JP5005369B2 - Electropolishing equipment - Google Patents

Description

  The present invention relates to an electropolishing method, and particularly to a method suitable for preparing a sample for analysis of a metal material.

  For example, when component analysis is performed in a steelmaking process, a molten steel is drawn up using a brick sampler, the solidified steel is cut to prepare a sample, and the sample surface is polished with a grinder or belter for analysis. Things have been done. For steel products, a sample is cut from an arbitrary part of the product, and the surface is polished with a grinder or a belter for use in analysis in the same manner as in the case of a molten steel sample. These surface-polished samples are samples for instrumental analysis and are generally called block samples. On the other hand, a drill is used to drill a hole in steel or the like to collect chips and use them as a sample for chemical analysis. There are two types of analysis samples.

  By the way, among the components contained in steel materials and special metal materials (hereinafter simply referred to as “metal materials”), especially carbon, sulfur, oxygen, nitrogen, hydrogen, etc. greatly affect the physical properties of metal materials. Analysis of the components is performed.

  For example, when performing oxygen analysis in a metal material, it is necessary to prepare a sample for analysis. Therefore, the sample is cut from the metal material to be analyzed with a small cutting machine, the sample surface is polished with a file, and the surface is polished with a belt or the like, followed by ultrasonic cleaning of the sample in alcohol or acetone for dehydration and degreasing. And used for analysis. In the case of oxygen analysis, since it is necessary to prevent atmospheric oxidation of the sample, it is generally processed as a block sample and used for analysis. This is generally called a dry method.

  When preparing a sample for oxygen analysis, if the surface is polished using a file or a bellder as described above, frictional heat is applied to the sample and the surface is oxidized due to oxygen in the atmosphere. It is difficult to accurately quantify the amount of oxygen produced. In particular, when the oxygen amount is in a minute range (10 ppm level), a correct measurement value cannot be obtained due to the effect of atmospheric oxidation.

  On the other hand, there is an electropolishing method as a method for preventing atmospheric oxidation as much as possible during sample preparation. The electrolytic polishing method is a method in which a sample is adjusted to an arbitrary sample weight in advance, immersed in an electrolytic solution, and subjected to electrolysis by applying a voltage between both the anode and the cathode.

  When the surface of the sample is electropolished, the sample is always in the electrolytic solution during electropolishing, so there is no contact with the atmosphere and the sample is less likely to be oxidized.

JP 05-214600 A JP 09-324300 A

However, when an analytical sample is polished by electrolytic polishing, there are the following problems.
1. Platinum electrodes are used for the anode and the cathode, but the portion of the sample that is in contact with the platinum electrode causes uneven dissolution of the sample surface and does not become a uniform and smooth surface.
2. During the electrolysis, the electrolyte in the tank becomes non-uniform.
3. When the electrode is energized during electrolysis, the temperature of the electrolytic solution rises and the temperature of the sample also rises. When the sample is taken out of the electrolytic solution, atmospheric oxidation may occur.
4). During electrolysis, the current flows in one direction from the anode to the cathode. However, impurities in the electrolyte may be deposited on the surface of the sample.
5. When the sample contains carbon, if the sample is in an annealed state, the carbon in the sample exists in the form of cementite (Fe3C) and does not dissolve even by electropolishing.

  In view of such problems, an object of the present invention is to provide an electrolytic polishing method suitable for preparing an analytical sample.

  Therefore, in the electrolytic polishing method according to the present invention, in electrolytic polishing the surface of the object to be polished, the electrolytic bath is provided with a pair of electrodes, the electrolytic solution is placed in the electrolytic bath, and the electrolytic solution is stirred by the rotation of the rotor. Then, one of the pair of electrodes is a saddle-shaped electrode, and an object to be polished is mounted on the saddle-shaped electrode. While the saddle-shaped electrode is moved up and down in the electrolytic solution, current is passed between the pair of electrodes for electrolytic polishing. It is characterized by having performed.

  The first feature of the present invention is that one of the electrodes has a bowl-like shape, and an object to be polished (hereinafter, “polishing object” is also simply referred to as “sample”) is mounted on the bowl-like electrode to move the bowl-shaped electrode up and down. It is in the point which did. As a result, every part of the sample comes into contact with the bowl-shaped electrode, so that there is no unevenness of dissolution and the surface can be polished to a uniform and smooth surface.

  The second feature of the present invention resides in that the rotor is put into the electrolytic cell and the electrolyte is stirred by rotating the rotor. Thereby, the electrolytic solution in the tank does not become non-uniform during electrolysis, and the electropolishing can be performed stably.

  Since the temperature of the sample also rises during electrolysis, atmospheric oxidation may occur when the temperature of the electrolyte rises and the sample is taken out of the electrolyte. Therefore, it is preferable to cool the periphery of the electrolytic cell with cooling water so that the electrolyte does not reach a temperature higher than the cooling water temperature.

  If the current flow is unidirectional during electrolysis, impurities in the electrolyte solution may be deposited on the surface of the sample. Therefore, it is preferable to switch the energization direction for the pair of electrodes at a predetermined time interval.

  When the sample containing carbon is in an annealed state, the carbon in the sample exists in the form of cementite (Fe3C) and does not dissolve even by electropolishing. Therefore, it is preferable to subject the sample containing carbon to a solution treatment, and to perform electrolytic polishing on the sample in which the carbon is dissolved. Although carbon is not dissolved even after solution treatment, it exists as a single element. Therefore, carbon can be removed during electrolysis by the polarity switching method, and is also removed during ultrasonic cleaning.

  The sample may be electrolytically polished as it is, but in order to obtain a smooth surface, it is preferable to use a surface whose surface is mechanically polished with a file or a belt.

  Immediately after the completion of the electropolishing, the sample is taken out from the electrolytic solution, washed with water, ultrasonically washed with an organic solvent such as alcohol or acetone, and dehydration / degreasing, whereby surface oxidation can be reduced. It should be noted that in any process, it is sufficient to give a time of several seconds. If ultrasonic cleaning is performed for a long time, the cleaning liquid is heated by the ultrasonic wave, which may cause surface oxidation. During the cleaning process, the surface of the sample must not be dried and is in a wet state with the cleaning liquid. If the sample surface is wet with the cleaning solution, the cleaning solution will evaporate and cover the sample surface even when the sample is taken out into the atmosphere. Is suppressed.

  That is, in preparing a sample for analysis, it is preferable that the electropolished sample is washed with water and then ultrasonically washed in an organic solvent for dehydration and degreasing. The sample may be dried with cold air, but when acetone is used as the organic solvent, the boiling point of acetone is as low as 53 ° C., so that the analysis can be performed as it is as a measure against atmospheric oxidation.

  Further, an electropolishing apparatus according to the present invention is an electropolishing apparatus suitable for electropolishing the surface of an object to be polished. An electrolytic bath in which an electrolytic solution is put, and the bottom of the electrolytic bath are charged and rotated. A rotor that stirs the electrolyte solution, a drive motor that is provided on the outside of the bottom of the electrolytic cell, and on which a magnet for magnetizing the rotor is attached to a rotating shaft, and is immersed in the electrolytic solution in the electrolytic cell. A pair of electrodes having a bowl shape on which one electrode can mount an object to be polished, a vertical movement mechanism for moving the bowl electrode up and down, and an energization circuit for passing current between the pair of electrodes. It is characterized by that.

  In the electropolishing apparatus of the present invention, it is preferable to provide a cooling water tank containing cooling water or a cooling water passage for circulating the cooling water around the electrolytic tank. The energization circuit may be configured to switch the energization direction for the pair of electrodes at a constant time interval.

  Further, the electrolytic polishing apparatus includes a cleaning cooling water tank in which the cleaning cooling water is placed, a cleaning tank immersed in the cleaning cooling water tank and in which an organic solvent is placed, and the cleaning cooling water in the cleaning cooling water tank. It is preferable to further include an ultrasonic generator that applies ultrasonic waves to the object to be polished in the cleaning tank to perform ultrasonic cleaning.

  Furthermore, it is good to provide the cover comprised in the closed space which can open and close the upper direction of an electrolytic cell, and the adsorption device which adsorb | sucks the vapor | steam of the electrolyte solution in a cover. The adsorber should contain a deodorant obtained by impregnating a glass wool with an alkaline agent and activated carbon.

  Hereinafter, the present invention will be described in detail based on specific examples shown in the drawings. 1 to 5 show a preferred embodiment of an electropolishing apparatus according to the present invention. In the figure, the housing 10 of the electropolishing apparatus has a substantially L-shaped side surface, and a flat quadrangular cooling water tank 11 is provided on the left half of the upper half of the upper surface of the housing 10, and a flat quadrangular ultra-high shape is provided on the right half. A sonic cleaning cooling water tank 12 is provided.

  An electrolytic tank 13 is provided in the cooling water tank 11, an electrolytic solution is placed in the electrolytic tank 13, and a pair of platinum electrodes 14 and 15 are immersed in the electrolytic tank 13, and one platinum electrode 15 is knitted. The sample P is formed in a bowl shape, and the other platinum electrode 14 is supported on the electrolytic cell 13 or the housing 10 by an appropriate jig.

  A braided platinum electrode (hereinafter referred to as a saddle electrode) 15 is suspended by a suspension member 16, the upper end of the suspension member 16 is attached to the tip of an arm 17, and the base of the arm 17 is attached to a rod 18. 18 is slidably supported on a mounting bracket 20 by a bush 19, and the mounting bracket 20 is attached to the housing 10.

  The lower end of the rod 18 is slidably contacted with the outer peripheral cam surface of the elliptical cam 21, and the cam 21 is fixed to the rotating shaft 22 </ b> A of the geared motor 22, and thus the column 18 is moved up and down by the rotation of the cam 21. A vertical movement mechanism 23 for moving the vertical movement is configured.

  In addition, cooling water is placed in the cooling water tank 11 so that the temperature rise of the electrolytic solution in the electrolytic tank 13 is suppressed.

  Furthermore, a rotor 25 made of a material that can be magnetized is placed on the bottom of the electrolytic bath 13, and a magnet 26 is provided on the outside of the bottom of the cooling water bath 11, and the magnet 26 rotates the drive motor 27. The rotor 25 is rotated by the rotation of the magnet 26 so that the electrolyte in the electrolytic cell 13 is agitated.

  An energization line is connected to the platinum electrode 14 and the saddle electrode 15, and a polarity switch 28, an ON / OFF switch 30 and a power source 29 are connected to the energization line, and between the platinum electrode 14 and the saddle electrode 15. In addition, a current is passed through the switch, and the direction of energization is switched at set time intervals.

  The cleaning cooling water tank 12 is filled with cleaning cooling water, the first and second cleaning tanks 31 and 32 are immersed, and the first cleaning tank 31 and the second cleaning tank 32 are filled with an organic solvent. An ultrasonic generator 33 is provided below the cleaning cooling water tank 12.

  In addition, a stepped portion is formed on the rear half of the upper surface of the housing 10, and the upper surface of the stepped portion is inclined. On the inclined surface, an ON / OFF switch 30, a pilot lamp 35, a polarity switching timer 36, a DC voltmeter 37, and a DC ammeter 38 are provided. The output regulator 39 and the ultrasonic cleaner switch 40 are laid out.

  Further, a deodorizer 41 is provided on the side of the housing 10, and a deodorizer and activated carbon are built in the deodorizer 41, and a suction fan and a drive motor (not shown) are provided. The suction port 42 is provided above the electrolytic bath 13, and a transparent cover 43 is provided above the electrolytic bath 13 and the cooling water bath 11 so as to cover them, while the deodorized exhaust gas is exhausted from the exhaust port 44. It has become so.

  When preparing the sample P for analysis, the sample P is cut, the surface is polished with a file and a belter, etc., and then subjected to a solution treatment as necessary to solidify the carbon. When the preparation is completed, the sample P is mounted in the saddle electrode 15 and the switch 30 is turned on. Then, a current flows between the platinum electrode 14 and the saddle electrode 15 and the sample P is electropolished.

  When the timer 36 reaches the set time, the polarity is switched by the polarity switcher 28, and the direction of the current flowing between the platinum electrode 14 and the saddle electrode 15 is switched.

  At this time, the voltmeter 37 and the ammeter 38 are monitored and adjusted by the output regulator 37 so that the energization current becomes an appropriate value. During electropolishing, the voltage is 1.5 V or less and the current is 1 A or less so as not to cause a very vigorous electrolytic reaction.

  The vertical electrode 15 is moved up and down by a vertical movement mechanism 23, and the rotor 25 is rotated by a motor 27 and a magnet 26 to stir the electrolytic solution in the electrolytic cell 13.

  After the electrolytic polishing is completed, the sample P is put into the first cleaning tank 31 and then pulled up and put into the second cleaning tank 32 to perform dehydration and degreasing. At this time, the ultrasonic generator 33 is operated to apply ultrasonic waves during dehydration and degreasing to perform ultrasonic cleaning.

  When the washing is completed, the organic solvent is removed by blowing cold air from a dryer, for example, and the analysis is performed.

For example, using the apparatus of this example, a sample was prepared under the following conditions.
Sample; high-purity iron (about 1 g)
Electrolyte solution: Concentrated hydrochloric acid Electrolytic current value: 0, 2A
Electrolysis time: Electropolishing was repeated three times while switching the polarity every about 5 seconds, and the electropolishing was performed for a total of 30 seconds.
Washing: Use water, ethyl alcohol and acetone for several seconds each.

1. Surface observation of sample Since the sample was filed, irregularities were observed on the surface before electropolishing, but the surface became smooth after electropolishing and a macrostructure was observed.

2. Measurement of surface oxygen by XSP FIG. 6 shows the result of quantifying the amount of surface oxygen by XSP in the sample depth direction. Thus, the amount of oxygen in the extreme surface layer is as high as 41 to 47%, and when this is integrated and converted in terms of the sample weight ratio, it corresponds to about 2 ppm. This is considered to be a result of the sample being dried in the cold air in the final stage and exposed to the atmosphere. Therefore, it is important to take measures to avoid exposure to the atmosphere as much as possible.

3. Example of Oxygen Analysis Results FIG. 7 shows a comparative analysis result of oxygen by the file polishing method and the electrolytic polishing method. In the electropolishing method, the results of oxygen analysis by performing cold air drying A with a drier at the final stage of cleaning with acetone (Method A) and the results of performing oxygen analysis without drying (Method B) are shown. In addition, the oxygen analysis used the inert gas atmosphere high temperature melt extraction-infrared absorption measuring method. In this way, it was confirmed that strict caution was required for atmospheric oxidation until the final stage of oxygen analysis. In this respect, the electropolishing method of this example was optimal for the preparation of the analytical sample.

  In this example, the vertical movement mechanism 23 shown in FIG. 4 is adopted, but other methods can be adopted.

It is a schematic perspective view which shows the whole structure of preferable embodiment of the electropolishing apparatus which concerns on this invention. It is a front view which shows the said embodiment. It is a top view which shows the said embodiment. It is a perspective view which shows one example of the vertical motive 23 in the said embodiment. It is a figure which shows the structure of the electric system in the said embodiment. It is a figure for demonstrating the effect | action of this example. It is a figure for demonstrating the effect | action of this example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing 11 Cooling water tank 12 Ultrasonic washing cooling water tank 13 Electrolytic tank 14 Platinum electrode 15 Vertical electrode 23 Vertical movement mechanism 25 Rotor 26 Magnet 27 Drive motor 31 1st washing tank 32 2nd washing tank 33 Ultrasonic generator 41 Deodorizer 43 Cover

Claims (4)

In an electropolishing apparatus suitable for electropolishing the surface of an object to be polished,
An electrolytic cell (13) in which an electrolytic solution is placed;
A rotor (25) that is put into the tank bottom of the electrolytic cell (13) and stirs the electrolytic solution by its rotation;
A drive motor (27) provided on the outside of the bottom of the electrolytic cell (13) and having a magnet (26) for magnetizing the rotor (25) attached to a rotating shaft;
A pair of electrodes (14, 15) that are immersed in an electrolytic solution in the electrolytic cell (13) and in which one electrode (15) has a bowl-like shape on which an object to be polished can be mounted;
A vertical movement mechanism (23) for moving the bowl-shaped electrode (15) up and down;
An energization circuit for energizing a current between the pair of electrodes (14, 15) ;
A cleaning tank (31, 32) in which an organic solvent is placed, and the object to be polished after electrolytic polishing is dehydrated and degreased by ultrasonic cleaning;
A washing cooling water tank (12) in which washing cooling water is put, the washing tank (31, 32) is immersed, and the washing tank (31, 32) is cooled by the washing cooling water;
An ultrasonic generator (33) for ultrasonically cleaning an object to be polished by applying ultrasonic waves to the organic solvent in the cleaning tank (31, 32) via the cleaning cooling water in the cleaning cooling water tank (12); ,
An electropolishing apparatus comprising: The cooling water tank (11) for cooling the periphery of the cell (13) or the electrolyzer electrolytic polishing apparatus according to claim 1 Symbol placement cooling water passage for circulating the cooling water is provided around the. The energization circuit, the pair of the electrode so as to switch the direction of current at regular time intervals and claim 1 Symbol placement of electrolytic polishing apparatus. The cover that constitutes the upper electrolytic cell between openable closed, electrolytic polishing apparatus according to claim 1 Symbol placement with a, and adsorber that adsorbs the vapor of electrolyte in the cover.

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