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836 |
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Thursday, June 21, 2007, Brüssel 11:00 AM Fügen von Leichtmetallen Joining of light weight metals |
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Benefit of Wider Gap at Brazing Aluminum Alloys to Stainless Steels in the Air using the Flux containing Zinc |
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Toshi-Taka Ikeshoji* / Kindai University, Research Institute of Fundamental Technology for Next Generation, Japan Toshi-Taka Ikeshoji / Tokyo Institute of Technology, Japan Shuying Liu/ Tokyo Institute of Technology, Japan Akio Suzumura/ Tokyo Institute of Technology, Japan Takahisa Yamazaki/ Tokyo Institute of Technology, Japan |
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The brazing of aluminum alloys to stainless steel was conducted using the aluminum-silicon brazing filler in the air under the existence of the flux. Aluminum alloys and stainless steel easily form the strong oxide layers on the surface and they are the obstacle to accomplish their dissimilar brazing joint in the air. To remove those oxide layers, the water soluble active corrosion chloride flux including zinc chloride was pasted. The zinc is considered to react with aluminum alloys to breakthrough the oxide film. In this experiment, it simultaneously diffused fast in the aluminum bulk. The EDX mapping showed the diffusion of zinc into aluminum alloys, on the other hand silicon was condensed in the center of the solidified layer. According to the mapping image and the element distribution analysis, the isothermal diffusion occurred from the surface of aluminum alloy by the aluminum-zinc system. By changing the brazing time, the athermally solidified layer width was measured and the isothermal solidification rate was estimated. The isothermal solidification was fast and considered to finish before the breakage of the oxide film on the stainless surface. This fast isothermal solidification was considered to prevent the joint formation in the air. The wetting time of the stainless steel surface using the flux with zinc and the aluminum-silicon brazing filler was measured. The numerical simulations on the Fickian diffusion of the zinc into aluminum alloys and silicon into aluminum alloys were also conducted to estimate the isothermal solidification time from the aluminum alloys? surface. Combining the results of the wetting time and the isothermal solidification simulations, the gap width required for formation of the brazing aluminum alloys and stainless steel was proposed. |