A method of producing a casting magnesium alloy refiner and a method of using the same
By treating zirconium carbide particles with chemical zinc plating combined with mechanical stirring and ultrasonic treatment, the problem of poor grain refinement in cast magnesium alloys was solved, achieving grain refinement and improved mechanical properties of magnesium alloys.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN UNIV OF SCI & TECH
- Filing Date
- 2024-01-31
- Publication Date
- 2026-06-02
Smart Images
Figure CN118086882B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing magnesium alloy refining agents and its application. Background Technology
[0002] Magnesium alloys possess numerous advantages, including high specific strength, high specific modulus, and good thermal conductivity, making them promising candidates for applications in aerospace, electronics, defense, and transportation. However, most cast magnesium alloys exhibit poor mechanical properties, limiting their engineering applications. To improve the mechanical properties of cast magnesium alloys, grain refinement can be employed.
[0003] Grain refinement methods mainly include adding alloying elements, melt stirring and vibration, thermoplastic deformation, and adding heterogeneous particles. Among these, adding certain alloying elements that refine the microstructure of cast magnesium alloys causes these elements to accumulate near the solid-liquid interface during solidification, leading to compositional supercooling at the interface and inhibiting grain growth. Additionally, some alloying elements can form a large number of second phases in the early stages of solidification. Some of these second phases can inhibit grain growth, while others can act as nuclei for α-Mg grains, thus refining grain size. Although alloying elements can refine grains, only a few have a significant refining effect on magnesium alloys. Taking Zr, which has excellent refining effects, as an example, Zr can effectively refine grains in aluminum-free magnesium alloys. However, when Zr is added to aluminum-containing magnesium alloys, it forms high-melting-point compounds with Al during smelting, significantly reducing or even eliminating its refining effect. Therefore, the use of Zr and other alloying elements to refine magnesium alloys is greatly limited. However, the refinement effect of melt stirring vibration method is not ideal, and the refined alloy microstructure is uneven. In addition, thermoplastic deformation is mainly used for magnesium alloy forgings and is not suitable for magnesium alloy castings, thus limiting its application range.
[0004] Obviously, from the perspective of the universality of the grain refinement method, the addition of heterogeneous particles is a widely applicable method for refining the grains of cast magnesium alloys, which is suitable for various magnesium alloy composition systems. However, existing heterogeneous particles have poor grain refinement effects on cast magnesium alloys. Summary of the Invention
[0005] The present invention aims to solve the problem that existing heterogeneous particles have poor grain refinement effect on cast magnesium alloys, and thus provides a method for preparing and using a cast magnesium alloy grain refiner.
[0006] A method for preparing a fine-refining agent for cast magnesium alloys, comprising the following steps:
[0007] 1. The zirconium carbide particles are sequentially subjected to degreasing, coarsening, sensitization and activation to obtain pretreated zirconium carbide particles;
[0008] The zirconium carbide particles have an average diameter of 50 nm to 1000 nm.
[0009] 2. Mix zinc sulfate, EDTA-2Na and deionized water, heat in a water bath to dissolve until the solution is clear, then stir evenly to obtain a mixed solution. Adjust the pH of the mixed solution to alkaline, then add stabilizer, pretreated zirconium carbide particles and sodium dihydrogen phosphate solution in sequence, stir magnetically to react, and finally let stand, wash and dry to obtain a finer agent for cast magnesium alloys.
[0010] The mass ratio of zinc sulfate to EDTA-2Na is 1:(1-5); the mass ratio of zinc sulfate to deionized water is 1g:(10-40)mL; the mass ratio of stabilizer to zinc sulfate is 1:(100-400); the mass ratio of pretreated zirconium carbide particles to zinc sulfate is 1:(1-3); and the mass ratio of zinc sulfate to sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 1:(1-3).
[0011] The application method for refining agents in cast magnesium alloys is as follows:
[0012] The magnesium alloy refining agent was pressed into flakes to obtain flake refining agent. The magnesium alloy raw material was heated and melted, and mechanical stirring and ultrasonic treatment were carried out under the conditions of heating temperature of 740℃~780℃, mechanical stirring speed of 100r / min~500r / min, and ultrasonic treatment power of 2kW~4kW. During the mechanical stirring and ultrasonic treatment, the flake refining agent was pressed into the eddy current formed by mechanical stirring and ultrasonic treatment. The mechanical stirring and ultrasonic treatment lasted for 5min~10min, and a covering agent was continuously added during the mechanical stirring and ultrasonic treatment. After mechanical stirring and ultrasonic treatment, the melt is cooled to 630℃~640℃ to make it semi-solid. Then, under the conditions of 630℃~640℃ and stirring speed of 100r / min~500r / min, it is mechanically stirred for 5min~10min. After stirring, it is reheated to the melting temperature and held at that temperature. After holding at that temperature, the waste residue is removed and the melt is poured into a mold. Finally, it is cooled and solidified, which completes the method of using the casting magnesium alloy refiner. The mass ratio of the flake refiner to the magnesium alloy raw material is 1:(0.002~0.02).
[0013] The beneficial effects of this invention are:
[0014] This invention prepares a novel magnesium alloy refining agent. By using chemical plating to treat zirconium carbide powder particles with zinc, a zinc layer can be formed on the surface of the particles. The zinc-plated zirconium carbide nanoparticles are then added to the magnesium alloy melt.
[0015] 1. The zinc layer reduces the surface tension between the liquid magnesium alloy and nano-zirconium carbide, thereby improving wettability. Magnesium atoms in the alloy melt are more likely to adhere to the surface of zirconium carbide particles with a zinc layer, increasing the nucleation rate of the zirconium carbide particles. When the liquid magnesium alloy adheres to the surface of the zirconium carbide particles, the zinc-plated zirconium carbide particles act as nuclei for heterogeneous nucleation, increasing the number of grain nucleation nuclei and achieving grain refinement.
[0016] 2. Zinc-plated zirconium carbide particles present at grain boundaries are obstacles to grain growth, which can hinder grain growth and thus refine the grains.
[0017] 3. Compared with traditional galvanizing methods, electroless galvanizing has the following advantages: First, electroless galvanizing can be applied to powders, broadening the application range of galvanizing treatment; second, compared with traditional galvanizing, electroless galvanizing requires relatively less space and is technically simpler. Whether hot-dip galvanizing, cold galvanizing, or mechanical galvanizing, the galvanizing process is relatively complicated, requires advanced equipment, and is difficult to apply to nanoparticle galvanizing.
[0018] 4. Compared with magnesium alloys with zinc-plated zirconium carbide particles, magnesium alloys with zinc-plated zirconium carbide particles have finer grain size and significantly improved mechanical properties. Therefore, zinc plating can improve the refining effect of zirconium carbide on cast magnesium alloys.
[0019] Instruction manual illustrations
[0020] Figure 1 A low-magnification scanning electron microscope image of the zinc-plated zirconium carbide particles prepared in Example 1;
[0021] Figure 2 Here is a high-magnification scanning electron microscope image of the zinc-plated zirconium carbide particles prepared in Example 1;
[0022] Figure 3 The images show the optical microstructure of magnesium alloys. a) is the magnesium alloy prepared in Comparative Experiment 1 without the addition of casting refining agent; b) is the magnesium alloy prepared in Comparative Experiment 2 with the addition of ungalvanized zirconium carbide particles; c) is the magnesium alloy prepared in Example 2 with the addition of galvanized zirconium carbide particles.
[0023] Figure 4 The results are as follows: 1 is the magnesium alloy prepared in Comparative Experiment 1 without the addition of casting refiner; 2 is the magnesium alloy prepared in Comparative Experiment 2 with the addition of ungalvanized zirconium carbide particles; and 3 is the magnesium alloy prepared in Example 2 with the addition of galvanized zirconium carbide particles. Detailed Implementation
[0024] Specific Implementation Method 1: This implementation method is a method for preparing a fine-refining agent for cast magnesium alloys, which is carried out according to the following steps:
[0025] 1. The zirconium carbide particles are sequentially subjected to degreasing, coarsening, sensitization and activation to obtain pretreated zirconium carbide particles;
[0026] The zirconium carbide particles have an average diameter of 50 nm to 1000 nm.
[0027] 2. Mix zinc sulfate, EDTA-2Na and deionized water, heat in a water bath to dissolve until the solution is clear, then stir evenly to obtain a mixed solution. Adjust the pH of the mixed solution to alkaline, then add stabilizer, pretreated zirconium carbide particles and sodium dihydrogen phosphate solution in sequence, stir magnetically to react, and finally let stand, wash and dry to obtain a finer agent for cast magnesium alloys.
[0028] The mass ratio of zinc sulfate to EDTA-2Na is 1:(1-5); the mass ratio of zinc sulfate to deionized water is 1g:(10-40)mL; the mass ratio of stabilizer to zinc sulfate is 1:(100-400); the mass ratio of pretreated zirconium carbide particles to zinc sulfate is 1:(1-3); and the mass ratio of zinc sulfate to sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 1:(1-3).
[0029] This specific embodiment modifies the particles based on the following principles: zirconium carbide is selected as the heterogeneous nucleation particle, and the surface wettability of the heterogeneous nucleation particle on the magnesium alloy is improved, which determines the effect of magnesium alloy grain refinement. To achieve the above effect, the surface of zirconium carbide nanoparticles is chemically zinc-plated, thereby improving the wettability of heterogeneous nucleation particles and magnesium alloy melt. This is beneficial to improving the adsorption capacity of magnesium atoms on the surface of the added heterogeneous nucleation particles during the solidification process of magnesium alloy, thus enhancing the refinement effect of magnesium alloy. Moreover, the chemically zinc-plated surface-modified particles are less prone to agglomeration after being added to the magnesium alloy melt, improving dispersibility and helping to improve the utilization rate of nanoparticles. On this basis, mechanical stirring and ultrasonic melt treatment can be further combined to improve the refinement effect of magnesium alloy melt.
[0030] The beneficial effects of this embodiment are:
[0031] This embodiment prepares a novel magnesium alloy refining agent. Zinc is plated onto zirconium carbide powder particles using a chemical plating method, which forms a zinc layer on the particle surface. The zinc-plated zirconium carbide nanoparticles are then added to the magnesium alloy melt.
[0032] 1. The zinc layer reduces the surface tension between the liquid magnesium alloy and nano-zirconium carbide, thereby improving wettability. Magnesium atoms in the alloy melt are more likely to adhere to the surface of zirconium carbide particles with a zinc layer, increasing the nucleation rate of the zirconium carbide particles. When the liquid magnesium alloy adheres to the surface of the zirconium carbide particles, the zinc-plated zirconium carbide particles act as nuclei for heterogeneous nucleation, increasing the number of grain nucleation nuclei and achieving grain refinement.
[0033] 2. Zinc-plated zirconium carbide particles present at grain boundaries are obstacles to grain growth, which can hinder grain growth and thus refine the grains.
[0034] 3. Compared with traditional galvanizing methods, electroless galvanizing has the following advantages: First, electroless galvanizing can be applied to powders, broadening the application range of galvanizing treatment; second, compared with traditional galvanizing, electroless galvanizing requires relatively less space and is technically simpler. Whether hot-dip galvanizing, cold galvanizing, or mechanical galvanizing, the galvanizing process is relatively complicated, requires advanced equipment, and is difficult to apply to nanoparticle galvanizing.
[0035] 4. Compared with magnesium alloys with zinc-plated zirconium carbide particles, magnesium alloys with zinc-plated zirconium carbide particles have finer grain size and significantly improved mechanical properties. Therefore, zinc plating can improve the refining effect of zirconium carbide on cast magnesium alloys.
[0036] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the degreasing in step one is carried out as follows: Zirconium carbide particles are mixed with anhydrous ethanol and ultrasonically treated for 10 to 60 minutes at an ultrasonic power of 0.2 kW to 0.5 kW. Then, the mixture is washed multiple times with deionized water and finally dried to obtain degreased zirconium carbide particles. Everything else is the same as in Specific Implementation Method One.
[0037] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the roughening process in step one is carried out as follows: The degreased zirconium carbide particles are mixed with a nitric acid solution of 30%–68% by mass, and ultrasonically treated for 10–60 minutes at an ultrasonic power of 0.2 kW–0.5 kW. Then, the mixture is washed multiple times with deionized water and finally dried to obtain the roughened zirconium carbide particles. The rest is the same as in Specific Implementation Method One or Two.
[0038] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the sensitization described in step one is carried out as follows: Under stirring conditions, SnCl2·H2O is dissolved in hydrochloric acid with a mass percentage of 10% to 37%. Then, under stirring conditions, water is added to dilute the concentration of SnCl2·H2O to 0.1 mol / L to 0.3 mol / L to obtain a mixed solution. The coarsened zirconium carbide particles are added to the mixed solution, and ultrasonic treatment is performed for 10 min to 60 min under ultrasonic power of 0.2 kW to 0.5 kW. Then, the solution is filtered, washed with deionized water, and vacuum dried to obtain sensitized zirconium carbide particles. The mass ratio of SnCl2·H2O to the volume ratio of hydrochloric acid with a mass percentage of 10% to 37% is 1 g:(1 to 4) mL. Everything else is the same as in Specific Implementation Methods One to Three.
[0039] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the activation described in step one is carried out as follows: Silver nitrate is dissolved in water, and then 10%–25% ammonia solution is added dropwise under stirring until the yellow-brown precipitate disappears. Ammonia solution is then added dropwise again, stirring until clear. The clear solution is mixed with the sensitized zirconium carbide particles, and ultrasonically treated for 10–60 minutes at an ultrasonic power of 0.2 kW–0.5 kW. The particles are then washed multiple times with deionized water and finally dried to obtain pretreated zirconium carbide particles. The mass ratio of silver nitrate to water is 1 g:(50–200) mL. Everything else is the same as in Specific Implementation Methods One to Four.
[0040] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step two, a sodium hydroxide solution with a concentration of 2 mol / L to 3 mol / L is added to the mixed solution to adjust the pH of the mixed solution to 8 to 12. Everything else is the same as in Specific Implementation Methods One to Five.
[0041] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the stabilizer mentioned in step two is 2-2'-bipyridine. Everything else is the same as in Specific Implementation Methods One to Six.
[0042] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in step two, the magnetic stirring reaction is carried out for 5 to 60 minutes at a magnetic stirring speed of 200 r / min to 500 r / min. Everything else is the same as in Specific Implementation Methods One to Seven.
[0043] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution described in step two is 0.2 mol / L to 0.5 mol / L. Everything else is the same as in Specific Implementation Methods One to Eight.
[0044] Specific Implementation Method Ten: The method of using the casting magnesium alloy refining agent in this implementation method is characterized by the following steps:
[0045] The magnesium alloy refining agent was pressed into flakes to obtain flake refining agent. The magnesium alloy raw material was heated and melted, and mechanical stirring and ultrasonic treatment were carried out under the conditions of heating temperature of 740℃~780℃, mechanical stirring speed of 100r / min~500r / min, and ultrasonic treatment power of 2kW~4kW. During the mechanical stirring and ultrasonic treatment, the flake refining agent was pressed into the eddy current formed by mechanical stirring and ultrasonic treatment. The mechanical stirring and ultrasonic treatment lasted for 5min~10min, and a covering agent was continuously added during the mechanical stirring and ultrasonic treatment. After mechanical stirring and ultrasonic treatment, the melt is cooled to 630℃~640℃ to make it semi-solid. Then, under the conditions of 630℃~640℃ and stirring speed of 100r / min~500r / min, it is mechanically stirred for 5min~10min. After stirring, it is reheated to the melting temperature and held at that temperature. After holding at that temperature, the waste residue is removed and the melt is poured into a mold. Finally, it is cooled and solidified, which completes the method of using the casting magnesium alloy refiner. The mass ratio of the flake refiner to the magnesium alloy raw material is 1:(0.002~0.02).
[0046] The beneficial effects of the present invention are verified using the following embodiments:
[0047] Example 1:
[0048] A method for preparing a fine-refining agent for cast magnesium alloys, comprising the following steps:
[0049] 1. The zirconium carbide particles are sequentially subjected to degreasing, coarsening, sensitization and activation to obtain pretreated zirconium carbide particles;
[0050] The zirconium carbide particles have an average diameter of 300 nm.
[0051] 2. Mix 2g zinc sulfate, 4g EDTA-2Na and 50mL deionized water, and heat in a water bath at 50℃ until the solution is clear. Then stir evenly to obtain a mixed solution. Add a 2.5mol / L sodium hydroxide solution to the mixed solution to adjust the pH of the mixed solution to 10. Then add 10mg stabilizer, 1g pretreated zirconium carbide particles and 50mL sodium dihydrogen phosphate solution in sequence. Stir magnetically at 200r / min for 1h. Finally, let stand for 30min, wash with deionized water and dry to obtain a casting magnesium alloy refining agent, i.e., zinc-plated zirconium carbide particles. The concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 0.4mol / L.
[0052] The degreasing process described in step one is carried out in the following steps: Zirconium carbide particles are mixed with anhydrous ethanol, ultrasonically treated for 10 minutes at an ultrasonic power of 0.5kW, then washed 2 to 3 times with deionized water, and finally dried at a temperature of 70℃ to obtain degreased zirconium carbide particles.
[0053] The roughening process described in step one is carried out in the following steps: the degreased zirconium carbide particles are mixed with a 50% nitric acid solution, ultrasonically treated for 30 minutes at an ultrasonic power of 0.5 kW, then washed with deionized water 2 to 3 times, and finally dried at a temperature of 70°C to obtain the roughened zirconium carbide particles.
[0054] The sensitization described in step one is carried out in the following steps: Under stirring conditions, 1.5g of SnCl2·H2O is dissolved in 3mL of 20% hydrochloric acid. Then, under stirring conditions, water is added to dilute the concentration of SnCl2·H2O to 0.2mol / L to obtain a mixed solution. The coarsened zirconium carbide particles are added to the mixed solution and ultrasonically treated for 30min under an ultrasonic power of 0.5kW. Then, the solution is filtered, washed with deionized water 2 to 3 times, and finally vacuum dried to obtain the sensitized zirconium carbide particles.
[0055] The activation described in step one is carried out as follows: Dissolve 0.05g of silver nitrate in 5mL of water, then add 20% ammonia solution by mass dropwise under stirring until the yellow-brown precipitate disappears. Continue to add 20% ammonia solution by mass dropwise while stirring until clear. Mix the clear solution with the sensitized zirconium carbide particles and sonicate for 10min under an ultrasonic power of 0.5kW. Then wash with deionized water 2 to 3 times and finally dry at a temperature of 70℃ to obtain the pretreated zirconium carbide particles.
[0056] The stabilizer mentioned in step two is 2-2'-bipyridine.
[0057] Example 2: The method of using the casting magnesium alloy refining agent prepared in Example 1 is as follows:
[0058] ① Press the casting magnesium alloy refining agent (zirconia carbide granules) into flakes to obtain flake refining agent;
[0059] ② Weigh out 895g of pure magnesium, 5g of pure zinc, 100g of Mg-25wt.%Nd master alloy, 5.5g of flake refining agent and 5g of covering agent; the covering agent is MgCl2;
[0060] ③ At a temperature of 720℃, pure magnesium is heated and melted, then heated to 750℃, and pure zinc and Mg-25wt.%Nd master alloy are added. After all the raw materials are melted, an alloy melt is obtained. The target alloy grade is Mg-2.5Nd-0.5Zn.
[0061] ④ Mechanical stirring and ultrasonic treatment are carried out under the conditions of heating temperature of 750℃, mechanical stirring speed of 500r / min and ultrasonic treatment power of 2kW. During the mechanical stirring and ultrasonic treatment, the flake-shaped refining agent is pressed into the vortex formed by mechanical stirring and ultrasonic treatment. Mechanical stirring and ultrasonic treatment is carried out for 10min, and a flame retardant covering agent is continuously added during the mechanical stirring and ultrasonic treatment. After mechanical stirring and ultrasonic treatment, the temperature is lowered to 635℃ to make the melt semi-solid. Then, mechanical stirring is carried out for 10min at a temperature of 635℃ and a stirring speed of 500r / min. After stirring, the temperature is reheated to the melting temperature of 750℃ and held at 750℃ for 2min. After holding, the waste residue is removed and poured into the mold. Finally, it is cooled and solidified, which completes the method of using the refining agent for casting magnesium alloy and obtains magnesium alloy with added zinc-plated zirconium carbide particles.
[0062] Comparative Experiment 1: This comparative experiment differs from Example 2 in that the casting magnesium alloy refining agent was omitted, resulting in a magnesium alloy without the added casting refining agent. Everything else is the same as in Example 2.
[0063] Comparative Experiment 2: This comparative experiment differs from Example 2 in that the refining agent for the cast magnesium alloy was replaced with ungalvanized zirconium carbide particles, resulting in a magnesium alloy with added ungalvanized zirconium carbide particles; the average diameter of the ungalvanized zirconium carbide particles was 300 nm. Everything else was the same as in Example 2.
[0064] Figure 1 A low-magnification scanning electron microscope image of the zinc-plated zirconium carbide particles prepared in Example 1; Figure 2 Here are high-magnification scanning electron microscope images of the zinc-plated zirconium carbide particles prepared in Example 1; Table 1 shows... Figure 2 The energy dispersive spectral analysis results at positions A, B, and C. (From...) Figure 1 , Figure 2As shown in Table 1, the zirconium carbide particles are well dispersed after galvanizing, and a zinc coating is formed on the surface of the zirconium carbide particles.
[0065] Table 1 shows... Figure 2 Energy dispersive spectral analysis results (at.%) at positions A, B, and C.
[0066]
[0067] Figure 3 The figures show optical micrographs of magnesium alloys. a) is the magnesium alloy prepared in Comparative Experiment 1 without the addition of casting refining agents; b) is the magnesium alloy prepared in Comparative Experiment 2 with the addition of ungalvanized zirconium carbide particles; and c) is the magnesium alloy prepared in Example 2 with the addition of galvanized zirconium carbide particles. As can be seen from the figures, the average grain size of the magnesium alloy without zirconium carbide particles is 55 μm, the average grain size of the magnesium alloy with ungalvanized zirconium carbide particles is 39 μm, and the average grain size of the magnesium alloy with galvanized zirconium carbide particles is 28 μm.
[0068] The mechanical properties of magnesium alloys were tested according to the tensile testing standard GB / T228.1 for metallic materials, with a tensile strain rate of 1×10⁻⁶. -3 s -1 ; Figure 4 The figures show the mechanical property test results of the magnesium alloys. 1 represents the magnesium alloy prepared in Comparative Experiment 1 without the addition of casting refiner; 2 represents the magnesium alloy prepared in Comparative Experiment 2 with the addition of ungalvanized zirconium carbide particles; and 3 represents the magnesium alloy prepared in Example 2 with the addition of galvanized zirconium carbide particles. As shown in the figures, the tensile strength and elongation of the alloy without zirconium carbide are 139 MPa and 9.8%, respectively; the tensile strength and elongation of the alloy with ungalvanized zirconium carbide are 153 MPa and 11.5%, respectively; and the tensile strength and elongation of the alloy with galvanized zirconium carbide are 206 MPa and 13.8%, respectively.
Claims
1. A method for preparing a fine-refining agent for cast magnesium alloys, characterized in that... It is done in the following steps:
1. The zirconium carbide particles are sequentially subjected to degreasing, coarsening, sensitization and activation to obtain pretreated zirconium carbide particles; The zirconium carbide particles have an average diameter of 50 nm to 1000 nm.
2. Mix zinc sulfate, EDTA-2Na and deionized water, heat in a water bath to dissolve until the solution is clear, then stir evenly to obtain a mixed solution. Adjust the pH of the mixed solution to alkaline, then add stabilizer, pretreated zirconium carbide particles and sodium dihydrogen phosphate solution in sequence, stir magnetically to react, and finally let stand, wash and dry to obtain a finer agent for cast magnesium alloys. The mass ratio of zinc sulfate to EDTA-2Na is 1:(1-5); the mass ratio of zinc sulfate to deionized water is 1g:(10-40)mL; the mass ratio of stabilizer to zinc sulfate is 1:(100-400); the mass ratio of pretreated zirconium carbide particles to zinc sulfate is 1:(1-3); and the mass ratio of zinc sulfate to sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 1:(1-3).
2. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 1, characterized in that... The degreasing process described in step one is carried out in the following steps: Zirconium carbide particles are mixed with anhydrous ethanol and ultrasonically treated for 10 min to 60 min under an ultrasonic power of 0.2 kW to 0.5 kW. Then, the particles are washed multiple times with deionized water and finally dried to obtain degreased zirconium carbide particles.
3. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 2, characterized in that... The roughening process described in step one is carried out in the following steps: the degreased zirconium carbide particles are mixed with a nitric acid solution of 30% to 68% by mass, and ultrasonically treated for 10 to 60 minutes under an ultrasonic power of 0.2 kW to 0.5 kW. Then, the particles are washed multiple times with deionized water and finally dried to obtain the roughened zirconium carbide particles.
4. The method for preparing a refining agent for cast magnesium alloys according to claim 3, characterized in that... The sensitization described in step one is carried out in the following steps: under stirring conditions, SnCl2·H2O is dissolved in hydrochloric acid with a mass percentage of 10% to 37%, and then water is added under stirring conditions to dilute the concentration of SnCl2·H2O to 0.1 mol / L to 0.3 mol / L to obtain a mixed solution. The coarsened zirconium carbide particles are added to the mixed solution, and ultrasonic treatment is carried out for 10 min to 60 min under ultrasonic power of 0.2 kW to 0.5 kW. Then, the solution is filtered, washed with deionized water, and vacuum dried to obtain sensitized zirconium carbide particles. The mass ratio of SnCl2·H2O to the volume ratio of hydrochloric acid with a mass percentage of 10% to 37% is 1 g: (1 to 4) mL.
5. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 4, characterized in that... The activation described in step one is carried out in the following steps: silver nitrate is dissolved in water, and then 10% to 25% ammonia solution is added dropwise under stirring until the yellow-brown precipitate disappears. Then, 10% to 25% ammonia solution is added dropwise and stirred until clear. The clear solution is mixed with the sensitized zirconium carbide particles and ultrasonically treated for 10 to 60 minutes under an ultrasonic power of 0.2 kW to 0.5 kW. Then, the particles are washed multiple times with deionized water and finally dried to obtain the pretreated zirconium carbide particles. The mass ratio of silver nitrate to water is 1 g: (50 to 200) mL.
6. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 1, characterized in that... In step two, a sodium hydroxide solution with a concentration of 2 mol / L to 3 mol / L is added to the mixed solution to adjust the pH of the mixed solution to 8 to 12.
7. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 1, characterized in that... The stabilizer mentioned in step two is 2-2'-bipyridine.
8. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 1, characterized in that... In step two, the magnetic stirring reaction is carried out for 5 min to 60 min at a magnetic stirring speed of 200 r / min to 500 r / min.
9. The method for preparing a fine-refining agent for cast magnesium alloys according to claim 1, characterized in that... The concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution mentioned in step two is 0.2 mol / L to 0.5 mol / L.
10. The method of using the casting magnesium alloy refining agent prepared according to claim 1, characterized in that... It is done in the following steps: The magnesium alloy refining agent was pressed into flakes to obtain flake refining agent. The magnesium alloy raw material was heated and melted, and mechanical stirring and ultrasonic treatment were carried out under the conditions of heating temperature of 740℃~780℃, mechanical stirring speed of 100r / min~500r / min, and ultrasonic treatment power of 2kW~4kW. During the mechanical stirring and ultrasonic treatment, the flake refining agent was pressed into the eddy current formed by mechanical stirring and ultrasonic treatment. The mechanical stirring and ultrasonic treatment lasted for 5min~10min, and a covering agent was continuously added during the mechanical stirring and ultrasonic treatment. After mechanical stirring and ultrasonic treatment, the melt is cooled to 630℃~640℃ to make it semi-solid. Then, under the conditions of 630℃~640℃ and stirring speed of 100r / min~500r / min, it is mechanically stirred for 5min~10min. After stirring, it is reheated to the melting temperature and held at that temperature. After holding at that temperature, the waste residue is removed and the melt is poured into a mold. Finally, it is cooled and solidified, which completes the method of using the casting magnesium alloy refiner. The mass ratio of the flake refiner to the magnesium alloy raw material is 1:(0.002~0.02).