Method for preparing high-purity beryllium based on vacuum induction zone melting

Abstract

The invention discloses a method for preparing high-purity beryllium based on vacuum induction zone melting, and relates to the technical field of high-purity beryllium, the method comprises the following steps: (1) polishing a beryllium rod, and then placing the beryllium rod in a graphite boat in a protective gas environment; and (2) the beryllium rod treated in the step (1) is placed in a vacuum environment, a melting zone with the controllable axial temperature gradient is formed in the local portion of the beryllium rod through a coaxial induction coil, the melting zone is moved at the preset speed and repeated for multiple times, directional enrichment and removal are achieved through the impurity segregation effect, and high-purity beryllium is obtained. According to the method, the beryllium rod is subjected to zone melting treatment for multiple times in the vacuum environment, purification of the beryllium rod is achieved, and the purity of the beryllium rod can reach 99.995% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity beryllium, and particularly relates to a method for preparing high-purity beryllium based on vacuum induction zone melting. Background Art

[0002] In cutting-edge fields such as nuclear reactor moderating materials and X-ray windows, beryllium with a purity of ≥99.99% is required, and the contents of impurities such as Fe, C, and O need to be controlled (e.g., Fe ≤ 50 ppm). Although the traditional electron beam zone melting method can effectively achieve the purification of beryllium, the equipment used in this method is complex and the beryllium vapor is highly toxic, resulting in high operation risks; when purifying beryllium by the conventional zone melting method, due to the high thermal conductivity of beryllium (200 W / m·K), the stability of the molten zone is poor and the impurity segregation efficiency is low (the purity after purification is usually <99.95%); chemical purification is prone to introducing secondary pollution and it is difficult to remove the impurities in the solid solution state. Therefore, there is an urgent need for a method for efficiently removing impurities to prepare high-purity beryllium. Summary of the Invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing high-purity beryllium based on vacuum induction zone melting. This method realizes the purification of the beryllium rod by performing multiple zone melting treatments on the beryllium rod in a vacuum environment, enabling the purity of the beryllium rod to reach more than 99.995%.

[0004] The technical solution of the present invention for solving the above technical problems is as follows: A method for preparing high-purity beryllium based on vacuum induction zone melting is provided, including the following steps:

[0005] (1) Polish the beryllium rod, and then place the beryllium rod in a graphite boat under a protective gas environment;

[0006] (2) Place the beryllium rod processed in step (1) in a vacuum environment, form a molten zone with a controllable axial temperature gradient locally on the beryllium rod through a coaxial induction coil, move the molten zone at a preset speed and repeat it multiple times, and use the impurity segregation effect to achieve directional enrichment and removal to obtain high-purity beryllium.

[0007] Further, in step (1), the beryllium rod is an industrial-grade beryllium rod with a purity of ≥99.9%.

[0008] Further, in step (1), the C content of the graphite boat is ≤10 ppm. The protective gas is argon.

[0009] Further, in step (1), the size of the beryllium rod is Φ20 mm × 200 mm, the initial Fe content is 180 ppm, and the O content is 600 ppm.

[0010] Further, in step (1), the surface roughness Ra of the polished beryllium rod is ≤0.8 μm.

[0011] Further, in step (2), the pressure in the vacuum environment is ≤1×10-3 Pa.

[0012] Further, in step (2), the moving speed v of the molten zone satisfies v ≤ (k·D) / [δ·(1 - k)], where k is the impurity distribution coefficient, D is the impurity diffusion coefficient (m 2 / s), and δ is the thickness of the boundary layer of the molten zone (m).

[0013] Further, in step (2), the moving speed of the molten zone is 0.8 - 1.2 mm / min. Preferably, the moving speed is 1.2 mm / min.

[0014] Further, in step (2), a two-way zone melting strategy is adopted, and the ratio of the number of forward movements to the number of reverse movements is 3 - 5:1.

[0015] Further, in step (2), the number of induction zone melting times is 15 times. Preferably, it is 12 times forward + 3 times reverse.

[0016] Further, in step (2), an intermediate frequency current of 10 - 50 kHz is passed through the induction coil, and the solid-liquid interface morphology of the molten zone is monitored in real time by an infrared thermal imager.

[0017] The present invention has the following beneficial effects:

[0018] The method of the present invention realizes the purification of beryllium rods by performing multiple zone melting treatments on beryllium rods in a vacuum environment, enabling the purity of the beryllium rods to reach more than 99.995%. Specific Embodiments

[0019] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, the operations are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0020] Example 1

[0021] A method for preparing high-purity beryllium based on vacuum induction zone melting, comprising the following steps:

[0022] (1) The raw material is an industrial-grade beryllium rod (purity ≥ 99.9%), with a size of Φ20 mm × 200 mm, an initial Fe content of 180 ppm, and an O content of 600 ppm. The beryllium rod is mechanically polished until Ra is reduced to 0.6 μm, and then the beryllium rod is placed in a high-purity graphite boat (C content ≤ 10 ppm) in an argon glove box;

[0023] (2) Place the beryllium rod processed in step (1) in a vacuum environment, and form a molten zone with a controllable axial temperature gradient locally on the beryllium rod through a coaxial induction coil. Move the molten zone at a speed of 1.2 mm / min and repeat it 15 times, including 12 times in the forward direction and 3 times in the reverse direction, to achieve directional enrichment and removal by using the impurity segregation effect, obtaining high-purity beryllium.

[0024] In this embodiment, the purity of the head of the beryllium rod obtained is 99.996%, the Fe content is reduced to 22 ppm, and the O content is 85 ppm.

[0025] Example 2

[0026] A method for preparing high-purity beryllium based on vacuum induction zone melting includes the following steps:

[0027] (1) The raw material is an industrial-grade beryllium rod (purity ≥ 99.9%), with a size of Φ30 mm × 200 mm and an initial C content of 350 ppm. Mechanically polish the beryllium rod until Ra is reduced to 0.7 μm, and then place the beryllium rod in a high-purity graphite boat (C content ≤ 10 ppm) in an argon glove box;

[0028] (2) Place the beryllium rod processed in step (1) in a vacuum environment, and form a molten zone with a controllable axial temperature gradient locally on the beryllium rod through a coaxial induction coil. Move the molten zone at a speed of 0.8 mm / min and repeat it 20 times, including 15 times in the forward direction and 5 times in the reverse direction, to achieve directional enrichment and removal by using the impurity segregation effect, obtaining high-purity beryllium.

[0029] In this embodiment, the purity of the head of the beryllium rod obtained is 99.997%, and the C content is reduced to 45 ppm.

[0030] Example 3

[0031] A method for preparing high-purity beryllium based on vacuum induction zone melting includes the following steps:

[0032] (1) The raw material is an industrial-grade beryllium rod (purity ≥ 99.9%), with a size of Φ25 mm × 200 mm. Mechanically polish the beryllium rod until Ra is reduced to 0.8 μm, and then place the beryllium rod in a high-purity graphite boat in an argon glove box;

[0033] (2) Place the beryllium rod processed in step (1) in a vacuum environment, and form a molten zone with a controllable axial temperature gradient locally on the beryllium rod through a coaxial induction coil. Move the molten zone at a speed of 1 mm / min and repeat it 20 times, including 16 times in the forward direction and 4 times in the reverse direction, to achieve directional enrichment and removal by using the impurity segregation effect, obtaining high-purity beryllium.

[0034] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity beryllium based on vacuum induction zone melting, characterized in that, It includes the following steps: (1) Polish the beryllium rod, and then place the beryllium rod in a graphite boat under a protective gas environment; (2) Place the beryllium rod processed in step (1) in a vacuum environment, form a molten zone with a controllable axial temperature gradient locally on the beryllium rod through a coaxial induction coil, move the molten zone at a preset speed and repeat induction zone melting, and utilize the impurity segregation effect to achieve directional enrichment and removal to obtain high-purity beryllium.

2. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, characterized in that, In step (1), the beryllium rod is an industrial-grade beryllium rod with a purity ≥ 99.9%.

3. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, characterized in that, In step (1), the surface roughness Ra of the beryllium rod after polishing is ≤ 0.8 μm.

4. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, characterized in that, In step (2), the pressure in the vacuum environment ≤ 1×10 -3 Pa.

5. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, wherein, In step (2), the moving speed v of the molten zone is ≤ (k·D) / [δ·(1 - k)], where k is the impurity distribution coefficient, D is the impurity diffusion coefficient, and δ is the molten zone boundary layer thickness.

6. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, wherein, In step (2), a two-way zone melting strategy is adopted, and the ratio of the number of forward movements to the number of reverse movements is 3 - 5:

1.

7. The method for preparing high-purity beryllium based on vacuum induction zone melting as claimed in claim 1, wherein In step (2), the number of induction zone melting times is 15 times.

8. The method for preparing high-purity beryllium based on vacuum induction zone melting according to claim 1, characterized in that, In step (2), the induction coil is passed through a medium-frequency current of 10 - 50 kHz, and the solid-liquid interface morphology of the molten zone is monitored in real time by an infrared thermal imager.