How to Braze Aluminum?

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dampfmann
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How to Braze Aluminum?

Post by dampfmann »

Hello,

I would like to repair a small crack in some aluminum poles. I searched the forum and some product by "Muggy Weld" came up. Does anyone have any experience with their products or can you suggest an alternative product? Please be specific. This is my first time trying to braze aluminum. Btw, I am using an air-acetylene TurboTorch (nice product!)

Thanks,

Martin
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steamin10
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Re: How to Braze Aluminum?

Post by steamin10 »

I have used the Bernzo-Matic stuff with mixed results. Heres what may help: Brush the joint completely to a dull shine with STAINLESS tooth brush. Steel brush will contaminate the surface, and complicate your efforts. Use a good FAST heat. Overheating aluminum will have it drop away suddenly, and flat destroy your effort. Your filler rod must be of similar temperature, and pressed/twisted into your work, immediately puddled, and backed off to let cool enough for another spot to be added. You will have very little to gauge from, as the surface will slick right before it drops. Some practice before the actual job is wise, aluminum becomes soft around 950 degrees, and liquid above 1200, with some level of pasty in between. But this will be a black heat and not readable to the eye, so you will have to watch the metal surface carefully. Using this method, most of the material added will lay on the surface bond and have shallow penetration. A crack will oxidize and pull apart as it melts, and not flow together, it has to be pushed when it gets pasty, and the filler metals are designed to melt a a slightly lower than base metal temp, but beware, they are close. Be scant with the heat, waving in at the end.
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powderhorn01
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Re: How to Braze Aluminum?

Post by powderhorn01 »

In the Navy we would sometimes have to braze aluminum, when we could not lay hands on a tig / mig welder. We would clean with a stainless brush, then make an acetylene rich flame to blacken the aluminum in the working area. When you got the area heated up to brazing temp the black would disappear, and you were at brazing temp. We used a Eutectic Aluminum brazing rod that had a flux that was red in color, the rod was sized to about the thickness of your work. Word of warning about there flux--it is not like when you are brazing steel and the fire ball bounce off of you, this flux sticks to you like glue.
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juiceclone
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Re: How to Braze Aluminum?

Post by juiceclone »

Those aluminum brazing products are hard to use as mentioned above. Scraping the rod on the spot until u see it flow/tin is one way to judge heat. Most of them u have to scrape them to get them to stick anyway! They are all alloyed to have a lower melting point than the aluminum, but not much!!
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