Development of single side single pass submerged arc welding procedure for C-Mn steel plates using reusable backing strip

A major portion of fabrication activity in a shipyard comprises of welding of which butt welding takes a substantial share. All the decks, side shells, double bottoms, platforms are made of flat stiffened panels. The conventional method of welding of such panels consists of several operations like welding from top, turning over of the panel, gouging of root followed by final welding. Usually these panels have very large overall dimensions making it difficult for such operations. Where turning over is physically not possible, overhead welding becomes the only alternative. This results in an uneven weld bead and a slower rate of production. The uneven bead shape calls for additional operation of grinding resulting in further man-hour requirement. The genesis of this investigation is based on the requirement of improving productivity by cutting down total welding time. Arc welding being a thermal process, it may lead to very complex physical and metallurgical changes in the work piece. It is practically impossible to establish an exact mathematical model of the same. An attempt therefore has been made in this study to establish a submerged arc welding procedure, which will enable producing sound welded butt joints. The combined effect of the basic welding parameters, i.e. voltage, current, speed along with the effect of thickness, on weld penetration, bead fort-nation, HAZ hardness and tensile strength of welded joint has been studied. An attempt has been made to develop a flux filled reusable backing strip. In the present investigation submerged arc welding flux in its powdered form has been used without application of any external pressure and also without any additives. The study also aims at investigating the effect of flux on the formation of the bottom reinforcement. Experiments have been carried out extensively on C-Mn steel plates of thickness 10mm and 12mm. The welds achieved in this single side single pass welding process indicate the feasibility of the process to achieve quality welds to meet relevant industry standards.