| The mold properties on the early stage of 2 CaO·SiO₂ self-hardening sand contained 1% of 2 CaO·SiO₂ powder, are investigated according to the molecular ratio of water glass, which are very useful for controlling of molding method and surface in fields. From the results obtained on this study, the following tendency could be found; 1) The higher molecular ratio-water glass seems to be reacted more rapidly with 2 CaO·SiO₂ than the lower does; thus the specimen of the higher appears higher compressive strength during the specimen is held for 15 min. through 7 hrs after molding. 2) The sand mixture might be usable within a definite time after mulling to have enough mold strength for preventing the drops and cracks within 15 min. through 30 min. depend on the molecular ratio. 3) The desirable moisture content, under 2% remained after holding the specimen for 24 hrs, would be shown when the water glasses are added of which molecular ratios are 2.77 through 3.25. 4) Regardless of the molecular ratio of water glass to be added, the longer holding time after ramming the mold, the better mold surface stability can be obtained. however the lower molecular ratio, the better early surface stability is shown. |
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