Effect of Isothermal Annealing Temperature and Cooling Rate on Mechanical Properties of Ductile Iron

Abstract

A block of ductile Iron of known composition was procured and samples for various testing were cut out from that block. Tensile test specimens were machined from the block according to the ASTM E8 (Flat sub-size specimen) standard. From a set of nine specimens, three were kept untreated whereas the other six specimens were annealed isothermally following different cooling rates. All the six specimens were heated isothermally to 1000°C and held there for 90 minutes. Out of the six, three specimens were first cooled to 700°C immediately after 90 minutes and held there for 330 minutes and followed by cooling to room temperature. The rest three were immediately cooled after 90 minutes to room temperature. All the six specimens were cooled inside the furnace. Tensile test was performed at room temperature using INSTRON 1195 UTM at a crosshead speed of 1mm/min. After completion of tensile test the broken specimens were cut down to small pieces to study the fracture surface. Hardness values were recorded from Vickers hardness tester by application of 20Kg load at room temperature. X-ray diffraction technique was employed for phase analysis with Philips PANalytica x-ray diffractometer. Graphs were plotted comparing yield strength, elongation and hardness values for the “as-cast” and both the annealed samples.