Ultrafine Spheroidal Graphite Iron Castings

Gravity die casting of spheroidal graphite iron had been attempted controlling free nitrogen during preparing base molten iron, magnesium treatment, inoculation and pouring. In this study, the actual CO/SiO2 reaction temperature of base molten irons was surveyed and magnesium treatment was conducted at that temperature. The mold was made of steel and the cavity size was thickness of 5.4 mm and diameter of 35 mm. As the results, ultrafine graphite nodules were obtained without chill in as-cast condition. They were average diameter of 7 µm and density count of over 3000/mm2. Knuckle for automobile was also cast taking the same procedure. Knuckle had no meager defect like shrinkage, chill etc. in as-cast conditions. The possibility of no chill has become extremely higher than former study.