In the field of lightweight metal materials, aluminum alloys are widely utilized due to their high strength-to-weight ratio, excellent stiffness, good plasticity, ease of forming, and relatively low cost. Among lightweight alloys, aluminum alloys are the most extensively applied and consumed. For high-pressure equipment components, such as cover plates, achieving weight reduction without compromising structural integrity is crucial for enhancing performance and reducing production costs. The casting part under investigation is a traditional high-pressure equipment component designed years ago. With the widespread adoption of low-pressure die-casting processes, the mechanical properties of aluminum alloy casting parts have significantly improved, providing a foundation for lightweight design. Concurrently, increasing competition and rising raw material costs necessitate weight reduction in casting parts to lower manufacturing expenses. Many aluminum casting enterprises have already embarked on lightweight design initiatives. In this study, we focus on the lightweight design and casting process optimization of an aluminum alloy cover plate casting part using advanced simulation tools.
The primary objective is to reduce the weight of the casting part while ensuring it meets the stringent requirements of hydraulic failure tests. We employ ANSYS simulation software for stress analysis during hydraulic testing and AnyCasting software for simulating the filling and solidification processes during casting. By integrating these computational tools, we aim to achieve an optimal balance between weight reduction and casting quality. The methodology involves iterative design modifications, simulation validation, and experimental verification. Throughout this paper, the term “casting part” will be frequently used to emphasize the focus on the manufactured component, and we will incorporate multiple tables and equations to summarize key parameters and theoretical foundations.
The casting part in question is a cover plate with a “hat-like” geometry, featuring a flange, a central boss, and internal reinforcements. Its basic dimensions are approximately Φ625 mm in diameter and 120 mm in height, with an initial mass of 15.4 kg. The material is ZL101A aluminum alloy, subjected to T6 heat treatment to enhance its mechanical properties. The flange section has a thickness of 28 mm with 16 through-holes, while the wall thickness between the flange and the top is 10 mm, reinforced with ribs. The internal cavity includes small bosses and a central recess. This casting part is typical in high-pressure applications, where it must withstand internal pressure without failure. Therefore, any lightweight design must carefully consider stress distributions and potential failure points.
To assess the structural integrity of the casting part under operational conditions, we model the hydraulic failure test using ANSYS finite element analysis (FEA). The test involves pressurizing the internal cavity with water until failure occurs, and a passing test requires no rupture or deformation at a specified pressure. The model includes the casting part and a sealing steel plate at the flange end. The contact between the casting part and the plate is defined as “bonded,” and the mesh is generated with an element size of 7 mm, resulting in approximately 150,000 elements. The internal pressure is set to 3.25 MPa, and gravity is applied downward. The material properties for the stress simulation are summarized in Table 1.
| Component | Material | Density (kg/m³) | Young’s Modulus (GPa) | Poisson’s Ratio | Linear Expansion Coefficient (K⁻¹) |
|---|---|---|---|---|---|
| Casting Part | Aluminum Alloy (ZL101A) | 2770 | 71 | 0.33 | 2.3 × 10⁻⁵ |
| Steel Plate | Structural Steel | 7850 | 200 | 0.3 | 1.2 × 10⁻⁵ |
The stress analysis is based on linear elastic theory, where the maximum stress is compared to the material’s yield strength. For ZL101A-T6, the minimum tensile strength specified for separately cast test bars is 295 MPa, but for casting parts, the acceptable strength can be as low as 75% of that value, i.e., 221.3 MPa. The stress $\sigma$ in the casting part under pressure can be approximated by the thin-walled pressure vessel formula for cylindrical sections:
$$ \sigma = \frac{p \cdot r}{t} $$
where $p$ is the internal pressure, $r$ is the radius, and $t$ is the wall thickness. However, due to the complex geometry of the casting part, this simplified formula is insufficient, necessitating detailed FEA. The simulation results before lightweight design indicate that the maximum stress occurs near small bosses in the internal cavity, with a value of approximately 190 MPa, which is below the allowable limit, suggesting the casting part can pass the hydraulic test with a safety margin.
For lightweight design, we propose reducing the wall thickness from 10 mm to 7 mm and the flange thickness from 28 mm to 23 mm. However, such reductions must be evaluated for stress concentrations. The stress simulation after reducing the wall thickness by 3 mm shows a maximum stress of about 245 MPa near the internal bosses, exceeding the allowable limit. To mitigate this, we increase the root fillet radius of the bosses from R5 mm to R10 mm, which reduces stress concentration. The modified design yields a maximum stress of 194 MPa, within the acceptable range. Further reduction of the flange thickness by 5 mm is feasible, but a 10 mm reduction leads to excessive stress in the sealing groove area (281 MPa), indicating a high risk of failure. Thus, the final lightweight design involves a 3 mm wall thickness reduction and a 5 mm flange reduction, resulting in a weight saving of 2 kg (approximately 13%). The stress distributions for various design scenarios are summarized in Table 2.
| Design Scenario | Maximum Stress (MPa) | Location of Maximum Stress | Risk Assessment |
|---|---|---|---|
| Original Design | 190 | Internal Bosses | Low Risk |
| Wall Thickness Reduced by 3 mm | 245 | Internal Bosses | High Risk |
| Wall Thickness Reduced by 3 mm with R10 Fillet | 194 | Internal Bosses | Low Risk |
| Flange Reduced by 5 mm (with above) | 194.3 | Internal Bosses | Low Risk |
| Flange Reduced by 10 mm (with above) | 281 | Sealing Groove | Very High Risk |
In parallel with structural design, the casting process must be optimized to ensure the lightweight casting part is free from defects such as shrinkage porosity and cold shuts. We use AnyCasting software to simulate the low-pressure die-casting process. The initial process parameters include a pouring temperature of 700°C, a mold initial temperature of 300°C, and a filling rate of 880 Pa/s. The simulation domain is meshed with approximately 5 million cells, and material properties are based on the software’s database. Key parameters are listed in Table 3.
| Parameter | Value |
|---|---|
| Mold Material | QT500-7 |
| Casting Part Material | ZL101A |
| Liquidus Temperature | 614°C |
| Solidus Temperature | 556°C |
| Pouring Temperature | 700°C |
| Insulation Sleeve Material | Asbestos |
| Initial Mold Temperature | 300°C |
| Initial Insulation Sleeve Temperature | 80°C |
The filling and solidification simulations for the original casting part show that the liquid metal front temperature remains above the liquidus temperature throughout the process, and the residual melt modulus analysis indicates no defects in the casting part body. However, for the lightweight design with thinner walls, the simulation reveals that the liquid metal temperature drops below the liquidus temperature in some areas during filling, leading to potential shrinkage and porosity defects in the solidified casting part. This is because thinner walls accelerate heat transfer to the mold, reducing the fluidity of the metal. The temperature distribution can be described by the heat transfer equation:
$$ \frac{\partial T}{\partial t} = \alpha \nabla^2 T $$
where $T$ is temperature, $t$ is time, and $\alpha$ is thermal diffusivity. To address this, we increase the filling rate from 880 Pa/s to 1100 Pa/s, which reduces the time for heat loss and maintains higher metal temperatures. The optimized simulation shows that the liquid front temperature stays above 627°C, and the residual melt modulus analysis confirms the absence of defects in the casting part. The comparison of simulation results is summarized in Table 4.
| Aspect | Original Design (880 Pa/s) | Lightweight Design (880 Pa/s) | Lightweight Design (1100 Pa/s) |
|---|---|---|---|
| Minimum Liquid Front Temperature | >642°C | ~613°C | >627°C |
| Defects in Casting Part Body | None | Multiple Shrinkage Porosities | None |
| Filling Time | 8.1 s | 8.2 s | 4.4 s |
To validate the simulation-based design and process optimization, we conduct trial production of 10 lightweight casting parts using the optimized parameters. The casting parts are manufactured via low-pressure die-casting, followed by T6 heat treatment. Prior to machining, the casting parts are inspected for dimensional accuracy and deformation, and no significant issues are observed. After machining, all casting parts pass leak tests. One casting part is randomly selected for hydraulic failure testing. The test setup involves pressurizing the internal cavity with water incrementally up to 3.8 MPa. The casting part withstands the pressure without rupture or permanent deformation, confirming that the lightweight design meets the required strength criteria. This successful validation underscores the effectiveness of integrating CAE simulations in the development of high-performance casting parts.
The lightweight design and process optimization presented here demonstrate a systematic approach to enhancing the efficiency of aluminum alloy casting parts. By reducing weight, material usage and production costs are lowered, contributing to sustainable manufacturing. The use of simulation tools like ANSYS and AnyCasting enables rapid iteration and risk mitigation, reducing the need for physical prototypes. For future work, we plan to explore further weight reduction through topological optimization and advanced materials, while maintaining the integrity of the casting part. Additionally, the methodology can be extended to other types of casting parts in various industries, promoting widespread adoption of lightweight strategies.
In conclusion, the aluminum alloy cover plate casting part was successfully lightweighted through a combination of structural modifications and casting process adjustments. The ANSYS stress analysis guided the reduction of wall and flange thicknesses, ensuring the casting part’s compliance with hydraulic test requirements. The AnyCasting simulations identified and resolved potential casting defects by optimizing the filling rate. Experimental validation confirmed that the lightweight casting part performs satisfactorily under pressure. This holistic approach highlights the importance of simulation-driven design in modern casting part manufacturing, where weight reduction and quality assurance are paramount. The insights gained from this study can inform similar projects, ultimately advancing the field of lightweight metal casting parts.