Application of Recycling Products of Aluminum Slags in Investment Casting Technology

Abstract

Based on studies of fractional, chemical, and phase compositions of Al-containing slags of different origin, it is established that they are multicomponent systems consisting of metal and nonmetal parts. The nonmetal part includes water-soluble and water-insoluble compounds. A practical flowsheet of recycling of Al-containing slags is proposed with the purpose of its further use as the secondary refractory dusting material (SRDM). The positive effect of the SRDM on the quality of refractory ceramic molds for investment casting and the surface finish of aluminum pilot castings is established. Its use promotes a ninefold increase in strength of refractory ceramic molds when compared with the quartz sand mold and an increase in gas permeability by 15 and 33% when compared with molds made of fused alumina and quartz sand, respectively. The formation of refractory ceramic mold formed based on the SRDM is investigated. The interaction mechanism of the dusting material particles with the suspension is substantiated from the viewpoint of colloidal chemistry. When forming the layers of the ceramic mold using the SRDM, negatively charged aluminum hydroxide micelles are formed. The interaction of oppositely charged Al(OH)₃ and SiO₂ micelles promotes the close engagement of the secondary refractory dusting material particles to each other. The theoretical substantiation of the formation of the ceramic mold layers with the application of the SRDM makes it possible to explain the decrease in the roughness characteristics on the surface of AK9ch alloy castings for the investment casting by a factor of 3.7 when compared with standard production processes.