Study of welding parameters on mechanical and corrosion properties of cupro nickel alloys Cu Ni

Abstract

Presently, welding of 90/10 and 70/30 Cu-Ni alloys in ship building industries can be performed adequately only by GTAW which uses ER Cu-Ni 70/30 filler wire. Earlier investigations explained on CC GTAW of 70º-80º single V butt 90/10 Cu-Ni alloys welds revealed excessive grain size in FZ and HAZ. This large grain size tends to promote ductility-dip cracking, distortion, hot cracking sensitivity, increase in width of HAZ and residual stresses. Because of the above mentioned problems, CC GATW of Cupronickel alloy welds exhibits inferior mechanical properties. The objective of the present work is to investigate the effects of the various welding parameters on the welding quality of PC GTAW of 90/10 and 70/30 Cu-Ni alloy welds and to obtain the optimal sets of welding parameters so that the quality of welding can be enhanced. In this, firstly investigation on CC GTAW and PC GTAW of 90/10 and 70/30 Cu-Ni alloy welds with same filler wire ERCu-Ni (70/30) is made use for both the welding techniques and alloys. Identification of PC GTAW process parameters such as Peak Current (PC), Base Current(BC), Pulse frequency(PF) and Welding speed(WS) and considering four levels from each welding parameter such as 200A,210A,220A,and 230A for PC, 95A,105A,115A, and 125A for BC, 0.5Hz,1Hz,3Hz,and 5Hz for PF and 140 mm/min,150 mm/min,160 mm/min, and 170 mm/min for WS.. Taguchi s method of approach to design of experiment has been used during optimization of selected parameters and levels for predicting the ultimate tensile strength (UTS) of the PC GTAW joints at 95% confidence level. Analysis of variance (ANOVA) conformation test was carried out for analysing the predicted ultimate tensile strength values obtained from Taguchi method with that of the experimental values of PC GTAW of 90/10 and 70/30 Cu-Ni alloy welds. Experiments were conducted to observe the influence of PC GTAW process parameters on mechanical properties and microstructures of 90/10 and 70/30 Cu-Ni alloy welds.