The fatigue strength of brazed butt joints made by joining hot-rolled mild steel plates with brass was investigated. The shape of the joint cross section was I-shaped, and the brazing material was completely melted into the joint cross section. Test pieces made from the brazing material alone were prepared as reference materials. Tensile tests and fatigue tests were performed on both the brazed butt joint test pieces and the brazing material test pieces. The fatigue test conditions were a stress ratio of 0.1, load control, and axial loading. The results of the tensile test showed that the tensile strength of the brazed butt joint was higher than that of the brazing material alone. It was found that when using the tensile strength of the brazing material alone as the design strength of the brazed butt joint, the safety factor would be 1.3 times.The results of the fatigue test showed that the fatigue strength of the solder material alone was lower than that of the soldered joint throughout the entire life span. It was found that the fatigue design of the soldered butt joint could be performed appropriately by setting the design strength to a value 6% lower than the average time strength of the solder material alone. SEM observation revealed the presence of voids inside the brazed joint. It was found that the strength of the joint can be accurately estimated by performing stress evaluation based on the effective cross-sectional area excluding the defect area.
MAEKAWA et al. (2025) studied this question.