Indian Welding Journal

P. K. Ghosh ¹, B. K. Rai ¹

Affiliations
1 Welding Research Laboratory, Deptt. of Mech. & Ind. Engg. University of Roorkee, Roorkee - 247 67, IN

Abstract

Characteristics of weld bead, deposited on steel plate by pulsed current gas metal arc welding (GMAW) process using flux cored steel wire, are studied. Variations in bead geometry and dilution are correlated to pulse parameters like mean current (Im), Pulse frequency (f) and pulse duration (tp). During pulse current welding the effect of arc voltage and welding speed on the bead geometry and dilution has also been investigated. It is observed that the change in any pulse parameter, as said above, significantly influences the peak (Ip) and base (lb) currents of the pulse and consequently affects the bead geometry and dilution. The change in arc voltage is also found to affect the Ip and lb of the pulse. A summarized influence of pulse parameters defined by a factor 0, as a function of Ip, lb, f and tb (pulse off time) has been found to be satisfactorily correlated to the bead geometry and dilution. The bead geometry and dilution observed in pulsed current GMAW process are compared to those found in continuous current GMAW process.

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Pallav Chattopadhyay ¹, B. K. Rai ¹, H. K. Patel ¹, K. B. Desai ¹, Sanjay Chaudhary ¹

Affiliations
1 Larsen & Toubro Limited, Hazira Works; Surat; Gujarat - 394510, IN

Abstract

Super Heavy Tubular Reactors have grown to the size of up to 10m dia and 1500MT weight. These reactors pose huge challenges for the equipment manufacturers since they involve fabrication of heavy thickness Tube sheets (up to 450mm thick), huge diameter shells (10m OD), large number of nozzles and enormous amount of Tube # Tube sheet welds (30000 per equipment). The present paper describes development of various manufacturing technologies to counter such challenges - namely Narrow Gap SAW of Longitudinal & Circumferential seams. Fabrication & Distortion control of super heavy tube sheet including weld overlay on it, Narrow gap orbital Nozzle welding by SAW, Strip cladding on channel shells and Automatic Tube # Tube sheet welding.

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