Method for area-reducing area-reduction material made of pure titanium, titanium alloy or nickel base alloy

Abstract

To provide a method that enables effective execution of area reduction of an area-reduction material made of pure titanium, a titanium alloy or a nickel base alloy, which is a material except stainless steel.SOLUTION: One embodiment according to the present invention is a method for area-reducing an area-reduction material made of pure titanium or a titanium alloy by using a device comprising a rotary area-reduction head having an electrode and a grinding wheel. The method includes a step of area-reducing the area-reduction material by the rotary area-reduction head, under conditions in which an electrolytic voltage between the electrode and the area-reduction material is in the range of 1-25 V, in which current density is in the range of 0.1-2.5A / cm2 and in which a flow rate of an electrolyte is in the range of 1.0-3.0 m / s.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[0002] Generally, steel products 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 of building materials, etc., the surface of the steel product is polished to a glossy finish, 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 applied. 2 An electrolytic surface reduction method is disclosed that effectively polishes stainless steel flat bars and square pipes under conditions of an electrolyte flow rate of 6 m / sec. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4878159 Summary of the Invention [Problem to be solved by the invention]

[0005] The conventional electrolytic surface reduction method described in Patent Document 1 is effective for polishing stainless steel objects, but when polishing objects made of materials other than stainless steel, there is a problem that polishing cannot be performed effectively 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. [Means for solving the problem]

[0007] The present invention includes the following aspects. [Aspect 1] A method for reducing the surface of a pure titanium or titanium alloy material using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, The electrolysis voltage between the electrode and the surface 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. [Aspect 2] The surface material to be reduced is pure titanium, 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. [Aspect 3] 3. The method of claim 2, wherein the pure titanium comprises, in addition to a Ti component, an Fe component in an amount of 0.50 weight percent or less, and an O component in an amount of 0.40 weight percent or less. [Aspect 4] The material to be reduced is a titanium alloy, 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] 5. The method of claim 4, wherein the titanium alloy comprises, in addition to the Ti constituent, an Al constituent in an amount of 3.5 to 4.5 weight percent, a V constituent in an amount of 15.0 to 17.0 weight percent, and a Cr constituent in an amount of 5.0 to 7.0 weight percent. [Aspect 6] A method for reducing the surface of a nickel-based alloy workpiece using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, comprising: The electrolysis voltage between the electrode and the surface 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. [Aspect 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. [Aspect 8] 8. The method of claim 6 or 7, wherein the nickel-based alloy includes, in addition to a Ni constituent, a Cr constituent in a range of 14.0 to 24.0 weight percent, a Mo constituent in an amount of 10.0 weight percent or less, and a Cu constituent in an amount of 34 weight percent or less. [Aspect 9] The method according to any one of aspects 1 to 8, wherein the step 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. [Aspect 10] Aspect 10. The method according to 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 method includes a step of reducing the surface of a pure titanium or titanium alloy material to be reduced using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, The step is performed such that the electrolysis voltage between the electrode and the surface 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. [Aspect 12] A method for producing a nickel-based alloy, comprising: The method includes 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, The step is performed such that the electrolysis voltage between the electrode and the surface 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. [Effects of the Invention]

[0008] The invention according to 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, the present invention can significantly reduce the amount of electrolyte flow and the amount of current (electric power) required compared to conventional techniques. Furthermore, because the surface area of ​​a material to be reduced that is made of pure titanium, a titanium alloy, or a nickel-based alloy and that still has oxide scale formed during hot rolling or air annealing attached, it is no longer necessary to wash the material to be reduced with nitric hydrofluoric acid or the like before reducing the surface area, thereby reducing the environmental impact caused by nitric hydrofluoric acid effluent. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective schematic view of a rotary surface-reducing head 10. [Figure 2] FIG. 2 is a schematic bottom view of the rotary surface-reducing head 10. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 1 is a schematic diagram of an electrolytic surface reduction device. [Figure 5] FIG. 4 is a schematic diagram showing the flow of the electrolyte in the area reduction process. DETAILED DESCRIPTION OF THE INVENTION

[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 this method is made of 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-beam, a column, a square pipe, or a flat bar.

[0011] Pure titanium is titanium that meets any one of the standards of JIS Class 1 to Class 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 and other metals containing other components, such as metals outside the range of components specified for pure titanium. For example, titanium alloys contain, as main components, Ti, as well as 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. Examples of titanium alloys include, but are not limited to, the DAT (registered trademark) series (DAT55G, etc.) manufactured by Daido Steel Co., Ltd.

[0013] Nickel-based alloys are alloys of nickel with other metals, with nickel being the most abundant component. For example, nickel-based alloys contain, as main components, Ni, 14.0 to 24.0 weight percent of Cr, 10.0 weight percent or less of Mo, and 34 weight percent or less of Cu. Examples of nickel-based alloys include, but are not limited to, JIS 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 pure titanium, titanium alloy, and nickel-based alloy examples listed above are shown in Table 1. [Table 1]

[0015] Next, the rotary surface-reducing head 10 used in the method for reducing the surface of a material to be reduced that is made of pure titanium, titanium alloy, or nickel-based alloy according to this embodiment will be described (FIGS. 1 to 3).

[0016] As shown in FIG. 1, which is a perspective schematic diagram of a rotary surface-reducing head 10, the rotary surface-reducing head 10 includes a head base 1, a rotating shaft 2, and electrodes 5a-5f and grinding wheels 6a-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. There are no particular limitations on the materials for the head base 1 and the rotating shaft 2 of the rotary surface-reducing head 10, but materials with excellent corrosion resistance, such as stainless steel, titanium, and titanium alloys, can be used.

[0017] As shown in FIG. 2, which is a schematic bottom view of the rotary surface-reducing head 10, 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 pipe 3 so that the electrolyte that has flowed into the pipe 3 flows into the liquid reservoir 4. Typically, sets of electrodes 5 and grinding wheels 6 are arranged alternately, and are arranged 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 (for example, 2 to 20 sets).

[0018] 3 is a cross-sectional view taken along line AA in FIG. 2, showing the positional relationship between the electrode 5, the grinding wheel 6, and the workpiece 9 facing 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] As shown in Figure 3, by arranging the grindstone 6 (6a, 6f in the figure) higher (thicker) than the electrode 5 (5a in the figure), even when the grindstone 6 is in contact with the surface-reducing material 9, the electrode 5 can maintain a predetermined distance from the surface-reducing material 9. This prevents sparks that may occur between the electrode and the surface-reducing material 9 during the surface-reducing process, and also ensures a flow path for the electrolyte to flow.

[0022] The electrode 5 is made of pure copper to minimize electrical resistance. The grinding wheel 6 is a commercially available ordinary grinding wheel (such as an 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, and then compressing and molding the mixture. The elastic grinding wheel has the functionality of a grinding wheel while also being elastically deformable.

[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 is equipped with a flow rate adjusting pump, and applies a predetermined pressure to the electrolyte, either manually or in response to a control signal from a control computer (not shown) of the electrolytic surface-reducing device 100, to supply the electrolyte to the rotary surface-reducing head 10. As shown in Fig. 5, the electrolyte is supplied to the liquid reservoir 4 through the rotary shaft 2 of the rotary surface-reducing head 10 so that the electrolyte flows at a predetermined flow rate (m / sec) in the space between the surface-reducing material 9 and the electrode 5 in Fig. 5, and flows through the space between the electrode 5 and the surface-reducing material 9. The electrolyte may be an aqueous solution of sodium nitrate, an aqueous solution of sodium sulfate, or the like. The flow velocity of the electrolyte may be in the range of 0.1 to 5.0 m / sec, 1.0 to 4.0 m / sec, 1.0 to 3.0 m / sec, 1.8 to 2.2 m / sec, 1.9 to 2.1 m / sec, 2.2 to 2.8 m / sec, 2.2 to 3.0 m / sec, 2.2 to 2.9 m / sec, 2.3 to 2.9 m / sec, 2.3 to 2.7 m / sec, 2.4 to 2.67 m / sec, 2.4 to 2.9 m / sec, or 2.6 to 2.9 m / sec, 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 between them, and passes a current of a predetermined current density.

[0026] The 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 included in the range. The value of the electrolysis voltage is selected depending on the type of material to be removed (pure titanium, titanium alloy, or nickel-based alloy).

[0027] The current density flowing through the electrolyte 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 V 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 connected 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 this range.

[0029] The material 9 to be surface-reduced is placed below the rotary surface-reducing head 10 so as to face it, and the lifting device 80 presses the rotating rotary surface-reducing head 10 against the material 9 to be surface-reduced with a predetermined pressure, either manually or in response to a control signal from a 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, or 1.0 to 3.0 kN, or any value within that range.

[0030] In detail, depending on the material of the material to be reduced 9, it is preferable that the electrolytic voltage, current density, and flow rate of the electrolyte in the process of reducing the surface area of ​​the material to be reduced be set to the following ranges or any values ​​included in the ranges. (1) When the surface material 9 to be reduced is pure titanium Electrolysis voltage: 8~20V, 10~20V, 12~20V, or 12~19V Current density: 0.1~2.0A / 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 2 Electrolyte flow rate: 2.2 to 2.8 m / s, 2.3 to 2.7 m / s, or 2.4 to 2.67 m / s (2) When the surface material 9 to be reduced is a titanium alloy Electrolysis voltage: 5~15V, 6~15V, 8~15V, or 10~15V Current density: 0.9~1.3A / cm 2 , or 0.93 to 1.24 A / cm 2 Electrolyte flow rate: 1.8 to 2.2 m / s, or 1.9 to 2.1 m / s (3) When the surface material 9 to be reduced is a nickel-based alloy Electrolysis voltage: 28~35V, 30~35V, 32~35V, or 32~34V Current density: 4.0~11.0A / 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 Electrolyte flow rate: 2.2 to 3.0 m / s, 2.2 to 2.9 m / s, 2.3 to 2.9 m / s, 2.4 to 2.9 m / s, or 2.6 to 2.9 m / s

[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 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 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, and the arrows in the figure indicate 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 concave liquid reservoir 4 through the pipe 3 in the rotating shaft 2. The electrolyte supplied to the liquid reservoir 4 flows through the gap between the electrode 5 and the material 9 to be 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.

[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 can be maintained between the electrode 5 and the material 9 to be reduced. This prevents sparks from coming into contact with the material 9 to be reduced and the electrode 5 during electrolytic surface reduction, and also ensures a flow path for the electrolyte. [Example]

[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 conditions of the surface reduction process listed in Tables 2 to 4. That is, in all examples, the same electrolytic surface reduction device was used, the feed speed of the material to be reduced was kept constant at 0.6 m / min, and the surface reduction process was carried out using the same electrolyte (aqueous sodium nitrate solution). Note that the feed width of 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 used had six sets of electrodes and grinding stones. The electrodes of the rotary surface-reducing head were made of pure copper, and the grinding stones were elastic grinding stones (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 hot-rolled pure titanium in Examples 1-4 and Comparative Examples 1-3, hot-rolled titanium alloy in Example 5 and Comparative Examples 4-5, and nickel-based alloy in Examples 6-11.

[0039] In Tables 2 to 4, the grinding wheel size is the diameter (mm) of 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 between the electrode and the material to be reduced. The rotation speed (rpm) is the rotation speed of the rotary surface reduction head, and the electrolyte flow velocity (m / s) is the flow velocity of the electrolyte flowing between the electrode and the material to be reduced.

[0040] [Table 2]

[0041] [Table 3]

[0042] [Table 4]

[0043] In all examples and comparative examples, the results of the surface reduction treatment of the surface material to be reduced in one pass were evaluated. Note that one pass means that the surface reduction treatment is performed by pressing a rotating rotary surface reduction head against the surface material to be reduced, and moving the surface material to be reduced in one direction at a constant feed speed, while passing the surface material once.

[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 after the surface-reducing process, and a metallic luster appeared. In other words, 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-reducing effect was obtained.

[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 (thickness reduction amount 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. [Explanation of symbols]

[0048] 1 head base 2 rotation axes 3 Pipe section 4. Reservoir 5 electrodes 6. Whetstone 9 Reduced surface material 10-rotation surface-reducing head 40 Electrolyte supply section 50 Electrical part 60 Insulated Coupling 70 Head rotation motor 80 Lifting device 100 Electrolytic area reduction device

Claims

1. A method for reducing the surface of a pure titanium or titanium alloy material using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, The electrolysis voltage between the electrode and the surface-reducing material 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 pure titanium, 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. 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 a titanium alloy, 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. 5. The method of claim 4, wherein the titanium alloy comprises, in addition to the Ti component, an Al component in an amount of 3.5 to 4.5 weight percent, a V component in an amount of 15.0 to 17.0 weight percent, and a Cr component in an amount of 5.0 to 7.0 weight percent.

6. A method for reducing the surface of a nickel-based alloy workpiece using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, comprising: The electrolysis voltage between the electrode and the surface-reducing material 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. 7. The method of claim 6, wherein the nickel-based alloy includes, in addition to the Ni constituent, a Cr constituent of 14.0 to 24.0 weight percent, a Mo constituent of 10.0 weight percent or less, and a Cu constituent of 34 weight percent or less.

9. The method according to any one of claims 1 to 8, wherein the step 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 according to 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: The method includes a step of reducing the surface of a pure titanium or titanium alloy material to be reduced using an apparatus equipped with a rotary surface-reducing head having an electrode and a grinding wheel, The step is performed such that the electrolysis voltage between the electrode and the surface-reducing material 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.

12. A method for producing a nickel-based alloy, comprising: The method includes 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, The step is performed such that the electrolysis voltage between the electrode and the surface 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 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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