Effects of Thermal Treatment Processes (TTP) on the Tensile Properties of 0.165% Carbon Steel

In practice, welded low carbon steels do fail at the welded joints in use, thus leading to structural defects, material wastages, structural failure, and at times loss of lives, among others. This has been a great concern to practicing Engineers and Researchers. This study tends to proffer solution to this problem of concern through application of post welded thermal treatments. The welded samples were subjected to some post-weld thermal-treatment (TTP) operations such as normalizing, annealing and quench-hardening using different quenching media (Water, Palm oil, Quartz 5000 Total Engine oil, and Ground nut oil). The Tensile properties of the steel (such as tensile stress, tensile strain, and toughness) were determined before and after welding operations. At yield points, the thermal treatment processes adversely affected the strength of the welded steel. Meanwhile, normalizing and annealing processes enhanced the steel’s ductility and toughness, while quench-hardening process, irrespective of medium of quenching used reduced the steel toughness value. The toughness of the welded steel at the fracture point was also reduced through all the adopted thermal processes, except for normalizing process. The steel ultimate tensile stress and strain and its toughness values were equally reduced after TTP. Improvement of the properties of welded low carbon steel and the reduction of mechanical hazard were achieved through effective TTP. Thus, a better tensile property of welded low carbon steel was elicited by post-weld normalizing and annealing operations. Hence, butt-welded annealed and normalized low carbon steel specimens tend to be more resilient to failures at welded joints.