Investigation of effects on mechanical and microstructure properties of heat treatment conditions of spheroidal graphite cast iron

In this study, during the heat treatment applied to spheroidal graphite cast iron, the parts were cooled in different cooling environments (heat treatment furnace, air, cooling fan, oil and water) after heating to austenitizing temperature. After the process, microstructure changes in the part and the effect of these changes on the material properties were investigated. Before the heat treatment, JMatPro simulation software was used to investigate the effect of different cooling conditions of the test material on cooling and to determine the cooling rate under these conditions. With this software, cooling curves of the material at cooling rates of 1 °C/s, 3 °C/s and 5 °C/s, graphs of TTT and CTT diagrams and diagrams of other properties were obtained. Within the scope of experimental studies, GGG40 quality spheroidal graphite cast iron parts which were austenitized for 38 minutes at 940°C temperature with heat treatment furnace were cooled at cooling rates of 10,44°C/sn (cooling in water), 4,48°C/sn (cooling in oil), 1,04°C/sn (cooling in fan), 0,31°C/sn (cooling in air) and 0,17°C/sn (cooling in heat treatment furnace) respectively. After the heat treatment, metallographic investigations were performed to determine the changes in phase distribution and grain size due to different cooling rates. In addition, micro-hardness test was applied to investigate the effect of different cooling rates on the material hardness. Strength transformation was performed with the obtained hardness values. Tensile strength values were obtained.