Effect of brazing temperature on tensile strength and microstructure for 304 stainless steel plate-fin structure

The vacuum brazing of 304 stainless steel plate fin structure was carried out, and the tensile tests were performed. The scanning electron microscope (SEM) and Energy-dispersive X-ray spectrometer (EDS) tests were carried out to reveal the microstructure and chemical components in the brazed joint. The effect of brazing temperature on tensile strength and microstructure for 304 stainless steel plate-fin structures was discussed. The results show that the tensile strength is increased with the brazing temperature increasing from 1025 to 1100°C. With the brazing temperature increasing, the boron is diffused more adequately, which increases the strength. The microstructure becomes more uniform with the brazing temperature increasing. Hence the brazing temperature is determined at 1100°C. When the brazing temperature is very low (1030°C), more brittle phases are generated in the brazing joint, which decreases the strength. When the brazing temperature is increased to 1100°C, full solid solution is generated in the middle of joint, and the microstructure in the fillet becomes more uniform.