A sand-mold gravity casting aluminum alloy and preparation method thereof

Abstract

The present invention belongs to the field of nonferrous metal materials and their processing, and specifically relates to a sand-mold gravity casting aluminum alloy, characterized in that the cast aluminum alloy includes the following elements by mass percentage: 3.0-5.0wt.% Mg, 4.0-7.0wt.% Si, 0.5-0.7wt.% Mn, 0.1-0.2wt.% Ti, 0.01-0.04wt.% Sr, 0.15-0.4wt.% RE, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al. Compared with the prior art, the aluminum alloy material prepared by the present invention has both good fluidity and toughness. While the present invention improves the casting performance of the alloy by an alloying method, it also improves the mechanical properties of the alloy, prepares a high-magnesium and high-silicon aluminum alloy with better performance and different from the current traditional Al-Mg series (high magnesium and low silicon) and Al-Si series (high silicon and low magnesium) aluminum alloys, and is suitable for sand casting, which can meet the requirements of the aluminum alloy performance in the field of automobile lightweighting.

Description

Technical Field

[0001] The invention belongs to the field of nonferrous metal materials and processing thereof, and particularly relates to a sand mold gravity casting aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum alloy is one of the most widely used lightweight structural materials. It has the characteristics of low density, good mechanical properties, and good processing performance. It is widely used in the fields of transportation and aerospace. In recent years, the demand for aluminum alloys with high strength and toughness in the field of automobile lightweighting has been increasing, and the application of aluminum alloys in the automotive field is mainly cast aluminum alloys. Therefore, it is urgent to develop a new type of high-strength and tough cast aluminum alloy with good casting performance suitable for the application in the field of automobile lightweighting.

[0003] At present, cast aluminum alloys are mainly Al-Si aluminum alloys. Although Al-Si aluminum alloys have good casting properties, the alloy strength is medium and the plasticity is poor. Although the strength and toughness of Al-Si aluminum alloys can be further improved by alloying, the improvement effect is limited. Al-Mg aluminum alloys have good strength and plasticity and good corrosion resistance, but their casting performance is poor. In response to this problem, Chinese patent CN 108754256 A effectively improves the casting performance of the alloy by adding Si elements to Al-Mg aluminum alloys, and develops a high-toughness die-cast aluminum-magnesium-silicon aluminum alloy with low silicon content and non-heat treatment strengthening. In addition, the Magsimal-59 alloy (patent publication number: EP0853133B1) developed by German Rhine Company has a good combination of strength and toughness. However, the Al-Mg-Si aluminum alloy currently used is easy to form eutectic silicon, primary silicon and Mg2Si after adding silicon, and as the silicon content increases, their content and size also increase accordingly. Although the casting performance of the alloy is improved to a certain extent, it is not conducive to the improvement of the mechanical properties of the alloy. Therefore, for the currently commercial Al-Mg-Si aluminum alloy, in order to avoid the formation of primary silicon and eutectic silicon, the mass ratio of Mg / Si in the alloy is controlled to be above 1.73, so the silicon content in the alloy is relatively low (about 2wt.%). However, if the eutectic silicon, primary silicon and Mg2Si formed in the modified alloy can be refined while increasing the silicon content in the alloy to improve the casting performance of the alloy, it can achieve a win-win goal of greatly improving the casting performance of the alloy and improving the mechanical properties of the alloy.

[0004] Therefore, developing a casting aluminum alloy that has both good casting performance and good strength and toughness can promote the development and application of casting aluminum alloys. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a sand-mold gravity casting aluminum alloy having both good casting performance and good toughness and a preparation method thereof. The casting performance of the alloy is improved by increasing the Si content in the alloy, and the mechanical properties of the alloy are improved by increasing the Mg content in the alloy, and a casting aluminum alloy containing eutectic silicon, primary silicon and Mg2Si strengthening phases is prepared, and the eutectic silicon, primary silicon and Mg2Si are refined and modified by rare earth (one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Y) and strontium, and the preparation process and method thereof are studied to prepare a casting aluminum alloy suitable for sand-mold gravity casting.

[0006] In a first aspect, the present invention provides a sand gravity casting aluminum alloy, characterized in that the casting aluminum alloy comprises the following elements in percentage by mass: 3.0-5.0wt.% Mg, 4.0-7.0wt.% Si, 0.5-0.7wt.% Mn, 0.1-0.2wt.% Ti, 0.01-0.04wt.% Sr, 0.15-0.4wt.% RE, wherein the RE is selected from one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb and Y, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0007] Preferably, the high-strength and toughness metal mold gravity casting aluminum alloy provided by the present invention includes the following elements by mass percentage: 4.0-5.0wt.% Mg, 6.0-7.0wt.% Si, 0.5-0.7wt.% Mn, 0.1-0.2wt.% Ti, 0.02-0.04wt.% Sr, 0.3-0.4wt.% RE, wherein the RE is selected from one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb and Y, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al; more preferably, the element combination of the RE element is, for example:

[0008] a. One or more of La, Ce and Y;

[0009] b.Nd, Sm and Yb;

[0010] c. Ce, Pr, Eu and Gd; or

[0011] d.La, Y, Dy and Er.

[0012] According to the present invention, the present invention reasonably designs and adjusts the silicon content in the alloy, as well as the modifier and the refiner, controls the morphology, size, and distribution of eutectic silicon, primary silicon, and Mg2Si in the alloy, and inhibits the formation of coarse eutectic silicon, primary silicon, and Mg2Si, thereby preparing a new type of aluminum-magnesium-silicon die-casting aluminum alloy with good casting performance and good toughness. The present invention fully utilizes the characteristics of Al-Si series (excellent casting performance) and Al-Mg series (excellent mechanical properties) alloys, and prepares a casting aluminum alloy with good casting performance and high toughness through the refinement and modification of alloying elements.

[0013] The cooling rate of sand casting (1-10℃ / s) is lower than that of metal mold gravity casting (10-30℃ / s) and pressure casting (30-100℃ / s). The longer the alloy solidification process, the more fully the compounds in the alloy grow, the larger the size, and the lower the requirement for alloy fluidity. Therefore, the alloy element content in sand casting alloy is lower than that in alloy used for metal mold gravity casting and pressure casting.

[0014] The Mg element in the alloy balances the strength and plasticity of the alloy through solid solution strengthening and the second phase strengthening effect of forming compounds in the alloy; the Si element in the alloy can improve the mechanical properties of the alloy, and the casting performance of the alloy will gradually improve with the increase of Si content, but when its content is too high, a large number of larger eutectic silicon, primary silicon and Mg2Si compounds will be formed, and the presence of these compounds will split the matrix, thereby reducing the strength and plasticity of the alloy; the Mn element in the alloy can improve the corrosion resistance of the alloy, and form compounds with heavy metal elements such as Fe in the alloy to reduce the toxic effect of the impurity element Fe; the Ti element in the alloy can refine the grains of the aluminum alloy and improve the mechanical properties of the alloy Energy; Sr and RE (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Y) in the alloy can act as modifiers to refine and modify the eutectic silicon, primary silicon and Mg2Si formed in the alloy. Sr, as an adsorptive modifier, will adsorb on the (111) crystal plane of Si, thereby inhibiting the growth of Si on the (111) crystal plane, and has a spheroidizing and refining effect on the primary silicon and eutectic silicon, thereby improving the primary silicon and eutectic silicon. The introduction of rare earth elements will form Al4RE and Al2RE compounds in the alloy, which can act as heterogeneous nucleation particles to refine the eutectic silicon, primary silicon and Mg2Si, and also refine the grains of the alloy. Therefore, the composite addition of Sr and RE (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Y) can significantly improve the microstructure of the alloy, thereby enabling the alloy to have excellent mechanical properties while obtaining better casting performance.

[0015] The main strengthening phase in Al-Mg alloys is Mg2Si, and the main strengthening phases in Al-Si alloys are eutectic silicon and primary silicon. The alloy system involved in the present invention combines the advantages of Al-Mg alloys and Al-Si alloys. Its strengthening phases are mainly composed of eutectic silicon, primary silicon and Mg2Si. By introducing metamorphic elements and other alloying elements, the strengthening phases such as eutectic silicon, primary silicon and Mg2Si in the metamorphic alloy are refined, and the microstructure of the alloy is optimized, so that the comprehensive performance of the alloy involved in the present invention is better than that of conventional Al-Mg alloys and Al-Si alloys.

[0016] In a second aspect, the present invention further provides a method for preparing the sand mold gravity casting aluminum alloy as described above, comprising the following steps:

[0017] Step (1), preheating raw materials: preheating pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy respectively;

[0018] Step (2), smelting the alloy: melting the raw materials preheated in step (1), protecting the melt after the alloy is completely melted, and then refining and cooling to obtain an aluminum alloy melt, or casting to obtain an aluminum alloy ingot;

[0019] Step (3), casting: remelting the aluminum alloy melt or aluminum alloy ingot obtained in step (2) and then performing sand mold gravity casting to obtain an aluminum alloy casting;

[0020] Step (4), heat treatment: subjecting the aluminum alloy casting obtained in step (3) to solid solution and aging heat treatment.

[0021] Preferably, in step (1), the aluminum rare earth master alloy is selected from one or more of an aluminum lanthanum master alloy, an aluminum cerium master alloy, an aluminum praseodymium master alloy, an aluminum neodymium master alloy, an aluminum samarium master alloy, an aluminum europium master alloy, an aluminum gadolinium master alloy, an aluminum dysprosium master alloy, an aluminum erbium master alloy, an aluminum ytterbium master alloy and an aluminum yttrium master alloy.

[0022] Preferably, in step (1), the preheating temperature is 200-250° C. and the preheating time is 1-2 h.

[0023] Preferably, in step (2), melting the raw materials preheated in step (1) comprises: melting the preheated pure Al, then heating to 720-750°C and adding the preheated aluminum-silicon master alloy and aluminum-manganese master alloy for melting; after the master alloy is completely melted, cooling to 680-700°C and adding the preheated pure magnesium, aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy, and pressing them into the bottom of the crucible with a bell jar for melting.

[0024] Preferably, in step (2), protecting the melt comprises: sprinkling a covering agent on the surface of the melt; the covering agent is a sodium salt-free covering agent for smelting aluminum-magnesium alloys, and the added amount is 1-3% of the total mass of all raw materials.

[0025] Preferably, in step (2), refining and cooling include: heating the melt to 700-730°C and then adding a refining agent for refining, standing at 700-720°C after refining, cooling to 680-700°C and then skimming off scum, and finally cooling to room temperature at a cooling rate of 1-10°C / s; the refining agent is a sodium salt-free aluminum-magnesium alloy refining agent, and the amount added is 1-5% of the total mass of all raw materials.

[0026] Preferably, in step (3), the aluminum alloy melt or aluminum alloy ingot is remelted and then cast into a sand mold preheated to 200-300°C at 680-700°C, cooled and solidified to obtain an aluminum alloy casting.

[0027] Preferably, in step (4), the solution treatment is to keep the casting at 520-540°C for 20-30 hours, and then cool it in 25°C water, and the aging treatment is to keep the casting after solution treatment at 170-200°C for 2-10 hours, and the cooling method after aging treatment is air cooling.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) Compared with the prior art, the aluminum alloy material prepared by the present invention has better fluidity and toughness. The present invention improves the alloy casting performance by alloying method, and also improves the mechanical properties of the alloy, and prepares a high-magnesium and high-silicon aluminum alloy with better performance and different from the current traditional Al-Mg series (high magnesium and low silicon) and Al-Si series (high silicon and low magnesium) aluminum alloys, and is suitable for sand casting, which can meet the requirements of aluminum alloy performance in the field of automobile lightweighting.

[0030] (2) The addition of Si significantly improves the casting properties of the alloy. At the same time, eutectic silicon, primary silicon and Mg2Si are inevitably formed in the alloy, and their content and size increase with the increase of Si content, which has a splitting effect on the matrix. However, the introduction of RE and Sr elements refines and modifies the eutectic silicon, primary silicon and Mg2Si in the alloy, optimizes their morphology and size distribution, and reduces their splitting effect on the aluminum matrix, thereby preparing a sand casting aluminum alloy with good casting properties and good strength and toughness.

[0031] (3) The preparation method of the present invention is simple, has good process stability and high process controllability BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a microstructure photograph of the sand mold gravity cast aluminum alloy obtained in Example 7 of the present invention.

[0033] Figure 2 This is the fluidity test result of the sand mold gravity casting aluminum alloy obtained in Example 7 of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the embodiments. The various master alloys used in the present invention are all commercially available products. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. All equivalent changes made using the present invention specification, or directly or indirectly applied in other related technical fields, are included in the protection scope of the present invention patent.

[0035] Embodiment 1:

[0036] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.01wt.% Sr, 0.15wt.% La, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0037] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 1 of the present invention are listed in Table 1.

[0038] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0039] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0040] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0041] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0042] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0043] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0044] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0045] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520° C. for 30 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 170° C. for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0046] The room temperature mechanical properties and fluidity test results of Example 1 of the present invention are shown in Table 2.

[0047] Embodiment 2:

[0048] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.01wt.% Sr, 0.1wt.% La, 0.05wt.% Ce, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0049] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 2 of the present invention are listed in Table 1.

[0050] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0051] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0052] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0053] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0054] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0055] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0056] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0057] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520° C. for 30 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 170° C. for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0058] The room temperature mechanical properties and fluidity test results of Example 2 of the present invention are shown in Table 2.

[0059] Embodiment 3:

[0060] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, 0.15wt.% La, 0.05wt.% Ce, 0.1wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0061] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 3 of the present invention are listed in Table 1.

[0062] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0063] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0064] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0065] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0066] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0067] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0068] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0069] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 530° C. for 25 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 185° C. for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0070] The room temperature mechanical properties and fluidity test results of Example 3 of the present invention are shown in Table 2.

[0071] Embodiment 4:

[0072] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, 0.1wt.% Nd, 0.1wt.% Sm, 0.1wt.% Yb, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0073] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 4 of the present invention are listed in Table 1.

[0074] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0075] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0076] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0077] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0078] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0079] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0080] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0081] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 530° C. for 25 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 185° C. for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0082] The room temperature mechanical properties and fluidity test results of Example 4 of the present invention are shown in Table 2.

[0083] Embodiment 5:

[0084] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.04wt.% Sr, 0.1wt.% Ce, 0.05wt.% Pr, 0.1wt.% Eu, 0.15wt.% Gd, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0085] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 5 of the present invention are listed in Table 1.

[0086] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0087] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0088] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0089] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0090] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0091] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0092] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0093] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0094] The room temperature mechanical properties and fluidity test results of Example 5 of the present invention are shown in Table 2.

[0095] Embodiment 6:

[0096] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.04wt.% Sr, 0.1wt.% La, 0.05wt.% Er, 0.1wt.% Dy, 0.15wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0097] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 6 of the present invention are listed in Table 1.

[0098] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0099] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 250° C. for 1 hour.

[0100] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0101] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0102] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0103] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0104] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0105] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0106] The room temperature mechanical properties and fluidity test results of Example 6 of the present invention are shown in Table 2.

[0107] Embodiment 7:

[0108] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 3wt.% Mg, 4wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.01wt.% Sr, 0.05wt.% La, 0.1wt.% Ce, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0109] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 7 of the present invention are listed in Table 1.

[0110] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0111] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0112] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 735 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 690 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0113] (3) Refinement and modification: When the melt temperature reaches 690 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0114] (4) Refining: The alloy melt is heated to 720 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 15 minutes.

[0115] (5) Casting: After refining, the aluminum alloy melt is cooled to 690°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 690°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0116] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0117] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520° C. for 30 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 185° C. for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0118] The room temperature mechanical properties and fluidity test results of Example 7 of the present invention are shown in Table 2.

[0119] Embodiment 8:

[0120] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 3wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, 0.05wt.% La, 0.1wt.% Ce, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0121] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 8 of the present invention are listed in Table 1.

[0122] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0123] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0124] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 735 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 690 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0125] (3) Refinement and modification: When the melt temperature reaches 690 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0126] (4) Refining: The alloy melt is heated to 720 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 15 minutes.

[0127] (5) Casting: After refining, the aluminum alloy melt is cooled to 690°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 690°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0128] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0129] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 530°C for 25 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0130] The room temperature mechanical properties and fluidity test results of Example 8 of the present invention are shown in Table 2.

[0131] Embodiment 9:

[0132] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 4wt.% Mg, 7wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.02wt.% Sr, 0.15wt.% La, 0.1wt.% Ce, 0.1wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0133] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 9 of the present invention are listed in Table 1.

[0134] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0135] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0136] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 735 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 690 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0137] (3) Refinement and modification: When the melt temperature reaches 690 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0138] (4) Refining: The alloy melt is heated to 720 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After the refining is completed, the mixture is allowed to stand for 10 minutes.

[0139] (5) Casting: After refining, the aluminum alloy melt is cooled to 690°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 690°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0140] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0141] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 170°C for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0142] The room temperature mechanical properties and fluidity test results of Example 9 of the present invention are shown in Table 2.

[0143] Embodiment 10:

[0144] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 4wt.% Mg, 7wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.04wt.% Sr, 0.1wt.% Nd, 0.1wt.% Sm, 0.1wt.% Yb, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0145] The weight percentages of the components of a sand-mold gravity casting aluminum alloy according to Example 10 of the present invention are listed in Table 1.

[0146] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0147] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0148] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 735 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 690 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0149] (3) Refinement and modification: When the melt temperature reaches 690 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0150] (4) Refining: The alloy melt is heated to 720 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After the refining is completed, the mixture is allowed to stand for 10 minutes.

[0151] (5) Casting: After refining, the aluminum alloy melt is cooled to 690°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 690°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0152] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0153] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 170°C for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0154] The room temperature mechanical properties and fluidity test results of Example 10 of the present invention are shown in Table 2.

[0155] Embodiment 11:

[0156] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 5wt.% Mg, 4wt.% Si, 0.6wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, 0.1wt.% La, 0.05wt.% Ce, 0.1wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0157] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 11 of the present invention are listed in Table 1.

[0158] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0159] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0160] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0161] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0162] (4) Refining: The alloy melt is heated to 700 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After the refining is completed, the refining agent is allowed to stand for 10 minutes.

[0163] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0164] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0165] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520°C for 30 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0166] The room temperature mechanical properties and fluidity test results of Example 11 of the present invention are shown in Table 2.

[0167] Embodiment 12:

[0168] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 5wt.% Mg, 4wt.% Si, 0.6wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, 0.1wt.% Nd, 0.1wt.% Sm, 0.1wt.% Yb, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0169] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 12 of the present invention are listed in Table 1.

[0170] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0171] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0172] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0173] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0174] (4) Refining: The alloy melt is heated to 700 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After the refining is completed, the refining agent is allowed to stand for 10 minutes.

[0175] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0176] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0177] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520°C for 30 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0178] The room temperature mechanical properties and fluidity test results of Example 12 of the present invention are shown in Table 2.

[0179] Embodiment 13:

[0180] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 5wt.% Mg, 6wt.% Si, 0.7wt.% Mn, 0.2wt.% Ti, 0.02wt.% Sr, 0.15wt.% La, 0.1wt.% Ce, 0.1wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0181] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 13 of the present invention are listed in Table 1.

[0182] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0183] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0184] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0185] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0186] (4) Refining: Heat the alloy melt to 700 degrees Celsius, add a refining agent (aluminum-magnesium alloy refining agent without sodium salt), and use a bell jar to press it into the melt to allow it to react fully. After refining, let it stand for 15 minutes.

[0187] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0188] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0189] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 170°C for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0190] The room temperature mechanical properties and fluidity test results of Example 13 of the present invention are shown in Table 2.

[0191] Embodiment 14:

[0192] The weight percentages of the components of a sand gravity casting aluminum alloy in this embodiment are: 5wt.% Mg, 6wt.% Si, 0.7wt.% Mn, 0.2wt.% Ti, 0.03wt.% Sr, 0.1wt.% Nd, 0.1wt.% Sm, 0.1wt.% Yb, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0193] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 14 of the present invention are listed in Table 1.

[0194] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0195] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0196] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0197] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0198] (4) Refining: Heat the alloy melt to 700 degrees Celsius, add a refining agent (aluminum-magnesium alloy refining agent without sodium salt), and use a bell jar to press it into the melt to allow it to react fully. After refining, let it stand for 15 minutes.

[0199] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0200] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0201] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 170°C for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0202] The room temperature mechanical properties and fluidity test results of Example 14 of the present invention are shown in Table 2.

[0203] Embodiment 15:

[0204] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 5wt.% Mg, 7wt.% Si, 0.7wt.% Mn, 0.2wt.% Ti, 0.04wt.% Sr, 0.1wt.% Ce, 0.05wt.% Pr, 0.1wt.% Eu, 0.15wt.% Gd, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0205] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 15 of the present invention are listed in Table 1.

[0206] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0207] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0208] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0209] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0210] (4) Refining: Heat the alloy melt to 700 degrees Celsius, add a refining agent (aluminum-magnesium alloy refining agent without sodium salt), and use a bell jar to press it into the melt to allow it to react fully. After refining, let it stand for 15 minutes.

[0211] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0212] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0213] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520°C for 30 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0214] The room temperature mechanical properties and fluidity test results of Example 15 of the present invention are shown in Table 2.

[0215] Embodiment 16:

[0216] The weight percentages of the components of a sand gravity casting aluminum alloy of the present embodiment are: 5wt.% Mg, 7wt.% Si, 0.7wt.% Mn, 0.2wt.% Ti, 0.04wt.% Sr, 0.1wt.% La, 0.05wt.% Er, 0.1wt.% Dy, 0.15wt.% Y, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0217] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy according to Example 16 of the present invention are listed in Table 1.

[0218] A casting process and heat treatment process of a sand-mold gravity casting aluminum alloy of the present embodiment comprises the following steps:

[0219] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy at 200° C. for 2 hours.

[0220] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 720 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added, and the mixture is fully stirred. When the temperature drops to 680 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After the melting is completed, the mixture is fully stirred.

[0221] (3) Refinement and modification: When the melt temperature reaches 680 degrees Celsius, add the weighed aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0222] (4) Refining: Heat the alloy melt to 700 degrees Celsius, add a refining agent (aluminum-magnesium alloy refining agent without sodium salt), and use a bell jar to press it into the melt to allow it to react fully. After refining, let it stand for 15 minutes.

[0223] (5) Casting: After refining, the aluminum alloy melt is cooled to 680°C and the scum is skimmed off to obtain an aluminum alloy melt, which is then cast at 680°C into a sand mold preheated to 300°C to obtain an aluminum alloy casting.

[0224] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0225] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520°C for 30 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 200°C for 2 hours. After aging treatment, the casting is air-cooled to room temperature.

[0226] The room temperature mechanical properties and fluidity test results of Example 16 of the present invention are shown in Table 2.

[0227] Comparative Example 1:

[0228] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy in this comparative example are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0229] The weight percentages of the components of a sand-mold gravity casting aluminum alloy of Comparative Example 1 of the present invention are listed in Table 1.

[0230] A casting process and heat treatment process of a sand mold gravity casting aluminum alloy in this comparative example comprises the following steps:

[0231] (1) Baking: Preheat pure Al, pure Mg, aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-titanium master alloy at 250°C for 1 hour.

[0232] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0233] (3) Refining: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy for refinement treatment. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0234] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0235] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0236] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0237] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 530° C. for 25 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 170° C. for 10 hours. After aging treatment, the casting is air-cooled to room temperature.

[0238] The room temperature mechanical properties and fluidity test results of Comparative Example 1 of the present invention are shown in Table 2.

[0239] Comparative Example 2:

[0240] The weight percentages of the components of a sand-mold gravity-cast aluminum alloy in this comparative example are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.03wt.% Sr, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0241] The weight percentages of the components of a sand-mold gravity casting aluminum alloy of Comparative Example 2 of the present invention are listed in Table 1.

[0242] A casting process and heat treatment process of a sand mold gravity casting aluminum alloy in this comparative example comprises the following steps:

[0243] (1) Baking materials: preheat pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, and aluminum strontium master alloy at 250° C. for 1 hour.

[0244] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0245] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy and aluminum-strontium master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0246] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0247] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0248] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0249] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 540°C for 20 hours, and then cooled in 25°C water. The casting after solution treatment is then kept at a temperature of 185°C for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0250] The room temperature mechanical properties and fluidity test results of Comparative Example 2 of the present invention are shown in Table 2.

[0251] Comparative Example 3:

[0252] The weight percentages of the components of a sand gravity casting aluminum alloy in this comparative example are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.15wt.% La, 0.05wt.% Ce, 0.1wt.% Y, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0253] The weight percentages of the components of a sand-mold gravity casting aluminum alloy of Comparative Example 3 of the present invention are listed in Table 1.

[0254] A casting process and heat treatment process of a sand mold gravity casting aluminum alloy in this comparative example comprises the following steps:

[0255] (1) Baking: Preheat pure Al, pure Mg, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, and aluminum-rare earth master alloy at 250° C. for 1 hour.

[0256] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0257] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0258] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0259] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0260] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0261] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520° C. for 30 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 185° C. for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0262] The room temperature mechanical properties and fluidity test results of Comparative Example 3 of the present invention are shown in Table 2.

[0263] Comparative Example 4:

[0264] The weight percentages of the components of a sand gravity casting aluminum alloy in this comparative example are: 4wt.% Mg, 5wt.% Si, 0.5wt.% Mn, 0.1wt.% Ti, 0.1wt.% Nd, 0.1wt.% Sm, 0.1wt.% Yb, the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al.

[0265] The weight percentages of the components of a sand-mold gravity casting aluminum alloy of Comparative Example 4 of the present invention are listed in Table 1.

[0266] A casting process and heat treatment process of a sand mold gravity casting aluminum alloy in this comparative example comprises the following steps:

[0267] (1) Baking: Preheat pure Al, pure Mg, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium master alloy, and aluminum-rare earth master alloy at 250° C. for 1 hour.

[0268] (2) Melting: Melting is carried out in a crucible resistance furnace. The inner wall of the crucible is evenly coated with coating. After drying, pure aluminum is melted. After the pure aluminum is melted, the temperature is raised to 750 degrees Celsius, and the weighed aluminum-silicon master alloy and aluminum-manganese master alloy are added and stirred thoroughly. When the temperature drops to 700 degrees Celsius, preheated pure magnesium is added and pressed into the melt with a bell jar to melt. After melting, it is stirred thoroughly.

[0269] (3) Refinement and modification: When the melt temperature reaches 700 degrees Celsius, add the weighed aluminum-titanium master alloy and aluminum-rare earth master alloy for refinement and modification. After sufficient stirring, sprinkle the sodium-free aluminum-magnesium alloy smelting covering agent on the surface of the melt.

[0270] (4) Refining: The alloy melt is heated to 730 degrees Celsius, a refining agent (aluminum-magnesium alloy refining agent without sodium salt) is added, and the refining agent is pressed into the melt using a bell jar to allow it to react fully. After refining, the mixture is allowed to stand for 10 minutes.

[0271] (5) Casting: After refining, the aluminum alloy is cooled to 700°C and the slag is skimmed off to obtain an aluminum alloy melt, which is then cast at 700°C into a sand mold preheated to 200°C to obtain an aluminum alloy casting.

[0272] (6) Casting performance test: After refining, the alloy melt cooled to 690 degrees Celsius was cast into a concentric triple helix alloy fluidity tester preheated at 200 degrees Celsius to test the fluidity of the alloy.

[0273] (7) Heat treatment: The casting obtained in step (5) is kept at a temperature of 520° C. for 30 hours, and then cooled in 25° C. water. The casting after solution treatment is then kept at a temperature of 185° C. for 6 hours. After aging treatment, the casting is air-cooled to room temperature.

[0274] The room temperature mechanical properties and fluidity test results of Comparative Example 4 of the present invention are shown in Table 2.

[0275] Table 1 Weight percentage of each component of a sand mold gravity casting aluminum alloy

[0276]

[0277]

[0278] Table 2 Room temperature mechanical properties and fluidity test results

[0279]

[0280] As can be seen from Table 1 and Table 2, the Mg content in Examples 9 to 10 and Examples 13 to 16 is 4-5wt.%, and the Si content is 6-7wt.%, and the casting performance of the obtained alloy is better than that of other examples and comparative examples. It can be seen that the high magnesium and high silicon aluminum alloy prepared by the sand mold gravity casting aluminum alloy formula of the present invention has better casting performance. As can be seen from Table 1 and Table 2, the embodiments provided by the present invention have good mechanical properties and casting properties. Increasing the Si content in the alloy can significantly improve the casting properties of the alloy. Although more large-sized primary silicon, eutectic silicon and Mg2Si are formed in the alloy with the increase of Si content, the refinement and modification of primary silicon, eutectic silicon and Mg2Si in the alloy by adding RE and Sr to the alloy makes the alloy have excellent mechanical properties while obtaining good casting properties.

Claims

1. A sand-mold gravity casting aluminum alloy, characterized in that: The cast aluminum alloy comprises the following elements by mass percentage: 3.0-5.0wt.% Mg, 4.0-7.0wt.% Si, 0.5-0.7wt.% Mn, 0.1-0.2wt.% Ti, 0.01-0.04wt.% Sr, 0.15-0.4wt.% RE, wherein RE is selected from one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb and Y, and the total amount of other impurities is less than or equal to 0.3wt.%, and the balance is Al; The preparation method of the sand mold gravity casting aluminum alloy comprises the following steps: Step (1), preheating raw materials: preheating pure Al, pure Mg, aluminum silicon master alloy, aluminum manganese master alloy, aluminum titanium master alloy, aluminum strontium master alloy, and aluminum rare earth master alloy respectively; Step (2), smelting the alloy: melting the raw materials preheated in step (1), including: melting the preheated pure Al, then heating to 720-750°C, adding the preheated aluminum-silicon master alloy and aluminum-manganese master alloy to melt, and after the master alloy is completely melted, cooling to 680-700°C, adding the preheated pure magnesium, aluminum-titanium master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy, and pressing them into the bottom of the crucible with a bell jar to melt; after the alloy is completely melted, protecting the melt, and then refining and cooling to obtain an aluminum alloy melt, or casting to obtain an aluminum alloy ingot; Step (3), casting: remelting the aluminum alloy melt or aluminum alloy ingot obtained in step (2) and then performing sand mold gravity casting to obtain an aluminum alloy casting; Step (4), heat treatment: subjecting the aluminum alloy casting obtained in step (3) to solid solution and aging heat treatment.

2. The sand mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (1), the aluminum rare earth master alloy is selected from one or more of aluminum lanthanum master alloy, aluminum cerium master alloy, aluminum praseodymium master alloy, aluminum neodymium master alloy, aluminum samarium master alloy, aluminum europium master alloy, aluminum gadolinium master alloy, aluminum dysprosium master alloy, aluminum erbium master alloy, aluminum ytterbium master alloy and aluminum yttrium master alloy.

3. The sand-mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (1), the preheating temperature is 200-250° C. and the preheating time is 1-2 h.

4. The sand-mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (2), protecting the melt includes: sprinkling a covering agent on the surface of the melt; the covering agent is a sodium salt-free covering agent for smelting aluminum-magnesium alloys, and the added amount is 1-3% of the total mass of all raw materials.

5. The sand-mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (2), refining and cooling include: heating the melt to 700-730°C and then adding a refining agent for refining, standing at 700-720°C after refining, cooling to 680-700°C and then skimming off scum, and finally cooling to room temperature at a cooling rate of 1-10°C / s; the refining agent is a sodium salt-free aluminum-magnesium alloy refining agent, and the amount added is 1-5% of the total mass of all raw materials.

6. The sand-mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (3), the aluminum alloy melt or aluminum alloy ingot is remelted and then cast into a sand mold preheated to 200-300° C. at 680-700° C., cooled and solidified to obtain an aluminum alloy casting.

7. The sand-mold gravity casting aluminum alloy according to claim 1, characterized in that: In step (4), the solution treatment is to keep the casting at 520-540°C for 20-30 hours, and then cool it in 25°C water. The aging treatment is to keep the casting after solution treatment at 170-200°C for 2-10 hours, and the cooling method after aging treatment is air cooling.

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