Method for preparing low-oxygen ultra-pure tin based on integration of magnetic levitation smelting and multi-tube vacuum suction casting

Abstract

The invention belongs to the field of ultra-pure tin preparation, and provides a method for preparing low-oxygen ultra-pure tin based on integration of magnetic suspension smelting and multi-tube vacuum suction casting, and the method comprises the steps of device building, magnetic suspension smelting and deoxidation treatment and multi-tube vacuum suction casting. A suction casting chamber of a multi-pipe vacuum suction casting device is communicated with a smelting chamber of a vacuum magnetic suspension smelting furnace through a suction casting pipe, and molten tin deoxidized in the smelting chamber is transferred into a suction casting mold from a tin casting pipe in the technological process by controlling the pressure intensity difference between the suction casting chamber and the smelting chamber and is cooled and shaped in the suction casting chamber. According to the method, preparation of the low-oxygen ultra-pure tin product with the purity larger than or equal to 99.999995% and the oxygen content smaller than or equal to 1 ppm is achieved, the problems that in the prior art, impurities are likely to be introduced during tin purification, and the oxygen content of the product is increased can be solved, and the requirement of the high-end electronic industry for ultra-pure tin can be better met.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ultra-pure tin preparation and relates to a method for preparing low-oxygen ultra-pure tin based on integrated magnetic levitation melting and multi-tube vacuum suction casting. BACKGROUND

[0002] As the core key equipment in the semiconductor industry, the current many research institutions are independently developing extreme ultraviolet lithography machines (EUV lithography machines). The light source is the core component of the EUV lithography machine. The light source of the EUV lithography machine is generated by means of high-energy laser (carbon dioxide laser) bombardment of tin droplets. The purity of tin is required to reach 99.999995% (7N5). At the same time, the oxygen content of tin is strictly required, and the oxygen content of tin is usually required to be below 1 ppm.

[0003] The traditional purification methods of high-purity tin mainly include vacuum distillation and zone melting. However, these methods need to use crucibles or containers, and the use of crucibles or containers is easy to introduce impurities such as Fe, Si, Al, etc., resulting in insufficient purity of the product. After the high-purity tin is purified, casting, extrusion and other methods are often used for forming. In the forming process, the product inevitably contacts oxygen in the environment. At the same time, the forming process is carried out at high temperature, and the high temperature condition will accelerate the reaction of tin and oxygen, resulting in the increase of the oxygen content of the product, affecting the performance of the product. For example, the purity and water content of the protective gas used in the forming process will affect the purity and oxygen content of the formed product. For extrusion forming, the heating process is also involved. The heating process not only accelerates the oxidation of tin, but also increases the energy consumption of the process. Overall, in the existing technology, the use of crucibles or containers limits the improvement of the purity of the product, and the traditional forming method cannot effectively control the oxygen content of the product, making it difficult to realize the preparation of ultra-pure tin products with high purity (≥99.999995%) and low oxygen content (≤1 ppm), and unable to meet the demand of high-end electronic industry for ultra-pure tin. SUMMARY

[0004] In view of the problems in the prior art that the use of crucibles or containers easily introduces impurities, and the oxygen content of the product increases when the purified tin is formed, the application provides a method for preparing low-oxygen ultra-pure tin based on integrated magnetic levitation melting and multi-tube vacuum suction casting, to realize the stable preparation of ultra-pure tin products with purity ≥99.999995% and oxygen content ≤1 ppm.

[0005] To achieve the above-mentioned application purposes, the technical solutions adopted by the application are as follows:

[0006] The method for preparing low-oxygen ultra-pure tin based on integrated magnetic levitation melting and multi-tube vacuum suction casting comprises the following steps:

[0007] (1) Device construction: place the suction casting chamber of the multi-tube vacuum suction casting device on the upper side of the vacuum magnetic levitation melting furnace through the liftable support frame, and connect the suction casting mold in the suction casting chamber of the multi-tube vacuum suction casting device with the melting chamber of the vacuum magnetic levitation melting furnace through the suction casting pipe, and a control valve is arranged on the suction casting pipe;

[0008] (2) Magnetic levitation melting and deoxidation treatment: close the control valve, and under the protection of high-purity inert gas, place the raw tin ingot in the center area of the levitation coil of the vacuum magnetic levitation melting furnace, and vacuumize the furnace cavity of the vacuum magnetic levitation melting furnace to a pressure of <10 -3 Pa in the furnace cavity, and then heat and melt, and then raise the temperature of the molten tin obtained by melting to 400-600 ℃ and keep the temperature for vacuum deoxidation to obtain deoxidized molten tin;

[0009] In this step, the purity of the raw tin ingot is 6N level, and the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <10 -3 Pa during the processes of heating, melting and vacuum deoxidation;

[0010] (3) Multi-tube vacuum suction casting: vacuumize the suction casting chamber of the multi-tube vacuum suction casting device to a pressure of <10 -3 Pa, and at the same time, fill the furnace cavity of the vacuum magnetic levitation melting furnace with high-purity inert gas until the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction casting chamber reaches the suction casting pressure, open the control valve, and then the deoxidized molten tin is sucked into the suction casting mold through the suction casting pipe, and then cooled to room temperature in the suction casting chamber to be shaped, and then collected into a low-oxygen ultra-pure tin product under the protection of high-purity argon, wherein the purity of the low-oxygen ultra-pure tin product is ≥99.999995%, and the oxygen content is ≤1 ppm;

[0011] In this step, the suction casting pressure is controlled to be 0.1-0.5 MPa, and the pressure in the suction casting chamber of the multi-tube vacuum suction casting device is controlled to be <10 -3 Pa during the cooling and shaping process.

[0012] In the above technical solution, the height of the suction casting chamber can be adjusted in the direction perpendicular to the horizontal plane by lifting the support frame, and then the position of the inlet end of the suction casting pipe is adjusted.

[0013] Further, in step (2), the inlet end of the suction casting pipe is controlled to be suspended above the melting chamber of the vacuum magnetic levitation melting furnace; and in the suction casting process of step (3), the inlet end of the suction casting pipe is controlled to be below the liquid level of the deoxidized molten tin, and the position of the inlet end of the suction casting pipe is adjusted by lifting the support frame.

[0014] In the above technical solution, in order to facilitate the operation of the control valve, the control valve on the suction casting pipe is located outside the multi-tube vacuum suction casting device and the vacuum magnetic levitation melting furnace.

[0015] In the process of sucking the deoxidized molten tin into the suction casting mold through the suction pipe, in order to avoid secondary pollution of the product caused by the suction pipe, the suction pipe is preferably a high-purity quartz pipe or a high-purity graphite pipe.

[0016] In the above technical solution, the melting temperature and the melting time in step (2) are controlled to be 300-500 DEG C and 1-2 hours, respectively, so that the raw tin ingot can be converted into uniform molten tin.

[0017] In the above technical solution, the holding time in step (2) is preferably controlled to be 1-2 hours.

[0018] In the above technical solution, the suction casting speed in step (3) is preferably controlled to be 10-50 mm / s.

[0019] In the above technical solution, the cooling rate in step (3) is controlled to be 5-10 DEG C / min during cooling.

[0020] In the above technical solution, the purity of the high-purity inert gas is greater than or equal to 99.999%, and the high-purity inert gas can be high-purity argon.

[0021] In the above technical solution, the quartz devices, such as the high-purity quartz pipe, need to be immersed in aqua regia, then washed with ultrapure water, and dried before use; the graphite devices, such as the high-purity graphite pipe and the high-purity graphite mold, need to be immersed in aqua regia, then washed with ultrapure water, and then calcined at 1000-1100 DEG C in vacuum to remove impurities before use. The purity of the high-purity quartz and the high-purity graphite is greater than or equal to 99.9999%.

[0022] Compared with the prior art, the technical solution provided by the present application has the following beneficial technical effects:

[0023] 1. The application provides a method for preparing low-oxygen ultra-pure tin based on the integration of magnetic levitation smelting and multi-tube vacuum suction casting, which communicates the suction casting chamber of the multi-tube vacuum suction casting device with the smelting chamber of the vacuum magnetic levitation smelting furnace through the suction casting pipe, and is equipped with a control valve on the suction casting pipe. In the process, by adjusting the pressure difference between the suction casting chamber and the smelting chamber and cooperating with the opening and closing of the control valve, the deoxidized molten tin in the smelting chamber is transferred to the suction casting mold through the suction casting pipe, and is cooled and shaped in the suction casting chamber, thereby avoiding the problem that the existing method needs to take out the purified tin from the purification equipment and transfer it to the forming equipment for forming, and the forming needs to be carried out at high temperature, which leads to the increase of the oxygen content of the ultra-pure tin. At the same time, the purification process of tin is carried out in the vacuum magnetic levitation smelting furnace, without crucible or container, which can avoid the problem of introducing impurities caused by the use of crucible or container in the existing method of purifying tin. The above two factors make the method of the application realize the preparation of low-oxygen ultra-pure tin products with purity ≥ 99.999995% (7N5 grade) and oxygen content ≤ 1 ppm, and the product quality can meet the requirements of EUV lithography machine for the purity and oxygen content of light source excitation material, and can better meet the demand of high-end electronic industry for ultra-pure tin.

[0024] 2. The method of the application directly transfers the deoxidized molten tin to the suction casting mold in a vacuum environment through the suction casting pipe connecting the suction casting chamber of the multi-tube vacuum suction casting device and the smelting chamber of the vacuum magnetic levitation smelting furnace, which can avoid the problem of reducing the forming quality caused by the involvement of gas in the forming process under vacuum conditions compared with the traditional casting forming method, and directly transfers the deoxidized molten tin to the suction casting mold for forming without the need for cooling and shaping the deoxidized molten tin and then heating and extruding for forming compared with the traditional extrusion forming method, which not only can effectively alleviate the problem of aggravating the oxidation of tin in the heating and extrusion forming process, but also can reduce energy consumption and shorten the production cycle, and improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of the connection of the multi-tube vacuum suction casting device and the vacuum magnetic levitation smelting furnace in the embodiment.

[0026] Figure 2 is a schematic diagram of the position of the inlet end of the suction casting pipe before charging and before smelting in the smelting chamber of the vacuum magnetic levitation smelting furnace.

[0027] Figure 3 is a schematic diagram of the position of the inlet end of the suction casting pipe in the vacuum suction casting process.

[0028] The reference signs are as follows: 1 is a furnace cavity of a vacuum magnetic levitation melting furnace, 2 is a melting chamber of the vacuum magnetic levitation melting furnace, 3 is a control valve, 4 is a suction casting chamber of a multi-tube vacuum suction casting device, 5 is a suction casting tube, 6 is a suction casting mold, 7 is a tin ingot, and 8 is molten tin. DETAILED DESCRIPTION

[0029] The method for preparing low-oxygen ultra-pure tin based on the integration of magnetic levitation melting and multi-tube vacuum suction casting according to the present application is further described below through examples. It is necessary to point out that the following examples are only used to further describe the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the specific implementation of the present application according to the above description, which still belongs to the protection scope of the present application.

[0030] In each of the following examples and comparative examples, the quartz devices involved, such as high-purity quartz tubes, need to be immersed in aqua regia for washing, then washed with ultrapure water and dried before use. The graphite devices involved, such as high-purity graphite tubes and high-purity graphite molds, need to be immersed in aqua regia for washing, then washed with ultrapure water, and then impurity removal by vacuum calcination at 1000-1100 ℃. The purity of the high-purity quartz and high-purity graphite is ≥99.9999%.

[0031] In each of the following examples, the multi-tube vacuum suction casting device and the vacuum magnetic levitation melting furnace used in the device construction process are existing devices in the prior art. The multi-tube vacuum suction casting device itself does not have a melting chamber. In order to connect the suction casting chamber of the multi-tube vacuum suction casting device to the melting chamber of the vacuum magnetic levitation melting furnace through the suction casting tube, a hole with a diameter matching the outer diameter of the suction casting tube is formed on the suction casting chamber of the multi-tube vacuum suction casting device and the furnace body of the vacuum magnetic levitation melting furnace. After the suction casting tube is installed, it is sealed with a sealing element. The suction casting chamber of the multi-tube vacuum suction casting device is placed above the vacuum magnetic levitation melting furnace through a liftable support frame. The height of the suction casting chamber can be adjusted in the direction perpendicular to the horizontal plane by lifting the support frame, thereby adjusting the position of the inlet end of the suction casting tube.

[0032] Example 1

[0033] In this example, a method for preparing low-oxygen ultra-pure tin based on the integration of magnetic levitation melting and multi-tube vacuum suction casting is provided, and the steps are as follows:

[0034] (1) Device construction: as shown in Figure 1As shown, the suction chamber of the multi-tube vacuum suction casting device (specifically the main part of the multi-tube vacuum suction casting device (except the part of the vacuum pump)) is placed above the vacuum magnetic levitation melting furnace through a liftable support frame (not shown in the figure), the suction chamber of the multi-tube vacuum suction casting device is communicated with the melting chamber of the vacuum magnetic levitation melting furnace through a suction tube, the outlet end of the suction tube is provided with a plurality of outlets, each outlet is respectively communicated with a suction mold in the suction chamber of the multi-tube vacuum suction casting device, the inlet end of the suction tube is communicated with the melting chamber of the vacuum magnetic levitation melting furnace, a control valve is arranged on the suction tube, and the control valve is located outside the multi-tube vacuum suction casting device and the vacuum magnetic levitation melting furnace. The suction tube is a high-purity quartz tube, and the suction mold is a high-purity graphite mold. The height of the suction chamber can be adjusted in the direction perpendicular to the horizontal plane through the lifting of the support frame, and then the position of the inlet end of the suction tube is adjusted.

[0035] (2) Magnetic levitation melting and deoxidation treatment: close the control valve, adjust the height of the suction chamber through the lifting of the support frame to make the inlet end of the suction tube suspended above the melting chamber of the vacuum magnetic levitation melting furnace, and place 100 g of tin ingot (purity 99.9999%, 6N level) in the center area of the levitation coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon, as shown in Figure 2 The furnace cavity of the vacuum magnetic levitation melting furnace is evacuated to a pressure <10 -3 Pa in the furnace cavity. The magnetic suspension system of the vacuum magnetic levitation melting furnace is started and the temperature is raised for melting, and the melting temperature is controlled to be 400 ℃ and the melting time is 1 h, and then the temperature of the molten tin obtained by melting is raised to 500 ℃ and is kept for 1 h for vacuum deoxidation treatment, to obtain deoxidized molten tin.

[0036] In this step, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <10 -3 Pa during melting and vacuum deoxidation, and the molten tin is in a suspended state during melting and vacuum deoxidation to avoid contact with the container to reduce pollution.

[0037] (3) Multi-tube vacuum suction casting: the suction chamber of the multi-tube vacuum suction casting device is evacuated to a pressure <10 -4 Pa in the furnace cavity, and high-purity argon is filled into the furnace cavity of the vacuum magnetic levitation melting furnace until the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber reaches the suction pressure (0.2 MPa), the height of the suction chamber is adjusted through the lifting of the support frame to make the inlet end of the suction tube inserted into the melting chamber of the vacuum magnetic levitation melting furnace, and the height of the support frame is continuously lowered during the suction process to make the inlet end of the suction tube kept below the liquid level of the deoxidized molten tin, as shown in Figure 3As shown, the control valve is opened, and the deoxidized molten tin is sucked into the suction casting mold through the suction casting pipe by the pressure difference between the vacuum magnetic levitation melting furnace cavity and the suction chamber, and is cooled to room temperature at a cooling rate of 5 ℃ / min in the suction chamber to be shaped, and the shaped low-oxygen ultra-pure tin product is collected under the protection of high-purity argon.

[0038] In this step, the suction casting pressure is controlled to be 0.2 MPa, and the suction casting speed is controlled to be 20 mm / s. During the cooling process, the pressure in the suction chamber of the multi-tube vacuum suction casting device is controlled to be <10 -4 Pa.

[0039] (4) Repeat the operations of steps (2) and (3) for 2 times, and a total of 3 batches of low-oxygen ultra-pure tin products are prepared.

[0040] The three batches of low-oxygen ultra-pure tin products prepared in this embodiment are detected for the content of total element impurities, and the results show that:

[0041] The first batch of products: the product purity is 99.999996% (7N6 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.01 ppm, and the oxygen content is ≤0.48 ppm.

[0042] The second batch of products: the product purity is 99.999996% (7N6 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.01 ppm, and the oxygen content is ≤0.45 ppm.

[0043] The third batch of products: the product purity is 99.999996% (7N6 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.01 ppm, and the oxygen content is ≤0.41 ppm.

[0044] From the above detection data, it can be seen that the quality of the three batches of products prepared by the method of this embodiment has high consistency.

[0045] Comparative Example 1

[0046] This comparative example is used for comparison with Example 1, and provides a preparation method of ultra-pure tin, and the steps are as follows:

[0047] (1) Magnetic levitation melting and deoxidation treatment: 100 g of tin ingot (purity 99.9999%, 6N level) is placed in the center area of the suspension coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon, and the furnace cavity of the vacuum magnetic levitation melting furnace is vacuumized to a pressure <10 -3Pa. Start the magnetic suspension system of the vacuum magnetic levitation melting furnace and warm up for melting, control the melting temperature to be 400 ℃ and the melting time to be 1 h, then increase the temperature of the obtained molten tin to 500 ℃ and keep for 1 h for vacuum deoxidation treatment, to obtain deoxidized molten tin.

[0048] In this step, during the melting and vacuum deoxidation process, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <10 -3 Pa. During the melting and vacuum deoxidation process, the molten tin is in a suspended state and avoids contact with the container, so as to reduce pollution.

[0049] (2) Casting forming: under the protection of high-purity argon, the deoxidized molten tin is transferred to a casting device, and then cooled to room temperature at a cooling rate of 5 ℃ / min (this process is a conventional casting forming process), to obtain a formed ultra-pure tin product.

[0050] (3) Repeat the operations of steps (1) and (2) for 2 times, to prepare a total of 3 batches of ultra-pure tin products.

[0051] The three batches of low-oxygen ultra-pure tin products prepared in the comparative example are detected for total element impurity content, and the results show that:

[0052] The first batch of products: the product purity is 99.999991% (7N1 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.05 ppm, and the oxygen content is ≤4.5 ppm.

[0053] The second batch of products: the product purity is 99.999992% (7N2 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.04 ppm, and the oxygen content is ≤4.6 ppm.

[0054] The third batch of products: the product purity is 99.99999% (7N level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd are all ≤0.04 ppm, and the oxygen content is ≤5 ppm.

[0055] From the above detection data, combined with example 1, it can be seen that the impurity element content in the ultra-pure tin product of comparative example 1 is higher, especially the oxygen content is significantly increased, and the purity of the three batches of products has differences, and the consistency of the product quality is poor.

[0056] Example 2

[0057] In this example, a method for preparing low-oxygen ultra-pure tin based on magnetic levitation melting and multi-tube vacuum suction casting integration is provided, and the steps are as follows:

[0058] (1) Device setup: same as Example 1.

[0059] (2) Magnetic levitation melting and deoxidation treatment: close the control valve, adjust the height of the suction chamber by lifting the support frame to make the inlet end of the suction pipe suspended above the melting chamber of the vacuum magnetic levitation melting furnace, place 100 g of tin ingot (purity 99.9999%, 6N level) in the center of the suspension coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon, and vacuumize the furnace cavity of the vacuum magnetic levitation melting furnace to a pressure <5x10 -4 Pa in the furnace cavity. Start the magnetic suspension system of the vacuum magnetic levitation melting furnace and heat to melt, control the melting temperature to be 450°C and the melting time to be 1.5 h, then raise the temperature of the molten tin obtained by melting to 550°C and keep it for 2 h for vacuum deoxidation treatment to obtain deoxidized molten tin.

[0060] In this step, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <5x10 -4 Pa during melting and vacuum deoxidation, and the molten tin is in a suspended state during melting and vacuum deoxidation to avoid contact with the container to reduce contamination.

[0061] (3) Multi-tube vacuum suction casting: vacuumize the suction chamber of the multi-tube vacuum suction casting device to a pressure <10 -5 Pa in the suction chamber, at the same time, fill high-purity argon into the furnace cavity of the vacuum magnetic levitation melting furnace until the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber reaches the suction pressure (0.2 MPa), adjust the height of the suction chamber by lifting the support frame to insert the inlet end of the suction pipe into the melting chamber of the vacuum magnetic levitation melting furnace, continuously lower the height of the support frame during the suction process to keep the inlet end of the suction pipe below the liquid level of the deoxidized molten tin, open the control valve, and use the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber to suck the deoxidized molten tin into the suction mold through the suction pipe, cool to room temperature at a cooling rate of 5°C / min in the suction chamber to shape, and collect the shaped low-oxygen ultra-pure tin product under the protection of high-purity argon;

[0062] In this step, the suction pressure is controlled to be 0.2 MPa and the suction speed is controlled to be 20 mm / s, and during the cooling process, the pressure in the suction chamber of the multi-tube vacuum suction casting device is controlled to be <10 -5 Pa.

[0063] The low-oxygen ultra-pure tin product prepared in this example was subjected to full-element impurity content detection, and the results showed that the product purity was 99.999996% (7N6 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd were all ≤0.01 ppm, and the oxygen content was ≤0.38 ppm.

[0064] Comparative Example 2

[0065] This comparative example is used for comparison with Example 2 to provide a preparation method of ultra-pure tin, and the steps are as follows:

[0066] (1) Device setup: same as step (1) of Example 1.

[0067] (2) Magnetic levitation melting: close the control valve, adjust the height of the suction casting chamber through the lifting of the support frame to make the inlet end of the suction casting pipe suspended above the melting chamber of the vacuum magnetic levitation melting furnace, and place 100 g of tin ingot (purity 99.9999%, 6N level) in the center area of the suspension coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon. The furnace cavity of the vacuum magnetic levitation melting furnace is evacuated to a pressure <5x10 -4 Pa in the furnace cavity. Start the magnetic suspension system of the vacuum magnetic levitation melting furnace and heat to melt, control the melting temperature to be 450 ℃, and the melting time to be 1.5 h to obtain molten tin.

[0068] In this step, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <5x10 -4 Pa during melting, and the molten tin is in a suspended state to avoid contact with the container to reduce contamination.

[0069] (3) Multi-tube vacuum suction casting: same as step (3) of Example 2.

[0070] The ultra-pure tin product prepared in this comparative example was subjected to full-element impurity content detection, and the results showed that the product purity was 99.999994% (7N4 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi, and Cd were all ≤0.01 ppm, and the oxygen content was ≤1.86 ppm. Compared with Example 2, the impurity element content in the ultra-pure tin product of Comparative Example 2 was higher, especially the oxygen content increased significantly. This indicates that even if the suction chamber of the multi-tube vacuum suction casting device is connected to the melting chamber of the vacuum magnetic levitation melting furnace through the suction pipe, and the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber is used to suck the deoxygenated molten tin into the suction mold through the suction pipe, if no special vacuum deoxygenation operation is performed, it is still impossible to prepare an ultra-pure tin product with an oxygen content ≤1 ppm.

[0071] Example 3

[0072] In this example, a method for preparing low-oxygen ultra-pure tin based on magnetic levitation melting and multi-tube vacuum suction casting is provided, and the steps are as follows:

[0073] (1) Device setup: same as step (1) of Example 1.

[0074] (2) Magnetic levitation melting and deoxidation treatment: close the control valve, adjust the height of the suction chamber by lifting the support frame to make the inlet end of the suction pipe suspended above the melting chamber of the vacuum magnetic levitation melting furnace, place 100 g of tin ingot (purity 99.9999%, 6N level) in the center area of the suspension coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon, and vacuumize the furnace cavity of the vacuum magnetic levitation melting furnace to a pressure <10 -4 Pa in the furnace cavity. Start the magnetic suspension system of the vacuum magnetic levitation melting furnace and heat and melt, control the melting temperature to be 300 ℃, and the melting time to be 2 h, then raise the temperature of the molten tin obtained by melting to 400 ℃ and keep it for 2 h for vacuum deoxidation treatment to obtain deoxidized molten tin.

[0075] In this step, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <10 -4 Pa during melting and vacuum deoxidation, and the molten tin is in a suspended state during melting and vacuum deoxidation to avoid contact with the container to reduce contamination.

[0076] (3) Multi-tube vacuum suction casting: vacuumize the suction chamber of the multi-tube vacuum suction casting device to a pressure <10 -4 Pa in the suction chamber at the same time as filling high-purity argon into the furnace cavity of the vacuum magnetic levitation melting furnace until the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber reaches the suction pressure (0.1 MPa), adjust the height of the suction chamber by lifting the support frame to make the inlet end of the suction pipe inserted into the melting chamber of the vacuum magnetic levitation melting furnace, continuously lower the height of the support frame during the suction process to keep the inlet end of the suction pipe below the liquid level of the deoxidized molten tin, open the control valve, and use the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction chamber to suck the deoxidized molten tin into the suction mold through the suction pipe, cool to room temperature at a cooling rate of 8 ℃ / min in the suction chamber to shape, and collect the shaped low-oxygen ultra-pure tin product under the protection of high-purity argon.

[0077] In this step, the suction pressure is controlled to be 0.1 MPa and the suction speed is controlled to be 10 mm / s, and the pressure in the suction chamber of the multi-tube vacuum suction casting device is controlled to be <10 -4 Pa during cooling.

[0078] The low-oxygen ultra-pure tin product prepared in this embodiment was subjected to full-element impurity content detection, and the results showed that the purity of the product was 99.999996% (7N6 level), and the contents of impurity elements S, Se, Zn, Fe, Pb, Bi and Cd were all ≤0.01 ppm, and the oxygen content was ≤0.46 ppm.

[0079] Example 4

[0080] In this embodiment, a method for preparing low-oxygen ultra-pure tin based on magnetic levitation melting and multi-tube vacuum suction casting is provided, and the steps are as follows:

[0081] (1) Device construction: same as step (1) of embodiment 1.

[0082] (2) Magnetic levitation melting and deoxidation treatment: close the control valve, adjust the height of the suction casting chamber through the lifting of the support frame to make the inlet end of the suction casting pipe suspended above the melting chamber of the vacuum magnetic levitation melting furnace, and place 100 g of tin ingot (purity 99.9999%, 6N level) in the center area of the suspension coil of the vacuum magnetic levitation melting furnace under the protection of high-purity argon. Vacuumize the furnace cavity of the vacuum magnetic levitation melting furnace to a pressure <10 -3 Pa in the furnace cavity. Start the magnetic suspension system of the vacuum magnetic levitation melting furnace and heat to melt, control the melting temperature to be 500 ℃, and the melting time to be 1 h. Then, raise the temperature of the molten tin obtained by melting to 600 ℃ and keep it for 1 h for vacuum deoxidation treatment to obtain deoxidized molten tin.

[0083] In this step, the pressure in the furnace cavity of the vacuum magnetic levitation melting furnace is controlled to be <10 -3 Pa during melting and vacuum deoxidation, and the molten tin is in a suspended state during melting and vacuum deoxidation to avoid contact with the container to reduce contamination.

[0084] (3) Multi-tube vacuum suction casting: vacuumize the suction casting chamber of the multi-tube vacuum suction casting device to a pressure <10 -4 Pa in the suction casting chamber, and at the same time, fill high-purity argon into the furnace cavity of the vacuum magnetic levitation melting furnace until the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction casting chamber reaches the suction casting pressure (0.5 MPa). Adjust the height of the suction casting chamber through the lifting of the support frame to make the inlet end of the suction casting pipe inserted into the melting chamber of the vacuum magnetic levitation melting furnace. During the suction casting process, continuously lower the height of the support frame to keep the inlet end of the suction casting pipe below the liquid level of the deoxidized molten tin. Open the control valve, and use the pressure difference between the furnace cavity of the vacuum magnetic levitation melting furnace and the suction casting chamber to suck the deoxidized molten tin into the suction casting mold through the suction casting pipe. Cool to room temperature at a cooling rate of 10 ℃ / min in the suction casting chamber, and collect the shaped low-oxygen ultra-pure tin product under the protection of high-purity argon.

[0085] In this step, the suction casting pressure is controlled to be 0.5 MPa, and the suction casting speed is controlled to be 50 mm / s. During the cooling process, the pressure in the suction casting chamber of the multi-tube vacuum suction casting device is controlled to be <10 -4 Pa.

[0086] The low-oxygen ultra-pure tin product prepared in the embodiment is subjected to full-element impurity content detection, and the results show that the product purity is 99.999996% (7N6 level), and the impurity element contents of S, Se, Zn, Fe, Pb, Bi and Cd are all less than or equal to 0.01 ppm, and the oxygen content is less than or equal to 0.40 ppm.

Claims

1. A method for preparing low-oxygen ultrapure tin based on integrated magnetic levitation melting and multi-tube vacuum casting, characterized in that, Includes the following steps: (1) Setup of the device: The casting chamber of the multi-tube vacuum casting device is placed above the vacuum magnetic levitation melting furnace through a liftable support frame. The casting mold in the casting chamber of the multi-tube vacuum casting device is connected to the melting chamber of the vacuum magnetic levitation melting furnace through the casting pipe. A control valve is provided on the casting pipe. (2) Magnetic levitation melting and deoxidation: Close the control valve, and under the protection of high-purity inert gas, place the raw tin ingot in the center area of ​​the levitation coil of the vacuum magnetic levitation melting furnace, and evacuate the furnace cavity until the pressure inside the furnace cavity is <10. -3 Pa, then heat up and melt, then raise the temperature of the molten tin to 400~600 ℃ and hold it at that temperature for vacuum deoxidation to obtain deoxidized molten tin; In this step, the purity of the raw tin ingot is at the 6N level. During the heating, melting, and vacuum deoxidation processes, the pressure inside the vacuum magnetic levitation melting furnace is controlled to be <10. -3 Pa; (3) Multi-tube vacuum casting: The casting chamber of the multi-tube vacuum casting device is evacuated until the pressure inside the casting chamber is <10. -3 Pa, while simultaneously filling the furnace cavity of the vacuum magnetic levitation melting furnace with high-purity inert gas until the pressure difference between the furnace cavity and the casting chamber reaches the casting pressure, the control valve is opened, and the deoxidized molten tin is sucked into the casting mold through the casting tube, and cooled to room temperature in the casting chamber for shaping. The low-oxygen ultrapure tin product is collected under the protection of high-purity argon gas. The purity of the low-oxygen ultrapure tin product is ≥99.999995%, and the oxygen content is ≤1 ppm. In this step, the suction casting pressure is controlled at 0.1~0.5 MPa, and during the cooling and solidification process, the pressure inside the suction casting chamber of the multi-tube vacuum suction casting device is controlled to be <10 MPa. -3 Pa.

2. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in claim 1, characterized in that, The height of the suction casting chamber can be adjusted in a direction perpendicular to the horizontal plane by raising and lowering the support frame, thereby adjusting the position of the inlet end of the suction casting pipe.

3. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting integration according to claim 2, characterized in that, In step (2), the inlet end of the suction casting tube is controlled to be suspended above the melting chamber of the vacuum magnetic levitation melting furnace; in step (3), during the suction casting process, the inlet end of the suction casting tube is controlled to be kept below the liquid surface of the deoxidized molten tin.

4. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in claim 1, characterized in that, The control valve on the suction casting tube is located outside the multi-tube vacuum suction casting device and the vacuum magnetic levitation melting furnace.

5. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in any one of claims 1 to 4, characterized in that, In step (2), the melting temperature is controlled to be 300~500℃.

6. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in any one of claims 1 to 4, characterized in that, In step (2), the heat preservation time is controlled to be 1~2 h.

7. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in any one of claims 1 to 4, characterized in that, In step (3), the suction casting speed is controlled to be 10~50 mm / s.

8. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting according to any one of claims 1 to 4, wherein in step (3), the cooling rate is controlled to be 5~10 ℃ / min during cooling.

9. The method for preparing low-oxygen ultrapure tin based on magnetic levitation melting and multi-tube vacuum casting as described in any one of claims 1 to 4, characterized in that, The high-purity inert gas includes high-purity argon.

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