Method for preparing tantalum rod for tantalum wire by vertical fusion sintering of metal waste tantalum blank strip

Abstract

The application provides a method for preparing a tantalum rod for a tantalum wire by using a metal waste tantalum blank strip vertical fusion sintering, and relates to the technical field of tantalum product production, and comprises the following steps: 1, various types of metal waste tantalum materials are prepared into waste metal tantalum powder respectively, and one or more of the waste metal tantalum powder is mixed to prepare a metal tantalum blank strip; 2, the metal tantalum blank strip is installed in a vertical fusion furnace; 3, the vertical fusion furnace is controlled to slowly heat to a first sintering power within a first preset time length, so that the diameter and length of the metal tantalum blank strip are prevented from shrinking too fast; 4, the first sintering power is maintained for a second preset time length, so that tantalum grains in the blank strip slowly grow, sintering density is gradually formed, and free state and low melting point impurity elements present are continuously volatilized; 5, the first sintering power is reduced to 0kW within a third preset time length, and the vertical fusion furnace is cooled to room temperature through cooling circulating water, and a tantalum rod is obtained through discharging. The method can improve the quality of the tantalum rod.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tantalum product production, and particularly relates to a method for preparing tantalum rods for tantalum wire by using metal waste tantalum blank strips. BACKGROUND

[0002] With the continuous development of smelting processing methods and production process technology of rare refractory metals, the production qualification rate and comprehensive utilization rate of metal materials, the preparation process and research and development level of new products are continuously improved. Especially, the smelting processing technology of metal materials has reached a relatively mature level. However, in actual production, the utilization rate of tantalum materials is not 100% qualified, and not every gram of tantalum material can be converted into new products. Due to the limitation of production process and processing technology, the process control level of product quality is not perfect, and various grades of metal tantalum materials will be produced in the production. For example, there are unqualified tantalum powder materials, tantalum wire materials, downgraded tantalum materials, especially a large amount of edge and corner waste wire materials produced in the tantalum wire production process, oxidized tantalum rod produced in the sintering process, broken tantalum rod, tantalum rod cutting head waste material, and tantalum rod cutting waste material in the rolling process. There are also a large amount of tantalum wire materials due to unqualified impurity content, physical property evaluation and surface quality, and other various tantalum materials produced in the production process. According to statistics, the various tantalum materials produced each year account for 3% of the total amount of tantalum raw materials used in production. At the same time, facing the shortage of foreign tantalum niobium mineral resources, the production cost of tantalum mining, processing and transportation is continuously increasing. Therefore, it is of great significance to recycle the large amount of tantalum materials produced in the production process for the production of tantalum products and the solution of resource shortage problem.

[0003] Currently, when waste tantalum materials are recycled, the commonly used method is to make metal waste tantalum powder into tantalum blank by isostatic pressing, and then prepare tantalum rod material for hydrogenation powdering of tantalum wire through high-temperature vertical melting sintering. However, the tantalum rod material for preparing tantalum wire through high-temperature vertical melting sintering of the tantalum blank pressed from the metal waste tantalum material is all the traditional melting and sintering production process of the tantalum blank pressed from the tantalum powder with large apparent density for metallurgical grade normal tantalum wire. When the tantalum blank is prepared from the metal waste tantalum material, the apparent density of the metal waste tantalum powder after powdering is low, the morphology of the tantalum particles in the tantalum blank pressed from the metal waste tantalum powder with low apparent density is complex, relatively loose, the spacing between the tantalum particles is relatively large, the pore size is large, and the porosity in the tantalum blank is large. The tantalum rod after sintering the tantalum blank by the traditional process suitable for large apparent density has problems such as hard base material, brittleness, low quality of tantalum grain formation, high impurity content, rough surface of tantalum rod, and the like, thereby causing large sintering quality fluctuation and frequent rework. In addition, the high rework rate of the tantalum rod also leads to high production cost of the concentrated recycling of the metal waste tantalum material, increased power consumption of the vertical melting furnace, long production cycle, large consumption of human resources, and the production progress and production capacity of the tantalum rod are difficult to meet the normal demand. SUMMARY

[0004] Therefore, in view of the above problems, it is necessary to provide a method for preparing tantalum rod for tantalum wire by vertical melting sintering of metal waste tantalum blank to improve the quality of the tantalum rod prepared from the metal waste tantalum.

[0005] The present application provides a method for preparing tantalum rod for tantalum wire by vertical melting sintering of metal waste tantalum blank, comprising the following steps:

[0006] Step 1: prepare various types of metal waste tantalum material into waste metal tantalum powder, and mix one or more of the prepared waste metal tantalum powder according to a certain proportion, and then prepare metal tantalum blank by isostatic pressing solidification forming;

[0007] Step 2: install the metal tantalum blank in the vertical melting furnace;

[0008] Step 3: control the vertical melting furnace to slowly increase from 0kW to the first sintering power within the first preset time length, so as to avoid the diameter and length of the metal tantalum blank shrinking too fast;

[0009] Step 4: after the vertical melting furnace is heated to the first sintering power, keep the temperature at the sintering power for the second preset time length, so that the tantalum grains inside the metal tantalum blank slowly grow, the sintering density gradually forms, and the free state and low melting point impurity elements existing on the surface and inside the metal tantalum blank continuously volatilize;

[0010] Step 5: After the second preset time, the vertical furnace is controlled to be cooled from the first sintering power to 0 kW within a third preset time, and after the vertical furnace is cooled to below room temperature by the cooling circulating water, the tantalum rod for preparing tantalum wire is discharged.

[0011] Preferably, in step 1, one or more of the prepared waste metal tantalum powder is mixed in a certain proportion to obtain a mixed waste metal tantalum powder with a loose bulk density of 1.0 g / cm 3 ~ 3.81 g / cm 3 , and the mixed waste metal tantalum powder is used to prepare the metal tantalum blank strip.

[0012] Preferably, the specifications of the metal tantalum blank strip are: weight 6.03 kg~6.52 kg, diameter size 28.5 mm~30.5 mm, and length size 845 mm~860 mm.

[0013] Preferably, step 2 specifically includes:

[0014] S21: The copper electrode is inspected to ensure that the clamping grooves at all positions on the copper electrode are clean and free of blockage of sundries, and it is confirmed that the lower end of the copper electrode can be freely and elastically contracted up and down;

[0015] S22: The molybdenum clamping head, spring and cross beam rod are installed on the copper electrode;

[0016] S23: The metal tantalum blank strip is slowly and smoothly vertically installed at both ends of the copper electrode, and clamped by the molybdenum clamping head and spring part; wherein the clamping head at both ends of the metal tantalum blank strip is not more than 20 mm.

[0017] Preferably, before the vertical furnace is heated in step 3, it further includes:

[0018] Starting the mechanical pump to vacuumize the vertical furnace;

[0019] When the vacuum degree in the vertical furnace is less than the first preset vacuum degree, the vertical furnace is subjected to a vacuum degree leak test;

[0020] If the leakage rate of the vertical furnace is less than the preset leakage rate threshold, the diffusion pump is started;

[0021] The vertical furnace is vacuumized by the combination of the mechanical pump and the diffusion pump, and when the vacuum degree in the vertical furnace is controlled within the range of the second preset vacuum degree, the vertical furnace heating operation is performed.

[0022] Preferably, the first preset vacuum degree is 5.0×10 0 Pa, the preset leakage rate threshold is 10 Pa / min, and the second preset vacuum degree is 5.0×10 -2 Pa~2.0×10 -2 Pa.

[0023] Preferably, the first preset time length is 90±5 min, and the first sintering power is 95±10 kW.

[0024] Preferably, the second preset time length is 90±5 min.

[0025] Preferably, in the step 3, the slow heating rate is 1.03 kW / min~1.16 kW / min; and in the step 4, the holding power deviation is not more than ±1.5 kW.

[0026] Preferably, in the step 5, the third preset time length is 5~20 seconds, the cooling time by using the cooling circulating water is 150±15 min, and the cooling rate is 0.6 kW / min~0.7 kW / min.

[0027] It can be seen from the above technical solution that, in the method for preparing a tantalum rod for tantalum wire by using a metal waste tantalum blank strip vertical fusion sintering provided in the embodiment of the present application, first, various types of metal waste tantalum materials are prepared into waste metal tantalum powder, then one or more types of the prepared waste metal tantalum powder are mixed in a certain proportion, and are solidified and formed into a metal tantalum blank strip by isostatic pressing. Further, the metal tantalum blank strip is installed in a vertical fusion furnace, then the vertical fusion furnace is controlled to slowly increase from 0 to a first sintering power within a first preset time length, so as to avoid that the diameter and length of the metal tantalum blank strip shrink too fast. Further, after the vertical fusion furnace is heated to the first sintering power, the vertical fusion furnace is held at the sintering power for a second preset time length, so as to slowly grow the tantalum grains inside the metal tantalum blank strip, gradually form the sintering density of the tantalum rod, and continuously volatilize the free state and low-melting-point impurity elements existing on the surface and inside the metal tantalum blank strip. Finally, after the second preset time length, the vertical fusion furnace is controlled to decrease from the first sintering power to 0 kW within a third preset time length, and is cooled to below room temperature by cooling circulating water before being taken out of the furnace. As can be seen, the present scheme adopts a slow heating sintering mode, which can avoid the problem that the diameter and length of the metal tantalum blank strip shrink too fast, and improves the sintering quality of the tantalum rod. Further, the present scheme can make the tantalum grains inside the tantalum rod slowly grow, and the sintering density of the tantalum rod gradually form, through high-temperature sintering at the first sintering power. At the same time, the oxygen, nitrogen, hydrogen, carbon and other elements in the free state form existing on the surface and inside the tantalum rod, and the low-melting-point metal impurity elements such as iron, magnesium, sodium, aluminum and calcium continuously volatilize in the high-temperature state, so as to achieve the purpose of high-temperature melting and sintering impurity removal and improving the sintering density of the tantalum rod. In summary, the present scheme can be applied to prepare a metal tantalum blank strip from a low bulk density waste tantalum powder, and can improve the quality of the tantalum rod for tantalum wire prepared by vertical fusion sintering. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A flow chart of the method for preparing a tantalum rod for tantalum wire by using a metal waste tantalum blank strip vertical fusion sintering provided in the embodiment of the present application.

[0029] Figure 2 A grain size chart of the tantalum rod prepared based on the present scheme.

[0030] Figure 3 A scanning electron microscope chart of the tantalum rod prepared based on the present scheme. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings described in the following embodiments are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0032] As shown in Figure 1 The present application provides a method for preparing a tantalum rod for tantalum wire by vertical fusion sintering of metal waste tantalum blank strips, which can include the following steps:

[0033] Step 1: Prepare various types of metal waste tantalum materials into waste metal tantalum powder, and then mix one or more of the prepared waste metal tantalum powder according to a certain proportion, and then solidify and form into metal tantalum blank strips by isostatic pressing;

[0034] Step 2: Install the metal tantalum blank strip in the vertical fusion furnace;

[0035] Step 3: Control the vertical fusion furnace to slowly increase from 0kW to a first sintering power within a first preset time length, so as to avoid the diameter and length of the metal tantalum blank strip from shrinking too fast;

[0036] Step 4: After the vertical fusion furnace is heated to the first sintering power, keep the temperature at the sintering power for a second preset time length, so as to slowly grow the tantalum grains inside the metal tantalum blank strip, gradually form the sintering density, and continuously volatilize the free state and low melting point impurity elements existing on the surface and inside of the metal tantalum blank strip;

[0037] Step 5: After the second preset time length, control the vertical fusion furnace to cool from the first sintering power to 0kW within a third preset time length, and then cool the vertical fusion furnace to below room temperature through cooling circulating water, and then take out the tantalum rod for preparing tantalum wire.

[0038] In this embodiment, the slow heating sintering method can avoid the problem of too fast diameter and shrinkage of the tantalum blank strip, and improve the sintering quality of the tantalum rod. Further, the high-temperature sintering under the first sintering power can make the tantalum grains in the tantalum rod grow slowly, and the sintering density of the tantalum rod is gradually formed. At the same time, the oxygen, nitrogen, hydrogen, carbon and other elements in the free state in the surface and interior of the tantalum rod, and the low-melting-point metal impurity elements such as iron, magnesium, sodium, aluminum and calcium will continuously volatilize under high temperature, so as to achieve the purpose of high-temperature melting and sintering of the tantalum rod and improving the sintering density of the tantalum rod. In summary, the present scheme can be applied to the preparation of metal tantalum blank strip from low bulk density waste tantalum powder, and can improve the quality of tantalum rod prepared by vertical melting sintering.

[0039] In addition, because the internal tantalum particles of the tantalum blank strip pressed from the metal waste tantalum powder with a small bulk density range have a complex morphology, are relatively loose, the spacing between the tantalum particles is relatively large, the pore size is large, and the porosity in the tantalum blank strip is large, if the high-temperature sintering is performed by the short-time rapid heating to the holding temperature in the traditional scheme, the diameter and length of the tantalum rod will shrink too fast during the sintering process, and the change is relatively obvious. At the same time, the spring at the upper end of the copper electrode has a low brittleness and a small elastic recovery force under high temperature, so that the clamping force of the spring to the end of the tantalum rod clamped by the molybdenum chuck becomes slow, the tantalum rod is not provided with a relatively fast recovery force synchronous shrinkage clamping process under high temperature, the higher the temperature, the more obvious the performance, so the diameter shrinkage rate of the tantalum rod is greater than the clamping force shrinkage rate of the molybdenum chuck transmitted by the spring at the upper end of the copper electrode, and the molybdenum chuck cannot tightly clamp the tantalum rod due to the heavy weight of the tantalum rod, which finally causes the end of the tantalum rod to easily fall off from the molybdenum chuck on the copper electrode under high-temperature melting and sintering, and even the tantalum rod is melted and broken, which causes the high-temperature melting and sintering process to be interrupted, the sintering process of the tantalum rod cannot be completely completed, and the whole melting and sintering process is unsuccessful, which leads to a low sintering yield of the tantalum rod and a high drop rate. According to statistics, the drop rate of the tantalum rod produced by the process with a large bulk density is as high as 9.44%, and a part of the tantalum rod is not successfully sintered. The tantalum rod that drops needs to be reloaded and sintered, which has a high rework rate, is laborious and time-consuming, consumes a large amount of production cost, cannot be normally supplied on time, and seriously affects the normal sintering production of the tantalum blank strip. The process suitable for a small bulk density provided based on the present scheme can effectively solve the above problem of high drop rate by slow heating and combining the blank strip preparation and vertical melting sintering process.

[0040] For step 1, various types of metal waste tantalum materials are prepared into waste metal tantalum powder, and one or more types of prepared waste metal tantalum powder are mixed according to a certain proportion and then formed into a metal tantalum blank strip by isostatic pressing solidification;

[0041] In this step, firstly, the unqualified waste wire material, the degraded waste wire material, the corner waste wire material, the sintering and rolling production process generated by the tantalum rod cutting head waste corner material, the waste tantalum material such as the oxidation fuse and the waste strip head material generated in the production process of tantalum wire are collected, and then the waste tantalum material is prepared into tantalum powder by ultrasonic cleaning and hydrogenation. Further, the prepared tantalum powder is mixed with any one or more of the sodium reduction degraded tantalum powder, the isostatic pressing tantalum powder and other grade tantalum powder according to a certain proportion to prepare a mixed waste metal tantalum powder, and then the mixed waste metal tantalum powder is solidified and formed by isostatic pressing to prepare a metal tantalum blank strip.

[0042] In this embodiment, when the mixed waste metal tantalum powder is prepared according to a certain proportion, one or more of the prepared waste metal tantalum powder is mixed according to a certain proportion to obtain a mixed waste metal tantalum powder with a loose bulk density of 1.0 g / cm 3 ~3.81 g / cm 3 , and the mixed waste metal tantalum powder is used to prepare a metal tantalum blank strip. The purpose of making the loose bulk density of the mixed waste metal tantalum powder for preparing the metal tantalum blank strip in the range of 1.0 g / cm 3 ~3.81 g / cm 3 is to achieve the reuse of various waste tantalum powders from different sources, and the chemical impurity content and physical properties (such as loose bulk density) of different waste tantalum powders are different, and to achieve the quality standard of tantalum powder used for tantalum wire production, and to fully utilize the waste tantalum powder from different sources. According to the process design, the mixed waste metal tantalum powder has a loose bulk density of 1.0 g / cm 3 ~3.81 g / cm 3 after mixing according to a certain proportion, the above purpose can be achieved. If the loose bulk density of the mixed waste tantalum powder is too high, the proportion of the waste tantalum powder with high loose bulk density needs to be increased during mixing, which will further cause the problems of poor flowability of tantalum powder, poor compression molding, high chemical impurity content of the mixed waste tantalum powder, which exceeds the quality standard of chemical impurities of tantalum rod used for tantalum wire production, and cannot be reduced by sintering, water pickling and other process treatments, and cannot be reused.

[0043] For example, 45%~50% of the sodium reduction grade tantalum powder and 50%~55% of the hydrogenated tantalum powder are mixed to obtain a mixed waste metal tantalum powder with a loose bulk density of 1.0 g / cm 3 ~3.81 g / cm 3 . For another example, 45%~50% of the sodium reduction grade tantalum powder, 40%~45% of the metallurgical grade tantalum powder and 10%~20% of the isostatic pressing tantalum powder are mixed to obtain a mixed waste metal tantalum powder with a loose bulk density of 1.0 g / cm 3 ~3.81 g / cm 3The mixed waste metal tantalum powder is mixed by a double-cone mixer at a rotating speed of 30-50 r / min for 2-3 hours to ensure uniformity of the mixed powder.

[0044] Further, the prepared metal tantalum billet has a weight of 6.03-6.52 kg, a diameter of 28.5-30.5 mm, and a length of 845-860 mm. The surface of the metal tantalum billet is smooth, free of cracks, slag, grooves, and contaminants. The two ends of the metal tantalum billet are intact, and the entire metal tantalum billet is free of bending deformation. The weight, length, and diameter of the metal tantalum billet at different positions are measured and recorded in detail.

[0045] For step 2, the metal tantalum billet is installed in the vertical furnace.

[0046] In this step, when the metal tantalum billet is installed in the vertical furnace, first, the upper end cover of the vertical furnace is opened, and the heat preservation sleeve is removed. Then, it is checked whether the copper electrode is intact and whether the clamping slots on the copper electrode are clean and free of blockage. It is also confirmed whether the lower end of the copper electrode can move freely and be elastically contracted up and down. Further, the molybdenum clamping head, spring, cross beam, and other components are installed on the copper electrode. Then, the metal tantalum billet is slowly and smoothly installed on the two ends of the copper electrode, and is clamped by the molybdenum clamping head and spring and other components to ensure that the metal tantalum billet is vertical and does not shake. The clamping head at the two ends of the metal tantalum billet should not exceed 20 mm to avoid poor contact caused by short clamping. Finally, the heat preservation sleeve is placed, the sealing ring on the furnace mouth is cleaned, and the furnace cover is slowly and smoothly covered.

[0047] In one embodiment, after the installation of the metal tantalum billet is completed and before the vertical furnace is heated, the following steps can be further included:

[0048] Starting the mechanical pump to perform vacuum pumping on the vertical furnace;

[0049] When the vacuum degree in the vertical furnace is less than a first preset vacuum degree, performing a vacuum degree leak detection on the vertical furnace;

[0050] If the leakage rate of the vertical furnace is less than a preset leakage rate threshold, starting the diffusion pump;

[0051] When the vacuum degree in the vertical furnace is controlled within a second preset vacuum degree range by the combination of the mechanical pump and the diffusion pump, performing a vertical furnace heating operation.

[0052] In this embodiment, when the vacuumizing of the vertical furnace is carried out, firstly, it is considered to check whether the cooling circulating water interfaces of each part of the vertical furnace body are intact, and whether the water outlet of the cooling circulating water total valve is unobstructed. Then, the equipment is normally powered on, and each operation is manually completed on the power distribution cabinet panel. Specifically, firstly, the green "control power supply" button is pressed, and after 2S-3S, the green "start" button of the mechanical pump is pressed, the mechanical pump is operated, and the pipeline connected with the vertical furnace hearth is vacuumized. After 3S, the "upper valve" start switch button on the pipeline is pressed, the vacuum gauge switch is opened, and the mechanical pump starts to perform the initial vacuumizing of the vertical furnace hearth. After about 30 min of vacuumizing, when the low vacuum degree value of the vacuum gauge is less than 5.0x10 0 Pa / min, the vacuum degree of the vertical furnace hearth is tested, and the leakage rate is less than 10 Pa / min. If the sealing property of the hearth is intact, the "diffusion pump" heating start button is pressed, the preheating is performed for 60 min, the "upper valve" close button is pressed, the "lower valve" start button and the "high valve" start button on the pipeline are pressed, the "lower valve" and the "high valve" are opened, and the "upper valve" is closed. The mechanical pump and the diffusion pump are combined to vacuumize the hearth. After about 30 min of vacuumizing, when the vacuum degree value in the vertical furnace hearth is 5.0x10 -2 Pa-2.0x10 -2 Pa, the power supply and temperature rising step is entered.

[0053] It should be noted that the vertical furnace adopted in the scheme should be a vertical furnace with a maximum power of 220kW or a maximum power of 430kW, and the vacuum degree should be above 5.0x10 -2 Pa.

[0054] For step 3, the vertical furnace is controlled to slowly rise from 0kW to a first sintering power within a first preset time length, so as to avoid that the diameter and length of the tantalum blank strip shrink too fast.

[0055] In this step, when the vacuumizing step is completed, the vacuum degree value in the vertical furnace hearth is 5.0x10 -2 Pa-2.0x10 -2 Pa, the "power supply heating" and "temperature rising control" buttons are manually pressed in sequence on the power distribution cabinet panel, and the time interval between the two steps is 3s. The high-temperature melting and sintering production process of the tantalum blank strip is automatically completed by the vertical furnace under the vacuum state and the industrial control system program. The temperature rising, temperature maintaining and temperature falling processes of the vertical furnace are all completed by the automatic control system according to the set curve procedure. The specific operation process of the tantalum blank strip melting and sintering process is as follows: after the "power supply heating" and "temperature rising control" buttons are started in sequence, the slow temperature rising program is started. After the temperature rising program is continuously operated for 90 min, the tantalum blank strip at both ends of the copper electrode is heated to 95kW.

[0056] It should be noted that since the melting point of tantalum metal is 3000℃, the temperature is too high to accurately display and control the temperature operation by using a thermometer, and therefore, in this embodiment, a power method is considered to be used.

[0057] Further, in an embodiment, a stepwise slow heating method can also be used to increase the sintering power from 0 kW to 95 kW within 90 min. For example, within 0-30 min, the sintering power is increased from 0 kW to 30 kW at a rate of 1.0 kW / min; then, within 30-60 min, the sintering power is increased from 30 kW to 65 kW at a rate of 1.17 kW / min; finally, within 60-90 min, the sintering power is increased from 65 kW to 95 kW at a rate of 1.0 kW / min. In this way, the average heating rate is controlled within the range of 1.03-1.16 kW / min, and by slow heating, the internal temperature gradient of the tantalum billet rod can be not greater than 5℃ / mm, thereby avoiding cracks caused by thermal stress.

[0058] For step 4, after the vertical furnace is heated to the first sintering power, it is kept at this sintering power for a second preset time length, so that the tantalum grains inside the tantalum billet rod slowly grow, the sintering density gradually forms, and the free state and low melting point impurity elements existing on the surface and inside the tantalum billet rod continuously volatilize.

[0059] In this step, the tantalum rod starts to perform the heat preservation program in the high temperature state of 95 kW, and the tantalum rod enters the high temperature heat preservation state. As the high temperature melting and burning proceed, the vacuum degree in the furnace reaches 7.0×10 -3 Pa~4.0×10 -3 Pa, the tantalum grains inside the tantalum rod start to slowly grow, the sintering density of the tantalum rod gradually forms, and the elements of O, N, H, C, etc. in the free state and the metal impurity elements of Fe, Mg, Na, Al, Ca, etc. with low melting point existing on the surface and inside the tantalum rod continuously volatilize under the high temperature and high vacuum state or volatilize to a certain level, achieving the purposes of tantalum rod high temperature melting and impurity removal and forming the sintering density of the tantalum rod.

[0060] It should be noted that when the high temperature melting and burning are maintained, the deviation of the heat preservation power should not be more than ±1.5 kW, so as to maintain a good high temperature sintering state.

[0061] For step 5, after the second preset time length, the vertical furnace is controlled to decrease from the first sintering power to 0 kW within a third preset time length, and after the vertical furnace is cooled to below room temperature by the cooling circulating water, the tantalum rod for preparing the tantalum wire is obtained.

[0062] In this step, when the tantalum rod is kept at high temperature of 95 kW for 90 min, the heating power is reduced from 95 kW to 0 kW within 5-10 s to avoid the re-adsorption of impurities caused by slow cooling. After the high-temperature holding and melting of the tantalum rod are completed, the tantalum rod also forms certain mechanical properties, and the entire temperature rising and holding program is completed. The industrial control system automatically stops power supply and heating to the tantalum rod at both ends of the copper electrode, and the "temperature rising control" button is automatically closed. The "power heating" button is manually closed, and the entire system starts to enter the cooling program. The cooling circulating water system starts to slowly cool the vertical melting furnace body. After natural cooling for 150 min, the temperature of the entire vertical melting furnace body is cooled from the high temperature point to room temperature below 25℃, and the high-temperature vertical melting and sintering of the tantalum rod are completed, and the qualified tantalum rod is obtained.

[0063] Specifically, when the tantalum rod is discharged, the following processes can be specifically included: after the vertical melting furnace body is naturally cooled to room temperature or below, the "diffusion pump" heating button is closed, the "high valve" button and the "low valve" button on the evacuation pipeline are closed, and after natural cooling for 60 min, the "mechanical pump" and the "vacuum gauge" buttons are closed. The broken air valve of the vertical melting furnace chamber is opened, and after the pressure in the furnace chamber and the air is the same, the crane is used to open the furnace cover, remove the heat preservation sleeve, and polish the two ends of the tantalum rod. The tantalum rod is sampled for various detection and analysis.

[0064] In this embodiment, the cooling time of the cooling circulating water can be 150±15 min, and the cooling rate can be controlled to be 0.6-0.7 kW / min.

[0065] The effect of the present scheme will be further described below in combination with specific experimental data.

[0066] The O, N analyzer, JY170 ULTRACE inductively coupled plasma atomic emission spectrometer, AA-7020 atomic absorption spectrophotometer and other equipment are used to analyze the content of various chemical impurities before and after sintering of the tantalum rod and the tantalum rod. The content of various chemical impurities before and after sintering of the tantalum rod and the tantalum rod is shown in Table 1. As can be seen from the numerical change in Table 1, the content of O, N, H, C, P, Fe, Mg, Al and other impurities in the tantalum rod is reduced after sintering, which achieves the purpose of purifying the tantalum rod. The units in the table are ppm.

[0067] Table 1

[0068] Serial number 1 2 3 4 5 6 7 8 Element symbol O N H C Fe Ni Cr Nb Tantalum billet 1320 51 30 18 24 6 5 ＜10 Tantalum rod 550 24 10 7 16 4 4 ＜10 Serial number 9 10 11 12 13 14 15 16 Element symbol W Si Al Ca Mn P Ti Mg Tantalum billet ＜4 25 25 ＜5 ＜1 20 ＜1 27 Tantalum rod ＜4 5 ＜5 ＜5 ＜1 10 ＜1 10

[0069] Further, the microstructure and structure of the prepared tantalum rod are analyzed in detail by using an X-ray diffractometer and a scanning electron microscope. The grain size of the tantalum rod after sintering is shown in Table 2, and the scanning electron microscope of the tantalum rod after sintering is shown in Table 3. Figure 2 Figure 3 ​As shown, from Figure 2 and Figure 3 As can be seen from the process scheme and processing method of this scheme, the tantalum grains in the tantalum rod grow, the grain boundaries are obvious and clear, the grain size reaches level 4, the morphology of the internal microstructure of the tantalum rod is intact, and there are no quality defects.

[0070] Furthermore, the weights of the tantalum billets and rods before and after sintering were measured and recorded using a direct-reading electronic platform scale. Table 2 shows the comparative analysis of the weights and sintering densities of the tantalum billets and rods before and after melting. Table 2 shows that the weight loss of the tantalum rods after melting was 0.074 kg, the weight qualification rate was 98.773%, and the average sintering density of the tantalum rods reached 15.374 g / cm³. 3 .

[0071] Table 2

[0072] Sample number 1 2 3 4 5 Average value Tantalum billet weight / kg 6.030 6.030 6.030 6.030 6.030 6.030 Tantalum rod weight / kg 5.961 5.952 5.958 5.954 5.957 5.956 Tantalum rod sinter density g / cm 3 ]]> 15.430 15.380 15.340 15.370 15.350 15.374

[0073] In summary, this invention provides a method for preparing tantalum rods for tantalum wire using sintering of scrap tantalum metal billets. This successfully solves and realizes the process of preparing qualified tantalum rods from scrap tantalum metal billets through high-temperature sintering. Compared to traditional methods, this invention employs a low-rate heating process, and the entire melting process includes heating, holding, and cooling steps. The entire process is completed under high-temperature and high-vacuum conditions. Specifically, it offers at least the following beneficial effects:

[0074] (1) This invention successfully achieves the preparation of tantalum powder from various recycled metal waste tantalum materials through centralized ultrasonic cleaning, hydrogen crushing, and pulverization. This waste tantalum powder is then mixed and modulated with any one, two, or more waste tantalum powders of sodium reduction downgrade tantalum powder, isostatic tantalum powder, and other grades of tantalum powder in a certain proportion to prepare a loose bulk density (SBD) of 1.0 g / cm³. 3 ~3.81 g / cm 3 The process involves preparing tantalum scrap powder particles. Further, this tantalum scrap powder is pre-formed by filling and packaging, isostatically pressed and solidified into tantalum billets, and then sintered at high temperature to produce qualified tantalum rods. This high-temperature sintering process for tantalum scrap billets has the advantages of a short overall sintering production cycle, slow sintering heating rate, and low high-temperature sintering power.

[0075] (2) The application successfully realizes centralized recovery and reutilization of a large amount of metal waste tantalum material generated in the daily production process of tantalum powder and tantalum wire and various waste tantalum materials such as sodium-reduced capacitor-grade degraded tantalum powder, and improves the new industry situation of the company in aspects of core competitiveness in the tantalum material market, industrial technology layout, and economic high-quality development;

[0076] (3) The application solves the problem that the upper end of the tantalum rod is easy to fall off from the molybdenum chuck of the copper electrode under the high-temperature smelting state, reduces the production technical problems of high tantalum rod dropping rate and high rework rate, and improves the sintering rate of the tantalum rod. Moreover, the weight loss of the tantalum rod obtained by using the production process method of the application can be controlled between 1.16% and 1.49%. The whole tantalum rod has uniform sintering density, smooth surface, straightness, no roughness, no melting, no oxidation, no splitting of the tantalum rod end, and no hollow advantages. The sintering density value of the tantalum rod can be controlled between 15.210 g / cm 3 ~ 15.470 g / cm 3 .

[0077] (4) The high-temperature smelting method has the advantages of high production efficiency, fast production progress, low human resource energy consumption, etc. Under the premise of meeting the raw material demand of tantalum wire production, the tantalum rod prepared by high-temperature vertical smelting sintering alleviates the current situation of tantalum resource shortage, improves the utilization rate of tantalum material, shortens the production cycle, and saves the production cost.

[0078] The modules or units in the device of the embodiments of the application can be combined, divided, and deleted according to actual needs. The above disclosure is only the preferred embodiments of the application, and of course cannot limit the scope of the rights of the application. Those skilled in the art can understand that all or part of the processes of the above embodiments are implemented, and equivalent changes made according to the claims of the application still belong to the scope covered by the application.

Claims

1. A method for preparing tantalum rods for tantalum wire using vertical melting and sintering of scrap tantalum metal billets, characterized in that, Includes the following steps: Step 1: Prepare waste tantalum metal powder from various types of waste tantalum metal materials, and mix one or more of the prepared waste tantalum metal powders in a certain proportion, and then prepare tantalum metal billet strips by isostatic pressing and solidification. Step 2: Install the tantalum metal billet into the vertical melting furnace; Step 3: Control the vertical melting furnace to slowly increase the temperature from 0kW to the first sintering power within a first preset time period to avoid excessive shrinkage of the diameter and length of the tantalum metal billet; the first preset time period is 90±5min, and the first sintering power is 95±10kW; wherein, the slow heating rate in Step 3 is 1.03kW / min~1.16kW / min; Step 4: After the vertical melting furnace is heated to the first sintering power, it is held at the sintering power for a second preset time to allow the tantalum grains inside the tantalum metal billet to grow slowly, the sintering density to gradually form, and the free state and low melting point impurity elements present on the surface and inside the tantalum metal billet to continuously volatilize; wherein, the deviation of the holding power in Step 4 shall not exceed ±1.5kW. Step 5: After the second preset time, control the vertical melting furnace to cool down from the first sintering power to 0kW within the third preset time, and then cool the vertical melting furnace to below room temperature by cooling circulating water, and then take it out of the furnace to obtain tantalum rods for preparing tantalum wires; In step 1, one or more of the prepared waste tantalum powders are mixed in a certain proportion to obtain a loose density of 1.0 g / cm³. 3 ~3.81 g / cm 3 The mixed waste tantalum metal powder was used to prepare tantalum metal billets.

2. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 1, characterized in that, The specifications of the tantalum metal billet are as follows: weight 6.03 kg to 6.52 kg, diameter 28.5 mm to 30.5 mm, and length 845 mm to 860 mm.

3. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 1, characterized in that, Step 2 specifically includes: S21: Inspect the copper electrode to ensure that all slots on the copper electrode are clean and free of debris, and confirm that the lower copper electrode can freely and elastically contract up and down. S22: Install the molybdenum tweezers, spring, and crossbeam onto the copper electrode; S23: Slowly and steadily install the tantalum metal billet vertically to both ends of the copper electrode, and clamp it with molybdenum clamps and spring components; wherein the clamps at both ends of the tantalum metal billet shall not exceed 20mm.

4. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 1, characterized in that, Before heating the vertical melting furnace in step 3, the process further includes: Start the mechanical pump to evacuate the vertical melting furnace; When the vacuum level inside the vertical melting furnace is less than the first preset vacuum level, a vacuum leak test is performed on the vertical melting furnace. If the leakage rate of the vertical melting furnace is less than the preset leakage rate threshold, the diffusion pump will be started. The vertical melting furnace is evacuated by a combination of mechanical pump and diffusion pump. When the vacuum level in the vertical melting furnace is controlled within the range of the second preset vacuum level, the vertical melting furnace heating operation is performed.

5. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 4, characterized in that, The first preset vacuum degree is 5.0 × 10⁻⁶. 0 Pa, the preset leak rate threshold is 10 Pa / min, and the second preset vacuum degree is 5.0 × 10 Pa. -2 Pa ~ 2.0 × 10 -2 Pa.

6. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 1, characterized in that, The second preset duration is 90±5 min.

7. The method for preparing tantalum rods for tantalum wires by vertical melting and sintering of scrap tantalum metal billets according to claim 1, characterized in that, In step 5, the third preset duration is 5 to 20 seconds, the time for cooling with circulating cooling water is 150 ± 15 min, and the cooling rate is 0.6 kW / min to 0.7 kW / min.

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