The cooler sand directly beneath the surface increases in volume as it passes through the alpha to beta quartz transformation. As the temperature of the mold or core surface increases, the length and volume of the sand decreases. This loss of volume at temperatures above 573 ☌ (1063 ☏) is the main cause of veining defects. Upon further heating, the sand loses its volume due to softening at the surface of the sand grains. The linear expansion of bonded silica sand causes the volume of sand to increase sharply until 573 ☌ (1063 ☏), where it changes phase from alpha quartz to beta quartz. It was found that two forces act on the surface of the sand that can either contribute or reduce the defect. Advanced testing methods along with computer casting simulations were used to evaluate various sand mixtures for the propensity to form casting veins. Studies were conducted at the University of Northern Iowa Metal Casting Center to determine the mechanisms that cause veining defects in iron and steel castings.
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