5th International High Manganese Steel Conference - HMNS 2022

The microstructure and tensile properties of an arc welding joint of a Medium Mn steel, with nominal composition of Fe-0.12C-1.7Al-1.8Si-10.4Mn-0.14V (wt%), before and after intercritical annealing (IA) treatment were analyzed. An E-71T-GS flux cored filler was used to weld with a butt joint the medium Mn sheets of 3mm thickness. The initial microstructure of the sheet was composed of retained austenite, α´-martensite and some ferrite. Thermodynamic simulations and experimental results were used to determine the optimal parameters for the IA treatment, in a previous work. The results revealed that before IA the microstructure of fusion zone (FZ) was nearly all martensite, the heat affected zone (HAZ) comprised austenite and α´-martensite, and the base metal (BM) had the initial microstructure that was mentioned above; after IA the major change was exhibited in the HAZ and BM zones which is reflected as an increment of austenite fraction. Microhardness profile after welding showed a notable difference between HAZ and BM compared to FZ, which presented the highest value; while, after IA a significant decrement in the microhardness of the FZ was observed and the values of the other areas were more uniform. The tensile strength of welded steel before IA was higher than the one obtained after IA. The steel experimented a reduction of around 40% of the tensile strength after welding in comparison to the initial condition.