Abstract <p>Metal active gas arc welding (MAG) was applied to join 304 stainless steel with Q235B/Q345 low-carbon steels. A voltage of 20&#xa0;V and a current of 160 A were chosen for the welding process. The MAG process was performed at a speed of 40&#xa0;cm/min, and a shielding gas composed of 98% Ar + 2% O2 was applied. The investigation encompassed analyses of the microstructure, crystal orientation, energy spectrum, microhardness and tensile properties of two dissimilar welded joints. In addition, a detailed analysis of their tensile fracture mechanisms was conducted. The findings revealed a uniform distribution of skeletal ferrite within the weld. Multiple parallel dendritic ferrites can be observed at the austenite grain boundaries within the heat-affected zone (HAZ) of the stainless steel. Conversely, the microstructures of the Widmanstätten, ferrite, and pearlite structures are much more intricate in the HAZ of the low-carbon steel than in that of the stainless steel. Furthermore, a significant quantity of carbides (M₂₃C₆) can be observed in the HAZ of Q345 steel. A distinct visible platform region of iron and chromium can be observed in the energy-dispersive X-ray spectroscopy (EDS) map of the 304-Q235B welded joint. In contrast, notable gradual variations in the iron and chromium components (region without a platform) can be observed in FZ-Q345, indicating that discernible elemental diffusion occurs in the fusion zone (FZ) of the 304-Q345 welded joint. Due to the inconsistent thermal conductivities between the stainless steel and the low-carbon steel, which are the two base metals, a high-angle grain boundary (HAGB) microstructure can be observed in the weld center of the two dissimilar welded joints. The 304-Q235B welded joint is observed to break in the weld for this reason. However, the 304-Q345 welded joint fractures at the HAZ of Q345 steel due to the presence of carbides.</p>