The selection of molding sand in the lost mold process is mainly considered from the following aspects:
1) Breathability. This refers to the ability of the sand to allow air to pass through, which is important for ensuring proper filling of molten metal and avoiding defects. For dry sand, air permeability mainly depends on sand size and particle size matching. When it comes to dry sand, air permeability is largely affected by the size of the sand particles. In lost mold casting, the sand particle size is generally larger compared to standard sand casting. As a result, the air permeability requirement is greater than 500. This is essential for accommodating larger cast iron pieces without any complications.
2) Liquidity. When it comes to molding sand, one of the essential properties that need to be considered is liquidity. This characteristic refers to how easily the sand flows through the mold and fills it evenly. A high level of liquidity is crucial for ensuring that the sand can be spread evenly and at an appropriate depth across the entire pattern. The molding sand should have sufficient flow capacity to ensure that the molding sand can be evenly filled into the cavity and depth of the pattern under the action of vibration. A depression.
3) Particle shape. It is better to use angular sand than round sand. After vibration, although the angular sand cannot reach a high enough compactness, it has a high resistance to sand movement, and at the same time, it has a high permeability.
