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Filler neck on fuel tank
A tank filler neck can be seen on both photos. When using this joining technique, the operating loads as a result of vibrations when travelling must be taken into account. If the tank is made of leaded sheet steel, it can be brazed using cadmium-containing alloy BrazeTec 4003 at a working temperature of 610°C.
If the parts to be joined consist of galvanised sheet steel, BrazeTec 60/40 brazing alloy with a working temperature of ca. 900°C can be used. The brazing can be carried out using the gas flux method. Here, gaseous flux, which mostly forms from volatile liquid mixtures, is used for brazing with a torch flame.
The torch gas flow is passed through the volatile liquid mixture in this method and so becomes enriched with flux. The boron compounds emitted in the flame, which takes on a green colour as a result, forms boric acid which is deposited in liquid form on the hot working material.
If there is simultaneous chemical decomposition of the existing oxide skin on the metal, the resulting coating protects the metal surface against oxidation by atmospheric oxygen. Networking and bonding of the liquid brazing alloy on the oxide-free metal surface is hence made possible.
If the fuel tank and filler neck are made of ordinary sheet steel, we recommend BrazeTec 5600 brazing alloy having a working temperature of 650°C. For normal flame brazing, BrazeTec h flux can be applied. It is essential that all residual flux be removed due to its high susceptibility to corrosion.