A production process for aluminum alloy castings without heat treatment

Abstract

The present invention provides a production process for aluminum alloy castings without heat treatment, belonging to the field of alloy technology, comprising: S1, alloy preparation; S2, smelting and refining, wherein pure aluminum ingots are melted, heated and mixed, and powder spray refining and degassing treatment are performed, with the amount of refining agent used being 0.1%-0.3% of the mass of the melt; S3, die casting, which adopts a high vacuum die casting process, an injection pressure of 80-150 MPa, a melt pouring temperature of 680-720°C, and a mold preheating temperature of 150-250°C; S4, natural aging treatment; Through a three-factor three-level orthogonal experiment, the specific parameters of refining agent addition, injection pressure, and pouring temperature were optimized. By testing the tensile strength, elongation, and hardness of the alloy, the optimal processing parameters were determined to be 0.20% refining agent, 120 MPa injection pressure, and 700°C pouring temperature. At this time, the tensile strength of the alloy increased to 389 MPa, the elongation increased to 8.5%, and the hardness increased to HV65.8, which were 9.0%, 26.8%, and 2.3% higher than those of the alloy before optimization, respectively.

Description

Technical Field

[0001] The invention belongs to the technical field of alloys, in particular to a production process for heat-treatment-free aluminum alloy castings. Background Art

[0002] Aluminum alloys are aluminum-based alloys with a certain amount of other alloying elements added. They are a type of light metal material. In addition to the general properties of aluminum, aluminum alloys also possess specific alloy properties due to the type and amount of added alloying elements. Traditional die-cast aluminum alloys require T6 heat treatment to improve their mechanical properties. However, this heat treatment process can easily lead to casting deformation, surface blistering, and high energy consumption. The pass rate for thin-walled, complex parts is particularly low, less than 85%. To avoid heat treatment defects, heat-treatment-free aluminum alloys have become a research and development focus in the industry.

[0003] Currently, a single rare earth element cannot provide a balanced balance of strength, toughness, and cost. Iron-rich phases and inclusions are not adequately controlled. At the process level, conventional refining processes require a hydrogen content of ≥0.15mL / 100gAl, and the rough injection parameters result in a high internal defect rate. At the post-processing level, the natural aging cycle is long, and the strength is insufficient, requiring reliance on heat treatment. Based on this, the present invention proposes a production process for aluminum alloy castings that does not require heat treatment. By determining the optimal process parameters through orthogonal experiments, the process improves the mechanical properties of the alloy, overcomes the limitation of traditional aluminum alloys that rely on heat treatment, reduces energy consumption, and shortens the production cycle. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems in the existing technology and to propose a production process for aluminum alloy castings without heat treatment.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A production process for aluminum alloy castings without heat treatment, comprising:

[0007] S1. Alloy preparation: The aluminum alloy comprises the following components by mass percentage:

[0008] Silicon 8.0%-12.5%; Magnesium 0.3%-1.2%; Copper 0.5%-2.0%; Manganese 0.1%-0.6%; Rare Earth Elements 0.05%-0.5%; Zirconium 0.05%-0.3%; Titanium 0.01%-0.15%; Iron ≤0.25%; Zinc ≤0.1%; Boron 0.001%-0.02%; The balance is aluminum and unavoidable impurities.

[0009] The rare earth elements include yttrium (Y) and cerium (Ce) added in combination, and the Y:Ce mass ratio is 2:1 to 4:1, forming Al8Cu4Y and Al4Ce nano-reinforced phases with a size of 50 to 200 nm;

[0010] Wherein, the mass ratio of titanium to boron is 5:1-15:1;

[0011] Wherein, the zirconium is added in the form of Al-Zr10 master alloy;

[0012] S2, smelting and refining, after melting the pure aluminum ingot, add Si, Mn, Ti master alloys in sequence, heat to 720-760℃, add Mg, Zr and other alloys, carry out powder spray refining and degassing treatment, the amount of refining agent is 0.1%-0.3% of the melt mass;

[0013] S3, die casting, using high vacuum die casting process, mold cavity vacuum ≤ 85mbar, injection speed 3.5-6.5m / s, injection pressure 80-150MPa, melt pouring temperature 680-720℃, mold preheating temperature 150-250℃;

[0014] S4, natural aging treatment, the casting is left to stand at room temperature for 24-120 hours, or combined with the paint baking process to achieve self-strengthening without additional heat treatment.

[0015] Preferably, in step S1, the rare earth element is at least one of yttrium, cerium, and lanthanum;

[0016] When yttrium and lanthanum are added simultaneously, the mass ratio of yttrium to lanthanum is 1:1-3:1.

[0017] Preferably, in step S2, the refining process adopts a composite rotary blowing process, firstly, argon + 0.5%~1% SF6 mixed gas is introduced for refining for 5~8 minutes, and then argon + 1%~3% Cl2 mixed gas is introduced for refining for 3~5 minutes. After refining, the hydrogen content of the melt is ≤0.10mL / 100gAl, and the inclusion content is ≤5 pieces / mm 2 .

[0018] Preferably, in step S3, the die casting process adopts gradient pressurization technology:

[0019] The first stage uses low-speed filling (0.5-1.5 m / s) to fill the cavity to 70% of its volume;

[0020] The second stage uses high-speed pressurization (6-8m / s) until it is full;

[0021] Among them, the third stage uses ultra-high pressure feeding (180~220MPa) to maintain pressure for 3~8 seconds.

[0022] Preferably, in step S4, the paint baking process is 100-200°C / 1-3h.

[0023] Preferably, the aluminum alloy casting is a thin-walled structural part with a wall thickness of 2 to 5 mm, which is subjected to natural aging and baking paint treatment after die casting, and has a fatigue limit of ≥140 MPa.

[0024] Compared with the existing technology, this heat treatment-free aluminum alloy casting production process has the following beneficial effects:

[0025] 1. The present invention provides a production process for aluminum alloy castings that does not require heat treatment. It uses yttrium / cerium dual rare earth to form Al8Cu4Y and Al4Ce nano-reinforcement phases, and cooperates with TiB2-Al3Ti composite cores to refine α-Al grains, so that the tensile strength reaches 389MPa and the elongation is 8.5%, avoiding heat treatment deformation.

[0026] 2. The present invention provides a production process for aluminum alloy castings that does not require heat treatment. It adopts a 720-760℃ gradient heating process to match the solubility characteristics of the intermediate alloy, ensuring uniform distribution of Si / Mn / Ti elements, and refining with argon + 1% SF6 mixed gas to achieve low hydrogen content in the melt, which is significantly better than traditional N2 refining.

[0027] 3. The present invention provides a production process for aluminum alloy castings that does not require heat treatment. Through gradient pressurization die casting, from low-speed filling to high-speed pressurization, and then to ultra-high-pressure shrinkage, internal defects are eliminated, the fatigue limit of 2-5mm thin-walled parts is improved, and the needs of long-term use of alloy workpieces are met.

[0028] 4. The present invention provides a production process for aluminum alloy castings that does not require heat treatment. It replaces the T6 process by eliminating heat treatment and using paint for self-strengthening, thereby reducing energy consumption, shortening the filling time through gradient compression, and extending the service life of the mold, thereby improving overall production efficiency.

[0029] 5. The present invention provides a production process for aluminum alloy castings that does not require heat treatment. Through a three-factor three-level orthogonal test, the amount of refining agent added (A), injection pressure (B), and pouring temperature (C) are optimized, and the optimal processing parameters are determined by testing the tensile strength (Rm) and elongation (A) of the alloy.

[0030] In summary, the present invention provides a production process for heat-treatment-free aluminum alloy castings. Through a three-factor three-level orthogonal experiment, the specific parameters of the refining agent addition, injection pressure, and pouring temperature are optimized. By testing the tensile strength, elongation, and hardness of the alloy, the optimal processing parameters are determined to be 0.20% refining agent, 120 MPa injection pressure, and 700°C pouring temperature. At this time, the tensile strength of the alloy is increased to 389 MPa, the elongation is increased to 8.5%, and the hardness is increased to HV65.8, which are 9.0%, 26.8%, and 2.3% higher than those of the alloy before optimization, respectively. DETAILED DESCRIPTION

[0031] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments. Specific embodiment one:

[0033] A production process for aluminum alloy castings without heat treatment, comprising:

[0034] S1. Alloy preparation: The aluminum alloy comprises the following components by mass percentage:

[0035] Silicon 8.0%-12.5%; Magnesium 0.3%-1.2%; Copper 0.5%-2.0%; Manganese 0.1%-0.6%; Rare Earth Elements 0.05%-0.5%; Zirconium 0.05%-0.3%; Titanium 0.01%-0.15%; Iron ≤0.25%; Zinc ≤0.1%; The balance is aluminum and unavoidable impurities;

[0036] The rare earth element is at least one of yttrium, cerium, and lanthanum. When yttrium and lanthanum are added simultaneously, the mass ratio of yttrium to lanthanum is 1:1-3:1. When Y:La=1:1-3:1, a thermally stable Al3(Y,La) phase is formed, which is beneficial to inhibiting the formation of needle-shaped β-Fe phase and improving high-temperature strength. La partially replaces the high-priced Y, reducing the rare earth cost by more than 20%.

[0037] The rare earth elements include yttrium (Y) and cerium (Ce) added in combination, and the mass ratio of Y:Ce is 2:1-4:1, forming Al8Cu4Y and Al4Ce nano-reinforced phases with a size of 50-200 nm.

[0038] It also includes 0.001%-0.02% boron, where the mass ratio of titanium to boron is 5:1-15:1, generating a TiB2+Al3Ti composite core, refining the α-Al grains to ≤25μm (≥50μm when there is no B), and improving the toughness of the casting by 25%. In addition, the upper limit of the ratio avoids excessive B to form coarse B2O3 inclusions, preventing boron poisoning.

[0039] Among them, the zirconium is added in the form of Al-Zr10 master alloy to synergistically refine the α-Al phase. The Al-Zr10 master alloy is convenient for improving the Zr solubility rate, forming Al3Zr nanoparticles, inhibiting recrystallization, and improving conductivity. The master alloy form reduces Zr oxidation loss and prevents burning.

[0040] S2. Melting and refining: After melting the pure aluminum ingot, add Si, Mn, and Ti master alloys in sequence, heat to 720-760°C, add Mg and Zr alloys, and perform powder spray refining and degassing treatment. The amount of refining agent used is 0.1%-0.3% of the melt mass;

[0041] The refining process adopts a composite rotary injection process. First, argon + 0.5%~1% SF6 mixed gas is introduced for refining for 5~8 minutes, and then argon + 1%~3% Cl2 mixed gas is introduced for refining for 3~5 minutes. After refining, the hydrogen content of the melt is ≤0.10mL / 100gAl, and the inclusion content is ≤5 pieces / mm 2 .

[0042] S3, die casting, using high vacuum die casting process, mold cavity vacuum ≤ 85mbar, injection speed 3.5-6.5m / s, injection pressure 80-150MPa, melt pouring temperature 680-720℃, mold preheating temperature 150-250℃;

[0043] The die-casting process uses gradient pressurization technology: the first stage uses low-speed filling (0.5~1.5m / s) to fill the cavity to 70% of its volume; the second stage uses high-speed pressurization (6~8m / s) to fill it; the third stage uses ultra-high pressure feeding (180~220MPa) to maintain pressure for 3~8 seconds.

[0044] S4, natural aging treatment, the casting is left at room temperature for 24-120 hours, or combined with the paint baking process (100-200℃ / 1-3h) to achieve self-strengthening, without additional heat treatment.

[0045] The aluminum alloy casting is a thin-walled structural part with a wall thickness of 2 to 5 mm. After die-casting, it is subjected to natural aging and baking paint treatment, and the fatigue limit is ≥140 MPa. Specific embodiment two:

[0047] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0048] Among them, the amount of refining agent is 0.15% of the melt mass;

[0049] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0050] The injection pressure is 100 MPa and the melt pouring temperature is 690°C.

[0051] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment three:

[0053] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0054] Among them, the amount of refining agent is 0.15% of the melt mass;

[0055] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0056] The injection pressure is 120 MPa and the melt pouring temperature is 700°C.

[0057] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment four:

[0059] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0060] Among them, the amount of refining agent is 0.15% of the melt mass;

[0061] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0062] The injection pressure is 140 MPa and the melt pouring temperature is 710°C.

[0063] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment five:

[0065] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0066] Among them, the amount of refining agent is 0.20% of the melt mass;

[0067] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0068] The injection pressure is 100 MPa and the melt pouring temperature is 700°C.

[0069] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment six:

[0071] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0072] Among them, the amount of refining agent is 0.20% of the melt mass;

[0073] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0074] The injection pressure is 120 MPa and the melt pouring temperature is 710°C.

[0075] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment seven:

[0077] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0078] Among them, the amount of refining agent is 0.20% of the melt mass;

[0079] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0080] The injection pressure is 140 MPa and the melt pouring temperature is 690°C.

[0081] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment eight:

[0083] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0084] Among them, the amount of refining agent is 0.25% of the melt mass;

[0085] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0086] The injection pressure is 100 MPa and the melt pouring temperature is 710°C.

[0087] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment nine:

[0089] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0090] Among them, the amount of refining agent is 0.25% of the melt mass;

[0091] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0092] The injection pressure is 120 MPa and the melt pouring temperature is 690°C.

[0093] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment ten:

[0095] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0096] Among them, the amount of refining agent is 0.25% of the melt mass;

[0097] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0098] The injection pressure is 140 MPa and the melt pouring temperature is 700°C.

[0099] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours. Specific embodiment eleven:

[0101] Through three-factor three-level orthogonal test, the amount of refining agent (A), injection pressure (B), and pouring temperature (C) were optimized, and the tensile strength (Rm) and elongation (A) were tested.

[0102]

[0103] Room-temperature tensile tests were performed using an electronic universal testing machine. The specimens were processed into dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) according to GB / T 228.1. The tensile rate was set at 1.0 mm / min according to ASTM E8. The stress-strain curve was collected in real time using an extensometer until the specimen broke.

[0104]

[0105] Regarding the data in the table above, the refining agent dosage regulates performance through gas reaction efficiency and melt rheology. At a 0.15% addition, insufficient SF6 content leads to incomplete decomposition, resulting in low AlF3 film coverage. This increases the melt surface tension, exceeding the ideal value, hindering hydrogen diffusion and escape, and resulting in a hydrogen content of ≥0.13 mL / 100 gAl. Honeycomb-like micropores form during solidification, becoming a crack source. The tensile strength is low, as the pores disrupt the matrix continuity, resulting in an elongation of only 6.0-7.2%. Increasing the addition to 0.20% increases the effective SF6 concentration, forming a uniform cluster of bubbles under the argon carrier flow. Hydrogen atoms adsorbed on the bubble surfaces are efficiently removed through a flotation effect, resulting in a hydrogen content of ≤0.08 mL / 100 gAl. The melt viscosity decreases, allowing inclusions to be captured and floated by the bubbles. The dense matrix increases the tensile strength to 368-389 MPa, and the elongation rises to 8.5% due to reduced dislocation slip resistance. When the addition level is further increased to 0.25%, the excessive SF6 causes a violent reaction, with sulfur reacting with Mg to form a brittle MgS phase. This increases melt viscosity, causing bubbles to merge into larger ones. During the upward movement, slag is entrained, forming slag inclusion defects. This reduces tensile strength (Rm), and the stress concentration associated with the MgS phase leads to a loss of elongation.

[0106] Injection pressure determines microstructure density through turbulence suppression and feeding pressure. When the injection pressure is low, insufficient feeding pressure during the low-speed filling phase causes defects, coarsening the α-Al grains, and resulting in tensile strength of 356-378 MPa and elongation of 6.8-8.1% (Specific Examples 2, 5, and 8). When the injection pressure is increased to 120 MPa, the alloy achieves tensile strength of 358-389 MPa and elongation of 7.3-8.5% (Specific Examples 3, 6, and 9). Further increasing the injection pressure to 140 MPa, turbulence is induced during the high-speed pressurization phase, causing gas entrainment and formation of vortexes, reducing strength to 345-368 MPa and elongation (Specific Examples 4, 7, and 10).

[0107] The pouring temperature regulates the solidification structure and phase morphology. At 690°C, the melt viscosity is high (>2.5 mPa·s), insufficient diffusion of Mn / Cu elements results in the formation of a brittle phase (Al6(Mn,Fe)), resulting in a tensile strength of 348-368 MPa and an elongation of 7.0-7.3% (Specific Examples 2, 7, and 9). At a casting temperature of 700°C, fluidity and undercooling are balanced, eutectic silicon is refined, and the nano-Al8Cu4Y strengthening phase is uniformly precipitated, resulting in a strength of 345-378 MPa and an elongation of 8.5% (Specific Examples 3, 5, and 10). When the temperature is raised to 710°C, the strength reaches 347-389 MPa (Specific Examples 4, 6, and 8).

[0108] In summary, the best combination is A2B2C3. The specific process parameters are: refining agent 0.20%, injection pressure 120MPa, and pouring temperature 710℃. At this time, the tensile strength reaches 389MPa and the elongation is 8.5%, with the best comprehensive performance. Specific embodiment 12:

[0110] Specific embodiment 12 is a mechanical property test test of the initial process and the optimized process mentioned in specific embodiments 1 to 11. The content of specific embodiment 12 is as follows:

[0111] The ratio of key elements such as Si, Mn, and Mg was previously optimized through experiments. Pre-weighing is now performed based on the mass percentage of each substance. The aluminum alloy contains the following components: 10% Si, 0.6% Mn, and 0.7% Mg. The remaining components are Cu1.5%, Y0.3%, Fe0.2%, Zn0.05%, Ti0.05%, B0.01%, Zr0.1%, and Ce0.15%, with the balance being Al. Smelting and refining are then performed. Pure aluminum ingots are added and heated to 740°C, where they are continuously smelted until the ingots are completely melted. Si, Mn, and Ti master alloys are then added in sequence. After heating to 720-760°C, Mg and Zr alloys are added. Powder spray refining and degassing are then performed, using argon + 1% SF6 as a refining agent.

[0112] Among them, the amount of refining agent is 0.20% of the melt mass;

[0113] The mixture of argon and 1% SF6 is introduced for refining for 5 to 8 minutes. High vacuum die-casting process is adopted. The vacuum degree of the mold cavity is ≤85mbar, the injection speed is 3.5-6.5m / s, and the mold preheating temperature is 150-250℃.

[0114] The injection pressure is 120 MPa and the melt pouring temperature is 710°C.

[0115] Finally, natural aging treatment is carried out and the casting is left to stand at room temperature for 24-120 hours.

[0116] The Vickers hardness of the alloy was measured using a digital microhardness tester with a test load of 1 kg and a dwell time of 15 seconds. The average of eight measurements was taken as the hardness value of the specimen. Tensile testing was conducted using an electronic universal testing machine. Dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) were machined according to GB / T 228.1. The tensile rate was set at 1.0 mm / min according to ASTM E8. Stress-strain curves were collected in real time using an extensometer until the specimen fractured.

[0117] Based on the above, the mechanical properties of the optimized alloy are significantly improved, specifically the tensile strength is increased to 389MPa, the elongation is increased to 8.5%, and the hardness is increased to HV65.8, which are increases of 9.0%, 26.8% and 2.3% respectively compared with the alloy before optimization.

[0118] Conclusion: From the above results, it can be seen that the optimal specific process parameters are: refining agent 0.20%, injection pressure 120MPa, and pouring temperature 710℃.

[0119] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A production process for aluminum alloy castings without heat treatment, characterized in that: include: S1. Alloy preparation: The aluminum alloy comprises the following components by mass percentage: Silicon 8.0%-12.5%; Magnesium 0.3%-1.2%; Copper 0.5%-2.0%; Manganese 0.1%-0.6%; Rare Earth Elements 0.05%-0.5%; Zirconium 0.05%-0.3%; Titanium 0.01%-0.15%; Iron ≤0.25%; Zinc ≤0.1%; Boron 0.001%-0.02%; The balance is aluminum and unavoidable impurities. The rare earth elements include yttrium (Y) and cerium (Ce) added in combination, and the Y:Ce mass ratio is 2:1 to 4:1, forming Al8Cu4Y and Al4Ce nano-reinforced phases with a size of 50 to 200 nm; Wherein, the mass ratio of titanium to boron is 5:1-15:1; Wherein, the zirconium is added in the form of Al-Zr10 master alloy; S2, smelting and refining, after melting the pure aluminum ingot, add Si, Mn, Ti master alloys in sequence, heat to 720-760℃, add Mg, Zr and other alloys, perform powder spray refining and degassing treatment, and the amount of refining agent is 0.2% of the melt mass; S3, die casting, using high vacuum die casting process, mold cavity vacuum ≤ 85mbar, injection speed 3.5-6.5m / s, injection pressure 120MPa, melt pouring temperature 710℃, mold preheating temperature 150-250℃; S4, natural aging treatment, the casting is left to stand at room temperature for 24-120 hours, or combined with the paint baking process to achieve self-strengthening without additional heat treatment.

2. A process for producing aluminum alloy castings without heat treatment according to claim 1, characterized in that: In step S2, the refining process adopts a composite rotary blowing process. First, argon + 0.5%~1% SF6 mixed gas is introduced for refining for 5~8 minutes, and then argon + 1%~3% Cl2 mixed gas is introduced for refining for 3~5 minutes. After refining, the hydrogen content of the melt is ≤0.10mL / 100gAl, and the inclusion content is ≤5 pieces / mm 2 .

3. The process for producing aluminum alloy castings without heat treatment according to claim 1, wherein: In step S3, the die casting process uses gradient pressurization technology: The first stage uses low-speed filling at a speed of 0.5-1.5 m / s until the mold is filled to 70% of the cavity volume. The second stage uses high-speed pressurization at a speed of 6 to 8 m / s until the cavity is completely filled. Among them, the third stage adopts ultra-high pressure feeding with a pressure of 180~220MPa and maintains the pressure for 3~8 seconds.

4. The process for producing aluminum alloy castings without heat treatment according to claim 1, wherein: In step S4, the paint baking process is 100-200°C / 1-3h.

5. The process for producing aluminum alloy castings without heat treatment according to claim 1, wherein: The aluminum alloy casting is a thin-walled structural part with a wall thickness of 2 to 5 mm. After die-casting, it is subjected to natural aging and baking paint treatment, and the fatigue limit is ≥140 MPa.

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