Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented. Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardened with microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.