Cleaning Effect of Interlayer Metal on the Joining Surface during Braze Pressure Welding

Braze Pressure Welding (BPW) with high frequency induction heating is a newly developed pressure welding technique using interlayer metals for welding the general steel pipes for pipe arrangement in buildings. BPW enables to make joints by solid-state welding in air with relatively small deformation. In this method, the interlayer metal is expected to play the primary role in making high performance joints. It removes contaminations from the joining surface of the base metal and forms fillets at the gaps around the joint. It had been revealed by some experiments and/or numerical analyses in previous research that the BPW joint had higher tensile strength than the brazed joint, and that the fillet can improve the joint strength. In this study, in order to investigate the cleaning effect of interlayer metal more closely, a low carbon steel plate specimen was brazed mainly by Ni-based brazing filler using a tungsten spacer. The microscopy and EPMA analysis on the joints made by various brazing temperatures and durations confirmed that the oxide films on the joining surfaces were removed and discharged from the joining region by the interlayer metal.