Re: Real pretty small alu welds??

On Wed, 26 Oct 2005 00:08:14 GMT, "Pete C." <aux3.DOH.4@xxxxxxxx>
wrote:

>carl mciver wrote:
>>
>> I know nothing about brazing aluminum. Hopefully someone else will
>> weigh in on it.
>>
>
>Don't think it can be done. The chart I'm looking at lists the melting
>point of aluminum alloys in the 1,100-1,200 F range and the melting
>point of brasses in the 1,800-1,900 F range. Rather the opposite of what
>you need for successful brazing.
>

You use a aluminum brazing alloy. Such as Alloy 31 from Esab. It's
melting point is a little lower than most alloys. It works super well
on things like car A/C condensers. Actually it's what they use to
build them in the first place.

As for how it works well if you clean the pieces like you would for
TIG then apply the flux your home free. The main thing is to use a
lower temperature diffused flame source for the heat and bring the
temp up slowly. In other words a propane or mapp torch works better
than a oxy-acet torch for lighter work. The oxy-acet torch is to hot
and will melt the surface before the heat gets a chance to soak into
the piece. Alloy 31 will flow about as well as most silver solders.

Another thought is that they sell it in a powdered form already
mixed with the flux so all you have to do is brush it on and heat it.
I've not used that form so I can't vouch for how well it works.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm
.

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