Hardening Characteristics Of Sodium Silicate Sand Microwave And Collapsibility

The sodium silicate sands were widely used in the commercial foundry for its notoxicity, high strength and low price. But the other adhesives in molding sands have not beenstill entirely replaced with the sodium silicate for its bad collapsibility. There are a lot ofmethods to improve the collapsibility, but their effects are not pleasing.An essential approach to solving the problem of low collapsibility is enhancing bondingefficiency of sodium silicate and reducing sodium silicate amount. Because the sodiumsilicate films covered sands heating by microwave can be cured at the same time, themicrowave-heating process was used in the present work. The bonding efficiency of thesodium silicate was obtained and the collapsibility was developed.The influences of the modulus of sodium silicate and the amount of modifying agentadded on the properties of sodium silicate sands with the different time and power ofmicrowave heating were investigated in this work. The results indicate that the tensilestrength of the unmodified sodium silicate sands reach the maximum value as heating for tenminutes. In the same parameter of hardening process, the lower modulus of sodium silicateis, the higher its tensile strength. With the same amount of sodium silicate, the tensilestrength of 4# modified sodium silicate sands is obviously higher than that of the unmodified.The retained strength of 4# modified sodium silicate sands is lower 0.47~0.6MPa than that ofthe unmodified so that the obvious low retained strength , i. e. a good collapsibility wasobtained. The amount of sodium silicate in the sands may reduce to 1.5 percent even lesswith the modified sodium silicate in foundry practice.