Q. Can you illustrate Sea Coal?
Sea coal or coal dust is finely ground soft coal (pulverized coal). It is added to moulding sand used to make ferrous castings. It tends to obtain smoother and cleaner surfaces of castings and also reduces the adherence of sand particles to the casting. It also increases the strength of the moulding sand. It is added up to 8%. Also, when molten metal fills the mould, coal dust burns and gives off volatile substances containing the gases CO and CO2 which from a gas spacing between the mould walls and metal. This "gas jacket" not only prevents interaction between the metal of the casting and the sand and thus prevents the metal penetration into the sand, but also makes the mould more collapsible when the metal shrinks. Other carbon rich materials which are sometimes substituted for sea coal are: finely group coke, pitch and Asphalt (2%), graphite (0.2 to 2%).