A refining agent for precisely controlling the ti content in aluminum alloys and methods of making and using the same

Abstract

The application discloses a refining agent for precisely controlling Ti content in aluminum alloy and a preparation and use method thereof. The refining agent is prepared by mixing sodium chloride and potassium chloride, potassium fluoborate or sodium fluoborate, sodium fluoroaluminate, calcium fluoride, sodium carbonate, aluminum oxide and a cosolvent in a specific ratio, roasting, crushing and screening, can guarantee the refining effect, and realizes the demand for regulating and controlling Ti component in a melt; the refining agent is blown into the furnace by using the powder spraying refining method in the refining process, reacts with the melt in the furnace, and with the aid of suitable process control conditions, accurate comprehensive regulation and control of Ti component in aluminum-silicon alloy can be realized, the process flow is shortened, the comprehensive regulation and control and product production cost are reduced, the operability of the process route is improved, part of the generated TiB2 particles are used as heterogeneous nucleation points, are uniformly dispersed in the alloy melt through stirring and homogenization treatment, and the aluminum alloy grain structure is further refined.

Description

Technical Field

[0001] This invention relates to a refining agent for precisely controlling the Ti content in aluminum alloys, and its preparation and application methods. Specifically, it relates to a refining agent for accurately controlling the Ti (titanium) content in aluminum alloy melt processing, a method for preparing the refining agent, and a method for using the refining agent in aluminum alloy production processes, belonging to the field of non-ferrous metal smelting and processing technology. Background Technology

[0002] Aluminum-silicon alloys produced by the molten salt electroeutectoid process have excellent microstructure and properties, making them widely applicable in fields such as transportation and 5G. However, during the production of aluminum-silicon alloys using this process, the raw materials are rich in TiO2. This leads to an increase in the Ti content of the aluminum-silicon alloy during electroeutectoid processing, exceeding the composition requirements for the corresponding grades of cast aluminum alloys in the national standard GB / T 8733-2016. Excessive Ti content in aluminum-silicon alloys reduces their plasticity, toughness, fluidity, and feeding ability. This necessitates the treatment of Ti content in the eutectoid aluminum-silicon alloy melt and requires a separate composition treatment process. Melt refining is an indispensable and crucial step in the production of aluminum-silicon alloys, and the quality of refining directly affects the alloy's basic physical properties. Therefore, refining agents with appropriate impurity and degassing effects must be used in the refining process. To simultaneously control the Ti content in the alloy melt during refining, a refining agent for accurately controlling the Ti content during the aluminum alloy melt treatment process has been designed, invented, and prepared.

[0003] Currently, the published patents for refining agents primarily focus on enhancing degassing and impurity removal capabilities to improve refining efficiency. None of them address the simultaneous adjustment of impurity elements (high-Ti alloy melts with Ti content in the range of 0.3–0.5%) during the refining process. To meet the needs of actual production where refining efficiency can be guaranteed while adjusting the alloy melt composition, there is an urgent need to develop a titanium-controlling refining agent. Combined with process control conditions, this would achieve comprehensive Ti treatment in the alloy.

[0004] In the prior art, invention patent CN116287799A discloses a method for adjusting the titanium content in aluminum-silicon alloy melt. This method involves preparing the aluminum-silicon alloy melt into an aluminum-silicon alloy liquid, then adding a boron-containing compound and smelting it. After smelting, a refining agent and refining gas are added for refining. After refining, slag is removed, followed by temperature-controlled settling and casting. Filtration is performed during casting, which effectively reduces the titanium content in the aluminum-silicon alloy melt, with an average titanium reduction efficiency of 75%. However, this patented method only provides a process and method for reducing titanium content and cannot achieve precise control of the titanium content. Since Ti is a beneficial element in cast aluminum-silicon alloys and needs to be maintained at a certain content (<0.2%), how to achieve precise control of the Ti element in the melt during the aluminum-silicon alloy casting process is the problem that this invention urgently needs to solve. Summary of the Invention

[0005] This invention aims to provide a refining agent for precisely controlling the Ti content in aluminum alloys. Through a comprehensive analysis and evaluation of various existing refining agents and refining mechanisms, and combined with the requirements for Ti content in the melt, a novel refining agent formulation is proposed. This refining agent meets the requirement of simultaneously refining aluminum-silicon alloy melts and regulating the Ti composition in the melt. With the assistance of process control conditions, accurate and comprehensive regulation of the Ti composition in aluminum-silicon alloys can be achieved.

[0006] Therefore, this invention also provides a method for preparing and using the refining agent, which, while ensuring the refining effect, allows for adjustment of the melt composition, shortens the process flow, and reduces overall control and product production costs. It also improves the operability of the process route. Some of the generated TiB2 particles, acting as heterogeneous nucleation sites, are uniformly dispersed in the alloy melt after stirring and homogenization, further refining the aluminum alloy grain structure.

[0007] This invention is achieved through the following technical solution:

[0008] A refining agent for precisely controlling the Ti content in aluminum alloys, comprising the following raw material components by mass percentage:

[0009] Sodium chloride and potassium chloride: 4-8%;

[0010] Potassium fluoroborate or sodium fluoroborate: 40-70%;

[0011] Sodium fluoroaluminate: 2-4%;

[0012] Calcium fluoride: 10-20%;

[0013] Sodium carbonate: 10-20%;

[0014] Alumina: 2-4%;

[0015] Cosolvent: 6-8%.

[0016] The above-mentioned refining agent preparation method involves mixing the raw material components of the refining agent according to the formula, followed by roasting, pulverizing, and sieving to obtain the finished refining agent. In the refining agent, the mass ratio of sodium chloride to potassium chloride is 1:0.9 to 1.1.

[0017] During mixing, a mixer is used to mix the raw material components of the refining agent. The mixer is a V-type mixer or other types of mixer. The mixing time is controlled between 10 and 60 minutes, depending on the properties of the raw materials and the required uniformity of the mixture.

[0018] The material is roasted in a heating furnace. During roasting, the furnace temperature is controlled at 100-200℃ for 3-5 hours. Then the temperature is raised to 600-750℃ for melting and held for 1-3 hours. Afterward, the material is cooled to room temperature with the furnace. The heating furnace can be a crucible furnace or other heating furnaces.

[0019] When crushing, a jaw crusher can be used to crush the material, and the particle size of the crushed material should be controlled to be <3mm; when screening, the aperture of the sieve should be controlled to be 5-100 mesh.

[0020] The above-mentioned refining agent is used in the aluminum-silicon alloy process. Specifically, in the alloy refining process of aluminum-silicon alloy, the refining agent is added into the melt by spray refining to remove gas and refine. At the same time, the refining temperature is controlled at 720-780℃ and the refining time is 15-75min. After refining, slag is removed, and the mixture is allowed to stand at a controlled temperature. After reaching the casting temperature, casting is carried out. Filtration is performed during the casting process.

[0021] The amount of the refining agent added is 0.2 to 1.0 of the titanium-boron concentration ratio in the alloy.

[0022] Furthermore, in the powder spraying refining process, inert gas can be used as the refining gas for powder spraying refining, with high-purity nitrogen or argon being preferred.

[0023] The temperature for both temperature control and setting, as well as the casting temperature, is controlled at 680–750℃, with a setting time of 15–60 minutes.

[0024] The filter plates used for filtration during the casting process have a mesh size of 30 to 40.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) This invention designs the composition of the alloy refining agent for the first time, and adds the element B that reacts with Ti in the aluminum-silicon alloy melt to the refining agent to obtain a new type of refining agent. This can precisely control the Ti content in the melt while satisfying the refining of the aluminum-silicon alloy melt, and can also improve the actual yield of the element B and reduce the production cost of controlling the Ti content in the alloy melt.

[0027] (2) The fluoride salt added to the refining agent in this invention can increase the surface tension between the solvent and the alloy melt, making it easier to separate the solvent and the alloy solution.

[0028] (3) This invention uses powder spraying to inject refining agent into the refining process so that it reacts with the melt in the furnace. The refining temperature and refining time are strictly controlled during the operation. This can ensure the refining effect while accurately controlling the Ti composition of the alloy melt. It can also shorten the process flow and has a significant slag-forming effect.

[0029] (4) In this invention, the alloy refining process allows some of the B elements in the refining agent to react directly with the Ti elements in the melt to form a small amount of high-concentration Ti-containing aluminum-silicon alloy that will settle at the bottom of the furnace. After the high-concentration Ti alloy melt is separated from the low-concentration Ti melt, the low-concentration Ti melt is homogenized and then cast into a cast aluminum alloy that conforms to the corresponding grade of the national standard GB / T 8733-2016 Cast Aluminum Alloy Ingot.

[0030] (5) In the process of bottom powder spraying refining, the high titanium compound formed by enriching some Ti elements in the melt floats up with the refining slag. In the subsequent slag removal process, it is separated from the melt and carried out of the furnace, which reduces the difficulty of subsequent impurity removal and improves the operability of the whole process route. In addition, some of the generated TiB2 particles are heterogeneous nucleation particles. After stirring and homogenization treatment, they are uniformly dispersed in the alloy melt, which further refines the grain structure of the aluminum alloy.

[0031] In summary, this invention provides a novel refining agent for precise control of Ti content in aluminum alloys. By adding an appropriate proportion of B element and introducing it during the alloy refining process using powder spraying, it can ensure the refining effect while accurately controlling the Ti composition in the alloy melt, achieving a Ti content of 0.3-0.5% in the alloy. Furthermore, by controlling various parameters in the refining process, it can also improve the slag-forming effect, reduce process steps, and lower the difficulty of process operation. Attached Figure Description

[0032] Figure 1 This is the process flow for preparing refining agents.

[0033] Figure 2 This describes the process flow for using refining agents. Detailed Implementation

[0034] The invention's objective, technical solution, and beneficial effects will be further explained in detail below.

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the claimed invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] This invention is the first to propose formulating relevant components in a refining agent and adjusting the composition of high-concentration (0.3-0.5%) Ti in aluminum-silicon alloy melt produced by molten salt electrocoelastication. Because the addition of element B is done by mixing it with the refining agent, this method effectively improves the actual yield of element B and the efficiency of Ti reduction (>90%), while simultaneously achieving precise control of the Ti content in the silicon alloy melt. Furthermore, it should be noted that although patent CN116287799A proposes adding element B to the aluminum-silicon alloy melt for smelting, this method is only used to reduce the Ti content in the aluminum-silicon alloy melt and cannot achieve precise control of the Ti content. That is, this patented method can only ensure that the Ti content in the aluminum-silicon alloy is below a certain range (such as below 0.12% or 0.15% as described in the patent), but cannot control the lower limit of the Ti content, for example, reducing it from 0.5% to 0.1%.

[0037] Therefore, this invention, by adjusting the refining agent and combining it with the refining process and parameter control, can accurately control the Ti content during refining. In addition, this invention has the following superior effects: it shortens the process flow. The method in patent CN116287799A requires melting and adjusting the Ti composition before refining, while this invention can directly perform refining and simultaneously adjust the Ti composition in the alloy during the refining process; it improves the actual yield and efficiency of B element, significantly reducing the overall production cost of controlling the Ti content in the melt; and it reduces the difficulty of process operation. In patent CN116287799A, high-titanium compounds deposit at the bottom of the furnace and need to be removed and separated separately, while in this invention, high-titanium compounds are partially enriched and float to the surface in the refining slag, separating from the melt during slag removal, reducing the difficulty of subsequent impurity removal processes and improving the operability of the entire process route. Therefore, it can produce high-quality, high-performance aluminum-silicon alloy products that meet standards.

[0038] The technical solution of this invention can be summarized as follows:

[0039] For the preparation process of the refining agent, please refer to [link / reference]. Figure 1As shown, the following components are mixed in the following percentages: sodium chloride and potassium chloride 4-8% (mass ratio of sodium chloride to potassium chloride is 1:0.9-1.1), potassium fluoroborate or sodium fluoroborate 40-70%, sodium fluoroaluminate 2-4%, calcium fluoride 10-20%, sodium carbonate 10-20%, alumina 2-4%, and co-solvent 6-8%. The above components are added to a mixer and mixed for 10-60 minutes. Then, the mixture is placed in a heating furnace for calcination. During calcination, the furnace temperature is controlled at 100-200℃ for drying for 3-5 hours. The temperature is then raised to 600-750℃ for melting and held for 1-3 hours. Afterward, the mixture is cooled to room temperature in the furnace and then crushed using a crusher. The particle size of the crushed material is controlled to be <3mm. The material is then sieved through a 5-100 mesh screen and packaged to obtain the finished refining agent.

[0040] Among them, the co-solvents can be selected from sodium sulfate, sodium fluorosilicate, potassium carbonate or potassium nitrate.

[0041] For the process flow of the above refining agent in the aluminum-silicon alloy process, please refer to [link / reference needed]. Figure 2 As shown, in the alloy refining process, an inert gas is used to blow a refining agent (the amount of the refining agent added is 0.2 to 1.0 of the titanium-boron concentration ratio in the alloy) into the melt through powder spraying refining to fully degas and refine the alloy. The refining temperature (720 to 780°C) and refining time (15 to 75 min) are strictly controlled during the process. After refining, slag is removed, and the mixture is allowed to stand at a controlled temperature until the casting temperature is reached. Casting is then carried out, and filtration is performed during the casting process. Specifically, the temperature for temperature control and the casting temperature are both controlled at 680 to 750°C, the standing time is 15 to 60 min, and the filter plate used for filtration during the casting process has a mesh size of 30 to 40 mesh.

[0042] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0043] Example 1: Refining Agent and Process Control Flow for Low-Silicon Alloys (Si < 7.5%)

[0044] Weigh and prepare the refining agent according to the material composition ratio in Table 1. First, mix the materials using a V-type mixer for 15 minutes. Then, add the mixed materials to a graphite crucible and dry them at 150℃ for 3 hours. Next, heat the crucible to 680℃ for melting and hold for 1 hour. Then, cool the crucible to room temperature and crush it using a jaw crusher. Control the particle size to <3mm and pass it through an 80-mesh sieve to obtain powdered refining agent.

[0045] Table 1. Material composition ratio of refining agent for low-silicon alloys (Si < 7.5%)

[0046] Component Name mass percentage Sodium chloride + potassium chloride 6％ Potassium fluoroborate / Sodium fluoroborate 50％ Sodium fluoroaluminate 4％ Calcium fluoride 15％ Sodium carbonate 15％ Alumina 4％ Other cosolvents 6％

[0047] Aluminum-silicon alloy liquid was prepared by molten salt electroeutectoid process, with Si content of 6% and Ti content of 0.35%. After melting in a converter, the melting temperature was controlled at 755℃ and held for 30 minutes. Once the temperature stabilized, refining was initiated using a manual powder refining cart. The aforementioned powdered refining agent was used, and high-purity nitrogen was used as the refining gas. The refining time was 25 minutes, followed by slag removal and a 30-minute settling period. The temperature was then lowered to 700℃ before casting was started. During casting, a 40-mesh foam ceramic filter was used for filtration. After treatment, the Ti content in the alloy could be precisely controlled at 0.03%, and the Ti content in the slag was 0.877%.

[0048] Example 2: Refining Agents and Process Control Flow for High-Silicon Alloys (Si > 7.5%)

[0049] Weigh and prepare the refining agent according to the material composition ratio in Table 2. First, mix the materials using a V-type mixer for 25 minutes. Then, add the mixed materials to a graphite crucible and dry them at 180℃ for 4 hours. Next, heat the crucible to 730℃ for melting and hold for 3 hours. Then, cool the crucible to room temperature and crush it using a jaw crusher. Control the particle size to <3mm and pass it through a 10-mesh sieve to obtain granular refining agent.

[0050] Table 2 Material composition ratio of refining agent for high silicon alloys (Si > 7.5%)

[0051]

[0052]

[0053] Aluminum-silicon alloy liquid was prepared by molten salt electrocoelastication, containing 10% Si and 0.55% Ti. After melting in a converter, the melting temperature was controlled at 765℃ and held for 30 minutes. Once the temperature stabilized, refining was initiated using an automatic powder-injection refining cart. The refining agent used was the aforementioned granular refining agent, and the refining gas was high-purity nitrogen. The refining time was 40 minutes, followed by slag removal and a 60-minute settling period. The temperature was then lowered to 700℃ before casting began. During casting, a 30-mesh foam ceramic filter was used for filtration. After treatment, the Ti content in the alloy could be precisely controlled at 0.05%, and the Ti content in the slag was 1.32%.

[0054] In summary, through the refining agent and refining process control of this invention, the Ti reduction efficiency of aluminum-silicon alloy melt can reach over 90%, and the Ti content in the alloy can be precisely controlled. For example, in Example 1, the Ti content is precisely reduced from 0.35% to 0.3%, and in Example 2, it is precisely reduced from 0.55% to 0.5%. The Ti content in the slag reflects the advantage of high Ti compounds in the slag floating with the refining slag, separating from the melt during the slag removal process, thereby reducing the difficulty of impurity removal in subsequent processes. Due to the improved Ti reduction efficiency (>90%), the yield of B element is naturally increased, and TiB2 is generated, resulting in a refinement of the aluminum alloy grain structure, with the average grain size reduced from 250-300 μm to <200 μm.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for precisely controlling the Ti content in aluminum alloys, characterized in that: In the alloy refining process of aluminum-silicon alloys, a powder injection refining method is used to add refining agents into the melt for degassing and refining. The refining temperature is controlled at 720–780℃, and the refining time is 15–75 minutes. After refining, slag is removed, and the melt is allowed to stand at a controlled temperature until the casting temperature is reached. Casting is then carried out, and filtration is performed during the casting process. The preparation steps of the refining agent are as follows: (1) Prepare the following raw material components by mass percentage: sodium chloride and potassium chloride: 4-8%, potassium fluoroborate or sodium fluoroborate: 40-70%, sodium fluoroaluminate: 2-4%, calcium fluoride: 10-20%, sodium carbonate: 10-20%, alumina: 2-4%, and co-solvent: 6-8%, and control the mass ratio of sodium chloride to potassium chloride to be 1:0.9-1.1; (2) Use a mixer to mix the raw material components of the refining agent, and control the mixing time to 10-60 min; (3) The material is roasted in a heating furnace. During roasting, the furnace temperature is controlled at 100-200℃ for 3-5 hours. Then the temperature is raised to 600-750℃ for melting and kept at that temperature for 1-3 hours. After that, the material is cooled to room temperature in the furnace. (4) After further crushing and sieving, the refining agent is obtained.

2. The method according to claim 1, characterized in that: During crushing, the particle size of the crushed material should be controlled to be <3mm; during sieving, the aperture of the sieve should be controlled to be 5-100 mesh.

3. The method as described in claim 1, characterized in that: Inert gas is used as the refining gas for spray refining.

4. The method as described in claim 1, characterized in that: The temperature for both temperature control and setting, as well as the casting temperature, is controlled at 680–750℃, with a setting time of 15–60 minutes.

5. The method as described in claim 1, characterized in that: The filter plates used for filtration during the casting process have a mesh size of 30 to 40.

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