LU502013B1 - High-purity fine platinum wire and preparation method - Google Patents

Abstract

A preparation method of high-purity fine platinum wire obtains a high-purity fine platinum wire with high-uniformity, high-precision and high-stability through casting, hot forging and wire processing. The high-purity fine platinum wire has a minimum wire diameter of up to 10 μm, a precision of ±0.2 μm, and a resistance ratio (W100) of ≥1.39254.

Description

DESCRIPTION 1060 HIGH-PURITY FINE PLATINUM WIRE AND PREPARATION

METHOD Field of the Application The invention belongs to the field of precious metal materials, and particularly relates to a high-purity fine platinum wire and a preparation method. Background of the Application Platinum wire is widely used in platinum resistance thermometers for accurate temperature measurement due to its high melting point, high sensitivity, fast response time, good stability and other excellent physical and chemical stability.

For the application of standard-grade, high-sensitivity standard platinum resistance thermometers, industrial platinum resistance thermometers, and other advanced sensors of instrumentation, a large amount of high-purity platinum wire needs to be used, and this type of platinum wire must meet the resistance ratio Wigo>

1.39254. The purity, trace elements, mechanical properties, structure and internal defects, wire consistency and uniformity of platinum wire directly affect the measurement precision, stability and service life of this type of sensor.

At present, in the preparation process of platinum wire, the platinum raw material is commercially available platinum sponge with the highest purity of 99.99%. Induction melting is used to obtain platinum ingots, and platinum wires are obtained by forging, rolling and drawing. The obtained platinum wires have low purity, poor mechanical properties, and great difficulty in microfabrication. The obtained platinum wires have a resistance ratio Wioo of about 1.3922. The obtained industrial-grade platinum wires have a wire diameter of more than 25 um, and a small amount of experimental-grade samples have a wire diameter of up to 20 um. The obtained platinum wires have a precision of +1 um, and the precision of platinum wires is not 1 easy to control, and the product consistency is poor. These problems lead to the shift LUS02013 of its temperature coefficient of resistance, which greatly reduces its temperature measurement precision, stability, service life and other performance.

Therefore, the engineering application of the fine platinum wire prepared in the prior art in high-tech fields such as instrumentation, energy, aviation, and aerospace 1s greatly limited.

SUMMARY OF THE INVENTION The purpose of the present invention is to provide a high-purity fine platinum wire and a preparation method. The platinum wire prepared by the method has a diameter of up to 10 um, a precision of £0.2 um, and a resistance ratio W100 of >1.39254, which meets the performance requirements of standard grade, high sensitivity standard platinum resistance thermometers, industrial platinum resistance thermometers and other temperature sensors and other instruments.

The technical solution of the present invention is as follows.

The preparation method of high-purity fine platinum wire comprises steps of: 1) casting placing platinum material in a vacuum induction smelting furnace to melt it under the protection of argon gas, keeping for 5-10 minutes after the platinum material being completely melted, and then performing rapid bottom-leak casting to obtain a platinum ingot; 2) hot forging performing homogenization heat treatment on the platinum ingot obtained in step 1) at 800-1100°C for 0.5-1 hour; performing hot-forging at 800-1100°C to form a round bar, and trimming the surface of the round bar; 3) wire processing performing rough drawing, medium drawing, fine drawing, and ultra-fine drawing on the round bar obtained in step 2) with a total deformation amount of each stage of <90% on a wire drawing machine; wire processing: sequentially performing the rough drawing with a deformation 2 amount of <15%, the medium drawing with a deformation amount of <10%, the fine LUS02013 drawing with a deformation amount of <6% on the round bar obtained in step 2) with the total deformation amount of each stage of < 80% on the wire drawing machine, and performing heat treatment in a temperature range of 400-700°C for 10-30 minutes to draw the fine platinum wire.

In the preparation of the high-purity fine platinum wire, the content of platinum raw materials is selected to be >99.999%.

The vacuum degree of the vacuum in step 1) is 1x102~1x107Pa.

The round bar obtained in step 2) needs to be heat treated, and the heat treatment method is to keep the temperature at 500-800 °C for 15-30 minutes.

The diameter of the round bar in step 2) is 4+1 mm, and the surface of the round bar is preferably smoothed by turning, In step 3), front and rear tension devices are added in the medium drawing and fine drawing, that is, the tension devices are added at both ends of the wire drawing machine (pay-off and take-up) to ensure smooth and no slippage during the drawing process, and ensure the dimensional precision and surface quality of the wire.

The heat treatment system of the rough drawing and the medium drawing in step 3) is that keeping the temperature at 400-700 0 for 10-30 min.

The cleaning after the rough drawing described in step 3) adopts a method of first alkaline boiling and then acid boiling, wherein a solution of deionized water and sodium hydroxide with a volume fraction of 1:1 is used for the alkaline boiling and a solution of deionized water and concentrated a solution of hydrochloric acid with a volume fraction of 1:1 is used for the acid boiling.

The cleaning after the medium drawing described in step 3) is cleaned with a drawing water-based emulsion lubricant.

The cleaning of the fine drawing in step 3) adopts ultrasonic on-line continuous cleaning, preferably, the medium for continuous cleaning is deionized water and absolute ethanol.

During smelting, the method of the invention adopts a high-cleanness induction 3 smelting bottom-casting casting process, and the smelting crucible adopts high-purity LU502013 zirconia or magnesia ceramics re-sintered at high temperature, so as to avoid foreign impurity pollution and play a refining role. The effect of re-sintering is to effectively remove impurities from the crucible at high temperature.

The hot forging of the invention can improve the crystal structure, fragment and rearrange the crystal grains, and improve the density of the matrix. the turning and smooth trimming of the surface of the round bar after forging can remove defects of the ingot such as loose surface structure and holes caused by the smelting, ensure the surface quality, and facilitate the subsequent fine wire drawing.

Reasonable heat treatment and deformation processing technology are adopted in the wire processing process, which can effectively ensure the generation of fibrous structure during the wire processing process, and reduce the damage to the surface of the wire caused by excessive work hardening, which affects the surface quality and yield, greatly improve the processing performance, and improve the quality of the wire. The tension device is used to ensure little or no slippage during wire deformation, thereby improving wire consistency and high surface quality.

Too high heat treatment temperature or too long heating time will cause the material to have coarse grains and inconsistent recrystallization during the heating process, resulting in the generation of "internal vacancies" and dislocations. "Internal vacancies" and dislocations are one of the key factors that reduce the stability and accuracy of temperature measurement. If the temperature is too low or the heating time is too short, the effect of stress relief will not be achieved, which will cause the surface of the wire to be easily damaged and the phenomenon of wire breakage during the drawing process. Similarly, if the deformation amount is too large, it is easy to cause work hardening too fast, and if the deformation amount is too small, the material cannot maintain a good rigidity, which is not conducive to microfabrication.

Cleaning and lubrication: In the rough drawing stage, boiling alkali and boiling acid solutions are used for cleaning to remove foreign matter such as ceramics, foreign metal impurities, micro-particles and oil stains attached to the surface; in the 4 medium drawing stage, a water-based emulsion lubricant is used to remove surface LUS02013 particle inclusions and oil stains, and have a good lubricating effect, which is conducive to the drawing of micro-filaments; in the fine drawing stage, ultrasonic continuous cleaning with deionized water or absolute ethanol or acetone is used to decontaminate the surface of micro-filaments and remove impurities, to ensure a clean wire surface, excellent surface quality, and wire consistency.

The fine platinum wire material with high uniformity, high precision and high stability obtained by the method of the invention solves the problems of matching and consistency of electrical properties and mechanical properties of such materials. The applicant has verified that the high-purity fine platinum wire of the present invention has a platinum content of >99.995%, a minimum wire diameter of up to 10 um, a precision of +0.2 um, and a resistance ratio of W100 > 1.39254, which meets the standard requirements for temperature sensors such as standard grade, high sensitivity standard platinum resistance thermometers, industrial platinum resistance thermometers, and other instruments. The material obtained by this method has the advantages of high uniformity, high precision, high stability, long life, radiation resistance, and is widely used in the fields of instrumentation, aviation, aerospace, and energy.

DETAILED DESCRIPTION OF THE EMBODIMENTS The technical solutions in the implementation cases of the present invention are described below in the form of steps with reference to examples.

The platinum raw material is prepared by the following method.

1. Hydrolysis Weigh commercially available platinum sponge with a purity of 99.95%, dissolve it by heating with dilute aqua regia, concentrate, use concentrated hydrochloric acid to exhaust the nitric acid, add solid sodium chloride, and evaporate to dryness. Add water to dissolve to obtain a platinum solution, boil, adjust the pH of the platinum solution to 8-10 with chlor-alkali with a mass concentration of 10% (the chlor-alkali concentration is the same below), stand at room temperature for 10-20 hours, filter to obtain filtrate 1, and recycle the precipitate. LUS02013 Concentrate the filtrate to 300ml-500ml, add 100ml-200ml concentrated hydrochloric acid, evaporate to dryness, add deionized water to dissolve, boil, then adjust the pH of the solution to 8-10 with chlor-alkali, keep a constant temperature for 30-60min, and then stand at room temperature for 3-4h, filter to obtain filtrate 2, and recycle the precipitate.

Add a cerium chloride solution with a mass concentration of 1 to 5% in the filtrate 2, boil, adjust the pH of the solution to 8-10, keep a constant temperature for 30min, and then stand at room temperature for 10-20 hours, filter to obtain filtrate 3, and recycle the precipitate; in this way, 3-5 times of hydrolysis are carried out according to the above steps to obtain the filtrate obtained after the multiple times of hydrolysis.

Through the above process steps, the content of Pd, Rh, Ir, Au, Fe, Ni, Cu, Mg, Al, Pb, Si, Co, Ag, Cd and other elements in the platinum powder can be greatly reduced, and the purity of the platinum powder can be improved.

2. Hydrazine hydrate reduction The above-mentioned filtrate obtained after the multiple times of hydrolysis is heated and boiled, slightly cooled and slowly added with hydrazine hydrate until the supernatant is clear, and boiled until there is no alkali liquid bubbles.

3. Filtration and calcination After filtering, the obtained platinum powder was washed with boiling water for several times until the pH value was neutral, calcined in a muffle furnace, kept at 800° C for 30 minutes, and cooled to room temperature. The high-purity platinum powder was taken out to obtain platinum raw materials.

Commercially available analytical reagents were used for other reagents in this example.

Example: Vacuum smelting: the platinum raw material is smelted in a vacuum induction smelting furnace with a vacuum degree of 1x102-1x107Pa and filled with argon for 6 protection. After the material is completely melted, it is kept for more than 3 minutes LUS02013 and then it is rapid bottom-leak cast into a water-cooled copper mold to obtain platinum ingots.

Hot forging: homogenization heat treatment is carried out at 800-1100°C for

0.5-1 hour; hot forging is carried out at 800-1100°C, and the forging uses round die forging to forge a round bar with a size of ®4+1mm. Heat treatment is carried out at 500 to 800°C for 15 to 30 minutes.

Wire processing: the alloy round bar is roughly drawn, medium drawn, and finely drawn on the wire drawing machine, and the front and rear tension devices are added to the medium and fine drawing, that is, the tension devices are added at both ends of the drawing (pay-off and take-up), the purpose is to ensure smooth and no slippage during the wire drawing process, to ensure the dimensional precision and surface quality of the wire. The deformation amount of the rough drawing is <18%; the deformation amount of the medium drawing is <15%, the deformation amount of the fine drawing is <8%; the deformation amount of ultra-fine drawing is <4%. The total deformation amount of each stage of wire drawing is < 90%. When the stage deformation reaches about 80%, an intermediate heat treatment is carried out. The heat treatment is carried out at 400-700° C for 10-30 minutes to eliminate the internal stress of the wire, make the grains in the material more uniform, and facilitate subsequent stretching. Fine platinum wires up to 10 um in diameter can be drawn.

Cleaning and lubrication: the rough drawing stage and intermediate heat treatment are mainly to remove foreign matter such as ceramics, foreign metal impurities, micro-particles and oil stains attached to the surface, and boiling alkali and acid solution are used for cleaning, that is, first alkali boiling (the volume fraction of deionized water and sodium hydroxide is 1:1), and then acid boiling (the volume fraction of deionized water and concentrated hydrochloric acid is 1:1). The medium drawing stage is mainly to remove the surface microparticle inclusions and oil stains, and the water-based emulsion lubricant is selected, which can play a good role in lubricating and facilitate the drawing of fine filaments. The fine drawing stage is the 7 key stage to ensure the clean surface of the wire, the excellent surface quality and the LUS02013 consistency of the wire. Ultrasonic cleaning is used for continuous online cleaning.

The medium is deionized water and anhydrous ethanol to decontaminate the surface of the micro-filament.

Fine platinum wires with different wire diameters (Examples 1, 2, 3) were obtained by the above method, and related performance tests were carried out, as shown in the following table.

Performance Wire Dimensional Resistance | Breaking Elongation parameters diameter tolerance( um ) | ratio( Wı00 )| force( cN ) (%) (pm) This method solves the matching problem of high strength, toughness, electrical properties and processability of such materials. The obtained materials have a series of advantages such as high purity, high uniformity, high precision, high stability, and excellent mechanical properties, and as a key material for advanced sensors, is widely used in instrumentation, measurement and control, aviation, aerospace and other fields.

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Claims (10)

WHAT IS CLAIMED IS: HUS02018

1. A preparation method of high-purity fine platinum wire, characterized in that, comprising steps of: 1) casting placing platinum material in a vacuum induction smelting furnace to melt it under the protection of argon gas, keeping for 5-10 minutes after the platinum material being completely melted, and then performing rapid bottom-leak casting to obtain a platinum ingot; 2) hot forging performing homogenization heat treatment on the platinum ingot obtained in step 1) at 800-1100°C for 0.5-1 hour; performing hot-forging at 800-1100°C to form a round bar, and trimming the surface of the round bar; 3) wire processing performing rough drawing, medium drawing, fine drawing, and ultra-fine drawing on the round bar obtained in step 2) with a total deformation amount of each stage of <90% on a wire drawing machine; wire processing: sequentially performing the rough drawing with a deformation amount of <15%, the medium drawing with a deformation amount of <10%, the fine drawing with a deformation amount of <6% on the round bar obtained in step 2) with the total deformation amount of each stage of < 80% on the wire drawing machine, and performing heat treatment in a temperature range of 400-700°C for 10-30 minutes to draw the fine platinum wire.

2. The method according to claim 1, wherein the high-purity fine platinum wire has a platinum content of greater than 99.995%.

3. The method according to claim 1, wherein the vacuum induction smelting furnace in step 1) has a vacuum degree of 1x107?-1x10*Pa.

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4. The method according to claim 1, wherein the round bar obtained in step 2) needs to be heat treated, and the heat treatment method is to keep the temperature at 500-800° C for 15-30 minutes.

5. The method according to claim 1, wherein the round bar obtained in step 2) has a diameter of 4+1 mm, and the surface of the round bar 1s preferably smoothed by turning.

6. The method according to claim 1, wherein a tension device is used for the medium drawing and the fine drawing in step 3) to control the smoothness of the drawing.

7. The method according to claim 1, wherein the heat treatment method of the rough drawing and the medium drawing in step 3) is to keep the temperature at 400-700°C for 10-30min.

8. The method according to claim 1, wherein cleaning is performed after the rough drawing in step 3), and the cleaning is performed by using a method of first alkaline boiling and then acid boiling, wherein a solution of deionized water and sodium hydroxide with a volume fraction of 1:1 is used for the alkaline boiling and a solution of deionized water and concentrated a solution of hydrochloric acid with a volume fraction of 1:1 is used for the acid boiling.

9. The method according to claim 1, wherein cleaning is performed after the medium drawing in step 3), and the cleaning is performed by using a drawing water-based emulsion lubricant.

10. The method according to claim 1, wherein cleaning is performed after the fine drawing in step 3), and the cleaning adopts ultrasonic on-line continuous cleaning,

and preferably, the medium for continuous cleaning is deionized water and absolute LUS02013 ethanol. 11