The paper presents the results of basic research on the influence of the properties of sand grains on electrical properties of water glass moulding sands. It shows electrical properties of the main component – sand grains, crucial to the kinetics of moulding sands heating, such as permittivity εr and loss factor tgδ. Measurements were carried out with the use of the perturbation method for silica, chromite and olivine sands of different mineral, chemical composition and particle size distribution, as well as for moulding sands with water glass grade 145. Analysis of the results of measurements of electrical properties shows that all moulding sands are characterized by a similar permittivity εr and loss factor tgδ. It was found that the electrical properties and the quantity and quality of other components may have a decisive influence on the effectiveness and efficiency of the microwave heating of moulding sands with sand grains. In determining the ability to efficiently absorb the microwave radiation for mixtures which moulding sands are, the impact of all components influencing their individual technological parameters should be taken into account.
Presented are results of a preliminary research on determining a possibility to use microwave radiation for drying casting protective coatings applied on patterns used in the lost foam technology. Taken were measurements of permittivity εr and loss factor tgδ at 2.45 GHz, as well as attempts were made of microwave drying of a protective coating based on aluminium silicates, applied on shapes of foamed polystyrene and rigid polymeric foam. Time and results of microwave drying were compared with the results obtained by drying at 50 °C by the traditional method commonly used for removing water from protective coatings. Analysis of the obtained drying kinetics curves demonstrated that selection of proper operation parameters of microwave equipment permits the drying time to be significantly shortened. Depending on kind of the pattern material, drying process of a protective coating runs in a different way, resulting in obtaining different quality of the dried coating.
In the paper presented are results of a research on influence of electrical and physico-chemical properties of materials being parts of multicomponent and multimaterial systems used in foundry practice on efficiency and effectiveness of microwave heating. Effectiveness of the process was evaluated on the grounds of analysis of interaction between selected parameters of permittivity and loss factor, as well as collective index of energy absorbed, reflected and transmitted by these materials. In the examinations used was a stand of waveguide resonance cavity for determining electrical properties and a stand of microwave slot line for determining balance of microwave power emitted into selected materials. The examinations have brought closer the possibility of forecasting the behaviour of multimaterial systems like e.g. model, moulding sand or moulding box in microwave field on the grounds of various electrical and physico-chemical properties. On the grounds of analysis of the results, possible was selecting a group of materials designed for building foundry instrumentation to be effectively used in electromagnetic field.