Apparent thermal properties and thremal conductivity of dry molds and furan resin bonded molds using silica, olivine, zircon and chromite sand were measured by the pouring method. The apparent thermal diffusivity, the apparent thermal conductivity and the apparent heat diffusivity of the dry sand molds obtained by pouring aluminum decreased with increasing void fraction of mold. These apparent thermal properties of the dry molds using silica, zircon and chromite sand obtained by pouring steel were much higher than those by aluminum. However, those of the dry olivine sand mold were not influenced by the pouring metal. The thermal conductivity decreased on heating up to about 600°C, but increased at higher temperatures. The rate of increase was much larger in the dry molds using silica, zircon and chromite sand beyond olivine sand mold and furan resin 1,000°C than that in the dry bonded molds. Furthermore, the solidification time of pure aluminum cylindrical castings coincided well with the values calculated using the obtained thermal properties.

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  The changes of grain sizes, loss of ignition, carbon and nitrogen in molding sands with furan resin or phenol-urethane resin were examined under repeated use. The grain sizes of both molding sands with furan resin and phenol-urethane resin became larger apparently due to residual resin binders, though the sands themselves became slightly smaller. The amounts of loss of ignition, carbon and nitrogen in the recovered sand increased at the initial stages, but later saturated at a constant value. Close relationships between loss of ignition and carbon, and between loss of ignition and nitrogen were observed. Nitrogen contents and weights of the iron castings were also examined after repeated use of the molding sands. Though there was a large increase in the nitrogen contents in the recovered sands, that in the castings increased only a little. The weights of castings increased to some degree. Therefore, it was found that the control of grain size distribution and loss of ignition were important for the repeated use of the molding sands with furan resin or phenol-urethane resin.

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  Machinability of water-soluble nylon added urea-resin was examined. It was excellent with respect to cutting force and tool life with the exception of surface finish. The material was very fragile in machining and was prone to damaging surface finish and precise edge formability. The followings are the proper machining conditions; Nose radius of the cutting tool in turning should be larger than 5mm, and the point angle of the drill less than 80°. Feed rate and effective cutting depth should be as small as possible. Cutting speed of more than 100m/min in turning and that of more than 6m/min in drilling are preferable. In milling, the up-cut is better than the down-cut operation.

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  The movement of molding sand and the distribution of mold density in the air flow press molding process were examined. Further, the distribution of air pressure was experimentally and theoretically analyzed to investigate its effect on the compaction of molding sand. In the process of air flow, the molding sand moves and is compacted along the stream of compressed air in the mold. The mold density becomes higher towards the vent in the pattern plate, and its distribution depends on the air pressure distribution. The location and area of the vent, which affect stream or pressure of the air in the mold, were shown to be the significant factors controlling the compaction of molding sand. By squeezing the mold after the process of air flow, the mold density becomes extremely uniform, and it is little influenced by the dimensional changes of the pattern. The distribution of mold density were compared with that of conventional jolt-squeeze molding process, and it was found that the air flow press molding process is superior in terms of molding performance, particularly with respect to the uniformity of molding sand compaction.

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  The influence of Si content on fracture toughness, such as K_IC, J_IC and R_SC, of ferritic spheroidal graphite cast iron were investigated in the Si content range between 2.34% and 3.47%. The fracture toughness tests were carried out by using 15mm thick CT test pieces at the temperatures of 20°C and −100°C. At 20°C, the specimens with Si contents up to about 3.2% showed ductile fracture. When Si content is about 2.6%, the J_IC and K_IC values are highest, 3.06kg/mm and 223kg/mm^3/2 respectively. As Si content increases up to 3.2%, J_IC and K_IC decrease gradually. But when Si content is about 3.5% the specimen is in the fracture-toughness-transition region, where the mode of fracture becomes brittle and the fracture toughness decreases greatly, and the J_IC and K_IC values decrease to 0.97kg/mm and 125kg/mm^3/2. At −100°C, the fracture conditions of all specimens are brittle. There is a large drop in the J_IC and K_IC values of each specimen compared to those at 20°C. The value of Si content in the fracture-toughness-transition region is about 1% less than that of 20°C.

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