The coating methods mainly include spraying, brushing, flow coating, dip coating and drenching coating. Uniform spraying coating and high dimensional accuracy of sand castings; At the same time, the spraying efficiency is high and the labor intensity is low, so the spraying process is selected in this study. When the sand sticking of cylinder block sand castings is very serious, coating is one of the most effective ways to solve the sand sticking and sintering. However, the problem of inadequate spraying is easy to occur in the actual spraying process. In addition, the coating spraying is too thick, which will also have a negative impact on the quality of sand castings, and it is easy to mold unqualified wall thickness and pore defects of sand castings. The appropriate coating thickness should not only prevent sand sticking, but also not affect the air permeability of the mold. The coating thickness is controlled by the spraying time, so the spraying time will affect the quality of sand castings. Objective to study the effects of different coatings and spraying time on the surface quality of sand castings.
The experiment mainly investigates the effects of coating type, spraying time and ignition on the surface quality of sand castings, so as to provide guidance for determining the coating process.
The main purpose of ignition is to evaporate the water contained in the coating through combustion, so as to avoid water explosion during pouring due to excessive water in the coating. If water explosion occurs due to high water content, manydefects such as sand sticking, sintering, pores and loose sand holes will occur.
If other methods such as blowtorch or resistance wire are adopted, it is easy to cause over baking, that is, the excessive baking will aggravate the migration of water in the sand mold, resulting in coating drying crust or too low water in the sand mold. If the water content in the sand mold is too low, it will lead to sand washing or large-area loose sand defects.