Soldering terminology

Brazing involves interposing a filler material with a lower melting point (hard solder or filler) between two work pieces t hen filling the soldering gap with molten filler metal simultaneous application of heat and pressure. This way, a connection is formed between the work pieces. Borax is used as fluxing agent. There is a distinction between soft soldering (up to 450 °C) and brazing ( above 450 °C) based on the temperature of soldering. Although in principle soft brazing and soldering are the same, soft and hard brazing is distinguished in English. Hard brazing is applied, for example, to attach a tungsten carbide tip (extra hard alloy) on a shaft (steel with 0.7 % C). In order to strengthen the plug connection between two iron pipes, a liquid copper solder is applied on the outer surface which rises in the gap between the two pipes due to capillary action. This is why English researcher Dr. C. J. Thwaites is on the view that soft and hard soldering do not represent to different technologies, but instances of what he calls “capillary joining”, because both methods rely on capillary action.