DESIGN AND FORMULATION OF ELECTRODE COATING FOR WELDING OF HSLA STEELS

Abstract

HSLA steels have acquired a significant position, in the engineering arena as the most important ferrous alloys for design and fabrication of structures. Application of HSLA steels at present is accepted, for almost all specific engineering structures namely — pressure vessels, bridges, buildings, electricals, pylons, penstocks, construction equipment and machines, trucks, tractors etc. Fabrication of structures of required designs for strategic applications makes use of different welding processes and techniques. Depending upon the nature of fabricated structure and its service conditions suitable HSLA steel is selected. For its welding, welding consumables of specific characteristics are required. Attempts have been made to develop coated electrodes for welding of such structures.. Present work involves design and development of electrode coatings, keeping in view the scientific findings for welding of I4SLA steels. Further, the welded Joints have been subjected to various tests to ascertain the mechanical as well as metallurgical properties of the welded Joints. The various test results have been evaluated and provide information regarding suitability of the use of coated electrodes developed in combination with the base plate. The three sets of experimental coated electrodes have been designed and manufactured in this work. The first set of electrodes are with high silica content, successive iterations were aimed at reducing the amount of silica and increasing the amount of ferro-alloys and the carbon it content of the welds The composition of the base plate has been kept in mind while trying to develop the welding electrodes. In the last set of electrodes nickel was introduced into the weld metal through flux addition to enhance the impact strength of the welds at sub-zero temperatures. iv