Effect of Post Welding Heat Treatment on the Mechanical Properties of Welds of AISI 1040 Medium Carbon Steel

Abstract

AISI 1040 steel is one of the grades of medium carbon steel of American standard and as such, is mostly being used in the industries. Again, when welding a piece of material, only the joint and surrounding area being welded (Heat Affected Zone, HAZ) is heated and cooled. This causes uneven expansion and cooling, and the piece begins to warp or distort at the point. Uncontrolled Distortion may lead to a serious dimensional defect/failure. In order to arrest this failure, Steps may be taken before, during, and after welding to minimize or control the effects of this heat distortion. Controlling the effects of heat distortion after welding forms the basis of this study. To this end, this work studied the effects of post welding heat treatments on the mechanical properties of welds of AISI 1040 medium carbon steel. Butt-welds of AISI 1040 medium carbon steel were prepared with the aid of electric arc welding and subsequently subjected to annealing, normalizing, hardening and tempering heat treatment processes. Finally, the welds were subjected to impact, tensile and Rockwell hardness tests. The results show that tempering improves the toughness of the steel at the HAZ. Normalizing refines the grain structure and relieve the internal stress, Annealing increases the ductility and softens the steel at the HAZ. Hardness and brittleness of the hardened and tempered pair increase while that of the normalized and annealed pair considerably reduced. The study recommends paired annealing and normalizing processes for welds of AISI 1040 medium carbon steel.