JP2017214614A - Method for producing electrolytically polished metal compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in a method for producing electrolytically polished metal compact, a method for producing metal compact in which, while shortening the polishing time, a uniform polishing surface with less polishing unevenness is obtained by a simple method and a simple apparatus.SOLUTION: Provided are: a method for producing a metal compact including 1 or more times of a first electrolytic polishing step of electrolytic polishing under the following condition of (a) in an electrolytic polishing liquid, and 1 or more times of a second voltage electrolytic polishing step of electrolytic polishing under the following condition of (b), and in which the final electrolytic polishing is carried out under the following condition of (b). (a) a condition of applying a voltage for a fixed time. (b) a condition of applying a voltage higher than the condition (a) for a fixed time; and a method for producing a metal compact in which the voltage under the condition of (a) is 10 to 30 V and the voltage of the condition of (b) is 20 to 45 V.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an electrolytically polished metal molded body in which a metal molded body is electrochemically polished in an electrolytic polishing liquid.

  Electropolishing is a processing method for finishing the surface of various metal molded bodies into a mirror surface, and is generally widely used in industry. Various methods of electrolytic polishing of metal molded bodies have been developed so far. For example, metal molded bodies containing iron, chromium, magnesium, aluminum, titanium, etc., which are base metals whose surfaces are easily oxidized, are formed on the surface. Due to the formed oxide film, electropolishing tended to be difficult. In particular, the electropolishing of a metal molded body made of titanium or a titanium alloy has a remarkable tendency because the oxide film on the surface is difficult to remove (dissolve).

  Titanium or titanium alloy has characteristics superior to other metals such as light weight, high strength, and excellent corrosion resistance. Therefore, titanium or titanium alloys are used in a wide range of fields such as electronic devices such as semiconductor devices, optical devices, chemical devices, and medical materials. In particular, nickel titanium alloys having an atomic ratio of nickel to titanium having shape memory characteristics and superelastic characteristics of approximately 1: 1 are being used as medical materials, such as orthodontic wires, guide wires, and stents. Widely used in medical devices.

  The surface of a medical device represented by such a stent is required to be very smooth. The rough surface can cause inflammation by damaging or excessively irritating tissues in the body during or after transplantation into the human body. The surface is finished with a smooth finish. As a method for processing the surface of such a medical device, an electropolishing method is suitably used.

  However, in the electrolytic polishing of the metal molded body, deterioration of the electrolytic polishing liquid to be used, or bubbles generated in the electrolytic polishing liquid due to electrolytic polishing over a long period of time, temperature change of the polishing liquid, ion concentration gradient in the liquid, etc. Due to the influence, the uneven metal oxide film layer formed unevenly is formed on a part or the whole of the polished surface, resulting in a white and cloudy polished surface.

  Electropolishing is performed by immersing an object to be polished in an electropolishing liquid and anodic dissolution and anodic oxidation in a well-balanced manner. When used, anodic oxidation predominated and the occurrence of white cloudy surfaces tended to be more pronounced.

  Incidentally, the deterioration due to the use of the electrolytic polishing liquid refers to a state in which the viscous resistance is increased due to consumption of ions contributing to the electrolytic polishing ability or dissolution of the metal component to be polished.

  In particular, in a metal material containing titanium, the formed titanium oxide film layer adheres firmly, and thus is difficult to peel off and tends to produce a white cloudy surface after electropolishing. Conventionally, many electrolytic polishing liquids containing fluoride have been used to dissolve and remove the strongly adhered titanium oxide film layer. However, since this involves a load on health and the environment, it contains fluoride. No electropolishing liquid is being used. However, the electropolishing liquid containing no fluoride has a tendency to easily remove a titanium oxide film, and tends to produce a white cloudy surface after electropolishing.

Patent Document 1 proposes an electrolytic polishing method including an operation of vibrating and agitating an electrolytic solution for the purpose of suppressing the growth of an oxide film on a metal molded body (current density: 3 to 500 A / dm ^2). = 30-5000 mA / cm < ² >).

In Patent Document 2, an electrolytic solution is applied for the purpose of applying a relatively low voltage (current density: 1 to 40 mA / cm ² ) to the metal molded body and performing electropolishing, and removing the film from the surface. Among them, an electropolishing method including a step of subjecting to ultrasonic treatment has been proposed.
In Patent Document 3, after electrolytic polishing is performed on a metal molded body at a relatively high voltage (current density: 40 to 200 mA / cm ² ), a relatively low voltage (current density: 5 to 40 mA / cm ² ). An electropolishing method has been proposed in which an electropolishing is performed to obtain a polished surface having no white cloudy surface.

  Moreover, in patent documents 1-3, the electropolishing liquid which does not contain the fluoride which contains alcohol and a metal chloride with respect to the electropolishing of a metal molded object is illustrated.

JP 2004-060004 A JP 2004-018954 A JP-A-2005-240144

  In the method of electropolishing a metal molded body of Patent Document 1 and Patent Document 2, it is essential to perform a vibration stirring operation or ultrasonic treatment for removing a metal oxide film generated during electropolishing, which makes the operation complicated. In addition, a device for this purpose was necessary. In addition, the electrolytic polishing method of Patent Document 2 has a problem that it takes a longer polishing time compared to a normal electrolytic polishing method because a relatively low voltage (current density) is applied to perform the electrolytic polishing.

  The method of electropolishing a metal molded body of Patent Document 3 does not require a vibration stirring operation or ultrasonic treatment that requires additional equipment as in Patent Document 1 and Patent Document 2, but finally has a relatively low voltage ( Therefore, there is a problem that the polishing time is longer than that of a normal electrolytic polishing method.

  In order to solve the above problems, the present invention can provide a uniform polished surface with less unevenness of polishing while reducing the polishing time by using a simple method and a simple apparatus in electrolytic polishing of a metal molded body. An object is to provide an electrolytic polishing method.

As a result of intensive studies for solving the above problems, the present inventor has completed the present invention. That is, this invention provides the manufacturing method of the metal molded object of following (1)-(15).
(1).
In the electropolishing liquid, the process includes one or more first electropolishing processes for electropolishing under the following conditions (a) and one or more second electropolishing processes for electropolishing under the following conditions (b). A method for producing a metal molded body, comprising performing final electrolytic polishing under conditions.
(A) Conditions for applying a voltage for a certain period of time (b) Conditions for applying a voltage higher than the condition (a) for a certain period of time (2).
The method for producing a metal molded body according to (1), wherein the voltage value of the condition (a) is selected from a range of 10 V or more and 30 V or less.
(3).
The method for producing a metal molded body according to (1) or (2), wherein the voltage value of the condition (b) is selected from a range of 20 V or more and 45 V or less.
(4).
The current value in the step (a) and the step (b) is selected from the range of 40 mA / cm ² or more, The metal molded body according to any one of (1) to (3), Production method.
(5).
The metal molded body according to any one of (1) to (4), wherein the voltage application time in step (b) is the same as or shorter than the voltage application time in step (a). Manufacturing method.
(6).
The voltage application time in the step (a) is selected in the range of 10 seconds to 60 seconds and the voltage application time in the step (b) is selected in the range of 1 second to 10 seconds. The manufacturing method of the metal molded object in any one of (1)-(5) to do.
(7).
The method for producing a metal molded body according to any one of (1) to (6), wherein the electropolishing liquid does not contain fluoride or the content of fluoride is 5% by weight or less. .
(8).
The method for producing a metal molded body according to any one of (1) to (7), wherein the electropolishing liquid contains an alkylsulfonic acid.
(9).
The method for producing a metal molded body according to any one of (1) to (8), wherein the electrolytic polishing liquid contains an aminocarboxylic acid type chelating agent.
(10).
The method for producing a metal molded body according to any one of (1) to (9), wherein the metal molded body is made of a base metal.
(11).
The method for producing a metal molded body according to (10), wherein the metal molded body contains one or more selected from iron, chromium, magnesium, aluminum, and titanium.
(12).
The method for producing a metal molded body according to (11), wherein the metal molded body is made of titanium or a titanium alloy.
(13).
The method for producing a metal molded body according to (12), wherein the metal molded body is made of a nickel titanium alloy.
(14).
The method for producing a metal molded body according to any one of (1) to (13), wherein the metal molded body is a medical tubular body.
(15).
The method for producing a metal molded body according to (14), wherein the medical tubular body is a stent.

  According to the present invention, it is possible to produce a metal molded body having a uniform polished surface with little unevenness while shortening the polishing time by using a simple method and a simple apparatus. Moreover, even if it is an electropolishing liquid used for a long period of time, it contributes to the lifetime improvement of an electropolishing liquid by providing the electropolishing method which can obtain the polishing surface without a white cloudy surface.

It is the schematic which shows the electrolytic polishing method which is one Embodiment of this invention. It is explanatory drawing which shows (i) current density value and (ii) voltage value in the 1st electropolishing process of the electropolishing method which is one Embodiment of this invention. It is explanatory drawing which shows the (iii) electric current density value and the (iv) voltage value in the 2nd electropolishing process of the electropolishing method which is one Embodiment of this invention. It is the schematic which shows the electrolytic polishing method which is one Embodiment of this invention. It is a stereoscopic microscope image of the stent which concerns on Example 1 of this invention. It is a stereoscopic microscope image of the stent which concerns on the comparative example 1 of this invention. It is a stereoscopic microscope image of the stent which concerns on Example 4 of this invention. It is a stereoscopic microscope image of the stent which concerns on the comparative example 4 of this invention. It is a stereoscopic microscope image of the wire which concerns on Example 5 of this invention. It is a stereoscopic microscope image of the wire which concerns on the comparative example 5 of this invention. It is a stereoscopic microscope image of the wire which concerns on Example 6 of this invention. It is a stereoscopic microscope image of the wire which concerns on the comparative example 6 of this invention. It is a stereoscopic microscope image of the wire which concerns on Example 7 of this invention. It is a stereoscopic microscope image of the wire which concerns on the comparative example 7 of this invention. It is a stereoscopic microscope image of the stent which concerns on the comparative example 8 of this invention. It is a SEM image of the stent which concerns on Example 1 of this invention. It is a SEM photograph of the stent which concerns on the comparative example 1 of this invention. It is a STEM cross-sectional image of the stent of the cross section which concerns on Example 1 of this invention. It is a STEM cross-sectional image of the stent of the cross section which concerns on the comparative example 1 of this invention.

The method for electropolishing a metal molded body of the present invention includes at least one first electropolishing step in which electropolishing is performed in an electropolishing liquid under the following condition (a) and second electrolysis in which electropolishing is performed under the following condition (b). It is characterized in that the final electrolytic polishing is performed under the following condition (b) including at least one polishing step.
(A) Conditions for applying a voltage for a certain period of time (b) Conditions for applying a voltage higher than the condition (a) for a certain period of time After applying a relatively high voltage and electrolytic polishing, a voltage higher than that voltage is applied. By carrying out the electrolytic polishing, a metal molded body having a smoothness with less white cloudy surface and excellent smoothness can be produced in a shorter polishing time than before.
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an electropolishing method for a metal molded body according to the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

<Metal molded body>
The metal molded body of the object to be polished in the present invention is not particularly limited as long as it is a metal that can be electropolished by the electrolytic polishing method of the present invention, but a metal molded body made of a base metal whose surface is easily oxidized is preferably used. As the metal molded body made of a base metal, for example, a metal molded body containing one or more selected from iron, chromium, magnesium, aluminum, and titanium is preferably used. The term “base metal” as used herein refers to a metal that has a higher ionization tendency than hydrogen. In particular, a metal molded body containing titanium or a titanium alloy that forms a strong oxide film on the surface (hereinafter sometimes referred to as a titanium-based metal molded body) can be particularly preferably used.

The titanium-based metal molded body of the object to be polished by the electrolytic polishing method of the present invention includes a molded body made of titanium and at least one other metal in addition to a molded body made of pure titanium.
The titanium-based metal is preferably one selected from pure titanium, a titanium alloy, and a titanium-based shape memory alloy.

  Specific examples of titanium or titanium alloy 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; Ni-Ti, Ni-Ti-Co, Ni-Ti-Fe, Ni -Ti-Cr-based, Ni-Ti-Cu-based, Ni-Ti-Cu-Cr-based shape memory alloys, and various shape memory alloys mainly composed of Ni and Ti Are, in particular, the atomic ratio of titanium and nickel of approximately 1: is preferably a nickel-titanium alloy is 1. Particularly preferred is a nickel titanium alloy containing about 50% to about 60% nickel.

  The metal molded body containing the above-described nickel titanium alloy is particularly used as a medical material. Specific examples thereof include a stent, an embolic device for treating an atrial septal defect, an aneurysm embolic coil, a thrombus filter, Examples include guide wires, orthodontic arch wires, and cerebral aneurysm wires.

<Stent>
A medical stent is one type of mesh-like medical tubular body that is placed in the body in order to prevent restenosis after expansion of a stenosis part such as a blood vessel. Examples of medical stents include: (a) a coiled type made of a single linear metal or polymer material, (b) a type in which a metal tube is cut out by a laser, etc. There are types that are assembled by welding the members with a laser or the like, and (d) types that are made by weaving multiple linear metals.

  As the stent according to the present invention, for example, the diameter is expanded from a first diameter which is a size to be inserted into the body lumen structure to a second diameter where at least a part of the outer surface of the tubular body contacts the blood vessel wall. And a tubular body.

  In particular, a stent can be preferably used as a medical tubular body used for the formation of a body lumen structure such as a blood vessel, a ureter, and a bile duct.

  As a material used for the stent, a nickel titanium alloy can be preferably used because it has shape memory characteristics and superelastic characteristics and is excellent in workability. Of the nickel titanium alloys, a nickel titanium alloy containing about 50% to about 60% nickel can be preferably used.

  As a method for producing a metal stent, a method of performing electropolishing after cutting a tube-shaped material into a mesh shape with a laser can be preferably used.

  Electropolishing is the removal of the surface oxide film generated by laser processing of the strut portion, which is the bent linear portion of the stent, or heat treatment after laser processing, and the rounding of the sharp edges of the cross section of the strut. Etc. for the purpose. The electropolishing is preferably performed as a final finishing step for various purposes such as reduction of metal elution, improvement of fatigue characteristics, and improvement of cleanliness.

<Electrolytic polishing liquid>
As the electropolishing liquid used in the electropolishing method of the present invention, a general electropolishing liquid used for electropolishing can be used, but an electropolishing liquid containing no fluoride can be preferably used. Examples of the fluoride include sodium fluoride, potassium fluoride, lithium fluoride, ammonium fluoride, hydrogen fluoride, and the like. Since the use of the electrolytic polishing liquid containing fluoride involves a load on health and the environment, it is preferable to use an electrolytic polishing liquid not containing fluoride, and the content should be 5% by weight or less. preferable.

  The electropolishing liquid used in the present invention preferably contains an alkyl sulfonic acid. The alkylsulfonic acid that can be used in the present invention is not particularly limited as long as it has an electropolishing effect, and a commercially available alkylsulfonic acid can be suitably used. Examples of commercially available alkyl sulfonic acids include methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, butane sulfonic acid, pentane sulfonic acid, hexane sulfonic acid, heptane sulfonic acid, and octane sulfonic acid. Among them, methanesulfonic acid is preferable because of its high polishing efficiency. The alkylsulfonic acid content is preferably 20% by weight or more and 99.9% by weight or less based on the total amount of the electrolytic polishing liquid.

  The electropolishing liquid used in the present invention preferably further contains an aminocarboxylic acid type chelating agent. The aminocarboxylic acid type chelating agent in the present invention is a compound having an amino group and a carboxyl group. Usually, it includes a polyvalent molecule having a plurality of carboxyl groups in which the carboxyl group is substituted with a hydroxyl group, and a derivative structure in which hydrogen of the carboxyl group is substituted with sodium or calcium.

  Specific examples of the aminocarboxylic acid type chelating agent include, for example, iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminetetraacetic acid, hydroxyethylenediaminetriacetic acid, hexamethylenediaminetetraacetic acid, diethylenetriamine-5 Acetic acid, triethylenetetramine hexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, bis (2-hydroxyethyl) glycine, diaminopropanoltetraacetic acid, ethylenediamine-2-propionic acid, glycol etherdiaminetetraacetic acid, bis (2- Hydroxybenzyl) ethylenediaminediacetic acid, or a salt thereof. In particular, ethylenediaminetetraacetic acid or a salt thereof, which is excellent from the viewpoint of cost, is preferably used.

  The content of the aminocarboxylic acid type chelating agent is preferably 0.1% by weight or more and 5% by weight or less based on the total amount of the electrolytic polishing liquid. The aminocarboxylic acid type chelating agent can be used alone or in combination of two or more.

  The electropolishing liquid used in the present invention preferably contains a nonionic surfactant. A nonionic surfactant is a surfactant that does not exhibit ionicity when dissolved in a liquid but exhibits surface activity.

  Specific examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene stearyl ether and polyoxyethylene lauryl ether, polyoxyethylene alkyls such as polyoxyethylene nonyl phenyl ether and polyoxyethylene octyl phenyl ether. Examples include phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene fatty acid amide, and perfluoroalkyl group-containing ethylene oxide adduct. In particular, polyoxyethylene alkyl ether or polyoxyethylene alkyl phenyl ether can be preferably used, and the number of added moles of these ethylene oxides is preferably 1 to 30, particularly preferably 2 to 15.

  The content of the nonionic surfactant is preferably 0.001% by weight or more and 0.1% by weight or less based on the total amount of the electrolytic polishing liquid. A nonionic surfactant can be used 1 type or in mixture of 2 or more types.

  The electropolishing liquid used in the present invention may further contain glycols. Glycols are compounds having a structure in which one hydroxy group is substituted for two carbon atoms of a chain aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon, and are also called diol compounds.

  Specific examples of glycols include, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, propylene glycol, dipropylene glycol, tripropylene glycol, 1, Examples include 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and the like. In particular, ethylene glycol can be preferably used.

  The content of glycols is preferably 1 wt% or more and 80 wt% or less in the electrolytic polishing liquid. Glycols can be used alone or in combination of two or more.

  The content of each component of the electropolishing liquid can be appropriately determined according to the type and shape of the titanium-based metal formed body to be electropolished, the size of the electropolishing area, and the like.

  Depending on the usage environment, the electrolytic polishing liquid may absorb moisture in the air, or the moisture content in the polishing liquid may increase due to the influence of residual moisture in the metal molded body. If the water content exceeds 2% by weight, a white cloudy surface tends to be generated on the polished surface after the electrolytic polishing of the metal molded body, and further, the surface smoothness tends not to be sufficiently obtained. For this reason, the amount of water contained in the polishing liquid is preferably 2% by weight or less with respect to the total amount of the polishing liquid from the viewpoint that a metal oxide film is hardly generated on the polishing surface or the smoothness of the polishing surface is excellent. However, according to the electropolishing method of the present invention, a white cloudy surface is unlikely to occur, so that there is an advantage that the electropolishing liquid can be used for a long time. The water content of the electrolytic polishing liquid can be measured by a known method, for example, the Karl Fischer method.

  In the conventional electrolytic polishing method, when the amount of electrolytic polishing (metal dissolution amount) of the metal molded body increases, a white cloudy surface tends to occur on the polished surface after electrolytic polishing. In particular, in an electrolytic polishing liquid, when a metal compact is dissolved by electrolytic polishing at 4 g / L or more (4 g or more of metal per 1 L of electrolytic polishing liquid), a white cloudy surface is generated on the polished surface after electrolytic polishing. This tends to occur more easily when the metal molded body is dissolved by electrolytic polishing at 8 g / L or more (8 g or more of metal per liter of electrolytic polishing liquid). The use of the electropolishing liquid in such a state should be refrained, and it is usually necessary to replace it with a new electropolishing liquid. However, according to the electropolishing method of the present invention, a white cloudy surface is unlikely to occur, so that there is an advantage that the electropolishing liquid can be used for a long time.

  The content of each component of the electropolishing liquid can be appropriately determined according to the type and shape of the metal molded body to be electropolished, the size of the electropolishing area, etc., and is not limited thereto.

<Electropolishing method>
In the electropolishing method according to the present invention, a cathode and a metal molded body acting as an anode are immersed in an electropolishing liquid, and electropolishing is performed under a condition (a) in which a voltage is applied between the cathode and the anode for a predetermined time. Including at least one electropolishing step, including at least one second electropolishing step in which a voltage higher than the voltage of the condition (a) is applied for a certain period of time and electropolishing at the condition (b), and ) The final electrolytic polishing is performed under conditions.

  Moreover, in order to fix a metal molded object according to the shape and grinding | polishing area of the metal molded object to be grind | polished, the anode electroconductive member which can electrically conduct an electrode and a molded object can be used.

  FIG. 1 shows an electrolytic polishing method in which an electrode is brought into contact with a metal molded body 14 which is a metal molded body and electropolished.

  In the electrolytic polishing, in the electrolytic polishing liquid 17 stored in the electrolytic solution tank 15, the anode conductive member 13 connected to the positive electrode of the power source 11 with the conductive wire 12 a is in contact with the metal formed body 14. Further, the cathode 16 connected to the negative electrode of the power source 11 by the conductive wire 12b is set apart from the metal molded body 14. In such an arrangement state, when a voltage is applied between the anode conductive member 13 and the cathode 16, the metal element on the surface dissolves in the electrolytic polishing liquid 17 in the metal formed body 14 acting as the anode. Thereby, the metal molded body 14 is electrolytically polished, and the surface becomes smooth and gloss can be generated.

  The material of the anode conductive member 13 can be appropriately selected according to the type of electrolytic polishing liquid used, and is not particularly limited as long as it has sufficient conductivity. For example, stainless steel, titanium, copper, aluminum And metals such as platinum and gold, or alloys thereof.

  The shape of the anode conductive member 13 can be appropriately selected according to the type of the metal molded body to be used, and is not particularly limited as long as the metal molded body 14 can be electrically connected and fixed. For example, a plate shape, a wire shape, It may be rod-shaped or core-shaped, or may be clip-shaped as shown in FIG.

  The material of the cathode 16 can be appropriately selected depending on the type of electropolishing liquid used, and is not particularly limited as long as it has sufficient conductivity. For example, stainless steel, titanium, copper, aluminum, platinum, Mention may be made of metals such as gold or their alloys.

  The shape of the cathode 16 can be appropriately selected according to the type of the metal molded body to be used, and is not particularly limited as long as the metal molded body 14 can be electropolished. For example, a plate shape, a core shape, a rod shape, a wire shape In order to increase the surface area of the cathode 16 and to avoid bubbles, temperature changes and concentration gradients of ions in the liquid generated during electropolishing, the cathode 16 is formed with a mesh shape or a punching shape. May be. Moreover, it is preferable to make it a shape which an electric current flows uniformly according to the shape of the product to grind | polish, for example, it can be set as the cylindrical shape surrounding a metal molded object.

  FIG. 2 shows an example of (i) the current density value with respect to the polishing time and (ii) the voltage value with respect to the polishing time in the first electropolishing step of the electropolishing method of the present invention.

  FIG. 3 shows an example of (iii) current density with respect to polishing time and (iv) voltage value with respect to polishing time in the second electropolishing step of the electropolishing method of the present invention.

  According to the method of the present invention, a first electropolishing process in which voltage 21 (current density 22) is applied and electropolishing is applied, and a voltage 31 (current density 32) higher than that in the first electropolishing process is applied. In combination with the second electropolishing step, and further performing the final electropolishing under the condition (b) of the second step, it is possible to obtain in a short time a metal molded body having a smooth surface without a white cloudy surface. it can.

  In the first electropolishing process or the second electropolishing process, the voltages 21 and 31 are preferably applied for a certain period of time. When the constant voltages 21 and 31 are applied, the current densities 22 and 32 increase rapidly immediately after the voltage application, and then stabilize while gradually decreasing. The current densities 22 and 32 in the present invention indicate a range of values measured from the maximum value shown by reaching the desired voltages 21 and 31 to the end of electropolishing. The time during which the voltages 21 and 31 are applied is referred to as electropolishing time 23 and 33. In addition, if the voltages 21 and 31 are not constant in the first electropolishing process or the second electropolishing process and are gradually increased or decreased, there is a tendency to cause uneven polishing. In particular, when the voltage 31 in the second electropolishing process is gradually increased, the deviation from the voltage 21 in the first electropolishing process is increased, which may cause uneven polishing.

  In the first electropolishing step in the present invention, in the range of 10 V or more and 30 V or less in terms of suppressing the generation of a metal oxide film having a rough surface shape and obtaining a smooth polished surface, which is excellent in terms of efficiency in that it can be processed in a short time. It is preferable to supply the voltage 21 and electrolytic polishing, and it is more preferable to supply the voltage 21 at 15 V or more and 25 V or less to perform electrolytic polishing.

  As shown in FIG. 2, the electropolishing time 23 of the first electropolishing process of the present invention is such that the current density 22 exhibits a maximum value after the voltage 21 is applied, and then gradually decreases until the current density 22 is stabilized. It is preferable to continue. By continuing the electropolishing until the current density 22 is stabilized, a good polished surface can be obtained in most portions, but a white cloudy surface due to a metal oxide film having a rough surface shape may be generated in some portions. However, the white cloudy surface can be removed in the second electropolishing process. Specifically, as the one-time electropolishing time 23 in the first electropolishing step, the lower limit is preferably 10 seconds or more, particularly preferably 20 seconds or more, and the upper limit is preferably 60 seconds or less. Within 40 seconds is particularly preferable.

  Next, in the second electropolishing process of the present invention, the surface is rough in the first electropolishing process by applying a voltage 31 (current density 32) higher than that in the first electropolishing process to perform electropolishing. When a metal oxide film is generated, the metal oxide film can be removed. Specifically, it is preferable to apply a voltage 0.1V to 30V higher than the first electropolishing step, and it is more preferable to apply a voltage 3V to 15V higher. In the second electropolishing step, it is preferable to apply the voltage 31 in the range of 20 V or more and 45 V or less, and it is more preferable to apply the voltage 31 in the range of 25 V or more and 35 V or less to perform the electropolishing. In order not to cause polishing unevenness in the second electropolishing process, it is preferable that the voltage 31 of the second electropolishing process is at least less than 50% larger than the first electropolishing process, and less than 40% larger. More preferably, it is particularly preferably in the range of less than 30%.

  The electropolishing time 33 of the second electropolishing process of the present invention is that the metal oxide film having a rough surface shape can be easily removed and the generation of a metal oxide film having a rough surface shape can be easily suppressed. Is preferably the same as or short. As shown in FIG. 3, it is preferable to stop the electropolishing until the voltage 31 is applied and the current density 32 shows a maximum value and gradually decreases.

  As the one electropolishing time 33 in the second electropolishing step of the present invention, the lower limit is preferably 1 second or more and particularly preferably 3 seconds or more in that a good polished surface is easily obtained. . The upper limit is preferably 10 seconds or less, and particularly preferably 5 seconds or less.

Note that in both the first electrolytic polishing process and the second electrolytic polishing process, it is preferred that the current density 22 and 32 is 40 mA / cm ² or more, and more preferably in the range of 50~5000mA / cm ^2.

  In both the first electropolishing step and the second electropolishing step in the electropolishing method of the present invention, the electropolishing liquid is preferably agitated. In particular, in order to stably obtain a good polished surface, it is preferable that the first electropolishing step and the second electropolishing step are stirred at the same flow rate. For example, if the second electropolishing process is agitated at a flow rate with a larger agitating force than the first electropolishing process, it may be a factor that causes polishing unevenness. The flow rate in the first electropolishing step is preferably 10 cm / sec or more and 1000 cm / sec or less, more preferably 20 cm / sec or more and 500 cm / sec or less, particularly preferably 40 cm / sec or more and 200 cm / sec or less. . The flow rate in the second electropolishing step is preferably 10 cm / sec or more and 1000 cm / sec or less, more preferably 20 cm / sec or more and 500 cm / sec or less, and particularly preferably 40 cm / sec or more and 200 cm / sec or less. As a method for stirring the electrolytic polishing liquid, any method can be used as long as a liquid flow of the electrolytic polishing liquid can be generated, and a pump, a stirring rod, a stirring plate, a stirring blade, a magnetic stirrer, or the like can be used.

  In the electropolishing method of the present invention, the first electropolishing step and the second electropolishing step only need to be included once or more, but both the first electropolishing step and the second electropolishing step may be performed a plurality of times. preferable. The first electropolishing step is preferably performed twice or more, more preferably 3 times or more, and particularly preferably 4 times or more. If the number of times is too large, the process takes too much time, so 30 times or less is preferable, 20 times or less is more preferable, and 15 times or less is particularly preferable. The second electropolishing step is preferably performed twice or more, more preferably 3 times or more, and particularly preferably 4 times or more. If the number of times is too large, the process takes too much time, so 30 times or less is preferable, 20 times or less is more preferable, and 15 times or less is particularly preferable.

  In addition, there is no particular limitation as long as the final process is the second electropolishing process, and after the first electropolishing process is continuously performed a plurality of times, the second electropolishing process may be performed a plurality of times, The first electropolishing step and the second electropolishing step can be performed alternately.

  In particular, since the second electropolishing step is applied with a higher voltage 31 than the first electropolishing step and is electropolished in a short electropolishing time 33 below the first electropolishing step, the electropolishing is divided into a plurality of times. When the step is carried out, it is possible to more efficiently suppress the removal of a white cloudy surface and new generation by a metal oxide film having a rough surface shape, and it is easy to obtain a smooth polished surface as a whole.

  The metal molded body 14 may be taken out of the electrolytic polishing liquid 17 for each step of the first electropolishing process or the second electropolishing process, and the metal molded body 14 may be washed with a solution of alcohol, water, nitric acid, or a combination thereof. it can.

  In addition, the cleaning is preferably performed by immersing in an ultrasonic bath at room temperature for 1 to 30 minutes.

  In the electrolytic polishing method according to the present invention, the electrolytic polishing is preferably performed at a temperature in the range of 10 ° C. or higher and 80 ° C. or lower. In particular, a temperature in the range of 20 ° C. or higher and 40 ° C. or lower is preferable, and a temperature in the range of 25 ° C. or higher and 30 ° C. or lower is more preferable.

  The electrolytic polishing method of the present invention can be preferably used for a medical tubular body such as a stent because a smooth surface can be easily obtained.

  Hereinafter, the electropolishing method of the present invention will be described more specifically with reference to FIG. 4 by taking a stent as an example of a metal molded body, but the present invention is not limited to this.

  The electropolishing apparatus shown in FIG. 4 is an electropolishing apparatus for electropolishing the stent 414 and the like. It is mainly composed of a power source 411, an electrolytic polishing liquid 417, an anode conductive member 413, a cathode 416, and an electrolytic polishing liquid tank 415. With the stent 414 expanded in a substantially uniform diameter so as to be substantially circular, An anode conductive member 413 that supports the inner surface of the stent 414 is provided.

  The anode conductive member 413 has four elongated members 41 so as to contact the stent 414 with four electrical contacts 418. Each elongated member 41 extends over the entire length of the stent 414 in the longitudinal direction, and four electrical contacts 418 are formed in the cross section thereof. Moreover, the extension part 42 extended outside from the vertex which the elongate member 41 joined is joined. The anode conductive member 413 is electrically connected to and connected to an anode connecting portion 43 for fixing the anode conductive member 413 of the electrolytic polishing apparatus main body.

  In the electrolytic polishing step of the electrolytic polishing method of the present invention, the power source 411 is operated in the state shown in FIG. 4, and a voltage is applied between the stent 414 and the cathode 416 to perform electrolytic polishing.

  The extension 42 can be removed by loosening the screw of the anode connecting portion, and the anode conductive member 413 is removed from the anode connecting portion 43 during the electropolishing process, and the stent 414 is attached to the anode conductive member 413. It can be cleaned while attached. Further, it is preferable to change the electrical contact 418 between the stent 414 and the elongated member 41 of the anode conductive member 413 by moving the stent 414 in the circumferential direction for each electrolytic polishing step.

  Since the anode rotation part 44 is provided on the anode connection part 43 and the anode whole rotation part 46 is provided on the anode support part 45, the stent 414 and the anode support part 45 are rotated in the electropolishing process. be able to. Since a concentration gradient and a temperature difference are hardly generated in the electrolytic polishing liquid 417, a smooth polished surface can be easily obtained.

  A rotary connector can be used for the whole anode rotating unit 46 and the anode rotating unit 44 for rotation and power supply.

Further, the cathode 416 has a cylindrical shape surrounding the periphery of each stent 414 so that the distance between the electrodes and the stent 414 is substantially equal.
In order to keep the temperature of the electrolytic polishing liquid 417 constant, the electrolytic solution tank 415 has a circulating water inlet 47 and a circulating water outlet 48.

  By rotating the stirrer bar 49 with the magnetic stirrer 400, the electropolishing liquid 417 can be stirred and the liquid can be kept in a uniform state. As described above, the method for electropolishing a metal molded body according to the embodiment of the present invention has been described using a specific example, but the present invention is not limited by the above embodiment, and the gist of the preceding and following descriptions. It is also possible to carry out the present invention while making modifications within a range that can be adapted to the above, and they are all included in the technical scope of the present invention.

  Hereinafter, the present invention will be described more specifically based on examples and comparative examples. In all of the following examples and comparative examples, electrolytic polishing was performed using the electrolytic polishing apparatus shown in FIG.

  About the embodiment of the present invention, Production Examples 1 to 3 of the electropolishing liquid according to the present invention, and Examples 1 to 7 and Comparative Examples 1 to 8 according to the present invention are specifically shown below. In addition, Table 1 shows component compositions of the electrolytic polishing liquids of Production Examples 1 to 3.

(Production Example 1)
10 g of ethylenediaminetetraacetic acid was dissolved in 990 g of methanesulfonic acid to prepare a mixed solution 1. After the nickel-titanium alloy (compatible with ASTM F2063-05) was dissolved by 4 g / L electropolishing with the obtained mixed solution 1, electropolishing liquid 1 in which 30 g of water was added to the solution was prepared.

(Production Example 2)
Electrolytic polishing liquid 2 was prepared by mixing 332 g of ethyl alcohol, 142 g of isopropyl alcohol, 36 g of aluminum chloride, and 150 g of zinc chloride.

(Production Example 3)
Electrolytic polishing liquid 3 was prepared by mixing 558 g of ethylene glycol and 50 g of lithium chloride.

Example 1
A stent made of a nickel titanium alloy (compatible with ASTM F2063-05) having an inner diameter of 8.0 mm was prepared as a metal molded body.

  The metal molded body was inserted into an anode conductive member made of SUS304 having an outer diameter of 8.5 mm so that the diameter of the metal molded body was evenly expanded. It was fixed so as to form an electrical contact with the elongated member of the conductive member at four points. A cylindrical member having an outer diameter of 1.2 mm was used as the elongated member of the anode conductive member.

  The electrolytic polishing liquid 1 prepared in Production Example 1 was put into the electrolytic polishing liquid tank, and then stored at 25 ° C. and stirred with a magnetic stirrer so that the stirring speed became 100 cm / sec on average, and between the electrodes with the metal molded body A curved cathode made of SUS304 was installed so that the distance was substantially equidistant from 45 mm to 55 mm.

<First Electropolishing Step (1)>
The metal molded body was immersed in the electrolytic polishing liquid, and power was supplied to the electrolytic polishing liquid at a voltage of 20 V for 30 seconds to perform electrolytic polishing of the surface of the metal molded body. After the power supply is completed, the metal molded body is taken out from the electrolytic polishing liquid, washed with water and dried, and the metal molded body is moved 45 ° in the circumferential direction so that the electrical contact between the metal molded body and the anode conductive member is made. changed.

<Second Electropolishing Step (1)>
The metal molded body was immersed in an electrolytic polishing liquid, and power was supplied to the electrolytic polishing liquid at a voltage of 25 V for 3 seconds to perform electrolytic polishing of the surface of the metal molded body. After the power supply is completed, the metal molded body is taken out from the electrolytic polishing liquid, washed with water and dried, and the metal molded body is moved 45 ° in the circumferential direction so that the electrical contact between the metal molded body and the anode conductive member is made. changed.

After the first electropolishing step (1) was continuously repeated 10 times, the second electropolishing step (2) was repeated 5 times continuously. The current density during all electropolishing was in the range of 100 to 2000 mA / cm ² . It is described in Table 2.

(Example 2)
A pure titanium wire having an outer diameter of 1.0 mm was prepared as a metal molded body.
Electropolishing was carried out in the same manner as in Example 1 except that the extension of the anode conductive member was removed and a wire was directly attached to the anode connection. In addition, the electrical contact in Example 1 was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 100 to 2000 mA / cm ² .

(Example 3)
A wire made of a titanium alloy Ti-6Al-4V having an outer diameter of 1.0 mm was prepared as a metal molded body.

Electropolishing was carried out in the same manner as in Example 1 except that the extension of the anode conductive member was removed and a wire was directly attached to the anode connection. In addition, the electrical contact in Example 1 was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 100 to 2000 mA / cm ² .

Example 4
A pure titanium wire having an outer diameter of 1.0 mm was prepared as a metal molded body.
The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

  After the electrolytic polishing liquid 2 prepared in Production Example 2 was put into the electrolytic polishing liquid tank, the electrolytic polishing liquid was stored at 25 ° C., and stirred with a magnetic stirrer so that the stirring speed became an average of 100 cm / sec. A curved cathode made of SUS304 was installed so that the distance between the electrodes and the body was substantially equal to 45 mm to 55 mm.

<First Electropolishing Step (2)>
The metal molded body was immersed in an electrolytic polishing liquid, and electric power was supplied to the electrolytic polishing liquid at a voltage of 25 V for 60 seconds to perform electrolytic polishing of the surface of the metal molded body. After the power supply was completed, the object to be polished was taken out from the electrolytic polishing liquid, washed with water and dried.

<Second Electropolishing Step (2)>
The metal molded body was immersed in an electrolytic polishing liquid, and power was supplied to the electrolytic polishing liquid at a voltage of 30 V for 10 seconds to perform electrolytic polishing of the surface of the metal molded body. After completion of power supply, the metal molded body was taken out of the electrolytic polishing liquid, washed with water and dried.

After the first electropolishing step (2) was continuously repeated 10 times, the second electropolishing step (2) step was repeated 10 times continuously. The electrical contact was not changed. The current density during all electropolishing was in the range of 50 to 300 mA / cm ² .

(Example 5)
As a metal molded body, a wire made of stainless steel SUS304 having an outer diameter of 1.2 mm was prepared.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

  After the electrolytic polishing liquid 3 prepared in Production Example 3 was put into the electrolytic polishing liquid tank, the electrolytic polishing liquid was stored at 25 ° C. and stirred with a magnetic stirrer so that the stirring speed became an average of 100 cm / sec. A curved cathode made of SUS304 was installed so that the distance between the electrodes and the body was substantially equal to 45 mm to 55 mm.

<First Electropolishing Step (3)>
The metal molded body was immersed in an electrolytic polishing liquid, and electric power was supplied to the electrolytic polishing liquid at a voltage of 20 V for 60 seconds to perform electrolytic polishing of the surface of the metal molded body. After completion of power supply, the metal molded body was taken out of the electrolytic polishing liquid, washed with water and dried.

<Second Electropolishing Step (3)>
The metal molded body was immersed in an electrolytic polishing liquid, and power was supplied to the electrolytic polishing liquid at a voltage of 25 V for 10 seconds to perform electrolytic polishing of the surface of the metal molded body. After completion of power supply, the metal molded body was taken out of the electrolytic polishing liquid, washed with water and dried.

After the first electropolishing step (3) was repeated 10 times continuously, the second electropolishing step (3) step was repeated 10 times continuously. The electrical contact was not changed. The current density during all electropolishing was in the range of 50 to 300 mA / cm ² .

(Example 6)
A wire made of magnesium alloy AZ61 having an outer diameter of 1.6 mm was prepared as a metal molded body.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Otherwise, electropolishing was performed in the same manner as in Example 5. The current density during all electropolishing was in the range of 50 to 300 mA / cm ² .

(Example 7)
As a metal molded body, a wire made of pure aluminum A1070 having an outer diameter of 1.5 mm was prepared.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

  After the electrolytic polishing liquid 2 prepared in Production Example 2 was put into the electrolytic polishing liquid tank, the electrolytic polishing liquid was stored at 25 ° C., and stirred with a magnetic stirrer so that the stirring speed became an average of 100 cm / sec. A curved cathode made of SUS304 was installed so that the distance between the electrodes and the body was substantially equal to 45 mm to 55 mm.

<First Electropolishing Step (4)>
The metal molded body was immersed in an electrolytic polishing liquid, and electric power was supplied to the electrolytic polishing liquid at a voltage of 20 V for 60 seconds to perform electrolytic polishing of the surface of the metal molded body. After completion of power supply, the metal molded body was taken out of the electrolytic polishing liquid, washed with water and dried.

<Second Electropolishing Step (4)>
The metal molded body was immersed in an electrolytic polishing liquid, and power was supplied to the electrolytic polishing liquid at a voltage of 25 V for 10 seconds to perform electrolytic polishing of the surface of the metal molded body. After completion of power supply, the metal molded body was taken out of the electrolytic polishing liquid, washed with water and dried.

After the first electropolishing step (4) was continuously repeated 10 times, the second electropolishing step (4) step was repeated 10 times continuously. The electrical contact was not changed. The current density during all electropolishing was in the range of 50 to 300 mA / cm ² .

(Comparative Example 1)
A stent made of a nickel titanium alloy (compatible with ASTM F2063-05) having an inner diameter of 8.0 mm was prepared as a metal molded body.

Electropolishing was carried out in the same manner as in Example 1 except that only the first electropolishing step (1) of Example 1 was repeated 10 times continuously. The current density during all electropolishing was in the range of 100-1600 mA / cm ² .

(Comparative Example 2)
A pure titanium wire having an outer diameter of 1.0 mm was prepared as a metal molded body.
The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 1 except that only the first electropolishing step (1) of Example 1 was repeated 10 times continuously. In addition, the electrical contact in Example 1 was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 100-1600 mA / cm < ² >.

(Comparative Example 3)
A wire made of a titanium alloy Ti-6Al-4V having an outer diameter of 1.0 mm was prepared as a metal molded body.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 1 except that only the first electropolishing step (1) of Example 1 was repeated 10 times continuously. In addition, the electrical contact in Example 1 was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 100-1600 mA / cm < ² >.

(Comparative Example 4)
A pure titanium wire having an outer diameter of 1.0 mm was prepared as a metal molded body.
The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 4 except that only the first electropolishing step (2) of Example 4 was repeated 10 times continuously. The electrical contact was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 50 to 250 mA / cm ² .

(Comparative Example 5)
As a metal molded body, a wire made of stainless steel SUS304 having an outer diameter of 1.2 mm was prepared.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 5 except that only the first electropolishing step (3) of Example 5 was repeated 10 times continuously. The electrical contact was not changed. Moreover, the current density at the time of all the electropolishing was in the range of 50 to 250 mA / cm ² .

(Comparative Example 6)
A wire made of magnesium alloy AZ61 having an outer diameter of 1.6 mm was prepared as a metal molded body.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 5 except that only the first electropolishing step (3) of Example 5 was repeated 10 times continuously. The electrical contact was not changed. The current density during all electropolishing was in the range of 50 to 250 mA / cm ² .

(Comparative Example 7)
As a metal molded body, a wire made of pure aluminum A1070 having an outer diameter of 1.5 mm was prepared.

  The extension of the anode conductive member was removed and the wire was attached directly to the anode connection.

Electropolishing was carried out in the same manner as in Example 7 except that only the first electropolishing step (4) of Example 7 was repeated 10 times continuously. The electrical contact was not changed. The current density during all electropolishing was in the range of 50 to 250 mA / cm ² .

(Comparative Example 8)
A stent made of a nickel titanium alloy (compatible with ASTM F2063-05) having an inner diameter of 8.0 mm was prepared as a metal molded body.

Electropolishing was carried out in the same manner as in Example 1 except that only the step of changing the voltage in the first electropolishing step (1) of Example 1 to 25 V was repeated 10 times continuously. The current density during all electropolishing was in the range of 100 to 2000 mA / cm ² .

(Appearance evaluation by stereo microscope)
About the metal molded object produced in each Example and each comparative example, the external appearance evaluation was performed by observing a surface external appearance by 50 time magnification using a stereomicroscope (MM-400 made from Nikon).

  As a result, in each Example, a smooth surface appearance was confirmed, but in each Comparative Example, it was confirmed that a white cloudy surface was present on the surface. In addition, Example 1, Comparative Example 1, Example 4, Comparative Example 4, Example 5, Example 5, Comparative Example 5, Example 6, Comparative Example 6, Example 7, Comparative Example 7, and Comparative Example 8 were applied to a stereomicroscope. Surface observation results obtained by connecting a digital single-lens reflex camera (EOS Kiss X5 manufactured by Canon) and taking magnified photographs are shown in FIGS. 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15.

(Appearance evaluation by SEM)
By observing the surface appearance of the metal molded body produced in Example 1 and Comparative Example 1 using an SEM (scanning electron microscope; Ultra Plus manufactured by Carl Zeiss) at an acceleration voltage of 2.0 kV and a magnification of 2000 times. Appearance evaluation was performed.

  As a result, it was found that Example 1 has a very excellent smooth surface appearance. Further, in Comparative Example 1, it was found that an uneven surface of about 2 μm was formed on the surface portion that appeared as a white cloudy surface by observation with a stereoscopic microscope. The observation results of Example 1 and Comparative Example 1 are shown in FIGS.

(Section analysis by STEM and EDX)
About the metal molded object produced in Example 1 and Comparative Example 1, a cross section was produced with an acceleration voltage of 40 kV (finishing 10 kV) by FIB (focused ion beam; FB-2100 made by Hitachi), and STEM (scanning transmission electron microscope; made by Hitachi). HD-2700) was observed at an acceleration voltage of 200 kV and magnifications of 30000 and 700000 times.

  As a result, the difference between Example 1 and Comparative Example 1 in the presence or absence of irregularities confirmed by SEM can also be confirmed by cross-sectional STEM observation, and a layer having a thickness of about 5 nm is confirmed on the surface of each sample. It was.

  Thereafter, elemental analysis of the cross section at a magnification of 700,000 was performed at an acceleration voltage of 200 kV using an EDX (energy dispersive X-ray analyzer; TEAM manufactured by EDAX). Considering the contamination residue and the like by measurement, the element concentration ratio was calculated for three elements of O, Ti, and Ni among the detected elements. As a result, in both the samples of Example 1 and Comparative Example 1, the strength of Ni and the strength of O increased on the sample surface (point1, point3) compared to the inside of the cross section (point2, point4). Was noticeable. On the other hand, the strength of Ti did not change greatly. From these results, it was found that the layer on the sample surface was an oxide film made of titanium oxide. Therefore, the presence or absence of irregularities on the sample surface was suggested to be the cause of the white cloudy surface.

  The cross-sectional observation results of Example 1 and Comparative Example 1 are shown in FIGS. The results of elemental analysis of Example 1 and Comparative Example 1 are shown in Table 3.

(Surface roughness measurement)
About the metal molded object produced in Example 1 and Comparative Example 1, arithmetic mean roughness Ra and maximum height Ry were measured based on JIS B0601-1994 using the laser microscope (KEYENCE company, VK-9510). The surface roughness measurement results of Example 1 and Comparative Example 1 are shown in Table 4. The arithmetic average roughness Ra and the maximum height Ry were both smaller in Example 1 than in Comparative Example 1, and it was found that Example 1 was superior in smoothness to Comparative Example 1.

(result)
In Examples 1 to 7, due to the effect of the present invention, a uniformly smooth and glossy polished surface was obtained without generating a white cloudy surface on the polished surface.

  In Comparative Examples 1 to 8, a white cloudy surface was generated on the polished surface, and a polished surface having unevenness and not much gloss was obtained. In particular, in Comparative Example 8, polishing unevenness was confirmed in addition to the white cloudy surface.

  From this, it can be seen that the present invention is an electropolishing method of a metal molded body that can obtain a uniform polished surface with less polishing unevenness while shortening the polishing time by a simple method and a simple apparatus. In addition, even if the electrolytic polishing liquid must be replaced, it is difficult to generate a white cloudy surface due to the effect of the electrolytic polishing method of the present invention. It turns out that there is an advantage that it can be used.

DESCRIPTION OF SYMBOLS 11 Power supply 12a, 12b Conductive wire 13 Anode conductive member 14 Metal molding 15 Electropolishing liquid tank 16 Cathode 17 Electrolytic polishing liquid 18 Electrical contact 21 Voltage 22 Current density 23 Electropolishing time 41 Elongated member 42 Extension part 43 Anode connection part 44 Anode rotating part 45 Anode support part 46 Anode whole rotating part 47 Circulating water inlet 48 Circulating water outlet
49 Stirrer bar 400 Magnetic stirrer 411 Power supply 412a, 412b Conductive wire 413 Anode conductive member 414 Stent 415 Electropolishing liquid tank 416 Cathode 417 Electropolishing liquid 418 Electrical contact

Claims (15)

In the electropolishing liquid, the process includes one or more first electropolishing processes for electropolishing under the following conditions (a) and one or more second electropolishing processes for electropolishing under the following conditions (b). A method for producing a metal molded body, comprising performing final electrolytic polishing under conditions.
(A) Conditions for applying a voltage for a certain period of time (b) Conditions for applying a voltage higher than the condition (a) for a certain period of time 2. The method for producing a metal molded body according to claim 1, wherein the voltage value of the condition (a) is selected from a range of 10 V or more and 30 V or less. The method for producing a metal molded body according to claim 1 or 2, wherein the voltage value of the condition (b) is selected from a range of 20 V or more and 45 V or less. The method for producing a metal molded body according to any one of claims 1 to 3, wherein a current value in the step (a) and the step (b) is selected from a range of 40 mA / cm ² or more. . 5. The metal molded body according to claim 1, wherein the voltage application time in the step (b) is the same as or shorter than the voltage application time in the step (a). Method. The voltage application time in the step (a) is selected in the range of 10 seconds to 60 seconds and the voltage application time in the step (b) is selected in the range of 1 second to 10 seconds. The manufacturing method of the metal forming body in any one of Claims 1-5. The method for producing a metal molded body according to any one of claims 1 to 6, wherein the electropolishing liquid does not contain fluoride or the content of fluoride is 5% by weight or less. The method for producing a metal molded body according to any one of claims 1 to 7, wherein the electropolishing liquid contains an alkylsulfonic acid. The method for producing a metal molded body according to any one of claims 1 to 8, wherein the electrolytic polishing liquid contains an aminocarboxylic acid type chelating agent. The method for producing a metal molded body according to any one of claims 1 to 9, wherein the metal molded body is made of a base metal. The method for producing a metal molded body according to claim 10, wherein the metal molded body contains one or more selected from iron, chromium, magnesium, aluminum, and titanium. The method for producing a metal molded body according to claim 11, wherein the metal molded body is made of titanium or a titanium alloy. The method for producing a metal molded body according to claim 12, wherein the metal molded body is made of a nickel titanium alloy. The method for producing a metal molded body according to any one of claims 1 to 13, wherein the metal molded body is a medical tubular body. The method for manufacturing a metal molded body according to claim 14, wherein the medical tubular body is a stent.