Effect of welding processes on mechanical and metallurgical properties of high strength low ALLOY (HSLA) STEEL joints

Abstract

High Strength Low Alloy (HSLA) steels were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higher-strength construction grade materials. During this period, micro-alloyed or HSLA steels became an indispensable class for different applications like automobile industry, ship building, line pipe, pressure vessels, building construction, bridges, and storage tanks. Different welding techniques are used in this study to evaluate the mechanical properties of weldments of HSLA steel. Weldments are prepared using three welding processes such as shielded metal arc welding (SMAW), flux cored arc welding (FCAW) and friction stir welding (FSW). Friction stir welding (FSW) is a solid state technology that has attracted considerable interest since it was invented at TWI in 1991. Structural integrity issues in welding of HSLA steels are associated with different problems encountered in friction stir welding of these steels. The other important problem in welding HSLA steels is to prevent brittle fracture of welded joints due to increased strength of HSLA steels. The solid state characteristics of FSW eliminate the susceptibility of porosity and cracking. The objective is to determine the best welding process for HSLA steel by evaluating weld metal microstructure and mechanical properties including weld metal tensile strength and Charpy V-notch impact toughness are investigated. Charpy impact and tensile tests are performed on standard notched specimens obtained from the welded and main sections of the material. The hardness distribution measurements on the differently welded specimens are conducted in order to gain a deep insight of different welding processes.