<p>Low transformation temperature (LTT) welding consumables exert a significant influence on mechanical properties. This study investigates the effects of LTT welding consumables on the microstructure and tensile deformation behavior of welded joints. The results show that, compared with the C joint (welds made with the CHW-95C wire), the LTT joint exhibits comparable strength while demonstrating superior ductility. The elongation of the LTT joint (10.5%) is approximately 50% higher than that of the C joint (7%). In both joint types, the weld zone exhibits the highest microhardness, whereas the outer heat-affected zone (OHAZ) shows the lowest, a hardness gradient that promotes strain localization. Compared with the C joint, the LTT joint possesses a smaller average grain size of ferrite and pearlite in the OHAZ, while the weld zone displays larger average martensite lath size, resulting in a reduced microhardness difference between the weld zone and the OHAZ. This diminished hardness difference suppresses strain localization, thereby enhancing joint ductility. Furthermore, stress concentrations arising from dislocation pile-up at grain boundaries in the OHAZ are likely the primary cause of failure in both joint types.</p>