Investigation of the Microstructure and Mechanical Properties of Quenched - Heat affected Zones of Mild Steel Weldments

Ifeanyichukwu U. Onyenanu, Ignatius E. Ekengwu, Ifunanya M. Mobi


The work investigates the microstructure and mechanical properties of quenched heat-affected zones of mild steel weldment. Here, fifteen samples of mild steel with weldment from metal arc welding process was used and five of the samples were each quenched in palm oil, water, and air respectively. Then the microstructure of the heat-affected zone of the samples were observed. Again, the tensile strength and hardness developed for each of the samples were also studied. For water quenched samples, high hardness, fine grain structure and high cooling rate was observed. This is because water has high specific gravity. Oil quenched sample revealed less hardness and coarse grain structure. While Air cooled sample has hardness and fine microstructure close to that of water quenched. Considering the tensile strength, water quenched samples has highest ultimate tensile strength followed by air cooled sample and oil quenched sample has the least. Again, it was observed that air cool is more ductile than water quenched and oil quenched samples. Finally, oil quenched samples has highest engineering fracture stress followed by water quenched and air cooled samples.


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