Foundry Fluxes

When the molten metal in mould cavity begins to solidify, it beings to contract. This may lead to voids in the solidifying casting. APC powders are used in risers to ensure that the molten metal present there stays liquid, and gradually fills the voids so formed. APC powders are available in three forms.
A. Exothermic Type
The compound is formulated so as to continuously and gradually release heat for long duration. The temperature reached is to the tune of 1000° C thus ensuring that the metal stays molten for greater duration. Even when the compound is used up entirely, it serves as an insulating shield to prevent heat loss from molten metal to the outer environment.
B. Feeding Type
This is iron oxide based APC powder, capable of reaching higher temperature upto 2000° C for longer duration. It also serves as a fresh resource of molten metal during casting solidification and is used especially for avoiding carbon pick-up problems in steel casting.