... 2.melting point 24500c, 3.density 2.51g/cm3 Boron Carbide, a black powder, is the hardest of the conventional abrasives, Its ... conductivity, low thermal conductivity,high grinding efficiency and no reaction with either acids or alkali etc. Boron carbide is widely used to ... grind and polish hard metal alloy, super-hard metal, high carbide steel, jewel, hard ...