Study On The Effect Of Components And Adding Rare Earth Elements To Restrain Chilling Tendency Of Thin Wall Ductile Cast Iron

The effect of Carbon、silicon、sulfur and rare earth elements to restrain chillingtendency in thin-walled ductile cast iron and high strength ductile cast iron werestudied. The thin-walled ductile castings with step ladder-like thickness wereprepared. The different graphite nodule counts and chilling tendency of thespeciments with different carbon and silicon were studied. On the basis of theresearch, the effect of sulfur and rare earth adding amount to the graphite nodulecounts and chilling tendency of3mm thick wall nodular cast iron were studied.Finally,using the effect of copper elements get subtle pearlite matrixt todevelope high strength nodular cast iron.(1) In order to obtain no chilling microstructure,different carbon and siliconamounts also the different graphite nodule counts were needed for the ductile castingswith different thickness. The plate specimen with3mm thickness has no chillingmicrostructure when the graphite nodule counts over670nod/mm2. The platespecimen with6mm thickness has no chilling microstructure when the graphitenodule counts over401nod/mm2. The plate specimen with9mm thickness has nochilling microstructure when the graphite nodule counts over210nod/mm2.(2) In order to obtain no chilling microstructure,different rare eath elementswere needed for the plate specimen with3mm thickness of base iron with differentamount of sulfur. Along with the increase of the sulphur content in the base iron, therare earth amount also increased when there was no chilling microstructure. The0.007%rare earth was needed when there was no chilling microstructure in the baseiron contained0.004%sulphur; The0.01%～0.1%rare earth was needed when therewas no chilling microstructure in the base iron contained0.02%sulphur; The0.1%～0.3%rare earth was needed when there was no chilling microstructure in the baseiron contained0.05%sulphur; The0.3%～0.6%rare earth was needed when therewas no chilling microstructure in the base iron contained0.08%sulphur.(3)The high strength thin walled ductile cast iron with no chill was produced by adding a certain amount of carbide forming element and pearlite stabilizing elementCu, and its structure is all fine pearlite.