The paper presents the experimental results regarding the influence of the multiple thermal cycles on the structural and mechanical characteristics of the weldable C-Mn steel used in energetic. Macro- and microscopic examinations, and mechanical testing made on the intersection welds show that the structural and mechanical characteristics are within the reference range of CMn (type S355JR) steel. So, the hardness of the pearlitic – ferritic structures in the welded joints characteristic zones is less than 216 HB; the tensile strength of the welded joints is more than 430 [N /mm2], imposed value for the C-Mn steel. Also, the weld toughness is between 38 [J] and 52 [J] (at 20 °C), more than 27 [J], value what must be assured for the investigated steel. So, the tendency to brittle fracture of the welded joints is diminished. The presence of some imperfections within the intersection welds imposes a carefully monitoring of all these welded joints by adequate nondestructive examinations.