Lost foam casting is a method of casting a refractory bonded paint, drying it and then performing dry sand molding, vibrating tightly, and then pouring the molten metal to heat the gasification to disappear, thereby obtaining a metal part having the same shape as the pattern. Lost foam casting is a new technology with no margin and precise forming. It does not need to take the mold and use the binderless dry sand to reduce the pollution. It is considered as the green casting technology.
Lost foam casting classification
The castings processed by lost foam casting have high dimensional accuracy, uniformity, clean environment and no pollution; low labor intensity, less labor, less technicians; less equipment investment. The processing for small and medium-sized enterprises reduces costs, improves the economics of the company, and understanding its process classification can help companies better choose the casting process.
1. Pressure lost foam casting technology
The pressure lost foam casting technology is a new casting technology combining the lost foam casting technology and the pressure solidification crystallization technology. It is in the pressure irrigation with a sand box. After pouring the molten metal to vaporize the foam, the pressure irrigation is quickly sealed. A casting method in which a certain pressure of gas is introduced to solidify and crystallize the molten metal under pressure. This casting technology is characterized by significantly reducing casting defects such as shrinkage, shrinkage, and porosity in the casting, increasing the density of the casting and improving the mechanical properties of the casting.
2. Vacuum low pressure lost foam casting technology
Vacuum low pressure lost foam casting technology is a new casting technology developed by combining negative pressure lost foam casting method and low pressure anti-gravity casting method. The characteristics of vacuum low pressure lost foam casting technology are: combining the technical advantages of low pressure casting and vacuum lost foam casting, the filling process is completed under controlled pressure, which greatly improves the casting filling ability of the alloy; compared with die casting, the equipment The investment is small, the casting cost is low, and the casting can be heat-treated and strengthened. Compared with the sand casting, the casting has high precision, small surface roughness, high productivity and good performance; under the action of anti-gravity, the sprue becomes the supplementary shortening channel and the pouring temperature. The loss is small, the liquid alloy is filled and solidified under the controllable pressure, the casting system of the alloy casting is simple and effective, the yield is high, and the structure is compact; the vacuum low pressure lost foam casting has a low pouring temperature and is suitable for various colored alloys.
3. Vibration lost foam casting technology
The vibration lost foam casting technology applies vibration of a certain frequency and amplitude during the lost foam casting process, so that the casting solidifies under the action of the vibration field. Since the solidification process of the lost foam casting is applied to the metal solution for a certain period of time, the vibration force makes the liquid The relative motion between the phase and the solid phase causes the dendrites to break, and the crystal core in the liquid phase is increased, so that the final solidification structure of the casting is refined, the feeding is improved, and the mechanical properties are improved. The technology utilizes the ready-made compact vibrating table in lost foam casting, and the mechanical vibration generated by the vibrating motor causes the molten metal to nucleate under dynamic excitation to achieve the purpose of refining the structure, and is an easy operation, low cost and no environment. The method of pollution.
4. Semi-solid lost foam casting technology
Semi-solid lost foam casting technology is a new casting technology that combines lost foam casting technology with semi-solid technology. Because the process is characterized by controlling the relative proportion of liquid-solid phase, it is also called transformation control semi-solid forming. This technology can increase the density of castings, reduce segregation, improve dimensional accuracy and casting performance.
5. Lost shell casting technology
The lost shell casting technology is a new casting method combining investment casting technology and lost foam casting. The method is to apply a plurality of layers of refractory material to the surface of the foam molding which is made of a foaming mold and has the same shape as the part, and after hardening and drying, the foamed plastic pattern is burned and disappeared to form a shell, and is fired. And then casting, to obtain a new precision casting method for higher dimensional precision castings. It has the characteristics of large size and high precision in the lost foam casting, and has the advantages of crust precision and strength in investment casting. Compared with ordinary investment casting, it is characterized by low cost of foam plastic molding, convenient combination of pattern bonding, easy disappearance of gasification, overcoming the problem of melt deformation caused by easy softening of investment casting mold, and can be produced. Large size of various alloy complex castings.
6. Lost foam suspension casting technology
The lost foam suspension casting technology is a new practical casting technology that combines the lost foam casting process with suspension casting. The technical process is that after the molten metal is poured into the mold, the foam plastic pattern is vaporized, and the suspending agent is mixed in the riser model (or the suspending agent is placed at a specific position of the pattern, or the suspending agent is foamed together with the EPS. Physicochemical reaction with molten metal to improve the overall (or partial) structural properties of the casting.
Due to the low cost, high precision, flexible design, clean and environmental protection, and suitable for complex castings, the lost foam casting technology meets the general trend of casting technology development in the new century and has broad development prospects.
