STRENGTH OF SAND-LIQUID-GLASS MIXTURES STRUCTURED BY STEAM-MICROWAVE TREATMENT
Purpose. Establishing the regularities of the influence of the conditions for cladding quartz sand with water glass, the parameters of steam-microwave hardening and the shelf life of the mixture on the value of its ultimate strength in compression in the structured state.
Methods. The studies used quartz sand with a clay component of less than 0.5 % by weight and a predominant size of sand grains of 0.23 mm, clad with soda sodium water glass with a silicate modulus of 2.8...3.0 and a specific gravity of 1.43…1.46 g/cm3. To determine the fracture load of structured mixtures in compression by the method of steam-microwave hardening, specimens with dimensions Ø50×50 mm and Ø30×30 mm were made. The samples were tested on an LRu-2e device. The temperature of the mixtures was measured with an error of ±1 °С.
Results. It has been established that the ultimate strength in compression as a result of long-term storage of clad sand, even in a hermetically sealed container, decreases 2...3 times compared with a freshly prepared mixture, which is due to the carbonization of water glass in the clad layer. It is recommended to use freshly prepared clad quartz sand with a temperature of 20...26 °C for structuring a sand-liquid-glass mixture by the method of steam-microwave hardening. At the same time, for cladding with sodium water glass, it is recommended to use quartz sand with a water content of up to 0.2 % water (by weight) and dry it to a moisture content in the hardened water glass of no more than 2...3 % of the weight of hydrated sodium silicate. Descriptions and analysis of the established patterns are given.
Originality. It was established for the first time that the cladding of quartz sand with liquid glass for its subsequent structuring by the method of steam-microwave curing should be carried out with a moisture content in the sand of no more than 0.2 % (by weight), followed by drying the sand to a moisture content in the hardened liquid glass of no more than 2...3 % by weight of hydrated sodium silicate.
Practical implications. The obtained data will be useful in foundry, namely in the field of shaping.
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