Sand mold bonded with sodium silicate and dicalcium silicate has more merits than CO_2 sand mold. But CO_2 and mold bonded with sodium silicate has difficulty in collapsibility because of its too high residual strength after heating at high temperaturse. Generally speaking the rseidual strength of this mold hsd been considered to depend on sodium silicate which is unconcerned in the chemical reaction between sodium silicate and calcium salt silicate. Therefore, it is expected that the residual strength of this mold will be influenced by varying the temperature and the humidity. In this experiment, we studied the effecst of the temperature, the humidity and the collapsing materials i.e., bentonite, pitch, glyoxal on the residual strength of self-hardening mold. The results obtained are as follows. (1) The residual strength decrease as the temperature rsise. (2) The residual strength increases as thehumidity lowers. (3) When the collapsing materiasl are added to self-hardening mold the residual strength of self-hardening mold and its collapsibility decrease.
展开▼
