A new cooling method for vacuum brazing of a stainless steel plate–fin structure

This paper presents a new cooling method for vacuum brazing of 304 stainless steel plate–fin structures with Nickel-based BNi2 filler metal. The tensile tests and scanning electron microscope (SEM) observations have been performed. Quick cooling method and a new developed slow cooling method have been used, respectively, to discuss the influence of cooling methods on tensile strength and microstructures. The quick cooling is performed by dry nitrogen and wind cooling system directly from brazing temperature 1050 °C. The new slow cooling method is self-cooling in vacuum furnace from 1050 to 620 °C, then it is changed to quick cooling with dry nitrogen and wind cooling. The results show that quick cooling method should not be used because thermal cracks will be created and decrease the strength. The new developed slow cooling method can greatly improve the brazing performance.