Why does chromite sand not stick to sand?
Chromite sand has a black glass appearance,
a Mohs hardness ： 5.5~6.5,
density：4.3~4.8g/cm’3,
high refractoriness :1850℃
and 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 cannot easily penetrate into the gaps between sand grains, thus preventing mechanical sticking.
The thermal conductivity and heat storage coefficient of chromite sand are very high, so the cooling rate is fast, so that the metal on the surface of the casting cools and solidifies quickly.
At this time, low-melting point cooling materials such as tiny fayalite formed during high-temperature pouring on the surface of the metal and mold shell also solidify rapidly as the molten metal cools rapidly.
Due to the fast solidification speed, an amorphous glass phase appears between the mold shell and the casting surface, so it is easy to clean it from the casting surface 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.
