Method for reducing surface of surface reduction material made of pure titanium or titanium alloy or nickel-based alloy

Abstract

One embodiment of the present invention provides a method for reducing the surface of a surface reduction material made of pure titanium or a titanium alloy by using a device provided with a rotary surface-reducing head having an electrode and a grindstone, wherein the method includes a step for reducing the surface of the surface reduction material using the rotary surface-reducing head under conditions in which the electrolytic voltage between the electrode and the surface reduction material is 1-25 V, the current density is 0.1-2.5 A / cm2, and the flow velocity of an electrolyte is 1.0-3.0 m / sec. Additionally, one embodiment of the present invention provides a method for reducing the surface of a surface reduction material made of a nickel-based alloy by using a device provided with a rotary surface-reducing head having an electrode and a grindstone, wherein the method includes a step for reducing the surface of the surface reduction material using the rotary surface-reducing head under conditions in which the electrolytic voltage between the electrode and the surface reduction material is 1-25 V, the current density is 1.0-15.0 A / cm2, and the flow velocity of an electrolyte is 1.0-4.0 m / sec.

Description

A method for reducing the surface area of ​​a material to be reduced that is made of pure titanium, titanium alloy, or nickel-based alloy

[0001] The present invention relates to a method for reducing the surface area of ​​a material to be reduced that is made of pure titanium, a titanium alloy, or a nickel-based alloy.

[0002] Generally, steel materials such as H-beams, columns, square pipes, flat bars, hot-rolled sheets, and cold-rolled sheets have extremely rough surfaces (pickled surfaces), minute surface defects, weld deformations, etc. Depending on the requirements for building materials, etc., the surface of the steel material is polished to a glossy finish, a hairline finish, etc.

[0003] Patent Document 1 discloses an electrolytic surface-reducing device and method for polishing objects such as stainless steel flat bars, square pipes, etc. Specifically, the electrolytic surface-reducing device is equipped with an electrode made of aluminum alloy or stainless steel and a polishing head having an elastic grindstone, and a current density of 20 to 21 A / cm is used. ２ and an electrolytic surface reduction method for effectively polishing stainless steel flat bars and square pipes under conditions of an electrolyte flow rate of 6 m / sec.

[0004] Patent No. 4878159

[0005] The conventional electrolytic surface reduction method described in Patent Document 1 is capable of effectively polishing a stainless steel object to be polished, but when polishing an object made of a material other than stainless steel, there is a problem in that it cannot be effectively polished under the polishing conditions described in Patent Document 1.

[0006] Therefore, the present invention aims to provide a method for effectively reducing the surface area of ​​a material to be reduced that is made of a material other than stainless steel, such as pure titanium, a titanium alloy, or a nickel-based alloy. In this specification, "surface reduction" refers to a process for reducing the thickness of the material to be reduced by grinding and electrolysis.

[0007] The present invention includes the following aspects: [Aspect 1] A method for reducing the surface of a material to be reduced, made of pure titanium or a titanium alloy, using an apparatus equipped with a rotary surface-reducing head having an electrode and a grindstone, wherein the electrolytic voltage between the electrode and the material to be reduced is 1 to 25 V, and the current density is 0.1 to 2.5 A / cm ２and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions of an electrolytic solution flow rate of 1.0 to 3.0 m / sec. [Aspect 2] The material to be reduced is made of pure titanium, the electrolysis voltage is 8 to 20 V, the current density is 0.3 to 1.7 A / cm ２ and the flow rate of the electrolytic solution is 2.2 to 2.8 m / sec. [Aspect 3] The method according to Aspect 2, wherein the pure titanium contains, in addition to the Ti component, 0.50 weight percent or less of an Fe component and 0.40 weight percent or less of an O component. [Aspect 4] The material to be reduced in surface is made of a titanium alloy, and the electrolysis voltage is 5 to 15 V and the current density is 0.9 to 1.3 A / cm. ２ and the flow rate of the electrolyte is 1.8 to 2.2 m / sec. [Aspect 5] The method according to Aspect 4, wherein the titanium alloy contains, in addition to the Ti component, 3.5 to 4.5 weight percent of an Al component, 15.0 to 17.0 weight percent of a V component, and 5.0 to 7.0 weight percent of a Cr component. [Aspect 6] A method for reducing the surface of a material to be reduced that is made of a nickel-based alloy using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, wherein the electrolysis voltage between the electrode and the material to be reduced is 25 to 40 V, and the current density is 1.0 to 15.0 A / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions of an electrolytic voltage of 28 to 35 V and a current density of 4.0 to 11.0 A / cm. ２and the flow rate of the electrolyte is 2.2 to 3.0 m / sec. [Aspect 8] The method of Aspect 6 or 7, wherein the nickel-based alloy contains, in addition to the Ni component, 14.0 to 24.0 weight percent of a Cr component, 10.0 weight percent or less of a Mo component, and 34 weight percent or less of a Cu component. [Aspect 9] The method of any one of Aspects 1 to 8, wherein the step is further carried out under conditions where a pressure applied to the rotary surface-reducing head is 1.0 to 3.0 kN and a rotation speed of the rotary surface-reducing head is 300 to 500 rpm. [Aspect 10] The method of any one of Aspects 1 to 9, wherein the electrode is made of pure copper. [Aspect 11] A method for producing pure titanium or a titanium alloy, comprising the step of reducing the surface of a material to be reduced, made of pure titanium or a titanium alloy, using an apparatus equipped with a rotary surface-reducing head having an electrode and a grindstone, wherein the step is carried out at an electrolytic voltage between the electrode and the material to be reduced of 1 to 25 V and a current density of 0.1 to 2.5 A / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions of an electrolytic solution flow rate of 1.0 to 3.0 m / sec. [Aspect 12] A method for producing a nickel-based alloy, comprising the step of reducing the surface of a material to be reduced, made of a nickel-based alloy, using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, wherein the step is carried out by applying an electrolytic voltage between the electrode and the material to be reduced of 25 to 40 V and a current density of 1.0 to 15.0 A / cm. ２ and reducing the surface area of ​​the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte is 1.0 to 4.0 m / sec.

[0008] One embodiment of the present invention can effectively reduce the surface area of ​​a material to be reduced that is made of pure titanium, a titanium alloy, or a nickel-based alloy, which are materials other than stainless steel. Furthermore, one embodiment of the present invention can reduce the amount of electrolyte flow and the amount of current (electric power) required compared to conventional techniques. Furthermore, one embodiment of the present invention can reduce the surface area of ​​a material to be reduced that is made of pure titanium, a titanium alloy, or a nickel-based alloy, even though oxide scale formed during hot rolling or air annealing remains attached. This eliminates the need to wash the material to be reduced with nitric hydrofluoric acid or the like before the surface reduction process, thereby reducing the environmental impact caused by wastewater from nitric hydrofluoric acid or the like.

[0009] 2 is a schematic perspective view of the rotary surface-reducing head 10. FIG. 3 is a schematic bottom view of the rotary surface-reducing head 10. FIG. 4 is a cross-sectional view taken along line AA in FIG. 2. FIG. 5 is a schematic view of an electrolytic surface-reducing device. FIG. 6 is a schematic view showing the flow of an electrolyte in a surface-reducing process.

[0010] This section describes a method for reducing the surface area of ​​a material made of pure titanium, a titanium alloy, or a nickel-based alloy according to one embodiment of the present invention. The material to be reduced by the method according to this embodiment is pure titanium, a titanium alloy, or a nickel-based alloy. The shape of the material to be reduced may be any shape, such as a flat hot-rolled plate, a cold-rolled plate, an H-section steel, a column, a square pipe, or a flat bar.

[0011] Pure titanium is titanium that meets any one of the standards of JIS Classes 1 to 4. For example, pure titanium contains, as main components, Ti, Fe at 0.50 weight percent or less, and O at 0.40 weight percent or less.

[0012] Titanium alloys are alloys of titanium with one or more other metals, with other elements outside the ranges specified for pure titanium. Titanium alloys may be alpha alloys, beta alloys, alpha and beta alloys, or combinations thereof. Other metals included in titanium alloys include, but are not limited to, Al, V, Cr, Mo, Zr, Sn, Fe, Pd, and the like. For example, titanium alloys may contain, in addition to Ti, 3.5 to 4.5 weight percent Al, 15.0 to 17.0 weight percent V, and 5.0 to 7.0 weight percent Cr as the main components. Examples of titanium alloys include, but are not limited to, the DAT® series (e.g., DAT55G) manufactured by Daido Steel Co., Ltd.

[0013] A nickel-based alloy is an alloy of nickel with one or more other metals, with nickel being the most abundant component. Examples of other metals contained in nickel-based alloys include, but are not limited to, Cr, Cu, Mo, Fe, Mn, and the like. For example, a nickel-based alloy may contain, as its main components, Ni, as well as 14.0 to 24.0 weight percent Cr, 10.0 weight percent or less Mo, and 34 weight percent or less Cu. Examples of nickel-based alloys include, but are not limited to, JIS standards NCF600, NCF625, NCF718, NW6002, and NW4400, as well as the NAS (registered trademark) series (e.g., NAS355N) manufactured by Nippon Yakin Kogyo Co., Ltd.

[0014] For reference, the components of the examples of pure titanium, titanium alloys, and nickel-based alloys listed above are shown in Table 1 (the numerical values ​​in the table are in weight percent).

[0015] Next, a rotary surface-reducing head 10 used in the method for reducing the surface of a workpiece made of pure titanium, titanium alloy, or nickel-based alloy according to this embodiment will be described (FIGS. 1 to 5).

[0016] FIG. 1 is a perspective schematic diagram of a rotary surface-reducing head 10. As shown in FIG. 1, the rotary surface-reducing head 10 includes a head base 1, a rotating shaft 2, and electrodes 5 (5a to 5f) and grinding wheels 6 (6a to 6f) provided on the base 1. The rotating shaft 2 has a hollow structure and includes a tube portion 3 for passing an electrolyte. The head base 1 and the rotating shaft 2 may be integrally molded, or may be formed by joining separate members together. The materials of the head base 1 and the rotating shaft 2 of the rotary surface-reducing head 10 are not particularly limited, but may be materials with excellent corrosion resistance, such as stainless steel, titanium, or titanium alloys.

[0017] 2 is a schematic diagram of the bottom of the rotary surface-reducing head 10. As shown in FIG. 2, the bottom of the rotary surface-reducing head 10 has electrodes 5 (EL) and grinding wheels 6 (WS) arranged in this order along the circumference of a circular head base 1, with a concave liquid reservoir 4 provided in the center. The liquid reservoir 4 is connected to the tube 3 so that the electrolyte flowing into the tube 3 flows into the liquid reservoir 4. Typically, sets of electrodes 5 and grinding wheels 6 are arranged alternately to cover the circumference of the head base 1. The number of sets of electrodes 5 and grinding wheels 6 is not limited to the six sets shown in the figure, and may be any number (e.g., 2 to 20 sets).

[0018] 3 is a cross-sectional view taken along line A-A in FIG. 2, showing the positional relationship between the electrode 5 and grinding wheel 6, and the workpiece 9 to be surface-reduced, which faces the rotary surface-reducing head 10. The illustrated arrangement shows the state when the surface-reducing process is not being performed.

[0019] As shown in Figure 3, the grinding wheel 6 (6a, 6f in the figure) is positioned so that its lower surface (the surface facing the material 9 to be reduced) is close to the material 9 to be reduced, and so that the lower surface of the electrode 5 (5a in the figure) does not come into contact with the material 9 to be reduced.

[0020] The electrodes 5 (5a to 5f) are arranged at the same height to maintain a constant current density during conduction. The grindstones 6 (6a to 6f) are arranged at the same height to maintain a constant surface reduction accuracy. The height of the grindstones 6 is greater than the height of the electrodes 5.

[0021] 3, by arranging the grinding wheel 6 (6a, 6f in the figure) higher (thicker) than the electrode 5 (5a in the figure), the electrode 5 can maintain a predetermined distance from the material 9 to be reduced even when the grinding wheel 6 is in contact with the material 9 to be reduced. This prevents sparks that may occur between the electrode and the material 9 to be reduced during the surface reduction process, and also ensures a flow path (space) for the electrolyte to flow between the electrode 5 and the material 9 to be reduced.

[0022] The electrode 5 is made of pure copper to minimize electrical resistance. The grinding wheel 6 is a commercially available ordinary grinding wheel (e.g., elastic grinding wheel). For example, an elastic grinding wheel is made by mixing abrasive grains such as alumina, silicon carbide, or zirconia with a heat-resistant binder such as epoxy resin, bakelite, or nylon nonwoven fabric, followed by compression molding. Elastic grinding wheels retain the functionality of a grinding wheel while being elastically deformable. The grit size of the grinding wheel 6 may be, for example, #80 to #400, #80 to #300, #80 to #250, #100 to #500, #100 to #300, #100 to #250, #150 to #500, #150 to #300, #150 to #250, #150 to #240, or #150 or #240. The "# number" in the grit size indicates the number of pieces per 1 cm of the grinding wheel surface. ２ For example, the number of abrasive grains in a grinding stone is "#150." ２ The number of abrasive grains contained therein is 150.

[0023] 4 is a schematic diagram of an electrolytic surface-reducing device 100 equipped with a rotary surface-reducing head 10 used in a method for reducing the surface area of ​​a workpiece made of pure titanium, titanium alloy, or nickel-based alloy. The electrolytic surface-reducing device 100 includes the rotary surface-reducing head 10, an electrolyte supply unit 40, a current-carrying unit 50, an insulating coupling 60, a head rotation motor 70, and an elevator 80.

[0024] The electrolyte supply unit 40 includes a flow rate adjusting pump, and applies a predetermined pressure to the electrolyte to supply the electrolyte to the rotary surface-reducing head 10, either manually or in response to a control signal from a control computer (not shown) of the electrolytic surface-reducing apparatus 100. As shown in FIG. 5 , the electrolyte supply unit 40 supplies the electrolyte to the liquid reservoir 4 through the tube 3 of the rotary shaft 2 of the rotary surface-reducing head 10, and supplies the electrolyte to the space 12 between the material to be reduced 9 and the electrode 5. By adjusting the pressure applied to the electrolyte by the electrolyte supply unit 40 and the rotation speed of the rotary surface-reducing head 10, the electrolyte is supplied so as to flow at a predetermined flow rate (m / sec) through the space 12 between the material to be reduced 9 and the electrode 5 in FIG. 5 . The electrolyte may be an aqueous solution of sodium nitrate, an aqueous solution of sodium sulfate, or the like. The predetermined flow rate of the electrolyte may be in the range of 0.1 to 5.0 m / s, 1.0 to 4.0 m / s, 1.0 to 3.0 m / s, 1.8 to 2.2 m / s, 1.9 to 2.1 m / s, 2.2 to 2.8 m / s, 2.2 to 3.0 m / s, 2.2 to 2.9 m / s, 2.3 to 2.9 m / s, 2.3 to 2.7 m / s, 2.4 to 2.67 m / s, 2.4 to 2.9 m / s, or 2.6 to 2.9 m / s, or any value within the range.

[0025] The current supply unit 50 is equipped with a voltage regulator and a current regulator connected to a power source (not shown), and generates a potential difference between the electrode 5 of the rotary surface-reducing head 10 and the material to be reduced 9, either manually or in response to a control signal from the control computer (not shown) of the electrolytic surface-reducing device 100, applies a predetermined electrolytic voltage to the electrolyte flowing in the space 12 between the electrode 5 and the material to be reduced 9, and passes a current of a predetermined current density.

[0026] The predetermined electrolysis voltage applied to the electrolytic solution may be, for example, in the range of 1 to 40 V, 1 to 30 V, 1 to 25 V, 1 to 20 V, 1 to 15 V, 5 to 25 V, 5 to 20 V, 5 to 15 V, 6 to 15 V, 8 to 25 V, 8 to 20 V, 8 to 15 V, 10 to 20 V, 12 to 20 V, 10 to 15 V, 12 to 19 V, 25 to 40 V, 25 to 35 V, 28 to 35 V, 28 to 34 V, 30 to 35 V, 31 to 35 V, 32 to 35 V, or 32 to 34 V, or any value within the range. The value of the electrolysis voltage is selected depending on the type of material to be reduced (pure titanium, titanium alloy, or nickel-based alloy).

[0027] The predetermined current density at which the electrolyte flows is, for example, 0.1 to 15.0 A / cm ２ ,0.1~10.0A / cm ２ ,0.1~5.0A / cm ２ ,0.1~2.5A / cm ２ ,0.1~2.0A / cm ２ ,0.1~1.7A / cm ２ ,0.1~1.3A / cm ２ ,0.2~2.5A / cm ２ ,0.2~2.0A / cm ２ ,0.3~2.5A / cm ２ ,0.3~2.0A / cm ２ ,0.3~1.7A / cm ２ ,0.31~1.65A / cm ２ ,0.9~1.3A / cm ２ ,0.93~1.24A / cm ２ ,0.9~2.5A / cm ２ ,0.9~2.0A / cm ２ ,0.9~1.7A / cm ２ ,0.9~1.3A / cm ２ , 1.0~15.0A / cm ２ , 1.0~11.0A / cm ２ , 1.03~1.65A / cm ２ , 3.0~15.0A / cm ２ , 3.0~11.0A / cm ２ , 4.0~11.0A / cm ２ , 5.0~15.0A / cm ２ , 5.0~11.0A / cm ２ , 5.3~11.0A / cm ２ , 5.5-11.0A / cm ２ , 5.5-10.7A / cm ２ , 7.0~10.7A / cm ２ , or 9.0 to 10.7 A / cm ２ The current density may be in the range of 0.1 to 1.0 mm, or any value within that range. The value of the current density is selected depending on the type of material to be removed (pure titanium, titanium alloy, or nickel-based alloy).

[0028] The insulating coupling 60 is a means for preventing current leakage, and the head rotation motor 70 and the rotary surface-reducing head 10 are directly or indirectly coupled to each other so that the rotational force of the head rotation motor 70 is transmitted to the rotary surface-reducing head 10. The head rotation motor 70 rotates the rotary surface-reducing head 10 at a predetermined rotation speed. The rotation speed of the rotary surface-reducing head 10 may be, for example, in the range of 100 to 1000 rpm, 100 to 700 rpm, 100 to 500 rpm, 300 to 1000 rpm, 300 to 700 rpm, 300 to 500 rpm, or 300 to 400 rpm, or any value within the range.

[0029] The material to be reduced (9) is placed facing downward from the rotary surface-reducing head (10), and the lifting device (80) presses the rotating rotary surface-reducing head (10) against the material to be reduced (9) with a predetermined pressure, either manually or in response to a control signal from the control computer (not shown) of the electrolytic surface-reducing device (100). The pressure applied to the rotary surface-reducing head 10 may be, for example, in the range of 0.1 to 10.0 kN, 0.1 to 5.0 kN, 0.1 to 3.0 kN, 0.5 to 10.0 kN, 0.5 to 5.0 kN, 0.5 to 3.0 kN, 1.0 to 10.0 kN, 1.0 to 5.0 kN, 1.0 to 3.0 kN, 1.0 to 2.5 kN, 2.0 to 5.0 kN, 2.0 to 3.0 kN, 2.0 to 2.5 kN, 2.0 to 2.3 kN, or 2.07 to 2.21 kN, or any value within the range.

[0030] Specifically, depending on the material of the material 9 to be reduced, the electrolysis voltage, current density, and flow rate of the electrolyte in the process of reducing the surface area of ​​the material 9 to be reduced are preferably set to the following ranges or any values ​​included in the ranges: (1) When the material 9 to be reduced is pure titanium: Electrolysis voltage: 8 to 20 V, 10 to 20 V, 12 to 20 V, or 12 to 19 V Current density: 0.1 to 2.0 A / cm ２ ,0.2~2.0A / cm ２ ,0.3~2.0A / cm ２ ,0.3~1.7A / cm ２ ,0.31~1.65A / cm ２ , or 1.03 to 1.65 A / cm ２Flow rate of electrolyte: 2.2 to 2.8 m / sec, 2.3 to 2.7 m / sec, or 2.4 to 2.67 m / sec. (2) When the surface-reducing material 9 is a titanium alloy, electrolysis voltage: 5 to 15 V, 6 to 15 V, 8 to 15 V, or 10 to 15 V. Current density: 0.9 to 1.3 A / cm. ２ , or 0.93 to 1.24 A / cm ２ Electrolyte flow rate: 1.8 to 2.2 m / sec, or 1.9 to 2.1 m / sec. (3) When the surface-reducing material 9 is a nickel-based alloy, electrolysis voltage: 28 to 35 V, 30 to 35 V, 32 to 35 V, or 32 to 34 V. Current density: 4.0 to 11.0 A / cm. ２ , 5.0~11.0A / cm ２ , 5.3~11.0A / cm ２ , 5.5-11.0A / cm ２ , 5.5-10.7A / cm ２ , 7.0~10.7A / cm ２ , or 9.0 to 10.7 A / cm ２ Flow rate of electrolyte: 2.2 to 3.0 m / sec, 2.2 to 2.9 m / sec, 2.3 to 2.9 m / sec, 2.4 to 2.9 m / sec, or 2.6 to 2.9 m / sec

[0031] The following describes an electrolytic surface reduction method for a material 9 to be reduced using an electrolytic surface reduction device 100 having a rotary surface reduction head 10. In the process of reducing the surface area of ​​the material 9 to be reduced, the rotating rotary surface reduction head 10 is lowered by an elevating device 80 and brought into contact with the material 9 to be reduced at a predetermined pressure, thereby reducing the surface area of ​​the material 9 to be reduced.

[0032] 5 is a partial cross-sectional view of the rotary surface-reducing head 10, cut through the central axis (rotation axis) and the plane including the electrode 5, with the arrows in the figure indicating the flow of the electrolyte. The electrolyte supplied from the electrolyte supply unit 40 of the electrolytic surface-reducing device 100 to which the rotary surface-reducing head 10 is attached is supplied to the liquid reservoir 4 through the pipe 3 in the rotary shaft 2. The electrolyte supplied to the liquid reservoir 4 flows through the gap (space 12) between the electrode 5 and the material 9 to be surface-reduced at the predetermined flow rate due to the pressure applied by the electrolyte supply unit 40 and the centrifugal force caused by the rotation of the rotary surface-reducing head 10.

[0033] A negative potential (or a positive potential) is applied to the electrode 5 by the current-carrying unit 50, and a positive potential (or a negative potential) is applied to the material 9 to be reduced, so that the electrolysis voltage and current density of the electrolyte between the electrode 5 and the material 9 to be reduced are set to be within the above-mentioned predetermined ranges. Hydrogen is generated from the surface of the electrode 5 due to the current flowing through the electrolyte, and electrolytic eluates are generated from the surface of the material 9 to be reduced, but these are discharged together with the electrolyte.

[0034] Since the grinding wheel 6 does not deform significantly under pressure, even if pressure is applied to the material 9 to be reduced by the lifting device 80 during the surface reduction process, a predetermined distance (space 12) can be maintained between the electrode 5 and the material 9 to be reduced. This prevents sparks from coming into contact with the electrode 5 during electrolytic surface reduction, and also ensures a flow path for the electrolyte.

[0035] Examples and comparative examples of the method of reducing the surface area of ​​a material to be reduced using an electrolytic surface-reducing device according to the present invention will be described below.

[0036] In each example and comparative example, the same conditions were used except for the surface-reduction process conditions listed in Tables 2 to 4. That is, in all examples, the same electrolytic surface-reduction device was used, the feed rate of the material to be reduced was kept constant at 0.6 m / min, and the same electrolyte (aqueous sodium nitrate solution) was used to perform the surface-reduction process. Note that the feed width of the rotary surface-reduction head on the material to be reduced was set to 160 mm, but this parameter does not affect the surface-reduction capacity (surface-reduction results).

[0037] The rotary surface-reducing head of the electrolytic surface-reducing device had six sets of electrodes and grindstones. The electrodes of the rotary surface-reducing head were made of pure copper, and the grindstones were elastic grindstones (grit size #150 or #240. #150 has a coarser grain size than #240. The abrasive grains were alumina).

[0038] The surface material to be reduced was a hot-rolled sheet made of pure titanium in Examples 1 to 4 and Comparative Examples 1 to 3, a hot-rolled sheet made of a titanium alloy in Example 5 and Comparative Examples 4 and 5, and a hot-rolled sheet made of a nickel-based alloy in Examples 6 to 11.

[0039] In Tables 2 to 4, the grinding wheel size is the size of the grinding wheel attached to the rotary surface-reducing head, and the pressure (kN) is the pressure applied to the rotary surface-reducing head. ２ ) and electrolysis voltage (V) are the voltage and current density applied to the electrolyte flowing in the space between the electrode and the material to be reduced. The rotation speed (rpm) is the number of revolutions per minute of the rotary surface reduction head, and the electrolyte flow rate (m / s) is the flow rate of the electrolyte flowing in the space between the electrode and the material to be reduced.

[0040]

[0041]

[0042]

[0043] In all examples and comparative examples, the results of the surface reduction treatment of the surface material to be reduced by one pass were evaluated. Note that one pass means that the surface material to be reduced is passed through only once while the rotating rotary surface reduction head is pressed against the surface material to be reduced and the surface material to be reduced is moved in one direction at a constant feed speed (0.6 m / min).

[0044] In all of the surface-reduced materials in Examples 1 to 4, 5, and 6 to 11, the pickled surface (black scale) that was visually observed before the surface-reducing process was no longer visible on the surface, and a metallic luster appeared. In other words, the surface-reduced materials (pure titanium, titanium alloy, or nickel-based alloy) with a metallic luster were obtained. Furthermore, the surface reduction amount per pass (thickness reduction amount of the surface-reduced material) in all of the surface-reduced materials in Examples 1 to 4, 5, and 6 to 11 after the surface-reducing process was 20 μm or more, and a sufficient surface-reduction effect was achieved.

[0045] On the other hand, visual inspection showed that black scale remained at least partially on all of the surface-reduced materials after the surface-reducing process in Comparative Examples 1 to 5. Furthermore, the surface-reduced amount per pass (the amount of thickness reduction of the surface-reduced material) of all of the surface-reduced materials after the surface-reducing process in Comparative Examples 1 to 5 was less than 10 μm, and a sufficient surface-reducing effect was not obtained.

[0046] Even under the conditions of the comparative example, it is not impossible to achieve a predetermined amount of area reduction (20 μm or more) and to make black scale invisible in visual inspection by performing the area reduction process multiple times (multiple passes) on the material to be reduced. However, the examples, which can achieve a predetermined amount of area reduction (20 μm or more) and make black scale invisible in visual inspection with a single pass of the area reduction process, achieve more effective area reduction.

[0047] The dimensions, materials, shapes, relative positions of components, and the like described in the above embodiments are arbitrary and may be changed depending on the structure of the device to which the present invention is applied or various conditions, and the present invention is not limited to the above-described specifically described embodiments.

[0048] The present invention further includes the following aspects: [1] A method for reducing the surface area of ​​a material to be reduced using an apparatus including a pure copper electrode, a rotary surface-reducing head having a grindstone, and an electrolyte supply unit that supplies an electrolyte to a space between the electrode and a pure titanium material to be reduced, wherein the electrolytic voltage between the electrode and the material to be reduced is 8 to 20 V, and the current density of the current flowing in the electrolyte through the space is 0.3 to 1.7 A / cm ２and reducing the surface of the material to be surface-reduced with the rotary surface-reducing head under conditions of a flow rate of the electrolyte flowing through the space of 2.2 to 2.8 m / sec. [2] The method according to [1], wherein the surface-reducing step is carried out under the additional conditions of: a rotation speed of the rotary surface-reducing head is 300 to 400 rpm, a pressure applied to the rotary surface-reducing head is 2.0 to 2.5 kN, 2.0 to 2.3 kN, or 2.07 to 2.21 kN, and the grinding stone has a grit size of #100 to #250, #150 to #250, or #150 to #240. [3] The method according to [1] or [2], wherein the pure titanium contains, in addition to a Ti component, an Fe component of 0.50 weight percent or less and an O component of 0.40 weight percent or less. [4] A method for producing pure titanium, comprising the step of reducing the surface of the material to be reduced using an apparatus equipped with a pure copper electrode, a rotary surface-reducing head having a grindstone, and an electrolytic solution supply unit that supplies electrolytic solution to a space between the electrode and the pure titanium material to be reduced, wherein the step is carried out such that the electrolytic voltage between the electrode and the material to be reduced is 8 to 20 V, and the current density of the current flowing in the electrolytic solution through the space is 0.3 to 1.7 / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte flowing through the space is 2.2 to 2.8 m / sec.

[0049] REFERENCE SIGNS LIST 1 head base 2 rotating shaft 3 tube section 4 liquid reservoir section 5 electrode 6 grinding stone 9 material to be surface-reduced 10 rotating surface-reducing head 40 electrolyte supply section 50 current-carrying section 60 insulating coupling 70 head rotation motor 80 lifting device 100 electrolytic surface-reducing device

Claims

1. A method for reducing the surface area of ​​a material made of pure titanium or a titanium alloy using a device equipped with a rotary surface-reducing head having an electrode and a grinding wheel, in which the electrolytic voltage between the electrode and the material to be reduced is 1 to 25 V, and the current density is 0.1 to 2.5 A / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte is 1.0 to 3.0 m / sec.

2. The surface material to be reduced is made of pure titanium, and the electrolysis voltage is 8 to 20 V and the current density is 0.3 to 1.7 A / cm ２ and the flow rate of the electrolyte is 2.2 to 2.8 m / sec.

3. The method according to claim 2, wherein the pure titanium contains, in addition to the Ti component, an Fe component of 0.50 weight percent or less and an O component of 0.40 weight percent or less.

4. The material to be reduced is made of titanium alloy, and the electrolysis voltage is 5 to 15 V and the current density is 0.9 to 1.3 A / cm ２ and the flow rate of the electrolyte is 1.8 to 2.2 m / sec.

5. The method of claim 4, wherein the titanium alloy includes, in addition to the Ti component, an Al component of 3.5 to 4.5 weight percent, a V component of 15.0 to 17.0 weight percent, and a Cr component of 5.0 to 7.0 weight percent.

6. A method for reducing the surface of a nickel-based alloy material to be reduced using a device equipped with a rotary surface-reducing head having an electrode and a grinding wheel, in which the electrolytic voltage between the electrode and the material to be reduced is 25 to 40 V, and the current density is 1.0 to 15.0 A / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte is 1.0 to 4.0 m / sec.

7. The electrolysis voltage is 28 to 35 V, and the current density is 4.0 to 11.0 A / cm ２ and the flow rate of the electrolyte is 2.2 to 3.0 m / sec.

8. The method of claim 6, wherein the nickel-based alloy includes, in addition to the Ni constituent, a Cr constituent in an amount of 14.0 to 24.0 weight percent, a Mo constituent not greater than 10.0 weight percent, and a Cu constituent not greater than 34 weight percent.

9. A method according to any one of claims 1 to 8, wherein the process is further carried out under conditions in which the pressure applied to the rotary surface-reducing head is 1.0 to 3.0 kN and the rotation speed of the rotary surface-reducing head is 300 to 500 rpm.

10. The method of any one of claims 1 to 8, wherein the electrodes are made of pure copper.

11. A method for producing pure titanium or a titanium alloy, comprising a step of reducing the surface of a material to be reduced, made of pure titanium or a titanium alloy, using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, wherein the step is carried out at an electrolytic voltage between the electrode and the material to be reduced of 1 to 25 V and a current density of 0.1 to 2.5 A / cm ２ and reducing the surface of the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte is 1.0 to 3.0 m / sec.

12. A method for manufacturing a nickel-based alloy, comprising a step of reducing the surface of a nickel-based alloy material to be reduced using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, wherein the step is carried out at an electrolytic voltage between the electrode and the material to be reduced of 25 to 40 V and a current density of 1.0 to 15.0 A / cm ２ and reducing the surface area of ​​the material to be reduced by the rotary surface-reducing head under conditions where the flow rate of the electrolyte is 1.0 to 4.0 m / sec.

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