Foundry industry plays an important role in the development of national economy. In recent years, the output and quality of castings in China have been greatly improved. Since 2000, the total output of castings in China has increased by an average of 11% per year. In recent years, it has maintained the position of the largest country in the world in terms of casting output, but it is still a long way from a powerful foundry country. Therefore, it is of great significance to improve the quality and performance of castings and research and develop new casting processes and methods of energy conservation and environmental protection.
The situation of China’s foundry industry is that the production is scattered, there are many small and medium-sized enterprises, the output of castings is large and the quality is low, and the labor productivity is far from that of foreign foundry powers. For example, according to 1998 statistics, the proportion of high-performance and high-quality castings in the total output of castings is only 2%, while the United States has accounted for 40.7%. At present, most enterprises in China are still unable to introduce advanced modern casting equipment. There are still some problems in actual production, such as high casting cost, difficult to control casting quality, long trial production cycle and so on.
The wide application of iron mold sand coated casting production line in China has proved its advantages of less investment and quick effect, which is suitable for small and medium-sized enterprises in China. The process principle combines the characteristics of metal mold casting and shell mold casting. The relatively thick iron mold is used as the backing to improve the heat dissipation conditions of the mold and accelerate the cooling speed of the casting. The casting has stable size, high precision, good mechanical performance and labor saving. The function of sand coating layer is equivalent to shell mold, separating high-temperature molten iron and iron mold, avoiding the heat excitation effect of molten iron on iron mold, prolonging the service life of iron mold, and preventing the white structure of castings due to the cooling effect of iron mold. Therefore, iron mold sand coated casting combines the advantages of metal mold and shell mold casting, while avoiding their disadvantages. Although the process began to be applied late in China, it has developed rapidly, and the process level and the types of applied castings have exceeded those abroad.
At present, nearly 100 enterprises in China have applied the iron mold sand coating casting process to produce more than 30 kinds of castings such as various nodular cast iron shaft parts, valve bodies, cylinder liners, wheel discs and bases. However, the research on the filling process and cooling process of iron mold sand coated casting is not sufficient.