The Volatile Matter: A Key Indicator of Coal Powder Quality – Volatile matter is the yield of volatile organic substances produced by heating coal powder under specified conditions while隔绝 air. It is primarily composed of water, carbon oxides, and hydrocarbons, but the physically adsorbed water and carbon dioxide in the coal powder are not classified as volatile matter. The level of volatile matter in coal powder is one of the main indicators of its quality. High-quality coal powder has a higher volatile matter content, which facilitates the formation of reducing gases in the mold cavity during casting, leading to the precipitation of large amounts of lustrous carbon and resulting in a smooth surface finish on the casting. However, not all higher volatile matter is better; a volatile matter content exceeding 40% can cause an increase in the gas evolution of the molding sand, leading to defects such as blowholes and underflows in the casting. The volatile matter content should generally be controlled between 32-38%. The residues left after the complete combustion of coal powder under specified conditions are the derivatives of minerals in coal, which are formed through a series of complex reactions like decomposition and combination under certain conditions.