Abstract

In the present research work, High-Strength Low-Alloy Steel (HSLA) is welded by the SAW process with two passes, one on the top side of the plate and the other on the bottom side of the plate, with heat input of 3.44 & 2.75 respectively. Further mechanical and microstructural characterization was done. Tensile testing of weld metal gave yield strength, UTS, & ductility of 520MPa, 678MPa, and 36.9%, which is an excellent combination of strength and ductility. The Charpy impact test gave impact strength of the base, HAZ and weld are 322J, 295J & 108J respectively which confirms very good toughness properties. The hardness values in base, HAZ, & weld are 211HV, 216HV 214HV respectively. An almost similar hardness value is found in all three regions. DWTT test gave an average shear area of 96.42%. Microstructural observation revealed the presence of acicular ferrite and grain boundary ferrite or polygonal ferrite or allotriomorphic ferrite in weld metal. SEM at higher magnification revealed the formation of acicular ferrite from inclusion. In HAZ acicular ferrite decreases, polygonal ferrite increases, along with a mixture of ferrite and carbide is also present.

Keywords:Acicular; HSLA; SAW; Polygonal; HAZ