Brazing Metals in HVAC and Refrigeration

lvzhiyong,

Conventionally, the conduits used in Refrigeration, in particular, are either Copper and in some cases, Aluminium. The reasons for their choice take cognizance of their cost, safety, physical, thermodynamic, electro-cathodic and other properties. So, brazing metals (filler rods-the language of local artisans here) in these units (most especially the heat exchangers - evaporators) are made of copper and its alloys that have lowest eutectic temperatures. To bring the eutectic temperatures further down, a brazing powder (cryolytes, Potassium salts, if I'm not mistaking) is added during the brazing operations which take place at relatively high temperatures. The same is applicable to Aluminium materials. As for lead, Pb, the area of its application as brazing metal is in electrical/electronics due to its malleability and probably, its low melting point and high electro-conductivity. For Chromium, Cr⁺⁶, it may probably be employed in stainless conduits.

hrecules53

Thank you very much!

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Brazing is so universally used in this industry because it's economical, easy to do and because it produces strong, leak tight joints. Leak tightness is especially critical in HVAC units because these are all closed systems; containing a liquid or gas as a heating or cooling medium. Leakage from any joint would allow the liquid or gas to escape, and prevent the unit from functioning properly.

These advantages, economy, strength and leak tightness are inherent in the brazing process.

Some elements are good for brazing process, but they do harm to the environment.

So they are fobbiden used in brazing metals. We must find enviromental element to replace them.