Influence of Holding Time before Pouring on Creep Recession of Vermicular Cast Iron

The influence of molten iron holding time before pouring and after creep treatment on microstructure, chemical composition and mechanical properties of vermicular cast iron was studied by microscopy, sclerometer, pull test machine and optical spectrum analyzer. The results show that the percent of graphite spheroidization and the pearlite content increased at a certain degree with the extending holding time. If the holding time after creep was less than 15 min, the vermicular graphite in vermicular cast iron exceeded 70% , the pearlite content in matrix was more than 60%, the tensile strength and the hardness surpassed 350 MPa and 220 HBS respectively, the creep recession was not specially obvious. The mechanical properties and microstructure of the vermicular cast iron finally depended on the ratio of the sum of residual rear earth and magnesium to sulfur content.