What is Lost Foam Casting?
In lost foam casting, the casting and gating system are made of foams of polystyrene and other materials. During pouring, the foam evaporates after encountering the molten metal, and the molten metal fills the cavity to form a casting. The technological process is making foam, then coating, drying, packing, sand filling, compacting, applying negative pressure, pouring, opening the box after cooling, and cleaning, etc. It is a simple and flexible casting technology, which greatly reduces the workload of modeling and cleaning, and is suitable for mass and automatic production.
EPC Filling Sand Requirements
From its process, we can conclude that the ideal EPC filling sand should meet the following process requirements:
1. High refractoriness, high thermal conductivity, reducing sand sticking and cleaning workload of castings.
2. Good fluidity, easy to fill and compact, ensuring casting quality and preventing box collapse.
3. Good air permeability, easy to exhaust gas.
4. The old sand is easy to handle and has high recycling rate.
5. The workshop has less dust and is environmentally friendly.
Silica Sand VS Fused Ceramic Sand
In the early stage of lost foam process production, silica sand was used as filling sand. Due to the limitation of silica sand performance, process and casting defects often appeared, such as poor filling, resulting in casting shape defects and box collapse; Sand sticking of castings, softening and caking of filling sand; Poor air permeability, casting porosity, fire choking and reverse spray during pouring; The treatment effect of old sand is poor, the removal rate of coating powder and foam combustion residue is low, and the consumption of new sand is large; Silica sand has high crushing rate, large workshop dust and harsh environment.
Fused Ceramic Sand Advantages
Fused ceramic sand has the advantages of nearly round particle shape, smooth surface, wide particle size distribution and arbitrary combination, high fire resistance, stable chemical properties, high particle strength and not easy to be broken. It is very suitable for the process characteristics of lost foam molding. Once popularized, it is widely welcomed, significantly improving the above limitations when using silica sand, At the same time, the comprehensive cost is reduced (the consumption of raw sand per ton of castings can be as low as 1-1.5kg in a well-managed foundry), the production efficiency and casting quality are significantly improved, the production environment is greatly improved, and both economic and environmental benefits are achieved. The application practice has proved that fused ceramic sand is an ideal lost foam filling sand at present.
At present, the particle size of the most commonly used fused ceramic sand as filling sand is 10/20 mesh and 20/30 mesh.