The Effects of Heat Treatment on The Microstructure and Mechanical Properties of EN19 Steel Alloy

The EN19 steel alloy finds its application in the automotive industry like manufacturing gears, spindles, and shafts. In this paper, we aim to improve the strength and ductility of the EN19 steel alloy by tempering process. Generally, heat treatment is the method of exposing the specimen to high temperatures and cooling it, to bring a change in its physical and chemical properties. In this experiment, the process of annealing, normalizing and quenching followed by tempering were performed on the steel specimens. On heating the specimens to 900⁰C, and cooling it from slower to a faster rate, we were able to observe and compare the changes in the microstructure, hardness, tensile strength and impact strength of the specimens before and after the heat treatment. On studying the microstructures and grain analysis of the specimens after each heat treatment process, we were able to observe the difference in the composition of the constituents and understand how this affects the mechanical properties of the material. The quenchants used are oil, water and brine solution for quenching. Since the specimens become brittle on quenching, tempering is performed on the specimens to improve the toughness of the material. It is found that the strength of the specimen is improved by quenching and toughness is improved by tempering it. On comparing the values of toughness of the tempered specimens with that of the quenched specimens, it is found that the oil tempered specimen increases by 25%, water tempered specimen by 80% and brine tempered specimen by 75% from the oil quenched, water quenched and the brine quenched specimens respectively.