In actual production, we prepare granular refractory materials for molding sand and core sand. If clay is used as the binder for molding sand, approximately 1 ton of new sand is required for every 1 ton of qualified castings produced. Therefore, casting sand constitutes a significant portion of the casting production.
In the 17th century, China utilized silica sand as a molding material to produce castings such as bell-shaped objects, mirrors, pots, and artillery. The natural silica sand contained clay, known as mountain sand and river sand, which were predominantly used in the early stages. Its excellent plasticity allowed it to be directly used for mold and core material production, making it suitable for the manual production conditions of the time.
Castings entering large-scale industrial production, especially after the molding process becomes mechanized, exhibit poor properties of clay containing natural silica sand, making it difficult to control the quality of molding sand and unable to meet process requirements. In response, we established a sand factory to clean the natural silica sand. The selection of grinding sand allows for various high-quality silica sands. Alternatively, artificial silica sand can be produced by粉碎ing silicon dioxide. At the same time, the use of various non-siliceous sands has been expanded. The application and development of resin sand molding and coremaking technologies have raised higher quality requirements for casting sand, such as finer powder, smaller specific surface area, and lower acid consumption.
In addition, new requirements have been set for the size, shape, and particle size distribution of sand grains. Due to the scarcity of good sand sources, a new froth flotation technology for silica sand has been developed, enhancing its grade and quality. Generally, there are three shapes of casting sand: ① Round sand: particles are spherical or nearly spherical, with a smooth surface and no sharp edges. ② Polygonal sand: particles are polygonal, with most having obtuse angles. ③ Angular sand: particles have sharp angles, with many of them being acute.
