The effect of sand quality on the bending strength and thermal distortion of chemically bonded sand cores

The quality of chemically bonded sand cores used during the manufacturing process of cast components is highly dependent on the properties of the sand, which constitutes the refractory base media of the core. One of the main advantages of the application of different types of sands as molding aggregates that after casting, they can be reclaimed and can be used again during core shooting. The properties of the sand, however, could be remarkably changed during the casting and reclamation processes. This study aims to investigate the effects of the properties of the base sand on the mechanical strength and thermal distortion properties of samples made from new and thermally reclaimed silica sand. For this purpose, particle size analysis, specific surface area, and loss on ignition measurements, as well as differential thermal analysis coupled with thermogravimetry, were executed on the base sands, and the sand grains were analyzed with scanning electron microscopy and X-ray diffraction. Test pieces were made with hot box and cold box technology for bending and hot distortion tests. It was found that by the utilization of reclaimed sand, cores with higher average bending strength and lower thermal deformation can be produced. These differences can be traced back to the more advantageous granulometric properties, lower impurity content, and lower thermal expansion of thermally reclaimed sand.