CN118006903A - Ultrapure metal production process using continuous UHV vertical float zone melting - Google Patents

Abstract

The process of preparing ultra-pure metal by continuous UHV vertical floating zone melting uses a double vacuum chamber structure combining a vacuum pretreatment chamber and an ultra-high vacuum zone melting process chamber. It is possible to perform plasma surface cleaning and n-pass vertical zone melting purification on metal rods in a full vacuum environment to obtain purified metal rods with a higher purity level. This is beneficial to exert the impurity evaporation effect, impurity condensation effect or segregation effect, and impurity slag removal effect, thereby realizing continuous metal rod purification operations and can be applied to industrial production.

Description

Ultrapure metal production process using continuous UHV vertical float zone melting

Technical Field

The invention relates to the technical field of metal purification, in particular to a process for preparing ultrapure metal by using continuous UHV vertical floating zone melting.

Background technique

Zone melting is a method of deep metal purification. Its essence is to locally heat a narrow ingot to form a narrow melting zone, and move the heating to make this narrow melting zone slowly move along the ingot in a certain direction. By using the difference in equilibrium concentration of impurities between the solid phase and the liquid phase, the impurities are redistributed or segregated into the solid phase or liquid phase during repeated melting and solidification, and then removed, thereby achieving the purpose of purification.

The molten zone is generally heated by resistance heating, induction heating or electron beam heating. Electron beam heating and high-frequency coil heating are usually used. Electron beam heating has the advantages of small melting volume, clear thermal gradient boundaries, high thermal efficiency and good purification effect, but because this method can only be carried out in a vacuum, it is greatly limited. Induction heating can be used in a vacuum or in any inert reducing atmosphere.

Zone smelting is widely used to purify high-melting-point metals such as tungsten, molybdenum, tantalum, and niobium in semiconductor materials, and is also used to purify high-purity aluminum, gallium, antimony, copper, iron, silver, and other metals. Zone smelting has a good purification effect on high-melting-point metals.

Compared with other purification technologies, zone smelting has the advantages of wide application range, no pollution, high product purity, simple operation and uniform composition, but it also has a series of problems and difficulties. In order not to affect the final performance of the material, high requirements are placed on the raw materials themselves. In addition, the number of smelting times is also high, and the melting zone movement rate is low, which prolongs the process time. Not only is the metal recovery rate low, but the energy consumption is high, so the production cost is high.

Therefore, the present invention provides a process for preparing ultrapure metal by using continuous UHV vertical floating zone melting, thereby realizing the preparation of ultrapure metal.

Summary of the invention

In view of the defects or shortcomings existing in the prior art, the present invention provides a process for preparing ultra-pure metal by continuous UHV vertical floating zone melting. By utilizing a double vacuum chamber structure combining a vacuum pretreatment chamber and an ultra-high vacuum zone melting process chamber, the metal rod can be subjected to plasma surface cleaning and n-pass vertical zone melting purification under a full vacuum environment to obtain purified metal rods of a higher purity level, which is beneficial to exerting the impurity evaporation effect, impurity condensation effect or segregation effect and impurity slag removal effect, realizes continuous metal rod purification operation, and can be applied to industrial production.

The technical solution of the present invention is as follows:

A process for preparing ultrapure metal by continuous UHV vertical floating zone melting is characterized by comprising the following steps:

Step 1, placing the metal rod to be purified into a vacuum pretreatment chamber, wherein the vacuum degree of the vacuum pretreatment chamber is on the order of 10 ^-5 Pa, and performing plasma cleaning on the surface of the metal rod using a high-voltage arc discharge device to obtain a clean metal rod;

Step 2, sending the clean metal rod into the induction coil in the ultra-high vacuum zone melting process chamber under vacuum conditions, the height of the induction coil is adapted to the height of the vertical floating zone to be formed by the clean metal rod, the end of the clean metal rod is clamped by a clamping mechanism, so that the axis of the clean metal rod coincides with the axis of the induction coil, and the vacuum degree of the ultra-high vacuum zone melting process chamber is on the order of ^10-8 Pa;

Step 3, the clean metal rod moves up and down in the vertical direction in the induction coil through the upper and lower clamping components while synchronously spinning around its own axis, and the induction coil is equipped with a power supply to form a vertical floating area on the clean metal rod through induction heating;

Step 4, performing n passes of vertical zone melting purification to obtain a purified metal rod with a higher purity level, wherein n is a positive integer, and in each pass, the vertical floating zone starts from the upper end of the clean metal rod, and the vertical floating zone gradually moves downward from the upper end to the lower end;

Step 5, sending the purified metal rod cooled to room temperature into a vacuum pretreatment chamber under vacuum conditions, introducing a protective atmosphere into the vacuum pretreatment chamber, and taking out the purified metal rod after the internal and external air pressures are consistent;

Step 6, cutting off the preset upper and lower parts of the purified metal rod, and the remaining part in the middle is the ultra-pure metal product.

The intermediate remainder in step 6 accounts for 85% to 95%.

The step 4 includes 7 to 10 passes of vertical zone melting purification, and the moving speed of the vertical floating zone from the upper end to the lower end is 1 to 100 μm/s.

In step 3, the rotation speed of the spin is 1-25 r/min, and the temperature range of the induction heating is 100-2000° C.

The ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are respectively connected to an ultra-high vacuum system, the ultra-high vacuum system is composed of a cryogenic pump, a molecular pump and a mechanical pump, and the ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are connected via a plug valve.

The ultra-high vacuum environment in the ultra-high vacuum zone melting process chamber can utilize the difference in saturated vapor pressure between the matrix and the impurities to remove impurities having a higher saturated vapor pressure than the matrix.

The ultra-high vacuum zone melting process chamber is respectively connected with a residual gas analyzer and a film thickness meter, and the probe of the film thickness meter is used to indirectly monitor and feedback the temperature of the vertical floating zone.

The metal rod to be purified is a pure iron rod.

The aluminum and silicon elements in the pure iron rod are removed by entering the slag in the vertical floating zone of step 4.

The technical effects of the present invention are as follows: the present invention utilizes a continuous UHV vertical floating zone melting process to prepare an ultrapure metal process, and utilizes a double vacuum chamber structure combining a vacuum pretreatment chamber and an ultrahigh vacuum zone melting process chamber, which can perform plasma surface cleaning and n-pass vertical zone melting purification on a metal rod in a full vacuum environment to obtain a purified metal rod of a higher purity level, which is beneficial to exert the impurity evaporation effect (for example, the saturated vapor pressure of elements such as Cu and Mn in a pure iron rod is higher than that of Fe, and can be removed by evaporation), the impurity segregation effect or the segregation effect (for example, the characterization parameter K of the impurity segregation effect is less than 1 for P, S Elements such as As and As can be effectively separated to the tail of the post-solidified pure iron rod, and individual impurity elements with K>1 can be separated to the head of the pure iron rod, K=Csolid/Cliquid, where Csolid represents the concentration of impurities in the solid phase, and Cliquid represents the concentration of impurities in the liquid phase) and impurity slag removal effect (for example, Al and Si elements, they all show different behaviors, different from segregation and evaporation, but can be partially removed by the formation of slag. It has been detected that Al and Si oxides are contained in the slag surface in the vertical floating zone), thereby realizing continuous metal rod purification operations, which can be applied to industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a process for preparing ultrapure metal by using continuous UHV vertical floating zone melting in the present invention. UHV is the abbreviation of ultra-high vacuum. FIG1 includes step 1, feeding; step 2, conveying; step 3, exchanging; step 4, fixing; step 5, zone melting; and step 6, taking out the material.

FIG2 is a schematic diagram of the change state of the vertical floating zone in the zone melting of the iron rod in FIG1. The vertical floating zone in the left figure of FIG2 indicates that the initial melting leads to the formation of small solid particles in the molten zone. These small solid particles are aluminum oxide and silicon oxide. The middle figure in FIG2 shows that the small solid particles begin to gather together to form larger solid particles. These larger solid particles are located at the lower solid-liquid interface. The vertical floating zone in the right figure of FIG2 shows that a slag film (containing aluminum element solid particles and silicon element solid particles) is formed at the lower solid-liquid interface at the end of the first zone melting (i.e., the first pass).

Figure 3 is a schematic diagram of the change of the vertical floating zone morphology in the zone melting of the iron rod with the zone melting pass. The left figure in Figure 3 shows that during the first downward pass, a large amount of insoluble particles were observed at the bottom of the vertical floating zone. The right figure in Figure 3 shows that during the second downward pass, the number of insoluble particles at the bottom of the vertical floating zone was greatly reduced.

Figure 4 is a schematic diagram of the morphology of the vertical floating zone in the iron rod zone melt under static conditions. Figure 4 illustrates that under static conditions, the insoluble particles in the vertical floating zone exhibit chaotic motion.

Figure 5 is a schematic diagram of the 3D distribution of Al and Si elements in the slag layer of the vertical floating zone of the iron rod after the 7th zone melting. The left figure in Figure 5 is a schematic diagram of the 3D distribution of the Al element, in which the intensity of the Al element signal decreases by an order of magnitude from the surface to the inside. The right figure in Figure 5 is a schematic diagram of the 3D distribution of the Si element, in which the intensity of the Si element signal decreases by an order of magnitude from the surface to the inside. Figure 5 shows that both Al and Si elements are concentrated on the surface of the slag layer, that is, after the iron rod is zone melted in multiple passes, Al and Si elements can be removed by slag with a certain film thickness.

Detailed ways

The present invention is described below with reference to the embodiments and accompanying drawings ( FIGS. 1 to 5 ).

FIG1 is a schematic diagram of the process of preparing ultrapure metal by continuous UHV vertical floating zone zone melting according to the present invention. FIG2 is a schematic diagram of the change state of the vertical floating zone in the zone melting of the iron rod in FIG1. FIG3 is a schematic diagram of the change of the morphology of the vertical floating zone in the zone melting of the iron rod with the zone melting pass. FIG4 is a schematic diagram of the morphology of the vertical floating zone in the zone melting of the iron rod under static conditions. FIG5 is a schematic diagram of the 3D distribution of Al and Si elements in the slag layer of the vertical floating zone of the iron rod after the 7th zone melting. Referring to Figures 1 to 5, a process for preparing ultrapure metal by continuous UHV vertical floating zone melting includes the following steps: Step 1, placing a metal rod to be purified into a vacuum pretreatment chamber, wherein the vacuum degree of the vacuum pretreatment chamber is on the order of ^10-5 Pa, and using a high-voltage arc discharge device to plasma clean the surface of the metal rod to obtain a clean metal rod; Step 2, sending the clean metal rod into an induction coil in an ultra-high vacuum zone melting process chamber under vacuum conditions, wherein the height of the induction coil is adapted to the height of the vertical floating zone to be formed by the clean metal rod, and clamping the end of the clean metal rod by a clamping mechanism so that the axis of the clean metal rod coincides with the axis of the induction coil, and the vacuum degree of the ultra-high vacuum zone melting process chamber is ^10-8 Pa level; step 3, the clean metal rod moves up and down in the vertical direction in the induction coil while spinning around its own axis, and the induction coil is equipped with a power supply to form a vertical floating zone on the clean metal rod by induction heating; step 4, performing n passes of vertical zone melting purification to obtain a purified metal rod with a higher purity level, n is a positive integer, and the vertical floating zone in each pass starts from the upper end of the clean metal rod, and the vertical floating zone gradually moves downward from the upper end to the lower end; step 5, the purified metal rod cooled to room temperature is sent into a vacuum pretreatment chamber under vacuum conditions, and a protective atmosphere is introduced into the vacuum pretreatment chamber. After the internal and external air pressures are consistent, the purified metal rod is taken out; step 6, the upper and lower preset parts of the purified metal rod are cut off, and the remaining part in the middle is the ultra-pure metal product.

The intermediate remainder in step 6 accounts for 85% to 95%. Step 4 includes 7 to 10 passes of vertical zone melting purification, and the moving speed of the vertical floating zone from the upper end to the lower end is 1 to 100 μm/s. The rotation speed of the spin in step 3 is 1 to 25 r/min, and the temperature range of induction heating is 100 to 2000°C.

The ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are respectively connected to an ultra-high vacuum system, and the ultra-high vacuum system is composed of a cryogenic pump, a molecular pump and a mechanical pump. The ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are connected through a plug valve. The ultra-high vacuum environment in the ultra-high vacuum zone melting process chamber can remove impurities with a saturated vapor pressure higher than that of the matrix by utilizing the difference in saturated vapor pressure between the matrix and the impurities. The ultra-high vacuum zone melting process chamber is respectively connected to a residual gas analyzer and a film thickness meter, and the probe of the film thickness meter is used to indirectly monitor and feedback the temperature of the vertical floating zone. The metal rod to be purified is a pure iron rod. The aluminum element and the silicon element in the pure iron rod are removed by entering the slag in the vertical floating zone of step 4.

As shown in FIG1 , the process of preparing ultrapure metal by continuous UHV vertical floating zone zone melting of the present invention includes step 1, feeding: opening the pre-vacuum chamber, and assembling the metal raw material rod into the vacuum pretreatment chamber through the magnetic rod. Turn on the spark plug and clean the surface of the rod-shaped material by high-voltage arc. Turn on the mechanical pump, molecular pump and cryogenic pump through the central controller to make the vacuum degree of the pre-vacuum chamber reach 10 ^-5 Pa and the vacuum degree of the process chamber reach 9×10 ^-8 Pa. Step 2, transmission: open the plug valve, and the magnetic sample delivery rod delivers the rod-shaped material until the specified position of the process chamber, and the vacuum degree of the process chamber drops to the transmission state of 10 ^-5 Pa. Step 3, exchange: the magnetic sample delivery rod in the process chamber clamps the rod-shaped material in the pre-vacuum chamber and performs a turn and transposition. Step 4, fixation: fix the rod-shaped material to a fixed rod at one end through the magnetic sample delivery rod, and then fix the other end, and the process chamber is restored to the background vacuum of 9×10 ^-8 Pa. Step 5, zone melting: set the parameters such as the temperature range of the induction heating coil, the vertical movement speed of the three-dimensional motion platform, and the rotation speed of the fixed rod through the central controller. Move the rod-shaped material from the initial position to the position where the bottom of the rod-shaped material is flush with the top of the heating device, then turn off the heating device. After the rod-shaped material cools to room temperature, return it to the initial position, and start the next zone melting process according to the set parameters. Repeat the above process, and perform n vertical zone melting purifications in sequence according to different process parameters. Step 6, material removal: After repeating the above steps for multiple times, turn off the power to the heating device, and after the rod-shaped material cools to room temperature, use the gripper to take it out to the pre-vacuum chamber, close the pre-vacuum chamber plug valve, let in the protective atmosphere, and take out the rod-shaped material after the internal and external air pressures are consistent.

A process for preparing ultrapure metal by continuous UHV vertical floating zone melting, which comprises placing a purified metal raw material rod in a vacuum pretreatment chamber for plasma cleaning; after cleaning, when the vacuum reaches a certain requirement, opening the gate valves of the vacuum pretreatment chamber and the ultra-high vacuum process chamber, and transferring the metal raw material rod from the vacuum pretreatment chamber to the ultra-high vacuum process chamber through a clamping assembly; transferring the metal raw material rod to a specific position of the ultra-high vacuum process chamber through a clamping assembly in the ultra-high vacuum process chamber, thereby realizing the exchange of the position of the metal raw material rod; through the operation of a central control system, the clamped metal raw material rod is vertically fixed and placed at the center of an induction heating coil; controlling the induction heating system to gradually increase the temperature of a certain area of the metal raw material rod until a zone melting state can be reached; performing multiple vertical zone melting purifications in sequence according to different process parameters, and obtaining ultrapure metal materials in the metal rod; transferring the zone-melted purified metal rod back to the vacuum pretreatment chamber through a clamping assembly without destroying the ultra-high vacuum, thereby realizing a continuous metal rod purification operation, which can be applied to industrial production.

The continuous UHV vertical floating zone melting process is used to prepare ultra-pure metals. The metal raw material rods that have been plasma cleaned in the vacuum pretreatment chamber are transferred to the ultra-high vacuum process chamber through a clamping assembly, fixed vertically and placed at the center of the induction coil; after the background vacuum is evacuated to 9× ^10-8 Pa, the metal raw material rods are regionally heated by the induction heating system until they are in a zone melting state; according to different process parameters, multiple vertical zone melting purifications are carried out in sequence; after the zone melting is completed, the metal rods are transferred back to the vacuum pretreatment chamber for removal; at the same time, new metal raw material rods can be added to prepare for the next zone melting, thereby realizing a continuous metal rod purification operation.

The process includes the following steps:

Step 1: Open the pre-vacuum chamber and assemble the metal raw material rod into the vacuum pretreatment chamber through the magnetic rod. Turn on the spark plug and clean the surface of the rod material with a high-voltage arc. Turn on the mechanical pump and cryogenic pump through the central controller to make the vacuum degree of the pre-vacuum chamber reach 10 ^-5 Pa and the vacuum degree of the process chamber reach 9×10 ^-8 Pa.

Step 2: Open the gate valve, and the magnetic sample delivery rod delivers the rod-shaped material until it reaches the specified position in the process chamber, and the vacuum degree of the process chamber drops to the delivery state of 10 ^-5 Pa. The magnetic sample delivery rod in the process chamber clamps the rod-shaped material in the pre-vacuum chamber and performs a turn and transposition. The magnetic sample delivery rod fixes the rod-shaped material to one end of the fixing rod, and then fixes the other end. The process chamber returns to the background vacuum and backfills the gas to 9×10 ^-8 Pa.

Step 3: Set the induction heating coil temperature range, the vertical movement speed of the three-dimensional motion platform, and the fixed rod rotation speed through the central controller.

Step 4: Move the rod-shaped material from the initial position to the position where the bottom of the rod-shaped material is flush with the top of the heating device, then turn off the heating device. After the rod-shaped material cools to room temperature, it returns to the initial position, and starts the next zone melting process according to the set parameters. Repeat the above process and perform n vertical zone melting purifications in sequence according to different process parameters.

Step 5: After repeating the above steps for multiple times, turn off the power of the heating device, wait for the rod-shaped material to cool to room temperature, use the gripper to take it out to the pre-vacuum chamber, close the pre-vacuum chamber valve, let in the protective atmosphere, and take out the rod-shaped material after the internal and external air pressures are consistent.

Step 6: Cut off the preset parts (5-15%) of the upper and lower ends of the rod-shaped material, and the remaining part in the middle is the purified product.

The induction heating coil is set to have a temperature range of 100°C to 2000°C, the three-dimensional motion platform is set to have a vertical movement speed of 0.1 to 200 mm/min, and the fixed rod has a rotation speed of 1 to 25 r/min.

The process of preparing ultrapure metal by continuous UHV vertical floating zone melting improves the purity efficiency of the purified metal, and the process has high repeatability in the continuous UHV vertical floating zone melting metal purification system, is simple to operate, and can be industrialized.

A superpure metal purification process, the method comprising the following steps:

Feed the material, open the pre-vacuum chamber, and assemble the rod-shaped material into the pre-vacuum chamber through the magnetic rod.

Cleaning, open the spark plug, clean the surface of the rod material by high-voltage arc, the vacuum degree of the pre-vacuum chamber reaches 10 ^-5 Pa, and the vacuum degree of the process chamber reaches 9×10 ^-8 Pa.

Transfer, open the gate valve, and the magnetic sample delivery rod transfers the rod-shaped material until it reaches the specified position in the process chamber, and the vacuum degree of the process chamber drops to 10 ^-5 Pa in the transfer state.

Transposition: the magnetic sample feeding rod in the process chamber clamps the rod-shaped material in the pre-vacuum chamber and performs a rotation and transposition.

Fix the rod-shaped material to one end of the fixing rod through the magnetic sample feeding rod, and then fix the other end, and the process chamber returns to the background vacuum: 9×10 ^-8 Pa.

Power on, set the moving speed and rotation speed of the three-dimensional motion platform on the central control system, and move the rod-shaped material to the initial position, that is, the bottom end of the rod-shaped material is flush with the top end of the induction coil.

Purification: Move the rod-shaped material from the initial position to the position where the bottom of the rod-shaped material is flush with the top of the induction coil, then turn off the induction heating system. After the rod-shaped material cools to room temperature, return it to the initial position, and start the next zone melting process according to the set parameters. Repeat the above process and perform n vertical zone melting purifications in sequence according to different process parameters.

Take out the sample: turn off the power of the induction heating system, close the vacuum valve of the pre-vacuum chamber, let in the protective atmosphere, and take out the rod-shaped material after the internal and external air pressures are consistent.

Cutting samples: Cut off the preset parts at the upper and lower ends of the rod-shaped material, and the remaining part in the middle is the purified product.

Furthermore, the heating temperature range of the induction heating system is 100-2000°C, and the vertical movement speed of the three-dimensional motion platform is set to 1-100 μm/s, and the rotation speed of the fixed rod is set to 1-25r/min.

Furthermore, the continuous UHV vertical floating zone melting metal purification system also includes a device for indirectly monitoring and feeding back the temperature of the melting zone using a film thickness meter probe, and judging the state of the melting zone by the deposition rate.

Furthermore, the continuous UHV vertical floating zone zone melting metal purification system can be automatically operated by the central control system to move up and down and spin. The initial position (0 position) of the zone melting system is located at the top of the induction coil, and the moving distance range of the three-dimensional motion platform is ±150mm. The maximum spin angle can rotate clockwise/counterclockwise bidirectionally 1-25r/min.

This embodiment provides a preparation process for ultrapure metals. A 4N-grade iron rod is placed in a pre-vacuum chamber, the bias power supply is turned on, and the surface of the rod-shaped material is cleaned by a high-voltage arc. The vacuum system is turned on by the central controller, and the sample delivery component transports the rod-shaped material to a specified position in the vacuum process chamber. The vacuum degree of the vacuum process chamber is 10 ^-5 Pa. The sample delivery component in the vacuum process chamber clamps the rod-shaped material and performs a turn and transposition. The rod-shaped material is clamped and fixed by the clamping component, the gate valve is closed, the vacuum system is turned on, and the vacuum degree of the vacuum process chamber is waited for to reach 9×10 ^-8 Pa.

The preparation process is purified according to the following steps.

The current and power are set by the induction heating system, and the parameters are input to manipulate the three-dimensional motion platform to move the iron rod from the initial position to the set position. The above process is repeated according to the set parameters, and 10 vertical zone melting purifications are carried out in sequence according to different process parameters.

The parameters of the first zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the second zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the third zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 4th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 5th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 6th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 7th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 8th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 9th zone melting are as follows: moving speed is 4.5 mm/min; current is 78 A, and vacuum degree is 10 ^-8 Pa.

The parameters of the 10th zone melting are as follows: the moving speed is 4.5 mm/min, the current is 78 A, and the vacuum degree is 10 ^-8 Pa.

After repeating the above steps 10 times, turn off the power of the induction heating system. After the iron rod cools to room temperature, use the sample delivery assembly to take it out to the pre-vacuum chamber, close the gate valve between the pre-vacuum chamber and the vacuum process chamber, let in the protective atmosphere through the micro-leak valve, and take out the iron rod after the internal and external air pressures are consistent.

The preset parts (5% to 15%) of the upper and lower ends of the rod-shaped material are cut off, and the remaining part in the middle is the purified product.

The contents not described in detail in this specification belong to the prior art known to the professional and technical personnel in this field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and/or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims (9)

1. A process for preparing ultrapure metal by continuous UHV vertical floating zone melting, characterized in that it comprises the following steps: Step 1, placing the metal rod to be purified into a vacuum pretreatment chamber, wherein the vacuum degree of the vacuum pretreatment chamber is on the order of 10 ^{- 5} Pa, and performing plasma cleaning on the surface of the metal rod using a high-voltage arc discharge device to obtain a clean metal rod; Step 2, sending the clean metal rod into the induction coil in the ultra-high vacuum zone melting process chamber under vacuum conditions, the height of the induction coil is adapted to the height of the vertical floating zone to be formed by the clean metal rod, the end of the clean metal rod is clamped by a clamping mechanism, so that the axis of the clean metal rod coincides with the axis of the induction coil, and the vacuum degree of the ultra-high vacuum zone melting process chamber is on the order of ^10-8 Pa; Step 3, the clean metal rod moves up and down in the vertical direction in the induction coil while spinning around its own axis, and a power supply is provided for the induction coil to form a vertical floating area on the clean metal rod through induction heating; Step 4, performing n passes of vertical zone melting purification to obtain a purified metal rod with a higher purity level, wherein n is a positive integer, and in each pass, the vertical floating zone starts from the upper end of the clean metal rod, and the vertical floating zone gradually moves downward from the upper end to the lower end; Step 5, sending the purified metal rod cooled to room temperature into a vacuum pretreatment chamber under vacuum conditions, introducing a protective atmosphere into the vacuum pretreatment chamber, and taking out the purified metal rod after the internal and external air pressures are consistent; Step 6, cutting off the preset upper and lower parts of the purified metal rod, and the remaining part in the middle is the ultra-pure metal product. 2. The process for preparing ultrapure metal by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the intermediate remainder in step 6 accounts for 85% to 95%. 3. The process for preparing ultrapure metal by continuous UHV vertical floating zone melting according to claim 1 is characterized in that step 4 includes 7 to 10 passes of vertical zone melting purification, and the movement speed of the vertical floating zone from the upper end to the lower end is 1 to 100 μm/s. 4. The process for preparing ultrapure metals by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the spin speed in step 3 is 1 to 25 r/min, and the temperature range of induction heating is 100 to 2000°C. 5. The process for preparing ultrapure metals by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are respectively connected to an ultra-high vacuum system, the ultra-high vacuum system is composed of a cryogenic pump, a molecular pump and a mechanical pump, and the ultra-high vacuum zone melting process chamber and the vacuum pretreatment chamber are connected by a gate valve. 6. The process for preparing ultrapure metals by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the ultra-high vacuum environment in the ultra-high vacuum zone melting process chamber can utilize the difference in saturated vapor pressure between the matrix and the impurities to remove impurities with higher saturated vapor pressure than the matrix. 7. The process for preparing ultrapure metals by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the ultra-high vacuum zone melting process chamber is respectively connected to a residual gas analyzer and a film thickness meter, and the probe of the film thickness meter is used to indirectly monitor and feedback the temperature of the vertical floating zone. 8. The process for preparing ultrapure metal by using continuous UHV vertical floating zone melting according to claim 1, characterized in that the metal rod to be purified is a pure iron rod. 9. The process for preparing ultrapure metal by continuous UHV vertical floating zone melting according to claim 1 is characterized in that the aluminum and silicon elements in the pure iron rod are removed by entering the slag in the vertical floating zone of step 4.