有機自硬性鋳型の高温破壊時間と浸食スクワレとの関係について

抄録

  Erosion scab is likely to occur at pourening when self-hardening mold with organic binder is used for large steel castings because of its low hot-strength. In order to study this phenomena, the initial load-fracture time curves were obtained by measuring the load change with respect to the time kept at 500°C and 1,000°C for the four organic no-baking binder systems such as phenolic-isocyanate, alkyd-isocyanate, phenol and frun-phenol. Furthermore, these results were compared with the actual pouring, while the theoretical pressure of the poured molten metal was calculated.
  The results obtained are as follows :
  1. Urethane hardening mold easily causes erosion scab, because its fracture time is shorter than that of condensation polymerisation hardening mold. In order to prevent the growth of these defects molding sand should be selected with care. It was found that zircon sand was effective.
  2. The possibility of the erosion scab formation can be predicted from the initial load-fracture time curve and theoretical pressure of the molten metal. However, there is an exception in that the mold with a large degree of softening such as phenol-isocyanate no-bake mold causes erosion scab before burn out.
  3. Especially, for the combustion fracture mold such as organic binder mold, the fracture process and time are important. Initial load-fracture time curves may be used as an effective means of estimation of mold properties at high temperatures.