STUDIES ON WELDABILITY OF HSLA STEEL UNDER SUBMERGED ARC WELDING PROCESS

Abstract

High -strength steels have often .tensile strengths in excess of 600 MPa. Those with strengths up to '1000 MPa are called ultra high strength steels. These steels contain carbon in the same range as mild steels, but in addition have. small quantities of alloying elements. The microalloyed steels sometimes. called as HSLA steels, in which the alloying elements serve the purpose of increasing the hardenability to some extent. The microstructure may consist of ferrite and bainite or ferrite and tempered martensite. These steels have -satisfactory weldability, as the carbon. content of martensite (if present) is low. HSLA steels can • be used advantageously in, any structural application where the greater strength can be utilized either to decrease the weight or increase the durability of the structure. Submerged Arc Welding Process is used, to fabricate the structure of HSLA Steels. After the welding of the work piece, due to the high temperatures involved and the relatively high rates of cooling, residual stresses are introduced in the material. These can lead to premature failure as they reduce the ductility of the material. High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties - and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they, are designed to meet specific mechanical properties rather than a chemical composition. Weight saving has been a. major consideration for using HSLA steels in automobiles, trucks in order to obtain better fuel economy. The use of HSLA steels in mobile equipment is expected to greatly expand as standards for fuel economy become more stringent while at the same time safety standard and environmental controls serve to increase the car weight.