Process specification for rapid shelling of silica sol in investment casting

During the 13th Five-Year Plan period, in response to the central green development concept, various environmental protection laws and regulations related to casting continued to be tightened. With the proposal of carbon peak and carbon neutral targets, during the 14th Five-Year Plan period, China’s majority of foundry enterprises should do more in green casting. As a special casting process, investment casting has many processes and long cycle. Its competitiveness is being challenged by similar processes in general industrial manufacturing fields such as automobiles, ships and machinery. In particular, the traditional water glass investment casting process, because it needs to use chlorine salt to harden, will volatilize various acidic substances in the process of shell making, dewaxing and baking, and faces the environmental risk of green and sustainable development. According to the development requirements of modern manufacturing industry, there are two biggest short plates in the traditional investment casting process: one is the environmental protection problem that sodium silicate binder needs to be hardened by chloride salts such as ammonium chloride; The second is the efficiency of circulating multi-layer shell making and single-layer drying. These two problems belong to investment casting shell making. Solving the environmental protection problems and shell making efficiency problems in the process of shell making is the guarantee for the sustainable development of investment casting industry.

The rapid shell making process of investment casting silica sol has been applied in a small range for more than ten years, but the rapid drying methods of shell making used by different enterprises are different, and the refractory materials and adhesives involved are also different, and the process control methods are not standardized and standardized, which brings more inconvenience to the second and third parties.

The formulation, promotion and implementation of the standards are conducive to promoting the improvement of labor efficiency, production environment and sustainable development of China’s investment casting industry. Of course, this standard is formulated and issued for the first time, and there will inevitably be mistakes. At the same time, with the development of various supporting technologies, the standard content also needs to be continuously upgraded and improved. The standard was approved on October 11, 2021 and will be implemented from May 1, 2022.

The standard specifies the raw and auxiliary materials involved in the rapid shell making of silica sol in investment casting, especially the quick-drying agent, silica sol and other materials, and the quick-drying time; The main influence parameters of refractory, especially the conductivity, are specially described; Considering that the conductivity of refractory materials is not stipulated in relevant national standards and industrial standards, this standard separately describes its test method in the form of an annex. The standard specifies the main process of rapid shell making by silica sol and the main process parameters of shell drying, providing guidance, reference and constraint for the normative promotion of domestic investment casting enterprises.