| 摘要 |
PURPOSE:To improve the corrosion resistance of a brazed joint part by executing brazing in such a manner that Cu of an adequate quantity is incorporated into a brazing filler metal, subjecting the joint to a liquid phase diffusion treatment at a temp. within a specific range after brazing and heating, thereby forming a state in which the Cu is solutionized into the base phase of Al. CONSTITUTION:The brazing is so executed that the brazed joint part has the average Cu content of the brazing metal within a 0.05 to 1.0wt.% range. The brazed joint part is held for 20 seconds to 20 minutes at the specified temp. within the 540 to 577 deg.C range of the solid-liquid coexistence temp. range during the course of cooling after the brazing and heating to diffuse the Cu in the liquid phase so as to substantially prevent the formation of an Al-Cu intermetallic compd. The liquid phase 6A of the high concn. of the Cu is locally formed and in succession, the diffusion 7 from the liquid phase 6A of the high concn. of the Cu to the periphery arises. The structure in which the Cu is solutionized into the base phase 4 of the Al of an Al-Si eutectic phase is obtd. As a result, the heat exchanger which is greatly improved in the corrosion resistance of the brazed joint part is obtd. |
