It is known that the water condensation zone generated during the green sand mold casting process is softer than the mold before pouring. In order to predict the deformations that occur during casting using FEM thermal stress analysis, it is necessary to take also into account the mechanical properties of the water condensation zone. This paper investigated the stress-strain relationship in the consolidation test of the water condensation zone. Consolidation tests were performed on the following two methods. One method used a test piece prepared with a fabricated device that generates water vapor and allows it to permeate the molded sand test piece. The other method used a test piece prepared by adding water equivalent to the water increase in the water condensation zone before mixing. During the generation of the water condensation zone, the sand skeleton does not move while air and water in the void within the test piece migrate. For this reason, the same water content and void ratio were set in the test pieces prepared by the two methods above by varying the squeezing pressure applied to form the test pieces. When permeating water vapor, the actual molding pressure (1.2 MPa) was applied in the preparation of the test piece. On the other hand, when adding water during mixing, a smaller pressure (0.17MPa) than the actual molding pressure was applied. The stress-strain curves obtained in the consolidation tests were compared to discuss which method is appropriate for clarifying the mechanical behavior of the water condensation zone. As a result, in the case of permeation of water vapor, the results did not follow the geotechnical engineering theory that granular materials yield at the maximum stress they are ever subjected to. In other words, yielding was not observed around the squeezing pressure (1.2MPa) in the preparation of the test pieces. On the other hand, when water was added before mixing, yielding was observed at the squeezing pressure (0.17MPa). However, the squeezing pressure 0.17MPa, which was used in order to standardize the void ratio of the test pieces, is unrelated to the formation of actual green sand mold, and yielding is not expected to occur at 0.17MPa in actual water condensation zones. Therefore, in order to obtain the required mechanical behavior of water condensation zone, test pieces must be prepared by allowing water vapor to permeate through them.
