Abstract: This article focuses on the investment casting process of ZL114A alloy seal sleeves. It begins with an introduction to the importance and challenges of investment casting in manufacturing components like seal sleeves. The structure and preprocessing settings of the casting are detailed, followed by numerical simulation results and discussions. The verification of simulation results through experiments is presented, and the optimization of the casting process to eliminate defects is described. The article concludes with a summary of the key findings and their implications for the industry.
1. Introduction
Investment casting is a widely used manufacturing process that offers high precision and quality in producing complex metal components. In the case of ZL114A alloy seal sleeves, it is crucial to ensure a defect-free casting process due to the demanding requirements of the application. The seal sleeves play a vital role in mechanical systems, providing sealing and protection functions. However, achieving a perfect casting is challenging due to factors such as complex geometries, varying wall thicknesses, and high metallurgical quality demands.
2. Structure Analysis and Preprocessing Settings
2.1 Casting Structure
The casting belongs to a shell II class structural part with significant manufacturing difficulties.
- Structural Complexity: It has a high level of integration and complexity. The structural function areas are distinct yet closely related, with an extremely complex .
- Metallurgical Requirements: The wall thickness varies greatly and irregularly, with numerous isolated hot spots. It is difficult to feed and has extremely high metallurgical quality requirements, especially for sealing, wall thickness tolerance, pipe surface quality, slag inclusion, and pinholes.
- Size Specifications: High dimensional accuracy is required, particularly for the oil passage interface positions. The casting has a three-dimensional geometric shape with an outer dimension of . The maximum thickness is , and the average thickness is .
2.2 Modeling and Preprocessing
- Modeling Software: The three-dimensional modeling software UG is used to model the casting and the pouring system. The casting material is ZL114A with a specific composition.
- Mesh Generation: Procast software is used to divide the mesh for the casting and its pouring system. The mesh type is tetrahedral. The casting mesh size is , and the pouring system mesh size is . There are a total of 1917916 mesh units.
- Parameter Settings: The material thermal physical parameters are set using the software’s built-in database. The interface heat transfer coefficient between the casting and the mold shell is set according to relevant literature. The pouring temperature of the metal liquid is set to , and the mold shell preheating temperature is set to .
3. Numerical Simulation Results and Discussion
3.1 Cooling Medium and Simulation Process
The cooling medium for the casting is set as air. The numerical simulation of the casting filling and solidification process and the prediction results of porosity defects are presented.
- Filling Process: During the filling process, the liquid level height of the metal liquid is consistent at 30% filling, and the filling is stable. At 50% filling, the liquid level remains consistent, and half of the casting is filled. At 70% filling, the height of the metal liquid in the casting is consistent, but the metal liquid in the runner begins to split, which may lead to metallurgical defects. At 90% filling, the casting is filled, and the thin-walled area has solidified. The overall filling process is relatively smooth and stable without splashing.
- Solidification and Defect Prediction: The positions where the casting has porosity are mainly distributed in the flanges at both ends and the thin-walled area in the middle of the casting. The thin-walled area in the middle of the casting solidifies first, and the two flanges solidify later. However, the temperature gradient distribution during solidification is uneven, resulting in a lack of sequential solidification and porosity defects.
4. Simulation Results Verification
4.1 Experimental Setup
- Wax Mold Preparation: IC35 single-station wax injection machines are used to prepare wax molds. The wax molds and the pouring system are assembled by a welding gun.
- Shell Preparation: A shell with a thickness of about 7mm is prepared.
- Casting Parameters: The casting pouring temperature is 710°C, the shell preheating temperature is 300°C, and the pouring time is 10 s. After pouring, the casting is cooled in the air.
- Temperature Measurement: K-type thermocouples are used to collect the temperature changes of the characteristic points of the casting. The positions of the thermocouples are shown in Figure [Figure number not provided in original text]. The temperature curves collected by the patrol instrument are shown in Figure [Figure number not provided in original text].
4.2 Results Comparison
- Temperature Comparison: The temperature curves of different characteristic points of the casting with time have a basically consistent trend. The maximum temperature difference between different temperature measurement points is 38°C, and the minimum is 0°C. The comparison between the experimental results and the numerical simulation results shows that the trends of the measured curves of simulation points 1, 2, and 3 and thermocouples 1, 2, and 3 are basically the same, and the maximum temperature difference is about 10°C, verifying the accuracy of the numerical simulation.
- DR Detection: After pouring, the casting is subjected to DR detection. The results show that the trends are consistent with the simulation results, further verifying the accuracy of the simulation.
5. Casting Process Optimization
5.1 First Version of the Process and Defects
In the first version of the casting process, although the filling process of the casting is relatively smooth and stable, there are porosity defects in the flanges and the thin-walled area in the middle of the casting due to the lack of sequential solidification.
5.2 Second Version of the Process and Results
- Process Modification: In the second version of the process, on the basis of the first version, only the boundary conditions of the casting are changed. After the casting is poured, air-cooling is carried out to make the casting cool rapidly and achieve sequential solidification.
- Results Verification: The porosity in the flanges and the thin-walled area at both ends of the casting has been solved. The temperature distribution of the casting is more uniform, and the casting can solidify sequentially. Actual production according to the second version of the casting process shows that after DR detection, there are no metallurgical defects such as porosity, inclusions, and pores in the casting, and it meets the use requirements.
6. Conclusion
The investment casting process of ZL114A alloy seal sleeves has been studied through numerical simulation and experimental verification. In the air-cooling condition, porosity defects may exist in the flanges and the thin-walled area of the casting. The process test verified the accuracy of the numerical simulation. Through air-cooling measures, sequential solidification of the casting is achieved, eliminating porosity defects and obtaining qualified castings. This research provides valuable insights and methods for optimizing the investment casting process of similar components and ensuring product quality.
In conclusion, investment casting remains a crucial manufacturing process for complex metal components, and continuous research and optimization are essential to meet the increasing demands of various industries. By addressing casting defects and improving process parameters, manufacturers can produce high-quality ZL114A alloy seal sleeves and other components with greater efficiency and reliability.