Joint Characteristics by Ni Brazing Alloy (Report 1)
In this study, the influence of brazing process conditions on the Ni brazed joint (Ni-Cr-B) strength of SUS304 stainless steel has been investigated by the tensile test, microscopy, EPMA and SEM. The effects of the brazing clearance, the brazing temparature, and the holding time at brazing temperature are described. The tensile test results show that the Ni brazed joint strength of SUS304 is found to depend on the brazing clearance and the brazing temperature.
The results obtained are as follows ;
(1) The brazed joint strength depends on the brazing clearance and its maximum strength is obtained at the brazing clearance of 20μm.
(2) In the metallographical analysis, it is observed that considerable amount of Ni rich fragments concentrate at the central line zone of the brazing layer. The mass of Ni element may correspond to the original brazing alloy. At the clearance more than 50 μm, the segregation (B-Cr) can be observed at the central line zone of the brazing layer.
(3) The brazed joint strength depends on the brazing temperature and its minimum strength is obtained at the brazing process temperature 1380 K with the brazing temperature holding time of 600 sec. This temperature (1380 K) fosters the segregation (B-Cr) of the brazing alloy and the joint strength is related to its segregation size.