INFLUENCE OF WELDING PARAMETERS ON MIG CLADDING OF M.S. PLATES

Abstract

In the present investigation, a study has been made to assess the influence of welding parameters on the weld deposit characteristics in a single pass normal mode and pulsed mode (25 Hz to 100 Hz) MIG-cladding process. The weld deposits were made on 10 mm thick mild steel base plate using a stainless steel wire of 1.2 mm diameter. The effect of welding current, arc voltage and travel speed was studied on the ferrite content, bead geo-metry and dilution of the overlay. It was found that the ferrite content at the surface of clad metal decreased with the increase in all the above parameters. The penetration and dilution were found to increase with the rise in these parameters. With the increase in welding current and arc volt-age, the bead width was found to increase but it decreased with increase in travel speed. The microhardness measurement in weld clad metal and base metal showed an increase in hardness at the interface with the increase in welding current, arc voltage and travel speed. Corrosion resistance study on the representative specimens was made by boiling them in Strauss solution for 24 hours continuously. The subsequent bend tests showed microcracks in some of these specimens. During root and side bend tests, the cracks were observed in specimens having higher carbon content. During chemical analysis of the clad metal deposits by vacuum emission photo-spectrometer, the chromium, nickel and manganese content were found to decrease with increase in welding current, arc voltage and travel speed but carbon and sulphur content increased with rise in the above parameters. With the introduction of pulsed mode (25 Hz and 100 Hz), bead geometry, dilution, microhardness and the content of carbon and sulphur were observed at lower level in comparison to normal mode of welding, the lowest being at 25 Hz. In contrast, the content of ferrite, chromium, nickel and manga-nese were found to increase in weld overlay, the highest being at 25 Hz. The susceptibility to corrosion (intergranular and uniform) and cracking was found to decrease with pulsed mode of welding.