Effect of welding conditions and flux compositions on the metallurgy of welded duplex stainless steel

Abstract

This research tends to investigate the influence of shielded metal arc welding (SMAW) parameters and flux compositions on the metallurgy of welded AISI 2205 duplex stainless steel (DSS). The consumable was developed using the Al2O3-TiO2-SiO2 flux system as major flux ingredients. The spectrophotometer was used for determining the chemical composition of the base core wire and the base plate. The six different fluxes (F1, F2, F3, F4, F5 and F6, with varied compositions were coated on a 3.2 mm diameter of ER2209 core wire with a coating factor of 1.65 mm. Basicity indexes of the six formulated fluxes were calculated to be less than 0.9 for the developed electrodes, which confirmed the electrodes to be acidic coated electrodes. The influence of welding parameters, particularly current on the hardness characteristics of the weldment was established to ascertain the integrity and applicability of the developed consumable. It was evident that the average welding current of 120A at a constant voltage of 22.5 V produced high hardness properties of the welded joint of DSS with an optimal heat input of 1.65KJ/mm. The hardness properties in most sceneries were observed to be high at heat affected zone (HAZ) and fusion zone (FZ) than in the base metal (BM) region which is attributed to the ferrite content. The average hardness value of the BM was found to be 241Hv/20, for the FZ and HAZ using the produced electrode F5 and F6 were found to be 250HV/20 and 301HV/20 respectively and for F6 was found to be 259HV/20 at FZ and 336HV/20 at the HAZ while that of the commercial electrode (C) was found to be: FZ-245/HV/20 and HAZ-319/HV/20 which is a good indication of its conformity to standard DSS. The SEM-EDS morphological characterization also reveals the austenite-ferrite phase with relatively coarse grains, inter-critical grains and fine grains at the HAZ regions of the welded joint.