High-vacuum casting forming device and method for low-melting-point high-purity metal

Abstract

The invention discloses a high-vacuum casting forming device for low-melting-point high-purity metal, which comprises a vacuum furnace body, a heating box body and a metal cover body, a melting crucible and an induction heater are arranged in the metal cover body, an inert gas filling valve is arranged on the metal cover body, a resistance heater is arranged in the heating box body, and a support frame and a plurality of layers of support plates are further arranged in the heating box body. A plurality of casting forming crucibles which are sequentially connected through an overflow groove are arranged in the melting crucible, and a flow guide pipe communicated with the casting forming crucibles is arranged in the melting crucible; the invention further provides a high-vacuum casting forming method for the low-melting-point high-purity metal, according to the method, after the low-melting-point high-purity metal in the material melting crucible is heated and melted, the melted low-melting-point high-purity metal flows into the casting forming crucible through the flow guide pipe by means of the filled inert gas, and after cooling, a non-oxidation low-melting-point high-purity metal ingot is obtained. The low-melting-point high-purity metal is melted in the vacuum environment, casting is conducted in the oxygen-free environment, pollution caused by oxidation in air is avoided, and the production efficiency and the product quality are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal purification, and particularly relates to a high-vacuum casting forming device and method for low-melting-point high-purity metals. Background Art

[0002] Low-melting-point high-purity rare and precious metals are widely used in the field of semiconductor material manufacturing. With the development of the semiconductor industry, researchers have basically mastered the preparation technology of low-melting-point high-purity metals (mass concentration ≥ 99.99995%, 6N5). However, although the purification technology of low-melting-point high-purity metals in China is becoming increasingly mature, Chinese semiconductor companies still import high-purity low-melting-point metals from developed foreign countries. It is found that the stability of domestic low-melting-point high-purity metal products is worse than that of foreign counterparts, and at the same time, the percentage of semiconductor products prepared with domestic low-melting-point high-purity metals reaching the first-class or above quality level is also lower than that of semiconductor products prepared with foreign similar materials.

[0003] By comparing the chemical compositions of domestic and foreign low-melting-point high-purity metal products, it is found that in addition to the worse chemical composition stability of domestic low-melting-point high-purity metal products compared with foreign counterparts, the chemical compositions of the vast majority of domestic-made low-melting-point high-purity metal products also contain a small amount of gaseous elements (such as O, H, N). The main reason is that there are problems with the casting forming method of low-melting-point high-purity metals. Currently, the mainstream casting process in China still melts low-melting-point high-purity metals naked in the air and then directly casts them into a forming crucible through a container, resulting in substances such as oxygen and moisture entering the liquid low-melting-point metal, forming oxides and remaining inside the entire metal matrix, reducing the purity of the low-melting-point metal, and thus affecting the performance of subsequent semiconductor materials. Therefore, the above casting forming method can only obtain low-melting-point metals with a certain purity and quantity, but it is very difficult to obtain non-oxidized low-melting-point high-purity metal products. In addition, there is a new casting method, that is, filling an inert gas in a closed box for protection, heating and liquefying high-purity low-melting-point metals, manually skimming the slag, then manually casting one by one, and after the cast samples are naturally cooled, packing and encapsulating. In short, the first method has a higher casting efficiency, but oxides enter the low-melting-point metal matrix; although the second method avoids the problem of oxide contamination of the low-melting-point metal matrix caused by oxidation, the casting process is complex and the efficiency is low. Therefore, these two methods still have certain limitations.

[0004] In view of the current problems such as the complex casting process of low-melting-point high-purity metals, the easy oxidation of low-melting-point metal liquid during the casting forming process, and the low casting efficiency, there is a need for a device and method that can cast a large amount of non-oxidized low-melting-point high-purity metals at one time. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-vacuum casting and forming device for low-melting-point high-purity metals in view of the deficiencies of the above-mentioned prior art. The device is provided with a material melting crucible and an induction heater for containing and melting the low-melting-point high-purity metal. A diversion pipe is provided to connect the material melting crucible and the casting and forming crucible. An inert gas charging valve and an inert gas source are provided to control the inert gas pressure in the metal cover. Under high pressure, the melted low-melting-point high-purity metal flows into the casting and forming crucible in the heating box through the diversion pipe and the overflow tank, thereby realizing the preparation of non-oxidized low-melting-point high-purity metal ingots, reducing the problem of loose and porous surfaces of non-oxidized low-melting-point high-purity metal ingots, improving the production efficiency of non-oxidized low-melting-point high-purity metal ingots, and increasing the profit.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a high-vacuum casting and forming device for low-melting-point high-purity metals, characterized in that the device includes a vacuum furnace body, a heating box is provided in the vacuum furnace body, a metal cover is provided on the heating box, a material melting crucible is provided in the metal cover, an induction heater is provided outside the material melting crucible, an inert gas charging valve and a pressure control valve inside the cover are further provided on the metal cover, the inert gas charging valve is connected to an inert gas source, a resistance heater is provided on the inner wall of the heating box, a support frame is further provided in the heating box, a multi-layer support plate is provided on the support frame, and a plurality of casting and forming crucibles sequentially nested and connected through overflow tanks are provided on each support plate. A diversion pipe communicating with the casting and forming crucible is provided in the material melting crucible, and a vent hole is further provided on the heating box.

[0007] The above-mentioned high-vacuum casting and forming device for low-melting-point high-purity metals is characterized in that both the metal cover and the material melting crucible are cylindrical, the induction heater is a heating coil, and the ratio of the distance from the inner wall of the metal cover to the outer wall of the induction heater to the inner diameter of the induction heater is not less than 0.2; an insulating board made of non-metallic material is provided under the metal cover.

[0008] The above-mentioned high-vacuum casting and forming device for low-melting-point high-purity metals is characterized in that the distances between the multi-layer support plates are equal, and the ratio of the area of the opening of the casting and forming crucible to the area of the bottom is not less than 2.

[0009] The above-mentioned high-vacuum casting and forming device for low-melting-point high-purity metals is characterized in that the overflow tank is provided at the opening of the casting and forming crucible.

[0010] The above-mentioned high-vacuum casting and forming device for low-melting-point high-purity metal is characterized in that the support plate has three layers. The material melting crucible is communicated with the casting and forming crucible in the middle of the first layer through two primary diversion pipes respectively. The casting and forming crucibles on both sides of the first layer are communicated with the casting and forming crucibles on both sides of the second layer through secondary diversion pipes. The overflow grooves on both sides of the casting and forming crucible in the middle of the second layer are communicated with the casting and forming crucible in the middle of the third layer through two tertiary diversion pipes. The number of discharge ports of the primary diversion pipes, secondary diversion pipes and tertiary diversion pipes is not less than 3, and the turning joints are arc-shaped. The distance from the inlet of the primary diversion pipe to the bottom of the material melting crucible is not less than 5 mm, and the distance from the outlets of the primary diversion pipes, secondary diversion pipes and tertiary diversion pipes to the bottom of the casting and forming crucible is not less than 5 mm.

[0011] The above-mentioned high-vacuum casting and forming device for low-melting-point high-purity metal is characterized in that a vacuum pump is provided on the vacuum furnace body, and a packaging machine is also provided in the vacuum furnace body.

[0012] In addition, the present invention also provides a method for using a high-vacuum casting and forming device for low-melting-point high-purity metal, which is characterized in that the method includes the following steps: Step 1: After adding low-melting-point high-purity metal to the material melting crucible, close the inert gas filling valve, then seal the metal cover, and then close the heating box and the vacuum furnace body in sequence to obtain the device to be heated. Step 2: Start the vacuum pump of the device to be heated obtained in Step 1, pump the vacuum pressure in the vacuum furnace body to the target pressure and maintain it for more than 30 minutes, then turn on the resistance heater in the heating box to start heating, turn on the induction heater in the metal cover to heat the low-melting-point high-purity metal in the material melting crucible. After the temperatures inside the heating box and the low-melting-point high-purity metal in the material melting crucible reach the target temperature, open the pressure control valve inside the metal cover and maintain it for more than 30 minutes, then close the pressure control valve inside the cover, then open the inert gas filling valve, fill inert gas into the metal cover, and maintain the pressure in the metal cover not less than 0.2 MPa for high-vacuum casting and forming. When the liquid level of the low-melting-point high-purity metal in the material melting crucible is lower than the position of the inlet of the primary diversion pipe, end the casting. Close the resistance heater, induction heater, inert gas filling valve and vacuum pump in sequence. After the temperature in the vacuum furnace body naturally cools to room temperature, take out the non-oxidized low-melting-point high-purity metal ingot in the casting and forming crucible, and perform packaging in the packaging machine. Finally, open the vacuum furnace body and take out the packaged non-oxidized low-melting-point high-purity metal ingot.

[0013] In the present invention, by starting a vacuum pump, the air in the vacuum furnace body, the heating box body and the metal cover body is discharged to form an oxygen-free environment. The low-melting-point high-purity metal is melted by an induction heater, and the gas elements in the low-melting-point metal melt are completely distilled and volatilized by controlling the pressure control valve in the cover body. The melted low-melting-point high-purity metal is prevented from solidifying during casting by a resistance heater, and the casting rate of the melted low-melting-point metal is controlled by controlling the pressure of the inert gas filled in the metal cover body. It is applicable to the treatment of large quantities of low-melting-point high-purity metal casting.

[0014] The above method is characterized in that in step one, the melting point of the low-melting-point high-purity metal is not greater than 500 °C, the mass purity is not less than 6N8, and the mass of the added low-melting-point high-purity metal is 30 kg to 200 kg. The present invention is applicable to the treatment of large quantities of low-melting-point high-purity metal casting.

[0015] It should be noted that 6N8 represents 99.99998%.

[0016] The above method is characterized in that in step two, the target pressure is 10 -3 Pa to 10 -1 Pa, and the target temperature is 300 °C to 500 °C. The present invention prevents oxygen from affecting casting by controlling the target pressure, and ensures that the low-melting-point high-purity metal is fully melted by controlling the target temperature.

[0017] The above method is characterized in that in step two, the volume purity of the inert gas is not less than 99.9995%. The present invention prevents the introduction of impurities by controlling the volume purity of the inert gas.

[0018] The present invention has the following advantages compared with the prior art: 1. The high-vacuum casting and forming device for low-melting-point high-purity metal of the present invention provides a sealing structure by setting a vacuum furnace body, is used for containing and melting the low-melting-point high-purity metal by setting a melting crucible and an induction heater, is communicated with the melting crucible and the casting and forming crucible by setting a diversion tube, controls the inert gas pressure in the metal cover by setting an inert gas filling valve and an inert gas gas source, and under high pressure, the melted low-melting-point high-purity metal flows into the casting and forming crucible in the heating box body through the diversion tube and the overflow tank. By setting a heating box body and a resistance heater, it is ensured that the casting and forming crucible cools slowly, and by setting a packaging machine for packaging, the preparation of non-oxidized low-melting-point high-purity metal ingots is realized, the problem of surface porosity of non-oxidized low-melting-point high-purity metal ingots is reduced, the production efficiency of non-oxidized low-melting-point high-purity metal ingots is improved, and the profit is increased.

[0019] 2. The present invention uses an induction heater to heat the low-melting-point high-purity metal in the material melting crucible to complete liquefaction and maintain it for a period of time, which is beneficial to fully distill and volatilize the gas impurity elements (such as O, N, H) dissolved in the low-melting-point high-purity metal liquid. By utilizing the advantages of vacuum distillation degassing, it ensures that no gas elements are introduced during the subsequent casting and molding process of the low-melting-point high-purity metal, thus ensuring the quality of the product during the casting process.

[0020] 3. The present invention encapsulates the cast low-melting-point high-purity metal ingot in a vacuum furnace, avoiding the contact of the non-oxidized low-melting-point high-purity metal ingot with the outside air, isolating the interference of gas elements and external impurity pollution, and ensuring the quality of the final cast product.

[0021] 4. The present invention controls the casting rate of the molten low-melting-point metal liquid by controlling the pressure of the inert gas filled in the metal cover body, which is suitable for processing the casting of a large quantity of low-melting-point high-purity metal.

[0022] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of the high-vacuum casting and molding device for the low-melting-point high-purity metal of the present invention.

[0024] Description of the reference numerals: 1 - Vacuum furnace body; 2 - Heating box body; 3 - Metal cover body; 4 - Material melting crucible; 5 - Induction heater; 6 - Inert gas filling valve; 7 - Pressure control valve inside the cover body; 8 - Resistance heater; 9 - Support frame; 10 - Support plate; 11 - Overflow tank; 12 - Casting and molding crucible; 13 - Vent hole; 14 - Heat insulation board; 15 - Primary diversion pipe; 16 - Secondary diversion pipe; 17 - Tertiary diversion pipe; 18 - Vacuum pump; 19 - Encapsulation machine; 20 - Furnace body support; 21 - Box body support; 22 - Thermocouple; 23 - Heat insulation and thermal insulation layer. Detailed Description of the Embodiment

[0025] A high-vacuum casting and molding device for a low-melting-point high-purity metal of the present invention is described in detail through Embodiment 1.

[0026] Embodiment 1 As Figure 1As shown in the figure, a high-vacuum casting and forming device for a low-melting-point high-purity metal in this embodiment includes a vacuum furnace body 1. A heating box 2 is arranged in the vacuum furnace body 1. A metal cover 3 is arranged on the heating box 2. A melting crucible 4 is arranged in the metal cover 3. An induction heater 5 is arranged outside the melting crucible 4. An inert gas filling valve 6 and a pressure control valve 7 inside the cover are also arranged on the metal cover 3. The inert gas filling valve 6 is connected to an inert gas source. A resistance heater 8 is arranged on the inner wall of the heating box 2. A support frame 9 is also arranged in the heating box 2. A multi-layer support plate 10 is arranged on the support frame 9. A plurality of casting and forming crucibles 12 nested with each other through overflow grooves 11 in sequence are arranged on each support plate 10. A diversion tube communicating with the casting and forming crucible 12 is arranged in the melting crucible 4. A vent hole 13 is also arranged on the heating box 2.

[0027] It should be noted that a vacuum environment is provided by setting the vacuum furnace body 1. The low-melting-point high-purity metal is melted by setting the metal cover 3, the melting crucible 4 and the induction heater 5. Inert gas is introduced into the metal cover 3 by setting the inert gas filling valve 6 and the inert gas source. The melted low-melting-point high-purity metal is cast into the casting and forming crucible 12 in the heating box 2 through the diversion tube by cooperation, avoiding contact with the outside air during the casting process, isolating the interference of gas elements and external impurity pollution, ensuring the quality of the finally cast non-oxidized low-melting-point high-purity metal ingot, reducing the problem of loose and porous surface of the non-oxidized low-melting-point high-purity metal ingot, improving the production efficiency of the non-oxidized low-melting-point high-purity metal ingot, and increasing the profit.

[0028] It should be noted that by setting the pressure control valve 7 inside the cover, it is opened when the vacuum furnace body 1 is evacuated to facilitate evacuating the metal cover 3 as well, and closed during casting to facilitate filling with inert gas, increasing the pressure inside the metal cover 3 and facilitating leading out and casting the melted low-melting-point high-purity metal through the diversion tube.

[0029] It should be noted that the casting process and the melted low-melting-point high-purity metal cast into the casting and forming crucible 12 are kept warm by setting the resistance heater 8, ensuring that the melted low-melting-point high-purity metal in the diversion tube will not cool and solidify, and at the same time enabling the melted low-melting-point high-purity metal cast into the casting and forming crucible 12 to cool slowly, improving the quality of the finally cast non-oxidized low-melting-point high-purity metal ingot.

[0030] It should be noted that by setting the support frame 9, it is convenient to install the multi-layer support plate 10. By arranging the casting and forming crucibles 12 on each support plate 10, the melted low-melting-point high-purity metal is cast into a plurality of casting and forming crucibles 12 to obtain a plurality of non-oxidized low-melting-point high-purity metal ingots of appropriate sizes.

[0031] It should be noted that by providing the vent holes 13, it is convenient to balance the air pressure between the vacuum furnace body 1 and the heating box body 2, and it is also convenient to evacuate the heating box body 2.

[0032] It should be noted that both the vacuum furnace body 1 and the metal cover body 3 adopt a double-layer water-cooled stainless steel structure, and both the vacuum furnace body 1 and the heating box body 2 adopt a side-opening structure, which is beneficial to the placement and removal of the support frame 9, the casting crucible 12, and the low-melting-point high-purity metal, and also facilitates the subsequent encapsulation of the vacuum furnace body 1.

[0033] It should be noted that the casting crucible 12 is made of polytetrafluoroethylene or high-purity graphite material with a graphite mass purity of not less than 99.995%. The flow guide pipe, the overflow tank 11, and the material melting crucible 4 are all made of quartz material, and the support plate 10 is made of high-strength graphite material. The material melting crucible 4 made of quartz material, compared with a common graphite crucible with a graphite mass purity of less than 99.9%, is not easy to contaminate the low-melting-point metal. Graphite powder is likely to fall off from the inner wall of the graphite crucible, and the graphite powder contains relatively high impurity elements such as Bi, Pb, Fe, and Ni, and the impurities enter the low-melting-point metal matrix. In addition, the material melting crucible 4 has a large loading capacity, is especially suitable for industrial production, and improves the production efficiency of the low-melting-point high-purity metal.

[0034] It should be noted that a furnace body support 20 is provided at the lower part of the vacuum furnace body 1, and a box body support 21 is provided at the lower part of the heating box body 2.

[0035] It should be noted that a thermocouple 22 is provided on the resistance heater 8 for monitoring the heating temperature.

[0036] It should be noted that an adiabatic insulation layer 23 is provided on the inner wall of the heating box body 2.

[0037] In this embodiment, both the metal cover body 3 and the material melting crucible 4 are cylindrical, the induction heater 5 is a heating coil, and the ratio of the distance from the inner wall of the metal cover body 3 to the outer wall of the induction heater 5 to the inner diameter of the induction heater 5 is not less than 0.2; an adiabatic plate 14 made of a non-metallic material is provided under the metal cover body 3. By using a heating coil as the induction heater 5, it is ensured that the low-melting-point high-purity metal is uniformly melted, and at the same time, it also plays a stirring role, making the components of the melted low-melting-point high-purity metal more uniform. By controlling the shapes of the metal cover body 3 and the material melting crucible 4 and the ratio of the distance from the inner wall of the metal cover body 3 to the outer wall of the induction heater 5 to the inner diameter of the induction heater 5, the heating effect of the induction heater 5 is ensured, and it is avoided that the electromagnetic induction lines of the electromagnetic field generated by the electromagnetic induction of the heating coil induce and heat the inner wall of the metal cover body 3, weakening the insufficient magnetic field intensity; by providing the adiabatic plate 14, it is prevented that the heat generated by the induction heater 5 affects the heating box body 2.

[0038] It should be noted that the metal cover body 3 and the adiabatic plate 14 are hermetically connected.

[0039] In this embodiment, the distances between multiple layers of the support plates 10 are equal, and the ratio of the area of the opening of the casting crucible 12 to the area of the bottom is not less than 2. By controlling the equal distances between multiple layers of the support plates 10, it is convenient to evenly place multiple layers of casting crucibles 12, ensuring the uniformity of casting. By controlling the ratio of the area of the opening of the casting crucible 12 to the area of the bottom, the casting crucible 12 is defined as an inverted trapezoid, which is convenient for taking out the non-oxidized low-melting-point high-purity metal ingots cast therein.

[0040] In this embodiment, the overflow groove 11 is arranged at the opening of the casting crucible 12. By arranging the overflow groove 11 at the opening of the casting crucible 12, it is convenient to overflow the excess molten low-melting-point high-purity metal to the adjacent casting crucible 12, realizing the one-time large-scale casting and forming of non-oxidized low-melting-point high-purity metal ingots.

[0041] In this embodiment, the support plate 10 has three layers. The material melting crucible 4 is connected to the casting forming crucible 12 in the middle of the first layer through two primary diversion pipes 15 respectively. The casting forming crucibles 12 on both sides of the first layer are both connected to the casting forming crucibles 12 on both sides of the second layer through secondary diversion pipes 16. The overflow grooves 11 on both sides of the casting forming crucible 12 in the middle of the second layer are connected to the casting forming crucible 12 in the middle of the third layer through two tertiary diversion pipes 17. The number of discharge ports of the primary diversion pipes 15, secondary diversion pipes 16 and tertiary diversion pipes 17 is not less than 3, and the turning connection parts are arc-shaped. The distance from the inlet of the primary diversion pipe 15 to the bottom of the material melting crucible 4 is not less than 5 mm, and the distance from the outlets of the primary diversion pipes 15, secondary diversion pipes 16 and tertiary diversion pipes 17 to the bottom of the casting forming crucible 12 is not less than 5 mm. By connecting the material melting crucible 4 and the three-layer casting forming crucibles 12 through the primary diversion pipes 15, secondary diversion pipes 16 and tertiary diversion pipes 17, the molten low-melting-point high-purity metal in the material melting crucible 4 first enters the casting forming crucible 12 in the middle of the first layer through the primary diversion pipe 15. After the casting forming crucible 12 in the middle of the first layer is filled, the excess molten low-melting-point high-purity metal is gradually overflowed to the casting forming crucibles 12 on both sides of the first layer through the overflow grooves 11. When the casting forming crucibles 12 at both ends of the first layer are also filled, the molten low-melting-point high-purity metal is cast into the casting forming crucibles 12 on both sides of the second layer through the overflow grooves 11 and the secondary diversion pipes 16. After the casting forming crucibles 12 on both sides of the second layer are filled, the excess molten low-melting-point high-purity metal is gradually overflowed to the casting forming crucible 12 in the middle of the second layer through the overflow grooves 11. When the two casting forming crucibles 12 in the middle of the second layer are also filled, the molten low-melting-point high-purity metal is cast into the casting forming crucible 12 in the middle of the third layer through the overflow grooves 11 and the tertiary diversion pipes 17. After the casting forming crucible 12 in the middle of the third layer is filled, the excess molten low-melting-point high-purity metal is gradually overflowed to the casting forming crucibles 12 on both sides of the third layer through the overflow grooves 11 until all the molten low-melting-point high-purity metal in the material melting crucible 4 is cast into the casting forming crucibles 12, completing the high-vacuum casting forming of the low-melting-point high-purity metal. By setting the number of discharge ports of the primary diversion pipes 15, secondary diversion pipes 16 and tertiary diversion pipes 17 to be not less than 3, it is convenient to disperse and cast the molten low-melting-point high-purity metal into the two casting forming crucibles 12, making the casting more uniform. By controlling the distance from the inlet of the primary diversion pipe 15 to the bottom of the material melting crucible 4 and the distances from the outlets of the primary diversion pipes 15, secondary diversion pipes 16 and tertiary diversion pipes 17 to the bottom of the casting forming crucible 12, it is prevented that the distance is too close, the molten low-melting-point high-purity metal is too thick, and the inlet or outlet of the diversion pipe is blocked.

[0042] In this embodiment, a vacuum pump 18 is provided on the vacuum furnace body 1, and a packaging machine 19 is also provided in the vacuum furnace body 1. By providing the vacuum pump 18, the inside of the vacuum furnace body 1 is evacuated. By providing the packaging machine 19, it is convenient to directly package the cast non-oxidized low-melting-point high-purity metal ingot under the condition of oxygen isolation, further preventing the occurrence of oxidation.

[0043] A high-vacuum casting method for a low-melting-point high-purity metal of the present invention is described in detail through Embodiment 2 to Embodiment 4.

[0044] Embodiment 2 This embodiment includes the following steps: Step 1: After adding 30 kg of low-melting-point high-purity indium with a purity of 6N8 to the melting crucible 4, close the inert gas filling valve 6, then seal the metal cover 3, and then close the heating box 2 and the vacuum furnace body 1 in sequence to obtain the device to be heated. Step 2: Start the vacuum pump 18 of the device to be heated obtained in Step 1, evacuate the vacuum pressure inside the vacuum furnace body 1 to 10 -3 Pa to 10 -1 Pa and maintain it for more than 30 minutes. Then turn on the resistance heater 8 in the heating box 2 to start heating, turn on the induction heater 5 inside the metal cover 3 to heat the low-melting-point high-purity indium in the melting crucible 4. After the temperature inside the heating box 2 and the low-melting-point high-purity indium in the melting crucible 4 reach 500 °C, open the pressure control valve 7 inside the cover of the metal cover 3 and maintain it for more than 30 minutes. Then close the pressure control valve 7 inside the cover. Then open the inert gas filling valve 6 and fill the metal cover 3 with an inert gas with a volume purity of not less than 99.9995%, and maintain the pressure inside the metal cover 3 to be not less than 0.2 MPa for high-vacuum casting. When the liquid level of the low-melting-point high-purity indium in the melting crucible 4 is lower than the position of the inlet of the primary diversion tube 15, end the casting. Close the resistance heater 8, the induction heater 5, the inert gas filling valve 6 and the vacuum pump 18 in sequence. After the temperature inside the vacuum furnace body 1 naturally cools to room temperature, take out the non-oxidized low-melting-point high-purity indium metal ingot in the casting crucible 12 and package it in the packaging machine 19. Finally, open the vacuum furnace body 1 and take out the packaged non-oxidized low-melting-point high-purity indium ingot.

[0045] Embodiment 3 This embodiment includes the following steps: Step 1: After adding 100 kg of low-melting-point high-purity indium with a purity of 6N8 to the melting crucible 4, close the inert gas filling valve 6, then seal the metal cover 3, and then close the heating box 2 and the vacuum furnace body 1 in sequence to obtain the device to be heated. Step 2: Start the vacuum pump 18 of the device to be heated obtained in Step 1, and pump the vacuum pressure in the vacuum furnace body 1 to 10 -3 Pa~10 -1 Pa and maintain it for more than 30 minutes. Then turn on the resistance heater 8 in the heating box 2 to start heating, and turn on the induction heater 5 in the metal cover 3 to heat the low-melting-point high-purity metal indium in the melting crucible 4. After the temperature inside the heating box 2 and the low-melting-point high-purity metal indium in the melting crucible 4 reach 400 °C, open the pressure control valve 7 inside the cover of the metal cover 3 and maintain it for more than 30 minutes. Then close the pressure control valve 7 inside the cover. Next, open the inert gas filling valve 6 and fill the metal cover 3 with an inert gas with a volume purity of not less than 99.9995%. Keep the pressure inside the metal cover 3 not less than 0.2 MPa for high-vacuum casting. When the liquid level of the low-melting-point high-purity metal indium in the melting crucible 4 is lower than the position of the inlet of the primary diversion tube 15, end the casting. Turn off the resistance heater 8, the induction heater 5, the inert gas filling valve 6, and the vacuum pump 18 in sequence. After the temperature in the vacuum furnace body 1 naturally cools to room temperature, take out the non-oxidized low-melting-point high-purity metal indium ingot in the casting crucible 12 and perform encapsulation in the encapsulator 19. Finally, open the vacuum furnace body 1 and take out the encapsulated non-oxidized low-melting-point high-purity metal indium ingot.

[0046] Example 4 This example includes the following steps: Step 1: After adding 200 kg of low-melting-point high-purity metal indium with a purity of 6N8 to the melting crucible 4, close the inert gas filling valve 6, then seal the metal cover 3, and then close the heating box 2 and the vacuum furnace body 1 in sequence to obtain the device to be heated; Step 2: Start the vacuum pump 18 of the device to be heated obtained in Step 1, and pump the vacuum pressure in the vacuum furnace body 1 to 10 -3 Pa~10 -1Keep Pa for more than 30 minutes, then turn on the resistance heater 8 in the heating chamber 2 to start heating, and turn on the induction heater 5 in the metal cover 3 to heat the low-melting-point high-purity metal indium in the melting crucible 4. After the temperature of the inside of the heating chamber 2 and the low-melting-point high-purity metal indium in the melting crucible 4 reaches 300 °C, open the pressure control valve 7 inside the cover of the metal cover 3 and keep it for more than 30 minutes. Then close the pressure control valve 7 inside the cover. Next, open the inert gas filling valve 6 and fill the metal cover 3 with an inert gas with a volume purity of not less than 99.9995%. Keep the pressure inside the metal cover 3 not less than 0.2 MPa for high-vacuum casting. When the liquid level of the low-melting-point high-purity metal indium in the melting crucible 4 is lower than the position of the inlet of the primary diversion tube 15, end the casting. Turn off the resistance heater 8, the induction heater 5, the inert gas filling valve 6, and the vacuum pump 18 in sequence. After the temperature in the vacuum furnace body 1 naturally cools to room temperature, take out the non-oxidized low-melting-point high-purity metal indium ingot in the casting crucible 12 and perform encapsulation in the encapsulator 19. Finally, open the vacuum furnace body 1 and take out the encapsulated non-oxidized low-melting-point high-purity metal indium ingot.

[0047] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-vacuum casting and forming device for a low-melting-point high-purity metal, characterized in that, The device includes a vacuum furnace body (1), a heating box body (2) is arranged in the vacuum furnace body (1), a metal cover body (3) is arranged on the heating box body (2), a material melting crucible (4) is arranged in the metal cover body (3), an induction heater (5) is arranged outside the material melting crucible (4), an inert gas filling valve (6) and a pressure control valve (7) inside the cover body are further arranged on the metal cover body (3), the inert gas filling valve (6) is connected with an inert gas gas source, a resistance heater (8) is arranged on the inner wall of the heating box body (2), a support frame (9) is further arranged in the heating box body (2), a plurality of layers of support plates (10) are arranged on the support frame (9), a plurality of casting forming crucibles (12) which are sequentially nested and connected through overflow grooves (11) are arranged on each support plate (10), a diversion pipe communicated with the casting forming crucible (12) is arranged in the material melting crucible (4), and a vent hole (13) is further arranged on the heating box body (2).

2. The high-vacuum casting and forming device for a low-melting-point high-purity metal according to claim 1, wherein, Both the metal cover body (3) and the material melting crucible (4) are cylindrical, the induction heater (5) is a heating coil, and the ratio of the distance from the inner wall of the metal cover body (3) to the outer wall of the induction heater (5) to the inner diameter of the induction heater (5) is not less than 0.2; an insulating board (14) made of non-metallic material is arranged under the metal cover body (3).

3. The high-vacuum casting and molding device for a low-melting-point high-purity metal according to claim 1, wherein, The distances between the multiple layers of support plates (10) are equal, and the ratio of the area of the opening of the casting forming crucible (12) to the area of the bottom is not less than 2.

4. The high-vacuum casting and forming device for a low-melting-point high-purity metal according to claim 1, characterized in that, The overflow groove (11) is arranged at the opening of the casting forming crucible (12).

5. The high-vacuum casting and molding device for a low-melting-point high-purity metal according to claim 1, characterized in that, The support plate (10) is in three layers, the material melting crucible (4) is communicated with the casting forming crucible (12) in the middle of the first layer through two primary diversion pipes (15) respectively, the casting forming crucibles (12) on both sides of the first layer are communicated with the casting forming crucibles (12) on both sides of the second layer through secondary diversion pipes (16) respectively, the overflow grooves (11) on both sides of the casting forming crucible (12) in the middle of the second layer are communicated with the casting forming crucible (12) in the middle of the third layer through two tertiary diversion pipes (17), the number of the discharge ports of the primary diversion pipe (15), the secondary diversion pipe (16) and the tertiary diversion pipe (17) is not less than 3, and the turning connection part is arc-shaped; the distance from the inlet of the primary diversion pipe (15) to the bottom of the material melting crucible (4) is not less than 5 mm, and the distance from the outlets of the primary diversion pipe (15), the secondary diversion pipe (16) and the tertiary diversion pipe (17) to the bottom of the casting forming crucible (12) is not less than 5 mm.

6. The high-vacuum casting and molding device for a low-melting-point high-purity metal according to claim 1, wherein, A vacuum pump (18) is arranged on the vacuum furnace body (1), and a packaging machine (19) is further arranged in the vacuum furnace body (1).

7. A method for using a high-vacuum casting and molding device for a low-melting-point high-purity metal as described in any one of claims 1-6, characterized in that, The method includes the following steps: Step 1: After adding low-melting-point high-purity metal into the material melting crucible (4), close the inert gas filling valve (6), then seal the metal cover body (3), and then close the heating box body (2) and the vacuum furnace body (1) in sequence to obtain the device to be heated; Step 2: Start the vacuum pump (18) of the device to be heated obtained in Step 1, pump the vacuum pressure in the vacuum furnace body (1) to the target pressure and maintain it for more than 30 minutes. Then, turn on the resistance heater (8) in the heating box (2) to start heating, and turn on the induction heater (5) in the metal cover (3) to heat the low-melting-point high-purity metal in the melting crucible (4). After the temperatures of the inside of the heating box (2) and the low-melting-point high-purity metal in the melting crucible (4) reach the target temperature, open the pressure control valve (7) inside the cover of the metal cover (3) and maintain it for more than 30 minutes. Then, close the pressure control valve (7) inside the cover. Next, open the inert gas filling valve (6) to fill the metal cover (3) with inert gas, and maintain the pressure in the metal cover (3) not less than 0.2 MPa for high-vacuum casting. When the liquid level of the low-melting-point high-purity metal in the melting crucible (4) is lower than the position of the inlet of the primary diversion pipe (15), end the casting. Then, turn off the resistance heater (8), the induction heater (5), the inert gas filling valve (6), and the vacuum pump (18) in sequence. After the temperature in the vacuum furnace body (1) naturally cools to room temperature, take out the non-oxidized low-melting-point high-purity metal ingot in the casting crucible (12), and perform encapsulation in the encapsulation machine (19). Finally, open the vacuum furnace body (1) and take out the encapsulated non-oxidized low-melting-point high-purity metal ingot.

8. The method according to claim 7, wherein In Step 1, the melting point of the low-melting-point high-purity metal is not greater than 500 °C, the mass purity is not less than 6N8, and the mass of the added low-melting-point high-purity metal is 30 kg to 200 kg.

9. The method according to claim 7, characterized in that, The target pressure described in Step 2 is 10 -3 Pa to 10 -1 Pa, and the target temperature is 300°C to 500°C.

10. The method according to claim 7, wherein In Step 2, the volume purity of the inert gas is not less than 99.9995%.

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