MATHEMATICAL MODELS OF DEPENDENCE OF JOINTS’ QUALITY ON THE TECHNOLOGY FACTORS WHEN BRAZING IN ZINC VAPORS

Brazing in zinc vapor allows not only to prevent zinc evaporation out of brass brazing alloys and to use furnace heating without limitations but also to eliminate the flux application when brazing carbon steels even if before heating the container for brazing has the atmospheric air (brazing in modified air environment). Brazing in a container with a filling-sealed stopper with the carburizer superinduction to the container and in the filling composition is currently the easiest and the most reliable option for brazing in zinc vapors. Such technology does not require the application of complex specialized equipment. Brass brazing alloys can be produced from copper billet by alloying it with zinc from a vapor phase. The work was carried out in relation to this variant. The formation and quality of brazed joints when brazing in a container, in particular in zinc vapors, is the result of a number of closely related physical and chemical processes. The construction of the analytical model of these processes combination is problematic at present. The challenge was solved by the method of mathematical design of experiments. The authors carried out the complete factorial experiment and then, using the composite design, they produced the second-order equations (including the coefficients of pair and triple interaction) describing pretty exactly the dependencies of breaking stress, strength, gaps filling factor and the ratio of brazed joints defects on the main technology factors (temperature and exposure time, the amount of zinc and the amount of carburizer). Two methods of brazing modes optimization were proposed and used. When selecting the modes, the most important quality indicators for a specific product should be considered.