1. Introduction
In the landscape of modern manufacturing, the demand for high – precision, high – performance castings has been on the rise, driven by the rapid development of industries such as aerospace, automotive, and machinery. Traditional casting processes often struggle to meet these stringent requirements. Lost foam casting (LFC) has emerged as a revolutionary technology, offering numerous advantages over conventional methods. This article aims to provide an in – depth review of the lost foam casting technology, covering its processes, simulation techniques, and future prospects.
1.1 Background and Significance
Traditional casting methods, like sand casting, face challenges in achieving high – precision and complex – shaped castings. The limitations include issues such as parting lines, rough surface finishes, and difficulties in casting intricate geometries. Lost foam casting addresses these issues by using a foam pattern that vaporizes upon contact with molten metal, leaving behind a cavity to be filled. This process eliminates the need for mold parting, reduces machining requirements, and enables the production of castings with higher dimensional accuracy and better surface quality.
1.2 Objectives of the Review
The primary objectives of this review are:
- To comprehensively summarize the current research status of different lost foam casting processes, including vacuum – low – pressure lost foam casting, vibration – assisted lost foam casting, and lost foam shell – mold casting.
- To explore the application of simulation techniques in lost foam casting, specifically in the filling and solidification processes.
- To discuss the challenges and future trends of lost foam casting technology, providing insights for further research and development.
2. Lost Foam Casting Processes
2.1 Vacuum – Low – Pressure Lost Foam Casting Process
2.1.1 Process Principle Vacuum – low – pressure lost foam casting combines the advantages of vacuum lost foam casting and low – pressure casting. In this process, a negative pressure is applied in the mold cavity, which helps to improve the filling ability of molten metal. The principle is illustrated in Figure 1.
2.1.2 Research Findings Jiang et al. integrated lost foam casting, investment casting, and vacuum – low – pressure casting technologies to study the vacuum – low – pressure investment shell – mold casting process. The results showed that this technology could enhance the filling and feeding capabilities of the melt, effectively eliminating casting defects such as misruns and cold shuts. The surface roughness of the castings produced by this method was only 3.2 – 6.3 μm, compared to 6.3 – 12.5 μm for those produced by ordinary LFC. The internal quality of the castings was excellent, and the problem of carburization in low – carbon steel LFC was eliminated. A comparison of the properties of castings produced by different methods is presented in Table 1.
| Casting Method | Surface Roughness (μm) | Porosity (%) | Density (\(g/cm^{3}\)) | Tensile Strength (MPa) | Elongation (%) | Hardness (HB) |
|---|---|---|---|---|---|---|
| Ordinary LFC | 6.3 – 12.5 | 1.97 | 2.660 | – | – | – |
| Vacuum – Low – Pressure LFC | 3.2 – 6.3 | 0.16 | 2.684 | 278.27 (after heat treatment, 20.2% increase) | 8.10 (after heat treatment, 166.4% increase) | 93.1 (after heat treatment, 17.6% increase) |
| Table 1: Comparison of Casting Properties |
Qin Huangu et al. studied the influence of the pressure control of the aluminum alloy lost foam casting cavity on the casting quality. They designed a PLC control system, which reduced the tracking error and stable time, and effectively reduced pores, improving the casting quality.
Jiang Wenming et al. compared the microstructures and properties of A356 aluminum alloy under different lost foam casting processes. They found that the vacuum – low – pressure lost foam shell – mold casting had a finer and denser microstructure, with smaller primary phase grains and eutectic silicon sizes. The porosity was significantly reduced, and the mechanical properties were improved after heat treatment.
2.1.3 Advantages and Challenges The advantages of vacuum – low – pressure lost foam casting include high casting precision, low surface roughness, and good mechanical properties. However, challenges remain in precisely controlling process parameters, as small variations in parameters can affect the quality and performance stability of different castings.
2.2 Vibration – Assisted Lost Foam Casting Process
2.2.1 Process Principle Vibration – assisted lost foam casting involves applying an external force with a certain amplitude and frequency during the filling of molten metal into the mold cavity. This causes the casting to solidify in a vibrating field. The schematic diagram of the process principle is shown in Figure 2.
2.2.2 Research Findings Qiu et al. investigated the effect of mechanical vibration on gray cast iron in lost foam casting. They found that as the amplitude increased, the elongation and tensile strength of the castings first increased and then decreased. This study revealed the relationship between vibration parameters and the microstructure and mechanical properties of gray cast iron, providing a reference for the selection of vibration parameters.
Zou et al. studied the influence of mechanical vibration frequency on the microstructure and properties of high – chromium cast iron in as – cast, quenched, and tempered states. The results showed that an increase in vibration frequency could refine the microstructure of as – cast high – chromium cast iron and improve its hardness, but had a relatively small impact on the hardness of quenched high – chromium cast iron.
Wang Junlong et al. studied the effect of different vibration frequencies on the interface structure and mechanical properties of solid – liquid composite Al/Mg bimetallic composites prepared by lost foam casting. They found that as the vibration frequency increased, the thickness of the intermetallic compound layer at the interface decreased, the brittle phase reduced, and the Mg₂Si phase was refined and its distribution became more dispersed.
2.2.3 Advantages and Challenges The advantages of vibration – assisted lost foam casting are that it can refine grains, is simple to operate, and has a low cost. However, the selection of vibration parameters is crucial. Improper parameters can have a negative impact on casting quality, and the relationship between vibration parameters and material properties is complex, requiring further in – depth research.
2.3 Lost Foam Shell – Mold Casting Process
2.3.1 Process Principle Lost foam shell – mold casting is a new casting method that combines investment casting and lost foam casting. First, a foam pattern is made according to the structure and size of the part. Then, a refractory coating is applied to the surface of the pattern. When molten metal is poured, the foam pattern burns and gasifies, and the metal fills the cavity under gravity or counter – gravity, obtaining high – precision and high – performance parts. The process flow is shown in Figure 3.
2.3.2 Research Findings Jiang et al. investigated the influence of different vacuum – low – pressure lost foam shell – mold casting process parameters on the filling ability of aluminum alloy liquid. They found that the gas flow rate had the greatest impact on the filling ability, followed by casting temperature, gas pressure, and vacuum degree. The filling length increased linearly with the increase of process parameters. Compared with ordinary lost foam casting, vacuum – low – pressure lost foam shell – mold casting had stronger filling ability, higher casting density, lower porosity, and better internal quality.
Liu Lizhong et al. explored the lost foam shell – mold casting process for cable socket castings. Through a series of processes such as making foam patterns, applying coatings, roasting and drying, filling sand, and negative – pressure pouring (0.02 MPa), they obtained high – performance cable socket castings without defects, which was of great significance for the mass production of high – quality cable sockets.
Wang Ronghua et al. studied the influence of mechanical vibration frequency on the structure and properties of ZL101 alloy in lost foam shell – mold casting. They found that as the vibration frequency increased, the tensile strength, yield strength, elongation, and hardness of the alloy first increased and then decreased, and the best microstructure refinement effect was achieved at 100 Hz, with the strength, hardness, and elongation reaching their maximum values.
2.3.3 Advantages and Challenges Lost foam shell – mold casting can produce parts with high dimensional accuracy and good performance. The castings have a dense structure and low porosity. Compared with vacuum – low – pressure lost foam casting, it may have similar advantages in terms of dimensional accuracy and performance, but there may be differences in process complexity and cost. Compared with vibration – assisted lost foam casting, it focuses more on dimensional accuracy and overall performance, while vibration – assisted lost foam casting focuses on improving the microstructure and mechanical properties through vibration.
3. Simulation Techniques in Lost Foam Casting
3.1 Filling Process Simulation
3.1.1 Simulation Principle Filling process simulation in lost foam casting uses computer technology and relevant physical – mathematical models to numerically simulate the complex dynamic processes of molten metal flow, foam pattern gasification, and gas discharge. This simulation can predict potential casting defects such as gas entrapment, slag inclusion, and cold shuts in advance.
3.1.2 Research Applications Li Xinran et al. used a combination of experimental research and numerical simulation to study the lost foam casting process of a cast – steel convex ring. They designed two stepped gating systems and found through simulation and casting that the casting produced by the second gating system had no obvious shrinkage defects and good surface quality, demonstrating the important role of numerical simulation in optimizing the casting process design.
Xie Yuanyuan et al. studied the filling process of a reducer box through numerical simulation, which could effectively predict casting defects such as slag inclusion and pores, providing a basis for the design of the casting process.
Li et al. established a physical model and developed a numerical algorithm to study the filling process of lost foam casting. The calculated results were in good agreement with the experimental results, and the deviation was acceptable, indicating that this method could be used to optimize the lost foam casting design and prevent casting defects.
3.1.3 Significance and Future Trends Filling process simulation is crucial for optimizing the casting process design. By simulating different gating systems, potential problems can be identified in advance, reducing the trial – and – error cost in actual production. In the future, efforts should be made to improve the simulation accuracy and efficiency, and more practical factors such as the fluidity differences of different molten metals should be considered to make the simulation results closer to actual production.
3.2 Solidification Process Simulation
3.2.1 Simulation Principle Solidification process simulation in lost foam casting uses computer technology to numerically simulate the complex dynamic processes of metal solidification and temperature cooling. By accurately simulating the solidification process, the optimal range of key parameters such as pouring temperature and cooling rate can be determined, and the relationship between the cooling rate and heat transfer mechanisms can be analyzed to avoid defects such as shrinkage cavities and porosity.
3.2.2 Research Applications Ma et al. used simulation to study the solidification shrinkage process of high – chromium cast iron in lost foam suspension casting. They found that at a negative pressure of 0.06 MPa, the shrinkage pores were smaller than those at 0.04 MPa, and the shrinkage pores were the lowest at 1540 °C. When the suspending agent addition was 1%, the shrinkage pores were almost eliminated.
Sun et al. studied the influence of the shape of refractory aggregates on the porosity of A356 alloy lost foam castings through numerical simulation. They found that the combination of cylindrical expanded graphite and bauxite chamotte could make the liquid polystyrene flow at the highest speed, resulting in better – quality castings.
Chekmyshev et al. established a coupled heat – transfer mathematical model for gray cast iron – austenitic stainless steel bimetallic castings in lost foam casting and solved it using the finite – difference method. They studied the cooling and solidification process and found that an increase in the thickness of the adjusting element could reduce the “liquid – austenite” phase – change time and the total cooling time, and could predict the location of defects.
3.2.3 Significance and Future Trends Solidification process simulation can provide a basis for optimizing the lost foam casting process parameters. By studying the influence of different factors on the solidification process, process parameters can be adjusted to prevent the occurrence of defects. In the future, more research should be focused on the solidification process simulation of complex alloy systems and special casting structures to meet the diverse needs of actual production.
3.3 Collaborative Application of Simulation and Preparation
3.3.1 Advantages of Collaborative Application The collaborative application of lost foam casting simulation and actual preparation has many advantages. It can accurately optimize the process, determine the best parameters through simulation for actual production, and ensure precise process control. It can also accurately predict and analyze the root causes of casting defects, effectively prevent defects, and improve casting quality. In addition, it can significantly reduce the trial – and – error cost, improve production efficiency, optimize resource utilization, and promote the development of the lost foam casting industry.
3.3.2 Research Cases Sun et al. used a combination of numerical simulation and experimental verification to study the lost foam casting of A356 aluminum alloy motor housings for new – energy vehicles. They constructed a mathematical model, established a three – dimensional model, and set parameters such as risers, pouring temperature, and speed. After repeated simulations to predict the defect locations, the optimal process parameters were obtained and verified by actual casting, resulting in good – quality castings.
Ablyaz et al. used rapid prototyping technology to manufacture lattice – structured patterns and studied their influence on ceramic shell molds in the casting process. They found that the lattice – structured patterns had high accuracy, could minimize the stress in the ceramic shell molds, and the nickel – alloy castings produced had good consistency with the CAD model.
Jiang et al. combined the measurement of casting density and cross – section porosity with simulated pore defect calculations to study the influence of process parameters such as gas flow rate, vacuum degree, and gas pressure on the internal quality of A356 aluminum alloy castings in vacuum – low – pressure lost foam shell – mold casting. The simulation results were consistent with the experimental results, and the castings produced by this process had certain advantages in internal quality, microstructure, and mechanical properties.
Zhang Jieqiong et al. analyzed the structure and lost foam casting process of a tractor transmission box housing, used the Huazhu CAE casting simulation system for simulation, and screened out the best lost foam casting process through comprehensive analysis. The experimental verification showed that the casting surface quality was good, and the blank deformation was within the process control range, saving two process tests compared with the traditional casting process.
Deng Chao et al. simulated the solidification process of ZG30SiMnMoV steel crawler plates and studied the influence of pouring temperature and pouring speed. According to the simulation results, when the pouring temperature was 1610 °C, the internal shrinkage cavities and porosity of the crawler plates were significantly reduced.
3.3.3 Significance of Collaborative Application The research on the combination of casting lost foam simulation and actual production has important significance in optimizing process design, reducing costs, improving production efficiency, enhancing the understanding of the casting process, and promoting the technological progress of the casting industry.
4. Challenges and Future Trends
4.1 Challenges in Lost Foam Casting
4.1.1 Process Parameter Control Accurately controlling process parameters is a major challenge in lost foam casting. In vacuum – low – pressure lost foam casting, parameters such as vacuum degree, gas pressure, and pouring temperature need to be precisely adjusted. In vibration – assisted lost foam casting, the selection of vibration amplitude and frequency is crucial. Small variations in these parameters can lead to significant differences in casting quality, and it is difficult to ensure the performance stability of different castings.
4.1.2 Defect Prevention Although lost foam casting has many advantages, casting defects such as porosity, shrinkage cavities, and gas entrapment still occur. These defects are mainly caused by the complex interaction between the molten metal, foam pattern, and gas during the casting process. Preventing these defects requires a better understanding of the physical and chemical processes involved and the development of more effective control methods.
4.1.3 Material Compatibility The compatibility between the foam pattern material, refractory coating, and molten metal is also a concern. Incompatible materials can lead to problems such as chemical reactions, coating peeling, and poor casting surface quality. Developing suitable materials and optimizing their combinations is necessary to improve the overall quality of lost foam castings.
4.2 Future Trends
4.2.1 Integration of Multiple Technologies The integration of multiple technologies will be a major trend in the future development of lost foam casting. For example, further integration of vacuum – low – pressure lost foam casting, vibration – assisted lost foam casting, and lost foam shell – mold casting can combine their respective advantages to produce higher – quality castings. In addition, the combination of lost foam casting with new technologies such as 3D printing, intelligent control, and advanced materials will open up new opportunities for the development of the industry.
4.2.2 Optimization of Simulation Techniques With the continuous development of computer technology, simulation techniques in lost foam casting will be further optimized. Higher – accuracy models, faster computing speeds, and more comprehensive consideration of actual factors will make simulation results more reliable and practical. This will help manufacturers better predict casting defects, optimize process parameters, and reduce production costs.
4.2.3 Development of Environmentally Friendly Processes In response to the global trend of environmental protection, the development of environmentally friendly lost foam casting processes is essential. This includes the use of biodegradable foam pattern materials, water – based refractory coatings, and energy – saving casting equipment. Developing green lost foam casting processes can reduce environmental pollution and meet the sustainable development requirements of the industry.
4.3 On – site Data – based Cost Calculation with the MES System
Modern casting enterprises are gradually introducing the Manufacturing Execution System (MES) in cost management to achieve real – time cost calculation and control. The MES is a management system oriented to workshop production, which plays a role in transmitting information to optimize production activities. The MES realizes refined on – site cost dynamic management through the automatic collection and analysis of on – site data.
- Cost Calculation Method of the MES:
- Real – time Data Collection: The MES can automatically collect production data from all links in the casting process, including melting time, pouring temperature, cooling time, equipment utilization rate, and labor input. These data provide an accurate basis for cost accounting.
- Dynamic Cost Accounting: The MES can perform dynamic cost calculations based on the real – time collected data. For example, it automatically calculates the actual cost of current production according to the material consumption, equipment operation time, and energy consumption. This real – time cost accounting enables enterprises to detect cost deviations during the production process and take immediate measures to adjust, thereby reducing unnecessary cost expenditures.
- Integration of Process Optimization and Cost Analysis: The MES can also integrate cost accounting with process optimization. By analyzing the costs of different production links, it helps enterprises identify the weak links in the process. For example, if the energy consumption of a certain link is continuously higher than expected, the MES can prompt managers to conduct equipment maintenance or process adjustments.
- Settings of the MES System in Casting Production: The MES system in casting production is set to conduct real – time metering and accounting by process.
- Actual Application Effects of the MES System: Some foreign casting enterprises use the MES system to obtain cost – difference data during production for in – process cost control, demonstrating more efficient cost management:
- Improved cost – management efficiency by 20%. The automatic collection and analysis of real – time data reduce the time and errors of manual accounting.
- Reduced energy consumption during the production process by 5%. By dynamically monitoring energy – consumption costs, enterprises can adjust the equipment operation status in a timely manner to reduce unnecessary energy consumption.
5. Research Conclusion
This research has deeply explored the manufacturing cost management issues in the casting process of heavy – duty machinery. By combining the advantages and disadvantages of the standard cost method and the actual cost method in current enterprise applications, it has analyzed the difficulties and challenges in casting cost accounting. The main conclusions are as follows:
- Complexity of Casting Process Cost Accounting: The composition of casting process costs involves multiple links, including material formula costs and production process costs. These costs are diverse and dynamic, and the interactions between different links make accurate cost accounting and management very difficult.
- Limitations of the Standard Cost Method and the Actual Cost Method: The advantage of the standard cost method lies in its ease of operation and management, but its indirect cost allocation method is difficult to accurately reflect the true costs of specific parts. The actual cost method can more accurately reflect the actual production costs, but the monthly fluctuations are large, resulting in poor cost – management stability. Both methods have problems of cost – accounting deviation and management difficulty.
- Potential of New – type Cost Management Methods: By referring to the experience of advanced foreign enterprises and introducing cost – model – based software, batch cost management, and the MES system, casting enterprises can achieve more accurate and flexible cost management. These new – type methods can overcome the limitations of traditional methods, improve the accuracy and real – time nature of cost accounting, and enhance the enterprise’s adaptability.
- Informatization and Intelligence: The Future Direction of Casting Cost Management: With the help of modern information technology and intelligent manufacturing tools, casting enterprises can achieve dynamic cost accounting and optimization during the design stage and production process. This method can not only improve cost transparency and accuracy but also enhance production efficiency and resource utilization rate, helping enterprises gain a greater cost advantage in the fierce market competition.
6. Conclusion
In the field of cost management for casting processes, future development will mainly focus on informatization, intelligence, and green manufacturing. These trends pose new challenges and opportunities for the cost management of casting enterprises.
In the future, casting enterprises will achieve full – process information sharing and data docking. Through the comprehensive application of information systems, enterprises can conduct dynamic cost monitoring and analysis in design, production, quality management, and other links, improving management efficiency. Digital twin technology, artificial intelligence, and other technologies can help casting enterprises simulate and optimize the casting process in a virtual environment, test different material formulas, process parameters, and production conditions, and thus find the optimal cost – reduction plan.
With the increasingly strict environmental protection requirements, casting enterprises need to pay more attention to the efficient use and recycling of materials. By optimizing material formulas, reducing waste generation, and promoting material recycling, material costs and environmental protection costs can be significantly reduced. The introduction of energy – saving equipment and technologies can also reduce energy consumption during the production process, as well as carbon emissions and energy – consumption costs in the casting process.
In conclusion, casting enterprises need to continuously innovate and improve in cost management. Future cost management will no longer be just simple accounting and control but a full – process optimization process that runs through design, production, and quality management. Only by organically combining informatization, intelligence, and green manufacturing can casting enterprises maintain their competitiveness in global competition and achieve the dual goals of economic benefits and sustainable development.
