Aluminum sand casting process from jiachuan's blog

Green sand is new or reclaimed sand mixed with natural or synthetic binders and is the most commonly used material for the manufacture of aluminum consumption molds. Wet sand molds get their name from the fact that they are still wet when molten metal is poured into them. The process flow of aluminum sand casting using green sand and gravity filling method can be summarized as follows:

A mold is created by placing a mixture of sand, clay and water on a model (a replica of the object to be cast). While this process can be done by hand, machinery is usually used for better mold accuracy. After removing the pattern, the clay will have cavities corresponding to the shape of the pattern

The sand mold has two or more parts, the upper part is called the upper part and the lower part is called the lower part. Additional parts called cheeks are also available. The molds are housed in a two-part (more if cheeks are used) box called a flask for protection. Any sand cores needed to create the detail of the part are placed in the mold halves before the flask is closed. The gating system is placed inside and forms a runner to feed the molten alloy into the casting

The halves are closed and clamped together, and the molten metal is poured into the mold. As the metal begins to cool and some shrinkage occurs, molten metal is fed from risers placed in the casting system

Because sand and clay do not absorb heat, the cooling time is much longer than permanent molds or die casting. Coolant (sheet metal) can be inserted into the sand mold to help provide the same cooling rate throughout the casting. Alloys such as Aluminum 319 and 356, Magnesium and Bronze have significantly reduced mechanical properties due to slower cooling rates compared to the same alloys cast using permanent or die casting methods based on secondary dendrite spacing between arms (SDAS) values

After a preset dwell time for the metal to solidify, the casting vibrates. The heat from the molten metal injected into it dries out the moisture, making the casting susceptible to cracking after the metal cools

Aluminium sand casting defects to be aware of are residual oxide film, inclusions, core erosion, porosity and shrinkage.

Aluminium sand casting components are widely used in the automotive and transportation industries, including aerospace. Parts typically produced in sand casting include drivetrains, brackets, suspensions, housings, gears, and more.