The present study is to investigate the effects of the single component oxide fluxes in the TIG process on surface appearance, weld morphology, microstructures and micro-hardness during welding of 6 mm thick low activation ferritic/martensitic (LAFM) steel. Herein, a novel variant of the autogenous TIG welding, wherein oxide powders such as CaO, CrO3, Fe2O3, MnO2, TiO2, and ZnO were applied through a thin layer before welding to produce a bead-on-plate joint. Experimental results indicated that activated TIG (A-TIG) process could increase the joint penetration and weld depth-to-width ratio (D/w) of LAFM steel weldment using CaO, Fe2O3, MnO2, TiO2, and ZnO fluxes. However, under same welding conditions, full penetration was achieved with the use of fluxes Fe2O3 and TiO2. Accordingly, it was proposed that, there might certainly be a specific dominant mechanism capable of giving superior penetration, although complete penetration was achieved through multiple mechanisms. Additionally to consider the metallurgical respects of A-TIG process, Vickers micro-hardness test was performed and microstructure characterization was carried out using optical microscopy. No noticeable change in microstructure and micro-hardness values of the TIG and A-TIG weldment was observed. A composite mixture of fine and coarse martensite was observed in weld and HAZ region.