Refining method for effectively reducing Sr consumption and remarkably modifying eutectic Si

Abstract

The invention discloses a refining method for remarkably modifying eutectic Si by effectively reducing the use amount of Sr. Belongs to the technical field of aluminum-silicon alloy preparation. According to the method, the Al-Li intermediate alloy is added and reacts with the impurity P in the melt to generate Li3P, and slag phase separation is performed through rotary injection, so that the purpose of removing the impurity P is achieved, the melt is purer and more compact in structure, the content of residual Li in the melt is extremely low, and new elements cannot be introduced to change the casting performance, the mechanical performance and the use performance of the alloy; after the impurity phase is removed, by reducing the adding amount of Sr, the defects of looseness and air holes of an alloy structure caused by hydrogen absorption are effectively reduced, eutectic Si is remarkably modified, different from a traditional superposition element (such as La and Ti), a performance improvement method is found, the adding amount of Sr is sharply reduced by introducing a trace Li element, the cost is reduced, and meanwhile, the purity and the mechanical property of a melt are synchronously improved; and the practicability and economical efficiency of casting the aluminum-silicon alloy are comprehensively improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-silicon alloy preparation technology, and particularly relates to a refining method that effectively reduces the amount of Sr and significantly alters the eutectic Si. Background Technology

[0002] Aluminum-silicon alloys possess advantages such as good fluidity, low hot cracking tendency, low shrinkage, and high specific strength, making them widely used in the automotive, aerospace, and other fields. Based on silicon content range, they can be classified into hypoeutectic (<12.6 wt.%), eutectic (~12.6 wt.%), and hypereutectic (>12.6 wt.%). Increasing silicon content can significantly improve the casting fluidity of the alloy and effectively reduce porosity defects. However, in the as-cast state, with increasing silicon content, the Si phase in the alloy exhibits coarse, long needle-like and lamellar shapes, which have a severe cutting effect on the matrix. Moreover, these Si phases often act as crack initiation points in the fracture process of Al-Si alloys, greatly reducing the alloy's plasticity. Furthermore, in hypoeutectic alloys, due to the introduction of trace amounts of phosphorus impurities from crystalline Si, even 10 ppm of phosphorus forming AlP is sufficient to cause primary Si to appear in a 9% Si hypoeutectic alloy, and to cause the eutectic Si to form coarse, lamellar shapes, significantly reducing the mechanical properties of aluminum-silicon alloys. The strength and elongation of cast aluminum-silicon alloys are only 60-90% of those of forged aluminum alloys, making it difficult to meet the increasingly high-performance requirements of the manufacturing industry. Therefore, how to remove phosphorus impurities and improve the morphology of the eutectic Si phase has become an important problem in industrial production.

[0003] Currently, researchers have conducted extensive studies on the modification treatment of eutectic Si in aluminum-silicon alloys. In the early 20th century, Na was discovered as a modifier for aluminum-silicon alloys, but due to its much lower density than molten aluminum, it could only remain on the surface, resulting in reduced modification efficiency and significant degradation. Sb is also a highly efficient modifier, but it is very sensitive to the cooling rate of the melt and is difficult to exert its modifying effect under slow cooling. Sr has also been found to be an excellent modifier for aluminum-silicon alloys. Sr produces a modifying effect in the alloy in a free state, with stable modification effects and minimal degradation after remelting, and the modification time can be as long as 6 hours or more. Furthermore, because Sr has a higher density than aluminum, it can mix thoroughly with aluminum after being added to the melt, resulting in high modification efficiency. However, its production cost is high, and its chemical reactivity makes it prone to hydrogen absorption, leading to a loose alloy structure and porosity defects. Therefore, how to effectively modify eutectic Si and reduce defect formation is a key technical challenge for improving the mechanical properties of cast aluminum-silicon alloys. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a refining method that effectively reduces the amount of Sr required and significantly alters the eutectic Si. This invention removes impurity P, resulting in a purer melt with a denser microstructure, and the residual Li content in the melt is extremely low, thus avoiding the introduction of new elements that alter the alloy's casting properties, mechanical properties, and service performance. Removing the impurity phase reduces the amount of Sr added, minimizing defects such as porosity and gas pockets in the alloy microstructure caused by hydrogen absorption, while significantly refining the eutectic Si. This reduces costs while simultaneously improving melt purity and mechanical properties.

[0005] This invention is achieved through the following technical solution: A refining method for effectively reducing the amount of Sr that significantly alters the eutectic Si, comprising the following steps: S1: The aluminum-silicon alloy raw material is placed in a preheated resistance furnace for melting. After the resistance furnace is heated, it is kept at a constant temperature to completely melt the aluminum-silicon alloy raw material and form an aluminum melt.

[0006] S2: Using a preheated graphite bell jar, press the dried Al-10Sr master alloy (aluminum-strontium master alloy containing 10 wt.% strontium) into the aluminum melt until the Al-10Sr master alloy is completely melted.

[0007] S3: Using a preheated graphite bell jar, press the dried Al-10Li (aluminum-lithium master alloy containing 10 wt.% lithium) master alloy into the aluminum melt until the Al-10Li master alloy is completely melted.

[0008] S4: After the temperature of the aluminum melt decreases, the rotary blower is inserted into the aluminum melt for rotary stirring. High-purity argon gas is used for safety protection. After the rotary blowing is completed, the mixture is allowed to stand, slag is removed, and impurities are eliminated. The aluminum melt is then heated up and poured to obtain the casting.

[0009] Further, in step S1, the aluminum-silicon alloy raw material is first placed in a graphite crucible, and then the graphite crucible is placed in a resistance furnace to melt the aluminum-silicon alloy raw material; the aluminum-silicon alloy raw material is A356 alloy raw material, A357 alloy raw material, or ADC12 alloy raw material; the preheating temperature of the resistance furnace is 300~400℃, and the preheating holding time is 20~30min to ensure effective removal of moisture in the furnace chamber and to ensure that the entire thickness direction of the furnace chamber reaches and stabilizes at the target temperature; after the resistance furnace is heated to 740℃, it is held to compensate for the heat loss during the refining process, improve the melt fluidity, and avoid component segregation.

[0010] Furthermore, in step S2, the preheating temperature of the graphite bell jar is 200℃ to prevent explosive evaporation of water vapor and avoid splashing of molten aluminum; the added Sr element content is 0.01-0.03wt.%, which can effectively and significantly modify eutectic silicon, and avoid excessive Sr addition leading to excessive porosity and pore defects in the alloy.

[0011] Furthermore, in step S3, the preheating temperature of the graphite bell jar is 200℃; the amount of Li added is determined to ensure that all impurity P is consumed and Li3P is generated.

[0012] Further, in step S4, when the temperature of the molten aluminum drops to 680~700℃, a rotating blower is inserted; the rotating blower extends to one-third of the depth below the surface of the molten aluminum, providing a sufficiently long bubble path and avoiding secondary slag contamination caused by violent churning of the liquid surface; the rotation speed of the rotating blower is 200~300 r / min, so that the rotor provides sufficient shear force to form a stable and uniform flow field without generating severe gas encapsulation and excessive eddies; the purity of the high-purity argon gas is 99.9% and the flow rate is 10~20 L / min; after the molten aluminum is heated to 720℃, it is poured to obtain the casting.

[0013] Furthermore, in step S4, the temperature of the aluminum melt is reduced to 680~700℃ during rotary blowing. By reducing the temperature, the solubility of hydrogen is reduced, providing a greater driving force for hydrogen removal. At the same time, secondary oxidation is suppressed and slag is stabilized while ensuring the fluidity of the aluminum melt. After rotary blowing, the aluminum melt is heated to 720℃ before casting. The increased temperature reduces the viscosity of the aluminum melt and improves its fluidity, ensuring complete filling and good feeding during casting.

[0014] The principle of this invention is to add Li to an aluminum-silicon alloy. Impurities P in the melt preferentially react with more reactive elements to form corresponding phosphides. Even in a low-P state, the product is still predominantly Li3P (lithium phosphide), until AlP coexists when Li is depleted. The generated Li3P is easily separated into slag phases by rotary jetting, thus removing impurities P. Furthermore, the residual Li content in the melt is extremely low, preventing the introduction of new elements that could alter the castability and mechanical properties of the aluminum-silicon alloy. This refining method effectively removes the negative impact of impurity phases, refines the eutectic Si, and effectively improves the performance of cast aluminum-silicon alloy materials, comprehensively enhancing the practicality and economy of cast aluminum-silicon alloys.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the added Al-Li master alloy efficiently removes phosphorus (P) impurities from cast aluminum-silicon alloys, preventing the formation of AlP from introducing primary Si and affecting material properties. Simultaneously, an appropriate amount of Sr significantly refines the coarse, plate-like eutectic Si, and removing P also prevents it from reacting with the added Sr to form Sr-P compounds, reducing Sr consumption and weakening the fibrous modification effect of the eutectic Si. This invention efficiently removes P impurities, resulting in a purer melt with a denser microstructure. The residual Li content in the melt is extremely low, preventing the introduction of new elements that alter the castability and mechanical properties of the aluminum-silicon alloy. The reduced Sr content effectively decreases porosity and defects in the alloy. Simultaneously, the eutectic Si undergoes effective modification. Unlike traditional methods that seek performance improvement by adding elements (such as La and Ti), the introduction of trace amounts of Li drastically reduces the amount of Sr added, lowering costs while simultaneously improving melt purity and mechanical properties, thus comprehensively enhancing the practicality and economy of cast aluminum-silicon alloys. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The accompanying drawings are used to provide further explanation of the present invention and constitute a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0017] Figure 1 This is a process flow diagram of the method of the present invention.

[0018] Figure 2 This is a metallographic micrograph of eutectic Si.

[0019] Figure 3 This is a SEM image of eutectic Si. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the present invention will be further described clearly and completely below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0021] Example 1 (A356-0.02Sr-Li) A refining method that effectively reduces Sr content and significantly alters the eutectic Si, such as... Figure 1 As shown, it includes the following steps: S1: First, place the A356 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A356 alloy raw material to form aluminum melt.

[0022] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0023] S3: Using a graphite bell jar preheated to 200℃, press the dried Al-10Li master alloy, calculated according to the element ratio, into the aluminum melt until the Al-10Li master alloy is completely melted; wherein, when calculating the element ratio, the amount of Li added is based on ensuring that the impurity P is completely consumed and Li3P is generated.

[0024] S4: After the temperature of the molten aluminum drops to 680℃, insert the rotary jetting rod into the molten aluminum for rotary stirring. The rotary jetting rod should be inserted to one-third of the depth below the surface of the molten aluminum, and the rotation speed of the rotary jetting rod should be 200 r / min. High-purity argon gas should be used for safety protection, with a purity of 99.9% and a flow rate of 10 L / min. After rotary jetting, allow the mixture to stand, remove slag and impurities, and then heat the molten aluminum to 720℃ before casting to obtain the casting.

[0025] Refer to Example 1 (A356) S1: First, place the A356 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A356 alloy raw material to form aluminum melt.

[0026] S2: The aluminum melt is poured into the casting after it cools down to 720℃.

[0027] Comparative Example 1-1 (A356-0.02Sr) S1: First, place the A356 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A356 alloy raw material to form aluminum melt.

[0028] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0029] S3: After complete melting, wait for the aluminum melt to cool to 720℃ before pouring to obtain the casting.

[0030] Comparative Examples 1-2 (A356-0.05Sr) S1: First, place the A356 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A356 alloy raw material to form aluminum melt.

[0031] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.05wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.05wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0032] S3: After complete melting, wait for the melt to cool to 720℃ before pouring to obtain the casting.

[0033] Example 2 (A357-0.02Sr-Li) A refining method that effectively reduces Sr content and significantly alters the eutectic Si, such as... Figure 1 As shown, it includes the following steps: S1: First, place the A357 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A357 alloy raw material to form aluminum melt.

[0034] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0035] S3: Using a graphite bell jar preheated to 200℃, press the dried Al-10Li master alloy, calculated according to the element ratio, into the aluminum melt until the Al-10Li master alloy is completely melted; wherein, when calculating the element ratio, the amount of Li added is based on ensuring that the impurity P is completely consumed and Li3P is generated.

[0036] S4: After the temperature of the molten aluminum drops to 680℃, insert the rotary jetting rod into the molten aluminum for rotary stirring. The rotary jetting rod should be inserted to one-third of the depth below the surface of the molten aluminum, and the rotation speed of the rotary jetting rod should be 200 r / min. High-purity argon gas should be used for safety protection, with a purity of 99.9% and a flow rate of 10 L / min. After rotary jetting, allow the mixture to stand, remove slag and impurities, and then heat the molten aluminum to 720℃ before casting to obtain the casting.

[0037] Refer to Example 2 (A357) S1: First, place the A357 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A357 alloy raw material to form aluminum melt.

[0038] S2: The aluminum melt is poured into the casting after it cools down to 720℃.

[0039] Comparative Example 2-1 (A357-0.02Sr) S1: First, place the A357 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A357 alloy raw material to form aluminum melt.

[0040] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0041] S3: After complete melting, wait for the aluminum melt to cool to 720℃ before pouring to obtain the casting.

[0042] Comparative Example 2-2 (A357-0.05Sr) S1: First, place the A357 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the A357 alloy raw material to form aluminum melt.

[0043] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.05wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.05wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0044] S3: After complete melting, wait for the aluminum melt to cool to 720℃ before pouring to obtain the casting.

[0045] Example 3 (ADC12-0.02Sr-Li) A refining method that effectively reduces Sr content and significantly alters the eutectic Si, such as... Figure 1 As shown, it includes the following steps: S1: First, place the ADC12 alloy raw material in a graphite crucible, and then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the ADC12 alloy raw material to form aluminum melt.

[0046] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0047] S3: Using a graphite bell jar preheated to 200℃, press the dried Al-10Li master alloy, calculated according to the element ratio, into the aluminum melt until the Al-10Li master alloy is completely melted; wherein, when calculating the element ratio, the amount of Li added is based on ensuring that the impurity P is completely consumed and Li3P is generated.

[0048] S4: After the temperature of the molten aluminum drops to 680℃, insert the rotary jetting rod into the molten aluminum for rotary stirring. The rotary jetting rod should be inserted to one-third of the depth below the surface of the molten aluminum, and the rotation speed of the rotary jetting rod should be 200 r / min. High-purity argon gas should be used for safety protection, with a purity of 99.9% and a flow rate of 10 L / min. After rotary jetting, allow the mixture to stand, remove slag and impurities, and then heat the molten aluminum to 720℃ before casting to obtain the casting.

[0049] Reference example 3 (ADC12) S1: First, place the ADC12 alloy raw material in a graphite crucible, and then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the ADC12 alloy raw material to form aluminum melt.

[0050] S2: The aluminum melt is poured into the casting after it cools down to 720℃.

[0051] Comparative Example 3-1 (ADC12-0.02Sr) S1: First, place the ADC12 alloy raw material in a graphite crucible, and then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the ADC12 alloy raw material to form aluminum melt.

[0052] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.02wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.02wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0053] S3: After complete melting, wait for the aluminum melt to cool to 720℃ before pouring to obtain the casting.

[0054] Comparative Example 3-2 (ADC12-0.05Sr) S1: First, place the ADC12 alloy raw material in a graphite crucible, and then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 300℃, and the preheating holding time is 25min. After the resistance furnace is heated to 740℃, it is held to completely melt the ADC12 alloy raw material to form aluminum melt.

[0055] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.05wt.% Al-10Sr master alloy (i.e., the mass of the Al-10Sr master alloy is determined by the addition content of Sr element of 0.05wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-10Sr master alloy is completely melted.

[0056] S3: After complete melting, wait for the melt to cool to 720℃ before pouring to obtain the casting.

[0057] The results showed that Figure 2 and Figure 3(a), (e), and (i) all indicate that the eutectic Si in Reference Examples 1, 2, and 3 exhibits coarse lamellar and needle-like structures without any alteration. This leads to stress concentration at the interface between the eutectic Si and the matrix, resulting in severe deterioration of mechanical properties. (b), (f), and (g) indicate that the addition of 0.02 wt.% Sr to the eutectic Si in Comparative Examples 1-1, 2-1, and 3-1 did not completely alter the alloy, and lamellar eutectic Si still exists. (c), (g), and (k) indicate that the addition of 0.05 wt.% Sr to the eutectic Si in Comparative Examples 1-2, 2-2, and 3-2 resulted in significant refinement, exhibiting a finer state and higher roundness, forming altered coral-like eutectic Si. (d), (h), and (l) indicate that after removing P impurities in Examples 1, 2, and 3, reducing the amount of Sr can significantly alter the eutectic Si, and the refined melt structure is purer and denser. This process can efficiently remove impurities such as phosphorus (P), making the melt purer and the microstructure denser. The residual lithium content in the melt is extremely low, which will not damage the castability and mechanical properties of the aluminum-silicon alloy. The reduction in Sr content effectively reduces porosity and gas defects in the alloy. At the same time, the eutectic silicon undergoes effective modification, significantly improving the alloy material properties and comprehensively enhancing the practicality and economy of cast aluminum-silicon alloys.

[0058] Example 4 (A356-0.01Sr-Li) A refining method that effectively reduces Sr content and significantly alters the eutectic Si, such as... Figure 1 As shown, it includes the following steps: S1: First, place the A356 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 400℃, and the preheating holding time is 20min. After the resistance furnace is heated to 740℃, it is held to completely melt the A356 alloy raw material to form aluminum melt.

[0059] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.01wt.% Al-Sr master alloy (i.e., the mass of the Al-Sr master alloy is determined by the addition content of Sr element of 0.01wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-Sr master alloy is completely melted.

[0060] S3: Using a graphite bell jar preheated to 200℃, the dried Al-Li master alloy, calculated according to the element ratio, is pressed into the aluminum melt until the Al-Li master alloy is completely melted; wherein, when calculating the element ratio, the amount of Li added is based on ensuring that the impurity P is completely consumed and Li3P is generated.

[0061] S4: After the temperature of the molten aluminum drops to 690℃, insert the rotary jetting rod into the molten aluminum for rotary stirring. The rotary jetting rod should be inserted to one-third of the way below the surface of the molten aluminum, and the rotation speed of the rotary jetting rod should be 300 r / min. High-purity argon gas should be used for safety protection, with a purity of 99.9% and a flow rate of 15 L / min. After rotary jetting, allow the mixture to stand, remove slag and impurities, and then heat the molten aluminum to 720℃ before casting to obtain the casting.

[0062] Example 5 (A357-0.03Sr-Li) A refining method that effectively reduces Sr content and significantly alters the eutectic Si, such as... Figure 1 As shown, it includes the following steps: S1: First, place the A357 alloy raw material in a graphite crucible, then place the graphite crucible in a preheated resistance furnace for melting. The preheating temperature of the resistance furnace is 350℃, and the preheating holding time is 30min. After the resistance furnace is heated to 740℃, it is held to completely melt the A357 alloy raw material to form aluminum melt.

[0063] S2: Using a graphite bell jar preheated to 200℃, press the dried 0.03wt.% Al-Sr master alloy (i.e., the mass of the Al-Sr master alloy is determined by the addition content of Sr element of 0.03wt.%) into the aluminum melt, and let it stand for 2~3 minutes until the Al-Sr master alloy is completely melted.

[0064] S3: Using a graphite bell jar preheated to 200℃, the dried Al-Li master alloy, calculated according to the element ratio, is pressed into the aluminum melt until the Al-Li master alloy is completely melted; wherein, when calculating the element ratio, the amount of Li added is based on ensuring that the impurity P is completely consumed and Li3P is generated.

[0065] S4: After the temperature of the molten aluminum drops to 700℃, insert the rotary jetting rod into the molten aluminum for rotary stirring. The rotary jetting rod should be inserted to one-third of the way below the surface of the molten aluminum, and the rotation speed of the rotary jetting rod should be 250 r / min. High-purity argon gas should be used for safety protection, with a purity of 99.9% and a flow rate of 20 L / min. After the rotary jetting is completed, let it stand, remove slag and impurities, and then heat the molten aluminum to 720℃ before pouring to obtain the casting.

[0066] The embodiments described above merely illustrate the preferred implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A refining method for significantly modifying eutectic Si by effectively reducing the amount of Sr, characterized by, Comprising the following steps: S1: the aluminum-silicon alloy raw material is placed in a preheated resistance furnace for smelting, the resistance furnace is heated and then kept at temperature, the aluminum-silicon alloy raw material is completely melted to form an aluminum melt; S2: the dried Al-10Sr intermediate alloy is pressed into the aluminum melt by using a preheated graphite bell, until the Al-10Sr intermediate alloy is completely melted; S3: the dried Al-10Li intermediate alloy is pressed into the aluminum melt by using a preheated graphite bell, until the Al-10Li intermediate alloy is completely melted; S4: after the temperature of the aluminum melt is reduced, the rotating blowing rod is inserted into the aluminum melt for rotating stirring, high-purity argon is used for safety protection, after the rotating blowing is completed, the aluminum melt is left to stand, slag is removed, and the castings are obtained by pouring after the aluminum melt is heated.

2. The method of claim 1, wherein the amount of Sr is reduced significantly to modify the eutectic Si. In step S1, the aluminum-silicon alloy raw material is first placed in a graphite crucible, and then the graphite crucible is placed in a resistance furnace for smelting the aluminum-silicon alloy raw material; the aluminum-silicon alloy raw material is A356 alloy raw material, A357 alloy raw material or ADC12 alloy raw material; the preheating temperature of the resistance furnace is 300-400℃, and the preheating and holding time is 20-30min; the resistance furnace is heated to 740℃ and then kept at temperature.

3. The method of claim 1, wherein the amount of Sr is reduced significantly to modify the eutectic Si. In step S2, the preheating temperature of the graphite bell is 200℃; the added content of Sr element is 0.01-0.03wt.%.

4. The method of claim 1, wherein the amount of Sr is reduced to significantly modify the eutectic Si. In step S3, the preheating temperature of the graphite bell is 200℃; the added content of Li element is determined to ensure that the impurity P can be completely consumed and Li3P is generated.

5. The method of claim 1, wherein the amount of Sr is reduced significantly to modify the eutectic Si. In step S4, the rotating blowing rod is inserted when the temperature of the aluminum melt is reduced to 680-700℃; the rotating blowing rod is inserted to a position one third below the liquid surface of the aluminum melt, the rotating speed of the rotating blowing rod is 200-300r / min; the purity of the high-purity argon is 99.9%, and the flow rate is 10-20L / min; the castings are obtained by pouring after the aluminum melt is heated to 720℃.

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