EFFECTS OF HEAT INPUT ON THE MICROSTRUCTURE OF DUPLEX STAINLESS STEEL SAF 2304 WELDED JOINTS USING GAS TUNSTEN ARC WELDING

Abstract

The effects of heat input on the microstructure of duplex stainless steel SAF 2304 was investigated. The duplex stainless steel rod of 9.6mm diameter was cut to 60 mm length. The specimen was further cut into two equal parts and the two faces beveled at 60° to the vertical with a root face gap of 2 mm. The specimen was then held by a Jig to maintain to root face gap at 2 mm while welding. The
specimens were then joined together using Gas Tungsten Arc Welding (GTAW) with argon as a shielding gas, Thoriated tungsten electrode and ER 25.10.4L filler rod. The heat input was varied at 0.3 kJ/mm, 1.1 kJ/mm, 1.8 kJ/mm and 2.6 kJ/mm. Specimens were then cut at the Fusion Zone (FZ) and Heat Affected Zone (HAZ) after welding and prepared for microstructure examination. Micrographs from the optical microscopy revealed that there was grain coarsening with increasing heat input from 0.3 kJ/mm 1.1 kJ/mm, 1.8 kJ/mm and 2.6 kJ/mm in both HAZ and FZ of all samples. It was also observed that at heat input of 1.8kJ/mm lesser ferrite was observed at HAZ while at 2.6kJ/mm, lesser ferrite was observed at both HAZ and FZ.