Method of drying refractory coated foam patterns

摘要

A method is disclosed of dehydrating a thin water based ceramic slurry coating on a foam pattern assembly having hidden internal surfaces. The method comprises sequentially subjecting the coated assembly to a first warm air flow at a sufficient temperature and time to dehydrate and remove 60-80% of the water of the coating, and secondly subjecting the dehydrated coating assembly to low level microwave energy to substantially remove the remainder of the water in all of the coating, the dehydrated coating being devoid of bubbles or cracking. The coating is made by use of a slurry comprising a thixotropic silica water suspension with the silica comprising only 40-50% of the slurry; the slurry also may include a small portion of clay and in some cases an acrylic or epoxy glue additive. The pattern assembly or cluster is comprised of a plurality of molding patterns integrally carried by a gating system and common sprue, the patterns being at least four in number and radiating from the common sprue. The patterns may be of a complex nature having tunnels or internal chambers not readily exposed, such as are present in an automotive manifold or head casting pattern.