Purification method and purification device for crystallized magnesium

Abstract

The invention discloses a purification method and a purification device for crystallized magnesium, and relates to the field of magnesium metal smelting. The method comprises the following steps: under the protection of an inert atmosphere, firstly carrying out pressure-applying melting treatment on a magnesium material to be smelted, and then carrying out pressure-applying filtering treatment on a product obtained after the melting treatment, so as to complete the flux-free smelting process of the magnesium material. And meanwhile, the metal magnesium liquid and most of the oxide shells are separated by utilizing the liquidity difference between the liquid metal magnesium and the solid oxide shells. Compared with a conventional smelting process without pressure application, the method has the advantages that the melting rate of the crystallized magnesium can be remarkably increased, most of oxide impurities are removed, a series of pollution problems caused by flux use are solved from the source, and low-cost, high-efficiency and high-quality smelting of the crystallized magnesium is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of metal magnesium smelting, and relates to a purification method and a purification device for crystalline magnesium. Background Art

[0002] Magnesium metal has significant advantages in the field of lightweighting due to its low density and high specific strength, and has extremely broad application prospects. At present, factories generally adopt the Pijiang method to obtain industrial raw magnesium through calcination of raw materials (dolomite), preparation of pellets, vacuum thermal reduction of pellets, and refining of crude magnesium. At present, the factory refining adopts the flux refining method to obtain industrial raw magnesium through melting, stirring, standing, insulation, casting and other processes. However, the crystalline magnesium produced by the reduction process often has loose structural characteristics. In addition, it is well known that magnesium metal has active chemical properties and strong affinity with oxygen. It is very easy to react with oxygen to form magnesium oxide in a high-temperature molten state. In industrial production, this characteristic makes the surface very susceptible to oxidation when the reduction device leaks or the furnace is opened at high temperature, and is quickly covered with a thick and hard magnesium oxide shell. Because the melting point of magnesium oxide is as high as about 2850℃ and its thermal conductivity is poor, the melting process becomes particularly complicated. During the heating process, it is difficult for the internal magnesium matrix to quickly reach the melting point and achieve effective melting. In addition, the magnesium oxide shell on the surface forms a barrier, which greatly hinders the natural outflow of the magnesium matrix after melting, making the direct melting process particularly difficult. For this reason, academia and industry have carried out a lot of theoretical research and technical development on the removal of solid inclusions in magnesium or magnesium alloy melts. The Chinese patent application with publication number CN10380648A discloses a method for purifying magnesium alloy melts, which first purifies the magnesium alloy melt by gas rotary blowing, and then performs foam ceramic filtration purification treatment. A Chinese patent application with publication number CN106011512A discloses a four-stage purification method for magnesium alloy melt, which consists of the following steps: in the first stage of purification, under the protection of hydrogen, a purification flux is added to a magnesium ingot or a magnesium intermediate alloy melt for refining to remove gas and non-metallic inclusions in the melt; in the second stage of purification, a rotating nozzle is used to spray mixed gas in a tundish to remove the gas contained in the magnesium alloy melt in the tundish; in the third stage of purification, a foam ceramic filter is used to filter the outflowing magnesium liquid before entering the flow channel at the liquid outlet of the furnace to remove gas and slag; in the fourth stage of purification, hydrogen is blown into the casting and holding furnace, and a purification flux is added to the furnace for secondary refining and slag removal. The Chinese patent application with the publication number CN101037729A discloses a flux-free remelting refining method and device for magnesium alloy furnace charge, which is to refine the magnesium melt by a composite multi-stage refining method after the magnesium alloy furnace charge is preheated and dried, including furnace charge melting, stirring refining or blowing refining, forced sedimentation, filtration refining, static refining and furnace pouring, which can effectively remove impurities and gases in various magnesium alloy furnace charges and achieve high-quality purification of the melt. In the above invention, gas refining, filtration refining and static refining are involved, and the filtration efficiency and sedimentation efficiency are poor. In addition, by adding a large amount of refining agent, the melting efficiency of crystalline magnesium can be partially improved, so that a large amount of impurities are introduced, which reduces the quality of the product. At the same time, as the smelting time increases, the crude magnesium is oxidized and burned under open smelting, which further reduces the yield and product quality, and the quality of the final magnesium ingot cannot be guaranteed. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a purification method and a purification device for crystalline magnesium, thereby solving the technical problems in the prior art that melt oxidation occurs during magnesium smelting, resulting in a long melting process of crystalline magnesium and low purity of the final magnesium ingot.

[0004] The present invention is achieved through the following technical solutions: A method for purifying crystalline magnesium comprises the following steps: In an inert atmosphere, the crystalline magnesium material to be purified is melted to obtain a mixture of molten magnesium and a magnesium oxide shell layer; and while the mixture is melted, the mixture of the molten magnesium and the magnesium oxide shell layer is subjected to a filter press to obtain a molten magnesium filtrate; During the filter press treatment, the pressure applied for:

[0005] In the formula, is the mass of magnesium material to be smelted, g is the acceleration due to gravity, is the area of ​​the filter press equipment (m 2 ), is a constant, 6~10; S3: Cooling the molten magnesium filtrate to obtain purified crystalline magnesium.

[0006] Preferably, the flow rate of the inert atmosphere is 400-700 sccm.

[0007] Preferably, during the melting process, the temperature is 750-850° C. and the time is 1-1.5 h.

[0008] Preferably, during the melt treatment, the heating rate is 3-5°C / min.

[0009] Preferably, the cooling rate during the cooling process is 3-5°C / min.

[0010] Preferably, before the inert gas is introduced into the system, the system is subjected to multiple vacuum treatments, wherein the vacuum degree during the vacuum treatment is -0.07 MPa and the treatment time for one time is 5 to 10 minutes.

[0011] A purified crystalline magnesium is obtained by smelting through the above method.

[0012] A purification device for implementing the above-mentioned purification method of crystalline magnesium comprises a body and a feeding member arranged inside the body; A loading plate for placing the crystalline magnesium material to be purified is provided inside the feeding piece, and a plurality of through holes are provided on the loading plate, and the plurality of through holes are used to separate the molten magnesium material and the solid magnesium oxide; a pressure control unit for realizing the filtration process of the molten magnesium material is provided above the loading plate, and the pressure control unit can be close to or away from the loading plate; The outside of the feeding piece is provided with a temperature control unit for melting the magnesium material to be purified, and the body is provided with a vacuum unit for providing vacuum degree, an atmosphere control unit for providing inert atmosphere and a cooling circulation unit for cooling the system.

[0013] Preferably, the thickness of the material placing plate is 3-6 mm.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a method for purifying crystalline magnesium. First, smelting is carried out under the protection of an inert atmosphere. The environment can effectively isolate oxygen, prevent magnesium from being violently oxidized at high temperatures, and ensure the stability of the melting process and the purity of the product. In addition, during the melting process, a filter press process is carried out. By applying a specific pressure, a mixture of the molten magnesium and the magnesium oxide shell layer is subjected to a filter press process, thereby effectively separating the molten magnesium from the high-melting-point magnesium oxide shell layer. The applied pressure value is related to the mass of the magnesium material to be smelted and the area of ​​the filter press equipment. The factors considered are more comprehensive and sufficient, making the pressure control more scientific and effective. The separation method effectively increases the yield. Compared with the traditional chemical refining method, the filter press process does not require the addition of additional refining agents, thereby avoiding secondary pollution introduced by the refining agent, and ensuring the cleanliness of the high-purity magnesium. Finally, the filtered molten magnesium is cooled and crystallized to form solid magnesium. In this process, the pressure applied during the filtration process fully considers the amount of material to be filtered and the contact area between the material to be filtered and the filter pressing equipment, and at the same time effectively improves the efficiency of the filtration through proper pressure control. If the pressure is too small, the physical separation rate of the molten magnesium from the magnesium oxide shell and other impurities will be significantly reduced, which will cause the filtration process to become lengthy and reduce production efficiency. When the pressure is too high, the filter cake will be too tight, affecting the filter holes on the filter plate, because under high pressure, the filter residue will enter the filter holes, which will also reduce the filtration efficiency and affect the purification process.

[0015] The yield is further improved. At the same time, during the smelting process, no refining agent needs to be added, thereby reducing the introduction of impurities, achieving clean smelting, and ensuring the quality of high-purity magnesium. In addition, the filter press process effectively improves the smelting efficiency. The method of the present invention achieves the refining of low-cost, high-efficiency, and high-quality crystalline magnesium.

[0016] Furthermore, the flow rate of the inert atmosphere is 400-700 sccm. The inert atmosphere (such as argon) flows over the surface of the molten magnesium at an appropriate flow rate, which can effectively isolate the magnesium melt from the oxygen in the air, thereby preventing the oxidation of magnesium. When the flow rate is within this range, it can ensure that sufficient inert gas covers the surface of the magnesium melt without causing excessive gas waste. A stable inert atmosphere flow rate helps to maintain the stability of the smelting environment and reduce the melt disturbance caused by air flow fluctuations, which helps to improve the controllability of the smelting process and the consistency of product quality. The appropriate flow rate of the inert atmosphere helps to reduce the loss of magnesium, thereby improving the yield. At the same time, the purity of the product is also improved due to the reduction in the generation of oxidized impurities.

[0017] Furthermore, during the melting process, the temperature is 750~850℃, and the time is 1~1.5h. Within the temperature range of 750~850℃, the magnesium material can be fully melted, making the solid impurities and inclusions therein more easily separated from the magnesium melt. This temperature range is conducive to the diffusion and aggregation of impurities, and is convenient for subsequent filter press treatment to remove them. The temperature is controlled between 750~850℃ to avoid burning and oxidation caused by overheating of the magnesium melt. Excessive temperature will increase the reaction rate of magnesium with oxygen, resulting in oxidation and burning of magnesium, reducing yield and purity. The melting treatment time is 1~1.5 hours. This time range not only ensures the full melting of the magnesium material, but also avoids energy waste and decreased production efficiency caused by excessive melting time. Appropriate time setting helps to achieve an efficient and energy-saving melting process. Furthermore, during the melting process, the heating rate is 3-5°C / min. The slow heating rate helps to achieve uniform heating of the magnesium material. When the heating rate is moderate, the heat can be more evenly transferred to various parts of the magnesium material to avoid local overheating or overcooling, which helps to ensure that the magnesium material achieves a uniform temperature distribution during the melting process, thereby improving the melting effect and product quality. Although inert atmosphere protection is the main means to prevent magnesium oxidation, an appropriate heating rate also helps to control the oxidation process. When the temperature rises too quickly, the surface temperature of the magnesium material rises rapidly, which may increase the reaction rate with residual oxygen in the air, while a slow heating rate can reduce this risk and further reduce the possibility of oxidation burnout.

[0018] Furthermore, the cooling rate during the cooling process is 3~5℃ / min. The molten magnesium is prone to thermal stress due to excessive temperature gradient during rapid cooling, which may cause cracks or deformation inside the product. By controlling the cooling rate to 3~5℃ / min, the temperature drop rate can be slowed down, so that the temperature difference between the inside and outside of the magnesium material is gradually reduced, thereby reducing the generation of thermal stress and protecting the integrity of the product. The slow cooling process helps the uniform formation of the internal structure of the magnesium material. At an appropriate cooling rate, the crystallization process of magnesium can proceed more smoothly, reducing the uneven structure caused by rapid cooling, and improving the physical and mechanical properties of the product. Magnesium will undergo a phase change from liquid to solid during the cooling process, accompanied by volume changes, generating internal stress. Too fast a cooling rate aggravates this stress, resulting in defects inside the product, and an appropriate cooling rate can slow down the phase change process, reduce the generation of phase change stress, and help maintain the structural integrity and performance stability of the product. The control of the cooling rate is particularly important for magnesium products that require high cleanliness and high performance.

[0019] Further, before the inert gas is introduced into the system, the system is subjected to multiple vacuum treatments, wherein the vacuum degree is -0.07MPa during the vacuum treatment, and the treatment time is 5 to 10min. The vacuum treatment can remove the air, water vapor and other possible impurity gases in the system. If these gases remain in the system, they will react with magnesium in the subsequent melting and purification process, resulting in oxidation, pollution or reduced purity. Through multiple vacuum treatments, it can be ensured that the gas content in the system is reduced to a minimum, providing a good foundation for the subsequent inert atmosphere protection. Since magnesium is a metal that is easily oxidized, it is very important to reduce the oxygen content in the system to prevent the oxidation of magnesium. The vacuum treatment significantly reduces the concentration of oxidizing gases such as oxygen by reducing the pressure in the system, thereby reducing the risk of magnesium being oxidized during the melting and purification process. After the vacuum treatment, the inert gas is introduced to ensure that the inert gas occupies a dominant position in the system, further reducing the presence of oxidizing gases. Since the vacuum treatment has removed most of the impurity gases, the inert gas introduced can more effectively protect the magnesium melt from oxidation and pollution. The time for each vacuum treatment is set to 5 to 10 minutes. This time range not only ensures the effectiveness of the vacuum treatment, but also avoids energy waste and reduced production efficiency caused by too long a treatment time. The appropriate treatment time helps to maintain the stability and production efficiency of the system while removing residual gas. Through multiple vacuum treatments and subsequent inert atmosphere protection, the risk of oxidation and contamination of magnesium during the melting and purification process can be significantly reduced, thereby improving the purity and quality of the product. This is especially important for magnesium products that require high cleanliness and high performance.

[0020] In addition, the present invention also discloses purified crystalline magnesium prepared by the method.

[0021] At the same time, the present invention also discloses a smelting device for realizing the purification method of the above-mentioned crystalline magnesium. During smelting, the magnesium material to be smelted is placed on a material placing plate provided with a plurality of through holes, the temperature of the system is increased by a temperature control unit, the atmosphere inside the device is controlled by a vacuum unit and an atmosphere control unit, and after the magnesium material to be smelted is melted, the molten product is pressed by a pressure control unit, thereby realizing efficient smelting of the magnesium material without a melting filter, and obtaining a magnesium material with high cleanliness.

[0022] Furthermore, the thickness of the material placing plate is 3-6 mm, which can effectively filter the molten liquid, effectively improve the impurity removal rate, and improve the yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 is a schematic diagram of a method for purifying crystalline magnesium in the present invention; Figure 2 It is a schematic structural diagram of a crystalline magnesium purification device in the present invention; Figure 3 The appearance diagrams of the magnesium ingot and the filter plate residue obtained after refining in Example 6 of the present invention, wherein (a) is a front view of the magnesium ingot, (b) is a side view of the magnesium ingot, (c) is a front view of the filter plate residue, and (d) is a side view of the filter plate residue; Figure 4 The appearance diagram of the magnesium ingot (a) and the filter plate residue (b) obtained after refining in Comparative Example 1 of the present invention; Figure 5 This is the XRD spectrum of the filter plate residue obtained after refining in Example 6 of the present invention; Figure 6 is a metallographic image of the surface of a magnesium ingot sample obtained after direct remelting of crude magnesium crystals in Comparative Example 1 of the present invention; Figure 7 is a metallographic image of the surface of a magnesium ingot sample obtained after filter pressing and melting of crude magnesium crystals in Example 6 of the present invention; Figure 8 It is a scanning electron microscope (SEM) image (a) and an energy dispersive X-ray spectrum (EDS) surface scanning image of the surface of the magnesium ingot metallographic sample obtained after direct remelting of the crude magnesium crystal in the exemplary comparative example 1 of the present invention, wherein (b) is the energy spectrum of Mg, and (c) is the energy spectrum of O; Fig. 9 The scanning electron microscope (SEM) image (a) and the energy dispersive X-ray spectrum (EDS) surface scanning image of the magnesium ingot metallographic sample obtained after the crude magnesium crystallization and pressure filtration in Example 6 of the present invention, wherein (b) is the energy spectrum of Mg, and (c) is the energy spectrum of O; Fig.10 It is a metallographic diagram of a magnesium ingot sample obtained after the crude magnesium crystals in the factory are refined by flux refining method; Fig.11 1 is an appearance diagram of a magnesium ingot obtained after filter pressing and melting of high-purity crystalline magnesium in Example 7 of the present invention, wherein (a) is a front view of the magnesium ingot, (b) is a side view of the magnesium ingot, (c) is a front view of the filter plate residue, and (d) is a side view of the filter plate residue; Fig.12 It is an appearance diagram of a magnesium ingot and a filter plate residue obtained after direct remelting of high-purity crystalline magnesium in Comparative Example 2 of the present invention, wherein (a) is a front view of the magnesium ingot, (b) is a side view of the magnesium ingot, and (c) is a front view of the filter plate residue; Fig.13 is an X-ray diffraction (XRD) analysis chart of residual impurities on the filter plate obtained after pressure filtration of high-purity crystalline magnesium in Example 7 of the present invention; Fig.14 is a metallographic diagram of a magnesium ingot sample obtained by directly remelting high-purity crystalline magnesium in Comparative Example 2 of the present invention; Fig.15 This is a metallographic diagram of the magnesium ingot sample obtained after filter pressing and melting of high-purity crystalline magnesium in Example 7 of the present invention.

[0025] Wherein: 1. main body, 2. feeding piece, 21. melting section, 22. crystallization section, 3. adjusting temperature control unit, 301. first temperature control component, 302. second temperature control component, 4. support, 5. atmosphere control unit, 501. air inlet, 502. exhaust port, 6. partition, 7. vacuum unit, 8. pressure control unit, 81. pressure plate, 82. pressure rod, 9. cooling circulation unit, 10. placing plate. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings: Example 1 The invention discloses a method for purifying crystalline magnesium, wherein the system is subjected to multiple vacuum treatments, wherein during the vacuum treatment, the vacuum degree is -0.07 MPa, the treatment time is 5 min, and then, under the protection of an inert atmosphere with a flow rate of 450 sccm, the crystalline magnesium material to be purified is first heated to 750°C for melting treatment for 1.5 h, and the heating rate during the melting treatment is 5°C / min; while the melting treatment is being carried out, the molten product is subjected to a filter press treatment, and the pressure is set to 6 mg, and the pressure is ,in, is the mass of magnesium material to be smelted (g), g is the acceleration due to gravity (N / kg), is the area of ​​the filter press equipment (mm 2 ), after the filter press treatment, the product is cooled at a rate of 5°C / min to complete the flux-free smelting process of the magnesium material; the purification method improves the melting efficiency by 55%. The pressure here can be intuitively controlled by the pressure instrument on the filter press equipment.

[0033] Example 2 The invention discloses a method for purifying crystalline magnesium, wherein the system is subjected to multiple vacuum treatments, wherein during the vacuum treatment, the vacuum degree is -0.07MPa, and the treatment time is 10min. Then, under the protection of an inert atmosphere with a flow rate of 700sccm, the crystalline magnesium material to be purified is first subjected to a melting treatment at 800°C for 1h, and during the melting treatment, the heating rate is 5°C / min. During the melting treatment, the molten product is subjected to a filter press treatment, and the pressure is set to 7mg. The pressure is ,in, is the mass of magnesium material to be smelted (kg), g is the acceleration due to gravity (N / kg), is the area of ​​the filter press equipment (m 2 ), after the filter press treatment, the product is cooled at a rate of 5°C / min to complete the flux-free smelting process of the magnesium material; the purification method increases the melting efficiency by 82%.

[0034] Example 3 The invention discloses a method for purifying crystalline magnesium, wherein the system is subjected to multiple vacuum treatments, wherein during the vacuum treatment, the vacuum degree is -0.07 MPa, and the treatment time is 8 minutes. Then, under the protection of an inert atmosphere with a flow rate of 500 sccm, the crystalline magnesium material to be purified is first subjected to a melting treatment at 850°C for 1.5 hours, and during the melting treatment, the heating rate is 4°C / min. During the melting treatment, the molten product is subjected to a filter press treatment, and the pressure is set to 10 mg. The pressure is ,in, is the mass of magnesium material to be smelted (kg), g is the acceleration due to gravity (N / kg), is the area of ​​the filter press equipment (m 2 ), after the filter press treatment, the product is cooled at a rate of 4°C / min to complete the flux-free smelting process of the magnesium material; the purification method increases the melting efficiency by 80%.

[0035] Example 4 The present invention provides a method for purifying crystalline magnesium, comprising the following steps: In an inert atmosphere, the crystalline magnesium material to be purified is melted to obtain a mixture of molten magnesium and a magnesium oxide shell layer; and while the mixture is melted, the mixture of the molten magnesium and the magnesium oxide shell layer is filter pressed to obtain a molten magnesium filtrate; and the molten magnesium filtrate is cooled to obtain purified crystalline magnesium.

[0036] Furthermore, during the filter press treatment, the pressure applied is related to the mass or gravity of the crystalline magnesium material to be purified and the area of ​​the filter press equipment, such as the cross-sectional area of ​​the pressure plate 81 in the present invention. for:

[0037] In the formula, is the mass of magnesium material to be smelted (kg), g is the acceleration due to gravity (N / kg), is the area of ​​the filter press equipment (m 2 ), i.e. the cross-sectional area of ​​the pressure plate 81, is a constant, in the present invention The preferred value of is 6~10.

[0038] The principle of this process is as follows Figure 1 As shown, when the magnesium to be treated is melted under inert gas conditions, a certain pressure is applied to it, and most of the oxide impurities on the surface are removed by filtering through a filter plate. This method can not only achieve rapid melting of crystalline magnesium and improve production efficiency, but also reduce the amount of refining agent used in the smelting process, reduce the introduction of non-metallic impurities, and can remove most of the oxide impurities on the surface of crystalline crude magnesium during the melting process, reducing the oxidation loss rate of the magnesium melt in the early stage of smelting.

[0039] The invention also discloses high-purity magnesium prepared by the method.

[0040] Example 5 In addition, if Figure 2As shown, the present invention also discloses a purification and smelting device for realizing the above-mentioned crystalline magnesium, the smelting device comprises a main body 1, and a feeding piece 2 arranged inside the main body 1; a loading plate 10 is arranged inside the feeding piece 2, and a plurality of through holes are arranged on the loading plate 10; a pressure control unit 8 is arranged above the loading plate 10, and the pressure control unit 8 can be close to or away from the loading plate 10; a temperature control unit 3 is arranged outside the feeding piece 2, and a vacuum unit 7, an atmosphere control unit 5 and a cooling circulation unit 9 are arranged on the main body 1.

[0041] Here, in the pressure control unit 8, by adjusting the pressure effect size and action time, the oxide shell on the surface of the crystalline magnesium is broken, so that the magnesium liquid can flow out smoothly, and the magnesium is pressurized and quickly melted during the heating process. At the same time, the atmosphere control unit 5 is combined with inert gas protection to reduce the oxidation burn-off of the melt.

[0042] The atmosphere control unit 5 in the present invention includes an air inlet 501 and an air outlet 502. In a preferred embodiment, the air inlet 501 is arranged at the bottom of the body 1, and the air outlet 502 is arranged at the top of the body 1. The gas introduced into the atmosphere control unit 5 is an inert gas, which can be argon. Argon enters the bottom of the body 1 through the air inlet 501 and is discharged from the exhaust port 502. Since the relative molecular mass of argon is greater than that of oxygen, as the volume of argon increases, oxygen gradually moves upward. Through the mutual coordination of the vacuum unit 7 and the atmosphere control unit 5, the oxygen in the furnace cavity is finally fully discharged.

[0043] The vacuum unit 7 is located at the upper part of the side wall of the body 1. Since the relative molecular mass of argon is greater than that of oxygen, most of the oxygen is located above the furnace body. The vacuum unit 7 is connected to the upper part to facilitate the full removal of oxygen in the furnace cavity.

[0044] The operation of the pressure control unit 8 is combined with the temperature control program of the smelting furnace. When heated to a specified temperature, the pressure control unit 8 starts to work and pressurizes the raw materials according to the program settings.

[0045] The cooling circulation unit 9 includes a water inlet pipe connected to the bottom of the body 1 and a water outlet pipe connected to the bottom of the body 1 .

[0046] In the present invention, the feeding member 2 includes a melting section 21 and a crystallization section 22 which are connected, and the feeding plate 10 is arranged between the melting section 21 and the crystallization section 22. The melting section 21 is arranged on the upper part of the crystallization section 22, so that the molten product can flow smoothly into the crystallization section 22. Here, the melting section 21 and the crystallization section 22 are integrally arranged or detachably connected. Under the filtering action of the feeding plate 10, the molten magnesium liquid enters the crystallization section 22, and the oxide impurities are retained on the feeding plate 10. As the amount of raw materials increases, the thickness of the impurity layer increases, forming an impurity self-filtration layer, further removing most of the oxide impurities of the crystallized magnesium, and realizing clean casting.

[0047] The temperature control unit 3 in the present invention includes a first temperature control component 301 and a second temperature control component 302 arranged on the outer wall of the feeding piece 2; the first temperature control component 301 is arranged on the outer wall of the melting section 21, and the second temperature control component 302 is arranged on the outer wall of the crystallization section 22, which are used to control the temperature of the melting section 21 and the crystallization section 22 respectively.

[0048] In a preferred embodiment, the material placement plate 10 is detachably arranged inside the feeding member 2. First, the arrangement is convenient for cleaning and maintenance. During the smelting process, magnesium material and its molten product will remain on the material placement plate, especially in its through hole. The detachable design allows the material placement plate to be easily taken out for thorough cleaning to remove attached impurities and residues, thereby maintaining the cleanliness and working efficiency of the equipment. In addition, this is also convenient for regular inspection and maintenance of the material placement plate to ensure that it is in good working condition. Secondly, the detachable arrangement makes replacement more flexible. According to different smelting requirements or material properties, it may be necessary to use material placement plates with different apertures, hole types or materials. The detachable design allows users to easily replace the material placement plates to adapt to different production requirements and improve the flexibility and adaptability of the equipment. At the same time, the detachable material placement plate can optimize the smelting effect. Different material placement plate designs (such as aperture size, distribution, etc.) will affect the melting rate of the magnesium material, the fluidity of the molten product and the filtering effect. By replacing material placement plates with different designs, users can adjust and optimize the smelting process according to actual conditions to improve the smelting efficiency of the magnesium material and the cleanliness of the product.

[0049] More preferably, the feeder 2 includes a melting section 21 and a crystallization section 22 connected, and the feed plate 10 is arranged between the melting section 21 and the crystallization section 22. The melting section 21 is arranged on the upper part of the crystallization section 22, so that the molten product can flow smoothly into the crystallization section 22. Here, the melting section 21 and the crystallization section 22 are arranged in an integral manner or detachably connected. Several through holes are arranged in an array on the feed plate 10; the diameter of the through hole is 4~8mm. The feeder includes a melting section and a crystallization section connected, and the feed plate is arranged between the melting section and the crystallization section. First, this segmented design optimizes the smelting and crystallization process. The melting section is mainly responsible for heating the magnesium material to a molten state, while the crystallization section is used to control the cooling and crystallization process of the molten magnesium. This staged design enables the smelting and crystallization process to be carried out more accurately and efficiently. By separating the melting and crystallization processes, the fluidity and temperature distribution of the molten magnesium can be better controlled, thereby forming a more uniform and dense crystal structure in the crystallization section, and improving the purity and physical properties of the product. The separation of the melting section and the crystallization section effectively improves the efficiency of smelting magnesium and improves the purity of the product. The melting section and the crystallization section are arranged in an integrated manner or in a detachable connection, wherein the integrated arrangement makes the structure of the entire smelting device more compact, reduces the connectors and gaps between the components, and thus improves the overall stability and sealing of the device. The integrated arrangement simplifies the operation process, and the operator only needs to control the operating parameters of the entire device without adjusting the parameters of the melting section and the crystallization section separately, thereby reducing the difficulty and complexity of the operation. The detachable connection allows the melting section and the crystallization section to be taken out separately for cleaning and maintenance, especially for the residues and scaling that may be generated in the crystallization section, which can be cleaned more easily to maintain the cleanliness and work efficiency of the equipment. When it is necessary to process different types of materials or adjust the smelting process, the configuration of the melting section and the crystallization section can be replaced or adjusted as needed, thereby improving the flexibility and adaptability of the equipment. Several of the through holes are arranged in an array on the material placement plate; the diameter of the through holes is 4 to 8 mm, and the array arrangement of the through holes makes the magnesium material more evenly distributed on the material placement plate, which is conducive to the uniform transfer of heat and the uniform melting of the magnesium material. The aperture range of 4~8mm ensures that the magnesium material can pass smoothly, and avoids the molten magnesium liquid flowing too fast and difficult to control due to the large aperture, or the poor melting due to the small aperture. The through hole plays a certain filtering role in the melting process, which can remove some impurities and particles that are not completely melted, and improve the purity of the molten magnesium liquid. The through holes arranged in an array reduce the risk of blockage of a single aperture. Even if some apertures are blocked, other apertures can still remain unobstructed, ensuring the continuity and stability of the melting process. The through holes arranged in an array enable the material plate to be evenly stressed when it is under the pressure of the molten magnesium liquid, avoiding deformation or rupture caused by local stress concentration.

[0050] Furthermore, in a more preferred embodiment, the pressure control unit 8 includes a pressure plate 81 and a pressure rod 82 connected to the pressure plate 81; the pressure plate 81 is in clearance with the inner wall of the feed piece 2. The thickness of the material placing plate 10 is 3-6 mm, and the diameter of the pressure plate 81 is 1-2 mm smaller than the inner diameter of the feed piece 2, that is, the gap between the pressure plate 81 and the inner wall of the feed piece 2 is 1-2 mm. The pressure control unit includes a pressure plate and a pressure rod connected to the pressure plate; the pressure plate is in clearance with the inner wall of the feed piece, and the pressure applied by the pressure plate to the molten magnesium material can be accurately controlled by adjusting the elongation of the pressure rod or the force applied to the pressure rod. This precise control helps to optimize the pressure conditions during the smelting process, thereby improving the quality and purity of the product. During the smelting process, the pressure of the pressure plate can be adjusted in real time as needed to adapt to different smelting stages or to process magnesium materials of different properties. The design of the pressure plate ensures that it can evenly distribute the pressure on the molten magnesium material, avoiding uneven smelting or quality problems caused by excessive or insufficient local pressure. The clearance fit design with the inner wall of the feed piece helps to reduce the deformation or friction of the pressure plate during the pressure application process, thereby maintaining the stability and uniformity of the pressure. After the molten magnesium material is melted, the pressure applied by the pressure plate is used for filter pressing, which can further remove impurities, bubbles and incompletely melted particles in the molten product, thereby improving the purity and density of the product. The efficient filter pressing process helps to shorten the smelting cycle, improve production efficiency, and thus increase output. The structure of the pressure plate and the pressure rod is relatively simple, easy to disassemble and clean, and the residues or impurities generated during the smelting process can be easily removed to maintain the cleanliness and work efficiency of the equipment. The diameter of the pressure plate is 1-2 mm smaller than the inner diameter of the feed piece, so that there is a gap between the pressure plate and the feed piece, reducing the friction between the pressure plate and the feed piece, facilitating the descent of the pressure plate, and also preventing the molten liquid from overflowing to the upper surface of the pressure plate, so that the molten liquid is effectively controlled on the lower surface of the pressure plate, thereby improving the yield of the product.

[0051] In the present invention, the body 1 may be a smelting furnace body, the feeder 2 may be a smelting crucible, and the pressure control unit 8 passes through the body 1 and is connected to the feeder 2. A partition 6 is provided on the top of the feeder 2, and a through hole is provided on the partition 6. The pressure rod 82 of the pressure control unit 8 is provided through the hole of the partition 6.

[0052] In addition, in a more preferred solution, a support 4 is provided inside the main body 1 , and the feeding piece 2 is arranged on the support 4 .

[0053] The use process of the above device is as follows: A. Place the loading plate 10 in the feeding piece 2, above the crystallization section 22, then place the crystallized magnesium raw material on the loading plate 10, then adjust the pressure control unit 8 so that the part located in the loading section does not contact the crystallized magnesium raw material, and then lower the partition 6 to cover the top of the feeding piece 2; B. Close the atmosphere control unit 5, close the air inlet 501 and the exhaust port 502, open the vacuum unit 7, and evacuate the body 1. After the evacuation is completed, close the vacuum unit 7, open the atmosphere control unit 5, open the air inlet 501, and pass inert protective gas into the furnace until the pressure in the furnace rises to a slightly positive pressure, then close the air inlet 501 and the atmosphere control unit 5. Repeat the above operation 3 to 4 times; C. The furnace is filled with inert protective gas, the atmosphere control unit 5 is turned on, the air inlet 501 is opened, and the exhaust port 502 is opened at the same time, and the gas flow rate is adjusted to keep the inert gas in the furnace in a circulating state; D. Turn on the cooling circulation unit 9, set the temperature control program, make the first temperature control component 301 and the second temperature control component 302 heat and keep warm at a temperature 50-100°C higher than the melting point of the raw material, turn on the temperature control unit 3, and make the first temperature control component 301 and the second temperature control component 302 heat up at a heating rate of 5°C / min; E. When the raw material melting temperature is reached, the pressure control unit 8 is turned on, and the molten magnesium liquid enters the crystallization section 11 through the material placement plate 10.

[0054] F. After all the melt enters the crystallization section 11, the pressure control unit is turned off and stops working, and the temperature control unit 3 is adjusted to cool the first temperature control component 301 and the second temperature control component 302 at a cooling rate of 5°C / min; G. When the temperature drops to room temperature, turn off the atmosphere control unit 5 and the cooling circulation unit 9.

[0055] Combined with the smelting device, its process principle is specifically as follows: 1 Before smelting, load the loading plate into the loading piece, then load the raw material crystalline magnesium on the loading plate, adjust the lower end height of the pressure control unit above the raw material, and then cover the top partition.

[0056] 2. Evacuate the body, then introduce argon gas to a slight positive pressure, repeat this operation, perform gas washing operation, and finally fill the body with argon gas and keep the gas flowing, then set the temperature control program and heat it.

[0057] 2 After heating to a certain time and temperature, the pressure control unit starts to work and pressurizes the raw materials. As the temperature rises, the magnesium matrix inside the crystalline magnesium reaches the melting point first. Under the action of pressure, the oxide shell layer with a certain strength and thickness is quickly broken, and the internal magnesium melt flows out in large quantities under the action of pressure, covering the surface of the material plate, realizing liquid sealing to isolate the entry of external oxygen and prevent further oxidation of magnesium.

[0058] 3 Under the further action of pressure, the magnesium liquid can flow to the bottom of the feeding piece, and the melting rate is improved. At the same time, the oxide shell layer is blocked by the feeding plate and remains on the upper part of the feeding plate. As the smelting raw materials increase, more oxide layers are retained above the feeding plate, forming a filter layer, which further plays the role of filtering impurities.

[0059] The present invention can effectively remove some oxide impurities while greatly increasing the melting rate of crystalline magnesium, whether it is a factory crystalline magnesium refining process or a melting and casting process of high-purity crystalline magnesium obtained by vacuum distillation. For the factory crystalline magnesium refining process, in the early stage of smelting, no refining agent is added as a fire extinguishing agent and flux, which greatly reduces the use of refining agent, thereby reducing the introduction of impurities, and at the same time, the oxidation loss of magnesium melt under the protection of inert gas is reduced, and the yield is improved. For the melting and casting process of high-purity crystalline magnesium obtained by vacuum distillation, no refining agent is added, and at the same time, clean melting and casting are achieved through inert gas protection, thereby ensuring the quality of high-purity magnesium. Therefore, the present invention has certain guiding significance for realizing low-cost, high-efficiency, high-quality crystalline magnesium refining process, and has great promotion value and broad application prospects.

[0060] Example 6 In order to further explain the technical solution of the present invention, it is described by the following examples: The crystalline magnesium raw material used in this embodiment is the crystalline crude magnesium obtained by Pidgeon reduction in the factory, and there is a lot of oxidation on the surface. Figure 2 The device is used for refining, and comprises the following steps: First, 130g of crystalline magnesium is placed on the loading plate 10, which is provided with 31 holes with a diameter of 6mm evenly distributed. After the loading is completed, the lower end of the pressure control unit 8 is adjusted to be above the raw material and not in contact with the raw material, and then the partition 6 is covered to seal the furnace body.

[0061] Close the air inlet 501 and the exhaust port 502, open the vacuum unit 7, evacuate to -0.07MPa, then close the vacuum unit 7, open the atmosphere control unit 5, open the air inlet 501, and introduce argon gas. When the pressure in the furnace chamber reaches 0.02MPa, close the air inlet 501, open the vacuum unit 7 to continue evacuating, repeat the operation 4 times, after the argon gas is introduced for the 4th time, open the exhaust port 502, and adjust the gas flow rate to make the gas in the chamber in a circulating state. Open the cooling circulation unit and set the temperature to 25°C.

[0062] The temperature control unit 3 is turned on, and the first temperature control component 301 and the second temperature control component 302 are heated to 800°C at a rate of 5°C / min, and kept at the target temperature for 90 minutes to fully melt the crystalline magnesium. When the temperature reaches 800°C, the pressure control unit 8 is started to extrude the crystalline magnesium until the lower end of the pressure control unit 8 stops moving and the melt fully enters the crystallization stage.

[0063] After the filter press is completed, the first temperature control component 301 and the second temperature control component 302 cool down to room temperature at a rate of 5°C / min, and the magnesium melt in the crystallization stage gradually solidifies into a magnesium ingot.

[0064] Comparative Example 1 At the same time, a control group experiment was set up, in which 119.2 g of crystalline magnesium raw material was placed in the loading section 10 so that it was located above the filter plate 10. The filter plate size parameters were the same as above. A single-hole plate was covered and the furnace body was sealed. The remaining steps were the same as above, without the filter press process, that is, a simple direct remelting process.

[0065] The magnesium ingot and filter plate residue obtained after melt-filtering combined with Example 6 and direct remelting comparative example 1, i.e., the residue on the material placing plate 10, were weighed. The results are shown in Table 1. The magnesium ingot and filter plate residue obtained after melt-filtering combined with Example 6 and direct remelting comparative example 1 are shown in Table 1. Figure 3 As shown, the magnesium ingot and filter plate residue obtained by direct remelting are as follows Figure 4 As shown in Table 1 and Figure 3~4 It can be seen that within the same time, the crude magnesium after filter pressing has faster melting efficiency and higher smelting efficiency.

[0066] Table 1 Comparison of melting efficiency of crude magnesium crystallization filter press melting and direct melting

[0067] The residue on the filter plate of the melt-filter combination was tested and analyzed by XRD. The results are as follows: Figure 5 As shown, it can be found that the impurities on the filter plate are mainly MgO. At the same time, the magnesium ingot obtained by direct remelting in comparative example 1 and the magnesium ingot obtained by melt-pressing in Example 6 were metallographically characterized, as shown in FIG. Figure 6 ,7, combined with the metallographic sample SEM and EDS surface scanning analysis results, such as Figure 8 As shown in Figure 9, it is found that the ingot after remelting contains large-sized oxide impurities, while the magnesium ingot obtained after filter pressing has relatively fewer large-particle impurities and a cleaner metallographic surface. Fig.10 As shown, by comparing the metallographic diagram of the magnesium ingot obtained by the factory flux refining method, it is found that the surface cleanliness of the magnesium ingot obtained by the filter press method is equivalent to that of the magnesium ingot obtained after refining.

[0068] The above experimental results show that the flux-free fast clean melting and casting method can not only increase the melting efficiency of crystalline magnesium, but also remove the impurities of the thick oxide layer on the surface of crude magnesium crystals, reduce the oxidation loss during the melting process, and thus obtain a cleaner magnesium ingot. Among them, the melting efficiency of crystalline magnesium = the mass of magnesium ingot in the crystallization stage / the mass of crystalline magnesium raw materials in the feeding stage.

[0069] Example 7 In order to achieve the rapid and clean melting and casting of high-purity crystalline magnesium without flux, this embodiment uses high-purity crystalline magnesium obtained by vacuum distillation as raw material, and Figure 2 The subsequent operation steps of the device shown are the same as those of Example 3.

[0070] Comparative Example 2 At the same time, the control group experiment was set up with the same raw materials as in Example 7. 121.2 g of crystalline magnesium raw material was placed in the loading section 10 so that it was located above the filter plate 10. The filter plate size parameters were the same as above. A single-hole plate was covered and the furnace body was sealed. The remaining steps were the same as above, without the filter press process, that is, a simple direct remelting process.

[0071] After the experiment, the magnesium ingot and filter plate residue obtained were weighed. The results are shown in Table 2. The magnesium ingot and filter plate residue obtained by melt-filtering, i.e., Example 7, are as follows: Fig.11 As shown, direct remelting, i.e. comparative example 2, the magnesium ingot and filter plate residue obtained are as follows Fig.12 As shown in Table 2 and Figures 11-12 It can be seen that through comparison, it is found that compared with direct remelting, the melting efficiency of crystalline magnesium treated by the filter press process is significantly faster and the smelting efficiency is higher under the same time.

[0072] Table 2 Comparison of melting efficiency of high purity crystalline magnesium by filter press melting and direct melting

[0073] The residue on the filter plate of the melt-filter combination was sampled and analyzed, and the XRD test results were as follows: Fig.13 As shown by Fig.13 It can be seen that the residual impurities are mainly MgO and Mg. At the same time, the metallographic diagram of the ingot after remelting and melt-filtering is compared. Among them, the metallographic diagram of the magnesium ingot sample obtained by directly remelting the high-purity crystalline magnesium in Comparative Example 2 of the present invention is shown in FIG. Fig.14 The metallographic image of the magnesium ingot sample obtained by melting and filtering the high-purity crystalline magnesium in Example 7 of the present invention is shown in Fig.15 ,Depend on Fig.14 , 15 It can be seen that compared with the ingot obtained by remelting, the magnesium ingot obtained by filter press has fewer surface inclusions and a cleaner and smoother surface. This shows that the flux-free rapid clean melting and casting method can also remove most of the oxide impurities on the surface of high-purity crystalline magnesium.

[0074] The present invention provides a method and device for fast and clean smelting of magnesium without flux, and relates to the field of magnesium metal smelting. Crystalline magnesium metal has a large specific surface area, active chemical properties, and is easy to form a thick high-melting point oxide layer on the surface. The metal magnesium crystals wrapped by the oxide layer have problems such as slow melting speed and difficult oxide separation during smelting, which will significantly affect the smelting efficiency and the purity and performance of downstream products. Therefore, the traditional method often uses a flux to assist the smelting of crystalline magnesium, but the use of the flux will bring about problems such as environmental and product pollution. The method provided by the present invention is to achieve rapid melting of crystalline magnesium by directly applying pressure to the crystalline magnesium to break the surface oxide shell without using a flux. At the same time, by utilizing the difference in fluidity between liquid magnesium metal and solid oxide shell, a porous filter plate is set to achieve the separation of magnesium metal liquid and most of the oxide shell. The device involved in the present invention includes: a pressure control system, a smelting crucible and a smelting furnace body, the smelting furnace includes an atmosphere control system, a cooling circulation system and a vacuum system, the smelting crucible includes a partition, a material placement section, a filter plate and a crystallization section from top to bottom, and the smelting crucible is arranged in the smelting furnace. The use of this device can increase the melting efficiency of crystalline magnesium by more than 50%, remove most of the oxide impurities, and cut off a series of pollution problems caused by the use of flux from the source.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for purifying crystalline magnesium, characterized in that: The following steps are involved: In an inert atmosphere, the crystalline magnesium material to be purified is melted to obtain a mixture of molten magnesium and a magnesium oxide shell layer; and while melting, the mixture of the molten magnesium and the magnesium oxide shell layer is subjected to a filter press treatment to obtain a molten magnesium filtrate; During the filter press treatment, the pressure applied for: In the formula, is the mass of magnesium material to be smelted, g is the acceleration due to gravity, is the area of ​​the filter press equipment, is a constant, 6~10; S3: Cooling the molten magnesium filtrate to obtain purified crystalline magnesium.

2. The method for purifying crystalline magnesium according to claim 1, characterized in that: The flow rate of the inert atmosphere is 400-700 sccm.

3. The method for purifying crystalline magnesium according to claim 1, characterized in that: During the melting treatment, the temperature is 750-850° C. and the time is 1-1.5 h.

4. The method for purifying crystalline magnesium according to claim 1, characterized in that: During the melting process, the heating rate is 3-5°C / min.

5. The method for purifying crystalline magnesium according to claim 1, characterized in that: The cooling rate during the cooling process is 3-5°C / min.

6. The method for purifying crystalline magnesium according to claim 1, characterized in that: Before the inert gas is introduced into the system, the system is subjected to multiple vacuum treatments. During the vacuum treatment, the vacuum degree is -0.07 MPa and the treatment time is 5 to 10 minutes.

7. The method for purifying crystalline magnesium according to claim 1, characterized in that: The crystalline magnesium material to be purified is crude crystalline magnesium obtained by Pidgeon reduction or crystalline magnesium obtained by vacuum distillation.

8. A purified crystalline magnesium, characterized in that: It is prepared by smelting according to the method described in any one of claims 1 to 7.

9. A purification device for implementing the method for purifying crystalline magnesium according to any one of claims 1 to 7, characterized in that: It comprises a main body (1), and a feeding piece (2) arranged inside the main body (1); A loading plate (10) for placing the crystalline magnesium material to be purified is provided inside the loading member (2), and a plurality of through holes are provided on the loading plate (10), and the plurality of through holes are used to separate the molten magnesium material and the solid magnesium oxide; a pressure control unit (8) for implementing a filter pressing process of the molten magnesium material is provided above the loading plate (10), and the pressure control unit (8) can be close to or away from the loading plate (10); The feeding member (2) is provided with a temperature control unit (3) for melting the magnesium material to be purified outside, and the body (1) is provided with a vacuum unit (7) for providing a vacuum degree, an atmosphere control unit (5) for providing an inert atmosphere, and a cooling circulation unit (9) for cooling the system.

10. A crystalline magnesium purification device according to claim 9, characterized in that: The thickness of the material placement plate (10) is 3-6 mm.

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