Optimising the production cycle of fins made of clad EN AW 3003 alloy brazed on plates: grain size effect

Processing cycles to produce rolled aluminium and its alloys are identified in such a way as to ensure a alloy structure showing fine and homogenous grain size that determines the mechanical properties required to produce numerous types of manufactured products. In some cases, however, the requirement may be completely different. Alloy ENAW3003 can be used to produce cooling fins that must be brazed onto heat exchanger plates used in the production of air conditioning systems. They consist of aluminium clad laminates composed of a 4XXX/3000/4XXX tri-layer. In these cases, to achieve a correct brazing, it is necessary to increase the grain size, and at the same time, ensure that good mechanical properties persist in the part. The aim of the work was to determine what changes in 3003 alloy composition and/or process must be implemented to achieve good brazing. Tests carried out by reducing the amount of refiners in the 3003 alloy, which seemed the most logical solution, did not lead to satisfactory results. A new approach to the problem was evaluated by varying the concentration of iron, silicon and manganese in the alloy. This solution, combined with a reduction in the work hardening ratio of the material from 40% to 30%, resulted in adequate grain sizes for effective brazing.