Homogeneous low melting temperatures brazing filler metal for joining ferrous and non-ferrous alloys

摘要

Most of the low melting brazing filler alloys for brazing of various steels and alloys in the range of 550°-850°C are silver-base. These alloys (BAg-series according to the American Welding Society) contain from 30 to 93wt% of silver and substantial amounts of melting temperature depressing elements like zinc and cadmium. Both zinc and cadmium increase wettability and flow during brazing. However, the presence of precious silver and carcinogenic cadmium in BAg-series alloys has always been a stimulus to develop new low-silver or silver and cadmium free alloys with brazing performance at least similar to those of BAg-series.;For these purposes, copper-base alloys particularly those derived from the Cu-Mn-Si system, seem to be a natural choice. This system has a ternary eutectic with melting temperature in the vicinity of 800°C and it consists of elements which dissolve readily in both iron and copper. Low melting temperature copper-base brazing filler metals, which have low silver concentration and are cadmium free, are disclosed here. These filler metals contain (at%): 0-10 silver, 4-16 manganese, 4-16 silicon, 0-20 zinc, 0-16 tin and 0-10 indium, the balance being copper and incidental impurities. These alloys are produced in a homogeneous ductile, metastable foil shape or as a homogeneous metastable powder by rapid solidification processing. A successful brazing is achieved for any combinations of steels, copper and its alloys, cemented carbides and various composite materials.