Among the total casting production, 60% -70% of castings are produced using sand molds, and about 70% of them are produced using clay sand molds. The main reason is that sand casting has lower costs, simpler production processes, and shorter production cycles compared to other casting methods. So castings such as the engine cylinder block, cylinder head, and crankshaft of automobiles are all produced using the clay green sand process.
When the wet mold cannot meet the requirements, consider using clay sand surface dry sand mold, dry sand mold, or other sand molds. The weight of castings cast with clay green sand can range from a few kilograms to tens of kilograms, while castings produced with clay dry mold can weigh tens of tons. Generally speaking, for medium to large castings, cast iron can be produced using resin self hardening sand molds, and steel castings can be produced using water glass sand molds. Castings with precise dimensions and smooth surfaces can be obtained, but the cost is relatively high.
Of course, the precision, surface finish, material density, metallographic structure, mechanical properties, and other aspects of castings produced by sand mold precision casting are relatively poor. Therefore, when these performance requirements of castings are higher, other casting methods should be used, such as investment casting (wax loss), die casting, low-pressure casting, and so on.
The casting method should correspond to the production batch, such as sand casting, and factories that produce in large quantities should create conditions to adopt better molding and core making methods. The production line of old-fashioned shock or shock compression molding machines is not high enough in productivity, and workers have high labor intensity and high noise, which is not suitable for the requirements of mass production. Therefore, it should be gradually transformed. For small castings, a box less high-pressure molding machine production line with horizontal or vertical parting can be used, which has high production efficiency and less floor space for solid molding; For medium components, various box high-pressure molding machine production lines and air impact molding lines can be selected to meet the requirements of fast and high-precision molding production lines. The core making method can use efficient core making methods such as cold core box, hot core box, shell core, etc. Medium batch large castings can be considered for resin self hardening sand molding and core making. For heavy castings produced in small batches, manual molding is still an important method. Manual molding can adapt to various complex requirements and is relatively flexible, without requiring many process equipment. It can be applied to water glass sand molds, VRH method water glass sand molds, mail ester water glass self hardening sand molds, clay dry molds, resin self hardening sand molds, and cement sand molds, etc; For heavy castings produced in a single room, the use of pit molding method has low cost and fast production. Mass production or long-term production of standardized products using multi box modeling or split box modeling is more suitable. Although the initial investment in molds, sandboxes, etc. is high, compensation can be obtained from saving molding time and improving product quality. Low pressure casting, die casting, centrifugal casting, and other casting methods are only suitable for mass production due to the high cost of equipment and molds.