New clad fin material with high post braze strength and excellent sagging resistance

摘要

The thickness of fin materials is trending down as with other heat exchanger materials. Consequently, the fin stock materials need to have a higher post braze strength, better sagging resistance and better corrosion resistance. The main use for thin, clad fin stock is in condensers. Usually these are brazed relatively rapidly in the early stages of the brazing cycle and more slowly at the higher temperatures. This poses a challenge for thin clad fin materials. A longer time at higher temperatures gives more time for diffusion of silicon from the braze cladding into the core material. For these brazing cycles and thin gauges a more tolerant, clad fin material is needed. The new clad fin material from Sapa has the name SSR, "Strong, Sagging Resistant". This is a fin material with good elongation in the as-delivered temper for good formability. The SSR fins are available with four different zinc contents (0 - 2,5%) for tailor-made material system corrosion solutions. By careful selection, the brazed fins will develop a chosen corrosion potential in the range -730mV to -850mV. The resulting SSR corrosion performance is better than that for clad FA6815 fins with corresponding zinc contents.