A method for refining a cast Al-Si alloy melt based on an anti-si poisoning refining agent

Abstract

The application belongs to the technical field of non-ferrous metal or alloy melt processing, and particularly relates to a casting Al-Si alloy melt refining method based on Si-poisoning-resistant refining agent. Basic components of the Si-poisoning-resistant refining agent are as follows: NaCl: 35-45 wt.%, KCl: 35-45 wt.%, NaF: 1-3 wt.%, KF: 1-3 wt.%, Na3AlF6: 2-4 wt.%, K2NbF7: 10-15 wt.%. The Si-poisoning-resistant refining agent is sent into aluminum liquid from a rotor internal injection channel by nitrogen, K2NbF7 releases solute Nb through in-situ reaction, and then a refiner and a modifier are added into the aluminum liquid. The application improves the removal effect of the refining agent on alumina inclusions and the slag-aluminum separation effect in the slag layer on the surface of the aluminum liquid, and improves the Si-poisoning resistance of TiB2 nucleation particles introduced into the melt by Al-5Ti-1B refiner.

Description

Technical Field

[0001] This invention belongs to the field of melt treatment technology for non-ferrous metals or alloys, and particularly relates to melt purification and grain refinement treatment of cast Al-Si alloys, specifically to a method for refining cast Al-Si alloy melts based on an anti-Si poisoning refining agent. Background Technology

[0002] Cast Al-Si alloys possess advantages such as low density, high specific strength, excellent casting and processing performance, and recyclability, making them widely used as lightweight materials in aerospace, rail transportation, and automotive fields. To address the increasingly severe energy shortages and environmental pollution problems, the recycling of waste aluminum is a future development trend. Compared to primary aluminum, the energy consumption and greenhouse gas emissions during the production of recycled aluminum are significantly reduced, resulting in substantial energy-saving and environmental benefits. However, the recycling process introduces more alumina inclusions, which are difficult to remove through subsequent heat treatment and machining processes, thus significantly weakening the mechanical properties of the castings and negatively impacting the product yield. Therefore, it is essential to remove alumina inclusions from the melt before casting to obtain qualified aluminum liquid.

[0003] Currently, in industrial production, aluminum liquid is mainly purified by blowing inert gases (nitrogen, argon) and adding refining agents (chloride and fluoride salts of alkali metals and alkaline earth metals). The removal of alumina inclusions mainly relies on the wetting, adsorption and dissolution of inclusions by the refining agents.

[0004] Besides aluminum molten metal purification, grain refinement is also a necessary step in the melt processing. Refining the grain size improves the casting and processing properties of the alloy, and simultaneously enhances its strength and plasticity through grain refinement strengthening. Currently, Al-5Ti-1B grain refiner is commonly used in industrial production to achieve this. A key reason why Al-5Ti-1B can effectively refine the grain size of aluminum alloys is that it introduces a large number of TiB2 particles into the melt. The TiAl3 modified layer on the surface of these TiB2 particles significantly reduces the lattice mismatch between them and α-Al, and enhances their heterogeneous nucleation potential for α-Al. However, when refining high-Si-content Al-Si alloys, the nucleation potential of TiB2 particles is significantly weakened due to the poisoning and destructive effect of Si atoms on the TiAl3 modified layer, resulting in a significant reduction in its grain refinement ability. Existing refining agents cannot effectively remove alumina inclusions while improving the resistance of Al-5Ti-1B refining agent to Si poisoning, thus making it difficult to simultaneously achieve efficient aluminum liquid purification and grain refinement in casting Al-Si alloys. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a refining agent and refining method for casting Al-Si alloys that resist Si poisoning, thereby simultaneously achieving the purification of molten aluminum in casting Al-Si alloys and the Si poisoning resistance modification of the Al-5Ti-1B refining agent.

[0006] To achieve the above objectives, the complete technical solution of the present invention is as follows:

[0007] A method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent, wherein the refining agent is composed of NaCl, KCl, NaF, KF, Na3AlF6 and K2NbF7.

[0008] Furthermore, the refining agent composition is as follows: NaCl: 35-45 wt.%, KCl: 35-45 wt.%, NaF: 1-6 wt.%, KF: 1-6 wt.%, Na3AlF6: 2-8 wt.%, K2NbF7: 6-20 wt.%, and the sum of the contents of the above components is 100 wt.%.

[0009] Furthermore, based on the role of each component and the Si content in the cast Al-Si alloy, the refining agent components are selected.

[0010] Furthermore, the refining method for cast Al-Si alloy melt based on anti-Si poisoning refining agent specifically includes the following steps:

[0011] Step 1: Melt the aluminum alloy ingot and heat it to a predetermined temperature, then hold it at that temperature to obtain molten aluminum;

[0012] Step 2: Weigh the required amount of refining agent and place it in the feeding hopper;

[0013] Step 3: Open the nitrogen valve and introduce nitrogen into the internal blowing channel of the rotor. Add the refining agent containing K2NbF7 of this invention and perform rotary blowing refining. During this stage, K2NbF7 reacts with Al in situ, releasing Nb. Then let it stand for 2-3 minutes and remove the surface dross. At this point, Nb in the aluminum liquid is evenly distributed.

[0014] Step 4: Add 0.2 wt.% Al-5Ti-1B refining agent and 0.2 wt.% Al-10Sr modifier to the aluminum melt; TiB2 particles are released into the melt, and the solute Nb is immediately adsorbed on their surface;

[0015] Step 5: Continue rotating and blowing nitrogen gas to ensure that TiB2 particles are in full contact with Nb;

[0016] Step 6: Let stand for 5-8 minutes to allow Nb to diffuse on the TiB2 surface and form a (Ti,Nb)Al3 modified layer.

[0017] Step 7: Pour the molten aluminum to obtain the casting.

[0018] Furthermore, during the refining process in step 3, K2NbF7 releases solute Nb through an in-situ reaction.

[0019] Furthermore, the Al-5Ti-1B refining agent accounts for 0.2 wt.% of the aluminum liquid mass, and the Al-10Sr modifier accounts for 0.2 wt.% of the aluminum liquid mass.

[0020] Furthermore, the method for preparing a refining agent based on anti-Si poisoning is characterized by comprising the following steps:

[0021] Step A: Weigh the required NaCl, KCl, NaF, KF, and Na3AlF6 raw material powders according to the target composition, and heat and dry them at 200-300℃ for 3-6 hours;

[0022] Step B: Mix the raw material powder obtained in Step A evenly and melt it. Heat it to 800-900℃ and keep it at that temperature for 0.5-2 hours to obtain a molten salt with uniform composition.

[0023] Step C: Pour the molten salt obtained in step B into a mold to cool and solidify, obtaining a blocky refining agent;

[0024] Step D: The lumpy refining agent obtained in step C is crushed and sieved to obtain granular refining agent with an average particle size of 0.05-0.5 cm;

[0025] Step E: Weigh the required K2NbF7 raw material powder according to the target composition, and then mix it evenly with the granular refining agent obtained in Step D to obtain the final anti-Si poisoning refining agent.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) Based on the function of each component, the refining agent components are optimized to ensure that the molten salt is completely liquid and has the lowest possible viscosity during refining. This increases the proportion of fluoride salt components in the refining agent, enhances the wetting, adsorption and dissolution capacity of the refining agent for alumina inclusions, and enables the two alkali metal fluoride salts to work synergistically. This avoids local component segregation and molten salt alkalinity imbalance caused by excessive single fluoride salt, thereby improving the refining agent's removal effect on alumina inclusions and the slag-aluminum separation effect in the slag layer on the surface of the aluminum melt. This can meet the aluminum melt purification requirements of recycled aluminum alloys with high impurity content.

[0028] (2) The refining agent composition has been enhanced with the addition of K2NbF7 functional component. The functional component is designed specifically for the silicon content in the target aluminum alloy. During the refining process, K2NbF7 can release solute Nb through in-situ reaction, which can enhance the anti-Si poisoning ability of TiB2 nucleation particles introduced into the melt by Al-5Ti-1B refining agent, and significantly improve its grain refining effect on cast Al-Si alloy.

[0029] (3) Adding Nb first and then TiB2 ensures that Nb is uniformly distributed in the aluminum liquid as a solute, directly forming a (Ti,Nb)Al3 composite modified layer, thus avoiding solid-phase diffusion. The addition of refining agent is improved from the traditional method of relying on the vortex of the aluminum liquid surface to direct injection into the aluminum liquid through a rotor, which significantly reduces the difficulty of adding refining agent and its dispersion uniformity in the aluminum liquid, thereby reducing the amount of refining agent used and the amount of dust emitted during the refining process. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to embodiments of the present invention. The described embodiments are merely examples and are not intended to limit this application.

[0031] The refining agent primarily removes alumina inclusions from molten aluminum based on the principle of adsorption and purification. The wettability of the molten aluminum, refining agent, and alumina inclusions has a significant impact. Addressing the high impurity content of recycled aluminum, this invention designs the refining agent to consist of NaCl, KCl, NaF, KF, Na3AlF6, and K2NbF7. These six components perform three functions: a basic molten salt carrier (NaCl+KCl), a refining active component (NaF+KF+Na3AlF6), and an anti-Si poisoning functional component (K2NbF7).

[0032] Based on the above functions, the basic components of the refining agent of this invention are first determined to be: NaCl: 35-45 wt.%, KCl: 35-45 wt.%, NaF: 1-6 wt.%, KF: 1-6 wt.%, Na3AlF6: 2-8 wt.%, K2NbF7: 6-20 wt.%. The sum of the contents of the above components is 100 wt.%.

[0033] Meanwhile, there is competition among the three functions. If the component design is unreasonable, the actual ratio may deviate from the optimal range. For example, if the NaCl:KCl ratio deviates from the eutectic point, the molten salt viscosity will increase; if the total amount of fluoride salt is insufficient, the refining will be incomplete; or if the amount of K2NbF7 is excessive, it will cause waste and deterioration of flue gas. Therefore, it is necessary to further optimize the components to achieve the optimal balance between refining effect, fineness effect and dosage.

[0034] This invention first analyzes the mechanism of action of each component:

[0035] The NaCl-KCl binary molten salt system: NaCl-KCl forms a simple eutectic system, and the eutectic temperature is within the aluminum refining temperature range. NaCl-KCl molten salts with near-eutectic compositions exhibit the lowest viscosity and best surface spreading properties, rapidly forming a continuous liquid molten salt layer on the aluminum surface, providing a mass transfer channel for the subsequent reaction of fluoride components with alumina inclusions. However, if the NaCl:KCl mass ratio deviates from the range of 0.44–0.56 (molar ratio), the liquidus temperature of the molten salt will increase significantly. At refining temperatures, solid phase precipitation or a sharp increase in viscosity may occur, leading to discontinuous molten salt coverage and a significant decrease in inclusion adsorption efficiency.

[0036] Fluoride refining components: In this invention, the three fluoride salts each have their own focus and need to work synergistically to achieve refining effects. For NaF and KF, they dissociate into fluoride ions in NaCl-KCl molten salt. These fluoride ions break the Al-O bridge bonds on the surface of Al2O3 inclusions through ion exchange, converting them into soluble aluminum fluoride complexes, thus achieving the chemical dissolution of the inclusions. Simultaneously, fluoride ions can significantly reduce the interfacial tension between the molten salt and Al2O3, improving the wettability of the refining agent on alumina inclusions, allowing the molten salt to penetrate oxide film cracks and micropores, pulling the inclusions from the molten aluminum into the molten salt layer. For Na3AlF6, it has the strongest dissolving ability for Al2O3; its mechanism of action is the AlF6 generated by the dissociation of cryolite. 3- Complex ions react with Al2O3 to form Al2OF6 2- Soluble species such as cryolite are present. Cryolite significantly reduces the slag-aluminum interfacial tension, promoting slag-aluminum separation, a key capability in handling high-slag-content melts during aluminum recycling. The mass ratio of the three fluoride salts affects the refining rate and depth; the NaF / KF ratio determines the fluoride ion activity and molten salt basicity, while the Na3AlF6 ratio determines the upper limit of Al2O3's saturated solubility.

[0037] The K2NbF7 functional component, which is the core component of this invention, undergoes an in-situ aluminothermic reduction reaction with aluminum at the temperature of molten aluminum. The released Nb solute enters the molten aluminum and diffuses to the surface of TiB2 particles introduced by the Al-5Ti-1B refining agent. Since Nb and Ti have similar chemical properties, Nb atoms can partially replace Ti atoms in the TiAl3 modified layer, forming (Ti...) on the TiB2 surface. 1-x Nb xThe Al3 composite modification layer. In this composite modification, the formation free energy of NbAl3 is more negative than that of TiAl3, and its affinity for Si is weaker. Si atoms are less likely to replace Nb sites in the composite modification layer, thus avoiding poisoning and damage from Si atoms. Furthermore, the d-electron structure of Nb further reduces the lattice mismatch between the (Ti,Nb)Al3 layer and α-Al, thereby endowing TiB2 particles with high nucleation potential in Al-Si alloy melts, reducing nucleation undercooling, and improving its grain refinement effect on α-Al.

[0038] Based on the above analysis, this invention designs the content of each component. First, the mass fraction of the six components is defined as follows: The sum of the mass fractions of all components is 100%.

[0039] First, to ensure that the molten salt is completely liquid at 720°C and has the lowest possible viscosity, the following constraint relationship is adopted:

[0040]

[0041] This range allows for a molten salt liquidus temperature ≤680°C, providing a high superheat margin at refining temperatures. Exceeding this range will result in a significant increase in molten salt viscosity, leading to a significant decrease in inclusion trapping efficiency.

[0042] For fluoride salts, if the total amount of fluoride salts is too low, refining will be insufficient; if it is too high, the loss of volatile fluorides (especially KF, which has a higher vapor pressure) will be aggravated, and pollution will occur. Therefore, the following constraint relationship is adopted:

[0043]

[0044] The above relationship ensures the minimum chemical solubility of Al2O3 inclusions and keeps the fluoride volatilization loss within an acceptable range.

[0045] For cryolite, which is a core component in Al2O3 dissolution and slag-aluminum separation, the following constraint relationship is adopted:

[0046]

[0047] The above relationship ensures the minimum cryolite concentration required for slag-aluminum separation and avoids excessive molten salt viscosity.

[0048] The ratio of NaF to KF affects the fluoride ion activity and Na+ in molten salt. + / K + To achieve balance, a synergistic ratio constraint is applied to both NaF and KF:

[0049]

[0050] This relationship ensures that the two alkali metal fluoride salts work synergistically, avoiding local component segregation and molten salt basicity imbalance caused by excessive amounts of a single fluoride salt.

[0051] Regarding the content of the K2NbF7 functional component, it is the core to achieving a refining-refinement balance and needs to be dynamically adjusted according to the Si content of the target cast Al-Si alloy. Based on experimental data and result analysis, the following constraint relationship is adopted:

[0052]

[0053] in The Si content (wt.%) of the target alloy.

[0054] In the above process, the higher the Si content, the faster the TiAl3 modified layer is poisoned by Si, and the higher the equilibrium concentration of Si in the modified layer. More Nb is needed to form a (Ti,Nb)Al3 composite modified layer with a higher Nb concentration to enhance the modified layer's resistance to Si poisoning. This quantitative relationship is based on (Ti... 1-x Nb x The threshold of Nb molar fraction that effectively suppresses Si substitution reaction in the Al3 layer was derived by combining the Nb partition coefficient and the amount of refining agent.

[0055] Based on all the above constraints, the precise proportions of each component under different target Si contents are given:

[0056] Low-silicon alloy refining agent composition (target alloy Si content 3–5%): NaCl: 39.5 wt.%, KCl: 41.5 wt.%, NaF: 2.5 wt.%, KF: 2.5 wt.%, Na3AlF6: 4.0 wt.%, K2NbF7: 10.0 wt.%.

[0057] The refining agent composition for medium-silicon alloys (target alloy Si content 5–8%) is as follows: NaCl: 38.0 wt.%, KCl: 40.5 wt.%, NaF: 2.5 wt.%, KF: 2.5 wt.%, Na3AlF6: 4.5 wt.%, K2NbF7: 12.0 wt.%.

[0058] High-silicon alloy refining agent composition (target alloy Si content 8–12%): NaCl: 36.0 wt.%, KCl: 38.0 wt.%, NaF: 3.0 wt.%, KF: 3.0 wt.%, Na3AlF6: 5.0 wt.%, K2NbF7: 15.0 wt.%.

[0059] To address the issue of increased dust generation during refining processes due to a higher proportion of fluoride salts in the refining agent, this invention further improves the method of adding the refining agent. Currently, in industrial production, the refining agent is typically drawn into the molten aluminum by a vortex formed on the surface of a high-speed rotating rotor. However, due to the poor wettability between the refining agent and the molten aluminum, effective addition via surface entrainment is difficult, requiring a higher amount of refining agent to achieve effective purification of the molten aluminum. Compared to surface entrainment, the method of directly injecting the refining agent into the molten aluminum through the bottom of the rotor using high-pressure nitrogen significantly reduces the difficulty of adding the refining agent and improves its utilization efficiency. This significantly reduces the amount of refining agent required, and consequently, the amount of dust generated by the refining agent reaction during the refining process is correspondingly reduced.

[0060] The preparation method of the refining agent includes the following steps:

[0061] Step A: Weigh the required NaCl, KCl, NaF, KF, and Na3AlF6 raw material powders according to the target composition of the refining agent, and heat and dry them at 200-300℃ for 3-6 hours;

[0062] Step B: Mix the raw material powder obtained in Step A evenly and melt it. Heat it to 800-900℃ and keep it at that temperature for 0.5-2 hours to obtain a molten salt with uniform composition.

[0063] Step C: Pour the molten salt obtained in step B into a mold to cool and solidify, obtaining a blocky refining agent;

[0064] Step D: The lumpy refining agent obtained in step C is crushed and sieved to obtain granular refining agent with an average particle size of 0.05-0.5 cm;

[0065] Step E: Weigh the required K2NbF7 raw material powder according to the target composition of the refining agent, and then mix it evenly with the granular refining agent obtained in Step D to obtain the final refining agent.

[0066] The method of using the refining agent includes the following steps:

[0067] Step 1: Melt 500-1000 kg of aluminum alloy ingots and heat them to a predetermined temperature of 720-750℃, then hold the temperature to obtain molten aluminum;

[0068] Step 2: Weigh 0.1-1.0 wt.% of the refining agent and place it in the feeding hopper;

[0069] Step 3: Open the nitrogen valve and introduce nitrogen into the internal blowing channel of the rotor at a flow rate of 30-50 L / min. Add the K2NbF7-containing refining agent of this invention and perform rotary blowing refining. During this stage, the K2NbF7-containing agent reacts in situ with Al, releasing Nb. Then let it stand for 2-3 minutes and remove the surface dross. At this point, Nb in the molten aluminum is evenly distributed.

[0070] Step 4: Add 0.2 wt.% Al-5Ti-1B refining agent and 0.2 wt.% Al-10Sr modifier to the aluminum melt; TiB2 particles are released into the melt, and the solute Nb is adsorbed on their surface.

[0071] Step 5: Continue to rotate and spray nitrogen gas at a flow rate of 15-30 L / min to ensure that TiB2 particles are in full contact with Nb.

[0072] Step 6: Let stand for 5-8 minutes to allow Nb to diffuse on the TiB2 surface and form a (Ti,Nb)Al3 modified layer.

[0073] Step 7: Pour the molten aluminum to obtain the casting.

[0074] In traditional operations, refining agents and refining agents are often added simultaneously or the refining agent is added first. This invention reveals that the in-situ reaction rate between K2NbF7 and Al is diffusion-controlled. If the refining agent and Al-5Ti-1B are added simultaneously, or Al-5Ti-1B is added first, TiB2 particles form a TiAl3 modified layer before Nb is fully released. Subsequent Nb atoms must penetrate the existing TiAl3 layer to reach the TiB2 / TiAl3 interface. The diffusion coefficient of this solid-phase diffusion process is 3–4 orders of magnitude lower than that of the liquid phase, resulting in extremely low efficiency. This invention, however, adds Nb first and then TiB2. Nb is uniformly distributed in the molten aluminum as a solute. When TiB2 particles are released from Al-5Ti-1B, Nb atoms and Ti atoms co-deposit on the TiB2 surface, directly forming a (Ti,Nb)Al3 composite modified layer, thus avoiding solid-phase diffusion.

[0075] Example 1

[0076] A refining agent for casting Al-Si alloys with anti-Si poisoning modification effect has the following specific composition: NaCl: 38.0 wt.%, KCl: 40.5 wt.%, NaF: 2.5 wt.%, KF: 2.5 wt.%, Na3AlF6: 4.5 wt.%, K2NbF7: 12.0 wt.%.

[0077] The preparation method of the refining agent is as follows:

[0078] Step A: Weigh the required NaCl, KCl, NaF, KF, and Na3AlF6 raw material powders according to the target composition of the refining agent, and heat and dry them at 250℃ for 4 hours;

[0079] Step B: Mix the raw material powder obtained in Step A evenly and melt it. Heat it to 800℃ and keep it at that temperature for 0.5-2 hours to obtain a molten salt with uniform composition.

[0080] Step C: Pour the molten salt obtained in step B into a mold to cool and solidify, obtaining a blocky refining agent;

[0081] Step D: The lumpy refining agent obtained in step C is crushed and sieved to obtain granular refining agent with an average particle size of 0.1 cm;

[0082] Step E: Weigh the required K2NbF7 raw material powder according to the target composition of the refining agent, and then mix it evenly with the granular refining agent obtained in Step D to obtain the final refining agent.

[0083] Step 1: Melt 500-1000 kg of aluminum alloy ingots and heat them to a predetermined temperature of 720-750℃, then hold the temperature to obtain molten aluminum;

[0084] Step 2: Weigh 0.1-1.0 wt.% of the refining agent and place it in the feeding hopper;

[0085] Step 3: Open the nitrogen valve and introduce nitrogen into the internal blowing channel of the rotor at a flow rate of 30-50 L / min. Add the K2NbF7-containing refining agent of this invention and perform rotary blowing refining. During this stage, K2NbF7 reacts with Al in situ, releasing Nb. Then let it stand for 2-3 minutes and remove the surface dross. At this point, Nb in the molten aluminum is evenly distributed.

[0086] Step 4: Add 0.2 wt.% Al-5Ti-1B refining agent and 0.2 wt.% Al-10Sr modifier to the aluminum melt; TiB2 particles are released into the melt, and the solute Nb is adsorbed on their surface.

[0087] Step 5: Continue to rotate and spray nitrogen gas at a flow rate of 15-30 L / min to ensure that TiB2 particles are in full contact with Nb.

[0088] Step 6: Let stand for 5-8 minutes to allow Nb to diffuse on the TiB2 surface and form a (Ti,Nb)Al3 modified layer.

[0089] Step 7: Pour the molten aluminum to obtain the casting.

[0090] The density after refining is 2.655 g / cm³. 3 The K-mode fracture surface showed 0 inclusions and a grain size of 200 μm.

[0091] Comparative Example 1

[0092] This embodiment serves as a comparative control group for purifying molten aluminum using commercially available common refining agents, and specifically includes the following steps:

[0093] Step 1: Weigh 800 kg of recycled A356 alloy, melt it completely in a melting furnace, and then transfer it to a tundish. Adjust the heating power of the tundish to control the temperature of the molten aluminum at 740±10℃;

[0094] Step 2: Weigh 1.6 kg of refining agent, dry it at 150℃ for 2 hours, and then load it into the feeding hopper above the rotor;

[0095] Step 3: Add 1.6 kg of Al-5Ti-1B refining agent and 1.6 kg of Al-10Sr modifier to the molten aluminum in the form of intermediate alloy wire rods;

[0096] Step 4: Introduce nitrogen into the internal injection channel of the rotor at a flow rate of 45 L / min; start rotating and injecting refining, with the refining agent addition rate at 8 g / s;

[0097] Step 6: After the refining agent is added, reduce the nitrogen flow rate to 25L / min and continue refining until the refining time reaches 25min.

[0098] Step 7: Pour the molten aluminum to obtain the casting.

[0099] The density of the refined aluminum liquid was measured to be 2.645 g / cm³. 3 The K-mode fracture surface showed two inclusions with a grain size of 550 μm.

[0100] Compared with the results in Example 1, the refining agent proposed in this invention achieves better aluminum liquid purification effect than commercially available ordinary refining agents at higher addition levels, even with lower addition amounts. Furthermore, commercially available ordinary refining agents do not possess the anti-Si poisoning modification effect on Al-5Ti-1B refining agents, while the refining agent proposed in this invention can significantly enhance the grain refining effect of Al-5Ti-1B refining agents on A356 (Al-7Si-0.3Mg) alloys.

[0101] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for refining cast Al-Si alloy melts based on an anti-Si poisoning refining agent, characterized in that, The refining agent consists of NaCl, KCl, NaF, KF, Na3AlF6, and K2NbF7.

2. The method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent according to claim 1, characterized in that, The composition of the anti-Si poisoning refining agent is as follows: NaCl: 35-45 wt.%, KCl: 35-45 wt.%, NaF: 1-6 wt.%, KF: 1-6 wt.%, Na3AlF6: 2-8 wt.%, K2NbF7: 6-20 wt.%, and the sum of the contents of the above components is 100 wt.%.

3. The method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent according to claim 2, characterized in that, The refining agent components are selected based on the role of each component and the Si content in the cast Al-Si alloy.

4. The method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent according to claim 1, characterized in that, Specifically, the steps include the following: Step 1: Melt the aluminum alloy ingot and heat it to a predetermined temperature, then hold it at that temperature to obtain molten aluminum; Step 2: Weigh the required amount of refining agent and place it in the feeding hopper; Step 3: Open the nitrogen valve, introduce nitrogen into the internal injection channel of the rotor, add the refining agent, perform rotary injection refining, then let it stand for 2-3 minutes and remove the surface scum. Step 4: Add Al-5Ti-1B refining agent and Al-10Sr modifier to the molten aluminum; Step 5: Continue rotating and spraying nitrogen. Step 6: Let stand for 5-8 minutes. Step 7: Pour the molten aluminum to obtain the casting.

5. The method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent according to claim 4, characterized in that, During the refining process in step 3, K2NbF7 releases solute Nb through an in-situ reaction.

6. The method for refining cast Al-Si alloy melt based on an anti-Si poisoning refining agent according to claim 4, characterized in that, Al-5Ti-1B refining agent accounts for 0.2 wt.% of the aluminum liquid mass, and Al-10Sr modifier accounts for 0.2 wt.% of the aluminum liquid mass.

7. A method for preparing a refining agent based on an anti-Si poisoning agent according to any one of claims 1-6, characterized in that, Includes the following steps: Step A: Weigh the required NaCl, KCl, NaF, KF, and Na3AlF6 raw material powders according to the target composition, and heat and dry them; Step B: Mix the raw material powder obtained in Step A evenly, heat it to melt it and keep it at that temperature to obtain a molten salt with uniform composition; Step C: Pour the molten salt obtained in step B into a mold to cool and solidify, obtaining a blocky refining agent; Step D: Crush and screen the lumpy refining agent obtained in step C to obtain granular refining agent; Step E: Weigh the required K2NbF7 raw material powder according to the target composition, and then mix it evenly with the granular refining agent obtained in Step D to obtain the final anti-Si poisoning refining agent.

8. The preparation method of the refining agent based on anti-Si poisoning according to claim 7, characterized in that, In step A, the raw material powder is heated at 200-300℃ and dried for 3-6 hours.

9. A method for preparing a refining agent based on an anti-Si poisoning agent according to claim 7, characterized in that, In step B, the temperature is raised to 800-900℃ to melt, and the holding time is 0.5-2 hours.

10. A method for preparing a refining agent based on an anti-Si poisoning agent according to claim 7, characterized in that, In step D, the average particle size of the obtained granular refining agent is 0.05-0.5 cm.

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