Abstract
Recently, the fatigue fracture in spheroidal graphite cast iron has attracted great attention. The present study is on the plane bending fatigue test of FCD 45 and 55 with tufftride treatment with a particular focus on the characteristic black-line which was formed in the test piece fracture.
With the tufftride treatment the fatigue limit of FCD 45 increased from about 21 kg/mm2 to 27-28 kg/mm2 and that of FCD 55 from 23-24 kg/mm2 to about 30 kg/mm2. The position of the black-line nearest to the ultimate destruction point for FCD 45 was farther away from the point than for FCD 55. It seemed that this black-line was formed because the particles of spheroidal graphite which were either ruptured or absent in the range between the destruction start-point and the black-line remained intact here.
