The high-temperature resistant mechanism of α-starch composite binder for foundry

A new binder composed of a-starch, kaolin, sodium silicate, dextrin, phosphate and water in proportions 2.5-4.0%, 1.5-3.0%, 0.55%, 0.35%, 0.04% and 2.5-3.5% by weight percent respectively has been developed. The high-temperature resistant mechanism of the mold and core sand bonded with alpha-starch composite binder was studied by way of differential scanning calorimetry (DSC). X-ray diffraction (XRD), infrared (IR) spectra and scanning electron microscopy (SEM) analyses without sand or on a sand base. It is believed that the high-temperature strength of the sand mold or sand core is mainly dependent on the cohesive strength of the adhesive membrane between sand grains. When the binder was heated over 600 degrees C, the kaolin in it reacted with the sodium silicate and phosphate separately, forming Al-O-Si three-dimensional skeleton and heat-resistant AlPO(4), thus, the binder is provided with higher high-temperature resistant strength. This conclusion is also confirmed by the experimental research on the high-temperature mechanical properties of the binder bonded sand and the microstructure observation of the binding film. The research on the high-temperature resistant mechanism of the starch binder bonded sand is helpful to its high-temperature performance optimization and its application in the foundry industry. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.