Effects of Si Content and Cold Rolling Condition on Brazeability of Al-Mn-Zn Alloy Core Brazing Sheet

Three layer clad brazing sheets composed of Al-7.5Si alloy (filler, thickness:10 mu m)/Al-1.2Mn-2Zn-(0.04-1.05)Si alloy (core, thickness:80 mu m)/Al-7.5% alloy (filler, thickness:10 mu m), were produced by laboratory fabrication, through casting, hot rolling, cold rolling, intermediate annealing, and final cold rolling. The effects of Si content in the core(O.04-1.05wt.%) and reduction rate of the final cold rolling(10-45%) on microstructure and brazing behavior were investigated. The results revealed that the microstructure and brazeability of the brazing sheet are governed both by Si content in the core and by the reduction rate of the final cold rolling. The excellent brazeability was obtained when the core alloy has the Si content of/cold rolled to 0.04%/10-45%, 0.41%/20-45% and 0.64%/30-45%. In these cases, a coarse grain structure was developed in the core during the brazing process, which suppressed the penetration of melting filler into the core.