Study of single side single pass submerged arc welding using reusable backing strip N. R. Mandal* and Rajiv Maiti An attempt has been made to establish a submerged arc welding procedure that will enable the production of welded butt joints in thin steel plate, having proper fusion and reinforcement geometry in a single welding run. In this work, the combined effect of the basic welding parameters, i.e. voltage, current, and speed, along with the effect of thickness, on weld penetration have been studied. Also 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. Experiments have been carried out extensively on 6 mm and 8 mm thick C–Mn steel plate specimens. This form of backing strip has shown great promise towards achieving single side single run welding. The welds achieved in this single side single pass welding process are not yet 100% satisfactory, however, the results indicate the feasibility of the process to achieve quality welds to meet relevant quality standards. Keywords: Single side welding, Submerged arc welding, Joint geometry, Backing strip, Heat input Introduction A major portion of welding activity in a shipyard comprises the butt welding of large flat plates for fabrication of flat panels. The conventional method of welding such panels consists of several operations such as welding from the top, turning the panel over, 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 grinding operations, resulting in further man hour requirements. The genesis of this investigation is based on the requirement to improve productivity by cutting down total welding time. Implementation of single side welding will result in improvement in productivity and this will be further enhanced if the desired deposition can be achieved by single run. However, this has to be achieved while maintaining the desired level of quality. Since the welding process leads to very complex physical and metallurgical changes in the workpiece, 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 that will enable the production of welded butt joints having proper fusion and reinforcement geometry in a single welding run through experimental investigation. Also the objective was to establish that submerged arc welding can be gainfully utilised to weld steel plates as thin as 6 and 8 mm. In the prevailing shipbuilding practice, the belief is that SAW is not an effective technique for welding such steel plates. The ultimate goal of a welding engineer is to develop a suitable welding procedure for a given welding technique such that full penetration is achieved, along with adequate top and bottom reinforcement. In order to achieve this, all the relevant process variables need to be suitably selected. Dryaton, 1 Doherty et al. 2 and Yang et al. 3 studied the influence of process parameters and the relationship between process variables and bead geometry in the case of submerged arc welding. Joarder, Saha and Ghose 4 studied the effect on microstructure of the heat affected zone and submerged arc weld metal in the case of plain carbon steel. Shin et al. 5 reported an analytical method for predicting through thickness distribution of residual stress in a thick plate undergoing multipass welding. Miyazaki et al. 6 reported one side submerged arc welding using flux copper backing. Malin 7 discussed the effect of joint geometry and welding variables in root weld formation using modified refractory flux one sided two electrode singlepass/ multipass welding. His work was based on using thermosetting backing flux. DuPont et al. 8 conducted a study on the arc and melting efficiency of various welding processes and concluded that with higher arc efficiency higher travel speeds are possible. Bonifaz 9 developed a simple 2D finite element model to calculate not only the transient thermal histories but also the sizes of fusion and heat affected zones in single-pass arc welds considering an arc efficiency of 0?95. Arc efficiency of 0?95 was reported by Goldak et al. 10 for submerged arc welding. Single pass submerged arc welding with three Department of Ocean Engineering and Naval Architecture, IIT Kharagpur, India *Corresponding author, email nrm@naval.iitkgp.ernet.in ß 2005 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 15 June 2004; accepted 4 September 2004 DOI 10.1179/174329305X40633 Science and Technology of Welding and Joining 2005 VOL 10 NO 3 319