Lost Foam Casting (EPC or LFC) is a casting method that uses foam plastic to make a solid mold with exactly the same structure and size as the parts, dip-coats refractory adhesive coating, dries, carries out dry sand molding, vibrates and compacts, and then pours molten metal into the mold to vaporize the mold under heat to obtain metal parts with the same shape as the mold. Lost Foam Casting (LFC) is a new technology with almost no allowance and accurate forming. It does not need to close the box and take the mold. It uses dry sand molding without binder to reduce pollution. It is considered as the most possible technology to realize green casting in the 21st century.
EPC technology mainly includes the following:
1. Pressure Lost Foam Casting Technology
The pressure lost foam casting technology is a new casting technology combining lost foam casting technology and pressure solidification crystallization technology. It is a casting method in which molten metal is poured in the pressure pouring with sand box to make foam plastic evaporate and disappear, then the pressure pouring is sealed quickly, and gas with a certain pressure is introduced to solidify and crystallize the molten metal under pressure. The characteristic of this casting technology is that it can significantly reduce the casting defects such as shrinkage cavity, porosity, porosity, etc. in the casting, increase 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 with low pressure anti-gravity casting method. The vacuum low-pressure lost foam casting technology is characterized by combining the technical advantages of low-pressure casting and vacuum lost foam casting, completing the filling process under controllable air pressure, and greatly improving the casting filling capacity of the alloy; Compared with die casting, the equipment investment is small, the casting cost is low, and the casting can be heat treated and strengthened. Compared with sand casting, the casting has high precision, small surface roughness, high productivity and good performance. Under the action of anti-gravity, the sprue becomes a filling and shortening channel, the loss of pouring temperature is small, the liquid alloy is filled and solidified under controllable pressure, the pouring system of the alloy casting is simple and effective, the yield is high, and the structure is compact; Vacuum low pressure lost foam casting has low pouring temperature and is suitable for various nonferrous alloys.
3. Vibration Lost Foam Casting Technology
Vibration lost foam casting technology is to apply certain frequency and amplitude of vibration in lost foam casting process to solidify the casting under the action of vibration field. Due to the application of certain time vibration to the metal solution during the solidification process of lost foam casting, the vibration force causes the liquid phase and solid phase to move relatively, thus breaking dendrites, increasing crystal cores in the liquid phase, refining the final solidification structure of the casting, improving the feeding and improving the mechanical properties. The technology utilizes a ready-made compaction vibration table in lost foam casting, and makes metal liquid nucleate under dynamic excitation through mechanical vibration generated by a vibration motor, so as to achieve the purpose of refining tissue. The method is simple and convenient to operate, low in cost and free of environmental 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 casting technology. Because the technology is characterized by controlling the relative proportion of liquid and solid phases, it is also called transformation control semi-solid forming. The technology can improve casting density, reduce segregation, improve dimensional accuracy and casting performance.
5. Lost Foam Shell Casting Technology
EPC shell casting technology is a new casting method combining investment casting technology and EPC. The method is a new precision casting method, which coats several layers of refractory materials on the surface of the foamed plastic pattern made by the foaming mold and having the same shape as the part, burns and vaporizes the foamed plastic pattern after it is hardened and dried to form a mold shell, and then carries out roasting and pouring to obtain a casting with higher dimensional precision. It has the characteristics of large pattern size and high precision in lost foam casting, as well as the advantages of shell forming precision and strength in investment casting. Compared with the common investment casting, it is characterized by low cost of foam plastic mold materials, convenient bonding and combination of patterns, easy vaporization and disappearance, overcoming the problem of deformation of the investment casting caused by easy softening of the investment casting mold materials, and being capable of producing various alloy complex castings with larger sizes.
6. Lost Foam Suspension Casting Technology.
Lost foam suspension casting technology is a new practical casting technology combining lost foam casting technology and suspension casting. The technical process is that after the molten metal is poured into the mold, the foam plastic pattern is gasified, and the suspending agent mixed in the riser model (or the suspending agent is placed at a specific position of the pattern, or the suspending agent and EPS are made into a foam pattern) and the molten metal undergo physicochemical reaction so as to improve the overall (or partial) tissue performance of the casting.
Due to its low cost, high precision, flexible design, cleanness, environmental protection and suitability for complex castings, EPC technology conforms to the general trend of casting technology development in the new century and has broad development prospects.