Interfacial distribution of elements and fracture behaviour of metal inert gas brazed joint with copper based filler metals

Metal inert gas brazing for joining galvanised A3 steel sheets or 1Cr18Ni9Ti stainless steel with Cu- 3 wt-%Si- 1 wt-%Mn or Cu- 10 wt-%Mn- 6 wt-%Ni brazing filler metal has been investigated. The experiment results indicate a Si and Mn rich band was produced at the interface of filler metal and base metal. X-ray diffraction analysis shows that Si existed as Fe₂Si and Mn existed in the form of solid solution. Tensile testing specimens using Cu–3Si–1Mn and Cu–10Mn–6Nias the filler metal fractured at the base metal with joint strengths of 308·2–308·7 MPa. The joint specimens of stainless steel 1Cr18Ni9Ti fractured at the brazing seam with strengths of 331·5 and 423·6 MPa. Tensile fracture analysis shows that the fracture area originated at the bottom of the lap brazing seam (brittle fracture composed of the components of base metal and filler metal), and ended in the brazing seam (Cu–3Si–1Mn/filler metal) or in the vicinity of the Cu–10Mn–6Ni/filler metal interface (ductile fracture).