With the development of the casting industry, the casting coating also began to change from the traditional alcohol-based casting coating to water-based casting coating. Especially in recent years, the casting industry began to set off a green wave, and the water-based casting coating with low pollution and low energy consumption developed rapidly. Compared with brush coating, flow coating, dip coating and spraying are more efficient, but flow coating and dip coating are only suitable for the modeling needs of small castings, but they can not be operated for large castings, while spraying is especially suitable for the modeling needs of large castings. The transition and development from traditional alcohol-based casting coatings to water-based casting coatings began with the production of large tonnage castings. However, the molding cost of large tonnage castings is often very high. In order to ensure the quality of sand mold and casting, priority should be given to the use of water-based spraying casting coating.
(1) Through the study of corundum water-based spraying casting coating for large castings, the best coating preparation process is determined: attapulgite suspension agent 2.5% ~ 3.0%, PVA 1.0%, CMC 0.2%, efka 3288 0.4% ~ 0.6%, and the dispersion time is controlled at about 30 min.
(2) Adding organosilicon additives to water-based casting coatings can significantly increase the shear dilution index of casting coatings and improve the spraying performance of casting coatings, but the amount should not be too large, otherwise the solid content of casting coatings will be reduced.
(3) The sintering temperature of single white corundum aggregate is too high, and sintering can not occur at the casting temperature. By adding the sintering additive composed of cerium oxide and zinc oxide (mass ratio 1:4), the sintering point can be reduced below the casting temperature, so that the refractory aggregate can be properly sintered to form a dense glass body, so as to improve the sand adhesion resistance of casting coating.
At present, some large domestic steel casting plants do not completely use water-based spraying casting coatings, but cross use brush coating and spraying, which not only affects the modeling efficiency, but also brings inconvenience to quality control and on-site management. The casting coatings used are not specific for spraying process, and the understanding of spraying casting coatings is also relatively weak. Based on these actual needs, the effects of suspending agent, binder, surfactant and dispersion time on the properties of water-based sprayed casting coatings for castings are emphatically investigated, which is of positive significance to the popularization and application of water-based sprayed casting coatings for large castings.