Zamiatin M. Theoretical and technological bases of water-based non-stick coatings application for frozen molds and cores.

The thesis is devoted to research the formation laws of aluminum alloys castings, which are produced by low pressure casting into a frozen mold with a non-stick coating to prevent the surface defects occurrence on them. In the paper the analysis of modern technological schemes of frozen molds manufacture for the castings production is implemented. The modern approaches on the surface defect formation mechanisms on the castings are spotlighted, the materials used in molds and cores, as well as non-stick coatings production applied for non-ferrous metals casting are analyzed. The basic physical, mechanical and thermal properties of non-stick coatings for frozen molds and cores are researched. The antiburning coating properties, thermal conductivity, gas exudation ability, gassing dynamics, gas permeability, sedimentation stability, adhesion and cohesion properties in dependence on the antiburning coating composition, as well as their influence on erosion and veining formation on the molds and cores are defined. The description of mold material heating mechanism is created, the direct relationship between the frozen core diameter with non-stick coating and casting wall thickness, with no premature demolition of the core, is established. The technology of aluminum castings production in the frozen molds with non-stick coating under low pressure is developed. The heat transfer fluxes mathematical model for calculation in the system "melt – non-stick coating – frozen mold (core)" is elaborated. The benefits of non-stick coatings use when casting in frozen molds with frozen cores are grounded, both theoretically and experimentally. The surface defects formation decrease by about 25% in result of non-stick coatings application is defined. The technological recommendations regarding the antiburning coating composition for the frozen molds and cores, the manufacturing technology of low pressure castings for aluminum alloys in the frozen molds and cores for the aviation industry are developed and given.