JP2006348336A - Electrolytic polishing liquid, and method for producing metal product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily treatable electrolytic polishing liquid having excellent safety. <P>SOLUTION: The electrolytic polishing liquid comprises a compound expressed by general formula (I), and an alkali metal chloride and/or an alkaline earth metal chloride. The method for producing a metal product having a specular part on the surface is provided. Electrolytic treatment is performed with the metal product as an anode and the electrolytic polishing liquid as an electrolytic liquid. In the formula, R is a hydrogen atom or a methyl group, and n is an integer in the range of 1 to 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electropolishing liquid that is easy to handle and excellent in safety.

  Known mirror finishing methods for metal products include mechanical polishing methods such as buff polishing and barrel polishing, chemical polishing methods, electrolytic polishing methods, and electrolytic composite polishing methods. Among them, the electrolytic polishing method has an advantage that it can polish relatively complicated shapes and wires, and because it is polished by an electrochemical action, the abrasive grains do not penetrate into the polished surface.

Conventionally, for example, perchloric acid-based or fluoride-based electropolishing liquids for titanium-based metal products have been used. In recent years, it has also been proposed to use an alcohol-based solution for electrolytic polishing of titanium (see Non-Patent Document 1). However, these electrolytic polishing liquids have problems such as ignition, explosion, and risk of toxic gas generation.
Naohisa Morita, Dental Technology and Instruments Vol. 9 No. 2 p218-239 (1990)

  An object of the present invention is to provide an electropolishing liquid that is easy to handle and excellent in safety.

Means for achieving the object is as follows.
[1] An electropolishing liquid containing a compound represented by the following general formula (I) and an alkali metal chloride and / or an alkaline earth metal chloride.
(In the formula, R is a hydrogen atom or a methyl group, and n is an integer in the range of 1 to 3).
[2] The electrolytic polishing liquid according to [1], wherein the compound is at least one selected from the group consisting of ethylene glycol, diethylene glycol, and propylene glycol.
[3] The electrolytic polishing liquid according to [1] or [2], wherein the alkali metal chloride is at least one selected from the group consisting of sodium chloride, lithium chloride, and potassium chloride.
[4] The electrolytic polishing liquid according to any one of [1] to [3], wherein the alkaline earth metal chloride is at least one selected from the group consisting of calcium chloride and strontium chloride.
[5] A method for producing a metal product having a mirror surface portion on the surface, wherein the metal product is used as an anode, and the electrolytic polishing solution according to any one of [1] to [4] is used as an electrolyte. The manufacturing method as described above.
[6] The metal product may be a titanium metal product, an aluminum metal product, a magnesium metal product, a nickel metal product, an iron metal product, a zinc metal product, or a stainless metal product. Production method.

According to the present invention, an electropolishing liquid that is easy to handle and excellent in safety can be provided.
Furthermore, according to this invention, the metal product which has a favorable mirror surface part can be manufactured.

Hereinafter, the present invention will be described in more detail.

[Electrolytic polishing liquid]
The electropolishing liquid of the present invention contains a compound represented by the following general formula (I) and an alkali metal chloride and / or an alkaline earth metal chloride.
(In the formula, R is a hydrogen atom or a methyl group, and n is an integer in the range of 1 to 3).

  Since the electropolishing liquid of the present invention contains highly safe alkali metal chloride and / or alkaline earth metal as a solute and a non-flammable glycol compound as a solvent, it is extremely safe and easy to handle. It has the advantage of being easy.

  In general formula (I), R is a hydrogen atom or a methyl group, and is preferably a hydrogen atom. Moreover, in general formula (I), n is an integer of 1-3, Preferably it is the range of 1-2.

  In the electrolytic polishing method, when an electrolytic treatment is performed, a solid film and a liquid mucus film are generated on the polished surface. It is considered that the generation of the solid film contributes to the polishing effect (mirror finish), and the mucus film contributes to the polishing effect (mirror finish) and suppresses oxidation. Therefore, if this mucus film is held on the polished surface for a predetermined period, it is considered that the oxidation of the metal surface is suppressed and the mirror surface progresses. Therefore, it is preferable that the compound represented by the general formula (I) has an appropriate viscosity and specific gravity such that the mucus film is held on the polished surface for a predetermined period. Furthermore, it is preferable that the compound represented by the general formula (I) can dissolve the solute used (alkali metal chloride and / or alkaline earth metal chloride) well. From the above viewpoint, the compound represented by the general formula (I) is preferably ethylene glycol, diethylene glycol, or propylene glycol, and most preferably ethylene glycol. In the present invention, two or more compounds represented by the general formula (I) can be used in combination.

  The alkali metal chloride is preferably at least one selected from the group consisting of sodium chloride, lithium chloride, and potassium chloride, and sodium chloride is most preferable in view of safety, availability, and the like. The alkaline earth metal chloride is preferably at least one selected from the group consisting of calcium chloride and strontium chloride. In the present invention, two or more alkali metal chlorides and alkaline earth metal chlorides can be used in combination.

  The concentration of the alkali metal chloride and alkaline earth metal chloride in the electropolishing liquid of the present invention is preferably set in consideration of the solubility of the chloride used and the viscosity of the solution. When ethylene glycol is used as the compound represented by the general formula (I), the concentration of sodium chloride and potassium chloride is, for example, 20 g to 75 g, preferably 40 g to 75 g, most preferably 60 g to 75 g, relative to 1 L of ethylene glycol. It can be. On the other hand, in the case of lithium chloride, for example, 20 g to 150 g, preferably 40 g to 150 g, and most preferably 60 g to 130 g can be used for 1 L of ethylene glycol. In the case of calcium chloride, for example, 20 g to 150 g, preferably 40 g to 150 g, most preferably 60 g to 110 g, and in the case of strontium chloride, 20 g to 1 g of ethylene glycol. ˜180 g, preferably 40 g to 180 g, most preferably 60 g to 160 g. In addition, when a compound other than ethylene glycol is used as the compound represented by the general formula (I), the concentration of the chloride is preferably close to saturation.

  The electrolytic polishing liquid of the present invention can be an anhydrous electrolytic solution. The electropolishing liquid of the present invention may contain a solvent other than the compound represented by the general formula (I), for example, for viscosity adjustment. Examples of the miscible solvent include ethanol, propanol, polyethylene glycol, glycerin and the like. However, in that case, 70% by mass or more of the solvent is preferably the compound represented by the general formula (I). The electropolishing liquid of the present invention is preferably composed of a compound represented by the general formula (I) and an alkali metal chloride and / or an alkaline earth metal chloride.

  In the present invention, good polishing can be confirmed by, for example, lowering the surface roughness value and improving glossiness. The electrolytic polishing liquid of the present invention is used for polishing, for example, a titanium metal product, an aluminum metal product, a magnesium metal product, a nickel metal product, an iron metal product, a zinc metal product or a stainless metal product. It is suitable for. Details of the polishing process will be described later.

[Production method of metal products]
The present invention further relates to a method for manufacturing a metal product having a mirror surface on the surface, wherein the metal product is used as an anode, and the electrolytic treatment is performed using the electropolishing liquid of the present invention as an electrolyte. Regarding the method.

  In the manufacturing method, since an electropolishing liquid that is excellent in safety and easy to handle is used, the operability is excellent. Furthermore, a mirror-finished metal product having a smooth surface can be produced by the method of the present invention.

The metal product obtained by the production method of the present invention has a mirror surface portion on the surface. In the present invention, the “mirror surface” represents a surface state of a metal product to be obtained, and refers to a surface having a mirror gloss of 400 or more. Here, the specular gloss refers to a 60 ° specular gloss measured according to JIS Z8741-1997.
The mirror surface portion of the metal product may be any part or all of the surface of the metal product.

  The metal product may be a titanium metal product, an aluminum metal product, a magnesium metal product, a nickel metal product, an iron metal product, a zinc metal product, or a stainless metal product. The metal product may be a pure metal or may be an alloy containing two or more metal components.

  In particular, titanium metal products are widely used in medical and dental instruments, including implants such as artificial bones and fracture joints, because of their corrosion resistance and biocompatibility. Mirror finish is performed for the purpose of improving the property (preventing the adhesion and propagation of various bacteria). As described above, in the present invention, since an electropolishing liquid excellent in safety is used, it is suitable for titanium-based metal products used for medical and dental applications as described above.

  The titanium-based metal product used in the present invention can be pure titanium or a titanium alloy. Specific examples of titanium-based metals include pure titanium; Ti-15Mo, Ti-5Al-2.5Sn, Ti-6Al-4V ELI, Ti-6Al-4V, Ti-6Al-7Nb, Ti-15Mo-5Zr, Ti -5Al-3Mo-4Zr, Ti-13Nb-13Ta, Ti-12Mo-6Zr-2Fe, Ti-15Zr-4Nb-2Ta-0.2Pd, Ti-35.3Nb-5.1Ta-4.6Zr, Ti-29Nb -13Ta-4.6Zr, Ti-15Sn-4Nb-2Ta-0.2Pd, and other alloys containing a large amount of Ti.

  In the method of the present invention, the metal product to be mirror-finished can be used as an anode, and the electrolytic polishing liquid of the present invention can be placed between the anode and the cathode to perform the electrolytic treatment. For example, the electrolytic treatment can be performed by immersing the anode and the cathode in an electropolishing liquid.

  The material of the cathode can be appropriately selected according to the composition of the electropolishing liquid. Examples of the material for the cathode include titanium, platinum, stainless steel, and copper. Titanium is preferable in order to prevent the adverse effect of precipitation at the anode. Moreover, there is no restriction | limiting in particular about the shape of a cathode, It is preferable to set it as the shape which an electric current flows uniformly according to the shape of the product to grind | polish, for example, it can be set as a cylindrical shape.

The electrolytic treatment can be performed by a known method, and the electrolytic conditions can be appropriately set according to the metal product to be treated. For example, the current density can be 3 to 400 mA / cm ² , and the interelectrode voltage can be 3 to 40V. The electrolytic treatment can be performed, for example, for 1 to 120 minutes.

  The temperature of the electrolytic solution during the electrolytic treatment can be, for example, about room temperature (room temperature), and is preferably in the range of 5 to 30 ° C.

As described above, in the electrolytic polishing method, a solid film and a liquid mucus film are generated on the polishing surface, and the generation of the solid film and the mucus film contribute to the polishing effect (mirror finishing). However, the solid film that can be peeled off by electrolysis or the retention of the oxide film originally present on the surface of the metal to be polished on the polished surface may hinder the progress or uniform progress of polishing. In particular, this is the case with titanium-based metal products. Therefore, when the metal product to be treated is a titanium metal product, an electrolytic polishing liquid is disposed between the titanium metal product (anode) and the cathode (for example, both electrodes) in order to shorten the polishing time and remove the film. It is preferable that the first electrolysis step at a relatively high current density is performed, and then the second electrolysis step at a lower current density than the first electrolysis step is performed. Specifically, a high current density electrolysis step of electropolishing at a current density in the range of 40 to 200 mA / cm ² is performed, and then the current density is lower than the current density in the high current density electrolysis step, It is preferable to perform a low current density electrolysis step of electropolishing at a current density in the range of 40 mA / cm ² . When electrolysis is performed at a constant voltage, the current value may fluctuate immediately after voltage application. The “current density” in the present invention refers to an average value of time (seconds) of current density.

When electrolytic polishing is performed at a relatively high current density, polishing can be performed in a short time. However, when mirror finishing is performed only by electropolishing at a high current density, heat, temperature, film, etc. tend to be non-uniform and bubbles are generated when the time exceeds a certain level. Such non-uniformity of heat, temperature, film, etc. and the generation of bubbles hinder the polishing effect, so that a white or gray cloudy surface is generated on a part or the entire surface of the polishing surface.
On the other hand, when electrolytic polishing is performed at a relatively low current density, a highly stable mirror surface can be formed, but it takes a long time. In addition, when electrolytic polishing is performed at a relatively low current density, after a film is formed on the surface, a part that naturally peels off and a part that stays are formed, and as a result, the polished surface becomes non-uniform. Therefore, in order to obtain a uniform mirror surface, it is necessary to perform a film removal process such as ultrasonic treatment and stirring of the electrolytic polishing liquid.
On the other hand, by combining electrolytic polishing at a relatively high current density and electrolytic polishing at a relatively low current density, a mirror-finished titanium metal product having a smooth surface can be obtained in a short time.
This point will be described in more detail.
In the electrolytic polishing of titanium metal products, it is considered that the reaction for forming a film and the reaction for removing the film proceed simultaneously. When voltage is applied to the cathode and anode (object to be polished), a mucus layer is formed in the vicinity of the anode surface. Immediately after the voltage is applied (initial stage), this mucus layer is thin. Proceed to. On the other hand, when time passes and the mucus layer becomes sufficiently thick, the reaction to peel off the film also proceeds and a polishing effect appears. That is, it is considered that the electropolishing of the titanium-based metal product proceeds by the formation of the film → peeling. By polishing in a short time in the high current density electrolysis process and switching to the low current density electrolysis process before the cloudy surface is formed, the portion that could not be polished in the high current density electrolysis process is polished to obtain a uniform mirror surface be able to. In the low current density electrolysis process, the reaction with a polishing effect proceeds only moderately, but the generation and separation of the film on the polished surface, heat generation and heat dissipation are balanced, and uniform electropolishing is maintained over time. Therefore, a highly stable mirror surface can be formed. Thus, a mirror surface with high stability can be formed in a short time by combining the high current density electrolysis process and the low current density electrolysis process.

The current density in the high current density electrolysis step may be in the range of 40~200mA / cm ^2, preferably in the range 50~100mA / cm ^2, particularly preferably of 60~80mA / cm ^2. When the current density is 200 mA / cm ² or less, a cloudy surface is hardly formed on the polished surface, and the temperature of the electrolytic solution rises due to heat generation on the polished surface, or convection occurs in the electrolytic solution, which occurs near the anode surface. The problem that the mucus layer is destroyed and the progress of electropolishing is hindered can also be avoided. On the other hand, if the current density is 40 mA / cm ² or more, the polishing time can be shortened. The current density in electropolishing can be set to a desired value by adjusting the applied voltage.

The current density is in the low current density electrolysis step, the high current density even at low current densities than the current density in the electrolytic process, can be in the range of 5 to 40 mA / cm ^2, preferably 5 to 30mA / cm ² Especially preferably, it is the range of 5-15 mA / cm < ² >. If the current density in the low current density electrolysis step is within the above range, good polishing can be performed.

  In the high current density electrolysis step, a mirror surface can be formed in a short time, but if it is carried out for an excessively long time, the polished surface may be clouded. Therefore, the high current density electrolysis step is preferably performed for 0.5 to 10 minutes, and more preferably for 1 to 5 minutes. On the other hand, the low voltage electrolysis step does not adversely affect the polished surface even if it is performed for a long time, but from the viewpoint of obtaining a stable mirror surface in a short time, for example, 5 to 40 minutes, preferably 5 to 20 minutes. It can be carried out.

  A product having a mirror surface portion can be obtained by performing the high current density electrolysis step and the low current density electrolysis step once, but in order to reduce the surface roughness, these steps may be repeated two or more times. preferable. The high current density electrolysis step and the low current density electrolysis step can be performed, for example, twice or more, preferably three times or more. However, if these steps are repeated, the shape accuracy of the object to be polished may decrease due to polishing. Therefore, the number of times of the high current density electrolysis step and the low current density electrolysis step is preferably set as appropriate in consideration of the balance between the shape accuracy and the surface roughness. The upper limit of the number of repetitions of the step can be, for example, 10 times.

  In the present invention, the entire process can be performed continuously without stopping the electrolysis, but between the high current density electrolysis process and the low current density electrolysis process and / or to the next high current density electrolysis process. The electrolysis can be temporarily stopped before the transition. In both the high current density electrolysis process and the low current density electrolysis process, as described above, immediately after the voltage is applied (initial), the mucus layer near the anode surface is thin, so the formation of the film is superior to the peeling. proceed. In electrolytic polishing of titanium-based metal products, a glossy surface (mirror surface) is obtained after the film is peeled off, so that the formation of the film is also considered a reaction necessary for reducing the surface roughness. That is, it is considered that film formation at the initial stage of electrolysis is effective in reducing the surface roughness. Therefore, in order to advance the formation of the film more preferentially than peeling, the electrolysis is suspended and the electrolyte is stirred, or the mucus layer is diffused in the electrolyte by vibrating the object to be polished. Thus, a mirror surface with a further reduced surface roughness can be obtained by returning the electrolytic solution to a state before applying voltage (initial state). Further, it is considered that suspending electrolysis also has an effect of releasing heat near the polished surface generated in the high current density electrolysis process and the low current density electrolysis process.

As described above, the retention of the film formed on the titanium surface on the polished surface may hinder the progress of polishing or uniform progress. Therefore, the production method of the present invention may further include a step for removing the film formed on the titanium surface after the electrolytic treatment in order to proceed the polishing well.
However, the film formed on the titanium surface in the above-mentioned method of performing electropolishing at two current densities, high or low, can be peeled off during electrolysis without any vibration, or the liquid can be stirred gently after electrolysis is stopped. The film removal process is not essential. Examples of the film removal method include liquid stirring and ultrasonic treatment. When performing ultrasonic treatment, an ultrasonic cleaning apparatus used for general ultrasonic cleaning can be used as it is. The ultrasonic wave to be used can be an ultrasonic wave having a frequency of 10 to 100 MHz and an output of 25 to 300 W, for example.

  The method of performing electropolishing at two current densities as described above is suitable for the treatment of titanium-based metal products in which a strong film is easily formed. However, aluminum-based metal products, magnesium-based metal products, and nickel-based metals. Of course, it can be applied to products, iron-based metal products, zinc-based metal products, and stainless-based metal products.

Hereinafter, the present invention will be described in more detail with reference to examples.

Polishing apparatus The structure of the electrolytic polishing apparatus is shown in FIG.
As the power source, a DC power source (A & D), AD-8723, 0 to 30 V) was used. A 300 ml glass beaker was used for the electrolytic cell, and the electrode (cathode) was a pure titanium plate (thickness 0.2 mm) bent into a cylindrical shape and arranged along the wall of the beaker.

Evaluation method (1) Surface roughness Ra
The surface roughness / contour shape measuring instrument SV-C624 (Mitutoyo Corporation) was used to measure the arithmetic average roughness based on JIS B0601-1994.
(2) Specular Gloss The glossiness was measured with a gloss meter VGS-300A (Nippon Denshoku Co., Ltd.) as a 60-degree specular gloss based on JIS Z8741-1997.

[Example 1]
The polishing sample shown in FIG. 2 was produced by the following method.
A pure titanium plate (thickness 1 mm; 2 types for industrial use) is processed into a strip shape (width 5 mm) with a wire electric discharge machine, and the polishing area is adjusted to 20 mm × 5 mm with a heat shrinkable tube as shown in FIG. Got. This sample had a surface roughness Ra of 0.28 μm before polishing and a mirror glossiness of 75.
An electrolytic polishing solution was prepared by dissolving 20 g of sodium chloride in 300 ml of ethylene glycol. Using this electropolishing liquid, an electrolytic polishing apparatus shown in FIG. 1 was used to electrolyze a polished sample at an interelectrode voltage of 25 V for 3 minutes, and then the electrolysis was suspended and the liquid was stirred, and then the interpolated voltage was 3 at an interelectrode voltage of 25 V. Electrolytic treatment was performed for 30 minutes at an interelectrode voltage of 10V. The state of the sample after the treatment is shown in FIG. The surface roughness of the sample after the treatment was 0.12 μm and the specular gloss was 444, and it was confirmed that the polishing was satisfactorily performed by the electrolytic treatment using the electrolytic polishing solution.

[Example 2]
Using the same electropolishing liquid and electropolishing apparatus as in Example 1 (however, a 2 L beaker was used instead of the 300 ml beaker), a pure titanium round bar (φ10 mm × 150 mm; manufactured by Niraco Co., Ltd.) The process of “interelectrode voltage 25 V, 3 minutes → interelectrode voltage 10 V, 30 minutes → liquid stirring” was repeated twice to perform the electrolytic treatment. The state of the sample after the treatment is shown in FIG. The surface roughness Ra of the round bar before the treatment was 0.67 μm, whereas the surface roughness Ra of the sample of the round bar after the treatment was 0.19 μm, and it was confirmed that the polishing was performed well. It was done.

[Examples 3 to 6]
The sample similar to the sample used in Example 1 was subjected to electrolytic treatment under various conditions shown in Table 1. As shown in Table 1, under any condition, it was confirmed that the specular gloss and the surface roughness were improved before and after the treatment, and the polishing was performed well.

[Examples 7 to 14]
Various metal samples were subjected to electrolytic treatment under various conditions shown in Table 2. The metal sample was processed in the same manner as in Example 1. As shown in Table 2, under any condition, it was confirmed that the specular gloss before and after the treatment was improved, the surface roughness after the treatment was low, and the polishing was performed well.

[Example 15]
A pure magnesium round bar (φ6 mm × 20 mm) was polished using the electrolytic polishing apparatus shown in FIG. The surface roughness Ra of this round bar was 0.49 μm. An electropolishing liquid in which 20 g of potassium chloride was dissolved in 300 ml of ethylene glycol was used. The liquid temperature was set to 25 ° C. After performing an electrolytic treatment for 2 minutes at an interelectrode voltage of 15 V, the step of stirring the liquid was repeated 10 times. The surface roughness Ra of the treated sample was 0.21 μm.

  According to the present invention, a mirror-finished metal product having a smooth surface can be obtained. The electrolytic polishing liquid and the metal product manufacturing method of the present invention include, for example, medical instruments such as stents, artificial roots, orthodontic wires, guide wires, and titanium citrus, and glasses, rings, and earrings that are less likely to contain impurities. It can be applied to accessories such as necklaces, watches, brooches, cell culture equipment parts, semiconductor manufacturing equipment parts, and the like.

It is the schematic of the electropolishing apparatus used in the Example. It is the schematic of the grinding | polishing sample used in the Example. The state of the sample processed in Example 1 is shown. The state of the sample processed in Example 2 is shown.

Claims (6)

An electropolishing liquid comprising a compound represented by the following general formula (I) and an alkali metal chloride and / or an alkaline earth metal chloride.
(In the formula, R is a hydrogen atom or a methyl group, and n is an integer in the range of 1 to 3). The electrolytic polishing liquid according to claim 1, wherein the compound is at least one selected from the group consisting of ethylene glycol, diethylene glycol, and propylene glycol. The electrolytic polishing liquid according to claim 1 or 2, wherein the alkali metal chloride is at least one selected from the group consisting of sodium chloride, lithium chloride, and potassium chloride. The electrolytic polishing liquid according to claim 1, wherein the alkaline earth metal chloride is at least one selected from the group consisting of calcium chloride and strontium chloride. It is a manufacturing method of the metal product which has a mirror surface part on the surface, Comprising: The said metal product is made into an anode, Electrolytic processing is performed using the electrolytic polishing liquid of any one of Claims 1-4 as electrolyte solution, It is characterized by the above-mentioned. The manufacturing method. The manufacturing method according to claim 5, wherein the metal product is a titanium metal product, an aluminum metal product, a magnesium metal product, a nickel metal product, an iron metal product, a zinc metal product, or a stainless metal product.