Method for preparing high-purity beryllium rod by Czochralski method

Abstract

The invention belongs to the technical field of beryllium material preparation, and particularly relates to a method for preparing a high-purity beryllium rod through a czochralski method. Comprising the following steps that 2N beryllium serves as a raw material, pretreated 2N beryllium is heated and smelted to be molten to form a melt, and the melt is kept in a stable convection state; when slag is generated in the melt, beryllium seed crystals are inserted into the melt, the temperature is reduced to 1000-1300 DEG C so that the slag can be solidified on the beryllium seed crystals to form slag blocks, then the slag blocks are taken out and serve as repetitive units till no slag block exists in the melt, and beryllium melt is obtained; and inserting the new beryllium seed crystal into the beryllium melt, enabling the beryllium melt to grow along the crystal orientation of the seed crystal by adopting a czochralski process, and cooling to room temperature to obtain the high-purity beryllium rod. The large-size high-purity beryllium rod with the purity reaching 99.9% or above is prepared through the czochralski method technology, the excellent physical performance and the high material utilization rate are achieved, the size can be accurately adjusted and controlled, large-scale production is achieved, and the method is suitable for the high-end industrial field.

Description

Technical Field

[0001] The invention belongs to the technical field of beryllium material preparation, and in particular relates to a method for preparing a high-purity beryllium rod by a Czochralski method. Background Art

[0002] Beryllium has irreplaceable importance in high-end fields such as aerospace, electronics, and nuclear energy due to its unique low density, high melting point, high specific stiffness, good thermal conductivity, and nuclear performance. The existing methods for preparing beryllium materials are mainly magnesium thermal reduction and vacuum distillation. Among them, the primary beryllium obtained by magnesium thermal reduction has low purity (≤98%); the vacuum distillation method can obtain 99.99% high-purity beryllium. Due to the vapor pressure limit, it is still difficult to remove impurities such as Fe and Si. The production capacity of the monomer device is only a few hundred grams per day, which cannot meet large-scale industrial applications. Application No. CN202211291915.3 discloses a method for preparing high-purity beryllium. The method uses a graphite condenser to vacuum distill beryllium to obtain 99.99% high-purity beryllium, and the distillation yield is 53.1%, which is relatively low in terms of production efficiency. Application No. CN202310704338.4 discloses a preparation device and preparation method of high-purity beryllium. The method uses a beryllium oxide crucible and a beryllium oxide condenser as carriers. The beryllium raw material undergoes two vacuum distillations and then undergoes corrosion cleaning to obtain 4.5N~5.5N high-purity beryllium. This method is limited by the size of the beryllium oxide crucible and the beryllium oxide condenser and cannot mass-produce beryllium rods. Therefore, the above-mentioned beryllium material preparation process is difficult to meet the growing demand for high-purity beryllium rods. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a method for preparing high-purity beryllium rods by Czochralski method. In an inert gas or vacuum environment, a beryllium seed crystal is inserted into a melt, the heating temperature is reduced to 1000°C to 1300°C, and a slag block is solidified on the beryllium seed crystal to form a repeating unit, impurities in 2N beryllium are removed, and then a large-sized high-purity beryllium rod with a purity of more than 99.9% is prepared by Czochralski method. The high-purity beryllium rod has excellent physical properties and high material utilization rate, can accurately control the size and realize large-scale production, and is suitable for high-end industrial fields.

[0004] The present invention solves the above technical problems through the following technical solutions.

[0005] The object of the present invention is to provide a method for preparing a high-purity beryllium rod by a Czochralski method, comprising the following steps: S1. Using 2N beryllium as a raw material, pre-treating the 2N beryllium, heating and smelting the pre-treated 2N beryllium in a protective gas atmosphere and vacuum until it is melted to form a melt, and keeping the melt in a stable convection state.

[0006] S2. When slag is generated in the melt, insert a beryllium seed crystal into the melt, reduce the heating temperature to 1000°C - 1300°C to solidify the slag on the beryllium seed crystal to form a slag mass, and then lift the beryllium seed crystal out of the melt to remove the slag mass.

[0007] S3. Replace with a new beryllium seed crystal, and use the process of inserting the beryllium seed crystal into the melt and reducing the heating temperature to 1000°C - 1300°C to solidify the slag on the beryllium seed crystal to form a slag mass as a repeating unit until there is no slag mass in the melt, obtaining a beryllium melt.

[0008] S4. Insert a new beryllium seed crystal into the beryllium melt, and use the Czochralski process to make the beryllium melt grow along the crystal direction of the seed crystal. After cooling to room temperature, a high-purity beryllium rod is obtained, and the purity of the beryllium material is ≥99.9%.

[0009] Furthermore, during the Czochralski process, it includes seeding, necking, shoulder formation, and shoulder transition. During seeding and necking, the temperature of the beryllium melt is reduced by 5°C - 10°C and then pulled, and the pulling speed ranges from 0 mm / min to 1.5 mm / min - 2 mm / min; during shoulder formation and shoulder transition, the rotation speed of the beryllium seed crystal is 5 rpm - 15 rpm, the pulling speed is reduced to 0.5 mm / min - 1 mm / min, and the temperature of the beryllium melt is decreased at a rate of 1°C / h - 2°C / h until the diameter of the beryllium rod reaches the required diameter.

[0010] Furthermore, during the Czochralski process, the temperature of the beryllium melt is 1200°C - 1400°C.

[0011] Furthermore, the beryllium seed crystal uses a high-purity beryllium crystal rod with the

[0001] crystal direction, the insertion depth of the beryllium seed crystal is 5 mm - 15 mm, and the speed during the insertion process is 1 mm / min - 5 mm / min.

[0012] Furthermore, the melting method uses high-frequency induction heating or graphite resistance heater heating, the melting temperature is 1200°C - 1400°C, and the frequency of high-frequency induction heating is 50 kHz - 200 kHz.

[0013] Furthermore, during the melting process, the vacuum degree is 10 -3 Pa - 10 -4 Pa, the pressure is 5 kPa - 10 kPa, and the protective gas is argon.

[0014] Furthermore, 2N beryllium is beryllium beads with a purity of 98% - 99%.

[0015] Furthermore, the pretreatment method of 2N beryllium includes the following steps: The 2N beryllium is pickled, washed with water and dried in sequence, and then metallic magnesium is added. Heating is carried out at 800°C - 1000°C in a vacuum environment to obtain pretreated 2N beryllium, wherein the heating is carried out at a heating rate of 10°C / min - 30°C / min to 800°C - 1000°C, holding for 1h - 3h, and then cooling to room temperature at a cooling rate of 5°C / min - 20°C / min.

[0016] Furthermore, the dosage of metallic magnesium is 0.5wt.% - 1.8wt.% of the mass of 2N beryllium, and the vacuum degree during the heating process is not lower than 10 Pa.

[0017] The present invention has the following beneficial effects compared with the prior art: (5) A method for preparing a high-purity beryllium rod by the Czochralski method provided by the present invention, in an inert gas or vacuum environment, with a beryllium seed crystal inserted into the melt, reducing the heating temperature to 1000°C - 1300°C, solidifying on the beryllium seed crystal to form a slag mass as a repeating unit, removing impurities in the 2N beryllium, and then adopting the Czochralski process to prepare a large-size high-purity beryllium rod with a purity of over 99.9%. It has excellent physical properties and high material utilization rate, can precisely control the size and realize large-scale production, and is applicable to high-end industrial fields.

[0018] (6) A method for preparing a high-purity beryllium rod by the Czochralski method provided by the present invention, by controlling the pulling speed of the Czochralski method and the temperature of the melt in an inert gas or vacuum environment, precisely controlling the temperature of the beryllium melt and the pulling speed, can precisely control the size and realize large-scale production. The Czochralski method can grow rods with larger sizes, is suitable for industrial production, can also realize a single-crystal structure, can reduce subsequent processing, single-crystal materials may reduce processes such as cutting and grinding, improve the material utilization rate, has strong controllability, can precisely control the diameter and length of the high-purity beryllium rod to meet different requirements, and the single-crystal material obtained by the Czochralski method has better physical properties, such as good plasticity and thermal conductivity, and is applicable to high-end applications.

[0019] (3) A method for preparing a high-purity beryllium rod by the Czochralski method provided by the present invention, in a protective gas atmosphere and vacuum, by adjusting the convection state of the melt, preventing local overheating or temperature non-uniformity, ensuring the stability and uniformity of the melt, improving the uniform growth of the beryllium rod structure during the crystal pulling process, and combining the high-purity magnesium chips deoxidation technology to prepare a large-size single-crystal high-purity beryllium rod with a purity of 99.999%. Specific embodiments

[0020] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] The existing methods for preparing beryllium materials mainly include the magnesium thermal reduction method and the vacuum distillation method, etc., but they cannot meet the large-scale industrial applications. However, the above-mentioned beryllium material preparation process is difficult to meet the growing demand for high-purity beryllium rods. Therefore, it is of great significance to develop a new method for preparing high-purity beryllium.

[0022] Based on the above problems, the present invention provides a method for preparing high-purity beryllium rods by the Czochralski method, including the following steps: S1. Using 2N beryllium as the raw material, after pretreating the 2N beryllium, heating and melting the pretreated 2N beryllium to form a melt under the atmosphere of a protective gas and in a vacuum, and keeping the melt in a stable convection state.

[0023] S2. When slag is generated in the melt, insert a beryllium seed crystal into the melt, lower the heating temperature to 1000°C - 1300°C to make the slag solidify on the beryllium seed crystal to form a slag mass, and then lift the beryllium seed crystal out of the melt to remove the slag mass.

[0024] S3. Replace the beryllium seed crystal with a new one, and use inserting the beryllium seed crystal into the melt and lowering the heating temperature to 1000°C - 1300°C to make the slag solidify on the beryllium seed crystal to form a slag mass as a repeating unit until there is no slag mass in the melt, obtaining a beryllium melt.

[0025] S4. Insert a new beryllium seed crystal into the beryllium melt, and adopt the Czochralski process to make the beryllium melt grow along the crystal direction of the seed crystal. After cooling to room temperature, a high-purity beryllium rod is obtained, and the purity of the beryllium material is ≥99.9%.

[0026] The method for preparing high-purity beryllium rods by the Czochralski method provided by the present invention, in an inert gas or vacuum environment, using inserting a beryllium seed crystal into the melt and lowering the heating temperature to 1000°C - 1300°C to make the slag solidify on the beryllium seed crystal to form a slag mass as a repeating unit to remove impurities in 2N beryllium, and then adopting the Czochralski process to prepare large-size high-purity beryllium rods with a purity of up to 99.999%, having excellent physical properties and high material utilization rate, capable of precisely controlling the size and realizing large-scale production, and being applicable to high-end industrial fields.

[0027] The present invention prepares high-purity beryllium rods by means of the Czochralski process, effectively overcoming many challenges brought about by the special properties of beryllium. The prepared high-purity beryllium rods show significant advantages in terms of purity, crystal structure and internal quality. At the same time, by strongly cooling to collect beryllium vapor and carrying out hazardous waste treatment, harmless purification is truly realized. The obtained beryllium materials have good performance in terms of size specifications from 3 inches to 8 inches and have broad application prospects.

[0028] In a specific embodiment, during the Czochralski process, it includes seeding, necking, shoulder formation, and shoulder transition. During seeding and necking, the temperature of the beryllium melt is reduced by 5°C to 10°C and then pulling is carried out. The pulling speed ranges from 0 mm / min to 1.5 mm / min to 2 mm / min. During shoulder formation and shoulder transition, the rotation speed of the beryllium seed crystal is 5 rpm to 15 rpm, the pulling speed is reduced to 0.5 mm / min to 1 mm / min, and the temperature of the beryllium melt is cooled at a rate of 1°C / h to 2°C / h until the diameter of the beryllium rod reaches the required diameter.It should be noted that during the Czochralski process, i.e., the pulling process, the temperature of the beryllium melt needs to be precisely controlled so that the temperature of the beryllium melt is maintained at 1200°C to 1400°C. The precise control of the temperature can be achieved by adjusting the heating power, and various parameters during the crystal pulling process, such as the pulling speed, rotation speed, temperature, etc., are monitored in real time. Based on the monitoring results, the process parameters are adjusted in a timely manner to ensure the smoothness of the crystal pulling process and the quality of the beryllium material. The Czochralski process includes procedures such as seeding, necking, shoulder formation, shoulder transition, equal diameter growth, detachment, and cooling. In a specific embodiment, during seeding and necking, the temperature of the crucible is cooled to 1250°C in a supercooled state. At the temperature in this supercooled state, the crystal pulling rod drives the seed crystal to insert into the melt in the crucible. After the temperature of the crucible stabilizes, it is cooled by 5°C to 10°C. After the cooling is completed, the temperature after cooling is maintained constant, and the crystal pulling rod is lifted. The pulling speed starts from 0 mm / min and is lifted until the pulling speed reaches 1.5 mm / min. During the process from starting the lift with a pulling speed of 0 until the pulling speed reaches 1.5 mm / min, the melt first gradually adheres and grows on the seed crystal and transforms into a solid, completing seeding and forming a rod. Then, the rod formed by seeding forms a thin neck and enters the necking process. When the pulling speed reaches 1.5 mm / min, the necking is completed. During shoulder formation, the rotation speed of the crystal pulling rod is 5 rpm to 15 rpm, so that the rotation speed of the beryllium seed crystal is 5 rpm to 15 rpm. The pulling speed of the rotating crystal pulling rod decreases from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible decreases at a rate of 1.5°C / h until the diameter of the rod becomes larger and approaches the target diameter. During shoulder transition and equal diameter growth, when the diameter of the rod after shoulder formation becomes larger and approaches the target diameter, the temperature of the crucible increases by 1°C to 1.5°C, and the diameter of the rod no longer increases, completing the shoulder transition. Then, it enters the equal diameter growth stage, and the lifting of the crucible is started. The lifting speed of the crucible is 0.045 mm / min. During the equal diameter growth stage, the temperature of the crucible is controlled at 1235°C to 1240°C. As the rotating crystal pulling rod lifts the rod and grows straight, after the length of the rod with equal diameter growth reaches the target length, it enters the detachment stage. During detachment, the crystal pulling rod is accelerated to lift or the crucible is accelerated to descend, and the rod detaches from the melt. During cooling, three-stage cooling is carried out. In the first stage, it drops to 800°C at a rate of 0.8°C / min. In the second stage, it drops from 800°C to 500°C at a rate of 1.2°C / min. In the third stage, it drops from 500°C to 200°C at a rate of 2.5°C / min. After dropping to 200°C, the crucible heater is powered off, and the crucible cools naturally to room temperature.

[0029] It should be noted that the Czochralski process is carried out using a Czochralski furnace. The Czochralski furnace heats and melts the pretreated 2N beryllium until it forms a melt. During the Czochralski process, the treated 2N beryllium is placed in a melting crucible, and then the melting crucible is placed inside the Czochralski furnace. The melting is carried out by high-frequency induction heating or graphite resistance heater heating to heat and melt the pretreated 2N beryllium until it forms a melt. However, beryllium has a certain volatility at high temperatures and will generate beryllium vapor, which is extremely harmful to the human body and can cause serious health problems such as berylliosis. Therefore, by filling the Czochralski furnace chamber or area with high-purity argon gas with a purity of ≥99.999%, the pressure inside the furnace is maintained at 5 kPa to 10 kPa, and an air flow guiding device is set above the melting crucible to make the argon gas form a stable laminar air flow, evenly covering the surface of the melt and the periphery of the growing beryllium material. On the one hand, the argon gas protection environment can serve as a physical barrier to prevent impurity gases such as oxygen and nitrogen in the air from contacting the beryllium melt and the growing beryllium material, preventing oxidation and other contaminations; on the other hand, due to the inertness of argon gas, it can effectively inhibit the diffusion of beryllium vapor, confine the beryllium vapor within a relatively small range, and reduce the risk of beryllium vapor volatilizing into the environment where the operators are located, thereby protecting the health and safety of the operators to the greatest extent. At the same time, an efficient filter, such as a bag filter or a ceramic filter, is installed in the exhaust gas discharge pipeline. The bag filter utilizes the filtering effect of fiber fabrics. When the exhaust gas passes through the bag, the dust particles are blocked on the surface of the bag, and the gas is discharged through the bag. The ceramic filter has the characteristics of high temperature resistance and corrosion resistance and has a good filtering effect on the dust in the high-temperature exhaust gas of the Czochralski furnace. By regularly cleaning or replacing the filter, the emission of beryllium dust particles can be effectively avoided.

[0030] It should be noted that the air flow guiding device is a device with guiding vanes inside. The angle of the guiding vanes can be adjusted between 30 degrees and 60 degrees to optimize the coverage effect of the argon gas laminar air flow. The air flow guiding device is made of stainless steel to make the protective atmosphere argon gas form a stable laminar air flow with an air flow speed of 0.5 m / s to 2 m / s, evenly covering the surface of the melt and the surrounding of the growing beryllium material. The high-purity argon gas needs to be deoxidized, dehydrated and decarbonized before being filled into the Czochralski furnace, with an oxygen content of less than 1 ppm, a water content of less than 1 ppm, and a carbon content of less than 0.5 ppm.

[0031] It should be noted that the melting crucible is a quartz crucible, and the inner wall of the quartz crucible is coated with a boron nitride (BN) coating with a thickness of 0.5 mm to 2 mm. The boron nitride coating is prepared by chemical vapor deposition. The deposition temperature is 800 °C to 1200 °C, the reaction gases are ammonia and borane, the flow rate ratio is 5 to 15:1, the deposition pressure is controlled at 1 kPa to 5 kPa, and the reaction time is 1 h to 5 h. In a specific embodiment, the thickness of the boron nitride coating on the inner wall of the quartz crucible is 1 mm, which is prepared by chemical vapor deposition. The deposition temperature is 1000 °C, the reaction gases are ammonia and borane, the flow rate ratio is 10:1, the deposition pressure is controlled at 3 kPa, and the reaction time is 2 h.

[0032] Furthermore, the beryllium seed crystal is a high-purity beryllium crystal rod with a

[0001] crystal orientation. The insertion depth of the beryllium seed crystal is 5 mm to 15 mm, and the insertion speed is 1 mm / min to 5 mm / min.

[0033] It should be noted that when removing the slag block in the melt, when 2N beryllium is completely melted, since the impurity content of the 2N beryllium raw material is relatively high, it is necessary to remove impurities. The generation of slag in the melt is monitored by a CCD with a resolution of not less than 1 million pixels. When a large amount of slag forms on the surface of the melt, the seed crystal is slowly lowered and inserted into the melt. When the slag solidifies along the seed crystal to form a pot lid-shaped slag block, it is quickly lifted to the secondary chamber at a lifting speed of 10 mm / s to 30 mm / s. The isolation valve plate of the Czochralski furnace is opened, and after evacuating for 10 minutes, the melt block is taken out by opening the secondary chamber, and then the seed crystal is reinstalled to extract the slag. Repeat this process 2 to 3 times until no slag is observed through the CCD.

[0034] In a specific embodiment, the melting method used is high-frequency induction heating or graphite resistance heater heating. The melting temperature is 1200 °C to 1400 °C, and the frequency of high-frequency induction heating is 50 kHz to 200 kHz.

[0035] It should be noted that during the crystal pulling process, a temperature compensation device is set around the crucible, which can compensate for the temperature difference between the crucible edge and the central region. The temperature control accuracy is ±5 °C, and various parameters during the crystal pulling process are monitored in real time through a high-precision sensor (with accuracies of not less than 0.1 °C, 0.05 mm / min, and 0.1 rpm corresponding to temperature, pulling speed, and rotation speed respectively).

[0036] In a specific embodiment, during the melting process, the vacuum degree is 10 -3 Pa to 10 -4 Pa, the pressure is 5 kPa to 10 kPa, and the protective gas is argon.

[0037] It should be noted that during the vacuum melting process, due to the high melting point of beryllium (about 1287 °C), sufficient high energy needs to be provided to melt the beryllium raw materials. In the present invention, methods such as frequency induction heating or graphite resistance heater heating are adopted to carry out the melting operation in a high vacuum environment. The maintenance of a high vacuum environment (the vacuum degree generally requires reaching 10 -3 Pa to 10 -4 Pa) is crucial. It can not only reduce the contact between the melt and gas impurities in the surrounding environment, avoid contamination such as oxidation, but also effectively reduce the possibility of beryllium reacting chemically with other substances at high temperatures. Under such vacuum conditions, the beryllium raw materials are gradually heated and melted to form a uniform melt. During this process, by precisely controlling the heating power and magnetic field intensity (for high-frequency induction heating), the convection state of the melt can be adjusted to prevent local overheating or uneven temperature, ensuring the stability and uniformity of the melt, which has a crucial impact on the uniform growth of the beryllium rod structure during the subsequent crystal pulling process.

[0038] It should be noted that during the frequency induction heating process, the coil of the high-frequency induction heating is made of copper material, with the number of turns being 10 to 50 turns, and the distance between the coil and the crucible being 5 cm to 20 cm. In a specific embodiment, the number of turns is 30 turns, and the distance between the coil and the crucible is 10 cm.

[0039] It should be noted that during the vacuum melting process, a strong cooling device is connected to the exhaust port of the evacuation system of the Czochralski furnace. This strong cooling device uses liquid argon cooling or other high-efficiency cooling media. The cooling power of the strong cooling device is not less than 10 kW, and the temperature of the cooling medium is maintained below -150 °C. The cooling medium is liquid argon to ensure that the beryllium vapor passing through the exhaust port can be quickly cooled to the solid state. A filtering unit is set between the strong cooling device and the evacuation system. This filtering unit can filter out beryllium particles with a particle size greater than 1 micron, and the filtering efficiency is not less than 95%. The solid beryllium collected by the strong cooling device is centrally treated as hazardous waste in accordance with relevant hazardous waste treatment standards.

[0040] In a specific embodiment, 2N beryllium is beryllium beads with a purity of 98% to 99%.

[0041] In a specific embodiment, the method for pretreating 2N beryllium includes the following steps: sequentially pickling, washing with water, and drying 2N beryllium, then adding metallic magnesium, and heating in a vacuum environment at 800 °C to 1000 °C to obtain pretreated 2N beryllium, where the heating is carried out at a heating rate of 10 °C / min to 30 °C / min to 800 °C to 1000 °C, holding for 1 h to 3 h, and then cooling to room temperature at a cooling rate of 5 °C / min to 20 °C / min.

[0042] It should be noted that pickling, water washing, and drying are alternately repeated at least three times to remove impurities, oxides, and other contaminants that may adhere to the surface. The purpose of using metallic magnesium is to remove oxygen. The pickling uses an acidic solution (such as hydrochloric acid solution with a mass concentration of 5% - 15%). When the acidic solution is used to clean the beryllium bead raw material, the soaking time is 10 min - 30 min each time, and after each cleaning, deionized water with a flow rate of 1 L / min - 5 L / min is used for rinsing, and the rinsing time is 5 min - 15 min. After the cleaning is completed, drying treatment is carried out. The drying treatment adopts a vacuum drying method with a vacuum degree of 10 Pa - 100 Pa and a drying time of 30 min - 120 min. In a specific embodiment, the soaking time is 30 min each time, and after each cleaning, deionized water with a flow rate of 3 L / min is used for rinsing, the rinsing time is 10 min, and after the cleaning is completed, drying treatment is carried out. The drying treatment adopts a vacuum drying method with a vacuum degree of 50 Pa and a drying time of 60 min.

[0043] In a specific embodiment, the dosage of metallic magnesium is 0.5 wt.% - 1.8 wt.% of the mass of 2N beryllium, and the vacuum degree during the heating process is not less than 10 Pa.

[0044] In a specific embodiment, the cooling of the beryllium crystal bar is divided into three stages. In the first stage, it is cooled at a rate of 0.6 °C / min - 1 °C / min to 700 °C - 900 °C, in the second stage, it is cooled at a rate of 1 °C / min - 2 °C / min to 400 °C - 600 °C, and in the third stage, it is cooled at a rate of 2 °C / min - 3 °C / min to 150 °C - 300 °C, and finally it is naturally cooled to room temperature.

[0045] In a specific embodiment, the beryllium seed crystal is prepared by machining a high-purity beryllium bar, generally by forging or rolling. It should be noted that the purpose of forging or rolling is to prepare the beryllium crystal bar into a beryllium seed crystal, and it has a good crystal structure and internal quality, and the dislocation density of the crystal structure is not higher than 10 6 / cm 2, there are no obvious inclusions and porosity defects inside, and the grain boundary angle deviation of the crystal structure does not exceed ±5 degrees to ensure the uniformity and stability of the crystal structure. Among them, the specific method of the forging method is: heat the high-purity beryllium rod to 500°C to 800°C, and then perform forging processing in a mold. By controlling the forging ratio in the range of 3 to 8, the forging temperature accuracy is ±10°C, and the forging speed is in the range of 10 mm / s to 50 mm / s, the grains inside the beryllium material are deformed and preferentially oriented, and then annealing treatment is carried out. The annealing temperature is 400°C to 600°C, and the annealing time is 1 h to 3 h to promote the recrystallization process, so that the grains grow along the

[0001] crystal direction, thereby obtaining a beryllium seed crystal with a certain

[0001] crystal orientation texture. The specific method of the rolling method is: heat the high-purity beryllium rod to 400°C to 700°C and then perform rolling. Through multi-pass rolling (the number of passes is 5 to 15) and controlling the rolling process parameters, the rolling pressure is 100 MPa to 500 MPa, and the rolling speed is 5 m / min to 30 m / min, the grains of the beryllium material are deformed and preferentially oriented to form a texture in the

[0001] crystal direction, and a beryllium seed crystal is obtained. The rolled beryllium seed crystal is then subjected to annealing treatment. The annealing temperature is 300°C to 500°C, and the annealing time is 0.5 h to 2 h to further improve its microstructure and properties and increase the texture degree in the

[0001] crystal direction, thereby obtaining a beryllium seed crystal with a certain

[0001] crystal orientation texture. In a preferred embodiment, the beryllium seed crystal is prepared by the forging method using a high-purity beryllium rod. After heating the high-purity beryllium rod to 700°C, forging processing is carried out in a mold. By controlling the forging ratio to be 5, the forging temperature accuracy is ±10°C, and the forging speed is in the range of 30 mm / s, the grains inside the beryllium material are deformed and preferentially oriented, and then annealing treatment is carried out. The annealing temperature is 500°C, and the annealing time is 2 h to promote the recrystallization process, so that the grains grow along the

[0001] crystal direction, thereby obtaining a beryllium seed crystal with a certain

[0001] crystal orientation texture.

[0046] It should be noted that the beryllium rod with a certain

[0001] crystal orientation texture is used to remove the surface oxide layer and possible defective parts with a diamond tool at a cutting speed of 50 m / min to 200 m / min. The edge radius of the diamond tool is 10 μm to 50 μm, and the cutting depth is 0.1 mm to 0.5 mm. Then ultrasonic cleaning is carried out. The cleaning frequency is 20 kHz to 50 kHz, and the cleaning time is 10 min to 30 min. Then drying treatment is carried out. The drying temperature is 50°C to 100°C to obtain a beryllium seed crystal with a length of 150 mm and a diameter of Ф12.5 mm. In a specific embodiment, the diamond tool removes the surface oxide layer and possible defective parts at a cutting speed of 1000 m / min. The edge radius of the diamond tool is 20 μm, the cutting depth is 0.2 mm, the cleaning frequency is 30 kHz, the cleaning time is 20 min, and the drying temperature is 100°C.

[0047] The following is a further illustration through specific embodiments.

[0048] Embodiment 1 A method for preparing high-purity beryllium rods by the Czochralski method includes the following steps: S1. Select beryllium beads with a purity of 98% as the beryllium raw material, and alternately wash them four times with a hydrochloric acid solution with a mass concentration of 10% and deionized water to remove possible impurities, oxides, and other contaminants attached to the surface. Subsequently, add 0.6 wt.% of 99.99% magnesium chips based on the mass of the beryllium raw material, mix them evenly, and heat them at 1000 °C in a vacuum environment. The heating is carried out at a heating rate of 20 °C / min to 1000 °C, hold for 2 h, and then cool to room temperature at a cooling rate of 10 °C / min to obtain pretreated 98% beryllium beads.

[0049] S2. Select a quartz crucible, coat a 1-mm-thick boron nitride coating on its inner wall, place the crucible in a Czochralski furnace, evacuate the furnace body to 10 -4 Pa after sealing, then fill it with high-purity argon gas to maintain the furnace pressure at 8 kPa, and ensure the normal operation of the strong cooling device (cooled by liquid argon, the temperature can be reduced to -196 °C) at the exhaust port of the evacuation system.

[0050] S3. Put the pretreated 98% beryllium beads into the quartz crucible, and melt the beryllium raw material by high-frequency induction heating to completely melt the beryllium beads to form a uniform melt. The melting temperature is controlled at 1300 °C to ensure the stability and uniformity of the melt. When a large amount of slag is generated in the melt, lower a beryllium seed crystal with a

[0001] crystal orientation into the melt. The insertion depth of the beryllium seed crystal is 10 mm, and the insertion speed is 3 mm / min. Then reduce the heating temperature to 1100 °C to quickly solidify the slag and lift it to the auxiliary chamber at a lifting speed of 20 mm / s. Open the isolation valve plate of the Czochralski furnace, evacuate for 10 min, and then lift the beryllium seed crystal out of the melt to remove the slag block.

[0051] S4. Replace the beryllium seed crystal with a new one, and use the solidification of the slag on the beryllium seed crystal to form a slag block as a repeating unit by inserting the beryllium seed crystal into the melt and reducing the power. Repeat this 3 times until there is no slag block in the melt to obtain a pure beryllium melt.

[0052] S5. Install a new beryllium seed crystal and immerse it into the melt from the melt surface with an immersion depth of 10 mm. Then, the pulling rod is pulled upward to grow a rod body to form a high-purity beryllium rod. The rod body growth includes processes such as seeding, necking, shoulder opening, shoulder turning, equal diameter, separation, and cooling. Among them: Before seeding, the pulling rod and the crucible start to rotate, and the rotation directions of the pulling rod and the crucible are opposite. The rotation speed of the crucible is 2 rpm, and the rotation speed of the pulling rod is 5 rpm. From seeding to separation, the crucible and the pulling rod maintain opposite rotation speeds unchanged.

[0053] When seeding and making the diameter of the rod thin, the temperature of the crucible is cooled to 1250 °C in a supercooled state. At the temperature in this supercooled state, the crystal pulling rod drives the seed crystal to insert into the melt in the crucible. After the temperature of the crucible stabilizes, it is cooled by another 5 °C. After the cooling is completed, the temperature after cooling is maintained constant. The crystal pulling rod is lifted, and the pulling speed starts from 0 mm / min and is lifted until the pulling speed reaches 1.5 mm / min. During the process from starting to lift at 0 to reaching a pulling speed of 1.5 mm / min, the melt first gradually adheres and grows on the seed crystal and turns into a solid, completing seeding and forming a rod. Then, the rod formed by seeding forms a thin neck and enters the process of making the diameter of the rod thin. When the pulling speed reaches 1.5 mm / min, the process of making the diameter of the rod thin is completed.

[0054] When shoulder broadening, the pulling speed of the rotating crystal pulling rod is reduced from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible is cooled at a rate of 1.5 °C / h until the diameter of the rod becomes close to 76.2 mm (3 inches).

[0055] When shoulder turning and equal diameter, when the diameter of the rod broadened during shoulder broadening becomes close to 76.2 mm (3 inches), the temperature of the crucible is increased by 1 °C, and the diameter of the rod no longer increases, completing shoulder turning. Then, it enters the equal diameter stage, and the lifting of the crucible is started. The lifting speed of the crucible is 0.045 mm / min. During the equal diameter stage, the temperature of the crucible is controlled at 905 °C to 909 °C. As the crystal pulling rod rotating at 5 rpm lifts the rod, the rod grows straight. After the length of the rod growing with equal diameter reaches 203.2 mm, it enters the separation stage. During separation, the crystal pulling rod is accelerated to lift, and the rod is separated from the melt to form a beryllium rod.

[0056] S6. After the rod growth is completed, stop heating, cool down, open the growth furnace, and cut the rod from the crystal pulling rod. Among them, during cooling, three-stage cooling is carried out. In the first stage, it drops to 800 °C at a rate of 0.8 °C / min. In the second stage, it drops from 800 °C to 500 °C at a rate of 1.2 °C / min. In the third stage, it drops from 500 °C to 200 °C at a rate of 2.5 °C / min. After dropping to 200 °C, the power supply of the crucible heater is cut off, and the crucible cools naturally to room temperature; among them, after cooling and before opening the growth furnace by 100, the argon gas is turned off. The high-purity beryllium rod is a rod material with a diameter of 3 inches (about 76.2 mm) and a length of up to 8 inches (about 203.2 mm). As shown in Table 1, the purity of the high-purity beryllium rod reaches 99.9%, the crystal structure is uniform, and there are no obvious defects.

[0057] Table 1 Purity results of the beryllium rod prepared in Example 1 Example 2 A method for preparing a high-purity beryllium rod by the Czochralski method, comprising the following steps: S1. Select beryllium beads with a purity of 99% as the beryllium raw material, and alternately wash them four times with a hydrochloric acid solution with a mass concentration of 10% and deionized water to remove possible impurities, oxides, and other contaminants on the surface. Subsequently, add 0.6 wt.% of 99.99% magnesium chips based on the mass of the beryllium raw material, mix them evenly, and heat them at 1000 °C in a vacuum environment. The heating is carried out at a heating rate of 20 °C / min to 1000 °C, hold for 2 h, and then cool to room temperature at a cooling rate of 10 °C / min to obtain pretreated 99% beryllium beads.

[0058] S2. Select a quartz crucible, coat a 1-mm-thick boron nitride coating on its inner wall, place the crucible in a Czochralski furnace, evacuate the furnace body to 10 -4 Pa after sealing, then fill it with high-purity argon to maintain the furnace pressure at 8 kPa, and ensure the normal operation of the cryogenic device (cooled by liquid argon, the temperature can be reduced to -196 °C) at the exhaust port of the evacuation system.

[0059] S3. Put the pretreated 99% beryllium beads into the quartz crucible, and melt the beryllium raw material by heating with a graphite resistance heater to completely melt the beryllium beads to form a uniform melt. The melting temperature is controlled at 1280 °C, and the convection state of the melt can be adjusted to prevent local overheating or temperature non-uniformity, ensuring the stability and uniformity of the melt. When a large amount of slag is generated in the melt, lower a beryllium seed crystal with a

[0001] crystal orientation into the melt. The insertion depth of the beryllium seed crystal is 10 mm, and the insertion speed is 3 mm / min. Then lower the heating temperature to 1100 °C to quickly solidify the slag and lift it to the auxiliary chamber at a lifting speed of 20 mm / s. Open the isolation valve plate of the Czochralski furnace, evacuate for 10 min, and then lift the beryllium seed crystal out of the melt to take out the slag block.

[0060] S4. Replace the beryllium seed crystal with a new one, and use the solidification of the slag on the beryllium seed crystal to form a slag block as a repeating unit by inserting the beryllium seed crystal into the melt and reducing the power. Repeat this 2 times until there is no slag block in the melt to obtain a beryllium melt.

[0061] S5. Install a new beryllium seed crystal and immerse it into the melt from the melt surface with an immersion depth of 10 mm. Then, the pulling rod is pulled upward to grow a rod body to form a high-purity beryllium rod. The rod body growth includes processes such as seeding, necking, shoulder formation, shoulder turning, constant diameter, separation, and cooling. Among them: Before seeding, the pulling rod and the crucible start to rotate in opposite directions. The rotation speed of the crucible is 2 rpm, and the rotation speed of the pulling rod is 5 rpm. From seeding to separation, the crucible and the pulling rod maintain opposite rotation speeds unchanged.

[0062] During crystal seeding and necking-down, the temperature of the crucible is cooled to 1250 °C in a supercooled state. At the temperature of this supercooled state, the crystal pulling rod drives the seed crystal to insert into the melt in the crucible. After the temperature of the crucible stabilizes, it is cooled by another 5 °C. After the cooling is completed, the temperature after cooling is maintained constant. The crystal pulling rod is lifted, and the pulling speed starts from 0 mm / min and is lifted until the pulling speed reaches 1.5 mm / min. During the process from starting to lift at 0 to reaching a pulling speed of 1.5 mm / min, the melt first gradually adheres and grows on the seed crystal and transforms into a solid, completing crystal seeding and forming a rod. Then, the rod formed by crystal seeding forms a thin neck and enters the necking-down process. When the pulling speed reaches 1.5 mm / min, the necking-down is completed.

[0063] During shoulder broadening, the pulling speed of the rotating crystal pulling rod decreases from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible is cooled at a rate of 1.5 °C / h until the diameter of the rod becomes close to 152.4 mm (6 inches).

[0064] During shoulder turning and equal diameter growth, when the diameter of the rod after shoulder broadening becomes close to 152.4 mm (6 inches), the temperature of the crucible is increased by 1 °C, and the diameter of the rod no longer increases, completing shoulder turning. Then, it enters the equal diameter growth stage, and the lifting of the crucible is started. The lifting speed of the crucible is 0.045 mm / min. During the equal diameter growth stage, the temperature of the crucible is controlled between 905 °C and 909 °C. As the crystal pulling rod rotating at 5 rpm lifts the rod, the rod grows straight. After the length of the rod with equal diameter growth reaches 203.2 mm, it enters the detachment stage. During detachment, the crystal pulling rod is accelerated to lift, and the rod detaches from the melt to form a high-purity beryllium rod.

[0065] S6. After the growth of the rod is completed, stop heating, cool down, open the growth furnace, and cut the rod from the crystal pulling rod. Among them, during cooling, three-stage cooling is carried out. The first stage drops to 800 °C at a rate of 0.8 °C / min, the second stage drops from 800 °C to 500 °C at a rate of 1.2 °C / min, and the third stage drops from 500 °C to 200 °C at a rate of 2.5 °C / min. After dropping to 200 °C, the power supply of the crucible heater is cut off, and the crucible cools naturally to room temperature. Among them, after cooling and before opening the growth furnace, the argon gas is turned off. The diameter of this high-purity beryllium rod is a rod material of 6 inches (about 152.4 mm), and the length can reach 8 inches (about 203.2 mm). As shown in Table 2, the purity of the high-purity beryllium rod reaches 99.999%, the crystal structure is uniform, and there are no obvious defects.

[0066] Table 2 Purity results of the beryllium rod prepared in Example 2 Example 3 A method for preparing a high-purity beryllium rod by the Czochralski method, comprising the following steps: S1. Select the cutting waste generated in machine tool processing with a purity of 98% as the beryllium raw material, and alternately wash it four times with a hydrochloric acid solution with a mass concentration of 10% and deionized water to remove possible impurities, oxides and other pollutants attached to the surface. Subsequently, add 99.99% magnesium chips accounting for 0.8 wt.% of the mass of the beryllium raw material, mix evenly, and heat it at 1000 °C in a vacuum environment. The heating is carried out at a heating rate of 20 °C / min to 1000 °C, hold for 2 h, and then cool to room temperature at a cooling rate of 10 °C / min to obtain pretreated beryllium cutting waste.

[0067] S2. Select a quartz crucible, coat a 1-mm-thick boron nitride coating on its inner wall, place the crucible in a Czochralski furnace, evacuate the furnace body to 10 -4 Pa after sealing, then fill it with high-purity argon to maintain the furnace pressure at 8 kPa, and ensure the normal operation of the strong cooling device (cooled by liquid argon) at the exhaust port of the evacuation system.

[0068] S3. Put the pretreated beryllium cutting waste into the quartz crucible, and melt the beryllium raw material by heating with a graphite resistance heater to completely melt the beryllium beads to form a uniform melt. The melting temperature is controlled at 1350 °C, and the stability and uniformity of the melt are ensured by adjusting the magnetic field strength to keep the melt in a stable convection state. When a large amount of slag is generated in the melt, insert a beryllium seed crystal with the

[0001] crystal orientation into the melt. The insertion depth of the beryllium seed crystal is 10 mm, and the insertion speed is 3 mm / min. Then, lower the heating temperature to 1100 °C to quickly solidify the slag and lift it to the auxiliary chamber at a lifting speed of 20 mm / s. Open the isolation valve plate of the Czochralski furnace, evacuate for 10 min, and then lift the beryllium seed crystal out of the melt to remove the slag block.

[0069] S4. Replace the new beryllium seed crystal, and use the solidification of the slag on the beryllium seed crystal to form a slag block as a repeating unit by inserting the beryllium seed crystal into the melt and reducing the power. Repeat 3 times until there is no slag block in the melt to obtain a beryllium melt.

[0070] S5. Install a new beryllium seed crystal and immerse it into the melt from the melt surface with an immersion depth of 10 mm. Then, the pulling rod is pulled up vertically to grow a rod body to form a crystal rod. The rod body growth includes processes such as seeding, necking, shoulder opening, shoulder turning, equal diameter, detachment, and cooling. Among them: Before seeding, the pulling rod and the crucible start to rotate and the rotation directions of the pulling rod and the crucible are opposite. The rotation speed of the crucible is 2 rpm, and the rotation speed of the pulling rod is 5 rpm. From seeding to detachment, the crucible and the pulling rod maintain opposite rotation speeds unchanged.

[0071] When seeding and thinning the diameter, the temperature of the crucible is cooled to 1250°C in the supercooled state. At the temperature of this supercooled state, the pulling rod drives the seed crystal to insert into the melt in the crucible. After the temperature of the crucible stabilizes, it is cooled by another 5°C. After the cooling is completed, the temperature after cooling is maintained constant. The pulling rod is lifted, and the pulling speed starts from 0 mm / min and is lifted until the pulling speed reaches 1.5 mm / min. During the process from starting to lift at 0 to reaching a pulling speed of 1.5 mm / min, the melt first gradually adheres and grows on the seed crystal and transforms into a solid, completing seeding and forming a rod. Then, the rod formed by seeding forms a thin neck and enters the process of thinning the diameter. When the pulling speed reaches 1.5 mm / min, the thinning of the diameter is completed.

[0072] When shoulder broadening, the pulling speed of the rotating pulling rod 3 is reduced from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible 1 is cooled at a rate of 1.5°C / h until the diameter of the rod becomes larger and approaches 203.2 mm.

[0073] When shoulder turning and equal diameter, when the diameter of the rod after shoulder broadening becomes larger and approaches 203.2 mm, the temperature of the crucible is increased by 1°C, and the diameter of the rod no longer increases, completing shoulder turning. Then, it enters the equal-diameter stage, and the lifting of the crucible is started. The lifting speed of the crucible is 0.045 mm / min. During the equal-diameter stage, the temperature of the crucible is controlled at 905°C - 909°C. As the pulling rod rotating at 5 rpm pulls the rod, the rod grows straight. After the length of the rod growing with equal diameter reaches 203.2 mm, it enters the detachment stage. During detachment, the pulling rod is accelerated to lift, and the rod detaches from the melt to form a high-purity beryllium rod.

[0074] S6. After the rod growth is completed, stop heating, cool down, open the growth furnace, and cut the crystal rod from the pulling rod. Among them, during cooling, three-stage cooling is carried out. The first stage drops to 800°C at a rate of 0.8°C / min, the second stage drops from 800°C to 500°C at a rate of 1.2°C / min, and the third stage drops from 500°C to 200°C at a rate of 2.5°C / min. After dropping to 200°C, the power supply of the crucible heater is cut off, and the crucible cools naturally to room temperature. Among them, before opening the growth furnace after cooling, the argon gas is turned off. This high-purity beryllium rod is a rod material with a diameter of 8 inches (about 203.2 mm) and a length of up to 8 inches (about 203.2 mm). As shown in Table 3, the purity of the high-purity beryllium rod reaches over 99.9%, the crystal structure is uniform, and there are no obvious defects.

[0075] Table 3 Purity results of the beryllium rod prepared in Example 3 It should be noted that when the present invention involves a numerical range, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step method is the same as that of the embodiment, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0076] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing high-purity beryllium rods by Czochralski method, characterized in that: The following steps are involved: Using 2N beryllium as a raw material, pre-treating the 2N beryllium, heating and melting the pre-treated 2N beryllium in a protective gas atmosphere and vacuum until it melts to form a melt, and keeping the melt in a stable convection state; When slag is generated in the melt, a beryllium seed crystal is inserted into the melt, and the heating temperature is lowered to 1000° C. to 1300° C. to solidify the slag on the beryllium seed crystal to form a slag block, and then the beryllium seed crystal is lifted out of the melt to take out the slag block; Replace the beryllium seed crystal with a new one, insert the beryllium seed crystal into the melt, lower the heating temperature to 1000°C to 1300°C, and solidify the slag on the beryllium seed crystal to form a slag block as a repeating unit until there is no slag block in the melt, thereby obtaining a beryllium melt; The new beryllium seed crystal is inserted into the beryllium melt, and the beryllium melt is made to grow along the crystal direction of the seed crystal by the direct pulling process. After cooling to room temperature, a high-purity beryllium rod is obtained with a purity of ≥99.9%.

2. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: The direct pulling process includes seeding, thinning, shoulder release and shoulder rotation. During seeding and thinning, the temperature of the beryllium melt is reduced by 5°C to 10°C and then pulled, and the pulling speed is from 0mm / min to 1.5mm / min to 2mm / min. During shoulder release and shoulder rotation, the rotation speed of the beryllium seed crystal is 5rpm to 15rpm, and the pulling speed is reduced to 0.5mm / min to 1mm / min. The temperature of the beryllium melt is cooled at 1°C / h to 2°C / h until the diameter of the beryllium rod reaches the required diameter.

3. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: During the direct pulling process, the temperature of the beryllium melt is 1200℃~1400℃.

4. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: The beryllium seed crystal adopts a high-purity beryllium crystal rod with a [0001] crystal orientation. The beryllium seed crystal is inserted to a depth of 5 mm to 15 mm, and the speed during the insertion process is 1 mm / min to 5 mm / min.

5. The method for preparing high-purity beryllium rods by Czochralski method and the Czochralski method crystal growth process according to claim 1, characterized in that: The smelting method is a high-frequency induction heating method or a graphite resistance heater heating method. The smelting temperature is 1200°C to 1400°C, and the frequency of the high-frequency induction heating is 50kHz to 200kHz.

6. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: During the melting process, the vacuum degree is 10 -3 Pa~10 -4 Pa, the pressure is 5kPa~10kPa, and the protective gas is argon.

7. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: 2N beryllium is a beryllium bead with a purity of 98% to 99%.

8. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: The method of 2N beryllium pretreatment includes the following steps: The 2N beryllium is pickled, washed with water and dried in sequence, and then metallic magnesium is added and heated at 800°C to 1000°C in a vacuum environment to obtain pretreated 2N beryllium, wherein the heating is heated to 800°C to 1000°C at a heating rate of 10°C / min to 30°C / min, kept warm for 1h to 3h, and then cooled to room temperature at a cooling rate of 5°C / min to 20°C / min.

9. The method for preparing high-purity beryllium rods by Czochralski method according to claim 8, characterized in that: The amount of metal magnesium used is 0.5wt.% to 1.8wt.% of the mass of 2N beryllium, and the vacuum degree during the heating process is not less than 10Pa.

10. The method for preparing high-purity beryllium rods by Czochralski method according to claim 1, characterized in that: The cooling of beryllium crystal rod is divided into three stages. The first stage is cooling to 700℃~900℃ at 0.6℃ / min~1℃ / min, the second stage is cooling to 400℃~600℃ at 1℃ / min~2℃ / min, the third stage is cooling to 150℃~300℃ at 2℃ / min~3℃ / min, and finally naturally cooling to room temperature.

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