Diagram showing the scabbing time depending on tensile strength and wet tensile strength of green molding sand. The scabbing time indicates the highest admissible casting time (see buckle test).
The operating point of green molding sand is changed by molding material additions, incoming used core sand, process water and repeated sand cycles.
In addition, the tendency towards buckles can also be estimated on the basis of the green tensile and green cleavage strength. Since there is a linear relation between green tensile strength and cleavage strength, conclusions regarding the tendency towards buckles can also be drawn from the relationship of cleavage strength and green cleavage strength which should be at least 0.15.
Sand extension defects