An Investigation in the Exothermic-insulating Riser of Spheroidal Graphite Cast Iron

In practice using sand open risers and pouring hot molten metal into it once or twice every 20~25 minutes after pouring to compensate the volume contraction of spheroidal graphite cast iron rolls is very common.This method consumes a large quantity of metal for riser which is about 15% of the gross weight of the rolls.In order to save metal and to improve the quality of the upper edge of the roll barrel, we make use of the riser covered with Al-exothermic compound, in combination with insulating sleeve instead of previous procedure in which straw-ash heat insulator was used to cover the dry-sand open riser.The results of experiment show;that the eutectic transformation time of spheroidal graphite cast iron elongates by 33~62%;shrinkage cavity transformas from conical-shape to basin-shape.The hight of denser part increases, and the riser hight may be decreased by about 25~50%. As a result, the riser metal can be saved up to 20~50%. It can be coucluded that using the exothermic-insulating riser is most efficient and advantageous for the production of spheroidal graphite cast iron rolls.