Mirror tungsten electrode wire and preparation method thereof

Abstract

The mirror tungsten filament electrode wire is internally provided with a high-purity tungsten filament, the surface of the high-purity tungsten filament is evenly coated with a copper layer, the roughness Ra of the mirror tungsten filament electrode wire is smaller than 0.2 micrometer, the diameter of the mirror tungsten filament electrode wire is smaller than or equal to 70 micrometers, the tensile strength of the mirror tungsten filament electrode wire is larger than 4500 MPa, and the natural suspension deflection of the mirror tungsten filament electrode wire within the length of each meter is smaller than or equal to 25 mm; the preparation method comprises the steps that S1, raw materials are prepared; S2, the surfaces of the raw materials are pretreated; S3, a brass coating is formed through electroplating; S4, multi-pass drawing is conducted; by combining the copper plating process and the multi-pass oil drawing technology, the surface mirror surface of the tungsten filament is achieved, the electric arc loss during electric discharge machining is remarkably reduced, the machining precision is improved, and meanwhile high strength and low deflection are both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of precision electric spark machining and micro-electrode manufacturing, in particular to a mirror tungsten wire electrode and a preparation method thereof. Background Art

[0002] Tungsten wire electrode is an electrode made of tungsten or tungsten alloy as the main material. It is widely used in various industrial and technical fields due to its high melting point, good conductivity and corrosion resistance.

[0003] Deficiencies of existing technology: At present, the surface roughness of traditional tungsten wire electrodes is relatively high (Ra>0.5μm), which easily leads to uneven loss and reduced processing accuracy during discharge machining. Currently, copper-plated tungsten wires mostly use graphite emulsion drawing technology, which has insufficient surface finish and the straightness is difficult to meet the requirements of high-precision machining. Summary of the Invention

[0004] The object of the present invention is to provide a mirror tungsten wire electrode and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a mirror tungsten wire electrode wire, wherein the interior of the mirror tungsten wire electrode wire is a high-purity tungsten wire, the surface of the high-purity tungsten wire is uniformly coated with a copper layer, the roughness Ra of the mirror tungsten wire electrode wire is less than 0.2μm, the diameter is ≤70μm, the tensile strength is greater than 4500MPa, and the natural suspension deflection of the mirror tungsten wire electrode wire is ≤25mm per meter of length.

[0006] The present invention also provides a method for preparing a mirror tungsten wire electrode wire, the preparation method specifically comprising the following steps: S1. Prepare raw materials; S2, pre-treating the surface of raw materials; S3, forming a brass coating by electroplating; S4, multi-pass drawing; S5. Perform performance testing on the finished product.

[0007] Preferably, in step S1, the raw material is a high-purity tungsten wire with a diameter of 50-390 μm, a high-purity tungsten wire with a purity of ≥98%, or an alloy tungsten with a purity of less than 10%.

[0008] Preferably, the step S2 specifically includes the following steps: a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a2. Clean with pure water and activate with ultrasound, wherein the ultrasound activation temperature is set to 50°C and the frequency is set to 40 kHz.

[0009] Preferably, the step S3 specifically includes the following steps: b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. Forming a brass coating by heat preservation in a furnace, wherein the thickness of the brass coating is finally 5-8 μm, wherein the furnace temperature is set to 540-580° C., and the furnace heat preservation time is 10-20 seconds.

[0010] Preferably, in step S4, a micro-wire drawing machine is used to draw the target diameter in multiple passes, from an initial diameter of 50-390 μm to 50-70 μm, with a single-pass diameter reduction of ≤3 μm to ensure dimensional consistency.

[0011] Preferably, in step S5, when the performance of the finished product is tested, a laser caliper is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

[0012] Preferably, the step a1 specifically includes the following steps: a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides.

[0013] Preferably, the processing degree of a single pass in the multi-pass drawing is controlled to be 7%-11%, the drawing speed is set to 4-8 m / s, the tolerance of the die aperture in the last pass is ±0.1 μm, the processing degree is reduced to 5%-7%, the diameter reduction is ≤1 μm, and the die inclination angle is set to , and the final drawing die uses a single crystal diamond die.

[0014] Preferably, a micro-filament drawing machine is used for multiple drawing passes and a drawing oil lubricant is added, wherein the drawing oil lubricant has a viscosity of 20-30 cSt and a flash point of >150°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention relates to a mirror-finished tungsten wire electrode and a preparation method thereof. The high-purity tungsten wire is used as the core material and the surface is coated with a copper layer. There is no peeling defect, the oxidation resistance of the copper layer is enhanced, and the electrode life is increased by 2-3 times compared with the traditional process. By combining the copper plating process with the multi-pass oil drawing technology, the surface of the tungsten wire is mirror-finished, which significantly reduces the arc loss during discharge machining and improves the machining accuracy, while taking into account high strength and low deflection.

[0016] 2. The present invention provides a mirror tungsten wire electrode and a preparation method thereof, wherein the thickness of the electroplated copper layer is 5-8 μm and the porosity is less than 0.1%; if the coating thickness is too thin, it is not conducive to lubrication and increases mold wear; if the coating porosity is too high, the coating bonding degree is low, the copper loss is large during drawing, and the mold wear is also aggravated; if the coating thickness is too high, the electroplating equipment and process requirements are high and are not conducive to cost control, and if the coating thickness is too high, the lubrication conditions are too good, which is not conducive to reducing roughness.

[0017] 3. The present invention provides a mirror tungsten wire electrode wire and a preparation method thereof, wherein the oil drawing lubricant has a viscosity of 20-30 cSt and a flash point of >150°C. The temperature in the mold cavity is relatively high during drawing. If the viscosity and flash point are low, the lubricant is likely to fail, increasing mold wear.

[0018] 4. The present invention provides a mirror tungsten wire electrode and its preparation method, the final drawing reduction is ≤1μm, the die inclination angle While ensuring the roughness is as low as possible, using a small diameter reduction and a suitable angle is beneficial to controlling the final diameter stability of the finished product.

[0019] 5. The present invention provides a mirror tungsten wire electrode and a preparation method thereof, which can produce ultra-fine wires with a diameter of 50-70 μm to meet the needs of micro-hole processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the mirror tungsten wire surface of the present invention; Figure 2 This is a schematic diagram of a cutaway view of the mirror tungsten filament of the present invention; Figure 3 This is a flow chart of the oil pulling process of the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0023] In the description of this patent, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "disposed" should be understood broadly. For example, they can refer to fixed connection or disposition, detachable connection or disposition, or integrated connection or disposition. Those skilled in the art will understand the specific meanings of the above terms in this patent based on the specific circumstances.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "several" means two or more, unless otherwise specifically defined.

[0025] Example 1 See also Figure 1-3 As shown, the present invention provides a technical solution for a mirror tungsten wire electrode: the interior of the mirror tungsten wire electrode is high-purity tungsten wire, the surface of the high-purity tungsten wire is evenly coated with a copper layer, the roughness Ra of the mirror tungsten wire electrode is less than 0.2μm, the diameter is ≤70μm, the tensile strength is greater than 4500MPa, and the natural suspension deflection of the mirror tungsten wire electrode per meter length is ≤25mm.

[0026] Example 2 The present invention also provides a method for preparing a mirror tungsten wire electrode wire, which specifically comprises the following steps: S1. Prepare raw materials. The raw materials are high-purity tungsten wire with a diameter of 80μm and a purity of ≥98%; S2, pre-treating the surface of raw materials; a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides; a2. Clean with pure water and activate with ultrasonic wave, wherein the ultrasonic activation temperature is set to 50°C and the frequency is set to 40KHz; S3, forming a brass coating by electroplating; b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. A brass coating is formed by heat preservation in a furnace, wherein the furnace temperature is set to 540-580°C and the furnace heat preservation time is 10-20 seconds. The thickness of the brass coating is finally 5 μm, the diameter of the final mirror tungsten wire electrode is 85 μm, and the porosity is less than 0.1%. A brass coating that is too thin is not conducive to lubrication and increases mold wear. A brass coating with a large porosity has a low bonding degree, resulting in large copper loss during drawing and aggravated mold wear. On the contrary, a brass coating that is too thick places high requirements on electroplating equipment and processes, which is not conducive to cost control, and the lubrication condition is too good, which is not conducive to reducing roughness. S4, multi-pass drawing: In multi-pass drawing, the processing degree of a single pass is controlled to be 7%-11%, and the diameter reduction of a single pass is ≤3μm to ensure dimensional consistency. Wire drawing oil lubricant is added, and the drawing speed is set to 4-8 m / s. The tolerance of the die aperture in the final pass is ±0.1μm, the processing degree is reduced to 5%-7%, the diameter reduction is ≤1μm, and the die inclination angle is set to 8°. Using a small diameter reduction and a suitable angle is conducive to controlling the final diameter stability of the finished product. The final drawing die uses a single crystal diamond die, and the final mirror tungsten wire electrode wire diameter is 70μm. The viscosity of the wire drawing oil lubricant is set to 20-30 cSt, and the flash point is greater than 150°C. The temperature in the die cavity is high during drawing. If the viscosity and flash point are low, the lubricant will easily fail, increasing die wear. S5. Performance testing of finished products: When testing the performance of finished products, a laser diameter gauge is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

[0027] Therefore, the final roughness of the mirror tungsten wire electrode is Ra = 0.15μm, the tensile strength is = 4500MPa, and the natural overhang deflection per meter length is ≤ 25mm.

[0028] Example 3 The present invention also provides a method for preparing a mirror tungsten wire electrode wire, which specifically comprises the following steps: S1. Prepare raw materials. The raw materials are high-purity tungsten wire with a diameter of 60μm and a purity of ≥98%; S2, pre-treating the surface of raw materials; a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides; a2. Clean with pure water and activate with ultrasonic wave, wherein the ultrasonic activation temperature is set to 50°C and the frequency is set to 40KHz; S3, forming a brass coating by electroplating; b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. A brass coating is formed by heat preservation in a furnace, wherein the furnace temperature is set to 540-580°C and the furnace heat preservation time is 10-20 seconds. The thickness of the brass coating is finally 6 μm, the diameter of the final mirror tungsten wire electrode is 66 μm, and the porosity is less than 0.1%. A brass coating that is too thin is not conducive to lubrication and increases mold wear. A brass coating with a high porosity has a low bonding degree, resulting in large copper loss during drawing and aggravated mold wear. On the contrary, a brass coating that is too thick places high demands on electroplating equipment and processes, which is not conducive to cost control, and excessive lubrication conditions are not conducive to reducing roughness. S4, multi-pass drawing: In multi-pass drawing, the processing degree of a single pass is controlled to be 7%-11%, and the diameter reduction of a single pass is ≤3μm to ensure dimensional consistency. Drawing oil lubricant is added, and the drawing speed is set to 4-8 m / s. The tolerance of the die aperture in the final pass is ±0.1μm, the processing degree is reduced to 5%-7%, the diameter reduction is ≤1μm, and the die inclination angle is set to 8°. Using a small diameter reduction and a suitable angle is conducive to controlling the final diameter stability of the finished product. The final drawing die uses a single crystal diamond die, and the final mirror tungsten wire electrode wire diameter is 50μm. The viscosity of the wire drawing oil lubricant is set to 20-30 cSt, and the flash point is greater than 150°C. The temperature in the die cavity is high during drawing. If the viscosity and flash point are low, the lubricant will easily fail, increasing die wear. S5. Performance testing of finished products: When testing the performance of finished products, a laser diameter gauge is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

[0029] Therefore, the final roughness of the mirror tungsten wire electrode is Ra = 0.12μm, the tensile strength is = 5000MPa, and the natural overhang deflection per meter length is ≤ 25mm.

[0030] Comparative Example 1 A method for preparing a mirror tungsten wire electrode is also provided: S1. Prepare raw materials. The raw materials are high-purity tungsten wire with a diameter of 80μm and a purity of ≥98%; S2, pre-treating the surface of raw materials; a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides; a2. Clean with pure water and activate with ultrasonic wave, wherein the ultrasonic activation temperature is set to 50°C and the frequency is set to 40KHz; S3, forming a brass coating by electroplating; b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. Form a brass coating by heat preservation in a furnace, wherein the furnace temperature is set to 540-580°C and the furnace heat preservation time is 10-20 seconds. The final thickness of the brass coating is 2 μm, and the final diameter of the tungsten electrode wire is 82 μm. S4, multi-pass drawing: In multi-pass drawing, the processing degree of each pass is controlled at 7%-11%, wire drawing oil lubricant is added, the drawing speed is set to 4-8 m / s, the tolerance of the die aperture of the final pass is ±0.1μm, the processing degree is reduced to 5%-7%, the diameter reduction is ≤1μm, and the die inclination angle is set to 8°. Using a small diameter reduction and a suitable angle is conducive to controlling the final diameter stability of the finished product. The final drawing die adopts a single crystal diamond die, and the final tungsten wire electrode wire diameter is 70μm. The viscosity of the wire drawing oil lubricant is set to 20-30 cSt, and the flash point is greater than 150°C. The temperature in the die cavity is high during drawing. If the viscosity and flash point are low, the lubricant will easily fail, increasing die wear. S5. Performance testing of finished products: When testing the performance of finished products, a laser diameter gauge is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

[0031] Therefore, the final roughness Ra of the tungsten wire electrode is greater than 0.2 μm.

[0032] Comparative Example 2 A method for preparing a mirror tungsten wire electrode is also provided: S1. Prepare raw materials. The raw materials are high-purity tungsten wire with a diameter of 80μm and a purity of ≥98%; S2, pre-treating the surface of raw materials; a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides; a2. Clean with pure water and activate with ultrasonic wave, wherein the ultrasonic activation temperature is set to 50°C and the frequency is set to 40KHz; S3, forming a brass coating by electroplating; b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. Form a brass coating by heat preservation in a furnace, wherein the furnace temperature is set to 540-580°C and the furnace heat preservation time is 10-20 seconds. The final thickness of the brass coating is 2 μm, and the final diameter of the tungsten electrode wire is 82 μm. S4, normal pull; S5. Performance testing of finished products: When testing the performance of finished products, a laser diameter gauge is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

[0033] Therefore, the final roughness Ra of the tungsten wire electrode is greater than 0.2 μm.

[0034] In summary, after comparing Example 2, Example 3, Comparative Example 1 and Comparative Example 2, by combining the copper plating process with the multi-pass oil drawing technology, the surface of the tungsten wire can be mirrored, the arc loss during discharge machining can be significantly reduced, the machining accuracy can be improved, and high strength and low deflection can be achieved at the same time.

[0035] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A mirror tungsten wire electrode, characterized by: The interior of the mirror tungsten wire electrode is high-purity tungsten wire, the surface of the high-purity tungsten wire is evenly coated with a copper layer, the roughness Ra of the mirror tungsten wire electrode is less than 0.2 μm, the diameter is ≤70 μm, the tensile strength is greater than 4500 MPa, and the natural suspension deflection of the mirror tungsten wire electrode per meter is ≤25 mm.

2. The method for preparing a mirror tungsten wire electrode according to claim 1, characterized in that: The preparation method specifically comprises the following steps: S1. Prepare raw materials; S2, pre-treating the surface of raw materials; S3, forming a brass coating by electroplating; S4, multi-pass drawing; S5. Perform performance testing on the finished product.

3. The method for preparing a mirror tungsten wire electrode according to claim 2, characterized in that: In step S1, the raw material is a high-purity tungsten wire with a diameter of 50-390 μm, a high-purity tungsten wire with a purity of ≥98%, or an alloy tungsten wire with a purity of less than 10%.

4. The method for preparing a mirror tungsten wire electrode according to claim 2, characterized in that: The step S2 specifically includes the following steps: a1. Remove surface oxides by electrolytic alkaline washing and acid washing; a2. Clean with pure water and activate with ultrasound, wherein the ultrasound activation temperature is set to 50°C and the frequency is set to 40 kHz.

5. The method for preparing a mirror tungsten wire electrode according to claim 2, characterized in that: The step S3 specifically includes the following steps: b1. Use copper pyrophosphate electroplating process to form a copper layer, where the coke ratio is set to 6.5-7.5 and the current density is less than 16 / dm 2 , the copper layer thickness is 3-6μm; b2. Use pure water to clean and then galvanize, where the concentration of zinc sulfate solution is greater than 150g / l and the current density is less than 35 / dm 2 , the zinc layer thickness is 1-3μm; b3. Forming a brass coating by heat preservation in a furnace, wherein the thickness of the brass coating is finally 5-8 μm, wherein the furnace temperature is set to 540-580° C., and the furnace heat preservation time is 10-20 seconds.

6. The method for preparing a mirror tungsten wire electrode according to claim 2, characterized in that: In step S4, a micro-wire drawing machine is used to draw the wire to the target diameter in multiple passes, from the initial 50-390 μm to 50-70 μm, with a single-pass diameter reduction of ≤3 μm to ensure dimensional consistency.

7. The method for preparing a mirror tungsten wire electrode according to claim 2, characterized in that: In step S5, when the performance of the finished product is tested, a laser caliper is used to test the diameter, a tensile testing machine is used to test the strength, and an optical microscope is used to test the roughness.

8. The method for preparing a mirror tungsten wire electrode according to claim 4, characterized in that: The step a1 specifically includes the following steps: a11. Use electrolytic alkaline washing, where the concentration is set to 120±20g / l, the temperature is set to 70±5℃, the current density is set to 3-10A / dm², and the time is set to 1-3 seconds; a12. Add pickling, where the concentration is set to 160±20g / l, the temperature is set to 68±3℃, and the immersion time is set to 2-4 seconds to remove surface oxides.

9. The method for preparing a mirror tungsten wire electrode according to claim 6, characterized in that: In the multi-pass drawing, the processing degree of a single pass is controlled to be 7%-11%, the drawing speed is set to 4-8 m / s, the aperture tolerance of the die in the last pass is ±0.1 μm, the processing degree is reduced to 5%-7%, the diameter reduction is ≤1 μm, the die inclination angle is set to 8°, and the drawing die in the last pass adopts a single crystal diamond die.

10. The method for preparing a mirror tungsten wire electrode according to claim 6, characterized in that: The wire drawing oil lubricant is added by using a micro-wire drawing machine for multiple drawing passes. The viscosity of the wire drawing oil lubricant is 20-30 cSt and the flash point is greater than 150°C.

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