鋳型内残留強度測定法の改善および水ガラスを粘結剤とした鋳型内残留強度に関する一考察

抄録

  As a substitute for high speed steel teeth, sintered hard alloy teeth were employed to improve the measurement of retained strength of sand mold. Effects of pouring conditions on retained strength of mold with sodium silicate-bonded silica sands were investigated by means of scratch test with sintered hard alloy teeth.
  The results obtained are as follows:
  (1) Sintered hard alloy teeth are much more excellent in durability than high speed steel teeth, and there is more accuracy in experimental results.
  (2) Retained strength of metal-mold interface in mold with sodium silicate-bonded silica sands has a characteristic curve, as shown in Fig. 13∼15. In this curve we have found the first maximum strength due to sintering of sands, the second maximum strength caused by a volume change with crystballite transformation of quartz and insufficient sintering of sands, and the minimum strength resulting from the formation of cracks in binder by the large expansion and contraction of sands during the α→β quartz transformation with heating and cooling. Though the shape of retained strength curve does not change with pouring conditions, it moves towards the right by increasing the head in molten bath or pouring temperature. The first maximum strength value rises by increasing the head in molten bath or by decreasing the pouring temerature. But, effects of pouring conditions on the second maximum and minimum strength values are not clear. The above-stated phenomena are greatly influenced by the thermal effect of molten metal.