Coal Dust in Foundry Applications: An In-Depth Exploration

Coal dust is primarily used in foundries as a carbonaceous additive in molding sand and as a source of carbon during metal casting. It enhances the quality of cast products by improving the surface finish, reducing defects, and preventing oxidation. The primary roles of coal dust in foundries include:

Molding Sand Additive

Coal dust is added to green sand (a mixture of sand, clay, and water) to create molds for metal casting. It serves multiple purposes:

• Surface Finish Improvement: During casting, the heat from molten metal decomposes the coal dust, forming a gaseous layer that prevents the metal from adhering to the mold surface. This results in smoother castings with minimal surface defects.
• Reduction of Scabbing and Veining: The gases produced by coal dust prevent the formation of scabs and veins on cast surfaces, reducing the need for post-casting machining.
• Enhancement of Mold Strength: Coal dust reinforces the mold’s structural integrity, ensuring it can withstand the thermal and mechanical stresses of casting.

Carbon Source for Cast Iron

In cast iron production, coal dust is used as a source of carbon. Its high carbon content contributes to the metallurgical properties of cast iron, such as hardness, wear resistance, and machinability. Coal dust also helps maintain the carbon balance in molten metal, ensuring consistent quality.