In the present study, Ramor 500 armor steel plates were automatically welded using cold metal transfer arc welding (CMT), gas metal arc welding (GMAW), and hybrid plasma arc welding (HPAW) methods. To investigate the effects of three different fusion welding methods on metallurgical and mechanical properties, the welded joints were examined using optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) and also subjected to radiographic, hardness, tensile, and notched impact tests. The weld metal (WM) region of the GMAW and HPAW joints consisted of massive austenite. In the CMT welded joint, the WM consisted mainly of dendritic austenite and a minor amount of δ-ferrite. Regardless of the welding process, the hardness of both the WM and heat-affected zone (HAZ) regions was found to be higher than the base metal (BM). The tensile strengths obtained by CMT, GMAW, and HPAW were 45%, 50%, and 65% of the BM, respectively. Cleavage-type brittle fractures occurred in the GMAW and HPAW welded joints, while localized ductile fractures occurred in the CMT joints. Tensile test specimens of the CMT joints fractured in the WM, while the GMAW and HPAW joints fractured in the HAZ. In terms of notch toughness, the CMT joints exhibited better impact resistance compared with the BM. GMAW and HPAW joints displayed less impact resistance than the BM, with values comparable with previous studies in the literature.