Sagging Resistance of Braze Clad Fin Material for Evaporators and Condensers

Braze clad fins of AA3003 type are used in evaporators and condensers. High strength of the thin fin material at the brazing temperature, generally referred to as sagging resistance, is needed in order to avoid collapse of the assembly during brazing.

The sagging resistance of braze clad fin material AA3003 from full scale production has been investigated. Previous work on laboratory scale material has been confirmed. A narrow range of final cold reduction can be specified which will lead to optimum sagging resistance of the fin material. Both lower and higher degree of cold reduction will lead to decreased sagging resistance. This can be related to the recrystallisation behaviour during the brazing cycle.

For a given heat treatment and core alloy composition there is a correlation between cold reduction and room temperature tensile strength before brazing of the fin material. The present work suggests that the strength can be used to predict the sagging resistance.