A method for preparing large-size high-purity metal beryllium ingot by two-step method

Abstract

The application discloses a method for preparing large-size high-cleanliness metal beryllium ingot by adopting a two-step method. The method comprises the following steps: pretreating beryllium beads to obtain clean beryllium beads; preparing a coarse beryllium ingot by vacuum induction melting; performing vacuum suspension melting to draw the ingot; and finally performing surface processing. The method is characterized in that: firstly, volatile impurities are efficiently removed and densification is achieved by vacuum induction melting, thereby avoiding splashing and suspension failure caused by directly suspending and melting the beryllium beads; and then, the suspension melting ingot-drawing technology is used to eliminate crucible pollution, and combined with directional solidification continuous production, the large-size high-cleanliness metal beryllium ingot without casting defects, with a density greater than or equal to 99% and with extremely low impurities is successfully prepared, thereby breaking through the size limitation of the traditional process and improving the production efficiency and product quality.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal metallurgy, specifically to a two-step method for preparing large-size, high-purity beryllium ingots. Background Technology

[0002] Metallic beryllium possesses a series of outstanding physical properties, including low density, high elastic modulus, excellent specific stiffness, and small thermal neutron absorption cross section, making it irreplaceable in high-end technology fields such as aerospace, nuclear reactors, inertial navigation systems, and X-ray windows. However, the metallurgical preparation process of metallic beryllium is complex and lengthy, and its purity and metallurgical quality directly affect subsequent processing performance and final service performance.

[0003] Currently, the mainstream industrial route for producing metallic beryllium is as follows: ammonium fluoride crystals are prepared from beryllium hydroxide, which are then decomposed by heating to obtain beryllium fluoride (BeF2). The beryllium fluoride is then reduced to metallic beryllium beads using a magnesothermal reduction method. Beryllium beads produced by the magnesothermal reduction method contain a large number of impurities, with a magnesium content as high as 0.6%–0.8%. They also contain a certain amount of fluoride slag (mainly including BeF2 and MgF2) and other metallic impurities (such as Fe, Al, Si, Cr, Ni, Cu, Mn, etc.), and must undergo subsequent refining and purification before they can be used to produce beryllium materials.

[0004] Traditional processes employ vacuum induction melting to refine beryllium beads. Beryllium beads are placed in a beryllium oxide crucible and heated to 1623–1723 K in a vacuum induction furnace. Taking advantage of the low boiling points of impurities such as Mg, Zn, and F in the beryllium beads, these impurities are removed through vacuum volatilization at temperatures much lower than the melting point of beryllium. After melting, the molten beryllium is poured into a graphite mold and allowed to cool and solidify naturally into ingots. However, this method, relying on graphite mold casting followed by natural cooling, results in slow cooling rates, leading to coarse ingot grains. The grain size deteriorates further with increasing ingot size, severely impacting the mechanical properties of the beryllium material. Furthermore, the solidification shrinkage during cooling creates numerous defects both internally and externally, failing to meet the requirements of subsequent beryllium processing. Traditional processes also employ an intermittent "one furnace, one ingot" production method, casting only one ingot per melting cycle, resulting in low production efficiency. Additionally, the ingot size is limited by crucible capacity and mold specifications, making it difficult to meet the demand for large-sized beryllium ingots. Furthermore, metallic impurities such as Fe, Al, Si, Cr, Ni, Cu, and Mn in beryllium beads cannot be completely removed during vacuum induction melting.

[0005] In recent years, vacuum suspension melting technology has demonstrated significant advantages in the preparation of high-purity, reactive metals. Suspension melting utilizes the electromagnetic force generated by a high-frequency electromagnetic field to suspend the molten metal in a cold crucible, achieving non-contact melting and fundamentally avoiding contamination of the melt by the crucible material. Studies have shown that a combination of high vacuum and semi-continuous ingot pulling, using induction heating and cold crucible melting, can achieve large-scale preparation of high-purity metals.

[0006] However, directly processing beryllium beads using vacuum suspension melting alone has the following drawbacks: the beryllium beads have a high magnesium content and a large amount of fluoride slag. Under suspension melting conditions, the concentrated volatilization of a large number of low-boiling-point impurities will destroy the suspension stability of the melt, causing violent splashing and leading to interruption of the melting process or even equipment damage. In addition, beryllium beads are granular and irregularly shaped, with low apparent density, limiting the amount of material that can be loaded. The processing capacity of a single suspension melting operation is limited, making it uneconomical for large-scale industrial production.

[0007] Therefore, there is an urgent need to develop a method that can effectively remove volatile impurities such as Mg, BeF2, and MgF2, as well as metallic impurities such as Fe, Al, Si, Cr, Ni, Cu, and Mn from beryllium beads, while obtaining high-density, large-size, and high-purity beryllium ingots, and is suitable for continuous industrial production. Summary of the Invention

[0008] The purpose of this invention is to provide a two-step method for preparing large-size, high-purity beryllium metal ingots, in order to solve the problems of direct suspension melting of beryllium beads, which easily leads to splashing and suspension failure, as well as the problems of coarse grains, numerous casting defects, and inability to remove impurities to the extreme in traditional single vacuum induction melting.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A two-step method for preparing large-size, high-purity beryllium ingots includes the following steps:

[0011] S1. The beryllium beads produced by the magnesia reduction method are sequentially washed, dried, magnetically separated and graded to obtain clean beryllium beads;

[0012] S2. The cleaned beryllium beads are subjected to vacuum induction melting, and the furnace is evacuated to a pressure ≤1×10⁻⁶. -2 Pa, then argon gas is introduced to bring the furnace pressure to 100-800 Pa; first, the temperature is raised to 700-750°C at a rate of 30-50°C / min and held for 15-30 minutes, then raised to 1350-1450°C at a rate of 50-150°C / min and held for 30-90 minutes; after melting, the beryllium liquid is poured into a casting and allowed to cool and solidify naturally to obtain a crude beryllium ingot;

[0013] S3. After surface cleaning, the crude beryllium ingot is subjected to vacuum suspension melting, and the furnace is evacuated to a pressure ≤5×10. -3Pa, and then argon gas is introduced into the furnace to a pressure of 0.1-5 Pa; the induction power is started, and first, the power is increased to 20-40 kW for 2-4 minutes, then the power is continuously increased to 60-100 kW for 4-7 minutes, and finally, the power is increased to 180-240 kW for 5-8 minutes for suspension smelting refining, and the refining temperature is controlled at 1350-1450 DEG C; after the refining is completed, the smelting power is decreased to 160-190 kW, the dummy bar drawing device is started, the dummy bar head is moved downward at a speed of 3-15 mm / min for drawing, and the coarse beryllium ingot is continuously added into the suspension smelting zone through the vacuum charging bin after the drawing starts, so that the suspension smelting liquid surface is always maintained unchanged, and the beryllium ingot is obtained by cooling;

[0014] S4, the beryllium ingot obtained in step S3 is subjected to surface processing to remove the surface oxide layer, and a finished high-cleanliness metal beryllium ingot is obtained.

[0015] Further, in step S1, the beryllium beads have a particle size range of 3-15 mm and contain the following impurities by weight percentage: Mg 0.6%-0.8%, BeF2 0.1%-0.3%, MgF2 0.1%-0.3%, Al 0.08-0.11%, Cr 0.02-0.03%, Cu 0.012-0.015%, Fe 0.046-0.127%, Mn 0.0077-0.015%, Ni 0.0037-0.005%, and Si 0.0096-0.023%.

[0016] Further, in step S2, the crucible used in the vacuum induction melting is made of beryllium oxide.

[0017] Further, in step S2, during the beryllium liquid casting, a graphite mold preheated to a temperature of 200-400 DEG C is used, and the inner diameter of the graphite mold is 80-150 mm.

[0018] Further, in step S2, the temperature rising smelting procedure of the vacuum induction melting is as follows: first, the temperature is increased to 700-750 DEG C at a temperature rising rate of 35-45 DEG C / min, and the temperature is maintained for 15-30 minutes; then, the temperature is increased to 1380-1430 DEG C at a temperature rising rate of 70-120 DEG C / min, and the temperature is maintained for 45-75 minutes.

[0019] Further, in step S3, the vacuum suspension smelting uses a water-cooled copper crucible with an inner diameter of 120-200 mm.

[0020] Further, in step S3, the speed of supplementing the coarse beryllium ingot raw material into the suspension smelting zone is the same as the drawing speed, and the supplementing mode of continuously adding the coarse beryllium ingot raw material is a rod continuous feeding mode.

[0021] Further, in step S3, the cooling water flow rate during the pulling ingot process is 5-30 L / min, the water inlet temperature is 16-21 DEG C, and the water outlet temperature is 25-30 DEG C.

[0022] The present application also provides the following technical solutions:

[0023] A large-size high-purity metal beryllium ingot prepared by the method has a diameter of 120-200 mm, a length of 500-1500 mm, and a density of greater than or equal to 99%.

[0024] Further, the impurity residual amount in the metal beryllium ingot is: Mg≤0.006%, Al≤0.06%, Cr≤0.006%, Cu≤0.006%, Fe≤0.04%, Mn≤0.007%, Ni≤0.0005%, and Si≤0.009%.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The impurity removal effect is remarkable. Through the synergistic effect of the vacuum induction melting and the vacuum suspension melting two-step method, the Mg content in the finished beryllium is as low as 0.006% or less, which is much better than the level of the traditional single vacuum induction melting.

[0027] (2) The beryllium ingot has high density. The beryllium ingot prepared by using the ingot pulling and directional solidification technology has a density of greater than or equal to 99%, and the beryllium ingot is free of casting defects such as shrinkage holes and shrinkage porosity.

[0028] (3) The continuous production of large-size beryllium ingots is realized. The suspension melting and ingot pulling technology breaks through the size limitation of the traditional intermittent production, and can prepare large-size beryllium ingots with a diameter of 120-200 mm and a length of 500-1500 mm, and the production efficiency is significantly improved.

[0029] (4) The crucible pollution is eliminated. The vacuum suspension melting makes the beryllium melt not in contact with the crucible wall, and fundamentally avoids the pollution of the crucible material to the high-purity beryllium liquid.

[0030] (5) The process has good stability and strong operability. Using the coarse beryllium ingot as the suspension melting raw material avoids the spattering and suspension failure caused by the volatilization of a large amount of low-boiling-point impurities during the suspension melting of beryllium beads, and the melting process is stable and controllable. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A preparation process flow chart of the large-size high-purity metal beryllium ingot is provided. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0033] Example 1

[0034] This example provides a method for preparing large-size high-purity metal beryllium ingot by a two-step method, and the process flow chart is shown as Figure 1 The specific steps are shown as follows.

[0035] S1, Beryllium bead pretreatment

[0036] Take the beryllium beads produced by magnesium hot reduction method, after washing, drying and magnetic separation, screen and take the clean beryllium beads with a particle size of 3-15 mm. The Mg content in this batch of beryllium beads is 0.8%, the BeF2 content is 0.2%, the MgF2 content is 0.2%, and the metal impurity contents of Al, Cr, Cu, Fe, Mn, Ni, Si, etc. are shown in Table 1. Take 20 kg of the clean beryllium beads for use.

[0037] S2, Vacuum induction melting to prepare crude beryllium ingot

[0038] Put 20 kg of clean beryllium beads into the beryllia crucible in the vacuum induction melting furnace, and the crucible capacity is 20 kg. After closing the furnace door, vacuumize to 8x10 -3 Pa, and introduce high-purity argon (≥99.999%) into the furnace to a pressure of 500 Pa. Start heating, first increase the furnace temperature to 720℃ at a rate of 40℃ / min, and keep it for 20 minutes to make the magnesium in the beryllium beads melt slowly, avoiding splashing caused by rapid volatilization; then increase the furnace temperature to 1400℃ at a rate of 100℃ / min, and keep it for 60 minutes. During the holding process, Mg, BeF2, MgF2 and other low-boiling-point impurities continuously volatilize under high temperature and micro-positive pressure argon conditions and are removed by the vacuum system. After the melting is completed, pour the beryllium liquid into a preheated graphite mold (inner diameter 100 mm) at 300℃, and naturally cool and solidify to obtain a crude beryllium ingot.

[0039] S3, Vacuum suspension melting and ingot drawing

[0040] The above crude beryllium ingot is surface turned to obtain an ingot blank with a size of about φ95mmx200mm, which is placed in a water-cooled copper crucible of a vacuum suspension melting furnace. The water-cooled copper crucible has an inner diameter of 150mm, and its core structure is composed of a water-cooled copper crucible side wall and a movable ingot head. The ingot head is used as the crucible bottom during melting. Another batch of crude beryllium ingots is prepared as a supplement and is loaded into the vacuum feeding bin.

[0041] Close the furnace door and vacuumize to 3x10 -3Pa, the high-purity argon is introduced into the furnace to make the pressure in the furnace 0.5 Pa. The induction power is started to perform gradient temperature rising smelting: in the first stage, the power is raised to 30 kW and maintained for 3 minutes; in the second stage, the power is continuously raised to 80 kW and maintained for 5 minutes; in the third stage, the power is raised to 200 kW to perform suspension smelting refining, and the refining temperature is maintained at 1400 DEG C. During the process, the beryllium melt is separated from the crucible wall under the action of electromagnetic force to form stable suspension, and the electromagnetic stirring promotes the residual impurities to float and volatilize.

[0042] After the refining is completed, the smelting power is reduced to 170 kW. The dummy bar drawing device is started, and the dummy bar head is moved downward at a speed of 5 mm / min to start drawing the bar. At the same time, the coarse beryllium ingot rod material is continuously fed through the vacuum feeding bin at a speed matching the drawing speed, and the suspension smelting liquid level height is maintained unchanged. During the drawing process, the water cooling crystallizer cooling water flow is controlled to be 15 L / min, the water inlet temperature is 19 DEG C, and the water outlet temperature is maintained at 28 DEG C. When the beryllium ingot length reaches 1000 mm, the drawing is stopped, and the beryllium ingot is taken out after cooling.

[0043] S4, post-treatment

[0044] The obtained beryllium ingot is subjected to surface turning processing to remove the oxide layer, and a finished beryllium ingot is obtained.

[0045] Table 1: Metal impurity element content in beryllium beads used in examples 1-3

[0046]

[0047] Example 2

[0048] The present example provides a method for preparing a large-size high-purity metal beryllium ingot by a two-step method, and the specific steps are shown as follows.

[0049] S1, beryllium bead pretreatment

[0050] The beryllium beads produced by magnesium hot reduction method are taken, and after washing, drying and magnetic separation treatment, the clean beryllium beads with a particle size of 3-15 mm are screened. The Mg content in this batch of beryllium beads is 0.8%, the BeF2 content is 0.1%, and the MgF2 content is 0.1%. The contents of the remaining metal impurities Al, Cr, Cu, Fe, Mn, Ni and Si are shown in Table 1. 20 kg of the clean beryllium beads are weighed as the starting material of the present example and are used.

[0051] S2, vacuum induction smelting to prepare coarse beryllium ingot

[0052] The above 20 kg of clean beryllium beads are loaded into the beryllia crucible in the vacuum induction smelting furnace, and the crucible capacity is 20 kg. After the furnace door is closed, the vacuum system is started to make the pressure in the furnace ≤1x10 -2Pa. Subsequently, high-purity argon gas (purity ≥ 99.999%) was introduced until the furnace pressure reached 100 Pa, establishing a micro-positive pressure argon protective atmosphere. The induction power was started for staged heating. First, the furnace temperature was raised to 700°C at a rate of 30°C / min, and the temperature was maintained at 700°C for 15 minutes. During this stage, the furnace temperature was controlled to be above the melting point of magnesium (650°C) and below the melting point of beryllium (1287°C), allowing the magnesium particles in the beryllium beads to melt slowly and partially volatilize, effectively avoiding splashing caused by rapid heating and concentrated boiling of magnesium. After the holding period, the furnace temperature was raised to 1350°C at a rate of 50°C / min, allowing the beryllium beads to completely melt. The temperature was maintained at 1350°C for 30 minutes. During the holding period, Mg in the beryllium liquid continued to volatilize in gaseous form, while BeF2 and MgF2 gradually decomposed and volatilized under high temperature and micro-positive pressure argon blowing conditions, and were discharged outside the furnace through the vacuum system. The pressure fluctuation in the furnace was continuously monitored during the holding period, and the furnace pressure was maintained stable near 100 Pa by fine-tuning the vacuum valve. After the melting and holding period ended, the beryllium liquid temperature was adjusted to 1370°C, and the beryllium liquid was smoothly cast into a graphite mold that had been thoroughly dried and preheated to 200°C at a casting speed of about 0.3 kg / s. The graphite mold had an inner diameter of 80 mm, and after casting was completed, it was naturally cooled to room temperature, and the crude beryllium ingot was removed by opening the mold. The crude beryllium ingot was cylindrical, with a diameter of about 78 mm and a height of about 280 mm, and the surface had a silver-gray metallic luster. The recovery rate of the beryllium beads per furnace was 91.5%.

[0053] S3, Vacuum Suspension Melting Ingot Drawing

[0054] The crude beryllium ingot obtained in the previous step was surface turned to remove the sprue, surface oxide scale, and possibly attached graphite particles, obtaining a cylindrical ingot blank with a smooth surface, with dimensions of φ76 mm x 270 mm. The ingot blank was placed in the water-cooled copper crucible of the vacuum suspension melting furnace. The water-cooled copper crucible had an inner diameter of 120 mm, and the crucible side wall was composed of multiple water-cooled copper fan-shaped segments that were insulated from each other. The core structure of the water-cooled copper crucible used in this embodiment consisted of a water-cooled copper crucible side wall and an ingot drawing head that could move up and down, and during the melting stage, the ingot drawing head was raised to the bottom of the crucible to serve as the crucible bottom. The ingot drawing head was made of red copper, and the end face was processed as a concave arc surface to facilitate good contact with the beryllium melt. Several crude beryllium ingots from the same batch were also prepared, and after surface cleaning, they were loaded into the vacuum feed bin as supplemental material for the continuous ingot drawing stage.

[0055] After closing the furnace door, the vacuum system was started, and the furnace pressure was pumped to 5 x 10 -3 Pa. Subsequently, high-purity argon gas was introduced, and the furnace pressure was adjusted to 1 x 10 -1Pa, under the low pressure argon atmosphere. Start the induction power, and melt according to the preset gradient temperature program: the first stage: with 20kW induction power, keep 2 minutes. This stage preheats the coarse beryllium ingot, and gradually increases the temperature of the whole ingot, and at the same time, the surface and shallow area begins to melt slowly. The second stage: the power is increased to 60kW, continue to heat and keep 4 minutes. This stage gradually changes the coarse beryllium ingot from solid to liquid, the volume of the melt gradually increases, and the electromagnetic suspension force begins to act on the melt, and the beryllium liquid begins to form a pool in the crucible and gradually separates from the crucible wall. The third stage: the power is increased to 180kW, and the beryllium liquid is refined by suspension melting, and kept for 5 minutes. In this stage, the beryllium liquid completely separates from the crucible wall under the action of strong electromagnetic field, and forms a stable suspended ellipsoidal melt with a suspension gap of about 3-5mm. The refining temperature is stably controlled at 1350℃. Under the suspension state, the electromagnetic stirring drives the beryllium melt to produce strong convection, which promotes the migration of residual trace impurities (including residual Mg, BeF2, MgF2 decomposition products and small non-metallic inclusions) to the surface of the melt and volatilizes and removes.

[0056] After the refining stage is completed, the melting power is slowly reduced from 180kW to 160kW, the temperature of the melt is appropriately reduced, and the viscosity is slightly increased, so as to prepare for the ingot drawing. Then the ingot drawing device is started, and the ingot head starts to move slowly downward at a speed of 3mm / min. When the ingot head descends, the beryllium melt on the upper end surface solidifies and is firmly connected with the ingot head. As the ingot head continues to move downward, the beryllium ingot is gradually drawn out of the suspension melting area and into the water-cooled crystallizer below. The water-cooled crystallizer is made of red copper material, the inner wall is chrome plated, and the drawn beryllium ingot is forcedly cooled to realize directional solidification. The cooling water flow is set to 5L / min, and the water inlet temperature is strictly controlled at 19℃, and the water outlet temperature monitoring value during the ingot drawing process is 25℃. At the same time of starting the ingot drawing, the rod continuous feeding device of the vacuum feeding bin is started, and the pre-loaded coarse beryllium ingot rod is continuously fed into the suspension melting area in the water-cooled copper crucible at a speed matching the ingot drawing speed. By observing the melt liquid level in real time, the feeding rate is adjusted, so that the suspension melting liquid level is always maintained during the whole ingot drawing process, ensuring the continuity and stability of the suspension state. When the continuous ingot drawing reaches 500mm in length, the ingot drawing and feeding are stopped, the induction power is gradually reduced to zero, and the melt is naturally cooled under the protection of the atmosphere. After the temperature in the furnace is reduced to room temperature, the furnace door is opened to take out the beryllium ingot.

[0057] S4, post-treatment

[0058] The beryllium ingot obtained in step S3 is subjected to surface turning processing, and the turning depth is about 1-2mm, so as to completely remove the surface oxide layer and small surface defects, and obtain the finished high-purity metal beryllium ingot.

[0059] Example 3

[0060] The embodiment provides a method for preparing large-size high-cleanliness metal beryllium ingot by using a two-step method, and specific steps are shown as follows.

[0061] S1, beryllium bead pretreatment

[0062] The beryllium beads produced by the magnesium hot reduction method are subjected to washing, drying and magnetic separation grading treatment, and then are screened to obtain clean beryllium beads with a particle size of 3-15 mm. The batch of beryllium beads has a relatively high impurity content due to batch fluctuation of the ore source and the reduction process, wherein the Mg content is 0.7%, the BeF2 content is 0.3%, and the MgF2 content is 0.3%. The contents of the remaining metal impurities Al, Cr, Cu, Fe, Mn, Ni and Si are shown in Table 1. 20 kg of the clean beryllium beads are weighed as starting raw materials.

[0063] S2, vacuum induction melting to prepare a crude beryllium ingot

[0064] The 20 kg of clean beryllium beads are loaded into a beryllia crucible in a vacuum induction melting furnace, and the capacity of the crucible is 20 kg. After the furnace door is closed, the vacuum system is started, the pressure in the furnace is extracted to 6x10 -3Pa. Subsequently, high-purity argon gas (purity ≥ 99.999%) was introduced into the furnace to a pressure of 800 Pa, establishing a micro-positive pressure argon protective atmosphere to inhibit the excessive volatilization loss of beryllium liquid at high temperature. The induction power was started, and the temperature was raised in stages according to the preset program. First, the furnace temperature was raised to 750°C at a rate of 50°C / min, and the temperature was maintained at 750°C for 30 minutes. During this stage, the metal magnesium in the beryllium beads was fully melted and began to volatilize slowly. The long low-temperature holding time (30 minutes) ensured that the volatilization process of magnesium was smooth, avoiding the concentrated release of magnesium vapor during subsequent rapid temperature rise, which could cause melt spatter or crucible damage. After the holding period ended, the furnace temperature was raised to 1450°C at a faster rate of 150°C / min to quickly and completely melt the beryllium beads. The temperature was maintained at 1450°C for 90 minutes. The higher smelting temperature of 1450°C and the longer holding time of 90 minutes were set based on the high impurity content of the beryllium beads in this batch, aiming to provide more sufficient volatilization driving force and escape time for low-boiling-point impurities such as Mg, BeF2, and MgF2, ensuring the effectiveness of impurity removal. During the holding period, the furnace pressure was automatically adjusted by the vacuum system to maintain around 800 Pa, and the volatilized impurity gas was continuously removed. After the smelting and holding period ended, the beryllium liquid temperature was adjusted to 1470°C, and it was smoothly cast into a graphite mold that had been thoroughly dried and preheated to 400°C at a casting speed of about 0.3 kg / s. The graphite mold had an inner diameter of 150 mm, and the higher preheating temperature (400°C) helped to slow down the cooling rate of the beryllium liquid in the mold, reducing internal stress in the ingot and preventing cracking of large-size ingots. After casting was completed, the mold was naturally cooled to room temperature, and the rough beryllium ingot was removed by opening the mold. The rough beryllium ingot was cylindrical, with a diameter of about 148 mm and a height of about 95 mm, and had a silver-gray metallic luster on the surface without obvious cracks. The single-furnace beryllium bead recovery rate was 85.8%, which was lower than that of Example 2, which was related to the high impurity content of the raw material, the high holding temperature, and the long holding time, leading to increased volatilization loss of the beryllium liquid.

[0065] S3, Vacuum Suspension Melting Ingot Drawing

[0066] The obtained rough beryllium ingot was surface turned to remove the sprue, surface oxide layer, and local burrs, obtaining a clean ingot billet with a size of about φ145 mm x 90 mm. The ingot billet was loaded into the water-cooled copper crucible of the vacuum suspension melting furnace. The water-cooled copper crucible had an inner diameter of 200 mm, and its core structure consisted of a water-cooled copper crucible side wall and a movable ingot head. During the melting stage, the ingot head was raised and placed as the crucible bottom. The end face of the ingot head was processed as a concave arc surface. Another batch of rough beryllium ingots was taken, surface cleaned, and loaded into the vacuum feeding bin for use.

[0067] The furnace door was closed, and the vacuum system was started to pump the furnace pressure to 2 x 10 -3Pa. Subsequently, high-purity argon gas was introduced, and the pressure in the furnace was adjusted to 5 Pa. The suspension melting operation was performed under this argon partial pressure. The induction power was started, and the following gradient temperature program was used for melting: First stage: the induction power was increased to 40 kW, and the temperature was maintained for 4 minutes. The higher initial power and longer preheating time were beneficial to the uniform heating of the large-size rough beryllium ingot, reducing the possibility of ingot cracking caused by thermal stress. Second stage: the power was increased to 100 kW, and the temperature was continued to rise and maintained for 7 minutes. In this stage, the rough beryllium ingot was melted layer by layer from the outside to the inside, the amount of melt increased, the electromagnetic suspension force gradually formed, and the beryllium melt began to separate from the crucible wall. Third stage: the power was increased to 240 kW, and the beryllium liquid was subjected to high-power suspension melting refining, which was maintained for 8 minutes. Under the action of high-power electromagnetic field, the beryllium liquid was completely suspended in the center position of the crucible, the suspension gap reached 8-10 mm, and the melt presented a stable ellipsoidal shape. The refining temperature was stably controlled at 1450°C. The higher refining temperature and longer refining time (8 minutes) provided a stronger driving force for the volatilization of residual impurities, and the strong electromagnetic stirring in the suspension state further promoted the homogenization of the melt composition and the deep removal of trace impurities.

[0068] After the refining stage, the induction power was slowly reduced from 240 kW to 190 kW, the melt temperature was appropriately reduced to increase the melt viscosity, and the initial conditions for stable ingot pulling were established. The dummy bar pulling device was started, and the dummy bar head began to move downward at a speed of 15 mm / min. As the dummy bar head descended, the bottom of the beryllium melt contacted and rapidly solidified with the dummy bar head, and the beryllium ingot sequentially solidified along the pulling direction under the forced cooling of the water-cooled crystallizer. The cooling water flow rate of the water-cooled crystallizer was set to 30 L / min, and the inlet water temperature was strictly controlled at 19°C. The outlet water temperature was monitored to be 30°C during the pulling process. At the same time of starting the pulling, the rod material was continuously fed into the water-cooled copper crucible through the rod material continuous feeding device of the vacuum charging bin at a speed accurately matched with the pulling speed. The feeding speed was adjusted in real time through the control system to maintain the suspension melting liquid level constant, ensuring the continuous and stable operation of the suspension melting and pulling process. When the beryllium ingot length reached 1500 mm, the pulling and feeding were stopped, and the induction power was gradually reduced to zero. After the temperature in the furnace cooled to room temperature, the furnace door was opened to take out the beryllium ingot.

[0069] S4, post-treatment

[0070] The obtained beryllium ingot was subjected to surface turning processing to remove the surface oxide layer and small defects, and a finished high-purity metal beryllium ingot was obtained.

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing a metal beryllium ingot, and the effect of directly using beryllium beads without vacuum induction melting treatment for vacuum suspension melting and dummy bar pulling is investigated. The same batch of beryllium beads as in Example 1 were directly placed in a water-cooled copper crucible. The specific steps are as follows.

[0073] S1, Beryllium beads pretreatment: same as example 1.

[0074] S2, Vacuum levitation melting ingot drawing: Clean beryllium beads were placed in the water-cooled copper crucible of the vacuum levitation melting furnace. The process parameters of vacuum levitation melting ingot drawing were the same as those of example 1.

[0075] Due to the low apparent density and irregular shape of the beryllium beads, the amount of single loading was small. When the temperature was raised to the point where the beryllium beads began to melt, a large amount of impurities such as Mg, BeF2, MgF2, etc. were concentrated and volatilized, causing a sharp fluctuation in vacuum degree and a violent boiling and spattering of the melt. The spatter not only caused the equipment to malfunction, but also disrupted the balance of the electromagnetic suspension force, causing the melt to come into contact with the crucible wall and even adhere to it, completely destroying the suspension state and making it impossible to carry out subsequent ingot drawing operations, thus forcing the test to be discontinued.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a beryllium ingot, the specific steps of which are shown below.

[0078] The difference between this comparative example and example 1 is that in the method of S3, vacuum levitation melting ingot drawing, the process parameters for gradient heating melting are as follows: in the first stage, the power is increased to 15 kW and maintained for 6 minutes; in the second stage, the power is further increased to 50 kW and maintained for 9 minutes; in the third stage, the power is increased to 170 kW for suspension melting refining, and the refining temperature is stabilized at 1320°C. During this process, the beryllium melt is separated from the crucible wall under the action of electromagnetic force, forming a stable suspension, and the electromagnetic stirring promotes the floating and volatilization of residual impurities. After refining, the melting power is reduced to 150 kW. The ingot drawing device is started, and the ingot head is moved downward at a speed of 5 mm / min to start drawing the ingot. At the same time, the coarse beryllium ingot rod material is continuously fed through the vacuum feeding bin at a rate matching the drawing speed, maintaining the suspension melting liquid level height unchanged. During the ingot drawing process, the cooling water flow rate of the water-cooled crystallizer is controlled at 15 L / min, the inlet water temperature is 19°C, and the outlet water temperature is maintained at 28°C. When the length of the beryllium ingot reaches 1000 mm, the drawing is stopped, and the ingot is taken out after cooling.

[0079] The remaining parameters of this comparative example are the same as those of example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing a beryllium ingot, the specific

[0082] The difference between the present comparative example and Example 1 is that the process parameters of gradient heating in the method of S3, vacuum suspension melting ingot pulling ingot are as follows: the first stage is heated at a power of 50 kW for 2 minutes; the second stage is continuously heated at a power of 110 kW for 3 minutes; the third stage is suspension melting refining at a power of 250 kW for 4 minutes, and the refining temperature is stabilized at 1460 DEG C. In this process, the beryllium melt is separated from the crucible wall under the action of electromagnetic force to form stable suspension, and electromagnetic stirring promotes the floating and volatilization of residual impurities. After refining, the melting power is reduced to 200 kW. Start the ingot pulling device, and the ingot head moves downward at a speed of 5 mm / min to start pulling the ingot. At the same time, continuously feed the coarse beryllium ingot rod into the vacuum feeding bin at a speed matching the pulling speed to maintain the suspension melting liquid level unchanged. During the pulling process, the cooling water flow of the water-cooled crystallizer is controlled at 15 L / min, the water inlet temperature is 19 DEG C, and the water outlet temperature is maintained at 28 DEG C. When the length of the beryllium ingot reaches 1000 mm, stop pulling and take out after cooling.

[0083] The present comparative example has the same parameters as the rest of Example 1.

[0084] Performance detection results

[0085] The performance of the finished beryllium ingot in the examples and comparative examples is detected, and the size (diameter x length), density, and internal defect detection results are shown in Table 2; the impurity element residual amount detection results are shown in Table 3.

[0086] Table 2 Performance detection results of finished beryllium ingot in examples and comparative examples

[0087]

[0088] Table 3 Impurity element residual amount detection results of finished beryllium ingot in examples and comparative examples

[0089]

[0088]

[0090] In summary, the present application uses the two-step process of vacuum induction melting and vacuum suspension melting ingot pulling to remove Mg, BeF2, MgF2 and other low-boiling-point impurities in beryllium beads efficiently and preliminarily densify, which completely solves the problem of splashing and suspension failure caused by the volatilization of impurities concentrated in direct suspension melting. Subsequently, the suspension melting ingot pulling technology is used to avoid crucible pollution, and through directional solidification and continuous feeding and drawing, high-purity large-size metal beryllium ingot without shrinkage and porosity defects, fine grains and density ≥ 99% is successfully prepared, which breaks through the size and efficiency bottleneck of the traditional "one furnace one ingot" process, and greatly improves the production efficiency and metallurgical quality.

[0091] The above describes some exemplary embodiments of the present application, it can be understood that the above-described embodiments are only used to explain the present application, and do not constitute a limitation on the protection scope of the present application. The features in these embodiments can be recombined in a suitable manner, and the schemes obtained thereby are still within the protection scope required by the present application. Based on the above-described embodiments, all other embodiments obtained by those skilled in the art without making creative labor, i.e. all modifications, equivalent replacements and improvements, etc. made within the spirit and principles of the present application, are also within the protection scope required by the present application.

Claims

1. A method for preparing large-size, high-purity beryllium ingots using a two-step process, characterized in that, Includes the following steps: S1. The beryllium beads produced by the magnesia reduction method are sequentially washed, dried, magnetically separated and graded to obtain clean beryllium beads; S2. The cleaned beryllium beads are subjected to vacuum induction melting, and the furnace is evacuated to a pressure ≤1×10⁻⁶. -2 Pa, then argon gas is introduced to bring the furnace pressure to 100-800 Pa; first, the temperature is raised to 700-750°C at a rate of 30-50°C / min and held for 15-30 minutes, then raised to 1350-1450°C at a rate of 50-150°C / min and held for 30-90 minutes; after melting, the beryllium liquid is poured into a casting and allowed to cool and solidify naturally to obtain a crude beryllium ingot; S3. After surface cleaning, the crude beryllium ingot is subjected to vacuum suspension melting, and the furnace is evacuated to a pressure ≤5×10. - 3 Pa, then argon gas is introduced to bring the furnace pressure to 0.1-5 Pa; the power supply is turned on, first heating at 20-40 kW and holding for 2-4 minutes, then heating at 60-100 kW and holding for 4-7 minutes, and finally suspending and refining at 180-240 kW for 5-8 minutes, with the refining temperature controlled at 1350-1450℃; after refining, the melting power is reduced to 160-190 kW, the ingot pulling device is started, the ingot head moves downward at a speed of 3-15 mm / min to pull the ingot, and after the ingot pulling begins, the crude beryllium ingot is continuously added to the suspension melting zone through the vacuum feeding chamber, so that the suspension melting liquid level remains unchanged, and the beryllium ingot is obtained by cooling; S4. The beryllium ingot obtained in step S3 is surface-processed to remove the surface oxide layer, thus obtaining the finished high-purity metal beryllium ingot.

2. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S1, the beryllium beads have a particle size range of 3-15 mm and include the following impurities by weight percentage: Mg 0.6%-0.8%, BeF2 0.1%-0.3%, MgF2 0.1%-0.3%, Al 0.08-0.11%, Cr 0.02-0.03%, Cu 0.012-0.015%, Fe 0.046-0.127%, Mn 0.0077-0.015%, Ni 0.0037-0.005%, and Si 0.0096-0.023%.

3. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S2, the crucible used for vacuum induction melting is made of beryllium oxide.

4. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S2, during the beryllium liquid casting process, a graphite mold preheated to a temperature of 200-400℃ is used, and the inner diameter of the graphite mold is 80-150mm.

5. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S2, the vacuum induction melting heating process is as follows: first, the temperature is raised to 700-750°C at a heating rate of 35-45°C / min, and held for 15-30 minutes; then, the temperature is raised to 1380-1430°C at a heating rate of 70-120°C / min, and held for 45-75 minutes.

6. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S3, the vacuum suspension melting uses a water-cooled copper crucible with an inner diameter of 120-200 mm.

7. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S3, the rate at which crude beryllium ingot raw material is added to the suspension melting zone is the same as the ingot pulling speed, and the feeding method for continuously adding crude beryllium ingot raw material is the bar stock continuous feeding method.

8. The method for preparing large-size, high-purity beryllium ingots using a two-step process according to claim 1, characterized in that, In step S3, the cooling water flow rate during the drawing process is 5-30 L / min, the inlet water temperature is 16-21℃, and the outlet water temperature is 25-30℃.

9. A large-size, high-purity beryllium ingot prepared by the method according to any one of claims 1-8, characterized in that, The beryllium ingot has a diameter of 120–200 mm, a length of 500–1500 mm, and a density of ≥99%.

10. The large-size, high-purity beryllium ingot according to claim 9, characterized in that, The residual impurities in the beryllium ingot are: Mg≤0.006%, Al≤0.06%, Cr≤0.006%, Cu≤0.006%, Fe≤0.04%, Mn≤0.007%, Ni≤0.0005%, Si≤0.009%.

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