Fabrication method for cobalt wire for self-powered neutron-sensitive element

Abstract

The present invention relates to a fabrication method for cobalt wire for a self-powered neutron-sensitive element. The cobalt wire fabrication method comprises the following steps: (1) cobalt powder reduction treatment; (2) mixing and compression molding; (3) vacuum induction melting; (4) forging, rotary swaging, and drawing; and (5) electrolytic polishing and annealing. Adopting the method described above allows for the fabrication of cobalt wire with a diameter of 1.00 mm-2.00 mm and having a purity greater than or equal to 99.95%, and the content of radiation-intolerant impurity elements (boron, cadmium, chromium, copper, and silicon) present in the cobalt wire is less than or equal to 30 ppm per element. The cobalt wire has an ovality precision of + / -0.003 mm, with a surface roughness less than or equal to Ra1.6 μm, a tensile strength greater than or equal to 900 MPa, and an elongation greater than or equal to 6%.

Description

Preparation method of cobalt wire for self-powered neutron sensitive element Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to a method for preparing a cobalt wire for a self-powered neutron sensitive element. Background Art

[0002] Fast-response cobalt self-powered neutron sensors are key components for neutron measurement and control in EPR nuclear reactors. Cobalt wire, a key emitter material for these sensors, is crucial for its performance. Its purity, impurity content, wire diameter uniformity, mechanical properties, and surface quality stability directly impact its sensitivity, measurement accuracy, and service life. Cobalt wire must have a purity of no less than 99.9%, contain no more than 30 ppm of radiation-sensitive impurities such as boron, cadmium, chromium, copper, and silicon, and possess an ellipticity of no more than 0.01 mm, a surface roughness of no more than Ra1.6 μm, a tensile strength of no less than 900 MPa, and an elongation of no less than 6%. Technical issues

[0003] Currently, cobalt wire is produced using common hot deformation processes (forging, hot drawing, etc.) or cold working processes (cold forging, cold drawing, etc.). These methods can lead to problems such as low purity, high content of impurities, difficult to control ellipticity, unstable surface quality, and poor product consistency. Hot deformation of cobalt wire, due to its body-centered cubic structure, causes a ductile-brittle transition during hot deformation. Oxidation begins at temperatures exceeding 300°C, and continued heating causes cobalt to react with oxygen and become brittle, making high-temperature deformation of the cobalt wire extremely difficult. Cold working of cobalt wire, however, can easily damage the surface quality of the cobalt wire due to its high hardness, making it difficult to ensure uniformity and consistency of the emitter. Technical Solutions

[0004] The present invention addresses the shortcomings of existing technologies and provides a method for preparing cobalt wire for use in self-powered neutron-sensitive components. Using this method, cobalt wire with a diameter of 1.00 mm to 2.00 mm can be produced. The purity of the cobalt wire is ≥99.95%, and the content of each of the radiation-intolerant elements boron, cadmium, chromium, copper, and silicon in the cobalt wire is ≤30 ppm. The wire also has an ellipticity accuracy of ±0.003 mm, a surface roughness of ≤Ra1.6 μm, a tensile strength of ≥900 MPa, and an elongation of ≥6%.

[0005] The object of the present invention is achieved like this:

[0006] A method for preparing a cobalt wire for a self-powered neutron sensitive element comprises the following steps:

[0007] 1) Cobalt powder reduction treatment:

[0008] The cobalt powder is loaded into a molybdenum boat and reduced under hydrogen conditions at a reduction temperature of 350-550°C and a holding time of 3-5 hours to obtain reduced cobalt powder;

[0009] 2) Mixing and pressing:

[0010] The reduced cobalt powder is added to the zirconium powder in a high-energy ball mill, and then pressed into shape after mixing. The amount of zirconium powder added is 0.1 to 0.3% of the weight of the cobalt powder;

[0011] 3) Vacuum induction melting:

[0012] The formed cobalt is placed in a vacuum melting furnace, the melting current is adjusted in the range of 0 to 30A, and the current adjustment interval is 2 to 5 minutes. After the cobalt is completely melted, electromagnetic stirring is performed for 2 to 5 minutes to form a cobalt ingot;

[0013] 4) Forging, rotary forging, drawing:

[0014] The cobalt ingot is forged into a cobalt metal rod, which is then rotary forged into a cobalt bar. After the surface of the cobalt bar is pretreated, the cobalt wire is drawn and annealed after drawing.

[0015] 5) Electrolytic polishing and annealing;

[0016] The annealed cobalt wire is electropolished and annealed.

[0017] The purity of the cobalt powder is ≥99.95%, the Fisher particle size is 15-35 μm, and the particle size is normally distributed; the purity of the zirconium powder is ≥99.99%.

[0018] In step 1), the flow rate of hydrogen is 4 to 8 L / min.

[0019] Step 2) During the high-energy ball milling, the ratio of the mixed material to the steel ball is 1:0.3, the high-energy ball milling time is 12 to 18 hours, and the rotation speed is 70 to 130 r / min;

[0020] The pressing pressure is 150-200 MPa, and the pressure is maintained for 15-30 seconds.

[0021] Step 3) The crucible is a zirconia crucible;

[0022] The vacuum melting furnace is firstly purged with argon gas and then evacuated to a temperature of <1×10 -3 Pa;

[0023] The diameter of the cobalt ingot is 30-50 mm.

[0024] Step 4) The heating temperature of the forging is 800-1000°C, the holding time is 8-15 minutes, the initial forging temperature is 900-1000°C, the final forging temperature is 650-750°C, and the deformation of each forging pass is 20-30%;

[0025] Before the cobalt ingot is heated, a layer of high-temperature resistant and anti-oxidation organic silicon lubricating coating is applied on its surface;

[0026] The diameter of the cobalt metal rod is 13-15 mm.

[0027] Step 4) The heating temperature of the rotary forging is 800-1000°C, the holding time is 5-10 minutes, and the deformation amount of each pass is 15-20%;

[0028] Before heating the cobalt metal rod, a layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is applied on its surface;

[0029] The diameter of the cobalt bar is 3-5 mm.

[0030] Step 4) Before the surface pretreatment, a lubricant is applied to the surface of the cobalt bar. The lubricant is a mixture of lubricating oil and chlorinated paraffin in a ratio of 1:1. The surface pretreatment temperature is 300-350° C. and the treatment time is 20-30 minutes.

[0031] The deformation of each drawing pass is 10 to 18%;

[0032] The diameter of the cobalt wire is (1.00-2.00 mm) ± 0.003 mm;

[0033] The annealing temperature is 800-1000°C, the holding time is 20-30 minutes, and the vacuum is drawn to <1×10 -3 Pa.

[0034] Step 5) The electrolytic polishing is carried out in a NaOH solution with an alkali concentration of 6 to 9% wt, and the electrolysis current is 5 to 12 A;

[0035] The pay-off speed of the cobalt wire during electrolysis is 4-7 m / min;

[0036] The annealing temperature is 650-750°C, the holding time is 20-30 minutes, and the vacuum is drawn to <1×10 -3 Pa. Beneficial effects

[0037] (1) The method of the present invention adopts a cobalt powder reduction treatment to effectively remove the free oxygen in the cobalt powder, reduce the effect of oxygen on the hot working brittleness of cobalt metal, and reduce the oxygen content of the cobalt wire.

[0038] (2) Zirconium powder is added during mixing, and high-energy ball milling is used to ensure the uniformity of powder particle size and improve the powder's molding ability. Zirconium powder plays a deoxidizing role during smelting and improves the processing plasticity of cobalt metal.

[0039] (3) In vacuum induction melting, step-by-step current adjustment and electromagnetic stirring are used to promote precise temperature control, while ensuring uniform distribution of trace elements, which is conducive to the floating of impurities and reduces solidification shrinkage cavities in cobalt ingots.

[0040] (4) High temperature forging ensures the homogenization of the grain structure of the cobalt ingot and avoids the generation of cracks on the surface of the cobalt ingot; high temperature rotary forging further refines the grain structure inside the cobalt ingot and improves the uniformity of the grain structure; lubricants are used in the drawing process to avoid burrs and cracks on the surface of the cobalt bar during drawing.

[0041] The applicant's experiments have verified that the method described in the present invention can produce cobalt wire with a diameter of 1.00mm to 2.00mm, the purity of the cobalt wire is ≥99.95%, the content of each element of boron, cadmium, chromium, copper and silicon in the cobalt wire that is not resistant to radiation is ≤30ppm, the accuracy of the ellipticity of the cobalt wire reaches ±0.003mm, the surface roughness is ≤Ra1.6μm, the tensile strength is ≥900MPa, and the elongation is ≥6%.

[0042] The cobalt wires prepared by the method of the present invention all meet the performance requirements of emitter materials for self-powered neutron sensitive elements of EPR nuclear reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG1 is a flow chart of the present invention. Best Mode for Carrying Out the Invention

[0044] Referring to FIG1 , a cobalt wire having a diameter of 1.00 mm is prepared, comprising the following steps:

[0045] 1) Cobalt powder reduction treatment:

[0046] Cobalt powder with a purity of 99.95% and a Fisher particle size of 15 to 35 μm was used. The cobalt powder was loaded into a molybdenum boat and placed in a hydrogen reduction furnace. The hydrogen flow rate was 8 L / min, the reduction temperature was 350°C, and the holding time was 5 hours. The reduced cobalt powder was sieved through a 120-mesh sieve.

[0047] 2) Mixing and pressing:

[0048] The reduced cobalt powder was weighed 700 g, and the zirconium powder was weighed 0.5 g. The weighed cobalt powder and zirconium powder were placed in an agate ball mill for high-energy ball milling. The ratio of the mixture to the steel ball was 1:0.3. The high-energy ball milling time was 12 h, the speed was 80 r / min, and the ball-milled mixture was placed in a mold and pressed into shape using a 500T hydraulic press. The pressing pressure was 150 MPa and the pressure holding time was 15 s. After demolding, a pressed cylindrical cobalt was obtained.

[0049] 3) Vacuum induction melting:

[0050] The cylindrical cobalt was placed in a zirconia crucible and placed in a vacuum melting furnace. Argon was introduced into the furnace and the vacuum was then evacuated to 1.80×10 -3 Pa, gradually adjust the smelting current from 5A to 25A, with an interval of 5 minutes, and increase the current by 5A each time until the cylindrical cobalt is completely melted, start electromagnetic stirring for 2 minutes, and then draw the ingot into a φ30mm cobalt ingot;

[0051] 4) Forging, rotary forging, drawing:

[0052] A layer of high-temperature resistant and anti-oxidation silicone lubricating coating is applied to the surface of the cobalt ingot, and the cobalt ingot is forged using a 200 kg air hammer. The heating temperature is 900°C, the holding time is 15 minutes, the initial forging temperature is 900°C, the final forging temperature is 500°C, and the deformation amount of each pass is 30%. The cobalt ingot is forged into a φ15 mm cobalt metal bar.

[0053] A layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is coated on the surface of the cobalt metal rod, and the cobalt metal rod is rotary forged using a rotary forging machine. The heating temperature is 1000°C, the holding time is 10 minutes, and the deformation amount of each pass is 20%. The cobalt metal rod is rotary forged into a φ5mm cobalt bar.

[0054] The cobalt wire was coated with lubricant on the surface and drawn at 650℃ for 25min. The deformation of each drawing pass was 12%, and the cumulative deformation reached 70%. The cobalt wire was drawn to a diameter of 1.00mm and vacuum annealed at 900℃ for 20min. The vacuum degree was 2.4×10 -3 Pa;

[0055] 5) Electrolytic polishing and annealing:

[0056] The cobalt wire was electropolished in a NaOH solution with an alkali concentration of 6% wt. The electrolysis current was 5 A. The pay-off speed of the cobalt wire during electrolysis was 5 m / min.

[0057] The cobalt wire after electrolytic polishing was vacuum annealed at 650℃ for 30min and the vacuum degree was 1.8×10 -3 Pa.

[0058] The wire diameter and ovality of the cobalt wire prepared in Examples 1 to 3 were measured using a micrometer; the surface roughness of the cobalt wire was measured using a surface roughness meter; the tensile strength and elongation of the cobalt wire were tested using a microcomputer electronic universal testing machine; and the surface quality of the cobalt wire was observed using a metallographic microscope. The above measurement results are shown in Table 1; the purity and elemental impurity content of the cobalt wire were analyzed using chemical analysis and inductively coupled plasma spectrometry, as shown in Table 2. Modes for Carrying Out the Invention

[0059] Example 1:

[0060] Referring to FIG1 , the preparation of a cobalt wire having a diameter of 2.00 mm includes the following steps:

[0061] 1) Cobalt powder reduction treatment:

[0062] Cobalt powder with a purity of 99.95% and a Fisher particle size of 15 to 35 μm was used. The cobalt powder was loaded into a molybdenum boat and placed in a hydrogen reduction furnace. The hydrogen flow rate was 4 L / min, the reduction temperature was 450°C, and the holding time was 3 hours. The reduced cobalt powder was sieved through a 120-mesh sieve.

[0063] 2) Mixing and pressing:

[0064] The reduced cobalt powder was weighed 1500 g, and the zirconium powder was weighed 2 g. The weighed cobalt powder and zirconium powder were placed in an agate ball mill for high-energy ball milling. The ratio of the mixture to the steel ball was 1:0.3. The high-energy ball milling time was 18 h, the speed was 120 r / min, and the ball-milled mixture was placed in a mold and pressed into shape using a 500T hydraulic press. The pressing pressure was 200 MPa and the pressure holding time was 15 s. After demolding, a pressed cylindrical cobalt was obtained.

[0065] 3) Vacuum induction melting:

[0066] The cylindrical cobalt was placed in a zirconia crucible and placed in a vacuum melting furnace. Argon was introduced into the furnace and the vacuum was then evacuated to 1.30×10 -3 Pa, gradually adjust the smelting current from 5A to 30A, with an interval of 5 minutes, and increase the current by 5A each time until the cylindrical cobalt is completely melted, start electromagnetic stirring for 5 minutes, and then draw the ingot into a φ50mm cobalt ingot;

[0067] 4) Forging, rotary forging, drawing:

[0068] A layer of high-temperature resistant and anti-oxidation organic silicon lubricating coating is applied to the surface of the cobalt ingot, and the cobalt ingot is forged using a 200 kg air hammer. The heating temperature is 1000°C, the holding time is 15 minutes, the initial forging temperature is 1000°C, the final forging temperature is 750°C, and the deformation amount of each pass is 30%. The cobalt ingot is forged into a φ15 mm cobalt metal bar.

[0069] A layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is coated on the surface of the cobalt metal rod, and the cobalt metal rod is rotary forged using a rotary forging machine. The heating temperature is 1000°C, the holding time is 10 minutes, and the deformation amount of each pass is 20%. The cobalt metal rod is rotary forged into a φ5mm cobalt bar.

[0070] The cobalt wire was coated with lubricant on the surface and drawn at 350℃ for 30min. The deformation of each drawing pass was 18%, and the cumulative deformation processing of drawing reached 90%. The cobalt wire was drawn to a diameter of 2.00mm and vacuum annealed at 1000℃ for 30min and a vacuum degree of 2.1×10 -3 Pa;

[0071] 5) Electrolytic polishing and annealing:

[0072] The cobalt wire was electropolished in a NaOH solution with an alkali concentration of 9% wt. The electrolysis current was 12 A. The pay-off speed of the cobalt wire during electrolysis was 7 m / min.

[0073] The cobalt wire after electrolytic polishing was vacuum annealed at 750℃ for 20min and the vacuum degree was 2.0×10 -3 Pa.

[0074] Example 2:

[0075] Referring to FIG1 , the preparation of a cobalt wire having a diameter of 1.50 mm includes the following steps:

[0076] 1) Cobalt powder reduction treatment:

[0077] Cobalt powder with a purity of 99.95% and a Fisher particle size of 15 to 35 μm was used. The cobalt powder was loaded into a molybdenum boat and placed in a hydrogen reduction furnace. The hydrogen flow rate was 6 L / min, the reduction temperature was 400°C, and the holding time was 4 hours. The reduced cobalt powder was sieved through a 120-mesh sieve.

[0078] 2) Mixing and pressing:

[0079] The reduced cobalt powder was weighed 1000 g, and the zirconium powder was weighed 1.5 g. The weighed cobalt powder and zirconium powder were placed in an agate ball mill for high-energy ball milling. The ratio of the mixture to the steel ball was 1:0.3. The high-energy ball milling time was 15 h, and the speed was 100 r / min. The ball-milled mixture was placed in a mold and pressed into shape using a 500T hydraulic press. The pressing pressure was 180 MPa and the pressure holding time was 20 s. After demolding, a pressed cylindrical cobalt was obtained.

[0080] 3) Vacuum induction melting:

[0081] The cylindrical cobalt was placed in a zirconia crucible and placed in a vacuum melting furnace. Argon was introduced into the furnace and the vacuum was then evacuated to 2.40×10 -3 Pa, gradually adjust the smelting current from 5A to 30A, with an interval of 5 minutes, and increase the current by 5A each time until the cylindrical cobalt is completely melted, start electromagnetic stirring for 3 minutes, and then draw the ingot into a φ40mm cobalt ingot;

[0082] 4) Forging, rotary forging, drawing:

[0083] A layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is applied to the surface of the cobalt ingot. The cobalt ingot is forged using a 200 kg air hammer with a heating temperature of 950°C, a holding time of 15 minutes, an initial forging temperature of 950°C, a final forging temperature of 700°C, and a deformation of 25% per pass. The cobalt ingot is forged into a φ14 mm cobalt metal bar.

[0084] A layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is coated on the surface of the cobalt metal rod, and the cobalt metal rod is rotary forged using a rotary forging machine. The heating temperature is 950°C, the holding time is 10 minutes, and the deformation amount of each pass is 18%. The cobalt metal rod is rotary forged into a φ4mm cobalt bar.

[0085] The cobalt wire was coated with lubricant on the surface of the cobalt bar and treated at a temperature of 320 ° C for 25 min before wire drawing. The deformation of each drawing pass was 15%, and the cumulative deformation processing of the drawing reached 80%. The cobalt wire was drawn to a diameter of 1.50 mm and vacuum annealing was performed at 950 ° C, holding time of 25 min, and vacuum degree of 2.5×10 -3 Pa;

[0086] 5) Electrolytic polishing and annealing:

[0087] The cobalt wire was electropolished in a NaOH solution with an alkali concentration of 7% wt. The electrolysis current was 8 A. The pay-off speed of the cobalt wire during electrolysis was 6 m / min.

[0088] The electrolytically polished cobalt wire was vacuum annealed at 700 °C for 25 min and a vacuum degree of 2.2 × 10 -3 Pa.

[0089] Example 3:

[0090] Referring to FIG1 , a cobalt wire having a diameter of 1.00 mm is prepared, comprising the following steps:

[0091] 1) Cobalt powder reduction treatment:

[0092] Cobalt powder with a purity of 99.95% and a Fisher particle size of 15 to 35 μm was used. The cobalt powder was loaded into a molybdenum boat and placed in a hydrogen reduction furnace. The hydrogen flow rate was 8 L / min, the reduction temperature was 350°C, and the holding time was 5 hours. The reduced cobalt powder was sieved through a 120-mesh sieve.

[0093] 2) Mixing and pressing:

[0094] The reduced cobalt powder was weighed 700 g, and the zirconium powder was weighed 0.5 g. The weighed cobalt powder and zirconium powder were placed in an agate ball mill for high-energy ball milling. The ratio of the mixture to the steel ball was 1:0.3. The high-energy ball milling time was 12 h, the speed was 80 r / min, and the ball-milled mixture was placed in a mold and pressed into shape using a 500T hydraulic press. The pressing pressure was 150 MPa and the pressure holding time was 15 s. After demolding, a pressed cylindrical cobalt was obtained.

[0095] 3) Vacuum induction melting:

[0096] The cylindrical cobalt was placed in a zirconia crucible and placed in a vacuum melting furnace. Argon was introduced into the furnace and the vacuum was then evacuated to 1.80×10 -3 Pa, gradually adjust the smelting current from 5A to 25A, with an interval of 5 minutes, and increase the current by 5A each time until the cylindrical cobalt is completely melted, start electromagnetic stirring for 2 minutes, and then draw the ingot into a φ30mm cobalt ingot;

[0097] 4) Forging, rotary forging, drawing:

[0098] A layer of high-temperature resistant and anti-oxidation silicone lubricating coating is applied to the surface of the cobalt ingot, and the cobalt ingot is forged using a 200 kg air hammer. The heating temperature is 900°C, the holding time is 15 minutes, the initial forging temperature is 900°C, the final forging temperature is 500°C, and the deformation amount of each pass is 30%. The cobalt ingot is forged into a φ15 mm cobalt metal bar.

[0099] A layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is coated on the surface of the cobalt metal rod, and the cobalt metal rod is rotary forged using a rotary forging machine. The heating temperature is 1000°C, the holding time is 10 minutes, and the deformation amount of each pass is 20%. The cobalt metal rod is rotary forged into a φ5mm cobalt bar.

[0100] The cobalt wire was coated with lubricant on the surface and drawn at 650℃ for 25min. The deformation of each drawing pass was 12%, and the cumulative deformation reached 70%. The cobalt wire was drawn to a diameter of 1.00mm and vacuum annealed at 900℃ for 20min. The vacuum degree was 2.4×10 -3 Pa;

[0101] 5) Electrolytic polishing and annealing:

[0102] The cobalt wire was electropolished in a NaOH solution with an alkali concentration of 6% wt. The electrolysis current was 5 A. The pay-off speed of the cobalt wire during electrolysis was 5 m / min.

[0103] The cobalt wire after electrolytic polishing was vacuum annealed at 650℃ for 30min and the vacuum degree was 1.8×10 -3 Pa.

[0104] The wire diameter and ovality of the cobalt wire prepared in Examples 1 to 3 were measured using a micrometer; the surface roughness of the cobalt wire was measured using a surface roughness meter; the tensile strength and elongation of the cobalt wire were tested using a microcomputer electronic universal testing machine; and the surface quality of the cobalt wire was observed using a metallographic microscope. The above measurement results are shown in Table 1; the purity and elemental impurity content of the cobalt wire were analyzed using chemical analysis and inductively coupled plasma spectrometry, as shown in Table 2.

[0105] Table 1 Measurement results of Examples 1 to 3

[0106]

[0107] Table 2 Purity and element impurity content of cobalt wires in Examples 1 to 3

[0108]

[0109] Conclusion: The cobalt wires prepared using the method of the present invention in Examples 1-3 all had a purity greater than 99.95%. The boron, cadmium, chromium, copper, and silicon contents in the cobalt wires were all less than 30 ppm, and the oxygen, nitrogen, and hydrogen contents were all less than 100 ppm, with no impact on the cobalt wire properties. The ellipticity accuracy of the cobalt wires reached 0.003 mm, and the surface roughness of the cobalt wires was no greater than Ra1.6 μm. The tensile strength of the cobalt wires was greater than 900 MPa, and the elongation was greater than 6%. The surface of the cobalt wires was smooth and free of defects such as cracks and burrs. The cobalt wires prepared using the method of the present invention in Examples 1-3 all met the performance requirements for emitter materials used in self-sufficient neutron sensitive elements of EPR nuclear reactors.

Claims

1. A method for preparing cobalt wire for self-powered neutron sensitive elements, characterized in that: The following steps are involved: 1) Cobalt powder reduction treatment: The cobalt powder is loaded into a molybdenum boat and reduced under hydrogen conditions at a reduction temperature of 350-550°C and a holding time of 3-5 hours to obtain reduced cobalt powder; 2) Mixing and pressing: The reduced cobalt powder is added to the zirconium powder in a high-energy ball mill, and then pressed into shape after mixing. The amount of zirconium powder added is 0.1 to 0.3% of the weight of the cobalt powder; 3) Vacuum induction melting: The formed cobalt is placed in a vacuum melting furnace, the melting current is adjusted in the range of 0 to 30A, and the current adjustment interval is 2 to 5 minutes. After the cobalt is completely melted, electromagnetic stirring is performed for 2 to 5 minutes to form a cobalt ingot; 4) Forging, rotary forging, drawing: The cobalt ingot is forged into a cobalt metal rod, which is then rotary forged into a cobalt bar. After the surface of the cobalt bar is pretreated, the cobalt wire is drawn and annealed after drawing. 5) Electrolytic polishing and annealing: The annealed cobalt wire is electropolished and annealed.

2. The preparation method according to claim 1, characterized in that The purity of the cobalt powder is ≥99.95%, the Fisher particle size is 15-35 μm, and the particle size is normally distributed; the purity of the zirconium powder is ≥99.99%.

3. The preparation method according to claim 1, characterized in that In step 1), the flow rate of hydrogen is 4 to 8 L / min.

4. The preparation method according to claim 1, characterized in that Step 2) The material-to-ball ratio of the high-energy ball mill is 1:0.3, the high-energy ball milling time is 12 to 18 hours, and the rotation speed is 70 to 130 r / min; The pressing pressure is 150-200 MPa, and the pressure is maintained for 15-30 seconds.

5. The preparation method according to claim 1, characterized in that Step 3) The crucible is a zirconia crucible; The vacuum melting furnace is firstly purged with argon gas and then evacuated to a temperature of <1×10 -3 Pa; The diameter of the cobalt ingot is 30-50 mm.

6. The preparation method according to claim 1, characterized in that Step 4) The heating temperature of the forging is 800-1000°C, the holding time is 8-15 minutes, the initial forging temperature is 900-1000°C, the final forging temperature is 650-750°C, and the deformation of each forging pass is 20-30%; Before the cobalt ingot is heated, a layer of high-temperature resistant and anti-oxidation organic silicon lubricating coating is applied on its surface; The diameter of the cobalt metal rod is 13-15 mm.

7. The preparation method according to claim 1, characterized in that Step 4) The heating temperature of the rotary forging is 800-1000°C, the holding time is 5-10 minutes, and the deformation amount of each pass is 15-20%; Before heating the cobalt metal rod, a layer of high-temperature resistant and anti-oxidation organic silicone lubricating coating is applied on its surface; The diameter of the cobalt bar is 3-5 mm.

8. The preparation method according to claim 1, characterized in that Step 4) Before the surface pretreatment, a lubricant is applied to the surface of the cobalt bar. The lubricant is a mixture of lubricating oil and chlorinated paraffin in a ratio of 1:

1. The surface pretreatment temperature is 300-350° C. and the treatment time is 20-30 minutes. The deformation of each drawing pass is 10 to 18%; The diameter of the cobalt wire is (1.00-2.00 mm) ± 0.005 mm; The annealing temperature is 800-1000°C, the holding time is 20-30 minutes, and the vacuum is drawn to <1×10 -3 Pa.

9. The preparation method according to claim 1, characterized in that Step 5) The electrolytic polishing is carried out in a NaOH solution with an alkali concentration of 6 to 9% wt, and the electrolysis current is 5 to 12 A; The pay-off speed of the cobalt wire during electrolysis is 4-7 m / min; The annealing temperature is 650-750°C, the holding time is 20-30 minutes, and the vacuum is drawn to <1×10 -3 Pa.

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