Welding of Naval Brass using GMAW process

Abstract

Carbon steel tube sheet of a Turbine surface condenser was planed with explosive bonded brass at shell side, as the working medium was seawater, Diameter of tube sheet is more than three meter and the maximum brass plate available was not able to meet size requirement making weld joint unavoidable in brass plate. Manufacturing cycle of tube sheet includes joining of two halves of brass plate, explosive bonding of brass plate on carbon steel and then cutting clad plate to make required size of tube sheet.

Naval brass grade UNS SB 171 C46400 selected as brass plate and planned for import from UK with a cycle time of 8 weeks followed by welding and explosive bonding at Orissa, India. After completion of bonding & Ultrasonic testing, tube sheet will be brought to Mumbai works for cutting followed by 8560 nos. Tube hole drilling on deep hole drilling machine and the final gasket face machining. The critical path is clear as Tube sheet, which is making hurdle in the timely delivery of the project. Over and above the tight manufacturing schedule. Weld joint of Naval Brass (Cu:Zn 60:40) needed to be porosity free to clear final DP test and to sustain the impact during explosive bonding.

Extensive trials taken before start of production welding followed by Procedure qualification. Job of welding total 30 meters of 13 mm thk naval brass completed within 12 days time as per schedule depositing 64 kg of weld metal using track mounted GMAW process.

The work undertaken exhibits that Naval Brass weld joints, when welded with automated process and with optimum duilution can give acceptable radiographic quality weld joints.