<![CDATA[S355J2 steel is widely used for load-bearing components in structures exposed to dynamic loads and low temperatures. It has high tensile strength and excellent weldability, making it ideal for railway underframe construction. Achieving optimal mechanical properties requires preheating as part of the welding process. This study investigates the effect of preheating on the tensile strength and microstructure of welded joints in S355J2 steel. Specimens were prepared using S355J2 steel plates with three preheating variations: no preheating, 65°C, and 137°C. Results showed that the highest tensile strength (581.5 MPa) was achieved with 65°C preheating, while the lowest (529.6 MPa) was observed without preheating. The specimen preheated at 137°C had a tensile strength of 549.5 MPa. Microstructural analysis revealed that non-preheated material consisted of pearlite and ferrite phases. Preheating at 65°C resulted in Grain Boundary Ferrite with more uniform, elongated grains, enhancing material strength. However, at 137°C, tensile strength decreased due to larger grain sizes and a structure approaching Grain Boundary Ferrite.]]>
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