Development of a high-temperature mold process for sand casting with a thin wall and complex shape

A new process has been developed for preparing a mold that can be sustained at a heat treatment of 1000 °C, resulting in fabricating cast product having a thin-wall and complex shape. In the new mold process, an inorganic binder composed of tetraethyl orthosilicate and sodium methoxide, and bead powder with a high heat resistance and a low thermal expansion to molten metal were used. The mold sample prepared through the resin-coated sand process using the bead powder showed higher green strength than those through the CO2process using the chamotte sand, while the firing strengths were improved and showed similar values by applying the new mold process using the inorganic binder. In particular, the glassification behavior of the inorganic binder and its phase were not changed even in the mold sample prepared with the recycled bead powder. The thermal expansion of the mold sample was linear and about 0.23% up to 1000 °C, indicating that the mold has a superior thermal stability. The actual product, an impeller, was well cast in the mold prepared by the new mold process, indicating that the new mold process is efficient method in improving mold strength.