Fabrication and brazeability of a three-layer 4343/3003/4343 aluminum clad sheet by rolling

A three-layer aluminum clad sheet composed of 4343 (filler alloy, thickness: 10 μm)/3003 (core alloy, thickness: 80 μm)/4343 (filler alloy, thickness: 10 μm), which is being used as brazing sheet materials for automotive condensers, was fabricated by casting→hot rolling→cold rolling→intermediate annealing (IA)→final cold rolling (CR), and the relationship between the IA/CR condition, microstructure and brazing characteristics was investigated. When IA/CR was performed under the condition of 600–690 K/10%, the core contained non-recrystallized structure, and the melting filler penetrated into the core along the subgrain boundaries during the brazing process, resulting in decreased brazeability with accompanying increase in eroded area. When IA/CR was carried out under the condition of 600 K/over 30% or 690 K/over 45%, finely recrystallized grains were formed in the core during the brazing process, which promotes filler penetration along the grain boundaries. In this case, the brazeability deteriorated with the increment in eroded area. If IA/CR was done under the condition of 690 K/20–45%, the specimens exhibited excellent brazeability with suppressed erosion owing to the formation of coarsely recrystallized grains.