Study of effects of Heat treatment on the Hardness and Microstructure of Welded Low Carbon Steel Pipes

Abstract

This paper reports investigations made on the effects of annealing heat treatment on the micro-structural and mechanical property behavior of 0.078wt % C steel weld. Welding operation was carried out on the low carbon steel of 0.078wt % carbon content in pair; followed by heat treating (annealing), the specimen was heat treated at the weld zone to a temperature of 850°C using digital heat treatment furnace. For effective study of the effect of annealing on the welded joint, mechanical test (hardness) was carried out and micrographs were obtained to reveal the microstructures of the heat treated (annealed) and un-heat treated samples. From the micro-structural analysis, the micrographs shows that the heat treated sample had a more predominant pearlite structure which is the reason larger areas of the structure is darker and less ferrite structure due to recrystallization and carbon diffusion; hence a significant improvement in ductility, toughness and grain refinement accompanied with decrease in hardness and brittleness.

Keywords: Annealing, Ductility, Hardness, Heat treatment, Microstructure, Welding