In the practical application of lost foam casting at home and abroad, ferroalloy is the most widely used metal material with the largest production. Compared with Zhaozhao (magnesium) alloy lost foam casting, the technology and materials are relatively mature, but compared with ordinary (cavity) sand casting technology, the grain structure of ferroalloy parts made by lost foam casting is relatively large and the performance is low Straight did not get a good solution. With the development of mechanical manufacturing technology, higher requirements are put forward for the properties of lost foam casting cast iron alloy parts. The problems of coarse grain structure and low properties of lost foam casting cast iron alloy parts are solved, and further improving the quality and properties of lost foam casting cast iron parts become one of the hot spots of lost foam casting technology research. At present, the main problems of lost foam casting cast iron alloy parts are as follows:
1) In lost foam casting process, dry sand is used for molding, the cooling rate of dry sand is slow, and the cooling rate of cast iron alloy parts is low, which results in the coarse structure and low mechanical properties of the final cast iron alloy parts. Refining the structure and improving the mechanical properties of lost foam cast iron alloy parts is one of the key problems to be solved.
2) The quality of cast iron alloy parts lost foam casting is affected by many factors. For example, the composition of the alloy, the technology of inoculation and modification, the temperature of molten iron treatment and other technological factors will have an important impact on the quality of the parts. How to optimize the lost foam casting process and improve the quality of iron alloy lost foam casting parts is another key problem to be solved.
3) in the process of lost foam casting, the non bonded dry sand is used for vibration modeling. In the process of casting, negative pressure is used to mould the mold, and the stability of the prayer type is maintained by the pressure difference method. In the process of molten iron passing into the prayer type, the high temperature liquid metal heat is injected to make the foam plastic vaporized and form a cavity in the model. At this time, if the speed of round injection, the rising speed of liquid metal, the exhaust speed, and the matching of the air pressure in the model can not meet the requirements of finalization during the round injection process, there will be some problems, such as missing type, tank collapse and so on.
Based on the above, there are some problems in lost foam casting cast iron alloy parts, such as coarse structure, low mechanical properties, etc.
Lost foam casting is a unique and innovative type of casting process, but like any manufacturing method, it comes with its own set of challenges, especially when used for cast iron alloys. Here are some of the main problems associated with this process:
- Gas Defects: One of the most significant issues in lost foam casting is gas defects. The process involves the vaporization of the foam pattern, which can produce gas. If this gas doesn’t escape properly, it can lead to defects in lost foam casting, such as porosity or gas pockets.
- Surface Finish and Accuracy: The surface finish of castings made with lost foam casting can sometimes be inferior compared to other casting methods. This is because the surface texture is dependent on the foam’s quality and the refractory coating. Small imperfections in the foam or coating can transfer to lost foam casting.
- Mold Filling Issues: The fluidity of the molten iron is crucial for the success of lost foam casting. If the molten metal does not fill the mold completely or evenly, it can lead to incomplete or weak castings. This is often due to the design of the foam pattern or the properties of the molten metal.
- Pattern Collapse: Since the foam pattern is designed to vaporize upon contact with the molten metal, there’s a risk of the pattern collapsing prematurely or unevenly. This can result in inaccuracies in the final casting.
- Sand Collapsibility: The sand used in lost foam casting process must collapse sufficiently to allow for easy removal of lost foam casting. If the sand doesn’t collapse properly, it can adhere to lost foam casting, leading to surface defects and a need for extensive finishing work.
- Control of Carbon Pick-up: In the case of iron alloys, there is a potential issue with carbon pick-up from the vaporizing foam. This can alter the properties of the iron alloy, affecting its strength, ductility, and other material properties.
- Economic and Environmental Concerns: The process can be relatively expensive due to the cost of the foam patterns, especially for small production runs. Additionally, environmental concerns arise from the gases released during foam vaporization.
- Complex Geometries: While lost foam casting is excellent for complex shapes, achieving dimensional accuracy and maintaining structural integrity in intricate designs can be challenging.
Each of these problems requires careful consideration during the design and execution of the lost foam casting process, particularly when dealing with the specific properties and requirements of cast iron alloys.