As one of the oldest metal forming processes, sand casting remains a mainstream technology in the foundry industry due to its simplicity, low cost, and wide applicability. Its performance directly impacts the quality and application of castings, primarily in the following aspects.
First, sand casting boasts a wide range of material adaptability and is suitable for a wide variety of metals and alloys, including cast iron, cast steel, aluminum alloys, and copper alloys. Because sand molds are made of refractory materials (such as silica sand) and a binder, they can withstand the impact of high-temperature molten metal, making them particularly suitable for producing large, thick-walled, or complex castings, such as engine blocks and machine tool beds.
Second, sand casting has relatively limited dimensional accuracy and surface quality. Due to the strength and permeability of the sand mold, dimensional tolerances for castings are typically within CT8-CT12 (ISO 8062 standard), and surface roughness Ra values typically range from 12.5 to 50μm. If higher precision is required, subsequent machining or optimization using precision casting processes (such as shell casting and lost foam casting) is necessary.
Furthermore, sand casting offers high process flexibility, making it particularly suitable for small-batch, high-variety production. Compared to metal mold casting, sand molds offer a shorter production cycle, lower costs, and the cavity structure can be quickly adjusted to meet design requirements. However, production efficiency is lower, production time per piece is longer, and sand molds are disposable, making them less environmentally friendly and requiring proper disposal of waste sand.
In terms of mechanical properties, sand castings are prone to internal defects such as shrinkage cavities and air holes, necessitating appropriate gating and riser design and process control. By optimizing sand mold compactness, air permeability, and cooling conditions, the density and mechanical strength of the casting can be significantly improved.
Overall, sand casting occupies a key position in industries such as machinery manufacturing, automotive, and shipbuilding, thanks to its low cost, high adaptability, and broad industrial applicability. Despite limitations in precision and efficiency, its mature and reliable technology remains the preferred process for producing many complex castings. In the future, with the application of environmentally friendly materials and digital technologies, the performance and sustainability of sand casting will be further optimized.
