Lost Foam Casting Technology (EPC or LFC) is made of foam plastic, which is exactly the same as the structure and size of the parts. It is impregnated with fire-resistant adhesive coating. After drying, it is made by dry sand molding, vibrated and compacted, and then poured into the metal liquid to make the mold heated and vaporized disappear, and the casting method of metal parts consistent with the shape of the mold is obtained. Lost foam casting is a new technology with nearly no allowance and accurate forming. It does not need to close the box and take the mold. It uses dry sand modeling without binder to reduce pollution. It is considered to be the most likely process technology to realize green casting in the 21st century.
Lost foam casting technology mainly includes the following types:
1.Pressure lost foam casting technology
Pressure lost foam casting is a new casting technology that combines lost foam casting technology with pressure solidification crystallization technology. It is a casting method for solidifying and crystallizing gold under pressure when the metal foam is poured into the sand box and the foam plastics are vaporized. The characteristic of this casting technology is that it can significantly reduce the casting defects such as shrinkage cavity, porosity and porosity in the casting, improve the density of the casting and improve 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 pouring method. The characteristics of vacuum low-pressure lost foam casting technology are: it integrates the technical advantages of low-pressure casting and vacuum lost foam casting, completes the filling process under controllable air pressure, and greatly improves the casting filling ability of the alloy; Compared with die casting, the equipment investment is small, the casting cost is low, and the casting can be strengthened by heat treatment; Compared with sand casting, the casting has high precision, small surface roughness, high productivity and good performance; Under the action of counter gravity, the straight gate becomes a complementary and shortening channel, the loss of pouring temperature is small, and the liquid alloy is fed and solidified under controllable pressure. The gating system of alloy casting is simple and effective, the yield is high and the structure is compact; The pouring temperature of vacuum low pressure lost foam casting is low, which is suitable for a variety of non-ferrous alloys.
3.Vibration lost foam casting technology
Vibration lost foam casting technology is to apply a certain frequency and amplitude of vibration in the process of lost foam casting to make the casting solidify under the action of vibration field. Due to the vibration of metal solution for a certain time in the solidification process of lost foam casting, the vibration force causes the relative movement between liquid phase and solid phase, breaks the dendrite, increases the crystalline core in liquid phase, refines the final solidification structure of the casting, improves the feeding and mechanical properties. This technology uses the ready-made compact shaking table in lost foam casting to nucleate the liquid metal under dynamic excitation through the mechanical vibration generated by the vibrating motor, so as to achieve the purpose of refining the structure. It is a method with simple operation, low cost and no environmental pollution.
4.Semi solid lost foam casting Technology
Semi solid lost foam casting technology is a new casting technology combining lost foam casting technology and semi-solid technology. Because the characteristic of this process is to control the relative proportion of liquid and solid, it is also called transformation controlled semi-solid forming. This technology can improve the density of castings, reduce segregation, improve dimensional accuracy and casting performance.
5.Lost foam shell casting technology
Lost foam shell casting technology is a new casting method combining investment casting technology and lost foam casting. The method is to coat several layers of refractories on the surface of the foamed plastic moulds made of foam mold and the shape of the parts. After hardening and drying, the foam plastic is burned and vaporized and disintegrated and made into shells. After roasting and pouring, a new precision casting method with high dimension precision castings is obtained. It has the characteristics of large pattern size and high precision in lost foam casting, as well as the advantages of crusting precision and strength in investment casting. Compared with ordinary investment casting, it is characterized by low cost of foam plastic pattern material, convenient combination of pattern bonding, easy gasification, easy to overcome the problem of deformation caused by mold softening caused by investment casting, and the production of large complex alloy castings of large size.
6.Lost foam casting suspension casting technology.
Lost foam casting suspension casting technology is a new practical casting technology combining lost foam casting process and suspension casting. The technological process is that after pouring the molten metal into the mold, the foam is vaporized and mixed into the suspending agent of the riser model (or suspending agent is placed in a specific position, or the suspension agent is made into foam pattern with EPS) to react with the metal liquid so as to improve the overall (or part) microstructure and properties of the casting.
Due to the characteristics of low cost, high precision, flexible design, clean and environmental protection and suitable for complex castings, lost foam casting technology is in line with the general trend of casting technology development in the new century and has broad development prospects.