Method for extracting deposits and / or inclusions

Abstract

According to the present invention, a metal material is electrolyzed in a flow of electrolyte solution. This makes it possible to correctly and conveniently extract deposits and / or inclusions (deposits or the like) that are in the metal material. The electrolysis is preferably performed such that the electrolyte solution flows along at least a portion of an electrolysis surface that is a surface of the metal material that contacts the electrolyte solution. The flow speed of the electrolyte solution that flows along the electrolysis surface is preferably at least 0.48 mm / s. The metal material and the electrolyte solution are preferably contained in an electrolytic bath, and the flow of electrolyte solution is preferably produced by infusion and discharge of the electrolyte solution into / from the electrolytic bath.

Description

Method for extracting precipitates and / or inclusions

[0001] The present invention relates to a method for extracting precipitates and / or inclusions.

[0002] Precipitates and / or inclusions (hereinafter referred to as "precipitates, etc.") present in metallic materials such as steel affect the properties of the metallic material depending on their amount and morphology. Therefore, analysis of precipitates, etc. is important for controlling the properties of metallic materials.

[0003] Conventionally, when analyzing precipitates and the like in a metallic material, the metallic material is electrolyzed using an electrolytic solution (Patent Document 1). That is, by dissolving the matrix element of the metallic material (Fe when the metallic material is a steel material), the precipitates and the like are exposed on the electrolytic surface of the metallic material (the surface in contact with the electrolytic solution), and the exposed precipitates and the like are observed or collected.

[0004] International Publication No. 2017 / 142084

[0005] The inventors used a steel material containing several mass percents of Ni and Mo as the metallic material, electrolyzed this metallic material, and extracted precipitates and the like. As a result, they found that Fe, Ni, and Mo may form some kind of compound (also referred to as "electrolytic products") on the surface of the deposits and the like to be extracted. In this case, the deposits and the like are not extracted accurately (in their original state). Since the electrolytic products formed on the surface of the deposits and the like affect the analysis of the deposits and the like, it is necessary to suppress the formation of the electrolytic products.

[0006] Incidentally, in order to address a similar problem, Patent Document 1 discloses a technique of adding to an electrolyte a chemical agent that forms a complex with an element (hereinafter also referred to as an "interfering element") that prevents accurate extraction of precipitates, etc.

[0007] However, when the technique described in Patent Document 1 is adopted, it is necessary to prepare an appropriate agent for each interfering element (e.g., Fe, Ni, and Mo), which is very cumbersome. Also, depending on the interfering element, it may not be possible to prepare an appropriate agent. For this reason, a method is desired that can extract precipitates, etc. without preparing an agent corresponding to the interfering element (i.e., simply).

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide a method capable of accurately and simply extracting precipitates and the like in metal materials.

[0009] The present inventors have conducted extensive research to achieve the above object, and as a result have found that: a) when a metallic material is electrolyzed, elements (interfering elements) constituting the metallic material are dissolved into the electrolyte, and electrolytic products are formed on the surface of deposits or the like through some kind of reaction; and b) in order to avoid the occurrence of the above reaction, when the metallic material is electrolyzed, the interfering elements dissolved into the electrolyte should be kept away from deposits or the like exposed on the electrolytic surface of the metallic material. Based on these findings, the present invention has been completed.

[0010] That is, the present invention provides the following [1] to [5]. [1] A method for extracting precipitates and / or inclusions in a metallic material, comprising electrolyzing the metallic material while flowing an electrolytic solution. [2] The method for extracting precipitates and / or inclusions according to [1] above, wherein the electrolysis is carried out while flowing the electrolytic solution along at least a portion of an electrolysis surface, which is a surface of the metallic material that comes into contact with the electrolytic solution. [3] The method for extracting precipitates and / or inclusions according to [2] above, wherein the flow rate of the electrolytic solution flowing along the electrolysis surface is 0.48 mm / s or more. [4] The method for extracting precipitates and / or inclusions according to any of [1] to [3] above, wherein the metallic material and the electrolytic solution are contained in an electrolytic cell, and the electrolytic solution is caused to flow by injecting and discharging the electrolytic solution into and from the electrolytic cell. [5] The method for extracting precipitates and / or inclusions according to any one of [1] to [3] above, wherein after the electrolysis, the precipitates and / or inclusions exposed on the surface of the metal material are extracted.

[0011] According to the present invention, precipitates and the like in metal materials can be extracted accurately and simply.

[0012] FIG. 1 is a schematic diagram showing an electrolysis system used for electrolysis of a metal material. FIG. 2 is a schematic diagram showing another example of an electrolysis system. FIG. 3 is a schematic diagram showing another example of an electrolysis system. FIG. 4 is a schematic diagram showing another example of an electrolysis system. FIG. 5 is a schematic diagram showing another example of an electrolysis system. FIG. 6 is a schematic diagram showing another example of an electrolysis system. FIG. 7 is a SEM image showing the residue of Invention Example 1. FIG. 8 is a SEM image showing the residue of Comparative Example 1.

[0013] The present embodiment will be described below. First, an electrolysis system 1 used for electrolyzing a metal material 13 in the present embodiment will be described with reference to FIG.

[0014] 1 is a schematic diagram showing an electrolysis system 1 used for electrolysis of a metal material 13. The electrolysis system 1 generally includes an electrolysis device 10, an electrolyte tank 20, a pump 30, a tube 35, and an electrochemical measurement device 40.

[0015] The electrolysis device 10 includes an electrolytic cell 11 having an opening 11a, and further includes a cathode 12 and an anode 14 made of a metallic material 13. The interior of the electrolytic cell 11 is filled with an electrolytic solution 5, and the cathode 12 and the anode 14 (metallic material 13) are immersed in the electrolytic solution 5. Note that, although the metallic material 13 shown in FIG. 1 is entirely immersed in the electrolytic solution 5, this is not a limitation, and it is sufficient that only a portion of the metallic material 13 is immersed in the electrolytic solution 5.

[0016] Each component of the electrolysis system 1 will be described in more detail below.

[0017] <Metallic Material and Anode> The metallic material 13 is not particularly limited as long as it contains precipitates and / or inclusions (precipitates, etc.), but a steel material is preferred. In the steel industry, precise control of the amount and form of precipitates, etc. present in steel materials can impart new properties to steel materials or improve existing properties. For this reason, it is important to accurately analyze precipitates, etc. in steel materials.

[0018] An example of the steel material is a steel material containing a few mass % of Ni and Mo. When this steel material is electrolyzed, nickel (Ni) and molybdenum (Mo) are also dissolved into the electrolytic solution 5 in addition to iron (Fe), which is the matrix metal of the steel material. Such steel material contains, for example, MnS and Cr compounds as precipitates.

[0019] The shape of the metal material 13 is not particularly limited, but as will be described later, from the viewpoint of allowing the electrolyte solution 5 to flow along the electrolysis surface of the metal material 13, a shape that does not hinder the flow of the electrolyte solution 5 (e.g., a cylindrical shape, a rectangular parallelepiped shape, etc.) is preferred.

[0020] The anode 14 is composed of a metal material 13 and a lead wire 25 wound around the metal material 13. An inert metal such as platinum (Pt) is preferably used as the material for the lead wire 25. By winding the lead wire 25 around the metal material 13, the metal material 13 is made conductive and is fixed in place.

[0021] The method for fixing the position of the metallic material 13 is not limited to this, and for example, when electrolyzing a specific surface of the metallic material 13 (for example, a surface to be observed using an SEM after electrolysis), the lead wire 25 may be soldered to a surface other than this specific surface. Also, the metallic material 13 may be clamped using an alligator clip (not shown) to which the lead wire 25 is connected.

[0022] If the metal material 13 is magnetic, a cylindrical member (not shown) made of the same material as the lead wire 25 may be used instead of the lead wire 25. The cylindrical member has one end closed by a bottom plate, and is placed inside the electrolytic cell 11 with the bottom plate facing downward. A magnet such as a neodymium magnet is then placed on the upper surface of the bottom plate (inside the cylindrical member), and the magnetic force of the magnet causes the metal material 13 to adhere to the lower surface of the bottom plate (outside the cylindrical member). In this way, the metal material 13 can be fixed in position while suspended.

[0023] 1, the entire metal material 13 is immersed in the electrolytic solution 5, and therefore, all of the areas of the surface of the metal material 13 where the lead wire 25 is not wound (areas not in contact with the wound lead wire 25) can be said to be electrolysis surfaces that are in contact with the electrolytic solution 5. Of the surfaces of the metal material 13, surfaces that do not require electrolysis may be covered with an insulating resin or the like.

[0024] The anode 14 (more specifically, the lead wire 25 constituting the anode 14 ) is connected to the electrochemical measurement device 40 using a conductor 15 .

[0025] <Cathode> Any of various counter electrodes currently in practical use can be used as the cathode 12. Among these, platinum (Pt) is preferred because it is highly stable with respect to the electrolyte 5 and is unlikely to contaminate the electrolyte 5. The cathode 12 is connected to the electrochemical measurement device 40 using a lead 16.

[0026] <Electrochemical Measurement Apparatus> As the electrochemical measurement apparatus 40, for example, a constant-potential electrolysis apparatus may be used when electrolyzing the metallic material 13 by controlling the potential of the metallic material 13, and a constant-current electrolysis apparatus may be used when electrolyzing the metallic material 13 by controlling the current of the metallic material 13. A potentio-galvanostat that has both functions may also be used.

[0027] By driving the electrochemical measurement device 40, the potential or current of the metallic material 13 is controlled, and electrolysis is performed on the metallic material 13. The electrolysis conditions are not particularly limited, but a potential or current that does not decompose the extracted precipitates and the like is preferred.

[0028] Although the electrolysis system 1 shown in Fig. 1 employs a two-electrode method, a three-electrode method using a reference electrode may also be employed. The three-electrode method is preferable from the viewpoint of control.

[0029] <Electrolyte Tank, Tube, and Pump> In the electrolysis system 1, the electrolyte 5 is contained not only in the electrolytic cell 11 but also in the electrolyte tank 20. One end of a tube 35 is connected to the electrolyte tank 20. The tube 35 is made of a soft material such as silicone. The other end of the tube 35 (inlet 19) is disposed at the opening 11a of the electrolytic cell 11. That is, the electrolyte tank 20 and the electrolytic cell 11 are connected by the tube 35.

[0030] A pump 30 is disposed midway through the tube 35. A peristaltic pump is preferably used as the pump 30 because it does not come into contact with the electrolyte 5 and is less likely to be contaminated. When the pump 30 is driven, the electrolyte 5 is sucked up from the electrolyte tank 20. The sucked up electrolyte 5 passes through the inside of the tube 35 and is injected into the electrolytic cell 11 from the injection port 19 at the end of the tube 35.

[0031] <Electrolytic Cell> As described above, the electrolytic cell 11 has the opening 11 a. If the electrolytic cell 11 is a sealed system without the opening 11 a, the gas generated by the electrolysis of the metal material 13 may accumulate, causing a positive pressure inside the electrolytic cell 11 and hindering the injection of the electrolytic solution 5. For this reason, the electrolytic cell 11 is preferably an open system having the opening 11 a.

[0032] A tubular outlet 17 is provided on the opposite side of the opening 11a in the electrolytic cell 11, facing the inlet 19. A cock 18 that can be opened and closed is disposed midway in the outlet 17. When the cock 18 is opened, the electrolytic solution 5 is discharged from inside the electrolytic cell 11.

[0033] <Electrolyte> The electrolyte 5 is not particularly limited, and an electrolyte having a conventionally known composition can be used as appropriate. However, an electrolyte having a composition that does not dissolve deposits of the metal material 13 is preferred. Specific examples include an AA electrolyte (acetylacetone-tetramethylammonium chloride-methanol), an MS electrolyte (4% by volume methyl salicylate-1% by mass salicylic acid-methanol), and a citric acid electrolyte (10% by mass sodium citrate-1% by mass potassium bromide-pure water-citric acid (for pH adjustment)). Note that, for example, if the metal material 13 is a steel material, Fe eluted into the electrolyte 5 may form iron hydroxide or the like, which may clog the outlet 17. In such cases, an agent for complexing Fe may be added to the electrolyte 5.

[0034] <Electrolysis> In this configuration, by operating the electrochemical measurement device 40, the electrolysis surface (the surface in contact with the electrolytic solution 5) of the metallic material 13 is electrolyzed, exposing deposits, etc. Here, when a steel material containing several mass % of Ni and Mo is used as the metallic material 13, the Fe, Ni, and Mo constituting the material are eluted into the electrolytic solution 5 as interfering elements, and may form electrolysis products on the surfaces of the exposed deposits, etc.

[0035] Therefore, in this embodiment, the cock 18 is kept open and the pump 30 is driven during electrolysis of the metallic material 13. As a result, the electrolytic solution 5 is injected into the electrolytic cell 11 through the inlet 19 and discharged through the outlet 17. In other words, the electrolysis of the metallic material 13 is carried out while the electrolytic solution 5 is flowing.

[0036] By flowing the electrolytic solution 5, even if interfering elements are eluted into the electrolytic solution 5, the eluted interfering elements are moved away from deposits and the like exposed on the electrolytic surface of the metal material 13. In this way, the formation of electrolytic products on the surfaces of deposits and the like can be easily suppressed without using chemicals corresponding to the interfering elements.

[0037] In this embodiment, the electrolytic solution 5 is preferably caused to flow along at least a portion of the electrolysis surface of the metallic material 13 (e.g., a surface to be observed using an SEM after electrolysis). In other words, the metallic material 13, the inlet 19, the outlet 17, and other components are preferably arranged so that the electrolytic solution 5 flows along at least a portion of the electrolysis surface of the metallic material 13. For example, in the electrolysis system 1 shown in FIG. 1 , the electrolytic solution 5 flows at least along the side surface of the cylindrical metallic material 13.

[0038] The flow velocity of the electrolyte 5 is determined, for example, by the reaction that generates the electrolytic product (the reaction of the interfering elements dissolved in the electrolyte 5), and is therefore appropriately set depending on the composition of the metallic material, etc. As the reaction time increases, the amount of electrolytic product generated also increases. On the other hand, by increasing the flow velocity of the electrolyte 5 flowing along the electrolytic surface of the metallic material 13 (e.g., the side surface of the cylindrical metallic material 13), the time that the interfering elements remain on this electrolytic surface is shortened, and the reaction time is reduced. In addition, a fast flow velocity of the electrolyte 5 is more effective in keeping the interfering elements away from precipitates, etc. exposed on the electrolytic surface of the metallic material 13. Therefore, when the above-mentioned steel material containing Ni and Mo is used as the metallic material, for example, the flow velocity of the electrolyte 5 flowing along the electrolytic surface is preferably 0.48 mm / s or more, more preferably 0.65 mm / s or more, even more preferably 0.75 mm / s or more, and particularly preferably 1.33 mm / s or more. The upper limit is not particularly limited, and is, for example, 2.00 mm / s. The method for measuring the flow rate of the electrolyte 5 will be described later (see Examples).

[0039] The electrolyte solution 5 discharged from the discharge port 17 to the outside of the electrolytic cell 11 may be returned to the electrolyte tank 20 and then injected again into the electrolytic cell 11 from the injection port 19. That is, the electrolyte solution 5 may be circulated. However, the electrolyte solution 5 discharged from the discharge port 17 contains interfering elements that have eluted from the metal material 13. For this reason, from the viewpoint of keeping the interfering elements away from the electrolytic surface of the metal material 13, it is preferable not to circulate the electrolyte solution 5. If the electrolyte solution 5 is circulated, it is preferable to remove the interfering elements from the electrolyte solution 5 using an ion exchange resin or the like.

[0040] <Extraction> Thereafter, the deposits and the like exposed on the surface of the metal material 13 are extracted by a known method. For example, the electrolyzed metal material 13 is immersed in an alcohol such as methanol, and ultrasonic vibrations are applied to the metal material 13, thereby causing the exposed deposits and the like to peel off into the alcohol. Next, the alcohol is filtered using a filter (filter paper), thereby collecting the deposits and the like.

[0041] In addition, observing precipitates, etc., exposed on the surface of the metal material 13 using a scanning electron microscope (SEM) or the like without peeling them off from the metal material 13 and collecting them is also considered to be "extraction."

[0042] The formation of electrolytic products on the surface of the extracted deposits is suppressed, meaning that the deposits can be extracted accurately (in their original state), allowing for highly accurate analysis.

[0043] 2A to 2F are schematic diagrams each showing another example of the electrolysis system 1. Note that in Fig. 2A to 2F, only the electrolytic cell 11, the inlet 19, the outlet 17, the metal material 13, and part of the lead wire 25 are shown, and the other components are not shown.

[0044] The configuration of the electrolysis system 1 used in this embodiment is not limited to the configuration described based on FIG. 1 as long as it can electrolyze the metal material 13 while causing the electrolytic solution 5 to flow.

[0045] For example, in the electrolysis system 1 described based on FIG. 1 , the inlet 19 is disposed at a position facing the outlet 17, but this is not limited thereto, and the inlet 19 may be positioned at a position that does not face the outlet 17, as shown in FIG. 2A .

[0046] In the electrolysis system 1 described based on FIG. 1 , the outlet 17 is provided on the bottom surface of the electrolytic cell 11, but this is not limited thereto. For example, as shown in FIG. 2B , the outlet 17 may be provided on the side surface of the electrolytic cell 11.

[0047] 1, the injection port 19 is disposed at the opening 11a of the electrolytic cell 11, but the present invention is not limited thereto, and for example, as shown in Figures 2C and 2D, a hole may be drilled in the side surface of the electrolytic cell 11 and the injection port 19 may be connected to this. Furthermore, for example, as shown in Figures 2E and 2F, a hole may be drilled in the bottom surface of the electrolytic cell 11 and the injection port 19 may be connected to this.

[0048] 1 and 2A to 2F, a method (Method A) in which the electrolytic solution 5 is injected into the electrolytic cell 11 through the inlet 19 while being discharged through the outlet 17 has been described. However, the method for flowing the electrolytic solution 5 is not limited to Method A. For example, a method (Method B) in which the electrolytic solution 5 injected into the electrolytic cell 11 is rotated at high speed using a stirrer or the like without being discharged through the outlet 17 may also be used. For example, when observing deposits or the like exposed on the surface of the metallic material 13 using an SEM, the amount of electrolysis of the metallic material 13 is usually small, and therefore the amount of interfering elements eluted into the electrolytic solution 5 is also small. In this case, even with Method B, the above-described effects can be expected. However, when collecting and quantitatively analyzing deposits or the like exposed on the surface of the metallic material 13, the amount of electrolysis of the metallic material 13 is relatively large. Therefore, Method A is preferred as a method for flowing the electrolytic solution 5 from the viewpoint of fully obtaining the above-described effects.

[0049] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.

[0050] Example 1 Using the electrolysis system 1 described based on FIG. 1, a metal material 13 was electrolyzed, and then precipitates and the like were extracted, as described below.

[0051] A Pt plate was used as the cathode 12. A cylindrical steel material (diameter: 3.8 mm, length: 33.6 mm) containing 2.1 mass % Ni and 1.1 mass % Mo was used as the metal material 13 constituting the anode 14. A Pt lead wire 25 was wound around the side surface of the cylindrical metal material 13 to prepare the anode 14.

[0052] An AA electrolyte solution (acetylacetone-tetramethylammonium chloride-methanol) was used as the electrolyte solution 5. The acetylacetone content was 10% by volume. The tetramethylammonium chloride content in 100 mL of the electrolyte solution was 1 g.

[0053] The electrolytic cell 11 was a cylindrical container with an opening 11a on one side. A hole was drilled on the side opposite the opening 11a of the container, and a hose with a cock 18 was attached to form an outlet 17. One end of a silicone tube 35 was connected to an electrolyte tank 20, and the other end served as an inlet 19, which was located at the opening 11a of the electrolytic cell 11. More specifically, the inlet 19 was located opposite the outlet 17. A peristaltic pump 30 was located midway along the tube 35. A cathode 12 and an anode 14 (metal material 13) were placed inside the electrolytic cell 11, and an electrochemical measurement device 40 (potentio-galvanostat) was connected. The line connecting the inlet 19 and the outlet 17 was parallel to the side of the cylindrical metal material 13 constituting the anode 14. Furthermore, the top surface of the cylindrical metal material 13 was located directly below the inlet 19.

[0054] The pump 30 was driven with the cock 18 of the outlet 17 open. As a result, the electrolytic solution 5 was injected into the electrolytic cell 11 through the inlet 19, while being discharged from the outlet 17. By injecting and discharging the electrolytic solution 5 in this manner, the electrolytic solution 5 was made to flow along the side surface of the cylindrical metal material 13. At this time, the flow rate of the electrolytic solution 5 was set to 0.75 mm / s. The flow rate was calculated as the volume (unit: mm ) of the electrolytic solution 5 discharged from the outlet 17 per unit time. ３ / s) was measured and calculated as the area of ​​the bottom surface of the electrolytic cell 11 (unit: mm ２ ) was calculated by dividing by

[0055] Separately, a float was placed in the electrolytic cell 11 to determine the flow velocity of the electrolyte 5 flowing along the side surface of the metal material 13, and the same results as above were obtained.

[0056] In this state, the electrochemical measurement device 40 was driven. In this manner, the electrolytic surface of the metal material 13 was electrolyzed while the electrolytic solution 5 was flowing. The amount of metal material 13 dissolved by electrolysis (amount of electrolysis) was set to about 0.02 g.

[0057] The electrolyzed metal material 13 was immersed in methanol and subjected to ultrasonic vibration, and then the methanol was filtered using filter paper. The filter paper used was "Nuclepore Membrane" (pore size: 0.2 μm) manufactured by Global Life Science Technologies Japan, Inc. The residue on the filter paper was observed using a scanning electron microscope (SEM).

[0058] Figure 3 is an SEM image showing the residue of Inventive Example 1. As indicated by the arrows in Figure 3, spherical precipitates and the like were clearly observed in the SEM image. Furthermore, analysis using an energy dispersive X-ray analyzer (EDS) mounted on the SEM revealed that the spherical precipitates and the like were MnS. At this time, no electrolytic products containing Fe, Ni, and Mo were observed on the surfaces of the spherical precipitates and the like.

[0059] Comparative Example 1 In Comparative Example 1, a metal material 13 was electrolyzed in the same manner as in Invention Example 1, except that a commercially available beaker was used as the electrolytic cell 11 and the electrolytic solution 5 was not allowed to flow, and then filtration was carried out using filter paper.

[0060] Figure 4 is an SEM image showing the residue of Comparative Example 1. As indicated by the arrows in Figure 4, the SEM image confirmed spherical precipitates and the like, as well as a coating covering their surfaces. Analysis using an EDS mounted on the SEM revealed that the spherical precipitates and the like were MnS, and that the coating was a compound containing Fe, Ni, and Mo. This compound was not confirmed in an SEM image (not shown) of the surface of the metal material 13 before electrolysis, so it can be assumed to be a compound (electrolytic product) generated by electrolysis.

[0061] From the above, it can be said that in Example 1 in which the metal material 13 was electrolyzed while the electrolytic solution 5 was flowing, the formation of electrolytic products on the surface of the deposits and the like was suppressed.

[0062] Inventive Examples 2 to 5, the flow velocity of the electrolyte 5 was changed to 1.33 mm / s (Inventive Example 2), 0.48 mm / s (Inventive Example 3), 0.37 mm / s (Inventive Example 4), or 0.12 mm / s (Inventive Example 5). Otherwise, the metal material 13 was electrolyzed in the same manner as in Inventive Example 1, and then filtered using filter paper. The residue on the filter paper was observed using an SEM. As a result, in the SEM images (not shown) of Inventive Examples 4 and 5, trace amounts of electrolysis products were sometimes observed on the surfaces of the deposits, etc. In contrast, in the SEM images (not shown) of Inventive Examples 2 and 3, similar to Inventive Example 1, no electrolysis products were observed on the surfaces of the deposits, etc.

[0063] 1: Electrolysis system 5: Electrolyte 10: Electrolysis device 11: Electrolytic cell 11a: Opening 12: Cathode 13: Metal material 14: Anode 15: Conductor 16: Conductor 17: Outlet 18: Cock 19: Inlet 20: Electrolyte tank 25: Lead wire 30: Pump 35: Tube 40: Electrochemical measurement device

Claims

1. A method for extracting precipitates and / or inclusions in a metallic material, comprising electrolyzing the metallic material while flowing an electrolyte.

2. The method for extracting precipitates and / or inclusions according to claim 1, wherein the electrolysis is carried out while the electrolyte is caused to flow along at least a portion of the electrolysis surface, which is the surface of the metal material that comes into contact with the electrolyte.

3. The method for extracting precipitates and / or inclusions according to claim 2, wherein the flow rate of the electrolyte flowing along the electrolysis surface is 0.48 mm / s or more.

4. A method for extracting deposits and / or inclusions according to any one of claims 1 to 3, wherein the metal material and the electrolyte are contained in an electrolytic cell, and the electrolyte is caused to flow by injecting and discharging the electrolyte into and from the electrolytic cell.

5. A method for extracting deposits and / or inclusions according to any one of claims 1 to 3, wherein after the electrolysis, the deposits and / or inclusions exposed on the surface of the metal material are extracted.

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