A method for preparing high-purity beryllium rod by czochralski method

Abstract

The application belongs to the technical field of beryllium material preparation, and particularly relates to a method for preparing high-purity beryllium rods by a Czochralski method. The method comprises the following steps: taking 2N beryllium as raw material, heating and smelting the pretreated 2N beryllium to form a melt, and keeping the melt in a stable convection state; when slag is generated in the melt, inserting a beryllium seed crystal into the melt, reducing the temperature to 1000-1300 DEG C to make the slag solidify on the beryllium seed crystal to form a slag block, then taking out the slag block, and taking the slag block as a repeating unit until there is no slag block in the melt, and obtaining a beryllium melt; inserting a new beryllium seed crystal into the beryllium melt, and making the beryllium melt grow along the crystal direction of the seed crystal by a Czochralski process, and obtaining high-purity beryllium rods after cooling to room temperature. The method adopts the Czochralski process to prepare large-size high-purity beryllium rods with a purity of more than 99.9%, has excellent physical properties and high material utilization, can accurately control the size and realize large-scale production, and is suitable for high-end industrial fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of beryllium material preparation, and particularly relates to a method for preparing high-purity beryllium rods by a Czochralski method. BACKGROUND

[0002] Beryllium has unique characteristics such as low density, high melting point, high specific stiffness, good thermal conductivity and nuclear performance, and has irreplaceable importance in high-end fields such as aerospace, electronics and nuclear energy. The existing methods for preparing beryllium materials mainly include magnesium hot reduction and vacuum distillation methods. The primary beryllium obtained by the magnesium hot reduction method has low purity (≤98%); the high-purity beryllium with a purity of 99.99% can be obtained by the vacuum distillation method, but it is still difficult to remove impurities such as Fe and Si due to the limitation of vapor pressure, and the production capacity of a single device only reaches several hundred grams per day, which cannot meet the large-scale industrial application. Application No. CN202211291915.3 discloses a method for preparing high-purity beryllium. The method obtains high-purity beryllium with a purity of 99.99% by vacuum distillation of beryllium single element through a graphite condenser, 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 method for high-purity beryllium. The method uses a beryllium oxide crucible and a beryllium oxide condenser as carriers, and the beryllium raw material is subjected to two vacuum distillations and then subjected to corrosion cleaning to obtain high-purity beryllium with a purity of 4.5N-5.5N. The method is limited by the size of the beryllium oxide crucible and the beryllium oxide condenser, and cannot be used for mass production of beryllium rods. Therefore, the above-mentioned beryllium material preparation processes cannot meet the increasing demand for high-purity beryllium rods. SUMMARY

[0003] To solve the above problems, the application provides a method for preparing high-purity beryllium rods by a Czochralski method. In an inert gas or vacuum environment, a beryllium seed crystal is inserted into a melt, the heating temperature is reduced to 1000-1300℃, a slag block is formed on the beryllium seed crystal as a repeated unit, impurities in 2N beryllium are removed, and then a large-size high-purity beryllium rod with a purity of 99.9% or more is prepared by a Czochralski method process. The method 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 application solves the above technical problems through the following technical scheme.

[0005] The purpose of the application is to provide a method for preparing high-purity beryllium rods by a Czochralski method, which comprises the following steps:

[0006] S1, using 2N beryllium as raw material, the 2N beryllium is pretreated, and then the pretreated 2N beryllium is heated and melted to form a melt under a protective gas atmosphere and vacuum, and the melt is kept in a stable convection state.

[0007] S2, when the slag is generated in the melt, insert the beryllium seed crystal into the melt, reduce the heating temperature to 1000-1300℃ to make the slag solidify on the beryllium seed crystal to form a slag block, then lift the beryllium seed crystal out of the melt to take out the slag block.

[0008] S3, replace the new beryllium seed crystal, insert the beryllium seed crystal into the melt, reduce the heating temperature to 1000-1300℃ to make the slag solidify on the beryllium seed crystal to form a slag block, and repeat the unit until there is no slag block in the melt to obtain the beryllium melt.

[0009] S4, insert the 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, and cool to room temperature to obtain a high-purity beryllium rod with a purity of ≥99.9%.

[0010] Further, in the Czochralski process, it includes seeding, thinning, shoulder releasing and shoulder turning. When seeding and thinning, the temperature of the beryllium melt is reduced by 5-10℃, and then the pulling is performed. The pulling speed is from 0mm / min to 1.5mm / min-2mm / min. When shoulder releasing and shoulder turning, the rotation speed of the beryllium seed crystal is 5-15rpm, the pulling speed is reduced to 0.5mm / min-1mm / min, and the temperature of the beryllium melt is reduced to the diameter of the beryllium rod at a rate of 1℃ / h-2℃ / h.

[0011] Further, in the Czochralski process, the temperature of the beryllium melt is 1200-1400℃.

[0012] Further, the beryllium seed crystal uses a high-purity beryllium crystal rod with a

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

[0013] Further, the melting method is high-frequency induction heating or graphite resistance heater heating, and the melting temperature is 1200-1400℃, and the frequency of high-frequency induction heating is 50-200kHz.

[0014] Further, in the melting process, the vacuum degree is 10 -3 Pa-10 -4 Pa, the pressure is 5-10kPa, and the protective gas is argon.

[0015] Further, the 2N beryllium is a beryllium bead with a purity of 98-99%.

[0016] Further, the pretreatment method of 2N beryllium includes the following steps:

[0017] The 2N beryllium is sequentially subjected to acid washing, water washing and drying, then magnesium metal is added, and heating is carried out at 800-1000 DEG C under vacuum, to obtain pretreated 2N beryllium, wherein the heating is carried out at a temperature increasing rate of 10-30 DEG C / min to 800-1000 DEG C, and then cooled to room temperature at a temperature decreasing rate of 5-20 DEG C / min.

[0018] Further, the amount of magnesium metal is 0.5-1.8 wt.% of the mass of 2N beryllium, and the vacuum degree during heating is not less than 10 Pa.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (5) The method for preparing high-purity beryllium rod by the Czochralski method provided by the present application can reduce the heating temperature to 1000-1300 DEG C in inert gas or vacuum environment, and solidify the molten slag block on the beryllium seed crystal as a repeating unit to remove impurities in 2N beryllium, and then the Czochralski method process is adopted to prepare large-size high-purity beryllium rod with purity of more than 99.9%, which 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.

[0021] (6) The method for preparing high-purity beryllium rod by the Czochralski method provided by the present application can accurately control the temperature of beryllium melt and the pulling speed by the Czochralski method in inert gas or vacuum environment, accurately control the size and realize large-scale production, the Czochralski method can grow larger-size rod, is suitable for industrial production, can also realize single crystal structure, can reduce subsequent processing, single crystal material can reduce cutting and grinding processes, improve material utilization rate, has strong controllability, can accurately control the diameter and length of high-purity beryllium rod, meet different needs, and the single crystal material obtained by the Czochralski method has better physical properties, such as good plasticity and thermal conductivity, and is suitable for high-end applications.

[0022] (3) The method for preparing high-purity beryllium rod by the Czochralski method provided by the present application can prevent local overheating or temperature inhomogeneity by adjusting the convection state of the melt under the protection gas atmosphere and vacuum, ensure the stability and uniformity of the melt, improve the uniform growth of the beryllium rod structure in the crystal pulling process, and combine the high-purity magnesium chip oxygen removal technology to prepare large-size single crystal high-purity beryllium rod with purity of 99.999%. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0024] The existing methods for preparing beryllium materials mainly include magnesium thermal reduction method and vacuum distillation method, etc., but cannot meet the industrial application of large quantities. However, the above beryllium material preparation process cannot meet the increasing demand for high-purity beryllium rods. Therefore, it is of great significance to develop a new method for preparing high-purity beryllium.

[0025] Based on the above problems, the present application provides a method for preparing high-purity beryllium rods by the Czochralski method, comprising the following steps:

[0026] S1, using 2N beryllium as raw material, the 2N beryllium is pretreated, and then heated and melted to form a melt under the protection of gas atmosphere and vacuum, and the melt is kept in a stable convection state.

[0027] S2, when the slag is generated in the melt, the beryllium seed crystal is inserted into the melt, the heating temperature is reduced to 1000-1300 DEG C, the slag is solidified 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.

[0028] S3, replace the new beryllium seed crystal, and insert the beryllium seed crystal into the melt, reduce the heating temperature to 1000-1300 DEG 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, and the beryllium melt is obtained.

[0029] S4, the new beryllium seed crystal is inserted into the beryllium melt, and the Czochralski process is used to make the beryllium melt grow along the crystal direction of the seed crystal, and the high-purity beryllium rod is obtained after cooling to room temperature, and the purity of the beryllium material is greater than or equal to 99.9%.

[0030] The method for preparing high-purity beryllium rods by the Czochralski method provided by the present application inserts the beryllium seed crystal into the melt in an inert gas or vacuum environment, reduces the heating temperature to 1000-1300 DEG C, solidifies the slag on the beryllium seed crystal to form a slag block as a repeating unit, removes the impurities in the 2N beryllium, and then uses the Czochralski method process to prepare a large-size high-purity beryllium rod with a purity of 99.999%, which 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.

[0031] The application utilizes the way of the Czochralski process to prepare high-purity beryllium rods, effectively overcomes many challenges brought by the special properties of beryllium, and the prepared high-purity beryllium rods exhibit significant advantages in purity, crystal structure and internal quality, etc., and through the strong cold collection of beryllium vapor and the hazardous waste treatment, the harmless purification is truly realized, and the prepared beryllium material has good performance in the size specifications of 3 inches to 8 inches, and has wide application prospect.

[0032] In specific embodiments, in the Czochralski process, including seeding, thinning, shoulder formation and necking, the temperature of the beryllium melt is reduced by 5-10°C before pulling, the pulling rate is from 0 mm / min to 1.5-2 mm / min, the rotation rate of the beryllium seed crystal is 5-15 rpm, the pulling rate is reduced to 0.5-1 mm / min, and the temperature of the beryllium melt is reduced at a rate of 1-2°C / h until the diameter of the beryllium rod reaches the desired diameter.It should be noted that, in the Czochralski process, the temperature of the beryllium melt needs to be precisely controlled to maintain the temperature of the beryllium melt at 1200-1400°C, the temperature can be precisely controlled by adjusting the heating power, and the parameters in the crystal pulling process, such as the pulling speed, the rotation speed, the temperature, etc., are monitored in real time, and the process parameters are adjusted in time according to the monitoring results to ensure the smoothness of the crystal pulling process and the quality of the beryllium material; the Czochralski process includes the processes of seed introduction, thin diameter, shoulder formation, shoulder rotation, constant diameter, separation and cooling; in a specific embodiment, during the seed introduction and the thin diameter, the temperature of the crucible is reduced to 1250°C in a supercooled state, at the temperature in the supercooled state, the seed crystal is inserted into the melt in the crucible by the pulling rod, after the temperature of the crucible is stabilized, the temperature is reduced by 5-10°C, after the temperature reduction is completed, the temperature after the temperature reduction is maintained constant, the pulling rod is pulled, the pulling speed starts from 0 mm / min and reaches 1.5 mm / min, during the process from the start of the pulling at the pulling speed of 0 mm / min to the pulling speed of 1.5 mm / min, the melt is first gradually attached to the seed crystal and changes into a solid to complete the seed introduction and form a rod, and then the rod formed by the seed introduction enters the thin diameter process to form a thin neck, when the pulling speed reaches 1.5 mm / min, the thin diameter is completed; during the shoulder formation, the rotation speed of the beryllium seed crystal is 5-15 rpm, the pulling speed of the rotating pulling rod is reduced from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible is reduced at a rate of 1.5°C / h until the diameter of the rod is close to the target diameter; during the shoulder rotation and the constant diameter, when the diameter of the rod after the shoulder formation is close to the target diameter, the temperature of the crucible is increased by 1-1.5°C, the diameter of the rod no longer increases, the shoulder rotation is completed, and then the constant diameter stage is entered, the lifting of the crucible is started, the lifting speed of the crucible is 0.045 mm / min, the temperature of the crucible in the constant diameter stage is controlled at 1235-1240°C, with the straight growth of the rod pulled by the rotating pulling rod, the length of the rod in the constant diameter growth reaches the target length, and then the separation is entered; during the separation, the pulling rod is accelerated to pull or the crucible is accelerated to descend, and the rod is separated from the melt; during the cooling, three-stage cooling is performed, the first stage is reduced at a rate of 0.8°C / min to 800°C, the second stage is reduced from 800°C to 500°C at a rate of 1.2°C / min, and the third stage is reduced from 500°C to 200°C at a rate of 2.5°C / min, after being reduced to 200°C, the crucible heater is powered off, and the crucible is naturally cooled to room temperature.

[0033] It should be noted that the Czochralski process is carried out by using a Czochralski furnace equipment. The Czochralski furnace heats and melts the pretreated 2N beryllium to form a melt. During the Czochralski process, the pretreated 2N beryllium is placed in a smelting crucible, and then the smelting crucible is placed in the Czochralski furnace equipment. The smelting is carried out by using a high-frequency induction heating method or a graphite resistance heater heating method to heat and melt the pretreated 2N beryllium to form a melt. However, beryllium has a certain volatility at high temperature, and beryllium vapor is generated. Beryllium vapor is extremely harmful to the human body and can cause serious health problems such as berylliosis. Therefore, high-purity argon gas with a purity of ≥99.999% is filled into the Czochralski furnace chamber or area to maintain the pressure in the furnace at 5kPa-10kPa. A gas flow guiding device is arranged above the smelting crucible to form a stable laminar flow of argon gas uniformly covering the surface of the melt and the periphery of the growing beryllium material. The argon gas protection environment can act 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, thereby preventing oxidation and other pollution. On the other hand, due to the inertness of argon gas, it can effectively inhibit the diffusion of beryllium vapor, limit the beryllium vapor in a relatively small range, and reduce the risk of beryllium vapor volatilizing into the environment where the operator is located, thereby protecting the health and safety of the operator to the greatest extent. At the same time, a high-efficiency filter such as a bag-type dust collector or a ceramic filter is installed in the tail gas discharge pipeline. The bag-type dust collector uses the filtering effect of fiber fabric. When the tail 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 good filtering effect on the dust in the high-temperature Czochralski furnace tail gas. By regularly cleaning or replacing the filter, the emission of beryllium dust particles can be effectively avoided.

[0034] It should be noted that the gas flow guiding device is an equipment with guide vanes inside. The angle of the guide vanes can be adjusted between 30 degrees and 60 degrees to optimize the coverage effect of the argon laminar flow. The gas flow guiding device is made of stainless steel material to form a stable laminar flow of the protective atmosphere argon gas. The gas flow velocity is 0.5m / s-2m / s, which uniformly covers the surface of the melt and the periphery of the growing beryllium material. The high-purity argon gas needs to be treated by deoxidation, dehydration and decarburization before being filled into the Czochralski furnace, wherein the oxygen content is less than 1ppm, the water content is less than 1ppm, and the carbon content is less than 0.5ppm.

[0035] It should be noted that the smelting 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 0.5mm-2mm. The boron nitride coating is prepared by chemical vapor deposition method, the deposition temperature is 800℃-1200℃, the reaction gas is ammonia and borane, the flow ratio is 5-15:1, the deposition pressure is controlled at 1kPa-5kPa, and the reaction time is 1h-5h. In a specific embodiment, the boron nitride coating on the inner wall of the quartz crucible has a thickness of 1mm, which is prepared by chemical vapor deposition method, the deposition temperature is 1000℃, the reaction gas is ammonia and borane, the flow ratio is 10:1, the deposition pressure is controlled at 3kPa, and the reaction time is 2h.

[0036] Further, the beryllium seed crystal adopts a high-purity beryllium crystal bar with a

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

[0037] It should be noted that when the 2N beryllium is completely melted, the impurity content of the 2N beryllium raw material is relatively high, so the impurities need to be removed, and the formation 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 is formed on the surface of the melt, the seed crystal is slowly inserted into the melt, and when the slag solidifies along the seed crystal to form a pot-shaped slag block, it is quickly lifted to the sub-chamber, the lifting speed is 10mm / s-30mm / s, the isolation valve plate of the pulling furnace is opened, vacuum is drawn for 10min, then the melt block is taken out, and then the seed crystal is loaded again, the slag is extracted, and the process is repeated 2-3times until no slag is observed by CCD.

[0038] In a specific embodiment, the smelting method is high-frequency induction heating or graphite resistance heater heating, and the smelting temperature is 1200℃-1400℃, and the high-frequency induction heating frequency is 50kHz-200kHz.

[0039] It should be noted that during the crystal pulling process, a temperature compensation device is arranged around the crucible, which can compensate for the temperature difference between the edge and the center area of the crucible, and the temperature control accuracy is ±5℃. The high-precision sensor (accuracy not less than 0.1℃, 0.05mm / min and 0.1rpm respectively corresponding to temperature, pulling speed and rotation speed) is used to monitor the parameters in the crystal pulling process in real time.

[0040] In a specific embodiment, the vacuum degree during smelting is 10 -3 Pa-10 -4 Pa, the pressure is 5kPa-10kPa, and the protective gas is argon.

[0041] It should be noted that, in the vacuum melting process, due to the high melting point of beryllium (about 1287℃), it is necessary to provide high enough energy to melt the beryllium raw material. The present application adopts high frequency induction heating or graphite resistance heater heating and other heating methods to carry out smelting operation in a high vacuum environment. The maintenance of high vacuum environment (the vacuum degree generally requires to reach 10 -3 Pa~10 -4 Pa) is crucial, which not only can reduce the contact of the melt with the gas impurities in the surrounding environment, avoid oxidation and other pollution, but also can effectively reduce the possibility of chemical reaction of beryllium with other substances at high temperature. Under such vacuum conditions, the beryllium raw material is gradually heated and melted to form a uniform melt. In this process, by accurately controlling the heating power and the magnetic field strength (for high frequency induction heating), the convection state of the melt can be adjusted to prevent local overheating or temperature unevenness, ensuring the stability and uniformity of the melt, which has a key influence on the uniform growth of the beryllium rod structure in the subsequent crystal pulling process.

[0042] It should be noted that, in the high frequency induction heating process, the coil of the high frequency induction heating is made of copper material, the number of turns is 10 turns to 50 turns, and the distance between the coil and the crucible is 5cm to 20cm. In a specific embodiment, the number of turns is 30 turns, and the distance between the coil and the crucible is 10cm.

[0043] It should be noted that, in the vacuum melting process, the strong cooling device is connected to the exhaust port of the evacuation system of the Czochralski furnace. The strong cooling device uses liquid argon cooling or other high-efficiency cooling medium, the cooling power of the strong cooling device is not less than 10kW, the temperature of the cooling medium is maintained below-150℃, the cooling medium is liquid argon, which can ensure that the beryllium vapor passing through the exhaust port is rapidly cooled to solid state. A filtering unit is arranged between the strong cooling device and the evacuation system, which can filter out beryllium particles with particle size greater than 1 micron, and the filtering efficiency is not less than 95%. The solid state collected by the strong cooling device is a dangerous waste, which is treated according to the relevant dangerous waste treatment standard.

[0044] In a specific embodiment, the 2N beryllium is beryllium beads with purity of 98% to 99%.

[0045] In a specific embodiment, the pretreatment method of 2N beryllium includes the following steps: the 2N beryllium is sequentially subjected to acid washing, water washing and drying, then magnesium metal is added, and heating is carried out at 800℃ to 1000℃ in a vacuum environment, to obtain pretreated 2N beryllium. The heating is carried out at a heating rate of 10℃ / min to 30℃ / min to 800℃ to 1000℃, and then cooled to room temperature at a cooling rate of 5℃ / min to 20℃ / min.

[0046] It is to be noted that the acid washing, water washing and drying are repeated alternately for at least three times to remove the impurities, oxides and other contaminants that can be attached to the surface, and the magnesium metal is used for oxygen removal; the acid solution (such as hydrochloric acid solution with a mass concentration of 5% to 15%) is used for the acid washing, the soaking time is 10 min to 30 min for each time, and the deionized water with a flow rate of 1 L / min to 5 L / min is used for flushing after each cleaning, the flushing time is 5 min to 15 min, and after the cleaning is completed, the drying treatment is performed, the vacuum drying is used for the drying treatment, the vacuum degree is 10 Pa to 100 Pa, and the drying time is 30 min to 120 min. In a specific embodiment, the soaking time is 30 min for each time, the deionized water with a flow rate of 3 L / min is used for flushing after each cleaning, the flushing time is 10 min, and after the cleaning is completed, the drying treatment is performed, the vacuum drying is used for the drying treatment, the vacuum degree is 50 Pa, and the drying time is 60 min.

[0047] In a specific embodiment, the amount of the magnesium metal is 0.5 wt.% to 1.8 wt.% of the mass of the beryllium, and the vacuum degree during the heating is not less than 10 Pa.

[0048] In a specific embodiment, the cooling of the beryllium crystal bar is divided into three stages, the first stage is to reduce the temperature to 700°C to 900°C at a rate of 0.6°C / min to 1°C / min, the second stage is to reduce the temperature to 400°C to 600°C at a rate of 1°C / min to 2°C / min, the third stage is to reduce the temperature to 150°C to 300°C at a rate of 2°C / min to 3°C / min, and finally, the natural cooling is performed to room temperature.

[0049] In a specific embodiment, the beryllium seed crystal is prepared by mechanical processing of a high-purity beryllium bar, and is generally prepared by forging or rolling. It is to be noted that the forging or rolling is used to prepare the beryllium seed crystal from the beryllium crystal bar, and the beryllium seed crystal has a good crystal structure and internal quality, and the dislocation density of the crystal structure is not higher than 10 6 / cm 2, and the grain boundary angle deviation of the crystal structure is not more than ±5 degrees to ensure the uniformity and stability of the crystal structure. The specific manner of the forging method is that the high-purity beryllium rod is heated to 500-800°C, and then is forged in a mold, the deformation and preferred orientation of the grains in the beryllium material are caused by controlling the forging ratio in the range of 3-8, the forging temperature precision of ±10°C, and the forging speed in the range of 10-50 mm / s, and then annealing treatment is performed, the annealing temperature is 400-600°C, the annealing time is 1-3 h, the recrystallization process is promoted, the grains grow along the

[0001] crystal direction, and thus the beryllium seed crystal with a certain

[0001] crystal direction texture is obtained. The specific manner of the rolling method is that the high-purity beryllium rod is heated to 400-700°C, and then is rolled, the deformation and preferred orientation of the grains in the beryllium material are caused by multi-pass rolling (5-15 passes) and controlling the rolling process parameters, the rolling pressure is 100-500 MPa, and the rolling speed is 5-30 m / min, the

[0001] crystal direction texture is formed, and the beryllium seed crystal is obtained. The beryllium seed crystal after rolling is subjected to annealing treatment, the annealing temperature is 300-500°C, the annealing time is 0.5-2 h, the structure and performance thereof are further improved, the

[0001] crystal direction texture degree is increased, and thus the beryllium seed crystal with a certain

[0001] crystal direction texture is obtained. In a preferred embodiment, the beryllium seed crystal is prepared by the forging method using the high-purity beryllium rod, the high-purity beryllium rod is heated to 700°C, and then is forged in a mold, the deformation and preferred orientation of the grains in the beryllium material are caused by controlling the forging ratio of 5, the forging temperature precision of ±10°C, and the forging speed in the range of 30 mm / s, and then annealing treatment is performed, the annealing temperature is 500°C, the annealing time is 2 h, the recrystallization process is promoted, the grains grow along the

[0001] crystal direction, and thus the beryllium seed crystal with a certain

[0001] crystal direction texture is obtained.

[0050] It should be noted that the beryllium rod with a certain

[0001] crystal direction texture is removed from the surface of the oxide layer and the possible defect part by using a diamond tool at a cutting speed of 50-200 m / min, the edge radius of the diamond tool is 10-50 μm, the cutting depth is 0.1-0.5 mm, then ultrasonic cleaning is performed, the cleaning frequency is 20-50 kHz, the cleaning time is 10-30 min, and then drying treatment is performed, the drying temperature is 50-100°C, and thus the Ф12.5 mm long 150 mm beryllium seed crystal is obtained. In a specific embodiment, the diamond tool is used to remove the surface oxide layer and the possible defect part 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.

[0051] The following is further illustrated by specific examples.

[0052] Example 1

[0053] A method for preparing high-purity beryllium rods by the Czochralski method, comprising the following steps:

[0054] S1, select beryllium beads with a purity of 98% as the beryllium raw material, use a 10% mass concentration hydrochloric acid solution and deionized water to clean it alternately four times to remove possible surface-attached impurities, oxides and other contaminants, then add 0.6wt.% of 99.99% magnesium chips to the beryllium raw material and mix uniformly, heat at 1000℃ in a vacuum environment, wherein the heating is at a heating rate of 20℃ / min to 1000℃, hold for 2h, then cool at a cooling rate of 10℃ / min to room temperature, to obtain pretreated 98% beryllium beads.

[0055] S2, select a quartz crucible, coat a 1mm thick boron nitride coating on the inner wall, place the crucible in the Czochralski furnace, after sealing the furnace, vacuumize to 10 -4 Pa, then fill in high-purity argon to maintain the pressure in the furnace at 8kPa, and ensure that the strong cooling device (using liquid argon cooling, the temperature can be reduced to -196℃) at the exhaust port of the evacuation system is operating normally.

[0056] S3, place the pretreated 98% beryllium beads into the quartz crucible, melt the beryllium raw material by high-frequency induction heating to completely melt the beryllium beads to form a uniform melt, control the melting temperature at 1300℃ to ensure the stability and uniformity of the melt, when a large amount of slag is produced in the melt, lower a

[0001] crystal direction beryllium seed crystal into the melt, the depth of insertion is 10mm, the speed during insertion is 3mm / min, then lower the heating temperature to 1100℃ to make the slag solidify rapidly and rise to the sub-chamber, open the isolation valve plate of the Czochralski furnace, vacuumize for 10min, then lift the beryllium seed crystal out of the melt to take out the slag block.

[0057] S4, replace the new beryllium seed crystal, insert it into the melt, lower the power to make the slag solidify on the beryllium seed crystal to form a slag block, which is the repeating unit, repeat 3 times until there is no slag block in the melt, to obtain a pure beryllium melt.

[0058] S5, install a new beryllium seed crystal to immerse into the melt from the surface of the melt, the immersion depth is 10mm, then pull the crystal rod upward for straight pulling to grow the rod to form a high-purity beryllium rod, the rod growth includes the processes of seeding, fine diameter, shoulder expansion, shoulder rotation, constant diameter, detachment and temperature reduction.

[0059] Before seeding, the crystal pulling rod and the crucible are started to rotate in opposite directions, the rotation speed of the crucible is 2 rpm, and the rotation speed of the crystal pulling rod is 5 rpm. During seeding and thinning, the temperature of the crucible is reduced to 1250℃ in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5℃. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process from the start of pulling at 0 mm / min to the pulling speed reaching 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0060] During the seeding and thinning, the temperature of the crucible is reduced to 1250℃ in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5℃. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process from the start of pulling at 0 mm / min to the pulling speed reaching 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0061] During the shouldering, 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 reduced at a rate of 1.5℃ / h until the diameter of the rod is increased to close to 76.2mm (3 inches).

[0062] During the shouldering and the constant-diameter process, when the diameter of the rod after the shouldering is increased to close to 76.2mm (3 inches), the temperature of the crucible is increased by 1℃, and the diameter of the rod is no longer increased. The shouldering is completed, and then the constant-diameter process is entered. The lifting of the crucible is started, and the lifting speed of the crucible is 0.045 mm / min. During the constant-diameter process, the temperature of the crucible is controlled at 905℃-909℃. With the pulling of the crystal pulling rod rotating at 5 rpm, the rod grows straight. When the length of the constant-diameter growth of the rod reaches 203.2mm, the rod is separated from the melt to form a beryllium rod.

[0063] S6, after the rod growth is completed, the heating, cooling, and opening of the growth furnace are stopped, and the rod is cut from the crystal pulling rod. During the cooling, three-stage cooling is performed. In the first stage, the temperature is reduced at a rate of 0.8℃ / min to 800℃. In the second stage, the temperature is reduced at a rate of 1.2℃ / min from 800℃ to 500℃. In the third stage, the temperature is reduced at a rate of 2.5℃ / min from 500℃ to 200℃. After the temperature is reduced to 200℃, the crucible heater is powered off, and the crucible is naturally cooled to room temperature. After the cooling and before the growth furnace is opened, the argon gas is turned off. The high-purity beryllium rod has a diameter of 3 inches (about 76.2mm) and a length of up to 8 inches (about 203.2mm). As shown in Table 1, the purity of the high-purity beryllium rod reaches 99.9%, the crystal structure is uniform, and there is no obvious defect.

[0064] Table 1 Purity results of the beryllium rod prepared in Example 1

[0065]

[0066] Example 2

[0067] A method for preparing high-purity beryllium rods by the Czochralski method, comprising the following steps:

[0068] S1, select beryllium beads with a purity of 99% as beryllium raw material, use a 10% mass concentration hydrochloric acid solution and deionized water to clean it alternately four times to remove possible surface-attached impurities, oxides and other contaminants, then add 0.6wt.% of 99.99% magnesium chips to the beryllium raw material and mix uniformly, heat at 1000℃ in a vacuum environment, the heating is at a heating rate of 20℃ / min to 1000℃, keep for 2h, then cool at a cooling rate of 10℃ / min to room temperature, to obtain pretreated 99% beryllium beads.

[0069] S2, select a quartz crucible, coat a 1mm thick boron nitride coating on the inner wall, place the crucible in the Czochralski furnace, after sealing the furnace, vacuumize to 10 -4 Pa, then fill in high-purity argon to maintain the pressure in the furnace at 8kPa, and ensure that the strong cooling device (using liquid argon cooling, the temperature can be reduced to -196℃) at the exhaust port of the evacuation system is operating normally.

[0070] S3, put the pretreated 99% beryllium beads into the quartz crucible, use a graphite resistance heater to heat the beryllium raw material to melt it completely to form a uniform melt, the melting temperature is controlled at 1280℃, the convection state of the melt can be adjusted to prevent local overheating or temperature unevenness, to ensure the stability and uniformity of the melt, when a large amount of slag is produced in the melt, lower a beryllium seed crystal with

[0001] crystal orientation into the melt, the insertion depth of the beryllium seed crystal is 10mm, the speed during insertion is 3mm / min, then lower the heating temperature to 1100℃ to make the slag solidify quickly and rise to the sub-chamber, the lifting speed is 20mm / s, open the isolation valve plate of the Czochralski furnace, vacuumize for 10min, then lift the beryllium seed crystal out of the melt to take out the slag block.

[0071] S4, replace the beryllium seed crystal with a new one, insert it into the melt, lower the power to make the slag solidify on the beryllium seed crystal to form a slag block, which is the repeating unit, repeat 2 times until there is no slag block in the melt, to obtain a beryllium melt.

[0072] S5, install a new beryllium seed crystal to immerse into the melt from the surface of the melt, the immersion depth is 10mm, then pull the crystal rod upward for straight pulling to grow a rod to form a high-purity beryllium rod, the rod growth includes the processes of seeding, fine diameter, shoulder expansion, shoulder rotation, constant diameter, detachment and temperature reduction.

[0073] Before seeding, the crystal pulling rod and the crucible are started to rotate in opposite directions, the rotation speed of the crucible is 2 rpm, and the rotation speed of the crystal pulling rod is 5 rpm. During seeding and thinning, the temperature of the crucible is reduced to 1250°C in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5°C. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process from the start of pulling at 0 mm / min to the pulling speed reaching 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0074] During the seeding and thinning, the temperature of the crucible is reduced to 1250°C in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5°C. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process from the start of pulling at 0 mm / min to the pulling speed reaching 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0075] During the shouldering, 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 reduced at a rate of 1.5°C / h, until the diameter of the rod is increased to close to 152.4 mm (6 inches).

[0076] During the shouldering and the constant-diameter process, when the diameter of the shouldered rod is increased to close to 152.4 mm (6 inches), the temperature of the crucible is increased by 1°C, and the diameter of the rod is no longer increased. The shouldering is completed, and then the constant-diameter process is entered. The lifting of the crucible is started, and the lifting speed of the crucible is 0.045 mm / min. During the constant-diameter process, the temperature of the crucible is controlled to be in the range of 905°C to 909°C. With the pulling of the crystal pulling rod rotating at 5 rpm, the rod grows straight. When the length of the constant-diameter growth of the rod reaches 203.2 mm, the rod is separated from the melt to form a high-purity beryllium rod.

[0077] S6, after the growth of the rod is completed, the heating, the temperature reduction, and the opening of the growth furnace are stopped, and the rod is cut from the crystal pulling rod. During the temperature reduction, the temperature reduction is performed in three stages. In the first stage, the temperature is reduced to 800°C at a rate of 0.8°C / min. In the second stage, the temperature is reduced from 800°C to 500°C at a rate of 1.2°C / min. In the third stage, the temperature is reduced from 500°C to 200°C at a rate of 2.5°C / min. After the temperature is reduced to 200°C, the crucible heater is powered off, and the crucible is naturally cooled to room temperature. After the temperature reduction and before the opening of the growth furnace, the argon gas is turned off. The high-purity beryllium rod has a diameter of 6 inches (about 152.4 mm) and a length of up to 8 inches (about 203.2 mm). As shown in Table 2, the purity of the high-purity beryllium rod reaches 99.999%, and the crystal structure is uniform without obvious defects.

[0078] Table 2 Purity results of the beryllium rod prepared in Example 2

[0079]

[0080] Example 3

[0081] A method for preparing high-purity beryllium rods by the Czochralski method, comprising the following steps:

[0082] S1, selecting cutting waste produced in machine tool processing with a purity of 98% as beryllium raw material, using a hydrochloric acid solution with a mass concentration of 10% and deionized water to clean it alternately four times to remove possible impurities, oxides and other contaminants attached to the surface, then adding 0.8wt.% of 99.99% magnesium chips to the beryllium raw material and uniformly mixing, heating at 1000°C in a vacuum environment, wherein the heating is heated to 1000°C at a heating rate of 20°C / min, and then cooled to room temperature at a cooling rate of 10°C / min, to obtain pretreated beryllium cutting waste.

[0083] S2, selecting a quartz crucible, coating a 1mm thick boron nitride coating on the inner wall, placing the crucible in a Czochralski furnace, and after sealing the furnace body, vacuumizing to 10 -4 Pa, then filling high-purity argon to maintain the pressure in the furnace at 8kPa, and ensuring that the strong cooling device (using liquid argon cooling) at the exhaust port of the evacuation system is operating normally.

[0084] S3, placing the pretreated beryllium cutting waste into the quartz crucible, using a graphite resistance heater to heat the beryllium raw material to melt it, making the beryllium beads completely melt to form a uniform melt, controlling the melting temperature at 1350°C, adjusting the magnetic field strength to keep the melt in a stable convective state, ensuring the stability and uniformity of the melt, when a large amount of slag is produced in the melt, lowering a beryllium seed crystal with a

[0001] crystal orientation into the melt, the depth of insertion of the beryllium seed crystal is 10mm, the speed during insertion is 3mm / min, then lowering the heating temperature to 1100°C to make the slag solidify rapidly and rise to the sub-chamber, the lifting speed is 20mm / s, opening the isolation valve plate of the Czochralski furnace, vacuumizing for 10min, then lifting the beryllium seed crystal out of the melt to take out the slag block.

[0085] S4, replacing the new beryllium seed crystal and inserting it into the melt, reducing the power to make the slag solidify on the beryllium seed crystal to form a slag block, which is the repeating unit, repeating 3 times until there is no slag block in the melt, to obtain a beryllium melt.

[0086] S5, installing a new beryllium seed crystal to immerse it into the melt from the surface of the melt, the immersion depth is 10mm, then pulling the crystal rod upward to perform the Czochralski method to grow the rod to form a crystal rod, the rod growth includes the processes of seeding, fine diameter, shoulder expansion, shoulder rotation, constant diameter, detachment, and temperature reduction.

[0087] Before seeding, the crystal pulling rod and the crucible are started to rotate in opposite directions, the rotation speed of the crucible is 2 rpm, and the rotation speed of the crystal pulling rod is 5 rpm. During seeding and thinning, the temperature of the crucible is reduced to 1250℃ in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5℃. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process of pulling at a speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0088] During the seeding and thinning, the temperature of the crucible is reduced to 1250℃ in a supercooling state. At this temperature, the seed crystal is inserted into the melt in the crucible by the crystal pulling rod. After the temperature of the crucible is stabilized, the temperature is reduced by 5℃. After the temperature reduction is completed, the temperature is maintained constant. The crystal pulling rod is pulled at a pulling speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min. During the process of pulling at a speed starting from 0 mm / min until the pulling speed reaches 1.5 mm / min, the melt is first gradually attached to the seed crystal and is converted into a solid, the seeding is completed, and a rod is formed. Then, the rod formed by seeding enters the thinning process. When the pulling speed reaches 1.5 mm / min, the thinning is completed.

[0089] During the shouldering, the pulling speed of the rotating crystal pulling rod 3 is reduced from 1.5 mm / min to 0.4 mm / min, and the temperature of the crucible 1 is reduced at a rate of 1.5℃ / h until the diameter of the rod is increased to close to 203.2 mm.

[0090] During the shouldering and the constant-diameter process, when the diameter of the shouldering rod is increased to close to 203.2 mm, the temperature of the crucible is increased by 1℃, and the diameter of the rod is no longer increased. The shouldering is completed, and then the constant-diameter process is entered. The lifting of the crucible is started, and the lifting speed of the crucible is 0.045 mm / min. During the constant-diameter process, the temperature of the crucible is controlled at 905℃-909℃. With the pulling of the crystal pulling rod rotating at 5 rpm, the rod grows straight. When the length of the constant-diameter growth of the rod reaches 203.2 mm, the rod is separated from the melt to form a high-purity beryllium rod.

[0091] S6, after the rod growth is completed, the heating, cooling, and opening of the growth furnace are stopped, and the crystal rod is cut from the crystal pulling rod. During the cooling, three-stage cooling is performed. In the first stage, the temperature is reduced at a rate of 0.8℃ / min to 800℃. In the second stage, the temperature is reduced at a rate of 1.2℃ / min from 800℃ to 500℃. In the third stage, the temperature is reduced at a rate of 2.5℃ / min from 500℃ to 200℃. After the temperature is reduced to 200℃, the crucible heater is powered off, and the crucible is naturally cooled to room temperature. After the cooling, the argon gas is turned off before the growth furnace is opened. The high-purity beryllium rod has a diameter of 8 inches (about 203.2 mm) and a length of 8 inches (about 203.2 mm). As shown in Table 3, the purity of the high-purity beryllium rod reaches more than 99.9%, and the crystal structure is uniform without obvious defects.

[0092] Table 3 Purity results of the beryllium rod prepared in Example 3

[0093]

[0094] It is to be understood that the numerical ranges recited herein are intended to include every integer value within the range and any fraction of the values within the range. The preferred embodiments of the application are described herein with the understanding that the present application is given only by way of example and that modifications and variations of the preferred embodiments are possible using available technology and materials. It is intended that the present application encompass all such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0095] It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

Claims

1. A method for preparing high-purity beryllium rods using the Czochralski method, characterized in that, Includes the following steps: Using 2N beryllium as raw material, after pretreatment of 2N beryllium, the pretreated 2N beryllium is heated and melted under a protective gas atmosphere and vacuum to form a melt, and the melt is kept 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 reduced to 1000℃~1300℃ to allow the slag to solidify on the beryllium seed crystal to form a slag block. Then the beryllium seed crystal is lifted out of the melt and the slag block is removed. Replace the beryllium seed crystal with a new one and insert it into the melt. Lower the heating temperature to 1000℃~1300℃ to allow the slag to solidify on the beryllium seed crystal and form a slag block. Repeat this process until there is no slag block in the melt to obtain beryllium melt. 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 5mm to 15mm, and the insertion speed is 1mm / min to 5mm / min. A new beryllium seed crystal is inserted into the beryllium melt, and the beryllium melt is grown along the crystal orientation of the seed crystal using a Czochralski process. After cooling to room temperature, a high-purity beryllium rod with a purity of ≥99.9% is obtained. During the Czochralski process, the temperature of the beryllium melt is 1200℃~1400℃; The Czochralski process includes seeding, diameter reduction, shoulder formation, and shoulder rotation. During seeding and diameter reduction, the temperature of the beryllium melt is reduced by 5°C to 10°C before pulling. The pulling speed is from 0 mm / min to 1.5 mm / min to 2 mm / min. During shoulder formation and shoulder rotation, the rotation speed of the beryllium seed crystal is 5 rpm to 15 rpm, and the pulling speed is reduced to 0.5 mm / min to 1 mm / min. The temperature of the beryllium melt is reduced at 1°C / h to 2°C / h until the diameter of the beryllium rod reaches the required diameter.

2. The method for preparing high-purity beryllium rods by the Czochralski method according to claim 1, characterized in that, The melting process is carried out using either high-frequency induction heating or graphite resistance heater heating. The melting temperature is 1200℃~1400℃, and the high-frequency induction heating frequency is 50kHz~200kHz.

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

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

5. The method for preparing high-purity beryllium rods by the Czochralski method according to claim 1, characterized in that, The pretreatment method for 2N beryllium includes the following steps: 2N beryllium was sequentially acid-washed, water-washed, and dried. Then, metallic magnesium was added, and the mixture was heated in a vacuum environment at 800℃~1000℃ to obtain pretreated 2N beryllium. The heating was carried out at a heating rate of 10℃ / min~30℃ / min to 800℃~1000℃, held at that temperature for 1h~3h, and then cooled to room temperature at a cooling rate of 5℃ / min~20℃ / min.

6. The method for preparing high-purity beryllium rods by the Czochralski method according to claim 5, characterized in that, The amount of metallic magnesium 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.

7. The method for preparing high-purity beryllium rods by the Czochralski method according to claim 1, characterized in that, The cooling process is divided into three stages. The first stage cools the temperature to 700℃ to 900℃ at a rate of 0.6℃ / min to 1℃ / min. The second stage cools the temperature to 400℃ to 600℃ at a rate of 1℃ / min to 2℃ / min. The third stage cools the temperature to 150℃ to 300℃ at a rate of 2℃ / min to 3℃ / min. Finally, the temperature is allowed to cool naturally to room temperature.

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