Sand casting is a long-standing and widely used metal forming process. Molten metal is poured into a sand mold, cooled and solidified, ultimately producing a casting of the desired shape. Due to its low cost, flexible process, and wide range of material compatibility, this method has become an important production method in the machinery manufacturing, automotive industry, and architectural hardware industries.
The core of sand casting lies in mold making. First, a wooden or metal mold (called a master mold) is created according to the casting design. Then, molding sand is mixed with a binder (such as clay, resin, or water glass), filled around the master mold, and compacted to form upper and lower sand boxes. After the sand boxes are separated, the master mold is removed, retaining a precise mold cavity. To ensure smooth molten metal flow and gas removal, a gating system and vents are pre-designed in the sand mold.
During the process, the raw metal is heated above its melting point to form liquid metal with the required composition. This liquid metal is then poured into the sand mold cavity through a gating system. The pouring temperature, speed, and mold preheating all directly impact the quality of the casting. After cooling and solidification, the sand mold is broken and the casting removed for subsequent processing, including cleaning, deburring, and heat treatment.
Sand casting's advantages lie in its ability to produce parts with complex shapes and diverse sizes, with relatively low equipment requirements, making it suitable for both small-batch and large-scale casting production. However, its precision and surface finish are generally inferior to those of precision casting, and the yield of the sand core may affect the integrity of thin-walled structures. Modern technologies, such as the introduction of self-hardening sand, 3D-printed sand molds, and numerical simulation to optimize casting strategies, have significantly improved process controllability and yield.
Overall, sand casting, due to its cost-effectiveness and adaptability, still holds an irreplaceable position in traditional manufacturing, and continuous technological innovation is driving its development towards higher precision and higher efficiency.
