Artificial spherical sands were cured using water glass as a binder with or without addition of porous silica to prepare the test piece and aluminum alloy casting core. In order to clarify the curing and collapsibility mechanism of inorganic sand mold, the cross-linked structure between their particles were evaluated by SEM observation. A three-dimensional network of crosslinking bridges derived from water glass formed between the spherical particles enables the preparation of a core with sufficient strength for casting. The water glass added to cure the core requires less than 2wt% by weight for the sand prepared by the melting method and about a third as much as that prepared by the sintering method. The high collapsibility of such an inorganic mold is due to the rapid elongation of crosslinking bridges between the particles when heated above a certain temperature so that the particles are separated from each other. Especially for spherical particles with a smooth surface, the relatively small amount of water glass for curing would cause collapsibility accelerated by the thinning of the crosslinked body wall occurring simultaneously with elongation. Further more, the addition of porous silica would induce elongation at a lower temperature as compared to when poroussilica is not added, and is extremely effective for improving the collapsibility of the inorganic sand mold.

  In general, the working environment of foundries is bad compared to other manufacturing industries. To improve this, dust collection facilities are installed or improved. However, they cannot be installed in some factories. Therefore, we attempted to change the sand type from natural silica sand to artificial sand to improve the working environment. Before switching, we investigated the problems that occur when switched to artificial sand and external shrinkage problems were found. After taking countermeasures for the problem, we changed the sand type. As a result, it was possible to reduce the amount of dust in the working environment, and the control class prescribed by the Ordinance on Prevention of Dust Hazard could be reduced from 3 to 2.

  A novel sand reclaiming system for artificial sand was proposed in this report. In this system, recovery sand was grinded by adding a small amount of water and dried. The residue of resin (LOI) was then removed by the reclamation machine with a fluidized bed. When this sand reclaiming system was adopted for recovering artificial sand using an alkaline phenolic binder, significant reduction of LOI was achieved. The use of reclaimed sand using this system made it possible to make molds using smaller quantities of resin. As a result, it was possible to realize lower gas emission mold, which contributed to the improvement of casting quality. The practical application of this system in the cast steel factory is also introduced.

  The cooling capacity of the mold and effect of sand fluidity on pattern deformation in the expendable pattern casting process using artificial sand, were investigated experimentally. The apparent thermal conductivity of the dry packed bed composed of artificial sand used in this work was approximately 10% smaller than that composed of natural silica sand. An aluminum alloy plate was cast using the artificial sand and the cooling curve during solidification was measured. When the artificial sand was used, the cooling curve was almost the same as the case of natural silica sand, and the solidification time was only approximately 2% shorter than the case of natural silica sand. The fluidity of sand during vibration was measured as the flow rate into horizontal hole. When the artificial sand was used, the internal friction coefficient of powder was smaller, and the flow rate into horizontal hole was considerably higher than the case of the natural silica. The deformation of the EPS pattern occurred during sand filling was relaxed by the vibration of the flask. In the case of artificial sand, this relaxation effect was more remarkable and the relaxation time was shorter, than the case of natural silica sand.