Friction welding of dissimilar joints copper-stainless steel pipe consist of 0.06 wall thickness to pipe diameter ratio

Abstract

This paper examines dissimilar friction welding between electrolytic tough pitch copper (ETP-Cu) and stainless steel (SS) of grade 304 L for pipe joint configuration, having 0.06 wall thickness to pipe diameter ratio. The welding is performed using the continuous drive friction welding method. The welded joint is evaluated by visual inspection, leak-proof ability by helium leak detection testing, microstructure features by optical and scanning electron microscopy, energy dispersive x-ray spectroscope, x-ray diffraction patterns, tensile testing, and hardness measurements. The continuity of welding is evaluated by peripheral inspection and testing on four different locations of pipe welded joint. The results revealed that sound joints between dissimilar materials of Cu-SS are established with evidence of resistance to leak at room temperature and after cryogenic shock test. The Cu-SS pipe joint received excellent strength of 242.48 N/mm2, which is nearly 80% of ETP-Cu base material. The microstructure changes are distinctly observed at the Cu side, whereas no significant microstructure changes are observed at the SS side. The microstructure features are consisting of full dynamic recrystallization zone and partial dynamic recrystallization zone that are identified at the Cu side. However, no adverse effect of microstructure on tensile strength and hardness is observed. The weld continuity in the periphery of pipe configuration is observed at four different locations. A continuous reaction layer at four investigated locations is identified, with the presence of Cu and Fe elements at the joint interface.