| 摘要 |
PURPOSE:To obtain composite brazing sheets for heat exchanger made of Al alloy with improved property of pitting corrosion resistance, by a following method which Al-Mn alloy is used for a core material and Al-Mn-Zn alloy is used for skin material, thereby reducing Mn content of the skin material to the lower content than that of the core material. CONSTITUTION:A composite brazing sheet is composed of a core material of Al-Mn alloy containing at least 0.3-1.5wt% Mn, and a skin material of Al- Mn-Zn alloy containing at least 0.1-1.3% Mn and 0.1-2.0% Zn. and further the following condition, i.e., Mn content of core material >=Mn content of skin material +0.2% is satisfied. By this constitution, the corrosion of a skin material is decreased, and also the occurrence of local corrosion is reduced. As the skin material is electro-chemically baser than core material, the corrosion which may grow to pitting corrosion is reduced, even if the skin material may be locally corroded. Consequently, when said material is used for tubes of a heat exchanger, the superior performance of the tube is kept for a long time. |
