voltage to obtain the required current density, and as mentioned above, if the applied voltage is increased to 12 V or more, leakage current will increase.
As a result, a large amount of pitting occurs in the periphery of the process, a white oxide is observed, and the surface to be polished becomes rough.

Therefore, the machining gap in electrolytic puff polishing is 0.5
mm or more, the applied voltage is 5 to 12 V, and the current density is 0.
A range of 5 to 2.5 A/crA is sufficient.

Next, we calculate the change in current density with respect to the change in applied voltage as a third equation.
As shown in the figure.

In the same figure, the machining gap for line A, line B, and line C is 1 mm, and the electrolyte is 10% for line A and 20% for line B.
, the C line is a 25% 2% by weight aqueous solution of sodium nitrate;
For the D line, the machining gap is 0.5 mm, and the electrolyte is sodium nitrate 25
%wt% aqueous solution.

As is clear from the figure, when the machining gap is 1 mm and the electrolyte is a 10 to 25% by weight aqueous solution of sodium nitrate, 5 to 1
1 at an applied voltage of 2V, optimum polishing current density 0.5~
2.5 A/cni is obtained.

However, when the machining gap is 0.5 mrtt, the sodium nitrate concentration is 25%.
For a wt% aqueous electrolyte, the optimum polishing current density is obtained between 5 and 7V.

Note that even if the applied voltage is set so that the current density is within a predetermined range, the current density will also change depending on the machining gap, and as the machining gap increases, the applied voltage will also increase, and the applied voltage will be 12V. If it exceeds this level, the leakage current will increase, a lot of pitting will occur around the machining area, and the surface to be polished will become rough.

Therefore, it is also necessary to limit the applied voltage.

As shown in Figure 2, exposed electrode surfaces and abrasive material are alternately arranged on the tool, and the metal of the object to be polished is anodic-dissolved by electrolysis, and the passivation oxide film formed on the surface to be polished is polished. In the electrolytic puff polishing method in which the polished surface is polished to a mirror finish by scraping and removing it with a material and selectively promoting electrolysis, a voltage of 5 to 12 V is applied between the electrode of the tool and the polished object, and By applying a current with a current density of 05 to 2.5 A/crA and polishing with a machining gap of 0.5 mm or more, stainless steel etc. can be polished to 0.5 μRm.
It can be finished to a clean mirror surface of less than ax.

Moreover, in addition to being able to finish a material surface of 3 to 5μRmax in one process, polishing can be partially promoted on the surface to be polished, making local correction processing possible.
This invention has various features.

[Brief explanation of drawings]

Fig. 1 shows an example of a tool used in the electrolytic puff polishing method of the present invention;
s' line cross-sectional view, FIG. 2 is a diagram showing changes in polished surface roughness versus current density, and FIG. 3 is a diagram showing changes in current density versus applied voltage. 1...Tool, 2...Electrode, 3...
...Abrasive material.

Claims (1)

[Claims] 1. Exposed electrode surfaces and abrasive material are alternately arranged on the tool, and the metal of the object to be polished is anodic-dissolved by electrolysis, and the passivated oxide film formed on the surface to be polished is removed by abrasion with the abrasive material. In an electrolytic puff polishing method that finishes the surface to be polished into a mirror surface by selectively promoting electrolysis, a voltage of 5 to 12 V is applied between the electrode of the tool and the object to be polished, and a voltage of 0.5 to 12 V is applied between the electrode of the tool and the object to be polished. An electrolytic puff polishing method characterized by applying a current with a current density of 2.5 A/ctit and polishing with a processing gap of 0.5 mm or more.