Process Characteristics of Water-based Self-curing Coatings for Sand Casting

The rheological and gas evolution characteristics of water-based self-curing coatings for sand casting were analyzed and the influence of coating thickness and graded coating on the self-curing rate of coating was studied. The results show that the new water-based self-curing coating has both the characteristics of thixotropic fluid and pseudoplastic fluid,which has moderate thixotropy rate and high brushing index, good brushability and excellent comprehensive balance of flow-leveling and anti-flowability. It can meet the rheological requirements of various coating methods. The self-curing speed of the water-based self-curing coating increases in an approximately linear manner with the decrease of its thickness. Thick coating should be best to paint at one time in the premise of ensuring its surface quality. The gas evolution volume of the new water-based self-curing coating is approximately equal to that of ordinary water-based baking coatings, but the gas evolution speed of self-curing coatings is almost half as that of the latter, which provides good conditions for preventing gas hole defect of castings.