1. The important parts of the casting should be placed as low as possible
The lower metal of the casting solidifies and is fed under the static pressure of the upper metal, and the structure is dense.
2. The important processing surface should be facing downward or upright.
Experience shows that defects such as pores and non-metallic inclusions mostly appear on the upward surface, while the downward surface or side elevation is usually smoother and less likely to cause defects. When individual processing surfaces must face upward, the processing allowance should be appropriately enlarged to ensure that no defects will appear after processing.
The guide rail surface of various machine tool beds is a critical surface. Defects such as blisters, pores, slag holes, cracks, and shrinkage are not allowed. The structure is required to be dense and uniform to ensure that the hardness value is within the specified range. Therefore, the important surfaces of cylindrical castings such as cylinders and drums are the inner and outer cylindrical surfaces. It is required that the metallographic structure after processing is uniform and defect-free, and the pouring position should be such that the inner and outer cylindrical surfaces are upright.
3. Keep the large flat surface of the casting facing downward to avoid defects such as sand inclusion and scarring.
For large flat castings, inclined pouring can be used to increase the rising speed of the metal liquid level and prevent defects such as sand inclusion and scarring. When pouring at an angle, the H value is generally controlled within the range of 200~400mm depending on the size of the sand box.
4. It should be ensured that the casting can be filled with
For castings with thin-walled parts, the thin-walled parts should be placed in the lower half or below the inner runner to avoid defects such as insufficient pouring and cold shut-off.
5. It should be conducive to the feeding of castings
For castings that are prone to shrinkage cavities and porosity due to large shrinkage of the alloy body or uneven thickness of the casting structure, the selection of the pouring position should give priority to the conditions for achieving sequential solidification and facilitate the placement of the riser and the feeding function of the riser. .
6. Avoid using hanging sand, hanging core or cantilevered sand core to facilitate core setting, box closing and inspection.
Experience shows that hanging sand is prone to collapse during box closing and pouring. It is very inconvenient to place the hanging core on the upper half of the mold. The cantilever sand core is unstable and prone to deflection under the action of metal buoyancy, so it should be avoided as much as possible. In addition, the convenience of core setting, boxing and inspection should be taken into account.
7. The box closing position, pouring position and casting cooling position should be consistent.
This avoids turning the mold over again after closing the box or after pouring. Turning the mold over is not only labor-intensive, but can also easily cause defects such as sand core movement, sand loss, and even misfire.
