Microstructure and Mechanical Behavior of Welded and Heat-Treated AISI 1020 Steel

Post weld heat treatment methods are widely adopted to improve the mechanical properties of AISI 1020 steel. AISI 1020 is a low-carbon grade of steel which is usually ductile and strong. It shows a fair weldability under all types of fusion welding techniques. This work deals with the microstructure and mechanical property analysis of AISI 1020 steel plates which were first welded by ‘shielded metal arc welding (SMAW)’ and then heat treated. During heat treatment, heating temperature and holding time were kept same for all the samples while the rate of cooling was changed for every welded sample. One welded plate was kept in ‘as received or original’ condition so that a comparative assessment can be done on its behalf. The microstructural appearance was found in good relationship with the tensile strength and hardness of the samples. A huge alteration of microstructure was reported in the study. The sand cooled sample, due to possessing coarse α + Fe₃C, imparts 7% lesser hardness and 85% higher tensile strength in comparison to ‘as received’ sample. The Also, XRD analysis was carried out to check the phases present in each type of sample. The XRD peaks of welded joint of each plate contains two planes of Fe i.e., α (110) and α (200). This means no defects or oxide formation were recorded after heat treatment.