Control of weld torch oscillation in automated multilayer welding of thick pipes with narrow- groove geometry is a challenge as groove width changes during progress of welding and improper oscillation can lead to incomplete fusion.

A novel method for automatic control of oscillation of welding torch in orbital welding using gas tungsten arc welding process for thick pipes was developed with a specially designed welding torch having feedback mechanism.

The oscillation of torch assembly along with filler wire feed nozzle is achieved using a linear slide with stepper motor and the speed of oscillation is controlled by a potentiometer. The controller controls the torch rotation, oscillation width and speed, wire feeding rate etc. Weld parameters like current, voltage, argon gas flow rate etc. are set suitably.

A special welding torch was designed and manufactured in-house and welding trials were conducted on 28-mm-thick Inconel 600 pipe with narrow J groove geometry.

The oscillation of welding torch could follow the geometry change in the welding groove during welding and oscillation parameters like oscillation amplitude and dwell time are consistent with groove geometry. The test piece after completion of welding was radiographed and ultrasonically tested.

The tensile test and bend tests were also conducted as per ASME SEC IX.

The results confirmed that the new methodology for oscillation control improved sidewall fusion and ensured uniformity and smoothness of the weld. This method improves the quality of welds in automated orbital welding by reducing the occurrence of incomplete side wall fusion and helps in increasing the productivity.

This article is shared by Niraj Uttam, A. Ibungohal, K. Prem Sai & I.V.N.S Kamaraju of BARC Facilities, Kalpakkam