A low-carbon aluminum-silicon cast alloy and a method for producing the same

Abstract

The application discloses a low-carbon aluminum-silicon casting alloy and a preparation method thereof. By adjusting the proportion of Fe and Mn, the morphology of the iron-rich manganese-rich phase is changed, and then the coarse iron-rich manganese-rich phase is modified by using Co and Sr and other elements to reduce the size of the coarse iron-rich manganese-rich phase, so that the damage to the mechanical properties is reduced. Therefore, the content limit of the harmful element iron can be greatly improved under the premise of ensuring the mechanical properties, and low-carbon, low-cost and high-performance are achieved.

Description

Technical Field

[0001] This invention relates to the technical field of cast aluminum alloys, and more particularly to a low-carbon aluminum-silicon casting alloy and its preparation method. Background Technology

[0002] Since the concept of a low-carbon economy was introduced in 2003, various industries have been promoting low-carbon practices and reducing carbon emissions. For the aluminum industry, increasing the use of aluminum alloy scrap and reducing the use of electrolytic aluminum is a powerful measure to reduce carbon emissions. Various sub-sectors of the aluminum alloy industry are actively promoting the reuse of aluminum alloy scrap. Aluminum alloys that can absorb large amounts of scrap are called low-carbon aluminum alloys, and they have received attention from all sectors of the aluminum alloy industry.

[0003] Aluminum alloy scrap comes in a wide variety of types, from diverse sources, and varies in quality, often containing impurities such as iron. Therefore, aluminum alloy scrap frequently contains high levels of iron. Elemental iron is considered an impurity element in most aluminum alloys and is a major obstacle to the reuse of aluminum alloy scrap. In Al-Si alloys, high Fe content leads to the formation of numerous coarse Al-Fe-Si phases, appearing as needle-like or lamellar shapes, severely impairing the alloy's mechanical properties. This significantly limits the use of aluminum alloy scrap in high-performance alloys.

[0004] In die-cast aluminum alloys, iron is a crucial process element used to improve the demolding performance of die-cast parts and prevent them from sticking to the mold. Since the mold is made of mold steel, iron and manganese in the mold tend to diffuse into the molten aluminum, easily forming iron- and manganese-rich intermetallic compounds on the mold surface, which then adhere to the mold. After the casting solidifies, this adhesion causes sticking, making demolding difficult and potentially damaging the mold. To prevent sticking, the Fe content in the alloy is generally increased, typically controlled above 0.6%. The mechanism is that maintaining a high Fe content in the molten aluminum prevents Fe from melting into the mold and thus inhibits the formation of Fe-rich intermetallic compounds on the mold surface. However, a high Fe content leads to the formation of large amounts of coarse Al-Fe-Si phases, severely impairing the alloy's mechanical properties. To reduce the relative damage to mechanical properties caused by these coarse Fe-rich intermetallic compounds, replacing Fe with Mn also achieves good demolding performance and eliminates the harmful effects of Fe, resulting in a significant improvement in mechanical properties. For example, Chinese patent ZL200410033014X discloses an Al-Si die-casting alloy, limiting the Fe content to below 0.15 wt% and the Mn content to 0.3-0.8 wt%. European patent EP0687742B1 discloses an Al-Si-Mg die-casting aluminum alloy, limiting the Fe content to below 0.15 wt% and the Mn content to 0.5-0.8 wt%. These low-Fe, high-Mn patented alloys have been applied, but the price of Mn is significantly higher than that of Fe, which undoubtedly increases the cost of the alloy. Furthermore, it limits the use of aluminum alloy scrap. Clearly, this does not align with the trend towards low-carbon aluminum alloys.

[0005] Chinese patent application ZL2020106514818 discloses a method for refining iron- and manganese-rich phases by using a higher content of Sr to modify and refine these phases. However, some studies have shown that increasing the Sr content leads to an increased tendency for molten aluminum to absorb gas, increasing the risk of porosity in castings. Furthermore, blocky AlSiSr phases are frequently found in Al-Si alloys with an Sr content greater than 0.1%, which may reduce mechanical properties.

[0006] Cobalt has a good effect on refining iron-rich and manganese-rich phases, but cobalt is a very expensive element, which leads to a significant increase in the cost of alloys.

[0007] Therefore, how to develop a new type of low-carbon aluminum-silicon casting alloy has become an urgent problem to be solved. Summary of the Invention

[0008] In view of this, the present invention provides a low-carbon aluminum-silicon casting alloy and its preparation method to solve the problem that the iron content in existing aluminum alloy scrap is high and difficult to reuse in high-performance aluminum alloys.

[0009] On one hand, the present invention provides a low-carbon aluminum-silicon casting alloy, which, by mass percentage, is made of the following components:

[0010] The composition is as follows: Si 6.5-10.0%, Mg 0-0.8%, Cu 0-1.5%, Zn 0-1.5%, Fe 0.25-0.7%, Mn 0.3-0.8%, Ti 0-0.25%, Zr 0-0.25%, Re 0-0.25%, Co 0.02-0.25%, Sr 0.02-0.25%, with the balance being Al and impurities. The percentage of any single impurity element is ≤0.1%, and the total impurity content is ≤1.0%.

[0011] The mass ratio of Fe to Mn is 1:(0.7-1.5), and Fe and Mn account for 0.6-1.5% of the alloy by mass percentage.

[0012] Preferably, the low-carbon aluminum-silicon casting alloy also contains Cr, and the Cr content is 0-0.25% by mass percentage.

[0013] Further preferably, the low-carbon aluminum-silicon casting alloy has a tensile strength of 229-365 MPa, a yield strength of 112-229 MPa, and an elongation of 8.3-13.5%.

[0014] On the other hand, the present invention also provides a method for preparing the above-mentioned low-carbon aluminum-silicon casting alloy, the method comprising the following steps:

[0015] 1) Material preparation: Prepare raw materials according to the composition of the low-carbon aluminum-silicon casting alloy, and prepare refining agent, modifier and grain refiner for later use;

[0016] 2) Smelting: After heating and melting the raw material Al, aluminum melt is obtained. The composition of the aluminum melt is determined and the amount of each component is calculated. Then, other raw materials except Mg are added to the aluminum melt until it melts. Then, raw material Mg is added. After Mg melts, it is stirred evenly to obtain a homogeneous alloy melt.

[0017] 3) Refining and modification: After refining the homogeneous alloy melt by adding a refining agent, a modifier is added to the refined alloy melt for modification to obtain a modified alloy melt.

[0018] 4) Transfer and degassing: The modified alloy melt is transferred to a transfer container, and argon gas is injected into the alloy melt for degassing using a degassing machine. Then, slag is removed, a grain refiner is added, and the alloy melt is poured into the machine side furnace of the die casting machine.

[0019] 5) Die casting: Die casting is performed using a die casting machine to obtain low-carbon aluminum-silicon castings. After demolding, the castings can be air-cooled or water-quenched.

[0020] Preferably, the preparation method of the low-carbon aluminum-silicon casting alloy further includes the following steps:

[0021] When preparing T6 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are subjected to solution treatment and aging treatment.

[0022] When preparing T5 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are only subjected to aging treatment.

[0023] Specifically, the solution treatment involves holding the solution at 500-550℃ for 2-12 hours.

[0024] The aging process specifically involves maintaining the temperature at 130-180℃ for 2-12 hours.

[0025] Further preferably, in step 5), the die-casting process is high-pressure die-casting. Vacuum high-pressure die-casting is used for castings requiring T6 treatment. When preparing T5-state low-carbon aluminum-silicon casting alloys, the cooling treatment is preferably water quenching.

[0026] Further preferably, the refining agent is RJ-1 refining agent, and the amount of the refining agent added is 0.5-1% of the total weight of the homogeneous alloy melt.

[0027] More preferably, the modifier is an Al-10Co master alloy and an Al-10Sr master alloy, used in combination, with an addition amount of (Co+Sr) = 0.1-0.3%.

[0028] Further preferably, the grain refiner is an AlTiB or AlTiC alloy, and the amount added is 0.05-0.25% of the total mass of the alloy melt.

[0029] Further preferably, the argon gas injection flow rate is 0.2-0.3 m³ / h. 3 / h.

[0030] The low-carbon aluminum-silicon casting alloy provided by this invention changes the morphology of the iron-rich and manganese-rich phase by adjusting the ratio of Fe and Mn, and then modifies the coarse iron-rich and manganese-rich phase with elements such as Co and Sr to reduce its size and thus reduce the damage to mechanical properties. Therefore, while ensuring mechanical properties, the content limit of the harmful element iron can be significantly increased, achieving low carbon, low cost and high performance.

[0031] The combined use of Co and Sr achieved better modification results. Compared with modification using Co alone, the amount of Co used was reduced, thereby lowering the alloy cost; compared with modification using Sr alone, the amount of Sr used was reduced, effectively preventing porosity defects caused by increased gas absorption tendency, and also eliminating the blocky AlSiSr phase.

[0032] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the present invention. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 Morphology of the Al15(FeMn)3Si2 phase in Example 1d (0.5Fe, 0.5Mn);

[0036] Figure 2 The image shows the morphology of the Al15(FeMn)3Si2 phase after refinement by 0.07% Co + 0.08% Sr. Detailed Implementation

[0037] The present invention will be further explained below with reference to specific implementation schemes, but this is not intended to limit the scope of protection of the present invention.

[0038] To address the issue that existing aluminum alloy scrap has a high iron content, making it difficult to reuse in high-performance aluminum alloys, this embodiment provides a low-carbon aluminum-silicon casting alloy. This alloy maintains high performance while allowing for a higher iron content, thus enabling the extensive use of scrap, reducing carbon emissions, and lowering alloy costs. Specifically, by mass percentage, this low-carbon aluminum-silicon casting alloy is composed of the following components:

[0039] The composition is as follows: Si 6.5-10.0%, Mg 0-0.8%, Cu 0-1.5%, Zn 0-1.5%, Fe 0.25-0.7%, Mn 0.3-0.8%, Ti 0-0.25%, Zr 0-0.25%, Re 0-0.25%, Co 0.02-0.25%, Sr 0.02-0.25%, with the balance being Al and impurities. The percentage of any single impurity element is ≤0.1%, and the total impurity content is ≤1.0%.

[0040] The mass ratio of Fe to Mn is 1:(0.7-1.5), and Fe and Mn account for 0.6-1.5% of the alloy by mass percentage.

[0041] Preferably, the low-carbon aluminum-silicon casting alloy also contains Cr, and the Cr content is 0-0.25% by mass percentage. Cr has a modifying and refining effect on phases such as Al15(FeMn)3Si2.

[0042] The alloy provided by the above implementation scheme changes the morphology of the iron-rich and manganese-rich phase by adjusting the ratio of Fe and Mn, and then reduces the size of the coarse iron-rich and manganese-rich phase by using elements such as Co and Sr, thereby reducing the damage to mechanical properties. Thus, while ensuring mechanical properties, the content limit of the harmful element iron can be significantly increased, achieving low carbon, low cost, and high performance.

[0043] The combined use of elements Co and Sr reduces the amount of Co used, thereby lowering the cost of the alloy; the reduced amount of Sr effectively prevents porosity defects caused by increased gas absorption tendency and also eliminates the bulk AlSiSr phase.

[0044] In the Al-Fe system, there is an Al6Fe phase; in the Al-Mn system, there is an Al6Mn phase; and in the Al-Fe-Mn system, there is an Al6(FeMn) phase. The Al6Fe, Al6Mn, and Al6(FeMn) phases are isomorphous. Adding Mn to an Al-Fe alloy causes Mn to partially replace Fe, transforming the Al6Fe phase into the Al6(FeMn) phase. The more Mn added and the smaller the Fe / Mn ratio, the higher the Mn content in the Al6(FeMn) phase. When Mn completely replaces Fe, the Al6(FeMn) phase transforms into the Al6Mn phase. In Al-Si alloys, depending on the Fe / Mn ratio, Al5FeSi, Al15(FeMn)3Si2, and Al15Mn3Si2 are formed. Similarly, the Fe and Mn composition in the Al15(FeMn)3Si2 phase depends on the Fe / Mn ratio in the alloy composition. The study of the effect of the Fe / Mn ratio in the alloy composition on the morphology of the Al15(FeMn)3Si2 phase revealed that different Fe / Mn ratios resulted in different morphologies of the Al15(FeMn)3Si2 phase. Metallographic analysis showed that in Al-Si alloys, when the Fe+Mn content was approximately 1, the phase morphology was needle-like or lamellar when the alloy contained little or no Mn. With the addition of Mn and a decrease in Fe content, the needle-like or lamellar morphology gradually transformed into a petal-like or coral-like morphology. When the Fe and Mn contents were essentially the same, the phase morphology was primarily petal-like, coral-like, or fishbone-like. Further increasing the Mn content and decreasing the Fe content caused the phase morphology to transform into a blocky morphology. When Mn was further increased and the Fe content decreased to trace amounts or even zero, the phase morphology remained blocky.

[0045] Studies have found that elements Co and Sr have a grain-refining effect on phases such as Al5FeSi, Al15(FeMn)3Si2, and Al15Mn3Si2. The Al5FeSi phase, after refinement, retains its needle-like and flaky shape; the Al15Mn3Si2 phase, after refinement, retains its blocky shape; while the Al15(FeMn)3Si2 phase, after refinement, becomes small blocky. Furthermore, the combined use of Co and Sr yields even better grain-refining results. Elements Ti, Zr, and rare earth elements also have a grain-refining effect, with Zr and rare earth elements exhibiting even better grain-refining properties when used together.

[0046] The tensile strength of the aforementioned low-carbon aluminum-silicon casting alloy is 229-365 MPa, the yield strength is 112-229 MPa, and the elongation is 8.3-13.5%.

[0047] This embodiment provides a method for preparing the above-mentioned low-carbon aluminum-silicon casting alloy, which includes the following steps:

[0048] 1) Material preparation: Prepare raw materials according to the composition of low-carbon aluminum-silicon casting alloy, and prepare refining agent, modifier and grain refiner for later use;

[0049] 2) Smelting: After heating and melting the raw material Al, aluminum melt is obtained. The composition of the aluminum melt is determined and the amount of each component is calculated. Then, other raw materials except Mg are added to the aluminum melt until it melts. Then, raw material Mg is added. After Mg melts, it is stirred evenly to obtain a homogeneous alloy melt.

[0050] 3) Refining and modification: After refining the homogeneous alloy melt by adding a refining agent, a modifier is added to the refined alloy melt for modification to obtain a modified alloy melt. The refining agent is preferably RJ-1 refining agent, and its addition amount is 0.5-1% of the total weight of the homogeneous alloy melt. The modifier is Al-10Co master alloy and Al-10Sr master alloy.

[0051] 4) Transfer and Degassing: The modified alloy melt is transferred to a transfer container. Argon gas is injected into the alloy melt using a degassing machine for degassing. Then, slag is removed, a grain refiner is added, and the alloy melt is poured into the machine-side furnace of a die-casting machine or gravity casting machine. The argon gas flow rate is 0.2-0.3 m³ / h. 3 / h, the grain refiner is a commercially available AlTiB or AlTiC alloy, and the amount added is 0.05-0.25% of the total mass of the alloy melt;

[0052] 5) Die casting: Die casting is performed using a die casting machine to obtain low-carbon aluminum-silicon castings.

[0053] When preparing T6 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are subjected to solution treatment and aging treatment.

[0054] When preparing T5 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are subjected to aging treatment.

[0055] Specifically, the solution treatment involves holding the solution at 500-550℃ for 2-12 hours.

[0056] The aging process specifically involves maintaining the temperature at 130-180℃ for 2-12 hours.

[0057] As a preferred step of the scheme, step 5) also includes: cooling the low-carbon aluminum-silicon casting obtained after die casting;

[0058] Specifically, when preparing the T6 state low-carbon aluminum-silicon casting alloy, vacuum high-pressure die casting is used in step 5), and the cooling treatment is air cooling or water quenching; when preparing the T5 state low-carbon aluminum-silicon casting alloy, the cooling treatment is water quenching.

[0059] The following provides a selection scheme for the composition and raw materials of low-carbon aluminum-silicon casting alloys. In actual production, the scheme can be adjusted according to the actual situation, and no specific restrictions are imposed.

[0060] Among them, the raw material Al can be one or more of electrolytic aluminum ingots, remelted aluminum ingots or cast aluminum alloy ingots, or it can be a mixture of recycled materials or recovered waste from the factory and Al ingots.

[0061] The raw material Si can be metallic silicon and / or aluminum-silicon master alloy. When metallic silicon is used as the raw material for silicon, the silicon block can be laid into the bottom of the furnace first, and then aluminum ingots can be added for melting. The modifier can also be added to the aluminum melt along with other raw materials.

[0062] The raw material Mg can be industrial pure magnesium ingots;

[0063] The raw material Cu can be selected from aluminum-copper master alloys and / or copper additives;

[0064] The raw material Zn can be industrial pure zinc ingots;

[0065] The raw material Fe can be selected from aluminum-iron master alloys and / or iron additives;

[0066] The raw material Mn can be selected from aluminum-manganese master alloys and / or manganese additives;

[0067] The raw material Zr can be selected from aluminum-zirconium master alloys and / or zirconium additives;

[0068] The raw material Ti can be selected from aluminum-titanium master alloys and / or titanium additives;

[0069] The raw material Cr can be selected from aluminum-chromium master alloys and / or chromium additives;

[0070] The raw material Co can be selected from aluminum-cobalt master alloys and / or cobalt additives;

[0071] The raw material Sr can be an aluminum-strontium master alloy;

[0072] The raw material Re can be La or / and Ce. The raw material Re is an aluminum-lanthanum master alloy or an aluminum-cerium master alloy, or an aluminum-(lanthanum-cerium mixed rare earth) master alloy.

[0073] In step 3), if the Co and Sr modifiers are not added in step 3), they can be added to the aluminum melt together with Mg in step 2), or they can be added to the aluminum melt together with other raw materials other than Mg.

[0074] The present invention will be further explained and described below with specific embodiments, but these are not intended to limit the scope of protection of the present invention.

[0075] The aluminum ingots used in the following examples are Al99.70 as specified in the national standard GB / T 1196-2008 "Aluminum Ingots for Remelting", with an aluminum content of not less than 99.70 wt%. Alternatively, pre-alloyed cast aluminum alloy ingots commonly used in the casting industry can be used, such as the aluminum ingots specified in the national standard GB / T 8733-2016 "Cast Aluminum Alloy Ingots". The aluminum alloy scrap can be remelted aluminum ingots or bulk scrap such as automotive chips and aluminum shavings. All raw materials are purchased from the market.

[0076] Example 01

[0077] A cast Al-Si alloy, with chemical composition shown in Table 1, was studied. The effect of different Fe / Mn values ​​on the morphology of the iron-rich and manganese-rich phases was investigated. The preparation method includes the following steps:

[0078] 1) Material preparation: Prepare the raw materials for each component according to the content of each component in the alloy;

[0079] 2) Feeding: The Al raw material is fed into a preheated melting furnace for heating and melting;

[0080] 3) Alloying: After the aluminum raw material is completely melted, all alloying materials other than Mg and Sr are added to the furnace. After the alloying materials melt, Mg is added. After the Mg melts, the mixture is stirred evenly to obtain an aluminum alloy melt. The composition of the aluminum alloy melt is measured to ensure that the alloy composition meets the requirements. Throughout the entire smelting process, the temperature of the alloy melt is controlled at 710℃.

[0081] 4) Post-melting treatment: RJ-1 refining agent is added to the aluminum alloy melt for refining. The amount added is 0.4% of the total mass of the alloy melt. Then, the aluminum slag is removed from the furnace, and Al-10Sr modifier is added for modification to obtain the modified alloy melt.

[0082] 5) Casting: to obtain cast Al-Si alloy.

[0083] Table 1: Chemical Composition of Example 01

[0084] serial number Si Mg Cu Zn Ti Fe Mn Sr Al 01a 7.0 0.35 0.2 0.2 0.15 1 0 0.02 margin 01b 7.0 0.35 0.2 0.2 0.15 0.8 0.2 0.02 margin 01c 7.0 0.35 0.2 0.2 0.15 0.6 0.4 0.02 margin 01d 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.02 margin 01e 7.0 0.35 0.2 0.2 0.15 0.4 0.6 0.02 margin 01f 7.0 0.35 0.2 0.2 0.15 0.2 0.8 0.02 margin 01g 7.0 0.35 0.2 0.2 0.15 0 1.0 0.02 margin

[0085] Studies have found that the morphology of the Al15(FeMn)3Si2 phase varies depending on the Fe / Mn ratio in the alloy composition. Metallographic analysis shows that in Al-Si alloys with a Fe+Mn content of 1, the phase morphology is needle-like or lamellar when the alloy contains little or no Mn; even in the 0.2% Mn sample O2b, the iron-rich phase still exhibits a needle-like or lamellar morphology. Further addition of Mn and reduction of Fe content gradually transforms the needle-like or lamellar morphology into a petal-like or coral-like morphology; when the Fe and Mn contents are essentially the same, the phase morphology is generally petal-like, coral-like, or fishbone-like; further increasing the Mn content and decreasing the Fe content causes the phase morphology to transform into a blocky morphology; when Mn is further increased and the Fe content is reduced to trace amounts or even zero, the phase morphology remains blocky. Figure 1 This is the morphology of the Al15(FeMn)3Si2 phase in Example 1d (0.5Fe, 0.5Mn).

[0086] Example 02

[0087] A cast Al-Si alloy, the chemical composition of which is shown in Table 2, is prepared by the same method as in Example 01, except that the raw material component Co is added and the amount of Sr added is increased.

[0088] Table 2: Chemical Composition of Example 02

[0089] serial number Si Mg Cu Zn Ti Fe Mn Co Sr Cr Al 02a 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0 0.12 0 margin 02b 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.15 0 0 margin 02c 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0 0 0.15 margin 02d 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.05 0.10 0 margin 02e 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.07 0.08 0 margin 02f 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.05 0.07 0 margin 02g 7.0 0.35 0.2 0.2 0.15 0.5 0.5 0.05 0.05 0 margin

[0090] Studies have found that Co and Sr can effectively refine phases such as Al15(FeMn)3Si2. The morphology of the Al15(FeMn)3Si2 phase varies after refinement depending on the Fe / Mn ratio in the alloy composition. Needle-like and blocky Al15(FeMn)3Si2 phases remain needle-like or blocky after refinement, only smaller in size. However, petal-like, coral-like, or fishbone-like Al15(FeMn)3Si2 phases become small blocks after refinement. Figure 2 This shows the morphology of Al15(FeMn)3Si2 phase after phase transformation with 0.07% Co + 0.08% Sr. (Comparison) Figure 1 and Figure 2 It can be observed that after modification treatment with 0.07% Co + 0.08% Sr, Al15(FeMn)3Si2 was significantly refined. Cr also has a refining effect on phases such as Al15(FeMn)3Si2, but the effect is not as significant as that of Co and / or Sr.

[0091] Example 1

[0092] A low-carbon aluminum-silicon casting alloy is prepared by the following method:

[0093] 1) Material preparation: Prepare the raw materials for each component according to the content of each component of the alloy listed in Table 3;

[0094] 2) Smelting: After heating and melting the raw material Al, aluminum melt is obtained. The composition of the aluminum melt is determined and the amount of each component is calculated. Then, other raw materials except Mg are added to the aluminum melt until it melts. Then, raw material Mg is added. After Mg melts, it is stirred evenly to obtain a homogeneous alloy melt. In the entire smelting process, the temperature of the alloy melt is controlled at 720℃.

[0095] 3) Refining and modification: A refining agent is added to the homogeneous alloy melt for refining treatment. The amount of refining agent added is 0.6% of the total weight of the casting alloy melt. Then, Co and Sr modifiers are added for modification to obtain the modified alloy melt. The Co and Sr modifiers are Al-10Co master alloy and Al-10Sr master alloy, respectively.

[0096] 4) Transfer and degassing: The modified alloy melt is degassed, and then the grain refiner AlTiB alloy is added. The amount of AlTiB alloy added is 0.1% of the total weight of the casting alloy melt. After stirring evenly, slag is removed, and then it is placed at 720℃ for a certain period of time before casting. The casting process adopts high-pressure die casting. After die casting, aluminum-silicon cast alloy castings are obtained, which are as-cast low-carbon cast Al-Si alloys.

[0097] 5) The obtained Al-Si alloy products were subjected to room temperature tensile property tests. The room temperature tensile properties are shown in Table 3.

[0098] Example 2-12

[0099] Examples 2-12 are the same as Example 1, except that the alloy composition is different. The alloy composition and the room temperature tensile properties of the prepared castings are shown in Table 3.

[0100] Elements Fe and Mn can effectively prevent castings from sticking to the mold, which is crucial for die casting production. Therefore, Fe and Mn are essential elements in die casting alloys. However, Fe, Mn, and Si form the Al15(FeMn)3Si2 phase, which appears as coarse needle-like, lamellar, or Chinese character-shaped structures, severely impairing the mechanical properties of the alloy. The ratio of Fe to Mn has a significant impact on the morphology of the Al15(FeMn)3Si2 phase. When the ratio of Fe to Mn is close, the morphology of the Al15(FeMn)3Si2 phase is petal-like, coral-like, or fishbone-like, which can mitigate the damage to mechanical properties.

[0101] Sr is a modifier for hypoeutectic Al-Si alloys, which can modify the eutectic Si phase and significantly refine it. The amount of Sr is generally controlled at 0.02-0.04%. High Sr content can effectively refine the Al15(FeMn)3Si2 phase. Especially when the ratio of Fe to Mn is close, the morphology of the Al15(FeMn)3Si2 phase is petal-like, coral-like, or fishbone-like. Under the combined modification effect of Co and Sr, the petal-like, coral-like, or fishbone-like phases are transformed into small blocks, which can further reduce the damage to the mechanical properties of Al15(FeMn)3Si2.

[0102] Examples 13-24

[0103] Examples 13-24 are the same as Example 1, except that the alloy composition is different and the castings were heat-treated after die casting. The alloy composition, heat treatment process, and room temperature tensile properties of the prepared castings are shown in Table 4.

[0104] Table 3: Chemical composition (wt%) and as-cast properties of die-cast alloys

[0105]

[0106]

[0107] *: Re represents Ce+La mixed rare earth elements; UTS represents tensile strength in MPa; YS represents yield strength in MPa; El represents elongation in %.

[0108] Table 4: Chemical composition (wt%) and heat-treated properties of die-cast alloys

[0109]

[0110] *: Solution treatment refers to the temperature and time (°C / h) of the solution treatment process; aging refers to the temperature and time (°C / h) of the aging process; Re is Ce+La mixed rare earth; UTS is tensile strength in MPa; YS is yield strength in MPa; E1 is elongation in %. Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0111] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A low-carbon aluminum-silicon casting alloy, characterized in that, The low-carbon aluminum-silicon casting alloy is made of the following components by weight percentage: The composition is as follows: Si 6.5-10.0%, Mg 0-0.8%, Cu 0-1.5%, Zn 0-1.5%, Fe 0.25-0.7%, Mn 0.3-0.8%, Ti 0-0.25%, Zr 0-0.25%, RE 0-0.25%, Co 0.02-0.25%, Sr 0.02-0.25%, with the balance being Al and impurities, wherein the individual impurity element is ≤0.1% and the total impurity is ≤1.0%. The mass ratio of Fe to Mn is 1:(0.7-1.5), and Fe and Mn account for 0.6-1.5% of the alloy by mass percentage. The low-carbon aluminum-silicon casting alloy has a tensile strength of 229-365 MPa, a yield strength of 112-229 MPa, and an elongation of 8.3-13.5%.

2. The low-carbon aluminum-silicon casting alloy according to claim 1, characterized in that, The low-carbon aluminum-silicon casting alloy also contains Cr, and the Cr content is 0-0.25% by mass percentage.

3. A method for preparing the low-carbon aluminum-silicon casting alloy according to any one of claims 1-2, characterized in that, Includes the following steps: 1) Material preparation: Prepare raw materials according to the composition of the low-carbon aluminum-silicon casting alloy, and prepare refining agent, modifier and grain refiner for later use; 2) Smelting: After heating and melting the raw material Al, aluminum melt is obtained. The composition of the aluminum melt is determined and the amount of each component is calculated. Then, other raw materials except Mg are added to the aluminum melt until it melts. Then, raw material Mg is added. After Mg melts, it is stirred evenly to obtain a homogeneous alloy melt. 3) Refining and modification: After refining the homogeneous alloy melt by adding a refining agent, a modifier is added to the refined alloy melt for modification to obtain a modified alloy melt. 4) Transfer and degassing: The modified alloy melt is transferred to a transfer container, where argon gas is injected into the alloy melt to degas it using a degassing machine. Then, slag is removed, a grain refiner is added, and the alloy melt is poured into the side furnace of the die-casting machine. 5) Die casting: Die casting is performed using a die casting machine to obtain low-carbon aluminum-silicon castings.

4. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, It also includes the following steps: When preparing T6 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are subjected to solution treatment and aging treatment. When preparing T5 state low carbon aluminum silicon casting alloy, the die-cast low carbon aluminum silicon castings are only subjected to aging treatment. Specifically, the solution treatment involves holding the solution at 500-550℃ for 2-12 hours. The aging process specifically involves maintaining the temperature at 130-180℃ for 2-12 hours.

5. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, Step 5) also includes: cooling the low-carbon aluminum-silicon casting obtained after die casting; The cooling process is either air cooling or water quenching. When preparing the T5 state low-carbon aluminum-silicon casting alloy, the cooling treatment is water quenching.

6. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, The refining agent is RJ-1 refining agent, and the amount of the refining agent added is 0.5-1% of the total weight of the homogeneous alloy melt.

7. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, The modifier is an Al-10Co master alloy and an Al-10Sr master alloy, used in combination, with the sum of the mass percentages of Co and Sr being 0.1-0.3%.

8. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, The grain refiner is an AlTiB or AlTiC alloy, and the amount added is 0.05-0.25% of the total mass of the alloy melt.

9. The method for preparing the low-carbon aluminum-silicon casting alloy according to claim 3, characterized in that, The argon gas injection flow rate is 0.2-0.3 m³ / h. 3 / h.

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