N. Mohan, Punjab Engineering College, Chandigarh, India; S. Pandey, Indian Institute of Technology Delhi, New Delhi, India
Submerged arc welding process contributes to approximately 10% of the total welding. It is one of the most widely used processes for fabrication of thick plates, pipes, pressure vessels, etc. Many of the alloys joined by submerged arc welding process have their designed physical and mechanical properties only within a confined compositional and micro-structural range. This limitation imposes a need for the strict control of the weld chemistry. Apart from the ‘welding wire-flux-base plate combination’, the weld metal composition also depends on the welding parameters. The research paper reports the development of CaO-SiO2 -CaF2 based fluxes with the minor addition of MnO and Al2O3. The use resulted in satisfactory profile, slag detachability, uniformity of ripples and surface appearance. During the development of the fluxes it was observed that the addition of sodium carbonate deteriorated the bead surface and did not reduce the weld metal sulfur content. The increase in calcium fluoride reduced the weld metal silicon content and increased the manganese content. The chemical composition, mechanical properties and radiographs of the groove welds laid with the developed fluxes were found to be satisfactory. To analyze and predict (within the selected range of welding parameters) the effect of welding wire feed rate, open circuit voltage, welding speed and basicity index on the loss & gain of the weld metal carbon, silicon, manganese and sulfur content, models were developed. Partial factorial designs were used to develop the models. The developed models were found to be adequate within the selected range of welding parameters. It was also observed that the welding wire feed rate, open circuit voltage, welding speed and basicity index affected significantly the loss & gain of the weld metal carbon, silicon, manganese and sulfur content.
Summary: The paper reports the development of CaO-SiO2 -CaF2 based fluxes with the minor addition of MnO and Al2O3. Models were developed for analyzing and predicting the effect of welding wire feed rate, open circuit voltage, welding speed and basicity index on the loss & gain of the weld metal carbon, silicon, manganese and sulfur content.
