Calciumcarbonate (CaCO3)

Limestone is added when melting in a cupola furnace for adjustment of the respective slag. In this process, unhydrated lime (calcium oxide CaO) is reduced and a uniform slag flow is achieved. As a general rule, between 20 and 30 % of limestone is added. The coke ash, the sand adhering to the charge material and burnt particles of the furnace lining are neutralized by the lime from their acid condition so that slag (s. Neutral slag) with a low melting point is obtained.