Why does chromite sand not stick to sand during casting?

Why does chromite sand not stick to sand?
Chromite sand has a black glass appearance, a Mohs hardness of 5.5~6.5, a density of 4.3~4.8g/cm’, and a neutral chemical property. Chromite sand has high refractoriness (about 1850℃), good high-temperature chemical stability, does not react with Fe0 at high temperatures, and has no phase change at 1700℃. The wetting angle of stainless steel liquid with the surface of chromite sand at a high temperature of 1500℃ is about 110°, and the wetting angle of 45# carbon steel molten steel with chromite sand at a high temperature of 1357℃ is about 95°. Chromite sand is not easily wetted by high-temperature molten steel, so molten steel is not easy to penetrate into the gaps between sand particles, and thus mechanical sticking defects are easily formed.
The thermal conductivity and heat storage coefficient of chromite sand are both high, so the cooling speed is fast, which makes the metal on the surface of the casting cool and solidify quickly. At this time, the low-melting-point cooling materials such as tiny iron olivine formed when pouring at high temperature on the metal and shell surface also solidify rapidly with the rapid cooling of the molten metal. Due to the fast solidification speed, an amorphous glass phase appears between the shell and the surface of the casting, so it is easy to clean from the surface of the casting during sand cleaning. After sand cleaning, the surface of the pulley casting is bright, and the sand sticking phenomenon on the casting surface before the test no longer exists.