This study examines the microstructural, mechanical, and fractographic characteristics of friction-welded (FW) joints between SA 213 T12 and SA 213 F12 low alloy steels at rotational speeds of 55, 60, and 65 rps. Microstructural analysis using optical and SEM imaging revealed distinct weld zones, including the interface (IF), partially deformed zone (PDZ), and heat-affected zone (HAZ). The IF exhibited refined bainite and acicular ferrite, with increased dynamic recrystallization at 60 rps, leading to enhanced mechanical properties. Elemental mapping through EDS confirmed uniform chromium and molybdenum diffusion across the IF, with greater mechanical mixing at higher speeds. Microhardness profiling showed peak values at the IF, particularly on the SA 213 F12 side, decreasing towards SA 213 T12. The hardness distribution narrowed at higher speeds due to increased flash generation. Tensile testing revealed that all joints exceeded the base metals in ultimate tensile strength (UTS), with the highest UTS at 60 rps. Fractographic analysis confirmed a predominantly ductile failure, with finer dimples at 60 rps, correlating with improved elongation and strength. These findings demonstrate that an optimal rotational speed of 60 rps yields superior mechanical performance and microstructural refinement, providing valuable insights for optimizing FW parameters in high-performance applications.