Automatic refining process method for large-tonnage magnesium alloy

Abstract

The invention discloses an automatic refining process method for large-tonnage magnesium alloy, and aims to solve the industrial problems that traditional manual refining is high in labor intensity, high in potential safety hazard and incapable of treating large-tonnage melt. According to the method, a special automatic refining device is adopted, magnesium alloy melt is sucked in from the bottom by driving rotating blades in a guide cylinder, the magnesium alloy melt is preliminarily filtered by a foamed ceramic filter screen to form directional rising liquid flow, the directional rising liquid flow is discharged from a single liquid outlet to form a stable wave crest, and a refining agent is added at the position to adsorb impurities. The core of the method lies in accurate control of key process parameters: the inner diameter of the guide cylinder and the inner diameter of the crucible need to meet a specific proportional relation (D is approximately equal to (1 / 2.5-1 / 3.5) * d); the distance from the bottom of the guide cylinder to the bottom of the crucible needs to be dynamically adjusted in the refining process to avoid disturbing a bottom impurity layer; and controlling the rotating speed to make the crest height. According to the magnesium alloy melt refining device, efficient, stable and full-automatic refining of 200-1000 kg of magnesium alloy melt is achieved, the quality of castings poured by the refined melt can meet the I-type casting requirements in the HB7780-2005 standard, and the production safety and the product quality consistency are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium alloy smelting, in particular to a large-tonnage magnesium alloy automatic refining process method. BACKGROUND

[0002] In the magnesium alloy casting industry, solvent slag inclusion defects are a common problem that leads to casting rejection, therefore, melt purification process has always been the focus of research in this field.

[0003] At present, the magnesium alloy refining operation process commonly used in the industry is as follows: after the alloy liquid is melted and heated to 750℃, when the weight of the melt is less than 300kg, 2 operators need to use a special stirring spoon to continuously alternate stirring; when the weight of the melt reaches 300kg-500kg, at least 3-4 operators need to cooperate in the same way, the stirring frequency is not less than 120 times per minute, and another operator is needed to sprinkle solvent into the alloy liquid to make the alloy liquid and the solvent fully combine to achieve the purpose of purification and fire retardation. This process lasts for 12-30 minutes, not only the manual labor intensity is extremely large, but also the skill requirement of the operator is high, and the operator needs to be near the high-temperature smelting furnace for a long time, which has significant safety hazards. More importantly, when the weight of the melt exceeds 500kg, simple manual stirring cannot effectively stir the melt, and the refining process is difficult to proceed.

[0004] In order to replace manual work, the industry has tried to use equipment for refining. However, due to the fact that key process parameters have not been properly explored, the refining effect is often not ideal, resulting in the fact that most production units still use semi-automatic refining methods combining manual work with machines. In addition, most domestic production units do not have integrated forming technology for large-tonnage magnesium alloy castings, especially lack of research on automatic refining technology for large-tonnage magnesium alloy melts.

[0005] In the prior art, for example, a stirring mechanism for magnesium alloy refining is disclosed in Chinese Utility Model Patent No. CN216620704U, which includes a crucible, an impeller assembly and a draft tube. By combining the impeller assembly and the draft tube, the magnesium alloy melt is guided to form an up-down circulating flow in the draft tube, aiming to ensure that the refining flux and inclusions are in full contact while avoiding the generation of new oxidation inclusions. However, this scheme still needs to be further improved in terms of achieving efficient and stable automatic refining of large-tonnage melts (e.g. more than 500kg), especially in terms of how to accurately control the flow state to avoid re-rolling of settled impurities, and how to systematically optimize the whole set of process parameters. SUMMARY

[0006] The purpose of the present application is to provide a large-tonnage magnesium alloy automatic refining process method.

[0007] The technical scheme of the present application: a large-tonnage magnesium alloy automatic refining process method adopts an automatic refining device, the device includes a flow guide cylinder, a rotating rod inserted into the flow guide cylinder, a driving motor and rotating blades connected to the upper end and lower end of the rotating rod respectively, and a single liquid outlet opened in the upper side wall of the flow guide cylinder, a lifting baffle is arranged at the liquid outlet, and a detachable foamed ceramic filter screen is arranged at the bottom of the flow guide cylinder, and the method comprises the following steps: Step 1: Place the refining device in the center of the crucible containing the magnesium alloy melt, vertically insert the flow guide cylinder into the melt, and ensure that the foamed ceramic filter screen at the bottom of the flow guide cylinder is higher than the impurity sediment layer at the bottom of the crucible; Step 2: Start the driving motor to drive the rotating blades to rotate at high speed, suck the metal liquid in the crucible from the bottom of the flow guide cylinder, form an upward flowing liquid flow in the flow guide cylinder after preliminary filtration by the foamed ceramic filter screen, and direct discharge from the single liquid outlet, forming a stable wave crest on the liquid surface; Step 3: continuously or intermittently sprinkle magnesium alloy refining solvent at the wave crest formed in step 2, the solvent fully contacts and adsorbs impurities with the rolling metal liquid, and then settles with impurities to the bottom of the crucible; Step 4: maintain the refining process for a predetermined time, and stop the driving motor and lift the device when the metal liquid reaches the predetermined purity; Among them, the process method satisfies the following core parameter relationship: 1) The outer diameter D of the flow guide cylinder and the inner diameter d of the crucible satisfy the relationship: D ≈ (1 / 2.5 ~ 1 / 3.5) * d; 2) At the beginning of refining, the distance H1 between the bottom of the flow guide cylinder and the bottom of the crucible is controlled within the range of 350mm-450mm; during the refining process, the distance is gradually adjusted according to the purity of the melt, but the final distance is not less than 240mm; 3) The distance H2 between the rotating blades and the bottom of the flow guide cylinder is greater than 300mm; 4) By controlling the rotating speed of the rotor, the lower edge of the single liquid outlet of the flow guide cylinder is basically flush with the metal liquid surface, and the wave crest height is maintained at 40mm-50mm.

[0008] Preferably, the predetermined refining time is 15min-20min, and the refining temperature of the magnesium alloy melt is 730℃-740℃.

[0009] Preferably, the rotating speed of the driving motor is 0-500r / min to adapt to the processing amount of 200kg-1000kg of magnesium alloy melt.

[0010] Preferably, the automatic refining device is also equipped with a control system for automatically controlling the lifting of the device, the rotating speed of the driving motor and the predetermined refining time.

[0011] Preferably, the pore size of the foam ceramic filter screen is 5 PPI-10 PPI, and the foam ceramic filter screen is replaced after each refining.

[0012] Preferably, the magnesium alloy melt refined by the method meets the quality requirement of the castings of class I in the standard HB7780-2005 The beneficial effects of the present application are: 1. The foam ceramic filter screen (5-10 ppi) is added at the bottom of the flow guide cylinder to block the relatively large impurities in the melt when the metal liquid is rolling.

[0013] 2. The distance between the bottom of the flow guide cylinder and the bottom of the crucible and the distance between the rotating blade in the flow guide cylinder and the bottom of the crucible can effectively prevent the impurities from being stirred up when the 200kg-1000kg metal liquid is rolling in the crucible, effectively ensure the quality of the alloy melt, and the flow guide cylinder is as close as possible to the bottom of the crucible, thereby effectively reducing the weight of the ingredients and saving the cost.

[0014] 3. The present application realizes the refining of 1000kg magnesium alloy melt, and the castings meet the requirements of class I in the standard HB7780-2005. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a schematic diagram of an automatic refining device; Figure 2 is a schematic diagram of the position relationship between the metal liquid surface, the device and the crucible during stirring; The reference signs are as follows: 1-flow guide cylinder, 2-rotating rod, 3-rotating blade, 4-foam ceramic filter screen, 5-liquid outlet, 6-metal baffle, 7-crucible, 8-metal liquid surface. DETAILED DESCRIPTION

[0017] The present application will be further described below in combination with the drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present application is limited to the following embodiments. Any modifications, replacements and changes made according to the ordinary technical knowledge and common methods in the art without departing from the above technical idea of the present application are included in the scope of the present application.

[0018] The application is characterized in that the magnesium alloy liquid is stably rolled in the crucible by the automatic refining device, fully contacts with the solvent to perform chemical reaction, the mechanical rolling causes the fluctuation of the metal liquid, the single liquid outlet 5 is arranged to effectively control the flow and direction of the rolling metal liquid, the irregular flow of the metal liquid in the crucible is avoided so that the settled impurities are brought into the upper melt again, meanwhile, the foam ceramic filter screen 4 (5-10 ppi) is arranged at the bottom of the flow guide cylinder to filter the metal liquid, filter out the relatively large impurities in the metal liquid, the wave peak contacts with the solvent to perform reaction, the solvent has poor wettability to the molten magnesium, but has good wettability to the oxide particles mechanically mixed in the magnesium, can absorb the impurity particles, and then settles at the bottom of the molten magnesium to be removed, the refining agent purifies the impurities and gas of the alloy liquid, and the melt is purified.

[0019] Referring to Figure 1 , the automatic refining device comprises a flow guide cylinder 1, a rotating rod 2, rotating blades 3, a metal liquid baffle 6, a rotating motor and a control system. The parameters involved include: the rotating speed of the rotor composed of the rotating rod 2 and the rotating blades 3 determines the height of the wave peak of the metal liquid surface 8 and the liquid outlet speed, the depth of the flow guide cylinder inserted into the metal liquid determines the impurity content contained in the circulating rolling metal liquid, the refining time determines the cost and efficiency, and the relationship between the diameter of the crucible 7 and the diameter of the flow guide cylinder.

[0020] The outer diameter D of the flow guide cylinder and the inner diameter d of the crucible satisfy the relationship: D ≈ (1 / 2.5 ~ 1 / 3.5) * d; the distance H1 between the bottom of the flow guide cylinder and the bottom of the crucible is initially controlled in the range of 350mm-450mm, which is gradually adjusted according to the purity of the melt, but finally is not less than 240mm, the distance H2 between the rotating blades and the bottom of the flow guide cylinder is greater than 300mm; the liquid outlet of the flow guide cylinder is basically flush with the metal liquid surface, and the wave peak height formed is maintained at 40mm-50mm. The rotating speed of the rotating blades in the flow guide cylinder is different when using crucibles with different diameters. The rotating speed can be linearly adjusted, and the operator gradually increases the rotating speed until the metal liquid at the metal liquid outlet of the flow guide cylinder forms obvious wave peak, which is 40-50mm. The metal liquid outlet is single directional, and a metal liquid baffle which can be adjusted in height is arranged at the liquid outlet to control the size of the metal liquid outlet. A foam ceramic filter screen is arranged at the bottom of the flow guide cylinder, the pore size range is 5-10 ppi, and it is replaced every furnace.

[0021] As Figure 2As shown, the working principle of this device is that the high-speed rotation of the rotor inside the guide tube forces the molten metal through a foam ceramic filter screen and out through the opening at the top of the guide tube, forming a wave crest. Solvent is then sprinkled into the crest, encapsulating impurities and causing them to sink to the bottom of the crucible. The molten metal is continuously tumbled for 15-20 minutes until most of the impurities have settled to the bottom. The device is equipped with a rotary motor and a control system at the top to control parameters such as lifting, rotation speed, and refining time. During this process, the following process parameters must be strictly controlled: (1) The relationship between the diameter D of the guide tube and the inner diameter d of the crucible. After the alloy liquid reaches the refining temperature, it will... Figure 1 The device shown is inserted into the crucible for refining. The device needs to be placed in the exact center of the crucible, and the outer diameter of the guide tube is about one-third of the inner diameter of the crucible. If the inner diameter of the crucible is too large, it will not be conducive to the sedimentation of impurities. If the inner diameter of the crucible is too small, the distance between the liquid outlet and the inner wall of the crucible will cause the molten metal to flow in a turbulent manner, which will not be conducive to the sedimentation of impurities. (2) The distance H1 between the bottom of the guide tube and the bottom of the crucible. After being coated by the solvent, the impurities in the magnesium alloy liquid fall to the bottom of the pot and form an impurity layer at the bottom of the crucible. If the guide tube is inserted too deeply into the impurity layer, the impurities will be carried back into the upper melt during the rolling of the molten metal, and the refining requirements cannot be met. Refining is carried out at a distance of 400 mm from the bottom of the crucible. When no obvious impurities are turned out of the molten metal, the height of the guide tube is lowered by 50 mm and refining is carried out for 2 minutes. If no obvious impurities are turned out, the height is lowered further. When it is lowered to about 220 mm, a large number of impurities are turned out, that is, they reach the impurity layer. Therefore, the distance between the bottom of the guide tube and the bottom of the crucible should be controlled to be no less than 240 mm.

[0022] (3) The distance H2 between the rotating blades inside the guide tube and the bottom of the guide tube. The rotating blades inside the guide tube should be as far away from the bottom of the crucible as possible. A distance of at least 300 mm from the bottom of the guide tube can effectively prevent the rotation of the rotating blades from causing impurities at the bottom to float to the surface.

[0023] (4) The distance between the liquid outlet of the guide tube and the surface of the liquid metal. The surface of the liquid metal is flush with the lower end of the outlet of the guide tube, so that the liquid metal can circulate and roll from bottom to top. The rotation speed is determined according to the weight of the feed, the size of the blades and the outer diameter of the guide tube, and the peak of the rotating liquid metal is controlled to be about 40-50mm.

[0024] Example 1: 600 kg of ZM6 magnesium alloy was refined using a crucible with an inner diameter of approximately 610 mm. Based on the proportional relationship proposed in this invention (D ≈ (1 / 2.5 ~ 1 / 3.5) * d), a flow guide tube with an outer diameter of approximately 200 mm (proportion approximately 1 / 3.05) was selected to ensure orderly melt circulation and avoid flow field disturbances caused by mismatch between the flow guide tube and crucible dimensions.

[0025] Refining process and parameter control: Initial stage: The guide tube 1 is placed vertically in the center of the crucible 7, with the distance H1 between its bottom and the bottom of the crucible settling layer settling layer settling layer to approximately 400 mm. The distance H2 between the rotating blades and the bottom of the guide tube is greater than 300 mm to ensure that the blades' agitation does not disturb the already settled impurities at the bottom.

[0026] Circulation and Refining: Start the drive motor and adjust the speed to 320 r / min. At this time, the upward-flowing liquid in the guide tube is discharged directionally from a single outlet, forming a stable wave peak with a height of about 45 mm on the liquid surface. Adjust the lifting baffle to keep the lower edge of the outlet flush with the surface of the molten metal.

[0027] Solvent addition and impurity adsorption: Magnesium alloy refining solvent is continuously and evenly sprinkled at the crest. The solvent spreads rapidly in the churning molten metal, efficiently adsorbing inclusions such as oxides and encapsulating them as they settle to the bottom of the crucible.

[0028] Dynamic optimization and process monitoring: After approximately 10 minutes of refining, no visible impurities were observed flowing out of the discharged molten metal, indicating a significant improvement in the purity of the upper melt. At this point, the guide tube was slowly lowered by 110 mm via the control system, adjusting H1 to approximately 290 mm to expand the circulation and purification range of the lower melt. Refining continued for another 6 minutes, for a total refining time of 16 minutes. Throughout the process, the melt temperature was stably controlled at 735℃±5℃.

[0029] Filtration Guarantee: A foam ceramic filter screen is installed at the bottom of the guide tube to pre-filter the incoming melt and effectively intercept larger initial inclusions. This filter screen is replaced after the furnace cycle.

[0030] After refining, samples were taken for melt purity analysis, and then cast into standard test bars and castings. Test results showed that the melt inclusion content was extremely low, and the internal quality and mechanical properties of the cast parts fully met the stringent requirements for Class I castings in the HB7780-2005 standard. Compared to the traditional semi-manual method requiring 3-4 people to stir intensely for more than 20 minutes, this embodiment achieves fully automated operation under single-person monitoring, shortening refining time, significantly reducing labor intensity and safety hazards, and significantly improving consistency.

[0031] Example 2: Refining 900 kg of ZM6 magnesium alloy using a crucible with the same inner diameter (610 mm) and a guide tube with an outer diameter (200 mm). Refining process and parameter adjustments: Parameter adaptive adjustment: due to the increase of melt weight, in order to maintain the required melt circulation intensity and wave height (40-50mm), the driving motor speed is increased to 370r / min. This reflects the advantage of the present application that it can adapt to different melt processing capacity by linear adjustment of speed. The initial H1 is also set to about 400mm. Given that the total amount of melt is larger, the total amount of impurities may be more, and the total refining time is set to 18 minutes. After refining to the 12th minute, confirming that the upper melt is pure, the flow guide tube is lowered to a safe distance of about 290mm to prevent touching the bottom impurity layer. During the entire refining process, the wave height formed by the outlet is stably maintained at about 48mm, indicating that the system still runs smoothly and the flow is controllable under high speed and large flow.

[0032] The purity of the 900kg magnesium alloy melt after refining is comparable to that of Example 1. The large castings poured are free of defects such as internal density and solvent slag, and also fully meet the requirements of HB7780-2005 Class I castings. This achievement is of great significance. The successful realization of high-quality, fully automated refining of a nearly 1-ton single-furnace magnesium alloy melt has solved the industry bottleneck of refining large-tonnage melts. Under the same core device (ratio of flow guide tube / crucible diameter), by optimizing the speed, refining time and flow guide tube lowering strategy, the processing capacity can be stably expanded from 600kg to 900kg, providing a reliable parameter adjustment paradigm for processing larger tonnages (such as 1000kg). It does not require multiple workers to work together at high temperature furnaces, improving the level of intrinsic safety; the refining time is controllable and relatively short, improving production efficiency; and the stable process ensures the uniformity and high pass rate of product quality.

[0033] The present application establishes a correlation system of key parameters such as the ratio of flow guide tube and crucible diameter, dynamically adjustable flow guide tube insertion depth H1, safe distance H2 of rotating blades, and speed control based on wave height. This is not a single component improvement, but a set of quantifiable, replicable and scalable automated refining process solution. The successful liberation of large-tonnage (200kg-1000kg) magnesium alloy melt refining from reliance on manual experience and high-intensity difficulties has realized safe, efficient, stable and high-quality automated production, laying the foundation for the manufacture of large-scale integrated magnesium alloy castings.

[0034] The above has carried out the detailed introduction to the large tonnage magnesium alloy automatic refining process method provided by the application, the structure and working principle of the application are described by applying specific examples in this paper, the above example is only used for helping understanding the method and core idea of the application. It should be pointed out that for ordinary skilled person in the art, without departing from the principle of the application, the application can be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the application.

Claims

1. An automated refining process for large-tonnage magnesium alloys, characterized in that: An automated refining apparatus is used, comprising a guide tube (1), a rotating rod (2) extending into the guide tube (1), a drive motor and a rotating blade (3) respectively connected to the upper and lower ends of the rotating rod, and a single liquid outlet (5) opened on the upper side wall of the guide tube (1). A lifting baffle (6) is provided at the liquid outlet (5), and a removable foam ceramic filter screen (4) is provided at the bottom of the guide tube. The method includes the following steps: Step 1: Place the refining device in the center of the crucible containing the magnesium alloy melt, insert the guide tube (1) vertically into the melt, and ensure that the foam ceramic filter screen (4) at the bottom of the guide tube is higher than the impurity settling layer at the bottom of the crucible; Step 2: Start the drive motor to drive the rotating blade (3) to rotate at high speed, and draw the molten metal in the crucible from the bottom of the guide tube. After being initially filtered by the foam ceramic filter screen (4), the liquid flows upward in the guide tube and is discharged directionally from a single outlet (5), forming a stable wave peak on the liquid surface. Step 3: Continuously or intermittently sprinkle magnesium alloy refining solvent at the peak formed in step 2. The solvent fully contacts the molten metal and adsorbs impurities, which then settle to the bottom of the crucible. Step 4: Maintain the refining process for a predetermined time. Once the molten metal reaches the predetermined purity, stop the drive motor and lift the device. The process method satisfies the following core parameter relationships: 1) The outer diameter (D) of the guide tube and the inner diameter (d) of the crucible satisfy the following relationship: D ≈ (1 / 2.5 ~ 1 / 3.5) *d; 2) In the initial stage of refining, the distance (H1) between the bottom of the guide tube and the bottom of the crucible is controlled within the range of 350mm-450mm; during the refining process, this distance is gradually reduced according to the purity of the melt, but it shall not be less than 240mm in the end. 3) The distance (H2) between the rotating blade and the bottom of the guide tube is greater than 300mm; 4) By controlling the rotor speed, the lower edge of the single liquid outlet of the guide tube is made to be basically flush with the metal liquid surface, and the height of the wave peak is maintained at 40mm-50mm.

2. The automated refining process for large-tonnage magnesium alloys according to claim 1, characterized in that: The predetermined refining time is 15-20 minutes, and the refining temperature of the magnesium alloy melt is 730-740℃.

3. The automated refining process for large-tonnage magnesium alloys according to claim 1, characterized in that: The drive motor has a speed of 0-500 rpm to accommodate magnesium alloy melt processing volumes of 200kg-1000kg.

4. The automated refining process for large-tonnage magnesium alloys according to claim 1, characterized in that: The automated refining device is also equipped with a control system for automatically controlling the lifting and lowering of the device, the speed of the drive motor, and the predetermined refining time.

5. The automated refining process for large-tonnage magnesium alloys according to claim 1, characterized in that: The pore size of the foam ceramic filter screen (4) is 5 PPI-10 PPI, and it is replaced after each batch of refining is completed.

6. The automated refining process for large-tonnage magnesium alloys according to claim 1, characterized in that: Magnesium alloy melt refined by this method produces castings that meet the quality requirements for Class I castings in the HB7780-2005 standard.

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