Coated Rods for Brazing Structures Used in High Safety Conditions

摘要

The paper presents research made in order to assure additional conditions, compared to those in the general standard, to brazing rods, in order to guarantee safety for the environment and for the brazed joints, against corrosion and embrittlement, in high risk conditions. Environmental safety is ensured by limiting the amount, at 0.25% in depositions, of dangerous residual elements at: Cd<0.1%; Hg<0.1%; Pb<0.1%; Cr<0.1%; As<0.1%. The safety of structures against corrosion is provided by the alloying level of deposits and by neutralizing the coat's activity. The structure safety towards the embrittlement of brazed joints is ensured by limiting the content of embrittling elements, namely: Sb+Fe+Bi at a maximum of 0.3% and the content of diffusible hydrogen at maximum 5 cm~3/100g raw material and by limiting the coat humidity at maximum 10%. The experiments were performed to ensure the set out requirements by following the selection of raw materials on the input criteria of prohibited chemicals, reducing the water content from the elements that make up the coat and by diminishing it's hygroscopicity by neutralizing it. Prescribing additional conditions has an effect on manufacturing costs, which requires productivity increase at brazing, diminishing work temperature, increasing the moistening capacity of products, reducing the smoke level, effects pursued by the research.