Influences of oxygen partial pressure and additive elements on flux-free brazing of aluminum alloys

2019 Fiscal Year Final Research Report

• Project/Area Number: 15H04136
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Composite materials/Surface and interface engineering
• Research Institution: Chiba Institute of Technology
• Principal Investigator: Ozawa Shumpei 千葉工業大学, 工学部, 教授 (80404937)
• Project Period (FY): 2015-04-01 – 2020-03-31
• Keywords: アルミニウム合金 / フラックスフリーろう付 / 表面張力 / 雰囲気酸素分圧

Outline of Final Research Achievements

The standard brazing process of aluminium alloys require use of non-corrosive fluxes to remove oxides from the base material and to prevent oxidation during the heating process. However it is difficult to used the Flux when brazing aluminum alloys containg a certain amount of Mg. Furthermore, residual flux even after brazing followed by cleaning may cause defects in the final product. In order to develop flux-free brazing of aluminum alloys, it was investigated the influences of sample composition and oxygen partial pressure of atmospheric gas on the brazability of allminum alloys. As a result, it was confirmed that the addition of Mg into the sample improves flux-free brazability of aluminum alloy. Furthermore, when oxygen partial pressure of atmospheric gas was down to ultra low value of 1e-30 atm, very good brazability was obtained comparable with that by flux brazing. It was indicated that surface tension of molten filler alloys influences on the shape of brazing fillets.

Free Research Field

高温融体プロセス

Academic Significance and Societal Importance of the Research Achievements

本研究では，ジルコニア式酸素ポンプによる極低酸素分圧においてAl合金のフラックスフリーロウ付を実現した．これは，従来は困難であったZn添加による防食や，Mg添加された高強度Al材への適用が可能となるもので，社会的に意義が高い．また単にロウ付実験を行うだけで無く，溶融ろうの表面張力測定も行うことで，添加元素がフラックスフリーロウ付に与える本質的な効果を明らかにした．特に酸素については，従来は酸化に対する影響のみが着目されてきたが，それは強力な表面活性元素であるため，表面張力の変化を介しても，ロウ付性に影響していることを示した．これは，高温融体の表面科学の観点から学術的にも意義が高い．