Abstract: This paper focuses on the lost foam casting process of medium thin-walled circular parts. A step gating system is designed based on the structural characteristics of the castings. Numerical simulation analysis of the filling and solidification processes during lost foam casting is conducted using ProCAST software. The simulation results and trial production verify the rationality of the proposed process, providing a basis for efficient production of medium thin-walled circular parts through lost foam casting.
1. Introduction
Thin-walled circular parts are widely used in construction, automobile manufacturing, petrochemical industries, and many other fields, requiring good comprehensive mechanical properties and compactness. However, defects such as misrun, cold shut, and shrinkage porosity often occur during the casting process of thin-walled circular parts, making the casting process challenging. Therefore, selecting an appropriate casting process is crucial.
2. Casting Model and Lost Foam Casting Process
2.1 Casting Model
The outer diameter of the circular part is 435mm, the inner diameter is 311mm, the thickest section is only 19mm, and the edge wall thickness is 10mm, making it a typical medium thin-walled part. The three-dimensional model of the circular part.
Due to the large radius and thin wall thickness of the circular casting, defects such as misrun and cold shut are prone to occur during the casting process. Considering the rapid solidification of molten metal under the chilling effect of the coating, which reduces alloy fluidity, a step gating system is adopted. Five castings are combined into a cluster, with two ingates for each casting. To ensure timely feeding of liquid metal to the casting, one blind riser and one open riser are set for each casting. The gating system.
2.2 Simulation Parameters
The finite element model of the foam pattern for the circular part, and the overall model consists of the foam pattern, coating, and virtual sand box. The simulation parameters for the lost foam casting process are summarized in Table 1.
| Simulation Parameters | Values |
|---|---|
| Casting Material | QT 500-7 |
| Liquidus Temperature | 1209.0°C |
| Solidus Temperature | 1127.4°C |
| Pouring Temperature | (1430±10)°C |
| Pouring Time | 30s |
| Ingate Cross-section Size | 20mm × 14mm |
| Riser Size | φ35mm × 125mm |
| Coating Thickness | 2mm |
| Interface Heat Transfer Coefficient | 500W/(m²·K) |
3. Solidification Process Analysis
3.1 Temperature Field
Using the step gating system, the liquid metal fills the mold smoothly, allowing five castings to be filled and solidified simultaneously. The temperature field during the filling and solidification process.
3.2 Solid Phase Field
To observe the solidification sequence more clearly, the solid phase field is analyzed. The solid phase field of the casting.
To intuitively observe the internal solidification sequence and the feeding situation of the risers, a cross-sectional analysis of the casting is conducted. The position of the analyzed cross-section, and the solidification process of the cross-section.
3.3 Simulation Results
The distribution of shrinkage defects in the circular part. It can be seen that the circular part has no defects such as cold shut, misrun, or shrinkage porosity. The equivalent stress distribution of the casting, and the deformation distribution.
4. Trial Production
The process scheme without obvious casting defects after simulation is adopted for the trial production of the circular parts using the lost foam casting method.
The foam pattern support and the machined parts.
5. Conclusion
- Gating System and Risers: A step gating system and reasonable blind and open risers are designed for medium thin-walled circular castings. This allows five castings to be poured simultaneously, improving pouring efficiency and maintaining good fluidity of the liquid metal in the mold cavity, thereby effectively avoiding defects such as cold shut and misrun.
- Simulation Analysis: The simulation analysis of the lost foam casting process shows that the circular casting, which is thin overall, exhibits layer-by-layer solidification characteristics at the initial stage of solidification due to the chilling effect of the coating. During the later stage of solidification, under the dual action of solid-state shrinkage of the outer layer metal and rapid growth and expansion of internal graphite, the casting has no shrinkage porosity defects, and its compactness is effectively guaranteed.
- Trial Production Results: The results of trial production are consistent with the simulation analysis results. The machined parts do not exhibit deformation such as out-of-roundness or warping, and the surface of the parts is compact, with no defects such as cold shut, misrun, shrinkage porosity, or porosity.
This study provides a theoretical and production basis for the efficient production of medium thin-walled circular parts through lost foam casting.