Investigations on weld bead geometry and microstructure in CMT, MIG pulse synergic and MIG welding of AA6061-T6

Abstract

This research paper focuses on a comparative study on weld bead geometries of three different welding techniques: Cold Metal Transfer (CMT), Metal Inert Gas Pulse Synergic (MIG P) and MIG Manual Standard (MIG M). Bead-on-plate tests were performed using ER4043 (AlSi5%) as a filler material on the 3.18 mm thick plates of AA6061-T6. Current (80 A, 100 A and 120 A) and welding speed (7.5, 10.5 and 13.5 mm sec−1) were used as input process parameters while shielding gas flow rate and contact tip to workpiece distance (CTWD) were maintained constant as 15 l min−1 and 10 mm respectively. The weld beads processed by all the three techniques are compared by analysing the weld bead geometry. Microstructural characterization is carried out using optical microscopy and Field Emission Scanning Electron Microscope (FESEM). CMT has high dilution and penetration with low heat input. Compared to MIG Pulse Synergic and MIG Manual, CMT shows a drastic reduction in residual stresses. A good amount of penetration and dilution with low heat input is necessitated for better joint efficiency.