A method for preparing high-performance platinum micro-wire

Abstract

The application relates to a preparation method of high-performance platinum fine wires and belongs to the field of metal materials. By adopting high-frequency vibration casting, the method can extrude gas and impurities in fluid liquid crystals, reduce crystal defects in the metal grain crystallization process, improve the material density, and improve the comprehensive mechanical properties of the material. The application solves the problems of high wire breakage rate, poor uniformity and stability of pure platinum fine wires. The product is especially suitable for rapid wire pairing of pure platinum with a wire diameter of Phi 0.01mm-Phi 0.02mm and platinum resistance wires.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of high-performance platinum microfilament, in particular to a method for reducing the breakage rate of platinum microfilament and improving uniformity and stability, and belongs to the technical field of metal smelting. BACKGROUND

[0002] The platinum-rhodium thermocouple filament is widely applied to the aviation, aerospace, steel smelting and other industries due to high sensitivity, fast response time and good stability. Due to the soaring price of raw materials, the market needs to provide thinner platinum-rhodium thermocouple filaments to save costs. With the decrease of the diameter, the internal defects of the material become the main factor affecting the processing of the platinum-rhodium thermocouple filament, and the platinum filament, as the lowest strength in the thermocouple filament, has the highest breakage rate in the processing, which becomes the biggest obstacle to the development of the fast thermocouple filament in the micro direction.

[0003] The platinum filament is also an important component of the platinum resistance thermometer, and the standard platinum resistance thermometer, industrial platinum resistance temperature sensor and other advanced sensors need high-purity platinum filaments with a resistance ratio R100 / R0 greater than or equal to 1.39254. The purity, uniformity, mechanical properties, structure and internal defects of the platinum filament directly affect the accuracy and stability of temperature measurement.

[0004] At present, the preparation process of the platinum microfilament is as follows: the sponge platinum with a purity of SM-Pt99.99 is smelted into a platinum ingot by high-frequency induction, and the platinum ingot is processed into a platinum filament by forging, rolling and drawing. The obtained platinum filament has low purity, many defects, poor mechanical properties, great difficulty in micro-filament processing, poor consistency and easy scratches on the surface. The existing technology cannot meet the above requirements, and therefore, it is imperative to research a high-performance platinum microfilament. SUMMARY

[0005] The main purpose of the application is to provide a high-performance platinum microfilament and a preparation method thereof. The platinum microfilament prepared by the application has high purity, good consistency, high accuracy and good stability in temperature measurement.

[0006] A preparation method of a high-performance platinum microfilament, comprising the following steps:

[0007] (1) Block reduction: put the sponge platinum into a high-frequency smelting furnace in batches of 300-500g, adjust the power to 15-20KW, and immediately turn off the power after the sponge platinum is inducted and extruded into a spherical shape by a high-purity alumina rod. Then, the platinum block is taken out from the crucible by platinum tongs and cooled on a clean alumina plate to obtain the platinum block;

[0008] (2) Melting: put the platinum block into a smelting crucible, smelt at a power of 18-25KW and a temperature of 1780-1900℃ for 10-20min to obtain a platinum melt;

[0009] (3) Vacuum exhaust: reduce power to 5-8KW, exhaust and then fill in argon gas for protection;

[0010] (4) Vibration casting: open high frequency vibration platform, pour the platinum melt into water-cooled copper mold, casting power is 13-15KW, casting speed is 110-130g / s, to get pure platinum ingot;

[0011] (5) Hot swaging: pure platinum ingot is swaged to φ6-φ8mm at 1200℃ by 3 passes, pass processing amount is 30%-35%;

[0012] (6) Wire drawing: coarse drawing, medium drawing, fine drawing and very fine drawing are carried out on the wire drawing machine, pass processing amount is 10-13% for coarse drawing, 8-10% for medium drawing, 5-8% for fine and very fine drawing, to draw micro platinum wire.

[0013] Preferably, the sponge platinum in step (1) is prepared by multiple hydrolysis of 99.95% sponge platinum, and the purity is not less than 99.995%.

[0014] Preferably, the exhaust time in step (3) is not less than 5min, and the exhaust times is not less than 2.

[0015] Preferably, the vacuum degree in step (3) is 1×10 -2 ~1×10 -3 Pa. The argon gas pressure is 4-8KPa.

[0016] Preferably, the water-cooled copper mold in step (4) is a round mold, water flows in a spiral form upward from the bottom and flows out from the top side.

[0017] Preferably, the vibration frequency of the high frequency vibration platform in step (4) is 5000-7000 times / min.

[0018] Preferably, in step (6), the medium drawing and fine drawing equipment are both non-slip wire drawing machines.

[0019] Preferably, in step (7), the cleaning after coarse drawing and medium drawing is carried out by first alkali boiling and then acid boiling, wherein, the alkali boiling is carried out by using a solution of 100g sodium hydroxide and 1000ml deionized water, and the acid boiling is carried out by using a solution of HCl and deionized water with a volume ratio of 1:1.

[0020] Preferably, in step (7), the cleaning after fine drawing and very fine drawing is carried out by ultrasonic continuous cleaning, preferably, the continuous cleaning medium is deionized water and anhydrous ethanol.

[0021] Preferably, the non-slip wire drawing machine has one mold, one motor and one wire speed monitoring probe, and the computer intelligently adjusts the speed ratio of each motor according to the signal feedback by the wire speed monitoring probe, so that the wire drawing speed is synchronized with the speed.

[0022] The present application has the following advantages: the present application obtains 99.995% sponge platinum through secondary hydrolysis, and through water-cooled copper mold from bottom to top rapid cooling, the gas in the solution is discharged from the matrix, high-frequency vibration casting is adopted to refine the grain, eliminate cold shut, remove the crystal defects generated in the crystallization process, reduce the gas content of the ingot, the inclusions are floated on the surface of the riser, and a good consistency and smooth platinum fine wire is obtained through the use of a non-slip wire drawing machine, thereby improving the processing yield of platinum fine wire and the accuracy and stability of temperature measurement. The pure platinum ingot prepared by the present application has small grain size, no cold shut, few internal defects and high density, and has good fine processing performance, which can greatly improve the yield; the platinum fine wire prepared by the method has a diameter of 0.01mm, an accuracy of ±0.2μm, and a resistance ratio R 100 / R0≥1.39254, and the yield is ≥75%. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0024] Figure 1 is a structure schematic diagram of a casting device used in the method of the present application;

[0025] Figure 2 is a schematic diagram of a water-cooled copper mold structure;

[0026] 1, vacuum furnace; 2, smelting crucible; 3, water-cooled copper mold; 4, high-frequency vibration platform; 5, vacuum pump; 6, argon cylinder;

[0027] Figure 3 is a comparison diagram of the appearance of the pure platinum ingot obtained by the method of the present application and high-frequency smelting;

[0028] Figure 4 is a comparison diagram of the metallographic phase of the pure platinum wire obtained by the method of the present application and high-frequency smelting. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings, and it should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and do not limit the present application.

[0030] Example 1

[0031] A preparation method of high-performance platinum fine wire, comprising the following steps:

[0032] (1) Block: 3000g of 99.995% sponge platinum was taken and put into a high-frequency melting furnace in batches of 300-500g, the power was adjusted to 17KW, and after the sponge platinum was inducted, it was immediately turned off after being pressed into a spherical shape by a high-purity alumina rod, and was taken out from the crucible by platinum tongs and placed on a clean alumina plate to cool, to obtain a platinum block;

[0033] (2) Melting: the platinum block was put into a melting crucible, the melting power was 22.5KW, the melting temperature was 1780-1900℃, and the melting time was 20min, to obtain a platinum melt;

[0034] (3) Vacuum degassing: the power was reduced to 6KW for degassing, and after the complete solidification of the melt surface was observed, the power was adjusted to 10kW for melting, and the time for one degassing process was not less than 5min. At the same time of degassing, vacuum operation was carried out, and when the vacuum degree reached 1×10 -2 ~ 1×10 -3 Pa, the vacuum was stopped and 5KPa of argon was injected;

[0035] (4) Vibration casting: the high-frequency vibration platform was turned on, the frequency was 6500 times / min, the platinum melt was poured into a water-cooled copper mold at a pouring speed of 110-130g / s, to obtain a pure platinum ingot, and the pouring power was 15KW;

[0036] (5) Hot swaging: the pure platinum ingot was hot swaged to φ6mm in 3 passes at 1200℃, and the pass processing amount was 30%-35%;

[0037] (6) Wire drawing: the φ6mm round bar obtained in step (5) was drawn to φ1mm in the rough drawing with a pass processing amount of 10-13%, to φ0.4mm in the medium drawing with a pass processing amount of 8-10%, and to the finished product φ0.01mm in the fine drawing with a pass processing amount of 5-8%.

[0038] (7) Cleaning: the cleaning after rough drawing and medium drawing was carried out by first alkali boiling and then acid boiling, wherein, the alkali boiling was carried out by using a solution of 100g of sodium hydroxide and 1000ml of deionized water, the acid boiling was carried out by using a solution of HCl and deionized water with a volume ratio of 1:1, and the main purpose was to remove the oil stains and base metal impurities attached to the surface. The fine wire finished product was continuously cleaned by ultrasonic wave, and the medium was deionized water and anhydrous ethanol, and the main purpose was to remove the drawing oil attached to the surface.

[0039] Specifically, as shown in Figure 1 , casting was carried out in a vacuum furnace 1, a melting crucible 2 and a water-cooled copper mold 3 were arranged in the vacuum furnace 1, the water-cooled copper mold 3 was arranged on a high-frequency vibration platform 4, and a vacuum pump 5 and an argon bottle 6 were arranged on the vacuum furnace 1. As shown in Figure 2 , the water inlet of the water-cooled copper mold 3 was arranged at the bottom, and the water outlet was arranged at the top.

[0040] Example 2

[0041] A method for preparing high-performance platinum fine wire, comprising the following steps:

[0042] (1) Block reduction: 3000g of 99.995% sponge platinum is weighed and put into a high-frequency melting furnace in batches of 300-500g, the power is adjusted to 17KW, and after the sponge platinum is inducted, it is immediately turned into a spherical shape by pressing with a high-purity alumina rod, then the power is turned off, the platinum block is taken out of the crucible with platinum tongs and placed on a clean alumina plate to cool, and a platinum block is prepared;

[0043] (2) Melting: the platinum block is put into a melting crucible, the melting power is 22.5KW, the melting temperature is 1780-1900℃, and the melting time is 20min, and a platinum melt is prepared;

[0044] (3) Vacuum exhaust: the power is reduced to 6KW for exhaust, and after the complete solidification of the melt surface is observed, the power is adjusted to 10kW for melting, and the exhaust time is not less than 5min. At the same time of exhaust, vacuum operation is carried out, and when the vacuum degree reaches 1×10 -2 ~ 1×10 -3 Pa, the vacuum is stopped and argon is injected at 5KPa;

[0045] (4) Vibration casting: the high-frequency vibration platform is turned on, the frequency is 7000 times / min, the platinum melt is poured into a water-cooled copper mold at a pouring speed of 110-130g / s, and a pure platinum ingot is obtained, and the pouring power is 15KW;

[0046] (5) Hot swaging: the pure platinum ingot is hot swaged to φ6mm in 3 passes at 1200℃, and the pass processing amount is 30%-35%;

[0047] (6) Wire drawing: the φ6mm round bar obtained in step (5) is drawn to φ1mm in the rough drawing with a pass processing amount of 10-13%, to φ0.4mm in the medium drawing with a pass processing amount of 8-10%, and to the finished product φ0.02mm in the fine drawing with a pass processing amount of 5-8%.

[0048] (7) Cleaning: the cleaning after rough drawing and medium drawing is carried out by first alkali boiling and then acid boiling, wherein the alkali boiling is carried out with a solution of 100g of sodium hydroxide and 1000ml of deionized water, and the acid boiling is carried out with a solution of HCl and deionized water in a volume ratio of 1:1, mainly to remove the oil stains and base metal impurities attached to the surface. The fine wire product is continuously cleaned by ultrasonic wave, and the medium is deionized water and anhydrous ethanol, mainly to remove the drawing oil adhered to the surface.

[0049] Comparative Example 1

[0050] The difference between Comparative Example 1 and Example 2 is:

[0051] (3) Exhaust: Argon gas is blown above the melt for protection, the flow is controlled at 4-5 L / min, then the power is reduced to 6 KW for exhaust, after the complete solidification of the melt surface is observed, keep for 1 min, then the power is adjusted to 10 kW for melting, the exhaust time is not less than 5 min, and the exhaust times is ≥6 times;

[0052] (4) Casting: The platinum melt is poured into a water-cooled copper mold at a pouring speed of 110-130 g / s to obtain a pure platinum ingot, and the casting power is 15 KW;

[0053] (6) Drawing: The φ6mm round bar obtained in step (5) is drawn to φ1mm on the rough drawing with a pass processing amount of 10-13%, to φ0.4mm on the medium drawing with a pass processing amount of 8-10%, and to the finished product φ0.02mm on the fine drawing with a pass processing amount of 5-8%.

[0054] The remaining steps are the same.

[0055] Comparative Example 2

[0056] The difference between Comparative Example 2 and Example 2 is that

[0057] (4) Vibration casting: open the high-frequency vibration platform, the frequency is 3000 times / min, pour the platinum melt into the water-cooled copper mold at a pouring speed of 110-130 g / s to obtain a pure platinum ingot, and the casting power is 15 KW.

[0058] Comparative Example 3

[0059] The difference between Comparative Example 3 and Example 2 is that

[0060] (4) Vibration casting: open the high-frequency vibration platform, the frequency is 8500 times / min, pour the platinum melt into the water-cooled copper mold at a pouring speed of 110-130 g / s to obtain a pure platinum ingot, and the casting power is 15 KW;

[0061]

[0062]

[0063] 1. Test method of test data in the above table.

[0064] (1) Tensile strength and elongation refer to GB / T 228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method"

[0065] (2) Resistance ratio R 100 / R0 refer to JJG160-2007 "Standard Platinum Resistance Thermometer Verification Regulation"

[0066] 2. Reasons for the performance of Comparative Examples 1-3 being worse than that of Example 2.

[0067] Disadvantages of Comparative Example 1: poor exhaust effect, deep cold shut, deep shrinkage cavity, high gas content, and coarse grains.

[0068] Disadvantages of Comparative Examples 2 and 3: high frequency vibration frequency being too high or too low will reduce the effect of refining grains and improving density. Figure 3 Appearance comparison chart of pure platinum ingot obtained by the method of the present application and high frequency melting, Figure 3 (a) Deep cold shut and deep shrinkage cavity of pure platinum ingot obtained by medium-high frequency melting, Figure 3 (b) Shallow cold shut and shallow shrinkage cavity of pure platinum ingot obtained by the method of the present application; Figure 4 Metallographic comparison chart of pure platinum wire in annealed state obtained by the method of the present application and high frequency melting.

[0069] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing high performance platinum microfilaments, characterized by It comprises the following steps: (1) Block reduction: Put the sponge platinum into the high-frequency melting furnace at 300-500 g / batch, the purity of the sponge platinum is not less than 99.995%; adjust the power to 15-20 KW, after the sponge platinum is inducted, extrude it into a spherical shape with high-purity alumina rod, immediately turn off the power, take it out from the crucible with platinum gold tongs, and place it on a clean alumina plate to cool down, and obtain platinum block; (2) Melting: Put the platinum block into the melting crucible, the melting power is 18-25 KW, the melting temperature is 1780-1900 ℃, and the melting time is 10-20 min, and obtain platinum melt; (3) Vacuum exhaust: Reduce the power to 5-8 KW for exhaust, and after vacuumizing, fill in argon protection; (4) Vibration casting: Open the high-frequency vibration platform, pour the platinum melt into the water-cooled copper mold, the casting power is 13-15 KW, and the casting speed is 110-130 g / s, and obtain pure platinum ingot; the vibration frequency of the high-frequency vibration platform is 5000-7000 times / min; the water-cooled copper mold is a round mold, the water inlet is at the bottom, and the water flow flows upward in a spiral form and flows out from the top side; (5) Hot rotary swaging: Hot rotary swaging the pure platinum ingot to φ6-φ8 mm in 3 passes at 1200 ℃, and the pass processing amount is 30%-35%; (6) Wire drawing: Coarse drawing, medium drawing, fine drawing and ultra-fine drawing are carried out on the wire drawing machine, wherein the pass processing amount of coarse drawing is 10-13%, the pass processing amount of medium drawing is 8-10%, the pass processing amount of fine drawing and ultra-fine drawing is 5-8%, and the platinum wire is drawn into fine platinum wire.

2. The method for preparing a high-performance platinum microfilament as described in claim 1, characterized in that: The exhaust time in step (3) is not less than 5 min, and the exhaust frequency is ≥2 times.

3. The method for preparing a high-performance platinum microfilament as described in claim 1 or 2, characterized in that: Step (3) The vacuum degree of the vacuumizing is 1 x 10 -2 ~ 1 x 10 -3 Pa.

4. The method for preparing a high-performance platinum microfilament as described in claim 3, characterized in that: The argon pressure of the argon protection in step (3) is 4-8 KPa.

5. The method for preparing a high-performance platinum microfilament as described in claim 1, characterized in that: The medium drawing and fine drawing equipment in step (6) are both non-slip wire drawing machines.

6. The method for preparing a high-performance platinum microfilament as described in claim 1, characterized in that: In step (7), the cleaning after coarse drawing and medium drawing is carried out by the method of alkali boiling and then acid boiling, wherein the alkali boiling is carried out with a solution of 100 g / 1000 ml of sodium hydroxide and deionized water, and the acid boiling is carried out with a solution of HCl solution and deionized water in a volume ratio of 1:

1.

7. The method for preparing a high-performance platinum microfilament as described in claim 5, characterized in that: In step (7), the cleaning after fine drawing and ultra-fine drawing is carried out by ultrasonic continuous cleaning, and the medium for continuous cleaning is deionized water and anhydrous ethanol.

8. The method for preparing a high-performance platinum microfilament as described in claim 7, characterized in that: The non-slip wire drawing machine is provided with one mold, one motor and one wire speed monitoring probe, and the computer intelligently adjusts the speed ratio of each motor through the signal feedback of the wire speed monitoring probe, so that the wire drawing speed is synchronized with the speed.

Images