Investigating the effect of brazing time and temperature on stainless steel sandwich joints

Brazing of low-carbon austenitic stainless steel sheets is applied to produce plate heat exchangers. In this study, the copper filler was used to join multiple layers of 316L steel plates due to its low cost, low melting temperature and relatively good bonding strength compared to other filler metals. For comparison, 2-layer and 5-layer specimens were brazed with the copper interlayer. fabricated. The sandwich joints have been fabricated under different process conditions of the brazing temperature (1070 and 1120°C) and the brazing time (30, 60, and 90 min). Detailed microstructural studies and hardness were carried out on the brazed joints. The microscopic studies showed that the joint formed at 1070 °C was not uniform compared to 1120 °C and the specimen brazed at 1120°C/90 min presented better properties due to enough time for melting of the interlayer and diffusion of elements. Also, 2-layer specimens with lower average grain size had higher hardness than 5-layer specimens.