INVESTIGATION OF STRUCTURAL CHARACTERISTICS ON FERRITIC NODULAR CAST IRON

The linear form of graphite in gray cast iron is not favorable due to the weakening of the metal base and strong sources of stress concentration at the ends of the lamellae. Converting the lamellar form of graphite into nodular form is done by adding modifiers and pre-secreting smaller amounts of magnesium or cerium. In this way, the stress concentration due to graphite inclusions in nodular cast iron is significantly lower than in gray cast iron. “Nodular cast iron is a foundry pseudobinary alloy of iron and carbon, which was mostly excreted in the form of spherical graphite”. Depending on the structure of the metal base, the properties of strength and plasticity also depend, but certainly the shape, size and arrangement of graphite nodules has a significant influence. For these reasons, the size of graphite nodules is also determined, the highest values of the average nodule being from 50 to 10 μm. In this paper, a researched nodular cast iron with a ferrite structural base is given. The mentioned nodular casting was isothermally improved and tribologically tested, on a “pin and disc” tribometer. The obtained results are presented tabularly and diagrammatically.