抄録
Better results are being obtained from extensive usage of the synthetic resin in molding sands. The advantageous points of the urea synthetic resin sand are favourable permeability, the high drying strength, easy separating of sand from castings and cheaper than oil sand, etc. The following conclusions were obtained by the results of experiments. 1. 2 to 3% mixture of synthetic resin is sufficient. 2. 2% mixture of ogin is adequate. 3. The water mixture of around 1% is adequate. 4. 1% mixture of wheat flour is adequate when the mixture of water is 1%. 5. The adequate time for mulling is 15 to 20 minutes. 6. The sufficient time and temperature for drying are 90 minutes at 150°C and 60 minutes at 200°C. The temperature above 200°C is not good. 7. Absorption of moisture is small when drying is sufficiently performed. 8. It appears that the mixture of bentonite and clay is inadequate. 9. Painting of the mold is necessary owing to a comparatively low temperature of thermal decomposition. The application of the above results of experiments to the quantitative production is greatly contributing to improvement of the operation.
