Effect of Intermediate Quenching and Tempering on the Mechanical Behaviour of Low Carbon Steel

This research has assessed the impact of intercritical annealing using the intermediate quenching technique and tempering on the mechanical properties of low carbon steel. The procedure involved austenitizing at 850OC for 1hour followed by quenching in water and thereafter annealed at 730OC, 750OC and 770OC (i.e. α + γ region) for 30 minutes and then quenched in water again. Some of the as-quenched samples were tempered at 320OC for 1hour and cooled in still air. Tensile, hardness and impact tests as well as microstructure characterization were conducted for samples from all the heat treatment schedules. It was observed from the results that martensite volume fraction increases almost linearly as a function of temperature. Ductility and impact decreased with increase in temperature. Tempering deteriorated the assessed mechanical properties. Hence, for a steel of this composition, intermediate quenching should not be followed by tempering.