The effect of wetting agent on the parameters of dry moulding silica sands bonded with sodium water glass

An attempt has been made to determine the effect of the addition of an agent wetting the surface of silica sand grains, introduced in order to increase the hardening efficiency of selected physical methods applied to the ecological foundry sands bonded with sodium water glass. The effect of water used as a wetting agent of the silica sand grains, added during the mixing process prior to the introduction of unmodified inorganic binders, was evaluated by comparing the mechanical and technological parameters of green sands and sands hardened by drying at 100°C. Tests and studies were carried out on silica sand of medium grain size and on three grades of hydrated sodium silicate, i.e. 137, 140 and 145. It has been found that modification of the method of the base sand processing by adding water prior to the addition of a small amount (1.5 parts by weight) of binder has a beneficial effect on the technological and mechanical parameters of moulding sands obtained after the hardening process. The results of measurements were confronted with the SEM studies of bonds formed between the grains of silica sand. The studies were completed with photographs and chemical analysis of the surface of silica sand grains. Based on a comprehensive evaluation of moulding sands hardened by the conventional drying process, the beneficial effect of a wetting agent, added to the sand mixture in an amount optimum for a given type of binder, has been confirmed.

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